水泥分解炉燃料型NO_x形成影响因素及源头防治研究

发布时间：2018-06-21 09:25

本文选题：水泥分解炉 + 燃料型氮氧化物　；参考：《华南理工大学》2016年博士论文

【摘要】：多年以来,我国水泥生产及消费量一直高居世界首位。随着大型水泥预分解窑的广泛应用,由水泥窑产生的氮氧化物已成为大气NOx的第三大来源。水泥窑的燃料约60%是在温度约900℃的分解炉燃烧,生成的氮氧化物基本上是燃料型氮氧化物。另外,利用废弃物作煅烧水泥熟料的原燃料,使废弃物资源化,具有十分重要的意义。但是随着废弃物广泛地应用于水泥生产中,也给水泥窑废气的排放带来重要影响,包括对NOx形成的影响。为此,结合废弃物在水泥窑中的应用,研究煅烧水泥过程中燃料型NOx形成的影响因素,实现从源头上有效控制水泥窑NOx排放,不仅具有科学意义,而且对环境保护也有重要价值。本论文通过实验室与工厂生产实际相结合的研究方法,通过量子化学数值计算、Fluent流体仿真、X射线光电子能谱分析(XPS)、气相色谱-质谱联用分析、热重差热分析、热重-红外联用分析、盐酸萘乙二胺分光光度法等手段,研究了利用废弃物煅烧水泥过程中氮氧化物的形成影响因素及源头防治技术,内容包括原燃料中各种氮形态及其对氮氧化物形成的影响；水泥窑无害化处理脱水污泥及其对燃煤氮氧化物的影响；废轮胎、废人造革、废真皮革对水泥窑燃料型氮氧化物排放的影响；水泥生料对燃料型氮氧化物形成的影响。通过研究取得了以下成果：(1)在分析了原燃料中氮形态的基础上,研究了氮形态对燃料型NOx形成的差异。在900℃燃烧时,原燃料中四类主要氮形态以废真皮革的氨基酸氮热稳定性最差,其生成的燃料型NOx浓度最高,其次为煤吡咯氮和吡啶氮,而热稳定性最好、生成燃料型NOx最小的是废合成革中的甲苯二异氰酸酯基团。另外,相同条件下,燃煤生成氮氧化物的量会随其吡咯氮含量增加而增加。因此,原燃料氮赋存形态的差异对燃料型NOx的形成产生明显影响作用。(2)通过计算量子化学方法分析了吡咯、吡啶、氨基酸、甲苯二异氰酸酯等基团受热化学反应过程。由量子化学Mulliken键布居数可得各氮形态的C-N键强度较弱,在受热时会优先发生断裂,从而引发基团的分解；由此计算反应活化能从小至大依次是氨基酸氮吡咯氮吡啶氮甲苯二异氰酸酯基团氮,而所对应的热稳定性正好反之,聚合甲苯二异氰酸酯型氮最强,其次为吡啶氮和吡咯氮,最差的是氨基酸氮。分解得到的含氮小分子产物影响NOx的形成,其中氨基酸氮分解得到NH3,吡啶氮的产物以HCN形式释放,吡咯氮生成产物则包括了NH3和HCN,废合成革聚合甲苯二异氰酸酯氮则分解产生HCN。相同条件下,NH3的氧化反应速率比HCN的大,当燃烧时,NH3的快速氧化更有利于氨基酸和吡咯的分解,使反应向右进行,从而也有更多的氮氧化物生成。(3)水泥窑应用废轮胎粉对NOx生成有好的抑制作用。虽然废轮胎粉氮的形态与废真皮革的相同,均是氨基酸氮为主,但在燃烧时氮的排放两者明显差别。分析结构内部元素表明,废轮胎粉中的NOx还原性元素C、H含量远大于废真皮革,而氧化性元素O却很小。另一方面,TG-DSC曲线表明,物质失重过程存在重叠区域。由于废轮胎挥发分释放比煤快。当煤刚开始逸放挥发分并伴有少部分固定碳的燃烧时,轮胎已释放出大量CH4、C2H4、C2H2、CH和CO等还原性物质,为抑制燃煤NOx生成创造了有利条件。因此,废轮胎粉NOx排放量远小于废真皮革的,且废轮胎粉与煤混合燃烧还能降低燃煤NOx排放量。(4)水泥生料对燃料型NOx排放综合作用的结果是促进NOx排放。在900℃条件下,水泥生料会促进燃料型NOx的生成。水泥生料矿物组分对燃料型NOx促进作用由大至小依次为CaOMgO Al2O3。而惰性组分Si02则因覆盖燃料延缓热传递而使NOx排放降低。另外,含S化合物对燃料型NOx生成具有一定的抑制作用,且受硫化合物结构形态的影响。硫化亚铁(FeS)和黄铁矿(FeS2)对NOx的减排作用效果明显,而硫酸钙和亚硫酸钙等硫酸盐对NOx抑制作用效果较小。总之,水泥原料对NOx综合作用的结果是促进NOx排放。(5)城市生活污水污泥烘干过程中产生的尾气不加以处理而直接排放会释放出大量有害物质,造成大气污染。其中烘干原状脱水污泥的尾气除含有芳香族、卤代烃、正己烷等31类有机化合物外,还包含有NH3、H2S和硫醇等恶臭物质。烘干以生物法除臭后的污泥所产生的尾气其有机化合物种类数增加至34类,除芳香族、卤代烃、正己烷等外,苯的种类数增加和还新增了胺类等化合物。(6)生活污水污泥烘干过程中产生的尾气直接排放会释放出大量有害物质,造成大气污染。将污泥烘干产生的尾气与空气混合作为燃煤载气,并输送至900℃高温炉内助煤燃烧,能有效去除尾气恶臭和芳香族化合物、卤代烃等大分子化合物。并且与煤在空气中燃烧时的烟气NOx排放浓度相比,掺入污泥烘干的尾气后,可以使燃煤烟气NOx排放浓度降低。为此,先尽量降低污泥的含水率,再采用回收回转窑筒体冷却热风或部分熟料冷却机热风等烘干城市污水污泥,其尾气与原状空气同时入水泥分解炉燃烧,既消除尾气的恶臭和有机物,又减少NOx排放。(7)氮含量相等,在相同实验条件下,由生活污水污泥产生燃料型NOx的浓度低于煤样的。污泥中氮形态包括氨基酸氮、亚硝基化合物和苯胺三大类,其中氨基酸热稳定性差,且富含氧元素是其NOx生成的主要来源,但亚硝基化合物为转化成更加稳定的硝基化合物,竞争了氧化性自由基,同时,苯胺受热快速释放出胺基,均不利于NOx的形成。此外,污泥特殊的轻质多孔结构为NOx还原提供了有利的条件。燃烧时随着挥发分的释放,使污泥骨架形成了活性炭状的多孔结构。巨大的比表面积是良好的还原剂载体。当与烟气(包括NO、HCN、NH3等)接触时,烟气随CH4、C2H2、CiHi等碳氢化合物、炭被吸附在多孔结构表面,通过发生气固和气气反应使NO还原。综合作用的结果使污泥产生燃料型NOx的浓度较低。(8)借助Fluent流体软件模拟研究了生活污水污泥对分解炉NO生成和转化过程的影响。模拟结果表明,生活污泥从分解炉中部喷入比从底部喷入对氮氧化物的减排效果更好。模拟结果在6000 t/d水泥生产线的双喷腾分解炉得以证实,在不影响生产的前提下,污泥从分解炉中部喷入比从底部喷入,氮氧化物减排幅度从18%提高至39%。水泥窑合理地协同处理废弃物,既能废物综合利用,又可从源头降低其氮氧化物排放。
