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Document Number: 

98) IV-J-41 

Docket Number: 

A-83-27 

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DIVISION 

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PITATION 

DIVISION 

11% 
SPRAY DRYER ABSORPTION APPLICATIONS 

FOR HIGH SULFUR COAL 

J. R. DONNELLY, Western Precipitation Division, Joy Manufacturing Company 

Los Angeles, California 90039 

K. S. FELSVANG, A/S Niro Atomizer, Soeborg, Denmark 

Abstract 

Spray Dryer Absorption (SDA) is a relatively new technology for the 

desulfurization of flue gases from coal-fired boilers. The first applications of SDA started up in 1980 for the desulfurization of utility low 

sulfur, coal-fired boiler flue gases. Since that time, the SDA process 

has been applied to industrial boilers firing high sulfur coals (3-3.5% 

sulfur) where high removal efficiencies (greater than 90%) and high 

availabilities have been demonstrated. 

Joy Manufacturing Company and A/S Niro Atomizer have been leaders in 

developing and supplying SDA systems for utility and industrial boilers 

in the United States. Since 1977, the two companies have worked together 

to improve the process for treating higher sulfur coals and to develop an 

SDA process for simultaneous removal of sulfur oxides and nitrogen oxides. Today, seven utility and four industrial coal-fired systems are in 

operation treating a wide variety of coal types and sulfur contents. 

This paper presents a description of the SDA process and a discussion of 

the development of the process for achieving high removal efficiencies 

for high sulfur coals. Results of pilot plant testing for inlet SO2 

concentrations up to 5,000 ppm are presented. Operating results from 

commercial systems treating 3-3.5% sulfur coal are given and test results 

from 4.2% sulfur coal are presented. Design parameters for systems under 

construction treating greater than 2,000 ppm inlet SO2 and requiring 

greater than 90% removal are given. 

Introduction 

The concept of dry flue gas desulfurization by spray dryer absorption 

(SDA) was first tested on utility coal-fired boilers during the mid-1970s 

and the first full scale system started up in 1980. The acceptance by 

the utility industry has grown quite rapidly and today more than 8,000 MW 

of coal-fired generating capacity are committed to SDA flue gas desulfurization. Since 1980, seven utility and four industrial units have started up which employ the SDA process as developed by Joy Manufacturing 

Company and A/S Niro Atomizer. 

Initially, the SDA process was selected for utility boilers firing low 

sulfur coal. As additional test results became available and knowledge 

of the process grew, the process was selected for high sulfur applications on industrial boilers. Today, systems are in operation treating 

flue gases from the firing of up to 3.5% sulfur coal. The process has 

been tested commercially on 4.2% sulfur coal at greater than 95% SO2 

removal. In addition, tests have been performed on a Joy/Niro developed 

SDA simultaneous S0X and N0X removal process. Systems are currently 

under construction for treating greater than 2,000 ppm inlet SO2 concentrations at greater than 90% removal efficiency. 

This paper reviews the development and application of the SDA process for 

high sulfur coal-fired boilers. Results of pilot and full scale tests 

are given as well as design parameters for high sulfur, high removal 

applications. 

Development 

Spray dryer absorption for flue gas desulfurization was first tested, as 

a part of a sulfur recovery process, on a coal-fired power plant in 1972. 

In 1976 tests were conducted on a throw-away, sodium-based process utilizing a spray dryer followed by a bag filter for dust collection. In 

1977 Joy Manufacturing Company and A/S Niro Atomizer signed an agreement 

to jointly develop and market the SDA process in the United States. 

Since then, Joy/Niro have been very active in testing the SDA process and 

developing ways to improve the process especially for higher coal sulfur 

DONNELLY 
P.4 

applications. Table I lists some key development milestones in application of the SDA to utility and industrial coal-fired boilers. 

