共查询到20条相似文献,搜索用时 15 毫秒
1.
In recent years, the utility industry has turned to baghouses as an alternative technology for particulate emission control from pulverized-coal-fired power plants. One of the more significant issues is to improve poor gas distribution that causes bag failures in baghouse operation. Bag failures during operation are almost impossible to prevent, but proper flow design can help in their prevention. This study investigated vertical velocity profiles below the bags in a baghouse (the hopper region) to determine whether flow could be improved with the installation of flow distributors in the hopper region. Three types of flow distributors were used to improve flow distribution and were compared with the original baghouse without flow distributors. Velocity profiles were measured by a hot-wire anemometer at an inlet velocity of 18 m/sec. Uniformity of flow distribution was calculated by the uniformity value U for the velocity profile of each flow distributor. Experimental results showed that the velocity profile of the empty configuration (without flow distributors) was poor because the uniformity value was 2.048. The uniformity values of type 1 (flow distributor with three vertical vanes), type 2 (flow distributor with one vertical and one inclined vane), and type 3 (flow distributor with two inclined vanes) configurations were reduced to 1.051, 0.617, and 0.526, respectively. These results indicate that the flow distributors designed in this study made significant improvements in the velocity profile of a baghouse, with the type 3 configuration having the best performance. 相似文献
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Flora JR Hargis RA O'Dowd WJ Karash A Pennline HW Vidic RD 《Journal of the Air & Waste Management Association (1995)》2006,56(3):343-349
A mathematical model based on simple cake filtration theory was coupled to a previously developed two-stage mathematical model for mercury (Hg) removal using powdered activated carbon injection upstream of a baghouse filter. Values of the average permeability of the filter cake and the filter resistance extracted from the model were 4.4 x 10(-13) m2 and 2.5 x 10(-4) m(-1), respectively. The flow is redistributed during partial cleaning of the filter, with flows higher across the newly cleaned filter section. The calculated average Hg removal efficiency from the baghouse is lower because of the high mass flux of Hg exiting the filter in the newly cleaned section. The model shows that calculated average Hg removal is affected by permeability, filter resistance, fraction of the baghouse cleaned, and cleaning interval. 相似文献
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《Atmospheric environment(England)》1983,17(10):1909-1913
A model based on Darcy's law allows prediction of pressure drop in a pulse-jet cleaned fabric filter. The model considers the effects of filtration velocity, dust areal density added during one filtration cycle, and pulse pressure. Data used to calibrate the model were collected in experiments with three fabric surface treatments and three dusts conducted at three filtration velocities, for a total of 27 different experimental conditions. The fabric used was polyester felt with untreated, singed, or PTFE-laminated surface. The dusts used were granite, limestone and fly ash. Filtration velocities were 50,75 and 100 mm s−1. Dust areal density added during one filtration cycle was constant, as was pulse pressure. Under these conditions, fabric surface treatment alone largely determined the values for two of the three constants in the model; the third constant depends on pressure drop characteristics of the venturi at the top of each filter bag. 相似文献
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考察了2种活性炭(活性炭A和活性碳B)对垃圾焚烧厂烟气中二恶英去除率的影响。通过采集与分析垃圾焚烧厂“活性炭喷射+布袋除尘”协同处置工艺前口和后口的烟气样品,得到前后口2,3,7,8-PCDD/Fs的浓度,并计算去除率。结果表明:2种活性炭对2,3,7,8-PCDFs的去除率相当,均为99%左右;而对2,3,7,8-PCDDs的去除率略低,分布在83.3%~99.9%之间,并且活性炭A的去除率高于活性炭B。通过对2种活性炭性能指标测试结果的比较,具备更丰富的中孔以及更大的微孔、中孔平均孔径可能是活性炭A去除率更高的原因。此外,比较了活性炭在不同投加速率(5、10和15 kg·h-1)下对二恶英的去除率,发现低投加速率时二恶英去除率随投加速率的增加而增加,而当投加速率从10 kg·h-1增加到15 kg·h-1时二恶英去除率无明显变化。 相似文献
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《Atmospheric environment(England)》1979,13(10):1427-1436
