Stratified beds

Where an organic trap is part of a demineralization plant system, it is placed in the train upstream of the strong base anion (SBA) resin unit. When the organic trap resin is placed within the same pressure vessel, physically on top of the anion resin (stratified bed), in which case, as it forms part of the overall anion capacity, a weak base anion resin operating in the free base form is employed. 

Stratified beds In some bed designs, and by use of carefully graded resins with specifically different densities, it is possible to combine both weak and strong resins in a single compartment vessel, in a stratified manner. There is a 100% freeboard. Supply water is from the top down, with the weak resin on top and the strong resin below. The treated water emerges from the bottom of the vessel. 

An important feature of the expanded bed compared with a conventional fluidized bed is its low backmixing, achieved by the proper design of the adsorbent and the column. The particle size distribution of the adsorbent gives a segregated or stratified bed in expanded-bed mode. This means that the larger adsorbent particles are found in the lower part of the bed and the smaller adsorbent particles are in the upper part. 

Example 7.2 A sharp filter sand has the sieve analysis shown below. The porosity of the nnstratified bed is 0.39, and that of the stratified bed is 0.42. The lowest temperatnre anticipated of the water to be filtered is 4°C. Find the head loss if the sand is to be nsed in (a) a slow-sand filter 76 cm dee ) operated at 9.33 mim d and (b) a rapid-sand filter 76 cm deep operated at 117 m /m d. 

For stratified beds. Equation (7.48) must be applied layer by layer. The back-washing head losses in each layer are then summed to produce the total head loss of the bed. Thus,... 

Stratabed. [Rdim Haas] Ion exchange resin for stratified bed systems. 

Whilst the backwash flow is a very effective means of cleaning the bed, it has also the feature that when the backflow is stopped, the fnlly expanded bed sinks back to its compact form, with all its constitnent particles settling at velocities dictated by their size and density. The resnlt is a stratified bed, with the coarsest and heaviest particles at the bottom, and the finest at the top. 

Vanadium phosphoms oxide-based catalysts ate unstable in that they tend to lose phosphoms over time at reaction temperatures. Hot spots in fixed-bed reactors tend to accelerate this loss of phosphoms. This loss of phosphoms also produces a decrease in selectivity (70,136). Many steps have been taken, however, to aHeviate these problems and create an environment where the catalyst can operate at lower temperatures. For example, volatile organophosphoms compounds are fed to the reactor to mitigate the problem of phosphoms loss by the catalyst (137). The phosphoms feed also has the effect of controlling catalyst activity and thus improving catalyst selectivity in the reactor. The catalyst pack in the reactor may be stratified with an inert material (138,139). Stratification has the effect of reducing the extent of reaction pet unit volume and thus reducing the observed catalyst temperature (hot... 

Angle of slope The optimum slope of inclined vibrating screens is that which will handle the greatest volume of oversize and still remove the available undersize required by the standards of the particular operation. To separate a material into coarse and fine fractions, the bed thickness must be limited so that vibration can stratify the load and allow fines to work their way to the screen surface and pass through the opening. Increased slope naturally increases the rate of travel, and at a given rate it reduces the bed thickness. 

Adsorption efficiency can be optimized by using finer particle size products which will improve the diffusion rate to the surface of the activated carbon. However, there is a tradeoff in using finer particles with pressure drop and, hence energy use. Note that during start-up of an activated carbon filter bed, a bed expansion of 25 to 35 % is recommended in order to remove soluble matter and to stratify particles in order to ensure that the MTZ is maintained when future backwashing is performed. 

Flotz, n. layer, stratum, bed, seam, -erz, n. ore in beds, -gestein, n. stratified rock, -kalk,... 

Anisotropic formation theory Stratified or anisotropic formations are assumed to possess different drillabilities parallel and normal to the bedding planes with the result that the bit does not drill in the direction of the resultant force. 

Stratified packed-beds A double compartment design that holds stratified weak and strong beds but without any freeboard. Designs vary, but typically the flow is opposite to that of the hold-down... 

Jigs separate solids by difference in density and size. The material is immersed in water, supported on a screen (Figure 10.5). Pulses of water are forced through the bed of material, either by moving the screen or by pulsating the water level. The flow of water fluidises the bed and causes the solids to stratify with the lighter material at the top and the heavier at the bottom. 

Stratum bed, couch, coverlet something beneath stratify (many layered) strata of rock (in geology) substrate (chemistry and physics)... 

In weakly consolidated, stratified sediments, the injection pressure must be controlled so that the surrounding formation is not fractured. If fracturing occurs, there is usually a severe loss in hydraulic conductivity because the bedding planes are disturbed. Pressures that will cause fracturing range from a low of 0.5 psi/ft of depth for poorly consolidated coastal plain sediments, to 1.2 psi/ft depth for crystalline rock. For most recharge wells in unconsolidated sediments, the injection pressure should be carefully controlled so that the positive head (in psi at the surface) does not exceed 0.2 x h, where h is the depth (in ft) from the ground surface to the top of the screen or filter pack. 

In fluidisation with a liquid, a bed of particles of mixed sizes will become sharply stratified with the small particles on top and the large ones at the bottom. The pressure drop is that which would be expected for each of the layers in series. If the size range is small however, no appreciable segregation will occur. 

There are two types of caverns used for storing liquids. Hard rock (mined) caverns are constructed by mining rock formations such as shale, granite, limestone, and many other types of rock. Solution-mined caverns are constructed by dissolution processes, i.e., solution mining or leaching a mineral deposit, most often salt (sodium chloride). The salt deposit may take the form of a massive salt dome or thinner layers of bedded salt that are stratified between layers of rock. Hard rock and solution-mined caverns have been constructed in the United States and many other parts of the world. 

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