High-temperature processing and recovery of autocatalysts

Abstract

This paper presents the results from an experimental study of the thermal method applied for obtaining platinum-group metals (PGMs) by melting used autocatalysts in an 80 kVA plasma reactor, using suitable fluxes and a reducing agent. As the collector of noble metals, grey cast iron was used during the melting. The melt products were the alloy, inert vitrified slag, syngas and fly ash. In the alloy, when melting the catalyser based on cordierite, there was 99.27 % PGMs and 99.00 % in the case of Cr/Ni-strip catalysts. The loss of PGMs in the slag during the melting of cordierite catalysts was 0.34 % and for Cr/Ni catalysts, it was 0.26 %. A chemical analysis of the ash confirmed that in addition to the mechanically removed CaO, SiO2, MgO, Al2O3, it also contained condensed vapours of Fe+PGMs. During the melting of the cordierite catalyst, the ash contained 0.40 % of the refined metals, while 0.74 % was the figure for the Cr/Ni-strip catalyst. The synthesis gas from the process had a very low heating value (0.16 MJ m -3 or 0.24 MJ m -3 ). Keywords: waste, catalyser, platinum-group metals, plasma technology V tem~lanku avtorji predstavljajo rezultate eksperimentalnih raziskav termi~nega postopka pridobivanja kovin platinske skupine (PGM, angl.: Platinum Group Metals) s taljenjem izrabljenih avtomobilskih katalizatorjev v 80 kVA plazemskem reaktorju z uporabo primernih talil in redukcijskega sredstva. Kot zbiralnik plemenitih kovin je bila med taljenjem uporabljena siva litina. Produkti taljenja so zlitina, inertna steklasta`lindra, sintezni plin in pepel. V zlitini je bilo pri taljenju katalizatorja na osnovi kordierita koncentriranih 99,27 % PGM, pri katalizatorjih s Cr/Ni trakom pa 99,00%. Pri taljenju kordieritnih katalizatorjev se je v`lindri izgubilo 0,34 % PGM, pri Cr/Ni katalizatorjih pa 0,26 %. Kemijska analiza pepela je potrdila, da poleg mehansko pridobljenih oksidov CaO, SiO2, MgO, Al2O3, le-ta vsebuje tudi kondenzirane pare Fe in PGM. V pepelu se je pri taljenju katalizatorja na osnovi kordierita nahajalo 0,40 % plemenitih kovin, pri katalizatorju s Cr/Ni trakom pa 0,74 %. Sintezni plin iz procesa taljenja je imel zelo nizko kurilno (kalori~no) vrednost (0,16 MJ m -3 oz. 0,24 MJ m -3 ).