Opening of a lye filter

Abstract

The present invention relates to a lye filtering unit (10) which is capable of filtering ferrous residues and iron precipitates as well as any other impurities in an electrolyte solution coming from an electrolysis unit, the lye filtering unit (10) comprising: - a tank (12) which extends in a main direction of vertical elongation (A) and comprises a side wall (18) and an upper face (16), the upper face (16) comprising an opening (20), and the side wall (18) comprising a shim (64) on a bearing edge (68) placed at a distance E from the opening (20); and - a cover (22) which is capable of cooperating with the upper face (16) of the tank (12) in order to seal the opening (20); - a basket (54) which comprises an upper face (58) and a peripheral rim (62) which is capable of resting on the shim (64); and - a bearing edge (68) which is capable of exerting a pressure on the upper face (58) of the basket (54).

Description

[0001] DESCRIPTION

[0002] TITLE: Opening the lye filter

[0003] Technical field of the invention

[0004] The present invention relates to a lye filtering unit capable of filtering ferrous residues and iron precipitates, as well as any other impurities, present in an electrolyte solution resulting from an electrolysis unit, for example for the production of dihydrogen (H2) and dioxygen (02).

[0005] The invention relates more particularly to a lye filtering unit designed to facilitate its maintenance and to a method of maintaining such a lye filtering unit.

[0006] Technical background

[0007] The lye filter, also called lye filter unit, is used to filter mainly ferrous residues as well as iron precipitates but also any other impurities, even in negligible quantities.

[0008] Figures 1 and 2 show a lye filtering unit 100 according to the prior art. The lye filtering unit 100 comprises a tank 12 having a lye inlet pipe 28 and a lye outlet pipe 30 as well as two impurity capture elements placed in the tank 12 including i) at least one magnetic bar 72 for recovering magnetic particles (regardless of size), and ii) a basket 54 supporting an inner screen formed of a tight metal mesh dedicated to capturing non-magnetic particles (regardless of size).

[0009] Following this particle capture action, the lye 100 filter must be cleaned of these iron agglomerates and / or any other substance on a recurring basis to maintain the efficiency of the system. All iron agglomerates, minority substances and filtered molecules are considered impurities.

[0010] At present, this maintenance operation is quite heavy and not very easy, given the mass and steric bulk of the lye filter 100 as well as those linked to the magnetic bar(s) 72 and the basket 54 within the lye filter 100.

[0011] The elements making the maintenance operation difficult are the following: i) the basket 54 containing a sieve formed of a tight metal mesh, extremely heavy, which is fixed using screws on a wedge of the side wall of the lye filter 100 and whose bottom is located near the lower end of the lye filter 100, and ii) the magnetic bar(s) 72 which is (are) directly fixed on the cover 22 of the lye filter 100, the cover 22 being surmounted by at least one handle necessary for lifting the assembly composed of the cover 22 and the magnetic bar(s) - 72.

[0012] Thus, when handling the 100 lye filter, various significant obstacles linked to points i) and ii) defined above can be listed, including:

[0013] - the detachment of the basket 54 which is quite complex given: a) the difficult accessibility of this basket 54 since it is located at a certain depth relative to the inlet of the lye filter 100, b) the significant mass of the basket 54 to be extracted, and c) human intervention to remove the screws, the intervention being difficult due to the narrowness inside the lye filter 100,

[0014] - handling the cover 22 using at least one handle when opening the lye filter 100 by human intervention which is particularly difficult, because the cover 22 alone has a significant mass.

[0015] During this manipulation, it is important to also take into consideration the mass and size of the magnetic bar(s) 72 directly attached to the cover 22 to be lifted. In other words, the cumulative mass is very high on the one hand and on the other hand, the manipulation is complex due to the significant length of the magnetic bar(s) 72 to be lifted and extracted.

[0016] Thus, there is an interest in facilitating the maintenance operation of the lye filtering unit 100 consisting of cleaning the different elements of the lye filtering unit 100. Another example of a filtering unit is described and represented in the document US2014 / 0373325A1.

