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1.
The emissions of CO 2 and H 2S from the aqueous solutions and wastewater were studied to determine and compare the times required to reach the equilibrium of H 2S and CO 2 between water and gas phases. The solutions of NaHCO 3 and NaHS were acidified and the change in the pressure of emitted gases was measured with a manometric OxiTop ® system. The average time required to achieve the equilibrium state of distribution of CO 2 between two phases was 16.7±1.5 min, and it did not depend on the initial amount of NaHCO 3 in the solution. The average time required to achieve the equilibrium of H 2S (sulfide) was 19.5±5.5 min, having the same value for solutions with different initial contents of sulfide ions. The average time required to achieve the equilibrium of H 2S in the wastewater was 16.2±3.6 min, and it showed the faster emission of gaseous H 2S to decrease the oversaturation of the solution. The ratio of measured values of pressure to the calculated values did not depend on the concentration of NaHS in the initial solution, and its average value was 0.86±0.14. The results showed that measured values of pressure of H 2S emitted from the wastewater were twice lower than the calculated values and it is necessary to take into account the catalyzed formation of polysulfide in the solution of sulfides. 相似文献
2.
A monitoring system enabling detection and determination of the nature of odour nuisance caused by industrial emissions of volatile organic sulphur compounds is presented. The system consists of two continuous, highly sensitive detectors for sulphur compounds at the ppb-level. One of the detectors is equipped with a SO x-scrubber and measures the total amount of non-S0 2 sulphur compounds. By the use of a newly developed scrubber retaining S0 2, H 2S and CS 2 the second detector monitors the presence of odorous mercaptans and organic sulphides in ambient air. Both these continuous detection signals are fed to a data processor which triggers air collection for the determination of the individual compounds by gas chromatographic analysis in the laboratory. The concept and operation, as well as the practical possibilities and applications of the system are explained 相似文献
3.
Lead acetate impregnated ceramic tiles are useful devices for determining H 2S levels in the outdoor air. The exposure of tiles in simple shelters and for an overnight period is effective in an areawide sampling program to determine: (1) whether a significant H 2S source exists, (2) the source location, (3) the area affected, and (4) the relative intensity pattern. On the basis of an overnight exposure, tiles can “see” a mean H 2S concentration range of 0.003 to 0.3 ppm. The lower level of sensitivity is near 0.03 ppm X hr. Hence, tiles offer a way to verify whether hourly air quality standards are being exceeded. Tiles can be qualitatively evaluated against: experience, known effects, or by ranking against each other. Tiles can be semi-quantitatively evaluated by visual grading against painted standards developed by exposing tiles of particular manufacture to known H 2S dosages. 相似文献
4.
Abstract Simultaneous removal of hydrogen sulfide (H 2S) and am- gases. monia (NH 3) gases from gaseous streams was studied in a biofilter packed with granule activated carbon. Extensive studies, including the effects of carbon (C) source on the growth of inoculated microorganisms and gas removal efficiency, product analysis, bioaerosol emission, pressure drop, and cost evaluation, were conducted. The results indicated that molasses was a potential C source for inoculated cell growth that resulted in removal efficiencies of 99.5% for H 2S and 99.2% for NH 3. Microbial community observation by scanning electron microscopy indicated that granule activated carbon was an excellent support for microorganism attachment for long-term waste gas treatment. No disintegration or breakdown of biofilm was found when the system was operated for 140 days. The low bioaerosol concentration emitted from the biofilter showed that the system effectively avoided the environmental risk of bioaerosol emission. Also, the system is suitable to apply in the field because of its low pressure drop and treatment cost. Because NH 3 gas was mainly converted to organic nitrogen, and H 2S gas was converted to elemental sulfur, no acidification or alkalinity phenomena were found because of the metabolite products. Thus, the results of this study demonstrate that the biofilter is a feasible bioreactor in the removal of waste gases. 相似文献
5.
An analysis of slag pit variables has been made and correlations obtained between pit dimensions, time interval between pours, and the slag temperature when the pit is filled and ready for quenching. Field trials have demonstrated the effect of temperature on the level of emission and how the level varies during the quench period. Quantitative information has been obtained to show the effects of slag filling rates, air cooling prior to quenching, and the influence of oxidizing agents added to the quench water. A significant reduction in H 2S emission level can be attained by proper application of these results. 相似文献
6.
