EPA/600/A-96/106
STATUS OF SULFUR OXIDES CONTROL TECHNOLOGY
Charles B. Sedman
National Risk Management Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711 USA
and
John P. Gooch
Southern Research Institute
P.O.Box 55305
Birmingham, AL 35255 USA
Abstract
The 1995 Sulfur Oxides Control Symposium, co-sponsored by the Electric Power Research
Institute, The U.S. Department of Energy, and the U.S. Environmental Protection Agency,
contained a wealth of technical papers on the current status of sulfur oxides (SOx) control
technology worldwide. The status of key commercial-scale flue gas desulfurization (FGD)
applications in the U.S., Japan, and Europe was documented, with emphasis on wet limestone
scrubbing. Dry FGD, furnace sorbent injection, and combined SO/nitrogen oxide (NOx)
applications were also described. Special sessions were devoted to FGD materials, component
selection, chemical additives, and chemistry. Research programs to improve existing concepts
and develop new approaches were described. This paper summarizes highlights of the above
papers and presentations which have implications toward the Eastern European market for SOx
control. All papers discussed herein are found in the Proceedings to this symposium [1],
Introduction
The opening remarks of the symposium by representatives of the U.S. Department of Energy
(DOE), U.S. Environmental Protection Agency (EPA), and the Electric Power Research Institute
(EPRI) echoed the history of the conference and the flue gas desulfurization (FGD)industry: the
reduced number of vendors and designs, the vast improvement in reliability and cost-effectiveness,
and the shift of markets away from the United States, Japan, and Germany toward Eastern
Europe and Asia. Subsequent sessions focused on the following topics;
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Session 1
Regulatory and Economic Issues
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Session 2
Full-Scale Optimization
0
Session 3
Poster Papers
D
Session 4A
Phase I Start-Ups
D
Session 4B
Dry FGD
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Session 5A
Operating Experiences and Recent Design
0
Session SB
Emerging Processes
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0
Session 6A
Wet FGD Advanced Design Issues
0
Session 6B
Air Toxics
D
Session 7A
Modeling and Fundamental Research
0
Session 7B
Combined SOx/NOx Removal
0
Session 8A
By-products and Wastewater
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Session 8B
Materials for FGD.
Session 1 - Regulatory and Economic Issues
The initial session focused on issues and case studies regarding the U.S. electric utility industry
attempts to comply with acid rain provisions of the 1990 Clean Air Act Amendments. Briefly, the
U.S. Congress mandated that nationwide annual sulfur dioxide (SOj) emissions be reduced from
20 million tons to 10 million tons by the year 2000, by meeting the following goals affecting the
largest sources (261 units at 110 existing power plant sites):
-by 1995, average S02 emissions not to exceed 2.5 lb/106 Btu heat input
-by 2000, average S02 emissions not to exceed 1.2 lb/106 Btu heat input
In order to minimize the cost of compliance with these mandates, U.S. EPA instituted an
emissions trading program, where utilities can voluntarily lower emissions below the levels above,
then claim credits for the difference, and subsequently bank or market these credits to other
utilities.
The first paper discussed the decision of utilities to improve existing FGD scrubbers to generate
credits for non-scrubbed units, switch to lower sulfur fuels, or simply purchase credits from other
utilities. A case study of a 255 MWC plant was presented, in which the scrubber was modified to
allow use of higher sulfur fuels.
The second paper presented some early statistics for utility decisions and economics of some
advanced FGD systems. Of the 89,545 MWe of capacity subject to the new regulations, only 10%
had chosen to install retrofit scrubbing technology. The current S02 trading market has remained
steady with offers to buy ranging from $140 to $150 per ton S02, and offers to sell from $160 to
$200 per ton. Economic evaluations of four new FGD systems were presented: Ammonium
Sulfate with Forced Oxidation, Dow Chemical Organic Solvent Process, AirPol Gas Suspension
Absorber, and the Condensing Heat Exchanger Process.
The last paper in this session focused on upgrading existing scrubbers to provide additional S02
absorption capacity. Options include (a) adding an organic acid buffer, (b) increasing the liquid-
to-gas ratio in the absorber, and (c) installing trays or other mass transfer devices. A case study
was presented for a 203 MWe FGD unit scrubbing a 0.9% sulfur coal rated at 12,400 Btu/lb,
where a combination of organic acid addition and fan modifications appeared to be the most cost-
effective strategy.
