Combustion of coal gas fuels in a staged combustor

Gaseous fuels produced from coal resources have been considered for use in industrial gas turbines. Such fuels generally have heating values much lower than the typical gaseous fuel, natural gas; the low heating value could result in unstable or inefficient combustion. Additionally, coal gas fuels may contain ammonia which, if oxidized in an uncontrolled manner, could result in unacceptable NO /SUB x/ exhaust emission levels. Previous investigations have indicated that staged, rich-lean combustion represents a desirable approach to achieve stable, efficient, low NO /SUB x/ emission operation for coal-derived liquid fuels containing up to 0.8-wt pct nitrogen. An experimental program has been conducted to determine whether this fuel tolerance can be extended to include coalderived gaseous fuels. The results of tests with three nitrogen-free fuels having heating values of 100, 250, and 350 Btu/scf and a 250 Btu/scf heating value doped to contain 0.7 pct ammonia are presented.