IRON ORES AGGLOMERATION

Agglomeration

The iron ore Fines are obtained by screening of good grade ores or flue dust or pyrite residue from sulphur production unit and the like need to be agglomerated in to lumps of suitable physical characteristics for rendering them useful as a blast furnace feed. The process that consider for agglomeration are :

1. Briquetting
2. Nodulising
3. Vacuum extrusion
4. Sintering
5. Pelletizing.

Briquetting :             Purpose of making

● For some operation the finely devided mill concentrate is not suitable and the particles must be agglomeration. The method of mechanical compressing of the powder in to small briquettes ore called briquetting.

● Briquetting essentially consist of pressing of ores fines with or without a binder in to a briquette of some suitable size and shape and then subjected it to Harding process. A wide range of organic or inorganic binders ore use in this process.

● Some short of binder most be mixed with mineral and the moisture content should be correct so that the briquets enough green strength to be handed. Usually they are given a subciqueat heating which arise them out and develops much greater bonding strength within the brequets.

Nodulising :

● In this process flue dust, pyrite residue or fine ore concentrate along with some carbonesious material like tar passed through a rotary kiln heated by gas or oil.

● The feed travel counter current to the gases. The temperature inside the kiln is just sufficient to transfer the ore but not high enough to the fuse the ore. The size of the nodules produce various considerable depending upon the tar contain and the temperature.

Vacuum Extraction :

In this process moist ore with or without binders (ex - bentonite) is feed in to the drying chamber and extracted in to a cylindrical product which is cut in to required small sizes. The product is dried and fired before use in blast furnace.

Sintering :

● This is an agglomeration process, in which heating of mass of fines particles to the stage of incipient fusion for the purpose of agglomeration in to lumps.

● There are basically two mechanism by which sintering takes place.

1. Incipent fusion of ore particle

Fe2O3 = Fe3O4 = FeO
In this iron ore particles combines with silica to give FeSiO2, if lime is present lime silicate may forms. FeSiO2 has low melting point that is 1210℃. This is known as fayalite.

2. Formation of diffusion bonds :

It take place by recrystallization and grain growth of the ores. The surface diffusion binds the material together. It gives porosity to the sinter. The sinter for blast furnace should have good reducibility. It depends on porosity of charge materials.

Charge in furnace : Sinter consist of one fines of size 100 mesh. Maximum limit is 5.0mm coke brick is available is steel plant utilize in sintering and domestic use. Sintering is carried out in rotary kiln in batch processes.

Pelletising :

● For some operation finely devided mill concentration is not suitable and the particle most be agglomeroted. The process of palletization consists of rolling of moist iron ore fines of less than 100 mesh size, with or without a binder, in to balls of usually7-20mm in size. Since the green balls lack necessary balls which are an excellent feed for a blast furnace.
Disc pelletized machine
Disc pelletiser

● Another method of pelletising process in that in which the finely devided material is rolled in a drum or inclined disc so that the particle clining together and rolled of in to small spherical pellets. Material discharge from the pelletizer in the screen and the pellets that an too much recirculated. Some short of binders most be mixed with mineral correct, so that the pellets will have enough green strength to be handed.

Share this

Related Posts

Previous
Next Post »

Contact Form

Name

Email *

Message *