Method for producing ammonium salt and apparatus for producing ammonium salt

Abstract

Provided are a method and an apparatus for producing an ammonium salt, capable of removing CO2 from a gas being treated and utilizing the captured CO2. A method for producing an ammonium salt according to the present invention comprises: a step for vaporizing liquid ammonia (31) to produce ammonia gas (32); a step for recovering cold energy associated with the vaporization of the liquid ammonia (31) in a heat exchanger (22); a CO2 removal step for reacting a gas (11) being treated that contains CO2 from a CO2 discharge source with a CO2 absorber (33) that contains the ammonia gas (32) and water, thereby converting the CO2 in the gas (11) being treated to an ammonium salt aqueous solution and removing the CO2; and a crystallization step for cooling a CO2 absorber (34) that has passed through the CO2 removal step by using the cold energy associated with the vaporization of the liquid ammonia (31) and precipitating an ammonium salt (35) that contains ammonium carbonate, ammonium hydrogen carbonate, or ammonium carbamate.

Description

Method for producing ammonium salt and apparatus for producing ammonium salt

[0001] The present invention relates to a method for producing an ammonium salt and an apparatus for producing an ammonium salt.

[0002] Flue gas from power plants, industrial plants, essential oil plants, ships, etc. is a major source of greenhouse gases, particularly carbon dioxide (CO ２ ). To comply with environmental emission control regulations, chemical processes and scrubbers are routinely used to treat flue gas to remove pollutants such as particulate matter, heavy metal compounds, nitrogen oxides, and sulfur oxides. However, there is a current need for science and technology that leads to economically feasible methods and systems for capturing (recovering) and storing (retaining) CO ２ .

[0003] As a method for removing CO ２ from flue gas, a method is to absorb the CO ２ gas in an amine-based solvent, further heat it to release the CO ２ , and then liquefy and accumulate it. However, such technologies consume a large amount of energy for heating to remove CO ２ from the solvent, liquefying the removed CO ２ , and further for transportation and storage. In addition, problems such as amine degradation and corrosion of pipes and the like occur. Therefore, new or improved methods and apparatuses (systems) for removing CO ２ from flue gas are needed.

[0004] For example, Patent Document 1 describes a system in which the residual pollutant concentration is made almost zero by cooling combustion gas, and then CO ２ in the gas is captured using an ammonia treatment solution or slurry, and the treatment solution that has absorbed the CO ２ is regenerated by increasing the pressure and temperature of the treatment solution.

[0005] Japanese Patent Application Laid-Open No. 2008-508099

[0006] The proposal of Patent Document 1 has the problem of consuming a large amount of energy when heating and cooling fluids. Also, the captured CO ２Storage methods for these substances have not been considered. Furthermore, the precipitated ammonium carbonate and ammonium bicarbonate have not been utilized.

[0007] This invention removes CO2 from the gas to be treated. ２ Remove the captured CO ２ The objective is to provide a method for producing ammonium salts and an apparatus for producing ammonium salts that can utilize [the specified technology / method].

[0008] The present invention includes, for example, the following inventions [1] to

[17] : [1] A step of vaporizing liquid ammonia to produce ammonia gas, and a step of recovering the cold energy associated with the vaporization of the liquid ammonia in a heat exchanger, and CO ２ CO2 emissions from the source ２ The gas to be treated, which includes the above ammonia gas and water containing CO2, is treated as follows: ２ By reacting with the absorber, the CO in the gas to be treated is ２ Convert to an ammonium salt aqueous solution and CO ２ CO2 removal ２ Removal process and CO ２ CO after passing through the removal process ２ A method for producing an ammonium salt, comprising a crystallization step of cooling an absorbent using the cold energy associated with the vaporization of the above-mentioned liquid ammonia to precipitate an ammonium salt containing ammonium carbonate, ammonium bicarbonate, or ammonium carbamate. [2] The method for producing an ammonium salt according to [1], characterized in that the heat of vaporization of liquefied natural gas is also used as the cold energy. [3] The above-mentioned CO ２ CO in the removal process ２ A method for producing an ammonium salt according to [1] or [2], characterized in that the temperature of the absorber is 60°C or lower. [4] CO in the crystallization step ２ A method for producing an ammonium salt according to any one of [1] to [3], characterized in that the temperature of the absorber is 10°C or higher. [5] The above CO ２ CO supplied to the removal process ２ A method for producing an ammonium salt according to any one of [1] to [4], characterized in that the ammonia concentration in the absorbent is 3% by mass or more and 15% by mass or less. [6] The above CO２ CO in the treated gas supplied per unit time to the removal process ２ The molar amount of the above CO ２ The above CO supplied per unit time to the removal process ２ Ratio of molar amount of ammonia in the absorber (CO ２ / NH ３ A method for producing an ammonium salt according to any one of [1] to [5], characterized in that the CO is greater than 1 and less than or equal to 5. [7] A method for producing an ammonium salt according to any one of [1] to [6], characterized in that the average particle size of the ammonium salt produced in the crystallization step is 0.1 mm or more and less than or equal to 10 mm. [8] A method for producing an ammonium salt according to any one of [1] to [7], characterized in that the coefficient of variation (CV) of the particle size of the ammonium salt produced in the crystallization step is 3% or more and less than or equal to 30%. [9] A method for producing an ammonium salt according to any one of [1] to [8], characterized in that seawater is also used as the cold energy.

[10] A method for producing an ammonium salt according to any one of [1] to [9], characterized in that a mixture of polyhydric alcohol and water is circulated in a heat exchanger as a medium for transporting the cold energy.

[11] The CO ２ A method for producing an ammonium salt according to any one of [1] to

[10] , comprising an ammonia recovery step in which the gas to be treated after passing through the removal step is brought into contact with water to separate ammonia in the gas to be treated.

[12] A method for producing an ammonium salt according to

[11] , characterized in that the water used in the ammonia recovery step is cooled using the medium that carries cold and heat.

[13] The liquid after the ammonium salt has been separated by the crystallization step is passed through the ammonia recovery step, and the liquid after passing through is again treated with the CO ２ A method for producing an ammonium salt according to

[11] or

[12] , characterized by supplying it to a removal process.

[14] The above CO ２A method for producing an ammonium salt according to any one of

[11] to

[13] , comprising an ammonia desorption step in which the gas to be treated before passing through the removal step is brought into contact with water used in the ammonia recovery step to desorb ammonia from the water into the gas to be treated.

