NO313422B1 - Method and apparatus for making asphalt - Google Patents

Description

The present invention relates to a device for producing asphalt according to the introduction to claim 1 and a corresponding method according to the introduction to claim 8 in the attached claims.

An earlier device for producing asphalt is disclosed in CH-628381. This device is a stationary asphalt installation comprising a rotating drum which has three different parts through which the stone material delivered to the drum passes. At the intake end of the drum there is a burner that leads into the drum. In the first part of the drum, which is a burner part, the delivered material is transported in closed channels. Then follows a second and a third part, where the material is transported in open chutes, which are attached to the inside of the drum wall. The channels serve to mix the material, thereby exposing it evenly to the heat. The gutters have different shapes and are located in the different parts. The drum rotates slowly, the material falls out of the chutes and down through the hot exhaust gases, which begin where the flame ends, to the bottom of the drum. From the bottom, the material is again moved upwards by the chutes. A binder is added at the beginning of the third part and mixed with the stone material to form asphalt.

The channels in the first part of the asphalt plant in the above-mentioned publication are closed to prevent the stone material from falling through the flames from the burner and disturbing the combustion. However, this has the disadvantage that the material in the closed channels is not heated to any particular extent. Therefore, the first part has extremely low efficiency. On the other hand, the efficiency in part two is good, where the material falls through the hot exhaust gases. At the same time, however, this entails another disadvantage. The material, which consists of crushed stone with a certain average particle size, also contains finer fractions, such as stone dust and coarse sand. Due to the high velocity of the gases, the fine fractions are blown through the drum and out through the outlet. There they must be processed by filtration, which results in additional costs, additional treatment and reduced gas flow through the drum. Furthermore, the device is not usable for asphalt recycling since the supply of material containing a binder leads to the unwanted emission of harmful gases. The harmful gases are formed when the binder is in contact with the hot exhaust gases when the material falls through the drum, above all in the second part, but also in the third part. Immediately after the flames, the gases have too high a temperature. In the third part, especially at the beginning, there is also a risk that harmful gases are formed in the new production of asphalt since a binder is added also exposed to the hot exhaust gases when the material falls through them.

US-4738539 presents another prior device which is made essentially in the same way as the device according to CH-628381.1 in this case, however, the material will not come into direct contact with the jet of heat emission gases after the addition of the binder, which takes place at the end of the drum.

The two known devices are constructed inefficiently, which makes them unnecessarily long.

One purpose of the invention is to produce a method and a device for the production of asphalt, which is equally applicable for asphalt recycling as for new production.

According to the invention, there is thus provided a device and a method for the production of asphalt as stated in the introduction to the accompanying claims 1 to 10. The device and the method are characterized by the characterizing features as stated in the independent claims, 1 and 8 respectively.

Preferred features of the device and method appear from the accompanying independent claims, respectively 2-7 and 9-10.

A further object of the invention is to produce a method and a device for the production of asphalt in which the material is heated faster and more efficiently compared to previous devices, and with no risk of the emission of harmful gases, which is caused by too high a temperature in the binder , and without having to deal with fine particles that would otherwise pollute the surroundings.

The introductions to claims 1 and 8 are based on CH-628381.

The invention and its further advantages shall now be described in more detail by means of embodiments and with reference to the attached drawings where: Fig. 1 is a schematic side view of a device for producing asphalt according to an embodiment of the invention; Fig. 2 is a schematic cross-section of a drum included in the device in fig. 1; and Fig. 3 is a schematic view of an enlargement of a detail in Fig. 2 and shows an alternative embodiment.

As shown in fig. 1, the device 1 according to an embodiment of the invention comprises a cylindrical drum 3 which has an intake end 5 and an exhaust end 7; a first feeding device 9; a burner 11; a uttørnraimgsinmeliiing 13; a second feeding device 15; a third feeding device 17; a drive device 19 and a frame 21.

The drum 3 has a front end wall 29 and a rear end wall 30. The end walls 29, 30 are attached to the frame 21.

The frame 21 comprises an adjustable support leg 63. The support leg 63 is set so that the drum 3 leans in relation to the horizontal plane.

