EPA
United States
Environmental Protection
Agency
Office of
Research and
Development
Industrial Environmental Research
Laboratory
Cincinnati. Ohio 45268
EPA-600/7-77-091
August 1977
ENVIRONMENTAL ASSESSMENT
OF WASTE-TO-ENERGY
PROCESSES: Source
Assessment Document
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.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/7-77-091
August 1977
ENVIRONMENTAL ASSESSMENT OF WASTE-TO-ENERGY PROCESSES
SOURCE ASSESSMENT DOCUMENT
by
K. P. Ananth
L. J. Shannon
M. P. Schrag
Midwest Research Institute
Kansas City, Missouri 64110
Contract No. 68-02-2166
Project Officer
Harry Freeman
Energy Systems Environmental Control Division
Industrial Environmental Research Laboratory
Cincinnati, Ohio 45268
INDUSTRIAL ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
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DISCLAIMER
This report has "been reviewed "by the Industrial Environmental Research
Laboratory-Cincinnati, U. S. Environmental Protection Agency, and approved
for publication. Approval does not signify that the contents necessarily
reflect the views and policies of the U. S. Environmental Protection Agency,
nor does mention of trade names or commercial products constitute endorsement
or recommendation for use.
11
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FOREWORD
When energy and material resources are extracted, processed, converted,
and used, the related pollutional impacts on our environment and even on our
health often require that new and increasingly more efficient pollution con-
trol methods be used. The Industrial Environmental Research Laboratory-
Cincinnati (lERL-Ci) assists in developing and demonstrating new and improved
methodologies that will meet these needs both efficiently and economically*
This report is an assessment of what is known about air and water emis-
sion from existing systems for converting waste to energy. The information
-contained herein will be of interest to those working with waste-to-energy
systems, either as developers or operators. Request for further information
concerning emission from waste-to-fuel systems should be directed to the
Fuel Technology Branch, lERL-Gi.
David G. Stephan
Director
Industrial Environmental Research Laboratory
Cincinnati
lii
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ABSTRACT
This report was prepared for the Industrial Environmental Research Lab-
oratory-Cincinnati under EPA Contract No. 68-02-2166, Environmental Assess-
ment of Waste to Energy Processes.
The program has the overall objective of identifying environmental im-
pacts which might result from waste-to-energy conversion processes. These
processes are categorized, on a generic basis, as: (a) waterwall incinera-
torsj (b) combined firing systems; (c) thermochemical (pyrolysis) processes;
(d) hog-fuel boilers; (e) biochemical systems; and (f) advanced combustion
systems such as the CPU 400.
This source assessment document is the first publication on the subject
program and it is intended to present what is currently known on emissions
and emission control techniques in waste-to-energy conversion systems. This
report discusses constituents in solid waste primarily with the idea of il-
lustrating the diverse nature of the feedstock used in such systems. Also
presented is an environmental impact analysis based on the contribution of
each waste-to-energy conversion system to criteria and other major pollutants.
Where emission data were lacking, engineering judgment was used to identify
probable levels. A simplified methodology for a preliminary environmental
assessment is illustrated. An overview of each of the waste-to-energy con-
version systems including their pollution potential and applicable control
technology is also contained in this document. The status of such systems
as well as their locations, capacities and processing steps involved is iden-
tified, to the extent possible.
iv
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CONTENTS
Foreword ill
Abstract iv
Figures vi
Tables vii
Acknowledgment viii
1. Introduction 1
2. Solid Waste Constituents 2
3. Environmental Impact Analysis k
Criteria pollutants it
Methodology for environmental assessment 9
U. Overview of Waste-to-Energy Conversion Systems 10
Waterwall incinerators 10
Combined firing systems IT
Thermochemical (pyrolysis) processes 28
Hog fuel boilers 35
Biochemical systems Ul
Advanced combustion systems (CPU-UOO) hk
5• Status of Waste-to-Energy Conversion Systems k6
References 50
Appendices 53
A. Summary of source severity concept for environmental
impact analysis 53
B. Illustration of environmental impact analysis 58
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FIGURES
Number Page
1 Average particle size data for uncontrolled emissions from
coal-only and coal/RDF systems. ...... 7
2 Schematic of combined firing system ........«••• 18
3 Schematic diagram of pyrolysis of refuse. ......... 29
4 Block diagram of the anaerobic digestion system ...... 42
vi
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TABLES
Number Page
1 Particle Size Distribution of Municipal Incinerator Fly Ash. . 6
2 Waterwall Incinerators in the United States. •.. 11
3 Analysis of Flue Gas from Nashville Incinerator. ...*••• 13
4 Combined Firing Systems. .......*..«.., 19
5 Air Emission Comparison Data for Oil and Coal Firing in Util-
ity Boilers 22
6 Pyrolysis Processes. ..................... 30
7 Analyses of Hogged Fuels ................... 36
8 Comparative Chemical Analysis of Wood and Bark, Goal, and
Oil 38
9 Emission Factors for Wood and Bark Combustion in Boilers with
No Reinjection ................ 39
10 Status of Waste-to-Energy Conversion Systems ......... 47
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ACKNOWLEDGMENT
The authors acknowledge the assistance rendered by Mr. Mark Golembiewski,
Mr. John Sealock, and Dr. Jim Galeski in providing background information for
the preparation of this document. The authors also appreciate the contri-
bution of Mr. Robert Olexsey of the U.S. Environmental Protection Agency (EPA)
in reviewing the draft version of this document.
viii
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SECTION 1
INTRODUCTION
Increased emphasis on conservation of energy and nonrenewable metal and
mineral resources plus the growing unacceptability of traditional techniques
for waste disposal have created the need for a critical evaluation of waste-
to-energy conversion systems. Environmental insults that might result from
waste conversion processes must not be overlooked. The object of this con-
tract is to evaluate waste-to-energy conversion systems with respect to their
degree of development, pollutant potential, and resulting impacts.
This source assessment document is the first publication on the subject
contract, and it is intended to discuss what is currently known regarding en-
vironmental emissions from waste conversion systems. The report presents a
brief discussion on the constituents of solid waste, an environmental impact
analysis to identify expected emissions from waste conversion processes, an
overview of waste-to-energy conversion systems (including their degree of de-
velopment, pollutants emitted, and control techniques used), and a status
summary on existing and proposed systems.
As part of the contract, several systems will be tested to monitor and
analyze emissions, some of which may be potentially hazardous. The test pro-
gram is currently underway, and separate reports for each system tested will
become available upon completion. This source assessment document will be
updated on an annual basis.
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SECTION 2
SOLID WASTE CONSTITUENTS
Environmental assessment of waste-to-energy conversion systems can be
simplified if the composition of the waste or "fuel" and the operating pa-
rameters of the process are known. In many cases, information on the pro-
cess is well documented, but only limited reliable information is available
on the waste itself because of wide variations iri the composition. Varia-
tions may be a result of different geographic regions in whic*h the waste was
generated, seasonal differences, or different analytical methods used in the
analysis of the refuse samples.
Concern is increasing that trace elements and organic constituents pres-
ent in refuse can result in their emission into the environment during the
waste-to-energy conversion process. Recently it was reported^- that analyti-
cal studies are being conducted at the Bureau of Mines in Maryland to deter-
mine the concentration of major, minor, and trace elements in the combustible
fractions of urban refuse. The following list contains representative ele-
ments known to be present in refuse. The same elements were also found in
refuse samples analyzed in the St. Louis study.2
Major Elements (1,000 to 100,000
Aluminum
Calcium
Chlorine
Iron
Magnesium
Phosphorus
Potassium
Silicon
Sodium
Sulfur
Titanium
Zinc
Minor Elements (0.1 to 999
Antimony
Arsenic
Barium
Beryllium
Bismuth
Boron
Cadmium
Cesium
Chromium
Cobalt
Copper
Germanium
Gold
Lead
Lithium
Manganese
Mercury
Molybdenum
Nickel
Niobium
Platinum
Rubidium
Selenium
Silver
Strontium
Tantalum
Tin
Tungsten
Vanadium
Zirconium
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Of these elements, several were found to be present in higher concentra-
tions in refuse-derived fuel (RDF) than in coal.^ These are listed as fol-
lows:
Antimony Mercury
Barium Nickel
Bismuth Phosphorus
Cadmium Silver
Chromium Sodium
Copper Tin
Lead Titanium
Lithium Tungsten
Zinc
Many of the elements listed are potentially hazardous, indicating that RDF is
not a clean fuel. To date, there are no measured data on the organic com-
pounds present in refuse. When these data become available, it is likely that
the number of potentially hazardous materials will increase significantly.
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SECTION 3
ENVIRONMENTAL IMPACT ANALYSIS
The environmental impacts of waste-to-energy conversion systems can be
evaluated on the basis of their contribution to each of the criteria and
other major pollutants. This information is currently unavailable. However,
based on the constituents in solid waste and an engineering analysis of the
waste conversion process, some comments can be made on expected emissions
from such systems. This section discusses emission contributions with re-
spect to each criteria pollutant and then presents a general methodology that
can be used for environmental impact assessment where only limited data are
available.
CRITERIA POLLUTANTS
Particulate
Uncontrolled particulate emissions from waste conversion systems such as
waterwall incinerators usually range from 2517.17 mg/nm3 to 2974.84 mg/nm3.
Recent emission tests conducted at the Nashville thermal transfer waterwall
incinerator show uncontrolled grain loadings varying from 2153.33 to 3837.55
mg/rmr, resulting in an average value of 2,746 mg/nm3 for three runs at 12%
C02»^ Outlet grain loadings (controlled by an electrostatic precipitator)
varied from 41.19 to 64.07 mg/nm3, with a three-run average of 54.92 mg/nm3
at 12% C02«^ Uncontrolled grain loadings reported here are comparable to
those from a recently tested coal-fired power plant that ranged from 3203.68
to 5492.02 mg/nm3.5
Particulate emissions may be comparable between coal combustion and
waterwall incineration on a grain loading basis. But information on poten-
tially hazardous trace element emissions from waterwall incinerators is too
limited to make such comparisons.
Trace elements such as arsenic, beryllium, mercury, silver, cadmium,
copper, tin, etc., are reported to be present in fly ash from coal and from
coal + RDF systems. However, no detailed sampling and analysis have been con-
ducted to determine concentrations of such pollutants from waterwall incin-
erators using refuse as fuel. In addition, no information is available to
-------
determine the enrichment, or preferential concentration, of potentially haz-
ardous substances in the fine particulate fraction. One would anticipate
that enrichment would occur in these systems in a manner similar to that re-
ported by Gordon et al«° for regular municipal incinerators.
Combined firing systems using coal and RDF emit particulates at the rate
of 4599.56 to 4897.05 mg/nrn^ without emission controls. With electrostatic
^•^ O O
precipitator control, the values range from 183.07 to 228.83 mg/nmj. Ref-
erence 2 also indicates that fly ash from coal-only tests is higher in iron
content but lower in lead, zinc, and chromium than is coal/RDF fly ash.
Changes in trace element composition of the fly ash were also noted when
coal and RDF were fired in the boiler. Combined firing caused an increase
in the concentration of antimony, arsenic, barium, cadmium, chromium, copper,
lead, mercury, zinc, bromine, and chlorine in the fly ash.2
Particulate emissions from boilers using wood waste as fuel can vary
depending on the extent of char reinjection, boiler type, excess air used,
wood waste type, and wood moisture content. A typical particulate emission
factor (uncontrolled) for a wood-fired boiler is reported to be 12.5 to 15
g/kg of wood without fly ash reinjection. For boilers with reinjection, the
uncontrolled emission factor is reported to be 15 to 17.5 g/kg.
Particle size information for emissions from municipal incinerators and
a coal/RDF-fired system is given in Table 1 and Figure 1, respectively.
These illustrations show that fly ash from incinerators is much finer than
that from a coal/RDF system, with 13% to 30% by weight less than 1 |j,m in di-
amet er•
Particulate emission rate and particle size data for other waste-to
energy conversion systems such as pyrolysis, biochemical systems, and ad-
vanced combustion processes like the CPU-400 are meager. But particulate
emissions from these systems should be much lower than those from other
waste conversion systems discussed above, namely, incinerators and com-
bined fired systems.
SO:
S02 emissions from waste-to-energy conversion systems are not expected
to be significant, since the concentration of sulfur in refuse is on the
order of 0.14 g S/1Q6 joule in contrast to 0.60 g S/106 joule in coal.2
Tests at the Nashville incinerator showed an average SO? concentration
of 38 ^il/liter. Another study reports a range of 33 to 162 fil/liter.8
These values are lower than would be expected with coal combustion. On the
other hand, tests with RDF and coal in a combined-fired boiler did not show
any reduction in S02 concentration when compared with coal-only tests.2
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TABLE 1. PARTICLE SIZE DISTRIBUTION OF MUNICIPAL INCINERATOR FLY ASH10
Diameter
(urn)
1,000
250
150
45
30
20
15
10
5
1
Wt 7= less than
Study 1
--_
—
45
41
36
30
23
13
stated diameter
Studv 2
81
74
59
55
51
48
45
40
30
-------
99.99 99.999.8 99 98
50
95
WEIGHT % GREATER THAN STATED SIZE
90 80 70 60 50 40 30 20 10
2 1 0.5 0.20.10.05 0.01
50
I I
I I
T
r F I i i
r
i
10
•o
5
5
40
O»
1.0
A
0«
Cool- Coal &
Only Refuse
O • 1973 Test!
1974-75 Terfs
0.1
I
J I
I I I
1 I
J I
1
I I
10
1.0
0.1
0.010.050.10.20.5 12 5 10 20 30 40 50 60 70 80 90 95 98 99 99.899.9 99.99
WEIGHT % LESS THAN STATED SIZE
Figure 1. Average particle size data for uncontrolled emissions from
coal-only and coal/RDF systems.
