Claims
- 1. A process when cooking wood chips containing knots in a digester to produce a chemical pulp, comprising the steps of:
(a) forming a low pressure slurry of comminuted cellulosic fibrous material in a vessel or conduit operating at essentially atmospheric pressure by mixing therein a liquid and the comminuted cellulosic fibrous material; (b) supplying the slurry to a low pressure inlet of a slurry transfer device; (c) forming a high pressure slurry of the comminuted cellulosic material in said transfer device; (d) discharging the high pressure slurry from the transfer device to be supplied to the digester; and (e) removing knots from a slurry of undercooked knot-containing cellulosic material at essentially atmospheric pressure, and thereafter transferring the removed knots directly to the vessel or conduit or downstream thereof so that the knots become part of the low pressure slurry supplied to the transfer device.
- 2. The process of claim 1, comprising using a high pressure transfer device having said low pressure inlet, a low pressure outlet for removing liquid from the slurry, a high pressure inlet for supplying a high pressure liquid to the transfer device, and a high pressure outlet discharging the high pressure slurry.
- 3. The process of claim 1 or 2, comprising directly feeding the removed knots into the slurry to be supplied to the transfer device before said low pressure inlet.
- 4. The process of claim 1 or 2, comprising using a knot drainer or separator to remove the knots from the slurry of undercooked comminuted cellulosic material.
- 5. The process of claim 1 or 2, wherein the vessel or conduit includes a chip chute, and a metering device discharging a metered amount of the comminuted cellulosic material to the chip chute, and wherein step (e) includes the step of introducing the removed knots to the low pressure slurry at the chip chute.
- 6. The process of claim 2, comprising recirculating at least a portion of liquid removed from the slurry at the low pressure outlet of the transfer device to the vessel or conduit.
- 7. The process of claim 6, comprising pumping the low pressure slurry including the removed knots to the low pressure inlet of the transfer device.
- 8. A system for producing a chemical pulp from a slurry of knot-containing cellulosic material, comprising:
(a) a digester for pressurized cooking the knot-containing cellulosic material; (b) a vessel or conduit operating at essentially atmospheric pressure for forming a low pressure slurry of comminuted cellulosic fibrous material; (c) a transfer device which includes a low pressure inlet and a high pressure outlet, wherein the low pressure inlet receives the low pressure slurry from the vessel or conduit, the transfer device forming a high pressure slurry of the comminuted cellulosic material which is discharged through the high pressure outlet; (d) means for supplying the high pressure slurry to the digester; and (e) a knot separator or drainer for removing knots from a knot slurry of undercooked knot-containing cellulosic material at essentially atmospheric pressure, and thereafter transferring the removed knots directly to the vessel or conduit so that the knots become part of the low pressure slurry supplied the transfer device.
- 9. The system of claim 8, wherein said knot separator includes a knot drainer to remove the knots from the slurry of undercooked comminuted cellulosic material.
- 10. The system of claim 9, wherein the knot drainer or separator is physically attached to said vessel or conduit or a metering device feeding the vessel or conduit.
- 11. The system of claim 8, 9 or 10 comprising a chip chute, and a metering device which discharges a metered amount of the comminuted cellulosic material to the chip chute, wherein means are provided for introducing the removed knots to the low pressure slurry at the chip chute.
- 12. The system of claim 8, wherein the transfer device includes a low pressure outlet allowing liquid to be removed from the slurry and a high pressure inlet for receiving high pressure liquid to the transfer device.
- 13. The system of claim 12, comprising a recirculation conduit for recirculating at least a portion of the liquid removed from the slurry at the low pressure outlet of the transfer device to the vessel or conduit.
- 14. The system of claim 8, wherein the vessel includes a chip chute, and a metering device which discharges a metered amount of the comminuted cellulosic material to the chip chute, and wherein the knots removed by said knot separator are introduced directly at the chip chute.
- 15. The system of claim 14, comprising a slurry pump for pumping the low pressure slurry including the removed knots to the low pressure inlet of the transfer device.
- 16. A method of returning knots removed from a knot slurry in a chemical wood pulping process, comprising feeding the removed knots directly into a chip handling system at essentially atmospheric pressure downstream of a chip bin, preferably downstream of a metering device.
