WO1990013347A1

WO1990013347A1 - Separation device

Info

Publication number: WO1990013347A1
Application number: PCT/SE1990/000155
Authority: WO
Inventors: Gunnar Fast
Original assignee: Svensk Industrimiljö Ab
Priority date: 1989-05-12
Filing date: 1990-03-12
Publication date: 1990-11-15
Also published as: SE465856B; SE8901709L; SE8901709D0; AU5555490A

Abstract

A device for separation of liquid and solid components of a mixture thereof comprises a filtering belt (1) with meshes, said filtering belt being arranged to receive the mixture on a surface facing upwardly and by means of its mesh size attain said separation by letting liquid components through while retaining solid ones. The device further comprises an apparatus (23) arranged to generate an active driving of the mixture liquid through the filtering belt (1). This apparatus is arranged to produce a negative air pressure on the underside of the filtering belt for sucking the liquid through the belt.

Description

Separation device

TECHNICAL FIELD OF THE INVENTION AND PRIOR ART

The present invention relates to a device for separation of liquid and solid components of a mixture thereof, comprising a filtering belt with meshes, said filtering belt being arranged to receive the mixture on a surface facing upwardly and by means of its mesh size attain said separation by letting liquid components through while retaining solid ones, and an apparatus arranged to generate an active driving of the mixture liquid through the filtering belt.

Such devices may be used for all kinds of separation purposes, where it is desired to obtain either solid substances relieved of liquid or liquid relieved of solid substances. An example of the first case is separation of water from peat material, while separation of grindings from oil used in grinding is an example of cleaning a liquid from undesired solid particles. Applica¬ tions in which the solid as well as the liquid components of a mixture each have a value may of course also exist.

In the devices already known of the type defined above the apparatus for active driving of the mixture liquid through the filtering belt consists of nozzles connected to a compressed air source, which nozzles blow compressed air towards the mixture so as to try to press the liquid therein through the filtering belt. However, this procedure not being as efficient as desired, a device having such an apparatus may only treat small mixture amounts per unit of time. In addition thereto another inconvenience resides in the fact that the mixture lying on the filtering belt tends to receive laterally directed forces from the compressed air jets, which forces may spread the mixture laterally, maybe outside the filtering belt, instead of pres¬ sing the mixture liquid through the meshes of the filtering belt.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a device of the type mentioned in the introduction, which reduces the drawbacks discussed in the prior art devices while considerably increasing the reliability and efficiency of the separation.

According to the invention this object is obtained by arranging the apparatus for active driving of the mixture liquid through the filtering belt in a device of the type discussed above to produce a negative air pressure on the underside of the fil¬ tering belt for sucking the liquid through the belt.

Thanks to the fact that a negative air pressure is produced on the underside of the filtering belt the mixture liquid may very rapidly be drawn through the belt. This suction action will be directed exactly in the direction in which it is desired for the liquid to move, and the liquid will not move along the filtering belt, but it will be drawn through the same. The efficiency is considerably increased with respect to what is possible to obtain by using the prior art devices. Additio¬ nally, it is possible to, in some applications, because of the application of the negative air pressure, make a liquid pass through very small meshes, so that the filtering belt may retain small solid contamination particles, although it was previously completely impossible to press the liquid through these meshes by means of compressed air applied from^' above. A very advantageous embodiment of the invention is defined in the appended claim 2. In this device the filtering belt is supported by another belt, which in its turn is arranged to bear upon a plate while forming free spaces between itself and the plate. A groove is arranged in the plate and emerges into an orifice connected to a device for generating a negative air pressure. Thanks to the spaces formed between the support belt and the plate the negative air pressure deriving from said orifice may be spread over the lower surface of the support belt so as to suck liquid through the filtering belt and the support belt.

As defined in claim 3, it is preferred that the support belt consists of a wire belt known per se with axles being inter¬ connected by rigid wires, for instance made of steel.

Further advantages and preferred characteristics of the inven¬ tion will appear from the following description and the other dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

With reference to the appended drawings, below follows a description of a preferred embodiment of the device according to the invention cited as an example.

In the drawings:

Fig 1 is a very schematic side elevation of an embodiment of the device according to the invention.

Fig 2 is a perspective view from above of a section cut away of the device according to Fig l.

