UnttrtSlius EPA-600/7-84-OU
February 1984
s>EPA Research and
Development
PILOT DEMONSTRATION OF
MAGNETIC FILTRATION WITH
CONTINUOUS MEDIA
REGENERATION
Prepared for
Office of Air Quality Planning and Standards
Prepared by
Industrial Environmental Research
Laboratory
Research Triangle Park NC 27711
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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-
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This report has been assigned to the INTERAGENCY ENERGY-ENVIRONMENT
RESEARCH AND DEVELOPMENT series. Reports in this series result from the
effort funded under the 17-agency Federal Energy/Environment Research and
Development Program. These studies relate to EPA's mission to protect the public
health and welfare from adverse effects of pollutants associated with energy sys-
tems. The goal of the Program is to assure the rapid development of domestic
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essary environmental data and control technology. Investigations include analy-
ses of the transport of energy-related pollutants and their health and ecological
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This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/7-84-011
February 1984
PILOT DEMONSTRATION OF MAGNETIC FILTRATION WITH
CONTINUOUS MEDIA REGENERATION
by
Carroll E. Ball
and
David W. Coy
Research Triangle Institute
Post Office Box 12194
Research Triangle Park, North Carolina 27709
Contract No. 68-02-3142
EPA Project Officer: William B. Kuykendal
Participate Technology Branch
Industrial Environmental Research Laboratory
Research Triangle Park, NC 27711
Prepared for
U.S. Environmental Protection Agency
Office of Research and Development
Washington, D.C. 20460
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ABSTRACT
A mobile pilot plant with a nominal flow capacity of 3,060 mVhr (1,800
cfm) was designed and built to evaluate the use of High Gradient Magnetic
Filtration (HGMF) for particulate emission control on an electric arc furnace
(EAF). A five-month test program was conducted at Georgetown Steel
Corporation's plant in Georgetown, South Carolina, to test the performance of
the HGMF. A 500 hour long-term test was scheduled and later changed in order
to perform additional characterization studies.
The pilot plant collection efficiency was less than expected for the
stainless steel wool matrix packed to a density of 1.5 percent by volume. The
matrix was then changed to an expanded metal packed to a density of 3.5 percent
by volume, which resulted in much lower pressure drop measurements but even
lower collection efficiencies. The expanded metal matrix was then packed to a
density of 6.0 percent by volume which gave higher collection efficiencies
than the steel wool and a slightly lower pressure drop.
During the field test operations, there were no significant problems with
the HGMF mobile pilot plant equipment.
The report describes the design and construction of the continuous HGMF
mobile pilot plant, as well as some of the background work in High Gradient
Magnetic Filtration done at RTI. The field start-up and performance
characterization of the mobile pilot plant are discussed in detail. The
experimental data and data analysis are given as well as an economic evaluation
and comparison of the HGMF with other particulate control devices.
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TABLE OF CONTENTS
Page
ABSTRACT rf
FIGURES v
TABLES vii
ACKNOWLEDGEMENT ix
1.0 SUMMARY 1
2.0 CONCLUSIONS 3
3.0 RECOMMENDATIONS 5
4.0 BACKGROUND DEVELOPMENT 6
4.1 BASIC CONCEPT 6
4.2 HGMF DEVELOPMENT AND APPLICATIONS 6
4.3 POTENTIAL APPLICATION TO PARTICULATE EMISSION CONTROL . 8
4.4 PRELIMINARY DESIGN AND DEVELOPMENT 10
4.5 MATHEMATICAL MODEL 13
4.6 SITE SELECTION FOR CURRENT FIELD TESTS 13
5.0 DETAILED DESIGN AND CONSTRUCTION OF THE HGMF MOBILE PILOT
PLANT 24
6.0 FIELD OPERATIONS 31
6.1 DESCRIPTION OF THE ELECTRIC ARC FURNACE AT GEORGETOWN,
SOUTH CAROLINA 31
6.2 INSTALLATION OF STARTUP OF THE PILOT PLANT 34
6.2.1 Temperature Control 34
6.2.2 Filter Cleaning 34
6.2.3 Magnet Operation 35
6.2.4 Flow Measurement and Control 35
6.2.5 Final Site Setup 36
7.0 PERFORMANCE CHARACTERIZATION 39
7.1 TEST PLAN 39
7.1.1 Performance Charcterization and Optimization . . 39
7.1.2 Performance Data for Principal Variables .... 39
7.2 TEST PROCEDURES 42
7.2.1 Sampling Procedures 42
7.2.2 Filter Operating Procedures 44
7.3 COARSE GRADE STAINLESS STEEL WOOL MATRIX 44
7.4 EXPANDED METAL MATRIX 53
7.4.1 Packing Density of 2.5 Percent by Volume .... 53
7.4.2 Packing Density of 6.0 Percent by Volume .... 61
7.4.3 Additional Testing 63
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8.0 DATA ANALYSIS 70
8.1 PERFORMANCE DATA 70
8.1.1 Overall Performance 70
8.1.1.1 Steel Wool-Packing Density 1.5 Percent. . 71
8.1.1.2 Expanded Metal-Packing Density 3.5
Percent ................ 73
8.1.1.3 Expanded Metal-Packing Density 6.0
Percent 73
8.1.1.4 Performance Summary-All Matrices, All
Packing Densities 78
8.1.2 Performance By Particle Size 82
8.2 CHEMICAL AND MAGNETIC CHARACTERISTICS OF ELECTRIC ARC
FURNACE DUST 89
8.2.1 Magnetic Analysis 89
8.2.2 Chemical Analysis 93
8.3 MODEL DISCUSSIONS 97
8.4 DISCUSSION OF RESULTS 103
9.0 ECONOMICS Ill
9.1 CAPITAL COSTS 113
10.0 REFERENCES 116
IV
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FIGURES
Number
Page
1 Magnetic analysis of dust samples from HGMF pilot plant tests. . 11
2 Particle size distribution, preliminary tests 15
3 Particle size distribution, average of runs 2, 3, and 4 16
4 Georgetown Steel HGMF test—preliminary sampling program .... 18
5 HGMF—Collection efficiency vs. particle size 20
6 Magnetic analysis of EAF dust samples 21
7 Flow schematic of continuous HGMF system 25
8 HGMF mobile pilot plant 26
9 HGMF pilot plant under construction 28
10 HGMF pilot plant under construction 29
11 Material balance of electric arc furnace based on 1,000 kg of
steel produced 32
12 Rough site map 33
13 HGMF pilot plant at Georgetown Steel 37
14 HGMF pilot plant at Georgetown Steel 38
15 HGMF test points 41
16 Filter train for determination of mass efficiency 43
17 Georgetown Steel HGMF test—steel wool matrix (packing
density 0.015) 47
18 Georgetown Steel HGMF test—steel wool matrix (packing
density 0.015) 48
19 Georgetown Steel HGMF test—steel wool matrix (packing
density 0.015) 49
20 Georgetown Steel HGMF test—steel wool matrix (packing
density 0.015) 50
21 Georgetown Steel HGMF test—steel wool matrix (packing
density 0.015) 51
22 Georgetown Steel HGMF test—steel wool matrix (packing
density 0.015) 52
23 Georgetown Steel HGMF test—expanded metal matrix (packing
density 0.035) 55
24 Georgetown Steel HGMF test—expanded metal matrix (packing
density 0.035) 56
25 Georgetown Steel HGMF test—expanded metal matrix (packing
density 0.035) 57
26 Georgetown Steel HGMF test—expanded metal matrix (packing
density 0.035) 58
27 Georgetown Steel HGMF test—expanded metal matrix (packing
density 0.035) 59
28 Georgetown Steel HGMF test—expanded metal matrix (packing
density 0.035) 60
29 Georgetown Steel HGMF test—expanded metal matrix (packing
density 0.06) 64
30 Georgetown Steel HGMF test—expanded metal matrix (packing
density 0.06) 65
31 Georgetown Steel HGMF test—expanded metal matrix (packing
density 0.06) 68
32 Georgetown Steel HGMF test—expanded metal matrix (packing
density 0.06) 69
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33 Georgetown Steel HGMF test—expanded metal matrix (packing
density 0.06) .- • 79
34 Georgetown Steel HGMF test—penetration vs. regression function
(all matrices and packing densities)
35 Georgetown Steel HGMF test—penetration vs. particle size
(steel wool matrix 0.015) 8<3
36 Georgetown Steel HGMF test—penetration vs. particle size
(expanded metal matrix 0.035) 84
37 Georgetown Steel HGMF test—penetration vs. particle size
(expanded metal matrix 0.06) 8b
38 Georgetown Steel HGMF test—penetration vs. particle size
(expanded metal matrix 0.06) 86
39 Georgetown Steel HGMF test—penetration vs. particle size
(steel wool matrix 0.015) 87
40 Georgetown Steel HGMF test—penetration vs. particle size
(expanded metal matrix 0.035) 88
41 Georgetown Steel HGMF test—specific magnetization vs. particle
size, steel wool matrix (packing density 0.015) 92
42 Georgetown Steel HGMF test—particle size elemental analysis,
expanded metal matrix (packing density 0.06) 98
43 Georgetown Steel HGMF test—particle size elemental analysis,
expanded metal matrix (packing density 0.06) . . 99
44 Georgetown Steel HGMF test—iron penetration vs. particle size
(packing density 0.06) 100
45 Georgetown Steel HGMF test—zinc penetration vs. particle size
expanded metal matrix (packing density 0.06) 101
46 Illustration of particle capture by a single wire 102
47 Georgetown Steel HGMF test—theoretical and actual penetration
vs. particle size, expanded metal matrix (packing
density 0.06) 106
48 Georgetown Steel HGMF test—theoretical and actual penetration
vs. particle size, expanded metal matrix (packing
density 0.06) 107
VI
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TABLES
Number Page
1 HGMF APPLICATIONS BEING INVESTIGATED 7
2 EXTENDED CHARACTERISTICS OF UNCONTROLLED GAS STREAMS
FROM SEVERAL SOURCES 9
3 COMPONENT MASS BALANCES BASED ON CHEMICAL ANALYSIS . . 12
4 ELEMENTS (PERCENT BY MASS)(OBTAINED BY ATOMIC
ADSORPTION 17
5 BAGHOUSE DUST ANALYSIS 19
6 GEORGETOWN STEEL HGMF TESTS (STEEL WOOL MATRIX-
PACKING DENSITY 0.015) 45
7 GEORGETOWN STEEL HGMF TESTS (EXPANDED METAL MATRIX-
PACKING DENSITY 0.035) 54
8 GEORGETOWN STEEL HGMF TESTS (EXPANDED METAL MATRIX-
PACKING DENSITY 0.06) 62
9 GEORGETOWN STEEL HGMF TESTS (EXPANDED METAL MATRIX-
PACKING DENSITY 0.06, NO RECYCLE) 67
10 HGMF OVERALL PERFORMANCE REGRESSION COEFFICIENTS,
STEEL WOOL MATRIX 72
11 HGMF OVERALL PERFORMANCE REGRESSION COEFFICIENTS
EXPANDED METAL MATRIX, 3.5 PERCENT 74
12 HGMF OVERALL PERFORMANCE REGRESSION COEFFICIENTS
EXPANDED METAL MATRIX, 6 PERCENT 75
13 COMPARISON OF REGRESSION STATISTICS EXPANDED METAL
MATRIX - 6 PERCENT 77
14 REGRESSION COEFFICIENTS FOR EACH FILTER MATRIX AND
PACKING DENSITY 81
15 PREDICTED FILTER PERFORMANCE FOR EACH FILTER MATRIX
AND PACKING DENSITY 81
16 SPECIFIC MAGNETIZATION OF BULK DUST SAMPLES 91
17 CHEMICAL ANALYSES OF BULK DUST SAMPLES - WEIGHT
PERCENT 94
18 ELEMENTAL PENETRATION PERCENT - BULK SAMPLES 95
vn
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Number
19
20
21
22
CORRELATION OF REENTRAINMENT CORRECTION
CORRELATION OF REENTRAINMENT CORRECTION FOR THE HGMF
TESTS AT GEORGETOWN STEEL
COSTS OF VARIOUS CONTROL OPTIONS FOR EAF PARTICULATE
EMISSION ...... .
DIRECT OPERATING COSTS
Page
104
105
112
115
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ACKNOWLEDGEMENTS
The authors wish to acknowledge the assistance and support of the follow-
ing individuals in various segments of this work.
William Kuykendal, Norman Plaks, and Dennis C. Drehmel from
EPA-IERL, who provided support and direction throughout the project;
Charles Gooding from Clemson University for his expert assistance during all
phases of the project.
The author would like to thank Georgetown Steel Corporation for allowing
us to perform the field testing at their electric arc furnace steel plant in
Georgetown, South Carolina, and Roscoe Hinson for his invaluable support
and assistance throughout the program.
Douglas VanOsdell and / >J. Spivey from RTI, were very helpful in the
design, construction, and operation of the pilot plant and the resultant data
analysis. Technicians Daryl Smith, David Carter, and Don O'Neal, also from
RTI, were key participants in the construction and field operation of the
pilot plant.
IX
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1.0 SUMMARY
Since the commercialization of High Gradient Magnetic Filtration (HGMF)
in the clay industry 10 years ago, the applications of magnetic separation of
process streams have been steadily increasing. Some of the applications are
mineral beneficiation, coal deashing, coal desulfurization, wastewater treat-
ment, and blood component separation. The application of HGMF to air pollu-
tion, however, is a recent development. From 1975 to 1977 RTI conducted
experimental work, funded by the U.S. Environmental Protection Agency, in the
application of HGMF to air pollution control. Magnetic separation was tested
in the laboratory on several dusts from the iron and steel industry. There
were promising results from the following iron and steel industry sources;
basic oxygen furnace (BOF); electric arc furnaces (EAF); blast furnace (BF);
open hearth furnace; scarfing machine; and the sinter machine.
Tests run on the laboratory pilot plant demonstrated high collection
efficiencies on the BOF and EAF dusts and identified the effects of important
operating variables. A mathematical model was also developed to correlate the
data and aid in the field pilot plant design.
A mobile pilot plant with a nominal flow capacity of 5,100 m3/hr (3,000
cfm) was designed and built by RTI and tested on a Pennsylvania Sintering
Plant.
The pilot plant was a cyclic design composed of two complete systems that
permitted filtering of the gas stream by one system while the other was
cleaning itself by backflushing. The overall efficiency data were low for
these tests, however, due to the low specific magnetization of the sinter
plant dust.
It was then decided to design and build a pilot plant with continuous
media regeneration and test it on a dust with higher specific magnetization
such as BOF or EAF dust.
A presentation was given to the American Iron and Steel Institute in
November, 1980 describing prior HGMF work and the present objectives. At this
time, Georgetown Steel Corporation offered to let us conduct field tests at
their electric arc furnace steel plant in Georgetown, South Carolina. The
1
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Georgetown steel plant was picked as the site for our pilot plant field test
work after performing magnetization studies and chemical analyses on dust
obtained from the EAF air pollution control system.
The mobile pilot plant is a continuous HGMF system which is designed for
a nominal flow capacity of 3,060 mVhr (1,800 cfm). The pilot plant contains
a Sala-HGMS® Carousel Model 120-05-00 (Sala Magnetics Inc., Cambridge, Mass.),
which is a continuous device that incorporates a magnet head and a filter
cleaning station mounted 180° apart on a rotating carousel.
In June, 1981 the pilot plant was moved to Georgetown, South Carolina and
connected to a slipstream from the exhaust of the three EAF's just upstream of
a baghouse. After startup and debugging, the test program was begun to give
results on the effects of filter density, applied magnetic field, and gas
velocity on overall and fractional collection efficiency. A 500 hour long
term test was planned at optimum operating conditions and later cancelled due
to the lower than expected collection efficiencies. It was decided to use the
remaining time for additional performance characterization tests with changes
in the pilot plant recycle stream. Total mass and fractional collection
efficiency tests were conducted and samples of the dust entering, exiting, and
captured by the pilot plant were collected for magnetic and chemical analysis.
The results of the field tests were used to make technical and economic
assessments of the application of HGMF to EAF's, and to compare HGMF to other
types of pollution control devices. In particular, capital and operating cost
were developed to compare HGMF to fabric filters, electrostatic precipitators,
and venturi scrubbers.
The following sections of this report present the background work done at
RTI in HGMF as applied to air pollution control and the detailed design,
construction, and operation of the continuous HGMF mobile pilot plant. The
results and analyses of the data from the field tests are presented along with
the economic analysis and comparison of a full scale HGMF system to the
generic pollution control systems, and conclusions.
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2.0 CONCLUSIONS
The following list of conclusions was drawn from the field operation of
the HGMF mobile pilot plant:
1. While no long term continuous 500 hour test was performed, the
continuous cleaning system for the filter was capable of maintaining
a stable pressure drop through the matrix at each of the velocity
conditions during one to two week periods of performance character-
ization.
2. Test series were performed on two types of matrices at three levels
of matrix packing density. The best overall performance of the HGMF
unit was achieved with the expanded metal matrix at a packing density
of 6 percent. The highest efficiency level achieved was 96.4 percent
with five of nine tests (excluding zero applied magnetic field
tests) in the range of 93.9 to 96.4 percent.
