The induration process comprises of 4 steps – drying, pre-heating, heating, and cooling of raw materials to act as feed material in the Blast furnace. The objective of the induration process is to impart mechanical strength and appropriate metallurgical characteristics to the said material.
The Induration burner has a design flow rate capacity of 450 kg/h of coal tar. These burners (Coal Tar burners) are located at the firing zone of the furnace and are operated 24 hrs in running plant. The desired temperature in the induration process is around 1330 oC. The refractories (high Alumina-Chrome refractory) in the burner port are designed to handle temperatures up to 1700 oC.
It has been observed that, when the flow rate of coal tar is more than 300 kg/h, the burner port temperature reaches > 1580 oC, which is close to the safe operating temperature of the refractories. As a result of attaining such high temperatures, refractory, and fines dust melt and percolate within the refractory gap, thus weakening the refractory wall and burner port. Keeping this in mind, the Burners are currently operating at a reduced capacity of 280 kg/hr coal tar flow. The refractory temperature at the burner port at this reduced flow is around 1500-1550 oC and the process temperature is around 1280-1300 oC.
Thus, the temperature withstanding capacity of Burner port refractory is a major constraint affecting the overall productivity. The challenge is to restore the coal tar flow in Induration burner to its designed capacity of 450kg/h without affecting the refractory material.
It is desired to increase the coal tar flow to the design limit of 450 kg/h, without any detrimental effect on Burner refractory.