燃煤电站布袋除尘器和静电除尘器脱汞性能比较

采用国际上通用的Ontario Hydro方法（OHM）对中国五个燃煤电站布袋除尘器（FF）/静电除尘器（ESP）前、后的烟气进行采样,应用美国EPA标准方法测定了烟气中Hg0、Hg2+和HgP的浓度。应用DMA80测定固体样品（煤、底灰、ESP飞灰）中的汞浓度。由汞平衡得出各个环节中汞所占的份额。由此得到FF和ESP脱除烟气中汞的性能。安装FF的电站1和2的综合脱除效率约为80%和20%,安装ESP的电站3、4和5的综合脱除效率分别为6%、20%和4%左右。这说明FF比ESP有更加优良的脱汞性能,而且FF/ESP脱除烟气中的汞受到很多因素的影响。     

410t/h煤粉锅炉的汞排放及其NID系统除汞特性研究

对配备有NID系统的410t/h燃煤电站锅炉的煤、底渣、飞灰进行取样,测定了样品中汞的含量。采用Ontario Hydro方法测定了NID前和ESP后烟气中汞的形态。实验结果表明,汞主要以飞灰形式排放,占总汞量的90%,烟气汞占10%。NID前和ESP后的烟气中,汞的浓度分别为21.3μg/m3~22.4μg/m3和1.93μg/m3~3.67μg/m3,说明该NID系统对烟气中汞具有相当高的脱除效率,达到83.6%~90.9%。对汞的化学形态研究表明,NID前烟气汞主要以Hg2+形式存在,占气态汞量的67%;ESP后烟气中Hg2+占气态汞量的71.8%~85.1%,Hg0的含量为零,说明烟气中Hg0在NID系统中经历一系列的氧化还原反应后,被氧化成Hg2+并吸附脱除。     

300 MW等级燃煤机组煤粉炉与循环流化床锅炉汞排放特性比较

选取某地330 MW煤粉炉(PC炉)和350 MW循环流化床锅炉(CFB)的燃煤电厂进行汞排放特性的研究。采用30B法和安大略法对两个燃煤电厂的除尘器入口、除尘器出口、脱硫塔出口和湿式电除尘器出口的烟气进行了取样和汞浓度分析,采集了入炉煤和副产物底渣、飞灰及脱硫石膏样品。通过样品中汞含量的分布,探讨了PC炉与CFB锅炉机组现有污染物控制设备对汞的协同脱除作用。结果表明,350 MW CFB电厂除尘器出口烟气平均汞浓度降低至0.43μg/m~3,布袋除尘器对汞的捕获效率达到98.9%,相应的燃烧副产物中飞灰是汞的主要富集对象。对于330 MW PC炉电厂,除尘器入口和除尘器出口烟气汞浓度均高于350 MW CFB电厂,烟气汞浓度从除尘器入口、除尘器出口到脱硫塔出口依次降低,在脱硫塔出口烟气汞浓度降低至0.42μg/m~3,静电除尘器和湿式脱硫塔对烟气汞的捕获效率分别为75.0%和22.4%,相应的产物中飞灰和脱硫石膏中汞都有一定程度的富集。     

煤燃烧中的汞转化模型和数值模拟

煤燃烧中汞高温下以单质形式存在,在烟道里随着温度降低,单质汞部分转化为二价汞,并再有部分汞吸附在灰渣中而被除尘设备收集,减少了环境的汞污染。针对煤燃烧汞的转化过程,用动力学模型和吸附模型结合来描述汞的转化机理,并用数值模拟方法研究了煤中氯的质量分数、烟气降温速率、烟气停留时间等因素的影响。结果表明,煤中氯的质量分数为0.08×10－6以上,烟气停留6s以上时,可以使汞的吸附率达到40％以上。对汞转化模型,用一组580MJ/h燃烧系统150℃烟道温度数据进行了验证,结果证实试验数据与计算数据能较好相符,模型具有一定的可靠性。     

