Intermediate-sized

The products are an oversize (underflow, heavies, sands) and an undersize (overflow, lights, slimes). An intermediate size can also be produced by varying the effective separating force. Separation size maybe defined either as a specific size in the overflow screen analysis, eg, 5% retained on 65 mesh screen or 45% passing 200 mesh screen, or as a d Q, defined as a cut-off or separation size at which 50% of the particles report to the oversize or undersize. The efficiency of a classifier is represented by a performance or partition curve (2,6), similar to that used for screens, which relates the particle size to the percentage of each size in the feed that reports to the underflow. 

The need for a pilot plant is a measure of the degree of uncertainty in developing a process from the research stage to a hiU commercial plant. A modification to a weU-known process may go directiy from basic research work to design of a commercial plant using this approach for a brand new process risks a significant failure. Hence, one or more intermediate size units are usually desirable to demonstrate process feasibiUty as well as to determine safe scale-up factors. 

Scale-Up Principles. Key factors affecting scale-up of reactor performance are nature of reaction zones, specific reaction rates, and mass- and heat-transport rates to and from reaction sites. Where considerable uncertainties exist or large quantities of products are needed for market evaluations, intermediate-sized demonstration units between pilot and industrial plants are usehil. Matching overall fluid flow characteristics within the reactor might determine the operative criteria. Ideally, the smaller reactor acts as a volume segment of the larger one. Elow distributions are not markedly influenced by... 

Commercial centrifuges of this type have bowl diameters ranging from 0.3 to 2.4 m (12 to 96 in). The large sizes are used on heavy-duty apphcations such as coal dewatering and are limited by stress considerations to operate at 300g. The intermediate sizes for chemical process service develop up to lOOOg (see Table 18-10). 

Typical pilot-plant top-suspended baskets are 305 mm (12 in) diameter by 127 mm (5 in) deep. Commercial machines are available in sizes from 508-mm (20-in) diameter by 305-mm (l2-in) depth to 1524-mm (60-in) diameter by 1016-mm (40-in) depth and develop up to 1800g in the smaller and intermediate sizes. Except in the sugar apphcation, operation with a two-speed motor (half speed for loading and full speed for purging) is typical. Hydraulic drives with variable-speed capability are commonly used in the chemical industiy To maximize the number of cycles per hour, a combination of electrical and mechanical braking is employed to minimize the deceleration period, which is a transition period of no value to the process. 

The hberation of a valuable constituent does not necessarily translate direclly into recoveiy in downstream processes. For example, flotation tends to be more efficient in intermediate sizes than at coarse or fine sizes [Mclvor and Finch, Minerals Engineeiing, 4(1), 9-23 (1991)]. For coarser sizes, failure to liberate may be the hmitation finer sizes that are liberated may still be carried through by the water flow. A conclusion is that overgrinding should be avoided by judicious use of size classifiers with recycle grinding. 

With other ores there has been a problem of buildup of intermediate-sized particles, but this has been solved either by adding a small load of steel balls, thus converting to a semiautogenous grinding system (SAG), or by sending the scalped intermediate-sized particles through a cone crusher. A flow sheet for a typical wet autogenous circuit is shown in Fig. 20-57. 

Turboexpanders eurrently in operation range in size from about 1 hp to above 10,000 hp. In the small sizes, the problems are miniaturization, Reynolds Number effeets, heat transfer, seal, and meehanieal problems, and often inelude bearing and eritieal speed eoneerns. In intermediate sizes, these problems beeome less signifieant, but bearing rubbing speeds and vibration beeome inereasingly important. 

There are no clearly discernable, broadly applicable, correlations between the 6-inch and 1 S-inch deflagration and detonation experiments. Therefore, comparisons were done on a parameter-byparameter basis. However, comparisons of data taken during experiments with the two pipe sizes reveal that enough scale-related differences exist that interpolation between the two scales for an intermediate size should be done only where conditions are very similar. Then, overpressure and specific impulse can be estimated based on L/D. 

Zwischen-mass, n. intermediate size, -masse, /. ground substance interstitial matter. 

Stacked Layers of Large and Intermediate Sized Pocking (Not Necessorily Some os Bulk of Tower Pocking) to Prevent Support Plate Plugging. 

The data in Figure 4.3 show that Baeyer s theory is only partially correct. Cyclopropane and cyclobutane are indeed strained, just as predicted, but cyclopentane is more strained than predicted, and cyclohexane is strain-free. Cycloalkanes of intermediate size have only modest strain, and rings of 14 carbons or more are strain-free. Why is Baeyer s theory wrong ... 

Multiple receive systems with multi-coil arrays have become widely distributed in medical MRI. The benefit is the enhancement of the signal-to-noise ratio per time or a reduction of the acquisition time. This technique is not used in NMR microscopy for objects of intermediate size in standard bore (52-mm id) and wide bore (89-mm id) magnets, which are the most widely distributed magnet types for NMR microscopy. The main reason is the restricted space in such magnets for the shim... 

In exclusion chromatography, the total volume of mobile phase in the column is the sum of the volume external to the stationary phase particles (the void volume, V0) and the volume within the pores of the particles (the interstitial volume, Vj). Large molecules that are excluded from the pores must have a retention volume VQ, small molecules that can completely permeate the porous network will have a retention volume of (Vo + Fj). Molecules of intermediate size that can enter some, but not all of the pore space will have a retention volume between VQ and (V0 + Fj). Provided that exclusion is the only separation mechanism (ie no adsorption, partition or ion-exchange), the entire sample must elute between these two volume limits. 

Mean pore size either the pore size distribution or the specific porosity divided by the specific surface area. Pores are divided into three categories macro (30-50 nm), meso (intermediate size), and micro (less than 2 nm). 

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