Answer. Ammonical brine is fed into carbonating tower and carbon dioxide is passed through it. Following reactions take place in the carbonating tower.
CO2(g) + NH3(g) + H2O NH4HCO3(1)
NH4HCO3(1) + NaCl (brine) NaHCO3(1) + NH4Cl(s)
The temperature of the mixture is lowered to 15°G and precipitates of NaHCO3 are obtained.