EPA-600/2-78-037
March 1978
Environmental Protection Technology Series
OPERATION AND MAINTENANCE
OF PARTICULATE CONTROL DEVICES
ON SELECTED STEEL
AND FERROALLOY PROCESSES
SSK
ol
O
Industrial Environmental Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
-------
EPA-600/2-78-037
March 1978
OPERATION AND MAINTENANCE
OF PARTICULATE CONTROL DEVICES
ON SELECTED STEEL
AND FERROALLOY PROCESSES
by
Michael F. Szabo and Richard W. Gerstle
PEDCo. Environmental, Inc.
11499 Chester Road
Cincinnati, Ohio 45246
Contract No. 68-02-2105
Program Element No. lAB012
ROAP No. 21ADL-037
EPA Project Officer: Dennis C. Drehmel
Industrial Environmental Research Laboratory
Office of Energy, Minerals, and Industry
Research Triangle Park, NC 27711
Prepared for
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Research and Development
Washington, DC 20460
-------
RESEARCH REPORTiNG SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the ENVIRONMENTAL PROTECTION TECH-
NOLOGY series. This series describes research performed to develop and dem-
onstrate instrumentation, equipment, and methodology to repair or prevent en-
vironmental degradation from point and non-point sources of pollution. This work
provides the new or improved technology required for the control and treatment
of pollution sources to meet environmental quality standards.
EPA REVIEW NOTICE
This report has been reviewed by the U.S. Environmental Protection Agency. and
approved for publication. Approval does not signify that the contents necessarily
reflect the views and policy of the Agency, nor does mention of trade names or
commercial products constitute endorsement or recommendation for use.
This document is available to the public through the National Technicallnforma-
tion Service. Springfield. Virginia 22161.
-------
ABSTRACT
This report deals with the control of fine particulate
emission from iron, steel, and ferroalloy plants using
electrostatic precipitators (ESP's), wet scrubbers, and
fabric filters (baghouses).
It provides information on the
selection, operation, and expected performance of conven-
tional air pollution control devices, based upon current
design practice, theoretical models, performance, cost
predictions, and information in the literature.
iii
-------
ABSTRACT
FIGURES
TABLES
CONTENTS
METRIC CONVERSION FACTORS
ACKNOWLEDGMENT
1.0
2.0
3.0
INTRODUCTION
1.1
1.2
1.3
Purpose of Report
Significance of Particulate Emissions
Scope of the Report
CONTROL SYSTEMS:
CORRELATIONS
2.1
2.2
2.3
2.4
2.5
2.6
DESIGN PARAMETERS AND
Emissions Sources, Characteristics, and
Control Systems Used
Comparison of Various Factors Which
Influence Control Device Collection
Dry Electrostatic Precipitators
Wet Electrostatic Precipitators
Wet Scrubbers
Fabric Filters
OPERATION AND MAINTENANCE AND COMMON MALFUNC-
TIONS OF PART~CULATE CONTROL DEVICES ON IRON,
STEEL, AND FERROALLOY APPLICATIONS
3.1
3.2
Electrostatic Precipitators
Wet Electrostatic Precipitators
iv
Page
iii
vi
ix
xii
xiii
1-1
1-1
1-1
1-2
2-1
2-1
2-35
2-37
2-75
2-81
2-92
3-1
3-1
3-18
-------
4.0
5.0
3.3
3.4
CONTENTS (continued)
Wet Scrubbers
Fabric Filters
FRACTIONAL EFFICIENCY RELATIONSHIP
4.1
4.2
4.3
4.4
Introduction
Dry Electrostatic Precipitators
Wet Scrubbers
Electrostatic Precipitators
5.1
SUMMARY AND CONCLUSIONS
5.2
5.3
5.4
Design Parameters
Operation and Maintenance
Frac.ional Efficiency Relationships
Costs
APPENDIX A
INSTALLATION LISTS FOR SELECTED
STEEL/FERROALLOY PROCESSESS
APPENDIX B
CAPITAL AND ANNUAL COSTS OF PRECIPITATORS
ON SELECTED IRON AND STEEL AND FERROALLOY
PROCESSES
APPENDIX C
ELECTROSTATIC PRECIPITATOR SUBSYSTEM AND
COMPONENT FUNCTION AND OPERATION
Page
3-30
~
3-41
4-1
4-1
4-3
4-27
4-30
5-1
5-1
5-10
5-12
5-15
A-l
B-1
C-l
PREDICTED PERFORMANCE OF VENTURI SCRUBBERS D-l
ON SELECTED IRON AND STEEL PROCESSES USING
RESEARCH COTTRELL'S MODEL
APPENDIX D
v
-------
Figure
2-1
2-2
2-3
2-4
2-5
2-6
2-7
2-8
2-9
2-10
2-11
2-12
2-13
2-14
2-15
2-16
FIGURES
A Composite Flow Diagram for a Steel Plant
Ferroalloy Production Process
Open Furnace
Semienclosed Furnace
Sealed Furnace
Sectionalization of a Precipitator
High Tension Splits
Selected Precipitator Collelations
Size - No. Density Distribution for
Ferroalloy Processes
Apparent Resistivities of Metallurgical
Dusts
Selected Precipitator Correlations for
Basic Oxygen Furnace
Selected Precipitator Correlations for
Open-Hearth Furnace
Selected Precipitator Correlations for
Electric Arc Furnace
Effect of Temperature and Sinter Basicity
on Resistivity of Sinter-Plant Particulate
Selected Precipitator Correlations for
Sintering Process
Venturi Scrubber System
vi
Page
2-2
2-25
2-27
2-27
2-27
2-47
2-51
2-57
2-62
2-63
2-65
2-66
2-67
2-69
2-70
2-83
-------
Figure
2-17
2-18
2-19
2-20
3-1
3-2
3-3
3-4
3-5
3-6
3-7
3-8
3-9
4-1
4-2
4-3
4-4
FIGURES (continued)
Diagram Showing Normal Operation and
Shake Cleaning of a Fabric Filter
Schematic for Reverse Flow Cleaning
During Continuous Filter Operation
Installed Cost of Fabric Filter Systems
Annual Operating and Maintenance Cost of
Fabric Filter Systems
Typical Electrostatic Precipitator with
Top Housing
Three Types of Wet Electrostatic
Precipitators
Research Cottrell Flooded Disc Scrubber
Reverse Air or Shaker Type Baghouse
Pulse Jet Type Baghouse
Poppet Valve
Typical Trough Hopper and Screw Conveyor
Arrangement
Bag-Cell Plate Attachments
Typical Shaker Arrangement
Cold Precipitator Penetration for Open
Hearth Furnace
Cold Precipitator Penetration for Basic
Oxygen Furnace
Cold Precipitator Penetration for Electric
Arc Furnace
Cold Precipitator Penetration for Sintering
Machine
vii
Page
2-100
2-103
2-112
2-113
3-5
3-20
3-32
3-45
3-46
3-55
3-59
3-60
3-64
4-8
4-9
4-10
4-11
-------
Figure
4-5
4-6
4-7
4-8
4-9
4-10
4-11
4-12
4-13
4-14
4-15
FIGURES (continued)
Cold Precipitator Penetration for Sintering
Machine (Precipitator Preceded by Mechanical
Collector)
Cold Precipitator Penetration for Ferro-
silicon Arc Furnace
Cold Precipitator Penetration for Ferro-
manganese Arc Furnace
Cold Precipitator Penetration for Ferro-
chromium Arc Furnace
Cold Precipitator Penetration for Miscel-
laneous Ferroalloy Arc Furnace
Fractional Efficiency Curve for an Electro-
static Precipitator Serving Seven Open
Hearth Furnaces
Percent Penetration Predicted Versus
Particle Size for 99.0 Percent Overall
Mass Collection Efficiency
Predicted and Actual Performance of the
Nikopol Venturi Scrubber on a Ferroalloy
Furnace
Measured and Predicted Efficiencies for a
Wet Precipitator Installed Downstream of a
Spray Type Scrubber on an Aluminum Reduction
Pot Line
Particle Size Distributions of Electric Arc
Furnace Dust at Inlet and Outlet of Baghouse
Fabric Filter Fractional Penetration Curves
viii
Page
4-12
4-13
4-14
4-15
4-16
4-18
4-19
4-26
4-28
4-33
4-35
-------
Table
2-1
2-2
2-3
2-4
2-5
2-6
2-7
2-8
2-9
2-10
2-11
2-12
2-13
TABLES
Summary of Emission Characteristics from
Various Literature Sources
Chemical Composition of Sinter Strand Wind
Box Dust
Electric Arc Furnace Fume Particle Size
Distribution
Typical Chemical Analysis of Electric Arc
Furnace Fume
Properties of Particulate Emissions from
Ferroalloy Furnaces
Factors Bearing on Control Device Selection
Design Philosophy
Design Power Density
Design Parameters and Design
Comparison of Performance of Electrostatic
Precipitators on Various Iron and Steel
Applications
Summary of Emission Characteristics (Steel/
Ferroalloy Applications) used to Determine
No. Density - Particulate Size Distribution
Typical Values and Ranges for Wet Precipi-
tator Basic Design Parameters
Comparative Cost Analysis of Wet Electro-
static Precipitators and High-Energy Venturi
Scrubbers for Scarfing Process
ix
Page
2-10
2-11
2-16
2-16
2-29
2-36
2-37
2-43
2-45
2-59
2-60
2-79
2-81
-------
Table
2-14
2-15
2-16
2-17
3-1
3-2
3-3
3-4
3-5
3-6
3-7
3-8
3-9
3-10
3-11
3-12
4-1
4-2
TABLES (continued)
Fabric Filter Design Criteria
Comparison of Fabric Filter Cleaning
Methods
Characteristics of Various Fabrics
Methods of Temperature Conditioning
Comparison of Design and Operational
Problems of Utility, Iron, Steel, and Ferro-
alloy Electrostatic Precipitators
Comparison of Major Maintenance Problems
for Utility and Metallurgical Precipitators
Maintenance Schedule for Wet Precipitators
Maintenance for Plugging and Scaling
Venturi Scrubber
Scrubber Maintenance
Spare Parts Inventory for Venturi Scrubber
Type of Maintenance Required - Venturi
Scrubber Systems
Page
2-95
2-98
2-106
2-111
3-16
3-19
3-28
3-38
3-39
3-42
3-43
Checklist for Routine Inspection of Baghouse 3-52
Baghouse Collector Maintenance
Approximate Cost of Replacement Bags
Bag Life in the Iron and Steel Industry
List of Replacement Parts for a Baghouse
Filter
Summary of Inlet Particle Size Distribution
Data
Nomenclature for Electrostatic Precipitator
Computer Model
x
3-53
3-61
3-61
3-63
4-4
4-5
-------
Table
5-1
5-2
5-3
5-4
5-5
A-I
A-2
A-3
A-4
A-5
A-6
A-7
A-8
A-9
C-3-l
TABLES (continued)
Advantages and Disadvantages of Using Dry
Precipitators on Steel/Ferroalloy Processes
Advantages and Disadvantages of Using Wet
Scrubbers on Steel/Ferroalloy Processes
Advantages and Disadvantages of Using
Fabric Filters on Steel/Ferroalloy Processes
Advantages and Disadvantages of Using Wet
Precipitators on Steel/Ferroalloy Processes
Summary of Usage of Various Control Devices
on Selected Steel/Ferroalloy Precesses
Sinter Reclamation Plants in the U.S.
Integrated Iron and Steel Industry
Inventory of Open Hearth Furnaces
Survey of BOF Plants in the U.S.
Survey of Electric Arc Furnaces in the
United States
Surface Conditioning Air Pollution Control
Systems in the U.S. Iron and Steel Industry
Submerged Electric Arc Ferroalloy Furnaces
in the United States
Research-Cottrell Precipitators on Sinter
Machine Gas
List of Research-Cottrell Designed Oxygen
Steel Making Cottrell Precipitators
Research-Cottrell, Inc. High Efficiency
Scrubber Installations
Troubleshooting Chart for Electrostatic
Precipitators
xi
Page
5-2
5-3
5-4
5-5
5-6
A-2
A-4
A-5
A-6
A-IS
A-18
A-23
A-24
A-26
C-36
-------
Table
C-3-2
C-4
TABLES (continued)
Page
Frequency of Failure and Repair Times
Required for Various Precipitators
Components
C-39
Procedures for Troubleshooting and
Correction of Baghouse Malfunctions
C-4l
xii
-------
METRIC CONVERSION FACTORS
To convert
English units
British thermal unit (Btu)
Cubic foot (ft3)
Degrees fahrenheit
Foot
Gallon (U.S. Liquid)
Gallon (U.S. Liquid)
Horsepower (hp)
Inch
Inch
Inches of water
Pound
Ton, short
Multiply
by
1054
0.0283
5/9 (OF-32)
0.3048
0.0038
3.7854
746.0
0.0254
2.54
248.8
0.4536
0.9072
xiii
To obtain
SI units
Joule (j)
Cubic meter (m3)
Degrees Celsium (C)
Meter (m)
Cubic meter (m3)
Liter (1)
Natt (w)
Meter (m)
Centimeter (cm)
Pascal (pa)
Kilogram (kg)
Metric ton (kkg)
-------
ACKNOWLEDGMENT
This report was prepared for the Industrial Environ-
mental Research Laboratory, U. S. Environmental Protection
Agency, Research Triangle Park, North Carolina, by PEDCo
Environmental, Inc., of Cincinnati, Ohio; Cottrell Environ-
mental Sciences, Research-Cottrell, Inc., Bound Brook, New
Jersey; and Midwest Research Institute, Kansas City, Missouri.
The project director was Mr. Richard W. Gerstle and the
project manager was Mr. Michael F. Szabo.
PEDCo Environ-
mental, Inc., as the primary contractor and editor, directed
and coordinated the entire project effort, as well as pro-
vided and integrated into the report, information additional
to that provided by the subcontractors.
Cottrell Environmental Sciences researched and coor-
dinated the electrostatic precipitator and wet scrubber
information.
The scope of work was managed and executed by
Mr. David V. Bubenick with the help of Mr. Chin T. Sui and
Dr. P. D. Paranjpe.
The CES effort was directed by Drs.
Paul L. Feldman and Richard S. Atkins.
xiv
-------
Midwest Research Institute performed the evaluation in
fabric filtration systems.
Messrs. Mark Golembiewski, V.
Ramana, and Stan Riegel were the principal investigators.
The MRI effort was directed by Dr. Krishnan P. Ananth.
xv
-------
1. 0 INTRODUCTION
1.1
PURPOSE OF REPORT
This report is intended to provide guidelines by which
environmental control personnel and the iron and steel and
ferroalloy industries can (1) determine which type of par-
ticulate control device is best for a certain process,
( 2 )
follow operational and maintenance practices that will
maintain high particulate collection efficiencies and
minimize malfunctions, and (3) relate the total mass effi-
ciencies of control devices to their efficiencies for col-
lection of particulate in specific size fractions.
1.2
SIGNIFICANCE OF PARTICULATE EMISSIONS
Many undesirable effects have been related to the dis-
charge of particulate matter into the atmosphere. Particu-
lates constitute a health hazard, cause poor visibility,
function as a transport vehicle for gaseous pollutants, and
(in many cases) are highly active both chemically and
catalytically.l
The full effects of submicron particulates on health
are not yet well defined.
They are regarded as constituting
a whole category of pollutants rather than being a single
1-1
-------
pollutant.
Once dispersed, they behave (depending on size)
similarly to coarse particles and gases.
They remain sus-
pended and diffused, are subject to Brownian motion, follow
fluid flow around obstacles, and can penetrate deep into the
respiratory system.
Particles larger than 5 ~m diameter are deposited in
the nasal cavity or nasopharynx.
Increasing numbers of
smaller particles, so minute that they are difficult to
measure, reach the lungs.
More than 50 percent of particles
between 0.01 and 0.1 ~m that penetrate the pulmonary com-
partment are deposited in the lungs.
This tendency to
penetrate and be captured in the respiratory system is more
a function of the geometry of the particles than of their
chemical properties.
The unhealthy effects of these captured fine particu-
lates are largely due to their chemical or toxic qualities,
although long, fibrous materials exist whose physical qual-
ities may also irritate tissue.
Many unknown factors re-
maln,
however,
so it is unwise to generalize concerning the
danger of fine particulates.
1.3
SCOPE OF THE REPORT
This study covers sintering, scarfing, electric arc (EAF) ,
open hearth (OHF) and basic oxygen furnace (BOF) processes
in the steel industry; and electric arc furnaces in the
ferroalloy industry.
1-2
-------
It also deals with the following high-efficiency par-
ticulate control devices:
dry and wet electrostatic pre-
cipitators, wet scrubbers, and fabric filters (baghouses).
Section 2.0 first provides process descriptions and
emission characteristics of these processes and the types of
conventional control devices used to collect their particu-
late emissions.
It then discusses control system design parameters, in
addition to design philosophy.
The major contribution for
precipitators and scrubbers in this section, as well as
sections 3.0 and 4.0, came from Research-Cottrell supple-
mented by PEDCo expertise.
Some information was obtained
from other equipment manufacturers and from the open liter-
ature.
Both cold-side and wet-type precipitators and
venturi-type wet scrubbers are included.
Fabric filter design parameters are based on the lit-
erature, site visits, personal communications, and a survey
of users by both Midwest Research Institute and PEDCo.
Section 3.0 describes maintenance and operational
procedures that contribute to operation of particulate
collection devices at maximum efficiency.
The discussion
encompasses start-up, shutdown, normal operational proce-
dures and common malfunctions.
1-3
-------
Fractional collection efficiencies of precipitators,
wet scrubbers, and fabric filters are discussed in section
4.0.
Computer models are used to predict the fractional
efficiency performance of dry precipitators and venturi
scrubbers on appropriate iron and steel and ferroalloy
Almost no test data are available for comparison
processes.
with the models.
The fractional efficiency relationships of
fabric filters are discussed only briefly because of the
lack of a computer prediction model.
There are likewise
limited fractional efficiency data for fabric filters.
Section 5.0 presents conclusions on the design, opera-
tion, maintenance, and the fractional efficiency capabil-
ities of particulate control devices used in iron and steel
and ferroalloy processes.
A comparison is made of the
advantages, disadvantages, and installation and operating
costs of each type.
1-4
-------
REFERENCES - SECTION 1.0
1.
Oglesby, Sabert Jr. Opening Remarks, EPA/Southern
Research Institute Symposium on Electrostatic Pre-
cipitators for the Control of Fine Particles. EPA-
650/2-016, Pensacola Beach, Florida, September 30 -
October 2, 1974.
1-5
-------
2.0
CONTROL SYSTEMS:
PARAMETERS AND CORRELATIONS
2.1
EMISSION SOURCES, CHARACTERISTICS, AND CONTROL SYSTEMS
USED
Following is a brief discussion of the processes
covered in this report, their particulate emission char-
acteristics, quantities of emissions produced, and the types
of conventional control devices used for each process.
2.1.1
Process Descriptions in the Iron and Steel Industry
A flow diagram depicting various processes in a typical
integrated iron and steel plant is shown in Figure 2-1.
The processes discussed in this report, however, are limited
to sintering and scarfing, as well as open hearth, basic
oxygen furnace, and electric furnace steelmaking.l
2.1.1.1
Sintering - Sintering is used to convert iron ore
fines and blast furnace flue dust into a product more
acceptable for charging the blast furnace.2 Materials such
as blast furnace flue dust, ore fines, and mill scale are
mixed with flux (limestone) and coke breeze and fed to a
traveling grate sintering machine.
The mixture is heated to
a fusion temperature, which causes agglomeration of the
iron-bearing particles.
Combustion is initiated on the
surface of the mixture in the ignition furnace, which is
2-1
-------
FLUE DUST FROM
COKE BREEZE BLAST FURNACEMffi
. OI\E
RR CA MILL SCALE REEL
LUMP ORE
ORE FINES
ORE
FI~t:S
~~. ~~~
BALLING DRUM
DRYING AND ~GRATE FEEDER
HARDENING
SINTER
PELLETS
PELL ETI ZI NG
(AT MINE SITE)
SOAKING PITS
t'0
I
t'0
BLAST
FURNACE
ELECTRIC
ARC
FURNACE
OPEN HEARTH
FURNACE
w
W~
NO
wU
W
cx:CI
caW
:J:
W(./)
~ ......
OZ:
U ......
LL.
STEEL FURNACE
~~ ~C~~
FURTHER
PROCESSING
QUENCHING
TOWER
COKING
Figure 2-1.
A composite flow diagram for a steel plant.
-------
either gas- or oil-fired.
Once the coke breeze is ignited,
combustion is maintained by a downdraft of air through the
flat, porous bed of mixture.
To provide for a reasonably
uniform distribution of combustion air, the section under
3
the bed is separated into compartments known as wind boxes.
Modern sintering plants have capacities ranging from 2000
to more than 6000 tons/day with exhaust fans drawing air
through the bed of the largest strands at a rate of more
than 500,000 acfm measured at a temperature of 350op.2
At the discharge end of the sintering machine, the
incandescent sintered material is dumped from the grate into
a crushing and screening section where large pieces are
broken up.
Directly below the breaker are screens to remove
fines for recycling to the sinter plant.
The crushed pieces
are conveyed to the sinter cooler.
In some of the newer
plants, discharged material may first enter the sinter
cooler and then be conveyed to a different location for
crushing and screening.
Sintering machines process a wide variety of feed
materials and produce a considerable amount of emissions.
The quantity and nature of the emissions vary from plant to
plant.
Small amounts of dust are created in the handling and
grinding of raw materials.
Emissions also include dust
2-3
-------
which has been sucked through the grate bars into the wind
box, combustion gases from ignition and firing, and dust
generated in the screening and cooling operations.
2.1.1.2
Open Hearth Furnace (OHF) Steelmaking - At one time
about 90 percent of the steel made in the United States came
from open hearth furnaces.
Recently, increased use of the
basic oxygen furnace and electric furnace has reduced open
d . 4
hearth pro uctlon.
In the open hearth process, steel is usually made from
a mixture of scrap and hot metal in varying proportions.
Impurities such as carbon, manganese, silicon, sulfur, and
phosphorus are reduced to specified levels by oxidation.
The refining operation is carried out by means of a slag
that forms a continuous layer on the surface of the liquid
metal.
This slag is composed essentially of lime combined
with the oxides of silicon, phosphorus, manganese, and iron,
all of which are formed or added during the operation.2
The furnace consists of a shallow, rectangular basin
enclosed by walls and a roof of refractory brick.4
Heat is
supplied from burners at one end.
The fuel used includes
coke oven or natural gas, oil, tar, or pitch.
The flame
from combustion of the fuel travels the length of the fur-
nace above the charge which rests on the hearth.
On leaving
the furnace, the hot gases are conducted in a flue down to
2-4
-------
regenerative chambers commonly called "checkers" or "check-
erwork."
This mass of refractory brick is systematically
laid to provide a large number of passageways for the hot
gases. It absorbs heat and reduces gas temperature from
approximately 3000°F to between 1200 and 1500°F.2,3 All
the elements of the combustionsystem (burners, checkerwork,
and flues) are duplicated at each end of the furnace.
After
a timed interval, the flow of flame and flue gases is re-
versed so that the heat stored in the checkers is given up
to a reverse-direction stream of air flowing to the burners.2
From the checkers, the gases are normally directed to a
waste heat boiler, where the temperature is further lowered
2
to an average of 500 to 600°F.
Open hearth furnace capac-
ities vary from as little as 30 tons to as much as 500
tons/heat (i.e., batch of finished steel).3
The median is
between 100 and 200 tons/heat.
The time required to produce
a heat is commonly between 8 and 12 h when normal amounts of
oxygen are used.2
In recent years with the practice of uSlng high oxygen
flow rates (oxygen lances) from hot metal addition to tap,
production rates of 90 to 100 tons/h are conceivable in a
300-ton furnace.
Oxygen consumption under these conditions
ranges from 600 to 1000 cu ft/ton (900 to 1667 scfm during
the period in which oxygen is added).2
2-5
-------
2.1.1.3
Basic Oxygen Furnace (BOF) Steelmaking - The basic
oxygen furnace is a relatively new development in the steel
industry.
The first of its kind in the United States was
installed in 1955.3
The furnace is a pear-shaped structure
with a refractory lining.
A water-cooled lance is used to
supply pure oxygen (typical ratio of 2000 ft3/ton steel
produced) to a mixture of steel scrap, hot metal, and flux
materials.
Furnace capacities range from 75 to 325 tons/heat
and the time required per cycle is very short.
A typical
. 4
150-ton BOF operation has the following heat tlme:
Charge scrap
Charge hot metal
Oxygen blow
Chemical tests
Tapping time
1 min
2 min
20 min*
5 min
5 min
Total time
33 min
The BOF process differs from open hearth practice in
that external heat need not be supplied to facilitate the
refining of the iron.
The sources of heat are (1) sensible
heat from the hot metal, and (2) heat released by the
exothermic reactions between oxygen and metalloids in the
charge (primarily silicon and carbon).4 The BOF has dis-
placed the open hearth as the major steel production proc-
ess, but is much less flexible because of the limited
amount of scrap (25 to 30 percent) that can be used in the
* Reblow and second analysis is also common because of
missed specifications.
2-6
-------
charge.
Its capacity in an integrated steel plant, there-
fore, is closely associated with the availability of hot
metals.
2.1.1.4
Electric Arc Furnace (EAF) Steelmaking - In the
electric furnace process, steel scrap and flux materials are
charged into a cylindrical vessel with a refractory lining
and three large carbon electrodes protrude through the
furnace roof.
Heat required for the metallurgical reaction
is generated by the arc from the three electrodes using
2
currents ranging from 10,000 to 20,000 amps.
Furnace
capacities vary widely, but generally range from 50 to 200
tons/heat.
Heat times vary up to approximately 4 h.
The electric furnace process cycle closely approximates
that of the open hearth, except for the fact that a shorter
overall time is needed.
The cycle consists of charging,
meltdown, the molten metal period, boil, the reducing or
2
refining period, and the pour (tap).
A series of charges
is required in this process owing to the low bulk density of
. d 3,4
scrap. As a rule, no hot metal 1S use. An exception is
Armco Steel in Houston, Texas.
Because of the limits the BOF process puts on the use
of scrap, the electric furnace has gained increasing im-
portance.
It permits a high degree of operational control
and is generally preferred for the manufacture of alloy and
2-7
-------
stainless steels.4
Variations of electric furnace opera-
tions include use of oxygen lancing, oxygen fuel gas
burners and preheated scrap.
The use of oxygen fuel during
the meltdown period has been reported to increase production
from 15 to 20 percent and to decrease power consumption by
2
15 to 20 percent.
Scarfing - Scarfing is a conditioning process for
2.1.1.5
removing surface defects from blooms, billets, and slabs
prior to their being rolled into semifinished steel prod-
ucts.
The operation is usually done after the slab, bloom,
or billet has been heated to the rolling temperature, but it
5
may also be performed on cold steel. The process consists
essentially of burning the surface of the steel with a jet
of oxygen in combination with a fuel gas, such as acetylene
or natural gas.
The purpose of the fuel gas is to ensure
that the steel is heated to a sufficiently high surface
temperature (about 1600°F) to bring about rapid oxidation
and localized melting of a thin layer of metal.2,5 Orig-
inally the process was a manual one.
In recent years the so
called hot scarfing machine has come into wide use.
Approxi-
mately 1/8 in. of metal is removed from all four sides of
the red-hot billets, blooms, or slabs as they travel through
the machine in a manner similar to the journey through
rolling mills.2
2-8
-------
2.1.2
Emission Characteristics - Iron and Steel
Emission characteristics for the various sources
discussed in this section are summarized in Table 2-1.
Estimations of volume flow rate, emission rates, and par-
ticle size distribution vary for the same process depending
upon the source.
Particle size distributions from most
literature sources do not list the percentage of particles
in the smaller size ranges « 2 ~m).
Therefore, when esti-
mating particle concentrations as a function of particle
size and predicting fractional efficiencies later in the
6
report, estimates by Weast et al. are used.
Discussions on
emissions (uncontrolled) from each process follow.
2.1.2.1
Sintering - The concentration of particulates in
the wind box under the grate during ignition appears to be
4
about 0.5 to 3 gr/scf. This effluent has a temperature of
about 160 to 390°F.2 Based on an average volumetric flow
rate of 60 scfm/tons/day capacity3 and plant capacities of
2
2000 to 6000 tons/day, an exhaust gas would have flow rates
of 120,000 to 360,000 scfm.
A typical particle size dis-
tribution in the windbox gases (given in Reference 7) is as
follows:
15 to 45%
9 to 30%
4 to 19%
1 to 10%
< 40 ~m
< 20 ~m
< 10 ~m
< 5 ~m
2-9
-------
Table
2-1.
SUMMARY OF
EMISSION CHARACTERISTICS
FROM
VARIOUS
LITERATURE
SOURCES
N
I
I-'
a
Uncontrolled Particle Size Distribution
Emission Gas temperature, Volume flow rate, particulate emission -~~
source OF scfm 'Jr/scf General Specific f
Slntering
Combustion waste 160-3902 120,OOO-360,OOOa 0.5-3.04 15-45% < 40 7 - 70, = 6.67 w/o
~m x = a
gas (wlnd box) 9-30% < 20 ~m mechanical collector
4-19% < 10 ~m x = 7.7, a = 3.50 w
1-10% < 5 ~m mechanical collector
Discharge end 170b 100,000-300,000c 3-83 50% >100 7
~m
40% 10-100 ~m -
10% < 10 ~m
Scarfing 100b 20,000-150,0007 0.4-0.87 no data available
hearth furnace 500d_15002,3 25,000-200,0007 0.4-0.62 69-92% < 10 7
Open ~m -
45-75% < 5 ~m x = 0.21, a = 2.86
20-45% < 2 ~m
BaS1C oxygen furnace
560d_30007 35,000-250,0007 2-107 85-95% < 1 7 - = 0.27, = 1. 82
Waste gas ~m x a
metal reladling 220 2609 100,0003 0.4-0.53 67% < 149 9 -
Hot - ~m
46% < 74 ~m
16% < 10 ~m
3% < 1 ~m
Ferroalloy furnace 100,000-400,00017 0.2-2.77 - = 0.19, = 3.00
215-3000 x a
(open) (openi (ferrosilicon alloys)
1000-700017 5-30 5 x = 0.78, a = 2.12
(semi-enclosed (closed) lferromanganese alloys)
and sealed) x = 0.86, a = 4.19
lferrochromium alloys)
x = 0.50, a = 3.36
(miscellaneous alloys)
Steel electric furnace e 215-30007 10,000-100,0007 0.1-107 60% ' 5 7 x = 0.80, = 9.30
~m c
I
a Based on an average flow rate of 60 scfm/ton/day capacity and plant capacities of 2000-6000 tonS/day.3
b Estimated by EPA personnel.8
c Based on a flow rate of 50 scfm/ton/day capacity and plant capacities of 2000-6000 tons/day.3
d With waste heat boiler.
e Both oxygen lanced and nonoxygen lanced operations are included in the reported values.
f From Weast et al. 23
-------
The chemical composition of a wind box dust is shown in
Table 2-2.
Table 2-2.
CHEMICAL COMPOSITION OF SINTER STRAND
WIND BOX DUST10
Compound Wt %
Fe203 45-50
Si02 3-15
CaO 7-25
MgO 1-10
A1203 2-8
C 0.5-5
S 0-2.5
Alkali 0-2
A second and the major emission point from the sinter-
ing process is the discharge end of the sintering machine.
A gas flow rate of 50 scfm/tons/day capacity is usually
required for ventilation, although one plant reportedly has
gas cleaning equipment with a rate of 100 scfm/tons/day of
't 3
sinter capacl y. Dust concentrations as high as 4 to 6
gr/scf have been measured in Britain, and one u.S. plant
, 3
reports 3 to 8 gr/scf in 100,000 scfm of ventilation alr.
Particle size data from Reference 7 are as follows:
2-11
-------
50%
40%
10%
> 100 ~m
10-100 ~m
< 10 ~m
Other major pollutants from sintering plants are SOx
and CO.
Gaseous and particulate fluorides are also emitted
from a few western sintering plants processing ore with a
2
high fluoride content.
2.1.2.2
Open Hearth Furnace
(OHF) -
Particulate emissions,
gas volumes, and gas compositions of open hearth furnaces
vary rather widely over a single heat.3 Factors which
affect emission rate include quantity and cleanliness of the
scrap iron charged.
Oxygen lancing generates considerably
more particulate matter.
The average emission rate appears
to be about 0.4 gr/scf for the conventional furnace and 0.6
2
gr for the oxygen-lanced furnace.
Usually up to 90 percent of particulates from open
hearth furnaces are iron oxides, predominantly Fe203"
During the lime boil period (approximately 38% of total
heat), however, the percentage of iron oxide may be less.
When large amounts of scrap are used in the charge,
zlnc
2
oxides may predominate during part of the heat.
Particle
size distribution varies considerably during the heat.
Over
the entire heat of a furnace that is not oxygen-lanced,
about 50 percent are less than 5 ~m.
For an oxygen-lanced
furnace, Reference 7 lists the following size distributions:
2-12
-------
During lime boil
Composite
92% < 10 l.lm
75% < S l.lm
45% < 2 l.lm
69% <10 l.lm
45% < 5 l.lm
20% < 2 l.lm
Weast et al.6 indicate a much smaller particle size dis-
tribution than the above data (see Table 2-1).
Other pollutants in the flue gas contain SO , NO , and
x x
fluorides.
ligible.3
Emissions of CO, however, are considered neg-
2.1.2.3 Basic Oxygen Furnace (BOF) - Particulate emissions
7
from BOF range from 2 to 10 gr/scf. The effluent gas may
have a temperature of 560 to 3000°F depending on utilization
of a waste heat boiler and a flow rate of 35,000 to 250,000
7
scfm. About 85 to 95 percent of these particulates are
h 1 . . 7
less t an l.lm ln Slze.
Waste gases from the BOF contain large amounts of CO,
which are normally burned in the hood.
According to Refer-
ence 3, there is one installation in the United States where
the gases are cleaned prior to combustion of the CO.
Transfer of hot metal to the BOF creates additional
particulate emission problems.
During the transfer, known
as reladling, significant quantities of kish (precipitated
graphite flakes) and iron oxide particulates are generated.
Dust loadings of 0.4 to 0.5 gr/scf in an air volume of
3
100,000 scfm are reported.
The gas stream temperature is
2-13
-------
reported to range from 220 to 260°F.9
The following par-
ticle size distribution is reported in reference 9:
33% <
54% <
84% <
97% <
149 ~m
74 ~m
1 0 ~m
1 ~m
2.1.2.4
Electric Arc Furnace (EAF) - During the melt cycle,
both particulate matter and carbon monoxide are produced.
The rate of particulate emissions varies considerably in a
given cycle.
Information from six steel plants indicates a
range of uncontrolled emissions of 23 to 58 Ib/ton of carbon
3
steel produced.
Most emissions occur during the early "melting" por-
tion, although significant quantities are also emitted
during charging, back charging, tapping, and oxygen-blowing
operations.
Information supplied by steel manufacturers on
the quantity of particulate matter collected by control
devices suggests that 30 Ib of dust are emitted per ton of
steel when melting carbon steel and 15 Ib of dust per ton
for alloy steel.
Particulate emissions may also vary from cycle to cycle
because of several factors:
1.
Contamination of the scrap steel with dust, oil,
or volatile metals will increase emissions during
charging.
2.
An increase in electrical power to a furnace will
increase emissions during the scrap melting.
2-14
-------
3 .
An increase in the quantity of oxygen blown will
increase emissions during the blow.
Carbon monoxide is generated by reaction of the carbon
electrodes (or carbon in the steel) with oxygen.
Much of
the carbon monoxide is oxidized to carbon dioxide as it
leaves the furnace in the fume exhaust system.
These carbon
monoxide emissions can be as high as 6 lb/ton of steel
3
produced, although they vary considerably during a furnace
cycle.
Peaks are observed during scrap melting when maximum
electrical power is on and also during oxygen blows.
Tables 2-3 and 2-4 give the particle size distribution
and composition of electric arc furnace fumes, as reported
in Reference 11.
Reference 7 gives a particle size distri-
bution of 60 percent < 5 ~m for electric arc furnaces.
6
particle size distributions presented by Weast et al.
The
indicate a much higher incidence of fine particles than do
references 7 or 11.
The gas volume required for proper ventilation of
electric arc furnaces depends on:
1.
Melting rate and electrical energy input per ton
of metal charged.
2.
Oxygen lance rate.
3 .
Scrap charge composition (especially oil content) .
4.
Type of hooding employed (discussed later).
2-15
-------
Table 2-3.
ELECTRIC ARC FURNACE FUME
PARTICLE SIZE DISTRIBUTION11
Particle size
( ]Jm)
Wt % in size range
0-2
2-4
4-8
8-12
12-44
>44
10
17
34
9
15
15
Total
100
Table 2- 4 .
TYPICAL CHEMICAL ANALYSIS OF
ELECTRIC ARC FURNACE FUME11
Compound Wt %
Total iron 32.2
Loss on ignition 10.1
CaO 18.6
Si02 10.8
Total carbon 8.3
MgO 7.1
A1203 5.7
cr203 1.3
MnO 1.2
ZnO 1.03
V205
-------
2.1.2.5
Scarfing - Information on pollutants generated in
the scarfing process is very meager.
Reference 7 gives a
range of particulate grain loadings from 0.4 to 0.8 gr/scf.
Gas volumes are reported to range from 20,000 to 150,000
scfm.7
2.1.3
Control Methods - Iron and Steel
Particulate control equipment used in the various
processes is discussed in the following section.
The infor-
mation presented here is primarily from Reference 3.
2.1.3.1
Sintering - Dry and wet electrostatic precipita-
tors, scrubbers, and cyclones are the principal means for
controlling emissions from the wind boxes of sinter ma-
chines.
However, due to large variations in the materials
being processed, no single control device can be generally
applied. 3
One problem, as far as electrostatic precipita-
tors are concerned, is that their performance is affected by
oil in the recycled fines and by increased limestone addi-
3 12
tions in the charge. '
Various types of pilot-scale scrubbers have been tested
by Kaiser Steel Company at Fontana, California.
They typi-
cally showed erratic efficiencies, sludge buildup, scaling,
. 13
and high energy requlrements. One steel company report-
edly tested a pilot-scale scrubber and found a problem with
unburned carbon.3
2-17
-------
Armco Steel Company pilot-tested both high energy
venturi scrubbers and the Lone Star Steel Steam Hydro
.' 14
Scrubber on their Houston Sinter Plant wind box emlSSlons.
Both were found to satisfactorily remove particulate and,
to a lesser extent, hydrocarbons, although the steam hydro
gave more efficient removal of hydrocarbons.
Thus, because
the hydrocarbons were a primary contributing factor to stack
opacity, the high hydrocarbon efficiency gave an edge to the
steam hydro system, which also had a slight economic advan-
tage, but only due to the availability of steam generating
capacity and low cost fuel to generate the steam.
The steam
hydro was installed in 1975 as six parallel units, five
operating, and one spare.
The greatest problems have been
with corrosion of carbon steel components of the water
treatment system because of poor pH control.
Bethlehem Steel Corporation has tested a full scale wet
ESP demonstration system for wind box emission control at
15
their Lackawanna, New York, plant.
They found that the
wet ESP operated satisfactorily during the 3-month test
period, with outlet loading lower than applicable regula-
tions.
However opacity was not reduced sufficiently to meet
visible emission regulations.
3
Kaiser Steel Company uses a baghouse for particulate
control of wind box gases.
The company decided that this
2-18
-------
method suited them best following 11 years of pilot plant
studies.
The Weirton Steel Company pilot-tested a baghouse,
but found that oil fumes were not condensed at the operating
temperature of the baghouse and left a visible plume.
h . 3
also found that the dust was pyrop orlC. Inland Steel
They
installed a baghouse on the wind box of their sinter machine
down-stream of a cyclone and precipitator in October 1975.
They have had numerous operating problems, the main one
being bag replacement.
Problems with bag cleaning systems
and anti-collapse rings have been partially responsible for
the high number of bag replacements.
Republic Steel at Gadsden, Alabama, is operating pulse-
jet baghouses on both wind box and discharge ends.
There
were initial problems with high pressure drop through the
wind box bags which now seem to be solved.
Wind box AIC
Ratio is 6:1 with dacron felt bags.
Discharge end AIC ratio
is 7.4:1 with Nomex felt bags.
Both baghouses and medium energy wet scrubbers have
been used on the discharge end of sinter plants.
It appears
that either technique reduces plume appearance to invisi-
bility, or nearly so.
The major equipment problems appear
to be abrasion and, in the case of wet systems, a buildup of
lime scale.3
Because the gas temperatures involved a range from 300
to 400°F, the actual bags used in all these cases were made
2-19
-------
of glass fabric.
It is also reported that the large size of
baghouses discourages their use in many plants.
A list of
u.s. integrated iron and steel plants and the type of equip-
ment used to control emissions from the wind box and from
the discharge end of the sinter plant is shown in Appendix
A-l.
2.1.3.2
Open Hearth Furnace - The majority of open hearth
furnaces are equipped with electrostatic precipitators.
Wet
scrubbers have been used in some cases, when the shop
either had no waste heat boilers or when existing boilers
could not lower gas temperatures enough to warrant instal-
4
lation of electrostatic precipitators or baghouses.
Two cases have been reported in the United States where
baghouses have been used for open hearth furnace gas clean-
. 3
lng.
The Bethlehem Steel Corporation's Sparrows Point
plant operated a baghouse on a single open hearth furnace
for about 2 years.
The baghouse was selected for this
unique application because it was considered best able to
handle fluctuations in gas volume, gas composition, and dust
concentration from a single furnace.
This particular
furnace was shut down when a basic oxygen furnace shop was
built.
Performance of the baghouse from the standpoint of
gas cleaning was reportedly excellent.
Outlet dust con-
centration was 0.007 gr/scf, but the stack was never clear
2-20
-------
because of leakage at a damper valve. The cost of this
installation was over three-quarters of a million dollars.3
The only other application of a baghouse to an open
hearth furnace is by the Ohio Steel Foundry, which uses
small (30 to 40 tons) open hearth furnaces at its plant.
These baghouses have been operating, apparently satisfac-
3
torily, for 3 to 4 years.
A list of U.S. open hearth installations and the asso-
ciated particulate control device is presented in Appendix
A-2.
2.1.3.3
Basic Oxygen Furnace - The two gas cleaning systems
applied to BOF's in the united States are high energy
venturi scrubbers and electrostatic precipitators.
They are
used in approximately equal numbers.
There is one reference
to the application of a baghouse to a BOF in Europe, but it
does not seem to be an attractive system.3 However, in the
United States, Crucible Steel at Midland, Pennsylvania,
is retrofitting a fabric filter to their BOF shop.
Two different hood systems are used to capture emis-
sions from BOF's.
One system uses an open (or combustion)
hood, which has a 1.5 to 2 ft clearance above the furnace
rlm.
The other system uses a retractable closed hood, which
fits rather closely around the top of the furnace and mini-
14
mizes air from being drawn into the exhaust system.
2-21
-------
The closed hood was designed to minimize exhaust
volume and to reclaim carbon monoxide.
In many countries
this carbon monoxide is collected for use as a fuel or as a
feed gas for petrochemical processing operations.
In the
two u.s. plants using closed hoods, however, exhaust gases
are currently flared and there is no heat recovery.
The
volumetric flow rate through the closed hood system is
generally less than 20 percent of the flow rate in an open
hood system.
However,
the high concentrations of combus-
tible carbon monoxide limit the choice of cleaning equipment
16
to a single type, the high energy venturi scrubber.
The particulate emissions from hot metal reladling are
a mixture of kish and submicron iron oxide fume.
Cyclones
and baghouses are the only control equipment installations
3
to be applied on a large scale.
Appendix A-3 provides a list of U.S. BOF installations
and their associated particulate control devices.
2.1.3.4
Electric Arc Furnace - Fabric filters (baghouses)
are the most commonly used devices for cleaning electric
furnace gases, although venturi scrubbers and electrostatic
. 11 . 17
precipitators are also occas~ona y ~nstalled.
When the
fume-capturing systems involve large volumes of ventilation
air, however, operating costs generally limit the control
device to fabric filters.17
2-22
-------
The capture systems normally used are:
(1) direct
shell evacuation in combination with natural ventilation
through the open roof,
(2) building evacuation in a shop
with a sealed roof,
(3) canopy hoods in a shop with a sealed
roof,
(4) canopy hoods in combination with natural venti la-
tion through the open roof, and (5) combinations of direct
shell evacuation with systems (2),
17
( 3), or ( 4) .
The direct shell evacuation system, which withdraws
emissions directly from within the furnace before they
escape and are diluted by ventilation air, has the lowest
gas volume.
When a fabric filter is used, however, the hot
furnace gas must first be cooled by water sprays, radiant
coolers, dilution air, or some combination of these to pre-
vent degradation of the fabric.17
A listing of electric arc furnaces in the United States
and associated control devices where known, are presented in
Appendix A-4.
2.1.3.5
Scarfing - Scrubbers, cyclones, baghouses, water
flumes with water sprays, and wet and dry ESP's are used to
control emissions from scarfing installations in the United
States.
Wet ESP's have been used more than dry ESP's.
Bethlehem Steel recently pilot-tested two wet ESP's at its
Lackawanna, New York, 44-inch rolling mill with excellent
15
results (outlet dry particulate loadings of less than 0.01
2-23
-------
gr/scfd for all but one test).
The only application of a
fabric filter to control particulate emissions from scarfing
operations in the integrated iron and steel industry is at
Bethlehem Steel Corporation's Los Angeles plant.
Scarfing
emissions in this case are exhausted to a baghouse, which is
1 d 1.. f h electr1.'c furnace.5,18
a so use to contro em1.SS1.ons rom t e
2.1.4
Process Description - Ferroalloy Furnaces
A ferroalloy is an alloy of iron with one or more other
metallic elements used for deoxidizing molten steels and
making alloy steels.
Ferroalloys are produced predominantly
in electric arc furnaces, so only this type of furnace will
be discussed.19
Emissions from such furnaces and the
control devices used will also be described.
A typical flow diagram of ferroalloy production is
h . . 2 2 19
sown l.n F1.gure -. The furnace itself consists of a
hearth lined with a high temperature refractory which has
holes to permit tapping of metal and slag.
The furnace
shell and its hood or cover components are made of steel and
are water-cooled.
Above the hearth are three electrodes
which extend 3 to 5 ft into the charge materials.
The
charge (i.e., raw ore, coke, and limestone or dolomite)
melts as the electrical energy is converted to heat.
Chem-
ical reactions between the coke and oxygen in the metal
oxides form carbon monoxide and reduce the ores to base
19
metal.
2-24
-------
N
I
N
U1
JI;bt --
" ~ UNLOADING
~ ASSORTMENT
FUMES
Figure 2-2.
Ferroalloy production process.
-------
The furnace design may be open, semienclosed, or sealed.
Diagrams of the three types of furnace are shown in Figures
2-3 through 2-5.19
Both the semienclosed and sealed fur-
naces are less flexible than the open furnace.
A specific
sealed furnace can be used to produce only one family of
ferroalloys.
It cannot be adapted to the production of
others without changing the electrode spacing (which is
determined by the product family) .
In addition, the furnace
cover must also be replaced.
Thus, modification of sealed
furnaces to produce other products is prohibitively expen-
sive.
Product flexibility is possible at minimum cost with
those open furnaces which have multiple transformer taps and
adjustable electrodes.19
2.1.5
Emission Characteristics - Ferroalloy Furnaces
The major pollutants from electric furnaces are par-
ticulates and carbon monoxide.
Carbon monoxide is formed as
a by-product of the electric arc furnace reduction process.
Depending on the type of furnace, this gas is either burned
at the surface of the charge material or cleaned by an
emission control system. After cleaning, it may be flared
19
or used for fuel for other chemical processes.
"th 19
Particulate emissions from the furnace vary Wl :
o
The type of alloy produced;
o
Choice and size of raw materials;
2-26
-------
TAP
HOLE
TO CONTROL
--- OEV I CE
HOOD
.' ~. .... . ...
'.:' OUST':'
:. ~ :~... .
.,...
-:;-~- ~ ~,
,.. ~ '""'"
~ - ".-.--""'\
~,......., "'"" L...-',....., "'"' ---.
:~.: . : ~.::.:...: :".,~ :.~:::': 0:: .: ":': '::': ";':':, :':.: : ~ ".:. ';"':. .:.: .~'.:: "
Figure 2-3.
Open furnace.
ELECTI(DOES
MIX FEED
(TYPICAL)
?~.; (~: :::.~':::: :~.~:~ :~:f;;~::!: )~:~:~'.:)/\~ ~?{:.::\.:'.:::'.:'~;. :<:;~: :'",:'~:~~:: :'.~:.~ ,::,'.j!;
Figure 2-5.
Sealed furnace.
2-27
EXHAUST TO t
ATMOSPHERE
MIX CHUTE
(TYPICAL)
,
ELECTRODES
HOOD
"
AIR
I'. t
: OUST:
i:~::"':,
,
INDUCED AIR
::. ~.:...:-: ':' .::.:.::..-:.::..:.......:::::..:~:..-.::;:.::..::..:<::....
Figure 2-4.
Semienclosed furnace.
-------
o
Choice of size of raw materials;
o
Operating techniques; and
o
Existence of a furnace shutdown or start-up
condition.
Uncontrolled grain loadings range from 0.2 to 2.7 gr/scf for
ferrosilicon production in open furnaces.7 Semienclosed and
sealed furnaces have lower flow rates and thus would have
higher particulate concentrations (5-30 gr/scf for closed
furnace).17 Table 2-5 lists properties of particulate
emissions from ferroalloy furnaces, as reported in Reference
18.
