Study On Bio-oil From Co-pyrolysis Of Sewage Sludge And Rice Husk Over Biochar Catalyst

With the continuous advancement of sewage treatment projects,the amount of sewage sludge increasing annually.The sewage sludge contains many organic components and has high utilization and energy development value.For the purpose of obtaining reasonable disposal and resource utilization of sewage sludge,this research mainly uses biochar catalytic co-pyrolysis technology combined with pretreatment to perform thermochemical conversion of sewage sludge and rice husk,with the goal of preparing high-quality liquid fuel.Firstly,the pyrolysis characteristics,yield,and bio-oil composition of copyrolysis of sewage sludge and rice husk under different blending ratios were investigated.When the rice husk blending ratio increases,the DTG max and D values increase,while the amount of carbon residue at 950? decreases.With the introduction of rice husk,the yield of bio-oil in each mixing ratio increased obviously.The best blending ratio is 1:1,because at this time the highest bio-oil yield of 17.21 wt.% is obtained.Compared with sewage sludge pyrolysis,co-pyrolysis can reduce the nitrogen-containing substances in bio-oil and reduce the content of phenols,but it has little effect on other oxygen-containing substances.Secondly,different types and different concentrations of acids were used for acidwashing pretreatment of rice husks,and the effect of acid-washing conditions on the co-pyrolysis of bio-oil of sewage sludge and pickled rice husks was discussed.After acid-washing pretreatment(except 7% hydrochloric acid),the yield of bio-oil was increased,and the yield was as high as 21.86 wt.% under 3% hydrochloric acid.Compared with co-pyrolysis,the acids,phenols,and ketones in the bio-oil are reduced after acid-washing.Finally,the influence of different biochar catalysts on the co-pyrolysis of bio-oil was explored,and the potential catalytic mechanism was summarized.After catalysis,the yield of bio-oil decreased to 9.45-12.03 wt.%,the yield of gas increased to 32.53-37.27 wt.%,and the yield of biochar remained stable.Compared with co-pyrolysis,the content of oxygen-containing substances(including acids and phenols)and nitrogencontaining substances(except RHA)has been drastically reduced,and hydrocarbon substances have increased significantly.This is consistent with the elemental analysis results,that is,the oxygen and nitrogen content in the bio-oil decreases,and the carbon content increases.This indicates that the quality of bio-oil has been significantly improved after catalysis,because the bio-char catalyst has a larger specific surface area and abundant functional groups,and RHC shows the best catalytic performance.In addition,the effect of the acid-washing combined catalyst on the co-pyrolysis is also discussed,which can not only make up for the decrease in bio-oil yield caused by the introduction of the catalyst,but also further enhance the deoxygenation effect and produce more hydrocarbon.