Inner lining of existing buried steel tank using fluororesin

Abstract

To provide a double-shell structure of a buried tank using fluororesin (PFA or PTFE) in particular for a storage tank and a storage facility using it.SOLUTION: The inner lining of an existing buried steel tank using fluororesin (PFA or PTFE) comprises: a fluororesin (PFA or PTFE) that is installed on the outer and inner periphery of a new steel tank and on the inner periphery of an existing steel tank to prevent leakage of oil, synthetic fuel, or hydrogen from the steel tank; a gap forming member that is installed between the steel tank and the fluororesin (PFA or PTFE); a leak detection sensor that is installed between the steel tank and the fluororesin (PFA or PTFE) to detect corrosion or pitting of the steel tank; and alarm means that alarms for defects in the steel tank based on the detection output of the leak detection sensor.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a storage tank and a storage facility using the same, and more particularly to an inner lining for an existing buried steel tank that uses a fluororesin. [Background technology]

[0002] In recent years, the need for organic solvents has been on the rise. For example, storage facilities such as hydrogen stations for refueling fuel cell vehicles (FCVs) need to store organic hydrides, which are organic solvents. Organic hydrides are organic compounds that reversibly release hydrogen through an appropriate catalytic reaction, and refer to saturated condensed ring hydrocarbons such as methylcyclohexane, decalin, and ketones. Like petroleum fuels, organic hydrides can be transported and stored as liquids at room temperature. For this reason, their use in hydrogen filling stations is anticipated.

[0003] For example, methylcyclohexane is produced by hydrogenating toluene, and hydrogen can be extracted by dehydrogenation using a catalyst. Therefore, research is being conducted on methylcyclohexane as a type of organic hydride and a means of stable storage and transportation of hydrogen. Toluene is an organic compound belonging to aromatic hydrocarbons, with one of the hydrogen atoms of benzene replaced with a methyl group. It is a colorless, transparent liquid that is volatile at room temperature, flammable, has an anesthetic effect on the human body, and is highly toxic. Methylcyclohexane is less toxic than toluene.

[0004] In addition to organic hydrides, it is expected that toxic organic solvents will be used in hydrogen filling equipment. There are locations where hydrogen filling equipment is expected to be installed, so it is important to more reliably prevent the leakage of organic solvents. For this reason, storage tanks for storing organic solvents are sometimes made to have a double-shell structure, with an inner shell made of FRP (fiber-reinforced composite material) or GFRP (glass fiber reinforced plastic) being formed as a storage space within an outer steel container (see, for example, Patent Document 1).

[0005] Such an inner shell can better prevent leakage of organic solvents from storage tanks. However, both FRP and GFRP are deteriorated by organic solvents. Therefore, it is important to be able to stably prevent leakage of organic solvents from storage tanks. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Utility Model Registration No. 3240923 Summary of the Invention [Problem to be solved by the invention]

[0007] Therefore, the present invention provides a buried tank having a double shell structure using a fluororesin that can more reliably prevent the leakage of organic solvents. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems, the present invention provides a storage tank comprising a steel container made of steel, a fluororesin placed inside the steel container and formed so as to be capable of storing a fluid, a gap forming member disposed between the steel container and the fluororesin, and a detector disposed between the steel container and the fluororesin for detecting any fluid that has infiltrated between the steel container and the fluororesin.

[0009] In order to solve the above-mentioned problems, the present invention provides a storage facility that includes a storage tank buried in the ground, a conductive member buried in the ground as an electrode, and a DC power supply device electrically connected to the storage tank. Effect of the Invention

