Asphalt Plant

Abstract

To provide an asphalt plant capable of producing asphalt mixture while uniformly forming molten asphalt.SOLUTION: In an asphalt plant, an asphalt supply pipe 19 on the downstream side of the supply pump 18 is equipped with a water injection nozzle 20 for injecting and adding water to molten asphalt, and an asphalt supply pipe 19 on the downstream side of the water injection nozzle 20 is equipped with a swirl mixing part 21 for mixing water and molten asphalt, and the swirl mixing part 21 is formed into an inverted cone shape whose inner diameter gradually decreases toward an outlet 22 at the lower part, while it is provided with an inlet 23 through which water-added molten asphalt is introduced from the upper side tangential direction, and the water-added molten asphalt introduced from the inlet 23 is mixed while swirling to the outlet 22 at the lower part and then supplied to the mixer 10.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an asphalt plant for producing an asphalt mixture for road paving, and more particularly to an asphalt plant for producing an asphalt mixture using foamed molten asphalt. [Background technology]

[0002] Conventionally, when producing an asphalt mixture, a predetermined amount of water, steam, etc. is added to molten asphalt, which is the raw material for the asphalt mixture, to foam it (make it foamy), and this foamed molten asphalt (hereinafter referred to as "foamed asphalt") is then mixed with aggregate, stone powder, etc. in a mixer to produce the asphalt mixture.

[0003] As an apparatus for foaming molten asphalt, the applicant has also applied for an asphalt plant as shown in Patent Document 1 (JP 2020-94367 A), which includes an asphalt supply pipe equipped with a supply pump that supplies molten asphalt measured in an asphalt measuring tank to a mixer, and a switching valve downstream of the supply pump that selects either a supply path that sends molten asphalt to the mixer or a circulation path that sends it back to the supply pump, and which has a water injection nozzle connected to the circulation path that injects water supplied from a water supply source into the molten asphalt, and which circulates the molten asphalt within the circulation path while injecting water from the water injection nozzle to foam the molten asphalt, and then supplies the molten asphalt to the mixer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-94367 Summary of the Invention [Problem to be solved by the invention]

[0005] However, while the above-mentioned conventional equipment can produce foamed asphalt almost uniformly by adding water to the molten asphalt and circulating it through a circulation path, the equipment configuration, which requires adding a circulation path to the asphalt supply piping just for foaming, is somewhat large-scale, and installation requires a certain amount of space and cost. Also, if a switching valve installed in the asphalt supply piping fails to switch, it could affect the production of the asphalt mixture, and the work of replacing a malfunctioning switching valve is very troublesome.

[0006] In view of the above, an object of the present invention is to provide an asphalt plant that can produce an asphalt mixture by foaming molten asphalt in a substantially uniform manner with a simple configuration. [Means for solving the problem]

[0007] In order to solve the above problems, the asphalt plant according to claim 1 of the present invention has a vibrating screen, aggregate storage bins, aggregate measuring bins, asphalt measuring bins, and mixers arranged in layers on an elevated platform, and is equipped with an asphalt supply pipe and a supply pump that supplies molten asphalt measured in the asphalt measuring bin to the mixer. The asphalt supply pipe downstream of the supply pump is equipped with a water injection nozzle that injects water into the molten asphalt, and the asphalt supply pipe downstream of the water injection nozzle is equipped with a swirling mixer that mixes water and molten asphalt, The asphalt supply pipe downstream of the swirling mixing section is provided with an asphalt injection nozzle, The swirling mixer is formed in an inverted cone shape with the inner diameter gradually decreasing toward the outlet at the bottom, while an inlet is formed at the top from the side tangent line direction to introduce molten asphalt with added water. and, Applicable The pipe diameters of the inlet and outlet are the same, The molten asphalt to which water has been added is introduced from the inlet and mixed while swirling towards the outlet at the bottom. From the downstream asphalt injection nozzle The present invention is characterized in that the mixture is supplied to the mixer. [Effects of the Invention]

