WO2000073049A1

WO2000073049A1 - Apparatus for separation

Info

Publication number: WO2000073049A1
Application number: PCT/SE2000/001110
Authority: WO
Inventors: Richard Bruke; Mattias Hedren; Staffan Tiliander
Original assignee: Spirac Engineering Ab
Priority date: 1999-05-31
Filing date: 2000-05-30
Publication date: 2000-12-07
Also published as: SE9902014L; AU5264500A; SE9902014D0

Abstract

The invention relates to an apparatus for separating solid substances from a liquid and increasing the total solids of the separated solid substances. A shaftless spiral (3) is disposed to rotate in a substantially horizontally oriented casing (2). Between the infeed section (15) of the apparatus and the discharge section (29), a portion (21) of the casing is provided as a drainage device (7) which forms a rotating part of the casing. The drainage device is followed by a compaction section (23a) with a stationary casing. The discharge end (31) of the spiral reaches only a distance into the compaction section which is followed by a discharge section (29) with a discharge aperture (240). A mechanical counterpressure device (8) is disposed to close and open the discharge aperture. The major fraction of the liquid in the mixture of liquid and solid substances is removed by the drainage device (7). The separated solid substances are displaced by the spiral to the compaction section (23a, b), where the total solids is increased by compression of the substances between the end (31) of the spiral and the counterpressure device (8). Thereafter, they depart from the apparatus through the discharge aperture (24).

Description

APPARATUS FOR SEPARATION

The present invention relates to an apparatus which separates solid substances from a liquid and thereafter increases the total solids (TS) of the separated solid substances in accordance with the preamble to the appended independent claim.

In many contexts, and particularly within industry, there is often a need to separate, from liquid, solid substances such as bodies, fibres and particles and thereafter reduce the liquid content in material which has been separated. The separated material includes solid or semi -sol id components of different sizes, densities, elasticities, etc. Grid and screenings from purification plants for waste water are also examples of material which is separated from a liquid and whose TS thereafter needs to be increased.

For some time, there has existed a need for equipment which, in one and the same apparatus, separates solid substances from a liquid and in addition substantially increases the total solids of the material which has been separated. By a controlled reduction of the liquid content in the separated material, it could, for example, be possible to improve the degree of efficiency in storage, recycling or destruction of the separated material.

Increased TS generally entails reduced costs for handling, transport and storage of the material, among other things because the material has become lighter in weight or attained a sufficiently high TS for fungus formation not to occur. Material of the above-disclosed type is handled daily in large quantities and it is a reality that its handling cannot take place without many problems occurring.

In the use of spirals lacking a mechanical shaft for compacting material as the technology is described in patent specification EP 0 179842 Bl, it is not possible to separate bodies from a liquid. On the other hand, the described apparatus is suitable for compacting compressible material. It is obvious that, in such compaction, the moisture content of moist material is reduced. For that reason, the casing of the apparatus is provided with drainage apertures in that part where compaction of the material takes place.

However, the apparatus has a limitation as regards the permitted maximum value of the compression forces which are applied to the material being compacted.

When the compression forces are applied to the material being com- pacted, both axially and radially directed force composants occur which act on the shaftless spiral of the apparatus. In the axial direction of the spiral, it is generally possible to permit relatively large dimensional changes without the spiral or helix being damaged, while large forces which occasion deformation transversely of the axial direction of the spiral often entail damage to the spiral to such an extent that the spiral must be replaced.

In intermittent operation of apparatuses according to the technology described in patent specification EP 0 179842 Bl a major risk occurs that a body of matter remaining in the discharge section after a time becomes stuck in the discharge section. The greater the forces which are employed in compaction of the material, the greater will be the risk that the compacted material fastens in the discharge section of the apparatus. Such plug-forming bodies must be removed before the apparatus is restarted, since they entail that the spiral is often broken and/or the casing of the discharge section is, in due course, ruptured when "new" material is fed in against a blocking plug-forming body. Since the apparatuses are often employed intermittently and occasionally with long time intervals, the above-described plug formation is a serious draw-back.

According to prior art technology, the spiral-free section of the casing entails that the material (the plug) in the compaction section of the apparatus is braked to a not insignificant degree by the fric- tion which occurs between the plug and the casing. This entails that the compression force the spiral exercises against material which is fed by the spiral into the region between the end of the spiral and the counterpressure device is not only determined by the total force at which the counterpressure device is set to withstand, but also by the friction between the casing and the compressed plug of supplied material. Uncertainty therefore occurs in the regulation of the desired maximum compression force against material which is fed in to the above-mentioned region when the regulation is based on the total force which the plug applies against the counterpresssure device. The uncertainty in control also entails that, in applications where the degree of compaction is employed to control the total solids of the material discharged from the apparatus, an undesirable uncertainty occurs as regards the actual total solids of material discharged from the apparatus.