Gas volumes from open furnaces range from 100,000 to
19
400,000 scfm.
Based on EPA test data, semienclosed and
sealed furnaces have volumetric flow rates of about 1000 to
7000 scfm.19
Carbon monoxide is the major by-product of ferroalloy
production. In fact, the weight of CO emitted from the melt
can exceed that of alloy produced.17 Other components of
the gaseous discharge include hydrogen and volatile hydro-
carbon.
The latter comes from the electrodes and from oil
on the surface of the steel shavings.
Operation of ferroalloy furnaces produces particulate
emissions at three principal points:
1.
The top of the furnace, transported reaction
gases.
2-28
-------
Table 2- 5 .
a
PROPERTIES OF PARTICULATE EMISSIONS FROM FERROALLOY FURNACES
N
I
N
I.D
Parameter Alloy 50% Fe Si SI Mn Fe Mn H.C. Fe Cr
type
Furnace hood type Open Covered Open Covered
Particle size, ]Jm
Maximum 0.75 0.75 0.75 1.0
Range of most particles 0.05-0.3 0.2-0.4 0.05-0.4 0.1-0.4
Chemical analysis, wt qb
0
Sio2 68-88 15.63 25.48 20.96
FeO 6.75 5.96 10.92
MgO 1.12 1. 03 15.41
CaO 2.24
MnO 31. 35 33.60 2.84
A1203 5.55 7.12
Cr203 29.27
Loss on ignition 23.25 8.38
a"Air Pollution Control Technology and Costs: Seven Selected Emission
Sources". Prepared by Industrial Gas Cleaning Institute; EPA-450j3-74-060.
bStandard metal oxides analysis-compounds not necessarily found in the chemical
forms listed.
-------
2 .
The furnace tap holes. Since most furnaces are
tapped cyclically rather than continuously, the
source is active only about 15 percent of the
time.
3 .
The ladle after tapping, which is also a non-
continuous source of particulates.
The mass median diameter of emissions from open fur-
naces producing ferrochrome silicon, silicomanganese, and
high carbon ferrochrome has been measured by EPA to be
This range is in good agreement
6
with the data presented by Weast et al., except for the
between 0.66 and 1.7 vm.
ferrosilicon alloy, which Weast reports as being lower than
0.66 vm, mass median diameter.
Particles of this size are difficult to collect and
usually require high expenditures of energy.
Agglomeration
of the particles, however, can make the effective particle
size to the collector much larger than that indicated in
Table 2-5.
2.1.6
Control Methods - Ferroalloy Furnaces
2.1.6.1
Open Furnace - The open furnace (Figure 2-3) has a
water-cooled canopy hood, normally located 6 to 8 ft above
the furnace crucible rim.
The large opening between the
furnace crucible and hood permits large quantities of am-
bient air to be drawn into the air pollution control system,
diluting the furnace off-gas by as much as 50 to 1.19
Carbon monoxide generated in the furnace is burned as the
2-30
-------
air combines with the hot gases.
High-energy venturi
scrubbers, electrostatic precipitators and fabric filters
19
have been used on open ferroalloy furnaces.
Because of the relatively low particulate concentra-
tions and a high proportion of submicron particulates,
scrubbers must operate with pressure losses as high as 60 to
80 in. H20 to achieve removal efficiency of 96 to 99 per-
cent.19 The power required to operate high-energy scrubbers
is equivalent to approximately 10 percent of that needed by
the furnace itself.19
Only two modern electrostatic precipitators are operat-
ing on ferroalloy furnaces in the United States.
Both are
installed on open furnaces producing chrome alloys.
Most
fumes from ferroalloy furnaces do not have proper electrical
resistivity for satisfactory precipitator operation, unless
the gases are humidified and conditioned with agents such as
19
ammonia, or their temperatures are maintained above 500°F.
Fabric filters are usually used with open furnaces.
The most common type in the United States is pressurized
(fan on the inlet) and exhausts through an open top or
monitor.
Open grates at the bottom of the baghouse permit
cooling by natural convection.
If the gas must be cooled
before it enters the baghouse, this is achieved with radiant
coolers or by dilution with ambient air.
Cooling with water
2-31
-------
sprays is much less common.
Both felted and woven fabrics
of many different materials have been used.
Cleaning of the
bags may be done by either reverse air or mechanical shak-
lng.
2
Air-to-cloth ratios vary between 1.2 and 2 acfm/ft of
cloth area.
Because the particulate matter has both a high
proportion of submicron particles and a high electrostatic
charge, the pressure drop across a filter fabric is relative-
ly high, 10 to 18 in. H20.l9
2.1.6.2
Semienclosed Furnace - The semienclosed furnace
(Figure 2-4) has a water-cooled cover which seals all but
the annular spaces around the three electrodes through which
raw material is charged.
Since very little air enters the
furnace,
'b 'd 19
the gases it emits are rich ln car on monOXl e.
Wet scrubbers are the most common air pollution control
devices applied to semienclosed ferroalloy furnaces.
Both
multistage centrifugal scrubbers and venturi devices are
used.
Centrifugal scrubbers are generally limited to a
maximum air
flow of about 2800 acfm, sufficient for a
medium-size semienclosed furnace.
For larger furnaces,
parallel centrifugal scrubbers or venturi scrubbers may have
efficiencies of up to 99 percent.
Venturi scrubber effi-
clencles are higher, but so, too, are their power and water
requirements.
Pressure losses of up to 80 in. H20 are
common in venturi scrubbers controlling emissions from
semienclosed furnaces.19
2-32
-------
No electrostatic precipitators or fabric filters have
been installed on semienclosed furnaces.
2.1.6.3
Sealed Furnace - The sealed furnace (Figure 2-5)
operates in a manner similar to that of the semienclosed
furnace, except that packing is used to seal around the
electrodes and charging chutes.
A slightly positive pres-
sure is maintained in the furnace to prevent air leakage
into it.
Gas volumes to the control device are minimal and
can be as little as 2 to 5 percent of those from an open
furnace. 19
The wet scrubber is the most common device used to
control air pollution from sealed furnaces.
Both multistage
centrifugal and venturi scrubbers are used.
Their effi-
ciency and energy requirements for control of sealed fur-
naces are similar to those of semienclosed furnaces.19
Only one sealed ferroalloy furnace is known to use a
fabric filter for air pollution control.
The baghouse is a
closed suction type, cleaned by reverse gas flow. Air-to-
2
cloth ratio is about 1.5 acfm per/ft of cloth area. Gas
from the furnace is treated in radiant coolers before
entering the baghouse. Added efficiency can be obtained by
running water over the coolers.19
No applications are known in which electrostatic
precipitators alone are used with sealed ferroalloy fur-
2-33
-------
naces.
However, systems consisting of two venturi scrubbers
and a wet electrostatic precipitator, all in series, have
been used to control emissions from three sealed ferroalloy
furnaces in Japan.
The venturi scrubbers serve as pre-
cleaners and gas conditioners and operate at relatively low
pressure drops (about 36 in. H20).
The precipitator removes
about 97 percent (according to EPA tests) of the particulate
remaining in the gas stream after it has been through the
scrubbers. 19
A list of U.S. ferroalloy furnaces, some with the
associated particulate control devices, is presented in
Appendix A-6.
2-34
-------
2.2
COMPARISON OF VARIOUS FACTORS WHICH INFLUENCE CONTROL
DEVICE COLLECTION
2.2.1
Selection and Evaluation
A number of factors must be carefully weighed in the
selection of a control device for a specific process and for
a specific plant.
Some of these correlations are given in
Table 2-6.
As to the suitability of any of the various control
devices under consideration, the processes themselves often
dictate which device should be used.
If the basicity of a
sinter plant product is high, for example, increased res is-
tivity occurs because of the presence of lime.
To achieve
high removal efficiencies on high basicity sinter, a much
larger precipitator collection surface is essential.
In
some cases, electrostatic precipitators have been replaced
by wet scrubbers to overcome this problem.
Increasing
efficiency requirements and the move to industrial energy
conservation may also influence the selection of the control
device.
In addition to describing design and operation/main-
tenance characteristics of each control device, it is the
intention of this document to compare the control devices on
the basis of fractional efficiency performance, where
possible.
2-35
-------
Table 2-6.
FACTORS BEARING ON CONTROL DEVICE SELECTION
Characteristics of
particles and gas stream
Facilities, costs, legal
factors
Particle characteristics
Plant facility
Electrical properties
(precipitators only)
Resistivity
Dielectric constant
Waste treatment
Space restriction
Product recovery
Water availability
Particulate concentration
Size distribution
Cost of control
Engineering studies
Hardware
Auxiliary equipment
Land
Structures
Installation
Start-up
Power
Waste disposal or recycle
Water
Materials
Gas conditioning
Labor
Maintenance
Taxes
Interest on borrowed capital
Depreciation
Insurance
Return on investment
Physical properties
Surface properties
Abrasiveness
Porosity
Density
Shape
Hygroscopic nature
Adhesivity
Cohesivity
Chemical properties
Ignition point (precipi-
tators, fabric filters)
Chemical composition
Gas stream characteristics
Flow rate
Temperature
Process
Viscosity
Chemical composition
Acid constituents
Alkaline constituents
Sulfur oxide content
Moisture content
Regulations
Maximum particulate and S02
emission rates allowed by
Federal, state, and local
laws
2-36
-------
2.3
ELECTROSTATIC PRECIPITATORS
2.3.1
General System Characteristics
This section of the report is intended to provide the
reader with insight into the major parameters that must be
carefully weighed in the design of an electrostatic precipi-
tator.
The procedure is straightforward; given certain
input variables (process application, process flow corre-
lations and parameters, and applicable particulate emission
standards) and applying experience and theory,
one can
arrive at a design that meets the criteria for efficiency
and cost.
This format is illustrated in Table 2-7.
Table 2-7.
DESIGN PHILOSOPHY
Basic design Specific design
System input parameters parameters System output
Process appli- Total ACFM Gas and dust Overall and
cation To ta 1 col- characteristics fractional mass
Process condi- lection area Precipitator collection
tions Power capacity efficiency
Applicable density Electrical/ Capital invest-
emission mechanical ment
standard Electrical Annual cost
energization
System perform-
ance
The process applications under consideration are open-
hearth furnace, basic oxygen furnace, electric arc furnace,
sintering and scarfing for the iron and steel industry, and
electric arc furnace for ferroalloy production.
The ferro-
alloys include ferrosilicon, ferromanganese,
ferrochromium,
and miscellaneous ferroalloys.
2-37
-------
Section 2.1 gave some indication of emission charac-
teristics as well as process descriptions.
The incidence of
usage of the devices, based on their technical feasibility
and operating limits,
(Sections 2.1.3 and 2.1.6) is also
known.
As far as possible, those limits will be clarified
in the discussion that follows.
Since these industrial applications are essentially all
retrofit pollution control systems (and therefore quite
site-specific), and given their limited applications in the
iron, steel, and ferroalloy industry compared with their use
in the utility industry, it will be difficult to generalize
about design philosophy-
Furthermore, the variation in
processes and emissions during individual process cycles can
cause wide differences in performance.
2.3.2
Design Philosophy
It is assumed that the reader is familiar with ESP
theory-
However, a brief discussion of operating principles
follows.
Additional background information on precipitator
operation is presented in Appendix C-2.
The theoretical collection efficiency of a precipitator
is often determined using the Deutsch equation:
1 - exp (-w A/Q)20
~ -
.. -
A = total effective collecting electrode area (ft2)
Q = total gas flow rate (acfm)
2-38
-------
w = effective migration velocity
This equation assumes that due to turbulent mixing, particu-
late concentration is uniform at any cross section perpen-
dicular to flow in the precipitator.
The effective migration velocity is the terminal veloc-
ity of a charged particle in the boundary layer near the
collecting electrode and is largely a function of five
variables:
particle size, current density in the inter-
electrode space, applied voltage, gas composition, and gas
temperature.
In order to use the Deutsch-equation, it is helpful to
know empirically the value of w for any specific applica-
tion, and even then problems arise because w is not con-
stant; it has been shown to vary with precipitator length,
efficiency, gas velocity, etc.
Changes in particle size
distribution as precipitation proceeds cause this variation
in w.
A semiempirical variation of the Deutsch equation,
.. 21
proposed by Matts and Ohnfeldt, essentially removes the
size dependence from w.
The equation is:
n = l-exp (-w
k
The
A/Q)k where k is said to equal about 0.5 in most cases.
modified migration velocity, wk' can be treated as indepen-
dent of changing current and voltage levels, and particle
size distribution within an ESP, as the precipitation
2-39
-------
process proceeds in the direction of gas flow.
However,
changes in the properties of dust entering the precipitator
(resistivity, size distribution) produce a change in wk just
as they also change the conventional w.
Values of wk range
from between 1.6 and 1.9 ft/s at moderate resistivity levels
(109 ollin-em) where as for a very resistive dust (1011_1012
ohm-ern) it may approach 0.5 ft/s or less.
Precipitator sizing curves presented in this section
use the modified migration velocity, and specific values of
wk can be computed from the SCA/efficiency curves for the
various applications.
2.3.2.1
Basic Design Parameters - The objective is to
determine from the process application, process conditions,
and emission regulations the values for gas volumetric
throughput (acfm), total plate collection area (ft2), and
power density (watts/ft2 of collecting surface). These
three parameters form the basis for precipitator design.
The total gas volume is dictated by process and pro-
duction level.
Knowing the total acfm and the specific
collection area (SCA, ft2/1000 acfm), one can determine the
total area required to meet an emission standard.
The
necessary equations are given below.
16.7 Inl/b (1 - n)
SCA =
wk
2-40
-------
C
T) = (1 - ~)
C.
1.
100
where
b = slope of line (reference line slope = 0.5)
T) = Overall mass collection efficiency, percent
wk = Modified migration velocity: ft/s
C = Allowable outlet grain loading, grains/DSCF*
o
C. = Inlet grain loading, grains/DSCF
1.
In = Natural log
State emission regulations have become much more
sophisticated often specifying allowable emissions in pounds
per hour and grains/ft3 as a function of the weight of raw
material processed.
Where "equivalent opacity" is used as a standard, the
presence of fines, although representing a small weight
fraction, may cause a visible plume.
Depending on the
opacity standard, a visible plume may not be acceptable.
Estimates of the required concentration to meet opacity
codes can be made.
The following excerpt from the State of Pennsylvania
Department of Environmental Resources Rules and Regulations
is given as an illustration of current standards.22
*
DSCF = dry standard cubic foot.
2-41
-------
PARTICULATE MATTER EMISSIONS
123.13 (b) Processes
"No person shall cause, suffer, or permit the
emission into the outdoor atmosphere of particulate
matter from any process" (examples of which are listed
below) "at anytime either in excess of the rate calcu-
lated by the formula" (presented below) "or in such a
manner that the concentration of particulate matter in
the effluent exceeds 0.02 grains per dry standard cubic
foot, whichever is greater."
Process
Primary iron and/or steelmaking
Process factor, F
(in pounds per ton)
Sintering windbox
Steel production
Scarfing
20 (dry solids feed)
40 (product)
20 (product)
Formula for Particulate Emission Limitation
A = 0.76 EO.42
Where
A = Allowable emissions in pounds per hour
E = Emission index = F x W pounds per hour
F = Process factor in pounds per unit and
W = production or charging rate in units per hour
Opacity cannot exceed 20 percent for a period or
periods of more than 3 minutes in anyone hour, or
exceed 60 percent at any time (unless uncombined water
is the only reason for failure to meet opacity limi-
tations.
Power Input
The third basic design parameter is the power density
required to establish the optimum voltage-current char-
acteristics of the corona, given the amount of dust entering
the precipitator.
Power density is a function of electrical
2-42
-------
resistivity, particle size characteristics and distribution,
gas loading and composition, gas temperature, and gas pres-
sure. It is often conveniently linked with
such that for a moderate resistivity of 109
value will be approximately 2.5 watts/ft2.
resistivity,
ohm-ern a typical
For a high
resistivity application the design value will be in the
neighborhood of 0.5 to 1.0 watts/ft2.
The selection of power density is often conveniently
based on resistivity of the dust (which is principally iron
oxide) .
Table 2-8 illustrates a general correlation between
power density and dust resistivity-
Table 2-8.
DESIGN POWER DENSITY
2
Watts/ft of
collecting plate
Resistivity (ohm-ern)
104-7
107-8
109-10
lOll
1012
4.0
3.0
2.5
2.0
1.5
>1013
<1. 0
Operating voltages may range from 25 to 45 kV (typi-
cally 40 kV) for 9-in. plate spacing.
Current densities
typically range from 0.04 to 0.07 mA/ft2 for iron and steel
application except for electric arc furnace applications,
2
where the range may be from 0.05 - 0.10 rnA/ft .
These
2-43
-------
values are not constant for each point in the precipitator.
At the inlet section, where dust loading is greatest,
voltage-current characteristics will be significantly
different from those at the outlet.
It appears that resistivity plays a significant role in
selection of wk and power density, yet there is no precise
method of predicting resistivity from the material entering
the furnace, process, or from the process conditions.
Specific Design Parameters - Table 2-9 is a com-
2.3.2.2
pilation of design parameters and input variables grouped in
logical categories.
Precipitator Size
One of the first structural parameters to be determined
is
the width of the precipitator(s) .
This value is depen-
dent on the total number of ducts as determined from the
following equation.
Total no. ducts =
ACFM
(T.V.) (60) (P.S.) (P.H.)
Eq. 1
where
ACFM = total gas volumetric throughput, acfm
T.V. = gas (treatment) velocity, fps
P.S. = plate spacing, ft
P.H. = plate height, ft
Treatment velocity (T.V.)
is a function of dust resistivity.
2-44
-------
Table 2-9.
DESIGN PARAMETERS AND DESIGN
CATEGORIES FOR ELECTROSTATIC PRECIPITATORS
Dust Composition
Fe
Si02
MgO
Na20
ZnO
S
C
Cu
Zn
FeO
A1203
CaO
K20
P
Mn
Pb
Alkali
Precipitator Capacity
Number of precipitators
Number of chambers (units)/precipitator
Number of ducts/chamber (unit)
Duct spacing
Plate height
Treatment length
Section lengths and total number of each (per precipitator)
Collecting area
Number of electrical sections parallel to gas flow (per
precipitator)
Number of electrical sections across gas flow (per precipitator)
Number of hoppers parallel to gas flow (per precipitator)
Number of hoppers across gas flow (per precipitator)
Rapping, Electrodes, etc.
Type of discharge electrode
Ft2 discharge electrode/vibrator or rapper
Type of discharge electrode vibrator or rapper
Type of collecting electrode
Ft2 collecting electrode/rapper
Type of collecting electrode/rapper
Electrical Energization (of each electrical section)
Watts/ft2 of collecting electrode
Ft2 of collecting electrode/transformer-rectifier
Mode (switching)
~?~?~a kilovolts _.2 -.
M~~l~am~eres/lOOO I~ of Gol~ect~ng electroae
Milliamperes/transformer-rectifier
Performance-Related Parameters
Gas flow
Gas temperature
Gas (treatment)
SCA
velocity
Overall mass collection efficiency
Fractional mass collection efficiency
Inlet grain loading
Outlet grain loading
2-45
-------
For open hearth furnace, basic oxygen furnace, and sintering
applications the precipitator treatment velocity ranges from
3.5 to 5.5 ft/s.
Electric arc furnace precipitators (pri-
marily for ferroalloy production emissions) have treatment
velocities in the range of 2.5 to 4.0 ft/s, whereas scarfing
ranges from 4.0 to 5.5 ft/s.
Since these figures are his-
torical and do not entirely correspond to more recent strin-
gent emission standards, the general range of 3.0 to 5.5 ft/s
may be considered typical.
In general, the more resistive
the dust, the more desirable it is to maintain a longer
treatment time, i.e., lower treatment velocity.
Plate spacing is more or less fixed by the manufacturer
of the precipitator, depending on his experience with (1)
the various process applications and conditions;
(2) sus-
pected velocity distribution across the precipitator; and
(3) the type of plate.
Plate spacing usually ranges from 6
to 15 in.
For control of particulate emissions from the
waste gas of a basic oxygen furnace, the inlet often has a
larger plate spacing (~ 11 in.) than the outlet (~ 9 in.).
This is due to the high grain loading (2-10 grains/DSCF) and
the fact that oxygen lancing produces a large number of fine
particles.
Plate height is determined by the necessity of simul-
taneously maintaining the required treatment velocity and an
2-46
-------
adequate aspect ratio.
The aspect ratio is defined as the
ratio of the length of a precipitator (collecting plate
dimension in direction of gas flow) to its height.
His-
torical data indicate that it can vary from 0.75 to 1.5.
The practical limitations on plate height imposed by struc-
tural stability requirements are obvious.
Each manufacturer
limits plate heights in accordance with the overall design.
Given the total number of ducts, one can calculate the
width of the precipitator.
What is required now is a de-
scription of the sectionalization of the precipitator,
whether it be chamber-wise (across the gas flow), field-
wise, also known as series sectionalization (in the direc-
tion of gas flow), or both.
Fig. 2-6 shows all three types
of sectionalization.
3rd FIELD
1st FIELD
2nd FIELD
r
ii
JC
L)
if
JC
L)
ii
JC
L)
PARALLEL
SECTIONALIZATION
SERIES
SECTIONALIZATION
r
SERIES AND PARALLEL SECTIONALIZATION
(DIRECTION OF GAS FLOW
INDICATED BY ARROW)
Figure 2-6.
Sectionalization of a precipitator
2-47
-------
A practical approach from the standpoint of energiza-
tion and reliability is to limit the total number of ducts
per chamber.
The number of chambers in a precipitator is
determined by the number of ducts, which itself is deter-
mined from Equation 1 and its associated criteria.
The
number of precipitators needed will depend on the degree of
reliability required, space limitations at the plant site,
and the relative ease with which the effluent gas can be
distributed to the precipitator(s).
The second general design equation provides a guide to
the design length of the precipitator.
As mentioned pre-
viously, the length is dependent on the selection of treat-
ment velocity, plate spacing, plate height, gas volumetric
throughput, and total collecting surface.
Eq. 2
Treatment Length =
Total collectin
(no. pptrs.) (No. chambers/pptr) (no.
(P.R.) (2)
The design treatment length will be determined by selection
of an integral value of standard section (field) lengths
that may be offered by the precipitator manufacturer.
If it
is found, for example, that four fields are required, two of
one length and two of another, structural considerations
such as hopper spans may determine the positioning of the
2-48
-------
fields in the direction of gas flow.
The size of the trans-
former-rectifier (T-R) sets is selected to provide lower
current density at the inlet.
A mechanical section resulted from a chamber-wise and
field-wise sectionalized electrostatic precipitator.
Hopper
selection is based on the size of the mechanical sections
and the suspected inlet grain loading.
Electrical/Mechanical Components
The geometry of the discharge electrode (fine, barbed,
rigid, etc.) will determine corona current-voltage charac-
teristics.
The smaller the wire or the more pointed its
surface, the greater the value of corona current for a given
voltage.
However there are problems with very fine or
exotic wires, such as the potential for breakage and possi-
ble dulling of spliced points with wire.
A standard wire
has a diameter of 0.109 in.
Typical values for length of discharge wire per vibra-
tor or per rapper can range from 2500 to 3500 ft.
The
number of square feet of collecting surface per rapper
usually varies from 2000 to 3000.
Baffles provide stiffness to the collecting plant and
create a region of low turbulence to minimize reentrainment
of dust, particularly during rapping.
Although a variety of
plates are available, their fundamental characteristics are
not substantially different. 23
2-49
-------
Rappers are either pneumatic, electromagnetic, or
mechanical.
Single-impact (magnetic-impulse, gravity-
impact) rappers are often used.
Rapping intensity is deter-
mined by the height of the rapper when released from its
elevated position and by plunger weight, which may be from 8
to 32 pounds.
The frequency of rapping is determined empir-
ically by observing the values of opacity and overall mass
collection efficiency, measured while intensity of rapping
is varied.
Mechanical rappers are attached to a rotating shaft and
are lifted by this means.
Impact is usually provided in a
horizontal direction.
Intensity and frequency of raps are
determined by the weight of the rapping hammers and by shaft
speed, respectively-
Electrical Energization
The way in which a precipitator is energized has a
great effect on its performance.
This decision is probably
as site-specific as it is process-specific.
In any event,
the same questions addressed in utility applications must be
examined for industrial applications.
These include the
number and size of T-R sets, the number of electrical sec-
tions, degree of high-tension sectionalization, half wave-
full wave (HW-FW) operation, and changes in voltage-current
characteristics as precipitation proceeds in the direction
of gas flow.
2-50
-------
A mechanical section by definition may become an elec-
trical section (bus section) if it can be separately ener-
gized.
Within an electrical section one may have a chamber-
wise or field-wise high tension split, or both (see Figure
2-7) .
MECHANICAL SECTION
MECHANICAL SECTION
MECHANICAL SECTION
FIELD-WISE
CHAMBER-WISE
CHAMBER-WISE
FIELD-WISE
t
t
t
(ELECTRICALLY DIVIDED
4 WAYS, PARALLEL
AND SERIES)
(ELECTRICALLY DIVIDED
2 WAYS, IN PARALLEL)
(ELECTRICALLY DIVIDED
2 WAYS, IN SERIES)
(DIRECTION OF GAS FLOW INDICATED BY ARROW)
Figure 2-7.
High tension splits.
2-51
-------
The advantages of splitting a mechanical section electri-
cally both chamber- and field-wise are directly translatable
ln terms of increased reliability and, of course, in terms
of increased cost.
For the applications under considera-
tion, both inlet and outlet sections are often split across
the direction of gas flow (chamber-wise).
In this configu-
ration, the effect of temperature and dust loading varia-
tions across the precipitator because of poor gas distribu-
tion are minimized.
This has the added advantage of in-
creased reliability at the inlet, which is often in the half
wave mode.
If one bus section fails, a jumper cable can be
engaged to apply full wave to the "companion" bus section,
thereby preventing that bus section from failing.
Reliability is defined not only in terms of sectional-
ization of a given collection area, but also in respect to
additional collection area or electrical fields.
The degree
of reliability can be defined in terms of redundant capacity,
which is a function of anticipated failures in sections of
the precipitator and time between maintenance periods.
Redundancy may be defined as that additional area in a
precipitator that compensates for an anticipated "normal"
level of unavailable collecting area.
It is clear that in
order to achieve a reliable yet cost-competitive design,
detailed information on dust characteristics are needed,
2-52
-------
along with a clear understanding of the effect of process
variations on precipitator performance.
The basic consideration in energizing the precipitator
is to maximize the power input to achieve the highest col-
lection efficiency from a given collection area.
The deci-
sion on the degree of sectionalization, however, is made
quite independently of the way in which the precipitator is
to be energized.
The number, size, and mode of operation
(HW or FW) of the T-R sets can be manipulated to provide the
required current density within each bus section of the
precipitator.
A commentary on the selection of HW or FW
operation is presented below.
In the spark-limited operation, half wave allows time
during the "off" half cycle for recovery from the sparking
condition (spark quenching) .
Complete decay of the charging
field and of collection efficiency during the
"off"
half
cycle is avoided because of capacitive effect of high-
resistivity dust, which tends to maintain the field poten-
tial.
In cases where the resistivity of the dust has been
reduced, i.e., because of increased temperature of operation
the capacitive effect of the dust is also reduced.
Thus the
charging field decays more in half wave than in full wave.
2-53
-------
The selection of the mode of operation is rather site-
specific, and the variability of performance measurements
in full-scale precipitators may outweigh any differences due
to operation in either half wave or full wave.
For the
processes under consideration, half wave historically has
often been used in the inlet fields and full wave in the
outlet fields.
In summary, it should be clear that the philosophy of
precipitator sectionalization and energization is based on
maximizing power input to the precipitator to achieve the
highest efficiency from a given collection area, while
minimizing decreased performance resulting from the various
possible failure patterns.
The reliability of precipitator
performance is a function of process flow conditions and
dust characteristics, reliability requirements, and the
designer's experience.
The way in which a precipitator is
energized depends on the sectionalization configuration and
on the current density to be supplied to each bus section,
as determined by chemical and physical characteristics of
the dust, by dust loading, and characteristics of the gas
stream.
The number, size, and mode of operation of the T-R
sets can be fitted to the sectionalized configuration after
the selection of bus section design has been established.
2-54
-------
2.3.3
Correlations
The preceding discussion of precipitator design shows
that three parameters are of central interest:
gas volu-
2
metric throughput (acfm); total collecting area (ft ); and
power density (watts/ft2 of collecting surface). The graph-
ical correlations discussed in this section relate these
basic design variables by process application.
As indicated
earlier, the designer's judgment, experience, and under-
standing of precipitator theory allow him to select the
values of overall mass collection efficiency, SCA, and power
density required for given process conditions and emission
standards.
A word of caution is needed, however.
It is not
intended that the broad-based approach presented here should
provide information that can be directly applied to a
specific site or installation.
A number of highly practical
points must be considered, such as design features to con-
trol and minimize large-scale turbulence, gas sneaking, and
particle reentrainment in the precipitator.
The design and sizing of electrostatic precipitators
are based both on a theoretical understanding of the control
device and on past field experience.
In the present work,
the objective is to justify some typical design trends that
have been established for precipitator sizing in the steel
and ferroalloy industry.
2-55
-------
The processes included in the present discussion are:
(1)
( 2 )
( 3 )
( 4 )
( 5)
(6 )
Basic oxygen furnace (BOF)
Open hearth furnace (OHF)
Electric arc furnace (EAF)
Sintering Process w/mechanical collector
Sintering Process w/o mechanical collector
Scarfing Process
Some typical operating data from the literature for
these processes has already been shown in Table 2-1.
Very
limited operating data on precipitator performance have been
obtained.
What information is available, however, is pre-
sented to support existing design trends.
Figure 2-8 shows representative sizing curves used for
the wire plate-type precipitator in the iron and steel and
ferroalloy industries.
The reference line has as its basis
the modified Deutsch equation.
In interpreting these data
the objective will be to explain the effect of different
input variables on precipitator design and to justify the
relative position of basic design correlations; viz. SCA
versus overall efficiency.
Those precipitator parameters
which require special attention are:
( 1)
(2 )
( 3)
Particle size distribtuion
Inlet grain loading
Flue gas temperature
2-56
-------
99.9
99.8
99.0
98.0 B.O.F.
LA.F.
--
>- 95.0 SCARF.
u
z
I'V LU
I -
u
U1 -
-....J u.. SINT.
u..
LU
90.0 O.H.F.
LEGEND
85.0
O.H.F.: OPEN HEARTH FURNACE
B.O.F.: BASIC OXYGEN FURNACE
80.0 LA.F.: ELECTRI~~RC FURNACE
SINT.: SINTERING ~ROCESS
SCARF: SCARFING PROCESS
70.0
000
CD 0\ 0
o
o
N
o
o
M
SPECIFIC COLLECTION AREA, ft2/1000 acfm
*BASED ON A MODIFIED DEUTSCH EQUATION COPYRIGHT 1974, RESEARCH COTTRELL, INC.
Figure 2-8.
Selected precipitator correlations*.
-------
Particle resistivity
(4 )
(5 )
Gas velocity
( 6 )
Gas treatment length
The information in Table 2-10 was extracted from Figure
2-8 to help identify the relative difficulties in collecting
process fumes from the various applications.
At 99 percent
overall efficiency, it is seen that sintering requires the
largest SCA at 455, BOP the smallest at 215.
Electric arc
furnaces, open hearth furnaces, and scarfing all having
SCA's in the vicinity of 300.
In explaining these design
trends, it will be of interest to consider the effects of
particle size distribution and of inlet grain loading on the
precipitator size required to achieve 99 percent overall
mass collection efficiency.
The particle size distribution characteristics derived
6
from Weast et al., along with selected average values for
process variables based on manufacturers' data and information
from the literature are given in Table 2-11.
Information on
mass mean diameters, geometric standard deviations, particle
material density, inlet grain loading, and gas temperature
is then used to generate the actual particle number density
as seen at the precipitator inlet.
The above information is very important in estimating
the relative magnitudes of the particle space charge dens i-
2-58
-------
Table 2-10.
COMPARISON OF PERFORMANCE OF ELECTROSTATIC
PRECIPITATORS ON VARIOUS IRON AND STEEL APPLICATIONSa
SCA (ft2/1000 acfm)b
Efficiency,
%
98.0
99.0
99.6
Application
Sintering
process 325 445 650
Electric arc
furnace 190 310 540
Scarfing
process 225 310 440
Open hearth
furnace 245 295 340
Basic oxygen
furnace 150 215 320
a
Manufacturers' data.
b Although specific values of SCA are given, it should be
clear that these are only some typical values within
broad ranges of SCAts possible for these applications.
2-59
-------
Table 2-11.
SU~WARY OF EMISSION CHARACTERISTICS (STEEL/FERROALLOY APPLICATIONS)
USED TO DETERMINE NO. DENSITY - PARTICULATE SIZE DISTRIBUTIONa
N
I
0"\
d
Gas Temperature, Volume Flow nate) Uncontrolled Particulate Particle Sizeb
Emission Source of acfm Emission, gr/dscf Distribution
x 0
Sintering
wi mechanical collector 350 106,000-2,000,000 0.6 7.7 3.50
wlo mechanical collector 350 106,000-2,000,000 6.0 70 6.67
Scarfing 125 20,000-120,000 0.55 NA NA
Open hearth furnace 575 50,000-200,000 0.7 0.21 2.86
Basic oxygen furnace 500 300,000-750,000 5.8 0.27 1. 82
Electric furnace 800 175,000-200,000 2 0.80 9.30
a
Manufacturers' data averaged for use in particle density - size distribution
prediction model
b Data derived from ~ef.23
-------
ties, which strongly influence the electric fields at the
collection plates.
It is known that these collection fields
directly influence particulate collection rates and hence
the overall collection.
The larger the space charge den-
sity, the higher the electric field is at the plate.
This
situation, however, weakens the field near the discharge
electrode and suppresses the corona generation process, a
phenomena commonly known as corona quenching.
The particle
size which contributes significantly to the particle space
charge lies in the 0.05 to 1.0 ~m range.
In Figure 2-9, it
can be seen that for BOF applications, the particle number
densities in the 0.1 to 1.0 ~m size range are at least an
order of magnitude higher when compared with electric
arc or open hearth furnace applications.
Other variables, such as particle resistivity and gas
temperature, must also be considered.
Assuming resistivi-
ties low enough not to cause back ionization (Figure 2-10) ,24
it can be concluded that higher space charge density favors
particulate collection in BOF applications relative to
electric arc or open hearth furnace applications.
The size-number density distribution in the size range
of interest (0.05 to 1.0 ~m) is almost identical for elec-
tric arc and open hearth furnace applications.
However,
Table 2-11 shows that electric arc precipitators operate at
2-61
-------
1016
ELECTRIC ARC FURNACE
(Particle density = 2.2g/cm3)
10 15
f"')
E
.........
0
z: 1014
>-
~
~
V')
z:
l.LJ
0
a::
l.LJ
a:I
:£
:::>
:z: 1013
l.LJ SINTERING PROCES
-J
u w/o MECHANICAL
......
~ COLLECTOR
a::
-------
o 101
I
.!
o
.
E 10'
:>
-
~
VI
-
VI
~ 109
~
z
1.0.1
~
c(
~
~
c(
Figure 2-10.
1013
1012
SCARFING BOF lIME
,......, 'II.......
\.. -..
I ;<::C, .
I & \. 'BASIC OXYGEN FURNACE
, f \
J l \
/ I \
'.: \
: \
J \
1 "
OPEN
HEARTH
106
100
500
600 . 700
800
200
300
400
o
TEMPERATURE, F
Apparent Resistivitie~ of
Metallurgical Dusts.l
2-63
-------
much higher temperatures as compared with open hearth appli-
cations.
This might have a favorable effect in decreasing
the effective resistivity of the dust layer on the col-
lecting plates, thereby enhancing the collection rate and
efficiency of electric arc as compared with open hearth
applications.
Information on in situ resistivity measure-
ments, however, is needed to support this point.
Figure 2-11 shows design and performance information
gathered for the BOF application.
The solid line refers to
the existing design trend.
Understanding that this line
represents only one typical curve within a design band of
values, the operational data from equipment manufacturers
and Southern Research Institute,25 generally support the
design trend.
The scatter in some of the test data points
is probably due to the variability in the BOF process con-
ditions.
For example, moisture content could be low,
resulting in high resistivity, or the gas temperature could
be low enough to shift the apparent resistivity to a high
value (Figure 2-10).
Figures 2-12 and 2-13 show the relationships between
precipitator test and design data for open hearth and elec-
tric arc furnace applications respectively.
Any changes in
the fuel used during the open hearth refining process can
affect the moisture content of the waste gases.26,27 Low
2-64
-------
99.9
99.8
99.0
98.0
....
>-
u
~ 95.0
.
u
-
tV
I
~
Ul
.....
.....
....
90.0
85.0
80.0
.
.
.
.
Note:
Line for design trend
represents range of values.
. DATA FROM MANUFACTURERS,
USERS, AND OPEN LITERATURE.
70.0
o 0 0
00 a'! ~
o
o
N
SPECIFIC COLLECTION AREA, ft2/1000 acfm
* BASED ON A MODIFIED DEUTSCH EQUATION
COPYRIGHT 1974, RESEARCH COTTRELL, INC.
Figure 2-11.
Selected precipitator correlations* for basic oxygen furnace.
-------
99.9
99.8
99.0
98.0
~
>-
u
:z
.....
;::; 95.0
N
I
0'\
0'\
u...
u...
.....
90.
85.0
80.0
Note:
Line for design trend
represents range of values.
. DATA FROM MANUFACTURERS
AND USERS.
70.0
o 0 0
co 0'\ :=
o 0
o 0
N .".
SPECIFIC COLLECTION AREA, ft2/1000 acfm
* BASED ON A MODIFIED DEUTSCH EQUATION
COPYRIGHT 1974. RESEARCH COTTRELL, INC.
Fiqure 2-12.
~0-1ected precipitator corre1ations* Cor open hearth furnace.
-------
99.9
99.3
99.0
98.0
~
>-
~ 95.0
UJ
rv
,
0"\
-...J
u
-
....
....
UJ
90.0
85.0
80.0
70.0
o
co
Note:
Line for design trend
represents range of values.
. DATA FROM OPEN
LITERATURE.
o 0
0'> 0
o
o
N
- ---
SPECIFIC COLLECTION AREA, ft2/1000 acfm
* BASED ON A MODIFIED DEUTSCH EQUATION COPYRIGHT 1974, RESEARCH COTTRELL, INC.
Figure 2-13.
*
Selected precipitator correlations for electric arc furnace.
-------
fuel-firing rates and lower use of atomizing steam could
lead to conditions more favorable for high apparent resis-
tivity (Figure 2-10).
Since the use of electrostatic precipitators in elec-
tric arc furnace applications is very limited, there are an
insufficient number of design and test data points to
develop a meaningful commentary.
In the sintering process it appears that the particu-
late, which consists mainly of metallic oxides, silica,
and limestone, is very resistive.
As indicated in Figure
2-14, it may be on the order of lOll and 1014 ohm-em.
This
limits the current densities and the applied voltage at the
discharge electrodes to avoid back corona formation.
Thus,
the particle charging process and the electric fields at the
plates for particulate collection are marginal.
This situa-
tion appears to be analogous to the behavior of high-resis-
tivity fly ash found in some utility applications.
Figure 2-15 shows the available design and test data
for electrostatic precipitators operating on sintering
machines equipped with mechanical collectors.
In general,
fairly good correlation is noted.
Of the applications
considered in this study, sintering can have the widest
variability in process operating conditions.
The materials
charged to the sinter machine can change during process
2-68
-------
~
I
.!
o
.
>-
.....
-
>
:;; 10 11
-
'"
....,
ell:
Figure 2-14.
TEMPERATURES. F
100
200
300
400
1010
PLANT A
BASICITY 4.0
1013
1012
PLANT C ~
BASICITY 4.0
109
50
100
150
200
TEMPERATURE.OC
Effect of Temperature and Sinter
Basicity on Resistivity of
Sinter-Plant Particulate.28
2-69
-------
99.9
99.8
99.0
.
98.0
....
:-
U 95.0
z
UJ
-
U
-
....
!\J "" .
UJ
I
--J 90.0
o
85.0
80.
.
.
Note:
Line for design trend
Represents range of values.
.. DATA FROM MANUFACTURERS,
USERS, AND OPEN LITERATURE.
70.0
o
CX)
o 0
a> ~
o
o
N
SPECIFIC COLLECTION AREA, ft2;1000 acfm
* BASED ON A MODIFIED DEUTSCH EQUATION
COPYRIGHT 1974, RESEARCH-COTTREll, INC.
Figure 2-15.
Selected precipitator correlations* for sintering process.
-------
cycles, depending upon the availability of ore, ore fines,
lime, etc.
The properties of the dust are therefore affected.
No test data were available for scarfing.
Typical
operating gas temperatures lie in the range of 100 - 125°F.
Resistivity-temperature data given in Figure 2-10 indicate
apparent resistivity on the order of 1010 to lOll ohm-cm.
This value could be considered high enough to cause back
ionization problems.
Thus, again, precipitator performance
can be limited by the operating voltage and the resulting
current density, to avoid back corona formation.
2.3.3.1
Precipitator Capital and Annual Costs - Capital and
annual costs were estimated for ESP's operating on the steel
processes listed in Table 2-10.
The SCA's and efficiencies
presented in Table 2-10 were used as inputs for the computer
model cost estimates, which are presented as a function of
gas flow in Appendix B-1.
Tables B-l-l through B-1-5
sum-
marize capital and annual costs for each process.
The total capital investment includes direct and in-
direct costs for the basic collector, auxiliaries, ducting,
dust handling, and preparation of a dust disposal pond
remote from the site.
Direct costs are comprised of the
equipment costs plus installation costs.
Equipment costs
are based on August 1976 numbers and escalated to June 1977,
using "Chemical Engineering" cost indexes.
2-71
-------
Indirect capital costs include the following items,
each as a percentage of the total direct costs:
Interest,
10 percent; engineering, 10 percent; field overhead, 10
percent; freight, 1.25 percent; off-site expenditures, 3
percent; taxes, 1.5 percent; spare parts, 1 percent; shakedown,
3 percent.
A contingency fee, is calculated as 20 percent of the
sum of the direct and indirect costs, and the contractors
fee is 5 percent of the sum of the direct, indirect, and
contingency costs.
10)
11)
12)
The annual costs consist of:
1)
2)
electricity usage ($0.03/KWh)
water usage ($0.30/103 gal)
3)
4)
direct labor ($9.00/man hour)
supervision (15% of direct labor)
5)
6)
labor and material (4.35% of capital investment)
supplies (15% of labor and materials)
7)
8)
plant overhead (50% of operating labor and materials)
payroll overhead (20% of operating labor)
dust disposal (10 mi. trucking distance @ $0.15/ton mi.)
9)
Fixed costs (18.6% of capital investment):
a)
b)
c)
d)
e)
Depreciation (5%)
Interim Replacement
Insurance (0.3%)
Taxes (4%)
Capital Cost (9%)
(0.3%)
Annual operating time is assumed to be 7000 hours/yr.
Useful life of the ESP is assumed to be 20 years
2-72
-------
The capital and annualized costs of electrostatic pre-
cipitators can vary significantly with design philosophy and
site-specific factors.
Input factors which affect the costs
presented here are the SCA and efficiency required, the gas
flow rate, and the inlet and outlet dust concentrations.
Gas flow rates for all of the processes range from 15,000 to
1,900,000 acfm at 300°F, the assumed temperature at the in-
let to the ESP with the exception of scarfing, which was
taken at 125°F.
Costs for gas cooling prior to the ESP,
were not estimated.
Inlet dust concentrations were based on
the uncontrolled particulate emission rates presented in
Table 2-11.
The outlet dust rates were calculated using the
collection efficiencies of 98, 99, and 99.6 percent.
The
SCA inputs from Table 2-10 were increased by 5 percent to
provide a measure of redundancy.
In addition some of the
actual required SCA values as calculated by the computer,
were higher than the input values, in order to maintain a
gas velocity of 4 ft/s and an aspect ratio of at least 1.20.
As would be expected, each set of cost curves shows an
increase in capital and annualized costs with increasing gas
flow and higher efficiencies.
Some of the plots show a
straight line relationship, but most of the lines show a
gradual leveling off of costs at higher gas flows.
2-73
-------
Most of the curves show costs that are closer together
for smaller gas flows than for larger gas flows.
Very small
equipment installations tend to have relatively high capital
costs, which do not correlate well with their size.
In many
cases small systems cost roughly the same regardless of the
treated gas throughput.
For the electric arc, sintering,
and scarfing processes, the costs at the 99 percent level
were not much greater than for the 98 percent level, but
showed a significant increase at the 99.6 percent level.
For the BOF and open hearth processes, the increase in cost
between the 98, 99, and 99.6 percent efficiency levels, was
relatively equal.
It is difficult to compare all processes at the same
gas flow since the range of gas flows used for electric arc
furnaces and scarfing are lower than for the other three
processes.
At 170,000 acfm, however, a gas flow at which
costs can generally be compared for each process, sintering
shows the highest range of capital costs, followed by the
electric arc, BOF, scarfing, and open hearth processes, in
that order.
The spread of the capital costs for all pro-
cesses is relatively narrow, at 170,000 acfm, at 3.25 to 6
million dollars, considering all three efficiencies used
(98, 99, and 99.6%).
2-74
-------
Annualized costs show a similar pattern to the capital
costs, with the same order of processes from highest to low-
est costs.
The range of the annualized costs for all pro-
cesses at 170,000 acfm considering all three efficiency
levels was 0.96-1.80 million dollars.
2.4
WET ELECTROSTATIC PRECIPITATORS
2.4.1
General System Characteristics
The use of wet electrostatic precipitators for control
of emissions from industrial sources has historically been
1, , 29
for specialized app lcatlons. These applications include
acid mist, coke oven pushing operations, blast furnace, and
detarring operations.
In the iron, steel, and ferroalloy
industry, however, the principal use of wet precipitators
appears to be in sintering, scarfing, and ferroalloy arc
furnaces, given the emission sources currently under study
in this report.
Wet precipitators now in use consist of either a plate-
or pipe-type design.
The pipe-type employs either
a weir-
overflow arrangement or a continuous spray-
Plate config-
urations usually have a combination presaturation spray or a
spray with intermittent wash.
Of all the wet precipitators used, the horizontal flow
plate-type, with or without baffles (for gas distribution
and additional saturation) and with continuous or inter-
2-75
-------
mittent sprays, has been used in all three major applica-
tions mentioned above.
In some of the electric arc furnace
wet precipitator applications, intermittent washing of the
plate-type electrode was found to be preferable to con-
o . . 30
tinuous lrrlgatlon.
Of the 25 domestic scarfing machine precipitator in-
stallations put into operation since 1971, 4 are of the
. 31
plate-type and 21 of the plpe-type.
The wet precipitator has certain characteristics which,
depending on the application, make it an attractive alterna-
tive to the wet scrubber, dry precipitator, or to fabric
filters.
The problem of high resistivity is eliminated
through the moisture conditioning effect and reentrainment
is minimized.
No rapping mechanism is required and pressure
drop is low, typical of dry precipitators.
The wet ESP
system, has a high potential for corrosion and scaling, and
requires a water treatment system.
2.4.2
Design Philosophy
As in the case of dry electrostatic precipitators, the
design philosophy for wet precipitators is based on a few
basic design parameters, the values for which are determined
by consideration of process applications, process condi-
tions, and the emission regulations to be met.
Six basic
design parameters have been identified in the literature and
2-76
-------
are given below.3l,32,33
Collecting Area
Operating Voltage
Discharge Current
Liquid-to-Gas Ratio
Treatment Time
Local Average Velocity
The level of performance of a wet precipitator can be
determined by using the standard Deutsch equation.
The
basis of that relation is the concept of migration velocity.
As indicated by Bakke,33 the effective migration velocity is
a "catch-all" parameter and therefore includes operating
parameters not indicated by the basic performance equation,
namely:
w = -(Q/A) {O.508} In(c /c.}
o 1
Eq. 1
where
Q = Actual volumetric throughput,
(acfm saturated)
A = Collection Area,
(ft2)
c. = Inlet grain loading,
1
(grains/SCF)
c = Allowable outlet grain loading,
o
(grains/SCF)
w = Migration velocity,
( cm/ s )
c /c. = Fractional loss of particulates or condensables
o 1
(O.508) = Conversion factor from ft/min to cm/s
The efficiency of the precipitator can be expressed
then in the general form:
2":'77
-------
~ = (1 - c Ie.) 100
o 1
or when substituting Eq. 1 into Eq. 2
~ = (1 - e-Aw/0.508 Q) 100
Eq. 2
Eq. 3
As a result of more stringent local, state, and federal
29
emission regulations in recent years, condensables have in
some areas been added to the total particulate loading to be
treated.
Wet precipitators operate at saturated temperature
and therefore are capable of removing organic materials with
a condensation temperature higher than, or equal to, the gas
saturation temperature.
The basic method in the industry has been "design by
analogy," based on empirical application of the Deutsch
equation. Recently some pilot plant studies have been
30
conducted.
In general, however, design data are very
sparse and very little data are found in the current litera-
ture.
(See Table 2-12).
To summarize, although the use of
wet ESP's appears to be a viable technology for sintering,
scarfing, and ferroalloy arc furnaces, as applied to this
report, design data for wet ESP system are generally con-
sidered confidential and are not available because of
intense competition between manufacturers with different wet
ESP designs.
