Process simulation and economic analysis of biodiesel production processes using fresh and waste vegetable oil and supercritical methanol

Abstract

Three continuous biodiesel processes with production capacity of 40,000 tonne/yr, including a conventional alkali-catalyzed process using both fresh and waste vegetable oil and a supercritical methanol process using waste vegetable oil as the raw material, were simulated in HYSYS. In order to improve the simulation accuracy, the properties of triolein, a model compound of vegetable oil, were re-evaluated. The normal boiling point of triolein was experimentally determined by thermogravimetric analysis and further incorporated in HYSYS simulation, which resulted in improvements in the values of specific heat capacity, mass density, and viscosity. Process economics were analyzed using Aspen In-Plant Cost Estimator. The alkali-catalyzed process using fresh vegetable oil had the lowest total capital investment, but the supercritical process was the most economically feasible overall, providing a lower manufacturing cost and higher net present value and a discounted cash flow rate of return. Sensitivity analyses of net present value were conducted using four parameters including oil feedstock costs, glycerol credit, biodiesel selling prices, and interest rates. Based on the analyses, prediction equations of net present value were developed.