AU620896B2

AU620896B2 - Apparatus for pressing, dewatering and filtering

Info

Publication number: AU620896B2
Application number: AU39015/89A
Authority: AU
Inventors: Dag Bergloff; Reinhart Pinter; Peter Scheucher; Rupert Syrowatka
Original assignee: Andritz AG
Current assignee: Andritz AG
Priority date: 1988-08-11
Filing date: 1989-07-27
Publication date: 1992-02-27
Anticipated expiration: 2009-07-27
Also published as: NL8902006A; AU3901589A; GB2221627A; CH685923A5; ES2014857A6; ATA201888A; FI893498A; AT390014B; DE3925326C2; NL191929C; SE8902708D0; JPH0757289B2; CA1334636C; NL191929B; FI89460C; IT8909504A0; IT1233731B; SE8902708L; FI893498A0; FR2635272B1

Description

PATENTS ACT 1952 COMPLETE SPECIFICATION

(ORIGINAL)

Lf, FOR OFFICE USE: Application Number: Lodged: Complete Specification Lodged: Accepted: Published: Priority: Related Art: 0 Class Int. Class ,Name of Applicant(s): MASCHINENFABRIK ANDRITZ ACTIENGESELLSCHAFT StatteggerstraBe 18 A- 8045 Graz

AUSTRIA

04 4 9 :~~Jress of Applicant(s): 4 09 4 0 0 Actual inventor(s): PETER SCHEUCHER DAG BERGLOFF 4 REINHART PINTER RUPERT SYROWATKA Address for Service: KevnLord Co., 4 Douro Place, WEST PERTH, Western Australia 6005.

Complete Specification for the invention entitled: "APPARATUS FOR PRESSIGN, DEWATERING AND FILTERING" The following statement s a full descripticn of this invention, including the best method of performing At known to me/ us I The invention relates to an apparatus, in particular a machine, for pressing ard dewatering or filtering of sludges, fibrous material suspensions or cellulosic material suspensions, having two circulating filter or screen belts between which the material to be pressed and dewatered or filtered is made to pass and two circulating pressure or supporting belts for supporting the two filter belts on their sides facing away from the material to be treated, as well as supporting and pressing means, in particular stationary during the operation of the apparatus for the pressure or supporting belts on their sides facing away froin the filter belts and the material to be treated. The material to be pressed or treated is preferably introduced into the apparatus as a pretreated or dewatered material, such as in the form of a web, which may consist of uniformly charged crushed filter cake.

It is the object of the invention to provide an apparatus or machine of the type previously mentioned which exerts a continuous pressure 0004 over an extended period of time on the material to be treated and o° whose compression zone is formed in such a manner that the differences in the thicknesses of press materials and filter -akes as well as the compression of material and filter cakes can be well accommodated 0 at. without loss of compression force.

This object is achieved according to the invention starting out from the apparatus or machine initially described in particular

SI

by providing for the supporting or pressing means to form a tunnel or the like, in particular a pressure space or cavity having a straight longitudinal axis, in the compression, dewatrring or filtering zones, S the pressure or supporting belts being sealed against the walls of -2-

II

the tunnel directly or indirectly, locally defined, in particular in several locations of the tunnel, by elastic belts or the like at least essentially enclosing the pressure and supporting belts and the filter belts and the material to be treated on all sides. This creates many possibilities of influencing the material to be treated within the apparatus or the machine, in particular because the pressures and thus the pressing of the material can be appropriately controlled in the sealed treatment tunnel. These effects can be particularly well influenced if the sealing belts are formed as closed or openhollow bodies, preferably as elastic hollow pads or bladders, in particular tube-like. A practical embodiment of the invention is characterized in that the cavities of the seals ar connected to a pressure source, in particular a pump.

A preferr'ed embodiment of the apparatus or machine according to the S invention is, characterized in that the elastic sealing belts, in ii o particular the hollow bodies or hollow pads, are attached to the tunnel wall by means of inserts.

A convenient control of the pressing or filtering operation can S be achieved according to the invention by providing at least three sealing belts between which compression zones, in particular of different pressures,are formed. If several compression zones are provided, it

(I

S is convenient for the pressure to increase from compression zone to I II, compression zone in the running direction of the belts and then to t t decrease towards the material outlet.

