FR2776207A1 - Gas treatment apparatus with at least one rotating absorbent filter element - Google Patents

Abstract

The filter element is an active carbon tissue layer (20) forming a cylinder about the filter's axis of rotation. The gas supply opens into a volume on one side of the filter element and the first outlet opens into a volume on the other side. Regeneration is carried out using an electrical supply to the element in the desorption zone to heat this part of the filter by the Joule effect.- DETAILED DESCRIPTION - The filter includes a gas supplier for gas to be treated to one side of the filter element (20), a first outlet (14) to receive the gas which has passed through the filter element in an adsorption zone forming a first part of the rotating trajectory of the filter, a filter element regenerator in a desorption zone at a second part of the rotating trajectory of the filter and a second gas outlet (16) to receive the gas which has passed through the filter in the desorption zone. The surface of the filter element has corrugations.The electrical supply is by brushing contact with feed electrodes. The gas supply to be treated is connected to one side of the element in the desorption zone so the gas received at the second gas outlet comprises a fraction of the gas to be treated enriched by the elements desorbed from the filter element. The apparatus contains several rotating filters mounted in cascade, with the second gas outlet of one being connected to the supplier of the next. Alternatively, the supplier connects to one side of the filter element in the adsorption zone only, and supplementary supplier of a gas flow communicates with one side of the filter element in the desorption zone

Description

Field of the Invention The invention relates to a treatment installation

  gas by rotary adsorbent filter. Such an installation can be used for filtration and / or concentration purposes, for example for the treatment of a flow of air charged with molecules in order to produce a flow of purified air after adsorption of these molecules and / or a flow air in which the concentration of molecules is

increased.

  BACKGROUND OF THE INVENTION Gas treatment devices using a rotary filter operating alternately in adsorption and in desorption during a

full turn are well known.

  Thus, document US 5,584,916 shows a rotor containing an adsorbent material forming a filter. During each complete rotation of the filter, each fraction thereof passes through a treatment zone receiving a gas flow to be treated charged with an organic solvent and delivering a purified gas flow, then a regeneration zone receiving a stream of hot air and delivering air loaded with desorbed solvent. The filter material, after regeneration, passes through a cooling zone before reaching the treatment zone again to adsorb the molecules

  of solvent contained in the gas stream to be treated.

  In this document, the adsorbent material of the filter is an artificial zeolite. According to other documents relating to rotary adsorbent devices, the adsorbent material can be activated carbon,

  possibly in fibrous form, as in JP 53-050 067.

  Object and Summary of the Invention The object of the invention is to provide an installation with a rotary adsorbent filter in which the continuous regeneration of the filter is carried out in a much simpler manner than in the installations of the prior art. This object is achieved with a gas treatment installation comprising at least one rotary filter which comprises: an adsorbent filter element made of activated carbon fibers, means for supplying a gas flow to be treated on one side of the element filter, a first gas outlet for collecting the gas flow having passed through the filter element in an adsorption zone corresponding to a first part of the rotary path of the filter, means for regenerating the filter element in a corresponding desorption zone to a second part of the rotary path of the filter, separate from the first part, and a second gas outlet for collecting a gas stream having passed through the filter element in the desorption zone, installation in which the filter element is formed by at least one layer of activated carbon fabric and the regeneration means comprise means for electrically supplying the fraction of the filter element located in the desorption zone in order to heat this fraction of the filter element by Joule effect. Thus, the installation is particularly advantageous since the regeneration of the filter element does not require the generation of a

  hot gas stream for desorption.

  Preferably, the means for supplying a gas stream to be treated communicate with one side of the filter element in the desorption zone, so that the gas stream collected on the second gas outlet consists of a fraction of the stream gaseous to be treated enriched by

  desorbed elements of the filter element.

  Thus, it is a fraction of the gas stream to be treated which is used as the gaseous stream for driving the desorbed elements of the filter element. It is therefore not necessary to use a particular desorption gas stream. In addition, the installation then functions simultaneously as a filter by eliminating by adsorption of the elements contained in a part of the gas flow to be treated and as an enrichment device, by increasing by desorption the concentration of the remainder

  of the gas flow into elements it contains.

  The arrangement of several rotary cascade filters allows

  then a multiplication of this concentration.

  According to a particular feature of the installation, the filter element is formed by at least one layer of activated carbon fabric describing a

  cylindrical surface around the axis of rotation of the filter.

  The cylindrical surface of the filter element preferably has undulations in order to increase the surface of exchange with the

gas flow to be treated.

