U.S. Environmental Protection Agency Industrial Environmental Research EPA-600/7-78-068
Off ice of Research and Development Laboratory - ,. 4O7O
Research Triangle Park. North Carolina 27711 April 197o
COMBUSTION
OF HYDROTHERMALLY
TREATED COALS
Interagency
Energy-Environment
Research and Development
Program Report
-------
RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. "Special" Reports
/
9. Miscellaneous Reports
This report has been assigned to the INTERAGENCY ENERGY-ENVIRONMENT
RESEARCH AND DEVELOPMENT series. Reports in this series result from the
effort funded under the 17-agency Federal Energy/Environment Research and
Development Program. These studies relate to EPA's mission to protect the public
health and welfare from adverse effects of pollutants associated with energy sys-
tems. The goal of the Program is to assure the rapid development of domestic
energy supplies in an environmentally-compatible manner by providing the nec-
essary environmental data and control technology. Investigations include analy-
ses of the transport of energy-related pollutants and their health and ecological
effects; assessments of, and development of, control technologies for energy
systems; and integrated assessments of a wide range of energy-related environ-
mental issues.
EPA REVIEW NOTICE
This report has been reviewed by the participating Federal Agencies, and approved
for publication. Approval does not signify that the contents necessarily reflect
the views and policies of the Government, nor does mention of trade names or
commercial products constitute endorsement or recommendation for use.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
-------
EPA-600/7-78-068
April 1978
COMBUSTION
OF
HYDROTHERMALLY TREATED COALS
by
E.P. Stambaugh, R.D. Giammar, E.L Merryman,
J.S. McNulty, K.C. Sekhar, T.J. Thomas,
H.M. Grotta, A. Levy, and J.H. Oxley
Battelle Memorial Institute
Columbus Laboratories
505 King Avenue
Columbus, Ohio 43201
Contract No. 68-02-2119
Program Element No. EHE623A
EPA Project Officer: James D. Kilgroe
Industrial Environmental Research Laboratory
Office of Energy, Minerals, and Industry
Research Triangle Park, N.C. 27711
Prepared for
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Research and Development
Washington, D.C. 20460
-------
ABSTRACT
This report presents the results of a study to evaluate (1) the
combustion characteristics of hydrothermally treated (HTT) coals as they
relate to environmental emissions, boiler design, and interchangeability of
solid fuels produced by the Hydrothermal Coal Process (HCP) with raw coals
currently being used as the source of energy and (2) conversion of solu-
bilized coal to terephthalic acid.
Several HTT coals were prepared from raw Martinka and Westland
coals by the Hydrothermal Coal Process using sodium hydroxide and a mixture
of sodium hydroxide and calcium hydroxide as the leachants. The HTT coals
and the corresponding raw coals were combusted in laboratory and Multifuel
Furnace Combustion units and the general combustor behavior, pollutant
emissions and ash properties were assessed to provide the necessary data for
impact evaluation of HTT coals. Conversion of solubilized coal to tereph-
thalic acid was examined by oxidation to benzene carboxylic acids.
Results indicate that the HTT coals prepared by the Hydrothermal
Coal Process from selected coals are clean solid fuels that in many instances
can be burned with little or no sulfur emissions. Sulfur oxide concen-
trations in the flue gases were well below Federal Sulfur Emission Standards
for New Sources. Also, the HTT coal was found to burn as well or better
than raw coal and trace metals emissions should be significantly reduced be-
cause of the lower concentrations in HTT coals. Therefore, the use of this
clean, solid fuel in conventional boilers and furnaces ought to reduce en-
vironmental pollution, resulting from the combustion of HTT coal. These HTT
coals appear to be more suitable for firing in wet bottom furnaces than in
dry-bottom furnaces because of potential slagging and fouling problems
associated with the alkali content of the coals. However, it may be possible
to alter the slagging and fouling characteristics by the use of additives.
The coal solubilized during the desulfurization step can be
converted to terephthalic acid by the oxidation-Henkel reaction. How-
ever, low yields suggest that this approach may not be economical.
-------
EXECUTIVE SUMMARY
An alternative approach for converting our major source of
coal-energy-to an environmentally acceptable solid fuel is to clean the
raw coal by chemical benefication prior to combustion. One potential
chemical beneficiation process is the Hydrothermal Coal Process. In
order to confirm this, the program entitled "Study of the Battelle
Hydrothermal Treatment of Coal Process" was conducted under the sponsor-
ship of the U.S. Environmental Protection Agency, Contract No. 68-02-2119,
The objectives of this program were to:
1. Evaluate the combustion characteristics of HTT
coals as these relate to environmental emissions,
boiler design and interchangeability of solid
fuels, and
2. Examine the conversion of that portion of the
coal solubilized during the hydrothermal treat-
ment of the coal to organic chemicals, for example,
terephthalic acid.
The objectives were achieved by
a. preparing several types of HTT coals in the
HCP Miniplant facility
b. Conducting combustion studies on these coals
in the 1 Ib/hr laboratory combustion facility
and in the Multifuel Furnace.
c. Evaluating the environmental impact of con-
verting conventional boilers to hydrothermal
treated coals
d. Assessing the interchangeability of hydro-
thermally treated coals in utility and
industrial boilers, and
e. Assessing the conversion of solubilized coal
to terephthalic acid by the oxidation-Henkel
process.
Research results to date have confirmed the initial assess-
ment that the Hydrothermal Coal Process is a potential method for pro-
ducing environmentally acceptable solid fuel from certain coals. HTT
coals prepared by this process from the Martinka and Westland coals are
clean solid fuels that can potentially be burned with little or no
sulfur emissions control. Sulfur oxide concentrations in the flue gases
from the Laboratory Test Facility and the Multifuel Combustion Unit were
well below Federal Sulfur Emission Standards For New Sources. Generally,
the sulfur dioxide concentration in the flue gases were less than 500
ppm.
ii
-------
The low sulfur oxide concentrations resulted, in part, from
(1) extraction of the sulfur from the raw coal by the Hydrothermal Coal
Process and (2) in part, as the result of the sulfur capturing effi-
ciency of the alkali contained in the HIT coals. Also the HIT coals
were found to burn as well or better than the raw coals and trace metals
emissions should be significantly reduced because of the lower concentra-
tions in the HIT coals. Therefore, the use of HTT coals in conventional
boilers and furnaces should reduce environmental pollution resulting
from the combustion of coal.
Because of the low-ash-fluid temperatures of the ash in the
HTT coals, firing of these coals in conventional dry-bottom furnaces
could present slagging and fouling problems. It would probably be
necessary to install additional slag blowers in the furnace and additional
soot blowers in the convection tube banks to control slagging and foul-
ing to an acceptable level. Some derating of the boiler may also be
required. However, it may be possible to alter the slagging and fouling
characteristics by the use of additives.
The HTT coals could be more suitable for firing in wet-bottom
(slag-top or cyclone) furnaces because of the low-ash-fluid temperatures.
Although firing in wet-bottom furnaces would avoid the slagging problem,
boiler fouling would be a problem requiring adequate soot-blower capacity
and, possibly, derating to lower gas temperatures in the convection
section.
Conversion to HTT coals could have a significant effect on
the atmospheric emissions from the combustion of coal. Preliminary
results indicate that, of the 4 localities analyzed, St. Louis,
Missouri and Detroit, Michigan could meet Federal Ambient Air Quality
Standard of 80 ^g/m of S0? by simple substitution of HTT coals
In all cases, significant decreases in SC^ concentrations are predicted.
Similarly, preliminary data show that emission of several of the trace
metals to the atmosphere could also be reduced by hydrothermal treatment.
Analysis of the environmental problems associated with dis-
posal of the combustion waste products revealed that direct disposal
of the cooler ash from the NaOH treated coal would not be advisable be-
cause of the high degree of solubility. However, the sodium sulfate
could be removed prior to disposal. With respect to trace metal values,
the ashes from the HTT coals are less polluting than those from the
raw coal.
Technically, the coal solubilized during the desulfurization
operation can be oxidized to benzene carboxylic acids and subsequently
converted to terephthalic acid. However, low yields suggest that
approach may be economical.
iii
-------
TABLE OF CONTENTS
Page
ABSTRACT L
EXECUTIVE SUMMARY u
LIST OF TABLES vii
LIST OF FIGURES ix
INTRODUCTION L
BACKGROUND 1
OBJECTIVES 2
SCOPE OF WORK 3
EXPERIMENTAL DETAILS 4
PHASE I. COMBUSTION CHARACTERISTICS OF HYDROTHERMALLY
TREATED COAL 4
Task 1A. Selection of Coals 4
Candidate Coals 4
Task IB. Preparation of HTT Coal Process (HCP; 7
Description of Hydrothermal Coal 7
Preparation of Various HTT Coals 7
Analyses of the Coals 10
Task 2. Combustion Characterization Experiments 13
Objective and Scope 13
Combustion Plan 14
Combustion Facilities 14
Operational Procedures 17
Sampling and Analytical Procedures 17
Combustion Results 20
General Combustion Behavior 32
Pollutant Emissions 35
SO - Sulfur Capture 35
NO Fuel-N-Conversion in
x J0
CO-C02-02 40
Particulate Loading 40
Carbon Burnout 42
Trace Elements 44
Polycyclic Organic Matter 45
Ash Characteristics 49
iv
-------
TABLE OF CONTENTS (Continued)
Viscosity ........................ 49
Sodium Content .................. .... 51
Ash-Fusion ......................... 52
Resistivity .......... . ........ ..... 53
Particle Size ....................... 56
Task 3. Impact Evaluation of the Use of Hydro thermally
Treated Coal .......... . ......... 56
Subtask 3A. Atmospheric Impact of HTT Coal ........ 56
Equivalent Sulfur Content of HTT Coal .......... 59
Current Mean Sulfur Dioxide Concentrations ........ 63
S0? Projected Concentrations ............... 63
Trace Metal Projected Concentrations. . . ........ 64
Subtask 3B. Environmental Problems of Combustion
Waste Products ................ 66
Leachability Tests .................... 69
Leaching Results ..................... 69
Subtask 3C. Interchangeability of HTT Coal ........ 74
Burning Characteristics ................. 74
Ash Properties ...................... 76
Coal Handling and Storage ................ gg
Moisture Content ..................... 81
PHASE II. TRACE METAL IDENTIFICATION AND RECOVERY FROM
HYDROTHERMALLY TREATED COALS ............. 82
Task 1. Trace Metal Analysis ................ 82
PHASE III- ORGANIC CHEMICAL BY-PRODUCT RECOVERY FROM
HYDROTHERMAL TREATMENT OF COAL ............ 89
Introduction ......................... 89
Background Discussion .................... 90
Experimental Procedure and Results .............. 91
Recovery of Humic Acid from Spent Leachant ..... .... 93
Conversion of Humic Acid to BCAs .............. 93
CONCLUSIONS ............................ 99
REFERENCES ............................. 101
-------
TABLE OF CONTENTS (Continued)
Page
APPENDIX A
DESCRIPTION OF THE HYDROTHERMAL COAL PROCESS A-l
APPENDIX B
MINIPLANT FACILITY B-l
Coal Preparation Segment B-l
Hydrothermal Treatment Segment B-l
Pressure Let-Down System B-6
Product Slurry Separation . . B-10
APPENDIX C
DESCRIPTION OF THE COMBUSTION FACILITIES C-l
ONE LB/HR LABORATORY TEST FACILITY C-l
Feeder C-l
Burner C-4
Combustion Chamber C-4
Cooler C-4
MULTIFUEL FURNACE FACILITY C-8
The Multifuel Furnace C-8
Burner Design C-ll
Simulated Boiler-Economizer Section C-13
APPENDIX D
OPTICAL EMISSION AND MASS SPECTROGRAPHIC ANALYSIS D-l
VI
-------
LIST OF TABLES
Table I.
Table 2.
Table 3.
Table 4.
Table 5.
Table 6.
Table 7.
Table 8.
Table 9.
Table 10.
Table 11.
Table 12.
Table 13.
Table 14.
Table 15.
Table 16.
Table 17.
Table 18.
Table 19.
Table 20.
Table 21.
Table 22.
Table 23.
Table 24.
Table 25.
Table 26.
Table 27.
Table 28.
Page
Analysis of HTT Coals and Corresponding Raw Coals 11
Analytical Methods for Sample Analysis 19
Coals Used in Various Combustion Experiments 21
Combustion Conditions and Results From
LTF Combustion Unit
22
Coal-Ash Analyses 25
Comparison of Raw and HTT Westland Coal Firings 31
Differential Thermal Analyses of Raw and HTT Coals .... 33
Thermogravimetric Analyses of Raw and HTT Coals 34
Sulfur Capture in Raw and Treated Coals 36
NO Data From Coal Firings in the LTF Combustor 39
Carbon Content of Filter and Cooler Ash
From LTF Combustion Unit
43
Element Enrichment 44
Element Enrichment of Specific Elements 46
POM Analyses 47
Ash Composition and Fouling Potential of Raw
and Treated Martinka 50
Fusion Temperature of Ash 54
Resistivity of Coal Ash Samples at 400 F 55
. . 60
. . 63
S02 Profile
Equivalent Sulfur Content of Coals (Weight Percent). .
Current Maximum Annual S0~ Levels in Five Urban Areas.
63
Projected S02 Levels With HTT Coal Ambient Annual
Concentration, yg/m Annual Average 65
o
Trace Element Decremental Concentrations (yg/m )
for Peoria, Illinois, From Coal Substitution 67
pH Reading on Leachants 70
Leachability of Cooler Ash (Westland Coals) 71
Analysis of Solids Content of Cooler Ash Leachates
From Westland Coals (ppm) 72
Trace Metals in Leachants 75
Summary of Slagging and Fouling Properties 77
Mass Spectrographic Analysis of Martinka
Raw and Selected HTT Coals 83
vil
-------
LIST OF TABLES (Continued)
Page
Table 29. Mass Spectrographic Analysis of Westland
Raw and Selected HIT Coals 84
Table 30. Trace Metals Content of Humic Acids 88
Table D-l. Optical Emission Analysis of the Eight
Coals Burned D-2
Table D-2. Mass Spectrographic Analysis of Coal and Ash (ppmw)
(Martinka Coals) D-6
Table D-3. Mass Spectrographic Analysis of Coal and Ash (ppmw)
(Westland Coals) D-8
viii
-------
LIST OF FIGURES
Page
1 . Schematic of ] Ib/hr LTF Combustion Unit 15
2. Schematic of the MuJtifuel Furnace Facility 16
Figure 3. Coulter Counter Ash Particle Size Distribution -
Martinka Firing 58
Figure 4. Coulter Counter Particle Size Distribution -
Westland Coals 59
Figure 5. Names and Structural Formulas of Benzenecarboxylic Acids . 93
Figure 6. Comparison of Total BCA Formation Rates Under
Various Conditions 96
Figure 7. Relative Formation Rates of Various BCAs
in 0.7N K0CO,. at 250 C 97
2. j
Figure 8. Fate of Pure Benzene Carboxylic Acids in
I resent Process 99
Figure A-l. Schematic of Hydrothermal Coal Process A-2
Figure B-l. Block Diagram of the BHCP Miniplant B-2
Figure B-2. Coal Slurry Preparation B-3
Figure B-3. Preheaters B-5
Figure B-4. Reactors B-7
Figure B-5. Product Cooler B-8
Figure B-6. Pressure Let-Down System B-9
Figure C-l. Sketch of Experimental Apparatus C-2
Figure C-2. Coal Feeder C-3
Figure C-3. Burner C-5
Figure C-4. Combustion Chamber C-6
Figure C-5. Cooler C-7
Figure C-6. Schematic of Laboratory Flue-Gas Conditioning System . . C-9
Figure C-7. Battelle Multifuel Furnace C-10
Figure C-8. Burner for Battelle Multifuel Furnace C-12
-------
CONVERTING UNITS OF MEASURE
EPA policy is to express all measurements in meter units. When
implementing this practice will result in undue cost or lack of clarity,
conversion factors are provided for nonmetric units used in this report.
Generally, this report used like English unit of measure. For conversion
to the metric system, use the following conversion factors.
Table of Conversion Factors
Multiply English Unit
pound/hour
British thermal unit
British thermal unit/pound
ton (short)
pounds/square inch
(gauge)
inch
feet
degree fahrenheit
gnllon
ton/year
pounds/million,
British thermal unit
pound
square inches
By Conversion
0.454
0.252
0.555
0.907
(0.06805 psig +1)
2.54
0.3048
0.55 (°F-32)(a)
3.785
0.907
1.8xlO-6
0.454
6.452
(a)
To Obtain
Metric Unit
kilogram/hour
kilogram - calories
kilogram - calories/
kilogram
metric ton (1000
kilograms)
atmospheres (absolute)
centimeters
meters
degree celcius
liters
metric ton/year
kilogram/ kilogram-
calories
kilogram
square centimeters
(a) Actual conversion, not a multiplier.
-------
STUDY OF THE BATTELLE HYDROTHERMAL
TREATMENT OF COAL PROCESS
by
E. P. Stambaugh, A. Levy, R. D. Giammar,
E. L. Merry man, J. S. McNulty, K. C. Sekhar,
T. J. Thomas, H. M. Grotta, and J. H. Oxley
SECTION I.
INTRODUCTION
BACKGROUND
Coal is the major source of energy for the United States and will
continue to be for many years. According to a recent survey, the United
States has a coal reserve totalling 436 billion tons. At the present rate
of consumption of about 620 million tons per year, the United States has
enough coal to last for about 700 years.
However, much of this abundant source of energy contains high
concentrations of sulfur, nitrogen, and mineral matter (ash)* which includes
significant quantities of toxic metals. Examples of these metals are mercury,
beryllium, and arsenic. During the combustion of coal, these materials are
emitted into the environment and thus constitute a health hazard through
atmospheric and food chain involvement. Consequently, the United States
government has established requirements which necessitate controlling the
effluent from coal combustion facilities by flue-gas scrubbing or by burn-
ing low-sulfur fuels.
Conceptually, the simplest option for meeting requirements for
controlling the effluent from coal combustion would be to burn run-of-the-
mine low sulfur coal. However, much of our coal supply has a sulfur content
too high to permit direct combustion and remain within S0~ regulations.
An alternative is to clean the coal prior to combustion by physical
or chemical beneficiation. Physical beneficiation is not adequate for the
removal of sulfur and other pollutant-forming constituents since, at the
best, only a portion of the pyritic sulfur and the mineral matter is removed.
* Mineral matter and ash are used interchangeably throughout the report.
-------
Furthermore, physical beneficiation cannot be applied to those coals having
the pyritic sulfur distributed as microscopic particles throughout the coal
particles.
Chemical beneficiation is an approach whereby pollutant-forming
constituents are reduced to acceptable limits by treating the raw coal with
a reagent or reagents that react with and liberate these constituents. This
approach could increase significantly the quantity of our coal reserves which
could be used directly as a solid fuel with minimal or no pollution control.
One chemical beneficiation process for the production of a clean solid fuel
from high sulfur coals is the Hydrothermal Coal Process. Basically, this
process entails heating an aqueous slurry of coal and selected leachant in
the autoclave at a temperature and corresponding steam pressure for a time
sufficient to solubilize a significant portion of the sulfur and the ash. After
which the product slurry is cooled and filtered. Then, the HTT coal is washed
and dried for combustion or it may be deashed by treatment with dilute acid,
for example IUSO,, to remove the majority of the mineral matter not extracted
during the hydrothermal treatment. Research results to date have confirmed the
initial assessment that this process is a potential means of producing an
environmentally acceptable solid fuel from certain coals.
Consumption of these processed solid fuels as the source of energy
for heat and power generation should reduce atmospheric emissions and, con-
sequently, result in a healthier environment. In order to confirm this, the
United States Environmental Protection Agency awarded Battelle's Columbus
Laboratories the contract entitled "Study of the Battelle Hydrothermal Treat-
ment of Coal Process". This report covers the results of the study from this
contract.
OBJECTIVES
The first objective of this program was to evaluate the combustion
characteristics of HTT coals as these relate to environmental emissions, boiler
design, and interchangeability of solid fuels. Coal produced by the Hydrothermal
Coal Process (HCP) were evaluated against raw (untreated) coals currently used
-------
as the source of fuel. The second objective was to examine the conversion of
solubilized coal, i.e., the humic acids leached from the coal during hydro-
thermal (desulfurization) treatment, to organic chemicals.
SCOPE OF WORK
The objective was achieved by
Conducting combustion studies on hydrothermally treated
coals and corresponding raw coals
Evaluating the environmental impact of converting
conventional boilers to burn hydrothermally treated
coals as the source of fuel
Assessing the interchangeability of hydrothermally
treated coals in utility and industrial boilers
Producing organic chemicals from solubilized coal.
-------
SECTION II.
EXPERIMENTAL DETAILS
A research program was conducted which has resulted in a prelimin-
ary evaluation of the process for hydrothermal treatment of selected coals
for the removal of pollutant-forming constituents. In order to achieve this,
the research as discussed in the following paragraphs was conducted.
PHASE I. COMBUSTION CHARACTERISTICS
OF HYDROTHERMALLY TREATED COAL
In the initial evaluation of the combustion characteristics of
hydrothermally treated coal, combustion studies were conducted in Battelle's
1-lb/hr combustion facility (LTF). Based on the results of these combustion
studies, Battelle selected the raw and mixed leachant treated Westland coals
for characterization in the Multifuel Furnace Facility (MFF) at a combustion
rate of 30 Ib/hr.
In carrying out this evaluation, the following tasks were conducted:
Task 1A. Selection of Coals
Candidate Coals. The criteria for selection of coals for this
study were:
(1) Known Reserves. The coals were selected from seams of
known large reserves from which adequate coal is avail-
abel for commercial processing.
(2) Susceptibility to Hydrothermal Cleaning. The coals were
known from prior research to be amenable to desulfurization
by the hydrothermal process.
(3) Composition of Coals. These coals had sulfur contents
too high for direct utilization by electric utilities
without violating Federal New Source Sulfur Emissions
Standards of 1.2 Ib of S02/10 Btu.
-------
The two raw coals selected for this study were (1) Westland coal
and (2) Martinka coal. Westland coal is an Eastern bituminous coal from
the Pittsburgh seam. The mine is located in Washington County, Pennsylvania.
The coal represented by this mine is one of the major seams in Pennsylvania
with estimated reserve of approximately 7 billion tons. As noted from the
following analysis, this coal is a relatively high sulfur, high mineral matter
content coal in the run-of-the-mine condition. However, it is subject to
physical beneficiation to remove a portion of the sulfur and the mineral matter,
but not to a level to permit direct firing without violating Federal Sulfur
Emission Standards.
Run-of-Mine Coal Washed Coal**
H20 (%)* 0 0.9
Mineral Matter (%) 30.1 8.4
Sodium (%) 0.023
Total Sulfur (%)(MAF)*** 3.61 2.04
Pyritic (%) (MAF) 2.38 1.32
Sulfate (%) (MAF) 0.32 0.04
Organic (%) (MAF) 0.91 0.68
* Water content after drying at about 90°C for 24 hours.
** Coal washed in a preparation plant.
*** Moisture ash free basis.
Martinka coal is representative of the lower Kittanning Seam in West
Virginia. This coal from the Martinka No. 1 Mine in Marion County is one of
the major seams in West Virginia with an estimated reserve of 10.3 billion
tons. The composition varies widely in the run-of-the-mine condition as
noted below:
Mineral Matter (%) 18.6 to 22.7
H20 (%)* 0.5
Total Sulfur (%) (MAF)*" 1.32 to 2.92
Pyritic sulfur (%) (MAF) 0.6 to 1.93
Organic sulfur (%) (MAF) 0.25 to 0.71
Sulfate sulfur (%) (MAF) 0.01 to 0.05
* Water content after drying at about 90°C for 24 hours.
** Moisture ash free basis.
-------
This coal, like the Westland coal, cannot be fired directly by electric
utilities under new source standards without the implementation of some
type of SCL pollution control.
From previous R&D at Battelle's Columbus Laboratories, each of
these coals was found to be suitable for desulfurization and deashing by
(2)
the Hydrothermal Coal Process (HCP) . For example, hydrothermal treat-
ment of Westland coal with the mixed leachant system produced a HTT coal
with the following composition:
Raw Coal HTT Coal
H20, % (product basis) 0.87 0.41
Mineral matter, % (product basis) 8.37 15.2
Total Sulfur, % (MAF) 2.04 0.82
S02, lb/106 Btu 2.72 1.07
Similar results were attained with raw Martinka coal. In this case, the
sulfur content of the HTT coal was lowered to a S02 equivalent (MAF) of 0.8 lbs/10&
Btu from 3.92 lbs/106 Btu.
Also, the sodium hydroxide-prepared HTT coals selected for this study
were susceptible to demineralizing with dilute sulfuric acid. For example,
the mineral matter content of a HTT Westland coal hydrothermally treated with
the sodium hydroxide leachant was lowered to 3.5 weight percent by leaching
in dilute sulfuric acid solution. The HTT coal before demineralization con-
tained 13.0 weight percent mineral matter.
From the above consideration, the following types of HTT coals were
prepared in the HCP Miniplant (pre-pilot plant) Facility for combustion in
the 1-lb/hr Laboratory Test Facility and the Multifuel Furnace.
-------
Coal
Westland
Prior to Combustion
Martinka
Coal Treatment J^esOan^ _ Types of Coal Combusted
Physically cleaned
at Preparation Plant x x x x x
Hydrothermally Treated
(NaOH Leachant) x x x
Hydrothermally Treated
(Mixed Leachant) x x
Hydrothermally Treated
(NaOH Leachant)-
Acid (H2SC>4) Leached x
These coals were prepared from the two raw coals - Westland and Martinka - as
discussed above.
