Results

In this section, we present an abstract of the results that ENSUREAL consortium has achieved. The following scheme presents the WP’s division of the studies carried out on the modified Pedersen process.

WP1: Identification of exploitable raw materials sources and recommendations to reduce EU imports’ dependence

The objective of this WP was to identify and gather quality, cost and availability information on all possible Alumina sources, located within the European continent, suitable for the Pedersen method and secure enough quantity for the execution of the ensuing work packages.

Even, this WP was officially finished after the first year of EnsureAL project, AdMiRIS continues to advise the rest of the consortium on the best resources both outside and within Europe. At the moment, EnsureAL team has investigated so far samples from bauxite of East Med (Greece, Turkey) and Jamaica. Guinea bauxite samples will be used too.

Prior industrial and laboratory experimental evidence shows that karst Mediterranean type bauxites are suitable to be used as feed for the under-development EnsureAL process. Their main advantages are their high aluminum content, elevated iron content, lower content in various kinds of impurities, lower Loss on Ignition and lower content in fine particle material. Bauxite residues could be a potential raw material for the under-development Pedersen process as they can be successfully subjected to reductive smelting for the extraction of iron.

Moreover, limestone is need to EnsureAL proposed Pedersen process. There are plenty of limestone resources in EU spread out mainly in France, Spain, Italy, Greece, Adriatic countries, Romania, UK and Ireland and a considerable number of world leading EU companies in limestone and lime production. Therefore, the provision of limestone and quicklime is not expected to be a big issue in the determination of the location of a possible Pedersen plant.

A workshop on the raw materials for the improved Pedersen process was held in Greece in January 2018 with participants from the partners with an interest in the raw materials for the process.

 

 WP2: Pyrometallurgy: process design

The objective of this WP is to design and optimise the pyrometallurgical part of the ENSUREAL process.

The first task is dedicated to the first stage of the Pedersen process is smelting-reduction of the bauxite with lime and carbon addition in an electric furnace, led by NTNU. In the smelting reduction of bauxite, the production of slags with proper characteristics for further hydrometallurgical recovery of Al2O3 and pig iron have been investigated.

The research activities in WP2 are supported by advanced analytical techniques to understand the system further, the behaviour of the materials, and assess the results. Some typical examples of microscopic observations are presented in the photos below for representative slag and metal samples obtained from the smelting-reduction of bauxite.

The second task is dedicated to the Pre-reduction process design, led by SINTEF. The pre-reduction of bauxite in H2 gas was studied as a possible option to lower the CO2 emissions from the smelting-reduction process. The main purpose being the reduction of iron oxides from bauxite in solid-state using a TGA furnace as can be seen in the figure below. In the pre-reduction trial, the weight losses of the ore are continuously recorded to obtain information about the reduction rate. It was found that the increase in temperature and H2 concentration increase the reduction rate while conversions higher than 70% can be achieved within 20 min of reduction at a process temperature of 900°C. The process conditions for doing the direct reduction of bauxite ore can be optimized so that a high metallization degree is obtained with not significant unreduced iron oxide.

WP3 – Hydrometallurgy: process and by-products’ recovery design

The objective of this WP is to optimize the parameters of the following downstream processing of slags before TRL7 demonstration (in WP4).

In the Pedersen leaching process, soluble calcium aluminate phases are imperative for successful alumina extraction. The main restraints for the optimization of Al extraction are: (1) the demand for minimum free Na2CO3 content in the pregnant aluminate solution, and (2) the surface precipitation of CaCO3 on the solid/liquid interface. To meet the first demand, agitation leaching experimental work was narrowed to Na2CO3 leaching solutions of low concentration. To meet the second demand, a dedicated mechanochemical reactor was set up to simultaneously achieve leaching of Al and breaking of the CaCO3 layer. In the photo there is Equipment used for mechanochemical leaching of Calcium Aluminate Slags.

Work performed by NTUA and NTNU confirmed early on in the course of the research that calcium carbonate is precipitated on the surface of slag particles, leading to a passive layer that inhibits further leaching.

The second task is to obtain alumina hydrates precipitation from the pregnant alkaline solution. The precipitation of alumina hydrates via carbonation (CO2 gas addition) is the most critical step in the Pedersen process. Considering the strict properties of metallurgical alumina, any deviation from excellence can have significant effects in the viability of the process.

As seen in the picture, a flowmeter to measure the flowrate of any gas in the outlet in line with a was installed and a CO2 analyzer to measure the percent of CO2 on the outlet. Combining these two measurements, we can have the knowledge of flowrate of CO2 on the outlet. Also, the CO2 analyzer is equipped with a pump. When the carbonation ends, since the reactor is filled up with CO2 gas above the liquid surface, gas is pumped until the CO2 analyzer shows 0% of CO2. This, along with the measurements taken during the experiments enables us to have a total understanding of how much CO2 was totally consumed for each experiment.

