WO2016097839A1

WO2016097839A1 - Filter plate groups for filter press machines

Info

Publication number: WO2016097839A1
Application number: PCT/IB2015/002336
Authority: WO
Inventors: Rosario Eduardo TAGLIAVINI; Davide COLLINI; Andrea Bassi; Fabio PARIS
Original assignee: Bilfinger Water Technologies Srl
Priority date: 2014-12-17
Filing date: 2015-12-10
Publication date: 2016-06-23

Abstract

The plate groups are mutually associated two-by-two, delimiting filter chambers of the suspension. Each plate group comprises: a vertical support wall (10), located in a vertical position, and a filter screen (20) for actuating filtration of the suspension, at least a filter screen (20) being provided for each filter chamber, in a form of a flat and slim element located in a vertical position adhering to the support wall (10). In the invention, the filter screen (20) comprises a flat front face free of roughness, slotted by a plurality of longitudinally-developing through-slits (F) which develop in a vertical direction, parallel to one another, having a width such as to retain the solid phase and enable passage of the liquid phase, the slits (F) having, in a horizontal transversal section, an increasing or constant width starting from the front face and going towards the rear side.

Description

FILTER PLATE GROUPS FOR FILTER PRESS MACHINES

TECHNICAL FIELD

The present invention relates to filter press machines.

PRIOR ART

The filter press is an industrial machine used for dehydrating sludges (solid- liquid suspensions) using solid-liquid separating processes. In other words, press-filtering is a volumetric reduction system of liquid substances which internally include suspended solids.

Very briefly, a filter press comprises a series of flat walls alternated with cloths which adhere two-by-two to one another forming filter chambers in which the sludge is pumped at high pressure. The liquid phase exits from the chamber through the cloth filter, while the solid phase is retained in the chamber where it forms a dehydrated cake of sludge.

Thereafter, the cakes that fill the chambers are removed by distancing the walls from one another, i.e. opening the filter chambers; the cakes then exit the chambers by force of gravity, possibly with the aid of the movement to which the cloth filters are subjected.

Filter press machines are at present used in various industrial sectors: for dehydration of slurry deriving from purifying processes of waste water, of civil and industrial origin, and in many chemical/pharmaceutical and mineral processes.

As regards the size range of the filtered suspensions (0.1 pm - 1 mm), the present technology avails of filter means having a polymeric matrix which in substance can be considered as textiles, both in regard to the production methods (woven products) and in regard to the structure and mechanical behaviour thereof. The chemical-physical parameters characterizing these textiles depend on their nature, as the chemical-mechanical properties describing them.

The main drawbacks the use thereof involves are:

- rapid wear (they are to all effects replaceable parts);

- long replacement times (machine downtime); - not insignificant periodic maintenance (a regular washing cycle).

Overall, as the solid-liquid filter technologies are progressively more involved in very high-productivity processes that are also considered heavy-duty (high risk of component wear), the present filter textiles are progressively more often accused of occasioning high operational costs (OPEX). This is particularly relevant in the case of filter press machines because of their special configuration and the high working pressures.

DISCLOSURE OF THE INVENTION

An aim of the invention is therefore to realise a new plate group for composition of the filter chambers, which provides the advantages of the present technology while obviating the defects therein.

This and other aims are attained by the present invention as it is characterised in the claims.

The invention is based on the idea of replacing the traditional filter means constituted by a cloth with a rigid filter screen (rigid though elastic), thus realizing a fixed coupling (but also removable) so as to obtain a single but complex filter component.

In correct operating conditions, the range of working life of a traditional plate is measured in years while a cloth filter lasts only weeks or months; on the other hand the working life of the plate group of the invention is years for all its components, including for the filter screen, which therefore becomes to all effects a fixed constituent.

Overall the following operational advantages are comprised for the plate group of the invention, with respect to the traditional plate + cloth coupling: - long duration;

- high mechanical and wear resistance;

- insignificant programmed and unprogrammed maintenance times.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in detail in the following, with the aid of the accompanying figures of the drawings, which illustrate some embodiments thereof, by way of non-exclusive example.

Figure 1 is a perspective view of a filter press machine. Figure 2 is a perspective view of a first embodiment of the plate group.

Figure 3 is an exploded view of figure 2.

