Effects of Operating Conditions on Dust Cake Behavior in Filters with High Surface-to-volume Ratios PDF Download
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Languages : en
Pages : 6
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Book Description
Generally, new filter elements with large S/V ratios typically have inlet passages with a small cross sectional area to reach a large filter surface area internal to the filter element. To prevent plugging of the inlet passages, or to prevent the filter passage inlet velocity from becoming dangerously high causing cake disturbance, the high S/V filter can only accommodate a very thin cake. The conventional backpulse cleaning technique may not be able to dislodge this thin cake. The multi-tier design using ceramic candles can tolerate a thick dust cake. The conventional back-pulse cleaning technique could then be used to remove the dust cake. However, due to the proximity of the neighboring tiers, the large-volume flow of the back-pulse mixing with a huge quantity of dislodged dust cake could potentially perturb the local flow distribution from its initially well-mixed uniform flow and dust concentration. As soon as one spot or patch of dust cake forms on the neighboring candle surface due to this redistributed nonuniform flow and dust concentration, patching dust redeposition will occur on the neighboring tiers, leading eventually to ash bridging. This is because the rigid ceramic candle, unlike the fabric filter, does not flex during back-pulse cleaning; therefore, it cannot tolerate the uneven flow distribution. The back-pulse flow universally seeks the least resistance path, resulting in an uneven or patchy cleaning. Ash bridging is known to cause ceramic candle breakage due to the pulse ratchet problem. To understand the back-pulse cleaning problem caused by the use of high S/V rigid filter elements or the implementation of a multi-tier design, a bench-scale, two-dimensional (2-D) cold flow filter test facility is being constructed, and is scheduled for shakedown and testing in July 1993.
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Category :
Languages : en
Pages : 6
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Book Description
Generally, new filter elements with large S/V ratios typically have inlet passages with a small cross sectional area to reach a large filter surface area internal to the filter element. To prevent plugging of the inlet passages, or to prevent the filter passage inlet velocity from becoming dangerously high causing cake disturbance, the high S/V filter can only accommodate a very thin cake. The conventional backpulse cleaning technique may not be able to dislodge this thin cake. The multi-tier design using ceramic candles can tolerate a thick dust cake. The conventional back-pulse cleaning technique could then be used to remove the dust cake. However, due to the proximity of the neighboring tiers, the large-volume flow of the back-pulse mixing with a huge quantity of dislodged dust cake could potentially perturb the local flow distribution from its initially well-mixed uniform flow and dust concentration. As soon as one spot or patch of dust cake forms on the neighboring candle surface due to this redistributed nonuniform flow and dust concentration, patching dust redeposition will occur on the neighboring tiers, leading eventually to ash bridging. This is because the rigid ceramic candle, unlike the fabric filter, does not flex during back-pulse cleaning; therefore, it cannot tolerate the uneven flow distribution. The back-pulse flow universally seeks the least resistance path, resulting in an uneven or patchy cleaning. Ash bridging is known to cause ceramic candle breakage due to the pulse ratchet problem. To understand the back-pulse cleaning problem caused by the use of high S/V rigid filter elements or the implementation of a multi-tier design, a bench-scale, two-dimensional (2-D) cold flow filter test facility is being constructed, and is scheduled for shakedown and testing in July 1993.
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Languages : en
Pages : 8
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High-temperature particulate control devices are an integral part of advanced coal-fired power systems. By efficiently removing minute particles from high-temperature gas streams, environmentally clean and efficient power systems can be realized. In recent years, economic incentives have prompted developers of high-temperature and high-pressure (HTHP) particulate filtration systems to pursue filter element designs with more filter surface area for a given volume. Although higher surface-to-volume (SV) ratio filter designs are driven by economic incentives, physical constraints and the fundamental behavior of dust cake formation and removal will limit the maximum SV ratio. In an attempt to improve the understanding of dust cake behavior in a well controlled environment, a two-dimensional cold flow filter module is being tested. This filter module can be used to investigate dust cake formation, removal, and re-entrainment over a range of operating conditions. Preliminary results suggest that the cohesive strength of the particulate media has a strong influence on how the dust cake is removed during reverse pulse cleaning. Furthermore, the properties of the particulate media play an important role in forming non-uniform dust cakes. In the following paragraphs, the experimental apparatus, preliminary results, and future plans will be discussed.
