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Analysis of the rotary furnace using ELFEN has been organised in three main steps to create a model: 5. Numerical simulation results 1 creation of the mesh and application of the boundary conditions; 2 optimisation of the mesh and load to optimise In order to predict the distribution of temperatures in a the CPU time; 3 determination of the parameters, such as rotary furnace, a static and transient dynamic analysis has flux, thermal conductivity, etc.
A 2D and 3D Consequently, at the end of this work, the model can be models were generated to evaluate the effects of different used to predict the change in temperature distribution over flame positions on the furnace body. A 2D model of the furnace points, line types, surfaces, volumes and objects.
The load- ing, boundary conditions and material data are assigned to The first model is a 2D rotary furnace, shown in Fig.
As it can be seen in Fig. The flame position is materials. Their thermal characteristics are assumed to be located at the top of the furnace, several different positions constant with variation of temperature and the material data were considered, with one of the possibilities shown here.
As can be seen later, the final result is not really dependent ELFEN allows the boundary conditions applied to a prob- on the flame position and this factor can easily be ignored. For the proposed transient thermal analysis, a time in Fig. The results are as expected in this case. A transient dynamic analysis has been carried out to sim- ulate the furnace rotation at different angular velocities.
In order to apply the heat generated at the flame position and the heat transfer between the melted material and the inter- nal surface of the furnace, the rotation is modelled by dif- ferent flux pulses applied successively to each segment to simulate the changes in thermal loading over time.
When a pulse sequence is complete for a segment, another identical sequence is applied in the following time steps so another cycle can begin again. Therefore, 20 loads are created for the 20 segments with two pulses at every cycle, as shown in Fig.
Note that the rotation of the cylinder is recreated by the rotation of the loadings around the model, rather than the movement of loads and elements. In the first case considered, a rotational speed of 3 rpm was used. Consequently, the rotation lasts for 20 s and the pulse width is 2 s for flame position and 6 s for the contact area between the melted material and furnace is considered.
The analysis was run for cycles and the distribution of tem- perature is obtained at the end of 80 s. The temperature Fig. Geometry of the rotary furnace. Finite element modelling and boundary conditions of a rotary furnace. Due to the large timescale and the short increment in rotation required, the analysis requires a very large num- ber of increments and the CPU time is very long, conse- quently, it is preferable to reduce the geometry.
Since the time required for heat to flow through the thickness of the furnace body is much more than the period of each revolu- tion, the real flux loading, defined by a cyclic impulse, can be approximated to a time-averaged uniform heat flux.
In this case, because of the symmetric plane in the thickness, if the convection is assumed to be the same on the internal and external surfaces of the furnace, it is appropriate to simplify the model by considering only a segment of the furnace. In Fig.
These results can be compared with the temperature contours given Fig. Temperature distribution for the transient dynamic analysis at Fig. Temperature distribution for a static analysis. These results show that the implementation of a segment of furnace can be used effectively in the analysis reducing the computing demands and CPU time.
However, the determination of this equivalent load is important, espe- cially as the complexity of the model increases and will be discussed in a later work. A comparison for different flame positions In order to illustrate a comparison of temperature distri- bution under different flame positions, a transient dynamic Fig. The creation of the model with this software, angular velocities of 3 and 5 rpm.
Finally, a comparison of temperature distri- different nodes are presented for a rotation of 3 and 5 rpm. These results clearly References indicate the temperature distribution for different angular velocities as well as for different flame positions.
Khoei, D. Gethin, I. Masters, Design optimisation of alu- minium recycling process using Taguchi approach, in: Proceedings 5.
The second simulation is a 3D finite element modelling  I. Masters, A. Gethin, The application of Taguchi of the rotary furnace, as illustrated in Fig. As in the 2D methods to the aluminium recycling process, in: Proceedings of model, a transient dynamic analysis has been carried out to the Fourth ASM International Conference and Exhibition on the simulate the furnace rotation.
To apply the heat generated Recycling of Metals, Vienna, Austria, , pp. Khoei, I. Masters, D. Gethin, Historical data analysis in quality at the flame position and melted material on the internal improvement of aluminium recycling process, TMS Conference on surface of the furnace, 50 segments are defined to simulate the New Technology for the Next Millennium, Pennsylvania, USA, the number of flux loading.
In this case, 50 loads are created , pp.
Gethin, Design optimisation of alu- The analysis is run for cycles and the distribution of minium recycling processes using Taguchi technique, J. Sullivan, C. Maier, O. Ralston, Passage of Solid Particles speed of 3 rpm. Friedman, A. Marshall, Studies in rotary drying, Chem. Perry, C. Chilton, S. Mu, D. Perlmutter, The mixing of granular solids in a rotary an accurate manner, which will not be discussed here.
