US2035447A - System of pulp preparation - Google Patents

Description

March 31, 1936. c. D. ALTICK SYSTEM OF PULP PREPARATION I l In] mi Patented Mar. 31, 1936 UNITED STATES PATENT- OFFICE 13 Claims.

The present invention relates to the reduction of pulp material for paper making and the like, and more particularly to a semi-continuous circulatory digester system and apparatus for fiber liberation by either sulphite, sulphate, or soda treatment.

The method and apparatus forming the subject tion, washing and bleaching, by being progressively withdrawn from the treatment tank and returned thereto, and during the several mentioned stages it is preferably, although not necessarily, circulated through a refiner, forming a part of the circulatory system, and after passing through a drain stage is ready to pass to beaters, filter press, wet machine or storage as may be desired. The object of the invention is to improve the method as well as apparatus for treatment of pulp 30v making material whereby such apparatus and method of procedure will not only be simpleand economical, but will be more efllcient, uniform in action, semi-automatic in operation and capable of producing a uniform product ,of superior 35 quality at minimum expense. r

A further object of the invention is to afford accurate control of the pulp production by regulation of its treatment throughsuccessive stages. A further object of the invention is-to enable 4 the concentration of cooking liquor to be changed and regulated according tovarying requirements ,the time required for digestion of the material by providing better and more uniform preparation of the material before its entry into the digesting stage.

A further object of the invention is to reduce the time required for digestion, and subsequent 5 washing and bleaching of the stock by thorough agitation and circulation of the material in each stage to enable the cooking liquor and subse-- quently the wash water and bleach material'to thoroughly and uniformly act upon every portion thereof.

A further object of the invention is to provide means whereby liquor may be withdrawn for recirculation or for replacement apart from the mass of material, or at will the intermixture of 16 material and liquor may be circulated or withdrawn.

A further object of the invention is to enable interstage variation of liquor concentration by withdrawal of any portion thereof for replaceo ment by stronger liquor.

A further object of the invention is to provide for mechanical reduction or refinement of the stock during the washing and bleaching stages of operation.

A further object of the invention is to materially increase the output of pulp for a given, digester capacity by reducing the time and utilizing the entiredigester space.

A further object of the invention is to effect more rapid and thorough washing of the material thereby economizing time and capacity.

A further object of the invention is to provide an apparatus and method of treatment of fibrous material, possessing the advantageous characteristics, features and steps as herein disclosed. I I A further object of the inventionis to provide improved apparatus for treatment of pulpmaterial and to provide improved treatment tanks from which the mixture of pulp and liquor or 40 liquor alone may be withdrawn.

A further object is to provide an assembly of apparatus wherein the material is subjected to mechanical disintegration in combination with the cooking and digesting process.

With the above primary and other incidental objects in view, as will more fully appear in the specification, the invention consists of the features of construction, the parts and combinations thereof, and the mode of operation, or their equivalents, as hereinafter described and set forth in the claims.

The accompanying drawing is a diagrammatic. illustration of the preferred assembly of appara-- tus, the several treatment tanks and associated parts being arranged in progressive sequence, it being understood that in commercial operation the several parts will be disposed as may best agree with the plan of the mill and convenience of operation.

Referring to the drawing, A indicates a storage and soak tank which may be of any suitable construction, into which the material is supplied through a filling chute or hopper l. Leading to the storage or soak tank A is a material conveyor 2 upon which bales of straw or other material may be carried past suitable gang saws 3 or other shredding devices, by which the raw material is divided into relatively small portions. In using baled straw the bales are sawed into comparatively thin slices which when broken up afford short lengths of straw suitable for easy and convenient treatment through the various stages of preparation and digestion. Other materials may be subject to the action of shredders in lieu of the saws 3, the action of which may be varied according to the character of the material operated upon.

Within the preparation or soak tank A the material is saturated with water, preferably hot water. If desired the material is intermixed with cooking liquor of the character which will later be used for digestion or subjected to other chemical treatment. To insure thorough and uniform saturation or chemical treatment of the raw material, the mixture of liquid and pulp making material is circulated through the preparation or soak tank A by being withdrawn from the bottom through an outlet conduit 4 communicating with a centrifugal pump 5 discharging upwardly through the conduit 6 which communicates with a conduit 1 common to the plurality of treatment tanks and which enables the material to be transferred from either of the tanks to others at will, and for this purpose is provided with a succession of control valves which later will be identified more specifically. For the purpose of circulation of the material in preparation, the valve 8 in the common distributing conduit 1 being closed, and the valve 9 therein opened, the material withdrawn from the storage or soak tank A is returned thereto. There is thus established a continuous circuitous circulation from the bottom of the tank A through the conduit 4, cen-v trifugal pump 5, up conduit 6 and the valve 8 being closed the material is returned to the tank A through the extension In of the conduit 1. By this means every portion of the material isacted upon and not only brought into intimate contact with the soaking liquid, but reduction is to some extent initiated by the attrition .action of the material in its passage through the conduits and pump.

