Asphalt plant operation method and asphalt plant

Abstract

To provide an operation method of an asphalt plant capable of suppressing heat loss from heated waste materials and improving quality of asphalt mixture while allowing discharge of defective materials having a predetermined particle diameter or less and oversized materials to outside of the plant by a simple constitution, and also to provide the asphalt plant.SOLUTION: An operation method of a self-weight dropping and feeding asphalt plant 1 includes: (a) a step to select an external discharge path 31 as a discharge destination during a starting operation of a waste material dryer 5; (b) a step to select a waste material storage bin 23 as a discharge destination during steady operation of the waste material dryer 5; and (c) a step to select the external discharge path 31 as the discharge destination during the starting operation of the waste material dryer 5. A damper 36 closes a feeding port 24 of the waste material storage bin 23 in the step (c).SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an asphalt plant and a method for operating an asphalt plant for producing an asphalt mixture for road paving. [Background technology]

[0002] In asphalt plants, in order to reuse waste asphalt pavement (hereafter referred to as "waste") dug up during road construction work etc., the waste is crushed and classified into a specified particle size (for example, 13 mm) or less, fed into a waste dryer, and exposed to hot air from a burner to heat it to a specified target temperature (about 160°C) and regenerated. The heated waste is then used as an ingredient for asphalt mixtures.

[0003] At this time, due to some factors such as malfunction of the crusher or adhesion or agglomeration of waste materials, oversized heated waste materials exceeding the specified particle size may be generated. If such oversized heated waste materials are used as material for asphalt mixture, it can cause problems such as depressions and cracks (potholes) in the road pavement.

[0004] As a countermeasure to these problems, the applicant has proposed a waste dryer configured as shown in Patent Document 1, in which a trommel for screening heated waste is connected to the rear end of the kiln body of the waste dryer, and heated waste of a certain particle size or less that passes through the mesh of the trommel is supplied to equipment within the plant (for example, a waste storage bin for storing heated waste) as a material for asphalt mixture, while oversized heated waste that does not pass through the mesh is discharged outside the plant.

[0005] On the other hand, in order to solve problems such as location, it is desired to reduce the space required for asphalt plants, and the applicant has proposed an asphalt plant in which the discharge end of a waste material dryer mounted on a frame is connected to the top of a waste material storage bin in the shape of a vertical cylinder, and the heated waste material discharged from the waste material dryer is directly dropped into the waste material storage bin by gravity, as shown in Patent Document 2. This configuration makes it unnecessary to use a conveying device as much as possible, and simplifies the equipment, and equipment incorporating the waste material dryer with a trommel of Patent Document 1 into such a gravity-drop-type asphalt plant has become mainstream in recent years. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Utility Model Application Publication No. 7-10009 [Patent Document 2] JP 2015-227598 A Summary of the Invention [Problem to be solved by the invention]

[0007] However, in the process of thermally regenerating waste materials using a waste material dryer, heated waste materials (defective materials) that do not meet the required quality may be produced due to various reasons such as insufficient heating, and it is desirable to discharge such defective materials that are not suitable as materials for asphalt mixtures outside the plant (discharge from the system). However, in the gravity-drop-in asphalt plant of the above configuration, even if the defective materials are smaller than a specified particle size, they will pass through the mesh part and fall directly into the waste material storage bin. In this case, for example, it is possible to take measures to discharge all of the heated waste materials in the waste material storage bin containing the defective materials, but this would be a waste of energy required to heat the waste materials, and is not economically preferable.

[0008] Therefore, as a measure to avoid the complete discharge of the heated waste material, for example, an asphalt plant 101 according to the conventional technology shown in Fig. 6 is adopted. In the conventional technology shown in Fig. 6, the discharge end of a waste material dryer 103 with a trommel 102 is connected to a waste material storage bin 104, and the asphalt plant 101 is a gravity-drop type asphalt plant 101. The asphalt plant 101 is provided with a first external discharge path 105 for discharging oversized heated waste material outside the plant, and a second external discharge path 106 for discharging defective waste material outside the plant. The first external discharge path 105 is connected to the end 102a of the trommel inside the waste material storage bin 104 and extends outside the waste material storage bin 104. The second external discharge path 106 is connected to the side of the waste material storage bin 104, and a large damper 107, which is a discharge destination switching means, is provided near the upper opening of the second external discharge path 106. The damper 107 is configured to be rotatable about a central axis 108. An exhaust flue 109 is connected to the top of the waste material storage bin 104.

[0009] In the asphalt plant 101, during the operation of the waste dryer 103, the oversized heated waste is sent to the end 102a without passing through the mesh part 102b of the trommel regardless of the rotation position of the damper 107, and is sequentially discharged from the first external discharge path 105 to the waste storage bin 104 and further to the outside of the plant. On the other hand, the heated waste that passes through the mesh part 102b and has a particle size of less than a predetermined size is sequentially dropped by its own weight into the waste storage bin 104 just below.

[0010] On the other hand, when defective material is generated, the damper 107 is rotated and tilted to a position where it overlaps with the gravity-fell path of the heated waste material in a planar view, so that even defective material of a predetermined particle size or less that passes through the mesh section 102b is blocked from falling due to gravity and is not allowed to fall into the waste material storage bin 104, but is instead guided to the second external discharge path 106 and discharged outside the plant.

[0011] However, the asphalt plant 101 is configured to have two separate external discharge pipes 105, 106, which tends to make the device somewhat large and complicated.

[0012] In addition, in the asphalt plant 101, the upper half of the waste storage bin 104, which is formed in a vertically elongated, approximately cylindrical shape, is connected to the discharge side end of the waste dryer 103, and the exhaust gas from the waste dryer 103 is discharged from the exhaust flue 109 provided at the top of the waste storage bin 104. In other words, since the waste storage bin 104 itself was configured to double as an exhaust chamber, the opening area of ​​the waste storage bin 103 was approximately equal to the cross-sectional area of ​​the main body, and was accordingly large. As a result, the hot air from the heated waste inside the waste storage bin 104 gradually flowed out of the plant, causing the temperature to drop, and there was room for improvement in suppressing such heat loss.

[0013] In order to prevent the hot air from escaping, it is possible to provide a damper 107 of a size capable of blocking the entire opening (the horizontal section of the waste storage bin 104 below the trommel 102), but this would place an excessive load on the shaft 108, and would interfere with the first external discharge passage 105 connected to the end 102a of the trommel inside the waste storage bin 104, making it difficult to adopt in practice. Therefore, although the damper 107 of the prior art is large in size in proportion to the area of ​​the opening, even when it is rotated to an inclined position, a considerable gap remains at the back side of the opening in the discharge direction, and it is not possible to prevent the hot air from escaping from the heated waste material being stored.

