脉冲放电等离子体烟气脱硫脱硝工业试验研究

40 000～50000 Nm3/h工业试验结果表明,烟气温度75～80℃,脱硫效率＞90%,脱硝效率＞40%,烟气温度90～95℃,脱硫效率＞80%,脱硝效率＞50%;脉冲能耗＜3 Wh/Nm3;随着温度升高,SO2热化学反应效率逐渐降低;随着氨硫化学计量比增大,氨泄漏逐渐增加,烟气温度90～95℃,氨泄漏增加更为迅速.并分析了副产物的成分,阐述了脱硫脱硝的机理,并探讨了烟气排放的温度.     

水蒸气/氨活化在脉冲电晕脱硫工业中试装置上的应用

在工业中试装置上进行了水蒸气／氨活化实验,同时开展了脉冲电源的调试运行、脱硫副产物收集一体化、工艺参数以及对副产物成份分析等实验。在烟气流量4500～11000m^3／h、反应器入口温度60-70℃、氨硫化学计量比约1：1、系统连续运行和采用一体化的单电场进行脱硫副产物收集的条件下．得到结果：水蒸气／氨活化脱硫效果明显,并且有较好的副产物收集功能,收集效率20％～30％;副产物中SO4^2-：SO3^2-大于95：5,脱硫效率稳定大于90％,副产物收率大于85％。     

半干半湿法烟气脱硫主要影响因素分析

建立了半干法气流床烟气脱硫实验反应装置。实验研究了温度、绝对含湿量和飞灰对烟气脱硫的影响。烟气温度在65～130℃之间，绝对含湿量通过改变蒸汽量调节，在0％～10％之间，并且采用飞灰一次加入来模拟返灰，石灰与粉煤灰的比例分别为1：3，1：5和1：8。结果表明，没有水蒸气加入时，温度的升高对脱硫效率影响不大，加入水蒸气后温度为68℃左右时，脱硫效率最高；65℃时，绝对含湿量在7．3％时脱硫效率最高；在T=68℃、Ca／S：1．2时，与不加粉煤灰的脱硫剂相比，利用石灰／粉煤灰=1：8的混合脱硫剂时，脱硫效率提高了12．8％。     

烧结烟气氨-Fe(Ⅱ)NTA法同时脱硫脱硝

研究了烧结烟气氨-络合法同时脱硫脱硝。实验结果表明,氨-络合法可以实现烧结烟气同时脱硫脱硝,脱硫脱硝效率最高可达99%和40%。最佳运行条件为:Fe(NTA)浓度为0.075 mol/L,p H为5~6,停留时间为1.24 s(350 L/h的烟气流量)及55℃运行温度。     

氧化锌吸收-空气氧化法烟气脱硫实验研究

采用次氧化锌配制成的悬浮浆液脱除吸收模拟烟气中的SO2，吸收产物亚硫酸锌浆液再通过鼓风湿式氧化成硫酸锌溶液，以验证氧化锌吸收-空气氧化法烟气脱硫的效果。通过改变气体流量、SO2浓度、浆液温度及pH值等工艺参数，探索吸收和氧化过程的最佳控制条件。结果表明，氧化锌浆液对含SO2浓度从5800～8600mg／m^3的烟气脱除效率均可达到90％以上，吸收容量为3．9gSO2／15g次氧化锌；氧化过程控制吸收终点浆液pH值为5．0以及浆液温度在38℃．氧化率可达95％。     

高活性脱硫剂脱硫工艺的实验研究

对以粉煤灰为原料制备的高活性脱硫剂进行了半干法烟气脱硫实验研究，考虑添加剂、脱硫剂加入量、反应温度、烟气流量工艺因素的影响时该活性脱硫剂的脱硫性能；实验结果表明，加入添加剂后，脱硫效率提高1．5％～8．1％；当烟气流量〈2m^3／min，钙硫比取1．5—2．0范围时，脱硫效率较高；一定范围内反应温度变化对脱硫效率影响不大。     

活性炭法烟气脱硫脱硝试验研究

将活性炭法烟气脱硫脱硝工艺和循环流化床技术相结合,在自行设计的试验台上进行烟气同时脱硫脱硝试验。结果表明,活性炭给料量及烟气流量对脱硫脱硝效果的影响较小;在烟气排放温度范围(100～200℃)内,升高温度对脱硝有促进作用,对脱硫有抑制作用;水蒸气对脱硫效果的影响大于脱硝,其最佳工作区域为10%～12%(质量分数);SO2浓度的增加会降低脱硫脱硝效果,而NO浓度的增加对脱硫有促进作用,对脱硝影响不大;当NH3∶NO摩尔比达到1∶1时,可得到最佳脱硝效果,此时工艺的脱硫率>70%,脱硝率>40%。     

