High Shear Processing of Recycled Aluminium Scrap for Manufacturing High Performance Aluminium Alloys

Final Report Summary - RECYCAL (High Shear Processing of Recycled Aluminium Scrap for Manufacturing High Performance Aluminium Alloys)

Executive Summary:
The RecycAl project aimed to use the novel high shear process (HSP) of melt conditioning to reprocess low grade aluminium scrap into a high quality aluminium feedstock for the automotive industry. This process uses a high shear device to de-agglomorate and disperse natural oxide films found in molten aluminium scrap into discreet oxide crystallites which enhance the nucleation of primary iron-containing intermetallics and facilitate their removal.

The aim of the RecycAl project was to develop a process for removing Fe impurities from aluminium scrap. Fe contamination impairs the properties of most aluminium alloys and prevents scrap material from being recycled into high performance grades of aluminium which have very tight controls on permissible Fe levels. The project has been successful in developing a lab scale process which can remove iron from scrap material particularly for the production of casting alloys which often contain high levels of Si which are favourable for the RecycAl process. In these cases the RecycAl process can remove Fe from selected sources of scrap material allowing the direct production of casting alloys from scrap. Automotive components cast from this material were found to have comparable material properties to components cast from conventional higher quality material in terms of; tensile strength, fatigue and corrosion performance. The process could also be used to reduce the Fe content of highly contaminated scrap material from other parts of the recycling process such as the ‘Lingoton’ alloy produced by smelters such as Idalsa. In this way the processed scrap material is effectively upgraded and may be recycled more times as a result of the RecycAl process.

Despite the success of the process on recycling casting alloy waste the project was not successful in reducing Fe levels enough to directly produce high quality wrought alloys from scrap. This is because the quantity of Fe which can be removed from a given type of scrap is thermodynamically fixed by the composition of the scrap and most cases wrought alloys limit Fe concentrations below this level. However, if some Fe can be removed from low quality scrap material the process could be used to reduce the need for further dilution of the processed scrap with primary aluminium in the production of high grade wrought alloys.

The primary limitations on the HSP process are identifying suitable sources of scrap material with favourable compositions and maximising the separation efficiency of the ‘clean’ aluminium and the Fe containing sediment. The quantity of Fe which can be removed from a given type of scrap is determined by the composition of the scrap; sources of scrap containing high concentrations of Fe, Si and Mn promote increased Fe removal. If such material could be selectively removed from the main aluminium recycling stream the Recyal process would be highly beneficial. Industrialisation studies found that investment the RecycAl process could be financially justified if the clean melt and sediment could be separated with >80%, in the case of ‘Lingoton’ and >90%, in the case of the ‘skimmings’ and most other waste types. A sedimentation efficiency of 80% is thought to be possible with existing technology however, 90% may be challenging on an industrial scale and a pilot plant demonstrating these high separation efficiencies was not achieved by the project.

The RecycAl technology has the potential to benefit both the aluminium industry and the automotive industry as it opens the door to cost effective light weighting of vehicles using aluminium sourced from increased quantities of low quality end-of-life scrap. This may tip the balance for aluminium to become the most cost effective and environmentally responsible choice for future automotive body structures, chassis and power train components. It will help to enable the EU28 reach their carbon targets for 2020 and beyond if widely developed and applied properly.

Project Context and Objectives:
Context
The EU aluminium industry is largely based on the use of primary aluminium for the production of cast and wrought aluminium alloys for structural applications. Primary aluminium production is both energy and carbon intensive with associated high costs and environmental impacts. Secondary aluminium (post-consumer scrap) is either downgraded into low quality cast products or exported, primarily as a result of high iron content of the scrap which leads to precipitation of intermetallic particles in the melt that can be detrimental to both mechanical and corrosion performance. This scrap could be transformed into a low cost, low carbon feedstock for wrought product and high quality castings by the adoption of High Shear Processing (HSP). This innovative process uses a high shear device to de-agglomorate and disperse the natural oxide films found in molten aluminium scrap into discreet oxide crystallites, which then enhances the nucleation of primary iron-containing intermetallics and facilitates their removal. The RecycAl project was conceived to refine this novel process and use it to re-process real end-of-life secondary aluminium, producing a low iron, high grade aluminium alloy feedstock from this scrap. In addition to using the HSP to directly remove iron from scrap it was also proposed to use HSP to make aluminium alloys more tolerant to higher iron concentrations. To demonstrate the properties of these HSP alloys the mechanical properties and microstructure of the ‘RecycAl’ alloys were characterised and the recycled alloys were cast to shape and rolled or extruded into representative industrial parts. The properties of the components produced using recycled HSP material was compared with components produced using virgin aluminium material. An industrialisation strategy was developed to consider how the HSP could be implemented industrially, what capital investment would be required and what additional profitability could be achieved. The environmental benefits of the HSP were also determined by carrying out a full lifecycle analysis of ‘RecycAl’ alloys.

Objectives

• Develop the HSP into a process to remove iron contamination from aluminium scrap.
In the HSP a rotor/stator device is lowered into a crucible of molten aluminium scrap. The rotor inside the mixing head is then activated and shears melt. This innovative process de-agglomorates and disperses the natural oxide films found in molten aluminium scrap into discreet oxide crystallites, which then enhances the nucleation of primary iron-containing intermetallics and facilitates their removal. Three approaches were considered to apply HSP in the processing of aluminium scrap.

Initial work focused on removing Fe from scrap material using the HSP process together with an inert gas which was bubbled through the melt. The concept was that the fine oxide dispersion, created by the HSP, would promote the nucleation of a similarly fine dispersion of iron based intermetallic particles which could be ‘lifted’ to the surface using the bubbles of inert gas and skimmed off from the top of the melt, leaving a low iron ‘clean’ melt behind.

A second sedimentation based approach was also considered in which intermetallic particles were allowed to sediment to the bottom of the HSP chamber allowing ‘melt to be extracted from the top of the chamber.

Finally, the third approach considered was to use the HSP to increase the tolerance of aluminium alloys to Fe contamination, without impairing the mechanical properties of the material. The HSP is known to have numerous beneficial effects including; breaking up oxide films, refining grain size and creating a fine dispersion of Fe containing intermetallic particles. It was thought these factors may allow higher Fe levels to be accommodated in wrought materials without reducing their properties. In this way larger volumes of scrap could be used to produce these materials with less primary aluminium needed to dilute the high iron content typically found in scrap materials.

• Model the melt flow and particle size distribution in the HSP chamber to maximise the effectiveness of the process.
Detailed simulations were developed of the HSP device including; a computational fluid dynamics (CFD) model of the melt flow through the mixing head and a particle size distribution model of the sheared intermetallic particles in the melt. The aim of the simulations was to predict the most effective processing parameters for the HSP. Specifically the speed of the rotor stator, design of the mixing head, size and geometry of HSP chamber were considered,

• Evaluate the effectiveness of the HSP process as a means of processing low quality scrap into a high quality feedstock for wrought and cast aluminium alloys.
An ambitious target was set to use the HSP to reduce the Fe content of aluminium scrap to below 0.4wt% Fe and, ideally, reduce it to less than 0.1wt%. If such low Fe contents could be achieved the process could be used to produce a high quality feedstock for wrought and cast automotive alloys. To evaluate the effectiveness of the HSP a range of compositional and metallographic analyses of the processed material was to be undertaken. A range of scrap materials were to be tested to identify suitable scrap materials for the process developed.

