The process, called sintering, causes the constituent materials to fuse to make a single porous mass with little change in the chemical properties of the ingredients.
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.
The largest sinter plant is located in Chennai, India, and employs 10,000 people.
Calcined lime is used as binder of the mixed material along with water (all in particular proportion by weight) to form feed-sinter of about 5 to 7 mm in size.
The second, covering layer consists of mixed materials, making for a total bed height of 350 to 660 millimetres (14 to 26 in).
The material, also known as a charge, enters the ignition furnace into rows of multi-slit burners.
After breaking into small sizes, it cools down in cooler (linear or circular) by means of forced air.
A lower silica content and higher hot metal temperature contributes to more sulphur removal.