Waste oil fly ash (OFA) collected from disposal of power generation plants was treated by physicochemical activation technique to improve the surface properties of OFA. This synthesized material was further used for potential hydrogen sulfide (H 2S) adsorption from synthetic natural gas. The raw OFA was basically modified with a mixture of acids (20% nitric acid [HNO 3] and 80% phosphoric acid [H 3PO 4]), and it was further treated with 2 M potassium hydroxide (KOH) to enhance the surface affinity as well as surface area of synthesized activated carbon. Correspondingly, it enhanced the adsorption of H 2S. Crystallinity, surface morphology, and pore volume distribution of prepared activated carbon were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) analyses. Fourier transform infrared (FTIR) study was also performed to identify the functional groups during different synthesis stages of modified activated carbon. The Langmuir, Freundlich, Sips, and dual-site Langmuir (DSL) models were used to study the kinetic and breakthrough behavior of H 2S adsorption over alkali-modified activated carbon. Modeling results of isotherms indicated that OFA has dual sites with high and low affinity for H 2S adsorption. The Clark model, Thomas model, and Yoon-Nelson model were used to examine the effects of flow rate and inlet concentration on the adsorption of H 2S. Maximum uptake capacity of 8.5 mg/g was achieved at 100 ppm inlet concentration and flow rate of 0.2 L/min. Implications: Utilization of worthless oil fly ash from power plant is important not only for cleaning the environment but also for solid waste minimization. This research scope is to eradicate one pollutant by using another pollutant (waste ash) as a raw material. Chemical functionalization of synthesized activated carbon from oil fly ash would lead to attachment of functional groups of basic nature to attract the acidic H2S. Such type of treatment can enhance the uptake capacity of sorbent several times. 相似文献
7.
The microstructure of 1/10 and 1/20 atmosphere, lean H 2S—O 2—N 2 flames is developed using the mass-spectrometric flame-sampling technique. The flame mechanism developed is in agreement with that determined from an earlier study on 1-atm H 2S flames. The formation of SO 2 appears to be primarily related to the production of SH and the ensuing oxidation steps SH + O 2 = SO + OH and SO + O 2 = SO 2 + O. While there is some question whether SO 2 formation occurs via an SO or an S 2O intermediate, the present study does not give direct support to the role of S 2O in the oxidation mechanism. However, the presence of significant quantities of free sulfur in the pre-flame zone may be indicative of S 2O formation via SO + S → S 2O, and, possibly, via the disproportionation of SO, 3SO → S 2O + SO 2. Kinetic analyses of some of the pre-flame reactions indicate an apparent activation energy of 17,300 calories/mole for the decomposition of H 2S. The actual initiation process in the flame mechanism requires further examination. The specific rate for the reaction step H 2S + O = OH + SH is given by k 6 = 1.45 × 10 15 exp ( – 6600/RT) cm 3 mole –1 sec –1, and the specific rate for the oxidation of SO, SO + O 2 = SO 2 + O, is given by k 5 = 5.2 × 10 14 exp (—19,300/RT) cm 3 mole –1 sec –1. 相似文献
8.
The current S0 2 emission test methods, based on wet chemistry, are time consuming and costly. Final results depend on at least 10 separate measurements of quantities which may introduce significant errors due to human factors especially under unfavorable field environment. Performance evaluation of several promising S0 2 instrumental methods indicated that results were reliable and reproducible, but instrumental problems still exist. The problems were found to be calibration, mechanical and electronic components, and sample conditioning system. An alternative method proposed requires only two separate analyses: ultimate fuel analysis and stack gas analysis for C0 2. This method can be further simplified with reasonable accuracy by a single measurement of sulfur in the fuel if results are corrected to 12% C0 2. The method can be a useful addition to the current methods, especially if cost and manpower preclude actual stack tests. A test program was conducted at four industrial and utility power plants. Results are presented with discussion to show the application and validity of the simplified method. 相似文献
9.
Abstract Simultaneous removal of NH 3 and H 2S was investigated using two types of biofilters—one packed with wood chips and the other with granular activated carbon (GAC). Experimental tests and measurements included analyses of removal efficiency (RE), metabolic products, and results of long-term operation (around 240 days). The REs for NH 3 and H 2S were 92 and 99.9%, respectively, before deactivation. After deactivation, the RE for NH 3 and H 2S were decreased to 30–50% and 75%, respectively. The activity of nitrifying bacteria was inhibited by high concentrations of H 2S (over 200 ppm) but recovered gradually after H 2S addition was ceased. However, the Thiobacillus thioparus as sulfur oxidizing bacteria did not show inhibition at the NH 3 concentration under 150-ppm conditions. The deactivation of the biofilter was caused by metabolic products [elemental sulfur and (NH 4) 2SO 4] ac-cumulating on the packing materials during the extended operation. The removal capacities for NH 3 and H 2S were 6.0–8.0 and 45–75 mg N, S/L/hr, respectively. 相似文献
11.
