AUTOMATIC PURGE RELIEF DEVICE

Abstract

This pressurized water expansion device, used for raw water clarification by dissolved air flotation, is suitable for implementation, in particular, within circular flotation tanks equipped with a rotating bridge or flotation scraper, or within rectangular flotation tanks equipped with surface scrapers. This device is immersed in the contact zone between the pressurized water and the raw water and is capable of diffusing the microbubbles formed during expansion directly into said contact zone. It includes mechanical purging means (15, 16, 17) mechanically actuated by the passage of a moving element (2) of the flotation tank, in particular by at least one actuator fixed to the rotating bridge or to a flotation scraper, or by a mechanism specifically dedicated to purging. Figure for the abstract: [Fig. 1a]

Description

Title of the invention: AUTOMATIC PURGE RELIEF DEVICE technical field

[0001] The invention relates to a device for depressurizing pressurized water used in dissolved air flotation systems. It can be used for depressurizing pressurized water on different types of flotation devices. Previous art

[0002] Dissolved air flotation uses the property of microbubbles of air (usually less than 100-120 micrometers in diameter) to adhere to solid particles present in natural or wastewater and cause them to rise to the surface like small buoys. The microbubbles are produced by returning water to atmospheric pressure after a significant amount of air has been dissolved in it under a pressure generally between 3 and 6 bar. At this pressure, the volume of air that water can dissolve is respectively 3 and 6 times greater than at atmospheric pressure. When the pressure of this water drops, the volume of dissolved air exceeding the maximum volume it can dissolve at atmospheric pressure is immediately released in the form of gaseous air bubbles. This is the principle of dissolved air flotation. Water enriched with dissolved air under a pressure of a few bars is called pressurized water.

[0003] The conditions under which the pressurized water is released play a very important, and in some cases even a determining, role in the size and stability of the bubbles. For best results, it is advantageous for these bubbles to be as small as possible (preferably less than 80-100 micrometers in diameter) and to be stable and not prone to coalesce rapidly into larger bubbles, which are much less efficient for clarification by dissolved air flotation.

[0004] The characteristics of the microbubbles formed during expansion depend on numerous factors related to the water composition, the expansion conditions, and the shape of the orifice creating the pressure drop that maintains the pressurized water circuit under pressure. The smaller this orifice (called the "expansion orifice"), the better the characteristics of the microbubbles produced during expansion. In clean water applications, such as water clarification for drinking water production, expansion orifices are on the order of 2 to 3 millimeters in diameter, sometimes even smaller. It is also advantageous to ensure maximum dispersion of the pressurized water immediately after expansion. In practice, the best results are obtained with multiple expansion nozzles having one or more orifices of relaxation. These relaxation nozzles are distributed at a certain distance from each other directly in the contact compartment of the microbubbles produced with the raw water loaded with solid particles that we seek to attach and make float.

[0005] Unfortunately, it is very difficult to use this type of pressure-reducing nozzle in wastewater treatment because the orifices frequently become clogged by large solid particles present in the water used for pressurization. Indeed, in the vast majority of cases, pressurization is carried out with clarified and recycled water, which may occasionally contain particles that escaped clarification. It is therefore preferable to use pressure-reducing means that are more resistant to clogging, such as much larger orifices or pressure-reducing valves. Large orifices are often impractical because they deliver too high a flow rate of pressurized water relative to the requirements. Valves have the advantage of being easy to unclog simply by opening them. Many types of automatic valves are available for this purpose.These automatic valves have the disadvantage of being mounted on piping that creates conditions favorable to microbubbles. Whether large-diameter orifices or pressure relief valves mounted on piping, the pressure relief conditions provided by these devices more or less promote the coalescence of the air bubbles produced during expansion. Consequently, some of the air dissolved in the pressurized water is "lost" in the form of large bubbles unsuitable for dissolved air flotation. In some cases, this loss can reach up to 40% of the dissolved air, and even more. This represents a significant energy loss in the pressurization circuit.

