United States
Environmental Protection
Agency
Air and Energy Engineering
Research Laboratory
Research Triangle Park NC 27711
Research and Development
EPA/600/S9-86/029 Mar. 1987
&EPA Project Summary
Proceedings: 1986 Joint
Symposium on Dry SO2 and
Simultaneous SO2/NOX
Control Technologies
Richard D. Stern and George R. Offen
The 1986 Joint Symposium on Dry
SO2 and Simultaneous SO2/NOX Con-
trol Technologies was held in Raleigh,
North Carolina, June 2 through 6,1986.
Forty-nine papers were presented by
EPA and EPRI staff members, repre-
sentative of utility companies, equip-
ment manufacturers, sorbent suppliers,
and research and development com-
panies under contract to EPA, EPRI,
and other research groups. Additionally,
researchers from Austria, Canada, Fin-
land, the Federal Republic of Germany,
and the Netherlands presented informa-
tion on world wide technological devel-
opments in dry SO2 control. Specific
topics discussed included enhanced
sorbent utilization through thermal pro-
treatment of sorbents or use of hydrated
or promoted calcium-based sorbents,
effects of temperature and other injec-
tion parameters on sulfur capture ef-
ficiency, economics of dry sorbent
injection, post-furnace injection for SO2
control, effects of dry sorbent injection
processes on electrostatic precipitator
performance, waste management op-
tions, and the global status of com-
mercial-scale dry sorbent injection
processes.
This Summary contains abstracts of
the 49 technical papers presented at
the Symposium and 3 unpresented
papers distributed at the meeting.
Abstracts denoted by an asterisk (*)
describe research wholly or partially
funded by EPA and have been reviewed
in accordance with EPA peer and ad-
ministrative review processes.
This Project Summary was developed
by EPA's Air and Energy Engineering
Research Laboratory, Research Triangle
Park, NC, to announce key findings of
the symposium that Is fully documented
in two separate volumes (see Project
Report ordering information at back).
Introduction
The 1986 Joint Symposium on Dry S02
and Simultaneous SO2/NOX Control
Technologies was held in Raleigh, North
Carolina, June 2 through 6, 1986. This
symposium, jointly sponsored by EPRI
and EPA, was the second meeting of its
kind devoted solely to the discussion of
emissions control processes based on
dry injection of calcium or sodium
sorbents to meet S02 and NOX regulations
for coal-fired power plants. Specific topics
discussed included enhanced sorbent
utilization through thermal pretreatment
of sorbents or use of hydrated or promoted
calcium-based sorbents, effects of tem-
perature and other injection parameters
on sulfur capture efficiency, economics
of dry sorbent injection, post-furnace
injection for SO2 control, effects of dry
sorbent injection processes on electro-
static precipitator performance, waste
management options, and the global
status of commercial-scale dry sorbent
injection processes.
Forty-nine papers were presented by
EPA and EPRI staff members, representa-
tives of utility companies, equipment
manufacturers, sorbent suppliers, and
research and development companies
-------
under contract to EPA, EPRI, and other
research groups. Additionally, research-
ers from Austria, Canada, Finland, the
Federal Republic of Germany, and the
Netherlands presented information on
worldwide technological developments in
dry S02 control.
Symposium cochairmen were George
R. Offen, Project Manager in the Air
Quality Control Program of EPRI's Coal
Combustion Systems Division; and
Richard D. Stern, Chief of the LIMB
Applications Branch of EPA's Air and
Energy Engineering Research Laboratory.
Participants in the introductory session
included keynote speaker John Riggs,
Staff Director of the U.S. House of Repre-
sentatives Subcommittee on Fossil Fuel
and Synthetic Fuels; and William
Holewinski, Director of Generating Station
Engineering at Wisconsin Power and
Light Company, who presented the utility
perspective on acidic deposition control.
Overviews of the EPA and EPRI acidic
deposition control programs were pre-
sented by John Skinner, Director of EPA's
Office of Environmental Engineering and
Technology, and John Maulbetsch, Pro-
gram Manager in the Air Quality Control
Program of EPRI's Coal Combustion Sys-
tems Division, respectively.
The Proceedings of the 1986 Sympo-
sium have been compiled in two volumes.
Volume 1, Sorbents, Process Research,
and Dispersion, contains papers from the
first four sessions:
• Session I: Introduction
• Session II: Sorbents
• Session III: Process Research
• Session IV: Mixing/Dispersion
Contained in Volume 2. Economics,
Power Plant Integration, and Commercial
Applications, are papers presented in the
remaining four sessions:
• Session V: Economics
• Session VI: Post-Furnace SO2
Removal
• Session VI: System Impacts
• Session VIII: Commercial Scale
Applications
Also included in Volume 2 are three
unpresented papers submitted in con-
junction with the Symposium or associ-
ated with a poster session held during
the Symposium.
SESSION I: INTRODUCTION
Chairmen, Richard Stern,
EPA, AEERL, and
George Offen,
EPRI Paper 1A
KEYNOTE ADDRESS
John Riggs,
Fossil and Synthetic
Fuels Subcommittee,
U.S. House of Representatives
This paper presents four political issues
that are of primary importance to most
elected officials in Washington: energy,
security, the environment, electricity
prices and the Federal budget deficit.
Following this, is a summary of how Con-
gress' attempt to reconcile these issues
brought about the creation of the Federal
Clean Coal Technology Reserve. Finally,
the impact of clean coal technologies on
the debate over acid rain legislation is
discussed.
Paper 1B
COAL COMBUSTION
OVERVIEW/TECHNICAL
PERSPECTIVE OF THE
EPA PROGRAM*
John H. Skinner,
Office of Environmental Engi-
neering and Technology,
EPA
This paper presents an overview of the
program being undertaken by EPA in the
area of control technology development
and evaluation for coal combustion pro-
cesses. It presents a perspective on the
Limestone Injection Multistage Burner
(LIMB) program and where it may fit into
a National Acid Rain Control Strategy.
Some of the technical issues which
require resolution are discussed.
Paper 1C
OVERVIEW/TECHNICAL
PERSPECTIVE OF THE
EPRI PROGRAM
John S. Maulbetsch,
Coal Combustion Systems
Division,
EPRI
This paper summarizes the technical
perspective of EPRI's program for dry SO2
control technology research and develop-
ment. The results of research conducted
since 1984 are discussed briefly. The
current EPRI view of the applicability of
dry SO2 control technologies is presented,
particularly in light of proposed acid rain
legislation.
Paper 1D
UTILITY PERSPECTIVE
William Holewinski,
Wisconsin Power & Light
Company
This paper describes the perspective of
Wisconsin Power & Light Company, a
medium-sized utility, on emissions con-
trol regulations and potential control
technologies used to meet them. Of
particular concern is development ol
cost-effective S02, control technologies
that may be applied to smaller, oldei
plants with cyclone-fired boilers. Dr>
sorbent injection is considered a prime
candidate for use in this application.
SESSION II, PART 1:
SORBENTS — SELECTION,
PREPARATION, AND
PERFORMANCE
Chairmen, Brian Gullet,
EPA, AEERL
Paper 2/
PRECALCINATION AND ITS
EFFECT ON SORBENT
UTILIZATION DURING UPPER
FURNACE INJECTION
V. P. Roman,
S. J. Bortz,
R. J. Yang,
KVB, Inc.
P. Flament,
International Flame Research
Foundation, and
G. R. Offen, Electric Power
Research Institute
An experimental program using eigl
sorbents was conducted to determir
optimum methods of producing high su
face area limes and to assess the
potential for achieving high sorbei
utilizations in the 1200°C-9OO°C sulfatic
window. The performance of a fixed b<
calciner operated at 750-800°C and
plug flow reactor operated at 900-920*
were compared on the basis of the surfa<
area produced versus the amount
calcining air on N2 used. The plug flc
reactor proved capable of producing 4
m2/g surface areas from CaC03 sorber
with about 25g air/g sorbent, while
produce a similar surface area with t
fixed bed reactor required an air/sorbe
ratio of 100/1.
The surface areas obtained were r
significantly affected by either the si
-------
bent's trace mineral matter or magnesium
content.
When the high surface area precalcines
were reinjected into a flue gas environ-
ment without SOj at 1100°C, the pre-
calcine was found to quickly (100 ms)
sinter to the surface area generated
within 100 ms when injecting the raw
(uncalcined sorbent) into the same condi-
tions. Sulfation experiments at 1100°C
and a residence time of 0.5 s showed
littler difference between the utilization
levels obtained with 40 mVg precalcines
or raw sorbents.
Paper 2B
PILOT SCALE FURNACE
EVALUATION OF HYDRATED
SORBENTS FOR SO, CAPTURE*
G. C. Snow and
J. M. Lorrain,
Acurex Corporation
S. L. Rakes,
U.S. Environmental Protection
Agency
Several candidate sorbent materials for
the full scale Limestone Injection Multi-
stage Burners (LIMB) demonstration at
Edgewater Station in Ohio were evaluated
in the EPA Innovative Furnace. Measure-
ments of S02 capture were made while
firing at 13.8 kW (47300 Btu/hr) on both
a Pittsburgh No. 8 coal (2.6% sulfur) and
doped natural gas. The sorbent injection
point was at 1200°C. With a furnace
quench rate of 260°C/s, the average
residence time at reaction temperatures
was 1.3 s. At molar Ca/S ratios of 2,
Vicron 45-3 limestone produced at 38%
reduction in S02emissionsfrom baseline
levels. Increased SO2 capture rates,
ranging from 60 to 69% were measured
for various calcitic atmospheric hydrates.
