Ahlstrom Machinery, Inc.

Andritz-ahlstrom Inc.

Kamyr, Inc.

Andritz Inc.

R Fred Chasse

J Robert Prough

Bruno S Marcoccia

Richard O Laakso

Rolf C Ryham

Joseph R Phillips

Jan T Richardsen

C Bertil Stromberg

Vic L Bilodeau

James R Prough

Craig A Walley

Kaj Henricson

Mark D Barrett

John D Weston

J Wayne Chamblee

Jay J Miele

Grant E Bechard

John Hefele

Larry W Laakso

Ella Sun Yu

Marco Marois

Jen T Richardsen

Chemical cellulose pulp is made from sawdust utilizing a static down-flow retention vessel. By adding steam and cooking liquor to a flow of sawdust a heated slurry, at a cooking temperature of about 250-350&deg; F., is produced. The heated slurry is, at superatmospheric pressure, moved downwardly in the static down-flow retention vessel while cooking temperature is maintained, for a time period of about 0.5-6 (preferably 1 to 3) hours, the slurry having a consistency of about 5-30%. At superatmospheric pressure, without significant reduction in pressure from the retention vessel, the slurry is cooled to well below cooking temperature by diffusing cooling liquid through it, as in a conventional pressure diffuser. The discharge from the retention vessel is preferably substantially solely gravity action (e.g. using a discharge with single convergence and side relief). Various mixing, diluting, thickening, steaming, and pumping devices are utilized in the system from initial steaming of the sawdust to passage into the top of the retention vessel.

Apparatus for pulping sawdust

Kraft pulp of increased strength and bleachability may be produced with decreased consumption of effective alkali, and at a lower H factor, by keeping the dissolved organic material (DOM) concentration low substantially through the entire kraft cook, including by extracting high DOM liquid from at least one part of a continuous digester and replacing it with much lower level DOM liquid. Existing pulp mills having two-vessel hydraulic, one-vessel hydraulic, or other systems may be retrofit to provide for extractions and additions of low DOM dilution liquor (including substantially DOM-free white liquor). Also, commercial size batch digesters (8 tons per day of pulp or more) can be operated with low DOM liquor to produce increased strength pulp. Using dilution with low DOM liquor also results in reduced H factor and effective alkali consumption, and increased bleachability.

Dissolved solids control in pulp production

Dense, tramp material, is efficiently separated in a comminuted cellulosic fibrous material feed system, for example in a chemical cellulose digester feed system, in a simple but effective matter. By merely utilizing a generally vertical conduit and a slurry flow within it (which may be augmented by high speed liquid introduction), that is caused to turn in a radiused path, centrifugal force allows separation of the tramp material into a cavity beneath the radius transition without requiring any mechanical element to engage the slurry. Appropriate purges, baffles, and discharge mechanisms may be provided. Alternatively, a tramp material separator may be built into an otherwise conventional metering screw in a digester feed system, or one or more centrifugal separators can be provided downstream of the slurry pump in a chip slurry transport system or digester feed system.

Tramp material removal from pulp feed system

Method for pulping sawdust

Dissolved organic material control in a cellulose pulp continuous digester

Useable steam, e.g. substantially clean useable steam, is produced from a chemical cellulose pulping system hot spent treatment liquor (e.g. black liquor) with optimum energy efficiency by passing the spent liquor to a reboiler, and then pressurizing (e.g. with an eductor, fan, or compressor) the clean steam discharged from the reboiler. The clean steam can be used to steam incoming chips (e.g. in a chip bin) without significantly increasing the TRS load on the pulp mill NCG system.

Heat economy enhancements for the recovery and use of energy obtained from spent cooking liquors

Kraft pulp of increased strength and bleachability may be produced with decreased consumption of effective alkali, and at a lower H factor, by keeping the dissolved organic material (DOM) concentration low substantially through the entire kraft cook, including by extracting high DOM liquid from at least one part of a continuous digester and replacing it wit much lower level DOM liquid. Existing pulp mills having two-vessel hydraulic, one-vessel hydraulic, or other systems may be retrofit to provide for extractions and additions of low DOM dilution liquor (including substantially DOM-free white liquor). Also, commercial size batch digesters (8 tons per day of pulp or more) can be operated with low DOM liquor to produce increased strength pulp. Using dilution with low DOM liquor also results in reduced H factor and effective alkali consumption, and increased bleachability.

Dissolved organic materials control in cellulose pulp production

In a pulp treatment vessel, such as a kraft pulp continuous vertical digester, a cellulose slurry is caused to flow in the vessel interior in a flow path. A substantially annular void is formed at at least one point along the flow path, and dilution or treatment liquor is introduced into the substantially annular void so that the liquor is substantially uniformly distributed about the periphery of or into the slurry. The annular void may be formed by a step out in the vessel, and the uniform introduction of dilution liquor may be accomplished utilizing one or more openings, such as a plurality of openings substantially evenly spaced around the substantially annular void, e.g. using a screen surface. The screen surface may be substantially vertical or conical.

Distribution of dilution liquor to the discharge of a cellulose pulp

DOM control in cellulose pulp production

Tramp material removal from pulp feed systems

Digester systems for producing paper pulp from comminuted cellulosic fibrous material take into account the level of dissolved organic materials (DOM), such as lignin, hemi-cellulose, and cellulose, maintaining the DOM level at about 100 g/l throughout the cook (particularly kraft cook). In order to make sure there is sufficient liquid to slurry the material in the feed system of a two vessel system, some liquid is withdrawn from the circulation conduits between the digester and impregnation vessel, cooled, and fed to the feed system. In a vapor phase digester, the level of liquid at the top of the digester is more precisely controlled by circulating some of the withdrawn liquid from a circulatory loop of the digester to the level tank associated with the feed system. An in-line drainer may be provided in the feed system between a make-up liquor pump and a liquid inlet conduit leading to the top of an impregnation vessel. Within the digester, a set of extraction/dilution screens is provided specifically positioned and spaced from each other, and with respect to a reintroduction conduit opening, so that mixing of different DOM concentration liquids is minimized.

Continuous digester having means for implementing low dissolved solids

Low dissolved solids control in pulp production

The pretreatment of cellulosic fibrous material is adjusted to improve pulp strength. The cellulosic material is initially pretreated with a low temperature alkaline liquid (e.g. 80.degree.-110.degree. C.), and then with a higher temperature (but still below cooking temperature), higher alkali concentration liquor. Only then is the material--which has alkali which has completely penetrated the cellulose fiber walls--subjected to cooking with white liquor at a temperature of about 150.degree.-180.degree. C. Green, white, or black liquor can be used in the first impregnation zone, while white liquor (with polysulfide addition) is preferably used in the second zone.

Continuous cooking of cellulosic fibrous material with cold alkali

Continuous digester with dissolved solids handling

Growing community of inventors

Queensbury, NY, United States of America

R Fred Chasse