基于CLP过程的燃煤烟气汞脱除回收及吸附剂再生的机理研究

Mercury emission from coal combustion has seriously harmed environment and human health. This project, based on the chemical looping process (CLP), proposes a novel technological concept of integrated mercury removal, mercury recovery and sorbent regeneration system. The technology can be used for mercury effective recovery and sorbents recycling for coal-fired power plants. The mercury oxidation and adsorption, the mercury desorption and recovery, as well as the sorbents activation and generation in CLP system will be thoroughly studied in experiments and mechanisms. The recycled mercury adsorption ability of the carrier sorbents will be studied to explore its preparation methods of high efficiency, its regeneration of the carrying oxygen and sulfur sorbents, and the mechanisms of sorbents activation and regeneration. The valence change of the oxygen-carrying metals (Mn and Co) and the sulfur (S), as well as the migration of O, S, and Hg elements on carrier sorbents surface in the processes of mercury adsorption, mercury desorption and sorbents activation will be recognized. The kinetic mechanisms of mercury oxidation and adsorption, and the mechanisms and conditions of mercury desorption and recovery on carrier sorbents surface will be detected. The reaction processes of CLP system and the reaction mechanism and pivotal technology parameters in each reactors in CLP system will be studied. The kinetic models describing the total process of adsorption, desorption, activation and regeneration in CLP system and the mechanism model describing O, S, Hg elements migration in reaction processes will be established. The theory system of mercury adsorption and recovery, as well as sorbent regeneration will be developed through this study. It is hopefully to see a new technique of chemical looping process for mercury recovery and sorbent recycling in power plants in the near future following accomplish of this project.

燃煤电厂超低排放中汞污染物的脱除至关重要。本项目首次提出基于化学链过程（CLP）的燃煤烟气汞脱除回收及吸附剂再生新工艺，实现汞的有效回收与吸附剂的循环利用。对CLP系统中汞的氧化吸附、脱附回收及吸附剂的活化再生机理进行深入细致的研究。探索新型可再生金属载氧体/金属载硫体高效脱汞吸附剂的制备方法；探明其循环汞吸附/汞脱附/活化再生的机理；揭示载体吸附剂表面元素（Mn、Co、O、Fe、S）在汞吸附、汞脱附和吸附剂活化再生过程中的价态转化规律；探究反应过程中O、S、Hg元素的迁移机理；阐明载体吸附剂汞氧化吸附/汞脱附/吸附剂再生过程的反应动力学机制；探讨CLP系统各个反应器的化学反应历程与最佳工艺参数；建立CLP过程吸附-脱附-活化-再生总过程的反应动力学模型。发展燃煤烟气汞吸附脱除、汞脱附、汞回收、吸附剂再生的理论体系。以期孵化出具有我国自主知识产权的燃煤烟气汞脱除回收及吸附剂循环利用新技术。

本项目提出可再生锰改性金属氧载体和硫改性金属硫载体脱汞吸附剂用于燃煤烟气汞脱除及吸附剂再生新工艺技术和方法。系统深入地研究了锰改性和硫改性可再生脱汞吸附剂的制备方法和工艺，探讨了金属氧载体和金属硫载体的汞脱除机理，阐明了活化再生前后吸附剂表面汞活性位的化学迁移机理，探究了汞吸附/汞脱附/吸附剂活化再生及循环脱汞特性，并建立了汞氧化吸附/汞脱附/吸附剂再生过程的反应动力学模型。采用热再生和低温等离子再生方法实现了锰改性氧化铝吸附剂的再生循环脱汞，低温等离子体通过提高样品表面活性氧的数量提高其循环脱汞性能。对MnxOy/Al2O3脱汞吸附剂进行铈掺杂提高其抗硫性能，铈掺杂能够促使烟气中的SO2优先吸附于铈活性位，减缓了锰的硫酸盐化作用。研究结果表明，α-MnO2表现出比γ-MnO2更强的热再生性能和高效的循环脱汞性能。α-MnO2具有较强的晶格氧结合力，经过多次热再生处理后依然维持其原有的物相组成和形貌结构。γ-MnO2由于其对晶格氧的结合力弱于α-MnO2，热再生后发生了结构重组和物相转变，导致其循环脱汞性能的下降。以硫化氢改性氧化铁制备了磁性可再生脱汞吸附剂，其脱汞机理是通过在氧化铁表面形成硫化铁和单质硫实现汞的高效脱除。恒温硫化热再生方法可实现硫化氢改性氧化铁吸附剂的高效循环脱汞。α-MnO2具有最佳的汞脱除性能和热再生稳定性，硫化氢改性可以实现磁性氧化铁吸附剂的再生循环脱汞。以α-MnO2或硫化铁为活性相的磁性复合材料作为脱汞吸附剂，具有高效的循环脱汞及再生性能，可用于燃煤烟气循环脱汞的吸附剂。