EP3110568B1

EP3110568B1 - Ballistic separator drum for moist materials

Info

Publication number: EP3110568B1
Application number: EP15708312.2A
Authority: EP
Inventors: Danilo Molteni
Original assignee: Sgm Magnetics SpA
Current assignee: Sgm Magnetics SpA
Priority date: 2014-02-28
Filing date: 2015-01-29
Publication date: 2018-12-05
Anticipated expiration: 2035-01-29
Also published as: EP3110568A1; WO2015128753A1

Description

The present invention relates to ballistic separators, and in particular to a ballistic separator drum for the treatment of a stream of moist material containing particles of different grain size. A typical application of this separator is in the treatment of heavy ash from incineration of solid urban waste and the like, quenched in water and thus having a moisture content of 10-20%. The ash is treated to separate smaller particles from larger particles and then be able to proceed through other techniques to recover any metals possibly present in the larger grain size that is less humid as a result of the action of the separator. Specific reference will be made in the following to this application, while being clear that what is said also applies to other streams composed of a material soaked with water and scarcely compact in which are dispersed compact particles that do not absorb water (typically metal, plastic and the like) .
It is known that a ballistic separator is basically composed of a feed device, typically a conveyor belt, which conveys the material to be treated to an underlying motorized drum that rotates rapidly about an axis arranged perpendicular to the feed direction. The traditional structure of the drum of a ballistic separator consists of a cylinder provided with a plurality of evenly spaced longitudinal throw slats, usually from two to four, which extend radially outward from the circumference of the cylinder and hit the material falling from the feed device thus projecting the different components of the material at different distances depending on the properties of each component, so as to achieve the separation.
More specifically, the components of the material that are richer in water and less compact during the impact dampen the hit and shatter and are launched relatively close, same as the smaller particles, while the more compact and larger components receive a thrust that throws them farther and makes them considerably less moist. Examples of this type of separator can be found in patent publications WO 2009/123452 and EP 2412452 , specifically relating to the recovery of metals from the heavy ash of waste incinerators, or in DE 2436864 and DE 9419448 showing the treatment of compostable waste for the separation of extraneous components (plastic, glass, etc.).
In the prior art ballistic separators mentioned above the throw slats have radial impact faces and therefore must hit the material in a vertical or nearly vertical position in order for the initial throw direction of the material to be substantially perpendicular to the fall trajectory, such a limitation resulting in a throw "fan" with a rather limited angle. Moreover, the parameters that can be varied to adapt the separator to the different characteristics of the material to be treated (grain size, moisture content, etc.) are only the rotational speed of the drum, the feeding speed of the material and the position of the point of fall of the material with respect to the drum. However, these three parameters affect each other whereby their adjustment ranges are rather limited, for example the feeding speed and the point of fall must take into account the position and the frequency of passage of the drum slats to obtain a correct impact on the material as described above.
Consequently, the separation obtained with these separators is rather inaccurate and each separator has a narrow scope of fairly effective operation. For example, the separators described in the above mentioned publications WO 2009/123452 and EP 2412452 operate on material with particles up to 15 mm and are designed to separate particles <2 mm from the larger particles between 2 and 15 mm.
There are also other types of ballistic separators that are not used for the treatment of a stream of moist material containing particles of different granulometry but rather for the subdivision of dry grains such as BE 410 965 , which discloses a ballistic separator drum according to the preamble of claim 1, DE 65106 and DE72777 or for the division of plastic waste from paper waste as in EP 1676645 . In these ballistic separators the throw slats of the drum have impact faces with a radially proximal end more advanced, in the direction of rotation, than the radially distal end whereby the angle α between the diametral plane containing said distal end and the impact face instead of being nothing has a value comprised between about 15° and 55°, said inclination being optionally adjustable.
Such an angle α is necessary for the type of material treated by these separators but said inclination is not sufficient to solve the aforementioned problems in the treatment of a stream of moist material comprising components of the material that are richer in water and less compact.
The object of the present invention is therefore to provide a ballistic separator drum which overcomes the above-mentioned drawbacks. This object is achieved by the ballistic separator drum in accordance with claim 1, in which the impact face of the throw slats has a linear development inclined according to angle α which is radiused in a distal portion to an involute-shaped curved segment over a height indicatively equal to 17±5% of the overall height of the slat, said slats being preferably replaceable. Other advantageous features are recited in the dependent claims.
A first important advantage of the drum according to the present invention is to ensure that in any case the trajectory of the compact components contained in the material that is impacted by the distal portion has a range sufficient to reach the recovery zone of the "positive", i.e. material with low moisture content, mechanically firm and with a high presence of metal, going beyond the collection area of the waste, i.e. the material soaked with water, of low mechanical consistency, of small or very small size and negligible or very reduced presence of metal.
A second significant advantage of this drum stems from the fact of being able to generate a broader throw "fan" which results in a better separation of the various components of the material. This allows to considerably extend the scope of operation of the separator, for example making it capable of treating material with particles up to 40 mm and/or moisture content of up to 30%.
Still another advantage of the present drum, in its preferred embodiment, is derived from the use of easily replaceable throw slats so as to minimize the downtime when the separator must be adjusted to treat a different material or even just for the replacement of worn slats.
These and other advantages and features of the ballistic separator drum according to the present invention will become apparent to those skilled in the art from the following detailed description of an embodiment thereof with reference to the accompanying drawings in which:

