Scrubber for absorbing high-concentration ammonia gas, high-concentration ammonia gas absorption apparatus, and ammonia recovery method.

Abstract

To provide a scrubber for absorbing high concentrations of ammonia gas, a high-concentration ammonia gas absorption apparatus, and an ammonia recovery method that can prevent backflow of external air into the tower, which is characteristic of high concentrations, when absorbing high concentrations of ammonia with a scrubber, and can simultaneously limit the explosiveness of the ammonia. [Solution] A scrubber 1 for absorbing high-concentration ammonia is provided, comprising a tower body 2 filled with a packing material 8 for gas-liquid contact, the tower body 2 having a high-concentration ammonia gas inlet 5 at the bottom, an exhaust gas outlet 4 at the top of the tower body 2 for discharged gas from the tower body 2, an absorbent liquid spraying section 7 for spraying absorbent liquid for absorbing ammonia gas at the top of the packing material 8, a storage section 6A at the bottom of the tower body 2 for storing absorbent liquid that has absorbed ammonia gas, an absorbent liquid outlet 6 for discharging the absorbent liquid in the storage section 6A to the outside of the tower body 2, and an inert gas space 12A formed above the inside of the tower body 2 and above the absorbent liquid spraying section 7.

Description

Technical Field

[0001] The present invention relates to a scrubber for absorbing high-concentration ammonia gas, a high-concentration ammonia gas absorption apparatus, and an ammonia recovery method that enable ammonia absorption without causing the inside of the tower body to become negative pressure or allowing external air to flow backward into the tower from the top of the tower when absorbing high-concentration ammonia gas using a scrubber.

Background Art

[0002] Conventionally, Patent Document 1 discloses diluting ammonia leaked from a refrigeration unit with air and introducing it into a scrubber. A packing material is installed in the scrubber, and treated water is sprayed from above the packing material. The treated water and ammonia come into contact at the packing material, and the ammonia is absorbed into the water of the treated water to become an alkaline solution. In this document, carbon dioxide gas is supplied to the treated water, making it acidic, so the alkaline solution is neutralized and becomes ammonium carbonate (hydrogen carbonate) by the reaction of ammonium hydroxide and carbonated water, rendering the ammonia harmless. However, this Patent Document 1 only discloses a method for removing low-concentration ammonia diluted with air and does not provide any suggestions for high-concentration ammonia gas. When the ammonia concentration is low, ammonia water is neutralized with carbonated treated water as in Patent Document 1. However, when the ammonia concentration is high, there is a problem that the amount of chemicals added for neutralization increases, resulting in high costs. Measures against the heat of neutralization generated by the neutralization reaction are also essential, and the neutralization treatment becomes inappropriate.

[0003] As a method for removing high-concentration ammonia gas, there is a method of incineration treatment at a temperature of around 1000°C in a combustion furnace. However, since ammonia gas is difficult to burn alone compared to fossil fuels, fossil fuels must be used as auxiliary fuels, resulting in a problem of carbon dioxide emissions. To solve these problems, the inventors have discovered a novel method for absorbing high concentrations of ammonia using a scrubber, which prevents the generation of negative pressure inside the tower that is characteristic of high concentrations, and prevents backflow of outside air into the tower, without the need for neutralization treatment or incineration treatment using auxiliary fuel. This has led to the present invention. Furthermore, if backflow of outside air into the tower occurs as described above, there is a risk of exceeding the ammonia explosion limit, so this problem also needs to be addressed at the same time. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2006-26555 [Overview of the project] [Problems that the invention aims to solve]

[0005] Therefore, the object of the present invention is to provide a scrubber for absorbing high-concentration ammonia gas, a high-concentration ammonia gas absorption device, and an ammonia recovery method that, when absorbing high concentrations of ammonia in a scrubber without neutralization treatment or incineration treatment using auxiliary fuel, can prevent the generation of negative pressure inside the tower that is characteristic of high concentrations, prevent backflow of external air into the tower, and at the same time avoid reaching the explosive limit of ammonia.

[0006] Furthermore, other problems of the present invention will become clear from the following description. [Means for solving the problem]

[0007] The above problems are solved by the following inventions.