• Use the HSP to re-process scrap aluminium into high quality wrought and cast components for the automotive industry.
Once developed the HSP was to be used to process aluminium scrap material, reducing the Fe content to very low levels. To prove the quality of the material produced by the HSP the material was then used to produce a range of ‘RecycAled’ wrought and cast aluminium automotive alloys. These alloys would be cast, rolled, extruded and formed into representative automotive components chosen by project partners from the automotive industry.

• Carry out a range of metallurgical and mechanical testing to verify the quality of the HSP materials.
The properties of these components were compared to existing materials in terms of the; corrosion resistance, weldability, formability, tensile strength, paint ability and hardness properties amongst others. The goal of these tests is to demonstrate the properties of the RecycAl materials are equivalent or better than existing material. All of these tests were coupled with a full metallographic investigation of the RecycAl alloy microstructures to validate and explain any differences between the performance of the RecyAL and traditional materials.

• Produce an industrialisation plan for implementing the HSP into the aluminium recycling industry.
In order for the HSP developed during the project to be taken up by the European aluminium recycling industry an industrialisation plan is needed. The plan includes an assessment of how the HSP process can be integrated into existing recycling infrastructure. In addition to the practical aspects of integration a cost-benefit analysis will be carried out indicating the cost of the initial investment in equipment and the savings achievable by applying the process.

• Carry out a lifecycle analysis (LCA) to evaluate the environmental benefits of HSP.
To quantify the environmental benefits of the HSP a LCA is required. This process looks at the environmental benefits and costs of the HSP material across the lifecycle to identify the environmental impact of the process.

Project Results:
• Development of the HSP + Sedimentation Process
Initially the project looked at removal of iron containing intermetallic particles using a combination of the HSP and bubbling the melt with inert gas. The hope was the fine dispersion of oxide particles, created by the HSP, would nucleate a similar fine dispersion of iron containing intermetallic particles which could be ‘bubbled’ to the surface of the melt. The results of the initial testing are shown in Figure 1, which shows two cross-sections of the HSP crucible comparing melt a) with gas bubbling only and b) with HSP and gas bubbling. The numbers in red indicate the concentration of Fe at different locations in the cross section, the results show that rather than allowing the Fe particles to ‘bubble’ to the top of the melt the HSP actually improves the sedimentation of these particles, increasing the Fe content at the bottom of the crucible and reducing it at the top.

To take advantage of this improvement in the sedimentation of iron containing particles the HSP was integrated into a HSP + sedimentation process which is shown in Figure 2. The figure shows the lab setup for the process in which the process was configured in a semi-continuous mode where melt is poured at a controlled rate into the HSP chamber. In this chamber the melt is sheared by the HSP to create a fine dispersion of oxide particles and the melt is passed through a temperature controlled launder into a sedimentation chamber. As the melt is poured into the sedimentation chamber it is allowed to cool to the temperature at which precipitation of primary iron containing intermetallic particles occurs. These particles sediment in the chamber as shown and ‘clean’ melt is extracted from the top of the chamber for further processing. The process was set-up as semi-continuous process at the lab scale to demonstrate the process could be used in this mode however, a batch process in which HSP and sedimentation occur in the same crucible, of various sizes, is also possible.

This process was used to reduce the concentration of a casting alloy scrap material from >1wt% Fe to <0.68wt%Fe, this is below the maximum iron concentration allowable by the relevant Standard meaning the HSP + sedimentation process could be used to directly process scrap aluminium into a casting alloy feedstock.
• Removal of Iron Contamination from Aluminium Scrap
The amount of Fe which can be removed from a given type of scrap material depends upon the composition of that alloy and, particularly, the concentration of Fe, Si, and Mn. The sedimentation process must occur at a temperature below which iron intermetallics begin to precipitate but above which the molten aluminium begins to solidify. The relative concentrations of Fe, Si and Mn were found to have the greatest influence on these temperatures defining the process window across which sedimentation of iron intermetallics occurs and, more importantly, the minimum iron concentration of the molten liquid. High levels of Si and Mn were found to maximise the amount of Fe removal as shown in Table 1 which shows the effect of Fe. Mn and Si additions to a type of scrap material provided by project partners Suldouro. The table shows that without any additions to the scrap the Fe content can be reduced from 1.0wt% to 0.89wt% by the HSP + sedimentation process, this can be improved to 0.48wt%Fe by the addition of 4wt% Si to the scrap. However, although the addition of Si increases the amount of Fe which can be removed the concentration of Si remaining in the material after processing remains high, often >2wt%. This means that despite the significant increase in Fe removal achieved by adding Si to the scrap production of most engineering alloys using this material would still require the material to be diluted with a purer feedstock, in order to reduce the Si concentration. Dilution is the process of mixing the scrap with a purer material that has a low concentration of Si and other alloying elements. Diluting the scrap with the purer material reduces the concentration of Si in the scrap at the cost of using higher quality aluminium scrap and/or virgin material which reduces or eliminates entirely the environmental benefits of the HSP.

The situation is similar for Mn additions where, although Mn additions can increase the amount of Fe which can be removed high residual Mn levels mean that significant dilution of the processed material is also required. For example in the case of the ‘heavy scrap’, in Table 1, addition of 0.5wt% Mn reduces the residual Fe concentration in the HSP product from 0.81 to 0.70wt% however, this increases the residual Mn from 0.81 to 1.0 which is too high for the product to be used directly as a feedstock for many aluminium alloys without dilution. This means the use of alloying additions such as Mn and Si to improve the efficiency of Fe removal by HSP + sedimentation is generally not beneficial because the intent of the HSP + sedimentation process is to avoid or significantly mitigate the need to dilute the scrap.
The complex interplay between scrap composition and the amount of iron the HSP + sedimentation process can remove from the scrap material mean that selection of appropriate scrap material for the process is critical. The concentrations of alloying additions in many wrought aluminium alloys, such as the 5xxx, 6xxx and 7xxx series alloys are too low to be directly produced from scrap material produced by the HSP + sedimentation process however, the process was found to be highly effective for alloys with high levels of Si typical of many aluminium casting alloys. To take advantage of the effectiveness of the process on casting alloys the process was targeted towards the production of an automotive cast component from recycled material.

• Casting of Automotive Exhaust Bracket Directly from Recycled Material

The consortium aimed to produce an automotive exhaust bracket component directly from scrap material, using the HSP + sedimentation process to reduce the levels of Fe contamination. The material targeted was AlSi9Cu1 a common casting alloy which is currently used to produce exhaust brackets in FIAT cars. A type of casting alloy scrap was produced by Idalsa containing high levels of Fe contamination as shown in Table 2. After the HSP + sedimentation process was applied the Fe levels were reduced to 0.68wt%, below the 0.8wt% required by the material Standard. The Mn levels of the processed material were slightly high, 0.06wt% out of specification, however, this is not throught to be significant and could be addressed by a small amount of dilution of the material produced.

