Title of invention: Fertilizer production plant and fertilizer production method
Technical field
[0001]
　The present disclosure relates to a fertilizer production plant and a method for producing fertilizer.
Background technology
[0002]
　Techniques for producing fertilizer using methane-containing gas such as natural gas are known. In this technique, first, hydrogen or the like is produced by reforming a methane-containing gas, and for example, ammonia is produced from nitrogen in the air and the produced hydrogen. Then, an aqueous urea solution is produced from the produced ammonia. Then, urea is granulated using the produced urea aqueous solution to produce fertilizer.
[0003]
　Off-gas containing ammonia is generated during the production of fertilizer, for example, during urea granulation. Therefore, the generated off-gas is released into the atmosphere after being treated with exhaust gas. The technique described in Patent Document 1 is known as a technique for treating a gas containing ammonia. Patent Document 1 describes a sulfuric acid scrubber for bringing an aqueous sulfuric acid solution into contact with a gas containing ammonia (see particularly FIG. 1). In scrubber sulfate, ammonium sulfate (ammonium sulfate) is produced by contact of an aqueous sulfuric acid solution with a gas containing ammonia. This removes ammonia in the off-gas.
Prior art literature
Patent documents
[0004]
Patent Document 1: US Pat. No. 9,464,009
Outline of the invention
Problems to be solved by the invention
[0005]
　The ammonium sulfate aqueous solution produced by the ammonia treatment in off-gas can usually be granulated and used as fertilizer. However, additional installation costs are required for the addition of ammonium sulfate granulation equipment. In addition, since a sulfuric acid aqueous solution is used in the sulfuric acid scrubber, maintenance is complicated. Therefore, there is a demand for a simple treatment technique that does not generate ammonium sulfate for off-gas containing ammonia.
[0006]
　One embodiment of the present invention aims to provide a fertilizer production plant and a method for producing fertilizer, which can easily treat off-gas containing ammonia without producing ammonium sulfate.
Means to solve problems
[0007]
　(1) The fertilizer production plant according to the embodiment of the present invention is a fertilizer production plant
　for producing fertilizer containing urea, and is
　a urea production apparatus for producing the urea using ammonia and the
　fertilizer. A scrubber having an internal space for bringing an off-gas of a production plant, which contains ammonia, into contact with an
　acidic absorbing liquid is provided, and the acidic absorbing liquid contains carbon dioxide
　.
[0008]
　According to the configuration of (1) above, ammonia in off-gas can be absorbed by using an acidic absorbing liquid containing carbonic acid that is easy to handle. As a result, ammonia in the off-gas can be removed without generating ammonium sulfate, and the off-gas generated in the fertilizer production plant can be easily treated.
[0009]
　(2) In some embodiments, in the configuration of (1) above
　, a reformer for reforming a methane-containing gas and
　a carbon dioxide recovery device for recovering carbon dioxide generated in the reformer. When,
　a carbonate production apparatus for producing the carbonate using the recovered the carbon dioxide
　comprises
　, characterized in that.
[0010]
　According to the configuration of (2) above, the above acidic absorption liquid can be produced by using carbon dioxide produced by reforming a methane-containing gas such as natural gas.
[0011]
　(3) In some embodiments, in the above configuration (2),
　a compressor for a recovered the carbon dioxide is pressurized carbon dioxide supplied to the urea production unit,
　boosted in the compressor A first carbon dioxide supply system for supplying the carbon dioxide produced to the urea production apparatus, and a
　second carbon dioxide supply system for supplying the carbon dioxide boosted by the compressor to the carbon dioxide production apparatus. ,
　comprises
　wherein the.
[0012]
　According to the configuration of (3) above, the boosted carbon dioxide can be supplied to both the urea production apparatus and the carbonic acid production apparatus. As a result, it is not necessary to separately provide a compressor for carbonic acid production, and the installation area of ​​the compressor can be reduced. Moreover, since carbonic acid can be produced from carbon dioxide after pressurization, the amount of carbonic acid produced can be increased.
[0013]
　(4) In some embodiments, in the configuration of (2) or (3)
　above, the carbonic acid producing apparatus includes a microbubble generator for producing the carbonic acid by dissolving carbon dioxide in water.
　It is characterized by that.
[0014]
　According to the configuration of (4) above, the existence time of carbonic acid in water can be extended.
[0015]
　(5) In some embodiments, in the configuration of any one of (1) to (4)
　above, ammonium carbonate for supplying the acidic absorption liquid after the off-gas contact with the scrubber to the urea production apparatus.
　It is characterized by having a supply system .
[0016]
　According to the configuration of (5) above, ammonium carbonate contained in the acidic absorption liquid after off-gas contact can be used as a raw material for urea production.
[0017]
　(6) In some embodiments, in any one of the
　above configurations (1) to (5), the fertilizer production plant comprises a solid content removing scrubber for removing solid content in the off-gas.
　The scrubber is arranged on the downstream side of the solid content removing scrubber in the flow direction of the off-gas
　.
[0018]
　According to the configuration of (6) above, the solid content contained in the off-gas of the fertilizer production plant can be removed. Then, the ammonia in the off-gas after removing the solid content can be removed from the off-gas by the scrubber.
[0019]
　(7) In some embodiments, in the configuration of (6) above,
　an acidic absorption liquid supply system for supplying the acidic absorption liquid after the off-gas contact with the scrubber to the solid content removing scrubber is provided
　. It is a feature.
[0020]
　According to the configuration of (7) above, the acidic absorbing liquid after the off-gas contact can be supplied to the solid content removing scrubber. As a result, even if the water content of the solid content removing scrubber is reduced by evaporation, the water content of the solid content removing scrubber can be recovered. As a result, it is possible to reduce the amount of new water used from the outside for the recovery of the water content in the solid content removing scrubber.
[0021]
　(8) In some embodiments, in the configuration of (6) or (7)
　above, the fertilizer production plant
　supplies urea aqueous solution produced by the urea production apparatus to the solid content removing scrubber. It is characterized by including an aqueous solution supply system and
　a urea aqueous solution return system for returning the urea aqueous solution after the off-gas contact with the solid content removing scrubber to the urea production apparatus
　.
[0022]
　According to the configuration of (8) above, the solid content in the off-gas can be removed by using the urea aqueous solution produced by the urea production apparatus. As a result, the amount of new water used from the outside for removing solid content can be reduced. In addition, the fertilizer production plant can produce fertilizer using the urea aqueous solution returned from the solid content removing scrubber.
[0023]
　(9) In some embodiments, in any one of the above (6) to (8), the
　solid content removing scrubber and the solid content removing scrubber are integrally formed above the solid content removing scrubber. It is
　characterized by including an integrated scrubber provided with the scrubber .
[0024]
　According to the configuration (9) above, since the scrubber can be integrally formed with the solid content removing scrubber above the solid content removing scrubber, the installation area of ​​the scrubber can be reduced.
[0025]
　(10) In some embodiments, in the configuration of any one of (1) to (9) above, a
　combustor for burning fuel and
　carbon dioxide generated in the combustor are transferred to the inside of the scrubber.
　It is characterized by including a third carbon dioxide supply system for supplying to the space .
[0026]
　According to the configuration (10) above, it is possible to increase the partial pressure of carbon dioxide in the gas phase in the internal space for bringing the off-gas into contact with the acidic absorption liquid. As a result, it is possible to suppress the release of carbon dioxide from the acidic absorption liquid into the gas phase, and it is possible to prolong the existence time of carbonic acid in the acidic absorption liquid.
[0027]
　(11) In some embodiments, in the configuration of (10) above, the
　fertilizer production plant comprises a reformer for reforming the methane-containing gas, and the reformer
　is in the combustor.
