MXPA99009302A - Centrifugal liquid pump with internal gas injection - Google Patents

Abstract

The centrifugal liquid pump (1) is of the rotary discs types and has an integrated gas injector of very simple yet efficient structure. This pump (1) has a casing (3) defining an inner, substantially cylindrical chamber (5) with an axial liquid inlet (11) and a tangential liquid outlet (13). A rotary impeller (15) is rotatably mounted within the chamber (5). This impeller (15) has first and second spaced apart discs (17, 19) which are rigidly interconnected at such a distance away from each other as to extend close to the opposite walls of the chamber (5). The first disc (17) that extends close to the wall (7) into which the liquid inlet (11) opens has a central opening (21) of the same diameter as the liquid inlet (11) to allow the liquid injected through the inlet to enter within the chamber in between the discs. The second disc (19) has a plurality of spaced apart openings (39) located at a constant radius, which is inferior to the radius of the discs. A coaxial power shaft (25) is connected to the impeller (15) so as to rotate it in a given direction. This shaft (25) extends out of the chamber (5) in a direction opposite to the liquid inlet (11). A gas feed pipe (31) is in open communication with one chamber (5). This gas feed pipe (31) is connected to a hole (35) made in the casing (3). This hole (35) is located in the second opposite wall of the chamber at a radial distance substantially equal to the above mentioned constant radius. In use, the pressurized gas fed through the hole (35) made in second opposite wall of the casing passes through the openings (39) made in the second disc (19) and enters into the chamber (5). The gas is then dissolved in the liquid while the same moves between the discs (17, 19) toward the outlet (13) of thepump (1).

Description

CENTRIFUGAL PUMP FOR LIQUIDS WITH INTERNAL GAS INJECTION BACKGROUND OF THE INVENTION Z a) Field of the Invention The present invention relates to a centrifugal pump of the rotating disk type, which incorporates a means for injecting and dissolving a gas, such as air, in a liquid that is preferably water, while pumping this liquid. b) Brief description of the prior art __ In the flotation processes that are currently used to "clarify" or otherwise treat wastewater, it is common practice to recycle part of the clarified water. Usually, the clarified water is pumped into the bottom part of the flotation tank of the clarifier or at the outlet thereof and is injected into the wastewater to be treated just before they enter the clarifier. It is also common practice to inject air into the wastewater that enters the clarifier, in such a way as to generate a multitude of very small bubbles that "capture" the solids in suspension in the wastewater and thus favor the flotation thereof. Such an injection can be done either directly in the wastewater fed to the clarifier, just before it enters the same, or preferably in the clarified water that is recycled before its injection into the wastewater. In both cases, the injection is preferably done under pressure to dissolve as much air as possible in the water. In order to recycle a sufficient amount of clarified water and simultaneously allow a sufficient amount of air to dissolve in it to generate a multitude of micro bubbles of 150 μm or less, as soon as the pressure is released, the pump should ideally generate a pressure of 550 to 825 kN / m2 (80 to 120 psi). Of course, you should also ideally have a low energy consumption (expressed in m3 per horsepower). To meet these objectives, up to now it has been used multistage centrifugal pumps with mobile pallet wheels that can increase the pressure up to 1380 kN / m2 (200 psi). However, these pumps have a lower flow rate. It has also been suggested to use rotating disk pumps comprising a plurality of closely spaced spaced discs rotatably mounted within a stator (see for example U.S. Patent Nos. 4,335,996; 4,514,139; 4,768,920 and 4,773,819). In this particular case, the pumping effect is obtained by cutting and friction forces developed between the rotating discs and the fluid. To improve such effect, it has also been suggested to provide straight, radial projections on each disc (see U.S. Patent No. 4,940,385). Rotating disk pumps are interesting in that, thanks to their structure, they can easily handle a fluid such as sewage, which can contain solids in suspension, however, they are really effective only when the pressure to be increased is less than 350 kN / m2 (50 psi). In addition, they are known to be energy consumers (maximum 1 m3 / HP). To provide the required solution of air in the recycled water (or in the wastewater fed to the clarifier), it is common practice to provide an air inlet in a Venturi tube located upstream of the pump, to suck the air with and to the water and compress it with it into the pump (see, for example, Canadian Patent No. 1,016,408, even though it is directed to another application). It has also been suggested to inject air directly into the stator of the pump, either through ducts made in the paddles of the moving wheel and openings in the outer ends of these blades (see U.S. Patent No. 3,485,484) or through stationary bolts. which extend in the stator of the pump, the rotor blades then being divided at a given radial distance from their axes of rotation so as not to interfere with the bolts (see U.S. Patent No. 4,744), 722). In both of these cases, the stator becomes complex and therefore expensive and difficult to repair. * "" Of interest, although joara a different application, French Patent No. 853,227 that uses a central duct connected to radial openings near the axis of a mobile wheel center, injects air and forms a foam with water. In this patent, the water fed to the mobile wheel is pressurized by a pump located upstream. The E.Ü. No. 5,385,443 granted to the present applicant describes a centrifugal pump for liquids of the rotating disk type that incorporates a "gas injection system of a structure, of the applicant but very simple, by means of which up to 15% of the volume of a gas such as it is found, it can be mixed with the pumped liquid.The gas injection is achieved with a gas feeding tube that goes axially into the pumps and with a plurality of gas injectors tubes projecting from the gas feeder tube radially and central between the discs of the mobile wheel.The gas injection tubes rotate in unison with the discs of the mobile wheel and allow the gas to be injected into the water between the discs.

