Ejector und its use in a process of aerobically treating water

Abstract: An ejector (10) includes a nozzle (12) through which a first fluid is ejected to produce a vacuum in a vacuum chamber (16). The vacuum chamber (16) includes an opening (18) through which a second fluid is introduced. The vacuum chamber further includes an inlet (22) through which a third fluid is introduced into the vacuum chamber. The ejector may be used in a water purification system for example.

Description: The present invention relates to ejectors and in particular, but not exclusively, to an ejector suitable for use in a water purification system. An ejector typically includes a nozzle from which a fluid is ejected at a high speed to create a vacuum in a vacuum chamber adjacent to the nozzle. This causes another fluid to enter into the vacuum chamber through an opening. These fluids are then discharged from the vacuum chamber. Such an ejector is widely used to substitute for a vacuum pump or to provide a mixture of air and liquid. Fig. 7 shows one example of an ejector well known in the art. As illustrated, the ejector includes a submersible or underwater pump 100 to feed water to a nozzle 102. The water is then ejected at a high speed to produce a vacuum in a vacuum chamber 106. This causes air to enter into the vacuum chamber through an inlet pipe 108. A jet of water together with the air is discharged through a discharge pipe 104. A disadvantage with the prior art ejector is that air can not sufficiently be introduced through the inlet pipe. Additionally, air and water can not be mixed to a full extent. Thus, a sufficient amount of air (oxygen) can not be added to (or dissolved into) water. According to the present invention, there is provided an ejector comprising: a nozzle having an open rear end through which a first fluid is introduced, and an open front end through which the first fluid is discharged; a casing surrounding the outer peripheral surface and the front end of said nozzle; a vacuum chamber defined by the inner surface of said casing and said nozzle; an outlet formed in said casing in line with the open front end of said nozzle; an outlet pipe connected through said outlet to said casing to allow the fluid to flow therethrough so as to produce a vacuum in said vacuum chamber; an opening formed in the side of said casing to allow a second fluid to flow into said vacuum chamber; and an inlet formed in the side of said casing to allow a third fluid, which is different from the second fluid, to flow into the vacuum chamber. Preferably, the inlet is formed upstream of the front end of the nozzle. The ejector of the present invention may be arranged in a purification tank to effect aerobic treatment or anaerobic treatment so as to purify a liquid in the tank. The ejector of the present invention may also be placed in an aeration tank. Water is ejected into the tank by the ejector, and air is introduced through the opening. The air is then discharged together with a jet of water. Raw water is fed from a raw water tank, located upstream of the vacuum chamber, or sludge is supplied from a sedimentation tank, located downstream of the vacuum chamber, to the vacuum chamber through the inlets. According to the present invention the vacuum chamber in the ejector includes an inlet or inlets through which a third fluid is introduced into the vacuum chamber. Generally, a fluid is introduced through the opening into the vacuum chamber under vacuum and then, discharged together with a jet of water from the nozzle (The ejector performs the same function when used to mix liquid and air or when used in place of a vacuum pump). If an inlet is formed in the vacuum chamber to introduce a third fluid (the third fluid is typically the same as the first fluid, but may be different from the first fluid), it might be thought that a degree of vacuum in the vacuum chamber would be reduced. This may result in a decrease in the amount of air to be introduced into the vacuum chamber. Such an inlet might, therefore, be assummed to deteriorate the effectiveness of the ejector. However, experiments, carried out by the inventor of the present invention, have shown that such an inlet increases the degree of vacuum in the vacuum chamber and thus, promotes introduction of the second fluid into the vacuum chamber or more effectively mixes the first fluid (normally, liquid) and the second fluid(normally, gas) together. It is found that KLa (overall coefficient of oxygen movement capacity) as an index to show how easily oxygen is added to a liquid can be increased by ejecting water from the ejector and mixing and discharging the water and air together. This is probably because turbulence is created in the vacuum chamber as the second fluid is forced or sucked into the vacuum chamber while a predetermined amount of third fluid is introduced through the inlet. This turbulence produces a higher degree of vacuum so as to introduce a greater amount of second fluid into the vacuum chamber. Also, the air and the fluid are well stirred or mixed under the influence of turbulence. According to a preferred feature of the present invention, the inlet is located upstream of the front end of the nozzle. By this arrangement, the third fluid is forced against the nozzle to promote turbulence. This results in an increase in the degree of vacuum. The fluid is thus stirred or mixed well together. It is found that the amount of the third fluid introduced through the inlet is preferably one third to one fifth of the amount of the second fluid introduced through the opening. In a preferred embodiment of the present invention, the ejector is used with a purification system and serves as an aerator or agitator. The ejector as an aerator can effectively purify fluid in a tank. The ejector may also serve as an agitator to effect anaerobic treatment of fluid in a tank. In the case of anaerobic treatment, the opening can be kept closed during operation of the ejector as