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%。     

Particle flow, mixing, and chemical reaction in circulating fluidized bed absorbers

A mixing model has been developed to simulate the particle residence time distribution (RTD) in a circulating fluidized bed absorber (CFBA). Also, a gas/solid reaction model for sulfur dioxide (SO₂) removal by lime has been developed. For the reaction model that considers RTD distribution inside the core and annulus regions of a CFBA, a macrochemical reaction can be simulated based on microchemical reaction dynamics. The presented model can predict SO₂ and lime concentration distributions inside the CFBA, and give the amount of lime needed to remove a given percentage of SO₂. It is found that SO₂ concentration decreases with the increase of CFBA distance from the bottom in the core region. However, lime concentration exhibits a very slight variation in the core region. This means that lime is efficiently utilized to remove SO₂. The model also predicts that SO₂ partial pressure at the exit of the CFBA decreases with the increase in the percentage of fresh lime injected in the CFBA.     

褐煤活性焦烟气脱汞的实验研究

燃煤电厂汞污染越来越受到关注,目前具有应用前景的脱汞方法为吸附脱汞,因此研发高效低成本的脱汞吸附剂被广泛研究。在搭建的固定床吸附反应系统上对自制的褐煤活性焦脱汞性能进行了实验研究,研究了汞污染物的入口浓度,吸附剂的量、烟气成分及吸附剂的种类对吸附汞的影响。结果表明:活性焦吸附剂对烟气中的气态汞均有一定的吸附能力,其吸附效果随着入口汞浓度和吸附剂量的增加而增加;烟气中的SO2、NO气体对活性焦吸附汞有一定的促进作用。活性焦脱汞效率与载硫活性炭、脱汞专用活性炭相比还存在一定差距,但可通过改进活性焦的活化方式提高脱汞性能。     

湿法脱硫净烟气中的细颗粒物对膜吸收CO2的影响

在使用膜吸收装置脱除燃煤电厂尾气中二氧化碳的实际应用中,膜吸收二氧化碳系统装配于湿法烟气脱硫系统(WFGD)出口是最适宜的选择。经过湿法脱硫的烟气中含有一定量的细颗粒物,这些颗粒物可能会影响膜的性能,因此有必要揭示细颗粒物对膜吸收二氧化碳的影响。本文采用模拟实验装置,选取飞灰、硫酸钙、硫酸铵3种颗粒物,考察了它们对聚丙烯(PP)中空纤维膜吸收二氧化碳的影响。结果表明:3种颗粒物通过膜组件时,均会在膜表面沉积,导致二氧化碳脱除效率下降;膜吸收二氧化碳的性能与颗粒物沉积程度呈负相关;3种颗粒物对膜吸收二氧化碳的影响程度从大到小依次为硫酸钙、硫酸铵、飞灰;颗粒物在膜表面沉积后很难被气体反吹,这会使膜基本失效。     

Elemental mercury vapor capture by powdered activated carbon in a fluidized bed reactor

A bubbling fluidized bed of inert material was used to increase the activated carbon residence time in the reaction zone and to improve its performance for mercury vapor capture. Elemental mercury capture experiments were conducted at 100 °C in a purposely designed 65 mm ID lab-scale pyrex reactor, that could be operated both in the fluidized bed and in the entrained bed configurations. Commercial powdered activated carbon was pneumatically injected in the reactor and mercury concentration at the outlet was monitored continuously. Experiments were carried out at different inert particle sizes, bed masses, fluidization velocities and carbon feed rates. Experimental results showed that the presence of a bubbling fluidized bed led to an increase of the mercury capture efficiency and, in turn, of the activated carbon utilization. This was explained by the enhanced activated carbon loading and gas-solid contact time that establishes in the reaction zone, because of the large surface area available for activated carbon adhesion/deposition in the fluidized bed. Transient mercury concentration profiles at the bed outlet during the runs were used to discriminate between the controlling phenomena in the process. Experimental data have been analyzed in the light of a phenomenological framework that takes into account the presence of both free and adhered carbon in the reactor as well as mercury saturation of the adsorbent.     

一步快速活化法制备生物质活性炭及其对乙酸乙酯的吸附再生

活性炭吸附法因技术成熟、简单易行、吸附效率高等优点而被广泛应用于挥发性有机化合物（VOCs）的处理中。本文以山林废弃物的野山桃核为原料,烟道废气及硝酸铁为活化剂,制备了一系列生物质活性炭,并利用固定床吸附装置对其吸附、再生性能进行了研究。利用二氧化碳和水蒸气模拟烟气,在固定流量的烟气活化氛围中进行活化,并探讨了不同硝酸铁的量对活性炭的孔隙结构及其吸附再生性能的影响。利用N₂ 吸附-脱附实验、扫描电镜、拉曼光谱和红外光谱等技术研究了活性炭详细特征。结果表明：当硝酸铁的质量分数为0.2% 时,所制备的活性炭AC-3具有最大的比表面积和平均孔径,分别为923m2/g及2.57nm。其对乙酸乙酯的饱和吸附量也最大,为973.04mg/g。利用烟气对AC-3活性炭进行活化再生处理,经过3次重复吸附-解吸再生实验,其饱和吸附能力仍可达91.5％以上,实现了废弃烟气资源化利用及活性炭的循环回收,从而达到废气治理的目标。     