粗媒体颗粒流化床半干法烟气脱硫

开发了粗媒体颗粒流化床半干法烟气脱硫技术。在流化床内加入惰性粗媒体颗粒，改善脱硫剂与烟气的接触。延长脱硫剂在床内的停留时间，促进脱硫反应进行，提高脱硫效率和脱硫剂利用率。以工业用石灰石为脱硫剂，实验研究了粗媒体颗粒的加入量及其他操作条件对此过程脱硫效率的影响。结果表明：随着粗媒体颗粒粒径减小及床内加入量增加，烟气脱硫效率提高；随着Ca／S增大、饱和接近度降低、空速及脱硫剂颗粒粒径减小，脱硫效率提高。当粗媒体颗粒的静止床高为122mm，饱和接近度为15～18℃、空速为2850h^-1、钙硫比为1．0—1．1、脱硫剂粒径为64μm时，脱硫效率可达90％以上。     

FeSO4/Ac脱硫剂脱硫性能的研究

为寻找经济适用且具有较高效率的烟气脱硫方法．研制了FeSO4／Ac脱硫剂。并对FeSO4／Ac脱硫剂的脱硫性能进行了实验研究。实验研究结果显示,烟气中O2、水蒸气含量的多少及脱硫温度的高低会影响FeSO4／Ac脱硫剂的脱硫性能。实验证明,当n(O2):n(SO2)=7～10、n(H2O)：n(SO2)=3～5、脱硫温度取120℃时,FeSO4／Ac脱硫剂具有良好的脱硫性能,脱硫效率可达92．1％～96．8％。FeSO4／Ac脱硫剂能够再生重复使用。采用水蒸气加热再生法对FeSO4／Ac脱硫剂进行再生,实验结果显示,经4次加热法再生的FeSO4／Ac脱硫剂的脱硫效率仍能达到91％。     

氧化镁基催化剂及脱硝性能研究

为控制燃烧烟气中NOx的污染,对共混合方法制备的氧化镁基催化剂进行烟气直接催化分解法脱硝实验研究,分析模拟烟气脱硝塔内温度及床层高度及氧气浓度、NO浓度和空速对脱硝效率的影响.研究表明:氧化镁基催化剂可以采用直接催化分解法对烟气脱硝,脱硝率85%～95%,氧化镁基催化吸附剂组成为氧化镁、固化剂、添加剂;脱硝的床层高度4～5 cm,脱硝反应温度130～170℃,烟气空速2 500～3 000 h-1;研究推测出氧化镁基催化剂存在活性缺陷,并对脱硝机理进行了初步分析.     

Evaluation of trichloroethene recovery processes in heterogeneous aquifer cells flushed with biodegradable surfactants

The ability of two biodegradable surfactants, polyoxyethylene (20) sorbitan monooleate (Tween 80) and sodium dihexyl sulfosuccinate (Aerosol MA), to recover a representative dense non-aqueous-phase liquid (DNAPL), trichloroethene (TCE), from heterogeneous porous media was evaluated through a combination of batch and aquifer cell experiments. An aqueous solution containing 3.3% Aerosol MA, 8% 2-propanol and 6 g/l CaCl(2) yielded a weight solubilization ratio (WSR) of 1.21 g TCE/g surfactant, with a corresponding liquid-liquid interfacial tension (IFT) of 0.19 dyn/cm. Flushing of aquifer cells containing a TCE-DNAPL source zone with approximately two pore volumes of the AMA formulation resulted in substantial (>30%) mobilization of TCE-DNAPL. However, a TCE mass recovery of 81% was achieved when the aqueous-phase flow rate was sufficient to displace the mobile TCE-DNAPL toward the effluent well. Aqueous solutions of Tween 80 exhibited a greater capacity to solubilize TCE (WSR=1.74 g TCE/g surfactant) and exerted markedly less reduction in IFT (10.4 dyn/cm). These data contradict an accepted empirical correlation used to estimate IFT values from solubilization capacity, and indicate a unique capacity of T80 to form concentrated TCE emulsions. Flushing of aquifer cells with less than 2.5 pore volumes of a 4% T80 solution achieved TCE mass recoveries ranging from 66 to 85%, with only slight TCE-DNAPL mobilization (<5%) occurring when the total trapping number exceeded 2 x 10(-5). These findings demonstrate the ability of Tween 80 and Aerosol MA solutions to efficiently recover TCE from a heterogeneous DNAPL source zone, and the utility of the total trapping number as a design parameter for a priori prediction of DNAPL mobilization and bank angle formation when flushing with low-IFT solutions. Given their potential to stimulate microbial reductive dechlorination at low concentrations, these surfactants are well-suited for remedial action plans that couple aggressive mass removal followed by enhanced bioremediation to treat chlorinated solvent source zones.     

