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总结了燃煤烟气中汞污染的现状及蛭石吸附剂研究的进展情况,对烟气中单质汞的脱除进行了研究,提出了蛭石在单质汞的吸附脱除方面存在的潜力,为今后燃煤烟气中单质汞的脱除提出了一定的研究思路. 相似文献
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介绍了燃煤电站汞的排放状况,并指出了汞危害性以及我国面临的脱汞压力,论述了烟气中汞存在形式以及影响其存在形式的因素.探讨了当前燃煤电站利用现有污染控制设备进行协同脱汞的研究进展,包括:燃烧器/反应器、选择性催化还原脱硝(SCR)、电除尘器(布袋除尘)(ESP/FF)、湿法烟气脱硫系统(WFGD)等设备.提出了脱汞吸附剂处理问题,并对今后烟气脱汞技术的研究趋势进行了展望. 相似文献
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近年来,燃煤电厂烟气中的汞成为继SO2、NOx和烟尘之后又一公认的大气环境污染物,我国已正式立法控制燃煤电厂汞排放,这使得燃煤电厂汞排放技术的研究迫在眉睫。不同形态汞的理化性质不同,元素态汞( Hg0)较之氧化态汞(Hg2+)和颗粒态汞(Hgp)更难去除,因此,脱汞的前提是提高Hg0的氧化率。介绍并简单分析了目前国内外已有的汞排放控制技术:燃烧前控制(清洁燃煤发电技术)、燃烧中控制(煤基添加剂技术和炉膛喷射技术),和燃烧后控制(利用现有的烟气控制设备协同控制),并对我国脱汞技术发展方向提出了展望。 相似文献
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电厂燃煤过程中汞控制技术研究 总被引:3,自引:0,他引:3
燃煤电厂汞控制技术分燃烧前、燃烧中和燃烧后脱汞,燃烧后脱汞技术为主要汞控制排放工艺,其中吸附剂吸附方法的研究较为广泛。基于国内外近几年燃煤电厂烟气脱汞技术的研究,综述了汞控制技术的最新进展。 相似文献
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燃煤电厂烟气中汞的排放与控制研究进展 总被引:2,自引:0,他引:2
对煤中微量元素的丰度和赋存状态进行了论述,综述了燃煤烟气中重金属汞的排放、形态转化及分布情况,并重点论述了燃煤烟气中汞的监测和控制方法的最新进展,分析了燃煤电厂在汞控制方面存在的主要问题,并结合我国国情提出了相关建议。 相似文献
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汞是煤中最易挥发的重金属元素之一,燃烧产物中汞的排放为火电厂锅炉汞污染的主流。烟气中的汞主要采用活性炭或者其他吸附剂、飞灰再循环、湿法烟气脱硫装置等手段来去除,但普遍存在吸附剂价格昂贵、经济效应不高,具体脱除效应不明显、仅适用中小型火电厂锅炉等实际问题。为配合脱汞市场,需要在完善测试手段和控制手段的基础上,着重解决多组分污染物联合脱除汞反应的竞争机制和活性/选择性调控规律、吸收剂固体表面物理化学、大容积/大流量反应器内超低浓度污染物的富集/反应机理等关键技术问题。在火电厂烟气零价汞形态转化机理、汞迁移转化动力学模型的研究以及高效价廉吸附剂的开发等方面取得突破,开发具有自主知识产权的新型燃煤电厂烟气中汞排放控制方法。 相似文献
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Helliwell R. C. Wright R. F. Evans C. D. Jenkins A. Ferrier R. C. 《Water, Air, & Soil Pollution: Focus》2002,2(2):47-59
The Cairngorms in north-east Scotland is remote from pollutant sources although it currently receives ca. 10 kg ha1 yr1 S and ca. 11 kg ha1 yr1 N deposition from the atmosphere.In 1955, 15 lochs (lakes) at a range of altitudes were sampled and analysed for major ion concentrations. A new survey of these and an additional 23 lochs and their catchment soils was conducted in 1999 to determine the impact of acid deposition, and the changes in loch chemistry since the 1955 survey. The bedrock geology of this region has a strong influence on the loch chemistry. Surface waters were generally more acidic in high altitude areas due to predominantly poorly buffered, thin alpine soils developed on granitic parent material (mean acid neutralising capacity (ANC) for 23 lochs = 30 eq L1). At lower altitudes where the geology is dominated by Dalradian metamorphic rocks surface waters are comparatively base rich and have higher ANC (mean ANC for 15 lochs = 157 eq L1). Surface water nitrate concentrations show a negative relationship with soil C:N status, in that higher nitrate only occurs at low soil C:N ratios. A comparison of data for 1955 and 1999 shows that sulphate concentrations are significantly lower (67.8 and 47.5 eq L1, respectively), and pH has improved (pH 5.6 and 5.9) in response to decreased S deposition since the mid 1970s. However, mean nitrate concentrations were found to increase from 2.48 >eq L1 in 1955 to 5.65 eq L1 in 1999. Differences in the sampling and laboratory methods from 1955 and 1999 are acknowledged in the interpretation of data. 相似文献
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Alain Copinet Christophe Bliard Yves Couturier 《Journal of Polymers and the Environment》2000,8(3):111-118
The nature and distribution of the acetylated groups were evaluated by 13C-NMR and 1H-NMR. The starch substrate with a DS of 1.5 comprises only two patterns: -(14)-d-glucopyranose and 2,3,6-tri-O-acetyl--(14)-d-glucopyranose. The starch with a DS of 3.0 also comprises two patterns: 2,3,4,6-tetra-O-acetyl--(14)-d-glucopyranose and 2,3,6-tri-O-acetyl--(14)-d-glucopyranose; whereas starch (DS = 1.9) contains 4 patterns: 2,3,6-tri-O-acetyl--(14)-d-glucopyranose, 2,3,4,6-tetra-O-acetyl--(14)-d-glucopyranose terminal, 2,6-di-O-acetyl--(14)-d-glucopyranose, and 3,6-di-O-acetyl--(14)-d-glucopyranose. Using esterase from Viscozyme, it has been possible to hydrolyze up to 7% of the DS 3.0 starch. An -amylase (Fungamyl 800) was then added to these acetylesterases. With a 2.4 FAU/mL fraction of -amylase and 2.4 U/mL from the Viscozyme's acetylesterase, 28% of the acetylated end groups were hydrolyzed for the starch substrates with DS 3.0. Moreover, a synergic action between -amylase and acetylesterase was noticed, allowing fragmentation of 32% for DS 1.5, 30% for DS 1.9, and 11% for DS 3.0. 相似文献
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R. W. Macdonald S. Carter Schofield P. R. Slawson 《Water, Air, & Soil Pollution: Focus》2002,2(5-6):541-554
