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1.
Sulfur hexafluoride (SF6) is an important gas for plasma etching processes in the semiconductor industry. SF6 intensely absorbs infrared radiation and, consequently, aggravates global warming. This study investigates SF6 abatement by nonthermal plasma technologies under atmospheric pressure. Two kinds of nonthermal plasma processes--dielectric barrier discharge (DBD) and combined plasma catalysis (CPC)--were employed and evaluated. Experimental results indicated that as much as 91% of SF6 was removed with DBDs at 20 kV of applied voltage and 150 Hz of discharge frequency for the gas stream containing 300 ppm SF6, 12% oxygen (O2), and 40% argon (Ar), with nitrogen (N2) as the carrier gas. Four additives, including Ar, O2, ethylene (C2H4), and H2O(g), are effective in enhancing SF6 abatement in the range of conditions studied. DBD achieves a higher SF6 removal efficiency than does CPC at the same operation condition. But CPC achieves a higher electrical energy utilization compared with DBD. However, poisoning of catalysts by sulfur (S)-containing species needs further investigation. SF6 is mainly converted to SOF2, SO2F4, sulfur dioxide (SO2), oxygen difluoride (OF2), and fluoride (F2). They do not cause global warming and can be captured by either wet scrubbing or adsorption. This study indicates that DBD and CPC are feasible control technologies for reducing SF6 emissions. 相似文献
2.
Abstract Sulfur hexafluoride (SF 6)-contained gas is a common pollutant emitted during the etching process used in the semiconductor industry. This study demonstrated the application of radio-frequency (RF) plasma in the decomposition of SF 6. The decomposition fraction of SF 6 [η SF6 (C in–C out)/C in x 100%] and the mole fraction profile of the products were investigated as functions of input power and feed O 2/SF 6 ratio in an SiO 2 reactor. The species detected in both SF 6/Ar and SF 6/O 2/Ar RF plasmas were SiF 4, SO 2, F 2, SO 2F 2, SOF 2, SOF 4, S 2F 10, S 2OF 10, S 2O 2F 10, and SF 4. The results revealed that at 40 W, η SF6 exceeded 99%, and the reaction products were almost all converted into stable compounds such as SiF 4, SO 2, and F 2 with or without the addition of oxygen. Sulfur oxyfluorides such as SO 2F 2, SOF 2, SOF 4, S 2OF 10, and S 2O 2F 10 were produced only below 40 W. The results of this work can be used to design a plasma/chemical system for online use in a series of a manufacturing process to treat SF 6-containing exhaust gases. 相似文献
3.
ABSTRACT As an odorless, nontoxic, and inert compound, sulfur hexafluoride (SF 6) is one of the most widely used tracer gases in indoor air quality studies in both controlled and uncontrolled environments. This compound may be subject to reactions with water vapor under elevated temperature to form acidic inorganic compounds such as HF and H 2SO 4. Thus, in the presence of unvented combustion sources such as kerosene heaters, natural gas heaters, gas log fireplaces, candles, and lamps, the SF 6 dissociation may interfere with measurements of the emissions from these sources. Tests were conducted in a research house with a vent-free natural gas heater to investigate these potential interferences. It was observed that the heater operation caused about a 5% reduction of SF 6 concentration, which can be an error source for the ventilation rate measurement and consequently the estimated pollutant emission rates. Further analysis indicates that this error can be much greater than the observed 5% under certain test conditions because it is a function of the ventilation flow rate. Reducing the tracer gas concentration has no effect on this error. A simple theoretical model is proposed to estimate the magnitude of this error. The second type of interference comes from the primary and secondary products of the SF 6 dissociation, mainly H 2SO 4, SO 2, HF, and fine particulate matter (PM). In the presence of ~5 ppm SF 6, the total airborne concentrations of these species increased by a factor of 4-10. The tests were performed at relatively high SF 6 concentrations, which is necessary to determine the interferences quantitatively. The second type of interference can be significantly reduced if the SF 6 concentration is kept at a low ppb level. 相似文献
4.
