Process optimization in the steel plant

Sammanfattning: Blast furnace is the heart of every steel plant. Steel production is based on the blast furnace process, as it is where the iron is extracted from the iron ore and turned into liquid iron, which will subsequently be used to make liquid steel. Therefore, without hot iron, steel can not be produced. Blast furnaces in this process are supplied among others with pulverized coal. Raw coal should be prepared for the blast furnaces in the form of fine coal powder. This fine coal powder should then be injected into the blast furnaces in order to continue the production. This process is carried out by the Pulverized Coal Injection System, which changes raw coal into dry fine coal powder. The system consists of a hot gas generator, a coal mill, a bagfilter as well as various valves, fans and piping. The general idea is to burn specific gases with the help of equipments and to use them to dry the coal in the cycle. When the amount of the gases inserted into the system is changed, the dried coal amount is directly affected. Based on this background the following project is carried out, which aims at the investigation of bottlenecks and critical points in the process. The most important bottleneck is the limited possibility of fresh air usage, as the oxygen in fresh air can cause explosions if existent in exceeding amounts in the system and thus, is dangerous. In order to prevent this explosive condition in the system, additional gases need to be added to the system. The aim of this project is to introduce additional gases to the system in order to increase the upper limit of the fresh air amount. Increasing the amount of fresh air in the recirculation gas should provide more amount of dried coal,hence increasing the drying capacity of the coal grinding plant. To understand the situation better, tests about gas injection are carried out in the system. The results of the tests are analyzed and the performance changes in the system are calculated. For this, programs in Excel and also inLabVIEW are created to interpret the situations easily. As it is understood from the results of the tests, when the amount of the additional gases isincreased, approximately 10% increase in the amount of dried coal is observed. Subsequently, Pulverized Coal Injection mill productivity isincreased. Additionally, oxygen percentage in the mill circuit will decrease and this is important for the safety conditions. To conclude, this project aims to show the usage and recycling of additional gases in “PulverizedCoal Injection” process by implying various programs and interpretations.