In practice, it may be particularly convenient to provide the

I

pressure belts on the side of the screen belts with longitudinal grooves for discharging the pressed-out filtrate, in particular counter to -3r_ ,m the running direction of the belts, and to provide tubes or the like stationary and gliding during the operation of the apparatus in the longitudinal grooves for the discharge of the filtrate, the tubes or hoses conveniently extending from the entrance side of the pressure belts into the first compression zone. The filtrate discharge can conveniently be enhanced by providing for the belts to pass from inlet to outlet in a, particularly slightly, ascending path.

The control of the sealing problem and thus of the pressure conditions in the treatment tunnel created according to the invention is enhanced according to a further development of the invention by providing for the pressure belts to be thicker in their marginal zones than in their centers and/or for the'outer edges of the pressure belts to be rounded, in particular in such a manner that the entire package of belts consisting of pressure belts, filter belts and material 8. being treated, has a cross section of approximately rectangular shape with an approximately semicircular lateral boundary.

rsmm Sealing problems, pressure conditions and dewatering success may o° also be favorably influenced by providing for the pressure belts formed in particular thicker in their marginal zones than in their central zones to be in contact with one another in the marginal zones and to be provided there with at least one longitudinal groove in which a co-advancing sealing cable or rope is provided and for the tunnel or 4 the like of in particular approximately rectangular cross section t !b be subject to pressure medium, in particular pressure fluid, conveniently at least between the first and the last sealing belt enclosing the belt package viewed in belt advancing direction.

The structural layout of an apparatus or machine according to the S The structural layout of an apparatus or machine according to the -4r: ii invention is conveniently such that the tunnel or the like in particular formed with rectangular cross section is formed by pressure plates and tong-like parts tightly gripping them laterally. It may be of advantage for the protection of the seals, but also for increasing the sliding capacity of the pressure belts, to provide wear protection sleeves between the belt package and the sealing belts, in particular the sealing hollow bodies, for instance sealing tubes,a gap conveniently being adjustable during the operation of the apparatus between sealing belts and pressure belts by means of leakage medium, in particular leakage fluid, for instance leakage water, but under certain circumstances also oil or alcohol.

In setting up the system according to the invention, the sealing belts may be formed divived, preferably at least once, the belt ends on the dividing joint(s) being mutually sealingly connected by clamping o' by means of inserts inserted into the tunnel or by means of adhesive.

The wear protection sleeves are also formed divided, preferably in two parts, the conveniently overlapping part ends being suitable for S mutual connection, in particular by means of adhesive.

In practice, the control of the pressure conditions is particularly facilitated by providing for the sealing belts formed as hollow bodies, hollow pads or bladders to be subject to various internal pressures exerted by a pressure medium. A particular influence on the pressure conditions can further be achieved by the individual, hollow sealing belts being composed of several hollow belt portions of which the cavities on the belt edge are subject to a medium of higher S pressure during the operation of the apparatus than the remaining belt portions. To this end, the in particular hollow sealing belts r in an approximately rectangular belt package or tunnel of approximately rectangular cross section can be composed of four, in particular hollow, portions, namely of one each portion extending above and underneath the belt package and one each portion extending over the lateral height or the thickness of the belt package, said four individual portions being :,iiutually sealingly connected in the area of the package edges which are there conveniently fased at an angle of 45 degrees.

Even if favorable pressure conditions are maintained, the consumption of operating engergy can be kept particularly low if only the zone with the highest pressure in the tunnel is connected to a pressure source, in particular a pump, which introduces in particular pressure med i um, conveniently pressure water, into said zone, and if the adjacent zones or the like flowing between the sealing belts and the belt packages.

o convenient circulation of the pressure medium can be achieved by S providing for the leakage or compressed water to be drained or drawn 0° off after flowing through the tunnel compression zones upstream of a m6 the sealing belts or sealing boxes in the inlet and outlet ends of the belts or of the tunnel, in particular to be connected to a working container taking up the pressure medium and connected to the pressure source, in particular the pump. The end sealing belts or sealing boxes are conventiently formed leakage-water-tight, in particular as hollow bodies with about 0.2 to 1 bar of superpressure in operation, preferably Swith air as the pressure medium.