Chloroaromatic pollutants in mussels incubated in two finnish watercourses polluted by industry

Concentrations of different chlorinated compounds were measured in mussels incubated in two polluted watercourses, a river (the River Kymijoki) and a lake (Lake Vanaja) for four weeks in summer 1995. The sum concentrations of polychlorinated phenols (PCP) and biphenyls (PCB) were both about 1 μg/g lipid weight (lw) in Lake Vanaja mussels, while in the River Kymijoki mussels PCPs were non-detectable and PCBs were measured 120 ng/g lIw. The concentrations of toxic polychlorinated dibenzo-p-dioxin (PCDD) and dibenzofuran (PCDF) congeners ranged between <17 and 370 pg/g Iw in Lake Vanaja mussels and between <38 and 11,000 pg/g lw in the River Kymijoki mussels. Polychlorinated diphenyl ethers (PCDE) were detected in the mussels incubated in the River Kymijoki (0.4–1.1 ng/g Iw), but not in those incubated in Lake Vanaja. Polychlorinated phenoxyanisoles (PCPA) were measured 33 ng/g lw and polychlorinated phenoxyphenols (PCPP) 300 ng/g lw in the mussels incubated in the River Kymijoki. PCPAs were also detected in reference samples, which were sediment and pike from the River Kymijoki and Baltic salmon, seal and white-tailed sea eagle.     

The variation of street air levels of PAH and other mutagenic PAC in relation to regulations of traffic emissions and the impact of atmospheric processes

The occurrence of particle associated PAH and other mutagenic PAC was determined in 1996 in the street air of Copenhagen. In addition, particle extracts were tested for mutagenicity. The measurements were compared with previous measurements in 1992/1993. The levels had decreased in this period. The decrease was caused by an implementation of light diesel fuels for buses and the exchange of older petrol-driven passenger cars with catalystequipped new ones. About 65% of the reduction was caused by the application of the light diesel fuels. Under special conditions, chemical processes in the atmosphere produced many more mutagens than the direct emissions. The concentrations of S-PAC and N-PAC were 10 times lower than those of PAH, while the levels of oxy-PAH were in the same order of magnitude as those of PAH. Benzanthrone, an oxy-PAH, is proposed to be formed in the atmosphere in addition to direct emissions. Benzo(a)pyrene, often applied as an air quality criteria indicator, was photochemically degraded in the atmosphere. A strong increase in the mutagenic activities was observed to coincide with a depletion of benzo(a)pyrene.     

Teratological effects of pesticides in vertebrates: a review

Abstract

In the last decades, the use and misuse of pesticides in the agriculture have increased, having a severe impact on ecosystems and their fauna. Although the various effects of pesticides on biodiversity have been already documented in several studies, to our knowledge no consistent overview of the impact of pesticides in vertebrates, both terrestrial and aquatic, is available. In this review, we try to present a concise compilation of the teratogenic effects of pesticides on the different classes of vertebrates – mammals, birds, reptiles, amphibians and fish.     

Book review

The Pesticide Manual ‐ A World Compendium, 8th Edition, C.R. Worthing, Editor and S.B. Walker, Assistant Editor, British Crop Protection Council, BCPC Publications Sales, Bear Farm, Binfield, Bracknell, Berkshire RG12 5QE, England. 1987, 1100 pp., UK £50; Overseas £56. ISBN 0–948404–01–9.     

Patterns of volatile metabolites and nonvolatile trichothecenes produced by isolates of <Emphasis Type="Italic">Stachybotrys,Fusarium, Trichoderma,Trichothecium</Emphasis> and <Emphasis Type="Italic">Memnoniella</Emphasis>