[0008] According to the asphalt plant of claim 1 of the present invention, a water injection nozzle is provided in the asphalt supply pipe downstream of a supply pump interposed in the asphalt supply pipe, and a swirling mixer that mixes water and molten asphalt is provided in the asphalt supply pipe downstream of the water injection nozzle, The asphalt supply pipe downstream of the swirling mixing section is provided with an asphalt injection nozzle, The swirling mixer is formed in an inverted cone shape with the inner diameter gradually decreasing toward the outlet at the bottom, while an inlet is formed at the top from the side tangent line direction to introduce molten asphalt with added water. and, Applicable The pipe diameter of the inlet and the outlet is the same, The molten asphalt to which water has been added is introduced from the inlet and mixed while swirling towards the outlet at the bottom. From the downstream asphalt injection nozzle Since the water is supplied to the mixer, the swirling mixing in the swirling mixing section allows for even dispersion of water in the molten asphalt, and when released into the mixer, a substantially uniformly foamed molten asphalt can be supplied. Furthermore, the asphalt supply piping has a simple structure that does not involve mechanical parts such as route switching valves, which reduces costs and prevents problems such as an inability to supply molten asphalt. Furthermore, the simple structure allows for the entire device to be made compact, and by reducing installation space, it can be easily installed in existing plants. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic explanatory diagram of an asphalt plant according to the present invention. [Figure 2] 1 is an explanatory diagram of a main part of an asphalt measuring and supplying device according to the present invention. [Figure 3] FIG. 2 is an enlarged view in which a part of the swirling mixer is omitted. [Figure 4] FIG. 4 is a cross-sectional view taken along line AA in FIG. 3, with a portion thereof omitted. DETAILED DESCRIPTION OF THE INVENTION

[0010] In the asphalt plant according to the present invention, in a plant of an existing structure, a water injection nozzle for injecting water into the molten asphalt is connected to the asphalt supply pipe downstream of a supply pump such as a gear pump that is interposed in the asphalt supply pipe that supplies molten asphalt from an asphalt metering tank to a mixer, and a swirling mixer that mixes water and molten asphalt is connected to the asphalt supply pipe downstream of the water injection nozzle. Asphalt spray nozzle Equipped with.

[0011] The swirling mixer has a circular horizontal cross section, an outlet provided at the bottom is arranged on the central axis of the circle, and is formed into an inverted cone shape with an inner diameter gradually decreasing toward the outlet, while an inlet for introducing molten asphalt with added water is formed from the side tangential line direction at the top, and, Applicable The pipe diameter of the inlet and the outlet is the same, The molten asphalt with added water is introduced through the inlet, mixed while swirling along the inner wall surface, and then discharged from the outlet at the bottom, supplying the molten asphalt with water evenly dispersed to the mixer.

[0012] When an asphalt mixture using foamed asphalt is produced in an asphalt plant with the above configuration, the required amount of asphalt is calculated from the blending ratio of the asphalt mixture being produced on the plant control panel, and one batch of molten asphalt is measured out in the asphalt measuring tank.

[0013] Meanwhile, aggregates of each particle size are discharged from the aggregate storage bin based on the mixing ratio and cumulatively weighed into the aggregate weighing tank. These cumulatively weighed aggregates, along with various materials such as stone powder that have been separately weighed, are then poured into the mixer to perform pre-mixing (dry mixing).

[0014] After premixing, the molten asphalt is discharged from the asphalt metering tank and the supply pump is driven, and a predetermined amount of water, for example, about 1 to 3% by weight of the measured amount of molten asphalt, is sprayed from the water spray nozzle onto the molten asphalt flowing down the asphalt supply pipe to the swirling mixing section.

[0015] The water added to the high-temperature molten asphalt flows down into the swirling mixing section along with the molten asphalt, and as it swirls within the swirling mixing section and flows down to the outlet at the bottom, it vaporizes and is dispersed evenly throughout the molten asphalt, and is then discharged from the outlet at the bottom into the asphalt supply pipe.

[0016] By swirling and mixing in the swirling mixer, the vaporized water is dispersed evenly within the molten asphalt, producing foamed asphalt with approximately uniform properties. From the downstream asphalt injection nozzle It can be added to a mixer after pre-mixing has been completed, and mixed with materials such as aggregate in the mixer to produce an asphalt mixture made from foamed asphalt.

[0017] In this way, the injected water is dispersed evenly in the molten asphalt fed into the mixer, and foamed asphalt with approximately uniform properties can be produced using a simple equipment configuration in which a swirling mixing section is inserted into the asphalt supply piping.By using this as a raw material, it is expected that materials such as aggregate and stone powder will be mixed well in the mixer, and it is expected that the desired asphalt mixture can be produced even if the production temperature is lower than conventional temperatures, for example.

[0018] Furthermore, because the molten asphalt with added water is supplied to the mixer simply by passing through the swirling mixing section, the time required from metering to discharging into the mixer is comparable to the time required to discharge normal molten asphalt without added water, and the production efficiency per hour does not decrease even when producing an asphalt mixture using foamed asphalt. [Example]

[0019] An embodiment of the present invention will now be described with reference to the accompanying drawings.

