4504840076
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EPA-450/4-84-007g
July 1984
Locating And Estimating Air Emissions
From Sources Of Chromium
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office Of Air And Radiation
Office Of Air Quality Planning And Standards
Research Triangle Park, North Carolina 27711
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This report has been reviewed by the Office Of Air Quality Planning And Standards, U.S. Environmental
Protection Agency, and has been approved for publication as received from Radian Corporation. Approval
does not signify that the contents necessarily reflect the views and policies of the Agency-, neither does
mention of trade names or commercial products constitute endorsement or recommendation for use.
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TABLE OF CONTENTS
List of Tables v
List of Figures viii
1. Purpose of Document 1
2. Overview of Document Contents 3
3. Background .- 5
Nature of Pollutant 5
Overview of Production and Use 9
Chromium production 9
Chromium uses 19
References for Section 3 27
4. Chromium Emission Sources 29
Direct Sources of Chromium 30
Chreunite ore refining 30
Ferrochromium production 33
Refractory manufacture 52
,*
Chromium chemicals manufacture 64
Chromium plating 77
Steel production 91
Electric arc furnaces and argon-oxygen
decarburization vessels .* 91
Basic oxygen process furnaces 124
Open hearth furnaces 135
Leather tanning 140
Indirect Sources of Chromium 147
Coal and oil combustion 147
Cement production 160
Municipal refuse and sewage sludge
incineration 165
iii
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TABLE OF CONTENTS (Continued)
5.
Cooling towers ,
Asbestos mining and milling
Coke ovens
References for Section 4 ,
Source Test Procedures ,
Literature Review of Sampling Methods
Faze
174
181
189
196
209
209
Literature Review of Analytical Methods 210
Extraction procedures . 210
Analysis procedures 213
References for Section 5 221
iv
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LIST OF TABLES
Table
1 Physical Properties of Chromium 6
2 Oxidation States of Chromium in Various Chromium
Compounds and the Major Physical Properties of
These Compounds 7
3 Composition of Typical Ferrochromium Alloys
and Chromium Metal 13
4 List of Commercially Produced Secondary Chromium
Chemicals and their General Uses 18
5 Major Chromium Uses and Key Chromium Chemicals Involved ... 25
6 Chromium Emission Factors for Chromite Ore Refining 33
7 Chromium Emission Factors from Processing of
Raw Materials at Ferrochrome Plants 48
8 Chromium Emission Factors from Finishing Operations
and Product Handling at Ferrochrome Plants 50
9 Chromium Emission Factors for Electric Arc Furnaces
Used to Produce Ferrochromes 51
10 Location of Plants Producing Chromium Ferroalloys
as of 1980 53
11 General Chromium Emission Factors for the
Refractory Industry 63
12 Controlled Chromium Emission Factors for the
Refractory Industry ..*,. 65
13 Locations of Plants Producing Chromium Refractory
Materials , 66
14 Chromium Emission Factors for Sodium Bichromate
Manufacturing * 75
15 Chromium Emission Factors for Chromic Acid Production 76
16 Locations of Sodium Chrornate and Sodium Bichromate
Manufacturing Plants 77
17 Locations of Companies Producing Secondary Chromium
Chemicals 78
18 Typical Chromium-Plating Conditions Using
Conventional Baths 87
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LIST OF TABLES (Continued)
Table Page
19 Uncontrolled Chromium Emission Factors from One
Hard Chromium Plating Facility 90
20 Fugitive Emissions Capture Technology Combinations
(Carbon and Specialty Steel EAF) 112
21 Fugutive Emissions Capture Technology Combinations
(Specialty Steel ADD) 115
22 Uncontrolled Chromium Emission Factors for Electric
Arc Furnaces (EAFs) and Argon-Oxygen Decarburization
Vessels (AODs) 117
23 Chromium Content of Electric Arc Furnace Dust for
Each Step of Furnace Operation at One Facility 118
24 Locations of Electric Arc Furnaces in the
United States — 1981 119
25 Location of Steel Plants with EAFs and
AOD Vessels — 1981 ; 122
26 Locations of Argon-Oxygen Decarburization (AOD)
Vessels in the United States in 1981 123
27 Locations of Basic' Oxygen Process Furnaces (BOPFs)
in the Iron and Steel Industry 137
28 Locations of Steel Plants with Open Hearth Furnaces 141
29 Largest U. S. Leather Tanning Facilities and Locations .... 145
30 Chromium Content of Domestic Coals by Type 148
31 Chromium Content of Domestic Coals by Source 148
32 Chromium Content of Various Crude and Fuel Oils 149
33 Chromium Collection Efficiencies for Electrostatic
Precipitators 152
34 Chromium Collection Efficiencies for Fabric Filters 152
35 Chromium Collection Efficiencies for Wet Scrubbers 153
36 Chromium Emission Factors for Oil Combustion 155
37 Chromium Emission Factors for Coal Combustion 157
vi
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LIST OF TABLES (Continued)
Table
38 Chromium Emissions Factors for Cement Plants 164
39 Design Temperature Profile of a Sewage Sludge
Multiple Hearth Furnace ..,.,, , 170
40 Emission Factors for Chromium from Municipal
Refuse and Sewage Sludge Incinerators 173
41 Population of Municipal Refuse and Sewage Sludge
Incinerators in the United States in 1983 175
42 Chromium Emission Factors for Fresh Water Utility
Cooling Towers 180
43 Chromium Emission Factors for Asbestos Mining
and Milling 188
44 Locations of Asbestos Mines and Mills in 1981 190
45 Coke Plants in the United States as of January 1980 193
46 Instrumental Methods for the Determination of
Chromium 214
vii
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LIST OF FIGURES
Figure
1 Simplified flowchart for the production of chromium
compounds and metallic chromium from chromite ,... 10
2 Industrial recycling/reuse flow of chromium scrap 15
3 Primary and secondary use distribution of chromium
in the United States 20
4 Final consumer use distribution of chromium in the
United States in 1981 21
5 End use tree for sodium dichromate in 1982 24
6 Flow chart for chromite ore "refining 31
7 Flow chart of ferrochrome production by the electric
arc furnace process 35
8 Open electric arc furnace * 37
9 Seraisealed electric arc furnace 39
10 Sealed electric arc furnace 40
11 Typical flow chart for the production of low-carbon
ferrochrome by the exothermic silicon reduction
process 42
12 Vacuum furnace for the production of low-carbon
ferrochrome 43
13 Flow chart for production of chromium-containing
basic brick by casting and pressing processes 55
14 Flow chart for production of chromic oxide bricks
by casting and pressing processes 56
15 Flow chart of production of unformed refractories 57
16 Flow chart for the production of sodium chrornate 69
17 Flow chart for the production of sodium dichromate
from chrornate liquor 70
18 Flow chart for chromic acid production 73
19 Flow chart for decorative chromium plating on a
steel substrate 83
20 Flow chart for hard chromium plating 84
21 Cut-away view of electroplating tank 86
viii
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LIST OF FIGURES (Continued)
Figure Page
22 Typical electric arc steel furnace 94
23 Argon-oxygen decarburization vessel 98
24 Direct-shell evacuation control (two views) 104
25 Side draft hood (two views) 105
26 Canopy hood capture system 107
27 Partial furnace enclosure 108
28 Total furnace enclosure 109
29 Diverter stack with canopy hood 113
30 Close-fitting hood with canopy hood 114
31 Top blown and bottom blown BOPF vessels 125
32 Steps for making steel by the basic oxygen process 128
33 Time sequence of top blown BOPF operations 129
34 Schematic cross section of a furnace shop '. 130
35 Geographic distribution of the U. S. BOPF steelmaking
facilities in 1982 136
36 Flow chart for leather tanning process at plants
which formulate their own chromium sulfate
tanning solution 143
37 Basic process flow diagram for. wet and dry cement
production plants 161
38 Basic configuration of a municipal refuse
incinerator 167
39 Schematic diagram of a typical multiple-hearth
sewage sludge incinerator 168
40 Schematic diagram of a fluidized-bed sewage sludge
incinerator 171
41 General mechanism of chromium emissions from
cooling tower drift 178
42 Concentration of chromium in air as a function of
distance from the cooling tower 179
43 Crushing of massive chrysotile ore 182
ix
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LIST OF FIGURES (Continued)
Figure Page
44 Generalized flow sheet of an abestos milling process 184
45 Metallurgical coke oven battery 191
46 Organic chromium species sampling configuration 211
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SECTION 1
PURPOSE OF DOCUMENT
The U. S. Environmental Protection Agency (EPA), States, and local air
pollution control agencies are becoming increasingly aware of the presence
of substances in the ambient air that may be toxic at certain concentrations
This awareness, in turn, has led to attempts to identify source/receptor
relationships for these substances and to develop control programs to.
regulate emissions. Unfortunately, very little information has been
available on the ambient air concentrations of these substances or on the
sources that may be discharging them to the atmosphere.
To assist groups interested in inventorying air emissions of various
potentially toxic substances, EPA is preparing a series of documents such as
this that compiles available information on sources and emissions of these
substances. This document specifically deals with chromium. Its' intended
audience includes Federal, State, and local air pollution personnel and
others who are interested in locating potential emitters of chromium and
making gross estimates of air emissions therefrom.
Because of the limited amounts of data available on chromium emissions,
and since the configuration of many sources will not be the same as those
described herein, this document is best used as a primer to inform air
pollution personnel about (1) the types of sources that may emit chromium,
(2) process variations and release points that may be expected within these
sources, and (3) available emissions information indicating the potential
for chromium to be released into the air from each operation.
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The reader is strongly cautioned against using the emissions
information contained in this document to try to develop an exact assessment
of emissions from any particular facility. Since insufficient data are
available to develop statistical estimates of the accuracy of these emission
factors, no estimate can be made of the error that could result when these
factors are used to calculate emissions for any given facility. It is
possible, in some extreme cases, that orders-of-magnitude differences could
result between actual and calculated emissions, depending on differences in
source configurations, control equipment, and operating practices. Thus, in
situations where an accurate assessment of chromium emissions is necessary,
source-specific information should be. obtained to confirm the existence of
particular emitting operations, the types and effectiveness of control
measures, and the impact of operating practices. A source test and/or
material balance should be considered as the best means to determine air
emissions directly from an operation.
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SECTION 2
OVERVIEW OF DOCUMENT CONTENTS
As noted in Section 1, the purpose of this document is to assist
Federal, State, and local air pollution agencies and others who are
interested in locating potential air emitters of chromium and making gross
estimates of air emissions therefrom. Because of the limited background
data available, the information summarized in this document does not and
should not be assumed to represent the source configuration or emissions
associated with any particular facility.
This section provides an overview of the contents of this document. It
briefly outlines the nature, extent, and format of the material presented in
the remaining sections of this report.
Section 3 of this document provides a brief summary of the physical and
chemical characteristics of chromium, its commonly occurring forms, and an
overview of its production and uses. A chemical use tree summarizes the
quantities of chromium produced by various techniques as well as the
relative amounts consumed in various end uses. This background section may
be useful to someone who needs to develop a general perspective on the
nature of the substance and where it is manufactured and consumed.
Section 4 of this document focuses on major industrial source
categories that may discharge chromium-containing air emissions. Section 4
discusses the production of chromium and chromium compounds, the use of
chromium as an industrial feedstock, and the discharge of chromium from
industrial sources due to its being a trace contaminant in fossil fuels.
For each major industrial source category described in Section 4, example
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process descriptions and flow diagrams are given, potential emission points
are identified, and available emission factor estimates are presented that
show the potential for chromium emissions before and after controls employed
by industry. Individual companies are named that are reported to be
involved with either the production and/or use of chromium based on industry
contacts and available trade publications. Where possible, the chemical
form of chromium emissions is identified as this parameter is important in
considerations of health effects.
The final section of this document summarizes available procedures for
source sampling and analysis of chromium. Details are not prescribed nor is
any EPA endorsement given or implied to any of these sampling and analysis
procedures. At this time, EPA has generally not evaluated these methods.
Consequently, this document merely provides an overview of applicable source
sampling procedures, citing references for those interested in conducting
source tests. .
This document does not contain any discussion of health or other
environmental effects of chromium, nor does it include any discussion of
ambient air.levels or ambient air monitoring techniques.
Comments on the contents or usefulness of this document are welcomed,
as is any information on process descriptions, operating practices, control
measures, and emissions information that would enable EPA to improve its
contents. All comments should be sent to:
Chief, Source Analysis Section (MD-14)
Air Management Technology Branch
U. S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
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SECTION 3
BACKGROUND
NATURE OF POLLUTANT
Pure chromium is a steel-gray, lustrous, hard crystalline metal. It
occupies the 24th position in the Periodic Table and belongs to transition
group VIB along with molybdenum and tungsten* It comprises about 0.037
percent of the earth's crust and therefore ranks 21st in relative natural
abundance. It is more abundant than cobalt, copper, lead, nickel, cadmium,
1-3
molybdenum, or zinc. '
are presented in Table 1.
1-3
molybdenum, or zinc. The major physical properties of elemental chromium
Elemental or pure chromium metal is not found in nature. Instead, it
occurs primarily in nature as a member of the spinel mineral group in the
form of 'chromite ore or chrome iron ore. The Cr/Fe ratio in chromite varies
considerably; therefore, the mineral is best represented by the general
formula (Fe, Mg)-0- » (Cr, Fe, AlKO.*- From a chromium recovery standpoint,
the ideal chromite ore has the composition FeO -Cr^O., which contains about
46 percent chromium. The majority of the world's chromite supply comes from
South Africa, Finland, the Philippines, and the U.S.S.R. Although chromite
deposits are found in the United States, concentrations are so low that
chromite mining is not economically feasible, and as such is not performed
in this country.
Chromium exhibits several oxidation states, ranging from -2 to +6,
which dictate its chemical reactivity, and therefore, its environmental and
biological significance. The oxidation states of chromium in various
chemicals, along with the physical properties of these chemicals, is given
4
in Table 2. The most common oxidation states of chromium are +3 and +6, or
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TABLE 1. PHYSICAL PROPERTIES OF CHROMIUM
Property
Value
atomic weight
isotopes, %
50
52 .
53
54
crystal structure
density at 20°C» g/cm3
melting point, °C
boiling point, *C
vapor pressure, 130 Pa. ,°C
heat of fusion, kJ/mol
latent heat of vaporization at bp« kJ/mol
specific heat at 25°C, kJ/(mol-K)D
linear coefficient of thermal expansion at 20°C
thermal conductivity at 20°C, W/(m-K)
electrical resistivity at 20°C, u8-m
specific magnetic susceptibility at 20°C
total emissivity at 100°C nonoxidizing atm
reflectivity, R
X, nm
2
refractive index
51.996
4.31
83.76
9.55
2.38
body centered cube
7.19
1875
2680
1610
13.4-14.6
320.6
23.9 (0.46 kJ/kg-K)
6.2 x 10"6
91
0.129
3.6 x 10"6
0.08
300 500 1000 4000
67 70 63 88
a
X
standard electrode potential, valence 0 to 3+, V
ionization potential, V
1st
2nd 51
half -life of Cr isotope, days
thermal neutron scattering cross section, m2
elastic modulus* GPa
compressibility * at 10-60 TPa
1.64-3.28
2,570-6,080
0.71 "
6.74
16.6
27.8
6.1 x 10"28
250
70 x 10"3
*o convert Pa to mm Hg, multiply by 0.0075.
To convert J to cal, divide by 4.184.
CTo convert GPa to psi, multiply by 145,000.
99% Cr; to convert TPa to megabars, multiply by 10.
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TABLE 2. OXIDATION STATES OF CHROMIUM IN VARIOUS CHROMIUM COMPOUNDS AND THE
MAJOR PHYSICAL PROPERTIES OF THESE COMPOUNDS4
Oxidation State
Compound
Oxidation s^te 0
Chromium carhonyl
Dlbenzene-
chromlum(O)
Oxidation state + 1
Bic(bipheiiyl)-
chromium (I)
Iodide
Oxidation state + 7
Chroraous acetate
Chroinous chloride
Chroraous ammonium
sulfate
Oxidation state + 3
Formula Appearance
Cr(CO)6 Colorless
crystals
(CfiH6)2Cr Brown
crystals
61I20 Blue crystals
Density Melting feint Boiling Point
(g/cm3) CC) CO Solubility
- '-1- - r ' - --- - '
1.77 150 (decomposes) 151 (decomposes) Slightly soluble in CC1.;
(sealed tube) Insoluble in HO,
1.519 284-285 Sublimes 15U Insoluble In H?0;
(vacuum) soluble in C,Hfi
1.617 • 176 Decomposes Soluble in
C-H-OH, C,II~H
1.79 Slightly soluble in
HjO; soluble In acids
2.93 815 1120 Soluble in H.O to blue
solution., absorbs 0.
Soluble in H20,
absorbs 0-
Chromic chloride
Chromic acetyl-
acetonate
Chromic potassium
sulfate (chrome
alum)
Chromic chloride
liexahydrate
Chromic chloride
hexahydrate
Chromic oxide
Oxidation state + 4
CrCl
Bright purple 2.87
plates
Cr(CH3COCHCOCH3)3 Red-violet 1.34
crystals
KCr(SO,) .1211^0 Deep purple 1.826
crystals
[Cr(H20)4Cl2|C1.2H20 Bright green
crystals
crystals
1,835
cr203
Green powder 5,22
or crystals
Sublimes
208
89
95
90
2435
885
345
Chvomium(lV) oxide CrO,
Dark-brown or 4.98
black powder (calculated)
3000
Decomposes
to Cr203
Insoluble in IUO,
soluble in presence of
Cr
Insoluble In HjO;
soluble in C.il,
Soluble In HnO
Soluble In 11,0,
green solution turning
green-violet
Soluble in H20, violet
solution turning
green-violet
Insoluble
Soluble in acids to
Cr3* and Cr"
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TABLE 2 (CONTINUED)
OXIDATION STATES OF CHROMIUM IN VARIOUS CHROMIUM, COMPOUNDS AND
THE MAJOR PHYSICAL PROPERTIES OF THESE COMPOUNDS
oo
Oxidation State
Compound
Chromium* IV
chloride
Oxidation state + 5
Barium chromate(V)
Oxidation state + 6
Chromtum(VI)
oxide
Chromyl chloride
Ammonium
dlchromate
Potassium
dlrhromate
Sodium dichr ornate
Potassium chronate
Sod tun chroma te
Potassium chloro-
chrnmato
Silver chromate
Barium chromate
Strontium chromate
Lead chromate
• Formula
CrCl4
Ba (Cr04>
CrO
Cr02Clj
(HH )2Cr 0
•ft P- r
K2Cr2>7
Ha2Cr20,.2H20
K2CrOft
Ha. CrO.
2 4
KCrOjCl
Ag CrO
BaCrO,
SrCrO,
.
PbCrO,
4
Appearance
Black-green
crystals
Ruby-red
crystals
Cherry-red
liquid
Red-orange
crystals
Orange-red
crystals
Orange- red
crystals
Yellow
crystals
Yellow
crystals
Oran'ga
crystals
Maroon
crystals
Pale yellow
solid
Yellow solid
Yellow solid
Orange; solid
Density
2.7
1.9145
2.155
2.676
1.348
2.732
2.723
2.497
5.625
4.498
3.895
6.12
Melting Point Boiling Point
Cc> CO
830
197 Decomposes
-96.5 . 115.8
Decomposes
180
398 Decomposes
84.6 Decomposes
971
792
Decomposes
PecoBposes
Decompose?
844
Solubility
Slightly decomposes
in H.O! soluble in
dilute acids to
Cr and Cr
Very soluble in HO;
soluble in CH.
COOH,
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3 4
equivalently trivalent and hexavalent chromium. * Trivalent chromium is
chemically basic and the most stable form of the element because of its
strong tendency to form kinetically inert hexacoordinate complexes with
4
water, ammonia, organic acids, sulfate, halides, and urea. This
characteristic has great relevance to the behavior of trivalent chromium in
biological systems. Hexavalent chromium is acidic and is the most
commercially, biologically, and environmentally important state of chromium.
Hexavalent forms of chromium are almost always linked to oxygen and are,
therefore, strong oxidizing agents. Characteristically, acidic hexavalent
2— 2— 3
chromium forms chrornate (CrO,) and dichrornate (Cr20?) ions.
At normal temperatures chromium metal resists corrosive attack by a
wide variety of chemicals. It will, however, dissolve in several common
acids including hydrofluoric, hydrochloric, hydrobromic, and sulfuric with
the evolution of hydrogen. Chromium is not attacked by phosphoric acid or
organic acids such as formic, citric, and tartaric; however, it is slowly
attacked by acetic acid. The corrosion resistance properties of chromium
can be increased by depositing a thin oxide film on the metal surface, and
thereby introducing a condition to the chromium known as passivity.
•
Chromium can be passivated and rendered relatively nonreactive by the action
of nitric acid (in which it is insoluble), chromic acid, or other oxidizing
agents* It can also be passivated by superficial exposure and oxidation of *
the metal in air, although this technique is not as effective as oxidation
3
by nitric or chromic acid.
OVERVIEW OF PRODUCTION AND USE
Chromium Production
Chromium Ore Mining
As illustrated in Figure I, all chromium metal and chromium compounds
that are produced in the United States are derived from various grades of
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Metallurgical
Grade Cbrosit*
(High CP)
Chemical Grade
Chromice
(High Fe)
Refractory
Grade Chromi.ce
(High Al/Lov Cr)
Chromite
(Fe, Mg)0 (Cr. Fe, Al)203
Befraecoriec
o w
£ 9
1- -O
« 11
U 06,
|J
Air roast with
C0 + C»0
High-Carbon
Low—Carbon
Ferrochro»i-
Ferrocbro-
miuw-Stlicoa
Sodiifft
10H0
Treat vitb
Leach end treat with
Sodium Diehronate
at 200°C
Aanonium Chrome
Alum
Eleccrolysia
Electrolysis
Electrolytic
Chroniun
Fuse vltb
sulfur and
leach
Purification Processes
Ca
Vacuum with
carbon
Ductile Chromium
Figure 1. Simplified flowchart for the production of chromium compounds
and metallic chromium from chromite.1
10
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chromite ore. Three basic grades of chromite ore are used to produce
chromium compounds (including chromium metal):
high chromium chromite ore, containing 46 percent or more of
chromic oxide (Cr20-)
high iron chromite ore, containing 40-46 percent of Cr^O.
high aluminum or low chromium chromite ore, containing more than
20 percent aluminum oxide (Al-0.) and more than 60 percent •
Chromite ores are generally classified according to the type of production
process the chromite ore is eventually used in. Metallurgical chromite
refers to the high chromium content chroiaite ore, chemical chromite to the
high iron content chromite ore, and refractory chromite to high aluminum/low
chromium content chromite ore.
. Chromite ore has not been commercially mined in the United States since
1961 when the U. S. Defense Production Act was phased out. The phasing out
of this program eliminated government sponsorship and subsidization of
chromite mining activities, thereby making them economically infeasxble.
The United States owns chromite deposits in Maryland, Montana,
North Carolina, California, Wyoming, Washington, Oregon, Texas, and
Pennsylvania; however, the low chromium content of these deposits makes
mining excessively expensive. In 1982, the U. S. imported 456 Gg
(507,000 tons) of chromite, mostly from Albania (0.8 percent), Finland
(8.9 percent), Madagascar (8.1 percent), Pakistan (0.6 percent), the
Phillippines (13.8 percent), South Africa (54.6 percent), Turkey
(6.3 percent), and the U.S.S.R. (6.7 percent).
Production of Ferrochromium and Chromium Metal from Metallurgical Chromite
Metallurgical grade chromite refers to chromite that is used to produce
several grades or types of fe rrochromium, chromium metal, and chromium
11
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additives. The primary forms of ferrochromium are classified as high-
carbon, low-carbon, and ferrochromium-silicon. High-carbon ferrochromium
generally contains 5 to 6.5 percent carbon and 65 to 70 percent chromium.
Low-carbon ferrochromium contains 67 to 75 percent chromium but only 0.025
to 0,05 percent carbon. Ferrochromium-silicon has a chromium content
ranging from 35 to 41 percent and a maximum carbon content of 0.05 percent.
Table 3 summarizes the compositional structure of the more prominent types
of ferrochromium and chromium metal*
High-carbon ferrochromium is produced in a submerged electric arc
furnace by reducing chromite with coke. Low-carbon ferrochromium is
produced by reducing chromite with silicon in an electric arc furnace. The
intermediate product of this reaction is ferrochromium-silicon. To obtain
low-carbon ferrochromium, this intermediate product is further treated in an
open, arc-type furnace with additional chromite or a chromic
oxide-containing slag. In every ferrochromium production process, molten
product ferrochromium is tapped from the furnace, hardened by rapid cooling,
broken into chunks, and graded into compositional subgroups. *
In the most prevalent electrolytic method of chromium metal production,
high-carbon ferrochromium, in solution with other compounds, is used to
generate a chromium ammonium sulphate solution or chrome-alum electrolyte.
This chrome-alum electrolyte solution undergoes electrolysis to produce
chromium metal. The deposition cycle for this process lasts 72 hours with
chromium metal eventually being deposited on stainless steel cathodes. The
chromium metal produced by this operation is about 99.3 percent pure. The
second type of electrolytic chromium metal production involves the
electrolysis of a chromic acid/ionic catalyst solution, with the resultant
deposition of chromium metal. The deposition cycle for this process lasts
80 to 90 hours and produces a final chromium metal that is slightly purer
than that obtained from chrome-alum electrolysis.
12
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TABLE 3. COMPOSITION OF TYPICAL FERROCHROMIUM ALLOYS AND CHROMIUM METAL
Grade
ferrochrooium
high-carbon
high-carbon, high-silicon
blocking chrome
exothermic ferrochrome
foundry ferrochromu
refined chrome
SM ferrochrome
charge chromium
50-55 percent chromium
66-70 percent chromium
low-carbon;
0.025 percent carbon
0.05 percent carbon
Simplex
ferrochromlum-slllcon:
36/40 grade
40/43 grade
chromium metal
electrolytic
alumino thermic
Chromium
66-70
55-63
41-51
55-63
53-63
60-65
50-56
66-70
67-75
67-75
63-71
35-37
39-41
99. 3C
99. 3C
Silicon
1-2
8-12
9-14
8-12
2.5 *
4-6
3-6
3*
'b
'* .
2.0*
39-41
42-45
0.01*
0.15'
Carbon
5-6.5
4-6
3.6-6.4
4-6
3-5
4-6
6-8
6-6.5
0.025*
0.05*
0.01 or 0.025
0.05*
0.05*
0.02*
0.05*
Sulfur*
0.04
0.03
0.03
0.03
0.04
0.04
0.025
0.025
0,03
0.015 •
Phosphor us
0.03
0.03
0.03
0.03
0.03
0.01
Other*
4-6 Manganese
0.5 oxygen
0.05 nitrogen
0.2 oxygen*
0.3 aluminum*
value. ;
Difference between aim of percentage* shown end 100 percent li chiefly iron content
Minimum value.
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The only other source of chromium metal production comes from recycling
chromium scrap metal. The main source of scrap chromium is scrap stainless
steels and chromium alloys. It is estimated that only about 15 percent of
the available scrap chromium is being recovered and recycled as new chromium
1 8
metal* The flow of chromium scrap through industry is shown in Figure 2.
Recycling is generally performed by the firms producing the stainless steels
and alloys and by specialty firms engaged in secondary metals recovery.
Although there is a considerable amount of chromium contained in various
industrial waste products (e.g., baghouse dusts* slags, pickling liquors,
plating and etching wastes, used refractories, and processing sludges),
collection and processing costs hinder economical recovery on a large
8
scale. Note, in Figure 2, the term runaround (home) scrap means scrap that
has been generated within a facility producing a chromium-containing steel
or alloy, while new (prompt industrial) scrap refers to chromium scrap
generated by consumers of chromium-containing metals.
In 1982, the United States ferrochromium and chromium metal industry
consisted of 11 plants operated by eight different companies. These plants
produced a combined total of approximately 83 Cg (91,900 tons) of high- and
low-carbon ferrochromium and 25 Gg (27,400 tons) of ferrochromium-silicon,
chromium metal, and chromium additives. Data are not available in the
literature to separate the production totals of individual ferrochromium
grades. However, in the first quarter of 1983, the Ferroalloy Association
reported that only one plant in the country was actively producing
ferrochromium. All other plants had suspended production of ferrochromium
due to low demand brought on by a depressed steel industry and the ability
of the steel industry to obtain cheaper ferrochromium from foreign sources.
The Ferroalloy Association estimated that in the latter part of 1982 and in
early 1983, 95 percent of the ferrochromium consumed in the United States
9
was imported. The increase in ferrochromium imports and the resulting
decline in domestic ferrochromium production is attributable to a worldwide
trend in chreunite-produeing countries to vertically integrate their chromium
industries. Now, instead of exporting all of their chromite, chromite
14
-------
r—
i
Producers of
Mill Products
(Steel Mills)
And
Producers of
Castings
(foundries)
Runarouud Scrap
(Home Scrap)
Runaround Scrap
(Home Scrap)
Consumers of Mill Products and Castings
(Manufacturers of End Products)
End Products
New(Prompt Indus-
trial) Scrap
Old Scrap
Purchased Scrap
8
i.
Figure 2. Industrial reeyeling/reuse flow of chromium scrap.
15
-------
producers are only exporting a portion. The major part of the chromite
supply Is being processed by the producing country directly into
ferrochromium and sold to the industrial users such as the United States or
Japan. Lower labor, energy, and transportation costs allow the
chromite-producing countries to sell their ferrochromium at lower prices
than domestic ferrochromium companies can. * Changes or upturns in the
domestic steel industry that significantly alter the demand for
ferrochromium could help bring several of the domestic ferrochromium plants
9
back on line.
Production of Sodium Chromate/Dichromate and Secondary Chromium Compounds
from Chemical Chromite
Chemical grade chromite refers to chromite that is used to produce
sodium chromate (Na_CrO, * 10 H-0) and sodium dichrornate (Na^Cr-O-- 2H.O}, the
basic chemicals from which all other secondary chromium chemicals origi-
nate. " In the United States there are three companies producing sodium
chromate and dichromate chemicals at three plant locations. Sodium chromate
14
is only produced as an end product chemical at two of the sites. Because
of concerns of disclosing proprietary data, production information on sodium
chromate is unavailable. However, the national sodium dichromate production
capacity as of January 1983 was 205 Gg (228,000 tons) per year.
Sodium chromate is produced by roasting finely ground chromite ore with
soda ash or with soda ash and lime in a kiln. When sodium chromate is the
desired endproduct, recovery is accomplished by leaching and crystallization
steps. However, sodium chromate is generally not recovered, but instead is
converted directly to sodium dichromate by treating it with sulfuric
acid. * * Following sulfuric acid treatment, the final sodium dichromate
product is obtained after a series of evaporation, crystallization, and
drying steps. A sodium sulfate by-product is also produced during the
dichromate process and is generally sold to the kraft paper industry.
16
-------
As many as 40 secondary chromium chemicals are produced commercially
from sodium dichromate raw materials. A list of the chromium chemicals
produced in the United States is given in Table 4 (excluding sodium chrornate
and dichromate). The more significant secondary chromium chemicals include
potassium chrornate and dichromate, ammonium dichromate, chromic acid, basic
chromic sulfate, chromic oxide, and chrome pigments (chrome oxide green,
chrome yellow, chrome orange, molybdate chrome orange, and chrome
green). ' Chromic oxide may be used subsequently to produce chromium
metal by a pyrometallurgical reduction process using aluminum
(aluminothermic process). In the aluminothermic process, chromic oxide is
mixed with powdered aluminum, placed in a refractory vessel, and ignited.
The reaction is exothermic and self-sustaining, with chromium metal and
aluminum oxide being generated. Chromium metal produced by this method is
97 - 99 percent pure. Additional thermal methods of chromium metal
production involve the reduction of chromic oxide with silicon in an
electric arc furnace and the low pressure reduction of chromic oxide with
carbon in a refractory vessel. * .
There are approximately 30 companies engaged in manufacturing secondary
chromium compounds from sodium dichromate. *
Production of Refractories from Refractory Chromite
Refractory chromite refers to the grade of chromite that is used in the
production of refractory brick and shapes. Refractory chromite is mostly
used to manufacture basic (as opposed to acidic) non-clay refractories.
Pure chromite ore, mixtures of chromite and magnesite, and mixtures of
chromite and alumina are used to manufacture the refractory brick. The
proportion of chromite used is related to the specific temperature and
19
corrosion resistance requirements imposed by the refractory's end use.
The production of chromite-containing refractory consists of four
general steps: raw material processing, materials forming, firing, and
final processing. In the raw material processing step, chromite, magnesite,
17
-------
TABLE 4. LIST OF COMMERCIALLY PRODUCED SECONDARY CHROMIUM CHEMICALS AMD THEIR GENERAL USES
1,14.18
Chromium Chemical
Number of Production Situ
General Use
Chromic acid (Chromium trloxlde)
Chromium acetate
Chromium acetylacetonate
Chromium monoborlde
Chromium carbide
Chromium carbonyl
Chromium chloride, baaic
Chromium chloride
Chromium diborlda
Chromium difluorlde
Chromium dioxide
Chromium 2-ethylexanoate (Chromic octoat«)
Chromium fluoride
Chromium hydroxide
Chromium hydroxy dlacetate
Chromium hydroxy dlchloride
Chromium naphthenate
Chromium nitrate
Chromium oleate
Chromium oxide (Chrome oxide green)
Chromium phosphate
Chromium potaaalum sulfata (Chrome alum)
Chromium aulfate
Chromium sulfate, baaic
Chromium triacetate
Chromium trlfluorlde
Chrome llgnosulfate
Potassium chromate
Potaeslum dlchromate
Lead chromate
Zinc chromate
Ammonium dichromate
Barium chromate
Calcium chromate
Cesium chromate
Copper chromate, baaic
Magnesium chromate
Strontium chromate
Iron chromlte
Electroplating
Printing and dyeing textiles
Catalysts* antiknock compounds
Unknown
Metallurgy
Catalysts
Hetal treatment
Metal treatment
Unknown
Catalyats
Magnstlc taps
Unknown
Mordants, catalysts
Pigments, catalysts
Unknown
Unknown
Textile preservative
Catalysts, corrosion control
Unknown
Pigments
Pigments, catalysts
Photographic emulsions
Catalyats, dyeing, tanning
Tanning
Unknown
Printing, dyeing, catalysts
Drilling muds
Metal treatment
Tanning, dyeing, pigments
Pigments
Corrosion control
Printing, pyrotechnics
Pyrotachnlca
Corrosion control
Electronics
Wood preservative
Refractory, catalysts
Corrosion control pigment
Refractory
List does not Include sodium chromate and sodium dlchromate,
Several sites product multiple chromium chemicals.
-------
dolomite, and other raw materials are crushed* calcined, ground, and sized.