[0017] Summary of the invention

[0018] In order to eliminate all the obstacles referenced above, the innovation is based on several modifications allowing, ultimately, easier and faster maintenance, even if the latter results from human manipulation as previously.

[0019] The invention relates to a lye filtering unit capable of filtering ferrous residues and iron precipitates as well as any other impurities in an electrolyte solution from an electrolysis unit, the lye filtering unit comprising:

[0020] - a tank extending in either a main direction of vertical elongation, or a main direction of horizontal elongation, or any main direction of elongation between the horizontal and vertical planes defined according to the reference V, L, T, and comprising a side wall and an upper face, the upper face comprising an opening, and the side wall comprising a wedge on a bearing edge placed at a distance E from the opening, and

[0021] - a cover capable of cooperating with the upper face of the tank to close the opening,

[0022] - a basket comprising an upper face and a peripheral rim capable of resting on the wedge, the lye filtering unit being characterized in that it further comprises:

[0023] - a support edge capable of exerting pressure on the upper face of the basket.

[0024] The lye filtering unit may further comprise a fixing support extending substantially in a first horizontal plane P1 and capable of receiving at least one magnetic bar integrally on a lower face, the bearing edge being integral with the fixing support and extending in the lower part in a second horizontal plane P2.

[0025] The lye filter unit may further comprise a compression element positioned between the mounting bracket and the cover and capable of being compressed into a closed position of the cover. The compression element may comprise a top plate and at least one spring extending vertically between the top plate and the mounting bracket.

[0026] The sum of the spacing H between planes P1 and P2 and the height h of the compression element in the compressed state can be substantially equal to the distance E: H+h=E.

[0027] The fixing bracket and the support edge may be connected by at least one vertical bar.

[0028] The lye filter unit may further include a tube topped with a pressure relief valve.

[0029] The assembly, consisting of the tube and the decompression valve, can be located in the cover.

[0030] The lye filter unit may further comprise a cam sleeve arranged to actuate the cover between a closed position and an open position.

[0031] The invention also relates to a method for maintaining a lye filtering unit according to the invention, characterized in that it comprises the following steps:

[0032] - unlocking the cover,

[0033] - detachment of the cover from the upper face of the tank under the effect of decompression of the compression element,

[0034] - placing the cover in the open position,

[0035] - removal of the assembly placed in the tank comprising the compression element, the fixing support, the support edge and the magnetic bar(s),

[0036] - removal of the basket placed in the tank

[0037] - carrying out the maintenance operation.

[0038] Brief description of the figures

[0039] Other characteristics and advantages of the invention will appear during the reading of the detailed description which follows for the understanding of which reference will be made to the appended drawings in which: [Fig.1] is a perspective view of a lye filtering unit of the prior art;

[0040] [Fig.2] is a schematic sectional view of the lye filter unit of Fig. 1 showing the arrangement of the magnetic bar and basket in the lye filter unit;

[0041] [Fig.3] is a perspective view of a lye filtering unit according to the invention showing an overall view;

[0042] [Fig.4] is a partial perspective view of the lye filter unit of Figure 3 with an angular section of 90° and axis A showing the interior of the tank;

[0043] [Fig.5] is a partial and exploded view of the lye filter unit of Figure 3 showing the elements placed inside the tank;

[0044] [Fig.6] is a perspective view showing the intermediate element provided with several magnetic bars of the lye filter unit of Figure 3;

[0045] [Fig.7] is an enlargement of an upper portion of Figure 6 showing the intermediate element;

[0046] [Fig.8] is a partial perspective view of the lye filter unit of Figure 3 with an angular section of 90° and axis A showing the cover in the locked position;

[0047] [Fig.9] is a partial perspective view of the lye filter unit of Figure 3 with an angular section of 90° and axis A showing the cover in the unlocked position;

[0048] [Fig.10] is a partial perspective view of the lye filter unit of Figure 3 with an angular section of 90° and axis A showing the cover in the open position;

[0049] [Fig.10] is a partial perspective view of the lye filter unit of Figure 3 showing the sleeve in an open cover position.

