【作者】 陆胜勇；

【导师】 严建华； 岑可法； 倪明江；

【作者基本信息】 浙江大学 ， 工程热物理， 2004， 博士

【摘要】 本文首先从城市生活垃圾焚烧利用产生的二噁英问题、垃圾焚烧择放二噁英占环境中排放的总量、不可控燃烧过程的二噁英排放、燃烧过程中二噁英的生成机理、燃烧过程中二噁英的抑制和控制作用等方面综述分析了国内外关于垃圾和煤燃烧过程中二噁英的研究现状。并依托国家自然科学基金项目（编号59878047）、国家重点自然科学基金项目编号号59836210)、国家重点基础研究发展规划项目（973项目G1999022211）等项目的支持，开展了内容丰富的垃圾和煤燃烧过程中二噁英生成、抑制及控制机理的基础实验研究，得到了一些具有现实指导意义的研究结果和研究结论。本文的主要内容包括以下5方面： 1) 飞灰是城市生活垃圾焚烧产生的二噁英污染物的主要载体，本文研究了我国两种典型炉排焚烧炉和循环流化床焚烧炉飞灰中二噁英按粒径分布的特性，比较了我国目前在运行的多家焚烧厂的布袋除尘器飞灰中的二噁英含量特性及规律。研究发现循环流化床焚烧炉产生的飞灰中的二噁英含量比炉排炉飞灰低很多，本文从焚烧炉炉型和燃烧工况的组织、燃料的组成、飞灰中残碳含量、飞灰中重金属和氯含量等方面详细阐述了导致飞灰中二噁英按粒径分布的规律，不同炉型飞灰中二噁英含量特性存在巨大差别的原因。 2) 在飞灰表面发生的异相催化反应是二噁英在燃后区形成的主要机理，本文以垃圾焚烧炉飞灰、燃煤锅炉飞灰、粉末活性炭等为原料，对影响飞灰表面异相催化反应生成二噁英的各种因素进行了较详细的实验研究，内容包括：氧、碳、催化剂、飞灰中C／Cu比例、飞灰粒径、无机氯源等，探讨和比较了燃煤锅炉飞灰、垃圾焚烧炉飞灰和粉末状活性炭发生低温异相催化反应生成二噁英的异同点及原因。同时还对飞灰表面发生低温异相催化反应过程中起重要作用的“氯化反应”进行了综述分析。 3) 当初以稳定燃烧为出发点的垃圾和煤混烧工艺路线，被发现对二噁英的生成具有很好的抑制作用，国内外对煤混烧抑制二噁英生成的现象解释为煤中硫的作用，本文从三个方面对硫在燃烧过程中抑制二噁英生成的机理进行了试验研究。采用二噁英前驱物PCP（五氯酚）和元素硫在不同温度条件下的加热试验表明，500℃附近，前驱物PCP生成二噁英时具有“毒性滞后”现象，而硫在超过500℃时才表现出较大的抑制作用，低于500℃时反而能促进前驱物生成更多二噁英，燃料中S／Cl比例不同对前驱物生成二噁英也具有重要影响。采用不同含硫量的标准煤样和PCP的混烧试验表明，煤燃烧对PCP高温燃烧生成二噁英的抑制效率超过80％，多组试验中达到99％以上。硫及其氧化物不仅在在较高温度条件下的燃烧过程中影响二噁英的生成和排放，在低温条件下也能对二噁英的低温异相催化反应产生影响，本所与美国EPA研究小组合作开展了这方面的研究工作。本文深入、详细探讨了各种燃烧条件下Cl₂和SO₂的反应机理，进一步揭示了飞灰、SO₂在Cl₂向HCl转化过程中的相互作用，分析了SO₂对Cl₂和飞灰发生异相催化反应的影响机理。 4) 燃烧过程也是我国环境中二噁英排放的重要来源。本文通过对大型燃煤锅炉、异重介质流化床煤和垃圾混烧焚烧炉的二呀英排放测试研究，进行了二嗯英在嫩烧系统中的输入输出平衡计算。研究结果发现，燃煤锅炉的静电除尘器对嫩煤锅炉的二嗯英排放具有重要影响，300MW机组每年向大气中排放的二嗯英毒性当量为:O川79 I-TEQ一台15（川d的煤和垃圾混烧焚烧炉每年向大气中排放的二嗯英为:0.1一15mg!一EQ。本文还在小型实验台上进行了垃圾和煤混烧的二嗯英排放特性，研究发现煤参与混烧可以抑制垃圾焚烧过程的二啥英排放，煤和塑料的流化床始烧得到了50⁷0%的抑制效果，煤和原生垃圾的管式炉嫌烧试验得到了95%的抑制效果（掺煤，6%）。 5）本文还对姗烧中和姗烧后的二嗯英控制技术和机理进行了较详细的基础研究实验。研究发现CaO、CaCoa对pCp高沮徽烧过程的二德英排放具有截然相反的影响效果，即CaC仇高温条件下可以有效抑制二嗯英的生成，而CaO却能促进二嗯英的生成。采用颖粒状活性炭、废轮胎热解半焦颖粒对嫌后烟气中二嗯英的吸附控制研究表明，160℃左右的温度段是进行二嚷英吸附控制的最适合温度区间，废轮胎热解焦碳可以吸附烟气中40%^oo%的二嗯英。改良活性炭粉末生成二嗯英能力的试验研究表明，适当的碱液浓度浸演活性炭后，可以大大降低活性炭本身生成二嚷英的能力。本文最后部分建立了烟气中采用以活性炭为代表的吸附剂进行二嗯英吸附控制的效率预侧模型，计算结果表明，烟气净化塔和布袋除尘器的温度是影响吸附效率的最重要因素，160℃或更低温度可以达到较高的吸附控制效率:在循环流化床焚烧炉中，飞灰本身可以大t吸附烟气中的二嗯英，而活性炭粉末的品种和品质对吸附效率的影响并不大。关键词:嫩烧，二嗯英，飞灰，硫，抑制，排放，控制，吸附效率更多还原