　It is characterized in that it is configured to reform the methane-containing gas by using the heat generated by the combustion of the fuel .
[0028]
　According to the configuration of (11) above, methane-containing gas such as natural gas can be reformed by using the heat generated by the combustion of fuel.
[0029]
　(12) In some embodiments, in the configuration of (10) or (11)
　above, the fertilizer production plant comprises a reformer for reforming methane-containing gas, and the
　combustor is a boiler. The
　reforming apparatus is configured to reform the methane-containing gas by using steam generated by combustion of the fuel in the boiler
　.
[0030]
　According to the configuration of (12) above, the steam generated in the boiler can be used to reform a methane-containing gas such as natural gas.
[0031]
　(13) In some embodiments, in the configuration of any one of (1) to (12)
　above, the fertilizer production plant provides a granulation apparatus for granulating urea produced in the urea production apparatus. includes,
　off-gas of the fertilizer manufacturing plant includes a off-gas of the granulation device
　, characterized in that.
[0032]
　According to the configuration of (13) above, ammonia generated during the granulation of the urea aqueous solution in the granulation apparatus can be removed from the off-gas by contact with the acidic absorption liquid.
[0033]
　(14) The method for producing fertilizer according to at least one embodiment of the present invention is a method
　for producing fertilizer containing urea, which comprises
　a urea production step for producing the urea using ammonia and the
　fertilizer. It comprises a contact step of bringing an off-gas generated during production and containing ammonia into contact with an acidic absorbing liquid, and the
　acidic absorbing liquid contains carbon dioxide
　.
[0034]
　According to the configuration of (14) above, ammonia in off-gas can be absorbed by using an acidic absorbing liquid containing carbonic acid, which is easy to handle. As a result, ammonia in the off-gas can be removed without generating ammonium sulfate, and the off-gas generated during fertilizer production can be easily treated.
Effect of the invention
[0035]
　According to at least one embodiment of the present invention, it is possible to provide a fertilizer production plant and a fertilizer production method capable of easily treating off-gas containing ammonia without producing ammonium sulfate.
A brief description of the drawing
[0036]
FIG. 1 is a system diagram of a fertilizer production plant according to the first embodiment of the present invention.
FIG. 2 is a system diagram showing an off-gas treatment unit 80 in the fertilizer production plant shown in FIG.
FIG. 3 is a flowchart showing a method for producing fertilizer according to the first embodiment of the present invention.
FIG. 4 is a system diagram of a fertilizer production plant according to a second embodiment of the present invention.
5 is a system diagram showing an off-gas treatment unit in the fertilizer production plant shown in FIG. 4. FIG.
FIG. 6 is a system diagram showing an off-gas treatment unit in a fertilizer production plant according to a third embodiment of the present invention.
FIG. 7 is a system diagram of a fertilizer production plant according to a fourth embodiment of the present invention.
FIG. 8 is a diagram showing components contained in each of a gas phase and a liquid phase in the internal space of the scrubber in FIG. 7.
FIG. 9 is a system diagram of a fertilizer production plant according to a fifth embodiment of the present invention.
Mode for carrying out the invention
[0037]
　Hereinafter, some embodiments of the present invention will be described with reference to the accompanying drawings. However, the contents described as the embodiments below or the contents described in the drawings are merely examples, and can be arbitrarily modified and implemented without departing from the gist of the present invention. In addition, each embodiment can be implemented in any combination of two or more. Further, in each embodiment, the common members are designated by the same reference numerals, and duplicate description will be omitted for simplification of description.
[0038]
　Further, the dimensions, materials, shapes, relative arrangements, etc. of the components described as the embodiments or shown in the drawings are not intended to limit the scope of the present invention to this, but are merely explanatory examples. Absent.
　For example, expressions that represent relative or absolute arrangements such as "in a certain direction", "along a certain direction", "parallel", "orthogonal", "center", "concentric" or "coaxial" are exact. Not only does it represent such an arrangement, but it also represents a state of relative displacement with tolerances or angles and distances to the extent that the same function can be obtained.
　For example, expressions such as "same", "equal", and "homogeneous" that indicate that things are in the same state not only represent exactly the same state, but also have tolerances or differences to the extent that the same function can be obtained. It shall also represent the state of existence.
　For example, an expression representing a shape such as a quadrangular shape or a cylindrical shape not only represents a shape such as a quadrangular shape or a cylindrical shape in a geometrically strict sense, but also an uneven portion or chamfering within a range in which the same effect can be obtained. The shape including the part and the like shall also be represented.
　On the other hand, the expressions "equipped", "equipped", "equipped", "included", or "have" one component are not exclusive expressions that exclude the existence of other components.
[0039]
　FIG. 1 is a system diagram of a fertilizer production plant 100 according to the first embodiment of the present invention. The fertilizer production plant 100 is for producing a fertilizer containing urea (urea fertilizer) from a hydrocarbon source such as methane-containing gas (natural gas or the like) or coal. FIG. 1 illustrates a methane-containing gas as a hydrocarbon source. The fertilizer production plant 100 includes a reformer 1, an ammonia production unit 10, a urea production unit 20, a granulation device 61, and an off-gas treatment unit 80. Further, in one embodiment of the present invention, a modifier 2, a carbon dioxide capture device 3, and a methanizer 4 are provided after the reformer 1.
[0040]
　The reformer 1 is for reforming the methane-containing gas. In one embodiment of the invention, the reformer 1 uses air and steam to reform natural gas as an example of a methane-containing gas to obtain at least hydrogen and carbon dioxide.
[0041]
　Although not shown, the reformer 1 includes a primary reformer that performs a steam reforming reaction and a secondary reformer that performs a partial oxidation reforming reaction and a steam reforming reaction. The specific reaction formulas performed in the primary reformer and the secondary reformer are shown below.
(A) Primary reformer (steam reforming reaction)
　CH 4 + H 2 O → CO + 3H 2　... formula (1)
　CO + H 2 O → CO 2 + H 2　... formula (2)
(b) Secondary reforming Vessel (partial oxidation reforming reaction and steam reforming reaction)
　CH 4 + 0.5O 2 → CO + 2H 2　... equation (3)
　CO + H 2 O → CO 2 + H 2　... equation (2)
[0042]
　Therefore, in the reformer 1, carbon dioxide is generated from the methane-containing gas. However, with respect to a part of carbon monoxide produced by the reactions of the formulas (1) and (3), the reaction of the formula (2) does not proceed and remains as carbon monoxide. The remaining carbon monoxide is converted to carbon dioxide in the denaturant 2 in the subsequent stage.
[0043]
　The reactions represented by the formulas (1) and (2) can be carried out using any reforming catalyst. As the reforming catalyst, for example, oxides of transition metals such as nickel and platinum can be used. The reaction conditions can be, for example, about 900 ° C. to 1000 ° C. and 2.5 MPa to 3.5 MPa at the outlet of the catalyst layer housed in the secondary reformer.
[0044]
　As described above, the reformer 1 also takes in air. Therefore, the gas discharged from the reformer 1 and supplied to the reformer 2 in the subsequent stage also includes components derived from air. Specifically, the gas discharged from the reformer 1 also includes nitrogen and the like.
[0045]
　The modifier 2 modifies carbon monoxide and steam in the gas supplied from the reformer 1 to obtain carbon dioxide and hydrogen. Therefore, in the modifier 2, the carbon monoxide concentration in the gas decreases, and the carbon dioxide concentration increases instead. By changing carbon monoxide to carbon dioxide, carbon derived from carbon monoxide can be removed as carbon dioxide by the carbon dioxide capture device 3 in the subsequent stage.
