Patent ID: 7422657
Filing Date: 2008-09-09
Classification: D21C

Abstract:
1. A method for feeding a slurry of cellulose chips and fluid from a low-pressure system to a high-pressure system during a continuous cooking of chemical cellulose pulp, comprising: providing an impregnation vessel, the impregnation vessel having an outlet defined therein at a bottom of the impregnation vessel; providing a digester in operative engagement with the impregnation vessel via a sluice feeder disposed between the impregnation vessel and the digester, the sluice feeder having a first inlet, a second inlet, a first outlet, and a second outlet defined therein, the first inlet being in operative engagement with the first outlet and an outlet of the impregnation vessel, and the second inlet being in operative engagement with the second outlet, the first inlet and the first outlet being in operative engagement with the low pressure system, the second inlet and the second outlet being in operative engagement with the high pressure system, the sluice feeder having a rotor with a first pocket and a second pocket, the first and second pockets being movable into a first position and a second position, the first pocket being in connection with the low-pressure system when in the first position while the second pocket being in connection with the high-pressure system, the pockets being alternately placed into connection with the high-pressure system and the low-pressure system where the first pocket, when located in the first position, is in operative engagement with the impregnation vessel via the first inlet, extending a re-circulation line from the first outlet to the second inlet, the re-circulation line having a high pressure pump separating a low pressure portion of the re-circulation line upstream of the pump from a high pressure portion of the re-circulation line downstream of the pump, filling the impregnation vessel with cellulose chips in an upper and lower section thereof, the cellulose chips having spaces defined therebetween, filling the impregnation vessel with a fluid in the lower section of the impregnation vessel to form a superior column of cellulose chips and fluid so that the fluid fills the spaces between the cellulose chips in the lower section while the cellulose chips disposed in the fluid retain a contact with each other in a manner as if no fluid was present in the impregnation vessel, the superior column creating a static pressure at the bottom of the impregnation vessel to compress the cellulose chips to obtain a degree of filling between 100% and up to 110%, using the static pressure of the superior column, without using a forced flow of fluid, to expel a chips mixture of the cellulose chips and the fluid to move out through the outlet and into the first pocket of the sluice feeder, filling the first pocket with the chips mixture while at the same time expelling an expulsion fluid that is present in the first pocket via the first outlet into the low-pressure portion of the re-circulation line, expelling previously filled chips mixture from the second pocket for transporting the chips mixture onwardly in a transfer line to the digester in the high-pressure system, the high-pressure pump pumping fluid, from the low-pressure portion of the re-circulation line to the high-pressure portion of the re-circulation line and into the second inlet, rotating the rotor so that the first and second pockets are moved from their first position to their second position, using the fluid from the low-pressure portion of the re-circulation line pumped by the high-pressure pump to the second inlet to expel the chips mixture from the first pocket into the transfer line to an upper part of the digester in the high pressure system, and conveying the chips mixture from the upper part of the digester down into the digester.