A theoretical and experimental study of bisphenol A (BPA) degradation by the UV/H2O2 process in water is presented. The effects of the H2O2 concentration and the specific rate of photon emission (EP,0) on BPA degradation were investigated. A kinetic model derived from a reaction sequence was employed to predict BPA and hydrogen peroxide concentrations over time using an annular photochemical reactor in batch recirculation mode. The local volumetric rate of photon absorption (LVRPA) inside the photoreactor was computed using a Line Source with Parallel Plane emission model (LSPP). From the proposed kinetic model and the experimental data, the second order rate constants of the reactions between hydroxyl radicals and the main reacting species (H2O2 and BPA) were estimated applying a nonlinear regression method. A good agreement between the kinetic model and experimental data, for a wide range of operating conditions, was obtained. For BPA, H2O2, and TOC concentrations, the calculated root means square errors (RMSE) were 2.3?×?10??2, 9.8?×?10??1, and 9.0?×?10??2 mmol L??1, respectively. The simplified kinetic model presented in this work can be directly applied to scaling-up and reactor design, since the estimated kinetic constants are independent of the reactor size, shape, and configuration. Further experiments were made by employing low BPA initial concentration (100 μg L??1) in water and real wastewater. A lower degradation rate of BPA was observed in the real wastewater, although the UV/H2O2 process has also been able to completely degrade the target pollutant in less than 1 h. 相似文献
12.
Alberta has recently experienced two sour gas well blowouts: Lodgepole and Claresholm. Sulphur emissions associated with the blowouts were about 1400 and 2 tonnes per day, respectively. The Lodgepole blowout was not only of much greater magnitude but also lasted significantly longer than the Claresholm blowout (67 vs. 4 days). Special air quality monitoring with respect to H 2S was conducted to assess impacts of the blowouts. Monitoring was especially extensive for the Lodgepole incident. Maximum observed ground-level H 2S concentrations were compared to predictions obtained using a Gaussian model which makes allowance for the effects of sonic exit velocity on plume spread and the effects of wind shear on plume transport. There was appreciable agreement between predicted and observed values. 相似文献
13.
To improve the removal efficiency on hydrogen sulfide (H 2S), a biofilter was developed and was made of polyvinyl chloride (PVC) pipes. The effects of three different packings (i.e., packing A, packing B, and packing C), containing different proportions of activated carbon, sawdust, wormcast, perlite, and pig manure compost, based on different biofilter parameters on H 2S removal efficiency, were investigated. With the extension of running time, the H 2S removal rate of packing A reached up to 90.12%, that of packing B reached a peak at 92.96%, and that of packing C was highest at 87.21%. The contribution rate of each packing at the bottom of the device was significantly greater ( p < 0.01) than that of other parts, and those of the top of the devices were all greater than those of the middle of the devices. The H 2S removal rate increased with greater filler layer height. The removal rate of group B increased first with humidity, and then declined, with the optimal humidity level for the removal of H 2S 50–65% in this study. With the prolongation of the run, the pH of packing A was reduced from 7.1 to 5.91, while the pH of packing B and C remained within the range of 6.53–7.10. An increase was found in the number of bacteria and fungi over time. The count of bacteria in packing B and C and following a decreasing order was bottom > middle > top, whereas that for fungi was the opposite. In conclusion, it is thought that packing B (comprising wormcast + sawdust + activated carbon) is more efficient in the removal of H 2S than the other packings and may thus be utilized in biofilters. These results hope to provide useful information for future related research on the removal efficiency of H 2S using packings. Implications: Wormcasts use as biological filter packing to remove H2S is limited and needs yet to be explored. A comparative study on the removal efficiency of H2S using three packings showed the packings that included wormcast were more efficient than others, and showed the combined features of physical absorption and biological removal with long sustainability and good efficiency, although these were largely influenced by environmental factors and nutrient content for the microorganisms. In summary, wormcast could be utilized in biological filters in the future in related research beacuse of its good efficiency and low cost. 相似文献
14.