OBJECTS AND SUMMARY OF THE INVENTION The object of the invention is to provide a centrifugal pump for liquids of the rotating disk type having an integrated gas injector, which is very simple in structure and has a minimum number of movable parts to reduce wear. . According to the invention, this object is achieved with a centrifugal pump to be used to pump a liquid and to inject and dissolve, at least in part, a gas in the liquid while pumping said liquid, which like all conventional centrifugal pumps, It comprises a stator that defines a substantially cylindrical inner chamber. This chamber has opposite walls, first and second, coaxial with each other. "A liquid inlet of a given diameter is in open communication with the camera, this inlet is coaxial with the camera and opens on the first opposite wall of the same.A liquid outlet is also in open communication with the camera. This outlet extends tangentially out of the chamber.A rotating mobile wheel is installed rotatably within the chamber.This mobile wheel comprises separate first and second disks of a given radius which are coaxial with the opposite walls, The first and second discs of the chamber, the first and second discs, are rigidly interconnected at such a distance from one another to extend close to the opposite walls, first and second of the chamber, respectively. Close to the first opposite wall in which the liquid inlet opens, J has a central opening of the same diameter as the inlet of liquids to allow the liquid to inject. cted through the entry between the inside of the camera between the discs. A drive shaft is coaxial with and rigidly connected to the moving wheel to rotate the moving wheel in a given direction within the chamber. The drive shaft passes through the second opposite wall of the stator and extends out of the chamber in a direction opposite to the liquid inlet. Finally, the means of injection and dissolution of gas are provided to inject a gas into the liquid while this liquid is pumped into the chamber. The invention is characterized in that the gas injection and dissolution means comprise a plurality of separate openings made in the second disk at a constant radius which is lower than the radius of the first and second disks. The gas injection and dissolution means also comprise a gas supply tube in open communication with the chamber. The gas supply tube has a first end that is rigidly connected to a hole made in the stator. This hole is located in the second opposite wall of the chamber at a radial distance that is substantially equal to the constant radius mentioned above. "" The gas supply tube also has a second end connected to a pressurized gas injector. In use, the pressurized gas fed through the hole made in the second opposite wall of the stator passes through the openings made in the second disk and enters the chamber. This gas then dissolves in the liquid as it moves between the disks towards the outlet of the pump. According to a preferred embodiment of the invention, the centrifugal pump has its drive shaft held sealed in the second opposite wall of the stator by a set of seals defining a closed space therebetween. A cooling system including a liquid feed tube and a liquid withdrawal tube is provided to supply liquid in the enclosed space and thereby cool the supports. According to another preferred embodiment of the invention, the disks of the movable wheel are connected to each other by a plurality of small rods and have opposite flat surfaces facing one of the other and in which a plurality extends. of outgoing. The protrusions project from the discs at such a distance to leave a space between them and are preferably thick and spirally formed, high and radially curved outwardly in a direction opposite to the direction in which the moving wheel is rotated. As can be understood now, the centrifugal pump for liquids according to the invention has a built-in gas nozzle. This pump has a structure that is very similar to the basic structure of conventional pumps of the rotating disk type, except for the addition of some openings, holes and feeding tubes. In this way it can easily be incorporated into the structure of a conventional pump without any major modification being made thereto. Because there are no new moving parts, the integration of the gas injector does not lead to additional wear. Tests carried out by the applicant have shown that the