Prediction of size reduction by batch ball milling process for crab shell powder prior hydroxyapatite conversion

The crab (Portunus pelagicus) shell is a marine biowaste produced by seafood industries. Traditionally, crab shells were collected to be converted into animal feed, however many of them are disposed of as industrial waste. A conversion of crab shells into hydroxyapatite is a better option for producing high-value biomaterial. Hydroxyapatite materials can be used as slow-release fertilizer while combining them with traditional fertilizer or as a stand-alone green fertilizer with high phosphatic content. Prior to hydroxyapatite conversion, the size reduction of crab shells is required. In this study, crab shell powder is derived from dried crab shell with the water content is approximately 10% wb. The size reduction is processed by using a customized batch type ball mill. This study is aiming at determining the kinetic model of milling parameters for crab shell milling by using the ball mills. An amount of 1.5 kg of dried crabs shell was milled by using 3-size mixed metal balls. The powder was then analyzed its particle size, and the particle size is used as an input in the mathematical model. The computational study focused on the calculation of optimal rotational velocity and kinetic model during the milling process. The kinetic model was based on Population Balance Equation of the mass balance principle, and the results are compared with experimented data characterized by particle size analyzer. It is observed that there are discrepancies between the model and experimental data due to the characteristic of raw materials; however the kinetic model can be used as a prediction of particle size reduction using the ball mill without conducting the real experiment.