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1.
ABSTRACT A new style of diffusion denuder has been evaluated specifically for sampling HNO 3. A coated fabric is used as the denuder substrate, which can be loaded directly into a standard filter holder. This approach allows direct denuder sampling with no additional capital costs over filter sampling and simplifies the coating and extraction process. Potential denuder materials and coatings were evaluated in the laboratory to test the removal efficiency. NaCl coatings were used to assess more than 20 materials for HNO 3 collection efficiency. Particle retention, which would cause a denuder to have a positive bias for gas concentration measurements, was evaluated by ambient air sampling using particulate sulfate as the reference aerosol. Particle retention varied from 0 to 15%, depending on the denuder material tested. The best performing material showed an average particle retention of less than 3%. Denuder efficiency of four fabric materials was tested under ambient conditions to determine removal efficiency. The fabric denuder method was compared with a long path-length Fourier transform infrared (FTIR) spectrometer, a tunable diode laser absorption spectrometer (TDLAS), and a denuder difference sampler to independently measure HNO 3. HNO 3 collection efficiency was typically 90% for the denuders, whether coated with NaCl or not. For 10-L/min sampling rates with the fabric denuder, the square of the correlation coefficient with the FTIR spectrometer was 0.73, compared to 0.24 with the TDLAS. 相似文献
2.
Compliance with particulate standards for utility boilers burning low sulfur western coal has resulted in the installation and proposed installation of several fabric filter collectors where cold or hot electrostatic precipitators would have traditionally been applied. Recently, SO3 conditioning has been used to improve cold precipitator performance resulting in considerable reduction in specific collection area (SCA). All this suggests that trade-offs exist indicating ranges of SCA, A/C ratio, and power plant size (Mw) where fabric filters become competitive with electrostatic precipitators. Conceptual cost models are presented which indicate total capital investment and annual costs for the control devices. Precipitator costs are correlated with collecting area, gas flow rate, and power input and are presented as functions of SCA and Mw. Fabric filter costs are keyed to gross filter area, pressure drop, and gas flow rate. Fabric filters become competitive when a cold precipitator requires SCAs in excess of 600 to 800 and competitive when a hot precipitator requires equivalent cold precipitator SCAs in excess of 600 to 1000 depending on A/C ratio, Mw, and hot precipitator SCA credit allowance. The S0 3 conditioned precipitator scenario is shown to be economically competitive with fabric filters. 相似文献
3.
Results with the EPRI 2.5 MW(e) Integrated Environmental Control Pilot Plant (IECPP) indicate the interrelationship of particulate penetration, SO 2 scrubber operation, waste production, and waste properties. Tests compared a fabric filter/wet scrubber and ESP/wet scrubber, the latter operated to simulate 1979 New Source Performance Standards (NSPS), 1971 NSPS, and pre-NSPS ESP units. Tests were conducted with low-sulfur coal producing a flue gas concentration of400ppm; flue gas spiking could be used to increase SO 2 to 2000 ppm. Scrubber waste was dewatered in a thickener and vacuum belt filter (to 55 percent solids content), and mixed with fly ash. The pilot SO 2 scrubber—when preceded by an ESP and forced to operate in zero-discharge—captured less SO 2 than when preceded by a fabric filter. Also, scrubber operation with the ESP produced a greater quantity of waste with difficult handling characteristics, as compared to operation with the fabric filter. These difficulties occurred with particulate penetration above 0.10 lb/MBtu, which could reduce reagent utilization to 80percent. These results are attributable to inhibited limestone dissolution due to accumulation of an aluminum/fluoride compound. For both lowsulfur and simulated high-sulfur test conditions, allowing wastewater discharge to purge aluminum/fluoride content restored performance to design levels. Particulate control efficiency also affected solid waste physical properties. The fabric filter/wet scrubber produced the lowest solid waste permeability (10 ?8 cm/s). ESP operation at 1979 NSPS and pre-1971 NSPS ESPs increased solid waste permeability to 10 ?7 and 10 ?6 cm/s, respectively. These results are meaningful for SO 2 scrubbers both for new plants and for retrofit to units with pre-NSPS ESPs, and could become significant with the increasing trend to restricted water discharge. 相似文献
4.
