METHOD AND MACHINE FOR FLOTATION OF MINERALS OR THE LIKE

• US 3,747,757 A
• Filed: 10/29/1970
• Issued: 07/24/1973
• Est. Priority Date: 05/03/1969
• Status: Expired due to Term

• Current Assignee: Carl-Heinz Kalthoff, Peter Wilczynski, Wilhelm Freis
• Original Assignee: Carl-Heinz Kalthoff, Peter Wilczynski, Wilhelm Freis
• Inventors: Kalthoff, Carl-Heinz, Freis, Wilhelm, Wilczynski, Peter
• Primary Examiner(s): Lutter, Frank W.
• Assistant Examiner(s): Halper, Robert
• Application Number:
  US05/085,147
• Time in Patent Office: 999 Days
• Field of Search: 209/162-168,170,211 55/22,459,417 261/126
• US Class Current: 209/164
• CPC Class Codes: B01D 3/24 with sloping plates or elements mounted stepwise
• CPC Class Codes: B03D 1/028 Control and monitoring of flotation processes; computer models therefor
• CPC Class Codes: B03D 1/1406 with special arrangement of a plurality of flotation cells, e.g. positioning a flotation cell inside another
• CPC Class Codes: B03D 1/1412 with baffles, e.g. at the wall for redirecting settling solids
• CPC Class Codes: B03D 1/1418 using centrifugal forces
• CPC Class Codes: B03D 1/1431 Dissolved air flotation machines
• CPC Class Codes: B03D 1/1456 Feed mechanisms for the slurry
• CPC Class Codes: B03D 1/1468 Discharge mechanisms for the sediments
• CPC Class Codes: B03D 1/24 Pneumatic mixing gases or vapours with liquids B01F23/20

Abstract

A flotation machine having a battery of centrifugal cells which are disposed at the same level. The first cell receives a continuous stream of reagent-containing slurry from a receptacle and each other cell receives a continuous stream of slurry from the bottom part of the preceding cell. Each cell has a sealed annular cyclone chamber which receives slurry from the bottom part of the preceding cell or from the receptacle, and a froth collecting chamber which is surrounded by the respective cyclone chamber. The slurry rises into the cyclone chambers under the action of compressed air which is pumped into the slurry in such quantities that the surplus of air forms in each cyclone chamber a cushion from which air is withdrawn in controlled amounts for introduction into slurry which is being drawn from the bottom part of the respective cell. Compressed air serves to convey as well as to be dispersed in the slurry with attendant formation of froth which rises in and is withdrawn at the top of the corresponding froth collecting chamber.

Claims

1. A flotation method of separating a first class of particles from a second class of particles which are intermixed with the particles of said first class in a pulp and wherein the particles of said first class exhibit the tendency to adhere to gas bubbles, particularly of separating one class of minerals from another class of minerals, comprising the steps of lifting said pulp by means of a compressed gas which is supplied in a quantity exceeding the maximum quantity capable of being dispersed in said pulp so that only a portion of said compressed gas becomes dispersed in the pulp together with gas in excess and forms bubbles therein;

introducing the thus lifted pulp tangentially into an at least substantially enclosed circular area and confining the thus introduced pulp to circulation in said enclosed area to prevent uncontrolled escape of undispersed gas and at least to maintain the dispersion of said portion of gas in the circulating pulp whereby the particles of said first class adhere to said bubbles with attendant formation of froth containing at least a substantial percentage of particles of said first class and with simultaneous formation of a residue containing the particles of said second class;

transferring said first and second particles to a collecting chamber spaced within said enclosed area and separating the froth from said residue; and

effecting a controlled removal of undispersed gas from said enclosed area.

2. A method as defined in claim 1, wherein said undispersed gas forms in the enclosed area a cushion above the circulating pulp.

3. A method as defined in claim 2, further comprising the step of maintaining the gas of said cushion at a pressure of less than 1 atmosphere above atmospheric pressure.

4. A method as defined in claim 2, further comprising the step of maintaining the gas of said cushion at a pressure of 0.4-0.6 atmospheres above atmospheric pressure.

5. A method as defined in claim 1, wherein said step of effecting controlled removal of undispersed gas comprises removing unidispersed gas from the enclosed area at several points which are equidistant from each other, as considered in the direction of circulation of pulp in the enclosed area.

6. A method as defined in claim 5, further comprising the step of independently regulating the withdrawal of gas at each of said points.

