【作者】 胡亿明；

【导师】 蒋剑春；

【作者基本信息】 中国林业科学研究院 ， 林业环境与能源工程， 2013， 博士

【摘要】 生物质是目前唯一能够同时提供固体、液体和气体燃料的可再生能源。然而由于生物质结构复杂，其热解也是一个包含物理化学变化的复杂过程。为了揭示热解过程中生物质及生物质组分的吸放热规律，以及组分间的相互影响规律，本文采用热分析技术及热重分析技术对生物质及其组分热解过程进行了研究，所做的工作主要有如下几个方面：采用热重分析仪（TG）和同步热分析仪（STA）对纤维素、木聚糖、木质素以及混合组分进行了热解研究，结果表明纤维素和木聚糖均有一狭窄的快速热解温度区间，在此对应温度区间有一明显的吸热峰，吸热量为547.98J/g和45.01J/g。木质素的热解温度范围比较宽，在320⁵00℃之间有两处放热趋势。木聚糖与纤维素的混合组分热解过程有两个失重峰，随着组分中比重的变化两个热失重峰此消彼长。木聚糖对纤维素的热解具有较大的抑制作用，纤维素的热解失重峰移往高温区，最大失重速率有较大幅度的减小，纤维素对木聚糖的热解影响较小。失重峰对应区域检测到两个独立的吸热峰，木聚糖吸热峰受组分中比重的变化影响较小，而纤维素吸热峰随着纤维素比重的下降而明显减小。纤维素与木质素的混合组分热解仅有一个主要由纤维素热解引起的失重峰，纤维素开始热失重温度有所提前，而峰值温度往后延，且最大失重值有较大的减小。在纤维素与木质素二比一混合时检测到纤维素的吸热峰，其它比例样品则未检测到吸热峰。木聚糖与木质素的混合组分热解也只有一个主要由木聚糖热解引起的失重峰，热解区域稍往高温区移动。木聚糖吸热峰仅在木聚糖含量较高时出现。利用热重与傅立叶红外光谱联用技术（TG-FTIR）和热重质谱联用技术（TG-MS）对生物质组分及其混合组分进行热解和产物分析。FTIR检测到的热解产物主要包括H₂O、CH₄、CO₂、CO和有机化合物，水分的析出几乎在整个热解过程，其余产物的析出温度对应于各自热失重区域。混合组分热解产物析出规律总体上是两者热解产物析出的叠加，其中CH₄、酸类、醛类、酚类和CO的产率增大，而CO₂的析出量有较大幅度下降。TG-MS的结果表明木聚糖与纤维素热解产物主要集中在快速热失重阶段，而木质素产物析出量较少，具有较宽的析出区域，混合组分热解的TG-MS结果与TG-FTIR结果相似。利用绝热加速量热仪（ARC）进行了多种生物质及生物质组分的慢速热解，检测热解过程的吸放热情况，结果显示在缓慢升温过程中，木聚糖在204.5²32.2℃之间有一尖锐的放热峰，放出热量约为566.205J/g，而纤维素的放热峰在242.3²60.5℃之间，放热量约为655.225J/g，木质素却在133.3²92.2℃有吸热趋势，抽提物在98.1¹86.1℃之间出现吸热趋势。木聚糖与纤维素的混合组分在180²77℃之间有两个放热峰，与单独热解时相比放热提前，纤维素的放热则受到明显抑制。木聚糖与木质素进行混合热解时，检测到一个放热峰，木质素的加入对木聚糖的放热抑制明显，木质素含量越多混合组分放热越微弱。纤维素与木质素进行混合热解时，木质素的加入导致放热量大为减少。木质生物质热解过程中一般均有两个相连的放热峰出现，分别来源于半纤维素和纤维素，而且木质素的吸热趋势同样被检测到。各生物质的起始放热温度在190℃前后，第一个峰值温度在220℃左右，第二个放热峰峰值集中在255℃前后，放出的热量也不尽相同。采用惰性溶剂分别从山毛榉和杨木木屑中抽提得到相应的抽提物及抽提残渣，对抽提物、抽提残渣及生物质原样进行结构表征，并利用TG-FTIR和管式炉进行热解。结果表明，抽提物结构中含有羟基、羧基、苯环和酯带等，而抽提物的去除没有改变生物质的基本结构，对其热失重行为的影响也很小。TG实验中抽提物的主要热失重区间为227⁴50℃，在227³00℃之间有一肩状峰，DTG峰值温度为362.9℃，最大失重速率为4.28%/min，剩余残渣为30.82%。FTIR检测到的产物主要有水、CH₄、CO₂、CO、酸类物质、芳烃类物质、酚类物质和烷烃类物质。管式炉热解实验结果表明，抽提物热解液体产物含有多核芳香烃类、烷烃类、酯类、酚类、酮类等物质。抽提残渣液体产物中酚类的总量和种类均比生物质原样多，其他产物则有所减少。利用加压热重仪对纤维素进行了热重分析，获得了不同升温速率（5、10、20K/min）和不同压力（0.1、0.5、1、1.5、2MPa）条件下的TG曲线，并通过热分析数学方法获得热解动力学参数。结果表明，提高升温速率，热解区间均往高温区移动。增大压力，热解区间均往移低温区，热解时间缩短，剩余残渣百分比增大。热解活化能随着压力的增大或升温速率的提高而增大，热解活化能和指前因子存在着较好的补偿效应。更多还原

【Abstract】 Biomass is the only renewable energy which could provide fuels in solid, liquid andgaseous. However, due to the complexity structure of biomass, its pyrolysis behavior is also acomplex procedure with chemical and physical changes. In order to reveal the regulations ofendothermal or exothermal during biomass pyrolysis and interaction between components, thepyrolysis process of biomass and its components had been investigated by thermal analysis andthermogravimetric analysis methods. The main contents of the work are summarized asfollows:The pyrolysis characteristics of microcrystalline cellulose, xylan, lignin and their mixtureshad been investigated by Thermogravimetric analyzer （TG） and Simultaneous thermal analyzer（STA）. The results showed that both cellulose and xylan were fast pyrolyzed in a narrowtemperature ranges, in which an obvious endothermic peak has been observed with theabsorbed heat of547.98J/g and45.01J/g. Lignin was with a