DEVICE FOR SEPARATION AND WASHING IN A MUD ABSTENTION FIBERS

The invention relates to the treatment of muds, in particular of paper mill.

Paper is produced in a manufacturing unit of paper, starting from fibres put in suspension in water.

These fibres are initially deposited according to on a carpet of draining to form a layer, and after draining, this layer is compressed mechanically, then heated to constitute a sheet of paper.

Such a manufacturing unit functions with great quantities of water: the production of a ton of paper requires about a hundred and fifty tons of water.

The various stages of production, such as draining and compression, generate fibrous suspensions, i.e. of water containing less than one to five pourcent in fibre mass.

These fibrous suspensions are recycled within the manufacturing unit, fibres and water being then separate to be reinjected in the cycle of production, which contributes to limit the water and fibre consumption.

Separation is ensured by draining in a filter which can be conical such as that which is located by 1 in figure 1, in order to concentrate fibres while recovering the water which contains them.

This filter comprises an enclosure 2 container a filter truncated wall 3, formant funnel, as well as a control 4 pouring on this wall the fibrous suspension to treat, and a rotary head 6 located at the top of the truncated wall to sprinkle it with water.

Such an installation has a diameter of about two meters, the basic truncated cone of the filter wall having an angle about forty-five degrees, and the rotary head turns at a speed ranging between five and fifteen turns per minutes.

Under operation, the fibrous suspension to reduce is poured partly higher wall 3, and it goes down along this one by forming a mattress covering the unit from surface from this wall.

During this descent, part of the water contained in the fibrous suspension runs out through the meshs of the filter wall 3, but the fibrous suspension tends nevertheless to clog the filter wall 3.

To avoid this filling, the rotary head 6 comprises several arms fed out of water, such as the arms 7 and 8, which extend the generators parallel to from the truncated wall.

Each arm produces a continuous water curtain formed by several water 11 jets overlapping, and which result from various spaced tubes 9 from/to each other along the arm.

The water curtain forms a scraper which raises the layer of fibrous suspension and supports its flow along wall 3, while cleaning this wall.

After reduction of fibrous suspension with this device of draining which is established within the manufacturing unit, fibres and water are reinjected in the production cycle.

In spite of the presence of recycling, such a unit generates waste in the form of waste water containing up to ten or fifteen pourcent of mud made up of various impurities and fibres.

This waste is treated in a purification plant distinct from the manufacturing unit of paper. They are initially elutriated there to form the mud, which is treated biologically, before being épandue or dispatched towards a technical center of hiding.

Such a mud however contains fibres a length from two to three millimetres which are lost whereas they could be recovered to be mixed with longer fibres so as to manufacture paper.

The goal of the invention is to propose a device making it possible to wash fibres contained in this mud in order to use them in the manufacture of paper.

For this purpose, the invention has as an aim a device of fibre extraction and washing contained in a mud, including/understanding a filter wall having the truncated shape of vertical axis opening to the top, a control conveying of mud to treat partly high this filter wall, and a rotary head carrying at least a series of tubes parallel to aligned a generator of the truncated filter wall, each tube projecting a water jet towards the filter wall, in which the tubes of a series of tubes are arranged to produce jets having on the filter wall of the prints which are spaced from/to each other.

Thanks to the spacing of the jets, mud forms a cord on the internal surface of the filter wall, which has an important adherence to the wall. Thanks to this adherence, the time necessary so that mud goes down along totality from the wall is sufficiently important so that the jets can wash the sufficiently effective mud of way to extract fibres from them.

The invention also relates to a device such as definite above, in which the truncated filter wall forms, compared to a normal plan with its axis of revolution, an angle ranging between ten and thirty degrees, being worth twenty degrees preferentially.

The choice of a truncated filter wall having a high aperture contributes to further decrease the speed of advance of mud towards the lower opening of this filter wall, to increase the time and the effectiveness of the washing of this mud.

The invention also relates to a device such as definite above, in which the rotary head comprises at least an arm carrying a series of tubes producing of the flat water jets having on the filter wall of the spaced prints from/to each other, and at least another arm carrying another series of tubes producing of the water jets known as conical having on the filter wall of the prints in the shape of discs which are spaced from/to each other.

