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Publication numberUS3661328 A
Publication typeGrant
Publication dateMay 9, 1972
Filing dateMar 30, 1970
Priority dateMar 30, 1970
Also published asCA969794A1, DE2053419A1
Publication numberUS 3661328 A, US 3661328A, US-A-3661328, US3661328 A, US3661328A
InventorsRaymond A Leask
Original AssigneeBauer Bros Co
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Pulp refining system and process
US 3661328 A
Abstract
A unique system and process for producing an improved refiner groundwood from a great variety of raw fibrous material including both softwoods, hardwoods and their waste residuals, characterized by a multi-stage disc refining of the raw materials. The first stage refining is effected in a pressurized environment and features an absence of liquid except for that moisture embodied in the raw material per se in delivery to the refiner. The first stage refining is conducted under controlled conditions providing a moderate elevated pressure and subsequent disc refining is effected under atmospheric pressure conditions. The unique result is a bright fiber yield equal to that available in straight atmospheric refining. More importantly, the yield is achieved with a minimum of power. A most significant result of the invention process is an unexpected reduction in bulk of the fiber furnished.
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United States Patent 1151 3,661,328 Leask 51 May 9, 1972 [54] PULP REFINING SYSTEM AND 3,411,720 11/1968 Jones et al. ..24l/28 PROCESS Primary E.\'aminer -Granville Y. Custer, .l r. Attorney-Jerome P. Bloom A unique system and process for producing an improved refiner groundwood from a great variety of raw fibrous material including both softwoods, hardwoods and their waste residuals, characterized by a multi-stage disc refining of the raw materials. The first stage refining is effected in a pressurized environment and features an absence of liquid except for that moisture embodied in the raw material per se in delivery to the refiner. The first stage refining is conducted under controlled conditions providing a moderate elevated pressure and subsequent disc refining is effected under atmospheric pressure conditions.' The unique result is a bright fiber yield equal to that available in straight atmospheric refining. More importantly, the yield is achieved with a minimum of power. A most significant result of the invention process is an unexpected reduction in bulk of the fiber furnished.

ABSTRACT 30 Claims, 5 Drawing Figures HTENTEDMAY 91912 SHEET 1 BF 2 INVENTOI? RAYMOND A. LEASK A TTOR/VE Y MTENTEDIIIII 91972 PARTICLE SHEET 2 0F 2 STORAGE SUP PLY F'IG Z Fl- 60 RBGIER PARTICLE 10 PARTICLE /0 PARTICLE FLUD CONDITIONER BIN BIN ADDmON 0 PARTICLE PARTICLE CONDITIONER CONDITIONER 25 .25 I 25 PRESSURIZED PREssURIzED PREssURIzED DOUBLE DOUBLE DOUBLE ROTATING ROTATING ROTATING DIS REFINER DIsc REFINER DISC REFINER 33 CYCLONE a: CYCLONE 33 CYCLONE I V Y AATMOSPHERIC ATMOSPHERIC ATMOSPHERIC I DOUBLE DOUBLE DOUBLE' ROTATING ROTATING ROTATING DISC REFINER DIsC REFINER DISC REFINER V V I ATMOSPHERIC \ATMOSPHERIC ATMOSPHERIC v DOUBLE DOUBLE DOUBLE ROTATING ROTATING ROTATING DISC REFINER DISC REFINER DISC REFINER M/VE/VTUR RAYMOND A LEASK A TTOR/VE' Y PULP REFINING SYSTEM AND PROCESS THE INVENTION BACKGROUND This invention relates to a new system and process for producing high quality refiner groundwood from a broader spectrum of fibrous materials than heretofore deemed possible and with minimalized power requirements. The fiber product produced in the use thereof is so reduced in bulk and otherwise improved as to more readily lend itself to the manufacture of quality paper products.

In recent times unexpected advantage has been found to exist in refining of groundwood type pulp in a pressurized double disc refiner. One of the discoveries is that the pressurized double disc refining reduces materials to a greater extent in a single pass and to a more desirable individual fiber form than previously possible utilizing single disc refiners in a pressurized environment or any refiners in an atmospheric environment. It has also been found, however, in previous efforts to use the benefits of pressurized double disc refining, that yield is somewhat reduced. Moreover, while the pressurized double disc refining has produced some uniquely advantageous results particularly beneficial in the manufacture of end products such ashardboard or pressed type boards, there has been no satisfactory procedure for producing fibers which are amenable to further treatment and refining after a first pressurized refining, as required to enable use of the fibers for quality paper products. Thus, while of recent years the potential of pressurized double disc refining has been recognized to some degree, no one has previously been able to fully exploit the potential of this relatively new concept.