Fig.1 is a perspective view of a ballistic separator comprising a ballistic separator drum according to the invention;
Fig.2 is a view in longitudinal section of the drum and of the relevant motor along a center plane comprising the throw slats;
Figs.3 and 4 are enlarged details in cross section of the preferred embodiment of the slats;
Fig.5 is a partial perspective view of the drum showing the mounting system of the slats;
Figs.6 and 7 are enlarged details in cross section of the mounting system of Fig.5;
Fig.8 is a cross-sectional view of the drum of Fig.5; and
Fig.9 is a schematic side view of the separator of Fig.1 completed with some additional elements for the collection of the separated materials.

Referring to figures 1 and 2, there is seen that a ballistic separator provided with a ballistic separator drum 1 according to the present invention conventionally includes a low-adhesion conveyor belt 2, driven by a variable speed motor 3, which conveys the material to be treated loaded through a hopper 4 provided with an output gate 5 for adjusting the thickness of the material layer. The conveyor belt 2 is provided with means for adjusting its position relative to drum 1, being mounted on slides whose position is defined by worms. In this way it is possible to properly set the fall trajectory of the material to make it coincide with the impact face of the throw slat 6 of the underlying drum 1 that rotates rapidly, driven by a variable speed motor 7, about an axis disposed perpendicular to the feed direction of the material.
Drum 1 conventionally includes a steel cylinder 8 on which there are welded end flanges 9 which are then keyed on a shaft 10, coaxial to cylinder 8 and coupled to motor 7 by means of an elastic coupling 11. In order to equilibrate and balance drum 1, since its speed of rotation may preferably vary between 500 and 1400 rev/min, cylinder 8 is provided with a plurality of evenly spaced longitudinal slats 6, typically two slats placed at a distance of 180° as in the illustrated example, or three placed at 120° or four placed at 90°.
In this regard it is noted that it would also be possible to mount the same drum 1 on adjustable slides to adjust the fall trajectory, but this is not advisable due to the high weight of the drum (1000-1500 kg), and the fact that it must rotate up to 1400 rev/min while maintaining it stably balanced and equilibrated.
Referring now to figures 3 and 4 there is seen that the impact face 6a of a throw slat 6, i.e. the face on the side towards the direction of rotation of drum 1, instead of extending exactly in the radial direction, as in prior art separators for moist material, presents a proximal end more advanced in the direction of rotation with respect to its distal end. In this way, the angle α between the diametral plane containing the distal end and the impact face 6a has a value comprised between 5° and 45°, preferably between 5° and 30°, and more preferably between 5° and 15° as in the embodiment illustrated in these figures.
This variability of angle α makes it possible to operate the separator with variable fall trajectories of the material by adjusting the position and the speed of the conveyor belt 2, since it is possible to arrange for each trajectory a specific inclination of the impact face 6a so as to obtain every time that the initial throw direction of the material is substantially orthogonal to the fall trajectory. This allows to optimize both the flow rate of the material as a function of its grain size and the dehumidification of the compact components to be recovered and the concentration of metal therein. Moreover, the feeding speed of the material can be increased to achieve a higher productivity of the separator, i.e. a higher hourly output of treated material.
A first novel aspect of the present ballistic separator drum resides in the fact that the impact face 6a has a linear development inclined according to angle α which is radiused in the distal portion 6a' to an involute-shaped curved segment over a height d indicatively equal to 17±5% of the overall height of the slat 6. In other words, said distal portion 6a' has always the same shape regardless of the angle of inclination of face 6a, in the illustrated example 5° ≤ α ≤ 15°, for ensuring that in any case the trajectory of the compact components contained in the material that is impacted by portion 6a' has a range sufficient to reach the recovery zone of the "positive" going beyond the collection area of the waste.
From tests carried out by the applicant it was found that for the material with particle size up to 40 mm the conveyor belt 2 can operate at a speed of 0,2 m/s and the impact face 6a must be inclined at least 5°, for intermediate particle size up to 25-30 mm the conveyor belt 2 can operate at a speed of 0,5 m/s and the impact face 6a must have an angle of inclination α of about 15°, and for smaller particle size up to 15-20 mm the conveyor belt 2 can operate at a speed of 0,8 m/s and the impact face 6a must have an angle α of approximately 30°.
Therefore the possibility of varying the fall trajectories of the material (and therefore the throw trajectories) allows a better targeting of the compact components with presence of metals to be recovered, both as a function of the percentage of presence of such components and as a function of the moisture level and of the feed rate of the material.