[0010] According to the present invention, leakage of the organic solvent can be prevented more stably. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram showing an example of a storage facility using the storage tank of the present embodiment. [Diagram 2] FIG. 2 is a diagram showing the cross-sectional configuration of an underground tank. [Diagram 3] FIG. 2 is a diagram illustrating the detailed cross-sectional structure of an underground tank. [Figure 4] FIG. 2 is a diagram illustrating an example of the configuration of a detector. [Diagram 5] FIG. 13 is a diagram showing a construction example of attaching a honeycomb board to a steel tank. [Figure 6] A diagram showing the structure near the inspection hatch of an underground tank. [Figure 7] FIG. 4 is a diagram illustrating an example of a detection circuit. [Figure 8] A cross-sectional view showing an example of an underground tank according to a modified example of this embodiment. [Figure 9] FIG. 13 is a diagram showing a modified example of the detection circuit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing an example of an underground tank having a double shell structure in which a fluororesin is used as a steel tank according to this embodiment. The fuel tank 1 is provided with an oil filling pipe 2 for filling, for example, synthetic fuel, hydrogen or oil, a fuel supply pipe 3 for drawing fuel from the fuel tank 1, a vent pipe 4 for ventilating the fuel tank 1, and a level gauge 5 for measuring the liquid level of the fuel stored in the fuel tank 1. The fuel tank 1 is buried at a predetermined depth below the ground surface, and concrete is laid on top of the fuel tank 1.

[0013] An oil filling port 7 is provided on the surface of the fuel filling pipe 2, and fuel is poured in through the oil filling port 7. In addition, equipment 8 such as a measuring device and a pump is provided on the surface of the fuel supply pipe 3, which draws fuel from the fuel tank 1 and measures the amount of fuel to be drawn. In addition, a valve 9 is provided on the oil filling pipe 2, and a valve 10 is provided on the fuel supply pipe 3, and when repairing / refurbishing the fuel tank 1, both valves 9, 10 are closed. In addition, a vent 12 is provided on the vent pipe 4, and gas generated inside the fuel tank 1 is discharged. A signal line 25 is connected to the monitor 18 installed in the office 20, and when a corrosion hole or pitting occurs in the steel tank, this signal line 25 notifies the monitor 18 of this information.

[0014] A DC power supply 40 is provided in the office 20. The DC power supply 40 is provided with a negative terminal 41 and a positive terminal 42. The negative terminal 41 is electrically connected to a steel container made of steel that is the outer shell of the solvent tank 1 by an electric wire 46, and the positive terminal 42 is electrically connected to a conductive member 45 buried in the ground by an electric wire 46. As a result, a current flows between the positive terminal 42 and the negative terminal 41 of the DC power supply 40 via the signal wire 46 ⇒ conductive member (electrode) 45 ⇒ ground ⇒ steel container of the solvent tank 1 ⇒ signal wire 46.

[0015] By passing such a current, the potential of the steel vessel is shifted to the inactive zone and the steel vessel is protected from rust (electrochemical protection of cathodic protection). This ensures the integrity of the steel vessel for a longer period of time and in a more stable manner. This means that the leakage of solvents through the steel vessel can be prevented for a longer period of time and in a more stable manner.

[0016] Fig. 2 is a diagram showing a cross-sectional configuration of the fuel tank 1, and is a DD' cross-sectional view of the fuel tank 1 shown in Fig. 1. As shown in the figure, the fuel tank 1 is made of a steel plate 13, and an inner shell 14 made of fluororesin is installed inside the steel plate 13. Furthermore, the fuel tank 1 stores oil, synthetic fuel, or hydrogen.

[0017] The inner shell 14 is formed to a predetermined thickness by applying a novolac vinyl ester resin or the like to a hollow glass fiber reinforcing agent, for example, and using a coating roll or the like. Carbon fiber is used as the reinforcing agent, and the reinforcing agent can be in the form of not only a mat but also cloth or nonwoven fabric. In addition to the hand lay-up lamination method described above, a spray-up lamination method in which the resin is applied to the reinforcing agent by spraying can also be used as a lamination method for the fluororesin in the inner shell 14.