[0008] 1. A scrubber for absorbing high concentrations of ammonia, comprising a tower body with one or more layers of packing material for gas-liquid contact inside, The lower part of the tower body has an ammonia gas inlet containing a high concentration of ammonia gas, The upper part of the tower body has an exhaust gas outlet for discharged gas from the tower body, The upper part of the filler has an absorbent liquid spraying section for spraying an absorbent liquid to absorb the ammonia gas, The lower part of the tower body has a storage section for storing the absorbent liquid that has absorbed the ammonia gas, The tower has an absorbent liquid outlet for discharging the absorbent liquid in the storage section to the outside of the tower body, A scrubber for absorbing high-concentration ammonia, comprising an inert gas space formed above the interior of the tower body and above the absorbent liquid spraying section. 2. The scrubber for absorbing high-concentration ammonia according to claim 1, characterized in that the inert gas space is a space formed by filter layers provided above and below, and filled with inert gas. 3. The scrubber for absorbing high-concentration ammonia according to claim 1, characterized in that a detector for detecting the gas pressure inside the tower body is installed in the tower body. 4. The scrubber for absorbing high-concentration ammonia according to 1, 2, or 3 above is provided, The absorbent liquid spraying section is connected to an absorbent liquid channel capable of supplying absorbent water. The storage unit has a tank for storing the ammonia absorbent water discharged from the absorbent liquid outlet, A high-concentration ammonia absorption device characterized by being configured to allow the supply of inert gas from an inert gas supply unit to the aforementioned inert gas space via piping. 5. The high-concentration ammonia absorption apparatus according to claim 4, characterized in that it detects when the gas pressure inside the tower body becomes negative and supplies inert gas from the inert gas supply unit through the piping to prevent outside air from flowing into the tower body. 6. The scrubber is provided with an adjustment absorbent water spraying section below the packing material for spraying adjustment absorbent water, The high-concentration ammonia absorption apparatus according to claim 4, characterized in that the absorbing water for adjustment sprayed from the absorbing water for adjustment section is brought into gas-liquid contact with high-concentration ammonia gas introduced into the tower body from the ammonia gas inlet to absorb ammonia, and the temperature of the ammonia gas is adjusted. 7. The ammonia absorbent solution is taken from the scrubber for high-concentration ammonia absorption described in 1, 2, or 3 above and stored in a recovered ammonia water tank. The recovered ammonia water stored in the aforementioned recovered ammonia water tank is introduced into the distillation column. The recovered ammonia water sent into the distillation column is heated in the recovery section at the bottom of the distillation column to release and remove the ammonia from the recovered ammonia water. The water from which the ammonia has been removed in the recovered ammonia water is sent to a clean water tank. The water stored in the fresh water tank is returned to the tower body within the scrubber and reused as absorbent water. The released ammonia is concentrated in the concentration section at the top of the distillation column and discharged from the distillation column as ammonia gas. A method for recovering ammonia, characterized in that the ammonia gas is cooled by cooling water in a heat exchanger after being discharged from the distillation column, and is recovered as concentrated ammonia by being stored in a recovery ammonia tank, and the cooling water is recycled. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a scrubber for absorbing high-concentration ammonia gas, a high-concentration ammonia gas absorption device, and an ammonia recovery method that prevent the generation of negative pressure inside the tower, which is characteristic of high concentrations, and prevent backflow of external air into the tower, while simultaneously avoiding reaching the explosive limit of ammonia, when absorbing high concentrations of ammonia in a scrubber without neutralization treatment or incineration treatment using auxiliary fuel. [Brief explanation of the drawing]

[0010] [Figure 1] Flowchart showing an example of the ammonia absorption apparatus of the present invention. [Figure 2] Principal part cross-sectional view showing details of the scrubber used in the absorption device of FIG. 1 [Figure 3] Block flow diagram showing a recovery device for implementing the ammonia recovery method of the present invention

Mode for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a flow diagram showing an example of the ammonia absorption device of the present invention, and FIG. 2 is a principal part cross-sectional view showing details of the scrubber for high-concentration ammonia absorption used in the recovery device of FIG. 1.

[0012] The scrubber 1 for high-concentration ammonia absorption shown in FIGS. 1 and 2 has high-concentration ammonia gas supplied from below (downward). The scrubber 1 in this aspect brings the ammonia gas into gas-liquid contact with clear water as the absorption liquid, and absorbs ammonia (NH3) into clear water (H2O). This scrubber 1 may also be referred to as an absorption tower. By this absorption, clear water becomes aqueous ammonia (NH4OH).

