A DEVICE FOR PREPARING ASPHALT

Abstract

 A device for preparing asphalt (1), comprising a rotatable heating chamber (2) having an intake end (3) and a discharge end (4), a base material feeder (6) arranged at the intake end, and a burner (7) arranged at the intake end for heating the interior of the heating chamber. The base material feeder comprises a pre-heating chamber (8) having a first end (9) and a second end (10), which second end is connected with the heating chamber, a base material bin (11), a base material transfer device (12), arranged to transfer the base material from the base material bin to the pre-heating chamber at its first end, and a gas suction device (13) connected with the pre-heating chamber at its first end. The pre-heating chamber is arranged to feed the base material into the heating chamber, and the gas suction device is arranged to suck gases from the heating chamber through the pre-heating chamber.

Description

FIELD OF THE INVENTION

[0001] The present invention relates to a device for preparing asphalt, comprising a rotatable heating chamber having an intake end and a discharge end, a first rotation driver for rotating the heating chamber, a base material feeder arranged at the intake end, and a burner arranged at the intake end for heating the interior of the heating chamber.

BACKGROUND OF THE INVENTION

[0002] A device for preparing asphalt, such as disclosed in WO 98/49398, is dependent on having an ability to dry and heat the base material to a sufficient extent also then the base material is cold and wet. In addition, it is important to remove hot gases from the heating chamber, in particular when they contain significant amounts of water vapour. In order to improve the heating function solutions have been made to use the heat content of the hot gases to pre-dry and/or preheat the base material. One example thereof is shown in WO 98/49398, where the gases are entered into the base material bin to act directly on the base material, and another example is shown in US 2010020630, where heat exchangers are used to extract the heat of the hot gases. However, in the mentioned prior art devices, the pre-heating of the base material is irregular.

SUMMARY OF THE INVENTION

[0003] It would be advantageous to provide a device for preparing asphalt where the base material is pre-heated in a more regular way by means of the hot gases from the heating chamber.

[0004] To better address this concern, in a first aspect of the invention there is presented a device for preparing asphalt, comprising a rotatable heating chamber having an intake end and a discharge end, a base material feeder arranged at the intake end, and a burner arranged at the intake end for heating the interior of the heating chamber, wherein the base material feeder comprises a pre-heating chamber having a first end and a second end, which second end is connected with the heating chamber, a base material bin, a base material transfer device, arranged to transfer the base material from the base material bin to the pre-heating chamber at its first end, wherein the pre-heating chamber is arranged to feed the base material into the heating chamber, and a gas suction device connected with the pre-heating chamber at its first end, wherein the gas suction device is arranged to suck gases from the heating chamber through the pre-heating chamber. By sucking the hot gases through the pre-heating chamber the base material is more regularly pre-heated than in the prior art devices, and the whole process is more efficient.

[0005] In accordance with an embodiment of the device the pre-heating chamber is rotatable. By rotating the pre-heating chamber, the effect of the preheating is further increased.

[0006] In accordance with an embodiment of the device the gas suction device comprises a fan, and a first duct arranged between the fan and the pre-heating chamber. This is a simple and reliable embodiment.

[0007] In accordance with an embodiment of the device the base material transfer device is connected with the first duct. Thereby the base material is introduced in a controllable way to the pre-heating chamber.

[0008] In accordance with an embodiment of the device the first duct comprises a sloping wall portion, sloping downwards from an end of the base material transfer device to the first end of the pre-heating chamber, wherein the sloping wall portion is arranged to receive base material from the base material transfer device. Thereby the base material is reliably fed into the preheating chamber.

[0009] In accordance with an embodiment of the device the gas suction device comprises a second duct, which is arranged between the fan and the base material bin, and which is arranged to conduct gas from the fan into the base material bin. Therby, an additional use is made of the hot gases, and the pre-heating is further improved.

[0010] In accordance with an embodiment of the device further comprising a mixer arranged at the discharge end of the heating chamber, and a binder feeder, connected with the mixer, wherein the mixer is arranged to receive heated base material from the heating chamber and mix it with the binder, and to output asphalt. It is advantageous to add the binder by means of a mixer at the discharge end.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The invention will now be described in more detail and with reference to the appended drawings in which:

Fig. 1.is a schematic view of an embodiment of the device for preparing asphalt according to the present invention; and

Fig. 2 is an enlarged view of a part of the device shown in Fig. 1.

