EPA-600/2-76-209
July 1976
Environmental Piotecticr. Technology Ss.ies
          PERFORMANCE OF  EMISSION  CONTROL
                     DEVICES  ON  BOILERS  FIRING
              MUNICIPAL SOLID  WASTE  AND OIL
                               industrial Environmental Research Laboratory
                                    Office of Research and Development
                                   U.S. Environmental Protection Agency
                              Research Triangle Park, North Carolina 27711

-------
               RESEARCH REPORTING SERIES

Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into five series. These five broad
categories were established to facilitate further development and application of
environmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The five series are:

     1.   Environmental Health Effects Research
     2.   Environmental Protection Technology
     3.   Ecological Research
     4.   Environmental Monitoring
     5.   Socioeconomic Environmental Studies

This report  has been assigned  to the ENVIRONMENTAL PROTECTION
TECHNOLOGY series. This series describes research performed to develop and
demonstrate instrumentation, equipment, and methodology to repair or prevent
environmental degradation  from point and non-point sources of pollution. This
work provides the new or  improved technology required for the control  and
treatment of pollution sources to meet environmental quality standards.
                    EPA REVIEW NOTICE

This report has been reviewed by  the U.S.  Environmental
Protection Agency, and approved for publication.   Approval
does not signify that the contents necessarily reflect the
views and policy of the Agency, 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-600/2-76-209

                                     July 1976
PERFORMANCE OF EMISSION CONTROL

      DEVICES ON BOILERS FIRING

   MUNICIPAL SOLID  WASTE  AND OIL
                      by

          J.B. Galeski and M. P.  Schrag

           Midwest Research Institute
              425 Volker Boulevard
           Kansas City, Missouri  64110
        Contract No. 68-02-1324, Task 40
          Program Element No.  EHB533
       EPA Task Officer: James D. Kilgroe

   Industrial Environmental Research Laboratory
     Office of Energy, Minerals, and Industry
        Research Triangle Park, NC 27711
                 Prepared for

  U.S. ENVIRONMENTAL PROTECTION AGENCY
        Office of Research and Development
             Washington, DC 20460

-------
                               ABSTRACT
     Existing data on particulate emissions from oil-fired electric  utility
boilers and from waterwall (steam generating)  incinerators firing  either re-
fuse or refuse-plus-coal/oil auxiliary fuel were used to  estimate  particulate
flue gas loadings for combined firing of shredded municipal refuse (MSW) and
oil. Estimates of control device performance were made for several planned
oil-MSW resource recovery systems. On the basis of  these  estimates,  installed
particulate emission controls, designed for coal, are predicted to be  signifi-
cantly less efficient for control of particulate emissions from combined fir-
ing of oil-MSW. Anticipated control difficulties result mostly from  relatively
high particulate loadings, high flue gas volumes, fine particulates, relatively
low particle density, and relatively high fractions of carbonaceous, low-
resistivity particulate.
                                     iii

-------
                                 CONTENTS
Abstract	iii

List of Figures	viii

List of Tables. .............. 	  ........    x

Acknowledgments 	 ....................... xiii

Section

  1     Summary ............................    1

           Information Acquisition. ..................    1
           Control Performance and Cost Correlations.  .........    2
           Analytical Model Development ................    2
           Case Studies	    3
           Recommendations. ......................    3

              Electrostatic Frecipitator Control.  .  .  	  .    4
              Cyclone Control	    4
              Novel Control Devices .......  	    4

  2     Introduction. .........................    5

  3     Particulate Emission Data Acquisition and  Evaluation.  .....    6

           Mass Emissions Data.	    7

              Uncontrolled Particulate Emissions from  Oil-Fired
                Electric Utility Boilers.  ...  	    8
              Uncontrolled Particulate Emissions from  Waterwall
                Incinerators.  ..............  	  ..    16
              Estimate of  Refuse Fly Ash  from Suspension  Firing
                of MSW	    16

-------
                            CONTENTS (Continued)

Section

              Estimated Particulate Emissions from Combined Firing
                of Oil and Municipal Solid Wastes	     22

           Flue Gas Volume	     24
           Fly Ash Density	     26
           Fly Ash Fusion Temperature.	     29
           Particle Size Distributions	     30
           Fly Ash Resistivity	••     33

  4     Cost and Effectiveness of  Particulate Emission Controls on
          MSW-Oil Fired Boilers	     38

           Inertial Collectors ........ 	 ....     38
           Wet Scrubbers 	 ............     41
           Electrostatic Precipitators  	     42

              Control  Costs  for Electrostatic Precipitator Control .     44
              Electrostatic  Precipitator Performance Model .....     44

  5     Case Studies	     43

           District of Columbia. ..................     48

              Program  Status	     51
              Refuse Derived Fuel  (RDF) Preparation and Facilities .     51
              Characteristics of Test Boiler ............     53
              Installed Air  Pollution Control Equipment. ......     53
              District of Columbia Emission Regulations. ......     56
              Estimated Performance of  Installed Air Pollution
                Control Equipment. ........ 	     50
              Cost of  Air Pollution Control. ............     53

           Wilmington, Delaware (New Castle County). ... 	     62

              Project  Status ............... 	     62
              Refuse Derived Fuel  Preparation and Facilities ....     62
              Characteristics of Test Boilers. 	 .....     6?
              Installed Air  Pollution Control Equipment. ......     65
              Delaware Emission Regulations	     65
              Estimated Performance of Air Pollution Control
                Equipment. .....................     69
              Cost  of  Air Pollution Control	     69

                                   vi

-------
                           CONTENTS (Concluded)

Section                                                                Page

           New York City	   72

              Project Status	   72
              Refuse Fuel Preparation Facilities. .... 	   73
              Boiler System Descriptions	   73
              Installed Air Pollution Control Equipment .......   73
              New York City Particulate Air Emission Regulations. . .   73
              Estimated Performance of Installed Air Pollution
                Controls	   73
              Cost of Emission Control. ...............   73

           State of Connecticut (Bridgeport). . 	 .....   74

              Project Status.	   74
              Boiler System Descriptions. ..............   75
              Refuse Preparation Facilities .............   75
              Installed Air Pollution Control Equipment .......   75
              Connecticut Air Emission Regulations. .........   75
              Estimated Performance of Air Pollution Control
                Equipment ......................   76
              Cost of Emission Control.	   76

  6     Recommendations ............ 	 ...   77

           Electrostatic Precipitator Control 	   77
           Cyclone Control	   78
           Scrubber Control	   78

References. .............................   80

Appendix A - Particulate Emissions from Oil-Fired Electric
               Utility Boilers	   87

Appendix B - Particulate Emissions Data for Waterwall Incinerators. .   97

Appendix C - Electrostatic Precipitator Performance Model 	  104
                                     vii

-------
                                  FIGURES

No,

  1     Solids Burden Plotted Against Excess Oxygen for Different
         Boiler Loads and Fuel Oil Types.  ......  	    13

  2     Uncontrolled Electric Utility Emission Versus  Capacity (no
         additives employed). ....................    14

  3     Controlled and Uncontrolled Particulate  Emissions  for  Residual
         Oil Burning Base Loaded Power Plant Boilers  Operating at
         ^ 70 MW (no additives employed)	    15

  4     Dimensionless Plot Showing Fractional Increase in  Total Fly
         Ash as a Function of Percent MSW  for Various Values  of
         Fuel Characterization Parameter (C). .  .  .  .  ........    19

  5     Theoretical Gas Flow Rates for Combined  Firing of  Oil  and
         Municipal Solid Waste (MSW) in a  75 MW Power Plant	    28

  6     Weibull Parameter Interpolation of  Andersen Impactor Data for
         Harrisburg Municipal Incinerator  •••...........    34

  7     Fractional Efficiency Data for Cyclone Collection  of Fly Ash
         from Coal- and Oil-Fired Electric Utility Boilers. .....    4Q

 8     Total Installed Cost of Wet Scrubbers	t    43

 9     Total Installed Cost for Electrostatic Precipitators 	    45

10     Process Flow for Preparation of RDF at District of Columbia. .    52

11     Effect of MSW Fly Ash Fraction (fr) on Calculated  Particulate
         Emissions (uncontrolled) from Combined Firing of MSW and
         No.  6 Residual Oil (from Tables 1 and 2)	     59


                                     viii

-------
                            FIGURES (Concluded)

No.                                                                      Page
12     ESP Efficiency (predicted) for Combined Firing of Oil and
         MSW at Pepco Benning Station No. 26.	   60

13     Estimated Particulate Emissions (controlled) for Combined
         Firing of Oil and MSW at Pepco Benning Station No. 26	   61

14     Schematic Representation of Materials Recovery Process, New
         Castle, Delaware .......................   63

15     ESP Efficiency (predicted) for Combined Firing of Oil and
         MSW at Delmarva Edgemoor Station No. 4 (150 MW).	   70

16     Estimated Particulate Emissions (controlled) for Combined
         Firing of Oil and MSW at Delmarva Edgemoor Station
         No. 4	   71

C-l    Block Diagram of ESP Performance Model	108

C-2    Current Density as a Function of Resistivity 	  .....  113

C-3    Comparison Between the Voltage Versus Current Characteristics
         for Cold-Side and Hot-Side Precipitators	114
                                     IX

-------
No.
                                  TABLES

                                                                         Page
 1     Estimated Total Particulate and Percentage of Refuse  Fly Ash
         in Fly Ash Composite from Combined Firing of  Oil  and
         Municipal Solid Wastes (MSW)	••   23

 2     Controlled Emissions for Combined Firing of Refuse  with Oil
         or Methane. ......«•••••••••••••••••••   25

 3     Theoretical Gas Flow Rates  for a 75 MW Power Plant  at 130° C,
         1 ATM	27

 4     Particle Size Distribution  for Oil-Fired Boilers. ........   31

 5     Particle Size Distribution  of Refuse Fly Ash	 .....   32

 6     Incremental Particle Size Data for Coal, Oil, and Refuse Fly
         Ash Determined Using Two  Parameter Weibull Distribution ....   35

 7     Summary of Effectiveness of Various Control Systems in Use on
         Oil-Fired Electric Generating Plants. .............   39

 8     Design and Cost Data for Electrostatic Precipitators  Designed
         for Collection of Waterwall Incinerator Fly Ash	46

 9     Estimated Materials Balance ••••••••...........   49

10     Target Analysis of Refuse Derived Fuel at SWRC-1	50

11     Pepco Benning Station Boiler No. 26 Design Ratings	54

12     Characteristics of Electrostatic Precipitator 	  55

13     Projected Analysis of Refuse Fuel-New Castle County, Delaware  .  64

-------
                             TABLES (Concluded)

No.

L4     Delmarva Edgemoor Station Boiler Design Ratings. .......    66

15     Design Data for Cyclone Collector/Delmarva Edgemoor No.  3.  .  .    67

16     Characteristics of Electrostatic Precipitator on Delmarva
         Edgemoor Unit No. 4	o . . .	„    68

C-l    Data Inventory for Electrostatic Precipitator Performance
         Model	107
                                     xi

-------
                              ACKNOWLEDGMENTS
     This report was prepared for IERL-RTP under Contract No. 68-02-1324. The
work was performed by Dr. Jim Galeski, Associate Environmental Engineer, and
Mr. M. P. Schrag, Head, Environmental Systems Section, with the assistance
of Mr. Joe Shum, Assistant Environmental Engineer.
Approved for:

MIDWEST RESEARCH. INSTITUTE
       .  >fe*/t--0^-rv-
-------
                                  SECTION  1

                                   SUMMARY
      Studies on the control  of  particulates  from the combined boiler firing
 of oil and municipal solid wastes  (MSW) were conducted for the Industrial En-
 vironmental  Research Laboratory, Research Triangle Park (IERL-RTP). Objectives
 of this project were to  develop quantitative emission forecasts and recommend
 control strategies  for  several  planned oil-MSW combined firing tests. Oil-MSW
 tests included planned EPA demonstrations and industry tests which are to be
 carried out  in utility boilers.

      The program was divided into  five major areas of activity:  (a) an in-
 formation search to acquire  particulate emissions data for oil-fired utility
 boilers and  municipal waterwall incinerators equipped with appropriate control
 devices;  (b)  development of  correlations for fractional efficiency and control
 costs as functions  of major  design, control, and operating variables; (c) de-
 velopment  of appropriate analytical models for control performance; (d) case
 studies to develop  preliminary  emission forecasts for plants where combined
 MSW-oil firing tests are planned;  and (e) development of recommendations for
 future work.

 INFORMATION  ACQUISITION

      Data  acquisition included  literature searches and contacts with govern-
ment  and private industry  sources. Literature sources included:  Air Pollu-
 tion Abstracts,  1970 to 1974  (all  entries); NAPCA Abstracts, 1970 to 1974 (all
 entries);  Applied Science  and Technology Index, 1958 to 1973 (all entries);
and Engineering Index, 1965 to  1971. In addition to these sources, an APTIC
Search was ordered  and a key word  index search was run on holdings in the Bay
Area Air Pollution Library.

     Data  inventories were acquired for:   (a) emissions from oil-fired electric
utility boilers; (b) control device performance for oil-fired utility boilers;
(c) emissions from waterwall incinerators;  and (d)  control device performance
for waterwall incinerators.

-------
  CONTROL PERFORMANCE AND COST CORRELATIONS

      Control system performance data were compiled  for  oil-fired  utility
  boilers and for refuse firing systems (waterwall incinerators, refractory
  wall incinerators, and combined firing systems).

      Data correlations for oil-fired boiler emissions  were  incorporated  into
  a  simplified model developed to predict uncontrolled particulate emissions
  as a function of percent fuel ash, percent fuel sulfur,  fuel  firing  rate, per-
  cent excess oxygen (or air), and fuel heating value. A range  of  uncontrolled
  particulate emissions was defined on the basis of  previous  analyses  of partic-
  ulate  levels generated in combined firing of coal  and  MSW.  For a given boiler,
  refuse fuel, and method of firing, variations in total fly  ash were  interpreted
  in terms of a dimensionless "fuel characterization factor"  comprised of  heat-
  ing values, ash contents, and fly ash-to-total ash ratios for both the con-
  ventional fuel and the auxiliary MSW fuel.

      For ESP control, a modified form of the Deutsch equation was used to de-
  scribe variations in collection efficiency resulting from changes in flue gas
  volume. The effect of particle size distribution was determined  by calculating
  a separate collection efficiency for each discrete particle size range and
  by applying appropriate Cunningham "slip correction" factors. Empirical  correla-
  tions were used to determine limitations in current density resulting from  in-
  creased particle resistivity and/or increased flue gas temperature.

      Installed cost data were acquired for new ESP installations, for retro-
  fitting ESP units designed for coal, and for wet scrubbers. Detailed cost and
  design data were acquired for two new ESP units designed specifically for col-
  lection of refuse fly ash.

  ANALYTICAL MODEL DEVELOPMENT

      Analytical model development efforts included the development  of predic-
  tive models for particle size, flue gas volume, total  fly  ash,  and  control
 device performance under combined firing conditions.  Installed control  systems
 on boilers in which combined firing tests were planned included ESP's and
 cyclones.  A semiquantitative predictive model was developed for ESP control.

     An analytical procedure was  developed for calculating  flue  gas  volumes as
a function of MSW fraction,  fuel moisture,  fuel sulfur,  higher heating values,
and elemental compositions (C, 0, H, N,  and S). Calculations  for representa-
tive oil and MSW fuels indicated  a  significant increase  in  flue  gas  volumes
corresponding to increasing MSW heat input.  For each percent  of  MSW heat input
the calculations indicate approximately  a  1% increase  in flue gas volume. It

-------
 is  anticipated  that  this  increase will  have  a  significant effect on fractional
 control  efficiencies.

      Control performance  evaluation methodology was developed for ESP control
 on  the basis of previous  performance  studies.  Use of the model was limited
 somewhat by the available data  for refuse properties, particle size distribu-
 tion, fly  ash density,  and resistivity  for the MSW fuel. In general, however,
 the problem of  fly ash  collection when  oil and MSW are fired in the same
 chamber  does not appear to have any characteristics which have not previously
 been  encountered in  designing electrostatic  precipitators for oil-fired units.
 On  the basis of the  present study, it is estimated that for most medium ef-
 ficiency ESP units designed for coal  fly ash (95.0 to 98.0% design efficiency)
 the efficiency  is expected to drop to 60 to  707., for oil, 70 to 85% for oil
 plus  refuse, depending  on refuse composition and MSW heat input.

      One multicyclone' control system was evaluated in the study because of a
 planned  oil-MSW combined  firing test at Delmarva Power and Light Company's
 Edgemoor Station No.  3. It was  found that for  cyclone control, the theoreti-
 cal basis  for pressure  drop and collection efficiency had not been well de-
 veloped  because of complexities of flow fields. Experimentally determined
 fractional efficiency data for  cyclone  control systems acquired in the litera-
 ture  study were used to adjust  performance for changes in particle size dis-
 tribution  under combined  firing conditions.

 CASE  STUDIES

      Planned combined oil-MSW systems which  were examined in detail included
 (a) District of Columbia,  (b) Wilmington, Delaware (New Castle County), (c)
 New York City,  and (d)  Bridgeport, Connecticut. On the basis of control per-
 formance estimates,  the performance of  installed control systems designed for
 coal  appears to be questionable for meeting  applicable regulations for partic-
 ulate emissions,  except at very low MSW heat input and/or boiler load. For
 ESP control, major expected control difficulties result from:  high flue gas
 dust  loading and flue gas  volume, low average  particle density,  fine particles,
 and large  percentages of  carbonaceous low resistivity particulate.

 RECOMMENDATIONS

     In view of the  rapid  projected growth rate of MSW fuel utilization in com-
 bustion  systems and  increasing  public awareness of associated air emissions,
 in-depth evaluation  of  several  existing and novel control systems appears justi-
 fied.

     The following recommendations are directed toward major deficiencies in
the control technology defined  in the present  study.

-------
 Electrostatic precipitator control

     In adapting existing theoretical studies to the development of a practi-
 cal performance model to predict ESP performance for combined firing applica-
 tions, there was found to be no quantitative information on the effects of:

      1.  Fly ash density;

      2.  Re-entrainment; and

      3,  Sneakage or bypassing.

      Analysis of the effects of fly ash density, re-entrainment, bypassing,
 and other  factors is recommended, based both on analysis and a survey of
 available  data including contacts with equipment manufacturing firms.

 Cyclone control

     The theoretical prediction of cyclone pressure drop and collection ef-
 ficiency is not possible because of complexities of flow fields. Other factors,
 such as the tendency of cyclone collectors to plug when in service on oil ash,
 and the performance decline in the corrosive atmosphere of incineration flue
 gases, need to be examined.

     As in the case of ESP control, additional work on this type of control
 system specific to the application of combined fossil fuel-MSW combustion is
 recommended. This would include contacts with vendors, literature review, and
 analysis beyond the scope of the present study to develop guidelines for use
 in  combined firing applications.

 Novel Control Devices

     High performance scrubbers and wet  electrostatic precipitators have utility
 for collection of particulates, gaseous  pollutants (SOX, NOX,  and others) and
potentially hazardous trace metals.  There were no scrubber or  wet ESP units in-
stalled on  the boilers  evaluated in the  present study.  An in-depth study of
these control  methods appears  justified.

-------
                                  SECTION  2

                                INTRODUCTION
      Resource recovery systems  involving combined firing of shredded municipal
 solid wastes  (MSW)  with fossil  fuels,  such as oil or coal, are relatively new.
 Consequently,  there is little available information from which to predict the
 performance of emission control systems. The present study was directed toward
 the analysis  of control performance when oil and MSW are fired concurrently
 in a conventional  electrical utility boiler.

      The  first demonstration plant to  process raw municipal waste for use as a
 supplementary fuel  in  power plant boilers—the St. Louis-Union Electric Refuse
 Fuel System--is presently demonstrating the potential and problems of coal-MSW
 firing.

      Oil-MSW  firing is potentially more attractive in terms of long range fuel
 conservation,  if a  number of operating problems can be resolved,  and if partic-
 ulate emissions can be successfully controlled.

      Oil-fired units have not utilized or needed very efficient control of
 particulates  in the past. Particulate  control from oil-fired steam generators
 normally  involves using mechanical collectors which are used primarily during
 soot  blowing.  In combined firing, the  resulting (controlled)  particulate levels
may be much higher  than the existing standard for oil-fired boilers. In addition,
 the performance of  those systems with  high efficiency collection  is in ques-
 tions. It is not known precisely how the various high efficiency  particulate
 control devices will behave for combined firing of refuse and oil.

      The objective  of  the present study was to acquire the data base required
 for  development  of  semiempirical control performance and cost models for the
control of  emissions from combined firing of oil and MSW and, using this in-
formation,  to  analyze  the performance  of installed control systems for planned
oil-MSW combined firing  systems.

-------
                                 SECTION 3

            PARTICULATE EMISSION  DATA ACQUISITION AND EVALUATION
      A review of information pertinent to concurrent firing of oil and MSW
 was made using both literature  searches and telephone contacts with private
 sources knowledgeable with (a)  waterwall incinerators and emission controls,
 and (b) combined firing applications. The objective of this part of the study
 was (1) to determine the properties of particulate and flue gas from firing
 oil and refuse which are pertinent to emission control using cyclones, electro-
 static precipitators, and high  performance wet scrubbers, and (2) to estimate
 the composite fly ash and flue  gas properties for combined firing. Pertinent
 variables for the control systems considered were determined to be:

      1.  Total fly ash per weight of fuel burned. Relative amounts of fly ash
 from burning oil and refuse fuels separately are needed to determine total
 fly ash emitted in combined firing and to estimate the physical properties
 of the composite fly ash which  are needed for control device sizing (resis-
 tivity, bulk density,  etc.).

      2.  Flue gas  volumes  per weight of fuel burned. Excess air levels and
 fuel composition data  (moisture, ash, ultimate analysis) chiefly determine
 the flue gas volume.

      3.   Particulate density. Although fly-ash density has not been considered
 in  previous  combined firing studies, discussions with equipment vendors indi-
 cate  that this may be an  important factor in ESP sizing in that a decrease  in
 density  requires a proportional decrease in flue gas velocity through the pre-
 cipitator. There is unfortunately no quantitative treatment available to de-
 scribe the influence of reduced particle density on collection efficiency.
 On the basis of classical  analysis, electrical or "capture" forces are in-
dependent of particle density, while aerodynamic or "drag"  forces  are in-
versely proportional to particle density for laminar flow. For particles of a

-------
 given diameter,  the rate of acceleration away from the  collection electrode
 during rapping cycles will also be inversely proportional  to particle diameter.
 Other key design parameters (e.g., particle resistivity, dielectric constant,
 etc.) may also vary systematically with particle  density.