Figure 4 is a perspective view of the support wall 10 of figure 3.

Figure 5 is a section along plane V-V of figure 2.

5 Figure 6 is a section once more along plane V-V of figure 2, of a plurality of plate groups arranged side-by-side together to form filter chambers.

Figure 7 is a perspective view of a second embodiment of the plate group.

Figure 7A is a section view of the embodiment of figure 7.

Figure 8 is a front view of figure 7.

l o Figure 9 is a section along plane IX-IX of figure 8.

Figure 10 is a section, once more along plane IX-IX of figure 8, of a plurality of plate groups arranged side-by-side to form filter chambers.

Figure 1 1 is a perspective view in larger-scale with respect to actual size, of a portion of a first embodiment of a filter screen according to the invention. 1 5 Figure 12 is a view from above of a portion of figure 1 1.

Figure 13 shows a series of different shapes A-G of sections of profiled element of the filter screen.

Figure 13A is the larger-scale detail of profiled element A of figure 13.

Figure 14 is a perspective view in larger scale with respect to the actual 0 dimensions of a portion of a second embodiment of filter screen according to the invention.

Figure 15 is a view from above of a portion of figure 14.

Figure 16 is a schematic view of the screen of figure 14.

Figures 16A-16C illustrate some alternative constructional details.

5 Figures 17A-17C illustrate a third embodiment of the plate group.

Figure 18 is a perspective view of a fourth embodiment of the plate group.

Figure 19 is an exploded view of the plate group of figure 19.

Figure 20 is a front view of the plate group of figures 8 and 19.

Figure 21 is a section view along plane XXI-XXI of figure 20.

0 Figure 22 is an enlarged detail of figure 21 .

PREFERRED EMBODIMENT OF THE INVENTION

Figure 1 illustrates in its entirety a filter press machine M for filtration of solid- liquid suspensions (for dehydrating the sludges) which uses a plurality of plate group P according to the invention, which are arranged in pack-form in series, such as to delimit a corresponding plurality of filter chambers; each filter chamber is delimited by two plate groups, opposite one another side-by- side and in contact with one another, and each plate group exhibits two active faces (the two larger faces) each of which is able to delimit, together with the opposite active face of another nearby plate group, a filter chamber; only the two plate groups located at the two ends of the plurality of plate groups of the machine exhibit only one active face, which is the face turned towards the inside of the plurality.

By way of example, the machine M illustrated in figure 1 exhibits a support structure comprising two vertical heads M1 and M2 and a horizontal and longitudinal upper beam M3 for supporting the plurality of plate groups P. In operation, as is known the sludge is pumped at high pressure (usually 10- 15 bar) through the plurality of plate groups in the filter chamber, in which the liquid phase is filtered by the filter screen and exits from the machine M through channels realized in the plate groups; the solid phase is instead retained by the filter screen and forms cakes of substantially flat dehydrated sludge which fill the filter chamber.

The cakes are then removed by distancing the plate groups from one another and then opening the filter chambers, thus enabling the cakes to fall by gravity out of the chambers.

Each plate group according to the invention comprises a support wall, located in a vertical position, and at least a filter screen for actuating the filtration of the suspension associated thereto, at least a filter screen being included for each filter chamber, located in a vertical position adhering to the support wall.

In the embodiment illustrated in figures 2-10, each plate group P comprises a vertical support wall 10, overall flat and rigid, located in a vertical positon, having two active faces 10a (if it is an intermediate plate group), and a filter screen 20 associated to each active face 10a, one for each filter chamber D which it delimits, for actuating the filtration of the suspension, in which the filter screen 20 is located in a vertical position adhering to the support wall 10.

As the plate group illustrated in the figures is of the intermediate type in the plurality of plate groups, it possesses two active faces able each to delimit, 5 together with the opposite face of another plate group, a filter chamber D; in particular the plate group P comprises a support wall 10 in an intermediate position and two filter screens 20, each adhering to the corresponding active face 10A of the support wall 10.

According to the invention, the filter screen 20 comprises a front face 20a 10 that is flat and free of roughness, slotted by a plurality of longitudinally- developing through-slits F (i.e. having a dimension - length - much greater than the width), which develop in a vertical direction, parallel to one another, having a width such as to retain the solid phase and enabling passage of the liquid phase, in which, furthermore, the slits F have, in a transversal section i s in the horizontal plane, an increasing or constant width starting from the front face and going towards the rear side.

