The Black Clawson Company

Air Products and Chemicals, Inc.

Larry D Markham

Vincent L Magnotta

Edward F Elton

David E Chupka

Peter Seifert

Derald R Hatton

Scott A Wallick

Andrew C Martin

Michael F Kinne

Ronald DeWayne Cruea

Jimmy L Winkler

Henrik J Eklund

Mark W Gilkey

Gregory D Kile

Apparatus for thickening a suspension of pulp material employs a single pair of liquid-impervious rolls and a single loop of wire trained around both rolls which are spaced from each other in substantially the same horizontal plane. The pulp stock to be thickened is delivered into the wedge zone defined by the upper wire run approaching the top of one roll and the surface of that roll, so that the pulp is trapped between the wire and roll as it travels around the roll with the wire, and the rolls are driven at sufficient speed to develop centrifugal forces which cause liquid to be expressed through the wire from the pulp trapped against the roll. The resulting partially dewatered pulp is redeposited from the first roll onto the lower wire run for travel to the other roll, where it is similarly subjected to centrifugal force for further expression of liquid through the wire, after which the pulp is removed from the surface of the second roll in the wedge zone defined by the surface of that roll and the wire run travelling therefrom to the first roll.

Apparatus and method for thickening pulp and paper stock

In screening apparatus for paper making stock including a housing, a cylindrical perforated screen member separating the interior of the housing into a supply chamber and an accepts chamber on the inside and outside respectively of the screen member, an inlet port for supplying stock to one end of the supply chamber, an outlet port from the accepts chamber, a reject port from the supply chamber, and a rotor mounted for rotation within the screen member, the rotor is characterized by comprising a substantially circular disk which is of a thickness constituting a very minor fraction of the axial length of the screen member and has vanes mounted on its outer periphery which extend lengthwise of the screen member for rotation with the disk in the annular space between the periphery of the disk and the inner surface of the screen member.

Disk rotor for selectifier screen

Rejects such as knots, shives, slivers, chops, and uncooked and partially cooked wood chips are separated from a pulp slurry and treated to produce a bleachable grade pulp. The rejects are dewatered to a 10-15% consistency, mechanically fiberized, and then delignified at the same 10-15% consistency in the presence of oxygen and alkaline pulping chemicals. The delignification is carried out at 80.degree.-140.degree. C. for 5-120 minutes. The process has low external power requirements, requires no expensive dewatering machinery, and proceeds at a rapid rate to yield a bleachable grade pulp which can be used alone or mixed with other pulp.

Process for the oxygen delignification of pulp mill rejects

Good temperature and pH control as well as uniform mixing of pulp or other fibrous materials is achieved in a medium consistency oxygen delignification method and system. Alkaline chemicals are sprayed, optionally using oxygen gas as the atomizing agent, into the gas space above the level of pulp maintained in one or more substantially horizontal tubular reaction vessels. At least a part of the steam requirement of the reaction is added only after the major portion of alkaline chemicals has been added to the system. In other embodiments of the invention, alkaline chemicals may be injected into the substantially vertical conduit connecting two reaction vessels or two different alkaline chemicals may be injected at different points in the system.

Method and apparatus for controlled addition of alkaline chemicals to an

A froth flotation apparatus for elimination of solid particle impurities contained within a liquid includes a vessel defining a flotation cell which includes an upstanding foam discharge conduit, an inlet conduit communicating with the vessel such that fluid flowing through the inlet conduit and into the vessel moves in a vortical fashion within the vessel, a skimmer, and a sparger. The skimmer consists of a generally cylindrical roller which is rotatably mounted between the discharge conduit and a side wall of the vessel and is buoyant so that it floats on the surface of the fluid within the vessel such that it is rotated by the vortical movement of the fluid within the vessel to prevent buildup of foam and maintain the motion of the fluid within the vessel. The sparger includes a substantially cylindrical porous element mounted on a tubular shaft which is rotatably mounted within the inlet conduit and driven by a motor. Compressed air is forced through the porous element to aerate the fluid entering the vessel. Two or more flotation cells may be arranged in a tower to provide series operation in which the liquid effluent of one cell flows downwardly by gravity into a subsequent cell, thereby eliminating the need for additional mechanical pumps.

Froth flotation apparatus and method

An apparatus and process for the oxygen delignification of pulp is provided in which the pulp is transported by means of timing screws in essentially plug flow through one or more substantially horizontal reactor tubes. Oxygen gas is injected into the system at a point adjacent to the pulp inlet and travels concurrently in substantially plug flow with the pulp through the system. In this manner, the pulp is initially exposed to gas of a high oxygen partial pressure while gas vented from the system adjacent the pulp outlet is of low oxygen partial pressure and has a high content of diluent gases. The process and apparatus avoid the formation of gas pockets and hot spots which may adversely affect the pulp. In an alternate embodiment, a countercurrent gas flow process is disclosed. Also provided is a catalytic treatment and recirculation system for the vented gas which permits efficient use of oxygen within the system.

Method and apparatus for oxygen delignification

Medium consistency oxygen delignification of pulp is carried out in a series of tubular reaction zones. Rapid delignification is achieved by agitating the pulp by rotating a timing screw in the first reaction zone at a speed in excess of 10 rpm, modifying the flights on the timing screw to increase the amount of agitation, or a combination of the two. Primary oxygenation is carried out in the first reaction zone while subsequent zones provide the retention time needed for the delignification reaction to go to completion. A thick stock pump is used to introduce the pulp into the first reaction zone.

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Middletown, OH, United States of America

Larry D Markham