2
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The reason could have been that only 10% RDF was used with coal. This in-
terpretation is supported by another RDF/coal study in which 1:1 and 2:1
mixtures (by volume) of RDF and coal were utilized.^ Jackson" indicates that
the 1:1 mix had significantly lower SC>2 emission levels than coal*
#
S02 emissions from wood-waste boilers should be negligible, since the
sulfur content of wood is about 0.1% by weight. For coal, the sulfur con-
tent can vary widely depending on the source of the coal.
Pyrolysis systems such as the Purox system do not report any S(>2 in the
fuel gas.
The concentration of NOX from waterwall incinerators is reported to av-
erage 146 p,l/liter.7 For a coal/RDF system, the NOX concentration was lower
than that obtained during coal-only tests." The NOx emission factor for
wood and bark combustion is reported to be 5 g/kg of wood.-*-*- Based on these
limited data, NOX does not appear to be a major pollutant of concern in
waste-as-fuel systems.
GO.
Carbon monoxide emissions from waterwall incinerators average 153 |j,l/
liter.7 For wood and bark combustion, the GO emission factor is 1 g/kg of
wood.^1 For the coal/RDF-fired system, no noticeable differences were ob-
served in GO concentrations when compared with GO emissions from coal-only
tests. 2
Hydrocarbons
Uncontrolled hydrocarbon emissions are reported to range from 0.4 to 42.5
|j, I/liter for municipal incinerator s»^ For a coal/RDF system, the hydrocarbon
concentration was lower when coal and RDF were used in a 1:1 ratio by volume
than when coal only was used."
Pyrolysis systems will probably result in high hydrocarbon concentra-
tions. The Purox system reports a methane concentration of 5% by volume
in the fuel gas.^ This should not be of concern, however, since the fuel
gas is the product itself and hence is not expected to be emitted into the
atmosphere before combustion.
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METHODOLOGY FOR ENVIRONMENTAL ASSESSMENT
Generally, the adverse effects of pollutants are evaluated from the ex-
tent to which they are deemed health hazards. In determining the degree of
hazard, some of the more important considerations include the emission rate
of the pollutant, the number of other sources emitting the same pollutant
and their emission rates, and atmospheric conditions governing the transport
of the pollutant in question. In addition, establishing the critical dosage
1 *^
level based on health studies is a very significant factor* For most pol-
lutants and substances considered to be hazardous, allowable ambient concen-
trations or exposure limits have not been established.
There are several recent reports in the literature that discuss methods
to estimate the impact of pollutants based on some sort of prioritization
procedure.14—16 por example, Eimutus^^- describes a prioritization procedure
for the rank-ordering of air pollution sources by computing a relative en-
vironmental impact factor for each of the sources investigated. The basic
proposition of this prioritization model is that emission sources can be ranked
based on the potential degree of hazard that they impose on individuals in
their environment. This degree of hazard can be expressed in different ways.
A traditional method of expressing degree of hazard has been to use the mass
of emissions from various source types. Other techniques have used ambient
air contributions of a given source type and the resulting degradation of
ambient air quality as an indicator of source severity.
Eimutusl5 has developed mathematical models to rank relatively the en-
vironmental impact of water and solid residue emissions using the air priori-
tization modell^ reported earlier. The water model is based on mass of emis-
sion, hazard potential of the emission, ambient water loading, and population
density in the emission region.^5 Eimutus-'-" uses a simulated approach to
compare the ground level concentration contribution of pollutants relative
to some potentially hazardous concentrations of the same species.
A simplified summary of the source severity concept and how it can be
utilized in the subject program is discussed in Appendix A.
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SECTION 4
OVERVIEW OF WASTE-TO-ENERGY CONVERSION SYSTEMS
The major waste-to-energy systems, on a generic basis, are:
* Waterwall incinerators
* Combined firing systems
* Thermochemical processes (pyrolysis)
* Hog-fuel boilers
* Biochemical systems
* Advanced combustion systems (CPU-400)
A brief description of each generic system including its pollution po-
tential and applicable control technology is presented below and followed by
a bibliographic list for each system.
WATERWALL INCINERATORS
System Description
Originally incinerators were designed to dispose of refuse and other
unwanted combustibles by thermal decomposition. However, increasing emphasis
on energy conservation has led to incorporation of heat recovery systems in
most modern incinerators.
The use of raw refuse as a fuel for steam production in waterwall in-
cinerators began in Europe and has now been technologically developed to a
fine degree. The European design has generally served as the basis for a
few recent U»S» installations, listed in Table 2.
Refuse is normally burned "as received" in a waterwall incinerator, with
size reduction equipment only for oversize or bulky refuse. Firing is usu-
ally accomplished using traveling grates. Combustion gases exchange heat in
the boiler section, superheater and economizer, thereby reducing flue gas to
an exit temperature of approximately 93°C to 232°C. Flue gas exit"temper-
atures and excess air levels are generally much higher than for suspension
firing, and boiler efficiencies are proportionately lower than those found
in electric utility boilers. Auxiliary fuels such as oil or coal are usu-
ally provided for supplementary steam generation.
10
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TABLE 2. WATERWALL INCINERATORS IN THE UNITED STATES?
Location
Akron, Ohio
Braintree, Massachusetts
Chicago, Illinois (Northwest)
Dade County, Florida
Detroit, Michigan
Harrisburg, Pennsylvania
Lexington-Fayette Urban County
Gov., Kentucky
Minneapolis -St. Paul, Minnesota
Nashville, Tennessee
Norfolk, Virginia
Saugus, Massachusetts
Haverhill, Massachusetts
Memphis, Tennessee
New Haven, Connecticut
Onondaga County, New York
Start up
date
UN
6/77
7/71
1/79
UN
10/72
1977
1980
7/74
1967
4/76
UN
UN
UN
UN
Capacity
Me/day
907 .18
217.72
1451.49
2721.54
2721.54
653.17
952.54
1088.62
653.17
326.58
1088.62
2721.54
1814.36
1632.92
907.18
Processing steps"
SH, AC, MS
MS
None
WP, MS, OS
UN
MS
SH, MS
UN
Non«
None
SC, MS
UN
UN
UN
UN
Products
Steam, ferrous
Steam, ferrous
Steam
Steam, glass, ferrous, aluminum
Steam
Steam, ferrous
Steam, ferrous
Steam
Steam
Steam
Steam, ferrous
Steam, ferrous
Steam
Steam
Steam, ferrous
a Includes facilities now under construction.
b SH, shredding; AC, air classification; MS, magnetic separation; SC, screening; OS, other mechanical separation;
UN, unknown; WP, wet pulping.
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Pollution Potential
Pollutants from waterwall incinerators include particulates, gases,
wastewater from ash sluicing, bottom ash, and captured fly ash. Recent
tests^ on the Nashville incinerator showed average inlet grain loadings of
2,746 mg/nm3 and an average outlet loading of 54.92 mg/nm^ after the electro-
static precipitator (ESP). Similar tests performed at other U.S. and for-
eign waterwall incinerators indicate that fly ash emissions range from ap-
proximately 0.064 to 0.65 g/106 joule of heat input, with the lower values
(0.064 to 0.128 g/106 joule) representative of U.S. installations.
Particle size data for fly ash particulates from municipal incinerators
indicate that 30% to 45% by weight are less than 10 urn, 23% to 40% are less
than 5 pm, and 13% to 30% are less than 1 |Im.
A more important environmental factor of fly ash particulates from
waste incineration is the enrichment or preferential concentration of sev-
eral trace elements in the smaller-sized portions. Gordon et al. report
enrichment factors from municipal incinerators of 1,000, 270, 18, and 10 for
cadmium, lead, copper, and zinc, respectively. The same phenomenon is
likely to occur in waterwall incinerators.
Gaseous emissions consist of S02, NOX, chlorides, and CO in addition to
CC>2, oxygen, and hydrocarbons. Table 3 summarizes the concentrations of
these gases observed in tests conducted at Nashville. Similar tests con-
ducted at the municipal incinerator in Babylon, New York, showed NOX concen-
trations ranging from 53 to 115 lal/liter.^ The S02 and chloride concentra-
tions at tb.e same facility were observed to be 56 to 195 ^I/liter and 214 to
1,250 |a,l/liter, respectively. 12 The differences in the gas concentrations
could be a result of using different sampling and analysis methods and/or
different incinerator operating characteristics.
In general, S02 emissions from incinerators will be lower than those
observed from coal-fired power plants since refuse has a lower sulfur level.
Chloride emissions can be high, since refuse can contain elevated quantities
of plastics. These chloride emissions can create a significant problem;
even though they can be easily scrubbed from the gas stream, their subse-
quent removal from the scrubbing water can result in water pollution.
Hydrocarbon emissions from municipal incinerators are reported to be
in the range of 0.4 to 42.5 |j,l/liter. » 2 Methane and ethylene appear to
be the predominant species. C^ through G^ hydrocarbons may be listed as
minor constituents of incinerator emission when combustion conditions are
I -y
good. *•
12
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TABLE 3. ANALYSIS OF FLUE GAS FROM NASHVILLE INCINERATOR'
Test number
Gas
co2 (%)
02 <%)
Excess air (%)
NOX \i I/liter
S02 |J,l/liter
CO p,l/liter
Chloride n I/liter
1
2-21-75
10.0
10.5
102
107
46
158
63
2
2-21-75
9.8
10.3
100
120
51
179
3
2-23-75
11.4
8.5
69
177
39
100
177
4
2-26-75
10.8
9.0
73
150
30
--_
120
and date
5
2-26-75
10.3
9.3
79
165
22
___
78
6
2-27-75
10.3
9.6
83
154
38
...
...
Average
10.4
9.5
84
146
38
153
110
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Relatively little information is available on water pollutants from
waterwall incinerators. The only significant water usage, other than for
steam generation, occurs in ash sluicing. Water quenching of ash from the
boiler is usually necessary to break up clinkers and to quench burning ma-
terials. Thus water pollution problems occur and create the need for treat-
ment facilities to be constructed as part of the incinerator plant. Other
wastewater sources include the sanitary system's boiler blowdown, demineral-
izer backwash, and quench channel overflow. At Saugus, the average waste-
water discharge is estimated to be approximately 0.0057 m.3/sec. No infor-
mation is available describing wastewater quality from the various waterwall
incinerator plants.
Solid waste emissions from waterwall incinerators consist of bottom ash
and captured fly ash. They can be disposed of in landfills.
Pollution Control Technology
Information presented here is primarily based on the Nashville and the
Saugus systems. Data on other locations are not readily available. However,
since the two systems discussed here are among the most recent facilities,
the discussion is probably more representative of current control technology.
Nashville--
Air emissions from the Nashville incinerator have been controlled at
various times using different types of wet scrubbers. The system now has
an electrostatic precipitator that meets the local regulation, and a second
electrostatic precipitator is in the process of being installed.
Recent test data^ on the American Air Filter ESP unit operating at
Nashville showed the following inlet/outlet particulate loadings when cor-
rected for 12% 002-
Inlet (mg/nm3) Outlet (mg/nm3)
2153.33 64.07
2219.69 41.19
3837.55 61.79
Average 2736.86 Average 55.68
The tests were conducted using U»S« Environmental Protection Agency (EPA)
methods and were done only to determine particulate loadings at full load.
No particle sizing or gas composition measurements were made.
14
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Experience with scrubbers was reported-^ to be both frustrating and ex-
pensive. The original low-energy scrubbers were ineffective in collecting
fine particulate. Stack sampling indicated that 90% of the particulate es-
caping the scrubber had an average diameter of less than 6 p,m. Modifications
to the original scrubbers increased the pressure drop and the collection ef-
ficiency, but not sufficiently to bring the units into compliance»
Pilot tests of two other wet collection devices (high pressure spray
scrubber and high temperature water flashing nozzle) indicated possible com-
pliance. However, excessive steam usage and stringent recycle water cleanup
requirements were factors that caused their rejection in favor of electro-
static precipitators.
A pilot baghouse program is being conducted in two phases. In the ini-
tial baghouse program, five fabrics of glass, stainless steel, and synthetic
fibers were utilized in two baghouses, a pulse type and a backflow type.
Meaningful stack sampling was not conducted, although visible emissions ap-
peared to be well controlled. The five fabrics held up for the test period
of approximately 3 months. Burst tests and other analyses of one of the fab-
rics (an aramid felt) indicated a projected total life expectancy of only 5
to 6 months. This result is not surprising because the fiber is not acid re-
sistant.
The second-phase EPA-sponsored program on fabric filters is just getting
under way at Nashville. An 84.95 m-Vmin slip steam from the heat recovery
incinerator is still being used as the gas source. Objectives of the cur-
rent testing program are to:-^ (a) screen three types of high-temperature,
acid-resistant filter mediaj (b) determine efficiency and optimum air-to-
cloth ratios for the various filter media; (c) make technical economic com-
parisons of a baghouse using these media versus other particulate control
methods such as ESP's and wet scrubbers; and (d) recommend a prime filter
media candidate for followup life expectancy programs.
The bags to be tested are in various stages of commercial development.
They include a microporous Teflon-type laminate, a woven glass fiber coated
with Teflon, and a coated glass felt.
Solid waste at the Nashville facility primarily consists of captured
fly ash and bottom ash. These materials could be disposed of in landfills.
No information is apparently available on any wastewater treatment facility
at Nashville. However, treatment of wastewater from this facility should
not pose any control problems.
Saugus--
The Saugus system has two Wheelabrator-Lurgi electrostatic precipitators
capable of handling 6796.1 m3/min each at 220°G. They are designed to
15
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control partxculates to 57.21 mg/nm3, corrected to 12% C02, and they are ap-
parently operating satisfactorily under the Metropolitan Boston Air Pollution
Control Distinct requirement of 114.42 mg/nmS at I27o C02. No test data are
available. ' z
Wastewater sources are the sanitary system, boiler blowdown, demineral-
izer backwash, and quench channel overflow. All blowdown and backwash is
neutralized as required and pumped to a holding tank that feeds the ash quench
conveyor channels. No ash quench water is recirculated, since it is progres-
sively removed in the wet ash with overflow to the sewer. Under operating
conditions, total flow to the sewer is expected to consist primarily of the
sanitary system discharge.17
The front ash discharge from the furnace and the mechanically conveyed
ash from the boiler and precipitator hoppers are mechanically conveyed from
a quench tank to a classifying house. In the house, the drag conveyor drops
the ash into a trommel screen where it is classified into three fractions.