[0014] Keeping heated waste (recycled material) warm during storage is important not only from the standpoint of energy efficiency, but also for ensuring that the recycled material and the asphalt mixture produced using it have the required qualities, such as fluidity, so further improvements are desired.

[0015] In view of the above, an object of the present invention is to provide an asphalt plant operating method and an asphalt plant that can reduce heat loss from heated waste materials while enabling defective materials having a particle size below a predetermined value and oversized materials to be discharged outside the plant with a simple configuration, thereby improving the quality of the asphalt mixture. [Means for solving the problem]

[0016] In order to solve the above problems, the inventors have studied diligently and came up with the idea of ​​a layout configuration for plant equipment that can limit the falling of defective materials by gravity with a minimum of rotational movement by separating the cold hopper (partition wall) corresponding to the exhaust chamber from the waste material storage bin at the lower part and arranging a damper for the discharge destination switching means inside the cold hopper. With this layout, it is possible to consolidate the two external discharge paths that were previously equipped into one. In addition, when limiting the falling of materials, the damper is in a rotational position that covers the upper part of the input port, and as a result, the damper also functions as an insulation cover, and the surrounding area of ​​the damper is covered in an almost airtight state by the cold hopper (partition wall), which is thought to make it possible to suppress heat radiation from the regenerated materials during storage.

[0017] In addition, we paid attention to the fact that low-temperature defective materials are likely to be generated immediately after the start of heating of the waste material dryer (during start-up operation), and we thought that with an asphalt plant with the above configuration, the damper's rotation operation would allow the low-temperature defective materials to be discharged at the appropriate time during start-up operation, and then during steady operation when the inside of the waste material dryer has risen to the required temperature, the heated waste material that has been heated and regenerated to the target temperature would be put into the waste material storage bin, and the heated waste material inside the waste material storage bin would then be effectively kept warm. This would prevent the inclusion of defective materials, and we thought that the well-kept, high-quality heated waste material could be used as a material for asphalt mixtures, and we came up with this invention.

[0018] That is, the method of operating an asphalt plant described in claim 1 of the present invention is a method of operating an asphalt plant in which a trommel is connected to the rear end of the kiln body of a waste material dryer that is supported at an angle so as to be freely rotatable on a frame, a waste material storage bin and an external discharge path are arranged in parallel below the trommel, a discharge destination switching damper is rotatably interposed between the waste material storage bin and the external discharge path and the trommel, and the damper and the rear end of the kiln body are covered with a partition body, and includes: (a) a step of selecting the external discharge path as the discharge destination during start-up operation of the waste material dryer; (b) a step of selecting the waste material storage bin as the discharge destination during steady-state operation of the waste material dryer; and (c) a step of selecting the external discharge path as the discharge destination during shut-down operation of the waste material dryer, and in the step (c), the damper blocks the inlet of the waste material storage bin.

[0019] In addition, the asphalt plant operation method described in claim 2 is characterized in that in the step (b), the temperature of the heated waste material after the heating treatment by the waste material dryer is monitored, and when the temperature falls below a predetermined value, the step proceeds to (d) a step of selecting the external discharge path as the discharge destination even during steady-state operation of the waste material dryer.

[0020] In addition, the asphalt plant described in claim 3 is characterized in that it includes a control unit that controls the rotational operation of the damper, and is configured so that the operating method described in claim 1 or 2 can be executed by the control unit. Effect of the Invention

[0021] According to the present invention, it is possible to provide an asphalt plant operating method and an asphalt plant that can discharge defective materials and oversized materials having a particle size below a predetermined value outside the plant with a simple configuration while suppressing heat loss from heated waste materials and improving the quality of the asphalt mixture. [Brief description of the drawings]

[0022] [Figure 1]1 is a schematic diagram of an asphalt plant according to the present invention. [Diagram 2] FIG. 2 is an enlarged cross-sectional view of a main portion of the asphalt plant of FIG. [Diagram 3] (a) is a diagram showing the case where the heated waste material with a particle size of 13 mm or less is discharged to an external discharge path, and (b) is a diagram showing the case where the heated waste material with a particle size of 13 mm or less is discharged to a waste material storage bin. [Figure 4] 1 is a flowchart showing a method for operating an asphalt plant according to the present invention. [Diagram 5] FIG. 1 is a diagram showing a modified example of an asphalt plant according to the present invention. [Figure 6] FIG. 1 is a schematic diagram of an asphalt plant according to the prior art. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] In the asphalt plant according to the present invention, a trommel is connected to the rear end of the kiln body of the waste dryer, which is supported on a stand at an inclination so as to be rotatable. A waste storage bin and an external discharge path are arranged in parallel below the trommel. A discharge destination switching damper is rotatably interposed on the gravity drop input path of the heated waste material, which is located at the intermediate position between the waste storage bin and the external discharge path and the trommel. The damper and the rear end of the kiln body are further covered with a partition. In addition, it is preferable to have a control unit that controls the rotation of the damper, and a temperature detection means for exhaust gas and / or heated waste material is provided and connected to the control unit so as to be able to communicate with the control unit. The above configuration will be specifically described below.

[0024] Specifically, in the asphalt plant according to the present invention, a waste material dryer for heating waste material is supported at an angle so as to be freely rotatable on an elevated platform having multiple floors. A hot hopper, which is a partition wall, is provided at one end of the cylindrical kiln body of the waste material dryer, and a cold hopper, which is a partition wall connected to an exhaust flue, is provided at the other end. The hot hopper covers one end (front end) of the kiln body on the higher side, while the cold hopper covers the other end (rear end) of the kiln body on the lower side.

[0025] The hot hopper side of the waste dryer is provided with a waste feed chute as a waste feed means and a burner for supplying hot air, while a trommel having a mesh of a specified shape and size for screening heated waste is connected to the rear end of the kiln body on the cold hopper side. Furthermore, an external discharge path for heated waste is provided below the end of the trommel and below the cold hopper, so that heated waste that does not pass through the mesh and has an oversized particle size of, for example, a particle size of more than 13 mm, can be discharged out of the plant via the end of the trommel and then the external discharge path.