7. A method as defined in claim 1, further comprising the step of introducing the removed undispersed gas into said residue subsequent to a separation of said froth so that the thus introduced gas is dispersed in said residue.

8. A method as defined in claim 1, further comprising the step of continuously lifting into said enclosed area fresh pulp so that the fresh pulp enters the enclosed area by flowing in the direction of circulation of pulp in said enclosed area.

9. A method as defined in claim 8, wherein the pulp is admitted into the enclosed area at several points which are equidistant from each other as considered in the direction of circulation of pulp in the enclosed area.

10. In a flotation machine for the separation of a first class of particles from a second class of particles which are intermixed with particles of said first class in a pulp and wherein the particles of said first class exhibit the tendency to adhere to gas bubbles, particularly for the separation of a first class of minerals from another class of minerals, a combination comprising a receptacle for a supply of pulp;

a cell having an annular chamber and a flotation and froth collecting second chamber surrounded by said annular chamber, said chambers having communicating lower portions and said annular chamber being at least substantially sealed from the surrounding atmosphere;

conduit means connecting said receptacle with said annular chamber and having at least one outlet disposed substantially tangentially of said annular chamber to promote the circulation of pulp therein;

pneumatic lifter means for admitting into said conduit means a compressed gas at such pressure and in such quantities that the thus admitted gas conveys the pulp into said annular chamber and a portion thereof is dispersed in the pulp during lifting of pulp into said annular chamber whereby the undispersed portion of said gas accumulates in said annular chamber and the circulating pulp contains bubbles of gas to which particles of said first class adhere to form a froth not later than on entry into said second chamber; and

means for effecting a controlled removal of undispersed gas from said annular chamber.

11. A combination as defined in claim 10, wherein said annular chamber is an upright chamber and said cell further comprises a lower end portion which establishes the communication between the lower portions of said chambers.

12. A combination as defined in claim 11, wherein said lower end portion is a funnel which is coaxial with and diverges upwardly toward the lower portions of said chambers.

13. A combination as defined in claim 10, further comprising at least one additional cell disposed at least substantially at the level of said first mentioned cell and additional conduit means connecting said cells, each additional conduit means containing a lifter means.

14. A combination as defined in claim 10, wherein said means for effecting controlled removal of undispersed gas comprises a plurality of discrete gas removing devices each of which is arranged to remove undispersed gas from said annular chamber independently of each other gas removing device.

15. A combination as defined in claim 10, wherein said means for effecting controlled removal of undispersed gas comprises a plurality of discrete gas removing devices each having means for adjusting the rate of gas removal.

16. A combination as defined in claim 10, wherein said means for effecting controlled removal of undispersed gas comprises a plurality of discrete gas removing devices, said gas removing devices being uniformly distributed as considered in the circumferential direction of said annular chaMber.

17. A combination as defined in claim 10, wherein said means for effecting controlled removal of undispersed gas comprises at least one adjustable regulating valve which controls the removal of gas from said annular chamber.

18. A combination as defined in claim 10, wherein said cell further comprises a lower end portion which establishes communication between the lower portions of said chambers and collects the residue of pulp which is not converted into froth, and further comprising a vessel and conduit means for admitting said residue from the lower end portion of said cell into said vessel, said means for effecting controlled removal of undispersed gas from said annular chamber being arranged to introduce the removed undispersed gas into the residue in said vessel.

19. A combination as defined in claim 18, wherein said vessel comprises two compartments one of which receives residue from the lower end portion of said cell, and an adjustable partition over which the residue flows into the other compartment.

20. A combination as defined in claim 10, wherein said outlet means comprises at least one substantially horizontal nozzle, said means for effecting controlled removal of undispersed gas from said annular chamber comprising at least one upwardly extending pupe having at its lower end an inlet located in said annular chamber at a level disposed at least 50 millimeters above the axis of said nozzle.

21. A combination as defined in claim 20, wherein said pipe extends substantially vertically upwardly to a level above the maximum levels of pulp and froth in said chambers.

22. A combination as defined in claim 10, wherein said cell further comprises a lower end portion which communicates with the lower portions of said chambers and the lower portion of said second chamber is apertured so that froth must pass through said apertured lower portion while flowing from said annular chamber into said second chamber.

23. A combination as defined in claim 22, wherein said apertured lower portion constitutes the bottom wall of said second chamber.

24. A combination as defined in claim 22, wherein the size of each aperture in said lower portion of said second chamber substantially exceeds the maximum size of particles in the pulp.