centrifugal pump according to the invention can easily increase a pressure of 550 to 1050 kN / m2 (80 to 150 psi) and allow injection and dissolution of up to 18% by volume of air in the pumped water, thus allowing the formation of very efficient micro bubbles of a few tenths of a micron. In addition, the flow velocity of the pump is appropriate and the energy consumption much better than expected (more than 2 m3 / HP). BRIEF DESCRIPTION OF THE DRAWINGS The invention and its advantages will be better understood after reading the following non-restrictive description of a preferred embodiment thereof, made with reference to the accompanying drawings in which: Figure 1 is an elevational view lateral cross-sectional lesson * of a centrifugal pump, according to a preferred embodiment of the invention; Figure 2 is a cross-sectional view along the line II-I of the pump shown in Figure 1, - Figure 3 is a comparative diagram giving the increased pressure as a function of the flow velocity when it makes use of (i) a conventional centrifugal pump without air injection, (ii) a centrifugal pump having a plurality of gas injection tubes, as described in the ETU patent. No. 5,385,443 and (iii) a pump as shown in Figure 1, the stator and the movable wheel of all these pumps being identical in shape and size; and Figure 4 is a comparative diagram giving the amount (expressed in ppm) of particles in suspension at the outlet of a same clarifier fed with (i) a centrifugal pump having a plurality of gas injection tubes, as described in the EU patent No. 5,385,443 and (ii) a pump as shown in Figure 1, the stator and the mobile wheel of both pumps being identical in shape and size and the operating conditions in each case being similar. DESCRIPTION OF A PREFERRED MODE In the following description, reference will be made exclusively to water as the liquid to be pumped, and to air as the gas to be injected into the pumped liquid. However, it is valid to mention that the invention is not restricted to the injection of air into water, especially clarified or residual water, and can actually be used to inject other gases into other liquids. The centrifugal pump for liquids 1 according to the "preferred embodiment of the invention, as shown in Figures 1 and 2 is of the type of" rotating disc. "It comprises a stator 3 defining a substantially cylindrical, inner chamber 5 which it has a pair of opposite end walls 7, 9 coaxial with one another The stator 3 is provided with a liquid inlet 11 which is coaxial with the chamber 5 and opens in one of the opposite end walls, eg the one numbered as 7. The stator 3 also comprises a liquid outlet 13 which is in open communication with the chamber 5 and extends tangentially therefrom. i A rotating mobile wheel 15 is installed rotatably within the chamber 5. This mobile wheel 15 comprises a pair of separate discs 17, 19 of a given radius which are coaxial with the chamber. The disks 17, 19 are connected to each other by a plurality of small rods 22 at such a distance from each other to extend close to the opposite end walls, respectively. The disc that is located adjacent the opposite end wall 7, in which the liquid inlet opens, has a central opening 21 to allow the liquid injected through the inlet 11 into the chamber 5. Both disks 17, 19 have opposite flat surfaces facing each other and in which a plurality of projections 23 extend. As is clearly shown in Figure 1, the projections 23 project from the disks at such a distance to leave a space between them. they. As best shown in Figure 2, the projections 23 are thick and high, spirally formed and radially curved externally in a direction opposite to the direction in which the movable wheel is rotated, to increase as much as possible the friction between the discs and the liquid being pumped and thus the pressure that can be increased - inside the pump The pump 1 also comprises a transmission shaft 25 coaxial with and rigidly connected to the second disc 19, viz. the opposite to the perforated disk 17. The shaft 25 is held in a sealed manner in the stator wall 9 by means of a set of seals 27. It extends out of the stator in a direction opposite to the liquid inlet 21 and is connected to an engine 29 for rotating the mobile wheel 15 inside the chamber 5. The structure of the pump 1 described above is known per se and does not need to be described further In accordance with the