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钢铁烧结烟气CO和NOx协同减排技术研究
李超群
Thesis Advisor朱廷钰
2020-07-01
Degree Grantor中国科学院大学
Degree Name博士
Degree Discipline环境工程
Keyword烧结烟气,选择性循环,Co,No,Cuce/tio2
Abstract

钢铁工业是我国重要的支柱产业,为我国国民经济发展做出贡献同时也消耗了大量能源,排放了大量污染物。随着钢铁行业超低排放改造的全面展开,烧结烟气污染治理成为钢铁治污的重心之一。烧结烟气排放具有污染物种类多、烟气量大、波动大等特点,造成其后续处理工艺设备投资大、运行费用高。烧结烟气循环工艺可同时实现烟气余热利用与降低排放烟气量,兼具节能和减排双重功效。本文针对烧结烟气NOx减排压力和CO控制需求,提出利用烟气循环的过程控制技术,结合CO催化氧化的末端治理技术,实现烧结烟气CO和NOx的综合治理。首先通过现场测试调研了5台烧结机的原始烟气排放特征和风箱烟气分布特征。进一步借助实验研究和模拟计算手段,研究了烟气循环过程中CO和NOx的减排机理,并提出了烧结烟气选择性循环工艺。基于烟气循环CO减排效果有限,探究了Ce掺杂Cu/TiO2催化剂在烧结烟气CO氧化中的应用效果,最后从工业应用角度归纳总结了烧结烟气选择性循环技术的运行效果和操作运行规律,取得的主要创新性成果如下:(1)实地监测和分析了烧结烟气排放特征和风箱烟气分布特征,结果表明烧结烟气排放具有污染物种类多、烟气量大、水含量高、CO排放量大等特点;在烧结机长度方向,受床层累积效应影响,温度和SO2呈现“火山型”分布,SO2峰值先于温度峰值;受燃烧影响,CO、NO和CO2均呈现倒“U”型分布,O2与之相反。(2)研究了烟气循环过程中烧结床层CO-NO的反应机理,研究结果表明烧结床层的铁酸钙对CO-NO反应有较好的催化作用,反应以E-R机理进行,其中NO的解离是反应的决速步,解离生成的N原子与气态CO生成NCO自由基为反应的主要发生路径,因此适当提高循环烟气中CO/NO比例有助于NO的脱除。而O2的存在对反应有明显毒化作用,还原后铁酸钙耐氧性有明显提升。(3)对烧结烟气高水含量下CO氧化催化剂进行了初步探究,结果表明在烧结烟气典型气氛下Ce改性的Cu/TiO2催化剂有良好的催化活性和抗水性能,Ce掺杂促进了Cu物种在催化剂表面的分散,同时Cu-Ce协同氧化还原对的存在有利于表面氧的活化和转移,从而为CO的吸附和氧化提供了一条更快速的通道,使其在烧结烟气气氛下可以实现高效催化氧化。(4)深入分析了烧结烟气选择性循环节能减排工程的工业运行数据,发现在不影响烧结生产情况下,采用烟气循环可明显降低外排烟气量和CO排放量,减排效果明显;另外,采用烟气循环热风烧结效果显著,固体燃耗降低,并改善烧结矿质量。;The iron and steel industry is an important pillar of our country, which contributes to the development of China's national economy and consumes a large amount of energy and emits a lot of pollutants. With the comprehensive development of ultra-low emission transformation in the steel industry, sintering flue gas pollution control has become one of the focus of steel pollution control. Sintered flue gas emissions are characterized by a large number of pollutant types, large flue gas volume and fluctuations, resulting in large investment in subsequent treatment process equipment and high operating costs. The sintering flue gas circulation process can simultaneously realize the utilization of flue gas waste heat and reduce the amount of flue gas emitted, and has the dual effects of energy saving and emission reduction.In this paper, we propose to use the process control technology of flue gas circulation, combined with the terminal treatment technology of CO catalytic oxidation, to realize the comprehensive treatment of sintered flue gas CO and NOx, in order to meet the requirements of sintered flue gas NOx reduction pressure and CO control. Firstly, the original flue gas emission characteristics and the distribution characteristics of the bellows flue gas of five sintering machines were investigated through field testing. The mechanisms of CO and NOx reduction in the flue gas circulation process were further investigated by experimental research and simulation, and the sintering flue gas selective circulation process was proposed. Based on the limited effect of CO reduction in flue gas circulation, the application of Ce doped Cu/TiO2 catalyst in sintered flue gas CO oxidation was investigated. Finally, the operation effect and operation rules of sintering flue gas selective circulation technology are summarized from the perspective of industrial applications. The main innovative results achieved are as follows.(1) Sintered flue gas emission characteristics and bellows flue gas distribution characteristics were field tested. The results show that sintered flue gas emissions are characterized by a large number of pollutant types, high flue gas volume, high water content and high CO emissions. In the longitudinal direction of the machine, affected by the cumulative effect of the bed, the temperature and SO2 exhibit a "volcanic" distribution, and the peak of SO2 precedes the peak of temperature. Under the influence of combustion, CO, NO, and CO2 all exhibit an inverted "U" distribution, and O2 is the opposite.(2) The reaction mechanism of CO-NO in the sintered bed during the flue gas circulation was studied. The results show that calcium ferrite in the sintered bed has a good catalytic effect on the CO-NO reaction. The reaction is carried out by the E-R mechanism, in which the NO dissociation is the rate-determining step. The main pathway of reaction is the reaction of the generated N atoms with gaseous CO to form NCO radicals. Therefore, an appropriate increase in the CO/NO ratio in the circulating flue gas will facilitate the removal of NO. The presence of O2 had a significant inhibitory effect on the reaction, and the oxygen resistance of calcium ferrate was significantly enhanced after reduction.(3) The CO oxidation catalyst under high water content of sintered flue gas was preliminarily investigated. The results show that the Ce-modified Cu/TiO2 catalyst has good catalytic activity and water resistance under the typical atmosphere of sintered flue gas. Ce doping promotes the dispersion of Cu species on the surface of the catalyst. At the same time, the presence of Cu-Ce synergistic redox pairs facilitates the activation and transfer of surface oxygen, thus providing a faster pathway for the adsorption and oxidation of CO, enabling efficient catalytic oxidation under sintered flue gas atmosphere.(4) In-depth analysis of the industrial operation data of the sintering flue gas selective circulation energy saving and emission reduction project. In terms of emission reduction, the use of flue gas circulation can significantly reduce the amount of external flue gas and CO emissions without affecting sintering production. In addition, the hot air sintering effect of flue gas circulation is significant, which can reduce solids consumption, and improve the quality of sintered ore.

Language中文
Document Type学位论文
Identifierhttp://ir.ipe.ac.cn/handle/122111/49660
Collection中国科学院过程工程研究所
Recommended Citation
GB/T 7714
李超群. 钢铁烧结烟气CO和NOx协同减排技术研究[D]. 中国科学院大学,2020.
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