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Energy 29 (2004) 525–546 www.elsevier.com/locate/energy The second law optimal path of a four-bed SO 2 converter with five heat exchangers Gelein de Koeijer 1 , Eivind Johannessen, Signe Kjelstrup Department of Chemistry, Norwegian University of Science and Technology, N-7491 Trondheim, Norway Received 19 August 2002 Abstract The entropy production rate of a common industrial SO 2 converter was minimized, simultaneously var ying the hei ght s of fou r cat aly tic beds, the temper atu re diff ere nces acr oss five int erme dia te hea t exchangers, and the distribution of a fixed area available for heat exchange. The entropy production rate had contributions from the chemical reaction, the pressure drop and the heat exchange. The total area for heat excha nge, inlet temper atur e, inlet pressure , inlet composit ion, outlet temper ature, and outlet composition remained constant in the minimization. A new path of operation was found for the given constraints that saved 16.7% of the entropy production rate compared to an industrial SO 2 converter. There were changes in chemical, mechanical and thermal contributions to the entropy production. The savings can be taken out as higher quality heat output, lower quality heat input, or reduction in the total area for heat transfer. The optimum operating conditions also indicate that the same product can be obtained under milder thermal conditions than now. Furthermore, the requirement for catalyst, as meas- ured by the total bed height, decreased with the area available for heat transfer, from 2.4 m at 2000 m 2 to 1.7 m at 6000 m 2 . We conclude that there is a significant potential to improve the second law efficiency of the particular industrial SO 2 converter that is studied. # 2003 Elsevier Ltd. All rights reserved. 1. Introduc tion The reactor is often the central unit around which a chemical plant is designed. Good reactor design is thus important for the performance of the plant [1] . Corresponding author. Tel.: +47-73594179; fax: +47-73591676. E-mail address: [email protected] (S. Kjelstrup). 1 Current address . Statoi l ASA, 7005 Trondh eim, Norway. 0360-5442/$ - see front matter # 2003 Elsevier Ltd. All rights reserv ed. doi:10.1016/j.energy.2003.11.002
