Pollution Abatement Energy Usage of Gas Treating and Processing Plants

The body of information presented in this paper is directed to individuals dealing with energy distribution and environmental issues. Production of natural gas demands energy for abatement of air pollutants. Perspective of energy requirements for natural gas production is presented by analysis of a survey of about 20% of the operating gas plants in Texas. The variation of fuel requirements for production is determined for inlet gas streams with increasing concentrations of toxic contaminants. Then the energy requirements of specific abatement devices is presented and the resultant cost of preparing natural gas for distribution is outlined. The average abatement energy requirement is 1.5% of the total energy requirement for gas processing or consumption of less than 0.1 % of the marketed production of natural gas.     

One-dimensional simulation of solute transfer in saturated-unsaturated porous media using the discontinuous finite elements method

A one-dimensional transport model for simulating water flow and solute transport in homogeneous-heterogeneous, saturated-unsaturated porous media is presented. The model is composed of a combination of accurate numerical algorithms for solving the nonlinear Richard's and advection-dispersion equations (ADE). The mixed form of Richard's equation is solved using a standard finite element method (FEM) with primary variable switching. The transport equation is solved using operator splitting, with the discontinuous finite element method (DFE) for discretization of the advective term. A slope limiting procedure for DFE avoids numerical instabilities but creates very limited numerical dispersion for high Peclet numbers. An implicit finite differences scheme (FD) is used for the dispersive term. The unsaturated flow and transport model (Wamos-T) is applied to a variety of rigorous problems including transient flow, heterogeneous medium and abrupt variations of velocity in magnitude and direction due to time-varying boundary conditions. It produces accurate and mass-conservative solutions for a very large range of grid Peclet numbers. The Wamos-T model is a good and robust alternative for the simulation of mass transport in unsaturated domain.     

One-dimensional simulation of solute transfer in saturated–unsaturated porous media using the discontinuous finite elements method

A one-dimensional transport model for simulating water flow and solute transport in homogeneous–heterogeneous, saturated–unsaturated porous media is presented. The model is composed of a combination of accurate numerical algorithms for solving the nonlinear Richard's and advection–dispersion equations (ADE). The mixed form of Richard's equation is solved using a standard finite element method (FEM) with primary variable switching. The transport equation is solved using operator splitting, with the discontinuous finite element method (DFE) for discretization of the advective term. A slope limiting procedure for DFE avoids numerical instabilities but creates very limited numerical dispersion for high Peclet numbers. An implicit finite differences scheme (FD) is used for the dispersive term.The unsaturated flow and transport model (Wamos-T) is applied to a variety of rigorous problems including transient flow, heterogeneous medium and abrupt variations of velocity in magnitude and direction due to time-varying boundary conditions. It produces accurate and mass-conservative solutions for a very large range of grid Peclet numbers. The Wamos-T model is a good and robust alternative for the simulation of mass transport in unsaturated domain.     

活性炭纤维净化印刷过程产生的VOCs废气

介绍了应用局部排气的方法,收集印刷过程的挥发性有机化合物(VOCs)废气,应用活性炭纤维(ACF)吸附脱附有机废气回收净化装置,进行印刷厂VOCs废气的回收与治理,详细描述了印刷车间VOCs废气的收集与处理工艺过程及其效果.测试结果表明,应用此工艺和设备可以有效地进行印刷过程大风量的VOCs废气的回收和治理.     

Detection of biomass burning smoke in satellite images using texture analysis

Classification results using texture analysis is presented for forest fire smoke from satellite remote sensing data. Texture analysis is carried out for normalized difference images calculated from visible and thermal infrared images of the Indonesian forest fire in 1997. Smoke regions are identified by assuming threshold values for the resulting texture feature as well as for radiances in the original and difference images. It is found that when the thresholds are chosen appropriately for GMS visible and infrared spin scan radiometer, 94% pixels exhibit agreement between the classification results using the texture analysis and the supervised Euclidean classification. Agreement is found for 96% pixels in mutual verification using the VISSR image and a concurrent NOAA advanced very high resolution radiometer image. A correlation coefficient of 0.91 is obtained between the results from the two sensors in the variation of the number of smoke pixels accumulated for 12 days in September 1997. Additionally, it is confirmed that as the threshold value of the texture feature is increased, the variation range of the aerosol optical thickness is also increased. As a whole, this study indicates that texture analysis provides quite reasonable results in the smoke detection when appropriately combined with the spectral information.     

