United States
                     Environmental Protection
                     Agency
Hazardous Waste Engineering
Research Laboratory
Cincinnati OH 45268
                     Research and Development
EPA/600/S2-85/098   Dec. 1 985
oEPA          Project Summary
                     Investigation  of Fluid  Bed
                     Combustion  of  Municipal  Solid
                     Waste

                     R. H. Eustis, Keith B. Wilson,  Lyn C. Preuit, and Maximilian M. Marasigan
                      A systems study was conducted for a
                     co-generation, 300-tons/day  power
                     plant to be located on the Stanford
                     University campus to supply all of the
                     process steam requirement and as much
                     of the electrical power as possible. The
                     size of the plant was determined by the
                     estimated available processed MSW
                     supply in 1983. Preliminary design of
                     components based on the 300-hour
                     test results and cost estimates were
                     made.  It was  estimated that the total
                     plant investment for the co-generating
                     plant, 6.7 MWe average and 200,000
                     pounds per hour of  steam average,
                     would be 23.1 million dollars, exclusive
                     of fuel processing and transportation
                     costs.
                      This Project Summary was developed
                     by EPA's Hazardous Waste Engineering
                     Research Laboratory. Cincinnati, OH to
                     announce key findings of the research
                     project that is fully documented in a
                     separate report of the same title (see
                     Project Report ordering information at
                     back).

                     Introduction
                      A concept which utilizes fluid-bed
                     combustion of municipal solid waste was
                     investigated for application to the power
                     generation and steam supply at Stanford
                     University. Preliminary investigation of
                     the system has shown considerable eco-
                     nomic promise, although the operation of
                     an  atmospheric fluid bed containing
                     steam-generating tubes had not been
                     tested.  Therefore, a program was rec-
                     ommended to the Department of Energy
                     and the U.S. Environmental Protection
                     Agency which would involve an  exper-
                     imental program to burn solid waste in a
fluid-bed combustor and to undertake a
more detailed economic study.
  An experimental program was designed
to investigate the favorable operating
regimes for a bed with steam-raising
tubes, to determine the combustion cor-
rosion of the tubes, and to investigate the
fouling of the tubes or system internals
caused by the combustion of municipal
solid waste. Two 50-hour preliminary
experiments were run in order to shake
down the equipment and to conduct a
parametric study to specify the  most
favorable operating regime for a subse-
quent 300-hour test. All of these exper-
iments were conducted in a 7 ft2 atmos-
pheric fluid bed located at the Combustion
Power Company  (CPC) in Menlo  Park,
California.
  An economic study was also undertak-
en to determine the promise of the system
as defined from the results of the exper-
iments. As described below, a complete
system was envisaged for application to
the Stanford University campus, and the
sizing and performance of the fluid-bed,
solid-waste combustor was based on the
experimental results. The application to
Stanford University was used only as a
specific application and was not neces-
sarily the most favorable one, because of
the  wide variety of requirements for
electric power and steam. However,  it
was felt that this would be a typical
situation and that there would be con-
siderable benefit in having a study made
to meet definite, realistic requirements.
  In the final report, the proposed system
at Stanford University is described, fol-
lowed by the results of the fluid-bed
testing program. The last section of the
final report is a presentation of the

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systems study showing the performance
and economics of a fluid-bed, municipal-
solid-waste  combustion system  which
incorporates electrical power generation
with process heating.

Proposed System
  In order to prevent the present study
from becoming merely an academic exer-
cise, a practical possible application was
defined so that the experimental program
would be conducted under realistic test
conditions and the economic study would
have  reference to a specific situation.
Therefore, consideration was given to the
energy requirements of Stanford Univer-
sity. This is a particularly favorable situa-
tion, inasmuch  as the University has a
central  steam-heating  system and an
electrical  power  requirement.  At the
present time  the electrical  power  is
supplied by the  local utility, and steam is
generated in the University's boiler sys-
tem with natural gas as the fuel, backed
up  by light fuel oil. The balance of the
heating  and electrical load  is such that
co-generation of electricity  and process
heat is feasible and very attractive from a
technical point of view.
  The general concept for the Stanford
Solid-Waste Energy Program (SSWEP) is
to process solid waste at a convenient
collection site,  where  some landfill  is
available to handle the non-combustible
part of the stream. The lightly processed
solid waste, which would be processed
only  so that  it  can  be fed  into the
combustors through a 5"-diameter pipe,
would be transferred to  the  University
campus with special transfer trucks. The
size of  the  system is specified  by the
available Municipal Solid Waste (MSW),
which is estimated to be 800 tons  of
processed MSW per day in 1983.  This
corresponds to  approximately 1200 tons
per day of raw MSW delivered  to the
remote  processing site. The plan would
be to feed the processed MSW to fluid-
bed boilers  which would be built  in a
modular fashion  for economy and for
improved turn-down as required for meet-
ing the variable  load on the campus.
Superheated steam at a modest pressure
and temperature would be delivered to a
steam turbine, with extraction at  a pres-
sure  of  approximately  170  psia.  The
extraction steam would condense  in a
heat exchanger and then be returned to
the fluid-bed boiler. The heat exchanger
would transfer heat  to the return  con-
densate from the Stanford  heating sys-
tem to produce 140  psia steam  for the
Stanford system. If all of the flow from the
high-pressure turbine was  not required
for the heat exchanger, the remainder
would flow to a condensing turbine  in
order to generate more electrical power.
A cooling tower would be provided for
cooling the condenser so that the fluid-
bed boiler steam would be self-contained
and could be carefully controlled.
  The fluid-bed boiler system involves a
combustion air blower, an air preheater,
and an exhaust clean-up system after the
fluid-bed boiler. The solid waste would be
introduced into the bed pneumatically,
and  the  present  design  incorporates
internal recycling of elutriated flyash and
bed material to the bed, as this was found
beneficial in the experimental program.
Most of the system is conventional, with
the fluid-bed boiler being the most novel
and  at the same time the most critical
component. Because of  this, an  exper-
imental program was performed in a 7 ft2
fluid-bed combustor with water-cooled
tubes. Air-cooled tubes were included for
corrosion tests in both the freeboard and
m the active bed, in which test samples
were subjected to the expected temper-
ature of superheater tubes in an actual
application.

