EPA
0. S. Environmental Protection Agency
Region VIII
Denver, Colorado 80295
EPA 908/4-78-008
DECEMBER 1978
FIMAL REPORT
TRACE ELEMENTS OF FLY ASH:
Emissions from Coal Fired Steam Plants
Equipped with Hotside and Coldside
Electrostatic Precipitators for
Particulate Control
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This report has been reviewed by this Region VIII Office of Energy Ac-
tivities, Q. S. Environmental Protection Agency and approved for
publication, mention of trade names or commercial products does not
constitute endorsement or recommendation for use.
This document is available to the public through the National Technical
Information Service, Springfield, Virginia 22161
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EPA 908/4-78-008
DCN 78-216-137-09
FINAL REPORT
TRACE ELEMENTS OF FLY ASH:
EMISSIONS FROM COAL-FIRED STEAM PLANTS
EQUIPPED WITH HOT-SIDE AND COLD-SIDE
ELECTROSTATIC PRECIPITATORS FOR
PARTICULATE CONTROL
By
R. M. Mann, R. A. Magee, R. V. Collins
M. R. Fuchs, F. G. Mesich
Radian Corporation
8500 Shoal Creek Blvd.
Austin, Texas 78766
EPA Contract No. 68-01-3702
Project Officer
Terry L. Thoem
U.S. EPA, Region VIII
Denver, Colorado 80295
U.S. Environmental Protection Agency
Region V, Library
December 1978 23° South Dearborn Street
Chicago, Illinois 60604
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ABSTRACT
This study was sponsored by U. S. Environmental Pro-
tection Agency, Region VIII. It describes results obtained by
sampling two coal-fired steam plants equipped with electrostatic
precipitators (hot-side and cold-side) for particulate control.
The field sampling conducted during September 1976 included the
following streams:
coal,
fly ash.
The objective of the program was to define both emission and
enrichment of trace elements in the flue gas particulates. Par-
ticulate loading of the flue gas was determined daily; particle
size distribution was determined by Andersen cascade impactor
with glass fiber filter substrates. Fly ash was collected using
both cyclones and cascade impactors for trace element analysis
of individual size fractions.
Samples of the feed coal at each station were subjected
to density (sink-float) separation to determine elemental associ-
ation with the mineral (ash) phase and organic (ash-free) phase.
The 15 elements included in both coal and ash studies are
Arsenic Copper Nickel
Beryllium Fluorine Selenium
Cadmium Lead Titanium
Calcium Manganese Uranium
Chromium Mercury • Zinc
ii
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TABLE OF CONTENTS
Page
TABLE OF CONTENTS iii
LIST OF TABLES vii
LIST OF FIGURES ix
ACKNOWLEDGEMENT xii
1.0 INTRODUCTION 1
2.0 CONCLUSIONS „ 10
2.1 Enrichment of Trace Elements in Fly Ash ... 10
2.2 Trace Element Emissions 11
2.3 Estimated Volatile Emissions 11
2.4 Correlation of Enrichment with Particle
Size 12
2.5 Phase Association of Trace Elements
in the Coal 12
2.6 General Conclusions 13
2.6.1 Particulate Loading at the
Point of Condensation 13
2.6.2 Degree of Element Volatility 15
2.7 Recommen tat ions for Future Studies 16
3.0 FIELD SAMPLING IS
3.1 Site Description 18
3.1.1 Hot-Side ESP Station (HS) 18
3.1.2 Cold-Side ESP Station (CS) 19
3.2 Sampling Procedures 22
3.2.1 Sampling Points 22
3.3 Fly Ash Collection for Analysis 25
3.3.1 HVSASS Cyclones 28
3.3.2 Low-Volume Cyclones 28
iii
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TABLE OF CONTENTS (CONT'D)
Page
3.3.3 Cascade Impactor 30
3.3.4 WEP Collector 30
4.0 SAMPLE ANALYSIS 32
4.1 Sink-Float Separation of Coal 33
4.2 Analytical Techniques 33
»
5.0 RESULTS OF COAL CHARACTERIZATION STUDIES 39
5.1 Chemical Analysis of Raw Coals 39
5.2 Sink-Float Separation Study of Coal 39
6.0 RESULTS OF ELEMENT ENRICHMENT STUDY ....... 55
6.1 Physical Characterization of Cyclone
Collected Ash 55
6.2 Element Concentration and Enrichment Ratios
of Cyclone Collected Fly Ash 64
6.3 Concentration and Enrichment Ratios of
Andersen Cascade Impactor Samples 69
6.4 Enrichment Model 73
6.5 Discussion of Results of Enrichment
Study 85
6.5.1 Effect of Sampling Method 85
6.5.2 Comparison of Results for the
Two Stations 89
6.5.3 Comparison of Element Behavior
Between the Two Stations 90
7.0 TRACE ELEMENT EMISSIONS 99
7.1 Total Trace Element Emissions 99
7.2 Volatile Trace Element Emissions 101
8.0 CONTROL EFFECTIVENESS AT EACH STATION 102
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TABLE OF CONTENTS (CONT'D)
BIBLIOGRAPHY 103
APPENDIX A - SAMPLING 106
1.0 INTRODUCTION .107
2.0 PLANT DESCRIPTION - STATION HS 108
2.1 Plant Operation During Sampling 108
2.2 Description of Sampling Points 110
2.2.1 Coal 110
2.2.2 Fly Ash 110
2.3 Flow Rate Measurements 114
2.3.1 Coal 114
2.3.2 Fly Ash Flow Rate 114
3.0 PLANT DESCRIPTION - STATION CS 115
3.1 Plant Operation During Sampling 115
3.2 Description of Sampling Points 117
3.2.1 Coal 117
3.2.2 Fly Ash 117
3.3 Flow Rate Measurements 121
3.3.1 Coal 121
3.3.2 Fly Ash Flow Rate 121
4.0 PARTICULATE COLLECTION BY SIZE FRACTIONS ..... 122
4.1 Andersen Cascade Impactors 124
4.2 One-acfm Cyclones 124
4.3 HVSASS Cyclones 129
v
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TABLE OF CONTENTS (CONT'D)
Page
APPENDIX B - ANALYTICAL PROCEDURES .......... 132
1.0 INTRODUCTION ....... 133
2.0 INSTRUMENTATION 134
3.0 SAMPLE PREPARATION ..... 135
3.1 Coal 135
3.2 Ash 136
3.3 WEP 136
4.0 ANALYTICAL PROCEDURES ...... 137
5.0 ANALYSIS OF STANDARD REFERENCE MATERIAL ..... 145
BIBLIOGRAPHY . ...... 147
VI
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LIST OF TABLES
Number 7age
1-1 Summarized Element Affinity Studies 8
3-1 Flow Rates for Streams at Station HS 21
3-2 Flow Rates for Streams at Station CS 24
5-1 Coal Analysis • 40
5-2 Analysis of Coal Sink-Float Fractions ...'.. 41
5-3 Trace Element Content of Theoretical 44
0% and 100% Ash Fractions
5-4 Comparison of Organic Association
of Western Coals 46
5-5 Ranking of Elements in Coal According
to Organic-Inorganic Affinities 47
6-1 Physical Characteristics of Cyclone
Particulates 56
6-2 Analytical Results of Cyclone Collected
Fly Ash Fractions 65
6-3 Enrichment Ratio for Cyclone Collected
Fly Ash Fractions 68
6-4 Analytical Results of Andersen Collected
Fly Ash Fractions 71
6-5 Elemental Enrichment Ratios of Andersen
Collected Fly Ash Fractions 72
6-6 7o Volatile Trace Elements in Wet Electro-
static Precipitator Collector 86
6-7 Comparison of Enrichment Results of Cyclone
and Cascade Impactor Samplers 88
6-8 Composite of Coal and Fly Ash Trends
for Elements 91
7-1 Stack Emission of Elements from
Cyclone Collection 100
7-2 Estimated Volatile Trace Element
Emissions from Impactor Collection 101
8-1 Control Efficiency of Trace Elements 102
VI1
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VI11
LIST OF TABLES (CONT'D)
Number
A-l Sampling Schedule at Station HS .
A-2 Grain Loading Data for Station HS
A-3 Sampling Schedule at Station CS
A-4 Particulate Loadings at Station CS
A-5 Summary of Data for Particulate Collection
by Andersen Cascade Impactor at Station HS . . 126
A-6 Summary of Data for Particulate Collection
by Andersen Cascade Impactor at Station CS . . 127
A-7 Summary of Data for Particulate Collection
With One ACFM Cyclones at Station HS 128
A-8 Summary of Data for Particulate Collection
With One ACFM Cyclones at Station CS 128
A-9 Summary of Data for Particulate Collection
With the HVSASS Cyclones at Station HS .... 131
A-10 Summary of Data for Particulate Collection
With the HVSASS Cyclones at Station CS .... 131
B-l Detection Limits for Trace Element
Analysis ..... 141
B-2 Analysis of NBS Standard Reference
Materials 146
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LIST OF FIGURES
Number
1-1 Retention of Particulate Matter in Lung in
Relation to Particle Size 4
3-1 Schematic of Station HS with Hot-Side
Electrostatic Precipitator 20
3-2 Schematic of Station CS with Cold-Side
Electrostatic Precipitator 23
3-3 Particle Size Distribution of Station HS
Fly Ash as Determined by Andersen Cascade
Impactor 26
3-4 Particle Size Distribution of Station CS
Fly Ash as Determined by Andersen Cascade
Impactor 27
3-5 Schematic of Sampling Train for Particulate
Sizing with HVSASS Cyclones 29
4-1 Sink-Float Separation of Coal 34
4-2 Analytical Flow Chart for Coal 36
4-3 Analytical Flow Chart for Ash 37
4-4 Analytical Flow Chart for WEP Liquor 38
5-1 Copper Concentration vs Ash Content
for Coal Fractions 43
5-2 Arsenic Concentration vs Ash Content 50
5-3 Beryllium Concentration vs Ash Content .... 50
5-4 Calcium Concentration vs Ash Content 50
5-5 Cadmium Concentration vs Ash Content 51
5-6 Chromium Concentration vs Ash Content 51
5-7 Copper Concentration vs Ash Content 51
5-8 Fluorine Concentration vs Ash Content 52
5-9 Mercury Concentration vs Ash Content 52
5-10 Manganese Concentration vs Ash Content .... 52
5-11 Nickel Concentration vs Ash Content 53
5-12 Lead Concentration vs Ash Content 53
5-13 Selenium Concentration vs Ash Content 53
ix
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LIST OF FIGURES (CONT'D)
Number
5-14 Titanium Concentration vs Ash Content ..... 54
5-15 Uranium Concentration vs Ash Content ..... 54
5-16 Zinc Concentration vs Ash Content 54
6-1 Cyclone #1 - Fly Ash Collected at
Station HS 58
6-2 Cyclone #2 - Fly Ash Collected at
Station HS . . 59
6-3 Cyclone #3 - Fly Ash Collected at
Station HS 60
6-4 Cyclone #1 - Fly Ash Collected at
Station CS 61
6-5 Cyclone #2 - Fly Ash Collected at
Station CS 62
6-6 Cyclone #3 - Fly Ash Collected at
Station CS 63
6-7 Arsenic Enrichment versus Diameter ..... 76
6-8 Cadmium Enrichment versus Diameter ..... 77
6-9 Chromium Enrichment versus Diameter ..... 78
6-10 Copper Enrichment versus Diameter 79
6-11 Lead Enrichment versus Diameter 80
6-12 Manganese Enrichment versus Diameter .... 81
6-13 Nickel Enrichment versus Diameter ...... 82
6-14 Selenium Enrichment versus Diameter .... 83
6-15 Zinc Enrichment versus Diameter ....... 84
6-16 Average Enrichment of Fly Ash (Station
HS vs Station CS) 87
A-l Schematic of Station HS . 109
A-2 Schematic of Station CS 116
A-3 Wet Electrostatic Precipitator (WEP) 123
A-4 Andersen Mark III Cascade Impactor 125
A-5 Schematic of Sampling Train for
Particulate Sizing with HVSASS Cyclones .... 130
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LIST OF FIGURES (CONT'D)
Number
B-l Analytical Flow Chart for Coal Samples 138
B-2 Analytical Flow Chart for Ash Samples 139
B-3 Analytical Flow Chart for WEP Solution ..... 140
xi
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ACKNOWLEDGMENT
This work was conducted under the direction of Mr.
Terry L. Thoem, Project Officer, Environmental Protection Agency
VIII, Denver, Colorado. The Radian program-staff included
Dr. F. G. Mesich as Program Manager and Mr. R. Magee as technical
Project Director. Principal contributors were R. V. Collins,
M. R. Fuchs, R. M. Mann and Dr. F. B. Meserole.
Acknowledgement is given to the station personnel
from each utility company whose full cooperation greatly
facilitated the field work. Mr. G. M. Crawford, Mr. D. L.
Heinrich and Mr. L. A. Rohlack contributed significantly to the
program during sampling and analysis. The assistance of Mrs. N.
P. Meserole in structuring and proofing the final report document
cannot go unmentioned.
XI1
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1.0 INTRODUCTION
Radian was contracted by EPA to perform a field sampling
and analysis program to investigate several aspects of trace
element emissions from coal-fired boilers. Specific objectives
were to:
• quantify trace element enrichment
in fly ash compared to raw coal,
* determine trace element enrichment
as a function of particle size,
• investigate affinity of elements
for inorganic or organic fractions
of coal, and
9 investigate particulate collection
efficiency and trace element enrich-
ment of emitted fly ash of hot side
and cold side electrostatic precipitation
control devices.
During September 1976, raw coal and flue gas streams
were sampled at two western power plants firing low-sulfur sub-
bituminous coals. One station was equipped with cold-side
electrostatic precipitators (ESP) and the other station used
hot-side ESP's for particulate control. Grain loading and par-
ticle size distribution of the fly ash was determined by sampling
the stack at each plant. Fly ash was collected in three size
fractions using three high volume cyclones in series and also
in eight fractions using an Anderson Mark II cascade impactor
as primary collectors. A wet electrostatic precipitator (WEP)
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was used downstream of both primary collectors to collect species
escaping the primary collector. The cyclone and Anderson sized
particulate samples and the WEP samples were analyzed for up to
15 trace elements.
Enrichment ratios were calculated for each element;
in this study the enrichment ratio was defined as the ratio of
the concentration of a given element in the ash fraction to its
expected concentration in the coal ash based on analysis of the
coal. Physical measurements of selected ash fractions were also
performed using scanning electron microscopy and specific sur-
face area techniques. The results of the physical and chemical
measurements were examined for possible correlations with the
particulate size data and control device.
In addition, the relative distribution of trace elements
in the inorganic and organic phases of coal were measured by
density separations of finely divided coal and analysis of the
fractions. The analytical results for each element were corre-
lated using a least squares technique.
Background
Trace element emissions from coal-fired boilers occur
both as fine particulates and volatile matter. Increased interest
in fine particulates emitted from coal-fired power plants has re-
sulted from the following findings:
• certain potentially toxic trace elements
are preferentially concentrated in
the fines,
• fine particulates are not as efficiently
retained by conventional control devices
as larger sized particulates,
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• fine particulates are primarily responsible
for visibility degradation since they are in
the effective light scattering region,
• slow settling rates for fine par-
ticulates result in long transport
distances, and
• fine particulates exhibit a high
degree of retention in the human
respiratory system.
Current EPA emission standards for particulates are
based on total mass; however, there is mounting evidence that
both size distribution and chemical composition are important
factors in human health effects. Of most concern are the
particles in the 0.5-2 micron size range, since the retention
in the respiratory organs shows a maximum in this area as shown
in Figure 1-1 (GO-075). EPRI is currently sponsoring a study
of the effects of fly ash particulates on a particular type of
lung cell called macrophages; these cells function as an
important defense mechanism in the human lung by ingesting
foreign materials which enter the lung (RE-295). Other related
health effects investigations are aimed at identifying toxic or
synergistic effects of trace particulate components such as
vanadium and cadmium on respiratory functions.
Several types of investigations of the trace element
enrichment phenomenon have recently been carried out to define
the mechanisms involved and the degree of concentration taking
place. A data base is being established in three areas:
• distribution of trace elements
throughout ash and flue gas fractions,
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Retention
(Percent)
80
70..
.25 .75 i.o 2.0 3.0 4.0
Particle Size (Microns)
5.0
Figure 1-1. Retention of Particulate Matter in Lung
in Relation to Particle Size
Source: GO-075
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• mode of occurrence of trace con-
taminants in fuel, and
• collection efficiency of existing
particulate control devices for
each element.
The results from these studies will be used to develop a predic-
tive capability for determining trace element emissions and
control requirements for individual plants based on coal analysis
and boiler and flue gas cleaning system characteristics.
In-depth field studies and trace elements distributions
in 10 different coal-fired power plant systems have been reported
by Radian and otKer investigators (KA-192, BO-124, BR-452,
CO-342, KL-095, RA-219, LE-289, DA-105, GO-253, and FI-167).
Comparison of fly ash analyses with trace element profiles in
the corresponding coals shows that some elements are enriched
by the coal combustion process. Enrichment is most evident in
the smallest fly ash particles. In most studies those elements
which were reported to undergo enrichment in the smaller particles
of emitted flue gas include:
Antimony Gallium
Arsenic Iodine
Bromine Lead
Copper Mercury
Cadmium Molybdenum
Chromium Selenium
Chlorine Sulfur
Fluorine Zinc
Of these 16 elements, mercury, selenium, zinc, bromine, fluorine,
sulfur, and chlorine are generally thought to be emitted from the
stack either totally or partially as vapors.
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Those which were reported approximately equally distributed
in all ash fractions include:
Aluminum Silicon
Barium Rubidium
Calcium Strontium
Iron Tin
Magnesium
There are differences of opinion with regard to some elements.
In some studies enrichment tendencies were found, while in other
studies no significant enrichment as a function of particle size
was reported. This type of disagreement was evident for the
following:
Beryllium Titanium
Cobalt Vanadium
Manganese
Further evidence of surface concentration of some
elements was reported by Linton (TO-087). Using a techni-
que described as "molecular sandblasting," surface concen-
trations of lead and thallium on coal fly ash particulates were
found to be 40,000 and 4,500 ppm, respectively. These surface
values are indicative of a surface concentration mechanism when
compared to measurements of 620 and 30 ppm lead and thallium in
coal fly ash.
The phenomenon of the observed element enrichment can
be explained by the volatilization of these elements or their
compounds in the fire box of the boiler. This volatilization
provides the mechanism for the selective partitioning of elements
during the fractionation of the ash between fly ash and bottom ash.
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The volatilized elements or their compounds subsequently remain
gaseous, condense partially or condense completely.
In the first case, a high percentage of an element
incoming with the coal will be discharged through the stack
unless flue gas control devices are designed for their collection.
Partial or complete condensation will lead to an increase in the
concentration in the fine particulate fraction of the fly ash.
