JP2526258B2 - Crucible for producing Pt, Pd-based granular noble metal particles - Google Patents

Description

TECHNICAL FIELD The present invention relates to a crucible for producing a noble metal granular mass such as Pt, Pt alloy, Pd, and Pd alloy.

(Prior art and its problems) Conventionally, in order to produce the above-mentioned noble metal granular lump, first, the noble metal ingot is melted in a melting furnace, this molten metal is transferred to a holding furnace and remelted, and the molten metal is continuously fed from a nozzle at the bottom. It was made to fall into water and made a noble metal granular mass. 2 in this method
Since there are times of remelting and transfer of molten metal, it takes time and effort,
Moreover, there was a problem in that when the molten metal was transferred, it was oxidized.

In order to prevent the above oxidation, a deoxidizer is added to the holding furnace, but the precious metal melt is contaminated with the deoxidizer. Further, since the melting furnace and the holding furnace are made of zirconia and have high fire resistance, they are easily damaged due to weak thermal shock resistance, and particularly the nozzle of the holding furnace is easily damaged. Further, since the melting furnace and the holding furnace made of zirconia release a large amount of heat, it is necessary to maintain a high temperature state so as not to cool the molten metal.

For this reason, a noble metal ingot is melted in a layered zirconia crucible, and a molten metal is continuously dropped from a nozzle at the bottom into water to form a noble metal granular mass.

However, even this layered zirconia crucible was insufficient for thermal shock, and damage to the nozzle portion could not be prevented. Further, there is a problem that a difference in thermal expansion occurs between the inner layer and the outer layer and the crucible is deformed.

(Object of the Invention) The present invention has been made to solve the above problems,
Pt that has fire resistance and excellent thermal shock resistance, can surely prevent not only the crucible body but also the nozzle damage, and can suppress the release of heat, and absorb the thermal expansion of the upper crucible, It is an object to provide a crucible for producing a Pd-based noble metal granular mass.

(Means for Solving Problems) A crucible for producing Pt and Pd-based noble metal granular lumps according to the present invention for solving the above problems covers an inner crucible made of zirconia with an outer crucible made of alumina and silicon oxide. A double crucible, and a nozzle integral with the inner crucible is formed at the bottom of this double crucible, and the gap between the outer periphery of the nozzle and the nozzle insertion hole at the bottom of the outer crucible is filled with slurry of alumina and silicon oxide. Firing, filling the gap between the arcuate bottom of the inner crucible and the arcuate bottom of the outer crucible with zirconia powder,
It is characterized in that a gap between the inner crucible and the outer crucible above it is filled with asbestos.

(Operation) The Pt, Pd-based noble metal granular lump producing crucible of the present invention configured as described above has a high fire resistance in the inner crucible, and the outer crucible covered therewith has a large thermal shock resistance. The inner crucible with low impact resistance is reliably protected. Also, since the outer periphery of the nozzle that is integrated with the inner crucible on the bottom of this double crucible is covered with the bottom of the outer crucible through the burned material of alumina and silicon oxide, the nozzle with low thermal shock resistance is surely protected. To be done. Therefore, when the precious metal ingot is melted in the double crucible and the molten metal is continuously dropped into the water from the nozzle at the bottom to form precious metal granular lumps, the nozzle as well as the inner crucible is not damaged. Between the inner crucible and the outer crucible, zirconia powder is filled in the bottom part and asbestos is filled in the upper part, so they act as a heat shield, suppressing the heat release from the inner crucible and cooling the molten metal. Is prevented. Further, although there is a difference in thermal expansion between the inner crucible and the outer crucible, asbestos is filled between the two, so that the thermal expansion can be absorbed and the inner and outer crucibles can be prevented from being deformed.