Dolomitic sorbents were able to achieve
captures of 73 to 75% and showed no
significant difference between atmos-
pheric and pressure hydrates. With the
addition of sodium bicarbonate (NaHCOa)
at molar Ca/Na = 15, captures of 83 and
88% were possible for the calcitic and
dolomitic hydrates, respectively.
Paper 2C
DRY SORBENT SO2 CONTROL
FOR NEW POWER PLANTS
BURNING LOW SULFUR
WESTERN COALS
D. P. Teixeria and
T. A. Lott, Pacific Gas and
Electric Company
L. J. Muzio,
Fossil Energy Research
Corporation
The Pacific Gas and Electric Company
is developing a dry calcium-based sorbent
injection S02 control process capable of
high levels of SO2 removal. The target is
95% S02 removal for new power plants
burning low sulfur Western coals. Sor-
bent performance at low sulfur combus-
tion conditions (500 ppm flue gas S02)
has been studied in a 105,000 kJ/hr
(100,000 Btu/hr) gas-fired combustion
reactor. Sorbent utilization was seen to
decrease significantly with decreasing
SO2 concentrations; gas-phase diffusion
is probably the limiting factor. Experi-
mental atmospheric dolomitic and calcitic
hydrates were prepared and tested. S02
removals exceeded those of commercial
materials; 60% removal was achieved at
calcium to sulfur ratios of 2 to 1.
Paper 2D
PHYSICAL PARAMETERS
GOVERNING THE REACTIVITY
OFCa(OH)2WITHSO2*
D. A. Kirchgessner and
B. K. Gullett,
U. S. Environmental Protection
Agency
J. M. Lorrain,
Acurex Corporation
SO2 capture data from bench- and
pilot-scale experiments show that, among
the calcium-based sorbents, Ca(OH)2 is
superior in performance to both CaCO3
and CaO. The available data also show
that hydrates vary in their ability to
capture SO2. A bench-scale atmospheric
hydration process, in conjunction with a
flow reactor for S02 reactivity testing, is
being used to determine the process
parameters and material characteristics
that affect sulfur capture by hydrates.
Thus far the effects of parent lime particle
size and degree of burn, and the hydration
water temperature have been evaluated.
Variations in each of these parameters
appear to be capable of altering the ability
of Ca(OH)2 to capture SO2.
Paper 2E
ENHANCED UTILIZATION OF
FURNACE INJECTED
CALCIUM-BASED SORBENTS
G. F. Weber,
M. E. Codings, and
M. H. Bobman
University of North Dakota
Energy Research Center
Simultaneous control of SOX/NOX
emissions is under investigation at the
University of North Dakota Energy Re-
search Center (UNDERC). Furnace injec-
tion tests have focused on the direct
injection of pressure-hydrated lime fol-
lowed by particulate collection in a bag-
house operated at temperatures of 63 to
149°C. S02 reduction as high as 80%
has been observed for high-calcium
pressure-hydrated lime (PHL) injected at
a Ca/SO2 mole ratio of 2.0 with all of the
S02 capture occurring in the flue gas at
temperatures exceeding 760°C.
Pilot-scale tests have shown that fur-
nace injection of high-calcium PHL at a
Ca/S02 ratio of 1.0 can result in 65 to
70% S02 capture if the baghouse is
operated at 71 °C, approximately 11°C
above the dew point. Improved sorbent
utilization has been observed both for
high-calcium PHL and for additive en-
hanced high-calcium PHL at baghouse
temperatures of 63 to 104°C. Of the 65
to 70% overall utilization, 45 to 50% of
the sorbent was utilized in the upstream
flue gas and an additional 15 to 25% in
the baghouse.
Paper 2F
REACTIVITY OF ATMOSPHERIC
AND PRESSURE HYDRATED
SORBENTS FOR SO2
CONTROL*
J. M. McCarthy,
S. L. Chen,
J. C. Kramlich,
W. R. Seeker, and
D. W. Pershing
Energy and Environmental
Research Corporation
The purpose of this study was to develop
an understanding of the factors that
control the reactivity of hydrated sorbents
toward SO2 in coal fired furnaces. The
study focused on the impacts of the
hydrate properties such as particle size,
surface area, and chemical composition,
and the furnace temperature of the injec-
tion location. Bench- and laboratory-scale
hydrators were used to produce atmo-
spheric and pressure hydrated sorbents,
with parameters pertinent to the hydration
process varied. The chemical and physical
properties were characterized for these
hydrates and several commercially avail-
able hydrates, and they were tested for
SO2 sorption reactivity on bench scale
(17.6 kW) and pilot scale (300 kW)
furnaces.
-------
The results of this study indicated that
pressure hydrates generated under well
controlled conditions were more reactive
than commercially produced atmospheric
hydrates. The important production and
operating parameters for the pressure
hydration process included the size and
composition of the quicklime, the hydra-
tion temperature and pressure, the water
addition, and the pressure progression
during discharge. Comparison of com-
mercial atmospheric hydrates significant
differences in reactivity, ranging from 40
to 58% at a calcium to sulfur molar ratio
of 2. All hydrates, atmospheric and pres-
sure, exhibited a strong dependence
injection temperature.
Paper 2G
SORBENT DEVELOPMENT AND
PRODUCTION STUDIES*
J. P. Gooch, E. B. Dismukes, and
R. Beittel,
Southern Research Institute
J. L. Thompson,
Dravo Lime Company
S. L. Rakes,
U. S. Environmental Protection
Agency
Recent pilot-scale studies have shown
that furnace injection (at temperatures of
approximately 1200°C) of commercially
produced calcitic hydrated lime will pro-
vide calcium utilizations in the range of
25% at Ca/S ratios of 2 to 1. This paper
presents results obtained to date on an
EPA-sponsored project with the objective
of developing calcium-based sorbents
which obtain higher utilizations than
those achieved with commercial hydrated
lime.
Sorbent preparation methods con-
sidered include: 1) production of high
surface area calcines using modified
kilns, 2) production of pressure-hydrated
calcitic limes, and 3) modified hydration
processes. Method 3 was chosen for
laboratory- and pilot-scale studies. Labo-
ratory experiments have produced hy-
drated lime with uncalcined surface areas
in excess of 80 m2/g. Preliminary cal-
cination experiments suggest that these
high surface area hydrates will sinter
more quickly than conventional hydrates
in a furnace environment. Efforts are
underway to produce quantities sufficient
for testing in a 106 Btu/hr (106 kJ/hr)
pilot-scale combustor. Sulfation studies
with coal-firing have been performed with
pressure-hydrated calcitic lime produced
by other laboratories. Results from these
tests are presented, together with results
obtained with several commercial atmo-
spheric hydrates.
SESSION II, PART 2:
SORBENTS - PROMOTERS
AND ADDITIVES
Chairmen, Blair Martin,
EPA, AEERL
Paper 2H
ENHANCED SULFUR CAPTURE
BY PROMOTED CALCIUM-
BASED SORBENTS*
D. M. Slaughter,
S. L Chen, and
W. R. Seeker
Energy and Environmental
Research Corporation
Injection of calcium-based sorbents are
currently being considered as a potential
method of reducing S02 in existing coal-
fired boilers. This study investigated the
ability of small concentrations of additives
to enhance sulfur capture with calcium-
based sorbents. The interaction between
the mineral ash (produced from coal
combustion) and the sorbent/additive
combination was also studied. Two fur-
nace facilities and an X-ray diffractometer
were used in the experimental study. The
furnances used included a 300 kW down-
fired furnace capable of simulating time
and temperature profiles for a variety of
boilers, and a bench-scale drop-tube
furnace.
The results show that calcium-based
sorbents, when in contact with mineral
ash, remove sulfur from the gas phase.
Under combustion conditions envisioned
for application of this technology, con-
tacting between mineral ash and sorbent
was small; therefore, changes in reactivity
of the sorbent were small.
Addition of known promoters with
sorbents has effectively increased sulfur
capture. Both sodium and chromium react
with the calcium to increase the acces-
sibility of CaO sites by particle frag-
mentation, creation of large cracks (or
pores), and the presence of a liquid phase.
In general, iron did not promote an in-
crease in sulfur capture under combustion
conditions in a coal-fired boiler or promote
physical changes in the sorbent.
In general the chromium eliminated by
ash interaction was small, while the ash
effectively prevented a significant portion
of the sodium from contacting and re-
acting with the calcium sorbent. If the
impact of the sodium promoter is to
change the physical characteristics, as
believed, process methods before injec-
tion may be implemented that allow
interaction of the sodium without inter-
ference from the mineral ash.
