Pressurized System For Pulp Refining Including Pressurized Double Disk Treatment

Abstract

A refining system for high consistency pulp wherein the raw fibrous materials are passed through a series of treatments under a steam pressurized atmosphere of 10 to 150 p.s.i.g. and a temperature of between 115.degree.C to 200.degree.C, and in the absence of accompanying liquid. The raw fibrous materials are initially passed through a tube in which they are conditioned by either the steam atmosphere, or by liquid chemicals under the steam atmosphere, and then are passed between simultaneously rotating disks of a double disk refiner which is under the same aforementioned steam pressurized atmosphere. Subsequent to this treatment the fibrous materials are passed to another conditioning tube, such as a digester or bleach tower, where they are further conditioned by liquid chemicals under the same steam pressurized conditions. The fibrous materials may be thereafter washed, cooled, and/or pressed.

Parent Case Text

BACKGROUND OF THE INVENTION

This application is a continuation of applicants' co-pending application Ser. No. 697,192, filed Jan. 11, 1968, now abandoned.

Description

This invention relates to systems and methods for achieving high yield pulp refining and improved fiber products featuring the use of disc refiners of the double revolving type.

The pulp refining art is a highly developed field of endeavor and an area of constant research. A prime target for much research is means and methods for getting the most pulp and the best quality pulp fibers from a given quantity of raw fibrous material for the least cost. This area of concern becomes increasingly important as supplies of our natural resources diminish, particularly the trees of our forests. As supplies diminish, the cost of raw materials is on the rise. An attendant problem is the constantly increasing cost of labor required for obtaining and processing the raw materials. Added to these basic problems is the fact that the amount of the equipment through which raw material must pass in a conventional refining procedure is substantial and very expensive. This is apart from the fact a conventional refining installation occupies a large amount of valuable space. Further, the substantial amount of equipment normally required for an effective refining system has dictated the passage of a considerable amount of time in achieving the delivery of a given quantity of a pulp product. All this affects the yield and its cost.

The present invention affords a significant advance in solution of the above problems. It provides pulp refining systems and methods of their use which enable a simple working of raw fibrous material such as wood in variously reduced form to achieve high fiber yield and quality pulp in a considerably reduced time and at a considerably reduced cost. The pulp produced is distinguished by fibers of generally greater length than normally anticipated. Moreover, there is no perceptible fiber damage in the refining procedure. Preferred embodiments of the invention contemplate balanced, fully pressurized refining systems which require a minimal amount of apparatus and provide, consequently, for installations which occupy a minimal amount of floor space as contrasted to conventional systems for the same rated output. A basic result of the present invention is an optimally high yield and an ability to utilize the benefits of high consistency pulp refining.

A primary object of the invention is to provide improvements in pulp refining methods and systems enabling the more economical production of pulp fibers, which methods and systems are most efficient and satisfactory in use and adaptable to a wide variety of applications.

Another object of the invention is to increase the yield of quality pulp fibers conventionally available from a given quantity of raw material.

A further object of the invention is to enable a high yield, high consistency pulp refining procedure requiring a minimal amount of equipment, featuring the use of double revolving disc refiners.

An additional object of the invention is to provide a significant reduction in the time involved in refining a given amount of raw fibrous material.

Another object of the invention is to provide means and methods for improving pulp products while holding costs.

A further object of the invention is to provide an improved high consistency pulp refining system and process characterized by a conditioning and/or refining of raw fibrous materials without the need for a conventional entraining liquid.

Another object of the invention is to provide systems and methods for refining pulp possessing the advantageous features, the inherent meritorious characteristics and the means and mode of use herein described.

With the above and other incidental objects in view as will more fully appear in the specification, the invention intended to be protected by Letters Patent consists of the features of construction, the parts and combinations thereof, and the mode of their operation and use hereinafter described or illustrated in the accompanying drawings, or their equivalents.

Referring to the drawings wherein are illustrated certain but not the only means and methods for practicing the invention,

FIGS. 1 through 6 respectively illustrate various systems which may be optimally utilized to practice the concepts of the present invention.

A basic concept of the invention may be shown with reference to FIG. 1 of the drawings. A double disc refiner 10 here illustrated is characterized by a housing the peripheral configuration of which provides an inner chamber having a shape approaching that of a flatted sphere. The latter is defined in part by a waist section including wall portions 11 and 12 which are flatted to occupy planes generally parallel to those of the intermediately contained refiner discs. As in the case of a conventional double disc refiner, the discs D and D' are opposed, and independently driven for rotation of one relative the other. Portions 11 and 12 are interconnected by waist portions 13 of a form to dispose in a spaced generally concentric relation to opposite sides of the disc peripheries. The refiner housing is completed by top and bottom portions 14 each of which has the general contour of a segment of a spherical shell complementary to the waist portions 13.

