Kamyr, Inc.

Ahlstrom Machinery, Inc.

Victor L Bilodeau

Mark D Barrett

Ronald G Bain

Joseph R Phillips

John D Weston

Brian F Greenwood

J Robert Prough

John Pietrangelo

Keith P Vogel

Jerry R Johanson

Jan T Richardsen

Carl L Luhrmann

Ron Bain

Peter E Warloff

John Hefele

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 is connected, through a low pressure pump, to the low pressure input of a high pressure transfer device which is connected to a digester (either directly or through an impregnation vessel). A metering device, preferably through a pressure isolation device for maintaining superatmospheric pressure in the vessel, feeds chips into the top of the vessel. A first level, of chips, is established in the vessel and a second, liquid, level below the first level is also established. Steam is supplied to a volume between the top of the vessel and the second level utilizing a conduit with an automatically controlled valve and a temperature controller for at least partially controlling the valve. A level controller 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.

Digester system containing a single vessel serving as all of a chip bin,

A chip bin construction, ideally suited for bins having a maximum diameter of twelve feet or more, uniformly discharges chips, after steaming, without the necessity of a vibratory discharge. A hollow transition portion is provided between a hollow substantially right circular cylindrical main body and a rectangular discharge. The hollow transition may have a substantially circular cross-section open top and a substantially rectangular cross-section open bottom and opposite non-vertical gradually tapering side walls. At least one feed screw may be mounted at the open bottom of the transition for cooperation with the discharge, and the feed screw(s)--or the equivalent--may provide for metering of the chips. Alternatively, the hollow transition portion may provide one dimensional convergence and side relief, and no screw feeders need be provided, in which case a conventional chip meter is used.

Chip feed system

Located within the annular screen of the pressure diffuser is a tubular baffle hung from adjacent the top of the vessel. The baffle has two headers disposed on its inner surface, with openings in the tube providing communication between the exterior of the tube and the headers. A conduit extends from each header to an arm at the top of the vessel, to allow extracted liquid to be discharged. Another extraction conduit is provided at the bottom of the vessel, in communication with the screen interior and the tubular baffle interior. Treatment liquid, such as wash liquid, may be introduced at two, three, or more positions along the vessel with the liquid extracted from the first and second headers being introduceable at different positions along the vessel. A flexible, elastomeric material, sealing element with integral annular skirt may extend from the bottom end of the tubular baffle and engage the screen to provide a seal minimizing mixing between stages.

Variable stage pressure diffuser

In the production of cellulose pulp (e.g. kraft pulp) utilizing a continuous digester having a number of different feed points for cooking (e.g. white) liquor and utilizing a high pressure feeder, the volume of cool white liquor that is applied to the feed system is reduced compared to conventional processing. This can cause excessive hammering, and damage the high pressure feeder and adjacent piping and equipment. In order to avoid this, liquid being recirculated from the top of the digester back to the high pressure feeder is cooled by passing it into a heat exchanger into heat exchange relationship with a cooler liquid, with the flow of coolant automatically controlled by sensing the temperature of the recirculated liquid. The temperature in the feed system can further be lowered by cooling the cooking liquor before it is added to the pulp slurry, as by passing it to a flash tank so that its temperature is reduced at least 10.degree. C., and the flashed steam can be used in an evaporator.

Top circulation line cooling for a modified cook digester

A drum washer has improved seal performance by providing a sealing body carried by the drum of a highly corrosion resistant material. The sealing body is preferably polytetrafluoroethylene or titanium, and is connected by mechanical fasteners, instead of welding, to the surrounding drum components. The annular sealing body may have a lip at its axialmost inward portion for engaging the axial outwardmost portion of the drum inner surface, and a radially outwardly extending annular flange which cooperates with a radially inwardly extending flange of the drum outer surface. Alternatively, the body may be smooth and have through-extending openings for receiving mechanical fasteners on its axially inwardmost end, and tapped openings for receiving screw threaded fasteners connected to an extension of the drum inner surface at the axially outwardmost portion.

