佛山市塑料行业VOCs排放现状的研究

塑料行业是佛山市的民营经济支柱产业,塑料制品在生产或使用过程中会排放挥发性有机物（VOCs）,危害人体健康和环境。正确使用塑料是环境可持续性发展的关键,因此通过开展佛山市塑料行业VOCs排放现状的全面调研监测,建立涉及塑料行业VOCs排放系数,同时提出塑料行业VOCs控制措施,为制定地区空气质量保障方案做充分的准备,具有十分重要的意义。     

气相色谱法测定粗苯中苯、甲苯和二甲苯含量

建立了毛细管气相色谱法测定粗苯中苯、甲苯、二甲苯含量的方法。采用HP-5毛细管柱分离,氢火焰离子化检测器检测,单点标准对照法定量。该方法分析速度快,测定重现性好,准确度和精密度高,三苯各个组分相对标准偏差均小于6%,回收率在96.0%~100.8%间。     

A new approach for estimating VOC emissions from anthropogenic non-point sources in urban communities

In an attempt to estimate VOC emission from anthropogenic, non-point sources in an urban area, a new approach (SKYEM) was introduced as a part of the integrated environment management (IEM) project. SKYEM was developed for consulting user convenience on a basis of emission inventory methodologies developed in the USA, Europe, Australia, and Korea. The inventory was obtained from mobile and area sources resolved to census tract levels (Dong or village levels). SKYEM was used to provide an annual emission inventory for major volatile organic compounds, BTXS (benzene, toluene, xylene, and styrene), PCE, phenol, and MEK, from 13 sources in multimedia (air, water, and soil) for 151 villages in northeastern Seoul. Toluene (73%) and Xlyene (16%) were largely emitted from important source categories, consumer solvents and mobiles, accounting for 60% and 26% of all estimated VOCs during the year 2002, respectively. BTXS were also measured at 10 sites located in the target area. Toluene presented the highest concentration (77%) with Xylene ranked second (15%). The similarity between concentration and emission may be explained by a model which describes scientific phenomena in or inter media. Therefore, a comparison of the prediction using the model with actual observations will be useful in examining uncertainties in, or the accuracy of the emission inventory from, non-point sources in an urban area.     

Process analysis of temperature swing adsorption and temperature vacuum swing adsorption in VOCs recovery from activated carbon

In order to better guide the design of industrial process for purification and recovery of VOCs, temperature swing adsorption (TSA) and temperature vacuum swing adsorption (TVSA) process for VOCs purification and recovery were studied systematically with activated carbon adsorbent. The adsorption and desorption behaviors of benzene on activated carbon in above two processes were investigated systematically. Effects of operating parameters on process performances were further analyzed, including as regeneration temperature, purging feed ratio and hot–cold purging ratio. The results showed that the increase of hot–cold purging ratio (HP/CP) could obtain the same regeneration effect as the increase of desorption temperature. Increasing the feed purge ratio without increasing the hot–cold purging ratio is not conducive to bed regeneration, because a large number of cold purge gases cannot utilize the residual heat of temperature wave, thus reducing the desorption effect of the cooling step on the bed. In addition, the vacuum step can enhance the regeneration ability of hot nitrogen to the bed at the same regeneration temperature, making the bed regeneration of TVSA process more thorough. Temperature in the middle and lower part of the bed in TVSA process was higher and the regeneration was more thorough. In conclusion, TVSA has more obvious advantages than TSA in terms of energy consumption, hot or cold purge volume and bed regeneration.     

