铜铁基改性活性炭对烟气中二价汞的吸附

随着工业的发展,环境问题日趋严重,而二价汞污染作为环境问题之一受到越来越多的关注。本文采用过体积浸渍法制备了铜基和铁基[CuCl₂,FeCl₃,Cu （NO₃）₂]改性的活性炭,考察了不同浓度以及煅烧温度制备的改性活性炭对模拟烟气中二价汞（HgCl₂）脱除性能的影响。通过吸附穿透实验的对比研究得出,无论是铜基或铁基改性的活性炭都对含氯化汞烟气有很好的吸附效果,并且300℃焙烧的0.01mol/L的氯化铜改性活性炭是深度脱除含氯化汞烟气效果最好的改性活性炭,其吸附量达到了4.55mg/g。在此基础上,进一步利用了XRD、BET、XPS常用表征手段研究了改性前后活性炭的物理化学特性,证明了铜基、铁基改性活性炭吸附氯化汞都是物理吸附与化学吸附共同作用的结果,并给出了相应的解释,以期为后续的科学研究提供一定的思路。     

改性活性炭的制备及其对气态汞的吸附研究

采用高温热处理法去除活性炭表面含氧官能团,并通过化学浸泡法分别将酚羟基和羧基添加到活性炭表面。利用氮气吸附-脱附、X射线衍射分析、X射线光电子能谱法对改性前后活性炭进行表征。研究发现：经高温热处理的活性炭比表面积增大为1139m2／g,孔径集中分布于1nm以下;热处理后活性炭内部晶格结构更加完整。经过化学改性后,酚羟基和羧基均可以一定比例负载到活性炭表面,且比表面积随着负载量增多而下降。对气态汞的吸附实验表明：经高温热处理的样品对气态汞的吸附能力与原始活性炭相比有所下降：当达到吸附饱和时,原始活性炭的吸附量为306．55μg／g,而经热处理的样品的吸附量是243．5μg／g;负载羧基的活性炭样品,其吸附容量高达865．3μg／g;负载酚羟基样品的吸附容量为133．1μg／g。由此得出结论：活性炭表面的含氧官能团对其吸附气态汞有重要影响,其中羧基的存在有利于对气态汞的吸附,而酚羟基的存在对气态汞的吸附不起促进作用。     

煤基吸附剂脱除烟气中气态汞的研究现状

综述了现阶段煤基吸附剂脱除烟气中汞的基本情况,重点介绍了飞灰炭与改性活性炭的研究现状。飞灰炭脱汞效果要比活性炭差,较高的飞灰烧失率、大量的中孔结构、表面有大量的含氧官能团和无机成分(S、Cl)对飞灰炭吸附汞有利;改性活性炭主要由含Cl或S的物质进行改性,并且分别介绍了它们各自脱汞的特征。还分析了烟气中极性气体对脱汞的影响。     

MnOx改性活性炭用于模拟烟气中Hg0的脱除

采用浸渍法制备了MnO_x改性活性炭(MnO_x/AC),用于模拟煤燃烧烟气中的元素态汞的脱除。实验研究了吸附剂的Mn负载量、吸附温度和烟气组分对所制备的改性活性炭的脱汞性能的影响,以及SO_2对活性炭脱汞的抑制作用机理。研究结果表明,当模拟烟气中含有5%(体积) O_2,Mn负载量为14%(质量),吸附温度为150℃时,改性活性炭的平均脱汞效率为97.0%(3 h)。模拟烟气中少量的O_2和微量的HCl、NO均对汞的脱除起促进作用,而微量的SO_2则对汞的脱除有抑制作用。通过吸附后的MnO_x改性活性炭的TG/DTG、XPS和Hg-TPD分析,推测SO2对改性活性炭脱汞的抑制作用是由于其消耗MnO_x中的晶格氧,形成的硫酸盐占据了14Mn/AC表面上的活性位点所致。模拟烟气中微量的NO可以有效降低SO_2对脱汞的抑制作用。     

