Method and apparatus for suppressing vaporization and diffusion of liquid ammonia

Abstract

To enable a quick emergency response without performing complicated adjustment, to enable a highly immediate response, and to maintain the effect of suppressing the vaporization and diffusion of liquid ammonia for a predetermined period, when suppressing the vaporization and diffusion of leaked liquid ammonia.SOLUTION: In the method for suppressing the vaporization and diffusion of liquid ammonia leaked from a storage facility or its incidental facilities, a liquid material which is solidified by being brought into contact with the liquid ammonia to form a solidified layer on the liquid surface of the liquid ammonia is charged onto the liquid ammonia staying under atmospheric pressure.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for inhibiting the vaporization and diffusion of liquid ammonia and an apparatus for carrying out the method. [Background technology]

[0002] Conventionally, when a liquid ammonia storage tank or associated piping is damaged due to an unexpected event and liquid ammonia leaks, a method for preventing the vaporization and diffusion of leaked liquid ammonia has been known (see Patent Document 1 below).

[0003] This conventional technology involves spraying an aqueous solution of a water-soluble foam-forming agent onto the surface of liquid ammonia that has accumulated on the ground surface, etc., and the heat generated when the water in the aqueous solution dilutes the liquid ammonia causes bubbles containing ammonia gas to form on the surface of the liquid ammonia. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 53-35700 Summary of the Invention [Problem to be solved by the invention]

[0005] According to such conventional techniques, it is necessary to adjust the amount of water in the aqueous solution to be sprayed to promote the generation of appropriate bubbles from an appropriate calorific value. However, at the site of an unexpected liquid ammonia leak, the situation varies widely and a quick response in an emergency is required, so that conventional techniques that require such complicated adjustments are difficult to adopt in practice.

[0006] Furthermore, in the above-mentioned conventional technology, after an aqueous solution of a water-soluble foam-forming agent is sprayed on the surface of liquid ammonia, the liquid ammonia itself foams due to heat generation, thereby forming bubbles containing ammonia gas. As a result, it takes a considerable amount of time from the spraying of the aqueous solution until bubbles are formed over the entire surface of the liquid ammonia, and during that time, there is a problem that the liquid ammonia continues to evaporate and diffuse. In other words, the above-mentioned conventional technology has a problem in that it is not possible to take highly effective measures against leaked liquid ammonia.

[0007] Furthermore, the above-mentioned conventional technology has a problem that even if the entire liquid surface of the liquid ammonia is covered with bubbles containing ammonia gas, when the bubbles disappear over time, the contained ammonia gas immediately diffuses into the atmosphere, and the diffusion suppression effect decreases over time. In other words, the above-mentioned conventional technology has a problem that the evaporation diffusion suppression effect of the liquid ammonia cannot be maintained for a predetermined period of time.

[0008] Furthermore, because liquid ammonia and ammonia gas are highly soluble in water, the ammonia gas dissolves in ordinary foam, making it difficult to maintain the diffusion-inhibiting effect of the foam for a long period of time.

[0009] The present invention aims to solve the problems of the conventional technology described above when preventing the evaporation and diffusion of leaked liquid ammonia. That is, the present invention aims to enable a rapid emergency response without complicated adjustments, to enable highly effective measures, and to maintain the effect of preventing the evaporation and diffusion of liquid ammonia for a predetermined period of time. [Means for solving the problem]

[0010] In order to solve such problems, the present invention has the following configuration.

[0011] One is a method for inhibiting the evaporation and diffusion of liquid ammonia that has leaked from a storage facility or its ancillary equipment, which involves pouring a liquid material onto the liquid ammonia that is stagnating under atmospheric pressure, the liquid material solidifying upon contact with the liquid ammonia to form a solidified layer on the liquid surface of the liquid ammonia.

