A method of preventing blockage of circulating bed material in a circulating fluidized bed reactor includes collecting a continuously flowing bed of solid particles in a gas lock in a return leg of a reactor, measuring gas lock bed pressure values within the bed of the particles, generating a gas lock bed height indication signal on the basis of measured gas lock bed pressure values. A definition stage includes defining and storing to a control system a range of normal gas lock bed height indication signals, formed in normal circulation flow conditions, as a function of the reactor load, and defining and storing to the digital control system a reactor load dependent alarm criterion. The method includes comparing a current gas lock bed height indication signal with the reactor load dependent alarm criterion, and decreasing the reactor load if the current indication signal fulfils the reactor load dependent alarm criterion.

A circulating fluidized bed boiler, comprising a furnace, a loopseal, and a loopseal heat exchanger arranged in the loopseal. The loopseal heat exchanger comprises at least an inlet chamber, a bypass chamber, and a first heat exchange chamber, heat exchanger pipes arranged in the first heat exchange chamber, and a primary particle outlet for letting out bed material from the first heat exchange chamber. The primary particle outlet has at least a first part and a second part separated from each other by a barrier element in such a way that the first part of the primary particle outlet has a first height and a first width, wherein a ratio of the first height to the first width is less than 0.5 or more than 2. Use of the circulating fluidized bed boiler such that fluidizing gas and bed material are let out from the first heat exchange chamber via the primary particle outlet.

A circulating fluidized bed (CFB) boiler has one or more bubbling fluidized bed enclosures containing heating surfaces and located within a lower portion of the CFB boiler to provide an in-bed heat exchanger (IBHX). Solids in the bubbling fluidized bed are maintained in a slow bubbling fluidized bed state by separately controlled fluidization gas supplies. The beds feature open bottom distribution grids with hoppers disposed below to collect solids. The enclosure defining the IBHX is supported from structures below the grids and the enclosure can be supported from the hoppers.

Energy is generated from cellulosic biofuel waste streams, specifically a lignin filter cake and a waste syrup, by combusting these waste products in a fluidized bed combustor under specified conditions. The heat and steam generated can be used to generate electricity and/or in cellulosic biofuel production processes.

A reactor system and control method. The method includes feeding solid fuel and oxygen containing gas to a first fluidized bed reactor to form a fluidized bed of particles and combusting a first portion of the fuel in the bed with the oxygen containing gas to generate hot bed particles and a first stream of hot flue gas, conveying the first stream to the flue gas channel, transferring hot bed particles including a second portion of the solid fuel at a predetermined hot particles transfer rate from the first reactor to a second fluidized bed reactor, feeding fluidizing gas to the second reactor to form a second fluidized bed, and transferring bed particles from the second reactor to the first. The method includes first and second operation modes. In the first, the fluidizing gas is oxygen containing gas and, in the second, the gas includes steam, CO.sub.2, or inert gas.

A circulating fluidized bed boiler, comprising a furnace, a loopseal, and a loopseal heat exchanger arranged in the loopseal. The loopseal heat exchanger comprises at least an inlet chamber, a bypass chamber, and a first heat exchange chamber, heat exchanger pipes arranged in the first heat exchange chamber, and a primary particle outlet for letting out bed material from the first heat exchange chamber. The primary particle outlet has at least a first part and a second part separated from each other by a barrier element in such a way that the first part of the primary particle outlet has a first height and a first width, wherein a ratio of the first height to the first width is less than 0.5 or more than 2. Use of the circulating fluidized bed boiler such that fluidizing gas and bed material are let out from the first heat exchange chamber via the primary particle outlet.

The invention relates to a system for recycling fluidized bed boiler bed material, comprising: a. a bottom ash removal device for removing bed material from a fluidized bed boiler, b. a mechanical classifier (10) comprising a mesh size from 200 to 1,000 μm designed to separate a coarse and a fine particle size fraction, c. a magnetic separator (12) designed to magnetically classify the fine particle fraction from the mechanical classifier, d. a device for recirculating the magnetic particle fraction into the boiler. The invention allows effective recirculation and reuse of ilmenite bed material.

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.