WO1979000789A1

WO1979000789A1 - Method and apparatus for disintegration of fibrous material

Info

Publication number: WO1979000789A1
Application number: PCT/SE1979/000058
Authority: WO
Inventors: A Asplund
Original assignee: A Asplund
Priority date: 1978-03-17
Filing date: 1979-03-15
Publication date: 1979-10-18
Also published as: NO790909L; GB2075862B; SE421217B; JPS6257755B2; EP0014199A1; SE8104758L; GB2075862A; FI68269B; JPS55500156A; NO150288C; NO150288B; FI68269C; CA1102158A; US4199114A; FI790902A

Abstract

Method and apparatus for controlling the refining of fibrous lignocellulose pulp material in which the pulp stock or grist is conveyed into a cylindrical stationary drum (10) and propelled therein in a linear direction in a pulsating fashion by a co-axial rotor (14) comprising a plurality of impellers (21) which attack the grist in a wedging action as it is compacted by the centrifugal force of rotation and pushed ahead of the leading edges of the impellers (21) and thus inducing in the grist internal frictional shear forces while it is forced through a gap defined between the terminal edges of the impellers (21) and a series of shear members (12) arranged axially along the interior surface (11) of the drum (10). The shear members (12) are detachably and adjustably anchored in slots in the peripheral wall of the drum (10) to vary the gap clearance. A plurality of adjustable plow members (34) for enhancing the linear flow of the grist through the drum (10) may be additionally mounted in the peripheral wall of the drum (10) to extend radially inwards to engage accommodating slots (35) in the impellers (21) to thereby regulate the amount of grist pushed ahead during each revolution of the impellers (21) and to control the centrifugal force exerted on the grist.

Description

Method and apparatus for desintegration of fibrous material

My invention relates to a method and machinery for the production of pulp and for postrefining of such pulp from fibrous 1 i gno-cel 1 ul ose raw materials for the production of paper, paperboard, fiberboard, formed products for shipping containers, dry formed board and many other useful products. The invention can also in certain cases be used for disper¬ sion and pulverizing of ceramics and other products, which for its further manufacture has to be kneaded or mixed with other additives. The material under processing will in the following be called "grist". The invention comprises a process where^* the material within a closed, or nearly closed, cylinder in the following called the "drum" is packed and accelerated by a rotary member concentric with the cylinder and equipped with blades, in the following called "impellers" compressing by centrifugal force the grist in a radial direction against the walls of the drum and the refining members in the following called "staves" located on the inside wall of the cylinder or drum equipped with edges perpendicular to the path of the accelerated grist, moving between the rotating impeller and the stationary edges creating within the grist surfaces of fiber refining fric- tional forces.

According to the Swedish patent No. 326 097 granted the applicant a similar method is disclosed where the inside wall of the cylinder in the axial direction is equipped with grooves of limited radial extent where small quantities of the grist is retarded whereas at the same time ^"the impellers keep the main part of the grist in rapid rotation. The layers of grist moved by the impellers and the layers of grist retarded by the grooves on the inside of the cylinder are refined in the surface of friction created between the two layers of grist. The obstructions formed by the grooves according to the known method follow each other with gradual slopes in order that the refining action shall be accomplish- ed mainly through the internal friction created between the fibers themselves when they pass the concentric slot between the impellers and the undulations of the inner wall of cyl inder.

The purpose of the present invention is to furth improve the refining action of a refiner working accordi to the above described principle in order to obtain a m efficient fibril1ization and a separation of fibers and fibrillae creating a pulp with properties well suited f the manufacture of paper and similar products. This is attained mainly through a simultaneous action on the co pacted grist by centrifugal forces creating surfaces of internal friction when it is acted upon by external for from edges of refining members arranged on the inner periphery of the closed cylinder slicing the surface la of the fibers. A drum designed according to the inventi can along its inside wall be equipped with axially arra refining members, suitably with rectangular cross secti which are made from harder material than the material o the drum and which with their edges cooperate with the impellers to refine the fibers of the grist. These refi members thus have the form of staves following the insi wall of the drum generally only protruding 1 to 2 mm fr the wall with a suitable distance from each other of 20 or more or less considering the refining effect desired. The surface of the drum between the staves can follow th cylindrical form of the drum or may be formed as slightl deepened grooves as shown on the accompanying drawings. final refining of the raw material is according to the i vention accomplished by the action on the grist both thr the use of the frictional surfaces created within the g as well as through the slicing action on the fibers crea when the body of grist with high velocity moves past the edges of the refining staves. A refiner according to th vention will have a higher capacity than the previously known design. The refining effect is created by the retarding action obtained on the flow of grist when it with high v city moves perpendicularly past the edges of the staves. The staves arranged perpendicularly or nearly so on the inner surface of the drum have a powerful retarding effect on the flow of the compacted grist and intensive sur¬ faces of friction are created because of the great diffe- rence in velocity between the fraction of grist retarded by the edges and the part of grist which continues to rotate with the impellers. When one part of the grist is retarded by the edges of the staffs and the other part continues to move the grist will be acted upon not only between the inter- nal surfaces of friction developed between the stationary and moving portions of the grist but also by direct mechanic¬ al action on the grist of the edges of the staves result¬ ing in an intensive and extended separation of the fibers. The staves on the inside wall of the drum are suit- ably held in axially milled grooves of such a depth that o-ne of the lengthwise edges protrudes somewhat, for instance one or two mm from the inside wall of the drum.

