Abstract:

Attrition of solid particles is one of the important problems of fluidization technology. The study of particle attrition characteristics and two attrition mechanisms in the process of gas-solid flow is of great significance to the application of fluidization technology. In this paper, a visualized cold fluidized bed was designed for coal tar pitch particles to study the effects of gas velocity, initial particle size and height-diameter ratio on attrition behavior, and to discuss attrition mechanisms. The results show that the sphericity of coal tar pitch particles increases and the surface tends to be smoother after fluidization, but the average diameter decreases. The attrition process is affected by two attrition mechanisms, fragmentation and abrasion respectively. In the high-speed attrition stage, abrasion plays a dominant role, and in the low-speed attrition stage, both fragmentation and abrasion work simultaneously. In the steady state, abrasion dominates again. In addition, increasing gas velocity and height-diameter ratio, decreasing initial particle size all aggravate the attrition process. With the fluidization number increasing from 2.7 to 3.9, the rate of fragmentation and abrasion increases by 3.6% and 1.4%, respectively. When height-diameter ratio doubles, the rate of fragmentation and abrasion increases by 1.4% and 8.2%, respectively.

Key words: coal tar pitch particles, fluidization, attrition, attrition mechanism, fragmentation, abrasion, dynamics

摘要：

固体颗粒的流化磨损是流态化技术重要的基础问题之一，气固流动过程中颗粒的磨损特性以及两种磨损机制的研究，对流态化技术的应用具有重要意义。针对煤沥青球设计可视化冷态流化实验系统，研究表观气速、初始粒径和高径比对颗粒流化磨损行为的影响，探讨颗粒流化磨损机理。结果表明：经过流化磨损后，仍在初始粒径范围内的煤沥青颗粒球形度增加，表面更光滑；流化磨损过程受到体相断裂和表面剥层两种磨损机制的共同作用：高速磨损阶段由表面剥层主导，低速磨损阶段表面剥层和体相断裂同时存在，稳态阶段再次由表面剥层主导；提高表观气速和高径比、降低初始粒径均会加剧流化磨损过程，流化数从2.7增加到3.9，体相断裂和表面剥层程度分别增加了3.6%和1.4%。

关键词: 煤沥青球, 流态化, 磨损, 磨损机制, 表面剥层, 体相断裂, 动态学