Winterization of biodiesel through progressive freezing for cold flow properties improvement

Abstract

In cold environment, pure biodiesel cannot be used directly as an alternative fuel as it crystalizes easily at low temperature due to its saturated fatty acid (SFA) content. Thus, the winterization method is used to reduce the SFA content that gives high melting point to biodiesel. However, the conventional winterization method was reported to be complicated and ineffective in separating the liquid and solid content formed. Progressive freezing (PF) is introduced to improve the separation efficiency in the winterization process by removing the solid SFA layer formed on the wall of the crystallizer without the use of complicated equipment. In this study, the initial value of cloud point (CP) and pour point (PP) of the biodiesel were measured and compared with the values obtained after the PF process. The effect of coolant temperature, freezing time and stirring rate towards the efficiency of the PF process were also determined. The obtained results showed that the best performance of winterization was observed at coolant temperature of 6 °C, freezing time of 20 minutes and stirring rate of 50 rpm. At this condition, the recovery of biodiesel is 65.46% while CP, PP and SFA content were reduced by 2.65 %, 14.29 % and 3.96%, respectively.