Superiority of Re-circulating Fluidized Bed Reactor Over Existing Reactor Arrangements for Chemical Looping Combustion—A Review

Chemical looping combustion (CLC) is an oxy-combustion CO₂ capture technique. In CLC, the fossil fuels combustion is carried out in two parts using metal oxides. First, the metal oxides are oxidized with air. Second, the metal oxides are reduced using the fuel. To fulfill this criterion of combustion for CLC, some researchers have used interconnected reactors arrangements and some have used single reactor. In interconnected reactors arrangement, metal oxides oxidation is carried out in one reactor and the reduction in other. However, in single reactor arrangement, the oxidation and reduction of metal oxide particles are carried out in cycles. The existing reactors arrangements suffer from the problems of high bed particle attrition, short residence time of the bed material/metal oxides in the air reactor (fast fluidized bed), and generation of fine particles, transfer of bed material from one reactor to another, complex loop-seal operation, heat losses during the transfer of bed material from one reactor to another and cluster formation. Re-circulating fluidized Bed (RCFB) reactor is proposed, here, to overcome some of the problems associated with the existing reactor arrangements. RCFB reactor has a concentric pipe arrangement. The inner pipe is known as riser and the outer pipe is known as downcomer.