Modifying water circulation of minerals processing plants for higher recovery, grade and environmental reasons
No Thumbnail Available
URL
Journal Title
Journal ISSN
Volume Title
Insinööritieteiden korkeakoulu |
Master's thesis
Authors
Makarov, Artem
Date
2020-08-17
Department
Major/Subject
Mcode
Degree programme
Master's Programme in Water and Environmental Engineering (WAT)
Language
en
Pages
51+4
Series
Abstract
Current thesis aimed to examine the possibilities to modify water circulation system of minerals processing sites that are working in concentration of sulphide ores. Such sites are facing the issues of thiosalts content in both recycling process water and water streams to be discharged into the environment. Recent studies confirmed that high enough concentration of thiosalts are damaging the site production in terms of worsened efficiency in flotation process leading to lower grade and recovery of the final products. Indirect toxicity of thiosalts for receiving water bodies has been also proved in latest studies. Conventional Fenton method for oxidizing thiosalts with liquid solution of hydrogen peroxide is considered to be efficient but yet costly and hard in an operational control. Current research was meant to find alternative solution of more advanced oxidation in a form of sparging the vaporized hydrogen peroxide into the process water containing thiosalts. It was presumed that increased interaction surfaces for oxidation and decreased contact time consequentially would result in more rapid oxidation and less reagent usage. The laboratory experiments have been conducted with the process water sample from the minerals processing site comparing both conventional Fenton and novel method of thiosalts oxidation. Promising results have been achieved for the advanced oxidation method in terms of process water treatment goals, where the removal percentage does not need to be as ideal as the environmental limits. For the removal of thiosalts till the needed natural levels for discharge water streams, the vaporized hydrogen peroxide yet has proved itself not as efficient. Novel method could reach 89% removal of thiosalts but within quite unrealistic retention time, compared to more rapid conventional Fenton, which reached more than 95% removal rates. The achieved results have been utilized in modeling and simulation work in order to get a full overview of the processes including needed chemical amounts for different volumetric flows of process water and impurities concentration as well as sludge production potential. As a final result, various alternatives and methods for modification in water circulation systems with thiosalts challenges have been compared technologically and economically regarding both thiosalts and sulphates removal technologies from process water streams. Those included methods of hydrogen peroxide oxidation, evaporation, adsorption, ettringite precipitation and membrane filtration. Assessment has been carried out from different perspectives of sustainability, feasibility, investments needed and operational costs to be expected during long term operations of the plants. Several ways towards the continuation of the research have been proposed in order to make sure that both plant and environment could achieve the desired benefits from technologies chosen.Description
Supervisor
Vahala, RikuThesis advisor
Yazdani, Maryam RozaSaari, Eija
Keywords
thiosalts, sulphates, minerals, processing, water, treatment