Session 2 - Full-Scale Optimization
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The first paper in this session was from a Finnish group describing how limestone blinding
problems were solved at four 260 MWe scrubbers on the south coast of Finland. The problem has
been diagnosed as fly ash adhering to limestone surfaces and hindering dissolution of calcium
species; therefore, several solutions are being considered:
-ESP retrofitting
-hydroclone addition to remove slurry fines
-prescrubber addition
-lime injection upstream of FGD
-conversion to lime FGD
-switching to lower ash fuel.
The second paper discussed the use of by-product sulfur from natural gas processing as an
oxidation inhibitor in natural oxidation FGD units. The concept was tested at bench-scale, small
pilot-scale (0.4 MWe), and full-scale (180 MWe) with successful results.
The third paper discussed the replacement of a packed bed with a sieve tray on a 515 MWe unit,
because of the following problems and considerations:
-scale formation on the packing
-maintenance costs for cleaning and replacing packing
-projected availability of lower sulfur fuel
-unit availability and reliability.
After replacing the packing with trays, S02 removal ranged from 91.7 to 99.9%, and both the
performance and maintenance were improved so that the modification costs are expected to be
recovered in 30 months. Based on this success, the other three units are currently being fitted
with sieve trays.
The next paper detailed the optimization of a dual-alkali scrubber on a 258 MWC boiler to reduce
operating costs. Operating costs were reduced by: (a) adding emulsified sulfur to the system to
reduce sodium sulfate formation; (b) decreasing lime consumption by bypassing part of the
absorber liquid to the thickener; (c) increasing bisulfite regeneration via better pH control; and (d)
optimizing filter cake wash. Additional improvements being considered include conversion to a
magnesium-lime FGD system.
The fifth paper describes the FGD system improvement on a 650 MWt boiler filing 2.4 to 3 .5%
sulfur coal. Four improvement schemes were tested and compared:
-sodium formate addition
-dibasic acid addition
-increasing slurry pH
-increasing liquid-to-gas ratio (L/G).
S02 removal was increased from 80 to 93% by increasing L/G and to 96-97% with both L/G
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increase and buffering additives.
The sixth paper compared the S02 removal of limestone, buffered limestone, and magnesium-lime
slurry FGD systems at a 440 MWe boiler. Both buffered limestone and magnesium-lime FGD
were able to meet S02 levels of 1.2 and 0.8 lb/106 Btu, the two target levels. Magnesium-lime
was judged to be the most cost-effective approach.
The last paper in this session described tests on a 700 MWe unit to determine the cost-
effectiveness of S02 removal using sodium formate buffer. SOz removal was increased from 85 to
97.8% at an estimated incremental cost of $76 per ton of S02 removed.
Session 3 - Poster Papers
The Poster Session at this symposium is a traditional mix of small-scale research, novel
applications, and FGD chemistry/analytical topics. At the 1995 Poster Session, 12 papers were
displayed:
- Simultaneous Desulfurization and Dechlorination of Spent Sorbent Material Derived
from Acid Gas Emission Control
- Study of the Reactivity of Sodium Compounds and Lime towards S02 and NOx
- Measurement of Quartz in Limestone Reagent Used in Gypsum-Producing FGD
Systems
- Performance of Electrostatic Precipitators (ESPs) Operating Downstream from Spray-
Drying Desulfurization Units
- Influence of Aluminum and Fluoride on the Limestone Reactivity in a Wet Limestone-
Gypsum FGD Process and the Influence of Sodium, Calcium, and Magnesium on Both
the Desulfurization and Gypsum Quality
- Dry FGD with High Surface Area Hydrates
- Statistical Analysis of FGD System Operating Costs
- N02 Removal by Hydrated Lime with S02 Present
- Utilization of Atmospheric Fluidized Bed Combustor (AFBC) Waste By-Product as a
FGD Sorbent for Circulating Dry Scrubbing
- Kinetic Approach to S02 Emission Control in Thermochemical and Plasma-Chemical
Processes
- Circulating Fluidized Bed (CFB) Boiler at Gardanne (France)
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- Reducing Mine Subsidence with Fixated FGD Sludge.
