Bleeding off a portion of the recycle stream is important in a production process to avoid the accumulation of undesirable material. For instance, if inert components from a reactor feed are not separated from the recycling stream in the separation units, they would build up in the recycle stream until they made up the whole stream. To keep the inert level within reasonable level, some of the stream would need to be purged. Normally, a continuous purge would be employed. Assuming steady-state circumstances:
Loss of inert in the purge = Rate of feed of inerts into the system
The concentration of any component in the purge stream will be the same as that in the recycle stream at the point where the purge is taken off. Consequently, the relationship shown below can be used to calculate the necessary purge rate:
[Feed stream flowrate] × [Feed stream inert concentration] =
[Purge stream flowrate] × [Specified (desired) recycle inert concentration]
Let’s see example below. Read More