.In the event that the material is to be subjected to chemical treatment during preparation, the liquor or other chemical solution is supplied from a storage reservoir l2 to the soak tank A through a supply conduit system H which also supplies other tanks of the system. The cooking liquor or other chemical solution is heated in the reservoir I 2 to required temperature by suitable steam coils 13 preferably under automatic thermal control. At the same time it is maintained at a uniform degree of concentration by' charged into the reservoir I 2 through the conduit I'I.

When the material is thoroughly prepared by saturation with water or chemical solution in the soak tank A, preferably after repeated cir- 5 desired degree. Live steam may be admitted directly to the tank B to cook the mass of material therein. A steam supply conduit I8 is provided with branch conduits i9 leading to this and the succeeding digester tank, and also supplies steam 2 to heater coils 20 by which the mixture is heated during circulation.

The first digester tank B is preferably operated under relatively low pressure or even at atmospheric pressure. Adjacent its bottom it is pro- 2 vided with a perforated diaphragm or screen 2| forming a liquid collecting chamber 22 communicating with the main compartment of the tank through the perforations of the wall or screen. The foraminous wall or screen 2| serves to sepa- 3 rate the liquor or other treatment solution from the mass of material within the tank B, and the cooking liquor may be drained off through the conduit 23 communicating with the collecting chamber 22. In lieu thereof the mixture of liquor 3 and pulp material may be drained from the tank B through the outlet conduit 24. The conduits 23 and 24 are valved, thus enabling either conduit to be utilized to the exclusion of the other.

Both of the valved conduits 23 and 24 communicate with the intake side of a centrifugal pump 25 from which a discharge conduit 26 leads upwardly to the common distributing conduit 1. Interposed within the conduit 26 is a heater unit 4 21 within which the temperature of the liquor or pulp material being circulated is raised by heat from the steam coil 20. The valve 28 in the conduit I being opened and the valve 28 therein being closed, either liquor alone or pulp 5 material intermixed with cooking liquor may be circulated through the digester tank B. By opening the valved conduit 23 and closing the conduit 24, liquor alone may be withdrawn from the bottom of the digester tank B by the action of 5 the pump 25 and after being reheated in the heater unit 21 such liquor is returned to the top of the digester tank B through the conduit 26 and conduit I having a branch extension leading to the top of the tank. Conversely, by closing the valved conduit 23 and opening the conduit 24, the intermixture of pulp material and cooking liquor is withdrawn from the bottom of the tank by action of the pump 25 for circulation, during which it is reheated during its movement through the heater unit 21 and returned thence to the top of the digester tank. In lieu of utilizing the heater unit 21, live steam may be introduced directly into the mass of material operated upon through the branch steam conduit l9. 7 The material being circulated by being withdrawn from the bottom of the tank and returned to the top thereof, every portion is uniformly subjected to the action of the cooking liquor, and the liquor is caused to penetrate the material more thoroughly and more quickly. Likewise, during the circulation through the pump and the conduits, the mechanical action and friction assists in the disintegration of the material.

When sufficient preliminary reduction and digestion has been accomplished in the tank '3, the valve 28 in the distribution conduit 1 is closed and the valve 29 is opened, whereupon the material and liquor being pumped from the bottom of the tank B by the pump 25 are discharged from the conduit 26 into the second digester tank C. In this tank the material is subjected to similar treatment, preferably at a higher pressure than that to. which the material is subjected in the initial digester tank B. During the treatment of the pulp material in the digester tank C, the inter-mixture of material and liquor is withdrawn from the bottom of the tank .through the outlet conduit 30 and is returned to the top of.

the tank by the action of the pump 3| discharging upwardly through the conduit 32 in which is interposed the heater unit 33. This heater unit serves to raise the temperature of the material by heat from the steam coil zll'therein, and the material is returned to the top of the tank C. The valve 34, in the distributing conduit 1, is maintained open and the valve 35 therein is kept closed during this operation.