In increased compression forces against the material which is com- pacted, the frictional forces increase between the material in the plug and the casing, which increases uncertainty in control and the risk of blocking material plugs.

The above-outlined wishes and needs are satisfied using an apparatus according to the characterizing clauses of the appended independent claim.

The present invention realizes an apparatus which includes a drainage device for separating solid and/or semi -sol id bodies from a liquid and a device for reduction of the liquid content in the material which the separated bodies form. The combination employed in the apparatus of spiral and casing creates a compact equipment unit which forms equipment providing efficient separation of the bodies and efficient reduction of the liquid content in the material which has been separated off. Since the separation takes place in a closed system, pressure on the ambient environment is negligible.

The present invention also realizes an apparatus which includes but a single drive means, which improves operational reliability and facili- tates maintenance of the equipment. The appended sub-claims disclose solutions to the sub-problems described above.

In certain embodiments of the present invention, the risk of radial de- formation of the spiral is substantially reduced in that the length of the spiral has been minimized.

In order to obviate the above-outlined problems as regards plug formation in the discharge section of the apparatus, and problems in con- trolling the displacement of the hatch, in embodiments of the present invention the discharge section of the apparatus is arranged to improve the supervision of the compression force of the spiral against the material which is fed in to the region between the spiral end and the body of compacted material located between the spiral end and the coun- terpressure device. This is attained in a first embodiment in that the distance between the hatch of the counterpressure device in a closed position and the free end of the spiral is extremely short (as a rule most approx. 1/3 of the spiral diameter and, in one preferred embodiment, at most approx. 1/4 of the spiral diameter). As a result, the size of the friction between the body of compacted material and the casing of the discharge section is so slight that its effect on the force the spiral applies against the body of compacted material is negligible. As a result of this embodiment, the risk is also reduced that compacted material remaining in the discharge section forms a blocking body or plug which prevents the apparatus from functioning.

In one alternative embodiment, the sought-for effect is attained in that the discharge section has a cross-section which, from the region of the free end of the spiral, increases with reduced distance to the aperture of the discharge section. This embodiment entails the desired low friction between the body of compacted material and the casing of the discharge section on displacement of the body in a direction from the spiral .

Further expedient embodiments of the present invention are disclosed in the appended sub-claims. The present invention and its properties will be more readily understood on the basis of the following description with particular reference to the accompanying drawings, in which:

Fig. la is an axial section through one embodiment of the apparatus where this includes only one shaftless spiral,

Figs, la-d show the sections A-A, B-B, C-C and D-D in Fig. 1,

Fig. 2 shows one embodiment in which the drainage device is of greater diameter than surrounding parts of the apparatus,

Fig. 3 shows an embodiment lacking a mechanical shaft;

Figs. 4, 4a show embodiments with the drive means located in the discharge section of the apparatus;

Fig. 5 shows the material distribution in the longitudinal direction of the apparatus; and

Figs. 6a-b show embodiments of the discharge section of the apparatus.

Figs. 1, la-c and 2 show one embodiment of an apparatus 1 according to the present invention. The apparatus includes an elongate tube-like casing 2 in which is placed a mechanical shaft 9 and a shaftless spiral 3. The mechanical shaft and the spiral are disposed to rotate about a geometric centre axis 34 which is substantially common to the casing, the spiral and the mechanical shaft. The casing 2 is composed of several mutually sequential casing sections. The one end portion of the casing forms the infeed section 15 of the apparatus and the other end portion of the casing forms the discharge section 29 of the apparatus.

The spiral is formed as a helical blade 33 which, as a rule, is up- right. The expression helical blade comprises also helical blades composed from several part helical blades which, for example, are arranged to radially abut edge-to-edge against one another or disposed to over- lap one another. The spiral has a free central passage 32 (see Fig. lb) which extends in the longitudinal direction at least along a part of the length of the spiral.

The mechanical shaft 9 is generally designed as a hollow cylinder 9. The wall of the cylinder carries reference numeral 90 (Fig. la and lc) .

The infeed section 15 has one or more infeed apertures 14 which, in the embodiment illustrated in Fig. 1, connect to an upwardly-directed drum 16. In the infeed section, the casing terminates with an end wall 12 to which, in the embodiment of the apparatus illustrated in Fig. 1, is connected a drive unit 6 (hereinafter generally referred to as drive means 6). The drive means 6 includes a motor 4, a gear unit 30 and a drive plate 10 to which the one end 96 of the mechanical shaft 9 (Fig. 1 and 2) or the one end 36 (the infeed end 96, 36) of the spiral 3 (Fig. 3) is fixed. The other end 91 of the mechanical shaft will hereafter also be designated the discharge end 91 of the shaft, and the other end 31 of the spiral will also hereafter be referred to as the discharge end 31 of the spiral. The designation free end 31 is also occasionally employed for the spiral 3.

