Chilling of Blast Furnace – its causes and recovery Mar31

Chilling of Blast Furnace – its causes and recovery...

Chilling of Blast Furnace – its causes and recovery The chilling of a blast furnace is a very serious happening during the operation of a blast furnace. The revival of a chilled blast furnace is a big herculean task and it takes a very long time and needs a lot of patience to bring back the furnace to normal condition. In case of hearth chilling, it is not possible to tap liquid slag and hot metal, since the temperature in lower part of the blast furnace becomes very low and the connection between the tap hole and tuyere is lost. This is due to the solidification of the liquid slag which obstructs the liquids flow to the hearth. The chilling of blast furnace is varying from minor to very severe. The chilling of a blast furnace is minor when connection between tuyere and tap hole is lost but there is sufficient heat in the hearth. When the hilling becomes more severe, the hot metal also starts solidifying. In case of most severe chill the hot metal in the hearth also gets solidified. A severe chill in a blast furnace is shown in Fig. 1                       Fig 1 Severe chill as seen from a tap hole Causes of blast furnace chilling Normally blast furnace should give warning signals before furnace shows the symptoms of chilling. The warning signals will consists of Reduction in wind volume and slow burden movement due to furnace running cold Very frequent hanging and slipping in the furnace Temperature of tapped hot metal and liquid slag is lower than normal Tapped liquid slag is viscous and not moving in the runner. Water coming out from the tap hole Blocking of tuyeres and blow pipes with slag or slag-metal mixture Excessive build up...