Disposal of Low Calorific Value Waste Gas

The utilisation of waste methane off gases from the ventilation of mines and water supplies was investigated. Waste gases with methane in air contents from 0.5–3% were investigated using a staged combustion system with a lean well-mixed radial swirier as a main burner with the secondary fuel and the waste gas as the premixed primary fuel carrying fuel and oxygen to the main burner. The radial swirl burner had low NOx well mixed combustion characteristics, using radial swirl vane passage fuel injection. The tests were carried out on a 76mm outlet diameter swirler with a dump expansion into a 140mm diameter combustor. The test flow conditions were at an isothermal Mach number of 0.02 at 600K inlet temperature. These conditions are representative of gas turbine combustion applications as well as process burner operating conditions. The results showed that the premixed waste gas promoted the combustion stability of the main burner. This enabled leaner overall combustion to be sustained, with reduced NOx emissions. The waste gas was completely burned with very low NOx, HC and CO emissions. All the energy content of the waste gases was recovered for all methane contents of the waste gases.