堆肥系统的通风设计

对堆肥系统的两种不同风机选型方法及计算结果进行了比较。根据计划结果,方法二所选风机的风量、风压和功率都大于方法一所选的风机。对于堆肥系统,目前常用的风机选型风机的风量比较适宜。     

烟热分离系统砖瓦隧道窑的数值模拟及烟气含氧量影响因素分析

为降低砖瓦隧道窑烟气含氧量,使烟气中的污染物稳定达标排放,设计了正交实验并应用数值模拟方法对影响砖瓦隧道窑烟气含氧量的因素进行了分析;在此基础上,调整了相关参数并进行了现场运行测试及数值模拟方法的实测验证.结果 表明:现场测试结果与数值模拟结果具有良好的一致性;降低排烟风机入口压力、急冷风机风量和冷却风机风量有利于降低烟气含氧量;以标况排烟风量为评价指标,各因素对烟气含氧量的影响程度依次为:排烟风机入口压力＞急冷风机风量＞余热风机入口压力＞冷却风机风量.在隧道窑稳定运行情况下,仅通过调整排烟风机运行状态进行烟气含氧量控制实验,结果表明,烟气含氧量由调控前的18.24％降低至16.57％～17.12％,标准状态下烟气量由24000 m3·h-1降至19000～20000 m3·h-1.在该隧道窑排烟风机运行状态优化调整后,已稳定运行6个月,且烟气含氧量稳定控制在18％以下.本研究结果可为隧道窑烟气含氧量控制及烟热分离系统的调控提供参考.     

两室堆肥生物反应装置研究

以堆肥过程中物料平衡、热量平衡以及垃圾生物发酵特性为依据,设计了二室堆肥生物反应装置,并通过堆肥试验实际检验反应装置设计的合理性.装置主要结构包括:二室堆肥发酵仓、保温层、通风供氧系统、空气加热系统以及二次污染控制系统.装置的主要特点为:两发酵仓能够独立完成堆肥发酵,也可以实现堆肥一次、二次发酵串联工艺组合;通过二次污染控制系统,可以很好地减少堆肥过程中产生的废水臭气排放;采用空气加热系统,可以快速均匀地加热堆体,以满足不同堆肥工艺的需要.装置在试验研究以及小规模垃圾堆肥处理领域有一定的应用价值.     

生活垃圾仓式静态好氧发酵供风系统工艺设计

生活垃圾堆肥厂的核心——发酵系统对堆肥产品的质量和成本起着决定性的作用，所以其设计显得至关重要。结合多年的科研及工程实践经验，就垃圾仓式静态好氧发酵供风系统工艺设计中供风形式、方式选择，风量、风压计算以及供风控制形式选择等几个关键部分做了详细介绍。     

城市生活垃圾堆肥试验装置的设计

堆肥装置是研究堆肥过程中各种参数变化和获取优化参数的必不可少的工具.本文从堆肥维持其温度的先决条件出发,并在大量调研的基础上确定了实验室好氧发酵装置的合理尺寸、渗沥水收集和回喷系统、布气系统等.该装置的尺寸为长1 m,宽0.5 m,高0.6 m,堆料的高度为0.48 m;根据垃圾样品的理化性质,确定了渗滤液回喷的时间为116 s、鼓风机的风量为0.055 m3/min,风压为300 Pa,并且对其引入自动控制设备,使通风工作5 min、休息35 min.最后利用生活垃圾堆肥试验验证该装置满足堆肥的一次发酵要求.该装置采用自动控制系统,布水、布气均匀,保温效果好,发酵过程温度测定方便快捷,而且还有功率消耗小、臭气集中易于处理的优点.     

