Pd/activated carbon sorbents for mid-temperature capture of mercury from coal-derived fuel gas

Higher concentrations of Hg can be emitted from coal pyrolysis or gasification than from coal combustion, especially elemental Hg. Highly efficient Hg removal technology from coal-derived fuel gas is thus of great importance. Based on the very excellent Hg removal ability of Pd and the high adsorption abilities of activated carbon（AC） for H2 S and Hg, a series of Pd/AC sorbents was prepared by using pore volume impregnation, and their performance in capturing Hg and H2 S from coal-derived fuel gas was investigated using a laboratory-scale fixed-bed reactor. The effects of loading amount, reaction temperature and reaction atmosphere on Hg removal from coal-derived fuel gas were studied. The sorbents were characterized by N2 adsorption, X-ray diffraction（XRD） and X-ray photoelectron spectroscopy（XPS）. The results indicated that the efficiency of Hg removal increased with the increasing of Pd loading amount, but the effective utilization rate of the active component Pd decreased significantly at the same time. High temperature had a negative influence on the Hg removal. The efficiency of Hg removal in the N2-H2S-H2-CO-Hg atmosphere（simulated coal gas） was higher than that in N2-H2S-Hg and N2-Hg atmospheres, which showed that H2 and CO, with their reducing capacity, could benefit promote the removal of Hg. The XPS results suggested that there were two different ways of capturing Hg over sorbents in N2-H2S-Hg and N2-Hg atmospheres.     

Experimental study on simultaneous desulfurization and denitrification based on highly active absorbent

Simultaneous removal of SO2 and NO from flue gas by the highly active absorbent prepared from fly ash, lime and a few oxidizing manganese compound additive was studied using a flue gas circulating fluidized bed （CFB） under different experimental conditions. The effects influencing the removal effiencies were discussed. The optimal flue gas temperature, flue gas humidity, gas velocity of CFB and Ca/（S＋N） molar ratio with this process were approximately 110℃, 6%, 1.8 m/s and 1.05, respectively. Removal efficiencies of 92.3% for SO2 and 60.88% for NO were obtained under the optimal experimental conditions. While the spent absorbent appeared in the form of dry powder, the mechanism of removal for SO2 and NO based on the highly active absorbent was investigated by a scanning electron microscope （SEM）, a X-ray energy spectrometer and the chemical analysis methods. The valuable references can be provided for industrial application by the process. The foreground of application will be vast in China and in the world.     

Removal of PCDD/Fs and PCBs from flue gas using a pilot gas cleaning system

A 100 Nm3 /hr capacity pilot scale dual bag filter (DBF) system was tested on the flue gas from an actual hazardous waste incinerator (HWI), the removal efficiency of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) and polychlorinated biphenyls (PCBs) was also studied. The first filter collected most of the fly ash and associated chlorinated organic; then activated carbon (AC) was injected and used to collect phase chlorinated organic from the gas. Concentrations of PCDD/Fs and PCBs after the DBF system were 0.07 and 0.01 ng TEQ/Nm3 , respectively, which were both far below the national emission standard. Comparing with the original single bag filter system, the PCDD/Fs concentration dropped a lot from 0.36 to 0.07 ng TEQ/Nm3 . Increasing AC feeding rate enhanced their collection efficiency, yet reduced the AC utilization efficiency, and it still needs further study to select an appropriate feeding rate in the system. These results will be useful for industrial application and assist in controlling emissions of PCDD/Fs and other persistent organic pollutions from stationary sources in China.     

Integrated removal of NO and mercury from coal combustion flue gas using manganese oxides supported on TiO2

A catalyst composed of manganese oxides supported on titania(MnO_x/TiO_2) synthesized by a sol–gel method was selected to remove nitric oxide and mercury jointly at a relatively low temperature in simulated flue gas from coal-fired power plants. The physico-chemical characteristics of catalysts were investigated by X-ray fluorescence(XRF), X-ray diffraction(XRD), and X-ray photoelectron spectroscopy(XPS) analyses, etc. The effects of Mn loading,reaction temperature and individual flue gas components on denitration and Hg~0 removal were examined. The results indicated that the optimal Mn/Ti molar ratio was 0.8 and the best working temperature was 240°C for NO conversion. O_2 and a proper ratio of [NH_3]/[NO]are essential for the denitration reaction. Both NO conversion and Hg~0 removal efficiency could reach more than 80% when NO and Hg~0 were removed simultaneously using Mn0.8 Tiat 240°C.Hg~0 removal efficiency slightly declined as the Mn content increased in the catalysts. The reaction temperature had no significant effect on Hg~0 removal efficiency. O_2 and HCl had a promotional effect on Hg~0 removal. SO2 and NH_3were observed to weaken Hg~0 removal because of competitive adsorption. NO first facilitated Hg~0 removal and then had an inhibiting effect as NO concentration increased without O_2, and it exhibited weak inhibition of Hg~0 removal efficiency in the presence of O_2. The oxidation of Hg~0 on Mn O x/TiO_2 follows the Mars–Maessen and Langmuir–Hinshelwood mechanisms.     