TABLE I 

HIGH SULFUR SPRAY DRYER ABSORPTION 

DEVELOPMENT MILESTONES 

1977-78 Pilot Testing - Fergus Falls, Minnesota (+2,000 ppm SO2) 

1979-86 Copenhagen Pilot Plant Tests (+2,500 ppm SO2) 

1980 Riverside Start-Up (1.6% Sulfur) 

1981 Argonne Start-Up (3.5% Sulfur) 

1982-83 Riverside High Sulfur Testing (3.2% Sulfur) 

1983 Argonne High Sulfur Testing (4.2% Sulfur) 

1983-85 Copenhagen High Sulfur Tests (+5,000 ppm SO2) 

1985 Buick Motor Division Performance Tests (1% and 3% Sulfur) 

In October of 1977 Joy/Niro joined forces to construct and operate a 

20,000 acfm pilot plant at the Hoot Lake Generating Station in Fergus 

Falls, Minnesota. This pilot plant was required to qualify for bidding 

on Basin Electric Power Cooperative's Antelope Valley Station. The pilot 

plant consisted of a spray dryer, a reverse air bag filter, an electrostatic precipitator, a reagent preparation system and equipment for testing the effects of partial product recycle. During 1977 and 1978, a series of parametric tests were performed to quantify the effects of the 

following variables: 

Single Pass Versus Recycle Operating Modes 

Lime Versus Soda Ash as the Adsorbent 

Influence of Fly Ash Grain Loading and Alkalinity 

Bag Filter Versus Electrostatic Precipitator 

Influence of Spray Dryer Outlet Temperature 

Influence of Inlet SO2 Concentration 

Stoichiometry Versus SO2 Removal 

Inlet SO2 concentrations as high as 2,000 ppm were tested at removal 

efficiencies around 90%. Spray dryer outlet temperatures as low as 

18° F. above the adiabatic saturation temperature were successfully 

tested. Partial product recycle to increase the feed solids to nearly 

-50% was tested and confirmed the positive effects of recycle. 

The pilot plant program was very successful. Much valuable design data 

was obtained to show the capabilities of the SDA process. Results of the 

test program led to the Antelope Valley Station contract to Joy/Niro and 

to the granting of the Felsvang, et al, patent (U.S. No. 4279873) in July 

1981 covering the product recycle concept. 

The success of the Fergus Falls pilot plant led to a decision to install 

a 5,000 acfm pilot plant at Niro Atomizer's research facilities in 

Copenhagen, Denmark. The pilot plant consists of two spray dryers, a 

pulse-jet bag filter, a reverse air bag filter, a rigid frame electrostatic precipitator, a reagent preparation system and an acid gas (SO2, SO3, 

HCl, HF, etc.) injection system. The system started up in 1979, and in 

its seven years of operation more than 3,000 parametric and longer term 

tests have been performed to quantify the influence of major and minor 

process variables. The pilot plant has been used for parametric testing, 

project specific testing and process development testing. Methods of 

increasing SO2 removal, especially for higher sulfur coals, have been 

developed using this pilot plant. Table II presents the results of some 

high sulfur tests conducted on the Copenhagen pilot plant. 

DONNELLY 
TABLE II 

PILOT PLANT RESULTS 

HIGH SULFUR APPLICATIONS 

P.5 

Test No. 2726 2727 4364 6145 6147 4385 

Temperatures, F. 

SDA Inlet 

SDA Outlet 

Delta T Saturation 

SO2 Concentrations, 

System Inlet 

System Outlet 

SO2 Removal, % 

Dust Collector 

Additive 

352 

148 

23 

ppm Dry 

3406 

430 

87 

PJF 

-chlor 

350 

147 

23 

3542 

507 

86 

PJF 

•ide-

, 

367 

147 

18 

5200 

931 

82 

ESP 

none 

400 

160 

18 

4360 

149 

96 

ESP 

402 

158 

18 . 

