Excellent early results
Between March 2005 and March 2006, CES conducted the durability and performance tests that the CEC program mandated. During this period, the combustor was started more than 300 times and accumulated 1,500 hours of operation. Individual test runs ranged in duration from less than 1 minute to about 105 hours. The plant's output was varied from 20% to 88% of its full rating. Power was exported to the grid at levels from 0.5 MW to 2.7 MW during 141 runs encompassing 1,243 hours of combustor operation. The combustor operated continuously for longer than 8 hours during 43 of these runs, and for longer than 24 hours during 11 runs. During the tests, the plant was fueled with natural gas, simulated syngas, and liquid fuels containing sulfur.
At 50% power, measured CO emissions ranged from 0.02 to 0.31 lb/mmBtu over a wide range of gas generator system operating conditions. (For comparison purposes, a typical gas turbine's CO emissions range from 5 to 80 ppmv, corrected to 15% O2.) CO emissions tended to increase when the gas generator was operated at higher power levels. At 50% power, measured NOx emissions ranged from 0.003 to 0.019 lb/mmBtu, corrected to 15% O2.
These measured CO and NOx emissions levels are considerably lower than those of state-of-the-art combined-cycle power plants fueled by natural gas and using selective catalytic reduction for NOx control. CES has developed strategies for further lowering emissions of CO and NOx from the first-generation gas generator and will experimentally evaluate them in future testing efforts. Unburned hydrocarbon emissions for two different operating stoichiometries were 0.9 ppmv and 1.8 ppmv, corrected to 15% O2. These emissions are only of interest if the noncondensible gases are vented to the atmosphere, but in most commercial installations, these emissions would be sequestered with the carbon dioxide.
In March 2006, the CEC notified CES that the program objectives had been met and that no further testing was required by the project. Around this time, representatives of two major insurers of power plant equipment toured the Kimberlina plant and reviewed the combustor's operating records (the number of starts, operating hours, shutdown circumstances, maintenance experience, and inspection findings). Following their inspection and review, the insurers declared that the combustor is insurable, and coverage is now in place. CES considers the insurability of the combustor essential to its commercial deployment.
With the conclusion of the CEC-sponsored durability evaluation, CES began configuring the Kimberlina facility for testing the performance and reliability of the oxy-combustor when burning lower-cost, lower-Btu fuels such as coal-derived syngas.
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