Partition Plates

Eig. 20. Cut view of Chlorine Engineers membrane bag cell a, manifold b, frame c, partition plate d, sealing plug e, recirculated NaOH inlet f, cathode g, anode h, cathode can i, membrane bag j, base k, butterfly valve 1, feed brine m, depleted brine n, caustic outlet. 

From Table 3-4 it is then possible to pick a shell diameter that can accommodate the number of tubes required. Please note that Equation 3-2 calculates the total number of tubes required and not the number of tubes per pass. Similarly, Table 3-4 lists the total number of tubes and not the number per pass. There are fewer total tubes in the same diameter exchanger for more passes of the tube fluid because of the need for partition plates. There are fewer tubes for floating head than fixai head designs because the heads and seals restrict the use of space. U-tubes have the lowest number of tubes because of the space required for the tightest radius bend in the U-tube bundle. 

The bundle diameter will depend not only on the number of tubes but also on the number of tube passes, as spaces must be left in the pattern of tubes on the tube sheet to accommodate the pass partition plates. 

The tube layout for a particular design will normally be planned with the aid of computer programs. These will allow for the spacing of the pass partition plates and the position of the tie rods. Also, one or two rows of tubes may be omitted at the top and bottom of the bundle to increase the clearance and flow area opposite the inlet and outlet nozzles. 

Stream F is the pass-partition stream. The fluid flowing through the gap in the tube arrangement due to the pass partition plates. Where the gap is vertical it will provide a low-pressure drop path for fluid flow. 

In practice, the number of tubes in a given shell diameter will be less than that predicted by Equation 15.35 because of the mechanical features such as pass partition plates, not accounted for. Combining Equations 15.33 and 15.35 gives ... 

When scaling-up the fluid-bed process, a major requirement is to produce fluidization behavior on the larger machines equivalent to that used on the scale that provided the basis for process development. To achieve this goal, and minimize attritional effects, the same air velocities for each scale of equipment are required. Thus, the overall increase in air volume required during scale-up will be related to the increase in area of the perforated base plate, and, in the case of the Wurster process, the open area of the partition plate immediately beneath each of the inner partitions. Such calculations are simplified when scaling-up from an 18" pilot scale machine to, say, a 32" machine, since the latter represents a three-multiple of the former, and thus would require a threefold increase in airflow. 

In order to prevent the brine and the chlorine from penetrating into the denuder, partition plates (not reaching the bottom) which act as hydraulic seals are placed conveniently both in the rear and in the front connecting device. In the denuder, the amalgam is decomposed by water into caustic solution and hy-... 

The rear connection device is made of rubber-lined iron. It has a partition plate under which the amalgam flows into the denuder. Between the rear connecting device and the denuder two partition plates form a purification chamber with a rubber-plated iron lid. 

Softened water is supplied through a rotameter into the front connecting device between the partition plate and the mercury pump. It flows over the mercury level (washes the mercury) and enters the denuder through a pipe which is dipped under the level of the caustic solution. By this arrangement the escaping of hydrogen from the denuder is prevented. In the denuder water flows countercurrently to mercury and is withdrawn from the end of the denuder in form of a caustic solution. 

The overall concentration distribution of solids in a multistage column depends upon the axial dispersion of the solids in each stage and the back flow of liquid (and solids) at the perforated plate. Kubota and Sekizawa69 proposed a model to describe the exchange of solid particles through the perforated partition plate. The model used a parameter K° which was defined as... 

The experimental data also showed that when the superficial liquid velocity is zero or very small, the presence of partition plates gives the stepwise profile of solid particles. This avoids uniform distribution and gives large solid holdup. Continuous operation in this range, therefore, results in a higher mean residence time of the solid particles than that in the column without partition plates. 

FIGURE 6.27 Possible nozzle and pass-partition plate configuration for four tube-side passes. 

The velocity of the fluid inside the tubes is a function of the number of tubes in parallel. To reduce the number of tubes in parallel, partition plates are used. For example, in the exchanger shown in Figure 2-3 cooling water flows through only half the tubes in parallel. Dividing the total number of tubes into two halves is accomplished very simply by welding a flat horizontal partition plate in the middle of the channel. 

FIGURE 58.19 Mechanism of siphonic action (a) standard centrifuge, (b) negative siphon, (c) positive siphon (1, basket 2, medium 3, hole 4, filtrate chamber 5, siphon chamber 6, partition plate 7, siphon pipe 8, filtrate 9, cake). (From Mitsubishi Kakoki Kaisha, Ltd., Catalog 7-1-1 02-01B-P. With permission.)... 

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