Asphalt Plant

Abstract

To provide an asphalt plant capable of efficiently heating and retaining bag filters and effectively suppressing the occurrence of dew condensation.SOLUTION: An asphalt plant comprises: a plant body 2 including a mixer 7, an aggregate weighing tank 8, an aggregate storage bin 9, and a vibrating sieve 10 mounted in layers on an elevated platform 6 having a plurality of floors 5a to 5d; a dryer 3 for heating the aggregate arranged on the side of the plant body 2; and a bag filter 4 for collecting dust from the exhaust gas discharged from the dryer 3. The bag filter 4 is mounted on the elevated platform 6 of the plant body 2. The side wall surface of a bag filter body 25 of the bag filter 4 faces the side wall surface of the aggregate storage bin 9 so as to be in close contact or close proximity.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an asphalt plant for producing asphalt mixtures, which are road paving materials. [Background technology]

[0002] An asphalt plant that produces asphalt mixture, a road paving material, is equipped with a plant main body consisting of an elevated platform with multiple floors, on which a mixer, aggregate measuring tank, aggregate storage bin, and vibrating sieve are mounted in tiers from the bottom up, a rotary kiln-type dryer for heating aggregate that is located on the ground surface to the side of the plant main body, and a bag filter that collects dust from the exhaust gas discharged from the dryer.

[0003] When producing an asphalt mixture in the asphalt plant, the aggregate fed into the drum body of the dryer is heated and dried to about 160 to 170°C by exposing it to hot air from a burner while rolling down with the rotation of the drum body, and then fed to a vibrating sieve at the top of the plant body by a vertical conveyor, where it is sieved by the vibrating sieve and stored by particle size in a lower aggregate storage bin. Next, the heated aggregate of each particle size stored in the aggregate storage bin is cumulatively weighed in a lower aggregate measuring tank in a predetermined amount according to the mixture of the asphalt mixture to be produced, and fed into the mixer at the bottom, while a predetermined amount of molten asphalt according to the mixture is weighed in an asphalt measuring tank, and stone powder and dust collected by the bag filter are weighed in a stone powder measuring tank, and then added to and mixed with the heated aggregate in the mixer to produce a desired asphalt mixture.

[0004] Incidentally, in conventional asphalt plants, efforts have been made to improve the heating efficiency of the dryer as much as possible from the standpoint of energy saving and reducing CO2 emissions, but as a result, the temperature of the exhaust gas discharged from the dryer drops to near the dew point temperature, and in some cases condensation occurs in the bag filter installed downstream of the dryer, which can lead to problems such as clogging of the filter cloth (filter) and corrosion. In response to this problem, the applicant has proposed an asphalt plant in which a bag filter is placed above the dryer and the bag filter is heated and kept warm by effectively utilizing the heat dissipated from the surface of the dryer (drum body), thereby suppressing condensation, as shown in Patent Document 1 (Japanese Utility Model Application Publication No. 59-156909). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Utility Model Application Publication No. 59-156909 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the case of the dryer using the rotary kiln system, since the drum body is a device structure that involves rotation, it is necessary to provide a certain amount of clearance between the drum body and the bag filter placed above it, which is somewhat disadvantageous in terms of effective use of the heat dissipated from the drum body.In addition, in recent years, with the demand for further energy saving and reduction in CO2 emissions, for example, there are increasing opportunities to manufacture asphalt mixtures called medium temperature mixtures in which the heating temperature of the aggregate is about 30°C lower than usual, and in such cases, the heat dissipated from the drum body naturally decreases, so it is expected that there may be cases where it is difficult to heat and keep the bag filter, which is located at a distance, sufficiently warm to prevent condensation.