Task IB. Preparation of HTT Coals
Dgscriptiojn of Hydrothermal Coal Process^ ^HCP) . Basically, the HCP
entails heating an aqueous slurry of coal and selected leachant in the autoclave
at a temperature and corresponding steam pressure for a time sufficient to
solubilize a significant portion of the sulfur and the ash. After solubiliza-
tion of the sulfur, the product slurry is cooled and filtered. Then, the HTT
coal is washed and dried. (See Appendix A for a description of the Hydro-
thermal Coal Process.) In this study, the dried product was stored in a
sealed container under a nitrogen atmosphere until burned.
Preparation of Various HTT Coals. The HTT coals evaluated in this
program were prepared in the Miniplant Facility which is capable of hydrothermally
cleaning coal on a continuous basis. (See Appendix B for a discussion of the
Miniplant.) The overall process entails five basic operations:
(a) coal preparation
(b) hydrothermal desulfurization
(c) product separation
(d) product drying
(e) leachant regeneration.
-------
Only the first four operations were employed in this program.
In this study, no effort was made to optimize the processing con-
ditions for preparation of the HIT coals. Instead, processing conditions
which were known from previous work to produce the desired HIT coals were chosen.
Coal preparation entailed a crushing and milling operation. The raw
coal which had been physically cleaned at a preparation plant to remove some
of the mineral matter including a portion of the sulfur was air-dried to re-
move excess moisture. The air dried coal was then crushed in a Fitzmill to
about 4-mesh. The crushed coal was then pulverized in a micro-pulverizer
and screened in a Sweco 24-in. vibro-energy sieve to separate out the minus
200-mesh fraction. The oversize was returned to the Mikro-pulverizer and
then rescreened. These operations were continued until the coal had been
ground to at least 70 percent minus 200 mesh.
Hydrothermal treatment (desulfurization) entailed basically three
operations. First, the ground coal was mixed with an aqueous alkaline leach-
ant consisting of (1) either an 8 percent sodium hydroxide solution or (2)
an 8 percent sodium hydroxide solution containing about 2.5 percent calcium
hydroxide. Then, the slurry was pumped into the feed tank. From the feed
tank, the raw coal slurry was pumped via high pressure pumps into and
through the series of autoclaves, preheated to 275 C (pressure of about
1050 psig which included the steam pressure and an over pressure of nitrogen).
In the autoclaves, the leachant reacted with the sulfur contained in the
coal to form water-soluble sodium sulfur compounds. The product slurry was
cooled by a water-cooled heat exchanger and exited from the hydrothermal
treatment segment into a receiving tank through a pressure let-down valve.
Residence time, the time the coal slurry was at 275 C, was 40 minutes.
The product slurry was then filtered to remove spent leachant.
Residual leachant was removed from the clean coal product by a series of
washing and filtration operations using water as the washing medium.
The wet, clean coal product containing 40 to 50 percent water was
dried in a steam jacket drier under a flow of nitrogen. The nitrogen blanket
was employed as a preventive measure to avoid any possible oxidation of the
coal surface. The moisture content of the HTT coal was lowered to 1 percent
or less by this drying operation.
-------
Deashing of the HTT coals was accomplished by sulfuric acid leaching
of the HTT prepared coal using sodium hydroxide as the leachant system.* This
operation entailed slurrying the HTT coal in dilute acid, generally 10 percent,
for approximately 30 minutes at ambient temperature. After which the slurry
was filtered and the deashed HTT coal was washed free of sulfate using water
as the washing medium. Then the deashed HTT coal was dried using the same
drying procedure as used to dry the other HTT coals.
Three types of HTT coals were produced:
(1) Low sulfur, residual .alkali**, residual ash in which the
residual alkali was sodium. In this case, the leachant
system was sodium hydroxide. Sodium content of the HTT
coal was at a level attainable by water washing of the
HTT coal. The sodium chemically bound to the coal and
that associated with the ash was not removed by the
water wash.
(2) Low sulfur, residual alkali, residual ash in which the
residual alkali was primarily calcium. Sodium content
was less than about 0.5 percent on a coal basis. In
this case, the mixed leachant system composed of NaOH-
Ca(OH) was used to desulfurize the coal and to reduce
the degree of'sodium retention by the coal.
(3) Low sulfur, low ash, low alkali coal noted as deashed
coal. This coal was prepared by leaching HTT coal type
(1) in dilute sulfuric acid at ambient temperature. As
discussed earlier, deashing of coal type (2) would have pro-
duced a product containing a high concentration of cal-
cium sulfate formed from reaction of the calcium in
the HTT coal with the sulfuric acid.
* Those HTT coals prepared using a mixture of sodium hydroxide and calcium
hydroxide as the leachant system are not amenable to deashing with sulfuric
acid. This is because the lime reacts with the sulfuric acid to form
calcium sulfate which is not water soluble.
** Residual alkali is that which is not removed from the HTT coal by water
washing. A portion of this alkali is chemically bound to the coal as the
alkali salt of a carboxylic acid group. The remainder is present as the
alkali inorganic salts such as complex aluminum silicates which are not
are not water soluble.
-------
For each combustion test in the 1-lb/hr Laboratory Test Facility,
approximately 20 to 30 pounds (dried) HIT coal were prepared. Two hundred
pounds were prepared for combustion testing in the Multifuel Furnace (MFF)
Combustion unit.
Analyses of the Coals. Proximate and ultimate analyses of the HTT
coals and the corresponding raw coals are shown in Table 1. Analysis of these
data revealed:
(1) Environmentally acceptable solid fuel, with respect to
sulfur content, can be produced by hydrothermal treatment
of Martinka and Westland coals using either sodium
hydroxide or a mixture of sodium hydroxide and calcium
hydroxide as a leachant system. These clean coals con-
tained a sulfur equivalent of 0.97 to 1.26 pound of
S02/106 Btu.
(2) A small loss in heating value of these coals resulted
from the hydrothermal treatment. Treatment of other
coals under other programs has resulted in a gain in
heating value. Normally, the heating value of the HTT
coals (moisture ash free basis) will vary from H- 3 to
10 percent.
(3) Mineral matter content of the HTT coals was dependent on
the leachant system. The mixed leachant resulted in an
increase in the mineral matter content as the majority,
if not all, of the calcium remained with the coal, whereas
about 30 percent of the mineral matter was extracted from
the Martinka coal by the sodium hydroxide leachant. Wash-
ing the sodium hydroxide leached HTT coal with sulfuric
resulted in the extraction of 85.5 percent of the mineral
matter to produce a product containing 2.25 percent
mineral matter.
(4) Alkali retention by the coal was dependent on the leachant
system, type of leachant, and mineral matter content of the
10
-------
TABLE 1. ANALYSIS OF HIT COALS AND CORRESPONDING RAW COALS
(a)
Proximate Analysis
H-0, %
Ash, %
Volatile
Fixed Carbon
Heat Value, Btu/lb(MAF)
S02, lb/106 Btu
Ultimate Analysis
H20, %
Carbon, %
Hydrogen, %
Nitrogen, %
Sulfur, %
Ash, %
Oxygen, % by difference
Sodium, %
Calcium, %
Raw
0.41
19.7
29.2(36.6)
50.7(63.7)
(15,210)
2.94
0.41
67.0(83.4)
4.4(5.5)
1.21(1.50)
1.79(2.24)
19.7
5.5(6.9)
0.02(0.03)
0.13(0.16)
Martinka Coal
NaOH Leachant
3.05
13.4
28.5(34.1)
35.0(65.8)
(14,800)
0.97
3.05
71.4(85.5)
4.5(5.4)
1.3(1.56)
0.60(0.72)
13.4
5.7(6.8)
4.6(5.51)
0.15(0.18)
Mixed
Leachant
0.40
28.0
26.3(36.7)
45.3(63.3)
(14,691)
1.16
0.4
56.4(81.2)
3.8(5.3)
1.1(1.54)
0.61(0.85)
28.0
7.7(10.75)
1.4(1.96)
6.6(9.2)
(a) Values in parenthesis denote moisture ash free basis; others are on a product basis.
(b) Heat value on coal containing 9.887. ash and 1.32% H20.
(c) Heat values on coal containing 16.48% ash and 9.18% water.
(d) Ash and moisture content of coal used to determine heat value were 1.82 and 7.02, respectively.
(e) Sulfur higher than usual because heater burned out during run. Normally sulfur content would
be equal to or less than 1.2 Ib S02/10° Btu.
Continued
-------
Proximate Analysis
Hr\ °y
2U» '
Ash, 7.
Volatile
Fixed Carbon
Heat Value, Btu/lb(MAF)
S02, lb/106 Btu
Ultimate Andlysis
H20, %
Carbon, 7.
Hydrogen, 7.
Nitrogen, 7.
Sulfur, 7.
Ash, 7.
Oxygen, 7. by difference
Sodium, 7,
Calcium, 7.
Raw
< 0.1
10.0
36.9(41.0)
53.1(59.1)
(14,950)
3.01
<0.1
73.9(82.1)
5.1(5.7)
1.5(1.7)
2.02(2.25)
10.0
7.5(8.3)
0.02(0.02)
0.08(0.09)
NaOH
Leachant
0.4
13.3
31.2(36.1)
55.1(63.8)
(14,320)
1.50(e)
0.4
70.3(81.5)
4.3(5.0)
1.5(1.7)
0.93(1.07)
13.3
4.3(10.8)
2.08(2.4)
0.20(0.23)
Westland Coal
(b)
Mixed Leachant x
8.2
16.5
30.4(40.4)
44.9(59.6)
(14,100)(c>
1.50(e)
8.2
63.7(84.6)
4.3(5.7) ~
1.4(1.9)
0.67(0.89)
16.5
5.2(6.9)
0.19(0.25)
6.0(8.0)
Acid (H2S04)
Leachant
4.31
2.19
31.5(33.7)
62.0(66.3)
13,079(14,349)(d)
1.26
4.31
76.0(81.3)
4.6(4.9)
1.5(1.6)
1.05(1.12)^
2.19
0.40(0.43)
0.84(0.09)
(a) Values in parenthesis denote moisture ash free basis; others are on a product basis.
(b) Heat value on coal containing 9.887» ash and 1.327. H20.
(c) Heat values on coal containing 16.487, ash and 9.187. water.
(d) Ash and moisture content of coal used to determine heat value were 1.82 and 7.02, respectively.
(e) Sulfur higher than usual because heater burned out during run. Normally sulfur content would
be equal to or less than 1.2 Ib S02/10° Btu.
TABLE 1. (Continued)
-------
raw coal. Sodium hydroxide leachant produced HIT coals
containing 2.08 and 5.51 weight percent sodium (MAF),
whereas the mixed leachant produced HTT coals containing
0.25 to 1.96 weight percent sodium (MAF). The high sodium
values in both cases - 5.51 weight percent and 1.96 weight
percent - in the HTT Martinka coals resulted from the high
mineral matter content of the raw coal.
Task 2. Combustion Characterization Experiments
As part of the overall evaluation of the feasibility of hydro-
thermally treated coal utilization from an environmental point of view,
combustion studies were conducted in experimental laboratory combustion
units to characterize the burning of these coals.
Objective and Scope. The overall objectives of these combustion
studies were to characterize the combustion behavior and to evaluate the
pollutant emissions from the burning of the HTT coals relative to the corres-
ponding raw coals. Factors that were considered included:
General combustion behavior
- Ignition
- Flame stability
- Carbon burnout
Pollutant emissions
- S02
- NO
- CO
- Hydrocarbons
- Polycyclic organic matter (POM)
- Particulate (including size distribution)
- Trace elements
Ash properties
- Fouling
- Slagging
- Disposal characteristics (leachability)
- Resistivity
- Particle size.
13
-------
Ignition behavior and flame stability data were obtained on a
qualitative basis by observing and comparing ignition behavior and flame
stability of the HTT coals with those of the raw coals.
In addition, S0?, NO , CO, and CO- concentrations in the flue gases
£. X £_
were obtained by direct readout from meters which are part of the facilities.
S0~ concentrations on selected firings were obtained by collecting and analyz-
ing samples of the flue gases. Likewise, the selected samples of the flue
gases were collected and analyzed for hydrocarbons and POM concentrations.
Carbon burnout data were obtained from analysis of the ash (particulate matter)
and feed coal for carbon.
Analysis of the fly ash, with respect to composition and melting
point, provided data from which the fouling and slagging properties of the
various coals were predicted.
Disposal characteristics of the fly ash were assessed by chemical
analysis of the ash and by conducting preliminary leaching studies followed
by analysis of the leach liquor.
Combustion Plan. Because the quantity of HTT coals was limited,
a small combustion facility was designed specifically to fire small
quantities of coal (approximately one pound of coal per hour) . This facility was
used to characterize the candidate coals selected in Task 1. A larger
combustion facility, with a firing rate of about thirty pounds per hour
was used to verify the results of pound-per-hour unit for a selected HTT
coal and the corresponding raw coal. Facility operating procedures were
standardized to minimize day-to-day variations, while data collection and
sample analyses were conducted utilizing standard procedures.
Combustion Facilities. Figure 1 is a schematic of the small
pound-per-hour (Ib/hr) Laboratory Test Facility (LTF). Figure 2 is a
schematic of the larger Multifuel Furnace Facility (MFF). Specific details
of the design and construction of these facilities are given in Appendix C
while a brief description of each facility is given below.
The basic elements of the LTF are the combustion chamber and the
cooler. The combustion chamber consists of an inner disposable alumina
14
-------
Air Heater
r
Coal
Feeder
Combustor
NO , Thermoelectron,
v
chemiluminescence
C0_, Bechman, non-
dispersed infra-
red
CO, Beckman, non-
dispersed infra-red
02, Taylor,para-
magnetic analyzer
S02 Faristor, dry
electrochemical
analyzer
FIGURE 1. SCHEMATIC OF 1 Ib/hr LTF COMBUSTION UNIT
15
-------
Burner
Air _
Fuel
\
NO, Beckman, non-
dispersed infra-red
CO, Beckman, non-
dispersed infra-red
CO-, Beckman, non-.
dispersed infra-red
HC, Beckman, Flame
ionization detector
0_, Taylor, para-
magnetic analyzer -
S02, Faristor, dry
electrochemical
analyzer
Particulate, EPA Method 5
Furnace
Simulated boiler
section
Excess
Flue Gas
Exhaust
FIGURE 2. SCHEMATIC OF THE MULTIFUEL FURNACE FACILITY
16
-------
tube, 2-1/2-in. I.D. and 18 inches long. (Initially, the combustion chamber
was 12 inches. The chamber was lengthened after Run 18 to increase the
residence time of the coal in the combustion chamber.) A second liner en-
cases the inner liner. Insulation surrounds the outer liner to control
furnace heat loss. Several platinum, platinum-rhodium thermocouples are
imbedded along the inner tube to provide a measure of axial temperature
distribution. The combustion gases pass from the combustion chamber to a
coolera 3-in. I.D. x 5-ft. long air-cooled, counterflow stainless steel
heat exchanger. Combustion gases are sampled in and or at the exit of the
cooler as indicated in Figure 1.
The MFF is capable of firing pulverized coal at rates from about
20 Ib/hr to 80 Ib/hr. The basic element of this facility is the refractory-
lines furnace which is about 15 inches in diameter and 90 inches long. The
furnace is lined with 4 layers of firebrick to minimize heat loss. Four
observation ports are provided along the length of the furnace for flame
observation and optical pyrometer readings at various distances from the
burner. At the outlet, the diameter of the furnace is reduced to enclose
the flame, provide for normal recircul.ation, and limit radiation loss.
Combustion gases leave the furnace and enter the simulated boiler convec-
tion passes where they are cooled to 400 to 600 F. Combustion gases are
sampled at the exit of this section as indicated in Figure 2.
Combustion air can be heated to temperatures of up to 800 F and
can be introduced axially, tangentially, or a combination of both. In
this study, air was admitted axialLy.
Operational Procedures. Both units were initially fired on gase-
ous fuels to a predetermined furnace temperature (about 1800 F for the LTF
and 2200 F for the MFF units). Pulverized coal was then fired for one to
two hours prior to data collection to establish the desired furnace opera-
ting conditions and furnace equilibrium.
Sampling and Analytical Procedures. Particulate and gaseous
samples were collected and analyzed utilizing standard or presently
acceptable procedures. Particulates were sampled during each run and the
17
-------
gaseous components listed in Figures 1 and 2 were continuously monitored
throughout a run. Table 2 indicates the various analytical methods used
for the samples collected. The procedures used in obtaining gaseous,
particulate, and POM samples are described below.
The major gaseous components of interest, S09, NO, CO, C09,
£. <'
unburned hydrocarbons (monitored only on the MFF), and 02 were monitored con-
tinuously throughout a given run. Figures 1 and 2 indicate the types of mon-
itors used for each facility. For the LTF unit, gaseous samples were drawn
from the cooler tube section about 1-1/2 feet from the exhaust end of the
tube and at the center of the duct. For the MFF, samples were drawn in
and near the simulated boiler convection pass section just upstream of
the particulate sampling port.
For the LTF unit, particulate was collected by passing the entire
flue gas stream through a Type A glass-fiber filter at a temperature of
about 300 F. In addition to this filter catch, particulate samples were
collected from the loose deposits on the wall of the cooler tube. The entire
cooler tube was scraped clean after each run to obtain sufficient sample and
to avoid contamination in subsequent runs. Both the filterable particulate
and the cooler tube particulate were weighed, divided, and analyzed. Due to
the nature of the combustor, a major portion of the particulate was retained
in the combustion liner as slag. This slag was not representative of the
particulate catch since it was subjected to high temperature and was highly
oxidized.
For the MFF, a filterable particulate sample was collected and analyzed
according to EPA Method 5.
POM samples were collected by a modified EPA Method 5 train with
an adsorbent column located downstream of the filter. The probe wash, filter
catch, an adsorbent column catch were all used to determine the POM levels
utilizing gas chromatography/mass spectrometry computer quantification procedure (2).
18
-------
TABLE 2. ANALYTICAL METHODS FOR SAMPLE ANALYSIS
Component
Coal
Ash
Gases
Analysis
C,H,N,0,S,SO , Ash, HO, Volatile Matter
Fixed Carbon
Na, Ca
Particle size
Trace elements
Heating Value
Thermal Analysis
C,H,N,0 ,S ,SO, , Ash, HO, Fixed Carbon
Na, Ca
Trace elements
Particle size
Resistivity
Leachability
CO, CO
so
NO; N0
Particulates
Method
ASTM D2492-68
ASTM D2492-68
AA
Coulter Counter, Sieve
SSMS, OES
Calorimeter/ASTM D2015
dTGA, DTA
ASTM D2492-68
AA
SSMS, OES
Coulter Counter
Test Cell
NDIR
Coulimetric
Chemiluminescence or NDIR
Polarographic or paramagnetic
GC/MS
Method 5
*AA - atomic absorption
SSMS - spark source mass spectrometry
OES - optical emission spectrometry
dTGa - derivative thermogravemetric analysis
DTA - differential thermal analysis
NDIR - non-dispersed infra-red
GC/MS - gas chromatography/mass spectrometry
-------
Combustion Results
Combustion characterization experiments were conducted in the LTF
and Multifuel Furnace units on a number of HIT coals and the corresponsing
raw coals as noted in Table 3. The results of these experiments are sum-
marized in Table 4, 5, and 6. (Run 8 was conducted for instrumentation
checkout purposes, and therefore was not included in these tables.) As shown
in Table 6, the results of the experiments in the LTF unit are consistent
with those of the MFF based upon the firing of the raw and mixed leachant
Westland coals in both facilities. The total capture of the SO- in the HTT
firing in the MFF may be an artifact of the combustion facility as well as
of the treated coal. The horizontal layout of the MFF allows more slag to
collect beyond the combustion zone, thus aiding the capture of ash and pro-
duct gases in the slag.
These results, supplemented by additional coal and ash analyses,
determined the
(1) General combustion behavior
(2) Pollutant emissions
(3) Ash characteristics
of the HTT coals as compared to the corresponding raw coals. A discussion
of the above three aspects of HTT coal utilization is presented in the
following sections.
20
-------
TABLE 3. COALS USED IN VARIOUS COMBUSTION EXPERIMENTS
A. Untreated (Raw) Run Numbers
1. Westland (high ash) - run-of-mine 9, 19
2. Westland (low ash) - washed (Prep. Plant) 14, 15, 22, 30
3. Martinka (moderate ash) - washed (Prep. Plant) 1, 3, 16, 23
B. HTT, Low Sulfur, Residual Alkali, Residual Ash
1. Martinka (NaOH) - Residual Na 2, 4, 5, 17, 21
to 2. Martinka (NaOH-CaO) - Low Na, Residual Ca 6, 7, 12, 25
M 3. Westland (low ash) - (NaOH) - Residual Na 10, 11, 13, 20
4. Westland (low ash) - (NaOH-CaO) - Low Na, Residual Ca 18, 29, 31
C. HTT, Low Sulfur, Low Alkali, Low Ash
1. Westland - acid leached 24, 26, 27, 28
-------
TABLE 4. COMBUSTION CONDITIONS AND RESULTS FROM LTF COMBUSTION UNIT
N>
ro
Run No. 1
Coal Type
Raw
Martinka
Combustion Conditions
Coal feed rate, Ib/hr
Air feed rate, Ib/hr
Sec: psi ratio
Furnace temp, °F
Gas_ Analysis (as measured)
CO^ , °l*
0 , 7.
CO, ppm
NO , ppm
Theoretical NOX, ppm
SO*, ppm
Theoretical SO., ppm
SO,, Ib/MM Btu
2 (MAF)
.Sulfur capture, %
Res. time , milli sec
Carbon burnout, % .
Particulate loadinp. mg/Nm
POM loading , (ig/Nm*
1.9
25.9
7.7
2105 )
12.7
6.6
115
600
2041
290
406
1.16
28.57
137
97.7
4612
7
Martinka
Mixed
Leachant
1.85
20.6
10.1
2265
-------
r-o
Run No. 9
Coal Type
Raw West land
High ash
Combustion Conditions
Coal feed rate, Ib/hr
Air feed rate, Ib/hr
Sec: psi ratio
Furnace cenp,0?
Gas Analysis (as measured)
co2, %
0 , %
CO, ppm
NOX, Ppm
Theoretical NO , ppm
SO^i ppm
Theoretical SO , ppm
SO,, Ib/MM Btu
2 (MAP)
Sulfur capture, 7.
Res. time , milli sec
Carbon burnout, %
Particulate loading, mg/Nm3
POM loading , jig/Mm3
1.98.
20.1
8.8
2100 (b)
12.8
11.5
125
NA
2245
2250
2312
5.2
2.68
61
97.4
4471
10
West land
NaOH
Leachant
0.44
8.1
7.2
1855 (b)
6.7
12.4
1200
215
1701
250
458
1.5
45.4
185
11
West land
NaOH
Leachant
1.15
17.0
10
2140 (b)
14.5
3.5
95
625
2114
415
570
1.5
26.6
78
--
39
12
warn inka
Mixed
Leachant
1.2
13.2
7.6
2080(b)
12.9
3.5
90
605
2254
320
448
28.3
103
__
--
24
13
Westiand
NaOH
Leachant
1.3
16.6
9.1
2060 (b)
13.2
2.0
67
695
2450
464
660
1.5
29.7
83
99.9
233
14
Raw
West land
Low ash
1.65
19.65
10.00
2320(b)
14.7
2.0
150
660
2608
1725
1537
3.00
__
63
.._
__
65
15
Raw
Westiand
Lew ash
1.33
16.25
8.00
2270(b)
14.5
2.0
135
715
2530
1790
1498
3.00
_ _
73
2335
(b) Inside wall temperature at tube center
TABLE 4 (Continued)
-------
1X5
-O
Run No.
Coal Type
Combustion Conditions
Coal feed rate, Ib/hr
Air feed rate, Ib/hr
Sec: psi ratio
Furnace temp,°F
Gas Analysis (as measured)
C02, 7.
0,, 7.
CO, ppm
NO , ppm
Theoretical NO' , ppm
SO , ppm
Theoretical SO , ppm
SO^, Ib/MM Btu
(MAF)
Sulfur capture, 7.
Res. time , milli sec
Carbon burnout, 7,
Particulate loading, mg/Nm
POM loading , ^g/.N,-'3
16 17
Raw Martinka
Martinka NaOH
Leachant
1.27
12.26
4.0
2095 (b)
14.4
1.5
705
650
2789
1910
1877
2.97
110
1.4
16.75
8.4
2080Cb)
14.3
3.7
100
625
2423
380
492
1.06
22.7
81
--
4490
18
Westland
Mixed
Leachant
1.28
14.6
7.8
2090 (b)
12.6
4.0
55
585
2779
250
580
1.27
56.9
93
--
1514
46
19
Raw
Westland
High ash
1.25
16.53
4.4
1656
-------
TABLE 5. COAL-ASH ANALYSES
Run No.
1
(I) Astl
Analysis (MF)
C
H
N
0
304^)
Ash
Na
Ca
V.M.
Fixed C
Heat value, Btu/lb (MAF) ^
Run No.
Analysis (MF)
C
H
N
0
SS04(5)
Ash
Na
Ca
V.M.