Test Results
  Two 50-hour runs were made to check
out  the  system and to determine  a
satisfactory operating point for the princ-
ipal  experiment of  300 hours' duration.
The test conditions were:

  superficial velocity = 4.5 ft/sec
  bed temperature  = 400 F
  freeboard temperature = 1500 F
  excess air = 44%
  internal recycle of elutriated solids  to
  bed

  The  300-hour test  was  performed
without incident and terminated on sched-
ule.  The combustor and ducting were
clean on inspection after the test, and bed
agglomeration did not occur. A corrosion-
erosion  tube placed  in  the  freeboard
showed considerable metal wastage for
carbon and low-alloy steels and some
wastage  for stainless steels.  Low-tem-
perature  carbon-steel water tubes in the
bed  showed negligible wastage.  It was
concluded that heat-exchanger tubes in
the freeboard require protection from the
high-velocity  elutriated solids. Combus-
tion efficiency was greater than 99%, and
pollutants were measured as follows1
                   Economic Summary
                     The material from the cost estimates
                   described in the final report is summar-
                   ized in Table 1. Each major subsystem is
                   shown, along with the additional  costs
                   which are recommended for a construc-
                   tion project such as this by the standards
                   of the Electrical Power Research Institute.
                   The total direct cost as estimated is 1 6.7
                   million dollars, and the total plant invest-
                   ment, using various  contingencies and
                   sales tax, amounts to $23.1 million. This
                   figure should  be  compared to plants
                   which handle 1 200 tons per day of raw
                   municipal solid waste and  produce both
                   steam and  electrical power. The  costs
                   presented do not  include processing  or
                   transporting the processed MSW to the
                   point of use.
   S02
   NOx
   CO
   Hydrocarbons
 58   ppm
178   ppm
242   ppm
  4.4 ppm

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Table 1.    Stanford Solid-Waste Energy Program Total Plant Investment
 1   Boiler system
 2   Startup system
 3.   Combustion air system
 4   Flue-gas system
 5.   Bed-maintenance system
 6.   F/yash-disposal system
 7.   Fuel-feed system
 8   Fuel-receiving bldg., equipment
 9   Main steam system
JO   Feedwater system
11   Electrical/controls/misc
12   Building, site work, construction, A & E
$ 2.239,700
    155,200
    798,900
  2,382,000
     84,100
     79,200
    457.800
    252.400
  5.421.000
  1,942,600
  1,204,100
  1,645,000
     Total Direct Costs
     Undistributed Costs <6%>
 16,662.000
    999.700
     Process Capital
     Engineering & Home Office Fees
 17,661.700
   1.666.700

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    R. H. Eustis is with Stanford University, Palo Alto, CA 94105; andK. B. Wilson, L
      C. Preuit, andM. M. Marasigan are with Combustion Power Corporation, Menlo
      Park, CA 94025.
    Michael I. Black is the EPA Project Officer (see below).
    The complete report, entitled "Investigation of Fluid Bed Combustion of Municipal
      Solid Waste,"(Order No. PB85-242 121 /AS; Cost: $11.95, subject to change)
      will be available only from:
           National Technical Information Service
           5285 Port Royal Road
           Springfield.  VA22161
           Telephone: 703-487-4650
    The EPA Project Officer can be contacted at:
           Hazardous Waste Engineering Research Laboratory
           U.S. Environmental Protection Agency
           Cincinnati, OH 45268
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
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