The HSP + Sedimentation processed AlSi9Cu1 was then used to manufacture an automotive exhaust bracket using an industrial scale casting process by project partner F.O.M.T. A photograph of the cast component is shown in Figure 3. The component was subjected to a detailed examination including, non-destructive testing, microstructural examination together with corrosion, fatigue and mechanical testing. For example Table 3 shows the tensile strength and ductility of the RecycAl material exceeded the requirements of the relevant Standard.

While some differences were observed between the RecycAl alloy and a typical cast material the RecycAl component demonstrated similar performance to commercial castings in terms of mechanical strength and fatigue and corrosion performance. The excellent performance of the RecycAl material is very encouraging for the use of the HSP + sedimentation process to produce high quality casing alloys from scrap material.

• Effects of HSP on Primary Intermetallic Formation

The results show the HSP + sedimentation process can be used to promote the sedimentation of Fe intermetallics from scrap material. It should be noted Fe sedimentation will occur with and without the HSP. Thus, in theory, the HSP is not required to reduce the iron content of scrap material by sedimentation. However, this process is not widely applied in industry primarily because sedimentation effect is quite slow. For the HSP + sedimentation process to be adopted by industry sedimentation would need to occur more quickly than without the HSP. Figure 4 which shows a plot of Fe content against time for the material produced by the sedimentation process with and without the application of the HSP. The green line indicates the initial Fe concentration of the scrap material and the red line indicates the theoretical minimum Fe concentration achievable by sedimentation.

With the HSP applied, the sedimentation process was immediately effective at producing low Fe material from the start to the end of the test. Without the HSP the initial material exiting the sedimentation chamber had relatively high Fe concentrations, approximately equivalent to the starting composition of the material, indicating little sedimentation had occurred. Over time, sedimentation has becomes more effective and converges on the Fe levels achieved when using the HSP. The difference in sedimentation efficiency between the two materials is thought to be related to the shape of the sedimenting intermetallic particles; Figure 5 shows these particles have a more rounded shape when the HSP is applied. The more rounded shape of the HSP particles is likely to reduce drag from the melt increasing sedimentation velocity under gravity.

In summary, although it is possible for sedimentation to remove Fe from the melt with or without the HSP, it is found that application of the HSP reduces the time it takes for this to become effective. While this process is not completely understood it is thought the reduced time required to produce a low iron product makes HSP + sedimentation an industrially viable process for removing Fe from scrap aluminium.

• Application of Computer Simulations to Optimise HSP

A 3D computational fluid dynamics (CFD) model was developed to simulate the melt flow in the HSP chamber, using the actual geometrical parameters of the mixer (including the size of gap of 0.25 mm between the rotor and the stator, and the component “bush” that sits between the rotor and stator) that are used in the actual HSP trials at Brunel. This CFD model was integrated with a population balance model (PBM) for computationally predicting the change of the size of oxide clusters resulting from the HSP. The key outputs of the modelling were;

• The length of the HSP mixing head should be increased to prevent recirculation of HSP material through the mixing head. The recirculation of the melt is shown in Figure 6. Adding a sheath extending below the holes in the mixing head was found to prevent this from occurring allowing faster processing of all the melt in the HSP chamber.

• A larger distance between rotor and stator is recommended to increase the mass flow without significantly influencing shear rate. When changing the size of the gap between the rotor and stator from 1 mm to 0.25 mm, the resultant maximum characteristic shear rate at the steady state varied only slightly while the total mass flow rate through the holes of the stator at its side significantly changes from 10.3 kg/s to 0.416 kg/s. These results mean that; wear of the mixing head will not have dramatic negative effects on the performance of the mixer and further decreasing the size of the gap between the rotor and stator will not effectively benefit the performance of HSP. This also means that a high tolerance on a narrow rotor-stator gap is not required.

• The size of the oxide phase produced by the current HSP was predicted to be 40 nm which corresponds to the size of individual oxide particles. Refinement of the oxide particles to this size was found to take less than 0.1s of HSP, using the empirically determined process conditions. This very short process time was relatively unaffected by varying process parameters demonstrating the HSP process to be quite robust and tolerant to varying process conditions.

• Using the existing HSP design (without recommended modifications) doubling the size of the rotor stator device could allow a volume over 4x larger to be processed (129kg within 1 minute). This potential processing rate is encouraging for industrialisation where multiple mixing heads could be employed in numerous schemes to process material at even higher rates.

• Applying the HSP to Wrought Aluminium Alloys
The HSP + sedimentation process was found to be effective at reducing Fe contamination in casting alloys with high levels of Si however, the process was not suitable for removing Fe from wrought alloys which are relatively low in Fe. While the wrought alloys cannot be produced directly from HSP + sedimentation processed scrap material, they can be produced by dilution of scrap with virgin aluminium feedstock. In this case, the environmental and energy savings are maximised by maximising the ratio of scrap/virgin material in the dilution. The dominant factor controlling this ratio is the maximum allowable iron content in these wrought alloys. It was proposed that, by applying the HSP to the wrought alloy scrap, the maximum iron tolerance of the alloys could be increased, while maintaining the required mechanical properties. This view was based on the beneficial effects of the HSP (without sedimentation) in terms of breaking up oxide films, refining grain size and creating a fine intermetallic distribution. To investigate if HSP could be used to increase the iron tolerance of wrought alloys, ‘high-iron’ end-of-life scrap based versions of the AA6016, AA5182 and AA6082 alloys were cast and rolled to sheets and extrusions as necessary. The compositions of these alloys were just above the maximum concentration of iron currently allowed in their specifications, as shown in Table 4. The HSP was then applied the materials produced, such that the properties of HSP and non-HSP ‘high-iron’ wrought material could be compared. These materials were processed into sheet and extruded products and a formed component was produced from HSP and non-HSP AA5182 sheet material.

Light micrographs of the DC cast 5182 material with and without the HSP are shown in Figure 7. The HSP has clearly had a significant impact on the as-cast microstructure in each case. The non-HSP material showed a mixture of very fine and coarse dendrites. The coarser dendrites are clustered in islands surrounded by much finer dendrites. In contrast, identical compositions processed by the HSP showed a different dendrite morphology: a large number of coarser dendrites with wider dendrite arm spacing’s than the non-HSP material but with shorter arm lengths. Between the coarser dendrites there were still some regions of fine dendrites but the area fraction of these finer regions was significantly lower than that observed in non-HSP material. The same trend was observed in all the as cast wrought material. Despite these significant differences in as-cast microstructure the rolled or extruded microstructures of these materials are more significant because these wrought alloys are not used in the as-cast condition. Electron backscatter diffraction (EBSD) maps showing the rolled microstructures of the 5182 material with and without the HSP are shown in Figure 8. The microstructures of both materials was similar, showing a bimodal grain size distribution of larger, often slightly deformed grains, surrounded by smaller recovered/recrystallised grains. The larger deformed grains had regions of colour gradient, within each grain, which is indicative of deformation. The intensity of the deformation and number of deformed grains was higher in the HSP material, which may imply a difference in material properties between HSP and non-HSP material.