Seen in the longitudinal direction of the apparatus, the combination of mechanical shaft, spiral and casing (cf. Fig. 1) is divided into an in- feed zone 20, a drainage zone 21, a precompaction zone 23a, a compac- tion zone 23b and a discharge zone 24.

In the drainage zone 21, the casing includes a casing portion 7 which is designed as a drainage device 7. The drainage device is disposed to rotate about the geometric centre axis 34 of the casing, while the cas- ing has a fixed position in the precompaction zone 23a, the compaction zone 23b and the discharge zone 24. The rotary drainage device 7 merges into the other non-rotary casing sections by the intermedially sealing couplings 200.

The drainage device 7 is provided with passages 25, hereafter generally referred to as drainage apertures 25 which are dimensioned such that bodies in the liquid exceeding a predetermined size are to be retained when the liquid passes through the drainage apertures 25. In the drainage zone, a sufficient quantity of liquid is removed for the function described below with precompaction and a subsequent compaction of the material to be achieved. Above the drainage device, there is provided in the illustrated embodiment a number of nozzles 60 for liquid which are directed towards the drainage device. In the embodiments shown in the figures, there are provided two elongate brackets 61 oriented in parallel with the spiral and supporting the nozzles (cf. Fig. la). Liquid jets from the nozzles remove material which has stuck to the drainage device and which blocks the drainage apertures 25 in the rotary drainage device.

The drainage device 7 includes a drum-like drainage section 70 whose circumferential surface is formed, for example, from a bent metal sheet which is provided with drainage apertures, from lamella which between them form gaps (such as helical lamella which surround the spiral or lamella disposed in the longitudinal direction of the apparatus), by a screenage net, by a screen mesh, etc. In certain embodiments, that side of the "casing" which is turned to face towards the geometric centre axis 34 is provided with guide means 71, for example panel-shaped guide means which are directed towards the centre axis in order, on rotation of the drainage device, to guide the displacement of the bodies towards the discharge end of the apparatus. The drainage section 70 is rigidly connected to the mechanical shaft 9 by means of mechanical devices 72, for example spokes in order to rotate synchronously with the mechanical shaft 9 and also to mechanically stabilize the drainage section.

In particular in those embodiments where the drainage section (screen section) of the drainage device 7 is yieldable, for example consists of a fine-mesh screen 62, one or more bracket members 63 are provided for mechanically stabilizing the screen section. The bracket devices are, for example, disposed between the screen member and the central shaft or the spiral, depending upon the embodiment. In other embodiments, the bracket devices are disposed on the opposite side of the screen member, as is apparent from Fig. 3a. The bracket devices also have passages for liquid. A large mesh metal net 63 of powerful gauge wire is wholly suited to be employed as bracket device. The length of the precompaction zone 23a is generally selected such that it at least is approximately equal to the spiral diameter and at most approximately equal to 1.5 times the spiral diameter.

In the precompaction zone, the accumulation of bodies which have been separated from the liquid and are extremely wet begins. The length of the precompaction zone is relatively short and, as a rule, it is of a length which is less than the diameter of the spiral. The precompaction zone 23a merges in the compaction zone 23b in the region of the discharge end 31 of the spiral. The compaction zone in turn continues a short distance after the discharge end of the spiral in a direction towards the discharge ends 21 of the apparatus. The length of the precompaction zone and of the compaction zone are adapted for each respective zone in response to the properties of the material which the apparatus is intended to handle. The casing has a substantially corresponding cross-section, at least along the entire length of the compaction zone (cf. Fig. 1, lc-d) and is also provided with drainage apertures for liquid, both in the precompaction zone and in the compaction zone.

The length of the discharge zone 24 is also relatively short. In the discharge zone, the casing generally lacks passages for liquid, since the material which reaches the discharge zone has already reached the desired dryness.

As a rule, it applies that the distance between the discharge end 31 of the spiral and a counterpressure device 8 as described below, also designated hatch, at most amounts to twice the diameter of the spiral.

The transitions between the zones for precompaction, compaction and discharge are not distinct, but the zones merge progressively in one another.