Adsorption of elemental mercury vapor by impregnated activated carbon from a commercial respirator cartridge

In order to protect workers from the harmful effects of mercury vapor, adsorption technology using impregnated activated carbon is currently in use in respirator cartridges to capture mercury vapor in breathing air. Adsorption onto the activated carbon can be improved through the modification of the carbon surface by impregnation with certain reagents that enhance the bonding of mercury either physically or chemically. The first objective of this study was to characterize the chemisorption behavior of a commercial adsorbent (3M-6009) by measuring the mercury breakthrough using a bench-top apparatus. The second objective was to develop a kinetic model describing the breakthrough behavior. Dynamic breakthrough concentrations were measured using a fixed bed to study the effects of the following adsorption parameters at room temperature: air flow-rate, adsorbent amount, inlet mercury concentration, and bed diameter. A model was developed in which, the rate of irreversible chemisorption was proportional to the concentration of mercury in the airflow, and the concentration of active sites of the surface of the carbon. A model incorporating two different types of the active sites was applied in an effort to differentiate the high initial adsorption rate mediated by readily accessible open sites from the lower adsorption rate mediated by the availability of hindered sites within micro-pores. The model developed herein was superior to a traditional isotherm model for describing the chemisorption behavior of impregnated activated carbon.     

基于改进型吸附等温线模型的空气预纯化TSA双层床模拟

为了掌握空气中CO2和水蒸气在空分装置双层床变温吸附(TSA)纯化器中的动态吸附特性,通过LDF传质假设及非绝热假设,建立了一维二元稀组分系统的双层床TSA过程数学模型。一种改进型的多组分等温线模型用于描述水蒸气的Ⅱ型吸附等温线以及水蒸气和CO2混合物的吸附平衡关系。通过对比模拟结果与TSA纯化器的现场监控数据发现,基于改进型等温线模型的模拟结果与现场数据吻合良好。最后对多种工况下的TSA纯化器中的温度、浓度及吸附量床层分布和穿透曲线进行了数值模拟和分析。     

Gas-phase mercury removal through sulfur impregnated porous carbon

Gas phase mercury removal is a vital unit operation in gas processing industries. The present work attempts to prepare a sulfur impregnated carbon at optimized experimental conditions and compares its elemental adsorption capacity with the number of commercially available carbon based adsorbents. The effect of adsorption temperature on mercury adsorption capacity has been estimated for the prepared sulfur impregnated carbon. The adsorption capacity was found to increase with increase in adsorption temperature owing to the chemisorption nature of the adsorption. The adsorption isotherms were generated at three different temperatures and were found to close adhere to the Langmuir Isotherm model. The adsorption capacity was found to increase until 140 °C, while decrease beyond, which was attributed to the softening and agglomeration of sulfur. The maximum adsorption capacity of 4325 μg/g was observed at a temperature of 140 °C. A comparison of the relative adsorption capacity of various adsorbent at 30 °C, revealed the adsorption capacity of the sulfur impregnated carbon prepared in the present work much higher than the commercially available carbons. The high adsorption capacities with simple preparation techniques favor the commercial mercury adoption process.     

Removal of elemental mercury from coal combustion flue gas by chloride-impregnated activated carbon

In this work, adsorption of vapour-phase elemental mercury (Hg⁰) from pulverised-coal combustion flue gas by commercially available granular activated carbons treated with zinc chloride (ZnCl₂) impregnation was investigated. The experiment results showed that ZnCl₂ impregnation significantly enhanced the adsorptive capacity for mercury vapour, but decreased the specific surface area of the activated carbon. This could be explained by the occurrence of chemisorption, which was confirmed by adsorption tests over a wide range of temperatures. The influence of ZnCl₂ solution concentration on the mercury removal performance was also studied. Mechanisms of mercury adsorption onto the Cl-impregnated activated carbon were proposed.     

