基于矩阵PBM的煤粉超细粉碎过程研究

Investigation on the ultra-fine grinding of coals based on a matrix population balance model

建立基于研磨过程机理的煤粉超细研磨动力学模型可以预测超细磨出料的粒度分布和指导优化磨机的研磨效率,降低研磨能耗,对制备低灰分的超净煤具有非常重要的作用。通过田口(Taguchi)正交实验设计,使用实验室1.5 L立式搅拌磨机考察了不同煤的物性参数、磨介尺寸和煤粉比处理量对于超细研磨的影响,将基于研磨过程特征的动力学模型矩阵粒群平衡模型(Matrix Population Balance Model,M-PBM)用于煤粉的搅拌磨机超细研磨出料的粒度预测,并结合Rosin-Rammler粒度分布模型,精确地预测出料产品在任意筛下累积含量对应的颗粒粒度。通过极差分析,探讨了煤的灰分、磨介尺寸和煤粉比处理量对于超细研磨能耗和比通量的影响大小,基于对煤粉超细研磨过程中煤-灰解离过程的分析并结合Tomoyoshi的比表面积能耗公式,探讨了煤的灰分与能耗的关系,并进一步建立了煤的灰分、磨介尺寸和煤粉比处理量与磨机研磨比通量和能耗的关系式,研究发现搅拌球磨机湿法超细研磨的粒度变化规律符合一阶线性动力学假设,在定搅拌转轴转速和所考查的研磨粒度变化范围内,煤的灰分对搅拌磨机的比通量和能耗的影响是最大的,建立的研磨能耗和比通量关系式表明在10μm(p50)以下的超细粉磨粒度范围内,煤的研磨能耗随着灰分的提高、磨介尺寸的减小(磨介尺寸在0.3~1.8 mm)和比处理量的增大而减小,而比通量随着灰分的提高、磨介尺寸的减小和比处理量的增大而增大。

The ultra-fine grinding kinetic model for pulverized coal based on the mechanism of grinding process can be used to predict the particle size distribution of the products in the grinding process,provide a guidance for optimizing the mill efficiency,and reduce the process energy consumption.It is very important for the preparation of ultra-clean coal powder with low ash content.In this paper,by using an orthogonal design of Taguchi plan,the effects of the physical parameters of different coals,the size of grinding medium and the specific load of pulverized coal on the ultra-fine grinding process are investigated by using a 1.5 L vertical stirred ball mill in the laboratory.A mechanistic approach based model,matrix population balance model(M-PBM),is proposed to predict the particle size distribution of the ultra-fine grinding products by the stirred ball mill,and by combining the Rosin-Rammler particle size distribution model,the particle size corresponding to any cumulative content under sieve can be accurately predicted.By range analysis,the influences of coal ash content,the size of grinding medium and the specific load of pulverized coal on the energy consumption and specific flux of ultra-fine grinding are discussed.Based on the analysis of coal-ash dissociation process in the ultra-fine grinding of pulverized coal and by combining Tomoyoshi’s energy consumption formula relating specific surface area of particles,the relationship between coal ash content and energy consumption is discussed,and the formulas relating coal ash content,grinding medium size,the specific load of pulverized coal with specific grinding flux and with energy consumption are further established.It is found that the particle size reduction during the ultra-fine wet grinding process of stirring ball mill conforms to the first-order linear kinetic hypothesis.Under a fixed rotating speed of agitating shaft and within the considered particle size reduction range,the ash content of coal has the greatest influence on the specific flux and energy consumption of the stirring ball mill.Within the ultrafine grinding size range which is below 10μm(p50),the established formulas of specific flux and energy consumption show that the increase in ash content,decrease in grinding medium size(0.3-1.8 mm)and increase in the specific load of pulverized coal will lead to the decrease in energy consumption and increase in specific flux,respectively.