CA1056964A - Apparatus for mixing a liquid with a gas in a vessel - Google Patents
Apparatus for mixing a liquid with a gas in a vesselInfo
- Publication number
- CA1056964A CA1056964A CA221,740A CA221740A CA1056964A CA 1056964 A CA1056964 A CA 1056964A CA 221740 A CA221740 A CA 221740A CA 1056964 A CA1056964 A CA 1056964A
- Authority
- CA
- Canada
- Prior art keywords
- gas
- blades
- liquid
- sparge ring
- tank
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
- B01F23/00—Mixing according to the phases to be mixed, e.g. dispersing or emulsifying
- B01F23/20—Mixing gases with liquids
- B01F23/23—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids
- B01F23/231—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids by bubbling
- B01F23/23105—Arrangement or manipulation of the gas bubbling devices
- B01F23/2312—Diffusers
- B01F23/23123—Diffusers consisting of rigid porous or perforated material
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
- B01F23/00—Mixing according to the phases to be mixed, e.g. dispersing or emulsifying
- B01F23/20—Mixing gases with liquids
- B01F23/23—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids
- B01F23/231—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids by bubbling
- B01F23/23105—Arrangement or manipulation of the gas bubbling devices
- B01F23/2312—Diffusers
- B01F23/23126—Diffusers characterised by the shape of the diffuser element
- B01F23/231266—Diffusers characterised by the shape of the diffuser element being in the form of rings or annular elements
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
- B01F23/00—Mixing according to the phases to be mixed, e.g. dispersing or emulsifying
- B01F23/20—Mixing gases with liquids
- B01F23/23—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids
- B01F23/233—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids using driven stirrers with completely immersed stirring elements
- B01F23/2331—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids using driven stirrers with completely immersed stirring elements characterised by the introduction of the gas along the axis of the stirrer or along the stirrer elements
- B01F23/23315—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids using driven stirrers with completely immersed stirring elements characterised by the introduction of the gas along the axis of the stirrer or along the stirrer elements through a hollow guide surrounding the stirrer element
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
- B01F23/00—Mixing according to the phases to be mixed, e.g. dispersing or emulsifying
- B01F23/20—Mixing gases with liquids
- B01F23/23—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids
- B01F23/233—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids using driven stirrers with completely immersed stirring elements
- B01F23/2334—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids using driven stirrers with completely immersed stirring elements provided with stationary guiding means surrounding at least partially the stirrer
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
- B01F23/00—Mixing according to the phases to be mixed, e.g. dispersing or emulsifying
- B01F23/20—Mixing gases with liquids
- B01F23/23—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids
- B01F23/233—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids using driven stirrers with completely immersed stirring elements
- B01F23/2336—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids using driven stirrers with completely immersed stirring elements characterised by the location of the place of introduction of the gas relative to the stirrer
- B01F23/23362—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids using driven stirrers with completely immersed stirring elements characterised by the location of the place of introduction of the gas relative to the stirrer the gas being introduced under the stirrer
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
- B01F23/00—Mixing according to the phases to be mixed, e.g. dispersing or emulsifying
- B01F23/20—Mixing gases with liquids
- B01F23/23—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids
- B01F23/233—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids using driven stirrers with completely immersed stirring elements
- B01F23/2336—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids using driven stirrers with completely immersed stirring elements characterised by the location of the place of introduction of the gas relative to the stirrer
- B01F23/23365—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids using driven stirrers with completely immersed stirring elements characterised by the location of the place of introduction of the gas relative to the stirrer the gas being introduced at the radial periphery of the stirrer
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
