United States
           Environmental Protection
           Industrial Environmental Research  EPA-600/2-78-118c
           Laboratory          June 1978
           Research Triangle Park NC 27711
           Research and Development
Pollution Effects  of
in Iron and Steel
Making  - Volume III.
Blast Furnace
Ironmaking, Manual
of Practice

Research reports of the Off ice of Research and Development, U.S. Environmental Protec-
tion Agency, have been grouped into nine series. These nine broad categories were
established to  facilitate further development and application of environmental tech-
nology. Elimination of traditional grouping was consciously planned to foster technology
transfer and a maximum interface in related fields. The nine series are:

          1. Environmental Health Effects Research
          2. Environmental Protection Technology
          3. Ecological Research
          4. Environmental Monitoring
          5. Socioeconomic Environmental Studies
          6. Scientific and Technical Assessment Reports (STAR)
          7. Interagency Energy-Environment Research and Development
          8. "Special" Reports
          9. Miscellaneous Reports

This report has been assigned to the ENVIRONMENTAL PROTECTION TECHNOLOGY
series. This series describes research performed to develop and demonstrate instrumen-
tation, equipment, and methodology to repair or prevent environmental degradation from
point and non-point sources of pollution. This work provides the new or improved tech-
nology required for the control and treatment of pollution sources to meet environmental
quality standards.
                             REVIEW NOTICE

          This report has been reviewed by the U.S. Environmental
          Protection Agency, and approved for publication.  Approval
          does not signify that the contents necessarily reflect the
          views and policy of the Agency, nor does mention of trade
          names or commercial products constitute endorsement or
          recommendation for use.
          This document is available to the public through the National Technical Informa-
          tion Service, Springfield, Virginia 22161.

                                                 June 1978
Pollution Effects of Abnormal Operations
  in Iron and  Steel  Making  -  Volume III.
           Blast  Furnace Ironmaking,
                Manual of Practice

             R. Jablin, D.W. Coy, B.H. Carpenter, and D.W. VanOsdell

                     Research Triangle Institute
                        P.O. Box 12194
                Research Triangle Park, North Carolina 27709
                      Contract No. 68-02-2186
                    Program Element No. 1AB604
                  EPA Project Officer: Robert V. Hendriks

                Industrial Environmental Research Laboratory
                  Office of Energy, Minerals, and Industry
                   Research Triangle Park, NC 27711
                         Prepared for

                  Office of Research and Development
                      Washington, DC 20460


     This study of the environmental effects of substandard, breakdown, or
abnormal operation of steelmaking processes and their controls has been made to
provide needed perspective concerning these factors and their relevance to
attainment of pollution control.  The use of the term Abnormal Operating
Condition (AOC) herein, in characterizing any specific condition should not be
construed to mean that any operator is not responsible under the Clean Air Act
as amended for designing the systems to account for potential occurrence in
order to comply with applicable State Implementation Plans or New Source
Performance Standards.


     This report presents the results of a study conducted by the Research
Triangle Institute (RTI) for the Industrial Environmental  Research Laboratory
of the Environmental Protection Agency (EPA) under Contract 68-02-2186.   The
EPA Project Officer was Mr. Robert V. Hendriks.
     The project was carried out in RTI's Energy and Environmental Research
Division under the general direction of Dr. J. J. Wortman.  The work was
accomplished by members of the Process Engineering Department's Industrial
Process Studies Section, Dr. Forest 0. Mixon, Jr., Department Manager, Mr. Ben
H. Carpenter, Section Head.
     The authors wish to thank the American Iron and Steel Institute for their
help in initiating contacts with the various steel companies and for their
review of this report.  Members of the AISI study committee were:  Mr. William
Benzer, American Iron and Steel Institute; Mr. Stephen Vajda, Jones and
Laugh!in Steel Corporation; Dr. W. R. Samples, Wheeling-Pittsburgh Steel
Corporation; Mr. Tedford M. Hendrickson, Youngstown Steel; and Mr. John R.
Brough, Inland Steel Company.  Acknowledgment is also given to the steel
companies who participated in this study.

                                TABLE OF CONTENTS
LIST OF FIGURES                                                             vi
LIST OF TABLES                                                             vii

CONVERSION FACTORS                                                        viii

1.0  INTRODUCTION                                                             1
     1.1  Purpose and Scope                                                   1
     1.2  Definition of AOC                                                   2
     2.1  Process Flow Sheet                                                  3
     2.2  Material Balance                                                    6
     2.3  Methods of Operation                                                7
          Charging                                                            8
          Emissions                                                         13
          Emissions Controls                                                14
          Water Pollution                                                   15
3.0  CONTROL TECHNIQUES AND EQUIPMENT                                       18
     3.1  Type of Control Equipment Used                                    18
          3.1.1  Blast Furnace Gas                                          18
          3.1.2  Blast Furnace Scrubber Water                               20
          3.1.3  Material Handling Emissions                                26
          3.1.4  Cast House Emissions                                       27
4.0  ABNORMAL OPERATING CONDITIONS                                          30
     4.1  Process Related                                                   31
          4.1.1  Startup                                                    31
          4.1.2  Shut Down                                                  34
          4.1.3  Abnormal Operating Conditions                              38

                 Slips                                                      38
                 Backdrafting                                               42
                 Water and Power Failures                                   45
                 Breakouts                                                  46
                 Charging Dusty Material                                    48
                 Gas Cleaning System                                        49
                 Gas Bleeders                                               51
                 Carbon Black Formation                                     52
                 Furnace Control                                             53


                           TABLE OF CONTENTS (cont'd)


     4.2  Control Equipment Related                                          55

          4.2.1  Startup                                                     55
          4.2.2  Shut Down                                                   56
          4.2.3  Abnormal Operating Conditions                               57

                 Water Quality                                               57
                 Pumps                                                       65
                 General Operation                                           69
5.0  GRAY AREAS                                                              74

     Emissions from Bells                                                    74
     Blast Furnace Top Emissions from Bells                                  75
     Emissions from Casting   <                                               79
     Tap Hole Related                                                        79
     Casting Emissions                                                       80
     Burning of Skull                                                        81

     5.1  Methods for Minimizing AOC                                         81

          5.1.1  Process Related                                             81
          5.1.2  Control Equipment Related                                   82

     5.2  General                                                            82

6.0  TABULATED SUMMARY OF AOC                                                85

7.0  REFERENCES                                                              91

                                 LIST OF-FIGURES

Figure                                                                     Page
  1     Blast furnace plant with auxiliary equipment                         4
  2     Blast furnace                                                        5
  3     Instrumentation and computer control  system of blast furnace         10
  4     Inland Steel recirculating water system                             23
  5     U.S. Environmental Protection Agency BPCTCA Model                    24
  6     Cast house dust collection system                                   29
  7     Schematic illustration of blast furnace top                         37
  8     Backdrafting through blast furnace stove                            43
  9     Tons of iron accumulated on hearth during years of service           47
 10     Swirl nozzle with replaceable insert arranged centrally above
        the throat of the scrubber                                          59
 11     Disintegration of the scrubbing liquid above the throat without
        any gas flow                                                        59
 12     Disintegration of the scrubbing liquid with the droplets
        exposed to the action of the gas flow                               60
 13     Swirl nozzles after years of operation                              60
 14     Inland Steel blast furnace water system                             71
 15     Gas cleaning system for No. 13 Blast Furnace - U.S. Steel,
        Gary Works                                                          73
 16     Plot of the data presented in Table 8                               77
 17     Example of AOC report form                                          84

                                 LIST OF TABLES

Table                                                                      Page
  1    Effluent Material Generated in a "Once-Through" System               22
  2    BPCTA - Effluent Limitations Guidelines                              25
  3    Gary Works, #13 Blast Furnace Major Delays                           33
  4    Effect of Alkali on Production at Geneva Blast Furnaces              40
  5    Quantities of Cyanide and Phenols from BF and Sinter Plant —
       Plant A                                                              61
  6    Reports from NPDES Files -- Malfunctions in Scrubber Water System    62
  7    Analysis of Flue Dust Particles                                      75
  8    Particle Size of Blast Furnace Dust                                  76
  9    Blast Furnace Abnormal Operating Conditions                          86

                             WITH CONVERSION FACTORS
concentration or
SI Unit/Modified SI Unit
Mg (megagram = 10  grams)
Gg (gigagram = 10  grams)
m  (cubic meter)
dscm (dry standard cubic meter)
son (standard cubic meter: 21 °C, 1  atm)
a (liter = 0.001 m3)
   o         q
g/m  (grams/m )
    3              3
mg/m  (mi 11 i grams/m )
J (joule)
kJ/m3 (kilojoules/m3)
MJ (mega joules = 10  joules)
kPa (kiloPascal)
1 Pascal = 1 N/m
m  (square meter)
                       1 Pascal = 1 N/m2 (Newton/m2)
Equivalent To
2.205 Ib
2205  Ib
1.1025 ton
35.32 cf
0.437 gr/ff3
0.000437 gr/fr
2  Ib/ton
0.000948 Btu
0.02684 Btu/ft"
0.430 Btu/lb
859 Btu/ton
0.146 lb/in2
                                                                 10.76 fr

                                1.0  INTRODUCTION
     Air and water pollution standards, generally based upon control  of
discharges during normal (steady-state) operation of a control system, are
frequently exceeded during "upsets" in operation.  When such upsets
become repetitive and frequent, the regional and local enforcement agencies
undertake, through consent agreements, to work with the plant toward
resolution of the problem, and plans are developed for such equipment and
operating practice changes as will eliminate or alleviate the frequent
violations.  Should the planning process fail to resolve abnormally frequent
occurrences of malfunctions, the problem may lead to litigation.   Thus,
periods of abnormal operation are becoming recognized as possibly contributing
to the emissions of high concentrations of pollutants.  Similarly, upsets
may contribute to spills of increased amounts of effluent-borne pollutants
into waterways.
     There is a need for information concerning abnormal operating conditions
(AOC):  their identity, cause, resulting discharges, prevention,  and  minimiza-
     The purpose of the manual is to alert those who deal with environmental
problems on a day-to-day basis to the potential problem areas caused  by abnormal
conditions, to assist in determining the extent of the problem created by
abnormal conditions in a specific plant, and to provide help in evaluating
any efforts to reduce or eliminate the problems.  The processes considered
are those in the primary section of the integrated iron and steel plant.
Included are the sintering, blast furnace ironmaking, open hearth, electric
arc furnace, and basic oxygen steelmaking.  This manual covers the blast
furnace ironmaking process.

     This manual is based on reviews of somewhat limited data, visits to a
few of the many steel plants, interviews with persons intimately involved
in either steelmaking or attendant environmental regulations, and the expertise
of the study team.  It is, therefore, a preliminary assessment which concen-
trates on enumerating as many of the conditions as possible, with emphasis on
those which have the most severe environmental impact.
     Each process is described separately.  Descriptions include flow diagrams
and material balances, operating procedures and conditions.  The flow sheets
and material balances presented are representative of the most typical process
     Within each process are variations, both in the process itself and in the
equipment for control of pollution.  Variations in equipment and process are
accompanied by  variations in AOC.  It is, therefore, of value to identify as
many of  the variations as possible.  At the same time, it is necessary to
limit consideration of the numerous alternatives to those which are currently
in greatest application and use.
     In  general, an abnormal operating condition (AOC) is considered to be
that which departs from normal, characteristic or steady-state operation,
and results in  increased emissions or discharges.  In addition to abnormal
operations, this study includes the startup and shutdown difficulties of
processes and control equipment.  It also includes substantial variations in
operating practice and process variables, and outages for maintenance, either
scheduled or unscheduled.
     The use of the term Abnormal Operating Condition (AOC) in characterizing
any specific condition should not be construed to mean that any operator is
not responsible under the Clean Air Act as amended for designing the systems
to account for  potential occurrence in order to comply with applicable State
Implementation  Plans or New Source Performance Standards.


     The blast furnace converts iron oxide to molten iron.  A typical burden
(feed) comprises ore, sinter, limestone, and coke.  The coke provides thermal
energy for the process.  The limestone becomes calcined, melts, reacts with and
partially removes sulfur from the molten iron.
     The burden material is charged into the top of the furnace and descends
slowly.  Heated air is injected through tuyeres near the bottom of the furnace.
The air moves countercurrent to the burden, consuming the coke carbon thereby
providing energy for the process.  Blast furnace gas leaves through offtakes at
the top of the furnace, is cleaned of particulates and used as a byproduct
fuel.  Molten iron and slag are tapped periodically from the bottom of the
     A flow sheet for the blast furnace ironmaking process is shown in Figure
     Burden material is charged through a device which allows the entry of lump
material and restricts the outward flow of blast furnace gas.  Blast furnaces
are generally over 100 feet tall and may be 30 feet or more in hearth diameter.
The blast furnace, Figure 2, is roughly pear-shaped, with the hot metal and
slag formed at the hearth.  The furnace uses more air than any other raw
material, fay weight.  Thermal economy demands that this air be preheated before
it is injected into the hearth through a series of tuyeres (nozzles).  The air
consumes coke to provide heat for the process.  Coke also is consumed by
reaction with the iron oxide, reducing it to molten iron.
     Blast furnace gas, which is mostly carbon monoxide (1/3) and nitrogen
(2/3), leaves the top of the furnace through offtakes.  The flow of gas through
the burden entrains dust.  The dust is removed by a dust catcher (which is a
low efficiency cyclone) and a high energy wet scrubber.  A gas cooler lowers
the temperature of the gas, thereby condensing most of its water vapor and
making it suitable for use as fuel.


••Hi i ^BM

0 . ., . . ... ,.,
•^ — r

                                                                      -y	..-
Figure  1.   Blast furnace plant with auxiliary equipment,

Urge Bell
Large Charging
                             Stotftllne Armor
                               Stack Coolers
                                       iustle Pipe
                                     Blow Pipe

                                     Iron Notch
 Figure  2.  Blast  furnace.

     The clean, cool gas is generally burned in blast furnace stoves and in the
boilers of the power plant.  It is also used as an auxiliary fuel  in the coke
ovens, the soaking pits and elsewhere in the steelmaking complex.
     Molten iron and slag are withdrawn in batches at periodic intervals from
the hearth of the blast furnace.  The usual time between taps is 3 to 4 hours.
Tapping is accomplished by drilling out or burning out the tap hole.  Iron and
slag flow from the tap hole into a small pool where slag floats to the top.
Separate runner systems in the floor of the cast house carry the iron from-the
pool to iron ladles and the slag from the pool to either slag ladles or to a
slag pit.  The ladles of iron are transported by railroad to the steelmaking
facility or, less frequently, to a pig casting machine.  The ladles of slag are
transported to a disposal area where the slag is dumped.  The solidified slag
may be crushed and then used as aggregate for concrete, roadbeds,  etc.
     In order to produce a ton of molten iron in the blast furnace the fol-
lowing burden materials are required:
     1.   Iron oxide materials, either lump ore, ore pellets, or sinter—
          3,000 to 3,400 pounds.
          The variation in quantity of iron oxide material is due
          primarily to the degree of beneficiation.  Oxide
          materials may be supplemented by fine scrap such as turnings,
          or even by partially reduced ore pellets.  The distribution
          of the various oxide materials is flexible; for example,
          the burden may have all pellets and no ore or sinter.
     2.   Flux materials—500 to 1200 pounds
          The variation is due to the impurities in the burden.
          The more sulfur the burden contains, the higher the
          flux requirements.  Flux is principally limestone/dolo-
          mite with some silica added to control fluidity of the
          slag.  Flux may be used as stone or combined with the
          sinter.  In the latter case, the flux is calcined by
          the sintering process and the thermal requirements
          of the blast furnace are reduced.
     3-   Fuel
          The range of fuel for a blast furnace, expressed as
          pounds of coke equivalent per ton of iron is 1000-
          1500 pounds.

          Factors that decrease the quantity of fuel  are de-
          creased amounts of ore or flux, increased blast air
          temperature, adequate sizing and screening of the
          burden and increased efficiency of operating controls.

          Although coke is the primary fuel, other fuels may be
          substituted for it in equivalent amounts.  Anthracite
          coal lumps, in moderate quantities, may be charged into
          the top of the furnace.  Fuel oil  or pulverized coal
          may be injected through the tuyeres.  Finally, oxygen
          may be added to the blast air.  This latter procedure,
          although not a substitution of fuel, decreases the
          amount of nitrogen that is heated in the blast furnace
          gas and the amount of total fuel required for the process.

     4.   Other Materials

          The amount of slag produced is essentially a function
          of the amount of flux charged into the blast furnace.
          The amount of dust in the blast furnace gas is a
          function of character of the burden and the amount of
          fine material contained in it.  The less fines there
          are in the burden, the less dust is carried out with
          the gas.


     The blast furnace is a vertical shaft furnace (Figure 1).  Raw materials

are charged into the top of the furnace and as they descend in  the furnace,

they are heated by a countercurrent flow of gas.  Heated air (the hot blast  or

wind) is injected through tuyeres which are located near the bottom of the

furnace just above the hearth.  Figure 2 shows a diagram of a typical  blast

     The system of introducing raw materials to the blast furnace is  usually a

system of two or three pressure sealing bells at the top of the furnace.

Research has shown that blast furnace production can be increased by  operating

the furnace under high positive pressures of approximately 100  in. H20 as

measured at the top of the furnace.  This high top pressure must  be dissipated

before the cleaned blast furnace gas is distributed as plant fuel.

