Different water removal methods for facilitating biodiesel production from low-cost waste cooking oil containing high water content in hybridized reactive distillation

Abstract

Abstract Waste cooking oil (WCO) as feedstocks for biodiesel production contains high free fatty acid and water, causing negative impacts on the biodiesel yield and its purity. In this work, three alternative methods for handling water content in WCO feedstocks using the earlier hybridization of esterification and transesterification in a single reactive distillation column (hybridized RD) were investigated. Our simulation results revealed that using two heat exchangers combined with the hybridized RD is a simple method to remove water from WCO. However, it requires the highest energy as well as biodiesel production cost (1.63 USD/kg biodiesel). The extended spacing stage modification of the hybridized RD was proposed to remove water content. It requires a new hybridized RD construction by spacing stages addition which can handle WCO with 10 wt% of water content and require less energy, resulting in lower biodiesel production cost (1.07 USD/kg biodiesel). The integration of pervaporation unit was found to be the best option. It offers the highest performance in terms of water removal and methanol recovery, resulting in the lowest biodiesel production cost (1.04 USD/kg biodiesel). This study shows that using pervaporation or extended spacing stages with hybridized RD are promising methods for biodiesel production from WCO.