WO2001059209A1

WO2001059209A1 - A method and a device for concentrating liquid-drenched material

Info

Publication number: WO2001059209A1
Application number: PCT/SE2001/000243
Authority: WO
Inventors: Ebbe HODÉN
Original assignee: Hoden Ebbe
Priority date: 2000-02-11
Filing date: 2001-02-08
Publication date: 2001-08-16
Also published as: SE0000435L; SE515706C2; SE0000435D0; AU2001232554A1

Abstract

The consistency of liquid-saturated material is increased by enclosing a string (20) of the liquid-drenched material in filter cloth (1, 2) and leading said enclosed material around a horizontal, rotating drum (16) while compressing the string between the drum and one or more pressure elements (8, 17, 18, 10). The drum (16) used is hollow and has a perforated barrel, and the string (20) enclosed in the filter cloth (1, 2) is led around the upper part of the drum. The pressure elements may conveniently comprise one or more pressure rollers (8, 17, 18, 10) that have a barrel part which can be deformed resiliently by said compression force. There is also described a device for increasing the dry substance content in accordance with the aforegoing.

Description

A METHOD AND A DEVICE FOR CONCENTRATING LIQUID-DRENCHED

MATERIAL

The present invention relates to a method of increasing the concentration, or dry solids content, of a liquid-drenched material, and then particularly to a method of concentrating liquid-containing particle pulps or fibre pulps, wherein a string of the liquid-drenched material embraced in filter cloth is passed around a horizontal, rotating drum while compressing the material between the drum and one or more pressure elements. The invention also relates to a device with which the method can be suitably carried out.

A method and a device for concentrating liquid-drenched material by rolling a string of said material whilst the string is embraced by an endless filter-cloth web is known from EP-B-670 747, for example. According to this known prior publication, an endless web of filter cloth is folded into a tubular shape in a folding device and a suspension or slurry of material to be concentrated is introduced into an upper end of the tube. The material is pre- concentrated by virtue of the fact that a major part of the suspension liquid departs as the tubular web enclosing the material is guided down through a steeply inclined or vertically positioned perforated support pipe. The tubular-shaped web, which at this stage embraces a string of partially concentrated but still liquid-drenched material, is then passed around the under part of a large horizontally rotating roller or drum and compressed between the drum periphery and a number of pressure rollers, for further concentration of the liquid-drenched material. The web is then folded out in an unfolding device, wherewith the concentrated material is fed-out and the unfolded endless web is passed back to said web folding device. A string of liquid-drenched material whose dryness shall be increased can be embraced by more than one endless web. Reference is made by way of example in this respect to WO 99/39048.

In known methods and devices for increasing the dry solids content of a liquid-drenched material by rolling a string of said material embraced by a filter-cloth web problems are experienced in respect of the significant re-absorption of liquid earlier pressed out of the material. Accordingly, an object of the present invention is to provide an improved method and an improved device with which the aforesaid problems are avoided at least to a substantial degree.

To this end, it is proposed in accordance with the invention that there is used in a method of the kind defined in the introduction a hollow drum that has a perforated barrel, and that the string embraced by said filter cloth is passed around the upper part of the drum. One advantage gained in this way is that liquid pressed from the material by compression is able to depart through the perforated drum barrel, resulting in higher dry solids contents and in structural simplifications. The pressure elements used may beneficially comprise a plurality of pressure rollers disposed along the upwardly facing peripheral -part of the drum. The use of one or more pressure rollers that have a barrel-part which will be deformed elastically by the compressive pressure is preferred, there being obtained in this way relatively broad compression zones between these latter pressure rollers and the drum periphery in the peripheral direction of the drum. The elastic deformation of the barrel regions of the pressure rollers also equalises the pressure on the string of material embraced by filter cloth, so as to avoid local high compression strains on the filter-cloth web or webs at the edges and at overlapping regions thereof.

As before mentioned, the invention also relates to a device for carrying out the novel method. This device is characterised in that the drum is a drum which includes a perforated drum barrel; in that the string embraced by filter cloth is passed around the upper part of the drum. Further characteristic features of the invention are set forth in the dependent Claims.

The invention will now be described in more detail with reference to the accompanying drawing, which is a highly schematic side view of an inventive device chosen merely by way of example.

