Acetone Recovery
Input - Output Structure
The input-output structure is quite straightforward. A flow
controller has been placed on the feed to indicate that this is set
upstream. It is clear that the composition of both product streams will
be important, and so quality controllers have been placed there without
indicating what will be adjusted.
It is sensible to show the solvent stream as a makeup. There
will always be some solvent loss to be made good. Figure 1 below shows
the control system at this stage.
Figure 1 - Acetone Recovery : Input/Output Structure
Recycle Structure
At the recycle structure level the air QC can be associated with
the rate of solvent supplied to the absorber. This is the main recycle
stream. Acetone quality control will be associated with the flash,
though the details of the loop cannot be defined at this stage. It is
not anticipating too much to have indicated that the solvent makeup will
be determined by some form of inventory control, as the purpose of that
loop is to maintain the inventory of solvent. Figure 2 shows the
results at this stage.
Figure 2 - Acetone Recovery : Recycle Structure
Final Structure
Finally, Figure 3 shows the absorber and flash. Both are standard and
straightforward. A tank is provided to add makeup solvent on level
control. Pumps and compressors have not been shown, their placement
being left as a further exercise. They do not, in this process, affect
the general control system structure.
Figure 3 - Acetone Recovery : Final Structure
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