CONVERTING | Unit of Pyrometallurgy


Converting

1.To remove iron, sulphur and other impurities form the matte or molten metal. The time taken for this converting is 2:30 to 3:00 hrs.

2. In the converting process side blown occurs to remove impurities from the molten matte, which produce as a result of smelting a charge from side blown.

3. In the converter the atmosphere is highly oxidising air or oxygen enriching air is injected to molten matte way. Oxidising of liquid and molten material by blowing air through is known as converting.

4. Converting of pig iron to remove the impurities like C, Si, Mn, P etc.
● In blast furnace iron is present with impurities like S, P, Mn, C, Si etc. The slag is oxidised and gas is O2, CO etc. CO is  an excess when the elements of iron ore are reduces and form in to Fe2O4, CaO and CO2. Equilibrium reaction is at 1000℃ that is CO +CO2. Above 1000℃ only CO exists, there will be also reversible reaction in this temperature.

● Sulphur is removed in blast furnace stage which is reducing atmosphere or iron in electric arc furnace. So that Sulphur is taken care of other impurities can be oxidise and taken care of slag and parent metal should not be oxidized more than impurities but parent metal bound to oxidised. The oxides may in term to help oxidise the impurities depending the thermodynamics equilibrium.

Distillation 

Distillation is the separation of the constituent of liquid mixture by partial vaporisation followed by separation recovery of vapour.

Explanation :

● When a liquid of composition 'X' is heated which as higher content of 'A'. The composition of vapour and liquid depend upon the temperature at which they are equilibrium differential remove from 'B' by distillation.

● Selective distillation is done when impurities are more Voltaire. Several metal like Zn, Hg, Mg, Cd are reduced to elemental stage at temperature above they are respective boiling point. The resulting metal vapour must be content liquid and solid state.
Distillation - pyrometallurgy
Disttilation
The several distillation are :
1. Fractional distillation
2. Vacuum distillation
3. Selective distillation

Zn may be separated from liquid lead by vacuum distillation, similarly many impurities such as Ar, Sb, etc are illuminated from liquid iron by vacuum dillisation.

Sublimation

It is a restarted to if a solid compound of the metal having vapour pressure is available. This method advantage is sublimation occurs at low temperature because of the decomposition of heat. Sensitive impurities is avoided and corrosion is minimised. After sublimation non volatile particles are very small, which in get carried away by the vapour.



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