[0007] In view of the above, an object of the present invention is to provide an asphalt plant that can efficiently heat and keep warm a bag filter and effectively suppress the occurrence of condensation. [Means for solving the problem]

[0008] As a result of intensive research to solve the above problems, the inventors of the present invention have noticed that in asphalt plants, in addition to the dryer, there is an aggregate storage bin mounted on the plant body as a structure that dissipates a lot of heat. In the aggregate storage bin, heated aggregate at about 160 to 170°C is stored during the production of normal asphalt mixture, and heated aggregate at about 130 to 140°C is stored during the production of asphalt mixture called medium temperature compound. The heated aggregate in the aggregate storage bin is often replaced in a relatively short time by repeatedly charging and discharging during plant operation, and the temperature rarely drops significantly during storage. Therefore, insulation material that leads to increased costs is usually not attached to the outer periphery of the aggregate storage bin, and as a result, it is expected that a considerable amount of heat is constantly dissipated from the surface of the aggregate storage bin. In addition, since the aggregate storage bin does not have an equipment structure that involves rotation like the dryer, there is no need to leave a gap, and the bag filter can be placed in close contact or close proximity, which is thought to be fully effective in heating and keeping the bag filter warm, leading to the invention.

[0009] That is, the asphalt plant according to the present invention includes a plant body having a mixer, an aggregate measuring tank, an aggregate storage bin, and a vibrating screen mounted in layers on an elevated platform having a plurality of floors, a dryer for heating the aggregate disposed on the side of the plant body, and A vertical conveying device that connects the vibrating screen to a discharge chute that discharges high-temperature aggregate that has been heat-treated in the dryer; A bag filter is provided to collect dust from the exhaust gas discharged from the dryer. The heated aggregate that has been heated in the dryer to the manufacturing temperature of the asphalt mixture to be manufactured is passed through the vertical conveyor and the vibrating sieve and stored in the aggregate storage bin by particle size. In this asphalt plant, the bag filter is mounted on the elevated stand of the plant body, and the side wall surface of the bag filter body of the bag filter is arranged facing the side wall surface of the aggregate storage bin in close contact or close proximity to the bin.

[0010] In addition, the asphalt plant described in claim 2 is characterized in that the discharge end of a screw feeder for discharging collected dust, which is provided at the lower end of the bag filter body, faces a stone powder metering tank provided in the plant body.

[0011] In addition, in the asphalt plant described in claim 3, the outer peripheral surface of the plant body together with the bag filter is covered with an exterior material to provide a heat-retaining structure.

[0012] In the asphalt plant described in claim 4, the upper surface of the bag filter body of the bag filter is configured to be approximately flush with the floor surface of the elevated stand on which the vibrating screen is mounted. Effect of the Invention

[0013] According to the asphalt plant of the present invention, the bag filter is mounted on an elevated stand of the plant body, and the bag filter body side wall surface of the bag filter is disposed on the elevated stand of the plant body. The aggregates are heated to the manufacturing temperature of the asphalt mixture to be produced and stored by particle size. Since the bag filter is positioned opposite the side wall surface of the aggregate storage bin and in close contact with or close to the side wall surface, the bag filter can be efficiently heated and kept warm by utilizing the heat radiated from the aggregate storage bin, thereby effectively suppressing the occurrence of condensation.

[0014] Furthermore, according to the asphalt plant described in claim 2, the discharge end of the screw feeder for discharging the collected dust, which is provided at the lower end of the bag filter body, faces the stone powder measuring tank provided in the plant body. Therefore, the collected dust in the bag filter, which is kept at approximately the same temperature as the heated aggregate, can be used as a raw material for the asphalt mixture. This prevents the temperature of the asphalt mixture from decreasing when the collected dust is used, and is expected to result in improved quality.

[0015] Furthermore, according to the asphalt plant described in claim 3, the outer peripheral surface of the plant body, together with the bag filter, is covered with an exterior material to create an insulation structure, thereby reducing heat dissipation from the bag filter body and confining the heat dissipated from the aggregate storage bin inside the exterior material, thereby enabling the bag filter to be heated and kept warm more efficiently.

