Benefits and risks of blast furnaces with high intensity

Abstract

Increase in the intensity of blast furnace smelting at NLMK JSC is achieved by improving quality of coke and iron ore materials, by increasing pressure under the blast furnace mouth and by oxygen enrichment. It is accompanied by an increase in the rate of wustite indirect reduction and decrease in specific heat losses with cooling water. However, the risks of burden yield problems are significantly lower with high intensity. It has been established that with the change in quality of charge materials, reason for burden yield problems can be also the variation in ore load ratio along the furnace radius. A new method for diagnosing causes of burden yield problems was developed. Using method of mathematical modeling, effect of change in ore load and size of iron-ore materials on peripheral gases temperature change and the degree of CO use were analyzed. The method is based on analysis of joint change in gas temperature and degree of CO use in peripheral area. Analysis of peripheral gases temperature variation and degree of CO use makes it possible to identify reasons of pressure drops along the furnace height. As a result of analysis of pressure drops dynamics changes along the furnace height, there have been found signs that can be used to judge the probability of burden yield problems. The possibility of reducing pressure drops due to redistribution of ore load along the furnace radius and the amount of gases is considered. It is shown that various methods of reducing the amount of gases are accompanied by different changes in coke consumption and furnace productivity. Mathematical model has been developed to select the best combination of parameters changing of the fuel-enriched blast in specific conditions.