Modeling of photocatalytic oxidation of VOCs in a packed bed reactor under continuous and discontinuous illuminations

In this paper, a mathematical model is presented to describe the photocatalytic degradation of VOCs in a packed bed reactor. Here, the adsorption of VOCs on the wall of the reactor is taken into account and the diffusion of VOCs in the axial direction is neglected. First-order kinetics is used to describe the photocatalytic oxidation of VOCs. The analytical solution of the present model is obtained by traveling wave method. The solution shows that the reactor performance is totally dependent on the inlet concentration of VOCs when the time is large enough. The present model is validated through the experimental result of the photocatalytic oxidation of trichloroethylene in a packed bed and the predicted results accord well with the experimental data. The influence of flow rate and inlet concentration on the performance of the reactor is discussed in detail. High flow rate offers high reaction rate and low conversion efficiency. The different inlet conditions and different reaction patterns are also investigated. The model would be useful to estimate the rate constant and help to the design of the reactor.     

德国乐器涂装过程中VOCs生物滴滤塔处理技术应用

乐器制造的涂装过程中会产生一定浓度涂料漆雾和挥发性有机化合物(VOCs),可采用微生物滴滤塔处理技术,降低VOCs排放浓度,达到环保要求.本文系统研究了德国GM(吉埃默)工厂微生物滴滤塔的设计参数、工艺制定、滤料优化、菌群结构及滴滤塔运行影响因素、日常维护等,开发基于天然滤料和自然降解规律、安全有效且低能耗、低成本的有...     

Air quality assessment in a highly industrialized area of Mexico: Concentrations and sources of volatile organic compounds

Parallel to the economical benefits brought by the oil industry in Mexico, there have been some negative environmental effects due to emission of pollutants to the atmosphere. Salamanca, a city located inside one of the most important industrial corridors of the country, has been frequently affected by elevated concentrations of sulfur dioxide and particle matter. However, little is known about volatile organic compounds (VOCs), which in this study are analyzed along with criteria pollutants and meteorological parameters during February–March 2003 at urban, suburban and rural sites. Although sulfur dioxide average levels were ∼0.017 ppm, a high concentration event (∼0.600 ppm), attributable to emissions from the oil refinery and the thermoelectric power plant, was observed at the urban site at night time. The VOCs concentration varied from 170 ± 50 ppbC (rural) to 699 ± 212 (urban) and were constituted by 40% alkanes, 13% aromatics, 11% olefins and 11% of halogenated. The most abundant species were propane (167 ± 40 ppbC), n-butane (91 ± 23 ppbC), toluene (51 ± 10 ppbC) and i-pentane (44 ± 7 ppbC), that are related to combustion processes. Freon-114, methyl bromide and 1,2-dichloroethane which are likely emitted by application of pesticides, soil fumigation and fabrication of chemicals, showed high concentrations (48 ± 10, 50 ± 10 and 32 ± 6 ppbC respectively) in the rural sites, highlighting the importance of control measurements implementation for these species, as they represent a potential hazard for public health. Moreover, these halocarbons showed similar ratios regardless the monitoring site, suggesting same source. Modeling results indicated that meteorological conditions generally transport air masses to the northeast rural areas where the highest concentrations of ozone were calculated.     

Emission of Particulate Matter 2.5 (PM2.5) from Sewage Sludge Incinerators in Japan

Because fine particulate matter ≤2.5 µm in diameter (PM2.5) causes health problems, PM2.5 emissions are of concern. However, little research on stationary sources has been conducted. To determine the concentration and filtration behavior of PM2.5, dust was collected from five fluid-bed sewage sludge incinerators (SSIs) sorted by particle size using cascade impactors. The average PM2.5 concentration was 0.00014–4.8 mg/Nm³. The total estimated amount of PM2.5 emissions from the SSIs for all plants in Japan was 0.96–8.9 tons/year. Since the SSIs with dry Electrostatic Precipitators (EP) contributed 75–99% of the total emissions, replacing dry EPs with bag filters would significantly reduce the PM2.5 emissions from SSI.     

