Evaluasi kecepatan pertumbuhan kristal pada reaksi diikuti kristalisasi pada pembuatan amonium sulfat dari amonia dan asam sulfat

ABSTRACT Chemical reaction followed by crystallization is industrially important because numerous materials are marketed in crystalline form. Its wide use has twofold advantages. Firs!, a crystal formed from an impure solution such as a reaction mixture is usually pure and second, crystalline form has preferable condition for packaging and storing. Beside the good yield and high purity, the most important objective of designing a crystallizer is to control the size range of the crystalline product. Crystal size distribution depends on nucleation and growth rates. When supersaturation can be kept low, such as in fluid-fluid reaction controlled by mass transfer rate. nucleation rate is low enough to be neglected and growth rate dominates the process. A model based on the concept of population density is proposed and then used to evaluate the growth rate. Based on the model proposed and the growth rate obtained, crystal size distribution can be predicted. The growth is assumed to follow LIL Law which states that the growth is independent of the crystal size. The model is verified using plant data from ZA III Plant of P.T. Petrokimia Gresik. It is found that in the operating conditions applied, the crystalline ammonium sulphate grows at constant rate of 0.0511 mm/hour. Having relatively small deviation between data and calculated results of mass fractions at any crystal size ranges, the model can well describe the process