3. Pressure drop through the filter matrices varied directly with the
superficial gas velocity through the filter, approximately as the
square of the velocity. In the velocity range of 4 to 8 m/s, the
expanded metal matrix at 6 percent had lower pressure drops (10 cm
H20 to 46 cm H20) than the steel wool matrix (16 cm H20 to 50 cm
H20). Given the better overall performance (both efficiency and
pressure drop) with the expanded metal at 6 percent packing density,
it was the preferred filter matrix.
4. Fractional penetration curves show performance of the HGMF to be
relatively poor (85 percent efficiency or less) in the particle size
range below 1 urn.
5. Elemental chemical analyses show iron removal efficiencies are
higher than overall mass efficiencies as determined from thimble
dust samples. However, elemental analyses performed on cascade
impactors samples show the iron penetration to be as much as 6
percent when overall mass penetration is 9 percent.
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Potential explanations for inadequate capture of iron-bearing par-
ticles include the following:
a. magnetic forces acting on the fine particles are not sufficent
to effect capture as the gas passes through the filter due to
insufficient residence time,
b. some of the iron occurs in complex compounds with zinc that is
not sufficiently magnetic to be captured; this is supported by
work done at Lehigh University on waste dusts from electric arc
furnaces, and
c. reentrainment.
6. The overall penetration of electric arc furnace dust through HGMF
measured in this program must be reduced by a factor of 2 or 6 to
compete with the performance of conventional particulate control
devices applied to new sources. Standards for existing sources in
some states might permit the retrofit of an HGMF.
7. Assuming HGMF performance can reach a competitive level in the
configuration and operating mode tested in this program (e.g. 99
percent efficiency), comparative annualized costs for HGMF, fabric
filters, ESPs, and venturi scrubbers show that HGMF can compete
economically with venturi scrubbers, but is more expensive than
fabric filters and ESPs. Since to achieve that level of performance
on EAF dust, it would be necessary to reduce the gas velocity and/or
%increase filter length, it will be difficult for HGMF to compete as
a control device for EAFs.
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3.0 RECOMMENDATIONS
It appears that high gradient magnetic filtration's potential as an
alternate participate control device is limited. While the high gradient
magnetic filtration achieved on electric arc furnace (EAF) dust was signifi-
cantly better than on sinter plant dust, it did not reach a level that would
compete with conventional pollution control devices. The cost estimates
presented in this report suggest that HGMF might compete best in applications
in which venturi scrubbers are usually applied. Basic oxygen furnaces (BOF),
particularly those of closed hood design yielding combustible waste gas, may
be an appropriate source. Magnetic susceptability data have shown BOF dust to
be more susceptible than EAF dust. The reason that a BOF was not chosen for
this program was lack of a host plant willing to accept the pilot plant and
associated risk of explosion from seal leaks and occupational exposures to
carbon monoxide. There is some risk, however, that BOF dust might exhibit
some properties of complex particles seen in the EAF dust in this study
depending on the type and amount of scrap used. Another application that
might prove more appropriate is the waste gas stream from steel scarfing. The
particles from this operation are expected to be virtually all iron oxide.
An alternative use not explored in this study is to separate magnetic and
non-magnetic components of EAF waste dust. EAF dust is classified as a hazar-
dous waste due to heavy metal contamination. Recovery of the iron bearing
portion for recycle would reduce the quantity for disposal. If the residue
were sufficiently rich it might be treated to recover zinc or other metals.
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4.0 BACKGROUND DEVELOPMENT
4.1 BASIC CONCEPT
The fundamental concept of the HGMF process is the interaction between
paramagnetic or ferromagnetic particles and ferromagnetic fibers while in the
presence of an applied background magnetic field. The applied magnetic field
induces a magnetic dipole in the particle and magnetizes the wire. This
creates a convergence of the field near the wire resulting in a net force
being applied to the particle. The magnetic force, in competition with the
viscous, inertial, and gravitational forces, causes the particle to be
attracted to the wire and held there until the applied field is removed.
The high gradient magnetic filter consists of several cassettes packed
with ferromagnetic fibers (such as stainless steel wool or expanded metal)
which are moved into a magnetic field as the particle laden gas is being
passed through. The particle laden gas is cleansed as the particles are
attracted to and held by the fibers. When the matrix is loaded, the cassette
is then moved out of the magnetic field and the particles are flushed from the
fibers.
4.2 HGMF DEVELOPMENT AND APPLICATIONS
The experimental work in high gradient magnetic filtration, with the
exception of the EPA sponsored development begun in 1975, has been most
concerned with the magnetic separation of particles in a slurry. Oberteuffer,1
Kolm, et al.,2 Oder,3 and lannicelli4 have published excellent reviews of the
process and its chronological development. A brief review of HGMF development
can also be found in the EPA report "Application of High Gradient Magnetic
Separation to Fine Particle Control" by Dr. C. H. Gooding.5
The most extensive development of HGMF has been within the last decade in
the clay industry. Here, the HGMF is used to separate small paramagnetic
color bodies from kaolin clay. The successful demonstration of this process
in the clay industry has sparked investigations of HGMF for many different
applications. Table 1 lists some of the HGMF applications being investigated.
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TABLE 1. HGMF APPLICATIONS BEING INVESTIGATED
Application
References
Mineral beneficiation-general
Taconite beneficiation
Coal deashing and desulfurization
Wastewater treatment-general
Steel mill wastewater treatment
Municipal wastewater treatment
Blood component separation
Catalyst recovery
Particulate emission control from
steel mill sinter plant
Aluminum extraction
Kelland, 19736
Murray, 19767
Kelland and Maxwell, 19758
Ergun and Bean, 19689
Trindade and Kolm, 197310
Vives, et al., 197611
Maxwell, et al., 197612
Maxwell, et al., 197713
Liu, et al., 197814
Maxwell and Kelland, 197815
Hise, et al., 1979l6
Mitchell, et al., 197517
Petrakis and Ahner, 197818
Oberteuffer, et al., 197519
Harland, et al., 197620
deLatour and Kolm, 197521
Yadidia, et al., 197722
Melville, et al., 197523
Whitesides, et al., 197624
Gooding, 198025
Friedlander, et al., 198026
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4.3 POTENTIAL APPLICATION TO PARTICULATE EMISSION CONTROL
The presence of iron in the waste gas particulate from several sources in
the iron and steel industry makes HGMF a potential candidate for air pollution
control. Table 2 lists the waste gas characteristics of several widely used
processes in the iron and steel industry.
A sinter plant is used to combine iron ore with flux and with other
iron-bearing materials such as flue dust, mill scale, turnings, and borings to
form a blast furnace feed. The blast furnace reduces the iron ore, pellets,
and sinter. The basic oxygen furnace, electric arc furnace, and open hearth
furnace are used to refine the iron to steels of various composition. The
scarfer is a surface improvement process which volatilizes a thin layer of the
hot steel slab by blasting it with oxygen. In each of these processes, iron
bearing particles are entrained in the waste gas stream and must be collected
by some air pollution control device. The control devices currently in use
are cyclones, baghouses, wet scrubbers, and electrostatic precipitators.
The iron content of the dust, the large throughput velocities, and current
magnet technology combine to make HGMF potentially competitive with other
pollution control devices. Also, if the HGMF matrix is cleaned by backflushing
with air, the process can remain completely dry and avoid water pollution
problems.
Consideration of application of HGMF to any of the above processes must
take into account magnetic susceptability, particle size distribution, and
waste gas composition. Presuming magnetic susceptability to be proportional
to iron content, the BOF, open hearth furnace, and scarfing operations seem to
be better candidates for HGMF than the others. The blast furnace with more
coarse dust and lesser iron content could be nearly as good.
The declining use of open hearths limits that potential application.
Blast furnaces and BOFs present problems relative to gas stream composition.
Closed hood BOFs (the recent trend) generate a gas stream rich in carbon
monoxide which would require the development of a sealing or containment
system more complex than used in the pilot plants. Blast furnaces likewise
generate a waste gas stream with carbon monoxide, but present the additional
complicating problem of pressurized operation. The advantage of dry dust
collection that HGMF could provide for blast furnaces might make seal develop-
ment a worthwhile effort.
8
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TABLE 2. EXTENDED CHARACTERISTICS OF UNCONTROLLED GAS STREAMS FROM SEVERAL PROCESSES.*
Process
Sinter machine
Wi ndbox
Discharge end
Blast furnace
Basic oxygen furnace
Open system
Closed system
Electric arc furnace
Open hearth furnace
Scarfing machine
Dust
concentration
g/m3
1-2
5-12
10-25
10-25
40-70
0.2-7
4-7
0.5-1
Mass median
diameter
urn
10
10
20
1
2
1
5
0.5
Iron
composition
% total Fe
25-50
25-50
35-50
55-70
55-70
15-40
55-70
50-70
Noteworthy gas
characteristics
5-15% H20, Hydrocarbons.
Flourides, SOX, 120-1806 C
120-180° C
20-40% CO, 2-6% H2>
200-300° C
250-300° C
75% CO, 250-300° C
40-120° C
7-15% H20, 250-300° C
H20 Satruated, 50-60° C
Compiled from numerous references including Hardison and Greathouse (1972)27, Dulaney (1974)28, Steiner
(1976)29, Jaasund (1977)30, and Whitehead (1977)31.
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4.4 PRELIMINARY DESIGN AND DEVELOPMENT
A laboratory pilot plant was constructed and operated by Research Triangle
Institute for EPA in order to demonstrate the feasibility of HGMF as an air
pollution control device on various iron and steel industry processes.5 Using
the data obtained during the operation of the laboratory pilot plant and the
mathematical model developed during this time, a mobile HGMF pilot plant was
designed and constructed. The pilot plant was connected to a slipstream from
the waste gas duct at a Pennsylvania sintering plant and operated for 4.5
months. The detailed design and resulting data from the operation of this
pilot plant are given in a prior report.25 This earlier mobile pilot plant
was a 5,100 mVhr (3,000 cfm) cyclic system housed in a 12.8 m (42 ft) freight
van. The cyclic design was actually two 5,100 mVhr systems that allowed one
system to be filtering the waste gas stream while the other system was cleaning
itself by backflushing with compressed air through a cyclone.
The operation of the pilot plant on the sinter plant gas resulted in
lower than expected mass efficiencies. Chemical anaysis of the dust samples
showed that the low efficiencies were due to the low iron content (7-11% Fe)
of the sinter plant dust and resultant low specific magnetization.
Figure 1 shows the specific magnetization (magnetization/unit mass,
measurement method described in Section 8.2.1) values of the sinter plant dust
samples collected at the inlet, outlet, and cyclone hopper. Table 3 shows the
component mass balances based on the chemical analysis of the samples. Samples
at the inlet and outlet were collected by isokinetic sampling. The cyclone
hopper was grab sampled.
Although the collection efficiency of the pilot plant on the sinter dust
was not satisfactory, earlier laboratory work showed that HGMF might be
practical for operations such as the basic oxygen furnace (BOF), the electric
arc furnace (EAF), and the blast furnace. These operations have dusts with
specific magetizations from 10 to 20 times higher than the sinter dust.
There were also problems with the cyclic HGMF design. The redundancy of
magnets necessary to achieve continuous operation would result in a severe
cost penalty when scaled up to a full size system.
For these reasons it was decided to design and build a new pilot plant
with continuous media regeneration and locate a test site at either a BOF,
EAF, or blast furnace.
10
-------
Cyclone
10/9
Cyclone
9/27 & 10/25
Inlet
10/10 & 10/26
Outlet 10/25
Outlet 9/27
1.0
2.0 3.0
Applied Field (kOe)
4.0
5.0
Figure 1. Magnetic analysis of dust samples from sinter plant HGMF pilot plant tests.
n
-------
TABLE 3. COMPONENT MASS BALANCES BASED ON CHEMICAL ANALYSIS
Fe Ca Mg Al Si Na K Cl" S04
Analysis
Avg. inlet (C.), mass %
Avg. outlet (C ), mass %
Avg. cyclone (c ), mass %
6.-C , %
rl_rO a,
r*"" f\ >
t
Component balance (based on
Inlet mass, kg
Outlet mass, kg
Cyclone mass, kg
Component closure, %
Component efficiency, %
8.92
1.38
13.0
7.54
11.62
0.649
E = 0.
8.92
0.54
7.93
95
89
5.20
2.32
7.73
2.88
5.41
0.532
1.60
0.60
2.20
1.00
1.60
0.625
8.09
3.12
11.4
4.97
8.28
0.600
61 and average measured
5.20
0.90
4.70
108
90
1.60
0.23
1.34
98
84
8.09
1.22
6.95
101
86
1.65
0.55
2.4
1.10
1.85
0.595
0.69
1.24
0.40
-0.55
-0.84
0.655
16.
32.
9.
-15.
-23.
7
6
3
9
3
0.
23.
34.
12.
-11.
-21.
1
4
9
3
5
1.62
1.80
2.33
-0.185
0.535
682 0.526
composition)
1.65
0.21
1.46
101
88
0.69
0.48
0.24
104
35
16.
12.
5.
110
34
7
7
7
23.
13.
7.
92
34
1
4
9
= overall mass collection efficiency
-------
4.5 MATHEMATICAL MODEL
The mathematical model was developed by Gooding, in conjunction with the
laboratory pilot plant work, in order to better understand the effects of
various design parameters. The final predictive equation for this model is:
4FLY p
E = 1 - exp [- c ]
E = fractional collection efficiency, dimensionless;
F = filter packing density (actual volume of steel wires/volume occupied
by filter), dimensionless;
L = filter depth, m;
S = wire radius, m;
YC = single wire collision radius, dimensionless;
p = probability of particle adhesion, dimensionless.
YC, the collision radius, is a dimensionless value derived from the
solution of the trajectory model taking into account inertial, viscous, and
magnetic forces. There are four parameters in the trajectory model -- A, G,
K, and W — which describe the particle behavior.
Parameter A accounts for the relative magnitudes of the applied magnetic
field and the induced magnetic field in the ferromagnetic wire. A was assumed
to be one since it can be shown that below the saturation values of stainless
steel wire, A ~ 1-
Parameter G accounts for the effect of gravity and was taken as zero
since the calculated value was less than 2 x 10 .
Parameters W and K take into account the effects of the applied magnetic
field and inertia on collection efficiency. More is given on parameters W and
K in Section 8.3. Details of the model are given in the report by Gooding.25
4.6 SITE SELECTION FOR CURRENT FIELD TESTS
Since RTI had attained high collection efficiencies on at least two steel
industry dusts, BOF and EAF, during the laboratory pilot plant work, it was
decided to try to locate a more suitable site for the continuous HGMF pilot
plant field tests. The higher iron content of BOF dust made it the first
choice for process type. In November, 1980, a presentation was made to the
13
-------
American Iron and Steel Institute and representatives of several steel
corporations to obtain their assistance in locating a suitable site. The only
site offer to result from the meeting was a scarfing operation.
Also at this time, there were negotiations with Dr. R. Hinson of
Georgetown Steel Corporation about the possibility of performing the field
tests at their electric arc furnace plant in Georgetown, South Carolina.
Georgetown Steel Corporation had been contacted earlier and had expressed
interest in performing the tests at their plant.
In December 1980 RTI performed particulate sampling tests at the
Georgetown Steel plant and analyzed the dust samples for size distribution,
chemical composition, and specific magnetization. The dust samples were taken
isokinetically from the duct just ahead of the baghouse with MRI cascade
impactors to obtain particle size distributions. Alundum thimbles were used
to obtain large quantity samples for chemical and magnetic analysis. Dust
samples were also obtained from the baghouse dust hoppers that Georgetown
Steel Corporation is presently using for emissions control.
Figure 2 shows the size distribution of the dust samples taken and Figure
3 shows the averaged particle size distribution for Runs 2, 3, and 4. Due to
the large differences between Run Number 1 and the others, it was felt that an
error may have been made in the sampling or weighing procedure and therefore
Run 1 was not included in the average particle size distribution. Table 4
shows the chemical composition of the samples while Figure 4 shows the
magnetization values. Table 5 gives the chemical composition of samples taken
from the Georgetown baghouse by Clemson University from February 25, 1980
through July 11, 1980. Based on the sample analysis, the mathematical model
was then used to calculate the expected collection efficiency, by particle
size, for two values of specific magnetization, and is presented in Figure 5.
According to the model, a collection efficiency of at least 99 percent could
be achieved for particle sizes of 0.9 microns and above. Below 0.9 microns,
the efficiency falls off rapidly.
Figure 6 shows a comparison of the Georgetown Steel dust magnetization
values with that of other electric arc furnace dusts. As can be seen from
Figure 6, the three samples from Georgetown Steel, fall in the middle range of
the specific magnetization values of the dust samples collected from three
EAF's across the country.
14
-------
99.9
99.8
99.5
99
98
I
M
s
s
o
.2
.1
.1
O Run No. 1
O Run No. 2
O Run No. 3
A Run No. 4
i i i i i i
ul
1 10
Particle Diameter (jutm)
Figure 2. Particle size distribution, preliminary tests.
15
100
-------
99.99 r-
8
s
'i
.01
1 10
Particle Diameter (/an)
Figure 3. Particle size distribution, average of runs 2, 3 and 4.
