FILTER ARRANGEMENT FOR CLEANING A GASEOUS MEDIUM

Abstract: A filter arrangement for cleaning a gaseous medium consisting of a number of layers of filter elements (3, 4) in the form of sheets. These are enclosed within a casing (2) and are situated at a certain distance from one another and exhibit an inlet side, on which the medium flows into the filter elements, and an outlet side, on which the medium flows out of the filter elements. The filter elements are in communication via a first space (13, 14) on their inlet side with an inlet to the casing, and are in communication via a second space (15, 16) on their outlet side with an outlet (6) from the casing, with said first and second spaces (13, 14, 15, 16) being defined for each layer of filter elements by an inclined wall (17, 20, 21) such that the first space is given a successively decreasing cross-sectional area, when viewed from the inlet (5), whereas the second space is given a successively increasing cross-sectional area.

Description: Filter arrangement for cleaning a gaseous medium Technical Field: The present invention relates to a filter arrangement for cleaning a gaseous medium. It is concerned with filter arrangements of the kind which consist of at least a first and a second layer of filter elements in the form of sheets, enclosed within a casing and situated at a certain distance from one another, and exhibiting an inlet side, on which the fluid flows into the filter elements, and an outlet side, on which the medium flows out of the filter elements, said filter elements being in communication via a first space on their inlet side with an inlet to the casing, and being in communication via a second space on their outlet side with an outlet from the casing. Background: Previously disclosed filter arrangements have been designed primarily in order to satisfy the requirement for a large filter area and thus high—quality cleaning, or, alternatively, in order to satisfy the requirement for a compact structure in the form of an easily handled and easily positioned unit in which less importance is attached to the cleaning capability. Technical problem: One problem which arises, therefore, is the ability to satisfy the requirements for a large filter area and for a compact structure simultaneously. The solution: Satisfaction of both requirements is achieved through the invention by means of a- filter arrangement which is characterized in that the first and the second spaces for each layer of filter elements are defined by an inclined wall such that the aforementioned first space, when viewed from the inlet, will be given a successively decreasing cross—sectional area, whereas the aforementioned second space will be given a successively increasing cross—sectional area. Brief description of the drawings: The invention is described below in greater detail as an illustrative embodiment with reference to the accompanying drawings, of which Fig. 1 shows a partially sectioned perspective view of a filter arrangement according to the invention, and Fig. 2 is a schematic representation of a cleaning plant of which the aforementioned filter arrangement forms a part. Best mode of carrying out the invention: The filter arrangement 1 according to the invention is, as may be appreciated from Fig. 1, constructed from a closed casing 2 made of sheet metal, for instance, enclosing a space which accommodates at least two layers of filter units 3, 4. The filter arrangement also exhibits an inlet 5, through which the medium to be cleaned is caused to flow into the filter units 3, 4, and an outlet 6, from which the aforementioned medium flows out from the inside of the filter arrangement 1. The medium which is to be cleaned by filtration consists of a gaseous medium,, for instance air, mixed with the dust and solvents which occur in the course of, for instance, paint spraying in a spray booth. The gaseous medium is introduced through the inlet 5 by the installation of, for instance, a suction fan on the outlet side of the filter arrangement, for instance in a duct, connected to the outlet 6. The space inside the casing 2 consists on the one hand of a main chamber which accommodates the layers of filter elements 3, 4 and certain subsidiary chambers ^ , which are described in more detail below, and on the other hand of an inlet duct 7 through which the medium flows in from the inlet 5 to the main chamber, and also of an outlet duct 8 through which the medium flows from the main chamber to the outlet 6. The inlet duct is in communication with the inlet side 9 of each of the filter elements, whilst the outlet duct 8 is in communication with the outlet side 10 of each of the filter elements. The inlet 5 and the outlet 6 are constituted by openings in the central part of the inlet duct 7 and the outlet duct 8 respectively, arranged symmetrically in the walls of the respective ducts. The filter elements 3, 4 consist of essentially flat, parallelepipedic bodies in the form of carbon filter elements, for example, which are divided up into a number of sections 11, 12, of which the downward—facing rectangular surface in the example illustrated constitutes the inlet side, whilst the upward—facing rectangular surface constitutes the outlet side, whilst the remaining surfaces, i.e. the lateral surfaces, are intended to be sealed so as not to permit the medium to pass through. The sections of the