Abstract The traditional technologies for odor removal of thiol usually create either secondary pollution for scrubbing, adsorption, and absorption processes, or sulfur (S) poisoning for catalytic incineration. This study applied a laboratory-scale radio-frequency plasma reactor to destructive percentage-grade concentrations of odorous dimethyl sulfide (CH 3SCH 3, or DMS). Odor was diminished effectively via reforming DMS into mainly carbon disulfide (CS 2) or sulfur dioxide (SO 2). The removal efficiencies of DMS elevated significantly with a lower feeding concentration of DMS or a higher applied rf power. A greater inlet oxygen (O 2)/DMS molar ratio slightly improved the removal efficiency. In an O 2-free environment, DMS was converted primarily to CS 2, methane (CH 4), acetylene (C 2H 2), ethylene (C 2H 4), and hydrogen (H 2), with traces of hydrogen sulfide (H 2S), methyl mercaptan (CH 3SH), and dimethyl disulfide. In an O 2-containing environment, the species detected were SO 2, CS 2, carbonyl sulfide, carbon dioxide (CO 2), CH 4, C 2H 4, C 2H 2, H 2, formal-dehyde, and methanol. Differences in yield of products were functions of the amounts of added O 2 and the applied power. This study provided useful information for gaining insight into the reaction pathways for the DMS dissociation and the formation of products in the plasmolysis and conversion processes. 相似文献
5.
ABSTRACT This work provides information concerning possible global environmental implications and personnel safety aspects that should be considered during the commercial uses of sulfur hexafluoride (SF 6). SF 6 is an anthropogenically produced compound, mainly used as a gaseous dielectric in gas insulated switchgear power installations. It is a potent greenhouse gas with a high global warming potential, and its concentration in the earth atmosphere is rapidly increasing. During its working cycle, SF 6 decomposes under electrical stress, forming toxic byproducts that are a health threat for working personnel in the event of exposure. Several precautions are recommended to avoid personnel exposure to toxic byproducts: oxyfluoride levels or other byproduct concentrations in the operating gas matrix should be traced to predetermine the overall gas toxicity; contaminants should be systematically considered during maintenance, chamber evacuation and system opening process; small SF 6 quantities leaking into air or stagnated pollutant concentrations in the operating field should be analyzed and compared to the threshold limit values and permissible exposure levels. New system design rules (i.e., hermetically sealed gas compartments, gas recycling or disposal in the field area) and different handling policies—both during maintenance and final disposal—now should be considered globally to provide for environmental and personnel safety. 相似文献
6.
Perfluorooctane sulfonate (PFOS), a widely used mist suppressant in hard chrome electroplating industry, has been listed in the Stockholm Convention for global ban. 6:2 Fluorotelomer sulfonate (6:2 FTS) acid and salts have been adopted as alternative products in the market, but no data about their abiotic degradation has been reported. In the present study, the degradability of 6:2 FTS potassium salt (6:2 FTS-K) was evaluated under various advanced oxidation processes, including ultraviolet (UV) irradiation, UV with hydrogen peroxide (H 2O 2), alkaline ozonation (O 3, pH = 11), peroxone (O 3/H 2O 2), and Fenton reagent oxidation (Fe 2+/H 2O 2). UV/H 2O 2 was found to be the most effective approach, where the degradation of 6:2 FTS-K followed the pseudo-first-order kinetics. The intermediates were mainly shorter chain perfluoroalkyl carboxylic acid (C 7 to C 2), while sulfate (SO 4 2?) and fluoride (F ?) were found to be the final products. The high yields of SO 4 2? and F ? indicate that 6:2 FTS-K can be nearly completely desulfonated and defluorinated under UV/H 2O 2 condition. The degradation should firstly begin with the substitution of hydrogen atom by hydroxyl radicals, followed by desulfonation, carboxylation, and sequential “flake off” of CF 2 unit. Compared with PFOS which is inert in most advanced oxidation processes, 6:2 FTS-K is more degradable as the alternative. 相似文献
7.