Empirical application of the Deutsch equation
in a design by analogy method has generally been used in the
industry, although use of the Deutsch migration velocity is
2-78
-------
Table 2-12.
Typical Values and Ranges for Wet Precipitator
Basic Design Parameters
Parameter Scarfinga,b SinteringC
Collecting Area, 7500, 15000 25,200 (3 field
ft2 (asstiming 1 field per chamber)
per chamber)
Operating Voltage, 40 - 60 55
kV
Discharge Current, 90-90/1000 ft2 1000
mA
Liquid/Gas Ratio,
gal/1000 acf 6.5
Treatment Time, 10 8.79
s
I
I
I
I
I I
Face Velocity, 1.5 i 2.73 I
ft/s (1.0-2.0) I
I
I
s
a
b
c
Derived from ESP Newsletter, April 20, 1977
Ref. 31-
Re f. 2 9 .
2-79
-------
subject to the same limitations as discussed in Section
3.2.2 for dry ESP's.
2.4.3
Correlations
Due to the general lack of data, no significant corre-
lations could be developed.
The only respondent in the
survey reported an SCA requirement of 300 to 330 for an
efficiency range of 98.23 to 99.27 percent.
Some cost data were available, however.
Hil131 (Table
2-13) indicated that although the cost of wet electrostatic
precipitator equipment can be as much as 45 percent greater
than that for a high-energy scrubber, its installation and
annual costs are far less.
Therefore, on an annualized cost
basis the wet precipitator is shown in this example to be
economically superior to a high-energy scrubber.
2-80
-------
Table 2-13.
COMPARATIVE COST ANALYSIS OF WET ELECTROSTATIC
PRECIPITATORS AND HIGH-ENERGY VENTURI SCRUBBERS
FOR SCARFING PROCESS3l
High-energy Electrostatic
First year costs scrubber precipitator
Equipment $365,000.00 $530,000.00
Installation 230,000.00 125,000.00
Operation 97,950.00 12,800.00
Total $693,450.00 $667,800.00
Assumptions
Gas flow rate: 100,000 acfm
Gas temp: 40-125°F, saturated
Particle size: 98 percent sub-micron (iron oxide dust and
fume)
Inlet dust load: 2.0 gr/acf
Desired collection efficiency: 99.5 percent
2.5
WET SCRUBBERS
2.5.1
General System Characteristics
The iron and steel industry's application of venturi
scrubbers is more complicated than that situation in the
electric utilities.
Because of the intermittent nature of
oxygen lancing in steelmaking processes, both the gas rate
and the dust loading vary considerably during the process
cycle.
Moreover, the dust sizes and corrosive components of
the furnace gases, which are often considered as key design
considerations affecting the scrubber system cost, also vary
with the furnace operating conditions.
2-81
-------
The venturi scrubber system shown in Figure 2-16 serves
as the basis for the following discussion on design para-
meters and cost.
2.5.2
Design Philosophy
In conventional terminology, the venturi scrubber is
categorized as a gas-atomized spray scrubber.
The collec-
tion process relies mainly on the acceleration of the gas
stream to provide impaction and intimate contact between the
particulates and fine liquid droplets generated as a result
of gas atomization.
Basically, this is a high-energy con-
suming device designed for high particulate collection.
Typically, the pressure drop is on the order of 60 - 80 in.
H20 or more for iron, steel, and ferroalloy applications.
Collection efficiency increases with the pressure drop and
the liquid-to-gas ratio.
However, there is an optimum L/G
ratio above which the introduction of additional liquid is
not effective at a given pressure drop.
In this device the
pressure drop can be increased by increasing gas velocity.
Gas velocities could be as high as 40,000 ft/min, but this
causes high wear.
To summarize,
the key parameters affecting the particu-
late collection are:
(a)
Gas velocities and gas flow rates
(b)
Particle size distribution
2-82
-------
[\.)
I
00
w
I
I
I
I
I
TO SLURRY TREATMENT I
I
1- --- ----- -- ---- -----,
I I
I I
I
I
I
I
I
I
ClEAN I NG GAS
PRECOOLING GAS
FAN
MIST
ELIMINATOR
VENTURI
SCRUBBER
MAKEUP WATER
I
RECIRCULATION I
PUMP I
I I
,___- - - - ---- - __~T~~~Y_.J
SUMP
Figure 2-16.
Venturi Scrubber System.
-------
(c)
(d)
Pressure drop
Liquid-to-gas ratio
Besides these parameters, the following information is also
required to justify the choice of equipment.
(a)
(b)
(c)
(d)
(e)
( f)
( g)
(h)
Gas handling capacity/module
Total number of modules required
Capital investment
Annual costs
Water requirement; water recirculation
Availability of the equipment or necessary downtime
Indication of fractional collection efficiency of
the device
Total power consumption as a fraction of the
generated power
Additional parameters to be used in the justification
of choice of pollution control equipment may be found in
Appendix B-2.
2.5.2.1
Velocity/Gas Flow Rate - Sizing a venturi scrubber
is often based on the inlet gas velocity and its flow rate.
Inlet gas velocity is usually about 60 ft/s while the inlet
gas flow rate is dependent on the designed scrubber diameter.
Typical scrubber diameters are under 10 ft.
Gas velocity through the venturi will decrease more at
higher temperatures than at lower temperatures.
Also,
higher liquid-to-gas ratios are required for heat transfer
2-84
-------
to higher temperature gases to reach saturation.
If gas
temperatures are in excess of 400°F, a gas prequencher is
often required as in the case of basic oxygen furnace scrub-
ber applications.
2.5.2.2
Liquid-to-gas (L/G) Ratio - The liquid-to-gas ratio
typically varies from 2 - 15 gal/min per 1000 ft3/min and is
basically a function of inlet gas temperature, inlet solids
content, and method of water introduction.34 At higher
inlet gas temperatures, evaporation of the scrubbing liquor
may occur at the point of liquid/gas contact.
In the case
of heavy inlet dust loading, the L/G ratio should be in-
creased to minimize solids buildup and plugging of trains.
Although pressure drop across the venturi is essentially
independent of the particular design, the less efficient
methods of water introduction will require additional scrub-
bing liquor in order to meet efficiency requirements.
2.5.2.3
Pressure Drop - The scrubbing design for a given
application requires careful selection of the throat veloc-
ity and liquid-to-gas ratio to achieve the maximum collec-
tion efficiency for energy spent.
Energy spent is often
indicated by the gas pressure drop across the scrubber,
which ranges typically from 60-80 in. H20 for the applica-
tions considered in this report.
In fact, the pressure drop
is a function of the throat velocity and the L/G ratio.
To
2-85
-------
achieve a given pressure drop, numerous relationships
between these two parameters can be used.
However, only one
set of conditions will yield the maximum efficiency for the
energy spent.
That one set of conditions is the only one
which will create maximum droplet surface with a minimum
liquid-to-gas ratio during atomization.
2.5.2.4 Particle Distribution - The particle size distribu-
tion in the inlet gas stream is a key factor in the process
design. However, particle size distribution in a source gas
often varies with process and operating conditions of the
source gas.
The fractional collection efficiency data on
submicron particles is particularly difficult to obtain.
When we are speaking of greater collection efficiencies, it
should be understood that this means increased fractional
collection efficiencies in the submicron particle size
range.
2.5.2.5
Material Selection - Scrubber slurry as well as gas
streams are often corrosive and erosive due to acid gases
and abrasive solids content, respectively-
Selection of
suitable construction materials must be considered.
Stainless steel is sometimes necessary, especially at
installations where S02 and fluorides are present.
S02 is
often present in ores and the fuel of sintering processes.
Fluorides occur in open hearth furnace and electric arc
35
furnace applications where fluorspar is added to the charge.
2-86
-------
Where corrosion and abrasion resistance requirements exceed
the limits of stainless steel, fiberglass reinforced plastic
(polyester) may be used.
Abrasion-resistant liners are also needed to withstand
high temperature and/or corrosion situations, such as where
chlorides are present and/or where fluorides are found at
elevated temperatures.
2.5.2.6
Mist Elimination - Mist eliminators are necessary
to control undesirable emissions of liquid droplets from
scrubbers, caused by atomization and carry-over of some
liquid during scrubbing.
Because of the solids in the
scrubbing liquor, the entrainment of water droplets can
cause system operating problems, not to mention liquid
losses.
Suspended or dissolved particles can cause solids
buildup, and suspended solids can cause erosion of the mist
eliminators.
Increased pressure drop is one of the many
problems caused by buildups.
Design Modules - Another difficulty in designing
venturi scrubbers is the lack of a reliable design model to
2.5.2.7
represent the actual system for particulate removal.
Nearly
all the published scrubber models show either by formulas or
by design curves that the empirical correlations are based
on inertial impaction or overall power input.
Empirical
models are often limited by empirical conditions.
In other
2-87
-------
words, both control variables and noncontrol variables vary
within certain ranges for empirical models.
Extrapolating
the design data from empirical models, therefore, involves
some risk.
Moreover, particulate collection in a venturi
scrubber is not only dependent on the particle size distri-
bution, but also on particulate properties such as specific
gravity, wetability, agglomeration, solubility in the scrub-
ber liquid, etc.
36
The K-factor in Brink's model, f-factor in Calvert's
mOdel,37 and the Sand y constants in the Power-law mode138
are all empirical constants emcompassing many of the above
parameters upon which particulate collection depends.
As to
which model is suitable is a matter of judgment.
In addi-
tion, other mechanisms such as diffusion may control col-
lection of submicron particles.
2.5.3
Correlations
Research Cottrell prepared a set of scrubber correla-
tions for steel/ferroalloy applications based on their model
which was developed for some utility applications.
The
processes covered were electric arc, basic oxygen, and open
hearth steel furnaces, ferroalloy arc furnaces, and sinter-
lng.
The results of these correlations in all cases except
for sintering, indicate that the conditions used as inputs,
(i.e., particle size distribution) are beyond the limits for
2-88
-------
which the model was designed.
PEDCo used Calvert's mode137
and came to the same conclusions.
Research Cottrell's correlations are presented in
Appendix B-3 for information purposes only.
The overall
mass efficiencies predicted by the computer performance
model for the steel and ferroalloy furnaces are too low,
considering the pressure drops at which they are calculated.
The reasons for the low predictions of efficiency are dis-
cussed further in Section 4.2.2.3.
In general, however, Figures B-3.l to B-3.9 show that
the effect of pressure drop on the collection efficiency is
uniquely strong, while the L/G ratio in the study limit
shows no great effect.
Theoretically, for a given particle
size distribution, the collection efficiency is a function
of the total droplet surface created by gas atomization.
If
the L/G ratio is too large or too small for gas atomization,
the collection efficiency will decrease.
Intuitively, in
the neighborhood of the optimum L/G, the L/G should have
little effect on the collection efficiency.
Of course,
other factors such as gas temperature, water injection
technique, and scrubber configuration also affect the
collection efficiency.
However,
in the strictest sense,
these are not control variables.
2-89
-------
2.5.3.1
Costs - Capital and annual costs have been esti-
mated by Research Cottrell for use of a venturi scrubber on
steel and ferroalloy processes.
A list of assumptions used
for the development of these costs, which were based on the
computer performance model, is presented below:
Basis of the Performance and Cost Analysis
4.
5.
1.
Major equipment included in the venturi scrubber
system consists of a flooded disc scrubber and a
mist eliminator with a sump tank, one forced draft
fan with driver, and two slurry pumps with drivers.
The auxiliaries included are ductwork, expansion
joints, piping, and instrumentation.
2.
The construction material for both major equipment
and auxiliaries is carbon steel without linings.
One exception is the throat of the venturi, which
is made of an extremely high grade of alloy stain-
less steel.
3 .
The temperature of the flue gas is taken to be
300°F.
The total capital investment for the system con-
sists of the major and auxiliary equipment costs,
tax and freight (average), installation costs,
engineering, and contingency costs.
The annual costs consist of:
(1) Fixed charges (15% of the total capital
investment), including depreciation, interest,
insurance and taxes.
(2) Maintenance (5% of capital investment),
including materials and labor.
(3) Labor cost ($ 9/man-h assuming 3500 man-h/yr
required)
(4 )
Administration (10% of labor cost).
2-90
-------
(5)
(6 )
Water usage ($ .30 per 1000 gallons.)
Electricity usage ($ .03/kWh).
(7) Overhead cost (10 % of the total cost of
water, electricity, labor and maintenance) .
(8) Annual operating time is taken to be 7000
hours/yr.
6.
Cost estimates are based on the material and labor
prices in the first quarter of 1977.
7.
Particulate properties (assuming a specific
gravity of 3.0 grams/cm3; (see particle size dis-
tribution in Table 2-1, by Weast et al.23)
The effects of pressure drop (or collection efficiency)
on the capital investment are shown in Figures B-4.1a to
B-4.9a, presented in Appendix B-4.
These effects are due to
the fan cost which is a function of pressure drop and gas
temperature, in addition to the gas rate.
Theoretically,
for a system with high gas temperature and high efficiency
of fine particulate removal, a gas precooler may be required
for reducing the temperature effects on the scrubber per-
formance as well as on the fan cost.
The materials of equipment construction, which depend
on the gas properties, is another key factor affecting the
capital investment.
If the gas contains corrosive com-
ponents, such as SOx' C12' etc. above a critical level,
stainless steel should be used.
In addition, pumps and
pipes must have liners to provide protection against abra-
sion.
With the additional costs for corrosion resistance
2-91
-------
and abrasion resistance, the capital investment of a venturi
scrubber system may be as much as two times more than that
with the base material (carbon steel).
However, since the
types of liner materials that are used are so variable,
costs were estimated for carbon steel only.
In Figures B-4.lb to B-4.9b, which represent annual
costs for the venturi scrubber, it is shown that the elec-
tricity usage has a considerable effect on the total opera-
ting cost for each application.
In fact, for high effi-
ciency of fine particulate removal, most of the electricity
usage is for fan operation.
In comparison with the elec-
tricity usage, the fixed charges which include equipment
depreciation, tax, insurance, and interest only playa minor
role.
However,
in a system where a gas precooler and/or
stainless steel equipment are required, the fixed charges
increase
sharply.
The labor, maintenance, water, and over-
head are grouped into the "others" category as shown in
these figures.
2.6
DESIGN RELATIONSHIPS FOR FABRIC FILTERS
Fabric filters are basically simple devices.
The
removal of particulate from waste gases is accomplished by
forcing the gases to flow through the fabric filter media,
which removes the particulates by one or more of the follow-
ing mechanisms:
2-92
-------
(l)
(2 )
(3 )
Inertial impaction
Diffusion to the surface of an obstacle by
Brownian diffusion
Direct interception because of finite particle
size
Sedimentation
Electrostatic phenomena
(4 )
(5)
Baghouses have been used successfully for control of
particulate emissions on each of the above described pro-
cesses.
By "operating successfully" it is meant that:
1. The baghouse removes approximately 99+ percent of
the material from the gas stream. No measured data are
available to document this performance. Results are
based on discussions with plant personnel.
2. The baghouse operates at a reasonable steady state
pressure drop (3 to 12 in. H20).
3. The baghouse has reasonable filter life. Less than
1 yr would be unacceptable, while more than about 7 yr
would be excellent.
4.
No serious corrosion or erosion problems exist.
Although users in general are satisfied with overall
baghouse performance (clean process area; no visible plume)
and operational aspects (reasonable bag life, pressure drop,
etc.), there have been cases of very expensive engineering
lessons learned.
One of these is described in the case his-
tory of a user's experience with a large fabric filtration
system, presented in Appendix B-5.
Parameters important to fabric filtration system design
include air-to-cloth ratio, pressure drop, cleaning mode and
frequency of cleaning, composition and weave of fabric,
2-93
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degree of sectionalization, type of housing, and gas cool-
ing.
Baghouses are relatively insensitive to process vari-
ables such as chemical composition (providing that the
correct bag fabric is chosen), particle size, electrical
resistivity, etc.;
thus, there tends to be very little
substantial design difference from one application, or in-
deed from one manufacturer, to the other, when comparing
baghouses with the same cleaning mechanism.
Differences
that do exist are generally related to maintenance (e.g.,
number of bag rows accessible from a given interior walkway;
method of bag cuff attachment to cell plate; etc.).
Table 2-14 lists the pertinent baghouse design criteria
for the applications treated in this report.
Each of these
criteria is discussed briefly below.
2.6.1
Air-to-Cloth Ratio
A major factor in the design and operation of a fabric
filter, the air-to-cloth (A/C) ratio is the ratio of the
quantity of gas entering the filter (ft3/min) to the surface
area of the fabric (ft2). The ratio is therefore expressed
as ft3/hlin per ft2, or sometimes also as filtering velocity
(ft/min) .
Most often only the first member of the ratio
term is given, e.g., an A/C ratio of 1.5 implies 1.5 ft3/min
2
per 1.0 ft .
In general, a lower ratio is used for filter-
ing of gases containing small particles or particles that
2-94
-------
Gas cooling
required
Baghouse
intermittent
or continuous
automatic
Pressure or
suction
Bag cleaning
method
Air to cloth
ratio
tV
,
1.0
V1
Pressure
drop
Fabric
Material
Weight
(oz/yd2)
permeabi~ity
(cfm/ft )
Bag size
(dia x
length)
Pyramid or
trough
hopper
Collected
material
handling
nique
tech-
Provisions for
fire or ex-
plosion
Table
Sintering
Generally, No
Continuous automatic
2-14.
FABRIC FILTER DESIGN CRITERIA
o
Both, but suction preferred
Shaker, reverse air and pulse but
shaker and/or reverse air used
most
-
Wind box from 1.5:1 to 6:1 dis-
char~e at < 3.3:1 for low ratio
and < 7.4:1 for high ratio
10-18 in. H20
(Typical)
Fiberglass
9
45 -6 0
8 in. x 22 ft to
12 in. x 30 ft
Trough-type preferred
Screw conveyors
Generally, No
Polyester
7
-
6 in. x 15 ft
Ferroalloy
Yes, generally via reduction/
convection or forced convec-
tion
Continuous automatic
Generally pressure
Reverse air and/or shake
~ 1.5-2.75:1
10-18 in H20
(Typical)
Nylon Polyester
5.2 8.7
20-35
30-40
8 in. x 20 ft
8 in. x 20 ft
Trough-type preferred
Screw conveyors
Generally, No
Steel
Only if direct evacuation system
Generally continuous automatic for large
systems and intermittent for small systems
Either, but pressure preferred for large
systems
Reverse air and/or shake
~ 2.5-3:1
10-18 in. H20
(Typical)
Fiberglass
8.9
Polyester
5.2
-
15-25
12 in. x 30 ft
8 in. x 20 ft to
12 in. x 30 ft
Trough-type prefe~red
Screw conveyors
Generally, No
-------
may otherwise be difficult to capture.
Selection of the
ratio is generally based on industry practice or the recom-
mendation of the filter manufacturer.
Design A/c ratios for the fabric filters now installed
on iron and steel and ferroalloy electric arc furnaces range
from 1.5 to 3.1.
For sintering the windbox air-to-cloth ratio is gen-
erally 1.5.
However, ratios as high as 6 have been used; at
the discharge, the low ratio is < 3.3 and the high ratio is
< 7.4.
In general, air-to-cloth ratios are limited accord-
ing to fabric type.
2.6.2
Pressure Drop
Pressure drop in a fabric filter is caused by the
combined resistances of the fabric and the accumulated dust
layer.
The resistance of the fabric alone is affected by
the type of cloth and the weave; it varies directly with air
flow.
The permeability of various fabrics to clean air is
usually specified by the manufacturer as the air flow rate
(ft3/min) through 1 ft2 of fabric when the pressure differ-
ential is 0.5 in. H20 in accordance with the American
Society of Testing and Materials (ASTM).
At normal filter-
ing velocities, the resistance of the clean fabric is
usually less than 10 percent of the total resistance.39
The
spaces between the fibers are usually larger than the
2-96
-------
particles that are collected.
Thus the efficiency and low-
pressure drop of a new filter are initially low.
After a
coating of particles is formed on the surface, the collec-
tion efficiency improves and the pressure drop also in-
creases.
Even after the first cleaning and subsequent
cleaning cycles, collection efficiency remains high because
the accumulated dust is not entirely removed.
The pressure drop through the accumulated dust layer
has been found to be directly proportional to the thickness
of the layer. Resistance also increases with decreasing
. 1 . 39
partlc e Slze. Even though several studies have been
devoted to filtration theory, it is difficult to relate
collection efficiency and pressure drop on an industrial
scale.
Maximum pressure drop on existing iron and steel and
ferroalloy processes ranges from about 10 to 18 in. H20.
2.6.3
Cleaning of Fabric Filters
Various cleaning methods are used to remove collected
dust from fabric filters to maintain a nominal pressure drop
of 2 to 6 in. H20.
briefly discussed below.
These are shown in Table 2-15 and
Shake:
Many mechanical shaking methods are in use.
Most
commonly, bags are shaken from the upper fastening.
Several
combinations of horizontal and vertical motion can be used.
The bags may all be fastened to a common framework moving
2-97
-------
Table 2-15.
COMPARISON OF FABRIC FILTER CLEN~ING METHODS a
N
I
\.0
OJ
Uniformity Appa-
Cleaning of Bag Equipment Type Fil ter ratus Power Dust
method cleaning attrition ruggedness fabric velocity cost cost loading
Shake Average Average Average Woven Average Average Low Average
Reverse air Good Low Good \voven Average Average Med. Average
low
Plenum pulse Good Low Good Felt, woven High High Med. High
Pulse-jet Average Average Good Felt, woven High High High Very high
Vibration, Good Average Low Woven Average Average Med. Average
rapping low
Sonic assist Average Low Low Woven Average Average Med.
a Based on data from Reference 39.
-------
horizontally or the frame may have slight additional upward
or downward swing, depending on the linkage holding the
framework.
The framework can also be oscillated vertically.
During the shake, the filtering should be stopped.
Otherwise, the dust will work through the cloth, reducing
the efficiency and possibly damaging the cloth by internal
abrasion.
An effective cleaning method involves a series of
alternate flows and shakes.
This gives a gentler treatment
to the cloth in addition to the cleaning being uniform and
thorough.
In a typical cycle, the inlet flow to the compartment
is first dampered off by a timer.
If necessary, the outlet
vent is also closed (Figure 2-17).
In the absence of an alr
lock between adjacent hoppers, it may be necessary to close
a damper there to prevent the intrusion of dirty air from
hoppers still operating.
There should be zero forward
pressure across the fabric during shaking, since otherwise
dust will work through the fabric.
The timer starts the
shaker motor and the bags are shaken.
Shaking continues for
about 10 to 50 cycles, each cycle taking about 0.2 to 1 s.
Then the timer may start a small flow of clean reverse air
using an auxiliary blower for 10 to 20 seconds. The shaking
may be repeated, this time during the small reverse flow.
Finally, the cleaning is stopped and after pausing to allow
2-99
-------
I
Figure 2-17. Diagram showing normal operation and
shake cleaning of a fabric filter41.
2-100
-------
the dust to settle, the inlet and outlet dampers are opened
and the compartment begins its filtering agaln.
The entire
cleaning cycle may take from 30 seconds to a few minutes.
Some installations do not return the compartment on line
until the next one is ready to be cleaned, thereby achieving
a fairly steady overall flow through the baghouse system at
the expense of some over-capacity.
Reverse Flow:
If the dust releases fairly easily from the
fabric, a low-pressure reversal of the flow may be enough to
loosen the cake without mechanical agitation.
To minimize
flexural attrition of the fabric, it is supported by a metal
grid, mesh, or rings and is usually kept under some tension.
The support is usually on the clean side of the tube or bag,
although dirty-side support can help to keep the sides of
the bag or the panels sufficiently apart to allow the cake
to fall to the hopper.
There are several ways of accomplishing flow reversal.
In addition to the standard dampers on each compartment,
each one can have its own reversing fan.
A few models have
a traveling apparatus that goes from bag to bag or from
panel to panel, blocking off the primary flow and intro-
ducing some air in the reverse direction with a secondary
blower.
Perhaps a simpler method is to take advantage of a
suction on the dirty side or a relative pressure on the
2-101
-------
clean side, without uSlng another blower as shown in Figure
2-18.
Any flow volume reversed through the filter must be
refiltered.
This means that in addition to taking cloth out
of the system for cleaning, this cleaning method increases
the total air flow in the remainder of the system.
The net
increase in air/cloth ratio is normally 10 percent or less.
Plenum Pulse:
This method attempts to overcome some of the
difficulties associated with other methods of cleaning.
In
this kind of equipment a sharp pulse of compressed air is
released in the plenum chamber giving rise to some combina-
tion of shock, fabric deformation and flow reversal.
The
result is the removal of the dust deposit without more than
a brief interruption of the filtering flow.
The fabric
receives a minimum of flexural wear, and the filter instal-
lation is smaller because the fabric is in use practically
all the time.
The main distinction of pulsed equipment is the brief
cleaning time,
typically around one-tenth of a second.
The
very low ratio of cleaning time to filtering time makes
pulsed equipment uniquely useful at high dust loadings.
Pulse Jet:
This cleaning method is essentially similar to
plenum pulse cleaning.
The difference is that in pulse jet
cleaning each bag is individually pulsed whereas in plenum
2-102
-------
t OPTIONAL, TO AVOID
TEMPERATURE CHANGES
~ --- ----l
I
\
SUCTION I
l t
~
F:
R:
COMPARTMENTS FILTERING
COMPARTMENT BEING CLEANED BY DAMPERED
CONTROL FROM SUCTION SIDE OF SYSTEM
Figure 2-18.
Schematic for Reverse Flow Cleaning
During Continuous Filter Operation.41
2-103
-------
pulse cleaning the whole compartment of bags is pulsed via
introduction of pulsing air in the plenum chamber.
Vibration or Rapping:
This method of cleaning is particu-
larly successful with deposits that adhere relatively
loosely to the bags.
The vibration or rapping causes
stresses at the fabric-cake interface which, in turn, re-
lease the dust cake from the fabric.
Sonic Assist:
Agitation frequencies still higher than those
used in vibration or rapping have been attempted with ultra-
sonic and sonic cleaning methods.
Although these frequen-
cies are known to slightly improve the preagglomeration of a
few fine dusts, they have not, on the whole, been very
effective in fabric cleaning.
All respondents in the ferroalloy industry use reverse
air as the cleaning mechanism; 85 percent of the baghouses
on electric arc steel furnaces use reverse air, while 15
percent use shakers; 50 percent of the baghouses on sinter-
ing strands use reverse a~r,
25 percent use shakers, while
25 percent use a combination of reverse air with a shaker
assist.
2.6.4
Frequency of Cleaning
The cleaning cycle should be as short as possible so
that no sizable portion of the total fabric will be out of
service at any given time.
With shake cleaning equipment,
2-104
-------
for example, a common cleaning-to-deposition time ratio is
40
0.1 or less.
With a ratio of 0.1, 10 percent of the
compartments in the baghouse are out of service at all times
during operation.
Therefore, the frequency of cleaning
should be designed to minimize this ratio.
As mentioned
previously, with pulsing equipment, the cleaning time is
very brief, thus a very low ratio of cleaning time to fil-
tering time.
2.6.5
Selection of Fabric
Selection of fabric is generally based on the operating
temperature and on the resistance of the fabric to abrasion
and corrosiveness of the gases.
Table 2-16 shows typical
characteristics of various fabrics, which include cotton,
wool, fiberglass, and other man-made fibers.39
Many fabric
weaves are available; or the fabric may be felted, a process
whereby the identity of the separate yarns tends to be
replaced by a more uniform mat.
Felted fabrics are almost
always cleaned by reverse jet or pulse-jet methods.
Fabric
characteristics may also be altered by further treatment for
specific purposes, such as to decrease adhesion or improve
wearability.
Silicones are often used on fiberglass to
reduce abrasion.
All of the baghouses identified in the questionnaire
survey use polyester, nylon, or fiberglass bags.
At
2-105
-------
Table 2-16.
CHARACTERISTICS OF VARIOUS FABRICS39
tV
I
I-'
o
0'1
Operating Sup- Air
Exposure, ports Permea- CostC
of Combus- bilitya, Abra- Mineral Organic
Fiber Long Short tion t3/min/ft Composition sionb Acidsb Acidsb Alkalib Rank
Cotton 180 225 Yes 10-20 Cellulose G P G G 1
Wool 200 250 No 20-60 Protein G F F P 7
Nylon d 200 250 15-30 Polyamide E P F G 2
Yes
OrIon 240 275 Yes 20-45 Polyacrylonitrile G G G F 3
Dacron d 275 325 Yes 10-60 Polyester E G G G 4
Polypropylene 200 250 Yes 7-30 Olefin E E E E 6
Nomex @ d 425 500 No 25-54 Polyamide E F E G 8
Fiberglass 550 600 Yes 10-70 Glass P-F E E P 5
Teflon @ d 450 500 No 15-65 Polyfluoroethylene F E E E 9
a 3/. f 2 0 5 .
ft m~n per t at . ~n. w.g.
b P = poor, F = fair, G = good, E = excellent.
c Cost rank, 1 = lowest cost, 9 - highest cost.
d DuPont registered trademark.
-------
temperatures above 400°F, the exclusive choice is fiber-
glass, whereas below 275°F polyester is preferred.
2.6.6
Degree of Sectionalization
Design of fabric filter sectionalization (the number of
separate filter compartments) requires knowledge of the
variation in gas flow with respect to process or plant
ventilation, the sizes of commercially available units, and
the expected frequency of maintenance.40 Individual com-
partments in small collectors may contain as little as 100
ft2 of fabric surface, although some large units with a
3 40
capacity of 50,000 ft /min may have only one compartment.
The largest collector to date is under construction in the
electric utility industry and has a capacity of 4.5 x 106
acfm.
with the exception of reverse jet and pulse jet
units,
it should be noted that at least one compartment in
any collector will be out of service during the cleaning
cycle.
2.6.7
Filter Housing
Configuration of the filter housing depends on the
required fabric surface area and on the temperature, mois-
ture content, and corrosiveness of the gases.
When the
baghouse is designed so that the dirty gas enters the inside
of the bags under positive pressure, housing may be needed
only for weather protection or for emission measurements.
2-107
-------
The floor area required for baghouses depends on the
filtering surface area, size of the bags, and spacing
between bags.
For example, 1750 ft2 of filtering area can
be provided in about 80 ft2 of floor area by using bags 6
in. in diameter, 10 ft long, and allowing 4 in. between
bags.
If 12 in.-diameter bags are used, they must be about
14 ft long to provide the same filtering area in the same
floor space, though 12 in.-diameter bags can easily be
obtained in lengths of 20 ft or more when there is adequate
head room.
This configuration (12 in. x 20 ft) would pro-
vide a baghouse having about 2500 ft2 of filtering area in
the same floor space (80 ft2) .41
The length/diameter ratio
affects the stability of vertical bags, so care must be
taken to ensure that bags do not rub together during opera-
tion or cleaning.
The length/diameter ratio ranges from 5
39
to 40, but more commonly varies between 10 and 25.
Re-
spondents in this study indicated a narrow range of 30 to 33
for the length/diameter ratio.
Design consideration must be given to allow adequate
space for the collecting hopper below the filter bags.
Hop-
pers are commonly designed with 45-degree or 60-degree
sloping sides to provide adequate sliding, and with some
dusts a 70-degree slope is required.
Dust collected in the
hopper can be removed by screw conveyors, rotary valves,
trip gates, air slides, and other methods.
2-108
-------
The most common construction material for the housing
is steel; other materials, such as concrete and aluminum,
are also used.
Corrugated asbestos cement paneling is often
used for the exterior roofing and siding of the housing in
.. f I 41
combination with interior walls and part~t~ons 0 stee.
2.6.8
Gas Conditioning or Cooling
The gases to be cleaned are frequently too hot to go to
the baghouse immediately, so they are cooled before entering
the filtration system.
Use of a fabric filter on a sinter-
ing process generally does not require gas cooling.
In the
ferroalloy branch, however, electric arc furnace fumes are
usually cooled by radiation or forced convection; whereas
electric arc furnace fumes in the steel industry are cooled
only if there is direct evacuation of the gases.
Three methods which can be used for cooling the hot
gases are radiation and convective cooling, addition of
outside air, and spray cooling with water.
Radiation and convective cooling do not dilute the gas
and do not raise the dew point, but require large and
costly equipment. '1'0 cool 100,000 ft3/min of air from 600°
to 300°F would require a surface area of 100,000 ft2 if the
heat transfer rate for the cooler were 1 Btu/h ft20F.41
Addition of outside air is simple, but it increases the gas
volume to be handled, thus requiring more filter area and
2-109
-------
energy consumption.
Spraying can provide the greatest
amount of cooling at the lowest total cost but its main dis-
advantage is that it increases the gas dewpoint.
this can
result in wetted bags and/or increased bag wear due to
. 41
higher gas corrOSlveness.
Table 2-17 cites the advantages
and disadvantages of different methods of temperature
conditioning.
2.6.9
Correlations
As stated in Section 2.6 it is difficult to establish
correlations between fabric filter design parameters and
specific processes such as those discussed in this study.
This is because of the similarities in the design of fabric
filters from application to application.
Thus only capital
and annual costs are presented for fabric filters.
Capital and Annual Costs For Fabric Filters -
Typical installed costs and operating costs for fabric
2.6.9.1
filters in the iron and steel industry are given in Figures
2-19 and 2-20 respectively.
Although several respondents to
the survey furnished cost figures, it was impossible to
display these figures in a meaningful way.
This arose from
the divergent accounting methods used.
Some respondents
reported costs in terms of product produced, while others
reported annual dollars, both with and without overhead
absorption.
2-11IT
-------
Table 2-17
METHODS OF TEMPERATURE CONDITIONING4l
Radiation-Convection Cooling (long, uninsulated inlet ducts)
Advantages:
Disadvantages:
Lowest flow volume of the three methods.
Smoothing or damping of flow, tempera-
ture, pressure or other surges, or peaks
in the process effluent stream.
Saving of heat (building space heating).
Cost of extensive ducting.
Space requirements of ducting.
Possibility of duct plugging by
tation.
sedimen-
Evaporation (by water injection well ahead of the filter)
Advantages:
Disadvantages:
Low installation cost, even with auto-
matic controls.
Capability of close and rapid control of
temperature.
Capability of partial dust removal and/or
gas control by scrubbing.
Danger of incomplete evaporation and
consequent wetting of the filter or chemi-
cal attack of the fabric or filter.
Increased danger of exceeding the dew-
point and increased possibility of
chemical attack.
Increased steam plume visibility, a
hazard near highways.
Possible increase in volume filtered.
Dilutio~ (by adding ambient air to the process effluent stream)
Advantages:
Disadvantages:
Lowest installation cost, especially at
very high initial temperatures.
Substantial increase in total filtering
volume.
Automatic control of both temperature and
filtering velocity is not possible.
Uncontrollable intake of ambient moisture,
dust, etc., without prior conditioning of
the dilution air.
2-111
-------
4,000,000
t,A-
\0
r--.
0'\
..
~
lLJ
I-
~ 3,000,000
V')
lLJ
V')
::::>
o
::t:
(.!>
c:(
c:a
u..
o
l-
V')
8 2,000,000
-'
c:(
I-
......
a..
c:(
u
1, 000 , 000
MODI FED
ARTHUR D.
LITTLE DATA
MODIFIED
BATTELLE
DATA
Figure 2-19.
Installed cost of fabric filter systems.
2-112
-------
2,000,000
~
\0
,.....
0'\
r-
~
I
i-'
f-'
W
..
~
tI)
o
U
l1J
U
z:
ex:
:z:
l1J
~
:z:
......
ex:
::E
~ 1,000,000
ex:
t!J
:z:
......
~
ex:
a:::
l1J
CL
a
--.J
ex:
=>
:z:
:z:
ex:
00
MODIFIED
ARTHUR D.
LITTLE DATA
Figure 2-20.
Annual operating and maintenance cost of fabric filter systems.
-------
Figures 2-19 and 2-20 were derived by Midwest Research
Institute from the 1969 Battelle study of the integrated
iron and steel industry4 and from the 1975 Arthur D. Little
. d 42
study of the steel ln ustry. A word of explanation is in
order.
In the original Battelle study, costs were related
to volumetric flow rates for various applications.
Here
costs are related to the filtration area in order to elimin-
ate effects of differences in air-to-cloth ratios.
To
illustrate this effect, consider that a baghouse of 100,000
ft2 filtration area can clean 300,000 acfm of canopy air
from an electric arc furnace shop, but only 150,000 acfm of
gas from a sintering strand wind box.
Cost figures from the original Battelle report were
updated according to the following:
1. Material cost was assumed to be 10 percent textile,
90 percent nontextile. The nontextile cost portion was
assumed to be 35 percent labor and 65 percent iron and
steel. Textile costs were escalated by the ratio of
indexes from 1969 to 1976 for "man-made fiber textile
products" from the U.S. Department of Labor.43 Iron
and steel prices were inflated by the ratio of indexes
for "iron and steel" from the same source. Labor was
escalated by using the ratio of "average weekly earn-
ings for manufacturing nonsupervisory workers" from
1969 to 1976, as published by the U.S. Department of
Labor.44
2. Job site construction labor was escalated by the
ratio of "average weekly earnings of contract con-
struction nonsupervisory workers" from 1969 to 1976, as
published by the U.S. Department of Labor.44
2-114
-------
3. Engineering charges were escalated by the ratio of
"engineers' salary" from 1969 to 1976, as reported by
the U.S Department of Labor.45
4. Electrical power charges were inflated by the ratio
of "average industrial charge for electrical power for
users of 200,000 kWh/yr and above" from 1969 to 1976,
as published by the Federal Power Commission.46
5. Operating and maintenance labor was inflated by the
ratio of "average weekly earnings for manufacturing
nonsupervisory workers" from 1969 to 1976, as published
by the u.s. Department of Labor.
6. Depreciation was charged to operation and main-
tenance based on a 10-year straight-line amortization
of the total installed costs.
7. Capital charges were applied to operation and
maintenance at 10 percent/yr of the total installed
cost.
In 1973 the American Iron and Steel Institute author-
ized Arthur D. Little,
I nc . ,
(ADL) to undertake a study of
the cost impact on the iron and steel industry of complying
with existing and proposed air emission and water effluent
regulations of the EPA.42 As part of this study ADL gen-
erated the following algorithms:
Equation 1
I = 179.8Ql.76 where:
I = total installed cost of high com-
plexity fabric filter system, 1972 $
Q = gas volume, scfm
Equation 2*
OC = Q [22.27x + 0.072y + 0.15] + 0.051
where:
OC = annual operating cost, $
*
Equation 2 is condensed from the original which was designed
to accomodate a variety of control devices.
2-115
-------
x = power cost, $/kWh
y = labor rate, $/man-h
I = total installed cost, $
Because these algorithms are insensitive to actual gas
volume flow rate and air-to-cloth ratio (both of which are
fundamental in the design of a real system), and because
Equation 1 generates 1972 costs, the above algorithms have
been modified according to the following considerations:
1. Fabric filters operate at 275°F, the maximum tem-
perature of most common synthetic fabrics (i.e., no
cooling is involved; therefore, no cooling cost penalty) .
2. Fabric filters operate at a 2.5:1 air-to-cloth
ratio.
3. Depreciation has been deleted from capital cost and
charged to operation and maintenance on a 10-year
straight line basis.
4. Capital charges have been deleted from capital
investment and charged to operation and maintenance at
10 percent/yr.
5.
Power cost is
$0.037/kWh.
6.
Direct labor is $4.98/man h.
7. General cost inflation compounded from 1972 to
1976 is 6 percent/yr.
2-116
-------
10.
REFERENCES - SECTION 2.0
1.
Letter from PEDCo to MRI, September 23, 1976.
2.
Schueneman, J.J., et al., "Air Pollution Aspects of the
Iron and Steel Industry," Public Health Service Publi-
cation No. 999-AP-l, June 1963.
3.
"Background Information for Establishment of National
Standards of Performance for New Sources--Iron and
Steel Industry," Draft Report by Environmental Engi-
neering, Inc., and Herrick Associates for EPA, March
1971.
4.
Varga, J., Jr., and H. W. Lownie, Jr., "A System Anal-
ysis Study of the Integrated Iron and Steel Industry,"
Prepared by Battelle Memorial Institute for NAPCA,
Contract No. PH 22-68-65, May 1969.
5.
Varga, J., Jr., "Control of Steel Plant Scarfing Emis-
sions Using Wet Electrostatic Precipitator," EPA Publi-
cation No. EPA-600/2-76-054, March 1976.
6.
Weast, T.E., L.J. Shannon, P.G. Gorman, and C.M.
Guenther, "Fine Particulate Emission Inventory and
Control Survey," Midwest Research Institute, Kansas
City, Missouri. PB 234 156, January 1974, p. 69.
7.
"Particulate Pollutant System Study: Volume III--
Handbook of Emission Properties," prepaIed by Midwest
Research Institute for EPA, Contract No. CPA 22-69-104,
May 1971.
8.
Personal communication with EPA personnel.
9.
Thaxton, L.A., "Kish and Fume Control and Collection in
a Basic Oxygen Plant," JAPCA, 20(5), 293-296, May 1970.
Particulate Pollutant System Study, Volume III, Hand-
book of Emission Properties. U.S. Environmental
Protection Agency. EPA No. CPA 22-60-104, 1971.
2-117
-------
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
Flux, J.H. "Containment of Melting Shop Roof Emissions
in Electric Arc Furnace Practice." Ironmaking and
Steelmaking (Quarterly), 1974.
Varga, J., Jr., "Control of Reclamation (Sinter) plant
Emissions Using Electrostatic Precipitators," EPA
Publication No. EPA-600/2-76-002, January 1976.
Nowak, T.T., "Sinter Plant Baghouse," AIME Ironmaking
Proceedings, 31, 75-84, 1972.
Steiner, B.A., and J.J. Thompson, Armco Steel Corpora-
tion, Middletown, Ohio. Wet Scrubbing Experiences for
Steel Mill Applications, Presented at the Second
Symposium on Fine Particle Scrubbing, May 2-3, 1977,
New Orleans, Louisiana.
Jaasund, S.A. and M.R. Mazer, Bethlehem Steel Corpora-
tion, Bethlehem, Pennsylvania. "The Application of Wet
Electrostatic Precipitators for the Control of Emis-
sions from Three Metallurgical Processes." Presented
at Particulate Collection Problems Using Electrostatic
Precipitators in the Metallurgical Industry, June 1-3,
1977.
"Background Information for Proposed New Source Per-
formance Standards: Iron and Steel Plants," Vols. 1 and
2, EPA Publication Nos. APTD-1352a and APTD 1352b, June
1973.
"Background Information for Standards of Performance:
Electric Arc Furnace in the Steel Industry," Vols. 1
and 2, EPA Publication Nos. EPA-450/2-74-107a and EPA-
450/2-74-017b, October 1974.
Venturini, J.L., "Operating Experience with a Large
Baghouse in an Electric Arc Furnace Steelmaking Shop,"
JAPCA, 20(12), 808-813, December 1970.
"Background Information for Standards of Performance:
Electric Submerged Arc Furnaces for Production of
Ferroalloys," Vols. 1, 2, and 3, EPA Publication Nos.
EPA-450/2-74-018a, October 1974; EPA-450/2-74-018b,
October 1974; and EPA-450/2-74-018c, April 1976.
Deutsch W., Ann der Physik 68:335 (1922).
2-118
-------
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
31.
32.
..
Matts, S. and P-O Ohnfeldt, "Efficient Gas Cleaning
with SF Electrostatic Precipitators."
Pennsylvania Department of Environmental Resources,
Rules and Regulations.
Marchello, J.M. and J.J. Kelly, Gas Cleaning for Air
Quality Control, Marcel Dekker, New York, 1975, p. 219.
Varga, J. et al., "A Systems Analysis Study of the
Integrated Iron and Steel Industry," Battelle Memorial
Institute, Columbus, Ohio, prepared for HEW (May 15,
1969), PB 184 577, p. IV-4.
Oglesby, S. and G.B. Nichols. "A Manual of Electro-
static Precipitator Technology, Part II: Application
Areas," Southern Research Institute, Birmingham,
Alabama, August 25, 1970, PB 196 381.
Peterson, H.W., "Gas Cleaning for the Electric Furnace
and Oxygen Process Converter," AIME Electric Furnace
Proceedings, 14, pp. 262-271 (1956).
Smith, J.H., "Air Pollution Control in Oxygen Steel-
making," AIME Open Hearth Proceeding, 44, pp. 351-357
(1961) .
Op. Cit., Reference 12, pp. 8-9.
~ Cit., Reference 13, pp. 50, 62-65.
Gooch, J.P. and A.H. Dean, "Wet Electrostatic Precipi-
tator System Study," SRI, Birmingham, Alabama, EPA-
600/2-76-142, PB 257 128, May 1976.
Hill, R.L. "Electrostatic Precipitation of Scarfer
Fume," Western Precipitation Division of Joy Manufac-
turing Co., presented at 1977 Spring Convention of the
Association of Iron and Steel Engineers, Dearborn,
Michigan, April 25-27, 1977.
Bakke, E. "The Application of Wet Electrostatic Pre-
cipitators for Control of Fine Particulate Matter."
Paper presented at the Symposium on Control of Fine
Particulate Emissions from Industrial Sources for Joint
US-USSR Working Group, Stationary Source Air Pollution
Control Technology, San Francisco, California. January
15-18, 1974.
2-119
-------
33.
34.
35.
36.
37.
38.
39.
40.
41.
42.
43.
44.
45.
46.
Bakke, E. "Application of Wet Electrostatic Precipita-
tors for Control of Emission from Soderberg Aluminum
Reduction Cells," Mikropul, Summit, N.J. Presented at
the SIME meeting, Dallas, Texas, January 15-18, 1974.
"McIlvaine Wet Scrubber Manual," Chapter III, p. 47.0.
"McIlvaine Wet Scrubber Manual," Chap. VII, p. 7.0.
Brink, J.A., Jr., and C.E. Contant, Ind. Eng. Chern.
~(8) 1157, 1958.
Calvert, S., D. Jundgren, and D.S. Mehta, JAPCA 22(7)
529, 1972.
Semrau, K.T.
JAPCA, 10(3) 200, 1960.
Gorman, P.G., A.E. Vandergrift, and L.J. Shannon.
"Fabric Filters in Gas Cleaning for Air Quality Control,"
Marchello, J.M. and J.J. Kelly (eds.). Marcel DeKker,
Inc., New York, 1975.
McKenna, J.D., J.C. Mycock, and W.o. Lipscomb. "Apply-
ing Fabric Filtration to Coal-Firing Industrial Boilers -
A pilot Scale Investigation," EPA-650/2-74-048-a,
August 1975.
Billings, C.E., and J. Wilder. Handbook of Fabric
Filtration Technology, Volume 1. Prepared by GCA
Corporation for National Air Pollution Control Adminis-
tration, Contract No. CPA-22-69-38, December 1970.
"Steel and the Environment - A Cost Impact Analysis,"
Report Commissioned by AISI and prepared by Arthur D.
Little, Inc. 1975.
Wholesale Prices and Price Indexes, u.S. Department of
Labor, Bureau of Labor Statistics, 1976.
Employment and Earnings, U.S. Department of Labor,
Bureau of Labor Statistics, 1976.
National Survey of Professional, Administrative, Tech-
nical and Clerical Pay, u.S. Department of Labor,
Bureau of Labor Statistics, 1976.
Typical Electrical Bills, Federal Power Commission,
1976.
2-120
-------
3.0
OPERATION AND MAINTENANCE AND COMMON MALFUNCTIONS
OF PARTICULATE CONTROL DEVICES ON IRON,
STEEL, AND FERROALLOY APPLICATIONS
As with other complex equipment, the successful func-
tioning of pollution control systems depends not only on
sound design and proper installation, but also on proper
operation.
Ideally, plant personnel who use and maintain
the equipment should understand the engineering principles
on which the system is based and apply this knowledge both
in routine operation and maintenance and in emergency
situations.
3.1
OPERATION AND MAINTENANCE OF ELECTROSTATIC PRECIPITATORS
Problems with electrostatic precipitators can arise
when the equipment is brought on line and also after ex-
tended operation.
Since the possible causes of poor per-
formance are diverse, it is impractical to outline a single
procedure for determining the nature of a specific problem.
When a malfunction occurs, the operator must depend on his
theoretical understanding of the equipment, backed by his
practical experience.
This section and related appendices,
therefore, provide background information on precipitator
3-1
-------
operation, together with detailed maintenance and trouble-
shooting procedures for the major component categories.
Since the basic precipitator function is that of charging
and collection of particles, the components and controls
associated with the transformer-rectifier sets, rappers, and
vibrators constitute the heart of the system.
The procedures presented in this report have been
abstracted from Research Cottrell manuals.
Although other
manufacturers might recommend different procedures as dic-
tated by details of system design, most of the major com-
ponents and therefore the operating procedures are similar.
Where possible, the recommended practices are interpreted in
terms of their effect on equipment performance.
3.1.1
Background on Precipitator Operation
Electrostatic precipitation requires two groups of
equipment:
(1) the precipitation chamber, in which the
suspended particles are electrified and removed from the
gas, and (2) the high-voltage transformer and rectifier,
which function to create the strong electrical field in the
chamber.
The chamber consists of an outside shell (precipitator
shell) made of metal, tile, or other material.
Suspended
within the shell are grounded steel plates (collecting
electrodes) connected to the grounded steel framework of the
3-2
-------
supporting structure and to an earth-driven ground.
Sus-
pended between the plates are metal rods or wires (discharge
electrodes) insulated from the ground.