The refiner 10 is designed for operation in a fully pressurized condition. In the instance shown its inlet 15 is sealingly connected to an adapter defining the discharge outlet of a horizontal hollow tube 16. The refiner outlet is defined by another adapter which sealingly connects about the inlet to a digester tube 17. The outlet from the digester 17 is bridged by a rotary discharge valve 18 of a conventional type which maintains a pressure seal at the terminal portion of the system. The inlet to the tube 16 is bridged by a similar rotary valve unit to provide for the passage therethrough of raw materials while maintaining a seal. Thus, the series related tube 16, refiner 10 and digester 17 may be operated under fully pressurized conditions. It is to be noted the system described is characterized by an absence of intervening valves intermediately of successive units. This facilitates the maintenance of a balanced system throughout which substantially the same conditions of temperature and pressure may be made to prevail.

In applying the invention method in this system to raw wood, the wood is introduced to the tube 16 in a natural, relatively dry, chip or other reduced form and without attendant liquid fluids. As seen in the drawings, the tube 16 contains a shaft mounting radial paddles conventionally powered to move the chips from the tube inlet to its outlet. In this particular instance, in their movement and agitation by the paddles, the chips in the tube 16 are subjected to steam only to establish pressures thereon from 10 to 150 p.s.i.g. at temperatures from 115.degree. to 185.degree.C. A supply of steam is conventionally and suitably connected to the tube 16 for this purpose, by way of an adapter 19. It should be here noted that the established pressure and temperature will be dependent on the particular wood and the desired end product.

Due to the fact that there are no intervening valves, the entire system is similarly pressurized to achieve a balanced environment, steam being added in the tube 16, as required, to this end. In tube 16 the chips are subjected to steam only, as noted, at temperatures from 115.degree. to 185.degree.C. for a selected period of from about 0.5 to 10 minutes and then moved by suitable means to the refiner 10. The retention period is, of course, also dictated by the material and end product and controlled, obviously, by the speed of the chip movement. The steam is applied under the conditions noted to create no attendant liquids but rather to be absorbed by the chips and only to a degree to soften the bonding agents, primarily lignin, between the individual wood fibers.

The steam impregnated chips per se are rapidly passed to and through the double disc refiner 10. Here they flow between/and are defiberized by the opposed refiner plate units or discs each of which revolves relative the other under the pre-established pressure and temperature conditions. Due to the prescribed treatment in tube 16 for softening the lignin connecting the fibers, as the chips move between the relatively rotating refining discs they are subjected inherently to opposed twisting and shear forces such that separation is achieved in longitudinal planes between the fibers. The refining procedure under such circumstances as here, where there is an absence of a liquid vehicle entraining the chips, results in fibers which issue from between the refiner discs in an elongate form and without perceptible damage. Moreover, the prevailing refining conditions result in each of the fibers issuing with a flowed, softened, lignin coating. The flow conditions are such that the fibers are substantially uniformly coated. It would appear that this contributes to their resulting relatively undamaged elongate form.

As the fibers are thrown outwardly of the refiner discs, the spherical contour of the impact surface of the refiner housing dictates a rapid and free movement thereof to exit from the refiner in an expeditious manner. They then move rapidly, under the influence of gravity, to the digester 17. It is noted that to this point the chips and then the fibers are substantially free of accompanying liquid. Moreover, the passage of the materials through the refiner, as described, is so free as to involve a period of retention in the refiner 10 of little more than five seconds.

There is negligible cooking of the fibers in the refiner 10 due to the work thereon by the refiner discs. In this instance, the cooking is primarily effected and quickly completed in the digester 17. Note that the digester 17 is in this case a vessel of the same character as the tube 16.

The production of primarily single elongate fibers from chip or like formed material under conditions free of accompanying liquid and then cooking is of considerable significance.

Unique results are achieved by the invention as the invention process provides, with reference to FIG. 1 of the drawings, that as the coated elongate fibers are moved to and through the digester 17 by conventional contained drive means, they are there subjected, to conditioning fluids such as the case may require. It will be dependent on the wood fibers and the desired end product.

In any event, dependent on the nature of the material and the end product desired, the fibers are retained in the digester 17 for a period of from five to sixty minutes. The longer time interval will be for those products wherein a lower yield is acceptable to obtain the particular cooked condition desired with reference to the particular fiber.

The fibers discharged from the digester 17 by way of the valve 18 resultingly provide a relatively finished quality product which is achieved in an unusually short period of time as contrasted to conventional procedures and systems directed to the same purpose. For example, in the described system Kraft fibers may be achieved at over an 80 percent yield, which fibers are completely individual and uniform as contrasted to the incidence of fiber bundles in prior art systems. With the use of the described system and procedure the impregnation problems normally encountered are substantially eliminated. Since this penetration problem is eliminated, it will be readily seen there is a good basic reason why the cooking cycle is substantially shortened.

