Patent EA-005036-B1 (EA)
Title: Method for assaying a mineral sample
Inventor: COWAN GEORGE MICHAEL
IPC: G01N33/20
Filed: 2001-07-12
Abstract: 1. A method of assaying a mineral sample for determining the concentration of selected metals in a sample comprising the steps of: providing a comminuted mineral sample; mixing such sample with a flux which forms a collector material during fusion thereof; causing the mixture to fuse whereby the mixture is transformed to a molten state to form a slag and to capture the metal to be assayed in a the collector material; and separating the slag from the collector material; characterized in that the collector material is separated from the slag by allowing the collector material to drain through an outlet aperture by force of gravity, the dimensions of the aperture being sufficiently restricted to prevent the slag from draining through the aperture by force of gravity. 2. The method according to claim 1 wherein the reaction vessel is preheated prior to introducing the mixture into the reaction vessel to cause fusion of the mixture. 3. The method according to claim 1 or claim 2 wherein the method includes the step of oxidizing the collector material or portion thereof before or after fusion of the mixture to reduce the volume of the collector material. 4. The method according to claim 3 wherein me collector material is oxidized by introducing oxygen or an oxygen producing material into the reaction vessel after fusion of the mixture. 5. The method according to claim 3 or claim 4 wherein oxygen is introduced into the collector material by means of a lance or the like. 6. The method according to claim 3 or claim 4 wherein, oxygen is introduced into the collector material through a low level outlet aperture of the reaction vessel for oxidizing the collector material, prior to draining of me collector material through such outlet aperture. 7. The method according to claim 6 wherein oxygen is introduced into a separation vessel through the low level outlet aperture from a supply source via a collector mould which sealingly engages the separation vessel below the outlet aperture. 8. The method according to claim 7 including the step of disengaging the collection mould from the separation vessel after oxidization of the collector material to release pressure in the collection mould to permit the collector material to drain into such collection mould, through the outlet aperture. 9. The method according to any one of claims 3 to 8 including the step of introducing an additional collector material which is resistant to oxidization into the reaction vessel, after or prior to fusion of the mixture and prior to oxidation of the collector material. 10. The method according to claim 9 wherein the additional collector material is silver or gold. 11. The method according to any one of claims 1, 9 or 10, including the step of separating the collector material from the slag after fusion of the mixture, and thereafter contacting the collector material with oxygen or oxygen forming material to oxidize the collector material or a portion thereof, to reduce the volume of the collector material. 12. The method according to claim 11 wherein a stream of oxygen gas is blown onto or into the collector material for oxidization purposes. 13. The method according to any one of claims 1 to 12 wherein the outlet aperture for collector material is disposed at the lower extremity of the vessel. 14. A method according to any one of claims 1 to 12 including the steps of separating the collector material from the slag comprising providing a separating vessel which defines an interior concavity which terminates in a lower portion for receiving the collector material, and which defines an outlet cavity in a position spaced from such lower portion, the outlet cavity including an outlet aperture for draining collector material from the outlet cavity by force of gravity, the dimensions of the outlet aperture being sufficiently restricted to prevent the slag from draining through the outlet aperture by force of gravity, and comprising the further steps of rotating the reaction and separating vessel transversely so that collector material in the lower-most portion flows to the outlet cavity. 15. Apparatus for assaying a mineral sample suitable for use in the method according to any one of claims 1 to 14 comprising separation vessel, an outlet aperture for draining collector material from the vessel by force of gravity, wherein the dimensions of the outlet aperture are sufficiently restricted to prevent the slag from draining through the outlet aperture by force of gravity. 16. Apparatus according to claim 15 wherein the aperture is substantially circular in cross-section and has a diameter of between 0.5 mm to 2.0 mm. 17. Apparatus according to claim 16 wherein the aperture has a diameter of 1.0 mm. 18. Apparatus for assaying a mineral sample suitable for use in the method according to any one of claims 1 to 14 comprising a reaction vessel having a low level outlet aperture for draining collector material from the vessel by force of gravity the dimensions of the aperture being sufficiently restricted to prevent slag from draining through the aperture by force of gravity, and a collection mould disposed below the outlet aperture and adapted sealingly to engage the separation vessel, and an inlet for oxygen or other gas in the collection mould to enable oxygen or gas to be ducted through the interior of the collection mould and the low level outlet aperture into the separation vessel. 19. Apparatus according to claim 18 wherein comprising a lifter means whereby the collection mould can be lifted into engagement with the separation vessel and lowered to a position removed from the separation vessel. 20. Apparatus according to claim 18 or 19 wherein the separation vessel comprises a downwardly directed tube formation extending from the outlet aperture and against which the collection mould sealingly engages. 21. Apparatus for assaying a mineral sample suitable for use in the method according to any one of claims 1 to 14 comprising a separating vessel which defines an interior concavity which terminates in a lower portion for receiving a collector material and which defines an outlet cavity for receiving collector material in the position spaced from such lower portion, (be outlet cavity including an outlet aperture for draining collector material from the outlet cavity by force of gravity, the dimensions of the outlet aperture being sufficiently restricted to prevent slag from draining through the outlet aperture by force of gravity. 22. Apparatus according to claim 21 wherein the separating vessel is rotatable angularly to cause the collector material to flow to the outlet cavity. 23. A flux suitable for use in the method according to any one of claims 1-14 which comprises the collector material adapted to combine with material in a mineral sample further comprising potassium hydroxide material. 24. The flux according to claim 23 wherein comprising between 5 % and 60%, preferably 7.5% potassium hydroxide by weight. 25. The flux according to claim 23 or 24 wherein comprising one or more additional compounds selected from the alkaline earth metal group of compounds. 26. The flux according to claim 25 wherein such alkaline earth metal group compounds are hydroxides. 27. The flux according to claim 26 wherein comprising between 5 % and 60%, preferably 7.5 % by weight of calcium hydroxide. 28. The flux according to any one of claims 23 to 27 wherein comprising one or more additional compounds selected from me alkaline metal group, preferably hydroxides. 29. The flux according to claim 28 wherein comprising between 10% and 19% sodium hydroxide, by weight.