Energy and exergy analyses of pellet smelting systems of cleaner ferrochrome alloy with multi-energy supply

Comprehensive energy and exergy analyses were performed to evaluate the thermodynamic performance of two ferroalloy pellet smelting systems named sintering-preheating-submerge arc furnace (SPSF) and rotary kiln-electric furnace (RKEF). The analyses considered the multi-energy supply and exergy destruction of the systems and identified the avoidable irreversibility of the processes. The energy efficiency of the SPSF and RKEF systems was 54.07% and 42.93%, respectively. The exergy efficiency of the two systems was found to be 28.37% and 30.71%, respectively. The largest exergy destruction of both systems was caused by the alternating current circuit which could be replaced by direct current circuit for better performance. The heat transfer between equipment was the major avoidable exergy destruction in systems. The integration of smelting equipment is a suitable method to reduce the avoidable exergy destruction. The environmental impact of the systems is also evaluated on the basis of resource utilization efficiency, system carbon dioxide emission rate and sustainability index. The SPSF is more environmental-friendly than the RKEF. The effective recycling of the exhaust gas in the preheating shaft kiln could pose significant energy saving. The present work could be employed for decision making on improving the existing smelting systems.