16
100
-------
TABLE 4. ELEMENTS PERCENT BY MASS (OBTAINED BY ATOMIC ABSORPTION)
Sample Al Si Fe Cr Ca Mg K Na Mn Pb S04 " Cl Zn
Duct sample 0.39 1.63 27.9 0.08 3.45 0.91 1.25 1.80 1.31 0.35 1.35 1.12 42.5
(12-17-80)
Baghouse sample 0.32 1.8 34.4 0.08 8.83 2.89 1.14 1.46 2.78 1.13 2.21 0.56 10.0
(1-7-81)
-------
30.0 -
rx
=>
-------
TABLE 5. BAGHOUSE DUST ANALYSIS
Below is a summary of the daily (Mon.-Fri.) Baghouse Dust Analysis from
2/25/80 through 7/11/80. The dust was sampled and then analyzed with
atomic absorption spectroscopy techniques. (The statistical parameters
are expressed as percentage composition.)
Fe, as Fe^Oa Ca, as CaO Mg as MgO
x =46.19
s = 8.96
lo = 31.0
hi = 69.0
n = 78
Mn, as MnO
x = 4.21
s = 1.47
lo = 1.69
hi =7.5
n = 79
Cu, as CuO
x = .21
s = .05
lo = .12
hi = .34
n = 79
x = 5.23
s = 2.68
lo = 1.3
hi = 14.0
n = 79
Zn, as ZnO
x = 18.36
s = 5.80
lo = 7.3
hi = 33.3
n = 79
K, as K20
x = 1.89
s = .63
lo = .66
hi = 3.52
n = 73
x
s
lo
hi
n
Pb
x
s
lo
hi
n
Cr
x
s
lo
hi
n
= 3.24
= 1.11
= 1.30
= 7.60
= 73
, as Pb02
= 3.06
= .73
= 1.51
= 4.50
= 79
= .09
= .02
= .05
= .15
= 79
x = arithmetic mean
s = standard deviation
n = number of determinations
19
-------
99.99 r-
LU
O
o
u
.1
O Sigma = 23 emu/g
O Sigma = 32 emu/g
10
100
Particle Diameter
Figure 5. HGMF -Predicted collection efficiency vs. particle size.
20
-------
1.0
2.0
Applied Field (kOe)
3.0
Figure 6. Magnetic analysis of EAF dust samples.
-------
PERFORMANCE CHARACTERIZATION TESTS
Specific Magnetization at 3.3 kOe Curve
Steel company (emu/g) No.
1.
2.
3.
4.
5.
6.
7.
8.
9.
Armco Steel (Houston Works)
J&L Steel (Cleveland, Ohio)
Bethlehem Steel (Bethlehem Plant)
Lukins Steel (Coatesville, Pa)
Bethlehem Steel (Steel ton Works)
Laclede Steel (Alton, 111.)
Georgetown Steel Baghouse Sample
(1/7/81)
Georgetown Steel Baghouse Sample
(2/27/81)
Georgetown Steel Duct Sample
66.8
41.5
25.6
20.5
19.3
13.6
32.3
29.6
22.5
1
2
3
4
5
6
7
8
9
(12/17/80)
Average specific magnetization for steel companies 1-6 = 31.2 emu/g
Average specific magnetization for Georgetown Steel = 28.1 emu/g
22
-------
Due to the relatively high magnetization values and the representative
composition of the Georgetown dust compared with other EAFs, it was decided to
test the continuous HGMF mobile pilot plant at Georgetown Steel Corporation
electric arc furnace in Georgetown, South Carolina.
23
-------
5.0 DETAILED DESIGN AND CONSTRUCTION OF THE HGMF MOBILE PILOT PLANT
The mobile pilot plant is a continuous HGMF system housed in a 12.8 m (42
ft) freight van. The system is designed for a nominal flow capacity of 3,060
mVhr (1,800 cfm). Figure 7 is a flow schematic of the continuous HGMF system,
while Figure 8 is a scale drawing of the HGMF mobile pilot plant.
The dirty gas enters the pilot plant through a 0.25 m ID stainless steel
pipe (10" schedule 5). The gas passes by test ports through which samples can
be drawn to determine inlet dust concentration, chemical composition, and size
distribution and then is directed to the HGMF device. The magnetic filter is
a Sala-HGMS® Carousel Model 120-05-00 (Sala Magnetics, Inc., Cambridge, Mass.)
incorporating a magnet head and a cleaning station mounted 180° apart on a
rotating carousel. The magnet coils are split into a saddle configuration to
allow the carousel to be rotated through the magnetized zone by a variable
speed drive. The carousel contains 48 removable cassettes which can be loaded
with filter material to a depth of 0.15 m (5.8 in). The magnet head encloses
an active face area of 0.085 m2 (133 in2) in the direction of fluid flow. The
magnet head is designed to provide an applied field from 0.0 to 5.0 kG. The
magnet head is energized by a dc modular power supply manufactured by
Controlled Power Company (Troy, MI). In the range of gas velocities tested, 2
to 10 m/s, the gas residence time in the filter varied from 0.015 to 0.075 s.
After passing through the magnet, the gas then passes by another set of
test ports and exists the pilot plant. Once leaving the pilot plant, the gas
is directed through an orifice, for velocity (flow rate) determination, through
an induced draft blower and then is exhausted to the atmosphere through an 8 m
(26 ft) high stack.
After the filter material has passed through the magnetized zone and
collected the dust particles, it then passes through the cleaning station.
The filter is cleaned by backflushing with compressed air from a 0.095 m3 tank
mounted directly over the cleaning station. To clean the filter, the com-
pressed air is released through a 0.10 m (4" nominal pipe size) Galigher Delta
valve (Galigher Company, Salt Lake City, UT). The Galigher valve is a pneu-
matically actuated pinch valve consisting of a pair of identical elastomeric
24
-------
«-HUSH STATION
Figure 7. FLOW SCHEMATIC OF CONTINUOUS HGMF SYSTEM
-------
Figure 8. H.G.MF MOBILE PILOT PLANT
-------
diaphragms contained within a cast aluminum split housing. The diaphragms are
closed by introducing compressed actuator air into the chamber between the
housing and the diaphragms. The valve can then be opened very rapidly by
exhausting the actuator air through two large ports in the housing. The
actuator air for the Galigher valve is controlled by a 0.38 m (15" nominal)
Model 168S poppet valve manufactured by Kay Pneumatics (Commack, NY).
The agglomerated dust that is cleaned from the filter material with the
cleaning air pulse is sent to a Kirk & Blum size 4, type C5 cyclone (Kirk &
Blum Manufacturing Company, Cincinnati, OH). Exhaust from the top of the
cyclone is then recycled into the dirty gas stream. Dust can be removed from
the cyclone while the pilot plant is in operation through the double seal
formed from two Morris butterfly valves (Dover Corporation/Morris Division,
Tulsa, OK) mounted on the bottom of the cyclone hopper.
Figures 9 and 10 are photographs of the interior of the pilot plant taken
during construction. Figure 9 was taken from the rear of the trailer and
shows the Sala Magnetics Carousel and the cleaning station in the foreground.
The large black magnet head is visible behind the cleaning station. Figure 10
was taken from the front of the trailer and shows the inlet and outlet pipes
connected to the magnet head. The magnet power supply and the surge tank
leading from the cyclone can also be seen.
The induced draft blower which moves the gas through the pilot plant is a
modified Centrifan Model RB50-2 (Centrifan Company, Greenville, SC). The
blower was modified so that it would exhaust 3,060 m3/hr at a suction pressure
of -13.7 kPa (-55 inches H20) and a temperature of 150° C. The entire system
is designed to allow continuous operation at temperatures of up to 200° C.
All interior and exterior pipe is insulated with jacketed fiberglass.
The front section of the trailer contains an enclosed air-conditioned
laboratory and control room. All of the gauges and controls are mounted on a
single control panel facing the operator in order to simplify operation of the
pilot plant.
A Robertshaw DCM-1000 Controller (Robertshaw Controls Company, Anahiem,
CA), is used to maintain a constant gas flow through the plant. The controller
receives its signal from a Robertshaw Model 117 differential pressure trans-
mitter which measures the pressure difference across an orifice located in the
clean gas pipe. The controller then sends a signal to adjust the butterfly
control valve located on the blower exhaust. The orifice pressure drop and
27
-------
Figure 9. HGMF pilot plant under construction,
28
-------
Figure 10. HGMF pilot plant under construction.
29
-------
the filter pressure drop are displayed and recorded on two Robertshaw Model
225 strip chart recorders located in the control panel. A Xanadu Model UPT
100-10-10 solid state programable timer (Xanadu Controls, Springfield, NJ) is
used to sequence the firing of the flush tank with the rotation of the filter
matrix. An Omega Model 199 KC digital temperature indicator (Omega Engineering,
Inc., Stamford, CT) is also mounted on the control panel and receives its
signal from the chromel/alumel thermocouples located in the inlet and outlet
piping of the pilot plant. A Flow Technology, Inc. portable turbine flow
meter with a digital readout of gas velocity is used to monitor the gas flow
in the plant and as a safety check against the orifice pressure differential
system.
The laboratory control room also contains a workbench, a wet sink, desk
space, a lab oven, a solvent sink and a lab hood. MRI Model 1502 cascade
impactors (Meteorology Research, Inc., Altadena, CA) are used to determine
particle size distribution and concentration. A Perkin-Elmer Model AD-2Z
microbalance (Perkin-Elmer Corporation, Norwalk, CT) is used to weigh the
filters and impactor substrates.
The utility requirements of the pilot plant are electricity and water.
The main power panel is breakered for 400 amperes of 440 ac volt input. The
total connected load is 300 amperes. Power consumption at 300 amperes would
be 0.043 kW/m3. The major equipment operates off 440 vac and a transformer is
provided to step down to 240 vac and 120 vac. Water consumption is approxi-
mately 2.3 mVhr (10 gpm) for magnet cooling, compressor aftercooler, and
occasional use of the lab sink.
30
-------
6.0 FIELD OPERATIONS
6.1 DESCRIPTION OF THE ELECTRIC ARC FURNACE AT GEORGETOWN, SOUTH CAROLINA
The dust source is an EAF shop utilizing three arc furnaces operating
continuously in a staggered batch operation. The Georgetown Steel raw steel
production facilities are composed of three 68 Mg (75-ton) per cycle DeMag
electric arc furnaces. The charge to the furnaces consists of scrap and
prereduced iron pellets. The scrap charged is obtained primarily from external
sources; about 5 to 10 percent is reclaim scrap. Prereduced pellets are
produced on-site from South American iron ores. Other materials added to the
furnaces during the course of the production cycle include limestone, coke,
ferromanganese, and ferrosilicon.
The air pollution control system serving the electric furnaces includes
direct shell evacuation combined with a canopy hood above each furnace to
capture fugitive emissions. Figure 11 shows a diagram of the typical EAF with
this type of control system. Gas cleaning is provided by a positive pressure
baghouse supplied by American Air Filter. The gas flow rate through the
system is about 17,800 m3/min (630,000 acfm) at an average temperature of 71°
C (160° F). Approximately 18,200 kg (40,000 pounds) of dust are collected
daily by the baghouse. The average dust concentration in the gas stream is
0.71 g/m3 (0.31 gr/acf). Composition of the gas stream is essentially that of
air because of the large fraction of air drawn in by the canopy hood.
The test location is shown roughly in Figure 12. A slipstream of gas was
taken from the duct at the approximate point marked "test site." The pilot
plant was located underneath the elevated duct at that point. The gas stream
conditions at the extraction point are listed below:
Pressure -1.7kPa (-7 inches H20)
Temperature 71° C (160° F)
Velocity 17 m/s (55.65 ft/s)
Reynolds Number 4.1 x 106
31
-------
Ctf ANED DAS lOUVf HS
CO
ro
•UUOIM IVACUAIION WillH - III Km/nil
t
IIIMtm/al*
f If CIRICIIV - 411 fa. fO MUf
f if cinooi coNsuumoN - i»t
AlKIVt - VAHIAIlf
1IUE -
IIUCA
CHARfilNI
•UCKCf
OIHfCf IHUlfVACUATION
HOOF lAriWAIfHCOOUOl
MOHOUSf
\7\7\7
ICHfWCQNVIVOM
CQUECHO
OUST III lit))
II tan/ml*
k>-O" I ^->~"""\
r^^^\ 1
COHIUSTION AW 8Af
llffl-IMIti
imi IADII
OXVIEN-4.I-IIKM
INOOfHOlOl
Figure 11. Material balance of electric arc furnace based on 1,000 kg of steel produced.
-------
n
c
co
£
Charleston
OOOOCKXXX
Guard
House
D
i
\
Highway 17
xxxxxxxxx
Myrtle
Beach
City
of
Georgetown
\
Figure 12. Rough site map.
-------
6.2 INSTALLATION AND STARTUP OF THE PILOT PLANT
The HGMF mobile pilot plant arrived at the Georgetown Steel plant on June
17, 1981, and the installation and utility hook up began. Approximately 30 m
of 0.25 m ID (10" schedule 5) stainless steel pipe was used to .connect the
pilot plant to the steel mill exhaust. A 0.21 m nozzle was placed in the
center of the 4.88 m diameter plant exhaust duct. The nozzle was facing into
the plant duct flow and was sized to give isokinetic flow at the average plant
and pilot plant flow conditions. The average temperature and pressure in the
plant exhaust duct was 71° C and -1.7 kPa (-7 inches H20) gauge.
The blower and stack were installed, piping insulated and electrical and
water connections made. The startup and debugging of the system was then
begun.
6.2.1 Temperature Control
A Universal Model 3500 FA forced-air construction heater (National
Riverside Co., Rancho Cucamonga, CA) was used for pilot plant cold startups.
The heater burns propane gas to heat 2,400 m3/hr of air to a maximum of 115°
C. A tee and appropriate valving were used so that the heater could preheat
the pipe coming from the steel plant duct and the pilot plant interior piping.
The preheat procedure usually required about 20 minutes to raise the piping to
approximately 60° C. The steady state temperature drop from the inlet to the
outlet of the pilot plant usually averaged about 10° C.
6.2.2 Filter Cleaning
The preliminary tests with the initial filter cleaning system seemed to
indicate that this system would work. The initial system used a 0.038 m (1.5"
nominal) Model 168S poppet valve to release the compressed air from the
cleaning tank. The first tests indicated that a tank pressure of 272 kPa gauge
(40 psig) and a carousel rotation speed of 0.000424 rev/s for every m/s of gas
velocity through the filter would achieve a steady state pressure drop across
the filter for each gas velocity. However, with each successive shutdown and
startup of the pilot plant, the pressure drop across the filter was slowly
increasing for each gas velocity. Neither the increase in cleaning tank
pressure to 340 kPa gauge (50 psig) nor the increase in carousel rotation
speed seemed to help.
It was then decided to install a 0.10 m (4" nominal pipe size) Galigher
Delta valve to exhaust the cleaning tank instead of the 0.038 m poppet valve.
34
-------
The Galigher valve exhausted the tank almost instantaneously achieving the
steady state pressure drop across the filter with a cleaning tank pressure of
272 kPa gauge (40 psig) and a carousel rotation speed of 0.000424 rev/s for
every m/s of gas velocity through the filter. This did, however, increase the
force of the pulse through the recycle line and into the inlet pipe just ahead
of the filter.
6.2.3 Magnet Operation
Several problems were experienced with the magnet operation initially.
The magnet cooling water outlet temperature was reaching approximately 55° C
(130° F) above the inlet temperature indicating insufficient cooling waterflow.
A small pump was installed to increase the cooling water flow through the
coils.
Initially the magnet power supply was only reaching a maximum of 400
amperes before the dc breakers tripped and shut the system down. This was
much less than the 500 amperes needed to give a maximum applied field of 5.0
kgauss. With the help of Controlled Power Company, the manufacturers of the
power supply unit, the voltages between several points in the power supply
were checked and found to be normal. All electrical connections between the
power supply and magnet were rechecked. The dc breakers were checked and
found to be satisfactory. The dc ampere output was then checked and the gauge
was found to be faulty. A new current gauge was installed and no further
problems with the power supply were experienced.
After a few hours of operation, the magnet carousel stopped rotating.
After checking the dc motor controllers the problem was found to be two
defective resistors. The resistors were replaced and no further problems
occurred.
6.2.4 Flow Measurement and Control
The flow measurement and control in the pilot plant utilizes the measure-
ment of the pressure difference across the orifice. A pitot tube traverse was
performed on several occasions to check the gas flow with that indicated by
the orifice pressure differential. The gas velocity indicated by the orifice
was within 10 percent of that indicated by the pitot tube traverse.
The approximate values for the proportional gain and integration constant
of the Robertshaw DCM-1000 Controller were obtained by adjusting these param-
eters while the pilot plant was in operation. Once these values were set, the
controller maintained a contant gas flow in the pilot plant with no problems.
35
-------
Due to an earlier problem with the output of one of the Robertshaw 117
differential pressure transmitters, magnehelic gauges were installed beside
the control panel as a safety check on the pressure drop readings.
6.2.5 Final Site Setup
Figures 13 and 14 are pictures of the HGMF Mobile Pilot Plant installed
at the Georgetown plant site.