Condensation can occur by nucleation or deposition on available
surfaces. At the relatively low residence times (5-10 seconds)
between volatilization and condensation, any nucleation that
occurs should result in small particles. Deposition on the fly
ash particles will be surface area dependent. This also will
result in increased concentrations in the small particulates
since the specific surface area is greater for the smaller ash
particles.
The form in which a trace element naturally occurs in
the coal may be one determinant of its distribution throughout
the combustion system. Some workers have speculated that certain
metallic elements preferentially associated with the organic
phase of coal are released during combustion as very fine par-
ticles of metal oxides. Several studies to identify tendencies
of elements to associate with either the mineral (inorganic) or
organic phase of coal have been reported (GL-077, R.U-039, ME-150,
ZU-019, HO-417, NI-095 and GO-252). The general findings as
summarized in Table 1-1 indicate good agreement among the studies
for several elements. Many elements, however, have been found
to be associated with the organic phase in one coal and the in-
organic phase in another coal. Sometimes no clear cut or pre-
ferential phase association is observed. The phase association
can vary within a coal seam. Variations can depend on mineral
and sulfur content which are directly effected by coal type and
format ion c ir cums tanc e s.
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TABLE 1-1.
P redominant ly
Organic Affinity
Br
B
Be
Ga
Ge
Ti
Sb
SUMMARIZED ELEMENT AFFINITY
Organic & Inorganic
Associations
Ca
Cr
Cu
Co
Cs
Mo
Ni
V
Y
Se
U
STUDIES
Predominantly
Inorganic Affinity
As
Ba
Cd
Fe
Hg
La
Mn
P
Pb
Sn
Sr
Zn
F - Not reported in literature.
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Element enrichment through the volatilization
mechanism may have a pronounced impact on the selection of par-
ticulate removal devices. The particulate collector most widely
used in the utility industry is the cold-side electrostatic
precipitator operating near 250°F. This collector has been
operated near 700°F as a hot-side precipitator (HS ESP) in some
existing stations and is being considered for new generating
stations burning Western low-sulfur coal. The hot-side pre-
cipitator has been found to be a more efficient particulate removal
device due to the lower resistivity of this type of coal ash at
higher temperatures. The use of the hot-side precipitator has been
theorized to be of questionable environmental assistance. If higher
volatile trace element emissions due to incomplete recondensation
at higher operating temperatures of the precipitator are observed,
the increased particulate removal capabilities might be offset.
This study was designed to compare the emitted ash from two
electrostatic precipitators operating at different temperatures.
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2.0 CONCLUSIONS
The occurrence and distribution of trace elements in
fine particulate emissions of two coal-fired generating stations,
one equipped with hot-side and one with cold-side electrostatic
precipitators, has been investigated in this study. Also the
association of trace elements with the organic (ash-free) phase
has been determined for the feed coal at each station. The
findings of this study are summarized in this section.
2.1 Enrichment of Trace Elements in Fly Ash
Higher average enrichment of the cold-side station fly
ash was found for ten of the thirteen elements analyzed in ash
samples size fractionated by cyclone collection. Two elements
exhibited higher enrichment in the fly ash at the hot-side
station.
HIGHEST ENRICHMENT
Hot-Side Station Cold-Side Station
Arsenic Beryllium Manganese
Selenium Cadmium Nickel
Chromium Uranium
Copper Zinc
Fluorine
Mercury
No enrichment was observed for the following elements:
Hot-Side Station Cold-Side Station
Beryllium Manganese Titanium
Cadmium Titanium
Chromium Uranium
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2.2 Trace Element Emissions.
Higher trace element mass emissions were found at the
hot-side ESP station for nine of the thirteen elements for cyclone
collected ash. The higher emissions are at least partly the
result of precipitator efficiency resulting in a higher partic-
ulate loading of the flue gas at the Station HS during the
sampling period and are not necessarily the result of precip-
itator location.
GREATER MASS EMISSIONS
Hot-Side Station Cold-Side Station
Aresenic Nickel Copper
Beryllium Selenium Fluorine
Cadmium Titanium Mercury
Chromium Uranium Zinc
Manganese
2.3 Estimated Volatile Emissions
Seven of the eight elements included in the cascade
impactor collected ash fraction study were estimated to be more
volatile under the conditions at the hot-side station. Volatile
trace elements were determined indirectly. A separate sample
fraction was not collected for volatiles, however an estimation
was made of volatiles collected by a wet electrostatic precipi-
tator (WEP). A comparison of the increased enrichment observed
in the WEP (vapor and fine particulate) fraction with the en-
richment predicted for that fraction from the enrichment versus
particle size correlation provided an estimate of volatile
emissions. The possibility of homogeneous nucleation of fine
particulate matter could not be evaluated or discerned in the
s tudy.
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HIGHER ESTIMATED VOLATILE EMISSIONS
Hot-Side Station Cold-Side Station
Arsenic Nickel Cadmium
Copper Selenium
Chromium Zinc
Manganese
2.4 Correlation of Enrichment with Particle Size
A good correlation of enrichment of fly ash with de-
creasing particle size was observed at each plant for four common
elements:
Arsenic Nickel
Copper Zinc
Three additional elements exhibited this correlation
only at the cold-side station:
Cadmium Chromium Manganese
Selenium also exhibited a good correlation of enrichment with
particle size but only at the hot-side station.
2.5 Phase Association of Trace Elements in the Coal
Although similar in trace element content, the two
feed coals differed in the association of elements with the organic
phase.
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Elements predominantly associated with the organic
phase of both feed coals include:
Beryllium Manganese
Calcium Nickel
Chromium Uranium
Fluorine did not exhibit a phase preference in either
coal. Selenium and titanium were inorganically associated in
the hot-side coal and .exhibited weak to moderate organic assoc-
iation in the cold-side coal.
Arsenic, cadmium, lead, mercury, and zinc were completely
associated with the inorganic (mineral) phase of the hot-side coal,
while the association ranged from non-preferention to inorganic
cold-side coal.
2.6 General Conclusions
The enrichment mechanism of volatilization followed
by condensation which was presented in Section 1.0 would predict
that the results of a comparison of enrichment between a hot-
side and a cold-side ESP would be dependent on the following
factors:
• particulate loading at the point of
condensation, and
• degree of element volatilization.
2.6.1 Particulate Loading at the Point of Condensation
Particulate loading at the point of condensation
determines the available mass upon which condensation can occur.
13
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A higher particulate loading of the gas at that point can dilute
enrichment by increasing the mass and therefore spreading the
surface condensed contribution over an increased available
surface area.
Particulate loading at the point of condensation is
dependent on the location of that point between the boiler and
the stack. Specific areas have different criteria that directly
affect the loading:
• upstream of ESP
- boiler configuration
- ash content of coal
• downstream of ESP
- particulate loading of inlet gas to ESP
- ESP collection efficiency
For this study stations were chosen to minimize
the effect of conditions prior to the ESP. Two stations
with similar boiler configuration and feed coal were identified.
The coals although similar in type, exhibit different ash content
The increased ash content of the cold-side coal provided a
higher particulate loading for the flue gas prior to the ESP.
Particulate loading beyond'the ESP is a function of
both the collection efficiency of the ESP and the inlet flue
gas loading. Although designed for high removal efficiency
capabilities, the ESP requires periodic maintenance to con-
tinually perform. Neither unit was operating at maximum
efficiency during the sampling period.
The point of condensation is also temperature depen-
dent for each element. The chemical form or species of an
element when vaporized and any possible alteration upon cooling
14
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defines the temperature at which condensation will occur.
Assuming a volatile element condens.es during the
temperature drop at the air preheater (as temperature decreases
from 700°to 250°F), the fly ash exiting the hot-side ESP
would be expected to exhibit a higher enrichment. This con-
dition results from a lower particulate loading at the point
of condensation. .Both arsenic and selenium exhibited higher
enrichment in the hot-side fly ash.
2.6.2 Degree of Element Volatilization
The degree of element volatilization is a function
of:
• characteristics of the element, and
• association in the coal.
An element such as mercury with a low boiling point
is volatilized at fairly low temperatures. Other elements
such as iron or nickel are susceptible to forming volatile
metal carbonyls in gas streams rich in carbon monoxide. Arsenic,
cadmium, chromium, lead, nickel, selenium and zinc exhibit boiling
points either as the element or as a compound which would result
in partial volatilization in the boiler.
The association of these and other elements in the
coal also defines the degree of volatilization possible.
Recent results presented by Kuhn (KU-175) indicate the mobility
(volatility) of elements during coal pyrolysis is related to
the degree of their organic association. This condition was
observed in the present study. Higher enrichment for the
following elements in fly ash was associated with higher organic
15
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phase association in the coal at the cold-side station indic-
ating phase association may influence volatilization:
Beryllium Chromium Fluorine Uranium
Cadmium Copper Mercury Zinc
Although a relationship of enrichment with organic
phase association appears, a larger data base including coal
and size fractionated fly ash from additional stations is
required to substantiate a valid correlation.
2.7 Recommendations forFuture Studies
Further investigation is necessary to document the
criteria controlling enrichment mechanisms for each element.
Important criteria to be considered in an enrichment mechanism
study should include:
• use of a common coal when comparing two
plants or collection devices,
• operation of each collection device at maxi-
mum efficiency, or in a two station study
at approximately equal efficiencies and
equal flue gas particulate loading,
• collection of several fine particulate
fractions (in range of .4 to .1 ym) with
a system to allow their separation from
vapor phase,
• sampling of flue gas at several points
of differing particulate loading and tem-
perature between the boiler and the stack,
16
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investigation of new fly ash sampling
techniques to allow larger quantities of
fly ash to be obtained within shorter
sampling periods, and
evaluation of phase association of trace
elements in the feed coal at additional
plants to biaild a data base for comparison
with fly ash enrichment.
17
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3.0- FIELD SAMPLING
Field sampling of two coal-fired power plants was
conducted in September 1976 to define the occurrence and distri-
bution of trace elements as a function of particle size in the
fly ash emitted from the units. Descriptions of the two facilities
are provided in Section 3.1, while the techniques used to collect
the coal and fly ash samples are discussed in the next section.
Further details of this aspect of the program are provided in
Appendix A which includes a description of each plant, plant
operation during sampling, sample points, sampling schedule and
techniques utilized.
3.1 Site Description
The two facilities selected have tangentially-fired
boiler configurations and are both fueled with Wyoming sub-
bituminous coals. They differ in the placement of their electro-
static precipitators (ESP) relative to the combustion air preheaters,
Station HS has "hot-side" ESP's; that is, the precipitators
are upstream of the air preheater. Station CS has the ESP's
positioned downstream of the combustion air preheater; this
configuration is termed "cold-side" ESP's.
3.1.1 Hot-Side ESP Station (HS)
The hot-side ESP station consists of two 350 MW tan-
gentially fired boilers. The newer of the two units, Unit 2,
was sampled. Hot-side electrostatic precipitators upstream of
the combustion air preheaters, designed for 350 MW at an inlet
gas temperature of 830°F, are used for fly ash control. The
boiler is fired with sub-bituminous coal transported by rail
from Wyoming, where it is strip mined. The coal typically con-
tains 30% moisture, 5% ash and 0.5% sulfur and has a heating value
IS
-------
of 8400 Btu/lb. The coal is initially stored in open piles from
which it is .conveyed to five storage silos. Coal from the silos
is fed to the mills where it is pulverized prior to delivery to
the boiler through a pneumatic conveying system.
Pyrites from the mills, economizer ash and bottom ash
are sluiced alternately to an ash pond at approximately 4-hour
intervals. The ash collected in the electrostatic precipitators
is tranferred to an ash storage silo by a pneumatic conveyor
system and removed from the plant site by truck. Flue gas exits
the system through a 500-foot stack, approximately 25 feet in
diameter.
A schematic of the station with the process streams
indicated is presented in Figure 3-1. A listing of flow rates
of process streams is provided in Table 3-1.
3.1.2 Cold-Side ESP Station (CS)
Station CS consists of four 500 MW boilers. Unit 1 was
sampled in this program. The plant design has electrostatic
precipitators located downstream of the combustion air preheaters,
hence the term cold-side precipitator. Each boiler is fired with
sub-bituminous coal which is mined near the plant and shipped by
truck to the plant site. The coal has an average heat content
of 9700 Btu/lb and contains approximately 19% moisture, 10% ash
and 0.670 sulfur. The coal trucked into the plant is initially
stored in piles at the plant site. Storage silos are filled from
these p/iles by conveyor. The coal from the silos is then fed to
mills where it is pulverized and then pneumatically conveyed to
the boiler.
Approximately three times per shift pyrites from the
coal mills, economizer ash and bottom ash are simultaneously
19
-------
CROSSED COU
ro
o
Inlet
Sluice Water
T F-
ELECTROSTATIC
PRECIPJTATOR
500'
Figure 3-1. Schematic of Station HS with Hot-Side Electrostatic Precipitator
-------
TABLE 3-1. FLOW RATES FOR STREAMS AT STATION HS
Stream
Flow Rate
Error
Limit
Method of Flow
Determination
Coal (moisture 2.6 x 10s Ib/hr
free)
Flue Gas (60 F/
1 ATM
Fly Ash
(moisture
free)
5.4 x 107 SCFHD
5.2 x 102 Ib/hr
±10% Metered at coal feeders
±10% Measured by stack traverses
±10% Determined from cumulative
grain loadings
21
-------
sluiced to a dewatering system. Ash collected in the
electrostatic precipitator is pneumatically conveyed to a
storage silo from which the ash is taken from the plant site
by truck. Flue gas exits the plant through a 500-foot stack
which is approximately 24 feet in diameter.
A schematic of the station showing process streams
is presented in Figure 3-2. Flow rates of process streams at
Station GS are found in Table 3-2.
3.2 Sampling Procedures
The procedures used to sample Stations HS and CS are
presented briefly in this section. Details are given in depth
in Appendix A, "Sampling". Sampling was performed during the
following periods:
• Station HS - September 2-16, 1976 and
• Station CS - September 20-October 1, 1976.
3.2.1 Sampling Points
During the two sampling efforts daily samples of the
following materials were collected at the plant sites:
• coal grab samples were collected
sequentially at the coal feeders,
and
• fly ash samples were collected from
the flue gas in the 500-foot stacks.
22
-------
(jo
CI1USHEO GOAL
r1
Mitt.
r^J—0J
ECONOMIZER ASH
Inlet
Sluice Hater
JOITOM ASH
TRANSFER
TANK
J
TO' ASH
POND
500'
Figure 3-2. Schematic of Station CS with Cold-Side Electrostatic Precipitator
-------
TABLE 3-2. FLOW RATES FOR STREAMS AT STATION CS
Stream
Flow Rate
Error
Limit
Method of Flow
Determination
Coal (moisture
free)
Flue gas
(60°F/1 ATM)
Fly ash
(moisture
free)
4.3 x 10s Ib/hr ±10%
6.4 x 107 SCFHD ±10%
1.28 x 102 Ib/hr ±10%
Metered at coal feeder
Measured by stack traverses
Determined from cumulative
grain loadings
24
-------
Velo-city measurements were taken daily at each plant to determine
the isokinetic sampling rate and the total gas flow through the
stack. The average particulate loading of the flue gas was
determined with in-stack Gelman filters. Both flue gas velocity
and particulate loading measurements were averaged over the stack
area.
Particulate size distribution of the fly ash was
determined by an in-stack Andersen cascade impactor. In this
device the ash passes through a series of multi-jet stages and
is aerodynamically separated and collected on eight plates and
a back-up filter. Figures 3-3 and 3-4 present the average fly
ash size distributions at Stations HS and CS, respectively.
3-3 Fly Ash Collection for Analysis
Fly ash was collected for elemental analysis at each
plant by three different methods:
• High-Volume Source Assessment
Sampling System (HVSASS) cyclones,
• low volume cyclones, and
• Andersen cascade impactor.
Each of these collection systems was followed by a wet electro-
static precipitator to collect the smallest fraction and vapor
species escaping the primary collector. The WEP is >9970 effec-
tive in removing particulate matter and >9570 efficient for most-
vapor phase trace elements. The only exception in this study
was mercury which was sampled in the gas phase by gold amalgamation
as an alternate technique. Chemical analysis was carried out on
the HVSASS and Andersen samples; the low-volume cyclone samples
were held in reserve.
25
-------
Figure 3-3.
10
9
8
7
6
5
I
•H
O
0)
r-l
o
•H
4J
M
a
,G
.5
.4
.3
.2
Particle Size Distribution of Station HS
Fly Ash as Determined by Andersen
Cascade Impactor
Avg. Grain Loading = .068 gr/SCF
Geometric Mean Diameter = 2.3 ym
Geometric Standard Deviation = 2.6
001 0.05 0.1 0.2 0.5 1
5 10 20 30 40 50 60 70
Cumulative Mass (%)
90
95
98 99
26
-------
Figure 3-4.
CU
•P
0)
•H
O
O
•rl
Particle Size Distribution of Station CS Fly
Ash as Determined by Andersen Cascade Impactor
O.
Avg. Grain Loading = .014 gr/scf
Geometric Mean Diameter = 2.3 vm
Geometric Standard Deviation =3.2
0.01 005 0.1 0.2 0.5 1
5 10 20 30 40 50 60 70 SO
Cumulative Mass (%)
90
98 99
27
-------
3.3.1 HVSASS Cyclones
The High-Volume Source Assessment Sampling System cyclones
are part of a system for source sampling developed by Aerotherm,
Inc. under contract to EPA. The system consists of three cyclones
designed for a 5ACFM sampling rate. The D5o's (diameter at which
50% of particles are collected) of the cyclone set at the 5ACFM rate
are 14 ym, 4 ym and 1 ym. The sampling system as modified for
this study is schematically represented in Figure 3-5. Fly ash
fractions resulting from HVSASS cyclone collection at isokinetic
sampling conditions were analyzed for the 15 trace elements shown
below:
Arsenic Copper Nickel
Beryllium Fluorine Selenium
Cadmium Lead Titanium
Calcium Mercury Uranium
Chromium Manganese Zinc
3.3.2 Low-Volume Cyclones
A series of three cyclones were used to isokinetically
collect sized fly ash fractions at 1 ACFM. The cyclones were
designed with D50's of 2.65 ym, 0.96 ym at 1 ACFM. The cyclone
system is similar to the HVSASS set except that they are operated
in-stack. The 1 ACFM cyclones were manufactured by Radian from
specifications provided by Southern Research Institute in Birmingham,
Alabama. Both high and low volume cyclone systems were followed
by a wet electrostatic precipitator to collect the vaporous and
fine particulate material escaping the last cyclone. The low
volume cyclone collected ash fractions were held as reserve samples.