Pieces larger than about 7.62 cm drop into a truck, and the ash that drops
through the screen is further classified into magnetic and nonmagnetic frac-
tions, each of which goes to a separate truck for sale to a steel plant and
disposal, respectively.
Recommended Reading
For additional information on waterwall incinerators the following ref-
erences are provided:
1. Astrom, L., F. Kranebitter, 0. Strandell, and D. W. Harris, "Com-
parative Study of European and North American Steam Producing In-
cinerators," in Proceedings of 1974 National Incinerator Confer-
ence, Miami, Florida, May 1974.
2. Bump, R. L., "The Use of Electrostatic Precipitators on Municipal
Incinerators in Recent Years," in Proceedings of 1976 National
Waste Processing Conference, Boston, Massachusetts. May 1976.
3. Garotti, A. A., and E. R. Kaiser, "Concentrations of Twenty Gaseous
Chemical Species in the Flue Gas of a Municipal Incinerator,"
JAPGA. 22(4), April 1972.
4. Corey, R. C. (ed.), Principles and Practices of Incineration.
Wiley-Interscience, New York, 1969.
16
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5. Roberts, R. M., S. T. Branhem, R. C. Hanson, S. B. Kilner, R. E.
Sommerlad, J. D. Shenker, R. W. Bryers, A. D. Konopka, J. McKenna,
Sy.st.ems. Evaluation of Refuse as a Low Sulfur Fuel, Vol. I and II,
Report to Environmental Protection Agency, Envirogenics Company,
November 1971.
6. Schwieger, R. G., "Power from Waste," Special Report in Power,
February 1975.
COMBINED FIRING SYSTEMS
System Description
Combined firing systems are those that use RDF with coal or oil for pro-
duction of electric power in utility boilers.
Combined firing systems being planned for the United States generally
utilize both materials and energy recovery. Figure 2 presents a simplified
schematic for this type of system. As shown in the figure, preconversion
processing of the waste is required for enrichment of the waste to RDF. The
preconversion processing also facilitates the recovery of ferrous and non-
ferrous metal and glass from the waste. RDF and a fossil fuel (coal or oil)
can then be readily combusted to generate steam or electricity. A represen-
tative list of combined firing systems is given in Table 4.
On a smaller scale, particularly in industrial boilers, wood waste (wood
chips) is commonly used with coal. In this case, there is usually no need
for processing the waste. However, in systems where bark is used with coal,
the bark must be shredded. Combined firing systems utilizing wood and coal
are generally located in areas where there is an adequate supply of wood
waste, and they are generally operated on a smaller scale than systems using
RDF and coal or oil.
Pollution Potential
Combined firing systems can consist of coal and RDF, oil and RDF, coal
and wood waste, and oil and wood waste. Where RDF is used, processing of
municipal solid waste is required. Depending on the type of wood waste (wood
chips or bark), processing may become necessary.
If processing of MSW or bark is undertaken, then the processing plant
becomes the first emission source in the waste-to-energy conversion chain.
MSW processing usually involves shredding, air classification, and removal of
ferrous and sometimes aluminum metal. Pollution problems from such a facility
can include residue to be disposed of and particulate pollutants from the air
17
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SOURCE
MATERIAL
PRE-CONVERSION
PROCESSING
SIZE REDUCTION
(VARIOUS PROCESSES)
SEPARATION
(VARIOUS PROCESSES)
ADDITIONAL GRINDING
AND DRYING STEPS
SOLID FUEL
DRY, FINELY
DIVIDED
FtNAL
DISPOSITION
Figure 2. Schematic of combined firing system.
18
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TABLE 4. COMBINED FIRING SYSTEMS
Loaation
Ames, Iowa
Chicago, Illinois (Crawford)
East Bridgewater, Massachusetts
Portsmouth, Virginia
St. Louis, Missouri
Capacity Processing stepsa
Mg/day mR/dav Products
362.87 SH, MS, AC, SC, OS RDF, ferrous, aluminum
907.18 SH, AC, MS RDF, ferrous
1088.62 SH, AC, MS, OS RDF, ferrous
145.15 UN RDF
5443.08 SH, MS, AC, OS RDF, ferrous, nonferrous, glass residue
Albany, New York
Monroe County, New York
New York, New York
Wilmington, Delaware
(New Castle County)
Bridgeport, Connecticut
Brockton, Massachusetts
Milwaukee, Wisconsin
544.31 SH, MS
1814.36 SH, MS, AC, FE, OS
UN UN
453.59 SH, AC, UN (others)
1632.92 SH, AC, MS, FF
1088.62. SH, AC, MS, OS
1088.62 SH, UN
RDF, ferrous
RDF, ferrous
UN
RDF, compost, ferrous, aluminum,
nonferrous, glass
RDF (Eco-Fuel II), ferrous, non-
ferrous, glass
RDF (Eco-Fuel II), ferrous
RDF, ferrous, glass, aluminum,
paper
a SH, shredding; AC, air classification; MS, magnetic separation; SC, screening; OS, other mechanical separa-
tion; FF, froth flotation; UN, unknown.
-------
classifier control system. If washdown operations are involved, this will re-
sult in waste-water discharge. Bark processing will usually involve only par-
ticulate discharge. A detailed pollutant characterization of a MSW processing
n
facility has been presented by Gorman.''
Among the combined firing systems cited above, detailed emission infor-
mation exists only for the coal and RDF system.2*9 Emissions from the power
plant fired with coal and RDF included solids in the form of bottom ash and
captured fly ash, air emissions in the form of particulates and gases, and
boiler sluice water. The bottom ash accumulation rate averaged 67.98 kg/min
for coal and RDF (at 5% to 10% RDF) in contrast to 10.07 kg/min for Orient 6
coal.2 Also, elements such as lead, antimony, and tin are present in greater
concentrations in fly ash collected by the ESP when coal and RDF are fired
together than when coal alone is used. A similar trend appears for lead and
chromium in bottom ash.2
Analysis of atmospheric emissions from the boiler fired with coal and
RDF indicates that hazardous pollutants such as beryllium, cadmium, copper,
lead, etc. are emitted in larger concentrations when RDF is fired with coal.
Similarly, chloride emissions increase when RDF is fired with coal. Emissions
of other gaseous pollutants such as CO, S02, NQjj, and HC were not signifi-
cantly different when RDF was fired with coal.2 One would expect the S02
concentration to decrease for coal and RDF, since refuse had a sulfur level
of only 0.14 g/10^ joule in contrast to Orient 6 coal, which has a sulfur
level of 0.60 g/106 joule. But because only 107» of the feed constituted RDF
in the study reported by Gorman .et al.2, the difference may not have been
noticeable. This interpretation is supported by another RDF/coal study in
which 1:1 and 2:1 mixes (by volume) of RDF and coal were utilized.' Jackson'
indicates that the 1:1 mix had significantly lower S02» HC, and NOX emission
levels than coal. Particulate emissions were unchanged, and lead, .chloride,
and fluoride emissions were significantly increased with the 1:1 mix. Another
important finding reported by Jackson9 is that lead was found predominantly
in the submicron-sized particle fraction. Particles in the stack effluent
contained 245 times more lead than particles collected by a multiclone.
Water effluent from a coal/RDF system is limited to sluice water. A
comparison was made between pollutants contained in sluice water from such a
system and from a system firing coal only.2 There was no significant dif-
ference between the two sluice water samples in potentially hazardous pollu-
tants such as antimony, arsenic, barium, beryllium, cadmium, chromium,
copper, lead, mercury, selenium, titanium, vanadium, zinc, bromine, chlorine,
and fluorine. However, total dissolved solids (TDS), biochemical oxygen de-
mand (BOD), and chemical oxygen demand (COD) were higher for sluice water
from the coal/RDF system.
20
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A decrease in the performance of the electrostatic precipitator was noted
in the test program at St. Louis when RDF was substituted for coal.2 The de-
crease in ESP efficiency was attributed to the 8% increase in gas flow rate
and changes in fly ash and gas composition. These results suggest that simi-
lar problems may occur for other boiler/control equipment systems modified to
fire RDF and coal.
Power plants fired with oil and RDF will most likely emit particulates
(carbon and ash), NOX, SOX, and hydrocarbons. Based on the St. Louis/Union
Electric combined firing demonstration of coal and refuse, it is thought that
gaseous emissions of CO, CC>2, NOX, and organics will be relatively unchanged
in oil/RDF systems.
Table 5 presents comparative data on the air emission characteristics
from oil- and coal-fired electric generating plants. Notable differences
between these systems that affect collection efficiency include a smaller
average particle size, a lower grain loading, and a higher carrier-gas flow
rate for oil units* Evidence indicates that the size distribution of partic-
ulate from oil-fired systems is bimodal, with large, hollow carbonaceous
particles and finer, condensed, spherical particulate and ash less than 1 |o,m.
The size distribution depends on the degree of atomization of the oil, the
efficiency of mixing, the number of collisions between fly ash particles, the
flame temperature, the air-fuel ratio, the design of the firebox, and the flue
gas path through the boiler to the stack. The lighter particles usually con-
tain less carbon and are smaller.
Installed particulate emission controls designed for coal are predicted
to be less efficient for the control of particulate emissions from combined
firing of oil and RDF« Anticipated control difficulties result mostly from
relatively high particulate loadings, high flue-gas volumes, fine particulates,
relatively low particle density, and relatively high fractions of carbonaceous,
low-resistivity particulate.
Emission data for combined firing systems using coal and wood waste and
oil and wood waste were not available at Midwest Research Institute at the
time this document was prepared. The use of wood waste as a supplementary
fuel is not expected to markedly alter air emissions, but bottom ash genera-
tion rates will probably increase. Degradation in particulate control system
performance may also occur.
The preceding discussion on co-fired systems indicates that the existing
data base on environmental impacts is more extensive than for waterwall in-
cinerators. The broad outlines of the environmental problems have been de-
fined. Existing data indicate that the major adverse impacts of the combined
firing systems are related to:
21
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TABLE 5. AIR EMISSION COMPARISON DATA FOR OIL AND COAL FIRING IN UTILITY BOILERS
NJ
Electric utility
oower olants
Coal-fired
Oil-fired
Particle size'3
Typical distribution
(pulverized unit)
81 < 40, 65 < 20,
42 < 10, 25 < 5
(particle size varies
with type of unit )
90 < 1
Particulate Carrier gas
Chemical Carrier-gas Chemical
* Outlet loading0 composition1! flow rate8 composition
457.62-12,813.36 Fly ash 1.25-15.8 C02, 02> N2,
(dependent on type Si02: 17-65 9.94-18.21 SOj, 503,
of unit) Fe202:2-36 and NOX
Al202:9-58
CaO:0.1-22
MgO:0.1-5
Na20:0.2-4
22.88-457.62 Carbon, ash, NiO, 47-12,400 C02, 02, N2,
V203, A1203, sul- 348-780 S02, S03, and
fates, and a wide NOx
variety of minor
component s
a All data for uncontrolled sources.
b Particle size
x = weight %,
c mg/nrn^ .
d Weight %.
e Flow rate data
data are presented as weight
y = particle size (microns).
are presented in thousands
% less or greater than a specific diameter x > y, x < y;
of normal cubic meters per minute.
-------
—increased air emissions of some trace elements (e.g., antimony,
beryllium, copper, lead, zinc, cadmium, and chlorine),
—increased bottom ash generation and associated disposal problems (i.e.,
1eachat e prob1ems ),
—increased levels of BOD, COD, and TDS in boiler sluice water, and
—apparent decrease in control system performance under conditions of
combined firing.
Pollution Control Technology
Combined firing systems discussed here are restricted to RDF and coal
and RDF and oil. No control technology information was available for systems
fired with wood and coal or wood and oil.
RDF and Coal—
The St. Louis study^ presents a comprehensive environmental evaluation
of a coal/RDF system involving both the firing and processing facility.
Power plant—Pollutant streams (from the coal/RDF-burning plant) for
which controls are employed are:
• Air emissions from stack (particulates and gases),
. Solids (boiler bottom ash and fly ash), and
. Wastewater (boiler sluice water).
Air emissions at the St. Louis facility are controlled by an electro-
static precipitator* Particulate emission measurements showed that refuse
firing did not apparently affect inlet grain loadings to the ESP.2
The firing of RDF did have an effect on ESP spark rate and power levels,
coincident with losses in ESP collection efficiency at output loads above 100
(MW).
Specific factors analyzed as having a direct bearing on ESP performance
were: (a) inlet particle size data; (b) particulate resistivity data; (c)
particulate reentrainment; (d) electrical operating conditions for the ESP;
and (e) gas-volume flow rates. The fractional efficiency of the ESP was also
studied to see if the decreased efficiency could be related to specific
ranges of particle sizes.
2
The analysis of ESP performance led to the following conclusions:
23
-------
1. ESP efficiency decreases with increasing gas-volume flow rate, both
for coal-only and coal and RDF conditions.
2. Decreases in efficiency when burning coal and RDF as compared to coal
are probably not attributable to changes in inlet particle size distribution,
inlet grain loading, or reentrainment problems.
3. Decreases in ESP efficiency when burning coal and RDF as compared to
coal are most likely due to the 8%-increased gas flow rate and to changes in
the ash and gas properties that occur with the burning of RDF.
4. Changes in the fly ash properties that result from burning RDF prob-
ably cause small changes in particulate resistivity.
5. The small changes in resistivity caused by burning RDF are probably
magnified in terms of their influence on ESP efficiency because measured
resistivities are in a very critical range for the onset of back corona and
other electrical problems.
6. The decreased overall ESP efficiency at high boiler loads primarily
results from an increase in emissions of particles in the 1.0 to 10.0 (j,m
size range.
