JP2010042411A - Surface aeration blade wheel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface aeration blade wheel which generates oxygen transfer efficiency and synthetic liquid force-feed speed substantially higher than the conventional design and can be used for a liquid charge tank, in particular, useful for aeration of sewage and other waste water. <P>SOLUTION: The blade wheel which rotates freely around the shaft line vertical to the surface of static liquid. The blade wheel has a plurality of blades attached to the under side of a disk or a disk-like surface. Each blade has a polyhedral or a curved geometrical shape over the range from a vertical state on the attachment place to the disk to a partially inclined state of the bottom part. Respective blades are disposed while leaving an interval from each other in the circumferential direction around the shaft line and are disposed so as to form an acute angle with respect to radial line when viewed from the rotation shaft line of the blade wheel. The under side part of the blade which is inclined and is not vertical is located on a place of the static liquid surface or below the place. When the blade wheel is rotated, the under part force-feeds the liquid to the upper part of the vertical part of the blades and, thereon, the liquid is released to the above and in the direction of departing to the outside from the blade wheel in the state of a spray umbrella. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

Related Applications This application is filed on July 21, 1999, which is a continuation of US patent application Ser. No. 09 / 162,088 filed Sep. 28, 1998 (currently US Pat. No. 5,972,661). Co-pending US patent application Ser. No. 09 / 895,418, filed Jul. 2, 2001, which is a continuation of US patent application Ser. No. 09 / 358,502 (currently abandoned). No.).
The present invention relates generally to rotary impellers. In particular, the present invention provides a surface that rotates about a vertical axis near the surface of the water in the tank to spray the liquid into the gas above the liquid and entrain the gas in the liquid by a liquid spray that strikes the liquid surface. It relates to an aeration impeller.

  In many industrial processes, it is desirable to facilitate the mass transfer of gas to liquid. Much of this need stems from the biochemical oxidation process using aerobic microorganisms. Aerobic microorganisms are used because they can convert raw materials into highly valuable substances. Some examples include aerobic fermentation processes that produce fragrances, flavors and pharmaceutical ingredients. Perhaps a more important process is aeration of sewage and other wastewater streams. All of these processes using aerobic microorganisms are common in that oxygen needs to be dissolved in the liquid in order for the microorganisms to be able to convert the raw material to the desired result. Although microorganisms work most efficiently when there is an adequate level of dissolved oxygen in the liquid, it is typically desirable to move additional amounts of oxygen or air into the liquid. This can be achieved in many ways, but the two most common methods are gas sparging and surface aeration. In the gas sparging method, gas (eg, air or oxygen) is bubbled in the liquid in such a way as to increase the amount of dissolved oxygen in the liquid. In contrast, the surface aeration method uses an impeller that is provided at the surface of the liquid and stirs or sprays the liquid into the gas. The spray then strikes the liquid surface, thereby entraining the gas into the liquid surface.

One of the basic procedures for the treatment of sewage and other wastewater streams is called the activated sludge process discovered or devised more than 70 years ago. This is a biochemical type reaction that involves the mass transfer of oxygen into water, and then the transfer and use of its dissolved oxygen to support the growth of aerobic microorganisms suspended in water. These microorganisms, called biomass, oxidize organic matter in wastewater in various ways to eliminate the wastewater biochemical oxygen demand (BOD).
In the original activated sludge process, air was introduced from the blower through a wide variety of devices located at the bottom of the aeration tank or basin. These devices generally have low oxygen transfer efficiency and poor solids suspension characteristics. More than 40 years ago, another method for aeration in the activated sludge process was adopted. This alternative method has been called mechanical surface aeration. This technique utilized a mechanical stirrer that worked at the liquid surface to inject or spray the liquid into the air, causing entrainment of air into the liquid surface, in which case the compressor and diffuser were It was not used. Since then, quite a number of different designs have been developed for surface aeration impellers to increase oxygen transfer efficiency and, secondarily, improve liquid agitation and solids suspension, if possible. However, the problem of solids suspension has obvious drawbacks because the surface aeration impeller is away from the bottom of the tank where the biomass solids tend to settle if the bulk liquid in the tank is not properly stirred.

  A standard measure of aeration efficiency is the number of pounds of oxygen transferred into the liquid per hour per horsepower of energy used to operate the aeration system. This measure is called standard aeration efficiency (SAE). SAEs related to the state of the art surface aeration apparatus range from about 2.0 to about 3.3 pounds of oxygen per hour per horsepower in large aerator sizes. If the size is small, the efficiency value may be somewhat higher. Wastewater treatment plants are purely cost-centric (ie, they do not sell products), and power is one of the major operating costs in such plants, so the oxygen transfer efficiency performance of such aerators Is extremely important, especially in large plants. Due to this need, many attempts have been made to produce surface aeration impellers designed with high oxygen transfer efficiency.

