Granular beds

Self and co-workers, "Electric Augmentation of Granular Bed Filters," EPA-600/9-80-039c, p. 309, 1980. 

Granular-bed filters may be divided into three classes ... 

Cleanable Granular-Bed Filters The principal objective in the development of cleanable granular-bed filters is to produce a device that can operate at temperatures above the range that can be tolerated with fabric filters. In some of the devices, the granules are circulated continuously through the unit, then are cleaned of the collected dust and returned to the filter bed. In others, the granular bed remains in place but is periodically taken out of service and cleaned by some means, such as backflushing with air. 

Granular Beds of Particulate Solids Beds of solids like sand or coal are used as filter media to clarify water or chemical solutions containing small quantities of suspended particles. Filter-grade grains of desired particTe size can be purchasea. Frequently beds will be constructed of layers of different materials and different particle sizes. 

Permeability Bulk sohd permeability is important in the iron and steel industiy where gas-solid reactions occur in the sinter plant and blast furnace. It also strongly influences compac tion processes where entrapped gas can impede compaction, and solids-handling equipment where restricted gas flow can impede product flowabihty. The permeabihty of a granular bed is inferred from measured pressure drop under controlled gas-flow conditions. 

Calcium oxide (lime) Rotary kilns, vertical and shaft kilns, fluidized bed furnaces Particulate matter Cyclones plus secondary collectors (baghouse, ESP, wet scrubbers, granular bed filters, wet cyclones)... 

Gurgel and Grenier [13] went on to make direct measurements of the bed thermal conductivity using the Bauer-Schliinder [14] model. This model is the most extensive and complete description of thermal conductivity within a granular bed. Previous models assumed either parallel isotherms perpendicular... 

A. Hougen and K. M. Marshall Adsorption from a Fluid Stream Flowing Through a Stationary Granular Bed, Chemical Engineering Progress, 43 197 (1967). 

Technology Description Fluidized bed incinerators utilize a very turbulent bed of inert granular material (usually sand) to improve the transfer of heat to the waste streams to be incinerated. Air is blown through the granular bed materials until they are "suspended" and able to move and mix in a manner similar to a fluid, i.e., they are "fluidized".In this manner, the heated bed particles come in intimate contact with the wastes being burned. The process requires that the waste be fed into multiple injection ports for successful treatment. Advantages... 

FUter medium The permeable portion of a filtration system that provides the liquid-solid separation, such as screens, papers, non-wovens, granular beds and other porous media. 

If the solution is allowed to flow through a granular bed such as sand, the larger particulate matter remains on the surface, while the smaller material is collected in the thickness of the granular bed. Pressurization of the filter accelerates the process. Besides sand, other materials used as filtering media are anthracites, manganese dioxide, and activated carbon. 

Camian, P.C., 1937. Fluid flow through granular beds. Transactions of the Institution of Chemical Engineers, 15, 150-166. 

I. Undisturbed granular bed at initial compaction. II. Explosive burning to give linear increase of pressure with time compaction occurs in most porous charges. III. Accelerated burning and pressure buildup to form precursor shock (Ref 69a)... 

M. Schier, R. Reimert 1999, (Investigation in droplet separation in granular beds in the inertia dominated regime), in High Temperature Gas Cleaning (vol. II), eds. A. Dittler, G. Hemmer, G. Kasper, Institut fur Mechanische Verfah-renstechnik und Mechanik, Universitat Karlsruhe (TH), Karlsruhe, 813-824. 

G. D Ottavio, S. Goren 1983, (Aerosol capture in granular beds in the impaction dominated regime), Aerosol Sci. Technol. 2 (2), 91-108. 

In practice, granular beds comprising a very large number of catalyst pellets are used. It is well known that the efficiency of a catalytic reactor depends crucially on the liquid phase distribution within the catalyst bed [14]. It is likely that the development of hot spots in a catalyst bed is also related to the character of liquid phase distribution. Therefore, it is very important to map the spatial distribution of the liquid phase in a catalytic reactor for various operation regimes. This eventually should lead to the formulation of the mechanisms responsible for the development of critical phenomena on both a micro- and macroscale. 

Granular Bed Filtration and Granular Activated Carbon Filtration. 282... 

Granular bed filters are used in ten coil coating plants to remove residual solids from the clarifier effluent, and are considered to be tertiary or advanced wastewater treatment. Chemicals may be added upstream to enhance the solids removal. Pressure filtration is also used in this industry to reduce the solids concentration in clarifier effluent and to remove excess water from the clarifier sludge. Figure 7.4 shows a granular bed filter and Table 7.13 presents the heavy metal removal data of a lime clarification and filtration system. 

Granular Bed Filtration, Granular Activated Carbon Filtration, and... 

Granular bed filters are used in porcelain enameling wastewater treatment to remove residual solids from clarifier effluent (sedimentation effluent or flotation effluent). Filtration polishes the effluent and reduces suspended solids and insoluble precipitated metals to very low levels. Fine sand and coal are media commonly utilized in granular bed filtration. The filter is backwashed after becoming loaded with solids and the backwash is returned to the treatment plant influent for removal of solids in the clarification step.10-12... 

The filtration system consists of a granular bed multimedia filter unit, a GAC filter unit, and/or a membrane filtration unit.10 12... 

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