负载Mn的Fe基MOFs脱汞剂烟气脱汞研究

基于Fe基金属有机骨架（MOFS）作为载体,采用浸渍法制备了负载6% Mn的Mn/MIL-100（Fe）脱汞剂。在模拟烟气中,搭建固定床研究了Mn/MIF-100（Fe）脱除单质汞（Hg⁰）性能。采用X射线衍射分析（XRD）、X射线电子能谱（XPS）、N₂吸附-脱附（BET）和热重分析（TGA）对材料进行表征。研究表明,Mn/MIF-100（Fe）脱除单质汞（Hg⁰）效率较高,在250℃,空速（GHSV）为180000h^-1时,脱汞（Hg⁰）效率达82%以上。Mn/MIF-100（Fe）主要的脱汞机理是催化氧化,Mn的负载促进了汞的吸附,并随着烟气温度的提高,单质汞的氧化效率逐渐提高。O₂和NO促进汞的脱除,SO₂和NH₃抑制汞的脱除。Mn/MIL-100（Fe）整体上对复杂烟气的适应能力强。     

循环流化床燃煤锅炉中的汞迁移研究

采用美国环保署颁布的吸附剂吸附汞采样方法30B(USEPA 40 CFR Part 60 30B)采集燃煤烟气中汞。选择一循环流化床燃煤机组进行现场采样,吸附剂吸附烟囱处烟气中的汞、入炉煤样、锅炉底灰、静电除尘器飞灰等样品同时采集。对该机组中汞质量平衡率进行衡算,通过汞质量平衡率说明了汞采样方法的准确性和有效性。评价了汞在飞灰、底灰和烟气中的分布,循环流化床锅炉底灰中对脱汞的贡献率仅0.55%,飞灰脱除汞的效率高达83.37%,剩余的16.08%的汞排放入大气环境,表明循环流化床机组是有效控制汞的清洁煤燃烧技术。     

300 MW燃煤电厂ESP和WFGD对烟气汞的脱除特性

采用燃煤电厂汞形态浓度取样测试OHM标准方法,对一座300 MW燃煤电厂静电除尘器(ESP)和湿法脱硫装置(WFGD)前后烟气进行了等速取样.使用美国Leeman Labs Hydra AA全自动汞分析仪检测烟气中的汞形态浓度.采集了固体样品,包括入炉煤、底渣、ESP电场灰、脱硫剂石灰石、脱硫产物石膏等,使用意大利Milestone公司生产的DMA80全自动汞分析仪检测固体样品中的汞浓度.计算锅炉系统的汞质量平衡,获得了ESP和WFGD前后烟气的汞形态浓度和分布规律,分析讨论了影响烟气汞形态转化的各种影响因素.结果表明,燃煤烟气中气态单质汞Hg⁰和气态氧化汞Hg²⁺占到总汞量的95%.煤渣中的汞可忽略不计;ESP对颗粒态汞Hg^p的脱除效率达到95%以上,但是对Hg⁰和Hg²⁺脱除率不高.ESP对烟气总汞Hg^T脱除效率为12.77%~17.38%;WFGD对Hg²⁺的脱除率达到79.93%~90.53%,但是对Hg⁰没有脱除效果,其含量不仅没有下降反而有少量上升,说明有部分Hg²⁺在WFGD中被还原成Hg⁰.WFGD对Hg^T脱除效率为9.68%~29.36%;该电厂现有污染控制设备ESP+WFGD可以脱除全部的Hg^p和大部分Hg²⁺,但是由于部分Hg²⁺的还原使得Hg^T的脱除效率在25.38%~38.38%.综合来看,该燃煤电厂的污染物控制设备在进行除尘和脱硫的同时,对汞的脱除率并不高,与燃煤中的氯含量较低有关.     

Total reflection X-ray fluorescence mercury analysis after immobilization on quartz surfaces

Quartz reflectors are a common substrate for total reflection X-ray fluorescence (TXRF) analysis. Especially low masses of trace elements can be determined on these surfaces. In the present work, various complexing reagents were immobilized on the surface of quartz reflectors. The reflectors were immersed in mercury solutions and selective mercury collection took place. The effect of immersion time was examined and a few minutes were found adequate. The reflectors were analysed for mercury by TXRF. Different complexing reagents showed different collection capabilities; 4-(2-pyridazo-resorcinol) gave the best among them. The effect of various experimental parameters was examined like pH, interferences from other ions, etc. Mercury speciation was successfully tested by comparing inorganic mercury results with the methyl mercury ones. A very good selectivity for inorganic mercury was found. It was achieved very good linearity in the 1-500 ng mL⁻¹ mercury concentration range and the minimum detection limit was equal to 2.5 ng mL⁻¹.     

