Gas emissions from the PFB combustion of solid fuels

The emission properties are reported for three solid fuels in pressurised fluidised-bed (PFB) combustion. The work was carried out in Helsinki University of Technology with a 130 kW PFBC test rig. The operating pressure ranged from 0.5 to 1.0 MPa and the operating temperature from 800 to 900-degrees-C. Excess air ranged from 10 to 55%. This paper presents results of sulphur-containing (SO2, SO3), nitrogen-containing (NO, NO2, N2O) and alkali metal vapour emissions, and their dependence on operating parameters. Emissions of nitrogen oxide were dependent primarily on the amounts of combustion air: with reduced air:fuel ratio, the NO(x) emissions fell. Nitrous oxide emissions were effectively reduced with higher reactor temperatures. The extent of sulphur removal depended on the feedstock used, on the Ca:S molar ratio and on the properties of the limestone. Over 90% sulphur capture was reached with bituminous coal by the use of limestone with d50 of 0.23 mm. This paper also presents the results of alkali vapour-phase measurements.