调浆过程为煤泥浮选提供良好的界面条件,是实现其高效分选的必要条件,其本质是一个多相流动过程,流体作用贯穿其中｡聚焦煤泥调浆过程中的“湍流效应”,搭建了实验室型搅拌装置,利用数值模拟分析其湍流特征参量,研究了不同流场条件下颗粒分散特性和颗粒表面疏水性变化规律,并通过浮选试验进行验证,以此构建了基于湍流能量密度适配的新型涡流强化煤泥调浆过程,并分析其流场特性｡研究结果表明:搅拌装置内存在流向相反的循环区,有利于颗粒分散,叶轮区流体流速和湍动能耗散率高于其他区域,叶轮叶片后存在尾涡,其发展状况与湍动能耗散率分布一致,叶轮区最小涡尺度最低,增强颗粒与药剂的相互作用,随着叶轮转速增大,流体流速和湍动能耗散率增大,最小涡尺度减小;颗粒分散浓度方差随着叶轮转速的增大而减小,低转速时搅拌装置底部颗粒浓度较高,分散效果差,包覆角随着叶轮转速的增大而增大,相同条件下,叶轮区颗粒包覆角最大,在试验范围内,叶轮转速增大,浮选产率增大;基于上述调浆过程中的湍流效应分析,构建了集成管流､错向旋流､撞击流等不同流场环境的煤泥调浆过程,并设计了MRM-800×3 600 mm型煤泥混合调质器,数值模拟表明该装置内湍流能量密度分配合理,旋流区流体流速较大,呈切向运动,撞击流区域流体运动剧烈,湍流能量密度大,最小涡尺度小,工业生产实践表明该装置矿浆通过量为300~500 m3/h,在原有工艺条件下,浮选精煤回收率提高超过4%｡

It has been acknowledged that a conditioning process can provide favorable interfacial conditions for fine coal flotation,thereby being a required premise of its efficient separation.  Essentially,a fine coal conditioning is a process involving multiphase flow,throughout which the role of fluid exists.This paper focused on the turbulence effect in the coal pulp conditioning process,and designed a laboratory stirring device.Numerical simulation was used to acquire the turbulent characteristic parameters of the stirring device.  Additionally,the properties of particle dispersion and surface hydrophobicity were analyzed under different conditions of flow field to characterize the influence of flow field characteristics on fine coal conditioning process,which was further verified by flotation tests. Based on the studied above,a new type vortex enhancing pulp conditioning process with adapted turbulence energy density was constructed for fine coal conditioning,and the flow field characteristics were analyzed.  The results indicated that there was a circulation area with opposite flow in the stirred tank to promote particle dispersion,and the fluid velocity,together with the turbulent kinetic energy in the vicinity of impeller,was higher than that of other region. Trailing vortexes were formed behind the blade,which exhibited similar development trends to the distribution of the turbulent kinetic energy. The Kolmogorov scale was the lowest in the impeller region to enhance particle collector interaction. With the raising impeller speed,the fluid velocity and turbulent kinetic energy increased,while the Kolmogorov scale and variance of particle dispersion concentration decreased. At low impeller speeds,the particle concentration of the cell bottom was high,corresponding to poor dispersion performance.The wrap angle increased with rising impeller speed,and under the same condition,the maximum wrap angle of particles collected near the impeller was measured. In this experiment,the lager impeller speed corresponded to higher flotation recovery. According to the above mentioned laws,the different conditions of flow field,including pipe flow,opposite rotational flow and impact flow,were integrated in the fine coal conditioning process,and an MRM 800×3 600 mm coal slime mixing conditioner was designed. The results of numerical simulation showed that the turbulence energy density was properly distributed,with a tangential fluid motion in the area of rotational flow,and a strong shearing fluid motion in the vicinity of impact flow corresponding to lager turbulence energy density and smaller Kolmogorov scale.It has been manifested in industrial practice that the slurry capacity of the equipment is about 300-500 m3/h,and under the original process technology,the flotation recovery of clean coal increases over 4%.

1 数值模拟与试验

   1.1 试样与试验系统

   1.2 数值模拟

   1.3 试验方法

2 结果与讨论

   2.1 流场特性

   2.2 颗粒分散特性

   2.3 包覆角分析

   2.4 浮选效果

3 新型涡流强化调浆过程

   3.1 过程构建

   3.2 流场特性

   3.3 工业应用

4 结论