Section stripping

Combining equations (6-20), (6-21), and (6-22), the operating line for the stripping section becomes 

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The concentrated cumene hydroperoxide solution from the cumene stripping section is fed to the cleavage reaction. The cleavage reaction is carried... 

Application. In addition to providing a relatively simple means for estimating the production of separation cascades, the separative capacity is useful for solving some basic cascade design problems for example, the problem of determining the optimum size of the stripping section. 

Similarly, one obtains a gradient equation for the stripping section that has the form... 

Equations 27 and 28 can be used in conjunction, along with the corresponding equations for the stripping section, to produce an ideal plant profile such as is shown in Figure 4 where F is plotted against for the example of an ideal cascade to produce one mol of uranium per unit time enriched to 90... 

The equation for the total flow in the stripping section is obtained in the same manner ... 

For the stripping section of the centrifuge, that is, the section between the point at which the feed is introduced and the end at which the waste stream is withdrawn, the gradient equation has the corresponding form... 

Fig. 13. The ideal efficiency of a five-stage enricher and stripper as a function of the product or waste withdrawal rate, where Zi represents stripping section...

Above the feed a typical equiUbrium stage is designated as n the stage above n is n - - 1 and the stage below n is n — 1. The section of column above the feed is called the rectification section and the section below the feed is referred to as the stripping section. 

Stripping section liquid and vapor flows, because the feed is at the boiling point. 

Ethylene Oxide Purification. The main impurities ia ethylene oxide are water, carbon dioxide, and both acetaldehyde and formaldehyde. Water and carbon dioxide are removed by distillation ia columns containing only rectifying or stripping sections. Aldehydes are separated from ethylene... 

In another alternative, shown in Fig. 13-3 7, the rectifying section may be operated at a pressure sufficiently higher than that of the stripping section such that heat can be transferred between any desired pairs of stages of the two sections. This technique, described by Mah et al. (op. cit.) and referred to as SRV (secondary reflux and vaporization) distillation, can result in a significant reduction in utihty requirements for the overhead condenser and bottoms reboiler. 

The simple and complex distillation operations just described all have two things in common (1) both rectifying and stripping sections are providea so that a separation can be achieved between two components that are adjacent in volatility and (2) the separation is effected only by the addition and removal of energy and not by the addition of any mass separating agent (MSA) such as in liquid-liquid extraction. 

A knowledge of the reflux ratio (obtained from the specified distillate and top vapor rates) permits the calculation of (f d) from which ( i/d) is obtained, etc. Equation (13-50) is applied to each stage in succession until the ratio 2/d in the overflow from the stage above the feed stage is obtained. The calculations are then switched to the stripping section. 

The equilibrium relationship for component in the stripping section can be expressed in terms of component flow rate in the bottoms, h = Bxg, and = KyjL as... 

The rate-based model gave a distillate with 0.023 mol % ethylbenzene and 0.0003 mol % styrene, and a bottoms product with essentially no methanol and 0.008 mol % toluene. Miirphree tray efficiencies for toluene, styrene, and ethylbenzene varied somewhat from tray to tray, but were confined mainly between 86 and 93 percent. Methanol tray efficiencies varied widely, mainly from 19 to 105 percent, with high values in the rectifying section and low values in the stripping section. Temperature differences between vapor and liquid phases leaving a tray were not larger than 5 F. 

The ratio of wash solvent to extraction solvent is the same in the enriching section as in the stripping section if no solvent is added in the feed. The degree of separation to be achieved can be chosen for the process design, such as 99 percent of component b into the extrac-t stream and 99 percent of component c into the raffinate stream. Then the feed rate can be chosen so that the solute loadings in the extrac-t stream and... 

One point is on the 45° line at Xr, and the slope is Ls/Vs, where S refers to the stripping section. Another point is the intersection of the rectifying section operating line with the q line. And still another point is on the Y axis at the location below the origin of -(B/Vs)(Xb). 

Our example system has a flow-controlled feed, and the reboiler heat is controlled by cascade from a stripping section tray temperature. Steam is the heating medium, with the condensate pumped to condensate recovery. Bottom product is pumped to storage on column level control overhead pressure is controlled by varying level in the overhead condenser the balancing line assures sufficient receiver pressure at all times overhead product is pumped to storage on receiver level control and reflux is on flow control. 

Differential pressure equipment to cover at least the rectifying and stripping sections separately, but ideally to cover every 10 trays or so. 

The main product, benzene, is represented by solute (B), and the high boiling aromatics are represented by solute (C) (toluene and xylenes). The analysis of the products they obtained are shown in Figure 12. The material stripped form the top section (section (1)) is seen to contain the alkanes, alkenes and naphthenes and very little benzene. The product stripped from the center section appears to be virtually pure benzene. The product from section (3) contained toluene, the xylenes and thiophen which elutes close to benzene. The thiophen, however, was only eliminated at the expense of some loss of benzene to the lower stripping section. Although the system works well it proved experimentally difficult to set up and maintain under constant operating conditions. The problems arose largely from the need to adjust the pressures that must prevent cross-flow. The system as described would be virtually impossible to operate with a liquid mobile phase. 

Figure 14. Construction of operating line for stripping section.

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