CA1119735A - Device for distribution of a gas in a liquid medium - Google Patents
Device for distribution of a gas in a liquid mediumInfo
- Publication number
- CA1119735A CA1119735A CA000322604A CA322604A CA1119735A CA 1119735 A CA1119735 A CA 1119735A CA 000322604 A CA000322604 A CA 000322604A CA 322604 A CA322604 A CA 322604A CA 1119735 A CA1119735 A CA 1119735A
- Authority
- CA
- Canada
- Prior art keywords
- impeller
- wings
- air
- wing
- rotor
- 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
Landscapes
- Structures Of Non-Positive Displacement Pumps (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
Disclosed is an impeller comprised of a hub and circumferentially spaced vanes extending radially therefrom, the impeller being located at the bottom end of an impeller drive shaft elongated to extend above a liquid into which the impeller is immersible for rotation within a closely surrounding ring of stator wings; said shaft being hollow for connection to an external supply of air which is dischargeable into the liquid from a chamber at the bottom end of the shaft through conduits extending therefrom to the periphery of the impeller but between the vanes; said conduits being disposed, preferably, tangentially to the shaft axis and said impeller vanes being preferably, of rubber and tapering, preferably, towards the bottom of the impeller and being also thinner at their lower ends.
Disclosed is an impeller comprised of a hub and circumferentially spaced vanes extending radially therefrom, the impeller being located at the bottom end of an impeller drive shaft elongated to extend above a liquid into which the impeller is immersible for rotation within a closely surrounding ring of stator wings; said shaft being hollow for connection to an external supply of air which is dischargeable into the liquid from a chamber at the bottom end of the shaft through conduits extending therefrom to the periphery of the impeller but between the vanes; said conduits being disposed, preferably, tangentially to the shaft axis and said impeller vanes being preferably, of rubber and tapering, preferably, towards the bottom of the impeller and being also thinner at their lower ends.
Description
73~
The instant invention relates to a device, particularly a rotor,for introduction of a gas in a finely divided form into a liquid medium. The rotor accordin~ to the invention is particularly suited for introduction of air in a finelv clivided S form in a flotation device. Flotation is a well-known technique bein~ used in order to separate one or more valuable constituents from non-wanted constituents. A typical field of use is enrichment of ores in which finel~ ~ivided air is introduced into an aqueous suspension of finely divided ore and water. The finely divided air bubbles will adhere to the metal values of the ore and carry the same to the surface of the basin in which the flotation is carried out. The metal values and the air bubbles will usually form a foam on the surface which can be removed by skimming.
In order to improve the selectivity and effectiveness oE the flotation process certain adjuvants such as surface active a~ents are added to the suspension, which bring about a be-tter adhesion between the metal values and the air bubbles.
A ~eneral account o F the flotation process is inter alia found in Kirk-Othmer: "Encyclopedia of Chemical Technology", second edition, volume 9, the pages 3~0-39B.
The air can be introduced in the suspension of the finely divided material in different ways, for instance, water saturated with air under pressure can be introduced to the suspension and,as a consequence of the pressure release,the absorbed air will be liberated in the form of finely divided bubbles.
Ilowever, the most common manner in which the air is finely divided is by means of mechanical agitation, for instance by means of a rotor wilich more or less "whips" added air into the suspension.
Such mechanical devices are inter alia described in Norwec~ian patent No. 116.156, US-patents Nos. 2.609.0g7, 3.070.229, 3.3~7.~51, 3.393.~02, 3.393.803, 3.409.130, 3.437.203, 3.485.484 and 3.752.313, and DOS 26.59.230.
For flotation purposes it is desirable for the added air to exhibit the ~reatest possible surface area with respect to the added volume of air, that is, the air should be introduced in the form of very finely divided and minute bubbles.
In US-~atent r~O . 2.609.097 a rotor is described into which air is introduced centrally via a~supply pipe and is radially distributed to the suspension via a number of conduits leadin~
to the periphery of the rotor, said conduits opening into a ~roove, one side of which is formed in such a manner that the air, durinc3 the rotation of the rotor, is forced into the adjacent suspension.
US-patent No. 3.485.434 discloses for instance a rotor in which the air is centrally supplied and lecl out throucJh conduits in the wings of the rotor and thus forced into the surroundincJ
suspension.