[0046]
　In the denaturant 2, the chemical reaction represented by the following formula (4) occurs.
　CO + H 2 O → CO 2 + H 2　... Formula (4) As
　the catalyst for modifying carbon monoxide (modification catalyst), any modification catalyst can be used. Examples of the modification catalyst include copper-zinc catalysts and the like. The reaction conditions can be, for example, about 200 ° C. to 450 ° C. and 2.5 MPa to 3.5 MPa at the outlet of the catalyst layer housed in the denaturant 2.
[0047]
　The carbon dioxide recovery device 3 is for recovering the carbon dioxide produced in the reformer 1. By recovering carbon dioxide in the gas, it is possible to suppress the introduction of carbon dioxide into the ammonia production apparatus 12 in the subsequent stage and suppress the influence on the ammonia production catalyst (described later). The carbon dioxide recovery in the carbon dioxide recovery device 3 can be performed, for example, by bringing an alkaline aqueous solution into contact with gas. The recovered carbon dioxide is separated from the alkaline aqueous solution by heating the alkaline aqueous solution or the like, and then supplied to the urea production unit 20 and the off-gas treatment unit 80 (specifically, the microbubble generator 116) described later.
[0048]
　The methanizer 4 includes carbon dioxide that could not be recovered by the carbon dioxide recovery device 3 and carbon monoxide that was not converted into carbon dioxide by the modifier 2 and was not recovered by the carbon dioxide recovery device 3. Are each converted to methane. By removing carbon monoxide, carbon dioxide, and other carbon oxides in the methaneization apparatus 4, the introduction of carbon oxides into the subsequent ammonia production apparatus 12 is suppressed. This makes it possible to suppress the influence of carbon oxide on the ammonia production catalyst (described later).
[0049]
　In the methanizer 4, the chemical reactions represented by the following formulas (5) and (6) have occurred.
　CO 2 + H 2 → CO + H 2 O ・ ・ ・ Formula (5)
　CO + 3H 2 → CH 4 + H 2 O ・ ・ ・ Formula (6) As the
　catalyst that causes methanation (methaneation catalyst), any methanation catalyst can be used. Can be done using. Examples of the methanation catalyst include a nickel catalyst and the like. The reaction conditions can be, for example, about 250 ° C. to 350 ° C. and 2.0 MPa to 3.0 MPa at the outlet of the catalyst layer housed in the methanation apparatus 4.
[0050]
　The ammonia production unit 10 is for obtaining ammonia by using at least the hydrogen obtained in the reformer 1 and the nitrogen in the air taken in by the reformer 1.
[0051]
　The ammonia production unit 10 includes a compressor 11, an ammonia production device 12, an ammonia recovery device 13, and a hydrogen recovery device 14.
[0052]
　The compressor 11 is for boosting the pressure of the raw material gas (containing hydrogen and nitrogen and containing methane as an impurity) introduced into the ammonia production apparatus 12 in the subsequent stage. In the ammonia production apparatus 12, the ammonia production reaction proceeds at a high pressure, so that the ammonia production reaction can be promoted by increasing the pressure of the raw material gas with the compressor 11.
[0053]
　The ammonia production apparatus 12 is for obtaining ammonia by using at least hydrogen and nitrogen in the raw material gas. Of the produced ammonia, the liquid phase ammonia is supplied to the urea production unit 20 described later through the ammonia supply system 71. On the other hand, the gas phase (purge gas) of the ammonia production apparatus 12 is supplied to the ammonia recovery apparatus 13 described later. The gas phase of the ammonia production apparatus 12 contains excess hydrogen and nitrogen (unreacted nitrogen), as well as unreacted methane.
[0054]
　In the ammonia production apparatus 12, the chemical reaction represented by the following formula (7) has occurred.
　N 2 + 3H 2 → 2NH 3　... Equation (7) As
　the catalyst for producing ammonia (ammonia production catalyst), any ammonia production catalyst can be used. Examples of the ammonia production catalyst include an iron catalyst containing triiron tetroxide. The reaction conditions can be, for example, about 400 ° C. to 480 ° C. and 12 MPa to 20 MPa at the outlet of the catalyst layer housed in the ammonia production apparatus 12.
[0055]
　The ammonia recovery device 13 recovers the ammonia contained in the gas phase in the ammonia production device 12. The ammonia recovery device 13 includes a refrigerator (not shown), and the gas phase is cooled to around 0 ° C. by driving the refrigerator. As a result, the ammonia in the gas phase is liquefied, and the liquefied ammonia is recovered. The recovered ammonia is compressed by the compressor 76 through the ammonia supply system 71 and then supplied to the urea production unit 20 described later, similarly to the ammonia in the liquid phase of the ammonia production apparatus 12.
[0056]
　The hydrogen recovery device 14 is for recovering excess hydrogen in the ammonia production device 12. The surplus hydrogen recovered by the hydrogen recovery device 14 is returned to the space between the methanizer 4 and the compressor 11 (previous stage of the compressor 11) through the hydrogen circulation system 72. On the other hand, the unrecovered hydrogen and the unrecovered methane are supplied to the reformer 1 or a boiler (which may be not shown) together with the unrecovered nitrogen, and are used for combustion as fuel.
[0057]
　The hydrogen recovery device 14 can have an arbitrary configuration as long as hydrogen can be recovered. Specifically, for example, hydrogen in the gas can be recovered by using an arbitrary hydrogen separation membrane.
[0058]
　The urea production unit 20 is for obtaining urea by using at least the carbon dioxide obtained in the reformer 1 and the ammonia obtained in the ammonia production unit 10. The carbon dioxide used in the urea production unit 20 is the one recovered by the carbon dioxide recovery device 3 described above. Further, the ammonia used in the urea production unit 20 is the ammonia produced by the above-mentioned ammonia production unit, which is supplied through the ammonia supply system 71.
[0059]
　The urea production unit 20 includes a compressor 21 and a urea production apparatus 22.
[0060]
　The compressor 21 is for boosting the carbon dioxide recovered by the carbon dioxide recovery device 3 and supplied to the urea production apparatus 22 (described later). The boosted carbon dioxide is supplied to the urea production apparatus 22 through the first carbon dioxide supply system 121. The first carbon dioxide supply system 121 is for supplying the carbon dioxide boosted by the compressor 21 to the urea production apparatus 22.
[0061]
　In the urea production apparatus 22, the urea production reaction proceeds at a high pressure, so that the urea production reaction can be promoted by increasing the pressure of the raw material gas with the compressor 21. The generated urea is supplied to the granulation apparatus 61 described later.
[0062]
　Further, the carbon dioxide boosted by the compressor 21 is also supplied to the microbubble generator 116 (carbonic acid production device, which will be described later) through the second carbon dioxide supply system 118. The second carbon dioxide supply system 118 is for supplying the carbon dioxide boosted by the compressor 21 to the microbubble generator 116.
[0063]
　By providing the compressor 21, the first carbon dioxide supply system 121, and the second carbon dioxide supply system 118, the increased carbon dioxide is transferred to both the urea production apparatus 22 and the microbubble generator 116 (carbonic acid production apparatus). Can be supplied. As a result, it is not necessary to separately provide a compressor (not shown) for carbonic acid production, and the installation area of ​​the compressor can be reduced. Moreover, since carbonic acid can be produced from carbon dioxide after pressurization, the amount of carbonic acid produced can be increased.
[0064]
　The urea production apparatus 22 is for producing urea using at least ammonia. In one embodiment of the present invention, the urea production apparatus 22 reacts carbon dioxide and ammonia in the raw material gas to produce urea. The urea produced is liquid here. In addition to carbon dioxide compressed by the compressor 21, the urea production apparatus 22 is supplied with ammonia that has been recovered by the ammonia recovery apparatus 13 described later and has been pressurized by the compressor (high pressure pump) 76. In the urea production apparatus 22, the chemical reaction represented by the following formula (8) has occurred.
