Rational Energy Recovery from the Condensed Steam as a Component of HEN Retrofit

Abstract

The paper is concerned with retrofitting a heat exchanger network (HEN) using a Pinch-based method (PT) and simultaneously minimizing energy losses caused by the expansion of steam condensate. The disadvantages of conventional multi-stage condensate expansion are identified, and the application of condensate subcooling is proposed. The case study considers a Methyl-Tert-Butyl Ether (MTBE) process plant where the consumption of hot utility (steam) in the existing HEN is 4,386 kW. Using the PT method to determine the maximum possible heat recovery, it is found that heat recovery from hot process streams can be increased, leading to an increase by 510 kW in the combined heat recovery from hot process streams and condensate. Additionally, electricity production in the CHP plant (coupled with the MTBE plant by steam and condensate streams) can increase by 120 kW. HEN reconfiguration is proposed considering local constraints like the existing heat transfer areas and locations of heat-transfer equipment units. The proposal leads to a new HEN structure and a new arrangement of the equipment units in the steam and condensate system.