[0013] In the present invention, high-concentration ammonia gas means ammonia gas having an ammonia concentration of 15% or more, preferably 50% or more, more preferably 80% or more. Even more preferably, it means 90% or more, 95% or more. The high-concentration ammonia gas introduced into the scrubber 1 is not particularly limited as long as it is high-concentration ammonia gas. For example, ammonia gas discharged and diffused from a storage facility for liquefied ammonia; ammonia gas diffused from boil-off gas discharged from a tank storing liquefied ammonia; ammonia gas used as a refrigerant; ammonia gas vaporized from liquefied ammonia stored as fuel for a cargo or ship engine or a thermal power generator, etc. can be mentioned.

[0014] The scrubber 1 includes, for example, a tower body 2 which is a hollow cylindrical body with its axis vertical. The tower body 2 may be referred to as a packed tower if necessary. Within this packed tower 2, ammonia gas is absorbed into the absorbent water (including clean water). Here, the clean water can be tap water, industrial water, or clear river water, but is not limited to these. The tower body 2 contains a packing material 8, which is filled in two stages with packing materials 8A and 8B for gas-liquid contact. The number of packing stages in the packing material 8 is not particularly limited and may be one stage or two or more stages. In this embodiment, there are two stages of packing materials 8A and 8B.

[0015] The tower body 2 has an exhaust gas outlet 4 at its upper part and an ammonia gas inlet 5 containing a high concentration of ammonia at its lower part. The location of the exhaust gas outlet 4 is not limited to the upper part of the tower body 2, but may be at the top of the tower as shown in the figure, or at any position on the upper surface of the curved mirror surface. The absorbent liquid, introduced from the absorbent liquid inlet 3 to absorb ammonia, is sprayed onto the top of the packing material 8 via the absorbent liquid spraying section 7. Below the main body of the tower 2, there is a storage section 6A that stores the absorbent liquid, which is water sprayed from the absorbent liquid spraying section 7 and into which ammonia has been absorbed, at the bottom of the main body of the tower 2, and an absorbent liquid outlet 6 that discharges the absorbent liquid from the storage section 6A to the outside.

[0016] The absorbent liquid, which is clean water, is supplied to the absorbent liquid inlet 3. As shown in Figure 1, the clean water is sent from the clean water tank 13 to the absorbent liquid inlet 3 via the absorbent liquid flow path 15 by the clean water pump 14. It is preferable that a pipe 15B equipped with a solenoid valve 15A is connected to the flow path 15 to the absorption liquid inlet 3. This is to allow other water to be supplied if the clean water in the clean water tank 3 becomes empty for any reason.

[0017] As shown in Figure 2, the clean water supplied to the scrubber 1 from above is sprayed by an absorbent liquid dispensing unit 7, which is installed inside the scrubber 1 and consists of, for example, a liquid distributor.

[0018] High-concentration ammonia gas is supplied to the ammonia gas inlet 5. Absorbent water (ammonia water, also called "ammonia water"), which is clean water that has absorbed ammonia, is discharged from the absorbent liquid (absorbent water) outlet 6.

[0019] As shown in Figure 1, the absorbed water is sent from the absorbed water outlet 6 to the absorbed water tank 17 by the absorbed water pump 16. The absorbed water in the absorbed water tank 17 is discharged to the outside by the discharge pump 18. In the ammonia recovery apparatus shown in Figure 3, which will be described later, it is sent to the distillation column 20.

[0020] As shown in Figure 2, the packed column 2 is filled with upper packing material 8A and lower packing material 8B, which are packed in a regular or irregular manner. Each packing material 8A and 8B is supported by a packing material support member 9, through which liquid and gas can pass. The packing material support member 9 is designed to prevent the packing material from falling downwards.

[0021] Fresh water (H2O) supplied from the top of the packed column 2 flows downward along each surface of the packing material 8A, passes through the liquid redistributor 10, and then flows downward along each surface of the packing material 8B. The structure of the liquid redistributor 10 is not particularly limited as long as it is capable of spraying clean water. Preferably, the liquid redistributor 10 has pores that prevent the packing material from falling downwards and do not obstruct the flow of gas from below upwards.