Paper 21
THE EFFECTIVENESS OF
ADDITIVES FOR ENHANCING
SO2 REMOVAL WITH CALCIUM
BASED SORBENTS
L. J. Muzio,
Fossil Energy Research
Corporation
G. R. Often,
Electric Power Research Institute
A. Boni,
Physical Sciences, Inc.
R. Beittel,
Southern Research Institute
Additives incorporated with calciun
based sorbents have been reported t<
enhance sulfur capture by increasing
mass transport within the sorbent particle
Alkali metal additives can be added to th
sorbent as physical mixtures or incorpc
rated with the sorbent during the hydra
tion process. Another class of additiv
compounds, alcohol water solutions, ca
be used to alter the hydration proces;
producing high surface area hydrate;
This paper focuses on both types (
hydrates. Theoretical considerations <
thermochemistry and vaporization/cor
densation mechanisms helped define th
additives used in the test program. Th
experimental work was carried out in tw
facilities: a coal-fired pilot scale con
bustor, and an intermediate scale con
bustor firing natural gas doped with SO
The experimental results discussed covi
the: 1) relative effectiveness of additive
(sodium, potassium, lithium, cesium, iror
2) method of incorporating the additiv
3) amount of additive, and 4) effect
coal ash. The SO2 removal characterise
of a high surface area (40 mVg) Ca(OK
material produced using alcohol additk
during hydration are also discussed.
Paper:
ALTERNATIVE SO2 SORBENTS
D. O. Ham,
G. A. Simons, and
G. A. Moniz
Physical Sciences Inc.
Sulfur sorption experiments have be
conducted in a fixed bed reactor in ore
-------
to screen potential mineral sorbents for
use downstream from convective super-
heater tubes. All tests were carried out
using a simulated combustion effluent
(74.0% N2, 12.1% C02, 4.6% 02, and
9.2% H20) at 100 kPa pressure, 3000
ppm S02, and in the temperature range
of 400 to 800°C. Four classes of sorbents
have been tested: calcium hydrate, alkali
based (trona), mixtures (alkali promoters),
and mixed cations (shortite and gaylus-
site). Shortite is consistently high over
the temperature range. Trona, gaylussite,
and Colton hydrate promoted by trona
are all very reactive at 800°C but much
less reactive at lower temperatures.
Promotion of Colton hydrate by trona
depends on close physical contact.
SESSION II, PART 3:
SORBENTS —
FUNDAMENTALS
Chairmen, Dennis Drehmel,
EPA, AEERL
Paper 2K
EPA STUDY OF HYDROXIDE
REACTIVITY IN A
DIFFERENTIAL REACTOR*
R. H. Borgwardt,
U. S. Environmental Protection
Agency
K. R. Bruce,
Acurex Corporation
Laboratory investigations of some of
the factors influencing the reactivity of
calcium hydroxides with SO2 are reported.
The materials examined included com-
mercial grade Ca(OH)2, pressure hydrated
Ca(OH)2, analytical grade Ca(OH)2, and
hydroxides prepared in the laboratory
from calcined dolomite and limestone. In
the latter case, the effects of limestone
calcination conditions (time, temperature)
and hydration technique were evaluated.
The methods of hydration included steam
(105 and 200°C) and water slaking. The
effect of S02 partial pressure on reactivity
was measured at 800°C for three types
of Ca(OH)2 over a range of 120 to 7000
ppm. Preliminary tests at 65°C are
reported for hydroxides exposed to SOz
and high humidity for times ranging from
5 to 120 seconds.
Paper 2L
FUNDAMENTAL STUDIES OF
SORBENT REACTIVITY IN
ISOTHERMAL REACTORS*
D. W. Pershing,
G. H. Newton, and
D. J. Harrison,
University of Utah
J. A. Cole,
J. C. Kramlich,
W. R. Seeker, and
G. D. Silcox,
Energy and Environmental
Research Corporation
Three aspects of sorbent reactivity were
investigated in fundamental studies
under isothermal conditions. The first
test series examined the relative reactivity
of a series of limestones, hydrated calcitic
limes, and hydrated dolomitic limes. The
second test series focused on the in-
fluence of particle size on sorbent utiliza-
tion. Precalcined sized carbonates were
sulfated under isothermal conditions. The
results showed that the limitation to large
stone utilization was the pluggage of the
porous structure at the surface caused by
local overutilization of the sorbent. Below
2-5 Aim, all portions of the stone are
equally accessible to the S02, and further
size reductions do not enhance utilization.
In the third series, carefully controlled
isothermal experiments were used to
characterize the CaO + S02 reaction. The
tests were performed on sized, pre-
calcined hydrated lime. The results show
a rapid utilization within the first 100
msec. At longer times a reduction in the
sulfation rate was noted which appears
to coincide with blockage of the
microporosity.
SESSION III, PART 1:
PROCESS RESEARCH
Chairman, George Offen,
EPRI
Paper 3A
A COMPARISON OF
COMBUSTION FACILITIES AND
CALCIUM-BASED SORBENTS
IN TERMS OF THEIR SULFUR
CAPTURE PERFORMANCE*
G. D. Silcox,
R. Payne,
D. W. Pershing, and
W. R. Seeker
Energy and Environmental
Research Corporation
Sulfur capture data from combustion
facilities using dry sorbent injection were
compared. The comparisons were per-
formed in order to determine the similari-
ties and differences between facilities
and to understand the effects of various
reaction parameters. Different sorbents
were also compared in terms of their
capability to capture sulfur. Gaps in data
were identified.
The data and the comparisons were
interpreted with the help of mathematical
models of the sulfation reaction and of
the calcination process. The calcination
model shows that the peak surface area
for hydrates occurs just milliseconds after
injection, while that for carbonates is on
the order of 0.2 second. This difference
may explain, in part, the higher reactivity
of hydrates. The sulfation model incorpo-
rates a nonlinear dependence on SO2
concentration which is understood in
terms of a surface reaction model. The
sulfation and activation models are
combined and used to explain the compli-
cated dependence of capture on injection
temperature and time.
Paper 3B
THERMAL ENVIRONMENT IN A
TANGENTIALLY PULVERIZED-
COAL-FIRED UTILITY BOILER:
COMPARISON OF FIELD TESTS
WITH HEAT TRANSFER
MODELING*
B. M. Cetegen and
W. Richter,
Energy & Environmental Systems
D. G. Lachapelle,
U. S. Environmental Protection
Agency
Effective implementation of the in-situ
desulfurization process in coal-fired
boilers requires a detailed description of
thermal characteristics of the boiler
furnace. This paper discusses the results
of the detailed field tests conducted at a
420 MWe tangentially fired utility boiler
and compares them with predictions
obtained from multi-dimensional furnace
heat transfer models. Results and com-
parisons are reported for two furnace
heat inputs: 1088 MW, (100% load) and
502 MW, (45% load). Sensitivity studies
with the model showed that significantly
accurate predictions of overall thermal
furnace performance require only the
approximate description of furnace flow,
but a realistic estimation of the overall
insulation effect of wall ash deposits.
Paper 3C
EFFECTS OFINJECTON
TEMPERATURE AND QUENCH
ON SORBENT UTILIZATION*
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R. Beittel,
Southern Research Institute
S. J. Bortz,
KVB, Inc.
G. R. Often,
Electric Power Research Institute
D. C. Drehmel,
U. S. Environmental Protection
Agency
Two coal-fired pilot combustors were
used to evaluate the effects of injection
temperature and quench rate on the
utilization of furnace-injected sorbents.
The quench rate was varied from 38 to
316°C/s by load and configuration
changes in one unit, and up to 593°C/s
in the second unit. Limestone and calcitic
and dolomitic hydroxides were tested.
Injection temperature was found to be
the primary effect. Quench rates were
significant only for the calcitic hydroxide
or above 316°C/s; however, increased
quench rate increased the optimum in-
jection temperature
Paper 3D
APPLICATION OF UPPER-
FURNACE SORBENT
INJECTION FOR SO2 CONTROL
IN COAL-FIRED CYCLONE-
EQUIPPED BOILERS
H. Farzan,
L. W. Rodgers, and
G. J. Maringo
Babcock and Wilcox Company
G. R. Often,
Electric Power Research Institute
Upper furnace sorbent injection for SO2
capture was examined utilizing a 6 x 106
Btu/hr (1 7 MWt), cyclone-equipped
boiler simulator The facility has a con-
vective pass to simulate full-scale time/
temperature histories, including quench
rates within the sujfation temperature
window (1260 - 871 °C) of approximately
649°C/s.
Two limestones, one calcitic hydrated
lime, a pressure-hydrated dolomitic lime,
and an atmospheric-hydrated dolomitic
lime were injected at the furnace exit at
1232°C. In-furnace surface area and
porosity measurements were performed
on the sorbents. No correlation between
sulfur capture and calcine surface area
was observed. Despite the rapid quench
rate, more than 50% sulfur capture was
achieved injecting the dolomitic materials
at a Ca/S of 2, independent of the hydra-
tion process Sulfur capture increased
with time due to tube and wall deposits.
The deposits could be removed with in-
creased sootblowing pressure, resulting
in similar recovery of heat flux as obtained
without sorbent.