The first feeding device 9, which is referred to below as feeder 9, comprises a material container 23 and a conveyor 25 which is preferably a belt conveyor. The feeder 9 feeds the material, which is either one or more parts of crushed stone, such as crushed stone and/or stone dust, or which is fully or partially old asphalt to be reused, to the drum 3 at the intake end 5 through a hole in the front road wall 29 to drum 3.

The material is heated in the drum. This process will be described in more detail below.

The second feeding device 15, which is referred to below as a sub-injection pump 15, and the third feeding device 17, which is referred to below as an end-injection pump 17, add a binder to the material at the intake end 5 and the discharge end, respectively 7. The sub-injection pump 15 is used to supply, when necessary, a small amount of binder to bind the dust in the material. The final injection pump 17 delivers a suitable amount of binder to the discharge device 13, thereby producing asphalt with the desired properties.

During the recycling of used asphalt, any addition of rock material and binder depends on the age of the asphalt and other properties of the asphalt, and which properties are desired in the manufactured asphalt.

The burner 11, which is a conventional burner for the purpose, is placed in the intake end 5 of the drum 3, so that the opening of the burner 11 is conventionally placed within the end wall 29 of the drum 3 or approximately in the plane of the end wall 29 e.g. as shown in the above-mentioned publications. The burner 11 comprises a fan which drives an adjustable flow of exhaust gases through the drum 3.

The drum 3 is supported by four support rollers 19 included in the drive device 19, two on each side of the drum 3. The drive device drives two of the support rollers for rotation of the drum 3 around its longitudinal axis. The end pieces 5,7 in the drum 3 are rotatably fitted into the end walls 29, 30 which thus help to keep the drum 3 in place. Each support roller 19 has a friction lining which is brought into contact with the outside of the drum.

At the discharge end 7 of the drum 3, the discharge device 13, which in this embodiment consists essentially of a conventional mixing feeder, is adapted to discharge material and the binder added during mixing. The mixing feeder 13 protrudes a certain distance into the drum 3 through the rear end wall 30 and captures the material. The mixing feeder 13 has a semi-cylindrical lower part and a drying device in the form of a longitudinal shaft with inclined vanes attached to the shaft and which, during rotation of the shaft, protrude and at the same time mix the material. The manufactured asphalt is emptied from the mixing feeder 13 into a nearby container, such as a loading platform of a truck 31.

A pipe 12 is placed in the end wall 29. It serves as an outlet for the gases, mainly water vapor and hot air, which have been passed through the drum 3. It is important that the water vapor does not remain in the drum 3 to any particular extent. The pipe 12, which is a pipe, is located at the top of the end wall, which, due to the slope of the drum 3, is at the same time the highest point in the drum 3. The hot gases that have been passed through the drum 3 return through the upper areas of the drum 3 and escapes through the pipe 12. This results in the further advantage that additional thermal energy is recovered from the gases for heating the material. A certain quantity of the gases is passed through the mixing feeder 13.

The above-described parts of the device are placed on a frame which is transportable by means of a truck, such as the frame 21, which is a demountable loading device. This makes the device 1 mobile and easily transportable by means of a truck to an optional production location. An important factor in allowing such a compact device to be placed on, for example, a demountable loading device 21, is the internal construction of the drum 3, which will now be described in more detail.

As shown in fig. 2 are carrier inflow directions, or channels 33, located on the inside of the drum 3. The channels 33 are oblong and extend as internal flanges along the inside of the drum 3, essentially all the way from the intake end 5 of the drum 3 to the discharge end 7. Each channel 33 comprises a radial wall part 35 and a pit-shaped or curved part 37 which is connected to the wall part 35. The wall part 35 is mainly flat and is connected to the wall 41 in the drum with a longitudinal clamping part 39. The clamping part 39 comprises two connected, elongated support parts 43,47. The support parts 43,45 are V-shaped in cross-section and at the tip of the V'n it passes into the rest of the wall part 35, while the legs of the V'n, i.e. the longitudinal side edges 47,49 of the support parts 43,45, are connected to the inside of the drum wall 41. The clamping part 39 also comprises fastening devices 51, such as threaded bolts, which are attached to the bottom in what can be said to be formed by the support parts 43,54 and which are placed at a suitable distance from each other along the support parts 43,44. The fastening device extends through holes in the wall 41 of the drum 3 and is removably anchored, for example, by means of nuts 53, to the outside of the drum 3. As a result, the channels 33 are removably connected to the drum 3. The support parts 43, 45, which is placed in the form of a V, in the fastening device, distributes the forces to which the clamping part is exposed due to the material present in the channels 33. This embodiment differs from the embodiment of previous devices.