They are negatively
charged at voltages ranging from 70,000 to 105,000 V.
The
great voltage difference between the wires and the collec-
ting plates sets up a powerful electric field, which imparts
a negative charge to the solid particles suspended in the
gas stream.
understanding this phenomenon requires some
knowledge of electricity and chemistry; for practical pur-
poses it is enough to know that the particles become elec-
trostatically charged.
The negatively charged particles are
attracted to the collecting plates, which are at ground
potential.
The particles cling to the collecting plate and
become electrically inert.
Removal of the collected dust is
best achieved by rapping the plates at an intensity and
frequency that causes the dust to fall from the plates in
sheets into a receiving hopper.
Rapping that is too intense
or too frequent will clean the collection plate, but it may
also cause reentrainment of the collected dust into the gas
stream.
Gas that enters the precipitator laden with particles
is channeled through the precipitator outlet, while the dust
collected in the hopper is removed by a dust handling
system.
3-3
-------
Figure 3-1 illustrates the major components of an
electrostatic precipitator with top housing (as opposed to
insulator compartments, which are used primarily for higher
temperature precipitator applications) .
Appendix C-l
contains a more detailed explanation of precipitator opera-
tions, including subsystems and components such as trans-
former-rectifiers, rappers, vibrators, the upper precipita-
tor, discharge wires, collecting plates, and the lower
precipitator.
The next section describes the fundamental
operational procedures necessary for routine usage.
3.1.2
Precipitator Start-up and Shutdown Procedures
Operation of an electrostatic precipitator involves
dangerously high voltage.
Although all practical safety
measures are incorporated into the equipment, extreme cau-
tion should be exercised at all times.
An electrostatic
precipitator is, in effect, a large capacitor which, when
deenergized, can retain dangerous electric charges.
Ground-
ing mechanisms provided at each access point should there-
fore be used before entering the precipitator.
3.1.2.1
Preoperational Checklist - Before placing the
equipment in operation, plant personnel should perform a
thorough check and visually inspect the system components in
accordance with the manufacturer's recommendations.
A
complete checklist of items is presented in Appendix C-2.
3-4
-------
Transformer Rectifier
I~ .
~.,
~.~
0.,
Top End
Frames
Top Housing
High Voltage
Conductor
Perforated
Distribution
Plates
Bottom End
Frames
Access Door
Between
Collecting Plate
Sections
Precipitator
Base Plate
Slide Plate
Package
Support Structure
Cap Plate
Steadying Bars
Collecting
Electrodes
Figure
3-1.
Typical electrostatic precipitator with top housing.
3-5
-------
Some of the major items that should be checked are summar-
ized below:
Control unit
Proper connections to control
Silicon rectifier unit
Rectifier-transformer insulating liquid level
Rectifier ground switch operation
Rectifier high-voltage connections made
High-voltage bus transfer switch operation
High-tension connections
High-tension bus duct
Proper installation
Vent ports properly installed
Equipment grounding
Precipitator grounded
Transformer grounded
Rectifier controls grounded
High-tension guard grounded
Conduits grounded
Rapper and vibrator ground
jumpers in place
3.1.2.2
Air Load Tests - After the precipitator is inspec-
ted (i.e., preoperational check adjustment of the rectifier
control, and check of safety features) the air load test is
performed.
Air load is defined as energization of the
precipitator with minimum flow of air (stack draft) through
the precipitator.
Before introduction of an air load or gas
load (i.e., entrance of dust-laden gas into the precipita-
tor), the following components should be energized:
3-6
-------
Collecting plate rappers
Perforated distribution plate rappers
High-tension discharge electrode vibrators
Bushing heaters, housing/compartments
Hopper heaters, vibrators, level indicators
Transformer rectifier
Rectifier control units
Ventilation and forced-draft fans
Dust-conveying system
The purpose of the air load test is to establish ref-
erence readings for future operations, to check operation of
electrical equipment, and to detect any improper wire clear-
ances or grounds not discovered during preoperation inspec-
tion.
Air load data are taken with the internal metal
surfaces clean.
The data consist of current-voltage charac-
teristics at intervals of roughly 10 percent of the T-R
milliampere rating, gas flow rate, gas temperature, and
relative humidity.
For an air load test the precipitator is energized on
manual control.
The electrical characteristics of a pre-
cipitator are such that no sparking should occur.
If spark-
ing does occur, an internal inspection must be made to
determine the cause.
Usually the cause is (1) close elec-
trical clearances and/or (2) the presence of foreign matter,
such as baling wire, that has been left inside the precipi-
tator.
After the precipitator has been in operation for some
time, it may be necessary to shut it down to perform inter-
3-7
-------
nal inspections.
This provides a good opportunity to take
air load data for comparison with the original readings.
3.1.2.3
Gas Load Tests - The operation of a precipitator on
gas load differs considerably from operation on air load
with respect to voltage and current relationships.
The air
load test is characterized by high current and low voltage,
whereas the converse is true in the case of the gas load
test.
The gas load effect governs operation of the precipi-
tator and the final setting of the electrical equipment.
In general, optimum precipitator efficiencies are
obtained when the d.c. voltage applied to the precipitator
is just at the threshold of sparking.
The spark rate at
this point will be on the order of 50 to 150 sparks/min and
may be controlled at this level with automatic control.
3.1.2.4
Shutdown Procedure - To shut down the precipitator,
the operator opens the control circuit start/stop switch and
then opens the main circuit breaker.
Before entering the
system, the operator should follow all recommended safety
procedures. Proper grounding of all precipitator parts is
important. The key interlock system prevents access to the
interior of each transformer-rectifier ground switch enclo-
sure until the individual set is deenergized and the ground
connections are made.
This system prevents access to the
interior of the precipitator, including top housing or
3-8
-------
insulator compartments, precipitator roof doors, side doors,
and hopper doors, until the transformer-rectifiers of each
precipitator are deenergized and ground connections are
made.
Purging the system with ambient air may also be
necessary from the standpoint of the safety of plant per-
sonnel who must inspect the precipitator internally.
3.1.3
Inspection and Maintenance During Normal Operation
A section has been included in Appendix C-3 consisting
of detailed directions for plant personnel who are assigned
responsibility for inspection and maintenance of precipi-
tator systems.
These instructions, while abstracted from
one manufacturer's operation and maintenance procedures, are
representative of the level of inspection and maintenance
required for successful precipitator operation with minimum
down time.
Although electrical portions of a precipitator
system require very little maintenance, the items enumerated
in Appendix C-3 should be attended regularly if the equip-
ment is to give optimum service.
It is considered good
practice to assign one operator on each shift the task of
checking and recording data on electrical equipment at the
start of the shift.
The cycle of inspection and maintenance during normal
operation includes the following system components:
Transformer-rectifier sets and associated equipment
and controls
Transformer enclosure
3-9
-------
Overhead half wave/full wave switchgear
Pipe and guard
Plate rappers
Vibrators
Top housing
Insulator components
Plate hanger anvil beam
Upper high-tension frame
Discharge wires
Collecting plates
Lower precipitator steadying frame
Hoppers and conveyors
Precipitator shell
3.1.4
Maintenance Schedule and Troubleshooting
A detailed list of maintenance procedures that should
be performed on a daily, weekly, monthly, quarterly, semi-
annual, and annual basis, is likewise presented in Appendix
C-3 as an example of the level of effort typically required
to maintain optimum operation.
For example, the annual
inspection covers the following conditions or subsystems:
Unusual dust accumulation
Discharge wires
Alignment of plates and wires
High-tension and plate rappers
High-tension frame support bushing
High-voltage electrical control cabinet
Transformer-rectifier sets
Table C-3-1 in Appendix C-3 lists a number of troubleshoot-
ing measures recommended by precipitator manufacturers for
determining the most probable cause of precipitator prob-
lems, and Table C-3-2 gives an example of the frequency of
failure and time required to repair various components of a
typical industrial ESP.
3-10
-------
3.1.5
General Precipitator Malfunctions
Many precipitator components are subject to failure or
malfunction, which can lead to increased emissions.
Faulty
design, installation, or operation of the precipitator can
cause these malfunctions.
The reduction in efficiency is
variable and depends on the severity of the malfunction.
Many malfunctions are interrelated, with one malfunction
causing another.
A brief discussion follows on common
precipitator malfunctions and how they affect emissions.
The most common malfunctions associated with precipita-
tors stem from broken discharge wires and plugged dust
hoppers.
Other problems result from failure of rappers or
vibrators and suspension insulators.
Broken Discharge Wires - When a discharge electrode
breaks, it usually causes an electrical short circuit between
3.1.5.1
the high-tension discharge wire system and the grounded co1-
1ection plate.
This electrical short trips the circuit
breaker, disabling a section of the precipitator.
E1ectri-
ca1 erosion, mechanical fatigue, and dust hopper buildup
are three common causes of electrode wire failure, along
with many others.
The impact of wire failures on precipitator availability
and efficiency is a function not only of the frequency of
failure, but also the degree of sectiona1ization and the
3-11
-------
difficulty involved in removing failed wires during unit
operation.
Most precipitators do not have suitable isola-
tion dampers to allow safe access to the interior while
the process is in operation; thus, the unit must shut down
for removal of these broken wires.
Inadequate sectionaliza-
tion causes a greater drop in efficiency, and a number of
wire breaks in different sections may seriously impair the
operation of the precipitator.
Design methods that can reduce wire failures include
fabricating discharge electrodes of the proper materials
and applying shrouds and rounded surfaces to reduce localized
k' 1
spar lng. Frequent inspection can help prevent failures
through detection of problems such as inadequate rapping
and ash hopper buildup before they cause wires to fail.
Because of the great number of wires in a precipitator,
some wire failure is to be expected, even with a good
operation and maintenance program.
3.1.5.2
Collection Hoppers and Dust Removal - Inadequate
dust removal is a major cause of precipitator malfunctions.
Most problems associated with hoppers are related to proper
flow of the dust.
Improper adjustment of the hopper vibra-
tors or failure of the conveyor system is usually the cause
of the hoppers failing to empty.
Low flue gas temperature,
which permits moisture condensation, can also cause plugging
3-12
-------
of the hopper.
This results from carrying the process exit
gas temperature too low or from excessive leakage of ambient
air into the hopper.
Buildup of dust can cause short-circuiting of the pre-
cipitator.
It can also cause excessive sparking, which
erodes electrodes and sometimes pushes internal components
out of position, causing misalignment that can drastically
affect performance.
Reentrainment of dust also increases
emissions.
Since dust buildup can affect so many of the precipita-
tor components, a proper inspection schedule of the dust
removal system is an important factor in eliminating or
minimizing many common precipitator malfunctions.
3.1.5.3
Rappers or Vibrators - Poor performance can result
from rapping forces that are either too mild or too severe.
Although some reentrainment always occurs, effective rapping
minimizes the amount of material reentrained in the gas
stream.
Rapping that is too intense and frequent results in
a clean plate, which causes the collected dust to become
reentrained rather than falling in sheets into the hopper.
Inadequate rapping of the discharge electrode results in a
heavy dust buildup with localization on the corona, excessive
sparking, impaired performance, and possible grounding of
the high-voltage system.
3-13
-------
The first step in dealing with problems related to
rappers and vibrators is to determine the adequacy of the
rapping acceleration.
An accelerometer can be mounted on
the plates for this purpose, and an optical dust-measuring
instrument in the gas stream can also be used to adjust the
rappers.
If discharge electrodes are kept as clean as possible
with minimum reentrainment, rapping intensity is then
limited only by the possibility of mechanical damage to the
electrodes and support structure.
3.1.5.4
Insulator/Bushing Failure - suspension insulators
are used to support and isolate the high-voltage parts of
precipitators.
Inadequate pressurization of the top housing
of the insulators can cause dust deposits and/or moisture
condensation on the bushing, which may result in electrical
breakdown.
Fouling and cracking of insulators reduce the
effective voltage levels and collector performance, but
rarely decommission a bus section.
Corrective or preventive measures include inspection of
ventilation fans for the top housing and availability of a
spare fan for emergencies.
Frequent cleaning and checking
the fans for damage from vibration are also necessary to
ensure trouble-free operation.
3-14
-------
Table C-3-3 in Appendix C-3 lists common precipitator
malfunctions, their causes, the effects on emissions, and
the corrective action required.
3.1.6
Operation and Maintenance Problems Which are Specific
to Iron, Steel, and Ferroalloy Precipitator Applica-
tions
The information presented in the preceding sections is
typical of most precipitators.
Table 3-1, however, illus-
trates the important differences between utility and iron,
steel, and ferroalloy precipitators.
Corrosion is clearly one of the basic problems contrib-
uting to loss in efficiency-
Corrosion attack causing loss
of collection area will probably increase sparking at the
end of the corroded plate, which temporarily collapses the
field and degrades performance.
In addition, loss of plate
area can cause secondary flows (cross-flows between gas
passages) which can result in particle reentrainment.
Localized turbulence at the corroded surface can also
adversely affect particle attachment and the quiescent zone
of particle migration near the plate surface.
Anticipation of severe corrosion potential is required
so that adequate protection can be provided for in the
initial design.
Also in this connection, all points of alr
in-leakage should be eliminated.
Cracked hopper welds and
missing bolts should be replaced.
Bolts on hopper doors
should be tight and all seals inspected.
3-15
-------
Table 3-1.
COMPARISON OF DESIGN AND OPERATIONAL PROBLEMS OF
UTILITY,
IRON,
STEEL, AND FERROALLOY ELECTROSTATIC PRECIPITATORS
Item
Utilities
Iron/Steel/Ferroalloy
Lubrication:
Screw bearings
Yes
Corrosion from air inleakage
Mild
Severe
Corrosion environment
Explosive environment
so] (Mild)
None (Rare)
S0], CI (can be of considerable severity)
CO, H2' CH4
Purge air
Air
Spent gas, natural gas may be used
(air cannot be used if explosive gas/02
ratios are likely to be met)
w
I
.......
0"1
Explosions from air inleakage
None (Rare)
Possible
Precipitator material selection
Mild steel
Stainless steel;
must be given to
corrosion, e.g.,
steel)
(special consideration
minimize rate of
Cl attacks stainless
Dust buildups
Normal rapping
These dusts can be very tenacious
Dust removal
Pyramidal hoppers,
Vacuum discharge
Trough hoppers, with rotary or double-
dump valves or pyramidal hoppers with
screw conveyors
Insulation
Required to minimize
temperature drop
Required to minimize cold spots and
thus corrosion particularly in corners,
roofs, and doors of hoppers
-------
In some cases the discharge electrodes can be attacked
by corrosion.
Ferrules on wires, in particular, may show
significant corrosion.
This could be the result of a
galvanic couple between the discharge electrode and the
ferrule, halogenic attack on the ferrule (which could lead
to stress corrosion), or acid attack on the ferrule.
To
remedy this, replacement wires for such an installation
should have ferrules made of the same material as the
discharge electrode (mild steel basic bright wire) .
This
change will not eliminate corrosion of the discharge elec-
trodes, but it will ensure that the rate of corrosion for
the discharge wire and ferrule will be equal and probably
slower.
Another problem area is high-voltage tracking on the
insulators as a result of the formation of condensables in
the insulator compartments of installations in areas with
cold, damp, winter climates.
In such cases, the pressure
and temperature of the insulator compartment stearn coil
supply can be increased to prevent condensate formation.
In
addition, the purge lines might be stearn-traced and re-
insulated.
A 1974 survey by the TC-l cornrnittee2 seems to confirm
the above observations.
In a comparison of precipitator
maintenance problems for various industries, respondents
3~17
-------
from the metallurgical industry indicated that rappers/
vibrators presented the largest maintenance problems,
followed by insulators and discharge electrodes, collecting
plates, and dust removal systems.
Table 3-2 compares main-
tenance problems for utility and metallurgical precipita-
tors.
3.2
WET PRECIPITATORS
Description
3.2.1
As discussed in Section 2.4, several types of wet
precipitators are available.
Basically, they can be cate-
gorized structurally as to whether they are the plate-type
or pipe-type, the latter being used principally on scarfing
operations, and also with regard to the method of water
introduction.
The pipe-type usually has a weir-overflow
arrangement or a continuous spray with a downward vertical
gas flow.
Plate units have either a combination presatura-
tion continuous spray or a spray with intermittent wash and
horizontal or vertical gas flow.
Figure 3-2 presents illus-
trations of the above three types of wet precipitators.
Realizing 1) that there are a number of different
configurations which wet precipitators can have; 2) that
there are a limited number of applications as compared to
more conventional devices; and 3) that generalized operating
and maintenance practices have not been disclosed in the
3-18
-------
Table 3-2.
COMPARISON OF MAJOR MAINTENANCE PROBLEMS FOR
UTILITY AND METALLURGICAL PRECIPITATORSa
w
I
.......
I.D
Dust
Discharge Rapper/ Collecting removal
electrodes, vibrator, plates, system, Insulators,
Industry % 9, % % %
o
Utilities b 35.2 5.7 13.6 31.8 1.1
Metallurgical c
25.0 33.3 22.2 19.4 25.0
a Indicates users' opinion of which category the major problem area in
his experience. (Reference 2)
b
Based on 63 utilities reporting on 88 precipitators.
c
Based on 22 metallurgical processes reported on 36 precipitators.
-------
.Tn ~,
/
A. Plate type
(horizontal flow)
"I~
WOLTA06E
LEADS
!lATE" ""ES
C. Conventional pipe type
W FLOW
GAS FLOW
HOOD MD STACK
TRANS IT JON
PRECIPITATOR
SECTION
TYPICAL METAL
ELECTRODE
DISCHARGE CAGE
CONTINUOUS FILM OF
LIQUOR FlOWS OOWN
POSITIVE COLLECTION
ELECTRODE SURFACES
(CYliNDER WAllS)
VENTURI INLET TO
PRECIPITATOR SECTION
BASE
R. Concentric plate type
Figure 3-2.
Three types of wet electrostatic precipitators.
3-20
-------
literature; only typical points will be covered in this
section.
Where components of a wet precipitator are similar to
those of a dry precipitator, the operation and maintenance
procedures outlined in Section 3.1 can be considered gener-
ally applicable.
3.2.1.1
Plate-type (horizontal flow) - The effluent gas
stream is usually preconditioned to reduce temperature and
achieve saturation.
Upon entering the inlet nozzle, the gas
velocity decreases due to the diverging cross section.
At
this point, additional sprays may be used to create good
mixing of water, dust, and gas as well as ensuring complete
saturation before the gas enters the electrostatic field.
In addition, baffles are often used to achieve good velocity
distribution across the inlet of the precipitator.
Within the charging section, water is sprayed in near
the top of the plates in the form of finely divided drops.
They become electrically charged and are attracted to the
plate.
In this manner, the plates obtain an even coating of
water.
Simultaneously, solid particles are charged and
"migrate" and attach to the plates.
Since the water film is
moving downward by gravity on both the collecting and
discharge electrodes, the particles are captured in the
water film, which is disposed of from the bottom of the
precipitator in the form of slurry.
3-21
-------
3.2.1.2
Concentric-Plate-Type - This design, applied to
scarfing applications, utilizes an integral tangential
pre scrubbing inlet chamber followed by a vertical wetted-
. . h b 3,4
wall concentric ring electrostatic preclpltator c am er.
The concentric cylindrical collection electrodes are
wetted by fluids dispensed at the top surface of the collec-
tion electrode system.
The discharge electrodes consist of
an expanded metal system with uniformly distributed corona
points formed on the mesh background.
This type of dis-
charge electrode system is supposed to provide a combination
of a high, nearly uniform electric field associated with a
parallel plate system, and a nearly uniform corona current
density distribution associated with the closely spaced
corona points on the electrode system.
Higher gas flows can
be handled by the addition of more concentric electrode
systems and by increasing the length of each electrode.
. 5
3.2.1.3 Conventional Plpe-Type - For scarfing applications
the pipe-type configuration is preferred to the plate-type,
since it appears to distribute water more adequately during
the washing cycle.
Weirs may also be used in some cases to
ensure that the tubes are kept clean.
The actual system consists of a number of vertical
collecting pipes.
In the center of each is a discharge
electrode (wire type), which is attached to the upper
3-22
-------
framework and held taut by a cast iron weight at the bottom.
The lower steadying frame keeps the weights and thereby the
wires in position.
The upper frame is suspended from high voltage in-
sulators housed in compartments on top of the precipitator
shell (casing).
Heating and ventilating systems help to
prevent moisture and dust from accumulating in the insulator
compartments.
The washing system usually consists of internal nozzles
located at the top of the plates.
At specified intervals
(after approximately 20 blooms have been scarfed) the
nozzles provide a thorough washing of the tubes.
While the
washing is taking place, the louver damper to the exhaust
fan is closed to prevent droplet carry-over.
3.2.2
Operation
3.2.2.1
Preoperation - Before initiating the start-up
procedure, all of the major items of equipment, connecting
pipes, lines, and auxiliaries must be inspected, cleaned,
and tested.
Checkout of the following items is suggested following
the recommendations of the manufacturer:
Water Spray System --
Check for adequate flow, leaks, and pressures in all
lines.
3-23
-------
Check orientation of nozzles.
Inspect drain system.
Check all clearances between piping and high voltage
(H.V.) system.
Precipitator Internals --
Inspect all H.V. system connections to transformer-
rectifier (T-R) sets, bus ducts, and grid.
Insulators should be checked for cleanliness, cracks,
and chips.
H.V. bus ducts to insulator connection should be
tight.
Both heaters and pressurizing fan should be in proper
operating condition.
Access doors and plates must have good seals and good
interlock contact.
T-R Sets --
Check oil level, tight electrical connections, and
proper operation of ground switch.
Control Panels --
All fuses and indicator lamps for all H.V. items,
heaters, and blowers should be functioning.
3.2.2.2
Start-up
Heaters on.
Pressure blower energized.
H.V- circuit breaker on.
Activate spray system allowing sufficient time to
clear air from lines.
Open damper to introduce effluent gases.
3~24
-------
3.2.2.3
Shutdown
Inlet damper closed.
Deenergize precipitator.
Shut down spray system.
Heater and blower system should remain energized
to prevent accumulation of moisture on the H.V.
insulators.
3.2.2.4
Normal Operation
Heaters and blowers are energized normally.
Spray system always activated just prior to energizing
the H.V. system.
Gas flow monitored by damper.
Water pH must be monitored at the waste discharge.
3.2.3
Inspection and Maintenance During Normal Operation
Actual inspection and maintenance practices are quite
specific to the particular system used and the manufac-
turer's instructions should be closely followed.
Since
precipitators operate with very high voltage, precipitator
internals must be properly grounded.
Before anyone enters
the precipitator, the gas flow must be turned off and the
unit cooled to a safe temperature.
Protective apparatus
such as a respirator may be needed.
General inspection and maintenance practices are
briefly outlined below.
3-25
-------
3.2.3.1
Mechanical Maintenance - All internal components
should be checked for alignment, excessive dust buildup,
tight bolts, structurally sound welds, and general struc-
tural integrity of the cross bracing and other support
members.
Since the support insulators perform such a vital
function in electrostatic precipitation, the structural
support end of the H.V. insulator in the H.V. housing must
be thoroughly inspected for cracks, chips, etc.
3.2.3.2
Water System
- All pumps, internal spray nozzles,
and related valving and piping should be checked.
Nozzles
are subject to plugging and therefore should be routinely
disassembled, cleaned, and/or replaced as necessary.
Main
water pressure supply pumps and all pipe joints must be
checked for leaks and all couplings for tightness.
Nozzle
orientation should be checked to ensure that the intended
spray pattern is being achieved.
3.2.3.3
Electrical System
General areas to check include
the H.V. control panel, the heater and blower control panel,
H.V. insulators, heater system thermostats, T-R sets, and all
related electrical connections.
Where wet precipitator
systems contain items similar to dry precipitators, many of
the inspection and maintenance practices outlined in Appen-
dix C-2 will apply.
3-26
-------
3.2.3.4
Schedule - The items outlined for maintenance with
their corresponding intervals appear in Table 3-3 by permis-
sion of MikroPul.
3.2.4
Characteristic Maintenance Problems of Wet ESP's
Pilot tests of the wet ESP on Bethlehem Steel's Lacka-
wanna,
New York, plant showed that while using recirculated
acidic water, the potential for corrosion of such reasonably
4
priced alloys, such as 3l6L stainless was great.
Operating
in a pH controlled mode, however, of greater than 7.0,
resulted in buildup of calcium and magnesium carbonate scale
on spray nozzles and other critical components of the wet
ESP, rendering it inoperable.
Water distributor plugging
and solids deposition resulting from the recirculation of
the acidic solids-laden liquor were also encountered, with
pilot testing of a second brand of wet ESP-
During full-scale testing, however, it was found that
with regular weekly maintenance which included a general
cleaning and inspection, the wet ESP performed very success-
fully.
It was noted that regular attention to the recircu-
lated water system was necessary to maintain the strict
water quality requirements necessary for successful wet ESP
. 4
operat10n.
3-27
-------
Table 3-3.
SUGGESTED MAINTENANCE SCHEDULE FOR ~'lET PRECIPITA'!'ORS
Component
Interval
Maintenance procedure
Key interlocks
Yearly
Yearly
Yearly
Ducts and dampers
Quarterly
Quarterly
Precipitator
Quarterly
Quarterly
W
I
N
co
Access doors
Quarterly
Quarterly
Collecting plates and
discharge electrodes
Quarterly
Quarterly
Baffles
Quarterly
Hopper
Quarterly
Quarterly
High voltage system:
T-R set
Quarterly
Yearly
Yearly
Yearly
Yearly
Yearly
Yearly
(Continued)
a.
b.
Check for corrosion and
Check that key fits and
as required.
Check proper positioning
of dust caps.
clean.
turns easily.
Lubricate
c.
a.
Open and close dampers. Operation must be smooth
and positive.
Check ducts for an accumulation of dust. Clean
as necessary.
b.
a.
b.
Check condition of paint and touch up as necessary.
Clean corroded areas inside casing thoroughly.
a.
b.
Check seal for tightness.
Inspect gaskets and replace if damaged.
a.
b.
Clean thoroughly.
Check hanging fixtures for damage.
a.
Clean thoroughly.
a.
b.
Clean thoroughly.
Check drain lines for clogging.
a.
b.
c.
d.
e.
f.
g.
Check oil level. Add oil if required.
Check and tighten electrical connections.
Replace damage wiring.
Clean output bushing.
Check output bushing for cracks or damage.
Check continuity of ground wire.
Check grounding switch for positive action.
-------
Table 3-3.
(Continued)
Component
Maintenance procedure
Interval
High voltage system:
Insulators
Control panel
Heater & blower system:
Hea ters
w
I
N
I.D
Blower
Control Panel
Spray system
Operating checks
Dampers
Quarterly
Quarterly
Quarterly
Quarterly
Yearly
Yearly
Yearly
Yearly
Yearly
Yearly
Yearly
Weekly
Yearly
Yearly
Yearly
Yearly
Yearly
Yearly
Weekly
Weekly
Daily
Daily
Daily
Monthly
a.
b.
c.
Clean thoroughly and dry.
Check for cracks or other damage.
Tighten electrical connections.
a.
b.
c.
d.
e.
Check
Check
Check
Clean
Check
panel switches for positive action.
and tighten electrical connections.
condition of internal components.
inside and outside of panel.
fuses for condition.
a.
b.
c.
Check continuity of each shipment.
Check and tighten electrical connections.
Check clearance around insulator.
a.
b.
Replace air filters.
Check condition of blower and blower motors.
panel switch for positive action.
and tighten electrical connections.
condition of internal components.
inside and outside of panel.
condition of fuses.
a.
b.
Check pressure at nozzle head.
Check spray pattern.
a.
b.
c.
Check pH of water system.
Visually check indicators for burned-out lamps.
Check input and output meters for correct readings.
a.
Lubricate operators.
a.
b.
c.
d.
e.
Check
Check
Check
Clean
Check
-------
3.3
WET SCRUBBERS
3.3.1
Description
Devices of this type use a moving gas stream to atomize
liquid into drops and then accelerate the drops.
Accelera-
tion of the gas provides impaction forces as well as inti-
mate contact with the liquid stream.
The typical gas-
atomized spray devices are the venturi scrubber and the
flooded disc scrubber.
In the venturi scrubber liquid is
introduced at the throat; whereas, in the flooded disc
scrubber liquid is introduced slightly upstream of the
throat, flows over the edge of the disc, and is atomized.
Many differences in design and operation may be noted
within this category with respect to the following:
method
of adjusting pressure drop (the difference being between the
true venturi and the annular orifice); the method of water
introduction (viz. sprayed in or cascaded in); and the
method of moisture elimination (viz. cen~rifugal moisture
eliminator with spinning vanes or multicentrifugals) .
In
any event, most gas atomized spray scrubbers use the conver-
ging and diverging section typical of the venturi throat.
A typical flooded disc scrubber system for particulate
collection consists of a flooded disc scrubber, a mist
eliminator with sump, two recirculation pumps, and one
booster fan or 1.0. fan.
Sometimes a gas prequencher is
required for treating high temperature gas.
3-30
-------
The flooded disc scrubber shown in Figure 3-3 is
composed of a disc in the tapered throat section of a verti-
cal hollow cylinder.
The disc is supported by a pipe and an
open annulus is formed between the wall and the disc.
Atomization takes place at the annulus as gas flows through
it and scrubbing water is simultaneously ejected across the
disc face.
As a result, millions of fine water droplets are
created and used for particle capture in the gas stream.
The particulate collection efficiency of the scrubber de-
pends on the degree of atomization, which in turn is indi-
cated by the pressure drop across the scrubber.
This
pressure drop can be regulated by controlling the vertical
displacement of the disc in the venturi throat section,
either automatically or manually-
The pressure drop for
fine particulate collection must be higher than that for a
coarse particulate if the same collection efficiency is
required.
When particle size is uniform, the pressure drop
for a high collection efficiency has to be higher than that
for a low collection efficiency.
The purpose of the mist eliminator is to separate dust-
laden water droplets from the gas stream by centrifugal
force.
This water then flows by gravity to a sump for
recirculation back to the scrubber.
The recirculated slurry
gradua-lly increases in solids content, the level of which is
3-31
-------
Figure
3-3.
Research
Cottrell
Flooded
Disc
Scrubber.
3-32
-------
monitored by a density control device equipped with an
alarm.
If the level of solids becomes too high, the slurry
can be purged from the system through the discharge vent of
the recycle pump.
Water is lost from the sump during
operation due to slurry purging and water vaporization, the
latter resulting from the contact of hot gas with the scrub-
bing liquor.
The amount of water lost is monitored by a
slurry level control, and if need be a makeup stream is
pumped to the recirculation sump.
All of the variables are controlled within the high and
low limit.
Any operation condition out of the control limit
is indicated by an alarm which warns the operator.
The
major controls and alarms designed in the scrubber system
monitor pressure drop across the scrubber, slurry density in
the scrubber, slurry level of the recirculation sump, and
slurry flow rate to the scrubber.
For the purpose of
safety, interlock circuits should be designed for the
scrubber system to protect the equipment in the event of an
emergency-
3.3.2
Operation
Preoperation - Before start-up, all major items of
equipment, connecting pipes and auxiliaries must be in-
3.3.2.1
spected, cleaned, and tested.
In newly installed systems,
the first step should be an air test of fans and ductworks,
3-33
-------
and a hydraulic test of pipings and valves to check for
leaks and instabilities.
A water test of the system should
also be carried out to ensure that equipment,
instruments,
and control/safety systems are working properly.
The items
which should be checked during preoperational tests on a
flooded disc venturi scrubber are summarized below:
o
FD/ID Fan
Electrical controls
Fan bearing coolant system
Alignment
Lubrication
Vibration sensors
Bearing temperature sensors
o
Pumps
Belt tension, pump rotation, pump alignment, lubrica-
tion, seal water, packing, pressure gauge, suction and
discharge valves, motor bearing temperature, hydraulic
system (for flooded disc control pump), etc.
o
Control Systems
Flue gas bypass
Flooded disc pressure drop
Makeup water rate
Recirculation sump level
Slurry density
Slurry purge rate
3-34
-------
o
o
3.3.2.2
Safety System (interlocks and alarms)
High flue gas pressure
Low level in sump
High and low density
Utilities
Electric power
Instrumentation air
Process water
Process return water
Start-up - To start a system for operation or for a
water test, one must follow the procedure described in the
designers' operating manual.
Several steps for the start-up
of a new venturi scrubber installation are outlined below:
6.
7.
1.
Close all drain valves.
2.
Turn on the circuit breakers for all instruments
and electric valves.
3.
Set all monitoring instruments to zero reading.
4.
Start the service water system and raise the water
level in the sump to the defined level.
5.
Turn on the recycle pump circuit breaker, and
start the operating and standby pumps.
Turn on the circuit breaker for the disc control
pump, start the disc control pump, and adjust the
high and low limits of the pressure drop indi-
cator.
Close the flue gas bypass dampers and start the
fan.
3-35
-------
3.3.2.3
8 .
Check the scrubber pressure controller and the
system monitoring instruments.
Shutdown - A general procedure for planned shutdown
of a flooded disc scrubber system is outlined below.
3.3.2.4
1.
Turn the flue gas damper to the bypass position
and stop the fan.
2.
Close the makeup water and slurry couple valves.
3.
Stop the recycle pumps (both operating and stand-
by) .
4.
Open the drain valves at the slurry pumping lines
and flush the lines, gauges, and pumps with water.
5.
Stop the disc control pump and leave the disc in
the fully raised position.
6.
Open the drain line on the pressure gauge to the
throat and disc and allow the line to drain.
Normal Operation - Under normal operating condi-
tions, all control variables should be operated in the
defined ranges.
These control variables include the scrub-
ber pressure drop, recycle pump rate, makeup water rate,
slurry density, slurry purge rate, and recirculation sump
level.
An abnormal condition would be indicated by an alarm.
If it cannot be corrected by the operator, under certain
circumstances an interlock will open the flue gas bypass
damper and shut down the scrubber system.
The alarm conditions involved in the system are out-
lined below:
3-36
-------
(1)
Scrubber pressure drop --
An alarm condition may occur owing to a malfunc-
tioning pressure drop controller, failure of the
disc control pump, a jammed disc, or a rapid
change of the boiler load.
(2)
Slurry density --
An alarm condition may occur because of a malfunc-
tioning control, a defect in the density control
valve, a malfunction in the sump level control, or
a makeup water rate change.
(3 )
Recirculation sump level --
An alarm condition may be due to a malfunctioning
control or excessive or insufficient slurry in the
sump.
(4)
Others --
An alarm condition may be caused by plugged lines,
closed valves, pump trouble, or fan trouble.
3.3.3
Inspection and Maintenance During Normal Operation
Many items on the preoperation check list should be
inspected during routine maintenance, which generally
includes unplugging lines, nozzles, pumps, etc.; replacement
of worn equipment parts, erosion/corrosion prevention
liners, and instruments (level indicators, density indi-
cators, etc.); and repairing damaged components (when prac-
tical from the standpoint of labor and materials) .
Table 3-4 indicates the manpower requirements for
maintenance involving scaling and plugging for both the wet
approach and liquid injection venturi scrubbers.
3-37
-------
Table 3-4.
MAINTENANCE FOR PLUGGING AND SCALING
VENTURI SCRUBBER6
(From interview with P. Wechselblatt, Chemico)
Type of problem
Plugging Scaling
Type of Chemical Hand
venturi Mechanical Cylinder
scrubber cleaners cleaners cleaning cleaning
Wet 1 man/shift/ 1 man/shift/ 3 men/shift/ 1 man/shift
approach mo mo wk wk
Liquid 1 man/shift/ 1 man/shift/ 3 men/shift/ 1 man/shift/
injection mo mo wk wk
Table 3-5 lists maintenance requirements for two ranges
of pressures, various lining materials, and gas character-
istics.
This table should be useful in the selection of
scrubber liners for venturi units for the various iron and
steel/ferroalloy applications.
The following check list is based on problems encoun
tered in scrubber operation.
These should be checked rou-
tinely and corrected according to the manufacturers' rec-
ommended procedures.
Check the scrubber disc to ensure even water distribu-
tion across its surface.
Check erosion and corrosion of all scrubber internal
surfaces, especially corrosion underneath scale build-
up. Repair as necessary.
Clean and descale all scrubber internal surfaces.
While descaling, exercise care to prevent damage to the
linings.
3-38
-------
Table 3-5.
SCRUBBER MAINTENANCE6
(From interview with P. Wechselblatt, Chemica)
W
I
W
1..0
Pressure drop
>30" !:J.p <30" !:J.p Gas characterJ.stl.cs
Life Life Corrosive
Type cycle, Repair cycle, Repair and
of liner yrs time yrs time Corrosive Abrasive abrasive Comments
Ceramic
Silicon 3-4 2 men/ 10 2 men/ Poor Excellent Good (midly
carbide wk 1 wk corrosive)
Cement 1 2 men/ 4 2 men/ Poor Poor Good (midly
wk 1 wk corrosive)
Rubber 1 2 men/ 5 2 menl Excellent Good Good For cutting type
2 wks 2 wks particles for ero-
sive but not sharp
Rubber 5 2 men/ 10 2 menl Excellent Good Good particles
2 wks 2 wks
Plastic Indefin- 1 d Patchable lining
ite
Steels
Carbon 2-6 Patch- 6 Patchable Poor Fair Fair Good for chlorides
able I
316 2-6 Patch- 6 Patchable Excellent Fair Fair-good Not good on
able I (arid) chlorides
304 2-6 Patch- 6 Patchable Good Fair Good Except for So;
able I (arid) and Cl-
Inconel 2-6 Patch- 6 Patchable Good Good Good
625 I
Hastoloy 2-6 Patch- 6 Patchable Excellent Good Good
able I
-------
Check the disc operation and perform maintenance on the
hydraulic packing.
Check the nozzles for buildup and/or damage.
replacement may be necessary.
Repair or
Check for solids buildup in blowdown lines.
may be effected without system shutdown and
connection may be installed to prevent this
in the future.
Cleaning
a flush
condition
Check for corrosion, erosion, and leaks in lines where
protective liners may have deteriorated. Replace
liners as required.
Check operation of mist eliminator. Formation of
droplets can be caused by excessive gas flow rate,
plugged drains from the moisture eliminator, or conden-
sation in the outlet duct.
Check pumps for wear, seal water, packing, and smooth
operation.
Check dampers and damper linkages for proper position-
ing and wear.
Fan check should include lubrication, fan bearing
coolant, belt wear, and belt tension, and impeller
erosion/corrosion.
Inspect all interior surfaces and condition of mist
eliminator and sump during major outages.
Exterior inspection should include a check for leaks in
all process and control lines, ductwork, and expansion
joints.
Note the condition of all instruments, e.g., level
probes and density probes with regard to solids build-
up. It is impractical and usually impossible to remove
solids buildup on the probes. In many cases the probes
must be replaced.
Perform a final check for proper operation of density
sensors, pressure drop control, and level elements.
3-40
-------
Spare Parts - The minimum inventory is one of each part for
each venturi scrubber.
is given in Table 3-6.6
The inventory for a venturi system
Manpower Requirements - The preceding dicussion has given an
indication of maintenance items, maintenance times, and
spare parts inventory for a venturi scrubber system.
Table
3-7 completes this picture by presenting the types of
personnel generally required to perform maintenance on
6
various parts of the venturi scrubber system.
3.4
OPERATION AND MAINTENANCE OF FABRIC FILTERS
3.4.1
Background Information on Fabric Filter Operation
A baghouse consists of a large metal box divided into
two chambers or plenums, one for dirty air and one for clean
air.
Rows of cloth bags form a partition or interface
between the plenums.
A polluted gas stream is ducted into
the dirty air plenum, where it is distributed evenly to the
bags.
The gas passes through the bags, enters the clean air
plenum, and is exhausted into that atmosphere through a
stack.
Greater than 99.9 percent of the particulate matter
in the process effluent can be filtered out by the bags if
the system is designed, operated, and maintained properly.
Upon start-up of a baghouse with new bags, some stack
emissions are usually visible.
This is because the bag
fabric which is the filtering medium, is porous, and allows
3-41
-------
Table 3-6.
SPARE PARTS INVENTORY FOR VENTURI SCRUBBER6
(From interview with P. Wechselblatt, Chemica)
w.
I
.l:>-
I\.)
Type of parts
Mist Adjust-
Section of elimi- Reamers able
the na tor (50% of Packing throat-
system Motors modules Seals Bearings Impeller total) material damper None
Scrubber X X
Separator X
Fan X X X X
Pump (s) X X X X
Mist eliminator X
,''\'\ "
-------
Table 3-7.
TYPE OF MAINTENANCE REQUIRED - VENTURI SCRUBBER SYSTEMS6
(From interview with P. Wechselblatt, Chemico)
W
I
,j::..
W
Type of worker
Maintenance man
Wastewater
Section of treatment
the system Laborer Electrical Plumber operator Mechanical
Scrubber X
Separator X
Fan X
Pump X X X
Piping, valves X
Water treatment X X X X
equipment
-------
some of the fine particulate to pass through the interstices
between the fibers.
After a short time, however, a dust
cake builds up on the surface of the bags and becomes the
actual filtering medium.
The bags then act as a matrix to
support the dust cake.
Buildup of the dust cake is desirable up to a certain
pressure drop, at which point the bags must be cleaned.
Improper cleaning will cause the pressure drop to increase,
and at a high enough pressure drop, particles of dust may be
forced into the bag filter, causing the bags to become
"blinded."
When this happens, air flow is restricted and
the bags may have to be replaced or removed and cleaned to
restore proper operating capacity.
In addition to the costs
of replacement and cleaning, high pressure drop increases
the cost of moving air through the system.
A typical reverse air or shaker type baghouse is shown
in Figure 3-4, and a pulse type baghouse is present in
Figure 3-5.
3.4.2
Preoperational Checks
The following checks are recommended prior to start-up:
o
Test control air lines (hydrostatically).
o
Check air dryers that supply control air to the
bag filters.
o
Check dust removal system.
3-44
-------
..
CLEAN AlP
I I
, '
DIRTY AIR
...,
r DUST CONVEYING
[ SYSTEM
i
ROTARY
DISCHARGE
Figure 3-4.
Reverse air or shaker type baghou~e.
3-45
-------
..
DIRTY AIR
..
CLEAN AIR
1
}
.....~
DUST
CAKE
Ii DUST CONVEYING
SYSTEM
ROTARY
DISCHARGE
Figure 3-5.
Pulse jet type bag house.
3-46
-------
o
Inspect collapse air fans for alignment and
rotation.
o
Check seals at gas inlet, collapse air, and gas
outlet damper.
o
Check baghouse compartments, remove debris.
o
Check filter bags for proper installation and
tension.
o
Check and sweep thimble floors clean. Dust
buildup on floor during operation is a positive
indication of a broken bag.
o
Calibrate pressure drop recorders and transmitters.
o
Check pressure taps for leakage.
3.4.3
Start-up
The operation of a fabric filter system is virtually
completely automatic.
However, start-up and shutdown are
extremely critical.
When the new equipment is started for the first time,
the fan should be checked for correct direction of rotation
and speed.
The ducting, collector housing, etc., should be
checked for leaks.
Gas flows and pressures should be
checked against the design specifications.
Instruments
should then be checked for correct reading and calibration
adjustments made as necessary.
Control mechanisms, and
especially all fail-safe devices, should be checked for
bOlo 8
opera 1 lty.
At the first start-up of the system, and also whenever
new bags have been installed by the maintenance crew, the
3-47
-------
bags should be checked after a few hours of operation for
correct tension, leaks, and expected pressure differential.
Initial temperature changes or the cleaning cycle can pull
loose or burst a bag.
It is wise to record at least the
basic instrument readings during this start-up period on new
bags, for ready reference and comparison during later start-
8
ups.
During any start-up, transients in the dust generating
process and surges to the filter house are probable and
ought to be anticipated.
Unexpected temperature, pressure,
or moisture has often badly damaged a new installation.
In
particular, running almost any indoor air or combustion
gases into a cold filter can cause condensation on the walls
and cloth, leading to blinding and corrosion.
Condensation
in the filterhouse may void the manufacturer's guarantee.
8
It can be avoided by preheating the filter or the gas.
A typical sequenced start-up procedure for a large
continuous automatic multicompartment fabric filter using
either reverse air, shake, or combination cleaning could be
summarized as follows:
1.
Check to see that all system monitoring instru-
ments are reading zero; especially fan motor
ammeters and compartment pressure manometers.
2 .
Close all system dampers except tempering air
damper (if used). This includes main compartment
isolation dampers, reverse air dampers (if used),
and fan modulation dampers.
3-48
-------
10.
3.
Start material handling system including any
motorized airlock devices and screw conveyors.
Hoppers should be empty on start-up.
4.
Sequentially start main fans allowing each to come
to speed before starting next fan.
5.
Start separate reverse air fan if used and allow
to come to speed.
6.
Engage fan modulating damper circuit(s).
7.
Engage tempering air damper circuit (if used).
8.
Slowly open main compartment isolation dampers.
If dampers are opened too quickly bags will pop
open, ultimately resulting in failure.
9.
Engage compartment cleaning circuit.
Check normalcy of readings on system monitoring
instruments; especially fan motor ammeters and
compartment pressure manometers.
The main precaution in shutting down the filter system
is prevention of moisture in the filterhouse.
Condensation
can appear through the cooling of gases containing moisture,
particularly combustion gases, if they are not completely
purged from the filter system and replaced with drier air
before the filter cools down.
This can also happen with air
at ambient moisture levels if the filter is in a colder
location.
To prevent condensation, the systems should be
purged carefully on shutdown and then sealed off completely.
Alternately, a flow of warm air can be continued through the
filter during the shutdown, which also helps prevent conden-
sation when it is started up again.
A shutdown procedure
is summarized below:
3-49
-------
1.
After process has been stopped and emissions have
ceased, allow baghouse to track through one com-
plete cleaning cycle; this will purge system of
process gas and collected dust.
2 .
Stop main fans.
3 .
Stop separate reverse air fan if used.
4 .
Allow material removal system to operate for 1
hour or until system is purged of collected
material.
Automatic operation extends to relatively complicated
applications, such as combination fourth-hole and canopy
ventilation of electric arc steel furnaces.
Here, limit
switches on the furnace open or shut the appropriate dampers
during each phase of the furnace cycle so that the canopy
section over the furnace is open during charging and back
charging; the direct evacuation system is operational during
meltdown and refining; and the canopy over the teeming aisle
is open during pouring.
In addition, if the canopy over the
furnace is left about 10 percent open during meltdown, it
will scavenge any emission that escapes the direct furnace
evacuation system.
3.4.5
Maintenance During Normal Operation
Maintenance of fabric filters in the iron and steel
industry centers around the bags and the moving mechanical
parts in the hostile interior of the baghouse (i.e., dampers,
screw conveyors, and shaker linkages).
The same maintenance
3-50
-------
procedures can be applied to baghouses operating on a sinter
plant or on electric arc furnaces in the steel or ferroalloy
industries.
Table 3-8 presents a checklist of items that require
regular inspection.
Plant personnel must learn to recognize the symptoms
that indicate potential problems in their fabric filter,
determine the cause of the problem and remedy it, either by
in-plant action or by contact with the manufacturer or other
outside resource.
For example, high pressure drop across the system is
one symptom for which there could be many causes, e.g.,
difficulties with the bag cleaning mechanism, low compressed-
air pressure, weak shaking action, loose bag-tension, or
excessive reentrainment of dust.
Many other factors can
cause excessive pressure drop, and several options are
usually available for corrective action appropriate to each
cause.
Thus the ability to locate and correct malfunction-
ing baghouse components is important and requires a thorough
understanding of the system.
A detailed list of trouble-
shooting and corrective measures is given in Appendix C-4.
Table 3-9 presents the frequency of failure of basic
fabric filter parts, including the frequency of inspection
and inspection time, as well as the time required for
repairs.
3-51
-------
Table 3-8.
6
CHECKLIST FOR ROUTINE INSPECTION OF BAGHOUSE
a
Component
Check for:
Shaker mechanism (S)
Proper operation without
binding; loose or worn bearings,
mountings, drive components;
proper lubrication.
Bags
Worn, abraded, damaged bags;
condensation on bags; improper
bag tension (S) (RF); loose,
damaged or improper bag
connections.
Magnehelic gauge or
manometer
Steadiness of pressure drop
(should be read daily).
Dust removal system
Worn bearings, loose mountings,
deformed parts, worn or loose
drive mechanism, proper lubri-
cation.
Baghouse structure
(housing, hopper)
Loose bolts, cracks in welds;
cracked, chipped, or worn
paint; corrosion.
Ductwork
Corrosion, holes, external
damage, loose bolts, cracked
welds, dust buildup.
Solenoids, pulsing valves
(RP)
Proper operation (audible com-
pressed air blast) .
Compressed air system
(RP, PP)
See above; proper lubrication
of compressor; leaks in headers,
piping.
Fans
Proper mounting, proper lubri-
cation of compressor; leaks in
headers, piping.
Damper valves (S, PP, RF)
Proper operation and synchroni-
zation; leaking cylinders, bad
air connections, proper lubri-
cation, damaged seals.
Doors
Worn, loose, damaged, or
missing seals; proper tight
closing.
Baffle plate
Abrasion, excessive wear.
a
RP-reverse pulse; PP-plenum pulse; S-shaker; RF-reverse flow.
3-52
-------
Table
3-9.
6
BAGHOUSE COLLECTOR MAINTENANCE
W
I
U1
W
-- ...
