Design of multi-pressure organic rankine cycles for waste heat recovery in site utility systems

Abstract

This work addresses the design of Organic Rankine Cycle (ORC) processes used for power generation from low-grade heat available in site utility systems. The Exergy Composite Curves approach is used within a systemic optimization framework to explore various complex ORC configurations. The method facilitates interconnectivity at several temperature and pressure levels, considering different types and numbers of turbines as design decision parameters simultaneously with other operating ORC features. It is employed to investigate the performance of two generic ORC configurations, namely one considering independent pressure loops with expansion turbines and the other considering pressure loops contacted through induction turbines. To optimize the number of pressure levels, ORC structural configuration, and operating parameters an inclusive objective function is used considering thermodynamic criteria. The application of the method is demonstrated by a case study on waste heat recovery and reuse in a utility plant.