活性炭变温脱附高浓度VOCs的工艺参数优化与评价

以甲苯为VOCs类代表性的目标污染物,通过搭建实验装置模拟活性炭吸附脱附处理VOCs工艺,并在不同工艺条件下 (脱附温度、表观风速、高径比) ,选取常见评价因子 (甲苯脱附率、甲苯浓缩比、脱附能耗比) 以探讨不同脱附工况下气体对各床层的脱附情况进行研究。结果表明,甲苯脱附率随脱附温度和表观风速的增加而增加。甲苯浓缩比随脱附温度和高径比的增加,随表观风速的减小而增加,即表观风速是浓缩比的主要控制因素。在中温范围内,低风速、高径比的甲苯浓缩比小于高风速、高径比。在高温范围内,低风速、高径比的甲苯浓缩比仅在峰值段大于高风速、高径比。脱附温度越高,表观风速越小,高径比越大,相同脱附率下的甲苯浓缩比越大。脱附能耗比随脱附温度和表观风速的减小,高径比的增加而降低,即表观风速是能耗比的主要控制因素。高温低风速时的能耗比比中温高风速时的能耗比低。当脱附温度80 ℃、表观风速0.3 m·s⁻¹时,脱附能耗比最低为1.170 6 kJ·g⁻¹。本研究可为变温脱附工程化应用的低碳化工艺优化提供参考。     

Dependence of the Wind Profile Power Law on Stability for Various Locations

Recent environmental regulations have increased the need for construction of meteorological towers at power generation facilities. Due to practical and economic considerations, tower heights are usually lower than effluent release heights. At heights where wind speed data are not available, the wind speed is usually estimated from the measured wind speed using the %th wind profile power law and assuming neutral stability conditions. This study examines published data for many locations and shows that the %th wind profile power law is often unrepresentative of actual conditions because the degree of variation of wind speed with height depends greatly on atmospheric stability. The frequency of neutral stability conditions also varies appreciably by site. These two considerations are especially important in dispersion models which extrapolate wind speed at stack height from low level wind speed data.     

高原山体遮挡对湖泊和城区风场的影响

为了探究高原山体遮挡对湖泊和城区上空风场变化的影响,选取昆明市西山和西山东侧的草海及部分城区为研究对象,以1∶1 800的缩尺比制作了实物模型,利用风洞实验模拟了有山体遮挡和无山体遮挡在主导风西南风作用下的风场变化,并结合数值模拟验证了有山体遮挡情况下的风洞实验。实验结果表明：山体遮挡对下风向的山脚区和湖泊区风速影响较大;山体高度为260和460 m时,距离山体4 500 m范围内山体对下风向山脚区和湖泊区中部及南部的风速削减较大;山体高度为110 m时,山体对下风向区域的影响主要体现在对山前风速的削减,并未对湖泊和城市区域产生较为明显的风速梯度变化。     

高原山地城市重气泄漏扩散的示踪实验研究

为分析高原山区城市(个旧市)重气泄漏扩散规律,进行了重气泄漏扩散环境风洞实验。实验表明,重气浓度主要集中于近地层,测点的重气浓度随风速增大先增大后减小,存在一个危险风速,通过曲线拟合所得危险风速值与风洞实验所得危险风速值相近。在该风速下,重气浓度达到最大,且粘滞系数也最大,结果表明,粘滞系数越大越不利于重气的扩散。     

防风网扬尘庇护区湍流流场模拟数值边界条件

防风网后方存在复杂的湍流结构,通过耗散能量、降低风速形成扬尘庇护区。数值风洞是研究防风网流场结构及预测堆场扬尘的重要方法,由于涉及复杂的大气边界层及多孔介质边界问题,建立高精度的数值风洞目前仍是计算流体的难题。通过一系列数值模拟并与物理实验对比分析,研究了影响防风网数值风洞模拟精度的3个边界条件,即紊流入流边界、地面粗糙边界和多孔介质边界。结果表明：计算域入流紊动强度对风场结构模拟结果具有较大影响,紊动不足能够造成高达50%以上的虚假庇护长度;数值风洞地面粗糙高度通过壁面函数影响流场结构,对防风网抑尘效应有较大影响;防风网阻风效果可利用多孔跳跃介质边界模型实现,模型中惯性阻力系数对模拟结果有较大影响,应根据风压损失系数、防风网厚度和雷诺数设定。     

