Examples of separation in double-entry separators

The quantity Y 21 may be Interpreted as the component cut 02, i-e. that fraction of species 2 entering the separator which appears in the light fraction j = 1. Similarly, Ti2 may be interpreted as (1 -0i), where 0i is the component cut for species 1. Note that both feed streams have to be lumped together here for determining 0i and 02. Thus 

Concentrate now only on the two feed streams and assume them to be product streams whose extent of separation is to be determined. Assuming feed stream to be streamy = 1 and feed stream ft to be stream j = 2, we get (with i = 1 for benzene) 

Example 2.3.1 described separation in a double-entry separator having two distinct phases - a vapor feed and a liquid feed, with both phases existing throughout the column. Double-entry separators are used even when two product streams and the two feed streams are of the same phase. 

However, the overall separation system incorporating the compressor has only one feed stream and two product streams. This arrangement is quite similar to the distillation column, and is called the continuous membrane column. 

The wall of the silicone capillaries separates the two gas streams in the permeator described above. It is not necessary to have a barrier between two streams within a separator. Later in the book we will come across double-entry separators in which two gas streams are in contact with each other and yet separation is taking place. 

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