THE INVENTION The present invention substantially advances the benefits available in the practice of pressurized double disc refining. It provides a unique system and process which produces several unexpected results. It enables the successful retention of the benefits of pressurized double disc refining while overcoming the previously known disadvantages. By virtue of the invention one may now apply pressurized double disc refining in a multistage refining process to result in a yield equivalent to that afforded by straight atmospheric refining and in a fiber product of reduced bulk, wherein the fibers are longer and stronger and adequately bright to enable their application not only to improved newsprint but even higher quality paper products.

It is a feature of the invention system and process which provides for multi-stage double disc refining that the first stage disc refiner, preferably, will be included in a segment of the system which is pressurized. The pressure in this segment will be elevated but moderate, as will be further described, and within the pressurized segment raw materials will be moved to and through the first stage refiner in a condition characterized by the exclusion of liquid except that embodied in the raw material per se. It is a characteristic of the invention system and process that the period the raw materials will be within the pressurized segment will be extremely limited, for example to a time interval of approximately oneminute. In the practice of the invention the pressurized double disc refining will be followed, normally, by at least one atmospheric refining stage.

It is therefore a primary object of the invention to provide an improved system and process for producing a highly versatile refiner groundwood product from a great variety of raw fibrous materials including waste and residuals.

It is a further object of the invention to provide means to expand the market for refiner groundwood.

It is another object of the invention to utilize pressurized double disc refining and the advantages thereof in a pulp refining system in a manner to produce a yield equal to that possible with atmospheric refining and a fiber product which is better than that possible with straight atmospheric refining.

An important object of the invention is to produce a refiner groundwood having reduced bulk and one in which the fibers are predominantly individual and have improved physical characteristics lending themselves to use in a variety of quality paper products.

Another object of the invention is to provide a system and process for producing refiner groundwood utilizing pressurized double disc refining whereby to make the resultant fiber product more susceptible to further treatment and refining for high grade paper products.

An additional object of the invention is to provide a system and process for producing improved fibers possessing the advantageous features, the inherent meritorious characteristics and the means and mode of application herein described.

With the above and other incidental objects in view, as will more fully appear in this 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 operation as hereinafter described or illustrated in the accompanyingdrawings, or their equivalents.

Referring to the accompanying drawing wherein are shown some but obviously not necessarily the only forms of embodiment of the present invention,

FIG. 1 is a generally diagrammatic view demonstrating the invention system in a preferred embodiment;

FIG. 2 is a crosssectional view of a double disc refiner such as utilized in the first refining stage of the system of FIG. 1;

FIG. 3 is a fiow diagram representing the invention system of FIG. 1; and

FIGS. 4 and 5 present modifications of the system as illustrated in FIGS. 1 through 3.

Like parts of the system are indicated by similar characters of reference throughout the several views.

In FIG. 1, the continuous flow system of the invention is shown to include a chip bin 10 having at its bottom a crossscrew feeder 11. A discharge outlet 12 of the feeder 11 opens directly to the top of a downwardly convergent hopper 13. The latter discharges directly to the inlet 14 of a rotary valve 15, the outlet 16 of which is in open communication with the inlet to a horizontal conditioning tube 17. Within and extending the length of the tube 17 is a feed screw 18, the shaft 19 of which bears in the respective closure plates to the ends of the tube. One end of the shaft 19 projects to mount a pulley 20 through the medium of which the screw 18 is driven from a power source in the form of a variable speed motor 21. In the diagrammatic illustration of FIG. 1 it is to be noted that the inlet of the tube 17 is to one end thereof and to its top. On the other hand,'the outlet or discharge opening of the tube 17 is at its opposite end and to its bottom. This last is connected by a tubular chute 22 to the inlet at one end of a tube housing a cross-feed screw 23. The screw 23 discharges directly to the inlet 24 of the double disc refiner 25.

As seen in FIG. 2 of the drawings, material passing through the inlet 24 will be conventionally directed to and through divergent passages 26 in the refiner disc 27 which positions most adjacent the inlet 24. The passages 26 are circularly spaced about the hub of the disc which mounts on one end of the drive shaft 27'. At the center of the relatively opposed disc 28, which mounts on the adjacent end of an aligned shaft 28', is a fiinger which on rotation thereof will function on the delivered material to direct the same outwardly for refining between the relatively rotating operating surfaces of the opposed refiner discs 27 and 28.

The housing 29 for the discs 27 and 28 has a discharge opening defined by one end of a discharge conduit 30. Incorporated in the conduit 30, in the example illustrated, is a V" type valve 31. This is a valve which may be automatically controlled in a conventional manner to maintain, as required, a pressure seal across the outlet from the housing 29. The valve 15 is also of the nature to fonn a pressure seal, in this case across the inlet to conditioning tube 17. Accordingly, between the valves 15 and 31 there is a segment of the invention system the components of which are in direct and open communication and such segment is thereby conditioned to be pressurized, as required. The efiect of the open communication in said segment is that the temperature and pressure therein will be substantially the same throughout. The conditions applied in accordance with the invention will be further described.

