A Novel Continuous Extractive Reactor for Biodiesel Production using Lipolytic Enzyme

There is currently a need to improve the commercial feasibility of lipasic biodiesel production in order to make it an attractive alternative to conventional biodiesel processes. One such means is to apply process intensification principles, by combining reaction and product separation steps into a stirred countercurrent extractive reactor (XRC). Benefits include continuous operation, enhanced biodiesel yield via removal of by-products into a separate phase and lower capital and operating costs due to fewer unit operations. This study involves steady-state modelling of an 8-stage XRC employing oil feed and aqueous ethanol solvent, using lipase as catalyst. Modelling utilised commercial process simulation software coupled to an iterative method for estimation of dispersed phase holdup to investigate the influence of operating conditions and feed compositions on XRC performance. Results suggest the optimum solvent composition lies in the range of 50 – 70 vol% ethanol for oil feeds containing between 0 – 50 wt% free fatty acids. Increasing stage efficiency was detrimental to biodiesel yield, indicating that non-ideal reactive stages are preferable in the XRC. Incorporation of a raffinate recycle stream improved biodiesel yield, while recycling extract led to only minor downturn in yield and glycerol recovery provided that solvent to feed ratio was maintained above 1.5.