Carbon consumption and regeneration of oxygen-containing functional groups on activated carbon for flue gas purification

Environmental Science and Pollution Research - High carbon consumption is an important factor restricting the wide application of activated carbon technology for flue gas purification. A fixed-bed...     

活性炭颗粒填充三维电极电化学烟气脱硫的研究

基于三维电极电化学技术较高的反应效率和不产生废弃物等优点,将这一先进的反应器运用到烟气脱硫领域.用活性炭作为工作电极,在通电状况下,将模拟烟气通入反应器发生反应.通过一系列试验,分析了填充床厚度、槽电压、进气流量、通电时间对脱硫率的影响,并且探讨了该反应的反应原理.     

Combined effect of adsorption and biodegradation of biological activated carbon on H2S biotrickling filtration

In order to evaluate the combined effect of adsorption and biodegradation of H(2)S on activated carbon surface in biotrickling filtration, four laboratory-scale biofiltration columns were operated simultaneously for 120h to investigate the mechanisms involved in treating synthetic H(2)S streams using biological activated carbon (BAC). The first three columns (A, B, C) contained a mixture of activated carbon and glass beads, with the carbons (BAC or virgin activated carbon (VAC)) and conditions (with or without liquid medium recirculation) differentiated. The last column (D) used 100% glass beads with liquid medium recirculation. Air streams containing 45ppmv H(2)S were passed through the columns at 4s of gas retention time (GRT) and liquid flow rate was set at 0.71mlmin(-1). Column D got its breakthrough in 3min of operation, indicating a negligible contribution of glass beads to the adsorption of H(2)S. The removal efficiency (RE) of Columns B and C using VAC dropped quickly to 30% within the first 8h, and afterwards continued to drop further but slowly. Column A using BAC stayed at 25% of RE throughout the operation time. A thorough investigation of the H(2)S oxidation products, i.e., various S species in both aqueous (recirculation media) and solid phases (BAC and VAC), was conducted using ICP-OES, IC, XRF, and CHNS elemental analyzer. BAC demonstrated a better performance than columns with adsorption only. Water film was found to enhance H(2)S removal. The percentage of sulphate in the total sulphur of the BAC system improved to twice of that of VAC system, indicating sulphate is the main product of H(2)S biofiltration. The observed pH drop in BAC system double confirmed that the presence of biodegradation in the biofilm over carbon surface did profound effect on the oxidation of H(2)S, compare to the systems with adsorption only.     

Adsorption of mercury by activated carbon prepared from dried sewage sludge in simulated flue gas

Conversion of sewage sludge to activated carbon is attractive as an alternative method to ocean dumping for the disposal of sewage sludge. Injection of activated carbon upstream of particulate matter control devices has been suggested as a method to remove elemental mercury from flue gas. Activated carbon was prepared using various activation temperatures and times and was tested for their mercury adsorption efficiency using lab-scale systems. To understand the effect of the physical property of the activated carbon, its mercury adsorption efficiency was investigated as a function of its Brunauer–Emmett–Teller (BET) surface area. Two simulated flue gas conditions, (1) without hydrogen chloride (HCl) and (2) with 20 ppm HCl, were used to investigate the effect of flue gas composition on the mercury adsorption capacity of activated carbon. Despite very low BET surface area of the prepared sewage sludge activated carbons, their mercury adsorption efficiencies were comparable under both simulated flue gas conditions to those of pinewood and coal activated carbons. After injecting HCl into the simulated flue gas, all sewage sludge activated carbons demonstrated high adsorption efficiencies, that is, more than 87%, regardless of their BET surface area.

Implications: We tested activated carbons prepared from dried sewage sludge to investigate the effect of their physical properties on their mercury adsorption efficiency. Using two simulated flue gas conditions, we conducted mercury speciation for the outlet gas. We found that the sewage sludge activated carbon had mercury adsorption efficiency comparable to pinewood and coal activated carbons, and the presence of HCl minimized the effect of physical property of the activated carbon on its mercury adsorption efficiency.     

Removal of SO2 from O2-containing flue gas by activated carbon fiber (ACF) impregnated with NH3

Adsorption of SO(2) from the O(2)-containing flue gas by granular activated carbons (GACs) and activated carbon fibers (ACFs) impregnated with NH(3) was studied in this technical note. Experimental results showed that the ACFs were high-quality adsorbents due to their unique textural properties. In the presence of moisture, the desulphurization efficiency for the ACFs was improved significantly due to the formation of sulfuric acid. After NH(3) impregnation of ACF samples, nitrogen-containing functional groups (pyridyl C(5)H(4)N- and pyrrolyl C(4)H(4)N-) were detected on the sample surface by using an X-ray photoelectron spectrometer. These functional groups accounted for the enhanced SO(2) adsorption via chemisorption and/or catalytic oxidization.     

