Batch or Plug Flow Fermentors

Consider the progress of this reaction. At the start C o is high, C q is low at the end, Ca 0 while Cq is high. Thus, the rate at the beginning and at the end of a run is low, but it will be high at some intermediate composition. By putting dr ldt = 0, we find that the maximum rate occurs at 

What this means is that with a feed Cco to any system, the key to proper design is to use mixed flow to reach max rate step, then use plug flow 

Now let us return to our batch (or plug flow) reactor. Applying its performance equation we find 

If a time lag is involved just add to the above times to find If we wish we can write the performance equation in terms of Cr instead of C and Cq. Just remember that 

The sketches of Fig. 29.1 show the main properties of this performance equation. 

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