煤基吸附剂脱除燃煤电厂烟气中汞的研究进展

燃煤电厂产生的烟气是汞排放的主要来源之一。概述了目前电厂烟气中汞污染情况和主要脱汞方法,介绍了煤基吸附剂在汞污染控制中的应用。煤基吸附剂应用于烟气脱汞时其吸附活性与多种因素有关,总结了烟气中SO2,CO2,CO,HCl等成分对活性炭吸附剂脱汞性能的影响,讨论了不同吸附温度和炭汞比例下活性炭的吸附效率,分析了不同改性方法对活性炭脱汞效率的影响机理。针对活性炭脱汞成本较高的问题,介绍了飞灰吸附剂的脱汞性能及吸附温度和入口汞含量对其的影响。此外,褐煤活性焦成本低廉,具有丰富的比表面积和孔径结构,化学活性高,吸附性能好,是一种很有前景的电厂烟气脱汞用吸附剂。     

改性沸石对气态汞吸附的实验研究

为了获得消耗量小、性能高效的燃煤烟气脱汞吸附剂,采用活性MnO2浸渍、FeCl3浸渍和不同温度下渗硫等方法,对沸石进行了改性,制得一系列改性沸石吸附剂。采用固定床吸附的方式,对吸附剂在不同条件下的吸附效果进行了测试,筛选出一种高效、廉价的MnO2浸渍沸石吸附剂,和原沸石吸附剂相比,改性沸石吸附剂对汞蒸气的吸附能力有较大提高,有效吸附时间大大增加,在有效吸附时间内,穿透率大大降低。改性后的沸石吸附能力大大提高的原因在于其吸附过程中,除了物理吸附,还发生了化学吸附。     

溴元素改性椰壳活性炭对实际燃煤烟气的脱汞性能

以椰壳活性炭（YAC）为原料,通过NH₄Br溶液浸渍改性,制备了溴素改性椰壳活性炭脱汞吸附剂（YAC-Br）。在固定床实验台上开展了YAC和YAC-Br的汞脱除实验,主要研究了入口汞（Hg⁰）浓度对YAC-Br脱汞性能的影响,并结合BET、SEM、XRF等表征手段分析了YAC-Br的脱汞原理。在0.3MW燃煤循环流化床锅炉上对YAC-Br进行了烟气管道喷射吸附剂脱汞（ACI）实验,验证了其在实际燃煤烟气中对汞的脱除效果。结果表明：改性过程不会破坏椰壳活性炭原有的孔隙结构和微孔容积,而会使活性炭表面更加平整;化学改性后活性炭表面Br负载量提高,成为Hg⁰的主要活性吸附位。固定床实验结果说明：改性后椰壳活性炭的初始汞吸附效率和单位累积汞吸附量分别提高了6.02倍和21.8倍,吸附效率随汞浓度增大而降低。0.3MW燃煤循环流化床实验结果表明：改性后椰壳活性炭对元素汞和氧化汞均有很好的脱除作用,脱汞效率随着吸附剂喷射量的增加而增加,当喷射量为0.7kg/h时,脱汞效率可达到76.38%。     

改性褐煤活性焦对模拟烟气中汞的脱除研究

为降低烟气脱汞成本,提高活性焦脱汞性能,以内蒙古锡林浩特褐煤为原料制备活性焦并进行化学改性,分析载硫、Na2S溶液和Zn Cl2溶液浸渍等改性方法对活性焦结构及性能的影响,研究改性方法、吸附温度、负载量和汞渗透量对活性焦脱汞性能的影响。结果表明,活性焦改性后,比表面积和孔容积有所降低,载Na2S、硫、Zn Cl2活性焦对汞的吸附量比原始活性焦分别提高了60%、113%和140%;吸附温度升高,化学反应变快,活性焦的初始脱汞效率由75.8%提高至95%以上,但穿透时间并不呈比例增加;当Zn Cl2负载量由5%提高至15%后,50%穿透率对应时间由75 min延长至120 min,活性焦对汞的吸附值由10.1μg/g增至17.5μg/g。随着汞渗透量的增加,活性焦脱汞效率有所提高,50%穿透率的对应时间由110 min缩短至95 min,最终总吸附值仅由14.4μg/g增至16.2μg/g。     