  Representative examples of the state of the art of conventional surface aeration impellers are Patent Document 1 (hereinafter referred to as “Chicotta”) assigned to Chicotta, Patent Document 2 and Patent Document 3 (hereinafter referred to as “Kaelin”) assigned to Caelin Patent Document 4 (hereinafter referred to as “Robertson”) granted to Robertson, Patent Document 5 granted to Lakin (hereinafter referred to as “Lakin”), Patent Document 6 granted to Bad et al. Patent Document 7 granted to Austin (hereinafter referred to as “Austin”), Patent Document 8 granted to Connolly et al. (Hereinafter referred to as “Connolly etc.”), Patent granted to Hove It is described in Document 9 (hereinafter referred to as “Hove”) and Patent Document 10 (hereinafter referred to as “MacWheat”) granted to MacWeater. The entire description of all of these patent documents is hereby incorporated by reference as forming part of this specification.

  Chicotta discloses a surface aeration impeller used in an activated sludge process. The Chicotta aerator has a flat circular impeller disk having a plurality of impeller blades depending from the lower surface of the disk. The vanes are generally flat and radially arranged and have a height that decreases from their inner edge to their outer edge. This design is primarily focused on liquid spraying and does not result in high up-pumping action or agitation of the tank liquid contents, resulting in relatively low system efficiency. Anderson and Austin also disclose a surface aeration impeller having a number of vanes provided on the underside of the disc. These vanes are radial or nearly radial and are generally flat, but have a horizontal plate fixed to the lower edge of each vane. Again, these designs focus primarily on the spraying of the liquid and do not provide high upward pumping action or agitation of the tank liquid contents.

  Unlike Chicotta, Robertson, and Austin, Leakin and Connolly have disclosed various forms of surface aeration impellers that have primarily vertically curved vanes. Most appear to have a large number of vanes provided on the disc-like mounting member. Caelin and Bud also teach surface aerator designs. Feathers such as bad are radial and Kaelin shows another design that represents the state of the art. Bad's design does not provide a strong stirring action, and in addition, kaelin has the disadvantage of being difficult to manufacture.

  Hobe teaches an apparatus and method for aeration of wastewater. This device has a number of vanes provided on a disc-like mounting member. The blades appear to be radial as a whole. The hove blades are characteristic in comparison to the above-mentioned US patent in that they are located both above and below the disc-like mounting member.

  McWeater teaches a surface aeration impeller, which is an axial flow impeller that may have either a gradient blade turbine or an airfoil blade. The blade of the McWee patent is not attached to the lower surface of the disc-like attachment member. In addition, the upper part of the McWeater wing is not strictly radial, but the lower part is radial (at least in one location). Although this impeller provides some upward pumping and stirring action, there is still room for improvement in liquid pumping and oxygen transfer efficiency.

  Although such surface aeration devices as described above function in a satisfactory manner as a whole, problems arise with excessive bounce or misting during operation, inadequate liquid pumping, agitation and circulation, and clogging of the impeller. It was. Accordingly, there continues to be a need for improved designs that increase the efficiency of the aeration process and / or solve some of these problems. In particular, surface aeration impeller designs and operating characteristics that increase the efficiency of oxygen transfer into the liquid and thereby reduce operating costs are particularly desirable.

  Many of the drawbacks associated with prior art design surface aerator impellers are due to a poor understanding of the basic mechanism and fluid dynamics of surface aeration. Current state-of-the-art oxygen mass transfer analysis for surface aerators is essentially limited to the simple idealized model used in the ASCE standard for measuring oxygen transfer in fresh water. This oversimplified and constrained model has been used for decades to characterize oxygen mass transfer performance of surface aerators. A more realistic and rigorous model was developed by NPL1. This mechanical model gives a more physically realistic explanation of the actual oxygen transfer mechanism of the surface aerator, and the oxygen mass transfer process is divided into two separate zones: a liquid spray mass transfer zone and a surface re-transfer. Separate into aeration mass transfer zone.