[0016] In addition, according to the asphalt plant described in claim 4, the upper surface of the bag filter body of the bag filter is configured to be approximately flush with the floor surface on which the vibrating sieve of the elevated stand is mounted, so that the aggregate storage bin located directly below the vibrating sieve and the bag filter body of the bag filter can be easily configured as one unit in a horizontally aligned state, and the bag filter body of the bag filter can efficiently receive the heat radiated from the aggregate storage bin, thereby enabling it to be effectively heated and kept warm. [Brief description of the drawings]

[0017] [Figure 1] 1 is a schematic front view showing an embodiment of an asphalt plant according to the present invention. FIG. [Diagram 2] FIG. [Diagram 3] FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] The asphalt plant of the present invention comprises a plant body having a mixer, an aggregate measuring tank, an aggregate storage bin, and a vibrating screen mounted in layers in that order from the lower layer on an elevated platform having a plurality of floors; a rotary kiln type dryer for heating aggregate that is disposed on the ground surface on the side of the plant body; A vertical conveying device that connects the vibrating screen to a discharge chute that discharges high-temperature aggregate that has been heat-treated in the dryer; The bag filter is mounted on the elevated stand of the plant body, and the bag filter body side wall surface of the bag filter is Heat-treated aggregate is stored by particle size after being heated to the manufacturing temperature of the asphalt mixture to be produced. The bag filter is disposed opposite to or in close contact with the side wall of the aggregate storage bin, thereby making it possible to effectively utilize the heat dissipated from the aggregate storage bin to efficiently heat and keep the bag filter warm, and effectively suppress the occurrence of condensation.

[0019] Also, preferably, the discharge end of a screw feeder for discharging the collected dust provided at the lower end of the bag filter body is arranged to face the inside of a stone powder measuring tank provided in the plant body. This allows the collected dust in the bag filter, heated and insulated to approximately the same temperature as the heated aggregate temperature (for example, about 160 to 170°C when producing normal asphalt mixtures, and about 130 to 140°C when producing medium temperature compound mixtures), to be used as a raw material for the asphalt mixture, and as a result, the temperature drop (or temperature fluctuation) of the asphalt mixture when using the collected dust can be suppressed, and an improvement in quality can be expected. Furthermore, unlike conventional equipment, it is not necessary to use long pressure pipes or air pressure equipment such as a blower, which are required to pressure-pump the collected dust from the bag filter above the dryer located at a distance from the side of the plant body to the metering tank in the plant body, thereby reducing costs.In addition, the transport path can be shortened, so problems such as a drop in the temperature of the collected dust during transport and adhesion to the inner walls of the pressure pipes are minimized, making this an ideal system.

[0020] Furthermore, it is preferable to cover the outer periphery of the plant body together with the bag filter with an exterior material to provide a heat-retaining structure. This reduces heat dissipation from the bag filter body, and also keeps the heat dissipated from the aggregate storage bin inside the exterior material, so that the bag filter can be heated and kept warm more efficiently. Also, by surrounding the bag filter with an exterior material, it is possible to prevent dust from scattering in the surrounding area when replacing the filter cloth (filter) installed inside the bag filter body, and the appearance is neat and suitable for the surrounding environment.

[0021] Furthermore, it is preferable that the upper surface of the bag filter body of the bag filter is substantially flush with the floor surface on which the vibrating sieve of the elevated stand is mounted. This makes it easy to integrate the aggregate storage bin located directly below the vibrating sieve and the bag filter body of the bag filter in a horizontally aligned state, and the bag filter body of the bag filter can efficiently receive the heat radiated from the aggregate storage bin and can be effectively heated and kept warm. Furthermore, plant workers can replace the filter cloth of the bag filter body while remaining on the relatively large floor on which the vibrating sieve of the plant body is mounted, which is advantageous in terms of maintainability and work safety compared to the case of a conventional bag filter installed above a dryer, which forces workers to work at an unstable high place under their feet.

[0022] Thus, according to the asphalt plant, by placing the bag filter body of the bag filter in close contact with or close to the side of the aggregate storage bin in which high-temperature heated aggregate is stored during plant operation, not only the bag filter body but also the collected dust in the bag filter body can be efficiently heated and kept warm, the occurrence of condensation can be effectively suppressed, and the collected dust can be suitably used as a material for asphalt mixture. In addition, since the asphalt plant operates the plant according to shipping requests, the dryer is forced to operate intermittently, and there is no (or little) heat dissipation while the dryer is stopped, and there are times (timings) when the conventional device in which the bag filter is placed above the dryer cannot fully receive heat. However, in the device of the present invention, high-temperature heated aggregate that has been subjected to heat treatment is stored in the aggregate storage bin even when the dryer is stopped, so the bag filter placed on the side can continuously receive heat, and a more stable effect of suppressing condensation can be expected. EXAMPLES

[0023] An embodiment of the present invention will now be described with reference to the drawings.