We reported previously that trichodiene, a volatile trichothecene derivative, was produced by a Stachybotrys isolate, also known to produce highly cytotoxic, non-volatile, macrocyclic trichothecenes (satrotoxins). We investigated the relationship between the production of trichodiene and various non-volatile trichothecenes for several molds. Volatile metabolites were concentrated by adsorption on Tenax TA and analyzed by GC/MS, while non-volatile metabolites were separated by HPLC, derivatized and analyzed by GC/MS. Stachybotrys chartarum isolates producing macrocyclic trichothecenes secreted significantly larger amounts of trichodiene and other sesquiterpenes than isolates which only produced simple trichothecenes. The amounts of secreted trichodiene were relatively small in all cases. With the exception of Memnoniella, which excreted small amounts of sesquiterpenes, the other isolates produced varying amounts of sesquiterpenes, including trichodiene, as well as simple tricothecenes, no detectable trichodiene, but large amounts of griseofulvin derivatives. In Stachybotrys there is apparently a correlation between trichodiene and macrocyclic trichothecene production. In the remaining isolates, there was no simple relationship between trichodiene and non-volatile trichothecene synthesis. Trichodiene is produced in larger amounts by Stachybotrys isolates, which also produce satratoxins, but it will be difficult to utilize this metabolite to detect toxic isolates in buildings due to the relatively small amounts excreted.     

Observations on the influence of water and soil pH on the persistence of insecticides

Abstract

The pH‐disappearance rate profiles were determined at ca. 25°C for 24 insecticides at 4 or 5 pH values over the range 4.5 to 8.0 in sterile phosphate buffers prepared in water‐ethanol (99: 1 v/v). Half‐lives measured at pH 8 were generally smaller than at lower pH values. Changes in half lives between pH 8.0 and 4.5 were largest (>1000x) for the aryl carbamates, carbofuran and carbaryl, the oxime carbamate, oxamyl, and the organophosphorus insecticide, trichlorfon. In contrast, half lives of phorate, terbufos, heptachlor, fensulfothion and aldicarb were affected only slightly by pH changes. Under the experimental conditions described half lives at pH8 varied from 1–2 days for trichlorfon and oxamyl to >1 year for fensulfothion and cyper‐methrin. Insecticide persistence on alumina (acid, neutral and basic), mineral soils amended with aluminum sulfate or calcium hydroxide to different pH values and four natural soils of different pH was examined. No correlation was observed between the measured pH of these solids and the rate of disappearance of selected insecticides applied to them. These observations demonstrate the difficulty of extrapolating the pH dependent disappearance behaviour observed in homogeneous solution to partially solid heterogeneous systems such as soil.     

The chemical stability of formulations of some hydrolyzable insecticides in aqueous mixtures with hydrolysis catalysts

Abstract

The active ingredients in commercial formulations of malathion, oxamyl, carbaryl, diazinon, and chlorpyrifos diluted to “spray tank”; concentrations with buffered distilled or natural water of pH 4–9 were stable for at least 24 hr. Formulations of trichlorfon were not stable at pH 7 or above but disappearance rates were slower than for the pure chemical in homogeneous solution. Cupric ion was observed to be an effective catalyst for the hydrolysis of a variety of pure organophosphorus insecticides but did not catalyze hydrolysis of the active ingredients of the formulations examined. Increasing the dilution of the formulation increased the susceptibility of malathion, oxamyl, and carbaryl to hydrolysis.     

Organochlorine compounds in a three-step terrestrial food chain

The concentrations of 15 organochlorine chemicals (PCBs and pesticides) were studied in a Central European oak wood food chain system: Great tit (Parus major), caterpillars (Tortrix viridana, Operophtera brumata, Erannis defoliaria), and oak-leaves (Quercus robur). Juvenile tits receive organochlorines from the mother via egg transfer and, eventually to a greater extent, from the caterpillar food source during nestling period. The concentrations of PCB 153 (2,2′,4,4′,5,5′-hexachlorobiphenyl, the most abundant in this study) was found in leaf material at ca. 1 ng/g, in caterpillars 10 ng/g, and in bird eggs 170 ng/g on an average and on a dry mass basis.     

Knowledge transfer initiative between molecular biologists and environmental researchers and regulators

A Natural Environment Research Council (NERC) funded Knowledge Transfer (KT) workshop was held in the United Kingdom (UK) to identify the needs and opportunities in the application of molecular biology and ‘omics’ techniques to environmental monitoring and risk assessment. Attendees highlighted a lack of effective communication between end-users and researchers as well as difficulties with data interpretation as reasons behind the slow uptake of molecular biology and omics techniques. A number of promising areas in which new techniques could be implemented at a practical level in the very near future were identified, thereby raising the profile of these recent technologies and providing vital proof of concept work. Molecular taxonomy, bacterial source tracking and pre-screening of chemicals for potential toxicities were all viewed as areas in which omics and molecular techniques could have immediate value, with the aim of reducing cost, increasing efficiency and providing more comprehensive data of improved quality.