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, an aqueous solution of a surfactant forming a deposition layer on the liquid surface of the liquid ammonia by mixing with the liquid ammonia is charged on the liquid ammonia staying under the 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 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 associated equipment, which involves pouring an aqueous surfactant solution onto liquid ammonia that is stagnating under atmospheric pressure, and which forms a precipitate layer on the liquid surface of the liquid ammonia when mixed with 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, comprising: a water storage section; a storage section for a surfactant that forms a precipitate layer on the liquid surface of the liquid ammonia by mixing with the liquid ammonia; and a foam generator that generates foam by mixing the water in the water storage section with the surfactant in the storage section, and the foam of the surfactant aqueous solution generated in the foam generator is released into the liquid ammonia that is stagnating under atmospheric pressure, thereby forming the precipitate layer on the liquid surface of the liquid ammonia. [Effects of the Invention]

[0013] According to the present invention having such characteristics, 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] (a) is an explanatory diagram showing the state in which a foam layer (B) of a surfactant aqueous solution is formed on the liquid ammonia (S), and (b) is an explanatory diagram showing the state in which a precipitate layer (P) is formed on the liquid surface of the liquid ammonia (S). [Figure 3] An explanatory diagram showing a state in which a foam layer (B1) is layered on a precipitate layer (P) 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, an aqueous surfactant solution is poured onto liquid ammonia stagnating under atmospheric pressure, whereby the aqueous surfactant solution mixes with the liquid ammonia to form a precipitate layer on the liquid ammonia surface. This precipitate layer airtightly covers the liquid ammonia surface, thereby shielding the stagnant liquid ammonia from the atmosphere. According to this method, the presence of the precipitate layer between the liquid ammonia surface and the atmosphere effectively prevents ammonia gas from diffusing into the atmosphere.

[0019] This method involves selecting a surfactant in advance that will form a precipitate layer on the liquid ammonia surface when mixed with the liquid ammonia, then mixing it with water and pouring it onto the liquid ammonia stagnating at atmospheric pressure. Alternatively, an aqueous surfactant solution that has been diluted to the required concentration can be poured onto the stagnating liquid ammonia. This method enables a rapid emergency response without the need for complicated adjustments at the leak site. In this case, the higher the surfactant concentration, the more precipitate is produced, reducing the exposed surface area of ​​the liquid ammonia. By keeping the surfactant concentration at 30% or higher (70% or less water), it is possible to eliminate the liquid surface exposure to some extent.

[0020] In this case, the precipitate layer is formed shortly after the surfactant aqueous solution is poured onto the liquid ammonia, enabling a highly immediate response. The formed precipitate layer is a solid layer that continues to airtightly cover the liquid ammonia surface even after the bubbles of the surfactant aqueous solution have disappeared. This allows the effect of inhibiting the evaporation and diffusion of liquid ammonia to be maintained for a predetermined period of time.

[0021] The surfactant used here is a surfactant containing a fatty acid salt (e.g., a sodium salt of a fatty acid or a potassium salt of a fatty acid), which is the main component of soap, and is sufficient as long as it produces the aforementioned precipitate layer by salting out the soap component when mixed with liquid ammonia. The fatty acid salt is preferably a vegetable fatty acid salt. Examples include sodium laurate, potassium laurate, sodium myristate, potassium myristate, sodium oleate, and potassium oleate.

[0022] The surfactant added onto the liquid ammonia is preferably released in a foamed state using a foam generator, etc. By foaming, the foam layer can suppress evaporation and diffusion in the initial stage, and the solid precipitate layer that is subsequently formed can further stably suppress evaporation and diffusion.

[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 in the vicinity thereof, the liquid ammonia S accumulates on the bottom surface of the pool-shaped surrounding wall W. In order to cover the liquid surface of the accumulated liquid ammonia S with the above-mentioned deposition layer, the evaporation diffusion suppression device 1 is provided with one or more bubble generators 10 around the surrounding wall W.

[0026] The foam generator 10 generates foam by physical processing by applying air sucked in by an aspirator or air blown by a blower to the surfactant aqueous solution supplied via the supply flow path 11, and by releasing the generated foam into the stagnant liquid ammonia S, a foam layer B is formed on the liquid surface of the stagnant liquid ammonia S.

[0027] The equipment for producing the surfactant aqueous solution can be implemented in various forms. In the example shown in Fig. 1, a reservoir 21 storing the undiluted surfactant solution and a water reservoir 22 are connected to a mixer 20. Alternatively, without using the water reservoir 22, an appropriately diluted surfactant aqueous solution may be stored in the reservoir 21 and supplied directly to the foam generator 10.