(Example) An example of a crucible for producing a Pt, Pd-based noble metal granular lump of the present invention will be described with reference to the drawing. As shown in FIG.
Inner crucible 1 made of zirconia, m, depth 216 mm, thickness 8 mm, alumina 92 wt, inner diameter 78 mm, depth 217 mm, thickness 8 mm
% And silicon oxide 8 wt% to cover the outer crucible 2 to form a double crucible. At the bottom of this double crucible, a nozzle 4 having an inner diameter of 4 mm, a length of 20 mm and a wall thickness of 1.5 mm is formed integrally with the inner crucible 1. are doing. A slurry 6 of 92 wt% alumina and 8 wt% silicon oxide is filled in the gap between the outer periphery of the nozzle 4 and the nozzle insertion hole 5 provided at the bottom of the outer crucible 2 and the mixture is fired and integrated with each other. Zirconia powder 7 is placed in the gap between the outer surface of the arcuate bottom of the inner crucible 1 and the inner surface of the arcuate bottom of the outer crucible 2.
Is filled, and asbestos 8 is filled in the gap between the outer peripheral surface of the inner crucible 1 and the inner peripheral surface of the outer crucible 2 above it.

In order to produce a Pt / Pd-based noble metal granular lump by the crucible 9 for producing a Pt / Pd-based noble metal granular lump configured as described above, the Pt / Pd-based noble metal granular lump is set in the high frequency induction heating device 10 as shown in FIG. 750 mm diameter concentric with nozzle 4 at a distance of 500 mm below
A water tank 11 with a depth of 900 mm is installed, and 3 kg of Pt is placed in the crucible 9.
An ingot is put in, and the high frequency induction device 10 is operated to melt the Pt ingot in the crucible 9. When the Pt ingot is completely melted, the Pt molten metal continuously drops from the bottom nozzle 4 into the water in the water tank 11 to form Pt granular lumps having a diameter of 4 mm or less. In the production of this Pt granular mass, the inner crucible 1 having high fire resistance but low thermal shock resistance is covered with the outer crucible 2 having high thermal shock resistance, and the nozzle 4 integrated with the inner crucible 1 is oxidized with alumina. Since the bottom portion of the outer crucible 2 is covered with the fired product of the silicon slurry, the inner crucible 1 and the nozzle 4 are reliably protected, and therefore the nozzle 4 as well as the inner crucible 1 is damaged by thermal shock. Never. Also, between the inner crucible 1 and the outer crucible 2,
Since the bottom part is filled with zirconia powder 7 and the upper part is filled with asbestos 8, they act as a heat shield, suppressing the release of heat from the inner crucible 1 and preventing the Pt melt from cooling. . Inside crucible 1 and outside crucible 2
Although there is a difference in thermal expansion between the two, since the asbestos 8 is filled between them, the thermal expansion is absorbed thereby, and the inner and outer crucibles 1 and 2 are prevented from being deformed.

(Effect of the invention) As can be seen from the above description, the Pt and Pd-based precious metal granular lump manufacturing crucibles of the present invention melt Pt and Pd-based precious metals by high-frequency induction heating, and melt the molten metal continuously from the nozzle. When falling into a water tank to form a granular mass, the crucible body and nozzle are not damaged by thermal shock. Further, when the Pt or Pd-based precious metal is melted or when the molten metal flows out and falls from the nozzle, the heat release from the inner crucible is suppressed, so that the molten metal is prevented from being cooled and the nozzle is not clogged. Furthermore, the thermal expansion of the inner and outer crucibles is absorbed by the asbestos filled in the gap between them, and the crucible body is not deformed.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing an embodiment of a crucible for producing Pt and Pd-based noble metal granular lumps of the present invention, and FIG. 2 shows a state in which the crucible is set in a high frequency induction heating device to produce granular lumps. FIG.

Claims (1)

(57) [Claims] 1. An inner crucible made of zirconia is covered with an outer crucible made of alumina and silicon oxide to form a double crucible, and a nozzle integral with the inner crucible is formed at the bottom of the double crucible, and the outer periphery of the nozzle is formed. And the gap between the nozzle insertion hole at the bottom of the outer crucible and alumina and silicon oxide slurry is filled and fired, the gap between the arc-shaped bottom of the inner crucible and the arc-shaped bottom of the outer crucible is filled with zirconia powder, which A crucible for producing Pt and Pd-based noble metal granular lumps, characterized in that a gap between an inner crucible and an outer crucible above is filled with asbestos.