      4.   Ash fusion temperature. This factor is important  with regard to pos-
 sible plugging of air passages and slagging of boiler tubes. It also indirectly
 influences excess air required.

      5.   Particulate size distribution.  Particle  size distribution data for
 each fuel burned separately are used, with the mass  emissions data, to estimate
 the particle size distribution of the composite fly  ash.

      6.   Particulate resistivity. Particulate resistivity  depends on many fac-
 tors including flue gas moisture level,  fuel sulfur, fuel  metals active as
 oxidation catalysts (principally vanadium), basic chemical constituents, and
 mass fraction of particulate from each fuel source.  In  firing of oil alone,
 high concentrations of metals active as oxidation catalysts, principally vana-
 dium, are believed to be responsible for "acid smuts" which are agglomerates
 of oil ash and sulfuric acid. In combined firing  of  oil-MSW, it is anticipated
 that HoSOA will be less of a problem than it sometimes  is  in oil-fired units.
 The higher particulate levels expected in combined firing  should serve to col-
 lect most of the sulfates formed, resulting in a  "well  conditioned" fly ash
 with reduced resistivity. In the combined firing  of  oil with coal, none of the
 problems associated with firing of oil alone are  encountered, indicating that
 the coal ash tends to adsorb excess moisture and  sulfur compounds..!/

      Data which were found for these properties for each fuel type, and meth-
 ods of estimation of composite properties  needed  for control system sizing,
 cost,  and performance estimation are described in the following subsections.

MASS  EMISSIONS DATA

      Data inventories  were compiled for particulate emissions from oil-fired
 electric  utility  boiler,s  and waterwall incinerators, as summarized in abbre-
viated form  in Appendices A and B,  respectively.  The objective of the data
acquisition  was to  use these data to estimate the range of particulate emis-
sions which  is probable when oil and MSW are fired concurrently in a utility
boiler. More precise estimates of particulate emissions require detailed in-
formation  about the fuel-oil ash content,  refuse  ash content, and type of
boiler.

-------
 Uncontrolled Particulate Emissions from Oil-Fired Electric Utility Boilers

      Particulate from oil firing  (uncontrolled) was found to vary from 0.0055
 to 0.87 g/106 joules of heat  input (approximately 0.013 to 2.02 lb/10  Btu)
 with an average value for 29  electric utility boilers of 0.0632 g/10  joules
 (0.147 lb/106 Btu).  In calculating the average, duplicate tests for the same
 boiler were averaged. A more  representative value for uncontrolled particulate
 from oil firing is obtained by  discarding extreme values. This yields a range
 of 0.01 to 0.154 g/106 joules (0.023 to 0.36 lb/106 Btu).

      As indicated by the above  range of values, uncontrolled particulate emis-
 sions from oil firing can vary  considerably. The lower value is approximately
 equivalent to 0.0237% by weight of oil-fired, which is in the same range as
 the ash content of No. 6 residual oil (0.002 to 0.3% by weight).!/ The upper
 value is approximately equivalent to 3.6% by weight of oil fired, or approxi-
 mately one order-of-magnitude higher than the expected ash content. It has
 previously been noted that particulate fly ash from oil firing can range from
 approximately the ash content of the oil up to 10 to 15 times the ash content,
 the higher range of  values being attributed to poor combustion.—'  The combus-
 tible portion of fly ash normally ranges from 60 to 90%..£/

      In order to determine the  expected range of uncontrolled particulate for
 a given installation, the influence of several factors must be quantitatively
 defined. The quantity, type and size of uncontrolled particulate emissions
 from oil-fired combustion operations are thought to depend mainly upon the fol-
 lowing f actor s:^i-i.'

      Overall fuel consumption rate
      Ash and sulfur  content of  fuel
      Use of mineral  fuel additives
      Degree of atomization (type and oil viscosity)
      Windbox air admittance
      Burner tilt
      Excess air
      Boiler load
      Flue gas  recirculation
      Age and condition of  boiler

      A  review  of  the  available  literature indicated that in most cases, quan-
titative  relationships describing the dependence of particulate emissions on
these factors  either  did not  exist or correlations developed were very un-
certain.  The reason for this  is probably that the number of variables involved
in a  given plant are very  large, and since these change from plant to plant,
it is impractical to obtain sufficient data on the effect of a single variable
while maintaining the others constant. Unfortunately, it is not always correct


                                     8

-------
to  assume  that  each factor exerts an independent  influence on the measured
emissions. It would be preferable to use  statistical methods (e.g., linear
regression analysis) to describe the influence of a single variable under con-
ditions  in which other variables are also changing, but unfortunately this
has not  been done.

     As  an illustration, consider the influence of excess air under variable
boiler load. Some boilers are designed specifically for peak power generation
and operation under variable load conditions. More frequently, when a convec-
tive superheater is used, decreasing the  boiler load causes a decrease in
steam temperature.—'  Under conditions of  reduced  boiler load, increased excess
air may  be required to maintain both boiler  stability and a constant steam
temperature. >  ' An empirical equation has been developed by MaartmanZ.'  to
describe these  variations which also includes the variation in dust concentra-
tion with  the sulfur content of the oil:

                                        a
                                G	-	r                            (1)
                                    0P  x  Q
                                      Q
where     G = dust  concentration:mg/Nm

          S = sulphur content  of  the  oil:percent

         02 = excess  oxygen:percent

          Q = capacity of  the  boiler:tons of  steam per hour

Based  on measurements made in England, Germany, and Sweden, it is thought that
the values of the  parameters  a,  p, and 6 are:

                                   0  <: a <:  1                            (2)

                                    9 =  1.0                            (3)

                                   0  £ 6 £  1                            <4>


     The literature  and data  inventories compiled during this study suggest
the following order-of-magnitude variations  in uncontrolled particulate emis-
sions with design  and operating  conditions:

     Overall  Fuel  Consumption Rate;   There is an apparent increase in partic-
ulate emissions (in  grams per 10° joules of  heat input) by a factor of two as

-------
 capacity decreases from 600 to 100 MW.-/ The lower emissions for larger units
 probably result  from better control, improved design, and better condition
 of  the burners in the newer and larger oil-fired boilers.

     Ash Content of Fuel;  There is no quantitative information on the varia-
 tion in particulate emissions with ash loading, although the average for No.
 6 residual oil is estimated from available literature to be 0.1% by weight.
 The approximation made in this study is that greater or lesser concentrations
 of  ash in the fuel oil will add or subtract from the total particulate in a
 1:1 proportion.

     Sulfur Content of Fuel;  Sulfur content in No. 6 residual oil may be-
 tween o73and^%7^Aleast squares linear curve fit of available data indi-
 cates that uncontrolled particulate emissions increase by about 25% over the
 range 1.0 to 2.5% sulfur by weight^./ The scatter in the available data is
 again quite large, probably for reasons of nonlinear influence of design and
 operating conditions, as discussed previously.

     Mineral Fuel Additives;  The typical recommended application of fuel oil
 additives is in the proportion of 1 kg of additive per 1,000 kg of fuel oil.—'
 The solid additive used is usually dispersed in slurry form in a light oil
 (e.g., No. 2 fuel oil) so the concentration of solids is usually less than
 0.5 kg/1,000 kg of fuel oil, or 0.05% by weight. This is significant in com-
 parison with normal fuel ash and should be included in calculating total fuel
 ash.

     Degree of Atomization;  The effectiveness of atomization is influenced
 mainly by the type of atomization (mechanical, steam, or air), the condition
 of  the burners, and the viscosity of the fuel oil. The viscosity is determined
 by  the intrinsic viscosity of the fuel and the temperature to which the oil
 is  heated prior to atomization. Studies have been made to determine the effect
 of  these variables on particulate emissions;.?-' however, there are little data
 and trends are insufficiently clear to permit a quantitative interpretation.

     Windbox Air Admittance;  Varying the settings on the main and auxiliary
 air dampers can cause pronounced effects on fly ash,!/ but there are insuf-
 ficient  data for a quantitative prediction.

     Burner Tilt;  There is evidence that burner tilt can influence fly ash
 loading  under certain conditions.!/ There are not sufficient data to permit
a quantitative prediction at this time.

     Flue Gas  Recirculation;  Uncontrolled fly ash emission is believed to
increase  significantly when more flue gas is recirculated into the firebox.
                                      10

-------
This increase is believed to be due to & cooling of the flame and combustion
gases.—' There are  insufficient data  for a  quantitative correlation.

     Excess Air and Boiler Load Level;  These are most significant operating
parameters, which can  exert an order -of-magnitude influence on uncontrolled
particulate emissions. As discussed previously, excess air is frequently
increased with decreasing load level  to maintain a constant steam temperature.
At a constant load  level, it was  observed in one test that as the oxygen con-
centration in the stack  gas decreased from  4 to 2% (corresponding to a decrease
in excess air of approximately 22 to  10%) the particulate loading increased
from 0.0086 to 0.060 g/106 joules .I/

     On the basis of the preceding discussion, the following empirical rela-
tionship was developed to predict the variation in fly ash from firing No. 6
residual oil as a function of:  excess air, expressed as percent oxygen; boiler
load;  fuel ash; fuel sulfur content;  and fuel heating value.
                g  (1 + A  - A)(l + CM(M  - H))(l + CS(S - 5)) H/H        (5)

                                    o2/o2


where    g = uncontrolled particulate emissions, g/10" joules

         g = mean  (uncontrolled)  particulate emissions for electric utility
               boilers firing No.  6 residual oil, g/106 joules

         A = ash content  of  fuel,  percent by weight

         A = average ash  content  of No. 6 residual oil-fired, percent by weight

         M = boiler load, MW

         M = average load of boilers firing No. 6 residual oil, MW

         S = sulfur content  of fuel, percent by weight

         S = average sulfur  content of No. 6 residual oil-fired, percent by
               weight

         H = higher heating  value  of fuel, joules/kg

         H = average higher  heating value of No. 6 residual oil-fired,
               joules/kg

                                    11

-------
         02 = excess oxygen, percent by volume

         •J32 = average  excess oxygen for boilers firing No. 6 residual oil,
                percent by volume

      Qyr»Cc = proportionality constants

      The functional dependence of total particulates on excess air (percent
  oxygen) used in Eq.  (5) is derived from the analysis of MaartmannZ/ the re-
  sults of which were  presented in the preceding discussion as Eqs. (1) through
  (4). The linear variation between total particulates and boiler load is based
  on regression analysis (Eq. (1), Ref. 4). The linear variation between total
  particulates and fuel sulfur is also based on regression analysis (Figure 6,
  Ref. 4). The linear  variation of total particulates with fuel ash (including
  additives)  is an assumption, as stated in the preceding discussion. The in-
  verse linear variation of total particulates with fuel heating value is pre-
  sented without attempting to justify the approximation.

      The overall range of validity of Eq. (5) for estimating oil emissions is
  unknown. For the purposes of the present study, this equation is considered
  to be sufficiently valid, if somewhat conservative. Comparisons between mea-
  sured and predicted  total particulate are presented in Figures 1, 2, and 3 as
  functions of percent oxygen, boiler load, and percent fuel sulfur, respec-
  tively. Several values of "g were used in Figures 1 to 3 ranging from "g = 0.0632
  g/106 joules (average from the data inventory in Appendix A) to "g = 0.00632 g/
  10  joules.  Other numerical values used were as follows:

        A = 0.1% by weight2./

       C^ = 5.324 x lO-4 (adapted from Ref. 4, Eq. (1))

       H = 263.87  MW  (calculated from the data inventory in Ref. 4)

       Cg  = 0.0670  (determined from Ref. 4, Figure 6)

       S  = 1.15% by weight (determined from Ref. 4, Figure 6)

       I = 4.233 x 107 joules/kg!/

      0  = 2.8942% by volume (calculated from an average excess air level
             of  15.0%-X)

     In Figure  1, conversion of total particulate to milligrams per normal
cubic meter was made by assuming an average heating value of 4.233 x 107
joules/kg and a volume equivalent of 13.4 Ifa3/kg of oil.

                                      12

-------
    400
        -O
    300
CO
 E
 Z
 CD
 -§  200

 00
 in
 T3

 ~O
 OO
    100
      0
          O
      = 0.0632g/106j

          ;


•g = 0.0063 g/106j

      = 0.0126g/106j
                           0.2% wt of Fuel

                           D 32mth* Oil D
                           O 24mth  Oil D
                           A32mth  Oil C
                           V 24mth  Oi I C
                           • 16mth  Oil C
                           — Equation 5
            *mth = Metric Tons Per  Hour

          I   I   I  I   I  I   I   I   I  I   I
       0   0.2   0.4  0.6   0.8  1.0   1.2   1.4  1.6   1.8   2.0
                         Vol % O2  in Flue Gas
 Figure  1.   Solids burden plotted against excess oxygen for
         different  boiler loads and fuel oil types.!/
                               13

-------
-o
 o
0.12
0.11
0.10
0.09
 §  0.08
 'a
 j=  0.07
 
                                                                                                  D
                                                                                                  U
                                                                                                  E
                                                                                                  «
 Figure  2.   Uncontrolled electric  utility emission versus capacity (no additives employed)."

-------
Ui
          •o
           o
            c
            o
 E
UJ
 o

 3
^O



I

JU

_Q

 S
 
-------
    Conversion of excess air to volume percent oxygen can be accomplished
using standard procedures,I/ provided that the heating value is known. For a
higher heating value of 4.233 x 107 joules/kg, the following expression is
approximately correct for excess air levels between 0 and 40%.

                                                ,   3
                      02 ^ 0.2 EA - 3.1338 x UT5EA                   (6)

where    EA = excess air, percent by volume

         02 — as previously defined.

    It should be emphasized that there are expected to be rather wide varia-
tions in emissions from boilers firing No. 6 residual oil, as a result of
factors not included in the data correlations, as  previously discussed. There-
fore, Eqs. (1) through (6) should be used only to  give an order-of-magnitude
estimate of the uncontrolled emissions.

Uncontrolled Particulate Emissions from Waterwall  Incinerators

    Uncontrolled particulate emissions from waterwall incinerators ranged
from 0.95 to 9.64 g/106 joules (approximately 2.21 to 22.4 lb/106 Btu). The
average value for seven boilers and 22 tests was 2.56 g/10  joules (5.95 lb/
10  Btu). Stack test data for particulate emissions from several waterwall
incinerator plants in the United States and West Germany were included, as
tabulated in Appendix B.

     In calculating the average, tests for the same boiler were not averaged,
since tests were usually made under conditions of  variable excess air, re-
fuse heating value, ash and moisture content, and boiler load.

     Possibly because of the limited data available at the time of this study,
there are no clear trends in uncontrolled particulate emissions with refuse
fuel heating value, ash content, or excess air level. Because of the limited
data available, absence of clear trends, and the fact that the waterwall in-
cinerator plants listed fired unshredded refuse, an empirically based representa-
tion of the available stack test data was  not considered justified. At the
time of the study, an in-depth investigation of emissions from waterwall in-
cinerator plants was being conducted for EPA, Office of Solid Waste Management
Programs,I2/ and data from this study, when completed, should be used to sup-
plement the data included in the present report.

Estimate of Refuse Fly Ash from Suspension Firing  of MSW

    There is no accepted design method for calculating particulate fly ash
from combined suspension firing of refuse and conventional fuels. Control

                                    16

-------
device sizing and performance  evaluation is therefore somewhat a stochastic
procedure. Estimates for the fraction of refuse ash which ultimately becomes
fly ash (here denoted  "fr") range from about 0.13 up to 0.50, according to
various sources. Estimates determined from the analysis of actual test data,
described in this section, range from 0.13 to 0.35.

    The approach for estimation of particulate loading favored by some in-
vestigators2J-L/ is to use a ratio of fly ash to bottom ash characteristic
of the fuel, the firing method, and the boiler system. This approach is of
particular value to those concerned with MSW fuel preparation since it allows
the fly ash to be related directly to MSW ash content and other fuel properties.

    Assumptions implicitly made are that the refuse fly ash does not depend
on the type of fuel fired, e.g., oil or coal, and that the presence of both
fuels in the combustion chamber does not influence bottom ash or carbon burn-
out in the fly ash. This assumption implies that fly ash from the two fuels
can be added in linear fashion to yield  a total fly ash particulate:—'

                         g = rg, + (1 - r)g_                          (7)
where
          g =
          r =
         g  =
         g  =
              total particulate, g/10  joules

              fraction of MSW heat input

              observed fly ash particulate from refuse burning, g/10
                joules

              observed fly ash particulate from burning No. 6 residual
                oil, g/10° joules.
    If it is further assumed that the carbon content of fly ash is negligible
by comparison with the total fly ash, Eq. (7) can be rewritten in terms  of
refuse fly ash fraction f  and fuel properties in the following form:
                      gx= 10'
                               X  f r   X.  f (1  -  r)
                                Ar r     Ac c
                                 H
                                           H
                                                                      (8)
                                      17

-------
where       g = grams of fly ash per 10  joules of composite fuel

           H  = average heating value of refuse, joules/kg

           H  = average heating value of auxiliary fuel, joules/kg
            c

          X   = weight fraction of ash in refuse
           Ar
          X   = weight fraction of ash in auxiliary fuel
           Ac

           f  = fraction of refuse ash which becomes fly ash
            r
           f  = fraction of ash in auxiliary fuel which becomes fly ash
            c
            r = fraction of refuse heat input


    Equation (8) is used to estimate the total  fly ash  loading  for a  given
boiler, firing method, and fuel properties.  Rearranging Eq«  (8),  the  follow-
ing dimensionless equation results, which relates the fractional increase in
fly ash particulate at a given refuse heat  input (r)  to a  dimensionless ratio
of fuel properties (c):
                               


-------
       20. Or-
         °-                     0.10                    0.20
                                  r = %MSW Heat Input

          * See Equation 9 for Definition of \l/, C
Figure 4.  Dimensionless plot  showing  fractional  increase  in total  fly ash
             as a function of  percent MSW for various values of  fuel char-
             acterization parameter  (C).
                                     19

-------
      fr = 0.15 (assumed)

     XAr = 0.223H/

      Hr = 11,572,000 joules/kgii/

      f  = 2.72 (assumed value, see p. 8)
     XAc =
      H  = 42,330,000 joules/kg^
    For these fuel properties, C depends on the assumed fly ash fraction as
 follows:

              £c                    £

             0.15                  45.9

             0.30                  91.8

             0.50                 153.1

    Previous experience  »'  indicates that variations primarily in MSW fuel
properties may also cause variations in the ratios XAr/X.c  and Hc/Hr.  Changes
 in these ratios  will also influence the rate of fly ash generation as de-
 scribed by Eq. (9).

    Methods which have been used for estimating the fraction of refuse ash which
ultimately becomes fly ash (fr) are described in the following paragraphs.

    Mass balance data;  St. Louis/Union Electric refuse firing demonstra-
 tion;!^,^/  Analysis of recent mass balance data from the  St. Louis/Union
Electric refuse firing demonstration indicates that from 39.9 to 98.5% of the
refuse ash was ultimately discharged from the boiler in the form of sluice
 solids (bottom ash). The average bottom ash fraction was 64.7% of the total
refuse ash.M/ By difference,  the average fly ash fraction  from the St. Louis
tests was equal to 35.3% of the total refuse ash.

    The analysis based on bottom ash assumes that, in addition to the assump-
tions stated for Eqs. (7) and  (8), a constant fraction (8.7%) of the ash present
in the coal is collected in the sluice solids as bottom ash.
                                     20

-------
    Particulate emissions data:  National Center for Resource Recovery (NCCRl
analysis of St. Louis/Union Electric refuse firing demonstration:^* 15/ The
NCKR method is based on analysis of the differences in fly ash emission rates
when firing coal-plus-refuse and firing coal only. The assumption made is that
the flue gas volume is constant at a given boiler load and is independent of
the MSW fraction. This assumption is somewhat at odds with the overall con-
clusions of the St. Louis/Union Electric Air Pollution Test Report,.!!/ but is
consistent with the test data  chosen for the example calculation. Notation and
dimensions used by NCKR have been altered as required for consistency.

    Following Gershman,  the particulate resulting from the MSW portion of the
fuel in combined  firing is given bytift/
                          g'r = g'r+c  -  8'c  U-r)                      (10)

                                                                O
where   g'r+c = total- flY ash  from firin8 coal-plus-refuse, g/Nm

           g«  = fly ash from refuse portion of  fuel, g/Nm

           g'  = fly ash from firing coal-only,  g/Nm3

The  fraction of refuse ash which becomes fly ash  (fr)  is determined from the
following equation.^/

                               _ g.r x 103 x V
                                    XAr  Wr

                                                  •3
where       V = flue gas volumetric flow rate,  Nm /min

            Wr = MSW mass feed  rate into the boiler, kg/min

                 fr> 8* » XAr  as Previously  defined.

The  NGRR  methodology yields fr = 0.21 for the data  chosen:

             r = 0, 0.1

        Kt   = 4.35 Nm3 (1.9  gr/dscf)  at  100 MW, r = 0.1
        O JLm\ "C

           gt  = 3.84 g/Nm3 (1.7 gr/dscf) at 100 MW, r = 0
                                   21

-------
         XAr = 0.21

          Wr = 151.2 kg/min (20,000  Ib/hr)

           V = 7,702 Ito3/min (272,000  dscfm)

     Calculated fly ash fraction (fr)  based on waterwall  incinerator  emissions
 data;  The average value of 2.56 g/10^  joules obtained from the  survey  of  emis-
 sions data for waterwall incinerators (Appendix B) corresponds to  a  value  of
 fr = 0.13 for an average heating value  Hr of 11,572,000  joules/kg  (4,975 Btu/
 Ib) and a total ash content of  22.3%.
     Calculated fly ash fraction  (fr) based on St. Louis/Union Electric  air
 emissions data at 140 MW,  10% MSW;  On the basis of test data from the  St.
 Louis/Union Electric refuse firing  demonstration, in which  shredded MSW was
 fired in suspension with coal, particulate loading increased with increasing
 MSW heat input in approximately  the same ratio as increasing gas volumes..!!/
 That is, there was no apparent net  increase  in flue gas grain loading.  At  10%
 MSW heat input and 140 MW,  the theoretical increase in flue gas volume  was
 approximately 5.2%.  Using  this information and average fuel properties, the
 value of fr was determined from  Eq. (8) to be 0.16. Average fuel properties
 used were as follows:—'

          XAc = 0.0703

           Hc = 29,226,000  joules/kg (12,565 Btu/lb)

           fc = 0.85

          XAr = 0.223

           Hr = 11,572,000 joules/kg (4,975 Btu/lb)

     The  value of  fr = 0.16 calculated from the St. Louis/Union Electric air
pollution test  resultsJLi/ agrees favorably with the average value for waterwall
incinerators (0.13), when adjusted to a total ash content characteristic of
shredded  refuse.

