Numerical Model to Predict Wax Crystal Size Distribution in Solvent Dewaxing Unit

Abstract

A mathematical model was implemented to predict the wax crystal size distribution of distillate lube oil SN500. The model solved the coupled equations for the heat transfer and moments of the population balance numerically. The predicted temperatures and wax crystal size distributions were validated with actual unit database and experimental measurements. The kinetics of the wax crystallization considered only the nucleation and crystal growth. N-alkanes from n-C22 to n-C36 were tested to select compound for representation of the wax fraction. The nucleation process order constant was fitted from wax recovery experimental measurements. The developed numerical model was proved to be capable to predict wax crystal size distribution in real solvent dewaxing plant. The model results were found to be in good agreement with the process data. wax is not. The advantage of the crystallization process as a separation technique is relatively demand low energy with high purity of the product. In addition of the performance analysis of the DPSSE as heat transfer equipment by using the conservation equations such as the heat transfer, mass or momentum (mainly fluid flow), design this instrument as a crystallizer in particulate system involved further transport formula to describe the crystals characteristics. This transport equation known as population balance equation (PBE) required accounting the crystals number, and crystal size distribution. Also, this equation quantifies processes such as nucleation, crystal growth, aggregation, and breakage and so on. The difficulties facing the designers of the industrial SSHE as a crystallizer arising from the scarcity of the experimental data for the individual processes rather than the limited and unreliability of these published data. The mathematical models of crystallization process in SSHE essentially, the ice crystallization from scours solution, sorbet, and ice cream processes, the description of the crystallization kinetics limited to the nucleation (homogenous or heterogeneous), crystal growth, and the breakage in some studies. In general the studies referring to develop a mathematical model of coupling the heat transfer, fluid flow, and the kinetics crystallization for the separation technique in scraped heat exchanger (SSHE) are limited. These studies introduced a numerical simulation of the fluid flow and heat transfer combined with the population balance to represent