invention, the previous pump 1 is improved in that it incorporates m Efficient but very simple edios to inject and dissolve, at least in part, a gas like air, in the liquid while pumping it. Referring again to Figures 1 and 2, the gas injection and dissolution means comprise a gas supply tube 31 in open communication with the chamber 5. The gas supply tube 5 has a first end 33 which is rigidly connected. to a hole 35 made in the stator 3. This hole 35 is located in the second opposite wall 9 of the chamber at a radius or radial distance "d" from the axis of the stator. The gas supply pipe 31 also has a second end which is located outside the stator and is connected to a source of pressurized gas 37, such as a slack compressor. The gas injection and dissolution means also comprise two or more separate openings 39 which are made in the second disk 19, viz. the one adjacent to the second opposite wall 9 of the stator. These openings 39 are separated equally and are located at a constant distance (or "radius") from the axis of the discs. This constant radius is substantially equal to the radius "d". As a result, the openings 39 pass just opposite the hole 35 when the mobile wheel 15 rotates with the stator. This allows the gas to be fed through the hole 35 via the gas supply tube 31 to pass through the openings 39 and enter the chamber 5 between the discs 17, 19 at a radial distance "d" from the stator shaft. . The gas that is fed in this way dissolves in the liquid while it is pumped. The number of openings 39 and the radius "d" to which these openings extend can vary and in fact depend on the intended use and application of the pump. The closer the openings 39 (and the hole 35) are to the pump shaft (the shorter the "d"), the lower the pressure required to inject gas into the pump. The further the openings are located 39 . { viz. the larger is "d"), the higher the pressure required to inject air and consequently the amount of gas injected into the pump. In a similar way, the higher the number of openings 39, the better the distribution of gas within the liquid. However, too many openings can affect the "efficiency" of the second disk 19. As already described above, the transmission shaft 25 is preferably held in a sealed manner in the wall 19 of the stator 3 by means of a set of seals 27 which they define a closed space 41 between them. A cooling system is provided to supply a continuous flow of liquid to the enclosed space 41 and thus cool the seals 27. This cooling system includes a liquid feed tube 43 and a liquid withdrawal tube 45 whose openings are longitudinally separated and radially one from the other to ensure a maximum flow of liquid in the closed space 41. The liquid feeding tube 43 can be connected to the liquid outlet 13 of the pump or to any other liquid source available in the plant where the pump it is located. The liquid withdrawal tube 45 can be provided with a valve to maintain a pressure inside the chamber 41. It can be connected to a culvert or to the inlet 11 of the pump in order to return the cooling liquid to the main liquid stream fed "to the pump A pump of the rotating disk type similar to that shown in Figures 1 and 2 was extensively tested by the applicant for recirculation in a wastewater clarifier (also called" white water ") from a fulling mill. Wetted in a de-inking plant This pump was also compared to a centrifugal pump of the same size, provided with a gas injection facility as described in US Patent No. 5,385,443". The radius "R" of the discs of the tested pump was "equal to 17.8 cm (7"). Its space was equal to 5.7 cm (2% "). Each disc had projections 22 that were 1.9 cm (%") high. Four openings 39 were made in the second disk Í9. Each opening 39 was located at a radius "d" "equal to 11.4 cm (4%") from the axis of the mobile wheel and had a diameter of 1.08 ^ cm (5/16"). The mobile wheel was rotated to 3600 The results obtained are reported in the diagram shown in Figure 3. As can be seen, a pressure of more than 630 kN / m / 2 (90 psi) is easily increased, with a flow rate as high as 180 In addition, up to 18% by volume of air is easily injected into the pumped water, without unduly affecting the efficiency of the pump, using an air pressure source of only 210 kN / m2 (30 psi). obtained were better than those obtained with the pump of the US patent No. 5,385,443 where 10% of air was injected into the pumped water.