[15] A method for producing an ammonium salt according to any one of [1] to

[14] , characterized by adding water to the ammonium salt produced in the crystallization step to dissolve it, and transporting the dissolved ammonium salt by pump.

[16] An ammonia vaporization unit that vaporizes liquid ammonia to produce ammonia gas, a heat exchanger that recovers the cold energy associated with the vaporization of the liquid ammonia, and CO ２ CO2 emissions from the source ２ The gas to be treated, which includes the above ammonia gas and water containing CO2, is treated as follows: ２ By reacting with the absorber, the CO in the gas to be treated is ２ Convert to an ammonium salt aqueous solution and CO ２ CO2 removal ２ Removal section and CO ２ CO after passing through the removal section ２ An apparatus for producing ammonium salts, characterized by having a crystallization section which cools an absorbent using the cold energy generated by the vaporization of the above liquid ammonia to precipitate an ammonium salt containing ammonium carbonate, ammonium bicarbonate, or ammonium carbamate.

[17] The above CO ２ The ammonium salt production apparatus according to

[16] , further comprising an ammonia recovery unit that separates ammonia from the gas to be treated by bringing the gas to be treated after it has passed through the removal unit into contact with water.

[18] The CO ２ The ammonium salt production apparatus according to

[17] , further comprising an ammonia desorption unit that brings the gas to be treated before it passes through the removal unit into contact with water used in the ammonia recovery unit, thereby desorbing ammonia from the water into the gas to be treated.

[0009] According to the present invention, CO ２ Remove the captured CO ２ We can provide a method for producing ammonium salts and an apparatus for producing ammonium salts that can utilize the aforementioned technology.

[0010] This is a diagram illustrating an ammonium salt production apparatus according to the first embodiment. This is a diagram showing an example of a crystallization section. This is a diagram showing another example of a crystallization section. This is a diagram illustrating an ammonium salt production apparatus according to the second embodiment. This is a diagram illustrating an ammonium salt production apparatus according to the third embodiment.

[0011] The present invention will be described below based on preferred embodiments.

[0012] In the method and apparatus for producing ammonium salt according to this embodiment, CO2 is extracted from the gas to be treated. ２ To remove ammonia (NH ３ ) is used. Furthermore, CO ２ and NH ３ To precipitate the ammonium salt produced by the reaction of and by a crystallization process, at least liquid NH ３ The cooling effect associated with vaporization is used.

[0013] The ammonium salt precipitated in the crystallization process is recovered as solid crystals or a dissolved solution. Alternatively, the crystallized ammonium salt may be dissolved in water and recovered as an ammonium salt solution. When transporting the solution, it may be transported via piping or other means using pumps. The means of transporting the solution are not particularly limited, but examples include tank trucks, ships, and pipelines. The solution may also be stored in a liquid tank.

[0014] The gases to be treated include CO ２ CO2 emitted from the emission source ２ Any gas containing CO is acceptable, and is not particularly limited, but examples include exhaust gas (gas after combustion), landfill gas, and associated gas. ２ CO emissions can come from facilities such as power plants, industrial plants, and oil refineries, as well as from transportation equipment such as ships. ２ If the waste generator is a facility, it may be installed in any location, such as on land, underground, underwater, on the sea, or on ice. When transporting gas, it may be transported via piping or other means using blowers or similar equipment.

[0015] The ammonium salt produced by the ammonium salt production method and apparatus according to this embodiment is CO ２ Carbon atoms derived from and NH３ Any compound containing a nitrogen atom derived from [(NH4] is acceptable. As an ammonium salt, ammonium carbonate [(NH4] is acceptable. ４ ) ２ CO ３ ), ammonium bicarbonate (NH ４ HCO ３ ), ammonium carbamate (NH ４ OCONH ２ Examples include ) and others. In addition, other substances besides ammonium salts include urea (NH ２ CONH ２ ) and others may be included in the ammonium salt obtained in the crystallization process. The ammonium salt may be either anhydrous (anhydrous) or hydrated (hydrated) salt. Depending on the composition of the gas to be treated and the treatment conditions, CO ２ Other acidic components (SOx, NOx, HCl, etc.) may be present, but the gas to be treated is NH ３ CO ２ It is preferable to remove other acidic components using a scrubber or the like.

[0016] CO ２ Ammonia gas or dilute aqueous ammonia can be used as the absorbent. Liquid ammonia is used as the ammonia source. This allows the cooling energy generated by the vaporization of liquid ammonia to be recovered by a heat exchanger and used to promote the precipitation of ammonium salts in the crystallization process.

[0017] Ammonia gas produced by vaporizing liquid ammonia can be used as ammonia gas, or as CO2 containing ammonia and water. ２ As an absorbent, CO2 can be used in scrubbers, etc. ２ It is supplied to the removal section, CO ２ It is brought into contact with the gas to be treated, which contains CO. ２ If an absorbent is used, ammonia gas may be dissolved in the liquid (dilute solution) remaining after separating the ammonium salt in the crystallization process.

[0018] CO2 ２ When supplying to the removal unit, CO ２It is preferable to supply water to the removal section and bring the water and ammonia gas into contact with the gas to be treated in a state where they can be mixed. ２ At least a portion of the water supplied to the removal section may be the liquid (dilute solution) remaining after separating the ammonium salt in the crystallization process.

[0019] The gases to be treated are CO2 containing ammonia gas and water. ２ By reacting with the absorbent, the CO in the gas to be treated ２ This is converted into an ammonium salt aqueous solution. As a result, CO is removed from the gas being treated. ２ It can remove CO2. Also, ammonium salts are soluble in water. ２ The contact process with the absorbent can consist of multiple stages.

[0020] If the equipment in question or other equipment uses liquefied natural gas (LNG) as fuel, LNG can also be used as a cooling source. The cooling energy generated by the vaporization of LNG can be recovered in a heat exchanger and used to promote the precipitation of ammonium salts in the crystallization process. The fuel gas remaining after the cooling energy is recovered can be used as fuel for boilers, turbines, burners, etc.

[0021] CO2 containing ammonia gas and water ２ CO2 absorbent ２ The aqueous solution containing the ammonium salt produced by the absorption of the ammonia can be cooled using cold energy. This cold energy may consist solely of the cold energy obtained from the vaporization of liquid ammonia, or it may be obtained in combination from the cold energy obtained from the vaporization of liquid ammonia and the cold energy obtained from the vaporization of liquefied natural gas.

