Experimental and modeling studies on biodiesel production and refining in a dedicated bench scale unit

Continuous production and refining of biodiesel (FAME) using a lab bench scale unit was explored. The unit consist of three major units i) a reactor consisting of a Continuous Centrifugal Contactor Separator (CCCS), ii) a washing unit consisting of a mixer and settler and iii) a drying unit. The methanolysis reaction of sunflower oil was undertaken in the CCCS, using sodium methoxide as a catalyst. The two immiscible liquids (FAME and glycerol stream) were separated in the CCCS unit due to centrifugal forces. The FAME stream was washed with acidic water to remove the excess of methanol and catalyst. The washed FAME was pumped into a column to allow FAME-water separation. Subsequently, the FAME was dried in a bubble column using air. The effect of water to biodiesel ratio, residence time, air flow rate, and temperature were studied in the respective units. The optimum conditions found were at a maximum Foil of 32 mL/min with an excess of methanol (7.5:1 molar excess to oil and 1.2% m/m of catalyst regarding to the oil). The TCCCS was maintained at 75°C and an anticlockwise rotational speed of 35 Hz was applied. A FAME yield of 93% mol with low yields of glycerides (4% mol) was obtained. A low 0.5:1 ratio of water (1 wt% acetic acid) to FAME at room temperature sufficed to totally remove the excess of methanol and catalyst in the FAME, with a residence time of 4 minutes of washing and 10 minutes of phase separation in the column. In the drying step, an air flow rate of 12 L/min (30 °C inside the unit) was needed to achieve a proper water removal. The refined FAME contained 99.5 wt% of esters, low glyceride content and, a not detectable amount of methanol and 0.04 wt% of water. Other critical product properties of the FAME such as density, viscosity, flash point, pour point, cloud point, sodium content and acid value were determined, and mostly all of them met the international standard specifications. Besides, an Aspen model of the biodiesel refining was developed and which was validated using the experimental data and used for calculation of up-scaling purposes. Keywords: Continuous centrifugal contactor separator, FAME, biodiesel refining, water washing, biodiesel drying, refining model.Outgoin