[0018] Fluorine resin is a general term for synthetic resin obtained by polymerizing olefins containing fluorine. It is chemically stable and has excellent chemical resistance. It is not dissolved even in hydrofluoric acid, which is highly corrosive. Therefore, by forming the inner shell 14 using fluororesin and using the inside of this inner shell 14 as a storage space for the solvent, the solvent can be stored in the solvent tank 1 for a longer period of time and more stably. This reduces the running costs for storing the solvent and makes it safer to handle the solvent. This fluororesin (PFA or PTFE) is not a name for a single substance, but is a name used for a variety of fluororesins. It is known as a high-quality, safe material.

[0019] FIG. 3 is a diagram showing a more detailed cross-sectional structure of the fuel tank 1. As shown in the figure, a 3D glass cloth 16 is disposed in the gap between the steel plate 13 and the inner shell 14. The 3D glass cloth 16 is available in products made of various materials such as paper, resin, and metal, but from the viewpoint of strength and liquid leakage detection described later, a resin or metal 3D glass cloth 16 is used. For example, this example is a structure using the 3D glass cloth 16. Also, the 3D glass cloth used in this example is arranged to avoid wiring of a leakage detection sensor described later.

[0020] That is, the structure of the fuel tank 1 in this example is a steel tank 13 with 3D glass cloth 16 interposed therebetween, and further with a fluororesin (PFA or PTFE) 14 attached thereto. The interposition of the 3D glass cloth 16 forms a predetermined gap between the steel tank 13 and the fluororesin (PFA or PTFE) 14.

[0021] Meanwhile, a leak detection sensor 17 is disposed at the bottom of the fuel tank 1. This leak detection sensor 17 is disposed over the entire longitudinal length of the fuel tank 1. Fig. 3 also shows an enlarged view of the bottom (part A) of the fuel tank 1. As shown in the figure, the leak detection sensor 17 is disposed in the gap between the steel tank 13 and the fluororesin (PFA or PTFE) 14, and guides the oil, synthetic fuel, and hydrogen that have accumulated at the bottom of the steel tank 1 to the leak detection sensor described below. Here, the organic solution is a liquid that is a mixture of underground moisture and organic components such as plants and bacteria contained in the soil that leak out from corrosion and pitting holes that occur when the steel tank 1 is used for many years.

[0022] Meanwhile, an inspection hatch, which will be described later, is provided at the top of the underground tank 1, and a detection signal detected by a leak detection sensor is sent via a signal line 25 through this inspection hatch to a monitor 18 in the office 20.

[0023] Next, the process of constructing the fuel tank 1 having the above-mentioned double shell structure will be described below. First, the inner surface of the steel tank 13 that has been used for many years is cleaned. After this cleaning, the plate thickness and pitting corrosion of the steel tank 13 are measured.

[0024] Next, the leak detection sensor 17 is installed. The leak detection sensor 17 is installed so that any infiltration of oil, synthetic fuel, and hydrogen from corrosion holes or pitting holes that have occurred in the steel tank 13 is guided to a detector via the leak detection sensor, and is installed along the bottom of the steel tank 13. The leak detection sensor 17 is also installed in a straight line along the bottom of the steel tank 13, and is fixed at regular intervals so that it does not become loose.

[0025] Next, the leak detection sensor 22 is attached. This leak detection sensor 22 is installed, for example, in the center of the leak detection sensor 17 arranged along the bottom of the steel tank 13. Figure 4 is a diagram showing the configuration of the leak detection sensor 22. As shown in the figure, the leak detection sensor 22 is composed of fluoropolymer sensors 23a, 23b on both sides and a detection circuit 24 provided between the fluoropolymer sensors 23a, 23b, and the capacitance changes when water, oil, synthetic fuel, or hydrogen comes into contact with either sensor 23a or 23b. The detection circuit 24 detects the presence or absence of a leak and the location of the leak based on this change in capacitance.