[0050] Detailed description of the invention

[0051] For the description of the invention and the understanding of the claims, the vertical, longitudinal and transverse orientations according to the reference V, L, T indicated in the figures, the longitudinal L and transverse T axes of which extend in a horizontal plane, will be adopted as a non-limiting example and without limiting reference to Earth's gravity. By convention, the vertical axis V is oriented from bottom to top and the longitudinal axis L is oriented from back to front.

[0052] In the following description, identical, similar or analogous elements will be designated by the same reference numbers.

[0053] The invention relates to a lye filtering unit 10 capable of filtering ferrous residues and iron precipitates as well as any other impurities in an electrolyte solution from an electrolysis unit.

[0054] A lye filtering unit 10 according to the invention is shown in Figure 3. The lye filtering unit 10 comprises a tank 12 extending in a main direction of vertical elongation A between a lower face 14 and an upper face 16.

[0055] The tank 12 comprises a side wall 18. The tank 12 has a generally cylindrical shape with axis A and a circular section. The side wall 18 is curved and extends along the circumference of the cylinder formed by the tank 12. The side wall 18 is parallel to the axis A. Any other geometric configuration defining the side wall 18 falls within the description of the present invention given that the technical characteristics associated with the latter are independent of the geometric configuration.

[0056] To allow access to the interior of the tank 12, for example for the intervention of an operator, the upper face 16 has an opening 20. The lye filtering unit 10 has a cover 22 capable of cooperating with the upper face 16 of the tank 12 to close the opening 20 and allow the tank 12 to be hermetically closed.

[0057] The tank 12 has a lye inlet orifice 24 and a lye outlet orifice 26. Thus, the lye coming from the electrolysis unit is introduced into the tank 12 of the lye filtering unit 10 through the lye inlet orifice 24. The lye introduced into the tank 12 through the lye inlet orifice 24 passes through the tank 12 to be filtered and exits through the lye outlet orifice 26. The lye, once filtered, can be reinjected into the electrolysis unit. The lye inlet orifice 24 and the lye outlet orifice 26 are placed in the side wall 18. The lye inlet orifice 24 and the lye outlet orifice 26 can be positioned, for example, one above the other. The lye inlet 24 and lye outlet 26 ports may also be positioned in diametrically opposite positions or may have any orientations.Preferably, the lye inlet orifice 24 is located in an upper portion of the side wall 18 and the lye outlet orifice 26 is located in a lower portion of the side wall 18 to allow the flow of the lye stream by gravity.

[0058] To allow the circulation of the lye, the lye filter unit 10 comprises:

[0059] - an inlet pipe 28 for lye in tank 12, and

[0060] - an outlet pipe 30 for lye from the tank 12.

[0061] The lye inlet line 28 is fluidly connected to the lye inlet port 24 in the side wall 18.

[0062] The lye outlet line 30 is fluidically connected to the lye outlet port 26 in the side wall 18.

[0063] Lye may circulate in a closed circuit between the electrolysis unit and the lye filter unit 10. The lye fed into the lye inlet pipe 28 comes from the electrolysis unit. The lye discharged into the lye outlet pipe 30 is redirected to the electrolysis unit, potentially after further treatment.

[0064] In the example, the lye outlet pipe 30 has a decreasing section portion 32 along the lye discharge direction which here corresponds to the direction pointed by the longitudinal vector L. The diameter of the decreasing section portion 32 decreases linearly along the direction L between a maximum diameter B and a minimum diameter C. The minimum diameter C corresponds substantially to the diameter D of the section of the inlet pipe 28.

[0065] The lye filter unit 10 has a purge orifice 34 placed in the lower face 14 of the tank 12.

[0066] The tank 12 comprises a horizontal fixing disc 36 projecting from the external face of the side wall 18 of the tank 12. The tank 12 also comprises fins 38 forming a buttress and extending vertically from an upper face of the fixing disc 36 and along the side wall 18.