The aerodynamic behaviour of large urbanagglomerations must be represented in increasingly greaterdetail, as large-scale numerical weather prediction and airpollution dispersion models are refined. The present studyprovides detailed measurements of the flow field in regulararrays of obstacles to obtain representative data on meanflow and turbulence statistics in urban-type areas. Obstacle arrays consisting of simple cubes and flat plateroughness commonly used in boundary layer simulations wereplaced in a simulated atmospheric boundary layer flow in ahydraulic flume. The scale factor was about 1:200 based onthe obstacle height (50 mm). The results show noappreciable `constant stress' region in the internalboundary layer above the buildings, since in any finite-length test array the boundary layer is always developing.However, if the RMS turbulence components are scaled by thelocal values of the shear stress, then there seems to be auniversal scaling, with u/u* = 2.1,v/u* = 1.65 and w/u* = 1.2. This greatly simplifies the parameterization of the first orderturbulence statistics in obstacle arrays. It was alsoobserved during the experiments that, compared to results inthe cube arrays, the turbulence kinetic energy and theReynolds stresses were almost doubled in the flat plateroughness arrays. 相似文献
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Sakie Miyazaki Kazuhei Takahashi Mari Shiraki Terumi Saito Yoko Tezuka Ken-ichi Kasuya 《Journal of Polymers and the Environment》2000,8(4):175-182
A poly(3-hydroxybutyrate) (PHB) depolymerase was purified from a fungus, Penicillium funiculosum (IFO6345), with phenyl-Toyopearl and its properties were compared with those of other PHB depolymerases. The molecular mass of the purified enzyme was estimated at about 33 kDa by sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis. The pH optimum and pI were 6.5 and 6.5, respectively. The purified protein showed affinity to Con A-Sepharose, indicating that it is a glycoprotein. Diisopropylfluorophosphate and dithiothreitol inhibited the depolymerase activity completely. The N-terminal amino acid sequence of the purified enzyme was TALPAFNVNPNSVSVSGLSSGGYMAAQL, which contained a lipase box sequence. This purified enzyme is one of the extracellular PHB depolymerase which belong to serine esterase. The purified enzyme showed relatively strong hydrolytic activity against 3-hydroxybutyrate oligomers compared with its PHB-degrading activity. PHB-binding experiments showed that P. funiculosum depolymerase has the weakest affinity for PHB of all the depolymerases examined. 相似文献
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Van Hees Patrick A. W. Jones David L. Godbold Douglas L. 《Water, Air, & Soil Pollution: Focus》2003,3(4):121-144
The effect of liming (3.45 and 8.75 t ha-1 dolomite; 16 yr after application) on the biodegradation of three low molecular weight organic acids (citrate, oxalate and propionate) in forest soils was investigated. The concentration of organic acids in the soil solution followed the series propionate > citrate > oxalate with liming having no significant impact on soil solution concentrations (mean organic acid concentration = 8.7 ± 2.3 M). Organic acid mineralization by the soil microbial community was rapid in surface organic horizons (mean half-life for citrate = 2–6 h), with biodegradation rate gradually declining with soil depth. Concentration-dependent biodegradation studies (0 to 350 M) showed that the mineralization kinetics generally conformed well to a single Michaelis–Menten equation with Vmax values following the series oxalate > citrate > propionate (mean = 9.8 ± 1.0 nmol g-1 h-1) and KM values following the series oxalate = citrate > propionate (mean 168 ± 25 M). The Vmax values declined with soil depth, which was consistent with a general reduction in microbial activity down the soil profile. Liming induced a significant increase in Vmax for citrate with no change for propionate and reduction in Vmax for oxalate. The latter was probably due to adsorption and precipitation of Ca-oxalate making it unavailable for microbial uptake. The higher adsorption/precipitation capacity for oxalate in the limed soils was confirmed by adsorption isotherms. Generally, liming increased soil microbial activity by approximately 10 to 35% with calculations based on soil solution concentrations indicating that organic acid mineralization constituted approximately 3 to 15% of the total soil respiration. 相似文献
