REFINER

Abstract: A refiner, preferably a disc or conical refiner, with two opposed, closely spaced bodies of which at least one, the so-called rotor (2), rotates and which are provided with blades (4, 8; 5, 9), the material to be refined being ground in the grinding gap between them, releasing steam, said matter to be refined being fed into the refiner substantially in the direction of the central axis of the blades. In existing refiners, endeavours have been made to remove steam from the refining process e.g. by making holes in the rotor. However, these holes tend to be blocked, and no finely ground material passes therethrough out from the process. With the aid of the present invention the problems have been eliminated in that the grinding gap contains a sorting zone in which the more completely ground fraction of the material to be refined and part of the steam separate from the less completely ground fraction.

Description: Ref i ner The present invention concerns a refiner, preferably a disc or conical refiner, with two opposed, closely adjacent bodies, wher one at least, the so-called rotor, rotates, and which are provid with blades, the material to be refined being ground in the grinding gap between them and releases steam, said material to b refined being fed into the refiner substantially in the directio of the central axis of the blades. Dispersing of a fibreous substance, for instance wood chips, to become fibres fit for use i n paper manufacturing may be accompli ed mechanically with a refiner, examples of such being a disc refiner and a conical refiner. This so-called defibration iε accomplished in that the chips are introduced into the refiner, whereto the material passes through between two opposed grinding blades. The surfaces of the blades are full of grooves and elongated eminences, teeth, and at least one of the blades rotat whereby the material is powerfully worked while passing through between the blades, and it is dispersed up to single fibre consistency. In the refining process plenty of steam iε produced and several ways have been tried to solve its removal. One problem solution i to mak apertures through the disc in a disc refiner, to the inpu or to the exit chamber. Such designs also exist in which passages piercing through the blade have been provided, and for them, continuation passages through the disc. A design is also known in the art in which steam removal passages have been formed through the disc and behind the disc are further provided continuation passageε. The aim of such solutions is merely steam removal, that is, they do not remove material which has already been properly ground, and the most difficult problem encountered in all of them is blocking of said passages or escaping of steam, in which case the steam escapes completely from the blade gap, and the operatio is disturbed. Such blocking is primarily due to the fact that the dimensioning cannot be made such that the flow could keep the passages open. The object of the present invention is to provide a refiner in which not only steam removal works properly but the more perfectly ground material travels together with the steam out from the blade gap and thereby reduces excessive refining. Said aim is implemented in the refiner of the invention, which is characterized in that the grinding gap comprises a sorting zone in which the more completely ground fraction of the material to be refined, and part of the steam, are separated from the less completely ground fraction. An advantageous embodiment of the invention iε characterized in that the sorting zone is located, in the radial direction of the blades, substantially at their centre, and that the sorting zone is substantially annular. Another advantageous embodiment of the invention is characterized in that in the stationary body, i n the so-called stator, is provided a substantially annular aperture close to the sorting zone, through which said removal of the more completely ground fraction and of the steam takes place. One more advantageous embodiment of the invention is characterized in that the sorting zone comprises a projecting, substantially annular member formed on the rotor, which extends into an annular aperture in the stator, whereby an exit passage for the more completely ground material and for the steam is defined between the annular member and the annular aperture. One more advantageous embodiment of the invention is characterized in that the mutually opposed surfaces of the annular member on the rotor and the mating aperture in the stator are fitted with blades. Among the most important advantages of the invention may be mentioned that the exit apertures are not susceptible to blocking and that the quantity of escaping steam and more completely ground material may easily be controlled. The pressure in the removal chambers for the constituents passing by different routes can similarly be controlled, independent of each other. The invention is described in the following in detail with the a of advantageous embodiment examples by referring to the drawings attached in which - Fig. 1 presents a vertical section of a disc refiner according t an embodiment of the invention. Fig. 2 presents a vertical section of a disc refiner according t another embodiment of the invention. Fig. 3 presents a vertical section of a disc refiner according t third embodiment of the invention. In Fig. 1 is presented a disc refiner comprising a stationary bod 1, or stator, and a rotating body 2, or rotor. The stator 1 and rotor 2 are on their mutually opposed surfaces provided with a stator blade 4,8 and a rotor blade 5,9. Into the so-called grindi gap between the blades is fed matter to be refined, such as wood chips, through a feed passage 3 with the aid of centrifugal force The material to be refined proceeds, to begin with, between the stator blade 4 and the rotor blade 5, whereat part of the materia is ground to the desired degree of fineness, and steam is produce at the same time. The refiner of the invention iε provided with a sorting