Expert Systems Controlling the Iron Making Process in Closed Loop Operation

Abstract

1.1 Iron making Since heavy industry is often big in physical size, loud and dirty, it is often considered as low technology. This applies also for the iron and steel industry, and here especially for the early phases of the production chain: Iron making, the process of turning solid iron bearing materials into liquid hot metal (typically 1500°C, 94.5% Fe, 4.7% C, 0.6% Si, some additional trace elements), is a process, which is known in its earliest form since thousands of years. It was improved over the centuries and builds still the starting point for about 65% of the world’s steel production. An average blast furnace, which is the predominant production unit for liquid hot metal, has an inner volume of about 3500 m3 and produces about 8000 t of hot metal per day, thus consuming about 12000 t of iron bearing material and 4000 t of coke per day. In many plants one or two blast furnaces feed the processes down stream. Therefore, any problems immediately have consequences on the whole plant. The furnace should operate continuously 24 hours a day. Restarts after shutdowns are technically challenging and very costly. Controlling a blast furnace is very difficult, because the properties of the used materials are not known exactly and are not stable over time. Control actions regarding the charged materials, the so called burden, take several hours before a reaction can be experienced. Moreover, such reactions are often overshadowed by other effects. Therefore, operating a blast furnace was for a long time considered somewhere between art and magic, and was entirely based on experience, but – as we will show in this paper – was turned over the last few decades into science. Blast furnaces are fed alternating with layers of coke, produced in a coke plant, and iron bearing materials like lump ore, pellets or sinter. For the latter two special production units, namely pelletizing plants and sinter plants are required. Coal cannot be charged into a blast furnace because it does not have enough physical strength to withstand the conditions inside of the furnace. Also, it is not possible to charge too many fine materials, because this would lead to a blockage of flow of the reducing gas. Therefore sinter plants are required to convert a mixture of iron carrier fines, coke and some additive materials into solid chunks of material with a Fe content of more than 60%. Source: Expert Systems, Book edited by: Petrica Vizureanu, ISBN 978-953-307-032-2, pp. 238, January 2010, INTECH, Croatia, downloaded from SCIYO.COM