ABMA
American
Boiler Manufacturers
Association
1500 Wilson Boulevard
Arlington VA 22209
DoE
United States
Department
of Energy
Division of Power Systems
Energy Technology Branch
Washington DC 20545
EPA
United States
Environmental Protection
Agency
Industrial Environmental Research
Laboratory
Research Triangle Park NC 27711
EPA-600/7-81-020a
February 1981
Field Tests of Industrial
Stoker Coal-fired Boilers
for Emissions Control and
Efficiency Improvement —
Sites L1-L7
Interagency
Energy/Environment
R&D Program Report
-------
RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the INTERAGENCY ENERGY-ENVIRONMENT
RESEARCH AND DEVELOPMENT series. Reports in this series result from the
effort funded under the 17-agency Federal Energy/Environment Research and
Development Program. These studies relate to EPA's mission to protect the public
health and welfare from adverse effects of pollutants associated with energy sys-
tems. The goal of the Program is to assure the rapid development of domestic
energy supplies in an environmentally-compatible manner by providing the nec-
essary environmental data and control technology. Investigations include analy-
ses of the transport of energy-related pollutants and their health and ecological
effects; assessments of, and development of, control technologies for energy
systems; and integrated assessments of a wide range of energy-related environ-
mental issues.
EPA REVIEW NOTICE
This report has been reviewed by the participating Federal Agencies, and approved
for publication. Approval does not signify that the contents necessarily reflect
the views and policies of the Government, nor does mention of trade names or
commercial products constitute endorsement or recommendation for use.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
-------
EPA-600/7-81-020a
February 1981
Field Tests of Industrial Stoker Coal-fired
Boilers for Emissions Control and
Efficiency Improvement — Sites L1-L7
by
J.W. Davis and H.K. Owens
Pennsylvania State University
University Park, Pennsylvania 16802
lAG/Contract Nos. IAG-D7-E681FZ (EPA), EF-77-C-01-2609 (DoE)
Program Element No. EHE624
Project Officers: R.E. Hall (EPA) and W.T. Harvey, Jr. (DoE)
Industrial Environmental Research Laboratory
Office of Environmental Engineering and Technology
Research Triangle Park, NC 27711
Prepared for
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Research and Development
Washington, DC 20460
U.S. DEPARTMENT OF ENERGY
Division of Power Systems/Energy Technology Branch
Washington, DC 20545
and
AMERICAN BOILER MANUFACTURERS ASSOCIATION
1500 Wilson Boulevard
Arlington, VA 22209
-------
Site L
ABSTRACT
This report presents results of field measurements to determine
particulate emission rate and particle size distribution made on seven
institutional-type stoker fired boilers firing bituminous coals.
Operational data was recorded during the test period to provide
necessary information to evaluate boiler emissions as a function of
boiler load, heat release rates, coal size and characteristics, percent
excess combustion air, and flue gas temperature. All boilers were
tested under normal operating conditions at loads of 50 to 75 percent
of maximum boiler capacity. The types of stokers tested included single
retort underfeed, multiple retort underfeed, traveling grate overfeed,
and vibrating grate overfeed. The test report contains a description
of the seven boiler-stoker units, test port location, test equipment
and procedures, and a summary of test results and observations.
-------
ACKNOWLEDGEMENTS
The authors wish to express their appreciation for the assistance
and direction given the program by project monitors W. T. (Bill) Harvey of
the United States Department of Energy (DOE) and R. E. (Bob) Hall of the
United States Environmental Protection Agency (EPA). Thanks are due to
their agencies, DOE and EPA, for co-funding the program.
We would also like to thank the American Boiler Manufacturers
Association, ABMA Executive Director, W. H. (Bill) Axtraan, ABMA Assistant
Executive Director, R. N. (Russ) Mosher, and the members of the ABMA
Stoker Technical Committee chaired by W. B. (Willard) McBurney of the
McBurney Corporation for providing support through their time and travel
to manage and review the program. The participating committee members
listed alphabetically are as follows:
R. D. Bessette Island Creek Coal Company
T. Davis Combustion Engineering
N. H. Johnson Detroit Stoker
K. Luuri Riley Stoker
D. McCoy E. Keeler Company
J. Mullan National Coal Association
E. A. Nelson Zurn Industries
E. Poitras The McBurney Corporation
P. E. Ralston Babcock and Wilcox
D. C. Reschley Detroit Stoker
R. A. Santos Zurn Industries
Finally, our gratitude goes to the host boiler facilities which
invited us to test their boiler. At their request, the facilities will
remain anonymous to protect their own interests. Without their cooperation
and assistance this program would not .have been possible.
ii
-------
TABLE OF CONTENTS
Section Page
ACKNOWLEDGEMENTS i±
LIST OF FIGURES iv
LIST OF TABLES v
1.0 INTRODUCTION , 1
2.0 EXECUTIVE SUMMARY 2
3.0 DESCRIPTION OF TEST SITES 6
3.1 Description of Test Facilities 6
3.2 Description of Units Tested 6
3.3 Test Port Locations 15
4.0 TEST EQUIPMENT AND PROCEDURES 21
4.1 Mass Emission Measurements and Procedures 21
4.2 Particle Size Distribution Measurement and Procedure .. 23
4.3 Coal Sampling and Analysis 26
4.4 Ash Collection and analysis 29
4.5 Boiler Performance Data 30
5.0 TEST RESULTS AND OBSERVATIONS 31
5.1 Particulate Mass Loading Results 31
5.2 Particle Size Distribution Results 33
5.3 Collection Efficiency 44
5.4 Particulate Loading Versus Operating Parameters 47
APPENDICES 54
iii
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LIST OF FIGURES
Figure
No.
3-1 Boiler Schematics 16
3-2 Port Locations and Sampling Grids 17
3-3 Port Locations at Boiler Outlet 18
4-1 RAC Staksampler 22
4-2 Bacho Centrifugal Classifier 24
4-3 Andersen Mark III In-Stack Impactor 25
4-4 Schematic Diagram of the Sampling Train Used to Collect Particles
for the Centrifugal Classifier and Impactor Analysis 27
5-1 Log Probability Plots of Particle Size Distribution of Particle
Matter at Boiler Outlet by Impaction 34
5-2 Log Probability Plots of Particle Size Distribution of Particle
Matter at Boiler Outlet by Centrifugal Classifier 35
5-3 Log 'Probability Plots of Particle Size Distribution at Stack
Outlet by Impaction 36
5-4 Log Probability Plots at Particle Size Distribution at Stack
Outlet by Centrifugal Classifier 37
5-5 Differential Percent Mass Plots of Particle Size Distribution at
the Boiler Outlet by Impaction at Sites LI, L2, L3, L4, L7 .... 40
5-6 Differential Percent Concentration Plots of Particle Size
Distribution at the Boiler Outlet by Impaction at Sites
LI, L2, L3, L4, & L7 41
5-7 Differential Percent Mass Plots of Particle Size Distribution at
the Stack Outlet by Impaction 42
5-8 Differential Percent Concentration Plots of Particle Size
Distribution at the Stack Outlet by Impaction 43
5-9 Collector Efficiency Curves 48
5-10 Stack Velocity vs Emission Rate 50
iv
-------
LIST OF TABLES
Table
No. Page
3-1 Description of Boilers Tested ; 7
3-2 Port Locations for Particulate Sampling 19
3-3 Preliminary Test Results 20
4-1 As-Fired Analysis of Pennsylvania Bituminous Coals Fired at Each
Site 28
4-2 Coal Sizing Data For Pennsylvania Bituminous Coals Fired at Test
Sites L5, L6, and L7 29
4-3 Percentage of Combustible Materials in Boiler Bottom Ash and
Collector Flyash at Test Sites , 29
4-4 Boiler Performance and Efficiency Data 30
5-1 Summary of Emission Test Data 32
5-2 Particle Size Distribution Comparison 39
5-3 Collector Efficiency Comparisons 45
5-4 Collector Efficiency Performance Information 46
5-5 Efficiency with Respect to Particle Size Calculated from Impactor
Results , 49
5-6 Uncontrolled Emission Rate, LB/10 BTU 52
5-7 Emission Factor, Lb/Ton 53
-------
1.0 INTRODUCTION
The objective of the Site L program is to produce information which
will (1) enhance the ability of small industrial, commercial and institutional
boiler users to install coal-fired steam generators, thereby significantly
expanding the utilization of coal; (2) provide data for better designs to
make the switch from oil and gas to coal usage less costly; (3) facilitate
preparation of intelligent and reasonable national emission standards for
smaller coal-fired boilers by the U.S. Environmental Protective Agency;
(4) refine application of existing pollution control equipment and more
closely control stack emissions under varied operating conditions through
more accurate boiler outlet dust loading data; (5) contribute to the design
of new and improved air pollution control equipment; and (6) facilitate
planning for coal supply contracts by users of the boiler-stoker equipment.