SESSION III, PART 2:
PROCESS RESEARCH
Chairman, George Often,
EPRI
Paper 3E
CONTROLLING POLLUTANT
EMISSIONS FROM COAL AND
OIL COMBUSTORS THROUGH
THE SUPPLEMENTAL USE OF
NATURAL GAS*
S. L Chen,
J. M. McCarthy,
M. P. Heap,
W. R. Seeker, and
D. W. Pershing
Energy and Environmental
Research Corporation
F. R. Kurzynske,
Gas Research Institute
Natural gas can be used to enhance
the economic acceptability of eastern
coals for power generation under more
stringent environmental regulations. The
sulfur and nitrogen in coal can lead to
emissions of acid rain precursors such as
SO2 and NOX, while the non-hydrocarbon
components in coal affect power plant
performance because of problems as-
sociated with the ash. The application of
technologies which take advantage of
the clean burning qualities of natural gas
offers an attractive and cost effective
option for acid rain precursor control. The
study discussed in this paper focuses on
the use of natural gas as a reburning fuel
combined with sorbent injection for
combined NOX/SO2 control. The work is
supported by the Gas Research Institute
and builds upon DOE/EPA research ef-
forts. Bench and pilot scale tests have
been performed on the natural gas re-
burning/sorbent injection process.
Results obtained indicate that 60% NOX
reduction and 70% S02 reduction can be
achieved when 20% natural gas reburning
is combined with hydrate injection (Ca/S
- 2), under realistic time/temperature
furnace profiles. Reburning with natural
gas was found to have several distinct
advantages over reburning with coal. In
addition, this study has demonstrated the
potential of using natural gas to enhance
calcium utilization.
SESSION IV:
MIXING/DISPERSION
Chairman, Nicholas Kresovich,
EPA, AEERL
Paper 4A
INFLUENCE OF SORBENT
INJECTION AERODYNAMICS
ON SO2 CONTROL
B. M. Cetegen,
T. R. Johnson,
D. Moyeda, and
R. Payne
Energy and Environmental
Research Corporation
Mixing conditions produced by injection
of calcium-based sorbents into large
boiler furnaces can influence the sulfur
removal efficiency. A practical means of
injecting pulverized sorbents into the
furnace flow is by sorbent-laden gas jets
issuing from nozzles on combustor walls.
This paper describes studies on the trajec-
tory and mixing of sorbent jets with the
cross-flow stream of combustion gases
in the upper furnace region of a boiler
Several aspects of the problem are dis
cussed: bench scale isothermal jet mixinc
experiments in boiler upper furnace con
figurations, modeling of jet mixing ir
such geometries, and pilot scale combus
tion tests identifying the effect of mixim
on sulfur removal. Key parameters con
trolling mixing are identified for furnaci
configurations, and a simple integra
model based on mass, momentum, an<
energy conservation is developed fo
predicting jet injection characteristics
The sensitivity of sulfur capture to mixini
conditions is presented for a calciur
hydroxide sorbent.
Paper 4
SORBENT INJECTOR DESIGN
FOR SULFUR OXIDE COA/TflOi
FROM TANGENTIALLY FIRED
FURNACES BY DRY SORBEN7
INJECTION*
R. W. Koucky,
D. K. Anderson,
P. R. Thibeault, and
J. L Marion
Combustion Engineering, Inc.
C. C. Masser,
U. S. Environmental Protection
Agency
-------
Combustion Engineering, Inc., under
Environmental Protection Agency spon-
sorship, is conducting a program to
develop design criteria for injection of dry
sorbents into tangentially fired furnaces
for the control of S02 emissions. The
program includes aerodynamic cold flow
testing and mathematical modeling of
sorbent injection, demonstration testing
of SO2 emission control in a 14.6 MW,
(50 x 106 Btu/hr) tangentially fired test
facility, and pilot-scale testing to evaluate
furnace slagging and fouling behavior
during sorbent injection. This paper
describes initial results of the flow testing
and mathematical modeling. Injector
development testing was conducted in a
large scale cold-flow model which ac-
curately simulates the geometry of a
tangentially fired utility boiler including
the pendant heat transfer surfaces in-
stalled in the sulfur capture temperature
window of the upper furnace. Several
sorbent injector configurations were
tested to optimize injection location and
injection method. The sorbent dispersion
mathematical model uses cold-flow velo-
city and concentration data to aid in the
selection of injector designs for combus-
tion testing, to extrapolate cold-flow dis-
persion results to hot furnace geometries.
Paper 4C
ANALYSIS OF THE SORBENT
INJECTION PROCESS FOR
IN-FURNACE SO2 CONTROL
R. M. Himes and
L. J. Muzio,
Fossil Energy Research
Corporation
G. R. Often,
Electric Power Research Institute
The effectiveness of in-furnace SO2
control is strongly dependent upon a
number of factors which primarily include
the sorbent material used, the injection
location in the furnace, and the degree of
mixing achieved with the combustion
products. The current study is directed
toward establishing a framework for the
design of an in-furnace sorbent injection
system to optimize the dispersion of the
sorbent in regions where mixing will oc-
cur under established temperature condi-
tions. This paper focuses on the use of
empirical correlations and cold-flow
modeling to facilitate the design process.
As the empirical correlations have been
typically developed under the controlled
conditions of a wind tunnel, the cold-flow
model is used to evaluate the correlations
under relatively uniform flow conditions
as well as a more representative furnace
flow field. The simplification of a two-
phase jet into an equivalent gas jet having
a modified density is also evaluated by
comparing the trajectories of single- and
two-phase jets, with identical momentum
ratio found to be the predominant para-
meter governing the penetration and
mixing of the jet under these conditions.
The bulk flow patterns and turbulence
generated under simulated burner flow
conditions, however, significantly im-
pacted the trajectory and mixing of the jet
such that the empirical correlations were
no longer valid.
SESSION V: ECONOMICS
Chairman, Dan Giovanni,
Electric Power Technologies, Inc.
Paper 5A
CONTROL COST MODELING
FOR SENSITIVITY AND
ECONOMIC COMPARISON*
N. Kaplan,
D. G. Lachapelle, and
J. Chappell,
U. S. Environmental Protection
Agency
Using computerized cost models
developed both internally and under con-
tract to EPA by the Tennessee Valley
Authority over a period of several years,
this paper presents costs for utility retrofit
applications of wet flue gas desulfuriza-
tion (FGD), dry FGD, and the limestone
injection with multistage burners (LIMB)
process. Capabilities of the models,
premises, and limits of the sensitivity
study are discussed. Tabular and graphical
presentations of the results are included.
For a base case of 300 MWe boiler size,
2.2% sulfur coal, 50% capacity factor,
intermediate sorbent cost ($71/ton lime
and $15/ton limestone), 1.6 retrofit factor
for FGD systems, and 15 year remaining
unit life, the unit control costs for wet
FGD, dry FGD, and LIMB are $1337,
$1220, and $997/ton of SO2 removed,
respectively. Sensitivity of costs to each
of the above parameters spanning the
base case is presented and discussed.
Unit control costs are developed for all
cases, while capital costs and levelized
annual revenue requirements are also
presented for the base case.
Paper 5B
ECONOMICS OF FURNACE
SORBENT INJECTION FOR SO2
EMISSION CONTROL
P. A. Ireland,
G. D. Brown, and
J. J. Sebesta,
Stearns Catalytic Corp.
M. W. McElroy,
Electric Power Research Institute
The concept of injecting various cal-
cium-based sorbent materials into coal-
fired utility boilers is currently under
development as an option for reducing
S02 emissions from new and existing
power plants. The major incentive for
this development is the anticipated lower
cost of furnace sorbent injection com-
pared to conventional flue gas treatment
technologies and the potential future need
for incremental SO2 control at existing
units.
This paper examines the economics of
furnace sorbent injection for S02 emis-
sion control and the major variables which
impact the overall process economics.
The economics examined focus primarily
on sorbent injection as a retrofit technique
to control SO2 emissions on existing
plants. The major variables found to affect
the sorbent injection economics are
sorbent performance (Ca/S ratio vs SO2
removal), sorbent cost, inflation rate, coal
sulfur content, plant capacity factor, plant
size, and sorbent transportation distance.
Furnace sorbent injection is also com-
pared to wet FGD on a $/ton SO2 removal
overall control cost basis.
Paper 5C
COMPARATIVE COSTS OF
FLUE GAS DESULFURIZATION:
ADVANTAGES OF FURNACE
INJECTION OF PRESSURE
HYDRATED LIME OVER DRY
SCRUBBING
M. H. Bobman and
G. F. Weber,
University of North Dakota
Energy Research Center
T. P. Dorchak,
U. S. Department of Energy
Costs of pressure-hydrated lime injec-
tion (PHLI) for the control of S02 emis-
sions were developed and compared to
lime spray dryer absorbers (SDA) oper-
ating under identical design conditions.