4490 

273 

93 

ESP 

-chloride370 

163 

18 

6650 

51 

99 

PJF 

other 

PJF - Pulse-Jet Bag Filter ESP - Electrostatic PRecipitator 

As can be seen, removal efficiencies in the 80 and 90% ranges can be 

achieved at typical boiler inlet gas conditions with inlet SO2 concentrations up to 6,650 ppm. The beneficial influence of small amounts of 

chloride (either as HCl in the flue gas or calcium chloride in the feed) 

on overall removal are evident. Greater than 90% removal can be achieved 

when either an electrostatic precipitator or pulse-jet filter is used as 

the dust collector. For very high inlet SO2 concentrations (greater than 

5,000 ppm), where high removal efficiencies (greater than 90%) are 

required, a bag filter is used as the dust collector and another additive 

is used to enhance removal. 

Joy/Niro committed in 1979 to demonstrate the SDA process on a full scale 

system at the Riverside Generating Station. This 110 MW system consists 

of a 45-foot diameter spray dryer absorber, a twelve-compartment reverse 

air bag filter and a reagent preparation system. In addition, the existing electrostatic precipitators can be used for dust collection. The 

Riverside system was operated as a demonstration/test unit for the first 

three years and then turned over to Northern States Power for continued 

operation as a commercial unit. During the demonstration phase of the 

project, six combinations of coal were fired having sulfur contents varying between 0.8 and 3.5%. Over 90% SO2 removal has been demonstrated for 

both low and high sulfur coal. Test results have been verified by independent testwork performed for EPRI and EPA. 

Since 1980, several other full scale systems have started up and passed 

performance testing. Each has added more knowledge to development and 

application data base for the SDA process and has resulted in the 

incorporation of many refinements in the system design. 

System Description 

Spray Dryer Absorption systems vary widely in size and number of components; however, they consist basically of the following subsystems: 

Spray Dryer Absorber Module(s) 

Dust Collector(s) 

Reagent Preparation System 

Recycle System 

Spray Drying Absorption is a special case of spray drying. Flue gas 

replaces other drying media to give the 'driving force for evaporation 

water from the atomized feed material. Lime slurry replaces the product 

feed slurry because of its reactivity for acid gases (SO2/ SO3, HCl, 

etc.). Key parameters in spray drying (atomization, gas mixing, outlet 

R. DONNELLY 
P.6 

temperature) are also key parameters for achieving the simultaneous reaction of SO2 with lime and drying of the feed and reaction products. 

Figure 1 shows the gas flow path for a typical multimodule SDA application. 

FIGURE 1 

seee «eiif« 

ems,.etme m m 

Flue gas passes through the air preheaters where it cools to between 

300-400° F. and is ducted to the inlet of the flue gas cleaning system. 

From here the gas flow is split between the operating spray dryers and 

enters the spray dryer through either a roof or compound gas disperser 

(compound shown here). For a compound gas disperser the flue gas flow 

is again split such that approximately 60% of the flue gas enters via the 

roof gas disperser and the remaining 40% via the central gas disperser. 

The selection of a roof or compound gas disperser is a function of turndown requirements and chamber size. Each disperser is equipped with 

adjustable vanes which are set during start-up to ensure proper gas 

rotation and mixing with the atomized cloud of droplets. 

The feed slurry, when contacted with the hot flue gas, simultaneously 

drys and reacts with SO2. A small portion of the dry product falls to the 

bottom of the spray dryer, while the remainder is carried over to the dust 

collector where additional SO2 removal takes place. The two-point discharge design ensures a clear gas passage even if upset occurs that 

results in deposit formation. 

A portion of the dust entering the bag filter will drop out in the hoppers 

and the remainder will stick to bag surfaces causing an increase in baghouse pressure drop. Periodically, one baghouse compartment is brought 

off line and blown back with reverse air to remove residual dust cake. 

This is sufficient to control operating pressure drop and SO2 removal in 

the bag filter. The dust collected is either transported back to the 

recycle bin or to the disposal silo. 

The spray dryer outlet temperature is typically maintained between 18 and 

35° F. above the adiabatic saturation. This temperature is selected to 

maintain the lowest safe outlet temperature to improve reagent usage yet 

maintain a dry product. 