wide pyrolysis temperature region,with two heat releasing trends in the range of320⁵00℃. There were two weight loss peaks indifferent ratios of xylan and cellulose mixed components, and the two weight loss peaks wereinversely proportional to the ratio of xylan and cellulose. In addition, the pyrolysis of cellulosewas inhibited grater by xylan and the weight loss peak was shifted to higher temperature, andthe maximum weight loss rate was decreased sharply. While the xylan pyrolysis was lessaffected by cellulose. Two independent endothermic peaks had been detected in correspondingDTG peaks temperature region. The peak of xylan is less impacted by ratio of xylan, however,the peak of cellulose decreased largely when the ratio of cellulose decreased either in DTG orin DSC curves. There was only one weight loss peak in cellulose-lignin mixtures pyrolysiswhich main caused by the degradation of cellulose. The addition of lignin, the weight lossstarting temperature of cellulose was forward, the peak temperature was increased and themaximum weight loss rate was decreased largely. On DSC curve, the endothermic peak was only been detected in sample C2L1（ratio of cellulose and lignin is2:1）. There was only oneweight loss peak caused by xylan during the pyrolysis of the mixtures of xylan and lignin, andthe peak temperature is higher than that of xylan pyrolysis individually. There was anendothermic peak when the ratio of xylan was higher than that of lignin.Thermogravimetric analyzer coupled with a fourier transform infrared spectroscopy andthermogravimetric analyzer coupled with a mass spectrometry were utilized to analyze thepyrolysis process and on-line analyze the product evolved out during pyrolysis process. H₂O,CH₄, CO₂, CO and other organic compounds were the mainly pyrolysis products. H₂O wasalmost released during the whole pyrolysis procedure and the released temperature of otherproducts was corresponding to weight loss area. The pyrolysis products of the mixedcomponent was the superposition of each biomass components, and the yields of CH₄, acids,aldehydes, phenols and CO were increased while the release of CO₂decreases drastically. Theresults of TG-MS showed that the pyrolysis products of xlyan and cellulose were mainlyreleased in the rapid weight loss phase, and the lignin pyrolysis products was less and had abroader release area. The results of TG-MS analysis of mixed components are similar to that ofTG-FTIR analysis.Accelerating Rate Calorimeter （ARC） had been utilized to investigate the pyrolysis ofbiomass components and several types of biomass. The results showed that in the process ofslow heating rate pyrolysis, xylan had a sharp exothermic peak at204.5²32.2℃, and thereleased heat was566.205J/g; cellulose exothermic peak was in the range of242.3²60.5℃and generated655.225J/g heat; lignin pyrolysis showed a endothermic trend between133.3²92.2℃; the extractives also showed a similar tendency between98.1¹86.1℃. Themixed