Exergy Analysis for Alternative Orangic Rankine Cycle (ORC) Based Combined Systems for Recovering Moderate-to-Low Temperature Waste Heat of Flue Gas

Utilization of waste heat in processes of oilfield plants has been taken into account as the most promising technology to improve thermodynamic performance. This paper proposes and investigates alternative Orangic Rankine Cycle (ORC) based combined systems for recovering moderate-to-low temperature waste heat of flue gas based on energy and exergy analysis. Advanced exergy analysis, splitting the exergy destruction into endogenous/exogenous and avoidable/unavoidable parts, is applied to reveal more detailed information about the components’ inefficiency on each other and the real potential of the optimized system for improvement. With the help of the presented model and the genetic algorithm optimization method, the optimal configuration and operating fluid in terms of power generation. The investment cost was chosen for low and medium heat demand. The results showed that the working fluid R123 has a better performance than toluene for medium heat demand, parallel configuration with preheater, and R123 working fluid and low heat demand, parallel configuration of preheater and recuperator with R123 working fluid is the most appropriate choice. In these cases, the maximum production power was calculated as 3.56 and 5.12 MW respectively, while the special investment costs for the proposed items were evaluated as 1.631 and 1.63 $/W respectively.