风机盘管回风口加装驻极体过滤器过滤PM_(2.5)性能分析

针对空调系统末端装置用风机盘管不具备过滤PM_(2.5)功能的问题,在风机盘管回风口加装具有低阻特性的驻极体空气过滤器进行了性能测试分析。以蜡烛燃烧产生的颗粒物作为室内PM_(2.5)的尘源,将3种不同过滤面积的驻极体空气过滤器分别安装在风机盘管回风口,测试了风机盘管在不同风量(额定风量、75%额定风量、50%额定风量)下运行时其对PM_(2.5)过滤性能及在30 min内室内PM_(2.5)浓度衰减率。结果表明:加装驻极体空气过滤器后风机盘管瞬时过滤效率可达到66%以上、在30 min内室内PM_(2.5)的浓度衰减率可以达到54.8%以上;在相同风量下风机盘管的瞬时过滤效率、处理风量随加装过滤器过滤面积增加而提高;以PM_(2.5)浓度衰减率作为指标,可以判断出回风口加装过滤面积为1.88 m2的过滤器净化效果最优,其在不同风量下30 min内PM_(2.5)浓度衰减率分别为87.4%、84.7%和77.3%,且在不同风量下工作时均能在30min内使室内PM_(2.5)浓度达到环境空气质量标准一级日平均浓度限值。     

烟气脱硫系统增压风机仿真模型开发及应用

在大型火力发电机组烟气脱硫脱硝系统的仿真过程中,增压风机是风烟系统仿真的核心。根据脱硫增压风机静态性能曲线的特点,采用偏最小二乘法的曲面拟合理论与风机有关定律,实现了回归建模、数据结构简化以及两组变量之间的相关性分析,可将增压风机的性能曲线簇转化为满足应用精度的函数,对风机的压头、导叶角度、风量和全压效率等关键参数进行实时仿真。太仓港环保电厂的工程应用表明：风机压头仿真模型曲线拟合值与实际值比较接近,绝对误差在0.005～0.06 kPa之间,相对误差在0.1%～1.5%之间;全压效率仿真模型曲线拟合值与实际值较风机压头大,绝对误差在0.1%～2.5%之间,相对误差在0.15%～3%之间,基本满足工程应用精度。     

城市污水污泥处置方式的温室气体排放比较分析

针对我国现在主流的城市污水污泥处置方法:填埋,焚烧,堆肥。用IPCC中推荐的方法和缺省值,对处置过程中产生的温室气体的直接排放、间接排放和替代排放做了计算和分析。填埋过程计算排放的温室气体有CH4,焚烧过程计算排放的有温室气体CO2和N2O,堆肥过程计算的排放的有温室气体CO2和N2O,最终比较的结果都折算成CO2的排放。结果表明,污泥填埋、焚烧、堆肥所产生的CO2的净排放量分别为695.847 kg CO2/t、443.643 kg CO2/t、511.817 kgCO2/t。由于考虑了堆肥以后的有机肥利用,从减排以及污泥资源化的角度分析,得出堆肥是相对好的污泥处置方式。     

城市污水处理厂鼓风曝气系统节能

鼓风曝气系统是城市污处理厂重要设施，其耗电量占全厂的４０％～５０％，因此是污水厂节能的关键，文章针对鼓风曝气系统节能技术，分析了控制风管，曝气深度等与氧传 关系进行并给出了不同条件下供气量的计算方法，最后论述了实施控制风量技术时应考虑民流率搅拌强度，风机本身调节限度以及经济性分析等问题。     

城市生活垃圾堆肥试验装置的设计

堆肥装置是研究堆肥过程中各种参数变化和获取优化参数的必不可少的工具。本文从堆肥维持其温度的先决条件出发，并在大量调研的基础上确定了实验室好氧发酵装置的合理尺寸、渗沥水收集和回喷系统、布气系统等。该装置的尺寸为长1m，宽0．5m，高0．6m，堆料的高度为0．48m；根据垃圾样品的理化性质，确定了渗滤液回喷的时间为116S、鼓风机的风量为0．055m^3／min，风压为300Pa，并且对其引入自动控制设备，使通风工作5min、休息35min。最后利用生活垃圾堆肥试验验证该装置满足堆肥的一次发酵要求。该装置采用自动控制系统，布水、布气均匀，保温效果好，发酵过程温度测定方便快捷，而且还有功率消耗小、臭气集中易于处理的优点。     