components of xylan and cellulose had two exothermic peaks between180²77℃.Compared to the pyrolysis of single component, the start exothermic temperature of xylan andcellulose were all declined. The exothermic reaction of cellulose was distinctively depressed inthe mixed components. There was an exothermic peak had been detected during thexylan-lignin mixtures pyrolysis. The addition of lignin had distinct prevented the heat release of xylan. With the lignin proportion increased, the exothermic peak of xylan became morefaint. The cellulose exothermic peak also depressed by the addition of lignin. There were twoconsequent exothermic peaks during the pyrolysis of each lignocellulosic biomass, and thesetwo peaks came from hemicellulose and cellulose respectively. The endothermic trend of ligninhas also been detected as well. Each biomass released different amount of heat, and the initialtemperature of was around190℃, the first peak was around220℃, the second peak wasconcentrated around255℃.Inert solvent was selected to extract beech and poplar sawdust, the correspondingextractives and extracted biomass were obtained. The structure of extractives, extractedbiomass and original biomass had been characterized by Fourier transform infaredspectrometer （FT-IR）. TG-FTIR and tube furnace were used to carry out pyrolysis. The resultshowed that the structure of extractives contains hydroxyl, carbonyl, benzene ring and esterbelt, and the removal of extractives did not change the basic structure of biomass and had lesseffect to the behavior of biomass pyrolysis. The mainly weight loss of extractives between227⁴50°C and a shoulder at227³00°C. DTG peak was362.9°C, the maximum weight lossrate was4.28%/min and the residue was30.82%. The mainly products detected by FTIR werewater, CH₄, CO₂, CO, acids, aromatics, phenols and alkenes. The pyrolysis of tube furnaceshowed that the main liquid products constituents of extractives were aromatic compounds,alkenes, esters, phenols, and ketones. Compared to original biomass, there were more totalcontent and type phenols for extracted biomass pyrolysis. However, the other competitionspecies were less than that of original biomass.Thermogravimetric analysis of cellulose was conducted in pressurized thermogravimetricanalyzer. TG curves under different heating rates （5,10,20K/min） and different pressures （0.1,0.5,1,1.5,2MPa） were obtained. Pyrolysis kinetic parameters were gained by thermalanalysis mathematical methodology. The results indicated that when heating rate was raised,the main pyrolysis region shifted to the higher temperature; pressure was enhanced, the mainpyrolysis region moved to the lower temperature, paralysis time became shorter and the ratio of residue raised. The activation energy increased along with the increase of pressure or heatingrate. There was a good compensation effect between preexponential factor and the pyrolysisactivation energy under all kinds of conditions.更多还原