WHITE LIQUOR PREPARATION AND PULPING PROCESS

摘要

This invention relates to producing white liquor in a sulphide-lean stream a nd a sulphide-rich stream to obtain improved efficiencies in a kraft pulp digesting process such as the Kamyr modified continuous cooking process. In a kraft pulping process including multiple phases of delignification of lignocellulosic materials an d utilizing split white liquor charges the improvement comprising producing a sulphide-lean white liquor stream and a sulphide-rich white liquor stream by leaching solids of a recovery boiler smelt (2) with water or sulphide-lean white liquor with a sodium hydroxide content less than 15 % by weight, to obtain a sulphide-rich white liquor (20) comprising sodium sulphide and sodi um hydroxide in aqueous solution and solid particles comprising sodium carbonate, separating the solid particles from the sulphid e- rich white liquor, dissolving the sodium carbonate content of the solid particles in water or a weak wash from a causticizing plant to form a sodium carbonate solution (28), causticizing the sodium carbonate solution to a sulphide-lean white liquor (14) in a causticizing plant, and recycling at least part of the sulphide-rich white liquor to an initial phase of the pulping process.