[Abstract]:Over the years, the amount of cement production and consumption in China has been ranked first in the world. With the wide application of large cement precalciner kiln, nitrogen oxides produced by cement kiln has become the third largest source of atmospheric NOx. About 60% of cement kiln fuel is burning in calciner temperature of about 900 DEG C, nitrogen oxides generated basically is the type of fuel nitrogen oxide . in addition, the use of wastes as raw fuel burning of cement clinker, the waste of resources, it has very important significance. But with the waste is widely used in cement production, but also bring important influence to cement kiln emissions, including the impact on the formation of NOx. For this, combined with the application of waste in cement kiln the study of calcined Influence factors of fuel burning cement in the process of NOx formation, realize the effective control of NOx cement kiln emissions from the source, not only has scientific significance, but also has important value for environmental protection. This paper through laboratory and factory production research method of combining the numerical quantum chemical calculation, Fluent simulation, X ray photoelectric Sub spectrum analysis (XPS), the analysis of gas chromatography-mass spectrometry, thermogravimetric analysis and differential thermal analysis by TGA-FTIR analysis, naphthyl ethylenediamine dihydrochloride spectrophotometric method, was studied by using the influence factors and source control technology of nitrogen oxide waste cement calcination process, including a variety of nitrogen the original form of nitrogen oxide fuel Influence of formation of cement kiln; harmless disposal of dewatered sludge and its influence on coal nitrogen oxide; waste tire, wasteartificial leather, leather waste really influence on cement kiln fuel NOx emission; influence of cement raw material to fuel NOx formation. The study obtained the following results: (1) in the analysis the original fuel Based on the study of nitrogen forms, different nitrogen forms on fuel NOx formation. In 900 degree burns, the thermal stability of four kinds of amino acid nitrogen nitrogen to form the main raw material and fuel waste real leather is the worst, the highest concentration of fuel NOx formation, followed by coal and pyridine and pyrrole nitrogen, heat the best stability, formation of fuel NOx is the smallest waste Synthetic leather in the toluene diisocyanate group. In addition, under the same conditions, the amount of coal to produce nitrogen oxides with pyrrole nitrogen content increased. Therefore, the difference of raw fuel nitrogen forms on the formation of fuel NOx produced significant effect. (2) calculated by quantum chemical analysis methods of pyrrole, pyridine. Amino acid, toluene Diisocyanate groups such as chemical reaction heat. By quantum chemical Mulliken bond population the number of available C-N bond strength is weak the nitrogen form, firstly broken in when heated, causing the group decomposition; calculated activation energy from small to large are the amino acid nitrogen of nitrogen, the pyridine nitrogen nitrogen group of toluene diisocyanate, The thermal stability and the corresponding right on the other hand, the polymerization of toluene diisocyanate type nitrogen was the strongest, followed by pyridine and pyrrole nitrogen, amino acid nitrogen is the worst. The decomposed nitrogen containing