　2NH 3 + CO 2 → (NH 2 ) 2 CO + H 2 O ... Formula (8) The
　conditions for producing urea are not particularly limited, but for example, at the outlet of the urea production apparatus 22, 170 ° C. to 200 ° C. and 13 MPa to 18 MPa. can do.
[0065]
　The granulator 61 is for granulating the urea produced in the urea production apparatus 22. In the granulation device 61, formaldehyde contained in the urea-formaldehyde aqueous solution functions as a binder, and the urea supplied from the urea production unit 20 is granulated. Granular urea obtained by granulating urea is shipped and used as fertilizer.
[0066]
　The size of the granular urea is not particularly limited, but for example, the particle size can be about 2 mm to 6 mm.
[0067]
　The off-gas treatment unit 80 is for treating off-gas in the fertilizer production plant 100. However, in one embodiment of the present invention, the off-gas processed by the off-gas processing unit 80 includes the off-gas of the granulator 61. As a result, the ammonia generated during the granulation of the urea aqueous solution in the granulation apparatus 61 can be removed from the off-gas by contact with the acidic absorption liquid.
[0068]
　The configuration of the off-gas processing unit 80 will be described with reference to FIG.
[0069]
　FIG. 2 is a system diagram showing an off-gas treatment unit 80 in the fertilizer production plant 100 shown in FIG. The off-gas treatment unit 80 includes a solid content removing scrubber 80A and a scrubber 80B. That is, the fertilizer production plant 100 includes a solid content removing scrubber 80A and a scrubber 80B.
[0070]
　The solid content removing scrubber 80A is for removing solid content in off-gas. The solid content referred to here is, for example, a powder of solid urea contained in the off-gas of the granulator 61. By providing the solid content removing scrubber 80A, the solid content (for example, solid urea powder) contained in the off-gas of the fertilizer production plant 100 can be removed. Then, the ammonia in the off-gas after removing the solid content can be removed from the off-gas by the scrubber 80B.
[0071]
　The solid content removing scrubber 80A has a housing 81 having an internal space 81a through which off-gas flows, a nozzle 83 for sprinkling water in the internal space 81a, and water (for example, fresh water, reclaimed water, industrial water, or the like) in the nozzle 83. (The pH is about 7)) is provided with a water supply system 87 for supplying. Since the inside of the solid content removing scrubber 80A is usually hot, liquid water evaporates. Therefore, in order to replenish the evaporated liquid water, water is sprinkled by the nozzle 83.
[0072]
　Since neutral water is sprinkled in the solid content removing scrubber 80A, some ammonia in the off-gas is absorbed. Therefore, from the viewpoint of suppressing the concentration of ammonia, a part of the water staying in the internal space 81a is extracted to the outside of the solid content removing scrubber 80A through a drainage system (not shown), and the ammonia in the extracted liquid is treated. You may do so.
[0073]
　The solid content removing scrubber 80A includes a extraction system 86, a pump 82, and a nozzle 84. The extraction system 86 is for extracting the water accumulated in the internal space 81a (including the dissolved solid content, the same applies to the retained water hereinafter) by being sprinkled by the nozzle 83 to the outside of the housing 81. The pump 82 is for extracting the water accumulated in the internal space 81a and flowing it to the system 86. The nozzle 84 is for sprinkling the water flowing through the extraction system 86 into the internal space 81a.
[0074]
　From the viewpoint of suppressing the concentration of solid content, a part of the water flowing through the extraction system 86 is extracted to the outside of the solid content removing scrubber 80A through a drainage system (not shown) and treated as wastewater. Further, the nozzle 84 is configured to inject water toward a tray 85 (for example, composed of a perforated plate) installed in the middle of the off-gas flow. As a result, the solid content deposited on the tray 85 is washed away (details will be described later).
[0075]
　The off-gas supplied to the solid content removing scrubber 80A through the off-gas supply system 111 flows upward in the internal space 81a of the housing 81. At this time, the off-gas is installed in the middle of the off-gas flow and comes into contact with the tray 85 made of, for example, a perforated plate. As a result, the solid content contained in the off-gas is deposited on the tray 85. Here, the nozzle 84 is configured to inject water toward the tray 85. Therefore, the solid content deposited on the tray 85 is washed away by the jetted water. As a result, excessive solid analysis output is suppressed in the tray 85, and an increase in pressure loss of off-gas is suppressed.
[0076]
　On the other hand, the off-gas from which the solid content has been removed by depositing on the tray 85 is supplied to the off-gas supply system 112 through an off-gas discharge port (not shown). Then, the off gas flowing through the off gas supply system 112 is supplied to the scrubber 80B arranged on the downstream side of the solid content removing scrubber 80A in the off gas flow direction.
[0077]
　The scrubber 80B is an off-gas of the fertilizer production plant 100 and has an internal space 91a for bringing the off-gas containing ammonia into contact with the acidic absorption liquid. The acidic absorbent that comes into contact with the off-gas contains carbonic acid. The off-gas after removing ammonia in the scrubber 80B is exhausted to the atmosphere through the exhaust system 113.
[0078]
　The scrubber 80B includes a housing 91 having an internal space 91a through which off-gas flows, a nozzle 93 for sprinkling water in the internal space 91a, and a water supply system 97 for supplying water to the nozzle 93. Since the inside of the scrubber 80B is usually hot, liquid water evaporates. Therefore, in order to replenish the evaporated liquid water, water is sprinkled by the nozzle 93.
[0079]
　The scrubber 80B includes a extraction system 96, a pump 92, and a nozzle 94. The extraction system 96 is for extracting the water accumulated in the internal space 91a by being sprinkled by the nozzle 93 to the outside of the housing 91. The pump 92 is for extracting the water accumulated in the internal space 91a and flowing it to the system 96. The nozzle 94 is for sprinkling the water flowing through the extraction system 96 into the internal space 91a. The nozzle 94 is adapted to inject water toward, for example, a tray 98 made of a perforated plate.
[0080]
　Here, in the scrubber 80B, as described above, the water retained in the internal space 91a is extracted to the outside of the housing 91. Then, in the scrubber 80B, although the details will be described later, the acidic absorbing liquid sprinkled from the nozzle 94 is brought into contact with the off-gas containing ammonia. Therefore, the water retained in the internal space 91a contains ammonia absorbed by the acidic absorbing liquid and the acidic absorbing liquid after contact with the off-gas. The water retained in the internal space 91a also includes water sprinkled by the nozzle 93. Ammonia in the off-gas can be absorbed to some extent by the sprinkled water. Further, the water retained in the internal space 91a also includes an acidic absorbing liquid supplied through the first acidic absorbing liquid supply system 117 (described later).
[0081]
　Therefore, in one embodiment of the present invention, the water retained in the internal space 91a is uniformly referred to as an "acidic absorbent" for convenience of explanation. Then, in one embodiment of the present invention, the acidic absorbing liquid staying in the internal space 91a is sprinkled from the nozzle 94 through the extraction system 96. Therefore, the acidic absorbing liquid circulates inside and outside the internal space 91a.
[0082]
　In the water (acidic absorption liquid) retained in the internal space 91a, ammonia exists in the liquid as at least one form of ammonia molecules or ammonium ions.
[0083]
　The extraction system 96 for extracting the acidic absorbing liquid from the housing 91 includes an opening degree adjusting valve 95 and a flow meter 99b. Then, the opening degree of the opening degree adjusting valve 95 is adjusted so that the flow rate measured by the flow meter 99b becomes constant. Therefore, the amount of water sprinkled through the nozzle 94 is constant.
