Exergetic evaluation and comparison of quintuple effect evaporation units in Indian sugar industries


Correspondence: S. M. Bapat, Department of Mechanical Engineering, Gogte Institute of Technology, Belgaum, India 590008.

E-mail: shribapat@rediffmail.com; smbapat@git.edu


Present work analyzes and compares two quintuple effect evaporation units with and without heat recovery devices being employed. It is based on actual operational data of sugar plant. This study is primarily based on exergy analysis. Case A is a quintuple effect evaporation unit without heat recovery devices, while case B is with heat recovery devices. The average exergy efficiency is found to be 70.53% for case A, while it is 86.71% for case B. Highest exergy destruction for case A is in second effect with a value of 1562.20 kW, and for case B, it is for the first effect with a value of 1871.68 kW. Steam economy for case A is 1.99, while for case B, it is 3.46. This is due to high evaporation rates and heat recovery devices being employed for case B. The fifth effect evaporator in case A and first effect evaporator in case B are found to be the least efficient components from exergy point of view. As energy economy is concerned in terms of exhaust steam demand, case B is more attractive than case A. However, in terms of exergy, case B is less sustainable than case A. A parametric study indicated that increase in the exhaust/inlet steam temperature is highly disadvantageous in terms of exergy and quality of the end product. The authors expect that the exergy analyses results would facilitate the designers and professional practioners in the field of sugar engineering in furthering the goal of improving energy systems. Copyright © 2012 John Wiley & Sons, Ltd.