Stage efficiencies countercurrent

Eo Over-all stage efficiency of a countercurrent cascade, as a fraction, dimensionless / A function... 

Constant-volume batch diafiltration is the most efficient process mode. Sequential batch diafiltration is a series of dilution-concentration steps. Continuous diafiltration practiced in one or more stages of a cascade system has the same volume turnover relationship for overall recoveries as sequential batch diafiltration. The residence time however is dramatically reduced. If recovery of permeable solids is of primary importance, the permeate from the last stage may be used as diafiltration fluid for the previous stage. This countercurrent diafiltration arrangement results in higher permeate solids at the expense of increased membrane area. 

Staging. Efficient use of heat and, to a lesser extent retorting yield, require some countercurrent staging to achieve the economic advantages expected for the SPHER process. About six stages are desired for the preheater, four in the heat recovery section and two or three stages may be desired in the retort. 

Example 17.2. Ammonia is stripped from a dilute aqueous solution by countercurrent contact with air in a column containing seven sieve trays. The equilibrium relationship is = O.Sjfc, and when the molar flow of air is 1.5 times that of the solution, 90 percent of the ammonia is removed, a) How many ideal Stages does the column have, and what is the stage efficiency (i>) What percentage removal would be obtained if the air rate were increased to 2.0 times the solution rate ... 

Because of its importance, only the continuous countercurrent method is discussed here. Also, since the stage method is normally used, the differential-contact method is not considered. In common with other stage cascade operations, leaching may be considered, first, from the standpoint of ideal stages and, second, from that of stage efficiencies. 

Since most continuous extraction methods use countercurrent contacts between two phases, one a light liquid and the other a heavier one, many of the fundamentals of countercurrent gas absorption and of rectification carry over into the study of liquid extraction. Thus questions about ideal stages, stage efficiency, minimum ratio between the two streams, and size of equipment have the same importance in extraction as in distillation. 

The reactor-exdactor chosen was a Podbielniak centrifugal extractor. These units are normally run with countercurrent feed for exdaction and are capable of having two- or three-stage efficiency. The operation, including the... 

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