- B01F27/00—Mixers with rotary stirring devices in fixed receptacles; Kneaders
- B01F27/05—Stirrers
- B01F27/11—Stirrers characterised by the configuration of the stirrers
- B01F27/115—Stirrers characterised by the configuration of the stirrers comprising discs or disc-like elements essentially perpendicular to the stirrer shaft axis
- B01F27/1152—Stirrers characterised by the configuration of the stirrers comprising discs or disc-like elements essentially perpendicular to the stirrer shaft axis with separate elements other than discs fixed on the discs, e.g. vanes fixed on the discs
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
- B01F27/00—Mixers with rotary stirring devices in fixed receptacles; Kneaders
- B01F27/05—Stirrers
- B01F27/11—Stirrers characterised by the configuration of the stirrers
- B01F27/111—Centrifugal stirrers, i.e. stirrers with radial outlets; Stirrers of the turbine type, e.g. with means to guide the flow
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
- B01F27/00—Mixers with rotary stirring devices in fixed receptacles; Kneaders
- B01F27/05—Stirrers
- B01F27/11—Stirrers characterised by the configuration of the stirrers
- B01F27/115—Stirrers characterised by the configuration of the stirrers comprising discs or disc-like elements essentially perpendicular to the stirrer shaft axis
Landscapes
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Mixers Of The Rotary Stirring Type (AREA)
- Physical Or Chemical Processes And Apparatus (AREA)
Abstract
APPARATUS FOR MIXING A LIQUID
WITH A GAS IN A VESSEL
Abstract of the Disclosure An apparatus for mixing a liquid and a gas in a tank includes a means for circulating the liquid in the tank and a sparge ring for introducing the gas into the tank. The sparge ring introduces the gas away from a suction side of the circula-ting means so that the circulating means encounters only liquid resistance.
WITH A GAS IN A VESSEL
Abstract of the Disclosure An apparatus for mixing a liquid and a gas in a tank includes a means for circulating the liquid in the tank and a sparge ring for introducing the gas into the tank. The sparge ring introduces the gas away from a suction side of the circula-ting means so that the circulating means encounters only liquid resistance.
Description
~569~4 MIXING APPARATUS
1. Background of the Invention 1. Field of use: While the invention is subject to a wide range of applications, it is especially suited for use in a system for mixing oxygen with industrial waste and will be particularly described in that connection.
1. Background of the Invention 1. Field of use: While the invention is subject to a wide range of applications, it is especially suited for use in a system for mixing oxygen with industrial waste and will be particularly described in that connection.
2. Description of the prior art: Mixing apparatuses biochemically treat BOD-containing waste water, such as munici-pal sewage, by oxygenation. This has customarily been accom-plished by providing a sparge ring in a tank beneath an 10. impeller. The impeller circulates the sewage and the sparge ring introduces the oxygen into the tank to be mixed. For example, see U.S. Patent No. 3,227,701 to Pennington and U.S.
Patent No. 3,547,813, to Robinson, et al.
In one known biochemical oxidation process, sewage is mixed with oxygen-containing gas, such as air, and activated sludge. The latter consists essentially of aerobic organisms which have the ability in the presence of sufficient dissolved oxygen to absorb and assimilate the biochemically oxidizable organic material of the municipal sewage, thereby converting the 20. organic material to forms which can be separated readily from the purified water. Under normal conditions the bacteria multiply rapidly in the aeration tanks during this treatment step. When the requisite period of BOD conversion is complete, the mixed liquor is settled, the purified affluent decanted to receiving waters, and sludge is withdrawn from the bottom of a clarifier.
AS pointed out above, it is known to use a sparge ring to supply oxygen-containing gas to the waste water. The sparge ring would be placed beneath a circulating impeller 30. with the gas traveling to the suction side of the impeller.
The impeller generally rotates at a fixed speed. When the . . .
lOS~964 1. sparge ring is supplying gas to the tank, the impeller is drawing a gassed power. When the sparge ring is not supplying gas to the tank, the impeller is drawing an ungassed power.
The ratio of ungassed power to gassed power is known as the K
Factor. Generally, the K Factor is quite low since the system draws more power when ungassed. This is because it requires more torque to rotate the impeller through liquid than through liquid and gas. Therefore, if a motor for the impeller is designed to operate at a given gassed power, and someone 10. accidentally turns off the gas, the power drawn increases and the motor may be damaged.
