Smelting is a process in metallurgy, where the metal is in element form or in the simple compound, from its ore by heating beyond its melting point, ordinarily in the presence of oxidizing agents, such as air, or reducing agents, such as coke.
Discovery of Smelting
The first smelting process of the metal occurred in the ancient Middle East, the first metal being copper and later by tin, lead and silver around the period(5000BCE).
Smelting requires very high temperature and this is by the development of forced-air draft, however, for iron very high temperatures are in need.
The process of smelting is therefore a major achievement in 18-century the introduction to coke was late. The blast furnace was also gaining prominence
Many preliminary steps occur out for the ore treatment nowadays before the smelting process.
This is done so as to concentrate the ore as much as possible. Depending on the nature of the ore, the ore is in subjection to the reduction process once the preliminary treatment is on completion.
1. Smelting or Reduction with Carbon. In this method, the calcination or roast ore is in reaction with an amount of coke or charcoal (reducing agent) and is subject to high temperatures above its melting point.
During the process, an additional reagent is useful to the ore to remove the impurities still present in the ore. This additional reagent flux. Flux combines with the impurities to form a fusible product called slag.
Flux + Impurities → Slag
The flux selection is on basis of the nature of impurities, if the impurities are acidic in nature the flux addition is basic in nature lime (Cao). Otherwise, if the impurities are basic in nature the flux addition is acidic such as silica (SiO2).
CaO + SiO2 → CaSiO3
(Basic (Acidic (Slag)
A reverberatory furnace is useful for modern copper smelting, at the top of the furnace, concentrated ore and flux, which is limestone are charged into the top and molten matte, which is a compound of copper, iron and sulfur called slag is present at the bottom. A second heat treatment, in another (converter) furnace, is necessary to remove the iron from the matte.
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