Distillation with reflux

BATCH DISTILLATION WITH REFLUX. Batch distillation with only a simple still does not give a good separation unless the relative volatility is very high. In many cases, a rectifying column tvith reflux is used to improve the performance of the batch still. If the column is not too large, it may be mounted on top of the still, as shown in Fig. 17.1, or it may be supported independently, with connecting pipes for the vapor and liquid streams. 

A reflux splitter is difficult to incorporate in continuous distillation MB control schemes because it couples variations of the material balance stream (i.e., the distillate) with reflux rate changes. This is especially troublesome when reflux ratio is high, and a rise in distillate rate will effect a severalfold increase in reflux rate. The author experienced one case of poor continuous distillation control which was attributed to the above shortcoming. The author recommends restricting application of reflux splitters to batch distillation, where they work well. In continuous distillation, Sutro weir dividers are far more suitable. 

DISTILLATION WITH REFLUX AND McCABE-THIELE METHOD... 

Sec. 11.4 Distillation With Reflux and McCabe-Thiele Method... 

FIGURE 11.4-17. Processflow for a rectification tower with a liquid side stream. Sec. 11.4 Distillation With Reflux and McCabe-Thiele Method... 

The calculations, in this respect, become similar to those employed for single-stage flash vaporization and multistage distillation with reflux and reboil, or for absorption or stripping. All the latter utilize the concept of an equilibrium stage. It should be emphasized, however, that the adaptations are constituted to apply to the nonequilibrium rate phenomena associated with membrane permeation. The calculations are similar in form but not in content. For one thing, the permeate flow rate per unit of membrane area (that is, the permeate flux) becomes part of the distribution coefficients or K-values for each component. An extra element of trial and error is therefore introduced. 

Preparation by a three-step synthesis first, tosylation of a-methoxyphloroaceto-phenone with p-tolnenesulfonyl chloride in the presence of potassium carbonate in refluxing acetone for 4 h. Dimethyl sulfate and potassium carbonate were then added and the mixture refluxed for 36 h more. Finally, saponification of the residue isolated by distillation with refluxing 5% methanolic potassium hydroxide for 4 h (42%) [4861]. 

Batch distillation with reflux in a multistage column... 

Figure 8.1.34. Batch distillation with reflux in a multiplate column, (a) Schematic of the device with total condensation, liquid reflwc and distillate product, (b) McCabe-Thiele diagram for constant reflux ratio with enriching section operating lines for three times, t = 0, t = tj, t = t2.

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