Recovery of Residual-Heat Integrated Steelworks

Downtrend of energy consumption per ton crude steel of Chinese steel industry since 1980 is analyzed and the energy consumption was reduced by 48% totally,in which 56% was obtained by directly energy saving and 44% indirectly.However,Chinese steel industry still consumes 112 kg equivalent coal per ton steel more than the advanced level.The calculated residual-heat of chinese steel industry is 8.4 GJ for 1 t steel,in which only 25.8% is recovered,so residual-heat recovery will play an important role in energy saving.The limitation of heat balance analysis,exergy analysis,energy level analysis and related efficiency indexes is discussed.The change of energy consumption per ton steel product of the process where the residual-heat is recovered is the criterion to evaluate the perfection of thermotechnical equipment and rationality of energy utilization.Based on the first and second law of thermodynamics,the expression of exergy,correlated with heat efficiency and energy level difference,is deduced.Exergy efficiency and change of energy consumption per ton product were used as the evaluating indexes to analyze the current technologies for recovery of residual-heat in steel industry,and the recommended residual-heat recovery mode and its effect is introduced.