[0022] If the equipment in question is located in a place where seawater is readily available, seawater can also be used as a cooling source. ２ After absorbing CO2 containing ammonium salts, ２ By exchanging heat with seawater, the absorber can absorb CO ２ The absorbent material can be cooled down.

[0023] Crystals of ammonium salts precipitate from the cooled aqueous solution. The ammonium salts can be separated from the solid and liquid phases and recovered as solids. The recovered ammonium salt crystals can be collected in a sealed container as solids. The liquid (dilute solution) obtained by solid-liquid separation can be used for dissolving ammonia gas.

[0024] According to the method and apparatus for producing ammonium salts according to this embodiment, CO in the gas to be treated ２ can be converted into ammonium salts and stored and transported at normal temperature and pressure without applying compression costs.

[0025] The above-mentioned ammonium salts (such as ammonium carbonate, ammonium bicarbonate, ammonium carbamate, etc.) can be thermally decomposed at a relatively low temperature, such as below 100 °C. The thermal decomposition of ammonium salts gives CO ２ , NH ３ , H ２ O. Separate and recover and store (CCS) CO ２ , and NH ３ can be recovered and liquefied again for reuse.

[0026] The ammonia concentration in the gas to be treated, such as exhaust gas, can be reduced and then dispersed into the environment. Thereby, the health of personnel at the CO ２ emission source and the amount of ammonia dispersed that affects the environment can be reduced.

[0027] At least a part of the energy required for cooling a CO ２ absorbent containing ammonium salts can be obtained as the cooling heat accompanying the vaporization of liquid ammonia. Also, when it can be utilized as ammonium salts such as ammonium carbonate, ammonium bicarbonate, ammonium carbamate, etc., storage as CO ２ is also unnecessary. <​​​​<First Embodiment> FIG. 1 is a configuration diagram illustrating an ammonium salt production apparatus according to the first embodiment. In the first embodiment, from the ammonia gas 32 generated by vaporizing the liquid ammonia 31, CO ２ absorbent 33 is prepared. The CO ２ absorbent 33 containing ammonia and water is used to absorb CO ２ from a CO ２ containing target gas 11 from a discharge source (not shown).

[0030] The ammonium salt production method according to the first embodiment generally includes: (1) an ammonia vaporization step, (2) a cold heat recovery step, (3) a mixing step, (4) a CO ２ removal step, and (5) a crystallization step.

[0031] (1) The ammonia vaporization step is a step of vaporizing the liquid ammonia 31 to generate ammonia gas 32. (2) The cold heat recovery step is a step of recovering the cold heat associated with the vaporization of the liquid ammonia 31 using the heat exchanger 22. (3) The mixing step is a step of preparing the CO ２ absorbent 33 containing ammonia gas 32 and water. (4) The CO ２ removal step is a step of reacting the target gas 11 to be treated with the CO ２ absorbent 3 to convert CO ２ in the target gas 11 to an ammonium salt aqueous solution and remove CO ２ . (5) The crystallization step is a step of cooling the CO ２ absorbent 34 after passing through the CO ２ removal step using the cold heat associated with the vaporization of the liquid ammonia 31 to precipitate the ammonium salt 35. [[ID=​​​​​​​(1) The ammonia vaporization unit 21 vaporizes liquid ammonia 31 to produce ammonia gas 32. (2) The heat exchanger 22 recovers the cooling energy associated with the vaporization of liquid ammonia 31. (3) The mixing unit 23 mixes ammonia gas 32 and CO2 containing water. ２ Prepare the absorbent 33. (4) CO ２ The removal unit 24 removes CO from the gas to be treated 11. ２ By reacting with the absorber 33, the CO in the gas to be treated 11 is released. ２ Convert to an ammonium salt aqueous solution and CO ２ Remove the following. (5) The crystallized part 26 is CO ２ CO after passing through the removal section 24 ２ The absorbent 34 is cooled using the cold energy generated by the vaporization of liquid ammonia 31 to precipitate the ammonium salt 35.

[0034] First, CO2 in the target gas 11 is treated using ammonia. ２ The following describes a series of steps for absorbing ammonia and recovering the resulting ammonium salt. In the figure, the liquid flow that may be involved in the dissolution of ammonia or ammonium salt is shown by a dashed line.

[0035] In the ammonia vaporization section 21, heat exchange occurs between the medium 20 that carries cold and heat and the liquid ammonia 31. As a result, the liquid ammonia 31 vaporizes and the medium 20 is cooled. The liquid ammonia 31 can be used by taking an appropriate amount from a container such as a cylinder or tank. In the figure, the flow of the medium 20 is shown by a dashed line.

[0036] The medium 20 is CO2 containing ammonium salts in the heat exchanger 22 provided in the crystallization section 26. ２ By exchanging heat with the absorber 34, the cold energy carried by the medium 20 is converted to CO ２ It is used to cool the absorber 34. As the medium 20, from the time of cooling with liquid ammonia 31, CO2 containing ammonium salts is used. ２It is desirable to maintain fluidity within the temperature range until the absorber 34 cools. A suitable substance can be used from among known heat transfer fluids, and it may be a single substance or a mixed composition. A pump or the like (not shown) can be used to transport the medium 20 as needed. In order for the temperature range in which the medium 20 is liquid to overlap with the temperature range in which liquid ammonia is liquid, the freezing point of the medium 20 must be below the boiling point of liquid ammonia (-33°C).

[0037] A suitable medium 20 is a mixture of polyhydric alcohol and water. Examples of polyhydric alcohols include glycols (dihydric alcohols) such as ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, and propylene glycol, and trihydric alcohols such as glycerin. The medium 20 may contain two or more polyhydric alcohols. By cooling the mixture of polyhydric alcohol and water with the cold energy generated by the vaporization of liquid ammonia 31 and circulating it through the heat exchanger 22, the crystallization of ammonium salts can be carried out efficiently.

[0038] In the example shown in Figure 1, the medium 20 is also available for use in the LNG vaporization section 42. In the LNG vaporization section 42, heat exchange occurs between the liquefied natural gas 41 and the medium 20, causing the liquefied natural gas 41 to vaporize and produce fuel gas 43 consisting of natural gas, while the medium 20 is cooled. The medium 20 contains CO2 containing ammonium salts in the heat exchanger 22. ２ By exchanging heat with the absorber 34, CO ２ It is used to cool the absorber 34. The fuel gas 43 is supplied to the combustor 44, mixed with oxygen in the air, and used as fuel.

