Study On Process Technology Of Biodiesel Preparation From Heterotrophic Chlorella

As a new fuel,biodiesel had the advantages of innocuity,harmlessness and biodegradability.Microalgae diesel had been the focus of research in recent years.Compared with autotrophic Chlorella vulgaris,heterotrophic chlorella had high cell density,fast growth rate and high intracellular lipid content,which shows a good prospect for development.Aiming at biodiesel preparation from heterotrophic chlorella,this thesis compared the traditional two-step process and new in-situ transesterification process,optimizes the process parameters and teste with a trial production.Firstly,two-step biodiesel process with cell disruption/oil extraction and transesterification was studied.By comparing the different cell disruption and extraction methods,the results showed that the combination of ultrasonic-high pressure homogenization method and extraction with ethanol ethyl ester could obtain high yield of chlorella oil.With algal oil and ethanol as raw materials,biodiesel was prepared by transesterification with concentrated H2SO4 as catalyst.,After the optimization with single factor test and response surface analysis,the suitable process parameters were found as the molar ratio of methanol to oil at 9:1,4.21%catalyst amount,reaction time of 3 h,esterification temperature of 77.80 ?.The biodiesel conversion rate was 97.01%.Secondly,new preparation process of biodiesel by transesterification in situ was studied.By comparing the different in-situ transesterification methods,the conversion rate of biodiesel of algae powder with water content of 10%as raw material showed higher conversion rate of biodiesel than that of dry powder.In addition,the broken wall algae powder was better than no-broken wall algae powder.It was also found that ultrasonic assistant could improve the conversion rate of biodiesel.Biodiesel was synthesized by in situ transesterification from algal powder with concentrated H2SO4 as catalyst and ethanol as the materials.After the optimization with single factor test and response surface analysis,the optimum conditions for in situ transesterification of biodiesel were 4.46%catalyst amount,the ratio of algae to alcohol at 7:1,ultrasonic power of 264.64,esterification temperature of 50 ? and esterification time of 1.27 h.The biodiesel conversion rate was 92.69%.Finally,the trial run of 3000 tons of biodiesel production line with heterotrophic chlorella was investigated.The analysis of Chlorella biodiesel by gas chromatography indicated that the main components were oleic acid ethyl ester,linoleic acid ethyl ester and ethyl palmitate.The total amount reached more than 93%,and the product could be mixed with petroleum diesel to meet the daily use of car.The production costs of two processes were compared.Without considering the cost of raw material production,the biodiesel cost of traditional two-step process was 3171 RMB/ton,while that of in situ transesterification was only 2050 RMB/ton.The advantages of in situ transesterification process were obvious.