Fixed C
Heat value, Btu/lb (MAF)
Coal - Cooler u;
67.3
4.4
1.2
5.5
1.8 0.52
19.8 87.9
0.03
0.2
29.32
50.9
') 15,100
4
Ash
Coal Cooler
69.6 8.0
4.3 0.1
1.4 0.1
7.0
0.6 2.4
2.2
17.1 90.6
2.6 13.6
0.1 0.6
27.4
51.2
14,900
Slag1"''
0.01
99.5
Coal
70.1
4.5
1.4
6.6
0.6
17.4
2.1
0.1
27.4
51.2
14,900
2
AStl
Coal Cooler
72.6 25.4
4.5 0.3
1.4 0.4
7.1
0.7 1.5
1.2
13.7 71.7
1.9 10.1
0.1 0.5
29.4
56.8
14,900
5
Ash
Cooler Slag
11.4
0.1
0.1
2.3 0.4
1.8
86.9 100.0
12.0 14.9
0.7 0.7
Coal
67.6
4.6
1.3
4.3
2.0
20.2
0.03
0.2
29.21
50.8
15,100
Coal
59.9
3.9
1.2
5,7
0.6
28.3
1.3
6.0
26.4
45.5
14,700
3
rtsh
Filter1'4'1 Cooler
28.9 5.6
0.2 0.1
0.4 0.1
0.4 0.4
2.6 0.2
2.2
65.9 93.5
6
ASH
Filter Cooler
22.5 13.3
0.2 0.1
0.4 0.2
3.8 0.2
0.7 1.6
71.0 86.3
3.0 3.9
16.2 20.2
(1) (MF)--moisture free
(2) Ash from cooler tube
(3) Slag from vicinity of burner
(4) Ash from filter
(5) Sulfate reported as percent sulfur
(6) (MAF)--mosture ash free
Continued
-------
ho
Run No.
Analysis
(MF)
C
H
N
0
S
S04 *
Aati
Na
Ca
V.M.
Fixed C
Heat value, Btu/lb (MAF)
Run No.
Analysis
Heat value
(MF)
C
H
N
0
S
SC-4 (*)
Ash
Na
Ca
V.M.
Fixed C
, Btu/lb (MAF)
7
Ash
Coal Filter
59.
3.
1.
5.
0.
28.
1.
6.
26.
45.
14,
Coal
70.6
4.3
1.5
9.3
0.9
--
13.4
2.1
0.2
31.3
55.3
14,400
9
9
2
7
6 1.2
«. - .
3 94.0
3 4.1
0 22.5
4
5
700
11
Ash
Cooler Slag
11.1
0.2
0.2
6.6 1.4
5.6 1.6
88.6 99.7
14.9 16.9
1.49 1.5
9
Cooler
6.6
0.1
0.1
--
2.3
"
95.3
4.7
22.5
12
Coal
59.9
3.9
1.2
5.7
0.5
--
28.3
1.3
6.0
26.4
45.5
14,700
Coal
55.6
3.8
1.1
8.2
2.6
28.7
0.08
0.4
29.6
41.7
14,100
Ash
Cooler
4.5
0.1
0.1
1.58
1.5
95.0
4.5
22.3
Ash
Filter
29.3
0.3
0.4
--
1.7
0.2
68.2
Coal
70.6
4.3
1.5
9.3
0.9
13.4
2.1
0.20
31.3
55.3
14,400
Cooler
22.2
0.3
0.4
--
0.72
0.4
75.1
13
Filter
22.4
0.3
0.4
--
2.3
2.0
79.2
10.9
1.25
10
Ash
Coal Cooler
70.6 29.4
4.3 0.6
1.5 0.7
9.3
0.9 4.8
4.7
13.4 66.4
2.1 11.5
0.2 1.2
31.3
55.3
14,400
Ash
Cooler Slag
8.2
0.1
0.1
_-
6.4 1.2
7.0 1.3
92.8 100.1
14.5 12.7
2.03 5.8
Slag
2.7
3.2
99.7
14.3
1.2
(*) Sulfate reported as percent sulfur
TABLE 5. (Continued)
-------
Run No.
14
15
16
Ash
Analysis
Heat value,
Run No.
Analysis
(MF)
C
H
N
0
S
S04 (*>
Ash
Na
Ca
V.M.
Fixed C
Btu/lb (MAF)
(MF)
C
H
N
0
S
S04 <*>
L-
Ash
Na
Ca
V.M.
Fixed C
nsn
Coal Ash Coal Filter Cooler Coal Filter
73.9
5.1
1.5
7.5
2.0
._
10.0
0.02
0.08
36.9
53.1
15,000
TT
Coal
70.1
4.5
1.4
6.6
0.6
--
17.4
2.1
0.12
27.4
51.2
73.9 61.7
5.1 0.4
1.5 1.1
7.5 7.5
2.0 2.6
0.29
10.0 34.9
0.2 0.03
0.08 0.21
36.9
53.1
15,000
Ash
Filter Cooler
59.8 55.4
2.8 2.4
1.2 1.2
._
1.0 1.44
0.49 0.99
31.8 36.6
4.8 5.40
0.3 0.5
Heat value, Btu/lb (MAF) 14,900
13.1 67.6
0.1 4.6
0.2 1.3
4.3
0.9 2.0
0.71
84.9 20.2
0.5
1.01
29.2
50.8
15,100
18
Ash
Coal Filter. Cooler
69.4 8.2 5.3
4.7 0.1 0.1
1.5 0.1 0.2
5.7
0.73 2.4 5.3
2.3 5.1
18.0 91.2 94.0
0.2 1.13 1.3
8.0 3.2 3.2
40.4
59.6
14,100
42.1
0.3
0.6
..
1.2
0.2
55.2
0.04
0.3
_ _
-.
--
Slag
60.1
60.1
20.1
-_
0.3
0.3
100.0
0.5
3.9
Cooler
19.1
0.2
0.2
__
0.6
0.3
79.4
0.19
0.7
__
--
(*) Sulfate reported as percent sulfur
TABLE 5. (Continued)
-------
00
Run No.
Analysis I
CMF)
C
H
N
0
S
S04 (*)
Ash
Na
Ca
V.M.
Fixed C
Heat value, Btu/lb (MAF)
Run No .
Analysis
Heat value
Off)
C
H
N
0
S
S04 (*)
Ash
Na
Ca
V,M.
Fixed C
, Btu/lb (KAF)
19
Coal
55.5
3.9
1.0
8.4
2.5
28.7
0.06
0.40
29.6
41.7
14,100
21
Coal
69.6
4.32
1.4
7.0
0.6
--
17.0
2.6
0.1
27.4
51.2
14,900
20
Filter
19.8
0.3
0.3
--
1.4
1.2
75.2
0.31
1.9
Filter
37.8
0.5
0.7
1.22
0.7
61.9
9.0
0.5
Ash
Cooler
16.3
0.2
0.2
--
0.8
0.6
80.4
0.2
1.1
Ash
Cooler
33.2
0.3
0.6
2.5
2.1
65.0
9.4
0.7
Slag
1.3
0.1
<0.1
--
0.27
0.2
98.2
0.09
1.0
Slag
73.9
0.3
0.3
>100.0
17.1
0.7
Coal
70.36
4.44
1.31
9.68
0.91
13.30
1.90
0.18
31.33
55.32
14,388
Coal
56.4
5.1
1.5
7.5
2.0
--
10.0
0.02
0.08
36.9
53.1
15 ,000
Filter
12.8
0.1
0.1
-.
2.6
2.4
87.0
12.8
1.41
22
Filter
49.4
0.7
0.9
1.3
1.30
0.2
38.7
0.06
0.3
Ash
Cooler
11.8
0.2
0.2
--
7.0
1.2
Slag
1.46
1.09
86.3 >100.0
13.6
1.7
Ash
Cooler
0.6
0.9
0.2
1.1
0.3
46.0
0.1
0.4
15.8
1.56
Slag
0.08
0.02
100.0
0.04
0.07
(*) Sulfate reported as percent sulfur
TABLE 5. (Continued)
-------
NJ
VO
Run No.
Analysis
HeaL val
Run No.
Analysis
(MF)
C
H
N
0
S
S04(*)
Ash
Na
Ca
V.M.
Fixed C
ne, Btu/lb
(MF)
C
H
N
0
S
304 W
Ash
Na
Ca
V.M.
Fixed C
Heat value, Btu/lb
23
Coal
67.6
4.6
1.3
4.3
2.0
--
20.2
--
29.2
50.8
(MAF) 15,100
27
Coal
76.0
4.6
1.5
10.3
1.0
--
2.2
0.4
0.09
31.5
62.0
(MAF) 14,300
24
Ash Coal
76.0
4.6
1.5
10.3
1.0
--
2.2
0.4
0.09
31.5
62.0
14,300
y
Ash
Filter Cooler
61.7 59.4
_-
__
0.5 1.5
33.9 32.1
0.2 0.5
0.8 1.4
Ash
--
--
__
.-
--
_ _
--
--
--
--
"
25
Coal
60.0
3.9
1.2
5.7
0.6
--
28.3
1.29
6.0
26.4
45.5
14,700
28
Ash
Filter
13.2
0.1
0.2
--
0.6
0.5
85.8
4.0
19.7
--
--
Ash
Coal Filter Cooler
76
4
1
10
1
-
2
0
0
31
62
14
.0 ^9.6
.6 0.3
.5 0.6
.3
.0
0.4
.2 47.0
.4 0.2
.09 1.0
.5
.0
,300
34.4
0.3
0.4
--
59.8
2.0.
1.01
26
Coal
76.0
4.6
1.5
10.3
1.0
2.2
0.4
0.09
31.5
62.0
14,300
Coal
69.4
4.67
1.5
5.7
18.0
0.21
8.0
40.4
59.6
Ash
Filter
62.2
--
--
0.9
0.6
45.4
0.2
0.8
--
-
29
Filter
8.3
0.1
0.2
--
1.1
89.6
1.4
34.7
--
Cooler
41.8
--
2.1
1.8
54.3
0.6
2.6
~
Ash
Cooler
12.1
0.2
0.2
2.9
85.0
1.4
34.2
-.
"Slag
<0.1
<0.1
<0.1
--
3.3
99.8
1.20
34.9
__
_-
14,100
(.Y.) Sulfate reported as percent sulfur
TABLE 5. (Continued)
-------
Run No.
Analysis
Off)
C
H
N
0
S
Ash
Na
Ca
V.M.
Fixed C
Heat value, Btu/lb (MAF)
30
Coal
73.9
5.1
1.5
7.5
2.0
10.0
.02
.08
36.9
53.1
15 .000
Ash
Filter
1.7
.09
.1
6.5
65.2
.31
.07
--
31
Coal
69.4
4.7
1.5
5.7
.6
18.0
.2
8.0
40.4
59.6
14,100
Ash
Filter
2.1
.08
<.l
3.0
85.9
35.9
1.45
--
(*) Sulfate reported as percent sulfur
TABLE 5. (Continued)
-------
TABLE 6. COMPARISON OF RAW AND HIT WESTLAND COAL FIRINGS
Ib/hr
Firing Rate, Ib/hr
Furnace Wall Temp, F
OQ, percent
C02> percent
CO, ppm
HC , ppm
NO, ppm
S02, ppm
S02~capture, percent
POM Loading, yg/Nm3
Particulate Loading,
mg/Nm3
RawTaJ
1.6
2270
2.0
14.7
150
NA
660
1730
0
65
2335
Treated (b)
1.3
2090
4.0
12.6
55
NA
585
250
57
46
1515
MFF
Raw^C-' Treated & )
30
2550
5.0
14.4
3
0
680
1230
0
0.12
N.A.
30
2300
5.
14.
3
0
780
0
100
0.
7500
0
4
12
(a) Run 14
(b) Run 18
(c) Run 30
(d) Run 31
31
-------
General Combustion Behavior. Certain general combustion characteristics
of both the raw and treated coals, such as ignition temperature and reactivity,
were determined quantitatively from the derivative thermogravimetric (dTGA)
and the differential thermal (DTA) fuel analyses. The results of the dTGA
and DTA are summarized in Tables 7 and 8, respectively.
From these analyses, the combustion characteristics of these
coals,in terms of ignition, reactivity, and possibly flammability, may
have been improved by the hydrothermal treatment. For example, the ignition
temperature of Westland coal was reduced from 426 C to 344 C (Table 7), a
reduction of 82 C, by treating the coal with sodium hydroxide and the
mixed leachant systems. A similar effect was noted by hydrothermal treat-
ment of the Martinka coal with these leachant systems.
This was expected in view of other hydrothermal work which has
been conducted at Battelle-Columbus. In this work, hydrothermal treatment
of coals resulted in alteration and modification of the coal structure to
a more simplified structure. This is evidenced by the fact that the
liquid products from the pyrolysis of HTT coals contained less
(4)
asphaltenes than the liquid products from the corresponding raw coals
These lower molecular weight organic liquids from the HTT coals should
have a lower ignition temperature and a higher degree of flammability
than the higher molecular weight liquids from the raw coals.
The increased reactivity is reflected in Table 8. For example,
treatment of the Martinka and Westland coals with the mixed leachant
system resulted in HTT coals which burned out at a maximum temperature
of about 470 C, whereas the raw coals burned out at a temperature of
about 585 to 600 C. A similar effect, but not to this degree, was
observed with the sodium-hydroxide treated coals.
While there may not be a direct correlation between combustion
and gasification, it has been observed that hydrothermal treatment of coal
with the mixed leachant system results in an increase in the steam and
(4)
hydrogasification rates by as much as 40 to 50 fold . This has been
attributed to (1) alteration and modification of the coal structure, and
(2) impregnation of the coal particle with a catalyst, in this case,
calcium and/or sodium. This work has also shown that the mixed leachant-
treated coal is more reactive than the sodium-hydroxide treated coal.
32
-------
TABLE 7. DIFFERENTIAL THERMAL ANALYSES OF RAW AND HTT COALS
(a)
Westland
Raw
Coal
Martinka
Raw
Coal(b)
Westland Coal
NaOH
Leachant(c)
Martinka Coal
NaOH
Leachant(d)
Westland Coal
Mixed
Leachant(
Martinka Coal
Mixed
Leachant( )
Starting Exotherm, C 233
Ignition Point, C 426
Secondary Exotherm, C
End of Exotherm, C 615
243
432
622
UJ
OJ
Air
252
344
488
564
Nitrogen
263
360
508
578
268
344
494
555
252
376
493
553
Starting Endotherm, C
Peak No. 1, C
Peak No. 2, C
Peak No. 3, C
End of Endotherm, C
Peak No. 4, C
400
442
516
555
584
""
405
455
530
563
585
385
462
519
--
550
622
375
466
513
--
557
"
329
467
514
--
550
678
414
475
520
--
554
665
(a) DTA performed with Stone Model 202 at 15 C/min and dynamic gas flow of 94 ml/min.
(b) Sample 41167
(c) Sample 31731-53 + -60
(d) Run # 5, 41169
(e) Sample 32135-24
(f) Run # 7, 41171
-------
TABLE 8. THERMOGRAVIMETRIC ANALYSES OF RAW AND HTT COALS
Ash, percent
Temperature Range ,
Maximum Rate of
Weight Loss, mg/min
Temperature at Maximum
Rate of 'weight Loss,
Raw
Westland
Coal
10.3
220-585
17.5
C 320
Martinka Raw
Coal, 41167
19.7
250-600
19.0
275
Westland Coal
NaOK Leachant
31731-53 '& 60
13.4
230-570
21.5
305
Martiuka Coal
NaOH Leachant
Run #5, 41169
17.0
240-510
27.5
275
Westland Coal
."lixed Leachant
32135-24
17.4
240-465
23.0
285
Martinka Coal
Mixed Leachant
Run #7, 41171
28.4
270-470
27.0
310
(a) TGA performed with Cahn Electrobalance at 15 C/min and air flow of 800 ml/rain.
(b) Temperature range over which most of the sample is lost.
-------
The results of the TGA and DTA analyses were not reflected in the
actual combustion experiments. Combustion of the raw and treated coals in
both the LTF and MFF facilities indicated no apparent (visible) difference
in the combustion behavior (ease of ignition and flame stability) between
the treated and corresponding raw coals. This is not surprising considering
the relatively small (but definite) difference in the TGA and DTA of analy-
ses of the raw and treated coals. However, qualitatively, the HTT coals
burned as well or better than the raw coals. Thus, hydrothermal treatment
did not have a detrimental effect on the combustion behavior of the coals
evaluated.
Pollutant Emissions. Pollutant emissions levels were measured
from the firing of the raw and treated coals in the LTF and MFF units
under typical utility boiler conditions of about 15 to 20 percent excess air.
Generally, from the analyses of the coal and knowing the type of combustion
system, these emissions can be predicted as indicated by the emission
factors contained in the literature . Accordingly, the combustion studies
were intended to verify these predictions and also to identify if there
are any factors in the coal processing that alter the predicted emission
levels.
S00 - Sulfur Capture. The SO level in the exhaust gases of the
2_ 2
burned coal was monitored continuously throughout a given run. In addition,
for each run, SO levels were calculated from the sulfur content of the coal
and the amount of combustion air assuming total oxidation of the sulfur to
SO . From the data, sulfur capture as defined by the equation
SO (theoretical) - SO (measured)
Percent sulfur capture (SC) = 7. : -^ x 100
r SO (theoretical)
was calculated. The measured and calculated SO values and sulfur capture
data, along with other pertinent data relating to composition of the coal
are shown in Table 9.
35
-------
TABLE 9. SULFUR CAPTURE IN RAW AND TREATED COALS
(a)
Rim
1
3
16
2
4
5
17
21
6
7
12
14
15
19
22
30
10
11
13
20
18
29
31
24
26
27
28
Cool
weight
No. S
Martinka -
1.80
2.00
2.00
Martinka -
0.68
0.64
0.65
0.65
0.64
Martinka -
0.55
0.55
0.55
West land -
2.02
2.02
2.54
2.02
2.0
Westland -
0.93
0.93
0.93
0.91
Westland -
0.73
0.73
0.61
Westland -
1.05
1.05
1.05
1.05
Analysis ,
percent (MF)
Na
raw
0.03
0.03
0.03
NaOH
1.90
2.61
2.1
2.1
2.61
mixed
1.29
1.29
1.29
raw
0.02
0.02
0.06
0.02
0.02
NaOH
2.09
2.09
2.09
1.90
mixed
0.21
0.21
0.21
acid
0.43
0.43
0.43
0.43
Ca
0.16
0.16
0.16
Leacliant
0.13
0.11
0.12
0.12
0.11
leachant
5.95
5.95
5.95
0.08
0.08
0.40
0.08
0.08
Lcschant
0.20
0.20
0.20
0.18
leachant
8.0
8.0
8.0
leached
0.09
0.09
0.09
0.09
S09 in Flue Gas,
ppm
The ar
1180
1440
0880
590
470
330
490
490
410
450
450
1540
1500
1740
1610
1400
460
570
660
650
580
540
450
630
660
660
660
Measured
1240
1300
1910
210
310
205
380
120
290
--
320
1725
1790
1220
1170
1250
250
420
465
220
250
125
0
560
510
520
500
Percent
Sulfur Capture
10
--
64
34
38
23
76
29
--
28
--
30
31
11
45
27
30
66
57
77
100
11
14
20
24
(a) In laboratory combustion unit.
36
-------
From these data, it is evident that sulfur is being retained
(captured by the ash), probably as sulfates. Additionally, the results
indicate that the HTT coals with residual alkali are significantly more
efficient in capturing sulfur oxides than are the raw coals. Analysis of
the ash from the burned coals also tend to confirm the greater capture
potential of the HTT coals as the ash from the combustion of the treated
coals contained a higher percentage of sulfates than the ash from the raw
coals.
Sulfur capture is attributed to the alkaline materials, sodium
and calcium, contained in the HTT coals and also may be related to the
ash composition. Corrosion studies at Battelle and elsewhere confirm
that sulfur oxides in gas streams can lead to the production of sulfates
( fi)
and complex alkali-metal sulfates in caustic-containing systems . It is
likely that similar sulfur-containing compounds are formed in the alkaline
systems derived from the HTT coals. Also, studies are being conducted
which indicate that the relationship between the sodium, aluminum, and
silicon content of lignite influence the degree of sulfur capture by the
alkali in lignite . For example, during the combustion of a lignite,
the sodium may react with the sulfur to form sodium sulfate and/or
with the aluminum and silicon values in the ash to form complex sodium
aluminum silicates. This may be occurring in the combustion of HTT coals.
If so, this may account for the variation in sulfur capture between the
various HTT coals.
The degree of sulfur capture (Table 9) appears to be related
to the concentration of alkali (sodium plus calcium) in the coal as noted
below:
Raw
20.5
0-30.7
HTT
NaOH
Leachant
44.8
22.7-75.0
HTT
Mixed
Leachant
58.2
28.3-100
HTT
Deashed
17
10.8-24.2
Sulfur capture, wt % (av)
Range
Alkali (Na+Ca) wt % (av) ^0.15 ^2.2 'W. 7 ^0.5 .
37
-------
In general, coals low in alkali content, such as the raw and acid-leached,
show a low potential for sulfur capture, whereas those containing higher
concentrations of alkali showed a higher potential for sulfur capture.
One somewhat surprising result that deserves additional attention
is the 100 percent sulfur capture in firing of the mixed leachant Westland
coal in the MFF. The sulfur in the coal should be found in the products of
combustion as SO and/or as a sulfate. Accordingly, the 450 ppm of S02
(theoretical value) must appear in the particulate catch as a sulfate or
gaseous SO . From the particulate loading of 7500 mg/Nm3 (Table 7) and
the weight percent of sulfur of 3.0 in the filterable particulate catch (Table
8) the sulfur concentration converts into an equivalent S02 level of 350
ppm or somewhat less than the predicted value of 450 ppm. This slight
discrepancy appears reasonable in view of sensitivity of these values to the
accuracy of the SO determination (by the Faristor) and the analyses of the
coal and the particulate catch for sulfur. Further confirmation of the
observation of complete SO removal is indicated by noting that the ratio of the
sulfur to the mineral matter in coal (0.33) is nearly identical to the ratio
of the sulfur to the ash in the filterable particulate sample (0.35). Thus,
the 100 percent sulfur capture appears real.
In the Ib/hr unit, sulfur captures of 57 percent with a 12-inch combustion
chamber and 77 percent with an 18-inch chamber were observed for Runs 18 and
19, respectively. Apparently the longer residence time (700 milliseconds)
and/or the slagging conditions in the MFF resulted in the higher sulfur cap-
ture.
N0__ Fuel-N-Conversion. In addition to the sulfur bearing compounds,
coals generally have a measurable amount of nitrogen (N)-bearing materials.
Although the HTT process has been shown to reduce significantly the sulfur
materials in the coals, it has not been effective in reducing the N-bearing
materials. The average NO levels observed in the seven different coals
X
used in the Ib/hr combustor are given in Table 10.
38
-------
TABLE 10. NO DATA FROM COAL FIRINGS IN THE LTF COMBUSTOR
x
Average NQ., ppm
Martinka Westland
Theore- Theore- Percent Conversion
Coal
Raw
Caustic
Mix-leachant
Acid-leachant
Measured
710
660
670
tical
2330
2340
2260
Measured tical
630
700
620
700
2340
2230
2700
2100
Average
Martinka
31
28
30
30
Westland
27
31
23
33
28
Most of the NO measured in the flue gases was in the form of
x
NO. The calculated NO values in Table 10 are based on (1) complete
X
conversion of the fuel-N to NO at the calculated excess air level used
in the runs for each coal, and (2) no contribution of thermal NO.
The measured average NO values are comparable for each coal burned,
X
reflecting the inertness of the HTT process toward removing the fuel-N com-
pounds. The measured NO values, on the other hand, are lower than the cor-
responding calculated values. These N0x conversions are quite typical of
results obtained in fuel-N conversion studies. Only at very low fuel-N
levels (^100 ppm) is high conversion of fuel-N to N0x observed in combustion
processes. As the fuel-N concentration increases in the fuel, the fraction
of fuel-N converted to NO decreases . In the present study, it appears
X
that the overall average conversion efficiency is about 30 percent, which
(8)
appears to be in line with results from other studies.
The NO emission levels measured during the two runs (Runs 30 and
31) in the MFF appear to be consistent with those measured in the LTF com-
bustor. It should be noted that, for the MFF, NO levels from the combustion
of the mixed-leachant coal were somewhat higher than those from the raw
Westland coal even though the furnace wall temperatures were somewhat lower.
These differences, however, appear to be within the data scatter of experi-
mentation. They also suggest that the contribution of thermal NO is
negligible.
39
-------
CO-CO,-00. The CO, C00, and 00 levels were used as indicators to
£. 'Z i L
establish the desired combustion operating conditions. These conditions
were controlled by varying the excess air to maintain CO levels below 300
ppm. Fluctuations in the coal feed rate for the LTF produced excursions
in the CO-CO^-O- levels, but overall, the 02-CO levels were maintained at
approximately the desired levels. However, CO levels on the order of 100
ppm were observed in the LTF unit indicating that carbon burnout was not
as complete as desired. For the MFF, CO levels less than 5 ppm could be
achieved at excess oxygen levels of about 5 percent.
Particulate Loading. For pulverized-coal-fired systems, particu-
late loadings are dependent upon the mineral matter content of the coal
and the design of the combustion system*. Coal mineral matter will either
be emitted as fly ash in the flue gases or retained in the combustion system.
In utility power plants, approximately 50 to 80 percent of the coal mineral
matter is retained in wet bottom or cyclone boilers while only 20 percent is
retained in dry-bottom boilers. Both the LTF and MFF systems tend to operate
as slagging units with the majority of ash being retained in the system. As
a consequence, the particulate loading data gives an indication of the coal
ash behavior (providing the carbon component is constant or negligible)
rather than a realistic measure of the fly-ash emission.