[0024] In the drawing, reference numeral 1 denotes an asphalt plant for producing an asphalt mixture according to the present invention, and is mainly composed of a plant body 2, a dryer 3 for heating aggregate, and a bag filter 4 for collecting dust. The plant body 2 has an elevated platform 6 having multiple floors 5a-5d, which is installed across an access passage A for an asphalt mixture transport vehicle T, and on the elevated platform 6, a mixer 7, an aggregate measuring tank 8, an aggregate storage bin 9, a vibrating sieve 10, etc. are mounted in layers in that order from the bottom up.

[0025] In the drawing, reference numeral 11 denotes an asphalt metering tank for measuring molten asphalt supplied from an asphalt tank (not shown), and reference numeral 12 denotes a stone powder metering tank for measuring stone powder supplied from a stone powder silo (not shown), both of which are provided alongside the aggregate metering tank 8 within the plant main body 2. Furthermore, the lower end of the asphalt metering tank 11 is provided with a supply pipe 13 for pressure-feeding the measured molten asphalt into the mixer 7, and the lower end of the stone powder metering tank 12 is provided with a screw feeder 14 for supplying the measured stone powder into the mixer 7.

[0026] The dryer 3 is a rotary kiln-type aggregate heating device placed on the ground surface to the side of the plant main body 2, and has a cylindrical drum body 15 with a plurality of scraping blades (not shown) for scraping up aggregate arranged around its inner wall surface, supported at an angle so as to be freely rotatable on a base 16, and rotated at a predetermined speed by a drive device (not shown).

[0027] A hot hopper 19 having a burner 17 for supplying hot air into the drum body 15 and a discharge chute 18 for discharging high-temperature heated aggregate that has passed through the drum body 15 and been heat-treated is provided at one end of the lower side of the inclined drum body 15, while a cold hopper 21 having a supply conveyor 20 for supplying aggregate into the drum body 15 is provided at the other end of the higher side of the drum body 15. The discharge end of the discharge chute 18 and the vibrating sieve 10 provided at the top of the plant body 2 are connected by a vertical conveying device 22 such as a bucket elevator, so that the heated aggregate that has been heat-treated in the dryer 3 can be successively lifted and supplied to the vibrating sieve 10.

[0028] The bag filter 4 is a dust collector that collects dust from the exhaust gas discharged from the dryer 3, and is composed of an inertial dust collection section 23 located upstream (in terms of the flow direction of the exhaust gas) that primarily collects coarse dust in the exhaust gas (for example, particle size of about 0.1 mm to 1 mm), and a bag filter body 25 located downstream that secondary collects fine dust in the exhaust gas (for example, particle size less than about 0.1 mm) using a plurality of filter cloths (filters) 24.

[0029] In addition, the bag filter 4 is mounted on the elevated stand 6 of the plant main body 2 (spanning the floors 5b to 5c on which the aggregate storage bin 9 is mounted), and the side wall surface of the bag filter main body 25 is positioned in close contact or close proximity to the side wall surface of the aggregate storage bin 9, which is similarly mounted on the elevated stand 6, so that the heat radiated from the side wall surface of the aggregate storage bin 9 is efficiently received by the entire side wall surface of the bag filter main body 25, thereby effectively heating and keeping the collected dust inside warm.

[0030] As described above, the bag filter 4 is composed of the inertial dust collecting section 23 and the bag filter main body 25, and may be arranged so that the side wall surface of the inertial dust collecting section 23, including the side wall surface of the aggregate storage bin 9, is opposed to and in close contact with or adjacent to the side wall surface of the aggregate storage bin 9. However, since the longitudinal size of the bag filter 4 is usually larger than the longitudinal size of the aggregate storage bin 9, it is preferable to give priority to the bag filter main body 25, which is more susceptible to the effects of clogging of the filter cloth 24 when condensation occurs, and to arrange at least the bag filter main body 25 in close contact with or adjacent to the side wall surface of the aggregate storage bin 9.