[0020] In Figure 1, reference numeral 1 denotes an asphalt plant that produces asphalt mixtures used for road paving, and is mainly composed of a plant body 2, an asphalt tank 3 that stores molten asphalt at an insulated temperature, and a control panel 4 for operating and controlling the various equipment in the plant. The plant body 2 has an elevated platform 5 with multiple floors erected thereon, and a bucket elevator 6 is installed next to the elevated platform 5 to lift new aggregate that has been heated and dried in a dryer (not shown) to the top of the elevated platform 5.

[0021] On the elevated platform 5, there are arranged in layers a vibrating sieve 7 that sieves the heated aggregate discharged from the bucket elevator 6 by particle size, an aggregate storage bin 8 that stores the aggregate sieved by the vibrating sieve 7 by particle size, an aggregate measuring tank 9 that cumulatively measures the aggregate of each particle size discharged from the aggregate storage bin 8, a mixer 10 that mixes various materials such as aggregate and molten asphalt, and an asphalt measuring supply device 11 that measures molten asphalt and supplies it to the mixer 10.

[0022] The asphalt metering supply device 11 is connected to an asphalt supply pipe 12 that supplies molten asphalt from the asphalt tank 3 and a water supply pipe 14 that supplies water from a water storage tank 13, which is a water supply source, and supply pumps 15 and 16 are provided in the middle of the asphalt supply pipe 12 and the water supply pipe 14, respectively.

[0023] Figure 2 is a schematic diagram of the asphalt metering supply device 11, which is equipped with an asphalt metering tank 17 that measures the molten asphalt supplied through the asphalt supply piping 12, and an asphalt supply piping 19 equipped with a supply pump 18, such as a gear pump, that supplies the measured molten asphalt to the mixer 10.

[0024] In addition, a water injection nozzle 20 is connected to the asphalt supply pipe 19 in the middle, which injects water supplied from the water supply pipe 14 into the molten asphalt, and a swirling mixing section 21 is interposed in the asphalt supply pipe 19 downstream of the water injection nozzle 20, which swirlingly mixes the water and molten asphalt.

[0025] As shown in Figures 3 and 4, the swirling mixing section 21 has a circular horizontal cross section, an outlet 22 located at the bottom on the central axis of the circle, and is formed into an inverted cone shape with the inner diameter gradually decreasing toward the outlet 22, while an inlet 23 is formed to introduce molten asphalt with added water from the tangential direction of the upper side surface, and the molten asphalt with added water introduced from the inlet 23 is caused to swirl along the inner wall surface and flow down to the outlet 22 at the bottom, thereby evenly mixing the water into the molten asphalt.

[0026] When water is injected from the water injection nozzle 20 into the high-temperature (approximately 160°C) molten asphalt flowing down the asphalt supply pipe 19 to the mixer 10, the water vaporizes and is introduced into the swirling mixing section 21, where it is swirled and mixed with the molten asphalt to form a nearly uniform foam, which is then discharged from the outlet 22.

[0027] The asphalt metering tank 17 is composed of a metering tank body 25 suspended and supported by a load cell 24, and a surge tank 26 that temporarily receives the molten asphalt discharged from the metering tank body 25.

[0028] The upper part of the metering tank body 25 is provided with an inlet 27 through which the discharge end of the asphalt supply pipe 12 is inserted, and the lower part is provided with a discharge outlet 28 for discharging the measured molten asphalt. The metering tank body 25 is also provided with an opening / closing mechanism consisting of a cylinder 29, a piston rod 30, and a plug 31, and the plug 31 is moved back and forth in the vertical direction in response to the extension and contraction of the piston rod 30, thereby opening and closing the discharge outlet 28.

[0029] Also, in the figure, 32 is a discharge gate that discharges aggregate of each particle size stored in each compartment of the aggregate storage bin 8, 33 is a load cell that supports and weighs the aggregate measuring tank 9 by hanging it, 34 is a discharge gate that discharges the aggregate that has been cumulatively measured in the aggregate measuring tank 9, 35 is an asphalt injection nozzle that injects and feeds the molten asphalt supplied from the asphalt supply pipe 19 into the mixer 10, and 36 is a mixing blade of the mixer 10.

[0030] When an asphalt mixture using foamed asphalt as a raw material is produced in the asphalt plant 1 having the above-described configuration, the type and production amount of the asphalt mixture to be produced are first input into the plant operation panel 4.

