JP7106220B2 - asphalt plant - Google Patents

Description

The present invention relates to an asphalt plant for producing an asphalt mixture, which is a road pavement material, and more particularly to an asphalt plant capable of producing an asphalt mixture while foaming molten asphalt, which is the material of the asphalt mixture.

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

By using the foamed asphalt instead of ordinary molten asphalt, the viscosity of the asphalt can be weakened and the volume can be increased. has the advantage of being able to reduce the amount of CO2 generated.

As a device for foaming molten asphalt, for example, in Patent Document 1 (Japanese Patent Application Laid-Open No. 2018-3289) and Patent Document 2 (Japanese Patent Application Laid-Open No. 2000-144621), an asphalt tank or an asphalt weighing tank is transferred to a mixer. It is disclosed that a water injection nozzle for injecting and adding water supplied from a water storage tank is attached in the middle of an asphalt supply pipe for supplying molten asphalt.

In addition, in Patent Document 3 (Japanese Patent Publication No. 2003-524054), a water injector for injecting water into the asphalt supply pipe is provided, and a static mixer is arranged in the pipe on the downstream side to melt after water injection. It is disclosed that the asphalt is passed through the static mixer to be stirred and mixed to form a uniform foam.

Japanese Patent Application Laid-Open No. 2018-3289 JP-A-2000-144621 Japanese Patent Publication No. 2003-524054

However, in order to form the molten asphalt uniformly, a static mixer for stirring and mixing may be arranged in the asphalt supply pipe as in the above-mentioned conventional device. If a circulation path is formed in the middle of and the molten asphalt after water addition is circulated in the circulation path for a certain period of time before being supplied to the mixer, the water mixed and added during that time is added to the molten asphalt I thought that it would be possible to disperse it evenly and foam it almost uniformly.

An object of the present invention is to provide an asphalt plant capable of producing an asphalt mixture while uniformly foaming molten asphalt.

In order to solve the above problems, in the asphalt plant according to claim 1 of the present invention, a vibrating screen, an aggregate storage bin, an aggregate weighing tank, an asphalt weighing tank, and a mixer are assembled in layers on an elevated platform, and the In an asphalt plant equipped with an asphalt supply pipe and a supply pump for supplying molten asphalt weighed in an asphalt weighing tank to the mixer, molten asphalt is supplied to the mixer downstream of the supply pump in the asphalt supply pipe. It is equipped with a switching valve that selects either a supply route to send in or a circulation route to send back to the supply pump, and a water injection nozzle that sprays and adds water supplied from a water supply source to the molten asphalt is installed in the middle of the circulation route. When the molten asphalt weighed in the asphalt weighing tank is discharged, the water injection nozzle is jetted to add water, and at the same time, the switching valve can be switched to the circulation path side.

The asphalt plant according to claim 2 of the present invention is characterized in that the circulation path passes through a surge tank that temporarily receives molten asphalt discharged from the measuring tank body of the asphalt measuring tank. .

According to the asphalt plant according to claim 1 of the present invention, either a supply route for sending molten asphalt to a mixer downstream of a supply pump in the asphalt supply pipe or a circulation route for returning molten asphalt to the supply pump is selected. and a water injection nozzle that injects and adds water supplied from a water supply source to the molten asphalt in the middle of the circulation path. Since the switching valve can be switched to the circulation path side at the same time as water is injected and added from the mixer, the molten asphalt to which water has been added can be circulated in the circulation path before being supplied to the mixer. It is expected that the water added after being mixed with the mixture can be uniformly dispersed and uniformly foamed. .

Further, according to the asphalt plant according to claim 2 of the present invention, the circulation path is configured to pass through a surge tank that temporarily receives the molten asphalt discharged from the measuring tank body of the asphalt measuring tank, so the plant Even if there is not much surplus space on the pedestal, the space occupied by the surge tank of the existing asphalt weighing tank on the pedestal can be used effectively to form a circulation path without difficulty, and it can be installed compactly in the existing plant.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic explanatory drawing of the asphalt plant which concerns on this invention. FIG. 2 is an enlarged view of a main portion of FIG. 1;

In the asphalt plant according to the present invention, in a plant with an existing structure, a supply route for sending molten asphalt to a mixer or a circulation route for sending back to the supply pump is provided downstream of a supply pump in the middle of an asphalt supply pipe. For example, a switching valve such as a three-way valve is provided.

