【作者】 谢荣；

【导师】 陆继东；

【作者基本信息】 华中科技大学 ， 热能工程， 2011， 博士

【摘要】 随着我国经济和人民生活水平的提高,医疗卫生事业迅速发展,越来越多的医疗垃圾引发了一系列环境、社会和生态问题。焚烧法因其在无害化与减容化上具有突出的优势,已成为公认的处理医疗垃圾的有效方法。热解焚烧技术是焚烧法中的热点技术,本文以热解焚烧技术为基础,进行整体式热解焚烧炉设计与实验研究。本文选取具有代表性的输液管、医用橡胶手套、竹签棒代表医疗垃圾中的塑料、橡胶及生物质三类组分,采用热重分析仪进行热解特性研究,运用化学反应动力学模型计算了热解表观动力学参数。研究表明:典型医疗垃圾颗粒粒径与样品用量的选取对热重的实验结果有一定影响,但当粒径为63~500μm,样品用量为10~25mg时,影响不明显。不同升温速率实验研究发现:升温速率越高,样品挥发份析出越容易,挥发份析出越强烈,总体热解反应过程越集中,各阶段分解量减小。混合热解实验结果表明:低温阶段可以认为各组份间不发生相互反应或相互反应程度较小,中高温阶段混合物内部相互反应影响趋于明显。为进一步了解医疗垃圾热解产物的生成特性,在管式炉实验台架上进行了典型医疗垃圾组份热解气体产物生成实验研究。采用红外气体分析仪测量析出组份随时间变化的规律。热解气的成分复杂,主要有甲烷、一氧化碳、酸类、醛类物质。本文选取产气中浓度高于100ppm的甲烷、一氧化碳等气体进行研究。结果表明:热解温度越高,气体产物的析出峰值越高。医用橡胶手套热解主要气态产物为甲烷,输液管热解主要气态产物为甲烷和氯化氢,竹签主要热解气态产物为甲烷与一氧化碳。在此基础上,进行了典型医疗垃圾混合组份HCl排放特性实验。结果表明:含有氯的混合组份热解过程中,掺混作用对氯化氢的转化具有抑制作用,均使氯转化为氯化氢的速率不同程度的下降,随着掺混比例增加抑制作用增强,这也表明含氯有机物发生氯化氢脱除反应前可能与其他物质结合形成含氯有机物。结合扫描电镜、比表面积及孔径分析仪对典型医疗垃圾样品的热解焦特性进行了研究。结果表明:热解温度越高,焦孔隙越发达,比表面积越大,有利于热解焦燃尽,降低燃烧污染物。在确保医疗垃圾无害化处理前提下,结合医疗垃圾热值较高的特性,开发了一燃室与二燃室同轴结构的新型热解焚烧炉并进行系统的热力分析与热态实验。热力分析的结果表明:当总过量空气系数不变,减少一燃室的过量空气系数,一燃室出口温度降低,二燃室温度增加。在此基础上,进行整体式热解焚烧炉批次给料与连续给料热态实验。批次投料实验结果表明:一燃室预热温度与给料量均对炉内温度变化有影响。连续给料实验结果表明:热解焚烧工况的温度稳定性要高于直接燃烧工况,可实现直接燃烧类似的稳定火焰及良好的燃烧效果,有效控制焚烧炉出口的一氧化碳浓度,同时有效降低总烟气产生量。建议新型连续热解焚烧炉总过量空气系数为1.3,一燃室过量空气系数为0.5。以整体式医疗垃圾热解焚烧炉为核心的焚烧系统为对象,进行实际医疗垃圾热解焚烧处理过程中的清洁排放控制研究。对烟道处烟气中颗粒物、二氧化硫、一氧化碳和氮氧化物的排放进行检测与分析,结果表明:整体式医疗垃圾热解焚烧系统能够控制二次中污染物生成,从机理角度对该型焚烧系统抑制二次污染物进行解释。结合气相色谱仪和扫描电镜仪对焚烧炉飞灰与炉渣进行了研究。结果表明:炉渣与飞灰中重金属含量较高,属于危险废物,必须固化处理后方可填埋。在全面总结垃圾焚烧炉内二噁英形成机理:高温气相生成、前驱物生成和从头合成的基础上,将本文研究对象与不同焚烧炉结构相同尾气净化装置的医疗垃圾热解焚烧系统的二噁英检测结果进行对比分析。结果表明:同轴结构的焚烧炉有效降低了焚烧炉的散热损失,利用了热解产物二次燃烧释放的热量维持炉内温度稳定,对二噁英的生成产生良好的抑制作用。更多还原