28
-------
OVEN
^M
to
SO
WET ELECTROSTATIC
PRECIPITATOR
Figure 3-5. Schematic of Sampling Train for Particulate Sizing with HVSASS Cyclones
-------
3.3.3 Cascade Impactor
Particulates entrained in the flue gas were separated
during isokinetic sample acquisition into eight size fractions with
the Andersen cascade impactor. The Andersen aerodynamically
separates the particles as they pass through a series of multi-
jet stages. Fine particulates passing through the last impactor
stage enter the wet electrostatic precipitator via a teflon-lined
probe. Andersen ash fractions were analyzed for the nine trace
elements shown below:
Arsenic Manganese
Cadmium Nickel
Chromium Selenium
Copper Zinc
Lead
3.3.4 WEP Collector
In each sampling train, the wet electrostatic precipi-
tator (WEP) served as the secondary collector of fine particulates
escaping the primary collection device. This method permits
sampling a large gas volume at isokinetic conditions without
plugging, which occurs with a filter. Thus, a sufficient
quantity of sample can be collected to permit repeated analyses
with low detectability. In addition, problems of trace element
contamination by the filter substrate are avoided.
The particulate concentration in the WEP samples was
estimated from the titanium concentration assuming that titanium
is evenly distributed in the particles with respect to particle
size. This assumption is based on work performed by Radian
(RA-219) and Davison (DA-105). The results of these two studies
indicate that the assumption of uniform ash composition with
respect to titanium holds within experimental limits.
30
-------
The particulate concentration estimated for each WEP
sample was subsequently used to determine the concentration of
each element in the WEP fraction, reported as mass of element
per mass of particulate collected. This is carried out for each
element of interest in the WEP sample, regardless of its physical
state when collected, i.e., particulate or vapor.
31
-------
4.0 SAMPLE ANALYSIS
Samples of coal and fly ash collected at each site were
analyzed for up to 15 elements:
Arsenic Mercury
Beryllium Manganese
Cadmium Nickel
Calcium Selenium
Chromium Titanium
Copper Uranium
Fluorine Zinc
Lead
This list was selected to include species representing several
categories of combustion behavior based on previous Radian studies
and other published reports. These groups are as follows:
• elements with enrichment in fly ash
(As, Cd, Cr, Cu, F, Hg, Ni, Pb, Se, Zn),
• elements with approximately equal
distribution throughout the sized
ash fraction (Ca), and
• elements with distributions in
disagreement in the literature (Be, Mn, Ti).
In order to substanitiate the particle size of cyclone
collected ash fractions, average particle size was determined by
electron microscopy and specific surface area by BET adsorption
analysis.
32
-------
Composite samples of the coal required density
separation to study association of element with the organic or
inorganic phase of coal. The approach used in the sink-float
study and the analytical techniques employed in sample characteri-
zation are described in this section. The analytical methods are
described in detail in Appendix B.
4.1 Sink-Float Separation of Coal
To investigate the association of elements with the
organic or inorganic phase of the coal, the composite coal samples
from both stations were separated into different fractions by
suspension in a liquid mixture of known specific gravity. The
inorganic components of raw coal are denser than the organic
fraction. The separating liquid is selected such that a
lighter fraction will be supported (i.e., remain in suspension)
while heavier components sink. In this study, mixtures of
benzene and carbon tetrachloride were used as the separation
liquors. Two separations were performed with mixtures with
specific gravities of 1.35 and 1.45. This resulted in four
density fractions which were subsequently analyzed and compared
to the total coal composition.
The initial composite coal sample was dried, ground and
reduced to <200 mesh. A 5 to 10 weight percent slurry of the
coal and separation liquor was then prepared and allowed to settle.
After 24 hours, the suspended coal was decanted from the container.
Both sink and float fractions were retained for characterization.
A schematic representing the separation is found in Figure 4-1.
4.2 Analytical Techniques
The techniques used for the quantitative determinations
included:
33
-------
RAW COAL
Dry Grind
to <200 Mesh
Slurry with Liquid
(Sp. Gr. 1.35)
24-Hour
Settling
Slurry with Liquid
(Sp. Gr. 1.45)
24-Hour
Settling
1.35
Sink
1.35
Float
v
1.45
Sink
1.45
Float
Figure 4-1. Sink-Float Separation of Coal
34
-------
• flame atomic absorption
• flameless atomic absorption,
• specific ion electrode,
• fluorometry, and
• colorimetry.
The methods are described in detail in Appendix B, "Analytical
Procedures." Brief summaries of dissolution and analytical
methods used for trace element determinations of coal, ash and
WEP liquor are found in Figures 4-2, 4-3, and 4-4.
35
-------
Gold Amalgamation
Atomic Absorption
to
COAL
Perchloric Acid
LTA* Digestion
Organic Extraction
Flame Atomic Absorption
Flameless Atomic Absorption
Fluorescence
Flameless Atomic Absorption
Inorganic Extraction Flameless Atomic Absorption
Flame Atomic Absorption
Colo rime try
Fusion
Flame Atomic Absorption
Specific Ion Electrode
Fluorescence
iig
Be
HI
Se
Cd, Pb
As
Cr, Cu, Zn
Ti
Ca, Mn
*L1'A - Low Temperature Asher
Figure 4-2. Analytical Flow Chart for Coal Samples
-------
Gold Amalgamation
Atomic Absorption
ASH
Perchloric Acid
Digestion
Organic Extraction
Flame Atomic Absorption
Flameless Atomic Absorption
Fluorescence
Flameless Atomic Absorption
Inorganic Extraction Flame less Atomic Absorption
Flame Atomic Absorption
Colorimetry
Fusion
Flame Atomic Absorption
Specific Ion Electrode
Fluorescence
Be
Hi
Se
Cd, Pb
As
Cr, Cu, Zn
Ti
Cn, Mn
Figure 4-3. Analytical Flow Chart for Ash Samples
-------
oo
do
Filter
Filtrate
WEP
Solids
i
Perchloric
Acid
Digestion
Cold Vapor Technique
Organic Extraction
Inorganic Extraction
Fusion
Atomic Absorptlpn
Flame Atomic Absorption
Fluorescence
Flame]ess Atomic Absorption
Flameless Atomic Absorption
Flameless Atomic Absorption
Flame Atomic Absorption
Colorlmetry
Fluorescence
Hg
Be
Se
Pb, Cd
Cr, Cu,- Zn,
Ca, Mu
Ti
Specific Ion Electrode
Figure 4-4. Analytical Flow Chart for WEP Solution
-------
-------
5.0 RESULTS OF COAL CHARACTERIZATION STUDIES
This section presents the results of the coal analyses
and the organic-inorganic elemental association study.
5.1 Chemical Analysis of Raw Coals
Proximate, ultimate and elemental analyses of composite
coal samples from each station were performed. The results
presented in Table 5-1 represent the average of duplicate deter-
minations .
5.2 Sink-Float Separation Study of Coal
Coal fractions resulting from sink-float separation
were analyzed to determine the concentration of 15 elements.
The separation methodology was designed to separate each coal
into four fractions as previously described in Section 4.1. The
ash content (percent) and analytical results (ppm) for each
coal fraction are presented in Table 5-2. The percentage of raw
coal indicates the distribution of the coal sample between the
sink and float fractions. The raw coal compositions are also
tabulated here for comparison.
Coal HS was very uniform in specific gravity; 97%
of the raw coal was within a specific gravity range of 1.35-1.45.
Coal CS, on the other hand, was more diversified; only 45% of this
coal exhibited density within that range.
Association of Elements with the Organic/Inorganic
Phase of Coal
To correlate the analytical results for each station,
the concentration of a given element in each sink-float fraction
. 39
-------
TABLE 5-1. -COAL ANALYSIS
Proximate Analysis
% Moisture
% Ash
% Volatile Jiatter
% Fixed Carbon
Btu/lb
Z Sulfur
Ultimate Analysis
Z Moisture
% Carbon
7. Hydrogen
7, Sitrogen
X Chlorine
% Sulfur
% Ash
Z Oxygen (Diff)
Elemental Analysis (pom)
Arsenic
Beryllium
Calcium
Cadmium
Chromium
Copper
Fluorine
Mercury
Manganese
Nickel
Lead
Selenium
Titanium
Uranium
Zinc
Coal HS
As Received Dry
29.3 —
5.4 7.7
31.2 44.1
34.1 48.2
7904 11181
0.40 . 0.56
29.3 —
47.4 67.0
3.2 4.5
0.7 1.0
0.00 0.00
0.40 0.56
5.4 7.7
13.6 19.2
1.2
1.05
9390.0
0.90
14.0
14.0
52.0
0.14
24.0
7.0
6.7
1.2
670.0
0.90
11.7
Coal CS
As Received Drv
19.0
9.2 11.4
30.1 37.1
41.7 51.5
9225 11388
0.69 0.85
19.0 — .
54.5 67.4
3.6 4.4
1.0 1.2
0.01 0.01
0.69 0.35
9.2 11.4
11.9 14.7
3.9
0.35
3730.0
0.70
13.0
14.0
54.0
0.11
34.0
5.1
11.7
1.8
990.0
2.0
6.5
Values represent Che average of duplicate determinations
40
-------
TABLE 5r,2, ANALYSIS OP COAL SINK-FLOAT FRACTIONS*
Coal Fraction
Coal IIS
Float at
Float at
Raw Coal
Sink at
Sink at
Coal CS
Flo.it at
KloaL at
Raw Coal
Sink at
Sink at
1.35
1.45
1.35
1.45
1.35
1.45
1. 15
1.45
7.
Raw
1.
98.
100
98.
1.6
41.
86.
100
58.
13.
of
Coal
6
4
4
5
5
5
5
%
Ash**
5.8
6.8
7.7
7.9
43.4
3.9
5.6
11.4
18.4
51.5
As
1.5
1.1
1.2
2.3
20
0.85
1.2
3.9
9.3
15.0
Be
1.00
0.55
1.05
0.75
1.4
1.15
1.60
0.85
0.95
0.75
Ca
8890
9280
9390
9240
8460
3100
3180
3730
4140
7975
Cd
0.50
0.47
0.90
1.4
8.6
0.55
0.45
0.70
0.70
1.2
Cr
9.5
19
14
11
31
16
10
13
21
14
Cu
12
12
14
17
70
6.3
10
14
25
43
F
61
60
52
67
190
25
32
54
54
92
_»&__
0.24
0.12
0.14
0.14
2.0
0.11
0.09
0.11
0.19
0.40
Mn
23
24
24
23
41
27
32
34
37
50
Nl
7.3
5.0
7.0
5.9
18
4.4
2.8
5.1
3.9
5.1
Pb
3.0
4.1
6.7
5.4
43
5.9
5.6
11.7
12.1
16.0
Se
0.70
1.1
1.2
1.4
6.1
1.6
1.6
1.8
1.0
4.5
Ti
520
620
670
660
2640
450
880
990
1110
2000
U
1.
0.
0.
0.
2.
1.
1.
2.
1.
2.
0
88
90
83
3
4
2
0
5
7
Zn
7.0
5.8
11.7
7.5
89
4.0
6.5
6.5
8.9
15.6
*A11 concentrations calculated on a dry weight basis and reported as ppm C^g/g) unless otherwise noted.
**Ash Content of the coal fraction.
All values represent the average of duplicate determinations.
-------
was compared with the ash content of that fraction. Throughout
this report, the ash component is considered to represent the
mineral or inorganic portion of the coal. The ash-free component,
on the other hand, is considered to be organic in nature. A
linear least squares fit of ash content and concentration was
performed for each element. Elemental concentrations were extra-
polated to 0% and 100% ash values to estimate concentration of the
element in each extreme case. In Figure 5-1 the concentration of
copper is plotted versus ash content. Analogous figures for all
15 elements are included at the end of this section.
To establish the validity of assigning element concen-
trations to the 0% and 10070 ash content fractions, estimated
concentrations for each case were proportionally combined according
to the ash content of the raw coal. The resulting concentration
for most elements in the mathematically derived raw coal concen-
trations compares favorably with the analytical values for the
raw coal. These results are presented in Table 5-3.
With an assigned element content in each extreme case,
the association with organic or inorganic phase is identified
by comparing the content of one phase to the calculated total
content. The association of any element for the organic phase
then can be represented as follows:
. . . . Mass of Element in Organic Phase x 100 _
Organic Association = — - -7— — : - ; — ° . — 7— - ; - — — - . . — r-
& Mass of Element in Total (Organic + Inorganic) Coal
100
C0 • (1-A) + Cioo'A
where, CQ = extrapolated concentration of an element at 0%
ash content ,
42
-------
Coal HS
Coal CS
•P-
CO
100
g.
6°
2
a
3
g
40
20
10 20
—I 1 1—
30 40 50
Ash Content (Z)
60
70
80
90
100
fl 100
O*
CL
\»x
g 80
40
20
-4-
"f
10 20 30 40 50 60 70 80 90 100
Ash Content %
Figure 5-1. Copper Concentration vs Ash Content for Coal Fractions
-------
TABLE 5-3,
CONCENTRATION (ppm)
Element
Arsenic
Beryllium
Calci urn
Cadmium
Chromium
Copper
Fluorine
Mercury
-P" Manganese
Nickel
Lead
So 1 en i urn
Titanium
Uranium
Zinc
Ash-Free
Fraction
(0% Ash)
0
0.73
9400
0
10
2.8
35
0
20
4.1
0
0.12
225
0.64
0
Coal HS (7
Ash
Fraction
(1002 Ash)
49
2.3
7350
21
59
158
392
4.8
68
36
103
14
5800
4.4
215
.7% Ash)
Whole Coal
Calculated*
3.7
0.85
9240
1.6
14
15
62
0.4
24
6.6
8
1.2
650
0.93
17
Analyzed
1.2
1.05
9390
0.90
14
14
52
0.14
24
7.0
6.7
1.2
670
0.90
11.7
Ash-Free
Fraction
(07. Ash)
0.68
1.3
2540
0.46
14
6.2
28
0.061
28
3.8
6.6
0.96
580
S.3
4.2
Coal CS (11.4% Ash)
Ash
Fraction
(100% Ash)
30
0.14
12900
.1.9
16
81
175
0.72 •
72
6.3
27
7.2
3400
4.0
27
Whole
Calculated*
4.0
1.1
3700
0.62
14
15
45
0.14
33
4.1
8.9
1.7
900
1.6
6.8
Coal
Analyzed
3.9
0.85
3730
0.70
13
14
54
0.11
34
5.1
11.7
1.8
990
2.0
6.5
*MaUiematically calculated concentration derived by combining 0% and 100% asli fractions in the ratio found in raw coal.
-------
Cioo = extrapolated concentration of an element
at 100% ash content, and
A = fraction of ash in raw coal sample.
The coal phase association results of this study are presented in
Table 5-4. All elements are ranked numerically according to their
calculated association with the organic (ash-free) portion of the
coal. Comparison is made with the results reported by Gluskoter
(GL-077) for another western coal, Black Mesa coal from Arizona.
Table 5-5 includes the results of Gluskoter (GL-077) for four eastern
coals. The four categories indicated in the table are defined on
the basis of the fraction of an element found in the organic phase.
The ranges of elemental fractions generally used for each category
are as follows:
• organic - >0.66,
• intermediate organic - 0.50-0.66,
• intermediate inorganic - 0.33-0.49, and
• inorganic - <0.33.
From Tables 5-4 and 5-5 the following specific observa-
tions can be made regarding the three western coals:
• calcium displays an extremely high
organic association in Coal HS, while
in the other two only intermediate
organic association is noted (in most
eastern coals Ca is found with the
mineral phase);
• beryllium and nickel are consistently
associated with the organic phase in
all three western coals;
45
-------
TABLE 5-4. COMPARISON OF ORGANIC ASSOCIATION OF WESTEBN COALS
Calcium
Nickel
Beryllium
Manganese
Chromium
Uranium
Fluorine
Titanium
Copper
Selenium
Cadmium -
Lead
Arsenic
Zinc
Mercury
Coal HS
Wyoming
94*
89
82
78
67
63
52
32
18
10
0
0
0
0
0
Coal CS
Wyoming
60
82
98
78
87
71
58
73
37
56
65
66
15
55
40
Black Mesa Coal**
Arizona
66
89
81
51
54
53
NR
31
74
60
NR
7
9
NR
20
*0rganic association as %
**Source GL-077
NR - Not reported
46
-------
TABLE 5-5. RANKING OF ELEMENTS IN COAL ACCORDING
TO ORGANIC-INORGANIC AFFINITIES
Coal HS Coal CS
Wvoming tfvoming
Organic Ca Be
Si Cr
Be Mi
Mn. Mn
Cr Ti
V
Intermediate U Pb
Organic F Cd
Ca
F
Se
Zn
Intermediate Ti Hg
Inorganic Cu
Inorganic Cu As
Se
Cd
Pb
As
Zn
Hg
Black. Mesa
Coal
Arizona*
B
Ma
P
Mg
3a
Fe
S
Si
Co
Br
Sr
Ca
Be
Yb
Cu
V
Lu
3b
Sc
Ca
M
La
Eu
.££
Ib
ff
Mn
W
K
5m
Hf
Zr
Ta
Al
Th
Ga
Rb
Ti
Sn
HS
AS
Si
Pb
Cs
Ga
Clochester
Coal
Illinois*
Ge
P
Be
B
Ga
Sfa
Co
Se
Ma
V
K
Hi
Pb
Cu
Si
Al
Zr
3
Hg
Fe
As
Mo
Cd
Cr
.33
Zn
Ca
Davis Coal
Illinois*
Ge .
B
Be.
p
Sa
Sb
Cr
Co
Ga
Ca
Si
K
7
Al
Cu
Si
Mn
Zr
S
As
Cd
Hg
Mo
Pb
Zn
Fe
Blue Creek
Coal
Alabama*
Br
Ge
Co
S
2i
H
Cu
Dy
Sr
Be
V
La
II
Pb
Sm
Tb
Su
Sb
Ce
3a
Ga
P
Cr
Zr
Se
Yb
Ti
Sc
Lu
Fe
Hf
Th
Al
Ta
B
Ca
Zn
Na
Si
K
Mg
Cs
Kb
Jfa
As
Pittsburgh >tS
Coal
Wast Virginia*
Sr
Br
3
U
Ba
P
S
Dy
Ge
Pb
Eu
Ma
Be
Co"
Ga
Ca
V
Cu
Hg
La
Sm
Mi
Zn
Sb
Sn
Ma
Cr
Ce
Sc
Se
Tb
Yb
Al
Fe
Hf
Lu
Zr
As
Ta
Th
Hb
K
Si
Cs
Ti
*Source: GL-077
47
-------
• chromium, manganese and uranium
exhibit higher organic association
in the two Wyoming coals than in the
Arizona coal; manganese is primarily
inorganically bound in eastern samples,
while chromium is not consistent in
phase association;
• fluorine is not primarily associated
with either phase,
• titanium is organically associated in
the coal CS, while inorganic association
is prevalent in the other two western
coals;
• copper in the Wyoming coals is found
associated with the mineral matter
while organically combined in the
Arizona coal;
• selenium, cadmium, lead, zinc and
mercury are completely inorganically
associated in Coal HS, no extreme
preferential association is apparent
in Coal CS;
® arsenic is primarily associated with
the inorganic phase in both eastern
and western coals,
• while Coal CS has a higher ash content,
there is a lower degree of association
48
-------
of the elements analyzed with the ash
or mineral phase. On the other hand,
five elements (Cd, Pb, As, Zn, Hg)
exhibit 1007=, association with the mineral
phase in the Coal HS even though this coal
has a lower ash content than Coal CS.