Referring further to FIG. 1, the discharge end of the conduit 30 connects with and opens to the tangential inlet 32 of a cyclone separator 33. The latter has a generally conical shape and is provided in the top or base thereof with an overflow tube 34 defining an outlet for discharge of steam and with an underflow opening formed at its dependent apex. Through this underflow opening are discharged the fiber products resulting from the pressurized refining procedure carried out in the double disc refiner 25. Attention is directed to the fact that there is connected into the separator 33, at the point where the tangential inlet merges with the body of the separator 33, nozzle means 37. The latter are connected to a suitable source of supply to direct a shower of water under pressure, or other suitable fluid, in a sense across the tangential inlet and at right angles to the inflow therefrom. The shower functions to wet and cool down the fiber products and by the nature of its direction will produce therein an added separation.

The fiber discharge from the apex opening of the separator is directed to a cross-screw feeding device 38, of a conventional nature, which directs the fiber products issuing from the separator to a further double disc refiner 39. This last may be similar to the refiner 25 with the exception that it is open to the atmosphere and there is produced therein a condition for atmospheric refining.

It is to be understood that only so much of the system structure is illustrated and here described as necessary to enable the understanding of the present invention by those versed in the art.

Attention is again directed to FIG. 1 and particularly to valve 15. It is shown in diagrammatic form that the valve 15 is a conventional rotary valve embodying a vaned rotor 41 which includes peripheral and circumferentially spaced pockets 42. In the process of rotation, each pocket 42 successively presents itself to receive from the hopper 13 a charge of raw material, which charge it then carries to the inlet to the tube 17 for delivery therein to one end of the feed screw 18. The discharged pocket then returns to receive another charge from the hopper 13. In the example illustrated, the vaned rotor turns in a counter-clockwise direction and it will be observed that there is connected in the periphery of its valve housing a conduit to relieve from each pocket, as it approaches the valve inlet to receive a fresh charge of raw material, the steam which exists therein as a result of its communication with the tube 17. This exhaust conduit, identified as 43, connects to the tangential inlet of an exhaust cyclone separator 44. The latter includes an overflow pipe 45 for discharge of any gas or steam delivered to the separator, while the open apex of the cyclone 44 delivers from the separator any fibers which are transmitted from the rotary valve and directs the same to the bin to re-enter the system with the fresh raw material.

Note further that provided for the invention system is a steam header 46, from which steam header leads two lines identified, respectively, as 47 and 48. The one line 47 is a conventional purge line in connection with the end bells of the rotary valve 15. On the other hand, the line 48 carries steam at system pressure and has a branch in connection with the rotary valve to pressure the charge in each valve pocket immediately prior to discharge to the tube 17 and a second branch 49 connecting into the tube 17 to provide therein the desired elevated pressure and conditioning environment. There is of course conventional valving to control the delivery of the steam to the tube 17. Further illustrated is a balance line 51 the respective ends of which inter-connect with and open to the discharge ends of the tube 17 and the cross-feed tube 23. As will be readily apparent, the object of this last line is to insure a maintenance of a substantially uniform pressure in the pressurized portion of the invention system between the valves and 31.

The best way to illustrate the benefits of the invention system is a description of the process enabled thereby and in reference to an actual practice.

Let us consider the application in the invention system, above described, of chips, shavings and sawdust derived from Pinus Radiata from which has been conventionally separated foreign materials without modification of the raw material per se. In its natural state the material has a 40 to 42 per cent consistency which would indicate a moisture content of 58-60 percent. In the method of the preferred process take particular note that no liquid is added to the raw fibrous material prior to its delivery in a refined condition to the cyclone separator 33.

In the practice of the invention process there is in this instance established in the pressurized segment of the system between the valves 15 and 31, by the application of steam in a conventionally obvious manner, a pressure at a level of approximately 30 p.s.i.g. A temperature of approximately C. is thereby established in such pressurized segment which is in direct correspondence with this moderately elevated pressure. The refiner plates 27 and 28 are preferably set to produce therebetween a spacing of from 0.005 to 0.040 inches, the setting being dependent on the operating tonnage.