36
-------
Figure 13. HGMF pilot plant at Georgetown Steel
37
-------
Figure 14. HGMF pilot plant at Georgetown Steel.
38
-------
7.0 PERFORMANCE CHARACTERIZATION
7.1 TEST PLAN
The test program was designed to test the effects of four parameters on
collection efficiency, and the reliability of the equipment during long term
operation. The four parameters to be varied were applied field, gas velocity,
filter type, and filter packing density. The long term testing was to be a
500 hour continuous operation. The 500 hour long term test was cancelled
however in favor of added performance characterization tests. As explained in
Section 7.4.2 the long term performance test was felt to be less important
than determining the reason for performance poorer than that achievable by
other particulate control devices.
7.1.1 Performance Characterization and Optimization
The selection of an optimum set of operating conditions was the goal of
this phase of the testing. The selection of optimum conditions was to be
based on statistical analysis of the performance data obtained under varied
operating conditions. Performance under each set of conditions was to be
measured by sampling the HGMF inlet and outlet particulate concentrations.
Overall efficiency would be determined on a mass basis and fractional
efficiency would be determined by measuring inlet and outlet particle size
distribution. Periodically during the characterization, bulk samples of the
particulate were to be obtained from the inlet, the outlet, and the cyclone
catch in order to obtain the chemical composition and its effect on performance
and vice versa.
7.1.2 Performance Data for Principal Variables
Following selection of the cleaning cycle parameters the test program
examination of principal variables on filter performance was to begin. The
priorities established for this group of measurements were as follows:
1) vary magnetic field strength and gas velocity through the filter,
2) vary the filter media, and
3) vary the packing density of the media.
39
-------
The variation of the filter packing density and filter type were lower on
the priority list due to the difficulty of changing these. Both require
shutdown of the unit and dismantling of the carousel, a time consuming process.
The program was to be started with a steel wool matrix at a packing
density of 0.015 (volume fraction occupied by steel wool), for which the
effect of magnetic field strength and velocity on performance would be investi-
gated. The second major step would be to switch from a steel wool matrix to
an expanded metal matrix for tests varying the magnetic field strength and
velocity. Superior performance for either filter type would lead to further
tests on that type for different packing densities, as time and budget allowed.
Within the initial tests on steel wool at a packing density of 0.015, a
statistical experimental design was selected for controlling the value of the
variables, field strength and velocity, as well as the number and pattern of
repetition of performance measurements. The purpose of the statistical design
was to examine the changes in performance over the range of variables and
provide for repetition of certain experimental points in order to better
estimate experimental error. In addition to error caused by measurement
inaccuracies, there would be error introduced by random process variations
(electric arc furnace operations). The repetitions would, however, allow us
to gauge both the measurement inaccuracy and furnace operation variation.
The statistical design selected was a central composite, second order
response surface design containing nine test points with repetitions as noted
in Figure 15. With the center point and extreme values of both variables
defined, the intermediate test points are given by the statistical design.
The pattern variable values permits ready computation of variance components
and estimation of coefficients for first and second order effects caused by
each variable. The order of the tests would be selected at random.
Following the initial test series the filter media was to be changed to
expanded metal and the tests repeated. Since no prior experimental work had
been done with expanded metal, performance difference was a principal question.
It was hoped that equivalent performance might be achieved at signficantly
lower pressure drops as compared to the steel wool, which would lead to lower
operating costs on a full scale system.
With respect to the fourth variable, packing density, there was expected
to be a tradeoff between performance and pressure drop. Better performance
could be achieved at higher packing densities, but with correspondingly higher
pressure drops.
40
-------
CD
o
LU
CD
5.0
4.0
2.5
1.0
0.0
4.0, 2.5
(1 test)
5.2, 4.0
(2 tests)
5.2, 1.0
(2 tests)
7.0, 5.0
(1 test)
7.0, 2.5
(5 tests)
7.0, 0.0
(1 test)
8.8, 4.0
(2 tests)
8.8, 1.0
(2 tests)
10.0, 2.5
(1 test)
4 5.2 7 8.8
GAS VELOCITY - m/s
Figure 15. HGMF TEST POINTS.
10
41
-------
Using the optimum conditions defined by the above tests, the continuous
500 hour test was to be conducted.
7.2 TEST PROCEDURES
7.2.1 Sampling Procedures
Particle size distribution measurements were made at the inlet and outlet
sampling locations with MRI Model 1502 cascade impactors. The particulate
sampling procedure utilized in these tests was adopted from EPA guidelines for
the use of cascade impactors (Harris, 1977). The majority of the impactor
substrates were precoated with Apiezon L grease and baked at 150° C for 4
hours. Several impactor runs were performed with Kapton substrates to allow
trace element analysis by particle size.
The nozzle sizes and sample rates were selected to obtain a velocity
isokinetic with the gas velocity in the pipe. The temperature of the impactors
was controlled to within ± 20° C of the stack gas temperature which ranged
from 30° C to 70° C. Several impactor blanks were also run as a control
measure to determine the weight gains attributed to reactions of the stack gas
with the substrate.
Since the impactors were used external to the pipes, the probes were
washed with acetone to recover any material that did not reach the impactor.
The probe wash mass was included in the total mass calculations but not in the
fractional efficiency calculations since no attempt was made to assign a size
to it.
The sampling nozzles used with the cascade impactors were 90° bend type.
Preparation of the particle size distributions graphs for this report assumed
no significant loss of impactor-sizeable particles to the nozzle wall. In
fact, such nozzle wall losses do occur. Calculations for the nozzle sizes
used in this sampling work show nozzle cut sizes in the range of 3 to 5 urn.
For this reason, data for impactor stages with cut points above 3 to 5 urn
probably incorrectly portray the weight distribution. The practical effect of
this data limitation is loss of resolution in the size distribution curve
above the nozzle cut point i.e., one is forced to begin extrapolation of the
curve at 3 to 5 urn rather than 8 to 10 urn.
A sampling train as shown in Figure 16 was used for the impactor sampling
and for the particulate concentration sampling.
42
-------
Heating Tape
or Jacket
250 ml 250 mL Dry Silica
H20 H20
Orifice
I T
0
Dry Gas
Meter
Pump
Figure 16. Filter train for determination of mass efficiency.
-------
The particulate concentration sampling utilized a 47 mm diameter fiber-
glass pad in a heated filter holder located outside the duct. The procedure
to measure the gas velocity and control the sampling flow was similar to that
described for the cascade impactor.
The weighing of the impactor substrates and the filters is a critical
operation in the successful execution of the test program. The balance, a
Perkin-Elmer Model AD-2Z microbalance, is calibrated with a class M weight
which is NBS traceable. Because a weighing-by-substition method is used, a
reference control disc is frequently weighed to verify the accuracy of the
balance.
7.2.2 Filter Operating Procedures
As stated in Section 6.0 of this report, the optimum carousel speed and
cleaning system firing cycle was determined by operation of the pilot plant.
The criterion was the optimum combination of filter dust loading and cleaning
pulse force and timing in order to achieve a steady state pressure drop across
the filter. The optimum dust loading was achieved with a carousel speed of
0.000424 rev/s for every m/s of gas velocity through the filter. The optimum
cleaning pulse pressure was 272 kPa gauge (40 psig) with the cleaning system
firing through each cassette once for each revolution of the carousel.
Whenever the gas velocity through the filter was changed, there had to be a
corresponding change in the carousel rotation speed and the cleaning tank
cycle in order to obtain the same filter dust loading.
The applied magnetic field in the filter was controlled by the current
output of the dc power supply operating the magnet. The dc current versus
applied field calibration curve was prepared and check by Sala Magnetics, Inc.
Whenever the applied magnetic field was to be changed, then the d.c. current
output of the power supply was set to the appropriate value according to the
calibration curve.
7.3 COARSE GRADE STAINLESS STEEL WOOL MATRIX
The initial filter medium was American Iron and Steel Institute Type 430
medium grade stainless steel wool packed to a density of 0.015 (1.5 percent by
volume) and came packed in the carousel from Sala Magnetics. The average
fiber diameter of this material is 120 pm.
Table 6 is a summary of the results obtained from the steel wool matrix
performance characterization tests. Measured overall efficiencies ranged from
44
-------
TABLE 6. GEORGETOWN STEEL HGMF TESTS (STEEL WOOL MATRIX—PACKING DENSITY 0.015)
4*
cn
Field strength
kilogauss
0*
1.0
1.0
1.0
1.0
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
4.0
4.0
4.0
4.0
4.0
4.0
5.0
Velocity
m/s
7.0
5.2
5.2
8.8
8.8
4.0
4.0
7.0
7.0
7.0
7.0
7.0
10.0
5.2
5.2
5.2
5.2
8.8
8.8
7.0
Pressure drop**
cm H20
38.1-58.0
25.4-35.6
25.4-35.6
61.0-76.2
61.0-76.2
15.2-22.9
15.2-22.9
38.1-50.8
38.1-50.8
38.1-50.8
38.1-50.8
38.1-50.8
76.2-91.4
25.4-35.6
25.4-35.6
25.4-35.6
25.4-35.6
61.0-76.2
61.0-76.2
38.1-50.8
Concentration
grams/scm
Inlet Outlet
0.458
0.226
0.773
0.844
0.730
0.270
0.291
0.862
0.153
1.048
0.435
0.611
0.657
0.270
0.602
0.178
0.201
0.430
1.025
0.693
0.197
0.041
0.082
0.265
0.108
0.048
0.046
0.096
0.025
0.059
0.053
0.078
0.085
0.050
0.053
0.053
0.043
0.046
0.108
0.066
Efficiency
percent
57.2
82.4
89.3
68.7
85.3
82.4
84.4
88.9
84.1
94.4
88.2
87.4
87.3
81.4
91.1
71.0
79.0
89.3
89.5
90.6
* The applied magnetic field was zero, however, a remnant field of about 100 gauss is present under this
condition.
**The low value of AP corresponds to the free flow of gas through the slotted entry of the carousel; the
high value occurs when two of the slots are covered by the gas seal as the carousel turns.
-------
a low value of 57.2 percent with no applied magnetic field to a high value of
94.4 percent. The bulk of the measured efficiencies at magnetic field strengths
at and above 2.5 kilogauss were in the range of 80 to 90 percent. Figures 17
through 22 present the particle size distribution calculated from the experi-
mental data. The curves drawn through the data points are produced from a
computerized data reduction scheme which calculates the stage cut points and
then transforms the cumulative distribution versus stage cut points to log-
normal space. It then fits a natural cubic spline to the transformed data and
differentiates the cumulative curve to obtain the differential distribution.
The differential distributions of corresponding inlet and outlet data are then
multiplied by the total mass concentrations (excluding probe washes) and
ratioed to obtain the fractional efficiency or penetration curve. The mass
mean particle diameter measured at the filter inlet ranged from 2 to 7 urn.
The mass mean diameters measured at the filter outlet ranged from 0.9 to 2.5
urn. Fractional efficiencies by particle size are present in Section 8.1.2.
As discussed in Section 7.2.1, caution should be used in drawing conclusions
about particle size data above 5 urn.
The data did show a general trend of increasing efficiency with an in-
crease in field strength, but there seemed to be very little correlation of
either collection efficiency or outlet concentration with gas velocity. Part
of the difficult in assessing the effects of operating variables is attribut-
able to the large variation in inlet concentrations. Statistical analyses of
the test data discussed in Section 8.0 more clearly demonstrates the effects
of these variables.
As is evident the pressure drop through the filter increased with in-
creasing gas velocity. A low value of 15.2 cm H20 occurred at a velocity of 4
m/s and a high value of 76.2 cm H20 occurred at 10 m/s. The low value in the
range of pressure drops accompanying each test run is the value considered to
be the potential steady state pressure drop. The upper value of the ranges
occurred when slots in the revolving carousel were partially covered by the
gas seals. In a full scale system design the impact of gas seals on pressure
drop could be minimized by changing the slot design.
The performance characterization tests for the steel wool matrix with a
packing density of 0.015 could not remove a sufficient percentage of the dust
while operating under practical conditions. It was then decided to change to
an expanded metal matrix for more performance characterization tests.
46
-------
99.99 r-
99
90
.§
CO
3 70
.1
- 50
§
•s
"a
o
30
10
Inlet
• 0612 7.0 rn/sec 5.0 kilogauss
A 0613 7.0 m/sec 5.0 kilogauss
• 0616 7.0 m/sec 0.0 kilogauss
O 0617 7.0 m/sec 0.0 kilogauss
.01
I
I
.1
.2
.5 1
Particle Diameter (/im)
Figure 17. Georgetown Steel HGMF test—steel wool matrix
(packing density 0.015).
10
47
-------
99.99
99
o
N
55
90
7°
u
1*
g 30
<£ 10
S
Outlet
• 0611 7.0m/sec 5.0 kilogauss
A 06I4 7.0m/sec 5.0 kilogauss
• 06!5 7.0 m/sec 0.0 kilogauss
O 06I8 7.0 m/sec 0.0 kilogauss
.01
I
I
.1
.2 .512 I
Particle Diameter (pirn)
Figure 18. Georgetown Steel HGMF test—steel wool matrix
(packing density 0.015).
10
48
-------
99.99,-
99
90
N
35
I70
^
- so
i 30
I
£ 10
I
.01
.1
Inlet
• 0311 7.0m/sec 2.5kilogauss
I
I
I
.2
.5 1 2
Particle Diameter (fan)
10
Figure 19. Georgetown Steel HGMF test—steel wool matrix
(packing density 0.015).
49
-------
99.99 r
99 -
90
N
55
1 70
GB
.2
1
I
- 50
3 30
8
I
2
I
o
10
Outlet
• 0312 7.0 m/sec 2.5 kiiogauss
.01
.1
.2
.5
10
Particle Diameter (/urn)
Figure 20. Georgetown Steei HGMF test—steel wool matrix
(packing density 0.015).
50
-------
99.99 r-
99
90
N
I70
Is0
8 30
3
o
10
Inlet
x 0412 10.0m/sac 2.5 kiiogauss
• 0414 10.0 m/sec 2.5 kiiogauss
• 04! 6 4.0 m/sec 2.5 kiiogauss
A 04I8 4.0 m/sec 2.5 kiiogauss
.01
.1
.2
.5
1
Particle Diameter (jzm)
Figure 21. Georgetown Steel HGMF test—steel wool matrix
(packing density 0.015).
10
51
-------
99.99 n
99
90
o
N
35
1 70
(8
I
§ 30
3
10
Outlet
X04I1
• 04I3
• 0415
0417
10.0 m/sec
10.0 m/sec
4.0 m/sec
4.0 m/sec
2.5 kilogauss
2.5 kilogauss
2.5 kilogauss
2.5 kiiogauss
.01
I
.1
.2
.5 1
Particle Diameter
10
Figure 22. Georgetown Steel HGMF test—steel wool matrix
(packing density 0.015).
52
-------
7.4 EXPANDED METAL MATRIX
The expanded metal matrix (layers of wide mesh screen) can be packed with
all of the fibers perpendicular to the magnetic field and in the optimum
position for particle capture. It was hoped this would allow us to obtain a
higher collection efficiency for the same pressure drop as was attained with a
i
stainless steel wool matrix.
7.4.1 Packing Density of 3.5 Percent by Volume
The average fiber diameter of the expanded metal matrix is 300 M^ as
compared to the steel wool fiber diameter of 120 (jm. The approximate packing
density of the expanded metal matrix with the same fiber to fiber distance was
calculated to be 0.035. This matrix was then packed into the carousel and a
series of performance characterization tests were run.
Table 7 is a summary of the results obtained from the series of perfor-
mance characterization tests run with the expanded metal matrix packed to a
density of 0.035.
Measured efficiencies ranged from a low value of 72.9 percent with no
applied magnetic field to a high value of 94.2 percent. As in the case of the
steel wool data, the bulk of the measured efficiencies at field strengths at
and above 2.5 kilogauss were in the range of 80 to 90 percent.
It is difficult to see a clear trend of efficiency changes with field
strength changes due mainly to the widely varying inlet concentrations.
Statistical analyses of test data discussed in Section 8.0 more clearly demon-
strate the effects of variable changes on efficiency. Pressure drops through
the filter matrix varied from a low value to 12.7 cm H20 at a velocity of 5.2
m/s to a high value of 53.3 cm H20 at velocity of 10 m/s. These values are
lower than the corresponding values for steel wool. More thorough pressure
drop comparisons are presented in Section 8.1.2.
Figure 23 through 28 show the calculated particle size distributions.
The mass mean particle diameter measured at the filter inlet ranged from 0.8
to 3 |jm during these tests. At the filter outlet the mass mean diameters
ranged from 0.7 to 2.6 urn. The highest outlet mass mean diameter, 2.6 urn, was
measured with no applied field. Excluding the no applied field cases the
highest outlet mass mean particle diameter was 1 pro. Fractional efficiencies
by particle size are presented in Section 8. As discussed in Section 7.2.1
caution should be used in drawing conclusions about particle size data above 5
urn.