The invention is explained in the following on the basis of exemplary embodiments with reference to the accompanying drawing, w ,erein Fig. 1, Fig. la and Fig. Ib are schemat.c representations Uf -6-

I

dewatering apparatus or machines provided with the pressiry or compression means according to the invention; Fig. 2 shows a cross section in enlarged scale through the core part of the machine or the apparatus along line I-II in Fig. 1; Fig. 2a to 2e show variants in similar sections, although only partially represented; Fig. 3, 3a and 3b represent schematic longitudinal sections along line Ill-Ill in Fig. 2; Fig. 4 and 5 show similar sectional views through the seals and immediately adjacent apparatus and machine parts.

The dewatering machine of compact construction schematically represented in Fig. 1 comprises a lower endless filter belt 4 and an upper endless filter belt 3 between which the material to be dewatered is made to pass. The lower filter belt 4 is formed as a supporting S screen and passed over a number of rolls, namely a screen belt o adjusting roll 111, a deflection roll 114 and a tension roll 113. The ",oo upper filter belt is formed as a cover screen and made to pass over lO0

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guide rolls 114', a tension roll 113' and an adjusting roll 111'.

The material to be dewatered is charged from a charging device 107 onto the lower filter belt 4 so that a cake of approximately uniform thickness is formed to be dewatered between the two filter belts 3,4.

In the compression zone, the two filter belts 3, 4 are supported by circulating, endless pressure belts 1 and 2. The lower pressure belt 2 and the upper pressure belt 1 are trained over deflection rolls 109, 109' and optionally over tension rolls and adjusting rolls. The :1 drive may act on rolls 108, 108'. Smaller deflection rolls may be t provided at the start and end of the pressing line. The pressure belts -7r' 1,2 are made of elastic material impermeable to water and liquids, such as rubber or plastics materials. The supports 105, 106 serve for subjecting the pressure belts 1,2, the filter belts 3, 4 and thus the press cake lodged therebetween to the required compression force. These supports 5, 6 take up the entire compression force and to this end are of very sturdy construction. On both sides of the dewatering machine, the upper and lower supports 105, 106 are connected to one another so as to obtain a short transmission path of the entire forces.

This has the advantage that the very high compression forces do not have to be transmitted to the machine bed (foundation) so that this machine bed can be of comparatively light and inexpensive construction.

According to the invention, the transmission of forces from the supports 105, 106 to the mobile pressure belts 1,2 is effected by a special hydrostatic pressure means represented in detail mainly in Fig. 2 to 1 o0 While the compression zone in Fig. 1 is linear, Fig. la schematically .0.I shows a curved compression Zone. The pressure belts in this case bear "0 the reference numbers while the filter or screen belts are designated The supports for the pressure belts are the drum 105', on the one hand, and the curved body 106', on the other hand.

The linear compression zone could be replaced by those of convex or concave curvature if necessary.

I Fig. lb shows a similar variant. Filter or screen belts are subject to the action of pressure means the pressure means being formed as a belt, the pressure means 2' being formed as a circulating, optionally driven torus or supporting ring resting or centered e.g. on supporting rolls 120. The material is charged at 121.

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A discharge means for the pressed material is designated 122. A pump 123 or another pressure source supplies the required pressure conditions outside of the pressure means (torus belt Supports 105', 106' act on the pressure means 2' and the filter belts or screen belts via hydrostatic pressure devices to be described in the following.

The pressure belts 1,2 are conveniently provided on the screen side with longitudinal grooves (Fig. 2) la, 2a through which the filtrate is discharged counter to the direction of belt advance (see arrow F!) (Fig. 1).