[0026] 5 is a diagram showing the state in which the above-mentioned 3D glass cloth 16 is attached after the above-mentioned leak detection sensor 17 and leak detection sensor 22 are arranged. For the sake of explanation, only half of the inner surface of the steel tank 13 is shown. 3D glass cloth 16 of a predetermined size is attached to the inner surface of the steel tank 1 (steel plate 13) at regular intervals. As described above, the 3D glass cloth 16 is attached to the inner surface of the steel tank 1 using resin.

[0027] Next, electrical wiring work is carried out. This work involves connecting a signal line 25 to the leak detection sensor 22 previously installed, and wiring this signal line 25 in the gap between the steel tank 13 and the fluororesin (PFA or PTFE) 14. Specifically, wiring is carried out to the inspection hatch using the space where the 3D glass cloth 16 is not installed, and further to the monitor 18 in the office 20. For example, as shown in Figure 5, wiring is carried out using the space 19 where the 3D glass cloth 16 is not installed.

[0028] Next, a leak detection sensor 17 is placed inside the 3D glass cloth 16 placed on the inner surface of the steel tank 13. The inner shell used in this example is, for example, a sheet based on epoxy acrylate resin and reinforced with carbon fiber, and one side is covered with a transparent plastic film. Therefore, this plastic film is peeled off and adhered to the 3D glass cloth 16. When adhering a sheet or tape of fluororesin (PFA or PTFE), overlap the ends to avoid leaving gaps.

[0029] Next, an airtightness test of the gap (microspace) is performed by attaching an airtightness test tool to the leak detection sensor outlet and injecting a test gas into the gap.

[0030] Figure 6 is a diagram showing the structure near the inspection hatch of the underground tank 1. An iron lid 27 is provided on the top of the inspection hatch 26, and a space for an inspection box 28 is formed inside this lid 27. For example, a CFRP cylinder 29, an inspection hatch 30, and a lower support cylinder member 31 are disposed below the inspection box 28. A handle 32 is provided at the inspection hatch. The signal line 25 is wired to the monitor 18 in the office 20 via this inspection box 28.

[0031] Furthermore, the signal line 25 is protected by a signal cable 33 and is wired to the monitor 18. The monitor 18 is equipped with an LED display unit, a speaker, etc., and when the leak detection sensor 22 detects water, oil, synthetic fuel, or hydrogen, for example, the LED lights up and a pre-recorded warning sound is generated from the speaker. As shown in FIG. 6, in addition to the signal line 25, the signal cable 33 also contains a signal line 11 for transmitting liquid level data detected by the aforementioned liquid level gauge 5, and the liquid level data of the gasoline in the underground tank 1, etc. are also notified to the monitor 18.

[0032] In the underground tank 1 having the above-mentioned configuration, the detection operation for detecting the occurrence of corrosion holes or pitting holes due to corrosion or pitting of the steel tank 13 will be described below. When the steel tank 13 deteriorates after many years of use, corrosion holes and pitting holes appear in the steel plate 13', and oil, synthetic fuel, and hydrogen can penetrate through these holes. However, with the double-shell structure of this example, the inner surface of the steel tank 13 is covered with a fluororesin (PFA or PTFE) 14, so oil, synthetic fuel, and hydrogen cannot penetrate into the underground tank 1. In addition, the oil, synthetic fuel, and hydrogen in the fuel tank 1 do not leak out to the outside. Therefore, soil contamination due to oil leakage, synthetic fuel, and hydrogen leakage can be prevented. That is, since the inner shell 14 is made of a fluororesin (PFA or PTFE), such soundness is maintained more stably for a longer period of time.

[0033] On the other hand, oil, synthetic fuel, and hydrogen that have entered through corrosion holes or pitting holes in the steel tank 14 pass through gaps formed between the steel tank 13 and the fluororesin (PFA or PTFE) 14 and accumulate on the underside of the steel tank 13. Furthermore, oil, synthetic fuel and hydrogen that have accumulated on the bottom surface of the steel tank 13 are guided to the leak detection sensor 22 by the above-mentioned leak detection sensor 17. For example, water or an organic solution that has entered through a hole that has appeared on the left side of the steel tank 13 reaches the left side bottom of the steel tank 13, passes through the leak detection sensor 17 (17a) and reaches the fluoropolymer sensor 23a. The fluoropolymer sensor 23a emits light when it detects oil, synthetic fuel or hydrogen, and the detection circuit 24 detects this light and converts it into a voltage change, thereby detecting a defect in the steel tank 13.

