A study of the potential improvement of Sydvaranger Gruve´s process water treatment through experiments with different flocculants and coagulants

Abstract

Mining is the process or industry of extracting valuable minerals or other geological materials from the earth. The nature of mining creates a potential negative impact on the environment both during the mining operations and several years after the mine is closed. Over the years regulations designed to moderate the negative effects are adopted, and environmental issues and challenges have gotten more attention. The mining industries aim to improve production efficiency and at the same time take care of the environment according to best practice. The latter is the subject in this thesis, which aims to look at Sydvaranger Gruve AS’s use of chemical treatment of process water within the mining industry.

Flocculants and coagulants are chemicals that are used in water treatment in many industries. In this approach the water resource is limited and the aim is to treat the process water in order to recirculate it. Despite the same mineral being processed the process water will not have the same properties due to the huge variations of influencing factors. Some theory regarding water treatment with chemicals exists, but there are still many assumptions and a lack of understanding. There are many chemicals on the market and it requires a lot of testing to assure that the most efficient chemical is used in the process water treatment.

Sydvaranger Gruve AS is a mining company located North in Norway close to the Russian border. The company has a history that dates back over a hundred years and it is known for its pioneering development of technology to process taconites, which is a low-grade ore. Sydvaranger Gruve AS is currently using a cationic coagulant with low molecular weight, Magnafloc LT 38, in combination with a slightly anionic flocculent with a medium molecular weight, Magnafloc 10.

The study presented in this thesis is based on existing literature, though the previous work in this area has proved to be limited. It is challenging to conclude the specific chemical reaction due to lack of literature, but assumptions will be made based on theory.

In this thesis the process is presented in the form of description and flowcharts. Influencing factors regarding the process and geology are identified and discussed. The existing theory regarding chemical water treatment is presented and various chemical products for water treatment are gathered from different suppliers. The procedure for testing is presented, the testing is performed in three main stages and are evaluated both quantitative and qualitative. A lot of effort has been put into finding a suitable chemical or a combination of chemicals and many chemicals were tested through experimental work. Zetag 8187, a strongly cationic flocculent with a medium high molecular weight, is the chemical that has shown the best result and has been examined further to compare its behavior against the chemicals in use today.

A quality assurance has been performed to illustrate the reliability of the test methods and procedures despite the large variations in the influencing factors. A risk assessment based on environmental issues has been done on the final chemical recommendation, Zetag 8187, versus the chemicals that are in use today, Magnafloc 10 and Magnafloc LT 38, in order to see if there are any environmental benefits by substitution of chemicals, other than performance. The results are presented and final recommendations are made based on the tests and other observations. Despite proving good results in small-scale tests, extensive plant scale tests should be carried out to verify the results shown in the thesis.