p.1 

OAR Box 1828 

Prepped by Ollie Stewart 

Document Number: 

297) IV-A-7 

Docket Number: 

A-83-27 

Printed 11/12/2008 11:12:59 AM Sheet 297 of 325 
1- A A-^-27 

TECHNICAL NOTE 

PARTICULATE MATTER EMISSIONS FROM 

RESIDUAL OIL-FIRED BOILERS 

Prepared for: 

Mr. Charles Sedman 

Industrial Studies Branch 

Emission Standards and Engineering Division 

U. S. Environmental Protection Agency 

Research Triangle Park, North Carolina 27711 

Prepared by: 

Radian Corporation 

3200 E. Chapel Hill Road/Nelson Highway 

Post Office Box 13000 

Research Triangle Park, North Carolina 27709 

June 4, 1984 

x 
P.3 

-I 

•1.0 INTRODUCTION 

This technical note reviews the capability of residual oil-fired 

boilers to achieve low levels of particulate matter (PM) emissions. 

Section 2.0 characterizes PM emissions from low-sulfur residual oil 

combustion and the effects of good boiler operation in controlling these 

emissions. Section 3.0 characterizes the performance of five wet scrubber 

types in controlling PM emissions from residual oil-fired boilers firing 

moderate- to high-sulfur residual oils (which characteristically exhibit 

higher uncontrolled PM emissions). 
P.4 

2.0 LOW SULFUR RESIDUAL OIL COMBUSTION 

Air Pollution Manual - 42, "Compilation of Air Pollutant Emission 

Factors" and other reports have noted that PM emissions from residual oil 

combustion are proportional to the sulfur level in the fuel oil, with lowsulfur residual oils exhibiting the lowest PM emissions rate. Thus, 

the use of low-sulfur residual oils could be a feasible PM emission control 

technique if they exhibit sufficiently low uncontrolled PM emissions. To 

understand and predict PM emissions from residual fuel oil combustion, 

information is needed on how PM emissions are generated. There are four 

sources of PM emissions from fuel oil combustion. These sources, discussed 

in the following sections, are: 1) inert ash in the oil, 2) sulfates and 

sulfites formed from the combustion of sulfur in the oil, 3) carbonaceous 

compounds formed from incomplete combustion of the oil itself, and 4) oil 

2 3 additives used to protect the boiler. ' 

2.1 INERT ASH 

Inert ash consists of the non-combustible compounds which naturally 

occur in fuel oils. These compounds are metals and salts that range in 

4 

concentrations from less than 0.01 to approximately 0.20 lb/MMBtu. The 

amount of ash present in fuel oils is generally proportional to the sulfur 

content. For low-sulfur residual fuel oils with sulfur contents less than 

1.0 weight percent (1.0 weight percent fuel oil would have a potential S02 

emission rate of roughly 1.1 lb S09/MMBtu heat input), the ash content 

1 3 generally ranges from 0.01 to 0.03 lb/MMBtu. ' Ash can be removed from the 

fuel oil during refining at a petroleum refinery. Modifications to the 

combustion process have negligible impact on the amount of fly ash formed 

during combustion. 
P.5 

2.2 SULFITE AND SULFATE 

Sulfite and sulfate components of PM emissions are the indirect result 

of elemental sulfur in the residual fuel oil forming S02 and S03 during 

combustion. Roughly 1 to 4 weight percent of these sulfur oxide gases react 

with metals in the fly ash and metal boiler components to form metallic 

2 5 sulfite and sulfate salts. ' These sulfur salts exit as PM emissions in 

the flue gas. Sulfites and sulfates generally contribute PM emissions of 

less than 0.03 lb/MMBtu for low-sulfur oil combustion (less than 1 weight 

percent sulfur) and 0.1 lb/MMBtu for high-sulfur oil (3 weight percent 

sulfur). 

2.3 CARBONACEOUS MATERIAL COMPONENT 

A tar-like carbonaceous material consisting of polymerized oil 

compounds results from incomplete combustion of residual fuel oil. This 

unburned carbonaceous component can account for as much as 90 weight percent 

of the PM emissions from a poorly operated residual oil-fired boiler. The 

formation of carbonaceous material can be reduced by up to 30 percent by the 

use of efficient oxygen trim controls, routine boiler maintenance 

o 

procedures, and/or the use of higher performance burners. 

