Question

why must the temperature of the lime mud in the lime kiln reach at least 900 degrees Celsius?

Answer 1

A lime kiln is used to produce quicklime through the calcination of calcium carbonate. The chemical equation for this transformation is given as:

                                                    CaCO₃ + heat → CaO + CO₂

This reaction takes place under controlled reaction temperature at 900 °C (at this temperature the partial pressure of CO₂ is 1 atmosphere), but a temperature around 1000 °C (at which temperature the partial pressure of CO₂ is 3.8 atmospheres) is usually used to make the reaction proceed quickly. Excessive temperature is avoided because it produces unreactive, "dead-burned" lime.