Further, a water injection nozzle is installed in the middle of the circulation path for spraying and adding water supplied from a water supply source to the molten asphalt flowing down the inside of the circulation path. Further, when the molten asphalt weighed in the asphalt measuring tank is discharged, the switching valve can be switched to the circulation path side at the same time as the water is injected from the water injection nozzle.

The circulation path may be configured to pass through a surge tank that temporarily receives the molten asphalt discharged from the weighing body of the asphalt weighing tank. Even in rare situations, the space occupied by the surge tank of the existing asphalt weighing tank on the stand can be effectively used to form a circulation path without difficulty, and the existing equipment can be easily modified, making it relatively adopted. It is expected that it will be easy to install.

When producing an asphalt mixture made of foamed asphalt in the asphalt plant with the above configuration, after weighing one batch of molten asphalt in the weighing tank body of the asphalt weighing tank, asphalt is supplied through a surge tank. Drain into piping. In the asphalt supply pipe, a supply pump is driven to send out the molten asphalt downstream, and at that timing, a predetermined amount (a weighed batch of molten asphalt is foamed) from the water injection nozzle ) is sprayed and added, the switching valve is switched to the circulation path side at the same time. As a result, the molten asphalt to which water has been added circulates in the circulation path for a certain period of time, during which time the water is gradually mixed and the added water is evenly dispersed in the molten asphalt.

On the other hand, in the aggregate weighing tank, the aggregate of each particle size discharged from the aggregate storage bin is cumulatively weighed. These are pre-mixed in the mixer, and when it comes time to charge the molten asphalt into the mixer, the switching valve is switched to the supply path side. As a result, the molten asphalt circulating in the circulation path is fed into the mixer, and is successively introduced into the mixer while foaming. At this time, the added water is evenly dispersed in the molten asphalt by circulating and mixing, and it is expected that a foamed asphalt with substantially uniform properties will be produced. etc., and even if the production temperature is lowered, the desired asphalt mixture can be suitably produced.

An embodiment of the present invention will be described below with reference to the drawings.

1 in FIG. 1 is an asphalt plant for producing an asphalt mixture, which is a road paving material, and includes a plant body 2, an asphalt tank 3 for thermally storing molten asphalt, and a control panel 4 for operating and controlling various devices of the plant. is mainly composed of The plant main body 2 has an elevated stand 6 having a plurality of floors 5a to 5c. A bucket elevator 7 is arranged side by side to lift it upward.

On each floor 5a to 5c of the elevated platform 6, a vibrating sieve 8 for sieving the heated aggregate supplied from the bucket elevator 7 by particle size, and the aggregate sieved by the vibrating sieve 8 are stored by particle size. Aggregate storage bin 9, aggregate weighing tank 10 for cumulatively weighing the aggregate of each particle size discharged from the aggregate storage bin 9, supply from the asphalt tank 3 through asphalt supply pipe 11 and supply pump 12 An asphalt weighing tank 13 for weighing the molten asphalt, and a mixer 14 for producing an asphalt mixture by mixing a predetermined amount of aggregate, molten asphalt, etc. weighed in the aggregate weighing tank 10 and the asphalt weighing tank 13. are placed in

FIG. 2 is an enlarged view of the main part of the plant main body 2. In the figure, 15a to 15e are discharge gates for discharging the aggregate of each particle size stored in the compartments 16a to 16e of the aggregate storage bin 9. Reference numeral 17 denotes a load cell for suspending and weighing the aggregate measuring tank 10; 18, a discharge gate for discharging the aggregate weighed in the aggregate measuring tank 10;

As shown in FIG. 2, the asphalt weighing tank 13 mainly comprises a weighing tank body 21 suspended by a load cell 20 and a surge tank 22 for temporarily receiving molten asphalt discharged from the weighing tank body 21. It consists of The weighing tank body 21 has an inlet 23 at its upper portion through which the discharge end of the asphalt supply pipe 11 can be inserted, and an outlet 24 at its lower end for discharging the measured molten asphalt. 25, a piston rod 26, and an opening/closing mechanism consisting of a plug 27. The plug 27 at the tip of the piston rod 26 moves forward and backward in accordance with the expansion and contraction of the piston rod 26 to open and close the discharge port 24. .