[0026] In the asphalt plant having the above-mentioned configuration, a damper (a means for switching the discharge destination of heated waste material) that can rotate around the central axis is interposed below the trommel and inside the cold hopper. The damper is a movable shielding plate that blocks the heated waste material on the gravity drop input path from the mesh part to the inlet of the waste material storage bin, forcibly changing the discharge destination, and the discharge destination of heated waste material with a predetermined particle size (13 mm) or less that passes through the mesh part can be selected from the waste material storage bin, whose inlet is located below (directly below) the mesh part of the trommel, or the external discharge path located to the side of the bin.

[0027] More specifically, when the external discharge path is selected as the discharge destination, the damper is configured to take an inclined state having a gradient equal to or greater than the angle of repose of the heated waste material, blocking the falling of heated waste material of a predetermined particle size or less by its own weight, guiding the heated waste material to the external discharge path arranged below in the inclined direction, and blocking the input port by being disposed in contact with or adjacent to the input port. On the other hand, when the waste material storage bin is selected as the discharge destination, the damper is configured to take an approximately vertical upright state and open the input port.

[0028] The method of operating the asphalt plant having the above-mentioned configuration includes the steps of: (a) during start-up operation of the waste dryer (after the burner of the waste dryer is ignited and until the temperature inside the kiln body rises to a required temperature sufficient to heat and regenerate the heated waste to the target temperature), selecting the external discharge path as the discharge destination, tilting the damper to block the inlet, and discharging heated waste of all particle sizes, including heated waste of a size equal to or smaller than a predetermined particle size that passes through the mesh part (insufficiently heated defective material) and heated waste of a size exceeding the predetermined particle size, to the outside of the plant; and (b) discharging heated waste of all particle sizes, including heated waste of a size equal to or smaller than a predetermined particle size that passes through the mesh part, to the outside of the plant. During normal operation (after the inside of the kiln body has been heated to the required temperature), the waste material is heated and regenerated by each process including the steps of selecting the waste material storage bin as the discharge destination, setting the damper to an upright position, opening the inlet, and allowing the heated waste material (regenerated material) that is a size equal to or smaller than a predetermined particle size that passes through the mesh of the trommel and has been heated and regenerated to the target temperature to fall by gravity into the waste material storage bin, and (c) after the burner of the waste material dryer is turned off, setting the damper to an inclined position to close the inlet, and keeping the heated waste material (regenerated material) inside the waste material storage bin warm. This makes it possible to obtain regenerated material that is well-insulated while suppressing the inclusion of defective material, thereby improving the quality of the (regenerated) asphalt mixture produced using this material.

[0029] Also, preferably, in the step (b), the temperature of the heated waste material after the heat treatment by the waste material dryer is monitored by direct measurement or by measuring each value correlated with the heated waste material temperature. For example, the exhaust gas temperature from the waste material dryer (for example, inside the exhaust flue downstream of the waste material dryer) and / or the heated waste material temperature after the waste material dryer is charged (for example, at the rear end of the kiln body or inside the waste material storage bin) are monitored by a temperature sensor provided at a predetermined position of each plant equipment, and when the heated waste material temperature falls below a predetermined value, it is preferable to proceed to (d) a step of selecting the external discharge path as the discharge destination even during steady operation of the waste material dryer. The exhaust gas temperature is correlated with the heated waste material temperature, and when the exhaust gas temperature is below a predetermined value, it can be determined that there is a state in which insufficiently heated defective material may occur. In addition, it can be seen that insufficiently heated defective material has occurred by direct temperature measurement. By forcibly discharging the waste material outside the system in such a case, the inclusion of defective material in the recycled material can be effectively suppressed, and the quality of the asphalt mixture can be further improved.

[0030] More preferably, in the step (c), while the waste material is being discharged by the rotational drive of the kiln body (during the shut-down operation of the waste material dryer), all heated waste materials of particle sizes, including heated waste materials (rejected materials) of a predetermined particle size or less that remain inside the kiln body after the burner is turned off and heated waste materials of oversized materials exceeding the predetermined particle size, may be discharged outside the plant. This effectively prevents the mixed in of defective materials with the recycled materials, and further improves the quality of the asphalt mixture.

[0031] Each step of the operating method is written as a computer program and can be executed by being installed in the control unit of the asphalt plant. EXAMPLES

[0032] An embodiment of the present invention will be described below with reference to the drawings. Fig. 1 is a schematic diagram of an asphalt plant 1 according to the present invention. The asphalt plant 1 is a manufacturing facility for asphalt mixture, which is a road paving material, and is provided with a vertical waste material conveying device 4 on the side of the ground floor 2f of an elevated platform 3 erected with multiple floors 2a-2f, for lifting the waste material toward the top floor 2a. The waste material is crushed and classified to an appropriate particle size of 13 mm or less in this embodiment by various devices such as a crusher and a vibrating screen, not shown.

[0033] A waste dryer 5 is mounted on the elevated stand 3, which heats and regenerates the waste lifted by the waste vertical transport device 4. Specifically, a base 6 is disposed slightly inclined on the top floor 2a of the elevated stand 3, and a roughly cylindrical kiln body 8 is placed on support rollers 7 on the base 6, so that the kiln body 8 is supported at an incline so as to be freely rotatable, and the waste can be sent out to the lower side in the inclined direction.

[0034] A hot hopper 10, which is a partition body covering the front end 9 of the kiln body, is connected to the front end 9 of the kiln body on the higher side of the inclined kiln body 8, while a cold hopper 12, which is a partition body covering the rear end 11 of the kiln body, is connected to the rear end 11 of the kiln body on the lower side of the kiln body 8.

[0035] The cold hopper 12 has a tapered wall D facing the rear end 11 of the kiln body. This makes it easier for workers to access the internal equipment, such as the movable mechanisms of the dampers described below, during maintenance, and is also expected to prevent hot air from escaping from the plant (preventing the temperature drop of heated waste materials). The upper part of the cold hopper 12, including the tapered wall D, mainly functions as an exhaust chamber to guide exhaust gas from the waste dryer 5 out of the plant.

[0036] Further, a lower expanded diameter section P is formed on the ground side of the reduced diameter section D of the cold hopper 12. The lower expanded diameter section P is formed on the cold hopper 12 below the lowest point of the rear end 11 of the kiln body. In this embodiment, the maximum diameter of the lower expanded diameter section P is approximately equal to the maximum diameter of the upper side of the cold hopper 12. The inside of the lower expanded diameter section P of the cold hopper 12 mainly serves as a drop input path for heated waste material that has been heated and regenerated in the waste material dryer 5.