[0006] Only one self-cleaning pressure relief device designed to be immersed in the contact zone of the float exists on the market. This device uses a double-acting pneumatic cylinder to open and close the relief orifice to clear any blockage. The flow rate of the pressurized water in this device is adjusted by regulating the stroke of the piston rod using adjustable stops. The more one seeks to reduce the flow rate of the pressurized water, the closer the piston rod must be brought to the relief orifice to obstruct it further and thus reduce the cross-sectional area for the water to pass through. This device is heavy and expensive because it is equipped with an integrated double-acting pneumatic cylinder. It is suitable for high flow rates of pressurized water, but does not allow for precise and well-regulated relief of low flow rates. Description of the invention

[0007] The device according to the invention uses mechanical means, and more specifically a relief orifice located opposite a movable shutter. This shutter is held opposite the relief orifice by a member ensuring a clamping force on said shutter, sufficient to compensate for the back pressure of the water at the outlet of the orifice. The pressure relief valve can be held open by a counterweight mounted on a lever or by another means, such as a jack or a shaft supporting the valve. This design allows the pressure relief valve to be purged by simple mechanical action, periodically moving the valve to briefly open the water passage and thus clear any blockage of solid material trapped between the edge of the pressure relief valve and the valve. The device according to the invention is intended for the pressure relief of pressurized water in circular floats equipped with a rotating bridge or scraper, or in rectangular floats equipped with surface scrapers. It can also be used in any other type of float equipped with mechanical means for triggering and managing the purging process, i.e., a mechanism specifically dedicated to purging.

[0008] In other words, the invention relates to a pressurized water expansion device used for the clarification of raw water by dissolved air flotation suitable for implementation in particular within circular flotators equipped with a rotating floating sludge bridge or scraper or within rectangular flotators equipped with surface scrapers, said device being immersed in the contact zone between the pressurized water and the raw water, and suitable for diffusing the microbubbles formed during expansion directly into said contact zone.

[0009] According to the invention, the device includes mechanical purging means mechanically actuated by the passage of a moving element of the floater, in particular by at least one actuator fixed on the rotating bridge or on a floating sludge scraper or by a mechanism specifically dedicated to purging.

[0010] According to one embodiment of the invention, the device comprises: - pressurized water supply means comprising at least one calibrated outlet for pressurized water; - at least one shutter carried by at least one arm, said arm pivoting around an axis fixed on at least one support; - at least one stop capable of supporting the arm holding the shutter facing the calibrated orifice at a certain distance from said calibrated orifice; - at least one weight fixed on an arm attached to the arm carrying the shutter and capable of pressing said arm against the stop so that the shutter is held facing the calibrated orifice at a certain distance from said calibrated orifice; - means of supporting the pivot axis of the arm carrying the shutter; - means for adjusting and locking the distance between at least one shutter and at least one calibrated orifice; - means enabling the lifting of the weight and, consequently, the separation of the obturator from the calibrated orifice.

[0011] According to another embodiment of the invention, the device comprises: - pressurized water supply means comprising at least one calibrated outlet for pressurized water; - at least one shutter carried by at least one arm pivoting around an axis fixed on at least one support, the surface of said shutter facing the calibrated orifice being spherical or other rotating shape whose axis of formation coincides substantially with the axis of rotation of the shutter; - at least one stop capable of supporting the weight-bearing arm, holding the shutter facing the calibrated orifice at a certain distance from said calibrated orifice; - at least one weight, fixed on an arm attached to the arm carrying the shutter and capable of pressing said arm against the stop so that the shutter is held facing the calibrated orifice at a certain distance from said calibrated orifice; - means for supporting the pivot axis of the arm and respectively bearing the weight and the shutter; - means for adjusting and locking the distance between at least one shutter and at least one calibrated orifice; - means enabling the rotation of the obturator around its pivot axis, said rotation causing the obturator to move away from the calibrated orifice.

[0012] In practice, the obturator includes at least one channel suitable, during the rotation of said obturator during purging, to pass in front of substantially the entire section of the calibrated orifice and to evacuate the purging water.

[0013] According to another embodiment of the invention, the device comprises: - pressurized water supply means comprising at least one calibrated outlet for pressurized water; - at least one rotating shutter carried by an axis fixed on at least one support, the rotating surface of said shutter facing the calibrated orifice being spherical or other rotating shape whose axis of formation coincides substantially with the axis of rotation of the shutter, said shutter being equipped with at least one opening capable of passing, during rotation, in front of substantially the entire surface of the calibrated orifice and opening outwards from said shutter; - means capable of rotating the shutter under the action of an external actuator so as to cause the opening to pass in front of the entire surface of the calibrated orifice during the rotation of said shutter; - means for adjusting and locking the distance between at least one shutter and at least one calibrated orifice. Brief description of the figures

[0014] The manner in which the invention can be implemented and the resulting advantages will become clearer from the following embodiment examples, given by way of illustration and not limiting, supported by the attached figures.