The comparative tests were carried out with the same pumps in water from the same wet batter under the following conditions: - generated liquid pressure: 630 kN / m2 (90 psi); - Injected air flow rate: 6.3 ScFM - concentration of suspended particles in the liquid fed into the machine: 180 ppm. The concentration of particles in suspension in the water recovered at the exit of the machine was as follows: These results are reported in Figure 4.

As can be seen, a better classification was achieved with the pump according to the invention, probably because more air dissolved in the pumped liquid, thus increasing the number of micro bubbles to capture the particles in suspension. Of course, numerous modifications may be made to the embodiments described above without departing from the scope of the instruction as defined in the appended claims.

Claims (6)

1. NOVEDGE OF THE INVENTION Having described - the present invention is considered as a novelty and therefore the property described in the following claims is claimed as property. A centrifugal pump for use in pumping a liquid and for injecting and dissolving, at least in part, a gas in the liquid while the liquid is being pumped, the pump comprising: a) a stator defining a substantially cylindrical inner chamber, having the chamber opposite walls, first and second, coaxial with each other; b) an inlet of liquids of given diameter in open communication with the chamber, the entrance with the chamber being coaxial and opening in the first opposite wall thereof; c) a liquid outlet in open communication with the chamber, the outlet extending tangentially out of the chamber; d) a mobile wheel - rotationally installed inside the chamber, the mobile wheel comprising separate discs, first and second, of a given radius coaxial with the opposite walls, first and second, of the chamber, interconnected in a rigid manner the disks, first and second, at such a distance away from one another to extend close to the opposite walls, first and second, of the chamber, respectively, having the first disc extending close to the first opposite wall, in which it opens the entrance of liquids, a central opening of the same diameter as the entrance of liquids to allow the liquid injected through said entrance into the chamber between the discs; e) a coaxial drive shaft with and rigidly connected to the movable wheel to rotate the movable wheel in a given direction within the chamber, the drive shaft passing through the second opposite wall of the stator and extending out of the camera in a direction opposite to the outlet of the liquid; and f) means for injecting and dissolving gas to inject a gas into the liquid while pumping the liquid into the chamber; characterized in that the gas injection and dissolution means comprise: a plurality of separate openings made at a constant radius in the second disk, the constant radius being lower than the radius of the disks, first and second; and a gas supply tube in open communication with the chamber, the gas supply tube having a first end rigidly connected to a hole made in the stator, the hole being located in the second opposite wall of the chamber at a radial distance substantially equal to the constant radius, the gas supply tube having a second end connected to a pressurized gas injector.
2. 2. The centrifugal pump according to claim 1, characterized in that the discs, first and second, of the mobile wheel are connected to each other by a plurality of rods and have opposite flat surfaces that face one another and in which a plurality of projections extend, the projections projecting from the disks at such a distance to leave a space therebetween.
3. 3. The centrifugal pump according to claim 2, characterized in that the projections are spirally formed and radially curved externally in a direction opposite to the given direction in which the movable wheel is rotated. The centrifugal pump according to any of claims 1 to 3, characterized in that: the transmission shaft is held in a sealed manner in the second opposite wall of the stator by means of a set of seals defining a closed space between them; and the pump further comprises a cooling system including a liquid feed tube and a liquid withdrawal tube connected to the enclosed space to supply liquid thereto and thus cool the seals. "5. The centrifugal pump according to any of the claims 1 to 4, characterized in that the openings of the second disk are equally separated and placed to extend all around the second disk 6. The centrifugal pump according to any of claims 1 to 5, characterized in that the liquid is residual or clarified water and the gas is air. SUMMARY The centrifugal pump for liquids (1) is of the rotating disc type and has an integrated gas injector of efficient but very simple structure. This pump (1) has a stator (3) that __ defines a substantially cylindrical inner chamber, "(5) with an axial entrance of liquids (11) and a tangential outlet of liquids (13) .A rotating mobile wheel (15) it is installed rotatably within the chamber 5. This mobile wheel 15 tends to separate, first and second discs 17, 19, which are rigidly interconnected at such a distance from one another to extend close to the walls. opposite of the camera (5). The first disk (17) that extends close to the "wall (7), in which the liquid inlet (11) opens has a central opening (21) of the same diameter as the liquid inlet (11) to allow that the liquid injected through the inlet enters the chamber between the discs The second disc (19) has a plurality of separate openings (39) located at a constant radius, which is less than the radius of the discs. The coaxial transmission shaft (25) is connected to the mobile wheel (15) to rotate in a given direction. (25) extends outside the chamber (5) in a direction opposite to the liquid inlet (11). A gas supply tube (31) "is in open communication with a chamber (5)." This gas supply tube (31) is connected to a hole (35) made in the stator (3). 35) is located in the second opposite wall of the chamber at a radial distance substantially equal to the constant radius mentioned above In use, the pressurized gas fed through the hole (35) made in Ya second opposite wall of the stator passes through the la3 openings (39) made in the second disk (19) and enter the chamber (5) Y. The gas then dissolves in the liquid while it moves between the discs (17, 19) towards the outlet (13) of the pump (l.