[0031] The control panel 4 starts cumulative weighing by discharging aggregate from each compartment of the aggregate storage bin 8 into the aggregate weighing tank 9 according to the input composition of the asphalt mixture to be produced, while in the asphalt weighing tank 17, one batch of molten asphalt is weighed.

[0032] Once the cumulative weighing of the aggregate has been completed, it is poured into the mixer 10 together with various materials such as stone powder that have been separately weighed, and pre-mixing (dry mixing) is carried out. In addition, in the asphalt metering tank 17, after the weighing of the molten asphalt has been completed, the discharge port 28 of the metering device main body 25 is opened to discharge the weighed molten asphalt, and the supply pump 18 interposed in the asphalt supply piping 19 is operated.

[0033] A predetermined amount of water corresponding to a preset water addition ratio is injected from water injection nozzles 20 onto the molten asphalt flowing down through asphalt supply pipe 19 into mixer 10. The water addition ratio to the molten asphalt can be set appropriately by determining through tests or the like the ratio that will produce an appropriate foamed asphalt, and should be set, for example, in the range of about 1 to 3% by weight.

[0034] The molten asphalt, to which a predetermined amount of water has been added from the water injection nozzles 20, is introduced from the inlet 23 at the top of the swirling mixing section 21 and flows down to the outlet 22 at the bottom while swirling along the inner wall surface. At this time, as the inner diameter becomes smaller in the lower part of the swirling mixing section 21, the molten asphalt and water accelerate, and a vortex is formed near the bottom discharge, allowing the molten asphalt and water to be mixed evenly.

[0035] In the swirling mixing section 21, the water in the molten asphalt vaporizes and is swirled and mixed with the molten asphalt, forming a substantially uniform foam that is then discharged from the outlet 22 into the asphalt supply pipe 19. The foam is then injected into the mixer 10, which has completed pre-mixing, through the downstream asphalt injection nozzle 35, and mixed with the aggregate and other materials in the mixer 10 to produce the desired asphalt mixture.

[0036] Furthermore, when producing an asphalt mixture using normal (no water added) molten asphalt as a raw material in the asphalt plant 1, the asphalt measuring supply device 11 can produce a normal asphalt mixture by supplying the molten asphalt measured in the asphalt measuring tank 17 to the mixer 10 without spraying water from the water injection nozzle 20, thereby enabling flexible production of asphalt mixtures using both foamed asphalt and normal molten asphalt as a raw material.

[0037] Furthermore, compared to conventional operational control, there are no major changes other than the control of water injection from the water injection nozzle 20, and molten asphalt can be foamed in existing asphalt plants simply by adding the water injection nozzle 20 and the swirling mixing section 21 to the asphalt supply piping 19. Since this system can be installed relatively easily and inexpensively, it can be suitably used even in existing asphalt plants.

[0038] Furthermore, the water injection nozzles 20 connected to the asphalt supply pipe 19 to inject water into the molten asphalt may be, for example, two water injection nozzles 20 arranged and connected at opposing positions on the asphalt supply pipe 19, or multiple water injection nozzles 20 arranged and connected at predetermined angles around the circumference of the asphalt supply pipe 19.Various modifications can be made as long as water can be injected into the flowing molten asphalt. [Industrial Applicability]

[0039] The present invention can be widely applied to asphalt plants that produce asphalt mixtures using foamed asphalt as a raw material. [Explanation of symbols]

[0040] 10... Mixer 11... Asphalt metering supply device 17...Asphalt measuring tank 18...Supply pump 19...Asphalt supply pipe 20...Water injection nozzle 21... Swirling mixer 22... Outlet 23...Entrance

Claims

[Claim 1] In an asphalt plant having a vibrating screen, aggregate storage bins, aggregate measuring tanks, asphalt measuring tanks, and mixers arranged in layers on an elevated platform, and an asphalt supply pipe and supply pump for supplying molten asphalt measured in the asphalt measuring tank to the mixer, the asphalt supply pipe downstream of the supply pump is equipped with a water injection nozzle for injecting water into the molten asphalt, and the asphalt supply pipe downstream of the water injection nozzle is equipped with a swirling mixer for mixing water and molten asphalt, and The asphalt supply pipe is equipped with an asphalt injection nozzle, the swirling mixing section is formed in an inverted cone shape with the inner diameter gradually decreasing toward the lower outlet, while an inlet is formed at the top from the side tangent line direction for introducing molten asphalt with added water, and the outlet and the inlet have the same pipe diameter, and the molten asphalt with added water introduced from the inlet is mixed while swirling toward the lower outlet, and then supplied to the mixer from the downstream asphalt injection nozzle.

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