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1. WO1990012485 - MULTIPLE SOURCE EVAPORATION FOR ALLOY PRODUCTION

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[ EN ]

CLAIMS

1. Apparatus for the production of an alloy by a process of
evaporating the alloy constituents under vacuum and condensing the constituent vapours upon a collector, said apparatus comprising:
a conduit defining a rising flue which has a discharge opening at its upper end;
a collector positioned so as to collect vapours issuing from the discharge opening of the rising flue;
a first evaporation crudble located and configured so as to discharge into the rising flue at a position remote from the discharge opening thereof;
a second evaporation crudble located within the rising flue at a position intermediate the discharge opening thereof and the first evaporation crudble said second evaporation crudble being configured and disposed such that there is an unobstructed flue passage
therearound;
a first heating means which heats a charge in the first evaporation crudble said first heating means being controllable so as to maintain the temperature of this charge at a desired level to generate an appredable vapour pressure;
a second heating means which heats a charge in the second evaporation crudble said second heating means being controllable so as to maintain the temperature of this charge at a desired level to generate an appredable vapour pressure, and
a wall heating means to heat the conduit in at least that portion thereof above the second evaporation crucible to a temperature at least as high as that of the hotter evaporation crudble in order to suppress condensation of vapour on the walls of the conduit and thereby enhance mixing of the respective vapour streams.

2. Apparatus as daimed in daim 1 wherein the wall heating means serves also to heat the second evaporation crudble by causing radiant emission from the walls of the conduit.

3. Apparatus as daimed in daim 1 or claim 2 wherein the first heating means is controllable to maintain an appredable vapour pressure of the most volatile constituent or constituents and the second heating means is controllable to maintain an appredable vapour pressure of a further constituent or further constituents, the first and second heating means being controllable to maintain a temperature gradient in the rising flue which promotes flow of the respective vapour streams towards the discharge opening.

4. Apparatus as daimed in daim 3 wherein the flue is constructed in longitudinal sections in which the lowermost section is formed from a thermally insulating material to minimise conduction of heat from the hottest regions of the apparatus to the first evaporation ¤âudble.

5. Apparatus as daimed in any preceding claim wherein the evaporation crudble containing the most volatile constituent or constituents has a nozzle to control the flow rate of vapour emanating therefrom.

6. A method for the production of an alloy by a process of
evaporating the alloy constituents under vacuum and condensing the constituent vapours upon a collector, said method comprising:
evaporating a charge of a first alloy constituent or first alloy constituents of relatively high volatility from a first evaporation crudble by heating this charge to a sufficient temperature to generate an appredable vapour pressure;
evaporating a charge of a further alloy consitituent or futher alloy constituents of relatively low volatility from a second evaportation crudble by heating this charge to a suffident temperature to generate an appredable vapour pressure;
maintaining a stream of constituent vapours from the respective evaporation crudbles by continued heating of the charges;
directing the constituent vapour streams into a rising flue defined by a conduit which houses at least the second evaporation crudble;
heating the walls of the conduit in at least that portion thereof above the second evaporation crudble to a temperature at least as high as that of the second evaporation crudble in order to suppress condensation of vapour on the walls of the conduit;

mixing the respective vapour streams in the conduit in that portion thereof above the second evaporation crucible, and
discharging the mixed vapours from the rising flue to impinge upon a colledor positioned above it.

7. A method as claimed in daim 6 comprising indirectly heating the charge in the second evaporation crudble by radiant emission from the heated walls of the conduit.

8. A method as claimed in daim 6 or daim 7 comprising evaporating the constituents from evaporation crudbles positioned one above the other and maintaining a temperature gradient in the rising flue to promote flow of vapour towards the collector by controlling the temperature of the first and second evaporation crucibles such that the second
evaporation crucible experiences a higher temperature than the first evaporation crudble.