Dual-bed system for preventing boiler heating surface from being contaminated

A dual-bed system for preventing a boiler heating surface from being contaminated comprising:

• a fluidized bed, a cyclone separator, a coal ash distributor, an ash-coal mixer, a lower pyrolysis bed, a return feeder and a cleaner, wherein
• the cyclone separator is connected with the upper lateral side of the fluidized bed so that the high-temperature coal ash from the fluidized bed enters the cyclone separator, the outlet end of the cyclone separator is connected with the inlet end of the coal ash distributor;
• the coal ash distributor is provided with two outlets one of which is connected with the inlet of the return feeder and the other one of which is connected with the inlet of the ash-coal mixer;
• the outlet of the ash-coal mixer is connected with the inlet of the lower pyrolysis bed;
• the lower pyrolysis bed is provided with two outlets one of which is connected with the inlet of the return feeder and the other one of which is connected with the inlet of the cleaner;
• the return feeder close to the lower lateral side of the fluidized bed is connected with the inlet on the lower lateral side of the fluidized bed;
• and
• the outlet of the cleaner is connected with the inlet on the lower lateral side of the fluidized bed.