Estimated Particulate Emissions from Combined Firing of Oil and Municipal
  Solid Wastes~~~—

     The estimated range of uncontrolled particulate stack  emissions from com-
binded firing of oil and MSW calculated from Eq. (8) are summarized in  Table
1.   An independent estimate of particulate, SOX, and NOX emissions made in

                                     22

-------
to
CO
          Table 1.  ESTIMATED TOTAL PARTICULATE AND PERCENTAGE  OF  REFUSE  FLY ASH  IN FLY ASH COMPOSITE FROM
                             COMBINED FIRING  OF OIL AND MUNICIPAL  SOLID WASTES  (MSW)-^

Flue gas particulate
% MSW
heat input
0.0
1.0
5.0
10.0
15.0
20.0
25.0
(g/106 ioules)
fr = 0.1
0.063
0,082
0.156
0..250
0.343
0.436
0.529
f r = 0. 15
0.063
0.092
0.205
0.346
0.487
0.629
0.770
fr = 0.3
0.063
0.120
t).349
0.635
0.921
1.21
1.49
fr = 0.5
0.063
0.159
0.542
1.02
1.50
1.98
2.46
fr = 0.1
0.0
23.5
61.1
77.2
84.3
88.4
91.0
% Refuse
fr = 0.15
0.0
38.1
76.2
87.1
91.5
93.8
95.3
fly ash
fr = 0.3
0.0
48.0
82.8
91.0
94.2
95.8
96.8

fr = 0.5
0.0
60.6
88.9
94.4
96.4
97.4
98.1
      &l   Estimate of uncontrolled fly ash emissions made using Eq. (8). Estimate based on average emission
            rate for oil-fired boilers (Appendix A) and  average MSW properties listed in Ref. 11:  heating
            value (Hr) of 11,572,000 joules/kg;  ash weight  fraction (X^r) of 0.223; and various fly ash
            fractions (fr)  as shown.

-------
 an earlier  study by another team of investigators at Battelle—' predicted
 uncontrolled particulate from oil-refuse firing intermediate between values
 listed  in Table 1 corresponding to fr = 0.15 and fr = 0.30. The results of
 this  study  are compared with the present estimates in Table 2. The Battelle
 emissions model for combined fuel firing was also based on an assumed linear
 addition of emissions from each fuel proportioned by relative heating value
 as described in Eq. (8).!Z/

      With regard to the physical properties of the fly ash particulate, it
 is evident  from Table 1 that both oil and refuse particulate will have an in-
 fluence on  the physical properties of the composite fly ash. This conclusion
 is emphasized because it appears to be opposite to the general consensus of
 several EPA and design engineers.

 FLUE  GAS VOLUME

      Flue gas volume for combined firing of different fuels depends on several
 factors, the most significant of which appear to be:

      1.  Boiler efficiency.

      2.  Excess air level.

      3.  Theoretical combustion air based on fuel composition and heating
 value.

 Since the total volume of flue gas is of primary importance in predicting con-
 trol  device performance, a significant part of the present study was devoted
 to analysis of previous attempts to predict the flue gas volume for combined
 firing  applications.

     It is anticipated that boiler efficiency will decrease somewhat with in-
 creasing substitution of refuse derived fuel (for fuel oil). The estimated
magnitude of major losses at 20% MSW heat input are summarized as follows:

     1.  Heating of additional excess air for combustion, 1.0%0

     2.  Incomplete fuel combustion,  2.0%.

     3.   Heating of additional fuel moisture (25% moisture in MSW), 4.0%.

     4.   Increased "dry" gas losses, due to  increased flue gas volume,
1.0%.
                                     24

-------
                 Table 2.  CONTROLLED  EMISSIONS  FOR COMBINED FIRING  OF REFUSE  WITH OIL OR METHANE
Cn

a/
Particulates"- Allowable
Heat input
from oil
or methane
(%)
90 (oil)
80 (oil)
70 (oil)
90 (methane)
80 (methane)
70 (methane)
Refuse
heat
input
(%)
10
20
30
10
20
30
(K/106
95%
Collection
efficiency
0.017(0.022)-^
0. 031(0. 044)^
0.046(0. 065 >r,
- (0.022)^.
- (0.043)-r'
- (0.065F-
joules) sulfur content
99% of oil for
Collection no SOX control
efficiency (%)— '
0.003(0.004^ °*77W
0.006(0.009)^, °«84r,
n / D /
0.009 (0.013 P. 0.92-
- (0.004P'
- (0.009)f
- (Q.013)^7


NOX ,.
(g/106 ioulesK
Oa2b/
°*12b/
0.099J^
°-099b1/
0.009s
      a/   Values from Table 1 used in calculating uncontrolled particulate correspond to fr = 0.15.
      y   Data from Ref.  16, Table 24.
      £/   If the allowable SOX emission is 0.344 g/10  joules (0.8  lb/10  Btu).
      d/   Assuming a 60% reduction in NOX by particulate control  system (for nontangentially-fired units).

-------
 The above approximate values are estimates based on information in Refs.  12
 and 18.  A precise determination of combustion efficiency requires detailed
 information on refuse fuel composition, ash, moisture and heating value,  and
 excess air level. The estimate for refuse fuel combustion efficiency (907= for
 MSW) is  based  on data for suspension firing of MSW and Illinois No. 6 coal
 in a tangentially fired boiler.!!/ It is not documented at this point whether
 there is any improvement in combustion efficiency when the refuse fuel is
 shredded to a  finer  average particle size.il/ Union Electric engineers claim
 that fine shredding  of refuse does result in better heat recovery. They in-
 terpret  a higher heat recovery with refuse ground to less than 3.18 cm (1.25
 in.) when compared to refuse less than 7.6 cm (3 in.) in size based upon MW
 generated per  megagram of refuse. The St. Louis study, however, reports that
 the combustion efficiency did not improve with fine ground refuse when based
 on the two data points for fine-ground refuse,!!'  Determination of improvements
 in combustion  efficiency as a function of refuse fuel particle size requires
 additional study.

      There is  evidence that excess air may need to be higher when firing refuse
 with oil than  when firing oil alone. The reasons for this are related to cor-
 rosion and "slagging," or deposition of fused ash on boiler tubes. Excess air
 levels used in waterwall incinerator plants are typically 70 to 1007, where
 corrosion is a problem (see Appendix B). There does not appear to be any method
 for determining the  excess air level a priori. There is some indication that
 an excess air  level  of 15% is sufficient for firing up to 107o refuse heat in-
 putiZHrJi'  and  that excess air should be increased to 257= for 207= MSW heat in-
 put .I/

      Theoretical air required for combustion was calculated from fuel composi-
 tion and heating values using standard procedures (see Ref. 5, p. 4-10). Fuel
 nitrogen was assumed to be converted to nitric oxide (NO). When dealing with
 refuse derived fuels, it was found to be important to correct "dry basis"
 ultimate analyses for fuel moisture actually present. When refuse derived fuels
 are substituted for  No. 6 residual oil, theoretical flue gas volumes will in-
 crease by as much as 17= for each 17= of MSW heat input at the same excess  air
 level, depending on moisture, heating value, composition, and MSW substitution.
 Representative gas volumes for a 75 MW boiler are listed in Table 3. Variations
 due to MSW fuel moisture and refuse substitution rate are illustrated in  Figure
 5 .

FLY ASH DENSITY

     It  is estimated that fly ash from combustion of municipal solid wastes
will be comprised of a significant fraction of very light particles having
a density on the order of half that of fly ash from pulverized coal.^./ The


                                     26

-------
Table 3.  THEORETICAL GAS FLOW RATES FOR A 75 MW
          POWER PLANT AT 130°C, 1 ATM

Power
output
(MW)
40


50


60


70


80


aj Basis
(1)
(2)
(3)

Fuel
moisture
(% wt. wet)
Oil Refuse
0.354 10
0.354 30
0.354 50
0.354 10
0.354 30
0.354 50
0.354 10
0.354 30
0.354 50
0.354 10
0.354 30
0.354 50
0.354 10
0.354 30
0.354 50
for calculation:
Ideal combustion to C02
157o excess air for oil
3 a/
Exhaust volume flow rates (m /min)~"
Oil 5% R 10% R
3,445 3,804 3,892
3,445 3,822 3,943
3,445 3,858 4,071
4,307 4,755 4,865
4,307 4,777 4,929
4,307 4,822 5,089
5,168 5,706 5,838
5,168 5,733 5,915
5,168 5,787 6,107
6,029 6,657 6,811
6,029 6,688 6,901
6,029 6,751 7,125
6,891 7,608 7,784
6,891 7,643 7,886
6,891 7,716 8,143
, H20, NO, S025
only; 25% excess air for oil plus
20% R
4,145
4,394
y
5,181
5,493
y
6,217
6,591
y
7,253
7,690
y
8,289
8,788
y

MSW;
Fuel properties used in the combustion calculations determined
as follows: data for
No. 6 residual oil from Ref. 20,
using
average values for refuse properties from Ref. 11.
b/ Refuse
fraction exceeds limits
for necessary boiler heat input.

                        27

-------
             300
CO
            Solid Lines Represent Theoretical Gas Flowrate for No. 6 Residual Oil
            and 30% Moisture Refuse Assuming 15% Excess Air (Data for Coal
            Based on 10% Moisture Coal and 40% Excess Air)
          U_
          u
          CO
          o
             200
O
_j
u_
CO
<
o
              100
                                                                                  30% Moisture

                                                                                  10% Moisture
                                           REFUSE ENERGY, PERCENT
                     Figure 5.  Theoretical gas flow rates for combined firing of oil and
                              municipal  solid waste (MSW) in a 75 MW power plant.

-------
particle  density overall ranges  from 1.8  to  3.8 g/cc23'24/ compared to an
average particle density of  2.3  g/cc for  fly ash  from coal fired boilersjl/

     The  reason for the wide range  in densities is that several mechanisms
for particulate formation all contribute  significantly to the total partic-
ulate  formation. The combustible fraction consists of entrained char ("black-
birds"),  soot  produced by the thermal cracking of pyrolysis products, and
"white smoke"  which is produced  by  condensation of pyrolysis gases.,24/ It is
the low density, low resistivity carbonaceous particles which are the most
troublesome to control, especially  by electrostatic precipitation, since they
tend to lose their charge on contact with the collection electrode and become
reentrained.25/

     Particulate from fuel oil combustion also is not composed primarily of
mineral particulate. The size distribution is characteristically bimodal, the
larger particles being skeletons of burn-out  fuel particles, called cenospheres,
which  are hollow, black, coke-like  spherical  particles. The smaller particles
formed by the  condensation of vapors are  of  regular shape and usually have a
maximum dimension of about 1.0 \im*  The average density is about 2.5 g/cc,J-3/
but densities  as low as 1.22 g/cc have been  reported.—' In combined firing
of oil and refuse, there will probably be a  sufficiently large proportion of
low density (<« 1.2 g/cc),  low resistivity, predominately carbonaceous partic-
ulate  that a major particulate control problem is expected.

FLY ASH FUSION TEMPERATURE

     In previous studies of  ash  fusion levels, using both test coupons and
tetrahedral cones, the minimum melting range  for ash from refuse incineration
was 454 to 1093°G (850 to  2000°F).^I/  Higher  levels of lead and zinc were found
than had  been  anticipated, presumably from pigments, solders, and galvanized
coatings.  The  melting range  correlated with total concentration of basic oxides
NaoO and  KoO.  The minimum range  occurred  at a level between 30 to 4070 of the
basic  oxides by weight, excluding zinc, lead, and sulfur. Unfortunately, no
relationship could be established between the presence of liquid state and
chemical  composition,  a much more sophisticated procedure apparently being
required.  It is possible that small portions  of a liquid phase could form at
low temperature and remain undetected  due to  the wetting of the larger quantity
of dry material.—'

     With  few  exceptions,  the ingredients  found in refuse deposits acceler-
ate gas side corrosion above 510°C  (950°F). In the presence of a reducing con-
dition the  threshold temperature  could be reduced to as low as 315°C (600°F).
In an oxidizing  atmosphere containing  HCl, it was found that corrosion could
take place  in  a  "dry"  unfused, powdery ash.ZL/

                                     29

-------
PARTICLE SIZE DISTRIBUTIONS

     Particle size distribution data for participate from firing No. 6 resid-
ual oil in electric utility boilers and from incineration of municipal solid
wastes in waterwall and conventional incinerators is summarized in Tables 4
and 5, respectively.

     It is widely believed that particulate from oil firing is extremely fine,
with the usual estimate being 90% less than 1 u-m. However, a search of avail-
able particle size data did not confirm this. The test data which showed the
largest proportion of submicron particulate was for an air atomized, tangen-
tially fired boiler which had originally been designed to fire coal and had
been retrofitted for oil firing. Based on Andersen impactor data,2§./ 13.3%
of the fly ash by weight was determined to be less than 1 urn in diameter.

     Because of the chemical nature of the oil ash, measurement of particle
size is extremely difficult. Compared to coal ash, the solids emitted by fuel
oil combustion are more hygroscopic.—^' When allowed to cool, the oil ash par-
ticles absorb moisture and tend to agglomerate into larger particles during
storage, transportation, and handling. Therefore, ex situ size determination
methods such as Bahco and electron microscopy are subject to considerable error.
In situ measurements made using heated impactors are probably better, but here
too, there is a chance for error resulting from inelastic collisions between
particles and impactor walls. This could result in a distribution erroneously
weighted toward the larger particle sizes.

     Fly ash particulate from incineration of municipal solid wastes is typi-
cally about 10% smaller than 1 urn in diameter.r_t' Andersen impactor data from
Harrisburg Municipal (waterwall) Incinerator indicate that in some cases the
particulate may be somewhat finer than this—about 20 to 30% less than 1 um.32/
The latter size distribution was used in the present study for particulate
from firing municipal solid wastes. Although use of the Harrisburg size distri-
bution data seems conservative, it is considered representative by other in-
vestigators, based on analysis of stack test data from the St. Louis/Union
Electric refuse firing demonstration.^./

     When firing oil with other fuels in the same combustion chamber, it is
anticipated that the particle size distribution for the combined fuels will
be determined by the fuel having the higher ash content. That is, in combined
firing of oil and refuse, the assumption is made that the particle size dis-
tribution of particulate fly ash will be the same as the size distribution
for firing refuse alone. This assumption is justified by:  (a) the observed
chemical nature of the oil ash, which tends to cause it to agglomerate with
other ash particles in the flue gas, (b) the high percentage of refuse ash
at MSW levels of 10 to 20% (Table 1), and (c) the observation that in combined

                                     30

-------
   Table 4.  PARTICLE SIZE DISTRIBUTION FOR OIL-FIRED BOILERS
Diameter               Wt % less than stated diameter

  (tan)       Ref. 26-^     Ref. 28^     Ref. 28£/     Ref. 28^

 1,000         100.0           -
   250          97.8
   150          92.7
    45          50.0           ...
    30          39.6         65.3          77.8          73.0
     9.2        13.2         52.3          55.6          46.0
     5.5         6.8         38.3          25.7          26.3
     3.3         3.2         29.0          10.5          15.9
     2.0         1.4         21.6           6.6           9.0
     1.0         0.3         13.3           1.3           5.7
     0.3         0.0           4.9           0.65          2.3
     0.1
a/  Bahco Data,  specific  gravity of oil ash = 1.22 (data inter-
       polated  graphically).
b/  Andersen impactor data,  air atomizing burners on a tangen-
       tially fired boiler.
c/  Andersen impactor data,  mechanically atomizing burners on a
       tangentially fired  boiler.
d./  Andersen impactor data,  steam  atomizing burners on a tangen-
       tially fired boiler.
                               31

-------
       Table 5.  PARTICLE  SIZE  DISTRIBUTION OF REFUSE  FLY ASH

Diameter

(urn) Ref. 24^
1,000
250
150
45
30
20
15
10
5
1

.,
95
70
65
53
52
33
8

a/ Average of six
b/ Taken from Ref.
£/ Average
of data
Wt % less than
^ Ref. 29-' Ref

75
65
40
37
34
-
30
-

stated diameter
. 30^ Ref. 31^
••
-
-
45
41
36
-
30
23
13
recently reported studies (see
29, Figure 2.
for U.S. Incinerators. Taken
^
87
71
28
-
-
-
_
-

Ref. 24,
from Ref.
Ref. 32£/
—
81
74
59
55
51
48
45
40
30
p. A-8).
30,
      Figure A-18.
d/  Based on sieve analysis of precipitator  catch  for  tests of
      Harrisburg waterwall incinerator. Average  of three  runs with
      various heating values.
_e/  Based on two-parameter Weibull  distribution  parametric repre-
      sentation of Andersen impactor data  for Harrisburg  Municipal
      Incinerator (average of six test measurements).  Distribution of
      particulate larger than 14 ^m was estimated  graphically.
                                 32

-------
 firing of coal and oil,  none of the difficulties encountered in collecting
 fly ash from combustion  of oil alone are  observed.!/

      It is helpful to use analytical techniques in interpreting particle size
 data because of the need to interpolate between data points to provide narrow
 size increments for control device performance evaluation. In the present study,
 a two parameter Weibull  distribution3-!/ was  fitted, using a least squares tech-
 nique, to the particle size data (Figure  6). Because of the different mechanisms
 operative for particulate formation,  the  portion of the size distribution less
 than 1 urn was curve fit  separately.  The Weibull parameter distribution can be
 expressed as follows:

                                          /   \b
                         F(R(j)) = 1 - e"  (^)                       (12)
                                          V  9/

   where  F(R(j)) = the weight fraction of particulate having diameters less
                      than R(j)

             6 , b = independent parameters

 Weibull parameters for the refuse  portion of the fuel are as follows:

                                                    b
                    (< 1 p-m)          1.48           2.91

                    (> 1 urn)        92.1            0.23

     Incremental  size data determined using Weibull parameters to fit selected
 size data  for  fly ash from pulverized coal, No. 6 residual oil, and MSW are
 shown  for  comparison  purposes  in Table 6. Note that for incineration of un-
 shredded municipal solid wastes, a two parameter Weibull curve fit predicts
 that a significant fraction of the particulate will be larger than 1,000 ym.
 Approximately  20  to 30% of the fly ash is predicted to be less than 1.0 \aa. in
 diameter.

 FLY ASH RESISTIVITY

     Resistivity  values for fly ash particulate from municipal solid waste
 incineration range from approximately 106 to 5 x 10   ohm/cm. The resistivity
maximum occurs between 149 and 204° C (300 to 400°F),25/ Bulk resistivity mea-
 surements were made of integrated hopper-catch samples from two German water-
wall incinerators; the bulk resistivity of fly ash from firing refuse only at
                                     33

-------
    1.0
I
o
5
I
s

c
o
™
u
2
   6.1
  o.oi
     0.1
8
                      A    A
O  5/8/73
D  5/8/73
   5/8/73
1:08 -  1:28 p.m.
5:03 -  5:23 p.m.
6:45 -  7:05 p.m.
                                                                                                     O  5/9/73 10:35-10:50 a.m.
                                                                                                     O  5/9/73  1:00 - 1:12 p.m.
                                                                                                     V  5/9/73  3:45 - 3:59 p.m.
                                                                                                     •  Sieve Analysis of ESP Catch
                                                                                                          (Average of 3 Samples) 31/
                                                                                                   -—• ~— Graphical Extrapolation
                                                                                                   —- —— Weibull Parameter Extrapolation
                                                       I    I   I   I  I  I I I
                                            10
                                   Aerodynamic Diameter, ftm
                                                                             100
                                                                                                             1000
                     Figure 6.   Weibull parameter interpolation of Andersen impactor data  for
                                        Harrisburg Municipal Incinerator.10?31?32/

-------
Table 6.  INCREMENTAL PARTICLE SIZE DATA FOR COAL, OIL, AND REFUSE
    FLY ASH DETERMINED USING TWO PARAMETER WEIBULL DISTRIBUTION
 Diameter
  range
   (utn)

100-1,000
12-100
8-12
4.5-8
2.65-4.5
0.975-2.65
Q.70-0.975
0.27-0.70
0.10-0.27
0.01-0.10
< 0.01
            MMET
Selected size distribution used in analyses
                      No. 6
      Pulverized     residual       Municipal
                       oil£/      solid wastes!/
            316.2
             34.6
              9.8
              6.0
              3.45
              1.61
              0.83
              0.43
              0.16
              0.03
                        coa
       0.6333
       0.1000
       0.0778
       0.0622
       0.0956
       0.0144
       0.0064
       0.0102
       0.0000
       0.0000
       1.0000
0.0749
0.4115
0.0824
0.1024
0.0773
0.1212
0.0309
0.0546
0.0256
0.0166
0.002.6.
1.0000
0.3150
0.2202
0.0307
0.0415
0.0358
0.0982
0.1508
0.1007
0.0067
0.0004
0.0000
1.0000
 a/
 c/
 d/
MMD =v^-^
10% ash, Illinois No. 6 coal; pulverized coal fired in tangen-
  tially fired boilerJ Andersen Impactor data (see Ref. 34).
Andersen Impactor data for No. 6 residual oil fired in a tangen-
  tially fired boiler with air atomization (see Ref. 28). Data
  interpolated using two parameter Weibull least squares fit
  (Ref. 33).
Average of six tests using Andersen Mark III Impactor for parti-
  cle size distribution of unshredded municipal solid wastes
  fired in Harrisburg Municipal Incinerator (Ref. 32). Data inter-
  polated using two parameter Weibull least squares fit (Ref.  33).
  Distribution of particulate larger than 14 (o,m was estimated
  graphically (Figure 6).
                                 35

-------
 Munich North Block 2  was  2  x  1Q9 ohm/cm at 160° C (320°F).|2/ Bulk resistivity
 of hopper ash from firing refuse at Dusseldorf was 6 x 10  ohm/cm at 222° C
 (432°F).—/ It is probable  that these  low values may have been influenced by
 the selective collection  of low resistivity ash by the electrostatic precipi-
 tators. In situ resistivity measurements were attempted during acceptance
 tests of the Harrisburg Municipal  (waterwall) Incinerator by Southern Research
 Institute. However, due to  the high flue gas temperatures, in situ resistiv-
 ity measurements could not  be performed. Bulk samples were collected at the
 inlet and outlet of the precipitator using a coarse cyclone, fine cyclone
 and back-up filters in series. Three inlet samples and one outlet sample were
 collected. Resistivity measurements were performed according to the ASME Power
 Test Code No. 28 at a temperature  of 218° G (425°F). The resistivity of the
 coarse material was 3 x 108 ohm/cm and the resistivity of the fine material
 was 5 x 106 ohm/cm.2i/