改性活性炭吸附脱除烟气中SO2 的研究进展

从研究应用角度出发,阐述了近年来国内外活性炭材料改性在烟气脱硫领域中的研究趋向及应用成果,包括金属离子或金属化合物的修饰、化学浸渍、高温热处理、微波处理和等离子体处理的研究进展;讨论了活性炭脱硫机理及其脱硫动力学,概述了吸硫后活性炭的再生方法,提出了利用改性活性炭进行烟气脱硫应用研究中存在的问题及今后的研究方向。     

燃煤烟气中单质汞脱除技术研究进展

综述了各种脱汞材料及改性技术研究现状,基于现有脱汞材料的优缺点及发展空间,提出了一体化吸附-催化材料脱除单质汞的结构设计理念,将脱汞材料的吸附性与催化性耦合起来,实现高效快速吸附单质汞的同时将其完全氧化脱除,为今后烟气脱汞技术设计提供新的思路。     

可循环再生吸附剂脱汞技术现状及发展趋势

总结了当前燃煤烟气脱汞常用的协同脱汞技术和贵金属、金属氧化物基可再生吸附剂技术发展现状,分析了各方法的优势与存在的问题,对未来磁性可回收吸附剂的发展方向和趋势进行了展望。针对现有脱汞技术效率低、易造成二次污染等缺陷,提出了使用飞灰磁珠制备廉价可回收脱汞吸附剂的新思路。通过大量试验开发了负载Co_3O_4或CuCl_2的磁珠改性方法以增强脱汞能力和抗烟气组分干扰能力,从而能够适用于低氯复杂烟气气氛。设计了改性磁珠吸附剂喷射脱汞工艺流程,可兼顾高效脱汞与低廉的运行成本,并通过磁珠回收再利用彻底避免汞进入环境造成污染。     

Characteristics of the mercury vapor removal from coal combustion flue gas by activated carbon using H2S

Removal of Hg⁰ vapor from the simulated coal combustion flue gases with a commercial activated carbon was investigated using H₂S. This method is based on the reaction of H₂S and Hg over the adsorbents. The Hg⁰ removal experiments were carried out in a conventional flow type packed bed reactor system in the temperature range of 80–150 °C using simulated flue gases having the composition of Hg⁰ (4.9 ppb), H₂S (0–20 ppm), SO₂ (0–487 ppm), CO₂ (10%), H₂O (0–15%), O₂ (0–5%), N₂ (balance gas). The following results were obtained: in the presence of both H₂S and SO₂, Hg removal was favored at lower temperatures (80–100 °C). At 150 °C, presence of O₂ was indispensable for Hg⁰ removal from H₂S–SO₂ flue gas system. It is suggested that the partial oxidation of H₂S with O₂ to elemental sulfur (H₂S+1/2O₂=S_ad+H₂O) and the Clause reaction (SO₂+2H₂S=3S_ad+2H₂O) may contribute to the Hg⁰ removal over activated carbon by the following reaction: S_ad+Hg=HgS. The formation of elemental sulfur on the activated carbon was confirmed by a visual observation.     

Pith based spherical activated carbon for CO2 removal from flue gases

Serials of pitch based spherical activated carbons (PSACs) were prepared and used as adsorbent for CO₂ adsorption from flue gases. The results indicate that the ultrafine micropores (<1 nm) are effective pores for CO₂ adsorption, and the equilibrium adsorption capacity of CO₂ has a linear relationship with the specific surface area of ultrafine micropores (S_{<1 nm}). The adsorption capacity of CO₂ can obtain 1.12 mmol/g at 15 kPa and 30 °C on one of PSAC sample due to its high S_{<1 nm} (845 m²_/g). Because the molecular CO₂ can be polarized into polar molecules and has four kinds of adsorption configuration, the adsorption selectivities of CO₂ vs. N₂ and O₂ are 86.99% and 69.91%, respectively. When the combined Electric Swing Adsorption and Vacuum Swing Adsorption were applied for CO₂ desorption, about 100% desorption efficiency can be obtained, the desorption rate is twice of that with Temperature Swing Adsorption (TSA) and the energy consumption is only 69% of that with TSA.     