金属改性碳脱除PH3和H2S动力学及反应机理研究

为综合利用黄磷尾气中的CO,通过计算平均活化能和测定XPS、TG／DTA和氮吸附特性的方法,研究了Cu2＋和某金属离子M^n＋改性碳脱除PH,和H2S的动力学和反应机理问题。结果表明：H2S在金属改性碳上反应时平均活化能为134．4J／mol为-0．76级反应,PH,在金属改性碳上反应时平均活化能为1247．6J／mol为-0．8级反应;减小改性碳粒径增加流量可以显著提高其脱除PH,和H。S的速率;XPS、TG／DTA和孔径分布分析证明,改性碳净化H2S和PH3是一个催化吸附过程,H2S和PH3首先与氧在改性碳表面进行催化氧化反应,然后生成S和P2O5沉积吸附在改性碳表面。     

凹凸棒石粘土脱硫剂脱除硫化氢实验研究

采用凹凸棒石脱硫剂在常温常压下脱除高浓度硫化氢(H2S),研究了凹凸棒石含量、活性组分含量和焙烧温度等因素在脱除H 2S中对脱硫效率和硫容量的影响.实验结果表明,以凹凸棒石为主原料、添加20%～30%(质量分数)的活性组分后,对高浓度低流速的H2S具有较高的脱除效率和较大的硫容量.     

A sulfur-resistant CuS-modified active coke for mercury removal from municipal solid waste incineration flue gas

Environmental Science and Pollution Research - Adsorption is a typical method for air pollutant removal from flue gas. A CuS-modified active coke (CuS/AC) sorbent was developed to improve the...     

Operational characteristics of effective removal of H2S and NH3 waste gases by activated carbon biofilter

Simultaneous removal of hydrogen sulfide (H2S) and ammonia (NH3) gases from gaseous streams was studied in a biofilter packed with granule activated carbon. Extensive studies, including the effects of carbon (C) source on the growth of inoculated microorganisms and gas removal efficiency, product analysis, bioaerosol emission, pressure drop, and cost evaluation, were conducted. The results indicated that molasses was a potential C source for inoculated cell growth that resulted in removal efficiencies of 99.5% for H2S and 99.2% for NH3. Microbial community observation by scanning electron microscopy indicated that granule activated carbon was an excellent support for microorganism attachment for long-term waste gas treatment. No disintegration or breakdown of biofilm was found when the system was operated for 140 days. The low bioaerosol concentration emitted from the biofilter showed that the system effectively avoided the environmental risk of bioaerosol emission. Also, the system is suitable to apply in the field because of its low pressure drop and treatment cost. Because NH3 gas was mainly converted to organic nitrogen, and H2S gas was converted to elemental sulfur, no acidification or alkalinity phenomena were found because of the metabolite products. Thus, the results of this study demonstrate that the biofilter is a feasible bioreactor in the removal of waste gases.     

Reduction of dioxin emission by a multi-layer reactor with bead-shaped activated carbon in simulated gas stream and real flue gas of a sinter plant

A laboratory-scale multi-layer system was developed for the adsorption of PCDD/Fs from gas streams at various operating conditions, including gas flow rate, operating temperature and water vapor content. Excellent PCDD/F removal efficiency (>99.99%) was achieved with the multi-layer design with bead-shaped activated carbons (BACs). The PCDD/F removal efficiency achieved with the first layer adsorption bed decreased as the gas flow rate was increased due to the decrease of the gas retention time. The PCDD/F concentrations measured at the outlet of the third layer adsorption bed were all lower than 0.1 ng I-TEQ Nm⁻³. The PCDD/Fs desorbed from BAC were mainly lowly chlorinated congeners and the PCDD/F outlet concentrations increased as the operating temperature was increased. In addition, the results of pilot-scale experiment (real flue gases of an iron ore sintering plant) indicated that as the gas flow rate was controlled at 15 slpm, the removal efficiencies of PCDD/F congeners achieved with the multi-layer reactor with BAC were better than that in higher gas flow rate condition (20 slpm). Overall, the lab-scale and pilot-scale experiments indicated that PCDD/F removal achieved by multi-layer reactor with BAC strongly depended on the flow rate of the gas stream to be treated.     