There are several control alternatives that could be considered for par-
ticulate emissions. A list of such alternatives includes: (a) adding another
control device (e.g., cyclone) before or after the ESP; (b) increasing the
size of the ESP (retrofit); (c) restricting power output or percent RDF; (d)
modifying the ESP operation (electrical or other characteristics); (e) use of
additives or conditioning agents to improve collectability of the particu-
lates (i.e., resistivity); and (f) using fuel of different characteristics
(either coal or RDF).
Gaseous stack emissions have also been tested. The only effects noted
from the burning of refuse was a moderate increase in Gl".
SC>2 emissions based on gram of S02/10& joule heat input exceeded federal
regulations for new sources and several individual state regulations for both
existing and new sources of the size of the Meramec boiler. The slight reduc-
tion in S02 stack gas concentration expected when the low sulfur RDF was sub-
stituted for the higher sulfur coal were not observed, probably because of
data scatter. Burning of RDF should help reduce 862 emissions, but such re-
ductions would probably not be sufficient to meet regulations.
A shift to lower sulfur coal or the installation of an S02 control sys-
tem are the viable options for achieving compliance with SOo emission regula-
tions.
24
-------
Few control methods are available for specific, potentially hazardous
pollutants that may be emitted from power plants in vapor form. SOo scrub-
bing systems may be effective in controlling some of these pollutants (e.g.,
Gl), but additional research will be needed to develop appropriate control
methods*
The disposal of fly ash resulting from the combined firing of coal and
RDF may present problems, especially if a poorly maintained landfill is used
as a disposal site. The changes and increases in trace element concentrations
in the fly ash that result when RDF is used to supplement coal may increase
leaching problems in landfills, and special disposal procedures might be re-
quired.
Bottom ash that results from firing coal or coal plus refuse is sluiced
from the boiler into an ash pond. In this pond, the bottom ash settles out
and the liquid is discharged into a nearby river. Therefore, this operation
represents two pollution control problems—bottom ash residue and liquid ef-
fluent.
Disposal of bottom ash residue will require more area when burning coal
and RDF because of the large increase in the quantity of bottom ash. Increased
concentrations of some pollutants that result from combined firing may in-
crease potential leaching problems in landfills.
Tests by the Union Electric Company showed that of many parameters eval-
uated for the refuse ash pond effluent, only three did not meet guidelines
proposed by the State of Missouri. These were BOD, DO, and TSS« Twelve other
parameters, for some of which there are no guidelines, are higher in the coal
plus RDF ash pond effluent than in the coal ash pond effluent. These include
ammonia, boron, calcium, GOD, iron, manganese, and total organic solids. Thus
it is likely that treatment facilities will be necessary in future plants to
control this pollution problem.
Aeration of a coal/RDF ash pond might be needed to improve BOD and dis-
solved oxygen. Flocculation techniques might also be required to meet-regula-
tions on suspended solids and possible future regulations on the content of
specific materials in the effluent.
Processing plant--There are four potential pollution problems at the
refuse processing plant:
. Nonferrous materials hauled to landfill
. Water discharge from washdown operations
. Air emission for the air classifier cyclone and hammermill cyclone
. Noise levels
25
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Nonferrous materials (mainly metals) are hauled to landfill, but they
represent only about 8% of the raw refuse received. Studies are being con-
sidered for evaluating leachability of this stream, but it is not expected
that they will present any special problem in this regard, especially not in
comparison with landfilling of raw refuse.
Water discharge from washdown operations has been studied, and increases
in TSS, BOD, and GOD were indicated. However, the quantity of effluent is
small («|2,000 gal.) and occurs only one to two times per week, so it is not
a significant problem for this size system.
Air emission tests on the hammermill cyclone showed that the particulate
emissions are negligible--on the order of 0.00015 to 0.00098 kg/min. How-
ever, particulate emissions from the classifier cyclone were significant.
These averaged 0.38 kg/min, equivalent to an emission of 0.62 g/kg of raw
refuse. A need for controlling or reducing emissions from this source exists.
Noise level measurements were made at several locations around the pro-
cessing plant, and several of these were above 90 dBA. But these levels did
not occur where operators would be subjected to them for periods exceeding
those prescribed by Occupational Safety and Health Administration regulations*
RDF and Oil —
For combined firing of oil and refuse, it is believed that particulate
levels will greatly exceed existing standards for fossil-fuel-fired boilers.
Experience with the St. Louis/Union Electric combined firing demonstration of
coal and refuse indicates that gaseous emissions of GO, C02, NOX, and organics
will be relatively unchanged. Although chlorides, mercury vapor, and trace
metals will be monitored in demonstration oil-refuse firing studies, particu-
late control appears to be the most difficult problem. ESP's, cyclones, and
scrubbers may be used as controls.
Electrostatic precipitators--The most probable units for oil-refuse com-
bined firing tests are those with ESP control. The efficiency of an ESP for
combined firing of oil and refuse is uncertain, however, because of the sig-
nificantly lower sulfur content of both the oil and the refuse. When oil is
fired in the boilers, the efficiency of an ESP designed for 99% efficiency
for firing of pulverized coal drops to about 50%, according to tests made by
the Consolidated Edison Company, New York. This disparity is believed to be.
due to the low sulfur content of the fuel oil and the extremely small parti-
cle size of the particulate. Other utility companies have also reported ESP
efficiencies for oil firing to be around 50% to 60%. However, for combined
firing with refuse, the efficiency of an ESP is expected to increase because
of the increased particulate loading as well as the increased moisture con-
tent of the flue gases. The designers of an ESP for combined oil-refuse
26
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firing in a unit in Stuttgart (West Germany) believe that an ESP designed
for 99% efficiency with pulverized coal will result in about 95% collection
efficiency for combined firing of oil and refuse.
ESP control modifications may be required for oil-refuse firing. Major
requirements for precipitators for stack gases from oil as compared to coal
may include reduction in velocity by about 50% or longer gas treatment path,
higher operating current, increased rapping intensity, etc.
Cyclone contro^--Generally speaking, cyclone control is more effective
for larger particulate than that encountered in oil firing. However, cyclones
are frequently used as precleaning devices for both ESP and high efficiency
scrubbers. Tests on No. 6 residual oil-fired boilers (Franklin Station,
Rochester, Minnesota) using Zurn TA Mechanical Collectors resulted in 85.7%
and 87% collection efficiency with and without fuel additives, respectively.
No special operating problems were noted. A large number of cyclone instal-
lations are reported in oil-fired utility boilers in Europe. Collection
efficiency is between 85% and 92% during sootblowing, and between 70% and 90%
during normal operation (finer particulate). Both the European and American
test reports are for low excess air operation (< 20% excess air), which yields
an increased fraction of coarse particulate.
High efficiency scrubber--As a result of recent EPA-sponsored tests at
Boston Edison's Mystic Station Unit No. 6 and TVA's Shawnee Wet Limestone
Scrubbing Test Facility, a fair amount of information is available on per-
formance of high efficiency wet scrubbers in controlling particulate from
oil firing. Reported collection efficiencies at Mystic No. 6 are: particu-
lates, 88.5% to 90.6%; SOX, 97.6% to 99.6%. Pressure drop across the
Chemico venturi scrubber is 24.13 cm 1^0 at 125 MW load, and 16.51 cm H20
at a reduced load of 85 MW» Fractional efficiency data obtained in smaller
scale tests at the Shawnee Test Facility appear to be reasonably consistent
with these test results.
Lack of precise information about the particulate size distribution and
other properties from combined oil-refuse firing prevents an estimate of
fractional control efficiency for different control devices at this time.
There is presently no direct experimental data on control of particulates
and other effluents from combined oil and municipal solid waste (MSW) fir-
ing.
Recommended Reading
The following articles and reports are suggested for additional infor-
mation:
27
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1. Funk, H. D., and S. H. Russell, "Operating Experience of the
Ames, Iowa, Resource Recovery Plant," paper presented at the
82nd Annual A.I.Ch.E. Meeting, September 1976.
2. Glatz, G. E., V. G. Murphy, W. H. Abraham, J. C. Hill, Energy
Recovery from Solid Waste; Air Pollution, draft report prepared
by Ames Laboratory and Iowa State University for U»S» Energy Re-
search and Development Administration, Washington, D»C»,
February 1977.
3. Gorman, P. G», L. J. Shannon, M. P. Schrag, D. Fiscus, "St. Louis
Demonstration Project Final Report: Power Plant Equipment Facil-
ities and Environmental Evaluations," Vol. II, prepared under EPA
Contract No. 68-02-1871, July 1976.
4. Jackson, J. W., "A Bioenvironmental Study of Emissions from Refuse
Derived Fuel," U.S. Air Force Health Lab, Prof. Report No. 76M-2,
Project No. AAF-520, January 1976.
THERMOCHEMICAL (PYROLYSIS) PROCESSES
System Description
Pyrolysis can be generally defined as thermal decomposition in an oxygen-
starved environment. The process is a complex one of several simultaneously
occurring chemical reactions, and it is poorly understood. Products of pyrol-
ysis can be combustible gas, liquid, or solid; therefore, pyrolysis offers an
option for various types of fuels in waste-to-energy systems.
Principal characteristics of pyrolysis processes vary and include such
factors as bed type, heating method, and pyrolysis temperatures. Bed types
that have been commonly used are fixed (shaft), rotary kiln, and fluidized
bed, and both direct and indirect methods of supplying heat have been em-
ployed. In general, fluidized-bed processes require direct contact with a
heating medium, whereas fixed-bed systems can be heated directly or indirectly.
The carriers that have been utilized for direct heating are steam, air, re-
cycled gases, sand, and metal balls. Figure 3 presents a general schematic
diagram for pyrolysis systems, and Table 6 delineates some of the pyrolysis
processes.
Among all the pyrolysis systems shown in Table 6, the Occidental system
in San Diego, the Torrax system in New York, the Union Carbide system in
West Virginia, and the Landgard system in Baltimore are the best known.
Based on recent information, 1 the San Diego Gas and Water and Electric Com-
pany has proposed a 21-month test program to assess the impact of combusting
pyrolytic oil (from the Occidental flash pyrolysis unit) on S02 and NOX
28
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Source
Material
Pre-conversion
Processing
Pyrolysis
Conversion
Processes
Pos t -c on ve rs i on
Processing
Row
Products
Final
Disposition
Figure 3. Schematic diagram of pyrolysis of refuse.
-------
TABLE 6. PYROLYSIS PROCESSES
Location
Baltimore, Maryland
San Diego County, California
Seattle, Washington
South Charleston, West Virginia
Riverside, California
Westchester County, New York
Capacity
me/dav
907.18
181.44
1360.77
181.44
45.36
2086.51
Processing stepsa
SH, MS
SH, AC, MS, OS, FF
UN
SH, MS
UN
UN
Products
Steam, ferrous, glassy, aggregate
Pyrolytic oil, ferrous and non-
ferrous, glass
Ammonia, ferrous
Gas, ferrous
Gas electricity
Gas, steam
a SH, shredding; AC, air classification; MS, magnetic separation; SC, screening; OS, other mechanical
separation; FF, froth flotation; UN, unknown.
-------
emissions. The Georgia Tech. system has had problems operating in the por-
table mode, but one unit is operating successfully 6 days/week and 24 hr/day
in the stationary mode. 2 This unit is fired with wood waste. Other fuels
that have been successfully used in the Georgia Tech. pyrolysis reactor in-
clude cotton gin waste, MSW and tires, MSW and sewage sludge, and MSW and
paper mill sludge. The Torrax system has been utilized in Europe on a com-
mercial scale but has not yet reached that level in the United States. The
Union Carbide Purox system is close to being commercially utilized, and the
process has been successfully demonstrated on a 200 ton/day plant at
Charleston, West Virginia. 9 The system can use shredded MSW or shredded MSW
and sludge to yield an inert slag and a fuel gas with a heating value of ap-
proximately 1.3 x 10? J/rmP. The Monsanto system is the largest of all ex-
isting pyrolysis systems (907.18 mg/day), but it is being plagued with severe
operational problems.21
Pollution Potential
Pollutants from pyrolysis systems are poorly characterized. Depending
on the specific process, the major pollutant streams can be air, solid, or
liquid. Air emissions can consist of particulates and gases in the form of
HCl, H2S, and NOX. The solids can contain undesirable leachates, and waste-
water from pyrolysis systems can be high in BOD, COD, alcohols, phenols, and
other organic compounds. Gas cleaning systems commonly used in pyrolysis
processes include wet scrubbers and ESP's, and wastewater treatment systems
are usually site specific.
Pyrolysis systems that require processing of waste (e.g., Purox,
Occidental) generate pollutants during the processing steps. These pollu-
tants will be characteristic of those generated in MSW processing to obtain
RDF,
Pollutants generated in the pyrolysis reactor and in subsequent opera-
tions of the process include solids in the form of slag, particulate and
gaseous pollutants in the gas stream, and water effluents.
In the Purox System, solids generated are slag from the reactor and
sludge from wastewater treatment. The amount of slag produced is reported
to be 440 Ib/ton refuse.19 An average slag analysis is as follows:
31
-------
Item
MnO
Si02
CaO
A1203
Ti02
BaO
P205
FeO
MgO
K20 1 .0
CuO 0.2
Miscellaneous 0.7
Total 100.0
The slag is reported to be inert and nonleaching. The gas cleaning train con-
sists of a scrubber and an electrostatic precipitator. Oil from the electro-
static precipitator is recycled to the pyrolysis reactor, and scrubber water
goes to a decant tank before being recycled. The wastewater from the decant
tank goes to a sewer.
Data on the wastewater pollutant concentrations are apparently 'not avail-
able. Union Carbide claims that their "commercial" Purox module will have the
UNOX water treatment unit available and that the pollutant potential of the
treated wastewater is inconsequential. However, water effluents from waste
pyrolysis processes, if untreated, can pose a significant pollution problem
because of the high amount of soluble organic and inorganic compounds. The
water effluent from the gas scrubbing system is expected to be high in COD
and BOD and is expected to contain alcohols, phenols, aldehydes, and other
organic compounds. Potentially hazardous trace elements could also be pres-
ent, since they are contained in EDF and sewage sludge, both of which can be
used as feed materials.
