Use of reactive distillation in biodiesel production: A simulation-based comparison of energy requirements and profitability indicators

The advent of biodiesel, as a viable alternative to replace crude-based diesel as transport fuel, has prompted growing interest worldwide due to the need for low-emission fuels. In this work, two reactive distillation processes using soybean oil as main feedstock along with the corresponding downstream separation units are simulated: the first process involves a homogeneous alkali catalyst; whereas the second involves a heterogeneous catalyst. Both processes yield a high purity biodiesel product. In the present work, ASPEN Plus v8.4 is used as the process simulation tool. The energy requirements of both processes were evaluated based on the optimization of the distillation column duties and performing heat integration on the process streams. The optimization of the column duties was performed by analyzing the Column Grand Composite Curves (CGCC). The process streams were heat integrated, and a Heat Exchanger Network (HEN) was designed to minimize utility consumption. Both processes were compared using profitability indicators such as Return-On-Investment (ROI), payback period and unit production cost. The results show that the heterogeneous-catalyzed process is more profitable than the alkali-catalyzed process for biodiesel production. The ROI, payback period and unit production cost were 486%, 0.2 years and $0.712 per kg of biodiesel respectively. For the analysis, an annual production capacity of 35.4 kilotonnes/year of biodiesel production was assumed.