zone whic in the embodiment of Fig. 1 consists of an annular, projecting member 6 attached to the rotor 1 and of a likewise annular apertu established for it in the stator 2 and extending into the stator chamber 3. While the annular member 6 is projecting, it also extends obliquely inwards towards the central axis of the refiner The surfaces facing each other of the annular member 6 attached t the rotor 1 and of the mating aperture formed in the stator 2 are provided with blades 10,11. At this point, however, the blade gap is larger than in the grinding gap proper between the blades 4,5 and 8,9. The annular member is provided with numerous radial aper ures 7 extending therethrough. The more completely ground material and part of the steam emergin from the gap between the blades 4 and 5 depart through the gap between the blades 10 and 11, or the exit pasεage into the stator chamber 13, and therefrom further to an exit 14 provided with a valve 15. The less completely ground constituent and the rest of steam pass through apertures 7 formed in the annular member, into the space between the blades 8 and 9, where the material is ground and proceeds under centrifugal force effect towards the refiner chamber 12 and thence to further treatment. In Fig. 2 is presented another embodiment of the invention, in which the stator 1 is located on both sides of the rotor 2. The stator iε provided with blades 16,17. The rotor in turn iε provided with blades 18,19,20. The rotor shaft is indicated by reference numeral 21. The feed tube for material to be refined iε indicated with reference numeral 3. The removal chamber for refined material in turn carries the reference numeral 12, as in the preceding figure. Between the refiner blades 22 and 23 are defined grinding gaps 22,23,24. Between the grinding gaps 22 and 23 iε located a sorting space 25, from which several passages 26 depart through the rotor 2, and which terminate in an annular space 27. The operation of the refiner of Fig. 2 is as follows. The material to be refined is fed fr-ofn the tube 3 into the grinding gap 22. W_en diεcharging into the space 25, the material contains fine-ground material and coarse, less finely ground material. From the gap 22 also a strong steam flow discharges because the powerful grinding evaporates a great part Df the water contained i n the material to be ground. Centrifugal force feeds material from the space 25 into the gap 23, where the material is more completely ground. The grinding gap 23 is so shaped that its initial part is spacious, i.e., material is admitted into the gap, while the ultimate part is very narrow. Therefore, the steam produced in the gap 23 dischargeε into the space 25, and thence further through the passages 26 into the space 27, and through the grinding gap 24 into the removal chamber 12, because the gap 24 iε short in comparison with the gap 23, and has no narrow portion like that in the gap 23. This steam flow transportε the fineε along with itself from the initial part of the gap 23, and from the space 25 through the gap 24 into the removal chamber 12. The coarse material remains in the initial part of the gap 23 by centrifugal action (the passages 26 also run against the centrifugal force) until it is finely ground and the iε removed, entrained with the steam. In Fig. 3 is presented one more embodiment of disc re iner emplo ing a sorting zone. Therein, the stator of the refiner is indica by reference numeral 28, and the stator blades with 29,30,31 and 32. The rotor is indicated by reference numeral 33 and its shaft numeral 34. The front bearing of the shaft iε indicated by numer 35 and the packing, by 36. Material to be ground is fed through feed tube 37. The removal chamber for refined material carries t reference numeral 38. The rotor 33 is provided with apertures 39 extending therethrough. The grinding gaps are indicated by reference numerals 40,41,42 and 43. In the initial part of the grinding gaps 42, in register with the apertures 39, is defined a sorting space 44, communicating with the space 45 through the apertures 39. From the sorting space 44 departs a sorting and transport gap 46, terminating in an annular space 47. The walls o the gap 46 present eminences 48 and 49. The operation of the refiner depicted in Fig. 3 iε as follows. Th material to be re i ed is fed through the tube 37 into the grindi gap 40 whence it discharges into the space 45 in partly ground condition. The apertures 39 are short and wide, whereby material immediately also supplied into the εpaceε 44. From the εpaces 44 and 45, centrifugal force feeds material into the grinding gaps 4 and 42, and which operate in like manner as the gap 23 in Fig. 2. It is thus understood that the steam produced in the gaps 40,41 a 42 discharges through the wide sorting gap 46 into the space 47, and through the low-resistance grinding gap 43 into the removal chamber 38. Along with the steam, the finely ground material is removed, like in Fig. 1. The gap 46 operates more efficiently than the passages 26 depicte in Fig. 2 because its walls are in motion relative to each other. The gap 46 may therefore be made considerably narrower without in ¬ curring risk of blockage, whereby high velocity and transporting effect of the steam is achieved. Departure of the coarse fraction The ultimate part Df the grinding gapε 41 and 42 may be almost totally dammed by the alternative implementation depicted in the bottom part of the figure, i n which the removal chamber is made to be very narrow at said gapε. In addition, teeth may be provided on the outer margin of the diεc, at the point 50, which comminute εuc material which has already entered the chamber and mix it so that it ends up back in the gap and i n sorting. It is obvious to a person skilled in the art that the invention is not confined to the above preεented embodiment examples, and that it may be varied within the scope of the claims following below. For instance, the invention does not exclusively concern disc refiners: it may equally be applied also to conical refiners.