In the LTF runs, particulate loadings were not determined according
to Method 5 but were based on the fly-ash catch on a filter located at the
exit of the cooler. The total combustion products passed through this filter.
Because the furnace wall temperature (which should have a significant effect
on ash retention in the system and thus on the particulate loading) was not
constant from one run to another, the relative differences of the particulate
loadings between the treated and raw coals could not be determined. However,
it can be noted by comparing runs of the same coal type in Table 4 (for example,
Runs 6, 7, and 25; Runs 11 and 13; Runs 15 and 22; Runs 18 and 29; and
Runs 9 and 19) but with different furnace wall temperatures that higher
particulate loadings were generally observed for those runs with lower furnace
^Incomplete carbon burnout can contribute to the overall particulate levels
but generally is small compared to the ash component,
40
-------
wall temperatures. Assuming that lower furnace wall temperatures are an
indication of cooler ash particles, this observation suggests that the ash
particles are not as "sticky" at lower temperatures and thus are emitted in
higher levels as fly ash.
For the MFF runs, because the mixed leachant coal contains about
80 percent more ash than tho raw Westland coal (Run 30), it was anticipated
that the particulate loading from the combustion of the treated coal would be
higher than that from the raw coal (Run 31). However, a significantly higher
particulate loading was observed. The high particulate loading of the
mixed-leachant coal is attributed to its relative narrow range of ash-fusion
temperatures between the initial deformation and the fluid temperatures of
the ash (about 100 F). Past experience indicates that for most coals fired
in the Multifuel Furnace, over 90 percent of the ash is retained in the
furnace system. This was the case for the raw Wes'.land coal as the slag
that formed in the furnace and the furnace exit duct* captured about 97
percent of the coal ash.
At the completion of the raw Westland run, the furnace exit duct
was nearly plugged by the fused ash. This was not the case when firing the
mixed-leachant coal as the furnace exit duct remained relatively "clean" as
approximately 50 percent of the coal ash was retained in MFF system. The ash
from the combustion of the mixed-leachant coal may have passed rapidly
through the softening (plastic) region (and thus did not have the opportunity
to collect in the furnace system) and exited as a dry dust.
The raw- and mixed-leachant Westland coals were fired in both
the LTF and MFF systems. For these coals, the values of the particulate
LTF unit are between those of the MFF. Because both the MFF and LTF retain
the majority of coal ash within the system, it is not surprising to see a
discrepancy between these values as the time-temperature history of the
system becomes the controlling factor.
*The temperature along this horizontal duct ranged from about 2400 F at
the furnace exit to about 1800 F before passing into the vertical duct
that simulates the convection passes of the boiler.
41
-------
Carbon Burnout. For the LTF unit, solid samples from the burned coal
were collected from three different regions of the combustion system. Samples
were collected from at least one region for every run. Referring to Figure 1,
these samples were designated as: slag (from the hot combustion chamber);
cooler ash (from the cooler tube); and filter ash (from the filter placed
in the gas stream). The carbon data from coal sample and the cooler and filter
ashes analyses (where available) were used to generate carbon burnout data from
the following equation:
C£ + C
fa ca_
percent unburned carbon - C - ^
and
percent carbon burnout = C = (100 - C^)
where C = weight of carbon remaining in filter ash
I cl
C = weight of carbon remaining in cooler ash
ca
C = weight of carbon fed to burner during ash
collection period.
The weight of the carbon remaining in the slag was found to be negligible
(as indicated in Runs 18 and 19 of Table 8) and therefore did not enter into
the calculation.
Table 11 lists the C, determination and includes data on the weight
bu
percent of carbon remaining in the filter and cooler ash. Although the weight
percent of carbon remaining in these ashes was often significant, the total
weight of unburned carbon was not. Since the total weight of the filter and
cooler ashes accounted for only about 10 percent of the coal ash, the other
90 percent remained on the combustion liner as slag. As seen from the data
in Table 11, carbon burnout was high in all runs, ranging from 95.4 to 99.9
weight percent. Furthermore, there was no appreciable differences in carbon
burnout between the raw and the treated coals. As previously discussed,
the raw Martinka did exhibit a slightly higher carbon burnout than the
Westland coals.
For the two runs in the MFF, analysis of the filterable particulate
for carbon indicated that essentially all the carbon in both the raw and
42
-------
TABLE 11. CARBON CONTENT OF FILTER AND COOLER ASH FROM LFT COMBUSTION UNIT
OJ
Type of
Coal
Raw
NaOH
Leached HTT
Mixed
Leached HTT
De-Ashed
HTT
Martinka Coal
Run Carbon Content, wt %
No. Filter Ash Cooler Ash Cbu
3 28.9 5.6 99.3
21 37.8 33.2 99.3
6 22.5 13.3 97.7
Run
No.
22
30
13
20
29
31
26
27
28
Westland
Coal
Carbon Content, wt %
Filter Ash
56.4
1.7
22.4
12.8
8.3
2.1
62.2
61.7
49.6
Cooler Ash
49.4
8.2
11.8
12.1
41.8
59.4
34.4
cbu
95.4
99.9
99.4
98.6
97.9
96.8
98.1
-------
mixed leachant Westland coals was burned completely. In comparison to the
LFT burner, the MFF provided a relatively long residence time (approximately
0.7 sec as compared to 0.16 sec) at elevated temperatures which promoted
the complete carbon burnout.
Trace Elements. Trace element analyses by spark-source mass spec-
trometry (SSMS) were obtained for 6 of the 7 coals burned. Trace element
data were also obtained by optical emission spectroscopy (OES) for all 8
coals burned.
Analyses of the SSMS data in terms of element enrichment in the
ashes are tabulated in Table 12 and Appendix D. With the Westland coal,
hydrothermal treatment had no observable effect on enrichment of trace
elements in the cooler and filter ashes during combustion. The same was
true for enrichment of the trace elements in the ashes from combustion
of the mix-leachant treated Martinka coal. However, enrichment of the
trace element in the ashes from combustion of the caustic treated Martinka
coal was observed.
TABLE 12. NUMBER OF ELEMENTS ENRICHED
(f,\
Martinka v '
Raw Coal
Caustic
Ash
Coal Ash
Mix-leachant coal
(+)
25
48
ash 29
(-)
28
22
31
(0)
10
12
12
Westland
(+)
57
59
57
(-)
6
3
4
(a)
(0)
2
3
4
(a) + indicates an increase of element concentra-
tion going from coal ash to filter ash.
- indicates a decrease of element concentra-
tion going from coal ash to filter ash.
0 indicates no change of element concentra-
tion going from coal ash to filter ash.
The reason for this behavior has not been determined. However,
it is possible that, during the hydrothermal treatment, the mineral matter
(trace elements) in the Martinka coal reacts with the sodium hydroxide
(caustic) leachant to form sodium salts which are nonvolatile. On the
44
-------
other hand, the mineral matter (trace elements) in the Westland coal is
not subject to attack by either the sodium hydroxide leachant or the mix-
leachant. Likewise, the mineral matter in the Martinka coal is not
attacked by the mix-leachant.
Element enrichment for the specific elements are shown in Table
13. Examination of this data indicates that hydrothermal treatment of these
coals has little or no effect on the enrichment of these elements in the
ashes during combustion. Element enrichment in the ashes appear to be
a function of the coal rather than dependent on the hydrothermal treatment
of the coal.
Polycyclic Organic Matter. Analyses of the polycyclic organic
matter (POM) from the combustion products of Runs 5, 11, 12, 14, and 18 in
the Ib/hr unit and of Runs 30 and 31 in the MFF are presented in Table 14.
Components found in measurable quantities in one or more of the samples
analyzed are listed in the first column in the table. A starred component
(9)
indicates carcinogenic potential \
4 stars the highest carcinogenicity.
(9)
indicates carcinogenic potential where 1 star indicates the lowest and
In addition to the POM noted in Table 14, the samples were also examined
for the following other POM compounds:
Perylene Dibenzo(a,h)anthracene
3-Methylcolanthrene Dibenzo(c,g)carbazole
Indeno (1,2,3-cd) pyrene Dibenz(ai and ah)pyrenes
Benzo(ghi)perylene Coronene.
None of these components was found in any of the samples, within detection
limits (vLO ng/volume of gas analyzed which was normally that from about 4
pounds of coal).
The relative differences of the POM loadings among the LTF firings
were quite small considering the differences in combustion conditions during
these runs. The state-of-the-art of POM sampling and analysis being what it
45
-------
TABLE 13. ELEMENT ENRICHMENT OF SPECIFIC ELEMENTS
Element "
0^ -vs> C
Coal
Martinka
Raw
Caustic HTT
Mixed Leachant HTT
Westland
Raw
Caustic HTT
Mixed Leachant HTT
Li Be B F Al P Cl V Cr Mn
--0-+--0 + -
0++-0- + 0
+ ___+_+___
NA + + + 0+ 0+ + +
NA + + + 0+ 0+ + +
NA + + + -+ 0+ + +
Fe Ni Cu Zn As Se Cd Sn Sb Pb
0- + + 0 + - + + -
+ + + + + + 0 + + +
+ -- + 0 + + +
0 + + + +NA + + + +
0 + + + + + + + + +
0 + + + +NA + + + +
* + indicates an increase of element concentration going from coal ash to filter ash.
- indicates a decrease of element concentration going from coal ash to filter ash.
0 indicates no change of element concentration going from coal ash to filter ash.
-------
TABLE 14. POM ANALYSES
Micrograms / (Meter)
NAS*
Component Notation
Anthracene /Phenanthrene
Methyl Anthracene
Fluor anthene
Pyrene
Methyl Pyrene /Fluoranthene
Benzo (c)phenanthrene ***
Chrysene/Benz (a)anthracene *
Methyl chrysenes >v
Benzo Fluor an thenes **
Benz (a)pyrene +
Benz (c ) pyr ene ***
3
Total POM Loading, |ig/m
Percent Carcinogenic
Material
Run 5
NaOH Leachant
Martinka
9.1
3.4
4.0
3.1
.6
.6
1.7
.2
.5
.1
23
14
Run 11
NaOH Leachant
Westland
18
19
.7
.8
.4
--
.3
--
--
39
.6
Run 12
Mix-Leachant
Martinka
11
12
.5
.6
--
--
--
--
--
24
0
Run 14
Raw Westland
23
37
.5
1.9
2.6
--
.4
.4
--
65
1.1
-- Below detection limits
* Stars designated degree of hazard as discussed in "Particulate Polyclyic
Organic Matter" published National Academy of Science (1972). The
lower the number of stars, the lower the hazard associated with the
material. No stars indicate material not reported as being carcinogenic.
Continued
-------
00
NAS
Component Notation
Anthracene /Phenanthrene
Methyl Anthracene
Fluoranthene
Pyrene
Methyl Pyrene /Fluoranthene
Benzo(c)phenanthrene ***
Chrysene/Benz (a)anthracene *
Methyl chrysenes *
Benzo Fluoranthenes **
Benz (a)pyrene +
Benz(c)pyrene ***
3
Total POM Loading, a.g/m
Percent Carcinogenic
Material
Run 18
Mlx-Leachant
West land
18
26
.3
.4
.9
.1
.1
--
--
45
0.5
3
Micrograms /(Meter)
Run 30
Raw West land
.020
.081
.0064
.0051
.0044
.0002
--
--
--
.12
.2
Run 31
Mix-Leachant
West land
.066
.028
oOlO
.0085
.0054
.0002
--
--
--
.12
.2
TABLE 14 (Continued)
-------
is, however, one might not expect to see statistically different POM results
from these firings.
The POM loadings appear low compared with the earlier work of
Hangebrauck , yet we have no basis to feel that they are in error in
any way. For firing rates of the order of 10 Btu/hr, Hangebrauck's results
would call for POM (as BaP) on the order of 30-3000 |ag/m3; our results are
3
at the low end of this spread, 23-45 u.g/m . POM from the MFF firings was
3
substantially lower, about 0.1 |j,g/m ; this might be compared with values
of 3-300 u,g/m for firing rates of 10 Btu/hr in Hangebrauck's earlier
work. In essence, we observe similar trends to lower levels of POM at
higher firing rates, but our data are an order of magnitude below that
reported by Hangebrauck.
Ash Characteristics. Several properties of the coal ashes in addition
to those already discussed were also considered and include (1) viscosity, (2)
sodium content, (3) ash-fusion temperature, (4) resistivity, (5) particle
size, and (6) leachability. These properties are important in the operation
and the design of the overall boiler facilities, and accordingly, the impli-
cations of these data presented below will be discussed under the task on
"Interchangeability of HTT Coals".
Viscosity. The viscosity of ash is used as a measure to estimate
the fouling and slagging potential of a coal ash/11'* Generally, the lower the
viscosity the greater is the potential for fouling and slagging. The weight
percent of minor elements, Si, Al, Fe, Mg, and Na contained in the coal ash
are used in this determination. Table 15 gives the ash composition based
on these data, the reported values of these minor elements are converted to
equivalent oxides because the ash constituents generally occur as oxides.
The total oxides usually approach 100 percent, but as noted in Table 15, the
total oxides in Runs 3 and 5 are somewhat low at 75 percent and 66 percent,
respectively, while in Run 7 they total 93 percent. For comparison pur-
poses, these values were normalized to total 100 percent. The "Silica
Percentage", the ratio of Si02 to Si02 + Fe^ + CaO + MgO was then calcu-
lated. This ratio is a measure of the viscosity in poises at 2600 F
49
-------
TABLE 15. ASH COMPOSITION AND FOULING POTENTIAL OF RAW AND TREATED MARTINKA
Ash Composition
(wt percent)
Si
Al
Fe
Cu
Mg
Na
Equivalent Oxide ^a'
(wt percent)
Si02
A1203
Fe2°3
CaO
MgO
Na20
Silica Percentage -
Si02/Si02+Fe203+CaO-mgO
p,, poises at 2600 F
Base/acid Ratio =
SiO +Ai 0 +Fe203/CaO+MgO-H'la20
Fouling Factor =
B/A x Na20
Run 3
Raw Martinka
21.9
8.73
7.30
.45
.09
.33
46.9 (62.7)
16.5 (22.0)
10.4 (13.9)
0.6 (0.8)
0.1 (0.1)
0.4 (0.5)
74.9 (100)
81 81
550
.18
0.09
Run 5
Martinka
NaOH Leachant
14.0
11.3
4.63
0.29
0.21
5.42
30.0 (45.5)
21.4 (32.4)
6.6 (10.0)
0.4 (0.6)
0.3 (0.4)
7.3 (11.1)
66.0 (100)
81
< 550
.28
3.11
Run 7
Martinka
Mixed Leachant
15.8
4.69
5.53
25.7
0.54
4.21
33.8 (36.3)
8.9 (9.5)
7.9 (8.5)
36.0 (38.6)
0.9 (1.0)
5.7 (6.1)
93.2 (100)
43
< 4
1.19
(a) Values in parens were normalized to total 100 percent
-------
The calculated data indicate that the hydrothermal processing of
the coals lowers the viscosity of the ash, making it more fluid. The
viscosity of the ash from the raw Martinka coal was calculated to be 550
poises (at 2600 F) . The NaOH treatment lowers the viscosity to a value
somewhat less than 550 poises but because of the high Na 0 content (11.1
percent on 100 percent basis) an accurate estimate of the viscosity cannot
be determined from the ash composition.
For the mixed leachant system, the high CaO content lowers the
silica percentage to only 43 indicating a viscosity of 4 poises (at 2600 F) .
In addition, the Na 0 is high at 6.1 percent, so that the actual viscosity
would be less than 4 poises. Combustion of the mixed-leachant coal would
produce a very fluid slag that could cause extreme fouling of heat-
receiving surfaces.
Sodium Content. The sodium content of the ash can also be used
as an indicator for slagging and fouling potential. Generally, for sodium
contents of greater than 2.5 percent in the ash, severe fouling can be anti-
cipated. Accordingly, the NaOH and mixed leachant treated coals would be
expected to have a high potential to slag in boiler furnaces.
The fouling potential of an ash can be qualitatively related to
its sodium content by the following analogy for usual ash compositions
Percent Na 0 in Ash Fouling
< 0.5 Low
0.5 - 1.0 Medium
1.0 - 2.5 High
> 2.5 Severe
For "lignitic" ash, where (CaO + MgO) is greater than Fe203 as found in
the mixed leachant Martinka coal, the following quantitative relations
apply
51
-------
Percent Na 0 in Ash Fouling
< 2.0 Low
2-6 Medium
6-8 High
> 8 Severe .
The Duzy "fouling factors" are not applicable to lignitic ash but
they too show that sodium is the major source of problems. From Table 17
with
°R a c Q
Rf = -^r^ x percent Na 0 (on ASTM ash) ,
the raw Martinka coal has an Rf of 0.09 and the caustic treated Martinka has an
Rf of 3.11. "Low fouling" is less than 0.2 and "severe" is more than 1.0. On
this basis, the raw Martinka is low fouling and the caustic treated Martinka
is severely fouling.
Ash-Fusion. The ash-fusion temperature determination is an empirical
laboratory procedure that is used to predict the fusion characteristics
of an ash as it is heated. A simple relation of these temperatures to actual
combustion operating conditions is as follows:
Initial Deformation Temperature (IDT) . The IDT is
used as an indication of the temperature at which
the ash particles become "sticky" and have a tendency
to agglomerate and slowly build up on heat adsorption
surfaces.
Softening Temperature. This temperature is related to
that at which the fuel ash shows an accelerated tendency
to mass together and stick in large quantities to heat
absorbing surfaces.
52
-------
Fluid Temperature. This temperature is related to the
temperature at which the ash is expected to flow in
streams and drip from heat exchanger surfaces.
These temperatures are only used as a guide as the measurement of ash viscosity
has been found to be a more useful design tool to predict boiler fouling.
Table 16 summarizes the ash-fusion temperatures obtained for
the coal burned in this program. In general, the processing of the raw
coal significantly reduces the ash-fusion temperatures. This is attributed
to the addition of sodium and calcium during coal treatment. The one
exception was the Westland coal treated with mixed leachant which raised
the ash fusion temperatures by about 200 F. [ This could be an anamoly
in the procedure due to large additions of calcium, or it may be, although
unlikely, that the mixed leachant processes alter this coal sufficiently
(by the addition of Ca and Na, and the reduction in Si, Fe, and Al) to
increase ash-fusion temperatures.] In addition, the ash-fusion data indi-
cate that processing of coal reduces the range between the initial deform-
ation and fluid temperatures.
Resistivity. Resistivity data are used to predict the behavior
of fly ash in electrostatic precipitators, which are designed for opera-
tion with ash resistivity in the range from 10 to 10 ohm-cm. Values of
resistivity below this range can result in operating problems, and values
above this range can result in reduced collection efficiency.
Table 17 summarizes resistivity data for 10 ash samples. It
will be noted that values are significantly below 10 10 ohm-cm for three
samples, all of which contain considerable carbon. Resistivity values
approach the normal for all other samples. These results are somewhat
inconclusive because of the possible influence of carbon in the samples.
Any further evaluation of resistivity should examine the effects of fuel
(13)
sodium, potassium, iron, and sulfur content
53
-------
TABLE 16. FUSION TEMPERATURE OF ASH
Temperature F
Initial Deformation
Coal
Raw Martinka
NaOH Lea chant Martinka
Mixed-Leachant Martinka
Raw Westland
NaOH Leachant Westland
Mixed-Leachant Westland
Deashed Wes tland
Reducing
1890
1800
1850
1960
1910
1890
1790
Oxidizing
2110
2110
2010
2070
1940
2000
1920
Softening
Reducing
2010
2030
1970
2100
2010
2300
1850
(H = W)(a)
Oxidizing
2400
2150
2100
2260
2020
2460
2000
Softening
Reducing
2410
2210
2000
2200
2030
2400
1870
(H = l/2W)(a)
Oxidizing
2490
2300
2210
2370
2050
2510
2090
Fluid
Reducing
2470
2230
2020
2240
2040
2440
1890
Oxidizing
2520
2390
2240
2400,
2070
2600
2120
(a) H » cone height; W = cone width.
-------
TABLE 17. RESISTIVITY OF COAL ASH SAMPLES AT 400 F
Coal Ash
Raw Martinka
NaOH Leachant
(Run 3)
(Run 3)(a)
Martinka sample (Run 4)
(Run 5)
(Run 5)_a'
Mixed leachant Martinka (Run 6)
Raw Westland
NaOH Leachant
(Run 7)
(Run 7)
(Run 15)
Westland (Run 13)
Resistivity,
(ohm- cm)
l.SxlO11
4.7xl09
5.1xl08
5.7xl08
l.SxlO8
5.9xl05
4.4xl05
8
3.0x10
l.lxlO5
l.SxlO9
Applied
voltage,
(volts)
500
500
500
500
500
150
300
500
90
500
Carbon
content, %
in ash
12.0
0.0
8.0
11.4
0.0
13.7
4.7
0.0
15.1
7.3
(a) These samples were completely ashed coals.
55
-------
Particle Size. Particle-size distributions were determined by
Coulter Counter measurements of the particulate catch of the filter for
both the raw and treated coals. Figures 3 and 4 summarize the ash and
coal particle size distributions. In essence, the results show that the
size distribution of ashes from the LTF combustor are quite normal. The
mass median diameters of the Martinka and Westland ashes were 13 microns
for some Martinka firings and 25-50 microns for some Westland firings.
The Martinka ashes do not appear to have been effected by the treatment
process, whereas the Westland ashes appear to be smaller for the treated
coal than for the raw coal.
Task 3. Impact Evaluation of the Use of
Hydrothermally Treated Coal
From the analysis and evaluation of the results obtained from
Phase I, Task 2, the atmospheric impact which could result from the use
of hydrothermally treated coals in industrial and utility boilers and
environmental problems associated with disposal of. the ash was assessed.
Also, problems which may be encountered in converting from raw coal to
hydrothermally treated coals in conventional boilers and the degree of
boiler modification which may be necessary were addressed.
Subtask 3A. Atmospheric Impact of HTT Coal. The atmospheric
impact of the utilization of hydrothermally-treated (HTT) coal on the air
quality has been investigated. This was accomplished by examining the
changes that would occur in sulfur dioxide (SCL) and trace element levels
as a result of substituting HTT coal for the high sulfur-content coals that
are presently being used in many of the nation's large cities. Two high
sulfur-content coals, Martinka coal and Westland coal, were chosen for the
study. Four large cities that currently use considerable quantities of
these coals (Birmingham, Alabama; Peoria, Illinois; Detroit/Port Huron,
56
-------
0)
U
a.
^
'A''
4
,
,<$'
l>'
\
#.
A'
<
' X
'A
^
/
J
-^
3
X
1
X
- +>^'r
^^*
X'/
(V
Run N
o |
a 3
* 5
+ &
A 7
D 2
-
If
A-
0.
0
J
''fy
//
4
9
(
H
*
0
6
Particle Diameter, microns
FIGURE 3. COULTER COUNTER ASH PARTICLE SIZE DISTRIBUTION
MARTINKA FIRING
57
-------
99,9
.c
QJ
"
CO
O)
o>
PL
-------
Michigan; St. Louis, Missouri) were chosen as representative cities for the
study of sulfur dioxide emissions. Houston, Texas was chosen as a city
representative of low coal consumption.
The coal consumption by sulfur category and by source type has
been published by EPA for each of these regions. These data are in Table 18,
together with SCL concentration data.
The goal of this subtask was to determine the change in these SCL
concentrations, and of trace elements (for which little documentation exists).
Several approaches were available, spanning a range of complexities and
required supporting information.
The approach taken here offered a reasonable estimate of change
of air quality to be determined with a minimal set of data. The quantities
determined under this subtask are as follows:
(1) "Equivalent"- sulfur content of HTT coal
(2) Current mean SCL concentrations in the five urban areas
(3) Trace elements particulate levels
(4) Projected 50^ levels as a result of substituting HTT coal.
Each of the four items will be discussed briefly and all results will be sum-
marized in tabular form.
(1) Equivalent Sulfur Content of HTT Coal. The equivalent sulfur
contents of HTT coal were determined for each of the following chemical
treatments:
(a) NaOH leachant Martinka coal
(b) Mixed leachant Martinka coal
(c) NaOH leachant Westland coal
(d) Mixed leachant Westland coal.
*The sulfur content which, when applying EPA emission factors, produces the
observed SO emissions. This approach was chosen because the HTT ash traps
significant fractions of the potential sulfur emissions, while EPA emis-
sions factors presume only 5 percent trapping. The equivalent S0« content
is found by multiplying the actual content by the fraction which leaves the
stack, and dividing by 0.95.