By means of the instant invention a rotor or an impeller is provided for introduction of air to a liquid medium and in which the rotor is so desic~ned that a more efficient distribution of very finely divided air bubbles are obtained in the suspension. The minute and finel~ divided air bubbles will rise slowly throucJh the suspension ancl thereby increase the possibility of contact beinc3 established between desired particles to be flotated and one or rnore air bubbles, whereby the effectiveness of the flotation is increased.
According to the invention this object is obtained in that centrally supplied air from a suitable source and at a suitable pressure and further under the action of the rotation of the impeller via conduits is ~uided tan~entially from a central supply conduit. The air initially forced into the suspension in the form of relatively lar~e air bubbles will further be broken down to smaller bubbles due to vortex formation behind ~-the rotor blade and by collision with the subsequent rotor blade.
The final distribution of the air bubbles thus formed occurs when the suspension containin~ the air bubbles impin~es on stationa~ry restrictions bein~ arranged in a circular manner around and in a suitable distance from the impeller. Thus, the air is first dispersed by the air bubbles formed bein~
disinte~rated to smaller bubbles by colliding with the rotor win~s. Subsequently, the partially dispersed air is further dispersed by collision a~ainst stator win~s arran~ed around the impeller in a circular pattern.
'l'he object of the invention is attained in the preferred embodiment of the invention described in the accompanyin~
description, and illustrated in the accompanyin~ drawin~s.
In fi~ure 1 a flotation device is shown partly in section, employin~ the rotor or impeller in re.
Fi~ure 2 shows a side view of the rotor.
Fi~ure 3 is a side view, partially in section, of the rotor.
Fi~ure 4 shows a cross-section alon~ the line A-A in fi~ures 2 and 3; and Fi~ure 5 shows how the injected air is broken down when the rotor is in a workin~ mode.
In fi~ure 1 the essential elements of a flotation vessel 1 are indicated, comprisin~ side walls 2 and a bottom part 3.
1342 P/2 CA ~ 3 ~
: , . .. .
.
~1~9~35 In the example shown two impellers 4 and 5 are driven by a common driving device (not shown) in such a manner that both the impellers rotate with the same rotational speed.
Further, air is supplied from the pressure tank 6 to the impellers 4 and 5 via hollow drivin~ shafts 7 and a at a pre-determined pressure varying in accordance with the consistenc~
of the suspension. ~`ixed to the lower part of the driving shafts 7 and 8 are impellers or rotors 9 the lower part 10 of which is at a pre-determined distance from the bottom 3.
A number of stator wings 11 are secured to the bottom 3 in a circular pattern around the rotor 9, with suitable clearence between the inner edges 12 of the stator 11 and the impeller wings-13 of the rotor 9.
A partition 14 partially divides the vessel 1 into two compartments.
Figure 3 shows the hollow part 15 of the driving shaft 8, through which compressed air is supplied to the impeller 9 from the pressure vessel 6.
Figure 4 shows the air conduits 16 of the impeller 9.
Figure S shows the relative movement of the air with respect to the rotating rotor. The air from the pressure tank 6 is supplied to the void 15 in the rotor 9 at a pressure being adapted to the consistency of the suspension. For a relatively dilute suspension a pressure of for instance 0.2 kp/cm2 will be sufficient.
nuring production stops, for instance by failure of the power supply, the suspended particles will descend to the bottom 3 and build a layer which can have a thickness sufficient to cover the impeller. During start-up a considerable torque is necessary in order to liberate the impeller from the settled 1342 P/2 CA ~ 4 ~
\~
particles, resulting in a very high power consumption during start-up. According to the invention this problem can be eliminated by constructing the impeller of rubber or a similar elastic material permitting the wings 13 to vield during S start-up and be forced a~ainst the boss of the rotor, whereby the starting torque is considerabl~ reduced. In order to further reduce the starting torque,the stiffness of the win~s can be reduced by giving the wings a gradually decreasing thickness such that the lower parts of the wings have a smaller thickness than the upper part. In this manner the lower part of the wings will be more flexible than the upper part. A reduced bending stiffness of the lower part of the wings 13 can optionally be obtained by providing the lower part of the wings with suitable grooves or holes.
Tests with the device accordin~ to the invention in a flotation plant have shown that when the wings are made from an elastic material and provided with a declining thickness, as indicated ~bove, the flotation plant can be re-started without the manual aid normally being necessary when starting-up a conventional plant with impellers of non-elastic material.