The 3rd task is the calcination of alumina hydrate precipitates. This task studies the calcination of gibbsite and boehmite, in order to be further upscaled.

The status of this task is that the Aluminium hydroxide produced by the Bayer process was sent from AoG to Outotec to benchmark the fluidized bed process. Later aluminium hydroxide produced in WP 4 will be tested to be compared.

The last task is to enable the recovery of REEs and Sc from the residue of the alkaline leaching of slags. The residue (Grey Mud) from the alkaline leaching of slags with a sodium carbonate solution contains almost all of the REEs as well as Sc contained in the Bauxites.

The Greek Bauxite that is being explored as a candidate resource for the Pedersen Process contains amounts of Sc, Y and Rare Earth Elements (REE) in the last task of this WP. These elements remain trapped in the Grey Mud as, in the conditions applied at the leaching stage, they cannot dissolve in the aluminate solution.

Scandium concentrations have been analysed for the raw material, the slags and grey mud by SINTEF. Moreover, Michail Vafeias and Elena Mikeli from NTUA, along with two thesis students, explore two different paths to extract REEs. The first one will use sulfuric acid as the extractant acid. The second one hydrochloric acid. Both paths are challenging, as the makeup of the Grey Mud suggests.

In the image it is presented the reactor set up that is being used in the leaching of Grey Mud with Acids.

WP4: Demonstration

The objective of this WP is to take WP1, WP2 and WP3 recommendations for the upscaling to TRL7 and demonstrate the technologies proposed, integrated, in an industrial setting for different raw materials.

In the first step MYTILINEOS has tested the smelting of Bauxite Residue in its 1MVA Electric Arc Furnace to produce pig iron and slag (photo 1).

Photo 1: BR smelting at MYTILINEOS Pyro Plant

With the appropriate lime fluxing (lime sourced from CaO Hellas) during the BR smelting process a slag can be engineered where alumina oxides are selectively leachable in sodium carbonate solutions. To demonstrate this, more than 500 kg of BR slag were produced at the MYTILINEOS EAF pilot under conditions that lead to the formation of rich calcioaluminate slag of specific minerology.

Photo2: Mayenitic slag produced at MYTILINEOS and gradually grinded to below 500 μm

This slag was crushed and grinded below 500 μm (photo 2) and then 300 kg of it was leached at MYTILINEOS Hydro Pilot plant with sodium carbonate solution, leading to the production of app 3 cubic meters of alumina bearing solution and 250 kg of a leaching residue called ‘grey mud’. Grey mud (mainly calcite with calcium-silicates and calcium-titanate impurities) can be used in building and agricultural applications, or it can be leached to recover critical raw materials like Scandium.

Photo 3 – Left MYTILINEOS Hyrdo Pilot, Right: Grey mud produced after slag leaching

The alumina bearing solution produced was tested for direct alumina precipitation through CO2 gas neutralization, resulting in a trihydrate alumina with less than 1%wt soda and silica impurities, respectively.

Photo 4: Alumina precipitation with CO2; Alumina produced at MYTILINEOS Hydro Pilot

The last task is the alumina calcination led by Outotec. The approximately 30 kg of alumina produced over multiple precipitation cycles to increase particle size distribution, will be sent to Outotec for testing in it’s calcination demo plant.

The flowsheet will be demonstrated also with Bauxite ore as the starting material to end up with a more pure alumina product- comparable to the established Bayer process. To this end a Rotary Kiln has been installed at the MYTILINEOS Pyro plant to alloy the bauxite ore drying and pre-reduction prior to feeding in the EAF. The rotary kiln is indirectly heated with Natural gas and has a capacity of 300kg/h, a total length of 6m and a rotating speed of up to 6rpm. The commissioning of the kiln is nearly completed and tests are expected to start soon.

WP5: Products and valorisation of products

The main objective of WP5 is to characterise and find routes to valorise the products/by-products obtained in the ENSUREAL process, namely alumina, pig iron, grey mud and REEs.

The valuation of this product has not started yet. We expected that the alumina characterisation and valorisation routes will start soon because ENSUREAL plant has obtain some aluminium hydroxide precipitation in spring 2021 (see photo 4 in WP4). The Bayerite has a high silicate content and its composition is close to that sold in the market

The pig iron, shown in Figure below was produced during two pilot scale smelting tests during the first period report. The structure of the cast metal is inhomogeneous thus it differs with chemical composition. It is essential to re-smelt the samples in order to get uniform chemical composition. The pig iron produced during the pilot tests at SINTEF were assessed as a feedstock for grey cast iron production by Odlwenie Polskie. In WP4, successful campaigns with smelting the red mud in EAF at Mytlineos were performed.

In February 2021, AoG has send pig iron from its plant to be used in a small scale test performed at a university in Krakow (AGH) and in a large scale test at Odlwenie Polskie.