[0067] The lye filter unit 10 comprises a base 40 comprising at least two feet 42. Each foot 42 is surmounted by a threaded rod 44. Each threaded rod 44 passes through a fixing orifice 46 formed in the fixing disc 36. The fixing orifices 46 are distributed regularly along the fixing disc 36. In the non-limiting example described in Figure 3, this corresponds to the four corners of a square considering four feet 42. Nuts 48 screwed onto the threaded rod on either side of the fixing orifices 46 make it possible to locally adjust the height of the tank 12. Washers can be added between the fixing disc 36 and the nuts 48 to more finely adjust the height of the tank 12.

[0068] The base also comprises a horizontal base 50 configured through any geometric shape, the base 50 being provided with a counterweight 52 projecting from the base 50 in the horizontal plane of the base. In the non-limiting example described in Figure 3, the base is annular in shape while the counterweight 52 has a T shape, the foot of the T being fixed to the base 50.

[0069] With reference to Figures 4 and 5, the lye filtering unit 10 comprises a basket 54, of any geometric shape, supporting an inner screen formed of a tight metal mesh and delimiting a cavity 56 extending in the vertical direction A. In the non-limiting example described in Figures 4 and 5, the basket 54 has a cylindrical shape of axis A. The basket 54 comprises an upper face 58 delimiting a central opening 60. The upper face 58 of the basket 54 also comprises a peripheral rim 62 capable of resting on a wedge 64 projecting from an internal face of the side wall 18. The wedge 64 may comprise in the upper part vertical positioning rods 65 making it possible to correctly position the basket 54 on the wedge 64. The basket 54 then comprises orifices for receiving the vertical rods 65.The upper face 58 of the basket 54 is placed at a distance E from the opening 20 corresponding to a height located between the lye inlet orifice 24 and the lye outlet orifice 26. Preferably, the upper face 58 of the basket 54 is located just below the inlet orifice 24 as shown in FIG. 4. Thus, the lye entering the tank 12 enters the cavity 56, passes through the walls of the basket 54 and exits through the lye outlet orifice 26.

[0070] According to a characteristic of the invention, the lye filtering unit 10 comprises an intermediate element 66, of any geometric configuration, between the basket 54 and the cover 22 making it possible to transmit to the basket 54 a pressure exerted on the intermediate element 66 by the cover 22.

[0071] The intermediate element 66 is shown in a non-limiting manner but more specifically in Figures 6 and 7. The intermediate element 66 comprises a bearing edge 68 resting on the upper face 58 of the basket 54 when the intermediate element 66 is placed in the tank 12. In the example, the bearing edge 68 is annular. The bearing edge 68 has a shape similar to that of the upper face 58 of the basket 54. Alternatively, the bearing edge 68 could have a discontinuous shape so as to exert pressure only at certain points of the upper face 58 of the basket 54.

[0072] According to an advantageous embodiment of the invention, the lye filtering unit 10 comprises a fixing support 70, of any geometric configuration, capable of receiving at least one magnetic bar 72, the magnetic bar 70 being intended to be fixed on a lower face 74 of the fixing support 70. In the non-limiting example, the fixing support 70 is a hollow disc to form a central crosspiece 75. Alternatively, the fixing support 70 could be a solid disc. The lower face 74 of the fixing support 70 extends substantially in a first horizontal plane P1.

[0073] In the example shown, the lye filter unit 10 comprises four magnetic bars 72. Alternatively, the lye filter unit 10 could comprise a different number (higher or lower) of magnetic bars 72, or even no magnetic bars. Each magnetic bar 72 is fixed to the underside 74 of the fixing bracket 70 and extends downwardly when the fixing bracket 70 is placed in the tank 12. In the example, each magnetic bar 72 is fixed to an arm of the crosspiece 75 by means of circlip pins. Alternatively, each magnetic bar 72 could be fixed by means of a screw whose head is located above the fixing support 70 and whose threaded portion is screwed into a complementary orifice in an upper face of the magnetic bar 72. The magnetic bars 72 being distributed on each of the arms of the crosspiece 75, they are arranged in a square centered on the axis A.This approach can be modified by considering any bar magnet 72, if any, placed randomly (ranging from zero to at least one) on each of the arms of the crossbar 75, both in terms of the total number of bar magnets 72 and the number of bar magnets 72 on each arm of the crossbar 75. The bar magnets 72 allow the capture of magnetic particles, regardless of size.