Since 1981, development work, spon-
sored by the U. S. Department of Energy
at the University of North Dakota Energy
Research Center (UNDERC), has focused
on PHLI as a cost effective control method,
producing a dry readily disposable waste
-------
product. In the PHLI process, dry sorbent
is injected into the upper furnace region
and the sulfated paniculate collected in a
downstream baghouse or electrostatic
precipitator. In SDA processes, increas-
ingly used for low sulfur coals, flue gas
S02 contacts lime slurries in large reactor
vessels with subsequent collection of the
dried paniculate in a downstream bag-
house. Therefore PHLI can have decisive
economic advantage over SDA due to the
elimination of complex absorption vessels
and water chemistry, and reactor pres-
sure drop with overall reductions in labor
and water consumption.
To determine the possible cost ad-
vantage of PHLI, costs were developed
for both PHLI and SDA applied to two
divergent baseline case scenarios. In the
first baseline case, a new 500 MW plant,
located in the upper Midwest, firing a low
sulfur (1%) lignite, was considered. A
stringent 90% control target was specified
due to anticipated stricter regulations or
location in a Class I control region. In the
second baseline case, an existing and
easily retrofitable 300 MW plant, located
in the central Midwest, firing a moderate
sulfur (2%) Eastern bituminous coal, was
considered. An incremental 50% control
target was specified primarily in anticipa-
tion of acid rain regulations. The impact
of sulfur content in the coal was assessed
at the 1, 2, and 3% sulfur levels, and for
PHLI, the effect of sorbent utilization rates
was determined at the 25, 50, and 75%
levels For SDA, the sorbent utilization
rate remained fixed at 80% for all cases
evaluated.
The evaluations demonstrated PHLI's
cost-effectiveness over lime SDA over
the entire range of operating conditions
investigated. Under the worst conditions
for PHLI (i e., operating at the larger new
plant, firing a 1 % sulfur coal with a 25%
sorbent utilization), PHLI affords a 25%
savings in levelized revenue over SDA,
for the analogous retrofit conditions, PHLI
produces a 35% savings. When sorbent
utilization rises to 75%, PHLI savings
increase to about 65% of SDA costs for
both new and retrofit designs In absolute
terms, capital costs for retrofit PHLI are
low, ranging closely about $55/kW at
the 50% sorbent utilization rate, for the
new plant, capital costs are more sensitive
to sulfur content, ranging from $33 to
$62/kW at a 50% utilization rate Under
all circumstances, operation and main-
tenance costs dominate, due to the high
sensitivity to sorbent consumption rates,
typically 70% of the total cost for PHLI.
Since the incremental impact of either
process on paniculate collection equip-
ment is site specific, costs of additional
flue gas handling, baghouses, or precipi-
tators have not been entered into the
evaluation.
Paper 5D
ECONOMICS OF SULFUR
REMOVAL USING "DRY"-
CARBONATED TRONA ORE
FGD SORBENT
J. P. Krieg,
G. W. Mortimer, and
L. W. Weiss,
Cogit Consulting Group
A great many potential commercial
sources of sodium are available for use in
dry injection FGD systems The sorption
performance of some of these materials
can be improved by processing prior to
injection Three examples involving raw
trona and dry-carbonated trona sorbents
are compared in this study, serving a
new 500 MW power generating unit and
starting with a selected trona ore f.o.b.
Green River, Wyoming, price of $50/ton
Dry carbonation at the utility site and by a
producer/supplier at Green River are
evaluated separately against the direct
injection of trona ore. The distance
between the utility site and the Green
River source of trona ore was considered.
The results show significantly lower first
year operating costs and lower 30-year
levelized costs for dry-carbonated trona,
and this advantage increases with rail
distance to the power plant from Green
River. The key factors likely to affect this
outlook are discussed.
SESSION VI: POST-FURNACE
SO2 REMOVAL
Chairman, Richard Rhudy,
EPRI
Paper 6A
LABORATORY TESTS ON
FURNACE LIMESTONE
INJECTION AND
DEVELOPMENT OF A SECOND
DESULFURIZATION STEP WITH
FLI ASH THROUGH DUCT
INJECTION
G. Staudinger,
Technical University Graz
H. Schrofelbauer and
H. Meier,
Osterreichische Draukraftwerke
AG
Furnace conditions were simulated in
a laboratory setup by putting single lime-
stone particles with diameters of 3 to
100 /um into a hot flue gas stream for 3 to
20 seconds. The specific surface area
was found to increase with calcination
and to decrease very quickly after passing
a maximum, the latter process being
faster at a higher temperature. Further-
more, single particles were cut into slices
of 2 /jm and analyzed with a raster elec-
tron microscope, and the sulfur distri-
bution throughout the particle was
measured. If limestone particles are
produced from one stone by milling and
fractionation on sieves, the particles with
40 jum diameter will have the smallest
B.E.T. surface area.
Since the utilization of the Ca in the
furnace limestone injection (FLI) ash is
only 10 to 15% and because the Austrian
emission regulations demand (for old
plants) desulfurization rates of 80% and a
maximum SO2 concentration of 800
mg/Nm3 (270 ppm) in the flue gas, simple
FLI will not be sufficient in the future. A
process was developed in which the FLI
ash is separated from the flue gas, milled,
treated with steam and reinjected into
the flue gas duct upstream from the dust
collector. A pilot plant, which processed a
slipstream of 500 NmVh from a cogen-
eration plant was operated for 190C
hours. The results are satisfactory: nc
technical problems were encountered
One project for installation of the process
is underway.
Injection of sodium bicarbonate intc
the flue gas duct was thoroughly in-
vestigated in a 15,000 mVhr pilot plant
more than 80% SO2-removal was founc
with a stoichiometric ratio (Na2/SO2) o
1 The retrofit of a 110 MW plant with
this process is under construction.
Paper 61
REACTIVATION OF SOLIDS
FROM FURNACE INJECTION
OF LIMESTONE FOR SO2
CONTROL*
W. Jozewicz and
J. C. S. Chang,
Acurex Corporation
T. G. Brna and
C. B. Sedman,
U. S. Environmental Protection
Agency
Six different post-furnace injectio
solids and flyash from Hoot Lake Static
8
-------
(Otter Tail Power Company) experiments
have been characterized using scanning
electron microscope (SEM), X-ray powder
diffraction, titration analysis for available
CaO, and ion chromatography. The
samples were tested in a bench-scale
reactor for the removal of S02 from a
mixture of N2 and SO2. Virtually no S02
removal was observed with untreated
solids. However, high SO2 capture oc-
curred when samples were hydrated and
dried prior to S02 exposure. The S02
capture by solids increased with increas-
ing time and temperature of hydration.
For the same time/temperature condi-
tions of hydration, higher S02 capture
was achieved with solids of higher flyash/
sorbent ratio. New crystals (ettringites)
were found in hydrated and dried samples.
The B.E.T. surface area of the solids was
significantly increased by the hydration
process. A possible mechanism of en-
hanced S02 capture by hydration of the
product solids is discussed.
Paper 6C
DRY HYDROXIDE INJECTION
AT ECONOMIZER
TEMPERATURES FOR
IMPROVED SO2 CONTROL
S. J. Bortz,
V. P. Roman, and
R. J. Yang,
KVB, Inc.
G. R. Offen,
Electric Power Research Institute
Bench and pilot testing injecting
hydroxides into temperatures between
427 and 649°C has shown a significant
potential for removing SO2 from a flue
gas stream. The reaction rates of calcium
hydroxide directly with both SO2 and CO2
at around 538°C are significantly faster
than the reaction of CaO with SO2 or CO2
near 1093°C. Hydroxide injection, at a
Ca/S = 1-2 into a pilot combustor
simulating a typical large utility boiler
quench rate of 538°C/s between 649
and 427°C, has achieved calcium utiliza-
tions (predominantly as CaSO3) of 25-
35% with commercially available calcium
hydroxides and 35-45% with specially
prepared high reactivity hydroxides.
The utilization levels achieved in 250
ms residence time near the optimum
injection temperature of 538°C appear to
be determined mainly by the initial
porosity of the hydroxide and the ratio of
CaS03/CaC03 formed during the re-
action. Sorbent preparation methods that
increase the initial hydrate porosity by
1.5 over a normal hydrate have been
identified and found to also yield a greater
ratio of CaSO3/CaC03. Injection of these
special hydrates resulted in a 60% in-
crease in sorbent utilization (to 45%)
compared to commercial hydrates.
Paper 6D
FUNDAMENTAL STUDIES OF
LOW-TEMPERATURE SULFUR
CAPTURE BY DRY CALCITIC
SORBENT INJECTION
W. R. Seeker,
S. L Chen, J. C. Kramlich,
S. B. Greene, and
B. J. Overmoe,
Energy and Environmental
Research Corporation
Three experimental studies were per-
formed to develop fundamental informa-
tion on low-temperature or duct capture
by dry injection of calcitic or dolomitic
sorbents. These were performed for the
Department of Energy's Pittsburgh Energy
Technology Center. The first experiment
simulated the surface of a baghouse upon
which sorbent had collected. Fresh
sorbent was exposed to varying concen-
trations of S02 and water vapor flowing
through a fixed bed. A bench-scale re-
actor was used to define the relative
contribution of dispersed phase and filter
capture. Finally, a baghouse connected
to a pilot-scale furnace was used to
observe baghouse behavior when the
sorbent was collecting during the
experiment.