[0037] The shape of the cold hopper 12 is not limited to that shown in the drawings, and may be a vertically long box or cylinder with approximately the same diameter in each part omitting the reduced diameter part D. Even in these cases, the upper part of the cold hopper 12 of the asphalt plant 1 according to the present invention corresponds to the exhaust chamber, and the lower part corresponds to the drop path for the heated waste material.

[0038] The waste material dryer 5 is integrally formed with the hot hopper 10, and is provided with a waste material input chute (waste material supply means) 13 and a burner 14 for supplying hot air on the hot hopper 10 side. As a result, the waste material lifted by the waste material vertical conveyor device 4 is supplied into the kiln body 8 of the waste material dryer 5 via the waste material input chute 13, and is exposed to the hot air from the burner 14, where it is heated to a target temperature of about 160°C and regenerated.

[0039] The burner 14 is constructed by incorporating a blower fan 16 for supplying air for combustion into a burner body 15. The type of the burner 14 is not particularly limited, and may be an industrial furnace burner capable of burning fossil fuels such as heavy oil and city gas, biomass such as wood fuel, and various other fuels (including gas, liquid, and solid).

[0040] The rear end 11 of the kiln body of the waste dryer 5 is equipped with a trommel 17 for screening heated waste. The trommel 17 has a mesh part 18 of a predetermined shape (a rectangular grid in this embodiment) and a size corresponding to the appropriate grain size (in this embodiment, the length of one side and the diagonal length do not exceed 13 mm).

[0041] As a result, among the heated waste materials that have been heated and recycled in the waste material dryer 5, recycled material R1, which is heated waste material with a particle size of 13 mm or less (proper particle size), passes through the mesh section 18 and is dropped into the material supply equipment described below, while oversized material R2, which is heated waste material with a particle size exceeding 13 mm (above the proper particle size range), does not pass through the mesh section 18 but rolls to the lower side and is discharged from the trommel end section 19. In other words, the heated waste material is sieved into recycled material R1 and oversized material R2 according to its particle size.

[0042] The rear end 11 of the kiln body penetrates into the cold hopper 12 from the wall surface (the wall surface facing the tapered surface of the reduced diameter section D) together with the trommel 17, and a seal member 20 is provided at the penetration point to improve airtightness. In addition, the uppermost part of the cold hopper 12 is connected to an exhaust flue 21, and an exhaust fan 22 is provided on the exhaust flue 21 side. As a result, when the exhaust fan 22, which is a negative pressure generating source, is operated, the exhaust gas from the waste material dryer 5 that fills the inside of the reduced diameter section D of the cold hopper 12 is sucked in and led to the exhaust flue 21 and then to a chimney (not shown) at the end of the exhaust flue 21, and is exhausted outside the plant. In other words, the upper part of the cold hopper 12 including the reduced diameter section D functions as an exhaust chamber that leads the exhaust gas from the waste material dryer 5 out of the plant.

[0043] On the other hand, a waste material storage bin 23 is disposed below the lower expanded diameter portion P of the cold hopper 12, and its (waste material storage bin 23) feed opening 24 is located therein. The waste material storage bin 23 is a storage container that temporarily stores recycled material R1 of an appropriate grain size in an insulated state, and in this embodiment, it is incorporated into the asphalt plant 1 by penetrating each of the floors 2a to 2c of the elevated platform 3. The waste material storage bin 23 is disposed directly below the mesh portion 18 of the trommel 17 (at a position where the feed opening 24 overlaps with the mesh portion 18 in a plan view).

[0044] With this arrangement, of the heated waste material that has been heated and recycled in the waste material dryer 5, recycled material R1 of appropriate particle size that passes through the mesh section 18 passes through the inside of the lower expanded diameter section P of the cold hopper 12 and falls into the waste material storage bin 23 directly below the mesh section 18.

[0045] At this time, since the feed opening 24 is smaller in diameter than the inner diameter of the maximum diameter part of the cold hopper 12 (lower expanded diameter part P) and the inner diameter of the waste storage bin 23 body, the upper opening area of ​​the waste storage bin 23 is suppressed compared to the prior art, but even so, when the exhaust fan 22 is operated with the feed opening 24 open, the air (hot air) inside the waste storage bin 23 can flow out through the feed opening 24 into the lower expanded diameter part P of the cold hopper 12. The hot air that flows out and rises can be sucked and exhausted from the upper part of the cold hopper 12 (part equivalent to the exhaust chamber) together with the exhaust gas from the waste dryer 5 that fills the vicinity of the inside of the reduced diameter part D.

[0046] Such outflow of hot air causes a drop in the temperature of the recycled material R1 during storage, and if the recycled material R1 with a lowered temperature is used to produce an asphalt mixture, it may become undesirable in terms of quality. However, in the present invention, the arrangement of the discharge destination switching mechanism for heated waste material, which will be described later, is used to suppress such outflow of hot air.

[0047] In this embodiment, the waste material storage bin 23 is a cylindrical body with a tapered shape at the bottom, but any desired shape can be adopted. In this embodiment, in order to improve the heat retention performance of the recycled material R1, a heat insulating material (not shown) is applied only to the waste material storage bin 23. In this case, since the waste material storage bin 23 is structured separately from the cold hopper 12, even if the cold hopper 12 does not have to be provided with a heat insulating material, heat radiation from the heated waste material is unlikely to occur, and the heat retention performance is relatively good. This makes it possible to suppress heat loss with a simple configuration and reduce the cost of the heat insulating material. However, the location where the heat insulating material is applied is not limited to this embodiment, and the application itself may be omitted.

[0048] A waste material measuring tank 25 is provided immediately below the waste material storage bin 23, and a mixer 26 is provided immediately below the waste material measuring tank 25. This allows the recycled material R1 stored in the waste material storage bin 23 to be discharged in turn to the waste material measuring tank 25 and then to the mixer 26, where it can be dropped by its own weight. The waste material storage bin 23, the waste material measuring tank 25, and the mixer 26 each have an opening and closing gate (not shown).

[0049] A new material dryer 27 for heating and drying new aggregate is provided separately on the ground floor 2f on the side of the elevated platform 3, and a dust-collecting bag filter 28 is disposed above the new material dryer 27. The new aggregate (new material) that has been heated and dried in the new material dryer 27 is lifted by a new material vertical conveyor 29 toward the top floor 2a of the elevated platform 3.