[0031] 3, an opening 26 for removing the filter cloth 24 is provided on the upper surface of the bag filter body 25 so as to be able to be opened and closed. In order to increase the filtration area, the filter cloth 24 has an elongated structure which is fixed along the height direction of the bag filter body 25 as shown in FIG. 2, and when replacing the filter cloth 24, the opening 26 is opened, the used filter cloth 24 is pulled out upward, and a new filter cloth 24 is inserted and fixed in place. Therefore, when replacing the filter cloth 24, a certain amount of working space is required above the bag filter body 25.

[0032] In the bag filter 4 of this embodiment, the upper surface of the bag filter body 25 is configured to be approximately flush with the surface of the floor 5d on which the vibrating sieve 10 of the elevated stand 6 is mounted, which makes it easy to integrate the aggregate storage bin 9 located directly below the vibrating sieve 10 and the bag filter body 25 of the bag filter 4 in a horizontally aligned state. As a result, the bag filter body 25 can more efficiently receive the heat radiated from the aggregate storage bin 9, and even when replacing the filter cloth 24, a plant worker can relatively easily and safely replace the filter cloth 24 while remaining on the floor 5d on which the vibrating sieve 10 of the elevated stand 6 is mounted, which is preferable in terms of maintainability and work safety.

[0033] Furthermore, two screw feeders 27, 28 that discharge the collected fine dust are connected to the lower end of the bag filter body 25 of the bag filter 4 in a generally L-shape in plan view, and the discharge end 28a of the rear-stage screw feeder 28 faces the stone powder metering tank 12 provided in the plant body 2. This allows the fine dust collected by the bag filter body 25 to be sent directly to the stone powder metering tank 12 via the screw feeders 27, 28, and after being measured in the stone powder metering tank 12, it can be fed into the lower mixer 7 and effectively used as a material for the asphalt mixture (substituting for part of the stone powder).

[0034] In addition, the inertial dust collecting section 23 upstream of the bag filter 4 and the cold hopper 21 of the dryer 3 are connected by an exhaust duct 29a, while an exhaust duct 29b is also connected to the bag filter main body 25 downstream of the bag filter 4, and the end of the exhaust duct 29b is connected to a chimney (not shown) via an exhaust fan (not shown) in the middle.

[0035] In the figure, 30 denotes an exterior material such as slate or decorative iron plate that covers the outer periphery of the elevated stand 6 of the plant main body 2 together with the bag filter 4 to provide a heat-retaining and dust-proof structure, and the exterior material 30 covers the outer periphery of the lowest floor 5a to the uppermost floor 5d of the elevated stand 6 and the ceiling surface. Note that a heat insulating material is built inside the exterior material 30 to improve the heat retention effect, which makes it possible to reduce heat dissipation from the bag filter main body 25 and also to keep the heat dissipated from the aggregate storage bin 9 installed alongside it inside the exterior material 30, making it possible to heat and keep the bag filter 4 warmer more efficiently.

[0036] When an asphalt mixture is produced using the asphalt plant 1, first, aggregate is heated and dried in the dryer 3, and the heated aggregate is passed through the vertical conveyor 22 and the vibrating sieve 10 and stored in the aggregate storage bin 9 according to particle size. Next, according to the composition of the asphalt mixture to be produced, a predetermined amount of heated aggregate of each particle size is discharged from the aggregate storage bin 9 to the aggregate measuring tank 8 and cumulatively measured, and then the heated aggregate is charged into the mixer 7 at the bottom together with the molten asphalt measured in the asphalt measuring tank 11 and the stone powder measured in the stone powder measuring tank 12, and mixed to produce the desired asphalt mixture. Meanwhile, the exhaust gas discharged from the dryer 3 is introduced through the exhaust duct 29a into the bag filter 4 installed in the plant main body 2, where the dust contained in the exhaust gas is collected and purified, and then released into the atmosphere through the exhaust duct 29b and the chimney.

