US2765645A - Washer for fibrous materials - Google Patents

Description

,v 395 L. J. HANNUNKARI ETAL WASHER FOR FIBROUS MATERIALS Fiied Feb. 24, 1951 2 Sheets-Sheet 1 c o o & 00000000 00000060 00000000 00000000 00000000 00000000 00060000 00000000 00 000000 'ooooooooooo INVENTOR.

1956 L. J. HANNUNKARI ETAL 2,765,645

WASHER FOR FIBROUS MATERIALS Filed Feb. 24, 1951 2 Sheets-Sheet 2 Patented Oct. 9, 1956 fifice 2,765,645 WASHER FOR FIBROUS MATERIALS Lasse Johan Hannunkari and Gunnar Kulvik, Oulu, Finland Application February 24, 1951, Serial No. 212,616 Claims priority, application Finland February 26, 1949 4 Claims. (Cl. 68-181) This application is a continuation in part of our application Serial No. 145,828 entitled, Arrangement in Washing Tanks, filed February 23, 1950, which matured into Patent No. 2,683,366 issued on July 13, 1954.

This invention relates to a vertical washer wherein pulp and the like fibrous materials may be treated, e. g. rinsed etc.

In the operation of washers for said purpose it has heretofore been customary to let in wash water at the top of the unit and drain it off through screen compartments in the bottom part of the unit. This method is disadvantageous in that during the washing operation the material to be treated will, under the influence of gravity, and the downward flow of the Wash water, tend to settle into a dense layer which naturally decreases the washer capacity.

To obviate the above described disadvantage it has been proposed to arrange the screen surfaces of the compartments in such positions that the formation of a compact layer of the kind described thereon will wholly or in part become impossible, e. g., by positioning the screen surfaces so that the weight of the overlying pulp pillar will not directly affect the screen surfaces. Then the screen surface or surfaces will form the obliquely turned wall of the compartment in the bottom part of the washer while the rest of the surfaces of the said compartment subject to the weight of the pulp pillar are unperforated and turned either entirely or at least substantially against the flow direction of the wash water.

While adopting the above described principle it is the object of the present invention to provide improved means for carrying the same into effect. The novel feature of the present invention lies in the provision of means for dividing the pulp pillar, in vertical direction, into two or more partial pillars superposed at least in part and having communication with each other.

In washers of the kind provided with means made in accordance with the present invention the stress of the pulp weight on the screen surfaces diminishes with height of partial pillars.

The invention can be carried into effect by employing multifarious means. For instance, the washer may be provided with annular plates rigidly secured to the washer wall and advantageously arranged to taper downwardly and cover entirely or in part the screen surfaces. The wire mesh screen bottom of an ordinary washer may serve as the screen surface in which case a suit-able plate, e. g. an annular intermediate bottom, either perforated or imperforate, arranged thereabove supports the overlying pulp pillar. It is also possible to arrange the screen surfaces directly in the washer wall under the above described intermediate bottom. I

Some embodiments of the invention will now be described with reference to the accompanying drawings, wherein Figs. 1, 4 and are vertical sectional views of a washer provided with different kinds of pulp supporting means.

Figs. 2 and 3 illustrate two different embodiments of a detail of Fig. 1.

Fig. 6 shows a special embodiment, likewise in vertical sectional view.

Referring to Fig. 1, at 1 is indicated a washer having intermediate bottom type partitioning means 2 in accordance with the invention and extending through a major portion of the cross-section of the tank so as to divide the pulp pillar into two partial pillars located in the upper chamber 3a and in the lower chamber 3b, respectively. The perforated intermediate bottom slants downwardly in the shape of a truncated cone, which shape in practise proved very advantageous. Instead of a truncated cone, said intermediate bottom can be shaped to form a truncated polygonal pyramid. It is possible also to have the bottom of imperforate plate.

The washer has an ordinary wire mesh screen bottom 4 through which the liquor is drained but in addition to this there is arranged under the plate 2 an annular vertical screen 5 between which and the wall of the washer is an annular chamber 6. After the liquor has passed through the screen bottom 4 it collects in the space between the washer bottom 8 and the screen bottom 4 from which it is conducted by a discharging pipe 9 into an annular pipe 16 and thence into the rising pipe 7. From the annular chamber 6 the liquor flows into an annular pipe 11 encircling the unit and therefrom into the said rising pipe 7.

