Patent ID: 9574302
Date: 2017-02-21
CPC Classifications: D21C

Claim:
1. A system for selectively producing pulp of different grades, comprising: a continuous digester operable to selectively carry out kraft cooking of paper grade pulp or dissolving pulp; a vertical pressure vessel upstream from said continuous digester and coupled to the continuous digester in a manner to allow contents of the vertical pressure vessel to be conveyed to the continuous digester for kraft cooking, said vertical pressure vessel operable to perform pre-hydrolysis and neutralization in a batch mode when the system is producing dissolving pulp but not utilized in connection with making paper grade pulp; a source of neutralization fluid selectively connected to an intake of the vertical pressure vessel; a source of cooking fluids suitable for kraft cooking selectively connected to an intake of the continuous digester; a feeder and pre-treatment system operable to selectively supply organic fiber-containing material to the vertical pressure vessel when making dissolving pulp and to the continuous digester when making paper grade pulp; and a storage tank interposed between the vertical pressure vessel and the continuous digester for storing treated chips that have been subject to pre-hydrolysis and neutralization in the vertical pressure vessel, to facilitate a steady flow of the treated chips to the continuous digester when making dissolving pulp.