Abstract: In the feeding of a slurry of comminuted cellulosic fibrous material to a digester (continuous or batch) in the production of chemical pulp, one of the tanks used in the feed system (which preferably includes a high pressure feeder) may be eliminated without consequent loss of its function by providing a single tank with the combined functions of controlling the level of liquid in a slurrying conduit which supplies slurry to a slurry pump, and storing and substantially continuously supplying liquid to a make-up liquid pump connected to the digester. The single tank preferably surrounds the slurrying conduit and is substantially concentric, and in liquid communication, with it. A gap of 3-48 inches may be provided between the bottom of the conduit and a connection to the slurry pump. A screen or strainer may be provided in the gap, which is substantially surrounded by the tank.

Abstract: In the feeding of a slurry of comminuted cellulosic fibrous material to a digester (continuous or batch) in the production of chemical pulp, one of the tanks used in the feed system (which preferably includes a high pressure feeder) may be eliminated without consequent loss of its function by providing a single tank with the combined functions of controlling the level of liquid in a slurrying conduit which supplies slurry to a slurry pump, and storing and substantially continuously supplying liquid to a make-up liquid pump connected to the digester. The single tank preferably surrounds the slurrying conduit and is substantially concentric, and in liquid communication, with it. A gap of 3-48 inches may be provided between the bottom of the conduit and a connection to the slurry pump. A screen or strainer may be provided in the gap, which is substantially surrounded by the tank.

Abstract: A system and method for feeding comminuted cellulosic fibrous material such as wood chips to the top of a treatment vessel such as a continuous digester provide enhanced simplicity, operability, and maintainability by eliminating the high pressure transfer device conventionally used in the prior art. Instead of a high pressure transfer device the steamed and slurried chips are pressurized using one or more slurry pumps located at least thirty feet below the top of the treatment vessel and for pressurizing the slurry to a pressure of at least about 10 bar gauge. A return line from the top of the digester may, but need not necessarily, be operatively connected to the one or more pumps and if connected to the pumps, the liquid in the return line may be cooled to a temperature at which it will not flash during handling. Recirculation loops may be established associated with one or all of the slurry pumps to facilitate startup.

Abstract: The strength properties of chemical cellulose pulp (particularly kraft pulp) are improved by substituting a cold impregnation soak for conventional impregnation procedures. After steaming, wood chips are soaked in an alkaline liquid at a temperature of about 80-110° C. (preferably 80-100° C., or 90-105° C.) for between one-half-72 hours (typically about 2-4 hours) at a pressure of about 0-15 bar (preferably about 1-5 bar), to dissolve at least about 8% of the wood (preferably about 10-20%) and at least about 15% of the lignin. The alkaline liquid used preferably contains sulfide (e.g. black liquor, green liquor, white liquor, or mixtures thereof), but almost any alkaline liquid having an alkali concentration of about 1.0 mole of NaOH/liter or less (typically about 0.75 m/l or less) is suitable. The wood chips are then raised to a cooking temperature of about 145-180° C. and cooked to produce the cellulose chemical pulp.

Abstract: A top separator assembly for a digester is disclosed comprising: a rotatable shaft for the top separator; a packing for the shaft; and a sealing ring operatively mounted to the shaft and having a nominal clearance with the pack box, said sealing ring mounted so that up lifting of said shaft provides a substantially fluid tight seal between said pack box and a side of said ring (in the digester) opposite the pack box.

Abstract: The strength properties of chemical cellulose pulp (particularly kraft pulp) are improved by substituting a cold impregnation soak for conventional impregnation procedures. After steaming, wood chips are soaked in an alkaline liquid at a temperature of about 80-110° C. (preferably 80-100° C., or 90-105° C.) for between one-half-72 hours (typically about 2-4 hours) at a pressure of about 0-15 bar (preferably about 1-5 bar), to dissolve at least about 8% of the wood (preferably about 10-20%) and at least about 15% of the lignin. The alkaline liquid used preferably contains sulfide (e.g. black liquor, green liquor, white liquor, or mixtures thereof), but almost any alkaline liquid having an alkali concentration of about 1.0 mole of NaOH/liter or less (typically about 0.75 m/l or less) is suitable. The wood chips are then raised to a cooking temperature of about 145-180° C. and cooked to produce the cellulose chemical pulp.