The Site L program consists of a series of seven tests to determine
particulate emission rate and particle size distribution of typical
small institutional-type stoker-fired boilers firing Western Pennsylvania
bituminous coals. Operational data were recorded during the test period to
provide the necessary information to evaluate boiler emissions as a function
of boiler load, heat release rates, coal size and characteristics, percent
excess combustion air, and flue gas temperature.
All boilers were tested under normal operating conditions with coal
supplied from the institution's contracted source. Test dates were selected
to obtain average boiler loads of 50 to 75 percent of maximum boiler
capacity. The types of stokers tested included single retort underfeed,
multiple retort underfeed, traveling grate overfeed, and vibrating grate
overfeed.
The test report contains a description of the seven boiler-stoker
units, test port locations, test equipment and procedures, and a summary of
test results and observations.
-------
2.0 EXECUTIVE SUMMARY
Seven typical small institutional-type stoker-fired boilers were tested
for particulate emission rate and particle size distribution. Emission
rates were evaluated as they relate to stoker type, coal size and
characteristics, operating conditions, and heat release rates. This section
summarizes the results of these tests.
UNITS TESTED:
Test Site
LI
L2
L3
L4
L5
L6
L7
Stoker Type
Multiple Retort
Vibrating Grate
Single Retort
Traveling Grate
Multiple Retort
Multiple Retort
Multiple Retort
Capacity, Ib/hr
34,500
40,000
31,000
30,000
38,000
27,000
55,000
Year Built
1966
1960
1951
1969
1950
1957
1968
COALS FIRED; Western Pennsylvania bituminous, double screened.
PARTICULATE EMISSION RATE TEST RESULTS
A relationship between mass emission rate and stack velocity was
observed. The rate in pounds per hour emitted from sites having high
stack velocities was greater than those sites with lower stack velocities.
This was true whether or not a collector was in place. While the relation-
ship was not strictly linear, the statistical correlation coefficient was
0.83 for sites with collectors and 0.98 for those without control devices.
Lower velocities sweep fewer pounds of particle matter from a stack than
higher velocities - not a surprising result.
It is instructive to examine the results from the site where the
lowest emission rate was found - Site L5. The tables in Sections 4 and 5
list the analyses of the coals, coal sizing, boiler performance, and the
emission rates. It is apparent that the performance at L5 had the
following characteristics:
-------
• the lowest percentage of volatiles (18.9% as compared to
the average of 32.4%),
• the highest percent of fixed carbon (68.7% as compared to the
average of 55.1%),
• the highest free swelling index (8),
• the largest percentage of fines in the coals of those coals
screened (11% passed through # 16 screen as compared to the
average of 6%),
• the second lowest percent excess air (33% as compared to
the average of 81%).
In addition, the stack temperature was among the lowest, the smallest
amount of sulfate was found in the impingers, and - in all fairness - it
must be added that the percent of operating capacity was also among
the lowest.
When the operating parameters at the site with the highest emission
rate (L2) are examined, no characteristics that are significantly different
from others are found. This would seem to indicate that the relationships
are not linear but that there may be curves with break points. Clearly
it would be helpful to establish such curves, but the present study was
not designed to accomplish this. The factors which may affect the
emission rate are:
1) type, sizing, and condition of the coal;
2) type and condition of the stoker grate;
3) air flow through the fuel bed;
4) firing rate and fuel bed thickness;
5) boiler operating parameters;
6) "caking" of the fuel bed and resulting high excess air
and flue gas temperatures.
The boiler-stoker types tested are capable of operating at a steaming
capacity of 50 to 75 percent with uncontrolled emission rates well below
the emission factor of 5A (potential emission rate in pounds of particulate
per ton of coal fired is equal to five times A - the weight percentage of
ash in coal) as reported in the U.S. Environmental Protective Agency
Publication AP 42, Compilation of Air Pollution Factors, Third Edition.
-------
Two of the multiple retort stoker units had particularly low emission rates,
while the other two multiple retort stoker units, plagued with caking fuel
beds, had much higher rates. Emission rates of the traveling grate,
vibrating grate, and single retort stoker units were progressively higher
than those of the two best multiple retort units. The calculated emission
factors, summarized in Table 5-7, indicate that the emission factor of 5A
for underfeed and overfeed stokers in the size range tested might be
reduced by a minimum of 50 percent.
PARTICLE SIZE DISTRIBUTION TEST RESULTS
The data obtained on particle size indicate that in all cases
50% of the mass at the boiler outlet is made up of particles less than
30 micrometers in diameter. In one extreme case 50% were less than 13
micrometers in diameter. It is safe to assume, therefore, that the
collection or elimination of the finer particles is essential if control
is to be achieved.
In two cases where collectors were installed (LI and L7), the mean
particle size was reduced by the collector to 7.4 at LI and 2.9 at L7.
Both were still in violation of the Pennsylvania regulations for emissions.
The particle size distribution at the boiler outlet indicates a marked
similarity in all five cases. Tlaere was a sizable fraction of particles
less than 10 urn. At sites LI and L7 the fraction of particles larger
than 10 urn were measureably reduced while those at L2 and L4 were not
significantly affected
In the case of large ducts with masonary stacks and no collectors,
low velocities were the rule. At L5 and L6 the velocities were less than
5 ft/sec while at L3 it was 10.7 ft/sec. This latter velocity was apparently
sufficient to carry larger particles through the system and up the stack.
The mean particle size at L3 did not change between the boiler outlet and
the stack and this is reflected in the emission rate. It would seem that
if large ducts and stacks are to be used as an aid to particle control,
the velocity must be very carefully chosen.
-------
COLLECTOR EFFICIENCY
The only collector operating near its design temperature and flowrate
was the one at L7. It actually brought this unit within the regulation
limit - provided the impinger catch was ignored. The other three flowrates
were much less than the recommended value and the consequences are
obvious. The efficiency of the' collector on the fine particle fraction
« 10 m) is the crucial element in particle control.
The data presented in this report indicate that there is a relation-
ship between collector efficiency and the coal used, the grate type and
boiler operating parameters, and the collector operating parameters.
The mechanical collectors on the boilers in this study were at best
marginal and at worst totally ineffective. Large ducts through which
the stack gas passed at low velocities proved almost as effective as the
collectors. The high velocities required by the cyclonic control units
kept particles airborne and, since these collectors were not operating
at the design conditions, large amounts of particle matter passed
through the duct work and mechanical collectors and into the atmosphere.
Proper installation, regular maintenance, and correct operating
procedures are necessary if the type of collectors in use at the test
sites are to have the desired effect. At small facilities where trained
personnel are at a premium collector operation will often be a problem.
-------
3.0 DESCRIPTION OF TEST SITES
This section provides a general description of the seven facilities
tested, the operational characteristics and general arrangement of the boiler-
stoker unit tested at each location, and the test port locations for each.
3.1 DESCRIPTION OF TEST FACILITIES
The facilities tested are central steam heating plants which are
providing energy for space heating, space cooling, domestic water heating,
dietary service, and laundry service for typical correctional, educational,
rehabilitation, and hospital type institutions. The sizes of the institutions
vary from approximately five to 25 million cubic feet of heated building
space. The coal requirements vary from four to 15 thousand tons of bituminous
coal annually, and the maximum steam requirements vary from 25,000 to 85,000
pounds per hour. The total installed capacities of the central heating
plants vary from 80,000 to 200,000 pounds of steam per hour.
The facilities and boiler-stoker units tested are designated herein
as Test Sites LI through L7. The names of the facilities and equipment
manufacturers have been omitted.
3.2 DESCRIPTION OF UNITS TESTED
The seven boiler-stoker units tested represent typical state-of-the
art designs for bituminous coal fired units installed in central heating
plants between 1950 and 1969. Maximum capacities of the units range from
27,000 to 55,000 pounds of steam per hour. The stokers installed in
these units represent the most common type of underfeed and overfeed
stokers available at the time.