Paper 6E
SORBENT IMPROVEMENT AND
COMPUTER MODELING
STUDIES FOR COOLSIDE
DESULFURIZATION
H. Yoon,
J. A. Withum,
W. A. Rosenhoover, and
F. P. Burke,
Conoco Coal Research Division
Coolside desulfurization is a retrofit
S02 control technology for coal-fired
utility stations. It consists of dry sorbent
injection and flue gas humidification
downstream of the air preheater. Boiler
lime/limestone injection (BLI) differs in
that the sorbent is injected into the
furnace. Field tests have shown that
Coolside and BLI/humidification can
achieve SO2 removals of 80 and 65%,
respectively, from high sulfur coal flue
gases. For both processes, sorbent utiliza-
tion is the most significant factor in
process economics. In addition, both pro-
cesses benefit from flue gas humidifica-
tion because it enhances the SO2 capture
reactions and the paniculate removal ef-
ficiency if, as is commonly the case, the
station is equipped with an electrostatic
precipitator (ESP). This paper describes
laboratory studies of methods to improve
Coolside and BLI sorbent utilizations
through changes in sorbent properties
and additives, and the use of sorbent
recycle. This paper also describes model-
ing studies conducted to determine nozzle
and humidifier design and operating
parameters, and to identify key design
issues for further development.
Paper 6F
RESULTS OF 1.0 MM BTU/
HOUR TESTING OF HALT
(HYDRATE ADDITION AT LOW
TEMPERATURE) FOR SO2
CONTROL
M. Babu and
R. C. Forsythe,
Dravo Corp.
C. Runyon,
Ohio Edison Company
E. Evans,
U. S. Department of Energy,
Pittsburgh Energy Technology
Center
J. Thompson,
Process Calx, Inc.
SO2 removal efficiencies of 60-70%
upstream of the baghouse can be
achieved for a 3.2% S coal using the
HALT process at a Ca/S of 2.0. Quality
control of the hydrate and uniform dis-
tribution of the sorbent across the duct
cross section is essential. Direct contact
water spray cooling of the gas with the
hydrate feed entering upstream gives high
removals. Removal efficiency with down-
stream injection is more sensitive to
approach to adiabatic saturation and
Ca/S. Cold hydrate feed increases re-
moval efficiency. Addition of NaOH to
spray water is beneficial. Of the hydrates
prepared with additives to hydration
water, methanol-sugar formulation per-
formed the best. Long term testing on a
larger scale is required to determine the
effect of approach to adiabatic saturation
temperature on removal, incremental
removal due to baghouse/ESP, and
-------
factors related to improving equipment
availability. These will be covered on a 5
MW pilot test unit program to follow.
Paper 6G
EPRI PILOT TESTING OF SO2
REMOVAL BY CALCIUM
INJECTION UPSTREAM OF A
PARTICULATE CONTROL
DEVICE
Q. M. Blythe,
Radian Corporation
R. Smith,
Fossil Energy Research
Corporation
M. McElroy and
R. Rhudy,
Electric Power Research Institute
V. Bland and
C. Martin,
KVB, Inc.
EPRI is developing a potentially low-
cost FGD process that involves dry injec-
tion of calcium-based reagents directly
into humidified flue gas upstream of a
paniculate control device. Currently,
process development tests are being
conducted on a 2000 acfm (0.9 amVs)
pilot fabric filter. Tests using an ESP are
also planned. Pilot-scale tests are being
supported by laboratory-scale screening
of the effects of reagent type and pre-
paration techniques. Future process
development efforts will include process
economics, an engineering evaluation of
the feasibility of applying the process to a
larger scale, and process modeling.
Initial process development tests have
been completed, and results are pre-
sented. These tests confirm that the
important performance variables are
Ca/S ratio and approach to adiabatic
saturation Both high calcium and dolomi-
tic hydrates have been studied. The
results also indicate that the use of addi-
tives, the use of high specific surface
area reagents, and sorbent reinjection
may promote greater S02 removals and
increased sorbent utilization.
SESSION VII: SYSTEM
IMPACTS
Chairman, Richard Stern,
EPA, AEERL
Paper 7A
PARTICLE PROPERTIES
RELATED TO ESP
PERFORMANCE WITH
SORBENT INJECTION AND
GAS CONDITIONING
J. L DuBard,
J. P. Gooch, and
R. Beittel,
Southern Research Institute
S. L Rakes,
U. S. Environmental Protection
Agency
G. R. Often,
Electric Power Research Institute
Processes employing dry sorbent in-
jection for S02 control require additional
particulate collection capability in existing
electrostatic precipitators (ESPs). Both
EPA and EPRI are sponsoring research
with the following objectives 1) to
quantify the impact on ESP performance
of various process plans, and 2) to develop
performance upgrading strategies de-
signed to provide cost-effective particulate
control within the constraints imposed by
existing plant configurations
This paper provides results from pilot-
and laboratory-scale measurements of
ash/sorbent particle properties related to
ESP performance. The measurements
were made on particulate matter gen-
erated in a 106 Btu/hr (293 kW) combus-
tor fired on high-sulfur coal, with hydrated
lime injected as a sorbent. The measure-
ments include: 1) dust resistivity obtained
in situ with a point-plane probe, 2) particle
size distributions obtained with cascade
impactors, and 3) the effects of increased
fine particle loadings of ESP voltage-
current relationships. Water vapor and
SO3 were each evaluated as conditioning
agents in situ and in the laboratory A
mathematical model was used to project
ESP performance with flue gas condition-
ing, over a range of SCA values up to 50
mVmVs.
Paper 7B
ELECTROSTATIC
PRECIPITATOR UPGRADES
FOR FURNACE SORBENT
INJECTION
D. J. Helfritch,
P. L. Feldman, and
B. Weinstein,
Cottrell Environmental Sciences
M. W. McElroy,
EPRI
The injection of calcium based sorbents,
such as limestone or calcium hydroxide,
directly into the furnace of coal-fired
boilers is currently under development as
an option for reducing SO2 emissions
from existing power plants. The sorbents
react with SO2 ' i form calcium sulfate
The calcium compounds can increase the
oarticulate loading to a downstream ESP
oy a factor of 2 or 3 and can increase the
resistivity of the particulate by orders of
magnitude. Methods which can be used
to restore ESP performance to pre-
sorbent injection levels are evaluated with
respect to feasibility, effectiveness, and
:ost Methods which are evaluated in-
clude increased collection surface area,
flue gas cooling by water evaporation,
cooling by heat exchange, pulse energiza-
tion, and SO3 conditioning.
Paper 7C
DESIGN CONSIDERATIONS
FOR WASTE MANAGEMENT
SYSTEMS FOR ADVANCED SO,
CONTROL TECHNOLOGIES
A. G. Ektund and
C. M. Thompson,
Radian Corporation
D. M. Golden,
Electric Power Research Institute
H. Ness,
Department of Energy
This paper is a review of waste char
actenstics likely to affect waste handlmc
systems design determined in separate
studies of a) calcium-based furnac<
sorbent injection wastes, and b) sodium
based dry scrubbing wastes Chemica
composition, leaching properties, an<
physical characteristics were determine!
Dy standard methods Areas of concert
that were identified for the calcium-basei
processes include' special handling re
quirements for powdery, alkaline material
high heats of hydration due to unreactei
lime, alkalinity of resultant leachates
large volumes of waste per weight, an<
rapid, flash setting upon exposure t
moisture Characteristics important fc
utilization potential for the calcium-base
wastes were identified as follows: po;
zolanic capability, high surface for re
action if used as reuse sorbent, and hec
generation upon hydration. For th
sodium-based processes, the solubility <
the sodium compounds and lack of coh«
sive strengths were the principal source
of waste management concern. Reger
eration of sodium compounds from tr
dry wastes may be a potential area fi
utilization of by-products from sodiun
based dry scrubbing systems.
Paper 7
ANALYSIS OF LIMB WASTE
MANAGEMENT OPTIONS*
-------
R. S. Dahlin and
C. L. Lishawa,
Southern Research Institute
N. Kaplan,
U. S. Environmental Protection
Agency
This paper presents the results of
laboratory testing and engineering
analyses intended to assess various ap-
proaches to the management of ash/
sorbent waste products from the LIMB
process. The feasibility of conventional
landfill disposal was assessed through
leachate analysis (pH and metals),
permeability measurements, and re-
activity (temperature-rise) studies. Based
on these tests, landfill disposal appears
feasible if the runoff is neutralized and
the temperature rise is controlled. Lab-
oratory tests showed that LIMB ash could
oe mixed with water and pelletized to
make a product suitable for use as ag-
gregate in asphaltic wearing courses.