Grey mud (image below) is being studied to be used in two sectors: building materials and agricultural sector. Moreover, it will be done a valorisation of Grey Mud for production of high added value materials. The grey mud that is being used in this studies comes from two different types of resources, bauxite and red mud. Depending on their origin, the composition of these grey muds is different and therefore they would be used in different sectors.

Due reduce soil acidity properties, can be successfully used in agriculture as a liming agent. However, currently functioning EU law might be a problem. Some hopes may be associated with the new EU regulation – however, the content of heavy metals may disqualify this product.

It was studied by Luvena S.A. Produced grey mud has much lower values of harmful elements in comparison to the first batch of the grey mud tested in 2018. New batch of grey mud meets the requirements for the content of heave metals impurities. Conclusion: Grey mud can be useful for use in agriculture as a liming agent.

Moreover, the assessment tests have been started to use grey mud as building materials. 4 grey mud samples from SINTEF has been tested and the preliminary results are relatively good.

The valorisation of grey mud for production of high added value materials has changed from the grant agreement. The solutions originally proposed cannot be implemented because of the low content in Si to produce the pozzolanic and geopolymer properties needed. So, it will be studied as a filler in OPC fire retardant cements or in inorganic polymeric fire-retardant cements.

WP6: Technical and environmental monitoring, LCA and LCCA

SINTEF is the leader of the task “technical and environmental monitoring”. This task goes in parallel to WP4. SINTEF planned to do emission measurements during the EAF pilot experiments at Aluminium of Greece (AoG) using a TESTO 350 analyser. Due to COVID-19, the tests were postponed.

The results of the tasks of LCA &LCC (Life cycle assessment and life cycle cost) are preliminary because the technical WPs has not finished. The outcomes of these WPs are feeding the two models that are changing continuously.

Based on feedback retrieved from WP1, the sustainability of the Pedersen method is being developed around two regions; Greece and Norway. Studying the Greek and Norwegian case, the major difference is the electricity mix, which is the major contributor on global warming impact category for the Greek case, while the emissions from limestone calcination is the major issue for the Norwegian case on the same category. The CO2 eq. for Pedersen in Norway is similar to Bayer, but no best solution is currently emerging from all the included impact categories.

A comparison of the LCA and LCCA analysis between the Bayer and the different alternatives of the Pedersen is on-going. The LCCA model in Matlab, using the SIMULINK environment, was completed. The preliminary results for the multiple scenarios in respect to raw materials, location of the plant, alternative processing on the pyro-metallurgical part and different valorization routes for grey mud are currently studied.

Life Cycle Costing (LCC) is a method consisting of estimating the total cost of a product (the alumina), taking into account the whole life cycle of the product as well as the direct and external costs. The whole process has been divided in four main blocks: Pyrometallurgic processes, hydrometallurgic processes, slag treatment and offgas treatment.

The last task, the socio-economic analysis, two models with input-output analysis are developed in Python. For the Norwegian case in Mo I Rana the model is developed and will contain cost-related data. For the Greece case, the under-development model can produce results on value-chain changes in different economic sectors on employment as well as changes in macro-economic variables such as GDP, value added and demand. This model will include relevant socio-economic and environmental indicators. Statistical data, results for the LCCA analysis and information related to the site of implementation are collected to feed the input-output analysis.

WP7: Business plan, exploitation and clustering with other EU projects

The Business Plan provides insight into the commercial activities connected to the exploitation of research results to determine the beneficiaries’ strategy and the specific actions that will be undertaken during the implementation of the ENSUREAL Project or after its conclusion. In 2020, the final report of D7.1 ENSUREAL Business plan have been completed. It included further advancement information in every field based on the conclusions reached from deliverable D.6.1 and D6.2 (LCA and LCCA reporting), which will aid consortium members in formulating a clear business plan and approach regarding the Ensureal Process and thus in determining the plant location.

Inside the deliverable, it has been identified the differential costs for the new Pedersen in the two selected sites of Mo Industrial Park and AoG. Once the LCA and LCC are completed, the applicability of the lower-grade alternatives will be verified and the differential cost for both regions will be recalculated.

The relevant market for ENSUREAL, divided in two main areas (alumina sector and primary aluminium sector), has been studied. The analysis of competitors, advantages and disadvantages, prices and more information are included in the business environmental analysis.

The business model includes a description of a business strategy and its specific characteristics in terms of value creation and market orientation to successfully put on the market the new technologies and products. The business model includes the following key elements: the value proposition, the definition of all aspects related to the customers, the partnership, the key resources as well as the mechanisms for revenue generation.

The Implementation plan has been drafted in order to take a closer look at target markets, perform a SWOT analysis to identify potential barriers to market and explore other funding opportunities. The final implementation plan will be presented at the end of the project.

In the pillars section, it is presented the Key Exploitable Results (KERs) coming out of the project. These KERs are the innovations that ENSUREAL consortium are thinking to take out to market.