Energy Management and Process Improvement of Methanol Production

A heat exchanger network (HEN) for the process of methanol synthesis has been studied by combination of pinch design method and the application of “Twisted Tube” heat exchanger units as a new technology. The HEN is reconstructed based on the full utilization of maximum allowable pressure drops for the process hot and cold streams. An algorithm is developed to generate design procedure for twisted tube application. The algorithm needs to extend and develop correlation among the pressure drops, heat transfer coefficients, and required surface area through a simple relationship for twisted tube exchangers. It is revealed that a great economic, energy savings and process improvement are realized by using pinch analysis and applying twisted tube units in comparison to existing plants. The paper reveals highly potential benefits of this technology in design and replacement of twisted tube heat exchangers with the conventional shell and tubes type. The HEN is reconstructed by adding 4 new twisted tube units with their detail design in methanol process as a case study. The results show that the application of twisted tube exchangers may achieve significant energy saving for the methanol process with a one-year payback. Moreover, these units may result in a great reduction of carbon emission, operational problems such as heat exchanger fouling, and tube bundle vibration of heat exchangers.