[0022] The fresh water flowing downwards comes into gas-liquid contact with the ammonia gas supplied from the bottom of the packed column 2 and moving upwards. During this gas-liquid contact, ammonia in the ammonia gas is absorbed into the fresh water. Through this absorption, the ammonia is recovered as aqueous ammonia (NH3 + H2O → NH4OH).

[0023] This scrubber 1 includes an inert gas space 12A between the upper and lower filter layers 12, 12, and this space 12A can be filled with an inert gas (N2). In the space 12A, an inert gas is supplied from the inert gas supply unit 11A via piping 11. Examples of inert gases include noble gases such as argon and nitrogen gas (N2), but N2 is preferred due to its availability and cost-effectiveness. The inert gas supply unit 11A may be, but is not limited to, a tank, cylinder, or PSA-type nitrogen gas generator.

[0024] The filter layers 12, 12 are formed from wire mesh, perforated metal, or the like. Forming a space 12A where N2 gas accumulates between the filter layers 12, 12, and configuring the system to allow purging of N2 gas is preferable in preventing backflow and backmixing phenomena in the packed tower 2 and the exhaust gas outlet 4.

[0025] In Scrubber 1, the ammonia absorption reaction into water occurs on the packing surface. However, when the amount of gas becomes extremely small compared to the amount of liquid due to the absorption reaction, Bernoulli's theorem (pressure decreases as fluid velocity increases) creates negative pressure in the rapidly flowing fluid, making backmixing of gases in the tower more likely and affecting the absorption performance.

[0026] At high concentrations, backmixing becomes more pronounced, which may interfere with the absorption of high-concentration ammonia gas. Furthermore, backflow or backmixing of air from the exhaust gas outlet 4 at the top of the tower body 2 could occur, potentially leading to the ammonia reaching its explosive limit. In addition, in the case of a 100% ammonia gas, there is no inert gas, and as the ammonia is absorbed by the water, the gas flow rate decreases, and the gas velocity inside the tower eventually becomes zero. As a result, the possibility of mixing with outside air increases, leading to reaching the explosive limit of ammonia.

[0027] The solution to these problems lies in the presence of the inert gas space 12A in the present invention. To elaborate on the effects of the present invention in this regard, when ammonia is at a high concentration, the amount of inert gas is small in ammonia gas absorption by water, and at 100% ammonia concentration, the amount of inert gas is zero. Therefore, the amount of ammonia gas approaches zero, meaning that the gas migrates to the absorbent liquid side, and no gas rises inside the tower and is discharged from the exhaust gas outlet 4.

[0028] At this time, the gas and water flow inside the tower is a downward flow, and there is almost no upward energy in the fluids inside the tower. As a result, the inside of the tower is under negative pressure, making it easier for outside air to enter.

[0029] In the present invention, the flow rate of the inert gas supplied to the top of the packed column 2 can be determined by referring to the amount of nitrogen purging that is conventional in the art. When liquefied ammonia storage equipment is maintained, the flow rate (purge linear velocity in the piping) of ammonia gas discharged from the storage tank and associated piping by purging with an inert gas such as N2 gas is about a few m / second to several tens of m / second, and it is preferable that the purging in the present invention is also of a similar magnitude.

[0030] In this invention, if the flow rate of the inert gas is sufficient, it can overcome the negative pressure caused by the flow of clean water and suppress the occurrence of backmixing. Considering that the ammonia in high-concentration ammonia-containing gas is absorbed by the clean water and the amount of gas decreases drastically, the inner diameter of the packed column 2 can be reduced to ensure the flow velocity of the inert gas. In this case, since the gas in the system that has been replaced with an inert gas is discharged first, it is preferable to set the inner diameter of the packed column 2 to a diameter that can accommodate that gas volume.

[0031] In this invention, it is preferable to include a detector 2A that detects whether or not the gas pressure inside the tower body 2 (pressure inside the tower) has become negative. This is because it can detect negative pressure as quickly as possible. Furthermore, it is preferable to install the detector 2A inside the tower body 2, but the detector 2A may also be configured to include an output unit that outputs a signal of the pressure inside the tower and a determination unit that determines whether or not the pressure is negative based on the output signal.

