A Study On The Performance Improvement Of Compound Biodiesel

With the increasing consumption of the fossil energy resources and the seriousenvironmental pollution caused by their use,biomass energy,a renewable,clean andenvironmental protection energy, emerged. Just because of its many advantages suchas the wide distribution, the various forms for utilizing, the low emissions of carbondioxide,biomass caused widespread concern.The study of liquid fuel from biomass,especially in utilization of vegetable oil as diesel engine fuel(biodiesel),has become acrucial research topic recently.In the application of using vegetable oil for dieselengine, we generally face some problem, higher viscosity,low cetane number,carbondeposition,etc.Despite vegetable oils can change its nature in multiple ways, there arestill many problems existed.The industrialization process is trans-esterification fromvegetable oil and short-chain alcohol. The major hurdle in commercialization ofbiodiesel via trans-esterification are large energy consumption, serious industrialpollution, high cost of biodiesel.The research object of this paper is compound biodiesel, produced by thephysical processes, directly mixing vegetable oil and various additives such asviscosity reducer in accordance with a certain proportion.The preparation method issimple and high economic, furthermoreits process is environmental. But there are alsomany obstacles in the course of its low cetane number, high carbon deposition forcompound biodiesel.Thus, the study on performance improvement of compoundbiodiesel seems to be more helpfuland important for its widespread use as well as itslarge-scale industrial applications.The cetane number improvers, the products which have high economic value,including butyl nitrate, isoamyl nitrate, isooctyl nitrate, dibutyl oxalate, diisoamyloxalate, diisooctyl oxalate, tert-butyl hydroperoxide, di-tert-butyl peroxide, tert-butylperoxy benzoate, were synthesized in this study from cheap chemical materials suchas alcohol, nitric acid, oxalic acid, hydrogen peroxide. Also, the structures of thesecetane number improvers were identified by Infrared Absorption Spectrometry(IR).A homemade self-ignition point test device was developed to assess the cetanenumber of compound biodiesel in this thesis. It can be used to test the self-ignition point of standard fuel consisting of different proportion of n-cetane and1-methylnaphthalene(heptamethylnonane). Then the correspondence relationship curve(X=（504.571-Y）/2.236； wherein X is cetane number, Y is a self-ignition point; squareof the correlation coefficient equation R2=0.940, standard error δ※=13.373), that isthe standard working curve, could be established between the self-ignition point andthe cetane number using unitary linear regression analysis. The subsequentexperiments on combustion characteristic of diesel engine fueled with compoundbiodiesel would be necessary to substantiate the above conclusions. According to theexperimental results, the method is feasible and reliable just as they indicate.Using the method of self-ignition point to measure the fuel cetane number,basedon ensuring correspondence relation between the self-ignition point and the cetanenumber, improvement and determination of the cetane number of the compoundbiodiesel was preformed when addition with nine kinds of different cetane numberimprovers separately. The results suggest that all kinds of cetane improvers can reducethe self-ignition point and enhance the cetane numberby different degrees whether thedifferent amount or the different category.When adding one additive respectively tocompound biodiesel, the cetane numberof fuel increased with the amount of thecetane number improver, while the dosage of improver was0.6%(wt%),the cetanenumber of compound biodiesel could be raised to a significant20units.Forcompounded cetane improvers, using together two additives, with a total dosage of0.6%(wt%), the compounded posed greater influence to cetane number. Thecompound consists of different proportions of di-tert-butyl peroxide and dibutyloxalate worked best under the same conditions for that the cetane number ofcompound biodiesel blend with it rose to24-29units. The conclusions that thereexists synergistic effect between two improvers when used together were easily drawnfrom the test result.In order to solve the carbon deposit problem caused by the compound biodieselused in diesel engine，slowing its formation method by the use of additives werestudied experimentally, the two important indicators,existed gum and carbon residue,associated withcarbon deposit were used as the evaluation.The results show thatin theexperiment of reducing existed gum by adding eleven different antioxidant tocompound biodiesel,2,5-di-tert-butyl hydroquinone achieved the best results, inaddition level of0.2%(wt%), it is possible that the existed gum value decreasedapproximately500mg/100mL; Whenadding eight kinds of detergent, polyether amineD-400worked best to reduce their carbon residue value of14unitsas the fuel blend with0.3%(wt%) of it, to a certain extent slowed the formation, a mixture of both (1:1)is added, the synergism effect appeares too.