环境湿度对PTFE覆膜滤料除尘性能的影响及其强化研究

Bag filters is a widely used dust removal technique with high efficiency. However, bag filtration has not been fully understood because of intrinsic difficulties in decreasing the dust cake resistance which leads to high energy consumption. In this project, based on the study of sandpile formation process and adhesion force between dust particles, liquid bridges can be introduced among particles by varying the humidity. The adhesion force can be significantly intensified so that filtration resistance could be greatly lowered and dust cake loading would be increased. The aim of this study is to give a better understanding of humidity effects on particle accumulation in bag filtration with a new hydrophobic PTFE membrane which has the high flux and the lower filtration resistance. The effect of humidity on the capillary force between particles is considered, and the influence of adhesion force on the particles accumulation behavior is also experimentally investigated. In order to confirm the effect of adhesion force on the cake formation, a special emphasis is given to the image analysis of the dust cake microscopic structure. A new method to immobilize the dust cake will be developed. To discuss the influence of the component and surface properties of particles on cake formation and adhesion forces between particles, experiments with different kinds of particles are carried. As a theoretical guidance, a simulation method that accounts for the effects of particle properties and adhesion force between particles on the compression behavior of dust cakes composed of monodisperse particles will be developed in this study.

袋式除尘技术是一种结构简单、除尘效率高且应用广泛的高效除尘技术，但滤饼过滤阻力过高一直是影响其能耗并阻碍袋式除尘技术发展的主要原因。本研究通过对滤饼颗粒间相互作用力的分析，借助物理学对砂堆过程的研究，通过改变环境湿度，促使颗粒间形成液桥，提高颗粒间粘附力，从而大幅度降低滤饼层的过滤阻力并提高滤料的荷尘量；研究制膜工艺，制备具有高通量、低过滤阻力的新型超疏水性PTFE膜滤料，并利用其作为高湿含尘气体过滤滤料，考察相对湿度对颗粒与滤料表面作用力的影响；研究不同湿度环境下颗粒间的液桥力，以及在不同作用力下的粉尘堆积行为；采用滤饼固定化方法，研究颗粒间粘附力与滤饼暂态微观结构的关系；研究颗粒物组成以及其表面性质对颗粒间作用力、滤饼堆积行为以及滤饼过滤阻力的影响；通过建立可压缩滤饼堆积模型，考察颗粒性质以及颗粒间作用力对滤饼形成的影响。

颗粒堆积是自然界最普遍存在的现象，对各类工业过程和日常生活中有着重要的影响。颗粒堆积行为与颗粒间作用力密切相关，调控颗粒间作力是改善颗粒堆积行为的有效途径。颗粒间作用力主要包括范德华力、静电力和液桥力，其中前两者调控难度高且调控范围窄，而液桥力的强度远高于前两者，却一直未有有效调控的方法。.项目通过改变环境湿度在颗粒间引入液桥，实现了液桥力在较大范围内的调控，显著提高了颗粒间作用力；参考袋式除尘过程，通过气流作用携带微细颗粒，利用曳力使微细颗粒在特殊介质上进行堆积，形成了一种新型的颗粒堆积行为研究方法。.项目考察了环境湿度对颗粒间作用力的影响规律，制备了一种小孔径、高孔隙率、低表面能的新型PTFE覆膜滤料为介质，研究了环境湿度、颗粒性质对颗粒堆积层阻力、颗粒堆积空隙率等堆积行为的影响。研究表明：高湿环境下颗粒间作用力增大，堆积空隙率大幅提高。颗粒粒径对堆积行为的影响较为显著；而颗粒表面润湿性能、颗粒形状等对其堆积结构与环境湿度变化的响应程度影响不大。建立了液桥力与颗粒间相互作用的数学模型，模拟并验证了环境湿度对颗粒间作用及其堆积结构的影响。