2.4 ADDITIVE COMPONENT 

Occasionally, alkaline additives are blended into residual oils to 

improve boiler operation. Most additives reduce the corrosive impacts of 

S02, which is formed during combustion of sulfur in residual oils. 

Additives can also be used to reduce the slagging effects of some high-ash 

residual oils. When used with high-sulfur oils, additives can contribute as 

much as 0.04 lb/MMBtu of PM emissions. However, additives are not generally 

required for residual oils with less than 1 percent sulfur. 
P.6 

2.5 PROJECTED PM EMISSIONS 

The contributions discussed above for the four primary components of PM 

emissions can be combined to project total PM emissions from residual fuel 

oil combustion. Table 2-1 presents the range and average contribution 

expected from each component for residual fuel oils containing less than 

1 weight percent sulfur. It is also assumed that the boiler is well 

operated (i.e., applying proper design and operating procedures to reduce 

carbonaceous PM emissions). From Table 2-1, the expected range of PM 

emissions is from 0.01 to 0.09 lb/MMBtu with a mean value of 0.06 lb/MMBtu. 

2.6 PM EMISSIONS DATA BASE 

Emission test results for 18 residual oil-fired boilers are presented 

in Table 2-2. These boilers fired residual fuel oils with sulfur contents 

less than 1.0 weight percent and had heat input capacities larger than 

4 

75 MMBtu/hour. The test data were collected using EPA Method 5. The 

average PM emissions were 0.07 lb/MMBtu. For 15 of the 18 boilers, PM 

emissions ranged from 0.02 to 0.10 lb/MMBtu. PM emissions exceeded 

0.10 lb/MMBtu from 3 units, probably from carbonaceous materials formed 

during incomplete combustion. 

Two Boston Edison units exhibited PM emissions of 0.15 and 

0.19 lb/MMBtu. These were identical steam-atomized boilers combusting 

identical fuel oils. However, two other Boston Edison boilers, one larger 

and one smaller, exhibited PM emissions of 0.04 and 0.07 lb/MMBtu heat input 

when combusting the same fuel oil. Since all four units were combusting the 

same fuel oil, the difference in PM emissions between the four boilers was 

most likely caused by carbonaceous material formed during incomplete 

combustion. Both units were old at the time of the test and have since been 

retired. 

A representative of the Boston Edison Company stated that both units 

9 had a history of high PM emission levels. The fuel injection nozzles in 

the units did not fully atomize the oil, resulting in large oil droplets 
P.7 

TABLE 2-1. EXPECTED PM EMISSIONS FROM LOW-SULFUR RESIDUAL FUEL OIL 

COMBUSTION IN A WELL-MAINTAINED AND OPERATED BOILER3 

PM Emission Range Average PMfiEmissions 

PM Emission Component (lb/10D Btu) (lb/10° Btu) 

Ash 0.01 - 0.03 0.02 

Sulfites and Sulfates 0.00-0.02 0.01 

Carbonaceous 0.00-0.03 0.02 

Additives 0.00 - 0.01 0.01 

Total 0.01 - 0.09 0.06 

Engineering estimate based on information in References 1-3 and 9. 
TABLE 2-2. EMISSION TEST RESULTS FOR LOW SULFUR RESIDUAL FUEL-OIL BOILERS 

cn 

Owner and Location 

Unit 

Designation 

Capacity 

(10 Btu) 

Fuel 

S 

(wt. %) 

Average 

PM 

Emissions 

lb/10° Btu 

Number 

of 

Tests Additives 

Boston Edison Co: L Street 

Kneel and Street 

M1not Street 

Mystic 

Company A: Station No. 2 

Station No. 1 

Bralntree Electric: Allen St. 

Potter Station 

Eastman Gelatin: Peabody 

Average Values: 

68 

74 

75 

76 

4 

6 

7 

3 

5 

5+6 

11+12 

1+2 

2+3 

4+5 

1 

2 

4 

5 

140 

376 

705 

376 

517 

235 

235 

470 

1,360 

141 

188 

235 

188 

188 

188 

112 

94 

94 

0.50 

0.50 

0.50 

0.50 

0.50 

0.50 

0.50 

0.50 

0.50 

0.47 

0.47 

0.42 

0.87 

0.89 

0.91 

0.89 

0.89 

0.93 

0.62 

0.04 

0.19 

0.07 

0.15 

0.02 

0.02 

0.04 

0.08 

0.07 

0.10 

0.04 

0.04 

0.08 

0.05 

0.07 

0.14 

0.07 

0.07 

0.07 

1 

1 

1 

2 

3 

1 , 

2 

2 

5 

3 

3 

3 

3 

3 

3 

3 

3 

3 

zzz z ooo o 

No 

No 

No 

No 

No 

No 

No 

Yes 

No 

No 

Yes 

Yes 

No 

No 

NOTE: 1. All PM emissions measured using EPA Standard Method 5. 

