Combustion Characteristics of Biodiesel Derived from Palm and Rapeseed Oil

Abstract

The chemical composition of palm and rapeseed biodiesel (fatty acid methyl ester, FAME) was analyzed by gas chromatography-mass spectrometry. Combustion characteristics of biodiesel were studied by thermogravimetry-differential scanning calorimetry and collision theory. Combustion characteristic index C was put forward for describing biodiesel combustion characteristic. The reactive atom combustion mechanism was put forward. Biodiesel combustion process comprised three steps, viz., volatilizing, dissociating and combining. First, biodiesel volatilizes, viz., FAME (liquid) volatilize and became FAME (gas). Second, FAME, O2 and N2 molecular were dissociated into C*, H*, O* and N* reactive atoms. Third, C*, H* and N* reacted, respectively, with O* to CO2, CO, H2O and NOx, and released energy. The study showed that the biodiesel was mainly composed of FAME: C14:0-C24:0, C16:1-C22:1, C18:2 and C18:3. Biodiesel had a good burnability. Combustion characteristic indexes of palm methyl ester (PME) and rapeseed methyl ester (RME) were 4.97E-05 and 3.65E-05, respectively. The combustion characteristic had relation to chemical composition. The combustion characteristic of biodiesel was better with increasing saturated fatty acid methyl esters and length of carbon-chain, and was poorer with increasing unsaturated fatty acid methyl esters and unsaturated degree. The combustion characteristic of PME was better than that of RME.