有氧辅助微波热解落叶松木材的特性及产物分布

Oxygen-assisted Microwave Irradiation Pyrolysis Characteristics and Products Distribution of Larch

针对生物质微波热解普遍存在的微波吸收差以及焦油产生快等问题,将有氧热解与微波加热相结合,研究了微波氧化热解落叶松的升温规律、产物产出规律以及产物特性。研究结果表明:氧的引入改善了微波加热行为,当氧碳比(n(O)/n(C))值达到0.44时,升温曲线由阶梯状变为近似直线;氧气促进了木材微波热解转化,当n(O)/n(C)值为0.22时,气体产物收率75.55%、液体产物收率15.61%、固体产物收率8.84%,显著优于无氧微波热解(气体产物19.37%、液体产物48.78%及固体产物31.85%)。落叶松木材热解产物中,热解气化指标显著提高,当n(O)/n(C)值从0升至0.22时,碳转化率从7.4%增至52%,燃气产率从0.16 m^3/kg升至0.82 m^3/kg,气化效率从14%增至37.5%,燃气电耗降幅80%,但n(O)/n(C)值超过0.055时,燃气热值呈降低趋势;焦油的副产品减少,产物以稠环芳烃为主,组成得到极大简化;焦炭酸值明显降低,副产品减少,适量氧的引入促进焦炭内部形成微孔-介孔共存结构,孔结构更加稳定,显著改善焦炭的比表面性质。当n(O)/n(C)值为0.22时BET比表面积为489 m^2/g,平均孔径4.13 nm。

A novel method based on oxidative pyrolysis in combination with microwave irradiation was proposed,which could overcome the poor microwave absorption ability and the tar production from microwave-assisted pyrolysis of biomass.The heating behavior,products output behavior and characteristics of the product of microwave-assisted oxidative pyrolysis of larch were studied.The results showed that heating rate of the microwave irradiation increased with the addition of oxygen,and it was close to linear when the molar ratio of oxygen to carbon was 0.44.The oxygen promoted the microwave irradiation pyrolysis and when the molar ratio of oxygen to carbon was 0.22,the yields of gaseous,liquid and solid products were 75.55%,15.61%,and 8.84%,respectively,which were much better than the results of microwave irradiation pyrolysis without oxygen(the yields of gaseous,liquid and solid products were 19.37%,48.78%,and 31.85%,respectively).The addition of oxygen led to the increase of the carbon conversion rate,gas yield,and gasification efficiency from 7.4%,0.16 m^3/kg,and 14%to 52%,0.82 m^3/kg,and 37.5%,respectively and the decrease of power consumption by 80%with increasing the molar ratio of oxygen to carbon from 0 to 0.22.However,when the molar ratio of oxygen to carbon was beyond 0.055,the heat value of gas declined.The addition of oxygen also reduced the amounts of by-products such as tar and char,and achieved liquid composed of polycyclic aromatic hydrocarbons and the low acid char.In addition,the appropriate amount of oxygen could significantly benefit the formation of micro-and mesoporous structure and improve the specific surface properties of the obtained char.When the molar ratio of oxygen to carbon was 0.22,the specific surface area and average micropore size of char were 489 m^2/g and 4.13 nm.