In-house salt slag processing solution which turns waste into a product
After iron, aluminium is the world’s most commonly used metal. Yet its recycling process can create salt slags which are increasing becoming an environmental concern as they are not easily disposed of; they can no longer be landfilled in Europe and the Middle East. Despite this, due to high set-up and operating costs there exists only nine, very large capacity, salt slag recycling facilities across Europe catering to over 270 processing plants. The EU-funded AluSalt project has developed a ‘mini’ salt slag recycling technology that can be installed at aluminium plants reducing, ultimately eliminating, the need to ship huge volumes of salt slag around Europe to the traditional large centralised salt slag recycling centres. Optimising the aluminium bank A large part of aluminium’s appeal is due precisely to its infinitely recyclable properties. Upon reaching its end of life, it can be recycled repeatedly to create new aluminium products, without a marked loss of durability or quality. Crucially, this can be accomplished at a cost of up to 95 % less than that of the original manufacturing process. Indeed, some figures suggest around 1 billion tonnes of aluminium still in use, sometimes referred to as the aluminium ‘bank’. The limited options for the aluminium recycling operators to recycle their generated salt slags, creates financial and operational insecurity for these plants as costs rise, threatening the industry as a whole. Additionally, the situation presents a hazard to the environment as, due to a lack of local options, some regions such as Scandinavia and Eastern Europe are compelled to transport thousands of tonnes of salt slag annually thousands of kilometres away for recycling. Explaining AluSalt’s inception, the project coordinator Mr Alan Peel recalls, “When discussing with many of our European customers what operational challenges they faced, many cited the management of their salt slag ‘waste streams’. As our business developed technology for aluminium dross management, a waste stream from aluminium recycling operations, this seemed like a good fit for us to explore.” The AluSalt solution takes the salt slag from the aluminium recycling ‘Rotary Type’ furnace which operates at a temperature of around 1000 degrees centigrade and is viewed as the most efficient way to recover aluminium from the drosses using molten salt. The slag is rapidly cooled before going through a crushing and screening phase to recover the trapped aluminium, which can be as much as 5-10 % of the salt slag volume. The slag remaining, which contains aluminium oxides, salts, and other aluminium compounds, is leached with water to remove the salt and allowing it to re-crystalised. The remaining oxides can then be sold as products suitable for various industry applications such as steel, cement, steel wool, ceramics, bricks or refractory. The project team built a full scale prototype facility in Northern Europe at an aluminium recycling operation, demonstrating the approach’s scalability. As Mr Peel summarises, “The AluSalt solution essentially means that what was previously considered a waste stream to be managed under certain strict conditions, can be converted to a variety of products for continued re-use in a circular, environmentally friendly and safe way.” For aluminium that no longer costs the earth The immediate impact of the widespread adoption of AluSalt’s aluminium recycling solution would be the opportunity to avoid up to 2 million tonnes of salt slags being transported across Europe by road, rail and ship. This would cut aluminium’s carbon footprint along with reducing the risk of other uncontrolled gaseous emissions, as well as decreasing overall energy costs. Additionally, for operations and their employees it would mean more security over their operations, as Mr Peel expands, “They will also no longer be reliant on the monopoly processors taking their waste material or on legislation, which could always be changed, to stop the transportation of this material. This gives security to the recycling facilities that employ lots of people in their local regions.” The project team has already started to commercialise the technology with many European aluminium operations visiting the operation with a view to invest in the technology.
Keywords
AluSalt, aluminium, recycling, processing plants, salt slags, CO2, pollution, emissions, energy costs, metals, hazards, extraction