This sensitive, albeit precarious, method for measuring ppb-ppt (V/V) concentrations of H 2S was examined for various sources of potential error within the procedure. Filter preparation, filter storage, filter extraction, fluorimetric reagent stabilities, matrix differences between standards and samples, and possible interferences from other sulfur-containing compounds were separately studied for their effects on the analytical performance of the method. The overall method showed no Interference from SO 2, CS 2, COS, CH 3SH, CH 3SCH 3, and SO 4 -2. To minimize bias and obtain a reliable estimate of precision, the method should be calibrated with H 2S standards rather than liquid bisulfide standards. The measurement precision is a function of the quantity of H 2S collected as Ag 2S and/or AgSH on the impregnated filters. Because of the method’s linear dynamic range, sufficient air should be sampled to achieve filter loadings of 15 to 35 ng S/filter. A quality control method based on fluorescein mercuric acetate (FMA) is presented that ensures data quality while reducing the otherwise frequent need for fluori-metric calibration. 相似文献
15.
ABSTRACT Experiments on different annular denuder system (ADS)arrangements for sampling nitrous acid (HNO 2) and ni-tric acid (HNO 3) gases were conducted in this study toevaluate their sampling artifacts. The evaluation basis isthe one that employed one sodium chloride denuder forsampling HNO 3 gas and two sodium carbonate (Na 2CO 3)denuders for sampling HNO 2 gas, which is a commonlyemployed ADS arrangement in many field applicationsin the United States. A field study was conducted inHsinchu, Taiwan, and the results indicated that this ADSarrangement may yield over 80% relative errors for HNO 3gas. It also showed that the relative errors for HNO 2 gascan be less than 10% as sampled with only one Na 2CO 3denuder. This is attributed to the fact that the ambientHNO 3 concentration measured in this study was relativelylow while the HNO 2 concentration was high, as comparedto typical concentrations of these two gases measured inthe United States. The sampling error of HNO 3 gas may be due to highconcentrations of N-containing interfering speciespresent in Taiwan’s atmosphere. Because the relative sam-pling errors of HNO 3 and HNO 2 gases depend mainly ontheir concentrations in the atmosphere as well as con-centrations caused by interfering species, the risk for higherror while measuring low HNO 2 concentrations by onlyone Na 2CO 3 denuder is also possible. As a result, it is sug-gested that pretests are necessary to evaluate possiblesources and degrees of sampling errors before fieldsampling of HNO 2 and HNO 3 gases. The sampling errorsof these two gases can, therefore, be minimized with abetter arrangement of the ADS. 相似文献
16.
The present research deals with the development of a new heterogeneous photocatalysis and Fenton hybrid system for the removal of color from textile dyeing wastewater as Rhodamine B (RhB) solutions by using Fe 2+/H 2O 2/Nb 2O 5 as a photocatalytic system. The application of this photocatalytic system for the decolorization of dye contaminants is not reported in the literature yet. Different parameters like dye concentration, Nb 2O 5/Fe 2+ catalyst amount, pH, and H 2O 2 concentration have been studied. The optimum conditions for the decolorization of the dye were initial concentration of 10 mg L ?1 of dye, pH 4, and Nb 2O 5/Fe 2+ catalyst concentration of 0.5 g L ?1/50 mg L ?1. The optimum value of H 2O 2 concentration for the conditions used in this study was 700 mg L ?1. Moreover, the efficiency of the Nb 2O 5/photo-Fenton hybrid process in comparison to photo-Fenton alone and a dark Fenton process as a control experiment to decolorize the RhB solution has been investigated. The combination of photo-Fenton and Nb 2O 5 catalysts has been proved to be the most effective for the treatment of such type of wastewaters. The results revealed that the RhB dye was decolorized in a higher percent (78 %) by the Nb 2O 5/photo-Fenton hybrid process (Fe 2+/H 2O 2/Nb 2O 5/UV) than by the photo-Fenton process alone (37 %) and dark Fenton process (14 %) after 120 min of treatment. Moreover, the Nb 2O 5 catalyst as a heterogeneous part of the photocatalytic system was demonstrated to have good stability and reusability. 相似文献
17.