Packed beds of molecular-sieve pellets have found application in the high-altitude collection of certain gases present in the atmosphere in low concentrations. To facilitate the design of such low-pressure gas samplers, a theory is developed establishing practical relations between pressure drop, gas flow rate, and various gas and packing characteristics. Pressure-drop vs flow-rate relations are confirmed experimentally over the range of ambient pressures of 0.0013-0.79 atm, and for conditions of flow that may be either viscous or inertial, compressible or incompressible, or with or without molecular slip.The theory shows that, for a given set of experimental conditions, there exists a critical gas velocity below which a pressure drop and its associated velocity are possible, if at all, at only a single ambient pressure. Above the critical velocity, however, a given pressure drop-velocity combination may occur, if at all, at either one or two ambient pressures.Methods are described for correlating experimental data in terms of dimensionless groups and, on the basis of relatively few measurements near atmospheric conditions, for estimating pressure drop over a broad range of ambient pressures and gas velocities.The theory derived is thought to be applicable, under appropriate conditions, to a variety of porous media including fibrous filters. 相似文献
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Mohebbi A Taheri M Fathikaijahi J Talaie MR 《Journal of the Air & Waste Management Association (1995)》2002,52(3):308-312
A mathematical model has been developed to predict pressure drop in an orifice scrubber. This model is based on a Lagrangian approach for droplet movement and a particle-source-in-cell (PSI-CELL) model for calculating droplet concentration distribution. The k-epsilon turbulent model including body force due to the drag force between fluid and droplets was used to evaluate the fluid velocity distribution. The effect of orifice size on pressure drop and the correlations for mean droplet diameter have been studied. The results from the model have been compared with experimental data. This comparison shows excellent agreement between the calculated results and the experimental data. 相似文献
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为了提高除尘器对细颗粒物的捕捉效率,制备了一种由蜂窝陶瓷、聚酰胺材质扭线刷和缚尘剂组成的除尘模块。其中填充了聚酰胺扭线刷的蜂窝陶瓷为除尘模块的主体,该主体独有的结构将拦截尘粒的滤料纤维分布在与气流方向垂直的平面上,有利于含尘气体的捕捉。缚尘剂为除尘模块的增强因子,它可以在除尘模块表面形成液膜,用来抑制除尘时的二次扬尘,提高除尘效率。通过对涂覆有缚尘剂的除尘模块的除尘效率的研究表明,含尘气体通过除尘模块,对粒径2μm的颗粒除尘效率最高可达到97.08%,表明了除尘模块去除细颗粒物的潜力;另外,在实验中设定的条件下,系统的压降保持在85 Pa以下。总体而言,该除尘模块在保持较低压降的同时对细颗粒物有较高的去除效率,有应用在工业除尘的潜力。 相似文献
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《Atmospheric environment(England)》1983,17(1):161-167
Computer simulations were conducted to investigate potential pressure drop reductions obtainable by combining cyclones, as pre-collectors, with fabric filters. The Leith-Licht model was used to characterize cyclone emissions and the specific resistance (K2) of the fabric filter dust cake was calculated from an empirical correlation. Several important dimensionless groups were identified and evaluated. One group, the product of the ratio of the dust cake specific resistances expected with and without the cyclone and the mass penetration of the cyclone, (K2/K2) Pn, indicates whether a pressure drop reduction is possible. A correlation was developed for this group as a function of the size properties of the inlet dust (particle mass median diameter and geometric standard deviation) and the cyclone particle cut diameter. Expressions were derived for the break-even time, the duration of filtration with the cyclone needed to show a pressure drop reduction in comparison with filtration without the cyclone. It is shown that in previously reported experiments and simulations indicating an advantage for the combined cyclone-fabric filter system, filtration cycles were typically longer than the break-even time; those showing no improvement typically had filtration times shorter than the break-even time. 相似文献
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Treatment wetlands have a finite period of effective nutrient removal after which treatment efficiency declines. This is due to the accumulation of organic matter which decreases the capacity and hydraulic retention time of the wetland. We investigated four potential solutions to improve the soluble reactive P (SRP) removal of a municipal wastewater treatment wetland soil including; dry down, surface additions of alum or calcium carbonate and physical removal of the accreted organic soil under both aerobic and anaerobic water column conditions. The flux of SRP from the soil to the water column under aerobic conditions was higher for the continuously flooded controls (1.1 ± 0.4 mg P m−2 d−1), dry down (1.5 ± 0.9 mg P m−2 d−1) and CaCO3 (0.8 ± 0.7 mg P m−2 d−1) treatments while the soil removal and alum treatments were significantly lower at 0.02 ± 0.10 and −0.07 ± 0.02 mg P