Overflow reflux line

Figure 1.3 shows a loop on the 12-oz can drain line. Without this loop, vapors flowing from the big can would partially bypass the No. 1 coil. Even worse, without the loop seal, the vapors flowing up through the reflux line would stop the flow of reflux. The 12-oz can would then fill up until it overflowed bad-tasting, watery vodka into om bottle. 

Figure 13.7. Features of McCabe-Thiele diagrams for constant molal overflow, (a) Operating line equations and construction and minimum reflux construction, (b) Orientations of -lines, with slope = ql q — 1), for various thermal conditions of the feed, (c) Minimum trays, total reflux, (d) Operating trays and reflux, (e) Minimum reflux determined by point of contact nearest xD.

Steam stripping is to be used to remove a solvent from contaminated soil. An enriching colunm will be used to recover the solvent from the stream. A vapor feed of 40 mol/hr with a composition of 20 mol% solvent and 80 mol% water enters an enriching column. The distillate stream is to have a flow rate of 5 mol/hr and a concentration of 90 mol% solvent. The internal reflux ratio is 0.875 and constant molar overflow (CMO) may be assumed. Graph the operating line to predict the number of equilibrium stages in this enriching column. 

Flooded condenser schemes shown in Fig. 17.5a to c and f can be used instead of coolant flow variations. In such cases, the inerts normally leave finm the top of the condenser instead of the reflux drum (Fig. 17.8e). If the reflux drum is not flooded, a pressure balance line must be included otherwise, a stable pressure will be impossible to keep in the reflux drum. An overflow line should also be included in this arrangement. 

Schemes 16.4a, b, and e do not suffer from the above instability. This is particularly true for schemes 16.4a and e, where reflux flow is maintained steady by a flow controller. In the Fig. 19.3 arrangement, these schemes can be configured with either the distillate or the reflux on overflow. If reflux is an overflow, the reflux flow controller manipulates a valve in the distillate line (e.g., Fig. 19.4a).

These lines are drawn on Pig. 7-21, and the corresponding steps are shown. A still plus approximately 12 theoretical plates are required. This is in close agreement with the result of Part 2, and this is generally the case. Thus, if a tower is calculated on the basis of a certain factor times the minimum reflux ratio, the theoretical plates required are usually approximately the same on either the (y x) or enthalpy-composition basis, provided the method chosen is used consistently throughout the calculation. However, the heat and cooling requirements may be seriously in error when calculated on the constant overflow basis. 

Horizontal tube bundle with coolant in tubes (Figure 3.3). The vapor comes up from below and condensate drops into an annular space around the vapor nozzle. The latter has a haf over it to prevent condensate from dropping back down the column. Reflux may return internally via an overflow weir, or externally through a gravity flow line with a control valve. 

We now develop the equation for an operating line for a separation system of type (3), illustrated in Figure 8.1.8(b), with a reflux at the top and at the bottom. Under the condition of constant molar overflow, we use equation (8.1.10) again between any axial location z and the top of the column z = L. After integradon, we get... 

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