The following figures present plots of element concen-
tration versus ash content derived in the sink-float coal
separation and analysis study.
49
-------
Concentration (ppm)
Concentration (ppm)
Coucentration (ppni)
Oi
O
o
o
(U
-------
280T
COAL HS
COAL CS
28T
24,
20
16'
12.,
a,
4
0
0
.2
.4 .6
Ash Content
.2 .4 .6 .8 1.0
Ash Content
Figure 5-5, Cadmium Concentration vs Ash Content
60
50-
40"
30
20;
10.
0
.4 .6
Ash Content
Figure 5-6,
i.o
.2
.4 .6
Ash Content
.8
1.0
Chromium Concentration vs Ash Content
280"
240"
200 '
160
120
80"
40
0
.2 .4 .6
Ash Content
1.0
0
.2
.4 .6
Ash Content
Figure 5-7. Copper Concentration vs Ash Content
.8
i.o
.8
1.0
51
-------
COAL HS
COAL CS
75
a
a
a.
= 50
|25
400
320
240
160
80
0
.4
Ash Content
1.0
.2
.4 .6
Ash Content
.3
1.0
Figure 5-8, Fluorine Concentration vs Ash Content
4.8
4.0
3.2
2.4 ••
1.6
.8.
0
.4 .6
Ash Content
1.0
.4
Ash Content
Figure 5-9. Mercury Concentration vs Ash Content
75
5C
25
.2 .4 .6
Ash Content
1.0
.2
.6
Ash Content
.3
1.0
.8
1.0
Fieure 5-10. Manganese Concentration vs Ash Content
52
-------
42 T
36
30
24
18
12'
6.
140.,
14T
12
10
I 44
COAL HS
COAL CS
42-r
36 •
30 •
24 •
18 •
12'
6'
0
.2 74
Ash Content
.8
1.0
.4 .6
Ash Content
.8
T.O
Figure 5-11.
Nickel Concentration vs Ash Content
140"
120 •
100 •
80-
60..
.2 .4
Ash Content
.8
1.0
.4
Ash Content
.3
1.0
Figure 5-12.
Lead Concentration vs Ash Content
14T
.4 .6
Ash Content
.8
1.0
.4 .6
Ash Content
1.0
Fisure 5-13. Selenium- Concentration vs Ash Content
53
-------
COAL HS
COAL CS
.2 .4 .6
Ash Conteac
.8
.2 .4 .6
Ash Concerte
1.0
Figure 5-14. Titanium Concentration va Ash Content
4.0
3.0
2.0.
1.0-
.4 .6
Ash Content
Figure 5-15
1.0
.2
.4 .6
Ash Content
1.0
Uranium Concentration vs Ash Content
5" .2 .4 .6
Zinc Concentration vs Ash Content
.3
1.0
54
-------
6.0 RESULTS OF ELEMENT ENRICHMENT STUDY
This section presents and discusses the results of the
fly ash element enrichment study. This part of the program in-
volved physical and chemical characterizations, of selected particu-
late samples. Data analysis involved application of mathematical
techniques to calculate enrichment in each sized fraction and
the composite ash-vapor samples. In this program, enrichment of
an element was defined so as to be independent of other chemical
species present. This approach differs from that used in other
studies in that other definitions assumed even distribution of
some selected species (e.g., Ca, Al or Fe) throughout all ash
fractions. This has not been shown to be consistently true in
every case, according to previous Radian work and other literature.,
The results of this study are presented in the following
order:
• physical characterization of cyclone
sized ash,
• element concentration and enrichment
ratios for cyclone ash,
• element concentration and enrichment
ratios for Andersen samples, and
• discussion of results.
6.1 Physical Characterization of Cyclone Collected Ash
The sized fly ash fractions collected by the cyclones
in the HVSASS train were physically characterized with respect
to particle size and surface area. Table 6-1 presents the results
of these measurements.
55
-------
TABLE 6-1. PHYSICAL CHARACTERISTICS OF CYCLONE PARTICULATES
Oi
Station HS:
Cyclone 1
Cyclone 2
Cyclone 3
Station CS :
Cyclone 1
Cyclone 2
Cyclone 3
'Particle
Expected1
>14
14-4
4-1
>14
14-4
4-1
Size Range, p
Observed^
4.8-0.4
3.8-0.4
1.8-0.3
8.7-0.5
4.4-0.3
2.1-0.4
Mean
2
Diameter , \i
2.0
1.9
0.8
2.0
1.8
0.9
Specific Surface
Calculated3
1.2
1.2
3.0
1.2
1.3
2.9
Area, m2/g
BET
1.9
1.9
4.0
IS
2.3
3.5
Cyclone system designed for these size ranges.
Mean diameter and range determined by count of SEM photographs of the ash.
3Surface area calculated assuming spherical particles, density of 2.5 g/cm3 and observed mean diameters.
IS - insufficient sample for analysis.
-------
The expected collection ranges were defined by cyclone
cut-off diameters for the High-Volume Source Assessment Sampling
System. The mean particle diameter and observed range were deter-
mined by numerical particle size counts of photomicrographs
obtained by scanning electron microscopy (SEM).
A four-point BET surface area analysis was performed
for each ash fraction. Calculated surface area was estimated
based on the mean particle diameter, observed spherical shape
and an assumed fly ash density of 2.5 g/cin3 (KA-192). Density
determination of precipitator ash at each station were performed
(p^ = 2.6, p.., = 2.5) to validate the assumed density since
no Go
insufficient quantities of fly ash were available for analysis.
The calculated surface areas were lower than measured
values for all analyzed ash fractions. Visual inspection of the
fly ash as shown by the SEM photomicrographs (Figures 6-1 through
6-6) indicates that the particles, though spherical in shape,
have rough irregular surfaces. This irregular surface, although
not considered in calculating the estimated area, actually increases
the overall surface area. This is thought to be the reason for
the difference between observed and calculated values, and sub-
stantiates the BET surface area results.
The particle size characteristics of the flue gas
particulates from the two plants were quite similar. The SEM
photomicrographs reveal the absence of large fly ash particles
(>30y) in the exiting flue gas. Although designed to collect
>14u particles, the first cyclone contained a significant amount
of fine ash. In fact, the lower limits of the particle size
ranges for all six cyclone samples (three each from both plants)
are nearly identical. The presence of fines coupled with the
absence of large particles resulted in the observed mean diameter
for all collected fractions being below the expected particle
size range for each fraction.
57
-------
-------
5 Vim
3000X
10 ym
1000X
Figure 6-1. Cyclone #1 - Fly Ash Collected at Station HS,
58
-------
-------
5 ym
3000X
1 ym
. 10,OOOX
Figure 6-2. Cyclone #2 - Fly Ash Collected at Station HS.
59
-------
-------
5 ym
3000X
1 ym
10,OOOX
Figure 6-3. Cyclone #3 - Fly Ash Collected at Station HS,
60
-------
-------
5 ym
3000X
10 ym
1000X
Figure 6-4. Cyclone #1 - Fly Ash Collected Station CS.
61
-------
-------
3000X
1 ym
10,OOOX
Figure 6-5. Cyclone #2 - Fly Ash Collected at Station CS.
62
-------
-------
3000X
1 ym
10,OOOX
Figure 6-6. Cyclone #3 - Fly Ash Collected at Station CS,
63
-------
-------
In addition, the average particle size of the first
and second cyclone fractions were found to be very similar. This
can be seen in Figures 6-1 and 6-2 of Station HS ash and Figures
6-4 and 6-5 of Station CS ash. Considering the similarity of
the ash collected in these two cyclones these fractions were
combined as a single sample for chemical analysis and subsequent
enrichment studies.
One possible explanation for the discrepancies between
expected and observed particle size in the cyclone fractions is
agglomeration. Clusters of ash particles were identified in the
photomicrographs. Agglomeration may take place either in the
precipitator or in the exiting gas. In the ESP, charged particles
are impacted on the plates, resulting in particulate build-up.
Build-up is reduced by rapping of plates to allow gravity settling.
Lighter particle clusters are susceptible to transport by the
exiting flue gas. Also, clustering can result from impaction of
charged gas particles in the cyclone collector. Particle clustering
could result in effectively larger particle diameters (as seen by
the cyclone fractionators) than were determined by SEM photomicro-
graphic techniques, thus resulting in a greater degree of impaction
earlier in the cyclone sampling train.
6.2 Element Concentration and Enrichment Ratios of Cyclone
Collected Fly Ash
Results of elemental analyses of cyclone collected ash
fractions are presented on a dry weight basis in Table 6-2. Also
included is the average concentration of the fly ash (including
vaporous species collected by the WEP) and the ash equivalent
concentration of the raw coal for comparison. The average fly
ash concentration is the result of proportionally combining the ash
fraction concentrations according to the collection distribution
64
-------
TABLE 6-2. ANALYTICAL RESULTS OF CYCLONE COLLECTED FLY ASH FRACTIONS.
o\
Fly Ash
Fraction As Be Ca (%)
Station US:
Cyclones 58 3.0 16.5
1 & 2 (2. OH)
Cyclone 3 62 2.4 16.8
(0.8U)
HEP (<0.8|i 70 48
+ Vaporous)
Average Fly** 60 5.1
Ash
Ash F.qulva- 15.6 13.6 12.2
lence of Coal
Station CS:
Cyclones 86 5.9 5.1
1 & 2 (1.9|i)
Cyclone 3 103 5.1 4.4
WEP ('0.911 102 64
•*• Vaporous)
Average Fly** 96 16
Ash
Ash Equiva- 34 7.4 3.3
leuce of Coal
Concentrations as ppm
Cd
5.
9.
77
9.
11
8.
3.
64
16
6.
All values represent the average of duplicate
*Titanium values are average of cyclone
sulCate by WEP electrolyte solution.
**Calculated by combining the individual
Cr
0 150
3 110
710
9 167
.7 182
7 270
4 230
865
355
1 114
Cu
235
360
720
295
182
235
400
1.8%
3340
123
F
860
1010
6.6%
4250
675
670
1120
35.5%
474
Dry Weight Basis Unless
Hg
0.24
0.11
190
9.9
1.8
0.11
0.14
476
82
0.96
Hn
190
240
240
207
312
624
980
675
780
298
Ni
101
104
580
126
91
130
120
650
215
45
Indicated
Pb
73
220
__
87
155
330
303
Otherwise Ash Fraction
Se
59
82
710
99
15.6
21
29
187
53
15.8
Ti U Zn D
8190 9.6 122
7830 9.7 225
(8000)* 19.5 650
8080 179
8700 11.7 152
7950 21 250
8870 22 305
(8400)* 41 2.27%
8400 24 4100
8680 17.5 57
istributlon
66.1%
28.7%
5.2%
100.0%
41.1%
41.8%
17.1%
100.0%
determinations.
collected fly ash.
ash concentrations
Calcium and lead content of
in proportion
to the
UEP was not determined due
ash distribution
by HVSASS
*
cyclone
to precipitation as the
collection.
-------
in the cyclone/WEP 'sampling train. The ash equivalent concentra-
tion is defined as that concentration of the element in the ash
if all of the element originally in the coal were retained with
the mineral content after combustion:
Ccae -
where ,
Ccae = ash equivalent concentration of coal
Cc = element concentration of raw coal
Xa = ash content of coal.
For example, the hot-side coal with 1,20 ppm As and 7.7% ash has
an ash equivalent concentration of:
ccae ' =15. 6 ppm As
Enrichment Ratios
Enrichment ratios is defined as the ratio of an element's
concentration in a given ash fraction to its ash equivalent con-
centration in the coal.
Cax
ERX = c^~ <6-2>
caex
where ,
ERX = enrichment ratio for element x
Ca = concentration of element x in the ash fraction
Ccaer = ash equivalent concentration of element x in the
coal.
Ratios greater than 1.0 indicate enrichment of the ash
while those less than 1.0 indicate depletion of an element.
66
-------
As mentioned previously, the use of this enrichment
definition provides a means to quantify enrichment for an element
independently of other chemical species present. Enrichment
ratios for three cyclone-sized fractions are presented in Table
6-3. Those elements found enriched in all fractions, i.e.,
ratios greater than 1, include:
Station HS Station CS
Arsenic Arsenic Nickel
Copper Chromium Selenium
Fluorine Copper Uranium
Nickel Fluorine Zinc
Selenium Manganese
Those elements, although not enriched in all fractions but dis-
playing increasing enrichment in the smaller fractions, include:
Station HS Station CS
Beryllium Mercury Beryllium
Cadmium Uranium Mercury
Chromium Zinc
67
-------
TABLE 6-3. ENRICHMENT RATIO* Fqg^YCLQjjE_jCOLLECTEI^J'LY ASH FRACTIONS
cr>
oo
Station HS
Element
As
Be
Ca
Cd
Cr
Cu
F
Hg
Mn
Ni
Pb
Se
Ti
U
Zn
Ash Frac-
tion Dis-
tribution
2.0u
3.7
0.22
1.35
0.43
0.82
1.3
1.3
0.13
0.61
1.1
.84
3.8
0.94
0.82
0.80
66.1%
0.8u
4.0
0.18
1.38
0.79
0.60
2.0
1.5
0.06
0.77
1.1
2.5
5.2
0.90
0.83
1.5
28.7%
<0.8y
4.5
3.5
ND
6.6
3.9
4.0
98
106
0.77
6.4
ND
46
0.92
1.7
4.3
5.2%
£**
3.8
0.38
ND
0.85
0.92
1.6
6.3
5.5
0.66
1.4
ND
6.3
0.93
0.87
1.2
100%
2.9u
2.5
0.80
1.56
1.4
2.4
1.9
1.4
0.11
2.1
2.9
1,5
1.3
0.92
1.2
4.4
41.1%
Station CS
o.9y
3.0
0.69
1.34
0.56
2.0
3.2
2.4
0.15
3.3
2.7
3.2
1.8
1.0
1.3
5 = 4
41.8%
<0.9y
3.0
8.6
ND
10
7.6
146
750
495
2.3
14
ND
12
0.97
2.3
400
17.1%
E**
2.8
2.1
ND
2.6
3.1
27
130
84
2.6
4.7
ND
3.3
1.0
1.4
72
100%
*Ratio of ash fraction concentration to ash equivalent concentration of coal.
*ftMean enrichment of flue gas particulate fractions determined by combining the individual values in
proportion to the ash distribution by HVSASS cyclone collection.
ND - Not Determined
-------
Those elements with no observable enrichment trends are:
Station HS Station CS
Manganese Titanium
Titanium
No evaluation of calcium or lead enrichment was possible because
of precipitation of insoluble sulfate salts in the WEP sample.
This resulted from the use of sulfuric acid as the electrolyte
in the collection device. However, calcium is enriched in the
tv7o cyclone ash fractions at each station and lead is enriched
in all ash fractions except that of the largest HS particulates.
Calculation of enrichment was possible from the cyclone
ash study, however an insufficient number of ash fractions was
available for complete correlation of enrichment with particle
size. An additional study of Andersen collected ash fraction was
performed for that purpose.
6.3 Concentration and Enrichment Ratios of Andersen Cascade
Impactor Samples
Based on the initial data from the cyclone train, nine
trace elements were chosen for a follow-up enrichment study. Eight
Andersen ash fractions plus the back-up WEP were analyzed for the
following elements:
Arsenic Manganese
Cadmium Nickel
Chromium Selenium
Copper Zinc
Lead
69
-------
These elements were selected to include those for which substantial
evidence of enrichment.has been shown or for which evidence of
volatilization or oxide formation mechanisms exist to account for
their enrichment. Mercury and fluoride were not included in this
study due to insufficient ash sample.
The purpose of this part of the study was to define
elemental concentration for a larger number of fly ash fractions,
each representing a statistically smaller size range. Analytical
results are found in Table 6-4 and converted to enrichment ratios
in Table 6-5. Several differences between the results from the
two stations were observed.
Analysis of the Andersen samples shows that arsenic and
selenium were more enriched in the fly ash exiting the hot-side
precipitator. Though enriched in all fractions, the increased
amounts as As and Se collected in the WEP sample appears to either
be vaporous or of such small particle diameter that significantly
more surface area was available for condensation than in the next
size fraction.
The remaining seven elements of the study exhibited higher
enrichment ratios for fly ash exiting the cold-side ESP. They
included:
Cadmium Manganese
Chromium Nickel
Copper Zinc
Lead
Cadmium is enriched only in the finest fraction at
each plant. Chromium and manganese are enriched only in the
finest fraction at Station HS while enriched in all fractions at
Station CS. Lead is not enriched at Station HS and enriched in
all fractions at Station CS. Again, no evaluation can be made
for lead enrichment in the WEP sample.
70
-------
TABLE 6-4. ANALYTICAL RESULTS OF ANDERSEN COLLECTED FLY ASH FRACTIONS
Fly Ash
Size
Fraction
(Mm)
Station HS:
>8.0
5.0-8.0
3.3-5.0
2.3-3.3
1.5-2.3
0.74-1.5
0.45-0.74
0.30-0.45
<0.30 + Vaporous
T.*
Ash Equivalent
of Coal
Station CS:
>8.2
5.1-8.2
3.4-5.1
2.4-3.4
1.5-2.4
0.77-1.5
0.47-0.77
0.32-0.47
<0.32 +' Vaporous
E*
Ash Equivalent
of Coal
Concentrations ;
As
64
69
70
71
75
72
74
87
695
82
15.6
33
57
62
89
75
77
90
140
770
95
34
Cd
7.0
5.9
6.5
9.0
8.0
5.0
6.0
13
51
7.7
11.7
4.0
3.0
3.8
5.0
4.4
5.5
6.5
5.5
89
7.6
6.1
Cr
125
110
107
110
96
89
99
115
515
110
182
225
205
200
220
190
200
205
340
570
221
114
Cu
265
320
275
310
375
445
475
490
1760
380
182
330
320
360
400
430
500
585
600
1140
408
123
Mn
235
225
250
285
330
355
320
265
2420
325
312
630
605
670
690
875
950
1070
1010
1930
860
298
Ni
112
126
119
95
106
127
165
130
295
122
91
155
131
127
129
130
148
148
290
130
144
45
...
>s UB/8
Pb
49
45
54
60
78
47
92
87
—
87
140
140
150
180
?00
210
220
210
NA
103
- ~ —
Se
110
120
145
170
185
255
305
420
8780
330
15.6
59
44
42
43
42
32
31
84
3160
145
15.8
— =— -
Zn
135
140
125
165
185
240
275
315
4250
253
152
365
265
245
225
275
315
600
1290
6200
550
57
•---- -= — =.-_=•=»-=„—
Ash Fraction
Ti Distribution (%)
8780 9.5
11.4
16.6
11.6
20.9
17.2
8.6
8080 2.7
(8430)** 1.6
00
100.0
8700
8800 15.3
6.8
10.1
10.4
16.6
21.8
13.2
9870 2.5
(9430)** 3.3
100.0
8680
All values represent the average of duplicate determinations.