[0039] The ammonia gas 32 obtained by vaporizing the liquid ammonia 31 is mixed with water in the mixing unit 23. This results in CO ２ An ammonia-containing material that will become the absorber 33 is prepared. ２ If the ammonia concentration in the absorber 33 is high, a higher concentration aqueous solution of ammonia salt can be obtained. On the other hand, if the solubility exceeds CO ２ If ammonia salts precipitate in the removal section 24, it is undesirable because it obstructs the flow of the gas to be treated and ammonia. Also, CO ２If the ammonia concentration in the absorber 33 is low, CO ２ The concentration of ammonia salts that can be produced by absorbing CO decreases, the recovery rate of ammonia salts in the crystallization process decreases, and CO ２ This is undesirable because it reduces the recovery rate of CO. ２ The ammonia concentration in the absorber 33 is preferably 3% by mass or more and 15% by mass or less. ２ If the ammonia concentration in the absorber 33 is high, the ammonia concentration in the emitted gas 13 will increase, potentially leading to environmental problems and health hazards caused by ammonia. From the above perspective, CO ２ The ammonia concentration in the absorbent material 33 should preferably be 10% by mass or less.

[0040] The water mixed with ammonia gas 32 may be the liquid 36 remaining after the ammonium salt 35 has been precipitated in the crystallization section 26. As the mixing section 23, a device for dissolving gas in a liquid can be used, such as a mixer. The water used in the liquid 36 may be the water remaining after the mixing section 23, CO ２ The material can be circulated within a loop including the removal section 24, the crystallization section 26, etc., and may be replenished or replaced periodically or irregularly as needed.

[0041] CO2 containing ammonia ２ The absorber 33 is CO ２ It is supplied to the removal unit 24 and comes into contact with the gas to be treated 11. This removes CO from the gas to be treated 11. ２ The absorbent 33 reacts with the CO2 in the gas to be treated 11. ２ The CO2 is converted into an ammonium salt aqueous solution, and the gas to be treated 11 is converted to CO2. ２ It can be removed.

[0042] CO2 per unit time ２ CO supplied to the removal unit 24 ２ The amount of molars is CO2 per unit time. ２ More than 1 times and less than 5 times the molar amount of ammonia supplied to the removal unit 24 (1 < CO ２ / NH ３ It is desirable to set it to ≤5). The ammonium salt produced is CO per unit weight ２Ammonium bicarbonate (CO2) accounts for a high proportion of CO2. ２ / NH ３ It is desirable to generate more of =1), but CO ２ When the molar amount of ammonium carbonate (CO2) in the product becomes less than 1, ２ / NH ３ This is because the proportion of (=0.5) increases. Also, CO ２ The molar amount of CO should preferably be 5 times or less the molar amount of ammonia. ２ When the molar amount exceeds five times, CO ２ In the removal section, solid carbonates exceeding the solubility limit may form, resulting in liquid CO2. ２ This is undesirable because it hinders the supply of the absorbent 33.

[0043] CO ２ The removal unit 24 is liquid CO ２ Any device that brings the absorbent 33 into contact with the gas to be treated 11 is acceptable. For example, CO can be absorbed by spraying from a sprayer, injecting from a nozzle, etc. ２ The absorbent 33 is in the form of a liquid droplet, liquid column, or liquid film, CO ２ It is preferable to increase the surface area of ​​the absorber 33.

[0044] CO ２ In the removal section 24, with respect to the flow direction of the gas to be treated 11, CO ２ It is preferable to have the flow directions of the absorbers 33 and 34 in opposite directions. ２ CO from the top of the removal section 24 ２ The CO after the absorber 33 is supplied and brought into contact with the gas to be treated 11 ２ absorber 34 is CO ２ The material may be recovered from the lower part of the removal section 24.

[0045] CO ２ The removal unit 24 may be arranged in multiple stages along the passage line of the gas to be treated 11, which will be described in more detail later. ２ When the removal section 24 is arranged in series, CO2 is released between the mixing section 23 and the crystallization section 26. ２ Absorbers 33 and 34 may be connected in parallel. Alternatively, a multi-stage CO2 system may be connected in series. ２CO2 is released between the mixing section 23 and the crystallization section 26 with respect to the removal section 24. ２ The absorbers 33 and 34 may be connected in series.

[0046] CO ２ CO after passing through the removal section 24 ２ The absorber 34 contains an ammonium salt. As described above, the ammonium salt 35 is precipitated by cooling using the cold temperature of the medium 20. The ammonium salt 35 precipitates and is recovered as a solid crystal from the crystallization section 26. The liquid 36 after the separation of the ammonium salt by the crystallization process is the CO2 after crystallization. ２ This is the supernatant liquid derived from the absorber 34. As described above, by dissolving ammonia gas 32 in the liquid 36, a CO2 containing ammonia is produced. ２ The absorbent material 33 is prepared.

[0047] In the example shown in Figure 1, CO ２ A pre-cooler 25 is positioned between the removal section 24 and the crystallization section 26. In the pre-cooler 25, CO2 containing ammonium salts is removed. ２ CO is released through heat exchange between the absorber 34 and the cooling water 25a. ２ The temperature of the absorber 34 can be cooled. Cooling in the precooler 25 is CO ２ It is preferable that the ammonium salt dissolved in the absorbent 34 does not precipitate in the pipes or other pathways. Examples of cooling water 25a include seawater, river water, lake water, industrial water, etc.

[0048] When the manufacturing apparatus and manufacturing method of this embodiment are carried out in a place where seawater is easily available, such as a coast, the sea, the seabed, or a ship, the precooler 25 contains CO2 in the crystallization process. ２ It is preferable to use seawater as the cold source for pre-cooling the absorber 34. ２ The cooling water 25a after pre-cooling the absorbent 34 may be released into the environment, such as oceans, rivers, lakes, and drainage channels.

[0049] Next, the operation of the manufacturing apparatus 101 will be explained along the flow of the gas to be processed 11. In the figure, the gas flow originating from the gas to be processed 11 is shown by a dashed line.

[0050] As described above, the gas to be treated 11 is CO ２CO2 emitted from an emission source (not shown) ２ It is a contained gas. In particular, if the gas to be treated 11 is exhaust gas produced by combustion, the gas is at a high temperature, and CO ２ It also contains other components that need to be removed. Therefore, the gas to be treated 11 is CO ２ It is preferable to perform an appropriate pre-treatment step before processing in the removal section 24.