Pulse-jet fabric filters (PJFFs) are widely used in U.S. industrial boiler applications and in utility and industrial boilers abroad. Their small size and reduced cost relative to more conventional reverse-gas baghouses makes the use of PJFFs appear to be an attractive particulate control option for utility boilers. This paper (Part 2 of a three-part series) summarizes the results of pilot PJFF studies sponsored by the Electric Power Research Institute at different utility sites in the United States. The purpose of these tests is to evaluate PJFF performance for U.S. fossil-fuel-fired applications. These data are also used to corroborate the results of a recent worldwide survey of PJFF user experience, as described in Part 1 of this series. Part 3 will provide a cost comparison of PJFFs to other particulate control options such as electrostatic precipitators and reverse-gas baghouses. 相似文献
5.
“Industrial fabric filtration, the sleeping giant, is stirring. It appears that we are about to experience a new period of innovation and development similar to the one that occurred during the 1950’s.” The above remarks by Professor First, as presented in the Symposium, unerscore the renewed interest in filtration as a means for controlling submicron particulate emissions. Bur-chard and others pointed out the significance of fine particulate emissions, especially with regard to health effects and visibility degradation, and Walsh discussed the data required to employ fabric filters appropriately for particulate emission control. 相似文献
6.
Encouraged by the successes attained with fly ash control by fabric filters in Pennsylvania Power & Light and Colorado Ute, other utilities are installing, planning, and/or considering baghouses as a practical and economical means for controlling emissions from the burning of low sulfur coals. Where deposits of alkaline reagents (i.e. nahcolite) are available, some power plants are also considering a process for dry scrubbing SO 2 from the flue gas. By introducing such reagents with the emission ahead of the fabric collector, both partlculates and SO 2 are removed. 相似文献
7.
This symposium sponsored by the Fiber Society and the Filtration Society has provided a clear indication that the “black-art” era of filtration has passed or is on its way out. The R & D efforts reviewed here by investigators from diverse disciplines provide evidence that these high efficiency particulate control devices can be made to function not only more consistently at high levels but now with even better control of the fine, health damaging particles. The outstanding improvement in every filtration parameter, reliably attainable by aerosol charging and/or by imposing an electric field on the filter, indicates clearly that fabric filtration has now reached an even higher plateau in particulate control technology. 相似文献
8.
Abstract Hydrogen sulfide (H 2S) generation in construction and demolition (C&D) debris landfills has been associated with the biodegradation of gypsum drywall. Laboratory research was conducted to observe H 2S generation when drywall was codisposed with different C&D debris constituents. Two experiments were conducted using simulated landfill columns. Experiment 1 consisted of various combinations of drywall, wood, and concrete to determine the impact of different waste constituents and combinations on H 2S generation. Experiment 2 was designed to examine the effect of concrete on H 2S generation and migration. The results indicate that decaying drywall, even alone, leached enough sulfate ions and organic matter for sulfate-reducing bacteria (SRB) to generate large H 2S concentrations as high as 63,000 ppmv. The codis-posed wastes show some effect on H 2S generation. At the end of experiment 1, the wood/drywall and drywall alone columns possessed H 2S concentrations >40,000 ppmv. Conversely, H 2S concentrations were <1 ppmv in those columns containing concrete. Concrete plays a role in decreasing H 2S by increasing pH out of the range for SRB growth and by reacting with H 2S. This study also showed that wood lowered H 2S concentrations initially by decreasing leachate pH values. Based on the results, two possible control mechanisms to mitigate H 2S generation in C&D debris landfills are suggested. 相似文献
9.
Synthetic textile materials are noted as one of the major contributors to microfiber release from household laundry. The higher usage of synthetic textiles was noted as one of the major reasons for the leaching of microfibers into the aquatic system. Though few laundry aids are available to control the release of microfiber from laundry, no successful methods were developed to control it in the fabric itself. Hence, this research aimed to analyze the effectiveness of surface modification of polyester fabric using lipase enzyme and its impact on microfiber shedding. Taguchi’s L9 orthogonal array was adopted to optimize the enzyme treatment process parameters to reduce microfiber shedding. The results showed that enzyme concentration was the major influencing factor with a contribution of 35.56%, followed by treatment pH (35.247%), treatment time (17.46%), and treatment temperature (11.74%). The optimization with S/N ratio showed minimum microfiber shedding at an enzyme concentration of 0.5 gram per liter (gpl), treatment temperature of 55°C, 6.5 pH, and a treatment time of 45 minutes. Knitted polyester fabric treated with the optimized enzyme treatment condition showed a significant reduction (p<0.05) in microfiber shedding (count—79.11% and mass—85.68%). The surface changes and the interaction of the enzyme on the fabric were confirmed by hydrolytic activity and FTIR analysis. The optimized treatment on different knit structures and fabric with different grams per square meter (GSM) indicated the versatility of the treatment irrespective of fabric parameters. The repeated laundry process (20 washing cycles) showed that the enzyme-treated samples had a significant level (p<0.05) of reduction in shedding than the control sample. The difference in shedding after 20 washes supports the efficiency and longevity of the enzyme treatment process in reducing microfiber shedding. 相似文献
10.
