纤维素热裂解反应机理数值模拟

A detailed mechanism analysis of cellulose pyrolysis was carried out according to the previous experimental results. On the basis of the Brodio-Shafizadeh model, a modified two-stage model was proposed to simulate the formation and decomposition of active cellulose (AC) and several main organic compounds, such as levoglucosan (LG), hydroxyl-acetaldehyde (HAA), acetol and furfural etc. During pryolysis, the temperature rise of cellulose can be divided into three stages. In the second stage, cellulose undergoes a main decomposition process in which the reaction temperature remains rather low because of the endothermic cracking of glucosidic bond of AC during the formation of LG. The components density of bio-oil, including LG and other competitive compounds, increased rapidly with the increase of temperature during the first stage. However, in the main decomposition process, LG density in bio-oil had an obvious decrease, while the competitive products appeared to increase gradually, which means the ring-opening and reforming reaction of pyranoid ring are superior to LG formation in high temperature.The secondary reaction of volatile components occurs largely in gaseous phase rather than in the solid phase. Short residence time of volatile materials in high temperature region will be advantageous to a high production of LG,which may otherwise decompose quickly under high temperature. An optimum yield of LG could be obtained when radiant source temperature is in the range of 730---920K and gas residence time is less than 1 s. In addition, the reaction temperature has a stronger effect than gas residence time on the formation of HAA, acetol, formaldehyde and furfural etc.     

生物质闪速热裂解制取生物油的试验研究

基于生物质资源的高效清洁能源化利用目的，对生物质热裂解制取生物油这一具有重要应用前景的技术开展研究。结合流化床的优质和生物质的特殊性，自行研制成功给料速达5kg/h的流化床热裂解反应器，并制取得到产率高达60％的生物油。同时针对木屑和秸秆的系统试验研究得出了反应温度和原料种类等主要参数对生物质闪速热裂解制油的影响规律。     

生物质热裂解制取液体燃料技术的发展

对生物质热裂解技术进行了系统的研究，阐述了其基本技术要求和发展现状，并将现有的生物质热裂解反应器进行分类，分析了相应的优势与不足。最后评估了生物质热裂解制取液体燃料技术的经济和社会效益，结果表明它具有广泛的应用前景。     

基于突变论的地铁车厢火灾中轰燃条件分析

以地铁一节车厢为研究对象,先分析地铁车厢内部的通风情况,假设其内部起火,对热烟气层建立能量守恒方程,对其无量纲化,并进行同胚微分,得到燕尾突变的势函数,并画出二维空间的突变分岔集．先根据计算数据判断是否处于系统突跳范围内,如果处于突变工况,再利用势函数的定性曲线和微商图得出系统不稳定点,从而计算出轰燃发生时热烟气层的温度,揭示了该系统具有燕尾突变的机理．     

纤维素热裂解过程动力学的试验分析研究

尽管针对纤维素热裂解动力学方面的研究已开展得比较广泛 ,但其表观动力学的确定仍是一具有争论性的问题 ,从而对纤维素热裂解机理的描述也就各不相同 .本文试图通过纤维素的热裂解动力学研究 ,对此种现象作出合理的解释 ,并给出相应的机理描述 .纤维素热裂解随温度的升高经历了五个不同的阶段 ,其中第三阶段是整个过程的主要部分 ,期间大量挥发分析出并造成明显失重 .试验发现随着升温速率的增加 ,热滞后现象的加重致使纤维素热裂解各个阶段向高温侧移动 ;同时高升温速率对炭的生成具有抑制作用 ,但有利于挥发分的生成 .通过对热裂解主反应区的热重分析 ,采用微商法求得对应的反应动力学参数 ,以 6 0 0 K作为分界点 ,低温段的活化能约在2 6 7k J/ m ol,较高温度段则体现为 174 k J/ mol左右的低活化能 .纤维素热裂解是一传热传质现象 ,与化学动力学机制相互影响、控制的过程 ,试验条件、传热传质过程的影响是造成结论存在差异的内在原因