The properties of these wrought products were evaluated through a programme of mechanical, corrosion, weldability and formability testing. The objective was to compare the performance of HSP and non-HSP material with equivalent high iron contents. In addition two casting processes DC casting, typically used for producing extrusion logs, and BM casting designed to replicate large scale rolling plates were investigated. The results showed that while the HSP did not impair the mechanical properties of the materials it was difficult to identify significant improvement in each case. In most cases the HSP and non-HSP materials demonstrated very similar mechanical properties as shown by the stress – strain curves in Figure 9 and 10 for the 5182 sheet in the T4 condition and the 6082 extruded material in the T6 condition respectively. The flow stress curves for the 5182 sheet shown in Figure 9 are serrated curves characteristic of the Portland le Chatelier (PLC) effect. The serrations are most severe in the commercial material but the effect was also observed in the high-iron materials of all types. The magnitude of the PLC effect was similar in both the HSP and non-HSP high-iron material and very little difference in in the properties of either material were observed. However, one notable effect of the HSP, in this material, was the absence of a sharp yield point, characteristic of the commercial and non-HSP materials. The reduced magnitude of the PLC effect, along with the reduced yield strength of the high-iron material, is indicative of the high concentration of iron in the material and suggests the HSP has not been effective at redistributing the iron through the material in such a way to improve properties.

The stress-strain curves for the 6082 extrusion in the T6 condition are shown in Figure 10. The plot shows that the high iron HSP and non-HSP material behave similarly to each other and display slightly lower yield stress than commercial material. Scanning electron microscope images of the extruded 6082 with and without the HSP are shown in Figure 11a and b, Figure 11c shows commercial extruded 6082 material for comparison. The images do not show a significant change in the second phase particle distribution in any of these materials which is consistent with the similar properties. While some differences in the performances of other alloys were observed these were thought to be primarily due to differences in the casting process rather than the application, or not, of the HSP.

The intergranular corrosion resistance of the HSP and non-HSP material was also compared, the results for the 6082 material are shown in Figure 12. In this case the HSP material was found to be more resistant to intergranular corrosion than the non-HSP material, this is clearly shown by the increased intergranular corrosion on the surface of the non-HSP material in Figure 12a. While the beneficial effects of HSP were quite dramatic in this case the majority of the corrosion tests showed the HSP had relatively little effect, with the casting process (DC casting or book mould casting) more influential.

Overall the results showed that, for wrought materials, while some of the HSP alloys demonstrated better performance in comparison to non-HSP alloys this effect was relatively small. In many cases any impact of the HSP was dominated by differences in the casting processes used between the different materials. In summary there is no evidence to suggest the HSP increases the Fe tolerance of aluminium alloys.
• Forming of an Airbag Bracket from RecycAl Sheet Material
The high iron 5182 sheet material produced to evaluate the effect of the HSP on the iron tolerance of wrought aluminium alloys was also formed into an airbag bracket component by partner Quantal. This forming operation represents a typical process which commercial 5182 sheets undergo. Proving the high iron HSP material have superior forming properties to non-HSP sheets would go a long way to demonstrating the benefits of the HSP. Some of the material produced for the project are shown in Figure 13, these sheets were cut into blanks and formed into the bracket component is two stages shown in Figure 14a and b. The completed components were then cut to form the completed component shown in Figure 14c. Forming of HSP and non-HSP material cast by DC and book mould casting techniques was attempted with varying results. None of the book mold cast sheets were successfully formed without application of the HSP, however both HSP and non-HSP DC cast sheets were successfully formed. Some parts failed after the initial forming process and others failed at the second stage, an example of a failed component is shown in Figure 14d. In summary the HSP did appear to have some beneficial effects on the BM cast material allowing some of these components to be formed successfully however, DC cast material of the same composition was successfully formed both with and without HSP. This suggests the casting process has the dominant influence on the formability of the material and while the HSP may have some beneficial effects these appear to be relatively small.

These results are supported by conventional formability testing which was carried out by the Erichson Cup and Hole Expansion Tests. The results are shown in Table 8. The formability of the BM cast 5182 material with and without HSP was found to be lower than the commercial 5182 material, as measured by the Erichsen Index, with the BM cast material measuring 2.8 and 1.8 on the Erichsen Index, with and without HSP compared to 11, for the commercial material. The DC cast material, without HSP, performed much better than the BM cast material in this test, reaching 10.8 on the Erichsen Index., Unfortunately however, testing of the DC cast material with HSP could not be completed, due to material shortage, as most of this material was used in component forming trials. However, the results of these trials suggest the HSP and non-HSP DC cast material have similar forming properties. The performance of all the 5182 materials in the hole expansion test was very similar, producing hole expansion ratios in the range of 37-39.

• Industrialisation of the HSP + Sedimentation Process
The objectives defined for the project are the analysis and quantification of the incurred costs of installing an industrial scale of the “Recycal” process and to evaluate the feasibility of the HSP to be introduced in the industry. Also, the technical challenges to improve the process and potential issues such as training of the operators, setting up of the device and conditioning of the workplace. The main purpose is to obtain an industrial process to reduce the iron content in composition of post processed aluminium, waste of aluminium, aluminium scrap and/or aluminium slags. It is expected the “Recycal” process causes the increasing of the benefits in the refining process due to the use of cheaper aluminium scrap and slag with higher iron content and the decreasing of the use of primary aluminium (lower operational costs and benefits for environment). The technical purpose of the activity is the study of the “Recycal” process viability to reduce the iron content of aluminium alloys with 1.5-5% Fe in composition below 1.3%. This will depend on the initial composition of the alloy and the possibility of introducing alloying material to promote the extraction of iron through the iron affinity, intermetallics formation and the removal of these iron enriched solid fraction. The Recycal project has conducted several analyses to study the viability and alternatives to scale up and industrialize the HSP process and to improve the performance of the process to reduce the iron content of aluminium alloys. The current continuous process design at Brunel University was evaluated with conclusions as below;

• Better mass flow control is needed to cope with the 100-250kg/minute flow rate when pouring aluminium slag up to 1000kg/minute in the first pour of a maintenance furnace.

• A better filtration system is needed in the sedimentation tank to prevent sedimented Fe intermetallics from being dragged into the low iron product.

• Identification of scrap material for the HSP is also key because the efficiency of Fe removal is dependent upon the initial composition of the scrap material.

One of the primary limitations of the HSP is the identification of adequate filtration systems, to separate the sedimented intermetallics and ‘clean melt’. Numerous solutions were considered including types of mesh filters but none of these are considered appropriate to operate at the required process temperatures. Therefore, inevitably, regardless of process set-up some sediment will be drawn into the low Fe product. As a result all simulations considered a proportion of this sediment contaminating the ‘clean’ melt, meaning projected profitability could be improved if an adequate filtration system could be identified. It was found that for commercially available scrap material such as the ‘skimmings’ from the remelter industry, containing 2.2wr%Fe, a separation efficiency of >90% is required to be economically viable, this is thought to be difficult to achieve with current commercial systems.