[0051] In the manufacturing apparatus 101 shown in Figure 1, a scrubber 10 is provided to remove acidic components such as sulfur oxides (SOx) and nitrogen oxides (NOx), as well as particulate matter (PM) such as soot and dust. The scrubber 10 in the illustrated example is a wet scrubber that takes in washing water 10a to wash the gas to be treated 11. Examples of washing water 10a include seawater, river water, lake water, and industrial water.

[0052] When the washing water 10a is brought into contact with the gas to be treated 11 in the scrubber 10, acidic components, particulate components, etc. in the gas to be treated 11 are dissolved or dispersed in the washing water 10a and removed. The washing wastewater 10b containing acidic components, particulate components, etc. may be treated as appropriate if necessary and then discharged into the environment such as oceans, rivers, lakes, drainage channels.

[0053] The gas to be treated 11 after passing through the scrubber 10 continues to be treated with CO ２ This includes CO. Also, if the gas to be treated 11 originates from a high-temperature gas such as exhaust gas, it may remain at a considerably high temperature even after passing through the scrubber 10. On the other hand, if the gas to be treated 11 is CO ２ The gas 12 that has passed through the removal section 24 is CO ２ CO is removed ２ It may contain unreacted components of the ammonia used for removal.

[0054] In the manufacturing apparatus 101 shown in Figure 1, CO ２ An ammonia desorption unit 14 is provided prior to the removal unit 24, and CO ２An ammonia recovery unit 15 is provided downstream of the removal unit 24. A path such as piping is provided between the ammonia desorption unit 14 and the ammonia recovery unit 15, through which circulating water 16 can be circulated. A pump or the like (not shown) can be used to transport the circulating water 16 as needed. A blower or the like (not shown) can be used to transport the gas to be treated 11 or the gas in the process of being treated 12 as needed.

[0055] In order to separate ammonia from the intermediate gas 12 described above, the ammonia recovery unit 15 performs an ammonia recovery process in which the intermediate gas 12 is brought into contact with water. The gas after ammonia has been separated from the intermediate gas 12 becomes a release gas 13 that can be released into the atmosphere. The release gas 13 can be released into the atmosphere from the top of the ammonia recovery unit 15 through an appropriate chimney, outlet, etc.

[0056] The water after ammonia recovery can be treated as appropriate, but in the illustrated example, the water used in the ammonia recovery process is circulated as circulating water 16 between the ammonia desorption unit 14 and the ammonia recovery unit 14, thereby reducing the frequency of wastewater treatment. The water used in the circulating water 16 may be replenished or replaced periodically or irregularly as needed.

[0057] The circulating water 16 that comes into contact with the gas 12 during processing absorbs ammonia and collects at the bottom of the ammonia recovery unit 15, and is then transported to the top of the ammonia desorption unit 14. In the ammonia desorption unit 14, the circulating water 16 containing ammonia is treated with CO ２ The circulating water 16 is heated by contact with the gas 11 to be treated before it passes through the removal section 24. As a result, ammonia contained in the circulating water 16 is desorbed and released into the gas phase (the gas 11 to be treated).

[0058] In the ammonia desorption step, in which ammonia is desorbed from the circulating water 16, it is preferable to raise the temperature to 70°C or higher because this promotes the desorption of ammonia. Note that the decomposition temperature of ammonium bicarbonate (the decomposition product is NH ３ +CO ２ +H ２ O) has a temperature of 58°C in solid form and 70°C in aqueous solution, and free NH ３ In addition to detaching NH ３ CO ２It is preferable to thermally decompose the ammonium salt formed by the combination with the other substance and remove it from the circulating water 16.

[0059] The gas to be treated 11, which contains ammonia, releases CO from the upper part of the ammonia desorption unit 14. ２ It is transported to the removal section 24. After the ammonia is released into the gas phase, the circulating water 16 collects at the bottom of the ammonia desorption section 14 and is then transported again to the top of the ammonia recovery section 15.

[0060] In order to separate ammonia from the gas 12 in the process of treatment by contact with the circulating water 16 in the ammonia recovery unit 15, it is preferable to lower the temperature of the circulating water 16 so that the solubility of ammonia increases. For example, the circulating water 16 may be cooled by heat exchange with cooling water 25a, as in the precooler 25 described above.

[0061] Furthermore, the cold energy from the crystallization process described above may be used to cool the water used in the ammonia recovery process. In the example shown in Figure 1, a heat exchanger 17 for cooling circulating water is provided between the circulating water 16 and the medium 20 to cool the circulating water 16 used in the ammonia recovery process. As described above, the medium 20 carries cold energy from the vaporization of liquid ammonia 31 or liquefied natural gas 41 in order to promote the precipitation of ammonium salt 35 in the crystallization process. In the heat exchanger 17 for cooling circulating water, the circulating water 16 is cooled using the cold energy carried by the medium 20. Note that in Figure 1, the transport path of the medium 20 between the heat exchanger 17 for cooling circulating water and the heat exchanger 22 of the crystallization section 26 is not shown.

[0062] <Details of the crystallization section and crystallization process> The crystallization section and crystallization process involve a liquid phase CO2 containing an ammonium salt. ２ The absorber 34 is used to precipitate crystals of ammonium salt 35 as a solid phase, CO ２ Appropriate apparatus and methods can be used depending on the temperature of the absorber 34 and the solubility of the ammonium salt 35. As described above, since cooling can be obtained using liquid ammonia 31, liquefied natural gas 41, cooling water 25a, etc., the manufacturing method 101 of this embodiment mainly uses a cooling method.

[0063] Using cold energy to CO ２ When cooling the absorber 34, CO２ The cooling conditions, such as the cooling area and temperature gradient, that the absorber 34 receives can be set as appropriate.

[0064] Next, an example of a crystallization section will be described with reference to Figure 2. The crystallization section 26 shown in Figure 2 comprises an upper section 26a where ammonium salt nucleation takes place, an intermediate section 26b where crystals grow and settle, and a lower section 26c that separates the settled crystals from the dilute supernatant. This type of apparatus is generally known as the Crystal Oslo type.

[0065] A heat exchanger 22 is positioned in the upper part 26a of the crystallization section 26, and CO2 containing ammonium salts is also provided. ２ The absorber 34 is supplied. The medium 20 that carries cold energy and CO2 are supplied via the heat exchanger 22. ２ Heat exchange occurs between the absorber 34 and CO ２ The absorber 34 is cooled. ２ As the temperature of the absorber 34 decreases, crystalline nuclei of the ammonium salt are formed. As the crystalline nuclei grow, they sink from the upper part 26a, through the middle part 26b, to the lower part 26c.

