The alternative fuels, such as biomass, municipal wastes, and underground coal gasification gas, become attractive to the power plants as renewable energy sources or economical fuels. However, the alternative fuels usually have much lower heating value and different chemical compositions from those of coal and natural gas. Firing these alternative fuels in the boilers that are originally designed for coal firing or natural gas firing may cause unexpected boiler operating issues and/or thermal performance degradation. A careful evaluation study is often required prior to implementation. This paper presents the results of a study that evaluated the feasibility of using an underground coal gasification gas as a reburn fuel. The evaluation was done on Eskom’s Majuba Unit 5, a 710 MWe opposed wall-fired boiler, located in South Africa. The study utilized heat transfer analysis and computational fluid dynamics models to (1) evaluate the impacts of firing low calorific fuel on boiler efficiency and the boiler auxiliary system performance, (2) develop a conceptual gas reburn injection system, and (3) evaluate the impacts of gas reburn on the boiler thermal performance and boiler NOx emissions. The results indicate that the underground coal gasification gas can be an effective reburn fuel for the Majuba boiler with upgrades on the auxiliary systems.

1.
Department of Energy and Environmental Protection Agency
, 2000, “
Carbon Dioxide Emissions From the Generation of Electric Power in the United States
,” http://www.eia.doe.gov/cneaf/electricity/page/co2_report/co2emiss.pdfhttp://www.eia.doe.gov/cneaf/electricity/page/co2_report/co2emiss.pdf
2.
Doerell
,
P. E.
, 2001, “
An Untapped Energy Source: Underground Coal Gasification
,”
World Energy Council 18th Congress
, Buenos Aires, Oct.
3.
van Loo
,
S.
, 2002, “
Biomass Co-Firing With Coal
,” presented at
Accelerating the Deployment of Renewable Energy in the Baltic’s Riga, Latvia
, Oct. 10–11.
4.
Moyeda
,
D.
, 2004, “
Experience With Reburn for NOx Emissions Control
,”
DOE NETL Conference on Reburning for NOx Control
, Morgantown, WV.
5.
Swanson
,
L. W.
, 2006, “
Impacts of Power River Basin Coal Firing on Boiler Thermal and Emissions Performance
,”
ASME IMECE Presentation
.
6.
Xu
,
G.
,
Yu
,
G.
,
Zhou
,
W.
, and
Swanson
,
L. W.
, 2009, “
Fuel Flexible Biomass Reburn Technology
,”
Proceedings of the 2009 ASME Summer Heat Transfer Conference
, San Francisco, CA, Jul. 19–23.
7.
Zhou
,
W.
,
Moyeda
,
D.
,
Payne
,
R.
,
Swanson
,
L.
, and
Nguyen
,
Q.
, 2005, “
CFD Investigation of Layered NOx Control Strategies for Coal Combustion in a Tangential-Fired Boiler
,”
ASME IMECE Presentation
.
8.
Folsom
,
B. A.
,
Engelhardt
,
D. A.
,
Payne
,
R.
,
Sommers
,
T. M.
,
Chang
,
S. S.
,
O'Dea
,
D. T.
,
Riggs
,
L. E.
, and
Rock
,
R. G.
, 1999, “
Reburn NOx Control
,” Pollution online, http://www.pollutiononline.com/article.mvc/Reburn-NOx-Control-0001?VNETCOOKIE=NOhttp://www.pollutiononline.com/article.mvc/Reburn-NOx-Control-0001?VNETCOOKIE=NO
9.
Maly
,
P. M.
,
Zamansky
,
V. M.
,
Ho
,
L.
, and
Payne
,
R.
, 1999, “
Alternative Fuel Reburning
,”
ASME J. Fuel Cell Sci. Technol.
1550-624X,
78
(
3
), pp.
327
334
.
10.
Zamansky
,
V. M.
,
Maly
,
P. M.
,
Sheldon
,
M. S.
, and
Seeker
,
W. R.
, 1998, “
Waste Products Can Serve For Effective NOx Control
,”
The 1998 Spring Meeting of the Western States Section of the Combustion Institute
, University of California, Berkeley, Mar. 23–24.
11.
FLUENT User’s Guide, ANSYS Inc.
12.
Zhou
,
W.
,
Moyeda
,
D.
,
Payne
,
R.
, and
Nguyen
,
Q.
, 2009, “
Comprehensive Process Design Study for Layered Low NOx Control in a Tangentially Coal Fired Boiler
,”
AIChE J.
0001-1541,
13
(
6
), pp.
1053
1070
.
13.
Zhou
,
W.
,
Moyeda
,
D.
,
Payne
,
R.
, and
Berge
,
M.
, 2009, “Application of Numerical Simulation and Full Scale Testing for Understanding Low NOx Burner Emissions,” Combustion Modeling Cofiring and NOx Control, ASME FACT Vol. 17, pp. 87–94.
14.
Li
,
B. W.
,
Wu
,
K. T.
,
Moyeda
,
D. K.
, and
Payne
,
R.
, 1993, “
Use of Computer Models for Reburning/Cofiring Boiler Performance Evaluations
,” FACT (Combustion Modeling, Cofiring and NOx Control, Vol.
17
).
15.
Stultz
,
S. C.
, and
Kitto
,
J. B.
,
Steam: Its Generation and Use
,
40th ed.
(
Babcock and Wilcox
,
Barberton, Ohio
, 1992).
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