United States
Environmental Protection
Agency
National Risk Management
Research  Laboratory
Cincinnati, OH 45268
Research and Development
EPA/600/SR-01/087  January 2002

Cost of                      Catalytic
Reduction  (SCR)  Application  for
NO    Control  on  Coal-fired
Boifers
Wojciech Jozewicz
  The report provides a methodology
for estimating budgetary costs associ-
ated with retrofit applications of selec-
tive catalytic reduction (SCR) technology
on coal-fired boilers. SCR is a  post-
combustion nitrogen oxides (NOX) con-
trol technology capable of providing NOX
reductions >90%. With SCR, NOX reduc-
tions are achieved by injecting ammo-
nia into the flue gas, which then passes
through layers of catalyst in a reactor.
The ammonia and NOX react on the sur-
face of the catalyst, forming nitrogen
and water. In the U.S., SCR has been
applied mainly to electrical utility boil-
ers firing coal and natural gas and tang-
ing in capacity from 25 to 800 MW.
  The costing methodology presented
in the report is applicable to SCR  retro-
fits on coal-fired boilers tanging  in ca-
pacity from 100 to about 850 MW and
with design efficiencies of 80-95% NOX
removal. The cost equations and vari-
ables  used in the methodology are
based on  information obtained  from
SCR system suppliers and reflect ex-
perience gained from >200 SCR  appli-
cations. Note,   however,  that the
budgetary cost estimates for typical
SCR applications that this methodology
provides  cannot  replace the detailed
site-specific engineering cost studies
or cost quotations that are developed
by SCR system suppliers.
  This Project Summary was developed
by the National Risk Management Re-
search Laboratory's Air Pollution Pre-
vention and Control Division, Research
Triangle Park, NC, to announce key find-
ings of the research project that is fully
documented in a separate report of the
same title (see Project Report ordering
information at back).

Background
  Selective catalytic reduction (SCR) is a
postcombustion nitrogen oxides (NOX)
control  technology capable  of providing
NOX reductions >90%. With SCR,  NOX
reductions are  achieved  by injecting am-
monia into the flue gas, which then passes
through layers of  catalyst in a reactor.
The ammonia and NOX react on the sur-
face of the catalyst,  forming molecular
nitrogen (N2) and water. In the U.S., SCR
has been applied mainly to electric utility
boilers firing coal and  natural gas.
  The report provides  algorithms for esti-
mating costs and performance of generic
SCR retrofit applications  on coal-fired
boilers. Specifically, the algorithms are
applicable to SCR systems with design
efficiencies of 80-95% NOX  removal that
can operate on coal-fired boilers ranging
in size from approximately 100 to 850 MW.
The  cost  equations and variables are
based on  industrial  experience  gained
from >200 SCR applications. Note that
the  algorithms  presented in this work are
not  meant  to replace  the detailed engi-
neering studies or  cost quotations that
are  developed  by  system suppliers, nor
should these algorithms be used to de-
termine detailed site-specific costs for ret-
rofit SCR applications.

The Costing Algorithms
  SCR  budgetary  costing algorithms for
capital as  well  as fixed and variable op-
erating and maintenance (O&M) costs (in
January 2000  dollars) are given below.

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The  capital  cost,  D  ($/kW), of an SCR
retrofit  application  is  estimated using
Equation (1):
D = 75 {300,000 Z/A}035             (1)
where:
Z = [(B/1.5)° °5(C/100)°4]
and
D = capital cost ($/kW)
75 = capital cost ($/kW) associated with a
    typical SCR retrofit on a 300,000  kW
    coal-fired unit
300,000  = reference to  a 300,000  kW
    baseline unit (basis for the economy-
    of-scale adjustment in the equation)
B =  NOX  (lb/106 Btu) at  the inlet of  the
    SCR reactor;  range of approximately
    0.15-2.5 lb/106 Btu
0.05 = exponent for inlet NOX concentra-
    tion
C = NOX removal  efficiency (%); range of
    80-95%
0.4 = exponent for NOX removal efficiency
A = plant capacity (kW); range of approxi-
    mately 100,000-850,000 kW
0.35 = exponent for an  economy-of-scale
    adjustment  factor  (scaled  from a
    300,000 kW unit)

  The complexity of an SCR system design
is dependent on the plant layout. For  ex-
ample, a relatively constrained plant lay-
out may involve a more difficult SCR system
design compared to a  relatively uncon-
strained  layout and, therefore, may require
more ductwork  and air  heater modifica-
tions.  In  contrast,  a  relatively  uncon-
strained layout  may not need  air heater
modifications and more than the  typical
amount of ductwork. To account for vary-
ing levels  of design  complexity, a degree
of difficulty  is associated with  an SCR
retrofit application. In this context, the  av-
erage degree of difficulty is assigned to a
retrofit where the SCR installation is rela-
tively simple (i.e., the facility has adequate
space for the SCR system).  Equation  (1)
assumes this average degree of difficulty.
  The  fixed O&M cost,  E ($/yr), is  as-
sumed to be 0.66% of the capital cost
and is  estimated using  Equation (2):
E = D«A«C                         (2)D
where: D
E = fixed O&M cost ($/yr)D
D = capital cost ($/kW) from Equation (1)D
A = plant capacity (kW); range of approxi-D
    mately 100,000-850,000 kW
C = a constant; 0.0066 yr1