To evaluate the influences of O 3, relative humidity (RH), and flow rate on the reaction between yellow sand and SO 2, the SO 2 deposition velocity and the oxidation state of sulfur were investigated by means of exposure experiments in a cylindrical flow reactor. Early in the reaction, the deposition velocity was not influenced by the RH or the presence of O 3; as the reaction progressed, however, the deposition velocity increased in the presence of O 3 and at high humidity. The oxidation of sulfur from S(IV) to S(VI) was also enhanced under these conditions. The amount of sulfur oxidation was positively correlated with the amount of deposited O 3. Furthermore, the SO 2 deposition velocity increased with increasing flow rate. However, changes in the flow rate had no noticeable effect on the amount of SO 2 oxidation. 相似文献
8.
为了弄清空速与二氧化碳含量对氧化铁脱硫剂硫容确定的影响,分别在实验气源为纯硫化氢,空速为40、80、120和160 h-1以及实验气源为二氧化碳含量分别在0%、20%、40%和80%,其余为硫化氢,空速为80 h-1条件下,对T502(粗脱硫剂)和HXT-2(精脱硫剂)2种氧化铁脱硫剂进行了不同测试条件对氧化铁硫容确定影响的研究。研究结果表明,T502和HXT-2氧化铁脱硫剂硫容测试结果随着空速和二氧化碳含量增加而减少,结果显示了在空速较低条件下(120h-1),二氧化碳含量在40%以下时对氧化铁脱硫剂硫容测试结果影响不大,但二氧化碳含量在40%以上时,对氧化铁脱硫剂硫容测试结果影响显著。 相似文献
9.
Concentration profiles for hydrogen fluoride(HF), sulfur dioxide(SO 2), ozone (O 3), nitrogen dioxide(NO 2), and nitric oxide(NO) generated in a standardized alfalfa canopy are presented. Wind, light, temperature, and carbon dioxide(CO 2) profiles, canopy pollutant uptake rates, and canopy structural data are also given. Canopy pollutant concentration profile characteristics were studied to evaluate the relative potentials for major air pollutants to penetrate into canopies. The study was conducted in an environmental growth chamber equipped to control automatically environmental conditions and monitor continuously gas exchange rates. HF, SO 2, and NO 2 profiles suggested that these gases were removed efficiently by the upper portion of the canopy as well as by the immediate subsurface vegetation. The steady state HF profile showed the greatest displacement within the canopy. The NO profile was displaced the least. The uptake rate of NO by plants was apparently too slow in comparison with gas transport and mixing within the canopy to affect the internal profile substantially. O 3 appeared to be readily deposited on the surface tissues, but the deeper tissues in the canopy had less effect on the concentration profile. Data are also presented to show the relationship between NO 2 concentration within the canopy and changes in the air concentration above the vegetation. The results indicated that gas transport between the atmosphere and canopy interior was rapid. The data presented should be of current interest to agriculturists, researchers, administrators, and environmental planners concerned with effects of air pollutants on plants and on the fate of pollutants in the microenvironment. 相似文献
10.
Foliar injury and shoot fresh weight responses of soybeans (Glycine max L.) ‘Lee 68’ and ‘Dare’ exposed to mixtures of ozone (O 3) and sulfur dioxide (SO 2) were greater than additive (synergistic), less than additive (antagonistic), or additive. The result depended on the concentrations of O 3 and SO 2, the exposure duration, and the amount of injury caused by each gas singly. Synergism usually occurred when injury from O 3 or SO 2 singly was slight to moderate. Antagonism usually occurred when injury from either gas singly was severe. In many cases of antagonism, the injury and fresh weight effects of the mixture were less than those from SO 2 alone, suggesting that O 3 can sometimes protect soybeans from SO 2. 相似文献
11.
A manual method for measuring reduced sulfur compounds in kraft pulp mill and sulfur recovery plant emissions was evaluated. The method involves removing SO 2 from the gas stream (if present) with a citric acid-potassium citrate buffer that passes reduced sulfur compounds; thermal oxidation of all reduced sulfur compounds to SO 2; collection of the SO 2 in H 2O 2; and a titrimetric analysis of the H 2O 2 for SO 4 2?. A heated filter removes alkaline particulate matter that would produce a negative interference if absorbed by the buffer. When used at kraft pulp mills, the method agrees closely with Reference Method 16, provided that nonregulated reduced sulfur compounds, such as carbonyl sulfide, are not present in the emissions. At sulfur recovery plants, nonregulated reduced sulfur compounds, such as thiophene, are likely to be present in the emissions and will produce a positive bias in the results obtained with this method. The precision of the method ranges from 1 to 7 percent relative standard deviation. 相似文献
12.
