Chemical and NPE Balances When Using Oxidized White Liquor In The Bleach Plant Extraction Stage

摘要

Oxidized white liquor (OWL) is an effective substitute for sodium hydroxide in the bleach plant Extraction or Oxidative Extraction stage. Its impact on a mill's sodium and sulfur balance is dependent on a number of variables including; white liquor sulfidity, the chlorine dioxide generation by-product type, the degree of oxidation, the potassium input and causticizing efficiency. Vector diagrams as described by Gosta Wiklander are used to illustrate the sulfur/sodium balances. Its use in the extraction stage also provides a purge point for chlorine, potassium and other alkali soluble non-process elements. Unlike most other purge methods, the potassium in the form of potassium hydroxide is used to advantage. Mass balances are presented that predict the equilibrium white liquor chloride and potassium concentrations associated with the vector diagrams.