[0032] Therefore, in order to resolve this situation, the present invention quickly detects a negative pressure state, supplies inert gas to the packed tower 2, and increases the gas pressure at the exhaust gas outlet 4 at the top of the packed tower 2, thereby preventing outside air from entering the tower and avoiding reaching the explosive limit of ammonia. In other words, in this invention, it is important to push back the gas entering from the outside using negative pressure, and in this invention, this pushing back is referred to as purging with an inert gas.

[0033] In the present invention, it is preferable to provide a temperature-regulating absorbent water spraying section 19 below the packing material 8 of the scrubber 1 for spraying temperature-regulating absorbent water. That is, as shown in Figure 1, it is preferable that the temperature-regulating absorbent water spraying section 19 for absorbing ammonia is provided above the vicinity of the ammonia gas inlet 5 in the tower body 2 and below the lower end of the packing material 8. The temperature-controlling absorbent water sprayed from the temperature-controlling absorbent water spraying section 19 is brought into gas-liquid contact with high-concentration ammonia gas introduced into the tower body 2 from the ammonia gas inlet 5 to absorb ammonia and adjust the temperature of the ammonia gas.

[0034] For the temperature-regulating absorbent water spraying section 19, it is preferable that a liquid distributor installed inside the scrubber 1 is used, similar to the absorbent liquid spraying section 7. In this temperature-regulating absorbent water spraying section 19, a portion of the absorbent water sent from the absorbent water outlet 6 to the absorbent water tank 17 by the absorbent water pump 16 is branched off and supplied as temperature-regulating absorbent water. The temperature-regulating absorbent water can circulate between the packed tower 2 and the absorbent water pump 16.

[0035] The ammonia gas discharged from the liquefied ammonia storage facility may be at an extremely low temperature, the boiling point of liquefied ammonia at atmospheric pressure (-33°C). In this case, supplying it into packed column 2 may cause the absorbent water to freeze, potentially reducing the ammonia recovery efficiency.

[0036] When ammonia is absorbed by water, heat is generated, and the amount of heat generated increases as the concentration of ammonia increases. By spraying the temperature-raised absorbent water, which has been heated by this heat generation, into the lower part of scrubber 1 (near the part where ammonia gas is supplied) and circulating it, the temperature of the ammonia gas in packed column 2 can be adjusted. This prevents the absorbent water from freezing even when extremely cold ammonia gas at -33°C enters packed column 2.

[0037] Adjustment absorption water can be supplied at various times. For example, it is preferable to supply adjustment absorption water when preparing to receive ammonia gas (standby operation) (to confirm the operation of the absorption water discharge pump), when the temperature of the ammonia gas is below freezing (to prevent freezing), when the temperature of the ammonia gas in the packed column is above a threshold (when the amount of ammonia gas exceeds the planned value), when the flow rate of the clean water is below a threshold and the ammonia gas has a certain ammonia concentration and flow rate (clean water supply trouble), or when the ammonia gas has a threshold or higher (packed column performance failure). In other words, adjustment absorption water can be used not only for temperature adjustment but also for adjusting the clean water supply, adjusting for fluctuations from planned values, and for operational adjustments to confirm operation.

[0038] The absorbent water (ammonia water) that has been sprayed into scrubber 1 and absorbed ammonia is discharged outside scrubber 1 through the absorbent water outlet 6 at the bottom of scrubber 1. The discharged absorbent water (ammonia water) is not returned to scrubber 1, making it a so-called one-pass system. By passing the absorbed water through a single pass and not returning it to scrubber 1, the ammonia concentration and temperature of the supplied clean water remain constant, allowing for stable absorption of ammonia into the clean water. In ammonia absorption into water via gas-liquid contact, if the water is not replaced, the ammonia concentration in the water will reach saturation and absorption will stop. For this reason, in scrubber 1, the water is sprayed from the top, and after absorbing ammonia, it is discharged to the outside from the storage tank 6A at the bottom of the tower body 2 of scrubber 1. This is why a single-pass system is employed. In some cases, a method is adopted in which ammonia is separated and removed from the absorbed water to obtain clean water, which is then reused.

[0039] In this invention, in order to keep the ammonia concentration of the recovered ammonia water constant, it is necessary to appropriately adjust the amount of clean water supplied. For example, if a safety valve device is activated due to abnormally high pressure in a liquefied ammonia storage facility, a large amount of ammonia gas will be released instantaneously. After that, the amount of released gas will fluctuate greatly until the release subsides. In order to absorb and recover the ammonia gas released here using Scrubber 1, it is necessary to adjust the supply of clean water in accordance with fluctuations in the amount of released gas.

