Characteristics And Optimum Design Of Hydrogenated Biodiesel- Ethanol-Diesel Ternary Fuel

Biodiesel has been extensively studied and applied,owing to its wide feedstock sources,high cetane number and in-built oxygen.However,its poor oxidation stability is not conducive to longterm storage,which brings restrictions on its application.The oxidation stability of biodiesel can be effectively improved by partial hydrogenation,while its volatility and cold flow property are greatly reduced.It also brings the limitation on the application of biodiesel on engines.As one of fuel additives,Ethanol can boost the volatilization and cold flow performances of fuel and have a good compatibility with biodiesel.Correspondingly,hydrogenated biodiesel-diesel-ethanol fuel blends possess the superior volatilization performance,cold flow performance,cetane number and oxidation resistibility.The addition of ethanol can optimize the application of biodiesel on engines.In this paper,the partial hydrogenation of cottonseed methyl ester(CME)and soybean methyl ester(SME)was conducted via catalytic transfer hydrogenation method.The ternary fuel blends of hydrogenated biodiesel,ethanol and diesel were constructed and their physicochemical properties,volatilization and low temperature performances were inspected.Meanwhile,the interaction mechanisms of hydrogenated biodiesel,diesel and ethanol in the ternary fuel blends during the volatilization and crystallization process were investigated.Finally,the multi-objective function method was applied to optimize the components ratios of the ternary fuel blends based on the test results.The specific research contents are as followed.(1)The partial transfer hydrogenation of CME and SME was carried out using isopropanol as the hydrogen donor and Raney-Ni as the catalyst.The reaction was in water environment and under 85?.The feeding ratio of biodiesel,isopropanol and water was 7:32:100.The most suitable reaction time of biodiesel hydrogenation was determined to be 100 minutes by measuring the iodine values of products under different periods.The compositions of biodiesel before and after hydrogenation were detected by GC-MS.It was revealed that the contents of high unsaturated fatty acid methyl esters in partial hydrogenated cottonseed methyl ester(PHCME)and partial hydrogenated soybean methyl ester(PHSME)decreased by 46.1% and 42.7% respectively,compared with that in CME and SME.It was found that the cetane number of PHCME and PHSME increased obviously,and their low heat value also increased slightly.Simultaneously,their kinematic viscosity had a mild growth.(2)The ternary fuel blends of PHCME,PHSME,ethanol and diesel were prepared.Constanttemperature thermogravimetric test and kinetic method were adopted to figure out their vapor pressure,enthalpy and activation energy.It was revealed that,compared with the PHCME and PHSME binary fuel blends,the ternary fuel blends of PHCME and PHSME had the lower kinematic viscosity and activating energy,while their vapor pressure and enthalpy were higher.It was found the distillation range of the ternary fuel blends were advanced compared with the binary fuel blends.The volatilization performances of PHSME fuel blends were slightly worse than that of PHCME fuel blends.(3)The crystallization point of multi-component fuel blends was calculated by the solution thermodynamic model.It was demonstrated that the crystallization point of the ternary fuel blends of hydrogenated biodiesel,ethanol and diesel greatly decreased compared with the corresponding binary fuel blends.The crystallization points of PHC5E5,PHC10E10 and PHC15E15 were lowered by 4.5K,5.7K and 6.1K.The crystallization points of PHS5E5,PHS10E10 and PHS15E15 reduced by 4.3K,5.3K and 6.1K.In addition,the crystallization quantity for the ternary fuel blends of hydrogenated biodiesel,ethanol and diesel was lower than that of the corresponding binary fuel blends at the same temperature.Ethanol precipitated at the crystallization point for each ternary fuel blend,which repressed the formation and growth of crystal nucleus.This can extremely augment the low temperature performance of the ternary fuel blends.(4)The characteristic equations of ignition,volatilization,cryogenic and flow performances were obtained from the test results in this study.The blending ratios of the ternary fuel blends of hydrogenated biodiesel,ethanol and diesel ternary fuel were optimized by multi-objective function method.The reasonable weight coefficients and blending ratio intervals were acquired by constructing evaluation functions of different performance trends.The optimum blending ratio range was determined to be less than 10% of hydrogenated biodiesel-ethanol.Correspondingly,the loss rates of characteristic parameters for PHC5E5 and PHC5E5 ternary fuel blends were small.In addition,PHC5E5 and PHC5E5 had the higher oxygen content and better comprehensive fuel performance.