an agitator. However, with a conventional ejector, an excessive degree of vacuum is produced in a vacuum chamber if the opening is closed. This restricts flow of fluid from a nozzle. As a result, the fluid can not smoothly flow out of the nozzle or the fluid can not be stirred well in the tank. With the ejector of the present invention, the third fluid flows into the vacuum chamber through the inlet so as to facilitate discharge of a jet of water and promote mixing of the fluid in the tank. The ejector of the present invention is advantageous particularly when it is used in a single tank to repreatedly effect aerobic and anaerobic treatment. In a further embodiment of the present invention, the ejector serves as an aerator in an aeration tank. Raw water is fed from a raw water tank, located upstream of the aeration tank, to the vacuum chamber and/or sludge is supplied from a sedimentation tank, located downstream of the aeration tank, to the vacuum chamber through the inlet. In such a system, the ejector effectively purifies water in the tank by high KLa value. The raw water or the sludge, as introduced into the vacuum chamber through the inlet, are well mixed with the fluid in the tank to provide a jet of water. In this way, the fluid in the tank can effectively be purified. Advantageously, this arrangement eliminates the need for a pump to feed raw water into the aeration tank and to return sludge from the sedimentation tank to the aeration tank. From the above it will be seen that in its preferred embodiments at least, the present invention provides an ejector which provides a high degree of vacuum in a vacuum chamber, and an ejector which fully forces air through water. Some preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Fig. 1 is a sectional view showing the principal parts of an ejector according to one embodiment of the present invention; Fig. 2 is a graph showing advantage of the ejector shown in Fig. 1; Fig. 3 is a sectional view showing the principal parts of an ejector according to another embodiment of the present invention; Fig. 4 is a schematic view of a water purification system according to one embodiment of the present invention; Figs. 5 and 6 are schematic views of purification systems according to different embodiments of the present invention; Fig. 7 is a schematic view of a conventional ejector; and Figs. 8 and 9 are schematic views of conventional water purification systems. In the drawings, an ejector is designed to provide a mixture of air and fluid. Referring to Fig. 1, there is shown an ejector 10. 11 is a pipe communicated with a pump. A nozzle 12 is connected to one end of the pipe 11 and has an open end through which a first fluid is introduced, and an other open end through which the first fluid is discharged. A casing 14 surrounds the nozzle 12 and defines a vacuum chamber 16. The casing 14 has an opening 18. An inlet pipe 20 extends from the opening 18 to introduce air into the vacuum chamber 16. The upper end of the inlet pipe 20 extends above the level of water. The casing 14 also includes water inlets 22. In the illustrated embodiment, the casing has two water inlets, but it may have a single water inlet. Water in a tank can flow into the vacuum chamber 16 through the water inlets 22. The diameter of each water inlet 22 is selected such that the amount of water entering the vacuum chamber 16 therethrough is approximately one third to fifth of that of air flowing through the inlet pipe 20 and the opening 18 into the vacuum chamber 16. Illustratively, the water inlets 22 are formed leftwardly or upstream of the front end of the nozzle 12, but may be located at any other places. 24 is an outlet pipe through which a mixture of air and water is discharged. Operation of the ejector will next be described. With the ejector 10 of this embodiment, water is fed from the water tank to the pump. The water is then ejected at a high speed through the nozzle 12. This causes air to flow out of the vacuum chamber 16 to reduce pressure in the vacuum chamber below atmospheric pressure. Air is then sucked into the vacuum chamber 16 via the inlet pipe 20 and the opening 18. The air thus sucked is thereafter discharged from the vacuum chamber 16 through the outlet pipe 24. In the meantime, water flows from the tank into the vacuum chamber 16 through the inlets 22. The amount of water introduced into the vacuum chamber 16 is approximately one third to fifth of the amount of air introduced into the vacuum chamber 16. When a predetermined amount of water is introduced into the vacuum chamber 16 through the water inlets 22, turbulence is created in the vacuum chamber 16 due to a jet of water through the nozzle 12 and a high speed flow of air through the opening 18. This provides a higher degree of vacuum in the vacuum chamber 16 so as to promote introduction of air into the vacuum chamber 16 through the inlet pipe 20 and the opening 18. The water and air are thus sufficiently mixed through the vacuum chamber 16 and the outlet pipe 24. In the ejector 10 of this embodiment, the water inlets 22 are located upstream of the front end of the nozzle 12. With this arrangement, water comes into contact with the nozzle 12 after it flows in through the water inlets 22. This applies more turbulence to a mixture of air and water. Fig. 2 shows KLa (overall coefficient of oxygen movement capacity) obtained by an ejector 10 of the present invention in comparison with that obtained by a conventional ejector with no water inlets. As illustrated, the ejector 10 provides substantially greater KLa than possible with the prior art ejector. As stated earlier, the number of water inlets 22 may be one rather than two in the illustrated embodiment. In addition, a conduit 26 (Fig.3) may be connected to the water inlet 22 to feed the desired liquid by means of a pump or other means. Fig. 4 shows one example of a water purification system with the use of the ejector 10 as described above. In Fig. 4, 28 is a flow control tank (raw water tank). 