【作者】 陈天举；

【导师】 刘荣厚；

【作者基本信息】 上海交通大学 ， 环境工程， 2012， 博士

【摘要】 随着煤和石油等化石燃料的日益减少和温室气体排放导致的全球变暖问题日趋严重，生物质作为一种清洁、可再生能源日益受到人们的重视。生物质热裂解是生物质材料在无氧或缺氧、常压和中低温（300-500℃）条件下发生裂解的一种热化学转换技术，其中快速热裂解可制得生物油，慢速热裂解可制得生物炭。生物油的化学成分和性质与石油燃料截然不同，生物油是一种复杂含氧有机化合物与水组成的混合物，包括了几乎所有化学类别的有机物，如醚、酯、醛、酮、酚、醇和有机酸等。生物油具有含水量高、pH值低、热值低等特点。本文首先采用数值模拟研究方法确定流化床反应器载气流速，研究热裂解产物收集系统（多级冷凝系统和热蒸汽过滤器）对生物油理化特性的影响，然后进行了生物油/柴油乳化和生物油重整制氢应用研究，最后对生物炭制取及生物炭燃烧动力学进行了机理研究。本研究对于提高生物油品质，开拓生物油和生物炭的应用途径具有指导意义。使用数值模拟软件FLUENT研究了流化床反应器载气流速与压降之间的关系，结果表明当载气流速较小时砂子流化状况不好，但当流速太大时，砂子会被吹散，在载气流速0.15m/s时，流化床反应器鼓泡良好，可以将砂子的体积分数、载气流速和流化床反应器内部各点的压力图象化，流化床反应器内部压降为1500Pa。流化床反应器冷态试验表明流化床反应器内部压降随着载气流速的增加先是增大，在0.13m/s时出现极大值，为1400Pa，然后呈现下降趋势并趋于稳定；数值模拟方法得到的结果与实际试验相对误差较小，对实际冷态试验具有指导意义。使用多级冷凝系统可将生物油中的有机物成分进行初步分离，然后根据各级生物油的性质确定应用途径。本文以松木屑为原料，研究了多级冷凝系统和静电捕集器对生物油特性的影响，其中主要研究的生物油理化性质包括：元素分析、水分含量、pH值、热值、运动粘度和组分，也对常温下不可冷凝气体的组分和生物炭做了详细的测试。结果表明，一级冷凝器得到的生物油最多，占生物油总量的65.3wt/%；前面冷凝器中的生物油具有较高的含水率、低固含量、较低的热值、pH值和运动粘度；通过GC-MS可以发现有102种化合物，其中含量最多的是酮和酚等环状化合物，许多不同的化合物在不同的冷凝器中冷凝；对不可冷凝气体进行GC研究发现，C₂-C₄（52.36%）气体含量最高，其次为CO（26.22%），H₂（1.66%）和CH₄（4.99%）含量较低；生物炭主要含有C、H和O三种元素，红外光谱显示生物炭化学键主要有-NH、-CH-、-C=C-、-CH₃和-C-O-C-，相对于松木屑原料，生物炭表面形貌发生了变化，壁面变薄并且产生了收缩。以稻壳粉为原料，在热解温度500℃时，研究了热蒸汽过滤器对生物油特性的影响，结果表明：当采用热蒸汽过滤器时，生物油产率由41.7wt.%下降为39.5wt.%，生物油的平均含水量由41.5wt.%上升到49.0wt.%，生物油具有高含水量、高pH值、低热值、低碱金属含量；GC-MS定量分析可以发现稻壳生物油化合物种类达112种之多，其中，苯酚、3-甲基苯酚、3-乙基苯酚、2,3-二氢苯并呋喃四种化合物在四种生物油中含量最高，热蒸汽过滤器中热裂解蒸汽的二次裂解降低了生物油中化合物的分子量；当采用热蒸汽过滤器后不可冷凝气体进行分析可得C₂-C₄气体含量明显降低，而H₂和CO的含量有很大的提高，这说明二次裂解导致产生了更多的H₂和CO。采用稻壳裂解生物油和市售0#柴油为原料进行了乳化燃油的制备，重点考察了乳化温度、乳化剂添加比例、单次能量投入量（乳化时间）和生物油添加比例对乳化燃油稳定性的影响。结果表明：最佳的乳化温度为60℃，适宜的比例为10%，单次能量投入量的增加可明显改善乳化燃油的稳定性，在能耗允许的前提下，综合考虑储存运输时间，可以确定较佳的乳化时间；当生物油添加比例不超过10%时，可以得到稳定时间超过72h的乳化燃油产品。采用稻壳制得的两种生物油在固定床反应器上进行水蒸汽重整制氢研究，研究了反应温度对气体产物、液体产物和催化剂积炭量的影响，同时考察了额外添加水蒸汽对三种产物的影响。结果表明：生物随着温度的升高气体产物H₂和CO₂含量升高，CO、CH₄和C₂-C₄的含量降低，气体产物中氢气的含量可达60％。当添加额外水进入反应体系时，生物油的产氢效率提高，最高为45.33%；生物油有机物含量大的生物油在反应过程中能够产生更多的氢气，但是产氢效率会有所降低。催化剂在中温750℃条件下，积炭出现极大值。采用固定床反应器以白腊木、倾草和玉米秸秆三种生物质为原料在三个反应温度下进行慢速热裂解研究表明：生物炭和生物油的产率随着反应温度的提高而降低，产生气体的体积随着反应温度的升高而升高，其中生物炭的产率为26-41％之间，其固碳率可达50％以上；生物炭pH值、热值随着反应温度的提高而呈现上升趋势；红外光谱显示生物炭的化学键随着反应温度的提高而呈现减少趋势；SEM-EDS显示生物炭在高温条件下结构呈现规整化趋势，有碳纤维生成，生物炭中的碱金属含量随反应温度的提高呈现上升趋势；可燃气的主要成分为CO、CO₂、H₂和CH₄。其中CO、CO₂、随着反应的进行含量有降低趋势，而H₂和CH₄含量有上升趋势，高温条件下产生更多的H₂和CH₄。采用热重分析仪研究生物炭燃烧动力学表明：随着升温速率的增大，热滞后现象的加重，TG、DTG曲线均向高温侧移动，采用等转化率方法计算活化能，采用主曲线方法确定反应机理，其动力学模型为f（α）=（1-α）^3.3，指前因子A=6.20×10¹²s^-1，活化能E=212.524kJmol^-1。更多还原

【Abstract】 The coal and fossil fuel shortage and globle warming problems have become bigthreats to the sustainable development of our society. With the depletion of fossilenergy reserves in the world, renewable energy sources have attracted significantattention. Biomass is a clean, cost-effective, CO₂neutral and low sulfur contentrenewable material which can be used for heat and fuel production. Thermal pyrolysisis a thermochemical process in the middle temperature （300-500℃） with the absenceof oxygen, atmospheric pressure. Bio-oil was produced using fast pyrolysis