煤粉炉和循环流化床锅炉飞灰吸附汞动力学及其吸附机制

在固定床吸附反应器内对两台300MW等级燃煤发电机组循环流化床锅炉和煤粉锅炉飞灰样品进行气相零价汞吸附实验,通过改变实验工况研究温度、入口汞浓度和入口气体流量对飞灰汞吸附能力的影响。采用颗粒内扩散模型、准一阶和准二阶动力学模型、耶洛维奇（Elovich）模型对实验数据分别进行拟合,从动力学的角度探讨两种锅炉飞灰对气相零价汞吸附的影响机制以及两种锅炉飞灰与气相零价汞之间吸附动力学行为差异。结果表明：相同工况下循环流化床锅炉飞灰汞吸附过程的穿透时间和平衡吸附量远大于煤粉锅炉飞灰。吸附温度为150℃时,两种锅炉飞灰对气相零价汞的平衡吸附量最大。由于外扩散阻力随气体入口流量的增加而减小,入口汞浓度的增加可提高传质推动力,飞灰对汞的吸附得以增强。动力学分析表明飞灰的零价汞吸附由外扩散、内扩散和表面化学吸附共同控制,其中表面化学吸附是该吸附过程中的控制步骤;准二阶动力学模型和Elovich动力学模型更适合于描述该吸附过程。相同实验条件下,循环流化床锅炉飞灰吸附过程拟合所得的颗粒内扩散系数、准一阶动力学常数和初始吸附速率均大于煤粉锅炉飞灰。     

Synthesis and characterization of activated carbon and bioactive adsorbent produced from paper mill sludge

Adsorption capacity and bioactivity of a novel mesoporous activated carbon (IIT Carbon) and bioactive (BAC_IIT) catalyst produced from papermill sludge were evaluated. Conversion of paper mill sludge to useful activated carbons and biocatalysts is a significant process since it reduces environmental problems associated with disposal of waste sludge, enhances wastewater treatment using carbons produced from industrial waste itself, and promotes conservation of the naturally available primary resources currently used to make activated carbons. Analysis was conducted using synthetic wastewater containing phenol and a commercially available activated carbon, sorbonorite 4 (used as reference carbon). Phenol removal was accomplished in batch and fluidized bed reactors containing mesoporous activated carbon, sorbonorite 4, and the produced bioactive catalysts. Isotherm adsorption data indicated that mesoporous activated carbon has a higher adsorption capacity and molecular surface coverage than sorbonorite 4 for phenol concentrations less than 10 mg/l. The mass transfer limitation was accounted for the lower adsorption capacity of the microporous carbon (sorbonorite 4) in dilute solutions. The fluidized bed reactor study, however, indicated similar but slightly lower phenol removal capability for the produced mesoporous carbon. While phenol removal efficiency of the carbons studied was in the range 65–70%, the produced bioactive catalysts were able to remove up to 97% of phenol during first few hours of operation. These results suggest that mesoporous carbon will feasibly be a good substitute for other commercially available activated carbons produced from natural resources, not only in physical adsorption processes, but also in fluidized bed bioreactors (FBB), used in biodegradation processes.     

烟气脱汞过程中活性炭喷射量的影响因素

在模拟燃煤烟气流动反应试验台上,对喷射吸附脱汞过程中影响活性炭喷射量的汞浓度、停留时间、温度、除尘设备等因素进行了试验研究.结果表明获得相同脱汞效率,在较低烟气汞浓度下活性炭的喷射量较大.停留时间对活性炭喷射量的影响最大,在较长停留时间下活性炭能够进行充分的吸附,相应的活性炭喷射量较少;在较短停留时间下受动力学限制,过多的活性炭喷射量不会引起脱汞效率相应增加.随着温度升高,活性炭的喷射量也随之增加;通过化学改性能提高活性炭在较高烟气温度下的吸附能力,从而减少喷射量.布袋除尘设备的使用能在较大程度上降低活性炭的喷射量.     

Combined adsorption and electrochemical processes for the treatment of acidic aqueous phenol wastes

This paper describes a combined adsorption/electrochemical reaction device for the treatment of acidic aqueous phenol wastes. The system works in batch mode. In each operation cycle there are two stages: (i) treatment of waste, in which the organic matter contained in the waste is removed from the aqueous solution and (ii) activated carbon regeneration, in which adsorbed organics are removed from the system and converted into carbon dioxide. The system leads to successful treatment of these wastes and transforms the organics contained in the waste into carbon dioxide and electrocoagulated solids. The granular activated carbon (GAC) bed of the system achieves rapid removal of the organics, with treatment time shorter than those reported for conventional electrochemical treatments. The regeneration of the GAC is achieved by electrochemical means and efficiencies close to 80% are obtained. The energy consumption of this system is similar to those reported for other electrochemical technologies used to treat aqueous wastes.     