[0015] [Fig. la] schematically represents a vertical section of a first embodiment of the device according to the invention shown in its normal operating position, i.e. with the shutter “closed”.

[0016] [Fig.lb] shows the same device in the purge position, i.e. with the obturator “open”.

[0017] [Fig.2a] schematically shows a vertical section of a second embodiment of the device according to the invention shown in its normal operating position, i.e. with the shutter “closed”.

[0018] [Fig.2b] shows the same device in the purge position, i.e. with the obturator “open”.

[0019] [Fig.3a] Figures 3a and 3b schematically show two vertical sections of a third embodiment of the device according to the invention shown in its normal operating position, i.e. with the obturator "closed" and respectively the same device in the purging position, i.e. with the obturator "open".

[0020] [Fig.3b] Figures 3a and 3b schematically show two vertical sections of a third embodiment of the device according to the invention shown in its normal operating position, i.e. with the obturator "closed" and respectively the same device in the purging position, i.e. with the obturator "open".

[0021] [Fig.3c] Figures 3c and 3d show a variant of the same device with the shutter in the closed position and respectively in the purge position.

[0022] [Fig.3d] Figures 3c and 3d show a variant of the same device with the shutter in the closed position and respectively in the purge position.

[0023] [Fig.4a] schematically shows a vertical section of a fourth embodiment of the device according to the invention.

[0024] [Fig.4b] Figs.4b and 4c show another vertical section of the same device, perpendicular to the first, in a purging cycle.

[0025] [Fig.4c] Figs.4b and 4c show another vertical section of the same device, perpendicular to the first, in a purging cycle. Detailed description of the invention

[0026] In order to better illustrate the concept and operation of the different forms of embodiment of the device according to the invention, it is described in the context of an embodiment in which the device is fully immersed in the contact zone of the floater in which the pressurized water, after expansion and formation of microbubbles of air, mixes directly with the raw water to be clarified without being conveyed in a pipe.

[0027] The device according to the invention is intended to create a pressure drop at the outlet of the pressurized water through it so that this pressure drop can maintain the pressurization circuit under the desired pressure, most often in the order of 3 to 6 bars.

[0028] According to the first embodiment, the device according to the invention, more particularly described in relation to Figures 1a and 1b, is equipped: - means of supplying pressurized water, such as a threaded tube (10) having a calibrated orifice (11) through which the pressurized water exits; - means of support such as a first support (12); - a pair of nuts (13) allowing the threaded tube (10) to be fixed in the desired position on the first support (12); - of an arm (16) comprising a pivot axis (18) and a weight (17) fixed to the end of the arm (16); - support means such as a second support (14) supporting the axis (18); - a shutter (15) fixed on the arm (16); - a stop (19) on which the arm (16) rests in the lowered position.

[0029] According to this embodiment, the device according to the invention functions as follows:

[0030] In "expansion" mode ([Fig. 1a]), the weight (17) holds the obturator (15) in a fixed position because the arm (16) rests on the stop (19). The distance (a) between the calibrated orifice (11) and the obturator (15) is adjusted using the two nuts (13) to ensure the desired pressure drop and flow rate of the pressurized water. The weight (17) is large enough to press the arm (16) against the stop (19) and thus hold the obturator (15) in position, despite the pressure of the water exiting the calibrated orifice (11) which pushes the obturator (15) upwards. In this configuration, the expansion of the pressurized water occurs as it passes between the outlet of the calibrated orifice (11) and the obturator (15). The distance (a) between the two is, by way of guide and not limitation, less than three-four millimeters.

[0031] To switch from "relaxation" mode to "purge" mode ([Fig.lb]), in order to remove any large objects trapped between the edge of the calibrated orifice (11) and the obturator (15), it is sufficient to briefly lift the weight (17) into the position shown in [Fig.lb] by means of weight-lifting means such as any external movable actuator (2) and a lever (1) attached to the arm (16). In this position, the obturator (15) is moved away from the calibrated orifice (11) to allow the pressure of the pressurized water to expel any large object larger than the slot (a). The external movable actuator (2) lifting the weight (17) may be attached, by way of example and not limitation, to a moving element of the float, such as a scraper or a rotating bridge. It may also be provided di directly by a suitably positioned pneumatic cylinder or by an intermediate mechanism.