Figure 2 is a simplified process flow diagram for the SDA system showing 

the feed preparation system. 

J. R. DONNELLY 
P.7 

FIGURE 2 

PROCESS FLOW DIAGRAM 

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•CCTCLC 

2TU 

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The feed preparation system typically consists of a lime silo, feeder and 

slaker, a recycle bin, feeder and agitated tank, an agitated feed tank and 

screen, and a head tank as well as the associated pumps, piping and 

valves. 

Pebble quick lime is fed from the storage silo or bin into a slaker 

where it reacts with water to form a fine suspension containing 20 to 30% 

hydrated lime. The slaker may be either a detention, attrition, paste or 

ball mill type, the choice depending upon the capacity, lime quality and 

customer preference. From the slaker the lime flows either to a storage 

tank or directly to the feed tank via a screen. 

Dry product collected from the spray dryer, baghouse or electrostatic 

precipitator is conveyed to a recycle feed bin. From here it is fed via 

a rotary feeder to an agitated recycle tank where a nominal 50% solids 

slurry is prepared. The recycle slurry is then transferred via a screen 

to the feed tank to produce a feed slurry containing from 30 to 45% 

solids. The ratio of lime to recycle slurry fed to the feed tank is 

controlled by an SO2 signal. 

From the feed tank the slurry is pumped to a head tank where approximately 

half of the slurry flows by gravity to the atomizer. Slurry flow control 

is based on boiler load and spray dryer outlet temperature. 

The atomizer converts the feed slurry into a cloud of discreet droplets 

due to the shearing action of the slurry leaving the high speed atomizing 

wheel. Figure 3 shows a Niro rotary atomizer and the patented KN abrasion 

resistant wheel. 

DONNELLY 
P.8 

FIGURE 3 

ATOMIZER AND WEAR RESISTANT ATOMIZER WHEEL 

1 

D ® ••$• 

I fa\ (a\ 

1 V-J i°J 

I 

, 

Abrasion Resistant Atomizer Wheel 

F-600 Centriiugal Atomizer 

The atomizer wheel consists of a wheel body, made of stainless steel or 

more corrosion resistant alloy, and inserts protruding into the wheel 

body to form a layer of slurry for protection of the inside of the wheel 

body when the wheel is rotating. The bottom plate and the inserts are 

made of abrasion-resistant material, e.g. silicon carbide. 

Operating results 

Three systems treating flue gases from the firing of 3% or higher sulfur 

coal have started up and undergone performance testing. These systems 

are located at the following sites: 

Argonne National Laboratory, Argonne, Illinois 

Riverside Generating Station, Minneapolis, Minnesota 

GM-Buick Steam Plant, Flint, Michigan 

The SDA system at Argonne was the first system applied to high sulfur 

coal and started up in 1981. The system was retrofitted on an existing 

stoker-fired boiler. The SDA system consists of a 25-foot diameter spray 

dryer equipped with compound gas disperser, a four-compartment pulse-jet 

baghouse using woven fiberglass bags, a paste type slaker and a recycle 

system. 

Table III presents results of testing conducted while the unit was firing 

•3.0 and 4.2% sulfur coal. 

R. DONNELLY. 
P.9 

TABLE III 

OPERATING RESULTS 

ARGONNE NATIONAL LABORATORY 

Type Coal 

Sulfur, % 

Inlet Temperature, _F. 

SO2 Removal, % 

Approach Temperature, F. 

Stoichiometric Ratio 

111 

3.0 

350 

90 

22 

1.3 

m o is 

3.0 

346 

80 

22 

1.0 

West Virginia 

4.2 4.2 

350 350 

90 96 

20 20 

1.33 1.60 

The results for the 3.0% sulfur coal are from performance tests conducted 

during 1982. As is shown, removal efficiencies between 80 and 90% can be 

achieved at stoichiometric ratios between 1.0 and 1.3. These results are 

for tests without chloride addition to enhance performance. 

