ANS:B - pellets

The Midrex process of sponge iron production typically uses iron ore pellets as the feed material. In the Midrex process, iron ore pellets are fed into a shaft furnace along with reformed natural gas (also known as syngas), which serves as the reducing agent. The iron ore pellets undergo direct reduction in the shaft furnace, where they are reduced to metallic iron by the syngas at high temperatures. Using iron ore pellets rather than lumps, briquettes, or sinter has several advantages in the Midrex process:

• Pellets have a uniform size and shape, which allows for consistent and controlled feeding into the shaft furnace.
• Pellets have a higher surface area to volume ratio compared to lumps, which facilitates the reaction between the iron ore and the reducing gas.
• Pellets typically have a higher iron content and lower impurities compared to other forms of iron ore, leading to higher overall process efficiency and product quality.