andbiochar was produced using slow pyrolysis method. Bio-oil is a complicated mixtureof organic compounds with water containing almost all kinds of organic compoundssuch as aether, ester, aldehyde, ketone, hydroxybenzene, alcoholic, organic acid andetc. As the bio-oil has the characteristic of high water content, high solid, low heatingvalue, it is difficulty to use as liquid fuel. The effects of collection system （selectivecondensation and hot vapor filtration （HVF）） on the characteristic of bio-oil wereinvestigated in this paper. And then bio-oil/desiel emulsion and bio-oil steamingreforming were used to investigate the application of bio-oil. The effect of thetemperature on the characteristic of biochar and the biochar combustion behavie werealso investigated.The numerical simulation （FLUENT） was used to simulate the process of fluidizedbed reactor. The solid volume, gas velocity and the pressure drop were simulated. Theresults showed that the pressure drop was1500Pa with the gas velocity of0.15m/s.In the real experiment, the effect of the carrier gas velocity with the pressure drop was also investigated. The results showed that the pressure drop is increased with theincrease of gas velocity at first. It is tending towards stability after0.13m/s and thepressure drop is1400Pa. The numerical simulation result fit the experiment data verywell.The fast pyrolysis of pine sawdust was conducted in a fluidized bed reactor with aselective condensation system. The selective condensation and electrostaticprecipitator were used to condense the pyrolysis vapours. The average yields ofbio-oil, the gases and the char were41.5%,43.3%,15.2%respectively. It was foundthat the condensed oils in the condenser1#contained higher water content and ratio ofcollected water content of oil was86.2wt%. The bio-oil condensed in the lattercondenser has a lower water content, higher pH value, higher heating value, higherkinetic viscosity compared to the former one. Analysis of1#,4#and5#bio-oil withGC-MS showed that102types of chemical compounds were detected and most of thecompounds were condensed at different condensers. Therefore, the selectivecondensation is useful to separate the water and chemical compounds from bio-oilcompared with direct contacting condensing. The selective condensation andelectrostatic precipitator can condense the pyrolysis vapours selectively. The gasproducts were mainly CO, H₂, CO₂, CH₄and C₂-C₄’s. It was also found that there arelarge amount of hydrogen and oxygen in the bio-char. A lot of bonds such as-NH,-CH-,-C=C-,-CH₃,-C-O-C-were found in the char samples. It was observed that thesurface morphology of pine sawdust particle changed after pyrolysis, and it becamethinner.Fast pyrolysis of rice husks in a fluidized-bed reactor was reported in this paper. Theeffect of HVF on the characteristic of bio-oil was investigated. It was found that thetotal bio-oil yield decreased and that the bio-oil has a higher water