Type of
Frequency of Frequency of Time required person
Item breakdown inspection to perform inspection Time to repair to repair COllU1lents
INSIDE BAG COLLECTION
Bags
5 in. Ii' 14 ft Monthly Monthly 1.5-3 man-h/100 bags a min/bag b Laborer c Complete
10-30
a min/ba"
Pneumatic 2-3 yr 6 mo 1 h 8 h Ma in t. "'\8""
Baffle plates 4 yr 1 yr 30 min A r, Maint. man
Damper valves 2- 3 yr Monthly 15 min/valve 1-24 h Maint. man
a 1.5 man-h/cag for 24 in. r~acn. 3.0 man-h/100 bags
partIcles and black lIght are used) .
b Low value is total changeout/bag and high value is
C Three-man crew ffiln1mum.
for 36 in. reach (time may be cut by 70% If reJectIon of fluorescent
individual bag change.
-------
Following is a discussion of major fabric filter com-
ponents requiring routine maintenance:
Inlet Ducting - Common problems such as abrasion,
3.4.5.1
corrosion, sticking or plugging of dust, and settling must
be dealt with on a routine basis.
Abrasion can be reduced
by using special materials at bends in ducting, for example.
Corrosion can be minimized by supplying insulation, especi-
ally in the long duct runs, which are most susceptible to
moisture condensation.
Regular inspection will help control
plugging and settling problems in ducts.
3.4.5.2
Blast Gate and Flow Control - Problems with flow
8
control equipment are reported frequently.
The blast gate
valve is especially vulnerable and should be checked peri-
odically and adjusted. Filter compartment inlet dampers are
h' h' , d 8
a 19 -malntenance ltem, an spare parts should be stocked.
A bad damper seal can shorten the life of bags in a shake-
type system, and caking bags, if not replaced, can foul
valves on the clean side of the baghouse and cause them to
malfunction.
The most popular dampers for compartment
isolation are air cylinder-operated poppets acting verti-
cally (see Figure 3-6).
Several users mentioned problems
with push rod guides when dampers were made to act hori-
zontally.
Maintenance on these dampers consists of periodic
inspection and replacement of packing and solenoids.
The
wafer and seat were not indicated as presenting severe
3-54
-------
WAFER
z:
0
..... o~
I- PUSH ROD
o
:=E:
....J
c(
U
.....
I- AIR CYLINDER
0:::
LLJ .
:> OPERATOR
Figure 3-6.
Poppet valve.
3-55
-------
maintenance problems.
Damper failures can sometimes be
detected by observation of a differential pressure chart.
As the dampers open and close, the differential pressure
swings.
If a damper fails, the absence of this pressure
swing leaves a "gap" on the differential pressure chart.
If
a high differential pressure is signaled, the dampers are
routinely checked for proper operation.
If not, the opera-
tor must observe damper operation through the complete cycle
directly at the baghouse.
3.4.5.3
Fans - Fans and blowers are reported to be a large
problem area, particularly those located on the dirty side
of the baghouse where material can accumulate on the vanes
8
and throw off the balance.
Corrosion and abrasion can also
cause problems.
The use of pressure style baghouses has
been dramatically reduced however, because of the necessity
for on-line maintenance, and the danger associated with
working on a pressure type inside bag collector.
Condensation and corrosion in the fan may be alleviated
. 1 . 8
with duct and fan lnsu atlon.
Most fan housings can be
drained, and the drains should be checked on a regular
basis.
Air flow and fan speed should be measured periodically
and belt condition and tension determined; the fan should
also be checked for direction of rotation.
These checks can
be combined with routine lubrication procedures.
3-56
-------
Entrance Baffles - Baffles may be added to improve
3.4.5.4
distribution of the gas to each compartment and bag.
They
should be adjustable, however.
They may cause problems by
accumulating dust or abrading too rapidly-
3.4.5.5
Hoppers - Hoppers are a common problem in any
fabric filter system.
Dust flow can be facilitated by the
use of vibrators and/or heaters (if they work properly); by
lining the hoppers with anti-friction material; by the use
of air-pulsed rubber-lined hoppers; by placing poke holes in
the side of the hoppers; or by insulation if condensation is
a problem.
Trough-type hoppers with integral screw conveyors are
by far the most common material handling systems in the iron
and steel industry.
Dust storage in baghouse hoppers is a
common industry practice, although this frequently results
in dust bridging and subsequent sledgehammering of hoppers
to break the dust bridge.
Hopper vibrators are not generally
used because of expense and the tendency of vibrators to
pack the dust and aggravate the problem if vibration amplitude
and frequency are not correctly selected.
Regular inspection (once per shift) of the hopper is
mandatory to alleviate suction-removal system or bridging
problems before they become serious.
The screw conveyor flighting inside the hoppers is
supported every 10 to 15 feet by nonlubricated sleeve-type
3-57
-------
hanger bearings (see Figure 3-7).
Wear on these sleeves and
on outboard packed bearings is the major screw conveyor
maintenance problem.
The most common sleeve material is
cast iron, although Babbitt, wood, and various other mate-
rial have been used.
3.4.5.6
Bag Replacement - The most expensive maintenance
operation for fabric filter systems is the complete change
of a set of bags.
This is accomplished by having a crew of
two to six men enter the baghouse and disconnect each bag at
the cell plate and top suspension level and install a new
bag in its place.
Two bag attachment techniques are illu-
strated in Figure 3-8.
The purchase price of replacement
bags is given in Table 3-10.
The bag life reported by
respondents to the questionnaire survey is given in Table 3-
11.
3.4.5.7
Tension - The amount of bag tension required for
best overall performance varies according to the make of the
equipment.
Correct tension is a function of filter dimen-
sions and cleaning mechanism.
A bag that is too slack can
fold over at the lower cuff, bridge across, and wear rapid-
8
ly.
Too much tension can damage the cloth and the fasten-
ings.
Shake cleaning in particular seems to require a
unique combination of tension, shake frequency, and bag
properties for best results.8
In any event, the manufac-
3-58
-------
8 = 60° MIN
70° BETTER
---------
e
SCREW CONVEYOR
FLIGHTING
BAGHOUSE
HOPPER
SIDE WALL
EXTERNAL
~
STI FFNER
BOLTED FLANGE
HANGER SLEEVE
BEARING
"U" - TROUGH
FLANGED DISCHARGE SPOUT TO
GATHER UP SCREW CONVEYOR
OR AIR LOCK DEVICE
Figure 3-7.
Typical trough hopper and screw
conveyor arrangement.
3-59
-------
BAG 7
w
I
0"1
o
/ BAG CUFF
I
CELL PLATE
SNAP BAND CONNECTION
Fiqure 3-8.
Bag-cell plate attachments.
CUFF WITH
SPRING STEEl.:
BAND
THIMBLE CONNECTION
GAS FLOW
-------
Table 3-10.
APPROXIMATE COST OF REPLACEMENT BAGS
Material
Nylon (5.3 oz/yd2)
Sewn in ring 2
Polyester (7 oz/yd )
Sewn in ring
Fiberglass (silicon/graphite finish;
9 oz/yd2)
Sewn in ring
Fiberglass (10% PTFE finish; 9 oz/yd2)
Sewn in ring
Top caps (mild steel, 12 in. dia)
Stainless steel clamps
1977 cost
(dollars)
O.64/ft2
2.00 each
0.31/ft2
1.30 each
0.26/ft2
1.25 each
0.42/ft2
1.50 each
2.80 each
1. 75 each
Table 3-11.
BAG LIFE IN THE IRON AND STEEL INDUSTRY
Bag life (months)
Application Range Average
Ferroalloy 48
Electric arc steel 18-72 55
Sintering 18-60 27
3-61
-------
turer's recommendations should be followed and the tension
checked periodically. especially a few hours after install-
ing a new bag.
Spare Stock - It is advisable to have a complete
3.4.5.8
set of filter elements in stock in case of an emergency.
The spare filter elements should be clearly labeled and kept
well-separated from used filter elements.8 Table 3-12
presents a typical list of items that should be stocked, the
approximate quantities, and if the parts are not stocked,
the approximate delivery time and cost.
3.4.5.9
Inspection Frequency - External maintenance in-
spection of the filter house is usually performed daily,
whereas the filter elements themselves are typically in-
spected once a week to once a month.8
3.4.5.10
Shake Cleaning - Shaker mechanisms are generally
simply supported from each end by knife-edge bearings set in
grooved blocks.
A fractional horsepower motor is used with
a yoke linkage to oscillate the shaker bars (see Figure 3-
9) .
Shaker mechanism maintenance is centered around the
drive arrangement.
Periodic lubrication of bearings and
checking of alignment are required.
The shaking machinery
should also be checked periodically for wear.
If the bags
are not being cleaned properly, sometimes a minor adjustment
of the shake amplitude on frequency can markedly improve
3-62
-------
Table 3-12.
LIST OF REPLACEMENT PARTS FOR A BAGHOUSE FILTER6
w
I
0'\
W
% of total parts Delivery time
in baghouse that if not stocked, Estimated cost
Type of part should be stocked weeks % Conunents
Bags 15 4-8 See Table 3-10
Door seals 20 2-4 10/seal Typical 18" x 48" door
Mechanism
Shaker 20 2-4 10/item Bearings, knife blades,
belts
Reverse air 100 6-10 25/item Belts
Pulse jet 20 2-4 3/item Valve rebuild kit
Pulsing plenum 20 2-4 5/item Solenoid valves, seals,
cylinders
Screw conveyor 20 8-10 10/item Bearings
Air locks 100 8-10 10/item Seals
Pnewnatic 8-10 Variable
Baffle plates 4-6 100/plate
Damper valves 20 4-6 10/item Solenoid valves, seals,
cylinders
-------
rBAG CAP
~ CLAMP
Figure 3-9.
Typical shaker arrangement.
3-64
-------
cleaning.
If a safe amount of shaking still does not
properly clean the clots, it may be necessary to reduce the
filtration velocity for a few hours.8
3.4.5.11
Reverse-Flow Cleaning - With this type of clean-
ing, the only maintenance requirement is to check the rate
of flow (back pressure) and the timing periodically to keep
the residual drag at an economical level.
3.4.5.12
Shake and Reverse-Flow Cleaning - As in the case
of shake cleaning, wherever the bag is flexed the rate of
wear is apt to be high.
Maintenance procedures outlined for
the shake and reverse-flow methods also apply here.
3.4.5.13
Pulse Jet Cleaning - Since there are almost no
moving parts in the pulse type apparatus, hardware mainten-
ance is reduced in comparison with other cleaning methods.
However, excessive use of air cleaning pressure can damage
bags by overstretching them.
Corrective measures include
reduction of the frequency of cleaning, the use of another
type of bag fabric, or reduction of the abrasiveness of the
dust.
Instrumentation - Proper operation of fail-safe
3.4.5.14
mechanisms and automatic control instrumentation is very
important to the safety of the filter cloth.8
The location
of all sensing instruments should be checked to see that the
proper temperature, air flow, etc. are being measured.
All
3-65
-------
instruments should be calibrated after installation and
rechecked monthly for sensor location, leaks {manometer},
sticking, and legibility.8 Instrument readings covering one
complete operating cycle should be recorded for future use
ln routine checks and troubleshooting.
This record should
be posted beside each instrument.
3-66
-------
REFERENCES - SECTION 3.0
1.
The Electrostatic Precipitator Manual.
Company- Copyright 1976.
The McIlvaine
2.
Bump, Robert L. "Electrostatic Precipitator Mainten-
ance Survey", TC-l Committee of the Air Pollution
Control Association.
3.
A.P. deSeversky. U.S. Patent 3,315,445 April 25. 1967.
4.
Jaasund, S.A. and M.R. Mazer, "The Application of Wet
Electrostatic Precipitators for the Control of Emis-
sions from Three Metallurgical Processes," presented at
symposium entitled Particulate Collection Problems
Using Electrostatic Precipitators in the Metallurgical
Industry, June 1-3, 1977.
5.
Gooch, J.P. and A.H. Dean, "Wet Electrostatic Precipi-
tator System Study," SRI, Birmingham, Alabama, EPA-600j
2-76-142, PB 257 128, May 1976.
6.
Industrial Air Pollution Guide, PEDCo Environmental,
Inc., Chapter 7.0. EPA Contract No. 69-01-4147.
(Draft report.)
7.
"Control Techniques For Particulate Air Pollutants,"
U.S. Dept. of Health, Education, and Welfare, NAPCA,
January 1969.
8.
Billings, C.E., and J. Wilder. Handbook of Fabric
Filtration Technology, Volume I. Prepared by GCA Corp-
oration for National Air Pollution Control Administra-
tion, Contract No. CPA-22-69-38. December, 1970.
3-67
-------
4.0
FRACTIONAL EFFICIENCY RELATIONSHIPS
4.1
INTRODUCTION
This section evaluates the fractional efficiency capa-
bilities of precipitators, scrubbers, and fabric filters on
selected iron and steel and ferroalloy processes.
However,
the availability of fractional efficiency test data for
conventional particulate control devices is very limited.
Numerous contacts with users and manufacturers have yielded
no fractional efficiency test data.
One set of test data
was obtained from the Fine Particle Emissions Inventory
System computer bank, for a precipitator serving seven open
hearth furnaces.
Another set of data was available from a
test of a venturi scrubber on a ferroalloy furnace in
Russia and one additional test run was obtained from the
literature for a fabric filter operating on two electric arc
furnaces.
Results from computer models are presented which pre-
dict percent penetration as a function of particle size for
precipitators and wet scrubbers on iron and steel and ferro-
alloy processes.
4-1
-------
Insufficient data are available for predicting the
fractional efficiency of wet precipitators, and an appropri-
ate computer model is not available for use with fabric
filters.
4.1.1
Limitation of Current Data
Only in the past 4 or 5 years has particle size distri-
bution been measured and recorded with any regularity by
control equipment manufacturers, independent testing com-
panies, and consultants; and because of operator error and
the inherent technical limitations of some particle-sizing
instruments, reliable data are still not readily available.
Meaningful evaluation of fine particulate emissions will
require development of a reliable and consistent fine-
particle measuring technique that can be applied widely.
A
broadly applicable technique for compliance monitoring of
fine-particle sources would have the added advantage en-
abling the collection of valuable data concerning various
iron,
steel, and ferroalloy processes under different oper-
ating conditions.
Summary of Inlet Particle Size Distribution Data
Used for Precipitator and Scrubber Models
4.1.2
Table 4-1 summarizes the inlet particle size distri-
bution data used in the precipitator and scrubber model pre-
dictions.
These particle size distributions are based on a
1974 fine particulate inventory by Midwest Research Institute,
4-2
-------
1
Inc.
This report presents particle fractions in the size
range of 7 ~m or less.
Log normal plots of particle size
distribution were developed from this data, resulting in the
means and standard deviations presented in Table 4-1.
4.2
PROCEDURES FOR DETERMINING FRACTIONAL EFFICIENCY
PERFORMANCE
4.2.1
Electrostatic Precipitator Computer Model
The electrostatic precipitator computer model computes
size distribution at the precipitator outlet, based on inlet
size distribution and overall mass collection efficiency.
From the inlet and outlet distributions, fractional effi-
ciencies can be calculated directly.
4.2.1.1 Design Equations and Assumptions - The following
relationships2 are used in the program to determine particle
collection as a function of particle size.
The electrical force on a charged particle in an
electric field is given by:
F = qE
P
where E (by the Deutsch model) is the electric field
p
(1)
strength at the precipitator collecting electrode.
Table
4-2 provides a definition of all terms in meter-kilogram-
second
(rnks)
system units.
The force opposing particle
motion through the gas is:
f = 3TT~dwd/C
( 2)
4-3
-------
Table 4-1.
SUMMARY OF INLET PARTICLE SIZE DISTRIBUTION DATA
INDUSTRIAL SOURCES
PARTICLE SIZE DISTRIBUTIONa
.
-
x
og
Iron and Steel
Open hearth furnace
Basic oxygen furnace
Electric arc furnace
Sintering process wlo mc
wi mc
Scarfing process
.21
.27
. 80
70.
7. 7
NA
2.86
1. 82
9.30
6. 67
3.5
NA
Ferroalloy
Electric arc furnace
Ferrosilicon alloys
Ferromanganese alloys
Ferrochromium alloys
Miscellaneous ferroa11oys
.19
.78
.86
.50
3.00
2.12
4.19
3.36
aDerived from Weast, T.E., MRI Fine Particulate Emission
Inventory and Control Survey Table 28, p. 69 (Reference 1).
NA = Not Available
4-4
-------
Table 4-2.
NOMENCLATURE FOR ELECTROSTATIC
PRECIPITATOR COMPUTER MODEL
A
=
. . 11' 2
preclpltator co ectlng area, m
a
C
d
d
E
o
E
P
F
fl(d)
g(d)
k
Q
q
w
Wd
£
o
11
I1d
A
IJ
a
=
defined by equation (6), dimensionless
=
Cunningham correction factor, dimensionless
=
particle diameter, m
=
geometric mean particle diameter, m
=
effective charging field,
(Vim)
=
effective precipitating field,
(Vim)
=
force, N
=
-1
inlet particle size distribution function, m
=
defined by equation (10), m
defined by equation (9), -1
m
volumetric flow 3
gas rate, m Is
=
=
=
particle charge, C
=
Deutsch effective migration velocity, mlsec
=
migration velocity for particle of diameter
d, mlsec
=
-12
permittivity' of free space, 8.86 x 10 F/m
=
overall collection efficiency, dimensionless
=
collection efficiency for particles of diameter d
=
mean free path of gas molecules, m
=
gas viscosity, kg (m/s)
=
geometric standard deviation of size distribution,
dimensionless
4-5
-------
Equating the forces and solving for the migration velocity
of particles of size d:
qE C
W ---=---.E......
d - 3Tqld
C is the Cunningham correction factor given by:
(3)
C = 1 + 2.5A/d + O.84A/d exp (-.435d/A)
(4)
The particle charge q can be represented by the Cochet
equation:
2A 2 2 2
q = [(1 +~) + (1 + 2A/d)] TIEoEod
(5)
The Cochet equation accounts for particle charging by
both field charging and diffusion charging mechanisms.
This
is important in analyzing the effects of particle size,
since the charging mechanism changes from field to diffusion
in the submicron range.
Combining (3) and (5) and defining
2A 2 2
a = [(1 +~) + (1 + 2A/d)]
( 6)
the particle migration velocity for particles of size d
becomes:
E E E
wd = ( 0 0 p ) aCd
3fl
For particles of a single size, d, the Deutsch equation
(7)
can be applied to calculate collection efficiency:
wdA [ ( E E E A)
(1 - ~d) = exp [-0-] = exp - 0 0 P
3flQ
(aCd) ]
(8 )
4-6
-------
defining new terms:
k =
E E E A
o 0 P
3~Q
( 9)
g(d) = aCd
(10 )
the single-size efficiency equation becomes:
(1 - Tld) = exp[-kg(d)]
(11)
The overall collection efficiency is found by integrating
over the inlet size distribution, fl (d):
00
(1 - Tl) = f 0 (1 - Tl d ) f 1 ( d ) dd
(12)
Assuming a log normal inlet distribution, this becomes:
(1 - ~) = 2TI,11na f~ exp[-kg(d) - 0.5 1~~~d)2] dlnd
(13)
The above procedures can be used to determine outlet
size distribution and fractional efficiencies (or percent
penetra tion) .
An important effect that the program cannot
model is that of reentrainment of particles on fractional
efficiency-
4.2.1.2
Percent Penetration as a Function of Particle
Size - Predicted penetration as a function of particle size
is presented for the various electrostatic precipitator
applications in Figures 4-1 through 4-9.
Use of the com-
puter program shows the important result of a minimum in
efficiency in the 0.2 - 0.4 ~m particle size range.
As
mentioned previously, the program does not model the effect
of particle reentrainment on predicted penetration.
In the
4-7
-------
100
10
..
.
z:
o
j:.
~
to-
....
z:
....
~
1.0
.1
.01
X. 0.21, a. 2.86
INLET
.10
1.0
10.
PARTICLE SIZE, MICRONS
Figure 4-1.
Cold precipitator penetration for open hearth furnace
4-8
-------
100
10
..
.
z:
o
....
.-
~
.-
IU
z:
IU
CI..
1.0
.1
.01
Figure 4-2.
i. 0.27, ~. 1.82
INLET
.10
1.0
10.
PARTICLE SIZE. MICRONS
Cold precipitator penetration for basic oxygen furnace.
4-9
-------
100
10
...
.
z
o
...
I-
~
I-
~
Z
~
~
1.0
.1
.01
Figure 4-3.
X. 0.8. ~. 9.3
INLET
.10
1.0
10.
PARTICLE SIZE, MICRONS
Cold precipitator penetration for electric arc furnace
4-10
-------
"'-- -
100
10
-"
.
~
....
I-
~
I-
UJ
Z
UJ
~
1.0
X. 70, Cf. 6.67
INLET
.1
.01
1.0
.10
10.
PARTICLE SIZE, MICRONS
Figure 4-4.
Cold precipitator penetration for sintering machine.
4-11
-------
100
..
.
~
....
I-
~
I-
...
z:
...
0.
1.0
10
.1
.01
Figure 4-5.
x- 7.711- 3.5
INLET
.10
1.0
10.
PARTICLE SIZE, MICRONS
Cold precipitator penetration for sintering machine
(precipitator preceded by mechanical collector).
4-12
-------
100
10
...
.
z:
o
-
I-
~
I-
Lt.I
z:
Lt.I
0..
1.0
.1
.01
Figure 4-6.
x . .19. Cf. 3
INLET
-1-
.10
1.0
10.
PARTICLE SIZE. MICRONS
Cold precipitator penetration for ferrosilicon arc furnace.
4-13
-------
Figure 4-7.
10C
..
.
z:
o
-
~
~
~
....
z:
....
C>.
X. 0.78, (f. 2.12
INLET
10
1.0
. ,
.01
.10
1.0
10.
PARTICLE SIZE. MICRONS
Cold precipitator penetration for ferromanganese arc furnace.
4-14
-------
100
10
..
.
z:
o
...
~
~
~
....
z:
....
0..
1.0
. ,
.01
Figure 4-8.
X .86, ff. 4.19
INLET
.10
1.0
10.
PARTICLE SIZE. MICRONS
Cold precipitator penetration for ferrochromium arc furnace.
4-15
-------
1 DC
..
.
~
....
....
~
....
UJ
z:
UJ
0..
1.0
x . 0.5. a. 3.36
INLET
10
.1
.01
.10
1.0
10
PARTICLE SIZE. MICRONS
Figure 4-9.
Cold precipitator penetration for
miscellaneous ferroalloy arc furnace.
4-16
-------
process of reentrainment, fine particles for agglomerates on
the collecting plates are reentrained as larger particles.
Thus, the measured fractional efficiencies must show a
decrease in efficiency at larger particle sizes.
For
utility fly ash applications, an increase in penetration
appears to occur in the neighborhood of 6 wm.
Similar
behavior with iron, steel, and ferroalloy applications is
expected, although limited data are available to confirm
this.
Figure 4-10, for example, presents percent penetra-
tion as a function of particle size from a precipitator
controlling off gases from an open hearth furnace.
These
test data show a decrease in efficiency in the 0.2 - 0.4 wm
range, and another decrease in efficiency at 6 wm, presum-
ably due to reentrainment effects.
Figure 4-11 shows percent penetration versus particle
size at 99 percent overall mass collection efficiency for
Basic Oxygen Furance (BOF) , Open Hearth Furnace (OHF), and
Electric Arc Furnace (EAF) applications.
The lower observed
penetration predicted by the precipitator performance model
for the BOF application confirms the explanation presented
in Section 2.3.3 that BOF precipitators are more efficient
than OHF or EAF precipitators.
One final point should be made with regard to the
efficiency levels noted in Figures 4-1 through 4-9.
The
4-17
-------
10
9
8
7
6
5
4
3
2
...
.
z:
0
-
~
~ 1.0
~ .9
......
z:
...... .8
Q.
.7
.6
.5
.4
.3
.2
Source:
Fine Particle Emission Inventory
System; Test Series 45,
Subseries No.2.
.
.
.1
.1
.2
.3
.4
.5 .6.7.8.910
PARTICLE SIlE, MICRONS
2
3
4
5
6 7 8 9 10
Figure 4-10.
Fractional efficiency curve for an electrostatic
precipitator serving seven open hearth furnaces.
4-18
-------
99.99
99.9
99.8
99
98
95
90
80
~ 70
z: 60
a
...... 50
t-
c:t
a:: 40
t-
I.J..J 30
z:
I.J..J
c... 20
10
5
2
1
.5
.1
1-
.,...-- - --- -
LA.F. ---
----
O.H.F. ----- ----
'J.O.F. ",,"'" --"""""................... .....---
""'.................. ..............
--
--
--
--
--
--
---
.01
0.1
0.4
0.3
0.5
0.6
0.8
0.9
1.0
0.2
0.7
PARTICLE SIZE~ MICRONS
Figure 4-11. Percent penetration predicted versus particle
size for 99.0 percent overall mass collection
efficiency-
4-19
-------
efficiencies are shown to range from 95.0 to 99.9 for all
applications.
This was done to provide continuity with the
performance comparison of the applications at comparable
efficiency levels.
In practice, the efficiencies normally
attainable or required to meet emission standards will
depend on the process and site, and they may vary substan-
tially within the 95.0 to 99.9 percent efficiency range.
4.2.2
Venturi Scrubber Computer Models
4.2.2.1 Design Equations and Assumptions - Research Cottrell
Model - Venturi scrubbers are well described in the availa-
ble literature.3,4
The particle collection process depends
mainly upon the acceleration of the gas to provide impaction
and intimate contact between the particles and fine liquid
droplets generated as a result of atomization by the high
velocity gas.
The other factor which plays an important
role in the effectiveness of the venturi scrubber is the
condensation effect.
If the gas in the reduced pressure
region in the throat is fully saturated, condensation will
occur on the particles in the higher pressure region of the
diffuser.
This is known as heterogeneous nucleation, an
effect which helps particle growth and also causes agglom-
eration which tends to enhance collection.
The detailed
particle collection mechanisms in the venturi scrubber have
been investigated by many researchers.4,5,6
4-20
-------
The venturi model used in this study is based on in-
ertial impaction. The general form of the expression for
ff' . f h . th
the collection e lClency 0 tel particle size can be
written as
E. = 1 - exp(-KL ~.)
1 1
( 1)
where E. = Fractional collection efficiency of particle size
1
K = System parameter
L = Liquid-to-gas ratio
~. = Inertial impaction parameter of particle size i.
1
Available experimental data have been used to develop a
correlation for inlet throat velocity, Vt in ft/s, based on
6P (in. H20) and outlet L/G measurements.
v = 6P
t 5.23 x 10-6 (L/G + 105)
1/2
( 2 )
Knowing the inlet throat velocity and measured outlet
L/G, the droplet diameter in microns can be calculated from
a modified form of an equation developed by Nukiyama and
7
Tanasawa.
D
c
=
16050 + 1.41(L/G)1.5
Vt
(3)
The system parameter K is determined by an iterative
procedure based on comparison of the actual measured overall
mass collection efficiency and that calculated from summing
the individual fractional efficiencies.
For a given parti-
cle size the inertial impaction parameter is defined below:
4-21
-------
I¥. = 0.85 (C) (Pp) (Dp) 2
1 ]J
Vt
D
c
= Cunningham correction
(4 )
where
C
coefficient
3
Pp = Particle specific gravity, (grams/em)
D = Particle diameter, (microns)
p
]J
= Dynamic gas viscosity,
(poise x 104)
and
D = Droplet
c
C=l+~
D
p
diameter,
(microns)
D
1.23 + 0.41 exp(-0.44 -E)
A
(5)
where
A = Mean free path of gas molecules,
(microns)
The value of K is modified during the course of itera-
tion to yield a closer match between measured and calculated
overall mass collection efficiencies for given input values
of L/G and l1P.
When the "optimum" value of K has been
found, it is inserted into the above equations to generate
the outlet particle size distribution and finally the frac-
tional penetration for the various particle sizes.
It
should be noted that this is really an averaged system
parameter since it is not a function of any specific parti-
cle size.
4.2.2.2
Design Equations and Assumptions Calvert Mode14 -
PEDCo used Calvert's Model to compare its results to those
generated by the Research Cottrell Model.
Design equations
for Calvert's Model can be found in reference 4.
In addi-
tion to the inertial impaction mechanism, an equation for
4-22
-------
8
collection by Brownian motion developed by Yung et. al. was
included in the evaluation.
An "f" factor of 0.5 was
assumed for all test runs.
4.2.2.3
Penetration as a Function of Particle Size - Both
the RC model and Calvert's model were used to predict
penetration as a function of particle size for the applica-
tions of open hearth, electric arc, basic oxygen, and
ferroalloy furnaces, and sintering.
Results of the Research
Cottrell model are presented in Appendix D-l.
Similar
results were obtained by PEDCo using Calvert's model.
In
contrast to Research Cottrell's model, Calvert's model
showed higher penetrations in the lower size ranges, but a
sharper decrease in penetration as the particle size in-
creased.
Predicted overall mass efficiencies tended to be
lower with Calvert's model.
These results indicate that the particle size distri-
bution used as inputs for the steelmaking and ferroalloy arc
furnaces, are outside the limits for which the models were
designed.
Information in the literature indicates that
with pressure drops of 40 to 80 inches of water, a venturi
scrubber on a BOF, open hearth, or steeljferroalloy arc
furnace,
should have overall mass efficiencies in the range
of 95 to 99.5 percent.
Both models predict substantially
less overall efficiency.
4-23
-------
One reason for the inability of the models to predict
the expected high overall efficiencies is that other mech-
anisms which could increase the collection efficiency of
fine particles, such as heterogeneous nucleation, electro-
static effects, or thermophoresis are not included in either
the RC or Calvert's model.
It was found that Brownian
motion in Calvert's model had no significant effect on the
overall collection efficiency presumably due to the high gas
velocities being used (150-250 ft/s).
Inertial impaction as
a collection mechanism is only significant down to a parti-
cle size of around 0.5 ~m.
Since the mass median diameters
for the steel making furnaces were all below 1 ~m, use of
both these models, which rely heavily on inertial impaction
as a collection mechanism, is actually an extrapolation
below the range of particle sizes for which both models are
designed to operate most efficiently.
The predictions for
the sintering process with and without a mechanical collec-
tor by contrast, show that with a larger particle size
distribution,
(for example, sintering preceded by mechanical
collector, x = 7, og = 35) the models predict efficiencies
well in excess of 99 percent with pressure drops of 1) 35 to
70 inches of water with the RC model, and 2) 20 to 30 inches
of water for Calvert's Model.
4-24
-------
Fractional efficiency test data are available for a
venturi scrubber on a silico-manganese ferroalloy furnace in
Nikopol, Russia.9 The venturi scrubber is preceded by 1) an
inclined gas line (500-mm diameter) into which water is
sprayed, and 2) a 1000-mm diameter spray chamber which con-
tacts the gas counter currently.
Average particulate inlet
concentrations into the scrubber are 5.19 g/Nm3; outlet con-
centrations are 5.94 mg/Nm3, with an average efficiency of
99.89 percent.
The particulate size of the fumes was initially small;
9
substantially less than 1 ~m.
However,
the particles would
agglomerate and increase the mass median diameter to as high
as 3 ~m.
Results of particulate sizing data gave a log
normal size distribution with an average mass median diam-
eter at the inlet to the scrubber of 1.7 ~m with a geometric
standard deviation (og) of approximately 2.9
A comparison of actual test results and predicted pene-
tration as a function of particle size using Calvert's
model,4 is presented in Figure 4-12.
Predicted and actual
penetrations are in agreement at a particle size of 0.3 ~m.
However, for particle sizes larger than 0.3 ~m, the pre-
dieted penetration decreases more rapidly than does the
actual penetration.
4-25
-------
100
~
~
z:
o
......
I-
~
I-
U.I
z:
U.I
~
50
10
PREDICTED .-/
(CALVERT'S MODEL)
n = 99.80
t,p = 55 in H20
L/G = 15
5
1
.5
. 1
.05
.01
PARTICLE SIZE DISTRIBUTION
x=1.7a=2
ACTUAL TEST
RESULTS
~ = 99.89
t,P = 92 in H20
L/ G = 18.3
o
o
Figure 4-12.
Predicted and actual performance of the
Nikopal venturi scrubber on a ferroalloy furnace.
4-26
-------
Unfortunately, additional scrubber test data on the
steel/ferroalloy processes covered in this report are not
available for comparison with the models.
4.3
FRACTIONAL EFFICIENCY RELATIONSHIPS FOR WET ESP'S
A mathematical model was not utilized to predict the
efficiency of a wet precipitator as a function of particle
size for the iron and steel processes covered in this
report.
Southern Research InstitutelO has used a mathe-
matical model to compare predicted efficiencies with test
results on an aluminum reduction pot line (see Figure 4-13).
They found that the model under predicted fine particle
collection efficiencies less than 0.6 ~m, and over predicted
efficiencies greater than 0.6 ~m.
The wet ESP test results from the aluminum reduction
pot linelO show uniform high collection efficiency in the
particle size range of 0.05 to 10.0 ~m.
These results also
do not show a reduction in efficiency in the 0.2 to 0.4 ~m
size range, which is characteristic of dry ESP's, due to the
transition from field charging to diffusion for collection
of fine particles.
Since reentrainment is kept to a minimum
in a wet precipitator, Figure 4-13 does not show an increase
in emissions at 6 to 7 ~m, which is characteristic of dry
ESP's, resulting from agglomeration of small particles and
subsequent reentrainment.
4-27
-------
99.98 CALCULATED BY SRI 0.02
WITH COMPUTER MODEL
99.9 0.10
99.8 0.20
0 6
<0< 99.5 6 0.50
~ 6 1
>- 99
u 6 0 6 6
z: <0<
w 98 2
....... ~
u 0 z:
....... a
L..i... .......
l..L 95 5 I-
w
-------
Since no fractional efficiency test results are avail-
able for wet precipitators on steeljferroalloy processes, it
is not certain that similar fractional efficiency perform-
ance to that shown on aluminum reduction potlines could be
expected.
Overall efficiencies from pilot tests of two
types of wet ESP's on scarfing fumes ranged from 87.20 to
11
99.43 percent.
Full-scale tests of a wet ESP on a sinter
plant showed overall mass efficiencies ranging from 96.20 to
98.75 percent, under various conditions.
However, collec-
tion of condensable hydrocarbons did not exceed 50 per-
11
cent.
Pilot scale tests on the same sinter plant showed a
range of 50 to 93.75 percent, for collection of condensable
11
hydrocarbons.
Since the operation of a wet precipitator is not
influenced by the resistivity of the dust layer, the dielec-
tric constant of the particle material and its size are the
two most important particle parameters.
Particles with a
dielectric constant of less than 10 are much more difficult
to collect than conductive particles, and fine particles, of
course, are the most difficult to collect; however, wet
precipitators with three fields have reportedly shown over-
all mass collection efficiencies on solid particles of
greater than 99.5 percent even if 80 percent of the parti-
cles were less than one ~m in size.12
Removal efficiencies
4-29
-------
higher than 95 percent have been measured on condensable
12
hydrocarbons (tar fumes).
4.4
FRACTIONAL EFFICIENCY RELATIONSHIPS FOR FABRIC FILTERS
It would be desirable to characterize baghouse col-
lection efficiency as a function of particle size for each
of the processes discussed.
However, manufacturers are
reluctant to base baghouse guarantees on fractional collec-
tion efficiency.
They prefer overall collection efficiency
or outlet concentration guarantees based on their past
experience with the same or a similar type of process.
There is little incentive for manufacturers to relate bag-
house performance to particle size on existing systems and
as a result, this information is practically nonexistent.
Even though fractional efficiency data for baghouses in the
iron and steel industry are lacking, there is adequate
evidence in the literature from other industries to document
the fact that fabric filters preserve good fractional effi-
ciency down to and through the submicron particle range.
In
other words, unlike scrubbers and ESP's, fabric filters
preserve high collection efficiency for the small particle
slze ranges without any modification to their design or
operation.
It must be pointed out, however, that there are
several subtleties reported in the literature regarding the
actual shape of the fractional efficiency curve for a fabric
filter.
These are briefly discussed here.
4-30
-------
There are reports suggesting that the collection effi-
ciency of a fabric filter tends to drop somewhat in the sub-
micron particle size range, particularly in the 0.2 to 0.4
micron region.
This behavior is also common to scrubbers
and ESP's except that in their case the drop in efficiency
is more pronounced.
In one recent report*, it is postulated
that mechanisms during high velocity filtration can actually
lead to decreased filtration efficiency on larger particles.
The three mechanisms are as follows:
1.
Straight Through Penetration:
Immediately after
cleaning, many particles collect upon the exposed fibers.
Soon, however, a continuous dust deposit forms on the fabric
surface and particles collect upon previously deposited
dust.
Particles not collected by the filter, but which pass
through without stopping penetrate the filter by the "straight
through" mechanism.
2.
Seepage:
Once a particle lands on or in the
fabric, it need not necessarily remain at its point of
initial impact.
As the dust deposit builds up, pressure
drop can increase to several times its initial value.
Mean-
while, the fabric substrate may stretch, allowing some pre-
viously collected particles to work through.
Filter be-
havior of this sort is "seepage."
* Leith, D., et al. High Velocity High Efficiency Aerosol
Filtration, EPA - 600/2-76-020, January 1976.
4-31
-------
3.
Pinhole Plug:
Small diameter pinholes occur at the
surface of dust deposit on woven fabrics.
Similar holes on
a needle-punched felt may correspond to the places where
needles penetrated the cloth during its manufacture.
A plug
of deposited particles may dislodge from the dust deposit
and pass through the fabric all at once as the supporting
fibers move and stretch beneath it, leaving behind such a
pinhole.
Particles which pass through the filter in this
way do so by a "pinhole plug" mechanism.
Therefore, particles can pass through the filter by the
"straight through" mechanism, without being stopped, whereas
previously collected particles can make their way through by
the "seepage" and "pinhole plug" mechanism.
In addition,
the fraction of the total fabric filter penetration repre-
sented by "pinhole plugs" can be as high as 70 percent.
This could account for the presence of large particles on
the outlet side of baghouses in amounts not expected by
considering classical filtration theory.
None of the respondents to the questionnaire survey
used in this study could provide reliable fractional effi-
ciency information, and only one could provide particle size
information on the baghouse inlet and outlet.
This infor-
mation is presented in Figure 4-14.
One fractional effi-
ciency test of a baghouse on two electric arc furnaces was
obtained from the literature.13
4-32
-------
40
30
20
E
;::1.
~
a::
UJ
I-
UJ
:IE:
<
.....
C
UJ
.....I
U
.....
I-
a::
<
Q,.
0.3
1
DESLAGING /
/
/
/
I
/ .
I
I
I
I
.1
I
I
I
/
/
I
./
I
I
/
/
I
~
1
INLET
~
.
,
I
I .
I /
I I
/ /~ MEL TDOWN
1 I
. I
, I
I It
I ~
18;8 I~/
,,"'1
,..'" I
",
"""," I
.,.. "" "
8,," 8 I
/~DESLAGING
I
1
I
.
I
8 I
1,/'
8/
8 /'
"
..-
..-
"
."
'"
'"
/
/
./
./
./
~
OUTLET
~
8
8
8
8
8
8
8
5
99
Figure 4-14.
10 20 30 40 50 60 70 80 90 95
CUMULATIVE MASS PERCENT SMALLER THAN SIZE
Particle size distributions of electric
arc furnace dust at inlet and outlet of baghouse.
4-33
-------
The particle size distribution data in Figure 4-14
were obtained as part of an overall baghouse testing program
which established the average baghouse collection efficiency
at 94.5 percent.
This result is considered atypical of bag-
house performance for this application and is probably
indicative of ruptured bags, broken welds in the cell plate,
etc.
Figure 4-15 presents penetration as a function of
particle size (1 - 10 ~m) for a baghouse operating on two
electric arc furnaces.13
These curves show that 1.0 ~m
particles have the least penetration while 6.0 ~m particles
have the greatest penetration, contrary to fabric filtration
theory.
These results indicated that agglomeration of
smaller particles was occurring, mainly as a result of
fabric rear face dislodgement of collected particles.
A
comparison of inlet and outlet differential size distribu-
tions suggested that because of their similarity in shape,
some of the influent aerosol was passing through the bag-
house without capture, indicating bag leakage during sam-
pIing.
Average overall mass efficiencies were 97.9 percent
with one furnace operating and 98.7 percent with two fur-
naces operating.
In summary, a wide variety of factors (inlet grain
loading, air-to-cloth ratio, type of cleaning employed, dust
4-34
-------
10
9
8 6 ONE FURNACE ON
7 0 TWO FURNACE ON
6
5
4
I-
z 3
UJ
U
0::
UJ
0..
..
z:
0
..... 2
I-
c(
0::
I-
UJ
z:
UJ
0..
1
0.9
0.8
0.7
0.6
0.50
2
4 5 6
PARTICLE SIZE, ~m
7
9
10
3
8
Figure 4-15.
13
Fabric filter fractional penetration curves.
4-35
-------
characteristics, etc.) can affect particle penetration, and
current understanding has not advanced to the point where
one can conclusively predict expected penetration as a
function of particle size for a particular source.
This
difficulty is enhanced by lack of measured field data.
At
this point, it can only be said that the fractional effi-
ciency of a fabric filter is normally high (99+%) and that
there is little reduction of efficiency in the submicron
region.
4-36
-------
REFERENCES FOR SECTION 4.0
1.
Weast, et. al., "Fine Particulate Emission Inventory
and Control Survey." Midwest Research Institute, Jan-
uary 1974. PB-234-156.
2.
Feldman, P.L. "Effects of Particle Size Distribution
on the Performance of Electrostatic Precipitators,"
Presented at the 68th annual meeting of APCA, #74-02.3,
June 15-20, 1975.
3.
The McIlvaine Scrubber Manual, Vol. I, The McIlvaine
Co ., 197 4 .
4.
Wet Scrubber Systems Study, Vol. I, Scrubber Handbook,
A.P.T., Inc., PB 213 016, July 1972.
5.
Johnstone, H.F., R.B. Field, and M.C. Tassler, Inc.
Engineering Chemical, Vol. 46 1601, 1954.
6.
Johnstone, H.F. and F.O. Eckman, Inc.
Chemical, Vol. 43 1358, 1951.
Engineering
7.
Nukiyama, S. and Y. Tanasawa, Trans. Soc. Mechanical
Engineers, Japan, Vol. 5 62-68, 1939.
8.
Yung, S.C., Seymour Calvert, and Harry F. Barbarika,
"Venturi Scrubber Performance Model," APT Inc., EPA-
600/2-77-172, August 1977.
9.
Drehmel, Dennis C. "Field Test of a Venturi Scrubber
in Russia," presented at 2nd EPA Fine Particle Scrubber
Symposium, EPA-600/2-77-193, New Orleans, Louisiana,
May 2-3, 1977.
10. Gooch, John P., and Alan H. Dean, "Wet Electrostatic
Precipitator System Study," Southern Research Insti-
tute, EPA-600/2-76-142, May 1976.
4-37
-------
11.
12.
13.
Jaasund, S.A., and M.R. Mazer. Bethelehem Steel
Corporation. "The Application of Wet Electrostatic
Precipitators for the Control of Emissions from three
Metallurgical Processes," presented at Particulate
Collection Problems Using Electrostatic Precipitators
in the Metallurgical Industry Symposium, Denver,
Colorado, June 1-3, 1977.
Bakke, Even. Mikropul Division of U.S. Filter Cor-
poration. "The Application of Wet Electrostatic Pre-
cipitators for Control of Fine Particulate Matter,"
presented at the Symposium on Control of Fine Parti-
culate Emissions From Industrial Sources, January 15-
18, 1974.
Cass, Reed W. and John E. Langley. "Fractional Effi-
ciency of an Electric Arc Furnace Baghouse". GCA
Corporation, EPA-600j7-77-023. Bedford, Massachusetts,
March 1977.
4-38
-------
5.0
SUMMARY AND CONCLUSIONS
This report has reviewed the use of conventional
control devices (dry/wet ESP's, scrubbers, and fabric
filters) for limiting particulate emissions from electric
arc, basic oxygen, open hearth and ferroalloy arc furnaces,
and sintering and scarfing processes in the steel and ferro-
alloy industries.
Important design parameters, operation
and maintenance procedures, and the fractional efficiency
capability of each control device were the areas of study.
The following sections present conclusions drawn from each
area of study.
5.1
DESIGN PARAMETERS
It is evident from study of the steel/ferroalloy
processes included in this report that there is much wider
use of scrubbers, fabric filters and wet ESP's, as opposed
to the use of dry ESP's as is the case almost exclusively in
the utility industry.
Many times, the characteristics of
the process dictate the choice of a control device.
Tables
5-1 through 5-4, however, present general advantages of the
four types of control devices considered in this report, as
applied to the steel/ferroalloy processes studied.
Table 5-5
5-1
-------
Table
5-1.
ADVANTAGES AND DISADVANTAGES OF USING DRY PRECIPITATORS
ON STEEL/FERROALLOY PROCESSES
Control device
Advantages
Disadvantages
Electrostatic
precipitator
lJ1
I
IV
1) Can be designed to provide high
collection efficiency for all sizes
of particles from submicron to the
largest present; new designs can
meet stringent particulate regula-
tions.
2) Economical in operation because of
low internal power requirements and
inherently low draft loss; high
reliabili ty.
3) Flexible in gas temperature used,
ranging from as low as 125°F to as
high as 800°F.
4) Long useful life, if properly main-
tained.
5) No water pollution potential.
6) Extensive history of application.
1) High resistivity of process dust
degrades performance of cold
precipitator not designed for this
type of fuel.
2) Insulator
breakage;
corrosion
problems.
tracking, discharge wire
ash hopper plugging and
are potential maintenance
3) Efficiency is sensitive to change
in dust characteristics.
4) Potential explosion and fire problems
during start-up because of high
voltage sparking.
5) High-voltage hazards to personnel.
-------
Table
5-2.
ADVANTAGES AND DISADVANTAGES OF USING WET SCRUBBERS
ON STEEL/FERROALLOY PROCESSES
Control device
Advantages
Disadvantages
Wet scrubber
1) Smaller space requirements than
precipitator or fabric filter.
1) Collection efficiency decreases
rapidly with decreasing particle
size.
2) Not affected by high resistivity
process dust; relatively insensitive
to chemical composition and
variations in gas temperature.
2) Maintenance costs are
for precipitators and
filters. (Corrosion,
plugging)
higher than
fabric
scaling,
3) No high-voltage hazard.
3) Water pollution control required
for scrubber effluent.
U1
I
W
4) Very high pressure drop and re-
sulting higher power demand needed
for high efficiency.
-------
Table
5-3.
ADVANTAGES AND DISADVANTAGES OF USING FABRIC FILTERS
ON STEEL/FERROALLOY PROCESSES
Control device
Advantages
Disadvantages
Fabric filter
1) Collection efficiency essentially
independent of chemical content
in dust.
1) Higher pressure drop than ESP result-
ing in higher energy consumption.
2) High overall mass and fractional
efficiency. (99+%)
2) Fabric life is difficult to estimate;
may be shortened in the presence of
acid or alkaline particles, fluorides.
U1
I
.I»
3) Collection efficiency and pressure
drop are relatively unaffected by
changes in inlet grain loadings for
continuously cleaned filters.
3) Space requirements are usually greater
than for precipitators or scrubbers,
except at high air-to-cloth ratios.
4) No water pollution potential.
4) Condensation of moisture may cause
crusty deposits or plugging of the
fabric or require special additives.
5) Corrosion is not a problem, with
bags.
6) No high-voltage hazard, thus sim-
plifying repairs.
-------
Table
5-4.
ADVANTAGES AND DISADVANTAGES OF USING
WET PRECIPITATORS ON STEEL/FERROALLOY PROCESSES
Control device
Advantages
Disadvantages
Wet Precipitator
1) Eliminates resistivity problems
through the moisture condition-
ing effect minimizes reentrain-
ment.
1) High potential for corrosion and
scaling.
2) Loss of plume buoyancy.
2) Enhances collection through the
condensation nucleation effect
of fine particles.
3) Requires water treatment system.
Spray nozzles subject to plugging
if water treatment system mal-
functions.
VI
I
VI
3) Eliminates cleaning (rapping
losses, since no rapping mech-
anism is required).
4) Has not been proved advantageous
on a large scale basis for many
applications.
4) Has a low pressure drop typical
of dry ESP's.
-------
Table 5-5.
SUMMARY OF USAGE OF VARIOUS CONTROL DEVICES ON
SELECTED STEEL/FERROALLOY PROCESSESa
V1
I
0"\
Number of each control
Number of plants device usedb
Process which list control
device used Dry Wet Wet Fabric
ESP ESP Scrubber Filter
Steel Electric Arc Furnace 70 2 - 4 64
Basic Oxygen Furnace 37 18 - 19 -
Open Hearth Furnace 13 12 - 1 -
Ferroalloy Arc Furnace 13 1 - 5 7
Sintering
windbox 18 7c - 10 2
discharge 5 - - 2 3
Scarfing 39 7 12 12 7
a
See Appendix A for available listing for each process.
b May exceed total since some installations use more than one control device.
c Does not differentiate between dry and wet ESP's.
-------
presents an estimate of the extent of use of the control
devices on each process covered.
5.1.1
Dry precipitators
Dry precipitators are used frequently on sintering
windboxes, open hearth, and basic oxygen furnaces, and
occasionally on electric arc and open ferroalloy furnaces
and scarfing process.
The basic unit used for sizing the specific collecting
area
(SCA) was presented a function of collection efficiency
instead of sulfur or iron and sodium content of coal, as is
the case in the coal fired utility industry.