      Because of higher flue gas temperatures characteristic of both conven-
 tional refractory and waterwalled  incinerator plants, it is unfortunately not
 possible to compare ESP collection performance for these installations with
 performance of precipitators  on electric utility boilers. Design methods also
 differ somewhat between these two  types of installations, with precipitators
 of European design being  used on all waterwall incinerators presently equipped
 with ESP control.iZ.'  Data on  the change in migration velocity with temperature
 indicate that the precipitation rate parameter decreases by about 25 to 50%
 as the flue gas temperature decreases from the range characteristic of water-
 wall incinerators (200 to 250°C) to the lower temperature range encountered
 in oil-fired electric utility boilers (150 to 2nnPn).25,27/

      Somewhat in contrast to U.S. manufactured equipment, the European pre-
 cipitator  design approach aims at  a more conservative migration velocity by
 using somewhat  lower  field  intensities. Thus, the size of the precipitator
 must  be increased commensurately. As a result of this, lower gas velocities,
 3  to  4  ft/sec,  are  employed in combined-fired applications. U.S. designers
 would typically specify gas velocities of 4 to 4-1/2 ft/sec for refractory
                    O *? /
 walled  incinerators.^1./

     Gas velocity  is  selected for  a discrete particle size distribution so
 that re-entrainment problems are minimized. For comparison, gas velocities
 used  in design of coal fly ash precipitators are typically 6 to 8 ft/sec^./
 while lower velocities on the order of 4 to 5 ft/sec are recommended for oil
 ashjti35/

     With respect to particulate emissions from oil-fired boilers, stack gas
temperature and sulfur content of the oil affect the resistivity of the non-
combustible portion of these solids;  however, the balance of these solids are
composed of highly conductive combustible carbonaceous solids. As a result of


                                     36

-------
these carbonaceous solids, the resistivity of the particulate emissions is
usually less than that for coal, 107 to 109 ohm/cm for oil versus 109  to 10
ohm/cm for coal.—' Difficulties which have been reported in collection of
oil ash result from the low concentration of fly ash having a relatively low
bulk density and a relatively fine particle size. As in the collection of in-
cinerator ash, there is frequently a high concentration of carbon in the oil
ash, which sometimes causes a resistivity so low that ESP collection becomes
difficult. In some cases, these solids are so conductive that they do  not re-
tain a charge and subsequently prevent the field from becoming saturated.
Another problem that has been encountered is that these solids, upon deposi-
tion on collecting curtain surfaces, sometimes lose their charge to the cur-
tain and become re-entrained in the gas stream*—'  At least part of the dif-
ficulty with ESP collection of oil fly ash could also result from the  breakup
of agglomerates. Collection efficiency is improved through the employment of
high voltage, large collection curtains, lower superficial gas velocity and
high retention times. There is adequate evidence to indicate that, for an ESP
unit suitably modified efficiencies of 90+% are possible for collection of oil
ash. It is anticipated that high efficiencies should also be possible  for refuse
ash, with similar modifications as for oil fly ash.
                                     37

-------
                                 SECTION 4

          COST AND EFFECTIVENESS OF PARTICULATE EMISSION CONTROLS ON
                           MSW-OIL FIRED BOILERS
      This section includes  a discussion of control performance (fractional
 efficiency)  as  well  as  cost data for estimation of control device cost and
 performance  for meeting specific particulate emission levels when firing oil
 and municipal solid  wastes  (MSW) in a single combustion chamber. Control sys-
 tems considered included cyclones, electrostatic precipitators, and high per-
 formance wet scrubbers.

 INERTIAL COLLECTORS

      The efficiency  of  a multicyclone is dependent upon the size and density
 of the particulates  in  the gas stream. On coal-fired cyclone furnaces the
 efficiency usually ranges from 30 to 40%, while on a pulverized unit it ranges
 from 65 to 75%.—'  These differences can be attributed to the fact that the
 mean particle diameter  of the emissions from a cyclone furnace is usually lower
 than that of the  emissions from a pulverized unit. The estimated range of ef-
 ficiency of  cyclone  collectors installed on oil-fired boilers is 82.5 to 90%
 as determined from a summary of National Emissions Inventory System data (NEDS)
 summarized in Table  7.
           estimates that a maximum efficiency of 40% might be obtained for
small oil-fired boilers and that this efficiency would decrease as the boiler
size increased. Though they are not efficient in the reduction of fine partic-
ulate emissions, mechanical collectors could help reduce acid smut emissions
since smut is composed of agglomerated solids and is usually large in diam-
eter. I/

     The range of overall collection efficiences for oil-fired boilers, based
on stack test data is 75 to 90%.3?7?26?35/  Fractional efficiency data for coal
fly ash and performance guarantees for oil ash are shown in Figure 7.
                                    38

-------
     Table 7.  SUMMARY OF EFFECTIVENESS OF VARIOUS CONTROL SYSTEMS IN
               USE ON OIL-FIRED ELECTRIC GENERATING PLANTS*/
      Cont ro1 method

Wet scrubber - low efficiency
Cyclone - medium efficiency
Cyclone - low efficiency
ESP - high efficiency^/
ESP - medium efficiencyW
ESP - low efficiency^/
Gravity collector - high
  efficiency
Cyclone (L)/gravity collector
  (L)b/
ESP (M)/eyelone (M)b/
Cyclone (M)/ESP (M)^/
Cyclone (L)/ESP (M)^/
Cyclone (M)/ESP (H)£/
Gravity collector (H)/ESP  (L)k/
   No.
installed

    1
   28
   11
    7
   11
   28
    3
    2
    6
    2
    4
    1
                                                 Range of
                                                efficiency
                Average
              efficiency
82.5-90
  20-85
  90-97
  35-97
  30-95
85.7-87.2

   85

   95
  96-98.5
   93
   99.2
   80
80
85.8
52.5
93.4
68.1
62.0
86.6

85

95
96.5
93
99.2
80
a/  Summarized  from NEDS  inventory  listing, Ref. 4.
b/  Controls—ESP = electrostatic precipitator, M = medium efficiency,
"     H - high  efficiency, L =  low  efficiency.
                                      39

-------
 X
 o
 QJ
 c
 o
 o
U
O  6 in
A  10 in
D  10 in
V  4in
2.5 in. AP (Coal)
2.5 in. AP (Coal)
       AP (Coal)
     dia.
     dia.
     dia., 2.5 in.
     AP (Coal)
6 in. dia., 6.0 in. AP
(Efficiency Guarantee for Oil 3/)
                               10           15
                            Particle Diameter, fj,m
                                                        L-/V-
                  20
                40
    Figure  7.  Fractional efficiency data  for cyclone collection of
      fly ash from coal- and oil-fired electric utility boilers.
                                   40

-------
      It  should be emphasized that there are operating problems with  the use
 of multicyclone collectors for control of oil-fired boilers.  If the  tempera-
 ture of  the combustion gas is below the 803 dew point, the hygroscopicity and
 corrosiveness of the oil ash can cause centrifugal collector  operational and
 maintenance problems. Build up of cement-like ash on tube and hopper surfaces
 results  in increased pressure drop as well as corrosion and cleaning problems .I/

      There are several European waterwall incinerators equipped with cyclone
 control, but no fractional control efficiency data were found for these plants.
 The reported efficiency of a cyclone installed at Nashville Municipal (water-
 wall) Incinerator is 57.7%.—'  This unit is used as a precleaner for a scrub-
 ber. Collection efficiency of ash from refractory walled incinerators by
 cylones  declines rapidly for dust smaller than 20 p,m.^ft/ Theoretical performance
 models for cyclone collectors have been developed,.3!/ but the application of
 theory to practical design problems has not been achieved.

 WET SCRUBBERS

      When applied to 170 MW coal-fired boilers, high efficiency wet  scrubbers
 have demonstrated an average 96% particulate removal efficiency at a  pressure
 drop of  37.4 mm Hg (20 in. I^O).^/ At. Boston Edison's Mystic  Station, a Chemico-
 Basic (Magnesia Slurry)  scrubbing system installed on Boiler  No. 6 (156 MW)
 has achieved particulate removal efficiencies as high as/69^.-£§/ The  Chemico-
 Basic system employs a single stage Venturi scrubber. There have been operating
 problems with the system installed at Mystic No. 6. Collection efficiency de-
 creases  rapidly with decreasing particle size.  Negative efficiencies  were ob-
 served at the Mystic MgOx system for particle diameters below 1.5. pm, presumably
 resulting from entrainment of scrubber solids..3-9-'  The lower stages of the im-
 pactor at the scrubber outlet were also found to be wet,  indicating poor per-
                                  on /
 formance of the mist eliminators.—'

      The estimated average efficiencies of scrubbers  installed on oil-fired
 electric generating stations (medium efficiency scrubbers)  is  85.8%  (Table 7).
 The only waterwall incinerator plant presently equipped with  a  scrubber for
 particulate control is Nashville's (Nashville Thermal, Transfer Corporation)
 Riverside No.  2 Unit.  A  low energy wet scrubber with a Venturi rod insert is
 used to  reduce particulate emissions from 2.31  g/Nm3  (1.01 gr/dscf at 12% C02)
 to  0.39  g/Nm3  (0.169  gr/dscf at 12% C02).—/  (This  emission level is  in viola-
 tion of  New Source Performance  Standards for Incinerators.) Also at NTTS, there
 are  plans  for  installation of a high energy two-phase scrubber  designed by
 Chemico-Aronetics.3!/  This scrubber is similar  in design  to the  Chemico-Aronetics
 "Adtec"  Scrubber.19_/ Based on the pilot plant  studies,  estimated particulate
 emission  levels  are 0.049  g/Nm3 (0.0214 gr/dscf  at  12% C02).3i/  This  corre-
 sponds to  an overall  efficiency for particulate removal of 98.0%. There are
no cost-performance data available at  this time from  Chemico.  Reasons given


                                     41

-------
 were that (a) present data  are  based only on a pilot plant installation, and
 (b) there are not enough data available at this time to determine whether con-
 ventional construction materials  will be sufficient to withstand the corrosive
 incinerator flue gas .-Li/

      The cost and performance of  Venturi scrubbers is highly dependent upon
 allowable pressure drop and economic tradeoffs between installed and operating
 costs. Typical installed costs  (1975 basis) for high energy 7ffturi scrubbers
 for fly ash removal are $48 to  $96/m3 ($1.35 to $2.70/acfm).—' The variation
 in installed cost with gas  volume and efficiency is shown in Figure 8.

 ELECTROSTATIC PRECIPITATORS

      When applied to cyclone-fired, coal-burning boilers, electrostatic pre-
 cipitators have demonstrated particulate collection efficiencies ranging from
 65 to 99.5%.  On general pulverized coal boilers, control efficiencies are usu-
 ally between 80 and 99.5%.—' As discussed, there are several difficulties in
 adapting fly ash precipitator, designed for coal-fired boilers to handle fly
 ash from firing oil.  For control  purposes, major differences are:  (a) lower
 ash density,  (b)  a higher concentration of carbonaceous, low resistivity partic-
 ulate, (c) a higher percentage  of submicron particulate, (d) a hygroscopic
 fly ash which tends to agglomerate, and (e) a reduced volumetric ash loading.
 As a result of these factors, when a coal-fired boiler with an electrostatic
 precipitator is converted to oil  with the precipitator unmodified, particulate
 control efficiency is usually reduced. A typical collection efficiency for
 an unmodified unit is reportedly  about 45%.—'  If the precipitator is modified,
 however,  control  efficiencies approaching 90% can be realized.—'

      Enlargement  of collection  electrodes can be used to minimize re-entrainment
 of low density,  low resistivity fly ashft/ which tends to easily lose its charge
 when  it comes  into contact with the collection electrode. Reduction in gas
 velocity,  increased rapping intensity, and decreased frequency are also recom-
 mended to minimize re^-entrainment.^,/ Because the average particle size is
 smaller, a  lower operating voltage, higher current, and longer gas treatment
 path are recommended.-!' Other modifications are required because of ash han-
 dling problems. The hygroscopicity of the particulate matter causes a solids
 buildup on high tension  electrodes, insulators, and collection curtains. When
 allowed to cool, these solids absorb moisture, become difficult to remove and
 cause arcing and shorts. By locating the precipitator on the hot side of the
 air preheater, solids accumulation is reduced on high tension wires and col-
 lection curtains. Build up on insulator bushings can be prevented by using
hot air ventilation. Hopper plugging can be avoided by either heating the hop-
per or employing a wet bottom system^.'
                                     42

-------
 o
U

-a
 
-------
     The  average collection efficiency for high efficiency electrostatic pre-
 cipitators on oil ash is estimated, based on NEDS inventory data (Table 7)
 to  be  93.4%. The average collection efficiency of ESP installions on water-
 wall incinerators is approximately 957o (see Appendix B).

 Control Costs for Electrostatic Precipitator Control

     Installed control costs for new high efficiency, multiple field electro-
 static precipitators typically range from $26.5 to $123.6/m  ($0.75 to $3.50/
 ACFM), based on data for 1975.—/ Retrofitting for collection of oil fly ash
 costs  an  additional $87 to $131/m3 ($2.50 to $3.75/acfm) (see Figure 9); a
 new installation designed for oil costs $218 to $350/m3 ($6.25 to $10/acfm).-/

     An alternative approach would be to install ESP collectors specifically
 designed  for refuse fly ash. This approach would be applicable for new installa-
 tions, but would probably not be suitable for existing units which may need
 to  be  converted back to coal at some later date. Installed cost and design
 data for  ESP units installed on existing waterwall incinerators are summarized
 in  Table  8.

 Electrostatic Precipitator Performance Model

     As previously discussed,  combined firing of oil and MSW will cause de-
partures  from fly ash properties and ESP operating conditions. Specifically,
changes may occur in dust loading,  flue gas volume,  particulate density, size
and resistivity.  Because ESP controls are installed on most units planned for
combined oil-MSW firing studies,  a  considerable effort in the study was directed
toward adaptation of available information to develop an analytical model for
prediction of ESP performance.   The model,  which is  intended to provide the
capability for rapidly estimating ESP performance for combined-firing conditions,
is described  in  detail in Appendix  C.
                                   44

-------
      0
 v>
 o
(J
 a

 (A




"jjj

 "o
Gas Volume,  104M3/min



     2
                                            Gas Volume, 105 ACFM

        *  Adjusted to 1st Quarter (January)  1976  Using Chemical

             Engineering (CE) Plant Cost Index.43/




                      Figure 9.   Total installed cost  for  electrostatic precipitators.—/

-------
  Table 8.  DESIGN AND COST DATA FOR ELECTROSTATIC PRECIPITATORS DESIGNED
              FOR COLLECTION OF WATERWALL INCINERATOR FLY ASH
 Installation A - 150 TPD Incinerator;

 A.  Sizing and performance data

    Gas volume                    = 1,130 m3/min (40,000 ACFM)
    Temperature                   = 290°C (560°F)
    Efficiency                    = 97.5% by weight
    Inlet loading                 = 4.6 g/Nm3 (2.0 gr/scf)  at 12% C02
    Residual                      = 0.1 g/Nm3 (0.05 gr/scf)  at 12% C02
                                      (Mass. Code)
    Maximum excess air            = 100%
    Migration velocity (w)        = 9.03 cm/sec
    Gas velocity                  = 1.10 m/sec (maximum) (3.70 fps)

    Precipitator size - One (1) precipitator
    14 Gas passages             Two (2) fields
    4.6 m (15 ft) field height  25 cm (10 in.) passage spacing
    Field length = 2.85 m (9.36 ft) x 2 = 5.70 m (18.72 ft)

    Precipitator will remove 97.5% by weight of the incoming dry solid par-
    ticulate provided the inlet dust is at least 4.6 g/Nm3  (2.0 gr/scf) at
    12% C02. If the inlet dust load is less than 4.6 g/Nm3  (2.0 gr/scf) at
    12% C02, the unit is guaranteed to have a maximum outlet emission of
    0.1 g/Nm3 (0.05 gr/scf)  at 12% C02.

B.  Prices (budgetary)

    1.  Basic E/P with electrics,  support
        steel,  access and dust valves                       $253,460

    2.  Thermal  insulation for entire
        precipitator including installation                 $ 34,125

    3.  Erection  of E/P and auxiliaries
        excluding L.V.  wiring                                $ 93,160

                                             Total          $380,745
                                     46

-------
                           Table 8.  (Concluded)
Installation B - 750 TPD Incinerator

A.  Sizing and performance data

    Gas volume                    = 5,660 m3/min (200,000 acfm)
    Temperature                   = 220°G (428°F)
    Inlet loading                 = 4.6 g/Nm3 (2.0 gr/scf) at 12% G02
    Residual                      = 0.1 g/Nm3 (0.05 gr/scf) at 12% C02
    Efficiency                    = 97.5% by weight
    Maximum excess air            = 100%
    Migration velocity (w)     —  = 9-.O em/sec.
    Gas velocity                  = 0.15 m/sec (4.25 fps) (maximum)

    Precipitator size - One  (1) precipitator
    37 Gas passages             Two (2) fields
    7.6 m (25 ft) Field height  25 cm (10 in.) Gas passage spacing
    Field length = 3.328 m (10.92 ft) x 2 = 6.657 m (21.84 ft)

    Precipitator will remove 97.5% by weight of the incoming dry solid  par-
    ticulate provided the inlet dust is at least 4.6 g/Nm3 (2.0  gr/scf)  at
    12% G02» If the inlet dust load is less than 4.6 g/Nm3 (2.0  gr/scf)  at
    12% CC>2, the unit is guaranteed to have a maximum outlet emission of
    0.1 g/Nm3 (0.05 gr/scf) at 12% G02.

B.  Prices (budgetary)

    1.  Basic E/P with electrics, support
        steel, access and dust valves                       $420,130

    2.  Thermal insulation for entire
        precipitator including installation                 $ 93,225

    3.  Erection of E/P and auxiliaries
        excluding L.V. wiring                               $258,990

                                            Total           $772,345
Source:  Wheelabrator Frye, Inc., Air Pollution Control Division, September
           26, 1975.
                                    47

-------
                                SECTION 5

                              CASE STUDIES
 DISTRICT  OF  COLUMBIA

     The Department of Environmental Services, District of Columbia, recently
 initiated a  combined-firing test program originally planned as an EPA re-
 source recovery demonstration program which would have involved concurrent
 firing of oil and coal with shredded municipal solid wastes (MSW). The planned
 test boiler  was the Potomac Electric Power Company (Pepco) Benning Station
 Boiler No. 26. The planned refuse processing capacity was 22.7 MT/hr of raw
 refuse, or approximately 16.3 MT/hr of refuse derived fuel (RDF) at a 75/25
 air classifier cut; considered sufficient to remove 90 to 957o of the aluminum
 cans for  aluminum recovery in the heavy fraction, and also yield a fuel of
 lower ash and higher burn-out than was prepared in St. Louis (see Tables 9 and
 10). This refuse capacity is equivalent to 20 to 2570 of the heat input to
 Benning Station No. 26 (75 MW) at 100% load. The actual steady-state refuse
 capacity  when firing oil would have been determined in the test. Three tests
 each on coal only and oil only were planned to establish steady-state baseline
 conditions.  Following these preliminary tests, one to three steady-state tests
 each with oil-plus-refuse and coal-plus-refuse were planned.  Benning Station
 Boiler No. 26 is equipped with ESP control; emission tests on Benning Station
 No.  26 (firing oil) have recently been performed by York Research Corporation.^'

     Notable  characteristics of the planned combined firing tests at Pepco were:
 (a)  the refuse preparation facility would have employed primary and secondary
 shredders, and it was planned to test the combustion characteristics of a wide
 range  of particle sizes; and (b) air emissions monitoring of NOX, SOX» Hg, HCl,
 and  particulates were to have been supplemented by an extensive program, con-
 ducted by a  separate subcontractor, to determine air emissions of trace heavy
metals, POM's, PCB's, and small organic moieties. Statistical methods were to
have been used for refuse sampling. Refuse analyses would have been done by
 the  same  laboratory as for the St. Louis/Union Electric test program.  Corro-
 sion would have been monitored by probes, waste measurements,  and test  specimens


                                    48

-------
                                         Table 9.   ESTIMATED MATERIALS BALANCE*

Estimated
% Composition
43.0
10.0
0.5
7.0
1.0
14.0
12.0
5.0
7.5
100
-p-
sO
Operations
Receiving
Shredder
Air Classifier
Lights
Heavies
Dust (Loss)
Pneumatic Feeder
Paper
10.75
10.75
10.75
9.93
.82

9.93
Glass
2.50
2.50
2.50
.49
2.01

.49
Non-
Fe
.13
.13
.13
.01
.13
-
.01
Fe
1.75
1.75
1.75
.03
1.72
-
.03
Al
.25
.25
.25
.04
.21
-
.04
Yard
Waste
3.50
3.50
3.50
2.89
.61

2.89
Food
Waste
3.00
3.00
3.00
1.98
1.02

1.98
Rags &
Wood
1.25
1.25
1.25
.50
.75

.50
Ash
Rock
1.87
1.87
1.87
1.07
.80

1.07
Total
(tons/
hr)
25
25
25
16.94
7.87
0.16
17.13
             *Table based on feed rate of 25 tons per hour
             Source:  Department of Environmental Services of the District of Columbia,  "Utilization of a Refuse-Derived
                      Fuel as Supplementary Fuel in  an Oil and Coal Fired Electric Utility Boiler", Proposed to
                      U.S. Environmental Protection Agency fora Research, Development and Demonstration Grant,
                      April 1, 1975.

-------
         Table 10.  TARGET  ANALYSIS  OF  REFUSE  DERIVED FUEL AT SWRG-1
                            (Washington,  D.C.)£/
 Higher heating value                    12,800-14,000 joules/g (11,600)1>/
                                         (5,500-6,000 Btu/lb)

 Moisture                                20-25%  (30%).k/

 Ash                                     15-20%  (30%)£/

 Sulfur                                  0.3%  (0.4%)^

 Chlorine                                0.6%  (1.0%)^/

 Particle size                            £3.8 emir/
                                         (£ 1.5  in.)