The pit-shaped part 37 forms a curved extension of the wall part 35 and is finished with a free longitudinal side edge 55 at a certain distance from the wall 41. The cross-sectional drawing in fig. 2 shows the interior of the drum 3 seen from the intake end 5. The channels 33 are hook-shaped in cross-section. The drum 3 rotates clockwise in fig. 2, i.e. the free edge of the channels 33 is placed in front of the wall parts 35 seen in the direction of rotation.

The belt conveyor 25 is placed near the circumference of the drum 3 and throws the material into the chutes 33 through the hole in the front road wall 29. The chutes 33 are designed and placed in relation to each other so that the material, which is shown as shaded areas in the chutes 33, is moved around during rotation in a room that is defined by two neighboring gutters, e.g. the channels 57 and 59, the part 61 of the wall of the drum 3 which is located between the two channels 57,59 and an opening 60 which is formed between the channels 57,59, by these being placed a certain distance from each other, seen in the circumferential direction to the drum 3. During a revolution, which begins when the chute 57 is at the top, the material in the chute 57 first falls out of the chute, past the opening between the chute 57 and 59 and onto the chute 59 located in front, seen in the direction of rotation, or more specifically on the rear side of the wall part 35 to the chute 59. The material then slides/rolls down on the wall part 61 to the drum and spreads over this wall part. Race 57 has now reached its bottom position. On its way up, the material slides/topples once more into the chute 57. During this process, the material is simultaneously moved towards the discharge end 7 thanks to the inclination of the drum 3 in relation to the horizontal plane. In an end part at the discharge end 7, the channels 33 are cut up in the pit-shaped part 37. As a result of this, the material falls out of the channels 33 and down into the mixing feeder 13.

There are several variable factors that affect the possibility of producing a device which, according to the invention, retains the material in the room so that it does not fall out through the opening 60. The variable factors are: the rotation speed of the drum 3; the execution and location of the chutes 33 in relation to each other and the amount of material in the chutes 33.

It is desirable to have a relatively low rotation speed so that the force that mainly acts on the material is the gravitational force. This results in good mixing of the material. Too high a rotation speed means that the material is pressed against the wall 41 and held in approximately the same position throughout one revolution. This also interferes with the transport of the material through the drum 3.

The design of the chutes 57, 59 and their position in relation to each other is such that the chutes can hold a significant amount of the material without the material falling out through the opening 60. Therefore, the chutes should be placed closer to each other than in the above-described previous arrangement, and the free edge 55 should be extended upwards so far that the pit-shaped part 37 can receive a suitable quantity of the material. In the embodiment shown, the pit-shaped part 37 has a radius of curvature of 0.15 m; the height of the wall part 35 is 0.3 m; the diameter of the drum 3 is 2.2 m and the number of chutes 33 is 12. The pit-shaped part 37 is in this embodiment a half-cylinder. It can be noted that in this embodiment the length of the drum is 4 m. These dimensions should only be considered as an example that fulfills the conditions so that the material does not fall through the interior of the drum 3, but mainly rotates in the space between two neighboring channels 33 on it the way described above. It should be noted that, of course, the quantity of the material is of great importance. If an extremely large quantity of the material is fed into the channels 33, it will fall over the edge 55 if the space between the edge 55 and the wall 41 is small. In previous devices, however, the relationship is reversed, i.e. the material will fall out between the chutes regardless of how small a quantity of material is fed in. The design and the relative position of the channels 33 are thus decisive factors for achieving the purpose of the invention. If the chutes are thus suitably designed and placed in relation to each other and the amount of material is adapted to this, the rotation speed has no effect on the retention of the material in the room. Even at the lowest possible rotation speed, the material is retained in said space. At the same time, it is still possible to keep the distance between two neighboring channels 33 sufficiently large so that hot gases can enter the room and heat up the material.

