Modeling of the Low Grade Coal Combustion in a Fluidized Bed Reactor Using Aspen Plus

Abstract

With ever-increasing usage of biomass to curb environmental pollution, it is imperative to develop new insights into coal combustion processes, for efficient and optimal usage. Many process models have been developed for combustion process, including fixed and fluidized bed combustion for different types of coal; however, they are designed for specific process and lack generality. More recently, Aspen Plus has introduced new tools, and particularly featured a built-in unit operation model, to design fluidized bed processes. Herein, we comprehensively apply the novel tool to analyze the low grade coal combustion with varying process conditions such as: temperatures, fuel/air ratio, pressure, and other. The model developed in Aspen Plus was validated with our experimental data performed in a pilot-scale fluidized bed combustor. The fuel type of combustion used in the experiments is Ekibastuz coal (a type of low-grade Kazakhstan coal). The data from experiments were used to fine-tune the Aspen Plus model. Eventually, results indicate accuracy of the model in predicting the gas compositions and the reactor hydrodynamics. Furthermore, sensitivity analyses were performed in order to analyze the effect of temperature and feed flow rate on the combustion efficiency and flue-gas compositions. Taken together, the model developed can be ubiquitously used for process design of fluidized bed reactor co-combustion of coal and biomass.