US2093267A - Treatment of fibrous material - Google Patents

Description

Sept. 14, 1937. T, DUNBAR I 2,093,267

TREATMENT OF FIBROUS MATERIAL Filed NOV. 20, 1934 'N Q h van ATTORNEY Patented Sept. -14, 1937 PATENT, OFFICE TREATMENT F FIBROUS MATERIAL Thomas L. Dunbar, Watertown, N. Y., assignor to Chemipulp Process, Incorporated, Watertown, N. Y., a corporation of NewYork Application November zo, 1934, serial No. 753,894

`Y3 Claims.

This invention relates to the treatment. of iibrous material, and more particularly to a normally continuous process of and apparatus for v the production of pulp. While the invention is -is of particular value in the production of so-called semi-chemical pulp from which the lignin is not entirely dissolved, its applicability is not limited thereto.

v An object of my invention is the provision Aoi! an improved ,process for the production of pulp, which may be carried on continuously, and the provision of apparatus suitable therefor. Intermittent iilling and drainin of a digester may be obviated by my process y nd I have provided 1li-means whereby the pulp is continuously discharged from the digestionA apparatus to improved washing and degassing apparatus. Economies in operation are eiiected by the practice l of my invention.

Generally speaking,my invention comprises a treatment of brous material in which this material is subjected first to a water pretreatment and then to the action of cooking liquor at elev vated temperatures and under hydrostatic pressure, procured, for example, by the use of novel apparatus hereinafter fully described. The i'lbrous material may pass continuously throughl this apparatus, wherein the pulp is liberated, and the cooking liquor may then be continuously drained off and the pulp washed while at the same time gases are liberated and vented back to a recovery system and the pulp is diluted with water or other suitable washing liquid. The re moval of digestion liquor from the pulp is very effectively accomplished in my process, lresulting in an improved pulp product. The invention is applicable to both acid and alkaline pulping processes.

My improved process and apparatus are adapted 4 for use in conjunction with a pretreatment of the iibrous material as described and claimed in my co-pendingapplication, Ser. No. '753,893

nl ed November 20, 1934.

Further lbeneiicial features of my invention will in part be set forth and in part be apparent as a description is given of the accompanying drawing,which illustrates diagrammatically apparatus suitable for the practice of my invention.

In this drawing, l is a pretreatment tank, pro- 5 vided with nozzles 2, through which steam may be admitted, and aline 3 with valve 4 for1 the Y admission of water or other suitable solvent liquid. This tank may be drained through valve 5, the contents being emptied into the casing 1,

55 which encloses a worm conveyor 6, driven by a motor 8. A steam admission line 9 with valved branch entrances I0 is provided to admit steam or hot liquid to the casing 1. A pump Il is provided at the end oi the worm conveyor, to pass the material up the leg or conduit l2, into 'which conduit steam may be admitted through the line I3 with its valve I4.

vThe leg I2'is a vertical conduit, connected to or integral with a further conduit l5, which contains a strainer I6. Beneath the strainer is a collecting apparatus I1 and a drainage line 2i, through which the drained water may pass. In conjunction with this collecting apparatus I1 I provide a gas vent 22, with valve 23. This gas vent 22 and the drainage line 2l are preferably both provided with seal legs or traps, `such as are show'n and described in my aforesaid co-pending application, Ser. No. 753,893, now U. S. Patent No. 2,038,925, such seal legs being provided to maintain 'uid pressure on the material as it passes through this part of the system. A storage tank for the liquid drained through the line 2l, connecting with the pretreatment tank l, may be provided as shown inmy said co-pending application. 4

Drop leg 23a is a conduit from the strainer I6 to another worm conveyor 24, encased in a casing 25, and driven by motor 26. Pipe line 21 withla valve 28 is an admission line for either hot or cold cooking liquor from a liquor storage tank or hot acid accumulator -(not shown). 29 is a steam admission line, controlled by the va1ve'30.

' Pump 3| is Aconnected between the casing 25 and a verticalv leg 32, 4which is enclosed in a steam jacket 33. Connected with the steam jacket is the steamadmission line 34 with valve 36 and also a condensate removal line 36 with valve 31.

I also provide a steam admission line 38 with valve 39 connected directly with the interior of the vertical leg 32.

Connected with the leg 32, or integral therewith, is a further conduit 40, which contains a strainer 4l above a second collector 42. The collector 42 terminates at its bottom'in .a drain pipe 43, which is provided with a. seal leg or trap 4'44, similar to the seal leg which may be pro- -vided in connection with pipe 2|, to maintain the pressure; This drain may lead to the sewer,- or to a tank for further treatment of the liquor.

A top relief line 45 with a control valve 46 passes from the conduit 40 to means for recovering the relief gases and liquids. These recovery means may conveniently comprise an eductor, drop les and accumulator, as shown in connection with a digester in my aforesaid co-pending application, Ser. No. 753,893. i,

A conduit or drop leg 5| connects the conduit 40 with a worm conveyor 52, which is contained in the bottom of a wash tank 53. The casing 6I) of this worm conveyor is open at 'the top to communicate with the interior of the tank 53, into which the worm discharges the pulp. This Wash tank 53 has a hot water admission line 54, with its valve 55. Tank 53 is also provided with steam admission nozzles -51, and a gas and vapor outlet line 58, which may lead to the l acid recovery or make-up system.