  According to another particular feature of the installation, the electrical supply of the fraction of the filter element located in the desorption zone is carried out by rubbing contact with supply electrodes.

Brief description of the drawings

  The invention will be better understood on reading the description

  made below, for information but not limitation, with reference to the accompanying drawings which illustrate: - Figure I: a very schematic view of an installation according to the invention - Figure 2: a view in longitudinal section of the filter of the 'installation of Figure 1; - Figure 3: a cross-sectional view of the filter of the installation of Figure 1; Figure 4: a detailed view of the mounting of the fabric filter element on a support bar; - Figure 5: a detail view in cross section of regeneration zone of the filter of Figure 3; and - Figure 6: a very schematic view of a variant of

  realization of an installation in accordance with the invention.

  DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS In the installation of FIG. 1, a rotary filter 10 receives a gas flow to be treated supplied by a pipe 12, for example air charged with toxic molecules coming from a room. The purified air is collected by a first pipe 14, on a first outlet of the filter 10, for example to be returned to the room where the air to be purified has been taken. Air with an increased content of toxic molecules is collected by a second line 16, on a second outlet of the filter 10, to be conveyed, by

  example, to a recovery or treatment device.

  The rotary filter 10 comprises a filter element 20 (Figures 2, 3)

  driven in rotation inside a fixed envelope 40.

  The filter element 20 consists of activated carbon fabric. This can be obtained by carbonization of a fabric of carbon precursor, then activation. A process for obtaining activated carbon fabric by carbonization of rayon fabric and activation for example by carbon dioxide, water vapor or air at a temperature of 600 C to 1000 C is described in document FR 2 741 363. Another process for obtaining an activated texture of carbon fibers is described in document FR 97 03 083. A fabric preferably having an electrical resistance of between 0 and 100 Q) / will be chosen: and a tensile strength at least equal to

  0.5 daN / cm to be able to be handled without tearing.

  The filter element 20 is mounted on a support structure comprising a plurality of bars 22a, 22b which extend parallel to the axis 111 of rotation of the rotary filter while being distributed regularly around it. The bars 22a, 22b are arranged respectively in two outer and inner rings of different diameters. The activated carbon fabric is mounted on the bars 22a,

  22b, in one or more superimposed layers, passing altemrna-

  tively around a bar 22a of the outer ring and around a bar 22b of the inner ring. In this way, the filter element 20

  describes a cylindrical surface with axis 11 forming regular undulations.

  In cross section (Figure 3), the filter element thus has a star-shaped profile. In the example illustrated, the number of undulations is equal to 12; it could of course be different. The activated carbon fabric is held in place on the bars 22a by means of rubber pieces 24 in the form of a half-tube which are engaged on the fabric and

  the bars as shown in Figure 4.

  The bars 22a, 22b are mounted between two plates 26, 28 perpendicular to the axis 11. One (26) of the plates has a central opening in which a hub 30 is mounted. The latter has a flange 30a which s presses on the external face of the plate 26 and is extended outwards by a tubular part 30b. An axis 32 passes axially through the hub 30 and the opposite plate 28 to allow the assembly of the plates 26, 28 and the bars 22a, 22b by screwing on the axis 32. The plates 26, 28 have a central part of greater thickness protruding from the inside and forming

  cylindrical recesses 26a, 28a of the same diameter.

  Parts 34 in the form of wedges (or disc sectors) are mounted against the internal faces of the plates 26, 28 between the recesses 26a, 28a and the periphery of the plates. The 34 pieces are

  slightly spaced from each other in circumferential direction.

  Each piece 34 has an outer rim 34a which covers the edge

  corresponding tray device.

  The parts 34 are in number equal to that of the bars 22b forming the inner ring of bars. Each bar 22b has ends of reduced diameter which penetrate into orifices formed in the vicinity of the internal end of rounded shape of a respective part 34. The bars 22b and the parts 34 are, on the internal side, tangent to the same surface cylindrical substantially confused with

that of the recesses 26a, 28a.

  The bars 22a forming the outer ring each pass between two neighboring pieces 34. They have ends of reduced diameter which penetrate into holes formed in the plates 26,

  28 projecting slightly from the outer face of the plate 26.

  The fabric forming the filter element 20 has a width greater than the distance between the central parts of the plates 26, 28, so that the edges of the fabric, at the level where it passes around the bars 22b,

  are based on the recesses 26a, 28a.