filter element together form layers of filter elements arranged in parallel with one another, being two layers in the example illustrated, with an upper layer of filter elements 3 and a lower layer of filter elements 4. The filter elements 3, 4 extend preferably horizontally so that the air flow through the filter elements moves in an essentially vertical sense from bottom to top. The two layers of filter elements are so arranged that, to either side of each layer of filter elements, there is present a subsidiary chamber 13, 14, 15, 16, which, . according to the invention, exhibits a progressively varying height in a direction from the inlet 5 of the filter arrangement to its outlet 6, that is to say a progressively varying cross—sectional area. The aforementioned subsidiary chambers consist of a pressure chamber 13, 14 for each layer of filter elements and an outlet box 15, 16 for each layer of filter elements. More precisely, the height of these subsidiary chambers is variable in a direction from the inlet 5 to the outlet 6 in such a way that .the pressure chambers 13, 14 decrease in height, whilst the outlet boxes 15, 16 increase in height. _ This variable height of the pressure chamber and the outlet box respectively is afforded in the subsidiary chambers between the two layers of filter elements by the provision of an inclined dividing wall 17 in the form of, for instance, a metal sheet. This extends from the longitudinal edge 18 at the inlet 5 of the lower layer of filter elements to the opposing longitudinal edge 19 of the upper layer of filter elements 3. The pressure chamber 13 for the lower layer of filter elements has its dimensions defined partly by one of the external walls of the casing 2, more precisely its under side 20, whilst the outlet box 16 for the upper layer of filter elements is defined partly by the opposing -filter wall of the casing, i.e. the upper side 21 of the casing, which is inclined and forms an angle with the filter surface of the filter elements. The casing 2 further exhibits two end walls, which may be essentially flat (see Fig. 2) and which close off the subsidiary chambers 13—16. The construction of the filter arrangement 1 according to the invention means that the two layers of filter elements 3, 4 are connected together in parallel at the inlet 5 and the outlet b f in such a way that a large filter surface is achieved in combination with the rapid throughput of the gaseous medium, The construction of the pressure chamber and the outlet box with a height which can be varied in the manner described above provides a uniform pressure distribution at the inlet side of the filter elements. The way in which this is achieved is for the cross—sectional area of the pressure chambers 13, 14 to decrease, starting from the inlet 5, for example in such a way that the inclination of the dividing wall 17 in relation to the filter elements is of. the order of 1:10. In this way a higher pressure will be created inside the pressure chambers than inside the outlet box, for which reason reinforcements should preferably be incorporated into the outlet boxes so as to prevent deflection of the dividing wall 17. The pressure drop is relatively low, however, for instance 75 mm water gauge at an air velocity of 0.25 m/s, which allows a long contact time for the gas in the filter units together with a high quality of cleaning. - The low flow velocity means that the heavier particles are not carried along in the upward—moving flow,, but fall down onto a metal plate 17, 20 below. The fi Iter ' elements 3, 4 should preferably be so arranged as to be capable of replacement, for instance by regeneration, i.e. by the removal of the particles of dirt from the filter elements , with this being made possible by the casing 2 exhibiting openable parts. These parts should preferably be positioned in such a way that, in the example illustrated, the upper layer of filter elements is withdrawn towards the right, i.e. above the inlet 5, whilst the lower layer of filter elements is withdrawn towards the left, i.e. beneath the outlet 6. The openable parts may, for instance, be executed in the form of removable plates which form sealing contact with other parts of the casing, or by causing the lateral parts 22, 23 of the filter units themselves to occupy openings in the wall of the casing, in so doing producing a tight seal against other parts of the casing. Each layer of filter elements may consist of the aforementioned filter sections, which may be loosely connected to one another and retained in position by means of guides (not shown) in the casing 2, in which they run as they are respectively inserted into and withdrawn from the casing 2. Each layer of filter elements may itself consist of a single, large coherent unit which accompanies the filter elements as they are withdrawn. It is important in this case for the. sections at all times to form a tight seal with one another and with the external wall of the casing, in such a way that the gaseous medium is unable to pass through the filter arrangement in an uncleaned state. The gaseous medium which is to be cleaned by filtration is thus fed in at the inlet through the rectangular opening shown in Fig. 1; see the arrows 24. After it has passed through the inlet duct 7, the gaseous medium flows into the two pressure chambers 13, 14; see the arrows 25. Inside the pressure chambers