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Investigation of the Aerobic Biodegradability of Several Types of Cyclodextrins in a Laboratory-Controlled Composting Test 总被引:1,自引:0,他引:1
Steven Verstichel Bruno De Wilde Eva Fenyvesi József Szejtli 《Journal of Polymers and the Environment》2004,12(2):47-55
The biodegradation of several types of cyclodextrins (CDs) under laboratory-controlled composting conditions was investigated. CDs are used in a broad range of applications in food, pharmaceutical, medical, chemical, and textile industries because of their specific chemical characteristics related to their hydrophobic interior and hydrophilic exterior. The three naturally occurring cyclodextrins -CD, -CD, and -CD proved to be completely and readily biodegradable. Chemical modification of these basic compounds can have a major impact on the biodegradation rate and final biodegradation percentage. Fully acetylated -CD and -CD were found to be nonbiodegradable during 45 days of composting. Reducing the degree of acetylation had a positive effect on the biodegradation. Complete biodegradation was obtained for partially acetylated -CD with a degree of substitution (DS) of 7. The methylation (DS = 13) of -CD resulted in an undegradable compound during the 47 days composting, while (2-hydroxy)propyl--CD reached a plateau in biodegradation at a percentage of 20%. The incorporation of the antimicrobial agents imazalil and allyl-isothiocyanate into -CD had no negative impact on biodegradation, which makes these antimicrobial agents/CD complexes suitable for incorporation into biodegradable active packaging. 相似文献
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Assessment of Bacterial Degradation of Aromatic Hydrocarbons in the Environment by Analysis of Stable Carbon Isotope Fractionation 总被引:4,自引:0,他引:4
Rainer U. Meckenstock Barbara Morasch Matthias Kästner Andrea Vieth Hans Hermann Richnow 《Water, Air, & Soil Pollution: Focus》2002,2(3):141-152
13C/12C stable carbon isotope fractionation was used to assess biodegradation in contaminated aquifers with toluene as a model compound. Different strains of anaerobic bacteria (Thauera aromatica, Geobacter metallireducens, and the sulfate-reducing strain TRM1) showed consistent 13C/12C carbon isotope fractionation with fractionation factors between C = 1.0017 and 1.0018. In contrast, three cultures of aerobic organisms, using different mono- and dioxygenase enzyme systems to initiate toluene degradation, showed variable isotope fractionation factors of C = 1.0027 (Pseudomonasputida strain mt-2), C = 1.0011 (Ralstonia picketii), andC = 1.0004 (Pseudomonas putida strain F1). The great variability of isotope fractionation between different aerobic bacterial strains suggests that interpretation of isotope data in oxic habitats can only be qualitative. A soil column was run as a model system for contaminated aquifers with toluene as the carbon source and sulfate as the electron acceptor and samples were taken at different ports along the column. Microbial toluene degradation was calculated based on the 13C/12C isotope fractionation factors of the batch culture experiments together with the observed 13C/12C isotope shifts of the residual toluene fractions. The calculated percentage of biodegradation, B, correlated well with the decreasing toluene concentrations at the sampling ports and indicated the increasing extent of biodegradation along the column. The theoretical toluene concentrations as calculated based on the isotope values matched the measured concentrations at the different sampling ports indicating that the Rayleigh equation can be used to calculate biodegradation in quasi closed systems based on measured isotope shifts. A similar attempt was performed to assess toluene degradation in a contaminated, anoxic aquifer. A transect of groundwater wells was monitored along the main direction of the groundwater flow and revealed decreasing concentrations accompanied with an increase in the 13C/12C stable carbon isotope ratio of the residual toluene. Calculation of the extent of biodegradation based on the isotope values and laboratory derived isotope fractionation factors showed that the residual toluene was degraded to more than 99% by microbial activity. Calculation of the theoretical residual toluene concentrations based on the measured isotope values described the strongly decreasing concentrations along the plume. Other aromatic hydrocarbons like benzene and naphthalene which were analysed in the same course also showed decreasing concentrations along the groundwater flow path accompanied by increasing 13C values indicating biodegradation. 相似文献