12. Long answer questions III

  

Smelting is an energy intensive process used to refine an ore into a usable metalmelt an ore into a usable metalpurify an ore into a usable metalseparate an ore into a usable metal.

The charge, made of roasted ore, coke, and limestoneemeraldhessonitesapphire in the proportions of \(8\):\(4\):\(1\), is melted in a blast furnace by introducing it through the top hopper arrangement.

  

In this region the temperature has reached \(1500\)°C. Here, coal burns with oxygenore burns with oxygeniron burns with oxygencoke burns with oxygen to form \(CO_2\) when the charge (solid iron ore, coke, and limestone) comes in contact with a hot blast of air.

 

\(C\) + \(O_2\) → \(CO_2\) + Heat.

 

It is an exothermic reactionendothermic reactiondecomposition reactioncombustion reaction because heat is released.

 

 
In this region the temperature is around \(1000\)°C, here \(CO_2\) is converted to \(CO\).

 

\(CO_2\) + \(C\) → \(2CO\) - Heat.

 

Limestone decomposes to lime dioxidecalcium oxidelime trioxidecalcium trioxide and \(CO_2\).

 

\(CaCO_3\) → \(CaO\) + \(CO_2\) - Heat.

 

The above two reactions are decomposition combustion endothermic exothermic due to the absorption of heat.

 

Calcium oxide bind with silica to form calcium silicate slag.

 

\(CaO\) + \(SiO_2\) → \(CaSiO_3\)\(LaSiO_3\)\(CeSiO_3\)\(KaSiO_3\)

 

 
In this region the temperature is \(400\)°C, here carbon monoxide reduces ferric oxide to form a relatively pure spongy ironpig ironwrought ironcast iron.

 

\(Fe_2O_3\) + 3\(CO\) → \(2Fe\) + \(3CO_2\)

 

After the remo val of slag, the molten iron is collected at the bottom of the furnace. This process formed iron is called pig ironcast ironspongy ironwrought iron.
It is remelted and cast into various moulds. This iron is known as pig ironcast ironwrought ironspongy iron.