The invention is especially well suited for the pre¬ paration of ther o echani cal pulp as well as for post refining of paper pulp in general.

The raw material fed into the refiner is accelerated by the impellers of the rotor throwing it against the inside wall of the drum. According to the Swedish patent No. 326097 it is known to utilize a plough, which can move the grist axially. The ploughing action according to the invention has been improved by extending the ploughs radially into corres¬ ponding slots in the impellers. The axial flow of the grist under processing in the drum is thus facilitated when the stationary ploughing members extend further into the flow of grist carried by the impellers.

By this steering of the grist the amount of grist can be increased or decreased. At a constant rotary speed of the rotor a varying pressure will be exerted by the grist against the staves depending on which amount of compacted grist is allowed to accumulate on the impellers.

The magnitude of the pressure in the zone of refining is also depending upon the angle of the surface of the impellers has in relation to their direction of rotation.

^*. -'PI If these surfaces are directed radially the outward forc on the grist will be lower than when they have a negativ angle in relation to the direction of rotation^'. The effe of the refiner can therefore be adjusted by an exchange impeller or by changing the angle of the impellers.

The grist is here compressed in the wedge-formed space between the modified impeller 23 and the inside su face 11 of the drum 10 the here highly compacted body of the grist is sliced by the edge 19 of the stave 12. The smaller the angle the higher compression is obtained.

The refining members or the staves are preferably made from ceramic material e.g. from silicon carbide, wh has a great resistance against wear and therefore will longer retain their angle of attack against the grist. A the same time the crystalline properties should favour t retention of the refining properties of their active edg

Refining bars of cobalt bound wolfram carbide can also be used. Further, it is of importance that the edge do not protrude too far from the inner surface of the dr generally from 1 to 2 mm inwardly in order to efficientl utilize the maximum slicing effect.

The mounting of the staves in their slots makes i possible to remove them and anew insert them in a new po tion to utilize all four edges before discarding them or renew their refining ability by regrinding the edges.

The geometrical form of the working edges of the staves should on account of the natural wear be 90° with about 1° give in negative direction. The invention will in the following be described references to annexed drawings exemplifying possible des of the refiner.

In Fig. 1 is shown a section along the line I-I i Fig. 2, which shows a view from above of a refiner and feeding device with the upper half of the refiner remove In Fig. 3 is shown a cross section of a part of t refiner drum and rotor. In Fig. 4 is shown an end view of two ploughs regulating the axial flow of the grist through the refiner.

In Fig. 5 is shown a cross section through part of the refiner drum and two ploughs shown in Fig. 4, seen in the transverse direction of the refiner.

In Fig. 6 is shown a cross section of the refiner drum and plough seen in the longitudinal direction of the refiner.

In all of the drawings the same numerals have been used for corresponding parts.

In Figs. 1 and 2 is shown a side view and a view from above of a refiner intended for industrial use for the production of mechanical refiner pulp or thermomec ani c- al pulp (TMP). The refiner has one rotor 14 with four impellers 21. The drum 10 is equipped with refiner means 12 made from material with a higher wear resistance than the material of the lining of the drum. In Fig. 1 the flange 42 (Fig. 2) is removed to show the transport screw 15 which feeds the preheated chips into the refining zone where they are accelerated by the rotating impellers. The drum 10 of the refiner according to Fig. 1 and Fig. 2 is at both ends closed by flanges 40 and 42 with openings for the shaft 22. The shaft 22 passes through the flange 40 through a packing box 41 and at its other end through the flange 42 through a packing box 43. The refiner can therefore be used for refining at elevated temperatures as in thermomechani cal refining of wood.

The refiner is equipped with a preheater 62 where the chips are brought up to the temperature required for TMP refining. The chips are fed into the TMP refiner by the feeder 60 and the finished pulp leaves the refiner through the exhaust valve 16 and pipe 17. The capacity of the re¬ finer is regulated by means of the feeder 60 and the exhaust valve 16. The feeder 60 can be of a continuous screw type preventing steam to escape from the inside of the drum. In the drum can be maintained an elevated steam pressure by the admission of steam or by the use of the steam developed during the refining process from the moisture present in grist.