In addition to the performance tests and normal operation with 3.0% sulfur coal, Argonne has conducted several series of special tests to evaluate SDA process for higher sulfur coals, effects of performance enhancement additive and demonstrate Joy/Niro's simultaneous dry SOx/NOx process. 

The results shown in Table III for the 4.2% sulfur coal are from tests 

performed by Argonne in conjunction with Conoco Coal Company. The program goal was to demonstrate that SDA is a cost-effective strategy for 

controlling SO2 emissions from high sulfur coal combustion under 1977 

NSPS requirements. The test demonstrated that 90% SO2 removal could be 

achieved at a cost competitive with a wet limestone FGD process, and that 

up to 96% SO2 removal could be achieved at normal boiler outlet conditions. These tests included the addition of calcium chloride to the 

feed slurry to enhance performance. As is shown, the stoichiometry 

required to achieve 90% removal for the 4.2% sulfur coal is nearly the 

same as for the 3% sulfur. This is due to the chloride addition. 

Table IV presents results of high sulfur coal tests performed in 1982 and 

1983 at the Riverside demonstration unit. For the high sulfur test series, one month burns of 3.2% Illinois bituminous coal were performed. 

Numerous parametric as well as longer term tests were performed. 

TABLE IV 

OPERATING RESULTS - 3.2% SULFUR COAL 

RIVERSIDE GENERATING STATION 

Seven-Day Chloride 

Test 1 2 3 Demo Run Addition 

Jl ^ a-r rGas Flow, acfm 531,000 510,000 470,000 500,000 500,000 

Inlet Temperature, F. 331 316 351 340 335 

Approach Temperature, F. 32 35 18 18 18 

S02 Removal, % 93.8 90.6 93.5 93.6 90 

Feed Slurry Solids, I 34 34 32 35 35 

Stoichiometric Ratio 1.6 1.46 1.34 1.37 1.1 

As shown in the table, better than 90% SO2 removal was demonstrated at 

stoichiometrics between 1.3 and 1.6 depending on the spray dryer outlet 

temperature. For the seven-day demonstration run, 93% removal was 

..achieved at a stoichiometric ratio of 1.37. For tests using chloride 

addition, 90% removal was achieved at a stoichiometric ratio of 1.1 •, 

The SDA system installed on boiler number three at General Motors Buick 

steam plant consists of a 32-foot diameter spray dryer equipped with a 

J. R. DONNELLY 
P.10 

compound gas disperser, an eight-compartment reverse air bag filter and 

an attrition type slaker. The boilers are CE pulverized coal, tangential 

fired process steam boilers rated at 450,000 pounds per hour. The SDA 

system is designed to handle a wide range of coals and a combination of 

coal and oily waste sludge firing. Table v presents results of performance tests conducted in January 1985. 

TABLE V 

PERFORMANCE TEST RESULTS 

GENERAL MOTORS - BUICK STEAM PLANT 

Fuel Sulfur, % 

Gas Flow, dcfm (dry) 

Inlet Temperature, F. 

Approach Temperature, F 

SO2 Removal, % 

Measured 

Guaranteed 

Stoichiometric Ratio 

Measured 

Guaranteed 

Low Sulfur 

0.8 

105,330 

327 

36 

73 

70 

0.69 

0.70 

High Sulfur 

2.7 

103,180 

303 

20 

91 

90 

1.40 

1.50 

The performance tests were conducted in two series. During the first 

series, a blend of low sulfur coal and oily waste sludge was fired, while 

a nominal 3% sulfur coal was fired during the second series. As is shown 

in the table, better than required removal efficiencies were achieved at 

lower than guaranteed stoichiometric ratios. 

