Numerical Simulation and Experimental Testing of Novel Sonochemical Reactor for Transesterification

Biodiesel is a powerful alternate fuel that has one of the best feedstock in the form of waste cooking oil (WCO). Producing biodiesel from WCO solves two major environmental and waste related issues. Firstly, biodiesel substantially reduces CO₂ and Sulphur emissions and is capable of directly replacing petro-diesel in vehicles. Secondly, using WCO for biodiesel reduces the wastage of a potential fuel source and reduces problems such as sewer clogging which are caused by WCO draining. The biodiesel industry currently needs a continuous, compact, inexpensive and efficient reactor to make biodiesel lucrative and sonochemical reactors seems to be the best option. Hence, in this work a much needed task of a sonochemical reactor design development for biodiesel production is carried out through multiphysics simulations which account for ultrasound waves, cavitation attenuation, reactive flow and chemical kinetics. Numerical simulation is a coupled system of equations like Helmholtz equation, Navier–Stokes and species transport. Additionally, a full scale, closely resembling prototype of the reactor design is experimentally tested. In the prototype testing, piezo-electric hydrophone was carried for three cases to evaluate the acoustic pressure in the reactor. Experiments were performed with the reactor and the final biodiesel product was tested in a GC/MS analyzer. The numerical simulation showed several advantages of the design. The average conversion of biodiesel achievable at as low as 100 W ultrasonic power and was found to be 84%. The experimental testing also showed very high conversion of 91.23% for 100 W power and 12 l/h flow rate.