Capital Repairs of a Blast Furnace Sep01

Capital Repairs of a Blast Furnace...

Capital Repairs of a Blast Furnace Capital repairs of a blast furnace are those repairs which are taken up after the end of a campaign of the blast furnace. During the capital repairs the main jobs which are normally taken up are (i) relining of the furnace, (iii) repairs of the damaged portion of the shell, (iii) Major revisioning of all the equipment with replacement of the worn out components, (iv) replacement of those equipments, instruments and automation items which have become obsolete or completed their useful life, and (v) modification work the need of which was felt during the running of the blast furnace in the campaign which has just ended. Since the campaign of a blast furnace lasts for a long time (10 years to 20 years), technology upgradation takes place during this period. Hence it becomes necessary to incorporate these technological upgradation features in the blast furnace during the capital repairs. This keeps the blast furnace up to date in its new campaign. Capital repairs also provide opportunity to steel plant to improve the lining features of the furnace and to enhance the internal volume and hence the capacity of the blast furnace. The improvement in the lining features also help in the enhancement in the campaign life of the blast furnace. Planning for the capital repairs Capital repairs of the blast furnace are normally a time bound activity which is to be completed within the shortest possible time and in the assigned budget and hence accurate and close planning is very important for the successful completion of the capital repairs. Planning is required to be done to the minute levels. The achievement of the success in timely completion of the capital repairs within the estimated costs depends on how accurate...

Refractory lining of blast furnace Aug15

Refractory lining of blast furnace...

Refractory lining of blast furnace  A modern blast furnace (BF) is refractory lined to protect the furnace shell from the high temperatures and abrasive materials inside the furnace. The refractory lining is cooled to further enhance the protection against the dispatch of excess heat that can destroy the refractory lining. BF has a complex refractory system to provide a long, safe life that is necessary for the blast furnace availability and for permitting nearly continuous furnace operation and casting. Conditions within the blast furnace vary widely by region and the refractories are subjected to a variety of wear mechanisms. Details are given in Tab 1. The application condition of different regions of a blast furnace is not the same due to the very nature of its geometry and also due to the pyrometallurgical process occurring at different stages. There are diverse physical and chemical wear mechanisms in the different regions of the blast furnace and they are complex in nature. For example mechanical wear or abrasion occurs mainly in the upper stack region and is caused by the decent of the charge materials and by the dust laden gases. High thermal loads are a major factor in the lower stack and the belly regions. In the hearth region, horizontal and vertical flow of hot metal combined with thermal stresses often form undesirable elephant foot shaped cavitation. The refractory materials in these regions are to take care of these wear mechanisms to avoid damage due to them. Therefore, the BF stack (upper middle and lower), belly, bosh, raceway and tuyere region, hearth, and taphole all require different quality of refractories depending on the respective application conditions. Tab 1 Attack mechanisms in different regions of blast furnace       Region Attack mechanism Resulting damage       Upper stack Abrasion...