With the above system and conditions established, the process is conducted by the continuous delivery of the Pinus Radiata in the chip, shavings and sawdust form into the bin 10. The material is fed from the bottom of the bin 10 by the feeder screw 11 which, in accordance with the control of its speed, meters the same to drop into the hopper 13. The latter functions to successively fill the pockets 42 of the vaned rotor of the valve 15 which successively present themselves to align with the valve inlet 14. As the vaned rotor turns the raw materials in the pockets are discharged in their natural raw state to the feed screw 18 in the pressurized segment of the system. Note that in all cases there will be a uniform feed rate by the screw 18 and the cross-feed screw 23 to move the raw material rapidly from the valve 15 to the eye of the pressurized refiner. The rate is so governed that the lapsed time between the valve 15 and the eye of the refiner is approximately one minute. During this interval of time the raw material will be conditioned by the steam in the pressurized segment of the system at the pressure of approximately 30 p.s.i.g. and the corresponding elevated temperature.

The degree of temperature and the pressure is so established to provide a moderate elevation thereof which is insufficient to irreversibly change the nature of the bonding agents in the raw materials. In reference to wood it is so limited to produce only some slight degree of softening of the lignin content. This is important to the practice of the invention. Moreover, together with the temperature and pressure control, the extremely rapid movement of the raw material into and out of the pressurized segment of the invention system insures the conditioning time is so controlled that there is insufficient exposure of the raw materials which would induce, in any way, any degradation of the material fibers or their brightness by reason of the pressurized environment and elevated temperature. Further, the level and condition of the environment as specified is such that there is essentially no change in the moisture content of the raw material.

Thus, as the raw material enters the housing 29 of the pressurized double disc refiner 25, it is characterized by a lack of attendant fluid or any moisture other than that contained in the body of the material per se. As the material moves into the eye of the refiner, it is inherently and quickly flung outwardly between the operating surfaces of the refiner discs 27 and 28 and almost instantaneously flung into the pressurized chamber defined by the housing 29 and caused to exit to the discharge conduit 30, its passage therethrough being controlled by the automatically functioning valve 31 which is set to function as needs require.

As a result of the condition of the raw fibrous material as it is refined in this first stage refining unit and the environment of the pressurized segment of the system, there is delivered from the housing 29 to and through the conduit 30 fiber products consisting predominantly of fibers which are long, strong, relatively bright and extremely fluffy and nonbonding in character, the remainder being fiber bundles. Even more than this, the condition of the fiber discharge from the pressurized refining unit, which is predominantly composed of single fibers, is found to be uniquely conditioned for optimal adaptability for further treatment and refining.

In evaluating the surface structure of the fibers produced from the raw material at this point by electron microscopy, it will be found that the fiber condition is distinctive. There proves to be a degree of surface lamellation and fibrillation, serrated failure, pit border failure and irregularities which produces unobvious benefits. In contrast to prior refining procedures and proposed procedures wherein there is either essentially full chemical reduction of the lignin bond of the raw materials or a combination of a substantial solubilizing of the lignin and mechanical separation, we do not find either a flowed coating on the fibers or fiber bundles that exist in the fiber product after refining nor do we find an irreversible change of the lignin coated fiber which will preclude a ready and further treatment of the fibers, as required for high quality paper products.

So as to insure it will be understood as to what has taken place in the fibers, where wall fragments of a fiber peel off a fiber surface in the form of lamellas of varying size and shape, this is lamellation. Where microfibrils of which a fiber is comprised are detached from a fiber surface or loosened, this is called surface fibrillation. To the extent it has been possible to analyze, it would appear that surface modification of this sort is particularly effected under the conditions specified in the present invention, and such enables a more ready further working, treatment and refining of the fibers. The conditions within the ranges contemplated establish that there is no fiber degradation of a material nature in the process. In any event, the total effect of uniquely advantageous surface roughness in the end product is produced in the pressurized segment of the invention system.

To complete an understanding of the irregularities possible in the surface portions of the fibers, where there is an exposed outer layer of a fiber wall and a stepped sawtoothed modification, the fiber structure is said to be serrated. Pit border failure and irregularities at the ray crosssings derive in the first instance from failure of the hollow wall structure of a fiber and in the second instance in the course of the breaking of the fiber bundles which are normally wrapped in rays which form a tie about the body thereof. It is of interest, at the moderate elevated pressures and corresponding temperatures practiced in the process of the invention that the type of surface irregularities produced in the fibers exposes microfibrillar surface which is rich in cellulose and contains smaller amounts of hemicellulose and lignin. This is in contrast to the coating of lignin and hemicellulose normally produced in prior practice and it is believed that this contributes to the fact that in the pressurized segment of the invention system the refining conditions produce better fibers and fiber bundles having far more receptivity to further treatment in an optimal state for use and conditioning to produce quality paper products than would be normally anticipated. It is because of the nature of the irregularities produced that the fiber surfaces will after atmospheric refining then bond and behave favorably in beating and result in additional fibrillation and lamellation which are desirable to develop bond strength in effecting quality paper. It is this ability of the fiber to have induced therein additional fibrillation and lamellation which is extremely important.