The rotor 14 can be rotated with a motor (not sho by a shaft 22. The impellers 21 on the nave 20 of the ro are on the drawing four in number, but may be eight or m depending upon the capacity of the refiner. The impeller are extended towards the inside surface of the drum wher on the unit shown staves 12 are shown with a rectangular cross section inserted in grooves 13 here axially machin in the inside surface 11 of the drum as shown also in Fi These staves 12 as well as the impellers 14 cover the wh or practically the whole part of the inside of the drum The grooves 13 follow the inside wall of the drum and ar preferably arranged as diametrically opposite pairs and therefore passed simultaneously by two likewise diametri ly opposite impellers 21. These impellers 21 extend to a limited distance from the staves 12 as is indicated by t 'broken line 18 in Fig. 3.

The staves 12 are made from a highly wear resista material as for instance silicon carbide or carborundum shown with rectangular cross section. They are to the ma part of their width sunk into the grooves 13 and extend only one or two mm above the inner wall of the drum. The rectangular cross section of the staves may be 3 x 15 o 4 x 18 mm. They thus form edges along their lengthwise s having an angle of 90° or near so.

The mode of application of the staves 12 in the s 13 of the cylinder segments 45 is of importance for tech al functioning of the refiner and how well it will funct economically.

The height of the operating edge 19 of the staves above the inside surface 11 of the drum (Fig. 3) is of g importance for the creation of the frictional surfaces wi the moving grist and how the surface of the single fiber be influenced by the edge. If the depth of the slot is m equal or nearly equal to the width of the stave 12 the chosen height of the edge 19 is determined by a metal st 44 introduced at the bottom of the slot. The side of the

OV ^" staves 12 is thereafter coated with a metal adhering glue and pressed down securely. The stave 12 should be held in place until the glue has set sufficiently. When the refiner is used for the production of thermomechanical pulp the heat resistance properties of the glue has to be considered. The drum can also be equipped with one or more radial holes 37 for each stave along the slots 13, where tools can be used for the removal of the staves 12. The exchange of the staves 12 is thereby facilitated and the unused edges of the staves can be successively utilized. The staves 12 can also be resharpened.

The depth of the slots should preferably be such that a working distance of the edge 19 above the surface 11 from 0.5 up to 2 or 3 mm can be selected. Under special conditions a greater distance may be considered but should not exceed^' 10 mm as then the uniform flow and exchange of material in the space walled in by the staves may be disturbed.

The length of the period of service of the function¬ ing edge of the refiner staves is depending upon the abrasive action and when staves of metallic origin are used also upon the chemical action by certain components of the grist. The edge will be rounded off also by uncontaminated raw material, an action which can to a yery high degree be accelerated by mineral contaminants. I have found that the selection of staves made from mineral material is important and that for certain types of refining the best results are obtained with materials which do not easily take polish but which develop a course surface when worn.

The refiner can preferably be equipped with imple- ments 30 for maintaining and regulating the axial flow of the grist through the refiner from the feeder to the outlet. A number of such axial flow feeders is shown in Figs. 3-6. They have each a cylindrical tampion 31 turning in a hole 32 in the drum 10. The tampion 31 can from the outside be turned and locked in desired position by the locknut 33 held by means of lock nuts 46, 47 in a holder 48 for the tampion 31. The tampion 31 also holds a connection 29 for addition of water, chemicals or the like through an axial channel in the tampion 31.

The tampion has on its inside a plough 34 extendin inwardly in radial direction passing through the space between the staves 12 and the impellers 21. In the impell are made corresponding openings 35 to allow the impellers to pass (Fig. 5). By turning the plough 34 from a true radial position 34a indicated with broken lines in Fig. 4 to a desired angle, the axial flow of grist through the refiner can be adjusted to maintain a desired refining action of the refiner.

The tampion 31 with its plough 34 can also be move by the nut 33 in radial direction and locked in its posi¬ tion by the locknut 46 to increase or decrease the amount of grist moved at each passage of the impellers 21 past the plough 34.

By the angular and radial positioning of the tampi 31 and the plough 34 the amount of grist carried by the impellers 21 can thus be regulated and thereby can also t pressure created by the centrifugal force on the grist against the refining edges 19 be changed within wide limi

The faster the grist is moved axially through the refiner the less weight of grist is carried by the impell 21 per unit of time. The pressure against the edges will then decrease.

