Iron ore: Sintering and pellet

 We basically know that steel products are made from iron ore. However, iron ore dug from the ground undergo a long and complicated to became useful steel product. We will have a short look on one of the most applied technologies - Blast furnace (BF)

I divide the whole process into 4 phases like below:

1. Iron ore exploited from nature 
2. processed iron ore 
3. sintered iron ore/ iron pellet 
4. pig iron and then liquid steel and then steel product

1. Iron ore exists in the nature in form of deposits of iron mineral like hematite, magnetite, limonite, etc. They are to hard to be excavated in a normal way. People usually use explosive to break them into smaller size. Let's them "run of mine" - not graded according to quality and size.

2. Iron ore with high content of total Fe (57%) can be directly broken into proper size (8-30mm) for metallurgical process. Let's call this type as large-sized iron ore

Iron ore with lower content of total Fe has to be process to enrich the Fe content by removing the waste. If we want to eliminate the impurities, we have to grind iron into even smaller size. We call the one with top size of 6.3mm as medium-sized iron ore, and the one with top size of 74 micrometer as iron fine. For medium-sized iron ore, a total Fe of minimum 53% is acceptable and for iron fine a total Fe of 60% is acceptable.

Medium-sized iron ore and iron fine can not be directly fed into the blast furnace because they are too small, there is not enough space among particles for blast.

3. Medium-size iron ore is then added with flux like dolomite or lime fine and baked at a temperature of approx. 1300 degree. The surface of the iron particles start to liquify and stick together to form sintered iron ore. Sintered iron ores are now rough pieces like large-sized iron ore.

Iron fine is added with adhesive like bentonite and pelleted into form of spheres with diameters of  8-16mm and then baked at a temperature of approx. 900 degree to become harder. Iron pellets are really strong and can resist up to 1800kN per pellet.

4. Now large-sized iron ore, sintered iron ore and Iron pellets are fed into the blast furnace with coke, hot air rich in oxygen (blast) and pulverized coal are blown into the furnace. Solid iron ore is melted and reduced into molten iron (with 2.14-4% of carbon). Molten iron then treated in BOF (basic oxygen furnace) and/or LF ladle furnace to eliminate more carbon and impurities to become pure liquid steel. Then liquid steel are casted to form blooms, slabs, billets and then rolled into rebar, bar steel, wire rod, steel sheet, steel coil, etc.

Mineral formation	Exploitation	Mineral process	Hot-preparation	Blast furnace	Basic oxygen furnace	Casting	Rolling
Iron ore	Iron ore run of mine	Large-sized iron ore		Molten iron	Liquid steel	Bloom, slab, billet	Bar, rebar, sheet, wire rod, coil
		Medium-sized iron ore	Sintered iron ore
		Iron fine	Iron pellet

Iron ore with 63.5% Fe is approx. $100-150 per ton while steel coil is $700-800 per ton. No doubt that steel industry is one of the most profitable sector.

Note: Data in this article (sizes, Fe content, price) is for reference only. They change according to many factor like market, time, equipment applied, etc...

Quangngai, November, 23rd, 2022