53
-------
TABLE 7. GEORGETOWN STEEL HGMF TESTS (EXPANDED METAL MATRIX—PACKING DENSITY 0.035)
on
Field strength
kilogauss
0*
1.0
1.0
1.0
1.0
2.5
2.5
2.5
2.5
2.5
2.5
2.5
4.0
4.0
4.0
4.0
4.95
Velocity
m/s
7.0
5.2
5.2
8.8
8.8
4.0
7.0
7.0
7.0
7.0
7.0
10.0
5.2
5.2
8.8
8.8
7.0
Pressure drop**
cm H20
38.1-50.8
12.7-20.3
12.7-20.3
38.1-50.8
38.1-50.8
—
25.4-38.1
25.4-38.1
25.4-38.1
25.4-38.1
25.4-38.1
53.3-66.0
12.7-20.3
12.7-20.3
38.1-50.8
38.1-50.8
25.4-38.1
Concentration
grams/scm
Inlet Outlet
0.524
0.517
0.327
0.496
0.679
0.915
1.174
0.936
0.446
0.469
1.288
0.577
1.235
0.355
0.501
1.039
0.844
0.142
0.101
0.085
0.133
0.160
0.124
0.069
0.094
0.066
0.114
0.194
0.062
0.146
0.073
0.082
0.153
0.169
Efficiency
percent
72.9
80.6
73.9
73.2
76.4
86.5
94.2
90.0
85.2
75.6
84.9
89.1
88.1
79.6
83.6
85.3
80.1
* The applied magnetic field was zero, however, a remnant field of about 100 gauss is present under
this condition.
**The low value of AP corresponds to the free flow of gas through the slotted entry of the carousel;
the high value occurs when two of the slots are covered by the gas seal as the carousel turns.
-------
99.99 r-
99
90
N
35
1 70
.1
•o
I"
a so
I
jo
3
O
10
Inlet
O18I2
7.0 m/sec
D 1814 7.0 m/sec
2.5 kiiogauss
2.5 kiiogauss
O18I6 7.0 m/sec 5.0 kiiogauss
A1818 7.0 m/sec 5.0 kiiogauss
.01
.1
.2
1
Particle Diameter (tan)
10
Figure 23. Georgetown Steel HGMF test-expanded metal matrix
(packing density 0.035).
55
-------
99.99 r-
99
90
8
35
1 70
8
'•$
T 50
§ 30
I
<£ 10
I
«s
Outlet
O 1811
D 1813
O18I5
A 1817
7.0 m/s
7.0 m/sec
7.0 m/sec
7.0 m/sec
2.5 kilogauss
2.5 kilogauss
5.0 kilogauss
5.0 kilogauss
.01
i
i
.1
.51
Particle Diameter
Figure 24. Georgetown Steel HGMF test— expanded metal matrix
(packing density 0.035).
10
56
-------
99.99 r-
99
90
J9
CO
1 70
.1
i"
s 30
I 10
O
Inlet
O19I2 7.0m/sec 0.0 kilogauss
D 1914 7.0m/sec 0.0 kilogauss
Q19I6 10.0m/sec 2.5 kilogauss
A 1918 10.0 m/sec 2.5 kilogauss
.01
I
I
.1
.51
Particle Diameter
Figure 25. Georgetown Steel HGMF test— expanded metal matrix
(packing density 0.035).
10
57
-------
99.99 ,-
99
90
s
35
1 70
-------
99.99 ,-
99
90
3
1 70
J
•o
•? so
§ 30
§
o
10
Inlet
O 20! 2 4.0 m/sec 2.5 kiiogauss
A 2014 4.0 m/sec 2.5 kiiogauss
.01
I
.1
.51
Particle Diameter
Figure 27. Georgetown Steel HGMF test— expanded metal matrix
(packing density 0.035).
10
59
-------
99.99 r-
99
a—-a
90
5
1 70
3
(8
8 30
8
I
.1
4*
"5
10
Outlet
o 2011 4.0 m/sec 2.5 kilogauss
D20I3 4.0 m/sec 2.5 kilogauss
.01
I
I
.1
.2
.5 1
Particle Diameter (/im)
10
Figure 28. Georgetown Steel HGMF test-expanded metal matrix
(packing density 0.035).
60
-------
While the pressure drop values were improved for the same gas velocities,
however, there was no improvement in the collection efficiency or in the
outlet concentration values. For this reason it was then decided to increase
the packing density of the expanded metal matrix and perform additional
characterization tests.
7.4.2 Packing Density of 6.0 Percent by Volume
The pilot plant was shutdown and the carousel dismantled in order to
repack the cassettes to a packing density of approximately 0.06. The unpacking
and repacking process was relatively time consuming, requiring about three
man-weeks to complete. The equipment was then reassembled and the testing
begun.
Because of concerns about remaining project funds, it was decided that a
complete set of 17 characterization test runs would not be performed.
Initially test runs were made varying field strength from 0.1 to 5 kilogauss
and velocity from 5.2 to 8.0 m/s. When relatively high pressure drops were
encountered, an additional group of 3 test runs was made at a velocity of 2
m/s for field strengths of 0.1, 2.S, and 5 kilogauss.
Table 8 shows the results from the tests with the expanded metal matrix
at this higher packing density. Measured overall efficiencies ranged from a
low value of 79.4 percent with no applied field (excluding an apparently
anomalous result of 68.5 percent at 2.5 kilogauss) to a high value of 96.4
percent. The measured efficiencies at field strengths of 2.5 kilogauss and
above are in the range of 89 to 96 percent, clearly higher than those
efficiencies measured for the previous two test series. As in the case of the
steel wool tests there is a trend of higher efficiency with increasing field
strength. Statistical analyses in Section 8 more clearly demonstrate the
effect of operating conditions on measured efficiencies.
Pressure drops ranged from a low value of 1.3 cm H20 at a velocity of
2m/s to a high value of 55.9 cm ^0 at a velocity of 8.8 m/s. Since no tests
were run at 2 m/s with the steel wool matrix or expanded metal matrix at 3.5
percent packing density, low end comparisons have to be made at 5.2 m/s. At
this velocity the pressure drops were 25.4 cm, 12.7 cm, and 22.9 cm H20 for
steel wool, expanded metal at 3.5 percent density, and expanded metal of 6
percent density, respectively.
61
-------
TABLE 8. GEORGETOWN STEEL HGMF TESTS (EXPANDED METAL MATRIX—PACKING DENSITY 0.06)
IVS
Field strength
kilogauss
0.0*
0.0*
2.5
2.5
2.5
2.5
4.0
4.0
5.0
5.0
5.0
Velocity
m/s
2.0
7.0
2.0
7.0
7.0
7.0
5.2
8.8
2.0
7.0
7.0
Pressure drop**
cm H20
1.3-5.8
30.5-48.3
1.3-3.8
30.5-48.3
30.5-48.3
30.5-48.3
22.9-27.9
55.9-68.6
1.3-3.8
30.5-48.3
30.5-48.3
Concentration
grams/son
Inlet Outlet
0.259
0.504
0.240
0.612
0.229
0.598
1.037
1.474
0.383
0.269
0.936
0.046
0.104
0.009
0.066
0.072
0.053
0.063
0.054
0.018
0.022
0.052
Efficiency
percent
82.4
79.4
96.4
89.2
68.5
91.1
93.9
96.3
95.3
91.7
94.4
The applied magnetic field was zero, however, a remnant field of about 100 gauss is present under this
condition.
**The low value of AP corresponds to the free flow of gas through the slotted entry of the carousel; the
high value occurs when two of the slots are covered by the gas seal as the carousel turns.
-------
Figures 29 and 30 show the particle size distributions for this test
series. The mass mean particle diameters measured at filter inlet were 2.1
and 2.9 urn, respectively. The filter outlet measured mass mean particle
diameters were 0.84 and 0.89 urn, respectively. Fractional efficiencies by
particle size are presented and discussed in Section 8.1.2. As discussed in
Section 7.2.1 caution should be used in drawing conclusions about particle
size data above 5 urn.
During the above particle measurements runs the impactors were loaded
with Kapton substrates to permit chemical analysis of the particles on a
particle size basis. Results of these analyses are presented in Section
8.2.2.
Although the overall efficiencies for this test series were significantly
improved over those of the previous two test series, a problem with the tech-
nology was still apparent in that measured efficiencies were not in a range
competitive with proven high efficiency technology i.e., scrubbers, precipita-
tors, and fabric filters. At this point field experimental work was inter-
rupted to analyze and review all the data obtained to date. The intent was to
determine the cause for residual mass penetration at the 5 to 10 percent level
and to consider whether changes could be made to the system to improve its
performance. With the HGMF not yet being competitive with other collecting
devices in performance there would be little justification for a 500-hour long
term test to examine reliability.
Results of the data review and analysis are contained in Section 8, as
well as a discussion of the bases for conclusions. Without further details in
this section, a decision was made to forego the 500-hour test and use the
limited remaining funds on additional performance characterization with the
expanded metal matrix at 6 percent packing density.
7.4.3. Additional Testing
Since the initial cleaning system consisting of a 0.045 m3 (12 gallon)
air tank and a 1*5 inch poppet valve had to be changed to a 0.095 m3 (25 gallon)
tank with a 4 inch Galigher valve, the surge tank was inadequate to dampen the
pulse from the cleaning system. This resulted in a considerable surge of gas
entering the inlet pipe just ahead of the filter each time the cleaning system
fired. A visible puff of smoke could be seen coming from the stack each time
the cleaning system was pulsed. It was thought that this surge of air just
ahead of the filter might be reentraining particles already removed from the
63
-------
99,99 ,-
99
90
N
35
1 70
ta
u
- 50
-------
99.99 r-
99
N
55
•
90
70
»
(A
09
.1
**
JO
3
30
10
Outlet
• 0711 7.0 m/sec 5.0 kilogauss
• 0713 7.0 m/sec 2.5 kilogauss
.01
I
.1
.2
.5 1 2
Particle Diameter (/zm)
10
Figure 30. Georgetown Steel HGMF test expanded metal matrix
(packing density 0.06).
65
-------
gas stream by the magnetic filter and consequently reducing collection
efficiency. For this reason it was decided to carry out additional perfor-
mance characterization tests with the recycle line disconnected. The velocity
selected for these tests was chosen to give a pressure drop somewhat similar
to that for a fabric filter system.
Table 9 shows the results obtained from these performance characteriza-
tion tests. Measured efficiencies ranged from a low value of 85.1 percent to
a high value of 93.5 percent. These performances were obviously not better
than those measured with the recycle line connected. Comparisons of the two
data sets for expanded metal at 6 percent packing density are presented in
Section 8.
Pressure drops averaged 31.8 cm H20 for these six test runs. Figures 31
and 32 show the particle size distributions calculated from the test data.
The mass mean particle diameters of the filter inlet ranged from 1.6 to 4.0
urn. At the filter outlet the mass mean particle diameter ranged from 0.8 to
1.1 urn. Section 7.2.1 discusses caution to be used in drawing conclusions
about particle size data above 5 pm.
66
-------
TABLE 9. GEORGETOWN STEEL HGMF TESTS (EXPANDED METAL MATRIX-PACKING DENSITY 0.06, NO RECYCLE)
Field strength
kilogauss
2.5
2.5
2.5
5.0
5.0
5.0
Velocity
m/s
5.2
5.2
5.2
5.2
5.2
5.2
Pressure drop*
cm H20
22.9-33.0
21.6-30.5
22.9-33.0
21.6-27.9
19.1-27.9
22.9-30.5
Concentration
grams/son
Inlet Outlet
0.551
0.355
0.769
0.412
0.369
0.805
0.070
0.024
0.074
0.041
0.055
0.052
Efficiency
percent
87.2
93.3
90.3
90.1
85.1
93.5
*The low value of AP corresponds to the free flow of gas through the slotted entry of the carousel; the
high value occurs when two of the slots are covered by the gas seal as the carousel turns.
-------
99.99 r-
99
90
-------
99.99 r-
99
90
I
1 70
CO
U
eo
30
§
<£ 10
I
+*
CO
Outlet
D 5.2 m/sec 5.0 kiiogauss
O 5.2 m/sec 5.0 kiiogauss
A 5.2 m/sec 2.5 kiiogauss
• 5.2 m/sec 5.0 kiiogauss
• 5.2 m/sec 2.5 kiiogauss
.01
I
I
I
.1
.2
1
10
Particle Diameter (/zm)
NOTE: Test with recycled gas stream disconnected.
Figure 32. Georgetown Steel HGMF test—expanded metal matrix
(packing density 0.06).
69
-------
8.0 DATA ANALYSIS
8.1 PERFORMANCE DATA
Analyses of HGMF system performance were made by examining overall inlet
and outlet mass measurements, and by examination of fractional particle size
efficiency (penetration) as affected by the controlled variables of magnetic
field strength, gas velocity through the filter, packing density, and packing
type. The statistical experimental design provided data over a range of
independent variable values facilitating statistical analysis of overall
performance and assisting graphical interpretation of effects on fractional
size efficiency.
8.1.1 Overall Performance
Multiple linear regression techniques were used to analyze the data. The
groups of data for each matrix type and packing density were obtained in
sequence, rather than randomly, owing to the difficulty of changing the
carousel cassettes. Also because of this factor, statistical analyses were
performed on the data grouped by packing type and packing density. At the end
of the data gathering period when data from all the tests were available the
data were lumped together and multiple linear regression was used to examine
relationships for the aggregated data. The ready availability of computer
facilities made an exhaustive approach to regression analyses on the data
possible.
Prior to beginning the statistical analysis there was no notion as to
whether penetration (1-efficiency) or outlet mass (or concentration) would be
a better choice for the dependent performance variable, therefore both cases
were studied. Another factor to remember as the statistical analyses are
discussed is that identification of effects of pilot plant operating variables
may have been easier had the inlet dust concentration been maintained at some
fixed value. Unfortunately, random process variations (three nearly indepen-
dently operated furnaces) produced about a 6:1 range of variations in inlet
concentrations, not to mention important variations in dust chemical composi-
tion.
70
-------
8.1.1.1 Steel Wool-Packing Density 1.5 Percent. There were twenty test
runs performed with this matrix and packing density. The test data were
previously listed in Table 6. Table 10 is a partial tabular display of the
regression forms examined. Multiple correlation coefficients are listed as
well as the significance of the regression (F-statistic).
While the statistical design was chosen to promote evaluation of first
and second order effects of the principle independent variables (field strength
and velocity), the regression model that gave the best fit was an exponential
model. As shown in Table 10, the model in column 1 with second order effects:
Outlet concentration = 0.0135 - 0.0067 FS + 0.001 (FS)2 + 0.0052 Vel
+ 0.001 (Vel)2 - 0.0042 (FS)(Vel) + 0.066 (In Cone),
had a correlation coefficient of 0.856 and F-statistic of 5.92. The exponen-
tial model listed in column 6:
In (Outlet mass) = -1.23 - 0.319 ln(FS) + 0.690 In (Inlet mass)
Outlet mass = 0-292 (Inlet mass)0'690
FS •*
had a correlation coefficient of 0.893 and F-statistic of 33.64.
Comparison of columns 4 and 6 show that a better correlation was achieved
using outlet mass (velocity x outlet concentration) as the dependent variable
than with penetration (1-efficiency) as the dependent variable.
One premise with which the experimental program began, namely that
velocity was a significant independent variable, was not clearly demonstrated
in the statistical analysis. In every case where velocity was treated as an
independent variable, the addition of velocity to the regression model did not
significantly improve the correlation coefficient or F-statistic. Stepwise
regressions, when adding velocity to a given model, gave insignificant
t-statisties for the velocity coefficient. In spite of this fact, velocity
does appear in the best fit regression equation since both inlet and outlet
mass rates are computed using the velocity. The benefit of using mass rate
instead of concentration is demonstrated by comparing columns 2 and 6. Both
71
-------
-J
ro
TABLE 10. HGMF OVERALL PERFORMANCE REGRESSION COEFFICIENTS, STEEL WOOL MATRIX
Dependent Variables
1234 5 6
Independent Outlet In In Outlet Mass In
Variables* Concentration (Outlet Cone.) Penetration (Penetration) (Vel x Outlet Cone.) (Outlet Mass)
cc
ro
/cc\2
\rb)
1 nfi:c\
1 n^ro )
\lal
ve i
f\la"\ ~\2
V.V6 1 )
1 r./lf«l A
in(.ve i )
CC v \/ol
r b x ve i
In Cone
in (.in Loncj
T n 1 j%4- Mr*f r
inlet Mass
(Vel x In Cone)
T 1-. flnTr.4- U-.^r\
in Ciniet Massj
Intercept
R (Correlation
Coefficient)
F- statistic
Onm f\
. UU IU
Onnco
. UUoZ
Onm r\
. UU IU
OflCC
. UDD
0.0135
0.856
5.92
0.143 u.llf
_n oic _ n OIQ __ _
U.olO -U.diy
Onno __ _
. UUo
u £ Q J -• •— ™- -i- -r— ^^^i— -_- — r-rri™^-^
-3.37 0.554 -1.23 0.772
0.846 0.629 0.734 0.747
13.42 2.45 9.95 10.73
_n 31 o
U. 6 la
OCQA
. byu
-1.23
0.893
33.64
*FS = Magnetic field strength. Vel = Velocity. In Cone = inlet concentration.