In the first embodiment of the filter screen 20, illustrated in figures 1 1 -13, this comprises a first series of profiled elements 21 that are rigid, slim and parallel0 to one another having a front face that is substantially solid 21 a and a second series of support rods 22, perpendicular to the profiled elements 21 and fixed to the rear side 21 b thereof, in which the front face 20a of the screen is defined by the front faces 21 a of the rigid profiled elements 21 . Further, the screen 20 is arranged with the support rods 22 adhering to the active face 5 10A of the support wall 10 and with the front face 21a of the profiled elements 20 facing towards the centre of the filter chamber. The profiled elements 21 define among themselves a plurality of longitudinal passage slits F, parallel to one another, able to retain the solid phase and enable passage of the liquid phase. These slits (F) exhibit, along the transversal section (see0 in particular figure 12) a growing or constant width, starting from the front face 21 a and going towards the rear side 21 b. The width of the slit (F), can, as a limit, be constant. Further, the filter screen is arranged with the profiled elements 21 of the first series orientated in a vertical direction.

In the second embodiment of the filter screen 20, illustrated in figures 14, 15, this comprises a sheet 26 having a substantially constant thickness and a flat front face free of roughness, in which thickness the plurality of through-slits F is fashioned. In this case too, as in the first embodiment, the slits (F) exhibit, according to the transversal section (see in particular figure 15), a width that does not increase, starting from the front face 20a and going towards the rear face 20b.

It has been found by experimentation that owing to the described characteristics, the external surface of the cake of dehydrated sludge that forms internally of the filter chamber, during the filtration of the sludge, exhibits a substantially flat and smooth conformation, but in any case free of projections/appendages insinuating themselves into the slits (F): the surface of the cake is entirely formed by solid particles located externally of the slits (F) and therefore is not able to grip to the surface defined by the front faces of the profiled elements 2 .

The fact that the front face of the screen 20 is smooth and the slits (F) are arranged vertically, also strongly facilitates detachment of the cake, as it does not offer anything for the cake to grip to.

Therefore, during the step in which the filter chambers D are opened, i.e. the plate groups P are distanced from one another, the sludge cakes readily detach from the front face 20a of the filter screen 20, without leaving a trace, or hardly any of sludge thereon, and the cake slides downwards by force of gravity, leaving the filter chamber substantially clean; this is completely different to traditional machines which use filter screens formed by textiles: in the latter case the external surface of the cakes form multiple very small projections which insinuate themselves between the pores of the textile and clutch the cake in a grip; and the cake tends to remain gripped to the surface of the filter cloth.

The above-described favorable behaviour of the plate group of the invention is considered to be produced especially by the fact that the majority of the particles of the solid phase cannot pass through the front mouth of the slits (F) (located on the front face 20a), and that the particles that pass, however, as the passage increases in dimension, are pushed away together with the drained liquid and therefore do not stop in the slit (F); further, the slits (F)

5 define vertical channels along which the water falls downwards and is drained away: this water washes and cleans the channel, as well as drawing with it any solid particles which might have passed through the front mouth of the slit (F). Therefore the solid particles which manage to pass through the front mouth of the slits (F) are effectively drawn away, leaving the slit and the

10 external surface of the cake perfectly smooth.

The practical realisation of the first embodiment of the filter screen 20 can be done, according to a known technology, by continuous enveloping of the profiled elements 21 about a structure of support rods 22 arranged in a i s cylinder fashion on a machine which automatically maintains the cylindrical structure in rotation and in controlled advancement and at the same time performs the welding with electrical pulses on the profiled elements 21.

Alternatively the welding of the profiled elements 21 can be done on support rods 22 arranged on a flat work bench, arranging them in a grill array and 0 welding each node.

The profiles of the transversal section of the profiled elements 21 of the invention can exhibit the geometries indicated by A-G illustrated in figure 14 or any derivation or combination thereof:

The construction materials of the screen 20 can be:

5 · steels

• carbon iron

• stainless metal alloys

• aluminium

• mixtures based on polyurethanes, polypropylenes, polyethylene.

