烧结烟气脱硫剂性能的研究

为了提高脱硫效率和合理利用烧结过程中产生的机头灰,在半干法烟气脱硫剂生石灰中,加入一定量的烧结机头灰作为脱硫催化剂。在测定机头灰与生石灰化学成分、粒度和比表面积的基础上,研究和分析了机头灰与生石灰的质量配比对于脱硫效率的影响。结果表明,脱硫剂与机头灰在粒径分布和比表面积上都较接近,但经过消化活化后的混合脱硫剂的比表面积明显增大。当机头灰添加量为脱硫剂质量的2%～5%时,脱硫效率提高了2%～3%。机头灰与生石灰的胶凝反应以及机头灰中Fe2O3的催化作用是主要的作用机理。     

三种钙基脱硫剂在CFBA烧结烟气脱硫中的对比试验研究

在一台处理能力5000m^3／h的循环流化床(CFBA)半工业性试验装置上,通过三种钢铁工业生产原料和废料构成的钙基脱硫剂的交叉对比试验研究,选择适于烧结烟气脱硫的脱硫剂。结果表明,以生石灰和烧结机头灰配制的脱硫剂各项技术指标较好,表现出良好的工业化运行效果。     

石灰石高温煤气脱硫的试验研究

采用天然石灰石做脱硫剂,在固定床上进行硫化氢高温脱除的试验研究,考察了脱硫剂粒径、反应温度、气速及高温煤气中H2对石灰石脱硫性能的影响,同时还用热重分析(TG)、扫描电镜(SEM)、X-射线衍射(XRD)等测试手段对脱硫剂的物相组成和结构等进行了表征。结果表明,脱硫剂的粒径对脱硫效果的影响很大,0.38～0.83 mm的石灰石脱硫效果最佳;温度对脱硫效果的影响比较复杂,最佳的操作温度为850℃;气速对脱硫效果的影响较明显,脱硫剂的穿透时间随气速的减小而加长;H₂对脱硫过程起阻碍作用,气速越小,这种阻碍作用越明显。     

制糖滤泥用于燃煤烟气的脱硫

介绍了以碳酸法制糖产生的固体废弃物——制糖滤泥作为脱硫剂进行湿法烟气脱硫的工程应用实例,分析比较了该工艺的运行状况、优势及成本。工程投产后,运行稳定,二氧化硫排放浓度可达到(85±10)mg/m3,远低于《山东省火电厂大气污染物排放标准》(DB37/664-2013)中的排放标准限值,与传统的石灰石/石灰湿法脱硫相比,燃煤烟气的脱硫运行费用降低了24.4%;同时,利用制糖滤泥作为脱硫剂进行烟气脱硫,彻底解决了制糖滤泥的处理难题,实现了废物资源化,提高了碳法制糖企业和燃煤企业的经济效益。     

半干法烧结烟气脱硫灰的氧化改性

半干法烧结烟气脱硫灰中含有大量CaSO_3,而CaSO_3对于脱硫灰的稳定性具有重要影响,限制了脱硫灰的处理和综合利用。为了解决该问题,采用低温静态氧化改性实验和高温动态焙烧改性实验,在掺加和不掺加催化剂条件下,对含CaSO_3的脱硫灰进行了氧化改性研究,并结合热重实验考察了半干法烧结烟气脱硫灰中CaSO_3的高温动态氧化改性效果。结果表明,在低温为45、75和90℃时,掺入不同催化剂对半干法烧结烟气脱硫灰中CaSO_3进行氧化改性2 h,效果依次为:MnO_2Fe_2O_3不掺催化剂V_2O_5,且CaSO_3的氧化率均低于2.2%;在不掺催化剂的条件下,在350℃以上焙烧30~60 min,CaSO_3的氧化率均可达到85%以上。结合热重分析结果发现,选择合适的焙烧温度和时间对提高CaSO_3的氧化率有重要作用。     

石灰和石灰石湿法脱硫系统运行控制指标探讨

钙基脱硫剂湿式脱硫系统是目前市场上广泛采用的烟气脱硫系统。文章分析了石灰和石灰石自身不同的物理化学特性对湿法脱硫系统运行控制指标的影响,得出了对于采用石灰和石灰石作为脱硫剂的湿式脱硫系统的最佳pH为8．0和5．8～6．2,脱硫浆液流量与烟气流量之比为10．0和5．6,钙硫比(化学过量比)为1．05～1．15和1．25～1．60。     

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＜2 m3/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.     