The illustrated device for concentrating liquid-drenched material, such as fibre suspensions for instance and then particularly paper pulp suspensions, comprises two filter-cloth webs 1 and 2, each of which is guided in a respective endless path and each consisting of plastic wire cloth. The web 1 is passed around guide rollers 3-8 and is broader than the other web 2, which is passed around guide rollers 9 and 10 and also around the guide rollers 6. 7 and 8 used to guide the web 1. The guide rollers 8 and 10 also function as pressure elements, as will be evident from the following text. The arrows 1 1 and 12 indicate the movement directions of respective webs 1 and 2.

A folding device, known for instance from WO 99/39048, is mounted beneath the guide roller 9, as illustrated symbolically at 13, this folding device functioning to fold the longitudinal edge parts of the broader web 1 in towards its centre part. This centre part has generally the same width as the web 2, said web 2 being led into the folding device 13 in conjunction with folding the edge parts of the web 1, such that the sides of the web 2 will be overlapped by the edge parts of the web 1. The webs 1 and 2 therewith form a tubular enclosure for accommodating a slurry of material to be concentrated, said slurry being introduced into the tubular enclosure through a funnel (not shown) in the direction of arrow 14. The webs 1 and 2 can be held together in their material-embracing state, by passing the webs through a perforated pipe (not shown) disposed between the web folding device 13 and the guide roller 7, therewith forming a string of partially concentrated material. This material is further concentrated whilst enclosed in the filter-cloth webs 1 , 2 by passing said string around a horizontal drum 16 that rotates in the direction of arrow 15 and compressing the material between the barrel of the drum and a number of pressure elements, in the illustrated case pressure rollers 8, 17, 18 and 10.

Subsequent to having finally concentrated the material, by compressing said material between the rollers 8, 17, 18, 10 and the drum 16, the edge portions of the web 1 are folded out by means of a symbolically illustrated unfolding device 19, for instance the device known from WO 99/39048. The webs 1 and 2 with the string of concentrated material therebetween are then passed to the guide rollers 5 and 6, where the webs mutually separate and the web 1 passes around the guide roller 5 in a direction towards the guide roller 4, whereas the web 2 passes around the guide roller 6 in a direction towards the combined guide and pressure roller 10. The string 20 of finally concentrated material departs for possible further treatment in the direction of arrow 21.

The webs 1 and 2 can be driven by driving the drum 16 and/or one or more of the guide and/or pressure rollers in a manner not shown. If desired, the string of material may be embraced by one single strip or web of filter cloth, for instance in the way illustrated in EP-B-670 747. Alternatively, when using two webs of filter cloth that have mutually the same widths and that can be displaced laterally in relation to one another to embrace the material to be concentrated, the enclosure can be formed by folding an outwardly projecting edge portion of one strip around an edge portion of the other strip, and by folding an outwardly projecting edge portion of said other strip around an edge portion of said one strip. When using two strips of different widths, it is possible to use separate edge strips that are folded around the mutually adjacent edges of the two first-mentioned strips. The folding device and unfolding device of the type illustrated in EP-B-670 747 and WO 99/39048, are convenient both with respect to the aspect of space and strain in comparison with successively reshaping strips from a flat to a tubular section in accordance with US- A-4,017,398 for example, although it will be understood that the invention is not restricted to the use of such known folding and unfolding devices.

Effective concentration of the liquid-drenched material is aided by using a hollow drum 16 that has a perforated barrel, wherein the string of material embraced by the filter-cloth strip 1, 2 is passed around the upper part of the drum 16, as clearly seen from the drawing. Pressure elements in the form of rollers 8, 17, 18, 10 that include respective barrel portions which deformed resiliently chosen compression forces are used, wherewith the roll nip between the drum 16 and respective pressure rollers 8, 17, 18, 10 increases in width as measured in the peripheral direction of the drum 16, therewith facilitating running of liquid pressed from the string into the drum and minimising re-absorption of liquid by the material. The liquid pressed from the material is allowed to pass freely through the perforated drum 16 and out through the lower part of the drum. The liquid leaving the drum 16 is collected in a tray 22 provided beneath the drum. The tray 22 is provided with a suitable drain through which the liquid collected is carried away.

There are used, beneficially, pressure rollers 8, 17, 18, 10 that are resiliently deformable to a chosen extent, such as to obtain between the barrels of the pressure rollers and the barrel of the drum a nip whose width, as measured in the peripheral direction of said barrels, corresponds to at least about 5%, suitably between 5 and 30%, of the diameter of said pressure rollers. A simple pressure roller construction can be obtained, by forming each pressure roller from a number of rubber wheels threaded on a common axle.