At the completion of the digesting operation, these valves 34 and 35 are reversed, the former being closed and the latter opened and the digested material pumped from the bottom of the tank C is discharged thence into the drainage or wash tank D. The tank D is constructed in a manner similar to the initial digesting tank B in that it is also provided with a perforated diaphragm or screen wall 36 forming at the bottom of the tank a drainage compartment 31 communicating with the-main compartment of the tank through the perforations of the wall or 'screen 36. The cooking liquor may be draned from the compartment 31 through the outlet conduit 38 leading to a suction pump 39 and water may be introduced into the tank in lieu of a cooking liquor to wash the material. This wash water may be supplied from any convenient or suitable source. Merely for purpose of illustration there is shown in the drawing a water supply reservoir 40 communicating with the washing and.- drainage tank D through the conduit 4|.

Leading from the bottom of the washing tank D is an outlet condut 42 leading to the intake side of a centrifugal pump 43, the discharge conduit 44 of which leads upwardly to the distributing conduit 1. The valve 45 therein being maintained open and the valve 46 closed, the material pumped from the bottom of the washing tank D is returned to the top thereof, the material being circulated through the tank D, the conduit 42, pump 43, and conduit 44 back to the tank. Such circulation of the material insures that every portion of the pulp material comes into-intimate contact with the wash water, and that the cooking liquor or other chemicals with which the material has been treated are thoroughly and rapidly removed. In its circulatory movement after leaving the pump 43, the material may be bypassed through a mechanical refiner of the through-flow type, such as a Jordan, Clafllin, Bauer, Behr, or other suitable apparatus which will mechanically disintegrate the pulp material. The refiner 41 is located in a shunt or bypass conduit 43 communicating with the conduit 44 dan, Clailiin or, Bauer machine.

which is provided intermediate the ends of the bypass with a valve 49. By closing the valve 49 and opening the valves in the .bypass conduit 48,

the material discharged from the pump 43 will be passed, through the refiner 47 prior to its return to the washing tank D. If the condition of the pulp material is such as not to require further mechanical disintegration, the valve 49 in the circulatory conduit 44 is left open and the valves in the bypass conduit 48 are closed, thereby returning the material withdrawn from the bottom of the washing tank D directly to the top thereof without passing it through the refiner 41.

During the washing operation, wash water may be drawnoff from the mass within the wash tank D either continuously or intermittently through the drainage conduit 38 and discharged through the pump 39. Such withdrawn wash water is replaced with fresh wash water from the supply tank 40.

When the material has been thoroughly washed and cleansed of cooking liquor or treatment chemical and has been refined to approximately the desired consistency, the'valve 45in the distribution conduit 1 is closed and the valve 46 therein is opened allowing the washed pulp material withdrawn from the bottom of the tank D to be discharged upwardly through the conduit 44 and thence into the bleacher tank E. Bleaching solution is admitted from the bleaching material supply tank 50 to the tank E. The material in the bleacher tank may be subjected to hydrostatic pressure by means of a pump 5! by which the bleaching solution withdrawn from the tank 50 may be introduced into the tank E under pressure, or it may be operated at atmospheric pressure according to the character and condition of the pulp being operated upon. v

Leading from the bottom of the bleacher tank E is an outlet conduit 52 communicating with the intake side of a centrifugal pump 53 from which the material being subjected to bleaching action is discharged upwardly through the conduit 54. The valve 55 in the distributing conduit 1 being opened and the valve 55 therein closed, such material being bleached is returned to the top of the tank E for recirculation therethrough. In the event that the material requires further refinement, it is subjected to such refining action during its circulation through the bleaching tank by being passed through another suitable refiner 41 in a shunt or bypass conduit 48. This refiner, as before described, may be of any suitable through-flow type such as a Jor- The bypass or shunt conduit 48' is suitably valved as is also the discharge conduit 54 intermediate the ends of the bypass conduit 48 whereby by 'control of such valve the material may be passed at will either directly back to the top of the bleaching tank, without passing through the refiner 41, or may be passed through the refiner for further mechanical reduction prior to being returned to the bleaching tank.

When the material has been sufliciently bleached, the valve 55 in the distributing conduit I is closed and the valve 58 at the opposite side of the discharge conduit 54 isopened, and i It is provided with a perforated diaphragm or wall in the lower portion thereof as indicated at 5'! forming a drainage compartment 58 communicating with the main compartment of the tank through the perforations of the screen or perforate wall 51. A drainage conduit 59 leads from the drain chamber 58 and communicates with the drainage conduit 38 leading to the suction side of the centrifugal pump 39. By this means wash water may be continuously or intermittently withdrawn from the tank F to which such wash water is supplied through a water supply conduit 41 leading from the water reservoir 40.

