School of Chemical & Environment Engineering,China University of Mining & Technology(Beijing),Beijing　 100083,China

针对目前物理法制超净煤工艺中絮团形成过程动力学指标和絮团形态学变化与超净煤分选效果之间关系研究的不足,应用分形维数分析了剪切力场中絮团形态和粒径的非线性变化并解释了其与超净煤分选效果之间的关系。通过量纲分析法,确立絮团分形维数与搅拌速度的函数关系;通过二维分形维数的研究,描述和表征颗粒群体的整体性和平均性;通过絮团多重分形图谱的研究,揭示絮团分形变化的动力学过程。进而确立絮团生成动力学过程中的控制指标,以期为超净煤制备过程中的工艺操作提供科学依据,为实际工程应用提供适当的控制参数的指导。研究表明,机械搅拌速度为2 000 r/min时,絮团的二维分形维数有最大值1.762,此时絮团具有密实的结构和合适的粒径;多重分形图谱特征参数f(αmax)具有最大值0.796,此时絮团粒径最大,数量最多。故此时分选出的超净煤有最高产率84.314%,最低灰分0.831%。

Currently the study on the relationship between the control of flocculation kinetics,the change of flocculation morphology and the quality of ultra-clean coal by physical method is limited. In this paper,the fractal dimension theory was used to analyze the nonlinear changes of the morphology and diameter size of the particles in the shear force field and used to study the separation effect of ultra-clean coal. According to the mathematical analysis on the density ex- pressions of flocculation,it was verified that the density of flocculation was the function of fractal dimension and the in- put of mechanical energy. Through the study of the two-dimensional fractal dimension,the whole and the average of the particle population are described and characterized. By analyzing the multifractal spectrum of the flocculation,the dy- namic process of the fractal changes of the clusters is revealed. In addition,the flocculation kinetics control factors were proposed which were expected to contribute to the scientific basis for the process operation of ultra-clean coal preparation and reasonable guidance for practical engineering application. The study shows that when the stirring speed is 2 000 r / min,the two-dimensional fractal dimension of flocculation has a maximum of 1. 762 that means at this point the flocculation has a dense structure and appropriate size,the characteristic parameters of multifractal spectrum like f(αmax ) has a maximum value of 0. 796,at this point the flocculation has largest size and maximum amount. Therefore under this condition the ultra-clean coal has the highest yield of 84. 314% and the lowest ash content of 0. 831% .

国家自然科学基金资助项目(51474221)；

Zhao Jing,Fu Xiaoheng,Wang Jie,et al. Effect of shear force field on the separation effect of ultra-clean coal based on fractal dimension of flocs[J]. Journal of China Coal Society,2016,41(8):2078-2085.