MnOx-TiO2吸附剂对燃煤烟气中汞的脱除

以锐钛矿型TiO_2为载体,采用浸渍法对其进行MnO_x改性制备脱汞吸附剂,探究了负载量、焙烧温度、反应温度及烟气组分等参数对吸附剂脱汞性能的影响。利用N_2吸附-脱附、TG/DTG、XRD、FT-IR、Hg-TPD、XPS等方法对吸附剂的理化性质进行了表征。结果表明,Mn的最佳负载量为12%,最佳焙烧温度和反应温度分别为450和300℃,在实验条件下MnO_x-TiO_2吸附剂可达到的最佳脱汞效率为98.46%。烟气中少量的O_2及微量的HCl对吸附剂的脱汞有较强的促进作用;SO_2对吸附剂的脱汞有较强的抑制作用,SO_2与Hg~0存在的竞争吸附作用以及脱汞反应中产生的硫酸盐覆盖活性位点表面,是导致脱汞效率下降的主要原因。烟气中的CO_2和NO也会对汞的脱除产生轻微的抑制作用。负载在吸附剂上的MnO_x存在Mn~(4+)、Mn~(3+)两种价态,其中,Mn~(4+)将Hg~0氧化为Hg~(2+),自身被还原为Mn~(3+)。结合实验和分析结果发现,Hg~0的吸附和氧化基本遵循Mars-Maessen和Langmuir-Hinshelwood机理。     

Experimental Study on Demercurization Performance of Wet Flue Gas Desulfurization System

The demercurization performance of wet flue gas desulfurization (WFGD) system was investigated by measuring mercury concentrations at the inlet and outlet of WFGD system with a QM201H mercury analyzer. The selected desulfurizer included NH₃·H₂O, NaOH, Na₂CO₃, Ca(OH)₂ and CaCO₃. The influences of adding oxidant and coagulant such as KMnO₄, Fenton reagent, K₂S₂O₈/CuSO₄ and Na₂S into desulfurization solutions were also studied. The results show that elemental mercury is the main component of gaseous mercury in coal‐fired flue gas, and the proportion of oxidized mercury is less than 36%. Oxidized mercury could be removed by WFGD system efficiently, and the removal efficiency could amount to 81.1%–92.6%. However, the concentration of elemental mercury slightly increased at the outlet of WFGD as a result of its insolubility and re‐emission. Therefore, the removal efficiency of gaseous mercury is only 13.3%–18.3%. The mercury removal efficiency of WFGD system increased with increasing the liquid‐gas ratio. In addition, adding KMnO₄, Fenton reagent, K₂S₂O₈/CuSO₄ and Na₂S into desulfurization solutions could increase the mercury removal efficiency obviously. Various additives have different effects, and Na₂S is demonstrated to be the most efficient, in which a mercury removal efficiency of 67.2% can be reached.     

钙基类吸附剂脱除烟气中气态汞的试验研究

用恒温水浴中汞渗透管的汞蒸气发生装置和其他烟气主要气体成分模拟烟气条件,在小型固定床试验台上开展钙基类物质作为吸附剂脱除单质汞的试验研究。结果表明,无SO2时,两种钙基吸附剂以及飞灰和熟石灰混合物对单质汞的吸附效率不高;当SO2存在时,对单质汞的脱除效率可增加15％～20％,30min时吸附量可增加50％以上,且吸附在较高温度下更有利。其原因在于SO2同钙基吸附剂之间的化学反应,在钙基物质表面产生了活性区域,有利于提高对Hg0的捕捉效率,化学吸附起到了促进吸附的作用。     

Determination of trace elements in Syrian medicinal plants and their infusions by energy dispersive X-ray fluorescence and total reflection X-ray fluorescence spectrometry

X-ray fluorescence (XRF) and total-reflection X-ray fluorescence (TXRF) techniques suited well for a multi-element determination of K, Ca, Mn, Fe, Cu, Zn, Rb, and Sr in some Syrian medicinal plant species. The accuracy and the precision of both techniques were verified by analyzing the Standard Reference Materials (SRM) peach-1547 and apple leaves-1515. A good agreement between the measured concentrations of the previously mentioned elements and the certified values were obtained with errors less than 10.7% for TXRF and 15.8% for XRF. The determination of Br was acceptable only by XRF with an error less than 24%. Furthermore, the XRF method showed a very good applicability for the determination of K, Ca, Mn, Fe, Cu, Zn, Rb, Sr, and Br in infusions of different Syrian medicinal plant species, namely anise (Anisum vulgare), licorice root (Glycyrrhiza glabra), and white wormwood (Artemisia herba-alba).     