[0040] Furthermore, the supply line (piping) that delivers ammonia gas from liquefied ammonia storage facilities to utilization facilities can reach high pressures of 3 MPa or higher, and the amount of gas blown out from safety valves installed in the supply line can also be instantaneous and substantial. Therefore, if ammonia gas is supplied directly to scrubber 1 from a safety valve or the like, there is a risk of flooding. Flooding is a phenomenon in which the liquid is unable to flow down because its linear velocity is greater than that of the gas, and instead it is blown upward. To prevent such flooding from occurring, it is necessary to appropriately adjust the amount of clean water supplied.

[0041] Figure 3 is a block flow diagram showing a recovery apparatus for implementing the ammonia recovery method of the present invention.

[0042] In this embodiment, since ammonia is recovered, a distillation column is used to separate ammonia from water, taking advantage of the characteristics of high-concentration ammonia. The ammonia absorbent solution is taken from the scrubber 1 used for high-concentration ammonia absorption as recovered ammonia water and stored in the recovered ammonia water tank 17.

[0043] Next, the recovered ammonia water stored in tank 17 is introduced into distillation column 20. Distillation column 20 has a concentration section 20A at the top and a recovery section 20B at the bottom. The ammonia water sent into the distillation column 20 is heated by a heat source in the first heat exchanger 201. When this heating reaches a temperature above the boiling point of ammonia water, it is separated in the recovery section 20B into a gas, which is ammonia-containing water vapor, and a liquid, which is ammonia water from which the ammonia has been released and the ammonia concentration has decreased. The gas, which is ammonia-containing water vapor separated in the recovery section 20B, is sent to the concentration section 20A. In the concentration section 20A, the ammonia concentration increases due to the ammonia-containing water vapor sent in.

[0044] The ammonia-containing steam, whose ammonia concentration has increased in the concentration section 20A, is discharged from near the top of the distillation column 20 via piping 202. The ammonia-containing steam discharged from the distillation column 20 is cooled by cooling water in the second heat exchanger 203, where it condenses and concentrated ammonia is recovered.

[0045] The concentrated ammonia is stored and recovered in recovery ammonia tank 205. The cooling water used as a cooling medium in the second heat exchanger 203 is configured to be circulated and reused in the second heat exchanger 203.

[0046] In this embodiment, the means by which the recovered ammonia water can be used are not particularly limited. For example, as shown in Figure 3, the ammonia gas separated from the ammonia water may be recovered and the separated water stored in the clean water tank 204 for reuse as absorbent water, or the recovered ammonia water may be stored and reused, or sulfuric acid may be added to produce ammonium sulfate for use. [Examples]

[0047] The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

[0048] Example 1 The experiment was conducted using Scrubber 1, shown in Figures 1 and 2.

[0049] (1) The specifications for Scrubber 1 were set as follows: • Scrubba tower body: Tower body diameter: 100mmφ • Filling material: Using "Terralet (registered trademark)" manufactured by Tsukishima Environmental Engineering Co., Ltd., two layers were stacked with a filling height of 500 mm per layer. • Inert gas layer Filter layer: Two pieces of perforated metal with pores 1 mm in diameter were used. The filter layers were spaced 30 mm apart, and an inert gas (N2 gas) supplied from the piping was sealed in between to form an inert gas layer. The inert gas was supplied from a gas cylinder via piping, and its pressure was set to 10-50 kPa.

[0050] (2) The ammonia gas used for recovery in the experiment was prepared as follows. <Experimental Sample 1> A high-concentration ammonia gas (100% ammonia) was prepared by mixing 100% ammonia gas with 0% inert gas (N2 gas). <Experimental Sample 2> A high-concentration ammonia gas with 95% ammonia content was prepared by mixing 5% inert gas (N2 gas) with 100% ammonia gas. <Experimental Sample 3> A high-concentration ammonia gas with 90% ammonia content was prepared by mixing 10% inert gas (N2 gas) with 100% ammonia gas. <Experimental Sample 4> A low-concentration ammonia gas with 50% ammonia content was prepared by mixing 100% ammonia gas with 50% inert gas (N2 gas). <Experimental Sample 5> A high-concentration ammonia gas with 10% ammonia content was prepared by mixing 100% ammonia gas with 90% inert gas (N2 gas).

