Transesterification of Triglyceride to Fatty Acid Alkyl Esters (Biodiesel): Comparison of Utility Requirements and Capital Costs between Reaction Separation and Catalytic Distillation Configurations

Abstract

The efficacy of catalytic distillation (CD) and the economic merits that it would bring into the biodiesel production process is studied. Process flow sheets depicting conventional and CD technology are modeled in Aspen Plus, and detailed operating conditions and equipment designs are provided for each process. The feedstock considered is soybean oil, and the transesterification reaction for the triglyceride is considered for biodiesel production. After optimal design of both process flow sheets to produce 10 million gallons of biodiesel per year, adhering to ASTM purity standards, a detailed cost analysis is carried out using the Aspen economic analyzer tool to predict capital, operating, and utility costs and to calculate the cost of production per gallon of biodiesel. Results depict CD to be a promising candidate to replicate the conversion and product purity of conventional biodiesel processes while having significant savings in capital (41.42% cheaper than the conventional process) and utility (18.12% less than the conventional process) costs, thereby making it a very competitive alternative. The total operating costs and price of production per gallon of biodiesel are only meagerly cheaper for a CD process because the most significant factor to the biodiesel production process is the raw material cost. For both processes, the price of production per gallon of biodiesel after accounting for revenue generated from glycerol product is predicted to be around 1.7 dollars/gallon. The Aspen model is flexible to accommodate higher flow rates for scale-up of operations, add or remove stages of operation into the biodiesel process, modify feedstock and stream prices, and predict associated capital and production costs.