基于燃料选择性分布的铁矿烧结NOx减排研究

Iron ore sintering is the main source of NOx emission in iron&steel industry. The idea of controlling NOx emission by combination of suppressing generation and catalytic degradation is proposed in this project, which is expected to be achieved by building granulation balls of double-layer with fuels selectively distributed in the inner layer. Fuels distributed inside can combust under low excess air coefficient, which not only facilitates suppressing generation of NOx, but helps to degrade NOx by reducing gases produced during combusting process. Meanwhile, CO generated form incomplete combustion in the inner layer can get secondary complete combustion with O2 in the outer layer. By researching the influences of combustion atmosphere on NOx formation and its degradation behaviors with reducing gases and mixtures as catalysts, the mechanism of NOx's generation inhibition and catalytic degradation during sintering is revealed, the theory of cooperative control of NOx emissions is established, as well with integrated application of pyrometallurgy, combustion theory, iron ore pelletizing technology etc.. By studying the influences of fuel constitution of inner layer, chemical composition distribution, granule structural parameters, etc. of granulation balls on its radial gas composition and sintering mineralization, granulation balls with reasonable double-layer are built, key technology of efficient emission reduction is developed, which will made a outstanding contribution for the green and healthy development of iron&steel industry.

铁矿烧结是钢铁工业NOx排放的主要发生源。本项目提出抑制生成和催化降解协同控制烧结NOx排放的思想。其关键是构建燃料选择性分布在内层的双层结构制粒小球，使内层燃料低空气过剩系数燃烧而抑制NOx的生成，并利用燃烧产生的还原气体实现NOx的降解，同时使内层不完全燃烧生成的CO在小球外层充分二次燃烧。项目综合应用高温冶金学、燃烧学等原理，结合铁矿制粒技术，通过研究燃烧气氛对NOx产生的影响，以及NOx在还原气体和烧结混合料催化作用下的降解行为，揭示烧结过程抑制NOx产生及催化NOx降解的机理，建立协同控制NOx排放的烧结理论；通过研究小球内层燃料构成、小球化学成分分布和结构参数等对制粒小球径向气体组成及烧结成矿的影响，构建合理的双层结构制粒小球，开发烧结NOx高效减排的关键技术，为钢铁工业的绿色健康发展作出贡献。

铁矿烧结工序是钢铁工业主要的NOx排放源，减少NOx排放对烧结清洁生产意义重大。本项目开展了NOx过程控制的理论与技术研究，通过查明燃料物化特性、燃烧气氛、空气过剩系数等因素对NOx生成和排放的影响，揭示了烧结过程中NOx的生成行为，发现高反应性燃料、低氧燃烧气氛和燃料适宜粒度是抑制NOx生成的核心因素；研究了烧结过程CO-NO的反应行为，查明了催化CO-NO反应的主要因素，揭示了烧结过程CaO-Fe2O3系化合物快速形成是NO催化降解的关键。在此基础上，通过揭示烧结混合料制粒小球中燃料分布状态对燃烧、NOx排放及小球中气体组成的影响规律，建立了低NOx排放的烧结过程控制方法，开发了燃料预制粒调控制粒小球结构、燃料及化学成分分布的技术，使得制粒小球结构有利于燃料低氧燃烧、成分有促于CaO-Fe2O3系化合物生成；在燃料适宜的包裹层厚度及组成条件下，通过生物质炭与焦粉的耦合燃烧，确保燃料燃烧速度不受影响的前提下，燃料N的转化率从59.66%降低至47.57%，实现了烧结烟气NOx的减排。本项目开发的控制燃料燃烧降低NOx排放的方法，具有投资省、运行成本低、适用范围广等特征，为烧结NOx减量排放提供了一条新的可行途径。