Biodiesel production from a butter factory effluent
Visser, Hendrik Petrus
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The production of biodiesel from a butter factory effluent was the main focus of the study. The alkali transesterification reaction was used to produce the biodiesel. The effect of the temperature, alcohol to oil molar ratio, catalyst concentration and the reaction time was investigated to determine the optimal reaction conditions. The reaction temperature varied from 45 °C to 65 °C with a 5 °C increment. The alcohol to oil molar ratio varied from 3:1 to 8:1 with an increment of 1:1. The experiments with varying catalyst load were carried out at 0.8 wt%, 1.0 wt% and 1.2wt%. The reaction time was kept constant at 120 minutes, but samples of the reaction mixture were taken at 10 minute intervals. The optimal reaction conditions according to the results were 50 °C, 6:1 alcohol to oil molar ratio, 1.0 to 1.2 wt% catalyst loads and a reaction time of 60 to 90 minutes. The optimal temperature was also the maximum temperature since a further increase in temperature lowered the ester content. Increasing the alcohol to oil molar ratio above 6:1 had no effect on the ester content. The increase in catalyst load decreased the time needed for the reaction to reach equilibrium. The purification process was also investigated. The biodiesel was washed with water, Magnesol® DSOLTM and Purolite® PD-206. The Magnesol® D-SOLTM was the best method for lowering the water content and the acid value of the fuel. A Magnesol® D-SOLTM content of 1.0 wt% was mixed with the biodiesel for 30 minutes in order to lower the water content and the acid value to below the maximum limit. A kinetic model for the biodiesel reaction was developed. The model was based on the second order reversible reaction. The temperature range for the model is from 45 °C to 55 °C. The forward reaction was found to be exothermic with an endothermic reverse reaction. The activation energy for the exothermic forward reaction varied between 9.478 and 26.937 kJ/mol while the activation energy for the endothermic reverse reaction varied between 74.161 and 136.433 kJ/mol for the reactions with a catalyst load of 1.2 wt%. The biodiesel was tested according to the SANS 1935:2011 standard. The biodiesel did not meet all the requirements of the standard. The flash point, sulphur content, carbon residue, oxidation stability, free glycerol, total glycerol and cold filter plugging point did not meet the specification of SANS 1935:2011. The biodiesel should be blended with mineral diesel if it is to be used commercially. The butter factory effluent can be used as a feedstock for the production of biodiesel.
- Engineering