Esterification Of Biomass Pyrolysis Oil And Its Combustion And Emission Characteristics In A Diesel Engine

Biomass pyrolysis oil has attracted more attention as a renewable clean energy.However,because of the higher water content and strong acidity,it can not be used as the engine fuel directly.Therefore,it must be pretreated and refined with proper measures to improve the fuel quality.In this paper,original biomass pyrolysis oil from wood pellet was used.At first,it was treated with extraction of dichloromethane,and the product was called as crude bio-oil.Then for this crude bio-oil,a catalytic esterification method was adopted to obtain refined bio-oil.The major fuel properties of the crude biomass pyrolysis oil and the refined bio-oil are measured or calculated by suitable methods.The volatility,combustion characteristic and oxidation dynamics of the crude bio-oil and the refined bio-oil were investigated by using thermagravimetric analyzer under O₂ atmosphere.Moreover,the effective thermal efficiency,cylinder pressure,combustion heat release rate and emission performance in a 186FA diesel engine fueled with diesel belends with various fractions of refined biomass pyrolysis oil were analyzed comprehensively.The main research content are as follows:?1?A variable-controlling approch was used to find the optimized reaction temperature,catalyst amount and oleic alcohol ratio for the the catalytic esterification reation of crude biomass pyrolysis oil.For 100ml crude bio-oil sample,the catalytic esterification reaction showed best result after 30 minutes under the reaction temperature of 50°C,the catalyst amount of 8g and the ratio of oil to alcohol ratio of2:1.Meanwhile,the components of the crude biomass pyrolysis oil the refined bio-oil were determined by gas chromatography/mass spectrometry.The GC-MS results revealed that after catalyzed esterification,the amount of acids,phenols and macroethers was decreased by 85.8%,18.1%,and 36.6%respectively,while esters and ketones was increased by 82.4%and 31.0%.?2?The cetane number,low heat value and viscosity of the biomass pyrolysis oil and the refined bio-oil were measured or calculated by suitable methods or empirical formulars.Compared with crude biomass pyrolysis oil,the low calorific value of refined bio-oil increased by 14.5%.Meanwhile,the viscosity and cetane number of refined bio-oil were favarably improved.?3?With using the thermagravimetric analyzer,the volatility,combustion characteristic and oxidation dynamics of the biomass pyrolysis oil and the refined bio-oil were investigated under O₂ atmosphere.It was revealed that the initial temperature of weight loss for the crude biomass pyrolysis oil was 6.1°C earlier due to its higher water content.In spite of this,the end temperature of weight loss for the refined bio-oil was 5.3°C earlier than that for the crude biomass pyrolysis oil.At the initial stage of temperature rising,the crude biomass pyrolysis oil needed lower activity energy for dehydration than the refined bio-oil,however,at the stage of high temperature,the refined bio-oil needed lower activity energy for oxidation than the biomass pyrolysis oil.Considering the entire oxidative combustion process,the refined bio-oil,although being slightly slower at the initial volatilization stage,was more combustible than the crude biomass pyrolysis oil at the practical oxidation stage.?4?At the same load of n=3600 r·min^-1,with the increase in the fraction of refined bio-oil in diesel blends,the effective thermal efficiency of diesel fuel,B5,B10and B15 were gradually reduced.At the full load,compared with reference diesel fuel,the effective thermal efficiency of B5,B10 and B15 were reduced by 0.9%,1.8%and2.9%,while they were reduced by 2.9%,7.6%and 9.7%at 25%load.At the full load,due to the higher oxygen content and some uncombustible components of heavy molecules in the refined bio-oil,the in-cylinder temperature was decreased.Compared with diesel fuel,the maximum pressure in cylinder was reduced by 1.8%,4.1%and5.3%for B5,B10 and B15 respectively,and the moment of in-cylinder pressure peak was postponed 2°CA,3°CA and 5°CA.Compared with diesel fuel,because of more air-fuel mixtures formed during the ignition delay,the peaks of instantaneous heat realease rate was increased by 9.1%,16.8%and 21.2%respectively.?5?The emission performances of a diesel engine fueled with the reference diesel,B5,B10 and B15 were analyzed.When the engine was operated at 3600 r·min^-1,compared with the reference diesel fuel,the HC,CO,and soot emissions of B5,B10 and B15 deteriorateed with the increase in the fraction of refined bio-oil in diesel blends.However,due to the higher oxygen contend and uncombustible components of heavy molecules of refined bio-oil,the combustion rate of fuel and the the in-cylinder temperature were reduced.As a result,the NO_x emissions of B5,B10 and B15 were gradually decreased.