[0050] A vibrating sieve 30 for sieving the heated new aggregate by particle size is provided near the waste storage bin 23 on the elevated platform 3, and an aggregate storage bin (not shown) for storing the heated new aggregate sieved by the vibrating sieve 30 by particle size in a warm state, and an aggregate measuring tank (not shown) for measuring the heated new aggregate stored in the aggregate storage bin are installed in a hierarchical manner in order, and the mixer 26 is arranged directly below the aggregate measuring tank, so that the heated new aggregate can be added by gravity, just like the recycled material R1. In addition, storage and supply equipment (not shown) for various materials for the asphalt mixture, such as stone powder, new asphalt, and recycled additives, is provided and connected separately to the mixer 26. This makes it possible to mix and adjust the recycled material R1, new aggregate, and various other materials supplied to the mixer 26 to produce the desired asphalt mixture (recycled asphalt mixture).

[0051] On the other hand, in case such heated waste material unsuitable for use as a material for recycled asphalt mixture is generated, an external discharge path 31 is connected to the lower part of the lower enlarged diameter section P of the cold hopper 12 (on the side of the inlet 24 and at the rear in the discharge direction) in order to discharge the heated waste material outside the plant. A typical example of heated waste material unsuitable for use as a material for recycled asphalt mixture is oversized material R2, and even if the waste material is crushed and classified to an appropriate grain size in advance, a certain amount of oversized material may be generated due to some factors. The asphalt plant 1 according to this embodiment employs a configuration that allows such oversized material R2 to be discharged outside the plant without falling into the waste material storage bin 23.

[0052] Specifically, the chute opening 32 of the external discharge path 31 faces the trommel end 19 (located directly below the trommel end 19) so as to be substantially flush with the inlet 24 of the waste material storage bin 23. The external discharge path 31 is formed by connecting an inclined chute 33 extending to the side of the elevated platform 3 with a vertical drop chute 34 disposed vertically along the side of the elevated platform 3, and is provided with an external discharge gate 35 at the bottom end of the vertical drop chute 34. The inclined chute 33 has a gradient steeper than the angle of repose of at least the various heated waste materials including the oversized material R2.

[0053] With the above-mentioned configuration, when the oversized material R2 is discharged from the trommel terminal end 19 without passing through the mesh portion 18 (and therefore without falling into the inlet 24 of the waste material storage bin 23 directly below), it passes through the inside of the lower expanded diameter portion P of the cold hopper 12 and first falls into the chute opening 32 directly below the trommel terminal end 19. Furthermore, the oversized material R2 passes through the inclined chute 33 and vertical drop chute 34 of the external discharge path 31 in this order, and is guided to fall into the external discharge gate 35.

[0054] The external discharge gate 35 into which the oversized material R2 falls is normally closed, but when a certain amount of the oversized material R2 accumulates inside the external discharge path 31, the external discharge gate 35 is opened at a required timing. As a result, the oversized material R2 is finally discharged outside the plant.

[0055] However, the heated waste material that is not suitable as a raw material for asphalt mixture is not limited to the oversized material R2. For example, heated waste material R3 (hereinafter referred to as "defective material R3") that does not meet the required quality for some reason such as insufficient heating may be generated during the operation of the waste material dryer 5, even if it falls within the appropriate particle size of 13 mm or less.

[0056] Such defective material R3 falls through the openings in the lattice of the mesh section 18, and if no measures are taken, it will follow a path that passes through the inside of the lower expanded diameter section P of the cold hopper 12 and falls into the waste material storage bin 23 directly below.

[0057] In this embodiment, therefore, a damper 36 is employed as a discharge destination switching means (movable shielding plate) for the defective material R3, and the damper 36 is provided over substantially the entire interior area of ​​the lower expanded diameter portion P of the cold hopper 12, and is configured to be rotatable about an axial center portion 37 below the trommel 17. The damper 36 is connected to a control portion 38 so as to be able to communicate with the control portion 38 by wire or wirelessly, and its rotation operation is controlled by a rotation controller 39 provided in the control portion 38.

[0058] As a result, if defective material R3 is generated during the operation of the waste material dryer 5, the damper 36 is rotated to a predetermined position to prevent the defective material from falling into the lower expansion section P, and the defective material R3 is guided to the chute opening 32 to the side of the inlet 24, making it possible to forcibly switch the discharge destination from the waste material storage bin 23 located on the initial (default) input path to the external discharge path 31.

[0059] In addition, when recycled materials R1 having a predetermined quality are produced, the waste material storage bin 23 is selected as the discharge destination by rotating (releasing) the damper 36 to a predetermined initial position that does not prevent the dropping of the materials. In other words, the damper 36 allows the discharge destination of each heated waste material R1, R3 having a particle size of 13 mm or less to be selected from either the waste material storage bin 23 or the external discharge path 31.

[0060] When the external discharge path 31 is selected as the discharge destination, the defective material R3 meets with the oversized material R2 on the way to be guided down to the chute opening 32, and follows the same discharge path. At this time, the inside of the lower enlarged diameter section P of the cold hopper 12 is a gravity drop input path common to the heated waste materials R1 to R3 of each particle size, and is connected to the gravity drop input destination, the external discharge path 31, and the waste material storage bin 23, so that the inside of the lower enlarged diameter section P is an extremely suitable location for installing the damper 36 of the discharge destination switching means, and this arrangement realizes simplification (compactness) of the equipment.

[0061] That is, recycled material R1 with a particle size of 13 mm or less is normally dropped from the trommel 17 into the waste material storage bin, but if defective material R3 occurs, a simple operation compared to the conventional technology (simply rotate the damper 36 at the upper part of the inlet 24 to a minimum) prevents the material from falling into the waste material storage bin 23 and allows it to be discharged outside the system together with the oversized material R2. This structural advantage is made possible by separating the cold hopper 12 from the waste material storage bin 23, narrowing the opening area of ​​the inlet 24, and arranging a damper 36 smaller than the conventional one (with a size corresponding to the narrowing diameter of the inlet 24) inside the lower expanded diameter portion P above the inlet 24.

[0062] In addition, the inlet 24 is positioned so as not to be on the path of the oversized material R2 falling due to its own weight, thereby preventing the oversized material R2 from falling and mixing into the waste material storage bin 23. This eliminates the need to directly connect the external discharge path 31 (FIG. 6, 105) to the trommel end portion 19 (FIG. 6, 102a) as in the prior art, which also simplifies the equipment in this respect.