Impregnated activated carbon for mercury removal

The problems of mercury removal from, in particular, industrial waste air are well known. This Paper discusses research and development of impregnated activated carbon, using various adsorbents, specifically for mercury removal. Sulphur impregnations are found to be most technically effective.     

Synthesis and characterization of a nano-structured sorbent for the direct removal of mercury vapor from flue gases by chelation

A novel adsorbent for the capture of mercuric chloride vapor from flue gases has been developed. The adsorbent uniquely combines a chelating ligand with an ionizing surface nano-layer on a mesoporous substrate. This enables selective, multi-dentate adsorption of mercury directly from the gas phase. The synthesis of the adsorbent is described, and detailed characterization data are reported. Based on elemental analyses, the maximum theoretical (equilibrium) capacity for mercury removal is estimated to be 33 mg Hg/g. Thermal stability tests indicate stable operation up to . The capture efficiency of the adsorbent was evaluated in the fixed-bed mode for oxidized mercury. A minimum operating capacity of 12 mg/g was observed, and removal of mercury through the formation of chelate was confirmed with Far-FTIR.     

The effect of methods of preparation on the performance of cupric chloride-impregnated sorbents for the removal of mercury from flue gases

Cupric chloride-impregnated carbon sorbents (CuCl₂-ACs) showed comparable performance in elemental mercury (Hg⁰) oxidation and adsorption to a brominated activated carbon sorbent (Darco Hg-LH) in our previously reported experimental studies using fixed-bed and entrained-flow systems. This study tested several CuCl₂-ACs prepared in different solvents to investigate the effects of solvents on the Hg⁰ removal capability of CuCl₂-ACs and find the most efficient and economical method of sorbent preparation. The performance of CuCl₂-ACs prepared in different solvents was also examined with respect to surface tension and pH of solvents. As a result, the sorbents prepared in isopropyl alcohol and acetone showed the best performance in these tests, but low surface tension and pH of isopropyl alcohol and acetone were not found to be critical factors.     

Stability of mercury on three activated carbon sorbents

The stability of adsorbed mercury on activated carbon (AC) is very important for avoiding reemission. Based on research concerning the stability of mercury on the AC relative to leaching and thermal desorption, our conclusions are as follows. Leaching tests show that mercury appears to be very stable on the AC. The Hg concentration in the leachate is much lower than the TCLP safety limit of 0.025 mg/l. Leaching time and liquid to solid (L/S) have some influence on the leaching results, but the influence is far less than which leads the Hg concentrate to exceed the safety limit. Leaching tests for mercury at lower and higher pH are aggressive compared with the neutral pH test. There is much more mercury released from the AC at longer heating time for mercury. At the same time, it seems that the stability of adsorbed original Hg⁰ on the AC is stronger than that of adsorbed original Hg²⁺.     

燃煤烟气脱汞吸附剂最新研究进展

对燃煤烟气吸附脱汞法中碳基吸附剂,包括活性炭、活性炭纤维、飞灰、碳/油焦吸附剂的优缺点进行了对比分析,对相关的改进工作和最新研究成果进行了综述.此外,贵金属、金属氧化物和钙基吸附剂是良好的脱硝或脱硫材料,在对这些吸附剂的吸附机理和影响因素进行分析的基础上,对多种污染物同时脱除的可行性和相关研究成果进行了介绍;对许多用于提高其脱汞效率的方法进行了总结,最后对该领域今后的主要发展方向做了展望.     

燃煤烟气脱汞吸附剂的研究

介绍了各种新型吸附剂的研究状况,主要包括壳聚糖、污泥、分子筛、竹炭、稻壳焦、煤焦、SCR几种吸附剂的制备方法、吸附性能和吸附机理,介绍了吸附材料的优缺点,并在最后展望了燃煤烟气脱汞吸附剂的进展。