Design and Evaluation of an LCV Combustor for the Volvo VT4400 Industrial Gas Turbine

Abstract

A combustor has been developed to burn a low calorific gas mixture reflecting a composition typically available from a bio-mass gasification plant. This reference composition contained (by volume) 11,7% H2, 15,4% CO, 5,9% CH4, 13,3% CO2, 46,7% N2 and 7% H2O. The combustor was subsequently tested with gas compositions having varying amounts of NH3, H2O and CO/H2 content. It was also tested with three compositions rich in CO, but lacking H2; these are typically available from blast furnace, or other metallurgical processes. The combustor is designed to be stoichiometric/lean and is suitable for up to 2,1 MW thermal input. The flame tube walls are predominantly effusion-cooled. A natural gas pilot is provided for ignition and operation up to 20% load. UHC emissions were only seen when operating on the reference LCV composition below 40% load. CO emissions were less than 20 ppmv between 40% and 100% load regardless of gas composition tested. Combined thermal and prompt NOX, when operating without ammonia addition, was found to be less than 9 ppmv at full load for the reference gas. When ammonia was introduced to the gas composition the molar ammonia conversion to NOX was approximately 60% for 2500 ppmv NH3 fuel concentration. This was seen to increase to 90% as the ammonia concentration was reduced to 500 ppmv. The combustor showed acceptable temperatures while operating on the reference composition. The compositions having higher net calorific value produced excessive flame tube temperatures. The combustor had excellent combustion stability regardless of gas composition and operating condition.