【Abstract】 The state-of-the-arts about dioxins from coal and waste combustion processes in the world is reviewed in details with concerning the following aspects: environmental problems about dioxin formation from municipal solid waste (MSW) incineration processes, the dioxin emission percentage of waste incineration to the total environment, dioxin formation from uncontrolled combustion processes, dioxin inhibition and control mechanisms for combustion processes. The project is sponsored by China National Key Basic Research Special Funds project (G1999022211), key project of National Nature Science foundation (N59836210), National Nature Science foundation (N59878O47). Through an experimental way, much detailed basic work was conducted to investigate the dioxin formation inhibition and control mechanisms from coal and waste combustion processes with variety points. All results obtained could serve as guidelines for practical application concerning dioxins. The main topics of this dissertation are as follows:1) Fly ash is the main carrier of dioxins from waste incineration process; its distribution with size fractions from two typical incinerators (grate fired and fluidized bed fired) in China is studied. Dioxin concentration in fly ashes from bag filters in several incinerators is also compared. The results suggest that dioxin concentration in fly ash from fluidized bed incinerators is much lower than that from grate-fired incinerators. The following aspects: incinerator type, combustion operation system, fuel component, char, heavy metal and chlorine content in fly ash, are discussed to explain the great differences of dioxin concentration for the fly ash from different incinerator types, and the distribution of dioxin concentration with size fraction.2 ) The heterogeneous catalyzed reaction in fly ash surface is the main mechanism for dioxin formation in post combustion zone. Different sources were used to study dioxin formation from heterogeneous catalyzed reaction in fly ash surface with concerning different factors, such as oxygen, carbon, catalyst, C/Cu, particle size and inorganic chlorine. The differences of dioxin formation from different sources at low temperature are discussed. Furthermore, chlorinating reactions playing important roles on heterogeneous catalyzed reaction process is discussed generally.3) In order to stabilize the combustion process, MSW is co-fired with coal. The co-firing of waste and coal was found to inhibit dioxin formation greatly, and the sulfur in coal was explained to this inhibition. In this dissertation, three series of experiments were done in order to better understand the influence of sulfur during dioxin formation process. The results from heating of PCP and element sulfur under different temperatures showed that, the toxic lag phenomenon could be observed about 500℃, sulfur could inhibit dioxin formation when heating temperature was setover 500℃ and on the contrary more dioxin formed when heating temperature is less than 500℃. The S/Cl in fuel also has a great influence on dioxin formation from precursors. When standard coal according to different sulfur content and PCP were co-fired, the dioxin inhibition efficiency was over 80% and even over 99%. Beside at high temperature, Sulfur and its oxides can influence dioxin formation at low temperature on heterogeneous catalyzed reaction. Collaboration with USEPA was carried out about this field. The reaction mechanism of Cl2 with SO2 was discussed in details under different combustion systems. There is an interaction with fly ash and SO2 on the transformation of Cl2 to HC1. The mechanism of SO2 on the heterogeneous catalyzed reaction of Cl2 and fly ash was suggested4 ) Combustion is a main dioxin emission resource in our country. Dioxin emission from coal combustion boiler, different density fluidized bed waste and coal co-fired incinerator was tested and dioxin input and output balance in incineration systems was calculated. The results suggested that ESP has a great influence on the dioxin emission from. The annual dioxin emission fr更多还原