【作者】 涂德浴；

【导师】 丁为民； 董红敏；

【作者基本信息】 南京农业大学 ， 农业机械化工程， 2007， 博士

【摘要】 全球能源紧张以及化石能源使用对环境的负面影响推动可再生能源的飞速发展。生物质能源储量大、可再生以及使用过程中温室气体零排放等优点，使得全球对其研究开发力度逐渐加强，现已成为仅次于石油、煤炭和天然气的第四大能源。发展和利用生物质能，对于我国的社会经济发展具有重要意义。生物质利用技术主要包括直接燃烧、生化、压缩成型和热化学转化等。畜禽养殖废弃物是生物质能的特殊形式，同时也是农业发展过程中的污染物之一，对其资源化转化利用具有环境和经济双重效益。本文在结合当前国内外生物质热化学转化技术研究的基础上，针对畜禽粪便展开热化学转化技术研究，通过对几种畜禽粪便的物理化学属性、热解特性、热解机理、热解动力学的研究，设计了一套流化床试验装置，并对猪粪展开了空气气化试验。总体研究结论归纳如下。（1）针对猪、牛、鸡和羊四种畜禽粪便的工业和化学分析，结合元素和热值分析以及其它项目分析来考察他们热化学转换的可行性。研究结果表明畜禽粪便在化学组成、灰分和碱金属含量等方面和农作物秸秆有很大差异，具体包括畜禽粪便的纤维素类物质含量偏低，而小分子中性洗涤剂溶解物含量偏高；灰分和碱金属、氮元素含量偏高；在热值方面则显示具有热化学转换潜力。这些不同特性要求在对畜禽粪便进行热化学转换研究时要区别对待。从热化学转化和生化转化的原理出发，理论分析了各自的能量转化效率。分别选择空气气化和厌氧发酵两个转化过程，通过建立化学平衡方程式，理论推导出各自燃气能量产出和能量转换效率，得出热化学处理方法较厌氧发酵过程在能量转化方面更彻底，更有优势。（2）利用热重-傅立叶红外光谱联用技术，对畜禽粪便的热解特性展开研究。研究结果表明畜禽粪便的热解过程可分为脱水、主要热解和炭化三个阶段。几种样品在各自热解最终残留物、微商热重曲线所体现的失重速率和特征峰等方面有差异性。逸出气体红外分析显示，其析出气体主要有H₂O、CO₂、CO、H₂、CH₄、醛、羧酸等。对红外波谱的分析发现每种气体的析出特性都有不同，其中水份的析出曲线呈双峰特性，分别对应于失去游离水和化合结晶水过程；CO和CO₂析出呈现明显双峰特性，分别对应于主要热解阶段和炭化阶段；区别是CO₂炭化阶段析出强度很弱；甲烷析出呈现单峰特性，对应于主要热解阶段末期和炭化阶段初期；其它碳氢化合物呈现单峰特性，对应于主要热解阶段。试验还考察了升温速率对猪粪热解过程和气体析出特性的影响，结果表明升温速率对失重过程的影响主要体现在失重速率上，对气体析出影响主要体现在能使各气体逸出峰向高温区移动。（3）采用热分析动力学的研究方法，利用热重试验获得的数据，对几种样品的热解过程通过建模和模型的求解，分别获得了各自的机理函数、表观活化能和频率因子，从而获得分解速率（α）对应于温度（T）的数学模型，为后续转化过程的模拟和控制提供数学基础。研究结果表明四种样品表观活化能的平均值分别是：猪粪72．89kJ／mol、牛粪75．38kJ／mol、羊粪50．83 kJ／mol、鸡粪74．76 kJ／mol，较一些秸秆类物质要低，说明畜禽粪便更容易受热分解。研究发现采用单组分全局积分模型能很好的表达猪粪的热解过程，而采用单组分分阶段模型计算具有双峰特征的牛粪、鸡粪及羊粪有很好的适用性。（4）设计加工了一套气化负荷在1-5kg／h的流化床反应器。整套装置主要包括主反应管、螺旋进料装置、旋风分离装置、冷凝装置、过滤装置、加热及控制装置和其它管路等。在主反应管设计方面同时兼顾了其它热化学工艺要求。螺旋进料装置考虑到了细粉物料的流动特性，设置了气力输送位置。采取套管水冷方式，实现了燃气和冷却水分离。加热元件为三个4kw加热丝，单独控制，可根据实际情况调节加热功率。设备和蒸汽发生器及蒸汽加热器联结即可以进行生物质的空气+水蒸汽气化或水蒸汽气化。整套装置各部件间采取法兰连接，容易拆卸，易于设备的改进。（5）对整套试验装置进行了冷态启动和热态空床试验。试验结果表明螺旋进料器的出料量可由调频器来线性控制，调频器输出频率和螺旋进料器的出料量线性相关性在0．9以上，能满足试验精度要求。在冷态条件下进行反应器的流速和压降试验，从△p-v曲线上获得粒径为0．2-0．5mm的石英沙的临界流化速度为0．035m／s，进而可以确定反应器的操作流化速度。试验流化曲线显示在流化区内床层压降变化幅度比较小，能满足试验流化要求。对反应器的加热元件和控制元件在空床状态下进行了启动试验，结果显示反应器加热和控制元件能在较短的时间内使反应器内温度升到试验要求。（6）对猪粪的空气气化过程展开了试验研究，考察了原料粒径、当量比和起始温度三个主要操作参数对反应器内温度场、产物分布、固体产物特性、气体产物成分、所产燃气的热值、碳转化率和气化效率等方面的影响作用，为课题下步试验提供参考的操作条件。试验结果表明粒径对反应器内的温度场没有显著影响，对产物分布有影响作用，产气最佳粒径为0．5mm，粒径对其它气化指标的影响也显示猪粪空气气化的最佳粒径为0．5mm。当量比ER对气化过程的影响具有利弊双面性，影响规律比较复杂，ER改变直接影响到反应器内温度场的变化和气固停留时间。ER=0．15有利于气体产物生成，结合其它气化指标，猪粪空气气化最佳ER为0．15。起始温度越高越有利于气体产物的生成，但从经济性和其它气化指标综合考虑，对于猪粪的空气气化300℃完全可以满足对燃气的使用要求。通过以上试验总结出猪粪空气气化的建议操作条件为：粒径0．5mm，ER=0．15，起始温度300℃。作为课题的基础性研究部分，作者在总结本身研究不足之处的同时，从热解机理、设备开发、气化工艺等方面为后续研究提出了建议和展望。更多还原

【Abstract】 Global energy shortages and environmental negative impacts by using fossil rules have caused the fast development of renewable energy. Biomass energy has been given more and more attention for its advantages of large storage capacity, recovery and neutrality of greenhouse gas emission, and it has become the forth energy resources followed by petroleum, coal and natural gas. Development and utilization of biomass energy have the social ,economic, and ecological meaning in China. The utilization technologies of biomass include direct combustion, densification briquetting, biochemical and thermochemical conversion. Animal manure is a special shape of biomass and also a kind of pollutants during agricultural development ,so there have ecocomic and environmental benefits to make them into available resources.On the base of current research progress in biomass thermochemical conversion technologies at home and abroad, the author carried out the study on physicochemical characteristics, pyrolytic characteristics and mechanics of animal maure. On the ground of above study, the author designed and developped a lab-scale fluidized bed gasifier and employed this system to carry out air gasification experiments on swine manure. The main conclusions are as follows.