An Efficient Sequential Synthesis Model for Optimization of Steam-Organic Rankine Cycles and Work–Heat Integration

Abstract

In light of the growing tension between global energy issues and economic and social development, the necessity of energy conservation is becoming increasingly apparent. The existing studies rarely investigate the multiple energy synergistic optimization of heat allocation, heat recovery, and work–heat conversion to achieve energy savings because they are confined to mixed-integer nonlinear programs that are difficult to solve. To address this challenge, this paper proposes an efficient two-stage sequential synthesis model for the optimization of steam-organic Rankine cycles (SORC) and work–heat integration. The innovative modeling method combines the pinch-location approach with mathematical programming techniques to derive several optimal network configurations from heat supply to heat recovery by balancing exergy consumption with total annualized cost. The pressure manipulation routes of low-/high-pressure streams, SORC operating conditions, and amount of multigrade steams are simultaneously optimized to determine the minimum exergy consumption in the first stage. Work-integrated heat exchange networks (WHEN) with interstage steams are synthesized in the second stage to obtain the optimal network configurations. Two examples are tested for illustration purposes, where the SORC-integrated network exhibits a 7.6–8.4% reduction in exergy consumption compared with the nonintegrated scheme.