Leaching of NaOH from 4:5 Sodium-Titanate Produced in an Autocuasticization Process Part 1: Kinetics and Equilibrium, 1998 International Chemical Recovery Conference Proceedings

Black liquor gasification, including autocausticization with titanates, is one of very few alternatives to the conventional recovery process in the Kraft pulp process. Autocausticization with titantes can be divided into two sub-processes: one where the reaction between the titanate and the black liquor occurs and one with the reaction between water and the titanate.

The aim of this paper was to investigate the second sub-process, i.e. the leaching of sodium hydroxide from 4:5 sodium titanate. A laboratory batch reactor was used in the experimental part and a programme was written to calculate the parameters in the overall reaction rate expression.

It was found that the overall reaction rate was dependent on both the bulk concentration of sodium hydroxide and the temperature. A low bulk concentration of sodium hydroxide gave a faster overall reaction rate than a high concentration. Temperature had the opposite influence: a high temperature gave a high overall reaction rate. Furthermore, the reaction was found to be a slightly endothermic reaction with a heat of reaction of 3.50 kJ/mol of produced sodium hydroxide. The equilibrium concentration was found to increase with increasing temperature.