TY - THES

T1 - Evaluation of the mechanisms of CO2-optimised chlorination reactions during the multi-metal recovery from precipitation residues of the zinc industry

AU - Lerche, Roberto

N1 - embargoed until null

PY - 2021

Y1 - 2021

N2 - Millions of tons of iron precipitation residues, predominantly jarosite, are accumulating in the primary zinc industry every year. Regardless of environmental concerns and its potential use as a secondary resource, the material is still commonly disposed of since none of the numerous already developed recycling techniques could prevail. In recent years, a new approach for a CO2-optimized multi-metal recovery from the residues jarosite and goethite by means of a selective chlorination extraction has been proposed. In this thesis, the theoretical and practical potentials of this process have been thoroughly evaluated. A comprehensive simulation algorithm was developed in the Python programming language which gave profound insights into the thermochemical aspects of chlorination reactions by support of the FactSage Equilib computational software. The algorithm allows the simultaneous iteration of relevant reaction parameters such as temperature, pressure or stoichiometry and offers a high degree of freedom in the choice of reactants. Furthermore, statements about the influences of different chlorination agents, atmospheres and secondary components are possible. Based on the results of tens of thousands of different simulated scenarios, it was found that the carbon- free extraction of the valuable metals indium, silver, zinc and lead from a calcined jarosite material in the form of volatile chlorides is already possible at moderate temperatures and low chlorine additions, while the undesired iron phase remains in the solid residue. Since real processes are influenced by further factors that cannot be easily simulated on the basis of thermodynamics, a kinetic study of four small-scale chlorination campaigns was carried out to identify reaction mechanisms in more detail. An automated interpretation of a set of DSC measurements at different heating rates was realised by developing another Python algorithm. This facilitated the determination of the sequence of chemical steps in the chlorination of Ag2O, In2O3 and ZnO with AlCl3.6H2O, MgCl2.6H2O and FeCl3.6H2O, respectively, and determined the activation energy of relevant reactions according to the Kissinger method. Due to its general applicability to any other suitable reactions, the algorithm poses the potential to facilitate future kinetic studies in multiple fields of science.

AB - Millions of tons of iron precipitation residues, predominantly jarosite, are accumulating in the primary zinc industry every year. Regardless of environmental concerns and its potential use as a secondary resource, the material is still commonly disposed of since none of the numerous already developed recycling techniques could prevail. In recent years, a new approach for a CO2-optimized multi-metal recovery from the residues jarosite and goethite by means of a selective chlorination extraction has been proposed. In this thesis, the theoretical and practical potentials of this process have been thoroughly evaluated. A comprehensive simulation algorithm was developed in the Python programming language which gave profound insights into the thermochemical aspects of chlorination reactions by support of the FactSage Equilib computational software. The algorithm allows the simultaneous iteration of relevant reaction parameters such as temperature, pressure or stoichiometry and offers a high degree of freedom in the choice of reactants. Furthermore, statements about the influences of different chlorination agents, atmospheres and secondary components are possible. Based on the results of tens of thousands of different simulated scenarios, it was found that the carbon- free extraction of the valuable metals indium, silver, zinc and lead from a calcined jarosite material in the form of volatile chlorides is already possible at moderate temperatures and low chlorine additions, while the undesired iron phase remains in the solid residue. Since real processes are influenced by further factors that cannot be easily simulated on the basis of thermodynamics, a kinetic study of four small-scale chlorination campaigns was carried out to identify reaction mechanisms in more detail. An automated interpretation of a set of DSC measurements at different heating rates was realised by developing another Python algorithm. This facilitated the determination of the sequence of chemical steps in the chlorination of Ag2O, In2O3 and ZnO with AlCl3.6H2O, MgCl2.6H2O and FeCl3.6H2O, respectively, and determined the activation energy of relevant reactions according to the Kissinger method. Due to its general applicability to any other suitable reactions, the algorithm poses the potential to facilitate future kinetic studies in multiple fields of science.

KW - Reststoffrecycling

KW - Fällungsrückstand

KW - Zink

KW - Indium

KW - Silber

KW - Blei

KW - Eisen

KW - Jarosit

KW - Goethit

KW - Chlorierung

KW - selektive Verflüchtigung

KW - Metallrecycling

KW - Automatisierung

KW - Simulation

KW - Programmieren

KW - Python

KW - FactSage

KW - DSC

KW - DTA

KW - Kinetik

KW - Reaktionsmechanismus

KW - Aktivierungsenergie

KW - Kissinger

KW - Residue recycling

KW - Precipitation residue

KW - Zinc

KW - Indium

KW - Silver

KW - Lead

KW - Iron

KW - Jarosite

KW - Goethite

KW - Chlorination

KW - Metal recycling

KW - Automation

KW - Simulation

KW - Programming

KW - Python

KW - FactSage

KW - DSC

KW - DTA

KW - Kinetics

KW - Reaction mechanism

KW - Activation Energy

KW - Kissinger

M3 - Master's Thesis

ER -