[0066] In the lower part 26c of the crystallization section 26, the crystals of the ammonium salt 35 are separated, and CO ２ The liquid 36, after the ammonium salt 35 has been separated from the absorbent 34, is transported to the mixing unit 23 described above.

[0067] Next, with reference to Figure 3, another example of a crystallization unit will be described. This crystallization unit 50 includes a crystallization apparatus 51 for crystallizing ammonium salt, a pump 52 for pumping a slurry 37 in which ammonium salt crystals are mixed with liquid, and a crystal separator 53 for separating crystals from the slurry 37.

[0068] The crystallization apparatus 51 is equipped with a heat exchanger 22, and also contains CO2 containing ammonium salts. ２ The absorber 34 is supplied. The medium 20 that carries cold energy and CO2 are supplied via the heat exchanger 22. ２ Heat exchange occurs between the absorber 34 and CO ２ The absorber 34 is cooled. ２ As the absorber 34 cools, ammonium salt crystals are formed and grow.

[0069] When ammonium salt crystals accumulate in the crystallizer 51, the slurry 37 is transported to the crystal separator 53 using the pump 52. In the crystal separator 53, the ammonium salt 35 crystals are separated from the slurry 37, and CO ２ The liquid 36, after the ammonium salt 35 has been separated from the absorbent 34, is transported to the mixing unit 23 described above.

[0070] Examples of crystal separators 53 include solid-liquid separators using gravity (natural sedimentation), solid-liquid separators using centrifugal separation (centrifugal sedimentation), and solid-liquid separators using filtration. The solid-liquid separator using filtration may also use a pressurized filtration system or a centrifugal filtration system.

[0071] The timing of transporting the slurry 37 from the crystallizer 51 by the pump 52 is not particularly limited and can be set as appropriate. The slurry 37 may be transported in small amounts so that crystallization in the crystallizer 51 is continuous. Alternatively, all or most of the accumulated slurry 37 may be transported at once so that crystallization in the crystallizer 51 is batch-type. The method of the crystal separator 53 is also not limited to continuous or batch-type and can be set as appropriate.

[0072] Next, CO ２ The preferred operating conditions for the removal and crystallization processes are described below. The amount of ammonium bicarbonate that dissolves in 1 L of water under atmospheric pressure is 592 g at 60°C and 161 g at 10°C. It is known that aqueous solutions of ammonium bicarbonate decompose into ammonia and carbon dioxide at 70°C. It is preferable to absorb as much carbon dioxide as possible below this decomposition temperature, and then cool the resulting aqueous solution of ammonium bicarbonate to form ammonium bicarbonate crystals. ２ CO2 absorption ２ The temperature of the absorber 33 is preferably 60°C or lower. Also, the CO2 during crystallization ２ The temperature of the absorber 34 is preferably 10°C or higher, and it is desirable that it decreases from the high-temperature side to the low-temperature side within the range of 10°C to 60°C.

[0073] CO ２When the temperature of the absorber 33 exceeds 60°C, some of the ammonium bicarbonate begins to decompose, preventing the concentration of ammonium bicarbonate in the aqueous solution from increasing. Furthermore, if crystallization occurs below 10°C, the surface temperature of the heat exchanger 22 falls below 0°C, making it easier for solidified aqueous solution material to adhere, significantly reducing the cooling efficiency. Also, CO ２ An increase in the temperature of the absorber 33 leads to a decrease in the ammonia concentration in the aqueous solution and a corresponding increase in the ammonia concentration in the emitted gas 13, thus CO ２ CO2 absorption ２ The temperature of the absorber 33 is more preferably 50°C or lower. Also, since the necessary cooling is supplied solely by the vaporization of liquid ammonia 31, CO2 during crystallization is preferable. ２ The temperature of the absorber 34 is more preferably 15°C or higher.

[0074] More CO per unit volume ２ For storage, it is desirable to separate the ammonium salt crystals and obtain crystals with minimal liquid adhesion. Generally, the larger the size of the ammonium salt crystals formed, the less liquid adheres to them. For example, when transporting a slurry containing ammonium salt crystals with a pump, it is desirable that the average particle size of the crystals be in the range of 0.1 mm to 10 mm. If the average particle size is less than 0.1 mm, the amount of liquid adhesion cannot be sufficiently reduced, and if the average particle size exceeds 10 mm, the crystals become brittle, and the broken crystals may obstruct the pump's sealing system, hindering the transport of the slurry.

[0075] More CO per unit volume ２ From the perspective of storage, a small coefficient of variation (CV) of crystal size is desirable. Here, CV is the value obtained by dividing the standard deviation σ, which is the square root of the variance, by the mean value μ. On the other hand, if this coefficient of variation is too small, the crystals are likely to dry out and form solidified bodies, which may make it difficult to remove them from storage. From this perspective, a CV value of 5 to 30% in percentage is preferable, and 10 to 25% is even more preferable.

[0076] <Second Embodiment> Figure 4 is a diagram illustrating an ammonium salt production apparatus according to the second embodiment. In the second embodiment, the ammonia gas 32 generated by the vaporization of liquid ammonia 31 and the liquid 36 after the ammonium salt 35 has been separated are separately CO ２ It is transported to the removal section 24. ２ Inside the removal section 24, CO2 containing ammonia gas and water is released. ２ An absorbent can be prepared.

[0077] The method for producing an ammonium salt according to the second embodiment generally comprises: (1) an ammonia vaporization step, (2) a cold energy recovery step, and (3) ammonia gas and water CO ２ The process of transporting to the removal process, and (4) CO ２ The process includes a removal step and (5) a crystallization step.

[0078] (1) The ammonia vaporization process is a process in which liquid ammonia 31 is vaporized to produce ammonia gas 32. (2) The cold energy recovery process is a process in which the cold energy associated with the vaporization of liquid ammonia 31 is recovered in the heat exchanger 22. (3) The ammonia gas 32 and water are converted to CO ２ The process of transporting to the removal process involves separating the ammonia gas 32 and the liquid 36 after the ammonium salt 35 has been separated into CO2 ２ This is the process of transporting to the removal section 24. (4) CO ２ The removal process involves reacting the gas to be treated 11 with ammonia in the presence of water, thereby removing CO from the gas to be treated 11. ２ Convert to an ammonium salt aqueous solution and CO ２ This is the process of removing CO. ２ CO after passing through the removal process ２ This step involves cooling the absorbent 34 using the cold energy generated by the vaporization of liquid ammonia 31 to precipitate the ammonium salt 35.