The gas stream might contain particulates even after going through an
electrostatic precipitator, but the particulate loading is not expected to be
high. The nature of the particulate pollutants in the fuel gas is presently
not documented. Analysis of typical Purox fuel gas itself is shown as fol-
lows: 19
32
-------
Item Volume %
H2 26
CO 40
G02 23
CH4 5
C2+ 5
N2 and A 1
Gas—higher heating value L.38 x 107 J/nm3
The gas has been analyzed for some pollutants, which are identified below:23
NOX <(j,I/liter
HC1 < 1 nI/liter
H2S = 300 to 600 (j, I/liter
COS < 1 ;j,l/liter
No major tests have been conducted on the Occidental pyrolysis system to
establish its pollution potential. As with the Purox system, the liquid ef-
fluent and gas streams are probably the important ones to be tested from a
pollution standpoint. Preliminary estimates indicate that S02 emissions are
about 700 |jl/lite:r; NOX, about 8 to "1,000 |jbl/liter; HCl, 100 (j,I/liter; and
particulates, 114.42 mg/nm3.23
The Monsanto Landgard System is also poorly characterized for its pollu-
tion potential. The off gases from the pyrolysis kiln go to an afterburner,
and the heat released is directed to two waste heat boilers. Waste gases from
the boilers go to a wet scrubber. The scrubber has not performed satisfac-
torily. In addition, there have been problems involving metallic residues in
the pyrolysis gas stream and excessive slagging of inerts in the solids dis-
charge system.
The Torrax Pyrolysis System and the Georgia Tech. Pyrolysis System have
not been tested for environmental pollution either. The Torrax system is sim-
ilar to the Purox system, except that air rather than oxygen is used for oxi-
dizing the char in the bottom of the vertical reactor. A 68 Mg/day Torrax
demonstration system has been tested at Orchard Park, New York, and a 181.4
Mg/day facility is in Luxembourg; but no emission test data are reported.
33
-------
The Georgia Tech. system now uses wood waste (sawdust and bark) as fuel
and operates three shifts/day, 7 days/week. The system is a 45.35 Mg/day
demonstration plant at Gordele, Georgia, and it is owned and operated by the
Tech. Air Corporation. The char and pyrolytic oil produced are sold. A por-
tion of the gas produced is used for drying the feed, and the rest is flared.
Knight et al.2^ report that an analysis of the combustion stack gases was
made and that it meets all the Federal standards. However, no details are
provided on gas composition or the results of the analysis.
From the above discussion, it is clear that adequate measured data are
not available to make an assessment of the environmental impact of pyrolysis
systems. An engineering analysis using the source severity concept outlined
in Appendix A can be used to obtain an insight to the potential impacts of
the pyrolysis systems. The same approach can be used for any waste-as-fuel
system. An example of the procedure is presented in Appendix B.
Pollution Control Technology
Control technology information on pyrolysis systems is minimal. A dis-
cussion of the Purox system follows to demonstrate what is available.
Pollutants requiring control from the Purox system are liquid effluents,
air emissions, and solids in the form of slag. In addition, there will be
emissions from preprocessing of MSW, which can be controlled by using tech-
niques similar to those discussed earlier under MSW and coal for preprocess-
ing MSW.
Liquid effluents from the Purox system are made up of scrubber water and
the condensate water, both of which go to a quench tank for recycling and dis-
posal. This wastewater stream is expected to have high concentrations of BOD,
COD, phenols, and other organics, and it will require treatment before dis-
posal. Union Carbide claims that their commercial Purox units will have the
UNOX wastewater treatment facility available and that, therefore, this should
not cause any environmental concerns.20
Control of air emissions from the Purox system should not pose any major
difficulty, since the air stream is the product gas stream. Some trace ele-
ments may be present in the particulate, even after passing through the wet
scrubber and ESP, but no data are as yet available.
The slag from the Purox system is claimed to be free of leachates and
could be disposed of in landfills or as a construction material.
Recommended Reading
The following major articles and reports are suggested as sources for
additional information:
34
-------
1. Alpert, S. B., "Pyrolysis of Solid Waste: A Technical and Economic
Assessment," Stanford Research Institute, West Virginia University
Report No. WVU-ENG-CHE-73-01, September 1972.
2. Anderson, J. E., "The Oxygen Refuse Converter—A System for Produc-
ing Fuel Gas Oil, Molten Metal, and Slag from Refuse," 1975
National Incinerator Conference, ASME Incinerator Division, Miami,
Florida, May 1974.
3. Hammond, V. L., "Pyrolysis--Incineration Process for Solid Waste
Disposal," Battelle Pacific Northwest Laboratories, Richland,
Washington, December 1972.
4. Hammond, V. L., and L. K. Nudge, "Feasibility Study of Use of Molten
Salt Technology for Pyrolysis of Solid Waste," EPA Contract No.
68-03-0145, Battelle Pacific Northwest Laboratories, Richland,
Washington, April 1974.
5. Knight, J. A., M. D. Bowen, and K. R. Purdy, "Pyrolysis—A Method for
Conversion of Forestry Wastes to Useful Fuels," presented at the
Conference on Energy and Wood Products Industry, Forest Products
Research Society, Atlanta, Georgia, November 1976.
6. Levy, S. J., "Pyrolysis of Municipal Solid Waste," Waste Age.
October 1974, pp. 14-20.
7. Preston, G. T., "Resource Recovery and Flash Pyrolysis of Municipal
Refuse," Waste Age, May 1976, pp. 83-98.
HOG FUEL BOILERS
System Description
In the manufacture of lumber, about 50% of the material from the log is
removed to produce sound lumber.25 Though the total waste usually averages
approximately 507°, distribution of the different types of waste such as slabs,
edging, trimming, bark, sawdust, and shavings, may vary depending on mill con-
ditions and product desired. The mills frequently use sawdust or sawdust and
shaving mixtures for steam production because they can be burned without fur-
ther processing. The remainder of the waste products requires further size
reduction in a "hog" to facilitate storage, feeding, combustion, etc. These
newly sized products together with varying percentages of sawdust and shav-
ings present constitute "hog fuel."25 Table 7 analyzes hogged fuels, includ-
ing moisture content, on an "as-received" as well as "air-dried" basis. The
heating value is also shown.
35
-------
TABLE 7. ANALYSES OF HOGGED FUELS25
(%, except as noted)
Item
Western
hemlock
Type of fuel
Douglas
Fir
Pine
sawdust
Moisture, as received
Moisture, air-dried
Proximate analysis, dry:
Fuel
Volatile matter
Fixed carbon
Ash
57.9
7.3
74.2
23.6
2.2
35.9
6.5
82.0
17.2
0.8
6.3
79.4
20.1
0.5
Ultimate analysis, dry:
Fuel
Hydrogen
Carbon
Nitrogen
Oxygen
Sulfur
Ash
Heating value, dry:
(joule/kg)
5.8
50.4
0.1
41.4
0.1
2.2
20.05 x 106
6.3
52.3
0.1
40.5
0
0.8
21.05 x
106
6.3
51.8
0.1
41.3
0
0.5
21.24 x 106
36
-------
Reports indicate that, based on sales of wood-burning and other types of
boilers, wood is the most significant fuel other than coal, oil, or natural
gas. The most prevalent size for wood-fired boilers is reported to be in the
range of 113.37 to 1133.7 kg steam/min.H The most common firing method for
wood-fired boilers in all size ranges is the spreader stoker, with overfeed
stokers also being common in sizes less than 1889.5 kg steam/min.11
There are several important considerations in burning wood. These re-
late to the fouling potential of wood as a result of its ash composition.
Wood ash is high in CaO (50% to 60%), and high in Na20 and K20 (4% to 7%).11
Generally speaking, substituting wood for residual fuel oil will increase
problems with fouled heat-receiving surfaces. Burning wood in boiler fur-
naces designed for pulverized coal will not be likely to pose fouling problems
worse than with coal alone, except that alkalies may tend to accumulate more
rapidly in the cooler parts of the boiler, such as the superheater.-'--'-
The substitution of wood firing in existing coal-fired stoker boilers
presents the fewest problems. In most cases, only minor modifications to the
boiler are necessary, such as addition of a wood-feeding system or firing
ports. Hogged fuel of less than about 5.08 cm in size, with a minimum of
slack (less than 0.635 cm) should be acceptable to most spreader and overfeed-
type stokers.-'--'-
Wood can also be fired in suspension in boilers designed for pulverized
coal or heavy oil. The wood should be reduced in size to less than 0.635 cm
and dried as much as possible to insure rapid combustion. Most suspension
wood-fired boilers have a small grate at the base of the unit to insure com-
plete burnout of any wood chips that do not burn in suspension. Firing wood
in boilers designed for natural gas or light fuel oil would represent a dif-
ficult problem since extensive boiler modifications will have to be under-
taken to provide ash handling capabilities.
Pollution Potential
The combustion of wood will result in particulate pollutant emissions
and ash in the form of captured fly ash and bottom ash. Wood, unlike coal
or oil, has a negligible sulfur content and should therefore create no S02
problems. Nitrogen oxide emissions should also be lower than that observed
during coal combustion because of the low nitrogen content of wood (see
Table 8).
Typical emission factors for wood and bark combustion, as reported in
the literature, are presented in Table 9.11 Values presented in Table 9 are
uncontrolled emissions. Based on these values, it appears that control of
criteria pollutants from wood or bark combustion should pose no serious
problems.
37
-------
TABLE 8. COMPARATIVE CHEMICAL ANALYSIS OF WOOD AND BARK, COAL, AND OIL
noted)
11
Wood and bark
Item
Proximate:
Volatile matter
Fixed carbon
Ash
Ultimate:
Hydrogen
Carbon
Sulfur
Nitrogen
w Oxygen
OO Ash
Heating value, joule/kg
Ash analyses:
Si02
Fe203
Ti02
A1203
CaO
MgO
Na20
K20
S03
Cl
Pine
bark
72.9
24.2
2.9
5.6
53.4
0.1
0.1
37.9
2.9
21 x 106
39.0
3.0
0.2
14,0
Trace
25.5
6.5
1.3
6.0
0.3
Trace
Oak
bark
76.0
18.7
5.3
5.4
49.7
0.1
0.2
39.3
5.3
19.47 x 106
11.1
3.3
0.1
0.1
Trace
64.5
1.2
8.9
0.2
2.0
Trace
Spruce
bark
69.6
26.6
3.8
5.7
51.8
0.1
0.2
38.4
3.8
20.33 x 106
32.0
6.4
0.8
11.0
1.5
25.3
4.1
8.0
2.4
2.1
Trace
Redwood
bark
72.6
27.0
0.4
5.1
51.9
0.1
0.1
42.4
0.4
19.42 x 106
14.3
3.5
.0.3
4.0
0.1
6.0
6.6
18.0
10.6
7.4
18.4
82.5
17.3
0.2
5.9
53.5
0
O.I
40.3
0.2
21.44 x 106
-
-
-
-
-
-
-
-
-
-
-
Pine
79.4
20.1
0.5
6.3
51.8
0
0.1
41.3
0.5
21.24 x 106
-
-
-
-
-
-
-
-
~
-
-
Washed
Pennsylvania
35.8
57.3
6.9
5.1
78.1
1.2
1.6
7.1
6.9
32.49 x 106
-
-
-
-
-
-
-
-
-
-
-
Coal
Western
43.4
51.7
4.9
6.4
54.6
0.4
1.0
33.8
3.3
21.91 x 106
30.7
18.9
1.1
19.6
-
11.3
3.7
2.4
-
12.2
-
Residual fuel
oil
Pennsylvania Range of
coal No. 6 oil
37.6
52.2
10.1
5.0 9.5-12.0
74.2 86.5-90.2
2.1 0.7-3.5
1.5
7.1
10.1 0.01-0.5
30.96 x 10 40.5 x 106-44.17 x 10
49.7
11.4
1.2
26.8
-
4.2
0.8
2.9
*
2.5
-
-------
TABLE 9. EMISSION FACTORS FOR WOOD AND BARK* COMBUSTION IN
BOILERS WITH NO REINJECTION1l
Pollutant
Particulate
Sulfur oxides (S02)c
Carbon monoxide
Hydrocarbons^
Nitrogen oxides (N02)
Emission (e/kg)
12.5-15
0-1.5
1.0
1.0
5
a Moisture content assumed
b This number is the atmost
to be 507o in wood and bark.
)heric emission factor without
fly ash reinjection. For boilers with reinjection,
the particulate loadings reaching the control equip-
ment are 15 to 17.5 g/kg fuel with 100% reinjection.
c Use 0 for most wood, and higher values for bark.
d Expressed as methane.
39
-------
Particulate emissions from wood-fired boilers can vary, depending on the
extent of char reinjection, boiler type, excess air used, wood waste type
(e»g., logs, sawdust, chips) and wood moisture content. Hall et al»^ re-
port that the single most significant factor is probably the extent of char
reinjection utilized.
Char reinjection systems, which return collected particles to the com-
bustion zone to achieve more complete combustion of the carbon, represent a
compromise between two conflicting objectives. While reinjection increases
boiler efficiency and minimizes the emission of uncombusted carbon, it also
increases boiler maintenance requirements, decreases the average fly-ash par-
ticle size, increases the dust load to the collector, and makes collection
more difficult .•'-•'• Properly designed reinjection systems should separate the
sand and the char from the exhaust gases, reinject the larger carbon fraction
to the boiler, and reinject the fine sand particles to the ash disposal system.
Pollution Control Technology
Emissions from hog-fuel boilers primarily consist of particulates. The
other environmental aspect is the generation of captured fly ash and bottom
ash, which can be disposed of in landfills.
Fly ash particulates from hog-fuel boilers are light in density and
larger in size than fly ash from coal-fired boilers.*•*• Also, particulate
emissions from wood-fired systems can vary depending on the extent of char
reinjection, boiler type, excess air, wood waste type, moisture content,
etc. Because of these variations, a specific dust loading cannot be estab-
lished. It is reported that dust loadings range from 1144.17 to 11,441.7 mg/
nrn^ and that multicyclones are the sole source of particulate removal for
most hogged fuel boilers. Wet scrubbers with moderate pressure drops can
also be used effectively on this source, since particle size is considered
to be large. However, this may result in secondary wastewater pollution.
