(35a) Instrumentation, Automation and Control Applications in a Pilot Scale Supercritical Biodiesel Process

The supercritical biodiesel process uses temperature and pressure to drive both the alcohol and the feedstock beyond their critical points so that the reaction occurs in one phase.  The critical point for methanol is 1415 psia and 480 °F.  These reaction conditions allow the methanol to lose its polar nature and solvates both the triglyceride and free fatty acid.  This method is able to use very high free fatty acid (FFA) feedstocks as there is no sodium hydroxide saponification reaction that competes with the transesterification with this method.  High FFA feedstocks are commonly found available as waste streams that have no other economic purpose.  The use of ethanol  instead of methanol at supercritical conditions presents what some may term a more complete “green” solution since ethanol can be fermented from renewable feedstocks whereas most methanol is currently produced from the hydrolysis of natural gas.  The greatest advantage with supercritical process is that the lowest value feedstocks may be used and the conversion has very few detrimental byproducts.  As with all transesterification, water is a concern and must be controlled carefully.