[0079] The ammonium salt production apparatus 102 according to the second embodiment generally comprises (1) an ammonia vaporization section 21, (2) a heat exchanger 22, and (3) ammonia gas 32 and water CO ２ A configuration for transporting to the removal unit 24, and (4) CO ２ It has a removal section 24 and (5) a crystallization section 50.

[0080] (1) The ammonia vaporization unit 21 vaporizes liquid ammonia 31 to produce ammonia gas 32. (2) The heat exchanger 22 recovers the cooling energy associated with the vaporization of liquid ammonia 31. (3) The ammonia gas 32 and water are converted to CO2. ２ The configuration for transporting to the removal unit 24 involves separating the ammonia gas 32 and the liquid 36 after the ammonium salt 35 has been separated into CO ２ Transport to the removal section 24. (4) CO ２ The removal unit 24 reacts the gas to be treated 11 with ammonia in the presence of water, thereby removing CO from the gas to be treated 11. ２ Convert to an ammonium salt aqueous solution and CO ２ Remove the following. (5) The crystallized part 50 is CO ２ CO after passing through the removal section 24 ２ The absorbent 34 is cooled using the cold energy generated by the vaporization of liquid ammonia 31 to precipitate the ammonium salt 35.

[0081] First, the CO in the gas to be treated 11 ２ The operation of the manufacturing apparatus 102 when recovering the ammonium salt 35 produced by absorbing the ammonium salt will be explained, focusing on the differences from the manufacturing apparatus 101 shown in Figure 1 above.

[0082] In the manufacturing apparatus 102 shown in Figure 4, the ammonia vaporization section 21 and the LNG vaporization section 42 are provided integrally with the heat exchanger 22. In this case, the medium 20 shown in Figure 1 is omitted, and liquid ammonia 31 or liquefied natural gas 41 is directly vaporized with CO2. ２ The absorbent 34 may be used for heat exchange. Also, although not specifically shown, a medium 20 that carries cold energy may be circulated between the ammonia vaporization section 21 and the LNG vaporization section 42 and the heat exchanger 22, similar to the manufacturing apparatus 101 shown in Figure 1.

[0083] In the manufacturing apparatus 102 shown in Figure 4, the crystallization section 50 includes a crystallizer 51, a pump 52, and a crystal separator 53, similar to those shown in Figure 3. The liquid 36 from the crystallization section 50 (more specifically the crystal separator 53) is separated from the ammonia gas 32 from the ammonia vaporization section 21 by CO2 ２It is supplied to the removal section 24. The crystallization section used in the manufacturing apparatus 102 is not particularly limited, and other apparatus configurations such as the crystallization section 26 shown in Figure 2 may be used.

[0084] The liquid 36 containing ammonia gas 32 and water is CO ２ It is supplied to the removal unit 24 and comes into contact with the gas to be treated 11. This causes the gas to be treated 11 to react with ammonia, and the CO in the gas to be treated 11 is removed. ２ The CO2 is converted into an ammonium salt aqueous solution, and the gas to be treated 11 is converted to CO2. ２ CO can be removed. ２ The details of the removal unit 24 can be configured in the same way as in the first embodiment. The same applies to the precooler 25 which is positioned before the crystallization unit 50. The water used in the liquid 36 is CO ２ It can be circulated within a loop including the removal unit 24, crystallization apparatus 51, crystal separator 53, etc., and may be replenished or replaced periodically or irregularly as needed.

[0085] Next, the operation of the manufacturing apparatus 102 will be described along with the flow of the gas to be processed 11. The gas to be processed 11 and the ammonia desorption unit 14 may be the same as in the first embodiment. In Figure 4, the scrubber 10 is not shown, but as in Figure 1, the scrubber 10 may be provided before the ammonia desorption unit 14. The circulating water 16 that circulates between the ammonia desorption unit 14 and the ammonia recovery unit 15 may also be generally the same as in the first embodiment. In the ammonia recovery unit 15, ammonia can be sufficiently separated from the gas 12 in the process of processing by contact with the circulating water 16 and then released into the atmosphere as the released gas 13.

[0086] In the example shown in Figure 4, in the heat exchanger 17 for circulating water cooling shown in Figure 1, the liquid 36 after the ammonium salt 35 has been separated is used for heat exchange instead of the medium 20 that carries the cold. Since the temperature of the liquid 36 is sufficiently low, it can cool the circulating water 16. For example, if the temperature of the liquid 36 transported to the heat exchanger 17 for circulating water cooling is about 5°C, the circulating water 16 after passing through the heat exchanger 17 can be cooled to about 10°C.

[0087] <Third Embodiment> Figure 5 is a diagram illustrating an ammonium salt production apparatus according to the third embodiment. In the production apparatus 103 of the third embodiment, instead of omitting the heat exchanger 17 for circulating water cooling, the liquid 36 after the ammonium salt 35 has been separated in the crystallization section 50 passes through the ammonia recovery section 15, and the liquid 36 after passing through is again treated with the above CO ２ Except for being supplied to the removal section 24, it is configured in the same way as the manufacturing apparatus 102 of the second embodiment.

[0088] In the third embodiment of the method for producing ammonium salt, the liquid 36 after the separation of the ammonium salt 35 by the crystallization step passes through the ammonia recovery step, and the liquid 36 after passing through is again treated with the CO2. ２ The manufacturing method is the same as that according to the second embodiment, except that it is supplied to the removal process.

[0089] The circulating water 16 that circulates between the ammonia desorption unit 14 and the ammonia recovery unit 15 can also be substantially the same as in the first and second embodiments. In the example shown in Figure 5, instead of omitting the heat exchanger 17 for cooling the circulating water, the liquid 36 after the ammonium salt 35 has been separated by the crystallization process is supplied directly to the ammonia recovery unit 15.

[0090] Within the ammonia recovery unit 15, the liquid 36 may be mixed with the circulating water 16. A portion of the mixture of circulating water 16 and liquid 36 is supplied as circulating water 16 from the ammonia recovery unit 15 to the ammonia desorption unit 14. The remaining portion of the mixture is supplied as liquid 36 from the ammonia recovery unit 15 to the CO2 desorption unit 14. ２ It is supplied to the removal unit 24.

[0091] By supplying liquid 36 to the ammonia recovery unit 15, the circulating water 16 transported from the ammonia recovery unit 15 to the ammonia desorption unit 14 can be cooled. In the ammonia recovery unit 15, ammonia can be sufficiently separated from the gas 12 in the process of treatment by contact with the circulating water 16 or liquid 36 before being released into the atmosphere as the release gas 13.