  These two separate independent mechanisms or zones are all created by a common type of mechanical surface aerator. A liquid spray mass transfer zone 11 is created in the immediately adjacent gas space that surrounds the periphery of the surface aeration impeller where liquid is released at high speed into the surrounding gas. The surface aeration mass transfer zone 13 is mainly present in the bulk liquid near the surface in a region circumferential to the outside of the spray umbrella and around the liquid spray mass transfer zone. Two zones are shown in FIG. The liquid spray mass transfer zone can be rationally characterized and modeled as a single stage gas-liquid contact zone where the liquid is dispersed into a virtually infinite continuous gas phase state of a certain gas composition on the liquid surface. In contrast, the mechanism in the surface re-aeration mass transfer zone is mainly characterized by oxygen transfer to a highly turbulent liquid surface containing entrained gas from the gas phase on the liquid surface. When the liquid spray zone hits the liquid surface of the tank, considerable entrainment of air bubbles into the surface is achieved and a “white-water” effect occurs around the liquid spray impinging on the surface of the tank liquid. The surface re-aeration mass transfer zone includes oxygen transfer to the highly turbulent liquid surface under the spray umbrella, thus resulting in bubble entrainment and gas contact with the highly turbulent liquid surface on the liquid surface Including the transfer of all oxygen into the surface liquid.

  In contrast to the generally known conventional opinion regarding the primary oxygen transfer mechanism of the surface aerator, the present invention provides that approximately 2/3 of the oxygen transfer of the surface aerator occurs in the surface re-aeration mass transfer zone and approximately 1/3. It was quantitatively shown that only occurs in the liquid spray mass transfer zone. This suggests that the impeller design that promotes oxygen transfer in the surface re-aeration zone (eg, by increasing turbulence and increasing volumetric flow) has an overall effect on the total oxygen transfer of the system, Greater than for impeller designs that focus primarily on increased oxygen transfer in the spray zone (eg, by improving spray characteristics such as height and distance). Thus, with a better understanding of oxygen mass transfer mechanisms in surface aerators, the inventor independently analyzed the oxygen transfer process within these two separate and independent mass transfer zones, and as disclosed herein. A surface aerator impeller with an improved design was obtained. These new designs pump large volumes of liquid per unit horsepower input through the liquid spray mass transfer zone and into the surface re-aeration zone, thereby maximizing the total oxygen mass transfer efficiency of the total surface aeration system.

US Pat. No. 3,479,017 US Pat. No. 3,576,316 US Pat. No. 3,610,590 U.S. Pat. No. 3,741,682 US Pat. No. 4,066,383 US Pat. No. 4,074,953 US Pat. No. 4,151,231 U.S. Pat. No. 4,334,826 US Pat. No. 5,522,989 US Pat. No. 5,988,604

McWhirter et al., “Oxygen Mass Transfer Fundamentals of Surface Aerators”, Ind. Eng. Chem. Res., 1995, P 2644-2654.

Accordingly, the following are selected objectives of various embodiments of the present invention.
It is an object of the present invention to provide an improved surface aeration impeller with improved gas transfer rate into the liquid, particularly in the surface re-aeration mass transfer zone of the system.
It is also an object of the present invention to promote turbulence at the liquid surface created by the liquid spray of the surface aeration system and to promote gas entrainment.
It is an object of the present invention to provide an improved surface aeration impeller that reduces torque and increases rotational speed, thereby reducing the cost of the motor and gear transmission for rotating the impeller.
It is also an object of the present invention to provide an improved impeller design with improved liquid pumping capacity and efficiency.

  The present invention is an improved surface aeration impeller for use in a liquid-filled tank having a free liquid surface and a sealed or open gas space on the liquid surface in the tank. The impeller can rotate about an axis perpendicular to the surface of the stationary liquid. The impeller has a plurality of blades attached to the underside of a disk or disk-shaped surface. Each vane has a multi-faceted or curved geometry ranging from a vertical state at the point of attachment to the disc to a partially inclined state at the bottom. The blades are provided at circumferential intervals around the axis, and are provided radially or at an acute angle to the radial line as viewed from the rotational axis of the impeller. The lower part of the vane having a lower inclination or a lower vertical degree than the upper part is positioned below the stationary liquid surface. When the impeller is rotated, the lower portion of the impeller blades pumps liquid onto the vertical portion of the blade, where the liquid sprays in a direction away from the stationary liquid surface and away from the rotating impeller. Released in the state of an umbrella.

FIG. 2 is a plan view of a preferred impeller design of the present invention. 1 is an isometric view of an impeller of the present invention. FIG. 6 is a profile view of a single blade with an end cap at the trailing edge. FIG. 6 shows a profile of a curved blade used in one embodiment of the present invention. It is a figure which shows the surface aeration impeller in operation in a tank.

