450482 Analysis about Effects of Operating Parameters on Fine Particle Grinding Process with Vertically Stirred Media Mills
This paper mainly evaluates fine particle grinding process with vertically stirred media mills by wet method. The particle size (e.g. D80) is key parameter in many industrial fields as ore liberation, pharmaceutical, cosmetic, paints and paper manufacture. Ground Calcium Carbonate (GCC) normally used as paper filler is a main product of IMERYS Mineral Limited. To obtain ultra-fine size (normally grain size<10um), large amount of energy is drawn by grinding mill to break particles through impact, shear attrition or compression or a combination of them. Stirred media mill recently is commonly utilized among mining process due to its high stressing intensity, remarkable energy efficiency and reliability. However, understanding for process is still not enough and some gap still exists for improving efficiency by using wet grinding method on vertically stirred media mill. Hence, the work is set up based on a bench scale laboratory mill and a pilot scale mill to evaluates grinding performance. The performance of the mills is investigated through particle size reduction and power consumption under different operating conditions by changing tip speed, types of grinding beads, configuration of impeller. A wide range of tip speed (5.23-9.81m/s) is tested under 65%(w/w) and 75%(w/w) solids concentration. Two types of grinding beads are used to study the effects of grinding media. Some novel design of impeller is implemented to obtain different flow pattern. Variation of particle size under various energy input is measured. Positron Emitting Particle Tracking (PEPT) technology is utilized to plot routine of particles movement map of velocity. Additionally, morphology of product is identified by Scanning Electron Microscopy(SEM). In the end, grinding performance of the pilot mill is compared with the bench scale to provide an insight for scale up procedure.