燃煤电厂污染控制单元对汞释放的控制作用

采用Ontario-Hydro方法和半连续汞排放监测仪,研究了电厂现有污染控制单元,选择还原催化(SCR)、静电除尘(ESP)、烟气脱硫(FGD)对烟气中汞的脱除能力。实验结果表明,在SCR催化剂V2O5/TiO2的作用下,50%以上的Hg0被氧化成Hg2+,但SCR本身不能控制汞释放量;ESP通过对飞灰的捕获直接降低了烟气中颗粒汞的比例;FGD依据Hg2+易溶于水的性质,通过吸收烟气中的Hg2+控制总汞的释放,部分Hg2+和FGD系统中的亚硫酸盐等发生反应,被还原为Hg0,发生了二次汞释放问题,造成脱汞整体效率降低。研究中考察了SCR开闭两种状态下整个系统汞的释放量,发现SCR单元启用时,由于烟气中Hg2+的浓度较高,二次汞释放现象更严重。     

SO2和NO浓度对TiO2-硅酸铝纤维脱除元素汞的影响

使用溶胶凝胶法制备了TiO₂-硅酸铝纤维纳米复合材料。使用此复合材料在波长为253.7 nm的紫外光照射下脱除模拟烟气中的元素汞,实验研究了SO₂和NO浓度对光催化脱汞的影响以及温度对脱汞率的影响。结果表明,常温时烟气中SO₂浓度对光催化脱汞表现出促进作用,当SO₂浓度为1 200 μg/m³时脱汞率最高可达93%。NO浓度对光催化脱汞表现出抑制作用,随着NO浓度的增加脱汞率逐渐降低。高温时SO₂和NO浓度对光催化脱汞的作用规律与常温时相似。随着模拟烟气温度的升高,脱汞率逐渐减低,升高温度对光催化脱汞表现出抑制作用。     

Removal of Elemental Mercury from Simulated Flue Gas by Combining Non-thermal Plasma with Calcium Oxide

Mercury emission from coal combustion has been the fourth biggest pollutant in China, following the dusts, SO₂ and NO_X. The technology of non-thermal plasma has been widely studied for oxidizing gaseous elemental mercury at low temperature. In this paper, a new method of combining non-thermal plasma with calcium oxide was proposed to remove elemental mercury from simulated flue gas. The effects of non-thermal plasma, input energy, combination mode of plasma and calcium oxide on Hg⁰ removal were investigated in a wire-cylinder non-thermal plasma reactor, whose energy was supplied by a high voltage alternating current power. The peak voltage and energy of the non-thermal plasma were measured by an oscilloscope and a high voltage probe (1000:1). The results showed that most of Hg⁰ was converted to oxidized mercury in simulated flue gas by non-thermal plasma treatment. The Hg⁰ removal efficiency of CaO was improved remarkably strengthened by the non-thermal plasma, which was closely related to input energy, and the maximum mercury removal efficiency was about 80 % at an optimal input energy. Through temperature-programmed decomposition and desorption and energy dispersive spectroscopy analysis, the majority of mercury species on CaO surface were Hg₂O and HgO₃ rather than HgO. Therefore, it can be concluded that O₃ plays an important role in Hg⁰ oxidation under the condition of non-thermal plasma.     

Fe/Al-SiO_2复合金属氧化物用于燃煤烟气中汞的脱除

采用不同方法制备了Fe/Al-SiO_2复合金属氧化物以模拟赤泥成分,模拟烟气条件下考察其脱汞性能。结果表明,采用溶胶-凝胶法得到的复合金属氧化物在300-450℃具有优异的脱汞性能,其中,在350℃、3 h内平均脱汞率可达到94.8%。Fe_2O_3为Hg~0的氧化提供了晶格氧和化学吸附氧;SiO_2形成的硅溶胶则有利于活性组分Fe_2O_3的分散,增强了Hg~0与活性位的接触。基本模拟烟气中存在微量HCl和NO时,Hg~0脱除率接近100%;当烟气中存在0.2 mL/min、0.4 mL/min的SO_2时,吸附剂的平均脱汞率分别降至90.7%、53.4%,这主要是由于SO_2与Fe_2O_3反应生成Fe_2(SO_4)_3,导致了Fe_2O_3的失活并抑制汞的脱除。     

