Lo-Solids(TM) Pulping: Principles and Applications, 1995 Pulping Conference Proceedings

Bruno S. Marcoccia, Richard Laakso - Ahlstrom Kamyr, Ridge Center
Geoffrey McClain - Gulf States

Results from laboratory studies have shown that improvements in pulping performance can be obtained by decreasing the concentration of dissolved wood solids throughout the bulk phase of delignification. This led to the development of a new continuous cooking process: Lo-Solids Pulping. The objective of the new pulping process is to minimize the concentration of dissolved wood solids throughout the bulk phase of delignification while maintaining, as with other forms of modified cooking, an “even” alkali profile, minimal cooking temperatures, and minimal concentrations of dissolved lignin at the end of the cook. In order to achieve this, use is made of split (or multiple) extractions, split white liquor additions, and split washer filtrate additions. Cooking profiles are manipulated by altering the relative flows of extraction and of diluent additions. In full scale applications it has been found that the concentration of dissolved wood solids in cooking liquors can be decreased by as much as 30%. Benefits which have been observed in 7 commercial installations to date include: increased pulp strength and viscosity; increaseddigester extraction capacity; improved digester washing; and decreased bleach chemical requirements. Modified cooking benefits can be obtained for digesters having little or no wash zone upflow. The process changes required to retrofit existing digesters are relatively minor and pose no risk to production capacity.