Low SO2 emission from CFB co-firing MSW and bituminous

Influence of co-firing rate on SO2 emission from co-firing municipal solid waste(MSW) and bituminous containing high amount of sulfur(1.79%) was studied in a 0.15 MWt circulating fluidized bed (CFB). The temperature selected is 1123 K, typical for MSW incineration using CFB. The particle concentration in the dilution zone of the furnace, the alkali metal concentration and sulfate concentration in the recirculating ash and fly ash, and flue gas composition were determined. The results showed that the addition of MSW leads to a significant decrease in SO2 emission. Concentration of SO2 in flue gas decreased to 0 with the co-firing rate greater than 51%. This reduction in SO2 emission is attributed both to the high particle concentration in the dilution zone of the furnace, the high content of alkali metals in the bed material, and to the comparatively high concentration of HCI in flue gas during co-firing of MSW and bituminous.     

Investigations on removal of SO2 from flue gas by aerosol formation in pulsed corona discharge process

The removal of SO₂ from flue gas by pulsed corona discharge in presence of ammonia was experimentally investigated. The results showed that the SO₂ removal mainly depends on thermal reaction of SO₂ with NH₃ and enhancements of 0%—25% by pulsed corona discharge in the range of the specific energy 0—5 Wh/Nm³. The aerosol mass concentration, mainly composed of ammonium sulfate, increased with specific energy dissipated into the reactor. With an initial concentration of 2000—2100 ppmv SO₂ and energy consumption of 3 Wh/Nm³, when a stoichiometric amount of ammonia is injected, the removal efficiency of SO₂ and percentage of ammonium sulfates in reaction products are all ≥80%. The collection efficiency of the reactor for aerosol is about 74% at a flue gas temperature of 60 to 65℃ and a water vapor content of 9% to 11% volume.     

Decomposition characteristics of toluene by a corona radical shower system

Non-thermal plasma technologies offer an innovative approach to decomposing various volatile organic compounds(VOCs). The decomposition of toluene from simulated flue gas was investigated using a pipe electrode with nozzles for the generation of free radicals. Corona characteristics and decomposition of toluene were investigated experimentally. In addition, the decomposition mechanism of toluene was explored in view of reaction rate. The experimental results showed that the humidity of additional gas has an important effect on corona characteristics and modes and stable streamer corona can be generated through optimizing flow rate and humidity of additional gas. Applied voltage, concentration of toluene, humidity of toluene and resident time are some important factors affecting decomposition efficiency. Under optimizing conditions, the decomposition efficiency of toluene can reach 80%. These results can give a conclusion that the corona radical shower technology is feasible and effective on the removal of toluene in the flue gas.     

Interference of iron as a coagulant on MIB removal by powdered activated carbon adsorption for low turbidity waters

Powered activated carbon (PAC) is widely used in water treatment plants to minimize odors in drinking water. This study investigated the removal of 2-methylisoborneol (MIB) by PAC adsorption, combined with coagulation using iron as a coagulant. The adsorption and coagulation process were studied through different case scenarios of jar tests. The analysis evaluated the effect of PAC dosing in the liquid phase immediately before or after the coagulant addition. Ferric sulphate was used as the coagulant with dosages from 10 to 30 mg/L, and PAC dosages varied from 10 to 40 mg/L. The highest MIB removal efficiency (about 70%) was achieved without the coagulant addition and with the highest PAC dosage (40 mg/L). Lower MIB removal efficiencies were observed in the presence of coagulant, showing a clear interference of the iron precipitate or coagulant in the adsorption process. The degree of interference of the coagulation process in the MIB removal was proportional to the ratio of ferric hydroxide mass to the PAC mass. For both cases of PAC dosing, upstream and downstream of the coagulant injection point, the MIB removal efficiency was similar. However, MIB removal efficiency was 15% lower when compared with experiments without the coagulant application. This interference in the MIB adsorption occurs potentially because the coagulant coats the surface of the carbon and interferes with the MIB coming in contact with the carbon’s surface and pores. This constraint requires an increase of the PAC dosage to provide the same efficiency observed without coagulation.     

