Grinding Characteristics And Process Simulation Of Fine Wet Grinding In Stirred Media Mill

Super fine grinding is an interdisciplinary, cross-industry high technology. It is an important non-metallic mineral processing technology in powder engineering and plays an important role in the development of modern high technology and new material industry. Horizontal ultrafine stirred mill is a widely used superfine grinding mill in grinding industy. Insufficient study about grinding principle of horizontal ultrafine stirred makes the ultrafine theoretical research of stirred media mill lags behind of the industy production. In order to solve this problem, this paper focuses on ultrafine grinding process dynamics, energy consumption, and mechanochemical about the wet horizontal ultrafine stirred media mill. The model of stirred media mill is presented too in this paper, and the author has carried on the simulation research. The main contents and conclusions are as follows:(1) Research on grinding dynamics of horizontal wet ultrafine stirred media mill.Choosing superfine ground calcium carbonate powder as raw materials, studied the effect of particle size range, media density, media size, media filling rate, type of grinding aids, the stirring shaft rotation speed and slurry concentration on grinding rate, and set up the ultra-fine grinding dynamics model at different experimental conditions. Results show that the grinding rate changes with the particle size range. That is the wider the particle size range is, the higher the value of the grinding rate becomes. Adding grinding aids can effectively improve the grinding rate. The grinding effect of Acume 9300 is better than that of sodium hexametaphosphate for ultafing grinding ground calcium carbonate powder. Grindinging rate increases with the increase of rotation speed and the relationship can be expressed as 4.30 10. Grindinging rate has a power function relationship with media size, the formula can be expressed as k=0.26843d-0.14478. Grindinging rate decreases with the increase of slurry concentration. That is the higher the concentration is, the bigger the value of the grinding rate becomes. The relation between slurry concentration and grinding rate can be expressed as the k =.. With the increase of media density, grinding rate increasing, the relationship between them can be expressed as 0.03073 0.00117. With the increase of media filling rate, the grinding rate increases, the relationship between them can be expressed as 0.003073.Considering the existsing of particle agglomeration phenomenon in superfine grinding process, the specific surface area of samples was determined and the degree of product agglomeration were analysed at different milling time. Aiming at the limitations of traditional dynamic model and combined with agglomeration phenomenon in super fine grinding process, a new model of the ultrafine grinding dynamics was proposed:" # $%. Comparing the fitting result of experimental data by using traditional dynamics model and new ultrafine grinding dynamics model proposed in this paper, the result shows that the new model has a better fitting precision.(2) Research on energy consumption princple of horizontal wet ultrafine stirred media mill.Factors influencing the grinding energy consumption can be divided into two kinds: quantifiable factors and unquantifiable factors. Grinding aid type, media type are factors unquantifiable and mill speed, slurry concenration, grinding aid dosage, media filling rate and the media size are quantifiable factors. In this paper, unquantifiable factors grinding aid type and media type were studied first. Choosing the superfine ground calcium carbonate powder as raw materials, based on rosing- laemmle granularity characteristic equation and energy consumption, with the help of mathematical analysis software MATLAB, the equation between granularity modulus and grinding energy consumption at proper conditions was established by fitting method. The reliablity of the equation was verified by the result of the experiments. Secondly, quantifiable factors were studied. The response surface methd in Design- Expert 6.08 software was adopted to study the factors significe to the grinding energy consumption. The mathematical model of grinding energy consumption with experimental condition is established:& 0.074 0.04' 0.016( 6.417 10)* 0.027& 5.500 10) 0.019& 0.012'& 0.016(& 0.016&.By comparing the predicted values and experimental values of energy consumption, it can be found that the experimental value and predicted are better alignment, suggesting that the expressions of energy consumption can be used to predict the required energy when mill ground calcium carbonate in horizontal superfine stirred media mill at different experimental conditions.(3) Mechanochemical effect of the horizontal wet ultrafine stirred media mill on mineral powder.The rutile titanium dioxide, anatase titanium dioxide, ground calcium carbonate and quartz powder were ground in stirred media mill for a long time. Samples were tested by centrifugal sedimentation granulometer, static nitrogen adsorption instrument X-ray diffraction(XRD) and scanning electron microscope to detect the change of particle size, specific surface area, morphology and crystal characteristic peak intensity and width in the grinding process. Results showed that the minimum D97 of rutile titanium dioxide powder is 0.95?m and the minimum D50 is 0.17?m. The smallest width of particle size distribution is 1.8. The maximum product specific surface area is 31.02 m2·g-1. The minimum average area diameter is 47.18 nm. The XRD characteristic peak intensity of rutile titanium dioxide decreases while characteristic peak width increases with the milling time. The minimum grain size is 16.41 nm. The stability of(211) crystal plane is the worst. The stability of(220) crystal plane is the best. The minimum D97 of anatase powder is 0.76?m and the minimum D50 is 0.19?m. The smallest width of particle size distribution is 1.45. The maximum product specific surface area is 22.19 m2·g-1. The minimum average area diameter is 70.23 nm. The XRD characteristic peak intensity of anatase titanium dioxide decreases while characteristic peak width increases with the milling time. The minimum grain size is 25.43 nm. The stability of(204) crystal plane is the worst. The stability of(105) crystal plane is the best. The minimum D97 of ground calcium carbonate is 4.61?m and the minimum D50 is 0.26?m. The maximum width of particle size distribution is 11.4 and the minimum is 2.31. The maximum product specific surface area is 55.21 m2·g-1. The minimum average area diameter is 40.25 nm. The XRD characteristic peak intensity of ground calcium carbonate decreases while characteristic peak width increases with the milling time. The minimum grain size is 25.59 nm. The stability of(018) crystal plane is the worst. The stability of(116) crystal plane is the best. The minimum D97 of quzrtz is 13.64?m and the minimum D50 is 1.08?m. The maximum width of particle size distribution is 11.4. The maximum product specific surface area is 169.19 m2·g-1. The minimum average area diameter is 13.13 nm. The XRD characteristic peak intensity of quzrtz decreases while characteristic peak width increases with the milling time. The minimum grain size is 26.25 nm. The stability of(203) crystal plane is the worst. The stability of(031) crystal plane is the best.(4) The flow field simulation and grinding strength analysis of the wet horizontal ultrafine stirred stirred mill.After observed and measured the horizontal stirred mill structure size, the geometry model about the mill was establlished by using solidworks software. The geometry model was meshed in GAMBIT software. The simulation of flow field is processed in FLUENT software. The simulation of media motion was studied using using EDEM software. The results show that the crushing effect is leading grinding forces at the wall of the mill and this way is not change with the rotating speed and the slurry concentration. This effect increases with the increase of rotational speed and decreases with the increase of slurry concentration. The friction effect is leading grinding forces at regions near the wall and the shaft pin. This friction effect increases with the increase of rotational speed and decreases with the increase of slurry concentration. Milling effect occurs mainly in the feeding section in cylinder. Collision frequency of particles increased with the increase of stirring shaft speed. Particle and particle collision for material crushing is the main forms of collision. Impact of particles in the normal collision force is less than the tangential collision force, which can illustrate that friction effect is dominative in crushing effect. the largest number of normal and tangential collisions decreases with the increase of rotational speed. The normal speed and the tangential velocity, corresponding to maximum number of collisions increase with the increase of rotational speed.