The filtrate is conveniently sucked off according to Fig. 2 by stationary tubes or hoses 5a (also refer to Fig. sliding in the longitudinal grooves la, 2a, one each tube or hose preferably being associated with each groove. As evident from Fig. 1, these tubes S conveniently reach from the inlet side of the belts 1,2 to the first compression zone to prevent filtrate sucked back from wetting the still unpressed cake. Sucking back of the filtrate is conveniently enhanced of* by a belt path Llightly ascending in running direction (see Fig. 1!) Fig. 2 shows a section along line II-II in Fig. 1, thus perpendicular to the advance direction of the apparatus or machine. The pressure belts 1,2 are thicker in their marginal zones and formed for instance rounded on their edges, so that the entire belt package composed of pressure belts 1,2, filter belts 3,4 and the treated material or cake is of approximately rectangular cross section with laterally attached semicircles. It is also possible, however, to provide chamfers instead IL of the roundings or a polygon as the edge boundary or a belt package S: with rectangular cross section.

-9i The pressure belts 1,2 are provided near their edges with grooves 6a in which sealing cables 5 preventing the penetration of compressed water between the pressure belts and at the same time mutually centering the two belts are co-advancing. This constitutes guiding and sealing grooves in circulating direction The belt package passes a rectangular channel charged or filled with a pressure medium, preferably a pressure fluid, said channel being sealingly enclosed on -top and bottom by the pressure plates 7 and on its sides by the tongs 12, so that a tunnel 21 is formed. This channel or tunnel 21 is subdivided in advancing direction into several compression zones Z1 to Z5 (Fig. for instance with pressures increasing in advance direction.

According to the invention, special boundaries allowing movement of the belt package at simultaneous tight sealirrg action are provided at the inlet and outlet of the belt package into the tunnel 21 and out of the tunnel 21 and at the separating sites between the individual a compression zones, Z1 to Z5. According to the invention, the seals

S

1 are elastic seals 8, in particular in the form of tubes or hoses, enclosing the b-lt package.

The boundaries of the compression zones Z1 to Z5 are preferably self-adjusting bladder seals 8 directly installed in the channel or tunnel 21 by means of an insert 9. A small amount of leakage water is allowed to flow between the belt package and an wear protection sleeve 1 F10 to be preferably provided so that the belt package can be pulled essentially without contact and thus with low friction through the seals consisting of bladder seal 8 and wear protection sleeve These bladder seals separate the compression zones Z1 to f t 23 23 belt ends on the separating joint(s) being mutually enclosing the entire belt package from one another and also insulate them against the environment. This is possible because this seal is disposed around the belt package normally to the belt advance direction and thus er closes the entire belt package.

The bladder seals 8 consist of resiliently elastic and dense material having tensile strength, for instance rubber with a fabric insert.

The bladder seal 8 is fastened by means of an insert 9 to be described later on.

Each bladder seal on principle encloses the belt package endlessly.

As previously described, a wear protection sleeve 10 is provided between the bladder seal 8 and the belt package and protects the bladder seal against wear.

The sleeve 10 also passes around or encloses the belt package endlessly on principle, but for assembling reasons is preferably formed in two portions, with top and bottom portion of the sleeve overlapping in the marginal zone.

o The bladder seal may also be divided into several portions instead 0000.0 S of only one. Each bladder seal thus consists of several portions, with the ends of the individual bladders possibly clamped into the insert 9. So, for instance, it is possible for better adaptation of the amount of leakage water to subject the individual bladders located in the zone of the belt edge to higher pressures than the individual bladders c" disposed on the plane belt surface.

At rectangular embodiment of the belt package, the division could be effected into four portions 8" according to Fig. 2e, with two individual bladders extending over the entire belt width and two individual bladders extending merely over the thickness of t I 4 4 Ct 0 6 11 '1< the belt package. The individual bladders 8" preferably abut at an angle of 45 degrees.

Fig. 3 shows a schematic longitudinal section in machine advance direction representing the arrangement of the compression zones. Fig.

3 shows an exemplary arrangement of several boundaries in the form of sealing inserts with pressure bladde-c so that five different compression zones Z1 to Z5 are created. Further seals 30 and 31 serve for separating the leakage water.

