Feed distribution

Poor feed distribution to falling-film units... 

Many different designs are available, the major difference among them being in feed-distribution methods and plate configurations. Operating capacities range from 1 to 3 m of feed/h/m" of projected horizont area [0.4 to 1.2 gal/(min ft)]. 

The need for a calculated baU-size feed distribution is open to question however, methods have been proposed for calculating a rationed baU charge [Bond, Trans. Am. Inst. Min. Metall. Pet. Eng., 153, 373 (1943)]. 

Let us consider the following case of removing an inorganic salt from an aqueous stream. It is desired to reduce the salt content of a 26 m /hr water stream (Qf) whose feed concentration, Cp, of 0.035 kmol/m (approximately 2,000 ppm). The feed osmotic pressure (rrp) is 1.57 atm. A 30 atm (Pp) booster pump is used to pressurize the feed. Sixteen hollow fiber modules are to be employed for separation. The modules are configured in parallel with the feed distributed equally among the units. The following properties are available for the HFRO modules ... 

Will the feed distribute itself evenly between the tubes This is a concern when there is a large change in viscosity due to reaction. The resulting stability problem is discussed in Chapter 13. Feed distribution can also be a concern with very large tube bundles when the pressure drop down the tube is small. 

Figure 5.4-41. Feed distribution in the vicinity of inlet of the reactor. 

TFF membrane systems generally use a common feed distributed among parallel modules with a collection of common retentate and common permeate streams. In some applications, it is also useful to plumb TFF modules with the retentate in series where the retentate flow from one module provides the feed flow to the next module. This type of configuration is equivalent to increasing the length of the retentate channel. Permeate flows may or may not be plumbed together. 

Like gas absorption, liquid-liquid extraction separates a homogeneous mixture by the addition of another phase - in this case, an immiscible liquid. Liquid-liquid extraction carries out separation by contacting a liquid feed with another immiscible liquid. The equipment used for liquid-liquid extraction is the same as that used for the liquid-liquid reactions illustrated in Figure 7.4. The separation occurs as a result of components in the feed distributing themselves differently between the two liquid phases. The liquid with which the feed is contacted is known as the solvent. The solvent extracts solute from the feed. The solvent-rich stream obtained from the separation is known as the extract and the residual feed from which the solute has been extracted is known as the raffinate. 

The overall collection efficiency shown in Table 1 is determined from Fig. 2 of the text for the feed distribution given in Fig. 18. From Fig. 4 of the text at 80 grains/cu.ft, EL = 98.7%, therefore ... 

The release of the dust is caused by the activity of animals or man or the function of technical equipments in the animal house. Feeding, particularly dry feeding (25), as well as bedding and cleaning activities, the use of different systems of feed distribution, manure removal and ventilation (26) can increase the dust level in the air of animal houses considerably (27). Figure 1 gives an example of the relation between the amount of dust in the air and different activities based on values as reported by CERMAK and ROSS (27) for poultry houses. 

A number of flat membranes are stacked with appropriate supporters (spacers) between the membranes, making alternate channels for the feed (retentate) and the permeate. Meshes, corrugated spacers, porous plates, grooved plates, and so on, can be used as supporters. Ihe channels for feed distribution and permeate collection are built into the device. Rectangular or square membrane sheets are common, but some modules use round membrane sheets. 

Fluidized bed reactors typrcally are vertical cylindrical vessels equipped with a support grid and feed sparger system for adequate fluidization and feed distribution, internal cooling coils for heat removal, and either external or internal cyclones to minimize catalyst carryover. Fluidizauon of the catalyst assures intimate contact between feed and product vapors, catalyst, and heat-transfer surfaces, and results in a uniform temperature within the reactor. Reaction heat can be removed by generating steam within the cooling coils or by some oilier heat-transfer medium. 

Figure 1.109 Platelet with star-shaped breakout for fluid carriage into the mixing chamber and feed conduits (left) and separation platelet with conduits for feed distribution to the platelets (right) [130].

For an open circuit ball mill 5 liters in volume operating at a flow rate of 1 liter per hr the product is a Z1O2 suspension with a Ros-lin-Rammler size distribution with a weight mean size of 0.5 jam and a volume to surface mean diameter of 0.7 jam. Determine the feed distribution to the mill assuming the value of j3 the grinding selectivity factor is 1.0 and k is 0.5 (hr/jam) . ... 

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