59
-------
TABLE 18. SO. PROFILE
Coal
Utilization
7 c
/o O
in Coal
Coal Consumption
1000 ton/yr
SO- Emissions
1000 ton/yr
Contributions to
Annual Average
SOn Concentration,
2 ^g/m3
City; Birmingham
Utility
Industrial
Res/Comm
Other
Total
City: Peoria
Utility
Industrial
Res/Comm
Other
Total
1.2
2.45
0.8
1.2
1.6
2.45
0.8
1.2
1.6
2.45
1.2
2.45
0.8
1.2
1.6
2.45
3.0
0.8
1.2
1.6
2.45
5,209
1,209
144
361
217
20
18
3,848
3
65
202
1
48
51
118.8
57.2
2.2
8.2
10.1
0.3
0.4
102.5
299.7
179.0
0.1
3.0
11.5
0
1.5
2.4
54.5
252.4
7.5
3.6
0.1
1.5
1.5
0
0
6.5
19.0
41.9
0
0.7
2.7
0
0.4
0.5
12.8
59.0
60
-------
Coal % S
Utilization in Coal
City: St. Louis
Utility 1-2
2.45
Industrial 0.8
1.2
1.6
2.45
4.0
Res/Comm 0.8
1.2
1.6
2.45
Other
Total
City: Detroit
Utility 1.2
2.45
Industrial 0.8
1.2
1.6
2.45
3.3
Res/Comm 0.8
1.2
1.6
2.45
nj-fn^T-
\J L 1 It: L
Total
Coal Consumption
1000 ton/hr
6,731
5,191
104
56
370
332
3
38
104
3,579
6,619
88
921
702
2,501
175
20
107
99
S0~ Emissions
1000 ton/yr
153.5
241.6
1.6
1.7
17.2
25.2
0.1
1.2
4.8
214.0
661.0
175.0
415.0
1.3
21.0
21.3
116.4
11.0
0.3
2.4
3.0
119.6
886.3
Contributions to
Annual Average
S02 Concentration,
|j,g/m3
27.7
43.0
0.3
0-3
3.0
4.4
0
0.2
0.8
38.2
115.0
16.2
38.4
0.1
1.9
2.0
10.8
1.0
0
0.2
0.3
~~
11.1
82.0
TABLE 18 (Continued)
61
-------
Coal
Utilization
% S Coal Consumption
in Coal 1000 ton/yr
SO Emissions
1000 ton/yr
City: Houston
Utility
Industrial
Res/Comm
Other
Total
1.2
2.45
0.8
1.2
1.6
2.45
0.8
1.2
1.6
2.45
Contributions to
Annual Average
SC>2 Concentration,
Lig/tn3
345.0
36.0
345.0
36.0
TABLE 18 (Continued)
62
-------
The average values of the sulfur content, in weight percent, were calculated
and compared with the sulfur content of untreated coals. Table 19 summar-
izes the results from averages of sulfur emissions of Runs 1 through 22.
TABLE 19. EQUIVALENT SULFUR CONTENT OF COALS
(WEIGHT PERCENT)
Treatment
NaOH treated
Mixed leachant-treated
Untreated
Martinka
Sulfur
Content, %
0.65
0.55
Coal
Equivalent
Sulfur, %
0.365
0.469
1.90
Westland
Sulfur
Content, %
0.93
0.74
Coal
Equivalent
Sulfur, %
0.566
0.331
2.02
(2) Current Mean Sulfur Dioxide Concentrations. The annual arith-
metic, mean of the current sulfur dioxide emissions in five urban areas (Birm-
ingham, Alabama; Peoria, Illinois; Detroit/Port Huron, Michigan; St Louis,
Missouri; Houston/Galveston, Texas) were determined for ultimate comparison
with S0? levels that would be projected from substitution to HTT coal. The
current levels, listed in Table 20 were obtained from U.S.E.P.A.'s Air
Quality Data - 1973 Annual Statistics.
TABLE 20. CURRENT MAXIMUM ANNUAL SO LEVELS
IN FIVE URBAN AREAS
City
Concentration,
Birmingham, Alabama
Peoria, Illinois
Detroit/Port Huron, Michigan.
St. Louis, Missouri
Houston/Galveston, Texas
19
59
45
115
36
(3) SO Projected Concentrations. Using a roll-back procedure,
it was possible to estimate for each city the ratio between emissions and
63
-------
annual concentrations. By multiplying this ratio with an increment (decre-
ment) in emissions, the resultant increment (decrement) in air quality can
be estimated. These multipliers were used in the trace metal analyses of
Section (4), as well as the SO analyses of this section.
The sulfur dioxide emission levels that would result as a consequent
of substituting HTT coal for untreated high sulfur-content coal were deter-
mined for three economic sectors: residential and commercial, industrial,
electrical. The following determinations were carried out: (a) 50^ levels
that would be obtained by replacing all coals with greater than 1.2 percent*
sulfur (weight basis) with HTT coal, for each of the economic sectors, (b) SO^
levels resulting from substituting all coals with greater than 1.2 percent
sulfur with HTT coal, for all three sectors combined, and (c) SO levels
resulting from replacing all coals with HTT coals, irrespective of the sulfur
content of the coal. Table 21 summarizes all the results.
It is significant that St. Louis, Missouri, and Detroit, Michigan
3
would meet the Federal Ambient Air Quality Standard of 80 yg/m by simple
fuel substitution. In all cases, significant decreases in SO concentrations
are predicted.
(4) Trace Metal Projected Concentrations. The process of producing
HTT coal alters the trace element compositions and release rates for trace
elements in the coal. For this reason, the impact of HTT coal substitution
on the ambient air trace element contributions was estimated. Peoria,
Illinois was chosen as the target city for trace metal studies because, of
the five, it is the city most heavily impacted by coal combustion emissions.
A mass balance between the incoming coal and resultant ash con-
centrations allowed the estimate of the atmospheric release rate of the
trace elements. When multiplied by the total coal consumption of Peoria,
and the ratio between coal consumption and ambient concentration, the con-
tribution of coal burning to the ambient concentration can be determined.
Simple subtraction yields the incremental concentration due to HTT coal
substitution.
*Coals with more than 1.2 percent S are generally considered high sulfur,
and replacement of these coals with HTT coal should receive preferential
consideration.
64
-------
TABLE 21. PROJECTED S02 LEVELS WITH HTT COAL AMBIENT ANNUAL CONCENTRATION,
IJg/m3 ANNUAL AVERAGE
1.
2.
3.
4.
Current (untreated coal) level
Replacing all coal with > 1.2% sulfur
-Residential and Commercial
-Industrial
-Electrical
Replacing all coal with ^ 1.2% sulfur
-All sectors
Replacing all coals irrespective of
sulfur content with HIT coals^
004
Birmingham,
Alabama
19
18.6
16.6
16.2
5.0
065
Peoria,
Illinois
59
58.5
56.6
31.9
29.0
26.6
123
Detroit,
Michigan
82
81.9
73.2
43.2
34.3
31.8
070
St. Louis,
Missouri
115
114.4
109.5
87.8
44.9
(a) Coals in each sector containing greater than 1.2% sulfur replaced by HTT coal (average, all runs).
(b) Assuming all coals containing greater than 1.2% sulfur replaced with HTT coal (average, all runs).
(c) HTT sulfur emissions averaged from all runs.
-------
Analysis for the concentrations of trace metals proceeds as in
the case of sulfur dioxide: by determining emissions and multiplying by
a predetermined constant, the annual average concentration (change) can
be determined. The results as presented in Table 22 indicates some of the
changes expected in trace element concentrations in Peoria providing all
coal for this city was replaced by HTT coal and assuming the ash containing
these elements were emitted to the atmosphere. However, most likely, the
majority of the ash would be collected by electrostatic precipitators and/
or baghouses.
While this data are preliminary in nature, the data do indicate
that the concentration of a number of the toxic elements beryllium,
boron, fluorine, phosphorus, chlorine, potassium, vanadium, arsenic and
bromine is lowered by the hydrothermal treatment. During the treatment,
these elements are extracted from the coal by the solubilizing effect of the
leachant. On the other hand, the concentration of some of the elements,
for example, sodium and calcium, is increased. This results from reaction
of the sodium and calcium contained in the leachant with the coal. During
combustion, the sodium and calcium becomes part of the ash.
Subtask 3B. Environmental Problems of Combust ion Waste Products.
Solid waste products known as fly ash and bottom ash are formed in any com-
bustion operation. These ashes are generally disposed of in a landfill.
Problems associated with disposal of the ashes by this method if the land-
fill is not properly prepared will depend on the r-omposition of the ashes.
For example, if the ashes contain a number of soluble components, these may
be leached from the landfill and subsequently contaminate our water system
by penetration of the underground water system or by runoff from the landfill
into the surface water.
It is expected that the chemical composition of the ashes from
HTT coals may be different from those of the corresponding raw coals. In
a gross manner, the HTT ashes will contain more alkali and more or less
66
-------
TABLE 22. CHANGE IN TRACE ELEMENT CONCENTRATION IN ASH (yg/m )
FOR PEORIA, ILLINOIS, FROM COAL SUBSTITUTION
Be
B
F
Na
Mg
Al
Si
P
Cl
K
Ca
V
Cr
Fe
Co
Ni
Cu
Zn
As
Br
- Means
+ Means
West land
NaOH
Leachant
.005
.101
.444
N/A
0
-6.909
-.395
0
-.099
2.47
-5.43
.041
-.086
.296
--044
-.173
-.034
-1.64
.004
.046
Coal
Mixed
Leachant
.003
.101
.128
-9.07
-3.16
-7.008
-.721
.405
.007
2.07
-4.64
.029
-.002
.890
.011
-.042
-.066
-.346
.004
.056
Martinka
NaOH
Leachant
.002
.063
.013
N/A
-.790
N/A
N/A
-.099
.194
18.8
0
.147
N/A
34.6
.178
N/A
N/A
-.003
-.009
.008
Coal
Mixed
Leachant
.003
.069
-.01
N/A
-.7
N/A
N/A
.395
.255
N/A
N/A
.144
-.069
-4.25
0
.484
0
-.014
.007
.007
higher concentration.
lower concentration
67
-------
Element
Y
Zr
Sn
Ba
Hf
Pb
Tb
West land
NaOH
Leachant
-.007
-.030
-.061
-.032
-.002
-.034
-.003
Coal
Mixed
Leachant
.014
0
.009
-.089
-.002
-.010
-.003
Martinka
NaOH
Leachant
.015
.190
N/A
.286
.007
N/A
N/A
Coal
Mixed
Leachant
-.138
-.158
-.014
-.*-32
-.005
.087
-.021
TABLE 22 (Continued)
68
-------
sulfate than the ashes from the untreated coals. Also, there will be lower
concentrations of certain traces in the treated coals. Effects of these
differences in chemical composition would be expected to be reflected in
other important characteristics such as solubility. Therefore, the objec-
tive of this subtask was to evaluate the environmental problems associated
with disposing of the ashes from the combustion of HTT coals.
This was achieved by conducting leachability studies on selected
coal ashes and subsequent analysis of the leachates.
Leachability Tests. Leachability tests were conducted by a pro-
cedure provided to us by Dr. Robert Statnick for EPA. Essentially, this
entailed leaching selected ashes with water at ambient temperature. For
this study, a slurry of 4 parts water and 1 part ash (by weight) was pre-
pared. This slurry was agitated for 3 days at ambient temperature, after
which time the solids were separated from the liquid by centrifuging.
Fresh water was added to the leached ash at the same ash/water ratio, the
slurry was agitated for another 3 days, and the solid separated. This was
repeated for an additional 8 times. The leachates were kept separate for
subsequent analysis.
Analysis. The analysis consisted of:
(a) pH measurements on al1 J eachates as a function of
leaching time, and
(b) Determining the solids content of the leachates and
composition of the solids in terms of trace metals,
alkali (sodium and calcium), and sulfate contents.
Leaching Results. As shown in Table 23, pH of the leachates
remained essentially constant throughout the leaching tests. In all cases,
the final leachate from the various ashes were slightly basic (7.65) to
strongly basic (about 11). The strongly basic solutions resulted from
leaching of the ashes from the mixed-leachant coal ashes. Apparently, the
calcium treatment is responsible for the higher pH solutions, possibly re-
sulting from reaction of the calcium with sodium sulfate to form sodium
hydroxide and calcium sulfate.
69
-------
TABLE 23. pH READING ON LEACHATES
Type of Coal /Ash
Raw West land #22
Cooler Ash (542144)
Ha OH Leachant West land #20
Cooler Ash (541979)
N2 Filter Ash (541978)
Mixed Leachant-Westland #18
Cooler Ash (541713)
Slag (541715)
Raw Martinka #3
Furnace Scraping (540117)
Cooler Ash (541168)
Filter Ash (540116)
NaOH Leachant Martinka #21
Cooler Ash (542066)
Filter Ash (542065)
Mixed Leachant-Martinka
Cooler Ash (541001)
Run#l
pH
4.
8.
8.
12.
11.
8.
7.
6.
7.
7.
11.
68
68
63
20
55
95
95
05
98
90
85
Run// 2
pH
6.73
9.18
8.40
12.00
11.18
9.23
8.48
6.60
8.10
9.03
10.93
Run//3
PH
7.60
8.48
8.70
11.78
11.25
9.20
8.35
6.90
8.20
9.00
10.85
Run#4
PH
7.50
8.03
8.93
11.55
11.13
8.30
8.63
7.13
8.18
8.95
10.50
Run#5
PH
8.00
7.83
9.25
11.45
10.60
8.38
8.68
7.78
8.45
8.70
7.93
Run// 6
pH
8.00
8.08
8.45
11.30
10.80
8.35
8.53
7.70
8.60
8.80
8.40
Run#7
PH
8.65
8.75
9.08
11.35
10.95
9.25
9.08
7.98
8.73
9.13
10.60
Run//8
PH
8.25
8.63
9.63
7.83
11.00
9.18
9.05
8.73
9.00
8.43
8.18.
Run// 9
pH
8.23
8.95
9.53
11.60
8.58
8.93
9.10
7.95
8.68
9.10
10.70
Run#10
pH
7.65
8.05
9.15
11.63
11.00
9.18
9.05
8.50
8.30
8.40
10.45
-------
The degree of solubilization of the 3 selected cooler ashes from
West land coals (1 raw and 2 HIT) and composition of the water soluble portion
in terms of sodium, calcium, and sulfate contents are shown in Table 24.
Trace metals content of this soluble portion is shown in Table 25.
The data show that the cooler ash from the NaOH leached West-
land coal is highly water soluble (V31 weight percent) with that from
the mixed leachant coal ranking second and that from the raw coal being
the least soluble. The high solubility of the cooler ash from the NaOH
leached coal is due, primarily, to the presence of sodium sulfate in the
cooler ash. Pure sodium sulfate (Na^O^) contains 32.2 weight percent sodium
and 67.6 weight percent sulfate. The solubilized material was found to con-
tain 33 weight percent sodium and 81 weight percent sulfate. The difference
in sulfate content between 67.6 and 81 weight percent could be due to the
presence of CaSO^ as the NaOH treated Westland coal contained 0.2 weight
percent calcium.
TABLE 24. LEACHABILTTY OF COOLER ASH
(WESTLAND COALS)
Ex per.
No.
22
20
18
Type
of
Coal
Raw
NaOH Leachant
HTT
Mixed Leachant
Degree of Ash
Solubilization, %
1.73
30.6
HTT 7 . 1
Composition
so4-
0.06
0.81
0.007
of Solubiles
Na~
NA
0.33
0.06
, wt %*
Ca~
NA
NA
0.045
Similar reasoning is not applicable to that leached from the cooler
ash from the mixed leachant-treated Westland coal (Experiment No. 18). In
this case, the sulfate content of the solubilized solids is too low. There-
fore, the sodium and calcium may be present in the leachate as carbonates
which were not analyzed for.
Mass spectrographic analyses of the solubilized solids are shown
in Table 25. Of those trace metal values which are of major concern, the
71
-------
TABLE 25. ANALYSIS OF SOLIDS CONTENT OF COOLER ASH
LEACHATES FROM WESTLAND COALS (ppm)
Element
Li
Be
B
F
Na
Mg
Al
Si
P
S
Cl
K
Ca
Sc
Ti
V
Cr
Mn
Fe
Co
Ni
Cu
Zn
Ga
Ge
As
SeOO
Br
Rb
Sr
Y
Zr
Nb
Mo
Ru
Rh
Pd
Ag
Cd
In
Sn
Sb
Te
I
Raw
(Run 22)
< 0.003
< 0.005
< 0.03
30
~ 27,
~ 1%
300
3000
3
~ 2%
500
2000
5000
< 0.3
30
5
10
200
200
20
50
5
200
< 0.1
50
3
< 5
100
30
5000
- 0.2
< 0.2
< 0.1
3
< 0.3
< 0.3
< 2
< 1
< 1
< 1
0.2
1 '
< 0.3
0.2
Source of Solids
Mixed Leachant
HTT Coal
CRun 18)
< 0.003
< 0.005
< 0.03
10
~ 2%
100
200
500
1
~ 1%
500
3000
~ 3%
< 0.3
30
1
5
1
100
< 2
5
1
10
< 1
1
2
< 5
20
50
3000
- 0.5
< 0.2
< 0.1
10
< 0.3
< 0.5
< 2
< 3
< 1
< 1
2
0.1
< 0.3
0.5
Continued
72
NaOH Leachant
HTT Coal
CRun 20)
< 0.01
< 0.01
< 0.05
1
Major
500
5
500
1
~ 5%
3000
~ 1%
~ 1%
< 10
30
2
2
20
30
< 10
100
< 20
30
< 2
1
10
< 10
5
5
500
- 1
< 0.2
0.1
< 0.5
< 2
< 2
< 1
< 0.5
< 0.5
< 1
0.5
< 0.5
< 1
< 0.5
-------
Element
Cs
Ba
La
Ce
Pr
Nd
Sm
Eu
Gd
Tb
Dy
Ho
Er
Tm
Yb
Lu
Hf
Ta
W
Re
Os
Ir
Pt(b)
Au
Hg
Tl
Pb
Bi
Th
U
Raw
(Run 22)
< 0.5
200
< 0.1
< 0.1
< 0.1
< 0.5
< 0.5
< 0.3
< 0.5
< 0.1
< 0.3
< 0.1
< 0.3
< 0.2
< 0.3
< 0.1
< 0.3
< 0.2
< 0.5
< 0.2
< 0.3
< 0.1
300
< 0.1
< 0.3
< 0.1
10
< 0.1
< 0-1
< 0.1
Source of Solids
Mixed Leachant
HIT Coal
(Run 18)
< 1
50
< 0.1
< 0.1
< 0.1
< 0.5
< 0.3
< 0.2
< 0.3
< 0.1
< 0.3
< 0.1
< 0.3
< 0.2
< 0.3
< 0.1
< 0.3
< 0.2
< 0.5
< 0.2
< 0.5
< 0.1
3000
< 0.2
< 0.3
< 0.1
3
< 0.1
< 0.1
< 0.1
NaOH Leachant
HTT Coal
(Run 20)
< 2
20
< 0.5
< 0.3
< 0.5
< 2
< 1
< 0.5
< 1
< 1
< 1
< 2
< 1
< 0.2
< 1
< 0.2
< 1
< 2
< 1
< 0.3
< 0.5
< 0.5
< 1
< 0.3
< 1
< 0.3
< 0.5
< 0.3
< 0.3
< 0.3
TABLE 25 (Continued)
73
-------
concentration of those shown in Table 26 in the leachate from the HTT coals
were significantly lower than those in the leachate from raw coals.
Complete analyses of all ashes associated with the combustion of
coal will need to be conducted before a definitive assessment can be made
on the expected environmental problems to be associated with disposal of the
combustion waste products (ashes). Preliminary assessment, based on the
leaching studies conducted on selected cooler ashes from the 1 Ib/hr
combustor appears to indicate that direct disposal of the cooler ash from
the NaOH treated coal would not be advisable because of the high degree
of solubility. Most likely, the sodium sulfate would be removed from the
ash before disposal.
Conversely as shown in Table 26, the ashes from the HTT coals are
less polluting than those from the raw coal with respect to the trace metal
values. Therefore, disposal would present less of a pollution problem.
Subtask 3C. Interchangeability of HTT Coal. HTT coal can be con-
sidered as a low sulfur substitute for conventional coal in utility boilers,
industrial boilers, and industrial processes now fired by coal. It can
also be considered as a potential substitute fuel for boilers and industrial
processes designed for firing with oil or gas, although such substitution
may require R&D. In these applications the low sulfur content and the
optional low ash content of the HTT fuel offer the possibility of utilizing
coal with minimum environmental impact and with minimum change in existing
equipment. The feasibility of interchanging HTT coals with other fuels
will be dependent on factors that include its burning characteristics, ash
characteristics, and handling and storage properties. The importance of
these factors that will affect the value or utility of HTT coal in various
applications is somewhat dependent and different for different applications.
Accordingly, it will be necessary to consider each application individually,
but a general discussion of these factors will identify the important
aspects of interchanging HTT coals.
Burning Characteristics. The combustion characteristics of impor-
tance in burning pulverized coal are good ignition at the burner to produce
74
-------
TABLE 26. TRACE METALS IN LEACHANTS
Source and Concentration (PPM) *
Trace
Metal
Al
Cu
F
Fe
Mn
Ni
Pb
Sb
V
Zn
Raw
Coal
(Run 22)
300
5
30
200
200
50
10
1
5
200
Mixed
Leachant
(Run 18)
200
1
10
100
1
5
3
0.1
1
10
NaOH
Leachant
(Run 20)
5
20
1
30
<20
100
<0.5
<0.5
2
30
* Cl concentrations were 10, 5 and 2 ppm,
respectively.
75
-------
a stable flame, and complete burnout of carbon within the furnace to mini-
mize combustible loss. Most bituminous coals containing more than 20
percent volatile matter are interchangeable from the aspect of combustion
characteristics. (Low-volatile coals, low-rank coals, and lignites may
require special furnace or burner design for satisfactory combustion.)
From the dTGA, DTA, and the proximate analysis of the raw and treated
coals, the hydrothermal process does not significantly alter the burning
characteristics of the treated coals. In fact, the process improves the
overall burning characteristics.
Ash Properties. One of the more important ash properties to
consider when interchanging coals is the potential for slagging and fouling.
Of lesser importance are resistivity, particle size, and leachability
characteristics.
Coals vary widely in their slagging and fouling characteristics,
and less widely in their combustion characteristics. The slagging and
fouling characteristics of the coal ash are the most important factors
in sizing of boiler furnaces. When interchanging different coals in
existing boilers, slagging and fouling characteristics determine the
degree of derating needed for satisfactory operation without excessive
slagging problems. In general, coals with high-ash-fusion temperatures
can be burned in small furnaces having high furnace exit gas temperatures,
and coals with low-ash-fusion temperatures must be burned in larger
furnaces having lower exit gas temperatures. When a low-ash-fusion coal
is fired in a furnace designed for a high-ash-fusion temperature coal,
it is necessary to fire at a reduced rate such that the furnace exit gas
temperature is below the ash softening temperature. It may also be
necessary to modify the boiler by adding slag blowers in the furnace and
soot blowers in superheater and boiler sections to control ash and slag
accumulation. The sintering strength of ash deposits is another impor-
tant variable that influences the difficulty of removing deposits after
they have formed.
Table 27 summarizes some of the properties of coals affecting
slagging and fouling performance in steam boilers. These include ash
76
-------
TABLE 27. SUMMARY OF SLAGGING AND FOULING PROPERTIES
Coal and Treatment
Martinka Coal
Raw coal
NaOH leachant
Mixed leachant
Westland Coal
Raw coal
NaOH leachant
Mixed leachant
Acid-leached
Ash Fusion Temp.
Oxidizing, F
IDT» AFT *
2110
2110
2010
2070
1940
2000
1920
2520
2390
2240
2400
2070
2600
2120
Ash
content ,
percent
20.2
17.1
28.3
10.0
13.3
18.0
2.2
Na20 Na in
in ash, ash,
percent percent
0.4 0.15
11.1 15.2
6.1 4.6
0.2
15.6
1.1
19.6
Fouling
Indication
Low
Severe
Severe
Low
Severe
Medium
Severe
*IDT initial deformation temperature.
ash fluid temperature.
-------
fusion temperatures, ash content, sodium content of the ash, and an
indication of boiler fouling characteristics based on sodium content.
A review of initial deformation temperatures (IDT) for the
various coals shows that the IDT is unaffected in some cases and reduced
in others. A reduction in IDT requires operation of a furnace at lower
furnace-outlet gas temperature to avoid boiler fouling and, thus, may
require some derating of the unit if it were satisfactory for the
untreated coal.
A review of the ash fluid temperature (AFT) shows that, in
almost every case, the AFT was reduced significantly by coal treatment.
The one exception was Westland coal treated with mixed leachant, which
raised AFT by 200 F. In general, when firing coal to a dry-ash removal
furnace, a reduction in AFT would lead to an expectation of more severe
furnace slagging problems. Ash deposits would have a greater tendency
to fuse as liquid slap; which is difficult to remove by furnace slag
blowers. As furnace slagging progresses, furnace-outlet temperature will
rise, leading to more severe fouling of convection surfaces. Thus, with
HTT coal, it may be necessary to install additional slag blowers in the
furnace, to operate slag blowers more frequently, and to derate the boiler
to control slagging in a dry-ash furnace.
Fouling of boiler convection tube banks is related to the
strength of sintered ash deposits on tubes, which may be very difficult
to remove for ash of high fouling potential. The severity of fouling
problems is closely related to the sodium content of the coal ash. As
seen in Table 27 the sodium content of treated coals can be much higher
than for raw coal, leading to indications of medium to severe boiler
fouling. The NaOH leachant produces a high-sodium ash having severe
fouling potential with both Martinka and Westland coals, while the mixed-
leachant treatment results in an ash of lower sodium content and lower
fouling potential. Although ash from the acid-leached Westland coal is high
in sodium content, its small quantity, at about 2.2 percent of the coal,
could result in a reduced rate of boiler fouling. However, the high
sodium content of the ash could lead to severe fouling.
78
-------
All of these characteristics suggest that the treated coals
would be less suitable for firing in a dry-bottom furnace than were the
raw coals. The reduction in ash fusion temperatures resulting from
some treatments may require some boiler derating to avoid furnace
slagging problems, and an even greater derating may be required to avoid
boiler fouling problems. If treated coals were to be fired in existing
dry-bottom furnaces, it would probably be advisable to install additional
slag blowers in the furnace and additional soot blowers in the convection
tube banks to control the slagging and fouling to an acceptable level.