[0063] Although the details of the control unit 38 are not shown in the drawings, the damper 36 is driven by a driving means (not shown) such as an air cylinder, and the driving means and a PLC (Programmable Logic Controller, not shown) are communicatively connected, and the PLC is further communicatively connected to an operating PC terminal (a computer consisting of a processor such as a CPU or GPU, a memory such as a RAM, and a storage medium such as a hard disk drive or SSD, not shown). Hereinafter, the control unit 38 is a general term for the PLC and the PC terminal.

[0064] The control unit 38 is also connected to the plant control panel 40 so that it can communicate with it, and at least a signal related to the operating state (operation / stop) of the waste dryer 5 is sent from the plant control panel 40 to the control unit 38. Furthermore, the exhaust gas temperature detected by a temperature sensor (temperature detection means) T provided in the exhaust flue 21 downstream of the waste dryer 5 is sent appropriately from the plant control panel 40 to the control unit 38. The plant control panel 40 has pre-registered values ​​of predetermined temperatures such as the target temperature of the heated waste and the required temperature inside the kiln body 8 required to heat the heated waste to the target temperature. Parameters such as the operating state and temperature of the waste dryer 5 are used appropriately for plant operation control, which will be described later.

[0065] 2 is an enlarged cross-sectional view of the main part in FIG. 1, and the kiln body 8 of the parallel heating type waste material dryer 5 has a liner (not shown) around the front half F where the burner 14 flame is formed, and has a plurality of scraping blades 41 in the rear half B. As a result, the waste material supplied into the kiln body 8 through the input chute 13 is scraped up in a veil shape by the scraping blades 41 while being exposed to the hot air of the burner 14 and heated and regenerated, and is sent to the rear end 11 of the kiln body and sieved by particle size by the trommel 17. Of the sieved heated waste material, the oversized material R2 is discharged from the trommel end 19 regardless of the rotation position and state of the damper 36, and is sequentially dropped by gravity into the external discharge path 31.

[0066] The axial center portion 37 of the damper 36 is located near an imaginary axis L that hangs down from the lower end of the trommel terminal portion 19. The axial center portion 37 is located approximately in the center of the damper 36 in the longitudinal direction.

[0067] The damper 36 is in an inclined state at one rotation position. Specifically, as shown in Fig. 3(a), the damper 36 in the inclined state has a gradient in the inclination direction (longitudinal direction) that is steeper than the angle of repose of at least the heated waste materials R1 to R3, and blocks the defective material R3 having a particle size of 13 mm or less on the gravity drop input path, and slides it down on the guide surface α of the damper 36 (the surface represented by the thick line that faces the trommel 17 in the inclined state) and guides it to the chute opening 32.

[0068] At this time, the inclined damper 36 is located above the inlet 24 of the waste storage bin 23 and closes the inlet 24. When the recycled material R1 is stored inside the waste storage bin 23, the damper 36 acts as a heat-retaining lid and can suppress the outflow of hot air H from the recycled material R1 (temperature drop during storage). Furthermore, the inlet 24 is smaller in diameter than at least the inner diameter of the lower enlarged diameter part P of the cold hopper 12 (the opening area corresponding to the connection part is narrowed), thereby enhancing the effect of suppressing the outflow of hot air H from the recycled material R1 during storage. This makes it possible to suppress the air (hot air H) in the waste storage bin 23 from being sucked into the cold hopper 12 connected to the inlet 24 even when the exhaust fan 22 is operating. Note that the guide surface α is omitted in each figure other than Figures 3(a) and (b).

[0069] When the damper 36 is in the inclined state shown in Fig. 3(a), one end of the damper 36 on the lower side in the inclination direction is in contact with or close to the upper edge β of the inlet 24 (the region indicated by the thick line, which is the connection between the waste material storage bin 23 and the cold hopper 12), and the other end of the damper 36 on the higher side is in contact with or close to the inner wall surface γ of the cold hopper 12 (the surface indicated by the thick line on one side of the cold hopper 12). Here, close to means that one end of the damper 36 and the upper edge β, and the other end of the damper 36 and the inner wall surface γ are separated by a gap of, for example, about 500 mm or less, preferably about 300 mm or less, and more preferably about 100 mm or less. In each of the figures other than Figs. 3(a) and (b), the upper edge β and the inner wall surface γ are omitted.

[0070] It is considered that the smaller the gap between each of these components, the greater the effect of suppressing the outflow of the hot air H, but even if some gaps are provided, the outflow of the hot air H can be suppressed to a considerable extent. Therefore, without being limited to these numerical values, a gap that can suppress the outflow of the hot air H may be allowed depending on the suction capacity of the exhaust fan 22, etc. It is considered that by providing some gaps at both ends of the damper 36, problems such as the damper 36 becoming stuck due to the old asphalt content of the heated waste material can be suppressed.

[0071] On the other hand, the damper 36 is in an upright state at another rotation position. Specifically, as shown in Fig. 3(b), when the damper 36 is in an upright state, the guide surface α of the damper 36 is in a vertical upright state (approximately overlapping with the imaginary axis L) and the insertion port 24 is fully opened.

[0072] In the asphalt plant 1 configured as described above, when a recycled asphalt mixture containing a specified proportion of recycled material R1 is manufactured, in order to pre-heat, regenerate, and store a corresponding amount of recycled material R1 before the recycled asphalt mixture is mixed and adjusted (before a shipping request is made), the waste material that has been crushed and classified in advance is lifted by the waste material vertical conveying device 4 and supplied to the waste material dryer 5 mounted on the top floor 2a of the elevated platform 3.

[0073] The steps of the operation method will be described below with reference to the flow chart of Fig. 4. In the figure, S1 to S10 represent steps of each procedure.

[0074] First, the burner 14 is ignited by operating both the burner body 15 and the blower fan 16 of the waste material dryer 5 (S1), and the heated waste material is sent out by rotating the kiln body 8 (S2). Note that, in the waste material dryer 5 immediately after the start of heating, the inside of the kiln body 8 has not yet risen in temperature sufficiently, and the waste material R3 is likely to be generated due to insufficient heating.

[0075] In response, the control unit 38 rotates the damper 36 to an inclined position, selects the external discharge path 31 as the discharge destination for heated waste material (defective material R3) with a particle size of 13 mm or less, and blocks the feed inlet 24 (S3). During start-up operation until the internal temperature of the kiln body 8 of the waste material dryer 5 reaches a required temperature sufficient to heat the waste material to the target temperature (for example, approximately 160°C) (S4: NO), all heated waste materials R2 and R3 of all particle sizes discharged from the waste material dryer 5 are discharged outside the system.