Session 4A - Phase I Start-Ups
Session 4A continued the series of wet FGD discussions, with the first paper presenting progress
on the installation of a limestone-forced oxidation scrubber on a two-unit, 441 MWC station which
started up in 1995, The FGD system design was for both boilers to use a common FGD unit with
the following specifications:
Total Capacity
Total Gas Flow
Absorber Type
Dust Collector
FGD Reagent
%S in Coal
Wet S02
Outlet S02
S02 Removal Efficiency
441 MW{
1,864,000 acfm @ 320°F
Open Spray Tower
ESP
Limestone
3.27
6.0 lb/106 Btu
0.24 lb/106 Btu
96%
The second paper offered a similar view of two 1300 MWe units retrofitted with limestone-
gypsum FGD units designed for 95% S02 removal. Initial results showed nearly 98% S02
removal. Absorber design parameters include;
Modules per Unit 3
Gas Flow per Module 2,000,000 cfin
Tower Velocity 8.3-12 ft/s
Tower dimensions 66 ft Dia Base; 60 ft Spray Zone; 119 ft High
Operating system parameters to achieve 95% S02 removal included:
Gas Flow per Absorber 2,251,000 cfin @ 300°F
Temperature Range 270-300"F
Absorber Gas Velocity 10 ft/s
Minimum L/G 54 gal per 1000 acf
Design Coal: 3.5% S
7.7% Ash
12,971 B tu/lb
A third paper presented design details for a 170 MWe wet limestone FGD unit designed for 93%
S02 removal and 70% particle control, producing wallboard gypsum. Substantial discussion of
wastewater treatment to control discharge of heavy metals, acids, and suspended solids was
included.
The fourth paper briefly described a 500 MWe retrofit wet FGD system with limestone forced
oxidation, augmented with organic acid buffering. A future FGD system on an adjacent unit will
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utilize spare absorbers on the 500 MWS FGD unit.
The fifth paper discussed FGD retrofit of two units, 100 MWC and 215 MWe both converted to
Orimulsion, a bitumen-in-water emulsion transported to New Brunswick, Canada, from
Venezuela. The limestone FGD units are designed to remove 90% S02 and have achieved this
during initial operation.
The sixth and seventh papers described the decision-making process for FGD selection involving
two 850 MWe and one 650 MW( limestone forced oxidation units.
Session 4B - Dry FGD
Seven papers in Session 4B covered various dry and semi-dry FGD processes attempting to
compete with wet FGD. The first paper described a furnace limestone injection process from
Austria, where the fly ash and calcined lime are reactivated with steam and then reinjected into the
ductwork. Over 90% S02 removal was reported on laboratory-scale experiments.
The second paper described testing of an in-duct process on a 105 MWe unit, where dry lime and
sodium solution were injected sequentially to achieve 70% S02 removal.
The third paper described a pilot evaluation of ammonia slip effects on a circulating bed dry
scrubber, which concluded that the effects of ammonia-based NOx control on dry lime scrubbers
were positive.
A fourth paper described the results of 1 year of testing a 10 MWe pilot-scale gas suspension
absorber (GSA) lime FGD system. The GSA system performed as well as spray drying, e.g., 90%
S02 removal at a Ca/S ratio of 1.2 and 20 T approach to saturation.
A West German circulating fluid bed FGD system was described on a 220 ton per hour industrial
steam boiler with S02 removal reported up to 97%.
The sixth paper discussed ongoing research at the University of Texas to develop a high surface
area sorbent for S02 from crushed recycled glass and lime.
For the final paper in this session, results from a 180 MWe furnace lime injection process
demonstration were reported. Up to 63% S02 removal and NOx reductions of 42% were
simultaneously achieved with a concentric-fired low NOx burner retrofit combined with furnace
injection of calcium hydroxide.
Session 5A - Operating Experiences and Recent Design
The first paper in Session 5 A highlighted a 2-year 100 MWe demonstration of the Chiyoda CT-
121 limestone scrubber with the jet bubbling reactor. In general, S02 removal exceeded 90% for
S02 inlet concentrations ranging from 1000 to 3500 ppmv when the reactor pressure drop
exceeded 14 in. w.g. Particle removal for the Chiyoda unit typically exceeded 98%.
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Another clean coal demonstration was described in the second paper— that of a Pure Air
limestone wet FGD system handing flue gas from two boilers totaling 528 MWe. A 99.99%
availability was recorded over the first 2 Vz years of operation, and S02 removal averaged 94%.
The third paper reported on the largest wall-fired boiler, 1000 MWe, in Japan fitted with wet
limestone FGD. Two 500 MWC modules have demonstrated 92% S02 removal while producing
98% pure gypsum.
The fourth paper discussed planned new and retrofit FGD units in East Germany for lignite-fired
power plants- 2 x 800 MWC new units at the Schwarze Pumpe station and 3 x 1000 MWe units
at power plant Janschwalde. Both plants will be equipped with limestone-gypsum producing
FGD units, scheduled for start-up in 1996 and 1997.
The fifth paper, from Taiwan, described a magnesium oxide slurry FGD system on a 140,000
Nm3/h industrial boiler (25 MWe equivalent); 95% S02 removal was reported.
A sixth paper discussed design of 4 x 550 MWe FGD units on a Taiwanese power plant and
contrasted the philosophy of international FGD design with U.S. design.