[0051] (Recovery experiment) Ammonia gas from experimental samples 1-5 is introduced through the inlet 5 at the bottom of scrubber 1, and the ammonia is brought into gas-liquid contact with the clean water sprayed from the top of packing material 8 on the surface of each packing material 8. The experimental samples were varied in ammonia concentration from 0% to 100%. If the ammonia concentration is 10% or 50%, even if all the ammonia gas is absorbed into the clean water through gas-liquid contact, 90% to 50% of the treated gas will remain. Therefore, there will always be some treated gas discharged from the outlet, and this treated gas will be discharged from the outlet at the top of the scrubber.

[0052] However, when the ammonia concentration reaches 90% or 100%, if all the ammonia gas is absorbed into the clean water through gas-liquid contact, the volume of the treated gas from which ammonia has been removed becomes 1 / 10 to 0. This leads to a problem specific to high concentrations where only an extremely small amount of gas is discharged from the outlet at the top of the scrubber, or no gas is discharged at all. When high concentrations of ammonia gas are absorbed by water, there is no more processed gas to be discharged from the outlet at the top of the scrubber. As a result, the only fluid flowing inside the scrubber tower is the absorbed water that has absorbed the ammonia. This ammonia-absorbing water moves downward, and in the absence of upward-moving gas, downward energy is applied to the fluid within the tower. This downward energy from the ammonia-absorbing water can be seen as energy generated inside the tower itself. If so, this downward energy extends throughout the entire interior of the tower within the enclosed space. As a result, a downward pulling force acts inside the tower due to this downward energy, and this force also acts at the exit at the top of the scrubber, creating a negative pressure or a similar state inside the scrubber (Bernoulli's principle). Furthermore, at the ammonia gas inlet at the bottom of the tower, there is enough pressure for the gas to rise and be absorbed by the absorbent water. Meanwhile, the absorbent water is subjected to the energy of gravity (fall) as gas-liquid contact occurs. It can also be considered that the high concentration of ammonia dissolves in the water, eliminating the pressure of the ammonia gas that would otherwise rise as it is absorbed by the water.

[0053] Furthermore, if the gas pressure inside the tower disappears, or if a negative pressure or similar condition occurs, a backflow phenomenon may occur inside the tower itself. In this embodiment, we investigate whether the pressure disappears or negative pressure is generated inside the tower due to the absorption of water from high-concentration ammonia gas (hereinafter abbreviated as "presence or absence of negative pressure inside the tower"), and whether or not backflow occurs.

[0054] (Evaluation criteria) • Presence or absence of inert gas space purging: In all experiments, an inert gas space was provided in the scrubber. If purging was performed, it was marked as "Inert gas space purging present," and if it was not performed, it was marked as "Inert gas space purging absent." We confirmed that purging can prevent the generation of negative pressure. • Presence or absence of negative pressure and backflow within the tower: This is confirmed by checking whether the gas flow within the tower is directed downwards or not.

[0055] (Experimental results) The experimental results are shown in Table 1.

[0056] [Table 1]

[0057] Of the experiments described above, experiments 5, 7, and 9 are examples of actual implementations, while the others are for reference only. In experiments 5, 7, and 9, purging the inert gas space resulted in no negative pressure being generated inside the tower, nor was there any backflow.

[0058] Example 2 The ammonia recovery efficiency was investigated by measuring the ammonia recovery rate (removal rate) by measuring the temperature change of the absorption solution into the scrubber before and after absorption. This is because ammonia generates heat when it reacts with water, so the temperature rises when ammonia is absorbed into clean water. The experimental results are shown in Table 2.