Three of the units tested are not equipped with particulate matter
emission control devices. Four of the units are equipped with multiple
cyclone dust collectors. However, the three units that are not equipped
with control devices discharge into expanded central breechings
and tall masonary stacks which provide a degree of emission control.
-------
Table 3-1 and Figure 3-1 provide a brief description and general
arrangement of the boiler-stoker unit tested at each of the seven test
sites. A Design Data Sheet for each site is also included for
informational purposes.
Table 3-1
DESCRIPTION OF BOILERS TESTED
Max. Schematic Arrangement
Test Year Type Capacity of Units
Site Built Stoker Ib/hr Reference Figure 3-1
LI 1966 MR 34,500 Figure 3-1 b
L2 1960 VG 40,000 Figure 3-1 c
L3 1951 SR 31,000 Figure 3-1 a
L4 1969 TG 30,000 Figure 3-1 c
L5 1950 MR 38,000 Figure 3-1 a
L6 1957 MR 27,000 Figure 3-1 a
L7 1968 MR 55,000 Figure 3-1 b
Nomenclature: MR - Multiple retort underfeed
SR - Single retort underfeed
TG - Traveling grate overfeed
VG - Vibrating grate overfeed
-------
DESIGN DATA
TEST SITE: LI
BOILER:
Year Built 1966
Configuration Multiple Pass
Rated Steaming Capacity 34,500 Ib/hr
Operating Pressure 125 psig
Feedwater Temperature 212°F
Steam Temperature Saturated
STOKER:
Classification Multiple Retort Underfeed
Effective Grate Area • 97.3 ft '
HEATING SURFACES:
3
Furnace Volume 1,225 ft
Water Wall 717 ft.
Boiler 4,283 ft
HEAT RATES:
Fuel Burning Rate 3,480 Ib/hr
Furnace Liberation 37,000 Btu/hr - ft
EMISSION CONTROL EQUIPMENT:
Mechanical Collector
-------
DESIGN DATA
TEST SITE: L2
BOILER:
Year Built ; 1965
Configuration Multiple Pass
Rated Steaming Capacity 40,000 Ifa/hr
Operating Pressure 125 psig
Feedwater Temperature 212°F
Steam Temperature Saturated
STOKER:
Classification Vibrating Grate
Effective Grate Area 126 ft
HEATING SURFACES:
3
Furnace Volume 1,665 ft?
Water Wall 1,641 ft^
Boiler 4,514 ft
HEAT RATES:
Fuel Burning Rate 4,000 Ib/hr
Furnace Liberation 30,000 Btu/hr - ft
EMISSION CONTROL EQUIPMENT:
Mechanical Collector
-------
DESIGN DATA
TEST SITE: L3
BOILER:
Year Built 1951
Configuration Multiple Pass
Rated Steaming Capacity 31,000 Ib/hr
Operating Pressure — 120 psig
Feedwater Temperature 212°F
Steam Temperature Saturated
STOKER:
Classification Single Retort Underfeed
Effective Grate Area • 73 ft
HEATING:
Boiler 4,490 ft2
HEAT RATES:
Fuel Burning Rate 3,100 Ib/hr
10
-------
DESIGN DATA
TEST SITE: L4
BOILER:
Year Built 1969 .
Configuration Multiple Pass
Rated Steaming Capacity 30,000 Ib/hr
Operating Pressure 150 psig
Feedwater Temperature 220°F
Steam Temperature Saturated
STOKER:
Classification Traveling Grate
Effective Grate Area 107 ft
HEATING SURFACES:
Furnace Volume 1,315 ft-
Water Wall 920 ft^
Boiler • 2,930 ft
HEAT RATES:
Fuel Burning Rate 3,470 Ib/hr
Furnace Liberation 30,300 Btu/hr - ft
EMISSION CONTROL EQUIPMENT:
Mechanical Collector
11
-------
DESIGN DATA
TEST SITE: L5
BOILER:
Year Built 1950
Configuration Multiple Pass
Rated Steaming Capacity 38,000 Ib/tir
Operating Pressure 150 psig
Feedwater Temperature — 212°F
Steam Temperature • Saturated
STOKER:
Classification Multiple Retort Underfeed
Effective Grate Area 80.6 ft2
HEATING SURFACES:
Furnace Volume 1,250 ft3
Water Wall 1,050 ft2
Boiler 4,440 ft2
HEAT RATES:
Fuel Burning Rate 3,800 Ib/hr
Furnace Liberation 40,000 Btu/ft3 - hr
12
-------
DESIGN DATA
TEST SITE: L6
BOILER:
Year Built 1957
Configuration -' Multiple Pass
Rated Steaming Capacity 27,000 Ib/hr
Operating Pressure 110 psig
Feedwater Temperature 212°F
Steam Temperature Saturated
STOKER:
Classification Multiple Retort Underfeed
Effective Grate Area 83.3 ft2
HEATING SURFACES:
Furnace Volume 1,130 ft3
Water Wall 720 ft2
Boiler 3,280 ft2
HEAT RATES:
Fuel Burning Rate 2,440 Ib/hr
Furnace Liberation 30,000 Btu/hr - ft3
13
-------
DESIGN DATA
TEST SITE: L7
BOILER:
Year Built 1968
Configuration Multiple Pass
Rated Steaming Capacity 55,000 Ib/hr
Operating Pressure 150 psig
Feedwater Temperature 218°F
Steam Temperature Saturated
STOKER:
Classification Multiple Retort Underfeed
Effective Grate Area 161.1 ft2
HEATING SURFACES:
Furnace Volume 2,300 ft3
Water Wall 1,503 ft2
Boiler 6,057 ft2
HEAT RATES:
Fuel Burning Rate • 5,650 Ib/hr
Furnace Liberation 33,200 Btu/hr - ft3
EMISSION CONTROL EQUIPMENT:
Mechanical Collector
14
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3.3 TEST PORT LOCATIONS.
The particulate emission rate test was performed at the port loca-
tions shown in the schematic diagram, Figure 3-1. In each case prelimi-
nary tests were taken to establish the temperature-velocity profile, the
moisture content of the stack gas, and the molecular weight of the gas.
Figures 3-2 and 3-3 show - in representative form - the stack, duct, and
boiler outlet configurations and relative port locations at all sites.
By using Table 3-2 with the three figures, the actual stack dimensions
and number of sampling points and ports as well as the relative location
of the sampling points can be determined at each site. Results of the
preliminary tests are recorded in Table 3-3. The locations at the seven
sites were far from ideal relative to EPA testing procedure recommenda-
tions. Since physical limitations were encountered, ports were installed
at points where easy access could be obtained. The number of sampling
points was selected as specified in EPA Method 1.
Particle size measurements were taken at the same locations. Only
impactor samples and samples for use with the Bahco were obtained at the
boiler outlet. In two cases - L5 and L6 - boiler outlet measurements
were not taken because access could not be obtained. Since isokinetic
conditions were required, it was not possible to traverse with the
impactor in the traditional way. Instead, grid points were selected in
the stack where the velocities were similar and several impactor samples
taken so that a representative sample could be collected.
15
-------
V J
1
\^ )
c\
°2
(a)
o2
(b)
0 2
5
^
5
\J
c
3
(
!3
0
^•••'•NH
6
^
7
;
x Q
J-^-
3
T
L
T
L
4
i'
T
Test Sites
L3, L5, L6
Test Sites
LI, L7
Test Sites
L2, L4
(c)
1. Boiler 5. Collector
2. Boiler Outlet Sampling Location 6. Induced Draft Fan
3. Stack or Duct Sampling Location 7. Stub Stack
4. Stack
FIGURE 3-1. BOILER SCHEMATICS
16
-------
+
4-
•f
+
+
+
4-
+
-i- -t- 4- 4
4-4-4-4-
+ 4- 4- 4-
+- 4- 4- 4-
+ 4-4-4-
4-4-4-4-
4- + 4- 4-
4-4-4-4-
4-
4-
4-
4-
4-
4-
4-
4-
3
3
3
3
3
3
3
3
Test Sites
L2, L3, L4,
L5, L6
(a)
Rectangular Duct Divided Into Equal Areas
Sampling Points Located at the Centroid of Each Area
Test Sites
LI, L7
Circular Duct Divided Into Equal Areas
Sampling Points Located at the Centroid 6f Each Area
FIGURE 3-2. PORT LOCATIONS AND SAMPLING GRIDS
17
-------
GAS FLOW
(a)
(b)
Test Site
LI
c
4-
4-
4- 4-
4- . +
4-
4-
4-
4-
4-
4-
4-
-f
Test Sit
L3
+ 4-4-4-
4- 4-
Test Sit*
L4, L;
(c)
u
+
U D
(d)
-h
U
Test Site
L2
FIGURE 3-3. PORT LOCATIONS AT BOILER OUTLET
18
-------
TABLE 3-2
Port Locations for Particulate Sampling
Boiler Outlet
Stack Outlet
Test
Site
LI
L2
L3
L4
L5
L6
L7
No. of Figure
Ports Ref.
