Energy, exergy, and economic (3E) analysis of novel heat recovery systems for recovery and optimization of waste flows at a combined cycle power plant

In different industries, waste heat recovery is considered an efficient approach of maximizing energy utilization. This study addresses the recovery of waste flows from the blowdown tanks (BTs) and deaerators of a Combined Cycle Power Plant (CCPP). To this end, three waste heat recovery scenarios were proposed using the organic Rankine cycle (ORC) and the distributed boosted multi-effect distillation (DBMED) integrated with the CCPP: Scenario 1 (ORC-DBMED), Scenario 2 (ORC-D-DBMED), and Scenario 3 (ORC P-DBMED). The proposed scenarios were evaluated through the energy, exergy, and economic (3E) analysis and were then optimized from an economic perspective. The main exergy destruction occurred in the combustion chamber of the CCPP, the evaporator of the ORC, and the condenser of the DBMED, accounting for 55.4 %, 52 %, and 29.9 %, respectively. According to the results, Scenario 1 demonstrated the shortest payback period (PP) of 1.62 years, while Scenario 2 achieved a slightly higher energy efficiency of 46.7 %. However, the payback period for Scenario 2 was longer, at 2.34 years. Scenario 1, which exhibits superior economic conditions compared to other scenarios, was proposed in this study. In this cycle, 730.1 kW of power and 278.56 m3/day of water were saved by recovering the flows of vents and producing water in the DBMED process. The integration of the cycle led to a 0.21 % rise in the energy efficiency and 0.13% increase in exergy efficiency for the CCPP.