Entropy Analysis Of Ironmaking System In Iron And Steel Enterprises

Energy is the material basis of national economic development, and the iron and steel industry is one of the important basic industries of the national economy. In China, the energy consumption of iron and steel industry accounts for about10%of total energy consumption, and the ironmaking system accounts for about70%of total energy consumption of the steel enterprises. Thus for the steel enterprises, reducing the energy consumption of ironmaking system is a key measure for the sustainable development of the steel enterprises.Based on the second law of thermodynamics and combining the first law of thermodynamics, entropy analysis method analyzes the process of energy transfer and conversion mainly from the point of view of "quality" of energy. It’s more scientific and reasonable than energy analysis method. Different from the exergy analysis method, entroy analysis lays extra emphasis on the irreversibility of the process or cycle. It reveals that the irreversible loss of the process is the primary cause of the devaluation of energy. Gouy-Stodola formula links the entropy generation and irreversible loss. It transfers the entropy generation to an energy evaluation index, and then the same thermal processes in different enterprises can be made quantitative comparison.Ironmaking system consists of four processes, which are sintering, pelletizing, coking and blast furnace.In this paper, calculations of charge, material balance and energy balance of each process were made, confirming the condition, quality of the inputs and outputs, as well as the heat exchanged between the system and the environment. Based on the calculations, the entropy analysis model was made, as well as the entropy equation. The calculated entropy generation provided reference for the enterprises to take measures to reduce entropy of each process. Through calculating, it was got that the entropy coefficient of the ironmaking system was blast furnace, sintering, coking and pelletizing in decending order, so the blast furnace process should be the key process for saving energy.The following parameters were adjusted respectively:the amount of returning ore, the proportion of CO2generated by the burning of carbon and the grade of mixed ore in sintering process; the content of FeO in pellet, the grade of concentrate, the proportion of the bentonite and the air leakage rate in pelletizing process; the moisture content of the coal as fired and the rate of coke oven gas in the mixed gas in coking process; the temperature and the rich oxygen rate of the blast, the proportion of H2that participates the reduction reaction and the burden structure of the blast furnace in blast furnace process. The influence of the change of those parameters was analyzed, and then measures to reduce entropy generation and improve energy utilization were got. Besides, the influence and energy-saving effect of the typical energy saving technologies (technology of recovering the sensible heat of sinter, CDQ and TRT) were studied. What’s more, the grade of both sinter and pellet, as well as the burden stucture of blast furnace were adjusted, and their influence on the total entropy generation and entropy generation coefficient of ironmaing system was got.Through making entropy analysis on ironmaking system, its energy utilization condition was got, as well as the influence of main parameters and the energy-saving technologies.It can provide reference for iron and steel enterprises to save energy of ironmaking system.