Abstract Two types of media, a natural medium (wood chips) and a commercially engineered medium, were evaluated for sulfur inhibition and capacity for removal of hydrogen sulfide (H 2S). Sulfate was added artificially (40, 65, and 100 mg of S/g of medium) to test its effect on removal efficiency and the media. A humidified gas stream of 50 ppm by volume H 2S was passed through the media-packed columns, and effluent readings for H 2S at the outlet were measured continuously. The overall H 2S baseline removal efficiencies of the column packed with natural medium remained >95% over a 2-day period even with the accumulated sulfur species. Added sulfate at a concentration high enough to saturate the biofilter moisture phase did not appear to affect the H 2S removal process efficiency. The results of additional experiments with a commercial granular medium also demonstrated that the accumulation of amounts of sulfate sufficient enough to saturate the moisture phase of the medium did not have a significant effect on H 2S removal. When the pH of the biofilter medium was lowered to 4, H 2S removal efficiency did drop to 36%. This work suggests that sulfate mass transfer through the moisture phase to the biofilm phase does not appear to inhibit H 2S removal rates in biofilters. Thus, performance degradation for odor-removing biofilters or H 2S breakthrough in field applications is probably caused by other consequences of high H 2S loading, such as sulfur precipitation. 相似文献
18.
A method is described for quantifying health risks to asthmatics briefly exposed to elevated levels of SO 2. By combining symptomologlcal and physiological measurements, we have developed a dose-response surface that relates both severity and incidence of response to ambient air quality levels. The complete model to assess potentially avoidable risks includes power plant emission data; ambient SO 2 background levels; demographic and activity patterns of asthmatics, the identified population at risk; and the dose-response surface. The estimated annual risk to persons experiencing an SO 2-lnduced response due to a nearby power plant is quite small (response rates under 3 percent). Uncertainties due to modeling errors, variations in activity patterns, demographics and physiological response are discussed. 相似文献
19.
建立了以EDTA和柠檬酸为铁盐络合剂的循环脱硫体系,采用络合铁法对垃圾填埋气中的H2S进行脱硫中试实验,结果表明实验所建立的络合铁脱硫体系运行稳定,脱硫效率高,适合应用于垃圾填埋气中硫化氢脱除。 相似文献
20.
Estimates of short-term, regional-scale spatial distributions of ozone (O 3) and hydrogen peroxide (H 2O 2) dry deposition over the northeast U.S. are presented. Dry deposition fluxes to surfaces are computed using a regional tropospheric chemistry model with deposition velocities which vary with local meteorology, land type, insolation, seasonal factors and surface wetness. A compilation of O 3 surface resistances is presented based on a survey of O 3 dry deposition measurements. The surface resistance for H 2O 2 is assumed to be small under most conditions, causing H 2O 2 to dry deposit at a rate which is frequently limited by surface-layer turbulence. Regional patterns of dry deposition velocities for these oxidants over the northeast U.S. are computed using landuse data and meteorological information predicted using a mesoscale meteorology model. Domain-averaged O 3 deposition velocities during a spring period reach a mid-day peak of 0.7–0.8 cm s −1 and drop to 0.1–0.2 cm s −1 at night. Domain-averaged H 2O 2 deposition velocities at a height of approximately 80 m are predicted to reach a mid-day peak of 1.6–2.0cm s −1, and fall to 0.6–0.9 cm s −1 at night. Time-averaged surface-layer H 2O 2 concentrations show a latitude dependence, with higher concentrations in the south. H 2O 2 concentrations are significantly reduced due to efficient wet removal and chemical destruction during the passage of a cyclonic frontal system. In contrast, O 3 concentrations are predicted to rise during the passage of a frontal system due to efficient vertical exchange of midtropospheric air into the boundary layer during convective conditions, followed by synoptic-scale subsidence occurring in the high pressure airmass following a cyclone. Maximum O 3 deposition during this 3-day springtime period occurs in polluted agricultural areas. In contrast, H 2O 2 dry deposition exhibits a latitude dependence with maximum 3-day accumulations occurring in the south. Domain-averaged mid-day deposition rates for O 3 and H 2O 2 were 45–50 μmol m −2 h −1 and 4–5 μmol m −2 h −1. At night, deposition rates were approximately 5–10 μmol m −2 h −1 and 1.5–2.5 μmol m −2 h −1 for O 3 and H 2O 2. These model results show that regional patterns of oxidant dry deposition are strongly influenced by oxidant concentrations, atmospheric stability, surface roughness and numerous other surface and meteorological factors. Each of these factors must be well-characterized before regional patterns of biological damage associated with oxidant dry deposition can be quantified. 相似文献
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