The treated coals appear more suitable for firing in wet-bottom
(slag-tap or cyclone) furnaces than for dry-bottom furnaces because of
their low-ash-fluid temperatures. This would be especially true of the
mixed leachant Martinka coal, for which the ash fluid temperature was
reduced from 2520 F to 2240 F by treatment, and for both the
acid leached Westland coal, which dropped ash fluid temperatures from
2400 to 2070 F and 2120 F, respectively. However, even when firing in wet-
bottom furnaces, which would avoid furnace slagging problems, the potential
for medium to severe boiler fouling would continue to be a problem requiring
adequate soot-blower capacity and, possibly, boiler derating to lower gas
temperatures in the convection region.
The HTT processing may affect fly-ash resistivity and dust loading
somewhat, with the possibility of influencing operation or efficiency of
electrostatic precipitators used for dust collection.
In comparison to the raw coals, the high sodium content of some
of the HTT coals presents some added consideration in the handling and
disposal problem. Depending on the type of system, the utilization of HTT
coals may require a modification of the ash-handling system.
79
-------
Coal Handling and Storage. Normally, for pulverized coal-fired
boiler systems, crushed coal is delivered to the power plant and pulverized
on site. This pulverized coal is then fed directly to the burners. In the
past, some systems have stored the pulverized coal in bins from which the
coal is eventually conveyed to the burners, but these systems are no longer
used. Accordingly, some modifications in the coal handling and storage
facilities will be required to utilize HIT coals as these systems were not
designed to handle prepulverized coal. Two factors that need to be con-
sidered in storage and handling of HTT coals are the size consist and the
moisture content of the coal.
HTT coal, as prepared, is in pulverized form with a size consist
similar to that usually fired in pulverized coal-fired boilers. Coal of
this fine consist is readily carried away by the wind, and clouds of dust
are raised by any handling. Also, care must be exercised in handling of
fine coal to prevent spontaneous combustion. This problem is not unique
with HTT coal but applies to finely ground coal from any source. Thus, if
used as a dry powder, it will be necessary to handle and store HTT coal in
enclosed containers and handling systems, much like cement. Instead of
shipping in hopper cars, it will be necessary to ship it in closed cars
with provision for fluidization for unloading. Instead of storing coal
in piles at the point of use, it must be stored in closed silos or bunkers
designed for pulverized coal. The handling of fuel from a storage into
the plant, and its feeding to burners, must be based on equipment suitable
for pulverized fuel instead of crushed coal. Finally, it may be feasible
to eliminate coal pulverization at the point of use. Thus, handling and
storage of HTT coal in pulverized form will require modification in
facilities and equipment to accomodate its pulverized form.
On the other hand, the HTT could be consolidated by briquetting
or pelletizing which would reduce the problems associated with transporta-
tion and storage. The consolidated coal would be repulverized prior to
combustion. Consolidation would also reduce the explosion hazards asso-
ciated with handling of fine coal.
80
-------
J.f HIT coal is to be used in smaller industiral boilers now
fittc-d with coal stokers, two alternative approaches might be considered.
The first is to modify the boiler for pulverized-coal firing, utilizing
the HIT coal as manufactured. The second is to briquette the HTT coal
into a form suitable for stoker firing. The first alternative would
require replacement of coal storage and handling systems to accommodate
pulverized coal. However, pulverized coal firing would be superior to
stoker firing for many boilers, especially if furnace volume is sufficient
that boiler derating would not be necessary. The alternative of briquetting
would increase the cost of HTT coal, but would avoid the necessity of
changes in the existing plant. Briquetting might also permit shipment
in hopper cars, storage in open piles, and handling in conventional coal-
handling equipment for crushed coal.
The handling and burning characteristics of briquettes made
from HTT coal have not yet been investigated. Information appears necessary
if conventional coal handling and stoker firing are to be evaluated.
Moisture Content. The handling of pulverized coal is affected
adversely by moisture content above about 3 percent. With more moisture
the coal will agglomerate and pack and will not flow freely in bins and
feeders. Thus, if HTT coal is to be handled in dry form, it must be
kept dry from the time of production to the time of firing. Alternatively,
it may be dried just before firing.
If wetted by exposure to rain, pulverized coal can absorb far
more moisture than crushed coal. If moisture concentration exceeds about
15 percent it can influence flame temperature, furnace heat absorption
rate, and steam temperature, and may require boiler derating to keep
steam temperature within design limits.
There appears to be some possibility that HTT coal could be
handled as a slurry in water for pipeline shipment, followed by dewatering,
or by firing as a slurry. Firing as a slurry containing about 1 Ib water
per Ib coal would require some boiler modification for superheat control
and would involve a moderate loss in boiler efficiency because of the
increased moisture loss of the stack gas. It would be especially attrac-
tive as a means of firing coal to equipment designed for oil firing, but
feasibility has not yet been demonstrated. The lower combustion tempera-
ture in firing a water slurry might also help reduce dry slagging problems.
81
-------
PHASE II. TRACE METAL IDENTIFICATION AND
RECOVERY FROM HYDROTHERMALLY TREATED COALS
Hydrothermal treatment of coal results in the extraction of
certain trace metals from the coal and subsequent solubilization in the
leachant. During regeneration of the leachant for recycle, the trace
metals may be removed from the leachant or, on the other hand, they may
build up in the regenerated leachant and contaminate the coal. Thus,
the objective of Phase II was to determine the disposition of trace metals
in the selected raw coals and to assess the need for removal of the trace
metals from the spent leachant for recycle.
Task 1. Trace Metal Analysis
Trace metal analyses were conducted on each raw coal and the
hydrothertnally treated coals produced from these raw coals. Originally,
optical emissions spectroscopy was employed; however, this technique was
not sensitive enough. Consequently, mass spectroscopy was utilized. In
addition to those elements listed below:
Aluminum Chromium Lead
Arsenic Fluorine Antimony
Boron Iron Selenium
Beryllium Lithium Tin
Cadmium Manganese Vanadium
Chlorine Nickel Zinc,
Copper Phosphorus
the coals were analyzed for a variety of other elements. The analyses
are shown in Table 28 (Martinka coals) and Table 29 (Westland coals).
Examination of this preliminary data revealed that hydrothermal
treatment of coals is effective in extracting many of the trace metals.
Sodium hydroxide appears to be more effective than the mixed leachant.
Of the elements listed above, the concentration (ppmw) of the following in
the caustic leached Martinka HTT coal was lower than in the raw coal.
82
-------
TABLE 28. MASS SPECTROGRAPHIC ANALYSIS OF
MARTINKA RAW AND SELECTED HTT COALS
Elcmont
LI
Bo
li
F
Na
Mg
Al
SI
1?
Cl
K
Ca
Sc
Tl
V
Cr
Ma
Fe
Co
Nl
Cu
Zn
Ga
Ce
As
Se
Br
Rb
St
Y
Zr
Nb
Mo
Ru
Rh
Pd
Ag
Cd
In
Sn
Sb
Te
I
Cs
6a
La
Ce
PC
Nd
Sen
Eu
Gd
Tb
Dy
Ho
Er
Tm
n
I.u
Hf
Ta
W
Re
Os
Ir
Ft
Au
"8
Tl
Pb
BL
Th
U
.R.iw
50
5
100
20
300
3000
~ 17.
~ 57.
2000
300
~ 27.
~ 27.
5
3000
300
200
300
~ 57.
300
1000
10
< 30
< 10
< 2
20
< 30
10
200
1000
50
300
30
10
< 1
< 0.3
< 3
< 1
< 5
< 1
5
1
< 1
3
0.5
500
100
100
30
50
10
5
10
3
10
2
5
< 3
< 5
< 2
< 5
< 10
< 5
< 3
< 5
< 3
< 5
< 2
< 10
< 3
100
< 2
5
20
c.iusutc HIT
50
3
20
10
~ 37.
2000
~ 17.
~ 37.
2000
100
5000
~ 27.
2
3000
100
100
200
~ 17.
200
300
5
< 30
< 10
< 2
< 10
< 20
3
30
500
30
100
20
3
< 1
< 0.3
< 2
< 1
< 2
< 1
1
< 1
< 1
< 1
< 1
< 1
50
100
10
10
2
0.5
1
< 0.3
3
< 1
< 2
< 3
< 2
< 0.5
< 3
< 3
< 3
< 3
< 5
< 3
< 5
< 2
< 3
< 3
5
< 2
< 2
< 2
Li<:irli--mt 1
20
I
10
30
3000
2000
~ 17.
~ 57.
1500
50
500
~ 57.
10
5000
100
200
300
~ 57.
300
500
10
< 30
< 10
< 2
< 10
< 30
3
50
2000
200
500
50
20
< 1
< 0.5
< I
< I
< 5
< 1
100
< 1
< 1
< 1
< 1
1000
100
300
50
200
10
5
10
< 3
10
3
5
< 10
< 10
< 2
< 10
< 3
< 3
< 10
< 5
< 3
< 5
< 2
< 20
< 5
30
< 2
30
20
83
-------
TABLE 29. MASS SPECTROHKAPHTC ANALYSIS OF
WESTLANI) RAW AND SELECTKJ.i HTT COALS
ElU"
LI
Be
B
K
Nn
Mg
Al
SI
V
Cl
K
Ca
Sc
TL
V
Cr
Mn
Fe
Co
Nl
Cu
Zn
Ga
Gc
As
Se
Br
Rb
Sr
Y
Zr
Mb
-Ho
Ru
Rh
PJ
Ag
Cd
In
Sn
Sb
Te
I
Cs
Ba
La
Ce
Pr
Nd
Sm
Eu
Gd
Tb
Dy
Ho
Er
Tra
Yb
Lu
Hf
Ta
W
Re
03
Ir
Ft
An
"B
Tl
Pb
1)1
Th
U
R.iu
50
5
100
20
300
3000
~ 17.
~ 57.
2000
300
~ 27.
~ 27.
5
3000
300
200
300
~ 57.
300
1000
10
< 30
< 10
< 2
20
< 30
10
200
1000
50
300
30
10
< 1
< 0.3
< 3
< 1
< 5
< 1
5
1
< 1
3
0.5
500
100
100
30
50
10
5
10
3
10
2
5
< 3
< 5
< 2
< 5
< 10
< 5
< 3
< 5
< 3
< 5
< 2
< 10
< 3
100
< 2
5
20
C.-iustlc HIT
50
3
20
10
~ 37.
2000
~ 17.
~ 37.
2000
100
5000
~ 27.
2
3000
100
100
200
~ 17.
200
300
5
< 30
< 10
< 2
< 10
< 20
3
30
500
30
100
20
3
< 1
< 0.3
< 2
< 1
< 2
< I
1
< 1
< 1
< 1
< 1
< 1
50
100
10
10
2
0.5
1
< 0.3
3
< 1
< 2
< 3
< 2
< 0.5
< 3
< 3
< 3
< 3
< 5
< 3
< 5
< 2
< 3
< 3
5
< 2
< 2
< 2
uf^'^i! ~nT
20
1
10
30
3000
2000
~ 17.
~ 57,
1500
50
500
~ 57.
10
5000 -
100
200
300
~ 57.
300
500
10
< 30
< 10
< 2
< 10
< 30
3
50
2000
200
500
50
20
< 1
< 0.5
< 1
< 1
< 5
< 1
100
< 1
< 1
< I
< I
1000
100
300
50
200
10
5
10
< 3
10
3
5
< 10
< 10
< 2
< 10
< 3
< 3
< 10
< 5
< 3
< 5
< 2
< 20
< 5
30
< 2
30
20
84
-------
Raw Treated
Arsenic
Boron
Beryllium
(possibly)
Chlorine
Copper
Chromium
20
100
5
300
10
200
< 10
20
3
100
5
100
Raw
Treated
Fluorine
Iron (possibly)
Nickel
Lead
Tin
Vanadium
20
5%
1000
100
5
300
10
vlZ
300
5
1
100
* Concentration in ppmw except where noted, same applies for
all in this table and following tables.
In addition, other trace elements were extracted from the Martinka
coal:
Raw
Treated
Raw Treated
Silicon (possibly)
Cobalt (possibly)
Bromine
Rub idum
Strontium 1000
Yittrium (possibly) 50
5%
300
10
200
<3%
200
3
30
Zirconium
Molybdenum
Barium
Lanthanium and
300
10
500
Con'
100
3
< 1
centrati
other elements of a number reduced
of the Lanthanium
series
500
30
Uranium
Thorium
20
5
< 2
< 2
Similar results were obtained in the treatment of Westland coal with
sodium hydroxide. However, with this coal, chlorine, copper, fluorine, nickel,
throium, and uranium were not extracted.
The mixed leachant was not as effective as sodium hydroxide in
extracting the trace elements from Martinka and the Westland coals. Only
those listed below were extracted from each coal:
85
-------
Martinka Coal
Westland Coal
Metal
Lithium
Beryllium
Boron
Chlorine
Potassium
Vanadium
Nickel
Arsenic
Lead
Rubidium
Raw
50
5
100
300
\.2%
300
1000
20
100
200
Treated
20
1
10
50
500
100
500
< 10
30
50
Metal
Beryllium
Boron
Potassium
Vanadium
Chromium
Arsenic
Bromine
Rubidium
Molybdenum
Raw
0.4
25
^2800
37
37
6
5
12
2
Treated
0.2
<3.5
280
7.0
13
1
1
2.2
0.1
Further reduction in the overall mineral matter content and the
concentration of other trace metals in an HTT coal was achieved by wash-
ing a sodium hydroxide treated Martinka coal with dilute (10 percent)
sulfuric acid at ambient temperature as discussed under "Task IB. Prepara-
tion of HTT Coals". Analysis for aluminum, boron, chlorine, fluorine,
nickel, phosphorus, and zinc indicated that concentrations of these elements
were significantly reduced by the deashing (acid leach) operation as noted below:
Concentration (ppmw)
Metal
Aluminum
Boron
Chlorine
Fluorine
Nickel
Phosphorus
Zinc
NaOH-Treated
> 1%
4.7
270
89
33
32
16
Raw Coal
> 1%
25
150
25
14
14
7.3
Acid Leached
5000
<0.1
10
< 3
10
10
5
On the other hand, acid leaching of the NaOH-HTT coal appeared to
have increased the concentration of several of the trace metals in the coal.
Examples of these are arsenic, copper, chromium, manganese, and possibly
86
-------
cadmium. However, total mass of elements in the HIT coal was significantly
reduced by the acid leach as discussed below. The source of these particu-
lar trace metals could be the sulfuric acid used as the leachant. It may
be that, under the conditions of this experiement, the coal acts as an ion
exchange resin and absorbs the trace metals from the sulfuric acid. This
observation may be in concurrence with some work which has been or is
being conducted at the University of Melbourne by Professor Geoffrey Cullen.
He has observed that brown coal is a very good ion exchange resin for
extracting such metals as nickel, lead, copper, and cadmium from aqueous
solutions.
The total mineral matter content of the NaOH leached coal was reduced
from 13.4 weight percent to 2.2 weight percent by the deashing operation. The
major mineral matter components remaining in the deashed HTT coal were silicon,
aluminum, iron, calcium, and sodium in concentrations (metal basis) of 0.3,
0.03, 0.6, 0.03, and 0.43, wt percent, respectively.
One method for regeneration of the spent sodium hydroxide leachant
for recycle entails sparging with carbon dioxide to liberate the sulfur
as H S which, on a commercial scale, would be converted to elemental sulfur
via the Glaus or Stretford Process. During the sparging operation, the
solubilized coal (humic acids) and, at least, a portion of the trace metals
are precipitated. While additional work will need to be conducted in this
area, it was established that a portion of the trace metals (Table 30) are
removed from the spent leachant by this method of regeneration.
Thus, hydrothermal treatment of Martinka and Westland coals using
either sodium hydroxide or a mixture of sodium hydroxide and calcium hydroxide
as the leachant system resulted in the extraction of certain trace metal
values along with a significant portion of the sulfur. Further reduction
in the concentration of other trace metals in the HTT coal was achieved by
leaching the HTT coal with a dilute sulfuric acid solution. The need for
removal of these trace elements from the spent leachant for recycle was not
established. This would require a series of regeneration-recycle experi-
ments. However, it was determined that a significant portion of these metals
may be removed from the spent leachant by treatment with carbon dioxide.
87
-------
TABLE 30. TRACE METALS CONTENT OF HUMIC ACIDS
Trace
Metal
Iron
Silicon
Calcium
Sodium
Nickel
Molybdenium
Potassium
Magnesium [
Manganese ;
Barium '
Cobalt |
Chromium *
Tin
Vanadium
Copper
Titanum <
Strontium
Concentration ^
Weight Percent
10-15
10-20
0.3
3-6
0.5
0-2
0.5
Were found at
"* 0.1 percent or
less level
On a metal basis,
88
-------
PHASE III. ORGANIC CHEMICAL BY-PRODUCT RECOVERY
FROM HYDROTHERMAL TREATMENT OF COAL
Introduction
During hydrothermal treatment of coal, a portion of the coal is
solubilized or converted to a colloidal suspension of a fine solid in the
alkaline leachant. The solubilized coal commonly referred to as humic
acids can be precipitated from solution by neutralization.
Exact composition of the humic acids will depend probably on the
type of coal. While no effort was made to identify the composition of the
humic acids derived from the coal used in this program, a previous study
conducted at Battelle's Columbus Laboratories under the support of the
Battelle Energy Program on the characterization of humic acids derived
from a subbituminous coal revealed that they contained approximately 69
percent carbon, 4.5 percent hydrogen, 1.0 percent nitrogen, and 0.5 percent
sulfur. Studies by infrared spectroscopy and nuclear magnetic resonance
indicated that the humic acids contained fused ring structures substituted
(14)
in the ring with phenolic hydroxyl and carbonyl functionalities .
Molecular weight determination showed the average molecular weight of the
components to be about 770, covering the range of 100 to 3000. It is
expected that humic acid derived from the bituminous coal used in this
study would have a similar composition and average molecular weight.
The degree of coal solubilization is dependent on the processing
conditions such as temperature, time, leachant system and concentration of
leachant and on the rank of coal. For example, upwards of 90 percent of a
subbituminous Western coal has been solubilized in 10 percent aqueous sodium
hydroxide solution, whereas, in some instances, less than 5 percent of
Eastern bituminous coals was solubilized under similar conditions.
In the conceptualized HCP in which the spent leachant containing
the solubilized coal is regenerated by the carbonation-lime route, this
solubilized coal would precipitate during the carbonation step and would be
recovered at this point by filtration. The filter cake could either be used
89
-------
as a source of process heat, mixed with the HIT coal product or possibly
converted to coal chemicals. Terephthalic acid has been identified as
one potential use for this solubilized coal.
Background Discussion
The concept of producing organic chemicals from coal is not
new. Franz Fisher, et al. , studied the production of chemicals by
direct oxidation of coal and related substances in the early 1900's. They
reported the conversion of a number of carbonaceous materials to benzene
carboxylic acids (BCAs) by wet oxidation with the following recoveries:
cellulose, 1.2 percent; lignin, 5.4 percent; sugar, 2.9 percent; lignite,
0.3 percent; and coal, 1.0 percent. Later, studies at Carnegie Institute
compared BCA yields from several domestic coal products by wet-pressure
oxidation. The following yields expressed as percent carbon converted
were obtained: Illinois No. 6, 33 percent; Pittsburgh, 36 percent, High
Splint, 37 percent; Pocahontas No. 3, 39 percent (equivalent to 69 percent
BCA); anthracite, 38 percent; 500 C coke, 33 percent; 700 C coke, 22
percent; high-temperature coke, 7 percent; graphite, 2 percent; pitch,
30 percent. An average of 3.3 carboxylic acid groups per benzene ring
was reported.
An extension of the Carnegie work was carried out at Dow
Chemical Company in a three-phase study with Pocahontas coal: first, in
a 2-liter autoclave; second in a 96 ft x 0.25 I.D. tube; third, in a
5-gal autoclave. Yields similar to Carnegie's earlier work were obtained.
Numberous similar studies of the production of BCAs by the
direct wet oxidation of coal and related materials have been made and are
the subject of a thorough review by A. E. Bearse, et al' ' .
In 1974, Battelle's Columbus Laboratories, as part of the on-going
Battelle Energy programs in coal utilization, conducted a study directed to-
ward conversion of coal to terephthalic acid via the oxidation - Henkel pro-
cess. Preliminary results indicated that terephthalic acid could be produced
by oxidation of a solubilized coal to BCAs and subsequent conversion of the
90
-------
BCAs to terephthalic acid. In this case, all 12 BCAs were produced and
rearranged to give terephthalic acid. However, the yield while not quanti-
tatively measured appeared low and no effort was made to optimize the pro-
cess conditions for production of either the BCAs or terephthalic acid.
As part of the combustion study, Battelle has conducted a program
to investigate the potential for recovery of organic chemicals for the
humic acids (solubilized coal) which are produced during the hydrothermal
treatment of coal.
Experimental Procedure and Results
Recovery and utilization of the solubilized coal (humic acids)
contained in the spent leachant entailed
(a) Recovery of solubilized coal (humic acid)
(b) Conversion of solubilized coal to BCAs.
Essentially the recovery and conversion of the humic acids to
terephthalic acid would involve three reactions:
(a) Precipitation of Humic Acids
Na salts of humic acids (spent leachant) + CO *
humic acids 4- + Na CO + NaHC03
(b) Preparation of BCAs
Humic acids + H20 +02^ C°2 + BCAS'
During the oxidation, humic acids of unknown composition are
oxidized to a single benzene ring containing carboxylic acid groups (BCAs).
Composition of this mixture may vary, but 12 benzene carboxylic acids as
shown in Figure 5 are possible.
The BCAs would be converted to terephthalic acid by Reaction C:
(c) Preparation of Terephthalic_Acj.d_
(1) BCAs + K?CO h.e.at> potassium terephthalate + H^COj
(2) Potassium terephthalate + HC1 * terephthalic acid + KC1.
91
-------
Benzole acid
(Eenzcr.ecarboxylie acid)
COCH
:OOH
^N ^~COOH
acid
acid)
COOH
Phthalic acid
(1,2-Eenzene-
dicarboxylic acid)
:OOH
Trirr.eHitic acid
(1,2,4-Senzer.e-
tricarboxylic acid)
COOH
COOH
Isophtrhalic acid.
(1,3-Benzcne-
dlcarboxylic acid)
COOH
HOCC
COOK
Tri:r.csic acid
(1,3,5-Benzene-
tricarboxylic acid)
COOK
i
C:CH
Terephthalic acid
(1,4-Eer.zcr.e-
dicarbox.ylic acid)
CCOH
vo
N3
COCH
:~:occ -^x. j^- COOH
?yro.T.cllicic acid
tetracarboxylic acid)
CCOH
COOK
HOOC
CCOH
Benzenepentacarboxylic acid
COOH
COOK
Mellophanic acid
(1,2,3,^-Bsnzene-
tccracarboxylic acid)
KOOC
*..
HOOC.
COOH
COOH
Prehnitic acid
(l,2,3,5-Ec:n7.ene-
tetracarboxylic acid)
COOH
IOOH
COOH
Mellitic acid
(Benzcnehexacarboxylic acid)
FIGURE 5. NAMES AND STRUCTURAL FORMULAS OF BENZENECARBOXYLIC ACIDS
-------
coon
Terephthalic acid has the formula /V
(
COOH
During this reaction, rearrangement of the carboxylic acid groups would occur
and excess carboxylic acid groups would be converted or lost as carbon dioxide,
Recovery of Humic Acid from Spent Leachant. In order to develop
a recovery process which was compatible with the overall HCP, the humic
acid fraction of a sodium hydroxide spent leachant was precipitated by
sparging the leachant at 60 C with carbon dioxide. Sparging was continued
until the pH of the solution decreased to 8.5. The resulting mixture was
vacuum-filtered. The filter cake was washed with water and vacuum dried.
The dried product was found to contain 33.9 percent organic carbon,
56.3 percent ash, 4.3 percent moisture and 0.7 percent sulfur. Carbon content
of the spent leachant was lowered from 0.35 percent to 0.01 percent, while
sulfur content was reduced to 0.06 percent from 0.19 percent.
Analysis of the ash component of the dried humic acid product
revealed the presence of iron (10-15 percent); silicon (10 to 20 percent),
calcium (0.3 percent), sodium (3 to 6 percent), aluminum (1 to 2 percent),
nickel (0.5 percent), molybdenum (0.2 percent) and potassium (0.5 percent).
Other metal values found at 0.1 percent or less level were: manganese,
magnesium, barium, cobalt, chromium, tin, vanadium, copper, titanium, and
strontium.
Conversion of Humic Acid to BCAs^ The oxidative approach was
employed to oxidize to the humic acids to BCAs. Typically, this entailed
the following processing steps:
(1) The dried humic acid (2.75 g) was dispersed in 250 ml
of water containing a small amount of wetting agent and,
in some cases, other reagents such as K^CO^, oxalic
acid, etc.
(2) The mixture from (1) was then heated in the autoclave at
temperatures ranging from 250 C to 300 C under an oxygen
93
-------
overpressure. Oxygen was added normally after the mixture
had reached the desire temperature.
(3) Samples were withdrawn during the run as a function of time
for analysis.
(4) The reaction products remaining in the autoclave at the
termination of the experiment were cooled to room
temperature, gas in the head space vented for analysis
and contents of autoclave removed for analysis.
