Toward the optimal integrated production of biodiesel with internal recycling of methanol produced from glycerol

In this article, we present the optimization of the production methanol from glycerol and its integration in the production of biodiesel from algae. We propose a limited superstructure where the glycerol from biodiesel is first reformed for which steam reforming and autoreforming are evaluated. The gas obtained is cleaned up and its composition is adjusted in terms of the ratio CO/H2 using three possible alternatives (bypass, PSA and water gas shift). Next, the removal of CO2 is performed by means of PSA and the syngas is fed to the methanol synthesis reactor and the products obtained are separated. This synthesis is coupled with the production of biodiesel from algae using heterogeneous catalyzed reaction based on previous results. The optimization of the system is formulated as a Mixed Integer Nonlinear Programming (MINLP) that is solved for the simultaneous optimization and heat integration of the production of biodiesel with recycle of methanol followed by water integration. The best process involves the use of autoreforming for a production cost of $0.66 gal−1, 3.65 MJ/gal of energy consumption and water consumption of 0.79 gal/gal. The integrated process is $0.2 gal−1 more expensive than the one that directly uses methanol but reduces in more than half the dependency of the process on fossil fuels.