  As described above, about 2/3 of the oxygen transfer in the oxygen aeration system occurs in the surface re-aeration mass transfer zone 13 and only about 1/3 occurs in the liquid spray mass transfer zone 11. Furthermore, the maximum efficiency of a surface aeration system is not maximized by simply increasing the discharge rate or travel distance of the liquid spray in the liquid spray mass transfer zone that many conventional designs assume. This discovery has led the inventor to be interested in surface aeration designs that fill both mass transfer zones, particularly the surface re-aeration mass transfer zone, to maximize overall oxygen transfer efficiency. This interest has resulted in surface aeration designs with operating principles that are significantly different from most conventional designs. In the present invention, the spray rate from the surface aeration impeller is much lower than the surface aeration impeller in the state of the art. This results in a liquid spray that does not move as high or far as current commercial designs. For example, in a preferred embodiment of the present invention, the liquid spray travels only about 8-12 feet (2.438-3.658 m) from the tip of the aerator impeller, whereas in the current state of the art. The surface aerator operates at a spray distance of about 15-18 feet or more (4.572-5.486 meters or more) from the tip of the impeller. However, although the spray travel distance of the present invention is short, a very large amount of liquid per unit horsepower input is pumped through the liquid spray mass transfer zone. This is a result of the low discharge rate of the liquid spray from the tip of the impeller. Increasing the liquid flow rate also results in a large amount of liquid flow and very strong turbulence in the surface re-aeration mass transfer zone, thus greatly increasing the oxygen transfer rate in the re-aeration zone. This increase in oxygen transfer rate in the surface re-aeration zone more than compensates for the decrease in oxygen transfer rate in the liquid spray zone. Accordingly, the surface aeration impeller of the present invention is designed in such a way as to maximize the liquid flow rate per unit horsepower input through the liquid spray and surface re-aeration zones. This result is achieved by dramatically increasing the upward pumping capacity of the surface aeration impeller.

Thus, the surface aerator design of the present invention has at least four significant advantages that distinguish it from the prior art. These four significant advantages are as follows.
1. The present invention provides higher liquid pumping and allows for the spraying of large amounts of liquid per unit horsepower input.
2. The present invention provides high oxygen transfer energy efficiency (SAE).
3. The present invention provides good overall tank agitation and high tank bottom speed so that an improved suspension of biomass (biomass) solids is obtained.
4). The present invention operates at high speeds and low torques that reduce equipment costs (reduction gears) while providing all of the above advantages.

  Referring to the drawings, FIG. 1 shows a plan view of an improved surface aeration impeller of the present invention. The impeller has a plurality of vertically extending blades 2 attached to the lower surface of a rotatable disk or disk-shaped mounting member 1. Each blade in the embodiment shown in FIG. 1 is at an angle (α) of about 30 ° to 38 ° with respect to a continuous circumferentially spaced circumferential line about the impeller axis 3. In the example shown in FIG. 1, eight blades are provided at intervals of 45 °. The blade 2 is shown more clearly in FIG. 2, which is an isometric view of the impeller. These vanes have a substantially vertical part 6 at the upper part thereof. The blade 2 further includes a non-vertical and non-horizontal lower portion 7 that extends upward and outward in the rotational direction of the impeller. This downward direction forms an angle β with the horizontal line shown in FIG. 3A. The lower portion 7 of the vane serves as an up-pumping pitched vane turbine that provides a large amount of liquid flow to the vertical upper portion 6 of the turbine blade that produces a liquid spray umbrella and liquid spray mass transfer zone 11.

  The blade 2 of the present invention comprises at least two parts, as shown in FIG. 2, namely (1) a generally vertical upper part 6 and (2) a non-vertical and inclined lower part 7. In FIG. 3, a third portion, the top or attachment portion 8, is also shown, but this is optional. This top is generally horizontal and has a hole for bolting (10) through a hole in the mounting disc 1. The provision of this part is optional since other means for attaching the blade to the disk are possible. For example, the vertical portion 6 may be directly welded to the mounting disk 1 or the vertical portion 6 may be directly mounted to a vertical flange provided on the mounting disk. This type of blade is similar in shape to the blades of a gradient blade turbine impeller.

  In order to facilitate manufacture and installation, the inventor has discovered that the overall rectangular shape works well for all of these parts. However, there is no doubt that other shapes can be used. In a preferred embodiment of the invention, the vanes are made from a single rectangular piece of metal that is creased at two locations. One fold is at an angle of 90 ° and is provided near the top edge of the vane, with a horizontal top 8 and a substantially vertical top to facilitate attachment to the underside of the mounting disc 1 Part 6 is formed. The second crease in this embodiment is provided at about 2/3 to 3/4 of the distance below the length of the entire rectangular metal piece. This fold provides a lower portion that extends below and outwardly (in the direction of rotation) of the vanes 7. The second fold has an angle β shown in FIG. 3A. The angle β is about 20 ° to 65 °, preferably about 30 ° to 50 °, and most preferably about 35 ° to 45 °.