Emission Factors for Aerial Pyrotechnics and Use in Assessing Environmental Impact of Firework Displays: Case Study from Malta

The measurement of emission factors for PM₁₀ for different aerial (display) firework devices, namely, flash crackers, stars, blast charges, and fuse matches as produced in Malta are reported herein. Additionally, the content in fireworks‐generated PM₁₀ of Al, Ba, Cu, Sr, and Sb is determined. PM₁₀ values were as follows in kg per kg composition: blast charges 0.054; flash crackers 0.43; stars 0.175 (red); 0.176 (blue); 0.254 (green); 0.123 (white); fuse matches 0.204. The metal content in PM₁₀ from fireworks (in kg per kg composition) depends on the type of device burnt, with green stars producing Ba at 0.0553, blue stars Cu at 0.0123, and red stars Sr at 0.0057. White stars and flash crackers containing Sb₂S₃ produce Sb at 0.0395 and 0.1083 kg per kg composition, respectively. We used these emission factors and trade information on chemicals used for the manufacture of pyrotechnics in Malta to estimate the total load of PM₁₀ and associated metalliferous content released to the atmosphere from aerial fireworks displays. In 2007, PM₁₀ emissions amounted to about 37 t and metal loads (in kg) were Al (2193), Ba (1161), Sb (504), Cu (331), and Sr (142). The data and modeling approach presented herein illustrates a general methodology for the assessment of environmental risk from display fireworks especially when more specific information is unavailable.     

Removal of Benzene/Toluene from Water by Vacuum Membrane Distillation in a PVDF Hollow Fiber Membrane Module

Abstract

Asymmetric polyvinylidene fluoride (PVDF) hollow fiber membranes were prepared by a phase inversion method using dimethylacetamide (DMAc) and a mixture of water/LiCl as solvent and a nonsolvent additive, respectively. The prepared membranes were characterized by scanning electron microscopy (SEM) for observing its microstructures and by a gas permeation method for measuring its surface porosity, pore size, and pore size distribution. Wetting pressures of the dry hollow fiber membranes were also measured. Using the prepared PVDF hollow fiber membranes, a membrane module was fabricated for removal of benzene/toluene from water. Effects of various operating parameters such as downstream vacuum levels, feed temperatures, and feed flow rates on performances of the module were investigated experimentally. The benzene/toluene removal was achieved over 99% under an optimal operating condition. Mass transfer of benzene or toluene removal is controlled not only by the liquid phase resistance but also by the membrane and gas phase resistances. Benzene and toluene can be removed from water simultaneously with no adverse coupling effects.     

Determination of non-methane hydrocarbon emission factors from vehicles in a Tunnel in Seoul in May 2000

Measurements of non-methane hydrocarbons (NMHC) were performed at the entrance and exit of the Sangdo tunnel to estimate emission factors (EF) of NMHC from vehicles in May 2000. About 50 species were analyzed by a combined GC/FID and GC/MS system. Ethylene was the most abundant compound, followed by n-butane and acetylene, respectively. Based on the measurement data, the real world vehicular EF in Seoul was estimated. The highest EF value was 89.8 mg (veh-mile)^-1 for n-butane, followed by ethylene and toluene.     

Deposition of C60, C70 and C84 fullerene molecules, in benzene via a change of the fluid state, from a gas–liquid two phase region to the critical point

We dissolve C₆₀, C₇₀ or C₈₄ molecules in benzene and change the fluid state from a gas–liquid two-phase region (25.0 °C) to the critical point (289.0 °C) and from the critical point to the original state (25.0 °C) along the gas–liquid coexistence curve. We find that particle-like and whisker-like nano/micro clusters, which are composed of C₆₀ molecules, deposit on the surface of a silicon substrate placed vertically in C₆₀/benzene solution during the temperature change, whereas no appreciable clusters are detected on the silicon substrate in either C₇₀/benzene or C₈₄/benzene solutions. The clusters, in which fcc lattice structures are formed by C₆₀ molecules, remain stable in the solution. The present result suggests that C₆₀ molecules can be separated and extracted from a mixture of C₆₀, C₇₀ and C₈₄ molecules dissolved in benzene.     