With this solution, mud forms a helicoid cord which is diluted when it passes under a conical jet, and which is gathered on itself when it passes between two contiguous plane jets.

The invention also relates to a device such as definite above, in which control is carried by the rotary head while being positioned to deposit mud on the filter wall with a position located upstream of a conical jet taking into account the direction of rotation of the rotary head.

In this manner mud is initially diluted by a conical jet, then gathered when pass the flat jets, so that it takes the form very early having a good adherence to the filter wall.

The invention also relates to a device such as definite above, comprising at least a tube producing a flat jet having an orientation called forwards, to produce a jet having on the filter wall a print shifted forwards compared to an orthogonal projection of this tube on the filter wall.

With this orientation forwards, the flat jets form scrapers ready to take off the mud of the wall for best gathering in the form of cord.

The invention also relates to a device such as definite above, comprising at least a tube producing a flat jet having an orientation called to the top, to produce a flat jet having on the filter wall a print inclined towards a higher edge of the filter wall in reference to the direction of advance of the print when the head turns.

This orientation appreciably to the top of the jets is opposed to the descent of the cord along the filter wall.

The invention also relates to a device such as definite above, comprising at least a tube producing a flat jet having an orientation called to the bottom, to produce a flat jet having on the filter wall a print inclined towards an opening of the filter wall by reference to the direction of advance of this print when the head turns.

The invention also relates to a device such as definite above, including/understanding an arm carrying at least a tube directed upwards and at least a tube directed to the bottom, these tubes being located respectively partly higher and partly lower arm carrying them.

The invention also relates to a device such as definite above, comprising an arm carrying a series of tubes producing of the flat jets, in which the tubes located on higher two thirds of this arm are directed upwards, and in which the other tubes carried by this arm are directed downwards.

The invention also relates to a device such as definite above, in which the tubes directed to the top are tilted according to a decreasing angle since the higher edge of the filter wall.

The invention also relates to a device such as definite above, in which the tubes directed to the bottom are tilted according to a decreasing angle since the lower edge of the filter wall.

• Figure 1 is a diagrammatic representation out of transverse section of a device known to drain mud containing of fibres;
• Figure 2 is a diagrammatic representation of the device according to the invention seen out of transverse section;
• Figure 3 is a diagrammatic representation of the flat jets in side sight and print of the flat jets on the filter wall in the device according to the invention;
• Figure 4 is a diagrammatic representation of the conical jets in side sight and print of the conical jets on the filter wall in the device according to the invention;
• Figure 5 is a diagrammatic representation for top of a device according to the invention under operation;
• Figure 6 is a diagrammatic representation of a conical jet seen of top when it sprinkles a mud cord;
• Figure 7 is a diagrammatic representation of the orientation of a flat jet showing the positions relative of its print on the filter wall and of projection on this wall of the tube seen according to a direction locally normal to this wall;
• Figure 8 is a diagrammatic representation of an alternative of orientation of the jets along an arm carrying the tubes producing these jets.

The idea at the base of the invention is to adapt a separation device of the fibrous suspension exploited within a manufacturing unit of paper, with the waste processing resulting from such an installation.

This is obtained by arranging the jets in such a way that mud is gradually diluted, but extends in the form of a cord on the filter wall to decrease its speed of descent along this wall. This makes it possible to have a sufficient processing time to carry out a washing able to correctly extract fibres from mud.

In the example hereafter, this is assured on the one hand with first jets known as flat jets which agglomerate the cord to collect it on itself and on the other hand with second jets known as conical jets which sprinkle the cord to wash it.

The device according to the invention which is schematically represented of figure 2 while there being located by 12 has a general structure of the same type as that of the apparatus of figure 1.

It includes/understands to him also an enclosure 13, a vertically directed filter wall truncated 14, opened to the top and comprising an opening lower 15, as well as a head of sprinkling 16 rotary printing-press engaged in the upper part of this filter wall. The filter wall 14 is carried out in a comprising material of the meshs measuring between hundred and two hundred and fifty microns so as to let pass the mud particles and recover fibres.