m−2 d−1, respectively. These results demonstrate that the two most effective management strategies at sequestering SRP were organic soil removal and alum additions. There are difficulties and costs associated with removal and disposal of soils from a treatment wetland. Therefore our findings suggest that alum addition may be the most cost effective and efficient means of increasing the sequestering of P in aging treatment wetlands experiencing reduced P removal rates. However, more research is needed to determine the longer term effects of alum buildup in the organic soil on the wetland biota, in particular, on the macrophytes and invertebrates. Since alum effectiveness is time limited, a longer term solution to P flux may favor the organic soil removal. 相似文献
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D. Bémer L. Wingert Y. Morele I. Subra 《Journal of the Air & Waste Management Association (1995)》2013,63(9):1119-1126
A process for filtering an aerosol of ultrafine metallic particles (UFP) has been designed and tested, based on the principle of a multistage granular bed. The filtration system comprised a succession of granular beds of varying thickness composed of glass beads of different diameters. This system allows the pressure drop to be regenerated during filtration (“on-line” mode) using a vibrating probe. Tests monitoring the pressure drop were conducted on a “10-L/min” low airflow rate device and on a “100-m3/hr” prototype. Granular bed unclogging is automated on the latter. The cyclic operation and filtration performances are similar to that of filter medium-based industrial dust collectors.Implications:?Filtration of ultrafine metallic particles generated by different industrial processes such as arc welding, metal cutting, or spraying constitutes a difficult problem due to the high filter clogging properties of these particles and to the high temperatures generally encountered. Granular beds represent an advantageous means of filtering these aerosols with difficult properties. 相似文献
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Fritsky KJ Kumm JH Wilken M 《Journal of the Air & Waste Management Association (1995)》2001,51(12):1642-1649
Phoenix Services, Inc., owns and operates the Baltimore Regional Medical Waste Incinerator in Baltimore, MD. New regulations for dioxins and furans imposed a limit that was considerably below historical emission levels. To determine a method to comply with the new dioxin/furan regulations, Phoenix Services performed trials with powdered activated carbon (PAC). Although the results with carbon were acceptable, Phoenix Services decided to replace their woven fiberglass filter bags with catalytic filters that simultaneously destroy dioxins and furans and collect particulate matter (PM). The catalytic filter system offered several advantages to Phoenix Services, including destruction of dioxins and furans instead of adsorption on carbon. The catalytic filters also offered a passive solution that did not require new carbon injection equipment. In January 2000, a campaign to measure dioxins/furans and PM was undertaken. The measurements allowed the catalytic filter system to be evaluated. Some of the key findings of this investigation are The dioxin/furan emission was less than 0.1 ng toxicity equivalents (TEQ)/Nm3 at 11% O2. This concentration is approximately 2 orders of magnitude less than historical averages and it is well below the new regulatory limits, for both existing and new sources of this type; the amount of dioxin/furans destroyed by the catalytic filters was approximately 1.73 ng TEQ/Nm3 at 11% O2; and the particulate emission was 12-17 times less than the regulatory limit. 相似文献
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14C-carbofuran underwent considerable mineralization (approximately 30% of the applied activity) in Vertisol soil under moist and flooded conditions during 60 days incubation. Bound residues were formed under both the conditions, the extent being more in moist soils (approximately 55% of the applied activity) than under flooded conditions (approximately 41% of the applied activity). 3-Keto carbofuran was the only significant metabolite observed under flooded conditions. 相似文献