Referring again to FIG. 1 of the drawings, as the discharge from the double disc pressurized refiner 25 is directed to the valve 31, the reduced raw material together with the embodied moisture content is at substantially the elevated temperature of the pressurized segment of the system. This material discharge which is in the form of fibers and fiber bundles as previously described is blown through valve 31 and to the tangential inlet of the cyclone separator 33. There is some temperature reduction immediately after the valve. At the point of entry the incoming material is hit crosswise by a quenching spray of water directed at right angles to the direction of its inflow. This wets down the fiber product consisting predominantly of fibers together with fiber bundles and reduces its consistency. The result of the conventional cyclone separating function is that any system steam is directed for discharge through its overflow nozzle while the cooled fiber product is directed through the apex of the separator in the course of a swirling motion thereof from the tangential inlet to the apex. It is noted that this procedure prevents the fiber product from being exposed, before cooling, to atmospheric conditions which would degrade its brightness. By this means, therefore, one avoids premature contact of the fiber product of the pressurized segment of the system with oxygen which would darken and degrade the fibers.

From the separator 33 the wet down fiber product is directed by way of a screw feeder 38 to an atmospheric double disc refiner 39. The latter will further refine the fiber product of the pressurized segment to increase the single fiber content. Even more, the use at this point, following the pressurized double disc refining, of atmospheric double disc refining creates a fiber condition which significantly reduces its bulk. As suggested heretofore, the refiner 39 is preferably a double disc refiner of the character described previously in reference to the double disc pressurized refiner 25.

Depending on the end use of the fiber product, one may add in sequence further atmospheric refiners. The number of added refining elements is not critical except for the requirements of the end use. Referring to the flow diagram of FIG. 3, it is there seen that the invention contemplates two refiners 39 in series for producing an extremely high quality newsprint.

In the system and process described, it has been found that not only is there a significantly improved end product but in achieving the same there has been a very significant conservation of power. Further, there is created a freeness of the fiber product to a degree required for quality paper end products. The fibers are stronger with no significant drop in tear factor. Their breaking length is improved and their brightness is maintained, irrespective of the pressurized first stage conditioning and refining segment of the system. Of most significance, however, is an unexpected reduction in bulk of the end fiber product. The significance of this lies, for example, in the fact that the fibers are found to interlace and interlock most readily so that in forming a paper sheet, one may form the same as a sheet of reduced thickness, thinner than previously possible, even though using and getting the benefits of pressurized refining. As related to newsprint, for example, this means that in a roll of given diameter one will achieve a much greater mileage of paper. This achieves an objective in constant demand by the newspaper industry.

Another feature of the invention system is that the fiber product which comes out of the pressurized segment of the system here disclosed can have essentially the same moisture content as the natural raw material which is fed into the system to produce thefiber products.

The preferred conditions in and with respect to the pressurized segment of the invention system has been described. However, there may be variations which do not materially alter its benefits and those of its process. For example, the pressure may be varied up to 10 p.s.i.g. with similar benefits and the conditioning time to the eye of the refiner varied by a minute more or less without departing from the basic concept of the invention and retaining its advantages. Also, depending on the refiner plate separation within the noted range, which is directly related to the nature of the raw material and desired end product, the I-IPD/T on may vary but in preferred environmental conditions will not exceed from about 15 to 20 HPD/Ton.

In application to certain raw materials and under certain conditions dictated by the nature of the desired end product, the system of FIG. 1 may be advantageously modified to eliminate the conditioning tube 17. In such event the outlet 16 of rotary valve 15 will be coupled directly to the inlet of the tube housing the cross feed screw 23. Thus the pressurized segment of the system between valves 15 and 31 will now be limited to include the housing for feed screw 23 and the double revolving disc refiner 25. The use and end result of the system will be essentially as previously described, the conditioning period from the valve 15 to the eye of refiner 25 being generally capable of being shortened to less than 1 minute. Brightness of the end product can be somewhat improved by this change. The further advantage is that where the material so permit there is a savings in capital investment and an added savings in power.

Further modifications of the invention system and process are illustrated diagrammatic and in flow sequence in FIGS. 3, 4 and S of the drawings. As noted in respect to FIG. 3, there is a second double disc refining procedure under atmospheric conditions to refine further the product of the first atmospheric double disc refining as previously described with reference to the system of FIG. 1. This additional atmospheric refining decreases the freeness of the fiber product previously described but produces the unexpected ability and capacity of the individual fibers discharged to interlock and interlace as incorporated in and forwarded for the creation of fiber products of a quality nature.