Resistivity of
the process dust, however, is still the main governing
factor that influences the SCA.
The correlational graphs
shown in section 2.0 for dry ESP's, indicate that the SCA
requirements for the steel/ferroalloy processes are not as
high as those required for low-sulfur coal in the coal fired
utility industry.
Dry precipitators for the sintering
process have the highest SCA requirements, followed by the
electric arc furnace, scarfing, open hearth furnace, and
basic oxygen furnaces.
5.1.2
Wet ESP's
Wet ESP's are being used on steel/ferroalloy processes
such as scarfing and sintering where other control devices
have performed unsatisfactorily.
Since the performance and
5-7
-------
collection efficiency of the wet ESP are not dependent on
the resistivity of the dust layer, the two most important
particle parameters are its size and dielectric constant.
The basic method of designing wet ESP's has been by
analogy based on empirical application of the Deutsch
equation, which does not account for changes in particle
size distribution as gas moves through the precipitator.
Recently some pilot plant studies have been conducted, but
very little design data could be obtained either from the
literature or from vendors.
Perhaps the design procedure
could benefit from application of some modification of the
Deutsch equation, such as use of the Matts-Ohnfeldt modified
1 . 1
migration ve OClty.
Since almost no design data were obtained, no specific
correlations could be developed for the application of wet
ESP's to the steel/ferroa11oy processes studied.
Organic
condensable materials from steel/ferroalloy processes are
likely to be the most difficult to collect, since they
usually have a low dielectric constant.
5.1.3
Venturi scrubbers
Venturi scrubbers are used frequently on semienc10sed
and sealed ferroal1oy furances, basic oxygen furnaces, in
some instances on the wind box and discharge end of sinter-
ing plants, and on open hearth and electric arc furnaces.
5-8
-------
One of the problems with using a venturi scrubber for
these steel/ferroalloy applications is the high pressure
drop (60-80 in. H20) and subsequent high energy use, re-
quired to meet particulate emission regulations.
The key
design parameters that affect particulate collection are the
same as for other applications, i.e., gas velocities/flow
rates, particle size distribution, pressure drop and liquid
to gas (L/G) ratio.
In developing correlations for the venturi scrubber, a
problem arose because most of the particle size distribu-
tions for the steel/ferroalloy processes studied are too
small for either the Research Cottrell model or Calvert's
model.
Therefore, the overall collection efficiencies
obtained were not high enough for the energy being expended.
However,
in general, the correlations showed a strong effect
of pressure drop on collection efficiency with L/G ratio
showing no great effect.
5.1.4
Fabric filters
Fabric filtration is the preferred technique for steel
and open ferroalloy arc furnaces; it is used fairly often on
the discharge end or sinter strands and occasionally on
sinter windboxes.
Use of fabric filters and ESP's on sinter
windboxes could be a developing market.
Some ferroalloy
producers design their own equipment, including baghouse and
5-9
-------
forced convection gas cooling, both of which seem to perform
well in the field.
In general, the design of fabric filters does not
differ substantially from application to application for the
same cleaning mechanism.
This is because baghouses are
relatively insensitive to process variables such as chemical
composition, particle size, and resistivity, although fabric
selection can be critical with respect to the chemical
composition of particles.
Some installations in the steel/
ferroalloy industry use pulse jet cleaning, which differs
from the reverse air and shaker methods.
Pulse jet cleaning
allows higher air-to-cloth ratios to be used because clean-
ing is done during operation and less space is required for
the fabric filter.
However, most baghouses and peripheral
equipment are almost the same physical size as the process
itself.
This makes the space requirement extremely large
and the total system very costly-
Current research in
fabrics and filtration technology could reduce both the size
and cost of fabric filtration systems.
5.2
OPERATION AND MAINTENANCE
In comparing operation and maintenance problems of
particulate control devices on steel/ferroalloy processes to
the coal fired utility industry, one finds many parallels
and some differences.
5-10
-------
For dry and wet ESP's corrosion 1S a major problem
contributing to the loss in efficiency.
High voltage
tracking on the insulators in dry ESP's as a result of the
formation of condensables in insulator compartments is also
a problem.
Strict pH control must be maintained on re-
circulated water for wet ESP's to minimize corrosion or
scaling and plugging of spray nozzles.
Wet scrubber problems in the steel/ferroalloy industry
are similar to those identified for utility applications:
plugging, scaling, and corrosion.
Inspection and mainte-
nance procedures are very similar for utility and steel/
ferroalloy applications.
Likewise, for fabric filters, maintenance procedures
for steel/ferroalloy applications are similar to those for
utilities.
Start-up and shutdown of a fabric filter are
extremely critical since unexpected temperature, pressure,
or moisture during start-up can badly damage bags in a new
installation.
Condensation is the main problem associated
with the shutdown procedure.
Bag replacement is the most
expensive maintenance operation, and other characteristic
maintenance problems center around dampers and screw con-
veyors for hoppers and shaker linkages.
5-11
-------
For all control devices, no data are available on the
effect of control device malfunctions on fractional effi-
clency performance, although it will degrade faster than the
overall mass efficiency, especially in the fine particle
range.
This is an area where further study could be direct-
ed, in anticipation of standards for performance for parti-
culate control devices, based on particle size in addition
to overall mass efficiency-
5.3
FRACTIONAL EFFICIENCY RELATIONSHIPS
Models for predicting performance as a function of
particle size were presented for dry ESP's and venturi
scrubbers.
The computer model for dry ESP's showed the same
characteristic increase in penetration in the 0.2 to 0.5 ~m
size range due to the transition region between field
charging and diffusion as collection mechanisms.
Only one
test result was available to confirm the model, that of an
ESP treating off gas from seven open hearth furnaces.
The
test data showed an increase in penetration at about 0.4 ~m
and another increase at 6 ~m, presumably because of agglo-
meration and reentrainment of smaller particles.
Two different computer models were tested for the wet
scrubber applications. Research Cottrell used their model
and PEDCo used Calvert's mode12 for the evaluation. Both
5-12
-------
models rely on inertial impaction as the collection mech-
anism and both models did not predict high enough overall
and subsequently fractional efficiency at the pressure drops
being used (~ 40 to 80 in. H20). PEDCo incorporated an
equation into Calvert's model for Brownian diffusion3, but
found that it had a minimal effect on efficiency, presumably
because of the high gas velocities used (150 to 250 ft/sec).
It was concluded that the particle size distributions for
the steel/ferroalloy furnaces were too small and thus out of
the range for which the models were designed.
Reasonable
results were obtained for the performance predictions for
the sintering process.
Inclusion of additional collection
mechanisms, such as diffusiophoresis, thermophoresis, and
electrostatic effects, were considered beyond the scope of
the project.
Test results from a venturi scrubber on a ferroalloy
. 4 d
furnace in RUSSla were compare with Calvert's model, and
reasonable agreement was obtained.
The test results showed
very high overall and fractional efficiencies (99.89%
overall) at very high pressure drops (88 to 94 in. H20).
A fractional efficiency prediction model was not
utilized in evaluating the fractional efficiency performance
of wet ESP's on steel/ferroalloy processes.
Wet ESP's have
shown excellent collection of solid particulates (>99.5%)
5-13
-------
even when 80 percent of the particles are less than 1 ~m in
diameter. 5 Removal efficiencies of 95 percent and higher
5
have been reported for condensible hydrocarbons. However,
no fractional efficiency test data are available to verify
this type of performance for the steel/ferroalloy processes
evaluated in this report.
A fractional efficiency prediction model was not
available for use in evaluating fabric filter performance.
Although fractional efficiency test data are likewise not
available, there is evidence in the literature from other
industries to indicate that fabric filters preserve high
fractional efficiency (>99%) down to and through the sub-
micron
range.
An increase in penetration is observed in
the 0.2 to 0.4 ~m size range, although it is not as pro-
nounced as with ESP's and scrubbers; Leith, et al. in one
6
recent report postulated collection mechanisms which
during high velocity filtration actually lead to a decrease
in efficiency at larger particle sizes.
However, given the
lack of test data and a proper prediction model, it can only
be said with reference to the steel/ferroalloy industry,
that the fractional efficiency of a fabric filter is nor-
mally high (99%+) with little reduction in efficiency in the
submicron particle range.
5-14
-------
The evaluation of the fractional efficiency relation-
ships for all the control devices brought out two important
facts.
One is the limited, scattered, and conflicting
particle size data available, pointing out the need for a
reliable, consistent, and widely used technique for measurlng
particle size distribution.
Valuable data could then be
collected on various steel/ferroalloy applications under
different operating conditions.
Second is the lack of
fractional efficiency test data on dry and wet ESP's, wet
scrubbers, and fabric filters for the steel/ferroalloy
applications under consideration.
This type of test data is
needed to characterize the performance of each control
device, is helpful in establishing and verifying fractional
efficiency prediction models, and would be essential to
developing accurate fine particulate emission standards in
the future.
5.4
COSTS
A model was not used to compare the costs of various
control devices on the various steel/ferroalloy processes
considered.
Literature sources were used in the cost
examples for wet ESP's and fabric filters.
In-house costs
from Research Cottrell and PEDCo were used to estimate costs
for wet scrubbers and dry ESP's, respectively.
For wet
scrubbers, the costs are based on the efficiencies generated
5-15
-------
by the Research Cottrell wet scrubber performance model,
which as discussed previously does not predict high enough
efficiencies at the pressure drops used as input.
These
costs, therefore, are somewhat lower than could be expected
at higher collection efficiencies.
However, it is important
to note that this cost information is very useful in a re-
lative sense,
irrespective of problems encountered with
particle size distribution/performance model combinations.
Since the cost estimates for each control device are
not on the same basis, no conclusions are drawn with regard
comparison of cost for various control devices on the same
process.
5-16
-------
REFERENCES FOR SECTION 5.0
1.
..
Matts, S. and P.O. Ohnfeldt, "Efficient Gas Cleaning
with S.F. Precipitators."
2.
Wet Scrubber Systems Study, Vol. I, Scrubber Handbook,
A.P.T. Inc., PB 213-016, July 1972.
3 .
Drehmel, Dennis C., "Field Test of a Venturi Scrubber
in Russia," presented at the 2nd EPA Fine Particle
Scrubber SYmposium, EPA-600/2-77-193, New Orleans,
Louisiana, May 2-3, 1977.
4.
Bakke, E., Mikropul Division of u.S. Filter Corpora-
tion, "Application of Wet Electrostatic Precipitator
for Control of Fine Particulate Matter," presented at
the SYmposium on Control of Fine Particulate Emissions
From Industrial Sources, Dallas, Texas, January 15-18,
1974.
5.
Leith, D., et al., "High Velocity High Efficiency
Aerosol Filtration," EPA-600/2-76-020, January, 1976.
5-17
-------
APPENDIX A
INSTALLATION LISTS FOR SELECTED STEEL/FERROALLOY PROCESSES
A-l
-------
APPENDIX A-l.
SINTER RECLAMATION PLANTS IN THE U.S.
a
INTEGRATED IRON AND STEEL INDUSTRY
:t>'
I
IV
Estimated
annual
No. of capacity, Ignition Machine Machine Crushing &
Company Location strands net tons fuel windbox discharge screening
Alan Wood Steel Co. Swede land, Pa. 3 475,000 Coke oven gas Scrubber Baghouse
Bethlehem Steel Johnstown, Pa. 2 1,100,000 Natural gas ESP Scrubber Scrubber
Corp.
u.S. Steel Corp. McKeesport, Pa. 1 325,000 Natural gas Scrubber
S. Chicago, Natural gas ESP
Ill.
Bethlehem Steel Lackawanna, 2 1,100,000 Coke oven gas ESP Scrubber
Corp. N.Y.
Sparrows Point, 6 3,600,000 Coke oven gas ESP Scrubber
Md. 1 4,250,000 Scrubber Baghouse Baghouse
W-P Steel Corp. E. Steuben- 1 550,000 Coke oven gas Scrubber
ville, W.Va.
Armco Steel Corp. Middletown, 1 900,000 Scrubber Recycle Baghouse
Ohio
National Steel Ecourse, Mich. 1 2,000,000 Coke oven gas Scrubber
Corp. I
Wierton, W.Va. 1 Gravel
bed
Bethlehem Steel Burns Harbor, 1 2,000,000 Scrubber Baghouse Baghouse
Corp. Ind.
National Steel Granite City, 1 1,000,000 Coke oven gas Scrubber
Corp. Ill.
(continued)
-------
APPENDIX A-I.
(continued) .
Estimated
annual
No. of capacity, Ignition Machine Machine Crushing &
Company Location strands net tons fuel windbox discharge screening
I-H, Wisconsin S. Chicago, 1 500,000 Coke oven gas Scrubber
Steel Ill.
Inland Steel E. Chicago, 1 1,530,000 Cyclone, Baghouse
Ill. ESP-
Baghouse
Lone Star Steel Co. Lone Star, Tex. 1 300,000 Natural gas Scrubber
U.S. Steel Corp. Geneva, Utah 2 900,000 Mixed gas ESP Scrubber
Gary, Ind. 3 Natural gas ESP Baghouse
Republic Steel Gadsden, Ala. 1 400,000 Natural gas Baghouse Baghouse
a Based on data from EPA 600/2-76-002, January 1976. "Control of Reclamation
(Sinter) Plant Emissions using Electrostatic Precipitators", by John Varga, Jr.,
Battelle-COlumbus Laboratories.
~
I
W
-------
~
I
*'"
APPENDIX A-2.
INVENTORY OF OPEN HEARTH FURNACESa
i Estimated
Furnace annual
No. of capacity, capacity, Type of control
Company Location furnaces net tons net tons equipment
Bethlehem Steel Corp. Sparrows Point, Md. 7 420 3,500,000 ESP
Bethlehem Steel Corp. Johnstown, Pa. 8 130 2,300,000 ESP
J & L Steel Corp. Pittsburgh, Pa. 6 350 3,000,000 ESP
Lukens Steel Co. 6 145 300,000
u.S. Steel Corp. Fairless, Pa. 9 395 3,500,000 ESP
Rankin, Pa. 10 320 3,250,000 ESP
Armco Steel Corp. Middletown, Ohio 6 300 1,250,000 Scrubbers
Cyclops Corp. Portsmouth, Ohio 3 300 750,000
U.S. Steel Corp. Youngstown, Ohio 15 160 1,500,000 ESP
YS & T Co. Campbell, Ohio 7 200 1,100,000 ESP
Youngstown, Ohio 11 185 1,500,000
Inland Steel Co. East Chicago, Ind. 7 335 2,000,000 ESP
Republic Steel Corp. South Chicago, Ill. 4 250 800,000 ESP
U.S. Steel Corp. Geneva, Utah 10 340 3,500,000 ESP
Kaiser Steel Corp. Fontana, Cal. 8 225 1,500,000 ESP
I
U.S. Steel Corp. Torrance, Cal. 4 60 I 125,000
ESP
Pacific States Steel Union City, Cal. 4 150 265,000
Co.
a
"Cost of Clean Air," Battelle Memorial Institute, 1974.
-------
APPENDIX A-3.
SURVEY OF BOF PLANTS
IN THE U.S.a
:x:-
I
\Jl
B1CMU1C/ Rate Gas Cleaning System
Date of Furnaces Des1.gn Present
C~y Plant Location Start-Up No. & Size Gas Cooling Dust Raroval Sys. M3.x. SCYM SCYM Capaci ty-<:FM /-btor Power
Alan Wc:x:d Steel Co. Conshoh::x::ken, Pa. 1968 2 x 150 Water sprays Precipitator 15,000 13,000 600,000 1400 liP
Allegheny Llrllum Steel Corp. Natrons, Pa. 1966 2 x 80 Water Scrubber 6,500 6,500 314,000 @ 550°F 3500 liP
Arnr:o Steel Corp. Ashlan:!, Ky. 1963 2 x 180 Water sprays Precipitator 15,000 15,000 700,000
Middleta./n, Ohio 1969 2 x 210 Water Scrubber 22,500 19,000 55,000 2000 liP
Bethlehem Steel Corp. Lackawanna, N. Y. 1964/66 3 x 300 Water sprays Scrubber 25,000 26,000 1,000,000 900 liP
Sparrows Point, Mj. 1966 2 x 215 Water sprays Venturi Scrubber 22,000 22,000 700,000 7500 liP
Bethlehan, Pa. 1968 2 x 270 Water sprays Precipitator 22,000 22,000 1,500,000
Burns Harror, Ind. ) 1969 2 x 300 Water quench ~~ 35,000 32,000 570,000 @ 180°F 4500 liP
Johnsta./n, Pa. ) 1976 1 x 300
C F & I Steel Corp. Pueblo, Colo. 1978 2 x 200
Crucible Inc. ~U.dlarrl, Pa. 1961 2 x 120 Water sprays Precipitator 6,500 11,000 300,000 700 liP
Ford /obtor Co. Dearrorn, Mich. 1968 2 x 105 Water quench Scrubber 11,000 14,000 350,000 5000 liP
Inlan:! Steel Co. East Chicago, Ind. 1964 2 x 250 Water sprays Precipitator 22,000 21,000 1,500,000
1966 2 x 255 Water quench Venturi Scrubber 22,000 25,000
Interlake, Inc. Chicago, Ill. 1974 2 x 210 Water quench Scrubber
Jones & Laughlin Steel Corp. Al1.quippa, Pa. 1959 2 x 75 Water sprays Precipitator 4,000 6,800 200,000 @ 20uoF
Clevelan:!, Ohio ) 1957 2 x 80 Water sprays Precip1.tator 6,000 228,000 @ 5600F 500 liP
) 1968 3 x 190 Water sprays Precipitator 13,000 17 ,000
1961 2 x 225 Water sprays Precipitator 20,000 18,000 1,300,000 5000 liP
Kaiser Fontana, Calif. 1958 3 x 120 Water sprays Precipi ta tor 13,000 13 ,000 550,000
/ob1Du th Trenton, Mich. 1958/69 5 x 110 Water sprays Disintegrator 10,000
National Steel,
Great Lakes Ecx:>rse, Mich. ) 1962 2 x 300 Water sprays Precipitators 26,000 1,260,000 3000 liP
) 1970 2 x 235 Water sprays Precipi tators 18,000 650,000 1600 liP
weirton Steel D1.v. weirton, W. Va. 1967 2 x 350 Water sprays Scrubber 25,000 25,000 420,000 @ 140°F
Granite City Steel Co. Granite City, Ill. 1967 2 x 235 Water sprays Precipitator 22,000 22,000 1,000,000
Republic Steel Corp. Warren, Ohio 1965 2 x 190 Water sprays Precipitator 15,000 14,000 720,000
Gadsden, Ala. 1965 2 x 180 Water sprays precipitatgr 15,000 14,000 700,000 @ 5500F 1800 liP
Clevelan:!, Ohio 1966 2 x 245 Water sprays Scrubber 20,000
Buffalo, N.Y. Ill. (o-BJP)d 1970 2 x 130 Scrubberc 9,000
South Chicago, 1976 2 x 200
Sharon Steel Corp. Farrell, Pa. 1974 1 x 150
United States Steel Corp. Dlquesne, Pa. 1963 2 x 215 Water quench Venturi Scrubber 20,000
Gary, 100. (L-D) 1965 3 x 215 Wa ter quench Venturi Scrubber 20,000
Gary, 100. (o-BJP)d 1973 3 x 200 Water sprays Venturi Scrubber 202,000 SCD1
South Chicago, Ill. 1969 3 x 200 Water quench Venturi Scrubber 20,000 19,000 47,500 2250 liP
Lorain, Ohio 1971 2 x 225 Wa ter Venturi Scrubber 20,000 20,000
Eraddock, Pa. (o-BJP)d 1972 2 x 230 Water sprays Venturi Scrubber 24,000
Fairfield, Ala. 1974 2 x 200 600,000 @ 550°F
Wheeling-Pittsburgh Steel Corp. t-bnessen, Pa. 1964 2 x 200 Water sprays Precipitator 15,000 15,000
Steubenvi11e, Ohio 1965 2 x 285 Water Venturi Scrubber 23,000 21,000 570,000 2250 liP
W1.sconsin Steel South Ch1.cago, Ill. 1964 2 x 120 Water sprays Precipitator 12,000 630,000 3750 liP
Youngsta./n Sheet & Tube Co. East Chicago, 100. 1970 2 x 280 Water sprays Precip1.tator 26,000 26,000
C-"!11phe ] 1, Oh i 0 1976 2 x 200
a aased on data prepared by Process Develq:rrent, Ka1.ser Er.:jineers Inc.,
Chicago, Ill., rev1.sed July, 1975.
b SUppressed canbustion (recent retrofit).
c Assumed to be scrul:Ver - no other deta1.1s ava1.laLle.
d o-BOP enploys oxygen an:! natural gas blc.wn through tuyeres in the hottan.
-------
APPENDIX A-4.
SURVEY OF ELECTRIC ARC FURNACES IN THE UNITED STATESa
~
I
0'1
Furnace Estim3.ted
N\J!1ber Capacity Annual Capacity
Ca11pany lDcation Furnaces Year net tons net tonsb Type of Control Equiprent
A-L Industries Inc. Brackenridge, Pa. 1 1925 25 400,000 Bagmuse
2 1928 10
2 1929 10
2 1941 35
1 1943 55
2 1949 70
2 1949 80
- - -
Armx> Steel Corp. Butler, Pa. 1 1948 60 1,000,000 Direct extraction and
3 1969 165 irrlividual scrubl:ers
- - -
Baba.x:k anj \"lilcox Co. Beaver Falls, Pa. 2 1942 25 200,000 Building evacuation to
1 1951 50 bagmuse
1 1952 75
1 1957 25
- - -
Koppel, Pa. 1 1967 50 425,000 Building evacuation to
1 1967 100 bagmuse
1 1968 50
1 1968 75
1 1968 100
- - -
B-L-H Corp. Burnham, Pa. 1 1958 18 200,000 Furnace txxxis and bagm
1 1958 40
1 1965 45
1 1971 70
- - -
Bethlehan Steel Corp. Bethlehem, Pa. 1 1938 25 300,000 Furnace txxxis and bagm
2 1940 50
2 1957 50
- - -
Johnstown, Pa. 1977 1,000,000
-
Steel ton, Pa. 2 1969 150 800,000 Furnace h:Jods and bagmu
1 1970 150
- - -
use
use
se
-------
APPENDIX A-4.
(continued) .
)::<
I
-...J
Furnace Estimated
Number Capaci ty Annual Capacity
C~ Location Furnaces Year net tons net tons Type of Control Fquipnent
Judson Steel Corp. Emeryvi lle , Ca 1. 1 1969 30 100,000 Direct extraction to ESP caoopy to
- - - baghouse
Pacific States Steel Union City, Ca1. 100,000
Corp.
Soule Steel Co. Long Beach, Ca1. 1 1959 15 105,000
1 1969 15
Southwest Steel Los Angeles, Ca1. -y- 1948 ---rs 108,000 Building evacuation, baghouse
RolliOJ Mills, Inc. -L 1952 15
-
Hawaiian Western Steel 1 35 100,000
- -
Keystone Steel & Cortlarrl, N. Y.
Wire Co.
Sim:m::ls Saw & Steel LcdqX)rt, N.Y. 3 15 Furnace hood, baghouse
Co.
Cabot, Corp. Parrpa, Texas 1 10 15,000
Cameron Iroo Works Houston, Texas ~ 60 75,000
- -
Firewater Corp. Oakm:::>nt, Pa. -L 1964 45 65,000 Side hoOOs & furnace hcx:rl
I>Ecca Machine Co. West Harestead, Pa. 1 1971 50 70,000 Baghouse
Midva Ie- Her:pens tall Philadelphia, Pa. ~ 30 270,000 Furnace hcx:rl & side hocrl
Co. 1 50
~ 100
Baldwin-Lima- Burnham, Pa. 1 1958 18 200,000 Furnace hoOOs, baghouse
Harni 1 ton Corp. 1 1958 40
1 1965 45
-L 1971 70
Nas= Latrobe, Pa. 1 1968 10 15,000
Braeburn Alloy Steel Braeburn, Pa. 2 -r 10,000
---L 1
National Forge Irvine, Pa. 1 20 240,000
1 45
Erie, Pa. 1 35
1 75
- -
a "Cost of Clean Air" - Battelle r-arorial Institute, 1974.
b
Where one hgure is given for !l1)re than one furnace, the net tons refers to the total of all furnaces listed for
that location.
(continued)
-------
APPENDIX A-4.
(continued) .
:t:'
I
00
Estimatoo
Number Capacity Aru1Ua 1 Capaci ty
CCI1lpaI1y Location Furnaces Year net tons net tons 'I'{pe of Control fAuiJ:ID=I1t
Texas S tee 1 Co. Fort YkJrth, Texas 1 1923 3 200,000 &ighouse
1 1942 7
1 1956 10
1 1958 20
1 1968 30
u.s. Steel Corp. Cedar Pt., Texas ----r- 1%7 2Qi) 550,000 Direct extraction quenc:her, venturi
-.L 1968 200 scrubber (irrli vidual)
Chaparra Steel Co. Midlothian, Texas 1 1975 120 220,000
- - -
Arnco Steel Corp. Sarrl Springs, Okla. 1 1962 70 400,000
1 1970 70
- -
Roc~ll r-Bnufac- Atchison, Kansas 1 1957 20 50,000
turing Co. - -
Necor Norfolk, Nebraska 2 1973 40 160,000
- -
C F & I Corp. Pueblo, Colorado 500,000
Allison Steel Mfg. TE!T1pe, Arizona 1 1959 15 180,000 &ighouse
Co. 1 1960 15
1 1968 25
- - -
Bethlehan Steel Corp. Seattle, Wash. 2 1958 100 500,000 Direct extraction, spray chamber,
- - baghouse
Northwest Steel Kent, Wash. 1 1967 50 440,000
Iblling Mills, Inc. - -
Cascade Steel M::Minnville, Oregon 2 1969 25 100,000 Side hoods, baghouse
Rolling Mills, Inc. - -
Oregon Steel Mills, Portland, Oregon 1 1941 18
Inc. 1 1942 18
1 1948 18
1 1968 75
- -
Jorgenson Co. Seattle, Wash. 2 40 55,000
- -
Areron Steel Etiwarrla, Cal. 1 1957 10 160,000 Side hoods, baghouse
1 1961 10
-.L 1967 18
Arnco Steel Corp. Torrance, Cal. 1 1941 "25 80,000
- - -
Beth1ehan Steel Los Angeles, Cal. 1 1948 75 575,000 Building evacuation furnace hoods,
Corp. 1 1950 I 100 baghouse
1 1951 100
- --
-------
APPENDIX A-4.
(continued) .
~
I
1.0
Estimated
Number Capacity Annual Capacity
Ca11pdI1y Location Furnaces Year net tons net tons Type of Control Fquipnent
U.S. Steel Corp. Chicago, Ill. 1 1941 50 750,000 Furnace hoods
1 1941 85
1 1943 85
2 1970 -1.Q.L
Republic- F inkl Chicago, Ill. 2 1 60 350,000 Direct extraction, baghouse
Columbia Tool Steel Chicago Heights, Ill. 1 I 5
1 8
Harper Co. MJrton Grove, Ill. 1 4
1 10
- -
Ingersoll New Castle, Ind. I 2 1941 15 130,000
, -L 1950 ---1L
Continental Steel KokaTD, Ind. i 2 1968 150 425,000 Direct extraction, heat exchan:Jer,
I - - - baghouse
Inlarrl Steel Corp. Indiana Haroor, 100. I 2 1970 120 500,000 Direct extraction, roof truss hoods,
- - - baghouse
Joslyn Stainless Fort Wayne, 100. 2 15 70,000
Steel 1 1963 25
- - -
Iowa Steel Mill, Inc. Cedar Rapids, Iowa 2 1975 150,000 Paghouse
- -
Amco Steel Corp. Kansas City, MJ. 1 1952 100 1,200,000 Direct extraction, spray charrbers,
1 1956 100 baghouse
1 1962 150
1 1969 170
- - -
Tennessee Forging Newport, Arkansas 1 1971 25 100,000
Steel - - -
Ross Steel Works Amite, La. 1 1967 40 100,000
- - -
Amco Steel Corp. Houston, Texas 1 1951 100 400,000 Direct extraction
1 1957 -.1:.QL
2 1966 175 1,200,000 Irrlividua1 high-energy venturi,
1 1970 175 scrubbers
-L 1971 .11L
Border Steel Co. Vinton, Texas 1 1960 25 140,000 Direct extraction, baghouse
---L 1967 25
LaTournew, Inc. Longview, Texas 1 1951 25 100,000
------L 1956 25
Structural ~tals, Sequin, Texas 1 1962 25 90,000 Direct extraction, baghouse
1 1964 25
- - -
( continued)
-------
APPENDIX A-4.
(continued) .
Canpany
NI.I1tJer
Furnaces
lJxation
Urban Rec:laIMtion
Technologies, Inc.
New Bedford, Mass.
Carpenter Techoology Bridgep::>rt, Conn. 2
Corp.
Washburn Wire Co. Phillisdale, R.I. 2
C F & I Steel Corp. Trenton, N.J. 1
2
New Jersey Steel & Savreville, N.J. 1
Struct.
Intercoastal Steel Chesapeake, Va. 1
Corp. 1
Roanoke Electric Roanoke, Va. 1
Steel 1
1
Timken Roller Bear- Canton, Ohio 2
ing Co. 1
~ 1
I 2
t-'
0 1
1
1
1
American Carq::>ressed Cincinnati, Ohio 1
Steel
Caltmet Steel Chicago Heights, Ill. 2
Ceo:> Corp. Laront, Ill. 2
l
Jones & r-tKnight Kankakee, Ill. 1
Steel 1
Keystone Steel & Peoria, Ill. l
Wire Co.
Lac1ede Steel Co. Alton, Ill. 2
Northwestern Steel Sterling, Ill. 1
& Wire 1
1
Republic Steel Corp. S. Chicago, Ill. 2
1
2
(continued)
Year
1
1974-5
1955
1964
1965
I 1971
1962
1968
1955
1960
1966
1926
1938
1952
1953
1964
1965
1970
1971
1959
1958
1959
1961
1962
1970
1965
Furnace Estimated
Capaci ty Annual Capacity
net tons net tons
Type of Control Eouipnent
65 150,000
35 110,000
45 120,000
45 220,000 Direct extraction, heat exchanger,
45 baghouse
-----so 140,000
15 100,000
15
6 170,000 Direct extraction, baghouse
15
15
40 1,000,000 Side Hoods curl baghouse
90
100
100 Furnace, roof hood curl side
140 extraction, curl baghouse
100
60 Sidehoods, baghouse
150
6
30 180,000
30 225,000 Irrlividua1 baghouse
30
20 155,000 Hood evaculation, baghouse
22
150 600,000
200 700,000
150 Flooded disc scrubber
250 1,000,000
400
100 Direct extraction, heat
140 700,000
150 exchanger, baghouse
Baghouse
-------
APPENDIX A-4.
(continued) .
~
I
f-'
I-'
Furnace Esti.JTated
NlI11ter Capacity Annual Capacity
Canpany Location Furnaces Year net tons net tons Type of Control Equipnent
Armx> Steel Corp. Marion, Ohio 1 1968 80 100,000 Baghouse
Copperwe1d Steel warren, Ohio "4 1940 50 750,000
Corp. 4 1941 75
Cyc1o~ Corp. Manesfie1d, Ohio 1 1963 100 375,000 Direct extraction, side extractioo,
1 1964 100 hcx:rls, baghouse
J & L Steel Corp. C1eve1arrl, Ohio 2 1959 150 450,000 Direct extraction, ESP
Republic Steel Corp. Canton, Ohio 5 1941 80 1,320,000 Direct extraction, baghouse
4 1967 200
warren, Ohio 2 1957 185 450,000
Cabot Corp. Kokaro, 1m.. 1 5
...L 10
General futors 3 1970 100,000 Baghouse
Corp. - -
Jones & Laughlin warren, Mich. 1 1933 65 350,000 RJof caoop:{ hcx:rls, building
Steel 1 1938 65 extraction, baghouse
1 1942 65
2 1949 65
1 1954 30
M:Louth Steel Corp. Trenton, Mich. -L 1954 ~ 480,000 Scrubber
National Steel Corp. Ecourse, Mich. 2 1968 150 400,000 Direct extractioo, spray tower,
- - baghouse
Ford futor Co. Dearborn, Mich. 2- 1975 200 750,000
Michigan Seamless Jackson, Mich. 1 1974 100,000
Tube Co. - -
Allegheny Llrl1lI!1 Watervliet, N.Y. 2 25 100,000 1972 building evacuatioo, baghouse
Ind. 1 15
...L 12.5
Crucible Steel Co. Syracuse, N. Y. ...L 1966 35 60,000 (1970)
Roblin Industries, Dunkirk, N.Y. 1 1963 25 150,000 Direct extraction, baghouse
Ire. ...L 1964 25
Auburn Steel Co., Autum, N.Y. 1 1974 55 165,000
Keystone Steel & Cort1arrl, N. Y. - -
Wire Co.
SaiIIIDnds Saw & Steel
Co.
Eastern Stainless Ba1 tirrore, r-tj. 1 1957 50 85,000 Baghouse
- -
Steel
Armco Steel Corp. Ba 1 tim::>re , r-tj. 2 1937 12 100,000 Baghouse
1 1941 25
3 1946 16
- - .
(continued)
-------
APPENDIX A-t!.
{continued) .
~
I
I-'
N
Furnace F.stimated
Nunbe.r Capacity Annual Capacity
Carpany Location Furnaces Year net tons net tons Type of Control Equipnent
Interlake Steel Newport, Ky. 2 1950 85 450,000 Baghouse
Corp. 1 1965 85
Jessop Steel Co. 0.lensl:oro, Ky. 1 1950 60 120,000
1 1956 60
Kentucky Electric Coal ten, Ky. 1 1964 ~ 120,000 Baghouse
Steel 1 1968 15
- - -
Connors Steel Huntington, W. Va. 1 1950 50 150,000 Baghouse
1 1959 50
- - -
North Star Steel St. Paul, Minn. 1 1967 60 300,000 Direct extraction & furnace hoods,
Co. 1 1970 60 baghouse
- - -
Jessop Steel Co. Washington, Pa. 2 14 65,000 Caoopy hocx:ls and baghouse
1 14
1 I 1962 20
Latrobe Steel Co. Latrobe, Pa. -y- 1964 -a- 40,000 Direct extraction
2 1964 30
La trobe Forge am Latrobe, Pa. 1 1972 35
Spring - - -
Lukens Steel Co. Coatesville, Pa. 1 1958 100 850,000 Direct extraction, bagoouse
1 1962 100
1 1965 150
1 1973 150
~ta Machine Co. West Harestead, Pa. 1 1971 ----so 70,000 Baghouse
Midva1e-Heppenstall Philadelphia, Pa. 1 30 270,000 Furnace hocx:l am side hocx:l
Co. 1 50
1 100
National Forge Co. Irvine, Pa. 1 ~ 100,000
-L 45
Erie, Pa. 1 35 140,000
-L ---.lL
Sharon Stee 1 Corp. Sharon, Pa. 1 1958 100 300,000 Furnace hood and baghouse
1 1962 100
- - -
U.S. Steel Corp. Dujuesne, Pa. 1 1942 75 350,000 Roof caoopies, building evacuation
2 1942 100 am baghouse
1 1946 100
-L 1953 30
Fairless, Pa. 2 1971 2M 550,000 Building evacuation, baghouse
Johnstown, Pa. 1 1966 30 80,000 Furnace hocx:l
Union Electric Steel Pittsburgh, Pa. 1 1966 40 80,000
Corp. - - -
Was::o Ioc. Latrobe, Pa. 1 1968 10 15,000
Washington Steel Washington, Pa. ~ ...lli1.. ~ 45,000 Direct extraction am. baghouse
Corp. -
(continued)
-------
APPENDIX A-4.
(continued) .
:J;i
I
I-'
w
Furnace Estimated
NLIitIer Capacity Annual Capacity
Crnq:xmy Lcx::ation Furnaces Year net tons net tons Type of Control Equiprent
Phoenix Steel Corp. Clayrn:>nt, Del. 2 1968 150 525,000 Direct extraction, heat exchanger,
- - - baghouse
Florida Steel Corp. Croft, N.C. 1 1961 15 100,000 Direct extraction, baghouse
1 1965 80
- - -
Georget:.o.m Steel Georget:.o.m, S.C. 2 1968 70 300,000 Direct extraction, cooling tower,
Corp. scn.1bbers (Wi vidual)
- - -
Nucor Darlington, S.C. 1 1969 20 150,000
1 1970 20
1 1973 20
- - -
(Men Electric Steel Cayce, S.C. 2 1961 10 50,000 Baghouse
Co. 1 1968 25
- - -
Atlantic Steel Co. Atlanta, Ga. 1 1952 85 450,000 Direct extraction, baghouse
1 1956 85
- - -
Florida Steel Corp. Irrliantown, Fla. 1 1970 30 90,000 Direct extraction, baghouse
1 1974 35
TaJT1[Xl , Fla. 1 1958 15 200,000 Direct extraction, baghouse
1 1961 20
1 1966 20
- - -
Ceco Corp. Birmingh3m. Ala. 2 1955 6 90,000 Side hoods, baghouse
-.L .J.25lL 10
Connors Steel Birntingh3m, Ala. 2 1972 30
Republic Steel Corp. Gadsden, Ala. 2 1957 JJl.L 450,000
-
Mississippi Steel Fl0.;0cd, Miss. 1 1957 10 60,000
1 1963 10
- - -
Knoxville Iron Kfx)xvi lle, Tenn. 2 10 100,000
1 1964 25
- -- -
Tennessee Forging Harr iman, Tenn. 1 1966 20 150,000
Steel 1 1970 20
- - -
(continued)
-------
APPENDIX A-4.
(continued) .
~
I
f-'
~
FurTlace EstirTated
Nunber Capacity Annual Capacity
O:JTpany Location FurTlaces Year net tons net tons Type of Control Equiprent
Braeburn Alloy Steel Co. Braeburn, Pa. 2 6 10,000
1 1
- -
Carpenter Tech. Corp. Reading, Pa. 5 12 90,000
- -
Ceo:J Corp. Milton, Pa. 2 1948 22 170,000 Bagmuse
1 1958 22
- - -
Crucible Steel Corp. Midland, Pa. 1 1939 75 250,000
1 1940 75
1 1941 25
2 1941 75
- - -
Cyclops Corp. Bridgeville, Pa. 4 12 120,000 Direct extraction, side
1 1962 40 extraction, hx:ds, bagmuse
- - -
Fdgewater Corp. Oakrront, Pa. 1 1964 45 65,000 Side hx:ds and furnace hx:d
- - -
-------
~
I
f-'
U1
APPENDIX A-5.
SURFACE CONDITIQNING AIR POLLUTION CONTROL SYSTEMS IN THE U.S.
AND STEEL INDUSTRya
IRON
Annual capacity Type of control Gas flow
3/ . ACFMb
Company & location Type of mill tonne net tons equipment Nm m~n
Atlantic Steel Co. Blooming 435,456 480,000 Baghouse c
Atlanta, Ga.
Armco Steel Corp. Blooming 589,680 650,000 High-energy scrubber 3,996 141,000
Houston, Tex. Slabbing 1,360,000 1,500,000 High-energy scrubber 2,834 100,000
Kansas City, Mo. Blooming 752,976 830,000 High-energy scrubber 1,304 46,000
Middletown, Ohio Slabbing 2,358,720 2,600,000 High-energy scrubber 2,834 100,000
Babcock & Wilcox Co. Blooming 453,600 500,000 High-energy scrubber 2,550 90,000
Koppel, Pa.
Bethlehem Steel Corp. Slabbing 3,084,480 3,400,000 High-energy scrubber 3,117 110,000
Burns Harbor, Ind.
Johnstown, Pa. Blooming 2,195,424 2,420,000 High-energy scrubber 2,834 100,000
Billet 884,520 975,000 Wet ESP 737 26,000
Los Angeles, Ca!. Blooming 612,360 675,000 Baghouse c
Sparrows Point, Md. Slabbing 2,721,600 3,000,000 Wet ESP 4,251 150,000
Blooming 2,639,952 2,910,000 Wet ESP 708 25,000
Copperweld Corp. Blooming 480,816 530,000 Wet ESpd 1,417 50,000
Warren, Ohio I
Carpenter Technology Blooming 181,440 200,000 Baghouse e !
Corp.
Bridgeport, Conn.
CF & I Steel Corp. Blooming 563,371 621,000 d
Pueblo, Colo.
Crucible, Inc. Blooming 1,020,600 1,125,000 d
Midland, Pa.
(continued)
-------
>'
I
t-'
0'\
APPENDIX A-5.
(continued) .
-- -
Annual capacity Type of control Gas flow
3/ . ACFMb
Company & location Type of mill tonne net tons equipment Nm m~n
Ford Motor Co. Slabbing 3,628,800 4,000,000 Water flume & sprays 2,692 95,000
Dearborn, Mich.
Inland Steel Co. Blooming 1,134,000 1,250,000 Water flume & sprays 2,550 90,000
East Chicago, Ind. Blooming 1,632,960 1,800,000 Water flume & sprays 2,267 80,000
Slabbing 2,903,040 3,200,000 Water flume & sprays 2,834 100,000
J & L Steel Corp. Blooming 1,918,728 2,115,000 Wet ESP 3,542 125,000
Aliquippa, Pa. I
Cleveland, Ohio Slabbing 2,449,440 2,700,000 Wet ESP 2,834 100,000
Pittsburgh, Pa. Blooming 1,647,475 1,816,000 Cyclones 2,834 100,000
Jessop Steel Co. Blooming I 145,152 160,000 Baghouse e
Owensboro, Ky.
Kaiser Steel Corp. Slabbing 2,830,464 3,120,000 Wet ESP 2,324 82,000
Fontana, Cal.
Lukens Steel Co. Plate 521,640 575,000
Coatesville, Pa.
I
Phoenix Steel Corp. f Venturi scrubber
Phoenixville, Pa.
Republic Steel Corp. Blooming 781,099 861,000 \vet ESP 1,700 60,000
Buffalo, N. Y.
Cleveland, Ohio Blooming 925,344 1,020,000 Wet ESP 2,343 75,000
Slabbing 2,574,634 2,838,000 Wet ESP 2,834 100,000
Billet 635,040 700,000 Wet ESP 1,275 45,000
Youngstown, Ohio Blooming 1,584,878 1,747,000 Baghouse e 1,417 50,000
(con tinued)
-------
APPENDIX A-5.
(continued) .
~
I
f-'
"
Annual capacity Type of control Gas flow
3/ . ACFMb
Company & location Type of mill tonne net tons equipment Nm m~n
Roblin Steel Co. g Baghousee
Dunkirk, N. Y.
Timken Co. h 535,248 590,000 Baghouse 5,951 210,000
Canton, Ohio
United States Steel Slabbing 2,268,000 2,500,000 Scrubber
Corp.
Braddock, Pa.
Duquesne, Pa. Slabbing 1,496,880 1,650,000 Wet ESP 2,834 100,000
Fairless Hills, Pa. Blooming 1,542,240 1,700,000 ESP~ 2,343 75,000
Slabbing 2,630,880 2,900,000 ESP~ 3,259 115,000
Gary, Ind. Slabbing 2,558,304 2,820,000 ESP 2,692 95,000
Billet 1,088,640 1,200,000 ESP 1,757 62,000
Rail 618,710 682,000 ESP 879 31,000
Bar 453,600 500,000 ESP 1,757 62,000
Bar 186,883 206,000 ESP 1,757 62,000
Homestead, Pa. Slabbing 2,792,362 3,078,000 Multi-cyclones e 232 8,200
W-P Steel Corp. Slabbing 1,385,294 1,527,000 Low-pressure scrubber
Steubenville, Ohio
Y.S. & T. Co. Slabbing 2,363,348 2,604,000 High-energy scrubber 2,834 100,000
East Chicago, Ill.
Campbell, Ohio Blooming 1,545,869 1,704,000 High-energy scrubber 2,834 100,000
c Scarfing emissions are exhausted to a
also controlling electric arc melting
d Under construction.
common baghouse
furnace emissions.
e Conditioning of slabs, blooms, or billets is done
by grinding.
f f.
Ingot scar ~ng.
h Selective scarfing of
i
To be replaced by wet
cold billets at several scarfing stations.
electrostatic precipitators.
a Battelle foBTorial Institute; EPA Re~rt No. 600/2-76-002.
b ACFM - actual cubic feet per minute.
-------
APPENDIX
a
SUbLERGED ELECTRIC: ARC rERROALLOY FURNACES IN THE UNITED STATES
A-6.
>'
I
i--'
00
Ferro- Furnace Estimated
No. of alloy rating, annual production,
Company Location furnaces Year produced kva net tons Equipment
Tenn. Metallurgy Co. 2 FeSi
Tenn-Tex Alloy Corp. Houston, Texas 1 FeMn
Foote Mineral Co. Wenatchee, Wash. 4 1942 FeSi 27,000 (45,000)
Ohio Ferro-Alloys Corp. Tacoma, Wash. 1 1941 FeCr 16,000 (31,000)
Foote Mineral Co. Grahma, W. Va. 5 1952 FeMn
FeSi
1 1953 FeCr
FeCrS
1 1965 SiMn
1 1967 50FeSi 54,700 (90,000)
1 1972 75FeSi 54,700 (51,000)
Diamond Shamrock Kingwood, W. Va. 1 FeMn
Union Carbide Corp. Alloy, W. Va. 1 1932
1 FeSi+Si 12,000 (11,000) Baghouse
1 Lime-Mn 18,000 Baghouse
Ore
1 FeMn+Si 20,000 (65,000) Baghouse
1 1967 FeCrSi 30,000 26,400
1 FeSi 30,000 (50,000)
Ohio Ferro-Alloys Corp. Powhatan, Ohio 1 1958 FeSi+Si
2 1959 FeSi+Si
1 1966 FeSi+Si 33,600 (1956)
( continued)
-------
APPENDIX A-6.
(continued) .
~
I
......
\0
Ferro- Furnace Estimated
No. of alloy rating, annual production,
Company Location furnaces Year produced kva net tons Equipment
Union Carbide Corp. Ashtabula, Ohio 1 1943
1
1 1951
1
1 1967 FeSi 40,000 66,000
1 1975 FeSi 48,000 75,000
Marietta, Ohio 3 1951
1 1952 50FeCrSi 45,000 (75,000) Scrubber
1 1952 FeCrSi 25,000 (24,000) Scrubber
1 1953 75FeSi 20,000 (19,000)
2 1953
1 1968 SiMn 30,000 (29,000) Scrubber
1 1969
1 1969 FeCr 30,000 (60,000) Scrubber
New Jersey Zinc Co. Palmerton, Pa. 2 FeMn 10,000 50,000
Air Reduction Co., Inc. Charleston, S. C. 2 1971 HCFeCr 35,000 (130,000) ESP
Chromium Mining & Woodstock, Tenn. 1 FeMn
Smelting 1 1951 FeSi
1 FeCr
1 FeCrSi
Air Reduction Co., Inc. Niagara Falls, N. Y. 1 1960 25,000 47,000 Baghouse
Union Carbide Corp. Niagara Falls, N. Y. 1
(continued)
-------
>'
I
1',,)
o
APPENDIX A-6.
(continued) .
Ferro- Furnace Estimated
No. of alloy rating, annual production,
Company Location furnaces Year produced kva net tons Equipment
Hanna Nickel Smelting Riddle, Oregon 4 1955 Ore Melt 14,00-0
2 1955 FeNi 2,500
1 1955 FeSi 13,500
Union Carbide Corp. Portland, Oregon 2 1941 FeSi 24,000 80,000
Foote Mineral Co. Vancoram, Ohio 2 1956 12,600 37,000
(Steubenville) 2 1956 10,000
1 1956 FeCr
3 1957 FeCr
1 1964 FeCrSi
1 1965 FeCrSi
Cambridge, Ohio 1 1953
1 1970
1 1971
Interlake Steel Corp. Beverly, Ohio 2 1953 HCFeCr 8,100 35,000
2 1954 HCFeCr 11,250
1 1963 FeSi+Si 29,000 (48,000)
1 1966 FeSi 26,500 (13,000) Baghouse
1 1967 FeSi 36,000 (60,000) Baghouse
Ohio Ferro-Alloys Corp. Brilliant, Ohio 3 1951
1 1965
Philo, Ohio 2 1958
2
2 (1965)
1 1966 50F'eSi 60,000 (100,000)
1 1971 75FeSi 60,000 (57,000)
NI Industries Niagara Falls, N. Y. FeCTi
FeTi
(continued)
-------
APPENDIX A-6.
(continued) .
:t:I
I
N
f-'
Ferro- Furnace Estimated
No. of alloy rating, annual production,
Company Location furnaces Year produced kva net tons Equipment
Agrico Chemical Co. Pierce, Fla. FeP
FMC Corp. Pocatello, Idaho FeP
Hooker Chemical Co. Columbia, Tenn. FeP
Mobil Chemical Co. Nichols, Fla. FeP
Monsanto Co. Soda Springs, Idaho FeP
Stauffer Chemical Co. Mt. Pleasant, Tenn. FeP
Silver Bow, Montana FeP
Tenn. Valley Authority Musele Shoals, Ala. FeP
Metalothermic Furnaces
Shieldalloy Corp. Newfield, N. J. FeV, FeTi,
FeB, FeCb,
etc.