-------
the correlation coefficient and F-statistic are better for the column 6 model
using mass rates.
8.1.1.2 Expanded Metal-Packing Density 3.5 Percent. There were 17 test
runs performed with this matrix at this packing density. The test data were
previously listed in Table 7. Table 11 is a partial tabular display of the
regression forms examined. As in Table 10 multiple correlation coefficients
and F-stati sties are also listed.
Table 11 only displays the logarithmic forms (which algebraicly convert
to an exponential model) of variables because the best fits of the data were
obtained in that form. As in the case of the steel wool matrix tests, the
best regression fit was provided by the exponential model listed in column 3.
The equation of best fit was:
Outlet rcass = °'372
However, the fit for this data is not as good as for the steel wool data. On
examination of residuals (actual outlet mass rate minus predicted outlet mass
rate) one data set stands out as a possible outlier. At the time of the
initial sampling results, the measured filter performance seemed unusually
high for the seventh test listed in Table 7. The sample weights and calcula-
tions were rechecked, but no error was discovered. Nevertheless, the residual
for this test run is about 7 times the standard error for the estimate regres-
sion and, therefore, subject to suspicion. If that set of test data is
deleted, the numbers in parentheses in column 3 are the revised regression
coefficients, correlation coefficient, and F-statistic. As expected, there is
a considerable improvement in the degree of fit. As with the steel wool data,
gas velocity by itself did not prove to be a significant correlating variable
in the expanded metal tests.
8.1.1.3 Expanded Metal - Packing Density 6.0 Percent. Initially there
were 11 test runs performed at this packing density. Subsequent to the pre-
liminary data review an additional 6 test runs were made with the system as
described in Section 7.4.3. Table 12 is a partial tabular display of the
regression forms examined for the initial 11 test runs. Multiple correlation
coefficients, F-statistics, and regression coefficients are presented.
73
-------
TABLE 11. HGMF OVERALL PERFORMANCE REGRESSION COEFFICIENTS
EXPANDED METAL MATRIX, 3.5 PERCENT
Independent
Variables
ln(FS)
1 ^/X/^l "\
1
In
(Outlet Cone.)
-0.130
_n non
Dependent Variable;
2
In
(Penetration)
-0.152
3
In
(Outlet Mass)
-0.152 (-0.155)*
ln(Inlet Cone)
ln(Inlet Mass)
Intercept
R (Correlation
Coefficient)
F-statistic
0.485
-2.319
0.574
2.13
-0.383
-0.989
0.651
5.14
0.617 (0.748)*
-0.989 (-1.18)*
0.699 (0.829)*
6.67 (14.35)*
Parenthetical values apply to regression without the seventh test in
Table 7, an apparent outlier.
74
-------
TABLE 12. HGMF OVERALL PERFORMANCE REGRESSION COEFFICIENTS
EXPANDED METAL MATRIX, 6 PERCENT
Dependent Variables
Independent
Variables
1
In
(Outlet Cone.)
2
In
(Penetration)
3
In
(Outlet Mass)
ln(FS)
In(Vel)
ln(Inlet Cone)
ln(Inlet Mass)
Intercept
R (Correlation
Coefficient)
F-statistic
-0.284
-0.803
0.304
-4.635
0.876
7.68
-0.302
0.0176
-2.291
0.609
2.36
-0.302 (-0.284)*
( 1.499)*
1.018 ( 0.304)*
-2.291 (-5.589)*
0.881 ( 0.957)*
13.90 (25.42)*
* Parenthetical values apply to regression including In(Vel) as an indepen-
dent variable.
75
-------
As in the case of the steel wool data and expanded metal at 3.5 percent
packing density, the best fit was the exponential model listed in column 3.
The equation matching the earlier two test series was:
Outlet mass = °-101
For this test series the velocity through the matrix was found to be an
important correlating variable, whereas it was not for either of the previous
two data sets. The parenthetical entry in column 3 lists the appropriate
values. Both the correlation coefficient and F-statistic are significantly
improved by addition of velocity to the model. The equation including velocity
is:
Outl et mass = 0-0037 (1.1* massA304(Ve1) ' • 4"
r o
That velocity should be an important correlating variable is not surprising.
By reference to the above equation, an increase in velocity would produce an
increase in outlet mass, if all other variables are held constant. A potential
explanation could be that higher velocity is indicative of increased
reentrainment losses. As to why velocity proved to be an important correlating
variable for expanded metal at packing density of 6 percent when it was not
for either the steel wool or less densely packed expanded metal, it may be
argued that the lower penetration levels observed for 6 percent packing were
predominantly reentrainment losses and, therefore, more sensitive to velocity
changes. While the data tend to support this argument, the experimental
program was not sufficiently rigorous to state it with certainty.
As explained in Section 7.4.3 an additional six test runs were made with
the filter cleaning system recycle line disconnected. The intent of these
measurements was to examine performance without the influence of recycled
fines and the periodic surge of the cleaning system recycled gas stream.
These performance data were added to the previous eleven test runs and
regression analyses performed for the same models given in column 3 of Table
12. Comparison of the regression coefficients, correlation coefficients, and
F-statistics is presented in Table 13. The addition of the last six test runs
76
-------
TABLE 13. COMPARISON OF REGRESSION STATISTICS
EXPANDED METAL MATRIX - 6 PERCENT
Regression Coefficients
Test runs In (FS) In (Inlet mass) In (Vel) R F
1-11 -0.302 1.018 0.88 13.90
(1-11)* -0.284 0.304 1.499 0.957 25.42
1-17 -0.233 0.987 0.848 17.97
(1-17)* -0.227 0.364 1.391 0.922 24.45
"Parentheses indicate model including velocity as an independent variable.
77
-------
to the 6 percent packing density expanded metal data base produced a small
decrease in the multiple correlation coefficient and F-statistic.
The hypothesis that disconnection of gas cleaning system recycle line
would improve overall magnet performance was examined graphically as shown in
Figure 33. The regression line shown is based on all 17 test runs. The
performance data from the last 6 test runs are clearly not better than the
data from the first 11 test runs. In fact the last six test runs, in general,
show poorer performance for given values of the regression function.
Disconnection of the recycle gas line did not produce an improvement in system
performance.
8.1.1.4 Performance Summary—All Matrices, All Packing Densities. The
comparative performance of the filter system for both matrices and packing
densities can be seen in Figure 34. The performance data are plotted as
penetration versus regression function. The line through each data set is the
regression curve for that data set. The regression coefficients a, b, and c
for each set of data are given in Table 14. To compare the performance one
must examine the penetration at low values of the regression function for each
data set. Looking at the functional relation of each variable in the
regression function it is expected that best performance would be measured for
low regression function values, i.e., low inlet mass, low velocity, and high
field strength. Differing absolute values of the regression function occur
between sets because of the different regression coefficients for each data
set. At low values of the regression function, poorest performance was
measured for expanded metal at 3.5 percent packing density, with clearly best
performance from expanded metal at 6 percent packing density.
Table 15 provides a comparison of predicted penetration for both matrices
and packing densities at fixed system operating conditions. Predicted
penetrations are lower for expanded metal at 6 percent packing density and the
observed pressure drop was also lower for this matrix than for steel wool.
Pressure drop was significantly lower for expanded metal at 3.5 percent packing
density, but its predicted penetration is about twice as high as that for 6
percent packing density at the higher field strengths. Based on Table 15,
expanded metal at 6 percent packing density would be the preferred matrix.
78
-------
100,-
•B 10
2
o o
o Data points from first eleven test runs
4- Data points from last six test runs
10
Regression Function (Inlet Mass)0-^64 (Velocity)1-39
Inlet Mass
(Field Strength)0-227 (Inlet Mass)
100
Figure 33. Georgetown Steel HGMF test—expanded metal matrix
(packing density 0.06).
79
-------
100 r-
Steel Wool
0.015
Expanded
Metal
0.035
o
10
0)
a.
Expanded
Metal
A 0.06
10
Regression Function (Inlet Mass)3 (Velocity)b
Inlet Mass
(Field Strength)0 (Inlet Mass)
100
Figure 34. Georgetown Steel HGMF test-penetration vs. regression function
(all matrices and packing densities).
80
-------
TABLE 14. REGRESSION COEFFICIENTS FOR EACH FILTER MATRIX AND PACKING DENSITY
Model: Outlet mass = Intercept x
-------
8.1.2 Performance By Particle Size
The MRI cascade impactor size data were used to generate particle size
fractional efficiency (penetration) curves. Simultaneously obtained inlet and
outlet distribution curves were used, and in some cases data taken under
duplicate conditions have been combined to provide composite fractional
efficiency curves. The solid portion of the curves represents the range of
particle sizes over which data were obtained, as opposed to the broken line
segments representing extrapolated portions. The curves were generated
assuming no nozzle wall losses. Discussion in Section 7.2.1 explains that
such wall losses do occur and, therefore, all p.article size distribution
curves above 5 urn may not correctly portray the size distribution.
Figures 35-38 display the effects of increasing magnetic field strength
at constant velocity for steel wool, expanded metal 3.5 percent packing
density, and expanded metal 6 percent density, respectively. The curves show
the predominant effect of increasing field strength to occur on particle sizes
in the range of 1 to 10 urn. The reduction in penetration occurring from the
2.5 kilogauss to 5.0 kilogauss change is much lower than that from the no
applied field (0.1 kilogauss remnant field) to 2.5 kilogauss change.
Figures 39 and 40 show the effect on penetration from changing filter
velocity keeping constant field strength, for velocities of 4, 7, 10 m/s. As
in the case of varying field strength, the predominant effect seems to be on
particle sizes greater than 1 urn. In Figure 39 penetration decreases as
velocity decreases. Potential explanations for this apparent effect are
improved performance with increasing residence time, and increased reentrain-
ment, thus, poorer performance with increasing velocity. The trend is not
consistently present in Figure 40. The 7 m/s and 10 m/s curves follow the
trend, but the 4 m/s curve does not. Looking at all the curves, Figures
35-40, it is evident that the filter is relatively inefficient for particle
sizes below 1 urn in diameter. This leads to the question of whether the
inefficiency in the smaller particle size range is inherent to the design and
magnet operating conditions chosen for these tests, or attributable to varia-
tion in size related particle characteristics. The next section discusses the
chemical and magnetic characterization of the electric arc furnace dust.
82
-------
1
**
2
10
• 7.0 m/sec 5.0 kilogauss
• 7.0 m/sec 2.5 kilogauss
A 7.0 m/sec 0.1 kilogauss
.1
.1
1
10
100
Particle Diameter (/im)
Figure 35. Georgetown Steel HGMF test—penetration vs. particle size
(steel wool matrix 0.015).
83
-------
100
10
o
I
o
a.
.1
D 7.0m/sec 5.0 kilogauss
O 7.0 m/sec 2.5 kilogauss
A 7.0 m/sec 0.1 kilogauss
10
100
Particle Diameter Qim)
Figure 36. Georgetown Steel HGMF test—penetration vs. particle size
(expanded metal matrix 0.035).
84
-------
1001-
10
O 7.0 m/sec
A 7.0 m/sec
2.5 kilogauss
5.0 kilogauss
.1
10
100
Particle Diameter
Figure 37. Georgetown Steel HGMF test— penetration vs. particle size
(expanded metal matrix 0.06).
85
-------
100
10
o
1
I
.1
\
D 5.2 m/sec 5.0 kilogauss
O 5.2 m/sec 5.0 kilogauss
A 5.2 m/sec 2.5 kilogauss
B 5.2 m/sec 5.0 kilogauss
• 5.2 m/sec 2.5 kilogauss
.1 1 10
Particle Diameter (^m)
NOTE: Test with recycled gas stream disconnected.
Figure 38. Georgetown Steel HGMF test-penetration vs. particle size
(expanded metal matrix 0.06).
100
36
-------
100
10
O 10.0 m/sec
O 7.0 m/sec
A 4.0 m/sec
2.5 kilogauss
2.5 kilogauss
2.5 kilogauss
.1
.1
10
Particle Diameter (/xm)
100
Figure 39. Georgetown Steel HGMF test—penetration vs. particle size
(steel wool matrix 0.015).
87
-------
1001-
10
1
— -A
Q
O
4.0 m/sec
7.0 m/sec
10.0 m/sec
2.5 kiiogauss
2.5 kiiogauss
2.5 kiiogauss
.1
10
100
Particle Diameter dan)
Figure 40. Georgetown Steei HGMF test—penetration vs. particle size
(expanded metal matrix 0.035).
-------
8.2 CHEMICAL AND MAGNETIC CHARACTERISTICS OF ELECTRIC ARC FURNACE DUST
Chemical and magnetic characteristics of the dust were determined for two
classes of samples. One class of samples was obtained by extracting dust from
the inlet and outlet ducts simultaneously over a period of 12 to 16 hours.
Due to the large quantities of dust expected, alundum thimbles were used as
the filtering media with sampling performed isokinetically to assure size
representativeness in the sample. During the sampling period dust samples
were also removed from the cyclone in the continuous matrix cleaning system.
The other class of samples used to determine chemical and magnetic
characteristics were obtained from the cascade impactors. For several particle
size test runs, the particulate captured on each impactor stage was recovered
and subjected to analyses. The quantity of sample obtained from the impactors
was minute in comparison with the thimble samples. Therefore, the kind of
analyses that could be performed was limited.
8.2.1 Magnetic Analyses
Measurement of specific magnetization was used as one indicator of the
range of particle characteristics encountered during the pilot plant tests.
The specific magnetization tests were performed by Dr. Herbert Hacker at Duke
University. The specific magnetization was obtained with a Faraday Balance
which consists of a Cahn Model RG electronic balance and a Varian 4005 electro-
magnet. The balance is capable of measuring the susceptibility and magnetiza-
tion of a wide range of materials as a function of temperature and magnetic
field intensity. Basically, the instrument measures the force on a small
magnetic sample when it is suspended in an inhomogeneous magnetic field
supplied by an electromagnet. The force is expressed as
Fx = am dH/dx
where a is the magnetization per unit mass, m is the mass of the sample, and
dH/dx is the field gradient in the vertical direction. The pole faces of the
electromagnet are machined so as to produce a constant value if dH/dx over the
volume of space containing the sample. The force is measured with a Cahn
Model RG electrobalance capable of determining forces in the 0.1 mg range.
In performing the measurements, the ferromagnetic effluent powders are
first demagnetized by simultaneously reversing and reducing the magnetic field
89
-------
from 3.3 kilo-oersteds (kOe) down to zero field. Then the force is measured
as a function of magnetic field as it is increased monotonically from zero up
to 3.3 kOe. Using this technique, the data yields the virgin magnetization
curve, i.e., data independent of remnant and hysteresis effects.
The calibration of the Faraday Balance depends on knowledge of the field
gradient (dH/dx) in the region in which the sample hangs. Measurements of
dH/dx have been carried out using a Rawson Rotating Coil Gaussmeter which
yields accuracies of 1 to 2 percent. In addition, measurements on high purity
samples of "standard" materials, whose magnetic properties are well known,
were used to determine values of dH/dx. Through these techniques confidence
is established that the magnetization is accurate to within 2 percent.
In calculating the magnetization, the mass of the sample must be
accurately known. Typical values of sample mass are in the range of 0.2 to
0.5 mg for effluent dust of the type used in this study. To accurately
determine these small masses, a separate Cahn Model RTL electrobalance with
digital readout is used with special precautions taken to eliminate small,
stray electrostatic forces of submilligram magnitude.
Table 16 lists the specific magnetizations of all thimble dust samples
and the cyclone dust samples at 3.3 kOe applied field. The overall variation
in specific magnetization was from 22.1 to 34.4 electromagnetic units/gram
(emu/g) which corresponds well with the values of 23 and 32 emu/gram found in
the preliminary test data.
Closer examination of the data in Table 16 reveals that the outlet dust
samples apparently contain a relatively significant amount of magnetic
material. For the low field case (0.1 kilogauss) the outlet dust specific
magnetization is about 80 percent of the inlet dust value. For the 2.5
kilogauss field cases, the outlet dust specific magnetization is about 65
percent of the inlet values. In the high field case (5.0 kilogauss), the
outlet value is about 50 percent of the inlet value.
To look at the magnetic properties as a function of particle size, one
set of simultaneously collected inlet and outlet cascade impactor plate samples
was analyzed. The impactor stages were labelled A through G in order of
descending particle size. Figure 41 shows specific magnetization at the
saturation field value of 3.3 kOe for each impactor stage. Unfortunately
there was not sufficient recovered dust on stages A and B of the outlet
impactor for this measurement to be made. The data tend to show that specific
90
-------
TABLE 16. SPECIFIC MAGNETIZATION OF BULK DUST SAMPLES*
Operating conditions Inlet Outlet Cyclone
Steel wool, packing density - 0.015
2.5 kilogauss, 7 m/s 22.1 14.7 27.3
0.1 kilogauss, 7m/s 27.7 22.5 33.3
Expanded metal, packing density - 0.035
2.5 kilogauss, 7 m/s 31.6 20.0 39.2
Expanded metal, packing density - 0.06
5.0 kilogauss, 7 m/s 34.4 17.6 37.8
2.5 kilogauss, 7 m/s 26.8 17.7 38.0
"Electromagnetic units/gram at an applied field of 3.3 kOe.