In the forming step, the prepared raw materials are homogeneously mixed and
formed into bricks and shapes. In the firing step, the formed brick and
shapes are either dried and fired in a kiln or they are fusion-melted and
cast into molds. The final processing step can consist of simple product
packaging or it can involve more detailed operations such as final grinding
and milling, tar impregnation, and tempering. Each of the more, detailed
finishing operations is performed to impart certain characteristics to the
20
refractory to improve its end use performance. In 1984, 26 companies
operating a total of 43 plants are producing refractory from chromite ore
21 22
raw material. *
Chromium Uses
In 1982, 491 Gg (545,000 tons) of chromite ore were consumed.in the
United States and converted into chromium-containing products. The
domestic consumption of chromite raw materials can essentially be attributed
to three primary user groups or industries: metallurgical, chemical, and
refractory (see Figure 1). Of the total chromite consumed in 1982,
49 percent or 240 Gg (267,000 tons) was for metallurgical uses, 36 percent
or 177 Gg (196,200 tons,) was for chemical .uses,.and 15-percent or 74 Gg -
(81,800 tons) was for refractory uses. ' Within these primary consumption
groups several secondary chromium materials are produced that function
either as a final product (e.g., refractory) or as an intermediate in the
manufacture of other consumer goods (e.g., stainless steel). Figure 3
illustrates the qualitative distributipn of chromium use in both the primary
23
and secondary consuming sectors. A broader and more quantitative
perspective of chromium consumption in the United States, as defined by the
Standard Industrial Classification (SIC) category in which final use of the
Q
chromium occurs, is presented in Figure 4. Domestic consumption and
distribution patterns of chromium within the metallurgical, chemical, and
refractory use groups are summarized in the following sections.
19
-------
ro
o
Iiport*
rt*nl tatt* In Il«etfl«*l,
Tr*«ipoit*[Ion, 1 Con*truetin
Equipment
CltetropUtlni * *•*•>
HnUhini
Figure 3. Primary and secondary use distribution of chromium in the
United States."
-------
United States
Chromium Demand
459,000 Mg
(510,000 tons)
Transportation Equipment
SIC 37
92,700 Mg (103,000 tons)
Construction Products
SIC 15,16
85,500 Mg (95,000 tons)
Machinery - SIC 35,36
81,000 Mg (90,000 tons)
Household Appliances
SIC 363
43,200 Mg (48,000 tons)
Refractory Products
SIC 33,3297
26,100 Mg (29-,000 tons)
Plating of Metals
SIC 3471
16,200 Mg (18,00'0 tons)
Chemicals - SIC 281
55,800 Mg (62,000 tons)
Other Miscellaneous Products
58,500 Mg (65,000 tons)
Figure 4. Final consumer use distribution of chromium in
the United States in 1981.
21
-------
Metallurgical Uses--
Chromium's use in the metallurgical industry is to enhance such
properties in steels and other alloys as hardenabillty, creep and impact
strengths, and resistance to corrosion, oxidation, wear, and galling (damage
Q
by friction or abrasion). In 1982, 71 percent of the chromium consumed (as
ferrochromium) in the metallurgical use group was used in the production of
stainless steels. Fifteen percent of the chromium was used to produce
full-alloy steels, 3 percent was used for low-alloy and electrical steels,
and 2 percent was processed into carbon steels. The remaining 9 percent
was used in a variety of other metallurgical products including cast irons
and nonferrous alloys. The chromium steels, alloys, and cast irons produced
by the metallurgical industry are used primarily in the manufacture of
transportation, electrical, and construction equipment, heavy machinery, and
fabricated metal products. Chromium is used in a wide variety of
transportation vehicles including automobiles, motorcycles, bicycles, boats,
trains, and snowmobiles. Both commercial and military aircraft engines are
produced, with chromium. Chromium is also used in volume in stainless steel
tankers to haul milk, acids, and chemicals, and in'bulk hopper trailers to
haul fertilizers and hygroscopic materials. In the construction industry,
chromium metallurgical products are used for oil and gas exploration and
production, petroleum refinery fabrication, power plant sulfur dioxide wet
8
scrubbers, and bridge construction.
In the machinery'industry, chromium metals are used to manufacture food
processing equipment, high speed machine tools, cutting and forming
equipment, and machine tool accessories, including dyes and measuring
devices. Chromium use in the fabricated metal products industry covers such
products as cutlery, hand tools, general hardware, hospital equipment, and
g
home appliances. Based on 1981 figures, the combination of transportation,
construction, machinery, and household appliance consumer uses of chromium
constituted about 66 percent of the total chromium used in the United States
(see Figure 4).
22
-------
Chemical Uses—-
In the chemical use group, chromium chemicals, primarily sodium
chrornate and sodium dichromate, are used to manufacture a wide variety of
consumer-oriented chromium chemicals and products that have uses in the
following areas.
paints and pigments
leather tanning liquors
metal plating and finishing solutions
- corrosion, inhibitors
- catalysts
drilling muds
- wood preservatives
textile mordants and dyes
A breakdown of the amount of chromium (as sodium dichromate) used in each of
the areas given above is shown in Figure 5. Approximately 70 percent of
the chromium consumed domestically for chemical uses is accounted for in the
preparation of pigment, metal plating, and leather tanning compounds.
Chromium pigments are used primarily in paints, inks, and roofing granules.
Metal plating solutions, primarily chromic acid, are used in producing
decorative automobile trim and appliance exteriors. Chromium leather
tanning liquors are the most widely used tanning products, except for the
tanning of heavy cattle hides in which vegetable tanning oils are
predominant. A list of the key chromium chemicals applied in all the end
use areas given above is presented in Table 5.
Refractory Uses—
In the refractory use group, chromium in the form of chromite ore, is
used primarily to produce chrome brick, chrome-magnesite brick, and
magnesite-chrome brick refractory, which is used to line furnaces, kilns,
24
converters, incinerators, and other high temperature industrial equipment.
Chromium refractory materials are also used as coatings to close pores and
23
-------
Chromium Consumed as
Sodium Bichromate in
1982 - 135,441 Mg
( 150,490 tons )
Chromic Acid/Metal Plating-28
37,923 Mg (42,137 tons)
Pigments and Paints - 24
32,506 Mg (36,118 tons)
Leather Tanning Liquors - 17 %
23,025 Mg (25,583 tons)
Drilling Muds/ Textiles - 8
10,835 Mg (12,039 tons)
Corrosion Inhibitors - 7
9,481 Mg (10,534 tons)
Exports - 8 Z
10,835 Mg (12,039 tons)
Wood Preservatives,Catalysts,
Other - 8 %
10,835 Mg (12,039 tons)
Figure 5. End use tree for sodium dichromate in 1982.
15
24
-------
TABLE 5. MAJOR CHROMIUM USES AND KEY CHROMIUM CHEMICALS INVOLVED
Chromium Chemical
Use Area
Key Chromium
Chemicals Involved
Paints and Pigments
Leather Tanning Liquor
Metal Finishing and Plating
Corrosion Inhibitors
Catalysts
Drilling Muds
Wood Preservatives
Textile Mordants and Dyes
Chrome Yellow
a
Chrome Orange
Chrome Oxide Green
a
Molybdate Orange
Chrome Green
Basic Chromium Sulfate
Chromic Acid
Zinc Chromate
Zinc Tetroxychromate
Strontium Chromate
Lithium Chromate
Cadmium- Chromate
Copper Chromate
Magnesium Bichromate
Nickel Chromate
Copper Chromite
Chromium Lignosulfonate
Chrome Copper Arsenate
Chrome Zinc Chloride
Chromic Chromate
Chromic Chloride (hydrated)
Chromic Fluoride
Chromic Lactate
Contains lead chrornate.
25
-------
12
for joining refractory brick within a furnace or kiln. By far, the major
consuming industry for chromium refractory materials is the iron and steel
industry. Other industrial sectors consuming significant amounts of
chromium refractory include glass manufacturing, nonferrous metal
19
production, primary minerals smelting, and ceramic production.
Chromium (in the form of chromite) consumption in the refractory
industry has been declining. From 1977 to 1981 for example, chromite
consumption by the refractory industry declined by approximately
23
37 percent. The increased use of magnesite and a depressed domestic steel
industry are the major reasons for the decline in the production of chromium
8
refractory.
26
-------
REFERENCES FOR SECTION 3
1. Kirk-Othmer Encyclopedia of Chemical Technology. Third Edition.
Volume 6. John Wiley & Sons, Inc. New York 1980. pp. 54-120.
2. Sittag, Marshall. (Noyes Data Corp.) Toxic Metals - Pollution Control
and Worker Protection. Noyes Data Corporation. Park Ridge,
New Jersey. 1976. pp. 97-131.
3. National Academy of Sciences. Committee on Biologic Effects of Atmos-
pheric Pollutants. Chromium. ISBN 0-309-02217-7. Washington, D.C.
1974. pp. 2-6.
4. Towill, L. E-., ej^ ^. Reviews of the Environmental Effects of Pollu-
tants: III* Chromium. EPA-600/1-78-023 and ORNL/EIS-80. May 1978.
pp. 12-17.
5. National Emissions Inventory of Sources and Emissions of Chromium.
(GCA Corporation). EFA-450/3-74-012. May 1973. p. 5.
6. Papp, J. F. (Bureau of Mines). Chromium. Preprint from the 1982
Bureau of Mines Minerals Yearbook. U. S. Bureau of Mines, Washington,
D. C. 1983.
7. Reference 5, pp. 11-12.
8. Papp, J. F. (Bureau of Mines). Chromium. Mineral Commodity Profiles
1983. U. S. Bureau of Mines. Washington, D. C. 1984.
9, Telecon. Brooks, G. W., Radian Corporation with Watson, G., Ferroalloy
Association. February 23.--1983'. Ferrochromium plant emissions.
10. Chromium and Chromium Compounds - Phase I Report. Office of Pesticides
and Toxic Substances, U. S. Environmental Protection Agency.
Washington, D. C. May 1978.
11. Reference 5, p. 15.
12. Sullivan, R. J. Preliminary Air Pollution Survey of Chromium and Its
Compounds. APTD No. 69-34. U.S. Department of Health, Education, and
Welfare. October 1969. pp. 19-20.
13. Proceedings of a Workshop/Conference on the Role of Metals in Carcino-
genesis. Atlanta, Georgia. March 24-28, 1980. NIOSH-210-79-0039.
Published by the New York University Institute of Environmental Medi-
cine. 1980.
14. SRI International. 1982 Directory of Chemical Producers-United States.
Menlo Park, California. 1982. pp. 893-895.
27
-------
15. Chemical Marketing Reporter. Volume 221, No. 22. May 31, 1982.
p. 50.
16. Foley, E. F. Chromium Chemicals Manufacture. (Paper presented at the
Symposium on Health Aspects of Chromium Containing Materials.
Baltimore. Maryland. September 15, 1977.) Published by the Industrial
Health Foundation. 1978.
17. Stern, R. M. Chromium Compounds - Production and Occupational Expo-
sure. The Danish Welding Institute. Glostrup, Denmark. 1982. pp.
4-6.
18. Reference 14, pp. 36 and 522-523.
19. Refractories, the Refractories Institute. TRI Publication 7901.
Pittsburgh, Pennsylvania. 1979.
20. Source Category Survey: Refractory Industry. EPA-450/3-80-006.
Emission Standards and Engineering Division, U.S. Environmental Pro-
tection Agency. Research Triangle Park, North Carolina. March 1980.
pp. 4-16 to 4-25.
21. Product Directory of the Refractories Industry in the United States.
The Refractories Institute. Pittsburgh, Pennsylvania. 1978.
pp. 21-154.
22. Letter from Olenn, S. F., the Refractories Institute to Lahre, T. F.,
U. S. EPA. February 27, 1984. Comments on draft chromium report.
23. Snyder, A. D., e^ al. Environmental Monitoring Nearing Industrial
Sites: Chromium. EPA-560/6-77-016. June 1977. p. 5.
24. Reference 5, pp. 7 and 14.
28
-------
SECTION 4
CHROMIUM EMISSION SOURCES
Chromium emission sources can be divided into two broad classes —
direct and indirect. The first part of this section deals with direct
chromium emission sources. The direct category primarily includes sources
that either produce chromium or consume chromium or a chromium compound to
manufacture a product. The source categories within the direct category
are:
chromite ore refining,
ferrochromium production,
- refractory production,
* chromium chemicals production,
- chromium plating
- • steel production,
leather tanning.
The second part of the discussion in this section deals with indirect
chromium emission sources. Indirect sources are generally those that do not
produce chromium or chromium compounds and only inadvertently handle and
emit chromium because it is present as an impurity in the feedstock or fuel
used in performing their primary activity. For example, during the
combustion of fossil fuels to produce energy, chromium is released to the
atmosphere because it is a constituent of the fuels burned. The source
categories within the inadvertent category are:
- coal and oil combustion,
- cement production
29
-------
municipal refuse and sewage sludge Incineration,
- cooling towers,
asbestos mining and milling, and
- coke ovens.
The following subsections describe the operations of both direct and
indirect chromium emission sources and the chromium emission points therein.
Where available, chromium emission factors are presented for each source, as
well as Information on the specific chemical form of chromium in the
emissions.
DIRECT SOURCES OF CHROMIUM
Chromite Ore Refining
Process Description—
As discussed in Section 3, no chreunite ore is currently being mined in
the United States. Also, the current standard practice of foreign chromite
mining operations is to clean and size the chromite ore to a customer's
specifications prior to export to the United States. This existing ore
supply structure largely eliminates the need for a specific domestic
chromite ore refining industry. Consequently the domestic chromite ore
refining industry is quite small. In 1983, only one plant was known to be
1 2
operating solely to process and refine chromite ore. ' Other domestic
consuming industries may perform some preliminary grinding and sizing of the
ore before it enters their processes.
As shown in Figure 6, the chromite ore refining process consists of
crushing, drying, and grinding the ore, and packaging it to customer speci-
fications. Ore is first crushed, screened, and dried in a rotary sand
3
dryer. It is then conveyed to a Hardinge mill for fine grinding. The fine
chromite ore particles are then air conveyed through a classifier to a
30
-------
Chromium
Emissions
Chromium
Emissions
ChroiaJ urn
Emissions
Chromium
Emissions
Chroinlte
Ore
Q C
Figure 6. Flow chart for chromite ore refining.
-------
cyclone separator. Ore collected in the cyclone is dropped into storage
bins and most of the air is recycled to the mill. The refined chromite ore
4 5
is then packaged in bags. '
Emission Factors—
Sources of chromium-containing emissions are indicated on Figure 6.
Emissions of chromite ore would occur during primary crushing and screening,
however, no data are available on emission rates or control procedures for
these steps. Chromite particles are also emitted when ore is dried in the
rotary sand dryers. These dryers are equipped with wet scrubbers, which
function at greater than 99 percent efficiency. The cyclone following the
Hardinge mill is another source of chromium emissions. Fine chrome ore
particles are pneumatically conveyed from the mill to the cyclone where they
are collected. However, the process cyclone is not 100 percent efficient,
so some chrome ore particles will be exhausted from the cyclone. Most of
the air is recycled to the mill,.but some is channeled through a fabric
filter and then exhausted to the atmosphere. Fabric filters in this
4
application have been determined to be 99.9 percent efficient.
The storage and packaging of the refined ore are the final sources of
chromium emissions. A bin vent dust collector gathers the air and chromite
dust displaced from the storage bins as the product is deposited there.
Filter cartridges are used to clean this air and are reported to be over
99 percent efficient.
Table 6 shows emission factors for the ore dryer, Hardinge mill and
cyclone system, and finished product storage. These factors were calculated
from state air quality permit data for the one domestic ore refining
3-5
plant. The permits listed total particulate emission rates as well as
throughputs of chromite ore. The emission rates for elemental chromium
shown on Table 6 were calculated using the assumptions that chromite ore
contains 45 percent chromic oxide (Cr203), and that chromic oxide is
68 percent chromium by weight.
32
-------
TABLE 6. CHROMIUM EMISSION FACTORS FOR CHROMITE ORE REFINING3
Chromium Emission Factor
kg/Mg (Ib/ton) .
Source of Emissions Control of chromite ore processed
Chromite ore dryer bag collector .005 (.009)
wet scrubber .001 (.002)°
Hardinge mill and cyclone fabric filter .003 (.005)
Refined ore storage uncontrolled .05 (.09)
dust collector .00005 (.00009)
(filter cartridge)
aEmission factors calculated as described in test from references 3, 4,
and 5.
All emission factors reported as total elemental chromium. Chromium exists
in the emissions as trivalent chromium.
Factor assumes 99.9 percent control efficiency.
Source Locations—
The only known chromite ore refining plant in the United States in 1983
2
was the American Minerals, Inc. plant in New Castle, Delaware.
Ferrochromium Production
Process Description-
Ferroalloys are crude alloys of iron "and one or more other elements
which are used for deoxidizing molten steels and making alloy steels.
Chromium is a component of about 16 percent of domestically produced
Q
ferroalloys. Types of chromium ferroalloys (ferrochromium) include high-
carbon ferrochrome, low-carbon ferrochrome, charge chrome, ferrochrome-
Q O
silicon, and other lower volume products. * Chromium ferroalloys can be
produced by four different processes. The primary method of producing high-
carbon ferrochrome, ferrochrome-silicon, and charge chrome is in an electric
arc furnace. Low carbon-ferrochrome can be produced by either an exothermic
process or vacuum furnace process, and chromium metal can be produced by an
33
-------
8 9
exothermic or electrolytic process. * All four types of processes have
been used in the past, but only the electric arc furnace process is
currently used in the United States.
o
In 1980, there were seven plants manufacturing ferrochromium. However
in the first quarter of 1983, only one plant was actively producing
ferrochromium. Other plants suspended production of ferrochromium due to
low.demand brought on by a depressed steel industry and the ability of the
steel industry to obtain its ferrochromium requirements more cheaply from
foreign sources. The Ferroalloy Association estimated that in early 1983,
95 percent of the ferrochromium consumed in the United States was
imported. The increase in ferrochromium imports and resulting decline in
domestic production is attributable to a trend in chromite-producing
countries to do more processing of the chromite ore into ferrochromium and
other products before shipment. Less raw chromite ore is therefore
available to be shipped to the United States. Lower labor, energy, and
transportation costs allow the chromite-producing countries to sell their
ferrochromium at lower prices than domestic ferrochromium companies can.
Changes or upturns in the domestic steel industry could alter the demand for
ferrochromium and bring domestic ferrochromium plants back on line.
The electric arc furnace method of ferrochrone production is pictured
in Figure 7. Chromite ore and other necessary raw materials are brought to
the plant by truck or rail and stored in a stockpile (Figure 7, point 1).
Depending on weather conditions and its moisture content, the chromite ore
may need to be dried (point 2) before being crushed (point 3), sized
(point 4), and mixed with other raw materials to meet process
specifications. The charge (raw materials) is then weighed and fed to a
89 11
submerged electric arc furnace (point 5) for smelting (point 6). * *
Three types of electric arc furnaces can be used. These are open,
7 8
sealed, and semisealed furnaces. * The operations of each type of furnace
are discussed in succeeding paragraphs. Electric arc furnaces may be
continuously or intermittently charged with chrome and iron ores, a reducing
34
-------
Ul
Cr
Emissions
Cr
Emissions
Reducing
Agent
Cr
Emissions
Smelting in
Electric Arc
Furnace
Recovered
Metala
Ferro-
.chrome
Slag
Concentration
of Slag
Sing
Dump
Cr
Emissions
Cr
Emissions
Cr
Emissions
Storing
and
Packaging
Figure 7. Flow chart of ferrochrome production by the electric arc furnace process
-------
r
agent such as alumina, coal, and/or coke* and slagging materials such as
silica or gravel. Three carbon electrodes are vertically suspended above
the hearth, and extend 1 to 1.5m (3 to 5 ft) into the charge materials.
Three-phase current arcs through the materials from electrode to electrode,
and the charge is smelted as electrical energy is converted to heat. The
intense heat around the electrodes (2204-2760°C or 4000-5000°F) results in
carbon reduction of the chrome and iron oxides in the charge and the
formation of ferrochromium. The molten ferrochromium is periodically tapped
811
into ladles from tapholes in the lower furnace wall. '
The molten ferrochrome is cast into molds and allowed to cool and
solidify (point 8). The casts are then removed from the molds, graded and
broken (point 9). The broken ferrochromium is passed through a crusher and
screened (points 10 and 11). The ferrochrome product is then stored,
Q I!
packaged (point 12), and shipped to the consumer. *
Impurities from the smelting process are trapped in a slag which forms
inside the electric arc furnace. The slag is periodically tapped and
treated by a concentration process (point 7) to recover metal values. Slag
is processed in a flotation system, where metal particles including chromium
sink to the bottom while slag floats. The recovered metals are recycled to
the furnace, and the remaining slag is removed and disposed of.
As previously stated, open, sealed, and semisealed furnaces may be used
to produce ferrochromium by the electric arc process. Open furnaces are the
most common type, and also have the highest potential for chromium-
containing particulate emissions. An open furnace is pictured in Figure 8.
A hood is usually located 1.8 to 2.4m (6 to 8 ft) above the furnace crucible
rim. Dust and fumes from the smelting process are drawn into the hood along
with large volumes of ambient air. Advantages of the open furnace include
the ability to stoke it during operation and the flexibility to manufacture
36
-------
ELECTRODES
EXTENDING
MIX FEED
CHUTE
(TYPICAL)
—I—I—I—.J 1 I 1
CHROMIUM
EMISSIONS
Figure 8. Open electric arc furnace.
37
-------
several types of ferroalloy without altering the furnace design. Claims
have also been made that open furnace operations have fewer accidents and
greater worker safety than sealed furnace operations.
The semisealed (or semi-enclosed) furnace is pictured in Figure 9. A
cover seals the top of the furnace except for openings around the electrodes
through which raw material is charged. These furnaces are either hooded or
maintained under negative pressure to collect emissions from around the
electrodes. Semisealed furnaces can be used to produce some chromium-
containing ferroalloys, but problems occur in the production of high-silicon
grades of ferrochrome because of the inability.to stoke the furnace.
Without stoking, crusting and bridging of ferroalloys around the electrodes
and charge holes may prevent uniform descent of the charge into the furnace
and blows (jets of extremely hot gasses originating in the high temperature
zone near the electrode tips) may emerge around the electrodes at high
velocity.
The third type of electric arc furnace, the sealed or closed furnace,
is illustrated in Figure 10. Packing is used to seal the cover around the
electrodes and charging chutes. The furnace is not stoked and a slight
positive pressure is maintained to prevent leakage of air into the furnace.
High-silicon ferrochrome and high-carbon ferrochrome are rarely produced in
sealed furnaces due to crusting and bridging and-the possibility of blows.
Care must also be taken to prevent water leaks which may cause explosive gas
release which could damage the furnace and threaten worker safety. Sealed
furnace designs are specifically used in the manufacture of narrow families
of ferroalloys, so plants using sealed furnaces have less flexibility to
produce different types of ferroalloys. Ferrochromium has not been
produced in sealed furnaces in the United States, however it has been
g
produced this way in Japan.
A recent innovation in sealed furnaces is the split-furnace design, in
which the upper ring of the furnace rotates more rapidly than the lower
furnace. This has a mixing effect on the furnace contents and reduces
38
-------
EXHAUST TO
ATMOSPHERE
COVER
TAP HOLE
MIX CHUTE
(TYPICAL)
INDUCED AIR
CHROMIUM
EMISSIONS
Figure 9. Semisealed electric arc furnace.
39
-------
ELECTRODES
MIX FEED
(TYPICAL)
V
COVER
ELECTRODE
SEAL
1
CHROMIUM
EMISSIONS
J* •"• !***•*•!• *.X**-*Vt**I*»»>^.*7rV*&iiI**^*i.* *.*V.vV "•.*•***•*• v*"."i*a
...*.- .*.*•*.«t;-V.X'**.**.'.•>*"•'*'* *<.*•.-.•'. •• A '-* "^ •*'»*v•" *
Figure 10. Sealed electric arc furnace.
40
-------
crusting and bridging problems. Another method used to provide mixing is
the insertion of stoking devices through seals in the furnace walls. Use of
these techniques, which are practiced in Japan and Norway, makes possible
the production of high-silicon ferrochrome and high-carbon ferrochrome in
sealed furnaces.
One alternative to the electric arc furnace process which can be used
to produce low-carbon ferrochrome is a type of exothermic process involving
9
silicon reduction. A flow diagram of the process is shown in Figure 11.
First chromium ore and lime are fused together in a furnace to produce a
chrome ore/lime melt which is poured into a reaction ladle (number 1). Then
a known quantity of molten ferrochrome silicon previously produced in
another reaction ladle (number 2) is added to ladle 1. In the ladle, a
rapid heat-producing" reaction results in the reduction of the chromium from
its oxide form and the formation of low-carbon ferrochrome and a calcium
silicate slag. The ferrochrome product is then cooled, finished, and.
packaged. Since the slag from ladle 1 still contains recoverable chromium
oxide, it is reacted in ladle 2 with molten ferrochrome-silicon produced in
a submerged arc furnace. The exothermic reaction in ladle 2 produces the
ferrochrome-silicon added to the number 1 ladle during the next production
9
cycle.
»
A vacuum furnace process can also be used to produce low-carbon
ferrochrome. The furnace, pictured in Figure 12, is charged with
high-carbon ferrochrome and heated to a temperature near the melting point
of the alloy. Decarburization occurs as the high-carbon ferrochrome is
oxidized by the silica oxide in the ferrochrome. Carbon monoxide gas
resulting from the reaction is pumped out of the furnace to maintain a high
9
vacuum and promote decarburization of the ferrochrome.
The electrolytic process is another alternative to the electric arc
furnace for producing chromium ferroalloys. Pure chromium metal is
generally produced this way. Chromite ore, high-chromic oxide slags, or
-------
Chrome
Ore
Lime
Chrome
Ore
Coke
Quart-
Site
Wood
Chips
i
Chrome Ore/
Lime Melt
Open-Arc Furnace
Ferrochrome
Silicon
Ferrochrome-
Silicon
Submerged-Arc
Furnace
Ferrochrome-
Silicon
34Z Cr
i
Tarpoine
Ladle
Product
Low Carbon
Ferrochrome
70% Cr
Secondary
Throw-away
Slag
Throw-away
Slag
Figure 11. Typical flow chart for the production of low-carbon
ferrochrome by the exothermic silicon reduction process.
42
-------
TO INERT
GAS COOLING
\'.J'}i"fy''' ^f *
%F^
ELECTRICAL
LEADS
5
TO VACUUM
PUMPING SYSTEM
CARBON
RESISTORS
iziJ
I I
J L
7 W
REMOVABLE
END CLOSURE
TRACK
HEARTH
CAR
FURNACE
CHARGE
Figure 12. Vacuum furnace for the production of low-carbon
ferrochrome.
43
-------
ferrochrome can be used as raw materials for the process. Preparation of
raw materials can include grinding, calcining and leaching. In the
electrolytic process, chromium ions contained in an electrolytic solution
are plated on cathodes by a low voltage direct current. The pure chrome
forms a film on the cathode about 0.3 cm (1/8 in.) thick, which is removed
q
and prepared for shipment.
Emission Factors—
Figure 7 shows possible sources of chromium emissions from the
production of chromium ferroalloys by the electric arc furnace process.
Depositing and removing materials from the chrome ore stockpile and wind
erosion of the stockpile result in emissions of chromite particulates. To
reduce emissions, storage piles can be sheltered by walls, covered with
plastic, or sprayed with water. The extent of such practices is unknown.
Drying, crushing, screening, and other chrome ore pretreatment steps also
produces chromium emissions. Scrubbers, cyclones, and fabric filters
typically control emissions from these operations, and are reported to be 90
9
to 99 percent effective for removal of chromium-containing particulates.
The smelting of chrome ore and other raw materials in the electric arc
furnace is the major source of chromium emissions in a ferrochromium plant.
All three types of electric arc furnaces-(open, sealeds and semisealed) emit
carbon monoxide and other gasses. Chromium-containing particulates are
entrained as this gas evolves and as ambient air passes over the charge
materials. Open furnaces have the highest uncontrolled chromium emissions
because the large opening between the furnace rim and hood allows more
circulation of air and gasses through the charge material which entrains
chrome and other particulates. Fumes and particulates may escape if
7 8
adequate draft is not maintained in the collection hood. '
Fabric filters were used to control emissions from 87 percent of the
8 12
open-arc ferroalloy furnaces operating in 1980. * Testing of these
control systems indicates total particulate removal efficiency of over
o
99 percent. Testing of fabric filters on combustion sources indicates that
44
-------
they are as effective at controlling chromium as they are at controlling
xi
9
13
total particulates. • Data from one ferrochromium plant support this
finding.
High pressure-drop venturi scrubbers and electrostatic precipitators
have also been applied to open-arc furnaces producing ferrochromium alloys,
but these plants have recently shut down. Reported particulate collection
efficiencies for scrubbers ranged from 94 to 98 percent. When ESPs were
used, the gas was conditioned with ammonia to enhance particulate
7 8
resistivity and increase collection efficiency. * Estimated particulate
9
removal efficiencies were 98 percent. There are little data from the
ferrochromium industry on chromium collection efficiencies of scrubbers arid
ESPs. However, testing of similar high-temperature processes at combustion
sources indicated that these devices control chromium to about the same
13
degree as total particulates.
In the case of semi sealed furnaces {Figure 9), offgases and entrained
chromium-containing particulates are drawn from beneath the cover through
ducts leading to the control device. However, fugitive chromium
particulates and fumes escape through the openings around the electrodes.
Hoods can be placed above the furnaces to entrap these emissions. Wet
scrubbers, including both-multistage ^centrifugal scrubbers and venturi
scrubbers, have been used on semisealed ferroalloy furnaces. Up to
99 percent particulate removal efficiency is reported for centrifugal
scrubbers, and venturi types are more efficient. Fabric filters and ESPs
are not known to be used on semisealed furnaces.
Because no air enters sealed furnaces (Figure 10)', gas volumes to the
control device are only 2 to 5 percent of those from open furnaces. This
results in a much smaller mass of entrained chromium-containing
particulates. Venturi scrubbers are commonly used to control particulates,
and therefore chromium emissions, from sealed furnaces, including one
45
-------
furnace which produced charge chrome but is now shut down. Fabric filters
a
have been used at a few sealed furnaces for particulate emissions control.
Another source of emissions from all three types of electric arc
furnaces is the tapping of molten ferrochrome from the furnace into a ladle.
Tapping takes place during 10-15 percent of the furnace operating time.
Hood systems are sometimes installed over the tapping hole and ladle to
capture and direct the chromium-containing emissions to a fabric filter or
i.u 7,8
scrubber.
Additional chromium emissions from ferrochromium plants occur as the
ferrochromium product is finished and handled. After smelting and tapping,
the ferrochromium is cast. Chromium-containing particulates and fumes
escape as the molten ferrochromium is poured into molds. Casting operations
may be hooded, but emissions from casting are uncontrolled at many
Q
ferroalloy plants. Other sources of chromium emissions include the final
crushing, sizing, and packaging of the ferrochromium product. The majority
9
of plants control these operations with fabric filters or scrubbers.
There is little information on chromium emissions or controls for the
production of ferrochrome by exothermic, vacuum furnace, or electrolytic
processes. Sources of particulate chromium emissions from the exothermic
silicon reduction process (Figure 11} would include the electric arc
furnaces used to manufacture the chrome ore/lime melt and the ferrochrome
silicon as well as the tapping ladle and the two reaction ladles. The
silicon reduction occurring in the reaction ladles causes a rise in
temperature and strong agitation of the molten ferrochrome for about five
minutes per production cycle. During this agitation, gases and entrained
9
chromium-containing particulates are emitted. Only one plant manufactured
a
ferrochromium using an exothermic process in 1980. According to the
Ferroalloy Association, it is not currently active. No information on
typical control technologies is available.
46
-------
Vacuum furnaces used to produce ferrochrome (Figure 12) emit only trace
9
quantities of particulates, and none are currently operative in this
country. Electrolytic processes used to produce chrome metals do not emit
particulates. However, chromium ions in the electrolyte solution can be
emitted in a mist which is released from the tank when hydrogen and oxygen
are evolved around the anode and cathode. The extent to which electrolytic
process emissions are controlled is unknown. The one plant which was
8 • 10
operating in 1980 is currently inactive.
Chromium emissions factors for the electric arc furnace method of
ferrochrome production can be calculated from data available in the
literature. A 1974 U.S. EPA study estimated particulate emissions from raw
materials handling and processing at sixteen electric arc furnace ferroalloy
9
plants. The specific types of ferroalloys these plants produced were not
specified. However, it was assumed that since raw materials handling
procedures are similar for chrome-containing and non chrome-containing
ferroalloy production, total particulate emissions factors for general
ferroalloy production would apply to the production of chrome ferroalloys.
To derive chromium emission factors from total particulate emission factors,
it was assumed that metallurgical grade chrome ore (a raw material for
14
ferrochrome production) contains 50 percent chromic oxide and that
elemental chrome is 68 percent of chromic oxide by weight. Ghromium
emission factors for raw materials processing steps are expressed in Table 7
in terms of pounds of chromium emitted per ton of chrome ore processed.
The 1974 U.S. EPA report cited above also listed particulate emissions
from handling and finishing of the ferroalloy products including casting,
9
crushing, and grinding. The chromium content of particulate emissions
would vary depending on the chromium content of the ferroalloy being
produced. The composition of chrome ferroalloys can range from 36 percent
chromium for ferrochrome-silicon to 70 percent chromium for charge chrome
14
and high-carbon ferrochrome. The chromium emission factors for
47
-------
TABLE 7. CHROMIUM EMISSION FACTORS FROM PROCESSING OF
RAW MATERIALS AT FERROCHROME PLANTS
Emission Source
Chromium Emission Factor3*
g/kg (Ib/ton) of Chrome Ore Processed
Receipt and Storage of Chrome Ore
in Stock pile.0
Drying, Crushing, and Sizing of
Chrome Ore.
.34 (.68)
.34 (.68)
.31 (.61)
Emission factors expressed in terms of total elemental chromium.
Emissions should contain chromium in predominantly the trivalent oxidation
state.
These factors are a composite of both controlled and uncontrolled emissions
sources. The percentage of controlled and uncontrolled sources used in
determining the composite factors is given in footnotes c, d, and e. The
degree of control in each case is unspecified.
Q
Only 15 percent of the sources used to determine this composite factor
were controlled.
Approximately 75 percent of the sources used to determine this composite
factor were controlled.
Q
20 percent of the sources used to determine this composite factor were
controlled.
48
-------
ferrochrome-silicon and high-carbon ferrochrome in Table 8 were obtained by
multiplying average total particulate emissions from finishing and handling
ferroalloy products by 36 and 70 percent, respectively.
Electric arc furnaces are the most researched source of chromium
emissions in the ferrochrome manufacturing process. Table 9 gives emission
factors for ferrochrome producing furnaces expressed in term of chromium
emitted per ton of product and chromium emitted per megawatt hour of furnace
operation. Uncontrolled emission factors are based on estimates of total
particulate emissions made by industry personnel at three plants and
9
reported in a 1974 U.S. EPA report. The total particulate emission factors
were multipled by the measured average percent chromium in particulate
9
emissions at similar furnaces producing the same types of ferrochrome.
Most of the controlled chromium emission factors were based on EPA tests of
total particulate emissions. These were again multiplied by the measured
typical percent chromium in particulate emissions from ferrochrome
furnaces. ' * If different particulate collection devices collect
chromium to a greater or lesser extent than they collect other particulates
in the emission stream, the calculated chromium factors for controlled
sources could be biased. Data on chromium collection efficiency for the
ferrochromium industry is inconclusive. But as previously stated, data from
similar high-temperature processes involving chromium (including power
plants) show that chromium is collected in a similar proportion to other
13
particulates. As Table 9 illustrates, chromium emission factors vary with
the type of ferrochrome produced and the type of emissions control system.