It is an object of the present invention to provide an apparatus for mixing a liquid with a gas.
It is a further object of the present invention to provide a mixing apparatus than can operate in a gassed or ungassed condition without concern for overloading the motor that drives the impeller.
It is a further object of the present invention to provide an apparatus for mixing a liquid with a gas at a higher 20. power level to increase the mass transfer rate.
It is a further object of the present invention to provide an apparatus for mixing a gas with a liquid being circulated by a radial flow turbine.
S~mmary of the ~nvention In accordance with the present invention, an apparatus mixes a liquid with a gas in a vessel such as a tank. Means, such as a submerged impeller driven by a motor, circulates the liquid in the tank. A sparge ring introduces the gas into the tank. The sparge ring i~ beneath the impeller and includes a 30. supply means, such as a plurality of holes spaced ahout the top surface of the sparge ring. The supply means are located to prevent the gas from entering the suction side of the impeller 1. and insure a good mass transfer rate. 'h For a better understanding of the present invention, together with other and further objects thereof, reference is made to the following description, taken in connection with the accompanying drawings, while its scope will be pointed out in the appended claims.
Brief Description of the Drawings Figure 1 is a diagrammatic, cross-sectional view of the mixing apparatus of the present invention;
10. Figure 2 is a bottom view of an impeller used in the present invention;
Figure 3 is a top view of a sparge ring used in the present invention; and Figure 4 is a cross-sectional view illustrating the relationship of the sparge ring and the impeller in the present invention.
Description of the~Preferred-Emb-odiment In accordance with the present invention, an apparatus mixes a liquid L with a gas G. The apparatus includes a tank 10 20~ with the liquid L therein. A means 20 circulates the Liquid L
in the tank 10. A sparge ring 40 introduces gas G into the tank 10. Sparge ring 40 introduces the gas away from a suction area 21 of the circulating apparatus 20 so that the circulating apparatus 20 encounters only liquid resistance.
Referring to Figure 1, there is shown a cross-sectional view of an apparatus in accordance with the present invention.
The apparatus includes the tank 10 having side walls 12, end walls ~not shown) and a base 14. The tank is generally con-structed of concrete. Inlet conduit 16 supplies the liquid L, 30. such a municipal or industrial waste, to tank 10. Outlet conduit 18 is provided for supplying liquid L to an additional apparatus, such as a clarifier, after the liquid has been 105f~964 1. oxygenated.
Circulating apparatus 20 may be any suitable sub-merged impeller-type mixer, preferably one having curved blades, such as Model No. 89Q125 sold by the Mixing Equipment Company, Rochester, New York. It includes a motor 22, such as, for example, a 125 horsepower, induction motor, for rotating a drive shaft 24. On the bottom end of drive shaft 24 is a collar 26, which is mounted to a disc 28 by several bolts, two of which are shown at 30 in Figure 4. Impeller or turbine 10. blades 32 are rigidly connected to disc 28 by any suitable means such as bolts or welds (not shown). Figure 2 is a bottom view of the disc 28 with impeller or turbine blades 32 mounted thereon. Shaft 24, disc 28, and blades 32 may be made of any suitable material, such as stainless or galvanized steel.
Blades 32 are oriented on disc 28 so that the liquid L is circulated substantially radially as it leaves impeller blades 32. While circulating apparatus 20 has been illustrated as being top-entering, a bottom-entering apparatus may also be used. Also, stabilizing rings or devices to limit radial shaft 20. motion have not been illustrated but they may be used.
Referring again to Figure 1, gas G is supplied to tank 10 via sparge ring 40 that is fastened to tank 10 by any suitable means, such as brackets (not shown) attached to base 14. The gas is pumped to sparge ring 40 through a gas supply line 38 by a suitable pump means 36. As shown diagrammatically in Figure 1, the gas enters an annular hollow portion 41 of sparge ring 40 from gas supply line 38 and leaves sparge ring 40 through a set of apertures 42 extending about the top surface 43 of sparge ring 40.