If one wishes to have the option of adding more material without the material falling out through the opening 60, this can be achieved by increasing the rotation speed. An upper limit to compensating for a larger amount of material by means of the rotational speed is achieved when the rotational speed has an adverse effect on the movement of the material in space.

There are, of course, many combinations of the above-mentioned variable factors that result in the device according to the invention. However, it is within the scope of a person skilled in the art to try out an appropriate combination in a given situation based on the above description.

An advantage of moving the material around in a limited space is that the above-mentioned problems of previous devices have been eliminated. This means that the material does not fall through the drum and come into direct contact with the hottest exhaust gases. At the same time, the defined space is not closed, which is the case with closed ducts, but hot gases can enter the space via the openings between the channels 33. As a result of this, the problem of harmful gases from reclaimed asphalt or from the small amount of binder which is supplied by means of the sub-irrigation pump 15, cleared of the way, while at the same time still effective heating is achieved. Moreover, the fine fractions are not sprayed out through the discharge end 7. The continuous movement of the material results in efficient mixing of hot air in the room for efficient heating of the material. In the lower half of the drum 3, the material is spread in a thin layer over a large surface, which results in good exposure to the hot gases. Since the jet of hot gases is not disturbed by the material falling through it, a significantly more uniform temperature is also achieved throughout the drum 3 compared to previous devices, which makes the process even more efficient.

Thanks to the above-described improvements compared to previous devices, the new device has significantly higher efficiency. This means, among other things, that it can be made significantly shorter than previous devices with the same production capacity. The amount of material that is delivered, i.e. the amount of the material per length unit that each chute 33 carries is regulated not only by a suitable degree of filling in the chute 33 so that the material does not fall out through the opening 60, but also by, e.g. the type of material.

Both the feed speed and the rotation speed are adjustable in the design to achieve the optimal result in each case.

The embodiment described above is only a non-limiting example of how the new device can be designed. As one skilled in the art will appreciate, several modifications are possible within the scope of the invention as defined in the accompanying claims. Below are some examples of modifications.

In a modification, the channels are equipped with one or more flanges that extend along the pit-shaped part. Such a flange is advantageously made in a simple way as a piece of flat iron, which is connected to the gutter on one side of its surface. The flange or flanges increase the supply of heat to the channels and, therefore, to the material, which accelerates heating. Consequently, the feed rate can be increased.

The shape of the channels 33 is variable. An example of a variant is shown in fig. 3 by dashed lines that start from the bracing part 39 and coincide with the pit-shaped part 37.1 this variant, the wall part 35 does not constitute an extension of the pit-shaped part 37 in its tangential direction, as in the embodiment described above, but forms an angle with this tangential direction. This means that the part of the pit-shaped part 37 which is closest to the wall part 35 forms a pit which effectively prevents the material from falling down from the wall part of the channels 33 when it falls down from the nearest channel above. There is a small risk of this happening in the above embodiment, which is however more cost effective to manufacture.

The trough-shaped part can e.g. have a cross-sectional shape other than a half cylinder, such as a polygonal or asymmetric shape.

The clamping part can be designed in an optional way, although in the shown embodiment the angled support parts 43,45 in the clamping part 39 help to move the material around the transition between the wall 41 of the drum 3 and the carrier device 33, and the design of the clamping parts results in easily removable carrier strap directions.

The size of the device is determined by the desired capacity. As described above, the device, due to its unique design, can be shaped as a mobile unit, which is an advantage not found in the previous devices described in the introduction. However, it is also possible to design the device as a stationary unit, and thus it is possible to make it significantly larger than the mobile variant. For mobile designs, the above-mentioned demountable loading device is only one of many suitable frames. A further variant is to design the device as a unit which is firmly anchored to a vehicle, such as a tractor or a trailer.