Addition of urea-based antifreeze admixtures during cement mixing in construction of buildings has led to increasing indoor air pollution due to continuous transformation and emission of urea to gaseous ammonia in indoor concrete wall. In order to control ammonia pollution from indoor concrete wall, the aqueous dispersion was firstly prepared with nano-scale TiO 2 photocatalysts and dispersing agent, and then mixed with some textile additives to establish a treating bath or coating paste. Cotton woven fabrics were used as the support materials owing to their large surface area and large number of hydrophilic groups on their cellulose molecules and finished using padding and coating methods, respectively. Two TiO 2-loaded fabrics were obtained and characterized by X-ray diffractometer (XRD) and scanning electron microscopy (SEM). Moreover, a specifically designed ammonia photocatalytic system consisting of a small environmental chamber and a reactor was used for assessing the performance of these TiO 2-loaded fabrics as the wall cloth or curtains used in house rooms in the future and some factors affecting ammonia decomposition are discussed. Furthermore, a design equation of surface catalytic kinetics was developed for describing the decomposition of ammonia in air stream. The results indicated that increasing dosage of the TiO 2 aqueous dispersion in treating bath or coating paste improved the ammonia decomposition. And ammonia was effectively removed at low ammonia concentration or gas flow rate. When relative humidity level was 45%, ammonia decomposition was remarkably enhanced. It is the fact that ammonia could be significantly decomposed in the presence of the TiO 2-padded cotton fabric. Whereas, the TiO 2-coated cotton fabric had the reduced photocatalytic decomposition of ammonia and high adsorption to ammonia owing to their acrylic binder layer. Finally, the reaction rate constant k and the adsorption equilibrium constant K values were determined through a curve-fitting method and the TiO 2-padded cotton fabric had the higher k value and lower K value than the TiO 2-coated cotton fabric. 相似文献
11.
The discoloration of exterior paint, has been shown to occur when H 2S in the air reacts with heavy metal salts used as pigments or fungicides in the paint. Simple field tests can give an indication whether H 2S was involved. An electron diffraction technique is described to identify the discolored compound in paint samples. Field experience in Jacksonville using this method is described. 相似文献
12.
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
13.
A monitoring program based on an indirect method was conducted to assess the approximation of the olfactory impact in several wastewater treatment plants (in the present work, only one is shown). The method uses H 2S passive sampling using Palmes-type diffusion tubes impregnated with silver nitrate and fluorometric analysis employing fluorescein mercuric acetate. The analytical procedure was validated in the exposure chamber. Exposure periods of at least 4 days are recommended. The quantification limit of the procedure is 0.61 ppb for a 5-day sampling, which allows the H 2S immission (ground concentration) level to be measured within its low odor threshold, from 0.5 to 300 ppb. Experimental results suggest an exposure time greater than 4 days, while recovery efficiency of the procedure, 93.0 ± 1.8%, seems not to depend on the amount of H 2S collected by the samplers within their application range. The repeatability, expressed as relative standard deviation, is lower than 7%, which is within the limits normally accepted for this type of sampler. Statistical comparison showed that this procedure and the reference method provide analogous accuracy. The proposed procedure was applied in two experimental campaigns, one intensive and the other extensive, and concentrations within the H 2S low odor threshold were quantified at each sampling point. From these results, it can be concluded that the procedure shows good potential for monitoring the olfactory impact around facilities where H 2S emissions are dominant. Implications: Passive samplers are very attractive tools to experimentally tackle a number of air pollution problems, especially those related to odor impact. Their small size and cost permit a denser sampling design and thus a more detailed spatial characterization than other techniques. On the other hand, the large inherent variability in passive sampler measures requires an uncertainty analysis of the chemical species and analytical procedures used. 相似文献
14.
