Eliminate mine waste and transform it into soil, sand and aggregates for the construction & agriculture sectors
The consortium’s approach offers several innovative technologies to support our proposal that include:
- Innovative bioleaching reactor using floating agitators to mix and suspend solids in solutions as well as inject gases recovery into the pulp.
- A flexible toolbox for transforming the remaining minerals into construction materials via carbon capture and utilisation or the use of the tailings as cement constituent or artificial sand.
- Soil remediation for site rehabilitation, erosion controls or intensive agriculture.
- A collaborative monitoring and predictive system and tools to provide current and future underground water quality and reserves according to varying mining, industrial, farming and urban developments. This also integrates climate change.
- Optimising water reuse using soil/sub-soil filtration, studying nature-based solutions and studying cost efficiency of solutions in water and water management.
- The development of collaborative digital platforms such as systems successfully operating in other industries by Dassault Systèmes.
The approach uses mainly existing solutions such as soil rehabilitation, tailings filtration, waste recycling, collaborative platforms and aquifer monitoring, but also involves advanced innovative solutions such as carbon capture by mineral carbonation. This is innovative, as it combines these existing or new technologies to create a flexible collaborative waste and water management tool covering an extended area around the mine site.
We transform your tailings into a resource
We eliminate hazardous waste storage dams in the future
We value sustainable solutions that care for businesses, water, communities and the environment
The conceptual process flow stream is continuous from one stage to the next, without double handling and represented in Figure 1. It’s expected that most of the process water recovered would be pumped back to the concentrator for recycling.
The sequencing of the process flow would be determined upon further testing and investigation of the tailing’s material physical and chemical characteristics.
Modelling existing socio economic and geographical conditions
Innovative Collaborative platform
The collaborative platform will be using the two platform already created by two of the members of our team.
The 3DEXPERIENCE platform provides a simple unified environment for all personnel in an organisation to communicate, collaborate and innovate beyond what can be achieved with traditional software products. The 3DEXPERIENCE platform provides a simple unified environment that supports product data and other critical information to be transferred seamlessly between all systems, employees and trading partners via a single, easy-to-use interface.
Powered by Industry Solution Experiences – based on 3D design, analysis, simulation, and intelligence software, the 3DEXPERIENCE platform is available both on premise and on cloud.
MétéEAU de nappes
(integrated aquifer management)
With an easy-to-use web interface, MétéEAU Nappes (fig 3) enables better anticipation of available water levels and restrictions on use decided locally during drought episodes.
Other innovative technical key processes to integrate
Biohydrometallurgy is well established for the treatment of sulphide minerals, where iron and sulphur-oxidising bacteria are used for the leaching of low-grade copper ores and the pre-treatment of pyritic gold ores and concentrates. The bacterial treatment of refractory gold concentrate using Stirred Tank Reactors (STR) is an industrial reality and the interest of using STR for the treatment of other minerals, such as the base metal sulphides like cobalt, has already been demonstrated.
An innovative bioleaching reactor using floating agitators to mix and to suspend solids in the solution as well as to inject gases in the pulp is under development. The results obtained confirmed the compatibility between the bacteria and the agitation device, the ability to use oxygen enriched air with no deleterious effect on the bacteria and the ability to regulate the temperature without an external temperature control system.
This new bioreactor concept aims at applying bioleaching to low-grade sulfidic materials (primary ores as well as tailings); it will have low CAPEX (316L stainless steel reactors replaced by ponds equipped with polymer liners)
This new bioreactor concept aims at applying bioleaching to low-grade sulfidic materials (primary ores as well as tailings); it will have low CAPEX (316L stainless steel reactors replaced by ponds equipped with polymer liners), it will be a very flexible and robust technology easy in terms of maintenance. All tailings containing residual sulphides and presenting some Acid Rock/Mine drainage phenomena, are a potential target for the new technology. It is proposed that the bioleaching facility would be located close to the concentrator.
As a result, sulphides are oxidized to sulphates (acidity production in the reactor as to be neutralized, the is done by adding calcite (for instance) to the Pregnant Leach Solution (PLS) at the output of the reactor/pond and metals are leaching most often under the form of cations in the PLS. Further hydrometallurgical steps allow to separate cations and recover metals (precipitation, electrowinning, cementation …).
Dewatering and Sorting
Traditional mineral processing equipment would be used to dewater, classify and sort the materials using screens as required. This would be determined after further testing and investigation of the tailing’s material physical and chemical characteristics. It’s expected that most of the process water recovered would be pumped back to the concentrator for recycling.
CO2 sequestration and Construction Materials
After taking out the valuable metals, the remaining minerals can be utilized for carbon sequestration and/or the production of construction materials. The optimal process and product choice is not generic for all mine tailings, as it depends to a large extent on the tailings mineralogy and the location of the mine site and its local market. To take this into account, the objective is to develop a decision tool: a software toolbox that can estimate techno-economic performance of a certain tailing based on the tailings’ characteristics and the location of the mine. Based on this information the toolbox will return suggestions for pathways to downstream use and products to produce. The VITO technologies that will be included in the toolbox are:
- Carbon sequestration: the carbonation of calcium/magnesium silicate minerals
- Supplementary cementitious material: the use as cement and concrete constituent
- Artificial sand: the use of agglomerated tailings as alternative for natural sand
The first option involves the use of tailings as raw material for carbon sequestration. The calcium/magnesium silicate minerals in the tailings are transformed into calcium/magnesium carbonate (CaCO3 – MgCO3) by the reaction with elevated concentrations of CO2. Before this transformation occurs, the tailings can be pressed to a block or pelletised into aggregates to shape the material. The reaction with CO2 causes hardening of the material in this shape and thus enables the use of these materials as construction products. Blocks similar to those shown in figure 4 below can be used for on-site constructions or sold as a construction product. The carbon sequestration process provides the opportunity to market the carbon credits. The current European price is approximately €25/tonne. The construction products facility could be located close to an industrial centre with suitable transport infrastructure.