【Abstract】 With the development of economy, the medical and health services developed rapidly in China. The huge amounts of medical waste result in a series of environmental, social and ecological problems. The incineration technology has many advantages such as volume reduction, quantity reduction and harmless treatment. It has become an effective method of medical waste treatment. The comprehensive research on pyrolysis incineration technology is very important. In order to obtain an important reference in the design and operation of medical waste pyrolysis incinerator, this thesis focuses on the basic research and applied research of integral incinerator technology.Perfusion tube, medical gloves and bamboo rods were selected to stand for three major components in medical waste: plastic, rubber and biomass. The thermal decomposition characteristics were analyzed by the thermogravimetric analyzer. The kinetic parameters of pyrolysis were calculated by using chemical kinetic model. The results showed: the particle size and the amount of medical waste sample influenced the result of TGA experiment. However when the particle size was between 63μm and 500μm, the sample amount was between 10 mg and 25mg, the effect was not obvious. It was found in the different heating rates experiment, when the heating rate was high; the sample volatilized quickly, the pyrolysis reaction was concentrated, the amount of each decomposed stages decreased. Mixture pyrolysis experimental results showed: in the low temperature, the reaction of different components was unnoticable. In the high temperature, the reaction of different components was strong.In order to obtain the properties of medical waste pyrolysis product, the experiment of pyrolsis gas generated from typical components of medical waste was carried out in the tube furnace. The pyrolysis gas products were measured continuously by the infrared gas analyzer. The composition of pyrolysis gas was complex, including methane, carbon monoxide, acids and aldehydes etc. Methane and carbon monoxide were chosen for analysis. The results showed: When the pyrolysis temperature was high, the peak value of gas products increased. The major pyrolysis gaseous products of medical rubber glove were methane. The major pyrolysis gaseous products of perfusion tube were methane and hydrogen chloride. The major pyrolysis gaseous products of bamboo rods were methane and carbon monoxide. On this basis, the experiments of the pyrolysis gaseous products characteristics of mixed medical waste were carried out. The results showed: In the different mixture sample, the translation rate of chlorine into hydrogen chloride decreased in different degrees. Mixing inhibited the direct product of hydrogen chloride. The inhibited effect became obvious with the quantity of mixture increased. This suggested that chlorine might combine with other small molecule to form chlorinated organic material before hydrogen chloride was formatted. The solid pyrolysis residents of typical medical wastes were studied in detail by scanning electron microscopy and pore size analyzer. The results showed the higher the pyrolysis temperature was, the more porous the solid products got. As more contact surface area for gas and solid were provided, the burning condition of the resident was improved. So, the pollutants of incineration could be controlled easily.To ensure harmless treatment of the medical waste, a new pyrolysis incinerator with two coaxial combustion chambers was proposed to use the heat value of medical waste effectively. The thermal analysis of the integral incinerator was carried out. The result showed: when the total excess air ratio was kept constant and the primary air ratio was reduced, the temperature of the primary combustion chamber decreased, but the temperature of the secondary combustion chamber increased. On this basis, the batch and continuous feeding experiment of combustion were conducted on the pyrolysis incinerator. The results of batch feeding experiment showed: the temperature of primary combustion chamber was influenced seriously by the preheating temperature and the feeding quantity. The results of continuous feeding experiment showed: The stable flame and combustion in the pyrolysis incinerator was achieved, which were similar to the direct combustion. The temperature of the primary combustion chamber was more stable in the pyrolysis incineration than in the direct combustion condition. The carbon monoxide in the outlet of the integral incinerator was controlled effectively. The total flue gas was also reducing effectively by reducing the total excess air ratio. This suggested that total excess air ratio and primary combustion chamber were 1.3 and 0.5 respectively in the continuous running of the integral pyrolysis incinerator.The performance tests were carried out on the medical waste thermal treatment system based on the integral pyrolysis incinerator. Particulate matter, sulfur dioxide, carbon monoxide and nitrogen oxides in the flue gas were measured continuously in two hours at the entrance to the stack. The results showed: the integral medical waste runs stably. The gas emissions were below the China national standard emission limits. The aim of clean emissions in the new incineration was achieved. Using the gas chromatography, scanning electron microscopy, X-ray diffraction analysis techniques, the fly ash and boiler slag of the medical waste incinerator were studied in detail. The results showed: The heavy metals content in bottom slag and fly ash were high. They were still hazardous waste and need be solidified before landfilling. Under the comprehensive summary and analysis of dioxin formation mechanism in the waste incinerators including the high-temperature gas generated, precursor formation and“de novo”formation, PCDD/Fs formation in the medical waste pyrolysis incinerator was analyzed. Compared with the different structures incinerator but with the same flue gas purifying device, the dioxin test results showed: The coaxial design incinerator reduced the heat loss effectively, used the combustion heat of pyrolysis products furnace to maintain temperature stability, and inhibited the formation of dioxins.更多还原