     As raw materials are introduced at the top of the blast furnace  they  fall

to the top of the burden of raw materials already in the furnace.  The hottest

temperature zone in the blast furnace is at the hearth level, where the burden

is molten.  One operating problem with blast furnaces is maintaining  an even

downward flow of the burden toward the hearth.  At times the burden does not
slide downward uniformly because of an arch of partially melted raw material.
If this arch breaks precipitously or "slips", the furnace top pressure in-
creases abruptly.  This opens a safety valve to prevent rupturing of furnace
components and results in heavy particulate discharges from the top of the
blast furnace.  Improved control of furnace operation and improved raw materials
have reduced the frequency of these slips.
     A modern blast furnace is capable of fully automatic or semi-automatic
operati on.
     The  furnace filling is contolled by the level of the burden in the furnace.
When the  level is below a preset (adjustable) point, the stockhouse functions
continuously, filling the skips with predetermined weights of material in
the ordered sequence.
     A typical charging control system consists of the following electrically
independent sub-systems:
     1.   Coke supply system consisting of:
          a.   bin vibrating feeder
          b.   vibrating screen
          c.   weigh hopper gate
          d.   interlock with fines handling system
     2.   Limestone and slag supply system consisting of:
          a.   limestone bin vibrating feeder
          b.   slag bin vibrating feeder
     3.   Ferrous materials supply system consisting of:
          a.   Sinter, ore, and pellet bin vibrating feeder
          b.   ferrous materials supply conveyors
          c.   ferrous materials vibrating screens
          d.   ferrous materials screen discharge chute gates
          e.   ferrous materials weigh hopper gates
          f.   interlock with fines handling system

     4.    Water charging and metering system
     5.    Dual-drive skip hoist
     6.    Furnace top operating equipment consisting of:
          a.   gas seal  valves
          b.   gas seal  seat steam purging valves
          c.   gas seal  seat steam blowoff valves
          d.   equalizer valve
          e.   relief valve
          f.   revolving chute
          g.   small bell
          h.   large bell
          i.   stock!ine recorder test rods
     Control of charging has improved in recent years.  An example of a  newer
system is found on Figure 3.
     Ironmaking in the blast furnace is essentially a continuous  process.  When
all process conditions,  including the nature of the burden, are under control,
smooth operation results and emissions and discharges from abnormal  operations
are generally absent.  It is obviously to the advantage of the operator  to
achieve good control of the process because it provides stable operation which
increases production and decreases operating costs.  Good control  of the pro-
cess also reduces adverse impact on the environment.  Good operating conditions
generally assure an operating reliability of 95 percent,  that is,  the furnace
is on-line for 95 percent of the time.  One company reported 96 1/2 percent
reliability over a long period of operation.
     Good control of the blast furnace process is of special importance  in
minimizing AOC's.  Such control acts in two ways.  First, a smoothly operating
furnace is conducive to  minimizing such environmental factors as  slips,  con-
tamination in blast furnace scrubber water, and emissions from casting.
Second, a smoothly operating furnace invariably minimizes the consumption of
coke per ton of iron produced.  The less coke consumed, the lower are the mass
of emissions from the coke plant.

    Dioqnosllc system of equipmenl
Operation control system
Figure  3.   Instrumentation  and computer control  system of  blast furnace.

     In the blast furnace process, the heated raw materials react chemically
with one another.  The principal set of reactions are the complex ones between
coke, air, and iron ore.  Part of the coke is consumed by the oxygen in the air
to produce heat for the process.  Another part of the coke combines with the
oxygen in the iron ore and releases free iron which melts, drips to the bottom
of the furnace, and collects in the hearth.  A final portion of the carbon,
approximately 4 percent, dissolves in the iron.
     The heat of the blast also serves to calcine the limestone.  The resulting
CaO reacts with the impurities in the ore, principally sulfur, and, in molten
form, descends to the hearth.  The slag, being about one third the density of
the iron, floats in a separate layer on the iron bath.
     The blast furnace gases are reducing in nature.  The reactions described
above produce a substantial amount of carbon monoxide, although a small per-
centage of carbon dioxide comes off as well.  Carried out of the furnace with
the gases are dusts which are principally a mixture of iron oxides, lime, and
carbon.  The gases are low-calorie, usually between 70 and 100 BTU per cubic
     About 30 percent of the blast furnace gas is utilized to preheat the hot
air blast by means of blast furnace stoves.  The remainder is used for other
heating purposes through the steel plant:  the production of steam in boilers,
the underfiring of coke ovens, heating of steel ingots, etc.
     The stoves, generally 3 or 4 per blast furnace, are tall cylinders of
steel plate which are almost completely filled with special refractory shapes.
The arrangement of the shapes in a modern stove provides a large number of gas
passages which are small in diameter.  Blast furnace gas, burned with air,
passes downward through the passages to heat the refractories.  When the latter
is fully heated, the stoves are switched from the firing mode to one in which
air, moving upward through the passages, extracts heat from the refractories.
The heated air becomes the hot blast for the furnace.  This use of refractories
for absorbing and retransmitting heat is termed regenerative heating.  It
provides thermal efficiency for the furnace and, at the same time, accelerates
the reactions within the furnace.  On modern furnaces, the temperature of the
hot blast may exceed 1093°C (2000°F).

     There are two conditions of the blast furnace process which, by them-
selves, contribute to the control of emissions.   One is the need to clean the
gas before combustion in the stoves.  If the gas contains particulates, even in
moderate concentrations, the gas passage in the  stoves quickly fill and become
clogged.  The nature of this piece of equipment  imposes the need for highly
efficient gas cleaning, 12 mg/dscm (0.005 grains per dscf) or better, being
usually considered good practice in a modern blast furnace.
     The other condition is the need to-control  the fate of sulfur in the
ironmaking process.  Sulfur originates in the raw materials of the burden;
however, the principal source is in the coke.  Sulfur is detrimental, even in
very small quantities, to the final steel product.  It is, therefore, necessary
to remove as much of the sulfur as is feasible.
     In combustion processes, sulfur is released in the form of sulfur dioxide,
thereby causing air pollution.  In the ironmaking process sulfur is combined
with slag.  Since the slag is generally cooled and crushed for such end uses as
road ballast, the slag provides an environmentally acceptable method for
disposing of the sulfur.  A small portion of the sulfur is released from the
cooling slag, causing emissions to the air.  These will be described later.
     Periodically, usually 6 to 8 times per day, the hearth of the blast fur-
nace becomes full of molten iron and slag.  The  tap hole (or holes)in the
furnace wall is drilled.  First, iron flows from the hole and travels to
receiving ladles via iron runners.  Finally, slag flows to slag ladles, to a
cooling pit alongside the furnace, or to a special slag processing machine.
After the flows of iron and slag cease, the tap  hole is plugged with a special
clay and the ironmaking process continues.
     Certain aspects of the blast furnace operation are not continuous.  One is
the periodic tapping just described.  The other is the process of filling the
furnace with the burden material.  Because the furnace is under pressure, an
arrangement of pressure locks is provided.  These locks, operating in sequence,
permit the entry of the raw material and restrict the outward flow of the gas.
Typically, the locks are in the form of two inverted cones called bells, one
above the other, the top bell being considerably the smaller of the two.
Operation consists of placing the material on the top bell, opening it to dump
material to the bottom bell, and repeating the action until the bottom


bell is full of material.  When this occurs, the top bell is closed, the bottom
bell is opened and the material passes into the furnace.  Gas flow is impeded
by virtue of only one bell being open at a time.
     The trend on newer furnaces is toward higher top pressures in the range of
1 to 3 atmospheres above ambient conditions, the purpose being to obtain more
production from a furnace of given physical dimensions.  Formerly, it was
common practice to operate with top pressures in the range of 0.2 to 0.33
atmospheres.  As a consequence of this trend, leakage of gas and erosion of the
bells has increased, the one effect augmenting the other.  To overcome the
problem, a variety of new designs have evolved including nitrogen pressurizing,
the three bell construction, and tops with one or more bells replaced by valves
with soft seats.  One new top  has no bell at all, the function of gas sealing
being achieved by valving and the function of distributing the burden by a
special revolving mechanism.
     The blast furnace usually operates continuously for 3 to 5 years, after
which it is shut down for relining with refractory and for effecting major
repairs.  All ancillary equipment for the blast furnace must, therefore, be
repairable with the furnace in operation, or at a minimum, in an idling or
banked condition.
     The only direct source of water pollution in the blast furnace process
itself is the relatively minor one of thermal pollution.  In order to contain
the hot gases of the furnace, to resist the pressure of the gases, and to
support the weight of the burden materials, the furnace has a heavy steel outer
shell which is lined with refractory.  Water is used to provide additional
cooling for the shell, for special copper cooling plates, for the jacket around
the hearth and for the tuyeres.  The heated water, although otherwise uncon-
taminated, constitutes a source of thermal pollution.

     A blast furnace is usually on or near a substantial  source of water.  Its

size is usually great enough to absorb the heat of the cooling water without

the creation of severe environmental  problems.   In addition, some modern blast

furnaces have evaporative cooling which releases the thermal energy by

evaporating part of the cooling water.  Evaporative cooling, therefore, avoids

the discharge of heat to the receiving body of water and  avoids thermal pollution.

Emissions Controls

     The accepted, proven method of cleaning the particulate from the blast

furnace gas is the dry cyclone followed by the wet, high  energy scrubber.  The

scrubber has several advantages which make it particularly adaptable to this

service.  They are:

     1.   No fan is required, nor energy required for running the fan.
          The pressure within the blast furnace is more than great
          enough to force the gases through the scrubber.

     2.   There is no danger of exploding the combustible blast
          furnace gas when using a wet scrubber.

     3.   Internal components of the wet scrubber are minimal compared
          to those in other air pollution control devices such as the
          electrostatic precipitator.  Such components as are exposed
          to the gas scrubbing action may be fabricated of wear
          resisting materials or lined with such materials.  In con-
          sequence of the minimized number of components  and the
          choice of materials, the scrubber used in blast furnace gas
          service is a highly reliable device well suited to an
          entirely continuous operation.

     4.   The modern scrubber is designed with provisions for varying
          the area of the gas passage (throat)  in which the scrubbing
          action takes place.  The purpose is to adjust the area to
          the variable flow of blast furnace gas from the furnace and
          to obtain a constant level  of differential pressure across
          the scrubber.  This, in turn, insures a constant level of
          gas cleaning.  A well-designed unit has automatic controls
          for varying the area.

     Blast furnace gas has a low calorific value, usually in the range of

2.6 to 3.7 MJ/m3 (70 to 100 BTU/CF).   Large volumes must, therefore, be burned

for a given heat duty and large gas mains are required.  The economics of

burning the low BTU, high volume of gas generally dictate its consumption in or

near the blast furnace complex.  Typically the gas is used in stoves for
heating the compressed air for the blast furnace (blast or the wind) and in
boilers for producing the large quantities of steam which are needed in iron
and steelmaking.  Less common uses include:  the coke ovens (all or part of the
heating fuel): the larger furnaces for heating steel; the soaking pits for
heating ingots.
     From an environmental standpoint, blast furnace gas is an ideal fuel.  As
indicated above, it is quite clean.  It also has almost no sulfur.  When burned
by itself, or in the proper combination with other fuels, the gas without
special treatment, may meet environmental regulations in respect to parti-
culates and sulfur dioxide.
Water Pollution
     Contaminated water comes from three main sources:  the venturi scrubbers,
the gas coolers, and from miscellaneous sources like gas main seals, gas main
downlegs, stove seals, etc.  Water from the blast furnace gas scrubber is
highly contaminated with suspended solids, dissolved solids, alkalinity, and
thermal energy.  Suspended solids are conventionally removed in a clarifier,
the underflow sludge being thickened and otherwise dewatered so that it may be
recycled to the sinter plant or disposed onto a landfill.  Thermal energy is
dissipated in a cooling tower.  Recycling of the water helps deal with the
problem of dissolved solids, especially those such as phenol, cyanide and heavy
metals which are toxic.  A small blowdown is required to avoid scaling and
plugging of pipes and nozzles.  If the concentration of toxic solids becomes
high, special treatment of the blowdown water may be required in order to
reduce toxicity to levels that are acceptable for discharge to the receiving
body of water.
     Recycling of the water from the blast furnace gas scrubbers causes the
water to increase in alkalinity.  Additions of acid serve two functions.  One
is to achieve neutral conditions in the water.  The other is to reduce the
quantity of cyanide in the water since it has been found that water which is
high in alkalinity tends to be high in cyanide.

     Most of the environmental problems from the blast furnace are emissions to

the air.  The major water problem is treating and disposing of the scrubber

water as described above.  Solid wastes are normally not an environmental
problem, the slag being used for such byproducts as aggregates and road
ballasts, and the dust and sludges from the gas cleaning being usually recycled

to the sinter plant.
     The emissions to the air result from a variety of causes, as follows:

     1.   Cast house emissions.  These are particulates of iron oxide and
          graphite, called kish, the graphite being emitted from the molten
          iron as it leaves the blast furnace and cools upon exposure to
          the ambient air.  Also emitted from the cast house, but in
          lesser quantities than kish, are the gaseous emissions of sulfur
     2.   Emissions from slag cooling.  The cooling of blast furnace
          slag with water creates emissions of sulfur dioxide and hydro-
          gen sulfide.  Various methods to reduce the amount of these
          emissions, espcially the hydrogen sulfide which has a noxious
          odor even in minute quantities is to add oxidants to the cooling
          water, to reduce the rate of cooling and to use a3special tech-
          nique which produces lightweight granulated slag.
     3.   Furnace slips.  These result from 'irregularities of the move-
          ment of the burden downward in the shaft of the blast furnace.
          A part of the burden may hang up for a while, creating a pocket
          below it.  When the release takes place, it is sudden and causes
          a sharp rise in gas pressure.  Relief ports at the top of the
          furnace open to protect structural integrity.  A large volume
          of gas then discharges to the atmosphere.  This gas is high in
          particulate matter and in carbon monoxide.
     4.   Gas bleeding.  In the process of filling the blast furnace with
          the burden, there is necessity of bleeding the pressure from
          the space between the large and small bells.  This action takes
          place after each opening and closing of the large bell.  In some
          furnaces, this gas bleeds to the atmosphere causing a discharge
          of particulates and carbon monoxide.  In other furnaces, the
          gas bleeds to the entry end of the blast furnace gas scrubber,
          thereby avoiding the emissions to the atmosphere.
     5.   Gas leakage.  There are numerous sources of gas leaks in the
          blast furnace complex.  One is at the bells which seat metal -
          to-metal and form a less than perfect seal against gas leakage.
          Similar leakage although generally smaller in amount, pertains
          at the numerous, large goggle valves which direct the flow of
          blast furnace gas to the stoves, the boilers, etc.  It is also
          possible to find gas leaks in the gas mains, the expansion
          joints, and the shells of the stoves and blast furnaces.  All
          such leaks result in the dishcarge of gas which is high in
          carbon monoxide.

Gas flaring.  On occasion there is an imbalance between the
production of blast furnace gas from the blast furnace and
its consumption in the various combustion units which requires
the release of blast furnace gas to the atmosphere.  The gas
which is so released is clean gas; however, it is high in
carbon monoxide.  Good practice requires that the gas be
discharged from a stack and that it be ignited.
Material handling.  Many of the raw materials which comprise
the burden of the blast furnace are dusty.  The dirtiest
are usually sinter, coke, and certain ores.  Handling such
materials causes fugitive emissions which may be high in
quantity and relatively uncontrolled.  Some sources of
such emissions are the discharge from the railroad car to
the storage bins at the blast furnace trestle, the discharge
from the bins to the scale car or conveyor belt, the filling
of the blast furnace skip car and the discharging of the skip
into the furnace bells.  Scrubbers or baghouses may be used
to control emissions from some or all of these sources.  Water
sprays, although less effective, may be of environmental value.

                      3.0  CONTROL TECHNIQUES AND EQUIPMENT

     Three areas in the blast furnace process require environmental  control
equipment:  the cleaning of blast furnace gas, the collection or suppression of
emissions from the handling of raw materials, and the collection of cast house
emissions.  In general, all of these emissions are reduced in severity by good
operating and maintenance practice.  For example, a well  operated furnace using
a screened, beneficiated burden produces less dust in the gas.  Likewise, the
improved burden results in minimized emissions to the atmosphere from the raw
material handling system.  Finally, a smoothly operating  furnace, casting iron
within appropriate metallurgical specifications produces the least amount of
emissions during the casting process.  There is usually no environmental
control equipment provided for the capture of emissions from slag processing
and handling, although some reduction in emissions may be obtained by modifi-
cations of process techniques.
3-1-1  Blast Furnace Gas
       The amount of dust generated and discharged with the blast furnace gas
depends upon the operation of the furnace and the amount  of preparation which
had been afforded to the burden.  The amount of dust leaving the furnace can
range from 14 to 150 g/Mg of molten metal.   Dust concentration may be as high
as 30 g/scm of gas.
     Most furnaces are equipped with a multistage dust collection system
consisting of a dry cyclone and a wet collection device.   The dry cyclone in
this service is commonly called a dust catcher.  The wet  device is usually a
scrubber either single or dual stage.  In some older gas  cleaning systems a wet
electrostatic precipitator has provided final cleaning; however, these high
maintenance devices are absent in the later systems.  Newer scrubbing systems,
especially the dual stage units operating at high pressure differentials are
capable of cleaning gas to concentrations of 5 to 10 rug/son.

