JPH0355603Y2 - - Google Patents

Description

[Detailed explanation of the idea]

[Industrial Application Field] The present invention relates to an asphalt mixture storage container for storing an asphalt mixture which is a road paving material. [Prior Art] It is known that asphalt mixtures used as road paving materials have a tendency to be oxidized by 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 inside the storage containers is forcibly replaced with water vapor, inert gas, etc., and measures are taken to prevent asphalt mixtures from being exposed to oxygen as much as possible. In addition, various airtight mechanisms are employed 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 conventional storage container described above, which has 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, causing the problem of release. 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 an asphalt mixture storage container that can be stored for a long time without changing the quality of the asphalt mixture. [Means for Solving the Problems] In order to achieve the above object, the present invention investigated the actual state of hardening of the asphalt mixture in the storage container through experiments. In fact, it turned out that the problem was much more attributable to the volatilization of low boiling point components of the asphalt mixture during long-term storage. As a result, the low boiling point content of asphalt evaporates from the asphalt mixture and rises in the storage container, and this phenomenon occurs where the volatilization progresses toward the bottom, which is thought to be one of the causes of hardening. The conclusion was reached that by preventing asphalt from curing as much as possible. That is, the present invention has an input port at the top and a discharge port at the bottom, and forms an airtight chamber surrounding the lower material discharge port of an asphalt mixture storage container with a heating and heat retention structure, and the airtight chamber and the upper part of the storage container. The present invention provides an asphalt mixture storage container characterized in that a gas circulation piping is disposed with an exhaust fan interposed between the asphalt mixture storage container and the asphalt mixture storage container. [Function] With the above-mentioned configuration, the present invention uses an exhaust fan to suck gases such as low boiling point components of the asphalt and water vapor that are volatilized and released in the storage container from the airtight room side, and installs piping for gas circulation in the upper part of the storage container. As a result of the reduction circulation through the storage container, the gas that volatilizes and desorbs within the storage container and rises inside the storage container changes to flow from the top to the bottom, and the gas saturated with volatile matter is concentrated in the upper part of the storage container. It will circulate inside the storage container without any damage. [Example] The process that led to the present invention will be explained below based on an example. The present inventor places emphasis on the phenomenon that 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 2 is a graph of the results,
When an asphalt sample is heated at a rate of 20℃ 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℃. 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 we replace this with the known production process for asphalt mixtures, 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 placed in the storage container;

[Table] Table 1 shows that when an asphalt sample is held in oxygen at 200°C for 30 minutes, the amount of asphalt increases by 1% of the total, but when it is held in an inert gas _N2 at the same temperature for 30 minutes, it increases by 0.6%. It also tends to decrease by 1% when held for 1 hour. Additionally inert gas _N2
Inside, when the temperature rises to 300℃, the temperature is 6.8 after being held for 30 minutes.
%, it was found that it decreased by 10.2% after holding for 1 hour. This means that in an oxygen atmosphere, the oxidation reaction of asphalt progresses and the weight increases due to the combination of oxygen, but in an inert gas _N2 , the weight decreases, so the low boiling point content of asphalt evaporates and leaves. It was found that this led 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. This is presumed to be due to separation, and the volatile content rises in the storage container, leading to a decrease in penetration as it gets closer to the bottom of the storage container, and the addition of the asphalt mixture's own weight accelerates hardening. An embodiment 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 airtight chamber 8 is opened and closed by a shutoff gate 12 that moves forward and backward by the expansion and contraction of a piston rod 11. When the shutoff gate 12 is closed, the airtight chamber 8
Appropriate airtight sealing mechanism 1 to prevent air from entering
3 should be applied. One end of a gas circulation pipe 15 with an exhaust fan 14 interposed therebetween is connected to the airtight chamber 8, and the other end of the pipe 15 is connected to the upper part of the storage container body 1. Reference numeral 16 denotes an input port for asphalt mixture, and an input gate 18 is opened and closed by a fluid cylinder 17. Reference numeral 19 denotes a small diameter exhaust port provided at the top of the storage container body 1;
The gas that accumulates in the tank is gradually exhausted to the outside.
An exhaust regulating valve may be provided at the exhaust port to exhaust excess gas to the outside when the pressure exceeds a predetermined pressure. Reference numeral 21 denotes an atmospheric suction port. When the asphalt mixture is discharged from the material discharge port 2, the suction gate 23 is opened and closed by the cylinder 22 to cancel the partial vacuum generated in the storage container main body 1. It is something that attracts attention. However, when storing asphalt mixtures,
Exhaust fan 1 from airtight chamber 8 at the bottom of storage container body 1
4 sucks the volatilized gas inside the storage container main body 1 so that the gas inside the storage container main body 1 flows from the top to the bottom, and the sucked gas passes through the gas circulation piping 15 to the storage container. It is returned to the empty space 20 at the top of the main body 1 and circulated,
Due to heating for heat retention, the low boiling point content in the asphalt rises in the storage container body 1 along with the upward airflow, and volatilization is prevented from progressing toward the lower part of the storage container body 1, thereby preventing hardening. It is. [Effect of the invention] As described above, in the present invention, the low boiling point content of the asphalt evaporates and leaves the asphalt mixture inside the asphalt mixture storage container and rises, and the upper space 20 of the storage container main body 1 rises. The exhaust fan 14 converts the gas that tends to stagnate into a gas flow from the top to the bottom, and circulates the gas saturated with volatiles, so that the asphalt mixture near the material outlet at the bottom of the storage container is It can prevent hardening as much as possible and can be stored stably for a long time.

[Brief explanation of the drawing]

FIG. 1 is a partially vertical schematic front view showing an embodiment of the present invention, and FIG. 2 is a differential thermal analysis curve diagram of asphalt. 1...Storage container main body, 2...Material discharge port, 8...
...airtight chamber, 14...exhaust fan, 15...piping for gas circulation, 16...inlet.

Claims (1)

[Scope of utility model registration request] An airtight chamber is formed by surrounding the lower material discharge port of the asalto mixture storage container, which has an input port at the top and a discharge port at the bottom, and has a heating and heat-retaining structure. An asphalt mixture storage container characterized in that a gas circulation pipe is provided with an air blower interposed therebetween.