Pilot combustor studies showed that LIMB
ash could be recycled by hydration and
remjection into the furnace These tests
yielded sulfur captures similar to those of
commercial hydrated lime when com-
pared on the basis of equivalent available
calcium Several ash/sorbent separation
techniques were evaluated including' use
of the existing particulate collector as a
separator, steam treatment for simul-
taneous hydration and separation, inertial
separation, magnetic separation, and froth
flotation The economics of various dis-
posal, utilization, and recycle schemes
are being analyzed using modified ver-
sions of the EPA LIMB cost and recycle
models
Paper 7E
APPLICATION OF SPRAY DRY
PRODUCTS AT THE
SAND-LIME PRODUCTION
P. J. C. Bloem and
B. J. G. Sciarone,
N V KEMA
The application of a fly-ash/spray-dry
product mixture was examined. There-
fore, sand-lime samples with various
quantities of different spray dry products
were prepared on laboratory scale Auto-
claving was performed for 8 hours at
187°C
After that the compressive strength,
the splitting tensile strength, the absorp-
tion coefficient at capillary action, and
the porosity were determined. Further
examination by means of SEM, EDX, and
X-ray diffraction were done.
It appeared that applying fly ash and
spray-dry product as a partial substitution
for sand leads to encouraging results, if
the quantity of spray-dry product in the
fly-ash/spray-dry product mixture is 30%
or less. The best results are obtained if
the ratio of sand and fly-ash/spray-dry
product mixture is about 1.0.
Paper 7F
TVA'S WASTE MANAGEMENT
PROGRAM FOR AFBC ASH
MATERIALS-UTILIZATION/
DISPOSAL
J. L. Harness,
M. W. Milligan, and
K. A. Cruikshank,
Tennessee Valley Authority
The Tennessee Valley Authority (TVA)
is involved actively in the development of
the atmospheric fluidized-bed combustion
(AFBC) technology for use by the utility
industry. As part of this effort, TVA has
instituted a program to develop methods
for the handling, disposal, and/or utiliza-
tion of the unique ash materials produced
by the AFBC process. Discussed will be
the operating and maintenance experi-
ence for the ash handling and disposal
systems of the TVA 20 MW AFBC pilot
plant, the design and development work
for those same systems for the 160 MW
AFBC demonstration plant, and the re-
search and development work underway
on utilization options for the ash
materials.
SESSION VIII:
COMMERCIAL SCALE
APPLICATIONS
Chairman, Michael McElroy,
EPRI
Paper 8A
WALL-FIRED LIMB
DEMONSTRATION DESIGN
FOR OHIO EDISON'S
EDGEWATER UNIT 4*
R. V. Hendriks,
U. S. Environmental Protection
Agency
P. S. Nolan,
Babcock & Wilcox
M. L Kunkle,
Ohio Edison
The paper describes and discusses key
design features of the retrofit of EPA's
Limestone Injection Multistage Burner
(LIMB) system to an operating, wall-fired
utility boiler at Ohio Edison's Edgewater
Station. It further describes results of
pertinent projects in EPA's LIMB program
and shows how these results were used
as the basis for the design of the system.
The full-scale demonstration is expected
to prove the effectiveness and cost of the
LIMB concept for use on large-scale utility
boilers. Final engineering drawings are
now being prepared and the equipment
procured to install the LIMB system on
the Edgewater boiler. System start-up is
scheduled for March 1987.
Paper 8B
RESULTS OF DIRECT
DESULFURIZATION FROM
COMMERCIAL POWER PLANTS
M. Y. Chughtai,
L & C. Steinmuller GmbH
One possible method of sulfur removal
is direct desulfurization sulfur capture
within the boiler itself. The alkalis which
naturally occur in the fuel already capture
a certain proportion of the S02 produced
during combustion and this sulfur capture
can be increased by the injection of suit-
able additives, such as CaC03, Ca(OH)2,
CaC03.MgCO3, and Ca(OH)2.Mg(OH)2, into
the furnace. If the additive employed is
Ca(OH)2 or CaC03/ the initial reaction in
the furnace is the dehydration or decar-
bonation of the additive according to the
following equations:
Ca(OH)2
CaC03
CaO + H20
CaO + C02
Capture of S02 within the furnace itself
and in the downstream parts of the boiler
•s affected by the exothermic hetero-
geneous gas/solids reaction
S02+1/2O2
•CaSO4
The calcium utilization ratio, which cor-
responds to the proportion of injected
calcium actually reacting with the S02, is
the figure which indicates the success or
otherwise of a process For the desul-
furization process to take place at all,
certain preconditions of reaction tempera-
ture and residence time must be met.
Depending on the firing concept, the
additive injection location has to be
selected to achieve a rapid mixing and a
proper time/temperature history of the
additive in the flue gas.
Desulfurization results from different
power plants with different firing systems
will be presented along with the side
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effects of additive injection on the boiler
and its ancillary equipment.
The results achieved so far show that a
desulfurization efficiency of around 60%
at a Ca/S of 2 is possible with Ca(OH)2.
No side effects on power plants are known
so far which could cause operational
problems. Extensive investigations on ash
disposal have shown that the ash from
direct desulfurization is definitely suitable
for land disposal.
The economic advantages of direct
desulfurization are considerable. Additive
consumption and disposal of the ash
represent the greatest operation costs.
Operating costs are a little bit higher than
for wet flue gas desulfurization (FGD),
but the plant costs are only about 10% of
those for the latter. The economic ad-
vantages with direct desulfurization in-
crease as the sulfur content of the coal
and the size of the plant decrease. This
process would seem to be of particular
interest for older power stations where,
for reasons of space, it is impossible to
install FGD equipment but where, in most
cases, it is relatively easy to retrofit the
plants for direct desulfurization.
Paper 8C
FIELD EXPERIENCE WITH
COMMERCIAL FURNACE
LIMESTONE INJECTION
G. Staudinger,
Technical University of Graz
H. Schrofelbauer,
Osterreichische Draukraftwerk
AG
In Austria, eight boilers, ranging from
20 to 330 MWe, having tangential or
wall burners are equipped with furnace
limestone injection. The fuel is local or
imported brown coal.
Operating experience is 1 to 3 years.
Ca/S molar ratios of 3 to 4 give average
sulfur removal rates of 50 to 60%,
depending on the fuel as well as on the
type and size of the furnace.
Some minor problems of operation were
overcome. Surprisingly, the performance
of the electrostatic precipitators was
significantly improved in several instal-
lations. In one particular case the solids
emission was reduced from 180 to 80
mg/Nm3 flue gas by furnace limestone
injection.
Other operating data and experiences
are reported.
Paper 8D
THE TAMPELLA LIFAC SO2
REMOVAL PROCESS
T. Kenakkala,
Tampella Ltd.
M. Suokas and
J. Hautanen,
Tampere University of Technology
Following successful laboratory and
pilot plant tests, a full-scale LIFAC desul-
furization plant was installed at the 250
MWe coal-fired boiler of Inkoo power
plant. Because of simplicity and suitability
of the LIFAC method, the plant was oper-
ating after 6 months.
By means of the LIFAC process a con-
siderable improvement of the reduction
results can be achieved as compared to
limestone injection alone. The test results
show that by the LIFAC process as high a
degree of desulfurization can be reached
as by the wet scrubbing method or the
semi-dry process.
This paper includes results from pre-
vious pilot tests as well as full-scale test
results which have been achieved during
the last few months.
Paper 8E
DEMONSTRATION OF FRONT
END ALKALI INJECTION AND
COMBUSTION MODIFICATION
TECHNIQUES AT BOUNDARY
DAM G.S. UNIT 4- PROGRESS
REPORT
R. Feindel,
C-E Canada Power Systems
D. Gass,
Saskatchewan Power Corporation
This report describes the field experi-
ments which evaluated the effectiveness
of a calcium carbonate and calcium
hydroxide injection system in addition to
combustion system modifications for the
simultaneous reduction of S02 and NOX
emissions. The combustion system modi-
fications consisted of the addition of both
overfire air and concentric firing to the
demonstration unit's tangential firing
system. The effects of this alkali injection
system with combustion modification
techniques on the fouling and slagging
behavior of the furnace were also deter-
mined. Preliminary experimental results
are reported for the injection of two
sorbents, calcium carbonate and calcium
hydroxide, while firing two Saskatchewan
lignites in a 476,190 kg/hr (1.05 x 106
Ib/hr) Combustion Engineering steam
generator. The demonstration plant, con-
sisting of the alkali injection system and
boiler modifications, is described.
Paper 8F
DESIGN AND TESTING OF A
RETROFIT DRY SORBENT
INJECTION SYSTEM ON A 300
MW PULVERIZED FUEL BOILER
D. Cameron and
J. A. Arnott,
Ontario Hydro
Ontario Hydro, as part of its overall
commitment to reduce S02 emissions,
undertook full scale development and
testing of a dry sorbent furnace injection
system. The injection system was retro-
fitted to a 300 MW tangentiafly fired
pulverized fuel boiler with electrostatic
precipitators at the Lakeview Generating
Station in Toronto.
Development of the overall design
parameters and system design of the
sorbent injection equipment, in coopera-
tion with Combustion Engineering anc
GATX-Fuller, occurred from late 1984
until the December 1985 test period.
This paper describes the Lakeview Uni
4 boiler, associated equipment, and the
retrofit injection system. Powdered lime
stone or calcium hydroxide can be injectec
into the furnace at a preselected elevatior
above the burners.
The testing procedures, equipment, an<
test results are described.