Unsteady Tall Stack Dispersion of Chimney Emissions and its Application to Varying Wind Directions

A procedure for calculating the concentration at any point and time under varying emissions and mean wind conditions is developed based on exact integration of the governing conservation equation. The procedure is simple, easy to use and has no numerical instability difficulties. Application of the procedure shows the fast achievement of steady state concentration under steady chimney emissions and mean wind conditions. It is also suggested that the procedure be used to calculate the correction factor to the time-averaged concentrations determined by conventional computer or physical modelling for constant wind condition to account for the actual fluctuating mean wind direction condition. If the wind databank does not contain detailed minute-to-minute data for exact calculation of the correction factor, the sinusoidal wind assumption should give good approximation without adversely affecting the margin of safety for environmental protection. It is also suggested that the meteorological data bank should contain information on hourly amplitude and standard deviations of wind directions if storage is insufficient to store minute-to-minute wind data.     

Verification of the shelter effect of a windbreak on coal piles in the POSCO open storage yards at the Kwang-Yang works

The use of windbreaks to reduce wind-blown coal dust at the POSCO Kwang-Yang open storage yards was studied using wind simulations on a scale model of the yards. Based on these simulation results, a full-scale wind fence was constructed on two sides of the yard. Here, we present results on the wind behavior both for the real yard and for the simulation results that guided its construction. Wind-tunnel simulations were used to study the effect of a porous wind fence of porosity ε=30% on the surface pressure and shear stress on coal piles using a 1/1200 model of the POSCO Kwang-Yang open storage yards. In addition, the shelter effects found in the model system were verified in field measurements on the full-scale system. The storage yard model was fully embedded in an atmospheric surface boundary layer over open terrain. The fence and coal pile model had the same height (12.2 mm) and Reynolds number (Re=1.6×10⁴, based on the model height). The mean and fluctuating surface-pressure distributions on the coal piles, which are closely related to the dust emission from the surface, were measured for several directions of the oncoming wind. The wind directions pertinent to the study were determined by statistical analysis of seasonal wind data over the storage yard. A porous wind fence of porosity ε=30% was found to be useful for reducing the wind speed without the formation of a recirculating bubble behind the fence. In addition, the fence caught the wind-borne particles when it was located behind the coal piles. The wind fence reduced the pressure fluctuations and surface shear stress on the coal piles to less than half of the levels observed in the no fence case. To verify the effectiveness of the porous wind fence installed around the Kwang-Yang open storage yard, the local wind speed and the concentration of suspended particles were measured directly. Full-scale porous fences installed around the Kwang-Yang open storage yard greatly decreased the turbulence intensity of the wind over the coal piles and reduced the total suspension particles by 70–80%.     

Applying hourly measurements of meteorological data and aerosol soluble ions in Taipei Basin, Taiwan

This study applies observational data composed of hourly weather and aerosol to discuss the aerosol characteristics within different weather systems. Based on cluster analysis, spring weather in Taipei Basin 2004 was characterised as five weather systems: humid/low south wind speed, dry cold/high east wind speed, humid cold/east wind, dry cold/northeaster, and northwestern convection wind. Under the humid/low south wind speed and northwestern convection wind systems, there are predominant influences of local vehicle/motor pollutant emissions and secondary pollution on the air quality. Asian dust storms were usually occurred under the weather of dry cold/high east wind speed. The regional air quality is more acceptable during the period of prevalent humid cold/east wind and dry cold/northeaster.     