DESCRIPTION OF EMBODIMENTS

[0012] An embodiment of the device 1 for preparing asphalt, as shown in Fig. 1, comprises a rotatable heating chamber 2 having an intake end 3 and a discharge end 4, a first rotation driver 5 for rotating the heating chamber 2, a base material feeder 6 arranged at the intake end 3, and a burner 7 arranged at the intake end 3 for heating the interior of the heating chamber 2.

[0013] It should be noted that the base material can be either merely aggregates, a blend of aggregates and recycled asphalt, or even merely recycled asphalt. That is, the amount of recycled asphalt can be from 0% to 100%. However, in order to obtain a homogeneous quality of the produced asphalt at least a fraction of aggregates is preferable.

[0014] The base material feeder 6 comprises a pre-heating chamber 8 having a first end 9 and a second end 10, which second end 10 is connected with the heating chamber 2, for delivering base material to the heating chamber 2, a base material bin 11, and a base material transfer device 12, arranged to transfer the base material from the base material bin 11 to the pre-heating chamber 8, which receives the base material at its first end 9. The base material feeder 6 further comprises a gas suction device 13 connected with the pre-heating chamber 8 at its first end 9.

[0015] The pre-heating chamber 8 is arranged to feed the base material 14 into the heating chamber 8. The gas suction device 13 is arranged to suck gases from the heating chamber 2 through the pre-heating chamber 8. Preferably, the pre-heating chamber 8 is rotatable, and the device further comprises a second rotation driver 15 for rotating the pre-heating chamber 8.

[0016] The heating chamber 2 is most schematically shown, to merely illustrate a general structure and function thereof. The heating chamber 2 is cylindrical and can be any known heating chamber 2 that is suitable, as will be understood by the person skilled in the art, such as the heating chamber disclosed in above-mentioned WO 98/49398. The heating chamber of WO 98/49398 is, however, advantageous in that the base material does not fall down through the flame of the burner 7 but is kept tumbling around in open grooves extending along the length of the heating chamber 2 at the interior thereof. The heated air is enabled to enter the grooves and heat the base material.

[0017] The rotation drivers 5, 15 can be realized by any suitable devices, such as electrically driven friction rollers. A friction roller 5, 15 rotates the chamber 2, 8 by means of a high friction surface which is engaged with the outer surface of the chamber 2, 8.

[0018] The gas suction device 13 comprises a fan 16, and a first duct 17 extending between the fan 16 and the pre-heating chamber 8. The duct 17 has a first mouth 18 at the fan 16, and second mouth 19 at the first end 9 of the pre-heater 8. At least a portion 20 of the first duct 17 is inclined, such that it extends obliquely upwards from the pre-heating chamber 8. The inclined portion 20 comprises, or is constituted by, a sloping wall portion 21, sloping downwards from an end of the base material transfer device 12 to the first end 9 of the pre-heating chamber 8, wherein the sloping wall portion 21 is arranged to receive base material 14 from the base material transfer device 12. The base material transfer device 12 comprises any kind of suitable material conveyor, e.g. a belt conveyor.

[0019] Consequently, the first duct 17 comprises an inlet 26 for receiving the base material from the base material transfer device 12. Furthermore, the first duct 17 comprises a pivoting door 27, which is arranged to pivot about a horizontal axis, and which is pivotally attached to a wall portion 28 defining an upper edge of the inlet 26. The door 27 is arranged to close the inlet when no base material is fed through it, and to be pushed away by the base material when fed. Thus, the door 27 rests on top of the fed through base material 14 and minimizes the leakage of hot gases rearwards out of the inlet. Depending on how the door is made its own weight can be sufficient to generate a closing force on the door 27, or a biasing spring can be provided. On the other hand, the closing force must not be too large because then the door 27 would prevent the base material from passing the inlet 26.

[0020] The gas suction device 13 comprises a second duct 22, which is arranged between the fan 16 and the base material bin 11, and which is arranged to conduct gas from the fan 16 into the base material bin 11.