Effect of Dust Concentration Upon the Gas-Flow Capacity of a Cyclonic Collector

The flow rate through an industrial gas-cleaning cyclone at a fixed pressure drop is greater when the incoming gas is dusty than when it is clean. This observation by Briggs for a single cyclone tube was extended to multiple tubes, and ike results compared to observations by Soo and Trezek that the fraction factor for turbulent flow in a pipe is less for dusty gas than for clean. Empirical considerations indicated tJtat both of these observations should be connected with a rather large reduction in gas viscosity due to the dust. This predicted viscosity decrease was later observed. A physical theory accounting for viscosity reduction by a dust cloud is proposed. This effect also offers a means for increasing the heat, transfer coefficient in gas heat exchangers.     

Non-isothermal gaseous exchange between soil and atmosphere

The theoretical and experimental basis of a non-isothermal rotary gas exchange (NRGE) between soil and atmosphere is given. A method of measurement for the NRGE intensity in porous media, including soil, is given and its validity is examined. The global NRGE of selected gases is determined. Relatively high NRGE intensities are found to exist for some gases. The heat transfer determination method is given. An electrical scheme for simulating the NRGE process is also described.     

酶体外定向分子进化技术:环境生物污染治理中的新星

环境生物技术在环境控制与污染治理中的应用主要是利用微生物降解和转换污染物.一些人类合成的化学物质由于具有高毒性,且难以被自然界微生物降解,已经严重威胁生态环境和人类的健康.生物治理以其低成本、完成矿质化和实现原位处理等特点,成为较好的治理技术.体外定向分子进化技术是一种发现新的生物表型和新酶的好方法,DNA改组是重要的体外分子进化技术,成功地改造了许多在医药、工业和环境保护等的商业酶.综述了近年来体外定向分子进化技术在环境生物污染治理中的研究进展和应用.     

海水改性沸石处理氨氮废水

沸石因具有独特的架状结构而表现出良好的选择吸附和离子交换性能,在废水处理中被广泛应用,但吸附容量偏低,需要进行改性。针对天然沸石的局限性,研究了不同改性方法对氨氮吸附的影响,确定了最佳的沸石改性方法,并进行了吸附等温模型,吸附动力学研究。结果表明,采用高温300℃焙烧后再用预处理后的海水浸泡24 h改性沸石去除氨氮效果最佳。当活化沸石投配量为10 g/L,接触时间为150 min,进水氨氮浓度为37.91 mg/L时,沸石对氨氮吸附容量为4.08 mg/g,氨氮去除率为90.45%;沸石及改性沸石对氨氮的吸附等温线符合Langmuir方程和准一级动力学方程。用海水来改性沸石的方法,不仅可提高沸石对氨氮的吸附容量和吸附速度,而且无任何添加药剂,具有简单易行、费用低廉的优点,为沸石在水处理工程中的应用提供技术支撑。     

Economic insight into municipal solid waste management in Mumbai: a critical analysis

Mumbai generates 6256 tonnes of waste every day, of which 17.20% is recyclable, but only a fraction of this is retrieved by rag-pickers. The economic value of the retrieved material is not considered by the Municipal Corporation of Greater Mumbai in valuing the waste management system as there is no retrieval mechanism except the informal rag-picking activity. Moreover, the cost of land used for the dumping of waste is also not accounted for. In the present paper, a comprehensive cost-benefit analysis for the present system of municipal solid waste management in Mumbai is carried out, with due consideration for implicit or hidden costs and benefits. Accounting for the implicit costs and benefits showed a difference of $6 per every tonne of waste disposal. This could show a considerable difference in policy development at the municipality level. Demand supply analysis proved that the present system of waste management would not yield a feasible market solution without private sector participation. With the increasing demand for improved waste management, private sector participation is essential and a Pigouvian tax is a necessary tool to make the private sector participation in solid waste management a success.     