2 3-3 a
4 3-3 d
2 3-3 b
I 3-3 c
No Data
No Data
1 3-3 c
No. of
Sample Pts.
24
4
16
7
2
Stack
Dimensions (in.)
36 D
102 x 18
96 x 24
96 x 14.5
120 x 24
No. of Figure
Ports Ref.
2
4
8
4
8
6
2
3-2
3-2
3-2
3-2
3-2
3-2
3-2
b
a
a
a
a
a
b
No. of
Sample Pts.
32
20
48
40
48
36
24 '
Stack
Dimensions (in.)
37
40
96
48
96
121
.25 D
x 22
x 48
x 24
x 64
x 72
46 D
-------
TABLE 3-3
tsJ
O
Test
Site
LI
L2
L3
L4
L5
L6
L7
Avg. Stack
Velocity ft/sec
@ STP
44.0
32.0
10.7
29.8
4.5
3.5
46.8
Preliminary
Avg. Stack
Gas Temp. °F
560
397
486
504
365
212
511
Test Results
Percent
Water Vapor
5.0
2.0
3.5
6.0
4.7
2.9
3.8
Avg. Mol.
Wt. Dry Ib/lb-mole
30.0
29.4
29.4
30.0
29.9
29.8
29.7
Static
Pressure "H?0
-3.3
-0.6
-0.6
-0.6
-0.6
+0.5
-0.1
-------
4.0 TEST EQUIPMENT AND PROCEDURES
This section presents details of the test equipment and sampling proce-
dures that were used to obtain accurate and reliable data.
4.1 MASS EMISSION MEASUREMENTS AND PROCEDURES
Particulate mass samples were taken at the sampling ports using an RAG
STAKSAMPLER (Figure 4-1). This system meets the EPA design specifications for
Test Method 5, Determination of Particulate Emissions from Stationary Sources
(Federal Register, Volume 36, No. 27, page 24888, December 23, 1971). The
initial velocity, temperature traverse, and the particulate sample collection
were obtained using this device. Method 5 was followed in setting up and
conducting all particulate emission tests.
This method calls for the probe to be attached to a cyclone collector and
a filter holder. Four impingers, connected in series, follow the filter holder.
The first, third and fourth are the modified Greenburg-Smith type while the
second is a standard Greenburg—Smith. The control unit is equipped with a
pump, a dry gas meter, an orifice meter, and two manometers. Temperatures were
measured using both dial thermometers and chromel-aluniel thermocouples. The
pitot tube, the dry gas meter, and the orifice meter were calibrated prior to
each series of tests in accordance with the procedures outlined in EPA bulletin
No. APTD-0576 (Maintenance, Calibration, and Operation of Isokinetic Sampling
Equipment by J. J. Rom).
Particle matter is collected by the cyclone and filter in a case heated
to >-•» 120°C. The water vapor in the gas stream and the condensable particles
condense out in the impinger train which is in an ice bath. The percent
moisture in the stack gas is calculated from the increased water volume.
Millipore filters are used to separate the insoluble condensables from the
impinger water, and the soluble fraction is measured by driving off the water
and weighing the residue.
The molecular weight of the stack gas was determined by withdrawing a
sample from the gas stream and storing it in a teflon bag. The analysis was
21
-------
PITOT LINES
SAMPL
•VENT
SAMPLE BOX
METER BOX
ELECTRICAL CORD
POWER CORD
CHECK VALVE
FIGURE 4-1. RAC STAKSAMPLER
-------
performed on site using a standard orsat and was checked in- the laboratory
using infra-red analysis for CO and CO and a micro-fuel cell
(Teledyne Instrument) for 0~.
An on-site sampling van was used for sample train clean-up. All particle
matter, filters, and liquid samples were stored in sealed containers for
laboratory analysis. The clean-up and laboratory procedures were those specifed
in the Federal methods and were performed in the particle laboratory at the
Pennsylvania State University. Calculations were performed using the Method 5
equations.
4.2 PARTICLE SIZE DISTRIBUTION MEASUREMENT AND PROCEDURE
The Banco centrifugal classifier and the Andersen in-stack impactor are
devices used to obtain particle size information. Figures 4-2 and 4-3 are
schematic diagrams of the two units. The method for using the Bahco is
described in Power Test Code 28 distributed by the American Society of
Mechanical Engineers. "Procedures for Cascade Impactor Calibration and
Operation in Process Streams" (EPA-600/2-77-004) is the manual that details
the use of impactors.
The centrifugal classifier requires that large samples (1 to 50 grams) be
removed from the gas stream by some sampling technique prior to sizing. In the
laboratory, the dust sample is introduced into a hopper in the center of the
device. Particles are fed into an air flow pattern whose spiral current imparts
velocities that carry the larger, heavier particles by centrifugal force to
the periphery of the instrument while the smaller particles are swept toward the
center of the wheel where they are deposited in a chamber. By varying the air
flow, the particle matter can be separated into the size fractions. A complete.
description of the instrument, the method, and the operating principles can be
found in the test code.
The cascade impactor operates directly in the gas stream. The Mark
III Andersen device used in this work is shown disassembled in Figure 4-3. It
is designed for use in gas streams with temperatures up to 815°C (1500°F). The
preseparator at the intake end removes large particles (> 10 urn). Stack gas is
drawn in through a nozzle (not shown), and passes through the preseparator and
impactor cone to the plate section. There are eight plates (or stages)—each
23
-------
\. ROTOR CASTING
2. TAN
a VIBRATOR
4, ADJUSTABLE SLIDE
5. FEED HOPPER
6. REVOLVING BRUSH
7. TEED TUBE
8. FEED SLOT
9. FAN WHEEL OUTLET
O. COVER
II. ROTARY DUCT
12. FEED HOLE
13. BRAKE
M, THROTTLE SPACER
IS MOTOR-352O RPM
16. GRADING MEMBER
17. THREADED SPINDLE
ia SYMMETRICAL DISC
19. SIFTING CHAMBER
20. CATCH BASIN
2). HOUSING
22. RADIAL, NANES
FIGURE 4-2. BACHO CENTRIFUGAL CLASSIFIER
24
-------
Isi
Ul
I. PRESEPARATOR
2. IMPACTOR CONE
3. IMPACTOR PLATES
4. IMPACTOR PLATE HOLDER
5. HOUSING
FIGURE 4-3. ANDERSEN MARK IE IN-STACK IMPACTOR
-------
with holes slightly smaller than those in the preceding plate. The holes in
each plate are offset from the plate above and the plate below so that the air
passing through a set of holes must impact on the surface of the lower plate
and turn sharply in order to pass through the holes in that plate. Since the
hole size decreases from plate to plate, the velocity increases and
successively smaller particles are collected at each level. The eight
stages are followed by an absolute back-up filter that captures the
final particle fraction.
A glass fiber collecting media was used on each stage; the media
were perforated to keep the holes clear and the collection surface
covered. Before and after exposure, the media and the final filter were
dried over Drierite for 24 hours and weighed. The difference in the
weights was the mass in that size fraction. Calibration of the inipactor,
based on the assumption of spherical particles of 1.0 g/cc density, was
accomplished in the laboratory prior to field tests.
The sampling train employed for both the centrifugal and impactor
methods is shown in Figure 4-4. A preseparator was used on both trains
to collect the large particles. This allowed these particles to be sized by
sieving. Power Test Code 28 specifies that the particulate matter is to be
removed directly from the gas stream by a sampling technique. A glass
fiber filter was utilized in this case, and multiple samples were taken
until about 2 grams of material were collected for particle size analysis
in the centrifugal classifier. To strengthen confidence in the particle
size distribution obtained by impaction, multiple samples were taken at
different points within the duct or stack. A standardized laboratory
procedure was instituted for the cleaning and handling of the collected
particle matter.
