MENETELMÄ RIKIN OKSIDIEN SITOMISEKSI HAPPIPOLTTOON TARKOITETUN KIERTOLEIJUPETIKATTILAN SAVUKAASUISTA

摘要

A method of reducing sulfur dioxide emissions of an oxyfuel combustion circulating fluidized bed boiler, comprising the steps of feeding a first stream comprising sulfur-containing carbonaceous fuel to a furnace of the boiler; feeding a second stream comprising CaCO3 to the furnace;feeding a stream of substantially pure oxygen to the furnace so as to combust the fuel, whereby SO2 and SO3 are formed and flue gas consisting mainly of carbon dioxide and water is produced;discharging the flue gas from the furnace to an upper flue gas channel; recycling a first portion of the flue gas from the upper flue gaschannel via a recycling channel back to the furnace, and discharging a second portion of the flue gas from the upper flue gaschannel via a discharge channel, wherein the second stream is fed at such a rate relative to the first stream that the molar ratio of calcium in the second stream to sulfur in the first stream (the Ca/S molar ratio) is between about 0.02and about 0.5 so as to capture atleast a portion of the formed SO3 in the furnace or in the upper flue gas channel to CaSO4.