FIELD: power engineering.
SUBSTANCE: circulating fluidised bed boiler sulphur dioxide emission reducing method includes the following stages: first flow consisting of sulphur-containing carbon fuel is supplied to boiler furnace; second flow consisting of calcium carbonate is supplied to the furnace with such velocity relative to the first flow that molar ratio of calcium in the second flow to sulphur in the first flow (molar ratio Ca/S) is at least approximately 0.6, and with velocity low enough to provide the degree of additional sulphur content reduction is at least approximately 0.355; fuel is burnt so that sulphur is oxidised thus forming sulphur dioxide, and slags are formed in the furnace; calcium carbonate is burnt and calcium oxide is formed in the furnace, and calcium oxide is used for sulphur dioxide sulphation thus forming calcium sulphate; flue gas and particles carried over with flue gas are discharged from the furnace; particles are separated from flue gas by using hot circuit separator, and then separated particles return to the furnace; slag is removed from boiler; and sulphur content in flue gas is additionally reduced at the stage of sulphur content reduction downstream the furnace. Additional reduction of sulphur content is performed by means of one of dry, semidry and wet methods of sulphur content reduction. The method also comprises the stage of improving efficiency of calcium carbonate use in the furnace, which is implemented in such a way that approximately more than 60% of calcium carbonate is used for sulphur dioxide sulphation thus forming calcium sulphate. Stage of improving efficiency of calcium carbonate use includes slag recirculation to furnace. Stage of improving efficiency of calcium carbonate use includes restriction of mean diameter of calcium carbonate particles supplied to furnace to approximately less than 200 microns. Stage of improving the efficiency of calcium carbonate use includes hot circuit separator configuring so that separation efficiency is at least approximately 99.9% of particles with diameter of 200 microns.
EFFECT: invention allows reducing sulphur dioxide emission from circulating fluidised bed boiler.
12 cl, 2 dwg