The discharge section 29 of the apparatus is provided with a discharge aperture 240. The mechanical counterpressure device 8 is disposed to close and open the discharge aperture 240. Fig. 1 shows one embodiment of the invention where, in at least one area between the drainage device 7 and the free end 31 of the spiral 3, a portion 27 of the casing 2 is disposed as a support device 26 for the spiral 3. The support device surrounds a portion of the spiral with relatively slight clearance between the surface 26 of the support device facing towards the centre axis 34 (the inner surface 26a of the support device) and the spiral. The support device thereby limits the displacement of the spiral transversely to the axial direction of the spiral. The length of the support device in the axial direction of the spiral corresponds to the length of at least approx. a half of a spiral turn and, as a rule, the length of at least approx. one whole spiral turn. The support device consists, at least in those portions where the spiral is intended to support against it, of a durable material with low friction coefficient. The support device generally lacks drainage apertures. Hereafter, the expression support zone 22 will occasionally be employed for that part of the apparatus where the support device 26 is located, and the expression casing portion 27 for the corresponding portion of the casing.

The support device 26 is placed such that, in its one end, it borders on the drainage zone 21 and, in its other end, on the precompaction zone 23a. It is obvious that, in extremely compact embodiments of the apparatus, the precompaction zone 23a is caused to include also the support device 26 or parts of it. In these embodiments, the support de- vice or at least parts of it is, as a rule, provided with drainage apertures 25. In all practical applications, the distance between the discharge end 31 of the spiral and the support device 26 amounts to at least approx. half of the spiral diameter and generally to at least approx. the whole of the spiral diameter. As a rule, the distance is maximized to three times the spiral diameter and normally to twice the spiral diameter.

In Fig. 1, the support device 26 is shown as a part of the casing 2. In certain embodiments, that part of the casing which forms the support device is provided with at least three guide rules 28 (cf. Fig. lb) which are disposed a distance from each other in the circumferencial direction of the casing. The rules are generally placed a substantially 10

corresponding distance from each other. The guide rules thereby form abutment members against which the spiral supports on its rotation, whereby the movement of the spiral in the radial direction of the spiral is restricted.

In those embodiments of the apparatus which are shown in Figs. 1 and 2, the mechanical shaft 9 is, in its one end 96 the infeed end, connected to the drive plate 10 and, in its other end 91, the discharge end 91, inserted in the central cavity of the spiral 3 and fixed to the spiral. The mechanical shaft is inserted in only a part of the spiral and only so far into it that at least approx. a half of a spiral turn and generally approx. a whole spiral turn at the discharge end of the spiral does not surround the mechanical shaft. The requisite length of the projecting spiral portion depends upon the properties of the material which is to be compacted, but also on the dimensions and pitch of the spiral. It will be obvious that the present invention also encompasses the notion that the spiral portion projecting from the mechanical shaft may be selected to be longer, but it is also obvious that each extension of the projecting portion increases the mechanical stresses on the spiral. It has proved that the above-disclosed length (at least approx. a half spiral turn and generally approx. one whole spiral turn) for the projecting spiral portion generally gives the sought-for compression and thereby the desired total solids of the material discharged at the apparatus.

Examples of cross-sections through each respective zone are shown in Figs. la-d. It will be apparent from the figures that the casing in the compaction zone 23 surrounds the spiral with slight clearance. In the precompaction zone and in the compaction zone, the casing is normally of circular cross-section.

Fig. 1 shows the counterpressure device in one embodiment where it consists of a counterpressure plate 8 disposed in conjunction with the discharge aperture 240 and, for example designed as a hatch 8 which is rotatably journalled in conjunction with the discharge aperture and is movable in the direction of the double-headed arrow D. In other embodiments, the hatch is disposed to be displaced in the axial direction of the spiral on closure or opening of the discharge aperture 240. Hereafter, the word hatch will generally be employed without any restrictive intent.

In the embodiment of the apparatus illustrated in Fig. 1, a drive means 80 for switching the hatch 8 is provided in conjunction with the discharge section 29 of the apparatus. The drive means is provided with a drivearm 81, e.g. designed as a piston. The drivearm is displaceable in the longitudinal direction of the casing 2. The end of the drivearm is movably journalled in a transfer device 82 which is rotatable about a shaft 83 adjacent the discharge aperture 240. The hatch 8 is fixed to the transfer device 82. With the drivearm in its protracted position (starting position of the drivearm), the transfer device is in a position in which it keeps the hatch closed. With the drivearm in its re- tracted position, the hatch is fully open. The size of the opening which is formed between the hatch and the casing is determined by how far the drivearm has been displaced from its starting position.

In one preferred embodiment of the present invention, the adjustment of the hatch is controlled by the size of the driving power or of the current which is fed to the motor 4 of the drive unit 6. To this end, a meter device is provided for measuring the driving power or the current. Based on measured value of power or current, a signal is transmitted to a switching device which, controlled by the signal, displaces the drivearm 81 from or towards its starting position. The size of the power or current which is fed to the motor 4 is determined by the quantity of material which is accumulated in the compaction section. An increased quantity of material requires that greater power or more current is fed to the motor for this to be able to rotate the spiral. An increased quantity of material also increases the pressure which the spiral exercises on the hatch via the accumulated material.