     The blast furnace gas has a heating value of 2.9 to 3.5 MJ/scm (700 to 850
kcal/scm) of gas.  The gas composition will contain 23 to 40 percent of carbon
monoxide and 2 to 6 percent of hydrogen.  It is a highly desirable fuel which,
although low in calorific value, is also extremely low in sulfur content.  Most
iron and steelmaking plants attempt to make full use of this byproduct fuel in
their operation.  Whenever conditions arise in which gas production exceeds
consumption, then the clean gas is flared.
     The preferred method of cleaning the gas is the venturi scrubber.  In it
gases are accelerated in the convergient section of the venturi throat in order
to impact at high velocity with the injected scrubber water.  The wetted parti-
cles of dust are agglomerated to form droplets in the venturi diffuser due to
decreasing velocity and surface tension.  The water droplets containing the
pollutants are then separated from the gas in the subsequent gas separator.
Most modern venturi scrubbers are designed with an adjustable throat section to
compensate for varied rates of gas flow from the blast furnace.  Wear in the
throat of the venturi is minimized by the provision of a hardened lining and
also by a protecting film of water on the convergent inner wall.
     At least two of the major consumers of blast furnace gas require that the
gas be as free of particulate matter as is possible.  These consumers are the
blast furnace stoves and the underfiring jets of the coke ovens.  Any excess
particulate matter that might remain in the gas would tend to deposit in the
combustion spaces of these units causing premature outages and failures.  Since
these units are necessary to the operation of the ironmaking process and since
they require a high investment of capital, even if there were no requirements
for reducing emissions to the atmosphere, the steel maker finds it necessary to
maintain and to operate the gas cleaning equipment at maximum efficiency.
     The cleaning of blast furnace gas is thus an essential part of the iron-
making practice over and above its environmental aspects.  For this reason, and
because there has been so much attention to the improvement and design and
construction of equipment for the scrubbing of blast furnace gas, there is
comparatively little potential for AOC resulting from malfunctions of this

     Other wet collection devices include the orifice scrubber, both fixed
and variable, the fixed venturi scrubber and the electrostatic precipitator.
Both forms of fixed scrubber have the disadvantage that the differential
pressure drop across the restriction changes in response to the variation in
the flow of gas from the blast furnace.  As the differential pressure varies
so also does the efficiency of cleaning particulates from the gas.   The
electrostatic precipitator suffers in respect to the venturi scrubber by
virtue of its increased maintenance, susceptibility to electrical  failure,
susceptibility to erosion, etc.
     The dry cyclone, or dust catcher, which preceeds the wet collection
device is usually a low energy, low efficiency dust collector.  Because the
raw blast furnace gas contains highly abrasive particulate matter the dust
catcher is provided with an abrasion-resistant lining of brick.
     Upon leaving the secondary, wet collection device, the blast furnace gas
enters a gas cooler where it is cooled by direct contact with water.  Usually
this water is reused, either wholly or in part, by collecting it and pumping
it to the scrubbing device.  An efficient gas cooler will provide an outlet
temperature within 10°F of the inlet water temperature.  Efficiency of cooling
is especially important in the case of the blast furnace gas because of its
low calorific value.  If the gas temperature remains high, there is an increase
in content of evaporated water which lowers the heating value of the gas and
makes it very difficult to burn.
     The gas cleaning system also includes goggle valves for isolating the
various portions of the system as well as barometric legs and water seals, at
all discharge points.
3.1.2  Blast Furnace Scrubber Water
       In many early systems of cleaning blast furnace gas by use of wet
scrubbing, the contaminated scrubber water was discharged directly to the
waterway.  Subsequent environmental measures required the provision of a
clarifier followed by discharge of the cleaned effluent directly to the
receiving body.  This effluent was normally combined with the effluent from
the gas coolers and from other miscellaneous discharges.  At Inland Steel

Company, it is reported  that the total load of parti oil ate matter thus
discharged amounted to 14,782 Ibs/day as given in Table 1.  Environmental
regulations required that company to change the once-through water system to a
recirculating water system.  This system consists of two loops as shown in
Figure 4.  One loop is for the gas cooler water and the other loop is for the
venturi water, seals, disintegrators, and miscellaneous sump water.  Each
system has independent pumping, piping, cooling, and treatment facilities.  The
systems are linked to one another by the blowdown of one loop supplying the
makeup water for the other loop.  As a result of this improved system, the
discharge of particulates was reduced to 575 Ibs/day as seen in Table 1.  There
are two thickeners, or clarifiers in the venturi scrubber loop.  In case one of
the thickeners is down because of malfunction or need for repairs, the second
thickener may handle the entire flow of water at some reduced level of cleaning
efficiency.  Figure 5 and Table 2, obtained from the EPA Document which forms
the basis for BPCTCA Effluent Limitations Guidelines, indicate the level of
                                            f\ »
discharge obtainable by this type of system.
     A system for recirculating the scrubber water from blast furnaces has
certain inherent problems that must be overcome.  The suspended solids in the
water are principally iron oxide and are highly abrasive.  Abrasiveness is
compounded by the fact that a fairly sizeable porportion of the particulate
matter is rather coarse.  In consequence, special precautions are required to
prevent deposition in the sumps accompanied by plugging of pump inlets.  The
pump application itself is an extremely difficult one and it is not uncommon
for the life of a pump impeller to be rather short.  Because of the heavy
nature of the particulates and because of the presence of coarse material, it
is not uncommon for the rakes of the clarifier to stall, thereby taking the
clarifier out of service.
     Another problem in blast furnace scrubber service is the high alkalinity
of the water.  This results from the carryover of particles of lime in the
blast furnace gas and their subsequent solution in the water.  Recycling this
water to achieve effluent guidelines and to minimize the amount of blowdown
leads to a buildup of dissolved solids and, unless special care is taken, to
the plugging of pipelines and spray nozzles.  Such plugging becomes particularly


Gas Coolers               Water Flow
No. 1 Furnace            711  Ibs/day
No. 2 Furnace            459 Ibs/day
No. 3 Furnace            577 Ibs/day
No. 5 Furnace            295 Ibs/day
No. 6 Furnace            322 Ibs/day
TOTAL GAS COOLER WATER FLOW                       2,364 Ibs/day
Venturi Scrubbers - Passing Through
Dorr Thickener
12,050 6PM @ 65 mg/liter of suspended solids      9,618 Ibs/day

Miscellaneous Flows Going Directly to Discharge
Miscellaneous Sumps
Miscellaneous Gas Main Seals
Miscellaneous Gas Downlegs
Cast House Drains                                 2,800 Ibs/day

                    TOTAL WATER DISCHARGE        14,782 Ibs/day

                        TOTAL SUSPENDED SOLIDS
                    611,796 Ibs/day generated
                     14,782 Ibs/day to discharge
                      97.56% Efficient
                    611,796 Ibs/day generated
                        575 Ibs/day to discharge
                      99.91% Efficient


T 5-
A '_


PUMP __K/" "\/^~^\ JT



Figure 4.  Inland Steel recirculating water system.


                                                                                      SUSR SOUOS
                                                                                         //•/3'73     (
                            Figure 5.   U.S. Environmental  Protection  Agency BPCTCA Model

Suspended Solids
Ammonia (as NH.,)
(lb/1000 Ib)
Control & Treatment Techno! ogyv '
Thickening with polymer addition
Vacuum filtration of thickener
Recycle loop utilizing cooling

$/KKg $/Ton

0.271 0.246


       6.0 - 9.0

Most probable value for tight system is  522 liters  effluent  per kkg  of
iron produced (125 gal/ton) (excluding all  non  contact  cooling  water)
    (1)  Kilograms per metric ton of iron produced or pounds per 1,000 pounds of iron produced.
    (2)  Milligrams per liter based on 522 liters effluent per kkg of iron produced (125 gal/ton).
    (3)  Available technology listed is not necessarily all  inclusive nor does it reflect all  possible com-
        binations or permutations of treatment methods.
    (4)  Costs may vary some depending on such factors as location, availability of land and chemicals, flow
        to be treated, treatment technology selected where competing alternatives exist, and extent of pre-
        liminary modifications required to accept the indicated control  and treatment devices.   Estimated
        total costs shown are only incremental costs required above those facilities which are  normally
        existing within a plant.

   *Total cyanide

severe in that portion of the system which follows the cooling tower.  The
water, having been reduced in temperature, becomes more susceptible to the
precipitation of scaling compounds.
     Finally there are the physical problems that result from retrofit of a
recycle water system to an existing scrubber system for which no provision had
been envisioned for installing the additional equipment.  Some blast furnace
complexes, particularly the older ones, were installed in a congested physical
surrounding that did not leave room for the modern technology, including the
recycle system.  In such plants, pump houses are often cramped, leading to
difficulty in maintaining and repairing a piece of equipment which is highly
susceptible to outage.  Other problems arise due to the necessity of modifying
piping systems without excessive shutdown to the ironmaking process, and so
3.1.3  Material Handling Emissions
       The raw materials which make up the burden of the blast furnace comprise
iron-bearing materials such as iron ore, pellets and sinter, coke, and flux
materials such as limestone and silica.  In a modern blast furnace, extensive
attention is paid to the sizing and screening of these materials, both at the
source of the materials and in the stockhouse of the blast furnace.  The latter
requres the operation of material screens, accompanied by the generation of
dusts.  If the initial burden preparation has been properly done, the amount of
dust is not severe and adequate environmental conditions can often be provided
by the judicial application of water sprays.
     In some of the older blast furnace installations, preparation of the
burden is less extensive.  The handling of material in the stockhouse becomes a
very dusty operation, especially for coke and sinter.  The dusting condition
carries over into the operation of filling the blast furnace skip and of
dumping the skip into the bell at the top of the blast furnace.  Dusting also
continues within the furnace itself leading to a high level of particulate
concentration in the raw blast furnace gas.  As in the case of the more modern
furnaces having highly beneficiated burdens, usually water sprays will suffice
to provide an acceptable environment in the cast house.  The application of
such sprays to the dumping of the skips into the bell is not a current practice
in the United States, thereby leaving this source uncontrolled.

3.1.4  Cast House Emissions
       The emissions from the casting of molten  iron and slag occur primarily
at the tap hole of the blast furnace and in the  pool immediately adjacent to
it.  There are also emissions which evolve from  the iron and slag runners
following the pool, however, these are considerably reduced in extent.
     The mechanism for these emissions results primarily from consideration of
the solubility of carbon in molten iron.  As the iron leaves the blast furnace,
it is saturated with carbon and as it cools, the solubility of carbon decreases
and flakes of graphite are emitted from the surface of the molten metal.  This
graphite, called kish, as well as other metallic oxide emissions escape to the
atmosphere.  In an uncontrolled situation, they  rise to the roof of the cast
house and discharge from there through open spaces to the atmosphere.  In most
ironmaking facilities in the United States, there is no provision for capturing
and filtering these emissions from the air.  Where such control  is absent,
there is obviously no associated abnormal operation.  There are, however,
abnormal operations concerned with the ironmaking process which cause an
increase in the rate of uncontrolled emissions.  These will be discussed in
greater detail in Section 4.0 of this manual.
     In October of 1974 tests were conducted at  the Sparrows Point Plant of the
Bethlehem Steel Company which yielded an emissions rate of 0.15 gm/kg (0.31
pounds of particulate per ton) of iron.  This compares to the results of an
evaluation of the cast house evacuation system at DOFASCO Blast Furnace No.  1
during the period of August 30, 1976 to November 19, 1976 in which the emission
factors ranged from 0.16 to 0.364 gm/kg (0.327 to 0.727 pounds per ton) of
molten iron over 14 samples.  The average emission factor was 0.26 gm/kg (0.52
pounds per ton) of molten iron.  The range of values given above attest to the
variation in the quantity of emissions from this source.  Variability is also
confirmed by numerous visual observations.
     The most common method of controlling emissions from the cast house is to
totally enclose the house and evacuate it to a fabric filter.  In Japan, where
control of casting emissions is more widely practiced than in the United
States, there are three different control options practiced, often in combina-
tion.  These control options involve the method of capturing the fume.  Figure

6, which derives from schematics provided by the Nippon Steel  Corporation
shows these methods.  The features of this control  are:
     1.   A curtain type comprising three wall  curtains which  are
          lowered over the tap hole area when the fume volume
          reaches its maximum.  At this time suction is commenced.
     2.   A fixed hood type which is erected over the tap holes and
          sinter notches for additional collection.
     3.   An accumulated type in which fumes are temporarily
          accumulated in the roof of the cast house and slowly
          vented to the baghouse.
     Because of the large air volumes, the concentration of particulates in
the air is low as is the temperature of the air.  Both of these factors lead
to long life of bags and minimum maintenance in a well designed baghouse.  At
this time, it is not known what sort of maintenance difficulties arise in
respect to the hooding, especially that immediately adjacent to the tap

                                      Secondary Dust Collection
  Primary Dust Collection
Figure 6.  Cast house dust  collection system.

                       4.0  ABNORMAL OPERATING CONDITIONS

     This section discusses abnormal operating conditions and techniques for
eliminating or minimizing discharges thereunder.   Abnormal  operating conditions
(AOC) can occur in the blast furnace, in its control  equipment,  during
startup and shut down.  AOC's are addressed relative  to resulting increases
in pollution.  From this perspective, their causes may be inherent difficiencies
in the design of equipment relative to standards  set  for pollutant control,
changes in operating practices and feed material, limitations in the applied
technology, equipment or power failure.  In assessing AOC's,  therefore,
attention is given to the role of and need for preventive maintenance,
redundant capacity, sensing impending upsets, redesign of control  equipment,
and alternative strategies for response to AOC's  at the plant.
     In the following sections, the discussion of AOC as related to the  blast
furnace is divided into a section related to the  process and  a  section related
to control equipment.  The importance of each individual AOC  in  terms of its
effect on the environment is not necessarily indicated by the length of  dis-
cussion.  A simple description of problems that produce serious  effects  are
possible while less severe problems may require more  elaborate  explanations.
     In the process area of the blast furnace, a  well designed  furnace that
is equipped with modern techniques and operated according to  well  established
practices both as to maintenance and operation tends  to reduce  susceptibility
to AOC.  Those factors which tend to produce high quality iron  at low operating
cost also tend to reduce the frequency and severity of the AOC.   In the
control area, the chief source of AOC is in the recirculated  water system
which serves the gas scrubbers.
     The description of AOC's given in the following  pages, especially those
which are process related are not applicable to all blast furnaces.  Procedures
and conditions which occur in one plant would not necessarily occur in another.
Unusual events in operating one blast furnace may not occur in another.   Many
accepted conditions of furnace practice, as viewed from the standpoint of

recent and future environmental regulations, may become questionable and
require future consideration.
4.1.1  Startup
       The startup, or lighting of a  blast furnace takes place after the
blast furnace has been relined or after  it has been banked for a prolonged
shutdown such as one caused  by a strike.  Two methods are used to heat the
hearth initially; blowing air into the tuyeres and out the tap holes and
blowing air in through a tap hole by  connecting it to an adjacent tuyere
pipe.  In either case, the air has been  preheated in the stoves and lights up
the furnace by igniting the  coke.  To prepare for the startup, the furnace
has been previously filled with a special burden which is high in coke.
Right after the furnace lighting begins, the brickwork starts opening up at
the bosh.  Until the gas has ignited  or  until the openings are closed with
blanks, a hazardous gas condition can possibly exist in the cast house.*
     The blow-in burden is one that will produce a very limey slag to protect
the bosh brick.  Blast furnace slag is also charged so that the initial slag
volume is very high.  The ore to coke ratio is slowly increased and the blast
furnace slag decreased until the furnace is eventually put on its full  burden.
The rate of increasing the burden ratio  and the wind rate is done according
to a predetermined schedule; however, this may be adjusted according to
conditions.  With a normal blow-in, the  full burden and rate should be reached
after about 70 hours.
     During the lighting of  the furnace, the large bell may be kept open as
are the dirty-gas bleeders.**  With the  blowing-in practice, the instant the
wind is blown into the furnace and the coke is ignited, part of the gas will
emerge from the open tap hole.  Ignition of the escaping gas which is forced
out in increasing velocity as the wind volume increases is extremely important.

*The gas can be lit immediately, however.
**The large bell need not be held open in all systems.

The blast furnace gas, which contains a high percentage of carbon monozide
is very explosive and highly poisonous to the human system.  After a good
ignition has taken place, a large quantity of the gas issues from the furnace
top.  This gas is also high in carbon monoxide and, because of the water gas
reaction in the furnace, with hydrogen as well.
     Gas tests are taken perioidically from the furnace top.  After obtaining
a satisfactory sample, i.e., one void of oxygen, the bleeders are closed, the
goggle valve is opened, and the furnace is connected to the gas system of the
plant.  The period of bleeding gas may last approximately 27 hours during
which the injection of heated air and the consequent flow of gas has been
gradually increasing.
     In an alternative blow-in practice the initial air may be injected
solely through the tap hole pipe assembly.  After about 14 hours, the two
tuyeres over the tap hole are opened and the remaining tuyeres are opened at
varying intervals.  Practice varies from one plant to another, however, at
the blowing-in of one furnace  the average wind rate during the bleed period
was approximately 13 percent of normal wind.
     When blowing-in from a bank, upon completion of the first cast, a casting
schedule is established.  For the next four to five days, the furnace operating
conditions are watched to spot any variations from the schedule.  Some problems
that may arise during this period are:
     1.   Sustained high silicon content.
     2.   Drop in slag temperature.
     3.   Sudden change in slag composition.
     When blowing-in a new furnace after a reline, additional problems may
occur.  Examples of these are:
     1.   Mechanical problems.
     2.   Electrical problems.
     3.   Charging difficulties.
     4.   Improper burden control.