[0084]
　A branch system 115 is connected to the extraction system 96. As an example of the carbonic acid producing apparatus, the branching system 115 includes a microbubble generator 116 for producing carbonic acid by dissolving carbon dioxide in water.
[0085]
　The micro-bubble generator 116 (an example of a carbonic acid producing apparatus) is for producing carbonic acid using carbon dioxide recovered by the carbon dioxide recovery device 3 (see FIG. 1). That is, the purpose is to generate carbonic acid in the acidic absorption liquid by dissolving the recovered carbon dioxide in the acidic absorption liquid. The produced acidic absorbent liquid is supplied to the housing 91 through the first acidic absorbent liquid supply system 117.
[0086]
　A second carbon dioxide supply system 118 for supplying carbon dioxide from the compressor 21 is connected to the microbubble generator 116. By doing so, an acidic absorption liquid can be produced by using carbon dioxide generated by reforming a methane-containing gas such as natural gas.
[0087]
　The microbubble generator 116 is configured to generate bubbles having a size of, for example, about 100 nanometers to several hundreds of micrometers in water. Specifically, for example, as the size of the bubbles immediately after the generation by the micro-bubble generator 116, for example, bubbles having a size of about 100 nm or more and 500 μm or less are generated. By providing such a micro-bubble generator 116, the existence time of carbonic acid in water can be lengthened.
[0088]
　The specific configuration of the micro-bubble generator 116 is not particularly limited, and any method such as an ejector method, a cavitation method, a swirling flow method, and a pressure melting method can be adopted.
[0089]
　The second carbon dioxide supply system 118 includes an opening degree adjusting valve 119 for adjusting the amount of carbon dioxide supplied. The opening degree of the opening degree adjusting valve 119 is controlled by the arithmetic control device 151 based on the pH measured by the pH meter 99a. That is, the pH of the acidic absorbing liquid staying in the internal space 91a gradually increases due to the absorption of ammonia by the scrubber 80B. Therefore, carbon dioxide is dissolved in the acidic absorbing liquid so that the pH of the acidic absorbing liquid staying in the internal space 91a (that is, the acidic absorbing liquid flowing through the extraction system 96) is on the acidic side. Specifically, the amount of carbon dioxide dissolved is controlled so that the pH of the acidic absorption liquid measured by the pH meter 99a (that is, the pH of the acidic absorption liquid sprinkled by the nozzle 94) becomes small.
[0090]
　Specifically, the pH of the acidic absorption liquid measured by the pH meter 99a can be, for example, about 4 or more and 6.5 or less, and is preferably a smaller pH within this range. By controlling the amount of carbon dioxide dissolved so that the pH range is within this range, it is possible to promote the absorption of ammonia into the acidic absorption liquid. In addition, the absorbed ammonia is likely to exist as ammonium ions in the acidic absorption liquid, and the re-scattering of ammonia into the gas phase can be suppressed.
[0091]
　Although not shown, the arithmetic control device 151 includes a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), an HDD (Hard Disk Drive), a control circuit, and the like. It is embodied by executing the stored predetermined control program by the CPU.
[0092]
　In the fertilizer production plant 100, the microbubble generator 116 generates microbubbles in the acidic absorption liquid flowing through the branch system 115, so that carbon dioxide is dissolved in the acidic absorption liquid flowing through the branch system 115. As a result, an acidic absorbing liquid containing carbonic acid is generated, and the acidic absorbing liquid generated by the micro-bubble generator 116 is supplied to the housing 91 through the first acidic absorbing liquid supply system 117. Then, the acidic absorbing liquid supplied to the housing 91 is sprinkled into the internal space 91a of the housing 91 through the extraction system 96 and the nozzle 94. The sprinkled acidic absorbing liquid absorbs ammonia in the off-gas by coming into contact with the off-gas and stays in the internal space 91a of the housing 19.
[0093]
　The retained acidic absorption liquid contains ammonium carbonate produced by the absorption of ammonia. Therefore, a part of the acidic absorption liquid containing ammonium carbonate is supplied to the urea production apparatus 22 through the extraction system 96 and the ammonium carbonate supply system 114. The ammonium carbonate supply system 114 is for supplying the acidic absorption liquid after the off-gas contact with the scrubber 80B to the urea production apparatus 22. By providing the ammonium carbonate supply system 114, ammonium carbonate contained in the acidic absorption liquid after off-gas contact can be used as a raw material for urea production.
[0094]
　According to the fertilizer production plant 100 having the above configuration, ammonia in off-gas can be absorbed by using an acidic absorption liquid containing carbonic acid, which is easy to handle, without using an aqueous sulfuric acid solution. As a result, ammonia in the off-gas can be removed without generating ammonium sulfate, and the off-gas generated in the fertilizer production plant 100 can be easily treated.
[0095]
　FIG. 3 is a flowchart showing a method for producing fertilizer according to the first embodiment of the present invention. The method for producing fertilizer shown in FIG. 3 relates to a method for producing fertilizer for producing fertilizer containing urea. However, in FIG. 3, for the sake of simplification of the description, the production of urea and the absorption and removal of ammonia in the off-gas of the granulator 61 are mainly described.
[0096]
　The fertilizer production method shown in FIG. 3 can be carried out, for example, in the fertilizer production plant 100 shown in FIG. 1 above. Therefore, in the following, FIG. 3 will be described with reference to FIG. 1 as appropriate.
[0097]
　In the fertilizer production plant 100, hydrogen is produced by reforming a methane-containing gas such as natural gas. Then, ammonia and methanol are produced using the produced hydrogen. Further, the carbon dioxide produced as a by-product during the reforming is recovered by the carbon dioxide capture device 3 (step S1). Then, urea is produced by using the recovered carbon dioxide and ammonia. At this time, as described above, the urea production apparatus 22 produces urea using ammonium carbonate supplied through the ammonium carbonate supply system 114 as a part of the raw material. Then, fertilizer is produced using the produced urea and ammonia and methanol.
[0098]
　Further, using the carbon dioxide recovered by the carbon dioxide recovery device 3, the micro-bubble generator 116 (see FIG. 2) produces an acidic absorbing liquid containing carbonic acid (step S2). The produced acidic absorbent liquid is brought into contact with the off-gas generated during the production of fertilizer and containing ammonia (for example, the off-gas of the granulator 61) in the scrubber 80B (step S3, contact step). As a result, ammonia in the off-gas is absorbed by the acidic absorption liquid, and ammonium carbonate is produced in the acidic absorption liquid.
[0099]
　Then, the acidic absorption liquid after the off-gas contact is supplied through the ammonium carbonate supply system 114 (step S4). Then, in the urea production apparatus 22, urea is produced using ammonium carbonate in the acidic absorption liquid after the off-gas contact (step S5, urea production step).
[0100]
　According to the above production method, ammonia in off-gas can be absorbed by using an acidic absorption liquid containing carbonic acid, which is easy to handle, without using an aqueous sulfuric acid solution. As a result, ammonia in the off-gas can be removed without generating ammonium sulfate, and the off-gas generated during fertilizer production can be easily treated.
[0101]
　Here, the present inventors show in FIG. 2 in order to confirm the influence of the amount of the acidic absorbing liquid sprinkled through the nozzle 94 and the amount of water sprinkled through the nozzle 93 on the ammonia removal rate in the scrubber 80B. The following tests were performed using the scrubber 80B. In this test, the solid content removing scrubber 80A shown in FIG. 2 is not used for simplification of the test. Further, in this test, for simplification, a small-scale test device imitating the scrubber 80B was manufactured. Then, the flow rate of the acidic absorption liquid and the off-gas flow rate at the time of the test shown below are shown in terms of the flow rate corresponding to the urea production amount (for example, 3500 tons / day scale) in the actual fertilizer production plant 100.　