地理信息系统在累积影响评价中的应用

累积影响评价是在可持续发展目标要求下环境影响评价的一种新类型,但目前进行累积影响评价的方法和工具仍较缺乏。文章分析了利用地理信息系统进行累积影响评价的能力,结果表明：地理信息系统能改善对发展行为和环境状况的监测和跟踪,能较好地分析环境影响的时、空累积特征,是进行累积影响评价的有效工具;但是,其对环境影响累积过程的本质考虑有限,需要与能反映累积过程的子模式相结合。     

Phase-in of nonpoint sources in a transferable discharge permit system for water quality management: setting permit prices

The composite market design is a proposal for a transferable discharge permit system that specifically includes agricultural non-point-source dischargers and addresses both property rights and transaction cost problems. The first step to implementation of a composite market scheme is the estimation of a supply curve for abatement measures in the catchment area. Estimation is performed by combining costs with modeled loss reductions from selected best management practices and then using this information to estimate the supply curve for abatement, which in turn can then be used to set permit prices. The R?nne? catchment in southern Sweden is used as a pilot study area for making this type of estimate. Costs for existing measures that reduce nutrient losses from farmland (catch crops and spring planting) are based on existing programs financed by the Swedish Agricultural Board. A set of supply curves is calculated for these measures using retention estimates for seven subcatchments and three soil types in the area. Although existing information is sufficient to calculate partial supply curves and may be used to set permit prices, additional measures should be included as well as an increased number of variables for differentiating site specific reduction costs.     

A model for contaminant mass flux in capped sediment under consolidation

The paper presents a model for contaminant transport and flux through a consolidating subaqueous sediment and overlying cap. The formulation is based on the effect of consolidation and excess pore pressure dissipation on transient, nonlinear advective component of transport through sediment and the cap. The consolidation is induced by the buoyant weight of the cap when it is placed on the contaminated sediments. One equation is presented for advective-diffusive transport through the sediment that is dependent upon soil/contaminant properties and transient advective velocity, which is calculated from a second equation based on the Terzaghi consolidation theory. A third equation is provided to describe the transport of contaminants in the cap. The parameters, including advective velocity, and boundary conditions used for contaminant transport through the cap are derived from the solution of the first two equations. The finite difference method is used to solve the system of equations for consolidation and contaminant transport. A hypothetical case is analyzed to demonstrate the formulation, and the results show that advection due to consolidation can accelerate breakthrough of contaminant through the cap by orders of magnitude. The derivation and results show that consolidation should be included for cap design, and that reactive caps are essential for delaying and reducing dissolved contaminant flux.     

Meteorological conditions at the release site during the two tracer experiments

The state of the boundary layer at the release site during the two tracer experiments is described, based on measurements of atmospheric turbulence carried out by a sonic anemometer, profiles of horizontal and vertical wind by a SODAR as well as frequent radiosonde releases. The boundary layer height is derived from radiosoundings, modelled and discussed. The study is meant as background for discussions of the tracer behaviour near the release site, and possible influence of the local meteorology at the release site on the long-range dispersion. The difference in the initial meso-meteorological conditions between the two experiments is discussed and some of its consequences for the dispersion of the released tracer are clarified. It is concluded that the first experiment is well suited for validation of long-range transport and dispersion models, whereas the second experiment calls for further model development. It is concluded that the micrometeorological measurements are very important as background information for the understanding of plume behaviour on small as well as long scales.     

An analytical model for the interpretation of pulse injection experiments performed for testing the spatial variability of clay formations

This paper presents an analytical model to describe pulse injection experiments. This model solves the advection-diffusion equation while taking into account back diffusion from the clay core to the inlet and from the outlet to the clay core. In most analytical models, back diffusion is neglected. For sufficiently high Péclet numbers, this is a good approximation. However, in experiments where the Péclet number is low, back diffusion is important and must be taken into account. An additional advantage of the present model is that both concentration and flux are conserved at the inlet and at the outlet of the clay core. This model is used to fit pulse injection experiments with iodide and tritiated water (HTO) in clay cores. The (new) model is required for fitting the experimental results since in clay layers advection is very slow leading to a low Péclet number. The experiments are performed on clay cores taken from different depths from the Boom Clay and the Ypres Clay layer under the site of the nuclear power plant of Doel (Belgium). The quality of all fits is excellent and the obtained parameter values are coherent. For HTO, the fitted value for the diffusion accessible porosity is consistent with measurements of the water content in Ypres Clay cores. In both types of clays, the apparent diffusion coefficient at zero flow is between 10(-10) and 2 x 10(-10) m(2)/s for iodide and between 2 x 10(-10) and 3 x 10(-10) m(2)/s for HTO. The dispersion length is in the order of 10(-3) m. The average value for the diffusion accessible porosity is between 0.35 and 0.4 for HTO and between 0.2 and 0.25 for iodide.     