*Mean concentration of flue gas particulate fractions determined by combining the individual concentrations in proportion to the
ash distribution by Andersen collection
**Titanium values are the average of largest and finest Andersen ash fraction concentrations.
-------
TABLE 6-5. ELEMENTAL ENRICHMENT RATIOS* OF ANDERSEN COLLECTED FLY ASH FACTIONS
Fly Ash
Size
Fraction (|Jm)
Station HS:
>8.0
5.0-8.0
3.3-5.0
2.3-3.3
1.5-2.3
0.74-1.5
0.45-0.74
0.30-0.45
<0. 30 + Vaporous
£**
Station CS:
>8.2
5.1-8.2
3.4-5.1
2.4-3.4
1.5-2.4
0.77-1.5
0.47-0.77
0.32-0.47
<0.32 + Vaporous
£**
Concentrations as Mg/g
As
4.L
4.4
4.5
4.6
4.8
4.6
4.7
5.6
44.6
5.2
1.0
1.7
1.8
2.6
2.2
2.2
2.6
4.1
22
2.8
Cd
0.6
0.5
0.6
0.8
0.7
0.4
0.5
1.1
4.4
0.7
0.7
0.5
0.6
0.8
0.7
0.9
1.0
0.9
14.5
1.2
Cr
0.7
0.6
0.6
0.6
0.5
0.5
0.5
0.6
2.8
0.6
2.0
1.8
1.8
1.9
1.7
1.8
1.8
3.0
5.0
1.9
Cu
1.4
1.8
1.5
1.7
2.0
2.4
2.6
2.7
9.7
2.1
2.7
2.6
2.9
3.2
3.5
4.0
4.8
4.9
9.3
3.7
Mn
0.8
0.7
0.8
0.9
1.1
1.1
1.0
0.8
7.8
1.0
2.1
2.0
2.2
2.3
2.9
3.2
3.6
3.4
6.5
2.9
Hi
1.2
1.4
1.3
1.0
1.2
1.4
1.8
1.4
3.2
1.3
3.4
2.9
2.8
2.9
2.9
3.3
3.3
6.4
2.9
3.2
Pb
0.6
0.5
0.6
0.7
0.9
0.5
1.0
1.0
—
—
1.4
1.4
1.4
1.7
1.9
2.0
2.1
2.0
—
—
Se
7.0
7.2
9.4
11.0
11.8
16.3
19.5
27
563
21
3.7
2.8
2.6
2.7
2.6
2.0
2.0
5.3
200
9.2
Zn
0.9
0.9
0.8
1.1
1.2
1.6
1.8
2.1
30
1.7
6.4
4.6
4.3
3.9
4.8
5.5
10.5
23
109
9.7
Ash Fraction
Distribution (%)
9.
11.
16.
11.
20.
17.
8.
2.
1.
100
15.
6.
10.
10.
16.
21.
13.
2.
3.
100%
5
4
6
6
9
2
6
7
6
3
8
1
4
6
8
2
5
3
*Ratlo of ash fraction concentration to ash equivalent concentration of coal
**Mean enrichment of flue gas particulate fractions determined by combining the individual values in proportion to the ash
distribution by Andersen collection.
-------
6 .4 Enrichment Model
To evaluate the dependence of trace element concentra-
tion (enrichment) of fly ash on particle size, the results of
this study have been compared with the volatilization/recondensa-
tion model reported by Davidson, Natusch, and Wallace (DA-105).
This model assumes:
• elements are partially or totally volatilized
during combustion
« volatile elements either partially or totally
recondense or adsorb on entrained particles
(fly ash) in the flue gas
• elements uniformly recondense or adsorb on all
particles according to their available surface
area
• specific surface area increases as particle size
deminished due to the surface area to volume ratio
• fly ash particles are spherical in shape
• the concentration of an element in the bulk
ash particle (excluding condensed contribution)
is independent of particle size
If element X is uniformly deposited (condensed or adsorbed)
on a spherical ash particle and also uniformly contained throughout
the bulk particle, the total concentration for element X can be
defined by the equation:
C* = Cu + C • SSA (6-3)
•"• D S
73
-------
where,
Cx -
CL, = bulk concentration of element x (yg/g)
C = total concentration of element x (yg/g)
X
C = surface concentration of element x (ug/m )
s
SSA = specific surface area of particle. (m3/g)
For spherical particles specific surface area is defined as
OCA - A _ A _ ID2 _ 6
DbA — — = — -, = 7 «rT\9 — — T7
m pv p'i/6 fiD3 pD
where ,
A = particle surface area
m = particle mass
p = particle density
V = particle volume
D = particle diameter
Assuming particle density is not a function of size, the total
concentration of element x is proporational to the- inverse diameter.
By combining Equation 6-3 with Equation 6-4:
Cx • CB + Cs ' fff C6-5)
Cx = CB +K'C8-D-' (6-6)
For purposes in this study, the comparison of concentra-
tion versus inverse diameter is complicated by an additional variable
the difference in feed coal at each plant. Normalizing the ash con-
centrations to the coal ash concentration (formulization of enrich-
ment ratios presented in Table 6-5) removes the effect of differing
trace element concentrations in the feed coals. Since the enrich-
ment ratio of an ash fraction is directly proportional to the con-
centration (Equation 6-2) , enrichment is proportional to the inverse
diameter.
74 .
-------
ER a D'1
Figures 6-7 through 6rl5 are the resulting plots for
the trace element enrichment data versus the inverse diameter
of the Andersen cascade impactor ash fractions.
The diameter used in the plots is the geometric mean
diameter. The geometric mean diameter in microns for each ash
t
fraction j is obtained from the upper and lower DSQ cut-off
diameters of the Andersen plates:
Geometric mean diameter = D =J(D50j) (D50j-i) (6-7)
For the largest fraction DSOJ is determined from the largest parti-
cle observed in the SEM photographs. In the case of the finest
fraction, D50J_i is defined as one-half of D50j. This assumption
may cause less confidence in the diameter of the finest ash
fraction than the other fractions. Therefore error ranges have
been added to enrichment plots for the finest fractions.
A linear least squares fit of the enrichment data for
each of the nine elements is also presented in enrichment plots.
The fit includes all points except the finest (WEP) fraction,
which has been omitted from the calculation due to the undetermined
volatile element contribution which is independent of particle
diameter. However, comparison of the observed enrichment of the
WEP fraction with the value predicted from the linear least squares
enrichment fit provides an'estimate of volatile trace elements
collected in the WEP sampler:
% volatile'WEP = Enrichment (Measured-Predicted) x 10Q (f^8)
Enrichment Measured
75
-------
8
i
ce
iu
FIGURE 6-7
ARSENIC ENRICHMENT VERSUS DIAMETER^
GHS
76
02-26:
-------
100
9
8
7
6
5
3 •
10
9
8
7
S
OE
t-
a
c
U)
i—B-
h--O-
345
(Dgm) "1
FIGURE 6-8
CADMIUM ENRICHMENT VERSUS DIAMETER'1
0HS
Qcs
77
02-262
-------
111
(Ogm)
-1
FIGURE 6-9
CHROMIUM ENRICHMENT VERSUS DIAMETER'
•1
©HS
78
02-2621
-------
(Dgm)
-1
FIGURE 6-10
COPPER ENRICHMENT VERSUS DIAMETER*1
OHS
79
02-26Z
-------
100.
3
s
7
6
5
oc
10.
9
8
7
6
5
4
1
Ul
1.0
y
8-
7
8-
3 4
(Dam)
FIGURE a-11
LEAD ENRICHMENT VERSUS DIAMETER
O US
E3 cs
80
-------
2
CE
LU
2
100
9
8
7
6
5
10
9
a
7
6
5-
4-
3-
2-
00
0
3 4
(Ogm)
-T"
5
T"
6
FIGURE 6-12
MANGANESE ENRICHMENT VERSUS DIAMETER
-1
O HS
Qcs
81
02-262!
-------
FIGURE 6-13
NICKEL ENRICHMENT VERSUS DIAMETER'1 Q HS
Qcs
82
02-262"
-------
FIGURE 6-14
SELENIUM ENRICHMENT VERSUS DIAMETER
-1
QHS
Qcs
83
02-2622
-------
©US
RGURE 6-15
ZINC ENRICHMENT VERSUS DIAMETER
-1
84
02-2623
-------
Table 6-6 presents the volatile mass contribution for
each element to the total element mass collected in the finest ash
fraction with the WEP sampler.
6.5 • Discussion of Results of Enrichment Study
Figure 6-16 graphically summarizes the enrichment
study. Several types of comparisons are evident from this presenta-
tion:
« effect of sampling method,
« comparison of results from the two
stations, and
e comparison of behaviors shown by
different elements.
6.5.1 Effect of Sampling Method
Fly ash collected by the two methods was analyzed for
eight common elements. A comparison of average enrichment of the
fly ash determined for cyclone collected and cascade impactor
collected samples at each station is presented in Table 6-7.
Enrichment results of cascade impactor samples versus cyclone
collection are higher at both plants for manganese, selenium, and
zinc. Enrichment results of cyclone collection samples are higher
for cadmium, chromium, and nickel at both plants. A comparison
of results for the eight elements indicate higher overall en-
richment by cascade impactor collection at the hot-side
station and by cyclone collection at the cold-side station.
However, at the 95% confidence level there is not a significant
difference for all elements to indicate collector bias on the
results.
85
-------
TABLE 6-6. % VOLATILE TRACE ELEMENTS IN WET
ELECTROSTATIC PRECIPITATOR COLLECTOR*
HS WEP
As
Cd
Cr
Cu
Mn
Ni
Se
Zn
86
58
76
62
87
42
93
89
(82-87)
(40-71)
(73-78)
(52-68)
(86-88)
(34-48)
(90-94)
(86-92)
CS WEP
77 (70-81)
91 (90-92)
33 (18-43)
27 (10-39)
28 (12-38)
**
97 (96-98)
70 (58-78)
*Determined by comparison of measured WEP enrichment with the
enrichment model.
**Enrichment not detected.
Results indicate the analyzed value and range.
86
-------
100
10
•u
0)
e
o
d
w
0.1
-t-
-f-
HS CS HS CS HS CS HS CS HS CS HS CS HS CS
Fluorine Mercury Zinc Copper Nickel Chromium Manganese
o
•rH
10
0.1
-l-
-H
HS CS HS CS HS CS HS CS HS CS HS CS
Cadmium Beryllium Uranium Titanium Selenium Arsenic
• HVSASS Cyclone Collection of Fly Ash
• Andersen Collection of Fly Ash
Figure 6-16- Average Enrichment of Fly Ash (Station HS vs Station CS)
8'7
-------
TABLE 6-7. COMPARISON OF ENRICHMENT RESULTS OF
CYCLONE AND CASCADE IMPACTOR SAMPLERS
Enrichment Ratio
Element
As
Cd
Cr
Cu
Mn
oo Ni
oo
Se
Zn
*2(C-CI)
(C+CI)
Cyclone
3.8
.85
.92
1.6
.66
1.4
6.3
1.2
Cascade
Impactor
5.2
.70
.60
2.1
1.0
1.3
21.
1.7
Mean ± 2 a
Difference*
-.31
+ .19
+.42
-.24
-.41
+.07
-1.08
- .34
- .21 ± .24
Enrichment Ratio
Cyclone
2.8
2.6
3.1
'27.
2.6
4.7
3.3
72
Cascade
Impactor
2.8
1.2
1.9
3.7
2.9
3.2
9.2
109
Difference*
.00
+ .74
.48
1.52
-.11
+ .38
-.94
-.41
.20 ± .36
-------
6.5.2 * Comparison of Results for the Two Stations
The mean concentration of the elements studied in the
flue ash particulate fractions indicated enrichment (i.e,
enrichment factor >1.0). The following exceptions were noted
at each plant:
Hot-Side Fly Ash . Cold-Side Fly Ash
Beryllium Manganese Titanium
Cadmium Titanium
Chromium Uranium
Fly ash exiting the cold-side ESP is generally more
enriched for all elements. Noted exceptions to this trend were
arsenic and selenium which exhibit higher enrichment in the hot-
side fly ash. These two elements may partially condense prior
to cold-side ESP particulate removal.
A definitive explanation of the observed enrichment
phenomena is clouded by two conditions:
• difference in feed coals, and
* particulate loading of the flue
gas exiting the precipitator.
Although the two sites were selected primarily with the particu-
late control device in mind, their use of similar feed coals was
considered as well. Analysis of the two coals (both low sulfur
sub-bituminous coal from Wyoming) identified different physical
and chemical characteristics. Specifically, although the mineral
and trace element content are similar, the distribution of
89
-------
trace elements with the organic/inorganic phase of the coal were
quite dissimilar (Tables 5-1 and 5-4).
During the sampling periods the average particulate
loading of the flue gas exiting the hot-side precipitator was
almost five times higher than that of the cold-side ESP. This
provided greater surface area for condensation to occur at
Station HS, possibly diluting the condensation effect expected
under ideal particulate removal operation.
6.5.3 Comparison of Elemental Behavior Between the Two Stations
Of the 15 elements in the study, all are discussed in
this section:
Arsenic Copper Nickel
Beryllium Fluorine Selenium
Cadmium Lead Titanium
Calcium Mercury Uranium
Chromium Manganese Zinc
Lack of information for calcium and lead enrichment in the WEP
prevent complete enrichment characterization.
Table 6-8 contains a summary of the behavior of the
elements. Important observations listed there and discussed
for each element in the following paragraphs include .-
« coal comparison - highest trace
element concentration.
e coal comparison - highest association of
element in organic (ash-free) phase.
90
-------
TABLE 6-8.
Element
Arsenic
Beryllium
Cadmium
Calcium
Ctirumium
Copper
Fluorine
Lead
MtJUgtlllCtie
Mercury
Nickel
Selenium
Titanium
Uranium
Zinc
Highest
Concentration
In Coal
CS
US
US
US
-
=
=
CS
CS
us
us
CS
CS
CS
us
Highest Organic
Association In Coal
(HS/CS)
CS
CS
CS
HS
CS
CS
CS
CS
HS
CS
us
CS
CS
CS
CS
(0/15)
(82/98)
(0/65)
(94/60)
(67/87)
(18/37)
(52/58)
(0/66)
(78/75)
(0/40)
(89/82)
(10/56)
(32/73)
(63/71)
(0/55)
Average Fly A!
HS
E*
0
D
ND
D
E
£
ND
D
E
E
E*
D
D
E
3h Enrichmentt
CS
E
E*
E*
ND
E*
E*
E*
ND
E*
E*
E*
£
D*
E*
E*
Enrichment Enrichment Progressive Enrichment
All Fractions HEP Fraction with Fine Particulates
HS CS HS CS HS CS
XXX
X
X
ND ND
X X
XXX
XXX
ND ND
X X
X
XXX
XXX
X
X X
X X
X
X
ND
X
X X
X X
ND
X
X
X
X X
X
X
X
X
X
X
X
X
X
X
X
I'E - Enrichment, D - Depletion, * Station with Higher Enrichment ND - Not Determined,
-------
• fly ash comparison - enrichment or
depletion of total flue gas particu-
late fractions and station with
highest enrichment,
o fly ash comparison - enrichment of
WEP (finest particulate and vapor)
fraction, and
• fly ash comparison - identification
of elements exhibiting progressive
(or increased) enrichment from the
larger to the finest particulate
fractions.
Arsenic
Arsenic is enriched in all fly ash fractions at both
stations. Corresponding fractions of the hot-side precipitator
are more enriched than the cold-side fractions. This may be
explained by condensation and subsequent removal of arsenic
with the larger particulates in the cold-side precipitator. The
Andersen results (Table 6-5) show progressive enrichment from
the larger to finer particulates, with highest arsenic enrich-
ment associated with the fine/vaporous fraction. This enrichment
increase, of the WEP fraction appears to result primarily from
collected arsenic vapor exiting the hot-side and cold-side ESP's.
Although associated with the inorganic phase of the coal, the
cold-side coal has a slightly higher organic association (HS-070,
CS-15%). This association does not seem to greatly affect the
enrichment results.
92
-------
Beryllium
Beryllium enrichment is identified only in the WEP
(fine ash and vapor fraction) for both stations in Table 5-3.
Observing the lower total enrichment ratio for the hot-side ESP
fly ash, less beryllium appears associated with Station HS fly
ash. Although beryllium is found in higher concentration in the
Station HS coal, this element displays higher organic association
in CS Coal (98% compared to 82% in HS Coal). This organic asso-
ciation may account for greater Be enrichment levels in Station
CS fly ash, since organically associated elements may be more
likely volitalized during combustion than elements bound in the
mineral phase.
Cadmium
The results for cadmium are similar to beryllium.
Andersen collected ashes show a depletion of cadmium in the
larger fractions. This is also true for cyclone collected ash
except for the largest fraction at Station CS. Increased cad-
mium enrichment is observed in the finest fraction at each
station, with higher enrichment at Station CS. While a higher
concentration was noted for HS Coal (HS, 0.90; CS, 0.70 ppm),
the degrees of organic association in the two coals are quite
different (HS - 0%, CS - 65%). The higher organic association
of cadmium in CS Coal is identified with increased volatilization
and subsequent enrichment of the finest fractions.
Figure 6-8 shows higher enrichment of cadmium at the
cold-side station. The deviation of the WEP concentrations from
the extrapolation of particulate fraction results indicate that
most of the cadmium collected by the WEP is in the vapor
state (58% at Station HS and 91% at Station CS).
93
-------
Calcium
Calcium enrichment of fly ash was found at both plants
(Table 6-3). Although not usually considered by most investigators
as an element displaying enrichment, results of a three station
study (RA-219) identified higher calcium content in the flue gas
Chan anticipated by from the ash content.
Flue Gas Flue Gas
Ash Distribution (%) Ca Distribution^)
Station I .3 .85
Station II .7 .8
Station III 12.9 16.6
Calcium is associated with the organic phase in both
coals (HS-94%, CS-607o); with the stronger association in the hot-
side coal. Insufficient results prevent the comparison of phase
association with enrichment.
Chromium
Station HS Andersen fractions are depleted in chromium
with exception of the WEP (fines and vaporous). All fractions at
Station CS are enriched. The chromium content of the two coals
are almost equivalent; however, again for CS Coal, chromium is
more organically associated (HS - 6770, CS - 87%) . The enrichment
curves presented in Figure 6-9 support the chromium enrichment of
ash fractions from cold-side collection, and chromium depletion
in the hot-side ash fractions. Estimation of possible vapor con-
tribution to the hot-side WEP collector was 76%.