A second option presents the use of the tailings as a fine filler or binder component in cement bound products. This presents the highest added value of the different options, but the lowest market volume.
This is thus an viable options for relatively small mines which are relatively close to construction product markets. However, compliance to demanding technical material specifications, needs to be verified and may enable destine only a fraction of the tailings to this type of use.The use as artificial sand enables the application of the tailings as construction aggregate, providing access to a much larger market volume, however at lower market value. The tailings are agglomerated in the presence of a small amount of binder or hardened by exposure to CO2. This process is currently being upscaled to the pilot level at VITO
The decision tool will be constructed using data obtained in the project. A high number of tailing samples will be studied (depending on the Amira sponsors) and their quality in the above mentioned processes and products evaluated. Finding a link between the tailing characterization and product performance will enable the programming of a generic algorithm that can enhance the wide applicability of the toolbox and evaluate the technical behaviour of tailings that were not studied. Thus, apart from an accurate view on the techno-economic performance of the tailings provided by Amira members in the VITO technologies, the toolbox can be used to assess other tailings or industrial residues in general. This technical evaluation will be presented as a quality score of a certain tailing in the VITO technologies. The technical evaluation can be coupled with potential economic value, which will form the basis of the decision algorithm together with the process parameters which will provide CAPEX and OPEX estimations. On top of the potential economic profit, the CO2 captured in minerals or CO2 saved by replacing primary materials such as Portland cement can be calculated. The result is a generic toolbox, which provides an effective, efficient and flexible analysis of the tailing quality and sustainability in construction materials. The utilization of this toolbox will boost the competitiveness of the mining industry by triggering the cost-effective exploitation of tailings in construction materials. Vast amounts of previously untapped resources are unlocked.
Figure 4 – Carbstone Construction Projects
SoilCyclers is the first and only accredited mixing contractor for RemBind in Australia and holds the worldwide distribution rights for usage of RemBind in non-PFAS applications in the mining industry. RemBind is a product developed in conjunction with CSIRO that permanently immobilises PFAS and several other heavy metals and contaminants including arsenic in soil. The product is completely natural and doesn’t interfere with plants or animals and has been independently proven to bind these elements for at least 1000 years in both a normal rainfall environment and an acid landfill environment.
One of the challenges with a circular economy in mining or infrastructure where the volumes of waste material can be enormous, is that there is rarely a customer or combination of customers big enough to cope with the quantity of material available.
SoilCyclers specialises in creating circular economy opportunities for large infrastructure projects, mine sites and waste facilities in Australia. helping client’s create a resource they can use out of waste they need to dispose of to overcome the traditional challenges of lack of local markets for recycled products.
A recycling plant will need to be in a strategic location close to existing transport infrastructure. The preferred location would be either on the mine site or next to the urban centre connected to the mining operation. Ideally, it would use an area provided by the mining company where space is readily available. The plant would need storage area for the raw material classified according to the product type. Another area will be necessary to store the product complete and ready for distribution.
Raw decontaminated and stabilised material not readily usable for specific product can be stacked on the mine site in areas away from potential future mining site. They should be easily accessible for usage such as civil work or backfill.
The plant should be located next to existing transport infrastructure. There is an expectation that if the plant is located on the mine site, an agreement will be made to use their infrastructure. This may require some modification.
The bioleach process goal is to extract all the metals (Cu, Pb, Ni, Sn, Co, Cu, Al, Mg) in the PLS solution to be further processed through an existing BHP solvent extraction-electrowinning plant. All solid waste from the bioleach process would be further processed for use as construction products with any residual materials transformed into organic soil suitable for rehabilitation. Refer to BRGM YouTube video below.
The optimal division of the tailings over the uses as construction products and soils, is dependent on the tailing characteristics. This will be looked at an implemented in the decision tool.
Where the opportunity exists, the value of the tailings as filler material for on-site applications such as backfill for abandoned sections of the mine or a road base in on-site infrastructure works can result in limiting the consumption of new natural resources.
The tailings could be used to produce construction industry building blocks or pelletised artificial aggregates for infrastructure works. The value is two-fold with the construction industry products and carbon capture. The use of CO2 to harden the material results in a negative greenhouse gas emission, which can create income via carbon emission trading. There isn’t any waste generated in any of these applications. Any remaining material, between 10 and 50% would be transformed into organic soil suitable for rehabilitation.
This could be used on the mine site as part of the mine rehabilitation process. The process doesn’t generate any waste. All natural binding agents are mixed with the material for remediation to build a structure and be converted into soil. Carbonated light weight aggregates could be integrated to improve the soil properties and improve water holding capacity.
Figure 5 – Illustration of Plant and Logistical Concept
Proof-of concept/pilot stage
This stage will be the final critical step to validate the model. This will be adapted to the local conditions.