It will be obvious to a person skilled in the art that, in other embodiments, the hatch 8 is disposed in order to co-operate with, for example, a spring which holds the hatch in a closed position when the material in the compaction section exercises a pressure against the hatch which is less than a predetermined size. The spring is set to withstand the predetermined maximum force. The size of the predetermined force is adjustable on each occasion of use. As a result, the user has the possibility of adapting the size of the maximum pressure against the hatch. In response to the properties of the pertinent ate- rial and in response to the desired total solids of the material which is to depart from the apparatus. An increased pressure in the compaction section, the pressure against the inside of the hatch increases and, when the spring has been loaded with a force exceeding the predetermined maximum force, the hatch opens the discharge aperture. When the hatch opens and material is discharged, the pressure of the material against the hatch is reduced, the spring moving the hatch towards the discharge aperture in order wholly or partly to close it.

In those parts of the casing where it is provided with the drainage apertures 25, the casing is surrounded by receptacle chambers, 5a, b for liquid which has passed through the apertures. Fig. 1 shows one embodiment where the apparatus includes two receptacle chambers which are connected to a conduit 50 for transport of liquid between the chambers. One of the chambers is provided with an outlet 51 through which the liquid is removed from the chambers.

Fig. 2 is an overview of an embodiment of the present invention where the drainage device 7 (the casing portion 7) is of greater circumference than the casing has in the support zone. The drainage device con- nects to the casing in the support zone via a conical adaptation member 201.

In certain embodiments, the adaptation member 201 is immovably fixed to the drainage device 7 and accompanies the drainage device on its rota- tion. In this embodiment, the adaptation member 201 is generally provided with passages 25 for liquid and constitutes a part of the drainage device. In other embodiments, the adaptation member is immovably connected to the casing in the support zone, the adaptation member generally lacking draining apertures. In the first alternative, the seal- ing coupling device 200 is disposed in the transition between the adaptation member and the casing in the support zone, while in the other alternative, the coupling device 200 is disposed between the drainage device and the adaptation member.

In practical application of the present invention, which of the alter- natives disclosed in the foregoing paragraphs is to be used is to be determined based on the properties of the mixture of bodies and liquid which will be fed into the apparatus. On use of an immovable adaptation member 201, the spiral is generally caused to project into the adaptation member. The spiral portion projecting into the adaptation member is, in such instance, adapted to the conical figuration of the adaptation member in that the distance from the edge surface of the spiral facing away for the centre axis 34 of the spiral is continuously changed in the projecting spiral portion in order, in each part of the spiral, to substantially correspond to the distance from the inner sur- face of the conical adaptation member to the centre axis 34 of the spiral .

In addition to that specified above for the embodiment according to Fig. 2, the apparatus according to Fig. 2 with a construction which corresponds to that described with reference to Fig. 1 and Figs. la-d.

Figs. 3 and 3a show one embodiment of the apparatus which lacks mechanical shaft. The spiral 3 is, in its one end (hereafter generally referred to as infeed-end), fixed to the drive plate 10. It will be apparent from the figure that the drainage device 7 surrounds the spiral 3 and is secured to it. The drainage device thereby accompanies the spiral when this rotates about its geometric axis. The size of the drainage apertures 25 of the drainage device is selected in view of the size of the bodies which are to be entrapped when the liquid passes through the drainage apertures. The drainage device is, as a rule, fixed to the spiral in an edge 35 directed away from the geometric axis of the spiral. Also in this embodiment, technologies described earlier in this specification for forming the drainage apertures are applicable.

In Figs. 4 and 4a is shown an embodiment of the apparatus where the drive means is disposed in the discharge section of the apparatus. The discharge aperture 240 is disposed in the casing. A device 290 (ejector) radially projecting from the mechanical shaft e.g. a sheet metal piece, accompanies the mechanical shaft on its rotation and presses the compressed bodies out of the discharge section of the apparatus. A return spring biased hatch (not shown) corresponding to the previously described hatch 8 opens and closes the discharge aperture.

The mechanical shaft 9 is journalled both in the infeed section of the apparatus and in the discharge section of the apparatus. According to the embodiment illustrated in Fig. 4a, the mechanical shaft is of tubelike configuration. The tube wall is, in that part which is located in the drainage zone, provided with passages 92 for liquid. As a result, in the embodiment illustrated in Fig. 4a, the mechanical shaft constitutes infeed means for the liquid admixed with bodies fed into the apparatus.

