基于气液悬浮旋切掺混的气动旋流塔脱硫性能测试与分析

为了研制低运行能耗和高脱硫效率的新型脱硫塔,以满足国家最新环保超低排放标准,采用基于气液悬浮旋切掺混的气动旋流塔脱除燃煤烟气中的SO_2污染物,对其内部气动旋流单元的强化传质脱硫性能进行探究,考察了空塔喷淋段和气动旋流段的喷淋层位置和液气比对脱硫效率及系统阻力的影响,并对气动旋流单元的脱硫效率进行了理论计算模拟。结果表明:喷淋层距浆液池高度越高,液滴在吸收区停留的时间越长,脱硫效率越高,系统运行阻力也越大;增加液气比,可显著提高系统的脱硫效率,单层喷淋层阻力约为150 Pa;在低pH工况下,SO_2吸收过程为液膜控制,气动旋流单元的脱硫效率较低;随着pH的增大,SO_2吸收过程逐渐由液膜控制转变为双膜甚至气膜控制,气动旋流单元的脱硫效率逐渐增强;当pH=5时,液气比=25 L·m~(-3),5层喷淋层运行工况下的脱硫效率高达99.82%。气动旋流单元的脱硫效率模拟计算结果表明:在高pH下,气动旋流单元的脱硫效率更高;当pH=5.5时,气动脱硫单元的脱硫效率为62.56%,阻力为360 Pa,实验数据与理论计算曲线吻合较好。以上研究结果可为新型高效燃煤机组脱硫超低排放改造技术的开发及其在环境污染控制领域的应用提供参考。     

双循环多级水幕吸收塔烟气除尘脱硫性能研究

以改进后的双循环多级水幕塔对烟气进行除尘脱硫性能的研究,利用双循环不同pH值控制的优点和多级水幕的效果,增加气液接触面积和传质动力,提高SO₂吸收效果。在正交实验的最佳运行工况基础上,实验从烟气流量、上下两段pH、L/G和SO₂进气浓度等方面进行单因素研究。结果表明,除尘效率维持在98%以上,进气SO₂浓度在5 000 mg/m³以下时,脱硫率在93%以上。上段pH值为6、下段pH值为5、L/G在15左右的脱硫效率和运行工况最佳,无结垢现象发生。改进后的吸收塔具有良好的应用前景,实验结果对于现场脱硫设备的调试和运行有很好的参考价值。     

湍球塔和喷淋塔的海水脱硫冷态实验对比

通过湍球塔和喷淋塔的海水脱硫冷态实验对比,研究海水脱硫过程中烟气和海水参数对湍球塔和喷淋塔脱硫的不同影响。实验结果表明,SO2分压力增大,脱硫效率和尾水pH值减小;海水碱度、pH值和液气比增大,脱硫效率和尾水pH值也随之增大;湍球塔的脱硫效率和尾水pH值与液气比改变方式无关,实验用湍球塔的合适液气比值为2.3 L/m3;湍球塔脱硫实验中,塔内气速为1.58 m/s,SO2分压力为20 Pa,水温为10.2℃,液气比为1.1~2.8 L/m3时,尾水pH值在2.4~2.8之间;增大液气比时,喷淋塔改变海水流量的脱硫效果要比改变气体流量的脱硫效果明显;塔内气速1 m/s以上时,一级喷淋塔的脱硫效率要比湍球塔小很多,有时只有湍球塔的1/2左右。     

NaClO2/NaClO复合吸收液同时脱硫脱硝

针对NaClO2氧化吸收法脱硫脱硝成本过高,难以实现工业化的现状,提出了以NaClO2/NaClO为复合吸收剂的同时脱硫脱硝新方法,比单独NaClO2方法效率高,成本低。考虑实际工况条件,给定SO2与NO的初始浓度分别为2 850 mg/m3和670 mg/m3。结果表明,吸收液初始pH为6.0,液气比L/G为20 L/m3,反应温度为55℃时,平均脱硫脱硝效率分别可达99.8%和94.0%。在此基础上对反应机理进行了分析,总结出实验反应主反应方程式。该方法设备简约,操作简单,容易实现全自动控制,综合成本可以接受,比较适合中小型燃煤锅炉的烟气污染治理。     

半干半湿法烟气脱硫技术的工业应用研究

探讨了日本半干半湿法脱硫除尘系统和中国环境科学研究院半干半湿法烟气脱硫除尘示范系统的主要差别 ,研究了半干半湿法烟气脱硫技术在出塔烟气温度、钙硫摩尔比和循环粉煤灰返灰等方面对脱硫效率的影响。结果表明 ,在脱硫塔出口烟气温度为 78℃、m(循环粉煤灰返灰 )∶ m(石灰 )为 1∶ 4、n( Ca)∶ n( S) <1.2时 ,脱硫效率达 85 .1%;在 n( Ca)∶ n( S) =1.4时 ,脱硫效率可达 88.3 %。     

内循环流化床烟气脱硫技术的实验研究

通过对流化床烟气脱硫吸收塔塔顶和塔底结构的改进,开发出一种新的内循环流化床烟气脱硫工艺。该工艺以60～80目细砂作为主要床料,在流化气速为2～5m/s情况下,实现了绝大部分固体颗粒在脱硫塔内的内循环,从而强化了热质传递,避免了粘壁现象。考察了各种因素对脱硫效率的影响,结果表明,绝热饱和温度差是影响脱硫效率的显著因素,颗粒浓度是保证系统稳定运行的关键因素。在Ca/S为12和颗粒浓度为10kg/m3条件下,系统能连续稳定运行,脱硫效率达90%以上。     

新型滤槽除尘器配套脱硫工艺试验研究

采用半干法脱硫系统与新型滤槽除尘器相结合 ,可有效提高系统的脱硫、除尘效率。研究了影响该技术脱硫效率的主要因素。该技术集脱硫、除尘于一体 ,工艺简单 ,运行成本较低 ,尤其适用于燃煤含硫量≤ 1 .2 %的锅炉烟气的脱硫。     

全沸腾式烟气脱硫除尘技术的研究

文中介绍了QFTC型全沸腾式脱硫除尘器的基本工作原理、装置结构形式及主要特点、主要技术经济指标、实际应用效果。结果表明 ,在未加脱硫剂情况下 ,脱硫效率达到 63.9% ,除尘效率达96.3%。它具有运行可靠、高效、简单和投资低等优点     

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.     

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73%时脱硫效率最高;在T=68℃、Ca/S=12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128%。     

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.