small molecules influence the formation of NOx, which is decomposed into NH3 amino acid nitrogen, the pyridine nitrogen release products in the form of HCN, pyrrolic nitrogen production it includes NH3 And HCN synthetic leather waste, polymerization of toluene diisocyanate nitrogen produced from the decomposition of HCN. under the same conditions, the NH3 oxidation rate is bigger than HCN, when burned, rapid oxidation of NH3 is more conducive to the decomposition of amino acid and pyrrole, the reaction to right, thus there are more nitrogen oxides (3) cement production. Application of kiln waste tire powder production of NOx Good. Although the inhibitory effect of waste tire powder nitrogen with the same waste real leather, are amino acid nitrogen, but the obvious difference in the combustion emissions of nitrogen. The analysis of the internal structure of the elements show that the waste tire powder in the reduction of NOx element of C, the content of H is much larger than the real leather waste, and oxidation the element O is very small. On the other hand, TG-DSC curve The material shows that there is an overlap region. Because of the weight loss process of waste tire volatile release than coal quickly. When the coal began to release volatile and accompanied by a small part of the fixed carbon combustion, the tire has release large amounts of CH4, C2H4, C2H2, CH and CO and other reducing substances, creating favorable conditions for the suppression of coal NOx generation of waste tire powder. Therefore, NOx emissions are much Less than the real leather waste, and waste tire powder mixed with coal combustion can reduce emissions of coal-fired NOx. (4) the cement raw material emission comprehensive effect on fuel NOx results is to promote the emission of NOx. Under the condition of 900 DEG C, cement raw materials will promote the formation of fuel NOx. The raw cement mineral composition of fuel NOx promoted from big to small in the order of CaO MgO Al2O3. and inert component Si02 due to delay of heat transfer to cover fuel NOx emissions decreased. In addition, the compound containing S has an inhibitory effect on fuel NOx formation, and affected by the structure of sulfur compounds. Ferrous sulfide (FeS) and pyrite (FeS2) emission reduction effect of NOx significantly, and sulfuric acid calcium sulfate and calcium sulfite etc. The inhibition effect of salt on the smaller NOx. In short, the results of the comprehensive effect of cement raw material NOx is to promote the emission of NOx. (5) gas produced sludge drying process in city sewage is discharged directly without treatment will release a lot of harmful substances, air pollution caused by exhaust gas. The drying of dewatered sludge containing aromatic in undisturbed halogen family Hydrocarbon generation, n-hexane and 31 kinds of organic compounds, including NH3, H2S and thiol odors such as biological deodorization to exhaust drying. After the sludge produced by the type of organic compounds increased the number to 34, in addition to aromatic, halogenated