 Bulk density                             32-116  kg/m3-/
                                         (2-11 lb/ft3)
ai/  Dry weight basis.
J>/  Extreme value for acceptance by Pepco.
£/  The maximum specified dimension of each particle is 95%/weight less than
      10 cm.
d/  The pneumatic delivery system as designed by Rader Pneumatics can deliver
      RDF as low as 32 kg/m3 (2 lb/ft3) only at the highest flow rate of
      400 m3/hr (14,000 GFH).
                                    50

-------
to determine  any incremental effects from burning RDF compared to the conven-
tional  fuel.  Slagging effects would have been monitored both visually and dur-
ing operations,  by monitoring manometers indicating draft loss. The combined
firing  test program  and estimated emissions  are  described in detail in the
following  subsections.

Program Status

    The District of  Columbia Department  of Environmental Service submitted a
joint proposal with  Pepco and National  Center for Resource Recovery (NCRR) to
EPA, Office of Solid Waste Management Programs on April 1, 1975. The program
is now  inactive  as an EPA resource recovery  demonstration program.

Refuse  Derived Fuel  (RDF) Preparation and Facilities

Shredding  of  MSW--
     The DBS  Solid Waste Reduction Center No. 1  (SWRC-1) is equipped with a
tipping floor and steel pan pit conveyor feeding a Williams 780, 2.684 x 10^
joules/hr  (1,000 hp)  horizontal hammermill.  Discharge is onto a Jeffrey vibrat-
ing oscillating  pan  feeder conveyor and  then to  a rubber belt conveyor. Full
rated capacity of the shredder system is 25  tons/hr; the limitation of capacity
is the  design of the conveying system, which was originally for oversized bulky
wastes  (OBW), and not any limitation of  the  shredder. The feeder was to have
been modified for larger capacity.

Air Classification—
     Modifications were planned to  install a 25  ton/hr  Triple/S "Vibrolutriator"
air classifier to SWRC-1. This classifier is the same as specified in Ames and
Chicago. A 75/25 split  was expected in the air classifier between light and
heavy fractions,  giving a maximum delivery of approximately 16.3 MT/hr of fuel.
The objective for the split was to  recover from  90 to 9570 of the aluminum cans
while also dropping  items such as wood,  textiles, and heavy food wastes.  Achiev-
ing these  objectives  would have yielded  RDF  of lower ash and higher burn-out
than was prepared in  St.  Louis.

Secondary  Shredding--
     Detailed engineering plans were approved by the district government for
the installation  of a cyclone and associated blower and rotary valve (all owned
by NCRR) as the  arrangement for de-entrainment of the air classifier light
fraction. The plans called for the  cyclone to discharge through a rotary valve
which,  in turn,  would have discharged to  either  a positive displacement feeder
or to the second  shredder.

    The secondary  shredder proposed for  this work was a verticle type, such
as the Heil 42F.  The  proposed arrangement  (Figure 10) was such that the

                                      51

-------
               Feed
      Williams 780 Hammermill
     Triple S Dynamics Air Class.
                                Frac.
1
Fraction

RDF Weigh
System





Cyclone
1
I
Shuttle
Conveyor





*Tower

PflAi 1 ^wc4*
r neu • oysr *
to Pit or
Conveyor
        Secondary
        Shredder
   I	,
      Pneumatic Delivery System to PEPCO Surge Bin
Figure 10.  Process  flow for preparation of RDF  at
               District  of Columbia.
                         52

-------
secondary shredder could have  been by-passed, or not, to deliver RDF to the
boiler. This arrangement would have  permitted testing of a wide range of
particle sizes of RDF.  It was  considered  impractical to obtain all sizes
using the secondary  shredder only. A second planned method for achieving
variable particle size  was  to  change the  grate of the Williamson 780 shred-
der.  A combination  of  both methods  would have extended the particle size
range from 95% minus 10 cm  to  something under 5 cm. Particles smaller than
this would have been produced  in  the second shredder.

Characteristics of Test Boiler

    Benning Station  Boiler  No. 26 is a tangentially fired boiler designed by
Combustion Engineering  for  a nominal capacity of 75 MW. The boiler system is
broadly similar to that used in St.  Louis except with a smaller capacity.
Another difference is that  this is a dry  ash handling system as contrasted to
the Union Electric wet  system. Boiler ratings for firing coal and oil are
listed in Table 11.

    Boiler No. 26 was designed to burn either 100% coal or oil at the maximum
capacity rating (MCR).  However, it may have been necessary to remove one level
of oil guns to accommodate  RDF burners, which would have reduced capability to
67%.

    The boiler modification to accept RDF would have consisted of removing one
level of oil guns and replacing them with (two) locally controlled, tiltable
refuse burners. If two-corner  burning were found unacceptable, the system would
have been modified to permit burning at four corners. Combustion Engineering
has also investigated the possiblity of locating the refuse nozzles in the wind-
box without removing one level of oil firing to allow refuse-oil firing at the
MCR.

Installed Air Pollution Control Equipment

    Boiler No. 26 employs   a mechanical-electrical precipitator system which
was initially installed by  Aerotec Corporation. The electrical section was
restored in 1968 by  Research-Cottrell to  original Aerotec specifications.—'
Design specifications are 99%  for both collectors in series when burning 1%
sulfur coal at a flue gas volume of  9,344 m3/min (330,000 acfm), 165° C
(330°F).ft6_/ When firing oil in Boiler No. 26, the mechanical collector, which
has a tendency to plug  under these conditions, is normally bypassed. When
the mechanical collector is bypassed, the design efficiency, under conditions
just described (i.e., for 1% sulfur  coal) drops to 90.8%.-£/ Design parameters
for the electrostatic precipitator are summarized in Table 12.
                                     53

-------
                                                             45 /
Table 11.  PEPCO BENNING STATION BOILER NO.  26  DESIGN RATINGS—
          Boiler rating

            Steam:   306,000 kg/hr
                    (675,000  Ib/hr)

            Temperature:  538°G
                         (1,000°F)
                                      2
            Pressure:  1,062 newtons/cm
                      (1,525 psig)

          Coal  firing

            Heat  in:  8.5565 x 1011 joules/hr
                     (811,000,000 Btu/hr)

            Boiler efficiency:  89%

            Heat  out:  7.6153 x 10   joules/hr
                      (721,790,000 Btu/hr)

         Oil firing

           Heat in:  8.6933 x 10   joules/hr
                     (823,961,180 Btu/hr)
           Boiler efficiency:  87.6%

                      7.6153 x 1011
                      (721,790,000 Btu/hr)
Heat out:  7.6153 x 10   joules/hr
                             54

-------
          Table 12.  CHARACTERISTICS OF ELECTROSTATIC PRECIPITATOR
Plate area—1,235.6 m2 (13,300 ft2)/section

Plate-to-plate spacing
  (a) Inlet*/
  (b) ChitletS/

Corona wire diameter—
                                 233    _i
Specific collection area—264.5 m /10  m -min
                          (80.6 ft2/!,000 acfm)

Migration velocity~15 .0 cm/sec
                    (29.6 ft/min)

Design voltage—45 kv
                                 oc/
Current density—16.8 nanoamps/cnr"

Electrical sets—two in parallel

Design efficiency—90.8% burning coal with 1% sulfur at approximately 75 MW
                     and 9,344 m3/min (330,000 acfm) into the precipitator
                     165°C  (with mechanical collector bypassed)
a/  Data not available; assumed value was 25.4 cm (10 in.).
b/  Data not available.
~c/  Average for particulate emission tests made when firing No. 6 residual
      oil..4!/
                                    55

-------
     The electrostatic precipitator is not  presently expected to  meet  design
 specification when firing coal.  Therefore,  the above specifications must be
 used with caution. Efficiency measurements with coal and using both the me-
 chanical and electrical sections have been made and indicate an  average ef-
 ficiency of only 96.5%.—/ Recent efficiency tests  with No.  6 residual oil
 reflect an efficiency of roughly 60%.li/  When burning coal, flue gas tem-
 perature is typically 204°C (4009F,  which  is higher than that for which the
 ESP unit was designed. Increasing temperature increases flue gas volume and
 frequently decreases ESP collection  efficiency for  this temperature range.

 District of Columbia Emission Regulations

 Administering Agency:

      Bureau of Air and Water Quality Control
      Department of Environmental Services
      25 K Street,  N.E.
      Washington, D.C.  20002

 Fuel-Burning Particulate Emission:

      For installations using more than 3,500,000 Btu/hr total input,  the
      particulate emission limitation shall  decrease as the rate  of heat input
      increases  as  summarized below:

                        H                     E
                  (106  Btu/hr)          (lb/106 Btu)

                         3.5                 0.13
                        10                   0.101
                       100                   0.059
                     1,000                   0.034
                 £  10,000                   0.02

H = total heat  input  in millions  of  Btu/hr

E = maximum emission  in pounds of particulate matter per million Btu  heat
      input

H £ 3.5; E = 0.13; 3.5 < H <  10,000; E = 0.17455 H" 0.23522  H ;>  10,000;
   E = 0.02
                                    56

-------
Sulfur Oxides:

     No person shall purchase, sell, offer for sale, store, transport,  use,
     cause the use of, or permit the use of, fuel oil which contains more
     than 17o sulfur by weight in the District, if such fuel oil is  to be
     burned in the District.

     On and after July 1, 1975, the sulfur content of such fuel oil shall not
     exceed 0.5% by weight.

Nitrogen Oxides:

     Emission limits for nitrogen oxide in fossil fuel fired steam  generating
     units of more than 100,000,000 Btu/hr heat input are as follows:

     1.  0.20 Ib per million Btu heat input (0.36 g per million cal.),
     maximum 2 hr average, expressed as N02»,when gaseous fossil fuel is
     burned.

     2.  0.30 Ib per million Btu heat input (0.54 g per million cal.),
     maximum 2 hr average, expressed as N02»,when liquid fossil fuel is
     burned.

     3.  0.70 Ib per million Btu heat input (1.26 g per million cal.),
     maximum 20 hr average, expressed as N02» when solid fossil fuel
     (except lignite) is burned.

     4.  When different fossil fuels are burned simultaneously in any
     combination the applicable standard (Ib NOX per Kr Btu) shall be
     determined by proration, according to the following fomula:


                     x (0.20) + v  (0.30) + z  (0.70)
                               x + y + z


where     x = the percent  of  total heat input derived from gaseous fos-
                 sil  fuel

          y = the percent  of  total heat input derived from liquid  fossil
                 fuel

          z = the percent  of  total heat input derived from solid fossil
                 fuel
                                    57

-------
 Estimated Performance of Installed Air  Pollution  Control Equipment

     On the basis of information  related to  the planned test program, the per-
 formance of the installed electrostatic precipitator was calculated for the
 tests which would have involved  combined  firing of oil and MSW. ESP design
 and performance data used in the calculation were summarized  in Table  12. The
 target composition data for  the  RDF fuel  in Table 10 were used; actual com-
 position data were not available.  The ESP analytical model is described in
 Appendix C. Dust loadings were estimated  using Eq. (8). An average value of
 0.0632 g/10  joules was used for total  particulate from the oil portion of
 the fuel based on data in Appendix A. The predicted variation in flue gas dust
 loading with RDF heat input  is shown in Figure 11, in comparison with an earlier
 estimate by another group of investigators.—'

     The predicted dust loading shown in Figure 11, for fr = 0.15 corresponds
 approximately to average emission  value for oil fired boilers, and combined
 suspension firing of MSW with coal.  The curve for fr = 0.50 corresponds ap-
 proximately to the highest estimate for the refuse fly ash fraction..6-'

     The calculated electrostatic precipitator performance is shown in Figure
 12.  Efficiencies range between 77  and 86%,  depending on boiler load and
 percentage of  refuse fired.  In making the calculation it was assumed:

     1.   The ESP  unit  would be put  into proper operating condition.

     2.   The cyclone precleaner would be bypassed,  as is done for oil
 firing.

     On  the basis of data for flue gas dust  loading and ESP performance, in
 Figures  11 and  12, the particulate  emissions under two different boiler loads
 and  with varying refuse heat input  fraction were calculated. These results
 are  shown  in Figure  13. As is evident from Figure 13, it is predicted that
 particulate emissions will exceed New Source Performance Standards for
 Fossil Fuel-Fired Steam Generators, except at low MSW and/or low boiler load.
 Referring to District of Columbia Emission Regulations, the particulate emis-
 sion standards for the District of  Columbia are lower than new source standards
 decreasing with fuel consumption rate.  At the MCR, the District of Columbia
 standard is 0.0161 g/106 joules (0.037  lb/106 Btu), about one-third the federal
new  source standard.

 Cost of Air Pollution Control

    The cost of new or modified control systems to meet existing particulate
emission standards when Benning Station No. 26 is burning oil and MSW was not
determined.


                                     58

-------
                                                 See Eq.  (8) for definition of f .
Figure 11,
                  10                      20
                       % MSW  Heat  Input

Effect of MSW fly ash  fraction (fr) on  calculated particulate
  emissions (uncontrolled) from combined firing of MSW and
  No. 6 residual oil (from Tables 1 and 2).
                                  59

-------
   .99
 u
 
-------
J)
~2
•i-
o
U^

Ju
O
c
O
D
U
                               \
                                  New Source Performance Standard for
                                  Fossil Fuel-Fired Steam Generators
                    D.C. Air  Quality Regulation @50 MW (Reduced Load)

                    D.C. Air  Quality Regulation @75 MW (MCR)
                             10                      20
                                 % MSW Heat Input
30
        Figure 13.  Estimated particulate emissions (controlled) for combined
                firing of oil and MSW at  Pepco Benning Station No. 26.
                                       61

-------
 Pepco estimated the required  control efficiency to be 99% when firing oil and
 refuse at 10% MSW,  based  on 1.16 x  107 joules/kg, 7,936 kg/hr (5,000 Btu/lb,
 8.75 tons/hr).^/ Based on a  lower  assumed inlet loading corresponding to
 fr = 0.15 in Figures 11 and 13, the required control efficiency at 10% MSW
 is 95.3%.

 WILMINGTON,  DELAWARE (New Castle County)

      The State of Delaware, Division of Natural Resources, was awarded a |9
 million resource recovery demonstration grant from EPA in October 1972.—'
 Delmarva Power and  Light  Company has agreed to participate in the program,
 and will modify either Edgemoor Station Units 3 or 4 to fire refuse. Delaware
 Division of  Natural Resource  will construct a new processing plant in New
 Castle County. There are  few  details available with regard to test schedule
 and emission tests  because these plans have not yet been finalized between
 the State of Delaware and Delmarva  Power and Light Company. If Edgemoor Sta-
 tion Boiler  4 (160  MW) is the test  boiler the Deinarva plan is to fire 5% MSW
 with oil at  242 ton/day of MSW.—'

 Project Status
                                                                             207
      A feasibility  study  was  completed by Combustion Engineering in May 1974.—
 Delaware plans to issue an RFP for  boiler modifications within FY 76. Delmarva
 estimates it  will require approximately 1 year to make boiler modifications;
 the Delaware  schedule is  presently  to begin tests by 1979.—'

 Refuse Derived Fuel Preparation and Facilities

      Presently,  the State of  Delaware is operating the 500 ton/day facility
 shown schematically in Figure 14 in New Castle County. The process uses air
 classification, magnetic  separation, screening, rising current, heavy media,
 and electrostatic separation  as well as optical methods for separating munic-
 ipal  solid waste into paper,  ferrous and nonferrous metals, glass, and organic
 fractions.^/  Regular markets have  already been developed for glass, paper,
 and metals.—' Typical analytical properties of the refuse fuel are listed in
 Table  13.

 Characteristics of Test Boilers

     Edgemoor  Station Boiler  No. 3  is a tangentially fired boiler with a nominal
 rating of 75  MW. Edgemoor Station Boiler No. 4 is a tangentially fired boiler
of the same design,   except with a capacity of 160 MW. Both boilers are designed
 for firing either fuel oil (No. 2 or No. 6 - residual) or pulverized coal. Both
boilers are equipped for  flue gas recirculation. The only modification required
                                     62

-------

f



)r



1 ' 1

Rolls
1


t

Elec.
Separator

	

                                                           Glass
                                                                 Magnetics
                                                             o
                                                             Other
                                                             Nonferrous
                             —i i—
                           Aluminum
           Flint/*~-\ Mixed Color
             (Glass!
Figure 14.   Schematic representation of materials  recovery process,
                        New  Castle, Delaware.51/
                                         63

-------
       Table  13.   PROJECTED ANALYSIS  OF REFUSE  FUEL-
                NEW CASTLE COUNTY, DELAWARE^/
                             (As fired - percent  by weight)
 Moisture                                  25.0
 Ash                                      15.0
 Sulfur                                    0.15
 Chlorine                                  0.40

 High  heating value
      joules/kg                        1.314 x 10
      (Btu/lb)                          (5,650)

 High  heating value (Dry, ash free)
      joules/kg                        2.093 x 10
      (Btu/lb)                          (9,000)

 Bulk  density
      kg/m3                              64-176
            )                           (4-11)

Ultimate                    (As fired - percent by weight)

Carbon                                   31.90
Hydrogen                                  4.70
Nitrogen                                  0.40
Oxygen                                   22.85
Sulfur                                    0.15
Moisture                                 25.00
Ash                                      15.00
          Total                         100.00
                             64

-------
for firing MSW will be to add one new nozzle in each corner for firing refuse.
Design ratings for Edgemoor Station Boilers Nos. 3 and 4 are summarized in
Table 14.

Installed Air Pollution Control Equipment

     Edgemoor Station Boiler No. 3 is equipped with a multicyclone collector
with conventional reverse flow, designed by Western Precipitator.  The design
efficiency is 83% at 7,044.6 m3/min and 149°C (248,775 acfm and 300°F).  Design
ratings are summarized in Table 15.

     Edgemoor Station Boiler No. 4 is equipped with a two stage ESP collector
designed by Research-Cottrell. The design efficiency (for coal or  oil)  is
95.0% at 12,560 m3/min and 135° C (440,000 acfm and 275°F). Design  ratings  are
summarized in Table 16.

                             20 /
Delaware Emission Regulations——'

Administering Agency:

     Department of Natural Resources and Environmental Control
     Air Resources Section
     Tatnall Building
     Dover, Delaware  19901

Particulates:

     Emissions from any fuel-burning equipment shall not exceed 0.3 lb/10
     Btu heat input.

Sulfur Oxides:

     Sulfur content of distillate oil used in fuel-burning equipment is limited
     to 0.3% by weight. Sulfur content of other fuels used in fuel-burning
     equipment is limited to 1.0% by weight in New Castle County and to 2%
     in Kent and Sussex counties. However, if between July 1, 1973 and October
     1, 1974 the national secondary ambient air-quality standard for the
     Metropolitan Philadelphia Interstate AQCR is exceeded due to an air-
     containment source located in New Castle County, then the enforcement
     agency may, after January  1, 1975, reduce the maximum allowable sulfur
     content of fuel to a level not lower than 0.3% by weight. High-sulfur
     fuel can be used if a state-approved S02-removal system  is employed.
                                      65

-------
              Table  14.   DELMARVA EDGEMOOR STATION BOILER DESIGN RATINGS
                                           Unit  3                     Unit 4

                    a/
 Boiler manufacturer"                       C-E                       G-E
 Type of firing^'      ,                   Tangential                 Tangential
 Turbo generator  size—    ,                   75  MW                     150 MW
 Design fuel  consumption"                 20.4 m /hr                 40.5 m /hr
                          ,          (128.34 Bbls(oil)/hr)      (254.53 Bbls(oil)/hr)
 Steam flow,  kg/hr  (coal)-   ,               260,800                    484,765
 Steam pressure,  newtons/m                1.04 x 10                  1.29 x 10^
                     b/                 (1,500  psig)               (1,850 psig)
 Steam temperature,  °C~                      538                       538
                   b/                     (1000°F)                   (1000°F)
 Furnace volume,  m^~                        1,319                      2,574
                                b/       (46,600 ft  )               (90,885 ft )
 Efficiency,  % (pulverized coal)-            89.33                      89.99
 Flue gas flow rate  (100% MCR>2/         7,045 m3/min               12,805 m3/min
                     /                 (248,775  acfm)             (452,187 acfm)
 Exit gas temperature—                       149° C                      135° C
                           a c/            (300°F)                    (275°F)
 Flue gas cleaning equipmentr~*—              MCAX                        E
aj  Information furnished by Delmarva Power  and  Light  Company,  December 30, 1975.
_b/  Information taken from G-E Power Systems  Study.—/
£/  MCAX = multiple cyclones-conventional reverse  flow with axial inlet;
       E = electrostatic precipitator.
                                         66

-------
  Table 15.  DESIGN DATA FOR CYCLONE COLLECTOR/DELMARVA EDGEMOOR NO. 3~
Manufacturer/Model No.--Western Precipitator/P37754A

Description—Multiple cyclones—conventional reverse flow;  axial inlet

No. of sections
  (a) Series—1
  (b) Parallel—6

Tube arrangement—14 x 20.3 cm (8 in.)

Pressure drop—4.95 mm Hg (2.65 in HO)

Design efficiency—83% at 7,044.6 m3/min and 149°C (248,775 acfm and 300°F)
 a/   Source:  D»  B. McClenathan, Delmarva Power and Light Company (Ref. 51).
                                    67

-------
     Table 16.  CHARACTERISTICS  OF ELECTROSTATIC PRECIPITATOR ON  DELMARVA
                            EDGEMOOR UNIT NO. 4£/
 Plate area—2,274.3 m2  (24,480  ft2)

 Plate-to-plate spacing
   (a) Inlet—22.86 cm (9  in.)
   (b) Outlet—22.86 cm  (9 in.)

 Corona wire  diameter—0.28 cm (0.109 in.)

                                 233    -1
 Specific  collection area—182.6 m /10  m -min
                          (55.7 ft2/!,000 acfm)

 Migration velocity—14.92 cm/sec
                    (29.4 ft/min)

 Operating voltage--45 kv avg.,  70 kv peak
                               ?b/
 Current density—70 nanoamps/cm •"

 Electrical sets—two in parallel and two in series

 Design efficiency—95.0% burning either coal or oil, with 2.7% sulfur coal,
                     at approximately 150 MW, flue gas volume of 12,459.5
                     m3/min (440,000 acfm) at 135°C (275°F)
a/  Data from Ref. 51.
bf  Data from Appendix C,  Figure C-3.
                                   68

-------
 Nitrogen Oxides:

      After Janaury 1, 1975, emissions from fuel-burning equipment  in New Castle
      County rated 500 x 106 Btu/hr fuel input and greater will be  limited to
      0.2 (gas fuels) or 0.3 (other fuel) pound NOX (calculated as  N02)/106
      Btu heat input.

      However, NOX laws do not apply to fuel-burning equipment  when the heat
      produced in the equipment is used for some purpose other  than steam
      production.

