|This article is part of the Global Steel Plant Tracker, a project of Global Energy Monitor.|
Pelletizing is the process of converting very fine iron ores into spheres (normally 8mm-20mm in diameter), known as pellets. These pellets are suitable for both blast furnaces and direct iron reduction processes.
Pelletizing normally has four processes: (i) receipt of raw materials, (ii) pretreatment, (iii) balling and (iv) induration and cooling.
Receipt of Raw Materials:
The location of a pelletizing plant affects the method of receiving raw materials such as iron ore, additives and binders (bentonite, clay, hydrated lime, etc.). Depending on the location of the pelletizing plant and the iron ore mines, the plants could receive the iron ore through rails, slurry pipelines, shipments or a combination of these methods.
The pretreatment process includes grinding iron ores to have a very fine texture, normally to enrich the quality of the ore, remove gangues containing impurities (sulfur and phosphorus), and for controlling the size of the grains.
The grinding methods can be characterized as such: dry grinding and wet grinding, closed circuit grinding or open circuit grinding, grinding in a single stage or grinding in multiple stages. These methods are used in a combination depending on the characteristics of the iron ore, mixing ratio and economic factors.
Balling equipment produces green balls from the grounded iron ore from the pretreatment process, typically from devices like the balling drum and disc pelletizer. Both of these units use centrifugal force to form the fine materials into spherical balls.
The main point of this stage is to harden and stabilize the pellets. This includes heating the pellets up to temperatures of 1350°C, allowing the hematite particles (the most important ore of iron) to bind. Depending on additives/binders added to the mixture, there could also be a bit of slag forming and binding.
The pellets are hardened, cooled and ready for the next stage in the steelmaking process.
- "Understanding Pellets and Pellet Plant Operations – IspatGuru". www.ispatguru.com. Retrieved 2021-07-12.
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