[0059] [Table 2]

[0060] Table 2 shows that the ammonia recovery efficiency was good, exceeding 99.9%. In an investigation into the ammonia recovery rate (removal rate) when there was a temperature change in the absorbent solution before and after absorption into the scrubber, the difference between the absorbent solution temperature and the feed solution temperature was 28°C, 31°C, and 27°C in experiments 11, 14, and 15, where the ammonia concentration was high. It was confirmed that the temperature rose by 30°C at an ammonia gas concentration of 95-100%. It was also confirmed that the temperature rose by 20°C at an ammonia gas concentration of 50%. It was confirmed that the temperature rise increased or decreased depending on the amount of NH3 absorbed. [Explanation of Symbols]

[0061] 1 Scrubber 2. Tower body (filled tower) 2A detector 3. Absorption liquid inlet 4. Exhaust gas outlet 5. Ammonia gas inlet 6. Absorbent liquid outlet 6A Storage section 7. Absorbent liquid spray section 8 Filler 8A Filler 8B Filler 9. Filler support member 10 Liquid redistributor 11 Piping 11A Inert Gas Supply Unit 12, 12 filter layers 12A Inert gas space 13. Fresh water tank 14. Clean water pump 15 Absorption liquid channel 15A Solenoid Valve 15B Piping 16. Absorption water pump 17. Absorption water tank (recovery aquatic water tank) 18 Discharge pump 19. Temperature control absorbent water spraying section 20 Distillation Columns 20A Concentration section 20B Recovery section 201 1st heat exchanger 202 Piping 203 Second heat exchanger 204 Clean water tank 205 Ammonia recovery tank

Claims

1. A scrubber for absorbing high concentrations of ammonia, comprising a tower body with one or more layers of packing material for gas-liquid contact inside, The lower part of the tower body has an ammonia gas inlet containing a high concentration of ammonia gas, The upper part of the tower body has an exhaust gas outlet for discharged gas from the tower body, The upper part of the filler has an absorbent liquid spraying section for spraying an absorbent liquid to absorb the ammonia gas, The lower part of the tower body has a storage section for storing the absorbent liquid that has absorbed the ammonia gas, The tower has an absorbent liquid outlet for discharging the absorbent liquid in the storage section to the outside of the tower body, A scrubber for absorbing high-concentration ammonia, comprising an inert gas space formed above the interior of the tower body and above the absorbent liquid spraying section.

2. The scrubber for absorbing high-concentration ammonia according to claim 1, characterized in that the inert gas space is a space formed by filter layers provided above and below, and filled with inert gas.

3. The scrubber for absorbing high-concentration ammonia according to claim 1, characterized in that a detector for detecting the gas pressure inside the tower body is installed in the tower body.

4. A scrubber for high-concentration ammonia absorption according to claim 1, 2, or 3 is provided, The absorbent liquid spraying section is connected to an absorbent liquid channel capable of supplying absorbent water. The storage unit has a tank for storing the ammonia absorbent water discharged from the absorbent liquid outlet, A high-concentration ammonia absorption device characterized by being configured to allow the supply of inert gas from an inert gas supply unit to the aforementioned inert gas space via piping.

5. The high-concentration ammonia absorption apparatus according to claim 4, characterized in that it detects when the gas pressure inside the tower body becomes negative and supplies inert gas from the inert gas supply unit through the piping to prevent outside air from flowing into the tower body.

6. The scrubber is provided with an adjustment absorbent water spraying section below the packing material for spraying adjustment absorbent water, The high-concentration ammonia absorption apparatus according to claim 4, characterized in that the absorbing water for adjustment sprayed from the absorbing water for adjustment section is brought into gas-liquid contact with high-concentration ammonia gas introduced into the tower body from the ammonia gas inlet to absorb ammonia, and the temperature of the ammonia gas is adjusted.

7. The ammonia absorbent solution is taken from the scrubber for high-concentration ammonia absorption according to claim 1, 2, or 3 and stored in a recovered ammonia water tank. The recovered ammonia water stored in the aforementioned recovered ammonia water tank is introduced into the distillation column. The recovered ammonia water sent into the distillation column is heated in the recovery section at the bottom of the distillation column to release and remove the ammonia from the recovered ammonia water. The water from which the ammonia has been removed in the recovered ammonia water is sent to a clean water tank. The water stored in the fresh water tank is returned to the tower body within the scrubber and reused as absorbent water. The released ammonia is concentrated in the concentration section at the top of the distillation column and discharged from the distillation column as ammonia gas. A method for recovering ammonia, characterized in that the ammonia gas is cooled by cooling water in a heat exchanger after being discharged from the distillation column, and is recovered as concentrated ammonia by being stored in a recovery ammonia tank, and the cooling water is recycled.

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