Abstract

This paper deals with the influence of different definitions for evaluating the sphericity factor on the prediction of minimum fluidization velocity (U_mf) of different agro-industrial/forestry biomass residues and sand. Three biowastes (sawdust, grape marc, and grape stalk) and sand were characterized by sieving, and sphericity was calculated using images obtained by scanning electron microscopy (SEM). Two particle size populations (with mean diameters and density corresponding to B and D Geldart groups) were adopted for each biomass. As for sand, particles with a mean diameter of 0.33 mm were used. Tests were carried out in a lab-scale fluidized bed. Bed pressure drop was measured as a function of the superficial velocity of air at two different initial bed heights, for each type of biomass and mixtures with sand. Ratios of 0.50 and 0.75 (v/v) were used for mixtures. For all cases, U_mf values were calculated experimentally and were compared against predicted values obtained from Ergun's equation and other correlations. It was found that the methodology adopted for determining sphericity significantly influences the obtained value of U_mf. The lowest relative error between predicted and experimental U_mf values was obtained using Riley’s sphericity method. Finally, a new correlation for U_mf was proposed.

摘要

本文讨论了评估球度因子的不同定义对最小流化速度 ( U _mf)预测的影响) 不同的农工业/林业生物质残留物和沙子。三种生物废物（锯末、葡萄渣和葡萄秆）和沙子通过筛分进行表征，并使用扫描电子显微镜 (SEM) 获得的图像计算球形度。每种生物量采用两个粒度群体（平均直径和密度对应于 B 和 D Geldart 组）。至于沙子，使用平均直径为 0.33 毫米的颗粒。测试在实验室规模的流化床中进行。对于每种类型的生物质和与沙子的混合物，在两个不同的初始床高度下，作为空气表观速度的函数测量床压降。0.50 和 0.75 (v/v) 的比率用于混合物。对于所有情况，U _mf值是通过实验计算的，并与从 Ergun 方程和其他相关性获得的预测值进行比较。发现用于确定球形度所采用的方法显着影响所获得的U _mf值。使用 Riley 球度方法获得预测和实验U _mf值之间的最低相对误差。最后，提出了U _mf的新相关性。