Future Applications 

The application of SDA to higher sulfur coals at high removal efficiencies continues because of operating advantages over competing technologies. Limiting factors affecting the maximum sulfur coal which the SDA 

process can treat effectively are: the removal efficiency required, the 

spray down temperature (SDA inlet temperature minus SDA outlet temperature) available and the type of dust collector employed. Very high 

removal requires high stoichiometrics which may require more lime than 

can be fed into the system. The spray down temperature determines the 

maximum water evaporation and the maximum lime which can be fed into the 

system. The type of dust collector (electrostatic precipitator versus 

bag filter) affects overall removal since a portion of the SO2 removal 

takes place in the dust collector. A bag filter is more efficient than 

an electrostatic precipitator. The use of performance enhancement 

additives, such as chloride and others, can increase this maximum sulfur 

level significantly. Table VI presents design parameters for three high 

sulfur systems under construction which require high removal efficiencies. 

TABLE VI 

DESIGN PARAMETERS 

HIGH SULFUR - HIGH REMOVAL 

Unit 

Gas Flow, acfm 

Inlet Temperature, F. 

Inlet SO2 Concentration, 

SO2 Removal, % 

Dust Collector 

Start-Up 

Shenyang/Liaoni 

China 

170,000 

320 

ppm 2,100 

90 

PJF 

7/87 

ng Brescia 

Italy 

490,000 

300 

2,000 

90 

PJF 

8/8 7 

Salzburg 

Austria 

350,000 

360 

2,500 

)97 

PJF 

10/87 

J. R. DONNELLY 
P.11 

As is shown, the inlet flue gas temperatures are all low (300-360° F.) 

which limits the spray down available and all systems include a pulse-jet 

bag filter as the dust collector. All three systems are being retrofitted on boilers firing low rank, high sulfur, high chlorine coals. 

Start-up and performance testing of these units is scheduled for 1987. 

Conclusions 

Spray dryer absorption is a relatively new technology which has gained 

rapid acceptance by the utility and industrial sectors as an effective, 

reliable means of achieving flue gas desulfurization. The process is a 

special application of spray drying and has been extensively tested at 

the pilot and full-scale levels. Commercial systems are in. operation 

which have demonstrated the ability to achieve 90% removal from 3% sulfur 

coal applications. 

Performance enhancement additives, such as chloride, can significantly 

extend the maximum sulfur level that can be treated, with chloride 

enhancement, up to 96% removal has been demonstrated on a commercial 

application firing 4.2% sulfur coal. 

Future applications now under construction will require even high SO2 

removal efficiencies. One system is designed to achieve greater than 97% 

SO2 removal when the inlet concentration is 2,500 ppm. As time progresses, it is expected that the SDA process will be applied to cover 

even more rigorous applications. 

REFERENCES 

Felsvang, K. s. "Desulfurization of Low Rank, High Sulfur Coal by Dry 

Flue Gas Desulfurization," 8th International Congress of Chemical 

Engineering, Chemical Equipment Design and Automation, Proha, 

Czechoslovakia, September 1984. 

Donnelly, J. R., et al, "Spray Dryer FGD Expereience, Joy/Niro Installations," EPA/EPRI 9th FGD Symposium, Cincinnati, Ohio, June 1985. 

Blythe, G. M., et al, "Field Evaluation of Utility Dry Scrubbing System," 

EPA/EPRI 8th FGD Symposium, New Orleans, Louisiana, November 1983. 

Donnelly, J. R., et al, "Industrial Spray Dryer FGD Experience," ASME 

Industrial Power Conference, Pittsburgh, Pennsylvania, October 1986. 

Farber, P. S., "Spray Dryer and Fabric Filter Installation - An Industrial Boiler Conversion," 74th Annual Meeting, APCA, Philadelphia, Pennsylvania, June 1981. 

Farber, P. S. et al, "Evaluation of a Spray Dryer Flue Gas Cleaning 

System on High Sulfur Coal, " Coal Technology '83, Houston, Texas, 

November 1983. 

McLeod, D. N., "The Start-Up and Debug of the Largest Industrial Flue 

Gas Desulfurization System in the United States," Coal Technology '84, 

Houston, Texas, November 1984. 

DONNELLY