A novel SWOG-fueled polygeneration system integrating CO₂ transcritical cycle and multi-effect desalination with thermal recovery and exergy-based evaluation through sophisticated multi-objective Bat-algorithm optimization

The necessity of effectively using industrial waste gases is highlighted by the rising demand for sustainable energy solutions. Often underutilized, steelwork off-gas (SWOG) presents a promising energy source for the production of multiple products. This study suggests a novel polygeneration system powered by SWOG that concurrently produces electricity, hydrogen, hot water, cold water, and freshwater in order to address the limitations of traditional systems in terms of cost and environmental impact. To improve thermal recovery and product diversity, the system incorporates advanced thermodynamic subsystems, including ammonia Rankine cycle (ARC), organic Rankine cycle, and carbon dioxide (CO₂) transcritical cycle, seawater desalination, and absorption chiller, along with a proton exchange membrane (PEM) electrolyzer. High accuracy was confirmed by validating the model against recognized references. With an exergy efficiency of 57.39 %, performance analysis showed that ARC was the most efficient unit. The system as a whole achieved energy and exergy efficiencies of 73.04 % and 31.18 %, respectively. In addition to producing 4659 kW of useful products and recovering 18251 kW of waste heat, the process kept its CO₂ footprint low at 0.68 ton/MWh. The economic analysis revealed a payback period of 2.6 years, a net present value of 7.96 million USD, and a levelized energy cost of 0.03377 USD/kWh. An optimized condition achieved 32.898 % exergy efficiency, 1.930 exergo-environmental impact index, and 19.827 USD/GJ total unit cost of product through Scenario 2 in three-objective optimization using the Bat algorithm. For practical implementation in industrial decarbonization and sustainable energy production, this integrated system offers a technically and financially sound strategy.