Variation of solid fraction with cold flow properties of biodiesel produced from waste frying oil

Biodiesel sample utilized in the study was produced from waste frying oil by a base catalyzed one step transesterification reaction. The feedstock oil and the samples produced were tested in accordance with the standards designated by European Committee for Standardization and also by American Society for Testing and Materials. Cold Flow Properties (CFP), namely Cloud Point (CP), Cold Filter Plugging Point (CFPP) and Pour Point (PP) were determined. Since the three CFP should occur at specific solid fractions during freezing, the objective was to examine in details the whole solidification history to estimate the corresponding solid fractions at these temperatures. The so-called computer-aided cooling curve analysis employed in metal casting industry was modified and applied to the current biodiesel sample. Indications of CP, CFPP and PP were noted as slope changes on the cooling curve and also on its first derivative curve. The Newtonian thermal analysis was utilized to estimate the solid fractions in the solid-liquid mixture at CP, CFPP and PP during solidification. The fraction of the solidified biodiesel in the mixture jumped from 0.18 to 0.39 when the CFPP temperature was reached. The visual observations were in agreement with the calculations.