Optimization of particle size distribution in circulating fluidized beds via adjustment of crushers and tuning parameters of two-toothed roll crusher

Abstract

Properties of coal gangue feed, especially its particle size distribution (PSD) and variable hardness, result in considerable impacts on both the efficiencies of the circulating fluidized bed (CFB) boiler and wastage of crushers. These two aspects are addressed in this study. First, the Aspen Plus software was used to optimize the coal gangue crushing system for the CFB boiler; it facilitated in predicting the PSD in with excellent accuracy, and optimized the PSD of the crushing system for the CFB. The optimized PSD for the CFB was approximately 80% within 2.3–7.5 mm. The applied PSD of coal feeding in the CFB improved the combustion efficiency of the CFB significantly. Furthermore, the two-toothed roll crusher was found to be the most vulnerable part in the optimized crushing system. Next, the two-toothed roll crusher was optimized based on the framework proposed by the Whiten model. The reasonable rolls gap and teeth length should be 75 mm and 23 mm, respectively. Further, a physical model of a two-toothed roll crusher was established to obtain the optimized roll diameter; it was later found to be >660 mm. The results were applied in optimizing an industrial-scale crushing system and two-toothed roll crusher of a coal gangue-fired power plant. Investigations demonstrated that the PSD can improve the combustion efficiencies of the CFB significantly by 3%, as well as a 3× extension of the original service life of the two-toothed roll crusher.