【作者】 闫志成；

【导师】 许国仁；

【作者基本信息】 哈尔滨工业大学 ， 市政工程， 2014， 博士

【摘要】 污水处理过程中会产生大量污泥，这些污泥含水率很高，且含有大量有机物、金属盐、病原微生物和寄生虫卵等，污泥性质不稳定且容易腐败。如果污泥不能采用合理的技术进行安全处理处置，会引起周围环境的二次污染。污泥也可被看作为一种资源，如果将污泥进行热解处理，资源化利用污泥热解三相产物，既可以解决污泥污染问题，同时实现了废物再生利用。本论文中研究了回收污泥中的铁盐和铝盐并作为混凝剂回用于污水化学一级强化处理。利用小试规模污泥序批式热解和连续式热解两种反应装置，研究污泥热解三相产物质量平衡，分析各种元素在热解过程中的迁移规律。测定不同温度条件下污泥热解三相产物热值和反应热，建立污泥热解能量平衡。定量分析污泥中有机物主要成分，结合各种成分热解过程中变化规律分析污泥热解机理，并利用表观动力学对污泥热解反应进行分段拟合。研发污泥热解设备开展工艺验证，对污泥热解工艺进行经济评价。污泥中铁盐回收最佳工艺条件pH值为1.5、搅拌时间60min，铝盐回收最佳工艺条件为pH值2.5、搅拌时间60min，回收率分别为79.2%和83.5%，污泥减量率为50.85%和35.51%。多次循环回收会导致铁盐或铝盐回收率下降，分解由83.78%和84.51%降低至70.06%和78.43%。利用污泥中回收的铁盐或铝盐处理污水，对浊度的去除效果接近或者略好于新鲜铁盐或铝盐对浊度的去除效果，出水UV254值略大于新鲜铁盐或铝盐出水的UV254值，对CODCr和SCODCr的去除率与使用新鲜的铁盐或铝盐处理效果没有明显的波动，对总磷去除率均高于97.00%，对色度的去除率由51.00%降低到41.00%。污泥热解过程中影响热解产物产率的主要因素是热解温度，热解液体和气体产物产率随热解温度升高而升高，热解升温速率和热解时间影响不明显。污泥中碳、氢、氧、氮和硫元素向气体产物中迁移量随热解温度升高而增加。污泥连续式热解工艺中污泥热解反应深度高于序批式热解工艺，在800℃以上热解温度下，更多的碳、氧、氮元素由污泥中迁移出去，但硫元素正相反，原因是污泥连续式热解工艺中热解温度高于800℃下硫元素可以与其他元素发生反应被固定在热解固体产物中，污泥连续式热解工艺中污泥中除碳、氢、氧、氮和硫元素外的其他元素含量减少幅度大于序批式热解，原因是连续式污泥热解工艺反应条件更利于这些元素由污泥向热解气体产物中迁移。低热解温度下热值明显降低。热解液体产物在450-600℃热解温度下热值达到很高水平，液体产物热值最大值为26433kJ/kg，热解液体产物能源化利用价值在600℃时达到最大。污泥序批式热解工艺在700-800℃温度段获得的热解气体产物热值最高。两种热解工艺分别在各自最优参数下从热解液、气体产物中可回收能量占污泥含有的化学能的77.50%左右。随着污泥热解温度上升，热解反应呈现先吸热后放热的规律，反应热由吸热转变为放热的温度点为588.56℃，整个热解过程反应热盈亏转换点为809.56℃，采用不同热解反应温度条件，反应热最大吸热量仅为637.24J/g，仅占污泥自身化学能的3.94%，由此可见，污泥热解能源化利用工艺是高效低耗的。污泥中主要有机物成分中蛋白质类、脂类、多糖类和以腐殖质为主的其他有机物分别占污泥质量的29.78%、16.62%、11.08%和11.77%。在25-180℃温度段内，主要是水分、易挥发有机物、碳氧化合物、氮和硫元素的氢化物气化。当热解温度超过240℃时，污泥中蛋白质类、脂类和多糖类开始热解。随着热解温度超过400℃，二次热解反应开始出现，污泥热解气体产物产率迅速升高，当热解温度达到428℃时，污泥中多糖类物质热解已经基本完成，464℃脂类物质气化完成，538℃蛋白质类物质热解完成，热解温度高于538℃后的污泥热失重主要由于腐殖质类物质热解导致。表观动力学分析表明，污泥热解过程中在148-220℃温度段时符合一级动力学模型，在220-475℃符合二级动力学模型，在475-630℃温度段时符合一级动力学模型。污泥热解工艺研究结果表明污泥热解产物产率和元素组成与小试规模相近，较高的热解温度下因为热辐射导致的能耗会增加，经济分析结果表明，污泥热解产物具有较高的利用价值，污泥热解资源化利用工艺具有优良的效益产出，如果作为一个项目进行建设，具有投资基金回收周期短，回报率高的优点。更多还原