The zone Z1 with the highest pressure is supplied with pressure fluid, preferably water, by a pump 32. The amount of water supplied passes the adjacent sealing inserts or boundaries 8 in the adjacent compression zones Z2, 75 of lower pressure as leakage water and passes to the subsequent compression zones Z3, Z4.If the arrangement is composed of seveal stages, the amount of leakage wcter need be used up only once and the pressure can be reduced via any given number of sealing inserts and thus compression zones. This means reduced pump output for the generation of compression force and moreover permits high compression forces, as the pressure bladder is only subject to the respective differential pressure between the two compression zones and the bladder material is thus not too highly stressed.

After the last compression zones in the direction of the leakage water flow (upstream of the seals 30 and 31), drains 356, 37 through which the compressed water is conveyed to a working cowier 38 and thus returned to the circulating pump 32 are provided in the channel or tunnel 21.

Sealing boxes 30, 31 provided outside of the drains 36 and 37 in the channel or tunnel 21 prevent the leaking of the nearly .4 a* 0 04 k p~c 9

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41 a 12 pressureless circulating water from the machine or apparatus. These sealing boxes are of the same construction as the zone boundaries, but subject to about 0.2 to 1 bar of superpressure and preferably fed with air as a pressure medium, so that the wear protection sleeves 10 oF these seals, for instance consisting of teflon, are tightly pressed against the belt package 41 so that virtually no leakage water escapes.

This is a sliding seaT without leakage water. Although the friction is higher as compared to a seal with leakage water, it can be controlled without difficulty due to the low pressures and by the selection of a material with good sliding properties for the sleeve.

In the compression zones, the pressure is preferably adjusted in such a manner that the pressure is increased up to the main compression zone 21 in machine advance direction at increasing dry matter content of the press goods or the cake and thus increasing strength of the material or cake. At the machine outlet, the pressure is decreased depending or the desired pressure difference per sealing insert in one or a plurality of sealing inserts 8 arranged one behind the other.

Fig. 3a and 3b show further variants schematically and in partial representations. According to Fig. 3a, pressure reducing valves 17' are provided. This embodiment applies to the case in which the subsequent zones Z2 et seq. are to be supplied with appropriate additional quantities. This is necessary if the desired pressure gradient or the geometry of the bladders calls for the amount of leakage fluid from zone Z1 to zone Z2 to be smaller than that from zone Z2 to Z3, and so forth. The supplementary quantities are supplied by the pump 32 via line 17"' and pressure reducing valve 17".

A further variant is shown in Fig. 3b. Again, the main volume of 1 a 13 o pressure fluid flows from the pump 32 first into the zone Z1 of the highest pressure; the subsequent zones Z2 et seq. are kept at the desired lower pressures via pressure maintenance valves 17'. Possible quantities ii excess are withdrawn. If the desired pressure gradient or the bladder geometry shows that the amount of leakage fluid from zone Z1 to zone Z2 exceeds that from Z2 to Z3, and so forth, controlled drainage from zone Z2 et seq. to the container 38 is applied.

Exemplary embodiments of seals according to the invention are described in the following. Reference is first made to Fig. 4 which represents a sectional view in longitudinal machine direction. The pr-ssure bladder 8 is arranged with pressure compensation to the compression zone. Fig. 5 shows a further variant in section in longitudinal ma hine direction. In this case, the pressure bladder 8 is subject to pressure applied from the outside.

First of all, the control of the pressure adjustment in the individual zones when using sealing inserts with pressure compensation according o 0o to Fig. 4 is described. The main compression zone (Zi) is sur'I^ied with compressed water by a pump 32. The amount of compressed water supplied passes the successively arranged sealing inserts 8 as leakage water and the pressure is gradually decreased, whereby approximately equal differential pressures per sealing unit (per flow direction) are adjusted. The value of the differential pressure is fractionally A approximated starting from the main compression zone (Z1) and the value of the pressure prevailing there and the number of sealing inserts 1 per leakage water flow direction.

At equal bladder geometry for all bladder seals, the amount of leakage water correspondingly increases upstream and downstream of 4* i

S.

14 _i the sealing insert 8 at increasing differential pressure.

Since the pressures in the zones are to be graduated according to the compressive strength of the treated material or cake increased by the dewatering, varying differential pressures at the individual sealing inserts are required.

These can be achieved by draining pressure fluid from individual zones (pressure controls 15 to 19) in the case of lower differential pressures and !y additional supply of pressure fluid to individual compression zones in the case of higher differential pressures.