[0076] Specifically, as shown in Fig. 3(a) during start-up operation of the waste dryer 5, the oversized material R2 falls from the trommel end 19 into the external discharge path 31 under its own weight, while the defective material R3 (undercooked) falling toward the input port 24 is blocked by the inclined damper 36, and the defective material R3 (undercooked) slides down the guide surface α of the damper 36 and is guided to the external discharge path 31, where the heated waste materials R2 and R3 to be discharged outside the plant are joined together. In this embodiment, the internal temperature of the kiln body 8 is calculated based on the exhaust gas temperature detected by the temperature sensor T.

[0077] Next, when the inside of the kiln body 8 of the waste dryer 5 reaches the required temperature and transitions to steady-state operation (S4: YES), the control unit 38 rotates the damper 36 to an upright position, selects the waste storage bin 23 as the discharge destination for heated waste (recycled material R1) with a particle size of 13 mm or less, and opens the feed opening 24 (S5).While the burner 14 is operating (S6: NO), oversized material R2 is discharged outside the system, while recycled material R1 that has been heated to about 160°C is fed into the waste storage bin 23.

[0078] Specifically, during normal operation of the waste dryer 5, as shown in FIG. 3(b), even if the waste is heated and regenerated at about 160°C, the oversized material R2 falls under its own weight from the trommel end 19 into the external discharge path 31, while only the recycled material R1 that has been heated and regenerated at about 160°C and has an appropriate grain size falls under its own weight into the inlet 24 of the waste storage bin 23. At this time, the damper 36 is in an upright position, so that the recycled material R1 falls under its own weight into the inlet 24 without being blocked. In addition, the damper 36 in the upright position blocks the side of the external discharge path 31 of the path through which the recycled material R1 falls under its own weight, preventing the recycled material R1, which is suitable for asphalt mixture materials, from being mistakenly discharged outside the system. This allows the recycled material R1 to be produced with a good yield.

[0079] Next, if the operation of the burner 14 is to be terminated (S6: YES), the burner 14 is extinguished and the supply of waste material from the waste material vertical transport device 4 and the waste material input chute 13 is stopped in advance (S7). At this time, a certain amount of waste material remains inside the kiln body 8, but since the burner 14 has been extinguished, there may be defective waste material R3 with various properties such as grain size that vary.

[0080] Therefore, after the burner 14 is extinguished, in order to prevent such defective material R3 from falling and mixing in, the control unit 38 again rotates the damper 36 to an inclined position, selects the external discharge path 31 as the discharge destination for heated waste material (defective material R3) with a particle size of 13 mm or less, and blocks the inlet 24 (S8).During the shutdown operation (S9: YES) until all heated waste material (residual material) R2, R3 of all particle sizes remaining inside the kiln body 8 is gone, the kiln body 8 continues to rotate (discharge of waste material) to discharge all particle sizes of residual material R2, R3 discharged from the waste material dryer 5 outside the system.

[0081] Specifically, during the start-up operation of the waste dryer 5, as shown in Figure 3(a), of the remaining materials inside the kiln body 8, oversized material R2 falls under its own weight from the trommel end 19 into the external discharge path 31, and defective material R3 falling toward the feed opening 24 is blocked by an inclined damper 36, and the defective material R3 slides down the guide surface α of the damper 36 and is guided into the external discharge path 31, and the heated waste materials R2 and R3 to be discharged externally are joined together and discharged outside the plant.

[0082] In this way, defective materials R3 that may occur during each operation of the waste material dryer 5 due to low temperature or insufficient heating (during start-up operation) and defective materials R3 that remain inside the kiln body 8 after the burner 14 is extinguished (during shut-down operation) are forcibly discharged from the system even though they are below the appropriate particle size of 13 mm. Therefore, only recycled materials R1 that meet the specified quality can be selectively stored in the waste material storage bin 23, and it is expected that the quality of the recycled asphalt mixture made by mixing these materials will be improved.

[0083] In addition, even when newly heated recycled material R1 is added to the waste storage bin 23 while recycled material R1 remains inside the waste storage bin 23, any defective material R3 that is generated can be pinpointed and discharged from the system. This is expected to improve the quality of the recycled asphalt mixture, and it is not necessary to discharge all of the recycled material R1 that has already been added from the waste storage bin 23 when defective material R3 is generated, which is economically preferable as it avoids energy loss.

[0084] Then, when all the residual materials R2 and R3 inside the kiln body 8 of the waste material dryer 5 are discharged (S9: NO), the rotation drive of the kiln body 8 is stopped to stop the discharge of the waste material (S10). This ends the thermal regeneration process of the waste material by the waste material dryer 5.

[0085] A series of steps of the thermal regeneration process can be executed as a "thermal regeneration operation mode" by sequence control or feedback control based on the detection result of the temperature sensor T. For example, during execution of the "thermal regeneration operation mode", the control unit 38 may move to an arbitrary next step after a predetermined time has elapsed (timer up) in each step. Also, in S4, the control unit 38 may move to the next step S5 of rotating the damper 38 based on the exhaust temperature detected by the temperature sensor T.

[0086] Even during the thermal regeneration process of the waste material by the waste material dryer 5 (corresponding to S5 during the material heating operation), the temperature inside the kiln body 8 may suddenly drop. In this case, as in FIG. 3(a), the control unit 38, for example, rotates the damper 36 by interrupt processing to make it tilted, selects the external discharge path 31 as the discharge destination of the defective material R3, and closes the input port 24 to discharge the heated waste material R2, R3 of all particle sizes including the defective material R3 out of the system. In this embodiment, the temperature of the heated waste material after the heat treatment is monitored by the exhaust gas temperature detected by the temperature sensor T, and transitions to the "defective material removal mode" as an interrupt processing on the condition that the exhaust gas temperature falls below a predetermined value (the temperature inside the kiln body 8 is equal to or lower than the required temperature). However, whether or not to transition to the "defective material removal mode" may be determined by an operator or by mechanical means. In addition, even if the temperature inside the kiln body 8 has risen to the required temperature, it is possible that for some reason defective material R3 that does not meet the specified quality will be generated. In this case, too, it is advisable to execute the "defective material removal mode" as described above.