Climax Molybdenum Co. Longeloth, Pa. FeMo
Kuwecki Chemical Co. Easton, Pa. FeCb
Reading Alloys Robesohia, Pa. FeCb, FeV
Molybdenum Corp. of Washington, Pa. FeMo, FeW,
America FeCb
Air Reduction Co., Inc. Mobile, Ala. 1 1972 50FeSi 40,000 (65,000) \oJet scrubber
Interlake, Inc. Selma, Ala. 1 I 1966 FeSi 18,000 30,000 I
I I
(continued)
-------
~
I
N
N
APPENDIX A-6.
(continued) .
. Furnace!
Ferro- Estimated
No. of alloy rating, annual production,
Company Location furnaces Year produced kva net tons Equipment
Tenn. Alloys Corp. Bridgeport, Ala. 3 FeSi
Union Carbide Corp. Theodore, Ala. 1 1940
Woodward Iron Co. Woodward, Ala. 1 FeSi
Foote Mineral Co. Keokuk, Iowa 1 FeSi 9,000 (9,000)
(8 furnaces) 1 1964 FeSi
1 1967 FeSi 54,700 90,000
Air Reduction Co., Inc. Calvert City, Ky. 1 1949 8,500
1 1949 11,000
1 1949 15,000
1 17,000
4 3,500
1 21,300
2 1965 48,000 180,000 Baghouse
a "Cbst of Clean Air," Battelle ~rial Institute, 1974.
-------
APPENDIX A-7.
Customer
Tennessee Coal & Iron - u.s.
u.s. Steel Corp.
Geneva, Utah
u.s. Steel Corp.
Fairless Works
Youngstown Sheet & Tube
Indiana Harbor, Ind.
U.s. Steel Corp.
Edgar Thomas Works
Bethlehem Steel Corp.
;Tohnstown, Pa.
:J:II
I
I\J
W
Bethlehem Steel Corp.
Bethlehem, Pa.
RESEARCH-COTTRELL PRECIPITATORS ON SINTER MACHINE GAS
No. of
machines
3
2
1
1
1
2
4
Gas Vol/
machine
150,000
ft 3/min
140,000
ft3/min
440,000
ft 3/min
375,000
ft3/min
19J,500
ft /min
213,000
ft3/min
385,000/
Pprt.
Temp.
250°F
450°F
300°F
180 -
350°F
250°F
240°F
240°F
Efficiency,
%
Guar. 90%
Act. 95 -
98%
Guar. 95%
Act. 95.5
- 97.4%
Guar. 93.75
Act. 98.7%
Guar. 96.5%
Guar. 98%
98
"
Dust inlet
1.0 - 2.0
grains/SCF
0.576 - .830
grains/SCF
1. 22 grains/SCF
1.4 grains/SCF
2 - 4 grains/
SCF
.02 grains/SCF
-------
APPENDIX A-8
LIST OP
RESEARCH-COTTRELL DESIGNED
OXYGEN STEEL ~ffiKING
COTTRELL PRECIPITATORS
-----------------------------------------------------------
No., Type Total Eff. %
CUstomer & Location & Size No. of ft3/min Grs .jSCF
--_l~~~~~~~~L_____- Purnaces ~E~;:~.=. _'!:~~E.=. Outlet
---------- ----------
u. S. Steel Corporation 4 Open Hearth 4 134,400 95.50
Torrance, California 35 Ton 450oP . 03
u. S. Steel Corporation 10 Open Hearth 8 440,000 96.00
Provo, utah 250 Ton 5000p .03
Jones & Laughlin Steel 2 LD Converter 1 238,000 99.50
Corporation 60 Ton 7000p .05
Aliquppa, Pa.
Kaiser Steel Corporation 2 LD Converter 2 403,000 99.80
Fontana, California 75 Ton 5600p .0045
Jones & Laughlin Steel 1 Open Hearth 1 101,500 97.50
Corporation 250 Ton 5000p .025
Pittsburgh, Pa.
Kaiser Steel Corporation 1 LD Converter 1 202,500 99.80
Fontana, California 75 Ton 560oF . 0045
Bethlehem Steel Company 3 Open Hearth 2 700,000 98.75
Lackawanna, New York 380 Ton 550oF . 03
Bethlehem Steel Company 6 Open Hearth 2 700,000 98.75
Lackawanna, Hew York 275 Ton 5500F .02
Republic Steel Corp. 2 Open Hearth 2 300,000 99.00
Chicago, Illinois 265 Ton .05
Bethlehem Steel Co. 8 Open Hearth 2 396,000 98,00
Johnstown, Pa. 185 Ton 4500p .05
(continued)
A-24
-------
Customer & Location
___l~~~~~~~~l_____-
Weirton Steel Company
Weirton, West Virginia
Bethlehem Steel
Bethlehem, Pennsylvania
Bethlehem Steel
Franklin Works
Johnstown, Pa.
U. S. Steel Corp.
Fairless Works
Fairless Hills, Pa.
U. S. Steel Corp.
Ohio Works
Youngstown, Ohio
APPENDIX A-8. (continued)
LIST OF
RESEARCH-COTTRELL DESIGNED
OXYGEN STEEL MAKING
COTTRELL PRECIPITATORS
No., Type
& Size
Furnaces
----------
2 Open Hearth
325 Ton
2 Basic Oxygen
250 Ton
8 existing
1 future
02 lanced
O.H.
9 O.H.
10 of 12
O.H. fees.
A-25
No. of
_~EEE~.:.
1
.3
1
2
2
Total
ft3jmin
_'E~IEE.:.
260,000
5000F
960,000
5000F
624,000
1391,000
556,000
(total)
Eff. %
Grs.jSCF
Outlet
---------
99.20
.02
99.7
.05
99.0
(0.5)
97
(.03 )
98
( . 0 5 we t )
-------
APPENDIX A-9.
RESEARCH-COTTRELL, INC.
HIGH EFFICIENCY SCRUBBER INSTALLATIONS
~
I
N
0'\
Gas Vol PD Outlet
# of ft3/min in. Conc.
Customer & Location Application Units Scrubber H20 Gr/SCF
McLouth Steel Corporation Sinter Dedusting 2 100,000 8 .03
Trenton, Michigan Systems
Allison Steel Company Elec. 2 9,000 40 .05
Phoenix, Arizona Furnace
Allegheny Ludlum Steel B.O.F. 1 314,000 42 .05
Corp.
Brakenridge, Pa.
Armco Steel Co. Elec. 2 204,000 46 .05
Sheffield Division Furnace
Houston, Texas
Union Carbide Corporation Elec. 2 115,000 55 .02
Alloy, W.Va. Furnace
Union Carbide Corporation Silicon - 2 127,000 57 .035
Marietta, Ohio Manganese
Elec. Furnace
Northwestern Steel & Wire Elec. Furnace 1 245,000 40 .05
Sterling, Illinois
Armco Steel Corp. Elec Furnace 3 194,000 45 .035
Butler, Pa. I
(conti.nued)
-------
APPENDIX A-g.
(continued)
Gas Vol PD Outlet
# of ft3/min In. Cone.
Customer & Location Application Units Scrubber H20 GrISC1='
Armco Steel Corp. Elec. Furnace 1 204,000 46 .04
Houston, Texas
Kaiser Engineers for 6 Open Hearth 6 218,000 47 .03
Armco Steel Corp. Furnaces
Middletown, Ohio
S&B Engineers for Ferrosilicon 1 32,600 39 -
Tenn-Tex Alloy Corp. Electric Furnace
>'
I Armco Steel Corp. Electric 1 204,000 46 .04
I\.) Arc
--.J Houston, Texas Furnace
Union Carbide Corporation Ferrochromium 2 127,000 57 .035
Marietta, Ohio Elec. Furnace
S&B Engineers for Elec. Furnace 1 200,000 45 .05
Tenn-Tex Alloy Corp.
Houston, Texas
Northwestern Steel & Wire Elec. Furnace 1 42,000 50 .02
Sterling, Illinois
U. S. Steel Corp. Elec. Furnace 2 42,000 50 .02
Fairless Works
Fairless, Pa.
-------
APPENDIX B-1
CAPITAL AND ANNUAL COSTS OF PRECIPITATORS ON SELECTED
IRON AND STEEL AND FERROALLOY PROCESSES
B-1
-------
50 10
45 CAPITAL COSTS 9 ANNUAL COSTS
40 8
35 7
30 6
I.D
tD I.D a
I ~ 25 ><5
N
x --
-- 20 4
15 3
10 2
5
0.20.40.60.81.01.21.41.61.82.0
106ACFM
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8
106ACFM
2.0
Figure B-l-l.
Capital and annual costs of cold side ESP's on sintering windbox.
-------
4.5 1.8
4.0 CAP IT AL COSTS 1.6 ANNUAL COSTS
3.5 1.4
99.6% EFF.
3.0 1.2
99% EFF.
tD ~o 2.5 ~o 1.0
,.... ,....
I
W >< ><
~ 2.0 - 0.8
1.5 0.6
1.0 0.4
0.5 0.2
20
40
60
80 100 120 140 160 180 200
106ACFM
Figure B-l-2.
20
60
40
80 100 120 140 160 180 200
106ACFM
Capital and annual costs of cold side ESP's on scarfing process.
-------
8 1.6
9.6% EFF.
7 CAPITAL COSTS 1.4 ANNUAL COSTS 99% EFF.
98% EFF.
6 1.2
99.6% EFF.
1.0 5 99% EFF. 1.0
0 98% EFF.
1.0
t:C >< 4 ~ 0.8
I
tl::> ~ ><
3 ~ 0.6
2 0.4
1 0.2
50
100 150 200 250 300 350 400 450
103 ACFM
Figure B-1-3.
50
100 150 200 250 300 350 400 450
103 ACFM
Capital and annual costs of cold side ESP on open hearth furnace.
-------
9
8 CAPITAL COSTS
7
6
tt1 \00 5
-
I
111 ><
~4
3
2
1
99.6% EFF.
99% EFF.
98% EFF.
50 100 150 200 250 300 350 400 450 500
103 ACFM
2.0
1.5
\0
o
><
~1.0
0.5
t
ANNUAL COSTS
99.6% EFF.
99% EFF.
98% EFF.
50 100 150 200 250 300 350 400 450 500
103 ACFM
Figure B-l-4.
Capital and annual costs of cold side ESP's on basic oxygen furnace.
-------
8 1.6
7 CAPITAL COSTS 1.4 ANNUAL COSTS
6 1.2
100 5 99.6% EFF. 100 1.0
r-
>< ><
IJj i4 4 99% EFF. - 0.8
I
0'\ 98% EFF.
3 0.6
2 0.4
0.2
20
40
60
80 100 120 140 160 180 200
103 ACFM
99.6% EFF.
99% EH.
98% EFF.
20
60
80 100 120 140 160 180 200
103 ACFM
40
Figure B-1-5.
Capital and annual costs of cold side ESP's on electric arc furnace.
-------
,--
APPENDIX B-2
CHECKLIST FOR OBTAINING DESIGN AND OPERATING DATA ON
PARTICULATE SCRUBBERS (Design and Operating Parameters)
Application
Vendor
Design type
No. of scrubber modules
Installed scrubber capacity,
acfm
Reheat?
Capital cost,
$/kw
Dust composition
Gas composition
Actual gas flow,
acfm
Gas flow/module
Temperature,
OF
Diameter of scrubber,
ft
Length of scr~bber,
ft
Gas velo:::ity,
fpm
Gas retention time, s
Particle size distribution
Inlet dust loading,
gr/scfd
L/G..
gal/1000 acf
Method of water injection
type
Average droplet size, micron
Average droplet speed, ft/s
Open or closed loop system?
Total pressure drop, in. wq
B-7
-------
APPENDIX B-2.
(continued)
Overall collection efficiency,
%
Fractional collection efficiency,
%
Water requirement,
acre-ft/yr
<
Electric power requirement,
kW
Electric power, ~ of generating capacity
Manpower, total operators
Availability,
%
B-8
-------
APPENDIX B-3
VENTURI SCRUBBER CORRELATIONS BASED ON
RESEARCH COTTRELL COMPUTER PERFORMANCE MODEL
B-9
-------
100
90
80
~
tJj
I
......
o
..
>-
u
:z:
~ 70
u
......
1..1..
1..1..
W
:z:
8 60
I-
U
W
....J
....J
a
u
50
40
L/G=8 -
L/G=12
INLET ~ARTICULATE SIZE DISTRIBUTION:
X :: 0.21, a :: 2.86
o
30
50
110
80
70
90
100
60
20
40
PRESSURE DROP 6P, IWC
Figure B-3-1. Effects of pressure drop and L/G ratio on the
particulate collection efficiency of venturi scrubbers for open
-------
100
90
L/G=12
80 ~-~:- =
~
..
>- ~(',"'CO
u
Z
I.U 70
......
u
......
LL.
LL.
t;Ij I.U
I
~ Z
f--' 0 60
......
t-
u
I.U
-.J
-.J
0
u
50
40
INLET PARTICLE SIZE DISTRIBUTION:
X = 0.27, a = 1.82
10
20
30
40
50
60
70
80
90
100
110
PRESSURE DROP ~P, IWC
Figure B-3-2. Effects of pressure drop and L/G ratio on the particulate
collection efficiency of venturi scrubbers for basic oxygen furnace gas
(T = 300°F).
-------
100
90
L/G:15
-=
L/G=12
L/G=8
80
---~
--
~
tJj
I
f-'
tV
..
>-
~ 70
L.I.J
.......
U
.......
lL.
lL.
L.I.J
z: 60
o
.......
t-
U
L.I.J
-J
-J
8 50
40
PAR1ICLE SIZE DISTRIBUTION:
X = 0.8. a = 9.3
10
20
30
40
50 60 70
PRESSURE DROP 6P, I~C
80
90
100
110
Figure B-3-3.
Effects of pressure drop and L/G ratio on the particulate
collection efficiency of venturi scrubbers for electric arc furnace gas
(T = 300°F).
-------
100
b:J
I
~
w
..
>-
~ 99. 5
L.1J
.....
U
.....
U.
U.
L.1J
z:
o
.....
~
U
L.1J
.....I
.....I
o
U
LfG= 5
~
99
~NLET PARTICLE SIZE DISTRIBUTION:
X = 70, a = 6.67
10
20
30
40 50 60
PRESSURE DROP 6P, IWC
70
80
90
100
Figure B-3-4. Effects of pressure drop and L/G ratio on the particulate col-
lection efficiency of venturi scrubbers for sintering machine gas (T = 300°F).
-------
100
tJ:j
I
f-'
.I::>
~
..
>-
u 99.5
:z:
w
......
u
......
u....
u....
w
:z:
0
......
~
u
W
-J
-J
0
u
99
L/G==8
INLET PARTICLE SIZE DISTRIBUTION:
X == 7.7 cr == 3.5
10
20
30
40
50
60
70
80
90
100
PRESSURE DROP 6P, IW~
Figure B-3-5. Effects of pressure drop and L/G ratio on the particulate col-
lection efficiency of venturi scrubbers for sintering machine gas pretreated
-------
100
90
~
; 80
u
z:
LLJ
......
U
......
1.1...
~ 70
to
I
~
U1
z:
o
......
t-
U
LLJ
.....J
.....J
o
U
50
40
Ii~LET PARTICLE SIZE DISTRIBUTION:
X = .19, a = 3
10
20
30
40
50
60
70
80
90
100
110
PRESSURE DROP ~P, IWC
Figure B-3-6. Effects of pressure drop and L/G ratio on the particulate col-
lection efficiency of venturi scrubbers for ferrosilicon arc furnace gas (T = 300°F).
-------
100
L/G=8
90
LI G= 1 5
~-=--
lIG=1'-
~
.; 80
u
:z:
I..LJ
......
U
......
LJ....
~ 70
tD
I
i--'
0'\
:z:
o
......
I-
U
I..LJ
:j 60
o
u
50
40
INLET PARTICLE SIZE DISTRIBUTION:
X = 0.21, a = 2.12
10.
20
30
40
50 60 70
PRESSURE DROP 6P, IWC
80
90
100
110
Figure B-3-7.
Effects of pressure drop and L/G ratio on the particle col-
lection efficiency of venturi scrubbers for ferromanganese arc furnace gas
(T = 3000P).
-------
100
90 L/G=8
-=
~~
U (;~ "\ '2.
80
~
..
>-
u
z: 70
L.LJ
......
U
......
I.L..
I.L..
L.LJ
tD z: 60
I 0
......
I-' t-
...j U
L.LJ
....J
....J
0
u
50
40
INLET PARTICLE SIZE DISTRIBUTION:
-
x . 86 , a = 4. 1 9
10
20
30
40
50 60 70
PRESSURE DROP 6P, IWC
80
90
100
110
Figure B-3-8. Effects of pressure drop and L/G ratio on the particulate col-
lection efficiency of venturi scrubbers for ferrochrorniurn arc furnace (T = 300°F).
-------
100
90
-=
80
~
\.~
\.IG.~-
u
z:
L.IJ
......
u 70
......
LL.
LL.
L.IJ
td
I
f-'
co
z:
o
......
t; 60
L.IJ
-oJ
-oJ
o
U
50
40
INLET PARTICLE SIZE DISTRIBUTION:
x = 0.5, a = 3.36
10
20
30
40
50 60
PRESSURE DROP liP, IW-C
70
80
90
100
110
Figure B-3-9.
Effects of pressure drop and L/G ratio on the particulate
collection efficiency of venturi scrubbers for miscellaneous ferroalloy
-------
APPENDIX B-4
CAPITAL AND ANNUAL COSTS OF VENTURI SCRUBBERS
ON SELECTED IRON AND STEEL AND FERROALLOY PROCESSES
B-19
-------
1000
300
s:;..
~
~
<:4,.
~
~
/.~
c:-
900
800
700
8 600
o
~
-
.
~
z:
u..o
z:
~
V>
~ 500
z:
~
c:c
~
-
Q.
c:c
u 400
200
(T-300.F ,L/G-12 AND PARTlC~E
SIZE OISTRIBUTION: x-O.21 0-2.86)
100
o
60 90
GAS RAn:, 1000 act.
120
Figure B-4-lA. Effects of collection efficiency and gas
rate on the capital investment of venturi scrubber systems
for open hearth furnace gas.
B-20
-------
1000
900
(T-3008F,L/G-12 AND PARTICLE
SIZE DISTRIBUTION: ..0.21 0-2.86)
800
80 % COLLECTION EFFICIENCY
..........,151 COLLECTION EFF IC I ENCY
OTHERS INCLUDE THE COSTS OF WATER,
LABOR AHD MAINTENANCE, ETC.
700
o
o
o
....
-
100
~'
~
\),>"~ ~,.
ec."~'\~~'
\.\.;,~
~~
~ ('~
,. e'" c.~\\.u-
~~ \J"u
~~ -" OTHER
.". .-. ....= = .-. .
~~ OTHER --##=~i1EOC.AARGE
", --- r
----
.--
,
."
."
."
."
."
",>' ."
\,'" '/
,~~ -."
-<,.,."
or",~"
~'/
"'~.,, ».<>\.
,,, ." ~':i
'" ",
'" o'\'
." \"T-
"," \.\,~
."
."
."
"
."
"
.
~
~
8 600
<.!J
Z
-
~
~
.....
0..
o
;i 500
;:)
z
~
~
<
~
o
~ 400
300
200
o
60 90
GAS RATE ,1000 acfnt
120
Figure B-4-1B.
fixed charge and
venturi scrubber
Effects of gas rate, electricity usage,
others on the annual operating cost of
systems for open hearth furnace gas.
B-21
-------
1000
900
300
~
~
~
9,.
~
~
/ .'b
~
800
700
8 600
o
-
I-
z:
....
2:
l-
V>
~ 500
z:
-
...J
<
I-
-
0..
5 400
200
(T-300.f. L/'-12, AND PARTICLE
SIZE DISTRIBUTION: x-.2l, 0-1.82)
100
o
30
60 90
GAS RATE, 1000 acfll
120
Figure B-4-2A. Effects of collection efficiency gas rate
on the capital investment of venturi scrubber systems for
basic oxygen furnace gas.
B-22
-------
1000
900
(T-3008F. L/'-12. AND PARTICLE
SIZE DISTRIBUTION: .-.21. 0-1.82)
800
751 COLLECTION EFFICIENCY
........801 COLLECTION EFFICIENCY
OTHERS INCLUDE THE COSTS OF WATER,
LABOR AND MAINTENANCE, ETC.
700
o
o
o
~
-
.
.....
VI
8 600
~
z:
....
.....
<
a:
...
Q..
o
~ 500
::>
z:
~
300
~
,/
,/
/
,/
,/
,/
/
~,/
r..,'\:),/
~~/
A....'
~'t-/
~ ,/
/
~~",/
,'\:)/
/
,/
/
/
/
/
/
/
,/
,/
,/
,/
,
4
... /
Ii)~' /
r- (,) .,
,~.s~~ .,
o,,~ /
Ii)' .,
"Ii)'\~ .,/
/
.,
.,
.,
.,
~" .,
~~ '/ Y.U~
\"..."., \" \)
~'\~/ c.,y.\c.
~~'\., ~\.~
~~ c.~R~
/ f\1.£.O ---
"'" ...- -- .-..-..'"
/ -~"'--OTHER
--
, ~---::-
-----~~....
~:.- F1~EO c.HARGE
-'
<
.....
o
..... 400
200
100
-
o
60 90
GAS RATE ,1000 ad..
120
Figure B-4-2B. Effects of gas rate, electricity usage,
fixed charges and others on the annual operating cost of
systems for basic oxygen furnace gas.
B-23
-------
1000
900
300
0-
~
~
9,.
~
~
/.~
~
800
700
8 600
o
~
-
-
~
z
~
~
VI
~ 500
z
....J
c:(
~
-
CI..
::5 400
200
(T-3008F. L/G-1Z. AND PARTICLE
SIZE DISTRIBUTION: x-.8.a.9.~)
100
o
60 90
GAS RATE. 1000 acf.
120
Figure B-4-3A. Effects of collection efficiency and gas
rate on the capital investment of venturi scrubber systems
for electric arc furnace gas.
B-24
-------
1000
900
(T-1OO-f. L/G-12. AND PARTICLE
SIZE DISTRIBUTION: x-.S.o-9.3)
800
851 COLLECTION EFFICIENCY
.........801 COLLECTlON EFFICIENCY
OTHERS INCLUDE THE COSTS OF WATER,
LABOR AHD MAINTENANCE. ETC.
700
o
o
o
100
-- .....
- -..... fIXED CHARGE
:1;~ --- ------
~~~-~~~~~~=~~~~~~.
::::------ OTHER
~'I:J~' _#'
\.~,~,.,.
..\ 'l:Jt.. .,
,'I:J~"
,."
,."
,."
.,-,.
\(.\''{'C
l\J.(."{~ .
--
-
.
I-
en
8 600
~
z:
-
I-
~
ex
....
Q.
o
~ 500
::::I
z:
:i
....J
~
I-
o
I- 400
300
200
o
60 90
GAS RATE ,1000 acf..
120
Figure B-4-3B. Effects of gas rate, electricity, fixed
charge and others on the annual operating cost of venturi
systems for electric arc furnace gas.
B-25
-------
1000
900
800
700
g 600
o
....
I-
z:
o..J
X
l-
V!
~ 500
z:
-
300
~(.."\
3,."
~.~
\.1:>
'0"
",,\ .
/~'
....J
c:(
I-
~
5 400
200
(T-300.f. L/G-B. AND PARTICLE
SIZE DISTRIBUTION: .-70. 086.67)
100
o
60 90
GAS RATE. 1000 act.
120
Figure B-4-4A. Effects of collection efficiency and gas
rate on the capital investment of venturi scrubber systems
for sintering machine gas.
B-26
-------
1000
900
(T-300.F, L/G-8, AND PARTICLE
SIZE DISTRIBUTION: .-70, Q-6.67)
800
99.8S COLLECTION EFFICIENCY
........ 99.5S COLLECTION EFFICIENCY
OTHERS INCLUDE THE COSTS OF WATER,
LABOR AND MAINTENANCE, ETC.
700
e
e
e
-
-
I-
'"
8 600
<.!I
z:
-
I-
~
.....
Q..
e
;;i 500
~
z:
~
-J
~
l-
e
I- 400
300
OTHER
~G( - - - - - '::.:. f I XED CHARGE
- -,.,... - - ---..-..-....-=-1tmRic i'TVUSAGE
--
200
100
o
60 90
GAS RATE ,1000 ad..
120
Figure B-4-4B. Effects of gas rate, electricity usage,
fixed charge and others on the annual operating cost of
venturi scrubber systems for sintering machine gas.
B-27
-------
1000
900
800
300
700
g 600
o
~
....
~
z
.....
~
VI
~ 500
z:
....
~
cc:
~
....
c..
:5 400
200
100
(T-300.F~ L/G-S AND PARTICLE
SIZE DISTRIBUTION: .-1.1. a-3.5)
o
60 90
GAS RATE, 1000 acf.
120
Figure B-4-5A. Effects of collection efficiency and gas
rate on the capital investment of venturi scrubber systems
for sintering machine gas pretreated with mechanical collector
B-28
-------
1000
900
(T-3008F. l/G-a AND PARTICLE
SIZE DISTRIBUTION: .-7.7, 0-3.5)
aoo
700
-99.51 COLLECTION EFFICIENCY
.......991 COLLECTION EFFICIENCY
o
o
o
-
.
....
V>
8 600
~
z:
....
....
~
....
Q..
o
;i 500
::;)
z:
~
100
--
£. --
1'i \)~--
l\..\J,1"'~~- Fl'#.£.O C~RG
'-'-
---- FIXED C~RG!..--
~ ..... .... ....
....................---.....---.....
---
'-' ..... ....
....J
""
....
o
.... 400
300
200
o
60 90
GAS RAT[ ,1000 acflll
120
Figure B-4-5B. Effects of gas rate, electricity usage, fixed
charge and others on the annual operating cost of venturi scrub-
ber systems for sintering machine gas pretreated with mechani-
cal collector.
B-29
-------
1000
900
300
800
700
8 600
o
~
-
I-
z:
...
:E:
l-
V')
~ 500
z:
....
~
c:(
I-
....
~ 400
200
(T-300-F. L/G-12. AND PARTICLE
SIZE DISTRIBUTION: .-.19 oe3)
100
o
60 90
GAS RATE. 1000 ad.
120
Figure B-4-6A. Effects of collection efficiency and gas rate
on the capital investment of venturi scrubber systems for ferro-
silicon and arc furnace gas.
B-30
-------
1000
900
(T-3008F. L/G-12. ANO PARTICLE
SIZE DISTRIBUTION: .-.190-3)
800
700
o
o
o
~
-
~
;;' ~~'r
/ / ,'\'
/ ~'\~
/ \,~'\:
/ \,\.:
/
/
/
/
300
200
"
-
--
\)~t-~" -
\"~ ~
,~\~ -
~\.~....
-
--
-
- ., H.E.O (.AAI\GE.
~~ ~~~~=~~
~ ~~~ ~~~
.- --
- --
OTHER- - - -:. =- - - f Uf,O(.AARGE
--
.-
100
a
60 90
GAS RATE ,1000 acflll
120
Figure B-4-6B. Effects of gas rate, electricity
charge and others on the annual operating cost of
ber systems for ferrosilicon arc furnace gas.
B-3l
usage, fixed
venturi scrub-
-------
1000
300
900
800
700
8 600
o
-
.
~
:z:
.....
:E
~
VI
~ 500
:z:
-
:;i
~
-
~ 400
200
(T-300.F, l/G-12 AND PARTICLE
SIZE DISTRIBUTION: .-.78 -2.12)
100
o
60 90
GAS RATE. 1000 acf.
120
Figure B-4-7A. Effects of collection efficiency and gas
rate on the capital investment of venturi scrubber system
for ferromanganese arc furnaces.
B-32
-------
1000
900
(T-3008F. l/6-12 AND PARTICLE
SIZE DISTRIBUTION: .-.78 -2.12)
800
........ 951 COLLECTION EFFICIENCY
80% COLLECTION EFFICIENCY
OTHERS INCLUDE THE COSTS OF WATER.
LABOR AND MA I NTEItANCE. nc.
700
8
o
300
;
/
/
/
/
/
/
/
/
~/
~'/
...,~"/
~/
~7
... ¥!/
,'\:>'/
7
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
rJ.. "
~~"/
........~:/
\~
~....~ (.0'>'
~\.~ nll..'\"~
7' oY\.~
// ,O\t-\::
/
/
/
/
/.
~
-
.
l-
on
8 600
~
z
-
I-
~
&..I
CL.
o
;;J. 500
::I
Z
~
-J
c(
I-
o
I- 400
200
100
~-
o
60 90
GAS RATE .1000 acf.
120
Figure B-4-7B. Effects of gas rate, electricity charge, fixed
charge, and others on the annual operating cost of venturi scrub-
ber systems for ferromanganese arc furnace gas.
B-33
-------
1000
900
300
~
~
10)
~.
;\
~
~
/.Oii
~
800
700
:5 600
o
-
.
~
z:
~
~
In
~ 500
z:
-
....J
-------
1000
900
(T-3008F, L/G-12 AND PARTICLE
SIZE DISTRIBUTION: x-.86.o-4.19)
800
901 COLLECTION EFFICIENCY
........851 COLLECTION EFFICIENCY
OTHERS INCLUDE THE COSTS OF WATER,
LA.BOR AND ~INT[NANCE. ETC.
700
o
o
o
~
-
l-
V>
8 600
(:I
z:
-
I-
~
...
~
o
300
UY.b'i.
cc.W.\~~ .
'i.\..:... -
--
--
- - c.I1ARbE
- ~EO __-OTHER
--
.... ~ .... .... .... .... .: :- .... --. ..... ~ .... .
---- FIXED CHARGE
...............................
.--
-
;i 500
~
z:
~
...J
cC
I-
o
I- 400
200
100
o
30
60 90
GAS RATE ,1000 acf.
120
Figure B-4-8B. Effects of gas rate, electricity usage,
fixed charge and others on the annual operating cost of
venturi scrubber systems for ferrochromium arc.
B-35
-------
1000
300
900
800
700
8 600
o
-
-
.
I-
z:
~
:E
l-
V')
~ 500
z:
-
~
<
I-
-
~ 400
200
(T-300-F. L/G-12 AND PARTICLE
SIZE DISTRIBUTION: x-.5. 0-3.36)
100
o
60 90
GAS RATE. 1000 ac"
120
Figure B-4-9A. Effects of collection efficiency and gas
rate on the capital investment of venturi scrubber systems
for miscellaneous ferroalloy arc furnace.
B-36
-------
1000
900
(T-3008F. L/G-12 AND PARTICLE
SIZE DISTRIBUTION: x-.5. 0-3.36
800
881 COLLECTION EFFICIENCY
........ 821 COLLECTION EFFICIENCY
OTHERS INCLUDE THE COSTS OF WATER.
LABOR AND MAINTENANCE. ETC.
700
o
o
o
-
l-
V'!
8 600
CJ
z:
....
I-
~
...,
G-
o
300
~
.."
.."
.."
.."
(.,f::J~" ..,,""
~,~..""
f::JVr,,;~
"f::J'~"" ..,
.."..,,""'~~
..,,"" (.,\"~
.." £~,,'t-'\
..,,"" \,.\.'"
.."
.."
ci 500
~
z:
:i
~
<
I-
o
I- 400
200
100
C.AARGE
--___-OTh£R
~ ~ .--. ~ ..... .... .-. ..... .-. .-
.... ...............-.""
.~.- ----fUED c.AARGE
.......-...-...........-.
--
U~Gl- --
l\.\.C.W.~\j1- -
-;,00000"" T f.R
--
-
oL,
30
60 90
GAS RATE ,1000 acfll
120
Figure B-4-9B. Effects of gas rate, electricity usage,
fixed charge and others on the annual operating cost of
venturi scrubber systems for miscellaneous ferroalloy arc
B-37
-------
APPENDIX B-5
CASE HISTORY OF A USER'S EXPERIENCE WITH A
LARGE FABRIC FILTRATION SYSTEM
This appendix is a case history of a fabric filter
system on a typical application in the iron and steel in-
dustry.
The plant is a midwestern electric arc furnace
steel shop.
The information contained herein was obtained
during a site visit and conversations with engineering,
operating and maintenance personnel.
The melt shop is a complex consisting of a six-strand
continuous casting unit and three primary aisles:
a scrap
aisle, furnace aisle, and teeming aisle.
The structure is
420 ft long, 250 ft wide, and 152 ft high.
An attached
servicing facility adds another 180 ft in length and 120 ft
in width.
Six cranes service the shop:
a 300-ton ladle crane and
25-ton maintenance crane service the teeming aisle, a 150-
ton and a 25-ton crane service the furnace aisle, and two
25-ton cranes service the scrap aisle.
The plant operates two identical 225-ton capacity 24 ft
diameter electric arc furnaces powered by a 76,000 kVA
B-38
-------
transformer.
Each carbon electrode in 24 in. in diameter, 8
ft long, weighs 2700 Ib and costs $1,900.
Each furnace
weighs 480 tons empty and can be tilted 15 degrees to pour
off slag and 40 degrees for tapping the 225 ton heat.
The
normal time from initial scrap charging to pouring is
approximately 4 h.
The molten steel from the furnaces is
either fed to the continuous casting machine or teemed into
molds.
If the steel is teemed, 50 to 60 3-1/2 ton ingots
are obtained from each heat; if the steel is cast, it is
cast into blooms 7 in. X 7 in. X 30 ft in length.
Scrap charges consist basically of low grade scrap--No.
2 bundles with galvanized, auto shredder scrap, and oily
turnings.
Maximum amount of turnings allowed is 20 percent
of the total charge (5% oil content) or two 10-ton buckets
which are always charged first.
Very little fluorspar flux
is used in the melt.
Each furnace heat lasts slightly under
4 h and consists of three charges (one primary and two back
charges) .
Oxygen lancing is used to burn out the door and
lower carbon content.
Occasionally, oxygen lancing will be
used to hype up the melt rate if production is lagging
behind continuous casting demands.
This increases the dust
emission rate from the furnaces.
The refining period en-
compasses the final 0.5 h of the heat.
Normal production is
12 to 13 heats per day (200 to 225 tons each) .
B-39
-------
The original air pollution control system was purchased
with the furnaces and was started up in 1965.
This system
was the direct furnace evacuation type.
One of the unique
features of this system is the mounting of the water-cooled
fume take-off duct or elbow on the furnace.
Originally, the
elbow was to mount on the furnace roof support beams.
~o
10-in. and two 4-in. pipe lines (water supply and return)
would also have to be mounted on the beams.
Because of the
additional weight introduced in this fashion, a tilt elbow
was used whereby the elbow and associated piping mounts
directly to the furnace platform.
Tilting onto or off of
the roof is accomplished through a hydraulic cylinder at
2,000 psi.
The elbow is normally on the furnace during
melting, slagging and pouring, and off the furnace for
charging.
The total exhaust volume of 220,000 acfm at 500°F from
the two furnaces was handled by an open pressure baghouse.
The baghouse had 144,200 ft2 of total filtration area
divided into 14 compartments for a net operating air to
cloth ratio of 1.78:1.
~o compartments were off line for
reverse air cleaning.
The bags were 11-3/4 in. diameter X
30 ft 7 in. long fiberglass with a silicon/graphite finish.
This $3,000,000 system never operated properly.
The
25000F furnace off gas required cooling to keep the tempera-
B-40
-------
ture at or below 500°F.
The cooling was done by spraying
water directly into the ductwork located above the charging
aisle craneway.
The material buildup inside the ductwork
due to this cooling method eventually caused structural
failure and required supporting the ductwork with cables
from the roof trusses.
The original baghouse system was
badly undersized (reasons for this are unclear), and this
resulted in a reduction of melt capacity to 75 ton/h for
both furnaces.
Dissatisfaction with the existing system and realiza-
tion that direct evacuation control systems should be
supplemented with canopy exhaust prompted management to make
extensive modifications to the system which were completed
in 1974.
The old direct evacuation control system was kept
intact (with the exception of the water spray system), and a
new baghouse was added in parallel.
In addition, canopy
hoods are installed over each furnace and tapping location.
During meltdown and refining, gases are removed to the
baghouses through the tilt elbow.
During charging with the
roof off, gases are collected in the canopy (approximately
100 ft X 70 ft) over each furnace.
The hood damper auto-
matically opens through limit switches when the roof is
raised and swung off.
The total exhaust volume 1S now
1,326,612 acfm at 275°F.
B-4l
-------
The baghouse addition consists of a l6-compartment open
pressure baghouse with 23,847 ft2 of polyester bags per
compartment.
The system, as a whole, now operates at 2.7:1
net air to cloth ratio with one old compartment and one new
compartment down for cleaning.
For bag cleaning, one compartment in one new unit and
one compartment in one old unit are simultaneously off line.
Thus, only two compartments out of the total system of two
baghouses are being cleaned at anyone time.
Cleaning is
accomplished on a continuous basis.
A compartment cleaning
cycle consists of:
1. 29 s reverse air,
2. 40 s null (settle),
3. 29 s reverse air,
4. 40 s null (settle),
5. 22 s repressure, and
6. Next compartment.
The emission limitation for the shop is 39.5 lb/h based
on the State Process Weight Rule.
The company has estimated
the amount of dust not collected by the baghouses with Hi-
Vol samplers positioned in the roof monitor area above the
canopy hoods and with samplers in the baghouse monitors to
determine emission concentrations.
Total uncontrolled
emissions were thus estimated to be 6 to 20 lb/h.
Dust
B-42
-------
collected by the baghouses ranges from 30 to 45 lb/ton of
steel produced, resulting in 3150 lb/h to 4725 lb/h (at a
production rate of 105 ton/h).
The bulk density of the
collected dust is about 75 lb/ft3.
The operating experience with the new modified system
has been satisfactory.
One man working 5 days per week is
responsible for inspection of baghouse compartments and
related equipment.
The total cost to the company for this
man is $17,000/year.
For bag replacement and other repairs,
men are drawn from the general maintenance pool.
The com-
pany estimates a total operating and maintenance cost of
$1.20/ton of steel produced.
Problems were initially encountered with the canopy
damper-operators.
The actuator arms were breaking or shear-
ing keys in the gearing in the drive units.
These drive
units were rated at 590 ft-lb torque.
The torque required
to operate the dampers was 1600 ft-lb at times.
Today, the
operators are rated at 2200 ft-lb and the problem no longer
exists.
Problems occurred with the vertical poppet damper
guides shortly after start-up of the new system.
The
original guides were made of brass and quickly became worn
resulting in the dampers sticking during operation.
The old
guides were replaced with new steel guides and the problem
was alleviated.
B-43
-------
The collected dust falls into a trough hopper.
An
auger ln the bottom of the hopper runs continuously,
con-
veying the dust to a discharge auger which conveys the dust
to the end of the baghouse, where it is discharged into a
covered pan.
Then the pan is full, the conveyors are shut
down and the pan is picked up and dumped.
A clean pan is
inserted and the conveyors are restarted.
zero-speed switches on the conveyors preclude packing
dust into a section which is inoperative and finally jams
the complete system.
When a section of conveyor ceases to
operate, all augers upstream stop.
This negates the neces-
sity of removing covers, augers, etc., to unpack a conveyor
system.
Maintenance problems have not plagued the screw con-
veyors except for the outboard bearings.
These were not
packed well enough, allowing dust to enter; the shafts
eroded from 1-1/2 in. diameter to 1-3/4 in. diameter.
This
problem was solved by improving the packing to keep dust
out.
The company reports that hoppers must be rapped with a
wooden mallet periodically to dislodge bridged dust.
They
investigated installing a mechanical rapping system, but
decided it was too costly.
B-44
-------
Only 119 bags have been changed since 1974, according
to maintenance personnel.
Bags are chanqed only as they
fail.
Disposable bag caps are not being used.
If a bag is
replaced, the top cap as well as top and bottom clamps are
reused.
There have been only five to six failures due to
abrasion around the support rings.
Most problems occur near
the bag bottoms where the dust enters.
The baghouses are
continuing to experience a buildup of dust in the thimbles
at the cell plate wherein the bag entrance becomes con-
stricted, thus, increasing the pressure drop slightly.
It
is easy to dislodge this buildup with a screwdriver or
similar tool, but no permanent solution has been found, even
with the equipment manufacturer studying the problem.
Stainless steel screw-type clamps are used and bags are
tensioned from 55 to 60 lb.
Bag tension is checked every 3
months by the maintenance man.
On both the new and the old
baghouses, there are six rows of bags between walkways.
B-45
-------
APPENDIX C-l
ELECTROSTATIC PRECIPITATOR SUBSYSTEM AND
COMPONENT FUNCTION AND OPERATION
Transformer-Rectifiers
The transformer-rectifier unit consists of a high-
voltage transformer, high-voltage silicon rectifiers, and
high-frequency choke coils.
The unit converts the low-
voltage alternating current to high-voltage unidirectional
current suitable for energizing the precipitator.
The transformer, rectifiers, and choke coils are sub-
merged in a tank filled with a dielectric fluid.
The tank
is equipped with high-voltage bushings, liquid level gauge,
drain valve, ground lug, filling plug, lifting lugs, and
surge arresters, which discharge to ground any harmful
transients that appear across the d.c. metering circuit.
The electrical equipment described below is necessary
to produce and control the high-voltage unidirectional
electrifield required to energize an electrostatic precipi-
tator:
the transformer-rectifier and control unit provide a
complete system for energizing with either half-wave or
full-wave voltages.
Not all precipitator installations
incorporate all of these subcircuits, but most will have
C-I
-------
many of them.
Certain automatic procedures described here
may be performed manually on some installations.
1)
A subsystem that automatically maintains and
limits line voltage to the high-voltage trans-
former, which is connected to the discharge wires.
2)
Silicon controlled rectifiers (SCR's), which
provide a wide range of precipitator current and
voltage control.
A current-limiting reactor, which limits current
surges during precipitator sparking.
3)
4)
Automatic restart to initiate system operation
after a line voltage failure or temporary ground
condition in the precipitator.
5)
6)
Overload protection for the high-voltage rectifiers.
Panels containing component modules.
The SCR power circuit, d.c. overload circuits, relays,
control transformers, resistors, the main contactor, current
transformer, and other components are mounted in the control
cabinet and are completely accessible for servicing.
Positive
ventilation for the control unit is provided by an intake
fan located near floor level.
ventilating air is exhausted
through an opening (grill-protected) in the upper rear of
the control unit.
The transformer enclosure is a square metal housing
bolted to the top of the transformer tank.
The enclosure
protects the transformer bushings and electrical connections
from weather and also ensures, by means of a key interlock
system, that none of the electrical connections or bushings
C-2
-------
can be handled until the associated control cabinet has been
deenergized and grounded.
The transformer pipe and guard are used to feed the
high-voltage output of the transformer-rectifier to the
support bushings, which in turn are connected to the upper
high-tension support frame, from which the discharge wires
are suspended.
Figures C-l-l and C-1-2 illustrate rapper
and insulator assemblies and their relationship to the rest
of the precipitator system.
During normal operation, optimization of applied power
to the precipitator is accomplished by automatic power
controls, which vary the input voltage in response to a
signal generated by the sparkover rate.
provisions are also
included to make the circuit current sensitive to overload and
to allow control in the event that spark level cannot be
reached.
Although the circuits may vary from one installa-
tion to another, many of the features described below are
common.
An SCR mainline control diagram (Figure C-1-3)
illustrates operation of the system described below-
When the circuit breaker and control circuit on-off
switch are closed, power flows through the current-limiting
reactor, current transformer, and current signal transformer
to the primary of the high-voltage transformer.
The SCR's
act as a variable impedance and control the flow of power in
C-3
-------
DISCHARGE
ELECiRODE ,
VIBRATOR k--
DISCHARGE
ELECTRODE
VIBRATOR
DISCHARGE ELECTRODE VIBRATOR
AND INSULATOR ASSEMBLY
COLLECTING
ELECTRODE
RAPPER
~
RAPPER
COUPLING
COLLECTING ELECTRODE RAPPER
AND INSULATOR ASSEMBLY
Figure C-l-l.
Insulator, rapper assembly, and
precipitator high-voltage frame.
C-4
-------
VIBRATOR OR-------
RAPP E R ---------
BRACKET
UPPER RAPPER ROD
POWER CABLE
ASBESTOS PAD
INSTALLATION
ACCESS DOOR
LOCATED TO SUIT
INSULATOR COMPARTMENT
VENTILIATING OR PRESSURIZING
AIR CONNECTION, LOCATED TO SUIT
INSULATOR SHAFT
ASBESTOS PAD
INSTALLATION
HIGH TENSION
DUCT CONNECTION
LOCATED TO SUIT
LOWER RAPPER ROD
SUPPORT BUSHING
HANGER
HANGER FRAME
ANVIL
SPACER BEAM
Figure C-1-2.
Precipitator insulator and rapper assembly.
C-5
-------
SCR
PHASE
CONTROL
n
I
~
STAB
POWER
430-480V.
60 HZ
COHTROL
CONTACT
CURRENT
LIMITING
REACTOR
H.V. -TRANS.
CURRENT, VOLTAGE AND
SPARK RATE COHTROL
H.V.
RECHflER
UNDER
VOLTAGE
AlARM
SECONDARY OVERLOADS
Figure C-I-3.
SCR mainline control.
PRECIP.
MA.
FUlL WAVE JUMPER
WIRES
l}JPlAT'~
CURRENT
METER
-------
the circuit.
An SCR is a three-junction semiconductor
device that is normally an open circuit until an appropriate
gate signal is applied to the gate terminal, at which time
it rapidly switches to the conducting state.
Its operation
is equivalent to that of a thyratron.
The amount of current
that flows is controlled by the forward blocking ability of
the SCR's.
This blocking ability is determined by the
firing pulse to the gate of the SCR.
The current-limiting
reactor reshapes the current waveform to essentially a sine
wave and limits peak current associated with sparking.
The firing circuit module provides the proper phase-
controlled signal to fire the SCR.
The timing of the signal
is controlled by (1) the potentiometer built in the module;
(2) the signal received by the automatic controller; and (3)
the signal received by the spark stabilizer.
The automatic control circuit performs three functions:
spark control, current-limit control, and voltage-limit
control.
Spark control is based on storing electrical pulses in
a capacitor for each spark occurring in the precipitator.
If the voltage of the capacitor exceeds the present refer-
ence, an error signal will phase the mainline SCR's back to
a point where the sparking will stop.
Usually this snap-
action type of control will tend to overcorrect, resulting
C-7
-------
in a longer downtime than is desirable.
At low sparking
rates, about 50 sparks per minute, the overcorrection is
more pronounced, resulting in reduced voltage for a longer
period, with subsequent loss of dust and reduced efficiency.
Proportional control is also based on storing of elec-
trical pulses for each spark occurring in the precipitator.
The phaseback of the mainline SCR's, however, is propor-
tional to the number of sparks in the precipitator.
The
main advantage of proportional control over spark control is
that the precipitator determines its own optimum spark rate,
based on four factors:
temperature of the gas, dust resis-
tivity, dust concentration, and the internal condition of
the precipitator.
In summary, with proportional spark rate
control, the precipitator determines the optimum operating
parameters.
With conventional spark control, the operator
selects the operating parameters, which may not be optimal.
Some precipitators operate at the maximum voltage or
current settings on the power supply with no sparking.
collection of low-resistivity dusts, where the electric
In
field and the dust deposit are insufficient to initiate
sparking, the no-spark condition may occur.
The fact that
the precipitator is not sparking does not necessarily mean
that the unit is underpowered.
It may have sufficient power
to provide charging and electric fields without sparking.
C-8
-------
The voltage-limit control feature of an automatic
control module limits the primary voltage of the high-
voltage transformer to its designated rating.
A transformer
across the primary supplies a voltage signal that is com-
pared with the setting of the voltage control, as in the
case of the current limit.
The voltage control setting is
adjusted to the primary voltage rating of the high-voltage
transformer.
When the primary voltage exceeds this value, a
signal is generated that retards the firing pulse of the
firing module and brings the primary voltage back to the
control setting.
For current-limit control, a transformer in the primary
circuit of the high-voltage transformer monitors the primary
current.
The voltage from this transformer is compared with
the setting of the current control, which in turn is adjusted
to the rating of the transformer-rectifier unit.
If the
primary current exceeds the unit's rating, a signal is
generated, as with spark control, which retards the firing
pulse of the firing circuit, and this brings the current
back to the current-limit setting.
With all three control functions properly adjusted, the
control unit will energize the precipitator at its optimum
or maximum level at all times.
This level will be deter-
mined by conditions within the precipitator and will result
C-g
-------
in anyone of the three automatic control functions operat-
ing at its maximum,
i.e.,
maximum voltage, maximum primary
current, or maximum spark rate.
Once one of the three
maximum conditions is attained, the automatic control will
prevent any further increase in power that would enable
either of the other two control functions from reaching a
second maximum value.
If changes within the precipitator
require it, the automatic control will switch from one
maximum limit to another.
Other features include secondary overload circuits and
an undervoltage trip capability; which are activated in the
event that the voltage on the primary of the high-voltage
transformer falls below a predetermined level and remains
below that level for a certain period.
A time-delay relay
is also used to provide a delay period in the annunciator
circuit while the network of contacts is changing position
for circuit stabilization due to an undervoltage condition.
Rappers
The rapper equipment is a completely electrically
operated system for the continuous removal of dust from the
collecting plates.
The system is composed of a number of
magnetic-impulse, gravity-impact rappers that are periodi-
cally energized to rap the collecting plates for removal of
dust deposits.
The main components of the system are the
rappers and the electrical controls.
C-IO
-------
The magnetic-impulse, gravity-impact rapper is a sole-
noid electromagnet consisting of a steel plunger surrounded
by a concentric coil, both enclosed in a watertight steel
case.
The control unit contains all the components (except
the rapper) needed to distribute and control the power to
the rappers for optimum precipitation.