Fig 3 is a partially sectioned side elevation of a support belt used in the device according to Fig 1, Fig 4 is a view from above of a section of a support belt shown in Fig 3, and

Fig 5 is a view of section taken along the line v-V in Fig 1.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

A preferred embodiment of the invention will now be described with reference to all Figures. The device comprises a filtering belt 1 with meshes of such a size that the solid substances contained in the mixture to be separated may not pass through the belt. However, it is not excluded that a small number of very small solid substances are allowed to follow the separated liquid through the filtering belt. The filtering belt may be made of any suitable material, for instance tissue, plastic or metal, and consists of a flexible, thin fabric. In case sepa¬ ration of grindings from oil is desired, it is possible to use a steel fabric with a mesh size of about 200 mesh (74,5 μ ) . However, the mesh size may vary considerably and be in the order of mm on separation of water from a wet peat material.

The filtering belt 1 is endless and driven by a diverting roller 2. The filtering belt l is supported by a support belt 3, also endless, which is diverted by two diverting rollers 4 and 5, one 4 of which is drivable. These two diverting rollers also participate in the diverting of the filtering belt 1. The rollers 2 and 4 are suitably arranged to drive the two belts 1 and 3 with the same speed. The support belt 3 is air and liquid permeable with considerably larger holes than the meshes of the filtering belt and consists here of a wire belt known per se with a plurality of mutually spaced transversal axles 6, which are interconnected by links 7 of rigid wire, in this case steel wire, which extends between the axles 6 on one and the same side, namely that belt side which is turned outwardly (see Figs 2 and 3) . The upper part of the support belt is in its turn arranged to bear upon a rigid underlayer in the form of a substantially flat plate 8, which has a groove 9 running downwardly and extending in the longitudinal direction of the belts, said groove emerging into a lower orifice 10 located in the middle of the plate, to which orifice a device for gene¬ rating a negative air pressure is connected.

Owing to the fact that the axles 6 of the support belt function as spacing elements for the support surface (the wires 7) of the belt when the support belt 3 is dragged upon the plate 8 on driving the support belt by the diverting roller 4, free spaces 11 are formed between adjacent axles. These spaces 11 extend in the transversal direction of the support belt, and the negative air pressure provided at the orifice 10 may be led to and propagate in said spaces thanks to the longitudinal extension of the groove 9, which crosses these spaces. It appears from Fig 3 that the axles in this case bear upon the plate through the wire links 7 bent therearound, and consequently said spaces 11 may also communicate through openings under the axles between adjacent wires. However, this is not an absolutely necessary characteristic. Thus, a negative air pressure will be built up on the underside of the filtering belt 1 over the length corresponding to the length of the groove 9. A sealing tympan strap 13, preferably of rubber, bears through spring loaded rollers 12 on both sides of the belts l and 3 upon the plate 8 so as to establish an accurate sealing and prevent lateral draughts along the belt borders.

The upper surface of the filtering belt is arranged to receive the mixture to be separated in the region 14 of one end of the upper belt part from an arbitrary supplying device (not shown) . The mixture is intended to follow the filtering belt in its movement in the direction of the arrow A (Fig l). As seen in this direction directly behind this region 14, a plough 15 is arranged immediately above the filtering belt l so as to uniformly distribute the mixture passing thereunder over the whole width of the filtering belt. A draining groove 16 with a lower orifice 17 for carrying liquid away is arranged in the plate 8 under the plough 15. The draining groove 16 is arranged to remove a first easily separated liquid amount from the mixture, which may pass through the filtering belt 1 solely by the influence of the gravitation. However, this draining groove 16 may be omitted in the case that the combination of the liquid contained in the mixture and the mesh size of the filtering belt makes it impossible for the liquid to pass through the belt solely by means of the gravitation.

When the mixture 18 arrives over the plate region over which the groove 9 extends, it will be effected by a negative air pressure propagating in the free spaces 11 on the underside of the filtering belt 1. As a consequence of this, the liquid con¬ tained in the mixture will be sucked through the filter belt and the support belt 3 towards the groove 9 and through this to the ori ice 10. Two spring loaded rolls 19 are arranged along the travel of the filtering belt from the diverting roller 5 towards the diverting roller 2 so as to press the mixture between themselves and the filtering belt 1, which thanks to the support belt 3 and the plate 8 lying thereunder may resist a very high pressure. The rolls 19 are arranged to press liquid out of and through the more compact mixture layer which could have been built up upon the filtering belt after the initial suction away of the liquid. The rolls 19 are also intended to be arranged in such devices, which have to treat mixtures with solid components with ability to absorb liquid. The rolls 19 then serve to press the liquid out of these solid components, when they pass under the rolls. This makes it possible to assure that also in such mixtures only solid, liquidpoor particles remain upon the filtering belt on arriving thereon to the region 20, where it is diverted downwardly. A collecting vessel 21 for solid particles is arranged in the region 20 below the filtering belt. The particles located on the under¬ side of the filtering belt after the diverting thereof will by means of the gravitation fall down into the vessel. It is not an obligation, but other means may also be arranged to remove the particles from the belt. A compressed air nozzle 22 ar¬ ranged to blow the particles off the belt and down into the vessel 21 is shown in Fig 1. In the case that magnetical solid particles, such as grindings, are treated one or more magnets could also be arranged under the belt for attracting the solid particles.