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Category : Power resources
Languages : en
Pages : 444
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Category : Coal
Languages : en
Pages : 346
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Category : Government publications
Languages : en
Pages : 1224
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Category :
Languages : en
Pages : 105
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In the spring of 1989, two separate test series were simultaneously conducted at the US Department of Energy's (DOE's) Morgantown Energy Technology Center (METC) to examine applied and fundamental behavior of dust cake filtration under high temperature and high pressure (HTHP) conditions. The purpose was to provide information on dust-cake filtration properties to gas stream cleanup researchers associated with the Tidd 70 megawatt (MW) pressurized fluidized-bed combustor (PFBC). The two test facilities included (1) a high-pressure natural-gas combustor with injected particulate, which was fed to two full-size candle filters; and (2) an atmospheric fluidized-bed combustor (AFBC) with coal and limestone sorbent to generate a particulate-laden combustion exhaust gas, which was sent to a single full-size candle filter and a small-scale disc filter. Several major conclusions from these studies are noted below. On average reducing the mean particulate size by 33% and the associated loading carried in the filtrate will increase the dust cake specific flow resistance (K2) by 498%. High-temperature and high-pressure filtration can be successfully performed with ceramic candle filters at moderate filtration face velocities and reasonable system pressure drops. Off-line filter cleaning can produce a filter system with a higher apparent permeability than that produced from on-line filter cleaning at the same face velocity. 19 refs., 89 figs., 13 tabs.
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Category : Science
Languages : en
Pages : 854
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Author: Dominique Thomas
Publisher: Elsevier
ISBN: 008102116X
Category : Science
Languages : en
Pages : 228
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Book Description
Filtration of aerosols is omnipresent in our daily lives, in areas as diverse as health, the protection of people and the environment, and air treatment inside buildings. However, the collection of particles within a filter media is not, contrary to popular belief, linked to a simple screen effect. The phenomena involved are much more complex and require the consideration of aerosol interactions, filter media and process conditions to select the best fiber filter for a given application. Aerosol Filtration, book for students, hygiene or process engineers, fibrous media manufacturers, designers, and filtration system suppliers or users addresses the filtration of aerosols in six chapters. These chapters cover physics and aerosol characterization, the fibrous media, and efficiency and filter clogging by solid or liquid aerosols, with special attention to the filtration of the nanoparticles. - Analyses the behavior of fibrous media against solid and liquid aerosols - Presents models of efficiency and pressure drop - Introduces computing elements for estimating the lifetime of filters - Provides guidance for designing filters and predicting their behavior over time
Author: Wallace Woon-Fong Leung
Publisher: Elsevier
ISBN: 0323859852
Category : Technology & Engineering
Languages : en
Pages : 572
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Book Description
Nanofiber Filter Technologies for Filtration of Submicron Aerosols and Nanoaerosols covers the nanoaerosols (less than 100 nanometers) to larger submicron aerosols due mostly to pollution, which are present in high number concentration in our surroundings. People are breathing these nanoaerosols daily without being aware of it. Airborne viruses from flu to coronaviruses are also nanoaerosols. During the COVID-19 pandemic, it took a long time for health authorities and the General Public to recognize the airborne transmission mode of the virus. This leads to inadequate protection and ineffective virus control strategies resulting in high infection and death rates. The book cites evidence and observations pointing to the airborne transmission mode of the coronavirus. It also discusses different filtration technologies using nanofibers to capture these aerosols for short-term filtration, where aerosols are trapped in the filter (depth filtration), and long-term filtration, where aerosols are trapped in the growing filter cake (cake filtration). This book provides a good understanding on how nanofibers, which is of size 1/1000 times that of a normal human hair, can effectively filter these tiny aerosols. NFT, organized in four sections – fundamentals, deep understanding, technologies, and application, covering comprehensively on the subject, is a valuable resource for undergraduates and graduates, engineers, researchers and practitioners in related industries. - Describes technologies with insight and use basic engineering principles to build-up technologies - Includes extensive clear and understandable figures and tables to enhance key concepts - Uses examples throughout to explain engineering principles and interdisciplinary concepts - The only book in the market focusing on nanofiber filter technologies for filtering submicron aerosols and nanoaerosols
Author: Andrew B. Andrew B. Cecala
Publisher: CreateSpace
ISBN: 9781511722186
Category :
Languages : en
Pages : 312
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Throughout the mining and processing of minerals, the mined ore undergoes a number of crushing, grinding, cleaning, drying, and product sizing operations as it is processed into a marketable commodity. These operations are highly mechanized, and both individually and collectively these processes can generate large amounts of dust. If control technologies are inadequate, hazardous levels of respirable dust may be liberated into the work environment, potentially exposing workers. Accordingly, federal regulations are in place to limit the respirable dust exposure of mine workers. Engineering controls are implemented in mining operations in an effort to reduce dust generation and limit worker exposure.