High temperature fabric filtration systems may also be another alternative
control system. The use of ESP's, however, will depend on particle resis-
tivity, which for this source might be in the lower range.
Recommended Reading
The following references are suggested for more information on wood-
fired boilers:
1. Hall, E. H., et al., "Comparison of Fossil and Wood Fuels," EPA
Report No. EPA-600/2-76-056, March 1976.
40
-------
U.S. Department of Agriculture, Forestry Service, "Final Report on
the Feasibility of Utilizing Forest Residues for Energy and Chem-
icals," by Forest Service, USDA, National Science Foundation Re-
port No. NSF-RA-760013, March 1976.
BIOCHEMICAL SYSTEMS
System Description
Controlled anaerobic digestion is a biological process whereby organic
matter decomposes in a regulated oxygen-deficient environment. Since the
organic matter in municipal solid waste is predominantly cellulose, conver-
sion of solid waste to methane by anaerobic digestion may be chemically repre-
sented as:
C6H10°5 + H20 > 3 C02 + 3 Ctfy
The system for converting solid waste to methane essentially consists of
feed preparation, digestion, gas treatment, and effluent disposal. Figure 4
is a conceptual flow sheet of the process.
On a commercial scale, this anaerobic digestion process is being designed
and developed by Waste Management, Inc., of Oak Brook, Illinois, for ERDA.
The facility is located in Pompano Beach, Florida. About 80% of the design
has been completed, and equipment procurement is 5070 complete} construction
has also begun.27 The shredding system now operates at 272.10 Mg/day but will
be expanded to handle 544.2 to 725.6 Mg/day. The system will use mechani-
cal mixing in the digester rather than a gas mixer, as originally proposed.
Pollution Potential
Pollutants from the anerobic digestion process include those that result
from preprocessing of solid waste, wastewater, and cake from the slurry de-
watering system.
Slurry dewatering can be accomplished either by vacuum filtration or
centrifugation.28 Both processes result in filter cake solids and waste-
water for disposal. Filter cake solids can be used for landfills or, pref-
erably, they can be incinerated to generate steam. Incineration, in turn,
will result in particulate pollutants and ash disposal, but techniques for
particulate pollutant control from incinerators are well established and
therefore should eliminate any environmental concerns. Wastewater from the
slurry could be high in pollutants, and no data are presently available to
characterize pollutants in this effluent stream.
41
-------
«*.
ft
g
I
>
1
SHRtDOCT ''*"*'* _ TR°MUtL
SCPAKATOfl SCREEN
r
RESOURCE
NCCOVEKY
9AKI
TO DISPOSAL
TO TREATMENT
Figure 4, Block diagram of the anaerobic digestion system.
26
-------
The product gas from the digester (i.e., CH4) contains G02 and trace
quantities of H2S. These two acid gases must be removed to upgrade the
product gas to pipeline quality. Depending on the technique employed for
acid gas removal, pollutants are likely to be encountered, and adequate pro-
vision should be made for their removal and/or ultimate disposal in an en-
vironmentally acceptable manner.
Pollution Control Technology
Controls are required to treat wastewater from dewatering sludge. The
liquid effluent can be partially recycled, and the remainder can go to a
waste treatment plant for clarification and purification. If not treated,
the wastewater can cause severe environmental problems.
The filter cake from the dewatering operation can either be incinerated
or sent to a landfill. The latter disposal technique should be investigated
further to determine if potentially hazardous bacteria or leachates are pre-
sent.
Air emissions can result from upgrading of digester gas to pipeline
quality methane, but no information is available on these control technology
aspects.
Recommended Reading
The following references are suggested for information on biochemical
waste utilization systems:
1. Bisselle, G», Urban TrashMethanation Background for a Proof-of-
Gonceot Experiment. Mitre Corporation, NSF/RANN Contract No. NSF-
C938, February 1975.
2. Hecht, N. L., and D. S. Durall, Characterization and Utilization
of Municipal and Utility Sludges and Ashes, Vol. I, II, and III,
U.S. Environmental Protection Agency Report No. EPA-670/2-75-033a,
b, and c, Cincinnati, Ohio, May 1975.
3. Pfeffer, J. T., and J. C. Liebman, "Energy from Refuse by Biocon-
verslon, Fermentation and Residue Disposal Processes," Resource
Recovery and Conservation. U295-313, 1976.
43
-------
ADVANCED COMBUSTION SYSTEMS (CPU-400)
System Description
Since 1967, the Combustion Power Company (Menlo Park, California) has
been involved in developing an advanced combustion system to convert the
energy in refuse to electrical power. The system uses a fluidized bed in-
cinerator as the combustor and a gas turbine-generator to produce electrical
power. At commercial scales, the system"is to be capable of converting the
heating value of 544.2 Mg/day of solid waste into 9 to 12 MW of useful elec-
trical power while also recovering secondary materials from the waste stream.
Development has progressed to a pilot-scale facility capable of converting
90.7 Mg/day of solid waste into energy.21
The pilot system has two modules, one for solid waste processing and the
other a power module. The waste processing module has two shredders (745-7 x
o o
10 w and 559.3 x 10 w), an air classifier, and a materials recovery system.
After wastes are shredded and air-classified, the light fraction is pneumat-
ically transported to the shredded waste storage vessel. A material recovery
system is used to recover steel and aluminum. A glass-rich fraction and a
nonferrous-rich fraction are also separated and are available for further re-
covery operations.21
The power module consists of a vertical, cylindrical, fluidized bed com-
bustor and its feed system, a three-stage gas cleaning system, a turbogenera-
tor, and an automatic control system. The gas cleaning system is made up of
two parallel 0.91 m cyclones, two parallel 0.76 m cyclones, and a granular
filter. A four-stage, axial-flow, gas turbine is used for extracting energy
from the hot gas stream to drive an air compressor and to run a 1,000-kw
electrical generator.
Pollution Potential
Processing of waste that is required to generate refuse feed to the
fluidized bed combustor will result in pollutants that have been identified
in an earlier section.
A high degree of particulate removal from the combustor exhaust gases is
required before use in the turbine generator set. Therefore, fly ash col-
lected upstream of the turbine can create a solid waste disposal problem if it
cannot be disposed of properly. Particulate emissions from the turbine ex-
haust should be of minimum concern.
\
The only other potential pollution problem could result from gases from
the turbine exhaust. A summary of some gaseous components in the turbine ex-
haust is given as follows:23
44
-------
Gas constituent Low-pressure Test High-pressure test
02 13.4% 16.1%
C02 5.8% 5.2%
CHX < 30 ^I/liter < 30 ^I/liter
S02 0 ^I/liter 2 ^.I/liter
HC1 161 |U/liter 63 u-I/liter
Pollution Control Technology
*
Hot combustion gases pass through a three-stage cleanup before entering
the gas turbine:
First stage—two parallel, 0.91 m diameter cyclones.
Second stage--two parallel, 0.76 m diameter cyclones, and
Third stage—granular filter (aluminum oxide).
The granular filter bed is continuously regenerated by slowly moving
downward through a screen. It is subjected to a cleanup process and then
reenters at the top of the bed. Recent information indicates that this sys-
tem is currently not operating because of structural problems.™
Particulate (including sand from the combustion bed) collected by the
three-stage separators is pneumatically conveyed to a sand bin (cyclone),
which exhausts to a baghouse filter. These control options appear viable
and should cause no environmental insults. Dust from the shredded waste
storage bin is controlled by two small cyclones.
No water effluents are generated in the CPU-400 process except for cool-
ing bearings.
Solids for disposal from the CPU-400 system are residue from waste
shredding and subsequent recovery operations. Magnetic materials, aluminum,
and glass are recovered. The residue goes to a landfill.
Recommended Reading
1. Trethaway, W., "Energy Recovery and Thermal Disposal of Wastes
Utilizing Fluidized Bed Reactor Systems," in Proceedings of the
1976 National Waste Processing Conference, Boston, Massachusetts,
May 23-26, 1976.
45
-------
SECTION 5
STATUS OF WASTE-TO-ENERGY CONVERSION SYSTEMS
Table 10 lists the different waste conversion systems, their locations,
plant capacities, processing operations, and products. The table also in-
cludes the capital cost of each system and its developmental status. For
most systems, no emission data are available.
The systems presented in Table 10 include those that are operational
as well as those that are in an advanced planning state. Some proposed
systems may not be included since the listing here is not intended to be a
comprehensive presentation of systems.
46
-------
TABLE 10. STATUS OF WASTE-TO-ENEHCY CONVERSION SYSTEMS
Location
Water-wall incineration:
Akron, Ohio
Braintree, Massachusetts
Chicago, Illinois (Northwest)
Dade County, Florida
Detroit, Michigan
Harrisburg, Pennsylvania
Lexington-Fay ette Urban County
Gov., Kentucky
Minneapolis-St. Paul, Minnesota
Nashville, Tennessee
Norfolk, Virginia
Saugus, Massachusetts
Haverhill, Massachusetts
Memphis, Tennessee
New Haven, Connecticut
Onondaga County, New York
Co-fired systems:
Ames, Iowa
Chicago, Illinois (Crawford)
Capacity
Me/day
907
217.7
1451.2
2721
2721
653
952.4
1088.4
653
326.5
1088.4
2721
1814
1632.6
907
362.8
907
Prneesninp stens3
SH, AC, MS
MS
None
WP, MS, OS
UN
MS
SH, MS
UN
None
None
SC, MS
UN
UN
UN
UN
SH, MS, AC, SC, OS
SH, AC, MS
Announced capital
Products costs (in millions) Status
Steam, ferrous
Steam, ferrous
Steam
Steam, glass, ferrous, aluminum
Steam
Steam, ferrous
Steam, ferrous
Steam
Steam
Steam
Steam, ferrous
Steam, ferrous
Steam
Steam
Steam ferrous
RDF, ferrous, aluminum
RDF, ferrous
$31
2.5
17.5
82
UN
9.5
UN
50
26.5
4.2
32
UN
UN
UN
UN
5.6
19
Construction began 12/76
Undergoing modification;
expected start-up, June
1977
Operational (1971)
Awaiting funding- -expected
start-up, 1979
Choosing contractor
Operational (1972)
Start-up expected 1977
Construction to begin
soon for 1980 start-up
Operational (1974)
Operational (1967)
Operational (1975)
Advanced planning
Advanced planning
Advanced planning
Advanced planning
Operational (1975)
Operational (1977)
-------
TABLE 10 (Continued)
Location
East Bridgewater, Massachusetts
Portsmouth, Virginia
St. Louis, Missouri
Albany, New York
Monroe County, New York
New York, New York
Wilmington, De.laware
(New Castle County)
Bridgeport , Connect icut
•t- Brockton, Massachusetts
00
Milwaukee, Wisconsin
Pyrolysis:
Baltimore, Maryland
San Diego County, California
Seattle, Washington
South Charleston, West Virginia
Riverside, California
Westchester County, New York
Capacity
Me/day
1088.4
145.1
5,442
544.2
1,814
UN
453.5
1632.6
1088.4
1088.4
907
181.4
1360.5
181.4
45.4
2086.1
ProcessinR steosa
SH, AC, MS, OS
UN
SH, MS, AC, OS
SH, MS
SH, MS, AC, FF, OS
UN
SH, AC, UN (others)
SH, AC, MS, FF
SH, AC, MS, OS
,SH, UN
SH, MS
SH, AC, MS, OS, FF
UN
SH, MS
UN
UN
Announced capital
Products costs (in millions)
RDF, ferrous
RDF
RDF, ferrous, nonferrous, glass
residue
RDF, ferrous
RDF, ferrous
UN
RDF, compost, ferrous, aluminum,
nonferrous, glass
RDF (Eco-Fuel II), ferrous, non-
ferrous, glass
RDF (Eco-Fuel II), ferrous
RDF, ferrous, glass, aluminum,
paper
Steam, ferrous, glassy, aggregate
Pyrolytic oil, ferrous and non-
ferrous, glass
Ammonia, ferrous
Gas, ferrous
Gas, electricity
Gas, steam
$10-$12
4.5
70
9
35
UN
UN
(20-30 est.)
52
10-12
18
26
14.5
110
UN
UN
UN
Status
Operational for tests
Shakedown
Abandoned
Design study
Bid requests
Advanced planning
Request for proposals
Unknown, scheduled
start-up, 1978
Operational
Under construction
Shakedown
Near completion
Expected start-up, 1980
Operational (1974)
Demonstration planning
Advanced planning
-------
TABLE 10 (Concluded)
Location
Capacity
Mg/dav
Processing steps3
Products
Announced capital
costs (in millions)
Status
Advanced combustion:
Menlo Park, California
Biochemical conversion:
Pompano Beach, Florida
State of Delaware
Altoona, Pennsylvania
362.8 UN
Gas
45.4-90.7 SH, AC, MS, AD RDF, methane, others
453.5 MSW, SH, AC, MS, OS, AD
208.6 sewage
sludge
RDF, ferrous, nonferrous, glass,
agricultural/horticultural
products
45.4 SH, AC, MS, AD, OS Compost/fertilizer
UN
$3
20
(approximately)
UN
Down for modification
Under construction; expected
start-up, 12/77
Review bid proposals
Operational (pilot scale)
a SH, shredding; AC, air classification; MS, magnetic separation; SC, screening; OS, other mechanical separation; FF, froth flotation; AD, anaerobic digestion;
UN, unknown; WP, wet pulping.
-------
REFERENCES
1. Marr, H. E., Ill, S. L. Law, and W. J« Campbell, "Concentration and Source
of Trace Elements in the Combustible Fraction of Urban Refuse," in
Proceedings of the Fifth Mineral Waste Utilization Symposium. Chicago,
April 1976.