91
-------
20
O>
"
.
I »
"•
1X3
s
1
5< 10
u
O
D
Inlet sample
Outlet sample
Operating conditions: 7.0 m/sec 2.5 kilogauss
B
Impactor Stage
Figure 41. Georgetown Steel HGMF test—specific magnetization vs. particle size, steel wool matrix
(packing density 0.015).
-------
magnetization decreases with decreasing particle size, except that stage C
seems to run counter to this trend on both inlet and outlet samples. The
magnetization data also tend to support the fractional-penetration-by-particle-
size data that show preferential removal of larger particle size material.
For impactor stages C, D, and E the specific magnetization is Tower for the
outlet than for the inlet, suggesting the larger magnetic particles are being
preferentially removed. Because the data are limited to one set of samples,
however, the above is a suggestion rather than a conclusion.
8.2.2 Chemical Analyses
The bulk samples collected with alundum thimbles from the inlet and
outlet ducts were analyzed by atomic absorption to determine the amount of
certain metals present. For aluminum and silicon, samples and varying amounts
of a known standard were digested as follows. Approximately 20-50 mg of
sample or standard were mixed with 0.2 g of LiBo2 and 0.05 g of KI in a
platinum crucible. The crucible was heated over an air-methane flame until
the mixture was a molten bead. Heating was continued for 5 minutes and the
bead was then dissolved in 10 percent HN03 and diluted to 50 ml with 10 percent
HN03. Measurements were then made by flame atomic absorption (N20 - acetylene
flame). For all other elements from 0.25 - 0.5 g of sample were digested with
3 ml of concentrated HN03 and then brought to dryness. The residue was taken
up in 3 ml Aqua Regia (1 part HN03 - 3 parts HC1), diluted to 100 ml, and
filtered. Any subsequent dilutions were performed with the same acid media.
Standards were prepared with the same acid media and a blank was run as well.
Measurements were made via flame atomic absorption (air - acetylene and N20 -
acetylene flame). The results of these analyses are listed in Table 17.
The inlet concentrations of iron varied between 29.2 percent and 35.7
percent. In every case the percentage of iron in the outlet sample was lower
than the inlet sample, showing preferential removal of iron compounds.
With one exception, the no applied field case (0.1 kilogauss remnant
field), the alkaline metals sodium and potassium increased in weight percent
from inlet to outlet. Zinc content increased in weight percent from the inlet
to outlet in four of the five cases with a small decrease occurring in the
fifth case.
Table 18 lists the elemental penetrations calculated from the alundum
thimble sample analyses. Variations in penetration can be seen with varied
93
-------
TABLE 17. CHEMICAL ANALYSES OF BULK OUST SAMPLES - WEIGHT PERCENT
ID
Steel wool
Packing density - 0.015
Element
Na
K
Ca
Mg
Fe
Zn
Al
S1
Pb
Cr
Mn
2.
In
4.46
2.64
4.56
5.79
29.2
8.77
0.40
1.93
1.98
0.09
23.9
5 kG.
Out
7.63
5.17
3.53
3.40
24.2
7.83
0.31
1.01
1.96
0.13
17.5
7 m/s
Cyclone
2.27
1.13
6.83
5.04
32.4
4.96
0.38
2.49
0.95
0.11
18.6
o;<
In
3.89
1.92
3.65
3.45
33.4
10.8
0.32
2.35
1.87
0.13
17.5
.1 kG,
Our
3.41
2.14
3.71
3.05
30.9
14.7
0.38
1.76
3.09
0.14
15.8
7 m/s
Cyclone
2.56
1.07
5.05
4.30
35.6
7.38
0.55
2.30
1.13
0.09
18.1
Packing density
2.5
In
2.84
2.14
5.57
5.18
31.9
7.95
0.39
2.66
0.56
0.07
20.6
kG, 7
Out
4.58
4.90
4.12
3.41
28.0
11.8
2.50
13.0
0.88
0.95
15.6
Expanded metal
- 0.035 Packing density
m/s
Cyclone
1.40
0.82
6.51
4.48
33.8
4.33
0.63
2.43
0.29
0.08
14.4.
5 kG7
In
1.53
1.93
7.25
4.13
35.7
5.79
0.70
3.22
0.92
0.08
31.5
7 m/s
Out
3.46
4.58
4.63
2.63
23.0
9.6
2.22
2.61
2.59
0.11
18.3
- 0.06
2.5 kG.
In
1.08
2.20
5.59
5.33
32.0
8.65
0.46
2.46
1.16
0.09
36.5
7 m/s
Out
3.18
4.55
4.29
3.34
26.2
12.2
1.09
2.24
1.99
0.10
30.8
-------
TABLE 18. ELEMENTAL PENETRATION PERCENT - BULK SAMPLES
Filter operating Overall
condition Na K Ca Mg Fe Zn Al Si Pb Cr Mn penetration
7/30/81
Steel wool -
0.015
2.5 kG, 7 m/s 21.8 25.0 9.9 7.5 10.6 11.4 9.9 6.7 12.6 18.4 9.3 12.8
7/31/81
Steel wool -
0.015
0.1 kG, 7 m/s 28.9 36.8 33.6 29.2 30.6 44.9 39.2 24.7 54.6 35.6 29.8 33.0
9/02/81
Expanded metal
0.035
2.5 kG, 7 ra/s 32.7 46.4 15.0 13.4 17.8 30.0 31.9 15.4 20.3
9/30/81
Expanded metal
0.06
5.0 kG, 7 m/s 21.3 22.4 6.0 6.0 6.1 15.6 26.5 7.6 26.3 13.0 5.5 9.4
10/01/81
Expanded metal
0.06
2.5 kG, 7 m/s 22.4 24.4 9.1 7.4 9.7 16.7 28.0 10.7 20.3 13.1 10.0 11.8
-------
operating conditions, as well as differences in penetration among the elements.
Sodium, potassium, aluminum, and lead penetrations are, in general, much
higher than overall mass penetration. Calcium, magnesium, iron, silica, and
manganese penetrations are, in general, lower than overall mass penetration.
Zinc and chromium penetrations are moderately higher than overall mass penetra-
tions. That removal efficiencies of the alkaline metals are relatively poor
and not particularly sensitive to varying magnetic field strengths is not
unexpected. The earlier HGMS pilot plant tests on a sintering plant waste gas
stream showed these metals to be significant contributors to the poor magnet
performance. Since calcium, magnesium, silicon, and manganese show similar
penetration to iron, it is presumed these elements may be chemically associated
with the iron in the dust particles. Calcium and magnesium enter the electric
arc process as fluxing agents and are principal constituents of the slag layer
that forms on top of the molten iron as the refining operation proceeds.
Manganese is an essential alloying element for steel and is introduced to the
process through the scrap charge, as well as through additions of ferro-
manganese to the melt.
The fact that incomplete elemental separations occur in the magnetic
filtering process suggests complex particle chemistry. One might expect that
zinc and lead, both diamagnets (weakly repelled), would significantly penetrate
the filter, and lead, in particular, does. While zinc penetration is higher
than the overall penetration, enough zinc is apparently associated with iron
in the particles to moderate its penetration.
Supporting data for the association of iron and zinc is provided in a
paper by Keyser et al.33 presented at the 1981 EPA Iron and Steel Pollution
Abatement Symposium. The paper reports work done at Lehigh University on
characterizing electric arc furnace dust. It found zinc and iron to be
associated in particles labelled mixed ferrite. Some of these particles were
found in both magnetic and non-magnetic fractions. Since some of the iron
occurs in ferrite particles that are non-magnetic, this may be one explanation
why iron penetration did not approach zero in these pilot plant tests. Further
this Lehigh study found a considerable variation among the thirty-three samples
from different plants as to the amount of zinc and iron occurring as magnetic
and non-magnetic ferrite. This fact suggests that HGMF applied to other
electric arc furnace waste gas streams might vary considerably in its overall
performance.
96
-------
Two sets of simultaneous inlet and outlet impactor runs were made with
kapton substrates. The kapton substrates were used to permit analysis of the
collected sample spots on each stage by x-ray fluorescence. The intent of
these analyses was to examine the distribution of elements, particularly iron,
by particle size. Figures 42 and 43 show the size distribution of iron and
zinc at the inlet and outlet for two filter operating conditions. For the 2.5
kilogauss test run about 12 percent by weight of the inlet iron and zinc were
below 1 urn in particle diameter. For the 5 kilogauss test run about 14 percent
of the inlet iron and 21 percent of the inlet zinc were in particles below
1 urn in diameter. The outlet curves for both elements under both operating
conditions show a finer elemental particle size distribution than at the
inlet. This indicates that larger particle sizes for both elements are
preferentially removed by the filter.
Figures 44 and 45, the elemental penetration curves for iron and zinc,
clearly show this preference. These data suggest that in spite of the higher
magnetic susceptability of iron, there is still a significant filter
inefficiency caused by fine iron bearing particles as opposed to more coarse
iron bearing particles. The HGMF efficiency was only 80 to 85 percent for
iron at the 1 urn particle diameter. The shape of the iron elemental penetra-
tion curve is similar to the elemental penetration curve for zinc, a diamag-
netic element. The association of these two elements in electric arc furnace
dust particles (in both magnetic and non-magnetic fractions) may prevent
achievement of high magnetic filter efficiency.
8.3 MODEL DISCUSSIONS
The theoretical HGMF model developed by Gooding25 was used to determine
how well the model would fit the experimental collection data.
In the model the particles are assumed to be spherical, uniformly dis-
tributed in the fluid stream, and moving at the same velocity as the fluid
system of the collector. The basic element of the filter is assumed to be a
clean, cylindrical wire of radius s, oriented so that its axis is perpendicular
to the fluid flow as shown in Figure 46. The collision radius of the wire YC,
is defined by the initial position of the particle whose trajectory just
touches the wire.
97
-------
99.99 r-
99
90
S
00
1 70
CO
O
!-
(B
8 30
I
£
.1
U
10
.01
.1
• Zinc (outlet)
• Iron (outlet)
O Zinc (inlet)
O Iron (inlet)
Conditions: 7.0 m/sec 2.5 kilogauss
J_
I
I
.2
.5 1
Particle Diameter (jan)
10
Figure 42. Georgetown Steel HGMF test-particle size elemental analysis,
expanded metal matrix (packing density 0.06).
98
-------
99.99 r-
99
8
35
90
70
I 30
*•
i
10
I
2
I
o
Zinc (Outlet)
D Zinc (Inlet)
• Iron (Outlet)
O Iron (Inlet)
.01
.1
.5
1
10
Particle Diameter (pim)
Figure 43. Georgetown Steel HGMF test—particle size elemental analysis,
expanded metal matrix (packing density 0.06).
99
-------
100 r-
,o
'•3
CO
g 10
c
a.
c
O 7.0 m/sec 5.0 kilogauss
Q 7.0 m/sec 2.5 kilogauss
0.1 1
Particle Diameter (/zm)
Figure 44. Georgetown Steel HGMF test—iron penetration vs. particle size
(packing density 0.06).
10
TOO
-------
100
10
Om
o
N
O 7.0 m/sec 5.0 kilogauss
O 7.0 m/sec 2.5 kilogauss
.1 1
Particle Diameter (/mi)
Figure 45. Georgetown Steel HGMF test—zinc penetration vs. particle size,
expanded metal matrix (packing density 0.06).
10
101
-------
o
ro
FLUID STREAMLINE
PARTICLE TRAJECTORY
FLOW
x
FLOW
figure 46. Illustration of particle capture by a single wire.
-------
The final predictive equation, as given earlier, is:
4 FL Y P
E = 1 - exp [- nas(1.F)2]
where P the reentrainment correction factor is defined as
P = a WbKc.
The reentrainment correction factor P is the probability of a particle adhering
to the wire once it collides. A multiple regression analysis was conducted by
Gooding on earlier data in order to correlate P with the previously defined
dimension!ess groups W and K. The results are given in Table 19.
The correlation values for the EAF dust calculated by Gooding did not
work well when used with the Georgetown Steel test data so another regression
analysis was conducted. Table 20 gives the results.
Figures 47 and 48 show the penetration versus particle size graphs for
the actual data compared with the theoretical model. The agreement between
the two runs and the model is fairly good until the particle diameter exceeds
1.0 urn at which point the agreement becomes very poor.
This could be due to the varying dust composition with particle size.
There is no way in the model to account for varying dust composition and the
resultant change in specific magnetization with particle size. More work will
need to be done with the HGMF model and with dust analysis according to
particle size before the model can be used confidently as a predictive tool.
8.4 DISCUSSION OF RESULTS
This pilot program was the first attempt at using a continuously cleaned
magnetic filter unit on a gas stream as opposed to a liquid stream. While no
long term continuous test was performed, the continuous cleaning system was
capable of maintaining a stable pressure drop through the filter matrix at
each of the velocity conditions over the period of performance characterization
tests. In general these were one to two week periods with no actions taken to
provide special extraordinary cleaning. Within the limitations of this
experimental program the continuous cleaning system with compressed air
satisfactorily maintained filter pressure drop.
103
-------
TABLE 19. CORRELATION OF REENTRAINMENT CORRECTION
Data
Number of
data points
Correlation
Correlation
coefficient
BOF dust
field-on
267
,0.087
P = 0.789
K
OTT90
0.727
BOF dust
field-off
61
P = 0.534 K
-0.317
0.669
EAF dust
field-on
52
P = 0.406
W'
,0.013
Ku.
0.634
104
-------
TABLE 20. CORRELATION OF REENTRAINMENT CORRECTION FOR THE HGMF TESTS
AT GEORGETOWN STEEL
Data
Number of
data points
Correlation
Correlation
coefficient
Steel wool &
expanded metal
131
0.048
0.516
Steel wool
53
0.063
0.394
Expanded metal
77
0.024
0.593
105
-------
1001-
10
0>
-------
100 r-
10
£
_o
1
\
\
V
o Actual data—physical diameter
& Theoretical prediction
Conditions: 7.0 m/sec
5.0 kilogauss
.1 1 10
Particle Diameter (;im)
Figure 48. Georgetown Steel HGMF test—theoretical and actual penetration vs.
particle size, expanded metal matrix (packing density 0.06).
100
107
-------
The performance data discussed in Section 7.0 and statistical analyses
discussed in Section 8.0 showed the best performance (efficiency) was achieved
with an expanded metal matrix at 6 percent packing density. This best perfor-
mance was achieved at a pressure drop lower than the second best performing
matrix, steel wool. This test program was the first in the HGMF development
program attempting to use an expanded metal matrix instead of steel wool.
Given the better performance at lower pressure drop observed in the initial
experiments, expanded metal matrices deserve further study.
For the given conditions of applied field, velocity (residence time), and
inlet concentrations, the best overall efficiencies achieved were in the range
of 94 to 96 percent with outlet concentrations in the range of 20 to 70 mg/m3.
The efficiency levels are much improved over those achieved in the previous
pilot plant work on sinter plant emissions. The performance levels, however,
are not competitive with conventional high efficiency control devices applied
to electric arc furnaces. The New Source Performance Standard for electric
arc furnaces limits particulate emissions to 12 mg/dsm3. The HGMF outlet
concentration in these tests were 2 to 6 times the required level. State
standards for existing sources vary considerably e.g., Pennsylvania equivalent
to 18 mg/dsm3, Michigan equivalent to 130 mg/dsm3. On a performance basis
HGMF might have some limited retrofit potential.
Given that this pilot plant design was not an optimum design specifically
for electric arc furnaces, one may question whether with design changes much
better performance can be expected, i.e., can pentration be reduced by a
factor of 2 or 6. One way to attempt an answer to this question is to examine
the empirical data correlation (regression equation) for the 6 percent expanded
metal case. The equation shows that outlet mass varied approximately as the
1.4 power of filter velocity. By halving the velocity (5 m/s to 2.5 m/s) one
might expect to reduce penetration by a factor of 2.6. Increasing field
strength above 5 kilogauss would not be nearly as effective in that outlet
mass varies inversely as the 0.23 power of field strength. Reduction in
filtering velocity is clearly the stronger effect, but halving the velocity
requires doubling the filter area to treat a given volume of gas. This means
the cost of the equipment will be significantly increased.
The theoretical model developed by Gooding suggests another way of improv-
ing performance. Instead of increasing residence time by reducing velocity,
residence time may be increased by increasing the filter length in the direc-
108
-------
tion of gas flow. This means of varying residence time could not be explored
in the pilot plant. The theoretical model discussed in Section 8.3 suggests
filter penetration is exponentially related to filter length. If the filter
length were doubled, from 0.15 m to 0.30 m, penetration would be reduced by a
factor of 1.6. Quadrupling the filter length would provide the needed reduc-
tion in penetration (a factor of 4) for the device to become competitive.
However in addition to increasing the equipment costs there would be a severe
energy penalty. Presumably the pressure drop across the magnetic filter would
also quadruple.
The fractional penetration data shows the HGMF was not as effective on
particles below 1 urn in diameter as on those above 1 urn. This behavior and
the curve shapes shown in Section 8.2 are characteristic of conventional
control devices. The leveling off and increase in penetration for particle
sizes over 5 urn, apparently due to reentrainment, are often present in precipitator
particle size versus penetration curves. In terms of fractional particle size
penetration, it is not evident that any significant qualitative differences
exist between HGMF and conventional control devices.