（1） Proximate and chemical analysis,as well as ultimate and heating value analysis, were carried out to investigate the feasibility of thermochemical conversion of four kinds of manure such as swine, cattle, goat and chicken manure.The results showed that animal manure have some obvious differences to some kinds of farm crop residues on chemical consititution, ash and alkali salt metal content. The detailed includes the lower content of cellulosic material, higher content of neutral dissolving solids（NDS）, ash, alkali metal and nitrogen. The heat value showed them having thermochemical conversion potential. These varible parameters require special handlings as we go on experimental research on them.Theoritical analysis on thermochemical and biochemical conversion efficiency was conducted on every kind of maure. By establishing the chemical equation, every kind of fule gases and total energy output were obtained and energy conversion efficiences were derived according to corresponding conversion processes. From the data we got the conclusion that thermochemical technology converts the raw material more thoroughly and efficiently than that of biochemical technology.（2） The pyrolysis characteristics of animal manure were investigated by the thermogravimetric analyzer coupled with the Fourier infrared spectroscopy（TG-FTIR）.The experimental results showed that animal maure pyrolysis process can be devided into three stages which are dehydration stage, pyrolysis stage and carbonization stage. There were some different features on end residuum, weight loss rate and peak features indicated by TG and DTG curves.The produced gas detected by FTIR consists of H₂O, CO₂, CO, H₂, CH₄, aldehyde, carboxylic acid, and so on. By analyzing the infrared spectrum, the evolving characteristics of each different gas could be found. Water evolving curve has two peaks corresponding to losing free moisture and combined crystal water. Carbon monoxide and carbon dioxide evolving curve have the similar two peaks corresponding to pyrolysis and carbonization stage, but the second peak of carbon dioxide is weaker than that of carbon monoxide. Methane evolving cure appears single peak corresponding to pyrolysis terminal stage and carbonization early stage. Other hydrocarbons evolving curve display single peak corresponding to pyrolysis stage.The effluence of heating rate on pyrolysis and gas evolving characteristics of swine manure were also conducted, and its effects mainly appeared on weight loss rate and making each gas evolving peak move to high temperature zone.（3） Thermoanalysis dynamics method was employed to get the mathematic model of weight loss rate （a） to temperature （T） so that mathematical foundation could be offered for subsequent thermochemical conversion process simulation and control. By establishing and solving pyrolysis model, the kinetic triplet of mechanics function[f（α）] apparent activation energy（E） and frequency factor（A） were achieved using thermogravimetric experimental data.The calculation results showed that the average apparent activation energy of swine, cattle, goat, and chicken manure is 72.89kJ/mol, 75.38kJ/mol, 50.83 kJ/mol, 74.76 kJ/mol separately, and they are lower than those of farm crop residues which indicats these manure are easy to thermal cracking. The research also found single constituent global integration model is adaptive