Converting Process with Partial Pre-Oxidation of PGM Collector Alloy

Abstract

Converting process with partial pre-oxidation of PGM collector alloy. The process includes partially pre-oxidizing a raw alloy, introducing an initial charge of the partially pre-oxidized alloy into a converter pot, melting the initial charge, introducing converter feed to the pool, oxygen injection into the pool, tapping the slag, and tapping the PGM-enriched alloy. The collector alloy contains no less than 0.5 wt % PGM, 40 wt % iron, and 0.5 wt % nickel, and no more than 3 wt % sulfur and 3 wt % copper. The process can also include low- or no-flux converting; using a refractory protectant in the converter; magnetic separation of slag; recycling part of the slag to the converter; smelting catalyst material in a primary furnace to produce the collector alloy; and / or smelting the converter slag in a secondary furnace with slag from the primary furnace.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]This application is a continuation-in-part of our earlier co-pending application U.S. Ser. No. 16 / 397,441, filed Apr. 29, 2019, now U.S. Pat. No. ______.BACKGROUND OF THE INVENTION[0002]The platinum group metals, i.e., ruthenium, rhodium, palladium, osmium, iridium, and platinum (“PGM”), are often recovered from used catalyst materials such as, for example, automotive catalytic converters. The catalyst materials are smelted in a furnace, typically with a flux material such as CaO, and the PGM are preferentially collected in an alloy pool below the slag. While the PGM are dilute in the furnace slag, nevertheless these losses can be significant due to the high volume of slag and a general inability to economically recover the dilute values. The PGM collector alloys may contain up to 12 wt % PGM, and usually contain more than 40 wt % iron. Enrichment is necessary if a higher PGM content is desired.[0003]PGM enrichment of iron-rich, sulfide-le...

AI Technical Summary

Benefits of technology

The present patent is about a new process for converting platinum group metals by smelting catalyst material in a primary furnace to produce the collector alloy, followed by smelting the converter slag in a secondary furnace with slag from the primary furnace. The converter is integrated into an overall PGM recovery process to inhibit the buildup of deleterious elements and reduce the buildup of solidified alloy in the converter. The process reduces the amount of added flux materials, limits the amount of refractory protectant, increases converting capacity, throughput, and reduces PGM losses. Additionally, recycling converter slag and high-grade slag can further reduce PGM losses and increase overall PGM recovery. The process also reduces the time periods required for melting the alloy pool and converting the collector alloy, and allows for more efficient oxidation of the alloy.

Problems solved by technology

While the PGM are dilute in the furnace slag, nevertheless these losses can be significant due to the high volume of slag and a general inability to economically recover the dilute values.

There are a number of drawbacks associated with known converters and converting processes preventing them from being practically implemented to process PGM collector alloy generated from smelting catalyst materials.

The converting process can be relatively slow.

Moreover, the converting process is exothermic, and the rate of oxygen addition is generally limited to avoid excessive temperatures.

Further, the severe conditions in the converter, especially at high oxygen injection rates, lead to corrosion and short lifespans for refractory lining.

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