Effect of process variables on volumetric mass transfer coefficient in wet purification of crude biodiesel

ABSTRACT

In this study, the effect of process variables on the volumetric mass transfer coefficient (Kca) of residual solutes in biodiesel during wet purification was investigated. A purification process was carried out using distilled water batch-wise at varying washing times, temperatures and biodiesel-to-water (BW) ratios. The amounts of solutes in biodiesel and water phases were determined at each washing stage using standard methods. The linear driving force kinetic model equation was used to estimate the Kca. The concentration of solutes in the crude biodiesel were 12.02 mg/dm³, 0.0168%, 0.00159% and 0.02749% for catalyst, methanol, soap and glycerol, respectively. Using a BW ratio of 1:2, a time of 30 min and a temperature of 40°C in a single-stage washing process, optimum solute removal was achieved. A minimum of 250 cm³ of water sufficiently washed 100 cm³ of the biodiesel in a five-stage washing process at 40°C to achieve a solute concentration of 0.13 mg/dm³, 0.002 × 10^(-4)%, 0.13 × 10^(-4)% and 0.057 × 10^(-4)% for catalyst, methanol, soap and glycerol, respectively. There was increase in Kca as the BW ratio was decreased from 2:1 to 1:4. The Kca also increased as the temperature was increased from 30 to 50°C.

KEYWORDS:

• Wet purification
• crude biodiesel
• mass transfer coefficient
• solutes
• washing

Acknowledgements

Our profound gratitude goes to the Petroleum Technology Development Fund (PTDF) Professorial Chair (Renewable Energy) housed in the Department of Chemical Engineering, University of Benin, Benin City, Nigeria, for providing the laboratory and equipment used in this study.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

Petroleum Technology Development Fund, Abuja, Nigeria [10000000].