0 Surface and electrolytic treatments can be applied on these materials, having an anti-abrasive and anti-oxidising function (galvanising, enamelling, resin- finishing...). The fundamental dimensions of the section of the profiled element 21 according to the profile A of figure 13 are (see figure 13A):

I (width) = 0.5 - 10 mm

h (height) = 1 - 12 mm

5 a (angle of aperture) = 0° - 40°

A (area of the profile) = 0.01 - 4 mm²

The same width, length and area values are valid also for the profile of the support rods 22.

The d istances between two consecutive profiled elements 21 are: 5 - 250 10 pm

The distances between two consecutive support rods 22 are 3 - 30 mm. The main properties of the filter screen 20 according to the invention are the following:

- high mechanical resistance and sturdiness of the filter screen 20;

i s - seal of the welds;

- flexibility of the filter screen 20 in all directions (isotropy), for enabling axial deformations up to 10% with respect to the planar dimensions of the filter screen 20;

- large rest surface of the support rods 21 for an effective distribution of 0 the pressure on the support wall 10;

- draining profile of the anti-occluding filter screen 20 (due to the geometry of the profiled elements).

The practical realisation of the second embodiment of the filter screen 20 (figures 14-16) includes realising the slits (F) by cutting (using Water Jet 5 technology, Laser technology or another) in an extruded or moulded laminate sheet 26.

The construction materials of the sheet 26 can be:

• steels

• carbon iron

0 · stainless metal alloys

• aluminium mixtures based on polyurethanes, polypropylenes, polyethylene. The main parameters (see figure 16) are:

height A: 5 - 50 mm

height B: 1 - 10 mm

5 height C: 2 - 5 mm

height D: 1 - 2 mm

In the embodiment illustrated in figures 2-10, the vertical support wall 10 has a generally-square shape; alternatively it can advantageously be rectangular, l o circular, elliptical, polyhedral.

The construction materials of the support wall 10 (and all the accessories associated thereto) can be:

• steels

15 · carbon iron

• stainless metal alloys

• aluminium

• mixtures based on polyurethanes, polypropylenes, polyethylene, wood.

0 The fundamental dimensions of the support wall 10 are:

(side) = 250 - 4000 mm

(thickness) = 30 - 100 mm

The plate group P, illustrated in figures 2-6, not only comprises the support 5 wall 10 and the filter screens 20 applied thereto, but also comprises a pair of perimeter frames 30, which run along the perimeter of the wall 10, applied on the two faces of the wall, the perimeter of the filter screen 20 being interposed between the frames. The group comprising the wall 10, the two screens 20 and the two perimeter frames 30 is pack-blocked by means of tap0 bolts 31 placed through through-holes 32 distributed along the perimeter of the perimeter frames 30 and the wall 10; however the screws 31 and the holes 32 do not involve the screens 20, the perimeter of which is confined internally of the border defined by the bolts 31.

The seal between the wall 10 and the perimeter frame 30, on each of the faces of the wall 10, is realised by a perimeter seal 33 housed on the wall 10. The seal between the filter screen 20 and the perimeter frame 30, on each of the faces of the wall 10, is realised by a perimeter seal 34 inserted internally of a special seating fashioned in the perimeter frame 30. In this way the filter screen 20 is free to move with respect to the support wall 10.

The seal between two plate-groups is realised by a perimeter gasket 35 positioned on the external face of one of the two perimeter frames 30.

This configuration enables working also in process temperature conditions in a range of values: T = 1 - 95 °C. In fact, the filter screen 20 is free to slide in the seating thereof without risking the seal of the system. The different dilations of the materials constituting the filter screen 20 and the wall 10 are compensated by the play present in the coupling.

The front face 30a of the perimeter frame 30 projects outwards with respect to the front face of the screen 20 (which is located adhering to the face of the support wall 10) and determines, on the plate group P, a concavity B (see figure 2) which defines a filtering semi-chamber. During functioning, the plate group P is flanked in a pack-fashion, placing the front faces 30a of the frames 30 two-by-two in reciprocal contact; in this configuration, the two concavities B together define the volume of the filter chamber D (see figure 6).

In the embodiment illustrated in figures 2-6, the plate group further comprises a smaller central frame 40 (or distribution ring) located substantially at the longitudinal axis of the group, which is fixed to the support wall 10 and projects outwards with respect to the front face of the screen 20.

