Steam System Network Synthesis Using Process Integration

• Published in: Industrial & engineering chemistry research 2008-07, Vol.47 (13), p.4405-4413
• Main Authors: Coetzee, Sternberg W. A, Majozi, Thokozani
• Format: Article
• Language: English
• Subjects: Applied sciences; Chemical engineering; Exact sciences and technology; Process Design and Control
• ISSN: 0888-5885; 1520-5045
• DOI: 10.1021/ie071195n

Steam boilers are used to generate steam in order to meet the duty requirements of cold process streams. The most common heat exchanger network layout associated with the boiler is a completely parallel design, where the duty of each cold process stream is met by an external hot utility stream. This observation suggests that the flow rate of steam needed for the system can be reduced, while maintaining the required duty, simply by introducing series connections to the layout of the network (Kim, J. K.; Smith, R. Cooling water system design. Chem. Eng. Sci. 2001, 56, 3641−3658). Phase change of saturated steam to saturated liquid plays a vital role in the targeting method as well as the design of the network layout, since the saturated liquid (and resulting reuse liquid) is also used to meet the cold process duty requirements. A hybrid graphical and mathematical technique for targeting and network synthesis is presented. The main objective of the technique is to reduce steam flow rate without compromising the duty requirements of the process heat exchangers. In order to assess the advantage of a hybrid technique, a case study is used where a steam savings of 29.6% is obtained, compaired with using just saturated steam. We further present a complete mathematical technique to demonstrate the advantage of the graphical targeting concept in solution time improvement.