4.3 COAL SAMPLING AND ANALYSIS
The coal storage and handling systems at Test Sites LI through L7
are very similar. Each receive coal by truck delivery to a receiving
hopper. From there the coal is transported to an in-plant overhead storage
bunker. The coal is weighed and transported to individual boiler stoker
coal hoppers by a suspended weigh larry. To obtain coal samples represen-
tative of the coal fired during the testing, incremental samples were
26
-------
47 mm FILTER HOLDER
I
PRESEPARATOR
I
EPA SAMPLING TRAIN
FIGURE 4-4.
SCHEMATIC DIAGRAM OF THE SAMPLING TRAIN USED TO COLLECT PARTI
CLES FOR THE CENTRIFUGAL CLASSIFIER AND IMPACTOR ANALYSIS
-------
obtained, using a standard coal shovel, from the weigh larry discharge
at the stoker hopper. The frequency of sampling from the weigh larry
load was varied in order to obtain a minimum 100 pound sample per test.
As each incremental sample was collected, it was placed in a clean metal
container with tight fitting cover.
The gross coal sample at each test site was prepared in a sample
crushing machine provided with riffle buckets. The final riffling of
the gross collection weighed approximately 12 pounds. This was placed
in four standard metal sample cans having a capacity of three pounds
each. The cans were sealed and delivered to an approved testing labor-
atory for analysis of moisture, heating value, ash, sulfur, volatile
matter, fixed carbon, ash softening temperature, and free swelling
index.
At Test Sites L5, L6, and L7 coal size data were obtained from
a portion of the uncrushed samples. A Gilson Porta Screen Model
PS-3, with Tyler square screens, was used to conduct these tests.
Test Results are shown in Tables 4-1 and 4-2.
Table 4-1
AS-FIRED ANALYSIS OF PENNSYLVANIA
BITUMINOUS COALS FIRED AT EACH SITE
Test Site LI L2 L3 L4 L5 L6_
% Moisture 3.6 1.6 1.0 1.6 2.0 0.6
% Ash 13.0 13.0 11.0 8.5 12.0 12.7
% Volatile 32.0 32.7 41.4 37.5 18.9 32.0
% Fixed Carbon 54.2 53.6 47.0 53.0 68.7 54.7
% Sulfur 3.0 1.4 1.3 1.6 2.1 1.6
Heating Value, Btu/lb 13,100 13,100 13,400 13,500 13,500 13,200
Ash Softening Temp. °F 2,550 2,650 2,650 2,500 2,540 2,550
Free Swelling Index 6 61/26 6 8 71/5
28
-------
97
89
95
59
24
34
36
15
18
20
9
11
11
5
2
Table 4-2
COAL SIZING DATA FOR
PENNSYLVANIA BITUMINOUS COALS
FIRED AT TEST SITES L5, L6, and L7
Test Percent Passing Stated Screen Size
Site 1 1/2" 3/4" 1/2" 1/4" #16
L5
L6
L7
Average 94 39 23 13
4.4 ASH COLLECTION AND ANALYSIS
At each of the seven Sites LI through L7 a bottom ash sample was collected
from the stoker ash pit at completion of testing. The samples were manually
crushed, mixed, quartered, and placed in a standard three-pound metal sample
container.
At Test Sites LI, L2, L4, and L7 a fly ash sample was collected from a
port near the base of the mechanical collectors. The samples were placed in
a standard three-pound metal sample container.
All samples were delivered to an approved test laboratory for analysis
of combustible content. The results of these tests are shown in Table 4-3.
Table 4-3
PERCENTAGE OF COMBUSTIBLE MATERIAL
IN BOILER BOTTOM ASH AND COLLECTOR FLYASH
AT TEST SITES
Test Site LI L2 L3 L4 L5 L6 L7
% Combustible, 22.4 40.0 25.0 19.3 22.5 8.1 22.4
Bottom Ash
% Combustible, 20.5 56.0 ND 21.8 ND ND 20.2
Collector Flyash
./
Note: ND = No Data
29
-------
4.5 BOILER PERFORMANCE DATA
Operating data from plant instruments were recorded every one-half
hour to provide information necessary to evaluate coal burning rate,
heat release rate, excess air, flue gas temperature, and boiler load
during the stack testing. Coal scales, instruments, and controls at the
seven test sites are checked and calibrated periodically by the manufac-
turer's service engineer. Special test equipment, other than an Orsat for
boiler flue gas analysis, was not provided. Boiler efficiency testing
was not included in the scope of Test Sites LI and L7. Table 4-4 presents
pertinent performance data.
Table 4-4
BOILER PERFORMANCE AND EFFICIENCY DATA
Test Site LI L2 L3 L4 L5 L6 L7
Coal Feed Rate, Ib/hr 3,060 2,578 1,483 1,903 2,075 1,991 3,27
Coal Burning Rate, Ib/hr-ft2 31.4 20.5 20.3 17.8 25.7 23.9 20.3
Grate Heat Release, 103Btu/hr-ft2 412 268 272 240 348 315 264
Furnace Heat Release,103Btu/hr-ft3 32.7 20.3 ND 19.5 22.4 23.3 18.5
Excess Air, % (by ASML formula) 71 26 186 72 33 61 116
Flue Gas Temperature, °F 564 520 484 556 497 475 599
Boiler Load, % of Capacity 75 65 60 70 55 65 50
NOTE: ND = No Data
30
-------
5.0 TEST RESULTS AND OBSERVATIONS
This section presents the results of tests performed on seven
boilers at seven different sites (L1-L7). The material includes infor-
mation obtained on emission rates, particle size distributions, and
collector efficiency.
Particulate mass loading was measured in each instance at a point
just upstream of the point at which the emissions entered the atmosphere.
Samples for particle size distribution measurements were taken at the
same location and at the boiler outlet. At four of the seven sites a
collector was in place, and the efficiency of each unit was determined
by actual measurements. The techniques used to obtain all samples were
described in section 4.0.
5.1 PARTICULATE MASS LOADING RESULTS
The test to determine the particulate emission rate at all seven
facilities was carried out in accordance with the procedures specified
in-Chapter 139 of Title 25 of the Commonwealth of Pennsylvania Code.
This code specifies the use of Federal Methods 1,2,3,4, and 5, but
requires the inclusion of the soluble and insoluble fraction of the
impinger catch in the calculation of the emission rate. The amount of
sulfate in the impinger water also must be determined using a specified
method. Since these tests were carried out in cooperation with the
Department of Environmental Resources of the Commonwealth, their proce-
dures were adopted. The results, however, are reported both with and
without the impinger catch.
Table 5-1 is a summary of all the emission test results. There are
a number of items that should be noted. The highest and the two lowest
emission rates (in lbs/10 Btu), with or without the impinger catch,
are on the boilers with no mechanical collectors. These three boilers
also operated at the lowest stack velocities which allowed the longest
settling times. In all three cases the stack gas concentrations are
lower than those found in the gas streams following collectors. The
significance of these results is discussed in section 2.0.
31
-------
Table 5-1
Test Site
Parameter
Emission Rate - With Impinger
Pounds Emitted per Ton of Coal Used
Concentration - With Impinger
(corrected to 70°F, not
corrected to 50% excess air)
Emission Rate - Without Impinger
Pounds Emitted per Ton of Coal Used
Concentration - Without Impinger
(corrected to 70°F, not
corrected to 50% excess air)
Sulfate
Stack Temperature
Stack Velocity
Coal Heating Value
Coal Feed Rate
Heat Input
Collector
Summary
lbs/106BTU
Ibs/hr
Ibs/ton
gr/scf
lbs/106BTU
Ibs/hr
Ibs/ton
gr/scf
lbs/10^BTU
(x 10~ ^)
°F
ft/sec
BTU/hr
Ibs/hr
106BTU/hr
of Emission Test
LI L2
0.456
18.3
12.0
0.19
0.446
17.9
11.7
0.19
1.03
549
51.0
13,100
3,060
40.1
yes
0.512
17.3
13.4
0.29
0.500
16.9
13.1
0.28
0.650
482
38.7
13,100
2,578
33.8
yes
Data
L3
0.709
14.1
19.0
0.13
0.664
13.2
17.8
0.12
1.25
382
11.6
13,400
1,483
19.9
no
L4
0.431
11.1
11.7
0.18
0.355
9.1
9.6
0.15
0.324
505
29.9
13,500
1,903
25.7
yes
L5
0.249
7.0
6.7
0.15
0.242
6.8
6.6
0.14
0.178
365
3.8
13,500
2,075
28.0
no
L6
0.356
9.4
9.4
0.08
0.332
8.7
8.7
0.08
0.456
286
5.0
13,200
1,991
26.3
no
L7
0.577
24.6
15.0
0.17
0.384
16.4
10.0
0.11
6.81
553
49.5
13,000
3,276
42.6
yes
-------
5.2 PARTICLE SIZE DISTRIBUTION RESULTS
The two methods used to obtain particle size information are described
in section 4.2. This section deals with the results obtained from the
Andersen in-stack impactor and the Bahco centrifugal classifier.