Source contributions to the surface O 3 concentrations in southern Ontario were assessed for the 1979–1985 period. Ozone episode analyses indicate a frequency of about nine episodes per year (15 episode-days). These occur primarily in the summer months and are generally manifestations of the northern extent of the O 3 problem in eastern North America. Widespread elevated O 3 levels tend to occur under weather classes indicative of back or centre of the high pressure situations and associated flow/trajectory from areas south/southwest of the lower Great Lakes. These episodes vary considerably from year-to-year. Local impacts on O 3 levels are generally small.A study of O 3 levels during cloud-free summer days for the period 1981–1985 gave local ‘background’ O 3 levels of about 20–30 ppb daily and 30–50 ppb hourly maxima. The O 3 contributions from the U.S. to southern Canada (assuming local ‘background’ O 3 levels to be independent of wind direction) were estimated to be 30–35 ppb daily and 30–50 ppb hourly maxima. These results indicate an overall O 3 contribution of about 50–60% from the U.S. to southern Ontario. For episode-days, the U.S. contribution is even more significant. 相似文献
15.
To understand the temporal variations and bioaccumulation of heavy metals in the coastal marshes, the concentrations of heavy metals (Cr, Ni, Pb, and Cu) in the two Suaeda salsa marshes [middle S. salsa marsh (MM) and low S. salsa marsh (LM)] of the Yellow River estuary were determined from May to November in 2008 by in situ sampling and inductively coupled plasma mass spectrometry (ICP-MS) analysis. Results showed that heavy metal concentrations in S. salsa of MM and LM were generally in the order of Cu?>?Cr?>?Pb?>?Ni, while those in sediments fell in the order of Cr?>?Ni?>?Cu?>?Pb. Heavy metal concentrations of S. salsa in MM and LM were different, and significant differences were observed in stems ( F?=?4.797, p?=?0.046) and litters ( F?=?6.799, p?=?0.026) for Ni. Litter was the main stock of heavy metals, and the allocations of Cr, Ni, and Pb reached 31.25–51.31, 28.49–42.58, and 29.55–66.79 % (in MM) and 36.73–48.60, 41.70–57.87, and 33.30–60.64 % (in LM), respectively. The ratios of roots/leaves (R/L) and roots/stems (R/S) for Cr and Ni in MM were mostly greater than 1, while those ratios in LM were mostly less than 1, indicating that Cr and Ni in S. salsa at LM had greater mobility compared with those at MM. Moreover, the [accumulation factor, AF] plant of Cr, Ni, Cu, and Pb in LM, especially [AF] root and [AF] stem of Cr and [AF] litter of Ni, was also higher than that in MM. These indicated that S. salsa grown in LM was more suitable for potential biomonitor or phytoremediation of Cr, Ni, Cu, and Pb if intertidal sediments were seriously contaminated with an increase of pollutant loading (especially heavy metals) in the Yellow River estuary. The use of biomonitor ( S. salsa) living and growing in LM could yield valuable information not only on the presence of anthropogenic stressors, but, more importantly, on the adverse influence the stressors are having on the environment. 相似文献
16.
An examination of the available toxicological literature indicates that sulfur dioxide itself would be properly classified as a mild respiratory irritant, the main portion of which is absorbed in the upper respiratory tract. The reported industrial experience of symptoms of mild chronic respiratory irritation from exposures at or above 5 ppm is compatible with what would have been predicted on the basis of available toxicological data. The basic physiological response to inhalation of pure SO 2 appears to be a mild degree of bronchoconstriction reflected in a measurable increase in flow resistance. Although the response is highly variable, most individuals tested have responded to 5 ppm and levels of 5 to 10 ppm have upon occasion produced severe bronchospasm in sensitive individuals. This serves to point up the fact that experience with the industrial Threshold Limit Value (5 ppm) is not applicable as a guide for the general population. Although the majority of individuals tested have shown no detectable response to levels of 1 ppm, there are again sensitive individuals who have responded. It is not known whether these individuals would have responded to concentrations lower than this. The response of these more sensitive individuals to 1 ppm would be classified as detectable response, not as severe bronchospasm. An examination of the available toxicological literature also indicates that sulfuric acid and irritant sulfates, to the extent that the latter have been examined, are more potent irritants than sulfur dioxide. This has been demonstrated in studies using morality and lung pathology as criteria as well as in studies using alterations in pulmonary function in experimental animals and human subjects. The irritant potency of these substances is affected by particle size and by relative humidity, which factors are probably interrelated. It is unfortunate that these substances have not been as yet studied in as great detail as has the less irritant sulfur dioxide. There is evidence which cannot be ignored, even though it is based entirely on animal experiments of one investigator, indicating that the presence of particulate material capable of oxidizing sulfur dioxide to sulfuric acid caused a three to fourfold potentiation of the irritant response. The aerosols causing this potentiation were soluble salts of ferrous iron, manganese and vanadium all of which would become droplets upon inhalation. Insoluble aerosols such as carbon, iron oxide fume, triphenylphosphate or fly ash did not cause a potentiation of the irritant action of SO 2 even when used at higher concentrations. The concentrations of SO 2 used in these various experiments were in some cases as low as 0.16 ppm. The catalytic aerosols were used at concentrations of 0.7 to 1 mg/m 3 which is above any reported levels of these metals in urban air. If the SO 2 present as an air pollutant remained unaltered until removed by dilution, there would be no evidence in the toxicological literature suggesting that it would be likely to have any effects on man at prevailing levels. Studies of atmospheric chemistry have shown that SO 2 does not remain unaltered in the atmosphere, especially under onditions of high humidity and in the presence of particulate material, but is converted to H 2SO 4. Such a conversion increases its irritant potency. On this basis the toxicological literature combined with the literature of atmospheric chemistry suggest that sulfur dioxide levels be controlled in terms of the potential formation of irritant particles. This means that control measures as far as feasible should be aimed at both SO 2 and particulate material and not against either alone. 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.
