Study on cold flow properties of waste oil biodiesel and improvement

The cold flow properties of waste oil biodiesel (WME) were studied by gas chromatography-mass spectrometry (GC-MS), multifunctional low temperature tester, differential scanning calorimetry (DSC) and solution crystallization theory. Three approaches for reducing cold filter plugging point (CFPP) of WME were investigated: crystallization fractionation, blending with winter petrodiesel and treating with cold flow improver (CFI) additives. A good correlation model was proposed for prediction CFPP by WME blending ratio. The study shows that the WME was mainly composed of fatty acid methyl esters (FAME): C_14:0-C_22:0, C_16:1-C_22:1, C_18:2 and C_18:3. The mass fraction of saturated fatty acid methyl esters (SFAME) and unsaturated fatty acid methyl esters (UFAME) was 31.04% and 64.51%, respectively. The CFPP of WME was 3°C. Crystallization fractionation and blending with -10 petrodiesel (-10PD) decreased the CFPP to -2 and -12°C respectively. Treating with CFI additives (volume fraction ≤ 0.5%) decreased the CFPP of WME and WME/-10PD to -1 and -26°C, respectively. This study has effectively improved cold flow properties of WME and provided guide for using WME during cold weather.