The mechanism and kinetics of ultrasound-enhanced electrochemical oxidation of phenol on boron-doped diamond and Pt electrodes

The research on ultrasound (US) enhanced electrochemical oxidation of Phenol (Ph) on boron-doped diamond (BDD) and Pt electrodes is studied. The enhancement by US on BDD is much greater than for Pt. With the assistance of US, the degradation rate and current efficiency on BDD are increased by 301% and 100%, respectively, while those on Pt are 51% and 49%. The difference of the enhancement on these two electrodes is caused by the fact that mass transport, adsorption amount and electrode reaction affected by US on BDD are different from those of Pt. The kinetics investigation on intermediates formed during electrochemical degradation show that the variety of intermediates produced on BDD is less than for Pt. In the presence of US, on both electrodes, no change occurred to the amounts of the intermediate species. However, time for intermediates to reach the highest concentration is cut down. This effect for degradation of Ph on BDD is more obvious than for Pt. The present research indicates that BDD is suitable for degradation of Ph by US assisted electrochemical oxidation.     

Multi-criteria analysis and risk assessment

ELECTRE or Concordance Analysis is a French system of multicriteria analysis which is used in economics.The application of ELECTRE for hazard evaluation and risk assessment of chemical substances is suggested, and a first attempt in adapting it for this purpose is presented.     

Determination of total arsenic content in water by atomic absorption spectroscopy (AAS) using vapour generation assembly (VGA)

Analysis of arsenic in water is important in view of contamination of ground water with arsenic in some parts of the world including West Bengal in India and neighboring country Bangladesh. WHO has fixed the threshold for arsenic in drinking water to 10ppb (microg/l) level, hence the methodology for determination of arsenic is required to be sensitive at ppb level. Atomic absorption spectrophotometry with vapour generation assembly (AAS-VGA) is well known technique for the trace analysis of arsenic. However, total arsenic analysis [As(III)+As(V)] is very crucial and it requires reduction of As(V) to As(III) for correct analysis. As(III) is reduced to AsH3 vapours and finally to free As atoms, which are responsible for absorption signal in AAS. To accomplish this the vapour generation assembly attached to AAS has acid channel filled with 10 M HCl and the reduction channel with sodium borohydride. Further sample can be reduced either before aspiration for analysis, using potassium iodide (KI) or the sample can be introduced in the instrument directly and KI can be added in the reduction channel along with the sodium borohydride. The present work shows that samples prepared in 3 M HCl can be reduced with KI for 30 min before introduction in the instrument. Alternatively samples can be prepared in 6 M HCl and directly aspirated in AAS using KI in VGA reduction channel. The latter methodology is more useful when the sample size is large and time cycle is difficult to maintain. It is observed that the acid concentration of the sample in both the situations plays an important role. Further reduction in acid concentration and analysis time is achieved for the arsenic analysis by using modified method. Analysis in both the methods is sensitive at ppb level.     

Sizing and Costing of fabric Filters Part II: Costing Considerations

This is the second of a two-part article that reviews baghouse filtration theory, presents size estimating methods, and gives costing procedures for a variety of baghouse types and sizes. Part I of the article discussed theory and sizing; this part presents costing. Information is given for estimating total capital investment including separate costs for the bare baghouse (five types), bags, and, where needed, cages and Venturis. Factors are given for installation and for indirect costs. Direct and indirect annual costs are discussed. An example problem is given. The material in this article is taken primarily from the EAB Control Cost Manual.     

Simple nomenclature for chlorinated camphenes and dihydrocamphenes from which structural information can be directly deduced

The systematic nomenclature for chlorinated camphenes and dihydrocamphenes is rather complicated and confusing. Therefore, a simple structure-related nomenclature is proposed for these compounds, which is based on the same logic as was recently used for the chlorinated bornanes, bomenes and bornadienes. Although final IUPAC rules for the systematic nomenclature for camphenes and dihydrocamphenes have not yet been presented, the present nomenclature can be used for retrieving the correct conformation without the help of extensive tables or computer programmes, and vice versa. When the final IUPAC rules will be presented, the present nomenclature can easily be adjusted, if necessary