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A computational model is applied to the optimization of pulsed pumping systems for efficient in situ remediation of groundwater contaminants. In the pulsed pumping mode of operation, periodic rather than continuous pumping is used. During the pump-off or trapping phase, natural gradient flow transports contaminated groundwater into a treatment zone surrounding a line of injection and extraction wells that transect the contaminant plume. Prior to breakthrough of the contaminated water from the treatment zone, the wells are activated and the pump-on or treatment phase ensues, wherein extracted water is augmented to stimulate pollutant degradation and recirculated for a sufficient period of time to achieve mandated levels of contaminant removal. An important design consideration in pulsed pumping groundwater remediation systems is the pumping schedule adopted to best minimize operational costs for the well grid while still satisfying treatment requirements. Using an analytic two-dimensional potential flow model, optimal pumping frequencies and pumping event durations have been investigated for a set of model aquifer-well systems with different well spacings and well-line lengths, and varying aquifer physical properties. The results for homogeneous systems with greater than five wells and moderate to high pumping rates are reduced to a single, dimensionless correlation. Results for heterogeneous systems are presented graphically in terms of dimensionless parameters to serve as an efficient tool for initial design and selection of the pumping regimen best suited for pulsed pumping operation for a particular well configuration and extraction rate. In the absence of significant retardation or degradation during the pump-off phase, average pumping rates for pulsed operation were found to be greater than the continuous pumping rate required to prevent contaminant breakthrough. 相似文献
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Azari Prisa Bostani Abdol Amir 《Environmental science and pollution research international》2017,24(25):20438-20445
Environmental Science and Pollution Research - Different methods, including the use of nanoscale zero-valent iron (NZVI), have been used to treat arsenic (As)-contaminated environments, with much... 相似文献
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Bench-scale packed zeolite columns were set up and operated to investigate the continuous removal of ammonium ions from compost leachate. The effects of hydraulic retention time (HRT), and particle size of the zeolite on the ammonia adsorption capacity were studied. For both the coarse particle and the powdered zeolite columns, higher ammonia removal efficiencies were achieved with longer HRT (i.e., lower influent flow rate) tests. At the same HRT, ammonia removal efficiencies from tests with powdered zeolite were generally 20% higher than tests with the coarse particle zeolite. A HRT of 6 hours was found appropriate for efficient ammonia removal, and an operating capacity of 1.31 mg N/g zeolite was obtained. Over 98% of the ammonia input from the influent was consistently removed for over 5 bed volumes (BV) of compost leachate flowing through the zeolite column. Zeolite proved to have a great potential as a medium for ammonia removal in treating composting leachate. 相似文献
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Kari B Fitzmorris Robert S Reimers Jan A Oleszkiewicz M Dale Little 《Water environment research》2007,79(4):388-395
From field studies conducted by Tulane University (New Orleans, Louisiana), efficiency of advanced alkaline disinfection in closed systems was found to depend on ammonia concentration, pH, exposure time, temperature, total solids content, pretreatment storage time, and mixing effectiveness. In this study of a closed alkaline system, an additional pathogen stressor pressure was tested. The effect of the alkaline dosing has been assessed for dewatered raw and aerobically and anaerobically digested municipal sludge cake that produce un-ionized ammonia at concentrations of 0.05 to 2% on a dry-weight basis. Inactivation of Ascaris suum eggs increased from 50 to 99% as the temperature was increased from 40 to 55 degrees C, thus achieving Class A levels. The systems studied were compared with an alkaline process operated under open conditions, which limited the concentrations of ammonia available because of Henry's Law. Under a closed pressurized system, the effect of un-ionized ammonia was greatly increased, and the resulting time required for inactivation was reduced from hours or days to minutes. In the next few years, it is expected that alkaline disinfection of biosolids will be optimized in relation to the factors stated above, at much lower doses of the alkaline agents. The closed-system alkaline processes that will be developed will be more energy-efficient, cost-effective, and have full control of potential odorous emissions. 相似文献