Sinter plant
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Sinter plants agglomerate iron ore fines with other fine materials at high temperature, such that constituent materials fuse together to make a single porous mass without much change in the chemical properties of each ingredient.
History
Many countries, including Russia, France and Germany, have underground deposits of iron ore in dust form (blue dust). Such iron ore cannot be directly charged in a blast furnace. In the early 20th century, sinter technology was developed for converting ore fines into lumpy material chargeable in blast furnaces. Sinter technology took 30 years to gain acceptance in the iron making domain, but now plays an important role in the blast furnace route of iron making. Though initially developed to use iron ore fines generated at the mining stage, it is now the only means of using most of the metallurgical waste generated in steel plants, helping not only the blast furnace operation but solving big environmental problems as well.
Sinter-making process
Charge material is put on a sinter machine in two layers, the first layer may vary in thickness from 30 to 75 mm, a 12 to 20 mm sinter fraction is used, also referred to as the hearth layer. The second layer, which covers the first layer, consists of mixed materials, making for a total bed height up to 600 mm (may vary from 350 to 660 mm). The mixed materials are applied with a drum feeder and nine roll feeders. The upper layer is evened out using a leveler. Then the charge enters the ignition furnace, where there are two rows of multislit burners. The first zone of the ignition furnace where eleven burners are installed is called the ignition zone, and the next part of the ignition furnace where 12 burners are installed is called the soaking zone (also referred to as the annealing zone). A total of 23 burners are used in the ignition furnace. The temperature is maintained between 1150 and 1250 °C in the ignition zone and between 900 and 1000 °C in the soaking zone to prevent sudden quenching of the sintered layer. The top 5 mm from screens of screen house two goes to the conveyor carrying the sinter for the blast furnace and along with blast furnace grade sinter either goes to sinter storage bunkers or to BF bunkers. Blast furnace grade sinter consists of sinter sizes 5 to 12 mm as well as 20 mm and above.[citation needed]
Advantages of Sintering
1. Better use of the huge quantity of iron ore fines generated at mines.
2. Gainful use of various metallurgical wastes like flue dust, mill scale, lime dust, sludge, etc.
3. Use of super fluxed sinter eliminates raw flux from the blast furnace burden. This leads to considerable coke saving and productivity improvement in blast furnaces.
4. Due to the higher reducibility of super fluxed sinter, direct reduction of iron oxide is enhanced, which contributes to further coke saving.
5. The softening temperature of sinter is higher and the softening melting zone is narrower. This increases the volume of granular zone and shrinks the width of the cohesive zone. Consequently, the driving rate of the blast furnace improves.
6. Hot metal quality (from the SMS point of view) improves due to lower silicon content and higher hot metal temperature. A higher hot metal temperature contributes to better sulphur removal from the hot metal.
7. Material handling in the charging section of the blast furnace is reduced, and fewer logistics are needed.
8. Blast furnace operation is more reliable and efficient.
See also
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