  In a preferred embodiment of the invention, where the upper portion of the vane meets the mounting member is a straight line (ie, the upper portion of the vane is straight in a horizontal plane). In another preferred embodiment, all portions of the vane are flat (eg, rectangular or trapezoidal) and thus are non-curved. Moreover, the outer edge part of the upper part typically touches the outer edge part of the disk-shaped mounting member. The inventor has discovered that rectangular vanes are most desirable, but other shapes can be used and this does not depart from the spirit of the invention. It is important that the vane starts at the top with a substantially vertical portion and ends with an outwardly facing (rotational direction) non-vertical portion at least partially located below the surface of the stationary liquid. This slope and size of the lower portion is sufficient to cause a significant amount of liquid upward pumping flow over the vertical portion when the impeller is rotated. These requirements can be met with the two-part vanes described above as well as multi-part (three or more) vanes and continuously curved vanes as shown in FIG. 3B. Such a continuous curved vane can be referred to as an “airfoil” shape as described in US Pat. No. 5,988,604, particularly in FIG. 6 (the contents of such US patent specifications are herein incorporated by reference). Cited here as part of it). The vanes of the present invention (both curved and non-curved vanes) preferably have a substantially constant width W along their entire length. Such vanes can be made relatively easily from a single rectangular piece of material (eg, stainless steel).

The number of blades of the surface aeration impeller of the present invention is generally about 6-12. The optimum number of blades depends on the particular application, but smaller diameter impellers typically have fewer blades and larger diameter impellers typically have more than eight blades. . In a preferred embodiment, the number of blades is about 6-8, and in a more preferred embodiment, exactly 8 blades are provided.
The positioning of the blades is important but can vary considerably. According to the discovery of the inventor, positioning the blades radially under the disc-like mounting member provides a surface aeration impeller that surpasses all conventional designs in terms of performance. However, according to the inventors' discovery, it is also possible to position the vane non-radially, i.e. by preventing the vane from projecting radially outward from an axis perpendicular to the stationary liquid surface. A surface aeration impeller with high liquid pumping capacity and oxygen transfer efficiency is obtained. In this non-radial embodiment, the inner edge of the vertical portion of the blade is pushed forward in the rotational direction at a non-zero angle (α), where α is the radial line (vertical portion And the top edge of the vertical portion 6 of the blade (see FIG. 1). This angle is typically 20 ° to 60 °, preferably about 25 ° to 50 °, and most preferably about 30 ° to 45 °. Another way to characterize vane positioning is to “sweep back” or “off-axis” (ie, non-radial or non-radial) the vanes. It is worth noting that in the non-radial version of the present invention there is no imaginary radial line located on the surface of any blade portion. In other words, there is no line that is located on the surface of any blade portion and is also a radial line.

The blade size also varies considerably. Referring to the figure, the blade width W is about 0.1 to about 0.4 times the disc diameter d. Preferably W is less than 1 / 3d, most preferably about 0.2-0.3d. The height H of the vertical part of the blade is 0.05 to 0.25d, preferably 0.1 to 0.2d. The length L of the lower part of the blade is typically smaller than the height of the vertical part. The length L may be 0.03 to 0.2d, preferably less than 0.1d, or about 0.05d. Finally, the width T of the top 8 that is optionally attached to the disc is not critical as long as it can be properly attached, for example by bolts.
The vanes of the present invention have an optional additional segment called an end cap. The end cap 9 is shown in FIGS. 2 and 3A. The end cap is a relatively flat geometric part positioned essentially perpendicular to the vertical part 6, and connects the outer or rear edges of both the vertical part 6 and the lower part 7 to each other. Yes. The exact shape of the end cap can vary greatly, but the hepatorenal feature of the end cap does not allow liquid to flow or “slide” from the trailing edge of the vane under the vertical portion 6 At the same time, the lifting or upward pumping ability of the impeller is increased. According to the inventor's discovery, the end cap can significantly increase the power delivered and at the same time increase the standard aeration efficiency as the following experimental example shows.

The blade 2 of the present invention is attached to a disk position that can be attached to a shaft 4 that causes axial rotation or a lower side of a disk-like attachment member. The disc is a convenient way to position the vanes in the radial direction or at an acute angle α as described above. The term “disc shape” is intended to include any rotatable attachment member that has at least a top surface and a bottom surface and can be attached to the vertical portion of the vane radially or at an angle α to the bottom surface. The term “disc-like” includes discs with saw-toothed edges and spoke and ring type structures.
Means for attaching the entire impeller (disk and blade) to the shaft does not form the main part of the present invention in a strict sense. This is because such means are well known to those skilled in the art of impellers. In a preferred embodiment, the attachment member is a substantially disc with a hole in the center, which accepts a rotatable shaft 4 and is attached to the disc by bolts 5 and attached to the shaft with pins. It is connected to this rotatable shaft 4 by means 12.
The overall diameter of the impeller of the present invention will depend on the particular application. For sewage or wastewater aeration, a typical diameter would be about 50-100 inches (127 cm-254 cm). In other applications, the diameter may be very small, especially when the tank size is small. The size of the impeller is primarily determined by the power required to meet specific process requirements (ie, oxygen transfer rate), but may also be affected by the size and configuration of the tank in which it is used.