     Any one of the above mentioned problems may delay and prolong the
startup time.  In view of the condition that emissions during startup are
greater than normal, such delays increase the environmental impact.
     Reline and the startup accompanying them are infrequent and occur at
intervals of approximately four to five years.  The blow-in from a bank,
since it depends upon such external uncontrolled factors such as business
conditions and strikes, may occur at longer or shorter intervals of time.
The startup of a brand new furnace obviously occurs only once and may be a
particularly difficult period through which to go.
     During the startup of one new large furnace in 1974 , many minor problems
were encountered and corrected.  These included stockhouse logic and computer
inadequacies, hydraulic system failures of various types involving the top,
mud guns, drill machines, and tilting spouts.  In addition, tap hole problems
were encountered early and continued until a suitable anhydrous tap hole mix
became available.  Some of the delays are shown in Table 3.
     April  3  and  4
     April  4
     April  5  and  6
     April  18
     May 20
     May 27
     June 2
     June 8 and 9

     July 11
     July 13

     August 9
32 hours -
 6 hours -
14 hours -
16 hours -
 6 hours -
 5 hours -
15 hours -
37 hours -

11 hours -
10 hours -

52 hours -
     August  23,  24,  25,  and  26     83  hours  -
Coke mess and iron spill
Hydraulic failure
Mud gun failure
Coke mess
Coke mess
Iron spill
No. 3 hole opened up
No. 1 hole opened up,
burned up hydraulics and
No. 2 hole opened up
No. 2 mud gun traverse
cylinder broke - missed
No. 2 taphole spill -
expanded into planned stop
for maintenance work
Lost No. 1 taphole

     The most persistent problem during the initial  operation was with
the tap holes.  The furnace was equipeed with rotary drill  machines and
hydraulically operated mud guns.  Prior to blow-in,  the original  tap hole
brick work was partially removed and rebricked to change the angle and length.
The rotary drills were not powerful  enough to drill  to the  skull, resulting in
an excessive amount of oxygen lancing.   This and other problems  made it
difficult to maintain long, strong tap  holes.  Short holes  were  a daily occur-
rence and spills were frequent and sizeable.
     One of the considerations during startup is to  insure  that  the iron and
slag will flow readily out the tap hole.  In order to achieve this, the furnace
is kept hotter than usual.  Because of  the excessively high temperatures, slips
are more frequent than they are during  a normal  operating campaign.  In
addition, the initial slag should be limey at the start.  This type of slag
tends to produce increased emissions from the cast house during  the casting
     In summary, increased emissions are usually present during  the startup of
a blast furnace.  These emissions include unburned raw gas, emissions from
increased lancing of the skull, increased emissions  during  the casting process,
increased slips, and emissions from various spills that may occur.  Careful
planning is required to reduce the length of the startup period  and in con-
sequence the amount of emissions.  The  interval  between startups is long,
generally in the order of four to five  years.  The interval between banks is
also long, but variable in frequency.
4.1.2  Shut Down
       There are two conditions under which a blast  furnace may  be shutdown.
One is in anticipation of a prolonged outage such as for a  strike.  In this
case, the furnace is banked so that it  may be restarted upon resumption of
normal operating conditions.  The other is in the case of taking a furnace
completely out of service such as for a major reline.  In this case, the burden
is quenched.
     A typical procedure in banking a blast furnace  is to charge it with a
suitably fluxed coke blank approximately 8 hours before the shutdown.  This
blank may be equal to approximately 40  percent of the working volume of the

furnace and the remainder of the furnace is filled with a burden in which the
ore to coke ratio is 50 percent of normal.  The coke blank at the tuyeres
provides the initial heat requirement when the furnace is blown back in.  An
estimate of the number of rounds required to be charged until the coke blank
reaches the tuyere zone is made.  The furnace is then shut down coincident with
the first coke blank reaching the tuyeres.  The tap hole should be blown hard
and long to drain the furnace of as much iron and slag on the last cast.  In
addition, the dust catcher should be blown many times to insure that it is
empty, since any dust remaining could consolidate into a hard mass that is
difficult to remove.  Both procedures increase emissions during banking.
     After shut down, stringent measures are taken to minimize the ingress of
both water and air into the furnace.  Water ingress is prevented by testing
cooling members for leaks, reducing water to coolers to 25 percent of normal,
and turning water off the tuyeres.  Air ingress is prevented by removing the
blowpipe and plugging the tuyeres, encasing the furnace shell with a sealing
compound, and making the last top charge to the furnace of uncleaned iron
bearing material to form a top seal.  Steam is also used to purge the furnace
and the gas system.  The last gas still being produced by the furnace is bled
out of the relief valve until the wind is taken off.
     There are several different methods of blowing out a blast furnace.  One
method is to blow the furnace down so that most of the stack is empty when
the last cast is finished.  Other methods leave the furnace full of materials
that can be raked out.
     Blowing the furnace down has the advantage of reducing the time required
for stock removal since the furnace  is left partially empty.  During blowdown,
it is necessary to  install water sprays in the gage rod holes to prevent
excessive temperatures in the furnace top.  There must be an ample volume of
water to quench the coke below its kindling temperature.  The last cast is
scheduled so that it will be finished when the stock is at the predetermined
level after which the wind is taken  off the furnace, the salamander is tapped
and the furnace completely quenched.

     The disadvantage of the blowdown method is the danger of an explosion in
the space above the burden.   The risk is even greater when the furnace is known
to have a scab or scaffold which may disrupt the distribution of water and
prematurely put out the flame of one or more tuyeres.  To reduce the danger of
explosion, coke or silica pebbles are used to fill  after the last burden
leaving an empty space only eight to 10 feet below the normal stock line.
     Some operators adopt the procedure of quenching the furnace filled with
its regular burden without scrap and other miscellaneous materials.  This
requires more time to clear the burden after quenching.  It is not wasteful
because the materials may be recharged after cleanout.
     A large furnace can be completely quenched in 24 hours if a sufficient
supply of water is available.  During this period, the cast house is roped off
and no one is permitted around the furnace or on top.  The tuyeres are solidly
plugged and the blowpipes either blanked with steel plate or taken down before
the quench.  All furnace bleeders are left open to relieve the steam and the
gas that is formed.  At some plants, the bells are also blocked open.
     During the quench, the furnace top may get very hot.  Due to the water gas
reaction, large quantities of hydrogen may be produced.  A gas fire may start
above the furnace in the superstructure.  For this reason, it is always advis-
able to clean as much grease off the furnace top as possible before starting
the quench.
     The pool of iron in the hearth of the furnace below the tap hole can
either be removed as a liquid by bottom tapping or be allowed to solidify and
removed when the lining is torn out.  If the bosh and hearth are not to be
relined, it is left in the furnace.  If bottom tapping is employed, a hole is
drilled through the bottom refractory from beneath the hearth plates and the
iron is drained onto the ground.
     As in the case of starting up the blast furnace, the process of shutting
it down involves greater than normal emissions.  The duration and concentration
of emissions during the latter procedure are much less severe than during the
former.  The frequency of both are essentially the same; that is, a shut
down is normally followed by a startup.

4.1.3  Abnormal Operating  Conditions
     Slips are  due  to  a  bridging of the stock in  the  furnace.   When  this  occurs,
the material  underneath  continues to  move downward creating  a  void.   The  void
increases  in  size until  the bridge collapses, causing a  sudden downward move-
ment in  the stock above  it.   In severe cases, this causes  a  sudden increase  in
gas pressure.   To relieve  this pressure, the raw  gas  bleeder at the  top of the
furnace  automatically  opens discharging a cloud of particulates and  blast
,furnace  gas to  the  atmosphere.  The bleeder is shown  in  Figure 7 which has been
reproduced from Reference  8.   This Reference also attributes the cause of
hanging  to the  following factors:
     1.    Resolidification of previously fused slag and  molten iron.
     2.   An  excessive quantity of fines in the coke. This  is
           confirmed by common operating experience in the  blast      g
           furnace and  is reported as  the result of model experiments.
     3.    Fine  carbon  formed via the  Boudouard reaction  may  also
           fill  the  spaces  in the burden and impede the upward
           flow  of gases.
     4.    Alkalis such as  the oxides  of sodium and potassium,
          may contribute to the hanging as well as to the
           formation of scabs which adhere to the  furnace wall.
     5.    Overblowing  the  furnace by  excess wind  tends to  prevent
           the smooth downward flow of material.   One  way of  over-
           conming this condition is to increase the top  pressure
           of  the furnace.

     This  same  Reference indicates that slip-induced  bleeder valve emissions,
based  on national production figures, appear to be small relative to  the
emissions  of  other  in-plant air pollution sources. Their  estimate of emissions
from slips  in the United States is 187 to 1842 tons per  year.   They  compare
this to  the blast furnace  cast house  emissions which  they  estimate to be  4790
to 24,370  tons  per  year.
     Bleeder  valve  openings which result from slips in the blast furnace  are
more serious  on an  individual basis than on a national basis.   Some  furnaces
may operate for an  entire  year without reporting  one  such  opening.   Others may

      noons AM COUNTER-
          comers MOT GASES
         LOAD TO
            ISEE ne.K
           ROTATES MMT Of A
          	 8 AUTOMATICALLY
                                                                           SKIP BfllPCg CARRIES TRACKS
                                                                            ON WHICH SKIP CARS CONVET
                                                                                   <£ ANO LIMESTONE
                                                                                   OF FURNACE.
     Figure 7.    Schematic  illustration of blast  furnace  top.

have 50 a month or more.  Older blast furnaces generally have more slips than
younger ones.  It is also possible for a bleeder valve to stick in the open
position, thereby increasing the duration of the AOC.
     High-alkali burdens are especially important contributors to slipping.
In addition they cause other operating problems in the blast furnace:10
     1.   Excessive tuyere losses.
     2.   Coke messes on the cast house floor.
     3.   Very high blast pressures.
     4.   Inwall scabbing.  The presence of scabs tends to restrict
          the area in the stack causing higher gas velocities and
          contributing further to the incidence of slips.
     5.   High coke rates.  More coke has to be produced by the
          coke ovens leading to increased emissions from that
     6.   Loss of production for removing scabs.  The process of
          removing the scabs in itself induces the emissions to the
     One of the most effective ways  to decreasing the alkali content of the
burden materials is to determine which materials are the principal sources of
the alkali and to eliminate them from the burden.  Alkali may be found most
usually in iron ores, but they are also present in coke and in flux material.
A  high slag volume and a lean slag practice (keeping the basicity ratio of
the slag at 1.00 or less) is effective in obtaining reasonably good operation
with a high-alkali input.  Analyses  show that lean slags remove significantly
more alkali than limey ones.  Alkali input not only causes abnormal operating
conditions, but also reduces production and increased coke rates as can be seen
on Table 4.10  The operational problems resulting from high alkali will increase
with a decrease in coke stability.
     The factors that induce good performance in respect to meeting metal-
lurgical specifications for iron are also conducive to reducing AOC from slips
and other causes as will be indicated below.  In one plant in which the bogey
for casts that are off-analysis is a maximum of 6 percent, the following
operating factors contribute to a satisfactory performance record:


Coke Rate
Carbon Wind
Blast Heat
Slag Volume
Ore Usage
Alkali Input
Alkali Input

T/Fce. Day
Prior to Pellets
100% Utah Ore Burden
35% Sinter 65% C. Ore
50% Pellets
30% Sinter 20% C, Ore
Two Periods in 1975
80% Pellets
10% Sinter 10% C. Ore

     1.    Control of materials

          a.   Coke stability.  Around 55 is excellent.  Below 48
               is poor.  The larger furnaces need better coke for
               good performance.  These numbers refer to a standard
               test of abrasion resistance.

          b.   Low alkali content of the burden.  High alkali contri-
               butes to slips.

          c.   A screened burden.

          d.   Low ash in the coke.

     2.    Uniform Operation.  Attention to all operating factors that
          contribute to the uniformity of operating conditions.   In
          one plant reliance is placed on thermocouples, located at
          the quadrants of the furnace, approximately 6 feet below the
          big bell.  The thermocouples indicate proper movement  of the
          burden and proper distribution of the gas.  Adjustments in
          the burden are based upon the temperature readings.

     3.    Moisture Control.  Moisture is controlled by the addition of
          steam into the tuyeres.  A desired control level  is 11  gms/schi
          (5 grains of moisture per scf) of air.  In the summertime,
          moisture may increase to levels as high as 25 gms/scm  (8 grains
          for which there is usually no correction provided.
     4.    Maintenance.  A high degree of preventive maintenance  will
          tend to keep all systems, instruments, and controls operating
          as designed.  In one plant which is located in a cold  cli-
          mate, the preparations for winter conditions begin in  August.

     5.    External desulfurization of molten iron in a facility  away
          from the blast furnace.  This permits the blast furnace to
          deliver molten iron which is higher in sulfur than required
          at the steelmaking facility and results in lower consumption
          of flux as well as a leaner slag thatis better able to
          deal with removal of alkali.  Another benefit is the increased
          production of iron from a given furnace up to about 15 percent
          and the reduction in coke, up to about 10 percent.  By virtue
          of the benefits mentioned above, external desulfurization of
          iron contributes to the reduction of AOC from the ironmaking
          process as well the reduction in normal emissions from this
          process and the coke making process.
     By carefully monitoring the pressure in the blast furnace,  the relief

openings due to slips may be minimized.  When the pressure first starts to

build up, a controlled slip can be made to occur by reducing blast pressure.

This procedure called checking helps to break up the bridge which has been

impeding the flow of the burden.   By a repeated checking procedure, the gas
channels become more evenly distributed and the stock movement may return to
normal.  If this procedure is not successful,  another procedure is to increase
the moisture in the blast and to  decrease its  temperature for a short period of
     The necessity of making certain repairs on the blast furnace requires that
the pressure in the furnace be relieved by taking the wind off the furnace,
backdrafting the bottom of the furnace through the tuyeres and opening the
relief bleeder.  Backdrafting refers to the condition in which the furnace
gases are drawn back through the  tuyeres to a  hot stove where the gas is
burned.  As an alternative to the use of a hot stove, some plants deliver the
gas to a special backdraft stack.
     Emissions of gas and particulate matter from the opening of the relief
valve and from the backdrafting occurs primarily during the first 15 minutes of
the outage.  It is not known how  much of these contaminants are emitted; how-
ever, visual observation indicate that it is minor in comparison to other
sources at the blast furnace.  Figure 8 diagrams the procedure that occurs
during backdrafting.
     Compared to all other blast  furnace water-cooled members, tuyere failures
are the single biggest cause for  furnace delays and for backdrafting associated
with their repair.  Tuyeres are nozzle-like water-cooled copper castings which
project into the hearth of the blast furnace.   Their function is to direct the
heated blast from the bustle pipe into the furnace.  Some reasons advanced for
their failure are:
     1.   Inadequate cooling due  to poor water circulation, dirty
          water, or water stoppage.  Newer designs of tuyeres have
          been developed which provide higher  water velocities at
          the tip of the tuyere which is exposed to severe operating
          conditions of the blast furnace.
     2.   Abrasion from the ceaseless swirling of incandescent
          coke due to the tremendous activity  which occurs at
          the nose of the tuyere.

                          Figure  8.  Bsckdrafting through bUst furnace stoye,

     3.    Iron cutting.   The impingement of a  large  amount of
          molten iron on the surface of the tuyere can  cause
          premature failure.  It has been surmised that a  sudden
          drop of the burden into the molten bath during a slip
          may splash an  excessive amount of slag and hot metal
          onto the tuyere.   It is also believed that weak  coke
          pulverizes excessively and forms a mass of fine  particles
          which retard the  passage of molten globular iron.   The
          impervious coke collects and forms a pocket at the tuyere
          nose for the molten iron.
     4.    High alkali burdens, as indicated in the previous  section
          are associated with excessive loss of tuyeres.
     On  one new blast furnace7 the initial  design of tuyeres resulted in a
large number of failures.  There were 197 tuyeres changed  during  the first 9
months of operation and 200 tuyeres in the next year.   Since the  furnace has 36
tuyeres, this works out to  an average life of  about  58  days  per tuyere.
Continued work on tuyere design and water flow is reported to have favorable
results.  In comparison, another furnace   reports eight tuyeres  out of  a total
28 lost in the first 209 days of operation. This works out  to  730 days  average
life per tuyere.
     Other repairs to the blast furnace that require backdrafting include
changing of bleeder valves, changing of furnace large and  small bells, etc.,
occur less frequently than  do tuyere changes but require longer downtime.  A
tuyere may be changed in a  comparatively short period of time.  To change a
bleeder valve may require about 8 hours of which approximately  3  hours is
required to rig up for the  job.  A small bell  repair may require  about 12
hours, whereas the replacement of a large bell may take 7  days.
     At one plant,   normal furnace repairs such as  welding  on  uptakes or down-
comers require 12 to 16 hours.  A repair job on both the large  and small bells
of the blast furnace has required a total 56 hour downtime.   The  delays  for
repairs have ranged from 25 hours per year to  268 hours.  Typically, furnace
downtime is estimated to be 5 percent per year; however, it  may be reduced to
as little as 3 to 4 1/2 percent.
     When an extended repair is anticipated, in addition to  backdrafting, the
tuyeres  may be sealed to prevent air from entering the  furnace.   During  alt
such repairs, gas measurements are made to insure safety for the  maintenance

crew.  After such a repair, when bringing the furnace back on-line, the mains
and dust catchers are purged with steam or an inert gas to avoid the potential
of explosion.
     In summary, the amount of time for backdrafting can be reduced by improved
design and maintenance practices as well as by careful attention to water flow
to the water-cooled members and by improved burden which minimizes such AOC's
as slips, tuyere failures, etc.  Emissions from backdrafting occur primarily
during the first 15 minutes of the backdraft and, although on some furnaces the
amount of backdrafting may be as frequent as 50 to 60 times per month, the
effect on the environment is small compared to other sources in the blast
Hater and Power Failures
     A massive power failure is perhaps the most potentially disastrous
occurrence in the blast furnace.  The  longer the power is off, the longer it
takes to bring the furnace back on-line.  If the outage is of short duration
and  cooling water pumps are restored during the period, very little damage will
occur to the furnace.  However, if the outage is long and there are not supple-
mentary steam driven cooling water pumps, the residual water in the tuyeres,
coolers, bosh plates, and stack plates will boil out and they may become so hot
as to melt.  In addition, the hearth cooling plates may become damaged.  During
power failures, blast furnace bleeders may be opened, thereby creating a source
of emissions.
     If the power outage continues, the gas mains may cool off, the vapors in
gases inside may condense, reduce in volume and create a vacuum.  If air is
sucked into the mains, explosions may  result.  Burned copper coolers may permit
large quantities of water to enter the furnace, chilling it and consuming large
quanitites of coke due to the water-gas reaction.  Finally, it may be exceed-
ingly difficult to isolate the blast furnace from the gas system because the
large goggle valves may be difficult to operate manually.
     On February 11, 1967, the Aliquippa Works of Jones & Laughlin Steel
Company suffered such a massive power  failure.  A series of explosions occurred
after the power was restored.  The low pressure steam, when turned into the
cold mains, apparently condensed and drew in air creating an explosive mixture.
These explosions wrecked the boiler house gas mains and a furnace gas cooler.