The last paper discussed the rebuilding in 1993 of an FGD unit originally constructed in the 1970s
in Texas, USA, and destroyed by a chimney collapse. The complete rebuild was finished in 17
months.
Session 5B - Emerging Processes
The first paper described a new regenerable S02 absorption process using amine sorbent and
steam stripping to regenerate the sorbent and produce a pure S02 by-product. The technology
has been evaluated on a 2 MWe field slipstream. Greater than 95% S02 removal was reported.
The second paper described the use of condensing heat exchangers with alkali spray gas cooling
to remove S02. Smaller scale tests on various pilot plants demonstrated S02 removal above 95%.
The third paper, from Japan, briefly described a U-shaped duct FGD concept which is under
development. Reductions of40-50% operating costs and 50-90% construction costs below that
for conventional FGD are promised.
The fourth paper discussed small (0.4 MWe) pilot results for a limestone dual-alkali FGD
evaluation. An accompanying cost study was presented comparing costs to wet limestone FGD.
The fifth paper describes a biological FGD system developed in the Netherlands. The concept is a
sodium liquor FGD absorber with two biological reactors which convert sulfites and sulfates to
elemental sulfur. A pilot system (2 MWe) is currently in operation.
The sixth paper presents design, operating, and cost projections for an ammonia-based wet FGD
system on three boilers totaling approximately 350 MWt. By-product ammonium sulfate will be
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produced for agricultural use at $100/ton.
A seventh paper describes a new variation of magnesium-lime FGD where magnesium hydroxide
is added to the process to produce a nearly clear scrubbing liquor. This results in the ability of
magnesium-lime FGD to produce gypsum as a by-product and lower overall costs. Slipstream
test results are presented showing greater than 95% S02 removal.
Session 6A - Wet FGD Advanced Design Issues
The session consisted of papers authored by Babcock & Wilcox Research and Development
Division; Radian Corporation and EPRI, ABB Environmental Systems; Babcock-Hitachi K. K.;
BETE Fog Nozzle, Incorporated; Mitsubishi Heavy Industries, Ltd.; South Carolina Electric and
Gas Co., and Raytheon Engineers and Constructors.
In the first paper of this session, B&W R&D Division described the use of hydraulic models to
identify and resolve design issues. Modeling procedures for scaling the wet scrubber design down
to laboratory size were described, along with validation by comparison with field data. Basic fluid
mechanics theory was used to develop modeling criteria, and to establish the relationship between
full-size field units and laboratory models. A one-eighth scale model was used to verify the
modeling criteria and establish empirical constants to coirelate wet scrubber pressure drop. The
model was then used to study several scrubber design issues.
The second paper of this session was concerned with the effect of high flue gas velocity on wet
limestone scrubber performance. These results were presented by Radian Corporation and EPRI,
and were obtained by operating a countercurrent spray tower at high gas velocity (>10 ft/sec) at
EPRI's Environmental Control Technology Center (ECTC). High gas velocities are of interest
because the compliance options of (a) retrofitting new FGD systems to previously uncontrolled
units, and (b) using existing FGD systems to treat additional, unscrubbed flue gas can both
potentially benefit from operating at higher gas velocities through the scrubber.
Test results indicated that S02 removal efficiency decreased as the gas velocity was increased
from 8 to 12 ft/s at a constant liquid rate. However, increasing the gas velocity from 12 to 15 ft/s
resulted in no additional decrease in S02 removal efficiency. The data also showed that as the
absorber velocity increases, the liquid-to-gas ratio (L/G) in the scrubber can be reduced to achieve
constant S02 removal efficiency. However, the resulting decrease in operating cost due to lower
L/G is partially offset by an increase in pressure drop through the absorber.
The third paper of this session described an evaluation of methods used to measure mist
eliminator carryover for full-scale FGD systems. These tests were also performed at EPRI's
ECTC Facility. Measurement methods evaluated were the phase Doppler particle analyzer
(PDPA), a hot-wire anemometer device, and a magnesium oxide-treated-paper method. The
PDPA method was found to be the most accurate of the three methods, but it was also the most
expensive.
A paper describing an advanced, cost-effective limestone wet FGD was presented by ABB
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Environmental Systems as the fourth paper of the session. This system, designated as the LS-2
System, was described, along with cost projections of the system relative to fuel switching. A
demonstration of the system was scheduled for start-up in mid-1995 at Ohio Edison's Niles
Station.