As noted previously, the retention time in the digester 17 will be dependent on the wood species, whether hard woods or soft woods, and the level of the pulp yield to be obtained. Within the range of its application, the insured level of yield in use of the system and procedure described will be between 50 percent and 90 percent. Power required will amount to less than 40 HPD/T.

Under special conditions a valve may be installed between the refiner 10 and digester 17. This will be done only where desirable to inhibit gases liberated under certain cooking conditions, employing certain chemicals, from moving back into the refiner. In such instances the objective would be to prevent the gases from attacking and damaging refiner parts. It should be observed, however, that by eliminating intervening valves as prescribed one avoids a pressure condition across such valves which often impairs operating efficiency and produces resultant maintenance problems.

A further desirable pressurized system in accordance with the invention is illustrated in FIG. 2. Here, the refiner 10 has in connection with its inlet a presteamer tube 21, identical in form and use with the tube 16, and in connection with its discharge an "M & D" digester 22. Rotary valves 24 corresponding in nature to valves 18 respectively bridge the tube inlet and digester outlet and operate to deliver and discharge while maintaining a seal of the system. Thus, the system is fully pressurized as in the embodiment first described and has no interventing valves.

In use, wood in chips or other reduced form are introduced to the tube 21 through a sealing valve in their raw natural form as in the first system. There are no attendant liquids. Again, as the chips are moved to refiner 10 steam is applied from an appropriate source to establish in tube 21 and in the communicating equipment a pressure between 10 and 150 p.s.i.g., the level being dependent on the material and application. The chips are correspondingly subjected to steam at a temperature from 115.degree. to 185.degree. C. and for a period from 0.5 to 10 minutes. From the tube 21 the chips are moved to and through the refiner 10 in a continuous flow. Again, in the manner described, the chips are presteamed to soften the lignin content. Other than the steam impregnated in the chips, there is essentially no liquid accompanying the chips as they move to and between the refiner discs. Fiberizing is achieved in a manner as previously described to produce a reduction of the chips to essentially a complete elongate fiber form. During and due to the short interval of time involved in passing through the tube 21 and the refiner 10, not exceeding approximately 10 minutes in view of the five seconds or so required for the refining operation, there is, as previously described, no perceptible damage to the fibers. The fibers therefore issue to the digester 22 in a relatively elongate form and having a uniform flowed coating of lignin. In passage of the fibers through the digester 22 one might achieve in this instance a completely bleached or fully conditioned fiber product ready for use.

In the "M & D" digester 22, to the level 23 shown in FIG. 2, one may include a conventional conditioning or bleaching aolution, for example a hydro-sulfite solution. The "M & D" digester provides the inclined tubular housing shown embodying therein a central partition about which paddles move on an endless chain. The impregnated fibers moving into the digester 22 are distinguished by an absence of attendant fluid and are dropped into the upper side of the digester 22 through its inlet to one side of the contained partition. As a result, the fibers fall to the level of the liquid in the bottom of the digester and for the first time travel through liquid. The moving paddles pick up and carry the fibers down, around and up the lower side of the partition in the process of which they move through the hydro-sulfite or conditioning bath. The travel through the digester in this instance will be controlled so as to involve as little time as 5 minutes. In the process the fibers receive the bleaching and brightening effect incident to the controlled passage through the hydro-sulfite.

The fibers, substantially devoid of entraining liquid, are lifted by the paddles to discharge from the digester 22 through the sealing discharge valve 24. It may be readily seen thereby that a bleached product ready for application may be obtained in 20 minutes or even less, dependent on the material.

Another embodiment of the invention may be observed with reference to FIG. 3 of the drawings. Here, again, a central element of the system is the refiner 10 such as first described. Connected to the inlet thereof in this case is the discharge adapter of an "M & D" digester 32 such as 22 described in reference to the system of FIG. 2. The discharge from the refiner 10 connects, in turn, to the inlet of a vertical washer tube 30. The lower or discharge end of the latter has a discharge outlet across which a pressure seal is maintained by a rotary discharge valve 31 corresponding in nature to the valve 18 in the first described system of the invention. The inlet to the digester 32 is bridged by a similar valve 31.

In use of the described system in this instance, it is contemplated that the bottom of the inclined digester 32 can be provided with a bath of cooking fluid, for example Kraft liquors. Steam is maintained in the top of this digester by manipulating an adapter 36 through which steam may be admitted from a suitable source. In this manner one can establish the system temperature and pressure. In the procedure, wood chips are introduced to its inlet in their raw natural form, without attendant fluid, to move to and through the bath for impregnation and chemical conditioning prior to movement to the refiner 10. The range of pressure under which the system is operated in this instance can again be between 10 and 150 p.s.i.g. depending on the nature of the raw material and the desired end product, but preferably between 75 and 150 p.s.i.g. The range of operating temperature will be limited to an area approximately between 140.degree. and 200.degree.C.

