United States
Environmental Protection
Agency
Air and Energy Engineering
Research Laboratory
Research Triangle Park NC 27711
Research and Development
EPA/600/S8-85/022 Nov. 1985
Project Summary
Low NOX Firing System for
Tangentially Coal-Fired Boilers:
Applications Guideline Manual
A. Kokkinos and R. D. Lewis
This applications manual, a concise
user's guide of Combustion Engineer-
ing's Low NO, Concentric Firing Sys-
tem, is based on extensive pilot-scale
and small and large utility-scale demon-
strations, in particular, a demonstration
program completed in May 1984 at
Utah Power and Light Company's 400-
MWe Hunter Unit 2 station.
The manual addresses six points for
the user to evaluate to determine the
applicability, feasibility, and cost of
installing the concentric firing system
to a particular steam generating unit:
(1) rationale, (2) applicability, (3) pre-
design evaluation, (4) design, (5) per-
formance optimization and evaluation,
and (6) economic analysis.
The manual follows the final project
report (a case study example of retro-
fitting this technology) for the Hunter
Unit 2.
This Project Summary was developed
by EPA's Air and Energy Engineering
Research Laboratory, Research Triangle
Park, NC, to announce key findings of
the research project that is fully docu-
mented in a separate report of the same
title (see Project Report ordering infor-
mation at back).
Introduction
This applications manual is a concise
user's guide of Combustion Engineering's
Low NOX Concentric Firing System. This
guide has resulted from extensive pilot-
scale and small and large utility-scale
demonstrations, in particular, a demon-
stration program of this system, complet-
ed in May 1984 at the 400 MWe Hunter
Unit 2 station of Utah Power and Light
Company.
The applications manual addresses six
points for the user to evaluate to deter-
mine the applicability, feasibility, and cost
of installing the concentric firing system
to a particular steam generating unit.
The first two sections of the manual
develop the general rationale and appli-
cability of the process. This is done by
presenting the areas of boiler perform-
ance and emissions potentially affected
by the concentric firing system and
permitting the potential user to ascertain
the applicability of the technology to
particular needs. Additionally, the general
requisites of the concentric firing process
have been developed with respect to the
firing system and auxiliary equipment
systems design. This allows the designer
to evaluate the technical feasibility of
applying the process to a particular steam
generator.
The third and fourth sections of the
manual extend and develop more detailed
system requirements and the design
details for the concentric firing system.
Included in these sections is the require-
ment to establish a unit characterization
that would be necessary for both new and
retrofit applications of this technology. It
would be used to determine existing or
design load patterns, excess air levels,
mill operating patterns, windbox damper
operation, slagging tendencies, boiler
turndown, steam temperature control,
actual or anticipated unit emissions, and
fan and unit performance.
Then, based on this characterization,
the various options or arrangements
available with the concentric firing sys-
tem are considered. These options include
modifications to windbox compartment
free areas, coal compartment and nozzle
-------
configuration, and fixed versus variable
horizontal offset.
The fifth section of the guideline man-
ual discusses the recommended proce-
dure for optimizing the system when
installed. The optimization would involve
recharacterizing the unit's performance
and emissions by conducting a short
series of parametric tests and closely
observing the longer term operating
trends.
The final section addresses the eco-
nomic viability of the concentric firing
system. The analysis is conducted using
the Electric Power Research Institute's
(EPRI's) economic premises. It covers new
and retrofit applications for utility size
steam generators. The analysis can be
directly applied to bituminous coal firing
plants, and appropriate factors have been
developed for applications of the cost
analysis to lignites and subbituminous
coals.
Conclusions
Major conclusions resulting from the
field work and subsequent feasibility/
economic studies are:
slag deposit on some boilers. Also, on
some boilers a reduction in the super-
heat and reheat spray flows has been
seen. These two effects appear to be
very coal dependent and should be
evaluated on a case-by-case basis.
The concentric firing system is tech-
nically retrofittable on most tangential
coal-fired or multifuel boilers. In many
cases it can be applied as part of a
normal windbox maintenance pro-
gram.
The cost of installing a concentric
firing system will depend on the unit
size, coal type, and existing firing
system configuration. The total capital
requirements (1985 dollars) have been
estimated to be $1 -4/kW.
A. Kokkinos andR. D. Lewis are with Combustion Engineering. Inc., Windsor. CT
06095-0500.
David G. Lachapelle is the EPA Project Officer (see below).
The complete report, entitled "LowNOx Firing System for Tangentially Coal-Fired
Boilers: Applications Guideline Manual," (Order No. PB 85-246 973/AS; Cost:
$9.95, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Air and Energy Engineering Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC27711
• NOX emissions from tangential coal-
fired boilers may be reduced by up-
wards of 40 percent by a combination
of overfire air, flame retention, and
concentric firing. To achieve NOX
reductions with concentric firing it
may be necessary to fire in conjunc-
tion with overfire air to reduce the bulk
lower windbox (furnace) stoichiometry.
• Boiler performance has been shown to
be minimally affected with concentric
firing. The only appreciable effect has
been a reduction in the slag accumula-
tion rate and/or a drier more friable
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300
EPA/600/S8-85/022
0000329 PS
U S ENVIS PROTECTION AGENCY
------- |