2. Gorman, P. G., L, J. Shannon, M. P. Schrag, D. Fiscus, St. Louis Demon-
stration Project Final Reportt iJPower Plant Equipment Facilities and
Environmental Evaluation. Vol. II, EPA Contract No. 68-02-1871, July
1976.
3. Environmental Assessment of Waste-to-Energy Processes. Monthly Report
No. 6, Prepared by Midwest Research Institute, EPA Contract No. 68-02-
2166, April 1977.
4. Nashville Thermal Transfer Corporation Compliance Test Report. Unit No.
3 - Incinerator, prepared by Particle Data Laboratories (PDL), Ltd.,
Elmhurst, Illinois, under PDL Project No. 15408, September 1976.
5. Bradway, R. M., and R. W. Cass, Fractional Efficiency of a Utility
Boiler Baghouse. Nucla Generating Plant. NTIS Document No. PB 246641,
August 1975.
6. Gordon, G. E., W. H. Zoller, and E. S. Gladney, "Abnormally Enriched
Trace Elements in the Atmosphere," presented at the 7th Annual Con-
ference on Trace Substances in Environmental Health, University of
Missouri, Columbia, Missouri, June 1973.
7. Bozeka, C. G., "Nashville Incinerator Performance Tests," in Proceedings
of the National Waste Processing Conference. Boston, Massachusetts,
May 1976.
8. Kaplan, L., and P. Franconeri, "Determination and Evaluation of Stack
Emissions from Municipal Incinerators," presented at the 68th Annual
APCA Meeting, Boston, June 1975.
9. Jackson, J. W., A Bioenvironmental Study of Emissions from Refuse De-
rived Fuel, Prof. Report No. 76M-2, Project No. AAF-520, USAF En-
vironmental Health Laboratory, January 1976.
50
-------
10. Galeski, J. B., and M. P. Schrag, Performance of Emission Control De-
vices on Boilers Firing Municipal Solid Waste and Oil. EPA Report
No. EPA-600/2-76-209, July 1976.
11. Hall, E. H., C. M. Allen, D. A. Ball, J. E. Burch, H. N. Conkle, W. T.
Lawhon, T. J. Thomas, and G. R. Smithson, Jr., Comparison of Fossil
and Wood Fuels. EPA Report No. EPA-600/2-76-056, March 1976.
12. Carotti, A. A., and E. R. Kaiser, "Concentration of 20 Gaseous Chemi-
cal Species in the Flue Gas of a Municipal Incinerator," J. APGA,
22/4), April 1972.
13* Industrial Ventilation, A Manual of Recommended Practice. American
Conference of Governmental Industrial Hygienists, Committee on In-
dustrial Ventilation, Lansing, Michigan, 1974.
14. Eimutis, E. C., Source Assessment; Priortization of Stationary Air
Pollution Sources—Model Description. EPA Report No. EPA-600/2-76-
032a, February 1976.
15. Eimutis, E. C., C. M. Moscowitz, J. L. Delaney, R. P. Quill, and D. L.
Zanders, Air, Water, and Solid Residue Priortization Models for Con-
ventional Combustion Sources. NTIS No. PB-257103, July 1976.
16. Eimutis, E. C., B. J. Holmes, and L. B. Mote, Source Assessment:
Severity of Stationary Air Pollution Sources - A Simulation Approach.
NTIS No. PB-256310, July 1976.
17. MacAdam, W. K., and S. E. Standrod, Jr., "Design and Operational Con-
siderations of a Plant Extracting Energy from Solid Waste for In-
dustrial Uses," presented at ASME Industrial Power Conference, May
1975.
18. Chambliss, C., "Paper on Nashville Testing Experience," presented at
the Engineering Foundation Conference on Present Status and Research
Needs in Energy Recovery from Wastes, Oxford, Ohio, September 1976.
19. Fisher, T. F., M. L. Kasbohm, and J. R. Rivero, "The Purox System" pre-
sented at the National Waste Processing Conference, Boston, May 23-
26, 1976.
20. Private communication with Dr. Charles Moses of Union Carbide at a proj-
ect meeting on the subject program at San Francisco, December 3, 1976,
51
-------
21. Wilson, E. M., and H. M. Freeman, "Processing Energy from Wastes,"
Environ. Science and Tech., 10, (5): 430, May 1976.
22. Private communication with D. J. Lohuis, President, Tech. Air, Chamblee,
Georgia, January 6, 1977.
23. Wilson, E. M., J. M. Leavens, N. W. Snyder, J. J. Brehany, and R. F.
Whitman, Utilization of Wastes as Fossil Fuel Energy^Substitutes.
EPA Contract No. 68-02-2101 to Ralph M. Parsons Company, draft final
report.
24. Knight, J. A., M. D. Bowen, and K. R. Purdy, "Pryolysis--A Method for
Conversion of Forestry Wastes to Useful Fuels," presented at the Con-
ference on Energy and Wood Products Industry, Forest Products Re-
search Society, Atlanta, Georgia, November 1976.
25. Combustion Engineering. G. R. Fryling (ed.), Combustion Engineering
Inc., New York, 1966.
26. Kispert, R. G., S. E. Sadek, and D. L. Wise, "An Evaluation of Methane
Production from Solid Waste," Resource Recovery and Conservation.
1:245-255, 1976.
27. Private communication with Peter Vardy, Waste Management, Inc.,
Oak Brook, Illinois, January 20, 1977.
28. Pfeffer, J. T., and J. C. Liebman, "Energy from Refuse by Bioconversion,
Fermentation and Residue Disposal Processes," Resource Recovery and
Conservation, 1_:295-313, 1976.
29. Private communication with Richard Wocasek, Combustion Power Company,
Menlo Park, California, January 20, 1977.
30. Turner, D. B., Workbook of Atmospheric Dispersion Estimates. Public
Health Service Publication No. 999-AP-26, May 1970.
52
-------
APPENDICES
APPENDIX A. SUMMARY OF SOURCE SEVERITY CONCEPT FOR ENVIRONMENTAL
IMPACT ANALYSIS.
Analysis of the environmental impact of pollutants is hindered by the
lack of well-defined allowable ambient concentrations or population expo-
sure limits. There are several recent reports in the literature that dis-
cuss methods to estimate the impact of pollutants based on some type of
prioritization procedure. *
The impact factor developed by Eimutus ^ is defined as the sum of the
lengths of the individual severity factors associated with the point sources
within the source type. Thus:
Kx r XT . . * -i 1/2
Iv =
(1)
where Ix = impact factor, persons/km^
Kx = number of sources emitting materials associated with
source type x
N = number of materials emitted by each source
P. = population density in the region associated with jth source,
persons/km
IT. . = calculated maximum ground level concentration of the ith
1:1 material emitted by the jth source, g/m3
F- = environmental hazard potential factor of the ith material,
O
X'ij = ambient concentration of the ith material in the region
associated with the jth source
53
-------
S- = corresponding standard for the ith material (used only for
criteria emissions, otherwise set equal to one)
As shown in Eq. (1) the impact factor takes into account various criteria
such as number of sources emitting a pollutant, population density, hazard
potential, ground level and ambient concentrations, etc. The assumptions
and limitations of the model are detailed by Eimutus. ^
A simpler method is identified by Eimutus et al., for determining
the severity of pollutants. For example, the maximum ground level concen-
tration, Xjn-vj for elevated point sources is given by:
where X = maximum ground level concentration, g/rar
TT = 3.1416
e = 2.72
u = wind speed (m/sec) = assumed to be 4.5 m/sec
h = emission height (m)
cz = vertical dispersion coefficient, m
a = horizontal dispersion coefficient, m
Q = emission rate (g/sec)
The average concentration, x> is a function of sampling time, t, and it
can be related to the maximum concentration, X , as follows:
where tj = 3 min
to = reference time period
p = 0.17
54
-------
The source severity(s) is defined as16
s' ? «>
where X = average concentration as defined above
F = hazard potential factor
Using Eqs. (2), (3), and (4) the severity equations for criteria pol-
lutants can easily be developed. Let us take CO as an example.
Since the primary standard for CO is for a 1-hr averaging time, t£
60 rain in Eq. (3). This results in:
0.17
x = Xm ( TO) (5)
Substituting Eq. (2) in Eq. (5)
, ^0.17
2Qo;
rreuh a
In Eq. (6), o- = a because the national atmospheric stability is approx-
imately neutral. This reduces Eq. (6) to
Substituting for TT, e, and u in Eq. (7),
- _ (3.12 x 10-2)Q
X (8)
Combining Eqs. (8) and (4),
s = (3.12 x 10 ,)..q
Fh2
55
-------
For the criteria pollutants, F is set equal to the primary standard, which
is 0.04 g/m3 for CO.
(3.12 x 10'2) Qh'2
Then, S = (10)
0.04
Further simplification results in
SCQ = 0.78 QIT2 (11)
Eq. (11) is the severity equation for CO. Similarly, for other cri-
teria pollutants, the severity equations are as follows:16
Particulate, S = 70 Qh~2
SC- , S = 50 Qh"2
25.
NOX, S = 315 Qh"2-1
Hydrocarbons, S = 162.5 Qh~2
To use these equations, only emission rate (g/sec) and emission height (m)
are required.
The severity can also be related to the threshold limit value (TLV).
This relationship is shown below,
X = x * ' (12)
F
TLV{ £-M
, 24/VlOO
Further simplification of Eq. (12) results in:
s = 5.5 Q (13)
(TLV)h2
Eq. (13) requires knowledge of TLV in addition to emission rate and emis-
sion height. For criteria pollutants, ambient air standards have been es-
tablished. Therefore, TLV was not needed. If the emission height is as-
sumed constant for pollutants from the same source, which is logical, then
Eq. (13) reduces to:
56
-------
c
S = - (14)
TLV
where K is a constant. In effect, Eq. (14) is the same as comparing emis-
sion rate with TLV.
For water effluents, the severity criterion could probably be repre-
sented as:
50
For solids discharge, the severity equation should probably include a
"leachability" factor. Information is limited at the present time to
develop and test a hypothetical severity equation for solids based on leach-
ability.
57
-------
APPENDIX B
ILLUSTRATION OF ENVIRONMENTAL IMPACT ANALYSIS
The Purox system was arbitrarily chosen for this illustration, but the
same approach can be used for other waste conversion systems. Pollutant
concentrations from Purox effluent streams were estimated based on avail-
able data and engineering analysis. The resulting values were then com-
pared with the TLV's to determine which of the pollutants have the most im-
pact. The methodology used in this approach is detailed below.
To estimate the concentration of pollutants from the Purox process, we
first had to identify pollutants from such systems. The following list of
pollutants are documented in the literature as being present in refuse or
are suspected to be in refuse because of their production and consumption
patterns. This list is by no means final and is merely intended to illus-
trate the estimation procedure used in this analysis.
Acrylonitrile
Aldrin/dieldrin
Aluminum
Antimony
Arsenic
Asbestos
Barium
Beryllium
Bismuth
Boron
Bromides
Cadmium
Calcium
Carbon
Cerium
Cesium
Chlorides
Chromium and compounds
Cobalt
Copper and compounds
Cyanides
DDT and metabolites
Dichlorobenzene
Dysprosium
Erbium
Europium
Fluorides
Gallium
Gadolinium
Germanium
Gold
Hafnium
Indium
Iodides
Iridium
Iron
Lanthanum
Lead
Lithium
Lutetium
Magnesium
Manganese
Mercury
Molybdenum
Neodymium
Nickel
Niobium
Nitrogen oxides
Osmium
Oxygen
Palladium
Phosphorus
Phthalate esters
Platinum
Polychlorinated biphenyls
Praseodymium
Rhenium
Rhodium
Rubidium
Ruthenium
Samarium
Scandium
Selenium and compounds
Silicon
Silver
Sodium
58
-------
Stronitium Tin Vanadium
Sulfur Titanium Vinyl chloride
Tantalum Thorium Ytterbium
Tellurium Toluene Yttrium
Terbium Tungsten Zinc
Thallium Uranium Zirconium
Based on analysis of refuse performed in the St. Louis, study,2 we were
able to identify concentrations for some of the pollutants listed. We as-
sumed these values to be representative for RDF in general and computed the
hourly rates of these pollutants entering the Purox process at a refuse feed
rate of 9.07 Mg/hr, as shown in Table B-l.
The major assumption made in the analysis is that all of the pollutants
are contained in the gas stream. This assumption may not be very realistic;
nonetheless, it provides a worst case for consideration and is the most con-
servative. The next step is to compute, from the hourly rate of incoming
pollutant, the pollutant concentration in the flue gas stream leaving the
combustor that burns the fuel gas from the Purox system.
To do this, an estimate of the dry flue gas per kilogram of fuel is
required. Figure B-l is a schematic showing the fuel gas produced per Mega-
gram of refuse and the approximate composition of the fuel gas. Based on
this composition, the molecular weight of the fuel gas and the resulting gas
volume per Megagram of fuel gas combusted, at 30% excess air, were computed*
These computations are shown in Tables B-2 through B-4. The main item from
these tables that is required for the analysis is the volume of dry flue gas
generated per Megagram of fuel gas combusted. This value is found to be
35,418 m3 for 6.3 Mg of fuel gas (or 9.07 Mg of refuse). Using this rela-
tionship and the incoming pollutant rates from Table B-l, the pollutant con-
centrations in the flue gas (in |j,g/m3) were calculated. These data are shown
in Table B-5. A dilution factor of 1,000 was further assumed, and the re-
sulting concentrations were compared to the TLV for the various pollutants.
Table B-5 also shows 1/10 and 1/100 of the TLV values to be more conserva-
tive.
A comparison of the pollutant concentration in flue gas at a dilution
of 1,000 with 1/10 and 1/100 of the TLV for the specific pollutant shows
that several pollutants may be of little concern. (A dilution factor of
1/1,000 was used to compute the maximum ground level concentration. Dilu-
tions of 1/10 and 1/100 of the TLV were estimated to account for a 40-hr
work week and to render the comparison more conservative.) The pollutants
whose concentrations are higher than 1/10 and 1/100 TLV and which may be of
greater concern are shown 'separately in Table B-6.
