Borate autocausticizing equilibria in recovery boiler smelt

The effect of the potassium and boron concentration in an alkali carbonate/borate mixture and the effect of CO, concentration in the gas were studied with thermogravimetry and thermal analysis up to 900 degrees C. Results show that the auto-causticizing reaction is readily reversible with 1 % CO2 or higher in the gas if the mixtures contain only sodium compounds. Both a higher CO, concentration and a higher potassium concentration lead to lower autocausticizing. In systems that contain only potassium compounds, the autocausticizing is low and no recarbonation is observed. In potassium-rich systems, volatilization of alkali- and/or boron-components becomes more prominent than in sodium systems.