Process design and simulation of industrial-scale biodiesel purification using membrane technology

Abstract

Biodiesel is commonly produced through a transesterification reaction of vegetable oil with alcohol in the presence of a catalyst to produce fatty acid methyl ester (FAME). The reaction also produces glycerol as a by-product that must be separated from the FAME to obtain a biodiesel product that meets international standards. The common method to remove glycerol from FAME is washing with water. However, it produces a vast amount of wastewater and consumes much energy. Membrane technology is a promising separation technique for removing glycerol from biodiesel on an industrial scale since the separation using membrane does not produce wastewater and the energy consumption is low. In this work, the application of membrane technology to separate biodiesel and glycerol was studied through a process design and simulation of an industrial scale biodiesel purification process with a production capacity of 723 kL/day. A multistage feed-and-bleed microfiltration membrane system was designed to purify biodiesel from glycerol, and the process simulation was carried out using computer programming. The result of the process simulation showed that purified biodiesel could be produced by using the multistage microfiltration membrane system. The minimum membrane area required for the separation process in each stage could be calculated using the computer program. It was found that the total membrane area decreased with the increasing number of stages. A reduction of the total membrane area of 37% was achieved using ten stages microfiltration system. The optimum number of the stages could be determined through a tradeoff analysis of the cost to minimize the capital cost of the multistage membrane system. For the case study in this work, a stage number of 4 was found as the optimum stage number of the microfiltration system. This result showed that the membrane technology has great potential to be applied for the industrial-scale biodiesel purification process.