[0034] 7 shows an example of the detection circuit 24, which is composed of transistors Tr1 and Tr2, resistors R1 and R2, and a power supply E. The transistor Tr1 detects the light emitted from the fluoropolymer sensor 23a and outputs a detection signal (output 1) to the signal line 25. This signal is output to the monitor mentioned above, lights up the LED, and also generates a pre-recorded warning sound from the speaker.

[0035] Meanwhile, oil, synthetic fuel, and hydrogen that have entered through the hole that has appeared on the right side of the steel tank 14 reach the bottom right side of the steel tank 13, pass through the leak detection sensor 17 (17b), and reach the fluoropolymer sensor 23b. When the fluoropolymer sensor 23b detects oil, synthetic fuel, or hydrogen, it emits light in the same manner as described above, and the detection circuit 24 detects this light and converts it into a voltage change, thereby detecting liquid leakage from the steel tank 13. In this case, transistor Tr2 detects the light emitted from the fluoropolymer sensor 23b and outputs a detection signal (output 2) to signal line 25. This signal is output to the monitor 18 mentioned above, causing the LED to light up and a pre-recorded warning sound to be emitted from the speaker.

[0036] Therefore, according to this example, the leak detection sensor 22 can detect corrosion holes and pitting holes in the steel tank 13, and can also detect whether a hole that has occurred in the steel tank 13 is on the right or left side of the steel tank 13.

[0037] In the above embodiment, the 3D glass cloth 16 is interposed between the steel tank 13 and the fluororesin (PFA or PTFE) 14, but as shown in Fig. 8, the fluororesin (PFA or PTFE) may be directly provided as the inner shell 37 on the outer shell 13, and a mesh-structured metal mesh member may be interposed between the inner shell 37 and the inner shell 14. That is, unlike the above-mentioned configuration, the fluororesin (PFA or PTFE) (e.g., a sheet or tape) may be first provided as the inner shell 37 on the outer shell 13, and then a metal mesh member 38 may be interposed instead of the 3D glass cloth 16, and the inner shell 14 may be disposed by covering the metal mesh member 38. In this case, since it is difficult to join the metal mesh member 38 to the inner shell 14, for example, a part of the 3D glass cloth 16 may be left, and the inner shell 14 may be attached to the remaining 3D glass cloth 16.

[0038] With this configuration, a gap is formed between the two inner shells 14, 37, and the above-mentioned leak detection sensor 17 may be disposed in this gap. In this case, the inner shell 37 provided directly on the outer shell 13 has a thickness of, for example, about 2.0 mm, and the wire mesh member 38 is disposed so that a gap of about 2.0 to 2.5 mm is formed between the two inner shells 14, 37.

[0039] In addition, in the description of the above embodiment, a fluoropolymer sensor that detects oil, synthetic fuel, and hydrogen was used as the leak detection sensor 22, but the present invention is not limited to a fluoropolymer sensor and can be applied to any sensor that detects oil, synthetic fuel, and hydrogen. For example, terminals P1 and P2 are provided in parallel to resistor R3 of voltage-dividing resistors R3 and R4 in the circuit shown in Fig. 9, and terminals P3 and P4 are provided in parallel to resistor R5 of voltage-dividing resistors R5 and R6, and terminals P1 and P2 are used in place of the above-mentioned fluoropolymer sensor 23a, and terminals P3 and P4 are used in place of the above-mentioned fluoropolymer sensor 23b. The other circuits shown in Fig. 9 are similar to those in Fig. 7 and are composed of transistors Tr1, Tr2, etc.