  The parts 34 are fixed to the plates 26, 28 by means of screws 36 which press on the edges 34a of the parts 34 in the direction of the periphery of the plates 26, 28 (a single screw 36 is shown in FIG. 3). In this way, the edges of the filter element are applied with pressure to the surfaces of the recesses 26a, 28a. Thus, any communication between the volume situated on the internal side of the filter element, at the level of the axis of the rotary filter, and the volume situated on the external side of the filter element can only take place through the latter. Spacers 38 parallel to the axis 11 help to keep the parts 34 applied against the

  plates 26, 28 in the vicinity of their periphery.

  The casing 40 comprises a cylindrical ferrule 42 surrounding the rotary filter, closed by two flanges 46, 48. The flanges 46, 48 support the rotary filter by means of bearings in which the tubular part 30b of the hub 30 and the end part of the axis 32 projecting beyond the plate 28. The tubular part 30b of the hub 30 is connected to the pipe 12 for supplying the gas flow to be treated and openings 30c are made without the hub 30, around the axis 32, to make the central part of the rotary filter 10 communicate with the pipe 12. The axis 32 extends outside the flange 48 of the casing 40 to be connected to a drive motor 50 of the filter

rotary (Figure 1).

  On the internal side, the ferrule 42 of the envelope 40 is provided with two neighboring sealing seats 52, 54 which each extend over the entire length of the envelope but over a limited sector, providing an internal surface 52a, 54a of reduced radius (Figures 3, 5). This radius is determined to allow, by contact between the surfaces 52a, 54a and the pieces of rubber 24 lining the bars 22a (FIG. 4), to share in a sealed manner the volume situated between the external side of the filter element and

the ferrule 42 of the envelope 40.

  As shown in Figure 3, this volume is shared between a first volume A which communicates with the first outlet 56 of the filter connected to line 14, and a second volume B which communicates with the second outlet 58 of the filter connected to line 16 The second outlet 58 of the filter is formed through the ferrule 42 between the ends closest to the sealing seats 52, 54, while the first outlet 56 of the filter is formed through the ferrule 42 substantially opposite to the

first exit.

  In addition, at substantially the same angular level as the sealing seats 52, 54, the flange 46 is provided with electrodes 62, 64 which each extend over a limited sector slightly less than the angular distance between two bars 22a (FIGS. 3, 5). The electrodes 62, 64 project towards the inside of the envelope so as to come into frictional contact with the ends of the bars 22a which project through the plate 26, when the rotary filter rotates. The electrodes 62, 64 are connected to an electrical power source 66, outside of

envelope 40 (Figure 1).

  The operation of the installation described above is the

following.

  The gas flow to be treated is admitted into the central part of the rotary filter 10 through the line 12 and the orifices 30c and is constrained to

pass through the filter element 20.

  The smallest part of the filter element located between the bars 22a in contact with the electrodes 62, 64 undergoes heating by the Joule effect causing desorption. In this way, the fraction of gas flow passing through this part of the filter element is charged with desorbed molecules and reaches the volume B from which it is evacuated through the

exit 16.

  The rest of the filter element acts as an adsorbent element. In this way, the largest fraction of the gas flow passing through the rest of the filter element is purified and reaches the volume A from which it is

evacuated through exit 14.

  Thus, the rotary filter successively passes through a treatment zone (adsorption) which extends between the ends furthest from the sealing seats 52, 54, and a regeneration zone (desorption) which extends between the upstream end (in the direction of rotation of the filter) of the sealing part 52 (the first encountered) and the upstream end of the sealing part 54. The speed of rotation of the filter is chosen in particular as a function of the degree of pollution of the gas flow to be treated. The

  filter is rotated continuously or stepwise.

  Figure 5 shows more particularly the arrangements and dimensions of the sealing seats and electrodes. The sealing seats 52, 54 are located on either side of the meridian plane P passing through the axis of the outlet 58 and extend to the immediate vicinity thereof. The electrodes 62, 64 are also located on either side of the plane P in

  being slightly spaced from each other.

  The sealing seat 52 has a surface 52a which extends over an arc slightly smaller than that separating two consecutive bars 22a, that is to say two consecutive external vertices of the filter element. In this way, the surface 52a is in contact with only one vertex of the filter element. The upstream end of the surface 52a, in the direction of rotation of the filter, therefore marks a limit between the adsorption zone and the

regeneration area.

  The electrodes 62, 64 extend over the arcs which are substantially equal and slightly lower than that separating two consecutive vertices of the filter element. The upstream end of the electrode 62 is slightly downstream from that of the sealing seat 52 and the angular pitch between the electrodes is chosen to be substantially equal to that separating two consecutive vertices of the filter element. In this way, an apex Si of the filter element comes into contact with the electrode 62, after contact with the sealing seat 52, and substantially at the same time as the next apex, S2 of the filter element (in the direction of rotation R) comes into contact with electrode 64, which starts heating of the part of the filter element

  located between these two vertices (shown in short dashes in Figure 5).