It will be seen that under these conditions the chips are conditioned and impregnated and delivered to the refiner 10 in a cooked condition. While the chips will be impregnated, they will otherwise leave behind the fluid from the bath. The lignin being softened in the cooking process, the movement of the chips to and through the refiner 10 will be as described in the first instance. The refiner discs will again separate the chips in the longitudinal planes between the fibers and the product issuing from the refining discs will be long fibers, this time previously conditioned by chemicals.

The fibers are dropped from the refiner 10 into the top of the washer tube 30 for rapid cycling to completion of the process.

The tube 30 is vertical and there will be maintained therein a body of weak wash liquor. The tube 30 is further provided with an inlet 33 at its bottom for a continuing inflow of weak liquor and an outlet 34 adjacent its top for its continuing discharge. Thus, a predetermined body of weak liquor is maintained in the tube 30 as a washing medium for the fibers which move therethrough under the influence of gravity. Concurrently, the fibers are subjected to the further washing influence of the countercurrent flow of weak liquor. By the time they leave the tube 30, the fibers are effectively freed of attached undesirable particles.

The movement of the fibers through the tube 30 will take between 5 and 15 minutes, dependent on the desired quench or washing effect required. As delivered, the fibers are ready for immediate processing in application to the manufacture of Kraft-type products. It is to be noted that the time in movement of the chips for impregnation in the "M & D" digester 32 will range from 3 to 40 minutes for Kraft while the time in flow through the refiner will be a matter of seconds. It must be remembered that the precise time will be in accordance with the objective of the procedure.

In the continuous system described the fiber end product desired may be achieved in a time period significantly less than that possible in a conventional system using conventional methods. For high yield the time lapse in effecting the complete procedure can be less than ten minutes in some cases.

The application of a system such as described in reference to FIG. 3 becomes clear from the following specific examples:

A. a mixture of spruce wood and Douglas fir chips (120 lbs. oven dry basis) can be passed through a bath in a digester such as 32, the bath being a solution prepared, for example, by dissolving 4.53 lbs. of Sodium Sulphide and 14.72 lbs. of caustic in 97 gallons of water. The pressure established in the system should be approximately 150 p.s.i.g. and the temperature about 180.degree.C. The controlled movement of the wood chips through the digester to the refiner discs should then be effected in about 14.15 minutes. The function of the refiner 10 and the washer 30 is as described previously with reference to FIG. 3, and the entire operation will involve less than thirty minutes. The significant aspect of the results of this procedure is a 70 percent pulp fiber yield having a K No. of 123. Note that the amount of chemical added, expressed as active alkali, will be about 5.4 percent Na.sub.2 O. This evidences the invention achievement of a high yield with excellent characteristics in a relatively short period of time, and with considerable reduction in equipment and handling costs as compared to conventional refining procedures to achieve the same results.

B. a mixture of the same lot of chips as in A can be similarly passed through a bath in the digester 32 of the system of FIG. 3 with the bath solution being prepared by dissolving 9.0 lbs. of Na.sub.2 S and 29.4 lbs. of NaOh in 97 gallons of water. The time in movement to the refiner will be the same as in A. Moreover, the system pressure and temperature will be the same, as would be the remaining procedure in the refiner 10 and washer 30. In this instance the pulp yield will be 60 percent and have a K No. of 93.4. In reference to the resultant fibers in this instance it is particularly significant that this pulp at 60 percent yield will have strength characteristics comparable to a regularly processed Kraft pulp made from the same chips, which conventional process will produce a yield of less than 50 percent.

It should be noted that the examples here illustrated could apply in cooking in an "M & D" digester in any of the invention systems.

FIG. 4 of the drawings shows yet a further system in accordance with the invention. This one includes the refiner 10 having connected to its inlet a pre-steamer tube 21 as in FIG. 2. Connected to its outlet is an "M & D" digester 22, also as described with reference to the system of FIG. 2. The distinction here is that appended to the outlet of the digester tube 22 is a further digester housing 40 similar to the vessel 10 shown in U.S. Pat. to Horstman No. 3,085,624. Connected across the discharge from the housing 40 is a rotary discharge valve 41 which may appropriately function and still seal the system outlet. Again, a similar rotary valve unit maintains a seal of the inlet to the system while providing for a feed of raw material to the tube 21.

It is again noted that intervening valves and their functions are preferably eliminated.

In use of the system of FIG. 4, the elements 21, 10 and 22 function as described in reference to the system of FIG. 2. Steam is introduced in the tube 21 through suitable means to establish and maintain the system in a pressurized condition. Dependent on the materials and objectives, the pressure is established in the range of 10 to 150 p.s.i.g. at temperatures between 115.degree. and 185.degree.. In the tube 21 the raw material is delivered thereto in the form of wood chips without added liquid. The chips per se are advanced by conventional screw or paddle means and are impregnated by the steam in the process of their movement to the refiner 10. The period of chip retention in the tube 21 will be from 0.5 to 10 minutes, predicated on the material and the nature of the objective. The impregnated chips are then moved through the refiner 10 which achieves its function as previously described and delivers the fibers in an elongate uniformly coated form to the inlet of the digester 22. There is no attendant slurry in any case. It will be seen that the operation is at an optimally high consistency.