30. It has been customary to place a sparge ring beneath the impeller blades so that the gas from the sparge ring is delivered to the suction area of the blades. This reduces -4~
. . .
~056964 1. the density of the medium being circulated by the blades. The medium, being of lower density, offers less resistance to blade rotation. Since the power drawn by the motor rotating the impeller is directly proportional to the resistance offered by the medium, the motor draws less power when gas is delivered to the suction area of the blades. This might seem desirable except that the mass transfer rate decreases as the power drawn by the motor decreases.
In accordance with the present invention, the sparge 10. ring introduces gas away from the suction area of the blades so that the blades encounter only liquid resistance. This is accomplished by locating the sparge ring so that it discharges gas within a volume V (shown as dashed lines in Figure 4).
Volume V comprises a ring having a radial dimension a and an axial dimension b. Radial dimension a extends from 1 to 1.5 time the diameter Dt of the blades. Axial dimension b extends downward from the disc 28 a distance approximately equal to the height of blades 32. As long as gas is introduced within volume V, the gas will not enter the suction area of the 20. blades. Figure 4 illustrates this relationship for sparge ring 40', but it should be understood that the principal is applicable to other sparge rings, such as sparge ring 40 in Figure 1. Preferably, the diameter Ds of the sparge ring at the apertures is approximately 1.2 times the diameter Dt of the turbine blades so that the gas is introduces at this location.
As used in this disclosure, the diameter Ds is taken at an imaginary circle that is formed by the radially innermost point of each aperture in a set of apertures such as imaginary 30. circle C for apertures 42'. The diameter Dt referred to herein as the diameter of the blades, is actually the diameter of a circle formed by the outer tips of the rotating blades. By 1056~64 1. positioning the apertures radially outward of the turbine blades, the turbine blades, as they rotate, encounter only liquid resistance. This draws more power and therefore increases the mass transfer rate. If gas is introduced radially outwardly of volume V, the mass transfer rate decreases significantly.
If gas is introduced above the volume V, the mass transfer rate will decrease. If gas is introduced below the volume V, gas may drift into the suction area of the blades 10. and reduce the power drawn. Freferably, the gas in introduced at approximately the midpoint of the blade (axially) for best mass transfer.
Referring to Figure 3, there is shown a top view of a modified sparge ring 40', also made in accordance with the present invention. The sparge ring 40' differs from sparge ring 40 in that it contains two sets of apertures. A first set of apertures 42' is spaced about top surface 43' of sparge ringe 40'. A second set of apertures 44' is also spaced about top surface 43'. The second set is radially outward of the 20. first set. As shown, each set of apertures lies along a circle in the top surface of the sparge ring, but this is a matter of convenience as long as the gas is directed away from the suction area of impeller blades 32.
Referring to Figure 4, the use of the two sets of apertures will become more clear. Sparge ring 40' includes an annular divider 46 for separating the interior of the sparge ring into two distinct hollow portions 41' and 41n.
Gas may be introduced into either Lor both~ hollow portion.
If the interior hollow portion 41' is used, gas is delivered 30. to the tank through apertures 42'. If the outside hollow portion 41" is used, gas is delivered to the tank through apertures 44'. Therefore, the diameter Ds may be changed ~: : . . .
- , . .
1. from Ds(l) to D (2)~ depending on which of hollow portions 41' or 42" are supplied with gas from line 38.
It should be noted that an annular slot (or slots) may be used in place of a set of apertures. Further, while it is convenient to make the sparge ring rectangular in cross-section, any cross-sectional shape may be used. It i9 also possible to use a divided sparge ring, such as the one shown in Figure 3 and 4, to mix more than one gas with a liquid.