[0012] Another example is a device for suppressing the evaporation and diffusion of liquid ammonia that has leaked from a storage facility or its ancillary equipment, the device comprising: an injector that injects a liquid material that solidifies upon contact with the liquid ammonia and a lightweight solid that makes the apparent specific gravity of the liquid material smaller than the specific gravity of the liquid ammonia into liquid ammonia that is stagnating under atmospheric pressure, and the device for suppressing the evaporation and diffusion of liquid ammonia is characterized in that it forms a solidified layer of the liquid material combined with the lightweight solid on the liquid surface of the liquid ammonia. [Effects of the Invention]

[0013] According to the present invention having such features, when suppressing the evaporation and diffusion of leaked liquid ammonia, a rapid emergency response is possible without complicated adjustments, highly effective measures are possible, and the effect of suppressing the evaporation and diffusion of liquid ammonia can be maintained for a predetermined period of time. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is an explanatory diagram showing a method and apparatus for inhibiting vaporization and diffusion of liquid ammonia according to an embodiment of the present invention; [Figure 2] An explanatory diagram showing a state in which a foam layer (B) is layered on top of a solidified layer (F) formed on the liquid surface of liquid ammonia (S). DETAILED DESCRIPTION OF THE INVENTION

[0015] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same reference numerals in different drawings denote parts with the same functions, and duplicated descriptions in each drawing will be omitted as appropriate.

[0016] The method for inhibiting the vaporization and diffusion of liquid ammonia according to an embodiment of the present invention is aimed mainly at liquid ammonia leaked from a storage facility or its ancillary equipment, and inhibits the liquid ammonia remaining under atmospheric pressure from evaporating and diffusing into the surroundings. Here, liquid ammonia (liquid ammonia: NH3) and aqueous ammonia (ammonia water: NH4OH) are collectively referred to as liquid ammonia.

[0017] Incidentally, the specific heat of ammonia is unusual for a liquid, being close to that of water, and it is slower to heat up and cool down than liquids other than water. Due to this physical property, it is difficult to evaporate, and its latent heat of vaporization is also large (high cooling effect). Immediately after a leak, ammonia vaporizes by absorbing (taking away) heat from the outside air and ground, but the outside air and ground from which it has absorbed heat are cooled. Repeated evaporation and cooling will eventually cause the ground to cool below -33°C, allowing liquid ammonia to remain on the ground.

[0018] According to a method of an embodiment of the present invention, a liquid material is poured onto liquid ammonia stagnating on the ground or the like under atmospheric pressure. The liquid material solidifies upon contact with the liquid ammonia, forming a solidified layer on the liquid ammonia surface. This solidified layer airtightly covers the liquid ammonia surface, thereby shielding the stagnant liquid ammonia from the atmosphere. According to this method, the presence of the solidified layer between the liquid ammonia surface and the atmosphere effectively prevents ammonia gas from diffusing into the atmosphere.

[0019] This method involves simply selecting a liquid material that will form a solidified layer on the surface of the liquid ammonia and pouring it onto the liquid ammonia that is stagnating under atmospheric pressure, enabling a rapid emergency response without the need for complicated adjustments at the leak site.

[0020] In this case, the solidified layer is formed on the liquid ammonia shortly after the liquid material is poured onto the liquid ammonia, making it possible to take highly immediate action. The formed solidified layer is a solid layer that continues to airtightly cover the liquid ammonia surface. This allows the effect of inhibiting the evaporation and diffusion of liquid ammonia to be maintained for a predetermined period of time.

[0021] The liquid material used here is selected to be one that does not dissolve in liquid ammonia (boiling point -33°C, water soluble) and solidifies on the liquid surface. Specifically, an oil-based material that is liquid at room temperature and solidifies immediately when it comes into contact with liquid ammonia can be used.

[0022] In this case, the specific gravity of the oil-based material may be greater than that of liquid ammonia when solidified. In this case, by incorporating a lightweight solid into the oil-based material, the apparent specific gravity of the solidified layer is made less than that of liquid ammonia, and the solidified layer is made to float on the liquid surface. Examples of lightweight solids that can be used include foamed beads, perlite, and vermiculite. The lightweight solid may be any material, whether artificial or natural, as long as it has an apparent specific gravity less than that of liquid ammonia when incorporated in an appropriate amount to maintain the airtightness of the solidified layer. Another method for reducing the specific gravity is to add a surfactant to the oil-based material or incorporate air to foam it.

[0023] 1 shows an example of the configuration of an apparatus (evaporation diffusion suppression apparatus) 1 for carrying out the above-described method for suppressing evaporation and diffusion of liquid ammonia. Here, a storage facility including a liquid ammonia storage tank T will be described as an example of the target facility, but the form of the target facility is not particularly limited to this.