The magnetic analyses data reveal that the HGMF did not remove all of the
magnetic material. The magnetic material penetrating the collector may do so
because of insufficient residence time or due to reentrainment. The chemical
analyses data reveal a significant amount of iron penetrated the filter,
especially in the small particle size (below 1 urn) fraction. Penetration of
the iron may be due to insufficient residence time and reentrainment. However,
the recent report33 indicating some iron in electric arc furnace dust to be
present in a "non-magnetic" form (probably meaning not ferromagnetic) suggests
a third mechanism for penetration. The HGMF's sensitivity to chemical composi-
tion of particles and their resulting magnetic susceptability is analagous to
the effects of chemical composition on particle resistivity and electrostatic
precipitator performance.
An alternative use for HGMF not explored in this study is to separate
non-magnetic components of waste EAF dust from magnetic components, i.e.
ferrous and non-ferrous. At present, EAF dust is classified as hazardous
waste as a result of heavy metals contamination. Separation of the ferrous
portion with minor contamination by zinc might permit its recycle to steel-
making, reducing the residue for disposal. With sufficient concentration of
zinc, the non-ferrous portion might be sold to zinc refiners. The association
of iron and zinc in non-magnetic particles identified in the study discussed
109
-------
above33 suggests that this potential application of HGMF needs further study
to determine the degree of separation achievable.
110
-------
9.0 ECONOMICS
Approximate costs have been developed for four different options for
participate emission control of electric arc furnace (EAF) dust. The accuracy
of these costs corresponds roughly to that of a study grade estimate (±30%)
and are shown in Table 21. Although a best estimate is presented for both
capital and annual expenses, it should be kept in mind that the absolute costs
of the four options may depend on special process details, plant location, and
material of construction. Consideration of these details was not within the
scope of the estimate. However, the estimates were made for the following
common base case:
Volumetric flow rate: 8,500 m3/min @ 66° C
Inlet dust loading: 1,050 mg/sm3
Outlet dust concentration: 12 mg/sm3
Annual operation: 8,500 hr/yr
For purposes of the economic comparisons, it was assumed that HGMF
performance could attain the outlet concentration needed to comply with the
EAF NSPS, or 12 mg/dsm3.
In addition, the following system parameters specific to each option were
specified based on engineering judgment:
HGMF
Superficial face velocity
Flow velocity 7 m/s5 m/s2 m/s
APHGMF-cm H20 33.0 17.8 ~2TT
Total fan static AP, design 63.5 50.8 38.1
operating 50.8 38.1 25.4
111
-------
TABLE 21. COSTS OF VARIOUS CONTROL OPTIONS FOR EAF PARTICULATE EMISSION
$/m3/s
Total annualized costs
Total capital costs 10 yr1 20 yr1 Direct operating costs2
HGMF3
2 m/s
5 m/s
7 m/s
31.31
20.99
14.16
7.06
5.21
4.07
5.64
4.26
3.43
0.71
0.95
1.20
ESP 11.944 3.43 2.89 1.01
FF 11.11 3.64 3.14 1.09
VS 17.58 8.11 7.31 4.55
1Total annual costs are computed for both 10 and 20 year capital recovery
periods. The capital recovery factor for 10 years is .16275 and for 20 years
is .11746.
2Direct operating costs include operation and maintenance labor, supervisory
overhead, and utility costs. It does not include capital recovery charges
or taxes, insurance, and administrative charges (taxes, insurance, and admin-
istration are computed at 4 percent of the total capital costs.)
3Values given for three separate face velocities.
4Capital costs for the ESP were calculated in four ways.
(a) Ratio from reference (34) below
using empirical factors Cost = $11.50/am3/s
(b) Itemized major equipment and cost factors Cost = 10.47/am3/s
(c) Escalate from reference (35) Cost = 13.11/am3/s
(d) Ratio from reference (34) using ".6 rule" Cost = 13.13/am3/s
112
-------
ESP
Migration velocity
Specific collection area
APESP
Total fan static AP, design
operating
4.6 cm/s
100 m2/m3/s
2.5 cm H20
5.9 cm H20
3.9 cm H20
FABRIC FILTER
Air/cloth
APFF
Total fan static AP, design
operating
1.0 cm/s
20.3 cm H20
50.8 cm H20
38.1 cm H20
L/G
AP
VENTURI SCRUBBER
VS
Total fan static AP, design
operati ng
Water recycle ratio
93 2/1,000 m3
152 cm H20
203 cm H20
191 cm H20
0.9
The scope of the cost estimates includes flange to flange costs from the
confluence of the particulate collection hoods (e.g., shell and canopy,) to
the discharge of the clean air from the control device. For the venturi
scrubber costs of sludge treatment equipment is also included. It is assumed
that utilities are available at the plant site at the following rates:
Electricity
Plant water
Cooling water
Compressed air
9.1 CAPITAL COSTS
$.05/kWh
$.066/1,000 2
$.026/1,000 &
$.706/1,000 m3
The total capital costs (TCC) were calculated using a modified Lang
method, i.e., applying factors to the purchased equipment costs to account for
direct and indirect installation costs.
113
-------
A substantial amount of engineering judgment is used in formulating these
factors. However, the relative order of these factors for the ESP, VS, and FF
is consistent with other data.36 These factors reflect the expense necessary
to install and put into operation each control option. The ratio between
installation costs and purchased equipment costs for HGMF was judged to be
lower than for either the ESP or FF.
Table 21 shows that HGMF is more capital intensive than either the ESP or
FF. Looking at the annualized costs, the venturi scrubber is not competitive
with any of the other three options at the given conditions. Direct operating
costs, which do not include the cost of capital over the life of the unit, are
slightly higher for the HGMF at 7 m/s than for either the ESP or FF. However,
the difference in both capital and direct operating costs among the HGMF, ESP,
and FF is well within the probable error of the estimate (±30%). In addition,
changes in labor and utility rates could alter the relative order of the
direct operating costs. For example, if labor and maintenance material costs
increased by 30 percent or if electricity were available at $.04 instead of
$.05/kWh, the direct operating costs shown in Table 22 would result.
Thus, although the capital required for HGMF is relatively high, HGMF is
cost competitive in direct operating costs both within the error associated
with the estimate as well as under two possible scenarios which could be
applicable to specific sites selected for HGMF. It is important to note that
tax considerations are not part of this estimate. Investment tax credits and
other tax incentives could offset some of the initially higher HGMF capital
costs by reducing the total annualized costs of Table 21.
114
-------
TABLE 22. DIRECT OPERATING COSTS
HGMF 2 m/s
5 m/s
7 m/s
ESP
FF
I*
$/am3/s
0.61
0.81
1.01
0.86
0.94
II**
$/am3/s
0.78
1.02
1.26
1.10
1.19
The result of changing electrical costs from $.05 to $.04 kWh.
**The result of a 30 percent increase in labor and maintenance material costs,
electricity still at $.05/kWh.
115
-------
10.0 REFERENCES
1. Obertueffer, J. A., "Magnetic Separation: A Review of Principles,
Devices, and Applications," IEEE Trans. Magn., Mag-10. 223 (1974).
2. Kolm, H. H., J. A. Oberteuffer, and D. R. Kelland, "High Gradient
Magnetic Separation," Sci. Am.. 223, 47 (Nov. 1975).
3. Oder, R. R., "High Gradient Magnetic Separation Theory and Applications,"
IEEE Trans. Magn.. Mag-12. 428 (1976).
4. lannicelli, J., "New Developments in Magnetic Separation," IEEE Trans.
Magn.. Mag-12, 436 (1976).
5. Gooding, C. H., T. W. Sigmon, and L. K. Monteith, Application of
High-Gradient Magnetic Separation to Fine Particle Control, PB
276-633/AS, National Technical Information Service, Springfield, VA
(1977).
6. Kelland, D.R., "High Gradient Magnetic Separation Applied to Mineral
Beneficiation, "IEEE Trans. Magn.. Mag-9, 307(1973).
7. Murray, H.H., "Beneficiation of Selected Industrial Minerals and Coal by
High Intensity Magnetic Separation," IEEE Trans. Magn., Mag-12, 498
(1976).
8. Kelland, D.R., and E. Maxwell, "Oxidized Taconite Beneficiation by
Continuous High Gradient Magnetic Separation," IEEE Trans. Magn., Mag-11,
1582 (1975).
9. Ergun, S., and E.H. Bean, "Magnetic Separation of Pyrite from Coals,"
Report of Investigation No. 2718, U.S. Bureau of Mines, Pittsburgh, PA
(1968).
10. Trindale, S.C., and H.H. Kolm, "Magnetic Desulfurization of Coal,"
IEEE Trans. Magn.. Mag-9, 310 (1973).
11. Vives, D.L., L.J. Hirth, and W.H. Summerlin, "Direct Reduction and
Magnetic Beneficiation of Alabama Brown Ore with Lignite," IEEE
Trans. Magn.. Mag-12, 490 (1976).
12. Maxwell, E., D.R. Kelland, and I.Y. Akoto, "High Gradient Magnetic
Separation of Mineral Particulates from Solvent Refined Coal,"
IEEE Trns. Magn.. Mag-12, 507 (1976).
13. Maxwell, E., I.S. Jacobs, and L.M. Levinson, Magnetic Separation of
Mineral Matter from Coal Liquids, EPRI AF-508, Electric Power Research
Institute, Palo Alto, CA (1977).
116
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14. Liu, Y.A., G.E. Crow, C.J. Lin, and D.L. Vives, "A Pilot-Scale Study of
High Gradient Magnetic Desulfurization of Solvent Refined Coal (SRC),"
IEEE Trans. Magn., Mag-14. (1978).
15. Maxwell, E., and D.R. Kelland, "High Gradient Magnetic Separation in Coal
Desulfurization," IEEE Trans. Magn.. Mag-14. 482 (1978).
16. Hise, E.C., et. al. Separation of Dry Crushed Coal by High-Gradient
Magnetic Separation. ORNL-5571, Oak Ridge National Laboratory, Oak
Ridge, Tennessee, October 1979.
17. Mitchell, R., G. Bitton, and J.A. Oberteuffer, "High Gradient Magnetic
Filtration of Magnetic and Non-Magnetic Contaminants from Water,"
Separation and Purification Methods. 4, 267 (1975).
18. Petrakis, L., and P.P. Ahner, "High Gradient Magnetic Separations in
Water Effluents," IEEE Trans. Magn.. Mag-14. 491 (1978).
19. Oberteuffer, J.A., I. Wechsler, P.G. Marston, and M.J. McNallan, "High
Gradient Magnetic Filtration of Steel Mill Process and Waste Waters,"
IEEE Trans. Magn.. Mag-12, 428 (1976).
20. Harland, J.R., L. Nilsson, and M. Wall in, "Pilot-Scale High Gradient
Magnetic Filtration of Steel Mill Wastewater," IEEE Trans. Magn.. Mag-12,
904 (1976).
21. DeLatour, C., and H.H. Kolm, "Magnetic Separation in Water Pollution
Control-II," IEEE Trans. Magn., Mag-11. 1570 (1975).
22. Yadidia, R., A. Abeliovich, and G. Belfort, "Algae Removal by High
Gradient Magnetic Filtration," Envr. Sci. and Tech.. 11, 913 (1977).
23. Melville, D., F- Paul, and S. Roath, "High Gradient Magnetic Separation
of Red Cells from Whole Blood," IEEE Trans. Magn.. Mag-11. 1701 (1975).
24. Whitesides, G.M., C.L. Hill, and J. Brunie, "Magnetic Filtration of Small
Heterogenous Catalyst Particles. Preparation of Ferrimagnetic Catalyst
Supports," Ind. Eng. Chem.. Process Des. Dev.. 15, 226 (1976).
25. Gooding, C.H., Pilot-Scale Field Tests of High-Gradient Magnetic
Filtration. EPA 600/7-80-037, U.S. Environmental Protection Agency,
Research Triangle Park, NC (1980).
26. Friedlaender, F.J., et al. "Diamagnetic Particle Capture and Mineral
Separation," IEEE Trans. Magn.. Mag-17, 2813 (1981).
27. Hardison, L.C., and C.A. Greathouse, Air Pollution Control Technology
and Costs in Nine Selected Area, PB 222-746, National Technical Information
Service, Springfield, VA (1972).
28. DeLatour, C., and H.H. Kolm, "Magnetic Separation in Water Pollution
Control-II," IEEE Trans. Maqn.. Mag-11. 1570 (1975).
117
-------
29. Steiner, B.A., "Air Pollution Control in the Iron and Steel Industry,"
International Metals Review. No. 209, 171 (1978).
30. Jaasund, S.A., and M.R. Mazer, The Application of Wet Electrostatic
Precipitators for the Control of Emissions from Three Metallurgical
Processes," Proceedings: Particulate Collection Problems Using ESP's
in the Metallurgical Industry. PB 274-017-AS, National Technical
Information Service, Springfield, VA (1977).
31. Whitehead, C., "Design and Operating Experience with Electrostatic
Precipitators on Electric Arc Furnaces," Proceedings: Particulate
Collection Problems Using ESP's in the Metallurgical Industry. PB
274-017/AS, National Technical Information Service, Springfield, VA
(1977).
32. Harris, D.B., Procedures for Cascade Impactor Calibration and Operation
in Process Streams, PB 263-623/AS, National Technical Information Service,
Springfield, VA (1977).
33. Keyser, N.H., et al., Characterization. Recovery and Recycling of
Electric Arc Furnace Dust. Paper presented at the Symposium on Iron and
Steel Pollution Abatement Technology for 1981, Chicago, Illinois, October
6-8, 1981.
34. Severson, S.D., F.A. Homey, D.S. Ensor, and G.R. Markowski, Economic
Evaluation of Fabric Filtration versus Electrostatic Precipitation for
Ultrahigh Particulate Collection Efficiency, FP-775, Research Project
834-1, prepared for EPRI by Stearns-Roger, Inc., (1978).
35. "ES&T Currents," Environmental Science & Technology, Vol. 12, No. 13,
December 1978.
36. Neveril, R.B., Capital and Operating Costs of Selected Air Pollution
Control Systems. EPA 450/5-80-002. U.S. Environmental Protection Agency,
Research Triangle Park, NC (1978).
118
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REPORT NO.
-600/7-84-011
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
2.
•j'TLE AND SUBTITLE
-Pilot Demonstration of Magnetic Filtration with
Continuous Media Regeneration
3. RECIPIENT'S ACCESSiQWNO,
B. REPORT DATE
February 1984
6. PERFORMING ORGANIZATION CODE
. AUTHOR(S) ~~~
Carroll E. Ball and David W. Coy
8. PERFORMING ORGANIZATION REPORT NO.
: AND ADDRESS
. PERFORMING ORGANIZATION NAME AND
Research Triangle Institute
P.O. Box 12194
Research Triangle Park. North Carolina 27709
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
68-02-3142
12. SPONSORING AGENCY NAME AND ADDRESS
13. TYPE OF REPORT AND PERIOD COVERED
EPA, Office of Research and Development
Industrial Environmental Research Laboratory
Research Triangle Park, NC 27711
14. SPONSORING AGENCY CODE
EPA/600/13
is. SUPPLEMENTARY NOTES
61. 919/541-7865.
project officer is William B. Kuykendal, Mail Drop
16. ABSTRACT xhe report describes the design and construction ot a continuous High Ura-
dient Magnetic Filtration (HGMF) mobile pilot plant, as well as some of the back-
ground work in HGMF at Research Triangle Institute. The field start-up and perfor-
mance characterization of the mobile pilot plant are discussed in detail. Experimen-
tal data and data analysis are given, as well as an economic evaluation and compar-
ison of HGMF with other particulate control devices. The mobile pilot plant, with a
nominal flow capacity of 3,060 cu m/hr, was designed and built to evaluate the use
of HGMF for particulate emission control on an electric arc furnace. A 5-month pro
gram was conducted at Georgetown Steel Corporation's plant in Georgetown, SC, to
test the performance of HGMF. A 500-hr long-term test was scheduled, and later
changed to permit additional characterization studies. The pilot plant collection
efficiency was less than expected for the stainless steel wool matrix packed to a
density of 1. 5% by volume. The matrix was then changed to an expanded metal
packed to a density of 3. 5% by volume, which resulted in much lower pressure
drops, but even lower collection efficiencies. The expanded metal matrix was then
packed to a density of 6.0% by volume, which gave higher collection efficiencies
(94-96%) than the steel wool and a slightly lower pressure drop.
7.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
Ib.lDENTIFIERS/OPEN ENDED TERMS
COSATI Field/Group
Pollution Aerosols ~ I Pollution Control
Filtration Electric Arc Furnaces Stationary Sources
Magnetic Separators High Gradient Magnetic
Magnetic Fields Separators
Particles
Dust
^ _ —
Particulate
ia.OlSTBIBUHON8TATfcMfcNI
Release to Public
2220-1 0-73)
19. SECURITY CLASS (This Report)*
Unclassified
13B
07D ISA
131
20C
14G
11G
21. NO. OF PAGES
128
2O. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
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