hydrocarbon, n-hexane and so on, the number of species and also with the increase of benzene the new amine compounds such as sewage sludge (6). Gas generated in the drying process of the emission will release a lot of harmful substances, causing air pollution. Drying the sludge produced gas mixed with air as carrier gas and coal, transported to the 900 high temperature furnace a coal combustion, can effectively remove the exhaust odor and aromatic compounds, halogenated hydrocarbons and other compounds in coal and. Empty Compared with the NOx concentration in flue gas during combustion gas, exhaust gas mixed with sludge drying, can make flue gas NOx emission concentration decreased. Therefore, first try to reduce the water content of the sludge, then the recovery of rotary kiln cooling hot air or hot air drying part clinker cooling machine city sewage sludge, and the exhaust gas and the original air into the water Mud decomposition furnace combustion exhaust, can eliminate odor and organic matter, and reduce the emission of NOx. (7) the nitrogen content is equal, under the same experimental conditions, the concentration of fuel type NOx produced by sewage sludge is lower than that of coal. Amino acid nitrogen nitrogen including sludge, nitroso compounds and aniline in three categories, including poor thermal stability and rich in amino acids, Oxygen is the main source of NOx generation, but the nitroso compound is transformed into nitro compound is more stable, competitive oxidative free radicals, at the same time, the rapid release of amino aniline heating, are not conducive to the formation of NOx. In addition, the special structure of porous lightweight sludge provides favorable conditions for the reduction of NOx combustion. With the volatile The release of the sludge skeleton forming porous structure of activated carbon shape. Huge surface area is good. When the reducing agent carrier and flue gas (including NO, HCN, NH3 etc.) contact with flue gas, CH4, C2H2, CiHi and other hydrocarbons, carbon is adsorbed on the surface of porous structure, the occurrence of gas solid gas reaction to NO reduction result. The concentration of sludge fuel NOx is low. (8) using Fluent fluid software the effects of sewage sludge on the decomposition furnace NO generation and transformation process. The simulation results show that the sewage sludge from decomposing furnace is sprayed into the middle is better than the reduction of nitrogen oxides into the spray from the bottom. The simulation results in t/d 6000 the double cement production line Spouted Calciner is confirmed, without affecting the production, sludge from decomposing furnace is sprayed into the middle than from the bottom spray, nitrogen oxides emission reduction rate increased from 18% to 39%. cement kiln co processing waste reasonably, can the comprehensive utilization of waste, but also reduce the NOx emissions from the source.
【学位授予单位】：华南理工大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：X781.5

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