[0040] With this configuration, for example, when water or the like penetrates between terminals P1 and P2, the base (B) potential of transistor Tr1 changes and a detection signal is output from output 1, making it possible to notify the occurrence of corrosion holes or pitting holes. Similarly, when water or the like penetrates between terminals P3 and P4, the base (B) potential of transistor Tr2 changes and a detection signal is output from output 2, making it possible to notify the occurrence of corrosion holes or pitting holes. In this case as well, it is possible to detect whether a hole that has occurred in the steel tank 14 is on the right or left side of the steel tank 14.

[0041] In addition, in the above embodiment, corrosion and pitting of the steel tank 14 was described, but for example, if a hole develops in the CFRP arranged on the inside due to years of use, the leak detection sensor 22 can similarly detect leaks of oil, synthetic fuel, and hydrogen.

[0042] In the above embodiment, an existing fuel tank has been described, and further, a fluororesin (PFA or PTFE) is used for a newly manufactured fuel tank, and the structure in which the fluororesin (PFA or PTFE) is used for the outer shell and inner shell as described above has also been described.

[0043] 1. Underground tank 2...Lubrication pipe 3. Oil supply pipe 4. Ventilation pipe 5...Liquid level gauge 7...Oil filler port 8. Machinery storage room 9, 10 Valves 11 Signal line 12 Ventilation hole 13. Steel tank 13´·steel plate 14. Fluorine resin (PFA or PTFE) 16··3D glass cloth 17, 17a, 17b Leak detection sensor 18. Monitor 19. Space 20. Office 21. Fuel supply area 22. Leak detection sensor 23a, 23b Fluoropolymer sensor 24 Detection circuit 25 Signal line 26 Inspection hatch 27...lid 28 Inspection box 29...Cylinder 30 Inspection cover 31...Lower support member 32 Handle 33 Signal cable 37 Fluorine resin (PFA or PTFE) 38. Wire mesh member 40...DC power supply equipment 41 -Terminal 42··+ terminal 45 Conductive material (electrode) 46··Electric wire (signal wire) Tr1, Tr2: Transistors R1, R2...resistance R3~R6: Voltage divider resistors P1~P4 terminals E...Power supply

Claims

1. Fluorine resin (PFA or PTFE) that is installed on the outer and inner circumferences of new steel tanks and on the inner circumferences of existing steel tanks to prevent leakage of oil, synthetic fuel, or hydrogen from the steel tanks; a gap forming member disposed between the steel tank and the fluororesin (PFA or PTFE); a leakage detection sensor disposed between the steel tank and the fluororesin (PFA or PTFE) for detecting corrosion or pitting of the steel tank; An alarm means for notifying a defect in the steel tank based on the detection output of the leak detection sensor; The inner surface structure of an existing buried steel tank using a fluororesin (PFA or PTFE), characterized by having the following:

2. 2. The inner surface structure of an existing buried steel tank using fluororesin (PFA or PTFE) as described in claim 1, characterized in that a leak detection sensor is disposed in the gap formed between the inner surface of the steel tank and the fluororesin (PFA or PTFE), and the leak detection sensor is disposed along the side and bottom of the steel tank to detect leaks of water, oil, synthetic fuel, and hydrogen from corrosion holes or pitting holes in the steel tank, and leaks of oil, synthetic fuel, and hydrogen from holes in the fluororesin (PFA or PTFE), and lead the detected leaks to a detector.

3. The inner surface structure of an existing buried steel tank using fluororesin (PFA or PTFE) as described in claim 1 or 2, characterized in that the gap forming member is composed of a 3D glass cloth or a mesh-like wire mesh member, and can detect from which direction oil, synthetic fuel, or hydrogen is leaking.

4. The buried tank according to claim 1 buried in the ground; a DC power supply device electrically connected to the conductive member buried in the ground as an electrode and to the buried tank; The inner surface structure of an existing buried steel tank using a fluororesin (PFA or PTFE), characterized by having the following:

Images