This rotary head comprises on the one hand an arm such as bearing arm 17 of the tubes 21 to 24 which produce flat jets 26 to 29, and on the other hand an arm such as bearing arm 18 of the tubes 31 to 34 which produce jets 36 to 39 known as conical.

Arm 17 extends the filter wall parallel to, which means that the distance separating it from this one is appreciably constant all along this arm 17. Tubes 21 with 24 qu ' it door are spaced from/to each other along this arm by distances such as jets 26 with 29 qu ' they produce do not overlap. On the contrary, there exists a substantial space between the successive jets along arm 17.

Thus, as illustrated on figure 3, the prints e27 and e28 on the wall 14 of two consecutive flat jets that are jets 27 and 28 are spaced one of the other. Each print is a rectilinear form, length L ranging between seven and eight centimetres, and the prints e27 and e28 are spaced one of the other of a variation E of approximately a centimetre, parallel to arm 17.

Arm 21 extends also parallel to him the filter wall 14, the distance separating it from this wall being same all along this arm 21. Tubes 31 with 34 qu ' it door are also spaced from/to each other of a distance such as jets 36 to 39 products by these tubes do not overlap, and on the contrary are spaced from/to each other.

Two consecutive conical jets such as jets 37 and 38 have prints on the filter wall 14 which are located by e37 and e38 in figure 4. Each print has the shape of disc, of a diameter noted It, and two prints of consecutive jets along the arm are spaced of a variation noted e'.

In figure 2, one represented only one producing arm of the flat jets, namely arm 17, and a producing arm of the conical jets, namely arm 18.

But the device according to the invention comprises a number of much higher arm advantageously, while for example being equipped with four producing arms of the flat jets and with four producing arms of the conical jets. Each producing arm of the conical jets being then intercalated, for top, between two producing arms of the flat jets.

The rotary head comprises eight arms, spaced then from/to each other of a eighth of turn, as in the example of figure 5 which partially shows such a device for top.

Advantageously, this head also carries a control 41 of mud 42 supply. This control radially extends so as to deposit mud partly higher, i.e. peripheral, of the filter wall 14 while turning with the head to form the mud cord.

This cord moves in a very slow way to the bottom of the filter wall 14 because of its actual weight. By reference within the meaning of rotation of the head 16, which turns at a speed ranging between five and fifteen turns per minute, after being deposited on the filter wall 14, the cord is sprinkled by a first conical jet 36.

This causes the first washing during which part of the impurities of mud 42 component this cord crosses the filter wall so as to be eliminated. Taking into account the pressure of the water of the jet which is applied to this cord, this one is crushed on the wall 14, so that its width increased after passage of the conical jet 37.

After this first washing, the cord of strong continuous width to go down slowly along the wall 14, until it is reached by flat jets produced by arm 17. The cord of strong width then has its center located between the two consecutive flat jets 26 and 27, but its width is higher than the spacing E which separates the prints e26 and e27 from these two jets on the wall 14.

These two flat jets 26 and 27 then sprinkle the edges of the cord to bring them closer one to the other, so that it takes more collected form again: its thickness increases whereas its width decreases.

After being given in form by the flat jets 26 and 27, the cord is again swept by a jet conical, nonvisible in the figure, which corresponds to a new stage of washing in which other impurities of this mud are evacuated through the filter wall 14, this stage causing a new crushing of the cord.

The cord passes thus on the level of various nonvisible arms on the figure, which, alternatively wash it by crushing it, then give it in the shape of cord. Before passing by again under conical arm 18 of jets of washing, the cord was given in form while passing under the arm 48 which produces the flat jets 43 to 47.

The whole of the cord thus has the general shape of helicoid of axis AX projected on the filter wall 14 truncated, which corresponds to a spiral for top. Like visible on the figure, the cord extends on several lathes from internal surface from the wall 14, and under operation, it walks on vertically to the bottom of this one, i.e. towards its opening lower 15.

This cord thus has its higher end continuously renewed by the mud 42 contribution deposited by the end of control 41, whereas its lower end is continuously evacuated by the central opening lower 15 of the filter wall 14.