No chromium emission factors are available for the exothermic, vacuum
furnace, or electrolytic methods of ferrochrome production.
Source Locations—
The only ferrochromium plant currently in operation is the Interlake,
Inc. plant in Ohio. Seven plants were in operation as recently as 1980,
but have been shut down for reasons previously described. A change in
49
-------
TABLE 8. CHROMIUM EMISSION FACTORS FROM FINISHING OPERATIONS
AND PRODUCT HANDLING AT FERROCHROME PLANTS
Emission Source
Chromium Emission Factors *
g/kg (Ib/ton) of Product
Ferrochrome-Silicon . High-Carbon Ferrochrome
Treatment of Molten Alloy with
Chlorine or other gas in Ladle
Casting of Ferrochrome Product
Crushing/Grinding of Product
1.7 (3.4)
.036 (.072)
.11 (.22)
3.3 (6.6)
.070 (.14)
.21 (.42)
a
Emission factors expressed in terms of total elemental chromium. Emissions
should contain chromium in both trivalent and hexavalent oxidation states.
These factors are a composite of both controlled and uncontrolled emissions sources.
The percentage of controlled and uncontrolled sources used in determining the composite
factors is given in footnotes c, d, and e. The degree of control in each case is
unspecified.
*
'Only 25 percent of the sources used to determine this composite factor were controlled.
Approximately 42 percent of the sources used to determine this composite factor were
controlled.
"93 percent of the sources used to determine this composite factor were controlled.
50
-------
TABLE 9. CHROMIUM EMISSION FACTORS FOR ELECTRIC ARC FURNACES
USED TO PRODUCE FERROCHROMES.3*5*8
Ferrochrome
Product
Chromium Emission Factors
kg/Mg (Ib/ton) of product kg/Mw hr (Ib/Mw hr)
Uncontrolled Sources
Ferrochrome-Silicon
High-Carbon Ferrochrome
and Charge Chrome
Chrome Ore/Lime Melt
Controlled Sources
Ferrochrome-Silicon
Q
Ferrochrome-Silicon
£
Ferrochrome-Silicon
Ferrochrome-Silicon
High-Carbon Ferrochrome
and Charge Chrome
High-Carbon Ferrochrome
High-Carbon Ferrochrome
High-Carbon Ferrochrome
High-Carbon Ferrochrome
1.6-5.8 (3.3-12)
24 (47)8
0.8 (1.6)1
.006 (.012)
.19
,20-.78 (,45-1.6r
3.9 (8.7)s
.63 (1.4)h
,0034 (.0076)1
.00081 (.0018)1
.00076 (.0017)1
.00002 (.00004):
.06 (.15)8
.0022 (,0049)S
.041 (,091)S
.040 (.090)8
.020 (.045)S
All factors expressed in terms of total elemental chromium. Emissions
, should contain chromium in both trivalent and hexavalent oxidation states
Open furnace controlled with a scrubber.
.Open furnace controlled with a fabric filter.
Closed furnace in Japan controlled with a scrubber.
,Qpen furnace controlled with an ESP.
Assumes-chromium is 0.4 to 1.4 percent of total particulate emissions by
weight.
?Assumes chromium is 14 percent of total particulate emissions by weight.„
.Assumes chromium is 15 percent of total particulate emissions by weight.
Assumes chromium is 0.4 percent of total controlled particulate emissions
by weight.
51
-------
demand could potentially cause these plants to be reopened, so they are
listed in Table 10. The trade group known as the Ferroalloy Association is
the best source of current information on the industry.
Refractory Manufacture
Process Description-
Refractories are heat-resistant materials which are used to build or
line high-temperature industrial furnaces. They must withstand excessive
thermal stress, physical wear, and corrosion by chemical agents. *
Several hundred types of refractory products are manufactured in the
United States, but not all contain chromium. Chromium-containing
refractories come in several different forms and compositions depending on
the end use for which they are intended.
Chromium is used primarily in the manufacture of chemically basic,
non-clay refractories, of which magnesia-chrome combinations are the most
prevalent. Magnesia-chrome refractories exhibit good mechanical strength
and volume stability in high temperature applications. The chromium compo-
nents of these refractories are effective in reducing refractory flaking and
cracking (spalling) under the fluctuating temperatures often encountered in
industrial furnaces. Magnesia-chrome refractories are also used because of
their ability to resist corrosion by chemically basic slags. Production
furnaces in the steel, copper, cement, and glass- industries make use of this
type of refractory. *
A second type of basic chromium refractory is known as
chrome-magnesite. Chrome-magnesite is very similar to magnesia-chrome
except that it contains a larger proportion of chromium, which causes it to
expand less when subjected to intense heat. Chrome-magnesite refractories
are used in the steel, glass, and non-ferrous metals industries. '
52
-------
TABLE 10. LOCATION OF PLANTS PRODUCING CHROMIUM
FERROALLOYS AS OF I9602
Producer Plant Location Process
Chromasco, Ltd. Woodstock, TN Electric Arc Furnace
Interlake, Inc.3 Beverly, OH Electric Arc Furnace
MacAlloy Corp. Charleston, SC Electric Arc Furnace
Metallburg, Inc. Newfield, NJ Exothermic
Satra Corp. Steubenville, OH Electric Arc Furnace
SKW Alloys, Inc. Calvert City, KY • Electric Arc Furnace
Union Carbide Corp. Marietta, OH Electrolytic
aOnly plant operating as of 1983.
Note: This listing is subject to change as market conditions change,
facility ownership changes, plants are closed down, etc. The reader
should verify the existence of particular facilities by consulting
current listings and/or the plants themselves. The level of chromium
emissions from any given facility is a function of variables such as
capacity, throughput, and control measures. It should be determined
through direct contacts with plant personnel. .
53
-------
Chromic oxide refractories are a third type of chemically basic
refractory, which contain only chromic oxide. They are used primarily in
furnaces in the steel and copper industries, but also have other specialty
16,17
uses.
A fourth type of chromium-containing refractory is chrome-alumina.
These alumina-containing refractories exhibit good volume stability at
extremely high temperatures. They have specific applications in the steel
17 18
and other industries such as synfuels and coal gasifiers. f
Chromium refractory material is manufactured as pre-formed bricks and
shapes and as unformed granulated or plastic compositions. Pre-formed
bricks and shapes are made into many sizes and configurations, and not just
standard rectangular bricks, to fit whatever the end-use application may be.
Unformed refractory compositions include products such as mortars, plastics
and gunning mixes, and castables which harden in place after being mixed
with water and applied. These unformed compositions are often used to line
and seal furnaces, or to repair furnaces in which refractory bricks have
.broken or deteriorated. *
Because of the many different forms, compositions, and end uses of
chromium-containing refractories» there are many variations on the
refractory manufacturing process. This report gives a general overview of
the manufacture of chromium-containing basic brick, chrome oxide brick, and
unformed chromium refractories. Figures 13 through 15 illustrate these
general manufacturing processes. It is important to recognize that there is
a distinction between refractory production using chrome ore and production
using chromic oxide. Chrome ore is mined and used in refractories in the
same chemical form as it exists in nature. Chromic oxide is chemically
derived from separate processes and refractory production using it are quite
18
different from those employing chrome ore. The production of chromium
refractory materials can'contain from one to four general operations,
depending on the type being produced. These operations include raw
materials processing, forming, firing, and final product preparation.
-------
Ul
Chromite — *~
,
.
Bonding
Agents
Chromium
Emissions
1
Initial
Crushing
Chromium
Emissions
1
_
1
1
Drying
Chromium
Emissions
1
Chromium
Emissions
1
1
Final
Grinding,
Sizing
i (3)
,
.
Fusion
Melting ~*- C
©
© ©
„. . Power
Mixing -«- pressi
1
Chromium'
Emissions
Chromium
Emissions
f
-_ Breakout.
acting »• FlnlBhing
© ©
®
ng -»- irtyi,,B »_
1
Trace
Chromium
Emissions
©
Firing _*- F
t
Fuse Cast
Basic Brick
©
Fired
Lnlshing H^_ Basic
Brick
t
Trace Chromium
Chromium Emissions
Emissions
Figure 13. Flow chart for production of chromium-containing basic brick
by casting and pressing processes.16
-------
Ln
Chromic -^
Oxide
Fugitive
Chromic-Oxide
Emissions
I
Storage
Chromic Oxide
Emissions
, t
Milling
^ Mixing
^^" Drying
t
Chromic Oxide
Emissions
Casting
Mixing
Trace
Emissions
1
Drying
Pressing
Trace Chromic Oxide
Emissions Emissions
f t
Finishing
•*" FJ r ing -^ (Gr ind ing)
Chromic Oxide
Emissions
Oxide
Figure 14. Flow chart for production of chromic oxide bricks by casting and pressing processes.
20
-------
Chromium
Emissions
Chromium
Emissions
Chromium
Emissions
i
I
Ch rome-Magnesit e
Aluminas or Other
Chromium-Containing
Materials
Grinding,
Sizing
Mixing
Packaging
Unformed
Refractory
Product
Ui
-4
Figure 15. Flow chart of production of unformed Refractories
-------
The raw materials processing step can include crushing, grinding.
drying, and sizing the raw materials (chromite, magnesite, etc.) to meet the
specifications of the particular refractory product. The second processing
step is forming, which includes mixing the raw materials and forming them
into shapes. The third processing step is firing, in which the refractory
is heated in a kiln to form a ceramic bond. This bond gives the product its
refractoriness (heat-resistant properties) and corrosion-resistant
properties. The final processing step includes post-firing operations such
as milling, grinding, sawing, coating, and packaging of the formed or
unformed refractory product.
Figure 13 illustrates the fusion casting and pressing processes that
can be used to manufacture chromium-containing basic brick. In both
processes the raw materials processing steps are the same. Chrome ore
undergoes initial crushing, drying in kilns, and final grinding and sizing
(Figure 13> pts. 1-3). Other components of the brick, such as magnesite and
periclase (a synthetic form of magnesite), are deadburned, ground and sized
(pts. 2 and 3). Fluxes and bonding agents are.added during mixing, which
16 18
occurs after final grinding and sizing. * A few refractory manufacturing
facilities use hexavalent chromium compounds such as chromic acid and sodium
chrornate in small amounts as raw materials in addition to trivalent chromite
19
ore. However, the amount of hexavalent chromium used is very small
relative to the amount of chromite ore used. Total consumption by the
refractory industry of chromic acid, the most widely used hexavalent
19
compound, was 630 Mg (700 tons) per year in 1980-82 versus 125,100 to
139,500 Mg (139,000 to 155,000 tons) per year of chromite ore consumed by
20
the industry during the same period.
The fusion casting and pressing processes differ most prominently in
the forming and firing operations. In the casting process the processed raw
materials are fusion melted together in an electric arc furnace (pt. 4) and
cast into molds (pt. 5). The final step in the casting process involves
breaking the shape out of the mold and grinding or sawing to specification
(pt. 6).16
58
-------
In the more common pressing and firing process, Che products of the raw
materials processing steps are combined in mixers (pt. 7). Then they are
shaped with a power press or occasionally a combination of heat and pressure
(pt. 8). The pressed bricks are then dried in a tunnel dryer (pt. 9) to
reduce the moisture content before firing and to develop strength for
u * u j-i- 16,18
subsequent handling.
Firing of the refractory (pt. 10) is usually accomplished in a tunnel
kiln. A few small use plants periodic kilns instead, which are slower and
less efficient. In a tunnel kiln, the formed brick travels along the tunnel
through different temperature zones. The zones include a pre-heating zone,
a zone of maximum temperatures, and a cooling zone. Maximum temperatures
range from 1,100 to 1,870'C (2,000 to 3,400°F) depending on the type of
refractory being produced. A ceramic bond can be formed at temperatures of
about 1,370°C (2,500°F). Chrome refractory bricks are meant to withstand
especially high temperatures and corrosive conditions and are fired at a
higher temperature of about 1,760°C "(3»200°F). At this temperature a strong
direct chemical bond is formed from recrystallization of the chromite,
magnesite, and bonding agents. Total residence time in the kiln ranges from
•
8 hours to over 4 days depending on the type of refractory being
A A 16>22
produced.
The last step in the pressing and firing process is finishing the
bricks (pt. 11). This step is similar to the finishing step in the fusion
casting process. It can include grinding or sawing the refractory bricks to
... t. 16,17
meet specifications.
Figure 14 is a process flow chart for the production of chromic oxide
basic brick by both the casting and pressing processes. Chromic oxide is
the raw material for this type of refractory. Chromic oxide may be ground
and sized at the plant (as in Figure 13, pts. 1-3), but it is often bought
pre-ground to specification. For this reason Figure 14 begins with the
storage of the pre-ground chromic oxide raw material at the plant
(Pt. i).16-21
59
-------
The casting process generally used to produce chromic oxide brick
differs somewhat from the fusion casting process for chrome-magnesite basic
brick previously discussed. The chrome oxide is mixed (Figure 14, pt. 2),
but not fusion melted* before casting (pt. 3). Therefore, the cast products
are dried (pt. 4) and fired along with the pressed products (pt. 8) to form
the ceramic or chemical bonds. The finishing step (pt. 9) includes grinding
21
or sawing the bricks to specification.
The pressing process which chromic oxide refractories undergo is very
similar to that used for production of other types of basic brick. An
additional step to dry the chromic oxide (pt. 5) has been added before the
mixing and pressing steps. But the mixing, pressing, firing, and finishing
of pressed chromic oxide bricks (pts. 6-9) are carried out as previously
21
discussed in connection with the basic brick pressing process.
Figure 15 illustrates the production of chromium-containing, unformed
refractory products such as mortars, plastic or ramming mixes, castables,
and gunning mixes. The process consists solely of preparing the raw
materials (i.e., grinding, sizing) at pt. 1, mixing them with additives
(pt. 2), and packaging the unformed products in bags or boxes (pt. 3).
Mixing is usually a dry process. The forming and firing steps are
i + -, ^ j 16,17,21
completely omitted.
Emission Factors—
The sources and amounts of chromium emitted from individual plants vary
widely depending on the type of refractory being produced and the type of
manufacturing equipment used. Most emissions are in the form of trivalent
chromic oxide, since hexavalent chromium compounds make up less than
19
1 percent of the industry's chromium-containing raw materials. The
chromium content of raw materials required for different refractory products
varies, causing chromium concentrations in raw material-derived particulate
emissions to vary. At some plants chrome ore is crushed and ground on-site,
causing chromium emissions, while other plants buy pre-ground chromic oxide.
60
-------
Chromium emission rates also depend on whether a casting or pressing process
is used. This section gives an overview of potential sources and rates of
chromium emissions occurring in the generalized manufacture of chrome
refractories. In order to estimate emissions from a particular plant, its
specific manufacturing process would need to be studied.
The discussion of chromium emission sources in the refractory processes
refers to Figures 13, 14, and 15. These show chromium emissions from the
manufacture of chrome-containing basic bricks, chromic oxide bricks, and
unformed refractory products, respectively. The raw materials processing
operations appear to be the most significant potential source of chromium
emissions from refractory plants. The chrome ore grinding mills (Figure 13,
pt. 1) and drying kilns (pt. 2) emit particles of chromite. The final
grinding and sizing of raw materials, shown in the formed and unformed
refractory flow-charts, also emit chromium-containing particulates.
Emissions from these sources are commonly controlled with fabric-
filters.16'21
Mixers where raw materials are combined may also be sources of
emissions. These occur at the start of the formed refractory pressing
process loops (Figure 13, pt. 7 and Figure 14, pt. 6) and in the manufacture
of unformed refractories (Figure 15, pt. 2). If the mixing is a damp
process, emissions are slight. Dry mixing, however, emits a substantial
quantity of particulates. Wet scrubbers or cyclone/fabric filter
•I £ ^l
combinations are used to control this source. *
Other sources of emissions from the pressing process include dryers and
kilns (Figure 13, pt. 9 and 2, Figure 14, pt. 5 and 8). Brick dryers and
kilns are viewed as minor sources of chromium emissions. These sources are
11 ^ 11 j 16,21,23,24
usually uncontrolled.
61
-------
In the manufacture of chrome-containing basic brick by the fusion
casting process, chromium emissions originate from arc furnaces where chrome
ore and other raw materials are fusion melted (Figure 13, pt. 4). The
fluxing action in these arc furnaces entrains chromium-containing fugitive
particulates, which are usually collected and controlled by means of a.
fabric filter.16
The finishing step is a potential source of chromium emissions during
the manufacture of all formed and unformed chrome refractory products. This
step, shown in Figures 13, 14, and 15, can include grinding, sawing, and
packaging final refractory products. As the chromium-containing refractory
products are finished and handled, chromium-containing dust can be
generated. Such emissions, if substantial, are usually ducted to fabric
filters.16
Table 11 presents controlled and uncontrolled emission factprs for
plants producing chrome-containing bricks by the pressing and fusion casting
processes. These figures are taken from a 1973 study that reports total
uncontrolled pressing process emissions from crushing, sizing and drying of
chrome ore raw materials to be 75 kg/Mg (150 Ib/ton). This study also
reports uncontrolled pressing process emissions from brick firing kilns to
23
be about 0.1 kg/Mg (0,2 Ib/ton). A control efficiency of 64 percent from
the 1973 study was used to calculate the controlled chromium emission
23
factors shown on Table 11.
For the fusion casting process, the 1973 EPA report estimated
23
uncontrolled chromium emissions to be 112 kg/Mg (225 Ib/ton). This factor
is also included in Table 11. Since the initial processing of raw materials
(crushing, sizing) is similar for the casting and pressing processes, it
would appear that about 75 Mg/kg (150 Ib/ton) would come from raw materials
processing. The additional 37 Mg/kg (75 Ib/ton) of chromium emitted in the
casting process would presumably come from arc furnaces and breakout and
finishing of the cast refractory products. The 1973 report assumed
77 percent efficiency in calculating controlled emission rates from the
23
casting process.
62
-------
TABLE 11. CHROMIUM EMISSION FACTORS FOR THE REFRACTORY INDUSTRY
23
Chromium Emission Factors, kg/Mj
(Ib/ton) of Refractory Produced*
Type of Process
Uncontrolled
Controlled
Total Pressing Process
- Ore Crushing, Sizing, Drying
- Brick Firing Kilns
Total Fusion Casting Process
- Ore Crushing, Sizing, Drying
- Fusion Melting, Casting,
Breakout, and Finishing
75
75
0.1
112
75
37
(150)b
*(150)
(0.2)d
(225)
(150)
(75.)
27
' 27
26
17
9
(54) <;
(54) c
e
(52)*
(34) r
(18)
Emission factors are expressed in terms of total elemental chromium.
Chromium emissions should predominantly contain trivalent chromium.
Reference 18 reported that this emission factor grossly overstates
uncontrolled emissions.
*his figure assumes a 64 percent control efficiency.
A 1980 study indicated that uncontrolled emissions from kilns are less
than 0.5 kg/Mg (1.0 Ib/ton).
This source is not controlled.
This figure assumes a 77 percent control efficiency.
63
-------
Recent data indicates that 90 to 99.9 percent control of chromium
emissions can be effected in the refractory industry. Controlled chromium
emission factors for Table 12 were developed using data on two plants
21 24
available through state government agencies. * Total particulate
emission rates from each source listed on Table 12 were available from the
agencies. Throughputs of chromium-containing raw materials were also given.
To calculate chromium emissions on the basis of per ton of raw materials
throughput, three assumptions were made. The first is that refractory grade
25
chrome ore contains 34 percent chromic oxide. The second is that the
weight of elemental chrome is 68.4 percent of the total weight of chromic
oxide (Cr-O-). The third is that concentration of chromium in particulates
emitted is the same as the concentration of chromium in the raw materials.
Table 12 gives the resulting controlled chromium emission factors for
different steps in the manufacture of chrome-magnesite and chromic oxide
bricks.
Source Locations—
Based on the most recent data available, there are; in 1984, 43 plants
owned by 26 companies in the United States producing chromium-containing
18 26
refractories. The locations of these plants are given in Table 13. '
Chromium Chemicals Manufacture
Process Description—
Approximately 40 different chromium chemicals are manufactured in the
United States, most of which are low volume chemicals. The largest volume
and most commercially significant chromium chemicals are sodium chrornate and
sodium dichromate. These chromium chemicals are significant because all
other domestically manufactured chromium compounds use sodium chrornate or
dichromate as their primary feedstock material. The more important secon-
dary chemicals include chromic acid, potassium chrornate and dichromate,
ammonium dichromate, basic chromic sulfate, and chrome pigments (chrome
oxide green, chrome yellow, chrome orange, molybdate chrome orange, and
, v 27,28
chrome green).
64
-------
TABLE 12. CONTROLLED CHROMIUM EMISSION FACTORS
FOR THE REFRACTORY INDUSTRY21*24
Emission Source
Chromium Emission Factor
kg/Mg (Ib/ton) of Raw
Materials Processed
Control
Device
Control
Efficiency %
Chrome-Magnesite Brick
Production
Chrome Ore Preparation
Ore storage, grinding,
and sizing
Dryer
Storage in raw
materials silo
.01-.05 (.02-.10)'
fabric filter
fabric filter
.0018-.002C.0035-.0041)
,0022-.0032(.0045-.0065)C fabric filter
Pressing and Firing
Mixer
Brick dryer
Brick kiln
Chromic Oxide Brick
Production
Casting Process
,0005-.0022(.0011-.0043)C fabric filter
.00037 (,00074)c scrubber
.00044 (.00099)
scrubber
99.9
99.9
99.9
99.9
90.0
90.0
Milling (ball mill)
Spray dryer
Pressing Process
Mixer
.48 (.96)°
.48 (,96)d
.48 (.96)d
wet scrubber
fabric filter
wet scrubber
97.0
97.0
97.0
Emissions reported as total elemental chromium. Chromium emissions should
contain predominantly trivalent chromium.
Raw materials processed in this step include only chrome ore.
«
"Raw materials processed in this step are a mixture of chrome ore and
magnesite.
Raw materials processed in this step include only chromic oxide.
65
-------
TABLE 13. LOCATIONS OF PLANTS PRODUCING CHROMIUM REFRACTORY MATERIALS
18,26
State, City
Company
Alabama
Anniston
Pell City
California
Moss Landing
Colorado
Pueblo
Georgia
Augusta
Illinois
Aurora
Addison
Chicago
Chicago Heights
Indiana
Crown Point
Hammond
New Carlisle
Kentucky
South Shore
Louisiana
New Iberia
Maryland
Baltimore
Michigan
Manistee
South Rockwood
Mississippi
Pascagoula
Donoho Clay Company
Riverside Refractories, Inc,
Kaiser Refractories
A. P. Greene Refractories Co.
Babcock and Wilcox
C-E Refractories
Magneco/Metrel, Inc.
Chicago/Wellsville Fire Brick Co,
Salazar and Sons, Inc.
C-E Refractories
BMI, Inc.
Harbison-Walker Refractories
The Carborundum Company
Didier Taylor Refractories Corp
the Carborundum Company
Harbison-Walker Refractories
General Refractories
Martin Marietta Chemicals
BMI, Inc.
Corhart Refractories Co.
66
-------
TABLE 13. (CONTINUED) LOCATIONS OF PLANTS PRODUCING
CHROMIUM REFRACTORY MATERIALS
State, City
Company
Missouri
Mexico
Wellsville
Webster Grove
New Jersey
Old Bridge
New York
Falconer
Ohio
• Cincinnati
Columbiana.
Irondale
Maple Grove
Negley
South Webster
Pennsylvania
Alexandria
Norristown
Plymouth Meeting
Snowshoe
Somerset
Tarentum
Womelsdorf
Zelienople
Utah
Lehi
A. P. Greene Refractories Co.
Kaiser Refractories
Chicago/Wellsville Fire Brick Co,
Missouri Refractories
The Quigley Company
The Carborundum Company
Coastal Refractories» Inc
Didier Taylor Refractories Corp,
Kaiser Refractories .
Maryland Refractories
Basic Refractories
Magneco/Metrel, Inc.
BMI, Inc.
Maryland Refractories
Resco Products, Inc.
Kaiser Refractories
J. H. France Refractories Co.
Bognar and Co.» Inc.
A. P. Greene Refractories Co.
North American Refractories Co.
Lava Crucible Refractories Co.
General Refractories Co.
West Virginia
Buckhannon
Cohart Refractories Co.
Note: This listing is subject to change as market conditions change,
facility ownership changes, plants are closed down, etc. The reader
should verify the existence of particular facilities by consulting
current listings and/or the plants themselves. The level of chromium
emissions from any given facility is a function of variables such as
capacity, throughput, and control measures. It should be determined
through direct contacts with plant personnel.
67
-------
The production of the primary compounds, sodium chr ornate and
dichromate, has the greatest potential for atmospheric emissions of all the
chromium chemical manufacturing processes. The emissions potential is great
because of the large volume level of production, the large quantity of
chromice ore processed, and the dry chemistry operations in the chr ornate and
dichromate processes. Chromium emissions from the production of many other
chromium chemicals are negligible or nonexistent because the processes
involve all wet chemistry and/or the processes are of relatively low
temperature to prevent any chromium volatilization. Little or no
information is available to characterize the production and emissions of
secondary chromium chemical compounds.
The processes used to manufacture sodium chr ornate and sodium dichromate
are shown in Figures 16 and 17, respectively. To initiate the sodium
chr ornate process chrome ore is crushed (if it was not bought already sized '
to specification), dried, and ground to a powder in a ball mill (Figure 16,
pt. 1). The ground chrome ore is then mixed (pt. 2) with soda ash, lime,
and usually leached calcine residue from a previous roasting operation. The
mixture is then roasted in a rotary kiln at temperatures of 1,100 to 1,150°C
(2,Q10-2,100°F) for about 4 hours (pt. 3). Oxidation occurs and sodium
chr ornate is produced with the basic reaction being:
4 FeCr204 + 8 N^O^ + 702 * 2 Fe^ -t- 8 Na2Cr04 + 8C02
At the American Chrome and Chemical plant, a gas-fired furnace equipped with
a revolving annular hearth is used instead of a rotary kiln to accomplish
27
the roasting reaction.
The kiln roast is then discharged through a cooler and leached (pt. 4).
The leached calcine is recycled to the raw materials mixing station (pt. 2)
for the purpose of diluting the kiln feed. If sodium aluminate is present
68
-------
Chromium
Emissions
Soda
Ash Line
Chromium
Emissions
Chromium
Emissions
Chromium
Emissions
Recycled
Bichromate
Mother Liquor
Chromium
Emisaiona
Chrome_
Ore
Pal)
Mill
CD
Mixer
Qj
Wash
Rotary
Kiln
0
er Residue
Leacli
Box
G>
Crude
Clir ornate
Liquor
Alumina
Precipi--
tatlon
0
Filter
|O
Chroma te
Liquor
•Dump
Alumina
(Gibbflite)
Refined
Chroma te
Liquor
Chromium
Emissions
f
Evaporator
and /or
Cryetalllzer
G>
Solution
®
Chromium
Emissions
^~ Dryer
CD
Chromium
Emissions
1
*• Packaging ' *•
O
Dry Technical Grade
Sodium Chromate
Sodium Chromate Solution
Final Product
To Manufacture of
Sodium Bichromate (Figure 2)
Figure 16. Flow chart for the production of sodium chromate.
27-29
-------
H
Refined
Chroma te ^
Liquor
(Figure 1)
O
„- Chromium
2 4 Emissions
1 1
Acid
Treatment
Tank
O
Crude
Dichromate
Liquor
Chromium
FjnlsBBlons
Evaporator
0
Centrifuge
©
1
Dryer
>-^
Chromium
Emissions
Settler
^,
Purified
Bichromate^ Crystal izer _ Centrif uee
Liquor *- -*- -3
Chromium
Emissions
I
Dryer
Sodium © ^ Dichromate ®
Sulfate Mother
Y Liquor
Packaging
1
Hay be recycled
Alumina Preclplt
Step of Chroma te
Sodium (Figure 1, pt. 5
—*~ Sulfate
Byproduct
to
at ion
Process
>
Chromium
Emlneiona
Packaging
-------
in the chrornate liquor, alumina must be precipitated before any further
chromium processing. To accomplish this, sodium dichrornate liquor from the
dichrornate manufacturing process is typically added to hydrolizing tanks
(pt. 5) and the pH of the solution maintained at 9. Alumina in the form of
gibbsite (A12°3% H2°^ tnen PreciPitates and is filtered off (pt. 6), leaving
a refined chromate liquor. A variation on this process, which involves
raising the pH to 10 and then lowering it to 6.5, is claimed to give very
27
readily filterable alumina.
The refined chromate liquor can then be sold as a solution, or it can
be evaporated to dryness or crystallized (pts. 7 and 8) and sold as tech-
27
nical grade sodium chromate or sodium chromate tetrahydride.
Most of the refined chromate liquor generated is used to produce sodium
dichromate. During this process, sodium chromate is converted to dichrornate
(Na.Cr.O.) by treatment with sulfuric acid (Figure 17, pt. 1). The sodium
dichromate liquor is evaporated and a sodium sulfate byproduct is
precipitated (pt. 2 and 3). The now purified and concentrated dichromate
liquor is crystallized (pt. 4), put through a crystal centrifuge (pt. 5),
and dried (pt. 6) and packaged (pt. 7) as the final sodium dichromate
, fc 27,29
product.
The sodium sulfate, which was precipitated at pt. 3, is centrifuged and
dried (pt. 8-and 9). The filtrate is recycled to the evaporator (from pt. 8
to pt. 2), and the dried sodium sulfate is packaged (pt. 10) and sold.
Sodium dichromate mother liquor is generated when the sodium dichromate is
crystallized and centrifuged (pt. 4 and 5). It can be packaged (pt. 11) and
sold as 69 percent sodium dichromate solution or recycled to the dichromate
evaporation (pt. 2) or alumina precipitation (Figure 16, pt. 5)
„< 27,29
operations.
71
-------
To illustrate the significance and role of sodium chrornate and sodium
dichrornate in the production of secondary chromium chemicals, brief process
descriptions are presented of chromic acid and potassium and ammonium
dichrornates production. The production of numerous other secondary chromium
chemicals is not described, nor are emissions data available therein. For
more details on these production processes, the reader should consult
references 27 and 29.
Chromic acid (CrO-), also known as chromium trioxide or chromic
anhydride, can be produced by more than one method. The traditional chromic
acid production process involves mixing sodium dichrornate dihydrate with
sulfuric acid in a reactor which is heated externally and stirred with a
sweep agitator. The chemical reaction taking place is shown below.
Na2Cr2Oy + 2H2S04 -*• 2Cr03 + 2NaHS04 + HjO
Water is driven off and the hydrous sodium bisulfate melts at 160°C (320°F).
The molten bisulfate provides a heat transfer medium for the melting of
chromic acid at 197°C (387°F). The agitator is turned off, and the mixture
separates into a heavy layer of molten chromic acid and a light layer of
sodium bisulfate. The chromic acid layer is tapped from the reactor and
27
flaked on water cooled rolls to produce the commercial product.
• A second method for producing chromic acid is illustrated by
27 30
Figure 18. * A large amount of sulfuric acid is first added to a
concentrated solution of sodium dichrornate (pt. 1). A crude chromic acid
containing sodium bisulfate and some sulfuric acid is precipitated and
separated by filtration (pt. 2). The crude chromic acid is then melted
(pt. 3)'in this small amount of sodium bisulfate, with sodium dichrornate
added to convert any excess sulfuric acid into chromic acid. The chromic
acid is then flaked as in the traditional process (pt. 4), packaged (pt. 5),
and sold. Less waste sodium bisulfate is produced by this process than by
27 30 31
the traditional chromic acid manufacturing process. * "
72
-------
Sodium
Dichromate
Solution
Sulfuric
Acid (H2S04)
Chromium
Emissions
Chromic
Acid
Reactor
Chromium
Emissions
\
Filter
Chromium
Emissions
Chromium ^
Emissions
Chromium
Emissions
f
Melter
oo
Sodium Dichromate and
Sodium Bisulfate as needed
Flakers
Packaging
f
Chromic Acid
Products
Figure 18. Flow chart for chromic acid production.
27,30
73
-------
Potassium and ammonium chromates and dichromates are also produced from
sodium dichromate. These are generally made by reacting sodium dichrornate
with an equivalent amount of potassium chloride or ammonium sulfate in a
crystallization process. Care must be taken in drying ammonium dichromate
because decomposition starts at 185°C (365°F). Potassium chromate Is made
27
from the reaction of potassium dichromate and potassium hydroxide.
Emission Factors-
Possible sources of chromium-containing emissions from the production
of sodium chromate are shown in Figure 16. The ball mill and mixer (pts. 1
and 2) emit chrome ore particulates. Fabric filters are typically used to
27 32 33
control these sources with efficiencies of over 99 percent. * '
Chromium emissions from kilns (pt. 3) are controlled with ESPs or cyclones
07 TJ ^./ *3 ^
and scrubbers. * * * Electrostatic precipitators can be over
99 percent efficient in controlling chromium emissions from this
27 32 35
source; * * cyclones and scrubbers are somewhat less effective.
Leaching tanks (pt. 6) also emit chromium. These are usually hooded and
emissions are funneled into stacks equipped with wet scrubbers. From 90 to
over 98 percent control has been achieved depending on the type of scrubber
27 36 *
and the throughput. * The filter (pt. 6) is the final chromium emission
source in the production of refined sodium chromate liquor. If the chromate
liquor is then converted to dry sodium chromate products, the evaporators
and dryers (pts. 7 and 8) will be sources of particulates containing sodium
chromate. These sources are controlled with ESPs or cyclones and wet
scrubbers. Chromium-containing dust arising from handling and packaging of
27 34
the final product (pt. 10) is usually channeled into fabric filters. '
Sources of chromium-containing particulate emissions from the sodium
dichromate manufacturing process (Figure 17} include the acid treatment
tank, evaporator, crystallizer, and dryer. These sources are controlled
with ESPs or cyclones and wet 'scrubbers. Emissions from packaging are
74
-------
controlled by fabric filters. Efficiencies of these devices are similar to
those reported in connection with the chrornate manufacturing
27,36,37
process.
The largest sources of chromium emissions from chromic acid production
are the reactor, the filter, and the packaging process. Melters and flakers
are minor sources. Scrubbers are commonly used to reduce chromium-
containing particulates at all of these points, although fabric filters may
also be used at the packaging step. Efficiencies of over 95 percent are
27 30 35
reported from testing at a plant which uses wet scrubbers. * *
Table 14 gives emission factors derived from a 1973 EPA report for the
23
combined production of sodium chrornate and dichromate. All chrornate is
assumed to be converted to dichromate. Actual emissions testing data were
used to determine the uncontrolled factor given for kiln emissions.
However, the uncontrolled factor which the 1973 report lists for total
process emissions is an estimate based on the assumption that other process
emission sources, mainly dryers, emit roughly the same amount as the kiln.
The figures given for controlled emissions in Table 14 were based on the
23
1973 report's assumption of 90 percent control efficiency. As the
preceeding discussion on emission sources and controls states, efficiencies
of well over 90 percent are achieved with modern control devices.
