Conceptual Design of a Batch Process for the Production of Biodiesel from High Free Fatty Acid Feedstocks

A batch process was developed for the production of biodiesel from high free fatty acid feedstocks. The mixed-integer nonlinear programming (MINLP) problem, caused due to applying the hierarchical procedure together with Malone’s algorithm for the conceptual design, was solved. Meanwhile, the optimum states of major process parameters such as the utilization of the process equipment, paralleling, splitting, and the merging of unit operations, the process cycle time (CT), and the combination of batch and continuous units were determined. Based on the present optimization study, the optimum value of the process cycle time and the optimum number of the esterification reactors in series were obtained as 3.257 h/batch and 3 stages respectively. The batch process was found to be suitable for a capacity of less than 260 tons/yr, while the continuous process was suitable for a capacity of greater production rates. The results showed that the production rate had a direct effect on the economic potential of the process and that it should be set at its maximum possible practical value. Also, the break-even point for the optimum state occurred at the production rate of 130 tons/yr.