     On August 28, 1974 the Gary Works of U.S.  Steel  Corporation suffered a
complete power failure and their No.  11  Blast Furnace lost all  wind, water, and
electrical power.   This resulted in  filling all  the  blow stocks, two of them
being burned through with the slag and iron running out.   All  35 tuyeres, eight
coolers, and four upper expansion joints had to be replaced.   This, as well as
repairing other damage, resulted in the furnace being down for five days.
     As a result of the breakouts and explosions  as described  above, the
emission to the atmosphere from a power failure can be very great.  Fortunately,
such occurrences are comparatively rare and may be minimized by building cer-
tain safety features into the plant as follows:
     1.   Provide a source of power which is separate from the
          outside utility company.  In addition,  provide  duplicate
          facilities such as power lines and breakers for supplying
          electricity to the consuming units.
     2.   Provide steam driven auxiliary units  such as cooling
          pumps for the most critical service.
     3.   Provide an overhead water storage tank  to insure an
          adequate supply of cooling water to the blast furnace
          under emergency conditions.
     4.   Provide training for operating and maintenance  per-
          sonnel in respect to dealing with problems  which
          may arise during power failures.
     Breakouts occur in the area of the hearth  and the bosh immediately above
it.  They are caused by the failure of the walls  which, in turn, results in the
uncontrolled flow of liquid slag and/or molten  iron out of the furnace.  This
can cause considerable damage to the furnace and the  auxiliaries.  It also
results in a substantial cloud of emissions to  the atmosphere.
     When a slag breakout occurs it can usually be chilled with water and the
hole plugged by pumping in fireclay grout or by ramming in refractory material.
An iron breakout is much more serious because there is more chance of explosions
if the molten iron comes in contact with water.  Also there is usually no prac-
tical way to stop the flow of iron out of the hole until  it drains completely.
Most breakouts of iron have occurred in furnaces that are lined with carbon.27
With more experience in the use of carbon, the incidence  of these breakouts
has decreased.


     Another cause of breakouts, especially  in  high tonnage carbon hearths may
occur when  restarting a furnace after a  comparatively short stop in which the
iron salamander is left in the hearth.   When this iron solidifies, the sala-
mander shrinks  as it cools and draws away  from  the brick.   These shrinkage
cracks then become filled with other material and upon reheating, the reexpan-
sion of the salamander creates enough stress on the hearth jacket as to burst
it.  If the cooling water on the jacket  is heated to 140°F just prior to blow-
in, the jacket  is allowed to expand and  the  stress is relieved.  Heated water
is maintained on the jacket for about 14 days after the blow-in after which
normal cooling  water is restored.  Typical of such outages which last at least
three days  but  are not long enough to drain  the salamander are for a bell
change, a  steel plant oxygen failure, a  power failure where a furnace cannot be
restored for  several days, major stove repairs, strike threats, etc.
     Figure 9    illustrates the amount of  iron  produced and the years of
                          Bethlehem "B" Hearth
                 i   s
                 I   6
  6 days stopped
Raptured jacket
                 Blow-in Jan. 1966
                13 days stopped
           338 days to reline
       16 days stopped
 200 days stopped due to business decline
27 days stopped
                                     4      6
                                   Years of Service
  Figure 9.  Tons of iron accumulated on hearth during years of service.  Starts
             and stops in production and duration of each are shown as well as
             point at which  hearth  jacket ruptured.

     An analysis of ten breakouts that occurred in various blast furnace
facilities during the period of 1961  to 1967 reveals one breakout in the bosh
                             1 9
three feet above the tuyeres.    The  remaining were breakouts in the hearth.
In only one of these incidents  was a  man injured being burned by metal and
slag.  Damage to equipment, however,  was common to all and in some cases,
fairly extensive.  One method of guarding against breakouts is to install
thermocouples at strategic places in  the hearth of the furnace.  These thermo-
couples tend to give early warning of a condition which may lead to breakout
thereby enabling the operating personnel to take the necessary corrective
action before the breakout occurs.
Charging Dusty Material
     The most common method of charging material into the top of the blast
furnace is by means of the skip.  If  the material being charged is weak and
friable and if it has not been beneficiated by crushing to size and screening,
the  filling of the skip and its subsequent dumping at the top of the furnace
may  give rise to a dust cloud of particulate matter.  The dust cloud at filling
is a low level source which tends to  remain within the blast furnace area. The
dumping operation is at a high level  and prevailing winds tend to entrap the
particulate matter into the atmosphere.
     From the standpoint of smooth operating conditions in the blast furnace
leading to high tonnages, low costs,  and minimum AOC, a sized and screened
burden is highly desirable.  It is desirable in many cases to screen the
burden twice.  Typical examples of this are pellets, sinter, and coke.  For
each of these materials screening may be performed where the material is
produced and once again in the stockhouse of the blast furnace being charged.
The  latter screening serves to remove fine particulate matter with may have
developed in the handling of the raw material from the source of production to
the  furnace itself.  Where such screening is performed and if it is done in an
efficient manner, the filling and emptying of the skips is relatively dust

     All blast furnace operators would prefer to have a screened and sized
burden which is strong and resistant to abrasion.  In spite of this, many
furnaces do not have adequate facilities for sizing and screening, either
because of limited space or because of economic considerations.  If the burden
is not screened, the filling and emptying of the skip can be quite dusty,
especially in the case of sinter and coke.  One way of reducing the amount of
such emissions is by the application of water sprays,23 and preferably in conjunction
with a wetting agent.
     A furnace may have up to 600 charges per day from the skip.  Each filling
and dumping operation may last five to ten seconds.  Thus the aggregate time
for each operation is 3 1/2 to 7 percent of the total operating time.   The
amount of emissions from each occurrence is variable depending upon the nature
of the material, the way it was handled, whether or not water was applied, etc.
At the present time there is no information available on the quantity  of
Gas Cleaning System
     This section refers to that portion of the gas cleaning system which
relates to the process itself, i.e., the dust catcher and the scrubber.  The
other portion of the system which relates to the recirculation of the  water is
covered under control equipment related AOC.
     The first element in the gas cleaning system is the dust catcher.   Because
this equipment is lined with abrasive resistant refractory and because it is a
low energy device, there is normally little AOC associated with it. The dumping
of the dust catcher should be done at frequent intervals, normally once per
shift.  Because the material is hot, dry, and dusty, steam and water sprays are
usually provided for control of emissions.  The dust may be discharged directly
from the catcher to a railroad car or it may be preconditioned in a pug mill by
adding water or blast furnace sludge.
     At times the flue dust may become hard and lumpy and it may be necessary
to free the dust catcher outlet by means of a small explosive charge.   This can
create a minor source of AOC.

     If the final cleaning device is a fixed orifice scrubber, the differential
pressure drop across it becomes a function of the rate of flow of gas from the
blast furnace.  If the rate of flow is low, the pressure differential becomes
low and the efficiency of gas cleaning suffers.  Efficiency may also suffer
because of wear in the lining of the scrubber which damages its internal
configuration.  Blockage may also occur in the spray nozzles due to the accumu-
lation and deposits of scale, thereby decreasing the flow of water.
     In most blast furnaces, the gas scrubbing equipment operates at high
cleaning efficiency because there is adequate pressure available from within
the blast furnace.  An outlet gas loading of 25 mg/scm (0.011  grains/scf) or
better is commonly found; in modern furnaces, the outlet loading may be as low
as 5 to 10 mg/scm (0.002 to 0.004 grains/scf).  The blast furnace operators find
it highly desirable and necessary to maintain high cleaning efficiency in order
to protect such costly fuel burning equipment as the blast furnace stoves and
the coke oven underfiring systems.  If such units were to burn dirty gas, they
would soon become blocked and inoperative.  Therefore, careful attention  is
paid to the operation and maintenance of the scrubbing equipment and AOC  from
this source is comparatively minor.
     The trend in gas scrubbing facilities for the blast furnace is toward
equipment that insures higher efficiency and greater reliability.  Constant
pressure differential and, therefore, cleaning efficiency is maintained by the
provision of variable orifices and automatic controls.  Wear of the scrubber
internals is minimized by the provision of abrasion resistant linings and by
configurations which establish a water film for additional protection. Scaling
of spray nozzles is minimized by attention to the quality of the water and by
provision of new designs which use a small number of large diameter inlet
nozzles that are less susceptible to the effects of such scaling that does
occur than are small nozzles.
     In some gas systems, final cleaning is provided by passing the gas through
a wet electrostatic precipitator.  This type of equipment is subject to mal-
function from corrosion of the precipitator internals and from electrical
failures.  Corrosion may be minimized by proper attention to water quality and
electrical failures by attention to maintenance practices.  In any event,

because the wet precipitator is almost invariably preceded by the dust catcher
and one stage of gas scrubbing, its malfunction causes minimal AOC as far as
the environment is concerned.
Gas Bleeders
     In most iron and steelmaking facilities, every effort is made to consume
all of the byproduct gas produced.  This is true of blast furnace gas as well
as coke oven gas.  There are several conditions under which blast furnace gas
is bled to the atmosphere, as follows:
     1.   During startup and shut down.
     2.   From furnace slips.
     3.   From backdrafts.
     4.   From bell leakage.
     5.   From the clean gas bleeders.
     The first three items on the list have been covered previously in this
manual.  The next item, that of bell leakage, will be covered in Section 5.0 at
the end of this manual.
     Whenever blast furnace gas is produced in an amount that exceeds its
useful consumption in various heating processes, it must be bled to the atmosphere.
Normally, the bleeder for blast furnace gas is equipped with an ignition torch
to assure that the gas burns upon entering the atmosphere.  The most common
ignition torches burn natural gas or coke oven gas.  On occasion, the ignition
flame is extinguished, primarily because of deposits in the coke oven gas
which may in time cause a plugged condition.  When this occurs and there is a
sudden opening of the clean gas bleed, the blast furnace gas enters the
atmosphere without being burned.  In consequence of the fact that the gas
contains 20 to 30 percent carbon monoxide and of the fact that the amount of
gas bled may be high in quantity, the amount of this contaminant in the
atmosphere becomes substantial.  Under certain climatic conditions in which
there are downdrafts from the stack, it is possible that the area around the
base of the stack may contain an atmosphere which is toxic to human beings.

     In some plants, the clean blast furnace gas may be bled to the atmosphere
without any ignition.  In this case, every time the bleeder opens, there is an
     The number of times that a clean gas bleeder will  open in a particular
steel plant depends upon the operating conditions in that plant.  A reasonable
average of frequency for such openings is about once a month and, if there is
failure of ignition, it might take one to four hours to correct the condition.
Carbon Black Formation
     Because heavy fuel oil is less expensive per heat unit that is metal-
lurgical coke, the current trend in blast furnace ironmaking is to replace as
much of the coke with heavy oil as is consistent with good operating practices.
Where oil is fired in large quantities, under certain conditions not all of it
is fully combusted by the wind of the blast furnace, forming carbon black which
finds its way into the gas and from there to the scrubber water system.  Oil  is
normally injected into the blast furnace by means of a pipe located at each
tuyere.  The reason for incomplete combustion accompanied by soot formation are
as follows:
     1.   The distribution of oil is nonuniform from tuyere to
          tuyere.  Thus, although the total amount of oil injected
          in all of the tuyeres may be capable of being burned by
          all of the wind which is being injected into the tuyeres,
          in one or more of the tuyeres the oil flow may be so
          high as to result in incomplete combustion.  Some plants
          meter the flow of oil at each tuyere and thereby are able
          to properly balance the distribution of oil to all the
     2.   If the oil lance is not properly centered in the blowpipe,
          or if the spray is partially plugged, deflecting the flow
          of oil, the oil may not come into proper contact with the
          incoming air and may not be completely burned.
     When the carbon black gets into the scrubber water, it has a tendency to
float on the surface of the clarifier.  The accumulation of carbon black may
become great enough to interfere with the proper operation of the clarifier.

     It is obvious that the preferred method of dealing with the problem of
carbon black is to go to the source of its formation and make the correction
there.  This not only corrects the environmental AOC but also improves the
utilization of energy in the blast furnace.  Failing this, in some plants a
wetting agent injection system has been provided.  The operator of the treat-
ment plant manually activates this system whenever carbon black is observed on
the top of the clarifier.  Although no actual data are available on the extent
of this problem or the extent of its environmental impact, it does not appear
to be widely spread nor of great severity where it does occur.
Furnace Control
     In the preceding sections of this manual there has been discussion of the
importance that smooth furnace operation plays in eliminating AOC.  This is a
particularly important subject and deserves special attention.
     The first element of good furnace control lies in burden preparation.  A
burden that is sized and screened, that contains coke of adequate stability is
conducive to a smooth operation.  Screening and careful proportioning of the
burden at the stockhouse is essential.  After this, the burden must be placed
in the furnace in such a manner that  there is uniform distribution which tends
to insure uniform flow of gas.  These are the elements of good furnace operation;
however, not all blast furnaces in the United States have all of these elements.
     The next step  in assuring smooth operation is to have a full set of appro-
priate and reliable indicators of operation.  Some of these are instruments to
measure top pressure, bottom  pressure, stock!ine movements, temperature distri-
bution at the top of the furnace, flow meters at the tuyeres for measuring oil
injection and so forth.  Once again,  not all furnaces in the United States have
these elements.
     Finally, having all of the above elements of control, the last element to
be applied may be a computer  for the  process itself.  Such application is
becoming more frequent in the larger  high productivity furnaces.  Smaller
furnaces of which there are many in the United States may not find economic
justification for computer control.

     On the subject of computer control, the following statement has been


     "To insure stable operation of large furnaces, it is essential
     to detect the condition in the furnace and the equipment main-
     tenance condition and to produce such information for subsequent
     control.  Key points in this operation are:

     1.   Top sampling and shaft sampling offer information on
          the radial gas distribution in the furnace, and provide
          guidelines for burdening control by charging sequence
          and moveable armors.
     2.   Venturi meters are provided to measure blast flow at each
          tuyere and thermometers mounted around the furnace stove
          monitor uniformity of circumferential burden distribution.
          If the distribution is not uniform, the oil injection
          control corrects for it.
     3.   The burden surface is monitored by infrared cameras and
          thermoviewers to maintain even gas flow.

     4.   Monitoring of slag extraction and tapping.
     5.   Information obtained by measurement of temperature,
          pressure, etc. is measured by computer to facilitate
          preventive maintenance.
     6.   Computer estimation of the furnace internal condition."

     Figure 3 in a previous section of this manual shows an example of the

primary means of instrumentation that is described above.
     Another author   wrote about benefits of computer control for blast
furnaces as follows:

     "The overall function intended for the computer has changed
     drastically in the last seven years from one of closed loop con-
     trol to one of process monitoring.  The primary purpose of the
     computer, however, is to improve the control and to some extent
     this was substantiated in a report prepared by our Research
     Department.  They analyzed the variations in silicon, sulfur,
     manganese, coke rate, and number of off-casts for the No. 5 fur-
     naces for two to three month periods; one with computer control
     and one without computer control....  The results were incon-
     clusive for the coke rate and manganese content but the variations
     in silicon and sulfur from cast to cast were considerably better
     in the computer period."

