Nick Hodgkinson, IBD director – non-ferrous, Foseco International Ltd, presents a white paper for non-ferrous foundries
Improving the energy efficiency of foundry operations reduces both energy costs and carbon emissions. It’s a vital win-win for foundries under pressure to reduce their environmental impact, while staying cost competitive. Foundries should therefore consider switching to energy-efficiency crucibles, such as the ENERTEK* crucible range from Foseco, even if this means challenging traditional price-based purchasing decision-making.
INTRODUCTION
Controlling energy consumption is a perpetual challenge for the foundry industry. But with energy costs rising in many regions and the industry’s carbon emissions coming under increasing scrutiny as the world moves to mitigate the impact of climate change, there is renewed impetus to improve the energy efficiency of the metal casting process.
This is particularly true in Europe, where changes to the EU Emissions Trading Scheme (ETS) will reduce both the overall number of allowances and the availability of the free allowances provided to energy-intensive industrial plants. The changes are designed to accelerate the process of decarbonisation in the EU to meet tighter emissions reduction targets. With ETS allowances already over €50.00 per tonne, the expectation is that prices will continue to rise, perhaps even doubling by 2030, while the phase out of free allowances will leave foundries exposed to high carbon costs. In Germany alone, for example, nearly one million tons of CO2 are emitted every year in the production of about 1.7 million tons of non-ferrous metal cast.
In light of the changing circumstances, solutions that improve the energy efficiency of the metal casting process are expected to gain increasing importance. Purchasing decisions will also need to focus more on sustainability and cost reduction over the lifecycle of a product, rather than simply on those with the lowest price tag.
CRUCIBLES AND ENERGY EFFICIENCY
Thermal efficiency
Thermal behaviour and performance is so significant because it directly impacts energy consumption. Crucibles are one such product where, traditionally, purchasing decisions have been made on the basis of price, rather than performance when in use. When performance is considered in the purchasing decision, it is often only the lifetime of the crucible that is taken into account by buyers. However, lifetime is not the performance parameter that has most impact on production costs or carbon emissions; that accolade goes to thermal efficiency.
Thermal performance is so significant because it directly impacts energy consumption. It is also a property that degrades over time as the crucible is used. The latter phenomenon can be controlled through careful design; it cannot however be eliminated altogether. The challenge therefore is not only to improve overall thermal efficiency but also to slow the rate at which degradation occurs over the life of the crucible. Improving thermal performance can also have a beneficial impact on production output and quality. Faster melt times, for example, improve process efficiency and therefore productivity, with a knock-on improvement in energy efficiency, as the same energy input achieves greater melt volumes.
Moreover, crucibles with high thermal performance enable greater stability and control of metal temperature in holding applications, resulting in fewer rejects for temperature-related casting problems, such as shrinkage, pressure test failures and misrun/ cold shut defects. Fewer rejects mean less reworking and recycling of metal, improving the energy efficiency per unit produced. These benefits ultimately combine to provide a crucible that offers greater cost efficiency over the lifetime of the product, improved productivity (greater output for lower inputs) and reduced environmental footprint in the form of a significant decrease in the carbon intensity (via reduced energy use and higher process efficiency).
ENERTEK ENERGY EFFICIENT CRUCIBLES
Originally designed for aluminium applications but now also available for zinc oxide production, ENERTEK energy-efficient crucibles from Foseco are formulated and manufactured to capture the benefits outlined above. They are available in most standard shapes and capacities and can be designed to fit most crucible furnaces without changes to current operating practice. Customised solutions are also possible.
Excellence in aluminium
For aluminium applications, ENERTEK crucibles are most suited to holding furnaces, particularly electrically-heated furnaces, although they can also be effective in gas-fired furnaces. Performance differentials compared to other crucible types will vary depending upon different factors, but typically ENERTEK crucibles will deliver a 5-15 per cent energy saving. Actual cost savings will naturally depend upon unit energy costs – however, we have seen examples where a 5 per cent energy reduction can result in > €800.00 savings annually, (figs.1 and 2).
Meanwhile, when it comes to temperature control during holding operations, the ENERTEK crucible has been proven to achieve a much smaller temperature variation within the liquid metal. Taking the example of an electric resistance furnace with an aluminium melt set temperature of 677°C, the ENERTEK crucible showed a delta of liquid metal temperature of only 26°C (fig.3). In contrast, a lower conductivity crucible material showed much slower heating reaction inside the crucible and a temperature delta of 42°C (fig.4).
Features and benefits
The benefits outlined here are a result of extensive research and development by Foseco. The features of this work are outlined in the published table, alongside the benefits derived.
Aluminium Case Studies
ENERTEK crucibles don’t just sound good on the pages of a white paper – they have been proven in practice. An aluminium diecasting foundry was looking to reduce the energy costs and carbon footprint of foundry operations. The foundry operated a 1,000kg capacity crucible for holding aluminium in an electric-resistance furnace, serving an automatic casting cell. Following the switch to ENERTEK crucibles, the foundry achieved a 13.4 per cent reduction in energy consumption at the same production volume (fig.5). The result was overall cost saving of more than €1,200.00 per furnace (fig.6) and a reduction in CO2 emissions of 7,993kg per year.
Another aluminium diecasting foundry, this time with a 900kg crucible for holding aluminium in an electric-resistance furnace, was being hit with rising energy prices. With ENERTEK crucibles, the foundry measured a 4.2 per cent drop in energy consumption at the same production volume over the twelve-month lifetime of the crucible (fig.7), resulting in an overall cost saving of €315.00 per crucible.
ENERTEK FOR ZINC
Following the success of ENERTEK crucibles at aluminium foundries, Foseco developed the ENERTEK ZnO range of clay graphite crucibles and retorts, which have been specially formulated to provide maximum performance in zinc vaporisation operations for production of both zinc oxide and zinc powder.
Again, performance differentials compared to competitive crucibles will vary according to process parameters; however, savings of more than 30 per cent have already been measured in several customer operations. Meanwhile, the faster melt rate that can be achieved using ENERTEK crucibles has resulted in up to 15 per cent increase in productivity.
CONCLUSION
Energy consumption and environmental sustainability are two of the most important challenges facing today’s foundries – and are the critical operation parameter for crucibles. The ENERTEK range of crucibles for aluminium and zinc applications helps foundries improve their performance in both areas. By prioritising high thermal performance, ENERTEK crucibles improve energy and process efficiency, resulting in lower energy and production costs, as well as reducing the carbon intensity of metals production.
Contact: Paul Jeffs, UK technical manager, Vesuvius UK Limited – Foseco Foundry Division, Tamworth, Staffordshire B78 3TL UK. Tel: +44 (0) 1827 289999, email: [email protected] web: www.foseco.com
*ENERTEK is a Trade Mark of the Vesuvius Group, registered in certain countries, used under licence.
To access copies of the figures and tables that accompany this article refer to the printed version in the February/March 2023 issue of Foundry Trade Journal or contact Marion Cottrell on, email: [email protected]