A comparison of numerical solutions of partial differential equations with probabilistic and possibilistic parameters for the quantification of uncertainty in subsurface solute transport

Traditionally, uncertainty in parameters are represented as probabilistic distributions and incorporated into groundwater flow and contaminant transport models. With the advent of newer uncertainty theories, it is now understood that stochastic methods cannot properly represent non random uncertainties. In the groundwater flow and contaminant transport equations, uncertainty in some parameters may be random, whereas those of others may be non random. The objective of this paper is to develop a fuzzy-stochastic partial differential equation (FSPDE) model to simulate conditions where both random and non random uncertainties are involved in groundwater flow and solute transport. Three potential solution techniques namely, (a) transforming a probability distribution to a possibility distribution (Method I) then a FSPDE becomes a fuzzy partial differential equation (FPDE), (b) transforming a possibility distribution to a probability distribution (Method II) and then a FSPDE becomes a stochastic partial differential equation (SPDE), and (c) the combination of Monte Carlo methods and FPDE solution techniques (Method III) are proposed and compared. The effects of these three methods on the predictive results are investigated by using two case studies. The results show that the predictions obtained from Method II is a specific case of that got from Method I. When an exact probabilistic result is needed, Method II is suggested. As the loss or gain of information during a probability–possibility (or vice versa) transformation cannot be quantified, their influences on the predictive results is not known. Thus, Method III should probably be preferred for risk assessments.     

Estimating the emission source reduction of PM10 in central Taiwan

Three theoretical parent frequency distributions; lognormal, Weibull and gamma were used to fit the complete set of PM10 data in central Taiwan. The gamma distribution is the best one to represent the performance of high PM10 concentrations. However, the parent distribution sometimes diverges in predicting the high PM10 concentrations. Therefore, two predicting methods, Method I: two-parameter exponential distribution and Method II: asymptotic distribution of extreme value, were used to fit the high PM10 concentration distributions more correctly. The results fitted by the two-parameter exponential distribution are better matched with the actual high PM10 data than that by the parent distributions. Both of the predicting methods can successfully predict the return period and exceedances over a critical concentration in the future year. Moreover, the estimated emission source reductions of PM10 required to meet the air quality standard by Method I and Method II are very close. The estimated emission source reductions of PM10 range from 34% to 48% in central Taiwan.     

Indoor pollutant mixing time in an isothermal closed room: an investigation using CFD

We report on computational fluid dynamics (CFD) predictions of mixing time of a pollutant in an unventilated, mechanically mixed, isothermal room. The study aims to determine: (1) the adequacy of the standard Reynolds Averaged Navier Stokes two-equation (k−) turbulence model for predicting the mixing time under these conditions and (2) the extent to which the mixing time depends on the room airflow, rather than the source location within the room. The CFD simulations modeled the 12 mixing time experiments performed by Drescher et al. (Indoor Air 5 (1995) 204) using a point pulse release in an isothermal, sealed room mechanically mixed with variable power blowers. Predictions of mixing time were found in good agreement with experimental measurements, over an order of magnitude variation in blower power. Additional CFD simulations were performed to investigate the relation between pollutant mixing time and source location. Seventeen source locations and five blower configurations were investigated. Results clearly show large dependence of the mixing time on the room airflow, with some dependence on source location. We further explore dependence of mixing time on the velocity and turbulence intensity at the source location. Implications for positioning air-toxic sensors in rooms are briefly discussed.     

