METHOD OF AND APPARATUS FOR COMBUSTING SULFUROUS FUEL IN A CIRCULATING FLUIDIZED BED BOILER

摘要

Sulfurous fuel and CaCO3-containing sorbent are combusted in a furnace of a circulating fluidized bed boiler. A dry circulating fluidized bed scrubber includes a reactor with water and Ca(OH)2 feeds for converting SO2 in the exhaust gas to CaSO3 and CaSO4 and a dust separator in gas flow connection with the reactor. A discharge removes CaO-containing bottom ash from the furnace. A classifier classifies a portion of the removed CaO-containing bottom ash into coarse and finer portions. A fine ash channel conveys some of the finer bottom ash portion from the classifier to a grinder. A ground ash channel conveys some of the ground bottom ash portion from the grinder to a hydrator to hydrate CaO in the ash to Ca(OH)2. A hydrated ash channel conveys some of the Ca(OH)2 from the hydrator to the dry circulating fluidized bed scrubber as a sorbent.

主权项

1. A method of combusting sulfurous fuel in a circulating fluidized bed boiler, the method comprising the steps of:
(a) feeding sulfurous fuel to a furnace of the boiler, combusting the fuel, and generating SO2-containing exhaust gas; (b) feeding CaCO3-containing sorbent to the furnace for converting the CaCO3 to CaO and utilizing a portion of the CaO in the furnace to convert a portion of the SO2 to CaSO4; (c) conveying the exhaust gas along an exhaust gas channel from the furnace to a dry circulating fluidized bed scrubber comprising a reactor having feeds for feeding water and Ca(OH)2 for converting SO2 in the exhaust gas to CaSO3 and CaSO4, and a dust separator in gas flow connection with the reactor for separating particulate matter from the exhaust gas; (d) removing CaO-containing bottom ash from the furnace; (e) classifying at least a portion of the removed CaO-containing bottom ash into a coarse bottom ash portion and a finer bottom ash portion in a first stage classifier, wherein the coarse bottom ash portion consists of particles having a particle size larger than a first predetermined limit; (f) removing the coarse bottom ash portion from the boiler as a first combustion product; (g) conveying the finer bottom ash portion from the first stage classifier to a second stage classifier to classify the finer bottom ash portion to a finest bottom ash portion and a middle size bottom ash portion; (h) removing the finest bottom ash portion as a second combustion product; (i) conveying the middle size bottom ash portion to a grinder so as to grind the bottom ash portion to have a median particle size of a second predetermined limit; (j) conveying at least a portion of the ground bottom ash portion from the grinder to a hydrator so as to hydrate CaO in the ground bottom ash portion with a controlled amount of water or steam to Ca(OH)2; and (k) conveying at least a portion of the CA(OH)2 from the hydrator to the dry circulating fluidized bed scrubber as a sorbent.