  The variable O&M cost, F ($/yr),  is esti-
mated using Equation (3):
F = G {225«[0.37B«H«(C/100)«
    (8760/2000)]«1.005«1.05  +
    0.025. D.A.Z+  1.45.A}         (3)
where:
F = variable  O&M cost ($/yr)
G = annual capacity factor (expressed as
    a fraction)
B = inlet  NOX (lb/106  Btu); range of 0.15-
    2.5 lb/106  Btu
H = heat input (106Btu/hr)
C = NOX removal efficiency (%); range of
    80-95%
D = capital cost ($/kW)
A = plant capacity (kW); range of approxi-
    mately 100,000-850,000 kW
Validation of the Costing
Algorithms
  The  costing  methodology presented
above was derived from information pro-
vided by SCR  system suppliers and is
deemed valid for typical  coal-fired SCR
retrofit  applications for NOX removal effi-
ciencies in the  range of 80-95%.  Note,
however,  that  this  methodology is in-
tended and  valid  for developing  budget-
ary cost estimates and  assumes typical
installations. Therefore, the methodology
should  not be  expected  to  account for
reported costs of  each site-specific SCR
retrofit  application.
  In a  1998 study conducted for North-
east States for Coordinated Air Use Man-
agement (NESCAUM)  and  Mid-Atlantic
Regional Air Management  Association
(MARAMA),  the capital cost for SCR  ret-
rofit  on dry-bottom wall- and tangentially
fired boilers  to achieve 85% NOV reduc-
tion was estimated to be 70-90 $/kW. Simi-
larly, the study estimated that the capital
cost of SCR retrofits to achieve 90% NOX
reduction from wet-bottom boilers would
also be 70-90 $/kW. Note that these esti-
mates  were based on 330 MW units.  In
comparison, the  costing methodology re-
sults in an  estimate of approximately 70
$/kW for similar units.
  Recent literature reflects a  range of 55-
140 $/kW as being typical of site-specific
retrofit  SCR capital costs for all types  of
utility boilers. By comparison, the costing
methodology estimates a capital cost  of
approximately  50-110  $/kW to  achieve
85-95% NOX removal  efficiency.
  The  NESCAUM/MARAMA report  esti-
mated  a combined fixed and variable
O&M cost of reducing  NOX by 70-80% for
a 330  MW dry-bottom boiler at approxi-
mately  $1.1 million/yr  and approximately
$2.8 million/yr for a similar-sized wet-bot-
tom boiler. The costing methodology esti-
mates  the  combined  fixed  and variable
O&M costs  for all boiler types to be about
$1.0 to 1.7 million/yr  for 85% NOX re-
moval.  In another  economic analysis  of
SCR retrofits on  300 and  500 MW boilers
to reduce  NOX  by 80-85%,  combined
O&M costs  were estimated to be $1.6-3.2
million/yr.
  Based on the  above comparisons, the
capital  and  O&M cost estimates derived
from applying   this  methodology are
deemed reasonably accurate and fall well
within  the  ranges reported elsewhere.
Actual  cost reported  from  site-specific
SCR retrofit applications,  as  well as indi-
vidual  facility engineering studies, would
more accurately reflect the circumstances
of individual facilities.  As a  result,  it  is
also reasonable  to expect that reported
actual  costs may not  always conform  to
budgetary cost estimates that have been
designed around  typical installations.
While the methodology has  been shown
to consistently estimate costs that fit well
with other reported actual and  estimated
costs,  occasionally  it  can be  expected
that there will be  data with higher or lower
costs.

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 Wojciech Jozewicz is with ARCADIS Geraghty & Miller, Inc., Research Triangle
   Park, NC 27709.
 Ravi K. Srivastava is the EPA Project Officer (see below).
 The complete report, entitled "Cost of Selective Catalytic Reduction (SCR) Appli-
   cation for  NOX Control on  Coal-Fired Boilers," will be available at http://
   www.epa.gov/ORD/NRMRLyPubs/600R01087/600R01087all.pdf.  It will also
   be available from NTIS (Order No. PB2002-100499; Cost: $23.00, subject to
   change)  at the following address:
         National  Technical  Information ServiceO
         5285 Port Royal RoadD
         Springfield, VA  22161-0001D
         Telephone: (703) 605-60000
                   (800) 553-6847 (U.S. only)
 The EPA Project Officer can be contacted at:
         Air Pollution Prevention and Control Division
         National  Risk Management Research Laboratory
         U. S. Environmental Protection Agency
         Research Triangle  Park,  NC 27711-0001
United StatesD
Environmental Protection Agency D
CenterforEnvironmental Research InformationD
Cincinnati, OH 45268D
PRESORTED STANDARDD
 POSTAGES FEES PAIDD
          EPAD
    PERMIT No. G-35D
Official Business
Penalty for Private Use
$300
EPA/600/SR-01/087

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