Exploring the Energy and Exergy Performance of an Integrated Heat Recovery System in Aluminum Smelters Using a Parallel Two-Stage Organic Rankine Cycle

Abstract The primary aluminum industry stands out as one of the most energy-consuming and occasionally inefficient sectors, with approximately 50% of energy lost as waste heat. The challenge lies in the multitude of heat sources in aluminum smelters, each varying in quantity and temperature levels. Addressing this, the study employs the Parallel Two-stage Organic Rankine Cycle (PTORC) to integrate wasted heat from cathode sidewalls and exhaust gases into a unified recovery system. Based on a series of simulations, the current analysis delves into the impact of primary and secondary evaporation temperatures, as well as the number of integrated aluminum pots, on the energy and exergy performance of PTORC. Under specific design conditions, the results reveal that optimizing the system occurs when the primary evaporation temperature decreases and the secondary evaporation temperature increases. This leads to a substantial enhancement in both output power and thermal efficiency, accompanied by a reduction in exergetic destruction. At a primary evaporation temperature of 111.5°C and a secondary evaporation temperature of 78.5°C, the net output power reaches an optimal value of 3,840 kW. However, despite the increase in generated power, the exergy destruction of the recovery system experiences a notable rise with the number of integrated cells.