to swine manure and single constituent phased integration model is suitable to other three kinds of manure. （4） A fluidized bed gasifier system with the load from 1 to 5kg/h was designed and manufactured which consists of main reacting tube, screw feeder, cyclone separator, condenser, filter, heating and controling elements, and so on.The main reactor tube is applicable to different types of thermochemical conversion technological requirements. The screw feeder has a air delivery position to ensure discharge the fine materials easily. Double pipe condenser make fule gas and condensing agent non-contacting. Three 4kw heating elements can be controled by thermostat independently so that the system power can be adjusted according to practical situation. The equipment attached to steam generator and steam heater can be applicable to air-steam or steam gasification technologies. All components assembly are connected by flange which make them to be demounted and the system to be modified easily.（5） Cold condition and hot condition start-up experiments were carried out on set of equipments.The output of screw feeder could be linearity control by frequency modulator and their linear dependent coeffient was above 0.9 which could meet the test requirements. Pressure drop to fludized flow velocity test was conducted to get theΔp-v curve from which the critical fluidized flow velocity could be found. The experimental results showed that the Vf of silica sand between 0.2-0.5mm particle size was 0.035m/s so that we could determine the operational velocity. The fluidizing curve obtained from the trial showed that amplitude of pressure drop variation was quite small which could satisfy the fluidization demand. The hot empty bed condition experiments were done to test the performance of the heating and controling elements and showed that they can heat the gasifier to demanded temperature in a short time.（6） The air gasification experiments on swine manure were conducted to discover the influence of three main operational parameters which are raw material particle size, equivalence ratio and initial temperature on gasification process. Subjects investigated included reactor inner temperature field, products distribution, solid product character, fule gas components and heat value, carbon conversion rate and gasification efficiency. The experimental main goal is to supply suggested operational parameters for actual work conditionsThe experimental results showed that the parameter of particle size had some effects on some gasification indexes except inner reactor temperature field and the size of 0.5mm was benefit to gas production. Combined with other effects the suggested particle size was 0.5mm.ER has double-faced and complicated influence on gasification process because it can directly effect reactor inner temperature field and residence time of gas and solid. The experimental results showed ER of 0.15 was favorable to gas formation and connected to other aspects the suggested ER was 0.15.The experiment showed higher initial temperature was advantageous to gas production, but integrated with economy and other aspects, temperature of 300℃could meet the application demand of producted fule gas.From above experiments the suggested operational parameters of swine manure air gasification was : particle size of 0.5mm, ER of 0.15 and initial temperature of 300℃.As the project fundamental research, the author not only generalized the shortages of this paper but put forward some advice on further studies.更多还原