Numerical study of atmospheric dispersion of a substance released from an industrial complex in the southern coast of Korea

Diurnal variations of wind field and pollutant dispersion in a complex terrain with a shoreline were investigated under the insolation conditions of summer and winter. The area is located in the south of the Korean Peninsula and includes a large petrochemical industrial complex. The Regional Atmospheric Modeling System (RAMS) was used in the simulation study. Initially, horizontally homogeneous wind fields were assumed on the basis of sounding data at the nearby upper-air station for days with morning wind speeds below 2 m s⁻¹. On these days, the sea breeze prevailed in summer while the land breeze lasted for a few hours in the morning; the effect of synoptic winds was strong in winter with some inclusion of wind variations owing to the interaction between sea and land. The predicted wind direction at the location of the weather station captured an important change of the sea/land breeze of the observed one. In the morning, both in summer and winter, complicated wind fields with low wind speeds resulted in high pollutant concentrations almost all over the area. On the other hand, in the afternoon, the wind field was rather uniform and the terrain effects were not significant even in the mountainous area with the development of a mixing layer.     

Control of particle re-entrainment by wetting the exposed surface of dust samples

Experiments have been conducted in a wind tunnel to measure the emission factor of re-entrained particles from a dry or wetted dust sample with a smooth or rough surface. Effects of wind velocities and water contents in the sample on the emission factor also were investigated. The results show that re-entrainment of particles can be controlled efficiently in a certain period of time when the surface watering density is between 60 and 80 g/m2 at a wind velocity from 7 to 15 m/sec for both smooth and rough surfaces. After the effective period is elapsed, which depends on wind speeds and environmental conditions, water will eventually evaporate, and re-entrainment starts to occur again. The experimental water evaporation rates at different wind speeds are in good agreement with theoretical values. After watering for 210, 130, and 110 min at average wind velocities of 0, 2, and 4 m/sec, respectively, the dust sample must be replenished with water to avoid dust re-entrainment.     

Efficiency of deposition of pesticide droplets on flat cards and spheres

Abstract

The mass flux of a cloud of droplets heading towards a collector can be decomposed into its horizontal and vertical components. While only the vertical mass flux contributes to droplet deposition on a flat card by the mechanism of sedimentation, both flux components contribute to deposition on a sphere by both mechanisms of inertial impaction and sedimentation. Calculated collection efficiencies decrease as wind speed increases for cards but as wind speed increases for spheres, a minimum collection efficiency is reached at a certain wind speed. The average collection efficiencies, as measured in the field trial portion of this study, are highly linearly correlated with wind speed for cards. For spheres, however, no correlation was found between the average collection efficiency and wind speed.     

裸土风蚀型开放源起尘机制研究进展

中国北方多个城市空气颗粒物来源解析结果表明,开放源是空气颗粒物污染的主要来源,裸土风蚀型开放源是主要的排放源类.对裸土风蚀型开放源起尘机制进行了诠释,提出了裸土风蚀型开放源、裸土风蚀起尘、裸土风蚀尘的概念,并对裸土风蚀型开放源的风蚀影响因素进行了研究,为城市空气质量达标及空气颗粒物污染防治提供科学参考.     

高架连续点源落地浓度预测中风速的确定

高架连续点源污染物排放落地浓度是大气环境影响预测的主要内容。由于大气污染物扩散明显受气象条件尤其是风速的影响,而现有预测模型中对于风速的取值都是按经验值来确定的。通过分析在不同气象和烟源条件下,平均风速的计算方法对烟羽抬升高度以及最大落地浓度产生的影响,与实测值相比较确定了风速取值的合理方法,缩小了预测偏差。     

煤堆内CO浓度分布与变化规律的数值模拟

为了明确空隙率和风速等对煤堆长期堆放过程中堆内CO浓度（体积浓度）的影响规律,为煤堆长期堆放过程中和受扰动后的安全及环境问题提供理论支持,使用COMSOLMultiphysics5.0建立二维数值模拟模型,研究了堆内CO浓度随堆放时间、空隙率、风速变化时的分布与变化规律。结果表明,空隙率和风速低时堆内CO分布具有"烟囱"现象,且浓度高,随堆放时间延长堆内最大CO浓度具有"增长-降低-稳定"三段式变化规律,风速低时最大浓度与时间之间服从Gauss Amp函数分布,风速较大或时间较长堆内最大CO浓度基本稳定。     