Figs. 2 and 3 show a part of the perforated intermediate bottom of Fig. l with different embodiments for the arrangement of perforations. Elongated slits are indicated by 62 in Fig. 2 and around perforations by 63 in Fig. 3. The wash water flows through the perforation while the intermediate bottom supports the pulp pillar. Because the stock ordinarily operated upon by the present washer is fairly thick liquid pulp and because no operation difficulties arise when using a perforated intermediate bottom although some fibres may escape with the drained water through the perforations into the lower partial pillar, the perforations may be made appreciably large in size, if so desired. By suitably spacing the perforations and by giving them an appropriate size liquid flow within the washer can be equalized. For instance, if the washing operation at the side parts of the unit 61 lags behind that at the centre 60 the distribution of perforations over the said surface area may be so arranged that on the side parts the perforations are more closely spaced than at the centre wherefore liquid flow at the side is maintained similar to that at the centre.

By way of example the approximately 20 mm. perforations 62 in Fig. 2 are so distributed that circumferentially they are about 50 mm. apart and radially from the was-her periphery spaced at a distance continuously increasing from about 45 mm. to mm. In Fig. 2 these perforations consist of slits 62 whose circumferential length continuously increases from the centre to the periphery (i. e. from 60 to 61), spaced equi-distantly apart both radially and circumferentially, in this case at a distance of 100 mm. Similarly in Fig. 3, the perforations 63 increase in number from the center 60 to the periphery 61.

It is to be understood that the size and relative positions of the perforations may be varied at will so as to meet the requirements of the suspension to be treated.

The material to be treated is charged through the top of the washer by employing a turnable inlet pipe 13 which renders unit. Wash water flow is indicated by arrows.

The rinsed pulp is discharged from the washer in the customary manner through the bottom discharge outlet 12.

Fig. 4 illustrates a washer 21 otherwise similar to that possible the even distribution of pulp into the shown in Fig. 1 except that the intermediate bottom in this case is of unperforated plate and that the annular screen surface under said bottom is omitted.

Fig. 5 shows how the, washer according to the present invention can be operated either for downward or upward liquid flow by using the intermediate bottoms hereinabove described. Liquid flow in the last'mentioned operation of the washer is indicated by arrows.

In the washer 31 three annular unperforated intermediate bottoms are arranged one above the other. It is, however, self-evident that said bottoms 30 may be perforated, for instance as shown in Fig. 23. Under each intermediate bottom and in the immediate vicinity of the Washer wall are arranged three annular screen surfaces 32, 33, 34 and also a screen surface 35, positioned at the top of the washer in a manner corresponding to the bottom screen 4 of Fig. l. Respective rising pipes lead from the screens to the vat 36 wherefrom the liquor is carried away by pipe 37. The rising pipes are provided respectively with valved extension tubes 32a, 33a, 34a and 35a of varying lengths which, for the purpose of creating the requisite back pressure, terminate at different levels, corresponding to the positions of the screen surfaces in the washer. By adjusting the length of the tubes it is possible to regulate back pressure in the manner desired. Also the discharge pipes may be closed successively as the material is rinsed from the bottom upwards. It is to be understood that the liquor drawn through the different pipes 32, 33, 34 and 35 can be conducted into different receptacles provided therefor or combined in any suitable manner according to the degree of dilution.

The washer is provided with a pulp inlet 37 which corresponds to pipe 13 of Fig. 1.

The washer according to this embodiment can be used just as advantageously as the ones according to Figs. 1 and 4 for downward rinsing of pulp, but it is also possible to operate the washer with the least possible liquor dilution so that the wash water is let in through the bottom by pipe 39 and consequently conduct the rinsing operation from the bottom upwards.

Probably the conical surfaces 30 render such a rinsing operation possible by preventing water from rising upwardly along the wall of the washer. Trial rinsing operations showed that lighter wash water is capable of effectively pushing away heaviercooking liquor, because, by the use of a suitably inclined surface it is possible to govern the wash water flow in such a manner as to prevent the formation of a compact pulp mass otherwise formed at the center of the washer in rinsing operations of the kind described and operated upon at the sides only. The advantage due to a less dense type of mass to be operated upon by the present washer is obvious.

Fig. 6 illustrates a washer 41 which greatly resembles those hereinabove described but deviates therefrom chiefly in that the upper face of the intermediate bottom 42 has arranged thereon a screen ring 46. This washer can at the same time be operated for upward and downward flow, in which case upward flow takes place in the lower part of the washer and downward flow in the upper part. Liquid flows are indicated by arrows.

