Columns bubble-cap

Solution gives T=51 trays. The indicated separation appears feasible in a bubble-cap column although the design engineer should not be content with the glib assumption of negligible liquid-side resistance. 

A thirty-plate bubble-cap column is to be used to remove n-pentane from a solvent oil by means of steam stripping. The inlet oil contains 6 kmol of n-pentane/100 kmol of pure oil and it is desired to reduce the solute content of 0.1 kmol/100 kmol of solvent. Assuming isothermal operation and an overall plate efficiency of 30 per cent, what is the specific steam consumption, that is kmol of steam required/kmol of solvent oil treated, and the ratio of the specific and minimum steam consumptions. How many plates would be required if this ratio is 2.0 ... 

Bubble-cap columns or sieve trays, of similar construction to those described in Chapter 11 on distillation, are sometimes used for gas absorption, particularly when the load is more than can be handled in a packed tower of about 1 m diameter and when there is any... 

Bruun column. A type of all-glass bubble-cap column. 

The NH3 and the C02 gas, recovered from the second decomposition stage, is cooled in the second absorption stage where all the C02 is reacted to carbamate and dissolved in water along with some of the excess NH3. The solution thus obtained is pumped back to the first absorption stage and thence to the reactor for total recovery. Only part of the excess ammonia is dissolved in the solution recovered from the second absorption stage. The remaining portion of the excess ammonia gas is separated from the aqueous carbamate solution, purified from the last traces of C02, in a bubble cap column, compressed to about 20 atm, condensed to... 

The benzene used was Analytical Reagent Grade from Mallinckrodt Chemical Company, distilled through a 25-plate bubble-cap column and stored in vapor contact with desiccant prior to use. High-quality 1-hexadecylpyridinium chloride (CPC) from Hexcel Corporation was used without further purification. Sodium dodecylsulfate (SDS) was HPLC-grade chemical from Fisher Scientific Company, purified by recrystallization from an ethanol-water mixture. 

Many modifications of the three types of contactors just discussed have been developed in an effort to reduce costs, reduce pressure drop, equalize vapor flow through each contactor, increase plate efficiencies, or, in general, improve the operating performance of the tower. An example of this for modification of bubble-cap towers is the old Uniflux tray originally developed by Socony-Vacuum, which consisted of a series of interlocking S-shaped sections which were assembled in the form of tunnel caps with slot outlets on one side only. Segmental downcomers, similar to the downcomers in conventional bubble-cap columns, were provided. The vapors issued from the Uniflux caps in... 

For standard types of finite-stage contactor columns operated in the range of allowable velocities where the overall column efficiencies are essentially constant, O Connell has correlated efficiency data on the basis of liquid viscosity and relative volatility (or gas solubility). The results for fractionators and absorbers are presented in Fig. 16-9. This correlation is based, primarily, on experimental data obtained with bubble-cap columns having a liquid path of less than 5 ft and operated at a reflux ratio near the minimum value. Figure 16-9 is adequate for design estimates with most types of commercial equipment and... 

For a typical bubble-cap column, the following pressure drops per tray are considered reasonable, and they also would be order-of-magnitude values for sieve trays or valve trays ... 

Because of the flow resistance of the caps and risers in bubble-cap columns, there is a decrease in liquid depth as the liquid passes across the tray. Figure 16-4 shows an extreme example in which this liquid gradient is so great that only one out of the form bubble caps is operating normally. In general, the dimensionless ratio of total liquid gradient to pressure-drop head caused by the bubble-cap assembly should be less than 0.4 in order to ensure adequate vapor distribution, and, for single-pass crossflow trays, the rate of liquid flow across the tray should be less than 0.22 ft3/(sXft) diameter. 

Figure 2 shows that the condensations and redistillations in a bubble cap column consisting of three plates correspond to moving on the boiling point-composition diagram from point A to point E. 

In the laboratory the successive condensations and distillations that occur in the bubble cap column take place in a distilling column. The column is packed with some material on which heat exchange between ascending vapor and descending liquid can take place. A large surface area... 

The bubble-cap column (Fig. 1-26) is a simple illustration of this principle. Each of the stages A, B, and C consists of a disk with a small cylinder sealed to a hole in its center and covered with a domeshaped cap. Let us consider the process of distilling through such a column after the distillation has been in progress for some time and each of the plates is filled with liquid up to the height of the cylinder. 

Another very good design for a bubble-cap column is that of Older-shaw. This is less commonly used than the Bruun column, probably because it is less readily available. 

Acetic anhydride (bp 140°) is commonly used as the solvent in acetylation reactions. It often contains a considerable amount of acetic acid formed by hydrolysis. Purification is most easily effected by distillation through a moderately efficient column. A bubble-cap column is very useful for this purpose. 

Ethyl acetate (bp 77°) is a very useful solvent for recrystallization. The commercial material may contain some water and hydrolysis products, ethanol, and acetic acid. If it is reasonably pure, it may be purified by distillation from phosphorus pentoxide with a 10-plate bubble-cap column or its equivalent. If it is quite impure, it should be washed with sodium carbonate solution, dried over a small amount of calcium chloride, and then distilled from phosphorus pentoxide. 

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