Radiation-chemical treatment of flue gases from thermal power stations for the removal of mercury vapor

The efficiency of radiation-chemical treatment of flue gases from thermal power stations for removing nitrogen and sulfur oxides was examined as applied to the removal of mercury vapor from the gases. A kinetic scheme of the process was developed. It involves the liquid-phase oxidation of Hg by O₃ molecules formed under the action of ionizing radiation on the gas macrocomponents followed by adsorption of the oxidation products at soot particles. It was found that almost complete removal of mercury vapor is attained at typical radiation doses and soot concentrations in the flue gases.     

Determination of Hg from Cu concentrates by X-ray fluorescence through preconcentration on polyurethane foam

A methodology was developed for the separation and determination of microamounts of mercury from copper concentrate samples by wavelength dispersive X-ray fluorescence (WDXRF) after solid-phase extraction of mercury from iodide medium using polyurethane foam (PUF). The best sorption conditions for the Hg-KI-PUF system were settled using X-ray fluorescence technique after collection of ground PUF on a filter paper by vacuum filtration and direct measurement of the intensity signal of the sorbed mercury on PUF. The main parameters of sorption such as iodide concentration, pH, shaking time and sample dilution effect were studied. The system shows rapid kinetic sorption and maximum X-ray intensity signal was achieved after shaking for 2 min a 0.01 mol l⁻¹ iodide solution containing microamounts of mercury in the pH range from 1.0 to 9.0. Effective sorption up to a volume of 0.9 l allows preconcentration of mercury. A linear fit up to 50 μg mercury was obtained by the plot of the initial mercury mass in the bulk solution (0.5 l) vs. its respective XRF intensity signal measurement on ground PUF after the sorption process. The calibration sensitivity, quantification and detection limits found were 9.09 CPS μg⁻¹, 9.0 and 2.7 μg, respectively. The sorption of many elements was also evaluated under the best conditions. High concentrations of Cu(II) and Fe(III) interfere seriously. Mercury-selective separation could be achieved using citrate or EDTA as masking agent; no interference due to copper matrix samples was observed in citrate medium. This methodology was evaluated by recovery for mercury determination in copper concentrate ore samples supplied by a mining industry and copper sulfate salts; the results were between 98% and 106%.     

XRF and TXRF techniques for multi-element determination of trace elements in whole blood and human hair samples

XRF and TXRF were established as useful techniques for multi-element analysis of whole blood and human head hair samples. Direct-XRF with different collimation units and different X-ray excitation modes was successfully used for the determination of S, P, K, Ca, Fe, and Br elements in blood samples and K, Ca, Mn, Fe elements in human hair samples. Direct analysis by TXRF was used for the determination of Rb and Sr in digested blood and human hair samples, respectively, while, the co-precipitation method using APDC for TXRF analysis was used for the determination of Ni, Cu, Zn, and Pb elements in both matrices. As a result, the improved XRF and TXRF methods were applied for multi-element determination of elements in whole blood and human hair samples in non-occupational exposed population living in Damascus city. The mean concentrations of analyzed elements in both matrices were on the reported range values for non-occupational population in other countries.     

300 MW燃煤电站砷、汞排放特征研究

对某300 MW燃煤电站煤、底灰和静电除尘器(ESP)飞灰进行采样并测定了其中的砷、汞含量,同时应用Ontario Hydro Method (OHM) 标准方法和设备对ESP前后烟气中的砷、汞分布进行了直接采样和测试.对砷的检测结果表明,ESP飞灰中砷含量约6.68×10^-6,是原煤中砷含量的2.5倍左右,而底灰中砷含量仅为1.70×10^-6,ESP前烟气中砷含量约153.27 μg/m³,ESP后砷含量急剧降低为41.13 μg/m³;对汞的检测结果表明,原煤中汞含量约2.5×10^-7,飞灰、底灰中的汞含量分别约1.9×10^-7、1.5×10^-7;ESP前后烟气中总汞含量分别为5.49、5.21 μg/m³.砷在飞灰中明显富集,而汞在飞灰和底渣中均不具有富集效果.ESP单元具有明显的协同脱砷效果,平均脱除率约在71%左右,而对汞的协同脱除效果不明显.