Particle size data are displayed in the Site L report in two ways.
The log probability plot is useful in that one can determine the percen-
tage of particles smaller than any given size, and the geometric mean or
median of the distribution is the 50 percent cut point diameter. The
geometric standard deviation is obtained by dividing the particle size
at 84 percent by the particle size at 16 percent and taking the square
root or, alternatively, dividing the particle size at 84 percent by the
geometric mean size. The selection of the method is based on the shape
of the distribution and it is assumed that the distribution can best be
represented by a straight line on log-probability paper. The geometric
standard deviation is, therefore, the slope of the line and provides a
measure of the variation.
The second method of plotting the data gives additional information
in a pictorial and graphical way. The particle size is plotted on a log
scale on the abscissa, while a linear scale is used on the ordinate.
This'axis is labeled either d%M/dlog D or dC/dlog D. The area under the
curve describes the change in particle mass or particle concentration
with respect to the change in particle size. More simply, the area
under the curve between any two selected particle sizes is the percen-
tage of the mass or concentration between the two sizes. A display of
this type is especially convenient in determining the efficiency of a
collector with respect to particle size. To obtain the data on effi-
ciency in the following section, the curves are carefully plotted from
the impactor information and the areas under the curves are measured
using a planimeter.
Figures 5-1 to 5-4 show the data:
a) from each site where samples were taken;
b) at the boiler outlet and in the stack prior to emission
to the atmosphere; and
c) for both the impactor and the centrifugal classifier.
33
-------
§*.•
u
K
ft.
*
10
1-
0.1-
04M
I III!
NO COLLECTOR
WITH COLLECTOR
L7 L2
L3/
1 I
I I 1 I 1
I • I I I A
0.1
1.0
10.0
100.0
Dp! MICROMETERS)
FIGURE 5-1 'LOG PROBABILITY PLOTS OF PARTICLE SIZE DISTRIBUTION OF PARTITl F
-------
M.M
M.t
o
H
K
10-
0.1- .
0.01
— NO COLLECTOR
WITH COLLECTOR
L4-
I I 1111
0.1
1.0
10.0
100.0
FIGURE 5-2
Dp (MICROMETERS)
LOG PROBABILITY PLOTS OF PARTICLE SIZE DISTRIBUTION OF PARTICLE
MATTER AT BOILER OUTLET BY CENTRIFUGAL CLASSIFIER
-------
M,tt-
T 1 r—i—till
I I I I I I I
•*§-
— NO COLLECTOR
WITH COLLECTOR
-I
O
H
&
HI
10--
LB
LI
0.1 -,
O01
' ' i t ' '
J L
0.1
1.0
10.0
Op (MICROMETERS!
fOO.O
" T * f* IX
-------
tO-
*
10-:
at- .
I 1
— NO COLLECTOR
WITH COLLECTOR
LS
L4
i i t i i
0.1
1.0
10.0
100.0
DplMICROMETERSI
FIGURE 5-4 LOG PROBABILITY PLOTS AT PARTICLE SIZE DISTRIBUTION AT STACK
OUTLET BY CENTRIFUGAL CLASSIFIER
-------
The data from the centrifugal classifier are somewhat different from the
impactor results particularly for particles less than 10 micrometers in
diameter. The lower cut off for the centrifugal device is about 2.5 um
while the impactor can classify particles down into the submicrometer
range. This lack of definition in the lower size ranges distorts the
distribution shifting it toward larger mean particle sizes. Table 5-2 shows
the geometric means and standard deviations based on the .log-probability
plots. The differences between the methods are obvious. Given the fact
that the impactor withdraws the sample directly from the gas stream and
has a finer definition across the entire size distribution, the data
from this sampling device are used in the extended analysis.
Using the second method of plotting provides a better understanding
of what the particle distribution looks like. The d%M/dlog D and dC/dlog
D plots for the boiler outlet (Figures 5-5 and 5-6) indicate that the
material coming from the boiler has very similar characteristics. Only
Site L7 deviates markedly from the others and then only in the region
above 10 micrometers. It appears that the lack of particles in this
region is accurate since it is also reflected at the stack outlet shown
in Figure 5-7 and 5-8. Once the particles pass through the collectors
and the long ducts, the distributions are changed as shown in the latter
two figures. It is clear from these data that the largest percentage of
particles emitted from boilers are larger than 10 micrometers and that
there is a significant fraction between 2 and 10 um. Collectors that
have little efficiency below 10 pm will probably not be able to provide
sufficient control for compliance purposes. On the basis of these data,
it would seem necessary to reduce the 2 to 10 um fraction in order
to achieve compliance with regulations.
The irregular curves in Figure 5-7 are caused by the reduction of the
large particle fraction through settling and multiclone collection. The
major percentage of the mass is thus shifted into the 1 to 10 ym range,
indicating that the largest fraction of the emitted particles are small
in size. Figure 5-8 which shows particle concentration with respect to
size is less irregular, but the effect of the cyclones at sites LI and
L7 is quite apparent. The concentration of larger particles is reduced
and, in the case of L7, fewer particles are to be found even in the 1 to
10 pm range. It is this fine particle fraction that must be reduced to
achieve control.
38
-------
Table 5-2
Particle Size Distribution
Comparison
Impaction
Centrifugal Classification
Test Site
LI
L2
L'3
L4
L5
L6
L7
Boiler
Outlet
x Sg
21.0 4.5
23.0 4.6
28.0 2.3
25.0 9.0
ND
ND
13.0 7.3
Stack
Outlet
x Sg
7.4
23.0
28.0
18.0
9.3
0.7
2.9
8.1
4.0
2.5
10.9
16.9
7.7
6.6
Boiler Stac
Outlet Outl
x Sg x
15.0 4.0 8.8
32.0 3.7 25.0
44.0 3.7 22.0
44.0 2.5 9.0
ND 70.0
ND 60.0
54.0 3.2 15.0
k
et
Sg
3.4
3.8
3.5
2.9
2.9
5.5
8.1
x = Geometric Mean Diameter in Micrometers
Sg = Geometric Standard Deviation
NOTE: ND = No Data
39
-------
140
iao - -
NO COLLECTOR
WITH COLLECTOR
10.0
100.0
yiOPOINT DIAMETER (MICROMETERS)
-------
•00- -
400- -
300- -
aoo - -
100--
•—NO COLLECTOR
WITH COLLECTOR
1.0 10.0
MIDPOINT DIAMETER (MICROMETERS)
100.0
FIGURE 5-6 - DIFFERENTIAL PERCENT CONCENTRATION PLOTS OF PARTICLE SIZE DISTRIBUTION
AT THE BOILER OUTLET BY IMPACTION AT SITES L1, L 2, L3, L4, & L7
-------
— NO COLLECTOR
WITH COLLECTOR
10.0
100.0
MIDPOINT OUMiTER (MICROMETERS)
-------
100
•00
— NO COLLECTOR
WITH COLLECTOR
FIGURE 5-8 -
1.0 10.0
MIDPOINT DIAMETER (MICROMETERS)
DIFFERENTIAL PERCENT CONCENTRATION PLOTS OF PARTICLE SIZE
DISTRIBUTION AT THF STACK OUTLET BY IMPACTION
100.0
-------
5.3 COLLECTOR EFFICIENCY
Collector efficiency can be estimated in two ways. First, the
Ibs/hr measured by the standard emission test can be used in conjunction
with the actual material collected per hour in the collector. In order
to make this estimate the collector is cleaned prior to the initiation
of the stack test. After the test is over the particle matter is removed
and weighed. The second method uses the total concentration from the
samples taken at the collector inlet and outlet. This latter technique
utilizes the fact that the mass concentration of particle matter in each
cubic meter of gas can be calculated from the samples obtained by impactors
and from centrifugal classification. By comparing the concentration
before and after the collector, the efficiency can be estimated. The
following example taken from Site LI results is illustrative:
Method 1 - Based on Stack Test and Mass in Collector
Emission Rate = 18.29 Ibs/hr. Collector Rate = 6.65 Ibs/hr.
