WO2019234816A1 - Fertilizer production plant and fertilizer production method - Google Patents

Abstract

This fertilizer production plant 100 is for producing a fertilizer containing urea, the fertilizer production plant 100 being characterized by comprising a urea production device 22 for the purpose of producing urea by using ammonia, and a scrubber 80B having an interior space for the purpose of bringing into contact with an acidic absorption solution an off-gas from the fertilizer production plant 100 that is an off-gas containing ammonia, wherein the acidic absorption solution contains carbonic acid.

Description

Fertilizer manufacturing plant and fertilizer manufacturing method

This disclosure relates to a fertilizer manufacturing plant and a method for manufacturing a fertilizer.

Technology for producing fertilizer using methane-containing gas such as natural gas is known. In this technique, first, hydrogen or the like is produced by reforming a methane-containing gas. For example, ammonia is produced from nitrogen in the air and the produced hydrogen. Next, an aqueous urea solution is produced from the produced ammonia. And the granulation of urea using the manufactured urea aqueous solution is performed, and a fertilizer is manufactured.

For example, off-gas containing ammonia is generated during fertilizer production, such as during urea granulation. Therefore, the generated off gas is discharged into the atmosphere after the exhaust gas treatment is performed. A technique described in Patent Document 1 is known as a processing technique for a gas containing ammonia. Patent Document 1 describes a sulfuric acid scrubber for bringing a sulfuric acid aqueous solution into contact with a gas containing ammonia (see particularly FIG. 1). In the sulfuric acid scrubber, ammonium sulfate (ammonium sulfate) is generated by contacting the sulfuric acid aqueous solution with a gas containing ammonia. Thereby, ammonia in off-gas is removed.

US Pat. No. 9,464,009

安 Ammonium sulfate aqueous solution produced by ammonia treatment in off-gas can usually be granulated and used as fertilizer. However, additional cost is required for the additional installation of ammonium sulfate granulation equipment. Moreover, since sulfuric acid aqueous solution is used in a sulfuric acid scrubber, maintenance is complicated. Therefore, a simple treatment technique that does not generate ammonium sulfate is desired for off-gas containing ammonia.

One embodiment of the present invention aims to provide a fertilizer manufacturing plant and a method for manufacturing fertilizer that can be easily processed without producing ammonium sulfate for off-gas containing ammonia.

(1) A fertilizer production plant according to an embodiment of the present invention is:
A fertilizer production plant for producing fertilizers containing urea,
A urea production apparatus for producing the urea using ammonia;
A scrubber having an internal space for contacting the offgas containing the ammonia, which is an offgas of the fertilizer production plant, with the acidic absorbent,
The acidic absorbing liquid contains carbonic acid.

According to the configuration of (1) above, ammonia in off-gas can be absorbed using an acidic absorbent containing carbonic acid that is easy to handle. Thereby, ammonia in off-gas can be removed without producing ammonium sulfate, and off-gas generated in the fertilizer production plant can be easily treated.

(2) In some embodiments, in the configuration of (1) above,
A reformer for reforming methane-containing gas;
A carbon dioxide recovery device for recovering carbon dioxide produced in the reformer;
A carbonic acid producing apparatus for producing the carbonic acid using the recovered carbon dioxide,
It is characterized by providing.

According to the configuration of (2) above, the acidic absorbing liquid can be manufactured using carbon dioxide generated by reforming methane-containing gas such as natural gas.

(3) In some embodiments, in the configuration of (2) above,
A compressor for increasing the pressure of the recovered carbon dioxide and supplied to the urea production apparatus;
A first carbon dioxide supply system for supplying the carbon dioxide boosted in the compressor to the urea production apparatus;
A second carbon dioxide supply system for supplying the carbon dioxide boosted in the compressor to the carbonic acid production apparatus;
It is characterized by providing.

According to the configuration of (3) above, the pressurized carbon dioxide can be supplied to both the urea production apparatus and the carbonic acid production apparatus. Thereby, 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 pressure increase, the production amount of carbonic acid can be increased.

(4) In some embodiments, in the configuration of (2) or (3) above,
The carbonic acid production apparatus includes a microbubble generator for producing the carbonic acid by dissolving carbon dioxide in water.

According to the configuration of (4) above, it is possible to lengthen the existence time of carbonic acid in water.

(5) In some embodiments, in any one of the above configurations (1) to (4),
An ammonium carbonate supply system for supplying the acid absorbing liquid after the off-gas contact in the scrubber to the urea production apparatus is provided.

According to the configuration of (5) above, ammonium carbonate contained in the acidic absorbent after contact with off-gas can be used as a raw material for urea production.

(6) In some embodiments, in any one of the above configurations (1) to (5),
The fertilizer production plant includes a solid content removal scrubber for removing solid content in the off gas,
The scrubber is disposed downstream of the solid content removal scrubber in the flow direction of the off gas.