[0102]
　Off-gas having an ammonia concentration of 100 mg / Nm 3 (normal lube, the same applies hereinafter) at the off-gas supply port (not shown) of the scrubber 80B was supplied to the scrubber 80B at a flow rate of 600,000 Nm 3 per hour . Further, an equal amount of water (fresh water) was sprinkled into the internal space 91a through the nozzle 93 while extracting 5% by volume of the acidic absorbing liquid flowing through the extraction system 96 through the ammonium carbonate supply system 114 of the scrubber 80B. Then, the ammonia concentration at the off-gas discharge port (not shown) in the scrubber 80B was measured while changing the amount (flow rate) of the acidic absorbing liquid sprinkled through the nozzle 94. At the same time, the pH was also measured with a pH meter 99a. These results are shown in Table 1 below (Examples 1 to 4).
[0103]
[table 1]

[0104]
　As shown in Table 1, it was found that the larger the amount of the acidic absorbing liquid sprinkled through the nozzle 94, that is, the larger the flow rate of the acidic absorbing liquid with respect to the off-gas, the better the ammonia removal rate.
[0105]
　Next, off-gas in the same manner as in Examples 1 to 4 above, except that the amount of the acidic absorption liquid extracted through the ammonium carbonate supply system 114 was changed to 15% by volume of the acidic absorption liquid flowing through the extraction system 96. Ammonia concentration and pH at the outlet were measured. These results are shown in Table 2 below (Examples 5 to 8).
[0106]
[Table 2]

[0107]
　As shown in Table 2, even if the extraction amount is large, as in Table 1 above, the larger the amount of the acidic absorbent liquid sprinkled through the nozzle 94, that is, the larger the flow rate of the acidic absorbent liquid with respect to the off gas It was found that the ammonia removal rate was improved. Further, when Table 1 and Table 2 are compared, for example, if the conditions are the same except that the extraction amount is different (Examples 1 and 5 and the like), the larger the extraction amount, the better the ammonia removal rate. I understood.
[0108]
　From the results of Tables 1 and 2 above, the larger the amount of water sprinkled by the acidic absorbent liquid through the nozzle 94 and the amount of water sprinkled through the nozzle 93, the better the ammonia removal rate in the scrubber 80B. I understood.
[0109]
　FIG. 4 is a system diagram of a fertilizer production plant according to a second embodiment of the present invention. The fertilizer production plant 100A shown in FIG. 4 includes a second acidic absorption liquid supply system 124 for supplying the acidic absorption liquid after off-gas contact with the scrubber 80B to the solid content removing scrubber 80A. Further, the fertilizer production plant 100A includes a urea aqueous solution supply system 123 and a urea aqueous solution return system 122. The urea aqueous solution supply system 123 is for supplying the urea aqueous solution produced by the urea production apparatus 22 to the solid content removing scrubber 80A. Further, the urea aqueous solution return system 122 is for returning the urea aqueous solution (including the solid content and the acidic aqueous solution supplied from the scrubber 80B) after the off-gas contact with the solid content removing scrubber 80A to the urea production apparatus 22.
[0110]
　FIG. 5 is a system diagram showing an off-gas treatment unit 80 in the fertilizer production plant 100A shown in FIG. In the scrubber 80B of the fertilizer production plant 100A, a part of the acidic absorption liquid extracted from the housing 91 and flowing through the extraction system 96 is solids removed through the second acidic absorption liquid supply system 124 (acid absorption liquid supply system). It is supplied to the water supply system 87 of the scrubber 80A. The supply amount is adjusted by adjusting the opening degree of the opening degree adjusting valve 120 provided in the second acidic absorbing liquid supply system 124. By supplying to the water supply system 87, the acidic absorbing liquid after the off-gas contact with the scrubber 80B is sprinkled into the internal space 81a of the solid content removing scrubber 80A.
[0111]
　By providing the second acidic absorption liquid supply system 124, the acidic absorption liquid after the off-gas contact can be supplied to the solid content removing scrubber 80A. As a result, even if the water content of the solid content removing scrubber 80A decreases due to evaporation, the water content of the solid content removing scrubber 80A can be recovered. As a result, the amount of new water used for recovering the water content in the solid content removing scrubber 80A can be reduced from the outside.
[0112]
　Further, the off-gas treatment unit 80 in the fertilizer production plant 100A includes a urea aqueous solution supply system 123 and a urea aqueous solution return system 122. The urea aqueous solution supply system 123 is for supplying the urea aqueous solution produced by the urea production apparatus 22 to the solid content removing scrubber 80A. Further, the urea aqueous solution return system 122 is for returning the urea aqueous solution after off-gas contact with the solid content removing scrubber 80A to the urea production apparatus 22.
[0113]
　By providing the urea aqueous solution supply system 123 and the urea aqueous solution return system 122, the solid content in the off-gas can be removed by using the urea aqueous solution produced by the urea production apparatus 22. As a result, the amount of new water used from the outside for removing solid content can be reduced. In addition, the fertilizer production plant 100A can produce fertilizer using the urea aqueous solution returned from the solid content removing scrubber 80A.
[0114]
　Further, in the solid content removing scrubber 80A, the solid urea powder is absorbed by water as described above. Then, the water that has absorbed urea is supplied to the urea production apparatus 22 through the urea aqueous solution return system 122. As a result, the discharge of urea to the outside can be suppressed and the yield of urea can be improved.
[0115]
　Further, the solid content removing scrubber 80A of the fertilizer production plant 100A is supplied with the acidic absorbing liquid after absorbing ammonia through the second acidic absorbing liquid supply system 124 as described above. Here, ammonium carbonate is contained in the acidic absorption liquid after absorbing ammonia. Therefore, the water retained in the internal space 81a of the solid content removing scrubber 80A contains ammonium carbonate. Therefore, the urea aqueous solution containing ammonium carbonate is supplied to the urea production apparatus 22 through the urea aqueous solution return system 122. As a result, the urea production apparatus 22 can produce urea using ammonium carbonate produced by absorbing ammonia.
[0116]
　Here, in order to confirm the influence of the supply of the solid content removing scrubber 80A of the acidic absorbing liquid through the second acidic absorbing liquid supply system 124 on the ammonia removal rate in the off-gas, the present inventors are shown in FIG. The following tests were performed using the off-gas treatment unit 80. However, for convenience, the urea aqueous solution return system 122 and the urea aqueous solution supply system 123 are omitted. Further, in the same manner as in Examples 1 to 8 above, in this test, for simplification, a small-scale test apparatus imitating the off-gas treatment unit 80 shown in FIG. 5 was manufactured. Then, each supply amount at the time of the test shown below was converted into a supply amount corresponding to the urea production amount (for example, 3500 tons / day scale) in the actual fertilizer production plant 100A.
[0117]
　First, as the ninth embodiment, the second acidic absorption liquid supply system 124 is not provided, and new water (fresh water) of 10.0 ton / h is supplied to the solid content removing scrubber 80A through the water supply system 87, and the water supply system is used. Through 97, 7.5 ton / h of fresh water (fresh water) was supplied to the scrubber 80B. Therefore, in Example 9, the total fresh water supply is 17.5 ton / h.
