Question

The following substances are put into the blast furnace when manufacturing iron : iron, coke, ore, limestone, and hot air. Name the two substances which separate at the bottom of the blast furnace?

Answer 1

• Calcium oxide or quick lime $\left(\mathrm{CaO}\right)$ which is formed from Limestone $\left({\mathrm{CaCO}}_3\right)$ reacts with silica$\left({\mathrm{SiO}}_2\right)$ to form slag Calcium silicate ${\mathrm{CaSiO}}_3$ which goes towards the hearth present at the bottom of the blast furnace.
• $\mathrm{CaO}\left(\mathrm{s}\right)+{\mathrm{SiO}}_2\left(\mathrm{s}\right)\to {\mathrm{CaSiO}}_3\left(\mathrm{s}\right)$
• The hot Carbon monoxide$\left(\mathrm{CO}\right)$ is the reducing agent for the iron ore and it reacts with the Iron oxide$\left({\mathrm{Fe}}_2{\mathrm{O}}_3\right)$ to produce molten iron$\left(\mathrm{Fe}\right)$ and Carbon dioxide$\left({\mathrm{CO}}_2\right)$.
• ${\mathrm{Fe}}_2{\mathrm{O}}_3\left(\mathrm{s}\right)+3\mathrm{CO}\left(\mathrm{g}\right)\to 2\mathrm{Fe}\left(\mathrm{s}\right)+3{\mathrm{CO}}_2\left(\mathrm{g}\right)$
• Depending on the temperature the different parts of the furnace are separated out (the warmest at the bottom and another one on top).

Hence, the two substances that separate at the bottom of the blast furnace are fusible slag (Calcium silicate) and molten iron.