Control Structure Design of Process Systems with Recycle and Purge

Abareshi, Mehdi | 2019

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 51983 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Vafa, Ehsan
  7. Abstract:
  8. In this research, self-optimizing method has been used to design a plant-wide control structure for processes containing purge and recycle streams. The method is based on the concept of self-optimizing variables to maximize the process profitability in the presence of possible disturbances. The purpose of this thesis is to perform this procedure on ammonia and methanol processes containing purge and recycle streams.Using the results obtained for the ammonia process and considering the constraints and operating conditions of the problem, the active constraints of this process were detected which were cooling water flow rates to exchangers. According to local analysis method, self-optimizing variables are selected as recycle compressor power, feed compressor power and the flow rate of purge stream. By implementing the proposed control structure, the dynamic response of the process had an acceptable performance in the presence of disturbances.Self-optimizing approach has also been applied on the methanol process for designing the most promising control structure from the economic point of view.The results show that when there is no limitation on the level of inert concentration in the purge stream, the set of controlled variables changes with changing the relative price of feed and purge streams. When the constraint on the inert concentration in the recycle stream becomes active inert concentration in the purge stream should be controlled
  9. Keywords:
  10. Purge and Recycle Streams ; Plantwide System ; Self-Optimizing Control ; Ammonia Process ; Methanol Process

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