【Abstract】 A significant amount of sludge is generated in wastewater treatment processes.There are a variety of constituents, such as organic matter, metals, pathogens,parasitic ovum and etc. making it unstable and prone to turn septic. Hence, wastewatersludge can be the source of secondary contamination of surrounding environmentwithout proper handling and treatment. On the other hand, sludge can be a sort ofresource after certain types of pretreatment, e.g. heat pyrolysis. The reclamation ofwastewater sludge pyrolysis products can minimize the threat to environment as atype of waste recycle and reuse.In this study, coagulants, e.g. ferric and aluminum salts recycled from biosolidsare examined for chemical enhanced primary wastewater treatment. Mass balance ofsludge thermal hydrolysis products in three phases are studied with lab-scale batchfeed and continuous thermal hydrolysis reactors, fate and transport of all kinds ofelements are also evaluated. Energy balance of thermal hydrolysis is established bymeasuring heat value and reaction heat at different temperatures. Mechanism study isconducted to all kinds of constituents in biosolids in the thermal hydrolysis process.Fitting of individual section in thermal hydrolysis reactions is conducted by apparentkinetics. Industrial scale equipments are developed, economical analysis is conducted.The optimal condition for ferric salt in chemical enhanced primary wastewatertreatment is: pH at1.5, stirring time at60min. For aluminum salt, the optimalcondition is: pH at2.5, stirring time at60min. Recovery rate are79.2%and83.5%respectively, biosolid reduction rate are50.85%and35.51%. Multiple stage recoveryrates get reduced from83.78%an84.51%to70.06%and78.43%, respectively. Theperformance of reclaimed ferric and aluminum salts are close to or better than regularsalts on turbidity removal. The UV254transmittance of reclaimed salts treatedwastewater is slightly better than regular ones, COD and SCOD removal rates aresimilar to regular ones, total phosphorous removal rate is always higher than97%,color removal rate reduces from51%to41%.The main factor in the sludge pyrolysis process is temperature, production ratesof pyrolysis liquid and gaseous products are proportional to temperature. Temperatureincreasing rate and time are not strong factors. Higher temperature is beneficial formass transfer to gaseous phase of a variety of elements, such as carbon, hydrogen,oxygen, nitrogen and sulfur. Continuous process gives better pyrolysis extent thanbatch feed process, at high temperature, more carbon, nitrogen and oxygen aretransferred from sludge to other phases, less sulfur gets transferred because sulfurgets involved in reactions that immobilize it in the solid phase. Reduction rate otherelements is slightly higher in continuous process, the reason is gaseous product generation rate is higher in continuous process, micro particles in aerosol are takenaway by gaseous products.Combustion heat of pyrolysis products reduce significantly with pyrolysistemperature. Combustion heat of liquid products hydrolyzed under450-600℃canreach as high as26433kJ/kg. Optimal temperature of liquid pyrolysis productsutilization is600℃. Highest combustion heat of gaseous pyrolysis products isachieved at temperature of700-800℃. Aiming at energy utilization, batch feedreactors are suitable for high combustion heat biofuel in liquid, continuous flowreactors are suitable for biogas. The two types of pyrolysis processes can achieve77.50%energy recovery in terms of chemical energy under optimal conditions fromeither liquid or gaseous pyrolysis products. With the pyrolysis temperature increases,the reaction absorbs then releases energy, the turning point of energy absorb-releaseis588.56℃, and the turning point of energy lose-gain is809.56℃. Under differenttemperatures, the maximum energy absorbed is as low as637.24J/g, only3.94%ofsludge chemical energy. Hence, the pyrolysis of sludge is energy positive.Protein, lipid, polysaccharides, and humic substances in wastewater sludgeaccount for29.78%,16.62%,11.08%and11.77%, respectively. Within25-180℃, itis mainly gasification of moisture, volatile organics, carbonhydrate and sulfur hydride.When temperature is higher than240℃, protein, liquid and polysaccharides start topyrolysis. When temperature goes up to400℃, secondary pyrolysis happens,gasification rate increases immediately. In wastewater sludge, pyrolysis ofpolysaccharides ends at428℃, lipids gasification ends at464℃, pyrolysis of proteinfinishes at538℃.In apparent kinetics, the pyrolysis reaction fits first order intemperature range of148-220℃, second order in220-475℃and first order in475-630℃.Sludge pyrolysis products generation rate and elemental composition is similarto lab scale. Energy cost can be higher because of heat radiation under hightemperature. As shown in economic analysis, sludge pyrolysis process as resourcereclamation has excellent benefit output, it has multiple advantages, such as shortpay-off period, high rate of capital return, etc.更多还原