High temperature desulphurization by fine limestone during staged fluidized-bed combustion

This paper reviews the SO2 emission from a 0.3 m(2) stainless-steel fluidiz ed-bed combustor. Fine coal was premixed with fine limestone and fed pneuma tically under the bed. The SO2 emission was found to depend largely on air staging ratio and bed temperature, which agrees with previous observations. The SO2 emission observed in sorbent-free tests (reported earlier by Khan and Gibbs, 1995) was found to be proportional to the sulphur content of the fuel when limestone was added, the sulphur capture at a fixed Ca/S molar r atio was dependent on oxygen stoichiometry ana bed temperature. Finely size d limestone enhanced the effectivity of the sorbent at low bed temperature and air staging ratio. During staged combustion, the combustion efficiency depended largely on primary air to Coal ratio. Around 90% combustion effici ency was observed at 1 m/s fluidizing velocity which was reduced when fluid izing velocity was increased to 1.5 and 2 m/s. This reduction is due to inc reased elutriation of finer coal particles from the combustor.