Perron, R. Much of the energy is consumed during the electrolytic extraction of pure aluminium from its ore Bauxite. In contrast to the expensive production of primary aluminium, recycling it is significantly cheaper. Therefore the recycling of aluminium is becoming an important economical and ecological part of the product life cycle .
According to results obtained by Duflou et al. In order to prevent sticking of the billet in the container, the die container is pre-heated. The ram is then pushed onto the billet with a dummy block in between to protect the ram from getting damaged over time. First upsetting of the billet occurs 3 since the billet initial diameter is slightly lower than that of the die container.
Next the billet is squeezed through the die mouth taking the shape of the mouth and emerging as a fully formed profile.
During the extrusion process, the lack of tensile forces coupled with the action of high compressive and shear forces, keep the billet material from tearing apart and allow high deformations that allow the material to be squeezed into the shape dictated by the mouth of the die. The extrudate is then either allowed to cool naturally or rapidly cooled using air or water quenching. The extrudates are then subjected to the age hardening process which can be again natural i. These processes are vital in order to achieve the optimum mechanical properties in the extruded profiles.
The process involves the cold or hot compaction of the chips by a hydraulic press into a solid body or billet, followed by the loading of the billet into an extrusion press. The billet is then extruded at temperatures ranging from to oC and at pressures between and MPa. The extrusion part of the process is carried out in hot extrusion presses as shown in figure 1 and explained in the conventional hot extrusion section.
Machined chips or powder based scrap have a high surface to volume ratio and so re-melting results in considerable material losses due to the presence of residual lubrication and contaminants from the production process, combustion oxidation , slag formation and improperly controlled furnace settings . And the use of low process temperatures means that major oxidation and metal losses can be avoided.
The skipping of the melting phase and the lower processing temperatures are the two primary reasons for the high material yield in SSR. The SSR technology is best suited for small scrap material such as chips, flakes, foils and powders. Larger material forms can be recycled more efficiently and economically by conventional re-melting processes . Iron, copper, cast iron, magnesium and aluminium alloys are some of the metals that can be recycled with this technique .
Subsequent sections will focus on the recycling of aluminium machining chips by hot extrusion. Figure 2 gives an overview of the techniques and process variations that have been used for the recycling of machined chips by SSR. Degreasing and cleaning of the chips is usually the first step that takes place. Degreasing is commonly performed by thermal or chemical means. It has been recommended to first perform a thermal decoating process and annealing followed by degreasing using acid or hydroxides to remove the surface oxides.
Since the degreasing and annealing processes reduce 6 oxide content and impurities and encourage softening of the chips , they enable the achievement of a higher green density  . Machined chips from semi-finished aluminium alloys can be very difficult to recycle due to their elongated spiral chips and so some researchers had suggested applying powder metallurgical techniques instead.
Zapata et al. While Gronostajski et al. The powder composite was then cold pressed and hot extruded to produce composite materials.
The addition of these alloying powders showed to improve the final mechanical properties of the chip based extrudates but also showed problems of inhomogenous hard phases distributions specially accumulations on the outer surfaces. However, in recent years researchers have started focusing more on avoiding the process of the breaking down of the chips into powder form altogether and directly compacting the chips instead, followed by hot extrusion, in order to implement a more lean process chain.
Two techniques have been commonly used in recent years for the compaction of chips, namely the powder metallurgy technique and hot extrusion. In powder metallurgy, the scrap in powder form is compacted and then sintered to form the final product, whereas in hot extrusion the chips or scrap are first compacted and consolidation happens via plastic deformation. Good bonding between the chips and elimination of porosities are the key factors that affect the consolidation process of aluminum chips, which subsequently influence the mechanical properties of the final extruded profiles .
These can be achieved by appropriately choosing the type of chip, chip morphology, compaction pressure and cold pressing time.
In the multilayer approach a number of compression strokes ranging from 2 to 8 can be used to progressively form the billet, giving higher billet density and therefore lower billet porosity. This effectively creates a counter pressure. The backpressure created depends on the flow stress and the thickness of the sheet metal used. In the natural state aluminium chips are completely covered with a layer of aluminium oxide.
This is what gives aluminium its high corrosion resistance. However in order for the chips to form a good bond during the so-called welding process during the hot extrusion, the oxide layer needs to be broken away so that the aluminium chips can form a direct metal- to-metal bond. This can most promisingly be achieved by implementing high compressive stresses i. Good mechanical properties in chip-based profiles are ensured by the use of a high extrusion ratio for the chip extrusion .
Not using a high enough extrusion ratio R, can potentially lead to the development of porosities in the final chip-based extrudate and consequently bad mechanical properties .
One of the challenges with achieving high extrusion ratios is that for a given size of the extrusion press the profile cross section size that can be achieved is limited. This can however be overcome by suitable die designs such that even with low extrusion ratios, high strain rates can be achieved to the extent that the final chip-based extrudates demonstrate mechanical properties that are similar to that of extruded cast material .
Misiolek et al.