Paper making and fiber liberation – Processes of chemical liberation – recovery or purification... – Charging and/or discharging fibrous material
Reexamination Certificate
2000-03-07
2002-04-09
Nguyen, Dean T. (Department: 1731)
Paper making and fiber liberation
Processes of chemical liberation, recovery or purification...
Charging and/or discharging fibrous material
C162S238000, C162S246000, C162S253000
Reexamination Certificate
active
06368453
ABSTRACT:
BACKGROUND AND SUMMARY OF THE INVENTION
U.S. Pat. Nos. 5,476,572; 5,622,598; 5,635,025; 5,736,006; 5,753,075; 5,766,418; and 5,795,438 disclose methods and devices for feeding a slurry of comminuted cellulosic fibrous material to a treatment vessel that have revolutionized the art of treating comminuted cellulosic fibrous material to produce cellulose pulp. The disclosed inventions, sold under the trademark LO-LEVEL by Ahistrom Machinery Inc., of Glens Falls, N.Y., employ one or more slurry-type pumps for treating and transferring comminuted cellulosic material to one or more treatment vessels. Not since the initial development of the continuous cooking process in the 1940s and 1950s have such dramatic improvements been made to the equipment used to transfer material to a treatment vessel, for example, a continuous or batch digester. This is confirmed by the broad acceptance of this technology by the Pulping Industry.
The present invention introduces improvements to the systems described in the above patents which further simplify and enhance the effectiveness of the methods and devices disclosed in the above referenced patents. U.S. Pat. No. 5,622,598 discloses a process of using a slurry-type pump to transfer a slurry of comminuted cellulosic fibrous material to a digester, for example, by pumping the slurry to a high-pressure transfer device and then-transporting the slurry via the transfer device to one or more digesters. In particular, the method and apparatus disclosed in U.S. Pat. No. 5,622,598 provide a separate supply of liquid to the slurry pump inlet to, among other things, facilitate the transfer of comminuted cellulosic fibrous material to the pump.
Typically, this liquid is supplied by a separate storage vessel having a conduit which can discharge liquid to the inlet of the pump. A level of liquid is maintained and regulated within this vessel.
The present invention further simplifies the equipment necessary to effect the feeding of comminuted cellulosic fibrous material to a digester by, among other things, substantially eliminating the need for a separate liquor storage vessel and substantially eliminating the need for a separate level controlling vessel or tank. The liquid supplying function of this vessel or tank and the maintenance of the level of liquid within this tank are replaced by a liquor storage vessel located integrally with the conduit that passes the slurry of material from the pretreatment vessel, for example, a chip bin, to the inlet of the slurry pump.
One aspect of this invention comprises or consists of a comminuted cellulosic fibrous material treatment system, comprising (or consisting of): a digester having a comminuted cellulose material inlet at the top thereof; a first vessel, at a first pressure, containing comminuted cellulosic fibrous material, and having a top, a bottom, and an outlet adjacent the bottom; a conduit having an inlet communicating with the outlet of the first vessel, and an outlet; a second vessel, having a width dimension greater than the conduit, for receiving the cellulosic material from the conduit and having a level of liquid therein; and a slurry pump having an inlet for receiving material from the second vessel and an outlet operatively connected to the inlet of the digester. The digester may be one or more continuous or batch digesters.
The system preferably includes some form of metering device, such as a star-type or screw-type metering device, located between the outlet of the first vessel and the inlet of the conduit. A pressure isolation device, for example, a star-type pressure-isolation device, may also be located between the outlet of the first vessel and the inlet of the conduit, with or without the presence of a metering device.
The second vessel preferably substantially surrounds a peripheral portion of the conduit, and the second vessel has a top through which the conduit passes and a bottom having an outlet communicating with the inlet of the slurry pump. In a preferred embodiment, the second vessel is concentric with the first vessel and the conduit, and the outlet of the conduit is located below the top of the second vessel, but above the outlet of the second vessel.
The present invention also preferably includes a high pressure rotary transfer device having a low pressure inlet, a low pressure outlet, a high pressure inlet, and a high pressure-outlet. The high pressure inlet is operatively connected to the outlet of the second vessel and the high pressure outlet is operatively connected to the digester for feeding the comminuted cellulosic fibrous material slurry to the digester.
The second vessel of the present invention also preferably includes a conduit for introducing cooking liquor into the second vessel.
The first vessel is preferably a chip bin for storing and treating the cellulose chips, preferably a chip bin having one-dimensional convergence and side-relief geometry, for example, a DIAMONDBACK Chip Bin as described in U.S. Pat. Nos. 4,958,741; 5,500,083; 5,617,975; 5,628,873; and 5,700,355 and sold by Ahlstrom Machinery Inc. The first vessel may also be a horizontal Steaming Vessel having a screw conveyor, as sold by Ahlstrom Machinery. The first vessel may also have “chisel”-type geometry as disclosed in co-pending application Ser. No. 09/055,408 filed Apr. 6, 1998 now U.S. Pat. No. 6,199,299. The pressure in the first vessel is typically between about 0 and 5 bar gauge, preferably between about 0 and 2 bar gauge. The second vessel may also have one-dimensional convergence and side-relief geometry or chisel-type geometry to minimize the potential for bridging or plugging.
The present invention also includes a method of feeding a slurry of comminuted cellulosic fibrous material in liquid to a digester having an inlet utilizing a pre-treatment vessel, and a slurry pump having an inlet. The method comprises (a) pretreating the comminuted cellulosic fibrous material in the pretreatment vessel; (b) passing the pretreated material from the pretreatment vessel into a first conduit; (c) discharging the material from the first conduit into a vessel having a width dimension greater than the first conduit; (d) entraining the comminuted cellulosic fibrous material in liquid to form a slurry; (e) feeding the slurry to the inlet of the slurry pump; and (f) transporting the slurry to the inlet of the digester.
The invention preferably also includes a high-pressure transfer device having a low-pressure inlet and a high pressure outlet and the method further includes, between (e) and (f), (g) pumping the slurry with the slurry pump to the low-pressure inlet of the high-pressure feeder, and (h) discharging the slurry from the high-pressure outlet of the high-pressure feeder. The method may also include, between steps (c) and (d), (i) metering the flow of comminuted cellulosic fibrous material from the pretreatment vessel. The method may also further comprise passing the liquid from the low pressure outlet through an in-line drainer; pressurizing the liquid from the in-line drainer in a pressurizing device, and passing liquid from the pressurizing device to the digester; passing some liquid directly from the tank to just prior to the pressurizing device; and/or passing some of the pressurized liquid from the pressurizing device to the high pressure inlet to or outlet from the high pressure feeder.
The present invention also includes a system for feeding-comminuted cellulosic material entrained in liquid to a high pressure feeder connected to a digester, comprising: a vertical treatment vessel having a discharge at the bottom thereof; a metering device connected to the discharge of the treatment vessel; a generally vertical chute extending downwardly from the metering device; a high pressure feeder connected to a digester; a slurry pump which pumps a slurry of comminuted cellulosic material in liquid, the slurry pump having an inlet, the pump connected to the high pressure feeder; and a vessel having a width dimension greater than the width dimension of the chute, positioned concentric with the chute, a
Kettunen Auvo K.
Laakso Richard O.
Miele Jay J.
Prough J. Robert
Stromberg C. Bertil
Andritz Inc.
Nguyen Dean T.
Nixon & Vanderhye P.C.
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