The systems engineering of automated fire assay laboratories for the analysis of the precious metals

[摘要] ENGLISH ABSTRACT: The objective of this work was to achieve a completely automated fire assay systemfor the analysis of process control samples on a flotation plant in less than 120minutes. With this in mind, a systems engineering approach was undertaken. Thephysical and chemical characteristics of the technology for each subsystem wereinvestigated in turn and the critical factors that influenced accuracy, precision andanalysis time were identified and optimised.Some of the key developments achieved during this work were:· Existing technology for the sampling, filtering, drying and grinding of flotationplant samples were evaluated and where necessary, modified for thisapplication.· The fusion system was totally re-designed with a bottom-loading configurationcalled FIFA (Fast In-line Fire Assay) to make automation with a central robotpossible. With the fast fusing flux developed, a quantitative collection of theplatinum group elements with a fifteen-minute fusion was achieved compared toan hour for the classical method.· A robust automated separator system was developed to isolate the leadcollector from the fusion in the molten state thereby separating it quantitativelyfrom the slag. This allowed the automation of the entire fire assay process.· Methods to prepare lead standards for calibration were developed. These wereused to optimise analytical protocols for the analysis of platinum group elementsin lead using a spark optical emission spectrometer. This made it possible toaccurately determine the quantities of platinum group elements in lead samplesprepared by the automated fire assay system.· A fully automated system was developed that could meet the accuracy andprecision requirements for the analysis of tailings and feed grade samples inconcentrator slurry streams in less than one hour compared with the 24-72hours required when using classical methods.The new fire assay technology including flux, FIFA system, oxygen lance andseparator were all patented along with the automation vendor. This technology hasmade the first fully automated fire assay system a reality.

[发布机构] Stellenbosch University