Thermodynamic analysis of thermal energy recovery and direct reduction (TER-DR) system for molten copper slag

Abstract

At present, air cooling and water quenching are traditional treatment methods for molten copper slag. However, the waste heat and valuable metals cannot be recovered efficiently by these methods. Exergy efficiency (EE) of this method is only 21.0%. This paper describes a feasibility of waste heat recovery and direct reduction of copper slag. To investigate the feasibility of this new thermal energy recovery and direct reduction system (TER-DR), thermodynamic compass method was applied. Based on physical and chemical recovery methods, TER-DR1 and TER-DR2 systems are put forward. TER-DR1 system decreases the exergy loss (EXL) and improves the EE to 57.3%, and 0.489 t DRI is acquired for every ton of copper slag. Exergy of six kinds of typical endothermic chemical reactions was analyzed. The exergy of reforming reaction of CH4 by CO2 is the highest and suitable for TER-DR system. Combined with chemical method, TER-DR2 system decreases EXL further and improves the EE to 61.3%. Steam, synthesis gas and DRI are produced by this method. By TER-DR2, for every ton of copper slag, 0.489 t DRI, 67.3 m3 CO and 67.3 m3 H2 are acquired.