     Except for the gas cleaning equipment, which is essentially a part of the
blast furnace process and as such not a pollution control device, there are two
general types of pollution control equipment that may be found.  The first is a
fairly common, highly developed system for recirculating the water which serves
the blast furnace gas scrubber and gas cooler.  The second, which is more
recent, and less common, is the baghouse which  is used for capturing emissions
from the casting of the furnace.
     The systems for capturing the emissions from casting are described pre-
viously under Section 3.1.  The major portion of the control system is directed
toward the evacuation of fumes from  the cast house building.  This is
supplemented by local fume hooding in some systems.  In other systems, sole
reliance is placed on the building evacuation portion.
     Because the cast house emission systems are relatively new in the United
States, there is little information  regarding AOC as related to it.  Never-
theless, because it is quite similar in nature  to the building evacuation
system for the electric arc furnace, it may be  reasonably projected that the
AOC associated with the cast house system will  be similar to that for the
electric arc furnace building.  Therefore, for  a discussion of this aspect of
control related AOC, the reader is referred to  the process manual on the
electric arc furnace.
     The control related AOC for the recirculated water system is given in the
succeeding sections.
4.2.1  Startup
       The major startup problems for a blast furnace recirculated water system
occur only once in its life, that is when it is newly commissioned.  Subsequent
to that, shutdowns and startups may  occur due to such uncontrolled situations
as strikes.  The startup and shutdown subsequent to the commissioning occur at
very infrequent intervals and are usually unaccompanied by AOC.  Therefore,
this section will deal with a discussion of the practices that should be
followed in achieving a successful initial startup.  Assuming that the system
is installed as a retrofit for existing blast furnaces, which is usually the
case, they are:

     1.    Prior to testing out the system,  all  water basins  and
          pipelines should be clean of debris such  as wood,  rags,
          welding rods, etc.
     2.    Testing of the system should begin well  before the actual
          system startup, possibly two months in advance.   It should
          comprise the following steps:
          a.   Fill all basins and piping systems with service water
               from the mi 11.
          b.   Pump the service water through all  of the major pieces
               of equipment including the clarifier and the  cooling
          c.   Run each of the pumps at least two days each  to verify
               pumping capacity and to check for any vibration at  the
               base of the pumps.
          d.   Check all instrumentation for calibration and dependa-
     3.   In preparation for activating the system there should be
          a meeting of personnel who will be involved with the system
          for the purpose of instructing them in its maintenance and
          operation.  Part of this training session should be the
          distribution of a simplified operating manual.
     4.   In a plant which has a multiplicity of blast furnaces, only
          a few of the furnaces should be initially tied into the  new
          water supply.  They should be run for about a month before
          tieing in the rest of the furnaces.

     In a recirculating water system, one problem which can  occur  is a system
imbalance caused by starting or stopping of pumps.   The result is  a  rising or
falling water level on clarifiers of sumps.  In the case of rising level, the
clarifier or sump may ultimately overflow,  spilling onto the ground  and potentially
into a storm sewer.

4.2.2  Shut Down

       Once a blast furnace recirculating water system has been in successful
operation, it is rarely shut down except as a result of an unscheduled outage.
Such outages will be covered under Abnormal Operating Conditions in  Section 4.2.3.
A planned shut down, if it should occur, is always accompanied by  a  planned
shut down of the blast furnaces associated with the system.   In this case, AOC
from the shut down of the water system is essentially non-existant.

4.2.3  Abnormal Operating Conditions
       In the recirculated water system which serves the scrubbers and the
coolers of the blast furnace gas system, there is a need for utmost reliability.
The system must operate 24 hours a day, day in and day out, without shut down.
Any malfunctions in the system which might cause a shut down would either
require a shut down of the blast furnace operation or an increased discharge
of effluents'into the receiving waterway.  Because blast furnace ironmaking
is a continuous operation which is exceedingly difficult to shut down without
considerable prior planning, the tendency might be to allow an increase
in the discharge of contaminants in the case of failure in the water system.
In order to prevent this, wherever it  is possible and feasible all operating
components of the recirculating water  system have in-place standby equipment
to take over in the case of equipment  failure.
     The requirements of service for the water system are severe.  Close
attention must be paid to the quality  of the recirculating water, otherwise a
scaling tendency arises which may result in plugging of the pipelines and
nozzles.  The suspended solids in the  system are heavy and abrasive.  The
former quality leads to difficulties of sumps being filled with suspended
solids, thereby plugging the pumps and overleaoding the drives for the rake
mechanisms of the clarifiers.  The latter quality leads to abrasion and high
wear in the pipelines and especially in the pumps, resulting in a shortened
life, even when special abrasion resistant materials are employed.  Finally,
the recirculation systems for blast furnace cooler and scrubber water are
almost invariably retrofits and in consequence, suffer from congested con-
ditions and other design restrictions. These problems are covered in greater
detail below.
Water Quality
     In order to minimize the discharge of pollutants to the receiving body
of water, blast furnace scrubber and cooler water is recirculated to the maxi-
mum degree possible.  The BPCTCA model for this system as envisioned by EPA
is shown on Figure 5 in Section 3.0.   It will be noted by reference to this
figure that the discharge allowances for contaminants are based on restricting
the flow of the blowdown water to 3.2  percent of the recirculated water.

     In 1969, Inter!ake, Inc.  undertook a project to evaluate the performance
of a blast furnace recirculation system under a grant from the Environmental
Protection Agency.  The results of this program are reported in References 14
and 15.  Attempts were made to maintain dissolved solids in the system at 1500
to 2500 ppm, resulting in a blowdown of 7 to 10 percent.  In about a year and
a half of operation in this mode, scaling problems developed.  One section of
pipe showed a buildup of 5/8 inch.  In the several succeeding years, acid
additions were made to the water in an effort to control the Ryzner Stability
Index of the water.  Detailed  discussion of this Index is given on pages 99
to 105 of Reference 14.
     This program for controlling scale was only partially successful.  In
time, scale began to accumulate again which was caused primarily by precipi-
tation of the dissolved solids in the recycle water.  Subsequently, the
addition of a commercial scale inhibitor to the recycle system was started.
This has been successful as evidenced by later examination of the internals
of the piping system during periodic shutdowns of equipment.  The inhibitor
itself caused a secondary problem, that of corrosion in the bronze impellers  of
the booster pumps.  This was corrected by the addition of a copper corrosion"
inhibitor to the scale inhibitor product.
     Figures 10 through 13 show one type of water nozzle.which is used in a
commercially available blast furnace scrubber.    The manufacturer claims that
its non-clogging feature is chiefly attributable to proper dimensioning of
the large discharge opening.  Figure 13 shows that the opening does not clog
after years of operation; however, it is clear that the size of the opening
is severely restricted.  There is no information available on the quality of
water that was used in the system.
     Table 5 provides information on the quality of water which was discharged
from one recirculation system which combines blast furnace and sinter plant
water.  This was tested for simple and complex cyanides.*  Another sample
downstream, after additional discharges, was tested for phenol, which in this
case could only have come from the blast furnace scrubber water stream 102.
*Simple = can be chlorinated.

Figure 10.   Swirl  nozzle with  replaceable  insert
            arranged centrally above the throat
            of the scrubber.
Figure 11.  Disintegration of the scrubbing
            liquid above the throat without
            any gas flow.

Figure 12.  Disintegration of the scrubbing
            liquid with the droplets exposed
            to the action of the gas flow.
figure 13.  Swirl nozzles after years of operation,
            External  deposits did not clog up the
            discharge opening.

Of particular interest is the high level of pH, the result of the cyanide

treatment system and its relationship to the level of cyanide in the





















Cyan Ido
«.— *
( 2.5)

( 3.7)










( 425
( 0 )
( 580)
( 75)
( 457)

• •»•
• ••
• ••
• »
• ••
 NOTES:   (1)  The Company monitors the blast furnace and sinter plant waste
             treatment  facility water for cyanides after the alakaline chlorina-
             tion  treatment  unit  (stream 102).  The phenol in this water is
             measured after  dilution  (002).  Quantities found using grab samples
             (one  each  seven days) are  shown above.  Three values are shown per
             month (min.,  avg., max.).
         (2)  By permit, the  allowable total cyanide from stream 102 is 261
             Ibs/day average and  761 Ibs/day maximum.

     The above Table was made available from the Pennsylvania Department of
Environmental Resources files.  Table 6, available from these files, gives
upsets in five other steel plants.  Those upsets relate to excursions in pH,
suspended solids, and phenol.  It is of interest that certain types of
contaminants are more of a problem to one plant than to another.  In other words,
problems of upsets in the blast furnace scrubber water system appear to be under
control in one plant and susceptible to AOC in another plant.  This fact
emphasizes the relationship between AOC in the water system and specific design,
construction, and operating conditions.
       Abnormal  Operation
pH < 6.0 during acid cleaning of blast
Furnace A, B, C, and D.   The acid was
sent to a sump that was  believed to
drain to a system where  neutralization
was available.  It drained direct to the
outfall, however.  A new piping arrange-
ment will be made.

pH < 6.0 due to acid cleaning of the Blast
Furnace C scrubber.  The scrubber sump had
a continuous overflow to the sewer; acid
overflowed because personnel were unaware.
Plant to institute a "field survey" before
all acid cleaning operations.

pH > 9.0 due to excessive addition of
KOH to the No. 1 Blast Furnace thickener.
The sample line for the  pH control became
plugged so an improper low pH signal con-
tinued requesting more KOH.

pH > 9.0  High cyanide output from the
blast furnaces necessitated pH increases
to prevent cyanogen chloride discharges
from the cyanide destruct station.

pH > 9.0 due to failure  in the pH probe.
Excess KOH entered the system; the
probe has been replaced.
1.5 hrs
over 75 min
1.5 hrs
10 mins



pH <
Abnormal Operation
6.0. During acid cleaning of
10 mins
the A-3 Blast Furnace precipitator
appraently some acid entered the sewer.
Spent acid is usually pumped to the
No. 1 Blast Furance thickener where it
can be neutralized by the alkali-chlori-
nation unit.
pH > 9.0 due to a faulty signal from
the pH controller of the alkaline
chlorination unit for No. 1 Blast Fur-
nace thickener.

Exceeded allowable cyanide discharge by
279 Ibs.  The outfall is from the blast
furnace, however, no further determina-
tion of cause was possible.
pH of cooling water for blast furnace
wind turboblowers outfall down to 5.9.


Total  suspended  solids  limit was
exceeded.  The No.  5  Blast  Furnace
thickener  slurry line was out  of  service
so  solids  were being  removed by truck.
Truck  breakdown  resulted in reduced  re-
moval  rate causing  more solids in the
thickener  overflow.
Total  suspended  solids  exceeded the  limit
by  125 kg/day due to  valve  repair (blast
furnace and  sinter  plant).
Total  suspended  solids  limit was  exceeded
by  16  kg/day due to downtime for  valve
repair (blast furnace and sinter  plant).
Total  suspended  solids  limit was  exceeded
by  77  kg/day due to frozen  pipes  (blast
furnace and  sinter  plant).
30 mins
Exceeded daily  B
tion present
for one of 3
July samples
Exceeded        A
daily limit
 Exceeded       C

 Exceeded       C
 daily limit

 Exceeded       C
 daily limit

TABLE 6.  (cont'd)
         Abnormal Operation
Total suspended solids limit was
exceeded by 112 kg/day due to excess
blowdown (blast furnace and sinter

Total suspended solids limit exceeded
due to line blockage causing overflow
from the settling basin (blast furnace
and sinter plant).

Total suspended solids exceeded the limit
by 1287 kg/day due to clarifier shut
down for cleaning and high river TSS
background (blast furnace and sinter

Suspended solids maximum concentration
exceeded by 10 mg/x, due to excess over-
flow from the recirculation system
(blast furnace and sinter plant).

Total suspended solids exceeded the limit
by 149 kg/day due to an electrical mal-
function (blast furnace and sinter

Same as above, but by 198 kg/day.
Phenol 8% high in one outfall.  Probably
due to discharge from gas drip legs in
the vicinity of the outfall.  These
will be incorporated in gas washer
water recirculation system.
Phenol high due to gas drip legs in
Blast Furnace non-contact cooling water
and process water.
daily limit
daily limit
 daily limit
 daily limit
 daily limit
 found in one

     In order to prevent AOC associated with water quality problems in a blast

furnace recirculation system the following measures should be taken:

     1.   Provide for the control of the scaling index in the system.
          This may require the addition of acid and scale inhibitor
          compounds.  It is necessary to have a scheduled program
          for analyzing the quality of water in order to assure
          that scaling conditions are avoided.

     2.   At points in the system that are particularly susceptible
          to scaling, it is desirable to provide a bypass section
          which will permit inspection for observation of actual
          scaling conditions without the necessity of having to
          interfere with the operation of the recirculated water

     3.   Scrubber spray nozzles should be as large as possible
          to minimize the effect of any scaling which does occur.

     4.   The blowdown from the recirculated system should be
          carefully monitored  in order to assure minimum quantity
          of blowdown consistent with permissible levels of dissolved

     5.   Components of the system should be selected with attention
          to the potential for scaling conditions.  In particular,
          the cooling tower should have open internals without baffles
          to avoid premature failure from the accumulation of scale

     If all of the above are observed AOC resulting from problems with water

 quality will be minimized.
     A  typical  recirculating water  system may have 20 to 30 pumps or more and

 in  addition,  perhaps  four times  as  many  valves.  Because of the heavy abrasive

 particulate matter in the water,  life  expectancy of a pump unit handling the

 slurry  is  usually  about  one to two  years, although reports of four to six

 months  are not  uncommon.    The  combination  of a large quantity of pumps with a

 relatively short life results in the necessity of almost constant attention and

 maintenance of  these  units to keep  the system operative.  It also mandates that

 all pumps  have  standby units in  order  to avoid AOC.

     There are two areas in the pumps which give particular problems.  One is
wear in the pump impeller.  This may be minimized by the use of hard abrasion
resistant materials or rubber linings and by the selection of as low impeller
speed as is feasible in consideration of pumping requirements.  The other
area of high maintenance is the pump seal.  The usual  method of overcoming
this problem is to use clean pressurized service water on the seals of
horizontal pumps or to avoid seals entirely by the use of vertical  pumps.  In
the latter case, it is desirable to have the shaft of cantilevered design so
as to avoid any bearings in the water.
     One of the special problems in the handling of slurry is that its high
density leads to rapid settling in the sumps and in pipelines.  It is impor-
tant when designing the system that any sections of piping or sumps which may
become isolated and, therefore dead, or that any pocket in which the circu-
lation rate becomes substantially reduced must be eliminated or held to the
minimi urn possible.
     In most recirculated systems for blast furnace scrubber water, the
system is retrofitted to existing furnaces.  If space is limited, the sumps
for collecting water from the coolers and scrubbers may be too small for
smooth pump operation.  Because they are small, they are unable to even out
the variations in flow from the system.  They are also unable to provide a
reasonable surge capacity without a large variation in head to the suction of
the pump.  Any small upset in the system may cause an overflow from the pump
to the plant sewers.
     Also, if space is congested at the blast furnace, the pump house for the
slurry pumps is apt to be too small for the condition of the pumps.  Bearing
in mind that the pumps must be serviced on a regular basis and repaired at
frequent intervals, it is of great importance that there is adequate space
around the pumps for servicing them, good handling facilities for removing
and replacing pumps and lay down area for working on the pumps that have been
removed.  Adequate floor drains should be provided to avoid any messes and
pools of water that may otherwise occur from leaking seals and the like.
Entrance and egress from the building should be convenient so as to facilitate
the movements of the operating and maintenance personnel.  Finally, ventilation
should be adequate so as to avoid the potential accumulation of toxic carbon
monoxide gas.

     The single most important item in avoiding AOC as a result of pump
failures is to provide an adequate amount of redundant pump capacity.  This,
coupled with a good preventive maintenance program and prompt repairs of worn
out pumps can substantially avoid AOC due to pump failures.  In one plant,
where pump problems are rather substantial, there is a diversion sump between
the sewer which receives the overflow from the slurry pumps and the receiving
body of water.  As the level in this sump raises, it returns contaminated
water via a second sump back to the slurry system.  This diversion sump has
an emergency weir which overflows to the sewer.  A level recorder on this
diversion sump has indicated that overflows have occurred about once a week.
     A clarifier for blast furnace service should have a specially high
capacity rake drive and provision for automatic lifting of the rake mechanism.
Both features are required because of the high density of the sludge.  They
are aggravated if very coarse particulate matter (-1/4 inch + 100 mesh) is
permitted to enter the clarifier.  Because this material also tends to plug
the piping from the clarifier to the sludge pumps, all pipelines should be
equipped with cleanout plugs and blowout connections in order to facilitate
the removal of stoppages.  One plant   which had experienced difficulties
with stalling of the rake drive and plugging of the underflow piping has
evolved a procedure which tends to overcome the problem.  The blast furnace
clarifier in that plant is equipped with two underflow lines and two pumps,
one on-stream and one on standby.  The pump on standby is given prompt corrective
and preventative maintenance so that it is always ready for immediate use.
If there is evidence of plugging, both underflow pumps are immediately put
on-stream.  This tends to clear the blockage.  In addition, this plant has
found it desirable to provide a second clarifier as backup for the first
which may then be shut down for repairs or cleaning without interfering with
the operation of the recirculated water system.
     One blast furnace plant27 has provided a coarse wire mesh screen over
the entire clarifier in order to avoid the entrance of large lumps of foreign
matter.  There have been occassions where nut coke from the blast furnace has
entered the recirculated water system and eventually plugged some of the

cooling tower sprays.  In one plant,   rake failures on one clarifier have
been found to occur up to 2 times per year, mostly as a result of heavy grit
material coming over from the blast furnaces.  This plant has two clarifiers,
both on continuous operation.  When a clarifier fails, all  of the dirty water
is diverted to the one still operating.  The quality of water leaving the one
still in operation decreases, but increased addition of polymer is used to
improve the rate of sludge settling.  Sometimes solids carry over into the
hot well and settle, necessitating the cleaning of the hot well.  In this
plant there are two hot wells, permitting one to be down for cleaning.
Occasionally, solids carry over to the cold well of the cooling tower making
it necessary to clean that sump as well.
     As discussed previously under process upsets, conditions may occur in
the injection of oil in the blast furnace which result in the formation of
carbon  black.  The carbon black enters the water systems, finds it way to the
clarifier where it floats on the surface and becomes a mass which interferes
with proper operation of the clarifier and which may be blown into the at
mosphere.  A wetting agent may be used to entrain the carbon black with the
water,  however, the best procedure is to avoid the formation of the carbon
     Filters for dewatering the blast furnace sludge are usually quite reliable,
although one plant   which initiated operation with only one filter found it
necessary to install a second one subsequent to commissioning the plant.
Originally, when one filter was down for maintenance the sludge was pumped to
a pond  in the ore yard.  This pond has two to three days holding capacity.
Further filling causes an overflow to the pellet storage area which, after
drying  takes place, becomes a source of fugitive emissions.  The second
filter  helps to overcome the necessity of having to pump to the pond because
it provides redundant capacity.  Another plant found it highly desirable to
provide variable capacity sludge pumps in order to insure uniform sludge
loadings to the filters with varying densities of underflow from the clarifier.
The installation of a barometric leg between the vacuum pump inlet and the
filtrate-air separation tank increased the reliability of that unit.  This

item prevents the entrance of abrasive slurry into the pump in case the
filtrate-air tank water level gets too high.  It is also desirable that all
overflows from the vacuum be run through open drains as opposed to enclosed
pipelines.  This facilitates the removal of any blockages which may occur.
As indicated under the heading Water Quality, above, it is necessary to
blowdown a portion of the recirculated water in order to avoid the buildup of
dissolved solids.  Common practice is to discharge a portion of the clarified
water to a receiving stream.  One plant14 has permission to discharge it to
the sanitary sewer system of the municipality.  Another plant17 uses this
water to cool the slag in the slag pits of the blast furnace where it is
evaporated.  This last practice increases emissions of dissolved organics
to the atmosphere.
General Operation
     One of the problems in retrofitting a recirculating water system to an
existing blast furnace is to prevent hydraulic imbalance.  Imbalance may be
the result of unaccounted-for discharges into the system, leakage into various
underground sewers and sumps that are too small.  Diligence must be applied
to isolate and remove from the system the unwanted in-flows.  Good communica-
tion between the operators of the blast furnace and the pump tenders
associated with the water system should be established in order that changes
in water flow at the furnaces can be made without upsetting the water balance
in the circulation loop.  In one plant,  the recirculation system incorporated
sealed dump tanks at each blast furnace.  When individual furnaces are
periodically shut down, the furnaces are isolated from the clean gas main by
filling the gas cooler with water until a seal is formed between the clean
gas main and the furnace.  When the furnace goes back on-line, this water has
to be dumped to permit the flow of gas through the gas cleaning system.  The
dump tank is designed to prevent a rapid surge of 15,000 gallons, the volume
of the water seal, through the water system which might cause an imbalance in
the pumping system.  A seal dump tank works as a holding tank into which the
water seal can be dumped quickly and then metered back at a much smaller flow