Copper
All ash fractions are enriched in copper, and a pro-
gressive increase in enrichment is noticed from the larger to
the finer particulates. Total enrichment is higher at Station CS
and condensation of copper on ash particles is the expected
94
-------
mechanism at both plants. From Figure 6-10 the volatile con-
tribution to the WEP is more significant at the hot-side station
(62% at Station HS and 27% at Station CS). Equal concentrations
of copper are found in the two coals, yet in Coal CS, the copper
is more organically associated (HS - 18%, CS - 37%). Organic
association of the element is noted with higher enrichment of
the resulting fly ash.
Fluorine
Fluorine is enriched in all cyclone ash fractions.
A surprising observation is the very high fluorine content of
the finest CS fraction (Table 6-3). Although this WSP collected
fluoride is assumed to be vaporous, the increased amount at
Station CS is unexplained. Inlet fluorine content of the coals
is approximately equal, and organic association of CS Coal is
slightly higher (HS - 52%, CS - 58%). The increased content of
fine particulate and vapor phase fluorine at the cold-side station
is noted with only slightly higher organic association with the
feed coal.
Manganese
Andersen collected fly ash from Station CS is enriched
in all fractions and progressive enrichment of manganese is ob-
served in the finer ash particles (Figure 6-12). The finest ash
fraction at each station is enriched; however, the larger particles
at Station HS are depleted in manganese and no strong enrichment
trend with particle size is identified. Enrichment by condensation
is apparent at Station CS (Figure 6-12); however, the high enrich-
ment of the fines and depletion of larger particles at Station HS
are not indicative of condensation. Eighty-seven percent of the
manganese present in the hot-side WEP is estimated to be vaporous
(28% at Station CS). Manganese concentration is higher in Coal CS
95
-------
and both coals have approximately equal association of manganese
with the organic phase (HS - 787,, CS - 75%) .
Mercury
Mercury is primarily associated with the WEP collected
fraction. Vapor phase presence of mercury has been documented
in past studies (BI-060, DI-043). A lower vapor phase mercury
emission was" identified with both plants in this study than the
reported emission of 9070 total inlet mercury with the flue gas
in the above studies. The mercury in Coal CS is more organically
associated (HS - 0%, CS - 4070) and resulting fly ash is more
enriched.
Nickel
All ash fractions are enriched in nickel with the cold-
side ash exhibiting predominantly higher enrichment. Enrichment
curves (Figure 6-13) indicate the WEP samples do not fit the model
Approximately 40% of the nickel in HS WEP appears to be vaporous.
The WEP sample for Station CS contains approximately one-third
the expected nickel content.
Lead
Lead is more enriched in cold-side ash fractions. Both
the lead content and organic phase association of the lead are
higher for CS Coal. Higher enrichment of the cold side ash frac-
tions are the result of condensed vaporous lead. No estimation
of volatile lead in flue gas was possible for the two stations.
Selenium
Selenium is primarily associated in the vapor phase,
with partial condensation on ash particles at Station HS
96
-------
(Figure 6-14). Station CS ash displays no strong enrichment
trend in the Andersen particulate fractions, yet the follow-up
WEP collector is highly enriched in selenium. The higher enrich-
ment of larger ash fractions (>2 urn) as compared to .5-1 vim,
identifies possible condensation of selenium prior to particulate
removal by the ESP and subsequent removal of selenium with the
precipitator ash. Organic association is more pronounced for
Coal CS (HS - 10%, CS - 56%).
Titanium
Titanium exhibits no enrichment in the cyclone collected
ash fractions. However, no noticeable depletion is observed.
This is consistent with previous findings (RA-219) in which the
titanium distribution was similar to ash distribution at Station HS.
Ash Ti
Distribution (%) Distribution (%)
Bottom Ash 22.2 21.1
Precipitator 77.1 78.3 .
Fly Ash 0.7 .0.6
Titanium of Coal CS is more organically associated
(A - 32%, B - 73%); however, this association, as well as cooler
temperature of the ESP, does not affect distribution of this element
Uranium
Analysis of cyclone fractions resulted in enrichment
of all ash fractions at Station CS and only the finest fraction
at Station HS. Total enrichment of flue gas particulate fractions
at the lower temperature of Station CS was approximately twice
that of Station HS. Uranium in Coal CS has a slightly higher
organic association (HS - 63%, CS - 71%) and Coal CS uranium
concentration was roughly twice that of Coal HS. The enrichment
97
-------
factor normalizes that increased coal concentration, so it
appears uranium associated with the organic fraction is condensing
on ash particles.
Zinc
Zinc, though depleted in the large particles at Station
HS, displays a progressive increase in enrichment with decreasing
particle size at both stations. Higher total flue gas enrichment
is noted at Station CS. The zinc content of Coal HS was twice
that of Coal CS. The association of zinc with the ash-free coal
fraction (organic) was more pronounced for Coal CS (HS - 0%,
CS - 55%). The observed progressive enrichment is indicative
of condensation. However, the increased enrichment of the finest
fraction at each station appears to be higher than anticipated
from condensation. In Figure 5-14, this increase of zinc content
of the WEP fractions when compared with the expected value sug-
gests that the following percentage of that fraction is vaporous:
Hot-Side WEP fraction - 89%
CoId-Side WEP fraction - 70%
98
-------
-------
7.0 TRACE ELEMENT EMISSIONS
A comparison of the emissions of the two electrostatic
precipitators was performed to compare total trace element
emissions and potential volatile emissions. Tables 7-1 and
7-2 present the comparative results.
7.1 Total Trace Element Emissions
Total trace element emissions for each element were
calculated based on cyclone collected ash distribution, average
particulate loading, and flue gas flow rate. The emissions in
terms of lb/105 tons dry coal are presented in Table 7-1 In
general, emissions are higher at the hot-side station due to
the higher particulate loading. Exceptions are copper, fluorine,
mercury, and zinc. These four elements are more organically
associated in the cold-side coal indicating a possible correlation
between organic association and enrichment.
For several elements significant amounts (>40%) of
the element's total emission are in the WEP fraction associated
with the cyclone collection system. The WEP fraction contains
both volatile elements and the finest particulate fraction.
Those elements with significant emissions in the finest ash
fraction include:
Station HS Station CS
Beryllium Beryllium Mercury
Cadmium Cadmium Nickel
Fluorine Chromium Selenium
Mercury Copper Zinc
Fluorine
99
-------
TABLE 7-1. STACK EMISSION OF ELEMENTS DETERMINED FROM CYCLONE COLLECTION
Fly Ash
Fraction
Station HS:
Cyclones
1 6. 2
(2. OM)
Cyc lone 3
(0.8M)
HEP (<0.8u
+ Vaporous)
Total Emission
Total Inlet
with Coal
Station CS:
Cyclones
1 & 2
(1.9M)
Cyclone 3
(0.9u)
WEP (<0.9M
+ Vaporous)
Total Emission
Total Inlet
with Coal
Concentration as lb/105
As
15.5
7.2
1.5
24
240
2.1
2.6
1.0
5.7
780
Be
0.80
0.28
1.00
2.1
210
0.14
0.13
0.65
0.92
170
Cd
1.3
1.1
1.6
4.0
180
0.21
0.08
0.65
0.94
140
Cr
40
13
15,
68
2800
6.5
5.6
8.8
21
2600
Cu
63
42
15
120
2800
5.8
10.0
182
198
2800
F
230
115
1370
1715
10400
16
28
3620
3660
10800
Hg
0.064
0.013
4.0
4.0
28
0.003
0.003
4.9
4.9
22
Tons Dry Coal
Mn
51
28
5.0
84
4800
15
24
6.9
46
6800
Ni
27
12
12
51
1400
3.2
3.0
6.6
13
1020
Se
16
9.5
15
40
240
0.51
•
0.72
1.9
3.1
360
Ti
2190
910
170
3300
1.3xl05
195
220
86
500
2.0xl05
U
2.6
1.1
0.41
4.1
180
0.51
0.55
0.42
1.5
400
Zn
32
26
14
72
2300
6.1
7.6
230
244
1300
Ash
2.67xl05
1.16xl05
2.11x10"
4.04X105
1.54xl07
2.45X101*
2.49X1011
1.02x10"
5.96x10"
2.28xl07
-------
7.2 Volatile Trace Element Emissions
Although volatile trace element content of the flue gas
was not measured directly, an estimation was made of the volatile
contribution to the wet electrostatic precipitator. Since limi-
ted data appears in the literature, estimated volatile emissions
have been reported in this section. Ranges have been assigned
to identify uncertainties in the values„
Based on the enrichment versus particle size correla-
tions (Figures 6-7 to 6-15) the volatile contribution to the
Andersen associated WEP was estimated for 8 elements. Table 6-6
presented estimates of the fraction of the elements in the WEP
which were collected as vapors in the flue gas. In Table 7-2
these vaporous emissions are presented as the estimated fraction
of each element entering with the coal which is exiting the
stack as a vapor. This method of presentation normalizes the
different coal compositions and facilitates comparison.
Table 7-2. ESTIMATED VOLATILE TRACE ELEMENT EMISSIONS
FROM IMPACTOR COLLECTION
Hot-Side Station Cold-Side Station
(Amount %)(Amount %)
As 1.6 - 1.7 .19 - .22
Cd .08 - .13 .16 - .16
Cr .09 - .10 .01 - .03
Cu .22 - .29 .01 - .05
Mn .3 - .31 .024 - .076
Ni .051 - .072 **
Se .22 - .24 2.5 - 2.5
Zn 1.16-1.24 .83-1.1
(*) Ratio of mass of element volatile in flue gas to mass of
element entering with feed coal.
** No volatile contribution observed.
10L
-------
-------
8.0
Control Effectiveness at Each Station
To evaluate the removal efficiency of a control device
(ESP), the inlet and outlet gas streams must both be character-
ized. In this study, the inlet gas streams to the ESP's were
not sampled. Therefore, the collection efficiency of the con-
trol device cannot be determined.
However, with the feed coalcharacterization at each
plant, the total plant collection (removal) efficiency can be
defined.
Table 8-1 presents the collection efficiency of each
plant defined by identifying total emissions from each plant and
the total inlet with the feed coal (from Table 7-1) under the
operation conditions of each plant during the sampling period.
Emissions at each plant during the sampling period are
not necessarily representative of maximum control device (ESP)
collection efficiency.
TABLE 8-1.
Element
As
Be
Cd
Cr
Cu
F
Hg
Mn
Ni
Se
Ti
U
Zn
Ash
CONTROL EFFICIENCY
Hot-Side Station
90.0
99.0
97.8
97.6
95.7
83.5
85.7
98.2
96.4
83.3
97.5
97.7
96.9
97.4
OF TRACE. ELEMENTS (%)
Cold-Side Station
99.3
99.4
99.3
99.2
92.9
66.1
77.7
99.3
98.7
99.1
99.8
99.6
81.2
99.7
102
-------
-------
BIBLIOGRAPHY
BI-060 Billings, Charles E., et al., "Mercury Balance on a
Large Pulverized Coal-Fired Furnace", J. APCA 23(9),
773 (1973).
BO-124 Bolton, N. E., et al., Trace Element Measurements at
the Coal-Fired Allen Steam Plant. Progress Report,
June 1971-January 1973. Oak Ridge National Laboratory,
March 1973.
BR-452 Brown, J. and A. Guest, Continuing Analysis of Trace
Elements in Coal. Toronto, Ontario, Hydro-Electric
Power Commission of Ontario, June 1973.
CO-342 Cowherd, C., Jr., Hazardous Emission Characterization
of Utility Boilers. Publication No. EPA-650/2-75-066.
Midwest Research Institute, July 1975.
DA-105 Davison, Richard L. , et al., "Trace Elements in Fly
Ash. Dependence of Concentration on Particle Size",
Env. Sci. Tech. 8(13), 1107, (1974).
DI-043 Diehl, R. C., et al., Fate of Trace Mercury in the
Combustion of Coal. TPR - 54. Pittsburgh, Pa.,
Pittsburgh Energy Research Center, 1972.
FI-167 Fisher, G. L. , et al., "Size Dependence of the Physical
and Chemical Properties of Coal Fly Ash", Preprints,
ACS, Division of Fuel Chemistry 22(4), 149, (1977).
GL-077 Gluskoter, H. J., et al., Trace Elements in Coal:
Occurrence and Distribution. Publication No. EPA-600/
7-77-064. Urbana, Illinois, Illinois State Geological
Survey, June 1977.
103
-------
Cont'd
GO-075 Goldberg, A. G., A Survey of Emissions and Controls
for Hazardous and Other Pollutants. NTIS Publication
No. PB 223 568. Washington, D. C., EPA, 1973.
GO-252 Goldschmidt, V. M., "Rare Elements in Coal Ashes",
Ind. Eng. Chem. 27(9), 1100 (1935).
GO-253 Gordon, G. E., et al., Study of the Emissions from
Major Air Pollution Sources and Their Atmospheric
Interactions. Prepared for the National Science
Foundation for the Period 1 November 1972 - 31 October
1974. College Park, Maryland.
HO-417 Horton, L., and K. V. Aubrey, "The Distribution of
Minor Elements in Vitrain: Three Vitrains from the
Barnsely Seam", J. Soc. Chem. Ind. 69 (Supplement No.
1), S41 (1950).
KA-192 KaaKinen, J. W., et al., "Trace Element Behavior in
Coal-Fired Power Plants", Environ. Sci. Tech. 9(9), 862
(1975).
KL-085 Klein, D. H., et al., "Pathways of Thirty-Seven Trace
Elements Through Coal-Fired Power Plants", Environ. Sci.
Tech. 9(10), 973 (1975).
KU-175 Kuhn, J. K., and N. F. Shimp, "Determination and
Mobility of Organically Associated Trace and Minor
Elements in Coal", Paper presented at Federation of
Analytical Chemistry and Spectroscopy Societies -
Convention, October 30 - November 3, 1978, Illinois
State Geological Society, Urbana, Illinois .
104
-------
Cont'd
LE-289 Lee, Robert E., Jr., et al., "Concentration and size
of trace metal emissions from a power plant, a steel
plant, and a cotton gin", Env. Sci. Tech. 9_(7), 643
(1975).
ME-150 Mezey, E. J., Surjit Singh, and D. W. Hissong, Fuel
Contaminants. Vol. 1. Chemistry. EPA-600/2-76-177a,
EPA Contract No. 68-02-2112, Columbus, Ohio, Battelle-
Columbus Laboratories, July 1976.
NI-095 Nicholls, G. D., "The Geochemistry of Coal-Bearing
Strata", in Coal and Coal-Bearing Strata. American
Edition. D. Murchison and T. S. Westoll, Editors.
New York, Elsevier, 1968. pp. 269-307.
RA-219 Radian Corporation, Coal-Fired Power Plant Trace
Element Study, 4 Volumes, Austin, Texas, Radian Corp.,
September 1975.
RE-295 "Researchers to Further Identify Pollutants", EPRI
Journal, Vol 2(10), 31 (1977).
RU-039 Ruch, R. R., J. H. Gluskoter, andN.,F. Shimp. Occur-
rence and Distribution of Potentially Volatile Trace
Elements in Coal, Final Report, Environmental Geology
Notes No. 72, EPA-650/2-74-054. Urbana, Illinois,
Illinois State Geological Survey, 1974.
TO-087 "Toxics on Stack Particle May Be More Hazardous",
Environ. Reporter, September 2, 1977.
ZU-019 Zubovic, P., et al., 1960-1976, Trace Elements in Coal
Occurrence and Distribution, as cited in GL-077.
105
-------
-------
APPENDIX A
SAMPLING
-------
-------
1.0 INTRODUCTION
Two coal-fired boilers were selected for study to
define the occurrence and distribution of trace elements as a
function of particle size in the fly ash emitted from the units.
The two facilities selected have the same boiler configuration
and are fired with similar coals. They differ in the placement
of their electrostatic precipitators (ESP) relative to the com-
bustion air preheaters. Station HS has a "hot-side" ESP; that
is, the precipitator is upstream of the combustion air preheater.
Station CS has the ESP positioned downstream of the combustion
air preheater; this is known as a "cold-side" ESP. As the
initial task of this program, Radian personnel sampled Station
HS during the period September 2-16, 1976 and Station CS during
the period September 20 - October 1, 1976.
Fly ash emitted from the plant stack was collected by
size fractions using three different methods. In addition samples
of the coal were collected. Analysis of these samples provided
data to study the distribution of trace elements as a function
of particle size and also provided information on the probable
mechanisms of trace element inclusion in the emitted particles.
The following sections describe the facilities sampled,
the sampling techniques utilized, and the flow rate measurements
performed.
107
-------
-------
2.0 PLANT DESCRIPTION - STATION HS
Station HS consists of two 350 MW tangentially-fired
boilers. The newer of the two units, Unit 2, was sampled.
Hot-side electrostatic precipitators, upstream of the combustion
air preheaters, designed for flow rates equivalent to 350 MW at
an inlet gas temperature of 830°F are used for fly ash control.
The boiler is fired with sub-bituminous coal transported by rail
from Wyoming, where it is strip mined. The coal typically
contains 30% moisture, 5% ash, 0.5% sulfur and 33% volatile
matter and has a heating value of 8400 Btu/lb. The coal is
initially stored in open piles from which it is conveyed to
five storage silos. Coal from the silos is fed to the mills
where it is pulverized prior to delivery to the boiler through
a pneumatic conveying system.
Pyrites from the mills, economizer ash and bottom ash
are sluiced alternately to an ash pond at approximately 4-hour
intervals. The ash collected in the electrostatic precipitators
is transferred to an ash storage silo by a pneumatic conveyor
system and removed from the plant site by truck. Flue gas exits
the system through a 500-foot stack, approximately 25 feet in
diameter.
A schematic of the station with all sampled streams is
presented in Figure A-l.
2.1 Plant Operation During Sampling
During the sampling period the boiler load varied from
290-355 MW operating essentially at full load during most of the
period. The electrostatic precipitator performance was not con-
sistent throughout the sampling effort. Particulate loading
ranged from 0.03 gr/scf to 0.12 gr/scf.
108
-------
CROSSED COAl
o
I
ELECTROSTATIC
mClPJfATOR
Inlet
Sluice Water
Figure A-l. Schematic of Station HS
-------
2.2 Description of Sampling Points
The sample point locations for coal and flue gas are
indicated in Figure A-l. The following section gives descriptions
of the sampling points and the sampling techniques used at these
points. .Table A-l shows the dates on which each type of sampling
was conducted.
2.2.1 Coal
Five coal feeders (A through E) meter the coal from the
five overhead storage silos to their respective mills for pulver-
ization prior to being fed to the boiler. A coal sample was
collected daily for eight days. The feeders A through E were
sampled sequentially so that the total sample was a compositie
of the coal being fed from all of the silos. The samples were
collected by passing the container through the stream of coal
falling from a conveyor in the feeder to the mill. Each of the
daily samples were stored in one-liter polyethylene containers.