The following example describes a control of the pressure adjustment when usiig sealing inserts 8 subject to pressure applied from the outside according to Fig. 5. This type of pressure control makes use of the following operating behavior of the bladder seals 8: at predetermined bladder geometry, the leakage water amount can be decreased by increasing the pressure in the bladder in respect of the pressure in the compression zone upstrea-4. At lower pressure in the bladder seal 8 as compared to the compression zone, the leakage water volume increases accordingly. This method permits an adjustment of the bladder seal at predetermined bladder dimension to different belt package thicknesses, for instance different cake thicknesses or belt and cake compressed by pressure.

Pressure control is preferably effected as shown in Fig. 3. A pump 32 supplies the main compression zone Z1 from a working container 38.

A throttle, eg. a throttle valve 34, downstream of the pump permits the volume adjustment. A flow resistance 33 from which a supply line 14 leads to the (adjustable) pressure controls 15 to 19 and further to the bladder seals 8 is provided downstream of the throttle valve.

Do** 00 0 0 0 0A0 oo a 0 0 0 0 00 0 0 o 0 S00 a fI 15 2

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The desired pressures can thus be adjusted by means of these pressure controls.

The leakage water volume passing through the individual sealing inserts 8 per flow direction is equal. A larger gap forms in the case of sealing inserts with lower pressure differential of the adjacent zones. The amount of water must be adjusted so that the gap is large enough at the sealing insert with the highest differential pressure of the adjacent zones to assure the proper operation of the machine.

In summarizing, the following featuires are emphasized as* ie a-tial to the present invention: the belt package, consisting of upper and lower supporting belts 1,2 with longituLnal grooves la, 2a for dewatering and lateral guiding grooves 6a, lateral sealing belts 6, upper and lower filter belts 3,4 with material to be pressed lodged therebetween, passes a pressure channel or tunnel 21 he,'ing one or a plurality of compression zone(s), for instance Z1 to Z5, the pressure fluid, preferably water, enclosing the belt package on all sides and the compression zones are separated by the seals 8 disposed in the pressure channel and enclosing the belt package perpendicularly to the advance direction. Added to this is the previously mentioned device with self-adjusting bladder seals 8 so that a small gap of e.g. 0.05 mm to the belt package is adjusted so that a leakage water volume fed to the main compression zone passes the zone boundaries arranged one behind the other and the belt package can be drawn through the seals S'.'with very little friction.

The bladder seals shown in Fig. 4 are of open connection to the compression zone upstream and the gap and thus the leakage water volume is self-adjusting as a function of the geometry and pressure S*16 i in differential between the adjacent zones. The bladder seals represented in Fig. 5 are separately subjected to pressure, the leakage water volume can be varied in this case by applying a pressure differential to the compression zone upstream at given bladder geometry and differential pressure of the adjacent zones. The bladder seal with separate pressure supply according to Fig. 5 is subjected to that pressure which is desired in the zone upstream.

The pressed-out filtrate is sucked off through the tubes or hoses extending in the longitudinal grooves up to the area of the first compression zone so as to prevent any remoistening of the cake in zones which are no longer (so strongly) pressed. This can also be achieved by blowing or sucking on the outlet side.

As already mentioned, a slight rise of the pressure channel or tunnel 21 and the belt package in advance direction can enhance the sucking off of the filtrate. To this end, the previously mentioned apparatus provided with leakage water discharge and secondary seals may be convenient, the secondary seals being bladder seals, but with 4 superpressure inside of the bladder and sliding arrangement. The aforementioned measures may be supplemented by a pressure control according to Fig. 3 and an automatic advance control of the belt package by bladder seals. A convenient feature is the self-centering effect of the bladder seals on the belt package.

rrt Fig. 2b and 2c show further variants of the pressure belt guiding t seal, namely, Fig. 2b with wedge-shaped strip 6b with corresponding r counter recess 6c and Fig. 2c with a kind of zippe r 6d.

t Fig. 2a shows a further exemplary embodiment in respect of dewatering and discharge of the filtrate. The pressure belts 1,2 are provided with t 4 i t I S• 17 transverse grooves 1b, 2b terminating in longitudinally extending drainage channel(s) 4.