Experimental Example An impeller substantially as shown in FIG. 1 was manufactured and tested in a 40 ft × 49 ft square tank containing about 17 feet of stationary liquid equivalent to about 320,000 gallons of water. In the test, the impeller was attached to a vertical shaft connected to a power source and gear reduction means. All the impellers used in the following experimental examples had 8 blades, and the overall diameter of the impeller was 76.25 inches. In addition, the width W of all the blades tested was 20.5 inches and the height H of the upper / vertical portion was 12.5 inches. The horsepower used in the experimental example was about 30 to 85 HP. The main variables are as follows: (1) “off-axis” angle α, (2) tilt angle β of the lower part, (3) liquid submergence (submergence is the vertical and lower part of the blade (4) the length L of the lower portion 7 and (5) the presence or absence of the end cap 9.
The results were mainly determined by standard aeration efficiency (SAE) calculations. Here SAE is defined as the pounds of oxygen transferred into the liquid per unit time in terms of horsepower of energy used to operate the aeration system. These tests and calculations were performed using the ASCE standard procedure for determining SOTR (standard oxygen transfer rate) at a liquid temperature of 20 ° C. and 1 atm pressure. The results shown for two or more runs (runs) are given as the average SAE for all runs.

Experimental example 1
This example has the impeller of FIG. 1, with α equal to 30 °, β equal to 30 °, blade size h = 12.5, w = 20.5, l = 12.0 inches. 1 illustrates one embodiment of the invention. Further, the blade does not have an end cap. These results (results expressed in SAE) show a very good efficiency with a certain degree of effectiveness when operating the impeller at various submersion levels.
[Table 1]
α β l Water immersion End cap? Number of runs SAE
30 ° 30 ° 12 in 1.0 in None 2 2.43
30 ° 30 ° 12 in 3.0 in None 1 2.74
30 ° 30 ° 12 in 5.0 in No 2 2.92
(Note: in is inches)

Experimental example 2
This example uses the same impeller shown in Experimental Example 1 with an end cap added. The top of the end cap was located approximately 1 inch above the crease that defined the intersection of the upper and lower portions of the impeller. The results (results expressed in SAE) show that there is little effect in operating this embodiment of the impeller at various submersion levels. The SAE results clearly show that oxygen transfer efficiency can be dramatically improved when using end caps.
[Table 2]
α β l Water immersion End cap? Number of runs SAE
30 ° 30 ° 12 in 0.0 in Yes 3 3.39
30 ° 30 ° 12 in 4.0 in Yes 3 3.40
30 ° 30 ° 12 in 7.0 in Yes 2 3.32
(Note: in is inches)

Experimental example 3
This experimental example uses the same impeller as shown in Experimental example 2, except that the length of the lower part was reduced from 12 inches to 8 inches. The results expressed in Results (SAE) show an improvement in efficiency compared to conventional designs currently advertised with SAE up to about 3.5. The SAE results also give a shorter 8 inch lower vane section length which gives a higher transfer efficiency than the 12 inch section for this configuration.
[Table 3]
α β l Water immersion End cap? Number of runs SAE
30 ° 30 ° 8 in 0.0 in Yes 3 3.56
30 ° 30 ° 8 in 2.5 in Yes 1 3.78
30 ° 30 ° 8 in 5.5 in Yes 3 3.79
30 ° 30 ° 8 in 7.8 in Yes 1 4.11
(Note: in is inches)

Experimental Example 4
This experimental example is the same as Experimental example 1, except that the lower part inclination angle β is increased to 45 ° and the length of the lower part 7 of the blade is reduced to 7 inches. The results (results expressed in SAE) are significantly improved compared to Experimental Example 1, which teaches that in this form a large β and a short lower portion l result in improved oxygen transfer efficiency. is doing. Again, this experimental example suggests a general trend that oxygen transfer efficiency increases with increasing submergence value.
[Table 4]
α β l Water immersion End cap? Number of runs SAE
30 ° 45 ° 7 in 4.0 in No 3 3.66
30 ° 45 ° 7 in 6.0 in No 2 3.97
30 ° 45 ° 7 in 7.5 in No 3 4.02
30 ° 45 ° 7 in 9.5 in None 1 4.09
(Note: in is inches)