[0118]
　Then, as a gas imitating the off-gas, a gas containing a predetermined amount of ammonia (simulated off-gas) was flowed through the solid content removing scrubber 80A and the scrubber 80B in this order. At this time, the simulated off-gas was continuously flowed at a predetermined flow rate. Then, the ammonia concentrations at the off-gas supply port and the off-gas discharge port (neither shown) of the scrubber 80B were measured, and the ammonia removal rate of the scrubber 80B was calculated. As a result, the ammonia removal rate was 55% (Example 9).
[0119]
　Next, as Example 10, the supply amount of new water to the solid content removing scrubber 80A was set to 2.5 ton / h, and the supply amount of new water to the scrubber 80B was set to 7.5 ton / h. The test was carried out in the same manner as in Example 9 except that the amount of the acidic absorbing liquid supplied from the scrubber 80B to the solid content removing scrubber 80A through the second acidic absorbing liquid supply system 124 was 7.5 ton / h. Therefore, in Example 10, the total supply of fresh water is 10.0 ton / h.
[0120]
　Then, the ammonia removal rate was calculated in the same manner as in Example 9. As a result, the ammonia removal rate was 55% (Example 10).
[0121]
　Further, as Example 11, the solid content removing scrubber 80A was not supplied with new water, and the amount of new water supplied to the scrubber 80B was set to 17.5 ton / h, and the second acidic absorbing liquid was supplied. The test was carried out in the same manner as in Example 9 except that the amount of the acidic absorbing liquid supplied from the scrubber 80B to the solid content removing scrubber 80A through the system 124 was set to 17.5 ton / h. Therefore, in Example 11, the total new water supply is 17.5 ton / h.
[0122]
　Then, the ammonia removal rate was calculated in the same manner as in Example 9. As a result, the ammonia removal rate was 58% (Example 11).
[0123]
　The results of Examples 9 to 11 above are shown in Table 3 below.
[0124]
[Table 3]

[0125]
　Comparing Example 9 and Example 10, the ammonia removal rate was the same. However, in Example 10, the total amount of new water supplied is reduced as compared with Example 9. Specifically, the total amount of new water supplied was 17.5 ton / h in Example 9, but decreased to 10.0 ton / h in Example 10. Therefore, in Example 10, the amount of new water used is reduced by 43%. Therefore, by supplying the acidic absorption liquid from the scrubber 80B to the solid content removing scrubber 80A through the second acidic absorption liquid supply system 124, the amount of new water used can be reduced while maintaining the ammonia removal rate.
[0126]
　Further, comparing Example 9 and Example 10, the total amount of new water supplied was the same. However, in Example 11, the ammonia removal rate is improved as compared with Example 9. Specifically, the ammonia removal rate was 55% in Example 9, but improved to 58% in Example 11. Therefore, by supplying the acidic absorption liquid from the scrubber 80B to the solid content removing scrubber 80A through the second acidic absorption liquid supply system 124, the ammonia removal rate can be improved while keeping the total amount of new water supplied the same.
[0127]
　FIG. 6 is a system diagram showing an off-gas treatment unit 80 in the fertilizer production plant 100B according to the third embodiment of the present invention. The fertilizer production plant 100B includes an integrated scrubber 80C as an off-gas treatment unit 80, which includes a solid content removing scrubber 80A and a scrubber 80B integrally configured with the solid content removing scrubber 80A above the solid content removing scrubber 80A. ..
[0128]
　In the solid content removing scrubber 80A, an off-gas discharge port 181 is formed on the upper surface of the internal space 81a. Further, above the off-gas discharge port 181, a member 191 that narrows upward is provided. The lower end of the member 191 is open, and an off-gas discharge port 181 is formed at the lower end of the member 191. Further, the upper end of the member 191 is also open, and the tubular member 193 is connected to the upper end of the member 191. An umbrella member 192 is arranged above the tubular member 193 to prevent the acidic absorbing liquid from entering the tubular member 193.
[0129]
　The umbrella member 192 is fixed to the tubular member 193 by a support member 194 arranged at equal intervals in the circumferential direction of the tubular member 193. An off-gas supply port 195 for supplying off-gas to the internal space 91a of the scrubber 80B is formed between the adjacent support members 194.
[0130]
　The off-gas supplied through the off-gas supply port (not shown) formed below the solid-removing scrubber 80A flows upward in the internal space 81a of the solid-removing scrubber 80A. At this time, for example, when the off-gas comes into contact with the tray 85 made of a perforated plate, the solid content in the off-gas is deposited on the tray 85, and the solid content in the off-gas is removed.
[0131]
　The off-gas flowing upward in the internal space 81a flows into the inside of the member 191 through the off-gas discharge port 181. Then, the off-gas that has flowed into the inside of the member 191 flows through the inside of the tubular member 193 and the off-gas supply port 195 as shown by a thick arrow in FIG. As a result, off-gas is supplied to the internal space 91a of the scrubber 80B. Then, in the scrubber 80B, the ammonia in the off-gas is absorbed by the acidic absorption liquid. The off-gas after removing ammonia is discharged to the outside of the scrubber 80B through an off-gas discharge port (not shown) formed above the scrubber 80B.
[0132]
　By providing the integrated scrubber 80C, the scrubber 80B can be integrally formed with the solid content removing scrubber 80A above the solid content removing scrubber 80A, so that the installation area of ​​the scrubber (specifically, the off-gas treatment unit 80) is provided. Can be reduced.
[0133]
　FIG. 7 is a system diagram of the fertilizer production plant 100C according to the fourth embodiment of the present invention. The fertilizer production plant 100C includes a reformer 1 for reforming methane-containing gas and a combustor 131 for burning fuel (heavy oil, kerosene, methane-containing gas, etc.). Then, the reformer 1 is configured to reform the methane-containing gas by using the heat generated by the combustion of the fuel in the combustor 131. By doing so, it is possible to reform a methane-containing gas such as natural gas by using the heat generated by the combustion of fuel.
[0134]
　Further, the fertilizer production plant 100C includes a third carbon dioxide supply system 133 for supplying the carbon dioxide generated in the combustor 131 to the internal space 91a of the scrubber 80B. The third carbon dioxide supply system 133 is connected to the off-gas supply system 112, and the carbon dioxide generated in the combustor 131 is supplied to the internal space 91a through the third carbon dioxide supply system 133 and the off-gas supply system 112.
[0135]
　FIG. 8 is a diagram showing components contained in each of the gas phase and the liquid phase in the internal space 91a of the scrubber 80B in FIG. 7. As shown in FIG. 8, in the internal space 91a of the scrubber 80B, at least ammonia contained in the off-gas and carbon dioxide generated by the combustor 131 are present as the gas phase. Ammonia (NH 3 ) and carbon dioxide (CO 2 ) in the gas phase are both present as molecules.
[0136]
　On the other hand, in the acidic absorption liquid as the liquid phase, carbon dioxide dissolved in the microbubble generator 116 (see FIG. 2) is present. Carbon dioxide varies depending on the pH of the acidic absorbent liquid carbon dioxide molecules (CO 2 ) or carbonate ions (HCO 3 - ) in at least one embodiment of the, present in the acidic absorbent solution. In particular, carbon dioxide molecules are present in the acidic absorption liquid as bubbles, and carbonate ions are dissolved as ions in the acidic absorption liquid. In one embodiment of the present invention, for convenience of explanation, carbon dioxide molecules and carbonate ions are collectively referred to as "carbonic acid".
[0137]
　When ammonia vapor is absorbed into an acidic absorbing solution through a gas-liquid interface L, it absorbed ammonia ions ammonium in an acidic absorbing solution (NH 4 + likely present as). Ammonium ion has a high affinity for water molecules. Therefore, the presence of ammonia as ammonium ions in the acidic absorption liquid suppresses the re-release to the gas phase through the gas-liquid interface L.