If the dimensions of the plate group require this, some buttons 45 can also be included (four in number in figure 2), also fixed, like the distribution ring 40, to the support wall 10 and projecting outwards with respect to the front face of the screen 20. The distribution ring 40 and the buttons 45 are centred on the plate group by milling on the wall 10 and are held in position by means of tap bolts 41 and 46 on the opposite side.

The plate group P is demountable. The mounting is simple and does not 5 require special tools.

In functioning, when the plate groups P are set in mutual pack-fashion, with the front faces 30a of the perimeter frames 30 positioned two-by-two in reciprocal contact, the distribution rings 40 also come into contact with one another, as do the buttons 45; the rings 40 and the buttons 45 function as l o structural elements for increasing the rigidity of the plate groups against the stresses to which they are subjected during operation.

The feeding of the sludge, under pressure, to the filter chambers D, is actuated through the central hole 1 1 , which crosses the whole plate group P, using known technology and via conduits (not illustrated in the figures).

15 The filter screen 20 is installed on the support wall 10 with the profiled elements 21 arranged in a vertical direction so as to have a greater facility of discharge of the sludge cake, as described in the foregoing.

The support rods 22 are, instead, horizontal and orientated perpendicularly to the surface of the support wall 10, so that they adhere along all the width 0 thereof to the wall 10, and enable drainage of the liquid phase along the surface 10A of the wall 0, on the back of the filter screen 20. To this end, the support wall 10 comprises a series of drainage channels 15, in the form of grooves, many of which are vertical, afforded on the surface of the wall 10 on which the filter screen 20 rests, which drainage channels 15 connect to 5 channels 16, internal of the thickness of the wall, which open into the thickness of circular through-holes 17, through which manifold tubes 18 are inserted (see figure 1 ) which conduct the filtered liquid externally of the machine.

The liquid phase filtering through the screen 20 is conveyed by the support0 rods 22 towards the face of the wall 10, where it is conveyed into the drainage channels 15, which in turn conduct the liquid phase through the internal channels 16 and the holes 17 into the manifold tubes 18 for evacuation to the outside.

The plate group of the embodiment illustrated in figures 7-10 differs from the preceding embodiment substantially due to the fact that it comprises a 5 flexible membrane 50, interposed between the support wall 10 and the filter screen 20, which defines, together with the face of the support wall 10, a closed space E communicating with conduits for the air (or for the water), which conduits are fashioned in the wall (not illustrated in the figures); the membrane 50 is able to deform in an inwards direction in the filter chamber l o D, on inserting pressurized fluid into the space E, and consequently is able to deform the filter screen 20.

In detail, in the embodiment illustrated in the figures, two membranes 50 are included, one on each active face 10A of the wall 10, each of which entirely coupled to the respective face 10A of wall 10, and is fixed sealedly thereto by 1 5 the action of the perimeter frame 30 which pack-compresses the membranes 50 against the two faces of the wall 10.

During functioning, by sending air (or water) under pressure into the space E, the membrane 50 is inflated, so that it presses on the filter screen 20, which, being elastic, deforms and narrows the thickness of the filter chamber D and0 thus compacts the sludge cake internally of the filter chamber D.

With the aim of guaranteeing a correct return of the filter screen 20 into the undeformed position, i.e. when pressing is completed and the membrane 50 is inflated, the number of buttons 45 is preferably reduced to an indispensable minimum or is totally zeroed (given an equal pressing run of 5 the machine M) so as to prevent plastic deformations of the filter screen 20.

The support rods 22 (which are horizontal and orientated perpendicular to the surface of the support wall 10) adhere along all the width of the front face of the membrane 50, enabling draining of the liquid phase along the back of the filter screen 20.

o To actuate the outflow of the liquid phase from the filter chamber, a free perimeter space is included in the form of a channel 55 which runs about the perimeter of the screen 20, delimited externally by the frame 20 and internally by the edge of the filter screen 20 and the frame. This perimeter channel 55 is in communication with the discharge manifold 18 via the channels 56 fashioned in the frame 30, which open into the circular through-holes 17, through which the manifold tubes 8 are inserted.

Therefore the drainage water crossing the screen 20 descends along the screen and along the front surface of the membrane 50, then collects in the perimeter channel 55 and is collected by the manifold tubes 18.

