Study On Mixing And Separation Characteristics Of Straw-Coal Binary Particle Mixtures

This study was motivated by entrained bed biomass-coal blends co-gasification process which was the study background.With FT4 Powder Rheometer, BT-1000 powder comprehensive characteristics analyzer, Scanning Electron Microscope and self-built experimental platform, the mixing and conveying properties of biomass-coal blends were investigated. The main contents are summarized as follows:The influence of straw moisture on the angle of internal friction of straw-coal binary granular systems was investigated theoretically and experimentally with a FT4 Powder Rheometer. The results show that the effect of straw moisture on angle of internal friction of blends is different from general cognition that angle of internal friction increases with the increase of moisture. The angle of internal friction is found to decrease first, then increase with increasing of straw moisture, and reaches the minimum value at the range of 8%-10% moisture content. In addition, an empirical model has been proposed to describe the quantitative relationship between angle of internal friction and straw moisture.Studied a new type of mixing method-pneumatic mixer. The new mixing method has simple equipment, dispenses with mechanical work and doesn’t cause grain abrasion. This study verified the feasibility of obtaining uniform straw-coal blends via pneumatic mixer. The result of further study of mixer design parameter shows that mixing quality of incline mixing is better than others feedstock angles. The effect of particle residence time are different between varieties of feedstock angles. As for incline pneumatic mixing, mixing quality increases with the increase of particle residence time. And with the increase of mixing ratio, all mixing groups’ mixing quality increase. In addition, an index(X) of pneumatic mixer has been proposed to comprehensively describe the mixing quality of different mixing parameters.With self-built conveying platform, online pressure detection system and piping sampler, the pneumatic conveying and separation properties of biomass-coal blends were investigated. The results show that conveying capacity is affected by delivery pressure which can’t be too high or too low, and 0.13MPa is best to enhance conveying capacity in this experiment. When delivery pressure is 0.13MPa, the conveying capacity of biomass-coal blends increases with the increasing mixing ratio of straw. Since the pressure in pipe is steady when conveying the biomass-coal blends, the straw-coal binary particle mixtures can be conveyed steadily by dense-phrase pneumatic conveying. Straw particles and coal particles separated along radial direction because of gravity and inertia force. However, when mixing ratio of straw was 10%, significant separation along axial direction of straw-coal binary particle mixtures didn’t take place.