METHOD AND SYSTEM FOR DRYING MINE TAILINGS

Abstract

A method and system to treat and dry fines tailings generated from mining operations, comprising spraying the tailings material into a vacuum chamber operated at less than atmospheric pressure to separate evaporated water from the residual solid materials.

Claims

1. A method for at least partially drying tailings materials from a mining operation, the tailings materials comprising water and solids, the method comprising the steps of: a. generating droplets of the tailings materials; b. introducing the droplets into a partial vacuum environment; and c. allowing at least some of the water in the droplets to evaporate to produce a water vapour and a solids-dominant residual material.

2. The method of claim 1 wherein the step of generating droplets is achieved by spraying.

3. The method of claim 2 wherein the spraying is atomizing.

4. The method of claim 1 further comprising the step after step c. of extracting the water vapour from the partial vacuum environment and allowing the water vapour to condense into liquid water.

5. The method of claim 1 further comprising the step after step c. of extracting the solids-dominant residual material from the partial vacuum environment.

6. The method of claim 1 further comprising introducing at least one chemical additive to the tailings materials before the step of generating the droplets.

7. The method of claim 6 wherein the at least one chemical additive is selected from the group consisting of gases, salt solutions, acids, bases, polymers and flocculants.

8. The method of claim 1 further comprising the step of heating the tailings materials before the step of generating the droplets.

9. The method of claim 1 further comprising the step of heating the partial vacuum environment.

10. The method of claim 1 further comprising transporting the tailings materials from a storage pond prior to generating the droplets.

11. The method of claim 1 further comprising obtaining the tailings materials directly from an extraction process.

12. The method of claim 1 further comprising the step after step c. of allowing the solids-dominant residual material to impact a surface to release additional water.

13. The method of claim 4 further comprising the step after the step of condensing the water vapour into the liquid water of transporting the liquid water for re-use in the mining operation.

14. A system for at least partially drying tailings materials from a mining operation, the tailings materials comprising water and solids, the system comprising: a tailings materials source; and a vacuum chamber comprising an inlet for receiving the tailings materials from the tailings materials source, the vacuum chamber configured to allow at least some of the water in the tailings materials to evaporate to produce a water vapour and a solids-dominant residual material; the vacuum chamber further comprising a vapour outlet for allowing the water vapour to leave the vacuum chamber; and the vacuum chamber further comprising a solids outlet for allowing the solids-dominant residual material to leave the vacuum chamber.

15. The system of claim 14 further comprising a condenser in fluid communication with the vapour outlet for receiving the water vapour and condensing the water vapour into liquid water.

16. The system of claim 14 further comprising a chemical additives source and a chemical additives input line for introducing chemical additives into the tailings materials before the tailings materials enter the inlet of the vacuum chamber.

17. The system of claim 14 further comprising a heat applicator to heat the tailings materials before the tailings materials enter the inlet of the vacuum chamber.

18. The system of claim 14 further comprising a gas injector to inject gas into the tailings materials before the tailings materials enter the inlet of the vacuum chamber.

19. The system of claim 14 wherein the inlet comprises a nozzle configured to atomize the tailings materials to generate droplets.

20. The system of claim 14 wherein the vacuum chamber is a vacuum tower of a height sufficient to allow production of the water vapour and the solids-dominant residual material as the tailings materials pass downwardly through the vacuum tower.

21. The system of claim 14 wherein the solids outlet is in communication with a solids removal subsystem.

22. The system of claim 21 wherein the solids removal subsystem comprises an open-close gate or a screw conveyor for transporting the solids-dominant residual material away from the vacuum chamber.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0063] In the accompanying drawings, which illustrate exemplary embodiments of the present invention:

[0064] FIG. 1 is simplified schematic of a first embodiment according to the present invention, wherein tailings material is transported from a tank and pumped to a nozzle which injects the tailings material into a vacuum chamber which is operated at lower than atmospheric pressure.

[0065] FIG. 2 is simplified schematic of a second embodiment according to the present invention, wherein chemical additives and gas additives are added to the tailings material before it reaches the nozzle. The gas can be used to improve the capability to spray the tailings material and disperse it in the air. Furthermore, the tailings material may be heated before it reaches the nozzle to accelerate the drying process.

[0066] FIG. 3 is sectional view of a nozzle that may be employed for embodiments according to the present invention, wherein the tailings material is flowed through an inner tube and gas is flowed through an annular space surrounding the tailings material port. The gas helps to disperse (or atomize) the tailings material into droplets. The gas can consist of any of air, carbon dioxide, nitrogen, methane, and combinations thereof.