[0032] According to this version shown in Figures 1a and 1b, the obturator is fixed to the arm (16), and the distance (a) between the edge of the calibrated orifice (11) and the obturator (15) is adjusted using adjustment and locking means such as nuts (13) for locking the position of the threaded tube (10) relative to the first support (12). The adjustment of the distance (a) can be achieved by other means, for example, by adjusting the position of the obturator relative to the arm (16). In this case, the obturator (15) is not fixed to the arm (16), as shown in Figures 1a and 1b, but is connected to the arm by means of a threaded rod that allows the obturator to be moved closer to or further from the arm. In this configuration (not shown) the adjustment of the distance (a) is done by varying the position of the shutter (15) relative to the calibrated orifice (11) which is itself fixed or, where applicable, also adjustable relative to the first support (12).

[0033] The stop (19) can be fixed either on the first support (12) or on the arm (16). It acts as a spreader to keep the obturator substantially parallel to the edge of the calibrated orifice (11).

[0034] According to the second embodiment, the device according to the invention, more particularly described in relation to figures 2a and 2b, differs from the device shown in figures 1a and 1b by the way in which the obturator (27) is supported and guided at the time of purging.

[0035] The device described in relation to Figures 2a and 2b is equipped with: - pressurized water supply means (20), comprising a calibrated orifice (21) through which the pressurized water exits; - of an arm (28) comprising a pivot axis (23) and a weight (29) fixed to the end of the arm (28); - of a shutter (27) fixed on the arm (28);

[0036] In this case, the shutter (27) is connected to the arm (28) via the axis (23). A second arm (26), parallel to the arm (28) and comprising a fixed axis (24), is connected to the shutter (27) via the axis (24) such that the arm (26) and the arm (28), together with the axes (22), (23), and (24), form a deformable parallelogram. This deformable parallelogram allows the shutter (27) to remain perpendicular to the axis of the calibrated orifice when the weight is lifted, unlike the configuration shown in Figures 1a and 1b.

[0037] The device according to this second embodiment of the invention functions in the same way as that of the first embodiment.

[0038] According to the third embodiment, the device according to the invention, more particularly described in relation to Figures 3a and 3b, differs from the devices shown in figures aa, 1b, 2a and 2b by the shape of the shutter (32) and its method of attachment to the arm (38) bearing the weight (35).

[0039] The device includes, however: - pressurized water supply means (30) comprising a calibrated orifice (31) through which the pressurized water exits; - means of support such as a first support (37); - of an arm (38) comprising a pivot axis (33) and a weight (35) fixed to the end of the arm (38); - support means such as a second support (34) supporting the axis (33); - at least one shutter (32) fixed on the arm (38); - a stop (36) on which the arm (38) rests in the lowered position.

[0040] In this case, the shutter (32) has the shape of a spherical segment. It is fixed to the pivot axis (33) of the weight-bearing arm (38) by a first support (37), the length of which is such that the center of the sphere of the shutter (32) lies on the pivot axis (33) of the arm (38) and the first support (37). In this configuration, in "relaxed" mode, shown in [Fig. 3b], the shutter (32) is held facing the calibrated orifice (31), not entirely by the force of the weight (35), but primarily by the bearing of said shutter on the axis (33), which absorbs almost all of the thrust of the water exiting the calibrated orifice (31). The weight (35) resting on the stop (36) serves mainly to keep the shutter in position by compensating for the (relatively weak) lateral forces caused by the change in direction of the water exiting the calibrated orifice (31).The spherical shape of the obturator (32) ensures that the distance between it and the calibrated orifice (31) remains constant during its pivoting to switch to the "purge" mode in the position shown in [Fig. 3b]. The weight at the end of the arm (38) no longer provides the counter-pressure to hold the obturator in position as in the first two embodiments of the device according to the invention. It serves to return the obturator to the "release" position after purging.