TABLE 14. CHROMIUM EMISSION FACTORS FOR SODIUM
DICHROMATE MANUFACTURING PLANTS23
Source of Emissions
Chromium Emission Factors
kg/Mg (Ib/ton) of Dichromate Produced*
Uncontrolled Controlled
Total Process
Kiln Only
15 (30)
7.5 (15)
1.5 (3.0)'
0.7 (1.5)1
All emission factors expressed in terms of total elemental chromium.
Emissions should contain chromium in predominantly the hexavalent
oxidation state.
Factor assumes a control efficiency of 90 percent.
75
-------
Table 15 lists chromium emission factors for chromic acid production
30
derived from test data on one plant. The total raw materials throughput
and particulate emission rates were given for each step of the plant's
chromic acid process. To derive the figures in Table 15, it was assumed
that partlculates emitted were mainly chromic acid and that chromium
constitutes 52 percent of chromic acid by weight.
No emission factors are available for the production of other secondary
chromium chemicals.
TABLE 15. CHROMIDM EMISSION FACTORS FOR CHROMIC ACID PRODUCTION30
Chromium Emission Factors kg/Mg (Ib/ton) Measured
of Raw Materials Processed3 Control
Emission Source Uncontrolled Controlled Efficiency
Chromic Acid Reactor,
Melter, and Flaker
Chromic Acid Filter
Packaging
0.2 (0.4)
1.4 (2.8)
0.7 (1.4)
.01 (.02)b 95%
.01 (,03)b 99%
.04 <.07)b 95%
a
chromium in predominantly the hexavalent oxidation state.
'Emission source controlled by scrubbers.
Source Locations-
There were three plants in the United States in 1983 producing sodium
38
chromates and dichromates. Their locations are given in Table 16. The
locations of plants producing secondary chromium chemicals are shown in
19
Table 17.
76
-------
TABLE 16. LOCATIONS OF SODIUM CHROMATE AND SODIUM DICHROMATE
MANUFACTURING PLANTS38
Owner
Location
Production of
Sodium Chromate
as End Product
Allied Corp.
American Chrome
& Chemicals, Inc.
Diamond Shamrock
Baltimore, MD
Corpus Christi, TX
Castle Hayne, NC
Yes
Yes
No
Note: This listing is subject to change as market conditions change,
facility ownership changes, plants are closed down, etc. The
reader should verify the existence of particular facilities by
consulting current listings and/or the plants themselves. The
level of chromium emissions from any given facility is a function
of variables such as capacity, throughput, and control measures.
It should be determined through direct contacts with plant
personnel.
Chromium Plating .
Process Description-
Chromium is plated onto various substrates in order to provide a
decorative and corrosion resistant surface. Steel, brass, aluminum,
plastics, and zinc die castings may serve as substrates. The two major
types of chromium plating are decorative and hard. Decorative plate
consists of a thin (0.25 urn thick) layer of chromium which is applied over a
layer of nickel to provide a bright, tarnish-resistant surface. Decorative
chrome plate is popular for consumer items such as auto trim. Hard plating
produces a thicker chromium layer (10 to over 300 urn thick) which has
excellent hardness and wear-resistance and a low coefficient of
40 41
friction. * Applications include drills, reamers, burnishing bars,
drawing plugs or mandrels, drawing dies, plastic molds, gages, pump shafts,
42
rolls and drums, hydraulic rams, and printing plates. The electroplating
process used to produce the two types of chromium plates are similar.
77
-------
TABLE 17. LOCATIONS OF COMPANIES PRODUCING SECONDARY CHROMIUM CHEMICALS
39
Chemical Compound and
Corporate Producer
Location
Ammonium dichromate
Allied Corporation
Richardson-Vicks» Inc.
Barium chromate
Barium and Chemicals, Inc.
National Industrial Chemical Co.
Chrome lignosulfonate
Dixie Chemical Co.
Chromic acid
Allied Corporation
Diamond Shamrock Corp.
Chromium acetate
American Cyanamid Co.
Blue Grass Chemical Specialties Co.
McGean Chemical Co., Inc.
The Shepherd Chemical Co.
Chromium acetylacetone
Gulf Oil Corp.
McKenzie Chemical Works, Inc* •
The Shepherd Chemical Co.
Chromium bromide mono-
Thiokol Corp.
Chromium carbide
Union Carbide Corp.
Chromium carbonyl
Pressure Chemical Co.
Strem Chemicals, Inc.
Chromium chloride, basic
Diamond Shamrock Corp.
Chromium chloride, (chromic)
Blue Grass Chemical Specialties, Inc.
McGean Chemical Co., Inc.
Baltimore, MD
Phillipsburg, NJ
Steubenville, OH
Chicago, IL
Bayport, TX
Baltimore, MD
Castle Hayne, NC
Charlotte, NC
New Albany, IN
Woodbridge, NJ
Cleveland, OH
Cincinnati, OH
Gloucester City, NJ
Bush, LA
Cincinnati, OH
Danvers, MA
Niagra Falls, NY
Pittsburgh, PA
Newburyport, MA
Ashtabula, OH
New Albany, IN
Cleveland, OH
78
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TABLE 17. (CONTINUED) LOCATIONS OF COMPANIES PRODUCING
SECONDARY CHROMIUM CHEMICALS
39
Chemical Compound and
Corporate Producer
Location
Chromium diboride
Thiokol Corp.
Chromium diflouride
Fennwalt Corp.
Chromium dioxide
E.I. DuPont de Nemours & Co., Inc.
Chromium 2-ethylhexanoate
Mooney Chemicals, Inc.
The Shepherd Chemical Co.
Chromium flouride
Gulf Oil Corp.
Chromium hydroxide
Pfizer Inc.
Chromium hydroxy diacetate
McGean Chemical Co., Inc.
Chromium hydroxy dichloride
McGean Chemical Co., Inc.
Chromium naphthenate
Mooney Chemicals, Inc.
Troy Chemical Corp.
Chromium nitrate
Allied Corporation
The Shepherd Chem. Co.
Chromium oleate
The Shepherd Chem. Co.
Troy Chemical Corp.
Danvers, MA
Tulsa, OK
Newport, DE
Franklin, PA
Cincinnati, OH
Cleveland, OH
Lehigh Gap, PA
Cleveland, OH
Cleveland, OH
Franklin, PA
Newark, NJ
Claymont, DE
Cincinnati, OH
Cincinnati, OH
Newark, NJ
79
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TABLE 17. (CONTINUED) LOCATIONS OF COMPANIES PRODUCING
SECONDARY CHROMIUM CHEMICALS39
Chemical Compound and
Corporate Producer
Location
Chromium oxide (chrome greens)
Ciba-Geigy Corp.
Minnesota Mining and Manufacturing Co,
National Industrial Chemical Co.
Pfizer Inc.
Rockwood Industries, Inc.
Chromium phosphate
Ciba-Geigy Corp.
National Industrial Chemical Co.
Chromium potassium sulfate
McGean Chemical Co., Inc.
Chromium sulfate
Blue Grass Chemical Specialties, Inc.
Hydrite Chemical Co.
Chromium sulfate, basic
Ciba-Geigy Corp.
Chromium triacetate
Diamond Shamrock Corp.
Chromium triflouride
Pennwalt Corp.
Lead chromate (chrome yellow)
Ciba-Geigy Corp. .
Hydrite Chemical Co.
National Industrial Chemical Co.
Rockwood Industries, Inc.
Molybdate orange
Ciba-Geigy Corp..
Potassium chromate
Allied Corporation
Glens Falls, NY
Copley, OH
Chicago, XL
Lehigh Gap, PA
Los Angeles, CA
Beltsville, MD
Glens Falls, NY
Chicago, IL
Cleveland, OH
New Albany, IN
Milwaukee, WI
Salem, MA
Ashtabula, OH
Tulsa, OK
Glens Falls, NY
Milwaukee, WI
Chicago, IL
Los Angeles, CA
Beltsville, MD
Glens Falls, NY
Baltimore, MD
80
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TABLE 17. (CONTINUED) LOCATIONS OF COMPANIES PRODUCING
SECONDARY CHROMIUM CHEMICALS39
Chemical Compound and
Corporate Producer ' Location
Potassium dichrornate
Allied Corporation Baltimore, MD
Strontium chromate
Barium and Chemicals, Inc. Steubenville, OH
National Industrial Chemical Co. Chicago, IL
Rockwood Industries, Inc. Beltsville, MD
Zinc chromate
National Industrial Chemical Co. Chicago, IL
Rockwood Industries, Inc. Beltsville, MD
Los Angeles, CA
Note: This listing is subject to change as market conditions change,
facility ownership changes, plants are closed down, etc. The reader
should verify the existence of particular facilities by consulting
current listings and/or the plants themselves. The level of chromium
emissions from any given facility is a function of variables such as
capacity, throughput, and control measures. It should be determined
through direct contacts with plant personnel.
81
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Figure 19 provides a generalized flow chart for decorative chromium
plating on a steel substrate. Figure 20 shows the hard plating process* for
which steel is the usual substrate. Possible variations on the processes
shown in Figures 19 and 20 are discussed below. Plating operations
generally Involve dipping the substrate into tanks containing various
solutions. The substrate items may be moved between tanks manually or using
automation. The decorative and hard plating processes both involve cleaning
and preparing the substrate followed by the electrodeposition of chromium.
It should be noted that rinsing is carried out between every cleaning and
plating step. When a part being plated is moved from one tank to the next,
some of the solution from the first tank will remain on the part and be
transferred to the next tank. This process is termed drag-in, and rinsing
between plating steps is necessary to reduce contamination of plating
solutions by drag-in.
The chromium plating processes start with a pretreatment step
(Figure 19, pt. 1 and Figure 20, pt. 1) which can consist of mechanical
buffing, polishing, and vapor degreasing or soaking in an organic solvent.
Alkaline cleaning (Figure 19, pt. 2 and Figure 20, pt. 2) removes surface
soil and is accomplished by soaking and/or electrolytic processes. Gas
evolution on the surface of the substrate aids the cleaning agent's action
in electrolytic alkaline cleaning. More details on electrolytic processes
are given in reference 41 in connection with chromium electroplating tanks.
After cleaning, the substrate is dipped in acid (Figure 19, pt. 3 and
Figure 20, pt. 3) to remove tarnish and to neutralize the. alkaline film on
its surface. At this point* the steel substrate is clean and ready to
accept a metal deposit.
In the case of decorative chromium plating, an undercoat of copper is
applied to the steel in two plating steps, with an acid rinse between each
step (Figure 19, pts. 4-6). Next a nickel plate is applied by
electrodeposition (pts. 7 and 8). These undercoats prohibit undesirable
reactions between the substrate and the final plate which could embrittle
82
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Steel Substrate
To Be Plated
Pretreatment Seep
(polishing, grinding,
degreasing)
Alkaline Cleaning
Rinse
Acid Dip
Rins*
Strike Plating of
Copper
Rinse
Acid Dip
Rinse
Electroplating of
Copper
Rinse
Electroplating of
Semibright Nickel
Rinse
Electroplating of
Bright Nickel
Rinse
Electroplating of
Chromium
Rinse
I
Decorative Chromium
Plated Product
Chromic Acid
Emissions
Figure 19. Flow chart for decorative chromium plating on a steel substrate.
42
83
-------
Substrate to be
Plated
Pretreatment Step
(Polishing, grinding,
degreasing)
1
Alkaline Cleaning
Rinse
1
Acid Dip
Rinse
Chromic Acid"
Anodic Treatment
Rinse
Electroplating of
Chromium
Rinse
Hard Chromium Plated
Product
Chromic Acid
Emissions
Chromic Acid
Emissions
Figure 20. Flow chart for hard chromium plating,
42
84
-------
the final product. Nickel also provides the basic protection and
wear-resistance of the plated part since the decorative chrome layer is very
thin. The final step in the decorative plating process is the
electrodeposition of a thin layer of chrome (pt. 9).
In the hard chromium plating process, the cleaned substrate undergoes
an anodizing treatment (pt. 4). This puts a protective oxide film on the
metal by an electrolytic process in which the substrate serves as the anode.
Then the hard chromium layer is electrodeposited (pt. 5} without any
40-42
undercoating of copper or nickel.
42
A typical chromium electroplating tank is pictured in Figure 21. The
system consists of a cathode and an anode, both immersed in electrolyte.
Generally the part to be plated functions as the cathode, and the anode is a
bar of lead-antimony or lead-tin alloy. The electrolyte contains ions of
hexavalent chromium (from chromic acid) and small amounts of another anion,
usually sulfate. The sulfate, or sometimes fluoride, improves the
42
electrical conductivity of the electrolyte bath.
To accomplish the plating process, low voltage direct current process
electricity is charged through the electrolyte bath. Electrolytic
decomposition of water in the bath releases hydrogen gas at the cathode and,
oxygen at the anode. As these gases rise to the surface of the bath, a mist
of electrolyte is .formed and chromium metal is deposited on the substrate.
Table 18 shows the composition of conventional chromium plating
solutions, and the temperature and current densities in a typical tank.
Recently developed proprietary processes substitute fluoride or fluor-
silicate ions for sulfate ions in the electrolytic plating solution,
resulting in more efficient chromium plating. Another area of present
investigations involves using trivalent chromium baths as an alternative to
hexavalent chromic acid plating baths. The extent of use of trivalent
chromium plating solutions is unknown.
85
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Anode bar
Anodes
Insulating
block
Cathode
bus
Flexible
conduct
Anode bus
brk bar
Low-rpm drive motor
to move work bar
in oscillating
motion
Connecting rod
Cooling or heating
coil
Rack load of parts
suspended from work
bar
Tank
Figure 21. Cutaway view of electroplating tank.
42
86
-------
TABLE 18. TYPICAL CHROMIUM-PLATING CONDITIONS USING
CONVENTIONAL BATHS42
Decorative Plates
Hard Chromium
Dilute
Concentrated
Chromic acid (CrO.) , g/1
Sulfuric acid
, g/1
Cathode current density,
Temperature, °C
Deposition rate, ym/hr
250-400
2.5-4
125.0-1750
38-43
8-13
250
2.5
3100
55
25
400
4
2200
50
13
87
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Current efficiency of chromium deposition is low, about 8 to 12 percent
for conventional baths and up to 20 percent for newer flouride ion
solutions. This and other factors combine to require long plating times for
depositions of the thickness required in bard chromium plating. Table 18
gives typical chromium plate deposition rates.
The chromium electrodeposition step is the same no matter what
substrate material is used. However, the cleaning and preparation of other
metal substrates may differ from those discussed for steel (Figures 19 and
20). For example, the copper undercoat may be applied in one plating step
rather than the two copper plating steps for steel substrates shown in
Figure 19. Similarly, nickel underplate may be applied in one rather than
two steps. On aluminum substrate, a zinc plate is usually applied before
the copper plate. When plating on plastic, the cleaned surface must be
activated, rendered catalytic, and given an electroless deposit of nickel or
40
copper before the electrolytic deposition of copper, nickel, and chromium.
these process variations, however, do not affect the procedures used in or
emissions front the final chromium electroplating step.
Emission Factors—
The only potential source of chromium emissions from the decorative
chromium plating process is the electroplating step (Figure 19, point 9).
Chromium emissions from the hard plating process (Figure 20) are generated
in the electroplating step and in the chromic acid anodizing treatment step.
In the chromium electroplating steps of the decorative and hard plating
processes, mists or aerosols of the electrolyte (primarily chromic acid) are
generated. Variables that affect electroplating emission rates include the
bath temperature, the concentration of bath constituents, the amount of work
being plated, and the plating current. The chromium plating tank in the
hard chromium process generates more -chromic acid mist than the plating tank
in Che decorative process because a higher current density is used for metal
deposition (see Table 18). The higher current density causes higher rates
40
of gassing thereby generating more chromic acid mist.
88
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Hooding is generally used on chromium electroplating tanks to collect
chromium-containing gasses and convey them out of the plating building. Wet
scrubbers are often used to control chromic acid emissions from plating
operations. The efficiency of wet scrubbers in collecting chromium
43 44
emissions from electroplating tanks is reported to be 95 percent. * A
system developed at one plating operation combines a wet scrubber, multiple
stages of electrostatic precipitators, and an activated carbon filter. The
44
tested chromium removal efficiency is 99.7 percent.
Chromium emission factors for electroplating operations are limited,
particularly for the decorative plating process. Table 19 shows chromium
emission factors developed from the testing of one hard chromium plating
45
operation. Emission factor data for decorative plating are much more
limited; however, uncontrolled emissions from one 4,920 liter (1,300 gallon)
tank used for decorative chromium plating were reported to be 0.20 kg
40
(0.45 Ib) of chromic acid per hour.
Source Locations-
There are several thousand chromium plating operations in the United
States. Listings can be found in standard manufacturing directories such as
the Thomas Register of American Manufacturers and Thomas Register Catalog
46
File. To access published directories of manufacturing firms and to
identify additional chromium electroplaters, use SIC Code 3471 — Electro-
plating, Plating, Polishing, Anodizing and Coloring. Sites of chromium
electroplaters may also be obtained from the membership roles of the trade
associations known as the American Electroplaters Society, Inc. and the
National Metal Finishers Association.
89
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TABLE 19. UNCONTROLLED CHROMIUM EMISSION FACTORS FROM
ONE HARD CHROMItJM~*&ATIflG TACILITY45
Source of Emissions
Chromium Emission Factor
kg/hr'm2 (ib/hr*ft2) of Tank Area
Hard Plating Tank
Hard Plating Tank
Hard Plating Tank
Chromic Acid Anodizing Tank
0.00041 (0.000084)
0.00026 - 0.0014 (0.000054 - 0.00029)
0.00043-- 0.0012 (0.000088 - 0.00025)
0.0093 (0.0019)
aFactors are expressed in terms of chromic acid. All chromium is in the
hexavalent form.
90
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Steel Production
In 1982, 49 percent of the chromite ore consumed in the United States
was used In the metallurgical industry* mainly to produce chromium
ferroalloys and metals used in steelmaking. Stainless steel accounted for
71 percent of the chromium ferroalloys consumed; full-alloy steel,
15 percent; high-strength, low-alloy, and electrical steels, 3 percent; and
47
carbon steel, 2 percent.
Steel is produced from the refining of pig iron, scrap, alloying
materials such as chromium, and other additives in a furnace. Three types
of furnaces are currently used. These are the open hearth furnace, the
electric arc furnace (EAF) and the basic oxygen process furnace (BOPFs).
Separate sections describing the-steel making process and chromium emissions
from each type of furnace follow.
Electric Arc Furnaces and Argon-Oxygen Decarburization Vessels
Process Description—-
Because some types of steel alloys produced in EAFs and Argon-Oxygen
Decarburization (AOD) vessels contain chromium, these furnaces are a source
of chromium emissions. In 1980, EAFs accounted for 27.9 percent of domestic
raw steel production (up from 10 percent in 1963). Growth in EAF capacity
was large in 1981 and such growth is expected to continue.
Electric arc furnaces are typically utilized in semi-integrated and
non-integrated steel mills and in specialty shops. Semi-integrated steel
mills use direct reduced iron (DRI) in addition to iron and steel scrap to
produce finished steel. Non-integrated steel mills use scrap or cooled pig
iron produced at another plant to manufacture steel. They typically produce
a limited range of products for a regional market. Electric arc furnaces
are particularly suited to non-integrated mini-mills producing less than
91
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544,200 Mg (600,000 toes) per year. Since EAFs can run on scrap, these
small mills do not need blast furnaces and coke ovens, keeping capital costs
relatively low. A number of mini-mills using EAFs entered the market in the
* A A 48
past decade.
Electric arc furnaces are used to produce common grades of steel
(carbon steel) as well as stainless and alloy steels (specialty steel).
Stainless steels contain from 12 to 25 percent chromium, which imparts the
14
stainless or corrosion-resistant property to the steel. Electric arc
furnaces used to to produce stainless steels have higher potential chromium
emissions than those used to produce carbon steel because the amount of
chromium consumed is greater.
In carbon steel facilities, EAFs are used to melt scrap metal. They
are also used as the refining vessel where oxygen blowing is performed to
oxidize impurities and perform the final chemical adjustment on the steel.
In specialty steel shops» EAFs are used primarily as the metal melter. The
molten steel from the EAF is then charged to an AOD vessel or other
secondary refining vessel. The use of AOD vessels is not expected to
increase significantly in the near future since demand for stainless steel
48
is not increasing. A recent development in the use of EAFs has been the
ultra-high power (UHP) furnace. The new UHP furnaces allow more power input
to the charge (and thus a faster melting rate) and increases the production
rate (a 100-ton normal power EAF has a heat time of about 3 hours while a
100-ton UHP EAF has a heat time of about 1 to 2 hours), Oxyfuel burners and
oxygen lances may also be used to increase the melt rate in UHP
f 48,49
furnaces.
92
-------
A typical EAF used for steelmaking operations is shown in Figure 22.
The production of steel in an EAF is a batch process where "heats," or
cycles, range from 1 to 5 hours* depending upon the size and quality of the
charge, the power input to the furnace, and the desired quality of the steel
produced* Each heat consists of three steps: charging and backcharging,
meltdown and refining, and tapping. Cold steel scrap and sometimes direct
reduced iron (DRI) are charged to begin a cycle, and alloy materials and
fluxing agents are added for refining. Direct reduced iron is produced from
iron ores that are reduced in the presence of excessive quantities of a
reducing agent (natural gas, noncoking bituminous coal, anthracite, lignite,
etc.) to produce low carbon iron which is used as melting stock along with
scrap iron and steel. The DRI is used as a scrap supplement and as a
diluent for residuals in the scrap. Many of the new electric shops are
designed to allow for continuous DRI charging through a slot in the roof or
side wall. The use of DRI is currently limited in the United States because
of the high cost and the availability of the primary reducing agent, natural
gas, and becau.se of the relatively low cost and adequate supply of scrap.
Currently there are several demonstration plants in the United States that
produce DRI with coal as the reducing agent. The coal-based reduction
process may provide a moVe economical means of producing DRI.
During the charging step, iron and steel scrap are loaded into a
drop-bottom (clam-shell type) charge bucket with an electromagnet that is
suspended from an overhead crane. The charge bucket is filled to a
specified weight. When the roof of the furnace has been opened, charging is
normally performed by carefully dropping the charge into the open arc
furnace from the charge bucket. Some smaller furnaces are charged with
scrap directly from the suspended electromagnet and do not utilize a charge
bucket. All steel plants except one charge cold scrap to the electric
furnaces. One melt shop routinely charges blast furnace metal to the EAFs,
and the molten metal is 36 to 40 percent of the total charged material.
93
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Tapping
Removable
Furnace Roof
Tap
Spout Hole
Retractable
Electrodes
Slagging
Door for Slagging
Sampling,_and
Additions"
^1
Refractory Lining
crap Charge
Figure 22. Typical electric arc steel furnace.
48
94
-------
A large variety of scrap is charged to EAFs. According to the
Institute of Scrap Iron and Steel, all grades of scrap are to be almost free
of dirt, nonferrous metals, and foreign material of any kind. Carbon steel
shops typically use No. 1 and No. 2 grades of scrap, while specialty shops
typically use No. 1 scrap, stainless scrap, and alloys such as ferroman-
ganese, ferrochrome, high carbon chrome, nickel, molybdenum oxide, aluminum,
manganese-silicon, and others.
Scrap size and bulk density vary from light scrap, such as machine
turnings, to heavy scrap, such as ingot butts. Alloying materials that are
not easily oxidized (such as copper, nickel, and molybdenum) and lime are
charged before, or along with, the scrap metal charge. The lime is a
fluxing agent to reduce the sulfur and phosphorus content in the molten
steel. Depending on the desired carbon content of the steel and the
finished product specifications, iron ore and coke may be charged prior to
n.j 48
meltdown.
During the charging process, the scrap must be introduced into the
furnace so that there is no damage to the refractory. If scrap pieces
remain above the furnace ring, the pieces must be repositioned so that the
roof can swing back into place for meltdown. This repositioning can be done
by hand or by compressing the scrap with the charge bucket or other large
mass of metal suspended from the crane. An oxygen lance is sometimes used
to cut any pieces blocking the roof. After the roof is rotated into place,
it is lowered onto the furnace in preparation for meltdown. Repositioning
of the scrap delays the closing of the roof, allowing more emissions to
escape from the furnace;
After the charging step, meltdown and refining occur. Once the roof is
in place, the electrodes are mechanically lowered to within 2.5 cm (1 in.)
52
of the scrap, and the power is turned on. When the current is applied to
the electrodes, the electrodes are slowly lowered by automatic controls
until they touch the scrap. During the first 3 to 5 minutes, an
95
-------
intermediate voltage is applied to the charge to allow the electrodes to
bore into the scrap, which, in effect, shields the sides and roof of the
52
furnace from the heat of the arc. Melting is accomplished by the
electrodes of the furnace and the metallic charge, by direct radiation from
the furnace lining, and by the resistance of the metal between the arc
paths. The arcs melt scrap directly beneath arid around the electrodes,
boring through the scrap charge and forming a pool of molten metal on the
48 52 53
furnace hearth. * * The molten steel pool enhances meltdown by the
radiation of heat from below into the cold scrap. After the initial period,
the maximum voltage is applied in order to melt the charge as fast as
possible. Before the scrap is entirely melted, a bank of refractory
material (such as dolomite) is built in front of the slagging door to
prevent the molten steel from spilling out the door. Water-cooled glands
are provided at the holes to cool the electrodes and minimize the gap
•between the electrodes and roof openings to reduce fugitive emissions, noise
levels, electrode oxidation, and heat losses.
When the initial scrap charge is almost entirely molten, a backcharge
of scrap may be added to the furnace (in some shops there may be more than
one backcharge). Following the backcharge, the roof is replaced, and
electrodes are lowered and energized to melt the scrap. Near the end of the
48
meltdown, oxygen lancing may be performed. Oxygen lancing results in
increased bath and gas temperatures, gas evolution, and generation of
particulates. Oxygen is now used almost universally (instead of iron ore or
mill scale) for boiling a heat of steel to flush out gases, mainly hydrogen
and nitrogen.
During the meltdown, phosphorus, silicon, manganese, carbon, and other
elements in the scrap metal are oxidized. Slag formation begins and is
carefully monitored during the meltdown stages to control the chemical
concentration and product quality. Basic EAFs use either single or double
slagging operations depending upon the desired quality of the end product.
The single slagging process uses an oxidizing slag that is formed by the
96
-------
addition of lime and coke breeze (or other source of carbon) during the
initial scrap metal charge. Other flux additions, such as fluorspar,
silica, and ferrosilicon, may be made through the slag door. The double
slagging process develops an oxidizing slag first, followed by a reducing
slag. The initially formed oxidizing slag is raked off, with the power to
the electrodes cut off, and is followed by additions of burnt lime, powdered
52
coke, fluorspar, silica, sand, and ferrosilicon.
The final step in the EAF process is tapping. To tap a heat, the power
is shut off and the electrodes are raised sufficiently to clear the bath.
The furnace is tilted (sometimes as much as 45 degrees), and the molten
steel is tapped into a ladle. The ladle is placed close to the tapping
spout to capture the batch of steel without excessive splashing and to
reduce the exposure of the molten steel to the air and thus minimize
excessive oxidation and cooling of the steel; Additions of ferromanganese,
ferrosilicon, aluminum, and other alloying agents are sometimes made to the
ladle to adjust the oxygen content of the steel. ' For certain steel
alloys, chrome is added just prior to the tap to avoid oxidation of the
chromium during meltdown.
After the molten steel is tapped into the ladle, the ladle is
transferred -to either an ingot teeming area, a continuous caster, or a
refining vessel (in a specialty steel shop).
In the manufacture of stainless and other alloy steels, molten steel
from the EAF is usually transferred to an argon-oxygen decarburization (AOD)
vessel for further refining. AOD vessels are closed-bottom, refractory-
lined, pear-shaped converter vessels with submerged tuyeres in the lower
portion of the vessel (Figure 23). The AOD vessel is constructed of welded
steel plate and mounted such that it may pivot for charging, slagging, and
tapping. Argon, oxygen and/or nitrogen gases are blown through the tuyeres
into the molten steel to adjust the bath temperature and chemistry and to
cool and maintain the air passage in the shrouds and tuyeres.
97
-------
VESSEL TOP
Figure 23. Argon-oxygen decarburization vessel.
48
98
-------
To begin the AOD process, molten steel from an EAF is transferred by
ladle to the AOD vessel, which rotates forward to accept the molten charge.
When the charging operation is complete, typically in 1 to 8 minutes
depending on the size of the AOD vessel, it is rotated back to an upright
position so that refining can begin. Before refining begins, additives
such as lime or alloys are added to the molten steel with a crane-held
48
charge pan'or through a charge chute.
Refining is accomplished by blowing argon, oxygen, and/or nitrogen
gases through the molten steel bath. The control of the gas mixutre and
flow is important to avoid the oxidation of alloys necessary for specialty
steel production. As the heat progresses, alloys and fluxing agents are
added to the molten steel in quantities that are determined by the chemical
analyses performed on samples of the bath. The fluxing agents are typically
lime and fluorspar, and the alloys include aluminum, chrome, nickel,
manganese, boron, silicon, vanadiaum, and titanium. Limited amounts of
scrap generated at the steel mill (home scrap) may also be periodically
added to the vessel as additivies to help reach the desired chemical makeup
of the final product.
The carbon-chromium equilibrium relationship is very important in
controlling the quantity of chromium in the final product. The amount of
chromium in the melt is in an equilibrium relationship with the carbon. The
carbon level is decreased with oxygen blowing; however, any excess chromium
may also be oxidized and lost. The amount of chromium that the melt can
retain decreases as the carbon content of the melt decreases.
The steel yield from an AOD vessel is very high. About 91 percent by
weight of a typical charge of molten steel and fluxes to an AOD vessel is
returned as product (specialty steel). * The metallic yield, i.e., the
steel tapped as a percent of the metal charge, is approximately
48
97 percent.
99
-------
New methods or combinations of methods for refining the steel from
EAFs, in addition to the use of ADD vessels, are currently being introduced.
These secondary refining processes, collectively known as ladle refining,
are being used to reduce the amount of refining that is performed in the
EAF, allowing the EAF to be used strictly as a metal melting device. Argon
bubbling is one technique where a gentle stream of argon is injected through
a porous plug at the bottom of the ladle. This technique improves the
quality of the steel and controls the composition of low-alloy and medium
alloy grades of steel. Another technique is vacuum-oxygen decarburization
(VOD) that is used to reduce the carbon content in the steel without
oxidizing the chromium. A consumable oxygen lance is inserted into the
molten steel through the ladle cover. While the ladle is under reduced
pressure, oxygen is blown into the melt. After the desired amount of oxygen
is blown, the vacuum is continued while argon is bubbled through the melt so
that the oxygen remaining in the steel can react with the remaining carbon.
48 "
This technique takes 2 to 2.5 hours to refine the molten steel.
Emission Factors—
The quantity and type of emissions from an EAF depend upon many
factors: furnace size, type and composition of scrap, quality of scrap,
type of furnace, process melting rate, number of backcharges, refining
58
procedure, tapping duration, and melt temperature. The majority of the
emissions from EAFs are ferrous and nonferrous oxide participates. Furnace
emissions are the highest during meltdown and refining operations, but
charging and tapping emissions can also be significant, especially if ladle
additions are made during the tap and dirty scrap is charged. The charging
and tapping emissions represent approximately 5 percent each of the total
58
emissions during a heat. Increases in electrical power to the furnace and
the use of oxygen lancing will cause emissions to increase during meltdown
A *• 4 48
and refining.
Electric arc furnace emissions are comprised of both a process and
fugitive component. Process emissions include those generated at the
furnace when the furnace roof is closed (e.g., during melting and refining)
100
-------
as well as those generated when the primary emission capture device (e.g.,
DEC system, side draft hood) is operative. Emissions generated when the
furnace roof is open (e.g., during charging) or when the primary emission
capture device cannot operate (e.g., during charging and tapping) are
48
considered to he fugitive emissions.
Process emissions from the meltdown operation consist of metallic and
mineral oxide particulates, carbon monoxide, and hydrocarbons generated from
the vaporization of iron and the transformation of mineral additives. *
Trace constituents (including hexavalent chromium) are emitted in
particulate form from EAFs. ' During the melting process, emissions
escape through electrode holes, the slag door, the roof ring, and sometimes
48
the tap spout. Most process emissions can be largely eliminated by the
control technology discussed later in this section.
Fugitive emissions from charging the open furnace are more difficult to
control. The level of charging emissions varies depending on the
cleanliness and composition of the scrap. Most charging emissions result
from (1) vaporization of oil, grease, or dirt introduced with the charge,
(2) oxidation of organic matter that may adhere to the scrap, and (3) the
48 54 58
vaporization of water from wet scrap. * * Emissions are made up of
58
particulate matter, carbon monoxide, hydrocarbon vapors, and soot. If
particles of the scrap charge are emitted, they may contain trace amounts of
chromium. Backcharging produces a large eruption of reddish-brown fumes.
Fugitive backcharging emissions are higher than fugitive emissions from the
initial charge because of the intense reaction that occurs due to the heat
48
of the molten steel in the furnace.
Fugitive emissions are also produced during tapping. These fumes
consist of iron oxides as well as other oxide fumes resulting from alloys
48
that are added to the ladle. Since chromium may be added at this point to
48
stainless and alloy steels, chromic oxide can be emitted.
101
-------
Particulate emissions from an ADD vessel are comprised of both ferrous
and nonferrous oxides. The quantity and type of emissions from an AOD
vessel depend upon several factors: the quality of the molten steel charge,
the quality of the final product desired, and the types and quantity of
alloys added. Almost all the emissions occur during the blowing (refining)
stage, with a dense cloud occurring when the concentration of oxygen in the
gas stream is the highest at the beginning of the heat. When the AOD vessel
is in a tilted position for temperature checks and sample-taking, there are
almost no emissions because no gases are blown through the molten steel.
The charging and tapping emissions are minimal because the charge is made to
an empty vessel, and the tap occurs after the carbon content has been
greatly reduced. Since AOD vessels are often used to refine stainless
48
steels containing 12 to 25 percent chromium,
particulate emissions from AODs is significant.
48
steels containing 12 to 25 percent chromium, the chromium content of
Fabric filters are the most widely used control device on EAFs and the
only system used on AOD vessels. Fabric filters are the most effective
control technology for the removal of small particles generated by EAFs and
AOD vessels. They have been shown to be as effective at removing chromium
as at removing total particulates. Both pressure type and suction type
fabric filters are used. Most bags are constructed of a Dacron polyester
blend with an. air-to-cloth ratio of about 3:1 and a pressure drop of 7.6 -
12.7 cm (3 to 5 in) water. Dust collected by fabric filters is often
recycled for the recovery of chromium, nickel, iron, and/or zinc. Some
plants pelletize the dust and feed it back to their furnaces. An ESF is
known to be in use at one EAF shop, but none have been installed since 1974.
Wet scrubbers are used by less than 2 percent of the existing EAF units.
These control devices are generally less efficient at particulate (and
therefore chromium) removal than fabric filters.
The capture of EAF and AOD vessel exhaust is a very important aspect of
emissions control. The following systems have been used at EAF shops to
capture emissions and route them to a suitable control device.
