【作者】 刘秀如；

【导师】 吕清刚；

【作者基本信息】 中国科学院研究生院（工程热物理研究所） ， 工程热物理， 2011， 博士

【摘要】 污泥热解技术在环境保护、废弃物处理和可再生能源利用等领域受到关注。目前,尚缺少可推广应用的污泥热解工艺装置及宽温度范围的流化床热解产物特性分析数据,热解机理仍需进一步探索。本文对流化床污泥热解技术进行实验及理论研究。采用热重分析仪研究了反应气氛、升温速率、与煤混合等因素对污泥热解反应过程的影响规律,分析了气体析出特性和反应表观动力学参数。建立假设条件和传热模型,对污泥颗粒在流化床中的受热升温过程进行数值计算。搭建了完整的鼓泡流化床热解实验台,研究了宽温度范围的热解产物分布及产物特性,探讨了流化床污泥热解反应机理。污泥在不同气氛中反应过程的特征参数不同。提高升温速率有利于增加热解反应最大失重速率,对总失重率影响不大。污泥热解的不同反应阶段具有不同反应机理和动力学参数,反应表观活化能为60-100 kJ/mol。煤与污泥混合热解时,污泥和污泥灰中所含的无机化合物对煤热解反应起到催化作用,两种原料之间的相互作用与原料特性及混合比例有关。通过流化床污泥宽温度范围热解实验研究,获得了不同热解温度下的热解产物分布。随着热解温度升高,液体产率先增加后减小,550℃时达到最大值,为50.35%。热解气体产率随热解温度升高而增加,950℃时气体产率为51.58%。随热解温度升高半焦产率降低,950℃时半焦产率为36.92%。对热解产物进行分析,获得了流化床污泥低温和高温热解产物特性数据。污泥低温和高温热解气体成分含量及变化规律有所差异。随着热解温度升高,低温热解气体中CO2含量逐渐降低,H2、CH4和CO的含量增加。550℃之后,热解气体中各成分含量关系为CO>H2>CH4>CO2。高温热解气体热值为15.36-16.35 MJ/m3,各成分含量关系为H2>CO>CH4>CO2。污泥热解气体可作为合成气用于化学工业,或是燃烧利用其中的热能。污泥热解焦油中检测到多种化合物,其成分及含量随热解温度变化规律不同。550℃热解焦油中甲苯不溶物含量为36%左右,沥青质和正庚烷可溶物含量分别为37.04%和26.96%。该焦油中汽油馏分为2%左右,柴油馏分为18%左右,减压馏分占15%左右,渣油占65%。低温热解焦油的毒性较低,以烯烃、烷烃、酯类和羧酸等化合物为主,多环芳烃化合物在600℃时开始出现,在高温热解焦油中占绝大多数。污泥热解焦油具有燃料用油的潜力,精制提纯后可获得多种化工原料。污泥热解过程中半焦产物的成分及结构发生变化,并具有明显的孔隙特征。随着热解温度升高,污泥热解半焦中的固定碳和水分含量变化不大,灰分含量增大,挥发分含量降低。半焦结构中孔型多样,主要集中在3-5 nm的中孔。热解温度为450℃时,半焦的BET比表面积为35.872 m2/g。热解半焦可进一步燃烧,或经炭化、活化制备成本低廉、吸附容量大的吸附材料。本文进行了流化床污泥热解实验,研究了热解过程和反应机理,获得了大量的热解产物特性数据,为污泥热解技术的推广和发展提供参考。更多还原

