煤泥离心过滤和机械压滤的滤饼层粒度分布及其影响

针对离心过滤和机械压滤过程中煤粒成饼机理的差异,采用分层取样法分析对比了煤泥离心过滤与机械压滤两种不同过滤方式形成的滤饼内部的粒度及水分分布特点,基于沉降理论探讨了离心过滤和机械压滤的成饼过程,并分析了入料级配对离心过滤过程中滤饼粒度分布的影响。结果表明:机械压滤形成的滤饼中,颗粒粒度和滤饼水分沿滤饼厚度的方向无显著变化,而离心过滤形成的滤饼中,颗粒粒度和滤饼水分沿滤饼厚度的方向存在较大变化,距离滤网越近,滤饼层颗粒的平均粒度越粗、水分越低;入料级配对离心过滤的滤饼层粒度的径向分布及脱水效果影响显著,随着入料平均粒度的减小,上述径向分布差异呈现缩小的趋势;沿着滤饼厚度的方向,压滤滤饼中的过滤比阻分布是相对均匀的,在理论分析中可近似为常数,而离心过滤的滤饼层的过滤比阻分布具有非均匀性,影响比阻分布的因素具有复杂性。

Particle size distribution of fine coal cake in filtering centrifuge and press filter and its influences on specific filtering resistance

In order to study the forming mechanism differences of filter cake under centrifugal force and mechanical stress，the particle size distribution of cakes from the press filter and filtering centrifuge were analyzed by stratified sampling，and the influences of feed grain-size composition on the particle distribution of cake in filtering centrifuge were studied in detail.Results indicate that the particle size distribution and moisture content in the cakes of press filter are uniform，while that of filtering centrifuge changes gradually.The nearer the particles are to the screen，the coarser the average particle size is，and the higher the cake moisture.Moreover，the feed particle size distribution influences the particle size distributions of the filtering centrifuge cake significantly.Due to the particle size distribution of cakes，it can be inferred that the specific filtration resistance in pressure filter cake is relatively uniform and can be treated as constant，but it decreases with the increase of cake radius in filtering centrifuge.It also shows that the recovery of fines smaller than screen mesh depends mainly on the cake bed structure in filtering centrifuge.