 Estimated Performance of Air Pollution Control Equipment

 Edgemoor Station No. 3--
      The C-E Power Systems estimate for 10% MSW heat input is  based on a col-
 lection efficiency of 70% with an inlet dust loading of 0.275  g/106 joules
 (0.64 lb/106 Btu).^P_/ This yields a net discharge rate of 0.0825 g/106 joules,
 which is nearly twice the New Source Performance Standard for  Fossil Fuel-Fired
 Steam Generators, but within the Delaware emission regulation  for  fuel burning
 equipment. MRI estimates a net discharge rate of 0.0939 g/106  joules, which
 is only slightly higher than C-E, based on an efficiency of 70% and an inlet
 dust loading shown in Figure 11. At 5% MSW, MRI estimates a net discharge rate
 of 0.0564 g/106 joules, about 30% above the New Source Standard.

      As discussed previously, there is not presently an adequate method for
 modeling the performance of the multicyclone collector. However, the design
 efficiency of 83% corrected for particle size (Table 6) yields an  efficiency
 of 67.5% based on the fractional efficiency curve in Figure 7. This is within
 10% of the C-E estimate.20/

 Edgemoor Station  No.  4--
      Estimated ESP performance for the unit on Edgemoor No. 4  is shown in Figure
 15  as a function  of flue gas  volume.  The estimate is  based on the particle size
 for refuse (Table 6)  and the  fuel properties listed in Table 13. The ESP per-
 formance model is described in Appendix C.

      On the basis of  calculations made,  the estimated range of emissions at
 5%  MSW is 0.034 to 0.077 g/106  joules,  which is within the Delaware Emission
 Regulation for Fuel Burning Equipment.  The  predicted  emissions for Edgemoor
 Station Boiler No.  4  are shown in Figure 16 as a function  of percent MSW heat
 input  and refuse  fly  ash fraction fr  at  the MCR of  150 MW.

 Cost of Air Pollution Control

     On the basis  of  calculations made  in this report,  it  is unlikely that
particulate emissions  when  Delmarva Edgemoor Station  No. 4 is burning No. 6

                                      69

-------
                    Flue  Gas  Volume, 103 M3/min

                           10                   15
                                             0% MSW

                                           20% MSW-
        !200
300         400         500
 Flue Gas Volume, 1Q3 ACFM
600
700
Figure 15.  ESP efficiency (predicted)  for combined  firing of oil and
         MSW at Delmarva Edgemoor Station No.  4  (150 MW).
                             70

-------
    0. r-
_0>

~o

 "c
 O
u
 3
 O_


O
O
 c
 O
 3
 U
 O
a.
Delaware  Emission  Regulation

for  Fuel Burning Equipment
                                New Source Performance Standard for

                                Fossil Fuel-Fired Steam Generators
                              10                      20
                                  % MSW Heat Input



       Figure  16.   Estimated particulate emissions (controlled) for combined

             firing of oil and MSW  at Delmarva  Edgemoor Station No. 4.
                                       71

-------
 residual oil and  5% MSW will exceed applicable Delaware standards. Therefore,
 no control modifications are indicated, provided MSW specifications are met.

     Estimated emissions from Edgemoor No. 3 will probably exceed the Delaware
 standard of  0.129 g/106 joules (0.3 lb/106 Btu) at 57, MSW unless control modi-
 fications are made. The cost of such control modifications has not been de-
 termined.

 NEW YORK CITY

      On March 6,  1975, the City's Board of Estimate awarded a $340,000 fea-
 sibility and preliminary design contract for the firing of 1,000 tons/day of
 solid RDF with oil in the Consolidated Edison No. 20 boiler at Arthur Kill
 in Staten Island  to Horner and Shifrin of St. Louis and Laramore, Douglass,
 and Popham Engineering Consultants of New York City. They will also devise
 an equitable formula for apportioning capital costs and determining the dollar
 value of refuse to Con Ed, which is also a party to the contract.ll/

      Originally the City assumed the cost of the contract. But a $50,000
 federal grant was awarded for the project, signifying recognition of refuse
 derived energy in the Project Independence strategy. Con Ed purchases most of
 its oil from foreign sources. Firing of RDF in this pilot project will cut
 this dependence by approximately 1,400 barrels of oil per day.ll/

      A notable characteristic of this program is its size; Arthur Kill No.
 20 has a net  generating capacity of 325 MW and planned MSW heat input is 20%.—'
 The Arthur Kill project will be the first of approximately 10 to 20 resource
 recovery projects  in New York City.ll/ A master plan, due in December 1975,
 will recommend a  construction timetable for specific processes at specific
 sites.ll/  Arthur Kill No. 30 (500 MW, tangentially fired) is also included
 in the master plan and will also fire MSW with No. 6 residual oil*2.'

 Project  Status

      The Arthur Kill No. 20 project feasibility study was originally due to
 be  completed  by Laramore, Douglass, and Popham Engineering Consultants (New
 York  City) by September 1, 1975. New York City granted an extension for com-
 pletion by December 1.  The major difficulties apparently result from the in-
 adequacies of existing air pollution control systems. The electrostatic pre-
 cipitator  installed on Arthur Kill No. 20 is not presently operational, and the
electrostatic precipitator on Arthur Kill No. 30 has never met design specifica-
tions when firing No.  6 residual oil.ll/
                                     72

-------
Refuse Fuel Preparation Facilities

     Detailed plans  for the refuse  shredding  system  are not available at this
time. A new installation will be built  at  an  estimated cost of $12 mi 11 ion.I5./

Boiler System Descriptions

     Arthur Kill  No.  20 is  a front-wall fired boiler designed by Foster Wheeler
for  a net  generating capacity of 325 MW. This unit was originally designed
for  coal and was  retrofitted to  fire oil.li/  Modifications to fire MSW include
additional burners for firing refuse and installation of a flue gas recircula-
tion system.—'

     Arthur Kill  No.  30 is  a tangentially  fired boiler designed by Combustion
Engineering for a nominal capacity  of 500+ MW.—/ This unit will also be con-
verted for flue gas  recirculation.

Installed  Air Pollution Control  Equipment

     Both  Arthur  Kills Nos.  20 and  30 are  presently  equipped with Research-
Cottrell ESP systems.  However, the  ESP  on  Arthur Kill No. 20 is not operational
and  the ESP on  Arthur Kill  No. 30 has not  met design specifications when firing
No,  6 oil.—' There  is no test data available for either unit when firing No.
6 oil.

New  York City Particulate Air Emission  Regulations

     Total air  emissions are rigidly controlled by a total allocation which
regulates  air emissions from a given piece of fuel burning equipment to present
levels.—' A proposed emission standard for particulate is 0.043 g/10  joules
(0.1 lb/106 Btu)  for  fuel oil or refuse and fuel oil.—'

Estimated  Performance of Installed  Air  Pollution Controls

     Since the  ESP unit  on Arthur Kill  No. 20 is not presently in operating
condition, the  control efficiency is zero. New York City officials are  appar-
ently aware of  deficiencies  in existing control systems for both Arthur Kills
Nos. 20 and 30. Because  of the present  early  status of the Arthur Kill  No.  30
project,  estimation of control efficiency  for combined firing is not considered
justified until city officials decide on which control system will actually be
used when  oil and MSW  are fired  concurrently  in either boiler.

Cost of Emission Control

     Laramore,  Douglass,  and  Popham Engineering Consultants, estimate the in-
stalled (erected)  cost of a new  ESP control system with 99% efficiency for
                                     73

-------
 Arthur Kill No.  20 to be $12 million.!/ There is apparently some difficulty
 in getting the control manufacturer to guarantee efficiency for this applica-
 tion,  however.—/ There is no cost estimate available for Arthur Kill No. 30.

 STATE  OF CONNECTICUT (Bridgeport)

     The Connecticut Resource Recovery Authority (CRRA) is currently planning
 three  resource recovery systems within the state. CRRA was formed following
 a study sponsored by the State of Connecticut Department of Environmental
 Protection. Funding is obtained both from the State and outside agencies.

     Three programs presently planned include Bridgeport (United Illuminating
 Company, Bridgeport Harbor Stations Nos. 1 and 2), Central Connecticut (Devon
 Station), and South Central ConnecticutjLP-/ The South Central Connecticut pro-
 gram will involve construction of boilers designed specifically for combined
 firing of refuse and oil.—'

     The Bridgeport project will be the first CRRA project undertaken. Orig-
 inal plans called for a pilot scale test, with oil and MSW fired in Bridgeport
 Harbor No. 1 (82 MW), for a period of about 2 months, followed by modification
 of Bridgeport Harbor No. 2 (160 MW) to fire refuse. The objective of the pilot
 scale  test is to determine required modifications to the larger unit.

     Notable aspects of these planned tests are that Bridgeport Harbor Nos.
 1 and  2 are both pressurized, cyclone-fired boilers. If this type of system
 can be successfully used to burn refuse, flue gas dust loading can be reduced
 by about 50% of that for front-wall and tangentially-fired suspension boilers.

 Project Status

     Engineering feasibility studies have been completed by Gibbs and Hill
 and C-E Power Systems.^!/ A contract was signed with Garrett Research Corpora-
 tion (now Occidental Research) to supply the refuse fuel. Site preparation
 began  in the fall of 1975. Construction was planned to begin in the spring of
 1976.—' Design changes are still being made.12./ Because of a recently formed
 joint venture between Occidental Petroleum and Combustion Equipment Associates,—'
 there  is  some consideration being given to use of the CEA Ecco II process.^2/

     The pilot scale oil-MSW combined firing test was originally planned to
begin in January 1976,i°>/  but this test was recently delayed because of dif-
ficulties in  locating  a source of refuse fuel and difficulties in funding.^2/
CRRA has recently applied for a $900,000 ERDA grant.59/
                                      74

-------
Boiler System Descriptions

     Bridgeport Harbor No.  1 is a pressurized, cyclone-fired boiler designed
by Babcock and Wilcox for a net output of 82 MW. The unit has two cyclone
burners.

     Bridgeport Harbor No.  2 is a pressurized, cyclone-fired boiler designed
by Babcock and Wilcox for a net output of 170 MW, of similar design to  Bridge-
port No. 1, except with five cyclone burners.

Refuse Preparation Facilities

     The design of the refuse preparation facility has not yet been finalized.

Installed Air Pollution Control Equipment

     Both Bridgeport Harbors Nos. 1 and 2 are equipped with electrostatic pre-
cipitators designed by Research-Cottrell.

Connecticut Air Emission Regulations

Administering Agency:

     Department of Environmental Protection
     State Office Building
     Hartford, Connecticut  06115

     Existing and new fuel  burning equipment must comply with the following
     regulations

Particulates:

     Emissions are restricted to 0.1 lb/106 Btu heat input. The heat-input
     value is the equipment manufacturer or designer's guaranteed maximum  in-
     put, whichever is greater.

Sulfur Oxides:

     Fuels are restricted to a maximum sulfur content of 0.5% by weight (dry
     basis). Under fuel-shortage conditions, variances can be obtained for
     burning higher sulfur  fuels on a temporary basis. High sulfur fuels also
     can be burned if state-approved stack-gas cleaning equipment is capable
     of limiting total sulfur-compound emissions to the ambient air to 0.55
     Ib S02 (equivalent)/106 Btu gross heat input, and if waste discharges
     from the stack gas cleaning system into State waters are approved by
     State authorities.
                                     75

-------
 Nitrogen  oxides:

      Emissions  from fuel burning equipment rated above 250 x 10  Btu/hr heat
      input  are  limited to 0.2 (gas), 0.3 (oil), or 0.7 (coal) pound NOX
      (expressed as N02)/106 Btu heat input.

 Estimated Performance of Air Pollution Control Equipment

      The  Connecticut Resource Recovery Authority is not optimistic about the
 performance of  ESP units on either boiler. As with most units designed for
 coal, the efficiency is expected to drop to 60 to 70% for oil, 70 to 85% for
 oil plus  refuse, depending on refuse composition and MSW heat input.

 Cost  of Emission Control

      Because the test program is not yet final, and refuse fuel characteristics
 and heat  input are not known, it is not possible to make significant estimates
 of emissions at this time.  However, we do know that CRRA and United Illuminating
 Company are not presently planning replacement or modification of either ESP
 unit. At 70% efficiency,  particulate emissions could well be as high as 0.052
g/106 joules (0.121 lb/106  Btu), at 10% MSW heat input, even allowing for a
50% reduction in fly ash because of cyclone burner characteristics. This would
exceed state regulations  of 0.043 g/106 joules (0.1 lb/106 Btu) applicable to
new and existing fuel burning equipment.
                                    76

-------
                                  SECTION 6

                               RECOMMENDATIONS
      Since the present study has emphasized the application of  existing air
 pollution control methodology for particulate air pollutants from power boilers
 firing municipal solid wastes and auxiliary fuel oil,  it  seems  appropriate to
 point out some deficiencies in the control technology,  as applied to this as-
 pect of resource recovery. An attempt should be made to resolve these diffi-
 culties in future studies. Difficulties encountered in  the present study are
 discussed according to the general types of control systems considered.

 ELECTROSTATIC PRECIPITATOR CONTROL

      In adopting existing theoretical studies to the development of a practi-
 cal performance model to  predict ESP performance for combined firing applica-
 tions,  there was found to be no quantitative information  on the effects of:

      1.   Fly ash density;

      2.   Re-entrainment;  and

      3.   Sneakage or bypassing.

 This  is  somewhat surprising,  in consideration of the influence of these ef-
 fects both on equipment cost  and collection efficiency. For  example, one source
 recommended a reduction in flow velocity directly proportional to a decrease
 in  fly ash density.12/  Referring to  Figure  8,  this would  increase installed
 cost  of  a  new ESP unit  in approximately the same proportion as the decrease
 in  flow  velocity.  There are sufficient  data on the resistivity of oil ash and
 refuse fly ash,  both of which are relatively high in carbon compared to coal
 fly ash, to  conclude that a significant  proportion of the ash will be low in
 resistivity  compared to the average.  In  other words, there  is probably a much
 larger resistivity range  for  oil and/or  refuse firing than  for a given coal.
The low  resistivity  fraction  is  comprised primarily  of carbon. Such low resis-
tivity particulate tends  to lose its  charge easily on contact with the collec-
tion electrode,  and  be  re-entrained.  In  the case  of  oil ash, a modification

                                    77

-------
 of the shape of the collecting electrodes  is  recommended  to prevent  re-
 entrainment. However, there is no method available to  quantatively relate
 the fraction re-entrained with ash properties (resistivity, shape, and
 density) and system parameters (velocity and  electrode geometry). There has
 been some work done on bypassing, or sneakage,  but this effect has not yet
 been quantitatively defined in terms of  system variables.

      What is needed is an order-of-magnitude  analysis  of  the effects of fly
 ash density, re-entrainment,  and bypassing based on both  approximate analysis
 and a survey of available data including contacts  with equipment manufactur-
 ing firms. None of the above  effects were  included in  the model used to esti-
 mate ESP performance in the present study. This is not too important in terms
 of the present objectives, since these effects  result  in  a control performance
 which is lower than predicted. However,  in consideration  of the preceding dis-
 cussion, it is perhaps not too surprising  that  one source^./ who attempted to
 acquire cost and performance  information for  a  new ESP unit for combined oil-
 MSW firing was unable to obtain a performance guarantee.

 CYCLONE CONTROL

      Because of the relatively low cost  of cyclone control, this type of sys-
 tem would seem to be useful,  in conjunction with ESP control, to collect low
 density, weakly charged particulate if placed after the ESP. The function of
 the cyclone used in this fashion would be  to  collect the  coarse fraction of
 ESP re-entrainment losses.  There is at least  one such  intallation on an oil-
 fired boiler.l/

      The theoretical prediction of cyclone pressure drop  and collection effi-
 ciency still is not possible  because of  complexities of flow fields. Other
 factors,  such as the tendency of cyclone collectors to plug when in  service
 on oil  ash,  and the performance decline  in the  corrosive  atmosphere of in-
 cineration  flue gases,  need to be examined.

     As  in the  case of  ESP  control,  there needs to be  additional work done
 on this  type of control system specific  to the  application of combined fossil
 fuel-MSW combustion.  This  would include  contacts with  vendors, literature
 review,  and  analysis  beyond the scope of the  present study to develop guide-
 lines for use  in combined  firing applications.

SCRUBBER  CONTROL

     High performance scrubbers  and possibly  wet electrostatic precipitators
have utility for collection of particulates,  gaseous pollutants (SO  , NOX,
and others) and potentially hazardous trace metals. There were no scrubber
or wet ESP units installed on the  boilers  evaluated in the present study.

                                      78

-------
However, there is at  least  one high performance Chemico Arotec scrubber planned
for installation at Nashville.36/ The manufacturer was contacted regarding the
feasibility of using  scrubbers for  emission control on boilers where MSW and
fossil fuels are being  fired. At the time the contact was made, Chemico was
very cautious about this  application, saying that some reports based on pilot
plant data may have been  premature. There is a general reluctance on the part
of the gas cleaning industry to recommend scrubbers for service on incinerator
flue gases. The problem,  as in cyclone  control, is with corrosivity. One other
equipment vendor was  contacted regarding the possible application of wet elec-
trostatic precipitators for combined MSW-fossil fuel firing. The manufacturer
was optimistic regarding  this application, but cost and design data have not
been received.

     Both wet scrubbers and a wet ESP unit have recently been evaluated on
a pilot plant scale as  part of the  evaluation of EPA's "Landgard" Demonstra-
tion Project in Baltimore,  Maryland. The Landgard system is a pyrolysis reac-
tor which fires approximately 7.1 gal.  of No. 2 fuel oil per ton of MSW.
Maryland particulate  emission regulations for this facility are 0.013 g/Nnr
(0.03 gr/dscf). Particulate emissions measured in shakedown runs in the spring
of 1975 reportedly were in  the vicinity of 0.069 g/Nm3 (0.2 gr/dscf)J>°_/  In
the summer of 1975, two Teller Crossflow Nucleating scrubbers were evaluated
adiabatically and in  condensing modes.  These systems could not achieve state
standards but could achieve the federal standards of 0.18 g/Nm3 (0.08 gr/
dscf).£2/ A Micropuls wet ESP test  could meet the state code; however, tests
were not conclusive.££/ An  expanded control evaluation program is now planned
which will include several  other control systems.6£/

     Because of the increasing public awareness of problems resulting from
gaseous and trace metal pollutants, an  in-depth study of these control methods
appears justified.
                                      79

-------
                               REFERENCES
  1.  Darby, K.,  and C.  Whitehead.  The Performance of Electrostatic Pre-
      cipitators  in Relation  to Low Sulfur Fuels.  In:  Proceedings of the
      Second International  Clean Air Congress, Washington, D.C., 1970.  pp.
      911-922.

  2.  Smith, W. S.   Atmospheric Emissions from Fuel Oil Combustion,  U.S.
      Public Health Service Publication No. 999-AP-2, November 1962.

  3.  Burdock, J. L.   Centrifugal Collectors Control Particulate Emissions
      from Oil-Fired  Boilers.  Tappi, 56(6):78-82, June 1973.

  4.  Sahagian, J., R. Dennis, and N. Supernant.  Particulate Emission Control
      Systems for Oil-Fired Boilers.  EPA-450/3-74-063, December 1974.

  5.  Steam, Its Generation and Use.  Babcock and Wilcox Company, New York,
      1963.

  6.  Tamlyn,  W., Laramore, Douglass, and Popham, Inc.  Private Communication,
      December 12,  1975.

  7.   Maartmann, S.   Collection of Dust from Oil-Fired Boilers in Multi-
      cyclones and Electrostatic Precipitators,  In:  International Clean
     Air Congress, London, October 4-7, 1966.

 8.  Pershing, D. W., et al.  Effectiveness of Selected Fuel Additives in
     Controlling Pollution Emissions from Residual Oil-Fired Boilers. EPA-
     650/2-73-031, October 1973.

 9.  Bunz, P., H. P. Niepenberg,  and L. K. Rendle.  Influences of Fuel Oil
     Characteristics and Combustion Conditions on Flue-Gas Properties in
     Water-Tube Boilers.  J. Inst.  Fuel, p. 406, September 1967.

10.  Rigo, H. G.   Systems Technology Corporation, Private Communication,
     October 16,  1975.


                                     80

-------
11.  Shannon, L.  J.,  et al.   St.  Louis/Union Electric Refuse  Firing
     Demonstration  Air Pollution  Test Report. EPA 650/2-75-037, April
     1975.

12.  Fiscus, D. E., P. G.  Gorman, and J.  D.  Kilgroe.   Bottom  Ash Generation
     in a Coal-Fired  Power Plant  when Refuse-Derived  Supplementary Fuel is
     Used.  Presented at the ASME Solid Waste Processing  Conference, Boston,
     Massachusetts, May 23-26,  1976.

13.  Gorman, P. G.  Midwest  Research Institute,  Private Communication,
     May 5, 1976.

14.  Gershman, H.   National  Center for Resource  Recovery, Private Communica-
     tion, January  14, 1976.

15.  Kilgroe, J.  D.,  L.  J. Shannon, and M. P. Schrag.   Emissions from the
     Suspension Firing of  Municipal Solid Waste  and Pulverized Coal.  Paper
     Presented at the 68th Annual APCA Meeting,  Boston, Massachusetts, June
     15-20, 1975.

16.  Hall, E. H., et  al.  Refuse  Combustion  in Fossil  Fuel Fired Steam
     Generators.  Final Report, Contract  No.  68-02-0611, Task 9 to Office
     of Air Quality Planning and  Standards, U.S. Environmental Protection
     Agency, Battelle-Columbus Laboratory, September  23,  1974.

17.  Hall, E« H.  Battelle-Columbus  Laboratory, Private  Communication,
     August 29, 1975.

18.  Blackwood, T.  R., and W. H.  Hedley.  Efficiencies in Power Generation.
     EPA-650/2-74-021, March 1974.

19.  Mullin, J. F.  Combustion Engineering, Inc.,  Private Communication,
     August 30, 1975.

20.  Mullin, J. F.  Combustion Engineering, Inc.  Solid Waste Study Report
     for Delmarva Power  and  Light Company's Edgemoor Power Plant.  OES No.
     11828, May 31, 1974.

21.  Schweiger,R. W.   Power  from  Waste.   Power,  pp. 5-21, February 1975.

22.  Stabenow, G.   Ovitron Corporation, Private  Communication, October 7,
     1975.
                                     81

-------
 23.  Vandegrift, A. E., et al.   Particulate Pollutant  System Study Volume
      III - Handbook of Emission Properties.  EPA Contract  No.  CPA 22-69-104,
      May 1971.

 24.  Funkhouser, J. T., et al.   Manual Methods for Sampling  and Analysis  of
      Particulate Emissions from Municipal Incinerators.  EPA-650/2-73-023,
      September 1973.