2. All Btu values are based on heat Input. 
P.9 

that did not combust completely and formed carbonaceous material. However, 

verification of these assumptions was not conducted by Boston Edison. 

One boiler at Braintree Electric's Station No. 2 also exhibited higher 

than expected PM emissions of 0.14 lb/MMBtu. The other three units at 

Braintree had emissions that averaged 0.07 lb/MMBtu. The four units were 

using similar, but not identical, fuel oils. Fuel sulfur contents ranged 

from 0.87 to 0.91 weight percent. Two fuels contained additives and two did 

not. As with the Boston Edison boilers, the relatively higher emissions 

from the Potter Station No. 2 boiler are most likely attributable to 

carbonaceous material from incomplete combustion. 
P.10 

2.7 REFERENCES 

, U. S. Environmental Protection Agency. "Compilation of Air Pollutant 

" Emission Factors." Publication No. AP-42. Research Triangle Park, 

North Carolinal. February 1976. 

2. Smith, W. S. Atmospheric Emissions from Fuel Oil Combustion. U. S. 

Department of Health Education and Welfare, Division of Air Pollution, 

Cincinnati, Ohio. November 1962. p. 16. 

3. GCA Corporation. Particulate Emission Control Systems for Oil-Fired 

Boilers. Prepared for U. S. Environmental Protection Agency. 

EPA-450/3-74-063. December 1974. p. 40. 

4. Reference 3, p. 68. 

5. Roy F. Weston, Inc. Characterization of Particulate Emissions from 

Refinery Process Heaters and Boilers. API Publication No. 4365. 

Washington, D. C. Prepared for American Petroleum Institute. 

June 1983. p. 32. 

6. Reference 2, p. 38. 

7. Reference 2, p. 36. 

8. Offen, G. R., et al. Control of Particulate Matter from Oil Burners 

and Boilers. U. S. Environmental Protection Agency, Research Triangle 

Park, North Carolina. Publication No. EPA-450/3-76-005. April 1976. 

p. 4-34. 

9. Telecon. Wehrum, W. L. Radian Corporation, with Gravallese, P., 

Boston Edison Company. May 3, 1984. Discussion of Units 74 and 76 at 

the Boston Edison L Street facility. 
P.11 

3.0 PARTICULATE MATTER CONTROL BY SCRUBBERS 

3.1 DATA SUMMARY 

To determine the effectiveness of wet scrubbers in controlling PM 

emissions from oil-fired boilers, information from 22 tests was compiled on 

11 scrubbers representing five scrubber types. This information, which is 

presented in Table 3-1, includes operating parameters, fuel composition, and 

removal efficiencies for both PM and S02 emissions. The boilers fired 

medium- to high-sulfur fuel with sulfur contents ranging from 1.1 to 

2.8 weight percent. The individual boiler capacities range from 22 to 57 

MMBtu/hour and operated at an average 91.2 percent of capacity. The 

scrubbers treat flue gas from single or multiple boilers equivalent to total 

capacities ranging from 22 to 250 MMBtu/hour. The average S02 removal 

efficiency was 95.2 percent with a range of 87.5 to 99.9 percent. All the 

scrubbers added caustic to the scrubbing liquor to remove S02; caustic does 

not affect PM removal. 

PM emissions in Table 3-1 were measured using Method 5. It has been 

found that Method 5 inherently overstates PM emissions, because sulfuric 

acid condenses in the sampling system and is measured as PM. To alleviate 

this problem, Method 5b has been developed for measuring PM from fossil 

fuel-fired sources. In Method 5b, the temperature of the sampling system is 

maintained above the sulfuric acid dew point so that condensation does not 

occur. Since these PM emissions were measured with Method 5, they are 

higher than actual PM emissions; thus, the scrubbers presented here are more 

effective in PM removal than the data indicate. 

