Abstract:
This work is an effort to model the gas-liquid droplet transesterification reaction to produce biodiesel, specifically to determine the hydrodynamic properties of soybean oil droplets produced by the liquid jet instability method as a model to the droplets produced in the spray reactor of Behzadi and Farid (2009), thus enabling the calculation of mass transfer coefficients. Soybean oil, chosen for this work because it is a typical vegetable oil used for biodiesel manufacture, is heated in a pressure tank and driven through a 0.34 mm diameter orifice using compressed air to produce a capillary liquid jet. The velocity of the emerging liquid jet was calibrated against driving pressures (gauge) between 41.4 to 137.9 kPa. Oil temperatures used were 80, 90 and 100oC. It was found that the liquid jet travels at speeds of 6.2 to 16.2 m/s depending on the driving pressure, with corresponding Reynolds numbers of 280 to 1670, and breaks up into a stream of droplets between 7.6 to 12.0 cm from the orifice opening. The manner in which the laminar jet breaks up into droplets, namely the breakup regime, droplet diameter and breakup length, was examined and observed through high-speed photography. In addition, the effect of having a source of external vibration (20 to 40 Hz) to the liquid jet breakup was also examined.