A modification of a different nature is exhibited in FIG. 4 of the drawings. In this instance, prior to the chip bin and the pressurized segment of the invention system, there is inserted between a primary source of supply of raw material and the chip bin 10 a press 60, preferably of the type known in the trade as a Pressafiner." In this screw press or Pressafiner there is a continuing feed from the source of supply to the chip bin 10, in the process of which feed there is a controlled pressing and squeezing of the raw materials. The net effect is to mechanically loosen, to a limited degree, the fibers of the raw materials and to simultaneously extract some of its resinous content and color bodies. This will increase the consistency of the raw material to a limited degree prior to its feed to chip bin 10 and its entrance to the valve and passage through the pressurized segment of the system as previously described. The result is that there is a further reduction of the horse power necessary for the system, in reference to the pressurized double disc refining of the raw materials. Accordingly, a primary advantage of the addition of the Pressafiner is a power saving and a reduction of the wear factor on the disc refining surfaces due to the reduced load resulting.

Looking now to FIG. 5, here in place of the Pressafiner, shown in FIG. 4, there is substituted what is known in the trade as an Impressafiner" 61. The latter functions not only to squeeze and press but as a medium to incorporate in the body of the raw material itself, some fluid which may be either water or chemical solution. It is noted that in this system the pressurized environment between the valves 15 and 31 is again as previously described.

As the natural raw material as here diagrammatically shown is delivered into and through the screw type press constituting the lmpressafiner," there is a pressing and squeezing action on the material which tends to machanically effect some separation of the fibers and to open up the raw material. A limited amount of fluid which may be water or chemical solution as above noted is metered into the housing of the Impressafiner" to provide that the same will enter the body of the fragments of the raw material to increase somewhat their moisture content. A chemical application may be used to introduce into the raw material, for example, about l to 2 percent Sodium Sulphite based on oven dry wood. In this manner, with the embodying or impregnating of the raw material with this or other conditioning chemical, properties are lent to the raw material which have the result of improving the strength and brightness in the final end product which issues from the described system. This has been proven in tests. It is emphasized that the amount of fluid introduced to the Impressafiner" is controlled to inhibit the incidence of unwanted free liquid.

It should be kept in mind that while there may be a change in consistency of the natural raw material from about 40 to 42 percent, in this instance, to 34 percent, there is still the situation that when the raw material is advanced through the valve 15 to tube 17 and feeder 23 for delivery to and refining in the refiner 25, the raw material is not accompanied by free liquid or chemical.

Therefore, there is no appreciable change in the basic invention concept as represented in the flow of block diagram of FIG. 5. Here there is only the added embodying in the fragments of raw material per se, a chemical which will produce desirable improvement in the length, strength and brightness of the resulting fibers. The system will otherwise operate as previously described with reference to the showing in FIG. I of the drawings.

In summary, the present invention concept has produced unexpected and unobvious results. It provides means for utilization of the new found advantages of refining in a double revolving disc refiner to the end of producing a quality refiner ground wood product with minimal bulk. Unique aspects reside also in the discovery of a method whereby to condition materials in their natural state without appreciably changing their moisture content, and in a double disc pressurized refining procedure which has proven to separate fibers so as to render them much more receptive and readily adaptable for a great variety of treatments for a great variety of purposes. The expansion of the market for refiner groundwood which is provided by the invention is unmeasurable. It opens new avenues for reducing the cost of high quality paper products including improved newsprint. It further provides means whereby power requirements for a system of pulp refining may be minimized with optimal advantages resulting.

It is to be kept in mind that the pressure and temperature conditions as prescribed herein together with the absence of dealing with large quantities of liquid and disposal of the same not only obviates the need for expensive fluid handling systems and controls but resulting disposal, air and stream pollution problems are obviated in the practice of the present invention. While all the theory behind the unexpected results and the benefits achieved by the present system and process have not been fully determined, it nevertheless has been established that there are advantages heretofore unobtained and unobvious in the context and area of the invention.

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.

I claim:

1. A pulp refining process comprising the steps of maintaining a refining segment ofa pulping system under seal, moving through said segment, in the initial portion thereof, raw fibrous material substantially exclusive of attendant liquid except that contained in the body thereof, during said movement subjecting said material to a conditioning fluid in a substantially gaseous state under conditions which inhibit addition to the moisture content of said raw material, in the final portion of said refining segment subjecting the raw material, which is still maintained substantially exclusive of attendant liquid except for its moisture content, to a separating action under the influence of opposed refining surfaces, one of which rotates relative the other, to produce elongate fibers and fiber bundles wherein outer surface portions are roughened to break their wall structure, said raw material being introduced into said segment in a high consistency form ranging from 30-92 percent solids, and controlling addition of the conditioning fluid to subject said raw material in said refining segment to pressure in the range of 25-35 p.s.i.g. and a correspondingly moderate elevated temperature whereby to condition the material for said separating action by producing only a limited reduction of the bonding power of the bonding agents which hold together its fibers, to contribute thereby to the surface roughened condition of the fiber products of said separating action, said separating action being effected by moving said conditioned material by opposed refining surfaces each of which rotates relative the other and in the process limiting the separation of said refining surface to a range from about 0.005 inches to 0.040 inches apart.