It is clear that if a drum 1 with throw slats 6 having an angle α = 30° is suitable to treat material with a smaller particle size so as to throw in the recovery zone also metal pieces smaller than 2 mm, which would not be recovered by a conventional separator, this drum 1 will perform less on a material with a larger particle size up to 40 mm for which it is preferable that the throw slats 6 have an angle α = 5°.
A second novel aspect of this ballistic separator drum, in its preferred embodiment, is therefore given by the possibility of easily replacing slats 6 to adapt drum 1 to the material to be treated, while maintaining the most stringent conditions for a safe operation necessary for an element that rotates so quickly. This aspect is illustrated with reference also to figures 5 to 8, in which slats 6 are represented without the distal portion 6a' for the sake of simplicity.
Each slat 6 is provided on its rear face, i.e. the face opposite to the impact face 6a, with a series of longitudinally aligned recesses 6b, a plurality of threaded holes 6c and a longitudinal tooth 6d facing towards the distal end of slat 6. These features are used to secure slat 6 to a connector 12 which is integral with cylinder 8, being inserted with a matching shape in a longitudinal T-shaped groove 8a prior to welding flanges 9. For reasons of safety and mechanical stability and to maintain the balance over time it is also preferable that connector 12 is welded to cylinder 8.
More specifically, slat 6 is frontally hooked to connector 12 through tooth 6d which engages a matching longitudinal tooth 12a formed on the front face of connector 12 and facing cylinder 8. This frontal undercut hooking between teeth 6d and 12a is made possible by a chamfer 6e at the base of the rear face of slat 6, and is maintained by means of eccentric studs 13 which engage recesses 6b by passing through corresponding threaded holes 12b formed in connector 12 (Fig.7).
The centrifugal push provided by the eccentric studs 13 guarantees the perfect coupling of the two parts 6 and 12 through their respective hooking teeth 6d and 12a. This coupling is subsequently secured by locking screws 14 which engage the threaded holes 6c by passing through corresponding holes 12c formed in connector 12 (Fig.6).
This mounting system allows to ensure the perfect holding of the throw slat 6, effectively counteracting the centrifugal force and maintaining over time a good stability and balance. At the same time, the simple removal of the eccentric studs 13 and of the locking screws 14 allows an easy replacement of slat 6 in case of wear and especially when it must be replaced with another slat having a different inclination α of the impact face 6a, according to the functional features described above.
To protect the above-mentioned fastening means 13, 14 of slat 6, a cover 15 is also preferably provided on the rear face of connector 12 to which cover 15 is hooked and fixed in a manner similar to that of slat 6 to overcome the centrifugal force and maintain balancing. In fact, cover 15 is provided on its front face with a longitudinal tooth 15a which, thanks to a base chamfer 15b, engages an undercut 12e formed on the rear face of connector 12, and is finally locked by screws 16 which engage threaded holes 12d formed in connector 12 by passing through corresponding holes 15c formed in cover 15.
Finally, Fig.9 shows schematically the separator of Fig.1 completed with a safety tunnel 16 arranged above the collection areas S, P of the waste and positive respectively (e.g. two conveyor belts or two hoppers). To reduce the overall length of the plant it is preferable to have in the final part of tunnel 16 adjustable and oscillating baffles 17, 17', 17" arranged at various heights and distances along the trajectories so as to intercept and drop the separated materials into the collection area P of the positive. The inclination of said baffles may vary between 46° and 90° from the horizontal, and they can have a pre-load for damping the impact that is adjustable as needed, i.e. depending on the mass and velocity of the materials to be intercepted.
This separation plant is thus suitable to treat various types of moist granular material (moisture content 10-30%, grain size up to 40 mm) with the presence of metals and other solid materials to be concentrated and dehumidified for a subsequent specific separation, for example through iron removal equipment, eddy current separators, gravity tables, airsifting etc.
It is clear that the above-described and illustrated embodiment of the ballistic separator drum according to the invention is just an example susceptible of various modifications. In particular, the mounting of slats 6 on connectors 12 as well as the fixing of connectors 12 to cylinder 8 may be made through means mechanically equivalent to those provided in the present description. Furthermore, the size and number of slats 6 and other elements of the plant which includes the present ballistic separator drum 1 may vary according to specific constructive requirements. By way of example consider that the plant used for the above-mentioned tests has the following characteristics:

distance from the top surface of belt 2 to the axis of drum 1: 825 mm
external diameter of cylinder 8: 450 mm
height of the throw slats 6: 100 mm
number of throw slats: 2
rotational speed of drum 1: 1400 rev/min

Claims

Ballistic separator drum (1) comprising a cylinder (8) provided with a plurality of evenly spaced longitudinal throw slats (6) extending in a substantially radial direction and provided with an impact face (6a) on the side towards the direction of rotation of the ballistic separator drum (1), said impact face (6a) having a radially proximal end more advanced, in the direction of rotation, than the radially distal end whereby the angle (α) between the diametral plane containing said distal end and the impact face (6a) has a value comprised between 5° and 45°, characterized in that the impact face (6a) has a linear development inclined according to said angle (α) which is radiused in a distal portion (6a') to an involute-shaped curved segment over a height (d) equal to 17±5% of the overall height of the slat (6).
Ballistic separator drum according to claim 1, characterized in that the angle (α) is comprised between 5° and 30°, preferably between 5° and 15°.
Ballistic separator drum according to claim 1 or 2, characterized in it further includes means for removably fixing the slats (6) on the cylinder (8).
Ballistic separator drum according to claim 3, characterized in that the removable fixing means include matching hooking means formed on the rear face of the slat (6) and on the front face of a relevant connector (12) integral with the cylinder (8), as well as fastening means suitable to secure said hooking through introduction in corresponding seats respectively formed on the rear face of the slat (6) and in said connector (12).
Ballistic separator drum according to claim 4, characterized in that the matching hooking means consist on the rear face of the slat (6) of a longitudinal tooth (6d) facing the distal end of the slat (6) and on the front face of the connector (12) of a longitudinal tooth (12a) facing the cylinder (8), the rear face of the slat (6) being provided with a bottom chamfer (6e) suitable to allow the frontal undercut hooking of said teeth (6d, 12a).
Ballistic separator drum according to claim 4 or 5, characterized in that the fastening means consist of eccentric studs (13) that engage recesses (6b) formed in the slat (6) by passing through corresponding threaded holes (12b) formed in the connector (12), as well as locking screws (14) that engage threaded holes (6c) formed in the slat (6) by passing through corresponding holes (12c) formed in the connector (12).
Ballistic separator drum according to any of claims 4 to 6, characterized in that it further includes a cover (15) fixed on the rear face of the connector (12) so as to protect the fastening means.
Ballistic separator drum according to claim 7, characterized in that the front face of the cover (15) is provided with a longitudinal tooth (15a) and a bottom chamfer (15b) suitable to allow said longitudinal tooth (15a) to frontally engage an undercut (12e) formed on the rear face of the connector (12), the cover (15) being locked by screws (16) that engage threaded holes (12d) formed in the connector (12) by passing through corresponding holes (15c) formed in the cover (15).
Ballistic separator comprising a low-adhesion conveyor belt (2), driven by a variable-speed motor (3), on which the material to be treated is loaded through a hopper (4) provided with an outlet gate (5) to adjust the thickness of the layer of material on said conveyor belt (2), which is provided with means for adjusting its position with respect to an underlying drum (1) that rotates, driven by a variable-speed motor (7), around an axis arranged perpendicularly to the feed direction of the material, characterized in that said drum (1) is a ballistic separator drum according to any of the preceding claims.
Ballistic separator according to claim 9, comprising a safety tunnel (16) arranged above collecting regions (S, P) of the waste and positive respectively, characterized in that it further includes in the final portion of said tunnel (16) adjustable and oscillating baffles (17, 17', 17") arranged at different heights and distances along the throw trajectories of the separated materials, so as to intercept and drop them in the collecting region (P) of the positive.
Ballistic separator according to claim 10, characterized in that the inclination of said baffles (17, 17', 17") is variable between 46° and 90° with respect to the horizontal.
Ballistic separator according to claim 10 or 11, characterized in that the baffles (17, 17', 17") have a pre-load for dampening the impact of the separated materials.