The analytical sample resulted from the combination of daily
samples.
2.2.2 Fly Ash
Fly ash exiting the 500-foot stack in the flue gas
stream at Station HS was sampled through ports located at the
375-foot level, where a work platform was located. The internal
diameter of the stack at this height is 25 feet. The average
flue gas temperature was 315°F.
The sample ports were greater than 10 stack diameters
downstream from the point of entry of the flue gas and therefore
provided a good test plane at the port level. The stack was
equipped with four ports 90° apart, 4 inches in diameter. In
110
-------
TABLE A-l. Sampling Schedule at Station HS
Type of
Sampling Location* 9/2 9/3 9/4 9/5 9/6 9/7 9/8 9/9 9/10 9/11 9/12 9/13 9/14 9/15 9/16
Grain Loading
Andersens
One acfm Cyclones
HVSASS Cyclones
Coal
*Location as noted
2 . . ....... o ' o
2 «• oo.oooo ..
2 ... .. ..
2 ...
1 ........
in Figure A-l.
-------
addition, there were two 10-inch ports 4 feet above the level
of the 4-inch ports.
Velocity and grain loading measurements were taken
at the south port using four traverse points. These points were
selected by dividing the cross-sectional area of the stack into
four equal-area concentric circles and finding the centroid of
the south half of each circle as described in EPA Method 1. The
distances from the inner stack wall for the four points were:
• 10 inches,
• 2 feet 7 inches,
• 4 feet 10 inches, and
• 8 feet.
Velocity measurements were taken daily during sampling.
The average velocity was found to be 61 fps. The velocity
traverses were used to determine the conditions necessary for
isokinetic sampling and to determine the total gas flow through
the stack.
Particulate loading determinations were made on 11 days
during the sampling period with in-stack Gelman filters. These
determinations were made by sampling an equal time at each of
the four points. Thus, the particulate loading value determined
is the average of points sampled. The results of each grain
loading determination are given in Table A-2.
The moisture content of the gas stream was determined
by condensing the moisture in a series of Smith-Greenburg impingers,
them passing the gas through an impinger containing dry preweighed
silica gel. The moisture content of the gas was calculated to be
12.1% based on the weight of water removed and the total volume
of gas metered.
112
-------
TABLE A-2. GRAIN LOADING DATA FOR STATION HS
Grain Loading
Date in gr/scf*
9/2/76 0.028
9/4/76 0.094
9/6/76 0.094
9/7/76 0.093
9/8/76 0.088
9/9/76 0.072
9/10/76 0.080
9/11/76 0.060
9/12/76 0.040
9/14/76 0.039
9/15/76 0.055
Mean ± std. deviation 0.068 ± .024
*60°F, 1
113
-------
2.3 Flow Rate Measurements
The following section describes the methods used to
determine the flow rates of the individual streams at Station HS.
2.3.1 Coal
Coal is fed from the storage silo to the mills by a
series of four feeders. The total throughput of each feeder in
100-pound units is indicated in the control room. Readings from
these feeders were taken at the beginning and end of each day's
sampling; thus, the total amount of coal fed to the boiler could
be determined as a function of time. The coal feed rate for
Unit 2 was determined to be 2.6 x 10s Ib/hr moisture-free coal.
2.3.2 Fly Ash Flow Rate
The flow rate of flue gas from Station HS was determined
to be 1.8 x 106 ACFM using the gas velocity (61 fps) and the
cross-sectional area of the stack at the test plane. The flow
rate of fly ash was determined using the average grain loading
and the flue gas flow rate. The average fly ash flow rate was
5.2 x 102 Ib/hr.
114
-------
-------
3.0 PLANT DESCRIPTION - STATION CS
Station CS consists of four 500 MW boilers of which
Unit I was sampled. The plant design has electrostatic precipi-
tators located downstream of the combustion air preheaters,
hence the term cold-side precipitator. Each boiler is fired
with sub-bituminous coal which is mined near the plant and
transported by truck to the plant site. The coal has an average
heat content of 9700 Btu/lb and contains approximately 1970 moisture,
10% ash and 0.6% sulfur. The coal trucked into the plant is
initially stored in piles at the plant site. Storage silos are
filled from these piles by conveyor. The coal from the silos
is fed to mills where the coal is pulverized and then pneumatic-
ally conveyed to the boiler.
Pyrites from the coal mills, economizer ash and bottom
ash are sluiced simultaneously to a dewatering system approximately
three times per shift. Ash collected in the electrostatic precip-
itator is pneumatically conveyed to a storage silo. This ash is
taken from the plant site by truck. Flue gas exits the plant
through a 500-foot stack which is approximately 24 feet in diameter.
A schematic of the station with the two sampled streams
indicated is presented in Figure A-2.
3,1 Plant Operation During Sampling
During the sampling period, the boiler load on Unit 1
varied from 380-510 MW operating essentially at full load during
the majority of the sampling period. For the first week of
sampling, the precipitator was operated at peak efficiency.
The grain loading was quite low, ranging from 0.008 gr/SCF to
0.022 gr/SCF. During the remainder of the sampling effort, the
precipitator was not operated at peak efficiency, allowing
collection of particulate samples at a faster rate.
115
-------
O>
CnUSMEDCOAl
SILO
MILL
PVniTES
ECONOMIZEn
HOPPER
^f
\
\
\
noiiEn
J
Yxm
ECONOMIZEn ASH
Inlet
Sluice Water
TO' ASH
POND
Figure A-2. Schematic of Station CS
-------
3.2 Description of Sampling Points
The sampling locations are schematically identified
in Figure A-2. The following sections describe the sampling
points and the manner in which each sample was collected. Table
A-3 shows the dates on which each type of sampling was conducted.
3.2.1 Coal
Five coal feeders (A through E) meter the coal flow
from the storage silos to their respective mills for pulver-
ization prior to pneumatic transfer to the boiler. The coal
feeders were sampled sequentially daily by station personnel
passing a container through the coal stream falling from a
conveyor. These samples were stored in one-liter polyethylene
containers. A composite coal sample was formed by combining
these samples.
3.2.2 Fly Ash
Fly ash was collected from the flue gas leaving Station
CS through the 500-foot stack. The sampling station was located
at the 250-foot level on a platform between the inner and outer
walls of the stack. The internal diameter of the stack at this
height is 24 feet. The average temperature of the flue gas was
220°F. The distance between the inner and outer walls of the
stack is approximately 4 feet. This distance prevented traversing
during sampling since a probe of sufficient length could not be
inserted through the sampling ports.
The sample ports were located more than 10 stack
diameters downstream of the entrance of the stack. Therefore,
the sampling location provided a good test plane. The sampling
location was equipped with four ports 90° apart. Each of these
117
-------
TABLE A-3. Sampling Schedule at Station CS
1 M
00
Type of Sampling Location* 9/20 9/21 9/22 9/23 9/24 9/25 9/27 9/28 9/29 9/30 10/1
Grain Loading 2 • ••••••
Andersens 2 ••••••••••
One acfm Cyclones 2 ••••••••••
HVSASS Cyclones 2 «••••••
Coal 1 ••••••••
*Locations as noted in Figure A-2.
-------
was a 10-inch port which had a plate attached which reduced the
port to a 4-inch male pipe fitting. There were also two 10-inch
ports 180° with respect to each other and 45° from the 4-inch
ports. The 4-inch ports were designated as .the north, south,
east and west ports. The 10-inch ports were designated as the
north-west and south-east ports.
Velocity measurements were taken daily from the east
and west ports using three points. These points were selected
by dividing the cross-sectional area of the stack into three
equal area concentric circles and determining the distance from
the centroid of each circle to the inner stack wall as specified
in EPA Method 1. The distances from the inner stack wall for
the .three points were:
• 1 foot 1 inch,
• 3 feet 6 inches, and
• 7 feet 1 inch.
The average velocity of the flue gas was 71 fps. The velocity
traverses were used to determine the sampling rates necessary
for isokinetic sampling and for the determination of total gas
flow through the stack.
Particulate loading measurements were conducted on
7 days during the sampling of Station CS using in-stack Gelman
filters. The grain loading measurements were conducted at the
north-west port. Table A-4 contains the results of these measure-
ments during the sampling period.
The moisture content of the stream was determined by
condensation in a series of Smith-Greenburg impingers and then
final drying in an impinger containing silica gel. The average
moisture content of the flue gas was found to be 9.3%.
119
-------
TABLE A-4. PARTICULATE LOADINGS AT STATION CS
Grain Loading
Date in gr/scf*
9/21/76 0.008
9/22/76 0.013
9/23/76 0.009
9/24/76 0.022
9/25/76 0.008
9/27/76 0.015
9/28/76 0.025
Mean ± std deviation 0.014 ± .007
*60°F, 1 ATM
120
-------
3.3 Flow Rate Measurements
The following section describes the methods used to
determine the flow rates of the individual streams at Station
CS.
3.3.1 Coal
Coal is fed from the storage silos to the mills by a
series of five feeders. The flow of the coal is measured in
100-pound units. The metering devices are located in the control
room. Readings from the meters were taken at the beginning and
end of each day of sampling. From these values the amount of
coal fed to the boilers as a function of time was calculated.
The coal feed rate of Unit 1 was determined to be 5.3 x 10s
Ib/hr.
3.3.2 Fly Ash Flow Rate
The flow rate of the flue gas was determined to be
1.9 x 10s ACFM using the average gas velocity of 71 fps and the
cross-sectional area of the stack at the test plane. The fly
ash flow rate was determined using the flue gas flow rate and
the average grain loading. The average fly ash flow rate was
calculated to be 1.3 x 102 Ib/hr.
121
-------
-------
4.0 PARTICULATE COLLECTION BY SIZE FRACTIONS
Fly ash was collected by size fractions using three
different sampling systems:
• Andersen cascade impactors,
• three one-acfm cyclones, and
• three five-acfm cyclones from
the HVSASS train.
Each of these systems used a wet electrostatic precipitator
(WEP) to collect the "less than" fraction escaping the primary
collection device. The WEP is shown schematically in Figure
A-3. Teflon-lined tubing carried the sample from the primary
collection device to the WEP. The sample entered by bubbling
through the electrolyte reservoir then passed up through a
cylindrical chamber, the walls of which were wetted by the
circulating electrolyte. Collection of fine particulate was
achieved in this area by the 12 KVDC potential between the ,
electrolyte and the center platinum electrode which induces
electrostatic collection. The circulating electrolyte for the
WEP was 57» sulfuric acid. The gas stream then exited the device
and continued to a series of impingers containing 670 hydrogen
peroxide and silica gel for the removal of corrosive gases and
moisture. Upon completion, the sample which includes both the
fine particualtes and vapor phase elements collected by the WEP
is contained in the electrolyte.
The remainder of this section describes the three
primary collection techniques used to collect particulate by
size fractions.
122
-------
Sample
Outlet
1
High Voltage
Power Supply
Platinum Electrode
-WEP 'Body
Peristaltic
Pump
Sample
Inlet
«/ Circulating
Electrolyte
Reservoir
Figure A-3. Wet Electrostatic Precipitator (WEP)
123
-------
4.1 Andersen Cascade Impactors
Particulate entrained in the flue gas was separated
into nine size fractions by an Andersen cascade impactor. This
device is shown schematically in Figure A-4. The Andersen
aerodynamically separates the fly ash particles into size
fractions as they pass through a series of multi-jet stages.
Fine particulates passing through the last impactor stage enter
the previously described WEP via a teflon-lined probe and teflon
tub ing.
During sampling, two Andersen/WEP trains were run
simultaneously. Tables A-5 and A-6 present the sample quanti-
ties collected at each stage with the Andersens at the two
stations.
4.2 One-acfm Cyclones
A series of three cyclones were used in-stack to
collect fly ash in four size fractions. The cyclones were
designed to operate at a. flow rate of one actual cubic foot
per minute and have Dso's of 2.65]_i, 0.96u and 0.60y. They are
constructed of 7075 T6 alloy aluminum and black anodized to
minimize corrosion. The cyclones were used in-stack and
clustered to minimize losses onto the walls of interconnecting
tubing.
The "less than" fraction escaping the last cyclone
was carried to a WEP via a teflon-lined probe and teflon tubing.
Following collection by the WEP, the gas stream entered a series
of impingers to remove moisture, then passed through a leakless
pump and dry gas meter. Particulate which lodged in the probe
was rinsed into the WEP. A summary of particulate collected
using the one-acfm cyclones is given in Tables A-7 and A-8.
124
-------
Plates
Figure A-4. Andersen Mark III Cascade Impactor
125
-------
TABLE.A-5. SUMMARY OF DATA FOR PARTICIPATE COLLECTION BY ANDERSEN CASCADE
IMPACTOR AT STATION HS
Stage
1
2
3
4
5
6
7
8
Size Range
in U
>8.0
5.0-8.0
3.3-5.0
2.3-3.3
1.5-2.3
0.74-1.5
0.45-0.74
0.30-0.45
Total Weight
Collected in g
0.741
0.892
1.300
0.908
1.635
1.344
0.675
0.214
% Fly Ash
Distribution
9.4
11.4
16.6
11.6
20.9
17.2
8.6
2.7
Total Weight Collected by Andersen 7.709 98.4
Total Volume Sampled - 1665 SCF
Ave. Flow Rate - .78 ACFM
WEP <.3 (0.122)* 1.6
Total Weight Collected by WEP - .0352g
Total Volume Sampled - 479 SCF
* Effective particulate collected by WEP for 1665 SCF.
Total Particulate Catch 7.831 100%
Grain Loading - .073 gr/SCF
126
-------
TABLE A-6. SUMMARY OF DATA FOR PARTICIPATE COLLECTION BY ANDERSEN CASCADE
IMPACTOR AT STATION CS
Stage
1
2
3
4
5
6
7
8
Total Wei
Size Range
in V
>8.2
5.1-8=2
3.4-5.1
2.4-3.4
1.5-2.4
0.77-1.5
0.47-0.77
0.32-0.47
Lght Collected b
Total Weight
Collected in g
0.851
0.375
0.559
0.575
0.923
1.207
0.732
0.137
y Andersen 5.360
% Fly Ash
Distribution
15.3
6.8
10.1
10.4
16.6
21.8
13.2
2.5
96.7%
Total Volume Sampled - 4158 SCF
Ave. Flow Rate - .67 ACFM
WEP <.32 (0.183)* 3.3
Total Weight Collected by WEP - .0466g
Total Volume Sampled - 1059 SCF
Total Partiuclate Catch 5.543 100%
Grain Loading - .021 gr/SCF
* Effective particulate collected by WEP for 4158 SCF.
127
-------
TABLE A-7. SUMMARY OF DATA FOR PARTICULATE COLLECTION WITH ONE ACFM CYCLONES
AT STATION HS
Unit
Size Range
in u
Total Weight
Collected in g
Cyclone 1
Cyclone 2
Cyclone 3
WEP
>2.65
2.65-0.96
0.96-0.60
<0.60
5.123
2.713
2.183
Total weight collected by cyclones - 10.019g
Total volume sampled - 1250 scf
TABLE A-8. SUMMARY OF DATA FOR PARTICULATE COLLECTION WITH ONE ACFM CYCLONES
AT STATION CS
Unit
Cyclone 1
Cyclone 2
Cyclone 3
WEP
Siae Range
in y
>2.65
2.65-0.96
0.96-0.60
<0.60
Total Weight
Collected in
2.325
1.245
0.444
S
Total weight collected by cyclones - 4.014g
Total volume sampled - 3022.05 scf
128
-------
4.3 HVSASS Cyclones
The three cyclones from the High-Volume Source
Assessment Sampling System train were used to collect particu-
late by size fractions. The train consisted of a nozzle, 5-foot
probe, and a heated oven containing three cyclones designed to
operate at 4 standard cubic feet per minute. The glass fiber
back-up filter normally used with the HVSASS train was removed
for this study. The flow leaving the smallest cyclone was di-
verted to a tee. Approximately one-fifth of the gas stream was
routed to a WEP and the remainder into the series of high-volume
impingers which are normally used with the HVSASS. These impingers
contained a 6% solution of hydrogen peroxide. The sampling train
as used in this study is shown in Figure A-5.
During sampling, the temperature of the cyclones was
held at 400 F. The particulate was collected in four size
fractions. Three were contained in the cyclones and the fourth,
the "less than" fraction, was collected by the WEP. However,
due to the flow rate limitation of the WEP, only part of the
gas stream was passed through the WEP. The D50's of the HVSASS
cyclones were established prior to sampling to be 14y, 4y and
lp. The weight of material collected in each of the cyclones
is summarized in Tables A-9 and A-10.
129
-------
u>
o
_ STACK
Thermocouple
OVEN
PITOT AP
MAGNEHELIC
•l\v
it>
I
i ~"
u »
WET ELECTROSTATIC
PRECIPITATOR
Figure A-5. Schematic of Sampling Train for Particulate Sizing
with HVSASS Cyclones
-------
TABLE A-9. SUMMARY OF DATA FOR PARTICULATE COLLECTION WITH THE HVSASS
CYCLONES AT STATION HS
Unit
Size Range
in u
Total Weight
Collected in g
Cyclone 1
Cyclone 2
Cyclone 3
WEP
14-4
4-1
5.359
7.399
5.526
(0.986)*
Total weight collected by cyclones - 18.284g
Total volume sampled (cyclones) - 2920 scf
Total volume sampled (WEP) - 571 scf
* Total weight collected by WEP - .159g
Total volume collected by WEP - 471 SCF
TABLE A-10. SUMMARY OF DATA FOR PARTICIPATE COLLECTION WITH HVSASS
CYCLONES AT STATION CS
Unit
Cyclone 1
Cyclone 2
Cyclone 3
WEP
Size Range
in u
>14
14-4
4-1
<1
Total Weight
Collected in g
2.870
5.949
8.943
(3.647)*
Total weight collected by cyclones - 17.762g
Total volume sampled - 12,540 scf
* Total weight collected by WEP - .260g
Total volume collected by WEP - 894 SCF
131
, - '! -
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APPENDIX B
ANALYTICAL PROCEDURES
-------
-------
1.0 INTRODUCTION
Trace element analyses on coal and ash samples from
the two coal-fired power plants were performed using dissolution
and analytical techniques adapted specifically for these matrices
The following sections provide brief descriptions of the sample
preparation and analytical procedures for.-
Arsenic Manganese
Beryllium Mercury
Cadmium Nickel
Calcium Selenium
Copper Titanium
Chromium Uranium
Fluorine Zinc
Lead
-------
-------
2.0 INSTRUMENTATION
The following instrumentation was utilized in the
analysis of the samples at the Radian trace analysis laboratories
• Perkin-Elmer Model 403 Atomic Absorption
Spectrophotometer,
• Perkin-Elmer Model 503 Atomic Absorption
Spectrophotometer,
• Perkin-Elmer Model HGA 200 Heated
Graphite Analyzer,
• Instrumentation Laboratory Model 351
Atomic Absorption Spectrophotometer,
• Instrumentation Laboratory Model 555
Flameless Atomizer,
• Perkin-Elmer Model 124 Double Beam
Spectrophotometer,
• Turner III Fluorometer,
• International Plasma Corp. Model 1001
Low Temperature Asher, and
• ETEC Scanning Electron, Microscope
with PGT 1000 Energy Dispersive X-Ray
Detector.