An outlet conduit 60 leadsfrom the bottom of the final washing and draining tank F to the intake or suction side of a centrifugal pump 6|. This pump 6| may discharge the material upwardly through a conduit 62 having therein a valve 63 enabling the material being washed to be returned to the top of the washing and drainage tank F for recirculation therethrough with additional fresh wash water until the pulp material is thoroughly washed and all cooking liquor, chemicals, and bleaching material entirely eliminated. When such condition has been achieved, the valve 64 in the discharge conduit 62 is closed, and the valve 65 in the final outlet conduit 66 is opened thereby enabling the pump 6| to discharge the finished pulp material through the conduit 66 to suitable beaters, Jordans, filter press, storage or stuff chest, or to a wet machine as may be desired.

As was before stated the second stage digester tank C is preferably operated under hydrostatic pressure. In order to create pressure within the tank, a pump 61 is provided to which cooking liquor is supplied through the supply conduit l I and from which the liquor is discharged under pressure into the digester tank.

The system of distribution of liquor from the reservoir I2 is such that it may be supplied to different tanks at will. The distributing conduit 1 provided at spaced intervals with control valves enables material to be discharged from any tank of the system to any other tank thus eliminating from the sequence such stages of operation as may be found unnecessary for the particular character and condition of the material operated upon. Thus if the material is sufficiently digested in the initial digester tank B it may be passed thence directly to the washing tank D without passing through the secondary digester C, and if the material is not to be bleached, the washed material withdrawn from the washer or drainage basin D may be discharged thence through the conduit 68 which communicates with the disqcharge side of the pump 43 and leads to the final .outlet discharge conduit 66. Thus the material may be passed to the heaters, stuff chest, or other apparatus without passing through the bleaching tank E or final washing tank F. It is also possible by manipulation of the proper valves to return unfinished stock from any one of the tanks of the series to a preceding tank for reworking if such operation should be deemed desirable.

Thus the method and apparatus hereinbefore described is quite flexible and is applicable to a wide rang of different pulp making materials and to different character and conditions of such material and is adapted to eifect the reduction thereof rapidly and uniformly without the necessity of extremely high cooking temperatures which are detrimental to the quality of the finished pulp. 3

In the drawing there is shown a mechanical refiner, which may be of any suitable type, such as a Jordan, Clafiiin, or Bauer, associated with each treatment tank. Each refiner is so connected into the return conduit of the corresponding tank with proper control valves that the material being circulated may be passed through such refiner or bypassed thereabout during any stage of treatment as in the judgment of the paper maker may be deemed expedient or desirable, according to the character and condition of the pulp making material and the quality and character of the desired product. Thus the flexibility of the system is materially increased, making it universal as to material and product.

For example in addition to the refiners before mentioned there is shown in association with the soak tank A a refiner 41 which may be set to crush and brush out the saturated material whereby the soaking liquid, whether water or cooking liquor, may more readilyand thoroughly penetrate the fibers of the material to further increase the rapidity of preparation. Likewise refiners 10 and II are shown in association with the digester tanks B and C. For certain quality offiber board it may not benecessary to carry the method beyond the first stage of reduction. For other qualities of material one stage of digestion with or without an accompanying refining operation, and in event of the material not bein bleached one stage of washing may be sufilcient. It is thus possible to utilize at will all or any number of treatment tanks with or without a refining operation during each stage of treatment.

From the above description it will be apparent that there is thus provided a device of the character described possessing the particular features of advantage before enumerated as desirable, but which obviously is susceptible of modification in its form, proportions, detail construction and arrangement of parts without departing from the principle involved or sacrificing any of its advantages.

While in order to comply with the statute, the invention has been described in language more or less specific as to'structural features, it is to be understood that the invention is not limited to the specific features shown, but that the means and construction herein disclosed comprise the preferred form of several modes of putting the invention into effect, and the invention is therefore claimed in any of its forms or modifications within the legitimate and valid scope of the appended claims.

Having thus described my invention I claim:

1. The herein described method of treatment of pulp making material including severing bales of pulp material into relatively thin slices, depositing the slices in broken condition in a soak tank, saturating the material with liquid, circulating the material through the tank by withdrawing it from the bottom and reintroducing it into the top of the tank and passing the material through a pulp refiner in said circulatorypath.

2. The herein described method of preparing pulp making material consisting in subjecting bales of raw material to the action of gang cutters by which the bales are cut into relatively thin slices and depositing the slices of short length material in a tank with sumcient liquid to reduce the material to a condition of saturation.

3. The combination with a receiving tank for pulp making'material, having a filling opening at the top thereof, a traveling conveyor for bales iii of raw stock leading to the filling opening, a cutter in the path of travel of the bales under influence of the traveling conveyor by which the bales are cut into relatively thin slices for deposit of short length material through said filling opening, and means for admitting liquid to the tank for saturation of the material therein.

