【作者】 李威；

【导师】 宋正昶；

【作者基本信息】 中国矿业大学 ， 热能工程， 2017， 硕士

【摘要】 生物质燃料作为一种可再生能源,并且具有资源分布广、CO2零排放、污染小、易点燃等特点,越来越受到全社会的关注。我国作为农业大国,生物质燃料资源丰富,开发利用生物质对我国的能源战略和环境保护有着重要作用。但是生物质中含有大量的碱金属元素钾、钠以及矿物质元素硅、氯、硫等,这些元素在生物质燃烧过程中发生着复杂的物理化学反应,生成低熔点的化合物或共晶体,将会在燃烧设备发生严重的结渣、沉积、聚团和高温腐蚀等相关问题,严重阻碍了生物质的规模化利用。因此,选择合适的预处理手段去除这些元素对改善生物质灰熔融特性,减小生物质积灰结渣,促进生物质的规模利用有重要意义。本文以我国典型的两种农作物秸秆(麦秆、稻杆)为研究对象,采用X射线荧光光谱(XRF)、X-射线粉末衍射仪(XRD)、灰熔点分析仪等,对两种秸秆灰特性进行分析并进行结渣预判,发现两种秸秆灰中碱性氧化物含量高达36%和30%以上,主要碱金属元素K是以KCl形式存在,同时预判结果都为严重结渣倾向。研究水洗、酸洗后秸秆灰特性发现,通过不同液固比水洗,发现麦秆和稻杆分别在液固比为30、20的工况下,灰熔点的温度都超过1260℃,当液固比继续增大时,两种秸秆的灰熔点变化很小。对于不同温度条件下水洗,确定了麦秆和稻杆的最佳水洗温度为70℃。酸洗能够有效去除灰中碱性金属,提高两种秸秆灰熔点,结渣预判结果为轻微。盐酸浓度的大小对两种秸秆灰熔点的影响很小。采用单一升温速率法,对两种秸秆原样以及预处理后的样品进行热重实验,考察了其可燃特性、综合燃烧特性,计算了燃烧动力学。结果表明,麦杆、稻杆原样固定碳燃烧阶段活化能要大于挥发分燃烧阶段活化能,同时,稻杆两个阶段的活化能都要小于麦杆。水洗后,麦杆、稻杆两个阶段活化能都增大。70℃热水水洗后,两种秸秆发挥分燃烧阶段活化能增大,固定碳燃烧阶段活化能减小,且都小于挥发分燃烧阶段活化能。酸洗使麦杆两个阶段活化能都减小,稻杆固定碳燃烧阶段活化能减少,挥发分燃烧阶段活化能增大。更多还原

【Abstract】 Biomass fuels,a renewable energy,have earn more and more focus worldwide.Biomass fuels have the characteristics of resources widely distributed,CO2 zero emission,low sulfur,low pollution,easy to ignite and so on.As an agricultural country,our country is rich in biomass fuel,so the development and utilization of biomass play an important role in China’s energy strategy and environmental protection.However,plenty of alkali metal elements contained in the biomass fuels,such as potassium,sodium,silicon and mineral elements,chlorine,sulphur,etc..These elements produce a complex physical and chemical reaction in the process of biomass combustion,generate low melting point compound or eutectic,and then lead to serious slagging,deposition,agglomeration,and high temperature corrosion of combustion equipment,which seriously hinder the large-scale use of biomass.Therefore,choosing the right way of removing ash pretreatment,will improve melting ash properties of the biomass fuels,inhibit the slagging of the biomass fuels,which have an important significance to promote the scale utilization of biomass fuels.In this experiment,two typical crop straws,wheat straw and rice straw,were chosen as research objects.And XRF fluorescence analyzer,XRD diffraction analyzer,ash melting analyzer,etc.were used to explore the composition and melting characteristics of the oxide in the two kinds of straw ash,and to prejudge of slagging.It was found that the alkaline oxide in the two kinds of straw ash was about 36% and 30%,alkali metal element K was mainly existed in the form of KCl,and the results of prejudgement both have serious slagging tendency.As straw ash has the problems of high alkali content,easy slagging and so on,washing and pickling were adopted to reduce certain elements content in straw ash,then to study the ash fusion characteristics and to prejudge of the slagging results.Through different liquid-solid ratio washed,it was found that,under the condition that liquid-solid radios of wheat straw and rice straw were 30,the straw ash melting temperatures were both more than 1260℃and the prejudgement results of slagging were all mild.With the increase of liquid-solid radio,the ash melting point of the two kinds of straw changed slightly,and the prejudgement results of slagging were mild as well.Taken washing temperatures,ash melting point and prejudgement results of slagging into consideration,it was conformed that the optimal washing temperature of wheat straw and rice straw was 70℃.Pickling can remove the alkaline metal of the ash effectively,improve the ash melting point the two kinds of straw.However,the concentration of hydrochloric acid has little impact on the ash melting point of the two kinds of straw and prejudgement results of slagging.Single heating rate method was adopted to thermogravimetry experiment of the two kinds of straw and the samples of pretreatment,and to investigate the combustible characteristics,comprehensive combustion characteristics,then to calculate the kinetics of combustion.It was showed that activity energy in wheat and rice straw fixed carbon combustion phase was higher than that in volatile component combustion phase.Meanwhile,activity energy of rice straw was less than that of wheat straw in both phases.After washing,activity energy of the two kinds of straw both increased in two phases.After 70℃ hot water washing,the activity energy of both kinds of straw increased in volatile component combustion phase,while decreased in fixed carbon combustion phase,less than in fixed carbon combustion phase.Pickling reduced activity energy of wheat straw in both phases.To rice straw,activity energy decreased in fixed carbon combustion phase,and increased in volatile combustion phase after pickling.更多还原