Drum washer sealing

In a pressure diffuser, clogging of the tapered inlet passageway at the bottom of the vessel is minimized by providing a number of lubricating fluid introducing nipples disposed circumferentially around the annular passageway. The nipples introduce lubricating fluid so that it flows upwardly along the inner wall of the vessel. The vessel inner wall and the bottom support for the screen at the passageway are polished and free of projections, so that friction is minimized. The nipples are provided in sets that are staggered so that a nozzle is placed about every 15.degree. around the circumference of the vessel, and a common annular header--mounted on the support legs of the vessel--provides the lubricating fluid. Should screen movement slow as a result of paper pulp properties near the screen bottom support, the flow rate of lubricating liquid can be increased so as to significantly dilute the pulp at the passageway until slow movement of the screen is overcome.

Preventing clogging in pressure diffusers

In an atmospheric diffuser for the treatment of paper pulp (thickening, bleaching, and/or washing) the flow of backflushing liquid is controlled so as to maximize the effective treatment of the pulp. The pulp passes upwardly in a vessel. A number of annular screen assemblies are provided, with at least one screen associated with each screen assembly. The lower screen includes a barrier wall with a passage in the barrier wall adjacent the bottom end of the screen. Liquid which flows through the screen must flow to the passage in order to be withdrawn from the vessel, as the screen is slowly moved upwardly. When the screen is rapidly moved downwardly to cause backflushing, the backflushing liquid at the top end of the screen is liquid that recently passed through the screen at that point, so the pulp at that point --which is the cleanest along the length of the screen--has a minimal chance of being contaminated. The barrier may be provided by a number of tubes separated by webs, or a number of channels separated by webs. A baffle may be mounted between each passage and screen to redirect the backflushing liquid so that it does not merely backflush the bottom portion of the screen.

Atmospheric diffuser improved lower screens backflushing

The proper pressure conditions are maintained within an atmospheric pre-steaming chips bin used in the production of paper pulp. Extending upwardly from the top of the chips bin is a vertical section of conduit, an elbow section, and a horizontal section. A door guide with a door opening in it is disposed in the horizontal section and precludes passage of gas through the horizontal section except through the door opening. A pivot pin mounts a door at its top so that it normally assumes a vertical orientation closing off the opening, and it is adjustably biased into that orientation by a counterweight mechanism. The counterweight includes weight discs which mount on a vertical section of rod having external screw threads, and a horizontal section of rod is connected by a flange to a flange of the pivot pin. The door remains closed unless the pressure differential between the chips bin and the surrounding environment is greater than about 2 psig, in which case gas may flow from the environment to the chips bin, or vice versa, to bring the pressure differential within the desired range.

Atmospheric pre-steaming chip bin vacuum and pressure relief device

In an atmospheric diffuser for the treatment of paper pulp (thickening, bleaching, and/or washing) the flow of backflushing liquid is controlled so as to maximize the effective treatment of the pulp. The pulp passes upwardly in a vessel. A number of annular screen assemblies are provided, with at least one screen associated with each screen assembly. The lower screen includes a barrier wall with a passage in the barrier wall adjacent the bottom end of the screen. Liquid which flows through the screen must flow to the passage in order to be withdrawn from the vessel, as the screen is slowly moved upwardly. When the screen is rapidly moved downwardly to cause backflushing, the backflushing liquid at the top end of the screen is liquid that recently passed through the screen at that point, so the pulp at that point--which is the cleanest along the length of the screen--has a minimal chance of being contaminated. The barrier may be provided by a number of tubes separated by webs, or a number of channels separated by webs. A baffle may be mounted between each passage and screen to redirect the backflushing liquid so that it does not merely backflush the bottom portion of the screen.

Growing community of inventors

Glens Falls, NY, United States of America

Victor L Bilodeau