多元溶液湿法撞击流燃煤烟气同时脱硫脱硝的机理研究

The methods for simultaneous removal of both sulfur dioxide and nitrogen oxides from flue gas in a single-stage process, with high removal efficiencies, lower capital and operating costs and without added trouble of waste disposal, are acknowledged as development trend. The novel method proposed in this project, which makes full use of the respective physicochemical characteristics of ammonia, urea and ammonium sulfite and nitrous acid from simultaneous desulphurization and denitrification processes to form synergistic effects between absorbents and intermediates for enhancing nitrogen oxides removal. In this project, for the crucial technology of removing nitrogen oxides, first the liquid additives are used to promote the oxidiability of NOx and solubility of NO from flue gas in the complex absorption solution made up of ammonia and urea, thereafter nitrogen oxides are reduced to nitrogen by ammonium sulfite fromed during the desulfurization process and nitrous acid fromed during the denitrification process is decomposed to nitrogen by urea in the absorption solution, which would carry out higher nitrogen oxides removal efficiency, meanwhile reaction products of simultaneous desulfurization and denitration in the liquid phase are ammonium sulfate and ammonium sulfite only.Besides, in order to promote the removal efficiency of sulfur dioxide and nitrogen oxide, in this project the impinging streams has been proposed as a promising method for enhancing mixing, turbulent and the mass and heat transfer rates of gas-liquid two-phase flow in the absorber. A mathematic model of coupled gas-liquid two-phase flow and chemical reactions for simultaneous removal of sulfur dioxide and nitrogen oxides from flue gas is proposed by using the two-film theory. Through the experimental research and numerical simulation, it is expected to disclose the mechanism of simultaneous removal of sulfur dioxide and nitrogen oxides from flue gas in the aqueous ammonia/urea solution with additive and obtain the coupled relations between the gas-liquid two-phase flow and complex chemical reaction for simultaneous removal of sulfur dioxide and nitrogen oxides from flue gas by wet scrubbing in the impinging streams reactor.This study would develop new theory system and motheds of simultaneous removal of sulfur dioxide and nitrogen oxides from coal-fired flue gas in wet scrubbing, and provide scientific theory support for the future development of environmental protection technology with independent intellectual property rights.

无二次污染的低成本、高效、副产物资源化利用的烟气同时脱硫脱硝方法是发展趋势。本项目提出的新方法，融合了氨、尿素、以及同时脱硫脱硝过程中生成的亚硫酸铵和亚硝酸的理化特性，使吸收剂与中间产物之间形成协同促进机制；对关键性的NOx脱除，先采用液相添加剂提高NOx氧化度和溶解度，再利用脱硫生成的亚硫酸铵对NOx还原分解性能和尿素对亚硝酸的分解特性，实现NOx高效脱除和副产物简单、易分离的目标；此外，引入撞击流技术强化气液间混合、湍动和热质传递，进一步提高烟气污染物的脱除效率；运用双膜理论建立气液两相流动与烟气同时脱硫脱硝反应相耦合的数学模型，通过试验和数值模拟研究，揭示多元吸收液湿法烟气同时脱硫脱硝的反应机理，掌握撞击流气液两相流动与烟气同时脱硫脱硝的复杂化学反应耦合机制。本研究将形成湿法燃煤烟气二氧化硫和氮氧化物同时脱除的新理论和方法，为将来开发新型、具有自主知识产权的环保技术提供科学理论支撑。

目前，我国燃煤烟气排放污染严重，制约着我国社会、经济的可持续发展。当前烟气脱硫脱硝方法普遍存在设备投资大、运行成本高、能耗大、工艺复杂及资源化回收困难等问题。因此，探索一种创新性的低成本、高效的同时脱除烟气中SO2、NOx及资源化利用，是我国当前亟待突破的难题。本课题主要针对燃煤电厂烟气的SO2和NOX同时脱除及其资源化过程中的相关科学问题开展了系统的研究。在烟气SO2和NOX同时脱除方面，从试验、热力学计算和动力学模型三个层面考察了氨基溶液对燃煤锅炉尾气中SO2和NOX的脱除机理，发现了NO气相氧化是脱除NO的决定性机制，以及SO2和添加剂与氮氧化物的协同促进脱除机制，提出了H2O2/铁基材料异相芬顿反应耦合氨基溶液同时脱硫脱硝的新方法，结合对系统内相关参数的实验探究结果和现代表征手段探究了该系统的相关反应机理，在该系统上实现了脱硫和脱硝效率分别为99.8％和92.5％，为实现燃煤电厂烟气的“低成本零排放”探索出了重要的技术方案。在撞击流反应器气液两相流流体动力学与多组分污染物复杂化学反应之间耦合机制的研究方面，进行了氨基溶液湿法撞击流同时脱硫脱硝的数值模拟与试验验证研究。采用双欧拉和欧拉-拉格朗日法对气液两相流进行数值计算，完成了对气相或是两相撞击流物理模型的构建和分析，结合尿素溶液湿法同时脱硫脱硝的反应机理，并基于双膜理论对撞击流物理模型进行化学反应的耦合，获得了尿素溶液湿法撞击流同时脱硫脱硝的脱硫脱硝效率随结构参数和工况的变化特性与趋势，为撞击流反应器的优化设计和最佳工况的选择提供了参考。在数值模拟研究的基础上，建立了多元吸收液湿法撞击流燃煤烟气同时脱硫脱硝的实验系统，验证了数值模拟的研究结果，同时也为进一步改进和优化湿法撞击流烟气同时脱硫脱硝的理论模型提供了重要的参考指标。在氨基脱硫脱硝废液资源化利用方面，系统地研究了操作参数对氨基脱硫脱硝废液电解制备高附加值过硫酸铵的影响，并深入探究了吸收液电解制备过硫酸铵的反应机理。详细地研究了副产物资源化过程中尾液对烟气同时脱硫脱硝的影响特性，分析了粉尘和重金属对氨基脱硫脱硝废液电解制备高附加值过硫酸铵的影响，并提出了一种氨基湿法脱硫脱硝工艺与吸收液电解资源化循环利用耦合的新型绿色高效的烟气净化技术路线。本课题研究丰富了湿法燃煤烟气多组分污染物（SO2和NOx）同时脱除的理论，推进了燃煤烟气净化技术的进步与发展。