Abstract

In this work, the effect of water on the packing and flow properties of cohesive powders was experimentally investigated. Two cohesive powders with small particle sizes were studied with weight percentages of added water of 0, 10, 25, 40, and 50%. Particle properties including conditioned bulk density, porosity, compressibility, flow function coefficient, cohesion, etc., were tested using the Freeman FT4 Powder Rheometer and examined as a function of water content. Results show that water content has a significant effect on the packing and flow of the powders. With small amounts of water added, the particle beds became more cohesive, due to the formation of liquid bridges, and the bed volume increased roughly in proportion to the mass of water added leading to a fairly constant conditioned bulk density. When greater amounts of water were added to the particle beds, there was a substantial increase in conditioned bulk density. The bulk densities of both powders increased from around 0.3–0.55 g/ml when the added water was increased from 40% to 50%. As the water weight fraction increased, there was generally an increase in basic flow energy and cohesion, while the porosity and pressure drop generally decreased.

摘要

在这项工作中，实验研究了水对粘性粉末的填充和流动性能的影响。研究了两种具有小粒径的粘性粉末，添加的水的重量百分比分别为 0、10、25、40 和 50%。使用 Freeman FT4 粉末流变仪测试颗粒特性，包括调节体积密度、孔隙率、可压缩性、流动函数系数、内聚力等，并作为含水量的函数进行检查。结果表明，含水量对粉末的堆积和流动有显着影响。加入少量水后，由于液桥的形成，颗粒床变得更具凝聚力，并且床体积的增加大致与添加的水的质量成比例，从而导致相当恒定的调节堆积密度。当将更大量的水添加到颗粒床中时，调节的堆积密度会显着增加。当添加的水从 40% 增加到 50% 时，两种粉末的堆积密度从大约 0.3–0.55 g/ml 增加。随着水重量分数的增加，基本流动能和内聚力普遍增加，而孔隙率和压降普遍降低。