Terrafame pilots four new solutions for process water management at the mine 4.11.2016 14:33
Terrafame Group Ltd.’s water technology project has progressed to the pilot phase where the purification solutions of the waters at the mine area will be tested in practice at the Sotkamo mine
Minimising the sulphate concentration would further decrease the mine’s environmental effects
Based on preliminary development work, Terrafame could also produce valuable fertiliser raw materials as a by-product
Terrafame Group Ltd.’s water management development project, the so-called Ariel project, has progressed to the pilot phase. Four technical solutions will be piloted in practice at Terrafame’s mine in Sotkamo. The solutions would help to clearly decrease the mine’s environmental effects further through minimising the sulphate concentration of the waters discharged from the mine area.
In addition to sulphate management, the studies carried out during the Ariel project have revealed business opportunities that the water management solutions could bring through new by-products.
The Ariel project started in autumn 2015. In June 2016, Terrafame Group Ltd. introduced the preliminary concept plan of the water management solution under which significant changes would be done in the management of sulphate, sodium and sulphur management and chemicals recycling at the mine.
The key changes would include partial or complete replacement of sodium hydroxide (NaOH), used as a neutralising agent in the process, with another agent, such as potassium hydroxide (KOH). However, the replacement of sodium hydroxide would increase the chemical costs of the mine. Therefore, the metals recovery plant process would be changed in the concept to utilise the value of the neutralising chemicals through possible new by-products.
“We have applied circular economy thinking in the Ariel project. By choosing new raw materials with the whole process in mind, it is possible to achieve synergies between different processes. By adding new phases into the process, it is possible to also make new products from the raw materials. When the resulting products can be combined with sulphate, we can answer the original challenge – decreasing the amount of sulphate,” says Jani Kiuru, Ariel Project Director at Terrafame Group Ltd.
“The laboratory tests carried out during summer and fall 2016 have shown that it would be possible to technically produce, for instance, financially significantly valuable potassium sulphate or potassium carbonate as Terrafame’s by-products which could be sold as raw material to the fertiliser industry. According to the current estimate, the financial effects of the shutdown of the water loops and chemical flows and selling of by-products could on a yearly basis increase considerably, up to tens of millions of euros. Investigation of the solution’s feasibility will continue in the ongoing pilot phase,” says Kiuru.
“This very moment, the water management and purification at Terrafame’s mine is handled with BAT technology so the mine is already operated in an environmentally sustainable way. In the Ariel project, we look for solutions that could further improve the mine’s water management on the long term and also enhance the mine’s business potential,” says Kiuru.
Terrafame Group Ltd. has applied for a patent for the new water management concept as well as a collection of individual innovations included therein. In addition, the parties involved in the development project have patents and applications related to their respective technologies.
During the summer and autumn, the Ariel project has focused on planning the pilot tests, building the pilot equipment as well as necessary modifications of the existing equipment to suit Terrafame’s production process. The four tests will start in phases between October 2016 and January 2017.
Four different technology solutions, realised by the Finnish companies listed below, will be tested in the pilot phase.
- Sofi Filtration is examining the removal of solids from the water circulating in the production process by testing the filter it has developed first at the metals recovery plant and, in the next phase, in the pre-treatment of the membrane purification equipment. The goal is to ensure water flow as consistent and suitable as possible for the new nanofilters as well as to increase the yield of Terrafame’s main products: nickel, zinc and copper.
- Skyscape is piloting a concept to replace the mine’s current reverse osmosis plant with a nanofilter (NF). In practice, the replacement would be done by switching the filter membranes. In addition, the concept would test different process operating procedure switches and material selections. The goal of Skyscape’s pilot is to enable the increase and maximal utilisation of the current filter capacity and to multiply the flow of clean water in the process without significant additional investments.
- Sulfator is developing so-called biological sulphate reduction that could result in, among other things, fertiliser raw materials, a more effective metals recovery process as well as improved material efficiency of the production process. In practice, the reject (the sulphate contained in the return flow) of the reverse osmosis plant will be reduced in the test to hydrogen sulphide in an anaerobic bioreactor. Then it will be examined whether the hydrogen sulphide formed in the bioreactor could be utilised in the metals recovery process. The alkaline solution formed in the bioreactor could possibly also be sold to be used as a raw material for fertiliser, bringing considerable additional income.