Experimental Example 5
This experimental example is the same as the experimental example 4 in the case where an end cap whose top edge portion is located 1 inch above the fold line where the vertical portion and the lower portion intersect is added. Again, the results are generally excellent with an SAE of 4 or higher. The addition of the end cap indicates that the oxygen transfer efficiency is improved to some extent as compared to the corresponding experimental example without the end cap.
[Table 5]
α β l Water immersion End cap? Number of runs SAE
30 ° 45 ° 7 in 7.5 in Yes 1 3.46
30 ° 45 ° 7 in 7.9 in Yes 1 4.20
30 ° 45 ° 7 in 8.6 in Yes 1 4.28
30 ° 45 ° 7 in 9.0 in Yes 2 4.35
(Note: in is inches)

Experimental Example 6
This experimental example is the same as the experimental example 5 except that the lower blade length l is reduced to 4 inches. This impeller also gave excellent efficiency values consistently above 4.0 for various submergence values.
[Table 6]
α β l Water immersion End cap? Number of runs SAE
30 ° 45 ° 4 in 7.4 in Yes 1 3.97
30 ° 45 ° 4 in 8.4 in Yes 1 4.26
30 ° 45 ° 4 in 9.5 in Yes 1 4.34
30 ° 45 ° 4 in 10.2in Yes 1 4.20
(Note: in is inches)

Experimental Example 7
The impeller used in this experimental example is the same as the impeller used in experimental example 6 except that the “off-axis” angle α is changed to 38 ° instead of 30 °. This impeller also gave excellent efficiency values that were important for most submersion levels and consistently above 4.0.
[Table 7]
α β l Water immersion End cap? Number of runs SAE
38 ° 45 ° 4 in 7.0 in Yes 2 4.00
38 ° 45 ° 4 in 8.5 in Yes 1 4.10
38 ° 45 ° 4 in 9.0 in Yes 1 4.21
38 ° 45 ° 4 in 10.8in Yes 1 4.31
38 ° 45 ° 4 in 12.3in Yes 1 4.23
(Note: in is inches)

Experimental Example 8
The impeller used in this experimental example was the same as in experimental example 7 except that the blades were positioned in the radial direction. That is, the top edge of the upper vertical portion was connected to the lower side of the radial disk mounting member in the radial direction. These results suggest that the radial embodiment of the present invention can provide a better SAE than the current state of the art of SAE of about 3.3. However, the radial embodiment does not work as well as the equivalent non-radial impeller embodiment described above.
[Table 8]
α β l Water immersion End cap? Number of runs SAE
0 ° 45 ° 4 in 2.5 to 4.0 in Yes 3 3.57
0 ° 45 ° 4 in 6.0 to 6.5 in Yes 2 3.80
0 ° 45 ° 4 in 9.0 to 9.5 in Yes 3 3.77
0 ° 45 ° 4 in 10.5 to 11.5 in Yes 3 3.33
(Note: in is inches)

  These experimental examples dramatically demonstrate the improved oxygen transfer efficiency of the present invention. The state-of-the-art surface aeration impeller design of the technology yields a standard aeration efficiency of about 3.3 compared to the same operating condition range used herein, whereas the present invention is For some non-radial embodiments consistently yields a standard aeration efficiency well above about 3.3 and a standard aeration efficiency well above 4.0. In addition, the present inventors have confirmed the high pumping capacity performance of the present invention compared to the conventional surface aeration impeller design. With the impeller design of the present invention, the liquid flow rate through the entire aeration tank is significantly increased. This improves overall bulk liquid agitation and can even eliminate the need for a stirring impeller provided near the bottom of the tank in certain applications.

Although the present invention has been specifically described with reference to preferred embodiments thereof, it will be appreciated by those skilled in the art that various changes in form and detail may be made to these embodiments without departing from the spirit and scope of the invention. I understand. In particular, although the illustrated invention shows specific positions, dimensions, and shapes for the impeller blades of the present invention, these parameters can be varied within the scope of the invention described herein. Further, the means for attaching the blades to the axially attachable member to allow the impeller to rotate axially varies considerably and is not limited by the preferred embodiments described herein and illustrated in the drawings. .
In addition, the present application generally addresses the use of surface aeration impellers in the treatment of wastewater, but the use of such impellers is not limited to this application. A surface aeration impeller similar to that of the present invention can be used in various industrial applications where improved aeration is desired. A specific example in addition to sewage treatment is aeration in biological reaction processes. These processes include fermentation by circulating a slurry containing a microbial growth medium. The present invention can improve oxygenation and agitation of such liquids to facilitate the fermentation process.