59
-------
TABLE B-l. CONCENTRATION OF POLLUTANTS IN REFUSE
El ement /compound
Amount contained
in refuse^
(M
(except as otherwise noted)
Kg/hr in feed
(at 9.07 Mg/hr feed rate)
Acrylonitrile
Aldrin/dieldrin
Aluminum
Antimony
Arsenic
Asbestos
Barium
Beryllium
Bismuth
Boron
Bromine
Cadmium
Calcium
Cerium
Cesium
Chlorine
Chromium and compounds
Cobalt
Copper and compounds
Cyanides
DDT and metabolites
Dichlorobenzene
Dysprosium
Erbium
Europium
Fluorides (Fl)
Gallium
Gadolinium
Germanium
Gold
Hafnium
Indium
Iodides (iodine)
Iridium
Iron
Lanthanum
Lead
Lithium
> 1%
86
22
1,967
0.26
9.3
2.77
58
28
> 1%
67
2.6
2,233
1,993
330
2,867
4.9
0.47
1.10
467
12
0.62
3.30
5.1
0.53
> 1%
36
2,167
106
0.78
0.198
17.703
0.002
0.084
0.025
0.522
0.252
0.603
0.023
20.097
17.937
2.97
25.803
0.044
0.004
0.0099
4.203
0.108
0.0056
0.0297
0.0459
0.0048
0.324
19.503
0.954
60
-------
TABLE B-l. (Continued)
Amount contained
in refuse^
(lig/g) Kg/hr in feed
Element/compound (except as otherwise noted) (at 9*0.7 Mg/hr feed rate)
Lutetium 1.0 0.009
Magnesium > 0.83%
Manganese 773 6.957
Mercury
Molybdenum 44 0.396
Neodymium 15 0.135
Nickel 827 7.443
Niobium 15 0.135
Nitrogen oxides
Osmium
Palladium
Phosphorus > 0.5%
Phthalate esters
Platinum
PGB
Praseodymium 5.7 0.051
Rhenium
Rhodium
Rubidium 78 0.702
Ruthenium
Samarium 2.7 0.024
Scandium 1.5 0.0135
Selenium and compounds 3.8 0.0342
Silicon > 1%
Silver 7.1 0.0639
Sodium -* 1%
Strontium 587 5.283
Sulfur > 1%
Tantalum 0.63 0.0057
Tellurium
Terbium 0.73 0.0066
Thallium 0.16 0.0014
Tin 130 ^ 1."
Titanium > 0.83% ~
-m. • 56 0.0504
Thorium -)»°
Toluene " ~ n
101 0.909
Tungsten J-UJ-
TT A 9
Uranium ^»^
61
-------
TABLE B-l. (Concluded)
Amount contained
o
in refuse
(|ig/g) Kg/hr in feed
Element/compound (except as otherwise noted) (at 9.07 Mg/hrfeed
Vanadium 35 ' 0.315
Vinyl Chloride
Ytterbium 2.8 0.025
Yttrium 19 0.171
Zinc 4,833 43.497
Zirconium 301 2.727
62
-------
0.9 Mg
Refuse
0.18 Mg
Oxygen
FURNACE
0.909Mg Gas,
0.63 Mg
^ •
Fuel Gas
Fuel Gas Composition
(% by Volume)
CO
CO2
H2
CH4
40
23
26
5
5
GAS
CLEANING
TRAIN
0.027MgOil
N2
^0.252 Mg
Wastewater
0.l98Mg
Sterile Residue
Figure B-l. Purox system - typical inputs/outputs.
-------
TABLE B-2. COMPUTATION OF FUEL GAS MOLECULAR WEIGHT
Fuel
gas
CH4
C2H6
H2
CO
C02
N2
% by
volume
5
5
26
40
23
1
Mole per mole
of fuel3
0.05
0.05
0.26
0.40
0.23
0.01
1.00
Molecular
weights
16 -
30
2
28
44
28
Total
Fuel gas
molecular weight
0.80
1.50
0.52
11.20
10.12
0.28
24.42
a Molecular weight of fuel = 24.42.
TABLE B-3. MOLE OF COMBUSTION PRODUCT PER MOLE OF FUEL
Item
Fuel gas:
CH4
C2H6
H2
CO
co2
N2
02 from
Combustion product
02 C02 H20
0.05 x 2 = 0.10 x I = 0.05 x 2 = 0.10
0.05 x 3.5 = 0.175 x 2 = 0.10 x 3 = 0.15
0.26 x 0.5 = 0.13 - x 1 = 0.26
0.40 x 0.5 = 0.20 x 1 = 0.40
0.23 — 0.23
0.01
0.605
N2
—
—
—
0.01
.__
theoretical air
N2 from — — — — 0>605 x 79/21
theoretical air = 2.276
Products at 07, — 0.78 0.51 2.286
excess air
30% excess air 0.1815 - - Q.683
Products at 0.1815 0.78 0.51 2.969
30% excess air
64
-------
TABLE B-4. COMPUTATION OF GAS VOLUME PER POUND OF FUEL GAS COMBUSTED
Item
Computation
Total air supplied
Total dry products
drv flue gas
lb fuel
....
3°° F'
Dry flue gas/0.9 Mg of fuel
Dry flue gas/6.3 Mg of fuel
= 0.787 x 100/21 = 3.748 mole
= 0.1815 + 0.78 + 2.969 = 3.931 mole
ft
_ 3.931 x 555
24.42
= 89.341 ft3
= 89.341 x 2,000 ft3
= 89.341 x 2,000 x 7 ft3
= 89.341 x 2,000 x 7 x 0.028317 m3
= 35,418 m3
65
-------
TABLE B-5. COMPARISON OF POLLUTANT CONCENTRATIONS WITH TLV OF POLLUTANT
Cone entration
in flue gas
E 1 ement /c ompound (mg/m3J
Acrylonitrile
Aldrin/dieldrin
Aluminum
Antimony
Arsenic
Asbestos
Barium
Beryllium
Bismuth
Boron
Bromine
Cadmxum
Calcium
Cerium
Cesium
Chlorine
Chromium and compounds
Cobalt
Copper and compounds
Cyanides
DDT and metabolites
Dichlorobenzene (ortho )
Dysprosium
Erbium
Europium
Fluorides (F)
...
22.05
5.641
...
504.33
0.066
2.384
0.710
14.87
7.179
17.1788
0.666
572.54
511.00
84.61
735.098
_..
1.256
0.1205
0.282
119.738
Concentration TLV for
with dilution of element
1,000 (mg/m3) (mg/m3)
...
...
0.022
0.005
...
0.5
0.00006
0.002
0.0007
0.014
0.007
...
0.017
0.0006
0.57
0.51
0.084
0.735
0.001
0.0001
0.0002
0.119
...
0.5
0.5
...
0.5
0.002
0.70
0.20
5 (as CaO)
3
0.5
0.1
0.1
5
1
300
...
2.5
1/10 of TLV
(mg/m )
...
0.05
0.05
...
0.05
0.0002
___
0.07
0.02
0.5
0.3
0.05
0.01
0.01
0.5
0.1
30
0.25
1/100 of TLV
(mg/m3 )
...
0.005
0.005
0.005
0.00002
...
0.007
0.002
0.05
...
0.03
0.005
0.001
0.001
0.05
0,01
3
...
0.025
-------
TABLE B-5. (Continued)
E 1 ement /coiaoound
Gallium
Gadolinium
Germanium
Gold
Hafnium
Indium
Iodides (iodine)
Iridium
Iron
Lanthanum
Lead
Lithium
Lutetium
Magnesium
Manganese
Mercury
Molybdenum
Neodymium
Nickel
Niobium
Nitrogen oxides
Osmium
Palladium
Phosphorus
Phthalate esters
Platinum
PCS
Praseodymium
Rhenium
Concentration
in flue gas
(me/m^ )
3.0768
0.16
0.846
...
1.308
...
0.136
...
...
9.23
555.62
27.18
0.256
198.20
11.282
3.846
212.04
3.846
...
...
...
...
1.46
Concentration TLV for
with dilution of element 1/10 of TLV
1.000 (me/m3) (me/m3 ) (me/m3)
0.003
0.0002
0.0008
...
0.001
...
0.0001
...
—
0.009
0.555
0.027
0.0002
...
0.198
0.011
0.003
0.212
0.003
___
...
...
...
0.001
...
—
...
0.5
0.1
1
...
1
...
0.15
0.025 (hydride)
...
10 (MgO)
5
0.05
5 (sol. compd.)
1
...
9 (N02)
...
0.1
0.002
0.5
-—
0.05
0.01
0.1
...
0.1
...
0.015
0.0025
...
1
0.5
0.005
0.5
...
0.1
...
0.9
...
0.01
...
0.0002
0.05
.—
...
1/100 of TLV
(me/m )
...
0.005
0.001
0.01
0.01
—
0.0015
0.00025
...
0.10
0.05
0.0005
0.05
...
0.01
...
0.09
...
...
0.001
— __
0.00002
0.005
...
...
-------
TABLE B-5. (Concluded)
oo
E 1 ement /compound
Rhodium
Rubidium
Ruthenium
Samarium
Scandium
Selenium and compounds
Silicon
Silver
Sodium
Strontium
Sulfur
Tantalum
Tellurium
Terbium
Thallium
Tin
Titanium
Thorium
Toluene
Tungsten
Uranium
Vanadium
Vinyl chloride
Ytterbium
Yttrium
Zinc
Zirconium
Concent rat i on
in flue gas
(me/nr^ )
19.999
...
0.692
0.385
0.974
...
1.82
...
150.51
...
0.162
0.187
0.041
33.33
1.436
...
25.9
1.077
8.97
...
0.718
4.87
1,239.6
77.69
Concent rat ion
with dilution of
1,000 (me/m3)
0.019
___
0.0006
0.0003
0.0009
...
0.0018
0.15
...
0.00016
0.00018
0.00004
0.033
0.0014
...
0.0259
0.001
0.008
0.0007
0.004
1.239
0.077
TLV for
element
(mg/m )
0.1
___
___
...
...
0.2
10
0.01
...
__.
5
0.1
__.
0.1
2
375
1 (sol. form)
0.2
0.5
510
1
1 (ZnCl2)
5
1/10 of TLV
(me An )
0.01
...
...
...
0.02
1
0.001
...
0.5
0.01
0.01
0.2
37.5
0.1
0.02
0.05
51
...
0.1
0.1
0.5
1/100 of TLV
(mp/m )
0.001
...
...
0.002
0.1
0.0001
...
___
0.05
0.001
...
0.001
0.02
...
3.75
0.01
0.002
0.005
5.10
...
0.01
0.01
0.05
-------
TABLE B-6. POLLUTANTS WHOSE CONCENTRATIONS IN FLUE GAS (AFTER DILUTION BY
A FACTOR OF 1,000) EXCEED 1/10 AND 1/100 OF TLVa
Pollutants with
concentration
> 1/10 TLV
Pollutants with
concentration
-> 1/100 TLV
Barium
Chlorine
Chromium and compounds
Cobalt
Copper and compounds
Lead
Lithium
Nickel
Silver
Zinc
Antimony
Barium
Bromine
Cadmium
Chlorine
Chromium and compounds
Cobalt
Copper and compounds
Fluorides
Lead
Lithium
Manganese
Nickel
Silver
Tin
Tungsten
Vanadium
Zinc
Zirconium
a See Table B-5.
The above approach is conservative and might include assumptions that may
not be wholly applicable. (The use of the TLV as a measure of pollutant haz-
ard is perhaps the most controversial assumption. However, it could serve as
a framework in which pollutants can be rank-ordered according to their tox-
icity. [See Environmental Science & Technology, p. 246, March 1977.]) In the
absence of measured data, the approach used could serve as a useful approxi-
mation to assess pollutant impacts. This type of approach can be particu-
larly useful if it becomes necessary to focus on selected trace pollutants
that are considered potentially hazardous.
69
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/7-77-091
3. RECIPIENT'S ACCESSIOI*NO.
4. TITLE AND SUBTITLE
Environmental Assessment of Waste-to-Energy Processes:
Source Assessment Document
5. REPORT DATE
August 1977 issuing date
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
K. P. Ananth, L. J. Shannon, M. P. Schrag
8. PERFORMING ORGANIZATION REPORT NO
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Midwest Research Institute
Kansas City, Missouri 64110
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
EPA 68-02-2166
12. SPONSORING AGENCY NAME AND ADDRESS
Industrial Environmental Research Lab.-Gin. OH
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
13. TYPE OF REPORT AND PERIOD COVERED
— Interim
14. STOroSTORTNG AGENCY CODE
EPA/600/12
15. SUPPLEMENTARY NOTES
EPA Project Officer - Harry M. Freeman - 513/684-4363
16. ABSTRACT
This source assessment document is the first publication on the subject
program and it is intended to present what is currently known on emissions and
emission control techniques in waste-to-energy conversion systems. This report
discusses constituents in solid waste primarily with the idea of illustrating the
diverse nature of the feedstock used in such systems. Also presented is an environ-
mental impact analysis based on the contribution of each waste-to-energy conversion
system to criteria and other major pollutants. Where emission data were lacking,
engineering judgment was used to identify probable levels. A simplified methodology
for a preliminary environmental assessment is illustrated. An overview of each of
the waste-to-energy conversion systems including their pollution potential and
applicable control technology is also contained in this document. The stat> : f such
systems as well as their locations, capacities and processing steps involved is
identified, to the extent possible.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS C. COSATI Field/Group
Pollution
Assessments
Solid Waste
Data Acquisition
Environmental Assess-
ment
Wastes as Fuel
Energy Sources
13B
14B
10B
12A
8. DISTRIBUTION STATEMENT
Release unlimited
19. SECURITY CLASS (This Report)
Unclassified
21. NO. OF PAGES
78
20. SECURITY CLASS (Thispage)
22. PRICE
EPA Form 2220-1 (9-73)
TO
•t, U.S. GOVERNMENT PRINTING OFFICE; 1977- 757-056/6525
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