Babcock-Hitachi K. K. presented a paper describing the development of an economical compact
wet limestone FGD process. Construction costs were said to have been minimized by increasing
gas velocity and by adopting a horizontal flow spray tower instead of the more conventional
vertical flow spray tower. The paper presented features of the compact FGD system, results from
pilot plant tests, and an example design study.
The sixth paper in this session was presented by BETE Fog Nozzle, Incorporated, and described
the effect of intersecting sprays on reported drop size. This effect is of interest because current
design and modeling practices incorporate data based on single nozzle tests with the assumption
that such data adequately represent the actual drop size spectrum of the typical closely spaced
nozzle array. The paper details die effects that are produced by intersecting sprays on reported
drop size and spray liquid distribution.
A description of a commercial application of a new type of scrubber, designated as the Double
Contact Flow Scrubber, was presented as the seventh paper by Mitsubishi Heavy Industries. The
scrubbing system was described as being able to obtain high desulfurization and particle capture
efficiency with low power consumption due to highly efficient liquid-gas contact at the liquid
layer.
The final paper of this session described a study performed by Raytheon Engineers and
Constructors to evaluate wet and dry FGD processes at three of South Carolina Electric and Gas
Company's coal-fired plants. The paper indicated that, as a result of the study and other inputs,
the company decided to purchase S02 allowances for the year 2000 and 2001 requirements, but
S02 technologies and compliance strategies will continue to be evaluated.
Session 6B - Air Toxics
The Air Toxics session was initiated with an overall view of "Air Toxics Risk Assessment Results
of a Utility Study" by Leonard Levin ofEPRI. EPRI's integrated assessment of the emissions,
transport, fate, and health effects of trace substances emitted from over 1700 operating power
units at 600 power plants was described. The results indicated that the risk of cancer through air
pathway or inhalation exposure was "well below one in one million for all locations under
'realistic' assumptions." The studies described in the paper were organized through two EPRi
projects: PISCES (Power Plant Integrated Systems: Chemical Emissions Studies), and CORE
(Comprehensive Risk Evaluation).
A characterization of hazardous air pollutant (HAP) emissions at 10 units equipped with both
particulate and S02 control systems was presented in the second paper of the air toxics session.
Results were obtained from field testing activities conducted by EPRI and DOE. Data from the
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field tests indicated that both wet and dry FGD systems provide additional control of trace
elements in the flue gas. Both wet and dry FGD systems effectively removed the acid gas anions,
chloride and fluoride. The results also indicated that the chemical form of mercury is a
determining factor in how much mercury is removed in a wet scrubbing system.
The third paper of this session described the use of an EDV™ system for controlling fine particles
and acid mist from a utility boiler firing residual oil. The evaluation was performed by Florida
Power and Light Corporation (FPL) in cooperation with EPRI and Belco Technologies
Corporation on a full-scale EDV™ module using a slipstream from a 400 MWe wall-fired boiler at
FPL's Sanford Plant. Results from the testing indicated that an EDV™ efficiency of 90% was
achieved, along with particulate emissions of less than 10 mg/Nm3, and sulfur trioxide (S03)
emissions of less than 1 ppmv.
Mercury removal in wet FGD systems was the subject of the fourth paper, which was based on
results obtained by Radian and EPRI at EPRI's ECTC. As indicated in the previous paper
concerning field measurements ofHAPs, this pilot plant study also indicated that the amount of
removal of mercury in a scrubber depends on the chemical form of mercury in the flue gas. The
data indicated that mercuric chloride was efficiently removed in the FGD system, whereas
elemental mercury was not collected. The lack of a validated gas sampling method for speciating
the different forms of mercury in flue gas complicated data interpretation.
The fifth paper of the session described the GE-Mitsui-BF activated coke process for reduction of
gas-phase air toxics from combustion and incineration sources. The process has been installed on
coal-fired boilers and fluidized catalytic cracker units in Japan and Germany.
The sixth paper was presented by ABB Environmental Systems and discussed hazardous air
pollutant removal in FGD systems. The subjects addressed included removal mechanisms,
manipulation of removal mechanisms to achieve more effective control, and advanced add-on
control technologies for improving HAP removal efficiencies.
Wheelabrator Air Pollution Control presented a comparison of the air pollution control equipment
effectiveness on two waste-to-energy facilities in the seventh paper. Pollutants considered
included particulate matter, acid gases, metals, and NOx, Each facility was designed to meet Best
Available Control Technology (BACT) for these classes of pollutants. Both facilities included a
selective non-catalytic reduction system, a two-fluid nozzle spray dryer absorber, and a fabric
filter. One of the installations was also equipped with a powdered activated carbon injection
system for additional mercury removal. Emissions test results and operational experience are
contained in the paper.