[0041] It is evident that the spherical segment shape of the shutter is advantageous, especially if the calibrated orifice (31) is circular. However, it is also possible to use a cylindrical shutter with a rectangular calibrated orifice, or, more generally, a shutter of any rotating shape combined with a calibrated orifice having the shape of a section of the shutter parallel to its axis of rotation.

[0042] The operation of this embodiment of the device according to the invention remains broadly identical to the two preceding ones. The obturator (32) is held in the "released" position by its weight. Purging is carried out by rotating the obturator around its axis (33) at an angle sufficient for the obturator to partially or completely clear the space in front of the calibrated orifice, thus allowing the purging of any large objects that may be trapped in the narrow space between the obturator and the orifice. calibrated, as shown in [Fig. 3b]. The rotation of the obturator is caused by means allowing the lifting of the weight, such as an external actuator (2) pushing the lever (1) attached to the first support (37) and the arm (38). This external actuator is fixed to a moving part of the float, such as a turntable or a scraper.

[0043] According to a second configuration of the same device shown in Figures 3c and 3d respectively, the obturator (32a) is equipped with a channel (39) which, in "expansion" mode, is not opposite the calibrated orifice (31) and does not influence the expansion conditions. However, during rotation of the obturator (32a) in "purge" mode, this channel (39) passes in front of the calibrated orifice (31) and allows the purged water to be evacuated without completely opening the entire space in front of the calibrated orifice (31). The same result can be obtained with any other orifice in the obturator (32a) conducting the purge water out of said obturator (32a), provided that this orifice passes substantially in front of the whole section of the calibrated orifice, and provided that its shape and section are sufficient to evacuate bodies of the desired size without uncovering at all times the whole section of the calibrated orifice (31).

[0044] According to the fourth embodiment, the device according to the invention, more particularly described in relation to Figures 4a, 4b and 4c, is equipped: - of an obturator (42), the area covering the calibrated orifice (41) of which is spherical, fixed on an axis of rotation (43). This obturator (42) has at least one opening such as a purge channel (44) or any other orifice of another shape suitable for connecting the calibrated orifice (41) and the outside of the obturator (42); - a steering wheel with at least three spokes (45) fixed on the axis of rotation (43); - at least one support (47);

[0045] This fourth version of the device according to the invention operates as follows:

[0046] In "normal" operation, i.e., in "decompression" mode, the purge channel (44) of the spherical obturator (42) is located outside the area of ​​the calibrated orifice (41) of the pressurized water supply means, such as the water inlet tube (40), and decompression occurs between the edge of the calibrated orifice (41) and the spherical obturator (42). The purge is initiated by rotating the spherical obturator (42) so that the purge channel (44) passes over the entire surface of the edge of the calibrated orifice (41). In this way, if a large body is stuck somewhere between the edge of the calibrated orifice (41) and the spherical obturator (42), it will find an "enlarged" exit path when the purge channel (44) passes over where it is located.The rotation of the spherical shutter (42) is caused by the passage of a movable actuator (46) fixed to a movable part of the clarifier, for example on the rotating bridge or on a scraper. This actuator (46). One of the spokes (45) of the flywheel, which is fixed to the axis of rotation (43), is pushed, as shown in Figures 4b and 4c. The spokes (45) of the flywheel are arranged so that with each quarter turn (if the flywheel has four spokes as shown in Figures 4a, b, c, d) of the spherical obturator (42), caused by the passage of the actuator (46), the purge channel (44) remains outside the area of ​​the calibrated orifice (41). In the configuration shown in Figures 4a, 4b, 4c, the flywheel has four spokes (45) and the spherical obturator (42) has only one purge channel (44). Thus, a purge is performed with each fourth pass of the movable actuator (46). But, in another possible configuration (not shown), the flywheel may have another number of spokes and the spherical obturator (42) - several purge channels (44).This would result in a different purging frequency, while maintaining the same principle, provided that after the passage of the actuator (46), no purge channel (44) is located opposite the area of ​​the calibrated orifice (41).

[0047] It is evident that the handwheel (45) is not the only possible means of rotating the shutter "step by step." Other mechanisms can be used to achieve this type of shutter rotation and ultimately obtain the same result. The choice of mechanism is not essential for the operation of the device according to the invention, provided that it allows the rotation steps described above to be followed.