Abstract: Disclosed is a pressure vessel comprising a pressurized chamber; an overflow chute having an inlet open to an upper level of the chamber, a chute passage extending from the upper level to a lower level, and a chute discharge; wherein the chute passage has a bend to defect a flow in the chute passage before the flow exits the discharge.

Abstract: A drainer for a feed system for a cellulose digester has a substantially open and hollow inlet (devoid of a spiral flow imparter or a like flow restriction) and a substantially annular screen within an elongated housing having a flow direction between the housing inlet and outlet. The screen is slotted and the slots are at an angle &agr; between 5-90° with respect to the flow direction, so as to minimize passage of cellulose material through the slots, or clogging of the slots.

Abstract: A feed system for a cellulose pulp treating vessel (such as a continuous digester) is not limited by the required L/W ratio of the pump feeding a wood chip slurry to a high pressure transfer device, the feed system may be kept at a low temperature to minimize flashing of liquid into steam, and a return conduit from the treatment vessel to the transfer device high pressure inlet may be eliminated. Some of the liquid is removed from the slurry just before the low pressure inlet to the transfer device, and/or just after the high pressure outlet, to reduce the L/W ratio of the slurry by at least 0.25, e.g. from 3.0:1 to 2.25:1 just before the low pressure inlet, and from, 7.0:1 to 5.0:1 substantially immediately after the high pressure outlet.

Abstract: A feed system for a cellulose pulp treating vessel (such as a continuous digester) is not limited by the required L/W ratio of the pump feeding a wood chip slurry to a high pressure transfer device, the feed system may be kept at a low temperature to minimize flashing of liquid into steam, and a return conduit from the treatment vessel to the transfer device high pressure inlet may be eliminated. Some of the liquid is removed from the slurry just before the low pressure inlet to the transfer device, and/or just after the high pressure outlet, to reduce the L/W ratio of the slurry by at least 0.25, e.g. from 3.0:1 to 2.25:1 just before the low pressure inlet, and from 7.0:1 to 5.0:1 substantially immediately after the high pressure outlet.

Abstract: A top separator assembly for a digester is disclosed comprising: a rotatable shaft for the top separator; a packing for the shaft; and a sealing ring operatively mounted to the shaft and having a nominal clearance with the pack box, said sealing ring mounted so that up lifting of said shaft provides a substantially fluid tight seal between said pack box and a side of said ring (in the digester) opposite the pack box.

Abstract: A feed system for a cellulose pulp treating vessel (such as a continuous digester) is not limited by the required L/W ratio of the pump feeding a wood chip slurry to a high pressure transfer device, the feed system may be kept at a low temperature to minimize flashing of liquid into steam, and a return conduit from the treatment vessel to the transfer device high pressure inlet may be eliminated. Some of the liquid is removed from the slurry just before the low pressure inlet to the transfer device, and/or just after the high pressure outlet, to reduce the L/W ratio of the slurry by at least 0.25, e.g. from 3.0:1 to 2.25:1 just before the low pressure inlet, and from 7.0:1 to 5.0:1 substantially immediately after the high pressure outlet.

Abstract: A system and method for feeding comminuted cellulosic fibrous material such as wood chips to the top of a treatment vessel such as a continuous digester provide enhanced simplicity, operability, and maintainability by eliminating the high pressure transfer device conventionally used in the prior art. Instead of a high pressure transfer device the steamed and slurried chips are pressurized using one or more slurry pumps located at least thirty feet below the top of the treatment vessel and for pressurizing the slurry to a pressure of at least about 10 bar gauge. A return line from the top of the digester may, but need not necessarily, be operatively connected to the one or more pumps and if connected to the pumps, the liquid in the return line may be cooled to a temperature at which it will not flash during handling. Recirculation loops may be established associated with one or all of the slurry pumps to facilitate startup.

Abstract: A system and method for feeding comminuted cellulosic fibrous material such as wood chips to the top of a treatment vessel such as a continuous digester provide enhanced simplicity, operability, and maintainability by eliminating the high pressure transfer device conventionally used in the prior art. Instead of a high pressure transfer device the steamed and slurried chips are pressurized using one or more slurry pumps located at least thirty feet below the top of the treatment vessel and for pressurizing the slurry to a pressure of at least about 10 bar gauge. A return line from the top of the digester may, but need not necessarily, be operatively connected to the one or more pumps and if connected to the pumps, the liquid in the return line may be cooled to a temperature at which it will not flash during handling. Recirculation loops may be established associated with one or all of the slurry pumps to facilitate startup.

