Thermodynamic and Exergoeconomic Evaluation of Heat Recovery of Gas Refinery Steam Network Using Organic Rankine Cycle and Kalina Cycle with Different Fluids

Abstract

This paper investigated the optimal use of surplus low-pressure steam in the Khangiran gas refinery, Iran. To manage energy and reduce surplus steam waste for heat sources at 150°C, three scenarios were proposed to use this energy. In these scenarios, while considering the thermodynamic conditions of steam, it was proposed to use an organic Rankine cycle with pure and mixture working fluids and a Kalina cycle, which is capable of producing power from low-temperature sources. Finally, all the scenarios were evaluated in terms of energy, exergy and exergoeconomic, and optimum conditions were specified. The results indicated that the organic Rankine cycle with isobutane as the working fluid had the best performance with a power output of 249.8 kW. Moreover, the optimal binary mixture was isopentane/cyclohexane (0.85-0.15, by mole fraction) and the power output was 279.6 kW. When using mixing fluids, the net power of the system was observed to increase by 12%. The results also revealed that the best ternary mixture was isohexane/R245fa/R365mfc (0.17-0.33-0.50, by mole fraction) and that the related net power output was 283.7 kW, which was higher than that of the binary mixture.