活性炭纤维在机动车尾气净化中的研究与应用展望

机动车尾气净化控制的一个难点在于冷启动阶段，此时由于温度较低，催化剂尚未完全起作用，导致排出的污染物浓度较高。阐述了活性炭纤维的基本特性，特别是其低温吸附与催化性能对NO和CO的转化作用，讨论了活性炭纤维作为机动车尾气净化材料所需的改性及方法，并展望了其应用前景。     

Partitioning and removal of dioxin-like congeners in flue gases treated with activated carbon adsorption

Activated carbon adsorption is commonly used to control dioxin-like congener (PCDD/Fs and PCBs) emissions. Partitioning of PCDD/Fs and PCBs between vapor and solid phases and their removal efficiencies achieved with existing air pollution control devices (APCDs) at a large-scale municipal waste incinerator (MWI) and an industrial waste incinerator (IWI) are evaluated via intensive stack sampling and analysis. Those two facilities investigated are equipped with activated carbon injection (ACI) with bag filter (BF) and fixed activated carbon bed (FACB) as major PCDD/F control devices, respectively. Average PCDD/F and PCB concentrations of stack gas with ACI+BF as APCDs are 0.031 and 0.006ng-TEQ/Nm(3), and that achieved with FACB are 1.74 and 0.19ng-TEQ/Nm(3) in MWI and IWI, respectively. The results show that FACB could reduce vapor-phase PCDD/Fs and PCBs concentrations in flue gas, while the ACI+BF can effectively adsorb the vapor-phase dioxin-like congener and collect the solid-phase PCDD/Fs and PCBs in the meantime. Additionally, the results of the pilot-scale adsorption system (PAS) experimentation indicate that each gram activated carbon adsorbs 105-115ng-PCDD/Fs and each surface area (m(2)) of activated carbon adsorbs 10-25ng-PCDD/Fs. Based on the results of PAS experimentation, this study confirms that the surface area of mesopore+macropore (20-200A) of the activated carbon is a critical factor affecting PCDD/F adsorption capacity.     

Sulfur and carbon cycling in a flue gas desulfurization sludge disposal site

Products of a power plant flue gas desulfurization scrubber are discharged into a pond as sludge consisting of calcite (initial delta13C 3.2-3.8 per thousand), gypsum (initial delta34S 7.6-8.6 per thousand), and aqueous solution. Reducing conditions exist below a boundary that appears to move vertically as a function of changes in pond water level. Under reducing conditions, bacteria partially reduce aqueous sulfate to low-delta34S sulfide, consuming organic carbon and generating low-delta13C bicarbonate. Under oxidizing conditions, sulfide is converted to sulfate, leading to calcite dissolution, gypsum precipitation, and isotopic re-equilibration of remaining calcite with dissolved bicarbonate near the pond surface. The gypsum has delta34S near 6 per thousand, and calcite has delta13C as low as -1.7 per thousand; the changes from initial values correspond to predictions based on isotopic balance and reaction stoichiometry. The pond largely contains the products of bacterial reduction. After the pond is abandoned, these products may adversely affect attempts to revegetate the site. Future bacterial reduction may be best controlled by dewatering and limiting the supply of organic matter in percolating surface water.     

光照对低浓度硫化氢气体生物法净化的影响

和种进行光照和避光的对比试验表明,光照能提高微生物对硫化氢废气的净化效率,最终产物为硫酸,净化效率和液相硫酸极的浓度随光照强度的增加而增加。避光时微生物对硫化氢废气的净化效率较低,但最终产物为单质硫。根据上述结果适宜的工艺流程应是首先将硫化氢废气通入避光的生物膜填料塔,把硫化氢转化为能回收的单质硫,然后再将废气通入光照的生物膜填料塔净化,进一步降低硫化氢废气的排放浓度。     

乙醇胺/N-甲基二乙醇胺/三乙烯四胺体系吸收烟气CO2的研究

在乙醇胺(MEA)/N-甲基二乙醇胺(MDEA)体系(简称二元复合胺体系)中加入少量活化剂三乙烯四胺(TETA),研究了MEA/MDEA/TETA三元复合胺体系(简称三元复合胺体系)对烟气CO2的吸收和再生情况。结果表明,MEA、MDEA、TETA3种组分之间存在交互作用,使得三元复合胺体系中的CO2吸收速率、CO2饱和吸收量均分别小于二元复合胺体系与TETA单体系的CO2吸收速率、CO2饱和吸收量之和。三元复合胺体系的再生温度稍高于二元复合胺体系,其一次再生率约为83.5%,比二元复合胺体系低了约13百分点,三元复合胺体系的再生较二元复合胺体系更困难。     