The results of these experiments are shown in Figure 6. Each point plotted
for total BCA yield reflects a corresponding terephthalic yield since the
total BCA yield could, by the Henkel reaction, be converted to terephthalic
acid.
From comparison of these three curves, the data suggests that at
300 C the rate of conversion of humic acids to EGAs was rapid. However,
the data further suggests that at this temperature BCAs are unstable, and
after the first few minutes, the rate of decomposition was faster than the
rate of formation. Thus, in order to obtain a high yield of BCAs at 300 C,
a means of removing the BCAs from the reaction product must be developed.
At 250 C in the presence of water alone and K CO plus water,
the rate of conversion of humic acids to BCAs was higher than the rate of
decomposition. The addition of K CO which reacted with the BCAs as formed
to produce the potassium and terephthalate carbonic acid (H?CO_) improved
the yield significantly because the potassium salt of the BCAs was more stable
than the BCAs.
The higher stability of the potassium salt of BCAs was evidenced
by analysis of the gaseous products for carbon dioxide which was converted
to carbon losses. For those experiments conducted in hot water, 60 to 85
percent of the carbon charged was converted to carbon dioxide. The addition
of K CO reduced the loss of carbon as carbon dioxide to 22 percent.
Interpretation of the gas chromatographic data from the K CO
£ -J
experiment revealed that all 12 benzene carboxylic acids were formed by
the oxidation of humic acids (Figure 7). The relative concentrations
increased accordingly: mono < hexa < di < penta < tetra < tri with the
concentration of mono-benzenecarboxylic acid being too low to plot. These
results are in general agreement with those obtained by Germain' ' from
the oxidation of a high volatile European coal in K CO .
Z, J
94
-------
60
50
tc
£
tn
d
H
in
H
iH
5?
s
«
u 20
\
\
\
f \
,,-' c
1
F^
'
X
x
e
^\
<
X
X
"^^
X
-"'
i 300°
,
"'
"
H?0
X
X
<
V*
-^-
y-
X
. -"
,
s
'
_--
"en.
250°
0 20 40 60 80 100 120 140 160 180 200 220 240
Time, minutes after oxygen injection
FIGURE 6. COMPARISON OF TOTAL BCA FORMATION RATES
UNDER VARIOUS CONDITIONS
95
-------
20
19
Hi
17
16
15
14
13
12
11
o
HI
< ti 10
CO
-------
While the above data clearly illustrate the technical feasibility
of converting humic acids to BCAs, the data also shows that at temperatures
between 250 and 300 C the BCAs are unstable. In an effort to learn the fate
of the BCAs, once generated by oxidation of humic acids, an experiment was
conducted using a synthetic nixture of pure BCAs in water. The experiment
was carried out at 250 C rather than at 300 C because of the rapid rate
of decomposition of BCAs at the higher temperature. After attainment of
temperature, samples were withdrawn prior to the injection of oxygen and
at intervals thereafter. Gas chromatographic analyses were made on the
samples. The results are summarized in Figure 8.
It appears that in water alone, the dicarboxylic acids are the
most stable of the six different acids. In fact, the dicarboxylic acids
present at zero time may have resulted in part from decarboxylation of the
higher acids before oxidation was initiated. Also,the data shows that
even at 250 C all of the benzenecarboxylic acids are unstable. Therefore,
in order to obtain the best yield, pressure oxidation of humic acids must
be carried out with rapid heating and cool down or quenching of the reaction
mixture. Again, these results are in agreement with some work performed
(14)
on alkaline oxidation of Pocahontas coal by Montgomery who found that
best yields were attained at a residence time of 1.5 minutes.
97
-------
170 -
140
130
120
110
(J <1)
o
1-1
60 O
n ^
§ 80
70
-
1
\
1
»
'.
\
1
\
- .
\
\
\
\
\
\
\
\
\
V
\
I
\
\
\
\
\
\
\
1
Te-U-;
!
(47 .-,-.
X
^ <- 1 1 ,'i r
X
_
*">
-..._
Di (1
n;i(
Mo::r
00 . 8
n 9 . '/
O, i-
11:' Che
"'.'J, Ci
irr-.O
i.--r.-;i-)
T " "
c.Viarvi-)
1
-' n S 10 13 .'0 '"i i!i J:. /iO
0
60
50
AO
30
20
'10
MinnU-K .'i f i ci 0, i n ') i l. i .MI
FIGURE 8. FATE OF PURE BENZENE CARBOXYLIC ACIDS IN PRESENT PROCESS
ABCA charge also included 51 mg penta carboxylic acid and 46 mg hexa car-
boxylic acid; neither was detected in product.
98
-------
CONCLUSIONS
(1) HTT coals prepared by the Hydrothermal Coal Process from Martinka
and Westland coals burn as well as or better than the corresponding
raw coals in the laboratory test facility and multifuel furnace com-
bustion units.
(2) Sulfur dioxide concentrations in the flue gases were well below current
Federal Sulfur Emission Standard for New Sources of 1.2 Ib, ranging
from about 125 to 500 ppm.
(3) The low sulfur dioxide and levels are attributed in part to the re-
duced sulfur concentration in the HTT coals, and in part to the sulfur
capturing ability of the residual alkali in the HTT coals.
(4) Hydrothermal processing is effective in extracting trace metals such
as beryllium, boron, vanadium, and arsenic from these coals. Alkali
content sodium and/or calcium is increased as a result of the
treatment.
(5) The potential slagging and fouling characteristics of the HTT coals
suggest that these coals would be less suitable for firing in dry
bottom furnaces than were the corresponding raw coals. The reduction
in ash fusion temperature may in some cases require some boiler derating
to avoid furnace slagging and boiler fouling problems. Firing
of the HTT coals in existing dry-bottom furnaces may require the
installation of additional soot blowers. Operation of the slag blowers
more frequently and derating of the boilers would most likely be
required. It may be possible to reduce the slagging and fouling
characteristcis of the treated coals through the use of additives
to raise the ash fusion temperature.
On the other hand, the low ash fusion temperature suggests that the
HTT coals may be utilized directly in wet-bottom (slap tap or cyclone)
furnaces. Firing in wet-bottom furnaces might avoid furnace slagging
problems; however, boiler fouling may continue to be a problem, requiring
adequate soot-blower capacity and, possibly, boiler derating to lower gas
temperatures in the convection region.
99
-------
(6) Data on the resistivity of the coal ash samples are inconclusive
because of the possible influence of carbon in the samples. However,
in general, the resistivity values of the ashes from the Martinka
HTT coals were comparable to those from the raw coal.
(7) Preliminary assessment of the environmental problems associated with
the combustion waste products indicate that direct disposal of the
cooler ash from the NaOH treated coal would not be advisable because
of high sodium sulfate content of the ash. However, the sodium sulfate
could be removed prior to disposal- Removal of the sodium sulfate
would produce an ash which would be less polluting with respect to trace
metals than the ash from the corresponding raw coal since a significant
portion of the trace metals would have been removed from the coal by the
leaching process.
(8) Heating the solubilized coal (Humic acids) under oxidizing conditions
in an aqueous medium resulted in the conversion of the humic acids to
benzene carboxylic acids (EGAs), precursor to terephthalic acid. Yield
of EGAs was low, less than about 10 percent. The majority of the coal
was converted carbon dioxide. Therefore, this approach does not appear
to be a viable process for conversion of the solubilized coal to
terephthalic acid.
100
-------
REFERENCES
(1) Stambaugh, E. P., Miller, J. F. , Tarn, S. S., Chauhan, S. P., Peldmann
H. F., Carlton, H. E., and Oxley, J. H. , "Environmentally Acceptable"'
Solid Fuels by Battelle Hydrothermal Coal Process", Second Symposium
on Coal Utilization, NCA/BCR Coal Conference and EXPO II, Louisville
Kentucky (October 21, 23, 1975).
(2) Jones, P. W., et al, "Efficient Collection of Polycylic Organic Com-
pounds From Combustion Effluents", presented at the 68th Annual Meeting
of the Air Pollution Control Association, Paper No. 75-33-3, Boston
Massachusetts (June 15-20, 1975).
(3) Stambaugh, E. P., Liu, K. T. , Chauhan, S. P., Feldmann, H. F. , and
Sekhar, K. C., "Improved Feedstock for Liquefaction/Pyrolysis Operations
by Hydrothermal Processing", Battelle Energy Program (April, 1976)
(unpublished).
(4) Stambaugh, E. P., et al, "Battelle Hydrothermal Coal Process", 12th
Air Pollution and Industrial Hygiene Conference on Air Quality Manage-
ment in EPI, University of Austin, Austin, Texas (January, 1976).
(5) Compilation of Air Pollutant Emission Factors, U.S. Environmental Pro-
tection Agency, AP-42 (April, 1973).
(6) Krause, H. H. , Levy, A., and Reid, W. T., "Sulfur Oxide Reactions:
Radioactive Sulfur and Microprobe Studies of Corrosion and Deposits",
Trans. ASME, Jour. Eng. for Power, Vol. 90, No. 1, 1968, pp 38-44.
(7) Tufte, P. H. , et al, "Ash Fouling Potential of Western Subbituminous
Coal as Determined in a Pilot Plant Test Furnace", American Power
Conference (April 20-22, 1976)
(8) Pohl, J. H. and Sarofim, A. F., "Fate of Coal Nitrogen During Pyrolysis
and Oxidation", Proceedings of the Stationary Source Combustion Symposium,
EPA, Atlanta, Georgia (September 24-26, 1975), p 1-125.
(9) Committee on Biologic Effects of Atmospheric Pollutants, Biologic
Effects of Atmospheric Pollutants; Particulate Polycylic Organic
Matter", National Academy of Sciences, National Research Council,
Washington, D.C. (1972), pp 375.
(10) Hangebrauck, R. P., von Lehmden, D. J., and Meeker, J. E., J. Air
Poll. Con. Assoc., 14., 267, July, 1964.
(11) Reid, W. T., "External Corrosion and Deposits", American Elsevier Pub-
lishing Company, Inc., New York (1971).
(12) Coal Fouling and Slagging Parameters, a special report prepared by the
Corrosion and Deposits Committee of ASME (1974).
101
-------
(13) Method of Laboratory Sampling and Analysis of Coal and Coke, ASTM
D271-70 (1972).
(14) Bickelhaupt, R. E., "Effect of Chemical Composition on Surface Reactivity
of Fly Ash", EPA-600/2-75-017 (PB 244 885), August 1975.
(15) Bearse, A. E., Grotta, H. M., Stambaugh, E. P., et al., "Utilization
of Coal Solutions Derived from Hydrothermal Processing", Battelle
Energy Program (April, 1975) (unpublished).
(16) Fisher, F., et al., Ges. Abhandl. Kennt. Kohle, 4, 342-59 (1919);
Ibid., 5^ 200-91 (1920).
(17) Franke, N. W., Kiebler, M. W., Relof, C. H., Savich, 1. R,, and
Howard, H. C., Ind. Eng. Chem., 44^ 2784-92 (1952).
(18) Montgomery, R. S., and McMurtrie, R., U.S. Bureau of Mines Information
Circular No. 8234 (1963).
(19) Bearse, A. E., Cox, J. L., and Hillman, M., "Production of Chemicals
by Oxidation of Coal", Battelle Memorial Institute, Columbus, Ohio (1975).
(20) Germain, J. E., Industrie Chimique Beige, Numero Special: Congress
International de Chimie Industrielle, Vol 32, Spec. No., Pt. 2,
pp 640-5 (1967).
102
-------
APPENDIX A
DESCRIPTION OF THE HYDROTHERMAL COAL PROCESS
-------
APPENDIX A
DESCRIPTION OF THE HYDROTHERMAL COAL PROCESS
The Hydrothermal Coal Process (HCP) is a method for producing
environmentally acceptable solid fuels (clean coal) from certain high-
sulfur coals. Basically the process involves heating an aqueous slurry
of coal and a chemical leachant at moderate temperatures and pressures to
extract a significant portion of the sulfur and some of the ash, depending
on the leachant, from the coal and subsequent regeneration of the leachant
for recycle. The process, as depicted in Figure A-l, entails five major
processing steps:
1. Coal preparation
2. Hydrothermal treatment (desulfurization)
3. Liquid/solid separation
4. Fuel drying
5. Chemical-leachant regeneration.
Coal preparation entails crushing or grinding of the raw coal,
as received from the mine or after washing, to the particle size suitable
for desulfurization, generally 70 percent minus 200 mesh.
Next, the coal goes to the slurry tank for mixing with the
leachant, or, alternatively, the coal may be physically beneficiated to
remove easily removable ash and pyritic sulfur and then pumped to the
slurry tank.
After mixing with the leachant, the coal slurry is pumped
continuously through the hydro thermal-treatment (desulfurization) segment
where it is heated to a desired temperature whereupon sulfur and ash are
extracted in amounts depending on the leachant.
-------
High-Sulfur
High-Ash
Coal
Coal
Pretrcatment
(Grinding/
Physical
Beneficiation)
Hydrothermal
Treatment
(Suifur Removal)
Chemical
Le^chant
Recencrction
Post-Treatment
(Washing/Drying)
De-Astiing
(Optional)
Low-Sulfur
(Low- or High- Ash)
Coa!
Chemical
Leachant
Recycle
Sulfur
Chemicals/
Fuol/r.'st-i!
Values
Eloctric
Power
Picnts
Industrial
Bolters
NJ
FIGURE A-l. BATTELLE HYDROTHERMAL COAL PROCESS
-------
A-3
The resulting coal-product slurry is passed through a heat
exchanger into the product-separation (washing) segment where the desul-
furized coal is separated from the spent leachant by a series of
filtration and washing operations.
Next, the desulfurized coal is dried in, for example, a steam
jacketed drier to remove residual water to produce a clean, solid fuel.
The spent leachant from the washing segment is regenerated in
the leachant-regeneration segment where the sulfur is also removed as
hydrogen sulfide by carbonation. The hydrogen sulfide on a commercial
scale would be converted to elemental sulfur by a Glaus or Stretford
sulfur-recovery process. The carbonated liquor after filtering to remove
solubilized coal and ash values is treated with lime and filtered to
remove the calcium carbonate precipitate. The calcium carbonate is
calcined to produce lime and carbon dioxide for recycle. The regenerated
leachant is concentrated, composition adjusted, and returned to the process.
The miniplant was used to produce sufficient quantities of HTT
coals for this combustion study. This facility encompasses the 5 process
steps discussed above but for this study only the first 4 steps - coal
preparation, desulfurization, liquid/solid separation, and product drying -
were utilized. Maximum production rate is about 500 Ibs per 24 hours.
-------
APPENDIX B
MINIPLANT FACILITY
-------
APPENDIX B
MINIPLANT FACILITY
The Miniplant is a small semi-continuous pilot plant with a pro-
duction capacity of about one-fourth ton per day (about 20 Ib/hr) of HTT
coal. The facility consists of five major segments: Coal Preparation,
Hydrothermal Treatment, Coal Washing, Leachant Regeneration, and Coal
De-ashing Segment (Figure B-l). While the Miniplant was designed for con-
tinuous operation, sufficient storage tanks were installed so each segment
could be operated independently.
Coal Preparation Segment. Since most of the coals received are
water washed, each is dried before pulverization. After drying in the
steam jacketed dryer, the coals are ground in a two-stage process: (1)
to about 4-mesh size with a Fitzmill Model P comminuting machine and (2)
to the desired sizes with a Bantam Mikro-pulverizer (hammer-type) . Various
sizes of coals are prepared by employing different sizes of screens in the
Mikro-pulverizer.
Classification of ground raw coals is conducted in large and small
scales. Large batches of raw coal are classified in a Sweco 24-inch vibro-
energy sieve. The oversize is reground in the Mikro-pulverizer. After
which the large batch of coal is mixed in a drum and a random sample is
taken to determine its size distribution. The technique employed for size
distribution determination in a mechanical Rotap is described in Appendix
A-l of ASTM Designation: D-197-30 (Reapproved 1971).
Hydrothermal Treatment Segment. The Hydrothermal Treatment Segment
consists of four major units: coal slurry preparation, reactor system, pres-
sure let-down system, and product coal slurry separation. These four units
are connected and operated continuously. The Hydrothermal Treatment Segment
was designed to process 4 to 30 Ib of coal per hour. However, its capacity
also depends on hydrothermal-treatment conditions. Reactors were designed
for a maximum operating temperature of 275 C.
Coal Slurry Preparation. The schematic diagram of the coal slurry
preparation unit is shown in Figure B-2. The mix tank and the feed tank are
two 30-gal, conical bottomed, polyethylene tanks. The coal slurry is pre-
-------
Coal
J.
Coal
Preparation
Sulfur
Soluble
Or^r-nic
Fraction
Hydrotheraal
Treatment
Coal
Washing
w
ho
Leachant
Regeneration
Coal
Low-Sulfur
N
Low-Ash Coal
FIGURE B-l. BLOCK DIAGRAM OF THE BHCP MINIPLANT
-------
Coal
On-Line
Strainer
Drain
Moyno Punp
w
i
Teel Purap
FIGURE B-2. COAL SLURRY PREPARATION
-------
B-4
pared in the mix tank and transferred into the feed tank installed on an
electronic scale equipped with a digital readout. The slurry is trans-
ferred from the mix tank to the feed tank with a Teel pump. A Moyno pump is
used to recirculate the coal slurry around the feed tank. Recirculation is
necessary to prevent coal from settling in the pipe. An in-line pipe strainer
installed in front of the recirculating pump (Moyno Pump) acts as a safety
device to trap foreign particles in the coal slurry.
Reactor System. The reactor system is constructed inside a steel
safety barricade. Major equipment in this system are high-pressure pumps,
preheaters, reactors, and cooler (Figures 23,24, and 25).
The high-pressure pumps are two Millroyal reciprocating pumps; a
6-gph low-flow equipped with maximum delivery pressure of 2100 psi and a
25-gph high-flow pump with a maximum delivery pressure of 1555 psi. The
flow rate on each pump is adjustable and the pumps are operated at a minimum
flow of 1/3 of its capacity. Actual feed rate is measured by weighing the
feed tank mounted on an electronic scale.
To prevent vapor locking of the pumps by air pockets check valves
and bleed valves were installed to bleed off the air without interrupting
an experiment. A rupture disc was installed between the check valve and the
pump discharge to protect the high-pressure pump.
Figure B-3 shows the heating system of the Hydrothermal Treatment
Segment. The heaters are short lengths of 1/4-inch nickel pipe. The first
heater is a double pipe heat exchanger, 3 feet long, with 60 psig steam used
to heat the slurry. The next four heaters are 2-foot lengths of 1/4-inch
pipe silver soldered into a 2-inch square copper bar. The copper is heated
with Chromalox strip heaters capable of up to 4 kw on each heater. Each
heater is insulated with pipe insulation. The final heater is an autoclave
with a 1-gal nickel-lined body and a 3.5 kw tubular furnace. The autoclave
heater is installed to reduce plugging problems in the tube heaters.
The temperature of the electrical tube heaters is measured in the
copper block near the fluid outlet. The temperature in the autoclave heater
is measured by a thermocouple inserted into a thermowell in the autoclave.
The temperature in the steam heater is controlled by an off-on valve.
The power to the electrical heaters is controlled by Chromalox
electronic proportional temperature controllers. The temperature is measured
-------
Steam
Stean
Heater
Electrical
Heaters
Solenoid
Valve
Safety Head
Y.
1
1
i
1
f
1
1
i
1
From High Pressure
Pump
.4 KW
Steam
Trap
Drain
To Reactors
Cd
I
t_n
1-gal Autoclave
with 3.5 KW
Tubular Furnace
FIGURE B-3. PREHATERS
-------
B-6
by thermocouples which are installed inside the copper bars of the outlet
ends of the electrical heaters and on the U-tubes between the heaters.
The autoclave system was designed as shown in Figure B-4. However,
the second 1-gal autoclave is replaceable with a 2-gal body to provide ad-
ditional capacity of the reactor system. The autoclave bodies are nickel-
lined.
Each autoclave is stirred magnetically. The first autoclave has
a 2-gal nickel-lined body, and the second autoclave has a 1-gal nickel-lined
body (Figure B-4). The 2-gal autoclave and the 1-gal autoclave is equipped
with two and one 3.5 kw furnaces, respectively. The temperature is measured
with a thermocouple inserted in a well extending into the coal slurry and
controlled by a Chromalox electronic proportional temperature controller.
The product cooler is a tubular water-cooled heat exchanger as
indicated in Figure B-5. Water is used in the shell-side as a coolant,
Pressure Let-Down System. A schematic diagram of the pressure
let-down system is shown in Figure B-6. The product slurry flows from the
product cooler into a 5-gal autoclave rated at 1150 psi. The autoclave is
mounted on an electronic scale which measured the amount of slurry in the
autoclave. Adjustable high- and low-limit switches are built into the scale.
Switches on the scale are arranged to open the valve to drain the autoclave
and to open a valve to admit nitrogen into the autoclave to maintain the de-
sired nitrogen overpressure between a high and a low limit. The switch
opens the valves at the high limit to drain product and close at the low
limit when a selected quantity of product has been removed. Normally, about
four points differential is set between the high and the low limit. The
low limit is set to prevent gas from venting through the liquid outlet.
Larger differentials causes an excessive pressure drop in the
system. To eliminate this effect, a second 5-gal autoclave was installed in
the system and connected to the gas space at the top of the receiver auto-
clave. With this arrangement, the pressure drop in the system is about three
percent of the system pressure. As first installed, vibrations, electrical
transients, etc., caused the scale to indicate the high level had been
reached before the three pounds of slurry was added to the autoclave. A 2
second time delay relay in the high-limit circuit prevents such indications.
-------
From Heater
To Product
Cooler
I I
I
w
I
J
2-gal Autoclave
with two furnaces,
3.5 KW Each
1-gal Autoclave
with one furnace,
3.5 KW
FIGURE B-4. REACTORS
-------
Vj toe laves
0
To Drain
i
oo
Control Valve
1L
Solenoid Valve
'Cooling Water
FIGURE B-5. PRODUCT COOLER
-------
Product Slurry
Frcra Cooler
100-gal.
5-gal.
Autoclave
v!
Scale
Regulator Valve
^XJ Bleed
Valve
To Centrifuge
Scale
Controller
?IX
u
Kitrc^en
Cy iirK'.
D=l
I
VD
FIGURE B-6. PRESSURE LET-DOWN SYSTEM
-------
B-10
The pressure controller prevents overpressure in the system by
venting nitrogen when the pressure exceeded its set point. The controller
is a Fischer proportional controller and the control valve is a Badger
Meter 1/4-inch air-actuated valve with size M trim (Cv = 0.0004 - 0.01).
The regulator valve on the nitrogen cyclinder is a high-pressure regulator
valve set at 1400 psi.
Product Slurry Separation. The solid fuel product is separated
from the spent leachant in the Product Slurry Separation Segment. The
slurry from the HTT Segment discharges into a 100-gal tank from which the
slurry is pumped into a centrifugal filter. The centrifugal filter is a
Bock basket centrifugal, 17 inches in diameter and 14 inches deep separating
at about 1725 rpm. Polypropylene is used as the filter cloth.
-------
APPENDIX C
DESCRIPTION OF THE COMBUSTION
FACILITIES
-------
APPENDIX C
DESCRIPTION OF THE COMBUSTION
FACILITIES'
Two laboratory-scale combustion facilities, a small onp Ih/hr labora-
tory test facility (LTF) and a larger Multifuel Furnace (MFF), were used during
the program and are described below.
ONE LB/HR LABORATORY TEST FACILITY
This facility consists of a coal feeder, a burner, a combustion
chamber, and a cooler as shown in the schematic of Figure C-l.
Feeder
The coal feeder, shown in Figure C-2, consists of a tubular reservoir
for coal, a double tube to supply air to the feed and remove the coal-air
suspension, a pulley and motor to slowly lift the reservoir from the air tube,
and lid mounted on the air tube. In operation, high pressure air is admitted
into the outer part of the double tube at the bottom and leaves at high velocity
through small holes near the top of the tube. This high velocity air suspends
coal particles that flow through the inner part of the double tube into
a line leading to the combustor. The motor and pulley combination lifts the
coal in the reservoir into the high velocity air jets. The lid on the dust
chamber confines the coal-air suspension to a definite volume and is necessary
for uniform feeding.
Several types of screw feeders were tried and found to be unsatis-
factory because the uniformity and control of coal feed rate was inadequate.
Screw feeders probably cannot be improved to the degree necessary for these
-------
C-2
Air Heater
Coal
Feeder
Combustor
Gas
Analyzer
FIGURE C-l. SKETCH OF EXPERIMENTAL APPARATUS
-------
C-3
"tin
jrm
m*&-
" !.;:-'Vf^
rt-ril I-.'V. !..-.-> pJ
(TTT iij
To Pulley
A Small Holes
Double Tube
Sliding Seal
Air in
Y-'Co'nl Dust Out
FIGURE C-2. COAL FEEDER
-------
C-4
small-scale combustion experiments without an unreasonable amount of research.
However, the new type of feeder is adequate for purposes of this program.
Burner
Figure C-3 shows a sketch of the burner. The brass burner construction
is mounted on top of the combustion chamber so that when in place the tip of
the burner emerges slightly into the combustion chamber.
The burner is designed to provide a tangential entry for hot
secondary air which mixes with the primary air and fuel emerging from the central
feed tube. The burner is cooled by air or water in a circular cooling chamber.
Modifications in swirl pattern and flame can be made by adjusting the entry
port of the secondary air and velocity of the mixture at the burner throat,
thus giving flexibility in operation to the system. Propane was used for
system warm-up prior to coal combustion.
