典型木质素气化动力学及产物析出特性

Study on gasification kinetics and product characteristics of typical lignin

选用四种典型木质素:碱木质素、木质素磺酸盐、水解木质素、G型木质素,分别在热重分析仪和固定床台架上对其气化失重特性、动力学机理及产物析出特性进行研究,以揭示木质素来源对其气化特性的影响。结果表明,均相模型对气化反应过程拟合度较好。碱木质素热解活性最高,最先发生热解,且热解活化能最低;但其热解焦结构较致密,气化反应性较差;G型木质素和碱木质素有相似的气化特性;木质素磺酸盐和水解木质素在热解阶段有两段失重过程,其焦炭气化反应性均较高。对于气化产物特性,气化气中H_(2)和CO为主要气体产物。碱木质素气化氢气产率高达55 mmol/g,碳转化率最高(87%),残余焦炭最少。而水解木质素和G型木质素气体产率较少,液体焦油和固体残渣相对较多,这主要与木质素中无机矿物质含量和组成有关。

Four typical lignins: alkali lignin, lignosulfonate, hydrolyzed lignin and G-type lignin, were selected to study their gasification weight loss characteristics, kinetic mechanism and product characteristics on a thermogravimetric analyzer(TGA) and fixed bed experiments, in order to reveal the influence of lignin sources on their gasification characteristics. The results showed that the homogeneous model fit the gasification reaction process well. Alkali lignin had the highest pyrolytic activity, reacted at lower temperature, and had the lowest activation energy. However, the structure of pyrolytic coke was dense and the gasification reactivity was poor. Glignin had similar gasification characteristics with alkali lignin. Lignosulfonate and hydrolyzed lignin had two pyrolysis stages, and their coke gasification reactivities were high. For products characteristics, H_(2)and CO were the main gas products. Alkali lignin had the H_(2)yield as high as 55 mmol/g, the highest carbon conversion rate(87%),and the minimum residual coke. However, hydrolyzed lignin and G-lignin had lower gas production, but tar and solid residue were relatively more, which was mainly related to the inorganic mineral content and composition.