用高压电弧放电产生的低温等离子体对含偶氮染料的废水进行了处理,以甲基橙为例研究了电压幅值、处理时间、溶液初始浓度、溶液初始pH值、投加Fe^2+和Fe^3+对染料脱色的影响。实验结果表明,甲基橙浓度为50mg/L时其降解率随时间和电压幅值的增加而增加。溶液初始浓度对染料去除效果影响较为明显,同等条件下初始浓度越低降解率越高。酸性条件下有利于低温等离子体处理甲基橙。Fe^2+和Fe^3+对低温等离子体降解甲基橙有一定的催化作用。电压8kV处理3min,Fe^2+为20mg/L时去除率由89.64%增至99.72%。Fe2(SO4),的最佳投加量为5mg/L(以Fe^3+计),而FeCl,的最佳投加量为80mg/L(以Fe^3+计)。 相似文献
13.
As a convenient method, the closed chamber method has been applied to determine gaseous emission fluxes from fully open animal feeding operations despite the measured fluxes being theoretically affected by deployment time, wind speed over the emitting surface and detected gas mass. This laboratory study evaluated the effects of deployment time (0 to 120 min) and external surface wind speed (ESWS) (0.00, 0.25, 0.50, 0.75, 1.00, 1.50 and 2.00 m sec -1) on the measurement accuracy of a 300 mm (diameter) × 400 mm (height) (D300×H400) closed chamber using methane (CH 4), nitrous oxide (N 2O) and sulfur hexafluoride (SF 6) as reference gases. The results showed that the overall deviation ratio between the measured and reference CH 4 fluxes ranged from 9.99 % to -37.32 % and the flux was overestimated in the first 20 min. The measured N 2O and SF 6 emissions were smaller than the reference fluxes using the chamber. N 2O measurement accuracy decreased from -14.47 to -35.09% with deployment time extended to 120 min, while SF 6 accuracy sharply increased in the first 40 min, with the deviation stabilizing at approximately -5.00%. CH 4, N 2O and SF 6 measurements were significantly affected by deployment time and ESWS (P<0.05), and the interaction of those two factors greatly influenced CH 4 and SF 6 measurements (P<0.05). With the D300×H400 closed chamber, deployment times of 20 to 30 min and 10 to 20 min are recommended to measure CH 4 and N 2O, respectively, from the open operations of dairy farms under wind speeds lower than 2 m sec -1. Implications: This study recommended the suitable deployment times and wind speeds for using a D300 × H400 closed chamber to measure CH4, N2O, and SF6 in an open system, such as a dairy open lot and manure stockpile, to help researchers and other related industry workers get accurate data for gas emission rate. Deployment times of 20 to 30 min and 10 to 20 min were recommended to measure CH4 and N2O emissions using the D300 × H400 closed chamber, respectively, from the open operations of dairy farms under wind speeds lower than 2 m sec?1. For the measurement of SF6, a typical tracer gas, a deployment of 70 to 90 min was suggested. 相似文献
14.
Previous studies demonstrated that short-term exposure to gaseous pollutants (nitrogen dioxide (NO2), sulfur dioxide (SO2), and ozone (O3)) had a greater adverse effect on cardiovascular disease. However, little evidence exists regarding the synergy between gaseous pollutants and cardiovascular disease (CVD). Therefore, we aimed to estimate the effect of individual gaseous pollutants on hospital admissions for CVD and to explore the possible synergistic effects between gaseous pollutants. Daily hospitalization counts for CVD were collected from January 1, 2014, to December 31, 2015. We also collected daily time series on gaseous pollutants from the Environment of the People’s Republic of China, including NO2, SO2, and O3. We used distributed lag nonlinear models (DLNMs) to assess the association of individual gaseous pollutants on CVD hospitalization, after controlling for seasonality, day of the week, public holidays, and weather variables. Then, we explored the variability across age and sex groups. In addition, we analyzed the synergistic effects between gaseous pollutants on CVD. Extremely low NO2 and SO2 increase the risk of CVD in all subgroup at lag 7 days. The greatest effect of high concentration of SO2 was observed in male and the elderly (≥ 65 years) at lag 3 days. Greater effects of high concentration of O3 were more pronounced in the young (< 65 years) and female at lag 3 days, while the effect of low concentration of O3 was greater in male and the young (< 65 years) at lag 0 day. We found a synergistic effect between NO2 and SO2 for CVD, as well as between SO2 and O3. The synergistic effects of NO2 and SO2 on CVD were stronger in the elderly (≥ 65) and female. The female was sensitive to synergistic effects of SO2-O3 and NO2-O3. Interestingly, we found that there was a risk of CVD in the susceptible population even for gaseous pollutant concentrations below the National Environmental Quality Standard. The synergy between NO2 and SO2 was significantly associated with cardiovascular disease hospitalization in the elderly (≥ 65). This study provides evidence for the synergistic effect of gaseous pollutants on hospital admissions for cardiovascular disease. 相似文献
15.