     In one plant,   monitoring instruments in the recycle water system that
alerts operators to impending upsets include the following:
                              HIGH PRESSURE ALARMS
                    1.   Slowdown discharge
                    2.   Hot well discharge
                               LOW PRESSURE ALARMS
                    1.   Slowdown discharge
                    2.   Hot well pumps
                    3.   Cold well pumps
                    4.   Seal water
                    5.   Instrument air
                         - Hot well high level
                         - Hot well low level
                         - Cold well pumps on hot well level control
                         - Cold well discharge low temperature
                         - Cold well discharge high temperature
                         - fans high vibration (cooling towers)
                    6.   Recorders are maintained on the following
                         - Cold well discharge rate
                         - Slowdown discharge
                         - Cold well discharge temperature
                         - pH of diversion chamber
                         - Hot well discharge pH
                         - Monitor rake torque
      In the above mentioned plant, staffing to operate the recycle system
 includes one operator, one pump man, and one filter man assigned on three
 shifts per day.  Maintenance requires two to four millwrights on the day
 shift plus two electricians as required.
     Figure 14 shows a simplified diagram of the recirculated water system at
 Inland Steel Company.  There are several features in this system that con-
 tribute to good operaton as follows:

                  BLAST FURNACES-31 to #6
                 1	T-
                    Gas  Coolers

* * * \ J 4 |
Gas Scrubbers
r I T" --



17cnn „,, • Cooling,
10900 G?
         Gas Scrubber
         (Dig out
       ones per year)
                                     Make up
                                      865 GPM
        Gas Cooler
slow down to ~~
Terminal Treatment
Basin  700/800 GP
Figure  14.  Inland Steel blast furnace water system.

     1.    The gas  cooler and scrubber systems  are separate loops,
          with the makeup water being supplied to the  cooler loop
          which in turn  blows down  to the scrubber loop.   This  has
          the advantage  of reducing the  hydraulic load to  the
          clarifier and  in consequence its size.   It also  assures
          a cleaner supply of water to the gas coolers.

     2.    The blowdown from the system is discharged to a  terminal
          treatment basin.  Thus any upset in  the recirculation
          system which might result in AOC is  prevented by further
          treatment of the effluent.

     Figure 15 shows the gas cleaning system for  No. 13 Blast Furnace at the

Gary Works of U.S. Steel.  Some noteworthy features here are as follows:

     1.    A pug mill at  the dust catcher is used  to condition the dust
          with water so  as to avoid emissions  from the handling of
          the dry  dust.

     2.    A high differential pressure for the gas scrubber provides  high
          efficiency of  gas cleaning.

     3.    The classifier which preceeds  the thickener  protects  that
          unit from coarse particulate matter  and reduces  the potential
          for jamming and plugging.

                                                 [SCRUBBER AP: 150-180 INCHES WATER]
                                                                                                  BLAST FURNACE	
                                                                                                  GAS TO STOVES, ETC.
                                                                                         SOLIDS t DISC FILTER (2)

                                                                                           SINTER PLANT
                 Figure 15.   Gas cleaning system  for No. 13  Blast Furnace - U,  S,  Steel,  Qary Works,

                                 5.0   GRAY AREAS

     There are three locations  in the  blast  furnace operation where  emissions
to the atmosphere take place  and  do so in variable quantities due  to certain
factors.  These are the emissions from cooling  the slag,  the emissions  from
bell leakage and emissions  from casting the  furnace.   Emissions  from handling
the slag may vary due to the  method of cooling  the slag and the  amount  of
water used, if any.  The emissions which result from  the  cooling operation
may be considered to be normal  with respect  to  the type of operation in-
volved.  There is also no control  equipment  applied in current technology.
For both of these reasons,  any  variations in emissions from the  cooling of
slag is not considered AOC.
     The other two locations  in which  variable  emissions  occur require  more
extended explanations as is given below.
Emi s s i on s from Be11s
     An estimate in a Battelle  document,   of leakage from the bells of blast
furnaces in the United States is  given by the expressions:
               Gas leakage  *  500  + 1500 N cfm = 14.2  + 42.5 N scm
     where N equals the number  of years in service.
     The same document uses the production data of 1973 where N  =  6.9 years
to calculate a total leakage  of blast  furnace gas in  the  amount  of 23.6 x
109 scm (833 x 109 cubic feet)  for 1973.
     The gas that leaves the  furnace contains the following gaseous  components:
                                            Typical        Range
                    Carbon  Dioxide, C02 =       11.5%        8-15%
                    Carbon  Monoxide, CO =       27.5         23-33
                    Nitrogen, NZ         =       60.0         50-60
                    Hydrogen, H2         =       1.0         1.0-3.5

                                  TOTAL     100.0

     The actual amount of each component will vary with the individual blast
furnace and its mode of operation.  For example, the amount of hydrogen will
be increased by such factors as high humidity of the hot blast and high rates
of fuel injection in the tuyeres.
Blast Furnace Top Emissions From Bells
     Blast furnace gas as it leaves the burden and enters the uptakes has an
average volume of 1800 scm/Mg  (63,500 scf/ton) and contains an average of 84
Ibs/ton (42 kg/Mg) particulate matter20  This dust loading equates to 21.2
g/scm  (9.26 grains per SCF).  A typical analysis of the flue dust particles
is as  follows:

El ement
Carbon (as coke fines)
           *Particles  are expected  to  show considerable variation in

      The typical  particle size for blast furnace dust is as follows:


Particle Size + 635
635 -
423 -
317 -
254 -
169 -
127 -
102 -
94 -



11 % by wt.
100 %

     A new bell  on a blast furnace is  normally machined  so that it fits to its

seat within 50 microns (0.002").   Referring  to Figure  16 which  is  a plot of
the data in Table 8, about 28 percent  of the particles in  raw blast furnace gas

is less than 50 microns and can pass through the seat  of the bells when the

seat is in new condition.   This means  that there is  a  potential of emitting

approximately 28 percent of the particulates in the  raw  gas annually through
the bells.

     There are several factors which must be considered  in assessing the above

     1.   Apparently the Battelle formula was based  on the graph
          which was derived from Japanese blast furnaces operating
          in the range of  69 to 148 KPa  (10  to 21.5  psig).  Since
          most blast furnaces in the United  States operate in the
          range of 31  to 34 KPa (4 1/2 to 5  psig), the correction
          factor for the formula and for the corresponding gas
          and dust quantities should be
                                         =  0 55 - -t/Av9- Pressure US
                                                 " if Avg. pressure Japan
     2.    The gas  leakage was  based on a service life of N = 6.9 years
          In the U.  S.,  most companies  change bells  every 5 years and
          the average life is N =  2.5 years.   The correction factor
          -   -  --,  li.-
for bell life is:

                                   =   0.36


                        x -*
                             4     6     100        2
                             Particle Slze-Mlcrona,
Figure  16.  Plot  of the data presented in Table  8,

     3.    The  amount of particulates which leaks from the bells may
          be reduced by virtue of the filtering action that takes
          place when burden material is on the bells.
     4.    The  amount of particulates (and gas) which leaks from
          the  bells may be increased substantially through seats
          that are worn out and cut by the dust-laden gas.
     5.    It  is assumed that  the calculations on gas leakage
          relates  to a furnace equipped with two bells.  Some
          new  ones have three bells and use nitrogen for
          pressurizing.   Some use an arrangment which replaces
          at  least one of the bells with a valve having a soft
     The correction estimate  for leakage of blast furnace gas from the  bells
     (23.6 x  109)  x 0.55  x 0.36 = 4.65 x 109 m3 (165 x 1011 ft3) annually
of which
          Carbon  monoxide is  about 27.5 percent or 1,498,000 Mg
          (1,650,000 tons)
          Hydrogen is about 1 percent or 3,630 Mg (4,000 tons)
     Using a  gross loading of 21.2 g/scm (9.26 gr/scf) for the raw gas  and  28
percent of that  amount  in the gas leaked, the estimate mass of particulates
          '28 X 7m x 1610   = 30»000 tons
          giving an emission  factor of  0.3  g/kg  (0.60  Ibs/ton) of  iron.
     The above estimates are  based  on data,  some  of which  has not  been  verified.
Members of the American Iron  and  Steel  Institute  task  force  assisting with this
study and review of the documents produced  believe that  the  above  estimates
significantly overstate the case  of bell  leak emissions.   Although they
cannot be accepted as accurate, they indicate that the problem may have
national significance to air  quality and  may be of particular significance in
certain non -attainment localities.   The available data are so few  that  this
is an area in which further research is a necessity.   On any particular blast
furnace, as service life on a particular  bell increases, the emissions  past
its seal become greater.  The question  is whether the  increase in  emissions

are "normal" or AOC.  The  former  appears  to  fit  better and  thus  the  problem
is listed as a "gray" area.
Emissions From Casting
     At the present  time,  there are only  a few blast  furnaces  in the United
States which are  equipped  with environmental  control  systems to  capture the
emissions which result  from casting the blast furnace.   In  such  systems as
are installed to  date,  one of the key elements of control is a building
evacuation system for the  cast house itself.   For those cast houses where no
control is installed, there are numerous  variations in process and operating
conditions which  may increase emissions to the atmosphere.  These are described
below.  For cast  houses that are  equipped with environmental controls, the
variations in emissions from the  process  do  not  have  a significant effect on
the atmosphere, but  only on the amount of capture in  the final control
     Generally speaking, smooth furnace operation leads to  minimal casting
emissions.  The blast furnace operator finds it  to has advantage in terms of
economic  production  of  iron to aim for as smooth a performance as is possible
consistent with the  technical capability  of  the  furnace, its raw materials,
etc.   He  thus has an incentive to operate in such a manner  and to minimize
emissions to the  atmosphere from  upsets.  If the current trend of providing
control for blast furnace  cast houses continues, such upsets as  do occur will
not produce significant AOC.  For these reasons, upsets which  cause excess
emissions are not classified under AOC in this report, but  are described
 below  under "gray" areas.
Tap Hole  Related
      Emissions from  casting are  particularly heavy at the tap  hole of the
furnace.  In recent  years, the trend toward  larger furnaces and  higher top
 pressure  has  increased  the problems with  the tap hole and the  potential of
emissions.  In the past, a carbonaceous clay tap hole mix with approximatly
 16 percent moisture  content was  used.  This  wetness caused  a cloud of iron
oxide  fumes to be released whenever the tap  hole was  opened.     Such a tap
 hole  eroded quite rapidly  and by  the end of  the  cast, it was usually necessary
to pull wind  in order to control  iron flow.   Recent work has been directed


toward altering the mixes  by using  chemical  binders  and  adding  calcines.   The
resulting mixes are stronger but more  difficult  to push.   To  accommodate  the
stiffer mix, the mud gun may have to be modified to  increase  nozzle  pressure.
At the same time, it is necessary to insure  that the tap hole drill  has
adequate capacity to penetrate the  new mixes.
     Conventional tap hole mixes are particularly deficient when  using higher
blast pressures.  In the Gary No. 13 Blast Furnace,  it was found  that when
the blast pressure was increased to between  275  to 345 KPa (40-50 psi) the
tap hole glaze could not withstand  erosion during the cast.   It was  not
uncommon to have the tap hole erode until it was larger  than  the  mud gun
nozzle, 15.5 cm (6").  With their current practice of using anhydrous mixes,
the erosion problem has been overcome.  This is  important in  regard  to
emissions because erosion  of tap holes increases the flow of  iron and slag
thereby causing increased  emissions even though  the  time period has  been
shortened.  Not only is there improvement in this area,  but there is a signi-
ficant decrease in the number of coke  messes which are caused by  coke being
thrown out of the eroded tap hole.
Casting Emissions
     A slow cast, because  emissions persist  over a longer period  of  time, can
result in an increased mass of emissions per cast.   This is especially true
when the slag is too limey, or there is a restriction of the  tap  hole.  It is
avoided by keeping a reasonable length of tap  hole and maintaining proper
slag chemistry.  It is reported that slow casts  may  occur five  times a week
on a particular furnace and may last for one to  one  and  a half  hours.
     Hot limey slags increase the amount of  white fume coming from the slag.
These are especially prevalant after the blow-in of  the  furnace as is discussed
earlier in the manual.  After that, it may occur as  frequently  as once per
day or as long as once in  several months.  Emissions from limey slag may last
45 minutes per cast.  They are avoided by keeping the furnace slag as lean as
is possible yet still meet sulfur specifications, the higher  the  sulfur
allowed the leaner the permissible  slag.  Lean slags also are conducive to
smoother furnace operation, lower coke rates,  and higher productivity.  One

way of permitting a blast furnace  to operate with higher sulfur in the iron
is to provide an external desulfurizing facility for the iron.
     When the molten  iron is  low in silica and high in sulfur, it tends to
tap colder than normal and  results in  increased emissions of reddish fumes
and kish.  This may occur twice a  week.   If the final blow of one cast is
"cold", the ensuing cast could also be cold.
Burning of Skull
     If a skull develops inside the tap hole of the furnace, it may be
necessary to  lance it with  oxygen. This  can cause an emission of reddish
fume for a period of  five to  10 minutes.  The necessity for lancing with
oxygen is more  likely to exist in  the  case of a rotary tap hole drill  than in
the case of a percussion type tap  hole drill.  The latter type drill  is
usually more  able to  penetrate the skull  than the former.
5.1.1  Process  Related
       In the preceding  sections of the manual, various methods of minimizing
process related AOC were described.  A summary is given below:
     1.   Provide a properly  screened  and sized burden.
     2.   Provide high stability coke, at least 50, although 55 is
          better.  This  tends to avoid coke messes.
     3.   Provide adequate  furnace instrumentation and control.
     4.   Use anhydrous  tap hole mixes to avoid fast casts and
          reduce coke messes.
     5.   Direct attention  to improved construction of the furnace
          top such as hard  facing  of bell seats, provision of bell
          sealing rings, nitrogen  equalization, etc.
     6.   Provide computer  control of  furnace operations, if tech-
          nically and economically feasible for the furnace involved.
     7.   Provide control of  moisture  in  the hot blast.  This will
          move  the furnace  better.
     8.   Provide control for the  distribution of fuels which are
          injected into  the tuyeres.   This helps to move the furnace,
          avoids formation  of carbon black and increases the
          efficiency  of energy utilization.

