【作者】 谢江坤；

【导师】 晏乃强；

【作者基本信息】 上海交通大学 ， 环境工程， 2013， 博士

【摘要】 近十多年来，汞污染问题引起了国际社会的广泛关注。随着《水俣公约》的出台，给作为世界最大汞排放国的中国带来巨大的履约压力。鉴于煤在中国能源结构中的重要地位，由燃煤产生的汞排放成为我国主要的汞排放源，因此，燃煤电厂的汞排放也就成为中国汞污染控制的重中之重。政府已出台了相关政策，修订了《火电厂大气污染物排放标准》（GB13223-2011），对燃煤电厂的汞排放提出了具体要求。目前，烟气脱汞的主流技术包括以下两类：（1）氧化脱除法：先将烟气中的零价汞氧化，然后利用现有的湿法脱硫装置去除；（2）吸附法：目前比较成熟的吸附法为活性炭喷射技术，将活性炭喷入烟道吸附烟气汞，然后利用现有除尘装置去除。但氧化脱除法仅将汞从大气转移到脱硫液或脱硫石膏中，容易造成二次污染；活性炭喷射法成本较高且影响飞灰品质；两种方法都有一定的局限性，并且活性炭喷射技术对高氯煤效果更佳，而国内的煤中氯含量普遍偏低。因此，开发适合中国煤况的、具有自主知识产权的脱汞技术具有重要意义。本文以锰基氧化物为基础，制备了一批具有较高汞吸附容量和较好再生性能的锰基复合金属氧化物，通过吸附试验对其吸附捕集零价汞的性能进行评价，并考察了吸附剂的活性温度窗口及烟气组分对汞在吸附剂表面吸附的影响，进而阐明汞在吸附剂表面的吸附氧化机制；另外，基于吸附剂的可再生性能，本文还提出了利用多级除尘技术（如电袋复合除尘装置）吸附工艺，将吸附剂喷入电除尘及袋式除尘之间，拟通过在袋式除尘装置上的架桥作用，不仅提高除尘效率，还能满足烟气在吸附剂表面停留时间的要求，达到除汞目的，为燃煤电厂的汞污染排放控制提供了新思路。论文主要得到了以下结论：以不同的锰盐为锰源制备了单组分锰氧化物，初步考察了其对烟气汞的吸附性能并分析了将其用于零价汞吸附剂的可行性及局限性。通过对比其宏观吸附性能和微观表征结果，发现以不同锰源制备的锰氧化物对零价汞具有不同的吸附性能，其中以硝酸锰为锰源制备的锰氧化物具有较高的吸附性能（100oC下10h吸附容量约为2.1mg/g），并且吸附性能与吸附剂的结构及锰的价态存在相关关系，高价态的锰更有利于汞在吸附剂表面的吸附氧化；通过对穿透后吸附剂再生性能的考察，发现通过简单的热处理能够使吸附在吸附剂表面的汞以零价汞的形式重新释放出来，从而实现吸附剂的再生。采用过渡元素锆对单组分锰氧化物进行修饰改性，制备了锆锰复合金属氧化物，并考察了其对零价汞的吸附捕集性能。结合吸附剂的吸附试验与其微观表征结果发现，锰是吸附剂的主要活性组分，锆的掺入能够提高吸附剂的比表面积和氧化能力，进而提高吸附剂在低温条件下的汞吸附容量（100oC条件下约5mg/g）；掺入锆后，锆锰复合金属氧化物可以通过热处理再生；然而，通过多轮吸附-再生-吸附实验发现，热再生后的吸附剂若直接回用吸附性能下降明显，但如果将热处理后的吸附剂加以简单的水洗处理，可以洗掉吸附剂表面形成的硫酸盐，进而恢复其大部分的捕汞能力。采用稀土元素铈对单组分锰氧化物进行改性修饰，制备了铈锰复合金属氧化物，并考察了其对零价汞的吸附捕集性能。结合吸附剂的吸附试验及表征结果发现，锰依然是吸附剂的主要活性组分；作为重要的辅助组分，铈的掺入不仅能够提高吸附剂的比表面积，还能够提高其氧化能力，进而提高吸附剂在低温条件下的汞吸附容量(100oC条件下可达6mg/g)；铈的掺入增强了吸附剂对SO2的耐受性，提高了吸附剂的再生性能，通过简单的热处理，铈锰复合氧化物吸附剂表面吸附的汞能够以零价汞的形式释放出来，从而实现吸附剂的再生；另外，文中还通过多轮吸附-再生-吸附实验探讨了吸附剂的循环使用性能，发现经过5轮循环使用，吸附剂的汞吸附容量未见明显降低。研究还采用主族金属元素锡对单组分锰氧化物进行改性修饰，制备了锡锰复合金属氧化物，并考察了其对零价汞的吸附捕集性能。结合吸附剂的宏观吸附性能与其微观表征结果发现，锡的掺入能够提高吸附剂的比表面积，增强吸附剂的氧化能力和表面酸性强度，进而提高吸附剂的汞吸附容量（100oC条件下约3.0mg）；另外，锡的掺入拓宽了吸附剂的活性窗口，使锡锰复合氧化物不仅可以应用于低温烟气中汞（100oC）的脱除，也可以应用于较高温度（350oC）烟气中汞的脱除，这种特性提高了吸附剂对开停车等工况的适应能力，可以作为改变工况时的备选吸附剂。本文通过简单的方法制备了一系列锰基复合氧化物，考察了其对零价汞的吸附捕获能力，发现制备的吸附剂具有较高的吸附容量和较好的再生性能，并基于以上性能提出了利用现有多级除尘装置除汞；本文比较系统地研究了锰基复合氧化物对零价汞的吸附性能，探讨了吸附性能与材料结构及表面元素价态之间的关系，阐明了汞在吸附剂表面的吸附-氧化机制，拟为锰基汞吸附剂的进一步修饰改性提供理论依据；另外，还基于汞的程序升温脱附数据，建立了脱附活化能计算模型，为后续研究提供热力学数据。更多还原