the gaseous medium is caused to pass from the inlet side of the two layers of filter elements 3, .4 and through these elements, in conjunction with which cleaning takes place through the absorption and/or adsorption of the foreign particles present in the gaseous medium, which, after it has passed through the filter elements, passes to their outlet side, passes through the outlet boxes, .see the arrows 26. and is guided across and into the outlet duct 8 through the effect of the inclined walls, -see the arrows 27 , whereupon the medium passes out through the outlet 6, -see the arrow 28 . Fig. 2 illustrates schematically an example of an installation in which the filter arrangement 1 according to the invention is used. The filter arrangement forms part of an installation for the partial recirculation of the cleaned air, which means that a certain amount of air from outside, for example 25% of fresh supply air, is provided together with 75% of recirculated air. The cleaning installation may, for example, be built inside a spray booth, in which case the high—quality recirculation means, on the one hand, that energy will be saved, and, on the other hand, that the surrounding environment outside the spray booth will not be impaired to any significant degree. The gaseous medium, i.e. the air inside the spray booth, for example, which contains paint particles and solvents, is sucked into the filter arrangement 1 through the inlet 5 by means of a suction fan 29 positioned at the outlet from the filter arrangement, The cleaned gaseous medium is fed by means of the fan 29 via a ventilation drum 30 and via an injection fan 31 and a further filter 32 back to the inside of the spray booth. In this case, however, as has already been mentioned, a proportion of the recirculated air is fed out via a ventilation duct 33 to the surrounding environment outside the area which is to be cleaned, whilst a corresponding volume of air is supplied from the surrounding environment via a ventilation duct 34 connected to the injection fan 31 which conveys the supply air into the spray booth. The invention is not restricted to the illustrative embodiment referred to and described above, but may be modified within the scope of the following Patent Claims. For example, the filter arrangement according to the invention may be constructed from more than two layers of filter elements. The filter arrangement may also be used in a large number of different applications in which the requirement fpr the cleaning of a gaseous medium exists.

Claims: Patent Claims: 1. A filter arrangement for cleaning a gaseous medium consisting of at least a first and a second layer of filter elements (3, 4) in the form of sheets enclosed inside a casing (2) and situated at a certain distance from one another . and exhibiting an inlet side, on which the medium flows into the filter elements, and an outlet side, on which the medium flows out of the filter elements, said filter elements being in communication via a first space (13, 14.) on their inlet side with an inlet to the casing, and being in communication via a second space (15, 16) on their outlet side with an outlet (6) from the casing, c h a r a c t e r i z e d in that the first and the second spaces (13, 14, 15, 16) for each layer of filter elements are defined by an inclined wall (17, 20, 21) such that the aforementioned first space is given a successively decreasing cross—sectional area, when viewed from the inlet (5), whereas the aforementioned second space is given a successively increasing cross—sectional area. 2. A filter arrangement according to Patent Claim 1, c h a r a c t e r i z e d in that there are situated between two adjacent layers of filter elements (3, 4) not only the aforementioned first space (14) for one of the layers of filter elements (3), but also the second space (15) for the second layer of filter elements (4), said two space being separated from one another by means of a common separating wall (17) which is inclined in relation to the position of the filter elements, whilst the aforementioned second space (16) is defined to the outside of the aforementioned layers of filter elements (3) and the aforementioned first space (13) is defined to the opposite outside of the layers of filter elements (4) externally by the outer wall of the cover, which is similarly inclined relative to the aforementioned filter elements. 3. A filter arrangement according to Patent Claim 2, c h a r a c t e r i z e d in that the casing (2) exhibits an inlet duct (7) which extends over the entire length of the first spaces (13, 14) and is open towards the first spaces over its entire length. 4. A filter arrangement according to Patent Claim 3, c h a r a c t e r i z e d in that the casing (2) exhibits an outlet duct (8) which extends over the entire length of the second spaces (15, 16) and is open towards the second spaces over its entire length. 5. A filter arrangement according to Patent Claims 3 and 4, c h a r a c t e r i z e d in that the inlet (5) is situated in the central part of the inlet duct (7). 6. A filter arrangement according to Patent Claims 3—5, c h a r a c t e r i z e d in that the outlet (6) is situated in the central part of the outlet duct (8).

Inventors: JAKOBSSON KLAS, JAKOBSSON, KLAS
Applicants: JAKOBSSON KLAS, JAKOBSSON, KLAS
Application year: 1985
Main classification: B01D46
IPC codes: B01D46