Flowfield Numerical Simulation And Application Of Ultrafine Stirred Mill

Ultrafine stirred mill is a kind of ultrafine grinding equipment with high efficiency and energy conservation, ultrafine grinding is the main industrial equipment to produce submicron powder or submicron pulp, the powder produced by this machine has the advantages of fine particle size, granularity distribution uniformity,great throughput and low energy consumption.hence, the manufacture of large-scale industrial ultrafine stirred mill is very important. But there are still no the design theory of ultrafine stirred mill and the few study of the basic theory, this status hinders the engineering enlargement and the application of ultrafine stirred mill. Therefore, this paper systematically reviewed the present status and the development of ultrafine powder, ultrafine comminution equipment and ultrafine stirred mill. On the basis of literatures, inclosing the structure of ultrafine stirred mill and the process parameter, much work had been done to the foundation of theory simulation,the study of comminution theory,the analysis of experiments,the equipment development and the practical application, the following are the main contents of this paper:The paper analyzed the basic structure, the comminution mechanism and the capability parameter of the ultrafine stirred mill in detail. The following are the conclusions: attrition comminution is the main mode of the ultrafine stirred mill. In the cavum of this machine, the stress intensity is a very important parameter. The conclusion can be educed by analying the stress intensity of the stick type and the spiral type of the stirred mill that different types of the stirred mill have different stress intensity, adapting to different material comminution. The paper concluded that the effect of abrading mineral mainly accured in the area of the annular abrading mineral and put forward the conception that large shear rate of dispersion can reach good effect of abrading mineral by analyzing the strength and speed of the medium ball in the area of the comminution, butnot former conclusion that large rapidity lead to good effect, this provided the basic theory for structural enlargement and optimizing design of the industrial ultrafine stirred mill.Computational fluid dynamics(CFD) method was utilized to the fiowfield numerical simulation of ultrafine stirred mill, the flowfield characters(velocity gradient, shear rate dispersion of flowfield and the dissipative force of viscosity and so on) of three kinds of stirrer(disc type, stick type and spiral type) were analyzed.Through the generalized analysis,discovered the stick-like stirred mill flowfield circumference direction velocity gradient in the largest way and the flowfield cutting rate distribution uniformity best,this is a kind of stirred mill with big velocity gradient ,uniform stress distribution and small resistance.The analysis of the flowfield simulation provided a new method for parameter optimization design and project enlargement of the ultrafine stirred mill.Through doing some contrast experiments by using different mixer, indicated that the stick-like stirred mill had good grinding effect,this result was consistent with the result of flowfield numerical simulation and confirmed that the accuracy and the reliability of the model establishment and the simulation analysis.In the 3600L large-scale ultrafine stirred mill,grinding the calcium carbonate and under the same condition,the enegy consumption can save 15%-17%,the throughput can inhance 13%-15% by using stick-like mixer comparing to using the disc-like mixer.It was proposed that the structural engineering enlargement method, the application synthesis enlargement principle of the industry ultrafine stirred mill, carried on the optimization to its design parameter and craft parameter; used the stick-like stir basic structure;determined the best ratio of high to diameter of the tube body and the topmost line speed of the mixer;designed and R&D 3600L large-scale ultrafine stirred mill by above analysis.Through the engineering practical application on ultrafine comminution to calcium carbonate and barite,confirmed that the structuredesign of the machine was reasonable and its parameter was superior.This kind of machine had been promoted and applied more than 10 sets in Shan dong,Guang zhou and Hunan.In order to more extend the applied areas of the ultrafine stirred mill, two kind of minerals, pyrite(as the submicron catalyst for the direct liquefaction of coal) and calcium carbonate(as the coarse whiting pulp for the pigment of paper manufacture coating), were experimented by this machine. The technical process, technical parameter and main influencing factor of ultrafine stirred mill were researched in detail. The submicron pyrite oil thick liquid(d50 ^ 0.7um)manufactured by the optimized late-mode ultrafine stirred mill can be regarded as the submicron catalyst for the direct liquefaction of coal;the submicron calcium carbonate(dso^ 0.6um) also manufactured by the optimized late-mode ultrafine stirred mill can be regarded as the pigment of paper manufacture coating.