The fibers are then moved to and through the digester bath constituted by the required cooking medium and up to again discharge relatively free of attendant liquids for a second cooking and washing in passage through the housing 40. The housing 40 is continuously open from top to bottom and forms a chamber in which liquor is maintained to a level 42. The nature of the liquor will be dictated by the required conditioning of the fibers. There is, of course, steam above the level 42, as dictated by the system steam, though here an adapter 43 is added for delivery of further steam, if required. As the fibers drop they descend by gravity through the upper level of the steam and through a spray of liquor delivered by way of adapter connection 44. As this occurs, there is both a washing and conditioning influence. If dissolved materials remain attached to the fibers they will be displaced by this spray. In moving down through the body of liquor the fibers are appropriately conditioned by the contained chemicals. It will be noted that the upper levels of the body of liquor in the housing 40 will be maintained at system temperature due to the proximate nature thereof to the steam in the head of the housing. In the lower portion of the housing 40 a weak and cooler liquor is moved in through mining nozzles 45. The latter draw down the fibers to influence their discharge through an outlet 46. In the process if any undesirable materials yet remain on the fibers, they tend to be washed free and the fibers are cooled to a degree as they are passed outwardly by the discharge valve 41.

Thus the system of FIG. 4 is an extension of that of FIG. 2 and its use will be dictated where a more involved conditioning is required prior to application of the fibers.

It should be noted in any respect that in each of the systems of the invention and the methods of practice thereof, the refining and conditioning or bleaching operation is achieved on a raw material which is basically in its natural form and thus of relatively high consistency. Moreover, the technique in employing the pressurized conditioning system and the manner of softening and refining dictate that the systems are relieved of any heavy power or heavy steam requirements and the fibers are refined in an exceedingly rapid manner. Further, note that the systems provide for minimal plumbing requirements due to the minimal use of liquids.

Turning to FIG. 5 of the drawings, there shown is a modification of the system of FIG. 4. The only change in the system is that the presteaming tube 21 is replaced by a "M & D" Digester 22. In this case a chemical preconditioning and cooking under the established temperatures and pressures previously described will take place and effect the softening of the lignin for refining. Otherwise the procedure in the various following apparatus is the same. The use of this system would be dictated where the fiber materials are such and the end product required necessitate a more involved chemical conditioning of the fibers. There would be, however, a change in the total time lapse in the conditioning process since the movement of the raw materials through the first digester 22 would take from 3 to 40 minutes in accordance with the objectives. Also, steam would be supplied to maintain the system preferably under pressure of 75 to 150 p.s.i.g., the temperature being maintained between 140.degree. and 200.degree.C.

With reference to the systems of FIG. 4 and 5, it should be here noted that in some instances an intervening valve such as that described with reference to the valve 41 may be placed between the housing 40 and the immediately preceding digester 22. This will be done where the particular chemicals employed and particular objective in moving the fibers through the housing 40 should present some difficulty in maintaining system pressure and temperatures therein.

Yet another application of the invention is illustrated in FIG. 6 of the drawing. In this instance a presteaming tube 21 and a double revolving disc refiner 10 are interconnected and employed in sequence as described with reference to these elements in the system of FIG. 2 of the drawing. In connection with the refiner 10 and bridging the discharge passage from the refiner 10 is a rotary valve 50 similar to the valves 18 and 41 previously described, and functioning similarly. The valve 50 discharges into the top of a bleach tower 52. The latter is also pressure sealed and discharges to a pressurized press 53 across the discharge outlet of which is a second valve 50'. Also, a third and similar valve 50" bridges the inlet to the presteamed tube 21.

In this case, depending on the material and desired end product, the tube 21 and the refiner 10 will be maintained under pressures of 10 to 125 p.s.i.g. with a temperature established therein in the range of 110.degree. to 175.degree. C. Steam will be delivered to the tube 21 to maintain the required conditions. Similarly, steam will be supplied to the vessels 52 and 53 to maintain therein a pressure close to atmospheric or above. At the top of the bleach tower 52 is an adapter providing a water inlet 55 functioning to deliver therein an expanding spray.