The concluding paper of this session discussed S02 and heavy metal capture by calcium-based
sorbents in a coal-fired boiler. The paper describes experiments and results obtained with a
laboratory-scale entrained flow reactor system and a high temperature reactor assembly for
selenium sorption studies.
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Session 7A - Modeling and Fundamental Research
The subject of the first paper of this session is "New Models for FGD Performance, Cost, and
Hazardous Air Pollutant Removal" by Rubin et al., of the Center for Energy and Environmental
Studies at Carnegie Mellon University. The paper presents an integrated modeling framework for
evaluating the cost and performance of power plant emission control systems. A unique capability
is described which allows performance and costs to be modeled probabilistically.
Investigation of optimization and removal enhancement options using EPRI's FGDPRISM model
was the subject of the second paper of this session. A brief update on the status of the model was
presented, along with results from several recent applications.
The third paper of the session dealt with "Development of an On-line Chemical Monitoring
System for FGD Processes" and was authored by representatives of Radian Corporation and
EPRI. This work was performed at an EPR1 facility, and focused on near-continuous
measurements of key chemical parameters. Development activities are presented, along with data
illustrating the reliability and accuracy of the system.
The next paper in the session returned to modeling of wet scrubbing systems and described
ABB's experience with the EPRI FGDPRISM computer model. The paper discussed strengths
and weaknesses of the program in general and presented cautionary steps required to obtain the
best possible results.
Modeling was also the subject matter of the fifth paper, describing assessment of boiler implosion
hazards. PowerGen, under EPRI sponsorship, is developing a program known as DUCSYS as a
dynamic model for general power plant gas systems. The paper described the physical process
involved in an implosion process, the main characteristics of the DUCSYS modeling system, and
an application ofDUCSYS in studying the implosion risks associated with retrofitting an FGD
system to an existing coal-fired boiler.
The sixth paper of the modeling and fundamentals session addressed the issue of nitrogen dioxide
(N02) absorption in limestone slurry. The paper reports on work performed at the University of
Texas at Austin Department of Chemical Engineering. The objective of the work described was
to gain a better understanding of the reaction kinetics, whereas the ultimate objective was
described as development of the ability to predict the rate of N02 absorption into a limestone
slurry of known composition.
The concluding paper of this session described laboratory studies conducted at the Department of
Chemical Engineering II, University of Lund, Sweden, concerning multiple utilization of limestone
sorbents for S02 removal. Use of spent sorbent for hydrochloric acid (HC1) removal was
discussed. Simultaneous SOz-NOx removal using additives (urea, ammonium citrate, ammonium
oxalate, ammonium bicarbonate) was studied using limestone and limestone slurry fed to an
entrained flow reactor at 100OC.
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Session 7B - Combined SO/NO, Removal
The first paper of the combined SOx/NOx session described work performed at Lawrence
Berkeley Laboratory in which an additive was used to remove NOx from flue gas in a wet
limestone scrubbing system. The results indicated that a nitric oxide (NO) removal efficiency of
50 (plus or minus) 20% could be achieved when the newly developed iron(II) thiochelate is
employed as an additive in an existing full-scale limestone scrubber.
Hokkaido Electric Power Co. and Mitsubishi Heavy Industries presented, in the second paper of
the session, the results from pilot-scale tests of LILAC sorbent for simultaneous S02 and NOx
removal. LILAC is an abbreviation for Lively Intensified Lime-Ash Compound. The pilot study
consisted of a two-step process, in which the first step is a spray drying process, and the second
step is a duct injection process using a powder-type LILAC absorbent.
Advanced dry scrubbing processes for SO„ and NOx control were described by the Babcock &
Wilcox Company in the third paper of the session. Results were presented from a recent 5 million
Btu/hr pilot test project which investigated the effect of low temperature operation on
conventional and advanced dry scrubber systems. The advanced systems included Limestone
Injection Dry Scrubbing (LIDS) and Ammonia and Limestone Injection Dry Scrubbing
(A+LIDS). Test results were presented, and the economics of the technologies were compared to
those of conventional wet and dry scrubbing processes.
The next paper addressed the economics of the SNOX process, which is a totally catalytic process
for removal of SOx and NOx in gas streams. This process is currently offered under license
throughout most of the world by ABB Environmental Systems, and it converts S02 to salable
sulfuric acid. The paper described the comparative economics between limestone scrubbing and
SNOX for high sulfur fuel in a situation requiring both S02 and NOx control as well as water
vapor plume control.