 25.  Oglesby, S., and G. Nichols.   A Manual of Electrostatic Precipitator
      Technology, Part II - Application Areas.   National Air  Pollution  Con-
      trol Administration, Contract  No. CPA 22-69-73, August  25, 1970.

 26.  Perry, R. E.  A Mechanical Collector Performance  Test Report on an Oil-
      Fired Power Boiler.  Combustion, pp.  24-28, May 1972.

 27.  Roberts, R. M., et al.  Systems Evaluation of Refuse  as a Low Sulfur
      Fuel,  Volume II - Appendices,  Report to Environmental Protection  Agency,
      Contract No. CPA-22-69-22,  Envirogenics Company,  November 1971.

 28.  McGarry, F. J., and C. J.  Gregory.    A Comparison of  the  Size Distri-
      bution of Particulates Emitted from  Air,  Mechanical,  and  Steam Atomized
      Oil-Fired Boilers.   J. Air Poll. Contr. Assoc., 22(8):636, August 1972.

 29.  Day and Zimmerman.   Special Studies  for Incinerators. Report Prepared
      for the Government  of the  District of Columbia, Department of Sanitary
      Engineering,  U.S.  Department of Health,  Education, and  Welfare,
      Cincinnati,  1968.

 30.  Shannon,  L.  J.,  et  al.  Fine Particulate  Emission Inventory  and Control
      Survey.   EPA Contract No.  68-02-1324, Task No. 1, Midwest Research In-
      stitute,  January 1974.

 31.   Schulz,  E.  J.,  et al.  Harrisburg Municipal Incinerator Evaluation.
      Final Report  to  Harrisburg  Incinerator Authority, Battelle-Columbus
      Laboratory, December  17, 1973.

32.  McCain, J. D.,  and G.  B. Nichols.  Letter Report  to R.  C. Lorentz,
     Environmental Protection Agency,  Control  Systems  Laboratory,  Southern
     Research Institute, February 8,  1974.

33.  Rigo, H. G.  Predicting Emissions from the Use of Refuse  Derived  Fuel.
     Paper Presented at the Midwest  Section Meeting, Air Pollution Control
     Association, September 1975.
                                     82

-------
 34.  McCain,  J.  D., A. B. Spencer, and W. B. Smith.  Precipitator  Operation
     as  Part  of  Midwest Refuse Firing Demonstration Project.   Coal Fire Test.
     Preliminary Report to Midwest Research Institute,  Southern Research In-
     stitute, December 20, 1974.

 35.  Bagwell, F. A., and R. G. Velte.  New Developments in Dust Collecting
     Equipment for Electric Utilities,  j. Air Poll. Contr. Assoc., 21(12):
     781,  December 1971.

 36.  Enforcement Proceedings.  United States Environmental Protection Agency
     Region IV in the Matter of Nashville Thermal Transfer Corporation,
     April 7, 1975.

 37.  Rao,  A.  K., M. P. Schrag, and L. J. Shannon.  Particulate Removal from
     Gas Streams at High Temperature and/or High Pressure.  EPA Contract No.
     68-02-1324, Task 30, Draft of Task Report, Midwest Research Institute,
     May 23,  1975.

 38.  Koehler, G. R., and E. J. Dober.  New England S02  Control Project Final
     Results. In:  Proceedings of the Symposium on Flue Gas Desulfurization,
     Atlanta, November 1974, EPA-650/2-74-126-b, December  1974.

 39.  Statnick, R. M., and D. C. Drehmel.  Fine Particle Control Using Sulfur
     Oxide Scrubbers.  Presented at the 67th Annual Meeting, Air Pollution
     Control  Association, Denver, Colorado, June 9-13,  1974.

 40.  McCain,  J.  D.  Evaluation of Aronetics Two-Phase Jet  Scrubber. EPA-650/2-
     74-129,  December 1974.

41.  Whitwell, J.  A.  Chemico, Private Communication, October  10,  1975.

42.  Power, p. 41, November 1975.

43.  Economic Indicators.  Chemical Engineering, 83(9):7,  1976.

44.  Allard,  N.   Potomac Electric Power Company, Private Communication,
     December 9,  1975.

45.  Department  of Environmental Services,  District  of  Columbia, Utilization
     of a Refuse-Derived Fuel  as a Supplementary Fuel in an Oil- and Coal-
     Fired Electric  Utility Boiler.   Proposal  to U.S. Environmental Protection
     Agency for  a  Research,  Development,  and Demonstration Grant, April 1, 1975.
                                    83

-------
 46.  Weiss, M,   Potomac Electric Power Company, Private Communication,  December
      8, 1975.

 47.  Alter, H.  A.   National Center  for Resource Recovery, Private  Communica-
      tion, August  4,  1975.

 48.  Gershnian,  H.   National Center  for Resource Recovery, Private  Communica-
      tion, September  12,  1975.

 49.  Hopper, R. E.  A Nationwide Survey of Resource Recovery Activities.
      U.S.  Environmental Protection  Agency, Office of  Solid Waste Manage-
      ment  Programs, Publication  SW-142, January 1975.

 50.  Cook, F. Delmarva Power and Light Company, Private Communication,
      August 22, 1975.

 51.  McClenathan,  D.  B.   Delmarva Power and Light Company, Private Communica-
      tion, December 8,  1975.

 52.  Bisselle,  C.,  et  al.   Urban Trash Hethanatipn Background  for  a Proof-
      of-Concept Experiment.  Mitre  Corporation, NSF/RANN Contract  NSF-C 938,
      February 1975.

 53.  Low,  R. A.  Energy  Conversion  in  New York.  In:  Proceedings  First Inter-
      national Conference  on Conversion of Refuse to Energy, Montreux,
      Switzerland, November  3-5,  1975.

 54.  O'Reilly,  L. J.   City  of New York, Environmental Protection Agency,
      Private Communication, August  4,  1975.

 55.   O'Reilly,  L.  J.   City  of New York, Environmental Protection Agency,
      Private Communication, December 18, 1975.

 56.   Busch, R.   Connecticut Resource Recovery Authority, Private Communica-
      tion, August 7, 1975.

57.  Finney, C.   Garrett Research Corporation, Private  Communication, August
      22, 1975.

58.   Chemical Engineering, December 8,  1975.

59.  Busch, R,    Connecticut Resource Recovery Authority, Private Communication,
     November 21, 1975.
                                     84

-------
60.  Sussman, D.  EPA Office of Solid Waste Management Programs, Private
     Communication, May 6,  1976.

61.  Govan, F. A.  Relationship of Particulate Emissions Versus Partial to
     Full Load Operations for Utility-Sized Boilers.  Presented at Third
     Annual Industrial Air  Pollution Control Conference, Knoxville, Tennessee,
     March 29-30, 1973.

62.  Zurn Industries, Inc.  A Mechanical Collector Performance Test Report
     on an Oil-Fired Power  Boiler, November 1971.

63.  Peterson, I. J.  Experience with the Operation of Electrostatic Precipi-
     tators on Oil-Fired Boilers.  Presented at 13th Annual New England Sec-
     tion APCA Meeting, 1969.

64.  Test Reports Provided  by Source Sampling Section, Division of Air
     Resources, New York State Department of Environmental Conservation.

65.  Test Reports Provided  by Air Compliance Section, United States Environ-
     mental Protection Agency, Region I.

66.  Allen, R. N.  Chicago  Northwest Incinerator Test Number 71-CI-ll.
     Resources Research, Inc., EPA Contract No. CPA 70-81, September 1971.

67.  Gooch, J. P., J. R. McDonald, and  S. Oglesby.  A Mathematical Model of
     Electrostatic Precipitation.  EPA  650/2-75-073, April 1975.
                                      85

-------
                         APPENDIX A
PARTIGULATE EMISSIONS FROM OIL-FIRED ELECTRIC UTILITY BOILERS
                               87

-------
                                                 PARTIGULATE EMISSIONS FROM OIL-FIRED  BOILERS
                  Boiler
              Identification
                                                                                         Participate  loading
      Undisclosed
                                      Description

                                   C-E tangentially
                                   fired, 250 MW
oo
00
      Franklin Station,
      Rochester,  Minn.
Boston Ed.,
Mystic No. 6
      Boston Ed.,
      Mystic No. 6
      Hartford Elect.,
      Middletown No. 3
                                   C-E Type VP-14-W
G-E tangentially
fired, 156 MW
                                    G-E  tangentially
                                    fired,  156  MW
                                    B and W 5 cyclone
                                    universal pressure
                                    unit, 240 MW
      Boston Ed.,
      Mystic No. 3—
                  e/
°L Load
!(>(#
8*r,
\%l
&
Jjjy
100^
94
92
97
95
80
80
80
51
51
&"F~
J2'
™
Of
-
D/
_/£'
—
% Excess
air
15.8
15.5
20.8
27.3
38.2
15.4
18.5
24.0
.
-
-
-
i
-
_
-
-
-
-
-
_
(e/10"
Inlet
-
..
0.1033
0.1256
0.2327 -
0.1015
0.0727
0.1269
0.0538
0.4010s'
0.7622s,
0.8676-,
0.6752s,
0.4113s'
0.0820s'
0.0361^
0.0293s'
0.0784
0.15
0.0490
0.0965
-
-
_
ioulesj
Cntlet
0.0085
0.0076
0.0061
0.0052
0.0210
0.0133
0.0172
0.0331
0.0310
0.0361
0.0478
0.0293
0.0501-'
0.0752s'
0.0633s'
0.0482s/
0.0418s
0.0104^'
0.0127s'
0.0086s
0.0486
0.0645
0.0142
0.0637
0.1050
0.0663
0.0663
                                                                        Control
                                                                        method^/    Reference
                                                                          ESP
61
                                                                           M
62
                                                                                                                                  37
                                                                                                                                  38
                                                                                                                    ESP
                                                                                                                    ESP
                                                                                         63
                                                                                                                         (Table 2)

-------
oo
VO
            Boiler
        Identification

Consolidated
Edison, Ravenswood No. 30~
      Consolidated
                     » .
                                            Description
Astoria, No. 5Cr

         No.


         No.
      L. I. Lighting  Company
      Northport, Suffolk  County
      Unit No. 3
      L.  I.  Lighting  Company
      Port  Jefferson,  Suffolk County
      Unit  No.  3

      L.  I.  Lighting  Company
      Barrett Station No.  2
      Island Park,  Nassau County
375 MW
                                          C-E
    type
       '
C-E tangentially
fired boiler
                      % Load
Excess
 air
                                                                                         Particulate loading
                                                                                           (g/106 loules)
98.1
98.1
98.1
98.1
96.8
96.8
•t
-
-
_
-
-
_
11
11
11
11
8.7
8.5
31.1
33.6
30.4
42.7
41.5
41.6
39.7
                                                                                   folet
                                                                                       0.0087
                                             0.0070
                                             0.0095

                                             0.010
                                                                                       0.011
Outlet
                                                           0.0073
                        0.0034
                        0.0052

                        0.0052
                                                          0.0052
                        0.0044,,
                        0.0049-*'
                        0.0150-*'
                        0.0085s
                        0.0057
                        0.0042
                        0.0116
                        0.0120
                        0.0125

                        0.0198
                        0.0261
                        0.0207
                        0.0197
Control .
method"
                                        ESP
                                                                                                                    ESP
                                                                                                                    ESP
                                        ESP
                                                                                                              ESP
                                                                                                              ESP
Reference

      4
(Table  2)

      4
(Table  2)

      4
(Table  2)

     4
(Table 2)

    64
                             64
                                                                                                                            64

-------
    Boiler
Ident i ficat i on
                              Description
                                                                                   Particulate  loading
                                                                    % Excess         (g/10   joules)
                                                                       air         Inlet        Outlet
                                                 Control.
                                                             Reference
Niagara Mohawk Power  Corporation    C-E tangentially
Albany Steam Station, Glenmont,     fired boiler
New York
                                                                                                                   64
  No.  1-
  (1974 test series)

  No.  2^7
  (1974 test series)

  No.  3*'
  (1974 test series)
       h/
  No.  4—
  (1974 test series)

  No.  1—
  (1973 test series)

  No.  2-
  (1973 test series)

  No.  3-
  (1973 test series)

  No.  4—
  (1973 test series)

Boston Edison Company
New Boston Station, Unit No.  1

Boston toison Company
Ednar Station, No.  10
87
96
95
                                                               31.9
                                                              104
                                                              128
                                                                                     0.0619
                                                                                     0.0821-
                                                                                     0.0576  .
                                                                                     0.0791-
                                                                                      0.0662  .
                                                                                      0.0765-
                                                                                      0.0464  .
                                                                                      0.0692^
                                                                                      0.0367
                                                                                      0.0367
                                                                                      0.0411
                                                                                      0.0355
                                                                                               0.0318
                                                                                               0.046CP
                                                                                                            Unknown^7
                                                  Unknown^'
                                                                  65
65

-------
                                                                                   Particulate loading
            Boiler
        Identification

Boston Edison, Edgar  Station,
Unit No. 9

Boston Edison Company
L-Street, Unit No. 76

Boston Edison Company
Kneeland Street, Unit No.  2

Boston Edison Company
Mystic Station, Unit  No.  5

           .b.e/
Undisclosed
Description
% Load
95
95
96
96
98
87
85
% Excess
air
112
122
304
181
206
75
77
(e/10° ioules)
Inlet Outlet
0.0219
0.0275^
0.0189^
0.0241 .
0.0813d'
0.0529 ,
0.0641-'
Control ,
, ^a/
method~
Unknown"
Unknown"
Unknown1"1
Unknown1^
Reference
65
65
65
65
                                                        0.0585
                                                        0.0641
                                                        0.0370
                                                        0.0568
                                                        0.0404
                                                        0.0809
                                                        0.0559
                                                        0.0568
                                                        0.0336
                                                        0.0426
                                                        0.0757
                                                        0.0805
                                                        0.0676
                                                        0.0688
                                                        0.0318
                                                        0.0611
                                                        0.0645
                                                        0.0417
                                                        0.0602
                                                        0.0413
                                                        0.0426
ESP
                                                                                                                        (Table 2)

-------
                  Boiler
              Identification
Description
      Undisclosed"
               Particulate loading
% Excess         (g/106  joules)          Control ,
   air         Inlet        Outlet        method""
                                                       0.0090          ESP
                                                                                  Reference
                                                                                                                              (Table 2)
      Undisclosed
      Hartford Elect., Middletown
      No. 2£/
      Undisclosed—*~"
vo
                                           0.0965
                                           0.0954
                                           0.1507
                          0.0275
                          0.0288

                          0.0301
                          0.0245
                          0.0288

                          0.0357
                          0.0267
                          0.0211
                                                                                                                    ESP
ESP+C
                                                                                  (Table  2)

                                                                                       4
                                                                                                                              (Table 2)
      Undisclosed
      Undisclosed""
                                                                                       0.0352
                                           0.0489
                                           0.0393
                                           0.0623
                                           0.0522
                          0.0065
                          0.0095
                          0. 0043
                          0.0047
                          0.0151
                          0.0086
                          0.0056
                          0.0043

                          0.0396
                          0. 0366
                          0.0181
                          0.0146
                          0.0207
                          0.0198
                          0.0224
                          0.0344
                                                                                  (Table 2)
                                                                                                                               (Table 2)

-------
                                                                                         Particulate loading
                  Boiler
              Identification
vo
u>
      Undisclosed
      Boston Edison
      L.  Street,  No. 68

                 No. 74
No. 75
                 No. 76
      Boston Edison
      N. Boston, No. 1

                 No. 2
       Boston  Edison
       Kneeland- Street,  No.  1

                        No.  2
                        No.  4
                                            Description
                                              % Load
% Excess (e/10° loules)
air Inlet
M ••
•* Wt
0.0168
0.0827
0.0290
0. 0665
0.0654
0.0228
0.0281
0.0137
0.0133
0.0258
0.0211
0.0055
0.0166
0.0052
Outlet
0. 0026
0.0013
0.0026
0.0026
0.0168
0.0827
0. 0290
0.0665
0.0654
0.0228
0.0281
0.0137
0.0133
0.0258
0.0211
0..0055
0.0166
0.0052
Control .
method"      Reference
                                                                                                   ESP
                                                                                                  None
                                                                                                  None
 None
                                                                                                                   None
                                                                                                                  None
                                                                                                 None
                                                                                                                  None
                                                                                                 None
                                                                                                 None
                                                                                                                              (Table 2)
                                                                                                             (Table 12)
                                                                                                                              (Table 12)
                                                                                                                              (Table 12)
                                                                                                                              (Table 12)
                                                                                                            (Table  12)
                                                                                                                              (Table 12)
                                                                                                             (Table  12)
                                                                                                                              (Table 12)
                                                                                                                              (Table 12)

-------
                   Boiler
               Identification

      Boston  Edison
      Minot Street, No.  6

                     No.  7
       Boston  Edison No.  9
       Edgar Station
Description
% Load
Excess
 air
                                            Particulate loading
                                              (e/106 loules)
vo
                     No.  10
Inlet
0. 0094
0.0110
0.0258
0.0564
0.0585
0.0254
0.0416
0.0375
0.0355
0.0400
0.0331
0.0272
0.0185
0.0222
0.0223
0.0238
0.0217
0.0495
0.0204
0.0170
0.0293
0. 0356
0.0290
0.0244
0. 0336
0.0296
0.0244
0.0302
0.0176
0.0271
0.0213
Outlet
0. 0094
0.0110
0.0258
0.0564
0.0585
0.0254
0.0416
0.0375
0.0355
0.0400
0.0331
0.0272
0.0185
0.0222
0.0223
0.0238
0.0217
0.0495
0.0204
0.0170
0.0293
0,0356
0.0290
0.0244
0.0336
0.0296
0. 0244
0.0302
0.0176
0.0271
0.0213
Control .
method~

 None
                                                                      None
                                                                      None
Reference
                                                                                 (Table 12)
                                                                                                                              (Table 12)
                                                                                 (Table 12)
                                                                       None
                                                                                                                              (Table  12)

-------
                                                                                   Particulate loading
            Boiler
        Identification

              No. 11
Boston Edison Company
Mystic Station No. 3
                No.  5
 Boston Edison Company
 Mystic No.  6
Description
 Braintree Elect. Potter
 Station No. 1
         No.  2
7, Excess (a/loo
air Inlet
0.1149
0.0478
0.0430
0.0209
0.0719
0.1050
0.0200
0.0455
0.1484
0.1024
0.0784
0.0490
0.0113
0.0402
0.0278
0.0175
0.0527
0.0564
0.0456
0.1196
0.0739

0.1213
0.0468
0.0234

0.0321
0.0306
0.0988
0.0398
0.0524
ioules )
Outlet
0.1149
0. 0478
0.0430
0.0209
0.0719
0.1050
0.0200
0.0455 /
0.1484-f,
0.1024f;
0.07847,
0.04902
0.0113
0.0402
0.0278
0.0175
0.0527
0.0564
0.0456b/
0.1196- ,
0.0739s/.
b/
0. 1213r'
0.0469s
0.0234-^
D/
0.0321-f,
0.0306-
0.0988-^
0.0398s
^,^.^-
Control ,
method— _ Reference
None 4
(Table 12)


None 4
(Table 12)


4
(Table 13)


None 4
(Table 12)



None 4
(Table 12)
(Table 13)



None 4

(Table 13)
None 4
(Table 13)


-------
                                                                                    Particulate loading
             Boiler                                                  % Excess          (g/lO0  loules)         Control .
         Identification                Description        % Load        air          folet       Outlet       method^     Reference

        No.  4                                               -                     0.0434       0.0434-(       None             4
                                                                                  0.0565       0.0565s                   (Table 13)
                                                                                  o.oeos       o.oeoak/
_a/   ESP = electrostatic precipitator, C = cyclone, M = multicyclone,  V — venturi  scrubber.
b/   Fuel  Additives;  First Test Series (Undisclosed Boiler), MgO in liquid carrier used  to  control  SO^ emissions  and  maintain
       a soft tube scale. Fuel-to-additive ratio was 2,300:1. Franklin Station.  Calgon Velvamag  (No.  2  fuel  oil  containing 8.6
       Ib  b%0/gal.). One gallon (14.3 Ib/gal) used per 4,000 gal. No.  6 oil).  Mddleton No.  3. CH-22 Fuel  Oil  Additive (additives
       not specified for other tests).
_c/   Grain loading in grams per million joules recalculated from values reported in gr/scf assuming  a ratio  of 9,917 million
       joules/MW-Hr (9.40 million Btu/MW-Hr).
d/   Test  measurements made during soot blowing.
_e/   Boiler originally designed for coal; retrofitted to fire oil.
fj   Control system designed for oil.
_g/   Control system not described.