134
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3.0 SAMPLE PREPARATION
Preparation procedures were performed on the following
types of samples to provide the primary analytical solution:
• coal,
• coal ash, and
• WEP (solids).
3.1 Coal
Perchloric Acid Digestion (PAD)
For the trace element analysis of coal, Radian combined
low-temperature ashing, with a perchloric acid digestion procedure
suggested by Theodore Rains (DE-218) of the National Bureau of
Standards.
The coal samples are ashed in 1-gram portions in a low-
temperature asher. Dissolution is achieved by a three-step acid
treatment using the following ultrex grade acids:
• nitric acid,
• a 2:1:1 mixture of nitric, hydrochloric
and hydrofluoric acids , and
• perchloric acid.
Lithium Metaborate Fusion
A lithium metaborate fusion procedure reported by
Boar and Ingram (BO-028) is used for the analysis of the major
constituents of coal.
-------
Coal which has been previously ashed is thoroughly
mixed with lithium metaborate in a platinum crucible and fused
at 1050°C for 15 minutes. The flux is cooled and then dissolved
using hydrochloric acid and water.
3.2 Ash
Perchloric Acid Digestion (PAD)
The ash is weighed into a Teflon beaker and digested
using the same dissolution procedure used for the coal.
Lithium Metaborate Fusion
The ash is fused using the same procedure used for the
coal.
3.3 WEP
The solids are filtered from the WEP solution using a
0.8u cellulose membrane filter. The solids and the filter are
digested using the perchloric acid digestion procedure and are
added back to the filtrate.
136
-------
4.0 ANALYTICAL PROCEDURES
The analytical techniques used were developed for trace
element determinations in coal, coal ash and WEP samples. Each
analytical technique has been screened for accuracy and reliability
by standard addition and interference studies. NBS coal (SRM 1632)
and fly ash (SRM 1633) standards were analyzed with the samples to
check analytical techniques.
The complete analytical schemes for the analysis of
trace elements in the samples are found in Figures B-l through
B-3. Detection limits for each procedure are summarized in Table
B-l.
Arsenic
The WEP liquor and the perchloric acid digestion of
the solids are used for arsenic determination. Arsenic is com-
plexed, in acidic medium, as the heteropolyacid of molybdenum
using the method proposed by Ramakrishna (RA-147). The aqueous
complex is injected into the heated graphite analyzer attachment
to the atomic absorption spectrophotometer at 193.7 nm. A
charring temperature of 1200°C is used to remove any interferences.
Beryllium
Beryllium in aqueous solution is complexed with 2,4-
pentanedione. Ethylenediaminetetraacetic acid (EDTA) is used to
mask interfering ions. The beryllium complex is extracted into
methyl-isobutyl-ketone (MIBK) and aspirated into the nitrous
oxide-acetylene flame of the AA at 234.9 nm according to a
procedure by Bokowski (BO-027). The perchloric acid digestion
is used for solid samples.
137
-------
Gold Amalgamation
Atomic Absorption
00
COAL
Perchloric Acid
LTA* Digestion
Organic Extraction
Flame Atomic Absorption
Flameless Atomic Absorption
Fluorescence
Flameless Atomic Absorption
Inorganic Extraction Flameless Atomic Absorption
Flame Atomic Absorption
Colorimetry
Fusion
Flame Atomic Absorption
Specific Ion Electrode
Fluorescence
Hg
Se
Cd, Pb
As
Cr, Cu, Zn
Ti
Ca, Mn
*LTA - Low Temperature Asher
Figure B-l. Analytical Flow Chart for Coal Samples
-------
Gold Amalgamation
Atomic Absorption
ASH
Perchloric Acid
Digestion
Flame Atomic Absorption
Organic Extraction
Flameless Atomic Absorption
Fluorescence
Flameless Atomic Absorption
Inorganic Extraction Flameless Atomic Absorption
Flame Atomic Absorption
Colorimetry
Fusion
Flame Atomic Absorption
Specific Ion Electrode
Fluorescence
Hg
Be
Nl
Se
Cd, Pb
As
Cr, Cu, Zn
Tl
Ca, Mn
Figure B-2. Analytical Flow Chart for Ash Samples
-------
WEP
Filter
Solids
Perchloric
Acid
Digestion
Filtrate
Cold Vapor Technique
Organic Extraction
Inorganic Extraction
Fusion
Atomic Absorption
Flame Atomic Absorption
Fluorescence
Flameless Atomic Absorption
Flameless Atomic Absorption
Flameless Atomic Absorption
Flame Atomic Absorption
Colorimetry
Fluorescence
Hg
Be
Se
Hi
Pb, Cd
As
Crt Cu, Zn,
Ca, Mn
Ti
Specific Ion Electrode
Figure B-3. Analytical Flow Chart for WEP Solution
-------
TABLE B-l. DETECTION LIMITS FOR TRACE ELEMENT ANALYSIS
Detection Limit
Element
As
Be
Ca
Cd
Cr
Cu
F
Hg
Mn
Ni
Pb
Se
Ti
U
Zn
Analytical Procedure
Atomic Absorption (AA)
Ext r act ion/ AA
Atomic Absorption
Atomic Absorption
Standard Addition/AA
Standard Addition/AA
Specific Ion Electrode
Cold-Vapor AA
Atomic Absorption
Extraction/AA
Atomic Absorption
Fluorometry
Spectrophotometry
Fluorometry
Atomic Absorption
Coal
0.1
0.2
10
0.1
10
1
0.5
0.01
10
2
0.4
0.1
5
0.0001
1
Ash
0.5
1.6
40
0.2
25
4
1.2
0.01
40
8
0.8
0.1
20
0.0001
4
(ppm)
WEP
0.001
0.001
0.1
0.0002
0.1
0.1
0.1
0.0005
0.01
0.006
0.004
0.0005
0.1
0.0001
0.01
141
-------
Cadmium and Lead
The WEP solutions and the perchloric acid digestions
of the solids are analyzed by direct injection into the graphite
furnace attachment of the AA. Using Perkin-Elmer standard condi-
tions (PE-082), cadmium absorbance is measured at 228.8 nm and
lead at 283.3 nm.
Calcium and Manganese
The WEP solutions and the lithium metaborate fusions
of the solids were analyzed by direct aspiration into the flame
of the AA at 422.7 nm for calcium and at 279.5 nm for manganese
under Perkin-Elmer standard conditions (PE-114). Species inter-
fering with the calcium analysis are suppressed by aspirating a
lanthanum chloride solution with the sample using double-capillary
aspiration. Single-capillary aspiration is used for the manganese
analysis.
Chromium, Copper and Zinc
Chromium, copper and zinc are determined by direct
aspiration of the perchloric acid digestions and WEP solutions
into the flame of the AA. Chromium and copper determinations
are made by the use of standard additions with a double-capillary
aspiration system at 357.9 nm and 324.7 nm, respectively. Zinc
determinations are made by a single-capillary system at 213.9 nm.
All are done under standard conditions (PE-114).
Fluorine
Baker (BA-131), Baumann (BA-137) and Thomas (TH-060)
describe standard addition techniques utilizing a specific ion
electrode for the measurement of fluorine. A citrate buffer is
142
-------
added to release fluoride complexed by uranium, thorium, aluminum
and iron and to cancel out variances in pH and ionic strength.
The observed potential changes can then be related directly to
fluoride concentration.
Solid samples are fused with sodium carbonate at 600°C
and the melt is extracted with hot water. After diluting the
extract to volume, an aliquot is neutralized with acetic acid
before analysis.
Mercury
Mercury in gaseous and solid samples is determined using
a double gold amalgamation procedures described by Kalb and Baldeck
(KA-086), Diehl, Haltman, Schultz and Haven (DI-043), and 0'Gorman,
Suhr and Walker (OG-004).
Gas samples are drawn through a plug of gold wool.
Deamalgamation is accomplished by heating the gold wool with a
nichrome wire heating element. The released mercury is purged
through the absorption cell of an atomic absorption spectrophoto-
meter (AA) at 253.7 nm.
Solid samples are analyzed for mercury by weighing a
sample into a platinum boat and heating the sample slowly in a
chamber. The off gases containing elemental mercury are purged
through a gold plug where the mercury is collected. Deamalgama-
tion and determination by AA follow the same procedure as described
above.
Mercury in the WEP was determined by the procedure of
Hatch and Ott (HA-087). Liquid samples are acidified and the
mercury oxidized with potassium permanganate. Hydroxylamine
hydrochloride and stannous choride are used to reduce the mercury
143
-------
to the metallic state. Air is bubbled through the solution. The
mercury-entrained air is passed through the absorption cell of
an AA at 253.7 nm.
Nickel
Joyner, Healy, Chakravarti and Koyanagi (JO-012) report
a procedure using diethyldithiocarbamate to chelate nickel for
extraction into MIBK. The organic extract is injected into the
graphite furnace attachment of the AA at 232.0 nm. Nickel is
extracted from the WEP liquor and perchloric acid digestion of
the solids.
Selenium
Selenium is determined by a fluorescence method
reported by Levesque and Vendette (LE-068), Rankin (RA-082),
and an instrument firm, Turner Associates (TU-082). WEP
liquors and perchloric acid digestions are heated with hydro-
chloric acid. Following stabilization with formic acid,
hydroxylamine hydrochloride and EDTA, the samples are complexed
with 2,3-diaminonaphthalene. The selenium complex is extracted
into cyclohexane and compared by fluorometry with extracted
selenium standards.
Titanium
The perchloric acid digestions and WEP Solutions are
used for the titanium analysis. A yellow complex of titanium
is formed with tiron (disodium-l,2-dihydroxybenzene-3,5-disulfonate)
and read at 430 nm with a spectrophotometer using a method by
Rader and Grimaldi (RA-125). Interference from ferric iron is
eliminated by adding sodium dithionate.
-------
Uranium
Uranium is determined at nanogram levels by fluorescence.
Solid samples are mixed with a sodium carbonate, potassium carbonate
and sodium fluoride flux mixture in a platinum crucible and fused
into a translucent disc at 650°C. WEP solutions are evaporated
to dryness in platinum crucibles and the residue fused with the
flux. The fluorescence is measured with a Turner filter fluoro-
meter (TU-025). The method of standard additions is used to
compensate for quenching.
5.0 Analysis of Standard Reference Materials
The analytical techniques described were applied to NBS
samples of Coal (SRM 1632 and Fly Ash 1633), The analytical
results for triplicate analysis are presented in Table B-2
for comparison with certified values. In instances where certified
values were not available the results of Ondov (ON-22) were
substituted for comparison. No reported values for fluorine were
identified.
145
-------
TABLE B-2. ANALYSIS OF NBS STANDARD REFERENCE MATERIALS
Coal NBS 1632
Element
As
Be
Ca
Cd
Cr
Cu
F
Hg
Mn
Ni
Pb
Se
Tl
U
Zn
Results
6.4 ± .9
1.4 ± .1
.37 ± .02%*
.17 ± .04
21 ± 2
22 ± 3
76 ± 8
.14 ± .03
45 ± 4
14 ± 1
24 ± 7
3.1 ± .3
1000 ± 100
1.5 ± .1
38 ± 5
Fly Ash NBS 1633
Reported Value Results
5.9 ± .
M.5
.43 ± .
.19 ± .
20.2 ± .
18 ± 2
NR
.12 ± .
40 ± 3
15 ± 1
30 ± 9
2.9 ± .
6 82 ± 8
9.5 ± 1.3
05% 4.9 ± .4
03 1,6 ± .2
5 125 ± 8
126 ± 9
180 ± 25
02 .16 ± .03
530 ± 30
89 ± 6
75 ± 9
3 9.5 ± 1.0
1040 ± 110 7200 ± 300
1.41 ± 0
37 ± 4
All values in ppm (yg/g) unless otherwise
Results are for triplicate digestions of
*Source ON-Q22 (not certified by NBS) .
NR - Not Reported.
.7 12.7 ± 1.4
210 ± 15
indicated.
each standard.
Reported Value
61 ± 6
M.2
4.7 ± 6%*
1.45 ± .06
131 ± 2
128 ± 5
NR
.14 ± .01
493 ± 7
98 ± 3
70 ± 4
9.4 ± .5
7400 ± 300
12.0 ± .5
210 ± 20
-------
BIBLIOGRAPHY
BA-131 Baker, R. L., "Determination of Fluoride in Vegetation
Using the Specific Ion Electrode", Anal. Chem. 44(7),
1326 (1972).
BA-137 Baumann, E. W. , "Trace Fluoride Determination with
Specific Ion Electrode", Anal. Chim. Acta. 42, 127-32
1968).
BO-027 Bokowski, D. L., "Rapid Determination of Beryllium by
a Direct-Reading Atomic Absorption Spectrophotometer",
Am. Ind. Hyg. Assoc.,J. 29(5), 474-81 (1968).
DE-218 Dean, John A. and Theodore C. Rains, eds., Flame
Emission and Atomic Absorption Spectrometry,
Volume 3, Elements and Matrices, N. Y., Marcel
Dekker, 1975.
DI-043 Diehl, R. C., et al., Fate of Trace Mercury in the
Combustion of Coal, TPR-54, Pittsburgh, Pa., Pittsburgh
Energy Research Center (1972).
HA-087 Hatch, W. R. and W. L. Ott, "Determination of Submicro-
gram Quantities of Mercury by Atomic Absorption
Spectrophotometry", Anal. Chem. 40(14), 2085-87 (1968).
JO-012 Joyner, T., M. L. Healy, D. Chakravarti and T. Koyanagi,
"Preconcentration for Trace Analysis of Sea Waters",
Env. Sci. and Tech. 1(5), 417-24 (1967).
5" 147
-------
Cont'd
KA-086 Kalb, G. W. and C. Baldeck, The Development of the Gold
Amalgamation Sampling and Analytical Procedure for
Investigation of Mercury in Stack Gases, PB 210 817,
Columbus, Ohio, TraDet, Inc. (1972).
LE-068 Levesque, M. and E. D. Vendette, "Selenium Determination
in Soil and Plant Materials", Canad. J. Soil Sci. 51,
85-93 (1971).
OG-004 O'Gorman, J. V., N. H. Suhr and P. L. Walker, Jr.,
"The Determination of Mercury in Some American Coals",
Applied Spectroscopy 26(1), 44 (1972).
ON-022 Ondov, J.M., et al., "Elemental Concentrations in the
National Bureau of Standards Environmental Coal and Fly
Ash Standard Reference Materials", Anal. Chem. 47,
1102 (1975).
PE-082 Perkin-Elmer, Analytical Methods for Atomic Absorption
Spectroscopy Using the HGA Graphite Furnace, Norwalk,
Conn. (March 1973).
PE-114 Perkin-Elmer, Analytical Methods for Atomic Absorption
Spectrophotometry, Norwalk, Conn. (1973).
RA-082 Rankin, J. M., "Fluorometric Determination of Selenium
in Water with 2,3-Diaminonaphthalene", Env. Sci. Tech.
7(9), 823 (1973).
148
-------
Cont'd
RA-125 Rader, L. F. and F. S. Grimaldi, Chemical Analysis for
Selected Minor Elements in Pierre Shale. U.S.G.S.
Professional Paper 391-A, Washington, D. C., GPO (1961)
RA-147 Ramakrishna, T. V., J. W. Robinson and P. W. West,
"Determination of Phosphorus, Arsenic or Silicon by
Atomic Absorption Spectrometry of Molybdenum Heteropoly
Acids", Anal. Chim. Acta 45, 43-49 (1969).
TH-060 Thomas, J., Jr. and H. J. Gluskoter, "Determination of
Fluoride in Goal with the Fluoride Ion-Selective
Electrode", Anal. Chem. 46(9), 1321-23 (1974).
TU-025 Turner Associates (G. K.), "Uranium", Fluprometry
Reviews Series, Palo Alto, Ca. (Feb. 1968).
TU-028 Turner Associates (G. K.), "The Fluorometric Determina-
tion of Selenium: A Literature Review", Fluorometry
Reviews, Ace. No. 11863, Palo Alto, Ca. (Sept. 1972).
149
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
REPORT NO.
EPA 908/4-78-008
3. RECIPIENT'S ACCESSION NO.
TITLE AND SUBTITLE
Trace Elements-of Fly Ash:
Emissions from Coal-Fired Steam Plants Equipped with
Hot-Side and Cold-Side Precipitators for Particulate
Control
5. REPORT DATE
December, 1978
6. PERFORMING ORGANIZATION CODE
Robert M. Mann, Robert A. Magee,
Robert V. Collins, Michael R. Fuchs, Frank G. Mesich
8. PERFORMING ORGANIZATION REPORT NO.
DCN #78-216-137-09
PERFORMING ORGANIZATION NAME AND ADDRESS
Radian Corporation
8500 Shoal Creek Blvd.
P. 0. Box 9948
Austin, Texas 78766
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
68-01-3702
2. SPONSORING AGENCY NAME AND ADDRESS
Office of Energy Activities
U.S. Environmental Protection Agency
Region VIII
Denver, Colorado 80295
13. TYPE OF REPORT AND PERIOD COVERED
Final Report •
14. SPONSORING AGENCY CODE
5. SUPPLEMENTARY NOTES
Limited Quantities of the report are available through EPA Region VIII Library.
This report describes the results of a sampling and chemical analysis
study of emissions from two coal-fired steam plants equipped with electrostatic
precipitators for particulate control. The program objective was to define both
emission and enrichment of trace elements in the flue gas exiting electrostatic
precipitators operated at different process temperatures. Fly ash collected from
the stack using cyclones and cascade impactors was analyzed to define trace element
concentration of individual size fractions. Trace element enrichment of ash fractions
was compared with an enrichment model to define the dependence of enrichment on
particle size. Samples of the feed coal at each station were subjected to density
separation to determine the association of each element with mineral (ash) and
organic (.ash-free) phases of the coal. The 15 elements included in the coal and ash
studies are:
Arsenic
Beryllium
Cadmium
Calcium
Chromium
Copper
Fluorine
Lead
Manganese
Mercury
Nickel
Selenium
Titanium
Uranium
Zinc
17,
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
COSATI Field/Group
Trace Elements
Coal
Fly Ash
Electric Power Plants
Electrostatic Precipitators
Particle Size Distribution
Enrichment
Organic Affinity
Emissions
7B
14B
21B
18. DISTRIBUTION STATEMENT
Unlimited
19. SECURITY CLASS (This Report)
Unclassified
21. NO. OF PAGES
2O. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (Rev. 4-77) PREVIOUS EDITION is OBSOLETE
230 South Dearborn Street
«o. Illinois 60604
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