Abstract: In the feeding of a slurry of comminuted cellulosic fibrous material to a digester (continuous or batch) in the production of chemical pulp, one of the tanks used in the feed system (which preferably includes a high pressure feeder) may be eliminated without consequent loss of its function by providing a single tank with the combined functions of controlling the level of liquid in a slurrying conduit which supplies slurry to a slurry pump, and storing and substantially continuously supplying liquid to a make-up liquid pump connected to the digester. The single tank preferably surrounds the slurrying conduit and is substantially concentric, and in liquid communication, with it. A gap of 3-48 inches may be provided between the bottom of the conduit and a connection to the slurry pump. A screen or strainer may be provided in the gap, which is substantially surrounded by the tank.

Abstract: Chemical pulp is produced from a slurry of comminuted cellulosic fibrous material using a beneficial additive such as AQ, or polysulfide. In the first treatment zone the effective alkali concentration and temperature conditions are such so that substantially no alkali degradation of the cellulose occurs, but so that the material is effectively impregnated with the additive. Then the material is treated with an alkaline cooking liquor, at cooking temperature, to produce a chemical cellulose pulp with higher yield or strength than if the low temperature, low alkali, additive pretreatment was not practiced. Typical alkali and temperature conditions in the first zone are less than 10 g/l expressed as NaOH; and between about 80-130° C., e.g. about 80-110° C. The first zone is preferably a feed system (which may include a separate impregnation vessel) for a continuous digester, while cooking is in a continuous digester.

Abstract: The strength properties of chemical cellulose pulp (particularly kraft pulp) are improved by substituting a cold impregnation soak for conventional impregnation procedures. After steaming, wood chips are soaked in an alkaline liquid at a temperature of about 80-110° C. (preferably 80-100° C., or 90-105° C.) for between one-half-72 hours (typically about 2-4 hours) at a pressure of about 0-15 bar (preferably about 1-5 bar), to dissolve at least about 8% of the wood (preferably about 10-20%) and at least about 15% of the lignin. The alkaline liquid used preferably contains sulfide (e.g. black liquor, green liquor, white liquor, or mixtures thereof), but almost any alkaline liquid having an alkali concentration of about 1.0 mole of NaOH/liter or less (typically about 0.75 m/l or less) is suitable. The wood chips are then raised to a cooking temperature of about 145-180° C. and cooked to produce the cellulose chemical pulp.

Abstract: A system and method for feeding a slurry of comminuted cellulosic fibrous material such as wood chips to the top of a treatment vessel such as a continuous digester also treat the material to remove metals before digestion. During pumping of the slurry with at least first and second series connected pumps, at or upstream of at least one of the pumps chemicals (acids and/or chelating agents) which dissolve the metals in the material are added, and preferably some of the liquid is removed so as to purge at least about 10% (e.g. about 20-80%) of the metals in the material. The metal removal preferably takes place substantially immediately before alkaline digestion.

Abstract: Dense, tramp material, is efficiently separated in a comminuted cellulosic fibrous material feed system, for example in a chemical cellulose digester feed system, in a simple but effective matter. By merely utilizing a generally vertical conduit and a slurry flow within it (which may be augmented by high speed liquid introduction), that is caused to turn in a radiused path, centrifugal force allows separation of the tramp material into a cavity beneath the radius transition without requiring any mechanical element to engage the slurry. Appropriate purges, baffles, and discharge mechanisms may be provided. Alternatively, a tramp material separator may be built into an otherwise conventional metering screw in a digester feed system, or one or more centrifugal separators can be provided downstream of the slurry pump in a chip slurry transport system or digester feed system.

Abstract: A system and method for feeding comminuted cellulosic fibrous material such as wood chips to the top of a treatment vessel such as a continuous digester provide enhanced simplicity, operability, and maintainability by eliminating the high pressure transfer device conventionally used in the prior art. Instead of a high pressure transfer device the steamed and slurried chips are pressurized using one or more slurry pumps located at least thirty feet below the top of the treatment vessel and for pressurizing the slurry to a pressure of at least about 10 bar gauge. A return line from the top of the digester may, but need not necessarily, be operatively connected to the one or more pumps and if connected to the pumps, the liquid in the return line may be cooled to a temperature at which it will not flash during handling. Recirculation loops may be established associated with one or all of the slurry pumps to facilitate startup.