- OWA Group is piloting evaporation crystallisation with the goal of evaporating the water of Terrafame’s metals recovery plant and, in a later phase, to crystallise metal sulphates from the evaporation residue. Unlike the other pilots, OWA’s pilot will not be carried out at the mine but at OWA’s facilities, utilising water from the mine.
“Compared to the project’s earlier study phases, the piloting phase has a significantly larger scale. In addition, the pilots will be conducted at the mine, excluding OWA’s pilot, which allows the use of real feedwater in realistic conditions. Thus, we will have a considerably clearer picture of the feasibility and applicability of the solutions, thanks to the pilot phase,” says Kiuru.
Based on the pilots’ results, detailed techno-economic examinations will be conducted and, with them as a basis, it will be possible to progress to the development and planning phases which are supposed to finish by the end of 2017. The construction of the demo plant could start at the beginning of 2018 at the earliest.
For more information about the Ariel project’s previous phases, please see the press releases below:
Terrafame Group Ltd.
Project Director Jani Kiuru, Tel. +358 40 823 8471, firstname.lastname@example.org
CEO Matti Hietanen, Tel. +358 40 823 8806, email@example.com
Terrafame Group Ltd. is a special-purpose company wholly owned by the State of Finland. It is responsible for managing the state ownership and exercising the owner's power at Terrafame Ltd. Terrafame Group's role is to secure private supplementary financing and support the stabilisation and development of the mining company's operations. Terrafame Group is also responsible for helping the development of new technological solutions related to mine water purification.
Terrafame Ltd. is a Finnish multi-metal company producing primarily nickel and zinc by bioheapleaching at its mine located in Sotkamo. The aim is environmentally sustainable, safe and economically viable mining operations. Terrafame is owned by Terrafame Group Ltd.
Appendix 1: Background on the Ariel project
In autumn 2015, Terrafame Group Ltd. started a development and pilot project (the Ariel project) to find solutions to purify the mine’s waters and to reduce the sulphate concentration. Terrafame Group Ltd. is investing two million euros in the project.
In the project’s first phase in winter 2015, Terrafame Group held a mini demonstration application aimed at companies, research institutes and universities. A mini demonstration is a small project where a proposed water purification solution, process optimization solution, process engineering solution or other similar method that can be used to reduce the sulphate concentration of the waters discharged from mine will be experimentally and computationally demonstrated. In addition, the feasibility and the cost effects of the proposals will be assessed in a larger scale. The central precondition states that the solution should not increase the current costs of water management or production.
The project has progressed according to plan and, following the water management concept introduced in June 2016, significant changes in the mine’s sulphate, sodium and sulphur management and chemicals recycling would be carried out. The new water management concept would significantly decrease the mine’s environmental effects as well as improve the mine’s production efficiency and business potential.
The new water management concept in brief
The key changes would include partial or complete replacement of sodium hydroxide (NaOH), used as a neutralising agent in the process, with potassium hydroxide (KOH). The sulphate in the purified waters discharged from the mine is caused mainly by the sodium hydroxide, as the sodium it contains binds sulphate and thus reduces the effectiveness of the lime treatment used in water purification with regard to the sulphate.
Replacement of sodium hydroxide would increase the chemical costs of the mine. Therefore, the metals recovery plant process would be changed in the concept to utilise the value of the neutralising chemicals. The changes are related to management of process flows and upgrade of the reverse osmosis plant as well as to setting up entirely new processes parts.
Regarding solution flow at the metals recovery plant, the concept would mean shutting down the return solution flow to the bioleaching heaps. The increased amount of water caused by this change could be treated in the current reverse osmosis plant after its capacity is increased through modifying the processes. The potassium sulphate extracted in the reverse osmosis plant could be treated further, for example, by using forward osmosis or evaporation. The potassium sulphate could be sold as raw material for the fertiliser industry, for example. Alternatively, the concentrate could be fed into the bioreactor in order to process the potassium into potassium carbonate. Potassium carbonate is also used as fertiliser. The sulphur generated in the process could be utilised in the precipitation of metals.
The feasibility of the solutions mentioned above will be investigated in the piloting phase which has now begun.
The Ariel project has a steering group comprised of leading Finnish water specialists from several organisations, such as VTT Technical Research Centre of Finland, GTK Geological Survey of Finland, the Finnish Water Forum, Aalto University, Lappeenranta University of Technology and the University of Oulu.