Like schematically illustrated on figure 6, the mud jets and flow delivered by control 41 are dimensioned in such a way that after being gathered or being collected by a pair of plane jets, i.e. before being washed by a conical jet, the cord has a width 1 which lies between half and the fifth of the diameter D of a conical jet on the wall 14.

The tubes forming the conical jets can be placed compared to the medium of the interval between two flat jets. But the position of these tubes depends on the operating conditions, in particular the speed of descent of the mud cord and the angle separating two successive arms. These tubes must simply be placed to be on the trajectory of the mud cord.

In the illustrations symbolic systems of the figures, each arm carries four tubes to produce four jets. But in practice, taking into account dimensions of the apparatus which measures about two meters in diameter, each arm increases a number of tubes largely higher than four.

In order to further decrease the speed with which the mud cord goes down along the filter wall 14, the jets have specific orientations advantageously.

Generally, the tubes producing the flat jets 21 to 23 which are located in higher two thirds of arm 17 are directed upwards to be opposed to the descent of the cord, and the tubes located on one the lower third of the arm are directed downwards to support its evacuation towards the lower opening.

In addition, the tubes producing of the flat jets all are directed to produce jets inclined as of the scrapers so as to effectively take off the mud of the filter wall 14 in order to gather this cord effectively.

Thus, as represented of figure 7 schematically, the tube 22 which is directed to the top product a flat jet 27 from which the rectilinear print e27 extends according to an axis a27 which is tilted compared to the line of greater slope p17 of the wall 14.

The axis a27 form thus an angle noted Dα with the axis p17, this axis p17 also corresponding to projection on the wall 14 of arm 17, i.e. to the intersection with the wall 14 of a plan containing the axis of rotation AX of head 16 and centers it arm 17.

The print e27 thus presents a lower end i27 which is ahead than its higher end s27, according to the direction of advance has jet along the wall 14. The distance dhi separating the lower end i27 and centers it p17 is thus higher than the distance dhs separating the higher end s27 and this axis p17.

The orientation of tube 21 also gives to the flat jet 27 qu ' it produces a forward tilt so that it constitutes a scraper, which results in the fact that the whole of the print e27 is located in front of the axis p17. Projection p27 of tube 27 on the wall 14, which is carried by the axis p17, is thus separated from the center c27 of the print by a noted horizontal distance DH.

With regard to tubes carried by third lower of arm 17, as the tube 24 they are downwards tilted, which means that they have each one a print whose higher end is more or as much advanced than the lower end, according to the direction of advance A. These lower tubes moreover they are also directed so that the jets which they produce are tilted forwards.

The orientation to the top of the higher tubes of arm 17 aims at slowing down the descent of the mud cord when it is partly high filter wall 14. On the contrary, the orientation to the bottom of the lower tubes of arm 17 aims at supporting the evacuation of the partly low part of the cord located of the wall 14.

The orientations of tubes 21 to 24 can, instead of being identical for two successive tubes, evolving/moving gradually along the arm, as in the example of figure 8.

In this case, each tube 21 to 23 tilted to the top has a slope |Dα| all the more important as it is close to the higher edge of the truncated wall 14. In a similar way, each tilted tube 24 to the bottom has a slope |Dα| all the more important as it is close to the lower edge of the wall 14, i.e. of opening 15.

Thus, the angle directed Dα, energy of the axis of the print considered towards the axis p17, decrease gradually since the top of arm 17 to the bottom of this one, like visible on figure 8.

It still should be noted that the slope of the flat jets 26 to 29, upwards or to the bottom, can also be accentuated by directing the corresponding tube to shift the print of the jet which it produces, either to the top, or to the bottom, compared to the orthogonal projection of this tube on the wall 14.

Referring to tube 27 represented of figure 7, this reverts introducing a vertical shift between the center c27 of the print e27 of its jet 27 compared to projection p27 of this tube.

The device according to the invention thus makes it possible to treat a not very viscous mud, such as a mud comprising of fibres having lengths lower than two millimetres and half, by controlling the descent of this mud along the filter wall 14, so as to prevent that this descent is too fast, making then the washing of fibres sufficiently effective.

The conical wall advantageously has an aperture ranging between a hundred and twenty and a hundred and sixty degrees, so that the angle of slope of this wall lies between thirty and ten degrees.