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Claims

1. An apparatus for the pressing and dewatering or filtering of sludges, fibrous material suspensions and cellulosic material suspensions, having two circulating filter belts between which the material to be pressed and dewatered is made to pass, and two circulating pressure or supporting belts for supporting said two filter belts on their sides facing away from the material to be treated as well as supporting or pressing means stationary during the operation of the apparatus for the pressure or supporting belts on their sides facing away from the filter belts and the material to be treated, characterized in that the- supporting or pressing means form a tunnel in the Scompression, dewatering or filtering zone, said tunnel having walls, the pressure or supporting belts being sealed against said walls of said tunnel, locally defined, by I, elastic belts at least essentially enclosing the pressure or supporting belts as well as the filter belts and the i material to be treated on all sides and edges and arranged transversely to the moving direction of the pressure or supporting belts as well as the filter belts.

2. The apparatus according to Claim 1, wherein the supporting or pressing means form a hollow pressure space or pressure cavity.

3. The apparatus according to Claim 1 or Claim 2, wherein the tunnel, the pressure space or the pressure cavity have a straight longitudinal axis.

4. The apparatus according to Claim 1 or Claim 2, wherein the pressure or supporting belts are'sealed against the walls of said tunnel, pressure space or pressure cavity in several locations of the tunnel, pressure space or pressure cavity by said elastic belts.

The apparatus according to Claim 1 or Claim 2, wherein said sealing belts are formed as hollow bodies.

6. The apparatus according to Claim 5, wherein said hollow bodies are hollow pads or bladders, or tube-or hose-like.

7. The apparatus according to Claim 5 or Claim 6, wherein the cavities of said sealing belts are connected to spaces between the pressure or supporting belts and the supporting or pressing means, respectively, between the individual sealing elastic belts.

S8. The apparatus according to Claim 5 or Claim 6, wherein the cavities of said sealing belts are connected to a 15 pressure source. 'ei

9. The apparatus according to Claim 1 or Claim 2, whereLn :the elastic sealing belts are attached to the wall of the tunnel, the pressure space or pressure cavity by means of inserts.

10. The apparatus according to Claim 1 or Claim 2, wherein at least three sealing elastic belts between which a compression zones are formed, are provided.

11. The apparatus according to Claim 10, wherein compression zones of diffe]'ent pressures are formed.

12. The apparatus according to Claim 10, wherein if a plurality of compression zones is provided, the pressure first increases from compression zone to compression zone viewed in advance direction of the belts and then decreases towards the material outlet. 21

13. The apparatus according to Claim 1 or Claim 2, wherein the pressure belts are provided with longitudinal grooves on the side of the filter belts for discharging the pressed-out filtrate.

14. The apparatus according to Claim 13, wherein discharging means adapted to evacuate the pressed-out filtrate from said grooves counter to the advance direction of the belt are provided.

The apparatus according to Claim 13, wherein tubes or 10 hoses stationary during the operation of the apparatus are E provided in the longitudinal grooves for discharging the filtrate, sliding in the longitudinal grooves during operation, optionally the tubes or hoses reaching from the inlet side of the pressure belts into the first compression 15 zone. a| ei

16. The apparatus according to Claim 13, wherein the pressure or supporting belts are made to pass in a slightly ascending path from the inlet to the outlet.

17. The apparatus according to Claim 1 or Claim 2, wherein the pressure or supporting belts are formed thicker in their marginal zones than in the centers. k

18. The apparatus according to Claim 1 or Claim 2, wherein the pressure or supporting belts are rounded off on their outer edges, optionally in such a manner that the entire belt package, consisting of pressure belts, filter belts and treated material, has a cross section of approximately rectangular form with an approximately semicircular lateral ~boundary.

19. The apparatus according to Claim 1 or Claim 2, wherein -7 22 22 the pressure or supporting belts are in contact with one another in the marginal zones and are there provided with at least one longitudinal groove in which a co-advancing sealing cable or rope is provided, and optionally, the pressure or supporting belts are formed thicker in their marginal zones than in their central zones.

