| Under the background of co-gasification of biomass and coal in an entrained flow gasifier, the present work focused on the pretreatment of biomass material and the research on the characteristics of biomass and coal blends. The shape and size distribution of biomass particles were studied firstly, and the 2 dimension finite stochastic breakup model of biomass particle was proposed based on the anisotropy of biomass material in organizational structure. There are great differences between biomass particles and coal particles in shape, density, and size, which would influence the packing, compressibility, friction, mixing, and fluidizing of the blends. Thus the flow ability and the behavior in the hopper of biomass and coal blends were also studied. The main contents are as follow:(1) Several typical biomass materials (pine, chinar, camphor tree, metasequoia, rice straw, reed, and beanstalk) were chosen. After being ground, the shape of biomass particles was studied with the method of statistics and fractal, and meanwhile, the particle size distribution was also researched with the sieving method. Results showed that the organizational structure of biomass materials is anisotropic, which induces the irregular shape of biomass particles. The stronger the anisotropy, the more needle-shaped the biomass particles. And the anisotropy decrease with particle size. It is also found that the fractal dimension of biomass particles increase with the roundness decreasing, just as C=-0.61D+1.20. The cumulative mass fraction of biomass particles has a linear relationship with particle size, w= 65.49d-16.37, and a good consistency could be obtained for different kinds of biomass.(2) The 2 dimension finite stochastic breakup model of biomass particle (2D-FSBM) was proposed based on the anisotropy of biomass material, which describes the breakup process of biomass particles. The parameters of the model were also determined by the experimental data. Comparing the experimental and simulation results, it was found that 2D-FSBM could predict the results after that the relative parameters were confirmed.(3) The characteristics of biomass and coal blends were studied, and the main object is to research the effects of content and size of biomass particle on the flow ability of the blends. Results showed that the Haunser ratio of rice straw particles is lower than coal, whereas the friction angle is much higher. When the content of rice straw is lower, the effect of rice straw particle size on the bulk density of the blends is weak, but become stronger with the increase of rice straw content. Hausner ratio is not a good indicator to the flow ability of the blends due to the segregation induced by the difference of size and density. The addition of rice straw leads to the increase of the angle of internal friction and angle of repose of the blends. When the content of rice straw is lower, the increment of tangent of friction angle (φ) has something with the rice straw content (w) and particle shape (A), just as follow: tanφ1-tanφ1,c=0.209w(A-1.87) tanα-tanαc=0.213w(A-1.87) in which,α=(φ1+φR)/2.(4) The effects of particle size, content, storage time on the flow rate of the blends from hopper under gravity were studied. Results showed that rice straw could enhance the flow rate when its content is lower, but it will act contrarily when the content is too high. Both the increase of coal particle size and decrease of rice straw size are positive to the flow of the blend when the content of rice straw is lower. But the effect of coal particle size becomes weaker with the increase of rice straw content. The flow rate of the blends in the cone of the hopper decrease with the increase of rice straw content. In addition, the storage time influences the flow ability of the blends, which is more serious in the cone of hopper.(5) The effects of fluidizing gas velocity and hopper pressure on the flow rate of the blends were studied in an aerated hopper with the blends of biomass particles and beisu coal paritcles. When the content of rice straw is lower, the flow state of the blends is similar to that of coal. And arching would occur easily if rice straw content is too high. Hopper pressure plays a positive role on the discharge, which get weaker with the increase of rice straw content. When the content of rice straw is high, fluidizing gas passes the material layer easily to block the discharge.(6) The segregation was researched in a fluidized bed and after the blends discharging from the hopper. Results showed that the blends of rice straw and quartz sand (or glass bead) could fluidize although there is a great difference in physical properties between different particles. And the content of rice straw is nearly the same at different heights of bed. In addition, the segregation of the blends is unobvious during the discharge and in the reviser hopper.
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