Four types of scrubbers achieved PM emission rates ranging from 0.05 to 

0.1 lbs/MMBtu; emissions from the fifth type ranged from 0.16 to 

0.43 lbs/MMBtu. This indicates that four of the five scrubber types can 

effectively control both S02 and PM. The following sections review the 

various scrubber designs and discuss their performances with respect to PM 

emissions. 
TABLE 3-1 . CAUSTIC SCRUBBER DATA 

Mobil 

Gen A-l, 

C-50 

Union #12, 

#23, 

#24, 

#30, 

#33-37, 

#22-4 

#24-

#24-

#30-

#30-

Run 

Run 

Run 

Run 

Run 

Run 

Run 

Run 

Run 

Run 

Run 

Run 

Run 

Run 

Run 

-1 

-3 

-7 

-7 

1 

3 

5 

6 

1 

3 

1 

2 

1 

2 

1 

1 

2 

4 

6 

Boiler 

Capacity 

(MMBtu/hr) 

22 

22 

50 

50 

50 

57 

57 

57 

57 

57 

57 . 

50 

50 

25 

25 

50 

50 

50 

50 

5-50 

5-50 

5-50 

Percent 

Load 

71 

97 

98 

105 

101 

86 

83 

70 

80 

104 

106 

92 

90 

91 

92 

87 

84 

90 

92 

90 

90 

89 

Testing 

Period 

(hour) 

2.5 

2 

3 

3.5 

3 

1.6 

1.6 

1.0 

1.0 

1.3 

1.3 

1.6 

1.6 

1.6 

1.6 

1.6 

Fuel 

Sulfur 

(wt. %) 

1.56 

1.65 

1.39 

1.58 

1.66 

1.1 

1.1 

1.1 

1.1 

2.8 

2.8 

1.65 

1.65 

1.46 

1.46 

1.46 

1.46 

1.34 

1.34 

1.14 

1.14 

1.14 

Percent 

SORemoval 

87.5 

90.7 

96.8 

89.7 

95.8 

99.0 

99.0 

99.0 

99.9 

99.9 

99.9 

95 

95 

98 

98 

96 

96 

92 

92 

99 

99 

99 

Controlled PM 

Emissions 

(lb/hWBtu) 

0.21 

0.43 

0.21 

0.17 

0.16 

0.04 

0.04 

0.06 

0.07 

0.06 

0.13 

0.08 

0.06 

0.10 

0.06 

0.07 

0.09 

0.09 

0.09 

0.06 

0.07 

0.06 

Percent PM 

Removal 

91 

92 

76 

70 

89.3 

77.5 

83 

65 

73 

L/G 

(gal/1000 acf) 

9.9 

8.15 

8.45 

10.0 

7.9 

160 

160 

20 

20 

45 

45 

160 

160 

20 

20 

20 

Mobil chevron 

Mobil chevron 

Mobil chevron 

Mobil chevron 

Mobil chevron 

Steam venturi 

Steam venturi 

Steam venturi 

Steam venturi 

Steam venturi 

Steam venturi 

Scrubber Type 

tray tower (2 trays) 

tray tower (2 trays) 

tray tower (3 trays) 

tray tower (2 trays) 

tray tower (3 trays) 

eductor with spray tower 

eductor with spray tower 

eductor with spray tower 

eductor with spray tower 

eductor with spray tower 

eductor with spray tower 

Heater Tech caustic scrubber, venturi 

Heater Tech caustic scrubber, venturi 

Koch caustic 

Koch caustic 

Andersen 2000 

Andersen 2000 

scrubber tray tower (3 trays) 

scrubber tray tower (3 trays) 

caustic scrubber, spray baffle 

caustic scrubber, spray baffle 

Heater Tech caustic scrubber, venturi 

Heater Tech caustic scrubber, venturi 

Koch caustic 

Koch caustic 

Koch caustic 

scrubber, tray tower (3 trays) 

scrubber, tray tower (3 trays) 

scrubber, tray tower (3 trays) 

to 
P.13 

3.2 CHEVRON TRAY SCRUBBER 

The scrubber design that proved least effective with respect to PM 

removal is the chevron tray scrubber. This scrubber was designed by Mobil 

Oil and was manufactured by Mustang Engineering. The scrubber consists of 

a vertical cylinder 18 feet high and 5 feet in diameter. From one to three 

trays are fixed at regular intervals within the cylinder in a chevron 

configuration. Caustic solution is introduced into a weir above the top 

tray. The solution cascades down through the column and is pumped out at 

the bottom. The flue gas from the boiler is drawn through the column by a 

fan at the top of the column. A mist eliminator is located near the top of 

the column between the top tray and the fan. 

