PROCESS FOR THE PRODUCTION OF A PGM-ENRICHED ALLOY

Abstract

A gas-coolable gas lance comprising an inner tube for a supply of a gas A, wherein the inner tube is surrounded by an outer tube, wherein the inner and the outer tube form a hollow space between themselves, wherein the inner tube has a bottom opening and a top opening, wherein the bottom opening comprises or is an exhaust for the gas A, wherein the hollow space is closed at its bottom and has a top opening, wherein the hollow space comprises an arrangement of tubes for a supply of a gas B to the bottom region of the hollow space, wherein the outer tube, the hollow space's bottom and the exhaust for the gas A are made of stainless steel. The gas lance can be used in a pyrometallurgical process for the production of a PGM-enriched alloy.

Claims

1. A process for the production of a PGM-enriched alloy comprising at least one PGM selected from the group consisting of platinum, palladium and rhodium, the process comprising the steps: (1) providing a PGM collector alloy comprising collector metal and one or more PGMs selected from the group consisting of platinum, palladium and rhodium, (2) providing a material capable of forming a slag-like composition when molten, (3) melting the PGM collector alloy and the material capable of forming a slag-like composition when molten within a converter until a multi- or two-phase system of a lower high-density molten mass comprising the molten PGM collector alloy and one or more upper low-density molten masses comprising the molten slag-like composition has formed, (4) contacting an oxidizing gas comprising 0 to 80 vol.-% of inert gas and 20 to 100 vol.-% of oxygen with the lower high-density molten mass obtained in step (3) until it has been converted into a lower high-density molten mass of the PGM-enriched alloy, (5) separating an upper low-density molten slag formed in the course of step (4) from the lower high-density molten mass of the PGM-enriched alloy making use of the difference in density, (6) letting the molten masses separated from one another cool down and solidify, and (7) collecting the solidified PGM-enriched alloy, wherein the contact between the oxidizing gas and the lower high-density molten mass is made by passing the oxidizing gas into the lower high-density molten mass by means of a gas lance the oxidizing gas exhaust of which being immersed into the lower high-density molten mass, wherein the gas lance comprises an inner tube for the oxidizing gas supply, wherein the inner tube is surrounded by an outer tube, wherein the inner and the outer tube form a hollow space between themselves, wherein the inner tube has a bottom opening and a top opening, wherein the bottom opening comprises or is the oxidizing gas exhaust, wherein the hollow space is closed at its bottom and has a top opening, wherein the hollow space comprises an arrangement of tubes for a cooling gas supply to the bottom region of the hollow space, wherein the outer tube, the hollow space's bottom and the oxidizing gas exhaust are made of stainless steel, wherein the gas lance is cooled during step (4) by means of cooling gas supplied to the bottom region of the hollow space via said arrangement of tubes, and wherein the cooling gas after having left said arrangement of tubes escapes the hollow space at its top opening.

2. The process of claim 1, wherein the PGM-enriched alloy comprises >0 to 60 wt.-% of iron and 20 to <100 wt.-% of the one or more PGMs.

3. The process of claim 1, wherein the PGM collector alloy provided in step (1) comprises 30 to 95 wt.-% of iron and 2 to 15 wt.-% of one or more PGMs selected from the group consisting of platinum, palladium and rhodium.

4. The process of claim 1, wherein the molten slag-like composition comprises or consists of 40 to 90 wt.-% of magnesium oxide and/or calcium oxide, 10 to 60 wt.-% of silicon dioxide, 0 to 20 wt.-% of iron oxide, 0 to 10 wt.-% of sodium oxide, 0 to 10 wt.-% of boron oxide, and 0 to 2 wt.-% of aluminum oxide.

5. The process of claim 4, wherein (i) the PGM collector alloy comprises 0 to 4 wt.-% of silicon and wherein the the molten slag-like composition comprises 40 to 60 wt.-% of magnesium oxide and/or calcium oxide and 40 to 60 wt.-% of silicon dioxide or (ii) wherein the PGM collector alloy comprises >4 to 15 wt.-% of silicon and wherein the the molten slag-like composition comprises 60 to 90 wt.-% of magnesium oxide and/or calcium oxide and 10 to 40 wt.-% of silicon dioxide.

6. The process of claim 1, wherein the PGM collector alloy and the material capable of forming a slag-like composition when molten may be melted in a weight ratio of 1:0.2 to 1.