EXAMPLE
10. A rectangular tank approximately 38 feet by 40 feet by 30 feet in depth contained approximately 20 feet of water.
A 125 horsepower induction motor rotated a steel disc at less than 100 revolutions per minute. Each blade had a radius of curvature of approximately 38 inches and each blade was approxi-mately 35 degrees from a radial line from the outer edge of the blade. Gas was supplied at a flow rate of approximateIy 3,000 standard cubic feet per minute through a sparge ring having a diameter Ds of approximately 7 feet. This diameter Ds com-prised 24 aperatures each approximately 3/4 inches in diameter 20. with a pressure drop of about 1.5 pounds per square inch across the aperture. The top surface of the sparge ring was approxi-mately 6 inches below the disc. The gassed horsepower drawn was approximately 93 1/2, and the ungassed horsepower was approximately 91 1/2, for a K Factor of appraximately 1.02.
One skilled in the art will realize that there has been disclosed a mixing apparatu~ including a sparge ring that provides a high K Factor and a high mass transfer rate.
While t~ere has been described what is at pres~nt considered to be the preferred emhodiment of the inYention! it 30. will be obvious to those skilled in the art that Yax~ous changes and modifications may ~e made therein without departing from the invention, and it is, therfore, aimed in the appendea -7~
- lOS6964 1. claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.
10.
20. ;~
: ' ,:
30.
.
.. . . . .
.
Patent No. 3,547,813, to Robinson, et al.
In one known biochemical oxidation process, sewage is mixed with oxygen-containing gas, such as air, and activated sludge. The latter consists essentially of aerobic organisms which have the ability in the presence of sufficient dissolved oxygen to absorb and assimilate the biochemically oxidizable organic material of the municipal sewage, thereby converting the 20. organic material to forms which can be separated readily from the purified water. Under normal conditions the bacteria multiply rapidly in the aeration tanks during this treatment step. When the requisite period of BOD conversion is complete, the mixed liquor is settled, the purified affluent decanted to receiving waters, and sludge is withdrawn from the bottom of a clarifier.
AS pointed out above, it is known to use a sparge ring to supply oxygen-containing gas to the waste water. The sparge ring would be placed beneath a circulating impeller 30. with the gas traveling to the suction side of the impeller.
The impeller generally rotates at a fixed speed. When the . . .
lOS~964 1. sparge ring is supplying gas to the tank, the impeller is drawing a gassed power. When the sparge ring is not supplying gas to the tank, the impeller is drawing an ungassed power.
The ratio of ungassed power to gassed power is known as the K
Factor. Generally, the K Factor is quite low since the system draws more power when ungassed. This is because it requires more torque to rotate the impeller through liquid than through liquid and gas. Therefore, if a motor for the impeller is designed to operate at a given gassed power, and someone 10. accidentally turns off the gas, the power drawn increases and the motor may be damaged.
It is an object of the present invention to provide an apparatus for mixing a liquid with a gas.
It is a further object of the present invention to provide a mixing apparatus than can operate in a gassed or ungassed condition without concern for overloading the motor that drives the impeller.
It is a further object of the present invention to provide an apparatus for mixing a liquid with a gas at a higher 20. power level to increase the mass transfer rate.
It is a further object of the present invention to provide an apparatus for mixing a gas with a liquid being circulated by a radial flow turbine.
S~mmary of the ~nvention In accordance with the present invention, an apparatus mixes a liquid with a gas in a vessel such as a tank. Means, such as a submerged impeller driven by a motor, circulates the liquid in the tank. A sparge ring introduces the gas into the tank. The sparge ring i~ beneath the impeller and includes a 30. supply means, such as a plurality of holes spaced ahout the top surface of the sparge ring. The supply means are located to prevent the gas from entering the suction side of the impeller 1. and insure a good mass transfer rate. 'h For a better understanding of the present invention, together with other and further objects thereof, reference is made to the following description, taken in connection with the accompanying drawings, while its scope will be pointed out in the appended claims.
Brief Description of the Drawings Figure 1 is a diagrammatic, cross-sectional view of the mixing apparatus of the present invention;
10. Figure 2 is a bottom view of an impeller used in the present invention;
Figure 3 is a top view of a sparge ring used in the present invention; and Figure 4 is a cross-sectional view illustrating the relationship of the sparge ring and the impeller in the present invention.