The interaction of a typical flue gas with active charcoal and bituminous coal char at temperatures between 600 and 800°C and atmospheric pressure has been studied. The SO 2 in the flue gas interacts with the carbon to form primarily H 2S, COS, and a carbon-sulfur surface complex. H 2S and COS break through the carbon bed much in advance of SO 2. At 800°C, sulfur retention on the bed exceeds at least 11% before SO 2 breakthrough occurs. The reaction of H 2S and COS with O 2 over active charcoal at 100–140°C to produce sulfur, which deposits on the carbon, has also been studied and found to be feasible. As a result of this study, a new process is outlined for the removal of SO 2 from flue gas, with the ultimate conversion 相似文献
16.
Atmospheric concentration of sulfur dioxide (SO 2) was intermittently measured at an air quality monitoring (AQM) station in the Yong-san district of Seoul, Korea, between 1987 and 2013. The SO 2 level was compared with other important pollutants concurrently measured, including methane (CH 4), carbon monoxide (CO), nitric oxide (NO), nitrogen dioxide (NO 2), ozone (O 3), and particulate matter (PM 10). If split into three different periods (period 1, 1987–1988, period 2, 1999–2000, and period 3, 2004–2013), the respective mean [SO 2] values (6.57 ± 4.29, 6.30 ± 2.44, and 5.29 ± 0.63 ppb) showed a slight reduction across the entire study period. The concentrations of SO 2 are found to be strongly correlated with other pollutants such as CO ( r = 0.614, p = 0.02), which tracked reductions in reported emissions due to tighter emissions standards enacted by the South Korean government. There was also a clear seasonal trend in the SO 2 level, especially in periods 2 and 3, reflecting the combined effects of domestic heating by coal briquettes and meteorological conditions. Although only a 16% concentration reduction was achieved during the 27-year study duration, this is significant if one considers rapid urbanization, an 83.2% increase in population, and rapid industrialization that took place during that period. Implications: Since 1970, a network of air quality monitoring (AQM) stations has been operated by the Korean Ministry of Environment (KMOE) for routine nationwide monitoring of air pollutant concentrations in urban/suburban areas. To date, the information obtained from these stations has provided a platform for analyzing long-term trends of major pollutant species. In this study, we examined the long-term trends of SO2 levels and relevant environmental parameters monitored continuously in the Yong-san district of Seoul between 1987 and 2013. The data were analyzed over various time scales (i.e., monthly, seasonal, and annual intervals). The results obtained from this study will allow us to assess the effectiveness of abatement strategy and to predict future concentrations trends in association with future abatement strategies and technologies. 相似文献
17.