This system is particularly advantageous for obtaining bleached fibers. Raw wood chips are moved into and through tube 21 to refiner 10, under the same conditions as previously described with respect to the same equipment, to be impregnated by steam in passage, retention time being from 0.5 to 10 minutes. As the chips, which have been considerably softened, move into the eye of refiner 10 and pass between the refiner discs, the fibers separated as provided by the invention are, simultaneous with separation thereof, subjected to a spray of bleach solution. This bleach solution 54 is introduced by suitable means in the eye of the refiner. Thus, a bleach operation is commenced as the fibers are actually separated to their elongate natural form. Continuously under influence of the applied bleach, the fibers drop to and through the valve 50 and finally into the top of the vertical bleach tower 52. Here a spray of water through the adapter 55 produces a quenching influence, which process is continued as the fibers fall under the influence of gravity. Issuing from the tower in a well bleached condition, the fibers are directed into the pressurized press 53 wherein attendant fluids from the bleach tower are extracted and the bleached fibers are again washed. This last is achieved by a spray directed thereon through jet orifices 55' in a collar in the discharge outlet of the press. From here the fibers pass from the system through the outlet valve 50. The press contemplated in this instance as the unit 53 is a "Pressafiner." Since the details thereof are well known in the commercial refining art, they need not be further described here.

Thus, utilizing the system of FIG. 6, one may very effectively use the presteamer and refiner to produce a bleached elongate fiber and the bleaching process is completed by continuing flow of the fiber through the bleach tower and the pressurized press to achieve in a relatively short period of time a completely bleached fiber product for use in the manufacture of quality fibrous end products.

In any instance of use of the invention concept it will be seen that there is a controlled and limited conditioning or cooking process that enables the undesirable coatings and content of the raw material to be readily dissipated and without perceptive damage to the fibers. In all cases one attains a relatively finished fiber element which is practically immediately available for use in paper making and like procedures. There is a speed obtaining in the described systems and minimal power consumption inherent, in part due to the elimination in preferred embodiments of intervening valves. Where valves are incidentally applied due to the necessities of a particular material and process, they will be used to either control undesirable effects of gases liberated during cooking from moving back into preceding units of the system or to define an area where a variation of pressure must be obtained. However, it must be emphasized, that in the preferred use of the invention concepts, valves will be essentially eliminated together with the problems that are normally attendant the use of an excess number of valves.

Attention is directed to the fact that in the invention system the necessary common pressure is applied by virtue and through the medium of a fluid environment, the fluid in the examples illustrated being steam.

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 but one 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.

Claims

We claim:

1. A process for reducing and refining segments of raw fibrous materials such as wood comprising the steps of subjecting the segments to a gaseous conditioning medium and then passing the segments between refining surfaces to reduce the material, characterized in that said segments are moved to the refining surfaces through a scaled environment in a continuing flow and in a state free of accompanying liquid, under pressure of said gaseous conditioning medium to soften them in planes between their fibers in a manner to inhibit the creation of liquid free of the segments, and, while still under pressure and characterized by an absence of accompanying free liquid, said segments are subjected for the first time to an application of mechanical forces, which forces are in the nature of twisting and shear forces applied through the medium of and in the course of a pass of said segments between a pair of rotating refiner discs, each of which rotates relative the other in a manner to separate the segments in planes between the fibers whereby to provide that the raw material issuing from between said discs will be composed of fibers which have a generally elongate form which exhibit no perceptible damage and, while within an extension of said sealed environment, the material issuing from between said discs is then subjected to a liquid conditioning medium under the influence of said pressure maintained in said sealed environment and further movement of the raw material issuing from between said discs is characterized by an absence of further disc refining prior to movement thereof from said sealed environment.

2. A process as set forth in claim 1 including the step of maintaining the temperature and pressure in said sealed environment at a level that in application of said opposed twisting and shear forces to the raw fibrous material under conditions characterized by an absence of liquid which is free of the material segments there is produced a substantially uniform flowed coating of its lignin on the fibers, providing thereby that the products of said mechanically applied twisting and shear forces are fibers of elongate and coated form substantially free of accompanying liquid, and applying said conditioning liquid medium to modify the coating produced on the fibers.

3. A process as in claim 2 including the step of maintaining the temperature in said pressurized environment in a range between about 115.degree. and 200.degree.C. and the corresponding pressure between 10 p.s.i.g. and 150 p.s.i.g.

4. A process as set forth in claim 2 wherein said flow coated fiber products are cooked in moving through said liquid conditioning medium while maintaining thereon the same said pressurized condition, and then washed or quenched whereby to produce chemically treated elongate fibers substantially ready for use in end products.

5. A process as in claim 4 wherein the cooking of the fiber products is effected in two stages immediately following one another.

6. The process of claim 5 applied to wood chips or like segments of a fibrous material wherein the raw segments thereof in the course of said continuing flow are first subjected to a first chemical conditioning liquid, which is impregnated under the influence of said gaseous conditioning medium, and the impregnated segments are then delivered for application thereto of said opposed twisting and shear forces exclusive of an attendant liquid vehicle.

