IMPROVEMENT OF BOF BOTTOM STIRRING AT RUUKKI, RAAHE STEEL WORKS

摘要

Ruukki Metals operates three 125 t LD-KG converters at Raahe Steel Plant with annual capacity of 2.8 Mt. Ruukki Metals strategy is to increase the share of special steel products, e.g. high-strength and wear-resistant steels. In order to increase the production of special steels, demand for BOF bath agitation has increased. Bottom stirring facilitates good steel quality, cost efficiency and process control. Earlier, the lifetime of the converter lining campaign was the determining factor. Bottom stirring was working only partly in the campaign due to wear and blockage. The first step was to change this principle and try to achieve 100 % availability for bottom stirring. With the new principle the converter will be relined once the bottom stirring is lost. The new method decreased the lifetime of converter campaigns but the total cost efficiency improved. After the bottom stirring availability was improved the next step was to improve the lifetime of the bottom stirring and optimize lining thickness and brick qualities on other areas in order to improve cost efficiency. During this improvement process, gas volume flow rates were optimized and gas controllers updated. Different bottom stirring elements were tested and the effect of the stirring element placement studied. This paper describes the process of performing these industrial scales tests and the achieved results.