Simultaneous Optimization and Heat Integration for the Coproduction of Diesel Substitutes: Biodiesel (FAME and FAEE) and Glycerol Ethers from Algae Oil

Abstract

In this paper, an optimal process for the simultaneous production of biodiesel (using methanol or bioethanol) and ethers of glycerol is proposed to increase the yield to diesel substitutes in current biodiesel production facilities. The problem is formulated as an optimization model including algae oil production, production of ethanol from starch, transesterification of the oil with bioethanol or methanol, etherification of glycerol with i-butene, which depends on a dynamic model to compute the complex chemical kinetics, and the purification of the ethers. Simultaneous optimization and heat integration are carried out and finally the water consumption of the integrated processes is optimized. Several comparisons are presented. First, the use of glycerol to produce ethers or as a byproduct. Second, the use of different alcohols for biodiesel synthesis in an integrated process. The production of glycerol ethers increases the yield of diesel substitutes by 20%. Furthermore, the energy and water consumptions are competitive with those processes when glycerol is the byproduct. For the integration of glycerol ethers with current biodiesel plants, the use of methanol instead of ethanol is cheaper. However, the current price of i-butene results in high production costs. Simultaneous production of ethanol, biodiesel and glyerol ethers reaches the target of $1/gal for biofuels production cost.