Study On Extraction Phenols From Wood Vinegar And Anaerobic Degradation Of Solution After Extraction

Biomass energy is a renewable resource that can generate solid,liquid and gas fuels.However,wood vinegar occupies a large proportion in the liquid products obtained from biomass pyrolysis.There are water of 80-90%,pH of 2-4,and dozens or even hundreds of chemical compounds in obtained wood vinegar.Wood vinegar contains large number of cracking monomer,such as phenolic compounds,which is regarded as protoplasm toxic substances.Therefore,untreated wood vinegar will do great harm to the environment without properly handling.Moreover,it is necessary to solve the problem of vinegar before developing pyrolysis technology for biofuel production.The extraction method was adopted to reduce the concentration of phenolic compounds in wood vinegar solution.In order to find the optimal extractant and extraction conditions,model compounds are used in this thesis instead of the complex wood vinegar.First of all,the extraction agent was determined by distribution coefficient?D?of methyl isobutyl ketone?MIBK?,isopropyl ether,ethyl acetate and biodiesel,with model compounds such as:acetic acid,phenol,furfural,guaiacol,pyrocatechol and 2,6-dimethoxyphenol,respectively.Remarkable distribution coefficient of phenols and furfural was found in MIBK.Besides,MIBK is easier to be distilled and regenerated than phenol since it has a lower boiling point.So MIBK was selected as the optimum extraction agent.Secondly,the standard curves of model compounds were established by HPLC,while the orthogonal design of four factors and four levels was established with MIBK solvent.The factors of pH,extraction temperature?T?,phase ratio?R?and oscillation time?t?were examined to achieve significant removal rate of the model compounds and COD.The optimal extraction conditions were obtained,i.e.,pH=5,T=30?,R=1:3,and t=2 h.Besides,the regenerated extractant of MIBK by distillation was applied on extracting the model compounds.The result showed that relatively high yield of phenols was observed by regenerated extractant,indicating stable extraction efficiency compared with the fresh one.Finally,anaerobic digestion was applied on degrading the wood vinegar solution after extraction of phenols further.The experiment was carried out after three-stage extraction of wood vinegar solution.After anaerobic fermentation,the GC analysis showed that there were 78.58%of CH₄ and 21.42%of CO₂ in gas production and the raw material gas production rate was 32 ml/g.In addition,the pathway of wood vinegar in the process of producing methane by anaerobic degradation was illustrated.In summary,the results proved that the method of extraction coupled anaerobic digestion could effectively extract and degrade organics in wood vinegar solution.