[0037] At this time, although the temperature of the exhaust gas discharged from the dryer 3 is close to the dew point temperature, the bag filter body 25 of the bag filter 4 is arranged in close contact with or close to the aggregate storage bin 9 that stores high-temperature heated aggregate, and therefore the bag filter body 25 is efficiently heated and kept warm by the heat radiated from the aggregate storage bin 9, and the occurrence of condensation can be effectively suppressed. Even when (timing is not) the aggregate is being heated by the dryer 3, heated aggregate is stored in the aggregate storage bin 9, and therefore the bag filter 4 can constantly receive the heat radiated from the aggregate storage bin 9, and a stable condensation suppression effect can be expected.

[0038] The fine dust collected by the bag filter body 25 of the bag filter 4 is appropriately sent to the stone powder measuring tank 12 equipped in the plant body 2 by the screw feeders 27 and 28, and is measured in the stone powder measuring tank 12 and effectively used as a material for the asphalt mixture (in place of a part of the stone powder). At this time, the fine dust collected by the bag filter body 25 of the bag filter 4 is heated and kept warm to approximately the same temperature as the heated aggregate (for example, about 160 to 170 ° C. when producing a normal asphalt mixture, and about 130 to 140 ° C. when producing a medium-temperature compound mixture) by the heat dissipated from the aggregate storage bin 9 installed in parallel, so that the temperature drop (or temperature fluctuation) of the asphalt mixture when the collected dust is used can be suppressed, and improvement in quality can be expected. In addition, since the fine dust can be immediately sent to the stone powder measuring tank 12 by the screw feeders 27 and 28, the temperature drop during transportation is also suppressed, making it even more preferable in terms of quality.

[0039] In this way, according to the asphalt plant 1 described above, by placing the bag filter body 25 of the bag filter 4 in close contact with or close to the side of the aggregate storage bin 9 in which high-temperature heated aggregate is stored during plant operation, not only the bag filter body 25 but also the collected dust within the bag filter body 25 can be efficiently heated and kept warm, the occurrence of condensation can be effectively suppressed, and the collected dust can be suitably used as a material for asphalt mixtures. [Industrial Applicability]

[0040] The present invention can be widely used in bag filters in asphalt plants. [Explanation of symbols]

[0041] 1... Asphalt plant 2... Plant body 3... Dryer 4... Bag filter 5a~5d…Floor (elevated platform) 6…Elevated platform 7...Mixer 8...Aggregate measuring tank 9...Aggregate storage bin 10...Vibrating sieve 11...Asphalt measuring tank 12...Stone powder measuring tank 15...Drum body 17...Burner 22... Vertical conveying device 23... Inertial dust collecting section (bag filter) 24…Cloth 25...Bag filter body (Bag filter) 26: Outlet 27, 28: Screw feeder 29a, 29b... Exhaust duct 30... Exterior material

Claims

1. 1. An asphalt plant comprising: a plant main body having a mixer, an aggregate measuring tank, an aggregate storage bin and a vibrating sieve mounted in a tiered arrangement on an elevated platform having multiple floors; a dryer for heating aggregate arranged on the side of the plant main body; a vertical conveying device connecting the vibrating sieve to a discharge chute for discharging high-temperature aggregate heated in the dryer; and a bag filter for collecting dust from the exhaust gas discharged from the dryer, wherein heated aggregate that has been heated in the dryer to the manufacturing temperature of an asphalt mixture to be produced is passed through the vertical conveying device and the vibrating sieve and stored in the aggregate storage bin by particle size, wherein the bag filter is mounted on the elevated platform of the plant main body, and the bag filter main body side wall surface of the bag filter is disposed opposite to or in close contact with the side wall surface of the aggregate storage bin.

2. 2. An asphalt plant according to claim 1, wherein a discharge end of a screw feeder for discharging collected dust provided at the lower end of the bag filter body faces a stone powder measuring tank provided in the plant body.

3. 3. The asphalt plant according to claim 1, wherein the outer peripheral surface of the plant body together with the bag filter is covered with an exterior material to provide a heat-insulating structure.

4. 4. The asphalt plant according to claim 1, wherein an upper surface of the bag filter body of the bag filter is configured to be substantially flush with a floor surface on which the vibrating screen of the elevated stand is mounted.

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