(448aj) 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.