     9.    Provide external  desulfurization  of iron.   This results
          in smoother furnace  operation  and uses  less stone and
          coke as well  as  produces  more  tons of iron.
     10.  Increase the emphasis  on  preventative maintenance.
5.1.2  Control Equipment Related
     1.    Provide all pumps with standby units.
     2.    Provide adequate space and means  for servicing pumps.
     3.    Provide adequate surge capacity in sumps and retention time
          in recycle systems in  order to avoid pumping problems
          and hydraulic imbalances.
     4.    Control pH in recycled water to avoid scaling.
     5.    Install instrumentation for monitoring  and alarm.
     6.    Use scrubbers which  have  large nozzles  which minimize
          plugging problems.
     7.    Use scrubbers which  have  variable throats  to maintain
          desired pressure drop.  Flooded scrubber walls are
          desirable to minimize  wear.
     8.    Provide a discharge  tank  for gas  seal water in order
          to permit rapid  dumping of the gas seal  so as to
          avoid system imbalances.
     9.    Cover clarifier  with wire mesh to avoid entrance of
          foreign objects.
     10.  Provide a barometric leg  between  the filter and the vacuum pump.
     11.  Collect and monitor  discharge  water. Routing it to a final
          treatment basin  provides  an increased measure of safety in
          avoiding AOC.
     12.  Maintain good communications between furnace operators and
          pump tenders.
     One of the most effective ways of measuring  AOC whether process or control
equipment related, is for  the  responsible environmental control agency to
persue an active and diligent  program of monitoring  AOC.  Monitoring reports
from such agencies are a most  valuable record from which to develop normal
operating patterns for the industry.  Frequency and  duration of specifically
defined  AOC's is not at this time clearly defined nor well-known in many cases.

It is recommended, therefore, that  the recording of AOC's be continued by
agencies already doing so, and  be initiated  by those agencies not doing so.
Figure 17 shows an example of a suitable  reporting form.  This example was
developed by drawing  upon the best  features  of several reproting forms
currently in use.
     As stated previously, the  factors that  avoid emissions from abnormal
process conditions also  provide an  incentive to the operator in terms of
increased production  and reduced costs of operation.  All blast furnace
operators would certainly prefer to have  the most modern and most well
maintained equipment  possible as well as  the best burden available so that he
may  be assured of smooth operation.  Unfortunately, factors of plant age,
existing plant limitations,  availability  of  raw materials, economic factors,
etc., prevent the realization of this ideal. In consequence, operations are
often less smooth than desired  and  abnormal  conditions result which cause
excess emissions.
      It  is to be expected that  abnormal emissions due to process upset will
decrease with time.   There are  several pressures which will accelerate progress
toward the goal of  avoiding  upsets.  One  is  the development of new knowledge
and  techniques  in the control of the blast furnace process.  Another is the
economic advantage  of implementing  such advnaces wherever implementation is
feasible.  Finally,  there  is the pressure imposed to meet environmental

Company, Department:

Date of Report:                       Time:
Name and Identification of Unit Involved:
           Telephone No;
Time Incident Occurred:
Starting time of scheduled corrections:
Cause and Description of Breakdown, Detailed:
Corrective action taken/proposed:
Estimated excess pollutant discharge:
Pollutant                Excess Ib/hr
Process Production rate t/hr
If Telephone call:
Person taking call:
Date Entered in Record:
                      Figure 17.  Example AOC report form.

                          6.0  TABULATED SUMMARY OF AOC

     Table 9 summarizes the AOC's described herein.  The identification
of an AOC carries no implication whatsoever concerning liability for
resulting air or water pollution.  Liability for an AOC can only be
determined by the enforcement officer responsible for a given set of
regulations  (NSPS, SIP) or permit requirements (NPDES, special conditions,

                              TABLE  9.    BLAST FURNACE  ABNORMAL OPERATING  CONDITIONS
Effect on
Initial slag Is

Dirty gas

Blowing out
through tap
Extended start-

Excess slips

Needed to coat heart!
& bosh walls to
avoid breakouts
To vent furnaces at

Open tap hole

Electrical & mechani-
cal failures

Hotter than usual

Reduces openings In

Heats furnace hearth

Run w/less basic
slags after 4 days

Close bleeder & put
gas Into mains when
gas conditions war-
Close tap hole when
Iron appears at
Check out equipment
before blowing— keep
mtn. crews available
Use properly screen-
ed burden — don't
overblow. Low blast
Once In 3-4 yrs/fur-

Once In 3-4 yrs/

Once In 3-4 yrs/

I/day during startup

0-2/day during


2-4 days, Bleeders
open 12-24 hours

12-24 hrs. normally.
Documented up to 336

12-48 hrs.

1-4 hrs.

15 sees.

Comments ,

Heavy white smoke
from limey slag —
generally small casts
)1rty gas discharge
to atmosphere

Sas Ignited, dust
Into cast house

Extended emissions
to atmosphere

Gas & participates to
the atmosphere

Some plants
Dpen large
bell as well,
.ess emission
*1th Buffee
Pipe, 2|

                                                           PROCESS RELATED — SHUT DOWN
Blow tap hole
hard after last
Blow dust
catcher hard
Bleeder valve
Power failure
Removes as much Iror
& slag as possible
from furnace

Completely empty
dust catcher
Releases  gas from
furnace after ore
blank or  burden
Plug hole after all
liquid removed

Steam & water sprays
to suppress dust
Plug tuyeres & seal
Once 1n 3-4 yrs/
6-15 times,  30 sees.
Once In 3-4 yrs/
                                                                                               15-45 mlns.
3-7 1/2 mlns/shut
16-24 hrs., Power
failure, 3-4 hrs.
                    Dirty gas to cast
Dirty gas  to
Dirty gas  to atmos-
Some pliants
use normal
dust catcher


         TABLE  9.    (cont'd)
Iron flush to
Effect on
To empty salamander

Once 1n 3-4 yrs/
furnace. 6-8 yrs/lf
hearth goes more
than 20 campaigns
Increased emissions
of participates
common to
all fur-
                                                             PROCESS RELATED — ABNORMAL OPERATING CONDITIONS
         Severe burden
         Water & power
         Charging dusty
         Gases vented to
         air ahead of
         Loss of  igni-
         tion on  gas
Japid movement of
Planned—to make
furnace repairs,
esp. tuyeres
 allure of utility
Failure of lining
cooler, tuyere, etc.
Dry, dusty burden
Stove plugged
Plugged flue line,
low gas pressure
ileeder opens to  re-
lieve excessive top
Gas flow to bustle
pipe reversed
Shut down, potential
of breakouts &

Immediate shut down
Increase participates
in gas
                                              Loss  of  heat values
Reduce wind momen-
tarily to settle
burden (short-term).
Improve burden &
operating practice
Complete repairs
Provide emergency
source of utilities
& steam operated
Repair Immediately

Improve burden pre-
paration of condi-
tioning sprays for
Clean stove
                      Restor  Ignition
1 -50/month

4-50 times/month2

Infrequent, 1/6 or
more months
Once In 2 yrs.

Up to 600 charges/
day average

Up to one/month

5-30 sees.

J hrs.-7 days for
large repair

Up to several days —
avg. 1-3 days
1-30 mins.

5-10 sees.

hr/day for 21 days

-4 hrs.

28 to 276 Ibs/slip
(solid material)

'articulate emissions
bo atmopshere.
tost emissions occur
1n first 15 mins. 8-
12 g/Mg Iron*
Increased emissions

Emission of gas t>
Emissions of partlcu-
ncreased emissions

Clean gas bled to

Based on
30 ft.
furnace ,
for re-

No data
or est.
avail., 24
Amt. of
gas bled

       TABLE 9.    (cont'd)
Formation of
carbon black

Unplugging dust

Improper combustion
of oil In tuyeres

Buildup of solids

Effect on
Inefficient use of

Interferes with gas

Reduce flow of oil
correct distribution

Poke out solids.
Possibly use small
explosive charge


1-8 tlmes/yr.

Variable, Persistent
till corrected

1-8 hrs.

Floating carbon
black In clarlfler

Emission of dirty gas

black may
be blown
to atrai,
29, 30
Can be
by regj
dumping &
                                                      PROCESS RELATED — "GRAY AREAS"
Leaky top

Slow cast

Cold metal

Hot, limey

Wet tap hole,
trough, or
Poor seal of small
or large bell, or
holes In bells

Small tap hole,
Hrney slag

Low silica, high
Improper slag

Improper drying

Loss of gas

Delays cast, lost

Incorrect Iron
cheml stry
High coke rate

Possible explosions

Repair or replace
bell. Change de-
sign of furnace top

Proper tap hole
openings & slag
Better operating
Lean out slag

Thorough drying

Constant 1f both
bells leak. 80
times/day If small,
600 times If large




Should be rare once
1n 3 months

Constant or 5-10
sees. /occurrence

10-60 mlns. excess
time on cast

15-45 mlns.

5-20 mlns.

Discharge of gas &
Dust - 300 g/Mg
CO - 16.5 kg/Hg
H2 - 40 g/Mg

Increased emissions
proportional to
longer tap time
Increased emissions
of klsh
White fumes from
slag. Excess sul-
fur fumes
Emissions from Iron,
sand, slag


      TABLE 9.    (cont'd)
Tap hole en-
larging during
Erosion of tap hole
Effect on
Iron flow Increases
Use of anhydrous
clay will retain
shape of hole better
than water based
4 times/day
20-45 mlns.
Excessive blowing of
dirty gas at tap hole
Very long
using an-
clay may
        Scrubber  pro-
        Loss of water
        Clarlfler rake
Plugged nozzles &
worn Internals

torn Impeller,
leaky seal, plugged
                        Jammed rake
                                                       CONTROL  EQUIPMENT RELATED ~ ABNORMAL OPERATING CONDITIONS
Bleeders opened to
allow large bell to

Loss of gas cleaning
System Imbalance
                     Shut down of clarl-
                                          Institute repairs
Institute repairs

Provide standby unit
make repairs
                      Clean out clarlfler
                      Prevent entrance of
                      coarse participates
                     3-4  tlmes/yr
                                                                                      Infrequent In well
                                                                                      designed scrubber

                    0-2 tlmes/yr
                                                                                                           0.2-48 hrs.
Continuous until

Variable.  Depends
on availability of
standby unit
Variable, 1-3 days
Raw dirty gas from
bleeders 5-10 sees.
80 times/day 42 kg/
1g hot metal
-linimal If repairs
Instituted limed.

Increased solids In
blowdown & Increased
Increased sol Ids 1n
blowdown & Increased
to ter-
may avoid
AOC, 31

to ter-
may avoid
28, 30,

TABLE 9.   (cont'd)
High or low
High TSS dis-
Failure of controls
Spills In cleaning
thickener, broken
lines, etc.
Effect on
High pH causes
scaling. Low pH
Improve pH control
Avoid spills
076 times/yr normal .
15 times/yr recorded

Variable. 1.5 hr 1s

Exceed discharge

samp lino
nay anti-

1.  Many furnaces on good burdens,  especially newer ones with high t6p pressures, rarely have slips.  Furnace prone  to slipping may slip 5-50  tlmes/mon*.
2.  Depends on  age and condition of furnace.
3.  Installation of control equipment  for the cast house will essentially avoid abnormal emissions from casting.
4.  Estimated.

                                 7.0  REFERENCES

1.   Hasegawa, Akira, "Large Blast Furnace Facilities in Nippon Steel  Cor-
     poration," Ironmaking Proceedings, 36_, 137 (1977).

2.   Legille, E. and K. H. Peters, "Operation of a Blast Furnace Incorporating
     a Paul Wurth Bell-Less Top Charging System and its Application to
     Large Blast Furnaces," Proceedings of the 32nd Ironmaking Conference.
     32_, (1973).	a	

3.   Jablin, R., "Expanding Blast Furnace Slag Without Air Pollution,"
     Journal Air Pollution Control Association. 22(3), March 1972.

4.   Steiner, B., "Air Pollution Control," International Metal Reviews.
     September 1976.

5.   White, Douglas, "Blast Furnace Water Recirculation System at Inland
     Steel Co.," Ironmaking Proceedings. 36_, 44 (1977).

6.   Parle, R. W., "Long-Term Shutdown and Subsequent Recovery of Blast
     Furnace Plant," Journal of the Institute of Fuel. June 1972.

7.   G. K. Jefferson, "Operating Experience of No. 13 Blast Furnace, Gary
     Works, U. S. Steel Corporation," Ironmaking Proceedings, 36, 162
8.   Mobley, C.E., A. D.  Hoffman, and H. W. Lownie, "Blast Furnace Slips
     and Accompanying Emissions as an Air Pollution Source," EPA-600/2-76-
9.   Wagstaff, J. B., "A  Report on Solid Movement on Blast Furnace Models,"
     Proceedings Blast Furnace, Coke Oven and Raw Materials Committee.
     AIME, 14, 1955.
10.  Lambert, C., "Operation of Geneva Works Blast Furnaces with High Alkali-
     Bearing Burdens," Ironmaking Proceedings. 35_, 324  (1976).

11.  Nanne, S. E., "Operating Experiences on Algoma's #7 Blast Furnace,"
     Ironmaking Proceedings, 35, 1976.
12.  James, T. E., "Cooling Hazards in High Tonnage Hearths," Ironmaking
     Proceedings, 35_, 241  (1976).
13.  Ziegert, W. L., "Blast Furnace Control at Inland Steel's Nos. 5 and
     6 Blast Furnaces," Ironmaking Proceedings, 36, 298 (1977).

14.  Touzalin, R. E., "Pollution Control of Blast Furnace Gas Scrubbers
     Through Recirculation," EPA/NTIS PB-250-435, July  1974.

15.  Weinberg, W. H., "Blast Furnace Recycle Water System,"  Ironmaking
     Proceedings, 36, 50  (1977).

16.  Bischoff Environmental  Systems,  "Gas Cleaning with Variable Annular-
     Gap Scrubbers," Catalogue.
17.  Farrow, T.  A., "Gary Works  No.  13 Blast Furnace Recycle Water Systems,"
     Ironmaking Proceedings, 36, 40  (1977).
18.  Battelle Columbus Laboratories,  "Potential  for Energy Conservation in
     the Steel Industry," PB-244-097,  pages  V-67 and V-68.
19.  Marks, L. S., Mechanical  Engineer's Handbook, 5th Edition, p. 786.
20.  McGannon, The Making. Shaping &  Treating of Steel, 9th Edition,  p. 457.
21.  Greenawald, R. A. and E.  L. Auslander,  "Burns Harbor High Top Pressure
     Operation - Its Problems  and Rewards,"  Ironmaking Proceedings, 33,
     167 (1974).
22.  Qp. Cit., Reference 7.
23.  Lindau, Lars and Lars Hansson,  "Fugitive Dust from Steel  Works,"  The
     National Swedish Environment Protection Board,  Bo Mansson, Stoft  Tekniska
     Laboratoriet AB, Sweden.
24.  EPA, Effluent Guidelines.
25.  Communication with Bruce  Miller,  EPA Region  IV,  Atlanta,  Ga., February 2,
26.  Trip Report, City of Cleveland Division of Air  Pollution  Control,  January
     25, 1977.
27.  Trip Report, U.S. Steel,  April 21-22, 1977.
28.  Trip Report, Republic Steel,  Gadsden, Alabama,  July 6-7,  1977.
29.  Trip Report, Inland Steel,  East Chicago,  Indiana,  April 19-20, 1977.
30.  Trip Report, Jones and  Laugh!in Steel,  Cleveland,  Ohio, August 2-3,  1977.
31.  Trip Report, Erie County  Department of  Environmental  Quality,  Buffalo,
     N.  Y., June 30, 1977.
32.  Data supplied by EPA, Region  III.

                                TECHNICAL REPORT DATA
                         (f lease read Instructions on the reverse before completing)
EPA- 600/2 -78-118c
                                                      3. RECIPIENT'S ACCESSION NO.
               Pollution Effects of Abnormal Oper-
ations in Iron and Steel Making - Volume D3. Blast
Furnace Ironmaking,  Manual of Practice
                                                      5. REPORT DATE
                                                       June 1978
                                                      6. PERFORMING ORGANIZATION CODE
R.Jablin, D.W.Coy, B.H.Carpenter, and
                                                      8. PERFORMING ORGANIZATION REPORT NO,
Research Triangle Institute
P.O. Box 12194
Research Triangle Park, North Carolina 27709
                                                      10. PROGRAM ELEMENT NO.
                                                      11. CONTRACT/GRANT NO.

 EPA, Office of Research and Development
 Industrial Environmental Research Laboratory
 Research Triangle Park, NC 27711
                                                      13. TYPE OF REPORT AND PERIOD COVERED
Final; 10/76-1/78
                                                      14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES ffiRL-RTP project officer is Robert V. Hendriks,  Mail Drop 62,
is. ABSTRACTTlie repOrt jg one ^ a six-volume series considering abnormal operating
conditions (AOCs) in the primary section (sintering, blast furnace ironmaking, open
hearth, electric furnace,  and basic oxygen steelmaking) of an integrated iron and
steel plant. Pollution standards,  generally based on controlling discharges during
normal (steady-state) operation of a process and control system, are often excee-
ded during upsets in operation. Such periods of abnormal operation are becoming
recognized as contributing to excess air emissions and water discharges. In gen-
eral, an AOC includes process and control equipment startup and shutdown,  substan-
tial variations in operating practice and process variables, and outages for mainten-
ance. The purpose of this volume, which covers the blast furnace ironmaking pro-
cess , is to alert those who deal with environmental problems on a day-to-day basis
to the potential problems  caused by AOCs, to assist in determining the extent of the
problems in a specific plant, and to help evaluate efforts to reduce or eliminate the
problems. The report enumerates as many AOCs as possible, with emphasis on
those which have the most severe environmental impact.  Descriptions include flow
diagrams, material balances, operating procedures, and conditions representing
typical process configurations.                              	
                             KEY WORDS AND DOCUMENT ANALYSIS
                                          b.lDENTIFIERS/OPEN ENDED TERMS
                                                                    cos AT I Field/Group
 Pollution             Shutdowns
 Iron and Steel Industry
 Blast Furnaces
                                          Pollution Control
                                          Stationary Sources
                                          Abnormal Operations

                                          19. SECURITY CLASS {This Report)
                                          20. SECURITY CLASS (Thispage)
                                                                  22. PRICE
EPA Form 2220-1 (9-73)