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122 mm,饱和接近度为15～18℃、空速为2850 h-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％。     

氟石膏中氟的分布及固氟脱酸改性

以工业副产物氟石膏为研究对象,通过筛分进行粒度分析,得到不同粒径pH值、水溶性氟以及总氟含量的变化规律;重点研究了掺入2种碱性工业副产物作为改性剂对氟石膏化学改性固氟脱酸的效果,从而确定改性剂的最佳掺量。结果表明,氟石膏中氟的分布有一定规律;掺加5%的电厂干法脱硫灰或2%钢铁厂烧结烟气脱硫灰能很好的起到固氟脱酸的效果。     

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.     

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.     

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.     

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.     

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.     

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.     

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.     

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.     

Radionuclides in pinon pine (Pinus edulis) nuts from los alamos national laboratory lands and the dose from consumption

Abstract

One of the dominant tree species growing within and around the eastern portion of Los Alamos National Laboratory (LANL), Los Alamos, NM, lands is the pinon pine (Pinus edulis). Pinon pine is used for firewood, fence posts, and building materials and is a source of nuts for food—the seeds are consumed by a wide variety of animals and are also gathered by people in the area and eaten raw or roasted. This study investigated the (1) concentration of ³H, ¹³⁷Cs, ⁹⁰Sr, ^totU, ²³⁸Pu, ^{239, 240}Pu, and²⁴¹ Am in soils (0‐ to 12‐in. [31 cm] depth underneath the tree), pinon pine shoots (PPS), and pinon pine nuts (PPN) collected from LANL lands and regional background (BG) locations, (2) committed effective dose equivalent (CEDE) from the ingestion of nuts, and (3) soil to PPS to PPN concentration ratios (CRs). Most radionuclides, with the exception of ³H in soils, were not significantly higher (p < 0.10) in soils, PPS, and PPN collected from LANL as compared to BG locations, and concentrations of most radionuclides in PPN from LANL have decreased over time. The maximum net CEDE (the CEDE plus two sigma minus BG) at the most conservative ingestion rate (10 lb [4.5 kg]) was 0.0018 mrem (0.018 μSv); this is far below the International Commission on Radiological Protection (all pathway) permissible dose limit of 100 mrem (1000 μSv). Soil‐to‐nut CRs for most radionuclides were within the range of default values in the literature for common fruits and vegetables.     

Degradation and sorption of imidacloprid in dissimilar surface and subsurface soils

Degradation and sorption/desorption are important processes affecting the leaching of pesticides through soil. This research characterized the degradation and sorption of imidacloprid (1-[(6-chloro-3-pyridinyl)-methyl]-N-nitro-2-imidazolidinimine) in Drummer (silty clay loam) and Exeter (sandy loam) surface soils and their corresponding subsurface soils using sequential extraction methods over 400 days. By the end of the incubation, approximately 55% of imidacloprid applied at a rate of 1.0 mg kg^?1 degraded in the Exeter sandy loam surface and subsurface soils, compared to 40% of applied imidacloprid within 300 days in Drummer surface and subsurface soils. At the 0.1 mg kg^?1 application rate, dissipation was slower for all four soils. Water-extractable imidacloprid in Exeter surface soil decreased from 98% of applied at day 1 to > 70% of the imidacloprid remaining after 400 d, as compared to 55% in the Drummer surface soil at day 1 and 12% at day 400. These data suggest that imidacloprid was bioavailable to degrading soil microorganisms and sorption/desorption was not the limiting factor for biodegradation. In subsurface soils > 40% of ¹⁴C-benzoic acid was mineralized over 21 days, demonstrating an active microbial community. In contrast, cumulative ¹⁴CO₂ was less than 1.5% of applied ¹⁴C-imidacloprid in all soils over 400 d. Qualitative differences in the microbial communities appear to limit the degradation of imidacloprid in the subsurface soils.