Feed stream velocity

Modify the cross-sectional design (Fig. 6-35) the slot is thus farther away from the influence of feed-stream velocity. 

A concentration boundary layer theory clearly is needed to relate C to C, so that membrane properties such as L, a, and P can be correlated with R, at various operating conditions. Slso, since ir in Equations 1 and 5 is an independently determined function of C, a boundary ayer theory could correlate the observed filtrate velocity, J (averaged along the fiber length), with average applied pressure AP. For sufficiently high axial flow velocities, C == C, and a major theoretical barrier to data analysis is removeS. Some early work in reverse osmosis ( ) was done with flat-sheet membranes and large feed stream velocities. 

Shallow feedweUs may be used when overflow clarity is not important, the overflow rate is low, and/or solids density is appreciably greater than that of water. Some special feedwell designs used to dissipate entrance velocity and create quiescent settUng conditions spUt the feed stream and allow it to enter the feedwell tangentiaUy on opposite sides. The two streams shear or collide with one another to dissipate kinetic energy. 

Operating principle. Particles of terminal velocity Vi > mq will tend to settle therefore design for Vi < mq of the smallest particle present in the feed stream. In other words, the settling time should be less than the mean residence time of the up-flowing fluid. 

We turn now to the numerical solution of Equations (9.1) and (9.3). The solutions are necessarily simultaneous. Equation (9.1) is not needed for an isothermal reactor since, with a flat velocity profile and in the absence of a temperature profile, radial gradients in concentration do not arise and the model is equivalent to piston flow. Unmixed feed streams are an exception to this statement. By writing versions of Equation (9.1) for each component, we can model reactors with unmixed feed provided radial symmetry is preserved. Problem 9.1 describes a situation where this is possible. 

Most molecular mixing models concentrate on step (1). However, for chemical-reactor applications, step (2) can be very important since the integral length scales of the scalar and velocity fields are often unequal (L / Lu) due to the feed-stream configuration. In the FP model (discussed below), step (1) is handled by the shape matrix H, while step (2) requires an appropriate model for e. 

Newton, MA). Microfluidization based on patented technology in which a split feed stream flows into an interaction chamber at ultrahigh velocities and pressures (up to 1500 ft and 16,000 psi respectively). The two streams collide head-on and exit the chamber at a right angle to the collision. The force of the collision creates cavitation and shear forces to decrease the particle size. The feed stream was prepared in a manner similar to the coarse emulsion in which the orange oil was blended into the carrier solution with a whisk. The Microfluidizer was operated at a pressure of 11,000 psi and the sample was collected after one pass through the interaction chamber. 

In the early 1960 s Engelhard developed and commercialized the Selectoxo catalyst and process for H2 plants. The heart of this technology is a highly selective catalyst, which oxidizes up to 10,000 ppm CO without significantly oxidizing the 70% H2 (dry) in the feed stream. CO levels were reduced to less than 5 ppm under steady state conditions (50°C, 10,000 h 1 space velocity and 200-400 psig). The Selectoxo catalyst contains 0.5% platinum (Pt) supported on y -alumina, /8 inch tablets promoted with a base metal oxide. 

Where the values for y and p are taken as those of air at 200°C and 1 atm. u is assigned a value of zero which means that no product B exists in the feed stream. The plug-flow velocity, v, is determined by the choice of the Reynolds number. The... 

Successful performance of inorganic membranes depend on three types of variables and their interactions. The first type is related to the characteristics of the feed stream such as the molecular or particulate size and/or chemical nature of the species to be separated and concentration of the feed to be processed, etc. The second type is membrane dependent Those factors are the chemical nature and pore size of the membrane material and how the membrane and its accessory processing components are constructed and assembled. The third type is processing conditions such as pressure, transmembrane pressure difference, temperature, crossflow velocity and the way in which the membrane flux is maintained or restored as discussed earlier in this chapter. 

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