[0024] In the illustrated example, the liquid ammonia storage tank T is installed on the bottom surface of a pool-shaped enclosure wall W. Here, an example is shown in which an existing enclosure wall W is installed, but in a facility without an enclosure wall W, after a liquid ammonia leak occurs, a temporary enclosure wall W may be installed to surround the leaked liquid ammonia.

[0025] In the illustrated example, when liquid ammonia leaks from the storage tank T or associated equipment (not shown) such as piping installed around the storage tank T, the liquid ammonia S accumulates on the bottom surface of the pool-shaped enclosure wall W. In order to cover the liquid surface of the accumulated liquid ammonia S with the above-mentioned solidified layer F, the liquid ammonia evaporation diffusion suppression device 1 is provided with one or more input devices 10 inside the enclosure wall W.

[0026] The feeder 10 is equipped with a supply device 20 having a liquid material storage section 21 and a lightweight solids supply section 22 so that the liquid material (oil-based material) and the lightweight solids can be fed simultaneously or separately. In the supply device 20, the liquid material in the storage section 21 is supplied to the feeder 10 via a supply flow path 11, and the lightweight solids in the supply section 22 are supplied to the feeder 10 via a supply flow path 12.

[0027] The feeder 10 opens the supply valve 12V of the supply flow path 12 to first feed the light solid material onto the liquid surface of the stagnant liquid ammonia S, and then closes the supply valve 12V and opens the supply valve 11V of the supply flow path 11 to feed the liquid material onto the fed light solid material. The feeder 10 can also simultaneously open the supply valves 11V and 12V to feed the liquid material L and the light solid material P together onto the liquid surface of the liquid ammonia S, as shown in the figure.

[0028] If the only thing placed on the liquid ammonia S were lightweight solids P, the liquid surface would become uneven, increasing the surface area of ​​the liquid, and there is a risk that vaporized ammonia would dissipate through the gaps in the lightweight solids P. For this reason, a liquid material L made of an oil-based material is placed between the lightweight solids P to fill the gaps. The weight ratio of the lightweight solids P to the oil-based material is lightweight solids:oil-based material = 1:3-4, so when the oil-based material is placed, it will penetrate downward through the gaps.

[0029] The liquid material L and the lightweight solid material P may be added in the following ways: first, by placing a mixture of the liquid material L and the lightweight solid material P on top of the liquid ammonia S, and second, by adding only the liquid material L after a predetermined time (several minutes to several tens of minutes). In this case, the added liquid material L passes through the gap and comes into contact with the liquid ammonia S, solidifying immediately, and as time passes after the addition, the upper layer also solidifies, until the entire layer is solidified.

[0030] Considering that the liquid material poured onto the liquid ammonia S solidifies soon after, it is preferable that the feeder 10 be able to feed the liquid material L and the lightweight solids P while moving relative to the stagnant liquid ammonia S. In the example shown, a movable rail R is provided on the surrounding wall W, and the feeder 10 is able to feed the liquid material L and the lightweight solids P while moving along the extension direction of the movable rail R. In this case, by providing a feeder (for example, a hose-shaped feeder) 10 that extends in a direction perpendicular to the extension direction of the movable rail R (a direction perpendicular to the plane of the paper in the figure), it becomes possible to efficiently feed the liquid ammonia S that has accumulated over a wide area.

[0031] The means for moving the input device 10 is not limited to the above example. For example, various forms of movement can be adopted, such as ground movement by a traveling vehicle equipped with the input device 10, or air movement by a drone equipped with the input device 10, etc.

[0032] The liquid ammonia evaporation diffusion suppression device 1 shown in Fig. 1 includes a control unit 30. The control unit 30 controls the opening and closing of a supply valve 11V provided in the supply flow path 11, and also controls the opening and closing of a supply valve 12V provided in the supply flow path 12. The control unit 30 also controls the driving of a moving mechanism (not shown) that moves the input device 10.

[0033] The control unit 30 can control various operations of the evaporation diffusion suppression device 1 using manual signals from an operation panel (not shown). In addition, a monitoring camera 31 and a gas sensor 32 may be provided around the storage tank T, and the leakage of liquid ammonia may be detected by receiving monitoring images from the monitoring camera 31 and detection signals from the gas sensor 32, thereby automatically controlling the operation of the evaporation diffusion suppression device 1. Specifically, when the monitoring camera 31 or the gas sensor 32 detects a leakage of liquid ammonia, the control unit 30 switches the supply valves 11V and 12V to an open state, and moves the feeder 10 appropriately to feed the liquid material L and the lightweight solid P onto the accumulated liquid ammonia S.