Claims

Demands

1. Installation for the clarification of raw water by dissolved air flotation comprising a pressurized water expansion device suitable for implementation in particular within circular flotators equipped with a rotating floating sludge bridge or scraper or within rectangular flotators equipped with surface scrapers, said device being immersed in the contact zone between the pressurized water and the raw water, and suitable for diffusing the microbubbles formed during expansion directly into said contact zone, characterized in that said device comprises mechanical purging means mechanically actuated by the passage of a moving element of the flotator, in particular by at least one actuator (2) fixed on the rotating bridge or on a floating sludge scraper.

2. Installation for the clarification of raw water by dissolved air flotation according to claim 1, characterized in that the pressurized water expansion device comprises: - means (10), (20) for supplying pressurized water comprising at least one calibrated orifice (11), (21) for the outlet of pressurized water; - at least one obturator (15), (27) carried by at least one arm (16), (28), said arm pivoting about an axis (18), (22) fixed on at least one support (14); - at least one stop (19) adapted to support the arm (16), (28) holding the obturator (15), (27) facing the calibrated orifice (11), (21) at a certain distance (a) from said calibrated orifice (11), (21);- at least one weight (17), (29) fixed on an arm (16), (28) attached to the arm carrying the shutter (15), (27) and capable of pressing said arm (16), (28) against the stop (19) so that the shutter (15), (27) is held facing the calibrated orifice (11), (21) at a certain distance (a) from said calibrated orifice; - means for supporting (12), (14) the pivot axis (18), (22) of the arm carrying the shutter; - means for adjusting and locking the distance between the at least one shutter (15), (27) and the at least one calibrated orifice (11), (21); - means (1), (2) enabling the lifting of the weight (17), (29) and, consequently, the separation of the obturator (15), (27) from the calibrated orifice (11), (21).;

3. Installation for the clarification of raw water by dissolved air flotation according to claim 1, characterized in that the pressure-reducing device

4.

5. pressurized water contains: - means (30) for supplying pressurized water comprising at least one calibrated outlet (31) for pressurized water; - at least one shutter (32, 32a) carried by at least one arm (38) pivoting around an axis (33) fixed on at least one support (34), the surface of said shutter facing the calibrated orifice (31) being spherical or other rotating shape whose axis of formation coincides substantially with the axis of rotation of the shutter (32, 32a); - at least one stop (36) capable of supporting the arm (38) carrying the weight (35), holding the obturator (32, 32a) facing the calibrated orifice (31) at a certain distance (a) from said calibrated orifice (31); - at least one weight (35), fixed on an arm (38) attached to the arm carrying the shutter (32, 32a) and capable of pressing said arm (38) against the stop (36) so that the shutter (32, 32a) is held facing the calibrated orifice (31) at a certain distance (a) from said calibrated orifice; - support means (34) for the pivot axis (33) of the arm (38) respectively carrying the weight (35) and the shutter (32, 32a); - means for adjusting and locking the distance between at least one shutter (32) and at least one calibrated orifice (31); - means (1), (2) allowing the rotation of the obturator (32, 32a) around its pivot axis (33), said rotation causing the obturator (32, 32a) to move away from the calibrated orifice (31). Installation for the clarification of raw water by dissolved air flotation according to claim 3, characterized in that the obturator (32a) comprises at least one channel (39) capable, during the rotation of said obturator during purging, of passing in front of substantially the entire cross-section of the calibrated orifice (31) and of evacuating the purging water. Installation for the clarification of raw water by dissolved air flotation according to claim 1, characterized in that the pressurized water expansion device comprises: - means (40) for supplying pressurized water comprising at least one calibrated outlet (41) for pressurized water; - at least one rotating shutter (42) carried by an axis (43) fixed to at least one support (47), the rotating surface of said shutter facing the calibrated orifice (41) being spherical or other rotating in shape, the axis of formation of which substantially coincides with the axis of rotation of the shutter (42), said shutter (42) being equipped with at least one opening (44) capable of passing, during rotation, substantially in front of the entire surface of the calibrated orifice (41) opening to the outside of said obturator; - means capable of rotating the shutter (42) under the action of an external actuator (46) so as to cause the opening (44) to pass in front of the entire surface of the calibrated orifice (41) during the rotation of said shutter; - means for adjusting and locking the distance between at least one shutter (42) and at least one calibrated orifice (41).

Images