Energy, exergy, economic and environmental (4E) analyses of a cleaner fused magnesia system

Abstract

This study performed a comprehensive energy, exergy, economic, and environmental analysis to evaluate the thermodynamic performance of a cleaner fused magnesia system (CFMS), compare with light burned magnesia process system (LMPS) and fused magnesia process system (FMPS). The analysis considered the multi-energy supply and exergy efficiency of the system, and determined its irreversibility under different processes. The yield rate of fused magnesia (34.2%) in CFMS, higher than that of LMPS (12.8%) and FMPS (7.7%). The energy and exergy efficiencies of the CFMS were 35.4 and 26.3%, higher than those of LMPS (29%; 21.2%) and FMPS (22.4%; 16.8%), the energy consumption per unit product were 3410.2 kWh/t, higher than those of LMPS (4800 kWh/t) and FMPS (3640 kWh/t), and the economic benefit of the fused magnesia product was 1476 ￥/t, higher than that of LMPS. The carbon dioxide emission in CFMS was 2.116 kgCO2/kgMgO, which is lower than that of LMPS (4.226 kgCO2/kgMgO), and almost equal to that of FMPS (2.077 kgCO2/kgMgO). The largest exergy loss in CFMS, which was caused by the heat transfer among magnesia products, furnace gas, and air, can be partially recovered using a waste heat recovery system. The improved fused magnesia system was more energy-saving and environmentally friendly. The findings of this study can be used to improve decision making in the smelting system.