COMPARATIVE ASSESSMENT OF BIODIESEL PRODUCTION PROCESSES USING ASPEN PLUS SIMULATIONS

Abstract

With escalating world-wide energy demands and depletion of the conventional fossil fuel reserves (the diesel fuels), there has been immense research done to create alternatives for them. The bio-based sources provide a promising and hopeful alternative for replacing the diesel fuels. Biodiesel is the most popular and highly demanded fuel amongst the present alternatives due to its several benign qualities and its sustainable nature of usage. It helps reducing the quantity of harmful emissions, reduces the greenhouse gas emissions, and improves the combustion efficiency inside the vehicles. Despite its many advantages, the existing biodiesel production processes faces severe problems and bottlenecks, owing to the high energy costs involved for its production and enrichment. This problem has been detrimental towards the commercialization of biodiesel production to a very severe extent. This work undertakes a comparative study between a conventional biodiesel formation process (consisting of a reactor and distillation columns in series) and a novel catalytic distillation process. By energy analysis of the two processes, we establish that the latter can help reduce the total energy requirements for biodiesel production and is therefore a more promising alternative. First, the simulation for conventional biodiesel production was performed in Aspen Plus v 8.4. The energy requirements for producing biodiesel were obtained for this conventional simulation. Then simulations on catalytic distillation were run using rate based modeling. The feed and product specifications as well as flow rates were kept similar to that of the conventional process so that then we can compare the energy requirements for both the processes. The comparison of energy analysis revealed that - catalytic distillation simulation helped in reducing energy demands for the biodiesel formation by over 30% compared to the conventional biodiesel formation processes. iv We also performed sensitivity analysis for both processes to decide on the various optimum unit operation parameters that governed the net heat duty requirements of the biodiesel process. The main idea was to have the biodiesel at the desired purity level (as guided by the ASTM standards) with minimum energy requirements possible. This analysis helped to simulate those parameters and find their best point of operation.