Combustion Chamber
Figure C-4 shows a sketch of the combustion chamber. The chamber
consists of inner disposable alumina tube, 2-1/2 in. I.D. and 10-in. long,
which contains the flame. A wire-wound furnace tube which in turn is
insulated with Fiberfrax insulation surrounds the alumina tube. The entire
assembly is encased in a stainless steel housing. The tubes are supported
at the ends by a piece of insulating firebricks. A platinum, platinum-
rhodium thermocouple is imbedded in the furnace tube for monitoring the
system temperature at all times.
During operation, the furnace is heated electrically to 1500 F;
then to approximately 1750 F with propane.
Cooler
The hot combustion gases emerging from the combustor enter the
cooler section. Figure C-5 shows details of the cooler and
-------
C-5
1'viinary Air
£ Coal Kntry
Secondary
Cooling Air
Jacket
Swirl Chamber
Burner Throat
FIGURE C-3. BURNER
-------
C-6
Primary Air and Coal
Furnace Tube
Enclosing Cylinder
-------
C-7
Cooling Air
Entry
["~f
^~i.
Hot Cnses From Combustion Chamber
Gas Sampling Probe
FIGURE C-5. COOLER
-------
Co
O
sampling process. The cooler is a 3-in. I.D. and 5-ft long counter-current,
externally air-cooled stainless steel heat exchanger. Cooling air flows
upward through an annulus between 4-in. I.D. and 3-1/2-in. O.D. tube. Hot
gases flow downward through the inner tube and are cooled to approximately
300 F before being sampled and exhausted to the atmosphere.
MULTIFUEL FURNACE FACILITY
The Multifuel Furnace Facility was designed to generate flue gas
and fly ash under conditions closely simulating those of a power-generation
station. This implies combustion at a high enough temperature with a proper
cooling schedule to produce flue gas and fly ash having physicohemical pro-
perties similar to those of a typical central-station boiler and its
associated stack and plume. In addition, the laboratory-scale system is
flexible enough to permit firing with either pulverized coal, residual or
distillate oil, or gas.
The Multifuel Furnace Facility is usually operated with an electro-
static precipitator for coal firing but without the electrostatic precipita-
tor in firing oils. However, in this program the electrostatic precipitator
was not used.
Figure C-6 is a schematic of the gas-combustion and flue-gas
conditioning system with major sections indicated. The major sections of
the facility are discussed below.
The Multifuel Furnace
Figure C-7 is a photograph of the Battelle-Columbus Multifuel Furnace
to be used on this program. This small-scale furnace consists of a cylindrical
combustion chamber approximately 17 inches in diameter by 90 inches in length.
The furnace is lined with three layers of firebrick and insulation to accom-
modate surface temperatures up to 2900 F. At the outlet, the diameter of the
-------
C-9
bo;!c-r
Excess
Flu-?-Gas
Ex.haur.t
FIGURE C-6. SCHEMATIC OF LABORATORY FLUE-GAS
CONDITIONING SYSTEM
-------
n
i
FIGURE C-7. BATTELLE MULTIFUEL FURNACE
-------
C-ll
furnace is reduced to 5 inches to enclose the flame, provide for normal re-
circulation, limit radiation losses, and provide sufficient gas velocity to
keept fly ash suspended in the gas stream. Viewpoints along the axial dimension
of the furnace provide for visual access during periods of adjustment of
firing conditions.
In normal operation of the furnace, natural gas is fired to maintain
system temperatures at approximately the desired levels on a more or less con-
tinuous basis while runs are not being made. Upon switching to either coal
or oil firing, the entire system is allowed to equilibrate for several hours
before any data are taken.
An adjustable-flow, positive-displacement pump that was precalibrated
is used to regulate the supply of residual oil to the furnace at about 3 gal/hr,
and the oil is preheated to insure the desired viscosity at the burner nozzle.
With coal firing, a dispersion of the fuel in air is fed to the burner (at a
«
rate of 20 to 80 Ib/hr) via a screw feeder mounted within a pressurized coal
hopper.
Furnace temperatures can be controlled by varying the firing rate.
However, when the firing rate is varied, the residence time varies also. If
it is ever determined to be necessary, a minor modification could be made to
the furnace to permit cooling surface (water-cooled loops) to be inserted into
the furnace to absorb heat and, thus, permit independent control of firing
rate and furnace wall (and combustion) temperatures. This approach has been
successful in previous studies with an early furnace of similar design.
Burner Design
To meet the special requirements of the furnace, it was important
that the burner be flexible enough to permit operation over a range of condi-
tions.
Figure C-8 is a cross-section drawing of the burner that was designed
for this furnace.
-------
Mounting plate
I
Coal Nozzle
Coal nozzle is
adjusting axially
^-Air-tight
seal
Axial air
(24) holes, l/4"diam
I
(-
NJ
12 vanes
2-/4" x 3/4"
opening 0.5"or less
View A-A
Detail of swirl vanes
Swirl air
FIGURE c-8. BURNER FOR BATTELLE MULTIFUEL FURNACE
-------
C-13
This burner design permits varying the firing rate, flame velocity,
swirl angle, type of fuel burner, atomizer type and size, and atomizer loca-
tion relative to the air-admission path. Combustion air may be admitted
through openings between 12 vanes positioned to give the air a high degree of
swirl, it may be admitted through axial holes in the plate behind the burner
throat (see Figure C-8) to provide axial flow, or a combination of swirl and
axial air may be used. In the latter case, adjustment of the proportion of
air flow to the swirl vanes and to the axial holes varies the percentage of
swirl in the burner throat. Air flows to the swirl-air plenum and the axial-
air plenum are separately manifolded, controlled, and measured. For coal
firing, all axial air is used.
The burner throat of a 3.5 in. diameter is designed for an axial
velocity of 15 fps, tp produce a large flame that will fill the furnace.
This flame should simulate residence times in the flame region that are
comparable to residence times in the flames of boiler furnaces.
A variety of fuel nozzles of the air-atomizing, steam-atomixing,
or pressure-atomizing types may be fitted to the nozzle holder. It is possible
to fire natural gas in this burner by replacing the fuel nozzle assembly with
a gas injector. Pulverized coal is fired by substituting a coal nozzle for the
oil atomizer. The coal nozzle requires a central cone to form a conical coal
dispersion much like an oil spray.
Simulated Boiler-Economizer Section
The simulated boiler-economizer section of the rig is constructed
of stainless steel pipe lined with a castable refractory material and insulated
on the outside. Gas velocities in horizontal portions of this section are
typically 60 ft/sec, and velocities in vertical portions are about 5 ft/sec.
Temperatures drop from about 2600 F at the inlet to about 600 F or less at
the outlet.
-------
APPENDIX D
OPTICAL EMISSION AND MASS SPECTROGRAPHIC ANALYSIS
-------
APPENDIX D
OPTICAL EMISSION AND MASS SPECTROGRAPHIC ANALYSIS
Optical emission analysis of the eight coals burned are shown in
Table D-l. Mass spectrographic analysis of coal and coal ashes are shown in
Table D-2 and D-3.
-------
TABLE D-l. OPTICAL EMISSION ANALYSIS OF THE EIGHT COALS BURNED
[li^nt
SI
Al
Pe
Ca
>!g
Na
t
Ti
Zr
Pb
Kn
Ba
B
Cr
V
Cu
Nl
Co
Sr
Sn
1 . Rau
Coal
1-3
1-2
1
0.1
0.1
0.1
0-5
0.1
<0.01
<0.01
<0.005
0.01
<0.01
0.01
<0.01
0.003
<0.005
<0.01
0.01
<0.01
Ash
5-10
: -20
7-12
1
0.3
0.3
1-2
0.5
0.02
0.02
0.02
0.05
0.01
0.1
0.02
0.01
0.04
0.01
0.03
<0.01
Slag
5-10
10-20
7-12
1
0.4
0.3
1-2
0.5
0.02
0.02
0.02
0.03
<0.01
<0.03
0.02
0.01
0.01
0.01
0.05
<0.01
We X as
Coal
1
1-2
0-5
0.05
0.05
0.5
0.1
0.02
<0.01
<0.01
<0.005
0.01
<0.01
0.01
<0.01
0.003
<0.005
<0.01
<0.01
<0.01
Met. il in Sa-:-,le
Ash
4-8
10-20
5-10
0.07
0.3
5-10
0.5
0.3
0.02
0.02
0.02
0.02
<0.01
0.1
0.01
0.01
0.04
0.01
0.03
<0.01
Slag
5-10
10-20
5-10
1
0.3
10-20
0.5
0.3
0.03
0.02
0.02
0.04
<0.01
0.03
0.02
0.01
0.02
0.02
0.05
=0.01
Coal
1-3
1-2
1
0.1
0.1
0.1
0.5
0.1
<0.1
0.02
<0.005
0.01
<0.01
0.01
eO.Cl
0.003
-------
TABLE D-l. (Continued)
Run No.
Si
Al
re
Ca
MB
Na
K
Tl
Zr
Pb
Wo
Ba
Cr
V
Cu
HI
Co
Sr
Sn
B
7. Mix-Leach. Martlnka
r.Ash
5-10
4-7
3-6
15-25
0.6
3-5
0.1
0.3
0.02
0.01
0.002
0.04
0.02
<0.01
0.05
0.02
<0.01
0.03
<0.01
C.Ash
2-4
1
1-2
4-7
0.1
1
0.1
0.1
<0.01
<0.01
'0.005
0.01
<0.01
<0.01
0.02
o.oos
<0.01
0.01
0.02
9. Raw Westland (high-nsh)
F.Ash
5-10
3-6
3-6
1
0.4
0.3
1
0.3
0.02
<0.01
0.01
0.04
0.01
0.01
0.005
0.01
<0.01
0.03
<0.01
0.03
C.Ash
5-10
3-6
3-6
1
0.4
0.3
1
0.3
0.02
0.01
0.01
0.04
0.02
0.01
0.01
0.02
<0.01
0.03
<0.01
0.03
10. Na-Tre.-ted Mestlnnd
C.Ash
3-5
3-6
3-6
1
0.4
8-12
0.5
0.2
0.01
0.01
0.01
0.02
0.03
<0.01
0.005
0.03
<0.01
0.03
'0.01
<0.01
11. Na-Treated VeBtland
C.Ash
5-10
5-10
3-6
1-2
0.5
10-15
1
0.3
0.02
0.02
0.02
0.04
0.03
<0.01
0.01
0.03
<0.01
0.04
<0.01
<0.01
12. Mix-Leach Martlnka 13. Na-Treated
C.A.ih
5-10
3-5
i.-f.
15-25
0.5
3-6
0.1
0.3
0.01
0.01
0.02
0.03
0.01
<0.01
0.005
0.01
<0.01
0.04
<0.01
<0.0l
F.Ash
1-2
1
1
0.1
0.03
'0.1
«0.1
0.03
<0.01
<0.01
<0.005
<0.01
<0.r>l
-------
TABLE D-l. (Continued)
Run No .
Si
Al
Fe
C3
Hg
Na
K
Tl
?T
Pb
Mn
Ba
Cr
V
Cu
HI
Co
Sr
Sn
B
15. Rai
1-2
1
1
0.1
0.03
'0.1
<0.1
0.03
<0.01
'O.oi
<0.005
3-^
C.3
o.;
0.1
1
0.1
£0.01
'0.01
'0.005
0.02
'0.01
'd.o;
O.Cl
'0.105
'0.01
0.01
'0.01
0.02
a
i
-------
TABLE D-l. (Continued)
Run No.
tlenent
Si
.U
Fc
Ca
MB
Sa
V.
Tl
7.T
Pb
»J.
Sa
Cr
V
Cu
SI
Co
Sr
So
B
Zn
23.
Slag
10-15
5-10
5-10
0.5
0.3
TO.l
1
0.3
0.02
TO.Ol
O.Oi
0.06
0.01
0.01
O.OG5
0.005
TO.Ol
0.05
TO.Ol
TO.Ol
Raw Marl-in'-ia
C.Ash
5-10
4-6
4-6
0.4
0.2
TO.l
0.5
0.3
0.01
TO.Ol
0.005
0.04
0.01
0.01
0.005
0.005
TO.Ol
0.03
TO.Ol
0.01
F.ABh
5-10
3-5
3-5
0.3
0.2
TO.l
0.5
0.2
TO.Ol
TO.Ol
0.005
0.03
TO.Ol
TO.Ol
0.02
0.005
TO.Ol
0.02
TO.Ol
0.01
it.Acld-Lexch.
Coal C.Ash
0.3 2-3
0.03 0.7
0.6 5-10
0.003 1
0.02 0.2
TO.l TO.l
0.1
0.03 0.2
0.01
0.01
TO. 005 0.005
TO.Ol 0.02
0.03
-
0.006
0.01
TO.Ol
TO.Ol
-
-
Westland
C.Aah
1-2
0.3
4-6
0.2
0.1
TO.l
0.1
0.2
0.01
TO.Ol
TO. 005
0.02
0.01
-
0.003
0.005
TO.Ol
TO.Ol
-
-
25. Mix-Leach. Martlnka
Coal C. Ash
2-4 5-10
1 3-6
1 5-10
5-10 20-40
0.1 1
0.3 2-3
0.5
0.06 0.2
0.01
0.01
<0. 005 0.01
0.01 0.04
0.01
-
0.006
0.01
TO.Ol
0.03
-
-
F. Ash
5-10
2-4
5-10
20-40
1
1-2
0.3
0.2
0.01
0.01
0.01
0.04
0.01
r
0.006
0.01
TO.Ol
0.03
-
-
Repeat
F. Ash
5-10
4-6
4-6
20-40
0.1
1-2
0.2
0.3
0.01
TO.Ol
TO.Ol
0.03
0.01
TO.Ol
0.01
TO.Ol
TO.Ol
0.02
-
TO.Ol
TO.l
26. Acid-l.e
C.Ash
5-10
1
10-15
3-5
0.3
0.3
0.2
0.2
O.Oe
0.02
0.01
0.03
0.1
TO.Ol
0.1
0.04
0.01
0.02
TO.Ol
TO.Ol
0.1
29. Mii-Leach. Vc-friind
«ch. West land 27. Acid-Leach. Veitland 28. Acid-Leach Hestland (dc1 tiriioi1 l!-t)
F.Ash
4-6
0.5
10-15
0.5
0.3
0.2
0.1
0.2
0.02
0.01
0.01
0.03
0.01
TO.Ol
0.03
0.01
TO.Ol
0.01
TO.Ol
TO.Ol
TO.l
C.Ash
4-6
0.5
5-iq
1
0.3
0.2
0.1
0.2
0.02
0.01
0.01
0.02
0.03
TO.Ol
0.03
0.02
TO.Ol
0.01
TO.Ol
TO.Ol
TO.l
7. Ash
4-6
0.7
10-15
0.8
0.3
0.2
0.1
0.3
0.03
0.01
0.01
0.03
0.01
TO.Ol
0.02
0.01
TO.Ol
0.01
TO.Ol
TO.Ol
TO.l
C.Aah
4-6
1-2
10-15
4-6
0.3
0.5
O.J
0.3
0.002
0.01
o.o:
0.03
0.1
TO.Ol
0.03
0.05
0.01
0.01
-
0.01
0.1
F.Ash
4-6
1
15-25
1
0.4
0.2
0.2
0.4
0.04
0.01
0.01
0.1
0.03
TO.Ol
0.03
0.02
0.01
TO.Ol
-
TO.Ol
TO.l
51*?,
4-6
2-3
5-10
20-40
0.4
1-2
0.2
0.2
0.01
TO.Ol
0.02
0.01
0.01
TO.Ol
0.01
TO.Ol
TO.Ol
0.02
-
TO.Ol
TO.l
C.A-ih
4-6
1-2
3-5
20-40
0.3
1
0.2
0.1
TO.Ol
TO.Ol
0.02
0.01
0.01
TO.Ol
0.01
TO.Ol
TO.Ol
0.01
-
TO.Ol
TO.l
.'.Ash
4-6
2-3
5-10
20-40
0.4
1
0.2
0.2
0.01
TO.Ol
0.02
C.01
0.01
TO.Ol
0.01
'0.01
TO.Ol
0.02
-
TO.Ol
TO.l
Ui
-------
D-6
TABLE D-2. MASS SPECTROGRAPHIC ANALYSIS OF COAL AND ASH (ppmw)
MARTINKA COALS
Mixed
i" lenient
Li
Be
B
F
Na
MB
Al
Si
P
S
Cl
K
Ca
Sc
Ti
V
Cr
Mn
Fe
Co
Hi
Cu
Zn
Ga
Ge
As
Se
Br
Rb
Sr
Y
Zr
Kb
Mo
Ku
Kh
Pd
Ag
Cd
In
Sn
Sb
Te
1
Run #1
(.n;il
50
5
100
20
300
3000
17.
~ 57.
2000
-37.
300
~27.
27.
5
3000
300
200
300
-57.
300
1000
10
<30
<10
<2
20
530
10
200
1000
50
300
30
10
<1
<0.3
<3
<1
<5
<1
5
1
<1
3
Haw
Run i'3
Ar.li
30
3
100
10
2000
1%
Major
Ma jor
1000
1000
100
2000
5000
50
5000
300
500
200
~ 57,
50
500
30
<100
100
<10
20
100
5
100
1000
50
100
10
20
<1
<0.5
<5
2
<2
<1
20
5
<1
2
Caunt Ic
Run #5
Co a 1
50
3
20
10
-37.
2000
17;
-37.
2000
-57.
100
5000
27.
2
3000
100
100
200
17.
200
300.
5
<30
<10
<2
<10
^20
3
30
500
30
100
20
3
<1
<0.3
<2
<1
<2
<1
1
<1
<1
-------
D-7
TABLE D-2 (Continued)
Elpiiic*nt
Cs
r.a
Ixi
a-
Pr
Nd
Sm
Eu
Gd
Tb
Py
}]0
Er
ttn
Yb
Lu
11 f
Ta
W
Re.
Os
IT
Tt
Au
us
Tl
Pb
Bi
Ih
U
Elnrifilt ;il i
Riu
Run tfl
Co.-.l
0.5
500
100
100
30
50
10
5
10
3
10
2
5
<3
<5
<2
<5
<1Q
*S
<3
<5
<3
<5
<2
<10
<3
100
<2
5
20
".nr iclir-,en_t
24+
28-
10 0
f
Run #3
Ar.h
5
500
30
50
10
50
20
10
10
3
10
1
5
1
10
0.3
'2
*1
10
<0.2
<0.3
<0.2
<0.5
<0.5
:-h, 0 no chnnEo)
-------
D-8
TABLE D-3. MASS SPECTROGRAPHIC ANALYSIS OF COAL AND ASH (ppmw)
WRSTLAND COALS
Mixed
F.) rmcnt
l.i
ho
K
r
Na
MR
Al
Si
I
s
Cl
K
Ca
Sc
Ti
V
Cr
Mn
Fc-
Co
Ni
Cu
Zn
Cn
Ge
AS
Se
Br
Rb
Sr
Y
Er
Kb
Mo
AK
Cd
Su
Sb
To
I
C;mr. tit-
Run /n:u
Ach
1?
o.r,
59
250
>0.5
V1800
>1%
>1%
720
>12
240
v2400
>1%
6.1
VL700
25
190
26
>1%
70
230
78
VI 7 00
11
1.4
4.1
4.4
12
22
470
36
150
16
3.3
0.3
6.7
83
2.9
fc.7
HIT
Kim /'JjC
Coo).
0.15
4.7
89
4100
400
>1%
>1%
32
V2300
270
VL200
V3800
3.7
400
3.7
20
17
>1%
8.0
33
3.9
16
0.4
0.46
0.93
6.0
80
9.4
10
1.5
0.11
O.H)
0.28
0.39
-0.37
Kaw
Rim I'/IJA
Ach
2?0
6.0
170
290
640
V1800
x-3000
>1%
720
>0.5r'
120
>0.5£
>0.5%
7.3
vl300
70
87
26
>U
25
46
44
40
5.3
3.0
8.7
4.4
60
20
160
29
120
9.6
3.3
0.3
1.4
21
1.2
-
5.8
I.ciichnnt HTT
Run <-'15C
Coa.1
0.13
0.35
25
53
210
710
>K;
>1Z
14
v2300
150
v2800
^1100
3.7
400
37
37
17
>1%
4.0
14
3.9
7.3
1.7
0.47
5.9
0.48
4.7
12
80
9.4
24
3.1
2.2
0.16
0.56
0.56
<0.37
Run 018A
AK!I
86
2.6
59
170
>12
>0.5%
>1%
>1%
310
>0.5%
120
%2700
>1%
3.7
VL700
38
S7
26
>1%
14
99
120
400
2.3
3.0
4.1
0.94
2.6
7.3
250
17
120
6.9
1.4
C.15
1.4
12.0
0.83
0.58
Run 018C
Coal
0.17
3.5
110
890
710
>0.5%
>1%
14
\-2300
150
280
>!'/
3.7
400
7.3
13
17
>1%
8.0
67
9.0
73
0.8
0.93
1.4
0.70
2.2
160
16
24
6.6
0.11
0.10
2.8
<0.39
<0.37
Continued
-------
D-9
TABLE D-3 (Continued)
. .
Elrment
Cs
Ba
Ln
Ce
Pr
Nd
Sin
Eu
Cd
Tb
Dy
Ho
Er
Tra
Yb
Lu
Hf
Ta
V
Tl
Pb
Bi
TJ,
V
Elemental
Cnufittc
Run 013A
Ash
8.7
490
45
80
20
50
8.3
1.9
1.6
0.95
4.7
1.2
1.2
0.3
7.0
1.0
3.7
1.3
3.2
4.0
43
1.3
5.7
4.0
Enrichment
3-
58+
3 0
R.m M:*C
Cc.'il
0.34
35
2.5
8.4
1.0
3.1
0.36
0.70
0.60
0.39
<0.21
0.2
0.22
0.22
0.50
0.23
U:«:
Kun M5A
Ash
4.3
180
15
44
4.0
10
3.6
0.5
0.69
O.S/i
2.0
0.54
0.42
1.6
0.38
1.8
1.9
1.8
1.1
8.7
0.80
2.4
0.8
Run tfl5C
Cool
0.65
76
5
8.4
5.0
15
0.36
0.40
0.70
0.44
0.23
0.20
0.22
0.25
1.1
1.0
0.23
55+
2 0
Mixed
l,o,icli.int
Hun /'18A
Ash
1.9
270
30
52
8.6
21
8.3
1.1
1.4
0.54
4.70
0.61
1.2
0.14
3.3
1.0
3.7
0.46
1.0
19
0.60
5.7
1.7
. IfTT
Run tflSC
Ccal
0.33
76
11
8.4
5.0
31
0.31
0.35
0.60
0.4^
0.21
O.]fi
0.22
0.18
0.22
1.0
o.?-.1
3-
55+
6 0
(+ increase in ash, - decree 1» »sh. 0 no cUnge)
-------
I. REPORT NO.
EPA-600/7-78-068
4. TITLE AND SUBTITLE
Combustion of Hydrothermally Treated Coals
9- PERFORMING ORGANIZATION NAME AND ADDRESS
--»»!«-. r-iiNLJ «LJUntdi>
Battelle Memorial Institute-Columbus Laboratories
505 King Avenue
Columbus, Ohio 43201
3. RECIPIENT'S ACCESSION NO.
5. REPORT DATE
April 1978
6. PERFORMING ORGANIZATION CODE
8. PERFORMING ORGANIZATION REPORT NO
10. PROGRAM ELEMENT NO.
E HE 62 3 A
11. CONTRACT/GRANT NO.
68-02-2119
IG AGENCY NAME AND ADDRESS
EPA, Office of Research and Development
Industrial Environmental Research Laboratory
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PERIOD COVERED
Final; 8/75 - 6/77
14. SPONSORING AGENCY CODE
EPA/600/13
S IERL-RTP Pr°Ject officer ^ James D. Kilgroe, Mail Drop 61,
The report gives results of an evaluation of: (1) the relationship of the com-
bustion characteristics of hydrothermally treated (HTT) coals to environmental
emissions, boiler design, and inter change ability of solid fuels produced by the
Hydrothermal Coal Process (HCP) with raw coals currently being used as the source
of energy; and (2) the conversion of solubilized coal to terephthalic acid. Results
indicate that the HTT coals are clean solid fuels that, in many instances, can be
burned with little or no sulfur emissions. Flue gas SO2 concentrations were well
below Federal Sulfur Emission Standards for New Sources. The HTT coal was
found to burn as well as or better than raw coal. Trace metals emissions should be
significantly reduced because of the lower concentrations in HTT coals. Therefore,
the use of HTT coal in conventional boilers and furnaces should reduce environ-
mental pollution. HTT coals appear to be more suitable for firing in wet-bottom
than in dry-bottom furnaces because of potential fouling and slagging associated with
their alkali content. However, additives may possibly be used to reduce fouling and
slagging. The coal solubilized during desulfurization can be converted to tereph-
thalic acid by the oxidation-Henkel reaction. However, low yields suggest that this
approach may not be economical.
7.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COS AT I Held/Group
Pollution
Coal
Combustion
Thermal Recovery
Methods
Boilers
Design
Phthalic Acids
Ashes
Sulfur Dioxide
Flue Gases
Additives
Pollution Control
Stationary Sources
Hydrothermal Treat-
ment
Hydrothermal Coal
Process
Terephthalic Acid
13B
21D
2 IB
13H
13A
14 B
07C
07B
11G
3. DISTRIBUTION STATEMENT
Unlimited
19. SECURITY CLASS (This Report)
Unclassified
151
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
------- |