102
-------
1. direct-shell evacuation control system (DEC)
2. side craft hoods
3. canopy hoods
4. partial furnace enclosure (PFE)
5. total furnace enclosure (TFE)
6. tapping hoods
7. scavenger duct system
8. roof monitors
9. building evacuation
Each system and its advantages or disadvantages are briefly described below.
For each system, the chromium capture efficiency can be assumed to be
similar to the reported total particulate emissions capture efficiency
because chromium exists in the emissions as a particulate.
A DEC system is illustrated in Figure 24. A duct attaches to a hole in
the roof and when the roof is in place, it joins a second duct leading to
the emissions control device. The DEC withdraws 90 to 100 percent of
melting and refining process emissions before they escape the furnace.
However, when the furnace is tilted or the roof is rotated aside for
charging, the DEC system is ineffective. ' The DEC system has been
widely used .in the industry- for many years and can. be used on EAFs producing
any type of steel.
Figure 25 shows a side draft hood. This system also captures emissions
only during melting and refining. It is mounted to the EAF roof, with one
side open to avoid restricting the movement of the electrodes. Particulate
(and therefore chromium) emissions capture is estimated to be between 90 and
100 percent. The side draft hood is not as widely used as the DEC and is
typically used only on small furnaces because of the larger exhaust volume
48
and higher operating costs.
103
-------
A. PLAN
ELECTRODES (3)
TAP
SPOUT
DUCT TO
/CONTROL DEVICE
ELECTRIC ARC FURNACE
REFRACTORY LINED
OR WATER-COOLED
DUCT
8. ELEVATION
Figure 24. Direct-shell evacuation control (two views).
48
104
-------
A. PLAN
SIDE DRAFT
HOOD
FURNACE—
-ROOF
TAP
SPOUT
ELECTRODES (3)
ELECTRIC ARC FURNACE
SMALL GAP TO
FACILITATE'
ROOF MOVEMENT
AND BURN
COMBUSTIBLES
B. ELEVATION
Figure 25. Side draft hood (two views)
105
-------
The canopy hood system, shown in Figure 26, involves one or more hoods
suspended from the shop roof directly above each furnace. The hood must be
high enough to provide clearance for crane movement during charging and
space for upward movement of the electrodes. The system is used alone to
capture both process and fugitive emissions, or in conjunction with another
process emissions capture device. Thermal currents from the hot furnace
help chromium-containing particulates rise to the hood to be captured;
however, cross-drafts and passage of the crane may disrupt the path of the
emission stream and cause it to escape capture. Partitions may be installed
to reduce cross-drafts. Capture efficiency of a single canopy hood is
typically 75 to 85 percent. Segmented (sectioned) canopy hoods have a
,61-
48
higher efficiency (85 to 95 percent). * Hoods are one of the oldest
and most widely used collection devices.
The partial furnace enclosure (FFE), pictured in Figure 27, has walls
on three sides of the furnace area that act as a chimney directing fugitive
emissions from charging and tapping to a canopy hood. They are often used
in conjunction with another process emission capture system. Partial
furnace enclosures are easier to install and less expensive than total
furnace enclosures. They allow the operators to see the furnace during
charging, and any explosions are vented out the front of the enclosure
rather than damaging the enclosure. Crane passage above the furnace can
still disrupt the emission plume. The amount by which PFEs increase the
capture efficiency of canopy hoods is not documented. They are installed
at several facilities on EAFs ranging in size from 154 Mg (170 tons) to
204 Mg (225 tons).48
Total furnace enclosures (TFEs) completely surround the furnace with a
metal shell that acts to contain all charging, melting and refining,
slagging, and tapping emissions (Figure 28). The air flow required is only
30 to 40 percent of that required for a canopy hood system. The front
charge doors are closed during charging after the crane and charge bucket
have been admitted. A duct at the top of the enclosure removes charging and
106
-------
ROOF MONITOR
CANOPY HOOD
o
-J
JBL
I—c:
TT
FABRIC FILTER
vvww
Figure 26. Canopy hood capture system.
48
-------
.U~' CANOPY MOO
F100B
Figure 27. Partial furnace enclosure.'
48
108
-------
ftoof
«oTo Contra! C«vJct
— z:
1
— 1— '— Main SxnatnJ1 Oge?
1 ^
,^....;
1 1
1 I
t 1
| i
— /— -
^•Topping Cxhausf Owet
SX«a Floor
FRONT VIEW
Figure 28. Total furnace enclosure.
48
109
-------
melting/refining emissions. A local hood under the enclosure collects
emissions from slag tapping. Tapping emissions are collected from a duct
.adjacent to the tapping ladle. Emissions capture efficiency is betveen 90
and 100 percent. Total furnace enclosures were installed on at least five
relatively small EAF furnaces in the United States between 1976 and 1981. A
165 Mg (182 ton) medium sized furnace in Italy was fitted with a TFE in
1980, and should provide operational data on the use of TFEs on larger
- 48,65
furnaces.
Tapping hoods are movable or stationary hoods located immediately above
the tapping ladle when the tapping operation is in progress. Since the hood
is close fitting, it is more efficient than a canopy hodd. Tapping hoods
are receiving increased usage throughout the industry to supplement capture
by TFE's, PFE's, canopy hoods, and DEC's.
48,60
A scavenger duct system consists of small auxiliary ducts that are
located above the main canopy hood(s) built into a closed shop roof. A
relatively low flow rate is maintained through these ducts to' capture
chromium-containing fugitive emissions not captured by the canopy hood.
This system would provide greater capture efficiency than just a canopy
hood, but can only be used with a closed or semi-closed roof. The extent of
, 48
use is unknown.
Roof monitor configurations can be open, open except over the furnace,
or closed over the entire melt shop. A variation of the closed roof shop
involves a louvered roof monitor that is mechanically controlled to allow
for closing the louvers during periods of fugitive emissions. Advantages of
an open roof include natural ventilation of the shop. However, a closed
roof promotes more effective capture of emissions by canopy hoods or
scavenger ducts. Louvered or partially closed roofs allow advantages of
both systems.
110
-------
A building evacuation system uses ductwork at the peak of a closed roof
shop to collect all emissions from the shop operations. A 25 percent
greater air flow is required than with a canopy hood, however all shop
emissions are captured. Capture efficiency for particulate matter, and
therefore chromium, is 95- to 100 percent. The capture rate, however, is
slower than with a canopy hood. Several plants utilize this type of
. . ^ . 48,60,65
emissions control.
* _
Some typical combinations of the previously described emissions capture
techniques for EAFs and the efficiencies of these combinations are shown in
Table 20.
Emissions from AOD vessels occur primarily when the vessel is in an
upright position. These emissions exert a strong upward thermal lift. They
are typically captured using two types of systems, a diverter stack with
canopy hood system and a close-fitting hood with canopy hood system.
The diverter stack (Figure 29) is located about 1.5 m (5 ft) above the'
AOD vessel and can be fixed in position or movable. It reduces cross-draft
and is narrower at the top, which accelerates the AOD vessel emissions
(containing chromium) toward the canopy hood.
A close fitting hood is pictured in Figure 30. It is situated 0.3 to
0.6 m (1 to 2 ft) above the AOD vessel and can be moved out of the way
during charging and tapping. Refining emissions are captured by the close
fitting hood and any fugitives are captured by the canopy hood. Most AOD
installations use this system because it achieves more efficient capture
with lower air flow volumes than the diverter stack system. *
Table 21 shows the estimated fugitive emission reduction efficiencies
of typical control combinations used at AOD installations.
Ill
-------
TABLE 20. FUGITIVE EMISSIONS CAPTURE TECHNOLOGY COMBINATIONS
(CARBON AND SPECIALTY STEEL EAF) 48
Combination Fugitive emissions capture equipment
1 Single canopy hood, open roof monitor.
2 Segmented canopy hood, closed roof (over
furnace)/open roof monitor.
3 Single canopy hood, local tapping hood, local
slagging hood, closed roof (over furnace)/
open roof monitor.
4 Segmented canopy hood, scavenger duct,
cross-draft partitions, closed roof (over
furnace)/open roof monitor.
5 Single canopy hood, total furnace enclosure,
closed roof (over furnace)/open roof
monitor.
EstiBated
fugitive
emission.
capture
(percent)
75-85
85-95
85-95
90-95
90-95
Segmented canopy hood, scavenger duct,
cross-draft partitions, closed roof
monitor.
95-100
l)irect-shell evacuation control (DEC) system used for process emissions
capture in all cases in addition to equipment listed above for fugitive
emissions capture.
Estimate based on engineering judgment. These figures apply to total
particulate emissions; however, an equivalent level of capture should be
achieved for chromium emissions.
112
-------
ROOF MONITOR
CANOPY HOOD
U>
DIVERTER
STACK
0
TT
FABRIC FILTER
WWW
Figure 29. Diverter stack with canopy hood.
-------
ROOF MONITOR
CANOPY 1(000
CLOSE-FITTING
HOOD
FABRIC FILTER
WWW
Figure 30. Close-fitting hood with canopy hood.
48
-------
TABLE 21. FUGITIVE EMISSIONS CAPTURE TECHNOLOGY COMBINATIONS
(SPECIALTY STEEL AOD) *8
Combination
Fugitive emissions capture equipment*
Estimated
fugitive
emission.
capture
(percent)
Single canopy hood, diverter stack,
open roof monitor.
Single canopy hood, scavenger duct, closed
roof (over vessel)/open roof monitor.
Single canopy hood, scavenger duct,
cross-draft partitions, closed roof (over
vessel)/open roof monitor.
Segmented canopy hood, scavenger .duct,
cross-draft partitions, closed roof
monitor.
75-85
85-95
90-95
95-100
Close-fitting hood used for process emissions capture on combinations 2,
3, and 4. All emissions are considered fugitive for combination 1.
Estimate based on engineering judgment. These figures apply to total
particulate emissions; however, an equivalent level of capture should be
achieved for chromium emissions.
115
-------
Table 22 lists uncontrolled chromium emissions factors for electric arc
furnaces producing different types of steel and for AOD vessels. The
percent chromium in electric arc furnace dust was determined from testing of
33 samples of electric arc furnace dust from 25 steel plants. The
chromium emission factors in kg/Mg and Ib/ton were calculated assuming total
uncontrolled particulate emissions of 7.5 to 22.5 kg/Mg (15 - 45 Ib/ton). '
The chromium emission factors for AOD vessels were reported in reference 48,
but the extent of testing behind that figure is unknown. Table 23 shows the
chromium content of dust emitted from an EAF during different steps of
54
operation. Chromium is emitted from EAFs and AODs primarily in the form
of chromic oxide
Chromium emission factors after controls are not reported in the
literature. However, chromium is typically controlled by fabric filters to
the same degree as total participates. Controlled chromium emission factors
would depend on the efficiency of capture of fugitive and. process emissions
as well as the efficiency of the fabric filter. Particulate collection and
control efficiencies of 99 percent have been reported using some of the
control technologies prev
is assumed to be similar.
control technologies previously discussed , and chromium removal efficiency
Source locations—
In 1981, there were 322 EAFs in the United States, which were operated
by 87 companies in 125 locations. The locations of these plants are listed
in Table 24. * Table 25 shows the distribution of these plants by
State.
In 1981, there were 27 AOD vessels operated by 19 companies at
23 locations in 9 states. These locations are listed in Table 26. '
116
-------
TABLE 22. UNCONTROLLED CHROMIUM EMISSION FACTORS FOR ELECTRIC ARC FURNACES
(EAFs) AND ARGON-OXYGEN DECARBURIZATION VESSELS (AODs)48'67
Type of
Furnace
Type of
Products
Weight % of
Chromium in
Particulate
Emissions
Chromium Emission
Factors, kg/Mg (Ib/ton)
of Steel Produced
EAF Stainless Steel and
Specialty Alloys
EAF Mixed Products Including
Stainless Steel and/or
Specialty Alloys
EAF Carbon and Alloy Steel
EAF Carbon Steel
AOD Stainless and Specialty
Alloys
10,6'
2.22'
0.20'
0.20*
6.6®
0.80 - 2.4 (1.6 - 4.8)
0.17 - 0.50 (0.33 - 1.0)
0.015 - 0.045 (0.03 - 0.09)
0.015 -"0.045 (0.03 - 0.09)
0.43 - 0.62 (0.87 - 1.2)
All factors expressed in terms of total elemental chromium and represent
emissions after capture equipment but prior to controls. Emissions are
known to contain chromium in both trivalent and hexavalent oxidation
states.
Average of six samples from different furnaces. -
+
'Average of seven samples from different furnaces.
Average of ten samples from different furnaces.
»
"Average of two samples from different vessels.
117
-------
TABLE 23. CHROMIUM CONTENT OF ELECTRIC ARC FURNACE DUST FOR
EACH STEP OF FURNACE OPERATION AT ONE
FACILITY54
Phase Weight % Chromium in Dust
Melting 1.32
Oxidizing . 1.32
Oxygen Lancing 0.86
Reduction 0.53
Chromium percentages were measured and are reported as chromic oxide
(Cr203).
118
-------
TABLE 24. LOCATIONS OF ELECTRIC ARC FURNACES IN THE UNITED STATES IN 1981
48
Plant/Location
AL TECH SPECIALTY STEEL CORP.
Watervttet. N.V.
ALLEGHENY LUOLUN STEEL CORP.
Brackenrldge, Pa.
ARHCO, INC.
• Baltiswre Work*
Baltianre, Hd.
• Butler Works
Butler. Pa.
• Houston Works
Houston, Tex.,
• Kansas Cfty Works
Kansas City, Ho.
• National Supply Division
Torrance, Calif.
ATLANTIC STEEL CO.
• Atlanta Works
Atlanta. Ga.
• CartersvHIe Work*
Carlersvtlle. Ga.
AUBURN STEEL CO.
Auburn, N.Y.
BABCOCK & WHCOK CO.
Beaver Falls, Pa.
BAVOU STEEL CORP.
New Orleans, La.
BETHLEHEM STEEL CORP.
• Bethlehe* Plant
BethlebM. Pa.
• Steelton Plant
Steelton. Pa.
• Johnstown Plant
Johnstown, Pa.
Plant /Location
i
8ETKLEHEH STEEL CORP. (cent. )
• Los Angeles Plant
lot Angeles, Calif.
• Seat lie Plant
StatUe, Wash.
BORDER STEEL HILLS. INC.
El Paso. Tex.
BW STEEL, INC.
Chicago Heights. 111.
CABOT CORPOMTION
Stellltt Otv.
Kokcau, Ind,
CAMERON IRON WORKS. INC.
Houston, Tex.
CARPENTER TECHNOLOGY CORP.
• Steel Division
Bridgeport. Conn.
• Reading Plant
Reading, Pa.
CASCADE ROLLING HILLS
HcMlnnvllle, Oreg.
CCS BRAEBURN ALLOY STEEL DIV.
Lower Burrell, Pa.
THE CECO CORP.
• Leftont Manufacturing Co.
Leflont, 111.
• Hilton Manufacturing Co,
Hilton, Pa.
Cfil STEEL CORP.
Pueblo, Colo.
CHAPARRAL STEEL CO.
Midlothian. Tex.
•
CHARIER ELECTRIC MELUNG CO.
Chicago, HI.
Plant/Location
COLT INDUSTRIES
- Crucible Sta Idlest Steel
01 v.. Midland. Pa.
• Crucible Specialty Metals
Dlv. . Syracuse, N.V.
COLUMBIA TOOL STEtL CO.
Chicago Heights. III.
CONNORS STEEL CO.
• Blralnghaa Works
8lra)ingha». At*.
* Huntlngton Works
Huntlngton W. Va.
COPPERVEIO STEEL CO.
Warren, Ohio
CYCLOPS CORP.
• Evpfre Detroit Steel Dlv.
Mansfield, Ohio
• Universal Cyclops
Specialty Steel
Brldgevllle, Pa.
EASTERN STAINLESS STEEL CO.
Baltimore, Md.
EDGEWATER STEEL CORP.
fljfcannt PA
WBMHVfll'1 r««<
ELECTRALLOY CORP.
Oil City. Pa.
F INK IE ft SONS CO.
Chicago, 111.
FLORIDA STEEL CORP.
• Charlotte Mill
Charlotte. N.C.
- Indlantown Mill
Indlantown, Fla.
-------
TABLE 24. (CONTINUED) LOCATIONS OP ELECTRIC ARC FURNACES IN THE UNITED STATES IN 1981
48
Plant/Location
FLORIDA SUCt CMP. (cent.)
• Baldwin NUI
Baldwin. Fit.
• Ta*a Mill
fHpa. FU.
• Jackson Ml 1 1
Jackson. Itnn.
GREEN RIVER S1EEL
Owensboro. Ky.
GUTERl SPECIAL STEEL CORP.
lockporl, N.V.
HAWAIIAN WESTERN STEEl ITD.
Ewa. Hawaii
HUNT S1EEI CO.
Youngs town. Ohio
HURRICANE INDUSTRIES INC.
Staly, Tex.
IUIHOIS IIRNINGHAH BOLT
Kanfcakee, III.
INGERSOl JOHNSON STEEL CO.
New Caitiff. Ind.
INGERSOL RAND-OIL FIELD PROD.
Paepa, Texas
INLAND STEEl CO.
Eait Chicago. Ind.
INTERCOASTAL STEEl CORP.
Chesapeake, Va.
INTERUKE, INC.
Hoeganaet Corporal Ion
CalUlin, lenn.
Ill HARPER
Morton Grove, 111.
Plant /Location
t
JARSCO
Roebllng, N.J. .
JESSOP STEEL CO.
• Washington Works
Washington, Pa.
JONES 4 LAUGHLIN STEEL CORP.
- Cleveland Works
Cleveland. Ohio
• Pittsburgh Works
Pittsburgh. Pa.
• Warren Works
Warren', Ntch.
EARIE N. JORGCNSCN CO.
Seattle, Wash.
JOStYN STAINLESS SICEtS
Fort Wayne, Ind.
JUOSON STEEl CORP.
Ewryvllle. Calif.
KENTUCKY ELECTRIC STEEl CO.
Ashland. Ky.
KEYSTONE CONSOLIDATED
INDUSTRIES. INC.
Keystone Group Stetl Works
Peorta, 111.
KNOXVIILE IRON CO.
KnoKvlllt, Tenn.
KORF INDUSTRIES
• Georgetown Steel Corp.
Gerogetown, S.C.
• Georgetown lexas Steel
Corp.. BeauBont, Tex.
LACLEOE S1EEL CO.
Alton, III.
LATR08E STEEL CO.
la t robe. Pa.
Plant/Location
IONESTAR STCEl CO.
lone Star, Tex.
LUKENS STEEL
' Coal tvl lie, Pa.
MARATHON LE TOURNEAU CO.
Long view, Tex.
MARATHON STEEl CO.
Teape. Arti.
MARION STEEL CO.
Marlon, Onto
McClOUTH STEEL CORP.
Trenton, Mich.
MISSISSIPPI STEEl DIV.
Flowood Works
Flowood, Mist.
NATIONAL FORGE CO.
• Erie Plant
Erie. Pa.
• Irvine Forge Division
Irvine, Pa.
NATIONAL STEEL CORP.
Great Lakes Steel Olv.
Ecorse, Mich.
NEW JERSEY STEEL 4 STRUCTURE
CORP.
Sayervllle. N.J.
NEWPORT STEEl
Newport. Ky.
NORTH STAR SIEEL CO.
• St. Paul Plant
St. Paul. Minn.
• Monroe Plant
Monroe. Mich.
• Wilton Plant
Wtlton. Iowa
to
o
-------
TABLE 24. (CONTINUED) LOCATIONS OF ELECTRIC ARC FURNACES IN THE UNITED STATES IN 1981
Plant/Location
NORTHWEST STEEL ROUING
NIUS. INC.
Kent, Wash.
NORTHWESTERN SIEEt 1 WIRE CO.
Sterling, 111.
NUCOR CORP.
• Darlington Mill
Darlington, S.C.
• Jewell Hill
Jewell, Tex.
• Norfolk Ml 11
Norfolk. Ncbr.
• Plywuth Hill
Plymouth, Utah
OREGON STEEl Ml US
Portland, Oreg.
OWENS ELECTRIC STEEL COMPANY
Cayce, S.C.
PENH-DIXIE STEEL CORP.
Kotow Plant
Kokooo, Ind.
PHOENIX STEEL CORP.
• PUte Dlv.
Clayftont, Del.
QUANTEX CORP.
- Kac Steel Michigan Olv.
Jackson, Mich.
- Mac Steel Arkansas Dlv.
Fort Sftlth. Ark.
RARITAN RIVER SHEL CO.
Perth Anboy. N.J.
RAZORBACK STEEL CORP.
Newport. Ark.
Plant/Location
REPUBLIC STEEL CORP.
• Central Alloy Works
Canton, Ohio
• South Chicago Works
South Chicago, III.
ROAMONE ELECTRIC STEEL CORP.
Roanoke, V«.
R06LIN SUEL CO.
Dunkirk Works
Dunkirk, N.V.
ROSS STEEL WORKS
Mile, la:
' *
ftOUGE STEEL CO.
Dearborn, Mich.
SHARON STEEL CORP.
Sharon. Pa.
SHEFFIELD STEEL CORP.
Sand Springs. Okla.
SOULE STEH CO.
Carson Works
Carson, Calif.
SOUTHERN UNITED STEEL CORP.
BtnringhaM. Ala.
STANDARD STEEL ENTERPRISE
Freedoa Forge Corp.
Burnha*. Pa.
Latrobe, Pa.
STRUCTURAL METALS, INC.
Sequin. Tex.
TAMCO
Etiwanda. Calif.
Plant/Location
TELEDVNE VASCO
latrobe, Pa.
TENNESSEE FORCING STEEL CORP.
• Harrlaan Works
Harrfaan, Tenn.
TEXAS STEEl CO.
Fort Worth. Tax.
TINKCN CO.
• Steel and Tuba Dlv.
Canton, Ohio
UNION ELECTRIC STEEL CORP.
Burgettstown, Pa.
UNITED STATES STEEL CORP.
- Falrtess Work
Fatrless Hills. P*.
• Johnstown-Center Works
Johnstown. Pa
• National Duquesm Works
Ouquesne, Pa.
• South Works
South Chicago. ITT.
• Texas Works
Bay town, Tex.
WASHINGTON STEEL CO.
Fitch Works
Houston, Pa.
WITTEHAN STEEL MILLS
fontana, Calif.
Note: This listing la subject to change an market conditions change, facility ownership changes.
are closed down, etc. The reader should verify the exifltence of partJc.ular facilities by
current listings and/or the plants themselves. The level of chromium emissions from any given
facl llty is a function of variables such a" capacity, throughput, 'and control mfimrirf"! It Rh
-------
TABLE 25. LOCATION OF STEEL PLANTS WITH EAFs
AND ADD VESSELS — 1981 48
State
Alabama
Arizona
Arkansas
California
Colorado
Connecticut , ,
Delaware
Florida
Georgia
Hawaii
Illinois
Indiana
Iowa
Kentucky
Louisiana
Maryland
Michigan
Minnesota
Mississippi
Missouri
Nebraska
North Carolina
New Jersey
New York
Ohio
Oklahoma
Oregon
Pennsylvania
Rhode Island
South Carolina
Tennessee
Texas
Utah
Virginia
Washington
West Virginia
EAF
3
1
1
6
1
1
1
3
2
1
11
5
1
3
2
2
. 6
1
1
1
1
1
2
5
6
1
2
27
1
3
4
12
1
2
3
1
125
Plants
AOD
. vessel
1
-
1
3
2
la
2
2
10
1
23
aAnother plant in Michigan has not operated its
AOD vessel since it was installed in 1977.
122
-------
TABLE 26. LOCATIONS OF ARGON-OXYGEN DECARBURIZATION (ADD) VESSELS IN THE UNITED STATES IN 1981
Plant/Location
Plant/Location
u>
AL TECH SPECIALTY STEEl CORP.
Watervlfet, N.Y.
ALLEGHENY IUOIUH STEEL CORP.
Brackenridge, Pa.
ARHCO, INC.
• Baltimore Works
BaltiM>r«, Hd.
• Butler Works
Butter, Pa.
BA8COCK AND WILCOX CO.
Beaver Falls, Pa.
CABOT CORP.
Stellite Olv.
Kokono. Ind.
CARPENTER TECHNOLOGY CORP.
• Steel Ofv. |
Bridgeport, Conn.
• Reading Plant
Reading, Pa.
CRUCIBLE, INC.
• Stainless Steel Olv.
Midland. Pa.
• Specialty Metals Div.
Syracuse, N.Y.
CYCLOPS CORP.
• Universal Cyclops
Specialty Steel
Bridgeville, Pa.
• ENpire-Detroit Oiv.
Mansfield, Ohio
EASTERN STAINLESS STEEL CO.
Baltimore, Md.
ELECTMLLOY CORP.
Oil City. Pa.
INGERSOL JOHNSON STEEL COL.
New Cattle. Ind.
JESSOP STEEL CO.
Washington Works
Washington, Pa.
JONES AND LAUGHUN STEEL CORP.
Warren Works
Warren, Hlch.
EARL H. JORGENSEN STEEL CO.
Seattle, Wash.
JOSYLN STAINLESS STEELS
Fort Wayne, Ind.
McLOOTH STEEL CORP.
Trenton, Mtch.
REPUBLIC STEEL CORP.
Central Alloy Works
Canton, Ohio
STANDARD STEEL DIV.
Burnhaa, Pa.
U.S. STEEL CORP.
South Works
Chicago, 111.
WASHINGTON STEEL CO.
Fitch Works
Houston, Pa.
Note: This listing Isisttbject to change as market conditions change, facility ownerohIp changes, piunto
are closed down[ «tc. The reader should verify the existence of particular facilities by connultlng
current listings and/or the plants itheraselvea. The level of chromium emissions from any givem
facility is a function of variables aticBi an capacity,, throughput, 'and' control measures. I
determined through direct contacts with plant personnel.
-------
The Iron and Steel Institute is a source of current information on
plant locations. The steel industry, including CAP and AOD shops, is
classified under SIC code 3312.
Basic Oxygen Process Furnaces
Chromium can be emitted from basic oxygen process furnaces (BOPFs)
because it may be a contaminant of scrap and pig iron feed, and because it
may be added to furnaces which produce alloy steels. Basic oxygen process
furnaces have recently accounted for about 60 percent of total domestic
steel production. * The main advantage of BOFF steelmaking is that pig
iron is converted to steel in about 45 minutes, so labor and certain other
72
costs are lower than in the once prevalent open hearth method. The main
disadvantage of the BOFF process is that the charge must consist of at least
72
70 percent molten iron. Therefore, the BOPF must be a part of an
integrated steel mill (one which uses iron ore, coke, and limestone to
produce molten iron in- a blast furnace and subsequently produces steel in a
72 73
BOPF or other steel furnace). ' The ability to substitute scrap metal
for pig iron in BOPFs is very limited and is dependent on steel market
conditions.
The future growth in the BOPF industry is uncertain. Existing BOPF's
should remain in use, and existing open hearth furnaces in integrated steel
mills will probably be converted_to BOPFs if demand is adequate to keep the
shops open. However the newer non-integrated and specialty shops typically
use electric arc furnaces (EAFs) rather than BOPFs or open hearths. *
The BOPF produces steel by blowing oxygen through molten iron. The
furnace is a large, open-mouthed vessel lined with a chemically basic
refractory material. The furnace is mounted on trunions that allow it to be
rotated through 360 degrees in either direction. A typical vessel can have
an opening 3.7 to 4.3 m (12 to 14 ft) in diameter and be 6.1 to 9.1 m (20 to
30 ft) high.72
124
-------
ro
TOP BLOWN
BOTTOM BLOWN
Figure 31. Top blown and bottom blown BOPF vessels.
72
-------
The furnace receives a charge composed of scrap and molten iron which
it converts to molten steel. This is accomplished through the introduction
of high-purity oxygen that oxidizes the carbon and the silicon in the molten
iron, removes these products, and provides heat for melting the scrap.
After the oxygen blow is started, lime may be added to the vessel to provide
a slag of the desired basicity. Fluorspar may also be added in order to
72
achieve the desired slag fluidity.
Two distinct types of furnaces are in general use (see Figure 31). The
most common type is the top blown furnace, in which oxygen is blown into the
vessel through a water-cooled lance that can be lowered into the mouth of
the upright furnace. The other type of furnace, commonly called a Q-BOP, is
bottom blown. In this furnace, oxygen is introduced into the vessel through
72
tuyeres (nozzles) in the furnace bottom.
The major reason for installing a Q-BOP furnace is that it does not
require a great deal of vertical clearance above the furnace enclosure and
can therefore fit into existing open hearth buildings. Existing ancillary
facilities can be adapted easily for serving Q-BOPs. Other advantages of
bottom blown furnaces are slightly increased yields and higher ratios of
72
scrap to hot metal.
A third type of furnace is currently being used with an increasing
frequency in the steel industry. This new form of BOPF is a top blown
furnace that has been modified to allow oxygen to be introduced through both
the conventional oxygen lance and to be injected through bottom and side
74 75
tuyeres within the vessel. * Because this technology is relatively new,
there is not much information available about its utility or about the
extent to which it has been applied in BOPF shops.
Steel is produced via the basic oxygen process in distinct operations
72
that occur in the following order:
126
-------
1. Charging—The addition of scrap metal or hot metal to the BOPF.
2. Oxygen blow—The refining stage of the process, in which pure
oxygen is blown into the BOPF. Lime and flouspar are also added.
3. Turndown—After the blow, the vessel is tilted toward the charging
aisle to facilitate taking hot metal samples and making
temperature measurements.
4. Reblow—-If the samples taken during the turndown indicate the
need, oxygen can again be blown into the vessel, usually for only
a very brief period.
5. Tapping—Pouring the molten steel out of the BOPF into the teeming
ladle. Alloying elements, including chromium, may be added to the
ladle.
6. Deslagging—Pouring residual slag out of the BOPF into a slag pot.
7. Teeming—The pouring .of molten steel into ingot molds.
These operations are illustrated in Figures 32 and 33. A cross section
of a furnace shop is shown in Figure 34.
Emission Factors—
Both process and fugitive emissions are associated with BOPFs. Process
(or primary) emissions evolve during the actual steel making or oxygen
blowing stage and are generally captured by the primary hood. These
emissions consist mainly of iron oxides which result from the reaction
between oxygen and molten iron. Particles of slag are also contained in the
72
emissions. When chr
oxide will be emitted.
72
emissions. When chromium is a contaminant of the raw materials, chromic
Two types of primary (blowing) emission collection equipment are in
common use. One type is an open hood directed to an ESP, similar to that
shown in Figure 34. The emissions that evolve during the oxygen blow are
captured by the hood and pass through a conditioning chamber where the gas
is cooled and humidified to the required levels for proper ESP operation.
Electrostatic precipitators can be used with open hoods because the
127
-------
00
Lance
Primary Hood
Charging
Ladle
CHARGING
Tapping Hood
(^BLOWING
TAPPING
DESLAGGING
\ /
Slag Pot
TUHNDOWN
Ingot
Mold
TEEMING
Figure 32. Steps for making steel by the basic oxygen process.
72
-------
SCRAP CHARGE
HOT METAL CHARGE
OoBLOW
TURNDOWN
TAPPING
DESLAGGING
TEEMING (FROM
PREVIOUS HEAT)
1.5
1.5
NumlMn abova tht lints indicata th« approximate
duration of that operation.
CONTINUOUS
12 16 20 24
MINUTES
28 32
36 40
Figure 33. Time sequence of top blown BOPF operations.
72
-------
CONVEYOR PROM
RAW- MATERIAL
STORAOC
STOWAGE BINS
BATCHING
HOPPER
LADLE
ysssi* FU"N?E
CAR ,
TAPHOLfc
DOTTED LfNES SHOW POSITIONS
OF TILTED FURNACE AND SCRAP
HOOD 00X WHCN CHARGING SCRAP
SCRAP
HOT-METAL
TRANSFER
LADLE ON
TRANSFER CAR
Y//////7777/
Figure 34. Schematic cross section of a furnace shop
72
130
-------
combustible carbon monoxide (CO) generated during the oxygen blow burns at
the mouth_of the vessel, reducing the risk of explosions set off by sparks
in the precipitator. Alternatives to ESPs are scrubbers or, as has been
72
tried at one plant, fabric filters. All three alternatives would be
effective at chromium removal. Testing at high temperature combustion
sources indicates that ESPs are as efficient at removing chromium as they
13
are at removing total particulates.
The other type of primary emission control is the closed hood, in which
the diameter of the hood face is roughly the same as the diameter of the
mouth of the vessel. The lower portion of the hood is a skirt that can be
lowered onto the mouth of the vessel. ' This seals off the space between the
hood and the vessel, limiting the amount of air that can enter the system to
about 15 - 20 percent of that entering an open hood system. Because the
emissions are rich In carbon monoxide, gas cleaning is performed by a
scrubber to minimize the risk of explosion. The cleaned gas is usually .
72
flared at the stack.
Because there is less danger of explosion in the open hood system, all
of the vessels in the shop may be connected to a common,gas cleaning system.
Conversely, the closed hood system must have a separate scrubber system for
each vessel because of--the--potential- explosion- hasard frcia -leakage of air
into the system from an idle furnace.
Fugitive emissions result from a number of sources, and chromium has
72 76
been detected in these emissions. * The major sources are molten iron
transfer, charging, tapping, and slag handling. Minor sources include
turndown, teeming, ladle maintenance, and flux handling. * Oxygen
blowing process emissions which escape capture by the primary hood may also
be considered fugitives. A discussion of the emissions from these sources
and typical control technologies follows. The efficiencies of most fugitive
collection systems are unknown.
131
-------
Reladling or hot metal transfer of molten Iron from the torpedo car to
the charging ladle is accompanied by the emissions of kish, a mixture of
72
fine iron oxide participates together with larger graphite particles.
Trace amounts of chromium may be present in the pig iron, causing minor
chromium emissions from this source. The usual method of control is to
provide a close-fitting hood and a fabric filter. A spark box between the
hood and the fabric filter protects the filter bags from destruction by
large, hot particulates. Normally, the spark box is built integrally with
72
the fabric filter. Skimming of slag from the ladle of molten iron keeps
this source of high sulfur out of the steelmaking process. Skimming is
often done under a hood because it resul
is usually connected to a fabric filter.
often done under a hood because it results in emissions of kish. This hood
72
Charging of scrap and molten iron into the BOPF vessel results in a
dense cloud of emissions. Emissions from the charging of hot metal are
particularly severe if the scrap is dirty, oily, otherwise contaminated, or
80
contains such potential sources.of explosion as water or ice. Charging
emissions have been shown to contain chromium. Chromium enters the charge
as a contaminant of the scrap. In some open hood shops, if the main hood is
large enough and the volume of air flow is sufficient, it is possible to
capture most of the charging fumes in the primary collection system of the
vessel. In this case, as much of the vessel mouth as possible is kept under
the hood and the iron is poured at a slow controlled rate. In other
facilities (closed hood primary systems), it is necessary to provide
auxiliary hoods in front of the main collection hood. On occasion, a
facility may also have a hood at the building monitor to capture any fumes
that escape the hoods at the vessel. More charging emissions are produced
in bottom blown than in top blown furnaces due to the constant flow of gas
through the tuyeres. *
Tapping of the molten steel from the BOPF vessel into the ladle results
in iron oxide fumes. The quantity of fumes is substantially increased by
81
additions into the ladle of alloying materials. Chromium may be added as
132
-------
72
an alloying material , which would result in chromium emissions from the
tapping ladle. Some BOPF facilities enclose the space, at the rear of the
furnace in such a manner that the fumes are ducted into the main collection
system. In other facilities the fumes are permitted to exit through the
- .„ 60,72
roof monitors.