The seal between the membrane 50 and the support wall 10 is realised by the membrane.

The seal between the membrane 50 and the perimeter frame 30 is realised by the membrane.

The seal between the filter screen 20 and the frame 30 is made by means of the perimeter gasket 34, which enables the filter screen 20 to deform and move.

The filter screen 20 is centred in the support wall 10 via the central hole of the central distribution ring 40; the filter screen 20 is held firm by the ring 40 and seal is ensured by a system of seals, as for the lateral frames.

Figures 17A-17C illustrate some constructional details, alternative to those illustrated in the embodiments shown in figures from 2 to 10, which enable the application of the screen 20 to already-existing plate groups.

In the embodiment illustrated in figure 17A, the screen 20 has a rubber gasket 61 (which could be made of an equivalent material) located along the perimeter edge thereof which is housed in a corresponding seating 62 fashioned on an existing support wall 10; a seating 63 is also fashioned on the same wall 10 along the perimeter of the wall, which seating 63 is able to receive a rectangular profiled element 63 (key) which extends along the whole perimeter edge of the screen 20; the key 64 is inserted in the seating 63 and blocks the screen 20 against the wall 10 and guarantees the perimeter seal thereof.

In the alternative embodiment illustrated in figures 17B and 17C, the screen 20 is fixed in position against the wall 10 by means of a series of rigid lintels 65 fixed externally on the inclined plane of the perimeter frames 30 (which in the illustrated case are made in a single body with the wall 10), in particular by means of tap bolts.

In this way the perimeter seal is ensured by the pressure exerted by the rigid element directly on the gasket.

5 This type of mounting enables differential dilations and therefore can advantageously be used also in high-temperature applications.

In figures from 18 to 22, a further embodiment of a plate group is illustrated, denoted in its entirety by reference P2, which enables installation of a filter screen 20 on a support wall 1 10 which initially was not predisposed for the l o filter screen 20.

The wall 1 10 comprises an active face 1 10a, substantially flat, in which the drainage channels 15 are fashioned, and on which the filter screen 20 is positioned.

In particular, the wall 1 10 comprises two active faces 1 10a, parallel and 15 opposite.

The support wall 1 10 further comprises a perimeter border 130, provided with a first face 130a and a second face 130b opposite the first, projecting and parallel with respect to the planes on which the active faces 1 10a lie.

The second face 130b comprises a seating 134, fashioned along all the0 perimeter, able to house a seal 135, for example and O-ring; the first face 130a, on the other hand, has a flat surface.

In this way when two plate groups P2 are pressed to one another, the seal 135 of a plate group is pressed into the seating 134 thereof by the flat surface of the border 130 of the other plate group, guaranteeing a seal along5 all the periphery of the filter chamber.

The perimeter border 130 and the support wall 1 10 can be made, as in the illustrated example, in a single monolithic block.

The wall 1 10 further comprises a perimeter seating 162, located at the attachment zone of the perimeter border 130 to the wall 1 10, and able to0 house a seal 161. The perimeter seating 162 is defined in the space comprised between the border 130, the active face 1 10a and the perimeter border of the filter screen 20.

The seal 161 comprises a first portion 161 a, able to be inserted in the 5 perimeter seating 162, and a second portion 161 b jutting substantially projectingly from the first portion 161a and able to superpose on a portion of the front face 20a of the filter screen 20.

The first portion 161 a comprises a pair of reliefs located on the side in contact with the vertical wall 10, and a further relief positioned on the l o opposite side, the reliefs being able to improve the sealing capacity of the seal.

The reliefs are for example continuous along the whole length of the seal 161.

The first portion 161 a is positioned with play internally of the seating 162 so is as not to obstruct the thermal dilation and displacements of the filter screen 20.

The plate group P2 further comprises a plurality of rigid lintels 165 defining a border able to press the seal 161 into its seating 162 and against the filter screen 20, so as to guarantee the seal.

0 The plate group P2 further comprises fixing means 170 able to maintain the rigid lintels 165 pressed against the seal 161 The fixing means 170 comprise a pair of screws 171 and a cylindrical body 172, provided at both ends with a female thread 173 and able to be inserted in an appropriate through-hole 1 15, fashioned in the vertical wall 1 10.

5 The screws 171 are inserted in appropriate holes fashioned in the rigid lintels 165 and in the filter screens 20, and thereafter screwed into the cylindrical body 172.

