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Page | 001 3.2.1.4.1
Trapped Vortex Combustion
3.2.1.4.1-1 Trapped Vortex Combustion
Benefi ts to IGCC Gas Turbines of Trapped Vortex Combustion
The Trapped Vortex Combustion (TVC) technology has the potential to:
• Burn a wide variety of medium and low-BTU gases including hydrogen-rich
gasifi ed coal, biomass products, and landfi ll gas;
• Operate in a low NOx, lean premixed mode combustor environment on
hydrogen-rich syngas to accommodate the high fl ame speed that is a
characteristic of these fuels;
• Achieve extremely low NOx emissions without the added expense of exhaust
gas after-treatment;
• Eliminate the costly requirement for high pressure diluent gas (nitrogen,
steam or carbon dioxide) for NOx emissions control;
• Accommodate more types of gas turbines for IGCC applications by decreasing
the mass fl ow through the turbine section;
• Improve the overall cycle effi ciency of the gas turbine by decreasing the
pressure drop through the combustor; and
• Extend the lean blowout limit offering greater turndown, (load following),
with improved combustion and process stability.
3.2.1.4.1-2 The Challenges of IGCC Gas Turbine
Combustion
Robert Charles Steele
Ramgen Power Systems
11808 Northup Way, Suite W-190
Bellevue, WA 98005
425-828-4919, ext. 288
rsteele@ramgen.com
The Integrated Gasifi cation Combined Cycle (IGCC) is emerging as a best
available technology to utilize low quality energy resources, such as coal or oil, and
meet emission limits not achievable by other conventional or advanced competing
technologies. However, the success of the IGCC in the energy sector requires
continuous enhancement in performance and reduction in capital costs. New, more
effi cient, gasifi cation technologies are in demonstration; hot gas cleanup is improving;
and gas turbines for IGCC applications are advancing in effi ciency, capability and
reliability.
Commercially available gas turbines have been developed for the use of
natural gas, (i.e. a methane-rich fuel with high calorifi c values of 800 to 1200 BTU/
scf). The gas turbines for these IGCC power plants have been adapted to burn syngas,
a hydrogen-rich fuel1 with low calorifi c values of 100-300 BTU/scf, but their design
features are not generally optimized for these fuel applications.
The gas turbine encounters two major changes when transitioning from
natural gas to syngas:
• For the same fuel heat input, the fuel mass fl ow is four to fi ve times greater
than for natural gas, due to the lower heating value.
• Premixed natural gas and air combustion systems have become common
place for controlling NOx emissions. These systems are not used with syngas
due to the high content of hydrogen and the potential for fl ashback of the
fl ame into the fuel injection system. Diffusion fl ame or “non-premixed”
combustors are used with syngas to control the NOx emissions by diluting
the syngas with nitrogen, steam or carbon dioxide. The diluent reduces the
fl ame temperature and consequently the formation of NOx
.
These two factors, greater fuel fl ow and the addition of diluent for NOx
emissions control, substantially increase the overall mass fl ow through the turbine.
This increase in fl ow creates backpressure to the compressor and can bring the engine
close to surge conditions. Some gas turbines such as the GE 9001 EC are able to
accommodate the increase in mass fl ow through the turbine expander. Unfortunately,
the majority of gas turbines are not able to accept the overcapacity to the turbine
expander.
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