Retrofit design of heat exchanger network (HEN) on Synthesis and Purification Unit of methanol plant

• Published in: 2011 IEEE Colloquium on Humanities, Science and Engineering pp. 33 - 36
• Main Authors: Ab Rashid, Siti Rafidah, Ibrahim, U. K., Mohd Alauddin, Sakinah
• Format: Conference Proceeding
• Language: English
• Published: IEEE 01.12.2011
• Subjects: Cooling; Feeds; heat exchanger network; Heat recovery; Methanol; methanol production; pinch technology; Purification; retrofit; Water heating
• DOI: 10.1109/CHUSER.2011.6163746
• ISBN: 1467300217; 9781467300216

Due to the current worldwide energy and economic crisis, all possible options of reducing the energy consumption are explored. This drives chemical processing plant as one of the energy-intensive consumers to strive for energy efficiency projects such as retrofitting the heat exchanger network (HEN). The retrofit project is focusing on the reduction of heat consumption in the plant to its minimum energy requirement (MER). As a result of this, the plant energy efficiency will increase tremendously. In this work, pinch technology is exploited in analysing the potential energy saving and economic gain. As a case study of the work, a typical methanol plant is considered. The pinch calculation shows the potential energy saving is 48,417 kW. This amount of energy accounts 74% and 57% of the current hot and cold utility consumptions. This indicates the high potential of attaining the economic gain. The violation of one of the pinch technology rule which is no cooling above the pinch is the reason of the excessive use of the utilities. In the analysis, there are two coolers situated above the pinch and four heat exchangers have low area efficiencies. Therefore, the plant heat exchanger network is retrofitted by modifying a minimum number of network structures and heat exchanger modifications. Minimal modifications are ensured to achieve economic feasibility. This is showed in the economic analysis which it gives the payback period of the investment by 0.4 years.