To guarantee the seal and a correct distribution of the pressures and tensions, a plurality of fixing means 170 is present along all the perimeter0 covered by the rigid lintels 165.

Obviously numerous modifications of a practical-applicational nature can be made to the invention, without its forsaking the scope of the inventive idea as claimed in the following.

Claims

1 . Filter plate groups for filter press machines for filtering solid-liquid suspensions, able to delimit, where associated two-by-two with respect to one another, filter chambers of the suspension, the filter-plate groups being distanced from one another in order to carry out the discharge of the retained solid part of the suspension,

where each plate group comprises:

- a vertical support wall (10), located in a vertical position, and

- a filter screen (20) for actuating filtration of the suspension, at least a filter screen (20) being provided for each filter chamber, in a form of a flat and slim element located in a vertical position adhering to the support wall (10),

the filter screen (20) comprising a flat front face free of roughness, slotted by a plurality of longitudinally-developing through-slits (F) which develop in a vertical direction, parallel to one another, having a width such as to retain the solid phase and enable passage of the liquid phase, the slits (F) having, in a horizontal transversal section, an increasing or constant width starting from the front face and going towards the rear wall,

characterised in that the filter screen (20) comprises a first series of profiled elements (21 ) that are rigid, slim and parallel to one another having a front face (21 a) that is substantially flat and a second series of support rods 22, perpendicular to the profiled elements (21 ) and fixed to the rear side (21 b) thereof, in which the longitudinal slits (F) are each delimited by two profiled elements (21 ) closed to one another, and in which the front face (20a) of the screen is defined by the front faces (21 a) of the rigid profiled elements (21 ).

2. The plate groups of claim 2, characterised in that the filter screen (20) is arranged with the support rods (22) adhering to an active face (10A) of the support wall (10) and with the front face (21a) of the profiled elements (21 ) facing towards the centre of the filter chamber.

3. The plate groups of claim 1 , characterised in that the filter screen (20) comprises a slim sheet having a substantially constant thickness and a flat front face free of roughness, in a thickness of which the plurality of through- slits is fashioned.

5 4. The plate groups of any one of the preceding claims, characterised in that in order to actuate outflow of the liquid phase from the filter chamber (D), the support wall (10) comprises a series of drainage channels (15), formed as grooves, many of which being vertical, fashioned on the surface of the wall (10) on which the filter screen rests (20), which drainage channels (15) l o connect to internal channels (16), internal of the thickness of the wall, which internal channels (16) are connected to manifold tubes (18).

5. The plate groups of any one of the preceding claims, characterised in that it comprises a flexible membrane (50) interposed between the support wall

15 (10) and the filter screen (20), which defines, together with the support wall (10), a closed space (E) communicating with air conduits; the membrane being able to deform in an internal direction to the filter chamber (D) on insertion of pressurized fluid in the space (E), and consequently to deform the filter screen (20).

0

6. The plate groups of claim 5, characterised in that in order to actuate the outflow of the liquid phase from the filter chamber (D), it comprises a perimeter space (55) having a channel-shape which runs about the perimeter of the screen (20), externally delimited by the frame (20) and internally5 delimited by the edge of the filter screen (20), which perimeter space (55) is in communication with discharge manifolds (18) via holes on the frame (30).

7. A filter machine of a filter press type, for solid-liquid suspensions, comprising a plurality of filter chambers (D) of the suspension, each chamber0 being defined by two plate groups, opposite one another, said plate group types being distanced from one another in order to carry out discharge of the solid part of the filtered suspension, in which the plate groups each comprise:

a vertical support wall (10), located in a vertical position, and at least a filter screen (20) for actuating filtration of the suspension, at least a filter screen (20) being provided for each filter chamber, located in a vertical position adhering to the support wall (10),

characterised in that each filter screen (20) comprises a first series of rigid profiled elements (21 ), slim and parallel to one another, having a substantially-flat front face (21a), and a second series of support rods (22), perpendicular to the profiled elements (21 ) and fixed to the rear side (21 b) thereof,

in which the filter screen (20) is arranged with the support rods (22) adhering to the active face (10A) of the support wall (10) and with the front face (21 a) of the profiled elements (21 ) facing towards the centre of the filter chamber.