Description of the~Preferred-Emb-odiment In accordance with the present invention, an apparatus mixes a liquid L with a gas G. The apparatus includes a tank 10 20~ with the liquid L therein. A means 20 circulates the Liquid L
in the tank 10. A sparge ring 40 introduces gas G into the tank 10. Sparge ring 40 introduces the gas away from a suction area 21 of the circulating apparatus 20 so that the circulating apparatus 20 encounters only liquid resistance.
Referring to Figure 1, there is shown a cross-sectional view of an apparatus in accordance with the present invention.
The apparatus includes the tank 10 having side walls 12, end walls ~not shown) and a base 14. The tank is generally con-structed of concrete. Inlet conduit 16 supplies the liquid L, 30. such a municipal or industrial waste, to tank 10. Outlet conduit 18 is provided for supplying liquid L to an additional apparatus, such as a clarifier, after the liquid has been 105f~964 1. oxygenated.
Circulating apparatus 20 may be any suitable sub-merged impeller-type mixer, preferably one having curved blades, such as Model No. 89Q125 sold by the Mixing Equipment Company, Rochester, New York. It includes a motor 22, such as, for example, a 125 horsepower, induction motor, for rotating a drive shaft 24. On the bottom end of drive shaft 24 is a collar 26, which is mounted to a disc 28 by several bolts, two of which are shown at 30 in Figure 4. Impeller or turbine 10. blades 32 are rigidly connected to disc 28 by any suitable means such as bolts or welds (not shown). Figure 2 is a bottom view of the disc 28 with impeller or turbine blades 32 mounted thereon. Shaft 24, disc 28, and blades 32 may be made of any suitable material, such as stainless or galvanized steel.
Blades 32 are oriented on disc 28 so that the liquid L is circulated substantially radially as it leaves impeller blades 32. While circulating apparatus 20 has been illustrated as being top-entering, a bottom-entering apparatus may also be used. Also, stabilizing rings or devices to limit radial shaft 20. motion have not been illustrated but they may be used.
Referring again to Figure 1, gas G is supplied to tank 10 via sparge ring 40 that is fastened to tank 10 by any suitable means, such as brackets (not shown) attached to base 14. The gas is pumped to sparge ring 40 through a gas supply line 38 by a suitable pump means 36. As shown diagrammatically in Figure 1, the gas enters an annular hollow portion 41 of sparge ring 40 from gas supply line 38 and leaves sparge ring 40 through a set of apertures 42 extending about the top surface 43 of sparge ring 40.
30. It has been customary to place a sparge ring beneath the impeller blades so that the gas from the sparge ring is delivered to the suction area of the blades. This reduces -4~
. . .
~056964 1. the density of the medium being circulated by the blades. The medium, being of lower density, offers less resistance to blade rotation. Since the power drawn by the motor rotating the impeller is directly proportional to the resistance offered by the medium, the motor draws less power when gas is delivered to the suction area of the blades. This might seem desirable except that the mass transfer rate decreases as the power drawn by the motor decreases.
In accordance with the present invention, the sparge 10. ring introduces gas away from the suction area of the blades so that the blades encounter only liquid resistance. This is accomplished by locating the sparge ring so that it discharges gas within a volume V (shown as dashed lines in Figure 4).
Volume V comprises a ring having a radial dimension a and an axial dimension b. Radial dimension a extends from 1 to 1.5 time the diameter Dt of the blades. Axial dimension b extends downward from the disc 28 a distance approximately equal to the height of blades 32. As long as gas is introduced within volume V, the gas will not enter the suction area of the 20. blades. Figure 4 illustrates this relationship for sparge ring 40', but it should be understood that the principal is applicable to other sparge rings, such as sparge ring 40 in Figure 1. Preferably, the diameter Ds of the sparge ring at the apertures is approximately 1.2 times the diameter Dt of the turbine blades so that the gas is introduces at this location.
As used in this disclosure, the diameter Ds is taken at an imaginary circle that is formed by the radially innermost point of each aperture in a set of apertures such as imaginary 30. circle C for apertures 42'. The diameter Dt referred to herein as the diameter of the blades, is actually the diameter of a circle formed by the outer tips of the rotating blades. By 1056~64 1. positioning the apertures radially outward of the turbine blades, the turbine blades, as they rotate, encounter only liquid resistance. This draws more power and therefore increases the mass transfer rate. If gas is introduced radially outwardly of volume V, the mass transfer rate decreases significantly.
If gas is introduced above the volume V, the mass transfer rate will decrease. If gas is introduced below the volume V, gas may drift into the suction area of the blades 10. and reduce the power drawn. Freferably, the gas in introduced at approximately the midpoint of the blade (axially) for best mass transfer.
Referring to Figure 3, there is shown a top view of a modified sparge ring 40', also made in accordance with the present invention. The sparge ring 40' differs from sparge ring 40 in that it contains two sets of apertures. A first set of apertures 42' is spaced about top surface 43' of sparge ringe 40'. A second set of apertures 44' is also spaced about top surface 43'. The second set is radially outward of the 20. first set. As shown, each set of apertures lies along a circle in the top surface of the sparge ring, but this is a matter of convenience as long as the gas is directed away from the suction area of impeller blades 32.
Referring to Figure 4, the use of the two sets of apertures will become more clear. Sparge ring 40' includes an annular divider 46 for separating the interior of the sparge ring into two distinct hollow portions 41' and 41n.
Gas may be introduced into either Lor both~ hollow portion.
If the interior hollow portion 41' is used, gas is delivered 30. to the tank through apertures 42'. If the outside hollow portion 41" is used, gas is delivered to the tank through apertures 44'. Therefore, the diameter Ds may be changed ~: : . . .
- , . .
1. from Ds(l) to D (2)~ depending on which of hollow portions 41' or 42" are supplied with gas from line 38.
It should be noted that an annular slot (or slots) may be used in place of a set of apertures. Further, while it is convenient to make the sparge ring rectangular in cross-section, any cross-sectional shape may be used. It i9 also possible to use a divided sparge ring, such as the one shown in Figure 3 and 4, to mix more than one gas with a liquid.
EXAMPLE
10. A rectangular tank approximately 38 feet by 40 feet by 30 feet in depth contained approximately 20 feet of water.
A 125 horsepower induction motor rotated a steel disc at less than 100 revolutions per minute. Each blade had a radius of curvature of approximately 38 inches and each blade was approxi-mately 35 degrees from a radial line from the outer edge of the blade. Gas was supplied at a flow rate of approximateIy 3,000 standard cubic feet per minute through a sparge ring having a diameter Ds of approximately 7 feet. This diameter Ds com-prised 24 aperatures each approximately 3/4 inches in diameter 20. with a pressure drop of about 1.5 pounds per square inch across the aperture. The top surface of the sparge ring was approxi-mately 6 inches below the disc. The gassed horsepower drawn was approximately 93 1/2, and the ungassed horsepower was approximately 91 1/2, for a K Factor of appraximately 1.02.
One skilled in the art will realize that there has been disclosed a mixing apparatu~ including a sparge ring that provides a high K Factor and a high mass transfer rate.
While t~ere has been described what is at pres~nt considered to be the preferred emhodiment of the inYention! it 30. will be obvious to those skilled in the art that Yax~ous changes and modifications may ~e made therein without departing from the invention, and it is, therfore, aimed in the appendea -7~
- lOS6964 1. claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.
10.
20. ;~
: ' ,:
30.
.
.. . . . .
.