7. A process as in claim 5 including the steps of maintaining in said system a pressure between 10 and 150 p.s.i.g. and temperature between 115.degree. and 185.degree.C., applying the said gaseous conditioning medium to said raw segments in the form of steam for a period not greater than 10 minutes, and conducting the second stage cooking while dropping the fiber products under the influence of gravity through a cooking chamber, within which chamber the fiber products are first subjected to a spray of conditioning liquor to wash them and then to condition them in the course of a downward movement to a body of liquor, in the lower portion of which chamber a cooling liquid is applied in discharge of the fiber products.

8. A process as set forth in Claim 1, wherein said gaseous conditioning medium is steam, the temperature and pressure condition of which is controlled to inhibit formation of liquid other than that added within said segments by impregnation thereof with said steam, the impregnation and refining being distinguished by an absence of excess liquid which is free of said segments and the raw material being reduced by said refiner discs to a relatively natural high consistency form.

9. A process as in Claim 8 wherein the raw segments of material are first steamed for a period between 0.5 to approximately 10 minutes and moved in a continuous flow in the course of being subjected to the steam.

10. A process as set forth in claim 1 wherein after separation of said raw material between said relatively rotating discs the said fiber products resulting are moved in a continuing flow to and through said liquid conditioning medium which is in the form of a chemical bath, said bath being subjected to the same said pressurized environment, and the time interval of exposure of the separated fibers to said bath is limited to a range between 5 and 60 minutes, dependent on the material and the desired end product.

11. The process of claim 1 applied to wood chips or like segments of a fibrous material wherein the raw segments thereof in the course of said continuing flow are first subjected to a first chemical conditioning liquid, which is impregnated under the influence of said gaseous conditioning medium and the impregnated segments are then delivered for application thereto of said opposed twisting and shear forces exclusive of an attendant liquid vehicle, the end products being fibers which have been pressure and chemically conditioned thereby to be substantially ready for application to paper products.

12. The process as in claim 11 characterized by deliver-ing the fiber products resulting from the application of said twisting and shear forces substantially free of attendant liquid to said liquid conditioning medium provided as a chemical bath, to further condition said fiber products in said pressurized environment, and discharging the resultant products, substantially free of attendant liquid as a high consistency fiber product ready for use in selected end products.

13. The process as set forth in claim 12 including subjecting said segments to said first chemical conditioning liquid for a period of 3 to 40 minutes and subjecting said fiber products to said chemical bath for a period from about 5 to 60 minutes, dependent upon the desired end product.

14. A process as in claim 12 wherein said first chemical conditioning liquid is comprised of sodium sulfide, sodium hydroxide and water.

15. A process for reducing and refining raw fibrous materials such as wood comprising the steps of moving segments of raw fibrous materials in a continuing free flow through a sealed pressurized environment, in the course of which first subjecting said segments to a first chemical conditioning liquid, impregnating and cooking the same under the influence of above atmospheric pressure and delivering the cooked and impregnated segments in a form substantially free of liquid except for that impregnated therein, in the course of the delivery of the cooked and impregnated segments subjecting said segments, while still under pressure corresponding to that of said sealed environment and substantially free of liquid other than that liquid which is embodied in the segments per se, for the first time to mechanical forces, which forces are opposed twisting and shear forces operating to separate the segments in planes between their fibers and produce thereby elongate fiber products, delivering said fiber products so resulting substantially free of attendant liquid and in the course of this delivery subjecting said fiber products to a second liquid conditioning medium in an extension of said pressurized environment while maintaining the same under the influence of said pressurized environment whereby to produce treated fibers which are substantially ready for use in end products such as paper, the movement of said fiber products subsequent to the production thereof being characterized by an absence of further application of opposed twisting and shear forces prior to their passage from said sealed environment.

16. A process for reducing and refining raw fibrous materials such as set forth in claim 15 including the step of wash-ing said fiber products immediately prior to delivery thereof from said pressurized environment.

17. A process for reducing and refining raw fibrous, materials such as wood as set forth in claim 15 including the step, immediately subsequent to the application to said cooked and impregnated segments of opposed twisting and shear forces, of subjecting the fiber products to said second liquid conditioning medium provided as a chemical bath, to further condition said fiber products in said pressurized environment, and discharging the resultant products substantially free of attendant liquid as a high consistency fiber product ready for use in selected end products.

18. A process as set forth in claim 17 including subjecting said segments in the first instance to the first said conditioning liquid for a period of 3 to 40 minutes and subjecting said fiber products to said chemical bath for a period of about 5 to 60 minutes.

19. A process as in claim 15 applied to wood chips and the like including the steps of, in the course of said continuing flow first introducing the raw segments to said first chemical conditioning liquid in the form of a bath of conditioning chemical and impregnating and cooking the segments with said chemical under the influence of applied steam which establishes said pressurized environment whereby the segments delivered for application of said twisting and shear forces will be first chemically treated, the pressure in said environment being held in a range between 75 and 150 p.s.i.g. and the temperature between 140.degree. and 200.degree.C., and, subsequent to the application of the twisting and shear forces and said second liquid conditioning medium, washing the resultant fiber products to free them of attached undesirable particles which still remain, the whole being effected under essentially the same prescribed conditions of temperature and pressure and the flow being relatively uninterrupted.