Adsorption/desorption of toluene on a hypercrosslinked polymeric resin in a highly humid gas stream

In many sources of volatile organic compounds(VOCs), large amounts of water vapor come from the air and the reactors. The relative humidity(RH) of exhaust gas is normally N60% and is supersaturated. Maintaining the property of adsorbent on VOCs in a highly humid gas stream is a serious industrial problem. In this study, the adsorption/desorption behavior of toluene in a micro-mesoporous polymeric resin was investigated in a highly humid environment to explore the influence of abound water vapor on resin adsorption and regeneration.This resin could selectively adsorb toluene at an RH of 80%, and its adsorption property was unaffected by the presence of water vapor. In the case of humidity saturation, the resin displayed a high adsorption capacity at a moisture content of b30%. Therefore, the polymer resin is an excellent water-resistant adsorbent of VOCs.In the regenerative experiment, the resin maintained its original adsorption capability after four adsorption/desorption cycles of toluene purging with nitrogen gas at 120 °C. The resin exhibited excellent regeneration performance at high humidity.     

Performance of an industrial biofilter from a composting plant in the removal of ammonia and VOCs after material replacement

BACKGROUND: Biofiltration is a suitable odor reduction technique for the treatment of gaseous emissions from composting processes, but little is known about the start‐up of full‐scale biofilters after material replacement and their performance after several years of operation. RESULTS: Biofilter material (wood chips used previously as bulking agent in a composting process) can effectively remove ammonia and most of the volatile organic compounds (VOCs) content, achieving removal efficiencies greater than 70% for VOCs and near 90% for ammonia immediately after material replacement. These removal efficiencies were maintained for several months after material replacement. In the studied full‐scale biofilter no lag phase was observed in the removal of ammonia whereas in the case of VOCs different patterns were detected during biofilter start‐up. For the old biofilter material, after 4 years of operation, a statistically significant decrease of removal efficiency for ammonia in comparison with the new material was detected. No statistically significant differences were found in the case of VOCs. CONCLUSIONS: Data on the emissions of several pollutants from biofilters treating composting exhaust gases have been systematically obtained. The tested filtering media presented adequate properties for biofiltration of gases emitted during the composting process. Copyright © 2009 Society of Chemical Industry     

燃油锅炉油雾燃烧过程中碳烟的排放特性

针对2 t/h卧式锅壳锅炉炉膛结构及换热特点,建立了炉膛换热条件下油雾燃烧的非预混燃烧模型,研究了风速对炉内燃料燃烧及碳烟颗粒物排放特性的影响. 结果表明,炉内燃料浓度在炉膛轴向0.3~0.7 m的范围内快速降低,碳烟颗粒物主要在距炉膛燃料喷口0.3~1.5 m的混合燃烧区内迅速生成,并随风速增大而远离喷口,生成速率在着火点位置最大. 风速过大或过小都会增加碳烟颗粒物的生成,风速7.5 m/s时炉膛碳烟排放浓度最小,出口浓度分布更均匀,约为0.042%(w).     

应用模拟室内环境试验箱研究涂层有机挥发物的散发性

本研究以双组分溶剂型涂料形成涂层为代表试样,应用模拟室内环境试验箱,采用一次热解吸气相色谱法测定涂层有机挥发物的散发浓度,研究不同模拟试验条件(暴露面积、温湿度、光源、通风等)对被测涂层有机挥发物的散发性影响.研究发现被测涂层有机挥发物散发浓度随暴露面积、温度、湿度的增大明显增大,使用普通蓝荧光灯或365nm的UV-A...     

