Mixing and segregation of binary mixtures of biomass and silica sand in a fluidized bed

In this work, mixing and segregation of binary mixtures involving biomass materials in a fluidized bed was experimentally investigated. A frozen bed method was employed to investigate both axial and radial distribution of biomass particles in silica sand. Three different biomass materials were studied: willow sawdust, pelletized soy and oat hull materials. Biomass loading investigated ranged from 5% to 30% by weight. The extent of mixing for each of the biomass composition was investigated using Lacey's mixing index which is based on the standard deviations of the sample at different axial positions in the bed. The radial composition was also investigated by means of digital imaging analysis using a high resolution digital camera. The experiments revealed the differences in the extent of particle distribution for pelletized biomass materials vs non-densified materials as a result of differences in particle size, density and importantly, the particle shape of the materials utilized. The results showed an increase in the extent of mixing as the fluidizing velocity increased for both pellet materials while the mixing index for sawdust decreased beyond a loading of 20%. With an increase in biomass loading, an increase in mixing index was found for the two pellet materials. A similar trend was observed for sawdust at the lower loading level. However, the mixing index started to decrease at higher loading level beyond 20%. The results greatly contributed to the understanding of the hydrodynamics of binary and multicomponent mixtures involving biomass materials, especially pelletized materials in fluidized beds. (c) 2021 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

在这项工作中，对流化床中涉及生物质材料的二元混合物的混合和分离进行了实验研究。采用冻结床方法研究了生物质颗粒在硅砂中的轴向和径向分布。研究了三种不同的生物质材料：柳木屑、颗粒状大豆和燕麦壳材料。所研究的生物质负载量按重量计为5%至30%。使用莱西混合指数研究了每种生物质组成的混合程度，该指数基于床内不同轴向位置处样品的标准偏差。还通过使用高分辨率数码相机进行数字成像分析来研究径向组成。实验揭示了由于所使用材料的粒径、密度以及重要的颗粒形状的差异，颗粒状生物质材料与非致密材料在颗粒分布程度上的差异。结果表明，对于两种颗粒材料，随着流化速度的增加，混合程度增加，而木屑的混合指数在负载量超过20%时下降。随着生物质负载量的增加，发现两种颗粒材料的混合指数增加。在较低负载水平下，木屑也观察到类似趋势。然而，在负载量超过20%的较高水平时，混合指数开始下降。这些结果极大地有助于理解涉及生物质材料（特别是流化床中的颗粒状材料）的二元和多组分混合物的流体动力学。(c) 2021中国颗粒学会和中国科学院过程工程研究所。由爱思唯尔公司出版。保留所有权利。