Despite this limitation another industrialisation case study found the HSP + sedimentation process could be economically viable with a sedimentation efficiency of only 80% when treating another kind of scrap material known as ‘Lingoton’. The study assumes the HSP is integrated in a batch process, as a means of applying the HSP because it is relatively cheap to implement and allows a great flexibility in the material they process. For the study production of the 226D aluminium die casting alloy was selected as this is a high demand material which could be produced directly by the HSP + sedimentation process. The ‘Lingotón’ scrap is a form of waste material produced by current recycling processes at smelters, like project partner Idalsa, with an Fe content of ~4.5wt%. Idalsa produce up to 65,000kg/month of this material. Processing with the HSP+ sedimentation process could reduce the Fe content to 1.09wt%. This ‘Recycaled’ material could then be used to directly produce the 226D die casting alloy. The industrialisation study indicates this could increase the value of the material from 145€/Tm to 157€/Tm by lowering the Fe concentration, this could produce an increase revenue by ~500€/year processing at the scale of the Idalsa plant, which is assumed to be representative of industry, assuming only 80% separation efficiency. These calculations assumed the capital investment in the HSP equipment was spread over a three year period.

Given the potential savings a plan was developed to install the HSP + sedimentation process into the Idalsa factory. The investigation found that to develop a new aluminium recycling plant, including the HSP + sedimentation system, an investment of 3,511,500€ would be required. In order to integrate the HSP + sedimentation process into an existing plant an investment of 145,500€ is required.

There are three options for the application of the HSP in industrial processes the choice of process is dependent upon the quantity of material being processed and the composition of the scrap material because, as discussed in WP2, the composition of the scrap determines the extent to which Fe can be removed by the HSP + sedimentation process. The three possibilities for implementing the HSP + sedimentation process in industry are;

1. Batch process; A batch process is used when a small volume of material is processed or there is a significant variability in the composition of the material to be processed.

2. Continuous process: A continuous process is used when a large quantity of material is processed for a long period of time for the same aluminium alloy.

3. Semi-continuous process; Semi-continuous process is used when a large quantity of material is processed but for a short period of time or in case to change periodically the aluminium alloy to be processed. The operation conditions can change to some predefined operation programs, but its flexibility is lower than a batch process. Using this arrangement, any quantity of metal can be processed.

Batch Processes
The computational simulations of the performance of the HSP device analyse the behaviour of a molten alloy volume when it is processed by the HSP device within a crucible (batch process). The results from these studies concludes the scaled-up HSP device is able to shear properly a maximum mass flow rate of 3.1kg/s (QHSP) at 2000rpm. In a batch process, it means the scaled-up HSP device working at 2000rpm for several minutes is able to shear properly the molten alloy of a maximum effective agitated volume of 450mmdiameter and 300mm deep dimensions. This is a quantity of material around 129kg/batch. However, if crucible is larger than 129kg volume other mechanisms must be used to ensure the melt is properly sheared. Figure 15 shows a variety of measures which could be easily applied to shear 500kg of melt. These calculations are based upon upgrading the HSP device to allow vertical and horizontal motion within the crucible to ensure the melt is fully processed.

Continuous process:
In case of a continuous arrangement instead of processing a volume, it is necessary to process a mass flow, that is the molten alloy comes into the processing chamber and leaves it in a “processing” mass flow rate (Qprocessing) while the alloy is being sheared. A mass flow around 25-50kg/min (QProcessing) may be processed through a smaller chamber than considered in batch process, if HSP device operates at 2000rpm or more the mass flow through the HSP device could reaches up to 186kg/min (QHSP). A diagram showing the set up of a continuous process is shown in Figure 16. Notably a buffer vessel is required to regulate the flow of the melt through the HSP chamber. Of course the flow rate could be effectively increased by adding additional HSP units in parallel. The processed melt would then be passed to a sedimentation chamber using a launder system.

Semi-continuous process;
The use of a semi-continuous process as Brunel’s design is possible although it may be challenging to control the processing mass flow rate through the processing chamber on an industrial scale. This flow rate has to be much lower than the mass flow rate of the HSP device to ensure the alloy is properly processed. This only is possible if the quantity of material that the process receives comes to a buffering chamber to match the pouring mass flow rate from the melting furnace to the processing mass flow rate.

The industrialisation study found that integration of the HSP + sedimentation process was likely to be best achieved, initially at least, as batch process. The majority of recycling activities occur in batches of scrap with differing unique compositions, so it makes sense to implement the RecycAl process as a batch. However, if large volume of scrap of a relatively consistent composition could be sourced, the RecycAl process could be integrated in a continuous process as shown in Figure 11. This process could use numerous HSP mixing heads to achieve the required process flow rate.

• Lifecycle Analysis of the HSP + Sedimentation Process

The environmental benefits of the HSP are described and quantified using a LCA technique. The analysis was applied to identify the environmental costs/drawbacks of industrially applying HSP. The Life Cycle Assessment methodology is applied in order to;

• Express with environmental balance the improvement in using secondary Al instead of primary one EnginSoft has conduct a LCA of FOMT production of exhaust pipe bracket in primary and secondary Al.

• Evaluate the real environmental advantage in the application of the HSP process to produce a secondary Al alloy that is respecting the composition target proposed requested by specific market EnginSoft has conduct a Life Cycle Assessment of the Idalsa Normal Production, the application of the HSP in their plant and an evaluation of the consumed energy of an Aluminium alloy with difference balances between primary and secondary aluminium

One of the most frequent applications of LCA methodology is the comparison of different processes. The energy-environmental applications of these results are able to provide an overall profile of each process that allows an evaluation in relative terms.

LCA of FOMT Process
FOMT is a RecycAl partner. It is an Italian foundry that employs 110 people and it has an average production of recycled aluminium of 1.71 thousand tonnes per year. FOMT is interested in evaluating how HSP could be integrated in its process with aim to reduce the use of primary aluminium. It is proposed the HSP could be added in-line with existing FOMT processes after the aluminium is melted but before the casting process. A LCA of the FOMT casting process was carried out considering the process used to produce the exhaust bracket using primary and secondary aluminium. The analysis was carried out using the GaBi software package. The results are interpreted according to ISO 14042 and CML 2001 (from Centre of environmental studies of Leida) which defines a methodology for classifying the model results into environmental impact factors, some key factors are shown in Table 7 and Figure 17. All the considered impact categories confirm the environmental advantage in using secondary Aluminium instead of primary Aluminium.

