Expansion of Granular Water Filters During Backwash

Akkoyunlu, Atilla

doi:10.1089/109287503770736168

Cited by 11 publications

(6 citation statements)

References 5 publications

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“…26 In contrast, very few general correlations applicable to nonspherical particles are available. 4,6,9,11,27,28 A large number of measurements were carried out by Akgiray and Soyer 26 and Soyer and Akgiray 1 using several sieved fractions of crushed glass, silica sand, garnet sand, perlite, and several different sizes of plastic and glass balls to develop the following general equation applicable to both spherical and nonspherical media:…”

Section: Introductionmentioning

confidence: 99%

“…While a slightly modified version of a correlation proposed by Richardson and Zaki remains the most widely quoted correlation for solid–liquid fluidization, numerous other correlations have been proposed in the literature to predict the expansion of liquid fluidized beds of spheres (for reviews, see refs − ), and a few of these correlations have been shown to perform significantly better than the still very popular Richardson–Zaki correlation . In contrast, very few general correlations applicable to nonspherical particles are available. ,,,,, A large number of measurements were carried out by Akgiray and Soyer and Soyer and Akgiray using several sieved fractions of crushed glass, silica sand, garnet sand, perlite, and several different sizes of plastic and glass balls to develop the following general equation applicable to both spherical and nonspherical media: The dimensionless groups Re 1 and φ in this equation are defined as follows: Here V = fluidization velocity based on the empty cross-section of the bed, μ = dynamic viscosity of fluid, ρ = density of fluid, and g = gravitational acceleration. The sphericity values used in developing eq were obtained by back-calculation from fixed-bed head loss versus velocity data in conjunction with the Ergun equation.…”

Section: Introductionmentioning

confidence: 99%

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Characterization of Granular Materials with Internal Pores for Hydraulic Calculations Involving Fixed and Fluidized Beds

Hunce

Soyer

Akgiray

2016

Ind. Eng. Chem. Res.

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This study focuses on the characterization of porous granular materials for applications in hydraulics of fixed and fluidized beds. Different density measurement procedures were tested using five different sieved fractions of each of zeolite, activated carbon, and anthracite coal media to compare these procedures and to ascertain the effect of the density measurement method used on the calculation of other particle and bed properties. The mentioned particle and bed properties are the following: (i) particle density, (ii) particle size (equivalent diameter), (iii) sphericity, (iv) fixed-bed porosity, and (v) expanded-bed porosity during fluidization. The density of each of the 15 fractions was determined using four different methods: (i) cone test (ASTM C128-12), (ii) Le Châtelier flask method, (iii) soaking and straining, and (iv) skeletal density. The first three of these measure “wet density” (i.e., pores filled with liquid), the difference between them being in how the particles are saturated with liquid before the density determinations. The results show that the standard cone test is the most suitable method for the type of applications considered in this work whereas the use of other simpler methods leads to varying degrees of error. An important finding of this work is that the fluidized-bed expansion data of the porous media studied here are in excellent agreement with the predictions of a correlation that Soyer and Akgiray (J. Water Supply: Res. Technol.--AQUA, 2009, 58, 336) developed by testing nonporous materials only.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Characterization of Granular Materials with Internal Pores for Hydraulic Calculations Involving Fixed and Fluidized Beds

Hunce

Soyer

Akgiray

2016

Ind. Eng. Chem. Res.

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“…Environmental engineering related applications such as biofilm processes ( − ) and filter backwashing operations ( − ) are among those where an estimate of the shearing stresses is required to assess the performance of the system. Turan ( , ) developed a model to calculate the area-averaged velocity gradients and shear stress in a fluidized bed during the filter backwashing process and also proved that there is an optimum shear stress value that corresponds to an optimum voidage value.…”

Section: Introductionmentioning

confidence: 99%

Assessment of the Energy Dissipation Parameters Inside the Draft Tube of a Liquid Spout-Fluid Bed

Erbil

Turan

2005

Environ. Sci. Technol.

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Spouted beds are fluid-particle contactors in which the fluid is introduced centrally through a nozzle instead of a distributor plate, resulting in a regular particle circulation pattern. To assess the suitability of such sytems to environmental engineering applications such as filter backwashing and biofilm systems, a priori knowledge of the energy dissipation parameters is essential. A new model is developed for evaluating the energy dissipation parameters inside the draft tube of spout-fluid beds. The shear stress, velocity gradient, and turbulence fluctuation parameters in the draft tube of a liquid spout-fluid bed are calculated with the help of an energy equation for flows carrying suspensions and the experimentally determined pressure losses inside the draft tube and compared with results for particulately fluidized beds. A spout-fluid bed with a draft tube provides higher shear stress inside the draft tube than a fluidized bed. The mean velocity gradient in the draft tube is comparable to and higher than in a fluidized bed and increases with solids fraction. The turbulence dissipation coefficient decreases very slightlywith increasing solids fraction for both systems. Consequently, according to the model calculations, a spout-fluid bed with a draft tube can be an alternative to the classical fluidized bed filter backwashing system.

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“…O aumento do fluxo causa uma expansão maior na camada e determina que as partículas de areia se acomodem de acordo com sua densidade, e quando a diferença de pressão entre a entrada e a saída do filtro fica igual ou equilibrada, a camada será fluidizada. Num leito fluidizado as partículas dentro da camada estão em movimentação, e teoricamente mantêm-se suspensas em equilíbrio (AKKOYUNLU, 2003).…”

Section: Numero De Reynolds Da Partículaunclassified

“…A Equação 17 tem a restrição de ser válida no caso de não existirem perdas do meio filtrante durante a fluidização, ou seja, se o volume de grãos dentro da camada permanece igual antes e depois da expansão (AKKOYUNLU, 2003).…”

Section: Expansão Da Camadaunclassified

Efeito das características granulométricas e da altura da camada filtrante no processo de retrolavagem em filtros de areia

Ramirez¹,

Testezlaf²

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Expansion of Granular Water Filters During Backwash

Cited by 11 publications

References 5 publications

Characterization of Granular Materials with Internal Pores for Hydraulic Calculations Involving Fixed and Fluidized Beds

Characterization of Granular Materials with Internal Pores for Hydraulic Calculations Involving Fixed and Fluidized Beds

Assessment of the Energy Dissipation Parameters Inside the Draft Tube of a Liquid Spout-Fluid Bed

Efeito das características granulométricas e da altura da camada filtrante no processo de retrolavagem em filtros de areia

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