Partial autocausticization of alkali liquors for wood pulping processes

摘要

A method for regenerating sodium hydroxide in a wood pulping process comprising the steps of: i) Partially autocausticizing a sodium carbonate-containing smelt by reaction with borate, thereby producing a reacted portion and an unreacted portion of the smelt. ii) Dissolving the partially autocausticized smelt in aqueous solution, thereby regenerating sodium hydroxide from the reacted portion of the smelt and forming dissolved sodium carbonate from the unreacted portion of the smelt. iii) Reacting the dissolved sodium carbonate with lime, thereby regenerating additional sodium hydroxide. Also described is a partially causticized aqueous liquor composition. The composition comprises sodium carbonate, sodium hydroxide, sodium borate, lime, calcium carbonate and water, and has a boron to carbonate molar ratio of less that 2:1 and a sodium to boron ratio of greater than 3:1.