iron smelting is the common way in which metals are produced. It is normally performed in a blast furnace In this article, you’ll get to know the definition and working principle of an iron ore smelting process.
What is iron smelting?
Smelting is the production of metal, especially iron, from ore in a process that involves melting and chemical reduction of metal compounds into purified metal. it can also be seen as the various liquids or semi-molten solids produced and used during the course of such production.
Read more: Raw materials used in making iron and steel
Iron Ore Smelting Process
Iron ore smelting requires some preparation before it can be done. It enables the furnace to work perfectly and sometimes economically. It needs a regular and uniform ‘diets’ from which as much as possible of the unwanted materials has been removed.
Either the richness or size and density of the lumps needs to be improved, which is done in numbers of ways:
- by the concentration (up-grading) of low-quality ores with the removal of unwanted materials by washing and/or gravity separation or, in the case of magnetic ores, by magnetic separation.
- by crushing and screening (sieving) to a suitable size. The powdering residue from the screening, known as ‘fines’ is mixed with coal dust or coke breeze, and the sintering (controlled burning) process follows, resulting in the fusion of the fines into hard lumps that can be included in the furnace charge. Sinter is being used more and more nowadays and in some plants, it forms 100% of the charge.
- the blending of different ores to obtain consistency in quality,
- and by forming powdery ores into pellets.
As mentioned earlier iron ore smelting process is needed to be performed to improves the efficiency of the furnace and to work economically. It is done by removing the unwanted materials and by improving the density of lumps, size or richness.
Iron smelting in blast furnace
Iron smelting involves two main processes in the blast furnace:
- the reduction of iron from its compounds and
- its separation from its physical mixture with gangue materials.
In a furnace, the charge is constantly moving to slow down against the force flow of the very hot gases which bring about the evaporation of moisture from the charge at the top. A little further down, limestone decomposes into lime and liberates carbon dioxide. The main reaction is the reduction of the iron oxides, forming carbon dioxide and leaving the iron-free. Reduction begins quite high in the stack and is progressive as the charge descends and, at the melting zone, both iron and slag trickle down into the hearth. The slag, being lighter floats on the iron.
Watch the video below to learn more on the smelting process:
At regular intervals, as the hearth fills, slag is tapped off, followed by the iron, which goes into huge storage vessels called ‘mixer’, for holding the molten state until required in the steel making plant, usually quite near the furnace. In addition to holding a reserve of hot metal, mixers serve a useful purposes in that they will compensate for variations in composition between successive additions of hot metal, giving a more uniform product.
An inactive mixer does no more than to hold a stock of metal but in an active mixer, some refining takes place with the making of slag therein.
And that is all for this article, where the definition of an iron smelting process and how it’s performed on blast furnace. I hope you get a lot from this post, if so, kindly share with other students. Thanks for reading, see you next time!