Throughfall below grassland canopies: a comparison of conventional and ion exchange methods

Sampling of canopy fluxes (throughfall and stemflow) below low structured vegetation with a small-scale, intricate canopy architecture is difficult, and representative sampling with most methods is questionable. In the present study, two sampling methods for canopy fluxes below grassland vegetation are compared. Method I sampled canopy fluxes of moisture inefficiently, because stemflow volumes were not quantitatively included. Canopy fluxes of ions calculated with method I necessitated assumptions on equal concentrations in actually sampled throughfall and non-sampled stemflow. Method II sampled canopy fluxes of ions quantitatively, because the total volume of throughfall and stemflow percolated through a mixed bed of ion exchange resins below the canopy. Ion-specific differences between the two methods were observed. For ions with foliar leaching, such as K+ and Ca2+, higher canopy fluxes were recorded with method II than with method I. In contrast, for ions with foliar uptake, such as NH4+ and NO3-, canopy fluxes were found to be less with method II than with method I. Canopy fluxes of inorganic nitrogen below Mesobrometum grassland were 2.35 and 1.52 kmol(c) ha(-1) year(-1) for methods I and II, respectively, and 2.85 and 7.90 kmol(c) ha(-1) year(-1) for K+. It is argued that these differences result from under-estimated (foliar leaching) or over-estimated (foliar uptake) concentrations in stemflow by the first method. Canopy fluxes for SO4(2-) were not statistically different, indicating that canopy exchange of SOx was quantitatively unimportant, and that both methods estimated atmospheric input equally well.     

Tank atmosphere perturbation: a procedure for assessing flashing losses from oil storage tanks

A new procedure to measure the total volume of emissions from heavy crude oil storage tanks is described. Tank flashing losses, which are difficult to measure, can be determined by correcting this value for working and breathing losses. The procedure uses a fan or blower to vent the headspace of the storage tank, with subsequent monitoring of the change in concentrations of oxygen or other gases. Combined with a separate determination of the reactive organic carbon (ROC) fraction in the gas, this method allows the evaluation of the total amount of ROC emitted. The operation of the system is described, and results from measurement of several storage tanks in California oil fields are presented. Our measurements are compared with those obtained using the California Air Resources Board (CARB) 150 method.     

Tank Atmosphere Perturbation: A Procedure for Assessing Flashing Losses from Oil Storage Tanks

Abstract

A new procedure to measure the total volume of emissions from heavy crude oil storage tanks is described. Tank flashing losses, which are difficult to measure, can be determined by correcting this value for working and breathing losses. The procedure uses a fan or blower to vent the headspace of the storage tank, with subsequent monitoring of the change in concentrations of oxygen or other gases. Combined with a separate determination of the reactive organic carbon (ROC) fraction in the gas, this method allows the evaluation of the total amount of ROC emitted. The operation of the system is described, and results from measurement of several storage tanks in California oil fields are presented. Our measurements are compared with those obtained using the California Air Resources Board (CARB) 150 method.     

Evaluation of Method 25 Nonmethane Organic Analyzer Design

Under contract to the U.S. Environmental Protection Agency, Research Triangle Institute has been conducting research to improve the precision, accuracy and limit of detection attainable with the EPA Method 25 nonmethane organic (NMO) analyzer. In Method 25, volatile organic carbon (VOC) samples are collected by drawing gas from an emitting source through a dry ice cooled sample trap and into an evacuated collection tank. The hydrocarbon concentration emitted from the source is determined on a per-carbon basis by catalytically converting the trap and tank sample fractions to CO₂ and quantitating the amount of CO₂ produced using the NMO analyzer. A reduction catalyst evaluation led to the selection of an NMO analyzer reduction catalyst which operates at a moderate temperature and displays no appreciable effect on peak shape. A gas chromatographlc column system which provides better permanent gas separation and hydrocarbon quantitation was also selected for use in the NMO analyzer.     