Production of Xylenes from Toluene and 1,2,4‐Trimethylbenzene over ZSM‐5 and Mordenite Catalysts in a Fluidized‐Bed Reactor

The production of various xylenes from toluene, heavy aromatics such as 1,2,4‐trimethylbenzene (1,2,4‐TMB) and their mixture was investigated over H‐ZSM‐5 (H‐Z), H‐mordenite (H‐M) and a dual zeolitic catalyst comprising ZSM‐5 and mordenite (H‐ZM). The experiments were conducted in a riser‐simulator reactor under different operating conditions to study the effect of temperature, reaction time and feed composition on conversion and product yields. At 400 °C, the conversion of toluene over the three catalysts yielded mainly benzene and xylenes with maximum conversion at 25 % and a xylene yield of 12.5 wt % over the H‐M catalyst. The transformation of 1,2,4‐TMB doubled the conversion level and xylene yield and suppressed benzene formation. However, a considerable portion of the 1,2,4‐TMB feed was isomerized into 1,2,3‐TMB and 1,3,5‐TMB accompanied by the formation of tetramethylbenzenes (TeMBs). The conversion of an equimolar mixture of toluene and 1,2,4‐TMB over the three catalysts resulted in higher toluene conversion and double xylene yield in comparison with 1,2,4‐TMB alone. The advantage of using a dual zeolitic catalyst was observed at an equimolar feed of toluene and 1,2,4‐TMB, exhibiting maximum toluene conversion, higher xylene yield and the formation of lower levels of undesirable products.     

NO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> emission from incineration of organic liquid waste in a circulating fluidized bed

An incineration test of a toxic chemical organic waste liquid was conducted on a circulating fluidized bed (CFB) incinerator. The flue gas was measured online with the advanced SAE-19 flue gas analyzer. The effects of several factors, in terms of flow rate of waste liquid, ratio of waste liquid injected into dense bed of the CFB, excess air coefficient, the secondary air fraction and bed temperature on NO _x emissions, were verified. The experimental results show that NO emissions in flue gas increase with increase in the flow rate of the waste liquid injected into the bed or the excess air coefficient or the bed temperature and those decrease with increase in the ratio of waste liquid injected into the dense bed of the CFB or the secondary air fraction. During the test runs, NO _x concentration in flue gas met the national regulation on NO _x emissions due to suppressive effect of low temperature and staged combustion in CFB on NO _x formation. This paper was presented at the 6 ^th Korea-China Workshop on Clean Energy Technology held at Busan, Korea, July 4–7, 2006.     

Comparing a process-based agro-ecosystem model to the IPCC methodology for developing a national inventory of N2O emissions from arable lands in China

Nations are now obligated to assess their greenhouse gas emissions under the protocols of Article 4 of the United Nations Framework Convention on Climate Change. The IPCC has developed `spreadsheet-format' methodologies for countries to estimate national greenhouse gas emissions by economic sector. Each activity has a magnitude and emission rate and their product is summed over all included activities to generate a national total (IPCC, 1997). For N₂O emissions from cropland soils, field studies have shown that there are important factors that influence N₂O emissions at specific field sites that are not considered in the IPCC methodology. We used DNDC, a process-oriented agroecosystem model, to develop an unofficial national inventory of direct N₂O emissions from cropland in China. We assembled county-scale data on soil properties, daily weather, crop areas, N-fertilizer use, livestock populations (for manure inputs to cropland), and agricultural management for the 2500 counties in mainland China. Total 1990 cropland area was 0.95 million km². Total N-fertilizer use in China in 1990 was 16.6 Tg N. The average fertilization rate was 175 kg N ha⁻¹ cropland. One-year simulations with DNDC were run for each crop type in each county to generate estimates of direct N₂O emissions from soils. National totals were the sum of results for all crop simulations across all counties. Baseline simulations estimated that total N₂O emission from arable land in China in 1990 was 0.31 Tg N₂O-N yr⁻¹. We also ran simulations with zero N-fertilizer input; the difference between the zero-fertilizer and the baseline run is an estimate of fertilizer-induced N₂O emissions. The fertilizer-induced emission was 0.13 Tg N₂O-N yr⁻¹, about 0.8% of total N-fertilizer use (lower than the mean but within the IPCC range of 1.25±1.0%). We compared these results to our estimates of county-scale IPCC methodology emissions. Total emissions were similar but geographical patterns were quite different. This revised version was published online in August 2006 with corrections to the Cover Date.