  The sealing seat 54 extends over a slightly arc

  greater than that separating two consecutive vertices of the filter element.

  In this way, after the top S2 of the filter element has left the electrode 62 and the sealing seat 52 and has come into contact with the upstream end of the sealing seat 54, the part of the element filter located between this vertex and the next vertex S3 in the direction of rotation R (part shown in long dashes in Figure 5) is temporarily inactive, the two vertices which border it being in contact simultaneously with the sealing seat 54. This allows this part of the filter element to cool before entering the

  adsorption zone, as soon as the apex S3 leaves the sealing seat 54.

  A particular advantage resulting from the use of an activated carbon fabric heated by the Joule effect lies in the rapidity of its heating and cooling. It is therefore not necessary for the sealing seat 54 to extend over a large arc, which allows

optimize the adsorption zone.

  In the example which has just been described, the fraction of the filter element during regeneration is between two consecutive vertices. However, depending on the number of corrugations of the filter element and the arrangements of the electrodes and sealing seats, the fraction being regenerated may extend between two non-consecutive peaks. An installation such as that described above was carried out with a filter element formed by a strip of activated carbon fabric 26 cm wide and 2.6 m long. The activated carbon fabric was obtained by heat treatment of a precursor fabric made of textile rayon fibers according to the technique described in patent application FR 97 03 083. The electrical resistance of each fraction of the filter element located between two vertices has been measured. Values

  obtained are between approximately 2 and 3.

  The temperature obtained for a fraction of the filter element varies from 70 C to 170 C when a voltage is applied varying from 12 V to

  24 V, the adjacent fractions remaining at room temperature of 25 C.

  The rate of temperature rise after application of the voltage is approximately 20 C / min. The cooling is faster,

  especially under the effect of the incoming gas flow.

  FIG. 6 schematically illustrates an alternative embodiment

  of an installation according to the invention.

  According to this variant, several rotary filters 10, similar for example to that described above, are placed in cascade, the second outlet pipe 16 of a filter being connected to the supply pipe 12 of the

next filter.

  Such an installation makes it possible to gradually enrich the concentration of the gas flow in the elements which it contains. It can in particular be used for the treatment of gas streams containing solvent molecules. Gradual increase in concentration

  facilitates the final recovery of the solvent.

Claims (7)

R CLAIMS   1. Gas treatment installation comprising at least one rotary filter which comprises: an adsorbent filter element (20) made of active carbon fibers, means (12) for supplying a gas flow to be treated on one side of the filter element, a first gas outlet (14) for collecting the gas flow having passed through the filter element in an adsorption zone corresponding to a first part of the rotary path of the filter, means for regenerating the filter element in a desorption zone corresponding to a second part of the rotary path of the filter, distinct from the first part, and a second gas outlet (16) for collecting a gas stream having passed through the filter element in the desorption zone, characterized in that that the filter element is formed by at least one layer of activated carbon fabric (20) and the regeneration means comprise means (66) for electrically supplying the fraction of the filter element located in the desorption zone in order to achieve a   heating of this fraction of the filter element by Joule effect.   2. Installation according to claim 1, characterized in that the means (12, 30c) for supplying a gas flow to be treated communicate with one side of the filter element in the desorption zone, so that the gas stream collected on the second gas outlet (16) consists of a fraction of the gas flow to be treated enriched with desorbed elements of the filter element.   3. Installation according to any one of claims 1 and 2,   characterized in that the filter element (20) is formed by at least one layer of activated carbon fabric describing a cylindrical surface   around the axis of rotation (11) of the filter (10).   4. Installation according to claim 3, characterized in that   the cylindrical surface has undulations.   5. Installation according to any one of claims 3 and 4, characterized in that the means for supplying a gas flow to be treated communicate with one of the faces of the filter element (20), while the first and the second gas outlet (14, 16) communicate with each other face of the filter element.   6. Installation according to any one of claims 1 to 5,   characterized in that the electrical supply of the fraction of the filter element located in the desorption zone is carried out by friction contact   with supply electrodes (62, 64).   7. Gas treatment installation according to any one of   Claims 1 to 6, characterized in that it comprises several filters   rotary cascaded (Figure 6), the second gas outlet (16) of a filter being connected to the supply means (12) of gas flow to be treated next filter.