engleski

Purification of the Ester Phase by Water Extraction in Biodiesel Production

Water extraction is an effective method forremoval of impurities from the post- transesterification reac-tion product in biodiesel production. It is commonly usedin downstream processing alongside evaporation/distilla-tion and filtration. The effects of process parameters on bio-diesel purity, biodiesel loss, and capacity of waterextraction were investigated. Soaps were found to be keyimpurities, which significantly influenced the process andare the only emulsifier species that have an impact on theprocess. The acid value of biodiesel after water extractionwas dependent on the initial soap content. Difficulties withsoaps can be solved by adding an adequate amount of citricacid (0.01– 0.10%) in wash water. The effects of tempera- ture, pH of water extract, and mixing were investigated.Higher temperature (>25C) and higher pH (>7.0)increased biodiesel loss during the extraction. Higher pHand lower temperature increased the ester content. With anoptimal amount of citric acid in the wash water, high inten-sity mixing (>1.0 kW m−3) is desired for the most effec-tive purification. Correlation for calculation of an optimalamount of citric acid based on the desired pH of extract, the ratio of wash water to ester, and the initial soap contentin ester was found. Excess hydrolysis of biodiesel duringextraction was not observed. For the first time, engineeringaspects of process-settling time, and mixing parameters andtheir influence on removal of impurities and subsequentseparation were determined. Optimal mixing power per unitof volume was 2.25 kW m−3, mixing time 2.5 min, andsettling time 30 min. From the results and data obtained, anoptimal system for water extraction of crude biodiesel wasalso proposed.

Biodiesel, Purification, Water, Extraction, Soaps, Mixing

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