- 17. The method of claim 16, comprising feeding the removed knots directly into a vessel or conduit, such as a chip chute, upstream of the digester operations.
- 18. The method of claim 16 or 17, comprising feeding the removed knots without pumping or other processing to the chip handling system.
- 19. A process for cooking wood chips containing knots in a digester to produce a chemical pulp, comprising the steps of:
(a) forming a low pressure slurry of comminuted cellulosic fibrous material in a vessel operating at essentially atmospheric pressure by mixing therein a liquid and the comminuted cellulosic fibrous material; (b) supplying the slurry to a low pressure inlet of a high pressure transfer device while removing liquid from the slurry through a low pressure outlet thereof; (c) supplying a high pressure liquid to the transfer device and forming a high pressure slurry of the comminuted cellulosic material; (d) discharging the high pressure slurry from a high pressure outlet of the transfer device, (e) removing knots from a slurry of uncooked knot-containing cellulosic material at essentially atmospheric pressure, and thereafter transferring the removed knots to the vessel so that the knots become part of the low pressure slurry supplied to the low pressure inlet of the transfer device.
- 20. The process of claim 19, comprising using a knot drainer to remove the knots from the slurry of uncooked comminuted cellulosic material.
- 21. The process of claim 19, wherein the vessel includes a chip chute, and a metering device which discharges a metered amount of the comminuted cellulosic material to the chip chute, and wherein step (e) includes the step of introducing the removed knots to the low pressure slurry at the chip chute.
- 22. The process of claim 19, comprising recirculating at least a portion of the liquid removed from the slurry at the low pressure outlet of the transfer device to the vessel.
- 23. The process of claim 22, wherein the vessel includes a chip chute, and a metering device which discharges a metered amount of the comminuted cellulosic material to the chip chute, and wherein step (e) includes the step of introducing the removed knots to the low pressure slurry at the chip chute.
- 24. A system for producing a chemical pulp from a slurry of knot-containing cellulosic material, comprising:
(a) a digester for pressurized cooking the knot-containing cellulosic material; (b) a vessel operating at essentially atmospheric pressure for forming a low pressure slurry of comminuted cellulosic fibrous material; (b) a high pressure transfer device which includes a low pressure inlet, a low pressure outlet, a high pressure inlet and a high pressure outlet, wherein the low pressure inlet receives the low pressure slurry from the vessel and the low pressure outlet allows liquid to be removed from the slurry; (c) a slurry pump for supplying a high pressure liquid to the transfer device through the high pressure inlet and thereby form high pressure slurry of the comminuted cellulosic material which is discharged through the high pressure outlet and supplied to the digester; (e) a knot separator for removing knots from a slurry of uncooked knot-containing cellulosic material at essentially atmospheric pressure, and thereafter transferring the removed knots to the vessel so that the knots become part of the low pressure slurry supplied to the low pressure inlet of the transfer device.
- 25. The system of claim 24, wherein said knot separator includes a knot drainer to remove the knots from the slurry of uncooked comminuted cellulosic material.
- 26. The system of claim 24, wherein the vessel includes a chip chute, and a metering device which discharges a metered amount of the comminuted cellulosic material to the chip chute, and wherein step (e) includes the step of introducing the removed knots to the low pressure slurry at the chip chute.
- 27. The system of claim 24, comprising a recirculation conduit for recirculating at least a portion of the liquid removed from the slurry at the low pressure outlet of the transfer device to the vessel.
- 28. The process of claim 27, wherein the vessel includes a chip chute, and a metering device which discharges a metered amount of the comminuted cellulosic material to the chip chute, and wherein the knots removed by said knot separator are introduced to the low pressure slurry at the chip chute.
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation-in-part of parent U.S. patent application Ser. No. 10/283,369 filed on Oct. 30, 2002, and is based on, and claims domestic priority benefits under 35 USC §119(e) from, U.S. Provisional Application Serial No. 60/334,963 filed on Dec. 4, 2001, the entire content of each prior filed application being expressly incorporated hereinto by reference.
Provisional Applications (1)
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Number |
Date |
Country |
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60334963 |
Dec 2001 |
US |
Continuation in Parts (1)
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Number |
Date |
Country |
Parent |
10283369 |
Oct 2002 |
US |
Child |
10308180 |
Dec 2002 |
US |