LCA of IDALSA Process
An LCA can be applied to the Idalsa process to determine the environmental benefits of using the HSP to reprocess the ‘Lingotón’ waste fraction which is currently a waste product. The Lingotón could now be reused because of a lower content of iron, then the HSP may allow to use more lower grade scrap to produce products. We compare the application of the HSP process to the lingotón vs the re-melting of it, that is the usual working process in order to re-use this material. The real advantage is the fact that now we can reuse the lingotón because of a reduction of Fe content in order to obtain specific target alloy. With the re-melting we can’t use it for these specific application.
EnginSoft has analysed the two alternative (re-melting and HSP application) in order to determine the environmental impacts generated by the different processes. The Life Cycle Inventory phase was done in order to have all the information necessary to evaluate the environmental impacts, Figure 18.

From an environmental point of view it is clear that the re-melting of the Lingotón is worse than the application of the HSP, this is directly connected to the different amount of energy necessary to re-melting the material instead of the application of the HSP. (23kW vs 2,2 kW)

Potential Impact:
Socio-Economic Impacts
The RecycAl Project
More than half of all the aluminium currently produced in the EU originates from recycled materials, and that trend is on the increase. Primary aluminium production from bauxite ore is both energy and carbon intensive: recycling uses only 5% of the energy required for extracting the primary metal. In other words, 95% of the energy used to produce the primary Al is still ‘stored’ in the scrap. Many countries (e.g. China) will pay premium prices for scrap, to lower their electricity consumption. Al scrap can therefore be regarded as a valuable resource. With this in mind, many producers are trying to increase their use of secondary (scrap) material. The EU is a world leading aluminium recycler recycling 89% of scrap generated in Europe in 2014, with 60% of packaging waste recycled and 90% of construction and automotive waste recycled. One of the challenges to recycling aluminium is that high performance Al alloys require careful control of specific alloying elements and impurities3. Accumulation of impurities in recycled material streams is a growing problem. For aluminium, the problematic impurities are mainly Fe, Si and Mn (mostly these are bound with Fe as Al-Fe-Mn-Si based intermetallics). The wider list of impurities includes Mg, Ni, Zn, Pb, Cr, Cu, and V but these are not the critical ones that control the recycling of scrap. Compared to many metals, it is very challenging to remove impurities from Al4. For example, simple oxide slag formation (as used in the steel industry) is not an option, as Al oxidises more readily than most of the impurity metals. Therefore, dilution with primary Al is the most common solution used today. This has a negative impact on recycling and results in a compositionally determined cap to recycling.

The main alloys affected are those used for fabricated goods, including extrusion billets and ingots for making wrought or rolled alloys and high-performance cast components such as those used in the automotive or aerospace industries. A high proportion of the Al alloy usage in the EU is in these demanding applications, which means that to increase the use of scrap, the EU must find a way to remove these impurities. Currently most EU scrap is either downgraded into low quality cast products with high levels of impurities (mainly Al-Fe-rich intermetallics), or exported.

The aim of the RecycAl project was to develop a process for removing these impurities, with a particular emphasis on Fe. The project has been successful in developing a lab scale process which can remove iron from scrap material particularly for the production of casting alloys which often contain high levels of Si which are favourable to the RecycAl process. In these cases the RecycAl process can removal Fe from selected sources of scrap material allowing the direct production of casting alloys from scrap. The process could also be used to reduce the Fe content of highly contaminated scrap material from other parts of the recycling process such as the ‘Lingoton’ alloy produced by smelters such as Idalsa. In this way the processed scrap material is effectively upgraded and may be recycled more times as a result of the RecycAl process. Despite the success of the process on recycling casting alloy waste the project was not successful in reducing Fe levels enough to directly produce high quality wrought alloys from scrap. However, in some cases the process could be used to reduce the need for the dilution of scrap with primary aluminium or other purer scrap in the production of high grade wrought alloys, provided suitable sources of scrap with optimal compositions of impurities could be identified.

Environmental Impact
Recycling aluminium allows the saving of 95% of energy required to produce it starting from the raw material. Aluminium is the second most used metal after iron. It is used in a wide number of products and sectors. Aluminium production is based on an electrolytic process, the Hall-Hérolt process, in which metallic aluminium is obtained from the reduction of aluminium oxide. The metal obtained with this process is called primary aluminium. Aluminium oxide is extracted from natural bauxite in the Bayer process. Since the development of the large-scale production of aluminium oxide, aluminium production has expanded enormously (http://www.worldaluminum. org). To obtain 1 kg of aluminium from bauxite in fact 14 kWh are necessary, whereas to recycle 1 kg of aluminium 0.7 kWh are necessary.

The recycling of aluminium is very important, since the residues of this metal can be reused without any loss of quality. The metal obtained in this way is called secondary aluminium. The aluminium destined for recycling can be divided into two categories: pre consumer by-products from the production of primary aluminium, and scrap, associated with postconsumer aluminium. By means of melting, in some cases with prior processing, the by-products and scrap are transformed into ingots, half balls and plates for subsequent commercialization.

Comparing primary and secondary aluminium production, the secondary process causes less environmental impact than the primary process. It consumes 20 times less energy; it emits 20 times less pollution to the atmosphere; it generates between five and nine times less solid wastes, and it consumes 35 times less water. For both processes, the greatest problems derive from the generation and management of wastes. Regarding waste generation, one of the major products of the alkaline extraction of aluminium oxide from bauxite in the Bayer process is red mud. This waste consists of iron, aluminium, silicon, and titanium, with oxides of zinc, phosphorous, nickel, and vanadium in smaller quantities (http://www.world-aluminum.org). The management of this waste is normally carried out by means of controlled landfill disposal. Secondary aluminium alloys are produced by melting and alloying aluminium scrap and alloying elements. Depending on the alloy and the scrap quality, primary or secondary aluminium ingots, as well as liquid aluminium, can be added to the melt. For re-melting aluminium scrap, the typical pre-treatment steps are pre-sorting, cleaning crushing, screening and separating the un-oxidized aluminium from aluminium oxide. This separation is usually done in a molten- salt bath. Alloying usually takes place at temperatures of 700- 730°C. The alloyed aluminum is processed into ingots called slabs (usually rectangular shape). The slabs are produced by DC (Direct Chill) casting in cast houses. Primary and recycled aluminium as well as alloying elements (Mg, Si, etc.) are used for producing aluminium slabs.

During the secondary recycling of aluminium, various types of waste may also be generated. One of the most significant ones, in terms of the amount generated, is the named as salt cake catalogued as hazardous waste (Order MMA/304/2002, BOE 43/2002). It is generated when salt fluxes are used to improve the aluminium recovery. The composition of salt cake is metallic aluminium, several oxides (fraction named as non-metallic products, NMP), flux brines and others components in smaller proportions (Drossel et al., 2003). Based in its composition, salt cake is an important by-product of considerable economic value that is recovered, as long as the process can be economically viable. There are two possibilities of management of salt cake, separation of its components for possible recovery and application, or storage in controlled landfills. The recovery process consists of an initial separation of the metallic aluminium present in salt cake by means of electromagnetic and mechanical procedures (Hryn et al., 1995). This process is economically viable if the content in metallic aluminium is higher than 4 to 6wt.%. The remaining waste consists of non-metallic products, and it can be recovered, i.e. by the HANSE process (Drossel et al., 2003). The idea is that the saline fraction must be separated from the oxides. For certain specific applications, the non-metallic fraction should be free of salts. It is considered free of salts when the salt content is lower than 2 wt.%. It should be noted that the recovery of the saline fraction and of non-metallic products is economically viable only if a concentrated flow of salt and a waste that is free of not metallic products can be obtained. The recycling of aluminium is very important, since the residues of this metal can be reused without any loss of quality. The metal obtained in this way is called secondary aluminium. The aluminium destined for recycling can be divided into two categories: pre consumer by-products from the production of primary aluminium, and scrap, associated with postconsumer aluminium. By means of melting, in some cases with prior processing, the by-products and scrap are transformed into ingots, half balls and plates for subsequent commercialization.