[0074] In the embodiment shown, the fixing support 70 is integrated into the intermediate element 66. The intermediate element 66 has the shape of a cylindrical cage formed:

[0075] - an upper ring comprising the fixing support 70 extending in the first horizontal plane P1, and

[0076] - a lower ring comprising the bearing edge 68 extending in a second horizontal plane P2 placed under the first horizontal plane P1.

[0077] The upper ring and the lower ring have the same shape and dimensions except for the central crosspiece 75. The intermediate element 66 also comprises four vertical lateral bars 76 of equal length. The bars 76 are distributed along the lower and upper rings and arranged to keep the bearing edge 68 and the fixing support 70 horizontal and parallel to each other. Alternatively, the fixing support 70 and the bearing edge 68 could be connected by a different number of bars 76, more or less high. Thus, within the intermediate element 66, the bearing edge 68 is integral with the fixing support 70.

[0078] The intermediate element 66 is for example metallic.

[0079] The lye filter unit 10 further comprises a compression element 78 placed between the fixing support 70 and the cover 22 and adapted to be compressed in a closed position of the cover 22. The compression element 78 can be part of the intermediate element 66 or be a separate element.

[0080] The sum of the spacing H between the planes P1 and P2 and the height h of the compression element 78 in the compressed state is substantially equal to the distance E: H+h=E.

[0081] According to a preferred embodiment, the compression element 78 comprises an upper plate 80 and six springs 82 extending vertically between the upper plate 80 and the fixing support 70. The upper plate 80 is a disc hollowed out in its center extending in a horizontal plane placed above the planes P1 and P2. The upper plate 80 has the same shape and the same dimensions as those of the lower ring comprising the bearing edge 68. Alternatively, the upper plate 80 could be a solid disc or comprise a crosspiece like the fixing support 70. The springs 82 are distributed regularly under the upper plate 80. Alternatively, the number of springs 82 could vary by having a number greater or less than that mentioned in the example above.

[0082] The springs 82 are used to store energy which is transmitted to them when they are compressed and to restore the energy to slightly lift the cover 22 when the cover 22 is unlocked. The phenomenon is illustrated in Figures 8 and 9.

[0083] In Figure 8, the cover 22 is locked so that the springs 82 are compressed and the cover 22 is in contact with the upper face 16 of the tank 12.

[0084] In Figure 9, the cover 22 is unlocked, the springs 82 release their energy and deploy. Under the action of the springs 82, the cover 22 is slightly raised relative to the upper face 16 of the tank 12.

[0085] The bolting defined between the upper face 16 of the tank 12 and the cover 22 already plays a locking role. The tabs 83 and 85 are intended for equipotentials.

[0086] Alternatively, the locking system is a lug secured to the cover 22 which can be retained in a pivoting hook fixed to the tank 12 or a lug movable in translation which can be housed in a hollow of the tank 12. A magnetic lock can also be envisaged.

[0087] The pressure inside the tank 12 may be different from atmospheric pressure. To allow the inside of the tank 12 to be returned to atmospheric pressure, the lye filter unit 10 further comprises a tube 84, commonly called a "nozzle" (the term used in English is the "nozzle"), arranged in the center of the external face of the cover 22. Above this tube 84 is grafted a decompression valve (not shown in the figures). Returning the tank 12 to atmospheric pressure makes it easier to open the cover and avoids any risk of projection.

[0088] Since the magnetic bars 72 are not fixed to the cover 22, unlike the filter units of the prior art, an improvement has been introduced into the filter unit 10 of the invention allowing the cover 22 to be pivoted to clear the opening 20 rather than lifting the cover 22. In fact, the bars no longer obstruct the pivoting of the cover 22. The improvement will be described with more specific reference to FIGS. 10 and 11.

[0089] The lye filter unit 10 comprises a cam sleeve 86 arranged to actuate the cover 22 between a closed position and an open position. The cam sleeve 86 comprises a hollow cylindrical portion 88 forming a cam by means of two diametrically opposed notches 90 formed in a lower face of the cylindrical portion 88.