30 is an aeration tank. 34 is a sedimentation tank. With this system, water is fed from the flow control tank 28 to the aeration tank 30 by a pump 36. Some of sludge as return sludge is returned from the sedimentation tank 34 to the aeration tank 30 by a pump 38. Raw water and return sludge are then mixed with air by the ejector 10 in the aeration tank 30. That is, aeration is effected to purify the raw water. Conventionally, a blower 110 is mounted to the aeration tank 30 to effect aeration as shown in Figs. 8 and 9. In this embodiment, the water purification system uses the ejector 10 in place of the blower 110 so as to more effectively perform aeration and thus, purify sewage. Fig. 5 shows a water purification system according to another embodiment of the present invention. In this example, raw water flows from the flow control tank 29 through the water inlets 22 of the ejector 10 into the vacuum chamber 16. This arrangement not only eliminates the need for a pump 36 to feed raw water, but also more effectively mix raw water with a liquid and air contained in the aeration tank 30. This results in an improvement in purification of the raw water. Sludge may be supplied from the sedimentation tank 34 through the water inlets 22 into the vacuum chamber 16, instead of or in addition to introducing the raw water through the water inlets 22. The sludge is then discharged from the aeration tank 30 together with the liquid and air in the aeration tank 30. This arrangement eliminates the need for a pump 38 to return sludge. Also, sludge can be more effectively mixed with the liquid and air contained in the aeration tank 30 so as to improve purification. Fig. 6 shows a system according to a further embodiment of the present invention. This system includes a treatment tank 40 to repeatedly effect aerobic treatment and anaerobic treatment so as to exclude nitrogen. The ejector 10 is arranged in the treatment tank 40. Conventionally, an agitator 112 is provided in the tank 40 as shown in Fig. 9. Also, a blower 110 is used to force air through water in the tank 40. In the case of anaerobic treatment, an agitator 112 is rendered operative, while the blower is stopped. In the case of aerobic treatment, only the blower 110 is operated. In this embodiment, the system utilizes the ejector 10 in place of the blower 110 and the agitator 112. When anaerobic treatment is performed with the use of the ejector 10, the ejector is operated while a valve in the inlet pipe 20 is kept closed. If the inlet pipe is closed in a conventional ejector, the vacuum chamber provides an excessively higher degree of vacuum. This restricts discharge of water through the outlet pipe 24. In fact, it is difficult for a conventional ejector to perform anaerobic treatment. According to the present invention, the liquid flows from the tank 40 through the inlets 22 into the vacuum chamber 16 even if the inlet pipe 20 is closed. Thus, the liquid can smoothly be discharged through the outlet pipe 24, and effective agitation takes place within the tank 40 to fully effect anaerobic treatment. Although the preferred embodiments of the present invention have been described in detail, various changes may be made in the invention. The ejector of the present invention may be used for various purposes. For example, the ejector can be used to produce vacuum or add gas to a liquid.

Claims: An ejector (10) comprising: a nozzle (12) having an open rear end through which a first fluid is introduced, and an open front end through which the first fluid is discharged; a casing (14) surrounding the outer peripheral surface and the front end of said nozzle; a vacuum chamber (16) defined by the inner surface of said casing and said nozzle; an outlet formed in said casing in line with the open front end of said nozzle; an outlet pipe (24) connected through said outlet to said casing to allow the fluid to flow therethrough so as to produce a vacuum in said vacuum chamber; an opening (18) formed in the side of said casing to allow a second fluid to flow into said vacuum chamber; and an inlet (22) formed in the side of said casing to allow a third fluid, which is different from the second fluid, to flow into the vacuum chamber. An ejector according to claim 1, wherein said inlet (22) is located upstream of the front end of said nozzle (12). An ejector according to any preceding claim, wherein the first and third fluids are liquids, and the second fluid is gas. An ejector according to claim 3, wherein the first and third fluids are water, and the second fluid is air. An ejector according to any preceding claim, wherein said inlet (22) is so constructed as to introduce said third fluid into the vacuum chamber, in an amount which is one third to one fifth of that of the second fluid introduced into the vacuum chamber through the opening (18). An ejector according to any preceding claim, wherein said inlet (22) is located rearwardly of said opening (18). A method of aerobically treating water comprising the steps of: providing an ejector as claimed in claim 1 in a treatment vessel (30); forcing water from said treatment vessel through said nozzle (12) to reduce the pressure in said vacuum chamber (16); introducing air into said vacuum chamber (16) through said opening (18); supplying water to be treated to said inlet (22) either directly, or indirectly via said treatment vessel; and discharging the mixture of water and air from said nozzle (12) into said treatment vessel (30). A method as claimed in claim 7, wherein treated water is fed from said treatment vessel (30) to a sedimentation tank (34), sludge being returned from said sedimentation tank (34) to said treatment vessel (30) or to an inlet (22) of said ejector directly, for passage through said ejector.

Inventors: YAMAMOTO TATSURO, YAMAMOTO, TATSURO
Applicants: INAX CORP, INAX CORPORATION
Application year: 1991
Main classification: C02F3
IPC codes: F04F5, C02F3, B01F3, B01F5