According to a modified version of the device, as indicated in broken lines, the width of the nip between the drum 16 and the pressure rollers 8, 17. 18. 10 can be increased with the aid of travelling, endless strips 23 that pass around at least two mutually adjacent pressure rolls, e.g. rollers 8, 17 or 18, 10, as shown in broken lines. When the strips 23 are suitably stretched, the strips will press against the drum barrel and therewith further reduce the tendency towards re-absorption of liquid pressed from the material. Such an arrangement of strips 23 enables the resiliently deformable barrel portions of the pressure rollers 8, 17, 18, 10 to be replaced with resilient compressibility in the thickness direction of the endless strips travelling around the pressure rollers.

It will be understood that the invention is not restricted to the embodiments described with reference to the accompanying drawing, and that the invention can be implemented in any desired manner within the scope of the inventive concept defined in the accompanying Claims.

Claims

1. A method of increasing the dry substance content, or concentration, of a liquid- drenched material, in which a string (20) of said liquid-drenched material enclosed in a filter cloth (1 , 2) is passed around a horizontal, rotating drum (16) while compressing said string between the drum and one or more pressure elements (8, 17, 18, 10), characterised by using a hollow drum (16) that has a perforated barrel; and leading the string (20) embraced by the filter cloth (1, 2) around the upper part of the drum.

2. A method according to Claim 1. characterised by using as pressure elements a number of pressure rollers (8, 17, 18, 10) disposed along the upwardly facing peripheral part of the drum (16).

3. A method according to Claim 2, characterised by using one or more pressure rollers (8, 17, 18, 10) that include a barrel part that can be deformed resiliently by said compression force.

4. A method according to any one of Claims 1-3, characterised by allowing liquid pressed from the material to pass freely through the perforated drum (16) and to be collected in and removed from an area (22) beneath said drum.

5. A method according to any one of Claims 1-4, characterised by pre-concentrating the liquid-drenched material prior to its compression but subsequent to enclosing said material in filter cloth (1, 2).

6. A method according to any one of Claims 3-5, characterised by using pressure rollers (8, 17, 18, 10) that can be deformed resiliently to a chosen extent such as to obtain between the roller barrel and drum barrel a nip which, at the compression force applied, has a width corresponding to at least about 5%, suitably between 5 and 30%, of the diameter of the pressure roller.

7. A device for increasing the dry substance content of a liquid-saturated material, said device comprising means (8, 6) for leading a string (20) of liquid-saturated material embraced by a filter cloth (1, 2) about a horizontal, rotating drum (16) whilst compressing said string between the drum and one or more pressure elements (8, 17, 18, 10) that press against the drum, characterised in that the drum (16) is a hollow drum provided with a perforated barrel; and in that the string (20) embraced by the filter cloth (1, 2) is led around the upper part of said drum.

8. A device according to Claim 7, characterised in that the device includes pressure elements in the form of a plurality of pressure rollers (8, 17, 18, 10) disposed along the upwardly facing peripheral part of the drum (16).

9. A device according to Claim 8, characterised in that one or more of the pressure rollers (8, 17, 18, 10) have a barrel portion that can be deformed resiliently by the compression force.

10. A device according to any one of Claims 7-9. characterised in that the drum (16) allows the free passage of liquid pressed from said material; and in that the device has located beneath the drum means (22) for collecting and removing liquid pressed from the material.

11. A device according to any one of Claims 7-10, characterised by means for pre- concentrating the liquid-drenched material prior to its compression but subsequent to enclosing it in the filter cloth (1, 2).

12. A device according to any one of Claims 9-11, characterised in that the pressure rollers (8, 17, 18, 10) are resiliently deformable to a chosen extent such as to obtain between roller and drum barrel a nip whose width corresponds to at least 5%, suitably between 5 and 30%, of the diameter of the pressure roller.

13. A device according to any one of Claims 9-12, characterised in that the pressure rollers (8, 17, 18, 10) are comprised of a number of rubber wheels threaded on a common axle.

14. A device according to any one of Claims 7-12, characterised by an endless strip (23) that travels around at least two pressure rollers (8, 17, 18, 10).

15. A device according to Claim 14. characterised in that the resiliently deformable barrel part of the pressure rollers (8, 17, 18, 10) is achieved through resilient compressibility of the endless strip (23) that moves around the pressure rollers in the thickness direction of said strip.