The negative air pressure generating device comprises a fan schematically indicated at 23, the low side 24 of which is connected to an air space 26' above the liquid surface of a closed recipient 25 for collecting the liquid separated from the mixture. A conduit 26 is arranged to connect said air space with the orifice 10 in the underlayer 8 for the transport of suction air with liquid drawn through the filtering belt 1 to the recipient 25. A draining means in the form of a liquid pump 27 is arranged at the recipient 25 for holding the volume of the air space 26' above the liquid surface over a predetermined value, which in Fig 1 is indicated by ^■■max", this mark defining the highest liquid surface level allowed in the recipient. This is in order not to jeopardize the separation function of the device through air suction. The liquid pump 27 is arranged at an essential height above the bottom of the collecting reci¬ pient and to pump liquid out of the recipient at time intervals being long enough to give a substantial part of the small solid particles passing with the liquid through the filtering belt, which particles have a smaller size than the meshes of the filtering belt, time to sink below said height and remain in the recipient when this is pumped out. Thus, a kind of decan- tation is carried out, since small solid contamination par¬ ticles settle and form a sediment. This may be an important feature of the purifying of oils used in machining in the engineering industry. However, the liquid level is never allowed to sink below a "min-'-level lying above the connection of the liquid pump, so that liquid in every desired moment may be pumped away from the recipient, for instance for immediate re-use.

The liquid pumped out of the recipient 2^'5 is then led to a vessel 28 for intermediate storing. The device according to the invention may be adapted to receive a mixture deriving from a process in which a liquid is utilized and gets contaminated by solid substances, and the purified liquid from the liquid pump 27 or the intermediate storing vessel 28 may then through a conduit be recirculated to the process. This is particularly advantageous in purifying oils used in grinding and other material machinings for bonding of grindings, cooling and the like.

A filter 29 is arranged between the fan 23 and the recipient 25 to clean the suction air sucked towards the fan, so that no contaminations or particles from the liquid flowing through the conduit 26 down into the recipient arrive to the fan 23. The hot air leaving the fan 23 on its exhaust side will accordingly be harmless to inhale. At the same time the liquid is purified by the removal of air. It is possible to connect the exhaust side 30 of the fan 23 to the compressed air nozzles 22 for blowing the solid particles away from the filtering belt, but it is also conceivable, in the case that it is desired to accelerate the separation of a mixture treated by the device, to lead the hot air from the exhaust side of the fan to the region above the filtering belt and blow the hot air onto the belt and the mixture located thereon, so that drying and consequently evaporation of the liquid in the mixture takes place. This possibility is very schematically indicated in Fig 1 by a conduit funnel 31. This measure may be suitable when water is to be separated from a mixture of solid particles and water in order to obtain dry solid particles. This may be the matter in treating peat or any other such material. However, it is also possible to provide the device with heating lamps, radiators or similar elements so as to make a drying desired even more efficient.

The invention is of course not limited to the preferred embodi¬ ment described above, but a plurality of possibilities to modify it will be apparent to a man skilled in the art without departing from the basic idea of the invention. It would for example be conceivable but hardly successful to arrange transversal ribs on the underlayer plate as spacing elements for the support belt, upon which ribs a support belt in the form of flexible wires will run.

In dependence of the mixture intended to be treated by the device different parts of the device described above may be modified or omitted, and adding of other auxiliary means may also be carried out. It would not be right to try to make a list of all these innumerable variation possibilities. Diffe¬ rent types of purifying plants, within the industry but also municipal ones, may be mentioned as examples of further fields of use of the device according to the invention.

Claims

1. Device for separation of liquid and solid components of a mixture (18) thereof, comprising a filtering belt (l) with meshes, said filtering belt being arranged to receive the mixture on a surface facing upwardly and by means of its mesh size attain said separation by letting liquid components through while retaining solid ones, and an apparatus (23) arranged to generate an active driving of the mixture liquid through the filtering belt, c h a r a c t e r i z e d in that the apparatus is arranged to produce a negative air pressure on the underside of the filtering belt for sucking the liquid through the belt.