Fig. 5 illustrates the flow 40 of bodies and liquid through the apparatus. In the mixture of liquid and bodies fed to the apparatus, the bodies constitute a very slight proportion. In the infeed zone and in the drainage zone, the major fraction of the liquid departs from the casing when the liquid passes through the drainage apertures 25, while the bodies remain in the drainage device 7. When the bodies reach the precompaction zone 23a, the proportion of liquid is so low that the bodies, when they are displaced by the spiral 3 towards the discharge sec- tion 29, form a substantially composite mass consisting of wet bodies. In the compaction zone 23b, the final reduction of the liquid content takes place when the spiral presses in the bodies into the compaction section and thence to the discharge section 29. It will be apparent from the figure that the semi -sol id or solid bodies fill out a very slight proportion of the cross-section of the casing as long as the material is located in the infeed zone 20 and in the drainage zone 21, and that the material during passage through the precompaction zone 23 takes up an increasingly large part of the cross-section in order, in the compaction zone 23b, substantially to fill out the entire cross- section. In Figs. 6a,b are shown embodiments of the apparatus where the discharge section 29 has a cross-section which, at least most proximal the discharge aperture 240, increases with decreasing distance to the aperture. Fig. 6a shows one embodiment where the increase of the cross-sec- tion is commenced a distance in the spiral -free region and Fig. 6b shows an embodiment where the increase of the cross-section begins already before the spiral -free region. As a rule, the "start point" for the increase of the cross-section is placed at a portion of the discharge section 29 which starts before the end 31 of the spiral at a distance at most amounting to approx. 1/4 of the diameter of the spiral and terminates after the end of the spiral at a distance at most amounting to approx. 1/4 of the diameter of the spiral. In one preferred embodiment, the casing, in the portion where the cross-section changes, is in the form of a cone which flares out towards the dis- charge aperture 240 of the apparatus.

In certain embodiments, the hatch 8 is provided with a mechanical device 84 facing towards the discharge end of the spiral. The device is substantially symmetrical about a geometric axis which, when the hatch is closed, substantially coincides with the geometric centre axis 34 of the spiral. In the figures, the device is shown in embodiments where it is in the form of a bulge 84 on the hatch or cone 84 whose apex 86 is directed from the hatch. When the hatch is closed in the embodiment of the device shown as a cone, its apex 86 reaches in to the precompaction zone. The device reduces the quantity of material in the centre of the compacted body, whereby the reduction of the liquid content in the material is improved.

Bodies which have been fed to the apparatus 1 through the infeed aper- ture 14 and separated from liquid by the drainage device 7 are displaced by the rotation of the spiral 3 in a direction towards the discharge aperture 240. As is apparent from Fig. 5, an accumulation takes place of material in the precompaction zone 23a because of reaction from material in the compaction zone 23b when the hatch 8 prevents the material from passing through the discharge aperture 240 or retards the material on its passage through the discharge aperture. In the compaction zone, the material generally fills out substantially the entire cross-section of the casing. The short length of the formed body of compacted material and/or the increasing cross-section of the discharge section entails that the friction between the body and the casing has a negligible effect on the drive power which is required for rotating the spiral compared with the drive power which is required for forcing in additional material towards the body of compacted material in the compaction zone.

In the infeed section 15 and in the drainage zone 21, the liquid is drained through the drainage apertures 25. The concentration of bodies increases to an extent which entails that, when the bodies are displaced into the precompaction zone, the liquid content is so low that the liquid no longer separates the bodies from one another. On the continued displacement of the material in the precompaction zone, a reduc- tion of the liquid content of the material also takes place. In the compaction zone 23b, the final reduction of the liquid content takes place. The size of the final reduction is determined by the force which is required to open the hatch 8.

In certain practical examples, the apparatus 1 is disposed somewhat inclined so that the material is displaced slightly upwards when it passes in a direction towards the discharge aperture 240. As a result, the drainage of the material is facilitated, since a part of the liquid passes in a direction opposite to the direction of displacement of the material and substantially in the centre of the shaftless spiral before the liquid runs out through the drainage apertures 25. The liquid will thereby have a possibility of reaching the drainage apertures of the casing in an area where the material has not yet had time to be compacted to any appreciable degree.

When the hatch 8 is closed, the material accumulates against the hatch and substantially the entire area from the end 31 from the spiral and the hatch 8 is filled with material. On displacement of the material into the compaction zone 23b, an increasing quantity of material is ac- cumulated in the zone, whereby the pressure of the rotating spiral end against the accumulated material progressively increases. In the compaction zone, there will thereby be formed a body of compressed mate- rial. Liquid which has been absorbed by or accompanies the material is pressed out of it when the spiral end presses the incoming material from the precompaction zone against the body of compressed material. The body which is highly compressed in the axial direction permits liquid to pass only in the region immediately after the spiral end.

Because of the slight extent of the compaction zone in the axial direction and/or its generally outwardly coned form, the friction which occurs as was disclosed above, between the body of compacted material and the casing is negligible. The pressure which the spiral end exercises against the body is propagated substantially in the axial direction and absorbed by the hatch 8.

