生物质再燃过程中碱(土)金属和氯迁移及其对氮汞协同控制机理研究

The technologies for controlling multi-pollutants, such as NOx and mercury, etc. in coal-fired flue gas has been gained high attention at home and abroad in recent years. The combination of sorbent injection and flue gas conditioning bas been considered as a promising mercury control technology, however, this techonology is not applied widely due to the limitation of sorbent cost and flue gas conditioning technology. On the basis of the characterics of low sulfur, low nitrogen and higher contents of AAEMs (Alkali and alkali earth metals, mainly K, Na, Ca and Mg) and chlorine bound in biomass, the new method of simultaneous removal of NOx and mercury through biomass reburning was put forward to form appropriate concentrations of AAEMs and chlorine in the flue gas and flyash, in order to promote the NO redution and the catalytic oxidation of elemental mercury, and finally to achieve simultaneous control of NOx and mecury in conventional air pollution control devices (APCDs). In this project, the migration of AAEMs and chlorine will be focused on, and the characteristics of migration and transformation of AAEMs and chloride bound in biomass will be carried out in a fixed-bed and an entrained-flow ractors, the effect of biomass species, reaction temperature, stoichiometric ratio, residence time, flyash and additives etc. on migration and transformation of AAEMs and chlorine during biomass reburning will be studied, and the control mechanism of NOx and Hg will be analyzed. The mechanism models based on the migration and interaction effects of AAEMs, chlorine, nitrogen and mercury will be put forward. The key influencing factors of multi-pollutants control during biomass reburning will be obtained. A mothod of selection and modification of biomass fuels and optimization of rebrning process will also be put forward. It will built a foundation to realize the maximum effect of the removal of NOx and mercury during biomass reburning.

燃煤烟气NOx和汞多污染物联合控制近年来得到了国内外高度关注。采用吸附剂喷射和烟气调质相结合是极具发展前景的汞污染控制技术，但由于吸附剂成本和烟气调制等问题限制了该技术应用。本项目基于生物质再燃脱硝脱汞的新方法，结合生物质含有较高碱(土)金属(AAEMs, 如K, Na, Ca和Mg)和氯的特点，通过生物质再燃在烟气和飞灰中形成合适含量的AAEMs和氯，强化NOx还原和单质汞催化氧化，使其在大气污染控制设备(APCDs)中高效脱除。本项目利用固定床和携带流反应装置，研究生物质种类、反应温度、反应气氛、停留时间、飞灰与添加剂等对生物质热解和再燃条件下AAEMs和氯的迁移转化规律，考察AAEMs和氯参与条件下烟气中NOx还原与单质汞形态转化的规律，探索再燃条件下AAEMs和氯迁移对烟气中NOx和Hg关联控制机理，建立以AAEMs、氯、氮和汞迁移和关联行为为核心的机理模型，获得生物质再燃多污染物联合控制的关键影响因素，以期通过对生物质的筛选、改性以及工艺优化，最大限度地发挥生物质再燃的功效。

燃煤烟气中的汞与NOx等多污染物联合控制技术受到国内外普遍关注。采用活性炭喷射与烟气调质相结合是最具工业应用前景的燃煤汞污染控制技术。然而，由于活性炭成本昂贵和复杂烟气组分调质等问题，限制了该技术广泛的工业应用。本项目基于申请者提出的生物质再燃脱硝脱汞新方法，结合生物质具有的低硫、低氮、含碱(土)金属（AAEMs, 如K, Na, Ca和Mg）与氯的特点，通过生物质再燃在烟气和飞灰中形成合适含量的AAEMs和氯，从而强化NOx还原和单质汞催化氧化，最终实现NOx和汞等污染物在大气污染控制设备（APCDs）中高效联合脱除。利用固定床和携带流反应装置，研究了生物质种类、反应温度、化学计量比、停留时间和初始氧含量等对生物质热解和再燃条件下生物质焦理化结构演变及生物质中AAEMs和氯迁移转化特性的影响，探讨了生物质热解过程中AAEMs和氯等元素迁移转化机理；利用携带流反应装置，研究了生物质种类、反应温度、烟气组分、停留时间、飞灰以及碱金属（Na/K）添加剂等因素生物质再燃/高级再燃和选择性非催化还原（selective non-catalytic reduction, SNCR）脱硝性能的影响，获得了生物质再燃/高级再燃和SNCR脱硝的关键操作参数；利用固定床吸附和管道喷射试验装置，研究了生物质种类、吸附温度、初始汞浓度、烟气组分（SO2、NO和HCl）、停留时间和改性剂种类等对生物质焦脱汞性能的影响，明确了AAEMs和氯参与条件下气-固非均相催化反应体系中气态单质汞（Hg0）脱除机理和动力学过程，获得了生物质焦脱汞的关键操作参数和动力学模型参数；基于气-固异相反应及烟气组分均相反应机理，建立了以Na、K、氯、氮和汞为核心的多污染物关联控制机理模型，通过数值模拟研究，深入揭示AAEMs和氯存在条件下NO还原和汞催化氧化脱除的反应机制。上述研究为生物质资源利用及燃煤烟气多污染物联合控制技术工业应用奠定了基础。