| abstract |
Digester systems for producing paper pulp from comminuted cellulosic fibrous material take into account the level of dissolvednorganic materials (DOM), such as lignin, hemi-cellulose, and cellulose, maintaining the DOM level at about 100 g/l throughout the cookn(particularly kraft cook). In order to make sure there is sufficient liquid to slurry the material in the feed system of a two vessel system,nsome liquid is withdrawn from the circulation conduits between the digester and impregnation vessel, cooled, and fed to the feed system.nIn a vapor phase digester, the level of liquid at the top of the digester is more precisely controlled by circulating some of the withdrawnnliquid from a circulatory loop of the digester to the level tank associated with the feed system. An in-line drainer may be provided in thenfeed system between a make-up liquor pump and a liquid inlet conduit leading to the top of an impregnation vessel. Within the digester, anset of extraction/dilution screens is provided specifically positioned and spaced from each other, and with respect to a reintroduction conduitnopening, so that mixing of different DOM concentration liquids is minimized. |