In this embodiment the upper part corresponds primarily to an ordinary washer charged through the top with the material to be treated as well as with wash water through the pipe 47. The screen surface 46 together with the annular intermediate bottom 42 provided near the middle part of the washer form an annular chamber wherefrom the discharge pipe 49 conducts liquor into the rising pipe 50. In the simultaneously occuring rinsing operation in the lower part of the unit, wash water admitted through the inlet'pipe 48 forces the liquor retained by the fibres upward and through the annular screen arranged under the intermediate bottom 42 and into the pipes 51 and therefrom into the rising pipe 50. It is to be noted that the recovered liquor can naturally be discharged separately through the pipes 49 and 51. It is also possibleto provide an intermediate bottom in each of the washing zones, hence both in the upper part and lower part of the washer, as a result of which the pulp pillars in the zones in turn divide up into partial pillars.

Although the intermediate bottoms as shown in the accompanying drawings are arranged co-axially one above the other it is to be understood that the arrangement of said bottoms otherwise than described falls within the scope of the invention. Consequently it is not necessary to form in the centre of the washer any continuous pulp pillar extending to the whole height of the washer, nor need the partial pillars be similar in size, but variously shaped intermediate bottoms diversely positioned relative to each other can be combined in the one and same washer according to the conditions desired.

Especially in washing operations with upward liquid flow it is necessary that the intermediate bottoms arrangement prevents wash water and liquor from mixing too much, i. e., the intermediate layer must be maintained sufficiently low wherefore measure should be taken to prevent wash water from forcing its way past the pulp mass, along the walls, and diluting the strong liquor.

Concerning the shape and form of the intermediate bottoms, there may be reason to mention, that the described truncated cone shape is very advantageous in emptying the washer because it functions as a guide surface for the pulp mass. When determining the angle between the cone surface and the horizontal consideration should also be given to this fact.

We claim:

1. An arrangement for washing fibrous material in liquid suspension, comprising, in combination, an elongated upright tank having first inlet means at the top end thereof for introducing fibrous material to be washed, and a first outlet means at the bottom end thereof for discharging washed material; at least one second inlet means for a washing liquid located at the top end of said tank; at least one second outlet means for said washing liquid located at the bottom end of said tank; a perforated screen bottom located at said bottom end of said tank covering said second outlet means and being arranged adjacent said first outlet means; partitioning means spaced from the top end of said tank and from said screen bottom, and having the shape of an inverted truncated cone with an opening at the apex thereof and having an outer annular edge secured to the inner surface of said tank, said partitioning means extending through a major portion of the cross section of said tank and being adapted to support the upper part of fibrous material located in said tank above the same so that the lower part of the material to be washed located between the said screen bottom and said partitioning means is uncompressed; an annular outlet means for said washing liquid located in said tank adjacent and underneath said annular edge; and an annular screen member located in said tank and covering said annular outlet means.

2. An arrangement as set forth in claim 1 wherein said partitioning means are formed with a plurality of small perforations.

3. An arrangement for washing fibrous material in liquid suspension, comprising, in combination, an elongated upright tank having first inlet means at the top end thereof for introducing fibrous material to be washed, and a first centrally located outlet means at the bottom end thereof for discharging washed material; at least one second inlet means for a washing liquid located at the top end of said tank; at least one second outlet means for said washing liquid located at the bottom end of said tank; a perforated frusto-conical screen bottom having a central opening at the apex thereof registering with said first outlet means and being located at said bottom end of said tank covering said second outlet means; partitioning means spaced from the top end of said tank and from said screen bottom, and having the shape of an inverted truncated cone with an opening at the apex thereof and having an outer annular edge secured to the inner surface of said tank, said partitioning means extending through a major portion of the cross section of said tank and being adapted to support the upper part of fibrous material located in said tank above the same so that the lower part of the material to be washed located between the said screen bottom and said partitioning means is uncompressed; an annular outlet means for said washing liquid located in said tank adjacent and underneath said annular edge, and an annular screen member located in said tank and covering said annular outlet means.

4. An arrangement as set forth in claim 3, wherein said partitioning means are formed with a plurality of small perforations.

References Cited in the file of this patent UNITED STATES PATENTS Andersen Jan. 19, 1926 Morterud Sept. 23, 1930 Bates Jan. 2, 1940 FOREIGN PATENTS Sweden July 11, 1923 Sweden Nov. 17, 1925 Norway July 7, 1930 Great Britain Dec. 29, 1936 Sweden Mar. 23, 1937 Sweden Apr. 8, 1938 Great Britain Oct. 27, 1938

Images