Communicating with the worm conveyor 52 -is a further vertical worm conveyor 6|, enclosed in a vertical casing 62, at the top of which is a discharge 63, which is provided with a water supply connectionv 64 having valve 65. This discharge 63 is directed to a washer 66, which may be any of a standard type, usually provided with a further water supply connection 68 having a valve 61. The washer 66 at its bottom is connected by a valve 69 and conduit 10, with a debering machine 1|, which may be of usual construction. 'I'he deiibering machine is also provided With outlet 12, containing valve 13.

In operation, fibrous material is placed in pretreatment tank I, where, in the presence of hot water and steam, admitted respectively by line 3 and nozzles 2, it is cooked at an elevated temperature. 'I'he material so treated may be drained from the pretreatment tank I through the valve 5 into the worm conveyor Ii, where, during its passage, it is mixed with steam supplied by the line 9, and is then pumped by the pump II into the vertical legl I2, andacross the strainer I6, where the water is removed and passes oil? through the drain pipe 2|. Gases pass through the gas vent 22. 'Ihis pretreatment to this point is the same as that described and claimed in my aforesaid copending` application. 'Ihe pretreatment may be continuous by addition of one or more pretreatment tanks as required.

My present invention is particularly concerned with the treatment oi' the pretreated material, from this point to the debering machine.. Although this treatment may be carried on withoutv the pretreatment referred to, the operation will be less efficient in this case.

. The drained pulp drops thrpugh the leg 23a into the operating worm conveyor 24, wherein it is mixed with either hot or cold bisulphite cooking liquor or an'y of the alkali cooking liquors from a storage tank (not shown) or from anaccumulator in the case of the hot acid method, through the admission pipe 21, and valve 28. I prefer that, as stated in my co-pending application above referred to, the cooking liquor be at an approximate temperature of C. at the time of introduction, although this is by no means essential. Steam at the same time may be admitted by opening the valve 30 in the steam inlet 29.

'I'he pump 3| is put in operation, and forces the material up the leg 32, in which the material is cooked, and which may be indirectly heated by steam admitted through the inlet 34 to the steam jacket 33. Steam may also be directly admitted to the leg 32 by the inlet 33, if so desired or conditions require, but this method of heating is optional and its use is usually dependent upon the moisture content of the particular material being treated.

The height of the leg 32 creates a hydrostatic pressure at its bottom, which varies according to the height of the leg.

After passing over the top of the leg 32, the material passes through the conduit 40 and the spent cooking liquor is drained oil. through the strainer 4I, collector 42 and pipe 43, either to the sewer or to a tank for further treatment, and gases escape through the top relief line 45 to the acid recovery system, thus conserving heat units.

The cooked pulp then drops through the leg 5I to the worm conveyor 52, which passes the pulp into the tank 53, where the pulp absorbs the water and steam supplied thereto, and wherefrom gases and vapors are allowed to escape back to the acid recovery or to the make-up system through y the connection 53. After absorbing water in the tank 53, the pulp is elevated by the worm conveyor 6I, mixed with further hot water from the pipe 64, and nallydischarged into the washer 66, where it is subjected to the usual washing and then is passed into the deiibering machine 1I..

The time required for the passage of the material through this apparatus will vary according to mill conditions and the character of the raw material, but in general, in making a socalled semi-chemical' pulp, normally about three or four hours time is required from'the time the pulp enters the line I5 after the pretreatment, until it is discharged into the worm constatic pressure necessary to secure the properf treatment.

The treatment secured in the tank 53 is, in the acid pulping process, mainly one of acid dilution, the pulp absorbing water and steam, which are present in the tank 53. As the pulp passes up the conveyor 6I, a certain amount of disintegration of the fibres takes place. The work of this conveyor may be done by a. good socalled trash pump, although theworm is considered more eiilcient. accomplished in the tank 66, and further removes acids from the material before the pulp passes to the deiibering machine.

Having thus described my invention, I claim:

l. In apparatus for cooking fibrous material in the presence of digestion liquor, means to separate said liquor from such materia/l, an outlet for said separated liquor including a trap to maintain pressure on said material while removing said liquor, and a gas relief line and a control valve in conjunction with said separating-means.

2. In apparatus of the character described, a pretreatment tank, a vertical conduit and means for forcing brous material from said pretreatment tank through said conduit, a strainer communicating with said conduit, means for-removing liquor separated by said strainer and a trap in conjunction with said removing means, a second vertical conduit communicating with said rst conduit, and means to force iibrous material therethrough,y means to inject digestion liquor into said second conduit, a second strainer connecting with said second conduit, means for removing digestion liquor separated by said strainer and a second trap in conjunction with said The iinal washing is then removing means, and means communicatingl 3. In a. process of the character described, treating brous material with heated Water, forcing the fibrous material so treated through a vertical conduit under decreasing hydrostatic pressure, straining Water from said material while maintaining the same under pressure, addthe same through a second conduit under decreasing hydrostatic pressure, straining digestion liquor from said material, diluting said material with Water and steam and Washing the same.

THOMAS L. DUNBAR.

ing digestion liquor to said material and forcing

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