[0034] As shown in Figure 2, when a solidified layer F containing light solids P is formed on the liquid surface of the stagnant liquid ammonia S, the liquid ammonia S is isolated from the atmosphere by the solidified layer F, thereby suppressing the vaporization and diffusion of the liquid ammonia S. In this case, the solidified layer F continues to maintain a solid state while the liquid ammonia S is in a liquid state, so the effect of suppressing the vaporization and diffusion of the liquid ammonia S can be maintained for a predetermined period of time.

[0035] In order to maintain the effect of inhibiting the vaporization and diffusion of liquid ammonia S for a long period of time, it is preferable to additionally layer a foam layer B on top of the solidified layer F formed on the liquid surface of liquid ammonia S, as shown in Figure 2. In this case, the foam layer B is formed by foaming an aqueous surfactant solution with a foam generator and releasing it onto the solidified layer F.

[0036] The foam layer B layered on top of the solidified layer F is cut off from contact with the liquid ammonia S by the solidified layer F, preventing the foam from dissolving and allowing the foam layer B to maintain a foam state for a long period of time. The foam layer B has the function of increasing the insulating effect against the liquid ammonia S, so by layering an additional foam layer B, the effect of inhibiting the evaporation and diffusion of the liquid ammonia S can be maintained for a long period of time. The purpose of increasing the insulating effect here is to block the solar radiant heat and outside air heat, as the boiling point of liquid ammonia is -33°C and it evaporates due to the radiant heat of the sun or the outside air temperature, etc., and this is done to maintain an environment in which the liquid ammonia does not easily evaporate.

[0037] As described above, the method and device for inhibiting the evaporation of liquid ammonia according to the embodiment of the present invention enable a rapid emergency response without complicated adjustments when inhibiting the evaporation of leaked liquid ammonia, and enables highly effective measures. In addition, the effect of inhibiting the evaporation of liquid ammonia can be maintained for a predetermined period of time. [Explanation of symbols]

[0038] 1: Evaporation diffusion prevention device 10: Insertion machine 11, 12: Supply flow path 11V, 12V: Supply valve 20: Supply device 21: Storage section 22: Supply section 30: Control unit 31: Surveillance camera 32: Gas sensor T: Storage tank W: Enclosure wall S: Liquid ammonia B: Foam layer F: Solidified layer L: Liquid material P: Light solid

Claims

1. A method for suppressing vaporization and diffusion of liquid ammonia leaked from a storage facility or its auxiliary equipment, comprising: A method for inhibiting the evaporation and diffusion of liquid ammonia, comprising: pouring a liquid material onto liquid ammonia stagnating under atmospheric pressure, the liquid material solidifying upon contact with the liquid ammonia to form a solidified layer on the liquid surface of the liquid ammonia.

2. 2. The method for inhibiting the evaporation and diffusion of liquid ammonia according to claim 1, wherein the liquid material is an oil-based material, and a lightweight solid material is mixed with the oil-based material to make the apparent specific gravity of the liquid material when solidified smaller than the specific gravity of the liquid ammonia.

3. 3. The method for inhibiting evaporation and diffusion of liquid ammonia according to claim 2, wherein the liquid material is poured onto the liquid surface of the liquid ammonia in a state where the oil-based material and the lightweight solid matter are combined together, thereby forming the solidified layer.

4. 3. The method for inhibiting evaporation and diffusion of liquid ammonia according to claim 2, wherein the liquid material forms the solidified layer by first pouring the lightweight solid material onto the liquid surface of the liquid ammonia and then pouring the oil-based material.

5. A device for suppressing the vaporization and diffusion of liquid ammonia leaked from a storage facility or its auxiliary equipment, a charger for charging a liquid material that solidifies upon contact with the liquid ammonia and a lightweight solid material that makes the apparent specific gravity of the liquid material smaller than the specific gravity of the liquid ammonia into the liquid ammonia that is retained under atmospheric pressure; A liquid ammonia vaporization diffusion suppression device, characterized in that a solidified layer of the liquid material containing the lightweight solid material is formed on the liquid surface of the liquid ammonia.

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