WO1996017995B1

WO1996017995B1 - Improved chip feed system and method for a digester

Info

Publication number: WO1996017995B1
Application number: PCT/US1995/015458
Authority: WO
Filing date: 1995-11-28
Publication date: 1996-07-25

Abstract

In a continuous digester system, the chip feed equipment is greatly simplified by substituting a single vertical vessel for the conventional chip bin, steaming vessel and chip chute. An outlet at the bottom of the single vessel (11) is connected, through a low pressure pump (28), to the low pressure input of a high pressure transfer device (30) which is connected to a digester (41) (either directly or through an impregnation vessel). A metering device(12), preferably through a pressure isolation device (42) for maintaining superatmospheric pressure in the vessel, feeds chips into the top of the vessel. A first level (13) of chips is established in the vessel, and a second, liquid, level (22) below the first level is also established. Steam (17) is supplied to a volume between the top of the vessel and the second level utilizing a conduit with an automatically controlled valve (19) and a temperature controller (20) for at least partially controlling the valve. A level controller (23) controls the supply of liquid to the vessel and is connected to the low pressure outlet from the high pressure transfer device. There is a reduction in cross-sectional area of the vessel of greater than 50 % between the second level and the outlet at the bottom of the vessel. Alternatively, the pump from the bottom of the vessel may be connected to one or more batch digesters.

Claims

AMENDED CLAIMS

[received by the International Bureau on 3 ϋune 1996 (03.06.96) ; original claims 2 and 12 amended; new claim 23 added ; remaining claims unchanged (7 pages) ]

1 1. A method of handling comminuted cellulosic fibrous

2 material to feed the material to a continuous or batch digester,

3 comprising the steps of:

4 (a) con-f-Lning comπiinuted cellulosic fibrous material in a

5 predetermined, open, volume; fi (b) in the predetermined volume, estabHshing a first level of

7 coniminuted cellulosic fibrous material, and a second level, below s the first level, of cooking liquor;

0 (c) subjecting the comminuted cellulosic fibrous material between the first and second levels to steam to effect steaming of i the comminuted cellulosic fibrous material in the predetermined 2 volume; 3 (d) slurrying the comminuted cellulosic fibrous material with 4 cooking liquor below the second level, to produce a slurry in the 5 predetermined volume; and 6 (e) removing the slurry from the predetermined volume, 7 further pressurizing the slurry, and feeding the pressurized slurry 8 to a continuous or batch digester.

1 2. A digester system, comprising: a continuous or batch digester;

3 a single generally cylindrical vertically oriented vessel

4 having a top and a bottom for receiving, steaming, and slurrying

5 comminuted cellulosic fibrous material before feeding to said

6 digester, functioning as all of a chip bin, steaming vessel, and chip

7 chute;

8 metering means for feeding coinminuted cellulosic fibrous

9 material into said vessel from the top thereof; 18

means for estabUshing a first level, of coiriminuted cellulosic fibrous material, in said vessel; means for estabUshing a second, Uquid, level in said vessel, said second level below said first level; means for supplying steam to a volume between said top of said vessel and said second level; and means for withdrawing a slurry of comminuted ceUulosic fibrous material in Uquid from adjacent the bottom of said vessel and feeding the slurry to said digester; said digester and said single verticaUy oriented vessel comprising the only coniminuted ceUulosic material handling vessels of said system.

3. An upright vessel having a top and a bottom, and comprising: a first conduit for supplying steam to said vessel; a first automaticaUy controUed valve in said first conduit; a temperature controUer for sensing the temperature within said vessel and controlling said first valve at least partiaUy in response thereto; a second conduit for supplying Uquid to said vessel; a second automaticaUy controUed valve associated with said second conduit; a level controUer for sensing the level of Uquid within said vessel and controlling said second valve at least partiaUy in response thereto; metering means for feeding comminuted ceUulosic fibrous material into said vessel from the top thereof; and means for withdrawing a slurry of comminuted ceUulosic fibrous material in Uquid from adjacent the bottom of said vessel. 19

4. A method as recited in claim 1 wherein steps (a)-(e) are practiced substantiaUy continuously, comininuted ceUulosic fibrous material being substantiaUy continuously introduced into the predetermined volume from above the first level, substantiaUy continuously flowing downwardly in the predetermined volume, and being substantiaUy continuously removed from the predetermined volume below the second level.