ABSTRACT The purpose of this research was to determine the efficiency of a polymer biocover for the abatement of H 2S and NH 3 emissions from an east-central Missouri swine lagoon with a total surface area of 7800 m 2. The flux rate of NH 3, H 2S, and CH 4 was monitored continuously from two adjacent, circular ( d = 66 m) control and treatment plots using a nonintrusive, micrometeorological method during three independent sampling periods that ranged between 52 and 149 hr. Abatement rates were observed to undergo a temporal acclimation event in which NH 3 abatement efficiency improved from 17 to 54% ( p = <0.0001 to 0.0005) and H 2S abatement efficiency improved from 23 to 58% ( p < 0.0001) over a 3-month period. The increase in abatement efficiency for NH 3 and H 2S over the sampling period was correlated with the development of a stable anaerobic floc layer on the bottom surface of the biocover that reduced mass transfer of NH 3 and H 2S across the surface. Analysis of methanogenesis activity showed that the biocover enhanced the rate of anaerobic digestion by 25% when compared with the control. The biocover-enhanced anaerobic digestion process was shown to represent an effective mechanism to counteract the accumulation of methanogenic substrates in the biocovered lagoon. 相似文献
19.
ABSTRACT This study investigated the effects of feedstock additives [polyvinyl chloride (PVC) and NaCl] and spray dryer additives (SiO 2, CaCl 2, NaHCO 3) on heavy metal and fly ash removal efficiencies, and on particle size distribution of heavy metals. A spray dryer with an integrated fabric filter was used as an air pollution control device (APCD). Removal efficiencies for fly ash and heavy metals were greater than 95 and 90%, respectively. When additives of PVC or NaCl were used, the concentration of heavy metals distributed in fly ash apparently varied when the particle diameter was <1 μm. Although the effects of the additives SiO 2, CaCl 2, and NaHCO 3 on the elemental size distribution of Cr were insignificant, these additives did slightly increase concentrations of Cd, Zn, and Pb partitioning in coarser particles (>1μm). 相似文献
20.
Abstract Recent regulations have required reductions in emissions of nitrogen oxides (NO x) from electric utility boilers. To comply with these regulatory requirements, it is increasingly important to implement state-of-the-art NO x control technologies on coal-fired utility boilers. This paper reviews NO x control options for these boilers. It discusses the established commercial primary and secondary control technologies and examines what is being done to use them more effectively. Furthermore, the paper discusses recent developments in NO x controls. The popular primary control technologies in use in the United States are low-NO x burners and overfire air. Data reflect that average NO x reductions for specific primary controls have ranged from 35% to 63% from 1995 emissions levels. The secondary NO x control technologies applied on U.S. coal-fired utility boilers include reburning, selective noncatalytic reduction (SNCR), and selective catalytic reduction (SCR). Thirty-six U.S. coal-fired utility boilers have installed SNCR, and reported NO x reductions achieved at these applications ranged from 15% to 66%. Recently, SCR has been installed at >150 U.S. coal-fired utility boilers. Data on the performance of 20 SCR systems operating in the United States with low-NO x emissions reflect that in 2003, these units achieved NO x emission rates between 0.04 and 0.07 lb/10 6 Btu. 相似文献
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