2. Device according to claim 1, c h a r a c t e r i z e d in that a second liquid and air permeable belt (3) is arranged under the surface of the filtering belt (l) facing upwardly to support the filtering belt, that the support belt (3) in its turn is arranged to bear upon a rigid underlayer in the form of a substantially flat plate (8), that the plate has a groove (9) running downwardly and emerging into a lower orifice (10) in the plate, that the orifice (10) is connected to a device (23) for generating a negative air pressure in the orifice, and that the support belt (3) is arranged to bear upon the plate (8) by spacing elements (6) for forming free spaces (11) between itself and the plate for the propagation of the negative air pressure prevailing in the groove also between the support belt (3) and the flat portions of the plate (8).

3. Device according to claim 2 , c h a r a c t e r i z e d in that the support belt (3) consists of a wire belt known per se with a plurality of mutually spaced transversal axles (6) forming said spacing elements, adjacent axles being intercon¬ nected by links (7) of rigid wire extending between the axles on the sides thereof turned away from the underlayer for forming a support surface for the filtering belt (1) at a height over the underlayer determined by the diameter of the axles, so that elongated spaces (11) are formed between adja¬ cent axles.

4. Device according to claim 2 or 3, ch a r a c t e r i z e d in that the filtering belt (1) and the support belt (3) consist of endless driven belts arranged to be driven by means of diverting rollers (2, 4, 5) with an upper part running on the underlayer (8) and a lower part running in the opposite dire¬ ction, that the upper surface of the filtering belt (l) is arranged to receive the mixture (18) in the region (14) of one end of said upper part and convey it to the region (20) of the other end of this part, where the filtering belt is diverted downwardly, while the liquid of the mixture is sucked through the filtering belt (1) and the support belt (3) and away through said orifice (10) in the underlayer by the negative air pressure propagating in said spaces (11), that the groove (9) formed in the plate (8) extends in the longitudinal direction of the belts, and that means (22) are arranged in the region of the diverting downwardly of the filtering belt to remove the solid particles remaining thereon.

5. Device according to claim 4, c h a r a c t e r i z e d in that a collecting vessel (21) for solid particles is disposed under the filtering belt (1) in the region of its diverting downwardly, and that said removing means comprises the gravita¬ tion acting on the particles located on the underside of the filtering belt after the diverting thereof and at least one compressed air nozzle (22) arranged to blow the particles off the belt and downwardly into the vessel.

6. Device according to claim 2-5, c h a r a c t e r i z e d in that the negative air pressure generating device comprises a fan device (23) connected through its low side (24) to an air space (26') above the liquid surface in a closed recipient (25) for collecting the liquid separated from the mixture, and that a conduit (26) is arranged to connect said air space to the orifice (10) in the underlayer (8) for transport of suction air with liquid sucked through the filtering belt to the collecting vessel.

7. Device according to claims 5 and 6, c h a r a c t e ¬ r i z e d in that a filter (29) is arranged between the fan device (23) and said air space (26') of the recipient to filter the suction air, and that the exhaust side (30) of the fan is connected to said compressed air nozzle (22) and provides this with compressed air.

8. Device according to claims 5 and 6, c h a r a c t e ¬ r i z e d in that a filter (29) is arranged between the fan device (23) and said air space (26') of the recipient to filter the suction air, and that the exhaust side (30) of the fan is led to the region above the upper part of the filtering belt (1) so as to blow hot air onto the belt and the-mixture lying thereon in order to accelerate said separation by drying and thereby evaporation of liquid from the mixture.

9. Device according to claim 6, c h a r a c t e r i z e d in that means (27) are arranged for draining the recipient for holding of the volume of said air space above a predetermined value, that the device is adapted to receive a mixture deriving from a process in which a liquid is utilized and becomes contaminated by solid substances, and that said draining means is connected to a conduit for recirculation of the separated liquid to said process.

10. Device according to claim 6, c h a r a c t e r i z e d in that means (27) are arranged for draining the recipient for holding the volume of said air space above a predetermined value, and that these means are arranged at a substantial height above the bottom of the collecting vessel (25) and to drain liquid at this height at time intervals long enough for achieving that a substantial part of small solid particles passing through the filtering belt (1) together with the liquid may have time to sink below said height and remain in the recipient when it is drained, said particles having a smaller size than the meshes of the filtering belt.

11. Device according to claim 4 and possibly any of the other preceding claims, c h a r a c t e r i z e d in that at least a roll (19) is arranged to press the passing mixture from above against the filtering belt (1) and the support belt (3) lying thereunder so as to press liquid out of solid mixture compo¬ nents containing liquid and/or between solid mixture components and down through the belts.

12. Device according to any of the preceding claims, c h a r a c t e r i z e d in that the filtering belt is a close-meshed wire cloth.