Method and apparatus for condensing metal vapours using a nozzle and a molten collector
Methods and apparatus are disclosed for condensing vapor phase compounds or elements, typically metals such as magnesium, obtained by reduction processes.
1. A method for condensing a vaporous material comprising:
providing a gas stream comprising the vapour,
passing the gas stream through a nozzle which has an upstream converging configuration and a downstream diverging configuration so that the vapour accelerates into the nozzle and expands and cools on exiting the nozzle thereby inducing the vapour to condense to form a beam of liquid droplets or solid particles in the condensing chamber,
wherein the beam of droplets or particles is directed to impinge onto a bath of molten liquid collection medium,
wherein the collection medium is maintained at a temperature above the melting point of the condensed vaporous material, and
wherein the collection medium comprises a salt flux which has a specific gravity lower than that of the condensed vaporous material.
2. The method of claim 1 , wherein the nozzle has an elongate transverse waist region so as to provide a generally planar or wedge-shaped output beam of condensed particles or liquid.
3. The method of claim 1 , wherein the gas stream comprises reaction gas and/or a non-reactive carrier gas in addition to the vapour to be condensed.
4. The method of claim 1 , wherein the beam of droplets or particles impinges onto the collection medium at an oblique angle with respect to a surface of the collection medium.
5. The method of claim 4 , wherein the oblique beam impinges onto the collection medium at a location radially spaced apart from a central rotational axis of the bath, thereby assisting or causing circumferential flow of the molten bath.
6. The method of claim 1 , wherein metal droplets in the beam are cooled to form solid particles before impinging on the collection medium.
7. The method of claim 1 , wherein the collection medium is cooled so as to prevent liquid metal from the beam vaporizing.
8. The method of claim 1 , wherein the vaporous material to be condensed comprises magnesium.
9. The method of claim 1 , wherein the vapour comprises a metal or metallic material.
10. The method of claim 9 , wherein the vapour is a metal comprising Mg, Zn, Sn, Pb, As, Sb, Bi, Si, Cd, or a combination thereof.
11. The method of claim 9 , wherein the vapour is provided by a metallothermic or carbothermic reduction apparatus and/or process.
12. A method for condensing a vaporous material comprising:
providing a gas stream comprising the vapour,
passing the gas stream through a nozzle which has an upstream converging configuration and a downstream diverging configuration so that the vapour accelerates into the nozzle and expands and cools on exiting the nozzle thereby inducing the vapour to condense to form a beam of liquid droplets or solid particles in the condensing chamber,
wherein the beam of droplets or particles is directed to impinge onto a molten liquid collection medium,
wherein the liquid collection medium comprises a thin sheet of a first liquid disposed above a second liquid, the sheet being sufficiently thin to be disrupted by impinging condensed droplets or particles, to an extent that the sheet parts in a region corresponding to the impingement so as to reveal a surface of the second liquid so as to permit direct access of the condensed particles or droplets to the underlying second liquid for absorption therein, and wherein the thin sheet remains as a protective covering over a remaining portion of the surface of the second liquid.
13. The method of claim 12 , wherein the first liquid comprises a salt flux.
14. The method of claim 12 , wherein the second liquid comprises liquid condensed vaporous material.
15. The method of claim 12 , wherein the second liquid is a molten metal.
16. A method for condensing a vaporous material comprising:
providing a gas stream comprising the vapour,
passing the gas stream through a nozzle which has an upstream converging configuration and a downstream diverging configuration so that the vapour accelerates into the nozzle and expands and cools on exiting the nozzle thereby inducing the vapour to condense to form a beam of liquid droplets or solid particles in the condensing chamber,
wherein the beam of droplets or particles is directed to impinge onto a molten liquid collection medium,
wherein the collection medium comprises a moving sheet of liquid.
17. The method of claim 16 , wherein the moving sheet is a stream of liquid falling under gravity.
18. The method of claim 16 , wherein the moving sheet is provided by an overflowing ledge region of a collection medium reservoir.
19. The method of claim 16 , wherein the nozzle is directed horizontally or substantially horizontally towards the sheet of liquid collection medium.
20. A method for condensing a vaporous material comprising:
providing a gas stream comprising the vapour,
passing the gas stream through a nozzle which has an upstream converging configuration and a downstream diverging configuration so that the vapour accelerates into the nozzle and expands and cools on exiting the nozzle thereby inducing the vapour to condense to form a beam of liquid droplets or solid particles in the condensing chamber,
wherein the beam of droplets or particles is directed to impinge onto a molten liquid collection medium,
wherein the collection medium is disposed as a circumferentially circulating bath of liquid.
21. The method of claim 20 , wherein the liquid is circulated by a mechanical means.
22. A method for condensing a vaporous material comprising:
providing a gas stream comprising the vapour,
passing the gas stream through a nozzle which has an upstream converging configuration and a downstream diverging configuration so that the vapour accelerates into the nozzle and expands and cools on exiting the nozzle thereby inducing the vapour to condense to form a beam of liquid droplets or solid particles in the condensing chamber,
wherein the beam of droplets or particles is directed to impinge onto a molten liquid collection medium,
wherein on exiting the nozzle the condensed droplets or particles form a first cone, the reaction gas and/or carrier gas form at least one further cone with the first cone accommodated inside the second cone and wherein a baffle means is provided around the first cone and substantially inside the further cone so as to provide a physical barrier which helps separate the carrier gas and other remaining gaseous species from the droplets or particles which pass through the baffle into the collection medium.
23. The method of claim 22 , wherein the baffle means comprises an axially elongate conduit having walls which provide separation of the first cone.
24. The method of claim 23 , wherein the baffle means is surrounded by a shoulder which covers at least a portion or all of a remaining surface of collection medium.
25. A method for condensing a vaporous material comprising:
providing a gas stream comprising the vapour,
passing the gas stream through a nozzle which has an upstream converging configuration and a downstream diverging configuration so that the vapour accelerates into the nozzle and expands and cools on exiting the nozzle thereby inducing the vapour to condense to form a beam of liquid droplets or solid particles in the condensing chamber,
wherein the beam of droplets or particles is directed to impinge onto a molten liquid collection medium,
wherein the beam of droplets or particles impinges onto the collection medium at an oblique angle with respect to the medium surface, and
wherein the collection medium is disposed in a circumferentially circulating molten bath.
26. The method of claim 25 , wherein the bath circulation induces an inverted coaxial centrifugal cone to form in an upper surface of the bath, which cone provides an oblique surface to receive the droplet or particle beam.
27. A method for condensing a vaporous material comprising:
providing a gas stream comprising the vapour,
passing the gas stream through a nozzle which has an upstream converging configuration and a downstream diverging configuration so that the vapour accelerates into the nozzle and expands and cools on exiting the nozzle thereby inducing the vapour to condense to form a beam of liquid droplets or solid particles in the condensing chamber,
wherein the beam of droplets or particles is directed to impinge onto a molten liquid collection medium,
wherein the collection medium comprises a liquid having a lower specific gravity than the condensed liquid material, which condensed liquid material is continuously or intermittently tapped from a collection medium reservoir and directed without intermediate solidification to a casting stage or alloying stage or other forming stage.