As is indicated in Fig. 3 the inside surface 11 of the drum 10 can be either purely cylindrical or be given suitably profiled grooves 36 between each pair of staves The grooves may be given a soft streamline contour. When rotating in the direction indicated by the arrow 38 (Fig. 1) the grist will be carried by the separa impellers 21 in smaller or greater quantities depending mainly on the quantity of grist fed to the refiner and th adjustment of the ploughs 34. As can be seen from Fig. 1 and Fig. 3 the angle between the impeller 21 and plough 3 is negative or a little less than 90°. A greater quantity carried by the impellers creates a higher pressure of the

^• '.PI grist against the edges of the staves 12 resulting in a more active refining action.

To increase the flow of grist towards the outlet the diameter of the drum may be enlarged to a conicity of 1:100 or even more to obtain the desired flow.

After entering the refiner the grist is accelerated by the impellers 21 and by centrifugal forces compacted in rotating flow along the inside surface of the drum. The grist may here move with a velocity of from 20 to 60 m per second or more depending upon the inside diameter of the drum and the speed of the rotor. When the body of the flowing grist is retarded by the edges of the staves inten¬ sive refining forces are developed acting on the fibers and simultaneously developing internal shearing forces fiber against fiber in the body of grist.

The kinetic energy of the parts of the grist brought to a full stop will be transformed into heat increasing the temperature of the grist causing a part of its water content to evaporate. Depending upon the moisture content of the chips water may therefore have to be added to the grist to prevent a harmful decrease in moisture ratio.

It has been observed that in the space along the surface between the staves no harmful retention of fiber pulp will take place. The flow of grist is sufficient to prevent stagnant pulp to accumulate.

By microscopic observations of pulp from spruce wood refined for production of news print it has been established that the refining action on the primary and secondary layers of the tracheids is even more advantageous than the effect obtained by conventional disc refiners.

Stroboscopic observations made of the flow of grist inside the refiner under operation show that the particles of the grist after having been retarded by the edges of the stave lose their speed and after having passed across the edges are collected on the surface of the next impeller where it accumulates the weight necessary to build up the desired refining pressure as it is again shaved off against a following stationary edge.

The accumulation of grist on the impellers is full at random and a large portion of the fibers have lost most of the stiffness characteristic for conventional mechanical pulp.

Claims

What I claim is

1. The mechanical pulping process of fiberizing and refining 1 ignocel 1 ulosi c materials e.g. chips from wood for the purpose of producing paper where the chips are accelerated by one within a drum (10) arranged rotating member (20) with multiblade impellers (21) compacting the flow of grist moving under the centrifugal force generated by the impellers (21) carrying the grist into the space (18) between the inner wall (18) of the drum (10) and the free edges of the impellers (21) causing frictional surfaces within the grist and forces separating the fibers from each other and through the impact and following sudden retardation against the edges (39 in Fig. 3) of refining members (12) protruding from the cylindrical inner wall of the drum creating a slicing and scouring action on the surface of the fibers causing a fibrillation improving the papermaking properties of the pulp produced.

2. An apparatus according to Claim 1 comprising: a stationary cylindrical or nearly cylindrical drum (10), inside the drum (10) a concentrical rotor (20), said rotor having a number of impellers (21) with front edges rotating at a narrow distance from the edges of stationary refining members (12), inserted on the inside circumference of the drum, said members (12) made from harder material than - the drum.

3. An apparatus according to Claim 2 where the stationary refining members (12) are to the main part of their radial dimension anchored in axial slots of the drum (11).

4. An apparatus according to Claim 3 where the stationary refining staves are detachably anchored in slots of such design that they can be attached in four different positions, enabling each lengthwise edge to be successively utilized in the refining of the grist.

5. An apparatus according to Claims 2 - 4 where the inside surface between the staves (12) of the drum (10) is cylindrical or nearly so.

6. An apparatus according to Claims 2 - 4 where the inside spaces of the drum (10) between the staves (1 have perpendicularly to the axis of the drum (10) the fo of a trough (36) hindering the grist to accumulate again the staves.

7. An apparatus according to Claim 2 where the cylindrical drum (10) at its inlet end is equipped with a feeder of screw type or rotary pocket type and on its outlet end is equipped with an adjustable exhaust valve (16) the apparatus thus being constructed for maintainin superat ospheric steam pressure during the processing of the grist.

8. An apparatus according to Claim 7 with from the outside adjustable ploughs (34) which' create an axia flow of the grist from the inlet end to the outlet end o the drum (11, Fig. 3), the ploughs extending from the inside wall (11) of the drum (10) radially inwardly past the path of the impellers through apertures at the edges of said impellers.

9. An apparatus according to each of the Claims 1 - 8 where the drum (10) has a slight conical inner surface with its greater diameter at the outlet end of the drum (10).

10. An apparatus according to Claim 3 where the stationary .refining members (12) are adjustable in the axial slots of the drum by means of spacers (44) in the bottom of the slots.