Chlorine removal from MSWI fly ash by thermal treatment: Effects of iron/aluminum additives

The high content of alkali chlorides in municipal solid waste incineration(MSWI) fly ash limit its resource reuse due to the potential environmental risks.In this paper, with superheated steam as the gasifying agent and inducer, chlorides in fly ash were removed by thermal treatment within a moderate temperature range.Thermal treatment experiments were performed under different conditions: temperature(500–800℃), steam addition(mass ratio of steam to fly ash = 0.25–1) and residence time(0.5–3 hr).Iron and aluminum powders were added to fly ash to improve the chlorine removal efficiency.Water-soluble chlorides included Na Cl and KCl, and insoluble chlorides mainly included Ca(OH)Cl.The heating process with the addition of water steam was more efficient than that without steam in terms of the removal performance of water-soluble chlorides.The removal efficiency of soluble chlorides reached 75.25% for a mass ratio of 1:1 after 1-hr thermal treatment at 700℃.When the residence time was increased above 1 hr, the total dechlorination efficiency was not increased dramatically.Moreover, adding iron and aluminum powder into the fly ash improved the removal of water-insoluble chlorides, and the total dechlorination efficiency was increased by 11.41%–16.64%.     

Removal of elemental mercury by iodine-modified rice husk ash sorbents

Iodine-modified calcium-based rice husk ash sorbents(I2/CaO/RHA) were synthesized and characterized by X-ray diffraction,X-ray fluorescence,and N2 isotherm adsorption/desorption.Adsorption experiments of vapor-phase elemental mercury(Hg0) were performed in a laboratory-scale fixed-bed reactor.I2/CaO/RHA performances on Hg0 adsorption were compared with those of modified Ca-based fly ash sorbents(I2/CaO/FA) and modified fly ash sorbents(I2/FA) .Effects of oxidant loading,supports,pore size distribution,iodine impregnation modes,and temperature were investigated as well to understand the mechanism in capturing Hg0.The modified sorbents exhibited reasonable effciency for Hg0 removal under simulated flue gas.The surface area,pore size distribution,and iodine impregnation modes of the sorbents did not produce a strong effect on Hg0 capture effciency,while fair correlation was observed between Hg0 uptake capacity and iodine concentration.Therefore,the content of I2 impregnated on the sorbents was identified as the most important factor influencing the capacity of these sorbents for Hg0 uptake.Increasing temperature in the range of 80-140°C caused a rise in Hg0 removal.A reaction mechanism that may explain the experimental results was presumed based on the characterizations and adsorption study.     

生物技术在微污染景观水处理中的应用

利用生物砂和多孔活性材料作为载体与滤料,投入硝化细菌和相容的复合菌群,构成小试规模的循环式过滤装置,模拟自然水体的生态净化系统,观察微污染的景观水中NH3-N,NO-2 -N,有机物,色度等等的去除效果。经长期运行测试表明,系统对 NH3-N去除率达99%, NO-2 -N 的去除率达 87%,对COD,浊度,都能较好地保持在较低水平。并使 DO、pH稳定在适合水生生物生长的范围。     

免烧粉煤灰陶粒作为BAF填料处理城市污水

以电厂粉煤灰为主要试验原料,辅以外加药剂(水泥、石灰、石膏、水玻璃),经混合、成球、陈化和养护等工序,制得免烧粉煤灰陶粒,并将其作为曝气生物滤池(BAF)工艺的载体填料处理城市污水.待挂膜启动成功后,考察了水力停留时间( HRT)、COD负荷、氨氮负荷对COD和氨氮去除效果的影响.实验结果表明:在温度为18～21℃、气...     

