【作者】 贺瑞雪；

【导师】 陈汉平； 杨海平；

【作者基本信息】 华中科技大学 ， 热能工程， 2008， 硕士

【摘要】 生物质作为唯一可以液化的清洁的可再生能源,利用其快速热解制取的生物油可以解决生物质直接气化带来的收集、运输和储存问题。但是,生物油的高粘度、高含水量、强酸性、低热值和热不稳定等性质严重影响了生物油的品质,阻碍了生物油的高端应用,因此,将生物油热解气化转化为H₂、CO、CO₂、CH₄、C₂、C₃等合成原料气,再经过进一步的技术处理合成高品位的燃料如甲醇、二甲醚等是实现生物油的高质化利用重要途径之一。本文从机理分析、模拟预测、实验研究三个层面对生物油的气化进行了较为全面的研究。首先,在热重分析仪上对生物油的热解及燃烧进行研究,分析其热解及燃烧特征,确定生物油热解与燃烧的动力学机理模型及参数结果,并采用TG-FTIR联用技术对生物油样品热解过程中气体产物的释放特性进行在线分析,确定热解产物及其随温度变化的释放特性。结果表明:生物油热解分为两个阶段,燃烧分为三个阶段,热解的主要产物为CO、CO₂、H₂O和碳氢化合物等小分子气体。然后,基于Aspen Plus软件,选取具有代表性的模型化合物模拟生物油,采用Gibbs自由能最小化法建立了生物油气化模型,进行生物油气化全过程的模拟计算,在物料平衡、化学平衡的前提下,分析了温度、压力、气化剂量、反应气氛对反应产物参数的影响:温度的升高使得生物油分解更为彻底,目标产物H₂、CO含量增加;反应产物中H₂、CO含量与压力的增加成反比;选用O₂和H₂O作为气化剂时,较小的量较为适宜;CO₂作为生物油的气化剂是较好的选择。最后,在固定床气化系统上对生物油在不同的实验条件（反应温度、载气流量、反应气氛、在生物油中加入水）下的热解气化反应进行了实验研究,并与模拟结果加以比较,综合比较之后得到生物油气化的较优反应条件:800℃为实验条件下热解最佳温度;75ml/min的N₂气体流量为热解反应提供了最佳停留时间;O₂不适宜作为外热式气化系统的气化剂,用于工业应用时,也应选择较小的量;CO₂气氛下,CO产量有较大增加,H₂产量基本不变,因而是较优气化剂;热解气成分主要来自于生物油中不溶于水的大分子有机物。更多还原

【Abstract】 Bio-oil made from fast pyrolysis of biomass is convenient for being collected, stored and transported with potential to be used as a fossil oil substitute. However, higher viscosity, higher moisture, higher acidity, lower heating value and heat instability are unbeneficial properties of bio-oil to be used in high class way. Therefore, it is one of the important approaches that changing bio-oil from the liquid into H₂, CO, CO₂, CH₄, C₂, C₃, etc. that could be used to synthesize high grand fuel such as methanol, dimethyl ether, etc. after further disposal. Form the aspects of mechanism, modeling and experiments, the gasification of bio-oil was fully investigated in this paper.Firstly, the investigations of pyrolysis and combustion of bio-oil were preformed using Thermo-gravimetric analyzer. The characteristics of pyrolysis and combustion of bio-oil were analyzed and kinetic mechanism model and parameters were obtained. The release behaviors of the products of pyrolysis were made on-line analysis by thermo-gravimetric analyzer coupled with Fourier Transform Infrared Spectroscopy.The products of pyrolysis were determined and the characteristics of release of them with temperature were studied. The results indicated that pyrolysis of bio-oil divided into two stages and combustion divided into three stages. The main products of pyrolysis are CO, CO₂, H₂O and hydrocarbons etc.Then, based on ASPEN PLUS, a bio-oil gasification model by the method of Gibbs free energy minimization was approached and representative model compounds were selected to simulate bio-oil. Analysis was made that the effects of relevant factors （such as temperature, pressure, the amount of gasification agent and reaction atmosphere） on parameters of products on the prerequisite of material balance and chemical equilibrium. The simulation results showed that the decomposition of bio-oil was more thoroughly and the concentration of H₂ and CO increased as temperature rised. The concentration of H₂ and CO was inversely proportional to the increase of pressure. It was more appropriate to choose a low amount when the gasification agent was O₂ and H₂O. It was a better choice that chooses CO₂ as gasification agent. Finally, experiments of bio-oil gasification were operated on fixed bed under various conditions （temperature, the flow of carrier gas, reaction atmosphere and adding water into bio-oil）. The more optimal reaction conditions were given after simulation results were compared with experimental results. The results indicated that 800℃was the best temperature of pyrolysis under experimental conditions. The flow of N₂ of 75ml/min provided best residence time of pyrolysis. It was not appropriate that choose O₂ as gasification agent of external heated gasification system. When used for industrial application the low amount of O₂ was a better choice. When choosed CO₂ as gasification agent the concentration of H2 was almost invariant and the concentration of CO increased significantly. Therefore CO₂ was an appropriate gasification agent. The products of pyrolysis mainly formed from macromolecular organic compounds that were not soluble in water.更多还原