We assessed confounding of associations between short-term effects of air pollution and health outcomes by influenza using Hong Kong mortality and hospitalization data for 1996–2002.Three measures of influenza were defined: (i) intensity: weekly proportion of positive influenza viruses, (ii) epidemic: weekly number of positive influenza viruses ≥4% of the annual number for ≥2 consecutive weeks, and (iii) predominance: an epidemic period with co-circulation of respiratory syncytial virus <2% of the annual positive isolates for ≥2 consecutive weeks. We examined effects of influenza on associations between nitrogen dioxide (NO 2), sulfur dioxide (SO 2), particulate matter with aerodynamic diameter ≤10 μm (PM 10) and ozone (O 3) and health outcomes including all natural causes mortality, cardiorespiratory mortality and hospitalization. Generalized additive Poisson regression model with natural cubic splines was fitted to control for time-varying covariates to estimate air pollution health effects. Confounding with influenza was assessed using an absolute difference of >0.1% between unadjusted and adjusted excess risks (ER%).Without adjustment, pollutants were associated with positive ER% for all health outcomes except asthma and stroke hospitalization with SO 2 and stroke hospitalization with O 3. Following adjustment, changes in ER% for all pollutants were <0.1% for all natural causes mortality, but >0.1% for mortality from stroke with NO 2 and SO 2, cardiac or heart disease with NO 2, PM 10 and O 3, lower respiratory infections with NO 2 and O 3 and mortality from chronic obstructive pulmonary disease with all pollutants. Changes >0.1% were seen for acute respiratory disease hospitalization with NO 2, SO 2 and O 3 and acute lower respiratory infections hospitalization with PM 10. Generally, influenza does not confound the observed associations of air pollutants with all natural causes mortality and cardiovascular hospitalization, but for some pollutants and subgroups of cardiorespiratory mortality and respiratory hospitalization there was evidence to suggest confounding by influenza. 相似文献
18.
A mass screening of lung function associated with air pollutants for children is limited. This study assessed the association between air pollutants exposure and the lung function of junior high school students in a mass screening program in Taipei city, Taiwan. Among 10,396 students with completed asthma screening questionnaires and anthropometric measures, 2919 students aged 12-16 received the spirometry test. Forced vital capacity (FVC) and forced expiratory flow in 1 s (FEV 1) in association with daily ambient concentrations of particulate matter with diameter of 10 μm or less (PM 10), sulfur dioxide (SO 2), carbon monoxide (CO), nitrogen dioxide (NO 2), and ozone (O 3) were assessed by regression models controlling for the age, gender, height, weight, student living districts, rainfall and temperature. FVC, had a significant negative association with short-term exposure to O 3 and PM 10 measured on the day of spirometry testing. FVC values also were reversely associated with means of SO 2, O 3, NO 2, PM 10 and CO exposed 1 d earlier. An increase of 1-ppm CO was associated with the reduction in FVC for 69.8 mL (95% CI: −115, −24.4 mL) or in FEV 1 for 73.7 mL (95% CI: −118, −29.7 mL). An increase in SO 2 for 1 ppb was associated with the reductions in FVC and FEV 1 for 12.9 mL (95% CI: −20.7, −5.09 mL) and 11.7 mL (95% CI: −19.3, −4.16 mL), respectively. In conclusion, the short-term exposure to O 3 and PM 10 was associated with reducing FVC and FEV 1. CO and SO 2 exposure had a strong 1-d lag effect on FVC and FEV 1. 相似文献
19.
The iron(III)-catalyzed autoxidation of sulfur(IV)-oxides results in the formation of two different oxidation products of sulfur(IV): dithionate, S 2O 62−, and sulfate, SO 42−. The yield of these reaction products depends on the experimental conditions. Under the studied conditions ([Fe(III)] : [SIV)] = 1:10, pH = 2–4) dithionate is the minor reaction product. The formation of dithionate is influenced by the initial pH but not by the initial O 2 concentration. The presence of CO 2+, Mn 2+, and Ni 2+ have no influence on the yield of dithionate, whereas in the presence of Cr 3+ less and, in the presence of Cu 2+, no dithionate is formed. 相似文献
20.
The evolution of H 2S and SO 2 from hot blast furnace slags by reaction with H 2O has been found to be dependent upon the presence of O 2 or H 2 in the reaction zone as well as on the temperature. H 2 has been found to produce a small increase in H 2S and a small decrease in SO 2 emission, while O 2 has been found to produce a very great inhibiting effect on H 2S emission and only a small increase in SO 2 emission. The total emission of sulfur bearing gases is much less when H 2O + air is blown at the slag than when H 2O + Ar is blown at the slag, particularly at 1200°C and above. These effects may be useful in attempts to design systems for slag quenching which will produce less pollution. 相似文献
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