水泥窑焚烧处置污泥过程中污泥脱硝作用机理及影响因素研究

As two research hotspots domestically in recent years, de-NOx of cement kiln flue gas and safe disposal of municipal sewage sludge are also the major environmental protection issues facing China currently. To combine the disposal of sewage sludge by the cement precalciner with sludge denitrification is one of the feasible means to resolve the aforementioned issues. Safe disposal and recycling of sewage sludge and synergistical removal of NOx from cement kiln flue gas will be achieved by using this method. However, there are few researches on the sludge denitrification technology internationally. Problems such as unclear sewage sludge denitrification mechanism and ambiguous influencing factors of denitrification are still existing. So, the technology can not guide the actual industrial production at present. Thus, through setting up the experimental platform and simulating operating conditions and components of the flue gas inside the cement precalciner, using traditional characterization methods and combining with thermal analysis, adsorption technology, catalytic reaction technology and site monitoring, etc., the study will be carried out. The release characteristics of reducing agent generated by sewage sludge combustion will be investigated. The species and factors influencing reducing agent release will be confirmed, and the formation and control measures of reducing agent will be explored. In the meantime, the ability and main influencing factors of gas-phase homogeneous denitrification reaction and gas-solid-phase heterogeneous denitrification reaction in sludge burning will be investigated. The sludge denitrification reaction pathway and dominating chemical reaction process will be explored. Finally, the denitrification mechanism of sludge burning will be revealed. Furthermore, the factors influencing sludge denitrification in cement precalciner will be studied, and the ability of sludge denitrification and emission characteristics of sludge burning flue gas pollutants will be confirmed. The environmental impact and adaptability of the technology will be evaluated. This work will provide a theoretical basis and data support for industrial application of sludge denitrification technology in the cement industry.

水泥窑烟气脱硝和市政污泥安全化处置是目前我国面临的两个重要环境问题，也是近年来国内的研究热点。将水泥分解炉处置污泥和污泥脱硝相结合是解决上述问题的可行方法，可实现污泥的资源化处置和烟气NOx的协同脱除，但国内外针对污泥脱硝技术的研究缺乏，存在污泥脱硝影响因素不清、脱硝机理不明等问题，无法指导实际工业生产。为此本项目通过搭建实验平台，模拟水泥分解炉工况和烟气组成，借助常规测试表征手段，结合热分析、吸附、催化反应技术以及现场监测等，研究污泥燃烧过程中还原性产物释放特性，明确还原性产物种类及其释放影响因素，探索其生成调控措施；研究污泥脱硝气相均相反应和气固异相反应能力及影响因素，探明污泥脱硝反应途径，确定主导的化学反应过程，揭示污泥脱硝反应机理；研究污泥脱硝影响因素，明确污泥脱硝能力及燃烧烟气污染物排放特性，评估技术的环境影响和适应性，为污泥脱硝技术在水泥行业的工业应用提供理论基础和数据支持。

水泥窑烟气脱硝和市政污泥安全化处置是目前我国面临的两个重要环境问题，也是近年来国内的研究热点。本研究创造性的将水泥分解炉处置污泥和污泥脱硝相结合，通过搭建实验平台，模拟水泥分解炉工况和烟气组成，借助常规测试表征手段，结合热分析、吸附、催化反应技术以及现场监测等，开展水泥窑焚烧处置污泥协同脱硝技术研究，得出系列创新性结论。首先，明晰了污泥燃烧过程中还原性产物（HCN、NH3、CH4及CO）产生特性、影响因素及其生成调控措施。其次，揭示了污泥脱硝气气均相反应和气固异相反应能力及影响机理，实验得出污泥最大脱硝率为61.67%，污泥焦的最大脱硝率为16%，确定气气均相反应是污泥脱硝主导反应；明确了CO和NH3是主要的气相脱硝还原剂，以NH3为主。再次，在中试试验平台上开展了污泥脱硝工艺条件和影响因素研究，优化了污泥脱硝工艺条件，在燃烧温度为900 ℃、O2浓度为3%、CO2浓度为25%的较佳条件下，无水泥生料时，NOx的平均去除率可达74.16%，有水泥生料时，NOx的平均去除率可达70.36%，水泥生料对NOx的去除呈现一定抑制作用。同时，如在污泥中加入适量添加剂，如尿素，整体脱硝效率可提升至90%。最后，选择某水泥厂水泥窑协同处置污泥项目，对其运行工艺进行指导优化，现场试验表明随着污泥投加量的增大，NOX去除率逐渐增大，当污泥投加量为熟料产量的3.6%时，去除率可达到68%。同时，结合实验室研究和现场监测，评估了本技术的环境影响，研究表明只要采取合适的污染治理设施，采用水泥窑协同处置污泥不会造成大气污染。本技术符合我国水泥窑烟气脱硝和污泥处置技术需求，研究成果能为污泥脱硝技术在水泥行业的工业应用提供理论基础和数据支持。