The hatch 8 is set to be opened at a predetermined pressure against the hatch. The size of the pressure is selected in response to the material properties of the material which is fed into the apparatus and the desired dryness of the material which departs from the apparatus.

When the apparatus is employed for reaching high total solids, as a rule total solids exceeding 30% in the material departing from the apparatus, extremely high pressure is required in the compaction zone. The forces which the spiral applies against the material in the compaction zone are so great that forces occur in the spiral which, in the absence of the support device 26, would result in the rotating spiral being deformed in the radial direction in its free end portion 31 or in a region between the end of the spiral and the anchorage of the spiral against the drive unit 6. The spiral would then rotate under powerful pressure against the casing, which could entail a considerable wear of both casing and spiral. Under certain circumstances, the drawback could even occur that the deformation of the spiral in a radial direction became permanent. A deformed spiral must be replaced by a straight spiral. The support device 26 makes it possible to have the spiral exercise a greater pressure against the material in the compaction zone than was previously possible, at the same time as the risk of the above described deformation and related problems is reduced. The mechanical support device thus makes it possible to cause the spiral to exercise a greater pressure against the material in the compaction zone than the pressure which could be permitted in an apparatus lacking a mechanical support device, at the same time as tolerances in other parts of the apparatus merely need be adapted to the requirements which must be satisfied for achieving the desired interaction between material and apparatus in each handling stage of the material.

By the employment of the above described technology, it has been possi- ble to achieve extremely high total solids levels in the material departing from the apparatus. For example, wet paper pulp (TS less than 5-10%) which has been fed into the apparatus has a total solids level increased to approx. 40%.

In certain practical applications of the present invention, the liquid which departs from the apparatus via the outlet 51 is the product which is taken care of and the material with reduced liquid content constitutes the reject, while in other practical applications of the invention it is the liquid which forms the reject.

The above described counterpressure device has, in certain embodiments, two or more counterpressure plates 8. Since the function of the apparatus is based on a progressive increase of the material quantity in the compaction section of the apparatus and the effect the accumulation has on the drive power which is required for rotating the spiral, the present invention entails major freedom as regards the design of the discharge section. Embodiments in which the discharge section has a cross- section which is greatest at the edge of the discharge aperture 240 are particularly suitable for use in installations where the need for re- ducing liquid content occurs intermittently and occasionally with long time intervals.

In embodiments including the mechanical device 84 disposed on the hatch, the quantity of material is reduced in the centre of the body of compacted material formed in the compaction zone. This contributes in increasing TS in the material in the body, since remaining liquid in the centre of the body of compacted material will have difficulty in reaching the drainage apertures 25 through the surrounding compacted material. With the mechanical device 84, guiding is also improved of the material which the spiral end 31 feeds in towards the body of compacted material .

A major need which the present invention satisfies is that a body of compressed material located in the discharge section of the apparatus must be simply able to be removed out of the discharge section when the hatch 8 is fully opened. The described extremely short distance between the discharge end 31 of the spiral and the hatch 8 which is employed in particular in the event of a cylindrical cross-section of the discharge section satisfies this need.

The embodiment which employs a cross-section which increases with re- ducing distance to the hatch 8 makes it possible to eliminate the risk that a residual body of compacted material in the discharge section after a time becomes stuck. As a result of the present invention, it is possible to adapt the length of the body in the axial direction in response to the properties of the material fed to the apparatus in order to be compacted therein and/or to achieve reduced liquid content. The conical design also affords the advantage that it is possible to permit extremely high pressures in the compaction section without material bodies which fasten in the discharge section being formed.

The described conical design of the discharge section obviates the risk that residual compacted material in the discharge section after a time forms a blocked plug which must be removed before the apparatus can be employed. The conical design also affords the advantage that it is possible to permit very high pressures in the compaction section with- out material plugs being formed which fasten in it.

It will also be obvious to a person skilled in the art that the drainage device 7 rotating about the centre axis 34 entails great freedom in the dimensioning of the requisite screening surface by choice of diame- ter and/or length of the drainage device. The embodiment also permits great freedom in the selection of screening medium. The embodiment with the mechanical shaft 9 to which the spiral 3 is fixed affords the possibility of an extremely short shaftless spiral section. The short and powerfully supported spiral makes it possible to dimension the spiral so that harmful deformation of it is avoided. This in turn entails that the spiral has a capacity of applying great com- pressive forces against the material which is compacted, whereby the TS of the compacted material will be high.

The above detailed description has referred to but a limited number of embodiments of the present invention, but a person skilled in the art will readily perceive that the present invention encompasses a large number of modifications and embodiments without departing from the scope of the appended claims.