1342 P/2 C~ - 5 -
The instant invention relates to a device, particularly a rotor,for introduction of a gas in a finely divided form into a liquid medium. The rotor accordin~ to the invention is particularly suited for introduction of air in a finelv clivided S form in a flotation device. Flotation is a well-known technique bein~ used in order to separate one or more valuable constituents from non-wanted constituents. A typical field of use is enrichment of ores in which finel~ ~ivided air is introduced into an aqueous suspension of finely divided ore and water. The finely divided air bubbles will adhere to the metal values of the ore and carry the same to the surface of the basin in which the flotation is carried out. The metal values and the air bubbles will usually form a foam on the surface which can be removed by skimming.
In order to improve the selectivity and effectiveness oE the flotation process certain adjuvants such as surface active a~ents are added to the suspension, which bring about a be-tter adhesion between the metal values and the air bubbles.
A ~eneral account o F the flotation process is inter alia found in Kirk-Othmer: "Encyclopedia of Chemical Technology", second edition, volume 9, the pages 3~0-39B.
The air can be introduced in the suspension of the finely divided material in different ways, for instance, water saturated with air under pressure can be introduced to the suspension and,as a consequence of the pressure release,the absorbed air will be liberated in the form of finely divided bubbles.
Ilowever, the most common manner in which the air is finely divided is by means of mechanical agitation, for instance by means of a rotor wilich more or less "whips" added air into the suspension.
Such mechanical devices are inter alia described in Norwec~ian patent No. 116.156, US-patents Nos. 2.609.0g7, 3.070.229, 3.3~7.~51, 3.393.~02, 3.393.803, 3.409.130, 3.437.203, 3.485.484 and 3.752.313, and DOS 26.59.230.
For flotation purposes it is desirable for the added air to exhibit the ~reatest possible surface area with respect to the added volume of air, that is, the air should be introduced in the form of very finely divided and minute bubbles.
In US-~atent r~O . 2.609.097 a rotor is described into which air is introduced centrally via a~supply pipe and is radially distributed to the suspension via a number of conduits leadin~
to the periphery of the rotor, said conduits opening into a ~roove, one side of which is formed in such a manner that the air, durinc3 the rotation of the rotor, is forced into the adjacent suspension.
US-patent No. 3.485.434 discloses for instance a rotor in which the air is centrally supplied and lecl out throucJh conduits in the wings of the rotor and thus forced into the surroundincJ
suspension.
By means of the instant invention a rotor or an impeller is provided for introduction of air to a liquid medium and in which the rotor is so desic~ned that a more efficient distribution of very finely divided air bubbles are obtained in the suspension. The minute and finel~ divided air bubbles will rise slowly throucJh the suspension ancl thereby increase the possibility of contact beinc3 established between desired particles to be flotated and one or rnore air bubbles, whereby the effectiveness of the flotation is increased.
According to the invention this object is obtained in that centrally supplied air from a suitable source and at a suitable pressure and further under the action of the rotation of the impeller via conduits is ~uided tan~entially from a central supply conduit. The air initially forced into the suspension in the form of relatively lar~e air bubbles will further be broken down to smaller bubbles due to vortex formation behind ~-the rotor blade and by collision with the subsequent rotor blade.
The final distribution of the air bubbles thus formed occurs when the suspension containin~ the air bubbles impin~es on stationa~ry restrictions bein~ arranged in a circular manner around and in a suitable distance from the impeller. Thus, the air is first dispersed by the air bubbles formed bein~
disinte~rated to smaller bubbles by colliding with the rotor win~s. Subsequently, the partially dispersed air is further dispersed by collision a~ainst stator win~s arran~ed around the impeller in a circular pattern.
'l'he object of the invention is attained in the preferred embodiment of the invention described in the accompanyin~
description, and illustrated in the accompanyin~ drawin~s.
In fi~ure 1 a flotation device is shown partly in section, employin~ the rotor or impeller in re.
Fi~ure 2 shows a side view of the rotor.
Fi~ure 3 is a side view, partially in section, of the rotor.
Fi~ure 4 shows a cross-section alon~ the line A-A in fi~ures 2 and 3; and Fi~ure 5 shows how the injected air is broken down when the rotor is in a workin~ mode.
In fi~ure 1 the essential elements of a flotation vessel 1 are indicated, comprisin~ side walls 2 and a bottom part 3.
1342 P/2 CA ~ 3 ~
: , . .. .
.
~1~9~35 In the example shown two impellers 4 and 5 are driven by a common driving device (not shown) in such a manner that both the impellers rotate with the same rotational speed.