Claims (4)
1. In an apparatus for mixing a liquid with a gas including a tank with said liquid therein, a circulating means for creating a radial flow of said liquid to circulate said liquid in said tank, said circulating means comprising a rotat-able shaft, a disc mounted on said shaft, and a plurality of blades extending downwardly from a bottom surface of said disc so that rotation of said plurality of blades creates a suction area, said suction area being the only suction area created by said circulating means, the improvement including:
sparge ring means having a discharge means with a radius that is larger than the distance from the center of said disc to outer tip of said blades, said discharge means being axially positioned so as to introduce said gas into a zone extending axially downward from said disc a distance approxi-mately equal to the height of said blades for introducing gas into said tank in a direction that bypasses said suction area to prevent gas from flowing into said suction area.
sparge ring means having a discharge means with a radius that is larger than the distance from the center of said disc to outer tip of said blades, said discharge means being axially positioned so as to introduce said gas into a zone extending axially downward from said disc a distance approxi-mately equal to the height of said blades for introducing gas into said tank in a direction that bypasses said suction area to prevent gas from flowing into said suction area.
2. The apparatus as defined in Claim 1, wherein said sparge ring means is hollow in cross-section with a plurality of apertures in its top surface communicating with the hollow portion and functioning as said discharge means.
3. The apparatus as defined in Claim 2, wherein the diameter of the sparge ring means at said apertures is between 1 and 1.5 times the diameter of the blades.
4. The apparatus as defined in Claim 3, wherein said sparge ring means introduces said gas at the approximate axial midpoint of said blades.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US45610774A | 1974-03-29 | 1974-03-29 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1056964A true CA1056964A (en) | 1979-06-19 |
Family
ID=23811452
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA221,740A Expired CA1056964A (en) | 1974-03-29 | 1975-03-10 | Apparatus for mixing a liquid with a gas in a vessel |
Country Status (6)
| Country | Link |
|---|---|
| AU (1) | AU7966975A (en) |
| CA (1) | CA1056964A (en) |
| DE (1) | DE2513917C2 (en) |
| FR (1) | FR2272723B1 (en) |
| GB (1) | GB1496924A (en) |
| SE (1) | SE410179C (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3818999A1 (en) * | 1988-06-03 | 1989-12-14 | Norbert Schneider | Gas-introduction and circulation apparatus for liquids |
| DE19836565A1 (en) * | 1998-08-12 | 2000-02-17 | Linde Ag | Process for mixing liquid foodstuffs by injecting gas into the space below the mixing blade so that it can rise as bubbles through the product |
| CN106474958A (en) * | 2016-11-19 | 2017-03-08 | 张奇 | A kind of Multi-stage stirring disk for reactor |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2243301A (en) * | 1938-12-15 | 1941-05-27 | Morse Bros Machinery Company | Aeration apparatus |
| US2433592A (en) * | 1945-05-09 | 1947-12-30 | Lionel E Booth | Aeration method and machine |
| US3227701A (en) * | 1962-05-29 | 1966-01-04 | Phillips Petroleum Co | Carboxylation and acidification of polymers |
| US3643403A (en) * | 1970-04-29 | 1972-02-22 | Richard E Speece | Downflow bubble contact aeration apparatus and method |
| US3792840A (en) * | 1971-06-15 | 1974-02-19 | Westinghouse Electric Corp | Submerged turbine aerator |
-
1975
- 1975-02-28 GB GB8577/75A patent/GB1496924A/en not_active Expired
- 1975-03-10 CA CA221,740A patent/CA1056964A/en not_active Expired
- 1975-03-17 FR FR7508190A patent/FR2272723B1/fr not_active Expired
- 1975-03-26 SE SE7503552A patent/SE410179C/en not_active IP Right Cessation
- 1975-03-27 DE DE2513917A patent/DE2513917C2/en not_active Expired
- 1975-04-01 AU AU79669/75A patent/AU7966975A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| SE410179C (en) | 1982-01-25 |
| SE7503552L (en) | 1975-10-03 |
| DE2513917A1 (en) | 1975-10-09 |
| SE410179B (en) | 1979-10-01 |
| AU7966975A (en) | 1976-10-07 |
| GB1496924A (en) | 1978-01-05 |
| DE2513917C2 (en) | 1986-02-27 |
| FR2272723A1 (en) | 1975-12-26 |
| FR2272723B1 (en) | 1980-06-27 |
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