Abstract: A continuous digester for producing chemical cellulose pulp from cellulose chips including: a digester vessel with an upper section attached to a top separator and said vessel at least partially filled with the cellulose chips and a liquor; a top separator at least partially in said upper section having a lower chip inlet port, a chip conveyor, a screen adjacent the conveyor, an upper chip discharge chute, and a liquor outlet facing a side of the screen opposite to the conveyor, and a chip inlet conduit extending into the vessel and having a first operational mode in fluid communication with the chip inlet port and a second operational mode in which the chip inlet conduit discharges directly into the vessel.

Abstract: Hardwood pulp rejects at a given Kappa number can be reduced by subjecting the hardwood pulp to specified cooking conditions at the end of cooking. In this regard, it has been discovered that s-lignin reacts faster than g-lignin and that there exists a higher proportion of g-lignin at the end of a hardwood cook as compared to the g-lignin present at the beginning of the cook. Thus, when cooking hardwoods, relatively harsher cooking conditions (e.g., higher cooking temperatures) at the end of the cooking have been discovered to decrease the g-lignin content which in turn decreases the percentage of pulp rejects at a given Kappa number.

Abstract: A continuous digester is disclosed for producing chemical cellulose pulp from cellulose chips, comprising: a continuous digester vessel having a lower section filled with the cellulose chips and an upper gas filled section; an inverted separator at least partially in said upper section which introduces chips and liquid into said digester vessel and separates some of the liquid from the chips, wherein said separator includes a drive shaft connected to a conveyor, and a liquid discharge port proximate to the drive shaft and arranged proximate to a chip discharge of the separator.

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 a single vane slurry pump in series with a centrifugal slurry pump both of which are 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.

Abstract: A continuous digester for producing chemical cellulose pulp from cellulose chips including: a digester vessel with an upper section attached to a top separator and said vessel at least partially filled with the cellulose chips and a liquor; a top separator at least partially in said upper section having a lower chip inlet port, a chip conveyor, a screen adjacent the conveyor, an upper chip discharge chute, and a liquor outlet facing a side of the screen opposite to the conveyor, and a chip inlet conduit extending into the vessel and having a first operational mode in fluid communication with the chip inlet port and a second operational mode in which the chip inlet conduit discharges directly into the vessel.

Abstract: An environmentally friendly (ECF), yet commercially viable, process produces fully bleached (typically having a brightness of over 89 or 90% ISO) cellulose pulp using a (ZEND) treatment. Typically pulp is produced in an essentially sulphur-free pulping process (such as an soda/AQ process), and is then treated by a D-EO-, D-EP-, or D-EOP-sequence before the (ZEND) treatment. Optional oxygen delignification may also be used, and subsequent elemental-chlorine-free bleaching sequences may also be employed, although normally not necessary since the pulp after the (ZEND) treatment has high brightness and good viscosity (e.g. over 21 cP).

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 method is disclosed for extracting liquor from a cellulose slurry for a continuous digester comprising the steps of: providing the cellulose slurry of liquor and chips of cellulose fiber material to a separator; extracting a first stream of liquor from the separator; extracting a second stream of liquor from the separator, where the second stream has an effective alkali (EA) concentration greater than the EA concentration of the first steam; outputting the first stream from the separator and outputting the second stream from the separator separately from the second stream, and outputting a condensed slurry from the separator to a digester vessel.

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 a single vane slurry pump in series with a centrifugal slurry pump both of which are 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.

Abstract: A continuous digester is disclosed for producing chemical cellulose pulp from cellulose chips, comprising: a continuous digester vessel having a lower section filled with the cellulose chips and an upper gas filled section; an inverted separator at least partially in said upper section which introduces chips and liquid into said digester vessel and separates some of the liquid from the chips, wherein said separator includes a drive shaft connected to a conveyor, and a liquid discharge port proximate to the drive shaft and arranged proximate to a chip discharge of the separator.

Abstract: A set of spaced apart screen assemblies are provided within a continuous kraft digester. Liquor is extracted from a first screen assembly of the set without recirculation of at least a portion of the extracted liquor into the digester above the first screen. In such a manner, the need for circulation flow below the first screen assembly of the set to the second screen assembly of the set is minimized, thereby also minimizing (if not eliminating entirely) the packing problems such flow may cause. The liquor extracted from the first screen assembly in the set could be reintroduced, however, into the digester at some other location in the cooking system (e.g., at a location just above the bottom screen). By employing the present invention, the distance between the first and second screen assemblies is greater than one digester diameter (D).

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 method is disclosed for extracting liquor from a cellulose slurry for a continuous digester comprising the steps of: providing the cellulose slurry of liquor and chips of cellulose fiber material to a separator; extracting a first stream of liquor from the separator; extracting a second stream of liquor from the separator, where the second stream has an effective alkali (EA) concentration greater than the EA concentration of the first steam; outputting the first stream from the separator and outputting the second stream from the separator separately from the second stream, and outputting a condensed slurry from the separator to a digester vessel.

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: Processes and systems are provided for cooking wood chips containing knots in a digester to produce a chemical pulp. Specifically, a low pressure slurry of comminuted cellulosic fibrous material is formed in a vessel operating at essentially atmospheric pressure by mixing therein a liquid and the comminuted cellulosic fibrous material. The low pressure slurry is thereafter supplied to a low pressure inlet of a high pressure transfer device while liquid is removed from the slurry through a low pressure outlet thereof. A high pressure liquid is supplied to the transfer device (e.g., via a slurry pump) so as to form a high pressure slurry of the comminuted cellulosic material which is then discharged from a high pressure outlet of the transfer device. Knots are removed via a knot separator from a slurry of uncooked knot-containing cellulosic material at essentially atmospheric pressure.

Abstract: Processes and systems are provided for cooking wood chips containing knots in a digester to produce a chemical pulp. Specifically, a low pressure slurry of comminuted cellulosic fibrous material is formed in a vessel operating at essentially atmospheric pressure by mixing therein a liquid and the comminuted cellulosic fibrous material. The low pressure slurry is thereafter supplied to a low pressure inlet of a high pressure transfer device while liquid is removed from the slurry through a low pressure outlet thereof. A high pressure liquid is supplied to the transfer device (e.g., via a slurry pump) so as to form a high pressure slurry of the comminuted cellulosic material which is then discharged from a high pressure outlet of the transfer device. Knots are removed via a knot separator from a slurry of undercooked knot-containing cellulosic material at essentially atmospheric pressure.

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: 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: 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.