Browsing by Author "Kleemola, Lotta"

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On the Kinetic Behavior of Recycling Precious Metals (Au, Ag, Pt, and Pd) Through Copper Smelting Process
(2021-09) Wan, Xingbang; Kleemola, Lotta; Klemettinen, Lassi; O’Brien, Hugh; Taskinen, Pekka; Jokilaakso, Ari
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
The recycling and recovery of precious metals from secondary materials, such as waste-printed circuit boards, are an important area of circular economy research due to the limited existing resources and increasing amount of e-waste produced by the rapid development of technology. In this study, the kinetic behavior of precious metals Au, Ag, Pt, and Pd between copper matte and iron-silicate slag was investigated at a typical flash smelting temperature of 1300 °C in both air and argon atmospheres. SEM–EDS, EPMA, and LA-ICP-MS-advanced analysis methods were used for sample characterization. The results indicate that precious metals favor the matte phase over slag, and the deportment to matte occurred swiftly within a short time after the system had reached the experimental temperature. With increasing contact times, the precious metals were distributed increasingly into the sulfide matte. The distribution coefficients, based on experimentally measured element concentrations, followed the order of palladium > platinum > gold > silver in both air and argon, and the matte acted as an efficient collector of these precious metals. The obtained results can be applied to industrial copper matte smelting processes, and they also help in upgrading CFD models to simulate the flash smelting process more precisely.
Precious metals reaction mechanisms in copper matte-slag system
(2019-07-31) Kleemola, Lotta
Kemian tekniikan korkeakoulu | Master's thesis
The amount of WEEE generated annually is growing, and effective means of recycling are required, in order to sustainably handle the growing waste quantity. WEEE is not only considered waste, but also a secondary resource of materials, including precious metals. Electronic devices can contain precious metals more than their respective primary ores, which in many cases are depleting. Pyrometallurgical methods of WEEE recycling are advantageous, because the processes can accept many forms of scrap and there are existing facilities for WEEE smelting. Downside of pyrometallurgical recycling route is the environmental concern that arises from high level of energy consumption. In this thesis, the time-dependent behaviour of precious metals in copper matte-slag system in simulated copper flash smelting conditions is studied. In the literature survey, the distributions of precious metals in equilibration studies were investigated. In the experimental part, the behaviour of precious metals is studied in air and argon atmospheres. Precious metals selected for this work are gold, silver, platinum and palladium. Compositional data was acquired with SEM-EDS, EPMA and LA-ICP-MS. The analyses indicated that the precious metals favour the copper and iron-bearing phases over slag phase and that formation of precious metal droplets and migration to matte phase begin almost instantly, when the system reaches high temperature. Precious metals concentrated in the matte phase as large droplets or smaller cluster distributed in the matte. There was significant scatter in the results with 300 s and 20 min contact time in air and argon atmospheres, respectively. For future work, it is suggested that the contact times in the proximity of 300 s in air atmosphere and 20 min in argon atmosphere are studied in more detail. The scatter in the results suggest the existence of some rate-limiting factor. In addition, the chemical dissolution behaviour of precious elements and their possible existence as sulphides in matte would require more detailed analysis. The formation of large precious metal droplets in air atmosphere should be studied further and the analysis of sample cross sections should be more extensive in order to find possible large droplets.
X-ray tomography of refractory bricks
(2023-10-10) Ahmed, Muhammad
Kemian tekniikan korkeakoulu | Master's thesis
This thesis explores the application of X-ray tomography (XRT) combined with image analysis software to locate and quantify the porosity and metal content of refractory brick samples obtained from converter s. The versatile approach of XRT and PerGeos software assists in obtaining 2D and 3D representations of bricks different phases. The aim is to visualize and quantify the distribution of porosity and metal content within the brick samples and to extract valuable insights from the results. The experimental setup involved drilling tubular brick samples with a carefully chosen diameter and placing them in an acrylic glass tube for subsequent XRT analysis. The XRT machine was configured with specific parameters such as voltage, current, resolution, and filter, to obtain high-quality images with minimal artifacts. The software approach, especially the threshold limit selection, played a crucial role in accurately segmenting porosity and metal phases in the obtained images. The analysis of the brick samples using PerGeos software showcased impressive precision in phase separation. The results indicated that metal content was significantly higher at the hot end of the samples, while the cold end exhibited lower metal penetration. Furthermore, the positioning of the refractory brick within the converter also impacted the eventual penetration of molten metal and mate. The software analysis provided precise data on the volume fraction change with each slice of the image for each sample, which complemented with the observations from 3D image analysis. Furthermore, PerGeos enabled the identification and characterization of closed and interconnected pores, aiding in the comprehensive evaluation of the samples porosity. However, the study also encounters limitations, including operator dependency during phase selection and the trade-off between image resolution and file size. Beam hardening artifacts in some samples posed hurdles, but the software and accurate machine input helped mitigate this impact.