JPH0423924B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to an asphalt mixture storage method for heating and keeping an asphalt mixture used as a road paving material and storing it for a long period of time, and a container thereof. [Prior Art] It is known that asphalt mixtures used as road paving materials have a tendency to deteriorate due to oxygen and harden when exposed to oxygen-containing air.
In storage containers in which asphalt mixtures are stored for long periods of time, the air in empty spaces within the storage containers should be forcibly exchanged with water vapor, inert gas, etc. to prevent asphalt mixtures from being exposed to oxygen as much as possible. In addition, various airtight mechanisms have been adopted to prevent air from being sucked in through the gate gap that closes the material discharge port at the bottom of the storage container. [Problems to be Solved by the Invention] However, even in the above-mentioned conventional storage containers that have been devised in various ways, when the asphalt mixture is stored for a long time, the asphalt mixture hardens near the material discharge port at the bottom of the storage container, resulting in the release of the asphalt mixture. It may become difficult to assemble the asphalt mixture, or hardened lumps may become mixed into the discharged asphalt mixture. The present invention solves these conventional problems, and aims to provide a method and apparatus for storing an asphalt mixture that can be stored for a long time without changing the quality of the asphalt mixture. It is. [Means for Solving the Problems] In order to achieve the above object, the present invention investigated the actual state of hardening of an asphalt mixture in a storage container through experiments, and found that hardening in a storage container is caused not only by oxidative deterioration but also by oxidative deterioration. In fact, it turned out that this was much more attributable to the volatilization and desorption of the low boiling point components of the asphalt in the asphalt mixture during long-term storage. We have reached the conclusion that the hardening of can be prevented. That is, the present invention provides an asphalt mixture storage container having an input port at the top and a discharge port at the bottom, surrounding the discharge port to form an airtight chamber, and having a heating and heat-retaining structure, which has a heating means near the bottom of the container. An oil storage tank is provided, and the oil storage tank and the airtight chamber are communicated with each other, so that the airtight chamber is filled with evaporated content from the oil storage tank, and the evaporated content is replenished into the lower part of the container where the asphalt mixture is likely to harden. The present invention provides an asphalt mixture storage container characterized in that it is configured as follows. [Function] With the above configuration, the present invention fills the airtight chamber surrounding the lower discharge port of the asphalt mixture storage container with the evaporated content from the oil storage tank, and allows the oil to evaporate from the gap in the gate that closes the discharge port. By sucking in the oil content, it is possible to replenish the oil content corresponding to the low boiling point content in the asphalt of the asphalt mixture that volatilized and released during storage, so it is possible to prevent the asphalt mixture from hardening, especially from the lower part of the container. [Example] The process by which the present inventor arrived at the present invention will be explained below based on experimental examples. The present inventor places emphasis on the phenomenon in which asphalt mixtures harden even in a non-oxidizing atmosphere, and focuses on other causes of hardening at the same time as deterioration due to oxygen in the air. The following experiment was conducted to explore this. As Experiment 1, the characteristics of the oxidation reaction of asphalt were investigated using differential thermal analysis, which is generally used to analyze the thermal properties of substances and find out the tendency of oxidation reactions. Figure 3 is a graph of the results,
When an asphalt sample is heated at a rate of 20°C per minute from room temperature while exposed to air, and the heat generation state of the sample is examined, the heat generation of the asphalt sample itself increases relative to the rate of increase in sample temperature by 125°C. It was found that the amount rapidly increased, generating a large amount of heat and promoting oxidation, and after passing 125℃ and reaching 180℃, there was almost no heat generation and an equilibrium state was reached. When the temperature exceeds 180℃, heat generation begins again, and oxidation progresses slowly.
It can be seen that it rapidly generated heat at around 295℃, reached the ignition point, and burned. This shows that most of the asphalt oxidizes relatively quickly when exposed to high temperatures.
If this is replaced with a known asphalt mixture manufacturing process, most of the oxidation reactions will be promoted in the mixing process of the asphalt mixture, which is spray kneaded while being exposed to air at a high temperature of around 160°C. This can be seen from the fact that, for example, asphalt with a penetration value of 60 before kneading has a penetration value of 30 to 40 after kneading. Therefore, most of the oxidation reaction has already progressed by the time the asphalt mixture is kneaded and put into the storage container, and the reaction will proceed gradually after that. (CO ₂ , H ₂ O) displaces the surrounding atmosphere of the asphalt mixture, so the inventors pondered the idea that the asphalt mixture hardens due to oxidative deterioration in the storage container, and conducted Experiment 2. Summer. Experiment 2 is called a thermal stability test, in which the asphalt sample was placed at a constant high temperature in oxygen and inert gas (N ₂ ), and its weight change was investigated. Table 1 shows the results. be.