【Abstract】 Due to the high toxicity, persistence, transportability and bioaccumulation,mercury has attracted increasing attentions since Minamata Disease occured. In recentyears, more national or international treaties on mercury have been issued aiming toreduce mercury pollution including “Minamata Convention”. These treaties hasbrought huge pressure to China, which is the biggest mercury emission country in theworld. Coal is the most important energy source in the current and a near-futureenergy structure of China, therefore, coal-fired related mercury emission has becomethe key point for mercury control in China. Actually, China government has alreadytaken some measures to reduce mercury emission from coal-fired power plant,including revising “Emission Standard of Air Pollutant for Thermal Power Plants”(GB13223-2011). The maximum mercury emission concentration is capped in thisstandard. So far, the main technology for mercury emission control falls into thefollowing two groups:1. Oxidation technology. Firstly oxidize the flue gas elementalmercury catalytically or by injecting oxidant, and then remove the oxidized mercurythrough existing wet flue gas desulfurization system;2. Adsorption method. Removemercury by adsorbent, currently, activated carbon injection is the most testedadsorption technology, and halide is found very important for mercury adsorption.Since halide concentration in coal of China is usually relative low, removal efficiencyof activated carbon injection technology may depreciate if it is used in China.Additionally, oxidized technology only transfers mercury from flue gas intodesulfurization solution or gypsum and may cause the secondary pollution. In otherword, each technology has its own shortcomings and merits, but none has beenproved universal in all flue gas condition. Therefore, developing novel, high efficiency technology with independent intellectual property rights is of significance.In this work, a series of manganese-based binary metal oxides with high mercurycapacity and good regenerablity were prepared and characterized, the adsorption andoxidation mechanism of mercury on the sorbents surface was investigated, moreover,an process based on electro-filter precipitator for mercury removal was proposedbased on the good regenerability of the sorbents in order to reduce the operational costof the power plant. The main contents of this dissertation are listed below:Three kind of manganese oxides were prepared using different manganese salt asmanganese source. Based on the adsorption experiment and characterization results,the relationship between mercury adsorption performance and physiochemicalproperty was built. It was found that low temperature facilitated the mercuryadsorption on sorbent surface and manganese prepared using different manganese saltshowed different physiochemical property and different adsorption performance; highvalence manganese would benefit the adsorption and oxidation of mercury on sorbentsurface; simple heating treatment could release the adsorbed mercury from sorbentsurface and achieve a facile regeneration of the sorbent;A series of Zr-Mn binary metal oxides with different mercury content wereprepared, characterized and their capabilities for elemental mercury removal wereinvestigated. Based on the adsorption experiment and characterization results, therelationship between mercury adsorption performance and physiochemical propertywas built. It was found that manganese was the main component for mercuryadsorption and oxidation in Zr-Mn system, Zr could not only increase the BETspecific surface area of the sorbent but also enhance the reducibility of the sorbentwhich may benefit the mercury adsorption and oxidation on sorbent surface atrelatively low temperature; the adsorbed mercury on the sorbent surface could bereleased by heating treatment, however, the reusability was found not good enoughafter simple heating treatment; It was also found that most of the mercury capacity ofthe sorbent could be recovered by a simple washing treatment after heating, themechanism was discussed; A series of manganese-based Ce-Mn binary metal oxides with differentmanganese content were prepared, characterized and their capabilities for elementalmercury removal were investigated. Based on the adsorption experiment andcharacterization results, the relationship between mercury adsorption performance andphysiochemical property was built. It was found that manganese was the maincomponent for mercury adsorption and oxidation, as an important auxiliarycomponent, the doping of Ce, a rare earth element, could not only increase the BETspecific surface area of the sorbent but also enhance the reducibility of the sorbentwhich may benefit the mercury adsorption and oxidation on sorbent surface atrelatively low temperature; moreover, Ce-Mn binary metal oxides also showed goodregenerability through simple heating treatment; additionally, the regenerated sorbentalso demonstrated good reusability in adsorption-regeneration-adsorptionexperiments.A series of Sn-Mn binary metal oxides with different manganese content wereprepared, characterized and their capabilities for elemental mercury removal wereinvestigated. Based on the adsorption experiment and characterization results, therelationship between mercury adsorption performance and physiochemical propertywas built. It was found that manganese was also the main component for mercuryadsorption and oxidation in Sn-Mn system, Sn could not only increase the BETspecific surface area of the sorbent but also enhance the reducibility of the sorbent andimprove the acidity on sorbent surface, as a result, mercury adsorption capacity of thesorbent was increased; interestingly, the doping of Sn could expand the activetemperature window of the sorbent for mercury adsorption.Furthermore, a model for calculation of mercury desorption activation energy wasbuilt based on Hg-TPD experiments, aiming to quatify the regenerablity of thesorbent.更多还原