20. A process according to claim 19 wherein the pressure of said environment is maintained at approximately 150 p.s.i.g. and the temperature about 180.degree.C., the time in which said segments are subjected to said bath of conditioning chemical being limited to between 10 and 15 minutes and the time in which said segments are subjected to twisting and shear forces being limited to a few seconds while the time in which the resulting fiber products are subjected to washing is limited to between 5 and 15 minutes.

21. A process according to claim 20 wherein the chemical solution used for said bath of conditioning chemical is comprised of sodium sulfide, caustic and water.

22. A high consistency pulp refining system comprising means defining a sealed environment including a first pressurized vessel having means to receive therein fragments of fibrous materials in their raw natural state, means to freely convey the materials through said vessel in the same said natural state, means for providing in said vessel and said sealed environment a gaseous conditioning medium for establishing and maintaining said sealed environment as a pressurized environment for said materials and for impregnating and softening said fragments in planes between their fibers and in the course of a continuing flow thereof in their natural state, mechanical means in said sealed environment for modifying said fragments by application of mechanical forces including rotating elements, there being a single pair of said rotating elements within said sealed environment portion of said system, each of which elements rotates relative the other in the same pressurized environment, said rotating elements being disposed in opposed relation to receive therebetween said fragments in their natural state as impregnated by said gaseous conditioning medium and characterized by an absence of attendant free liquid, said conveying means in said vessel including feed elements providing that said fragments move through said vessel and to said relatively rotating elements in relatively uninhibited continuing flow, said relatively rotating elements providing means to twist and shear said fragments in longitudinal planes between the fibers thereof, said means for establishing and maintaining said pressurized environment being arranged to produce a temperature and pressure in said system so that the material between the fibers will form a substantially uniform flowed coating on the fibers in the course of their separation and discharge by said relatively rotating elements and a second pressurized conditioning vessel in said sealed environment having an unobstructed inlet means connecting the same in open communication with said relatively rotating elements for inflow thereto of the coated fibers delivered from said relatively rotating elements, said second vessel including means for conveying said coated fibers through a liquid conditioning medium to condition the fibers and there being means for discharge of the fibers from said second vessel in a conditioned form.

23. A high consistency pulp refining system as in Claim 22 wherein said means defining said sealed pressurized environment include pressurized sealing inlet and discharge valves at the remote ends of said system and there is an absence of intervening valves within said system.

24. Apparatus as set forth in claim 22 including an additional pressurized vessel connected to receive from said second vessel said conditioned fiber products.

25. A system as set forth in claim 24 including means in said additional pressurized vessel for applying to the delivered fiber products, in the course of their entry, a spray of conditioning chemical or liquor in a manner to produce both a washing and a conditioning influence thereon.

26. A system as set forth in claim 22 wherein said second vessel is a bleach tower having in connection therewith means for washing the fiber products in the course of their discharge following bleaching.

27. Apparatus as set forth in claim 26 characterized by a further pressurized vessel in connection with said bleach tower incorporating therein means for extracting fluids attendant the fiber products discharging from said bleach tower and there being means in said pressurized environment for washing the fiber products following extraction of the attendant fluids to produce thereby bleached fibers substantially ready for use in end products.

28. Apparatus as set forth in claim 27 characterized by said bleach tower having connected therewith means for applying to fiber products which enter said bleach tower a quenching medium in a spray form.

29. A high consistency pulp refining system as in claim 22 characterized by said first mentioned pressurized vessel being a digester.

30. A high consistency pulp refining system as in claim 29 characterized by said second mentioned pressurized vessel being a second digester and there being in connection therewith a further pressurized vessel incorporating means for cooking and washing the fiber products in the course of discharge.

31. A high consistency pulp refining system as in claim 22 characterized by said first mentioned pressurized vessel being a cooking vessel, said second mentioned pressurized vessel being a secondary cooking vessel and having in connect-ion therewith a further pressurized vessel to receive the dis-charge of treated fibers from said second pressurized vessel and including means for washing the fibers free of dissolved materials and quenching chemical thereon prior to discharge of the fiber products ready for use in an end product.

32. A high consistency pulp refining system as in claim 22 wherein said first pressurized vessel is a pressurized tube and said second vessel is a vertical tower providing a housing for free fall therethrough of treated fibers issuing from between said relatively rotating elements and having spray devices in connection therewith for applying a medium to the fibers to quench the reaction occurring thereon in transit and an extractor in connection with and exposed to the environment of said housing for extracting the liquids applied to the fibers in transit and having further means for washing the fibers prior to discharge to atmosphere.

33. A system as set forth in claim 22 characterized by said second vessel including washing means.