Test data were obtained from four boilers that use chevron tray 

2 

scrubbers for emission control. Two of the boilers have a 22 MMBtu/hour 

heat input capacity and two are rated at 50 MMBtu/hour. The boilers 

operated at an average 94.4 percent of full load. The sulfur content ranged 

from 1.39 to 1.66 weight percent and averaged 1.57 weight percent. This 

scrubber had an average S02 removal efficiency of 92 percent. Towers with 

three trays performed significantly better with respect to SO, removal than 

2 

those with two trays. 

Controlled PM emissions ranged from 0.17 to 0.43 lbs/MMBtu heat input. 

The number of trays had little impact on PM removal efficiency. A two-tray 

tower installed on a 50 MMBtu/hour boiler emitted PM at a rate of 

0.17 lb/MMBtu. The same scrubber with three trays emitted PM at a rate of 

0.16 lb/MMBtu. 

There are a number of reasons for the relatively inefficient PM control 

performance of the chevron tray scrubber. One factor is the low 

liquid-to-gas (L/G) ratio relative to similar tray scrubbers. The L/G ratio 

3 

of the chevron tray scrubber was less than 10 gallon/1,000 ft , compared to 

3 

20 to 160 gallon/1,000 ft for the other scrubbers. Since PM removal is a 

function of liquid and gas contact, a large L/G ratio would increase the 

probability that a particle would contact the liquid. Therefore, a higher 

L/G ratio would increase PM removal efficiency. 

11 
P.14 

A second major factor is the configuration of the trays in the chevron 

tray scrubber. Particularly high PM removal can be obtained by accelerating 

fine liquid drops into the PM in the gas stream. This is usually 

accomplished by passing the flue gas and liquid through a venturi opening or 

by passing the gas through a high-pressure liquid spray. These methods have 

been employed in other scrubbers, but were not used in the chevron tray 

tower. In this scrubber, the gas stream enters the column through a duct 

near the bottom. Caustic solution is introduced at the top and flows 

through each of the three trays to the holding tank at the bottom. 

Liquid-gas contact occurs inside the chevron trays as the liquid and gas 

travel counter-currently. The trays provide a large liquid surface area, 

which promotes gas absorption. This was verified by the drop in SO- removal 

efficiency when a tray was removed. However, since very little turbulence 

or acceleration is achieved, the chevron tray scrubber does not perform well 

as a particle-liquid contactor. This is supported by the poor correlation 

between the number of trays and PM removal efficiency. 

3.3 VENTURI TRAY SCRUBBER 

The venturi tray scrubber presented in Figure 3-1 is manufactured by 

Koch, Inc. The scrubber consists of an induction fan followed by a vertical 

column containing a spray stage, three venturi trays, and a mist eliminator. 

A venturi tray is a horizontal tray perforated with many small holes; each 

hole is shaped to produce a venturi effect. The net result of these many 

small Venturis is the same as that of a single large venturi. Caustic 

solution enters the column above the top tray and through spray nozzles 

3 

below the first tray. The L/G ratio of this scrubber averages 20 

gal/1,000 ft3. 

4 5 Test data were obtained from two venturi tray scrubbers. ' One 

scrubber was installed on a 25 MMBtu/hour boiler. The other scrubber serves 

five 50 MMBtu/hour boilers. The boilers operated at 89 to 92 percent of 

total capacity. The sulfur content of the oil ranged from 1.14 to 

12 
r-^rScrubber 

Liquor 

(Recycled) 

—<3& -

ConstantControlled 

Disposal 

< B -

RecycleDisposal 

Pump 

Stack 

(Outlet) 

Spray 

(Recycled] 

yy 

SSSS^SSSSSW.NVJ » (Mist Eliminator 

/IIIIII I 

/ i i i i i. i i 

/—•»**— » 

• • • • • • 1 

Caustic Make-Up / pH Controlled 

Fresh Water Make-Up / Float Controlled 

By-Pass Valve 

(Open For Gas Fired) 

Duct 

N Transition 

(Inlet) 

25,000.000 BTU/HR 

Stean Generator 

Figure 3-1: Koch Flue Gas Scrubber System. 
P.16 

1.46 weight percent. The S02 removal efficiency for this scrubber design 

ranged from 98 to 99 percent. Emissions of PM averaged 0.07 lb/MMBtu and 

ranged from 0.06 to 0.10 lb/MMBtu. 

