Abstract: An apparatus and method for treating cellulosic wood chips in a digestion process for the liberation of pulp in a caustic hydroxide solution at high pressures and temperatures by delivering preconditioned wood chips to a first chamber and circulating a low temperature black liquor through the chamber to preheat the chips, while continuously feeding the chips through the chamber to a second chamber at high temperature and pressure, circulating high temperature black liquor to the chips in the second chamber to advance them to cooking temperature, feeding white liquor and the chips to a digester for the digestion process over a predetermined period of time, and removing digested pulp and delivering the pulp to a washer with the black liquor for washing being utilized for the first chamber, and heating the white liquor through a heat exchange process with the high temperature black liquor.

Abstract: An apparatus and method for use in a batch digesting process to quantitatively displace fluids in the digester by pumping into the digester under pressure a first volume of displacing fluid at the upper end and a second volume of displacing fluid at the lower end of the digester. Displaced fluids are collected and removed form the digester near the midline between the top and the bottom of the digester.

Abstract: An apparatus and method for use in a batch digesting process to quantitatively displace fluids in the digester by pumping into the digester under pressure a first volume of displacing fluid at the upper end and a second volume of displacing fluid at the lower end of the digester. Displaced fluids are collected and removed from the digester near the midline between the top and the bottom of the digester.

Abstract: A method for bringing a digester up to cooking temperature efficiently and rapidly wherein wood chips are packed in the digester, covered with a hot spent liquor, and then a hot liquor displacing liquid is used to displace the hot spent liquor from the digester and send it to an alkali adjustment zone in an accumulator. After the hot spent liquor has been displaced, the hot liquor displacing liquid is passed through the digester and into a lower portion of the alkali adjustment zone. Hot liquor is constantly passed from a constant volume heating zone into the alkali adjustment zone by overflow or otherwise. Hot liquor at the cooking temperature is passed from the top of the heating zone into the bottom of the digester and relatively cool liquor after passage through the digester passes from the top of the digester to the bottom of the heating zone.

Abstract: A method for utilizing hot spent liquor, produced in a digester as the result of cooking a mass of cellulosic material with cooking liquor, is displaced from the top of the digester by pumping under pressure a displacing liquid into the base of the digester. The hot liquor so displaced is collected in an accumulator, and used to preheat another mass of cellulosic material as a preliminary to cooking of this other mass of material.