Examples and challenges of control of processes with recycle were presented in Section 15.2. In this section we give the reader more experience with plantwide control strategies by studying two more examples: MPN and HDA.
Consider the process flow sheet shown in Figure 15-17. Here, methanol is reacted with acrylonitrile to form MPN. A slight excess (2%) of ACN is supplied and essentially all of the MeOH is reacted. There is no purge stream, so the excess ACN appears in the MPN product stream. Here the recycle stream is liquid-phase distillate stream.