DESCRIPTION OF SYMBOLS 1 Disc-shaped attachment member 2 Blade | wing 6 Vertically upper part of blade | wing 7 Lower part of blade | wing

Claims (20)

  A surface aeration impeller designed to rotate about an axis of rotation perpendicular to the surface of the stationary liquid, the surface aeration impeller having a plurality of blades attached to the lower surface of a generally disk-shaped mounting member, said mounting In a surface aeration impeller that is parallel to the surface of the stationary liquid when the member is attached to a shaft that can rotate about the rotation axis, the blades of the impeller have a generally vertical upper portion. The vertical upper portion has a generally rectangular surface, and the lower edge of the generally rectangular surface has a generally rectangular lower portion attached to the lower edge of the generally rectangular surface. The lower portion extends downward and outward in the direction of rotation, and is sufficient to provide an upward pumping flow of a significant amount of liquid on the vertical upper portion when the impeller is rotated. Size Surface aeration impeller, characterized in that it has a.   The surface aeration impeller according to claim 1, wherein the upper portion of the blade is flat and is positioned radially with respect to the rotation axis.   The surface aeration impeller according to claim 1, wherein the upper portion is flat and is positioned non-radially with respect to the rotation axis.   2. The inclined lower portion of each vane forms an angle [beta] with respect to the generally disc-shaped mounting member, [beta] being between 20 [deg.] And 60 [deg.]. Surface aeration impeller.   The flat, generally vertical upper portion of the vane is non-radial with respect to the axis of rotation, and the angle α is an imaginary radial line through the outer edge of the upper portion and the top edge of the upper portion. The surface aeration impeller according to claim 3, wherein the surface aeration impeller is formed between a line formed by a portion and the angle α is 20 ° to 60 °.   The surface aeration impeller according to claim 5, wherein α and β are 30 ° to 50 °.   The surface aeration impeller according to claim 5, wherein α is 30 ° to 45 °, and β is 35 ° to 50 °.   The surface aeration impeller according to claim 1 having 6 to 12 blades.   The surface aeration impeller according to claim 8 having 8 to 12 blades.   The upper and lower portions of the blade are flat and have a rectangular shape with a width W of 0.1 to 0.4d, and the height H of the upper portion is 0.05 to 0.25d. The surface aeration according to claim 1, characterized in that the length L of the lower part is 0.03 to 0.2d, and d is the diameter of the mounting member in the form of a disc. Impeller.   The surface aeration impeller according to claim 10, wherein the ratio L / H is 0.32 to 0.64.   The surface aeration impeller according to claim 10, wherein W is less than 1 / 3d, H is 0.1 to 0.2d, and L is less than 0.1d.   The surface aeration impeller according to claim 1, wherein the blade further includes an end cap.   14. A surface aeration impeller according to claim 13, wherein the vertical height of the end cap at the location of attachment to the upper portion is about 1 / 4H or less. A surface aeration impeller designed to rotate about an axis perpendicular to the surface of the stationary liquid, the mounting member having a plurality of blades attached to the lower surface of a mounting member that is generally disk-shaped In a surface aeration impeller that is parallel to the stationary liquid surface when mounted on a shaft that is rotatable about the axis,
The blades are continuously curved downward and outward in the direction of rotation, the blades starting at a portion where the top is substantially vertical, at least a portion located below the liquid surface, and the impeller A surface aeration impeller characterized by terminating in an outwardly directed non-vertical portion of sufficient size and shape to provide a significant amount of upward pumping flow of liquid when rotated.   The surface aeration impeller according to claim 15, wherein the blade further includes an end cap.   The surface aeration impeller according to claim 15, wherein the upper portion of the blade has a curved upper edge. A surface aeration impeller designed to rotate about an axis perpendicular to the surface of the stationary liquid, comprising a plurality of blades attached to the underside of a generally disk-shaped mounting member, said mounting In a surface aeration impeller that is parallel to the stationary liquid surface when the member is attached to a shaft rotatable about the axis,
The blade is generally vertically upward having a top edge coupled to the generally disk-shaped mounting member and a bottom edge coupled to an inclined lower portion extending downward and outward in the rotational direction. Has a part,
A surface aeration impeller characterized in that the bottom edge of the generally vertical upper part is parallel to the disc-shaped mounting member. A surface aeration impeller designed to rotate about an axis perpendicular to the surface of the stationary liquid, comprising a plurality of blades attached to the underside of a generally disk-shaped mounting member, said mounting In a surface aeration impeller that is parallel to the stationary liquid surface when the member is attached to a shaft rotatable about the axis,
The blade has a generally vertical upper portion and an inclined lower portion extending downward and outward in the rotation direction, and the blade has an end cap.   11. The surface aeration impeller according to claim 10, wherein the upper portion has a height H where H> 0.1d, and the ratio L / H is 0.32-0.64.

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