[Table] Table 1 shows that when an asphalt sample is held in oxygen at 200℃ for 30 minutes, the amount of asphalt increases by 1% of the total amount, but when held in oxygen at 200℃ for 30 minutes, the amount of asphalt increases by ₁ % of the total amount.
On the contrary, if held for a minute, it decreases by 0.6%, and if held for one hour, it tends to decrease by 1%. Furthermore, in an inert gas (N ₂ ) environment, it was found that when the temperature was raised to 300°C, it decreased by 6.8% after 30 minutes of holding, and by 10.2% after 1 hour of holding. This means that in an oxygen atmosphere, the oxidation reaction of asphalt progresses and the weight increases due to the binding of oxygen, but in an inert gas (N ² ), the weight decreases, so the low boiling point content of asphalt is reduced. It was found that it evaporates and leaves, leading to a decrease in weight. This suggests that the cause of hardening of asphalt mixtures in storage containers in an inert gas atmosphere is not due to oxidative deterioration, but rather due to the volatilization of low boiling point components in the asphalt during storage at relatively high temperatures. The inventor concludes that the separation causes a decrease in penetration, and that the weight of the asphalt mixture is also added to the lower part of the storage container, accelerating hardening. Therefore, as a method to prevent this hardening, in order to adjust the penetration level of the asphalt after kneading the asphalt mixture, the lower part of the storage container should be added with an appropriate amount of oil to the extent that it is practically no problem. The system replenishes oil corresponding to the low-boiling point component that volatilizes and leaves the tank. Embodiments of the present invention will be described below with reference to FIG. Reference numeral 1 denotes an asphalt storage container body, and the peripheral wall of the storage container body 1 is provided with a heating heat-insulating structure to prevent the asphalt mixture, which is the stored material, from hardening due to a drop in temperature. A material discharge port 2 is provided at the lower end of the storage container body 1, and a pair of butterfly-shaped gates 3, 3', which are effective for discharge control, are swingably mounted around pivot shafts 4, 4'. The material discharge port 2 is opened and closed by the expansion and contraction of the piston rod 6 of the fluid cylinder 5. Although the butterfly gates 3 and 3' are effective for controlling the release, it is difficult to form an airtight seal for the material outlet 2. Therefore, FIG. 2 is surrounded by a cover body 7 to form an airtight chamber 8, and a lower end opening 9 of the airtight chamber 8 is connected to the fluid cylinder 1.
The asphalt mixture is opened and closed by a shutoff gate 12 that moves forward and backward as the piston rod 11 expands and contracts. Selectively controlled by sequential opening and closing. An appropriate airtight sealing mechanism 13 is provided to prevent air from flowing into the airtight chamber 8 when the cutoff gate 12 is closed. 14 is an inlet for the asphalt mixture, and a piston rod 16 of the fluid cylinder 15
The input gate 17 is opened and closed by expanding and contracting. Reference numeral 18 denotes a small diameter exhaust port provided at the top of the storage container body 1, which gradually exhausts the gas accumulated in the cavity 19 inside the storage container body 1 to the outside. When the asphalt mixture is discharged from the material discharge port 2, a partial vacuum tends to be formed in the storage container, and simply sucking in outside air through the exhaust port 18 is not sufficient to eliminate this vacuum. A suction port 20 having a size of
The suction port gate 23 is opened and closed by expansion and contraction. Reference numeral 24 denotes an oil storage tank for storing oil for replenishing the low boiling point content in the asphalt of the asphalt mixture that volatilizes and leaves during storage. oil passage 25
is communicated with. A temperature sensor (not shown) is provided in the oil storage tank 24 or the oil path 25, and a heater 26
energization is controlled to maintain a predetermined temperature. The oil stored in the oil passage 25 is heated and evaporated, filling the airtight chamber 8. As time passes, the low boiling point content of the asphalt in the storage container evaporates and leaves, and is exhausted from the exhaust port 18 at the top. When this occurs, oil corresponding to the oil content is sucked into the interior through the gap between the butterfly gates 3 and 3' and diffuses. FIG. 2 shows an example in which the discharge gate 29 is moved forward and backward by the expansion and contraction of the piston rod 28 of the fluid cylinder 27 to open and close the material discharge port 2 at the lower part of the storage container main body 1. An annular airtight chamber 30 is provided surrounding the oil, and the airtight chamber 30 is filled with evaporated oil.
Evaporated matter is sucked in through the gap between the steel plates of the storage container body 1 and the discharge gate 29. Alternatively, the oil supply pipe 31 drawn out from the upper part of the oil storage tank 24 may be introduced into the storage container main body 1 while being protected by the protective material 32 to replenish the oil into the storage container main body 1. [Effects of the Invention] As described above, in the present invention, oil corresponding to the low boiling point content that evaporates and leaves in the asphalt of the asphalt mixture stored in the asphalt mixture storage container is replenished from the lower part of the storage container. The hardening of the asphalt mixture near the bottom of the storage container, which tends to harden, is also reduced, and the area around the material outlet is no longer blocked, allowing stable storage for a long period of time without degrading the quality of the asphalt mixture.

[Brief explanation of drawings]

Fig. 1 is a partially vertical schematic front view of an embodiment of the container of the present invention, Fig. 2 is a partially vertical schematic front view of another embodiment of the container of the present invention, and Fig. 3 is a differential thermal analysis curve diagram of asphalt. be. DESCRIPTION OF SYMBOLS 1...Storage container main body, 2...Material discharge port, 3...Butterfly gate, 8...Airtight chamber, 12...Block gate, 17...
Input gate, 18...Exhaust port, 23...Suction port gate, 24...Oil storage tank, 25...Oil passage, 26...Heater,
30...Airtight chamber, 31...Oil supply pipe.

Claims (1)

[Claims] 1. In an asphalt mixture storage container having an input port at the top and a discharge port at the bottom and having a heat-insulating structure, the oil is heated and the evaporated content is poured into the container from between the discharge port at the bottom of the container. The asphalt mixture is supplied into the container and refilled from the lower part of the container with an oil component corresponding to the low boiling point content of the asphalt that volatilizes and leaves during storage to prevent the asphalt mixture in the lower part of the container from hardening. How to store the mixture. 2. In an asphalt mixture storage container that has an input port at the top and a discharge port at the bottom, and has an airtight chamber surrounding the discharge port and has a heating and insulation structure, an oil storage tank having a heating means near the bottom of the container is provided. The oil storage tank and the airtight chamber are arranged so that the oil storage tank and the airtight chamber are communicated so that the airtight chamber is filled with evaporated content from the oil storage tank, and the evaporated content is replenished into the lower part of the container where the asphalt mixture tends to harden. An asphalt mixture storage container characterized by: