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(11) | EP 0 562 234 B1 |
| (12) | EUROPEAN PATENT SPECIFICATION |
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| (54) |
Drum mixer-drier for the continuous preparation of bituminous mixes with recycling of reclaimed materials Misch-Trocken-Trommel für die kontinuierliche Aufbereitung von bituminösem Mischgut unter Wiederverwendung von rückgewonnenem Material Tambour mélangeur et sécheur pour la préparation en continue des enrobés bitumineux en recyclage de matériaux récupérés |
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| Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention). |
[0001] The present invention relates to a drum mixer-drier for the continuous preparation of bituminous mixes with recycling of reclaimed materials, as defined in the preamble of the appended claim 1 and as disclosed in EP-A-0 347 281.
[0002] Drier-mixers of the described type (hereinafter termed simply "mixers" for the sake of brevity in description) are already known. They comprise a drum with internal blades which rotates about an axis which is slightly inclined with respect to a horizontal plane; the aggregates are introduced at the upper end of the drum and, by means of the rotation of the drum, move toward the opposite lower end, where the discharge outlet is located. A burner, orientated along the axis of the drum, is arranged in said upper end and dries and heats the aggregates.
[0003] The bitumen inlet is located at a certain distance from the burner; the bitumen, with the addition of additives, is mixed together with the aggregates. The bitumen inlet is located at a distance from the burner which is sufficient to avoid the formation of fumes. In known mixers there is also, in a point of the drum located upstream of the bitumen inlet, the inlet for the reclaimed material, generally constituted by mixes which originate from the demolition of old paving. This reclaimed material (recyclable asphalt pavement, hereinafter abbreviated as RAP) is mixed with the aggregates and the bitumen.
[0004] A drawback of the known mixers is the difficulty encountered in heating the aggregates to a high temperature while at the same time preventing the bitumen and the RAP from reaching temperatures which cause the formation of fumes.
[0005] A technical aim of the present invention is therefore to provide a drier-mixer which obviates the above described problems related to the exposure of bitumen and RAP to excessive heat.
[0006] This aim, and objects of the invention, which will become apparent from the following description, are achieved by a drier-mixer for the continuous preparation of bituminous mixes for pavings, as defined in the appended claims.
[0007] Further characteristics and peculiarities will become apparent from the following description of a preferred embodiment, illustrated only by way of non-limitative example in the accompanying drawings, wherein:
figure 1 is a partially sectional side view of a drier-mixer according to the invention and
figures 2, 3, 4 and 5 are sectional views, taken respectively along the planes II-II, III-III, IV-IV and V-V of figure 1.
[0008] With reference to the above figures, the mixer is generally designated by the reference numeral 1 and comprises a base 2 which may be mounted on wheels for the transfer of the mixer to the work site.
[0009] A drum 3 is mounted on the base for rotation about the axis A. When the mixer is working, the axis A is slightly inclined with respect to the horizontal plane, so that the drum has an uppermost or upper end 4 and a lower end 5. Outside the drum, proximate to the ends 4 and 5, there are two hoops or annular flanges 6 and 7 which constitute two rolling tracks engaged by pairs of rollers 8 and 9 on which the drum rolls. The rollers 8 and 9 are rotatable in appropriate supports fixed to the base. The rotation of the drum is produced by a gearmotor 10 which is fixed to the base and is provided with an output pinion 11 on which a chain 12 is entrained; said chain is also entrained around a toothed wheel 13 which is fixed to the outside of the drum 3, thus defining a closed-loop formation.
[0010] The reference numeral 14 designates a cylinder which is arranged concentrically around the lower portion of the drum and defines, together with said drum, an annular interspace 15. The cylinder 14 is rigidly coupled to the base 2, on which it rests by means of lateral feet 16, and comprises two flanges 17 and 18 which are at right angles to the axis A and have an annular crown shape; the inner edge of the flanges 17,18 skims or slidingly contacts the outer surface of the drum 3 so as to close the interspace 15 at its opposite ends.
[0011] The upper end 4 of the drum is closed by a fume expansion chamber 19, outside which a hopper 20 for feeding the aggregates is fitted; said aggregates are introduced in the drum through an opening of the chamber 19. The drum is furthermore connected, by means of an opening 21 of the fume expansion chamber, to a stack 22 for aspirating the volatile substances and the dust which form during preparation of the bituminous mix.
[0012] In addition to the aggregates it is possible to load the drum with reclaimed material (RAP) originating from the demolition or milling of road paving. The RAP is introduced into the drum through a funnel 23 which leads into an annular duct 24 located at a preset distance from the flange 18 of the cylinder 14. The annular duct 24 defines, around the drum, an annular chamber 25 in which blades 26 rotate; said blades are fixed to the outside of the drum 3. Openings 27 are defined on the drum between the blades 26 and allow the RAP to pass inside the drum during its rotation. The blades 26 are rigidly coupled to the drum 3 at the annular chamber 25 along a band 30 which is as wide as said chamber and defines recesses 28a. The recesses 28a are open towards the end 5 and are closed toward the end 4.
[0013] Wings 28 and 29 are rigidly coupled to the inner surface of the drum. The wings 29 extend up to the end 4 and the wings 28 extend from the annular duct 24 toward the end 5, end at the level of the flange 18 and are shaped so as to cause advancement of the material in the direction B. The wings 29 furthermore have a substantially L-shaped profile which, during rotation of the drum, facilitates the tipping or cascading of the material through the combustion gases and enhances heat exchange with them.
[0014] The wings 28 are instead shaped so as to shield the internal surface of the drum 3 from the radiant heat of the flame. They simultaneously prevent the rise of the material and thus its falling through the flame. The heat received by the wings 28 is transferred, upon each rotation of the drum 3, to the material which flows in the lower region in this portion of the drum.
[0015] The wings 28 are aligned, at the level of the flange 18, with openings 31 defined in the drum 3. The openings 31 connect the inside of the drum to the end of the annular interspace 15 which is adjacent to the flange 18. In this manner the material can be transferred from the drum into the interspace 15. Downstream of the openings 31, inside the drum, there is a plurality of baffles 32 which are connected to a flange 33 and are orientated so as to deflect backward any material which might have gone beyond the openings 31, by causing such material to fall back into the openings.
[0016] The portion of the drum which extends from the flange 33 to the end 5 constitutes the combustion chamber 34, into which the flame of a burner 35, which is coaxial to the axis A, is directed.
[0017] The combustion chamber 34 is internally covered with a lining of ceramic fibers 36 which protects the drum against excessive temperatures.
[0018] The burner 35 is mounted on a flange 37 which is supported by a support 38 fixed on the base 2. The flange 37 is arranged adjacent to the end 5 of the drum in order to allow rotation of the drum with respect to the burner.
[0019] The drum 3 is externally provided, along the portion which corresponds to the length of the cylinder 14, with fins 39 for mixing the material and conveying it toward a discharge outlet 40 located adjacent to the flange 17. The outlet 40 leads into a hopper 41 provided with a discharge shutter 42.
[0020] The described mixer is completed by two ducts 43 and 44 for feeding bitumen and respectively additives (fillers) into the interspace 15. The ducts 43 and 44 are arranged on the fixed cylinder 14 on a plane which is perpendicular to the axis A and is located downstream of the flange 18.
[0022] Upon rotating the drum 3, aggregates introduced through the hopper 20, due to the inclination of the drum 3 and of the wings 29, advance in the direction B and along the path leading to the ring 24 and are heated due to the hot air generated by the burner 35. The aggregates have a temperature in the range of 150-250o, by the time they reach the ring 24, where RAP is added; said RAP is transferred into the interspace 15 through the openings 31 together with the aggregates, after covering the portion of the blades 28.
[0023] In the interspace 15, the blades 39 thoroughly mix the aggregates and the RAP with bitumen and additives, added through the ducts 43 and 44 to produce a final mix which has a temperature in the range of 150-180° and is discharged into the hopper 41 through the outlet 40.
[0024] One important feature of the described mixer is to be found in the location of the inlet 23, 24 for the reclaimed material, which is sufficiently spaced from the burner to avoid the formation of fumes but is such as to ensure a softening of the bitumen for facilitating mixing with the aggregates. Equally, the cylinder 14 creates a mixing region in which the bitumen and the materials are protected against direct exposure to the flame and kept at such a temperature as to avoid the formation of fumes.
[0025] It should be noted that the inside of the drum, due to aspiration through the stack 22, is at a negative pressure, so that any gases released from the mix during mixing in the interspace 15 pass through the openings 31 into the drum, where they are burned.
[0026] Numerous modifications and variations are possible in the practical embodiment of the mixer within the scope of the inventive concept expressed in the following claims.
[0028] Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly such reference signs do not have any limiting effect on the scope of each element identified by way of example by such reference signs.
a drum (3) which is rotatably supported about a longitudinal axis (A) which is inclined with respect to a horizontal plane so as to have a lower end (5) and an upper end (4);
means (10-12) for rotating said drum about said axis;
a burner (35) located at the lower end (5) of said drum (3) for directing a flame along said longitudinal axis (A) toward the upper end (4) of the drum (3) in order to heat it internally;
means (20) for introducing aggregates at the upper end (4) of said drum (3);
a stationary cylinder (14) which concentrically surrounds the lower portion of said drum (3) and defines an annular interspace (15) together with said portion, said cylinder (14) having a lower end, which is proximate to the burner (35), and an upper end;
means (23-27) for introducing reclaimed bituminous material into said drum (3) at a point which has a preset distance from the upper end of said cylinder (14);
means (31-32) for transferring said reclaimed material and said aggregates from said drum (3) into said annular interspace (15) at the upper end of said cylinder (14);
means (28-29) which are operatively associated with the inside of said drum (3) in order to cause the advancement of said aggregates and of said reclaimed material toward said means (31-32) for introducing them in the annular interspace (15);
means (43-44) for introducing bitumen, filler and additives proximate to the upper end of said cylinder (14); and
means (39) which are operatively associated with the outside of said drum (3) along said stationary cylinder (14) in order to mix said aggregates and said reclaimed material with said bitumen, said filler and said additives, so as to obtain a bituminous mix and cause the advancement of said mix toward a discharge outlet (40) arranged at the lower end of said cylinder (14);
the drier-mixer being characterised in that:said interspace (15) is completely isolated from the inside of said drum (3) at the lower portion of said drum (3) and at the lower end of said cylinder (14);
said means (31-32) for transferring said reclaimed material and said aggregates from said drum (3) into said annular interspace (15) are adapted for transferring all of said reclaimed material and aggregates out of the inside of said drum (3) and into said annular interspace (15);
the outlet of said burner (35) is located at the lower end (5) of the drier-mixer; and
said means (43-44) for introducing bitumen, filler and additives are adapted for introducing the materials directly into the isolated annular interspace (15) such that the materials do not enter into the inside of said drum (3).
substantially L-shaped profile wings (29) coupled to the inner surface of the drum (3) and extending from said upper end (4) to the zone of introduction of the reclaimed bituminous material into said drum (3);
recesses (28a) arranged inside the drum (3) in communication with openings (27) of the drum for passage of reclaimed bituminous material into the drum, said recesses being open towards said lower end (5) and closed toward said upper end (4); and
wings (28) coupled to the inner surface of the drum (3) and extending from the zone of introduction of the reclaimed bituminous material to said means (31-32) for transferring said reclaimed material and said aggregates from said drum (3) into said annular interspace (15), said wings (28) being shaped so as to define shields for protecting the internal surface of the drum (3) against irradiation and so as to transfer the heat to the material.
- eine Trommel (3), die drehbar um eine Längsachse (A), welche bezüglich einer horizontalen Ebene geneigt ist, so daß sie ein unteres Ende (5) und ein oberes Ende (4) hat, gelagert ist,
- Mittel (10-12) zum Rotierenlassen der Trommel um die Achse,
- einen am unteren Ende (5) der Trommel (3) gelegenen Brenner (35) zum Richten einer Flamme entlang der Längsachse (A) gegen das obere Ende (4) der Trommel (3), um sie inwendig zu erhitzen,
- Mittel (20) zum Einleiten von Zuschlagstoffen am oberen Ende (4) der Trommel (3),
- einen stationären Zylinder (14), der den unteren Abschnitt der Trommel (3) konzentrisch umgibt und zusammen mit dem Abschnitt einen ringförmigen Zwischenraum (15) bildet, wobei der Zylinder (14) ein unteres Ende, das unmittelbar an den Brenner (35) angrenzt, und ein oberes Ende hat,
- Mittel (23-27) zum Einleiten von rückgewonnenem bituminösem Material in die Trommel (3) an einer Stelle, die einen vorgegebenen Abstand vom oberen Ende des Zylinders (14) hat,
- Mittel (31-32) zum Überführen des rückgewonnenen Materials und der Zuschlagstoffe von der Trommel (3) in den ringförmigen Zwischenraum (15) am oberen Ende des Zylinders (14),
- Mittel (28-29), die wirksam mit dem Inneren der Trommel (3) verbunden sind, um die Beförderung der Zuschlagstoffe und des rückgewonnenen Materials zu den Mitteln (31-32) zu ihrer Einleitung in den ringförmigen Zwischenraum (15) zu bewirken,
- Mittel (43-44) zum Einleiten von Bitumen, Füllmaterial und Additiven unmittelbar angrenzend an das obere Ende des Zylinders (14) und
- Mittel (39), die wirksam mit der Außenseite der Trommel (3) entlang des stationären Zylinders (14) verbunden sind, um die Zuschlagstoffe und das rückgewonnene Material mit dem Bitumen, dem Füllmaterial und den Additiven zu vermischen, so daß man ein bituminöses Mischgut erhält, und um die Beförderung des Mischguts zu einem Entleerungsauslaß (40), der am unteren Ende des Zylinders (14) angeordnet ist, zu bewirken,
wobei die Trocken- und Mischvorrichtung dadurch gekennzeichnet ist, daß:- der Zwischenraum (15) vollständig gegenüber dem Inneren der Trommel (3) isoliert ist und sich am unteren Abschnitt der Trommel (3) und am unteren Ende des Zylinders (14) befindet,
- die Mittel (31-32) zum Überführen des rückgewonnenen Materials und der Zuschlagstoffe von der Trommel (3) in den ringförmigen Zwischenraum (15) so ausgelegt sind, daß sie das ganze rückgewonnene Material und die ganzen Zuschlagstoffe aus dem Inneren der Trommel (3) heraus und in den ringförmigen Zwischenraum (15) hinein überführen,
- der Auslaß des Brenners (35) am unteren Ende (5) der Trocken- und Mischvorrichtung gelegen ist und
- die Mittel (43-44) zum Einleiten von Bitumen, Füllmaterial und Additiven so ausgelegt sind, daß sie die Materialien direkt in den isolierten ringförmigen Zwischenraum (15) einleiten, so daß die Materialien nicht in das Innere der Trommel (3) eintreten.
- im wesentlichen L-förmigen Profilflügeln (29), die an die innere Oberfläche der Trommel (3) gekoppelt sind und sich vom oberen Ende (4) aus zur Einleitungszone des rückgewonnenen bituminösen Materials in die Trommel (3) erstrecken,
- Ausnehmungen (28a), die im Inneren der Trommel (3) angeordnet sind und in Verbindung mit Öffnungen (27) der Trommel zum Durchleiten von rückgewonnenem bituminösem Material in die Trommel stehen, wobei die Ausnehmungen gegen das untere Ende (5) geöffnet und gegen das obere Ende (4) verschlossen sind, und
- Flügeln (28), die an die innere Oberfläche der Trommel (3) gekoppelt sind und sich von der Einleitungszone des rückgewonnenen bituminösen Materials zu den Mitteln (31-32) zum Überführen des rückgewonnenen Materials und der Zuschlagstoffe von der Trommel (3) in den ringförmigen Zwischenraum (15) erstrecken, wobei die Flügel (28) so geformt sind, daß sie Abschirmungen zum Schutz der inneren Oberfläche der Trommel (3) gegen Bestrahlung bilden und daß sie die Wärme auf das Material übertragen.
- un tambour (3) qui est supporté à rotation autour d'un axe longitudinal (A) qui est incliné par rapport au plan horizontal, de façon à présenter une extrémité inférieure (5) et une extrémité supérieure (4),
- des moyens (10 à 12) pour faire tourner ledit tambour autour dudit axe;
- un brûleur (35) disposé à l'extrémité inférieure (5) dudit tambour (3) pour diriger une flamme le long dudit axe longitudinal (A) vers l'extrémité supérieure (4) du tambour (3) afin de le chauffer intérieurement;
- des moyens (20) pour introduire des agrégats à l'extrémité supérieure (4) dudit tambour (3),
- un cylindre fixe (14) qui entoure concentriquement la partie inférieure dudit tambour (3) et définit un espace intermédiaire annulaire (15) avec ladite partie, ledit cylindre (14) représentant une extrémité inférieure qui est proche du brûleur (35), et une extrémité supérieure;
- des moyens (23 à 27) pour introduire du matériau bitumineux de récupération dans ledit tambour (3) en un emplacement qui est situé à une distance prédéterminée de l'extrémité supérieure dudit cylindre (14);
- des moyens (31 à 32) pour transférer ledit matériau de récupération et lesdits agrégats depuis ledit tambour (3) dans ledit espace intermédiaire annulaire (15), à l'extrémité supérieure dudit cylindre (14);
- des moyens (28 à 29) qui sont fonctionnellement associés à l'intérieur dudit tambour (3) afin de provoquer l'avance desdits agrégats et dudit matériau de récupération vers lesdits moyens (31 à 32) pour les introduire dans l'espace intermédiaire annulaire (15);
- des moyens (43, 44) pour introduire du bitume, de la matière de charge et des additifs à proximité de l'extrémité supérieure dudit cylindre (14); et
- des moyens (39) qui sont fonctionnellement associés à l'extérieur dudit tambour (3) le long dudit cylindre fixe (14) afin de mélanger lesdits agrégats et ledit matériau de récupération avec ledit bitume, avec ladite matière de charge et lesdits additifs, de façon à obtenir un mélange bitumineux et à provoquer l'avance dudit enrobé vers une sortie de décharge (40) disposée à l'extrémité inférieure dudit cylindre (14);
le mélangeur-sécheur étant caractérisé en ce que:ledit espace intermédiaire (15) est complètement isolé de l'intérieur dudit tambour (3) à la partie inférieure dudit tambour (3) et à l'extrémité inférieure dudit cylindre (14);
lesdits moyens (31 à 32) pour transférer ledit matériau de récupération et lesdits agrégats dudit tambour (3) dans ledit espace intermédiaire annulaire (15) sont aptes à transférer la totalité dudit matériau de récupération et des agrégats hors de l'intérieur dudit tambour (3) et dans ledit espace intermédiaire annulaire (15);
la sortie dudit brûleur (35) est disposée à l'extrémité inférieure (5) du mélangeur-sécheur; et
lesdits moyens (43, 44) pour introduire du bitume, de la matière de charge et des additifs sont aptes à introduire les matériaux directement dans l'espace intermédiaire annulaire isolé (15), de telle façon que les matériaux ne pénètrent pas à l'intérieur dudit tambour (3).
- des ailes (29) à profil sensiblement en forme de L, couplées à la surface intérieure du tambour (3) et s'étendant depuis ladite extrémité supérieure (4) jusqu'à la zone d'introduction du matériau bitumineux de récupération dans ledit tambour (3);
- des cavités (28a) agencées à l'intérieur du tambour (3) en communication avec des ouvertures (27) du tambour pour le passage du matériau bitumineux de récupération dans le tambour, lesdites cavités étant ouvertes vers ladite extrémité inférieure (5) et fermées vers ladite extrémité supérieure (4); et
- des ailes (28) couplées à la surface intérieure du tambour (3) et s'étendant depuis la zone d'introduction du matériau bitumineux de récupération jusqu'auxdits moyens (31 à 32) pour transférer ledit matériau de récupération et lesdits agrégats depuis ledit tambour (3) dans ledit espace intermédiaire annulaire (15), lesdits ailes (28) présentant une forme propre à définir des écrans pour protéger la surface intérieure du tambour (3) contre le rayonnement et de façon à transférer la chaleur au matériau.