2. A process as in claim 1 characterized by maintaining steam in said segment under a pressure of about 30 p.s.i.g. while maintaining the separation of said opposed refining surfaces under 0.040 inches.

3. A process as in claim 2 characterized bylimiting the time interval of said raw material in said refining segment of the pulping system to a period of from approximately 5% minute to about 2 minutes.

4. A process as in claim 3 characterized by limiting the conditioning interval to about 1 minute.

5. A pulp refining process comprising the steps of maintaining a refining segment of a pulping system under seal, establishing therein an elevated pressure under 50 p.s.i.g., moving through said segment, in the initial portion thereof, raw fibrous material substantially exclusive of attendant liquid except that contained in the body thereof, during said movement subjecting said material to a conditioning fluid in a substantially gaseous state under conditions which inhibit addition to the moisture content of said raw material, and in the final portion of said refining segment subjecting the raw material, which is still maintained substantially exclusive of attendant liquid except for its moisture content, to a separating action under the influence of opposed refining surfaces, one of which rotates relative the other, to produce elongate fibers and fiber bundles wherein outer surface portions are roughened to break their wall structure, said process as applied to wood and like substance in the form of chips, shavings and sawdust separating the raw materials so as to produce in the separated fibers irregularities of a nature to expose their microfibrillar surface which is rich in cellulose, continuously forwarding the fiber discharge from said first mentioned refining segment to a second refining segment and further refining therein the fiber discharge under atmospheric pressure condition to produce elongate, soft, strong fibers having a tendency to interlace and interlock, in the process of forwarding the fiber discharge to said second refining segment cooling and quenching the same, and in said second refining segment subjecting the cooled product to atmospheric refining between double revolving opposed refining surfaces.

6. A pulp refining process comprising the steps of maintaining a refining segment of a pulping system under seal, establishing therein an elevated pressure under 50 p.s.i.g., moving through said segment, in the initial portion thereof, raw fibrous material substantially exclusive of attendant liquid except that contained in the body thereof, during said movement subjecting said material to a conditioning fluid in a substantially gaseous state under conditions which inhibit addition to the moisture content of said raw material, in the final portion of said refining segment subjecting the raw material, which is still maintained substantially exclusive of attendant liquid except for its moisture content, to a separating action under the influence of opposed refining surfaces, one of which rotates relative the other to produce elongated fibers and fiber bundles wherein outer surface portions are roughened to break their wall structure, and mechanically loosening the fibers of the raw material prior to said refining segment.

7. A process as in claim 6 characterized by introducing conditioning fluid in the body of the raw material having loosened fibers to the extent it will accommodate the same, immediately prior to the said refining segment, and inhibiting in the process free liquid attending the raw material in moving to and between the opposed refining surfaces.

ill

8. A system for refining fibrous materials comprising a double revolving disc refiner, means for feeding raw fibrous material to said refiner in fragment, shavings and dust form and means for directing said materials from said disc refiner for further treatment characterized by means sealing therebetween at least a portion of said feeding means and said disc refiner to provide in said system a pressurized segment thereof, and, applied to said pressurized segment, means to provide a controlled and limited weakening of said raw material in an environment wherein there is essentially an absence of free liquid, said refiner receiving the weakened material and providing means for a breaking and fibrillation of surface portions of the separated fibers.

9. A system as in claim 8 characterized by said weakening means including steam delivery means for establishing in said pressurized segment a pressure not greater than 50 p.s.i.g. and a correspondingly moderate elevated temperature.

10. A system as in claim 9 characterized by an initial portion of said feeding means including means for pressing and squeezing said raw material to partially loosen the bond between fibers thereof prior to the material entering said pressurized segment and moving to and between the double revolving discs therein, thereby providing in part said weakening means.

11. A system as in claim 9 characterized by means connected to said pressurized segment for mechanically loosening fibers of said raw material prior to entering said pressurized segment and applying in the body of said material conditioning fluid in a manner to inhibit the creation of free liquid attendant the raw material as fed to said pressurized segment.

12. A system as in claim 8 characterized in that the double revolving discs of said refiner are opposed and have the operating surfaces thereof spaced apart a distance not greater than about 0.040 inches.

13. A system as set forth in claim 12 characterized by said operating surfaces being spaced apart a distance between about 0.005 to 0.040 inches.

14. A system as set forth in claim 8 and including means for quenching and cooling the fiber products issuing from said pressurized segment prior to direct exposure thereof to atmosphere.