Claims (10)

1. Device for producing asphalt comprising a cylindrical drum (3) which is arranged to be able to rotate about its longitudinal axis, which longitudinal axis tends towards the horizontal plane, and which has an intake end (5) and a discharge end (7); a feeding device (9) located at the intake end of the drum (3) and adapted to feed the material, in the form of suitable fractions of rock material and/or used asphalt, to said drum (3); a further feed belt direction (15,16) for supplying a binder to the material; a discharge device (13) located at the discharge end of the drum (3) and adapted to discharge ready-made asphalt material from the drum (3); a drive device (19) for rotating the drum (3); a burner (20) which is located at the intake end (5) and which supplies exhaust gases to the interior of the drum (3); and a number of carrying devices (33) which are placed in the drum (3) and connected to this and which extend along the drum (3), to receive the material from the feeding device (9) and transport the material through the drum (3), each carrying device (33) comprises a wall part (35) which is connected to the drum wall (41) and extends inwards from the drum wall (41), and a pit-shaped part (37) which is connected to the wall part and which is terminated by a longitudinal free edge (55 ), which is placed a certain distance from the wall and in front of the wall part (35) seen in the direction of rotation of the drum (3), characterized in that the support devices (33) extend from the intake end (5) of the drum (3) to the discharge end (7) ), and that the carrier devices (33) are so designed and interpositioned that the material in a carrier device (57) during one revolution falls over said free edge, is caught by the carrier device (59) placed in front, seen in the direction of rotation, and via the drum wall part (6 1) between the two neighboring carrier devices (57, 59) is returned to the carrier device (57) that the material originally left. 2. Device according to claim 1, characterized in that the support device (33) is hook-shaped in cross-section, the wall part (35) being mainly flat. 3. Device according to claim 1 or 2, characterized in that said additional feeding device (15) for supplying a binder to the material is located at the intake end (5) of the drum (3). 4. Device according to claim 3, characterized in that a third feeding device (17) for supplying a binder to the material is located at the discharge end (7) of the drum (3), and that the discharge inlet (13) is located for discharge during mixing. 5. Device according to any one of the preceding claims, characterized in that the wall part comprises a clamping part (39) with two connected oblong support parts (43,45), which is V-shaped in cross-section and which at the tip of the V'n passes over in the rest of the wall part (35) while the legs (47,49) of V'n butt against the inside of the drum wall (41). 6. Device according to claim 5, characterized in that the clamping part (39) comprises a fastening device which extends through the drum wall to the outside (41) and is removably attached to the outside. 7. Device according to any one of the preceding claims, characterized in that it comprises a demountable loading device (21) which consists of a frame in which the other components that are included are placed, whereby mobility of the device is achieved. 8. Process for the production of asphalt by means of a device comprising a cylindrical drum (3), which is arranged to rotate about its longitudinal axis and which has an intake end (5) and a drying end (7), which longitudinal axis rather in relation to the horizontal plane; the method comprises the steps of rotation of the drum (3); feeding the material, in the form of appropriate proportions of the stone material and/or used asphalt, to the drum (3) at its intake end to a number of support devices (33) which are placed in the drum and which are connected to and extend along the drum and which contribute to mix and transport the material through the drum; supplying hot gases to the interior of the drum to heat the material; adding a binder to the material; at the discharge end (7) of the drum, discharge ready-made asphalt material from the drum (3); design each support device to include a wall part (35) which is connected to the wall (41) of the drum (3) and which extends inwards from the wall of the drum (3), and a pit-shaped part (37) which is connected with the wall part (35) and which ends in a longitudinal free edge (55), which is placed a certain distance from the wall and in front of the wall part (35) seen in the direction of rotation of the drum, characterized in that the support arm directions (33) are designed so that they extend from the intake end of the drum to the discharge end; in that the carrier devices and their placement in relation to each other are arranged so that the material in a carrier device (57) is moved around in a predetermined loop during one revolution, the material falling over said free edge and being caught by the carrier device (59) placed in front, seen in the direction of rotation, and is returned via the drum wall part (61) which is between two neighboring support devices, to the support device that the material originally left. 9. Method according to claim 8, characterized in that the feeding of the material to the drum is regulated so that the quantity of the material in the carrier is maximized on the condition that the material is retained in said loop. 10. Method according to claim 8 or 9, characterized in that the rotation speed is set so that rotation of the drum helps to keep the material in the loop.