[0092] Although the present invention has been described above based on preferred embodiments, the present invention is not limited to the embodiments described above, and various modifications are possible without departing from the spirit of the invention. Modifications include adding, substituting, omitting, or otherwise changing the components in each embodiment. It is also possible to combine components used in two or more embodiments as appropriate.

[0093] According to the present invention, CO ２ Remove the captured CO ２ We can provide a method for producing ammonium salts and an apparatus for producing ammonium salts that can utilize the aforementioned technology.

[0094] 10... Scrubber, 10a... Washing water, 10b... Washing wastewater, 11... Gas to be treated, 12... Gas in the process of treatment, 13... Released gas, 14... Ammonia desorption section, 15... Ammonia recovery section, 16... Circulating water, 17... Heat exchanger for cooling circulating water, 20... Medium, 21... Ammonia vaporization section, 22... Heat exchanger, 23... Mixing section, 24... CO ２ Removal section, 25... Pre-cooler, 25a... Cooling water, 26, 50... Crystallization section, 26a... Upper part of crystallization section, 26b... Middle part of crystallization section, 26c... Lower part of crystallization section, 31... Liquid ammonia, 32... Ammonia gas, 33, 34... CO ２ Absorber, 35... Ammonium salt, 36... Liquid, 37... Slurry, 41... Liquefied natural gas, 42... LNG vaporizer, 43... Fuel gas, 44... Combustor, 51... Crystallization apparatus, 52... Pump, 53... Crystal separator, 101, 102, 103... Manufacturing equipment.

Claims

1. A process of vaporizing liquid ammonia to produce ammonia gas, a process of recovering the cold energy associated with the vaporization of the liquid ammonia using a heat exchanger, and CO ２ CO2 emissions from the source ２ The gas to be treated, which includes the above ammonia gas and water containing CO2, is treated as follows: ２ By reacting with the absorber, the CO in the gas to be treated is ２ Convert to an ammonium salt aqueous solution and CO ２ CO2 removal ２ Removal process and CO ２ CO after passing through the removal process ２ A method for producing an ammonium salt, characterized by comprising a crystallization step of cooling an absorbent using the cold energy generated by the vaporization of the above-mentioned liquid ammonia to precipitate an ammonium salt containing ammonium carbonate, ammonium bicarbonate, or ammonium carbamate.

2. The method for producing an ammonium salt according to claim 1, characterized in that the heat of vaporization of liquefied natural gas is also used as the above-mentioned cooling method.

3. The above CO ２ CO in the removal process ２ The method for producing an ammonium salt according to claim 1, characterized in that the temperature of the absorber is 60°C or lower.

4. CO in the crystallization process described above ２ A method for producing an ammonium salt according to claim 1, characterized in that the temperature of the absorber is 10°C or higher.

5. The above CO ２ CO supplied to the removal process ２ A method for producing an ammonium salt according to claim 1, characterized in that the ammonia concentration in the absorbent is 3% by mass or more and 15% by mass or less.

6. The above CO ２ CO in the treated gas supplied per unit time to the removal process ２ The molar amount of the above CO ２ The above CO supplied per unit time to the removal process ２ Ratio of molar amount of ammonia in the absorber (CO ２ / NH ３ A method for producing an ammonium salt according to claim 1, characterized in that the coefficient of the coefficient is greater than 1 and less than or equal to 5.

7. The method for producing an ammonium salt according to claim 1, characterized in that the average particle size of the ammonium salt produced in the crystallization step is 0.1 mm or more and 10 mm or less.

8. The method for producing an ammonium salt according to claim 1, characterized in that the coefficient of variation (CV) of the particle size of the ammonium salt produced in the crystallization step is 3% or more and 30% or less.

9. The method for producing an ammonium salt according to claim 1, characterized in that seawater is also used as the cold water.

10. The method for producing an ammonium salt according to claim 1, characterized in that a mixture of a polyhydric alcohol and water is circulated through a heat exchanger as a medium for transporting the above-mentioned cold and heat.

11. The above CO ２ A method for producing an ammonium salt according to claim 1, further comprising an ammonia recovery step in which the gas to be treated after passing through the removal step is brought into contact with water to separate ammonia from the gas to be treated.

12. The method for producing an ammonium salt according to claim 11, characterized in that the water used in the ammonia recovery step is cooled using the medium that carries the cold and heat described above.

13. The liquid remaining after the separation of the ammonium salt by the crystallization process is passed through the ammonia recovery process, and the liquid remaining after passing through is then subjected to the CO2 recovery process again. ２ A method for producing an ammonium salt according to claim 11, characterized by supplying it to a removal process.

14. The above CO ２ A method for producing an ammonium salt according to claim 11, further comprising an ammonia desorption step in which the gas to be treated before passing through the removal step is brought into contact with water used in the ammonia recovery step to desorb ammonia from the water into the gas to be treated.

15. A method for producing an ammonium salt according to any one of claims 1 to 14, characterized by adding water to the ammonium salt produced in the crystallization step and dissolving it, and transporting the dissolved ammonium salt by pump.

16. An ammonia vaporization unit that vaporizes liquid ammonia to produce ammonia gas, a heat exchanger that recovers the cold energy associated with the vaporization of the liquid ammonia, and CO ２ CO2 emissions from the source ２ The gas to be treated, which includes the above ammonia gas and water containing CO2, is treated as follows: ２ By reacting with the absorber, the CO in the gas to be treated is ２ Convert to an ammonium salt aqueous solution and CO ２ CO2 removal ２ Removal section and CO ２ CO after passing through the removal section ２ An apparatus for producing ammonium salts, characterized by having a crystallization section that cools an absorbent using the cold energy generated by the vaporization of the above-mentioned liquid ammonia to precipitate ammonium salts containing ammonium carbonate, ammonium bicarbonate, or ammonium carbamate.

17. The above CO ２ The ammonium salt production apparatus according to claim 16, further comprising an ammonia recovery unit that separates ammonia from the gas to be treated by bringing the gas to be treated after it has passed through the removal unit into contact with water.

18. The above CO ２ The apparatus for producing an ammonium salt according to claim 17, further comprising an ammonia desorption unit that brings the gas to be treated before it passes through the removal unit into contact with water used in the ammonia recovery unit, thereby desorbing ammonia from the water into the gas to be treated.

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