【Abstract】 The pyrolysis technology of sewage sludge has been greatly concerned in the fields of environmental protection, waste disposal and renewable energy, etc. Nowadays, practicable devices and product characteristics data of sewage sludge pyrolysis at wide temperature range are scarce. The pyrolysis mechanism of sewage sludge needs further research.In this thesis, a series of experiments were conducted in fluidized bed to explore the pyrolysis of sewage sludge with theoretic analysis. Thermogravimetric analysis was applied to investigate the effects of factors of reaction atmosphere, heating rate, and mixture of sewage sludge and coal on the pyrolysis reaction. The releasing characteristics of gases and apparent kinetics parameters were analyzed. The assumption condition and heat transfer model were established for numerical calculation of the heating process of sewage sludge particles in fluidized bed. A bubbling fluidized bed reactor was designed to study the products distribution and characteristics of sewage sludge pyrolysis at wide temperature range. The pyrolysis reaction mechanism of sewage sludge was discussed.The reaction characteristic parameters of sewage sludge are different in different atmospheres. The maximum weight loss rate increases with the increase in heating rate, which has little influence on the total weight loss rate. In different reaction stages, there are different reaction mechanisms and kinetics parameters for sewage sludge with apparent activation energy within the range of 60-100 kJ/mol. In the co-pyrolysis of coal and sewage sludge, sewage sludge and the inorganic matters in sewage sludge ash play a catalytic role in coal pyrolysis, and the interaction between sewage sludge and coal is related to the characteristics of samples and the mixing ratio.The pyrolysis product distribution at wide temperature range is obtained by the pyrolysis experiments of sewage sludge in fluidized bed. With the increase in pyrolysis temperature, liquid production rate increases and then decreases. At 550℃, liquid production rate reaches the maximum,50.35%. With the increase in pyrolysis temperature pyrolysis gas production rate increases and reaches 51.58% at 950℃. With the increase in pyrolysis temperature char production rate decreace which is 36.92% at 950℃. The pyrolysis products are analyzed to obtain product characteristics data of sewage sludge pyrolysis at low temperature and high temperature.The compositions and content change trends of pyrolysis gas at low temperature and high temperature are different. With the increase in pyrolysis temperature, CO2 content of low temperature pyrolysis gases decreases, and the contents of H2、CH4 and CO incerease. After 550℃, The relation of gas compositions is CO>H2>CH4>CO2. The heating values of high temperature pyrolysis gases are 15.36-16.35 MJ/m3 and the relation of gas compositions is H2>CO>CH4>CO2. Sludge pyrolysis gas is used for chemical industry as syngas or burning application.Many kinds of compounds are identified in pyrolysis tars and the composition and content are different with pyrolysis temperature variation. Analysis results of pyrolysis tar made at 550℃show that the toluene insoluble is 36%, the contents of asphaltene and components dissolved in heptane account for 37.04% and 26.96%, respectivey. In this tar sample, gasoline fraction is 2%, diesel distillate fraction is 18%, vacuum distillate fraction is 15% and residue fraction accounts for 65%. The contents and quantity of single ring aromatic, aliphatic compounds, oxygen compounds, nitrogen compounds, nitrogen and sulfur heterocyclic compounds, steroid compounds and polycyclic aromatic hydrocarbons are different with pyrolysis temperature changes. Low temperature pyrolysis tasr are less toxic and the main compositions are alkanes, alkanes, esters,carboxylic acid compounds, etc. Polycyclic aromatic hydrocarbons appear at 600℃witch are the majority of high temperature pyrolysis tar. The tars can be potentially used as liquid fuel, from which many chemical raw materials can be extracted.The compositions and structures of chars change during sewage sludge pyrolysis which have distinct orous characteristics. Pyrolysis temperature affects the compositions and structural characteristics of char samples. With the pyrolysis temperature increases, in char samples, the fixed carbon and water contents change a little, ash contents increase, volatile contents decrease. There are various hole structures in char mainly with 3-5 nm micro-porous. The specific surface area of char at 450℃is 35.872 m2/g. The pyrolysis char of sewage sludge can be burned, and cheap absorption material can be preparated by carbonization and activation.According to the pyrolysis experiments of sewage sludge in fluidized bed, the pyrolysis process and reaction mechanism are studied, and the plenty of data on product characteristics can provide great reference for the promotion and development of sewage sludge pyrolysis technology.更多还原