Dry Removal of Gaseous Fluorine Pollutants

The conservation equations governing buoyant plume rise are solved for the case of non-uniform wind conditions. A power law is selected to represent the actual wind profile. Analytical solutions are presented both for uniformly stable and neutral atmospheric conditions. These solutions are shown to be of the same form as those obtained in the simpler uniform case but with the plume rise now depending explicitly on the wind speed shear. A sensitivity analysis of the effects on plume rise of typical variation in wind shear and entrainment reveals that the two quantities have an almost equal effect therefore justifying the use of the present model. To simplify computations a “uniform wind” is introduced such that when used in conjunction with Briggs' equations the results become consistent with those of the present theory.     

A routine to compute mean and standard deviation of fluctuating wind direction

A computer routine schematic, developed for use with micro-processor to compute mean wind direction and standard deviation of fluctuations in wind direction, is described. The main feature of the routine is overcoming of the ‘gap’ problem which arises due to discontinuity in the potentiometer of the wind vane.     

Numerical modeling on air quality in an urban environment with changes of the aspect ratio and wind direction

Due to heavy traffic emissions within an urban environment, air quality during the last decade becomes worse year by year and hazard to public health. In the present work, numerical modeling of flow and dispersion of gaseous emissions from vehicle exhaust in a street canyon were investigated under changes of the aspect ratio and wind direction. The three-dimensional flow and dispersion of gaseous pollutants were modeled using a computational fluid dynamics (CFD) model which was numerically solved using Reynolds-averaged Navier–Stokes (RANS) equations. The diffusion flow field in the atmospheric boundary layer within the street canyon was studied for different aspect ratios (W/H?=?1/2, 3/4, and 1) and wind directions (θ?=?90°, 112.5°, 135°, and 157.5°). The numerical models were validated against wind tunnel results to optimize the turbulence model. The numerical results agreed well with the wind tunnel results. The simulation demonstrated that the minimum concentration at the human respiration height within the street canyon was on the windward side for aspect ratios W/H?=?1/2 and 1 and wind directions θ?=?112.5°, 135°, and 157.5°. The pollutant concentration level decreases as the wind direction and aspect ratio increase. The wind velocity and turbulence intensity increase as the aspect ratio and wind direction increase.     

江苏辐射沙洲潮间带风电场对海洋水动力场的影响分析

为了分析潮间带风电场对海洋水动力条件的影响,建立和验证了江苏辐射沙洲潮间带风电场工程二维潮流数学模型,根据风电场区的地形条件对模型范围及网格划分进行了探讨,分析风电场实施前后水动力条件的变化.结果表明:模型计算值与实测值拟合较好·建立的二维潮流数学模型计算结果合理、可信,可用来预测风电场建设对附近海域水动力条件的影响;...     

Comparison of Wind at 500 Feet Over Minneapolis and Louisville With Geostrophic Wind

Measurements of wind speed at 500 ft on a television tower in the Minneapolis-St. Paul area are compared with geostrophic wind speeds and lapse rates. The roughness length for the builtr-up area surrounding the tower is estimated using geostrophic boundary-layer models. Similar data for Louisville are also considered. The results are relevant to-the application of existing boundary-layer models to the estimation of wind speed and turbulent mixing over a city.     

Seasonal variation of the structure of the atmospheric boundary layer over a Suburban area

The long-term observational data of wind and temperature obtained from a 213-m instrumented tower in a suburban area were analyzed to investigate the seasonal variation of the structure of the atmospheric boundary layer.It was found from the daily variations of wind and temperature and the seasonal variation of the power spectrum of wind that in the summer the atmospheric boundary layer below 200 m is well mixed by convective turbulence, but in the winter the inversion layer near the ground suppresses the turbulent mixing, and the diurnal variation caused by turbulent mixing is confined to below 50–100 m height.Power spectra of wind speed were computed for different seasons of the year. In the summer season there is no significant variation of the shape of the spectrum with height. However, in winter the spectrum varies with height. The spectrum also varies annually and the characteristic of the long period (a few days) spectral peak of wind is related closely to the synoptic weather situation, and this suggests the possibility of a spectrum climatology.