【作者】 罗凯；

【导师】 陈汉平；

【作者基本信息】 华中科技大学 ， 热能工程， 2007， 硕士

【摘要】 生物质是唯一可以液化的清洁的可再生能源,利用生物质快速热解制取的生物油便于运输和储存。作为液态燃料的生物油在替代化石燃料方面具有相当广阔的前景。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,阻碍了生物油作为燃料的应用。因此,为提高生物油的品质,增强生物油燃料的应用性,本文在自行设计建造的流化床热解液化系统上完成制取生物油的实验,一方面探求生物质原料和热解反应条件在热解过程中对生物物油产率和品质的影响规律,另一方面利用微波对生物质进行干燥,通过研究微波干燥对生物质原料以及对热解产物的影响规律,揭示微波干燥预处理对生物质热解过程的影响机理。本文研究的目的是实现生物质热解液化的控制转化,优化反应参数,揭示微波干燥的预处理工艺对生物质热解液化的积极意义。首先,对世界能源背景、生物质能及生物质热解液化技术进行了简单介绍,强调了液化产物生物油的特性及其应用难点,引出本文研究的目的和主要内容。其次,介绍了国内外流化床热解液化系统,描述了本文流化床热解液化系统的结构和工艺流程,选择了合适的试验参数,概括了试验操作方法和步骤。然后,通过试验研究了生物质原料种类、粒径和热解温度、气相停留时间对生物油产率和品质的影响规律。试验研究表明:原料的种类、热解温度和气相停留时间是影响生物油产率和品质最重要的参数:①、原料中纤维素、木质素和灰分的含量是主要影响因素。松木屑最适合生产高产率高品质的生物油。②、基于松木屑油的研究发现,450～550℃是生产高产率高品质松木屑油的最佳温度范围。③、热解蒸气的停留时间决定二次反应的发生几率,从而影响生物油的产率和品质。最后,试验研究微波干燥对生物质原料以及对生物质热解机制的影响。研究发现:微波干燥能迅速降低生物质原料的含水率,功率越大,干燥速率越快;微波干燥能扩大生物质的孔隙结构,有效增大原料的比表面积;微波干燥更有利于挥发分在热解过程中迅速析出,提高热解速率;微波干燥明显抑制了热解产物的二次反应,提高了生物油和焦炭的产率,减少了不凝气体的产率,同时减少了热解过程中水分的生成,提高了生物油的品质。更多还原

【Abstract】 Biomass is the only clean renewable energy resource that can be liquefied. Bio-oil made from fast pyrolysis of biomass is convenient for being 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 as liquid fuel. Thus in this paper, experimental studies were carried out in a bench-scaled fluidized bed reactor. On the one hand, the influences of the parameters such as raw material characteristics and pyrolysis conditions on the yield and quality of bio-oil were studied, on the other hand, the influences of microwave drying on biomass and its pyrolysis products were investigated. The purpose of these studies was to optimize reaction parameters for improving the bio-oil quality and enlarging the application of bio-oil as liquid fuel.At first, the background of energy all over the world, the bio-energy and the fast pyrolysis technique were introduced. As liquid product, the properties of bio-oil and the difficulties on its application were emphasized.Secondly, the system of the bench-scaled fluidized bed and the choices of trial parameters were described, followed by the description of the experimental process.Thirdly, experimental studies on the influences of raw material and the pyrolysis conditions on the yield and quality of bio-oil were performed, which indicated that the raw material sorts, reaction temperature and vapor residence time were key factors. At the same time, the content of cellulose and lignin as well as the ash in biomass were critical parameters, and the pine was most suitable raw material for bio-oil. For getting high quality pine-oil, the favourable reaction temperature was between 450℃and 550℃. The residence time affected the secondary reaction of the vapor, which was important for the yield and the water content of bio-oil.Finally, compared with heated air drying, the influence of microwave drying on raw material characteristics and the mechanism of biomass fast pyrolysis were studied. It was found that microwave drying rate was far faster, moreover, greater the microwave power level was, faster the dehydration rate was. The biomass dried by microwave had greater surface area and more inner paths, which was benefited for the release of volatiles, meanwhile the secondary reaction of pyrolysis products was suppressed because of the shorter contacting time between vapors and char. As a result, the yields of bio-oil and char increased while the yield of gas decreased. The bio-oil from biomass dried by microwave has lower water content and higher heating value, which was good for used as fuel.更多还原