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Cold model testing of a re-circulating fluidised bed reactor working in alternate aeration— fuel burning cycles for chemical looping



A re-circulating fluidised bed (RCFB) reactor is proposed here for gaseous fuel combustion using chemical-looping combustion (CLC). A single RCFB reactor was operated in alternate oxidation and reduction cycles for simulating the interconnected reactors arrangement for CLC. For this, a Perspex made transparent, concentric, semicircular cold model of RCFB reactor was used with three grades of Indian Standard sand. Operational parameters like bed inventory, pressure drop, particle size, suspension density, solid circulation rate, bed voidage and fluidisation gas velocity were studied to how they affect the performance of the RCFB reactor. The solid circulation rate has been found to increase with the increase in the bed inventory. Proper solid circulation rate is very much required for proper heat and mass transfer in an interconnected fluidised bed reactors system. The bed voidage is observed to be high during the aeration cycle and low during the reduction cycle. A high bed voidage during the oxidation cycle is appropriate for the fast oxidation reaction of the metal oxides. However, a low bed voidage is required for proper heat transfer for an endothermic reduction reaction in the fuel reactor. Suspension density in the downcomer of the RCFB reactor has been found to be increasing with bed inventory for both the oxidation and reduction cycles, which is good for the bed-to-wall heat transfer. A good observed solid circulation rate, operating voidage and suspension density add to the capability of RCFB to run CLC.

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