Further, air is supplied from the pressure tank 6 to the impellers 4 and 5 via hollow drivin~ shafts 7 and a at a pre-determined pressure varying in accordance with the consistenc~
of the suspension. ~`ixed to the lower part of the driving shafts 7 and 8 are impellers or rotors 9 the lower part 10 of which is at a pre-determined distance from the bottom 3.
A number of stator wings 11 are secured to the bottom 3 in a circular pattern around the rotor 9, with suitable clearence between the inner edges 12 of the stator 11 and the impeller wings-13 of the rotor 9.
A partition 14 partially divides the vessel 1 into two compartments.
Figure 3 shows the hollow part 15 of the driving shaft 8, through which compressed air is supplied to the impeller 9 from the pressure vessel 6.
Figure 4 shows the air conduits 16 of the impeller 9.
Figure S shows the relative movement of the air with respect to the rotating rotor. The air from the pressure tank 6 is supplied to the void 15 in the rotor 9 at a pressure being adapted to the consistency of the suspension. For a relatively dilute suspension a pressure of for instance 0.2 kp/cm2 will be sufficient.
nuring production stops, for instance by failure of the power supply, the suspended particles will descend to the bottom 3 and build a layer which can have a thickness sufficient to cover the impeller. During start-up a considerable torque is necessary in order to liberate the impeller from the settled 1342 P/2 CA ~ 4 ~
\~
particles, resulting in a very high power consumption during start-up. According to the invention this problem can be eliminated by constructing the impeller of rubber or a similar elastic material permitting the wings 13 to vield during S start-up and be forced a~ainst the boss of the rotor, whereby the starting torque is considerabl~ reduced. In order to further reduce the starting torque,the stiffness of the win~s can be reduced by giving the wings a gradually decreasing thickness such that the lower parts of the wings have a smaller thickness than the upper part. In this manner the lower part of the wings will be more flexible than the upper part. A reduced bending stiffness of the lower part of the wings 13 can optionally be obtained by providing the lower part of the wings with suitable grooves or holes.
Tests with the device accordin~ to the invention in a flotation plant have shown that when the wings are made from an elastic material and provided with a declining thickness, as indicated ~bove, the flotation plant can be re-started without the manual aid normally being necessary when starting-up a conventional plant with impellers of non-elastic material.
1342 P/2 C~ - 5 -
Claims (8)
PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A device for introduction and dispersion of a gas in a liquid medium, comprising a rotatable rotor or impeller provided with wings and a surrounding stator also provided with wings, the impeller being provided with means for introduction of a gas such as air to a centrally provided void in the rotor, from which void conduits are provided for exhausting of air into the liquid medium, characterized in that the conduits terminate between two adjacent wings and are provided in the boss of the rotor in the vicinity of the back-side of a wing and that the axis of each conduit intercepts a radius through the wing at the back-side of which the conduit terminates.
2. A device according to Claim 1, wherein the axis of each conduit intercepts the radius through said wing at an angle in the range 20 - 60°.
3. A device according to Claim 1, wherein one of the sides of the conduit terminating at the base of a wing extends approximately tangentially and linearly from the periphery of the plenum.
4. A device according to Claim 2, wherein one of the sides of the conduit terminating at the base of a wing extends approximately tangentially and linearly from the periphery of the plenum.
5. A device according to Claim 1, 2 or 3, wherein at least the wings of the impeller are constructed of rubber or other elastic material.
6. A device according to Claim 1, 2 or 3, wherein at least the wings of the impeller are constructed of an elastic material and wherein the lower part of each wing exhibits a lower bending stiffness than the upper part of the wing.
7. A device according to Claim 1, 2 or 3, wherein the wings are formed from a yieldable material, and wherein the lower part of the wings is mechanically weakened to reduce the stiffness thereof.
8. A device according to Claim 1, 2 or 3, wherein the thickness of the wings is tapered downwardly to reduce the stiffness of lower portions thereof.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000322604A CA1119735A (en) | 1979-02-28 | 1979-02-28 | Device for distribution of a gas in a liquid medium |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000322604A CA1119735A (en) | 1979-02-28 | 1979-02-28 | Device for distribution of a gas in a liquid medium |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1119735A true CA1119735A (en) | 1982-03-09 |
Family
ID=4113657
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000322604A Expired CA1119735A (en) | 1979-02-28 | 1979-02-28 | Device for distribution of a gas in a liquid medium |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1119735A (en) |
-
1979
- 1979-02-28 CA CA000322604A patent/CA1119735A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |