An external bed type double-fluidized bed system for preventing boiler contamination includes a fluidized bed combustion furnace, a cyclone separator, a coal ash distributor and a fluidized bed pyrolysis furnace. The fluidized bed combustion furnace is connected with the coal ash distributor, the coal ash distributor is connected with the coal ash inlet on a side wall of the fluidized bed combustion furnace through a return feeder with which the coal ash outlet of the fluidized bed pyrolysis furnace is also connected through an external bed, and the return feeder is connected with the fluidized bed combustion furnace. A fuel coal is pyrolyzed in the fluidized bed pyrolysis furnace at a temperature to volatize alkali chlorides into a pyrolysis gas, thereby reducing the content of the alkali chlorides contained in the coal in the fluidized bed combustion furnace and relieving the contamination to a convective heat-absorbing surface.

Various aspects provide for a fluidized bed reactor comprising a container having a bed of bed solids and a splashgenerator configured to impart a directed momentum to a portion of the bed solids. A bedwall may separate the bed solids into first and second reaction zones, and the directed momentum may be used to transfer bed solids from one zone to the other. A return passage may provide for return of the transferred bed solids, providing for circulation between the zones. A compact circulating bubbling fluidized bed may be integrated with a reactor having first and second stages, each with its own fluidization gas and ambient. A multistage reactor may comprise a gaswall separating at least the gas phases above two different portions of the bed. A gaslock beneath the gaswall may provide reduced gas transport while allowing bed transport, reducing contamination.

Aspects provide for volatilizing a biomass-based fuel stream, removing undesirable components from the resulting volatiles stream, and combusting the resulting stream (e.g., in a kiln). Removal of particles, ash, and/or H2O from the volatiles stream improves its economic value and enhances the substitution of legacy (e.g., fossil) fuels with biomass-based fuels. Aspects may be particularly advantageous for upgrading otherwise low-quality biomass to a fuel specification sufficient for industrial implementation. A volatilization reactor may include a fluidized bed reactor, which may comprise multiple stages and/or a splashgenerator. A splashgenerator may impart directed momentum to a portion of the bed to increase bed transport via directed flow.

Various aspects provide for a multistage fluidized bed reactor, particularly comprising a volatilization stage and a combustion stage. The gas phases above the bed solids in the respective stages are separated by a wall. An opening (e.g., in the wall) provides for transport of the bed solids from the volatilization stage to the combustion stage. Active control of the gas pressure in the two stages may be used to control residence time. Various aspects provide for a fuel stream processing system having a pretreatment reactor, a combustion reactor, and optionally a condensation reactor. The condensation reactor receives a volatiles stream volatilized by the volatilization reactor. The combustion reactor receives a char stream resulting from the removal of the volatiles by the volatilization reactor.

Various aspects provide for a multistage fluidized bed reactor, particularly comprising a volatilization stage and a combustion stage. The gas phases above the bed solids in the respective stages are separated by a wall. An opening (e.g., in the wall) provides for transport of the bed solids from the volatilization stage to the combustion stage. Active control of the gas pressure in the two stages may be used to control residence time. Various aspects provide for a fuel stream processing system having a pretreatment reactor, a combustion reactor, and optionally a condensation reactor. The condensation reactor receives a volatiles stream volatilized by the volatilization reactor. The combustion reactor receives a char stream resulting from the removal of the volatiles by the volatilization reactor.

Various aspects provide for a multistage fluidized bed reactor, particularly comprising a volatilization stage and a combustion stage. The gas phases above the bed solids in the respective stages are separated by a wall. An opening (e.g., in the wall) provides for transport of the bed solids from the volatilization stage to the combustion stage. Active control of the gas pressure in the two stages may be used to control residence time. Various aspects provide for a fuel stream processing system having a pretreatment reactor, a combustion reactor, and optionally a condensation reactor. The condensation reactor receives a volatiles stream volatilized by the volatilization reactor. The combustion reactor receives a char stream resulting from the removal of the volatiles by the volatilization reactor.

Aspects provide for volatilizing a biomass-based fuel stream, removing undesirable components from the resulting volatiles stream, and combusting the resulting stream (e.g., in a kiln). Removal of particles, ash, and/or H2O from the volatiles stream improves its economic value and enhances the substitution of legacy (e.g., fossil) fuels with biomass-based fuels. Aspects may be particularly advantageous for upgrading otherwise low-quality biomass to a fuel specification sufficient for industrial implementation. A volatilization reactor may include a fluidized bed reactor, which may comprise multiple stages and/or a splashgenerator. A splashgenerator may impart directed momentum to a portion of the bed to increase bed transport via directed flow.

A dual-bed system for preventing a boiler heating surface from being contaminated comprises 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; the inlet end of the coal ash distributor; the two outlets of the coal ash distributor are respectively connected with the inlet of the return feeder and 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 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.