活性焦吸附对煤化工废水膜处理工艺的影响

煤化工废水经过生化处理后一般难以达到回用标准,须采用有效的深度处理工艺才能实现废水的资源化利用。通过对比研究方式,采用“混凝-超滤-反渗透工艺”及“混凝-活性焦吸附-超滤-反渗透”2种处理工艺,考察了活性焦吸附对后续膜处理工艺的影响。结果表明,活性焦对废水中的芳香族类等主要污染物具有很好的吸附性能,混凝出水经活性焦吸附后进人膜系统可有效减缓膜污染,降低膜通量的衰减程度并提高产水水质,因此,将活性焦吸附用于煤化工废水膜系统的前处理,采用“混凝-活性焦吸附-超滤-反渗透工艺”深度处理煤化工废水是有效可行的。     

ZnCl2法污泥含炭吸附剂对模拟烟气中气态汞的吸附

采用改进的ZnCl2学活化法制备污泥含炭吸附剂,利用EDS以及氮吸附等多种测试手段对所制得的污泥含炭吸附剂进行表征,并利用其处理模拟烟气汞污染物,实验结果表明,污泥含炭吸附剂对Hg^0吸附包括物理吸附作用和化学吸附作用,以物理吸附作用为主;随着Hg^0入口浓度的提高,污泥含炭吸附剂的Hg^0饱和吸附容量增大;随着吸附反应温度的升高污泥含炭吸附对Hg^0的吸附作用减弱;在吸附反应温度125℃,Hg^0入口浓度60．4μg／m3污泥含炭吸附剂和选定的活性炭对Hg^0吸附容量分别为81．2gg／g和53．8μg／g,污泥含炭吸附剂对Hg^0吸附作用好于选定的活性炭。     

Hydrodehalogenation of chlorobenzene on activated carbon and activated carbon supported catalysts

Chlorinated aromatic compounds in (waste) gases can be removed and/or dehalogenated by passing over a bed of activated carbon (AC) in a hydrogen containing atmosphere. Dehalogenation of the model compound chlorobenzene (PhCl) to HCl is complete at 490 degrees C--rather than the approximately 900 degrees C needed for the mere gas-phase reaction--but part of the benzene moieties is retained on the AC, resulting in its rather rapid deactivation, apparently due to a large decrease in surface area. Therefore, <1 mmol PhCl per gram of 'catalyst' could be processed. At 600 degrees C chlorobenzene yields 100% of both HCl and benzene, but still the AC lost most of its activity in time. Performances are compared of three different commercial ACs. As a HCl-washed AC is just as active, metals are not involved. This acid-washed AC was used as a support for 10 wt% Ni or Fe catalysts. While Fe did not show appreciable activity, results with Ni are promising. The yields of HCl and benzene from PhCl are approximately 100% already at T<400 degrees C, and T(50%) congruent with 260 degrees C, over 200 degrees C lower than with AC alone. There is no appreciable decrease of activity after having injected >20 mmol PhCl per gram of catalyst at partial conversion.     

络合铁法脱除垃圾填埋气中的H2S

建立了以EDTA和柠檬酸为铁盐络合剂的循环脱硫体系,采用络合铁法对垃圾填埋气中的H2S进行脱硫中试实验,结果表明实验所建立的络合铁脱硫体系运行稳定,脱硫效率高,适合应用于垃圾填埋气中硫化氢脱除。     

柔性集尘极应用于湿法脱硫烟气深度净化的试验研究

为揭示柔性绝缘疏水纤维织物用作集尘极材料的可行性及电场性能,为解决传统湿式静电技术由集尘极材料选择及表面水膜布置不均引发的系列问题,利用浸润质量在线监测法,得到水对柔性集尘极的毛细浸润特性;通过测量不同给水率条件下柔性集尘极电阻率及伏安特性曲线,揭示柔性集尘极表面水膜特性与静电场性能之间的耦合关系;建立小试/中试试验台,研究了柔性集尘极对燃煤脱硫烟气气溶胶污染物组分的净化性能。结果表明,水能够在柔性集尘极表面形成均匀水膜;试验工况下,柔性集尘极电场性能优于导电刚性材料,柔性集尘极对酸雾气溶胶脱除率达98%以上;中试装置出口烟气酸雾<10mg/m3、浆液滴<15mg/m3、微细粉尘<5mg/m3;工业化装置较高的烟羽透明度表明柔性集尘极实际运行性能良好。