Claims: C l a i ms 1. A refiner, preferably a disc or conical refiner with two opposed, closely spaced bodies, of which at least one, the so-called rotor (2), rotates and which are provided with blades (4,8;5,9) the material to be refined being ground in the grindin gap between them, releasing steam, said material to be refined being fed into the refiner substantially in the direction of the central axis of the blades, characterized in that in the grindin gap is defined a sorting zone in which the more completely ground fraction of the material to be refined and part of the steam separate from the less completely ground fraction. 2. Refiner according to claim 1, characterized i n that the sorti zone is located, in radial direction of the blades (4,855,9), substantially at their centre, and that the sorting zone is substantially annular. 3. Refiner according to claim 1 or 2, characterized in that in t stationary body, in the so-called stator (1), is established a substantially annular aperture close to the sorting zone, where¬ through said removal of the more completely ground fraction and o the steam takes place. 4. Refiner according to any one of claims 1 to 3, characterized that the sorting zone comprises a projecting, substantially annul member (6) formed on the rotor (2) and extending into an annular aperture in the stator (1) and in which several radial apertures (7) are formed, whereby a removal passage for the more completely ground material and for the steam is formed between the annular member (6) and the annular aperture. 5. Refiner according to claim 4, characterized in that the mutua ly opposed surfaceε of the annular member (6) on the rotor (2) an the mating aperture in the εtator (1) are fitted with blades (10, 11) . 6. Refiner according to claim 4 or 5, characterized in that the gap between the annular member (6) on the rotor (2) and the matin aperture in the stator fl), the removal paεεage, iε larger than th grinding gap between the rotor blade (5,9) and the stator blade (4,8). 7. Refiner according to any one of claims 4 to 6, characterized i that the diameter of the annular member (6) at the point fartherst away from the rβtor (2) is smaller than that at the rotor. 8. Refiner according to claim 1 in which the stator (1) is locate on both sides of the rotor (2), whereby the grinding gap (22,23,24 is established on both sides of the rotor, characterized in that the sorting zone comprises paεεages (26) passing through the rotor (2) from the first grinding gap (22,23) to the second (24). 9. Refiner according to claim 8, characterized in that the paεεages (26) run obliquely towards the shaft of the refiner. 10. Refiner according to claim 1, characterized i n that the sortin zone consists of mutually parallel grinding gaps (41,42) defined b the εtator (28) and the rotor (33), into the firεt of theεe being fed the material to be refined, and of a sorting gap (46) defined by the stator and the rotor and which is wider than the grinding gaps, and that the constituent which has been more completely ground along the sorting gap goes to a different grinding gap from that receiving the iesε completely ground constituent. 11. Refiner according to claim 10, characterized in that on the surfaces of the sorting gap (46) are provided eminences (48,49), which mix the material flow. 12. Refiner according to claim 10 or 11, characterized in that th sorting gap (46) runs obliquely towards the shaft (34) of the refiner. 13. Refiner according to any Dne of claims lO to 12, characterize in that the outermost part of the grinding gap (41) through which the less completely ground constituent goes iε εo εhaped that the passing capacity of said gap is substantially lower than that of the grinding gap (43) through which the more completely ground con stituent passes after the sorting zone.

Inventors: SURAKKA JORMA, SURAKKA, JORMA
Applicants: SUNDS DEFIBRATOR JYLHA OY, SUNDS DEFIBRATOR JYLHAE OY
Application year: 1987
Main classification: D21B1
IPC codes: B02C7, D21B1, D21D1