-------
                     APPENDIX B
PARTIGULATE EMISSIONS DATA FOR WATERWALL INCINERATORS
                         97

-------
                                          HARRISBURG MUNICIPAL INCINERATOR
vD
00
     Test No.
     Refuse
       metric tons/hiT"
                     a/
       HHV, joules/kg x 10
       % moisturti "ll"
Auxiliary fuel, kg/hr
         3
Steam, 10  kg/hr

Fly ash, kg/hr
  ESP inlet
  ESP outlet
  % control efficiency
                          6a.b/
     Residue, metric tons/hiT"*""
                            c/
     Ratio:  fly ash/residue""

     Excess air, %

                     o«d/
     Flue gas temp.,  C^

     Fly ash        f/
       kg/metric ton"T
       g/106 joules-
                              c/

II
15.69
58.0
8.70
26.7
37.10
259.91
5.40
97.68
3.29
0.079
153.8
225.0
16.57
1.90
(tests

12
15.69
58.0
8.70
26.7
37.10
339.11
8.16
97.59
3.29
0.103
94.8
225.0
21.61
2.42
made May 1973 X2i/

il
15.88
54.2
9.30
25.1
48.94
172.50
7.30
95.77
4.28
0.040
93.0
207.8
10.86
1.17
Unit No.
i£
15.88
54.2
9.30
25.1
48.94
183.75
10.07
94.52
4.28
0.043
71.5
207.8
11.57
1.24
1
15
14.61
54.2
9.30
25.1
40.87
308.04
5.67
98.16
3.59
0.086
71.5
203.9
21.00
2.26

16.
14.61
54.2
9.30
25.1
40.87
240.63
7.98
96.68
3.59
0.067
73.0
203.9
16.47
1.77

iz
12.97
35.9
15.10
15.30
51.71
265.67
14.11
94.69
3.48
0.076
76.2
227.8
20.48
1.37

18
12.97
35.9
15.10
15.30
51.71
-
3.48
-
-
227.8
-

-------
                                          HARRISBURG MUNICIPAL INCINERATOR
vO
     Test No.
     Refuse           .
       metric tons/hr^
       HHV,  joules/kg x 10
Auxiliary fuel, kg/hr
         3
Steam, 10  kg/hr

Fly ash, kg/hr
  ESP inlet
  ESP outlet
  % control efficiency

Residue, metric tons/hr" A
                        c.1
Ratio:   fly ash/residue"

Excess  air, %
                o  d/
Flue  gas temp.,   G~
     Fly  ash
       kg/metric  tori"
       g/106  joules^'
                     f/

(tests
made May 1973)li/
Unit No. 2
I
13.88
58.0
8.70
26.7
38.42
203.12
9.12
95.51
2.29
0.089
52.3
221.7
14.63
1.69
2
13.88
58.0
8.70
26.7
38.42
170.28
8.62
94.94
2.29
0.074
131.1
221.7
12.27
1.41
.3
14.06
54.2
9.30
25.1
48.63
200.81
10.84
94.60
3.16
0.064
109.8
209.4
14.28
1.54
4
14.06
54.2
9.30
25.1
48.63
252.88
10.25
95.95
3.16
0.080
83.5
209.4
17.99
1.93
3.
14.70
54.2
9.30
25.1
44.82
195.77
8.66
95.58
4.33
0.045
74.2
225.0
13.28
1.43
j6
14.70
54.2
9.30
25.1
H
44.82
288.40
10.16
96.48
4.33
0.067
74.5
225.0
19.62
2.11
1
11.97
35.9
15.10
15.30
49.62
174.09
10.80
93.80
2.51
0.069
119.5
235.6
14.54
0.95
&
11.97
35.9
15.10
15.30
49.62
185.43
12.70
93.15
2.51
0.074
87.0
235.6
15.49
1.03

-------
                  CHICAGO NORTHWEST INCINERATOR TESTS MAY 1971—^
Test No.                 PE-X    PE-1    PE-2/PD-2   PE-3/PD-3    PE-4/PD-4

Refuse
  metric tons/hr           -
  % ash                    -
  HHV, 10  joules/kg       -
  % moisture               -       -         -           -           ~

Auxiliary fuel, kg/hr      -
         9
Steam, 10  joules/hr       -

Fly ash, kg/hr
  ESP inlet                -       -       92.99      226.80      215.46
  ESP outlet               -       -       10.61        8.21        7.03
  % efficiency             -       -       88.6        96.4        96.7

Residue, metric tons/hr    -

Ratio:  fly ash/residue    -

Excess air, %            136     136      130          78.1        78.1

Flue gas temp., °G       252.2   225.6    179.4       181.1       180.0

Fly ash        ^/
  kg/metric ton*"           -
  g/106 joules^           -

-------
                                            27/
STUTTGART (W. GERMANY) WATERWALL INCINERATOR—

Test No.
Refuse
metric tons/hr
% ash
% moisture .
HHV, 106 joules/kg^
Auxiliary fuel, kg/hr (oil)
9
Steam, 10 joules/hr
Fly ash, kg/hr
ESP inlet
ESP outlet
% efficiency
c/
Residue, metric tons/hr^
Ratio: fly ash/residue
Excess air, %
Flue gas temp., C
Fly ash f ,
kg/metric tori"1
1/106 ioulea^7'
Stuttgart
&

24.10
25.9
30.5
7.624
5,484
342.1

532.1
-
-
5.10
0.104
25.5
190.6
22.08
2.90
Unit 28
5.

21.04
28.5
41.0
6.780
2,951
209.1

294.4
-
-
4.98
0.059
40.9
190.6
13.99
2.06
Stuttgart
A

22.33
31.3
38.4
6.836
6,108
331.9

681.3
-
-
5.49
0.124
30.3
183.3
30.51
4.46
Unit 29
1

21.54
30.6
37.6
6.918
2,774
203.3

686.8
•M
-
5.18
0.133
53.0
182.2
31.88
4.61

-------
                               DUSSELDQRF (W. GERMANY) WATERWALL INCINERATOR AND MUNICH
o
ro
(W. GERMANY) WATERWALL INCINERATOR?!/

Test No.
Refuse
metric tons/hr
% ash
% moisture ,
HHV, 106 joules/kg^
Auxiliary fuel, kg/hr
g
Steam, 10 joules/hr
Fly ash, kg/hr
ESP inlet
ESP outlet
% efficiency
Residue, metric tons/hiT"
Ratio: fly ash/residue
Excess air, %
Flue gas temp. , C
Fly ash ~,
kg/metric ton""
a/106 ioule&£'
Dusseldorf
Jk

10.52
33.7
32.4
7.227
0.0
42.7
499.0
-
M
2.76
0.181
112.0
235.0
47.43
6.56
Munich North I
6

26.10
30.0
44.4
6.413
0.0
97.1
1,613.9
-
M
8.67
0.186
131.3
157.2
61.84
9.64
Munich North II
A

45.50
36.8
28.0
7.501
0.0
246.4
648.2
-
-
13.61
0.048
44.5
164.4
14.25
1.90

-------
a/  Based on daily average  (composite) measurements.
b/  Average values for low, medium, and high Btu runs.
c/  Excluding metals in residue*
jd/  Measured at ESP inlet.
ej  Recalculated  from lower heating value of refuse fuel.
f/  Based on refuse portion of  fuel.
                                    103

-------
                  APPENDIX G
ELECTROSTATIC PRECIPITATOR PERFORMANCE MODEL
                      104

-------
Concurrent firing of oil and MSW will  cause  departures  from ESP operating
parameters which apply to  firing oil alone.  The ESP model is used to cal-
culate the magnitude of resulting  changes  in performance.

As discussed previously, the most  significant departures anticipated when
refuse is fired concurrently with  oil  are  in flue gas volume, moisture and
composition, particulate density,  size distribution, resistivity, fusion
temperature, and dust loading.   The calculation of resulting ESP perfor-
mance, as described below,  is based on the simplifying  assumptions that:

1.  The electric field is  unaffected by the  changes in  particulate properties,

It is well known that the  introduction of  a  significant number of fine dust
particles into an electrostatic  precipitator significantly influences the
voltage-current characteristics  of the  interelectrode space.   Qualitatively,
the effect is seen by a decrease current for a given voltage  compared to
a dust-free situation.^2.'   If the dust  loading increases as expected  for
combined oil-MSW firing, this approximation will yield a higher  limit value
for the corona current, and therefore an upper limit value for collection
efficiency.

2.  Charging time is negligible.

This  is the assumption (implicitly made) when the saturation  charge is used
to describe the instantaneous charge on each particle.  Order-of-magnitude
calculations indicate that a particle  residence time of less  than 1 sec is
required to achieve 90% of saturation  for  a  0.18 p-m particle. For larger
particles, the required residence time  to  achieve charge saturation will
decrease.£l/  Therefore, this approximation will yield an upper  limit to the
calculated collection efficiency.

3.  Precipitator performance is  not current-limited.

It is felt that this will  be a reasonable  assumption for gas volume and
dust  loadings expected.

4.  The Deutsch-Anderson equation  is applicable in integral form for  a
discrete particle size range.

This  is the usual approximation  which  is made when this equation is used
to describe the average performance of an  electrostatic precipitator  in
design applications.

In addition to the approximation described,  several nonideal effects which
are known to exist in full-scale electrostatic precipitators are not dealt
with  explicitly in the present model.
                                    105

-------
The  factors of major importance are:

1.   Gas velocity distribution,

2.   Gas sneakage, and

3.   Rapping reentrainment.

These departures from ideality will reduce the collection efficiency that
may  be achieved for a precipitator operating with a given specific collecting
area.67/

In the application of the model to actual conditions for combined firing,
the  particle  size distribution, resistivity, dielectric constant, flue gas
volume, precipitator design specifications, and at least one set of perfor-
mance data must be known or estimated as summarized in Table C-l«  The test
data need not correspond to conditions for combined firing.  A computerized
model, recently developed by Southern Research Institute under EPA sponsor-
ship, was used as the basis of the analytical model.xZ/  Electric field cal-
culations are omitted, and a system-dependent parameter is calculated in-
stead from known performance data.  This is a one-parameter "fit" in which
effective migration velocities are determined for each particle size range
and  particle resistivity under a fixed set of design or test conditions.
This step was done using trial-and-error, or iterative procedures.  A block
diagram illustrating the computational procedure is shown in Figure G-l.
The  computation procedure is divided into two parts.  Initially, precipi-
tator design or sizing data and at least one set of performance data are
used to determine the distribution of migration velocities for the known
performance data over the range of particle sizes.  In the second calcu-
lation stage, migration velocities are a'djusted for changes in flue gas
temperature and viscosity, particulate resistivity and relative dielectric
constant, operating current and voltage.  ESP performance is then deter-
mined for anticipated combined-firing test conditions.  The computation
procedure is described in detail in the remainder of this section.

1.   Determine migration velocities for each particle size based on known
performance data.

Step 1 - Calculate the saturation charge on the median diameter particle
         within the jtn discrete particle size range, based on performance
         data.  A "modified" saturation charge expression, developed by
         Southern Research Institute^.' is used:


                     (R(j) + Xm)2(1.2E)l + 2 -=-	-     (C-l)
                                               K
                                   106

-------
             Table C-l.  DATA INVENTORY FOR ELECTROSTATIC
                    PRECIPITATOR PERFORMANCE MODEL
             Precipitator design data

               Plate area
               Plate-to-plate spacing, inlet
               Plate-to-plate spacing, outlet
               Length of electrical sections
               Corona wire diameter
               Number of Series electrical sections
               Number of Parallel electrical sections

             Performance data

               Average  efficiency
               Flue  gas volume
               Flue  gas temperature and composition
               Precipitation rate parameter
               Operating voltage
               Current  versus resistivity curve  (if known)—'
               Voltage  versus current curve  (if  known)—'
               Particle size distribution (if known)
               Particle resistivity

           •   Test Conditions

                Percent  MSW on a Btu  basis
               MSW composition, ash,  and moisture
               MSW heating value
                Oil composition, ash,  and moisture
                Oil heating value
                Percent excess air
                Boiler efficiency curve (if known)


a/  A conservative estimate  of the allowable current density as a function
      of resistivity is given in Figure C-2.
b/  A reasonable approximation of the  average electrical conditions in the
      precipitator is given  in Figure  C-3 by the curves labeled "typical."
                                     107

-------
New Trial
Value of K
          No
                   Data  Inputs
                    (ESP Design Data
                    & Performance Test Data)
                              i
                       Calculated
                       Saturation Charges
                              1
                      Calculate
                      Cunningham Factors
                              I
                      Calculate
                      Effective Migration
                      Velocity
                              I
                     Calculate Migration
                     Velocity Distribution
                              I
                     Calculate Fractional
                     Efficiencies
   I
                        Calculate
                        Average
                        Efficiency (fj)
                              i
Calculated
Agrees with
Measured
Yes
                             Data I nputs
                             (Combined Firing)
                                    I
                                Estimate
                                ESP Current,
                                Voltage
                              Calculate
                              Flue Gas Volume
                                    I
                             Calculate  Adjusted
                             Migration  Velocity
                             Distribution
                              Estimate  Particle
                              Size Distribution
                            Calculate Fractional
                            Efficiencies
                               Calculate
                               Average
                               Efficience (17)
    Figure C-l.   Block diagram of ESP performance model.
                               108

-------
where       £Q = permittivity  of  free  space

               = 8.85  x 10~l-2  cou!2/newton-m2

          R(j) = mass  median particle  radius,  corresponding to the jth
                 discrete particle size  range,  m

            Xm = an adjustable parameter = mX                          (G_2)

where         X = ion mean free path, m

              m = number of mean free paths

            EQ = average charging field, volts/m

              X = relative dielectric constant  of the particle

                 The mean free path X  is calculated using the following
                 expression which is valid for the  range  of temperatures
                 of interest for fly ash precipitators  and at one atmos-
                 phere:

                 X = 1.9176 x 10"10 (T°K)

 Step 2 - Calculate the Cunningham correction factor, or slip correction
          factor  for each discrete particle size range,   j , using performance
          data:

                                 C(j)  = 1 + AX/R(j)                     (C-3)

 where        A =  1.257 + 0.400 exp (-1.10 R(j)A)

 Step 3 - Calculate the effective or length averaged migration velocity for
          the  different particle size ranges from the Deutsch  equation using
          performance data.

                             we =2- ln/-J^-\                       
-------
Step 4 - From the test or design data used for Steps  1  to 3,  estimate the
         effective migration velocity,  w (j),   for each discrete particle
         size range in the distribution.  The  distribution of migration
         velocities for each discrete size range  we(j)  can be expressed
         in terms of the overall effective (length averaged)  migration ve-
         locity  w   as follows:
                        °       *     q; C/K

where        K = complex function of particle size distribution,  precipi-
                 tator geometry, and operating condition,  having  dimension
                 of length (m)

            q' = q'OO  is the value of modified saturation charge corre-
             S    3
                 spending to a radius of size "K"

             C = C(K)  is the value of the Cunningham correction  factor cor-
                 responding to a radius of size "K"

                 The system-dependent parameter  K  is determined using an
                 iterative procedure described in the next two computational
                 steps.  A convenient starting trial value is the mass median
                 radius of the particle size distribution.

                 From classical theory, the migration velocity is given by:

                          w (j) . q(1) EP C(1)                        (c.6)
                           eU'     6TrR(j) u

where       Ep = electric field near the collection electrode, volts/m

             u = gas viscosity, kg/m-sec

    C(j), R(j) = as previously defined

The direct solution ofEq. (C-6) would require the solution of two simulta-
neous second-order partial differential equations in order to calculate the
field adjacent to the collection electrode Ep.  The alternative approach
used here is to assume that the ratio of instantaneous charges on particles
in the  jtn  size range is approximately the same as the saturation charge
ratio.  Use of the modified saturation charge to describe the instantaneous
charge will yield an upper limit value of the migration velocity for  each
particle size range, which  in turn will yield an upper limit value for  the
collection efficiency.
                                   110

-------
Step 5  - Calculate  the fractional efficiency for each discrete  particle
         size  range and each stage or series electrical section.  The
         Deutsch  equation is used in the following form:
                               = 1 - exp(-we(j)A/Q)                    (G_7)

where     T](j) =  the  fractional collection efficiency

   we(j), A, Q =  as previously defined

                  For  multiple  stage precipitators, the overall fractional
                  efficiency  corresponding  to a given size range  j  is ob-
                  tained  as follows:

                             Tl(j)  = E  TKi,j)                          (C-8)
                                     i

Step 6 - Calculate the overall fractional  efficiency.

                       Tl = 1 - ZXj  exp(-wp(j)A/Q)                     (C-9)
where       Xj = the mass  fraction of the  jth  discrete particle size
                 range

If the fractional efficiency calculated in Eq. (C-9)differs significantly
from the test efficiency,  a new  trial value of  K  is used, and Steps 4
through 6 repeated until convergence is obtained.

2.  Determine fractional efficiency for combined firing test conditions.

The major inputs from Part 1,  computation Steps 1 through 6, are migration
velocities  w (j)  for each discrete particle size range  j  based on known
performance data.  These data,  which implicitly contain system dependencies,
and test data summarized in Table C-l are used to calculate the electro-
static precipitator performance  for combined  firing according to the fol-
lowing procedure.

Step 7 - Calculate adjusted value of average  corona current density.

Current and voltage relationships in a precipitator are governed by  elec-
trode geometry and by the  mobility of the charge carriers.  Electrical con-
ditions are limited by either  breakdown of the gas in  the  interelectrode
space or by breakdown in the collected dust  layer.
                                    Ill

-------
At present  there is no theoretical basis for predicting either the cur«.ent-
resistivity behavior or the maximum allowable corona current.  Ideally,
therefore,  an experimentally determined current versus resistivity curve
should be used.

If current-resistivity data are not available the curve in Figure C-2 may
be used  to  estimate the current density for a given value of dust resistiv-
ity.  Figure C-2 was obtained from the literature, and is based on the ob-
servation that critical current densities in full-scale precipitators can
be reduced  from the theoretical dust breakdown values by a factor of about
10.  The use of this curve should give a conservative estimate of the allow-
able current density as a function of resistivity.ilZ/
 Field  experience has shown that current density for cold-side precipitators
 is  limited  to around 50 to 70 nA/cm  (1 x 10"' A = 1 nA) due to electrical
 breakdown of the gases in the interelectrode region.
 Step  8  - Calculate adjusted value of voltage corresponding to the maximum
         allowable corona current.

 As  in Step 7, the voltage-current relationships for an electrostatic pre-
 cipitator are governed by the mechanical design of the collector system,
 the size and concentration of dust particles in the gas stream, the pres-
 ence  of a dust layer on the collection electrode, and the temperature and
 composition of the gas stream.  Therefore, it is preferable to determine
 the operating voltage from an experimentally determined current-voltage
 curve (see Table C-l).

 Lacking this experimental data, a reasonable approximation to the average
 electrical conditions in the precipitator is given in Figure C-3 by the
 curves labeled "typical."£Z/

 Step  9 - Calculate adjusted flue gas volume.  The flue gas volume for a
         given combined firing application is calculated by standard pro-
         cedures based on data inputs summarized in Table C-l "test condi-
         tions."  In general, flue gas volume will increase significantly
        .with increasing MSW fraction for combined firing of oil and MSW:
         (a) at 10% MSW on a Btu basis, assuming 25% excess air and 5,650
         Btu/lb (HHV) for the MSW portion, the theoretical gas volume will
         increase by 5.770; and (b) on the same basis, the theoretical in-
         crease in flue gas volume at 20% MSW is 18.0%.

Step  10 - Estimate the particle size distribution for combined firing.
                                   112

-------
CN



 U
 Q.


 O
 O


 O
 c
 z
 LU
 Q

 I—

 z
 LU
       10
       Source:  Ref. 67
10"                   1012


   RESISTIVITY, ohm/cm
1013
      Figure G-2.  Current density as a  function of  resistivity.
                                  113

-------
    70
    60
    50
cs
4
 Q.
    40
 CO
 z
    30
 (J
                                                 •370°C
                                                  150°C
                           Outlet
                    Typical
                    (150°C)
                           Inlet
Outlet
(Typical
 (370°C)
                                       i
     0
    Source:  Ref. 67
           30          40
    APPLIED  VOLTAGE, kilovolts
                                                     50
                                     60
    Figure  C-3.   Comparison between the voltage versus
    current characteristics for cold-side and hot-side
       precipitators.   Corona wire radius = 0.277 cm
       (0.109  in.),  plate spacing = 22.86 cm (9 in.).
                            114

-------
The particle size distribution for combined  firing is presently based on a
linear combination of Weibull (or Rosin-Ramler) parameters. !!/ The particle
size distribution for firing refuse alone must be estimated.  Weibull param-
eters are calculated separately  for submicron particulate and particulate
larger than 1 urn.  The two-parameter Weibull distribution function is fit
by a least squares technique in  the following form:
                         F(R(J)) =  1  - e-                             (c-10)
                                           \  9 '

where  F(R(j)) = the weight  fraction  of particulate having diameters less
                 than  R(j)

          8 , b = independent parameters

Weibull parameters  for the refuse portion  of the  fuel are as follows:

                               9 (um)       b

                 (< 1 um)       1.48        2.91

                 (> 1 urn)       92.1        0.23

The particle size distribution and  ash content of the fossil-fuel portion
must be known independently  to determine the particle size distribution for
the composite fly ash.

Step 11 - Calculate fractional efficiencies.  When ESP current and voltage,
          flue gas volume, migration  velocities, and particle size distri-
          bution have been adjusted for combined  firing conditions, frac-
          tional efficiencies for each discrete particle size range are
          calculated using Eq.  (C-7).

Step 12 - Calculate effective, length averaged (total) efficiency.  Total
          efficiency  T|  for the ESP  under  combined- firing conditions is
          calculated using Eq. (C-9).

The ESP performance calculation, as described in Appendix C, can be per-
formed using a moderately sophisticated calculator, such as Hewlett-Packard
9810-A, or equivalent.
                                    115

-------
1 TECHNICAL REPORT DATA "
1 (Please read Instructions on the reverse before completing)
J1. REPORT NO. 2.
EPA-600/2-76-209
J4. TITLE AND SUBTITLE
Performance of Emission Control Devices on Boilers
Firing Municipal Solid Waste and Oil
7. AUTHOR(S)
u . B. Galeski and M. P. Schrag
9. PERFORMING OR3ANIZATION NAME AND ADDRESS
Midwest Research Institute
K25 Volker Boulevard
Kansas City, Missouri 64110
112. 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
July 1976
6. PERFORMING ORGANIZATION CODE
8. PERFORMING ORGANIZATION REPORT NO.
10. PROGRAM ELEMENT NO.
EHB533
11. CONTRACT/GRANT NO.
68-02-1324, Task 40
13. TYPE OF REPORT AND PERIOD COVERED
Task Final; 7/75-6/76
14. SPONSORING AGENCY CODE
EPA-ORD
15. SUPPLEMENTARY NOTES Task officer for this report is J.D. Kilgroe , Mail Drop 61,
Ext 2851.
|16. ABSTRACT
The report gives results of estimating particulate flue gas loadings for
combined firing of shredded municipal waste (MSW) and oil, using existing data on
particulate emissions from oil-fired electric utility boilers and from waterwall
  (steam generating) incinerators firing either waste or waste-plus-coal/oil auxiliary
 fuel.   Control device performance was estimated for several planned oil/MSW
 resource recovery systems.  On the basis of these estimates, installed particulate
 emission controls, designed for coal, are predicted to be significantly less efficient
 for control of particulate emissions from combined firing of oil/MSW.  Anticipated
 control difficulties result mostly from relatively high particulate loadings, high flue
 gas volumes, fine particulates, relatively low particle density, and relatively high
 fractions of carbonaceous low-resistivity particulate.

J17. KEY WORDS AND DOCUMENT ANALYSIS
la. DESCRIPTORS
Air Pollution
Boilers
Fuels
I Wastes
Fuel Oil
Dust
18. DISTRIBUTION STATEMENT
Unlimited
b.lDENTIFIERS/OPEN ENDED TERMS
Air Pollution Control
Stationary Sources
Combined Fuel
Municipal Solid Waste
Oil/Municipal Solid Wash
Particulate
19. SECURITY CLASS (This Report)
Unclassified
20. SECURITY CLASS (This page)
Unclassified
c. COSATI Field/Group
13B
13A
21D
i
11G
21. NO. OF PAGES
128
22. PRICE
EPA Farm 2220-1 (9-73)
                                         116

-------