Retrofit on In-furnace Desulfurization System of CFB Boilers

In order to satisfy relevant pollutant emission standards,retrofit on the in-furnace desulfurization system of 3×460 t/h circulating fluidized bed(CFB) boilers was carried out,during which the limestone conveying method was changed from the secondary into the primary type.In the newly retrofitted system,when limestone enters into two ash return legs,it mixes with high temperature re-circulating ash and then goes into furnace together with the ash.The in-furnace desulfurization system can now meet relevant pollutant emission requirements after proper choosing of limestone category and reasonable retrofit on the system itself.Statistics on one-month data of boiler operation show that under the conditions of 2.21% sulfur content in inlet coal as received basis,and an average calculated SO_2 emission of 5 557 mg/m~3,while with an average of 10.08 t/h limestone supplied(limestone purity 95%,Ca/S ratio 2.56),the actual average SO_2 emission can then be reduced to 121.9 mg/m~3,i.e.the desulfurization rate reaches 97.8%.