The surge tank 22 has a substantially cylindrical shape with an open upper portion, and is fitted on the outer wall surface of the lower side of the measuring tank main body 21 with a slight gap so as not to interfere with weighing. Preferably, the bottom surface of the metering tank body 21 and the bottom surface 22a of the surge tank 22 are separated by a relatively large distance from the existing surge tank to form a storage space 28 in which asphalt having increased volume due to foaming can be temporarily stored. is doing. Molten asphalt discharged from the discharge port 24 of the metering tank body 21 is temporarily received in the storage space 28 of the lower surge tank 22, and then flows to the lower side of the surge tank bottom surface 22a having an inclined structure. , and discharged from a discharge port 29 provided at the lowermost end.

30 in the figure is an asphalt supply pipe having a bent pipe structure that supplies the molten asphalt weighed in the asphalt weighing tank 13 to the mixer 14 arranged on the same floor 5c as the asphalt weighing tank 13. While the base end is connected to the discharge port 29 of the surge tank 22 of the asphalt weighing tank 13, the tip end faces the upper opening of the mixer 14, and the tip end is provided with an injection nozzle for asphalt injection injection. 31 are fixed, and in the middle of the asphalt supply pipe 30, a supply pump 32 for supplying molten asphalt is provided.

Further, on the downstream side of the position of the supply pump 32 in the middle of the asphalt supply pipe 30, either the supply route A that sends the molten asphalt to the mixer 14 or the circulation route B that sends it back to the supply pump 32 is selected. For example, a switching valve 33 such as a three-way valve is provided.

Reference numeral 34 in the figure denotes a return pipe having a horizontal straight pipe structure forming a part of the circulation route B, the base end of which is connected to the switching valve 33 and the tip end of which is connected to the asphalt weighing tank 13 . The molten asphalt returned from the return pipe 34 passes through the storage space 28 on the lower side of the surge tank 22 and is discharged from the discharge port 29. It is configured to be discharged and circulated and supplied to the supply pump 32 again.

In the middle of the circulation path B, water supplied from a water storage tank 35, which is a water supply source shown in FIG. A water injection nozzle 38 is attached to spray and add to the hot molten asphalt. It should be noted that the water storage tank 35 does not necessarily have to be provided, and may be configured to be connected to the water injection nozzle 38 via the water supply pipe 36 from the water pipe, for example.

In this embodiment, as shown in FIGS. 1 and 2, the water injection nozzle 38 is installed downstream of the supply pump 32 of the asphalt supply pipe 30, but it is not limited to this. Instead, it may be installed on the upstream side of the supply pump 32 or in the middle of the return pipe 34 . Further, the water supply pipe 36 is branched in the middle, and the water injection nozzles 38 are fixed to the respective ends, and these water injection nozzles 38 are arranged at predetermined intervals in the middle of the circulation route B (including the return pipe 34). It may be placed and attached, in which case it is possible to efficiently disperse and mix the water added to the molten asphalt.

Further, under the control of the plant operation panel 4 shown in FIG. 1, when the molten asphalt weighed in the asphalt weighing tank 13 is discharged, a predetermined amount of water is injected from the water injection nozzle 38 and at the same time the switching valve 33 is can be switched to the circulation path B side.

When producing an asphalt mixture made of foamed asphalt in the asphalt plant 1 having the above configuration, after weighing one batch of molten asphalt in the weighing tank main body 21 of the asphalt weighing tank 13, the surge tank 22 is filled. It is discharged to the asphalt supply pipe 30 via. In the asphalt supply pipe 30, the supply pump 32 is driven to send out the molten asphalt downstream, and a predetermined amount (one batch of molten asphalt weighed in the asphalt weighing tank 13) is emitted from the water injection nozzle 38 in accordance with the timing. An amount of water suitable for foaming the asphalt (for example, about 2% by weight with respect to the amount of molten asphalt) is sprayed and added, and at the same time, the switching valve 33 is switched to the circulation path B side. As a result, the molten asphalt to which water has been added continues to circulate in the circulation path B for a certain period of time, during which the added water is gradually mixed and evenly dispersed in the molten asphalt.

It should be noted that the timing of injecting water from the water injection nozzle 38 is preferably determined by timing when the molten asphalt discharged from the surge tank 22 just reaches the mounting position of the water injection nozzle 38, but in the present invention, , the molten asphalt after water is injected is mixed while circulating in the circulation path B for a certain period of time. It can be evenly distributed in the asphalt.