In summary the use of primary aluminium is associated with significantly higher environmental costs than recycling secondary aluminium for the same applications. The goal of the RecycAl project is to increase the potential applications of the scrap aluminium by removing contaminating impurities, particularly Fe from the material. The project has shown the HSP + sedimentation process is capable of directly producing some casting alloys directly from scrap, the process may also be used to produce higher purity wrought alloys after dilution of the processed scrap with virgin material. The application of the RecycAl process in this case reduces the levels of contamination meaning less virgin material is needed to dilute the scrap to achieve the correct composition.

To clarify, with some numerical data, the advantage in the application of the HSP process in order to reduce
the Fe content of scrap aluminium, a simple practical example is considered. The standard level of iron for P1020 primary aluminium is 0,15%. If we should use primary aluminium to adjust a scrap alloy containing 1.7wt% to iron 1,1%, required by some casting alloys, we can calculate the quantity of primary aluminium required for dilution. For example if we have 10t of Aluminium with iron 1,7% and we need to adjust to maximum 1,1% Fe content we would need approximately 7 t of primary P1020 Aluminium (with Fe 0,15%). Reducing the Fe starting content of the secondary Al (this is the objective of the RecycAl) in order to reach the target of 1.1% of the final Al alloy we need less primary Al and the environmental impacts associated to this process are decreasing, as shown in Table 8 and Figure 19.

In order to quantify the decreasing of the necessary primary Al the following evaluation can be done:

The necessary energy needed for the production of the Al alloy with 1,1% Fe is decreasing in function of the amount of primary and secondary Aluminum used. To obtain 1 kg of primary aluminum 14 kWh are necessary, whereas to obtain 1 kg of secondary aluminum 0.7 kWh are necessary. The environmental impacts are proportionally correlated to energy requested for the production of the final alloy. The advantage of the use of secondary scrap instead of the primary material in order to reach a final target Fe % in the alloy is directly correlated to these evaluation. Less is the consumed energy, less are the environmental impacts and more sustainable is our process, as shown in Figure 20.

From an environmental point of view, the improvement in use HSP process can be summarized into the following bullet points:
• The HSP process aims to reduce the Fe content in order to increase the use of secondary Aluminum for a specific Aluminum alloy production with low iron level.
• Different types of scraps are analysed and for skimming’s Aluminium and Lingotón the HSP process gives optimum results.
• Less is the initial Fe content in the secondary aluminum less is the amount of primary Aluminum necessary to reach specific targets.
• Less is the primary Aluminum that is used less are the environmental impacts associated to the production of the final alloys.
Economic Impact
The industrialization studies carried out by the project identify aluminium refining companies as the target market for HSP technology. IDALSA is characterised as a reference company at European level due to the size of the company, its turnover and the type of recycling technology it integrates.
Compared with the annual turnover of these types of companies, the cost of investing to introduce HSP into an existing recycling plant is found to be relatively low and the returns the investment in the order of one-three years, based on the process being applied only to waste products produced by the existing recycling process.

The process defined in the Recycal project enables an easy integration into a recycling plant. The quantity of material to be processed and the configuration of the Recycal process are adaptable to the needs of the plant where it is integrated. The process can be configured as a batch wise, continuous or semi-continuous manufacturing process depending upon the recycling plant and selected feedstock material. The effective integration of the Recycal process is conditioned by the amount of sedimented material which is drawn into the ‘clean’ melt at the end of the process. This limitation can be overcome if we are able to introduce an effective method of separating the solid fraction, with a high Fe content, from the liquid fraction, with low iron content. The Recycal process is able to reduce the amount of primary aluminum needed to reduce the iron content in the refined aluminium alloy and to reduce the energy consumption associated with the primary aluminum dilution process as can be deduced from the conclusions and the economic analysis carried out and thus, reducing the economic costs of the current recycling process. A preliminary economic assessment carried out as part of the RecycAl project considered the production of Alloy 226D from scrap material, a common product of project partners Idalsa. The analysis considered the production of this alloy with and without the HSP using different types of scrap feedstock including; existing recycling waste materials ‘Lingoton’ and ‘Skimmings’. The results showed that significant savings could be achieved by using the HSP to reduce the Fe content of these waste materials which could then be further diluted with higher quality scrap to produce the 226D product. Over one year the profit per tonne of 22D sold by Idalsa was estimated to increase from 145€/T to 157€/T with the ‘Lingoton’ material and from 211€/T to 215€/T if the ‘Skimmings’ scrap is used.

Dissemination Activities
A number of dissemination activates have been undertaken by the consortium including production of a promotional video, papers and presentations at relevant international conferences and open days involving industry and members of the public. Highlights of these activities are presented below.

Promotional Video:
A summary of the project and its key outputs was summarized in a video involving all project partners but led by project partner Suldouro. The video is available on via the project website and via YouTube. A screenshot of the video is shown in Figure 21. The video is aimed at the general public and explains the aims and objectives of the project, how the project was carried out, how the HSP works and what the achievements are. The video finishes with an outlook on the impact of the research on the EU recycling industry.

Academic Papers
To date three academic papers have been published as a result of work carried out by the project;
• Gil and S.A. Korili (UPNA), “Management and valorization of aluminium saline slags: current status and future trends”, Chemical Engineering Journal, 289 (2016), 74-84.

• M. Tong, S.C. Jagarlapudi, J.P. Patel, I.C. Stone, Z. Fan and D. J. Browne (UCD and Brunel), “Computational prediction of the refinement of oxide agglomerates in physical conditioning process for molten aluminium alloys”, 2015 IOP Conference Series: Materials Science and Engineering, 84 012092 [Published as a full paper in the IOP conference series and presented at the international conference MCWASP XIV 2015 – modelling of casting, welding and advanced solidification processes – in Hyogo, Japan]

• M. Tong, J. Patel, I. Stone, Z. Fan, D. Browne (UCD and Brunel), Identification of key liquid metal flow features in the physical conditioning of molten aluminium alloy with high shear processing, Computational Materials Science, 131 (2017), 35-43.

The partners are hoping to submit a couple more papers covering some of the work carried out at the very end of the project which should be submitted in the near future.