Turndown of the vessel for the purpose of talcing samples or for pouring
out the slag results in emissions. These emissions are particularly copious
in the case of the Q-BOP due to the flow of nitrogen through the tuyeres in
72
the bottom of the vessel. Particulate emissions from turndown may contain
chromium which can be a contaminant of the raw materials in the furnace.
Some facilities have a pair of sliding doors on the charging floor in front
of the vessel. These doors are kept closed as much as possible to direct
72
the fumes into the primary collection system.
Slag handling may consist'of transporting and dumping the ladle of
molten slag from the shop to a remote dump area or to an area at the end of
the shop. The dumping of slag and its subsequent removal by bulldozer is a
dusty operat;
in the slag.
72
dusty operation that is generally uncontrolled. Chromium may be contained
Teeming of steel from the .ladle to the ingot mold or continuous caster
results in emissions that are normally uncontrolled. Chromium can be
emitted from the teeming operation, especially if it was added to the
tapping ladle as an alloying material. In some shops where leaded steels
are poured, the resultant fumes are extremely hazardous to the health of the
72
workers. In these cases, local hooding is provided.
The flux handling system is comprised of receiving hoppers for
accepting deliveries from trucks or railroad cars, a belt conveyor, large
overhead storage bins, weigh hoppers, feeders, and controls. Hooding is
provided at the various transfer points to capture the particulates that
133
-------
escape when the bulk material falls. Exhaust ducts lead from the hoods to
one or more fabric filters. Chromium would be only a trace component of the
72
flux.
Ladle maintenance may be a minor source of chromium emissions,
especially if the ladle has been used to produce chromium containing steel
alloys. The molten steel that remains in the ladle after teeming may cool
and solidify between successive uses forming what are known as skulls. In
the vessel, skulls may build up around the lip, and after accumulating for
some time, may interfere with proper operation. To prevent this, skulls are
burned out with oxygen lances. This lancing procedure results in the
emission of iron and other metal oxide fumes. Ladles must also be relined
at intervals to protect the steel shell. The ladles are turned upside down
to dump loose material onto the shop floor. This generates fugitive dust
7281
potentially containing chromium. *
Fugitive blowing emissions (puffing emissions) are process emissions
that escape capture by both primary and secondary emission control devices.
Occasionally, during a blow, chemical reactions within the heat or splashing
of the slag will generate large quantities of excess emissions that cannot
be handled by the hoods in the furnace enclosure. The frequency or severity
of these episodes cannot be predicted or anticipated during the blow.
Chromium emission factors for BOFF furnaces are limited. An analysis
of charging emissions at one top blown BOPF revealed an elemental chromium
3 76
concentration of 0.51 mg/m . Process emissions were not analyzed for
chromium. Since EAFs rather than BOFFs are used to produce most high-
chromium stainless and specialty steel alloys, BOFFs would be expected to be
a relatively small source of chromium emissions in the iron and steel
industry. Trace contamination of the materials would be the main source of
chromium in BOPF emissions.
134
-------
I
Source Locations—
In 1982, there were approximately 35 steel plants using BOFF furnaces.
Typically each plant has two or three furnaces with the exception of four
larger plants. The locations of these facilities are given in
72 82 83
Table 27. »°*»°-' jj^ geographic distribution is mapped in Figure 35. The
American Iron and Steel Institute's publication, Directory of Iron and Steel
Works of the United States and Canada, is the best source of information on
BOFF steel manufacturing facilities. The steel industry including BOPFs can
also be accessed in standard manufacturing directories and is classified
under SIC code 3312.
Open Hearth Furnaces
The open hearth furnace is one type of furnace used to make steel from
scrap and pig iron, however, it is being replaced by electric arc furnaces
(EAFs) and basic oxygen process furnaces (BOPFs). In 1982 open hearth
furnaces accounted for only 8.2 percent of the steel produced in the U.S.
(down from 82 percent in 1963). No new open hearth furnaces are planned
and production is expected to continue declining. The open hearth furnace
is not economically competitive with other types of furnaces because of the
long time (8 - 12 hrs) it takes to produce a batch of steel. Basic oxygen
73
furnaces take less than 1 hour. The open hearth furnace also requires up
to twice as many labor hours per unit of steel as the BOFF, and uses
2.5 times more energy than an EAF.
One advantage of open hearth furnaces is that they can run on a charge
of 100 percent scrap, 100 percent pig iron, or any combination of the two,
depending on availability. A reverberatory type open hearth furnace is
heated alternately by a combustion flame from either end of the hearth. At
regular intervals, the gas flow is reversed in order to recover sensible
heat from the exhaust gases. This is accomplished by passing them through
brick checkers which are at either end of the furnace. At each reversal,
the brick checkers are hot enough to heat the incoming combustion air so
that the high flame temperatures needed to melt and refine raw materials are
135
-------
LIQENO
• BOPF SHOPS
Figure 35. Geographic distribution of the U.S. BOPF steelmaking facilities in 1982.
72
-------
TABLE 27. LOCATIONS OF BASIC OXYGEN PROCESS FURNACES (BOPFs)
T) ft? ft^
IN THE IRON AND STEEL INDUSTRY7**0** J
State and City
Corporation
Alabama
Fairfield
Gadsden
California
Fontana
Colorado
Pueblo
Illinois
Chicago
Granite City
South Chicago
Indiana
Burns Harbor
East Chicago
Gary
Kentucky
Ashland
Maryland
Sparrows Point
Michigan
Dearborn
Ecorse
Trenton
New York
Buffalo
Lackawanna
U. S. Steel Corporation
Republic Steel Corporation
Kaiser Steel Corporation
CF&I Steel Corporation
Interlake, Inc.
National Steel Corporation
Republic Steel Corporation
U. S. Steel Corporation
Bethlehem Steel Company
Inland Steel Company
Jones and Laughlin Steel Corporation
U. S. Steel Corporation
Armco Steel Corporation
Bethlehem Steel Corporation
Ford Motor Company
National Steel Corporation
McLouth Steel Corporation
Republic Steel Corporation
Bethlehem Steel Corporation
137
-------
TABLE 27. (CONTINUED) LOCATIONS OF BASIC OXYGEN PROCESS FURNACES
(BOPFs) IN THE IRON AND STEEL INDUSTRY72*82'83
State and City
Corporation
Ohio
Cleveland
Lorain
Middleton
Steubenville
Warren
Pennsylvania
Aliquippa
Bethlehem
Braddock
Duquesne
Farrell
Midland
Monessen
Natrona
West Virginia
Weirton
Jones and Laughlin Steel Corporation
Republic Steel Corporation
U. S. Steel Corporation
Arraco Steel Corporation
Wheeling-Pittsburgh Steel Corporation
Republic Steel Corporation
Wheeling-Pittsburgh Steel Corporation
Jones and Laughlin Steel Corporation
Bethlehem Steel Company
U. S. Steel Corporation
U. S. Steel Corporation
Sharon Steel Corporation
Crucible, Incorporated
Wheeling-Pittsburgh Steel Corporation
Alleghany Ludlum Steel Company
National Steel Corporation
Note: This listing is subject to change as market conditions change,
facility ownership changes, plants are closed down, etc. The reader
should verify the existence of particular facilities by consulting
current listings and/or the plants themselves. The level of chromium
emissions from any given facility is a function of variables such as
capacity, throughput, and control measures. It should be determined
through direct contacts with plant personnel.
138
-------
more readily reached. The furnace is charged with scrap and heated to
Incipient melting by oil, gas, or tar flames which move across the top of
the hearth. Hot metal is added to the furnace at this point. The next step
involves addition of the necessary flux and oxidizing materials to refine
the mix while it boils. Preheated combustion air, sometimes enriched with
pure oxygen, is forced into the furnace to aid the oxidation of
impurities. A slag forms containing the impurities. This is removed by
an operation termed slagging. After the molten steel has formed, it is
tapped from the furnace.
Emission Factors-
Small chromium-containing particulate matter is emitted from the
furnace during steel formation. The amount of oxygen consumed will
4
influence total particulate emissions. The percent of chromium in the
scrap and the type of steel being produced will effect chromium emissions
rates. Sources of fugitive emissions from open hearth furnaces include •
charging, leakage, tapping, and slagging. Charging emissions result from
the addition of hot metal or scrap into the hot furnace. Leakage may occur
if charging or tapping doors are improperly positioned. Leaks from the
oxygen lance-port also occur. Tapping and slagging emissions result from
the violent mixing of the poured molten material. *
Emissions from open hearth furnaces are generally controlled with ESPs,
although other types of equipment have been used,. In 1976, 80 percent of
furnaces were controlled with ESPs. Testing of two open hearth furnaces
85 86
with ESPs showed a total particulate control of 96.6 to 98.8 percent. *
Chromium collection efficiency was not measured, but other trace metals such
as nickel, zinc, copper, lead, and cadmium were removed with about
85 86
98 percent efficiency. * Venturi scrubbers are also used to control
particulate, and therefore chromium, emissions at some open hearth furnaces.
Fabric filters, which are typically more efficient particulate (and
chromium) removal devices than ESPs, have been installed at a few locations.
The disadvantage of fabric filters is that gases must be cooled prior to
73
entering the control device.
139
-------
Fugitive emissions from open hearth furnaces are generally controlled
by the use of tapping and charging doors or by hooding. In 1976, about
20 percent of open hearth furnaces were uncontrolled. The number of
uncontrolled facilities has probably decreased since that time as several
open hearth furnaces have shut down for reasons previously discussed.
No emission factors are available specifically for chromium. According
to the American Iron and Steel Institute, open hearth furnaces are used to
produce carbon and non-chromium alloy steel, rather than chromium-containing
83
stainless steel alloys. Thus one would expect a relatively low level of
chromium in raw materials and particulate emissions.
Source Locations—•
A partial listing of open hearth facilities operating as of 1980 is
83
given in Table 28. A source of current information on the location of
steel manufacturing facilities using open hearth furnaces is the American
Iron and Steel Institute's Directory of Iron and Steel Works of the United
83
States and Canada. The steel industry, including open hearth furnaces, is
48
classified under SIC code 3312. Standard manufacturing directories can be
consulted for lists of steel producers, although not necessarily the types
of furnaces they use.
Leather Tanning
Process Description-
Chromium can potentially be emitted into the air from leather tanning
facilities because chromium-based chemicals are used as tanning liquors.
Chromium based liquors are used to tan about 95 percent of the hides
87
produced in the United States.
140
-------
TABLE 28. LOCATIONS OF STEEL PLANTS WITH OPEN HEARTH FURNACES
83
State, City
Company
California
Fontana
Indiana
East Chicago
Gary
Maryland
Sparrows Point
Ohio
Middleton .
Pennsylvania
Fairless Hills
Homestead
Johnstown
New Castle
Phoenixville
West Homestead
Texas
Lone Star
Utah
Geneva
Kaiser Steel Corporation
Inland Steel Company
Jones & Laughlin Steel Corporation
United States Steel Corporation
Bethlehem Steel Corporation
Armco, Incorporated
United States Steel Corporation
United States Steel Corporation
Bethlehem Steel Corporation
Mesta Machine Company
Phoenix Steel Corporation
Mesta Machine Company
Lone Star Steel Company
United States Steel Corporation
Note: This listing is subject to change as market conditions change,
facility ownership changes, plants are closed down, etc. The reader
should verify the existence of particular facilities by consulting
current listings and/or the plants themselves. The level of chromium
emissions from any given facility is a function of variables such as
capacity, throughput, and control measures. It should be determined
through direct contacts with plant personnel.
141
-------
The leather tanning process is illustrated in Figure 36. First, the
hides are prepared to receive the tanning agent, a solution predominantly
87
composed of trivalent basic chromium sulfate. Many tanning facilities buy
the chromium sulfate solution made to specification, whereas others buy dry
88 89
chromium sulfate and formulate their own tanning solutions. *
The tanning is accomplished by soaking the hides in the chromium
sulfate solution. The purpose of tanning is to stabilize the collagen
fibers in the hides so that they are no longer biodegradable. The initial
pH of the tanning solution is about 2.8 so that the chromium sulfate is in
soluble form. After the solution has penetrated the hides, the pH is
gradually raised to 3.4 or 3.6. As this occurs the chromium reacts with the
87
collagen to produce the preserved, tanned hide.
The hides are then stacked overnight to allow further fixing of the
chromium. They are then put through a hide wringer until almost dry and
sorted. Finishing steps vary depending on the end product, but usually
include the application of an oil and water emulsion (fat liquoring),
coating with various polymers and dyes, and drying. Drying is accomplished
by hanging or laying the hides on plates in a controlled temperature
environment or by using a vacuum dryer. If suede is being produced, the
8? 88
leather is buffed, or brushed repeatedly. * -
Emission Factors—
The two potential sources of chromium emissions from the leather
tanning process are the formulation of the chromium sulfate tanning solution
and the buffing procedure. At plants which formulate their own tanning
solution, chromium sulfate dust containing a trivalent form of chromium is
emitted during storage, handling and mixing of the dry chromium sulfate raw
material. The formulation process is intermittent and of short duration,
which lessens the potential chromium emissions. Furthermore, because the
dry chromium sulfate is valuable, care is taken to minimize losses during
storage and handling. Little information on specific control technologies
is available.
142
-------
Chromium
Emissions
Dry Chromium
Sglfate
Formulaeion of
Chromium
Sulfate Solution
Chronlum
Emisainna
t
*-
u>
Salt-cured
Hides
Preparation
of Hides
Tanning of Ifldea
(aoaking in chromlun
sulfate solution)
Stacking
Sorting
Finishing
(rat liquoring* dry-
ing, colorlng(
buffing)
Leather
Product
Figure 36. Flow chart for leather tanning process at plants which formulate
their own chromium sulfate tanning solution.
-------
There are no atmospheric emissions from the soaking of leather in the
tanning solution or from the drying of hides. The methods used for drying
87
would not dislodge particulates or chromium from the leather.
The buffing of tanned hides during the suede finishing process is a
possible source of chromium emissions. The repeated brushing, or buffing,
of the leather dislodges small particles of leather which contain trivalent
chromium. Particulates from this process are contained within the building
88 90
and are not exhausted to the atmosphere. * Buffing operations are
intermittent, the extent of which will depend on the demand for suede.
Leather tanning facilities have not been viewed as sources of chromium
88 90
air emissions by the states in which they are located. * Maine conducted
ambient monitoring for chromium and found atmospheric chromium levels near
90
tanneries to be the same or slightly less than areas without tanneries.
Although not conclusive, these results indicate that tanneries are not
emitting enough chromium to affect ambient chromium levels in surrounding
areas. No chromium emission factors for leather tanning operations are
available in the literature.
Source Locations—
In 1977, there were about 500 leather tanneries in the United States.
Tanneries are located throughout the country, with the greatest
concentration in the Northeast. Essex County, Massachusetts has the highest
concentration of tanneries in the United States. Table 29 lists some of the
91
larger tanning facilities and their locations. Standard manufacturing
directories could be consulted to find the locations of other tanneries
using SIC code 3111.
144
-------
TABLE 29. LARGEST U.S. LEATHER TANNING FACILITIES AND LOCATIONS
91
State, City
Company
Arizona
Phoenix
Southwest Hide Co.
Illinois
Chicago
Iowa
Spencer -
Maine
East Wilton
Massachusetts
Beverly
Boston
Danvers
Haverhill
Holbrook
Peabody
Salem
Tauton
Woburn
New Jersey
Newark
New York
Brooklyn
Gloversville
New York
Middleboro Tanning Co.
National Rawhide Mfg. Co.
Spencer Foods, Inc.
Wilton Tanning Co.
Speco, inc.
W. Milender & Sons, Inc.
Algy Leather Co., Inc.
Hoyt and Worthen Tanning Corp.
Moran Leather Co.
Bob-Kat Leather Co., Inc.
Fermon Leather Co., Inc.
HDC Leather Co., Inc.
N.H. Matz Leather Co.
Modern Leather & Finishing Co,
Rex Tanning Corp.
Hawthorne Tanners, Inc.
Mason Tanning Co., Inc.
Geilich Tanning Co.
Braude Bros. Tanning Corp.
Murray Bros. Tanning Co., Inc.
A.J. and J.O. Filar, Inc.
Mercury Foam Corp.
Cayadutta Tanning Co.
Leather Group Inc.
Liberty Dressing Corp.
Eastern Tanning Co., Inc.
Walter Hochhauser Leather Co., Inc.
Marshall Leather Finishing Co., Inc
145
-------
TABLE 29. (CONTINUED) LARGEST U.S. LEATHER TANNING
FACILITIES AND LOCATIONS91
State. City Company
Oregon
Dallas Muir and McDonald Co.
Pennsylvania
Philadelphia Wm. C. Brown Leather Co.
Texas
San Antonio Nelson and Sons, Inc.
Utah
North Salt Lake Wills Tannery, Inc.
Vernal J.G. Drollinger and Associates
Wisconsin
Milwaukee Seidel Tanning Corp.
. Thiele Tanning Co.
Shebbygan Armira Corp.
South Milwaukee Midwest Tanning Co.
Note: This listing is subject to change as market conditions change,
facility ownership changes, plants are closed down, etc. The reader
should verify the existence of particular facilities by consulting
current listings and/or the plants themselves. The level of chromium
emissions from any given facility is a function of variables such as
capacity, throughput, and control measures. It should be determined
through direct contacts with plant personnel.
146
-------
-------
INDIRECT SOURCES OF CHROMIUM
Coal and Oil Combustion
Process Description—
Chromium is a trace element common in most coals and oils. Of the many
trace elements in coal and oil, chromium is considered to be minor in
iai
92,93
92
abundance. Tables 30 and 31, respectively, present data chat summarize
the chromium content of domestic coals by coal type and coal source.
Table 32 provides information on the chromium contents of typical oils used
in the U. S. Residual oils appear to have higher chromium contents, on the
average, than crude oils as a result of the refining process. A heavy metal
such as chromium has a very low vapor pressure and exists as a low vapor
pressure organo-metallic complex with the higher molecular weight
hydrocarbons in crude oil. As such, the metal concentrates in the heavy
98
residual part of the crude as it is distilled. This concentration -
phenomena explains why chromium contents of distillate oils are generally
lower than residual and crude oils. In analytical tests of several
distillate oils by a major oil refiner, chromium was not found at a limit of
95
detection of 0.01 ppm.
The amount of chromium emitted to the atmosphere during coal and oil
combustion is dependent primarily on the following factors:
the chromium content of the fuel,
the type of boiler used and its firing configuration,
the partitioning of .chromium between fly ash and bottom ash,
- the degree of chromium enrichment on fine fly ash, and
- the chromium removal efficiency of any controls that may be
present.
The effect of each of these factors is described in the following para-
graphs .
147
-------
TABLE 30. CHROMIUM CONTENT OF DOMESTIC COALS BY TYPE93
Coal Type
Bituminous
North Dakota
Lignite
Texas Lignite
Anthracite
TABLE 31.
Mean Chromium
Content, wt ppm
25.9
7.5
20.4
35.6
CHROMIUM CONTENT OF
Standard
Deviation, wt
2.0
3.7
1.5
7.3
DOMESTIC COALS BY
Number of
ppm Samples
130
10
29
53
92
SOURCE
Coal Source
Mean Chromium
Content, wt ppm
Standard
Deviation, wt
Number of
ppm Samples
Eastern U.S.
(Appalachia)
Midwestern U.S.
(Illinois Basin)
Western U.S.
20
18
9.0a
16
9.7
4.2
23
113
29
iiata presented in reference 94 show measured chromium levels in an
unwashed and washed western coal to 39 ppm and 43 ppm, respectively.
148
-------
TABLE 32. CHROMIUM CONTENT OF VARIOUS CRUDE AND FUEL OILS93'95"97
Average Chromium Range of Chromium
Oil Type Content, wt ppm Content, wt ppm
Crude Oil
Residual No. 6
Residual No. 6
Residual No. 5
Distillate No. 2
Distillate No. 2
Distillate No. 2
NAa
0.90
NA
NA
0.048
1.15
< 0.01 ppm
0.0023
0.09
0.095
0.045
0.51
- 0.640
- 1.9
- 0.84
- 6.2
NA
- 2.8
NA
means data not available.
149
-------
The concentration of chromium in the feed coal or oil has been
determined to be the major factor affecting uncontrolled chromium emissions
99
from combustion sources. The greater the chromium concentration in the
fuel* the higher the uncontrolled rate of chromium emissions. For the
combustion of coal, the type of boiler and its firing configuration both
affect chromium emissions by affecting the amount of coal ash that ends up
as bottom ash. The bottom ash contains some concentration of chromium that
will not be emitted to the atmosphere. The combustion of oil produces
essentially no bottom ash, minimizing the effect of boiler type and firing
configuration on the level of chromium emissions from oil fuels.
The emission of chromium from coal or oil combustion is generally
explained by the volatilization/condensation mechanism (VCM) theory. The
theory basically states that in the firebox of a boiler or furnace peak
temperatures of approximately 1650°C (3000°F) volatilize fuel elements such
as chromium. The hot flue gases from the combustion process then undergo
cooling through convective heat transfer and other mechanisms, condensing
the volatilized species. Volatilized chromium may condense or adsorb onto
existing particles in the exhaust stream according to the available
particulate surface area, or may homogeneously condense into fine
chromium-containing particles. Through this procedure, the chromium
concentration in the bottom ash is depleted, while the concentration in the
fly ash is enriched. This phenomenon occurs because the fly ash has more
relative surface area for condensation than the bottom ash and because the
bottom ash does not come in contact with the volatilized chromium long
enough for it to condense. * As an example, in an analysis of three
coal-fired utility boilers, chromium was reported to be 23 percent .
102
partitioned to the bottom ash and 77 percent to the fly ash.
The degree of partitioning and small particle enrichment that goes on
during the volatilization and condensation of chromium has been studied by
several researchers, especially for coal combustion. These researchers have
devised several classification schemes to describe the partitioning and
150
-------
enrichment behavior of many trace elements, including chromium. One of the
more simplistic, but effective classification systems is given below: *
Class I. Elements which are approximately equally distributed
between fly ash and bottom ash, showing little or no enrichment
onto small particles.
~ Class 2. Elements which are enriched in fly ash relative to
bottom ash, or show increasing enrichment with decreasing particle
size.
~ Class 3. Elements which are intermediate between Classes 1 and 2.
~ Class A. Elements which are emitted entirely in the gas phase.
Chromium emissions from coal combustion have been shown to demonstrate the
behavior of Classes 1, 2, and 3, and are usually categorized under Class 3.
Class 3 elements such as chromium are apparently not totally volatilized
during the coal combustion process, and, therefore, exhibit a capability for
bottom ash or fly ash deposition. Chromium emissions from oil combustion
generally demonstrate the behavior of Class 2 elements, primarily because
little bottom ash is present in the combustion system.
Chromium emissions from both coal and oil combustion show preferential
enrichment on fine fly ash particles. * Because of this enrichment
factor, the type of control device used plays an important role in
determining how much chromium is removed from the flue gas exhaust. Control
devices not designed to remove fine particulates do not perform as well on
chromium emissions as devices which are so designed. A summary of the
collection efficiencies for chromium that have been determined for ESPs,
fabric filters, and wet scrubbers is given in Tables 33 - 35. In addition
to control devices, fuel cleaning has also been shown to be an effective
method of reducing chromium and other trace element emissions from
combustion processes. Physical coal cleaning has been shown to remove from
27 to 65 percent of the chromium in coal depending on the source of the
coal. Physical cleaning is 50-65 percent efficient on eastern and
151
-------
TABLE 33. CHROMIUM COLLECTION EFFICIENCIES FOR
ELECTROSTATIC PRECIPITATORS104'105
Source Identification
Power Plant A
Power Plant B
Power Plant C
Power Plant D
Power Plant E
Power Plant F
Power Plant G
Power Plant H
Power Plant I •
TABLE 34. CHROMIUM
Fuel
Coal
Coal
Coal
Coal
Coal
Coal
Coal
Coal
Coal
COLLECTION
Percent Collection Efficiency
99.8
98.6
99.8
98.7
97
97.6
99.2
85.6
96.2
EFFICIENCIES FOR FABRIC FILTERS104'105
Source Identification
Power Plant A
Steel Mill
Fuel
Coal
__
Percent Collection Efficiency
99.8
99.9
152
-------
TABLE 35. CHROMIUM COLLECTION EFFICIENCIES FOR WET SCRUBBERS
104,105
Source Identification
Power Plant A
Power Plant B
Industrial Boiler A
Industrial Boiler A
Power Plant C
Fuel
Coal
Coal
Coal
Oil
Coal
Percent Collection Efficiency
96. la
88. 9a
95b
90b
97C
. Controlled by a venturi scrubber.
Scrubber was designed primarily for SO. control.
The scrubber is proceeded by an ESP.
153
-------
I
midwestern coals, but is only 27 percent efficient on western coals. Oil
fuels have successfully been cleaned of trace metals by hydrotreating
processes* but no specific removal data for chromium are available. Removal
efficiencies of greater than 95 percent have been achieved for nickel which
should be a good indicator of potential chromium removal levels because both
104
nickel and chromium exhibit Class 3 enrichment behavior.
Emission Factors--
Chromium emission factors for coal and oil combustion are presented in
Tables 36 and 37. In both tables, calculated and measured emission factors
are given. For oil combustion, calculated factors have been developed by
determining the amount of chromium in the fuel and then by assuming that
100 percent of the chromium is emitted. This approach results in an
emission factor that is theoretically the maximum.for the fuel under
analysis. The only means by which actual emissions could be greater than
the calculated value are that chromium is added to the emission stream from
metal erosion in the boiler or control device, or chromium is present in
combustion air at a significant level. Calculated emission factors for oil
combustion are generally much greater than the same factors determined by
testing. In one series of tests, calculated chromium emission factors were
consistently two times higher than what was determined by actual emissions
97
testing.
Calculated chromium emission factors for coal combustion also rely on
the amount of chromium in the fuel as a primary input. The application of
average chromium enrichment ratios (which have been estimated by testing)
and average control device efficiencies are also an integral part of the
calculation. For coal combustion, particularly sources controlled by an
ESP, measured chromium emission factors were found to be greater than the
amount of chromium that could be calculated to be emitted based on fuel
chromium levels. This inconsistency again indicates an influx of chromium
93
into the emission stream. Measured chromium emission factors for oil anc
coal combustion are based on actual emissions generated during source
154
-------
TABLE 36. CHROMIUM EMISSION FACTORS FOR OIL COMBUSTION
97,106-111
Oil Type
Uncontrolled Chromium
Emission Factors
Type of Factor
tn
In
Distillate #2
Distillate #2
Distillate #2
Residual #4
Residual #5
23.8 - 29 pg/J°
1.1 - 55 pg/Jd
0.040 - 0.042 kg/10* liters
(0.32 - 0.35 lb/10° gal)C'e
0.035 kg/106,liters
(0.29 lb/10° gal)e
0.083 kg/10,liters
Measured
Calculated
Measured
Measured
(0.69 lb/10" gair .
Residual #6 0.41 kg/10* liters
(3.4 lb/10° gal)e
Residual (No. Unspecified) 28.6 pg/J
Residual (No. Unspecified) 2.1 - 50 pg/J
Residual (No. Unspecified) 5.7 pg/Jd'f
Measured
Measured
Measured
Calculated
Calculated
Chromium emissions from oil combustion are most likely to exist as chromium eulfate, complex
oxides of chromium and other metals* and chromium oxide.
'Calculated emission factors have been developed by determining the chromium content of the oil and
making the assumption that all chromium in the fuel is emitted. Measured emission factors have
been determined by actual emissions source testing and sample analysis combined with a knowledge
of the amount of fuel burned.
-------
TABLE 36. (CONTINUED) CHROMIUM EMISSION FACTORS FOR OIL COMBUSTION97*106"111
/•
Reference 95 indicated the pg/J equivalent of this emission factor would be 1.05 - 1.15 pg/J»
assuming that all the chromium present in the emissions came from the fuel. This factor is
significantly lower than the other measured values for distillate oil combustion of 23.8 - 29,pg/J.
This difference can basically be reconciled by examining the chromium content of the fuels burned.
In the case of the lower emission factor* the fuel chromium level was about 0.05 - 0.06 pprow.
The fuel chromium content in the tests that produced the higher value ran as high as 2.8 ppmw.
Emission factor expressed as total chromium emitted per unit of heat energy contained in the fuel.
e
Emission factor expressed as total chromium emitted per mass of oil fired.
This emission factor represents controlled emissions. The factor Is applicable to control by
either wet scrubber or ESP.
Ut
Ov
-------
TABLE 37. CHROMIUM EMISSION FACTORS FOR COAL COMBUSTION94'103*104'106"108'110"112
G
Coal Type
Anthracite
Anthracite
Anthracite
Anthracite
Bituminous
Bituminous
Bituminous
Bituminous
Bituminous
Bituminous
Bituminous
Bituminous
Bituminous
Bituminous
Bituminous
Bituminous
Bituminous
Bituminous
Bituminous
Bituminous
Bituminous
Bituminous
Bituminous
Bituminous
Bituminous
Bituminous
Lignite
Lignite
Lignite
Lignite
Boiler Type
Stoker
Stoker
Stoker
Pulverized
Pulverized
Pulverized
Pulverized
Pulverized
Pulverized
Pulverized
Pulverized
Pulverized
Pulverized
Pulverized
Cyclone
Cyclone
Cyclone
Cyclone
Cyclone
Cyclone
Stoker
Stoker
Stoker
Stoker
Stoker
Stoker
Pulverized
Pulverized
Pulverized
Pulverized
Control Device
None
None
MC
ESP
None
None
MC
MC '
. ESP
ESP
WS
US
MC/WS
FGD
None
MC
ESP
ESP
WS
us
None
None
MC
MC
ESP
FF
MC
MC
ESP
ESP
Chromium Emission
Factors, pg/J >C
102 - 648
200
16.3
60.2
1,505 - 2,600
825
71.8 - 770
5.3
45 - 60.2
2.5 - 3,430
54.2 - 170
0.26 - 5.3
7.8
54
495 - 645
130
8 - 9.3
290 - 2,300
14
46
38.3 - 2,000
8.1 - 129
16.3 - 590
26.8 - 1,040
58
66
253
29 - 32
9.2 - 26.5
8.6
t
Type of Factor
Measured
Calculated
Calculated
Calculated
Calculated
Measured
Calculated
Measured
Calculated
Measured
Calculated
Measured
Measured
Measured
Measured
Calculated
Calculated
Measured
Calculated
Measured
Calculated
Measured
Calculated
Measured
Measured
Measured
Calculated
Measured
Calculated
Measured
-------
TABLE 37. (CONTINUED) CHROMIUM EMISSION FACTORS FOR COAL COMBUSTION94'103*104'106"108'110"112
Ul
00
Coal Type
Boiler Type
Control Device
Chromium Emission
Factors, pg/J '
Type of Factor
Lignite
Lignite
Lignite
Lignite
Lignite
Lignite
Lignite
Lignite
Pulverized
Cyclone
Cyclone
Cyclone
Cyclone
Stoker
Stoker
Stoker
ws
MC
ESP
ESP
WS
MC
MC
ESP
75
245 - 430 .
5 - 17.8
< 3.3
40
16.3
13
< 2.3
Calculated
Calculated
Calculated
Measured
Calculated
Calculated
Measured
Measured
The key for the control device abbreviations is as follows:
MC - multicyclones
ESP - electrostatic precipitator
WS - wet scrubber
FF - fabric filter
FGD - flue gas desulfurization
Emission factors expressed as total chromium emitted per unit for heat energy in the fuel.
*
'Chromium emissions from coal combustion are most.likely to exist as chromium sulfate, complex
oxides of chromium and other metals, and chromium oxide.
Calculated emission factors have been developed using average fuel chromium contents, average
chromium enrichment ratios, and demonstrated average control device efficiencies. Measured
emission factors have been determined by actual emissions source testing and sample analysis
combined with a knowledge of the energy content of the fuel burned.
-------
testing and analysis of a boiler and a knowledge of the quantity and
characteristics of the fuel burned.
As shown in Tables 36 and 37, wide variability exists in some of the
emission factor estimates for coal and oil combustion. Although it is
beyond the scope of this document to reconcile all the reasons for these
large ranges* available data suggest that the most important factor
102
influencing the situation is the chromium content of the fuel.
Limited chromium emission factors are also available for the combustion
of wood. In one set of tests for five furnaces burning wood, measured
chromium emission factors ranged from 0.76 - 11.7 pg/J with the average
being 6.4 pg/J. A measured
was reported in reference 111.
108
being 6.4 pg/J. A measured chromium emission factor for wood of 4 pg/J
Several recent studies have produced results strongly indicating the
forms of chromium occurring in emissions from coal and oil combustion.
Reference 113 examined the 100 - 200 \JM size fraction of fly ash captured by
electrostatic precipitators from coal fired utility boilers. Using magnetic
separation and hydrochloric and hydrofluoric acid leaching steps, the fly
ash was separated into a glass matrix, a mullite-quartz matrix, and a
magnetic spinel matrix of composition Fe_ A1Q 70,. Analysis by X-ray
diffraction and X-ray fluorescence of the separated matrices indicated that
approximately 74 percent of the chromium present was associated with the
spinel. The theory was put forth that chromium probably existed as a
substituted spinel of the form Fe. Cr 0..
r 3-x x 4
Other studies have been performed with results that indicate and
support the estimation that a significant part of chromium-containing
emissions from coal and oil combustion exist as complex oxides of chromium
and other metals. Additionally, the same studies indicated that a
large part of the metal-containing emissions from coal and oil combustion
159
-------
exist as metal sulfates. Together chromium sulfates and complex
oxides of chromium and other metals appear to constitute the bulk of
chromium emissions from coal and oil combustion.
Source Locations-
Due to the large number of combustion sources in the U. S., individual
source listings are not attempted here. However, data on the location of
*
large emitters such as power plants and industrial boilers are available
through published government data bases maintained by the U.S. EPA and DOE,
the Electric Power Research Institute (ERPI), and the American Boiler
Manufacturers Association.
Cement Production
Process Description—
The production of cement is a potential source of chromium emissions
because chromium can be a component of both the process feed materials and
the fuels such as coal and oil that are burned in cement process kilns and
dryers. In 1981 approximately 67.6 million Mg (75.1 million tons) of cement
were produced in the U. S. Cement is produced by either a wet or dry
method. In the dry method, feed materials are sent to the processing steps
in a dry solid form. In the wet method, feed materials are mixed with water
and sent to the processing steps as a slurry. Of the total domestic cement
production, about 42 percent or 28.4 million Mg (31.2 million tons) is made
by the dry method, and 58 percent, or 39.2 million Mg (43.9 million tons),
by the wet method.
The basic process flow diagram for cement production by the wet and dry
methods is shown in Figure 37. The raw materials used to make cement can be
divided into four basic categories: lime, silica, alumina, and iron.