Simulation of mercury emission control by activated carbon under confined-bed operations

Mercury emissions from coal-fired power plants have been a great environmental and regulatory concern due to the toxic nature of mercury and the significant amount of emissions from these plants. An effective method for controlling mercury emission is to employ activated carbon to adsorb mercury from the combustion flue gas. In this study, an activated carbon mercury sorption model was applied to simulate a confined-bed mercury emission control process. Model simulations were performed to generate dynamic mercury concentration profiles and the corresponding profiles of mercury uptake by activated carbon at various bed locations under various process conditions. The simulation parameters included flue gas flow rate, inlet mercury concentration, and adsorption bed temperature. The study has demonstrated the applicability of the model for simulating the process and provided insights into the mercury control process especially the effects of flue gas flow rate, inlet mercury concentration, and activated carbon bed temperature on the process. Such information is critically needed in the design and operation of a mercury emission control process involving activated carbon adsorption.     

天然气中汞的脱除技术

鉴于环保、设备安全以及人身健康的要求,有效脱除天然气中汞的应用技术日渐受到重视。简述了物理吸附、化学吸附、溶液吸收和低温分离等具有代表性的天然气脱汞的工艺进展。对活性炭汞吸附剂、负载金属吸附剂、卤化或载硫活性炭和其他类型汞吸附剂在天然气中汞脱除的应用进展进行了阐述。研究了入口天然气的温度和湿度对脱汞效果的影响,较低的温度和湿度有利于汞的脱除。     

Influence of Calcareous Sorbents on Particulate Emissions from Fluidized Bed Combustion of Lignite

The composition and morphology of coarse and fine fly ashes from atmospheric fluidized bed combustion of 2 lignites without additives or with hydrated lime and limestone as sorbents for sulfur dioxide removal were investigated. The ashes were separated and size segregated by cyclone and low pressure BLPI impactor. The properties of both coarse (sizes >10 θm) and fine (sizes < 10 θm) particles were investigated using INAA, PIXE, and SEM. The application of sorbents increased the emissions of coarse particles, but reduced the emissions of fine particles. The increase was caused by additional carry over of particles of additives; the decrease of emission of fine particles probably resulted from the combined increase of scavenging of fine particles by particles of sorbents and reduction of their formation due to reduced concentrations of sulfur dioxide in flue gas. Most of the trace elements investigated in this study showed substantial enrichment in fine particles. However, due to simultaneous reduction of concentration of fine particles the emissions of most trace elements decreased.     

Evidence of powdered activated carbon preferential collection and enrichment on electrostatic precipitator discharge electrodes during sorbent injection for mercury emissions control

Removal of mercury from coal-derived flue gas by injecting powdered sorbents often involves a substantial portion removed within an electrostatic precipitator (ESP). The present investigation uses a lab-scale ESP to assess the potential for injected sorbents to collect preferentially on discharge electrode wires. Such preferential collection would increase the adsorption capacity of the accumulated dust cake on the discharge electrodes, increasing their potential contribution to the total mercury removal performance of the ESP. The lab-scale results involving various fly ashes and both carbon-based and non-carbon mercury sorbents confirm that powdered activated carbon is enriched in the discharge electrode dust cake relative to its concentration in suspension in the gas flow. Other results explore the effects of applied ESP polarity, voltage, and power, percent PAC added to the fly ash, and total particulate matter loading entering the ESP on the collection behavior.     

Effluent organic matter removal from reverse osmosis feed by granular activated carbon and purolite A502PS fluidized beds

Applying pre-treatments to remove dissolved organic matter from reverse osmosis (RO) feed can help to reduce organic fouling of the RO membrane. In this study the performance of granular activated carbon (GAC), a popular adsorbent, and purolite A502PS, an anion exchange resin, in removing effluent organic matter (EfOM) from RO feed collected from a water reclamation plant located at Sydney Olympic Park, Australia were evaluated and compared through adsorption equilibrium, kinetics and fluidized bed experiments. The maximum adsorption capacity (Q_max) of GAC calculated from the Langmuir model with RO feed was 13.4 mg/g GAC. The operational conditions of fluidized bed columns packed with GAC and purolite A502PS strongly affected the removal of EfOM. GAC fluidized bed with a bed height of 10 cm and fluidization velocity of 5.7 m/h removed more than 80% of dissolved organic carbon (DOC) during a 7 h experiment. The average DOC removal was 60% when the bed height was reduced to 7 cm. When comparing GAC with purolite A502PS, more of the later was required to remove the same amount of DOC. The poorer performance of purolite A502PS can be explained by the competition provided by other inorganic anions present in RO feed. A plug flow model can be used to predict the impact of the amount of adsorbent and of the flow rate on removal of organic matter from the fluidized bed column.     

固体碳酸盐吸附剂干法捕集二氧化碳实验研究

以负载型固体碳酸盐为吸附剂,采用流化床反应器对烟道气中二氧化碳的捕集进行了研究.测定了不同吸附剂、操作温度和反应时间对吸附效果的影响及吸附剂再生性能.结果表明,吸附剂为负载的固体碳酸钠,在65℃～85℃范围内,吸附时间为4 min～10 min,二氧化碳的脱除率达97.5％,吸附剂经过10次再生后达到稳定状态,可以长期使用.