The results of the program indicati
that 40% S02 reduction can be achieve!
at partial loads (up to 220 MW) witl
limestone injected at a 3 to 1 Ca/S ratic
Results of calcium hydroxide injectioi
show greater S02 reductions with lowe
Ca/S ratios.
Paper 8(
FULL SCALE DEMONSTRATE
OF DRY SODIUM INJECTION
FLUE GAS DESULFURIZATION
AT CITY OF COLORADO
SPRINGS RAY D. NIXON
POWER PLANT
D. W. Albin and
J. J. Hammond,
FMC Corporation
D. B. Watts and
R. L. Ostop,
Colorado Springs Department o
Utilities
R. G. Hooper,
Electric Power Research Institut
The Department of Utilities of the Ci
of Colorado Springs, Colorado, FM
Corporation, and the Electric Pow
72
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Research Institute are conducting a full-
scale demonstration and test program of
the injection of dry sodium sorbents up-
stream of a fabric filter for SO2 and NOX
removal The program was conducted on
the Unit 1 boiler at the Ray D. Nixon
Power Plant in Fountain, Colorado. This
boiler is rated at 223 MW, fires low-
sulfur western coal, and is equipped with
two reverse-gas-cleaned fabric filters,
each designed to handle 50% of the total
flue gas flow. Sodium-based sorbents
are injected upstream of one of the fabric
filters thus providing a 100+ MW demon-
stration, side-by-side with an identical
fabric filter operating without sorbent
injection
The program consisted of three phases.
Phase I was the initial start-up and char-
acterization of the system. Phase 2 was
the demonstration of 70% S02 removal
on a 30-day rolling average basis using
sodium sesquicarbonate as the sorbent.
Phase 3 consisted of parametric testing
using sodium sesquicarbonate and
sodium bicarbonate as sorbents, as well
as testing the process while burning a
different coal in the boiler
The full-scale demonstration proved
that dry injection of sodium sesquicar-
bonate can consistently and reliably meet
the current federal regulation of 70%
S02 removal. During the 55-day con-
tinuous run to demonstrate 70% S02
removal efficiency on a 30-day rolling
average, the system averaged 74% SO2
removal with better than expected utiliza-
tion of the sodium sesquicarbonate
sorbent. In addition, an unexpected bene-
fit in the operation of the fabric filter was
realized: the injection of sodium sesqui-
carbonate resulted in significantly re-
duced flue gas pressure drop Distribution
of sorbent in the flue gas stream was
shown to be important in achieving maxi-
mum sorbent utilization.
Paper 8H
EVALUATION Of SORBENT
INJECTION TEST AT
TIEFSTACK, WEST GERMANY*
R. Payne and
J. Reese,
Energy and Environmental
Research Corporation
Y. Chughtai,
L & C Steinmuller GmbH
Sorbent injection for S02 control was
evaluated at the Tiefstack Power Station,
Unit 6, located near Hamburg, West
Germany The boiler is tangentially fired
with low sulfur bituminous coal and pro-
duces 160,000 kg/hr (352,000 Ib/hr) of
steam. A temporary sorbent injection
system was installed and operated by the
utility owner. The evaluation involved field
measurements over a 3-week test period
combined with flow and heat transfer
modeling and small scale testing. Results
of the field test showed S02 reductions of
22 and 43% at a Ca/S of 2 for high
calcium limestone and atmospheric
hydrated lime, respectively. Analysis of
the results showed the injection con-
figuration to have minimal impact on
capture, with injection at a furnace gas
temperature of 1520 K and adequate
dispersion of the sorbent.
UNPRESENTED PAPERS
PILOT SCALE STUDIES OF
LIMESTONE INJECTION
PROCESS
M. S. Mozes,
R. Mangal, and
R. Thampi
Ontario Hydro Research Division
The limestone injection process for
SO2 control has been studied at Ontario
Hydro's 620 MJ/h combustion research
facility under conditions simulating the
Lakeview TGS quenching rate. Various
combinations of operating conditions af-
fecting S02 and particulate removal have
been evaluated using a non-porous local
limestone, while burning a 1.7% S eastern
U S. bituminous coal. The program is
aimed at improving the overall efficiency
of sulfur capture and sorbent utilization,
and minimizing the impact of in-furnace
injection on particulate removal by the
electrostatic precipitator (ESP). Process
variables such as limestone injection
location, addition rate, and particle size
have been optimized. Under optimized
conditions, SO2 removal efficiency was
about 43% and sorbent utilization up to
17%. The process produced finer and
about twice as much ash as coal. The
carbon level of the waste on a sorbent-
free basis was about 20%. Resistivity of
the waste ranged between 105 and 106
ohm. cm. The ESP performed with a 10%
reduced efficiency, probably because of
the fineness of the waste and increased
dust loading.
FLUE GAS DESULFURIZATION
BY DRY ALKALINE SODIUM
SORBENT INJECTION USING
AN ELECTROSTATIC
PRECIPITATOR
T. W. Sonnichsen,
J. H. Jansen Company, Inc.
M. J. Pilat and
J. C. Wilder,
University of Washington
Pilot scale tests of flue gas desulfuriza-
tion using the dry injection of sodium
sorbents in combination with an electro-
static precipitator have been conducted
at the University of Washington. The pilot
facility draws flue gas from a pulverized-
coal-fired boiler using low sulfur western
coal. An extended duct arrangement has
been used to provide a residence time of
up to 6 seconds prior to collection in the
ESP.
Test results indicate SO2 removals of
50 to 80% using pulverized sodium bi-
carbonate at a normalized stoichiometric
ratio of 1.0, pilot gas temperature of
204°C, and 300 to 550 ppm S02. Re-
movals were affected by sorbent injection
rate, in-stream residence time, and
sorbent particle size. Sodium sesquicar-
bonate appears to be less effective than
sodium bicarbonate in removing S02
under test conditions.
Essentially all research and develop-
ment activities conducted prior to this
program involved the application of dry
injection in combination with a fabric
filter baghouse. Accumulation of sorbent
material on the baghouse surface was
believed to be necessary to provide an
extended contact and reaction period.
The results of the University's pilot tests
indicate the potential for application of
the dry injection technology to both new
and existing coal-fired boilers equipped
with ESPs. S02 removal rates of 50% and
greater would appear to be possible. Ad-
ditional research will be required to more
completely evaluate the potential of this
technology for higher sulfur coals and
varied flue gas temperatures. It is antici-
pated that more efficient SO2 removal
will be achieved with higher flue gas SO2
concentrations.
The economics of retrofit installation of
the dry injection process to typical in-
dustrial and utility boilers has been briefly
examined. In all cases, installed capital
costs for dry injection are significantly
below those of available alternate tech-
nologies such as spray dryers and wet
scrubbers. Operating costs are strongly
dependent on the price and quantity of
sorbent used. Levelized busbar costs for
dry injection are significantly below those
of alternative technologies for low sulfur
coals. Levelized costs are comparable for
small to intermediate sized utility boilers
13
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with relatively low capacity factors firing
medium (2%) sulfur coals.
RATE CONTROLLING
MECHANISMS OF SULFATION
Girard A. Simons,
Physical Sciences, Inc.
A sulfation model is used to analyze
the S02 sorption data from a wide range
of CaO particle diameters (1 /^m - 1 mm),
SO2 partial pressures (60 Pa to 5 kPa),
and temperatures (973 to 1478 K) An
intrinsic SO2 reaction order of unity has
been validated through fixed bed experi-
ments in the 60 to 300 Pa S02 partial
pressure range, while fluidized bed data
were used to validate the reaction order
from 500 Pa to 5 kPa SO2 partial pressure.
The absolute value of the intrinsic rate
constant and the activation energy
(10,000 ± 1000 K) was derived from data
on small (1 nm) sorbent particles that are
in the limit of kinetic control. Rate limiting
processes include' 1} the filling of the
smallest pores and the subsequent loss
in the internal surface area, 2) the
activated diffusion of the S02 through
the produce deposits, and 3) the loss of
mtraparticle diffusion due to the complete
plugging of the largest pores. It is shown
that the reaction kinetics and the filling of
the smallest pores are generally rate con-
trolling on time scales of 1 to 10s, but
product layer diffusion may become rate
controlling after approximately 100s.
The EPA author R. Stern (also the EPA Project Officer, see below) is with
the Air and Energy Engineering Research Laboratory, Research Triangle Park,
NC 27711; and G. Often is with the Electric Power Research Institute, Palo
Alto, CA 94303.
The complete report consists of two volumes, entitled "Proceedings: 1986 Joint
Symposium on Dry S02 and Simultaneous SOz/NO* Control Technologies:"
"Volume 1. Sorbents, Process Research, and Dispersion," (Order No. PB 87-
120 465/AS; Cost: $30.95)
"Volume 2. Economics, Power Plant Integration, and Commercial Applica-
tions," (Order No. PB 87-120 457/AS; Cost: $48.95)
The above reports will be available only from: (costs subject to change)
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone. 703-487-4650
The EPA Project Officer can be contacted at:
Air and Energy Engineering Research Laboratory
U.S Environmental Protection Agency
Research Triangle Park, NC 27711
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