content, higher pHvalue, and lower alkali metal content when a HVF is used in the system. Analysis ofthe bio-oil with GC-MS showed that the molecular weight of the chemical compoundsdecreased after HVF. The content of C₂-C₄’s gases from gas products was decreasedafter HVF. The bio-char has many chemical bonds and its alkali metal content ishigher compared to the bio-oils. Bio-oil from the rice husks was used to emulsion with diesel. The temperature,percentage of the emulsifier, time and the percentage of bio-oil were investigated inthis paper. The results showed that the emulsion temperature should be at60℃andthe suitable percentage of emulsion was10%. The emulsion fuel can get a stable timemore than72h if the bio-oil percentage less than10.Steam reforming of two kinds of bio-oil from rice husks fast pyrolysis was conductedfor hydrogen production at three temperatures （650,750and850℃） with Ni-basedcatalyst in a fixed-bed reactor. Mole fractions of H₂and the CO₂increased, while thevolume fraction of CO, CH₄and C₂-C₄gases decreased with the increase of thetemperature from650to850℃. The highest H₂efficiency was45.33%whenadditional water was added at850℃for F1bio-oil. Bio-oil with lower content ofchemical compounds has a higher H₂efficiency, but its hydrogen volume wasdecreased. Analysis of the liquid condensate showed that most of the organiccompounds were circularity compounds. Carbon deposition can decrease the bio-oilconversion, and it was more readily formed at750℃.The slow pyrolysis of white ash, switch grass and corn stover were used as thefeedstock at three temperatures （300,400and500℃）. The results showed that theyield of the biochar and bio-oil were decreased and the volume of syngas wasincreased with the increase of the temperature. The yield of the biochar was26-41%.The carbon sequestration rates canbe60wt%. The pH, heating value and solid contentof the biochar were increased with the increase of the temperature. FT-IR showed thatthere are a lot of chemical ponds in the biochar, and they were decreased with theincrease of the temperature. The SEM-EDS analysis showed that the structure hascarbon fiber at higher temperature, and the content of alkali metals （Na, K, Ca, Mg）were increased with the increase of temperture. The main content of the syngas wereCO、CO₂、H₂and CH₄.The mole fraction of CO and CO₂were decreased and the molefraction of H₂and CH₄were increased with the time. More H₂and CH₄wereproduced at high temperature.The combustion characteristic and kinetic behaviour of the biochar were studied byusing a thermogravimetric analyzer at four heating rates （5,10,20and50K min-1）. The FWO and KAS methods, two commonly used isoconversional methods, wereapplied to estimate the effective activation energy, and the master plot method wasused for the determination of the kinetic model f（α）. The kinetic parameters of biocharcombustion are obtained as follows: f（α）=（1-α）^3.3, A=6.20×10¹²s^-1, E=212.524kJmol^-1.更多还原