A moving-bed cross-flow adsorber, known as the Copper Oxide Bed Regenerative Adsorber, or
COBRA, was the subject of the next paper. The use of COBRA for S02 control in a Low
Emissions Boiler System was described. Results were presented from a sensitivity analysis with
the objective of optimizing the design of a 400 MWe system for integration into a low emissions
boiler system.
The sixth paper of the session contained a description of pilot testing of an electron beam system
for cleaning flue gas from a coal-fired boiler at the Shin-Nagoya Thermal Power Station in
Nagoya, Japan. A pilot-scale system treating 12,000 NmVhr was operated for 1 year. Results
from the test indicated that 94% S02 removal efficiency and 80% NOx removal could be achieved
with appropriate operating conditions, which included temperature, electron beam dose, and
amount of ammonia added. Reaction products were collected in an ESP.
The final paper of the combined SOx-NOx session described a modified version of the NOXSO
process, which has been named SNAP, for SOx and NOx Adsorption Process. The NOXSO
process consists of a dry, regenerable system for removing SOx and NOx using a proprietary
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sorbent bead of 1.23 mm diameter, FLS Miljo and NOXSO have entered into a relationship
under which FLS will market the NOXSO system in 33 countries This paper described both
processes and a test program designed to develop the SNAP process. A brief discussion was also
provided on the economics of both processes.
Session 8A - By-products and Wastewater
The first two papers of this session were concerned with utilization and disposal issues. Fluidized
bed combustion residues were considered in the first paper, which reported on an investigation
performed at the Department of Civil Engineering and Mechanics at the Southern Illinois
University at Carbondale. The paper described an in-depth investigation of the engineering
properties of FBC spent-bed-based cement and non-cement concrete mixtures. The second paper
discusses both disposal and utilization options for byproduct gypsum produced by the Chiyoda
CT-121 FGD Process. A DOE Clean Coal Project at Georgia Power Company's Plant Yates was
the source of the by-products used in the study.
Disposal of boiler chemical cleaning waste (BCCW) was the subject of the third paper, which
was authored by Radian Corporation, EPRI, and Hoosier Energy. A lull-scale test of adding
BCCW to an FGD system as an alternative disposal method was described in the paper. The
results indicated that disposal of an Ethylene Diamine Tetraacetic Acid (EDTA) BCCW to an
FGD system using landfill disposal of FGD wastes appeared to be a viable alternative to other
more conventional disposal methods.
The fourth paper of the session described operational experiences with wastewater treatment
plants for wet limestone FGD systems in the Netherlands. The treatment plants employ a
treatment method based on coprecipitation of heavy metal hydroxides and sulfides.
The effect of water balance in wet FGD systems was discussed in the fifth paper by Guild
Associates, Inc. Regulatory demands were described as the driving force behind the need to re-
examine the water balance and optimize FGD system design for stringent wastewater emission
standards.
The final paper of this session described the "Development of Ash and Waste Water Mixture
Treatment System" and was authored by Chubu Electric Power Co., Inc., and Mitsubishi Heavy
Industries. A process is described which involved use of FGD waste water for preparing a slurry
of fly ash captured in an ESP, when heavy oil was burned in the furnace. Ammonia, which was
injected into the flue gas from combustion of the high sulfur oils, was recovered from the fly-ash
waste water mixture for reinjection in the flue gas treatment section.
Session 8B-Materials for FGD
The final session of the symposium contained presentations concerned with materials selection
and performance issues for FGD processes. Topics addressed included:
-Performance of Alloy Linings in Wet Scrubber Outlet Ducts
13
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-Specification of Materials of Construction for Non-Metallic Flue Duct Expansion Joints
-New Methods of Nozzle Attachment to Fiber Reinforced Plastic (FRP) Headers
-Safety Measures During Application of Rubber Linings in Scrubber Vessels
-Acid Cleaning of Stainless Steel and Nickel Alloys for FGD Applications
-Lining Materials for Wet Limestone Absorber Modules
-Evaluation of Fiber-Reinforced Plastics for Use in Chiyoda Thoroughbred-121 Flue Gas
Desulfurization Process Vessels
In addition to these topics, a brief summary of the EPRI Wet Stacks Design Guide was presented
in a paper authored by Burns & McDonnell Engineering Company, DynaFlow Systems Division
of Acentech, Inc., EPRI, and New York State Electric and Gas. Wet stacks are of interest
because of the high cost of reheat and are therefore being considered for both new and retrofit
applications in the U. S.