[0138]
　In addition, the carbonate ions in the acidic absorption liquid are also suppressed from being released into the gas phase through the gas-liquid interface L due to the high affinity between the carbonate ions and water. However, since the carbon dioxide molecules in the acidic absorption liquid do not have a very high affinity between the carbon dioxide molecules and water, they are easily released into the gas phase through the gas-liquid interface L. Then, when carbon dioxide molecules are released from the acidic absorption liquid into the gas phase, the pH of the acidic absorption liquid becomes high, and ammonia is hardly absorbed.
[0139]
　Therefore, in the fertilizer production plant 100C, carbon dioxide is supplied to the gas phase of the internal space 91a. By doing so, it is possible to increase the partial pressure of carbon dioxide in the gas phase in the internal space 91a for bringing the off-gas into contact with the acidic absorption liquid. As a result, it is possible to suppress the release of carbon dioxide molecules from the acidic absorption liquid into the gas phase, and it is possible to prolong the existence time of carbonic acid in the acidic absorption liquid.
[0140]
　FIG. 9 is a system diagram of the fertilizer production plant 100D according to the fifth embodiment of the present invention. The fertilizer production plant 100D includes a reformer 1 for reforming the methane-containing gas. Further, the fertilizer production plant 100D includes a boiler 141 for generating water vapor by combustion of combustion as an example of a combustor for burning fuel (heavy oil, kerosene, methane-containing gas, etc.).
[0141]
　The reformer 1 is configured to reform the methane-containing gas by using the steam generated by the combustion of the fuel in the boiler 141, and the carbon dioxide generated by the combustion of the fuel in the boiler 141 is generated. The carbon dioxide generated in the boiler 141 (combustor) is supplied to the internal space 91a through the third carbon dioxide supply system 142 for supplying the internal space 91a of the scrubber 80B.
[0142]
　By doing so, it is possible to reform a methane-containing gas such as natural gas by using the water vapor generated in the boiler 141. Further, the partial pressure of carbonic acid in the gas phase in the internal space 91a of the scrubber 80B can be increased, and the presence time of carbonic acid in the acidic absorption liquid can be lengthened.
Description of the sign
[0143]
1 Reformer
2 Reformer
3 Carbon dioxide recovery device
4 Methanization device
10 Ammonia production unit
11,21,76 Compressor
12 Ammonia production device
13 Ammonia recovery device
14 Hydrogen recovery device
19,81,91 Housing
20 Urea production unit
22 Urea production equipment
61 Granulation equipment
71 Ammonia supply system
72 Hydrogen circulation system
80 Off- gas treatment unit
80A Solid content removal scrubber
80B Scrubber
80C Integrated scrubber
81a, 90a, 91a Internal space 82,92
Pump
83,84,93,94 nozzle
85,98 Tray
86,96,122 system
87,97 Water supply system
95,119,120 Opening adjustment valve
99a pH meter
99b Flow meter
100, 100A, 100B, 100C, 100D Fertilizer production plant
111, 112 Off- gas supply system
113 Exhaust system
114 Ammonium carbonate supply system
115 Branch system
116 Micro bubble generator
117 1st acidic absorber supply system
118 2nd carbon dioxide supply system
121 1st carbon dioxide supply system
123 Urea aqueous solution supply system
124 2nd acidic absorption liquid supply system
131 Combustor 133,
142 3rd carbon dioxide supply system
141 Boiler
151 Arithmetic control device
181 Off- gas exhaust port
191 Member
192 Umbrella member
193 Cylinder member
194 Support member
195 Off-gas supply port
L Gas-liquid interface
The scope of the claims
[Claim 1]
　A fertilizer production plant for producing fertilizer containing urea, and
　a urea production apparatus for producing the urea using ammonia, and
　an off-gas of the fertilizer production plant containing ammonia as an acidic absorber. A 　fertilizer production plant
　comprising a scrubber having an internal space for contact, wherein the acidic absorbent contains carbon dioxide
.
[Claim 2]
　A reformer for reforming a methane-containing gas,
　a carbon dioxide recovery device for recovering carbon dioxide generated in the reformer , and
　carbonic acid for producing the carbonic acid using the recovered carbon dioxide. 　The fertilizer production plant according to claim 1 , further
　comprising a production apparatus
.
[Claim 3]
　A compressor for boosting the carbon dioxide that is recovered and supplied to the urea production apparatus, and first carbon dioxide for supplying the carbon dioxide that has been pressurized in the compressor
　to the urea production apparatus. carbon supply system,
　a second carbon dioxide supply system for the carbon dioxide has been boosted is supplied to the carbonate production apparatus in the compressor
　provided with
　, characterized in that, fertilizer production plant according to claim 2 ..
[Claim 4]

　The fertilizer production plant according to claim 2 or 3, 　wherein the carbonic acid production apparatus includes a microbubble generator for producing the carbonic acid by dissolving carbon dioxide in water .
[Claim 5]

　The fertilizer production plant according to any one of claims 1 to 4, further comprising an 　ammonium carbonate supply system for supplying the acidic absorption liquid after the off-gas contact with the scrubber to the urea production apparatus. ..
[Claim 6]
　The fertilizer production plant, equipped with a solids removal scrubber for removing solid content of the off gas,
　the scrubber is positioned downstream of the solids removal scrubber in the flow direction of the off-gas
　and wherein the The fertilizer production plant according to any one of claims 1 to 5.
[Claim 7]

　The fertilizer production plant according to claim 6, further 　comprising an acid absorption liquid supply system for supplying the acid absorption liquid after the off-gas contact with the scrubber to the solid content removing scrubber .
[Claim 8]
　The fertilizer production plant uses
　a urea aqueous solution supply system for supplying the urea aqueous solution produced by the urea production apparatus to the solid content removing scrubber, and
　the urea aqueous solution after the off-gas contact with the solid content removing scrubber.
　The fertilizer production plant according to claim 6 or 7, further comprising a urea aqueous solution return system for returning to the production apparatus .
[Claim 9]

　Any of claims 6 to 8, further 　comprising an integrated scrubber including the solid content removing scrubber and the scrubber integrally configured with the solid content removing scrubber above the solid content removing scrubber. The fertilizer production plant according to item 1.
[Claim 10]
　Any of claims 1 to 9 　, further
　comprising a combustor for combusting fuel and a third carbon dioxide supply system for supplying carbon dioxide generated in the combustor to the internal space.
The fertilizer production plant according to item 1.
[Claim 11]
　The fertilizer production plant is equipped with a
　reformer for reforming the methane-containing gas, and the reformer uses the heat generated by the combustion of the fuel in the combustor to reform the methane-containing gas.
　The fertilizer production plant according to claim 10, characterized in that it is configured to perform quality .
[Claim 12]
　The fertilizer production plant is equipped with a reformer for reforming methane-containing gas, the
　combustor includes a boiler, and the
　reformer uses steam generated by combustion of the fuel in the boiler.
　The fertilizer production plant according to claim 10 or 11, wherein the fertilizer production plant is configured to reform the methane-containing gas .
[Claim 13]
　The fertilizer production plant, equipped with a granulator for granulating urea produced in the urea production unit,
　the off-gas of the fertilizer manufacturing plant includes a off-gas of the granulation device
　, characterized in that, claims The fertilizer production plant according to any one of 1 to 12.
[Claim 14]
　A method for producing fertilizer containing
　urea, in which the urea production step of producing the urea using ammonia and
　the off gas generated during the production of the fertilizer, which contains ammonia, are brought into contact with the acidic absorbent. A 　method for producing a fertilizer , which comprises a contact step of causing the
　acid absorption liquid to contain carbon dioxide