Total material generated per hour = 24.94 Ibs/hr.
Efficiency = ^'^"g^8'29 x 100 =26.6%
Method 2 - Based on concentrations as measured by the Impactor
(or Centrifugal Classifier)
Before collector = 427.7 mg/NCM
After collector = 271.1 mg/NCM
Efficiency = 427>742~ ' x i00 = 36.6%
Since it is quite difficult to remove all the material from the
collector and since there would be losses in the breaching, it is not
surprising that the methods do not yield identical results. In the four
cases where efficiency was measured by these methods, the outcome was
similar to that shown above.
The collector efficiency information is shown in Table 5-3. Methods
1 and 2 are discussed above. The similarity of the results is quite
striking. Only at site L4 do the values differ by significant amounts and,
even in this case, it is still apparent that the efficiency is quite low.
44
-------
There is not a single instance in which the collector was operated
at the design flowrate (see Table 5-4). When design flowrates differ by
large amounts (Sites L2 and L4) the penalty is quite severe and leads to
collector efficiencies that are extremely low. The device operating
closest to design conditions (Site L7) has the most reasonable efficiency,
but this is not reflected in the overall emission rate when the rate
includes condensables. About 33% of the particle matter was found in
the impingers. If the impinger catch is excluded, the particle concentration
at site L7 is the next to the lowest recorded (See Table 5-1, Concentration
Without Impinger Catch).
The sulfate concentration in Table 5-1 should also be noted. The
sulfate is determined using the barium sulfate turbidity method* as
specified by the Commonwealth of Pennsylvania. It is performed on the
impinger water. The only number that is quite different from the others
— 7 f\
is the 6.81 x 10 lbs/10 Btu at site L7. It appears that the soluble
fraction collected in the impingers at site L7 contains a considerable
amount of sulfate. The reason for this is not clear but may be related
to the coal used.
Table 5-3
Collector Efficiency Comparisons
Method 2
Impactor Centrifugal
Test Site Method 1 Measurement Classifier Measurement
L-l 26.6% 36.6% 36.0%
L-2 10.9% 10.9% 7.2%
L-4 22.8% 2.8% 12.6%
L-7 42.9% 66.3% 65.4%
*The method is described in Standard Methods for the Examination of Water and
Wastewater prepared and published by the American Public Health Association,
the American Water Works Association, and The Water Pollution Control Federation
(pgs 334-335) 13th Edition, 1971
45
-------
TABLE 5-4
Collector Efficiency Performance Information
Collector Efficiency with Re- Design Flow- Nominal Design Flow- Operating Flow- Nominal Oper-
Test Efficiency spect to Particle Size rate (cfm) & rate @ Std. Temp. rate (cfm) & ating Flowrate
Site From Impac- Eff.>10 Eff.<10 Temp. °F Temp. °F @ Std. Temp.
tor (%) (NDF) (NOF)
LI 36.6 59.8 0.4 28,000 @ 14,000
600°F
L2 8.9 9.0 8.0 22,000 @ 11,200
580°F
L4 2.8 2.8 0.0 19,270 @ 9,500
615°F
L7 66.3 82.3 56.6 35,400 @ * 18,040
580°F
Facility NOF
NDF
LI 0.80
L2 0.62
L4 0.77
L7 0.95
21,200 @
540°F
12,400 @
480°F
13,200 <§
500°F
32,000 @
530°F
11,240
6,990
7,290
17,130
-------
The collection efficiency curves based on the impactor data are
shown in Figure 5-9. On the basis of these results one could assume
that the collectors at sites LI and L7 are performing near the design
criteria while the collectors at the other two sites are not removing
even the larger particles with reasonable efficiency. This is born out
more directly by examining the data as presented in Table 5-5. These
data are obtained by measuring the area under the curve in Figures
5-6 and 5-8. Note that at site LI the efficiency drops off dramatically
below 20 micrometers while at site L7 the multiclone appears to have
a 50% cut point diameter of about 10 micrometers. At sites L2 and L4
the collectors have rather low efficiency values across the whole operating
spectrum.
Figure 5-10 is a plot of the emission rate from the stack in Ibs
per hour versus the stack velocity in feet per second. The sites with
collectors and without are grouped for analysis. Note that in both
cases the statistical correlation coefficient is relatively high—0.83
for the sites with collectors and 0.98 for those without control devices.
The lines shown are based on a least squares fit to the data on the
graph. The results are not surprising; the higher velocity gas streams
tend to carry more particles out into the atmosphere even in cases where
a collector is in place.
5.4 PARTICULATE LOADING VERSUS OPERATING PARAMETERS
The Site L test program did not provide for the testing of individual
boilers at various loads and operating conditions, or with coals other than
those supplied from the contracted source. However, a comparison of the types
of stokers, fuels fired, and performance data versus uncontrolled emission rates
downstream of the boiler outlet as listed in Table 5-6 provides some
interesting observations.
Type of Stoker
Two multiple retort stoker units (L5 and L6), not equipped
with emission control devices, had the two lowest emission rates.
The other two multiple retort stoker units (LI and L7), equipped
with multiple cyclone collectors, ranked fifth and seventh with
47
-------
% COLLECTION EFFICIENCY
o
c
33
m
01
i
to
o
o
m
O
H
O
33
m
•n
•n
O
m
z
o
o
c
33
<
m
(A
-------
TABLE 5-5
Efficiency with Respect to Particle Size
Calculated from Impactor Results
Test
Site '
LI
Particle
Size Range
(Micrometers)
125-30
30-20
20-10
L2
125-30
30-20
20-10
L4
125-30
30-20
20-10
L7
125-30
30-20
20-10
Boiler Outlet
Concentration
mg/NCM
183.7
47.9
63.7
108.4
280.5
75.2
86.7
95.6
173.8
57,
63,
111.1
85.2
6.7
65.9
140.6
Stack
Concentration
mg/NCM
51.6
12.6
54.9
107.9
243.4
71.1
93.0
86.2
165.1
55.7
62.2
111.8
5.9
1.7
20.3
61.0
Collector
Efficiency
71.9
73.8
13.9
0.4
13.2
5.6
0.0
5.0
3.5
2.0
0.0
93,
74,
69,
56.6
49
-------
30T
25-
ft/sec
51.0
37.8
11.6
29.9
3.8
5.0
49.5
Ib /hr
18.3
17.3
14.1
11.1
7.0
9.4
24.6
A y= 0.844x+4.43 Corr. Coef. * 0.98
® a0.460x+1.53 Corr. Coef. » 0.83
®L7
20-
£
M
L2®
UJ
5
cc
L3<
CO
i
UJ
10-
L6A/
5-
L5
A NO COLLECTOR
® COLLECTOR
10
20 30 40
STACK VELOCITY (ft/sec;
50
60
FIGURE 5-10. STACK VELOCITY vs EMISSION RATE
50
-------
respect to increasing emission rate. The higher emission rates
from the latter two units may be attributed to "caking" fuel bed
problems resulting in high excess air and high flue gas temperature.
Higher gas velocity in the flue gas discharge systems of the latter
two units also contribute to the higher emission rates.
The traveling grate stoker (L4), vibrating grate stoker (L2),
and single retort stoker (L3), units ranked third, fourth and sixth
with respect to increasing emission rate. The high emission rate
from the single retort stoker unit also may be attributed to "caking"
fuel bed problems.
Coal Sizing and Characteristics
Coal size data (Table 4-2) was obtained at Test Sites
L5, L6, and L7 only. These data do not indicate any particular
relationship to the emission rates. There also was no apparent
relationship between the various coal characteristics listed in
Table 4-1 and the emission rates.
Excess Air/Flue Gas Temperature
A good relationship is indicated, for multiple retort stoker
units, between emission rate and the inter-related variables
of excess air and flue gas temperature listed in Table 4-4.
Emission rates increased as excess air and flue gas temperatures
increased.
Boiler Capacity, Coal Feed Rate, and Heat Release Rate
A good relationship is indicated, for multiple retort stoker
units, between emission rate and the coal feed rate listed
in Table 4-4. However, no relationship can be established between
emission rate and the boiler design capacity, boiler load in
percent of steaming capacity, or heat release rate.
