DYNAMIC AND PHYSICAL-CHEMICAL ASPECTS OF SULPHATE PULP WASHING.

The role of physical-chemistry and how it affects the process dynamics in pulp washing are generally underestimated. There are differences in washing efficiency between black liquor components. The substances can, owing to slight changes in conditions, precipitate, adsorb or foam. Consequently, the washing efficiency decreases. Crude tall oil is the most crucial substance and very large amounts are accumulated in different washing circulations. What is most needed today is a control strategy based on chemical understanding of the washing process.