Abstract: As a basic equipment for the high-quality utilization of biomass energy, the design of dust suppression structure plays a critical role in the safe and environment friendly operation of straw pulverizer. In this study, a new type of pulverizer with variable diameter was designed. In this pulverizer, the rotating rotor blade and shell with variable diameter help to produce a low pressure zone, resulting in an inward pressure difference at the inlet. Therefore, the escape resistance of the particles is increased and the dust is suppressed. Firstly, the pressure difference of the particle escape from diameter-variable pulverizer was obtained by theoretical analysis. Secondly, the MRF (moving reference frame) method and the DPM (discrete phase model) were used to simulate the gas-solid two-phase flow in the pulverizer. The results show that the number of the particles escaping from inlet in diameter-variable pulverizer is reduced about 30% compared with that of the previous pulverizer, which means the dust suppression effect is remarkable. Then, the working parameters of pulverizer with variable diameter were further optimized and analyzed within a rotating speed range of （500~6000）r/min, particle size of （1~5000）μm, and the variable diameter ratio of 1~1.2. Finally, the optimized pulverizer with dust suppression performance of 57% improved is obtained. This work provides a theoretical basis for the structure design as well as safe and environment friendly operation of straw pulverizer.

Key words: straw pulverizer, variable-diameter structure, gas-solid two-phase flow, dust suppression