51
-------
Particulate emission test results are listed in Table 5-1. However,
the results shown for Test Sites L3, L5 and L6 represent uncontrolled boiler
emissions, and results shown for Test Sites LI, L2, L4 and L7 represent
controlled emissions downstream of multiple cyclone collectors. To provide
a means of comparing uncontrolled emission rates of all sites, uncontrolled
boiler emissions from units equipped with collectors were calculated by
applying the collector efficiencies, shown in Table 5-3, to the controlled
emission rate. A summary of the test and calculated uncontrolled boiler
emission rates are listed in Table 5-6.
Table 5-6
UNCONTROLLED EMISSION RATE, LB/10 BTU
Test By By Calculation
Site Test Average High Low
LI — 0.684 0.719 0.621
L2 — 0.563 0.575 0.552
L3 0.709
L4 — 0.498 0.588 0.433
L5 0.249
L6 0.356
L7 — 1.464 1.712 1.011
The particulate emission factor for coal combustion without control
devices for all stoker types except spreaders, as reported in the U.S.
Environmental Protective Agency Publication AP-42, Compilation of Air
Pollution Factors, Third Edition, is 5A (potential emission rate in
pounds of particulate per ton of coal fired is equal to five times the
weight percentage of ash in the coal). The uncontrolled emission rates
shown in Table 5-6 were converted to equivalent particulate emission
factors provided by this publication. A summary of the calculated
factors are listed in Table 5-7.
52
-------
Table 5-7
EMISSION FACTORS, LB/TON
Test
Site
LI
L2
L3
L4
L5
L6
L7
AP 42
By
Test
0.7A
0.6A
0.8A
5A
By Calculation
Average High Low
1.4A 1.4A 1.3A
1.1A 1.2A 1.1A
1.6A 1.8A 1.4A
2.9A 3.6A 2.1A
53
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APPENDICES
Page
APPENDIX A English and Metric Units to SI Units 55
APPENDIX B SI Units to English and Metric Units 56
APPENDIX C SI Prefixes 57
54
-------
APPENDIX A
CONVERSION FACTORS
ENGLISH AND METRIC UNITS TO SI UNITS
To Convert From ' To Multiply By
in
in2
ft
ft
ft
Ib
Ib/hr
lb/106BTU
g/Mcal
BTU
BTU/lb
BTU/lb
BTU/hr
J/sec
J/hr
BTU/ft/hr
BTU/ft/hr
BTU/ft2/hr
BTU/ft2/hr
BTU/ft3/hr
BTU/ft3/hr
psia
"H20
Rankine
Fahrenheit
Celsius
Rankine
cm
cm2
m
m2
m3
Kg
Mg/s
ng/J
ng/J
J
J
J/kg
w
W
W
W/m
J/hr/m
W/m2
J/hr/m2
W/m3
J/hr/m3
Pa
Pa
Celsius
Celsius
Kelvin
Kelvin
2.540
6.452
0.3048
0.09290
0.02832
0.4536
0.1260
430
239
1054
1054
2324
0.2929
1.000
3600
0.9609
3459
3.152
11349
10.34
37234
6895
249.1
C = 5/9R-273
C = 5/9(F-32)
K = C+273
K = 5/9R
55
-------
APPENDIX B
CONVERSION FACTORS
SI
To Convert From
era
cm ^
m
m2
m3
Kg
Mg/s
ng/J
ng/J
J
J/kg
J/hr/m
J/hr/m2
J/hr/m3
W
W
W/m
W/m2
W/m3
Pa
Pa
Kelvin
Celsius
Fahrenheit
Kelvin
UNITS TO ENGLISH AND METRIC
To
in
in2
ft
ft2
ft3
Ib
Ib/hr
lb/106BTU
g/Mcal
BTU
BTU/lb
BTU/ft/hr
BTU/ft2hr
BTU/ft3/hr
BTU/hr
J/hr
BTU/ft/hr
BTU/ft2/hr
BTU/ft3/hr
psia
"H20
Fahrenheit
Fahrenheit
Rankine
Rankine
UNITS
Multiply By
0.3937
0.1550
3.281
10.764
35.315
2.205
7.937
0.00233
0.00413
0.000948
0.000430
0.000289
0.0000881
0.0000269
3.414
0.000278
1.041
0.317
0.0967
0.000145
0.004014
F = 1.8K-460
F = 1.8C+32
R = F+460
R = 1.8K
56
-------
Multiplication
Factor
1018
1015
1012
109
106
103
102
ioi
10-1
10-2
10-3
10~6
10-9
10-12
10-15
10-18
APPENDIX C
SI PREFIXES
Prefix
exa
peta
tera
giga
mega
kilo
hecto*
deka*
deci*
centi*
mllli
micro
nano
pico
f era to
atto
SI Symbol
E
P
T
G
M
k
h
da
d
c
m
u
n
P
f
a
*Not recommended but occasionally used
57
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO. 2
EPA-6QO/7-81-020a
4. TITLE AND SUBTITLE TT4-1J rp,, i r T J j. • i n- i ^ i
Field Tests of Industrial Stoker Coal-
fired Boilers for Emissions Control and Efficiency
Improvement- -Sites L1-L7
7. AUTHOR(S)
J.W. Davis and H.K. Owens
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Pennsylvania State University
University Park, Pennsylvania 16802
12. SPONSORING AGENCY NAME AND ADDRESS
EPA, Office of Research and Development*
Industrial Environmental Research Laboratory
Research Triangle Park, NC 27711
3. RECIPIENT'S ACCESSION- NO.
5. REPORT DATE
February 1981
6. PERFORMING ORGANIZATION CODE
8. PERFORMING ORGANIZATION REPORT NO
10. PROGRAM ELEMENT NO.
EHE624
11. CONTRACT/GRANT NO.
EPA-IAG-D7-E681FZ and
DoE-EF-77-C-01-2609
13. TYPE OF REPORT AND PERIOD COVERED
Final; 2/78-5/79
14. SPONSORING AGENCY CODE
EPA/600/13
15. SUPPLEMENTARY NOTES JERL-RTP project officer is R.Hall. (*) Cosponsors are DoE(W.
Harvey Jr. ) and the American Boiler Manufacturers Assn. Reports are available for
Sites A-K.
The report gives results of field measurements to determine particulate
emission rate and particle size distribution for seven institutional-type stoker-fired
boilers firing bituminous coals. Operational data were recorded during the tests to
provide information for evaluating boiler emissions as a function of boiler load,
heat release rates, coal size and characteristics, percent excess combustion air,
and flue gas temperature. All boilers were tested under normal operating conditions
at loads of 50-75% of maximum boiler capacity. The types of stokers tested included
single retort underfeed, multiple retort underfeed, traveling grate overfeed, and
vibrating grate overfeed. The report describes the seven boiler-stoker units, test
port locations, and test equipment and procedures, and summarizes test results and
operations. The particulate mass emission rate from high stack velocity sites was
greater than from lower stack velocity sites, whether or not a collector was used:
the statistical correlation coefficient was 0. 83 with collectors and 0, 98 without. The
units tested can operate at 50-75% load with uncontrolled particulate emission rates,
well below the calculated value of five times the weight percentage of ash in coal
recommended in 'Compilation of Air Pollution Factors,' AP-42. Data indicate that
'% of the mass at the boiler outlet consists of <30 micrometer diameter particles.
17..
a.
Pollution
Field Tests
Boilers
Bituminous
Stokers
Combustion
13. DISTRIBUTION
Release to
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
Measuring
Dust
Emission
Coal Particle Size Distri-
bution
Efficiency
STATEMENT
Public
b. IDENTIFIERS/OPEN ENDED TERMS
Pollution Control
Stationary Sources
Particulate
19. SECURITY CLASS (This Report)
Unclassified
20. SECURITY CLASS {This page)
Unclassified
C. COSATI
13B
14B
ISA
2 ID
2 IB
21. NO. OF
6
Field/Group
11G
14F
PAGES
4
22. PRICE
EPA Form 2220-1 (9-73)
-------
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Office of Research and Development
Center for Environmental Research Information
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OFFICIAL BUSINESS
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AN EQUAL OPPORTUNITY EMPLOYER
POSTAGE AND FEES PAID
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tear off; and return to the above address.
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