Modelling the adsorption of mercury onto natural and aluminium pillared clays

Introduction

The removal of heavy metals by natural adsorbent has become one of the most attractive solutions for environmental remediation. Natural clay collected from the Late Cretaceous Aleg formation, Tunisia was used as a natural adsorbent for the removal of Hg(II) in aqueous system.

Methods

Physicochemical characterization of the adsorbent was carried out with the aid of various techniques, including chemical analysis, X-ray diffraction, Fourier transform infrared and scanning electron micrograph. Batch sorption technique was selected as an appropriate technique in the current study. Method parameters, including pH, temperature, initial metal concentration and contact time, were varied in order to quantitatively evaluate their effects on Hg(II) adsorption onto the original and pillared clay samples. Adsorption kinetic was studied by fitting the experimental results to the pseudo-first-order and pseudo-second-order kinetic models. The adsorption data were also simulated with Langmuir, Freundlich and Temkin isotherms.

Results

Results showed that the natural clay samples are mainly composed of silica, alumina, iron, calcium and magnesium oxides. The sorbents are mainly mesoporous materials with specific surface area of <250 m² g^?1. From the adsorption of Hg(II) studies, experimental data demonstrated a high degree of fitness to the pseudo-second-order kinetics with an equilibration time of 240 min. The equilibrium data showed the best model fit to Langmuir model with the maximum adsorption capacities of 9.70 and 49.75 mg g^?1 for the original and aluminium pillared clays, respectively. The maximum adsorption of Hg(II) on the aluminium pillared clay was observed to occur at pH 3.2. The calculated thermodynamic parameters (?G°, ?H° and ?S°) showed an exothermic adsorption process. The entropy values varied between 60.77 and 117.59 J?mol^?1 K^?1, and those of enthalpy ranged from 16.31 to 30.77 kJ mol^?1. The equilibrium parameter (R _L) indicated that the adsorption of Hg(II) on Tunisian smectitic clays was favourable under the experimental conditions of this study.

Conclusion

The clay of the Aleg formation, Tunisia was found to be an efficient adsorbent for Hg(II) removal in aqueous systems.     

Air Pollution Control Measures for Hot Dip Galvanizing Kettles

ABSTRACT

Three commercially available conversion varnish coating “systems” (stain, sealer, and topcoat) were selected for an initial scoping study. The total volatile content of the catalyzed varnishes, as determined by U.S. Environmental Protection Agency (EPA) Method 24, ranged from 64 to 73 weight%. Uncombined (free) formaldehyde concentrations, determined by a sodium sulfite titration method, ranged from 0.15 to 0.58 weight% of the uncatalyzed varnishes. Each sealer and topcoat was also analyzed by gas chromatography (EPA Method 311). The primary volatile organic constituents included methyl ethyl ketone (MEK), isobutanol, n-butanol, methyl isobutyl ketone (MIBK), toluene, ethylbenzene, the xylenes, and 1,2,4-trimethylbenzene.     

A New Audit Technique for EPA Method 25

A simple, inexpensive, and accurate technique for evaluating or auditing the sampling, recovery, and analytical phases of EPA Source Reference Method 25 has been developed. The technique involves spiking a U-shaped stainless steel cartridge containing Tenax® with known quantities of selected organic compounds and thermally desorbing them at temperatures from 160°C to 180°C to generate organic vapors quantitatively. The major advantages of this technique are that no other measurement methods can be used to determine the generated organic concentrations in lieu of Method 25; and that the cartridge can easily be taken to the field for evaluation. The organic compounds generated in test runs are collected and analyzed using the Method 25 procedure. The generation of organics is quantitative and recoveries were found to be 100 ± 10%. The time required for desorption of the majority of organics is generally less than forty-five minutes at a flow rate of 100 mL/min; however, based on laboratory experience the recommended sampling time is sixty minutes. These spiked cartridges are stable at room temperature over a two-month period. Results of interlaboratory studies showed close agreement with the expected concentrations based on calculations from the mass loadings and sample volumes.