Conference Attendances:
Members of the consortium have presented the project findings at numerous technical confrences including those outlined below;

• M. Tong and D. Browne (UCD), “Multiscale modelling of fusion welding and liquid metal conditioning”, invited oral presentation at the International Conference on Computational Design and Simulation of Materials, 17-20th August 2015, Shenyang, China.

• E. Arrieta, S.A. Korili and A. Gil (UPNA), Valorisation of activated saline slags as adsorbents for the removal of acid dyes from aqueous solutions, NanoSpain Conference, 7-10th March, San Sebastian, Spain.

• Gil, E. Arrieta and S.A. Korili (UPNA), Management and valorization of aluminium saline slags, 6th EuCheMs Congress, 11-15th September 2016, Sevilla, Spain

News Letters and Dissemination Days
The project findings have also been disseminated at numerous events held by various partners for a range of stakeholders from academic and industrial audiences to the general public and schoolchildren across Europe. Some of the activates and the audience addressed are highlighted below;

Undergraduate and Postgraduate Students at the University College Dublin and NUI Galway:
M. Tong presented the RecycAl work as part of lecture courses delivered to final year undergraduate and first year post graduate students on teaching modules “Advanced Materials Processing” and “Advanced Manufacturing”. Several lectures highlighted the achievements of the modelling undertaken as part of the RecycAl project, including “Optimising the quality of castings produced by physically conditioning the liquid metal before casting” and “Physical conditioning of aluminium alloys using high shear processing”. The modules were run in 2015 and 2017 and continue to be part of the curriculum in the form of a successful case study.

Industry;
In addition to the formal conference events attended by project partners several training events and workshops have been held by consortium members to outline the achievements of the project in their respective industries. Events have been held by GIF, CRF and Quantal. The events reached a diverse range of audiences from customers working on aluminium forgings and CNHi – heavy duty truck applications to Magneti Marelli Suspension Systems. Quantal also disseminated the project on their stand at a careers event held by the University of Porto which was attended by a range of professionals and students.

Newsletters;
Progress of the project has already appeared in a regular newsletter issued by Quantal. A final newsletter will be produced at the end of the project which all partners will have the opportunity to circulate amongst stakeholders in their industry.

Website:
The project website was created in 2014 and has been updated throughout the project. It contains numerous articles on the HSP + sedimentation process, the commercial casting process carried out at FOMT, the UCD simulation work on the HSP mixing head and chamber and the processing of the HSP scrap. The RecycAl video is also available on the project website.

Exploitation of Results:
The project successfully demonstrated the HSP is capable of removing Fe contamination from aluminium scrap at the lab scale. The process is suitable for reducing the Fe content of some scrap materials to levels low enough for the direct production of some commercial automotive casting alloys. The reduced Fe content of the RecycAl processed scrap also increases the maximum amount of scrap material which can be used to produce other very low Fe automotive alloys. The environmental and economic drivers of the technology are thus both associated with the increased use of recycled material which is cheaper and less environmentally damaging than primary material. However, the process has only been demonstrated at the lab scale and is not applicable to the production of most wrought alloys directly from scrap material.

The process has two critical aspects; first the selection of appropriate scrap material to feed the process and second development of system to maximize the efficiency of separating the Fe sediment from the melt at high temperatures. Industrialisation studies showed the existing, lab scale, HSP could be scaled up and applied to the Idalsa smelting facility to successfully process waste products currently produced by their process. The Fe removed from these products would allow increased re-use of this waste material reducing material costs for the company. Economic studies showed the investment in a HSP + sedimentation system could be justified based on processing of these waste materials alone however, the monetary savings of the system were found to be relatively small compared to the operating costs of the Idalsa site in general. The primary challenge to taking the HSP into full commercial use is the identification of a source of scrap material with a favorable composition for Fe removal by the RecycAl process. If such a source of material could be identified the economic benefits of applying the HSP would become much more compelling. Scrap material high in Fe, Si and Mn is ideal for the process, allowing the largest amount of Fe removal from the material. There is no doubt such scrap fractions exist however, the challenge is often sorting these fractions from existing waste streams such that the RecycAl process can be applied to the most relevant scrap only. A secondary, but related, challenge is increasing the efficiency of the sedimentation system designed to separate the solid iron containing intermetallic particles from the ‘clean’ melt. To be commercially applicable an efficiency of >90% separation of intermetallics from melt would be required to produce significant profits during the processing of readily available scrap materials. The present sedimentation chamber in the lab scale design includes a simple baffle system to prevent sediment being ‘washed’ into the low iron product. The current design of this system is not presently capable of achieving the 90% efficiency target and so further work is required in this area to achieve full industrialisation. As the profitability of the HSP is a strong function of this separation more investment in the separation and filtration methods is needed to demonstrate the ability of the present process to achieve such high separation efficiencies. Alternative separation schemes, including the use of a variety of filters was considered however, existing filters are not able to operate in the required temperature range. If sedimentation efficiencies of over 90% could be demonstrated it is likely the technology would be taken up by smelting companies such as Idalsa. Given the project has shown HSP material has broadly equivalent properties to existing aluminium alloys the HSP material could also be integrated into the supply chain at the alloy production stage making it applicable to all existing casting and other production processes however, it is more efficient to place the technology within existing recycling streams..
European Resource Independence

The demand for aluminium in Europe is growing with a 2% increase across in the industry reported by the European Aluminium Association in 2016. This growth included an increase in primary aluminium production of 1.1%, or 4.3 million tonnes. A further increase of 1.3% was also forecast in 2017, despite the growth of the industry in Europe approximately 50% of European primary aluminium is still imported, 5.9Mt in 2016, and even where primary production is based in Europe the raw material, bauxite, is typically sourced outside Europe. Clearly recycling existing supplies of European aluminium is a critical factor in making up this shortfall in the European aluminium supply and working towards resource independence for Europe. Despite growth in the European recycling industry and the clear benefits of recycling the European aluminium supply large quantities of scrap aluminium are still exported from Europe approximately, 900kt in 2016. This is partly due to the difficulties in removing Fe from ‘low quality’ scrap which limits the applications of the material after recycling and consequently lowers the value of the material. The RecycAl process offers a way to mitigate this problem and increase European resource independence by removing Fe from low quality scrap. By applying the RecyAl process some scrap fractions can be ‘upcycled’ to higher quality grades. The ultimate applicability of the process is dependent upon identifying a suitable source of scrap for the process and a high efficiency filtration process, as discussed above.

Job Creation and Retention

The EU Recycling industry generated €8.6billion revenue in 2014 and directly employed over 6,000 people with 25,000 employed indirectly at this time. With the industry growing in 2016 and 2017 these numbers are projected to increase. The ReccyAl process has the potential to increase these numbers if it is taken up by the recycling industry, this will create additional jobs by enabling the industry to economically re-introduce a larger quantity of ‘low quality’ aluminium scrap into the European aluminium market.

List of Websites:
David Griffiths: david.griffiths@twi.co.uk 01223899000
http://www.recycal-project.eu/

Final Report Summary - RECYCAL (High Shear Processing of Recycled Aluminium Scrap for Manufacturing High Performance Aluminium Alloys)

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