Modeling of Flow Behavior at Downer and Riser in Triple Bed Circulating Fluidized Bed Using Equivalent Circuit

To obtain high power generation efficiency, an advanced integrated coal gasification combined cycle (AIGCC) based on exergy recuperation concept that recycles waste heat from gas turbine to steam gasification of coal is being developed in our laboratory. This system uses a triple bed circulating fluidized bed for coal gasification. The proposed triple bed circulating fluidized bed is a very complex system. For stable operation and to gain control over the system, a model of the flow behaviour in the circulating fluidized bed is necessary. A novel method for analyzing the systems using a simple model of the flow behaviour inside of circulating fluidized bed is proposed in this research. We found the analogy between flow behaviour of fluidized bed and equivalent circuit with correlations of pressure to voltage, solid mass flux to electric current and hydraulic resistance to electric resistance. Based on these analogies, flow behaviour in the fluidized bed can be modelled simply. By using this model, the dynamic characteristics of the pressure response at downer and riser when the sold mass flux has been changed were examined. According to these investigations, this proposed method proved to be a promising method for analyzing the systems when designing a circulating fluidized bed.