某海洋平台上海水篮式过滤器事故分析

目的研究分析东海某一海上平台海水用篮式过滤器发生的腐蚀和堵塞事故原因。方法从海洋平台海水系统用篮式过滤器的原理、工艺流程、材料选择、滤网精度,滤芯设计、人工操作等多方面进行分析。结果受内压滤芯结构要优于受外压滤芯结构,如果过滤精度选择过高,会增加压差,造成滤芯堵塞。结论篮式过滤器滤芯单元应采用多滤芯的受内压结构,过滤精度应根据下游用户要求来确定。     

滴滤床在小城镇生活污水处理中的应用

针对小城镇生活污水的特点,开发出了以滴滤床为主的生活污水处理技术路线,讨论了滴滤床技术原理及其构造,分析了运行效果和运行成本,得出该技术具有处理效果好且水质稳定、操作简单,维护量小,符合国家倡导的"高效-低耗的城镇污水处理技术".     

搅拌式多介质过滤器在三元复合驱采出水处理中应用

三元复合驱采出水粘度高导致现有过滤器滤料板结,形成致密滤饼层,滤料无法彻底清洗,严重影响了过滤效果,出水水质难以达标。鉴于此,本项目开发了适合于高粘度废水处理用过滤器,通过采用桨式搅拌装置破坏滤料表层滤饼层,提高反冲洗效果,实现滤料彻底反冲洗。在大庆油田杏二中污水处理站采用该技术新建两座滤罐,研究了两级过滤处理效果。新建滤罐反冲洗压力维持0.2 mpa以内,水量稳定在400 m^3/h以上,解决了滤罐反冲洗憋压、跑料、滤料清洗不彻底问题,保证滤料彻底再生,提高了过滤效果,经二级过滤后出水油痕量,悬浮物在20 mg/L以下,达到油田污水回注标准。     

处理含油废水的新型过滤器

本文介绍了Ａｕｔｏ－ｓｈｅｌ过滤器的特点，通过现场试验，证明它是一种新型废水处理设备，在操作性能、处理效果及控制大气污染等方面均优于目前炼油厂常用的溶气浮选池。     

对重力势二阶垂直偏导数的一种新的取样方法

从目前的研究来看,二阶垂直导数(X和Y两个方向)的求解方法较简单,它采用的五个因子的数字滤波的最小二乘法来优化数据。但是在较小区域面积时(对工程和环境应用中的重力数据),重力异常很容易放大和被区域重力场掩盖,我们认为产生的缘由是表示重力场的x和y方向上的二次多项式引起的。因此,为了逼近重力水平方向的偏导可以设计一个好的滤波器来拟合在xy平面的重力场值,再得出想要的重力垂直方向偏导,文中最后对提出的方法在前人经典模型上和野外实践进行了验证。     

应用物化法检测废水COD组分SI的研究

溶解性不可生物降解COD(S1)是活性污泥数学模型应用中的关键组分.通过一系列实验验证了应用物理化学的方法检测SI的可行性,并采用该方法对武汉市某大型污水处理厂的SI进行了检测.     

BAF净化尿素废水的启动特性研究

文章以曝气生物滤池(Biological Aerated Filter,BAF)净化尿素废水为研究对象,考察了曝气方式、载体特性及运行方式对BAF启动特性的影响。试验结果表明,预曝气方式对加快BAF启动进程有利,但以预曝气运行3～4d为宜;作为BAF的载体,活性炭较陶粒更有利于BAF的启动,只需运行4d,前者对尿素去除率便可稳定在75%以上,且表现出较强的抗冲击负荷能力;相比于低滤速启动运行,高滤速(2.8m/h)运行方式能够加快BAF启动进程。     

污水处理厂CANON工艺小试

在污水处理厂进行CANON工艺小试.试验以污水处理厂A/O除磷工艺出水为基质,启动并运行CANON生物滤柱.第48 d时,反应器氨氮去除率连续10 d大于90%,总氮去除率在70%以上,CANON生物滤柱启动成功.第49~129 d,反应器内部DO控制在较低水平(0.2~0.5 mg·L~(-1)),出水几乎不含氨氮.最大出水总氮浓度为15.6 mg·L~(-1),超过一级A排放标准,硝化细菌(NOB)出现了过量增殖的现象.第129、169和213 d对滤柱进行反冲洗,使得反应器长期总氮去除率大于70%,出水总氮浓度小于12 mg·L~(-1).出水氨氮和总氮浓度达到了一级A标准,硝化细菌得到了有效抑制.结果表明,反冲洗几乎不会影响滤层结构,对滤料生物膜厚度和功能微生物活性影响较小,对硝化细菌抑制作用较大.在实际工程应用中可以通过定期反冲洗维持CANON工艺稳定运行.