The apparatus accordin- to Claim 1 or Claim 2, wherein the tunnel, the pressure space or the pressure cavity are subjected to pressure medium, preferably at least between the first and the last sealing elastic belt enclosing the belt package viewed in belt advance direction.

21. The apparatus according to Claim 20, wherein th6" tunnel, the pressure space or the pressure cavity are formed Sa* with approximately rectangular cross sections.

22. The apparatus according to Claim 1 or Claim 2, wherein Vnt the tunnel, the pressure space or the pressure cavity are formed by pressure plates and tong-like parts tightly gripping them laterally.

23. The apparatus according to Claim 1 or Claim 2, wherein wear protection sleeves are provided between the belt package and the elastic sealing belts, and preferably, the wear protection sleeves are divided in parts, the part ends of said sleeves being mutually sealingly connected.

24. The apparatus according to Claim 1 or Claim 2, wherein a gap is adjustable between elastic sealing belts and pressure belts in operation by means of leakage medium, preferably automatically.

The apparatus according to Claim 1 or Claim 2, wherein p. the elastic sealing blts are divided at least once, the 23 belt ends on the separating joint(s) being mutually sealingly connected by insert parts installed in the tunnel, pressure space or pressure cavity.

26. The apparatus according to Claim 1 or Claim 2, wherein the elastic sealing belts formed as hollow bodies are subjected to different internal pressure by a pressure -medium.

27. The apparatus according to Claim 1 or Claim 2, wherein the individual elastic hollow sealing belts are composed of several hollow belt portions of which the cavities of belt portions arranged on the belt edge are subjected to a medium of higher pressure in operation than the remaining belt portions.

28. The apparatus acccrding to Claim 1 or Claim 2, wherein t a. 15 in an approximately rectangular belt package or tunnel, pressure space or pressure cavity of approximately ,rectangular cross section, the elastic sealing belts are composed of four portions, namely, one each portion extending above and beneath the belt package and one each portion ey.cending over the lateral height or thickness of e the belt package, the four portions being mutually sealingly connected in the zone of the package ends.

29. The apparatus according to Claim 12, wherein only the zone of the highest pressure in the tunnel, the pressure space or the pressure cavity is connected to a pressure source which introduces pressure fluid or liquid into said zone, and the adjacent zones of the tunnel, the pressure 'p R space or the pressure cavity a, e subjected to pressure by the leakage fluid or liquid flowing between the elastic I H' *t 9 .9. t 5 4 4 4 4 44 4 1( 4 24 sealing belts and the belt packages.

The apparatus according to Claim 20, wherein the leakage or compressed fluid or liquid is suitable for being drained or drawn off after flowing through the compression zones of the tunnel, the pressure space or the pressure cavity upstream of the elastic sealing belts and the inlet and outlet ends of the belts of the tunnel, the pressure space or the pressure cavity.

31. The apparatus according to Claim 30, wherein the leakage or compressed fluid or liquid is connected to a working container receiving the pressure medium and connected to the pressure source.

32. The apparatus according to Claim 31, wherein the end elastic sealing belts are formed leakage-water-tight in 15 operation, and preferably, the end elastic sealing belts are formed as hollow bodies with 0.2 to 1 bar of internal pressure.

33. The apparatus according to Claim 29, wherein the main volume or quantity of pressure fluid flows into the zone of the highest pressure and the successive zones are kept at the required pressures by means of pressure reducing valves or nressure maintaining valves.

34. The apparatus according to Claim 29, wherein the main volume or quantity of pressure fluid flows into the zone of the highest pressure and the successive zones are kept at the required pressure by feeding the appropriate additional volumes or quantities of fluid, respectively, by withdrawing the required differential volume or quantities. S35, An apparatus for the pressing and dewatering or -zL pc I r filtering of sludges, fibrous material suspensions or cellulosic material suspensions substantially as hereinbefore described with reference to any one of the accompanying drawings. DATED DECEMBER 11 1991 MASCHINENFABRIK ANDRITZ ACTIENGESELLSCHAFT By their Patent Attorneys KELVIN LORD AND COMPANY PERTH, WESTERN AUSTRALIA. I i 1tr1 t rott I I