Abstract: A method and continuous digester system provide for a high Na.sub.2 S concentration in the beginning of the cook of comminuted cellulosic fibrous material to produce cellulose pulp, providing a more selective cook and potential to lower cooking kappa. Two different streams of spent (e.g. "sulphurous" and "black") liquor are removed from different screens associated with continuous digesters. The spent liquor removed from the uppermost screen has a relatively high effective alkali and Na.sub.2 S concentration. The second spent liquor, removed from the second screen, has effective alkali and Na.sub.2 S concentrations which are at least 25% less than for the first spent liquor. The first spent liquor is circulated to an impregnation vessel, or other part of a chip feed system, to enhance the amount of sulphur present at the beginning of the cooking stage in the digester.