On the other hand, in the aggregate weighing tank 10, the aggregate of each particle size discharged from each compartment 16a to 16e of the aggregate storage bin 9 is cumulatively weighed. They are put into the mixer 14 and pre-mixed (dry-mixed) as necessary. Then, when it is time to introduce the molten asphalt into the mixer 14, the switching valve 33 is switched to the supply path A side. As a result, the molten asphalt circulating in the circulation path A is sent to the mixer 14 and sequentially introduced into the mixing tank of the mixer 14 while foaming. At this time, the added water is evenly dispersed in the molten asphalt, and it is expected that the foamed asphalt with substantially uniform properties will be produced. Efficient mixing.

According to the test results conducted by the present inventors, it was confirmed that it takes about 2 seconds for the molten asphalt to which water has been added to go around the circulation path B of the asphalt plant 1 of this embodiment. On the other hand, when each batch of asphalt mixture is produced in the asphalt plant 1 in about 60 seconds, it takes about 10 seconds from the completion of weighing the molten asphalt in the asphalt weighing tank 13 to feeding it into the mixer 14. Since there is a certain amount of waiting time, the molten asphalt to which water has been added can be circulated about 4 to 5 times in the circulation path B before being put into the mixer 14, and during that time, it can be effectively mixed. It is expected that the added water can be evenly dispersed.

In this embodiment, the circulation path B of the molten asphalt is configured to pass through the surge tank 22. In that case, the molten asphalt to which water is added is stored in the surge tank 22, which is an open space communicating with the atmosphere. Since some foaming occurs even when passing through the space 28, if the capacity of the storage space 28 is insufficient for the amount of volume expansion accompanying the foaming of the molten asphalt, a A buffer tank may be provided to separately secure an empty space.

In this embodiment, the end of the return pipe 34 is connected to the surge tank 22 of the asphalt weighing tank 13 to form the circulation path B. However, the present invention is not limited to this. If sufficient excess space can be secured above, the tip of the return pipe 34 is connected to the asphalt supply pipe 30 located between the discharge port 29 of the surge tank 22 of the asphalt weighing tank 13 and the supply pump 32. A circulation path may be formed.

In this case, if a check valve is provided near the discharge port 29 of the surge tank 22 and the check valve is closed while the molten asphalt is circulating, the molten asphalt to which water is added is supplied to the closed space. Since the liquid continues to circulate through the circulation path while confined within the pipe 30, foaming during circulation can be suppressed, and installation of a buffer tank or the like is not required.

In addition, in the asphalt plant 1, not only foamed asphalt but also an asphalt mixture made from ordinary molten asphalt may be produced. It can be manufactured under normal operation control, and can flexibly respond to the manufacture of asphalt mixtures made from both foamed asphalt and ordinary molten asphalt.

INDUSTRIAL APPLICABILITY The present invention is widely applicable to asphalt plants that manufacture asphalt mixtures using foamed asphalt as a raw material.

1... Asphalt plant 2... Plant main body 3... Asphalt tank 4... Operation panel 6... Elevated stand 8... Vibrating screen 9... Aggregate storage bin 13... Asphalt measuring tank 14... Mixer 19... Mixing blade 21... Measuring tank main body (asphalt measuring tank)
22 Surge tank (asphalt weighing tank)
30... Asphalt supply pipe 32... Supply pump 33... Switching valve 34... Return pipe 35... Water storage tank (water supply source) 38... Water injection nozzle A... Supply route B... Circulation route

Claims (2)

A vibrating screen, an aggregate storage bin, an aggregate weighing tank, an asphalt weighing tank, and a mixer are assembled in layers on an elevated platform, and asphalt supply pipes and supplies for supplying molten asphalt weighed in the asphalt weighing tank to the mixer. In an asphalt plant equipped with a pump, a switching valve that selects either a supply route for sending molten asphalt to the mixer or a circulation route for returning molten asphalt to the supply pump on the downstream side of the supply pump in the asphalt supply pipe. In addition, a water injection nozzle for spraying and adding water supplied from a water supply source to the molten asphalt is installed in the middle of the circulation path, and when the foamed asphalt mixture is produced, the water is added to the molten asphalt discharged from the asphalt weighing tank. An asphalt plant, characterized in that the switching valve can be switched to the circulation path side at the same time when water is injected and added from the injection nozzle. 2. An asphalt plant according to claim 1, wherein said circulation path passes through a surge tank for temporarily receiving molten asphalt discharged from the asphalt measuring tank main body.

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