Conclusion
The papers included in the 1995 S02 Control Symposium provide an excellent overview of the
status of the technology. In general, capital intensive scrubbing processes were the main focus of
attention in the Symposium. Processes of interest for Eastern Europe are likely to include those
systems which require minimum capital investment, and which generally achieve somewhat lower
overall S02 removal efficiencies than wet scrubbing systems. Two such processes, not discussed
at this symposium, are the ADVACATE dry injection process for S02 control and the E-SOx
process for combined particulate and S02 removal. These processes have been under
development at the U. S. EPA's Air Pollution Prevention and Control Division, and are the
subject of planned demonstration projects in Russia, Ukraine (E-SOx), and Poland
(ADVACATE). Descriptions of these processes and their current stage of development have
been presented and published elsewhere [2,3,4,5],
References
[1] Proceedings of the 1995 Sulfur Oxides Control Symposium, EPRI TR105258 v. 1-4, Electric
Power Research Institute, Palo Alto, California, March 1995.
[2] Hall, Brent W. et al., "Current Status of ADVACATE Process for Flue Gas Desulfurization,"
EPA-600/D-91 -173 (NTIS PB91-226423), 1991.
[3] Sedman, Charles B. et al., "Commercial Development of the ADVACATE Process for Flue
Gas Desulfurization," EPA-600/D-90-147 (NTIS PB 90-263930), 1990.
14
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[4] Sparks, L. et al., "Results of Pilot Scale Tests of E-SOxProceedings: Sixth Symposium on
the Transfer and Utilization of Particulate Control Technology, Volume 1, EPA-600/9-86-
03 la(NTIS PB87-147617),pp.22-1 through 22-15, December 1986.
[5] Marchant, G. H, et al., "Effects of E-SOx Technology on ESP Performance," Final Report,
EPA- 600/R-92-196(NTIS PB93-107258), October 1992.
Conversion Factors
The summaries presented in this paper report results as in the original text, whether in English
or SI units. English units in this paper may be converted to SI units via the following:
English
SI
ton
0.02917 kg
lb/106Btu
430.5 ng/J
Btu/lb
2324 J/kg
Btu/hr
0.29 W
ft3/m (cfin)
4.719 x 10"4 m3/s
°F
1.8°C + 32
ft
0.3048 m
gallon
3.785 liters
in. w.g.
2.49 kPa
15
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nrrT1 in 1CA TECHNICAL REPORT DATA
WriMrvL~Ki Jr~Jr""IOU (Please read Inumctions on the reverse before camplenr
1. REPORT NO. 2.
EPA/600/A-96/106
3. I
4. TITLE AND SUBTITLE
Status of Sulfur Oxides Control Technology
S. Rli un 1 I c
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
C. B. Sedman (EPA) and J. P. Gooch (SoRI)
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Southern Research Institute
P. O. Box 55305
Birmingham, Alabama 35255
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
CR 822780
12. SPONSORING AGENCY NAME AND AOORESS
EPA, Office of Research and Development
Air Pollution Prevention and Control Division
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PERIOD COVERED
Published oaoer: 4-7/96
14. SPONSORING AGENCY CODE
EPA/600/13
is. supplementary notes ^PPCD project officer is Charles B. Sedman, Mail Drop 4, 919/
541-7700. For presentation at Ukraine-U. S. Technology Meeting, Kiev, Ukraine,
9/10-11/96.
16. abstractpaper discusses the status of sulfur oxides (SOx) control technology, as
outlined at the 1995 SOx Control Symposium, cosponsored by the Electric Power Re-
search Institute, the U. S. Environmental Protection Agency, and the U. S. Depart-
ment of Energy. The symposium provided many technical papers on the current sta-
tus of SOx control technology worldwide. The status of key commercial-scale flue
gas desulfurization (FGD) applications in the U. S., Japan, and Europe was documen-
ted, with emphasis on wet limestone scrubbing. Dry FGD, furnace sorbent injection,
and combined SOx/nitrogen oxides (NOx) applications were also described. Special
sessions were devoted to FGD materials, component selection, chemical additives,
and chemistry. Research programs to improve existing concepts and develop new
approaches were described. The paper summaries highlights of the papers and pre-
sentations which have implications toward the Eastern European market for SOx con-
trol.
17. KEY WORDS AND DOCUMENT ANALYSIS
a. descriptors
b.IDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Pollution Sorbents
Sulfur Oxides
Flue Gases
Desulf uriz ation
Limestone
Furnaces
Pollution Control
Stationary Sources
13 B 11G
07C
21B
07A»07D
08G
13 A
18. DISTRIBUTION statement
Release to Public
19. SECURITY CLASS (This Report/
Unclassified
21. NO. OF PAGES
20. SECURITY CLASS (This page)
Unclassified
22. PRICE
EPA Form 2220-1 <9-73)
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