[0090] The cam sleeve 86 also comprises a T-shaped tube 92 mounted in the cylindrical portion so that the vertical bar of the T passes through the cylindrical portion 88. The tube 92 is for example welded or glued in the cylindrical portion 88. The horizontal bar of the T of the tube 92 is fixed at one of its ends to a lateral face of the cover 22. The fixing of the tube 92 to the cover 22 is carried out for example by fitting, by welding or by gluing or any other fixing means not listed above.

[0091] The lye filter unit 10 comprises a support 94 in the form of a hollow cylinder capable of receiving a lower portion of the tube 92. The support 94 is fixed to the side wall 18 of the tank 12 by means of a horizontal fixing arm 96. The horizontal fixing arm 96 is for example welded or glued to the tank 12. The cam sleeve 86 is then capable of pivoting in the support 94 around the axis of the tube 92.

[0092] The support 94 comprises an upper face having a shape complementary to the lower face of the cylindrical portion 88. When the cover 22 is in the closed position, the upper face of the support 94 perfectly matches the lower face of the cylindrical portion 88 so that an upper end of the support 94 is housed in a notch 90 of the cylindrical portion 88. When the cover 22 is pivoted 90° around the axis of the tube 92 relative to the closed position, the upper end of the support 94 is opposite a lower end of the cylindrical portion 88 so that the cover 22 is raised by a height I equal to twice the height i of the notch in the cylindrical portion 88. Thus, in accordance with the operating principle of a cam, the rotational movement around the axis of the tube 92 is accompanied by a translational movement along the axis of the tube 92.

[0093] The lye filter unit 10 according to the invention allows a less risky and less painful maintenance process. The maintenance method of the lye filter unit 10 comprises the following steps.

[0094] When an operator wishes to clean the elements of the lye filter unit 10, he carries out a first step consisting of unlocking the cover 22, for example by removing the screw holding the cover 22 closed.

[0095] Following the unlocking of the cover 22, the latter 22 is automatically detached from the upper face 16 of the tank 12 under the effect of the decompression of the compression element 78, for example under the effect of the thrust of the springs 82. The lye filtering unit 10 is then in the state shown in figure 9.

[0096] The operator can then manually pivot the cam sleeve 86 in the holder 94 without effort to bring the cover 22 into the open position. The cover 22 is then shifted to the side to clear the opening 20 and raised a height I above the tank 12 as shown in Figure 10.

[0097] The operator then removes the assembly placed in the tank 12 comprising the compression element 78, the fixing support 70 and the support edge 68 in order to release the basket 54 and remove the magnetic bar(s) 72.

[0098] The operator can then remove the basket 54 from the tank 12.

[0099] The operator then has the possibility of cleaning all of the elements constituting the lye filter unit 10.

[0100] At the end of the maintenance operation, to restore the lye filter unit 10 to operating condition, the operator replaces the basket 54, taking care to place the vertical positioning rods 65 in the corresponding receiving holes of the basket 54. The operator then replaces the intermediate element 66 when it is in one piece, the intermediate element 66 comprising the bearing edge 68, the fixing support 70 and the compression element 78. When the intermediate element 66 is not in one piece, the operator successively replaces the bearing edge 68, the fixing support 70 and the compression element 78.

[0101] Finally, the operator pivots the cover 22 by means of the cam sleeve 86 to the closed position and finishes by locking the cover 22 by screwing the screw back into the nut so as to keep the cover 22 pressed against the upper face 16 of the tank 12.

[0102] The improvement based on the compression and decompression of the inner springs 82 considerably facilitates the opening of the cover 22, the maintenance of the magnetic bar(s) 72 as well as that of the basket 54. After opening the cover 22, the human effort is significantly less since: i) the magnetic bar(s) 72 is (are) partially outside the lye filter unit 10 without being associated with the cover 22 anymore, and ii) the basket 54, also partially reassembled, is more easily accessible since it is no longer attached to the side wall 18 of the lye filter unit 10 by the screws but is kept under pressure only by the force of the intermediate element 66 overhanging it when the cover 22 is closed.

