BRIEF DESCRIPTION OF PROCESS
The main raw materials used for process of pelletization are Iron ore, Additives like Bentonite, Limestone, dolomite & Coke.
The sources of fuel are coal and Furnace oil. Recently we are using Producer gas also as means of fuel in Travelling grate furnace.
The Fe content required for producing pellets is 62.5% to 63%. The process used for Pelletization is Grate-Kiln process. This process is a unique technology adopted for producing pellets. The input to the process is Iron ore concentrate of size -45μ 75 – 80% passing, having blain of 1800-1900 cm2/gm and moisture content of 10 – 12%.
The Iron ore concentrate of above characteristics is fed to the Mixer along with additives like Limestone, Bentonite, dolomite and coke in certain ratio. This mixture is homogenously mixed in the Mixer & the mixture discharge called as mixed material is stored in Mixed material bins through which again the material fed further to Pelletizing Disc for formation of green balls. The Pelletizing disc will be rotating at variable speed and with control of addition of water, speed and feed, green balls of varying size are formed and gets discharged from disc. Since Pelletization requires 8 – 16mm, these green pellets are screened through roller screens, the green pellets that are below size 8mm & above 16mm are screened out. The screened out green pellets are sent back to mixed material bins for further balling. The sized pellets between 8~16mm are fed to the Traveling grate furnace for drying and preheating. In Travelling grate furnace the pellets are dried to remove moisture and preheated to temperature of 1100 °C to give partial strength for the pellets. The main source of heat in Travelling grate furnace are Gas/oil fired burners total 10Nos. The preheated pellets are then fed into rotary kiln where pellets by rotary and tumbling action are exposed to temperature of 1225 °C – 1280 °C for firing purpose to impart final strength to Pellets. In Rotary kiln the main source of heat is Tri fuel kiln burner where Pulverised coal is main fuel and fired with supporting fuel of furnace oil or Producer gas.
From kiln the fired pellets are fed into annular cooler for cooling purpose. The pellets are passed from three different zones where the pellets are cooled from temperature 1100 °C to 360 °C, the heat energy liberated during cooling are reused in the travelling grate furnace and kiln. These pellets are finally stored in the Pellet storage yard, from where it is transported to the required place.