15. A system as set forth in claim 14 characterized by said quenching and cooling means being embodied in a cyclone separator in connection with said double revolving disc refiner to receive its discharge, said quenching and cooling means being positioned at the entrance to said cyclone separator.

16. A system as set forth in claim 15 characterized by said quenching and cooling means being arranged to direct fluid directly across the inflow of the discharge from said double revolving disc refiner to said cyclone separator.

17. A system as set forth in claim 16 characterized by at least one atmospheric double revolving disc refiner connected with said cyclone to receive the fiber products discharge therefrom and to apply thereto a secondary atmospheric refining whereby to produce elongate strong fibers having a tendency to interlace and interlock and to achieve a reduced bulk form.

18. Apparatus as set forth in claim 17 characterized by a second atmospheric double revolving disc refiner in series connection with said secondary refiner.

19. Apparatus as set forth in claim 18 and mechanical means forming part of said feeding means for loosening fibers of the raw material prior to disc refining.

20. A pulp refining system comprising means for conditioning raw fibrous material to only partially weaken the agents which bond its fibers, further means to act thereon to reduce the same to elongate fibers and fiber bundles and means to control the pressure of the environment of said conditioning and refining means providing that said fibers and fiber bundles issue from said refiner with surface portions thereof lamellated and fibrillated.

21. A pulp refining process comprising the steps of defining a closed refiner segment including a treatment chamber and beyond said chamber a disc refiner comprised of opposed counter rotating double discs, putting raw fibrous material through said segment first through said chamber and then between the discs of said double disc refiner, admitting steam to said segment to maintain pressure and temperature conditions therein of such elevation to be insutficient to irreversibly change the nature of the bonding agent in the raw materials and in the case of wood to produce a limited degree of softening of the lignin content, cooling the fibrous material after its discharge from said refiner, and establishing a brevity of time and closed condition of confinement of the fibrous material in its movement through said segment and to and through said cooling step to obviate degradation of the material fibers and their brightness.

22. A pulp refining process according to Claim 21 wherein the opposed discs are set to define a clearance therebetween on the order of0.005 inches to 0.040 inches.

23. A pulp refining process according to claim 21 wherein the step of defining a closed refiner segment includes the provision of valves at opposite ends of said segment, at least one of said valves being a rotary valve containing supply pockets communicating successively with said segment in response to rotation of the valve.

24. A pulp refining process according to claim 23 wherein said rotary valve is positioned at an input end of said refiner segment intermediate said segment and a supply bin containing dry raw fibrous material, further characterized by the steps of utilizing pressure fluid to scavenge pockets of said rotary valve after communicating with said segment and of returning scavenged material to said supply bin under conditions inherently separating pressure fluid from the returned material and discharging separated pressure fiuid away from said supply bin.

25. A pulp refining process according to claim 21 wherein the pressure in said refiner segment is maintained at about 30 p.s.i.g. with a corresponding temperature ofabout 135 C.

26. A pulp refining process according to claim 21 wherein the step of cooling refined material is carried out in a centrifugal separator disposed beyond said refiner segment and to which material discharged from said refiner is conducted under conditions excluding the refined material from atmospheric contact, a substantial separation of fluids from the refined fibrous material occurring in said separator.

27. A pulp refining process according to claim 26 wherein cooling is effected by spraying liquid into the centrifugal separator at a location substantially to intersect the path of incoming fibrous material discharging from said refiner.

28. A pulp refining process according to claim 21, characterized by the step in said double disc refiner of breaking and fibrillating surface portions of the natural fibers in said fibrous material.

29. A pulp refining system, comprising means defining a closed refiner segment including a treatment chamber and beyond said chamber a disc refiner having opposed counter rotating double discs, means for putting raw fibrous material through said segment first through said chamber and then between the discs of said double disc refiner, means for admitting steam to said segment to maintain pressure and temperature conditions therein of such elevation to be insufficient to irreversibly change the nature of the bonding agent in the raw materials and in the case of wood to produce a limited degree of softening of the lignin content, means for cooling the fibrous material after its discharge from said refiner, means establishing a brevity of time and closed condition of confinement of the fibrous material in its movement through said segment and to and through said cooling step to obviate degradation of the material fibers and their brightness, and means operable in the double disc refiner to break and fibrillate surface portions of the natural fibers in said fibrous material.

30. A pulp refining process according to claim 26, characterized by the step of subjecting cooled separated fibrous material discharging from s aid centrifugal separator to additional refining under conditions of open atmospheric communication.

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Classifications
U.S. Classification241/18, 241/28, 241/161, 241/29, 241/65
International ClassificationD21D1/30, D21B1/12, D21D1/20
Cooperative ClassificationD21D1/303, D21B1/12
European ClassificationD21D1/30B, D21B1/12