7. The process of claim 1, wherein the temperature of the converter contents is raised to 1200 to 1800 C.

8. The process of claim 1, wherein the contacting with the oxidizing gas takes 1 to 5 hours.

9. The process of claim 1, wherein an immersion depth of the oxidizing gas exhaust into the lower high-density molten mass is in the range of from >0 to 10 cm.

10. The process of claim 1, wherein the inner tube is equidistantly surrounded by the outer tube.

11. The process of claim 1, wherein the gas lance takes a non-horizontal orientation during the oxidizing gas supply of step (4).

12. The process of claim 1, wherein the arrangement of tubes for the cooling gas supply is symmetrical along the gas lance's length axis.

13. The process of claim 1, wherein the cooling gas is air.

14. The process of claim 1, wherein the cooling gas is supplied with a flow rate allowing for the stainless steel parts of the gas lance to be cooled below the stainless steel's softening temperature.

15. A gas-coolable gas lance which can be used in a process of any one of the preceding claims, said gas-coolable gas lance comprising an inner tube for a supply of a gas A, wherein the inner tube is surrounded by an outer tube, wherein the inner and the outer tube form a hollow space between themselves, wherein the inner tube has a bottom opening and a top opening, wherein the bottom opening comprises or is an exhaust for the gas A, wherein the hollow space is closed at its bottom and has a top opening, wherein the hollow space comprises an arrangement of tubes for a supply of a gas B to the bottom region of the hollow space, wherein the outer tube, the hollow space's bottom and the exhaust for the gas A are made of stainless steel.

Description

EXAMPLE

[0126] A premix of 500 kg of a PGM collector alloy comprising 47 wt.-% of iron, 14.1 wt.-% of nickel, 8.1 wt.-% of silicon, 4.6 wt.-% of palladium, 3.2 wt.-% of chromium, 2.5 wt.-% of titanium, 2.2 wt.-% of platinum, 1.8 wt.-% of manganese, 0.6 wt.-% of rhodium and 0.9 wt.-% of copper, 123 kg of calcium oxide, 75 kg of silicon dioxide, 15 kg of sodium carbonate and 15 kg of borax was portionwise introduced into an already 1500 C. hot cylindrical natural gas-heated furnace and further heated to 1700 C. After a melting time of 10 hours a two-phase system of a lower high-density molten mass comprising the PGM collector alloy and an upper low-density molten mass comprising a slag-like composition was formed. Oxygen was introduced into the lower high-density molten mass via the exhaust of an air-cooled gas lance with an oxygen flow of 900 l/min.

[0127] The air-cooled gas lance had a 1.70 meters long inner stainless steel tube with an inner/outer diameter of 0.5 cm/2.5 cm for the oxygen gas supply. The inner tube was equidistantly surrounded by an outer stainless steel tube (1.70 meters long, inner/outer diameter of 7.5 cm/8.0 cm) forming a hollow space between the inner wall of the outer tube and the outer wall of the inner tube.

[0128] The inner tube's bottom opening served as oxygen gas exhaust. The hollow space had a closed bottom and an open top and it comprised a symmetrical arrangement of six stainless steel tubes (1.68 meters long, inner/outer diameter of 0.5 cm/2.5 cm) for cooling air supply to the bottom region of the hollow space. The six tubes were arranged such that their bottom openings had a distance of 2 cm from the inner bottom wall of the hollow space. Air-cooling was performed with a total air flow of 2500 l of air of 20 C. per minute. The cooling air was fed into the six tubes and left those at the tubes' bottom ends finally escaping the hollow space hot at its open top into the atmosphere.

[0129] After 2.5 hours the oxygen introduction was stopped and the gas lance was removed. The upper low-density molten mass was poured into cast iron slag pots in order to cool down and solidify. The lower high-density molten mass was then poured into graphite molds in order to cool down and solidify. After solidification and cooling down to ambient temperature both materials were analyzed by XRF.

Results:

[0130] 1. The PGM enriched alloy comprised 15 wt.-% of iron, 53 wt.-% of nickel, 3 wt.-% of copper and 29 wt.-% of PGMs (platinum plus palladium plus rhodium). [0131] 2. The slag comprised 46 wt.-ppm of PGMs, 34 wt.-% of iron and 1 wt.-% of nickel. [0132] 3. The gas lance showed some damage but could be used for the same procedure a second time.