钢铁企业余热资源的回收与利用

Recovery of Residual-Heat Integrated Steelworks

剖析了自1980年以来国内钢铁企业吨钢可比能耗的下降趋势,总下降率为48%,其中直接节能56%,间接节能44%,但仍比国外先进产钢国高出112 kg标煤。国内生产1 t钢产生余热资源8.4 GJ,目前回收利用的仅占25.8%,高效回收利用余热资源是未来钢铁工业节能的主攻方向。论述了热平衡法、分析法、能级分析法及其相关效率指标的局限性,指出余热回收利用环节所在工序产品能耗的改变量是评价热工装备完善性和过程系统用能合理性的统一判据。依据热力学第一、第二定律推导了与热效率和能级差相关联的效率表达式,用效率和产品能耗改变量等评价指标比较了若干典型余热回收技术的优劣,给出了它们中的推荐模式及其节能效果。

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 thermoteehnieal 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.