External Bed Type Double-Fluidized Bed System for Preventing Boiler Contamination

An external bed type double-fluidized bed system for preventing boiler contamination, comprising a fluidized bed combustion furnace (4), a cyclone separator (5), a coal ash distributor (6) and a fluidized bed pyrolysis furnace (8), wherein the outlet on the upper end of a side wall of the fluidized bed combustion furnace (4) is connected with the inlet of the cyclone separator (5), the cyclone separator (5) separates the high-temperature coal ash from the fluidized bed combustion furnace (4);

• the outlet on the bottom of the cyclone separator (5) is connected with the inlet of the coal ash distributor (6) to feed the separated high-temperature coal ash into the coal ash distributor (6), a smoke outlet is provided on the top of the cyclone separator (5);
• a first coal ash outlet and a second coal ash outlet are provided on the coal ash distributor (6), the first coal ash outlet is connected with the coal ash inlet on a side wall of the fluidized bed combustion furnace (4) through a return feeder (13), and the second coal ash outlet is connected with the coal ash inlet on a side wall of the fluidized bed pyrolysis furnace (8);
• a pyrolysis gas outlet is provided on the upper end of a side wall of the fluidized bed pyrolysis furnace (8), a raw coal inlet is provided in the middle or on the lower part of a side wall of the fluidized bed pyrolysis furnace (8);
• a coke-coal ash mixture outlet is provided on the lower end of a side wall of the fluidized bed pyrolysis furnace (8), the coke-coal ash mixture outlet is connected with the return feeder (13) through an external bed (15) and further connected with the coal ash inlet of the fluidized bed combustion furnace (4) through the return feeder (13).