Approximately 1600 kg (3520 Ib) of dry raw materials are required to produce
118
1 Mg (1.1 ton) of cement. Following quarrying, raw materials are crushed
to a suitable size for processing and are entered into either the wet or dry
160
-------
l}tmri'ytnft Rnw
MntprlnlH
Primary mid
Secondary
Cr until OR
Raw
HuterlnlB
Storage
I'roco
— ^
Hot
Trace
IB
a*
RJIW Mttcirlal
Propurtlcnnil
•
Raw Mntorlnl
Frn|>nrtloiifld
-^^
Grinding
Htli
r
•^
Air
Sopnratnr
RrlmllnR
Hill
f
J
f
J
Water
f
CEHUtT
PRODUCT
Primary ChronitM Enlsslon Point
Figure 37. Basic process flow diagram for wet and dry cement production plants.
118
-------
processing loop. In both wet and dry processes the materials are
proportioned, ground, and blended prior to initiating the primary cement -
production steps.
In the dry process, the moisture content of the raw material is reduced
to less than 1 percent either before or during the grinding operation. The
dried materials are then ground to a powder, blended, and fed directly into
an inclined rotary kiln. The powdered raw materials are fed into the upper
end of the kiln and travel slowly to the lower end. The kilns are fired
from the lower end so that hot gases pass upward and through the raw
materials. Drying, decarbonating, and calcining are accomplished as the
material travels through the heated kiln, finally burning to incipient
fusion and forming what is known as clinker. The clinker is then cooled,
mixed with about 5 percent gypsum by weight, and ground to a final product
118 119
size. The cement product is then stored for packaging and shipment. *
In the wet process, a slurry is made by adding water to the raw
materials at the initial grinding operation. After blending and mixing,
excess water is removed and the slurry is adjusted to achieve the proper
composition. The homogeneous mixture which is fed to the kilns is usually
either a slurry of 30 to 40 percent moisture or a wet filtrate of about 20
percent moisture. The remaining kiln burning, clinker cooling, and gypsum
118 119
addition steps are carried out the same as in the dry process. *
Emission Factors—
The primary chromium emission sources in cement production are the
rotary kilns and grinding mills. The majority of the cement industry
uses controls such as multicyclones, ESPs, ESPs with cyclones, and fabric
filters to reduce particulate, and consequently chromium emissions, from
these sources. Typical collection efficiencies for control devices in these
117,118
applications are:
multicyclones, 80 percent
ESPs, 95 percent
162
-------
- ESPs with cyclones, 97.5 percent
fabric filters, 99.8 percent.
Few direct measurements of chromium emissions from cement plants have
been made. However, total particulate emissions are reported for each stage
of the process and the chromium content of the particulate emissions has
also been measured. A 1970 study reported that particulate emissions from
28
cement plants contained 0.03 percent chromium, by weight. The value of
0.03 percent is the median value determined from tests of several cement
plant sources including kilns, dryers, air separators, and clinker coolers.
According to a 1979 review conducted for the EPA, kiln dust typically
contains 0.011 percent chromium.
To obtain the chromium emissions factors in Table 38, particulate
emission factors from EPA reports * were multiplied by 0.011 percent
(the percent of chromium in particulate emissions). Factors for controlled
and uncontrolled kilns, grinders, and clinker coolers are listed. The.
0.011 percent chromium factor was used to calculate emission factors instead
of 0.03 percent because better documentation and support was provided to
substantiate the 0.011 percent number.
Few data were found which identified the chromium content of particles
from cement processing. Chromium emitted from preliminary crushing and
grinding would be in the same form as it is found in raw materials, most
likely as a trace constituent of silicate minerals. Chromium emissions from
kilns are probably in the forms of oxides of chromium and other metals,
chromium oxide, and to a lesser extent chromium sulfate because of the high
temperature, oxidizing conditions present in kilns. Chromium emissions from
the clinker cooler would be in the same forms as those emitted from the
kilns because the chromium particles would not be undergoing any reactions
in the cooler. During milling and packaging, chromium would also be emitted
in the forms that are produced in the kiln. Chromium emitted from the
163
-------
TABLE 38. CHROMIUM EMISSIONS FACTORS FOR CEMENT PLANTS
117,118
Emission Source
Control
Chromium Emission Factor
- kg/103 Mg (lb/103 tons)
a,b
Dry process
kilnc
dryers and grinders
Wet process
kilnc
dryers and grinders
Clinker cooler
Uncontrolled
ESP
Fabric filter
Uncontrolled
Uncontrolled
ESP
Fabric filter
Uncontrolled
Fabric filter
Gravel bed
Wet scrubber
13 (26)
.002-.01 (.004-.03)
.001-.01 (.003-.03)
5 (10)
12 (25)
.002-.02 (.004-.03)
.005-.01 (.01-.03)
1.7 (3.4)
.0006-.007 (.001-.014)
.002-.005 (.005-.01)
.002 (.005)
Emissions are expressed as total chromium. These emission factors
include emissions from fuel combustion, which should not be calculated
separately.
Emission factors are expressed in terms of the amount of cement produced.
*
'Chromium emissions from this source are expected to be in the forms of
oxides of chromium and other metals, chromium oxide, and to a lesser
extent chromium sulfates.
Chromium emissions from this source are expected to predominantly be
in the form of chromium silicate minerals.
164
-------
combustion of fossil fuels and dryers should be in the forms of chromium
sulfates, complex oxides of chromium and other metals, and chromium oxide,
as discussed previously in the combustion section.
Source Locations—
In 1983 there were approximately 160 cement plants in the United
States. The majority of plants were located in California, Texas,
120
Pennsylvania, Michigan, and Missouri. Indiv
determined from a variety of sources including:
120
Pennsylvania, Michigan, and Missouri. Individual plant locations can be
- cement trade associations (e.g., Portland Cement Association)
published industrial directories (e.g., Thomas Register, Standard
& Poor's)
the EPA National Emissions Data System (NEDS).
For sources indexed by SIC code, SIC 3241 should be used for cement
manufacturing.
Municipal Refuse and Sewage Sludge Incineration
Process Description—
Chromium is released during the incineration of municipal refuse and
wastewater sewage treatment sludge because these materials contain varying
quantities of chromium. The chromium content of municipal refuse consisting
of paper and plastics ranges from 10 - 175 ppm, with an average content
121
being 30 ppm. Dry sewage treatment sludges have chromium contents
ranging from 22 - 30,000 ppm, with a mean content of 1,800 ppm and a median
122
of 600 ppm. The workings of refuse and sewage sludge incinerators and of
factors affecting chromium emissions and described below.
The majority of municipal refuse incinerators have either
refractory-lined or water-walled combustion chambers that are equipped with
a grate upon which refuse is burned. The grate can be stationary,
165
-------
travelling, or vibrating depending on the design of the incinerator. In
most cases* natural draft or slight induced draft is used to pull air up
through the grate to carry out the primary refuse combustion process. The
combustion gases from the primary chamber pass through a flame port where
they are reheated and mixed with air to achieve more complete oxidation.
Exhausts from the secondary combustion chamber are either vented directly to
the atmosphere or to a control device. The basic configuration of a
123
representative municipal refuse incinerator is given in Figure 38.
Sewage sludge incineration refers to the oxidation of sludge material
generated by wastewater sewage treatment plants. The most prevalent types
of incinerators for sludge oxidation are multiple-hearth and fluidized-bed
units. Multiple-hearth incinerators are relatively simple pieces of equip-
ment, consisting of a steel shell lined with refractory. The interior of
the incinerator is divided by horizontal brick arches into separate compart-
ments or hearths. Alternate hearths are designed with openings to allow
solid material to drop onto the hearth below. At the center of the unit, a
shaft rotates rabble arms that are located on each hearth. To enable the
incinerated material to move inward and then outward on alternate hearths,
teeth on the rabble arms are placed at an angle. As sludge is fed through
the roof of the incinerator, the rotating rabble arms and rabble teeth push
the material across the hearth to drop holes where it falls to the next
hearth. This process continues until the sterile ash produced by the
oxidation steps is discharged from the bottom of the incinerator* Figure 39
presents a schematic diagram of a typical multiple-hearth sewage sludge
124
incinerator.
The majority of multiple-hearth incinerators have three distinct
operating zones. The first zone includes the top hearths where the
water-laden sludge feed is partially dried by rising hot combustion gases.
The second operating zone is the -incineration/deodorization zone where
temperatures of 760°- 980°C (1,400 - 1,800°F) are reached and maintained.
The third zone of the multiple-hearth unit is the cooling zone when hot ash
166
-------
\
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Charging
Chute
Superstructure
\v\\\
\.\\\\\\\\-\\ \ \
Curtain
Wall
Curtain
-Wall
Inclined Charging and
Burnine Grate
muuv
Chromium-containIng
exhaust flue gases
Combustion .Chamber
Ash and Clinker
Discharge
Horizontal Burning Grate
'
-*•
Furnace
Access
Door
Figure 38. Basic configuration of a municipal refuse incinerator.
123
-------
oolirtg Air Discharge
Floating Damper
*• Sludge Inlet
Chromium-Containing
Flue Gases Out
Drying Zone
Combustion Zone
Cooling Zone
Ash Discharge"
Rabble Arm at
Each Hearth
.Combustion
Air Return
Rabble Arm
Drive
Cooling Air Fan
Figure 39. Schematic diagram of a typical multiple-hearth
sewage sludge incinerator
168
-------
from incineration releases heat to incoming combustion air. The design
temperature profile of a typical multiple-hearth incinerator is given in
125
Table 39 to illustrate the break in operating zones.
The second technique used to oxidize sewage sludge is fluidized-bed
incineration. Figure 40 represents the basic operations found in a
125
fluidized-bed unit. In this operation dewatered sludge is introduced
into the freeboard area of the incinerator just above the fluidized-bed
material (which is usually sand) . Hot combustion gases rising from the bed
evaporate remaining water in the sludge and sludge solids then enter the
fluidized bed. The organic constituents of the sludge are oxidized to
carbon dioxide and water vapor which exit the system as exhaust gases.
During this reaction the bed is vigorously mixed and the bed temperature is
maintained at 704 - 816°C (1,300 - 1,500°F). Remaining inorganic sludge
material either deposits on the bed sand particles and is removed from the
bottom of the reactor, or it can be made to exit with the exhaust gases,
Air velocity- through the bed is used to control the method of inorganic
sludge material removal. Chromium emissions from this type of system are
dependent on air flow velocity through the bed and the chromium content of
125
the sludge.
Emission Factors — •
The primary factors affecting chromium emissions from municipal refuse
incinerators are the chromium content of the refuse and the manner in which
combustion air is supplied to the combustion chambers. The manner in which
air is supplied can affect the combustion temperature achieved and conse-
122
quently the level of fly ash emissions. The types of control devices
used to reduce overall incinerator par ticu late emissions have some effect on
reducing chromium emissions. The configuration of controls found in the
U. S. varies from simple settling chambers and baffle plates to more sophis-
ticated ESP, wet scrubber, or fabric filter systems. An ESP used to control
emissions from a travelling grate refuse incinerator was measured to be
81 percent efficient at removing chromium from the exhaust stream.
169
-------
TABLE 39. DESIGN TEMPERATURE PROFILE OF A SEWAGE SLUDGE
MULTIPLE HEARTH FURNACE X
a
Furnace Hearth No. Nominal Design Capacity, °C (°F)
1 (Sludge drying zone) 427 (800)
2 649 (1200)
3 900 (1650)
4 788 (1450)
5 649 (1200)
6 (Ash cooling zone) 149 (300)
Hearth 1 is at the top of the furnace and 6 is at the bottom.
170
-------
Sight Glass
Chromium-
containing
Exhausts
Preheat
Burner
enoo-
couple
Pressure
Tap
Access
Doors
Sludge
Inlet
Fluidized
Air Inlet
Figure 40. Schematic diagram of a fluidized-bed sewage sludge incinerator
125
171
-------
Chromium emission factors for chromium from municipal refuse
incinerators and sewage sludge incinerators are given in Table 40. These
factors are expressed both as a percent of total participates emitted and as
the amount of chromium emitted per ton of refuse incinerated. Chromium
emissions at one plant did not change much when sludge was burned with the
refuse (see Table 40).
Chromium emissions from sewage sludge incinerators are influenced by
the chromium content of the sludge, the combustion temperature of the
incinerator, and in the case of fluidized-bed units, the method of inorganic
122 125
material removal from the bed. ' . Wet scrubbers are extensively used
with good success to control multiple-hearth and fluidized-bed sewage sludge
. . _ 122,125
incinerators.
The data in Table 40 suggest that the weight percent of chromium in
particulate emissions appears similar for multiple hearth and fluidized-bed
incinerators.. Those plants emitting higher amounts of fly ash emit more
chromium per ton of refuse burned. Results of EPA testing of one fluidized-
bed incinerator operated at three temperatures is also shown in Table 40.
These data demonstrate clearly that increasing the temperature of a
fluidized-bed incinerator significantly increases chromium emissions.
Very few data are available in the literature specifying the species of
chromium contained in incinerator emissions. Chromium emissions from refuse
and sludge incineration are expected to contain both trivalent and
hexavalent forms of chromium. Chromium generally exists in refuse and
sludge as trivalent chromium. Upon incineration at high temperature,
chromium will be oxidized to hexavalent chromium to some extent. The
existence of hexavalent chromium in sewage sludge incinerator emissions has
133
been confirmed.
172
-------
TABLE 40. EMISSION FACTORS FOR CHROMIUM FROM MUNICIPAL
REFUSE AND SEWAGE SLUDGE INCINERATORS
Emission Source
Chromium Emission Factors
Weight Z of
Farticulates
Emitted
kg/Mg (Ib/ton) of
Solid Waste Incinerated*
Municipal Refuse Incinerators
Multiple Hearth
Refuse Only ,
Refuse and Sludge
Rocking Grate
Travelling Gratec
0.10
0.13
0.049
0.02
0.0039 (0.0077)
0.0046 (0.0091)
0.0024 (0.0048)
0.0003 (0.0006)
Sewage Sludge Incinerators
Fluidized-Bed0 704°C
816«C
. 927aC
Fluidized-Bed ,
Multiple Hearth
Multiple Hearth
0.08
0.10
0.10
0.28
0.68
O.ll3
0.00004 (0. 00008) g
0.00003 (0.00006)8
0.0002 (0.0004)*
0.0003 (0.0006)n
0.0077 (0.014)1
— —
All factors expressed in terms of total elemental chromium. Chromium
is expected to exist in the emissions in both hexavalent and trivalent
oxidation states.
Source is controlled by a wet scrubber.
Source is controlled by an ESP.
Emissions from three incinerators were measured. Two were controlled by
wet scrubbers and one by a single-pass cyclonic scrubber.
0
Emissions from two incinerators Were measured. One was controlled by a
water spray baffle and one by an ESP.
Emission factor determined from testing of one municipal incinerator by
the National Air Pollution Control Administration .
or
^Emission factor determined by U.S. EPA testing of one sewage sludge
incinerator run at three different temperatures.
Emission factor determined from U.S. EPA testing of one sewage sludge
incinerator.
Emission factor determined from U.S. EPA testing of three sewage sludge
incinerators. The average is reported.
JEmission factor determined from testing of fly ash from two sewage
sludge incinerators. The same study reported the average chromium
concentration on suspended particulates for three incinerators to be
0.05 percent.
173
-------
120
System (NEDS). Table 41 lists the distribution of municipal refuse and
Source Locations-
There are approximately 129 municipal refuse incinerators and
141 sewage sludge incinerators in the United States according to recently
published U.S. EPA reports and information in EPA's National Emissions Data
120
System (NEDS). Table 41 lists the distributioi
sewage sludge incinerators in the U. S. by State.
Cooling Towers
Cooling towers can be sources of atmospheric chromium emissions because
chromium-containing compounds are sometimes added to cooling tower water as
a corrosion inhibiting agent.. Corrosion inhibitors are primarily used to
142
protect the heat exchanger and piping in the tower. Although chromium
corrosion inhibitors are used in towers of all size applications including
electric utilities, industrial plants, and commercial/institutional sites,
use is greatest in the industrial sector, particularly in refineries and
142-145
petrochemical plants. Utilities generally locate hear sources of
once-through cooling water so towers are not needed or they construct the
necessary towers out of corrosion resistant materials. The majority of
commercial/institutional towers rely on non-chromium water treatments such
142-145
as maintenance of high pH or phosphate treatment chemicals.
Chromium corrosion inhibitors that are added to cooling tower water
contain chromium in the form of chromates or hexavalent chromium. Chromium
concentrations in cooling tower water are generally maintained at 15 to
146-148
20 wt ppm for corrosion inhibiting purposes. Cooling tower chromium
emissions occur as a dissolved component of cooling tower drift. Drift is
essentially entrained water droplets that have been mechanically formed in
the tower and are carried out of the tower by the system air flow. Chromium
concentrations in cooling tower drift are approximately equal -to the
concentrations found in the recirculating cooling water. Cooling
tower drift and tower chromium emissions primarily are a function of the
quantity of heat rejected in a tower, tower air flow, tower design, and
146-149
ambient meteorological conditions. Tower design is important because
174
-------
TABLE 41. POPULATION OF MUNICIPAL REFUSE AND SEWAGE SLUDGE INCINERATORS
IN THE UNITED STATES IN 1983120>134-L41
State
Alabama
Alaska
Arizona
Arkansas
California
Colorado
Connecticut
Delaware
District of Columbia
Florida
Georgia
Hawaii
Idaho
Illinois
Indiana
Iowa
Kansas
Kentucky
Louisiana
Maine
Maryland
Massachusetts
Michigan
Minnesota
Mississippi
Missouri
Montana
Nebraska
Nevada
New Hampshire
New Jersey
New Mexico
New York
North Carolina
North Dakota
Ohio
Oklahoma
Oregon
Pennsylvania
Rhode Island
South Carolina
No. of Municipal
Refuse Incinerators
0
0
0
29
0
0
4
0
1
16
0
1
0
1
1
0
0
1
6
3
2
5
0
0
0
2
0
0
0
11
1
0
7
2
0
1
5
2
4
0
0
No. of Sewage
Sludge Incinerators
0
3
0
0
1
0
5
0
0
3
5
0
0
1
8
2
3
7
0
0
0
8
20
10
0
1
0
1
2
4
6
0
5
1
0
13
1
0
10
2
0
175
-------
TABLE 41. (CONTINUED) POPULATION OF MUNICIPAL REFUSE AND SEWAGE SLUDGE
INCINERATORS IN THE UNITED STATES IN 198312°*134~141
No. of Municipal No. of Sewage
State Refuse Incinerators Sludge Incinerators
South Dakota . 0 0
Tennessee 3 3
Texas 4 4
Utah 0 , 0
Vermont 0 0
Virginia 7 4
Washington 8 3
West Virginia 0 1
Wisconsin 2 4
Wyoming 0 0
TOTAL 129 141
176
-------
most towers are specifically constructed to have a certain fraction of the
recirculating water emitted as drift. Baffles and other mechanical
obstructions are used to attain a specified drift rate. For cooling towers
at utilities that were built prior to 1970, drift losses of from 0.1 to
0.2 percent are common. Newer utility cooling towers have drift losses on
149
the order of 0.002 to 0.005 percent of total recirculating water.
The general mechanism of chromium emissions from cooling tower drift is
shown in Figure 41. Dissolved chromium is carried out of the tower as a
constituent of drift. Because the drift is cooler and denser than the
ambient air it will begin to fall to the ground due to the influence of
gravity. As the drift falls to the ground, evaporation of the water
droplets occurs. At some height, which is dependent on site-specific
meteorological conditions, the moisture is evaporated leaving a
chromium-containing dust. The form of chromium in the dust is predominantly
hexavalent; however, trivalent chromium could be emitted if hexavalent
chromates are reduced in the tower as a result of performing their corrosion
inhibiting function.
The deposition of chromium around cooling towers has been
146-148
demonstrated. Test work on several utility cooling towers has
confirmed a localized impact on ambient chromium levels. The results of one
147
such test are illustrated in Figure 42. As shown in the figure, ambient
chromium concentrations decrease exponentially with distance from the
cooling tower. The concentrations in Figure 42 represent the average of
4 days of testing.
Emission Factors—
The only data available on chromium emissions from cooling towers are
149
summarized in Table 42. These data were derived from cooling towers in
utility applications. No information is available on chromium emissions
from industrial and commercial/institutional size towers.
177
-------
00
Drift
(Saturated
Air)
Dissolved
Chromium
* * * *• *. Droplets (Influenced by Gravity)
• _
• . Evaporation Taking Place
Critical Size/Height
Chromium Dust
Dispersion by Wind
Figure 41. General mechanism of chromium emissions from cooling tower drift.
-------
3
O
00
03
AJ
0.020
0.018
0.016
0.014
0.012
0.010
0.008
0.006
0.004
0.002
J I
J I
10 20 40 60 80 100 200 400 600 1000 2000 4000
Distance From the Tower, meters
Figure 42. Ambient concentrations of chromium as a function of distance
from the cooling tower.
179
-------
TABLE 42. CHROMIUM EMISSION FACTORS FOR FRESH WATER
149
UTILITY COOLING TOWERS
Drift Loss Range Drift Loss Range
a b
Chromium Emission Factors, pg/J *
ec Drifi
of 0.1 to 0.2% of 0.002 to 0.005%
2.5 0.06
Emission factors are expressed as weight of pollutant per thermal energy
input to the power plant associated with the cooling tower. Emissions
are expressed as total chromium; however, it is likely that emissions will
contain chromium in both trivalent and hexavalent oxidation states.
Emission factors are based on source tests of three separate cooling
towers.
Drift loss range refers to the fraction of recirculating water emitted
(by design) as drift.
180
-------
Source Locations—
There are no data available describing the number or distribution of
cooling towers in general or of cooling towers using chromium chemical
corrosion inhibitors.
Asbestos Mining and Milling
Process Description—
Asbestos is a generic name for a group of naturally occurring,
hydrated, mineral silicates, the type of asbestos ore mined in the United
States is called chrysotile. For commercial uses, the mined asbestos ore
must be separated into fibers and further subdivided into fibrils at a mill.
The mining and milling of chrysotile can result in chromium emissions
because chromium is a component of chrysotile. * *
There are four asbestos mines in the United States. Underground mining
is practiced at one site where ore is deeply buried. At the other sites,
where ore lies near the surface, removal is carried out with a bulldozer or
by open pit mining. In the latter case, blasting is done before removal to
loosen the overburden (materials above the chrysotile) and to reduce
ore-containing boulders to a manageable size. Mechanical shovels then load
the chrysotile onto trucks for transport to a stockpile at the mill. The
material may be wetted during transport and stockpiling to reduce
, „. 150,151
dusting. *
The asbestos mill may be situated at the mine site or at a separate
location. To prepare the chrysotile ore for milling, it must be crushed in
a manner similar to that illustrated in Figure 43. The chrysotile ore is
fed into a primary jaw-type crusher which accepts boulders up to 122 cm
(48 in) in diameter and reduces them to under 15 cm (6 in). Screens are
used to separate out materials over 3.2 cm (1*$ in) in diameter which then
undergo a second crushing in a cone crusher. The outputs of the crushers
are then conveyed to a wet stockpile outside the mill. *
181
-------
WET ROCK
(MAXIMUM 48 in. DIAMETER)
PRIMARY CRUSHING STAGE
(JAW CRUSHER TO MAXIMUM 6 in. DIAMETER)
SCREENING
(PASSAGE OF MAXIMUM M/4 in. DIAMETER)
(OVERSIZE)
(UNDERSIZE)
.
SECONDARY CRUSHER STAGE
(CONE CRUSHER TO
MAXIMUM 1-5/16 in. DIAMETER)
WET-ORE STOCKPILE
Figure 43. Crushing of massive chrysotile ore,
151
182
-------
A simplified flow chart of the asbestos milling process is given in
Figure 44. There are generally four phases in the milling process: the
drying and crushing phase* the rock "circuit." (circuit means subprocess
within the overall asbestos milling process), the fiber cleaning circuit,
and the grading circuit. To begin the drying and crushing phase, wet ore is
removed from the bottom of the stockpile (Figure 44, pt. 1) into an under-
ground tunnel by a vibrating-chute feeder. The vet ore is then fed into a
rotating cylindrical dryer (pt. 2). Dry ore is conveyed to a vibrating
screen (pt. 3) which sizes the ore for final crushing. Oversized ore is
removed from screens and ground in cone crushers, while undersized material
bypasses the crushers and is sent to a stockpile. The dried, crushed
chrysotile from the cone crushers is also stored in the same stockpile
t „ « 150,151
(pt. 5).
The main purpose of the rock circuit (pts. 6-9) is to separate asbestos
fibers from rock. The process is initiated by screening the ore with a
vibrating screen (pt. 6). Oversized materials pass to fiberizers (pt. 7)
which further disintegrate rock to release asbestos fibers. The materials
are then routed to shaker screens (pt. 8) equipped with aspirators (air
suction hoods). The light asbestos fibers are entrained into the airstream
of the aspirators, while the heavier rock is left behind for transport to a
tailing dump (pt. 9). The efficiency of recovery of asbestos fibers from
chrysotile is between 5 and 50 percent, so a large amount of
chromium-containing chrysotile can be present in the tailings. *
In the fiber cleaning circuit (pts. 10-13), the asbestos
fiber-containing air streams from the aspirators are channeled through
cyclone collectors to remove the fibers. These fibers then pass through
graders where rotating beater arms break (open up) the bundles of asbestos
fibers into smaller units (pt. 11). 'The asbestos fiber stream then passes
through another aspirator and cyclone collector for further cleaning and
refinement. Waste materials from the aspirator are recycled to the start of
the rock circuit. Asbestos fibers are collected in the cyclones. *
183
-------
Drying and Final Crushing
Chromium Chromium Chromium Chromium Chromium
Emissions Emissions Emissions Emissions Emissions
» f 1
Wet Ore
Stockpile
Dryer
\ 1 f
Screen
Q @ ©
Oversize
Material *
Cone
Crusher
Dried Ore
Stockpile
Under size ^ | ^
Material
Rock Circuit, Cleaning Circuit,.
Grading Circuit
Emissions
Chromium
Emissions
Chromium
Emissions
Chromium
Emissions
00
*-
Dried Ore
Stockpile
,
f
»•-
Screen
©
Oversize
Material
««.
Underslze Material
Chromium
Emissions
*
Aspirator
Cyclone
Collector
Aspirator
5)f Rock
/ \
Tailing
Dump
Asbestos in Cyclone Asbestos
air stream Fibers
© 0
Chromium © I Chromium
Emissions chromium Emissions
1 Emissions 1
F
G
inal
radlng
^-' fjtejecta ^ ^,
Rejects ^
Figure 44. Generalized flow sheet of an asbestos milling process.
-------
Final grading (p. 14) consists of further cleaning and separating of
the fibers into standard grades. The asbestos is then packaged by
compressing the material into a dense bundle or blowing it into 'a
. 150,151
bag.
Emission Factors—
Potential emission sources of chromium-containing chrysotile during
mining include drilling, blasting, bulldozing, loading ore onto trucks, and
transporting ore from the mine to the mill. The type of chrysotile mining
performed (open pit-, surface bulldozing, or underground), weather con-
ditions, chrysotile moisture levels, and the chromium content of the
chrysotile ore affect chromium emission rates. Control methods currently
being used at mines to reduce particulate emissions are also effective at
reducing chromium emissions. Drilling emissions are controlled by using
fabric filters to collect drilling rig exhausts and by using wet drilling
practices. The latter dust reduction technique cannot be used when tempera-
tures are below freezing. Blasting emissions from chrysotile mining are
difficult to control due to their highly fugitive nature. Currently gel
blasting agents or water and wetting agents are injected into the holes
drilled prior to blasting. Reductions in dust emissions of 20 to 80 percent
have been reported using this method. Careful planning and placing of
charges can also reduce the amount of blasting necessary. *
The overburden removal, surface bulldozing, and ore loading operations
are typically uncontrolled sources of chromium-containing particulate
emissions. Emissions arising from ore transport are controlled by using
covered trucks. Roads around the mine which are surfaced with asbestos mill
tailings are periodically wetted to reduce dust emissions, and trucks are
required to travel slowly. *
Chromium-containing chrysotile particulates are emitted at several
points in the primary crushing and milling processes (Figures 43 and 44).
Chromium emission sources from the primary crushing of chrysotile ore
(Figure 43) include the following:
185
-------
unloading ore at the crushing site
primary crushing
- screening
secondary crushing
- conveying and unloading ore to the wet ore stockpile
Sources of emissions from the milling process (Figure 44) include:
- wind erosion of wet stockpile surfaces (pt. 1)
ore dryers (pt. 2)
screens (pts. 3 and 6)
crushers (pt. 4)
dry ore storage (pt. 5)
fiberizer (pt. 6)
cyclone collectors (pts. 10 and 13)
graders (pts. 11 and 14)
bagging.of asbestos (pt. 15)
wind erosion of the tailing piles (pt. 9)
- conveyors moving asbestos ore, fibers, and tailings
between these operations
conveyor transfer points
Control techniques used to reduce particulate emissions from asbestos
crushing and milling also reduce chromium emissions. The primary and
secondary crushers and screens (Figure 43) are usually equipped with fabric
filters.
Periodic spraying of the wet ore stockpile reduces wind erosion of
chromium-containing particulates. Conveyors outside the mill are typically
enclosed or their contents are wet. '
186
-------
Crushers* fiberizers, screens, and grading operations in the mill
(Figure 44) are usually contained under negative pressure, and
dust-containing air is exhausted through a fabric filter. Cyclone and dryer
exhausts containing chromium are also vented through fabric filters.
Ventilation systems at the asbestos bagging stations channel
chromium-containing asbestos dust through fabric filters. Measured
efficiency of fabric filters at one U. S. asbestos plant was over
99.9 percent.150
Large quantities of mill tailings are generated each year which contain
waste rock and unrecovered asbestos ore. Points where tailings are
deposited from conveyors onto the tailing piles are either hooded and the
dust exhausted through fabric filters, or tailings are sprayed with water as
they are deposited. Chemicals may be added to the water to help bind
particles together and thereby reduce emissions upon drying. In time,
natural wetting and freezing may help consolidate dust into larger particles
and reduce wind erosion. Attempts to vegetate tailing piles have not been
very successful because the high alkalinity inhibits plant growth.
No factors are available in the literature specifically for chromium
emissions from asbestos mining and milling. However, total particulate
emissions have been estimated and measured, and chroazium emission factors
can be calculated from these data. The chromium emission factors shown on
Table 43 were calculated from estimates of total annual particulate
emissions, from U. S. mines and mills in 1969, divided by total domestic
asbestos production. These particulate emission factors were multiplied
by 0.15 percent, which is the typical weight percent of chromium in
chrysotile. Resulting factors are expressed as pounds of chromium emitted
per ton of asbestos produced.
More recent information was used to compute the value of .000008 kg/Mg
(.000015 Ib/tou) for milling listed on the last line of Table 43. This
factor was based on a mill producing 36,300 Mg (39,930 tons) of asbestos/yr
187
-------
TABLE 43. CHROMIUM EMISSION FACTORS FOR ASBESTOS MINING AND MILLING
Source
Chromium Emission Factors kg/Mg (Ib/ton)
of Asbestos Produced
Mining and Milling
Mining
Uncontrolled
50% Controlled
80% Controlled
Milling
Uncontrolled
80% Controlled
99% Controlled
Milling
Controlled
.07
.008
.004
.002
(.14)
(.015)
(.008)
(.003)
.08 (.15)
.02 (.03)
.0008 (.0015)
.000008 (.000015)
Factors reported as total elemental chromium. Chromium is emitted in the
form of the chrysotile silicate mineral; however, the oxidation state of
chromium is unknown.
Degree of control unspecified. The proportion of chromium emissions from
mining versus milling is also unspecified.
188
-------
152 153
and an asbestos particulate emission rate of 180 kg (396 Ib/yr). ' To
calculate the chromium emission factor* it was again assumed that emissions
contained 0.15 percent chromium. This factor is probably more represen-
tative of current control technology and chromium emission rates than the
higher rates shown in Table 43.
Source Locations—
In 1981, there were four asbestos mines and four asbestos mills in the
United States. The locations of these are shown on Table 44.
Coke Ovens
Process Description—
The production of metallurgical coke is a potential source of chromium
emissions because of chromium in the coal being processed. Coke production
involves the destructive distillation of coal by heating it in a low oxygen
atmosphere, driving off gases generated By the decomposition of organic
compounds in the coal. After distillation only the relatively involatile
coke remains. The primary method of coking in the U. S. is the byproduct
154
method, which accounts for 98 percent of domestic production.
. The byproduct method is designed to recover gases generated during the
coking process. A coke battery comprises a series of 40 to 70 narrow
rectangular, slot-type coking ovens interspersed with heating flues.
Figure 45 illustrates the arrangement of a typical coke oven battery. Coal
is charged into ports on the top of the ovens by a device called a larry
car. After charging, the ports are sealed, and heat is supplied to the
ovens by the combustion of gases passing through the flues between ovens.
The fuels used in the combustion process are natural gas, coke oven gas, or
gas from an adjacent blast furnace. Inside the ovens, coke is first formed
near the exterior walls and then the process progresses toward the oven
center, where temperatures of 1,150°C (2,100°F) can be reached. The
complete coking process takes 16 to 20 hours. Once the process is complete,
189
-------
TABLE 44. LOCATIONS OF ASBESTOS MINES AND MILLS IN 1981
150
City and State
Corporation
Mines
Gila County, AZ
Copperopolis, CA
Santa Rita, CA
Orleans County, VT
Mills
Globe, AZ
Copperopolis, CA
King City, CA
Orleans County, VT
Jaquays Mining Corp.
Calaveras Asbestos Corp
Union Carbide Corp.
Vermont Asbestos Group
Jaquays Mining Corp.
Calaveras Asbestos Corp,
Union Carbide Corp.
Vermont Asbestos Group
Note: This listing is subject to change as market conditions change,
facility ownership changes, plants are closed down, etc. The reader
should verify the existence of particular facilities by consulting
current listings and/or the plants themselves. The level of chromium
emissions from any given facility is a function of variables such as
capacity, throughput, and control measures. It should be determined
through direct contacts with plant personnel.
190
-------
Potential Chromium
Emissions Sources
(D Pushing emissions
(2) Charging emissions
(3) Door emissions
(7) Topside emissions
® Battery underf Ire emissions
•ssssssssssssssssssssssssssssss/sssssssssssss.
Figure 45. Metallurgical coke oven battery.
142
-------
coke is removed from the oven simply by pushing it out with a ram into a
quenching car. The quenching car full of extremely hot coke is moved into
the quench tower and cooled by applying several thousand gallons of water.
The coke is then allowed to dry before being separated into various size
154
fractions for future uses.
Emission Factors—
The possible process related chromium emission points from a coke oven
battery are indicated in Figure 45. Chromium emissions may also be
generated during quenching operations and from materials handling operations
154
involving coal unloading, crushing, and sizing. The form of chromium
emissions from these coking sources has not been determined 'and expressed in
the literature.
No emission factors for chromium from metallurgical coke production are
available from the literature.
Source Locations— .
Table 45 presents the complete listing of coke production plants in the
United States as of January 1980.
192
-------
TABLE 45 . COKE PLANTS IN THE UNITED STATES AS OF JANUARY 1980
155
Company Name
Plant Location
Armco* Inc.
Bethlehem Steel Corp.