4. In a pulp making apparatus, a tank for reception of a mixture of pulp making material, and a liquid, a foraminous wall therein separating the tank into a drain compartment into which the liquid may be separated from the pulp and a pulp compartment, valved outlet conduits leading from each of the compartments, a common return conduit leading to the pulp compartment of the tank and means for inducing a circulatory flow from either compartment through the return conduit back to the tank.

5. In an apparatus for treatment of pulp making material, a tank for reception of a mixture of pulp material and a liquid, means therein for separating at least a portion of the liquid from the pulp, separate outlet conduits for withdrawing at will either liquid alone or an intermixture of liquid and pulp material from the bottom of the tank and reintroducing the withdrawn liquid or intermixture of liquid and pulp material into the top of the tank, and means for establishing a circulatory fiow of liquid or intermixture of liquid and pulp material through the tank and conduit at the will of the operator.

6. In an apparatus for treatment of pulp material, a dlgester tank, for reception of pulp making material and cooking liquor, means for heating the cooking liquor, a conduit through which the mixture of pulp material and cooking liquor may be withdrawn from the bottom of the tank and returned to the top thereof, means for inducing a circulation of pulp material and liquor through the tank and conduit, and a mechanical pulp refiner through which the material is passed intermediate its withdrawal from and return to the tank.

7. In a pulp treating apparatus, a washing tank to receive pulp material to be washed, a water supply conduit leading thereto, strainer means for separating at least a portion of the wash water from the pulp material, a discharge outlet for the separated wash water, a conduit through which the pulp material intermixed with wash water may be withdrawnfrom the bottom of the tank and reintroduced into the top thereof, and means for establishing a circuitous flow of pulp material through the wash tank and conduit.

8. In a pulp treating apparatus, a washing tank to receive pulp material to be washed, a water supply conduit leading thereto, strainer means for separating at least a portion of the wash water from the pulp material, a discharge outlet for the separated wash water, a conduit through which the pulp material intermixed with wash water. may be withdrawn from the bottom of the tank and reintroduced into the top thereof, a mechanical refiner through which the pulp is passed intermediate its withdrawal from and return to the tank, and means for establishing a circuitous flow of pulp material through said tank, the conduit and refiner.

9. In a pulp treating apparatus, a bleaching tank to receive pulp material to be bleached, a supply conduit for bleaching solution leading thereto, strainer means for separating at least a portion of the bleaching solution from the pulp material, a discharge outlet for the separated bleaching solution, a conduit'through which an intermixture of the pulp material and bleaching solution may be withdrawn from the bottom of the tank and reintroduced into the top thereof, and means for establishing a circuitous flow of an intermixture of bleaching solution and pulp material through the bleaching tank and conduit.

10. In a pulp treating apparatus, a bleaching tank to receive pulp material to be bleached, a supply conduit for bleaching solution leading thereto, strainer means for separating at least a portion of the bleaching solution from the pulp material, a discharge outlet for the separated bleaching solution, a conduit through which an intermixture of the pulp material and bleaching solution may be withdrawn from the bottom of the tank and reintroduced into the top thereof, a mechanical refiner through which the pulp material passes intermediate its withdrawal from the tank and its return thereto, and means for establishing a circuitous fiow of pulp material and bleaching solution mixture through the tank, conduit and refiner.

11. In an apparatus for treatment of pulp making material, a digester tank to receive pulp material to be operated upon and cooking liquor for treatment thereof, means for maintaining the temperature of the cooking liquor, separator means within the tank for separation of at least a portion of the liquor from the pulp material, and circulatory conduits through which either the separated liquor or an intermixture of liquor and pulp material each to the exclusion of the other may be withdrawn from and returned to the tank at the will of the operator.

12. In an apparatus for treatment of pulp making material, a digester tank to receive pulp material to be operated upon and cooking liquor for treatment thereof, means for maintaining the temperature of the cooking liquor, separator means within the tank for separation of at least a portion of the liquor from the pulp material, circulatory conduits through which either the separated liquor or an intermixture of liquor and pulp material each to the exclusion of the other may be withdrawn from and returned to the tank at the will of the operator, and a pulp refiner through which the intermixture of pulp and liquor may be passed intermediate their withdrawal from and. return to the tank.

13. In an apparatus for treatment of pulp making material, a tank to receive a supply of pulp.

,material and liquid may be bypassed around the refiner and returned to the tank without being passed therethrough at the will of the operator.

CHARLES D. ALTICK.

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