[0021] The device for preparing asphalt 1 further comprises a mixer 23 arranged at the discharge end 4 of the heating chamber 2, and a binder feeder 24, connected with the mixer 23. The mixer 23 is arranged to receive heated base material 14 from the heating chamber 2 and mix it with the binder, and to output asphalt 25.

[0022] The device for preparing asphalt 1 is operated as follows. The base material 14 is fed, by means of the base material transfer device 12 from the bottom of the base material bin 11 to the inlet 28, where the base material 14 falls down onto the sloping wall portion 21 and slides through the inlet 28, passed the door 27 and further down into the pre-heating chamber 8. The base material then moves forward through the pre-heating chamber while being tumbled by the rotating pre-heating chamber 8, which is slightly sloping down towards the heating chamber 2. In the heating chamber the base material 14 is also tumbled while being heated by the burner 7. The heating chamber 2 is slightly sloping down towards the mixer 23, and feeds the heated base material into the mixer at its second end 4. In the mixer 23 the base material 14 is mixed with the binder the final asphalt 25 is produced and delivered from the mixer 23. There are several different ways of providing the mixing function, e.g. by means of a mixing device arranged within the mixer 23, or by rotating the whole mixer 23.

[0023] The hot gases, often containing water vapour, generated by the burner 7 are sucked by means of the fan 16 out of the heating chamber 2 rearwards through the pre-heating chamber 8, i.e. opposite to the feeding direction of the base material 14, through the first duct 17, through the fan 16, and through the second duct 22 into the base material 14. In the pre-heater 8 the tumbling base material 14 is subjected to the hot gases and becomes pre-heated. When the base material 14 is wet, the pre-heating primarily involves drying the base material, but also heating it to a certain extent. As regards the pre-heating of the base material 14 in the base material bin 11, the second duct 22 can be arranged to end a distance down into the inner of the bin 11, or at an upper rim of the bin 11. In the latter case, only the base material at and close to the surface is pre-heated, but on the other hand the flow through the pre-heater 8 is kept on approximately the same level independent of the kind of base material in the bin 11. If the second duct ends deep down in the base material and base material contains fine fractions it may become an obstacle to the hot gases, and thereby decrease the flow through the preheating chamber 8.

[0024] While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments.

[0025] Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.

Claims

1. A device for preparing asphalt (1), comprising a rotatable heating chamber (2) having an intake end (3) and a discharge end (4), a base material feeder (6) arranged at the intake end, and a burner (7) arranged at the intake end for heating the interior of the heating chamber, wherein the base material feeder comprises a pre-heating chamber (8) having a first end (9) and a second end (10), which second end is connected with the heating chamber, a base material bin (11), a base material transfer device (12), arranged to transfer the base material from the base material bin to the preheating chamber at its first end, wherein the pre-heating chamber is arranged to feed the base material into the heating chamber, and a gas suction device (13) connected with the pre-heating chamber at its first end, wherein the gas suction device is arranged to suck gases from the heating chamber through the pre-heating chamber.

2. The device as claimed in claim 1, wherein the pre-heating (8) chamber is rotatable.

3. The device as claimed in claim 1 or 2, wherein the gas suction device (13) comprises a fan (16), and a first duct (17) arranged between the fan and the pre-heating chamber (8).

4. The device according to claim 3, wherein the base material transfer device (6) is connected with the first duct (17).

5. The device according to claim 4, wherein the first duct (17) comprises a sloping wall portion (21), sloping downwards from an end of the base material transfer device (6) to the first end (9) of the pre-heating chamber (8), wherein the sloping wall portion is arranged to receive base material (14) from the base material transfer device.

6. The device according to any one of the claims 3 to 5, wherein the gas suction device (13) comprises a second duct (22), which is arranged between the fan (16) and the base material bin (11), and which is arranged to conduct gas from the fan into the base material bin.

7. The device according to any one of the preceding claims, wherein the base material transfer device (6) comprises a belt conveyor (12).

8. The device according to any one of the preceding claims, further comprising a mixer (23) arranged at the discharge end (4) of the heating chamber (2), and a binder feeder (24), connected with the mixer, wherein the mixer is arranged to receive heated base material from the heating chamber and mix it with the binder, and to output asphalt.

Drawing