CF&I Steel Corp.
Crucible Steel, Inc.
Cyclops Corp. (Empire-Detroit)
Ford Motor Co.
Inland Steel Co.
Interlake, Inc.
J&L Steel Corp..
Kaiser Steel Corp.
Lone Star Steel Co.
National Steel Corp,
Republic Steel Corp.
U. S. Steel Corp.
Hamilton, OH
Houston* TX
Middletown, OH (2)
Bethlehem, FA
Burns Harbor, IN
Johnstown, PA
Lackawanna, NY
Sparrows Point, MD
Pueblo, CO
Midland, PA
Portsmouth, OH
Dearborn, MI
E. Chicago, IN (3)
Chicago, IL
Aliquippa, PA
Campbell, OH
E. Chicago, IN
Pittsburgh, PA
Fontana, CA
Lone Star, TX
Granite City, IL
Detroit, MI
Weirton, WV
Brown's Island, W
Cleveland, OH (2)
Gadsden, AL
Massillon, OH
S. Chicago, IL
Thomas, AL
Warren, OH
Youngstown, OH
Clairton, PA (3)
Fairfield, AL
193
-------
TABLE 45. (CONTINUED) COKE PLANTS IN THE UNITED STATES AS
OF JANUARY I960155 -
Company Name
Plant Location
Wheeling-Pittsburgh
Alabama By-Products Corp.
Allied Chemical Corp.
Carondelet Coke Company
Chattanooga Coke and Chemical Comp.
Citizens Gas and Coke Utility
Detroit Coke
Donner-Hanna Coke Corp.
Empire Coke Comp.
Erie Coke and Chemicals
Indiana Gas and Chemical
Ironton Coke Corp. (McLouth Steel)
Keystone Coke Comp.
Jim Walter
Koppers Co., Inc.
Milwaukee Solvay
Philadelphia Coke
(Eastern Assoc. Coal Corp.)
Fairless Hills, PA
Gary, IN
Lorain, OH
Provo, UT
E. Steubenville, WV
Monessen, FA
Tarrant, AL
Ashland, KY
St. Louis, MO
Chattanooga, TN
Indianapolis, IN
Detroit, MI
Buffalo, NY
Holt, NY
Painesville, OH
Terre Haute, IN
Ironton, OH .
Swedeland, PA
Birmingham, AL
Erie, PA
Toledo, OH
Woodward, AL
Milwaukee, WI
Philadelphia, PA
194
-------
TABLE 45 . (CONTINUED) COKE PLANTS IN THE UNITED STATES AS
OF JANUARY 1980 155
Company Name
Plant Location
Shenango, Inc.
Tonavanda Coke Co.
Neville Island, FA
Buffalo, NY
numbers in parentheses indicate the number of plants at that location.
If no number is indicated, only one plant exists at that location.
NOTE: This listing is subject to change as market conditions change,
facility ownership changes, plants are closed down, etc. The
reader should verify the existence of particular facilities by
consueling current listings and/or the plants themselves.
The level of nickel emissions from any given facility is a
function of variables such as capacity, throughput, and control
measures, and should be determined through direct contacts with
plant personnel.
195
-------
-------
REFERENCES FOR SECTION 4
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3. State of Delaware Division of Environmental Control, Wilmington Office.
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4. State of Delaware Division of Environmental Control, Wilmington Office.
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5. State of Delaware Division of Environmental Control, Wilmington Office.
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6. Towill, L. E. e£ al. Reviews of the Environmental Effects of Pollu-
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9. Dealy, J. 0. and A. M. Killin. Engineering and Cost Study of the
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Protection Agency, Research Triangle Park, NC. May 1974.
10. Telecon. Brooks, G. W., Radian Corporation with Watson, G., Ferroalloy
Association. February 23, 1983. Chromium Emissions from Ferroalloy
Production.
11. Katari, V. ^t_ al_. Trace Pollutant Emissions from the Processing of
Metallic Ores. EPA 650/2-74-115. The U. S. Environmental Protection
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196
-------
12* National Emissions Data System. Maintained by the Monitoring and Data
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24. Letter from McHugh, G. D., General Refractories Company to Behling, M.,
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32. North Carolina Environmental Management Commission, Raleigh,
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33. North Carolina Environmental Management Comnission, Raleigh,
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198
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35.
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North Carolina Environmental Management Commission, Raleigh,
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January 1976. 17 pages.
North Carolina Environmental Management Commission, Raleigh,
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51. Hogan, W. T. Does Direct Reduction Have a Future? Iron and Steel
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Submittal of requested information.
56. Memo and attachments from Terry, W., Midwest Research Institute, to
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57. Junker, A. Electric Steelmaking - The Bottom Tapping Combined Process
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200
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59. Emission Test Report. AL Tech Specialty Steel Corporation. The U. S.
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61. Memo and attachments from Terry, W., Midwest Research Institute, to
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62. Memo and attachments from Banker, L.» Midwest Research Institute, to
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63. Memo and attachments from Terry, W., Midwest Research Institute, to
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64. Hutten-Czapski, L. Efficient and Economical Dust Control System for
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66. Telecon. Terry, B_., Midwest Research Institute, with Sarlitto, R.,
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117. Barrett, K. W. (Mitre Corp.). A Review of Standards of Performance for
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118. Compilation of Air Pollutant Emission Factors. Third Edition. U. S.
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205
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124. Hefland, R. M. (Mitre Corp.). A Review of Standards of Performance
for New Stationary Sources - Sewage Sludge Incinerators.
EPA-450/2-79-010. (Prepared for the U. S. Environmental Protection
Agency, Research Triangle Park, NC). March 1979. p. 4-11.
125. Environmental Engineer1s Handbook, Volume 3 - Land Pollution.
by Liptak, B. 6. Published by Chilton Book Company, Radnor,
Pennsylvania. 1974. pp. 253-267.
Edited
126. Golembiewski, M., e£ al. Environmental Assessment of Waste-to-Energy
Process: Braintree Municipal Incinerator. EPA-600/7-80-149.
December 1978.
127. Law, S. L. and 6. E. Gordon. Sources of. Metals in Municipal
Incinerator Emissions. Environmental Science and Technology.
13(4):.432-438. April 1979.
128. Greenberg, R.R. et_ al. Composition and Size Distribution of Particles
Released in Refuse Incineration. Environmental Science and Technology.
12(5):566-573. 1978.
129. Greenberg, R. R. e_£ al. Composition of Particles Emitted from the
Nicosia Municipal Incinerator. American Chemical Society. 12(12):
1329-1332. 1978.
130. Cross, Jr., F. L. e_£ al. Metal and Particulate Emissions from Incin-
erators Burning Sewage Sludge and Mixed Refuse. Paper presented at the
1970 National Incinerator Conference of the American Society of Mechan-
ical Engineers.
131. Trichon, M. e^ al. The Fate of Trace Metals in a Fluidized Bed Sewage
Sludge Incinerator. Paper presented at the 74th Annual Meeting of the
Air Pollution Control Association. 1981.
206
-------
132. Bennett, R. L. and K. T. Knapp. Characterization of Particulate
Emissions from Municipal Wastewater Sludge Incinerators. Environmental
Science and Technology. 16(12): 831-836. 1982.
133. Pelland, A. S., et^ al. (Radiain Corporation). Definition of the Air
Toxics Problem at the State/Local Level. Final Report. EPA Contract
No. 68-02-3513, assignment 45. (Prepared for the tt, S. Environmental
Protection Agency, Research Triangle Park, NC). June 1984.
134. Letter and attachments from Courcier, J., U. S. EPA Region I to
Mitsch, B. F., Radian Corporation. February 24, 1983. Sewage sludge
incinerators.
135. Letter and attachments from Giaconne, F. W., U. S. EPA Region II to
Mitsch, B. F*, Radian Corporation. March 21, 1983. Sewage sludge
incinerators.
136. Letter and attachments from Mitchell, J. W., Georgia Department of
Natural Resources to Wilburn, J. T., U. S. EPA Region IV, March 21,
1983. Sewage sludge incinerators.
137. Letter and attachments from McCann, R. B., Kentucky Natural Resources
and Environmental Protection Cabinett to Mitsch, B. F., Radian
Corporation, March 21, 1983. Sewage sludge incinerators,
138. Letter and attachments from Nuncio, M. G., U. S. EPA Region Vlt to
Mitsch, B. F., Radian Corporation, March 7, 1983. Sewage sludge
incinerators.
139. Letter and attachments from Hooper, M. H., U. S. EPA Region X to
Mitsch, B. F., Radian Corporation. April 4, 1983. Sewage sludge
incinerators.
140. Survey of Cadmium Emission Sources: GCA Corporation. New Bedford,
Massachusetts. EPA-450/3-81-013. September 1981.
141. Coleman, R., et al. Assessment of Human Exposure to Atmospheric
Cadmium. EPA-45075-79-007. June 1979.
142. Telecon. Brooks, G. W., Radian Corporation with Pucorius, P., Pucorius
and Associates. March 2, 1983. Cooling tower emissions.
143. Telecon. Brooks, G. W., Radian Corporation with McCloskey, J., Betz
Laboratories. February 22, 1983. Cooling tower emissions.
144. Telecon. Brooks, G. W., Radian Corporation with Augsburger, B.,
Pucorius and Associates. February 23, 1983. Cooling tower emissions.
207
-------
145. Telecon. Brooks, G. V., Radian Corporation with Townsend, J., Cooling
Tower Institute. February 22, 1983. Cooling tower emissions.
146. Alkezweeny, A. J., et^ al. Measured Chromium Distributions Resulting
from Cooling Tower Drift. Presented at the Cooling Tower Environment -
1974 Symposium. College Park, Maryland, March 4-6, 1974.
147. Jallouk, P. A., e£ al. Environmental Aspects of Cooling Tower
Operation. Presented at the Third Environmental Protection Conference
of the U. S. Energy Research and Development Administration. Chicago,
Illinois, September 23-26, 1975,
148. Taylor, F. G., e£ al. Cooling Tower Drift Studies at the Paducah,
Kentucky Gaseous Diffusion Plant. Presented at the Cooling Tower
Institute Annual Meeting. Houston, Texas, January 22 - 24, 1979.
149. Reference 13, pp. 4-9 to 4-13.
150. RTI. Review of National Emission Standard for Asbestos (Draft).
Prepared for the U. S. Environmental Protection Agency, Research
Triangle" Park, North Carolina. EPA contract number 68-02-3056.
October 1981.
151. Control Techniques for Asbestos Air Pollutants. The U. S. Environmental
Protection Agency, Research Triangle Park, North Carolina. Publication
number AP-117. February 1973.
'.52. Telecon. Acurex Corporation with Clifton, R. A., U. S. Bureau of Mines.
July 1980. Asbestos Emissions.
153. Telecon. Acurex Corporation with Wood, G., U. S. Environmental Pro-
tection Agency. July 1980. Asbestos Emissions and Controls.
154, Compilation of Air Pollutant Emission Factors. Third Edition -
Supplement 11. U. S. Environmental Protection Agency, Research
Triangle Park, NC. October 1980. pp. 7.2-1 to 7.2-4.
155. Coke Wet Quenching - Background Information for Proposed Standards,
Draft Report. Emission Standards and Engineering Division, U. S.
Environmental Protection Agency, Research Triangle Park, NC. May 1981.
pp. 9-18 to 9-21.
208
-------
SECTION 5
SOURCE TEST PROCEDURES
Source sampling and analysis procedures have not been published by the
U. S. EFA for chromium emissions. The sampling and analysis methods
presented in this chapter represent a collection of chromium air emission
detection and quantification techniques that have been published in the open
literature as viable methods. The presentation of these published methods
in this report does not constitute endorsement or recommendation or signify
that the contents necessarily reflect the views and policies of the U. S.
EPA.. • . -
LITERATURE REVIEW OF SAMPLING METHODS
Because of its physical and chemical properties, chromium emissions in
• i
air are highly unlikely to be in a gaseous form. Chromium-containing
particulate emissions behave like other particulate matter to the extent
that they may be collected by whatever techniques are suitable or applicable
2
in a given application. The U. S. EPA has promulgated Methods 5 and 17 for
measuring particulate emissions from certain new stationary sources to
3
indicate compliance with new source performance standards (NSPS). Method 5
uses an out-of-stack particulate filtration technique and Method 17 uses an
in-stack filtration technique.
The National Air Sampling Network uses high-volume (hi-vol) filters to
4
collect ambient particulate samples. Typical filter media have included
cellulose, polyethylene, polystyrene, and glass fiber. Care should be taken
because some filter media are contaminated with large amounts of chromium.
As an example, millipore filter material was found to contain chromium at a
209
-------
level of 17,600 ppb.
1,5,6
In contrast to the hi-vol, Bagnoche and Risby
sampled for chromium participates with a low-volume sampler using porous
polymer filter media.
In one set of tests, air samples were collected for organic chromium
species at chromium chemical plants, electroplating plants, leather
tanneries, and ferrochromium plants. These samples were taken using the
sampling train illustrated in Figure 46. Ambient air was pumped through a
3
glass fiber filter and an XAD-2 resin tube at between 230 and 330 cm /s
3
(0.0081 - 0.012 ft /s) over a period of 4 hours. The volume of gas sampled
in each run was measured by a dry test meter. After sampling, the resin
tubes were capped and sent for analysis.
Chromic acid mists in air have successfully been collected by:
absorption using water or caustic solutions in an impinger or sintered-glass
bubbler, by absorption in distilled water and alkaline solutions, and by
1289
filtration with absorbent paper. ' * * Of these methods, filtration offers
the greatest collection efficiency and ease of collection. The AA type of
membrane filter has a 0.8u pore size and therefore provides a highly
• 9
retentive matrix for chromium particulates in the mists.
LITERATURE REVIEW OF ANALYTICAL METHODS
Extraction Procedures
Prior to analysis, chromium samples may need to be concentrated or
extracted from potential sample contaminants. One of the most widely used
extraction techniques for atmospheric chromium samples is liquid-liquid
solvent extraction. In this method an Immiscible organic solvent is
equilibrated with an aqueous solution containing chromium in a complexed
state. The phases are then separated and the organic phase, in which the
chromium species preferentially concentrates, is analyzed or undergoes
further separation/concentration processes. Ammonium pyrrolidine
210
-------
Source
to
Stainless Steel Probe
Polymer
Packed
Tube
Gas Meter
Figure 46. Organic chromium species sampling configuration.
-------
dithiocarbamate (APDC) is a commonly used complexing agent for chromium
extraction. Generally, methyl isobutyl ketone (MIBK) Is used as the
organic solvent. This extraction technique only recovers hexavalent
chromium; if trivalent chromium is to be extracted, it must first be
oxidized. The oxidation step may be .accomplished by treatment of the sample
with silver nitrate and potassium peroxydisulfate or with potassium
permanganate and sodium azide. The solvent extraction technique is popular
because it allows for the elimination of interfering elements and for
increased sensitivity through concentration of the sample.
Snyder, $t_ a^. employed the solvent extraction technique in tests of
12
several chromium sources. Prior to the solvent extraction procedure, the
hi-vol filter samples containing chromium were dried at 60°C (140°F) to
constant weight, placed in a Pyrex^boat, and low temperature ashed at
425 watts until the plasma discharge reverted to a blue color Indicating
completion of the ashing. The typical ashing time was two hours. . The ashed
(BS
samples were quantitatively transferred to a 25 mm Pyrex0*extraction thimble
(coarse grade). The extraction thimble was then placed into an extraction
apparatus which had been charged with 8 ml of 19 percent hydrochloric acid
(HC1) and 32 ml of 40 percent nitric acid (HNO ). The extraction flask was
•J
fitted with an Allihn condenser and acid was refluxed over the sample for
three hours. After this time the Allihn condenser was removed and the acid
extract was concentrated to 20 ml on a hotplate. After cooling, the acid
concentrates were quantitatively transferred to 100 ml volumetric flasks,
diluted with distilled water, and transferred to 200 ml polyethylene sample
bottles for storage.
The solvent extraction procedure carried out by Snyder, et al. was a
13
modification of that described by Midgett and Fishman. The extraction of
hexavalent chromium in the samples was accomplished by first pipeting
exactly 20 ml of sample into an acid-cleaned 60 ml bottle. After adding two
drops of 0.1 percent methyl violet indicator, either NaOH or HNO,. was added
until the indicator changed from yellow to blue-blue green (pH 2.4-2.6).
212
-------
Then. 5 ml of 5 percent APCD solution, 3 ml of saturated sodium sulfate
(Na2SO.) solution, and 20 ml of MIBK were pipetted into the 60 ml bottle.
The bottle was capped and shaken on a wrist-action shaker for 3-5 minutes.
The extracted hexavalent chromium (or total chromium if trivalent chromium
12
was oxidized) is contained in the top organic layer of the solution.
Analysis Procedures
*
A wide variety of analytical methods have been used to determine and
quantify chromium levels in environmental samples. A number of these
methods are summarized in Table 46. Analytical methods that have been used
include titration of liberated iodine with standardized sodium thiosulfate
solution, colorimetry with hematoxylin of sym-diphenylcarbazide, and field
analysis by means of an impregnated filter paper based on the colorimetric
reaction between chromium and sym-diphenylcarbazide and comparison with
permanent standards. The iodide-thiosulfate method is subject to
interferences from a large number and variety of compounds because of its
nonspecific iodide reaction and the tendency for errors in color definition.
The hematoxylin method is a visual colorimetric technique and is intended
only as a check for very small amounts of chromium. The colorimetric
diphenylcarbazide method does not react with trivalent chromium but produces
9
a color only with hexavalent chromium.
Until the last decade or two-, spectrophotometric methods utilizing the
chromium diphenylcarbazide reaction were predominantly used for chromium
analysis purposes. This analytical procedure involves forming colored
molecular species which absorb radiation in the visible or near ultraviolet
range of the spectrum. The amount of radiation absorbed is compared with a
previously obtained calibration plot and is related to the metal concen-
tration by the calibration data. Photometric measurements at concentrations
near 400 mg/liter can be made with a precision of about 30 percent.
Accuracy depends on the promptness of the analysis. Spectrophotometric
comparisons should be made at least five but not more than 15 minutes after
the addition of reagent to the sample.
213
-------
TABLE 46. INSTRUMENTAL METHODS FOR THE DETERMINATION OF CHROMIUM*
..... ... . I»pnrtant «... .. .. (relative standard _ .
Analytical Method ti,,_»i Detection Halt * . Relative error
appl Icatlun devlatlon/aaMple
*\T.f)
Atonic absorption Biologic Builds and 0.2 ug/IUnr IM (ft itg/llter) 7X <5 iig/llter)
epec t roarupy f 1 u Ida : 1 1 Maue ,
(f lamelr.as) blond, urln<<;
Induntrlal waaiv-
watem i air
pollution t
participate;!
Atonic absorption Fraah and aallne 0.05 ug/llter SX (1 tig/liter) JX (% Mg/llier)
apertroacnpy waters, InJim-
(flaw) Itlal wnate
fluids, doat and
_j Medlmenta, lilo-
l_t logic aollda
•P* and 1 IqiildM,
alloy*
Neutron cctlVBtton Air pollution Semill Ivlty varlea IX (fl hg/g) »X (100 ng/ru •)
•nslyits partlculates, with iianple mid 6X (*i itg) (air pollution
fresh and tullnr procenalng con- , part Irulatita)
waters, biologic dltlona. Typical 20X (?.A itg/g)
liquids and arnall Ivltnn nrel ' (orchard
Hnllda, qcdlMitta. 0.2 ng/R/ (pe.lro- , leaven)
•etala, fwida let*). 10 ng/g
fenvlroiwnntal
nnnpleft), 0.1
t'g/R (hlolitglc
Malitrlal)
SpactrophotiMStrlc Natural water and 1 ng/llter U (400 hg/lltrr) . JX (0.4 Hg/g)
Induntrlal want*
in lul Ititin having
% tn 4OO ng/l lift
hexavalenl
Interfering
atibntnnrea
No Interfering
substaiire.a nrs
reported for
nanplea of
tirlnp and
Mood.'J Una
than IOX Inter-
ference la ob-
served for Ha*,
*'. «:.'*, Hg".
cr, r~, so*1',
and P04 * In
certain Indita-
trlal vaatewatera.
Interfering stib-
atancra preannt
In the original
sample *r«* usual-
ly mil extracted
Into the nrgnnlc
solvent.
Interference nay
ar|ae Iron gam-
RM ray activity
fron other ele-
pentn, capeclally
Ma-24, Cl-18, K-*2
and Hii~5ft. Rrema-
strahlimg frum
P-12 mny h*
truublcnnne.
Iron, vanadium,
and mercury nay
Interfere.
Selectivity
Total chronliM Is
Measured.
All of the
emrarted chro-
Mlina Is Measured,
hut only Cr(VI)
Is extracted fro*
the original
aamplr tin It AM
oxldstlve pre-
treatMent la
unnd.
Total cliroMliM Is
Measured.
This method
detemlnes only
the heftavslent
chrositum In
so hit ton.
analysed.
rnncentriit Inn*
wnat he rf>dnrrd
hy dilution . Air
pollution par-
ticulatea.
-------
TABLE 46. (CONTINUED) INSTRUMENTAL METHODS FOR THE DETERMINATION OF CHROMIUM
Prrrlalon
Analytical Pathod "ft"!?1 l>«ectlon ll.lt '^'M* ?*«***
application devfatlon/aAmpIe
•tee)
X-ray fluorescence Atcmoaphartc parti- 2 to 10 |ig/g (liver) 4Z (25 iig/g)
culatca, geologic 1.$ ug/g (coal) (coal)
Materials
Emission spectroscopy A wide variety of 0.5 ng 1« (0.2 Mg/ai1)
(«r»-> envlronnental 61 to I2Z (SO ng/
samples liter)"
rn In si on apectroacopy - A wide variety of 0.000 I, 0.001 + 5r
Inductively coupUd biological and wg/nl
plasma source envtronaiental
sanplea
Ni
Ul
Relntlve error IUJJuUil" Selectivity
IX to 4X (12(1 ug/ The particle nice Total chronfiM la
CM') (air pnrttr- ' of the aanple daterailned.
ulates) and the sample
natrlK atay tn-
floetire the
nhaerved Meaaure-
awnta.
IflX to IAZ (SO Total chroHltra ta
UK/liter) det«rsilned.
No ioterferlng Total chroatlusi Is
aubatancea ara determined.
. reported.
References 5,10,14-30.
-------
Recently, spectrophotometrie methods have been largely replaced by
methods that are more sensitive and/or convenient including atomic
absorption spectrometry, neutron activation analysis, emission spectroscopy,
and x-ray fluorescence.
Atomic Absorption Spectrometry (Flame)—
The most prevalently used of the newer procedures is atomic absorption
spectrometry. In this method, a previously prepared (extracted) chromium
sample is injected into an air-acetylene flame through which light of
357.9 nm wavelength is passed. The flame atomizes the sample and light from
the lamp is selectively absorbed by chromium atoms in proportion to their
concentration in the vapor. A photodetector measures the intensity of the
357.9 nm radiation after its passage through the flame and compares it with
the intensity of the original line spectrum emitted, by the lamp. The
results are converted and calibrated to be read out directly as
concentration values. The air-acetylene flame can be replaced with a
nitrous oxide-acetylene flame to provide greater sensitivity and freedom
from chemical interference.
The absorption of chromium in this procedure has been found to be
31
suppressed by the presence of iron and nickel. If the analysis is
performed in a lean flame, this interference can be lessened, but
sensitivity will also be reduced. The interference caused by iron and
32
nickel does not occur in the nitrous oxide-acetylene flame.
Atomic Absorption Spectrometry (Flameless)—
Flame less atomic absorption spectrometry is a relatively new variation
of the previously described method in which the sample is atomized directly
in a graphite furnace, carbon rod, or tantalum filament instead of a flame.
This innovation frequently results in a tenfold to thousandfold increase in
sensitivity and can eliminate the need for sample preparation in certain
cases.
216
-------
The analysis of chromium by the flame less atomic absoption technique is
influenced by a number of factors. Henn (1974) observed a variation in
absolute sensitivity as a function of sample volume and ascribed the effect
33
to the manner in which the sample was distributed in the graphite furnace.
Schaller ^C al. (1973) found that the specificity of the method was
14
influenced by smoke and nonspecific absorption during atomization.
This
difficulty was satisfactorily resolved by modifying the charring procedure
to destroy the smoke-causing components.
Neutron Activation Analysis —
Neutron activation analysis is probably second only to atomic absoption
spectrometry in frequency of use for analysis of chromium samples. Its
popularity stems from three factors: its great sensitivity, its wide
applicability to a variety of sample types with minimal sample preparation,
and its ability to determine a variety of elements from a single sample.
Neutron activation analysis is one of the most sensitive modern
analytical techniques for the determination of trace elements such as
chromium. Samples and known standards are irradiated in a nuclear reactor
during which time neutrons are captured by various nuclides in the sample.
By comparison with the activity induced in the standards, the amount of
sample isotope can be calculated. The induced activity, and hence the
sensitivity for determining the parent nuclide, is proportional to the
12 14
amount of the parent isotope present. Neutron fluxes of 10 to 10
-2 -1
neutrons cm sec are easily available in modern reactors; thus, for
irradiations of reasonable length (a few seconds to a few days) most
elements can be determined at" levels of 10~ to 10~ grams.
The commonly used reaction for chromium activation analysis 'is
Cr(n,y) Cr. Chromium-50 has a thermal neutron absoption cross section of
35
51,
17.0 barns and a natural abundance of 4.31 percent."" The resulting "*Cr
decays with a half-life of 27.8 days and is usually determined by measuring
the intensity of the 320-keV gamma ray.
217
-------
The minimum chromium concentrations which can be detected varies with
sample type and processing conditions. Greater sensitivities generally can
be achieved for given irradiation conditions if the sample is chemically
processed to separate and concentrate the chromium fractions. MeClendon
reported -sensitivities at the parts per billion level for chromium extracted
O£
from previously irradiated biological and environmental samples. The
precision and accuracy of neutron activation analyses of chromium also vary
with sample type and processing conditions but may be generally
characterized as good to excellent. Relative standard deviations of ±10
percent have been commonly reported for samples containing chromium in the
17 19
microgram per gram and nanogram per gram ranges. *
The use of neutron activation for chromium analyses does have one
24
disadvantage. Due to intense x-ray or bremsstrahlung activity from Na,
38 42 56 32
Cl, K, Mn, and F in many samples, the irradiated sample usually must
be cooled several weeks before measuring the chromium concentration. The
procedure is thus not amenable to rapid or on-line applications. The
lengthy cooling period can be reduced to about 24 hours by chemically
36
separating the offending nuelides from the irradiated chromium.
Emission Spectroscopy—
In this analytical procedure the prepared chromium sample is excited
with a flame, arc, spark or plasma and the resulting light is dispersed with
a monochromator. The characteristic emission lines of each excited element
are recorded electronically or on a photographic plate. The concentration
of each element is determined by comparing the density of its emission line
with that of an internal or external standard. The preparation of* each
sample depends in part on the mode of excitation used. Generally, samples
are dissolved and the solution is deposited on metal or graphite electrodes
which are dried prior to analysis. The precision and accuracy achievable
with emission Spectroscopy varies with sample type and actual chromium
concentration. Sealy and Skogerboe have monitored air containing 0.2
27
mg/liter chromium with a precision of ±19 percent. Emission Spectroscopy
218
-------
using an inductively coupled plasma as a light source has been shown to be a
very sensitive analytical method. Sensitivities down to 0.3 ppb have been
37
reported using direct aspiration of sample solutions.
X-Ray Fluorescence—
With x-ray fluorescence the sample is first irradiated with low-energy
x-ray or gamma photons which displace K or L orbital electrons from elements
of interest such as chromium. A series of characteristic x-ray lines are
then emitted as the electron defects are filled by electrons from higher
orbitals. The intensity of the fluorescence is related to the
concentration of the metal in the sample by comparison with radiation from
an internal standard.
Sample preparation is important in x-ray fluorescence analysis because
particle size and shape affect the extent to which the irradiating beam is
scattered or absorbed. Also, quantitative measurements of trace elements
like chromium can be complicated by radiation from surrounding atoms. To
minimize these matrix effects, solid samples, such as air participates, can
be pressed into thin wafers.
As with several other analytical techniques, the precision and accuracy
of x-ray fluorescence varies with sample type and pollutant concentration
3
level. In an analysis of samples of air particulates containing 120 mg/cm
chromium, a relative error of 1 to 4 percent was obtained with x-ray
-. 26
fluorescence.
The energy-dispersive x-ray fluorescence analytical technique is not
yet in widespread use for chromium measurements. However, it appears to
have considerable potential for rapid, accurate analysis of air pollution
particulates (containing chromium and other trace metals) which have more or
less homogeneous surfaces.
219
-------
Other—
The concentration of chromic acid mists in air can be estimated by a
38-40
direct field method described by Ege and Silverman. The Ege-Silverman
technique is a spot-test method using phthalic anhydride and
sym-diphenylcarbazide. The concentration of chromic acid mists in the
atmosphere can also be quickly estimated using a lightweight sampler
41 42
developed by the Mine Safety Appliances Co. ' The operating principle of
this device is based on the phthalic anhydride/sym-diphenylcarbazide method
developed by Ege and Silverman.
220
-------
REFERENCES FOR SECTION 5
1. Towill, L,E., J££,2i" Reviews of the Environmental Effects of
Pollutants: III. Chromium. ORNL/EIS-8Q and EPA-600/1-78-023.
May 1978. pp. 28-55.
2. Sullivan, R.J. Preliminary Air Pollution Survey of Chromium and Its
Compounds. EPA/APTD 69-34. October 1969. pp. 33-45.
3. Code of Federal Regulations. Title 40, Part 60. Appendix A.
pp. 387-404 and 498-515. Office of the Federal Register, Washington,
D.C. 1982.
4. Thompson, R.J., et _al_. Analysis of Selected Elements in Atmospheric
Particulate Matter by Atomic Absorption, Preprint. Presented at the
Instrument Society of American Symposium. New Orleans, Louisiana.
May 5-7, 1969.
5. Bhagat, S.K.» et_ a^* Trace Element Analysis of Environmental Samples
by Neutron. Activation Method. Journal of the Water Pollution Control
Federation. 43(12): 2414-2413. 1971.
6. Snyder, A.P. Environmental Monitoring Near Industrial Sites: Chromium.
EPA-560/6-77-016. June 1977. pp. 31-33.
7. Begnoche, B.C. and T.H. Risby. Determination of Metals in Atmospheric
Particulates Using Low-Volume Sampling and Flameless Atomic Absorption
Spectrometry. Analytical Chemistry. 47:1041-1045. 1976,
8. West, P.W. Chemical Analysis of Inorganic Pollutants. Chapter 19 in
Air Pollution, Volume II, 2nd Edition. A.C. Stern, Ed. Academic Press,
New York.. 1968.
9. Criteria for a Recommended Standard - Occupational Exposure to Chromic
Acid. National Institute for Occupational Safety and Health,
Washington, D.C. 1973.
10. Goulden, P.P., et_ al. Automated Solvent Extraction for the
Determination of Trace Metals in Water by AAS. Am. Lab. August: 10-17.
1973.
11. Brown, E., et, al. Methods for Collection and Analysis of Water Samples
for Dissolved Minerals and Gases. Techniques of Water-Resources
Investigations of the United States Geological Survey. U.S. Government
Printing Office. Washington, D.C. 160 pp. 1970,
12. Reference 6, pp, 37-56.
221
-------
13, Midgett, M.R. and M. J. Fishman. Determination of Total Chromium in
Fresh Waters by Atomic Absorption. Atomic Absorption Newsletter.
£: 128-131. 1967.
14. Schaller, K. H., ££. £1 - The Quantitative Determination of Chromium in
Urine by Flameless Atomic Absorption Spectroscopy. Atomic Absorption
Newsletter. 12(6): 147-150. 1973.
15. Morrow, R.W. and R.J. McElhaney. Determination of Chromium in
Industrial Effluent Water by Flameless Atomic Absorption Spectroscopy.
Atomic Absorption Newsletter. 13(2): 45-46. 1974.
16. Gilbert, T.R. and A.M. Clay. Determination of Chromium in Sea Water by
Atomic Absorption Spectrometry. Anal. Chim, Acta (Netherlands).
67: 289-295. 1973.
17. Shah, K.R., ££ al. Determination of Trace Elements in Petroleum by
Neutron Activation Analysis. Journal of Radioanalytical Chemistry
(Switzerland-Hungary). 6: 413-422. 1970.
18. Spyrou, N.M., et^ al. Realistic Detection Limits for Neutron Activation
- Analysis of Biological Samples. Proceedings of a Symposium on Nuclear
Techniques in Comparative Studies of Food and Environmental •
Contamination. Otaniemi, Finland. International Atomic Energy Agency.
Vienna, Austria, pp. 471-487. 1974.
19. Harrison, P.R., e£ a^. Areawide Trace Metal Concentrations Measured by
Multielement Neutron Activation Analysis. Journal of the Air Pollution
Control Association. 21: 563-570. 1971.
20. Dams, R., et al^. Nondestructive Neutron Activation Analysis of Air
Pollution Particulates. Analytical Chemistry. 42(8): 861-867. 1970.
21. De Goeij, J.J. M., e_£ al. Neutron Activation Analysis Trace Element
Studies of Dover Sole Liver and Marine Sediments. Proceedings of a
Symposium on Nuclear Techniques in Comparative Studies of Food and
Environmental Contamination. Otaniemi, Finland. International Atomic
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO. 2.
. EPA-450/4-84-007g
4. TITLE AND SUBTITLE
Locating And Estimating Air Emissions From
Sources Of Chromium
7. AUTHOR1S)
Radian Corporation
Durham, NC 27705
9. PERFORMING ORGANIZATION NAME AND ADDRESS
12. SPONSORING AGENCY NAME AND ADDRESS
Office Of Air Quality Planning And Standards
U. S. Environmental Protection Agency
MD 14
Research Triangle, NC 27711
3. RECIPIENT'S ACCESSION NO.
5. REPORT DATE
July 1984
6. PERFORMING ORGANIZATION CODE
8. PERFORMING ORGANIZATION REPORT NO.
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
13. TYPE OF REPORT AND PERIOD COVERED
14. SPONSORING AGENCY CODE
1S. SUPPLEMENTARY NOTES
EPA Project Officer: Thomas F. Lahre
16. ABSTRACT
To assist groups interested in inventorying air emissions of various
potentially toxic'substances, EPA is preparing a series of documents such
as this to compile available information on sources and emissions of these
substances. This document deals specifically with chromium. Its intended
audience includes Federal, State and local air pollution personnel and
others interested in locating potential emitters of chromium and in making
gross estimates of air emissions therefrom.
This document presents information on 1) the types of sources that may
emit chromium, 2) process variations and release points that may be expected
within these sources, and 3) available emissions information indicating the
potential for chromium release into the air from each operation.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTlFIERS/OPEN ENDED TERMS C. COS AT! Field/Group
Chromium
Air Emission Sources
Locating Air Emission Sources
Toxic Substances
18. DISTRIBUTION STATEMENT
19. SECURITY CLASS (This Report)
21. NO. OF PAGES
234
20. SECURITY CLASS (Thispage)
22. PRICE
EPA Form 2220-1 (R«v. 4-77) PREVIOUS EDITION is OBSOLETE
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