Chemical Mass Balances

5. Recycle and Bypass
It is rare that A  B proceeds in completion in a reactor. A will always be present in the product of B, no matter how long the reaction remains in the reactor. The unreacted A can be separated from the product stream and be sold or recycled by charging it back into the reactor.
The fresh feed to the process and the feed to the reactor, which is the sum of the fresh feed and the recycle stream.
If the stream variables were unknown, you could determine them by writing balances on the overall process and about the reactor, separator, and mixing point.