Claims

1. An apparatus for separating solid substances from a liquid and for compacting the separated solid substances, where the apparatus in- eludes an infeed section (15) with one or more infeed apertures

(14), and a discharge section (29) with a discharge aperture (240) for substances separated from the liquid, where a rotary, shaftless spiral (3) is disposed in a casing (2) which, at least along a part of its length surrounds the spiral, the spiral having an end (31) facing towards the discharge aperture (240) and located a distance from the discharge aperture, where drive means (6) is disposed to rotate the spiral, where the spiral is disposed, on its rotation, to displace the solid substances towards the discharge aperture, where an end portion of the casing (2) which lacks spiral forms the discharge section (29), where at least one closure member (8) is disposed to be displaced between a position in which the discharge aperture (240) is closed and positions in which the discharge aperture is wholly or partly open, and where the casing is provided with a plurality of drainage apertures (25) which pass through the wall of the casing in a region (23) where the compaction of the substances separated from the liquid takes place, c h a r a c t e r i z e d in that, in a region between the infeed section (15) and the discharge section (29), the casing includes a casing portion (7) which is rotary about its centre axis (34), and that said casing portion is provided with drainage apertures (25).

2. The apparatus as claimed in Claim 1, c h a r a c t e r i z e d in that the casing portion (7) has a circumference which differs from the circumference of that part of the casing which is located be- tween the casing portion (7) and the discharge aperture (240), and that a substantially conical adaptation member (201) is disposed between the casing portion (7) and said part.

3. Apparatus as cl aimed in Cl aim 1 or 2, c h a r a c t e r i z e d in that the casing portion (7) is formed from a mechanically stable material such as sheet metal provided with drainage apertures (25) and which, via mechanical devices (72) is rigidly connected to a mechanical shaft (9).

4. The apparatus claimed in Claim 1 or 2, c h a r a c t e r i z e d in that the casing portion (7) is formed from a mechanically stable material such as sheet metal which is provided with drainage apertures (25) and which is fixed against the edge (35) of the spiral (3) directed away from the geometric centre axis (34) of the spiral .

5. The apparatus as claimed in any of the preceding claims, c h a r a c t e r i z e d in that, in a region between the casing portion (7) and the free end (31) of the spiral (3), there is disposed at least one support device (26) which surrounds a part of the spiral with relatively slight clearance in order to restrict the displacement of the spiral transversely of the axial direction of the spiral .

6. The apparatus as claimed in Claim 5, c h a r a c t e r i z e d in that the spiral (3) is only located at the support member (26) and adjacent parts of the region (33) for compaction of substances separated from the liquid.

7. The apparatus as claimed in any of Claims 1-6, c h a r a c - t e r i z e d in that the mechanical shaft (9) is journalled on both sides of the casing portion (7) that said shaft passes through the central cavity of the spiral, and that said shaft is fixed to the spiral (3) .

8. The apparatus according to Claim 7, c h a r a c t e r i z e d in that the spiral (3), in the region of the support device (26) has a radial extent which substantially corresponds to the smallest distance between the mechanical shaft and the inner defining surface (26a) of the support device.

The apparatus as claimed in Claim 7 or 8, c h a r a c t e r i z e d in that the mechanical shaft (9) is, in its discharge end (91), inserted in the central cavity of the spiral (3) and fixed to the spiral .

10. The apparatus as claimed in Claim 8, c h a r a c t e r i z e d in that the mechanical shaft (9) is inserted in only a part of the spiral (3) and only so far that at least approx. a half spiral turn does not surround the mechanical shaft.

11. The apparatus as claimed in Claim 8, c h a r a c t e r i z e d in that the mechanical shaft (9) is inserted in only a part of the spiral (3) and only so far that approx. one whole spiral turn does not surround the mechanical shaft.

12. The apparatus as claimed in any of the preceding claims, c h a - r a c t e r i z e d in that the discharge section (29), most proximal the discharge aperture (240), has a cross-section which increases with decreasing distance to the discharge aperture (240).

13. The apparatus as claimed in Claim 12, c h a ra c t e r i z e d in that the increase of the cross-section of the discharge section

(29) commences in a portion of the discharge section which begins before the discharge end (31) of the spiral at a distance from the end corresponding to approx. 1/4 of the axial length of a spiral turn and terminates after the end (31) at a distance therefrom cor- responding to approx. 1/4 of the axial length of the spiral turn.

14. The apparatus as claimed in any of the preceding claims, c h a r a c t e r i z e d in that the distance between the discharge end (31) of the spiral (3) and the counterpressure device (8) in a closed position amounts to at least approx. 1/10 of the diameter of the spiral and as a rule to at least approx. 1/5 of the diameter of the spiral and that said distance amounts to at most approx. 1/3 of the diameter of the spiral and generally to at most 1/4 of the diameter of the spiral.