[0103] The opening of the cover 22 is also facilitated following the appearance of two essential elements: i) the tube 84 surmounted by the decompression valve arranged in the center of the external face of the cover 22, and ii) the cam sleeve 86.

[0104] The assembly consisting of the tube 84 and the decompression valve makes it possible to gradually depressurize the lye filter unit 10 so as not to be faced with an excessively violent opening and a rise with splashing of the internal components (magnetic bar(s) 72 and basket 54) too quickly.

[0105] The cam sleeve 86 facilitates the control of the opening of the cover 22 in the sense that it no longer has to be lifted as previously but translated in rotation by means of this cam sleeve 86, which gradually unclips after a slight vertical impulse to remove it from its notch.

[0106] The preferred modes described above nevertheless allow any orientation of the lye filter unit 10 to be considered. Thus, the latter can be arranged in a horizontal main elongation direction or any main elongation direction between the horizontal and vertical planes defined according to the reference V, L, T. Regardless of the orientation followed, all the technical characteristics associated with the geometric configurations of the lye filter unit 10 and constituent elements of the invention (fixing support 70, compression element 78, magnetic bars 72, basket 54, etc.) described in the description remain identical, giving a set of identical results.

Claims

CLAIMS 1. Lye filtering unit (10) capable of filtering ferrous residues and iron precipitates as well as any other impurity in an electrolyte solution resulting from an electrolysis unit, the lye filtering unit (10) comprising: - a tank (12) extending along either a main direction of vertical elongation (A), or a main direction of horizontal elongation, or any main direction of elongation between the horizontal and vertical planes defined according to the reference V, L, T, and comprising a side wall (18) and an upper face (16), the upper face (16) comprising an opening (20), and the side wall (18) comprising a wedge (64) on a bearing edge (68) placed at a distance E from the opening (20), and - a cover (22) capable of cooperating with the upper face (16) of the tank (12) to close the opening (20), - a basket (54) comprising an upper face (58) and a peripheral rim (62) capable of resting on the wedge (64), - a support edge (68) capable of exerting pressure on the upper face (58) of the basket (54), - a fixing support (70) extending substantially in a first horizontal plane P1 and capable of receiving at least one magnetic bar (72) integrally on a lower face (74), the bearing edge (68) being integral with the fixing support (70) and extending in the lower part in a second horizontal plane P2, the lye filtering unit (10) being characterized in that it further comprises: - a compression element (78) placed between the fixing support (70) and the cover (22) and capable of being compressed in a closed position of the cover (22).

2. Lye filter unit (10) according to claim 1, characterized in that the compression element (78) comprises an upper plate (80) and at least one spring (82) extending vertically between the upper plate (80) and the fixing support (70).

3. Lye filter unit (10) according to claims 1 or 2, characterized in that the sum of the spacing H between the planes P1 and P2 and the height h of the compression element (78) in the compressed state is substantially equal to the distance E: H+h=E.

4. Lye filter unit (10) according to any one of claims 1 to 3, characterized in that the fixing support (70) and the support edge (68) are connected by at least one vertical bar (76).

5. Lye filtering unit (10) according to any one of the preceding claims, characterized in that it further comprises a tube (84) surmounted by a decompression valve.

6. Lye filtering unit (10) according to the preceding claim, characterized in that the assembly, consisting of the tube (84) and the decompression valve, is located in the cover (22).

7. Lye filter unit (10) according to any one of the preceding claims, characterized in that it comprises a cam sleeve (86) arranged to actuate the cover (22) between a closed position and an open position.

8. Method for maintaining a lye filtering unit (10) according to claim 1, characterized in that it comprises the following steps: - unlocking the cover (22), - detachment of the cover (22) from the upper face (16) of the tank (12) under the effect of the decompression of the compression element (78), - placing the cover in the open position (22), - removal of the assembly placed in the tank (12) comprising the compression element (78), the fixing support (70) and the support edge (68), - removal of the basket (54) placed in the tank (12) - carrying out the maintenance operation.

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