[0087] After the material heating operation of the waste dryer 5 is completed, the control unit 38 keeps the damper 36 in an inclined state unless additional heated waste R1 is added to the waste storage bin 23 (selecting the external discharge path 31 as the discharge destination for heated waste R1 and R3 with a particle size of 13 mm or less, and keeping the inlet 24 in a closed state). This operation method can be executed as a "warm mode". Even when the burner 14 is turned off, the exhaust fan 22 is operated and the blower fan 16 is operated independently as necessary to keep the air inside the kiln body 8 clean, so that the ventilation operation of the waste dryer 5 can be performed. Even in this case, the hot air H can be prevented from flowing out of the waste storage bin 23 during the execution of the "warm mode".

[0088] In this way, in the asphalt plant 1 of the present invention, the mixing of defective material R3 is suppressed to improve the quality of the recycled material R1, and the recycled material R1 inside the waste material storage bin 23 is effectively kept warm in preparation for shipment.

[0089] Then, when there is a request to ship the recycled asphalt mixture, the recycled material R1 stored in the waste storage bin 23 is dropped under its own weight into the waste measuring tank 25 directly below according to the mixing ratio of the recycled material R1 in the recycled asphalt mixture being produced, and after the specified amount is measured, it is dropped under its own weight into the mixer 26 directly below.

[0090] In addition, heated new aggregate of each particle size that has been separately heated and dried in a new material dryer 27 is dispensed from the aggregate storage bin, weighed in an aggregate weighing tank, and then dropped under its own weight into the mixer 26 directly below. The recycled material R1 and heated new aggregate are then mixed and adjusted while adding a specified amount of new asphalt, stone powder, recycled additives, etc. to produce the desired recycled asphalt mixture. The produced recycled asphalt mixture is dispensed, for example, to a shipping transport vehicle (not shown) that has entered below the mixer 26, in preparation for the production of the next batch of asphalt mixture.

[0091] The oversized material R2 and the defective material R3 are discharged from the discharge gate 35 and can be appropriately reused by being classified, crushed, heated and recycled again.

[0092] The asphalt plant 1 according to the present invention described above is not limited to the above embodiment, and various modifications can be made without departing from the spirit and scope of the invention.

[0093] For example, as shown in a modified example in Fig. 5, a guide portion 42 may be provided below the trommel terminal end 19. The guide portion 42 is configured to prevent the oversized material R2 discharged from the trommel terminal end 19 from coming into contact with the damper 36. Specifically, the guide plate 42 is a bent plate material, and includes a vertical guide portion 43 that is approximately parallel to the damper 36 in the upright state, and an inclined guide portion 44 that is approximately parallel to the damper 36 in the inclined state. The vertical guide portion 43 is located on the discharge direction side of the damper 36 in the upright state, and the inclined guide portion 44 is located above the damper 36 in the inclined state.

[0094] As a result, the opportunity for the guide surface of the damper 36 to come into contact with the heated waste material is limited to specific cases, such as when defective material R3 is generated, and the old asphalt components of the heated waste material are prevented from adhering to the damper 36, thereby reducing the burden of cleaning work during maintenance, etc.

[0095] In addition, the predetermined particle size that is the reference value for the appropriate particle size of the recycled material R1 is not limited to a particle size of 13 mm. Therefore, various sizes and shapes of the mesh portion 18 may be adopted. For example, the size of the mesh portion 18 may be changed from a size that allows recycled material R1 with a particle size of 13 mm or less to pass through to a size that allows heated waste material with a suitable particle size, such as a particle size of 20 mm or less, to pass through. In addition, the shape of the mesh portion 18 is not limited to a square shape.

[0096] In addition, the descriptions in each figure do not in any way limit the gradient (degree of gradient) of the inclined damper 36, the inclined chute 33, the inclined guide plate 45, etc., but it is preferable to determine the gradient in accordance with the angle of repose of the heated waste material so that it is at least steeper than the angle of repose.

[0097] In addition, the target temperature during the thermal regeneration of the waste material is not limited to 160°C. In this embodiment, the exhaust gas temperature is used to monitor the temperature of the heated waste material, but the plant equipment such as the rear end portion 11 of the kiln body, the inside of the cold hopper 12, and the waste material storage bin 23 may be provided with a temperature detection means such as a temperature sensor to directly measure the temperature of the heated waste material. In particular, the temperature of the heated waste material thermally regenerated by the waste material dryer 5 may be directly measured and monitored, and when the temperature falls below a predetermined value, the system may switch to the "defective material removal mode". In addition, various types of temperature detection means such as contact type and non-contact type may be adopted, and the detected temperature value may be an estimated value or a predicted value in addition to a direct measurement value.

[0098] The modified examples of the above disclosure and the configurations appearing in the above embodiments may be combined as appropriate to the extent that no contradiction occurs. [Industrial Applicability]

[0099] INDUSTRIAL APPLICABILITY The present invention can be widely applied to asphalt plants that produce asphalt mixtures for road paving (particularly recycled asphalt mixtures obtained by mixing heated waste materials) and to methods for operating the same. [Explanation of symbols]

[0100] 1...Plant body 3...Elevated platform 5...Waste dryer 8...Kiln body 8...Exhaust flue 10...Hot hopper 12…Cold hopper 14…Burner 17... Trommel 21... Exhaust flue 23...Waste storage bin 24...Feeding port 31...External exhaust passage 36...Damper R1…Heated waste material (recycled material) R2…Heated waste material (oversized material) R3…Heated waste (defective material)

Claims

1. A method for operating an asphalt plant in which a trommel is connected to the rear end of the kiln body of a waste material dryer that is supported at an angle so as to be freely rotatable on a stand, a waste material storage bin and an external discharge path are arranged in parallel below the trommel, a discharge destination switching damper is rotatably interposed between the waste material storage bin and the external discharge path and the trommel, and the damper and the rear end of the kiln body are covered with a partition body, the method comprising: (a) a step of selecting the external discharge path as the discharge destination during start-up operation of the waste material dryer; (b) a step of selecting the waste material storage bin as the discharge destination during steady operation of the waste material dryer; and (c) a step of selecting the external discharge path as the discharge destination during shut-down operation of the waste material dryer, and the damper is characterized in that in the step (c), the damper blocks the inlet of the waste material storage bin.

2. The method for operating an asphalt plant according to claim 1, characterized in that in the step (b), the temperature of the heated waste material after the heating treatment by the waste material dryer is monitored, and when the temperature falls below a predetermined target temperature, the method proceeds to a step (d) of selecting the external discharge path as the discharge destination even during steady-state operation of the waste material dryer.

3. 3. An asphalt plant comprising a control unit for controlling a rotational operation of the damper, the control unit being configured to be able to execute the operating method according to claim 1 or 2.

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