The washing efficiency of digester displacement: new aspects based on laboratory studies and improved calculation procedures.

ABSTRACT Displacement batch cooking is nowadays a common practice in the production of kraft pulp. The cook is terminated by a cool filtrate displacement, in which the temperature of the digester is brought down. The terminal displacement is the first washing stage in the pulp mill. The displacement operation is widely practiced, but knowledge of the washing effect of the…

Towards complete impregnation of wood chips with aqueous solutions. Part 4. Effects of front-end modifications in displacement batch kraft pulping.

ABSTRACT The front-end of kraft cooking, i.e. steaming, impregnation and heating, controls the cooking performance in terms of mass transfer, delignification and cooking uniformity. Therefore, it is of vital importance to understand the process mechanisms and optimise the front-end process conditions. This article discusses the effect of applying chip presteaming and higher pressure at the front-end of kraft displacement batch…

Efficiency of chip presteaming – result of heating and air escape processes.

SUMMARY Efficient removal of air from the wood chips prior to impregnation with cooking liquor is important for achieving pulping uniformity and improving the overall digester performance. Because of its effectiveness, relative simplicity and other advantages, steaming of wood chips became a primary process in pulp industry to fulfil this task. In the present article the process of chip presteaming…

Towards complete impregnation of wood chips with aqueous solutions. Part 2. Studies on water penetration into softwood chips.

ABSTRACT Importance of the chip impregnation stage is widely recognised in chemical pulping processes. However, there is limited amount of direct data on mass transfer during the impregnation stage. Most methods used for studying the liquid penetration process were based on indirect approaches. A new laboratory impregnator with a special weight sensor was developed, which allowed the direct measurements of…