3.4 STEAM VENTURI EDUCTOR WITH A SPRAY TOWER 

As shown in Figure 3-2, this scrubber design consists of a steam 

injection eductor jet, and a vertical spray tower. Two baffles in the 

first stage of the tower create turbulence in the gas stream and promote 

liquid-gas interaction. The gas then proceeds through three counter-current 

spray stages. Next, it passes through a cocurrent spray and a mist 

eliminator; finally, it is vented to the atmosphere. 

Data were obtained from two 57 MMBtu/hour boilers with steam venturi 

eductor scrubbers. The boiler load ranged from 71 to 106 percent of 

capacity. The fuel contained 1.1 and 2.8 weight percent sulfur. This unit 

averaged over 99 percent SO~ removal efficiency. Emissions of PM ranged 

from 0.04 to 0.13 lb/MMBtu and averaged 0.07 lb/MMBtu. The steam venturi 

and four stages of high pressure sprays contributed to the low PM emissions. 

3.5 VENTURI CAUSTIC SCRUBBER 

This venturi scrubber, shown in Figure 3-3, is manufactured by Heater 

Technology, Inc. The scrubber consists of a steam venturi followed by a 

chamber partially filled with caustic solution. A set of baffles direct the 

gas onto the surface of the solution. The gas then travels through a mist 

eliminator, up a stack, and through another mist eliminator; finally, it is 

3 

vented to the atmosphere. 

Emissions data were obtained from two 50 MMBtu/hour boilers equipped 

with a venturi caustic scrubber. The boiler load ranged from 90 to 

92 percent of total capacity. The sulfur content of the oil ranged from 

1.34 to 1.65 weight percent. This scrubber-type achieved S02 removal 

efficiencies of 92 to 95 percent. Emissions of PM ranged from 0.06 to 

14 
on 

Controlled 

By-Pass Damper 

Flue Gas From 

Steam Generator 

/ (Inlet) \ 

Steam Injection 

Jet Nozzle 

Recycle 

Punp 

Recycle 

Pump 

Figure 3-2: STEAM VENTURI EDUCTOR WITH SPRAY TOWER 
P.18 

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at -. 

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vt c 

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o 

ca k (0 © E 

8 CM 

r 

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t/1 <J 

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£. X. 

z. 9 . 

u 

IS. 

vt 

co 

cs OJ > 1 cn 

o 

-cz 

o cu CU 

• M <0 CU 

I 01 
Spray Manifold (15 Nozzles) 

Recirculation Tank 

Disposal 

Mist Eliminator 

Figure 3-4: Struthers-Andersen Spray-Baffle Scrubber System. 

CO 
D 

0.09 lb/MMBtu and averaged 0.08 lb/MMBtu. The low PM emissions result from 

the turbulence in the venturi and the impaction of PM onto the surface of 

the caustic solution. 

3.6 SPRAY BAFFLE SCRUBBER 

The spray baffle scrubber, manufactured by Andersen 2000, Incorporated 

and shown in Figure 3-4, consists of a high-pressure spray venturi and a 

horizontal column. The column has six hemispherical baffles placed at 

regular intervals. Each baffle is off-set 90 degrees from the previous one 

to produce cyclonic gas flow. The baffles also provide a surface where PM 

impacts and adheres. Fifteen high pressure nozzles spray caustic solution 

into the column between the first and last baffle. After passing the last 

baffle, the gas passes through a mist eliminator and is vented to the 

atmosphere. 

Emission data were obtained from one spray baffle scrubber on a 

5 

50 MMBtu/hour boiler. The boiler operated at 85.5 percent of total 

capacity. The fuel oil had a sulfur content of 1.46 weight percent. The 

SOp removal efficiency of the spray baffle unit was 96 percent and PM 

emissions averaged 0.08 lb/MMBtu. Effective PM removal is obtained via the 

venturi, the high pressure sprays, and the baffles. 

3.7 CONCLUSION 

Four of the five scrubber types examined in this study were very 

effective in PM emission control. PM emissions for these scrubber types 

ranged from 0.04 to 0.13 lb/MMBtu and averaged 0.07 lb/MMBtu. In only one 

of the 17 tests did PM emissions exceed 0.10 lb/MMBtu. The data indicate 

that venturi action and high pressure sprays were key contributors to the 

low PM emission levels. With the addition of caustic, S02 emissions were 

also effectively controlled. This performance was attained for scrubbers 

installed on boilers ranging in size from 22 to 250 MMBtu/hour and fuel 

sulfur contents of 1.1 to 2.8 weight percent. 

18