Abstract:

Entrained flow bed gasification technology has stringent requirements for raw material particle size, as it significantly affects transportation performance, gasification efficiency, and product quality. This paper, setting against the backdrop of biomass entrained flow bed gasification, uses agricultural waste rice husks as the experimental material to explore the impact of particle size on the morphological characteristics, flowability, and reactivity of the powder. The results indicate that reducing particle size can reduce the anisotropy of rice husk powder, enhance the adaptability of the entrained flow bed process to biomass feedstocks, and facilitate the resolution of challenges associated with the diversity, regionality, and seasonality of biomass. The bulk density of rice husk powder shows a trend of increasing and then decreasing with decreasing particle size. The inter-particle interactions at small particle sizes and the needle-like characteristics of particles at large sizes are the main reasons for the loose packing structure and high porosity of the bed layer. The feeding flow rate of rice husk powder first increases and then decreases with particle size. For rice husk powder with large particle sizes, gravity plays a dominant role in the feeding process, and the Beverloo model predicts quite accurately. However, for rice husk powder with particle sizes less than 100μm, the influence of inter-particle forces cannot be ignored, and correcting for this factor makes the model prediction closer to the experimental values. The smaller the particle size, the faster the reaction rate of rice husk powder; however, rice husk powder with large particle sizes still exhibits high reactivity. Therefore, for biomass entrained flow bed gasification, when using feedstocks with good reactivity such as rice husk powder, it is feasible to increase the particle size of the feedstock entering the furnace to reduce the cost of powder production. This study has certain reference significance for the conversion and utilization of agricultural waste such as rice husks.

Key words: biomass, entrained-flow bed, gasification, flowability, particle morphology, reactivity

摘要：

气流床气化技术对原料粒径要求较高，因粒径对其输送性能、气化效率及产品质量等诸多方面存在显著影响。本文以生物质气流床气化为背景，以农业废弃物稻壳为实验原料，探究了粒径对粉体形貌特征、流动性能及反应活性的影响。结果表明，减小粒径可以改善稻壳粉的各向异性，增加气流床工艺对生物质原料的适应性，有利于解决生物质多样性、区域性和季节性等难题。稻壳粉堆积密度随粒径减小，呈现出先增大后减小的趋势，小粒径时颗粒间相互作用和大粒径时颗粒针状特征，是导致床层堆积结构疏松、空隙率较大的主要原因。稻壳粉下料流率随粒径先增大后减小，对于大粒径稻壳粉，在下料过程中重力占据主导作用，Beverloo模型预测较为准确；而对于粒径小于100μm的稻壳粉，颗粒间作用力的影响无法忽视，通过修正这一影响因素使得模型预测更接近实验值。粒径越小，稻壳粉的反应速率越快；但大粒径稻壳粉仍然具有很高的反应活性。因此，对于生物质气流床气化，当使用如稻壳粉等反应活性较佳的原料时，可适当提高入炉原料粒径以减少制粉成本。本研究对稻壳等农业废弃物的转化利用具有一定参考意义。

关键词: 生物质, 气流床, 气化, 流动性, 颗粒形貌, 活性