[0067] Exemplary embodiments will now be described with reference to the accompanying drawings.

DETAILED DESCRIPTION OF THE INVENTION

[0068] Throughout the following description, specific details are set forth in order to provide a more thorough understanding to persons skilled in the art. However, well known elements may not have been shown or described in detail to avoid unnecessarily obscuring the disclosure. The following description of examples of the invention is not intended to be exhaustive or to limit the invention to the precise form of any exemplary embodiment. Accordingly, the description and drawings are to be regarded in an illustrative, rather than a restrictive, sense.

[0069] The present description relates to treatment of tailings material to yield a dry or high solids content layered product comprising the solid components of tailings material. The resulting product can still contain water as long as the overall structure can be deposited in a terrestrial method for conventional reclamation.

[0070] At present, there are no commercially viable large-scale processes that exist to consolidate and dry tailings materials.

[0071] The present invention takes a new approach with respect to the following factors: additional forces (inertial forces imparted to the droplets when sprayed within the vacuum chamber) and thermodynamics of water at depressed pressure below that of atmospheric pressure.

[0072] FIG. 1 illustrates a first embodiment of the present invention where tailings material is transported from a tank and pumped to the nozzle which injects the liquid tailings material as droplets into a vacuum chamber. The source of the tailings material can also be a tailings pond. The nozzle can be positioned at the top or near the top of the vacuum chamber.

[0073] Due to the low pressure within the vacuum chamber, the temperature at which the water boils (the saturation temperature) is lower than the normal boiling point (100° C. at atmospheric pressure). If the tailings are injected into the vacuum chamber at a sufficient temperature above the saturation temperature corresponding to the pressure in the vacuum chamber, then the water in the tailings material will start to boil and evaporate from the tailings material. For example, if the vacuum pressure in the chamber is equal to 10 kPa, the corresponding saturation temperature of water (the temperature at which it boils) is equal to 45.8° C. This implies that if the temperature of the tailings material entering the vacuum chamber is equal to or above 45.8° C., the water in the tailings material will boil and convert to vapour phase, thus drying the tailings material. If the chamber temperature is maintained equal to or above 45.8° C., then the conditions in the vacuum chamber will lead to boiling of the water from the tailings droplets. Prior to entering the vacuum chamber, the tailings material can be heated by using standard heaters or heat exchangers.

[0074] The droplets have greater surface area than a continuous bulk flow. This enables greater heat and mass transport and thus accelerates the vaporization of the water (and other volatiles) within the tailings leading to faster drying or partial drying of the tailings material.

[0075] The dry or partially dry tailings material that collects at the bottom of the vacuum chamber is removed from the chamber for subsequent processing or storage.

[0076] More than one nozzle can be used at the top of the vacuum chamber to form a greater number of droplets.

[0077] FIG. 2 illustrates a second embodiment of the present invention where chemical and gas additives are added to the tailings material before it reaches the nozzle in the vacuum chamber. The chemicals that can be added to the tailings material prior to the spraying device include mixtures of metal halide (for example, MXn, where M=aluminum, iron, sodium, potassium or copper, and X=fluoride, chloride, bromide or iodide) solutions with and without acid and/or base (to adjust pH as required). Other chemical additives that may be used include polymer or cellulose nanocrystals. A gas can be used to improve the capability to spray the tailings material and disperse it in the air. Examples of gases that can be used include air, nitrogen, carbon dioxide, flue gas from combustion (mixtures of nitrogen and carbon dioxide), and natural gas (methane). [069] Furthermore, the tailings material may be heated before it reaches the nozzle and/or vacuum chamber to accelerate the drying process. The temperature can be in the range from 10 to 99° C. and is preferably in the range from 20 to 60° C.

[0078] FIG. 3 provides a sectional view of an exemplary nozzle showing the inner tailings material tube and an annular gas injection zone surrounding the tailings material. The gas injection zone can also be from one or both sides of the tailings material port.

[0079] The spray device may consist of any appropriate form of nozzle or atomizer that yields droplets of tailings materials, in the judgment of the skilled person.

[0080] The foregoing is considered as illustrative only of the principles of the present invention. The scope of the claims should not be limited by the exemplary embodiments set forth in the foregoing, but should be given the broadest interpretation consistent with the specification as a whole.