[0028] 1 includes a control unit 30. The control unit 30 controls the opening and closing of a supply valve 11V provided in a supply flow path 11. The control unit 30 may also control a supply valve 12V provided in a supply flow path 12 connecting the reservoir 21 and the mixer 20, and a supply valve 13V provided in a supply flow path 13 connecting the reservoir 22 and the mixer 20.

[0029] The control unit 30 can control various operations of the liquid ammonia evaporation diffusion suppression device 1 by 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 liquid ammonia evaporation diffusion suppression device 1. Specifically, when a leakage of liquid ammonia is detected by the monitoring camera 31 or the gas sensor 32, the control unit 30 switches the supply valve 11V etc. to an open state, operates the foam generator 10, and pours foamed surfactant aqueous solution onto the stagnant liquid ammonia S.

[0030] As shown in Figure 2(a), when a foam layer B of a surfactant aqueous solution is formed on the surface of liquid ammonia S stagnating under atmospheric pressure, the thermal insulating effect of the foam layer B can temporarily suppress the evaporation of liquid ammonia S. Then, when the lower layer of the foam layer B mixes with the liquid ammonia S, a solid precipitate layer P is generated as shown in Figure 2(b), and this precipitate layer P covers the liquid surface of the liquid ammonia S.

[0031] In the state where the precipitate layer P is formed, the foam layer B is partially defoamed and dissolved to become a thin layer, but the solid precipitate layer P covers the liquid surface of the liquid ammonia S, so that the vaporization and diffusion of the liquid ammonia S is largely suppressed. With the passage of time, most of the foam layer B disappears, but even when the foam layer B has almost completely disappeared, the precipitate layer P continues to cover the liquid surface of the liquid ammonia S. This makes it possible to maintain the effect of suppressing the vaporization and diffusion of the liquid ammonia S for a predetermined period of time.

[0032] In order to maintain the effect of inhibiting the evaporation and diffusion of liquid ammonia S for a long period of time, it is preferable to additionally laminate a foam layer B1 on the precipitate layer P formed on the liquid surface of liquid ammonia S, as shown in Fig. 3. The foam layer B1 formed in this case may be the same as the foam layer B described above, or may be a different type of layer using a different type of surfactant aqueous solution.

[0033] The foam layer B1 layered on top of the deposition layer P prevents contact with the liquid ammonia S by the deposition layer P, preventing the foam from dissolving and allowing the foam layer B1 to maintain a foam state for a long period of time. The foam layer B1 has the function of increasing the insulating effect against the liquid ammonia S, so by adding an additional foam layer B1, 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 solar radiant heat or outside air temperature, etc., and this is done to maintain an environment in which the liquid ammonia does not easily evaporate.

[0034] 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]

[0035] 1: Evaporation diffusion prevention device 10: Bubble generator 11, 12, 13: Supply flow path 11V, 12V, 13V: Supply valve 20: Mixer 21: Storage section 22: Water storage section 30: Control unit 31: Surveillance camera 32: Gas sensor T: Storage tank W: Enclosure wall S: Liquid ammonia B, B1: Bubble layer P: Deposit layer

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: introducing an aqueous surfactant solution onto liquid ammonia stagnating under atmospheric pressure; the aqueous surfactant solution being mixed with the liquid ammonia to form a precipitate layer on the liquid surface of the liquid ammonia.

2. 2. The method for inhibiting evaporation and diffusion of liquid ammonia according to claim 1, wherein the aqueous surfactant solution is released onto the liquid ammonia in a foamed state.

3. 2. The method for inhibiting the evaporation and diffusion of liquid ammonia according to claim 1, wherein the precipitate layer contains a salted-out fatty acid salt.

4. A device for suppressing the vaporization and diffusion of liquid ammonia leaked from a storage facility or its auxiliary equipment, A water reservoir; a reservoir for a surfactant that forms a precipitate layer on the liquid surface of the liquid ammonia by mixing with the liquid ammonia; a foam generator that mixes the water in the water reservoir with the surfactant in the reservoir to generate foam; The liquid ammonia evaporation diffusion suppression device is characterized in that bubbles of a surfactant aqueous solution generated in the bubble generator are released into liquid ammonia stagnating under atmospheric pressure, and the deposition layer is formed on the liquid surface of the liquid ammonia.

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