The electrical
controls provide a number of separate adjustments, so that
all rappers can be assembled into a number of different
groups, each of which can be independently adjusted from
zero to maximum rapping intensity.
Some installations have mechanical rappers.
In these
installations each frame is rapped by one hammer assembly
mounted on a shaft.
A low-speed gear motor is linked to the
hammer shaft by a drive insulator, fork, and linkage assem-
bly-
Rapping intensity is governed by the hammer weight,
and rapping frequency by the speed of rotation of the shaft.
During normal operation, a short-duration d.c. pulse
through the coil of the rapper supplies the energy to move
the steel plunger.
The plunger is raised by the magnetic
field of the coil and then is allowed to fall back and
strike a rapper bar, which is connected to a bank of collec-
ting electrodes within the precipitator.
The shock trans-
mitted to the collecting electrodes dislodges the accu-
mulated dust.
C-II
-------
The electrical controls provide a number of separate
adjustments, so that rappers can be assembled into a number
of different groups and each group independently adjusted
according to transmissometer readings.
The controls are
adjusted manually to provide adequate release of dust from
collecting plates while preventing undesirable stack puf-
fing.
In some applications the magnetic impulse, gravity
impact rapper is also used to clean the precipitator dis-
charge wires.
In this case the blow is imparted to the
electrode supporting frame in the same manner, except that
an insulator isolates the rapper from the high voltage of
the electrode supporting frame.
Vibrators
The purpose of a vibrating system is to create vibra-
tions in either the collecting plates or the discharge wires
in order to dislodge accumulations of particles so that the
plates or wires are kept in optimum operating condition.
The vibrator is an electromagnetic device; of which the
coil is energized by alternating current.
Each time the
coil is energized, the vibration set up is transmitted
through a rod to the high-tension wire supporting frame
and/or collecting plates.
The number of vibrators depends
on the number of high-tension frames and/or collecting
plates in the system.
C-l2
-------
The control unit contains all devices for operation of
the vibrators, including means of adjusting the intensity of
vibration and the length of the vibration period.
Alter-
nating current is supplied to the discharge wire vibrators
through a multiple carn-type timer to provide the sequencing
and time cycle for energization of the vibrators.
For each installation, a certain intensity and length
of vibration time will produce the best collecting effi-
ciency.
Insufficient intensity of vibration will result in
heavy buildup of dust on the discharge wires, which can
cause the following adverse operating conditions:
A reduction of the spark-over distance between the
electrodes, which limits the power input to the pre-
cipitator.
A tendency to suppress formation of negative corona and
the production of unipolar ions required for the
precipitator process.
An alteration of the normal distribution of electro-
static forces in the treatment zone. Unbalanced
electrostatic fields can cause the discharge wires and
the high-tension frarne to oscillate.
Upper Precipitator
On positive or negative pressure installations, a
pressurizing fan is supplied (located on the cold roof) to
force air into the top housing and down through the support
bushings.
This air prevents the process gases in the pre-
cipitator from entering the top housing and contaminating
the support and high-tension frame rapper (vibrator) insula-
tors.
Electric heaters are also used.
C-l3
-------
In place of a top housing, some installations have
insulator compartments.
The insulator compartment is a
steel enclosure that surrounds the high-tension frame sup-
port insulators and rapper rod insulators.
Fans are pro-
vided to prevent condensation of moisture on the high-
voltage support insulator, and sometimes electric heaters
are installed near each bushing in each insulator compart-
mente
The purpose of the high-tension anvil beam, which is
part of the high-tension frame, is to transfer the impact of
the high-tension vibrator to the discharge wires.
Discharge Wires
The discharge electrodes are small-diameter wires
suspended from a structural steel wire supporting frame,
held taut by individual cast iron weights at the lower end
and stabilized by a steadying frame at the top of the cast
iron weights.
Unshrouded and shrouded discharge wires are
illustrated in Figures C-I-4 and C-I-5, respectively.
Collecting Plates
The gas flows horizontally in the precipitator through
individual gas ducts formed by the collecting plates.
The
discharge wires are located midway between the plates for
the purpose of ionizing the gases and imparting an electric
charge to the dust particles.
It is important that the
C-l4
-------
plate and wire spacing be held to close tolerances.
Figure
C-l-6 illustrates the type of collection plate used in many
electrostatic precipitators manufactured by Research-Cottrell.
Lower Precipitator
The lower steadying frame limits or restricts the
horizontal movement of the discharge wires.
C-15
-------
Fisu~c C-1-4. Discharge
electrode unshrouded.
SHROUD CAP
SHROUD
WIRE
SHROUD
Figure C-1-6. PrecipitJto
collecting electrodes.
CAST IRON
WEIGHT
Figure C-1-5. Discharge
electrouc sh~cu~ed.
C-16
-------
1.)
2. )
a)
b)
c)
d)
e)
f)
APPENDIX C-2.
PREOPERATING CHECKLIST FOR PRECIPITATORS
General
Before start-up of the precipitator(s) and auxiliary
equipment, a complete check and visual inspection of
the following items should be performed.
Precipitator
Check Initial Date Recheck Remarks
Duct spacing
Collecting plates
o
Bowing
Bellying
Supports
Spacer bars
Corner guides
o
o
o
o
Gas sneakage baffles
Anti-swing devices
Hoppers
o
Dust level indicators
Outlet connections
Access doors
Poke holes - anvils
Vibrators
o
o
o
o
Insulator housing
o
Support bushings
Access doors
Ventilation system
Bushing connections
Bushing heaters
o
o
o
o
C-17
-------
g)
h)
i)
j)
k)
1)
m)
n)
Flues
o
Nozzle connections
Expansion joints
Louver dampers
Guillotine dampers
Perf. distribution
plates
o
o
o
o
Line voltage
o
460/480 volts-60 Hz
575 volts - 60 Hz
120 volts
Line matching transformer
o
o
o
Discharge electrode wires
o Upper steadying frame
o Lower steadying frame
o Hanger pipes
0 Lifting rods
0 C. 1. weights -
15 25 35
High-tension guard
o
Installation
Vent ports open
Ground connections
o
o
Drag bottom conveyor
Wet bottom agitators
Heat jacket system
o
Recirculating fan
Electric heater - kW
Steam heater coils
Temperature transmitters
Pneumatic recorders
Steam control valve
Starters - pushbuttons
Thermostats
o
o
o
o
o
o
o
Roof enclosure
o
Ventilation
Air conditioning
Monorail system
Roof exhausters
Lou'lers
Heaters
o
o
o
o
o
"
Check Initial Date Recheck Remarks
('-1,1
-------
0)
3.)
a)
b)
c)
d)
Gaskets for high
temperature
~uxiliary Equipment
Transformer-rectifier
units
o Surge arrestor gap
o Transformer liquid level
o Ground connections
00 Precipitator
00 Transformer
00 Rectifier
00 H.T. bus duct
00 Conduits
00 FW/HW switch box
00 Alram connections
00 Contact making
thermometer
o Ground switch
operation
o High-voltage connections
o Telephone jacks
o Sound power jacks
o Resistor board
o Space heaters
Rectifier control units
o
Controls grounded
Connections to
equipment
Space heaters
Internal light and
switch
Alarm connections
Space heaters
o
o
o
o
o
Rapper control unit
o
Connections
Lights
Space heaters
o
o
Vibrator control unit
o
Connections
Lights
Space heaters
o
o
Check Initial Data Recheck Remar
-
.
ks
C-19
-------
m)
n)
0)
p)
q)
e)
F.D. Ventilation
controls
o
Motor
Starters
Pushbutton stations
Alarm connections
Filters
o
o
o
o
f)
Electric heater controls
o
Hoppers
Insulator housing/
compartment
Roof enclosure
Control house
o
o
o
g)
Control house
o
Heaters
Ventilation
Motor control centers
Distribution
panelboards
Lighting panelboards
Starters
<>
o
o
~
o
h)
Screw conveyors
i)
Rotary feeder valves
j)
k)
Zero speed detectors
Speed reducers
1)
Trough type hoppers
Inner doors - drag bottom
level
Air vibrators-Navco 3 in.
Air vibrator controls
Water spray piping
Pillow block assembly
Check Initial Data Recheck Remarks
-
C-2Q
-------
r)
Automatic back draft
pampers
s)
Filter boxes - filters
t)
Butterfly dampers
Check Initial Date Recheck Remarks
-
C-2l
-------
APPENDIX C-3
ESP INSPECTION, ~1AINTENANCE, AND
TROUBLESHOOTING PROCEDURES
Transformer-Rectifier Sets and Associated Equipment and
Controls
Check the liquid level in the transformer weekly.
If
it is low, fill the tank to the level indicated on the gauge
with the dielectric liquid specified on the nameplate.
Dielectric fluid should be handled with extreme caution.
Clean high-tension insulators,
during each outage to minimize
porcelain is best cleaned with
abrasive cleaner.
bushings, and terminals
surface leakage. Glazed
a damp cloth and a non-
Once each year or more often, clean the contacts of
relays and dress them with a fine grade crocus cloth.
Check the dustop filter weekly. The air filter as-
sembly, easily attached and convenient for servicing,
is mounted on the control cabinet.
Transformer Enclosure
Inspect all bushings and insulators. Replace those
that are damaged; clean those that are dusty with a
nonabrasive cleaner.
Clean all interlocks and lubricate with powdered graph-
ite to ensure smooth and proper action.
Lubricate all bearing points on the ground-operated
lever, connecting rods, and bevel gears.
C-22
-------
Check all electrical connections to ensure that they
are corrosion-free and tight. Loose electrical connec-
tions can cause electrical erosion of connections and
failure of metering circuits and electrical components
in both the control cabinet and transformer.
Overhead HW-FW Switchgear
Inspect all insulators for cracks, chips, and/or dust
buildup. Replace all damaged insulators and remove
dust accumulations with a nonabrasive cleaner.
Inspect all visible contacts to be sure that they are
free of corrosion and pitting due to electrical arcing.
Handcleaning, filing, and/or wire-wheel cleaning may be
required.
Inspect for a tight fit on all couplings associated
with transformer output bushings and switching insula-
tors.
Lubricate mechanical bearing surfaces under the switch-
ing insulators to ensure smooth and proper operation.
Pipe and Guard
Remove all internal rust and/or scaling. Rust appear-
ing on the internal walls of the guard could peel off
and fall against the pipe, causing a ground on the
secondary of the transformer.
Check the condition of the wall and post insulators for
signs of electrical tracking (arcing), dust' buildup,
and cracked insulators. Clean or replace parts as
required.
Check the pipe to ensure that all connections to wall
bushings and post insulators are tight and that the
pipe elbows used to redirect the pipe at various turns
in the guard are tight and secure.
Ensure against water leakage by checking and main-
taining the seal on the inspection plates of the pipe
and guard.
C-23
-------
When replacing the inspection covers, be certain to
reinstall the ground jumper between the guard and cover
plate; this ensures that any static charge or high-
voltage leak goes to ground.
Plate Rappers
Check the rappers periodically for any possible binding
of the plunger or misalignment of assembly. The maxi-
mum amount of energy can be transmitted from coil to
plunger only when the plunger is properly located with
respect to the coil. Any deviation will decrease the
energy transmitted. Adjusting bolts allow changes of
the distance between the lower casing and the mounting
and thereby allows variation of the plunger insertion
in the coil.
If boot seal or service sheet gasket has deteriorated,
dismantle the rapper assembly and inspect the rapper
rod sleeve for ash accumulation. Packed ash in this
area will dampen shock wave to the collecting plate and
cause excessive ash accumulation on the plates (wires).
[A boot seal is the rubber seal that is stretch-fitted
over the end of the rapper rod. On negative-pressure
installations, the boot seal prevents air and water
from entering the precipitator chamber through the
rapper rod guide sleeve. On positive-pressure instal-
lations, the boot seal prevents precipitator gases from
flowing up the rapper and guide sleeve and entering the
rapper coil tube.]
Inspect striking end of plunger to insure that the end
has not been flared or otherwise deformed due to exces-
sive height in its lift and/or misalignment.
When reassembling the rapper assembly after maintenance
has been performed, make certain that the coil and coil
cover are plumb and level, and that the plunger is
properly aligned in a vertical plane on the rapper rod.
The maintenance checks outlined above apply also to
wire rappers.
Vibrators
Inspect each vibrator for proper gas setting.
Inspect boot seal for holes or tears and replace if
necessary.
C-24
-------
Inspect the service sheet gasket between the guide
plate and the mounting nipple for signs of deteriora-
tion and replace if necessary.
If boot seal or service sheet gasket has deteriorated,
dismantle the rapper rod assembly and inspect the
vibrator rod nipple for ash accumulation. Packed ash
in this area will dampen the vibrations to the dis-
charge wires and cause excessive ash accumulation,
close electrical clearances, and reduced precipitator
performance.
Check for dust or signs of inleakage of air and/or
water where the rapper rod passes through the packing
ring retainer plate. This condition is indicative of a
loose retainer plate providing an inadequate seal
between the packing and the rapper rod, or of failure
of the packing rings. A loose retainer plate should be
tightened and in case of gas leakage, the packing
should be replaced.
Upper Precipitator
Top Housing
Inspect the fan to ensure that it is working and that
the filters are in good condition.
Inspect vent elbows for accumulation of foreign matter,
which would reduce or cut off the air flow.
Check access doors, inspecting the gaskets for signs of
deterioration and leaks. Replace defective gaskets and
lubricate door lugs and hinges as required.
Check that interlocks are clean, and lubricate with
powdered graphite.
Inspect the upper rapper (or vibrator) rod on the high-
tension frame to ensure that it is centered in its
guide nipple and that no dust has packed between the
nipple and the rapper/vibrator rod. If the rapper/
vibrator rod needs to be centered in the nipple, cover
the insulator with an asbestos blanket, and with a
torch cut the nipple loose from the cold roof. Reposi-
tion the nipple, centering the rod, and reweld the
nipple to the cold roof. Care must be taken that the
C-25
-------
new weld is a complete seal; water and ambient air
could flow through pinholes and contaminate the in-
sulators.
Note: Whenever it is necessary to do any welding on
the high-tension wire supporing frame, the electrical
bus connection to the high-tension support bushing
should be disconnected. A heavy, temporary ground,
sufficient to carry total welding current, should be
solidly connected to the high-tension frame. The dis-
connected bus should be securely grounded at both ends;
i.e., in the rectifier ground switch enclosure and at
the support bushing end.
Insulator Compartments
Energize high-tension frame vibrators and check for
smooth operation. Check field wiring and vibrator
control cabinet if an inoperative vibrator is found.
vibrator insulator nuts and all pipe plugs should be
secure.
Check all nipples and seals.
Inspect all dampers in the duct connections to the com-
partments to ensure that they are in the open position.
Operate pressurizing fan and check that air is flowing
uniformly into each insulator compartment.
The vent elbow should be equipped with a pipe plug
unless the installation is operating under negative
pressure, in which case there should be no plug.
Inspect the elbow for dust and/or other foreign material.
Inspect the pipe and guard through the inspection hatch
to ensure that the inside surface is free from dust
accumulation and/or rust and scale. Remove all dust
accumulations and/or rust and scale buildups to prevent
high-voltage arcing from the pipe to the guard. Inspect
insulators to ensure that they are free from cracks,
chips, and dust accumulations. Replace any cracked or
chipped insulators and clean dirty insulators with a
nonabrasive cleaner.
Inspect the gasket on the inspection door for deteriora-
tion and leaks; replace worn or leaky gaskets. Make
sure that all bolts are in place and securely fastened.
Determine that interlock is operable and well-lubricated
with powdered graphite.
C-26
-------
Inspect upper rapper rod (see Section 3.1.3.3).
Inspect the rapper rod insulator for dust accumula-
tions, chips, cracks, and electrical tracking. Elec-
trical tracking that has not damaged the glazed surface
of the insulator and dust accumulations should be
cleaned off with a nonabrasive cleaner. Replace
cracked, chipped, or glaze-damaged insulators.
Inspect the area between the rapper rod and the hanger
pipe for packed dust accumulations. Remove any accumu-
lation, since it tends to dampen the vibration trans-
mitted to the upper high-tension frame. Check to see
that the rapper rod is centered in the support pipe.
If the support pipe is off center, chances are that the
weld between the lower rapper rod and the upper high-
tension frame was broken. Recenter the rod and reweld
it to the high-tension frame. As with the upper
rapper rod, inspect the insulator clamp, ensuring that
all bolts are in place and tight.
Check the high-tension frame support pipe. Inspect the
round nut screwed onto the support pipe to prevent pipe
movement.
Remove the cover plates and inspect the inside and
outside surfaces of the support insulator for dust
accumulations, electrical tracking, cracks, and chips.
Dust accumulations and electrical tracking that have
not damaged the glazed surface of the insulator should
be cleaned with a nonabrasive cleaner.
Plate Hanger Anvil Beam
Inspect the anvil beam hanger rod clips to ensure that
they are straight. Excessively heavy plate rapping can
in time cause these clips to bend, causing the plate
bank to shift out of alignment. This shift results in
electrical clearances out of tolerance and reduced
precipitator performance.
Inspect the hanger rods themselves to ensure that none
are broken, missing, or bent.
Inspect the area behind the plate hanger anvil beam for
packed dust. Remove dust, since it can force the beam
out of plumb.
C-27
-------
Inspect the weld between the rapper rod an~ the anvil
beam. If this weld is broken or cracked, lt should be
replaced.
Upper High-Tension Frame
Check bolts and welds on the high-tension frame.
Replace broken, bent, or missing support rods.
Check wire support angles for broken welds where they
attach to the spacer beam. Repair broken welds, making
sure that the wire support angles are parallel and on
9-in. centers (assuming 9-in. plate-to-plate spacing).
Check to determine whether the high-tension frame is
level both perpendicular and parallel to the gas flow.
If the frame is not level in the direction of gas flow,
adjust at the appropriate high-tension frame support
rods. If the frame is not level perpendicular to the
gas flow, adjust at the appropriate high-tension frame
hanger pipes.
Check for excessive accumulation of dust on this frame.
Accumulations are excessive if they interfere with
specified clearances of 4-1/2 in. + 1/4 in. between the
discharge wires and collecting plates, or if they
create a clearance of less than 4-1/2 in. between the
high-tension frame and any other grounded surface
(assuming 9-in. plate-to-plate spacing).
Discharge Wires
Whenever possible, determine the condition of the dis-
charge wires with regard to dust buildup. The amount
of buildup will indicate whether the high-tension
vibrators, when furnished, are operating at the proper
intensity.
The discharge wires should be kept as clean as is
practical.
Inadequate rapping of the discharge wires can result in
heavy dust buildup, with localization of the corona
current and excessive sparking.
A deposit on the discharge wires results from many
things, including poor gas distribution and charac-
C-28
-------
teristics of the dust. Doughnut-shaped deposits often
are formed. They are composed generally of finer dust
particles. Deposits on the discharge wires do not
necessarily result in poor performance, although de-
pending on resistivity, power supply range, and uni-
formity of the deposit they can reduce efficiency.
The discharge wires should be perfectly centered be-
tween the plates from top to bottom for optimum pre-
cipitator operation. Any broken discharge wires should
be removed and if time permits, replaced with new
wires. Since a cast iron weight is connected to each
wire at its lower end, a resistance will be felt when
pulling on the wire. A wire that gives no resistance
is broken.
Broken wires can sometimes be seen from catwalks
located between the collecting plate banks. With a
flashlight, look down each duct noting any bottle
weight that is hanging on its bottle guide and any
wires that are out of alignment.
The location of a broken wire that is removed but not
replaced should be recorded on a permanent log sheet.
This recording will save time during future outages
when time permits the installation of a new wire. A
record of broken wire locations is also helpful in
determining the cause of wire breakage, i.e., if a
number of wires break in the same area of the pre-
cipitator, there are alignment problems. If the wire
breakage is random, the breakage is probably caused by
dust buildups on wires or plates.
The damaged wire may be cut away and the replacement
wire brought into the precipitator through the top
upper high-tension frame area, placed in the proper
duct, lowered into place, and attached.
Collecting Plates
Whenever the precipitator is out of service and internal
inspections are possible, the collecting plates should
be checked for proper alignment and spacing. Check all
hangers. Make sure that spacers at the bottom of the
plates do not bind plates to prevent proper rapping.
Check the lower portion of all plates and the portion
of plates adjacent to any door openings for signs of
corrosion. If corrosion is present, it usually indi-
cates air inleakage through hoppers or around doors.
C-29
-------
Observe the dust deposits on the collecting plates
before starting any cleaning of the precipitator.
The normal thickness of collecting dust is about 1/8
in. with occasional buildups of 1/4 in. If the buildup
exceeds this amount, the intensity of the plate
rappers should be increased. If the collecting plates
are almost metal clean, this may be an indication of
high gas velocity, extremely coarse dust, too high a
rapping intensity, or too Iowan operating voltage
for good precipitation. This condition may be noted
if a section has been shorted-out prior to the
inspection.
The plate may be in effect removed from service by
removing the discharge wires surrounding it. When
bellying or bowing of the plates is noted, the
concave side of the plate may be heat-treated with a
torch, depending upon the severity of the deformity.
Lower Precipitator Steadying Frame
Cast iron weight rings that are bent out of their
normal configuration must be straightened. This can
usually be done by hand.
Inspect the steadying bars for cracked or broken welds
where they mount to the steadying bar support. Perform
any needed repairs.
Make sure that the lower steadying frame is level both
in the direction of gas flow and perpendicular to gas
flow. If the frame is not level, readjust the support
wires, adjusting both until the frame is level. Place
equal tension on each of the support wires connected to
adjusting bolts, since slack wires will cause excessive
sparking.
Inspect the steadying frame for downward bow in the
steadying bars (usually occurs after operating the
precipitator at overdesign temperatures). Downward
bows can usually be removed by cutting a wedge-shape
slot in the vertical member of the steadying bar angle,
pushing with jacks or pulling with a block-and-tackle
until the frame is straight, then welding an additional
piece of angle iron inside the steadying bar angle and
across the wedge slot.
C-30
-------
Inspect the steadying frame for twisting. A twisted
frame causes excessive weight on some wires and slack-
ness in others. To straighten a twisted frame, grasp
one end of the frame and twist the frame until that end
is straight and level. While holding the frame in this
position, weld the frame to the hopper walls. Repeat
for the other end of the frame. Once the frame has
been welded to the hopper walls and is straight and
level, using a torch, stress-relieve the frame by
heating each connection between the steadying bar
supports and the steadying bars until it glows to a
cherry red. After all joints have been relieved, allow
the frame to cool, then cut it free of the hopper
walls. If the frame is still twisted, repeat the
procedure. If after the second heating the frame is
still twisted, a new frame will have to be installed.
When checking the lower steadying frame anti-sway
insulators, check the surface for dust accumulation,
glaze damage caused by electrical tracking, cracks, and
chips. Insulators with dust accumulation and/or
electrical tracking that have not damaged the glazed
surfaces may be cleaned with a nonabrasive cleaner.
Cracked, chipped, broken, or glazed-damaged insulators
must be replaced.
Hoppers
Hoppers are often of the trough type with screw conveyors.
If properly sized, screw conveyors offer reliable
operation and continuous removal of collected dust.
Pyramidal hoppers are also installed using rotary and
double-dump valves. Given these systems, hoppers are
not generally used as "storage bins" for collected dust
as is often the case with fly ash utility installa-
tions. To prevent corrosion, heaters can be used to
prevent the formation of corrosive condensables. Any
abnormal buildups should be removed. If this condition
becomes chronic, it is an indication of low operating
temperatures, insufficient heat insulation, or inade-
quate hopper emptying. Heat tracing of the hoppers
will usually correct this condition unless it is due to
inadequate hopper emptying.
C-3l
-------
Precipitator Shell
Sulfur trioxide, chlorine, and moisture can promote
serious corrosion. The traces of sulfur trioxide
result in fairly rapid corrosion of the interior of gas
ducts, fans, and dust-collecting equipment if these
interior surfaces become cool for any reason. It is
therefore recommended that thorough internal inspection
be made during the first year of operation. If interior
corrosion is noted, apply some means of correction as
soon as possible. Heat insulation applied to exteriors
of the corroded components will normally correct this
condition. Since iron and steel process operations can
fluctuate widely, covering interior surfaces of side
frames, end frames, and roof with Gunite will prevent
damage to the steel.
Maintenance Schedule and Troubleshooting
Annual Inspection/Maintenance
Prior to any inspection, it is of utmost
that the precipitator is deenergized and
that the necessary precautions are taken
the equipment cannot be energized during
inspection.
importance
grounded and
to ensure that
the internal
Dust Accumulations
Observe the dust accumulations on both plates and
wires. The discharge wires should have only a slight
coating of dust with no corona tufts (doughnut-shaped
dust accumulations). Thickness of dust buildup on
plates is normally between 1/8 and 1/4 in. If the
plates have more than 1/4 in. of dust, the rappers are
not cleaning properly.
Discharge Wires
Replace any broken discharge wires, necked-down wires
or ~atigued w~res to avoid the possibility of breakin~
durlng,operatl~n: Breakage,of ~ust one wire may render
an entlre preclpltator sectl0n lnoperative. Record the
exact location of all wire failures as well as the
location of breakage on the wire.
C-32
-------
Alignment of Plates and Wires
The plate-to-wire clearances at both top and bottom
of plates should not be less than 4-1/4 in., while
the minimum acceptable plate-to-wire clearance at
the vertical midpoint of the plates is 4 in. (assuming
9-in. duct spacing). Close electrical clearances create
excessive sparking and prevent optimum operation.
High-Tension and Plate Rappers
Check all high-tension and plate rappers for misalign-
ment and/or binding of the rapper rods through the
roof sleeves. Binding in this area prevents transmission
of rapper energy to the collecting plates and high-
tension discharge wires and results in excessive dust
accumulations.
High-Tension Frame Support Bushing
The internal and external surfaces of the high-tension
frame support bushing must be maintained free of dust
to guard against high-voltage electrode tracking across
insulator surfaces. This condition will lead to ther-
mal fracturing of the bushings through heat concentra-
tion. Clean all high-voltage insulators and check
thoroughly for sign of cracks; replace where necessary.
All electrical connections should be secure.
High-Voltage Electrical Control Cabinet
Clean all components of dust accumulation and lubricate
where necessary- Replace the ventilating fan filter.
Transformer-Rectifier Sets
Check the oil level in the high-voltage transformer
and add the proper oil if necessary. Check all bushings,
terminals, and insulators for dust buildup and evidence
of electrical tracking. Check the surge arrester gap
setting on the high-voltage transformer and readjust
if necessary. Check high-voltage switchgear and
interlocks.
C-33
-------
Hoppers
Check for dust buildup in upper corners of hoppers and
debris such as fallen wires and weights in the hopper
bottom and valves. Inspect antisway insulators to se~
that they are clean and not cracked. If a discharge
electrode weight has dropped 3 inches, this indicates a
broken wire.
Precipitator Shell
Interior corrosion could indicate inleakage of air or
moisture through the housing. Exterior inspection
should focus on loose insulation and joints, air leak-
age, and general damage as well as corrosiono
Daily Inspection and Readings
Record all control set electrical readings once per
shift. Any abnormalities in shift-to-shift readings
may well be the first clue of a malfunction within the
precipitator. In addition, the daily log should in-
clude process operating data, flue gas analysis, dust
analysis, verification of transmissometer calibration,
and a record of all transmissometer readings.
Rappers
Ensure that all collecting plate and discharge wire
(high-tension) rappers are functioning properly and
operating at the proper intensity level. Lack of
rapping will result in dust buildup on both the plates
and wires, which reduces electrical clearances and
necessitates operation of the equipment at reduced
power levels. Over-rapping of the internals leads to
reentrainment of collected dust; therefore, it is
important that proper intensity values be used for
optimum precipitator performance.
Hoppers
Thoroughly check all hoppers, particularly the unload~
ing mechanism and system, for proper operation. Check
thoroughly for air inleakage at the hoppers. The
siphonin9 of cold. ambient air into the hoppers usually
results ln formatlon of condensation and agglomeratinq
of dust, resulting in plugging of the hopper. -
C-34
-------
A troubleshooting chart for ESP's is presented in Table
C-3-l.
Frequency of failure of various precipitator components
and repair times for a typical industrial precipitator are
presented in Table C-3-2.
C-35
-------
Table
C-3-1.
TROUBLESHOOTING
FOR
ELECTROSTATIC
PRECIPITATORS
------
cause
Remedy
Symptom
CHART
Probable
Spark meter reads h1gh, primary voltage
and current very unstable
Neither spark rate, current,
at maXlffiurn
nor voltage
No spark rate indicat1on, voltmeter and
ammeter unstable, 1nd1cat1ng spark1ng
No response to current-l~mit adjustment,
response to other adJustments
No response to voltage-limit adjustment,
response to current adjustment
n
I
W
0'1
No response to spark rate adJustment,
response to other adJustment
Precip1tator current low with respect to
pr1mary current, low or no voltage across
ground return resistors
(continued)
MisadJustment of automatic control, loss
of l~miting control
M~sadJustment of automatic control, auto-
mat1c control not at maximum, failure of
slgnal circu1ts
Failure of spark meter, failure of inte-
grat~ng capacitor, spark counter sen-
sitivity too low
Controlling on
lim~t, failure
current signal
defect~ve
spark rate or voltage
of automatic control,
to automatic control
Controlling on current limit or spark
rate, voltage signal to automatic control
defective, failure of automatic control
Controll~ng on voltage or current,
failure of automatic control
Surge arresters shorted,
failed, H.V. transformer
or part~al ground in the
clrcuit
H.V. rectifiers
failed, ground
ground return
ReadJust automatic control, replace
automatic control
Readjust sett1ng of automatic con-
trol, readjust automatic control,
check signal circuits
Replace spark meter, replace capac-
itor, readjust potentiometer on
automatic control
None needed ~f unit is operating at
maximum spark rate or voltage adjust-
ment; reset voltage or spark rate if
neither is at maximum; replace auto-
mat1c control; check signal circuit
None needed if unit is operating at
maximum current or spark rate, reset
current and spark rate adjustment if
nelther is at maximum; check voltage
circuit, replace automatic control
None needed 1f unit is operating at
maximum voltage or current, reset
voltage and current adjustment, if
neither 1S at maximum, replace auto-
matic control
Reset or replace surge arresters, re-
place H.V. rectifiers, replace H.V.
transformer, repair ground return
Clrcult
-------
n
I
LV
-J
Table
C-3-l.
(Continued)
Symptom
Remedy
Probable cause
No primary voltage, no primary current,
no prec~pitator current, vent fan on,
alarm energized
No primary voltage, no primary current,
no precipitator current, vent fan off,
alarm energized
Control unit trips out on overcurrent
when sparking occurs at high currents
High primary current, no precipitator
current
No primary voltage, no primary current,
no precipitator current, vent fan on,
alarm not energized
Low primary voltage, high secondary
current
Abnormally low precipitator current and
pr~mary voltage w~th no sparking
Spark meter reads high-off scale, low
primary voltage and current, no spark
rate indication
(continued)
Transformer-Rectifier Controls
D.c. overload, misadjustment of current
limit control, overdrive of SCR's
Control panel fuse blown, loss of power
supply, circuit breaker tripped
Overload circuit incorrectly set
Short circuit in primary current,
transformer or rectifier short
SCR and/or diode failure, no firing
circuit
Short circuit in .sec6ndary circuit or
precipitator
Misadjustment of current and/or voltage
limit controls, misadjustment of firing
circuit control
Continuous conduction of spark counting
circuit, spark counter counting 60 cycles
peak, failure of automatic control
Check overload relay setting, check
wiring and components, check adjust-
ment of current-limit control set-
ting, check signal from firing cir-
cuit module
Replace fuse or reset circuit breaker,
check supply to control unit, reset
circuit breaker
Reset overload circuit
Check primary power wiring, check
transformer and rectifiers
Replace, check signal from firing
circuit
Check wiring and components in H.V.
circuit and pipe and guard. Check
precipit~tor for interior dust
buildup, full hoppers, broken wires,
ground switch left on, ground jumper
left on, foreign materials on H.V.
frames or wires, broken insulators
Check settings of current and voltage
limit controls
Deenergize, allow ~ntegrating capac~-
tor to discharge and reenergize,
adjust spark control circuit, replace
automatic control
-------
()
I
w
co
Table
(Continued)
C- 3-1.
Symptom
Remedy
Probable cause
--,-
Primary current and secondary current
normal, primary voltmeter drops from
normal to zero and remains for a second
then jumps back to normal, repeating
this sequence rhythmically
Circuit breaker trips
Fuses blown, indicator light not flashing
lndicator light not flashing, no fuse
failure
No manual intensity control
Vibrator inoperative
Abnormal ammeter reading
Line breaker trips
Broken wire, swinging frame
Rapper Controls
Short circuit or component failure in con-
trol circuit or power transformer
Control circuit failure, rapper coil
failure, distributor switch firing two
coils at once
Control circuit not operating effectively,
no rotation of distributor switch
Failed potentiometer,
control module
faulty intensity
Remove broken wire, check for
broken anti-sway bushings
Check wiring and c0~ponent
Replace defective component, re-
place coil, repair or realign dlS-
trlbutor switch
Repair or replace component, check
motor and drive train
Replace potentiometer, replace in-
tensity control module
Replace coil, adjust vibrator
Adjust vibrator, replace cOlI
Check circuit
Vibrators and Controls
Vibrator coil open circuited,
improperly adjusted
vIbrator
Vibrator improperly adjusted,
coil short circuited
vibrator
Short cIrcuit in control wiring
-------
Table
C-3-2.
FREQUENCY OF FAILURE AND
REPAIR TIMES
REQUIRED
FOR VARIOUS
PRECIPITATOR COMPONENTS.al
()
I
w
'"
Electrical repair Mechanical/electrical repair
- external - - internal -
Lowe r
high
Top and tension
Rel iabll1 ty Rectifler Rapper Pressure Collecting Discharge bottom high Support stabllizer Rapper
and repalr controls Transformer cOll fans electrodes electrodes tension frames bushings bars shafts
Frequency of Seldom Seldom Seldom Seldom No failure 5-7 a No failure b 5-10 Seldom No
yr yr
failure failures
Tlme to 1-6 h 1 day 1 h 2 h 1 wk (one 1 r 2 t. 1 t.
repai"r section)
Parts Stocked Stocked Stocked Not Not stocked Not stocked Not stocked Stocked Stocked Stocked
stocked
Complete 12 wk 12 wk Stocked 6-8 wk 4-6 wk 1 wk 2 wk
urn ts
a Average life; replace with collecting electrodes.
b Posslbly replace with collectlng electrodes.
-------
REFERENCES - APPENDIX C-3
1.
"Industrial Air Pollution Guide," PEDCo Environ-
mental, Inc., Chapter 7.0, (draft report) EPA
contract No. 69-01-4147.
C-40
-------
APPENDIX C-4.
PROCEDURES FOR TROUBLESHOOTING AND CORRECTION OF
BAGHOUSE MALFUNCTIONSl
(RP-reverse pulsei PR-plenum pulse: S-shakeri RF-reverse flow)
Symptom
Remedy
Cause
High baghouse
pressure drop
Baghouse under-
sized
Bag cleaning
mechanism not ad-
justed properly
Compressed air
pressure too low
(RP,PP)
Repressuring pres-
sure too low (RF)
Shaking not
strong enough (S)
Isolation damper
valves not closing
( S, RF, P P )
Bag tension too
loose (S)
Pulsing valves
failed (RP)
C-4l
Consult manufacturers.
Install double bags.
Add more compartments
or modules.
Increase cleaning
frequency-
Clean for longer
duration.
Clean more vigorously.
Increase pressure.
Decrease duration and/
or frequency-
Check dryer and clean
if necessary-
Check for obstruction
in piping.
Speed up repressuring
fan.
Check for leaks.
Check damper valve
seals.
Increase shaker speed.
Check linkage.
Check seals.
Check air supply on
pneumatic operators.
Tighten bags.
Check diaphragm.
Check pilot valves.
-------
APPENDIX C-4
(continued)
PROCEDURES FOR TROUBLESHOOTING AND
CORRECTION OF BAGHOUSE MALFUNCTIONS
Cause
Symptom
Cleaning timer
failure
Not capable of
removing dust
from bags
Excessive re-
entrainment of
dust
Incorrect pres-
sure reading
Low fan motor
amperage/low alr
volume
High baghouse
Fan and motor
sheaves reverse
Ducts plugged
with dust
Fan damper closed
C-42
Remedy
Check to see if timer
is indexing to all
contacts.
Check output on all
terminals.
Condensation on bags
(see below).
Send sample of dust
to manufacturer.
Send bag to lab for
analysis for blinding.
Dry clean or replace
bags.
Reduce air flow.
Continuously empty
hopper.
Clean rows of bags
randomly, instead of
sequentially (PP,RP).
Clean out pressure
taps.
Check hoses for leaks.
Check for proper fluid
in manometer.
Check diaphragm- in
gage.
See above.
Check drawings and
reverse sheaves.
Clean out ducts and
check duct velocities.
Open damper and lock
in position.
-------
APPENDIX C-4
(continued)
PROCEDURES FOR TROUBLESHOOTING AND
CORRECTION OF BAG HOUSE MALFUNCTIONS
Symptom
Cause
Remedy
System static
pressure too high
Fan not operating
per design
Belts slipping
Dust escaping at
source
Low air volume
Ducts leaking
Improper duct
balancing
Improper hood
design
Dirty discharge
at stack
Bags leaking
Bag clamps not
sealing
C-43
Measure static on both
sides of fan and review
with design.
Duct velocity too high.
Duct design not proper.
Check fan inlet config-
uration and be sure
flow is even.
Check tension and ad-
just.
See above.
Patch leaks so air
does not bypass source.
Adjust blast gates in
branch ducts.
Close open areas
around dust source.
Check for cross drafts
that overcome suction.
Check for dust being
thrown away from hood
by belt, etc.
Replace bags.
Tie off bags and re-
place at later date.
Isolate leaking com-
partment if allowable
without upsetting
system.
Check and tighten
clamps.
Smooth out cloth under
clamp and re-clamp.
-------
APPENDIX C-4 (continued)
PROCEDURES FOR TROUBLESHOOTING AND
CORRECTION OF BAGHOUSE MALFUNCTIONS
Cause
Remedy
Symptom
Failure of seals
in joints at
clean/dirty air
connection
Insufficient
filter cake
Bags too porous
Excessive fan
wear
Fan handling
too much dust
Improper fan
Fan speed too
high
Excessive fan
vibration
Buildup of dust
on blades
Wrong fan wheel
for application
C-44
Caulk or weld
seams.
Allow more dust to
build up on bags by
cleaning less fre-
quently.
Use a precoating of
dust on bags (S, RF).
Send bags in for
permeability test
and review with
manufacturer.
See above
Check with fan manu-
facturer to see if
fan is correct for
application.
Check with manufac-
turer.
Clean off and check
to see if fan is
handling too much
dust (see above) .
Do not allow any
water in fan (check
cap, look for con-
densation, etc.).
Check with manufacturer.
-------
APPENDIX C-4 (continued)
PROCEDURES FOR TROUBLESHOOTING AND
CORRECTION OF BAGHOUSE MALFUNCTIONS
Symptom
High compressed
air consumption
Reduced com-
pressed air
pressure (RP, PP)
Premature bag
failure -
decomposition
Cause
Sheaves not
balanced
Bearings worn
Cleaning cycle too
frequent
Pulse too long
Pressure too high
Damper valves not
sealing (PP)
Diaphragm valve
failure
Compressed air
consumption too
high
Restrictions in
piping
Dryer plugged
Supply line too
small
Compressor worn
Bag material im-
proper for chemi-
cal composition
of gas or dust
C-45
Remedy
Have sheaves dynamically
balanced.
Replace bearings.
Reduce cleaning cycle
if possible.
Reduce duration (after
initial shock all other
compressed air is
wasted) .
Reduce supply pressure
if possible.
Check linkage.
Check seals.
Check diphragms and
springs.
Check pilot valve.
See above.
Check piping.
Replace dessicant or
bypass dryer if
allowed.
Consult design.
Replace rings.
Analyze gas and dust
and check with manu-
facturer.
Treat with neutralizer
before baghouse.
-------
APPENDIX C-4
(continued)
PROCEDURES FOR TROUBLESHOOTING AND
CORRECTION OF BAGHOUSE MALFUNCTIONS
Symptom
Cause
Remedy
Operating below
acid dew point
Moisture in
baghouse
Insufficient pre-
heating
System not
purged after
shut-down
Wall temperature
below dew point
Cold spots
through insulation
Compressed air
introducing
water (RP, PP)
Repressuring air
causing condensa-
tion (RF, PP)
High screw
conveyor wear
Screw conveyor
undersized
Conveyor speed
too high
High air lock
wear
Air lock under-
sized
C-46
Increase gas temperature,
Bypass at start-up.
Run system with hot air
only before starting
process gas flow.
Keep fan running for
5-10 minutes after pro-
cess is shut down.
Raise gas temperature.
Insulate unit.
Lower dew point by
keeping moisture out
of system.
Eliminate direct metal
line through insulation.
Check automatic drains.
Install aftercooler.
Install dryer.
Preheat repressuring
alr.
Use process gas as
source of repressuring
air.
Measure hourly collection
of dust and consult
manufacturer.
Reduce speed.
Measure hourly collection
of dust and consult
manufacturer.
-------
APPENDIX C-4
(continued)
PROCEDURES FOR TROUBLESHOOTING AND
CORRECTION OF BAGHOUSE MALFUNCTIONS
Symptom
Remedy
Cause
Material bridging
in hopper
Frequent screw
conveyor/air lock
failure
High pneumatic
conveyor wear
Pneumatic con-
veyor plpes
plugging
Thermal expansion
Speed too high
Moisture in bag-
house
Dust being stored
in hopper
Hopper slope in-
sufficient
Conveyor opening
too small
Equipment under-
sized
Screw conveyor
misaligned
Overloading com-
ponents
Pneumatic blower
too fast
Piping under-
sized
Elbows too short
radius
Overloading pneu-
matic conveyor
Consult manufacturer to
see if design allows
for thermal expansion.
Reduce speed.
See above
Remove dust con-
tinuously.
Rework or replace
hoppers.
Use a wide flared
trough.
Consult manufacturer.
Align conveyor.
Check sizing to see
that each component
is capable of handling
a 100% delivery from
screw conveyor.
Reduce blower speed.
Review design and reduce
speed of blower or in-
. .
crease plpe Slze.
Replace with long
radius elbows.
Review design.
C-47
-------
APPENDIX D-l
PREDICTED PERFORMANCE OF VENTURI
SCRUBBERS ON SELECTED IRON AND STEEL
PROCESSES USING RESEARCH COTTRELL'S MODEL
D-l
-------
1 DC
10
...
.
z:
o
....
~
~
~
LoJ
z:
.....
0..
1.0
.1
.01
~ lLp"81 " IIIg; rr-79%
/ ~ lLp=53" wg; ~=75%
6p.33" wg; n"70%
x=0.21, a=2.86
(I NLET)
.10
1.0
PARTICLE SIZE, MICRONS
Figure D-1-1.
venturi scrubber penetration for open
hearth furnace; L/G - 15
D-2
-~~I:
~
I
l
"1
j
"
""i
!
J
~
I
l
!
-1
!
Ii
J
::
~
~
~
-~
!
_-L~J
10.
-------
100
10
--
.
z
o
....
~
~
~
...
z
...
CL.
1.0
. ,
.01
~ f1p=79" '119; n=80%
/ ~ f1p=53" '119/ ~=78%
~ ~f1p=39" '119; n=75%
x=.27 0"=1.82
(INLET)
.'0
1.0
10.
PARTICLE SIZE, MICRONS
Figure D-1-2.
Venturi scrubber penetration for open
hearth furnace; L/G = 15
D-3
-------
100
10
..
.
~
-
I-
~
t;J
z
.....
Q..
1.0
. ,
.01
tJp=86" wg; n=85%
~ tJp=30" wg; n-80%
/ ~ tJp=12" wg; n=75%
x=.80. 0"=9.30
(INLET)
.10
1.0
PARTICLE SIZE. MICRONS
Figure D-l-3.
venturi scrubber penetration for electric
arc furnace; L/G - 15
D-4
]
!
~I
J
I
!
~"
1
I
~
J
I
-I
I
--r
j
J
~
10.
-------
..
.
z:
o
....
I-
~
I-
...,
z:
...,
~
100
10
1.0
.1
.01
IIp=79'' wg; 0=99.9%
~lIP=14" wg;_0=99.7%
/ ---- IIp=7'' wg; n"99. 5%
x=70.. cr=6.67
(INLET)
.10
1.0
10.
PARTICLE SIZE. MICRONS
Figure D-1-4.
Venturi scrubber penetration for
sintering machine; L/G ~ 15
D-5
-------
100
--
~
...
I-
~
t;
x
""'
CL
10
tlp=70" wg; n=99.5%
~tlP=36" wg; ~=99.2%
/ ~ ~ tlp"26" wg; n=99%
1.0
x=7.7.0=3.5
(INLET)
.1
.01
1.0
.10
, O.
PARTICLE SIZE, MICRONS
Figure D-1-5. Venturi scrubber penetration for
sintering machine; L/G = 15
(scrubber preceded by mechanical collector)
D-6
-------
100
10
....
.
z:
o
.....
.....
~
~
z:
I.IJ
~
1.0
.,
.01
t>p=86" wg; ~75%
~ t>p=62" wg; n=72%
t>p=49" wg; n=70%
x=.19, a=3.00
(INLET)
.10
PARTICLE SIZE, MICRONS
1.0
10.
Figure D-1-6.
venturi scrubber penetration for ferrosi1icon
arc furnace; L/G = 15
D-7
-------
100
10
--
8
......
~
~
z:
...
&:L.
1.0
.1
.01
IIp:66'' wg; n=94%
IIp:28'' wg; n:90%
lIpz12" wg; nz85%
x=. 78. (1-2.12
(INLET)
.10
1.0
10
PARTICLE SIZE. MICRONS
Figure D-1-7.
venturi scrubber penetration for ferro-
manganese arc furnace; L/G = 15
D-8
-------
100
10
..
.
z
o
.....
~
~
tj
z
~
0..
1.0
.1
.01
- t,p=77 " wg; n=90%
t,p=29" wg. n=85%
~t,P=13" wg; n=80%
x=.86. a=4.19
(INLET)
.10
1.0
10.
PARTICLE SIZE. MICRONS
Figure D-1-8.
Venturi scrubber penetration for ferro-
chromium arc furnace; L/G - 15
D-9
-------
x=.50, a'"3.36
(INLET)
IIp'"81'' wg; 0=88%
IIp=99'' wg; 0=85%
~lIP=23" wg; 0=80%
100
10
..
~
z
o
......
~
~
t;:j
z
....
0..
1.0
.1
.01
.10
1.0
1( , , , ,
PARTICLE SIZE, MICRONS
Figure D-1-9.
Venturi scrubber penetration for miscellan-
eous ferroalloy arc furnace; L/G - 15
D-IO
-------
TECHNICAL REPORT DATA
(P/rase read [UUTucliulIs all Ihe reraSe be/ore comp/clil/g)
1. REPORT NO. r. 3. RECIPIENT'S ACCESSIOr-./- NO.
EPA-600/2-78-037
4. TITLE AND SUBTITLE 5. REPORT DATE
Operation and Maintenance of Particulate Control March 1978
Devices on Selected Steel and Ferroalloy Processes 6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S) 8. PERFORMING ORGANIZATION REPORT NO.
Michael F. Szabo and Richard W. Gerstle
9. PERFORMING OROANIZATION NAME AND ADDRESS 10. PRCJGRAM ELEMENT NO.
PEDCo. Environmental, Inc. lAB012; ROAP 2lADL-037
11499 Chester Road 11. CONTRACT/GRANT NO.
Cincinnati, Ohio 45246 68-02-2105
12. SPONSORING AGENCY NAME AND ADDRESS 13. TYPE OF REPORl/,ND PERIOD COVERED
EPA, Office of Research and Development Final; 6/76-11 77
Industrial Environmental Research Laboratory 14. SPONSORING AGENCY CODE
Research Triangle Park, NC 27711 EPA/600/13
15. SUPPLEMENTARY NOTES IERL-RTP project officer is Dennis C. Drehmel, Mail Drop 61,
919/541-2925.
16. ABSTRACT
The report deals with the control of fine particulate emission from iron, steel, and
ferroalloy plants using electrostatic precipitators, wet scrubbers, and fabric filters
(baghouses). It provides information on the selection, operation, and expected per-
formance of conventional air pollution control devices, based on current design
practice, theoretical mode ls, performance, cos t predictions, and information in the
literature.
17. KEY WORDS AND DOCUMENT ANALYSIS
a. DESCRIPTORS b.IDENTIFIERS/OPEN ENDED TERMS C. COSA TI held/Group
Air Pollution Fabrics Air Pollution Control 13B HE
Dust Dust Filters Stationary Sources HG l3K
Iron and Steel Industry Particulate llF
Ferroalloys Fabric Filters
Industrial Processes Baghouses l3H
Electrostatic Precipitators 07A
Scrubbers
18. DISTRIBUTION STATEMENT 19. SECURITY CLASS (T/lis Report) 21. NO. OF PAGES
Unclass ified 392
Unlimited 20. SECURITY CLASS (Tilis page) 22. PRICE
Unclassified
-
EPA Form 2220.1 (9-73)
D-ll
-------
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Research and Development
Technical Information Staff
Cincinnati, Ohio 45268
OFFICIAL BUSINESS
PENALTY FOR PRIVATE USE, $300
AN EQUAL OPPORTUNITY EMPLOYER
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Book
§
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------- |