Integrating pyrometallurgy and robotic systems engineering: Fully automated fire assay laboratory for rapid PGE analysis
The pyrometallurgical fire assay still remains the only widely accepted technique to concentrate platinum group elements (PGE) and gold from low grade ores and metallurgical intermediates. The traditional technique is labour intensive batch process where samples are not necessarily processed in a first-in-first out (FIFO) sequence. To get to the point of making fire assay based information useful for process control, a number of challenges had to be addressed. The process of sample preparation, the whole fire assay process and the final analysis for the PGE had to be automated so that the samples would be processed rapidly and analysed in a FIFO sequence. This is particularly difficult due to the amount of materials handling in conjunction with the high temperatures associated with the fire assay. The flux blend had to be "designed" or optimised for rapid fusion, insignificant metal entrainment and effective (quantitative) transfer of the PGE to the lead collector phase. This could only be done through a re-evaluation of the pyrometallurgical principles that control the slag chemistry so that the fusion sequence, slag viscosity and slag-metal interfacial tensions are well controlled. The slag separation from lead alloy had to ensure that no slag contamination of metal occurred. This was achieved through furnace re-design, and the development of a novel slag separator. Both stages (fusion and separation) had to be integrated and designed for robot manipulation and materials handling. Moreover, the traditional cupellation step of fire assaying had to be eliminated. To achieve the last stage an analytical methodology had to be developed to automatically weigh the lead and determine the concentration of the individual PGE using spark-OES based on the lead-PGE alloy matrix. The whole process, automated with a robotic carousel and meeting all the required objectives, was successfully implemented at Anglo Platinum. Turnaround time on analysis was reduced from 24 h to 60 min from the submission of a slurry sample to the laboratory. The accuracy of the new analytical method was confirmed using certified reference materials. © 2005 Elsevier Ltd. All rights reserved.