5. A method as recited in claim 4 wherein steps ( a )-(d) are practiced at superatmospheric pressure.

6. A method as recited in claim 1 comprising the further step of causing the comminuted ceUulosic fibrous material to flow in a reduced cross sectional area from the first level to where the slurry is removed from the predetermined volume in step (e) through a single convergence volume, the cross-sectional area being reduced more than 50%.

7. A method as recited in claim 4 wherein the digester is a continuous digester, and wherein step (e) is practiced by feeding the pressurized slurry directly to the top of a continuous digester using a metering device, pump, and high pressure transfer device.

8. A method as recited in claim 1 wherein step (e) is practiced by feeding the slurry to a metering device and then via a slurry pump to the digester.

9. A digester system as recited in claim 2 wherein said means for supplying steam comprises a first conduit operatively connected to said vessel, a first automaticaUy controUed valve in 20

5 temperature within said vessel and controUing said first valve at

6 least partiaUy in response thereto.

1 10. A digester system as recited in claim 2 wherein said

2 means for estabUshing a second, Uquid, level in said vessel

3 comprises a second conduit for supplying Uquid to said vessel, a

4 second automaticaUy controUed valve in said second conduit, and a

5 level controUer for sensing the level of Uquid within said vessel and controUing said second valve at least partiaUy in response thereto.

1 11. A digester system as recited in claim 2 wherein said

2 vessel includes, between said second level and said bottom of said

3 vessel, a single convergence type configuration providing a reduced

4 cross sectional area of more than 50% compared to the cross l sectional area at said second level.

1 12. A digester system as recited in claim 2 wherein said

2 digester is a continuous digester, and wherein said means for

3 feeding the slurry from said vessel to said digester comprises a high

4 pressure transfer device.

1 13. A digester system as recited in claim 12 further

2 comprising a pressure isolation device between said metering

3 means and said vessel for maintaining superatmospheric pressure

4 within said vessel.

5

1 14. A digester system as recited in claim 2 wherein said

2 withdrawing means comprises a metering device and a pump.

3 l 15. A digester system as recited in claim 2 wherein said

995 PC17US95/154S8

21

a recirculation line from a low pressure output of said high pressure transfer device through a sand separator and a flow controUed valve back to said vessel.

16. A digester system as recited in claim 12 further comprising a pressure isolation device between said metering means and said vessel for maintaining superatmospheric pressure within said vessel.

17. An upright vessel as recited in claim 3 further comprising a pressure isolation device between said metering means and said vessel for maintaining superatmospheric pressure within said vessel.

18. An upright vessel as recited in claim 3 wherein said vessel has a single convergence type cross sectional area reduction between said first conduit and said means for withdrawing slurry, providing a reduction in cross sectional area of the vessel greater than 50%.

19. In a continuous digester system having a chip feed system including a chip bin, steaming vessel, and a chip chute connected to a high pressure transfer device, a method of simplifying the chip feed system comprising the steps of: (a) removing the conventional chip bin, steaming vessel and chip chute from operative connection to the high pressure transfer device; (b) replacing the chip bin, steaming vessel and chip chute with a single vertical vessel having steaming means and chip slurrying means associated therewith and having an outlet from than the chip bin, steaming vessel and chip chute combination and easier to construct, operate and maintain; and (c) connecting the outlet from the bottom of the replacement vessel to the high pressure transfer device.

20. A system as recited in claim 19 wherein the single vertical vessel has a volume at least 20% less than the combined volumes of the chip bin, steaming vessel, and chip chute.

21. A digester system comprising a batch digester; and an upright vessel having a top and bottom and including a first conduit for supplying steam to third vessel; a first automaticaUy controUed valve in said first conduit; a temperature controUer for sensing the temperature within said vessel and controUing said first valve at least partiaUy in response thereto; a second conduit for supplying Uquid to said vessel; a second automaticaUy controUed valve associated with said second conduit; metering means for feeding cornminuted ceUulosic fibrous material into said vessel from the top thereof; and means for withdrawing a slurry of con-uninuted ceUulosic fibrous material in Uquid from adjacent the bottom of said vessel; said withdrawing means comprising a metering device and a pump connected to said batch digester.

22. A digester system as recited in claim 21 further comprising at least one additional batch digester and a distributing valve connected between said pump and said digesters. 23

23. A digester system as recited in claim 2 wherein said digester comprises a pluraUty of batch digesters; and wherein said means for feeding the slurry to said digester comprises a distribution valve for alternatively feeding slurry to each of said batch digesters.