According to the configuration of (6) above, the solid content contained in the offgas of the fertilizer production plant can be removed. And the ammonia in off gas after solid content removal can be removed from off gas by a scrubber.

(7) In some embodiments, in the configuration of (6) above,
An acidic absorbing liquid supply system for supplying the acidic absorbing liquid after the off-gas contact in the scrubber to the solid content removing scrubber is provided.

According to the configuration of (7) above, it is possible to supply the acidic absorbing liquid after the off-gas contact to the solid content removing scrubber. Thereby, even if the water content is reduced in the solid content removal scrubber by evaporation, the water content of the solid content removal scrubber can be recovered. As a result, it is possible to reduce the amount of new water used from the outside for recovering the amount of water in the solid content removing scrubber.

(8) In some embodiments, in the above configuration (6) or (7),
The fertilizer production plant is
A urea aqueous solution supply system for supplying the urea aqueous solution produced by the urea production apparatus to the solid content removing scrubber;
A urea aqueous solution return system for returning the urea aqueous solution after the off-gas contact in the solid content removing scrubber to the urea production apparatus.

According to the configuration of (8) above, the solid content in the off-gas can be removed using the urea aqueous solution manufactured by the urea manufacturing apparatus. Thereby, the usage-amount of the new water from the outside for solid content removal can be reduced. Moreover, the fertilizer manufacturing plant can manufacture a fertilizer using the urea aqueous solution returned from the solid content removal scrubber.

(9) In some embodiments, in any one of the configurations (6) to (8) above,
An integrated scrubber comprising: the solid content removing scrubber; and the scrubber configured integrally with the solid content removing scrubber above the solid content removing scrubber.

According to the configuration of (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.

(10) In some embodiments, in any one of the above configurations (1) to (9),
A combustor for burning fuel;
And a third carbon dioxide supply system for supplying carbon dioxide generated in the combustor to the internal space of the scrubber.

According to the configuration of (10) above, the partial pressure of carbon dioxide in the gas phase in the internal space for bringing the off gas into contact with the acidic absorbent can be increased. Thereby, it can suppress that a carbon dioxide is discharge | released to a gaseous phase from an acidic absorption liquid, and can extend the presence time of the carbonic acid in an acidic absorption liquid.

(11) In some embodiments, in the configuration of (10) above,
The fertilizer manufacturing plant includes a reforming device for reforming methane-containing gas,
The reformer is configured to reform the methane-containing gas using heat generated by combustion of the fuel in the combustor.

According to the configuration of (11) above, it is possible to reform methane-containing gas such as natural gas using heat generated by fuel combustion.

(12) In some embodiments, in the configuration of the above (10) or (11),
The fertilizer manufacturing plant includes a reforming device for reforming methane-containing gas,
The combustor includes a boiler,
The reformer is configured to reform the methane-containing gas using steam generated by combustion of the fuel in the boiler.

According to the configuration of (12) above, the reforming of the methane-containing gas such as natural gas can be performed using the steam generated in the boiler.

(13) In some embodiments, in any one of the above configurations (1) to (12),
The fertilizer production plant includes a granulation device for granulating urea produced in the urea production device,
The offgas of the fertilizer manufacturing plant includes the offgas of the granulator.

According to the configuration of (13) above, ammonia generated at the time of granulation of the urea aqueous solution in the granulator can be removed from the off-gas by contact with the acidic absorbent.

(14) A method for producing a fertilizer according to at least one embodiment of the present invention comprises:
A method for producing a fertilizer for producing a fertilizer containing urea,
A urea production step of producing the urea using ammonia;
A contact step of contacting offgas generated during the manufacture of the fertilizer and containing ammonia with an acidic absorbent.
The acidic absorbing liquid contains carbonic acid.

According to the configuration of (14) above, ammonia in the offgas can be absorbed using an acidic absorbent containing carbonic acid that is easy to handle. Thereby, ammonia in off-gas can be removed without producing ammonium sulfate, and off-gas generated during the production of fertilizer can be easily treated.

According to at least one embodiment of the present invention, it is possible to provide a fertilizer manufacturing plant and a fertilizer manufacturing method that can be easily processed without producing ammonium sulfate for off-gas containing ammonia.

It is a systematic diagram of a fertilizer manufacturing plant concerning a 1st embodiment of the present invention. It is a systematic diagram which shows the off gas processing unit 80 in the fertilizer manufacturing plant shown in FIG. It is a flowchart which shows the manufacturing method of the fertilizer which concerns on 1st Embodiment of this invention. It is a systematic diagram of the fertilizer manufacturing plant which concerns on 2nd Embodiment of this invention. It is a systematic diagram which shows the off gas processing unit in the fertilizer manufacturing plant shown in FIG. It is a systematic diagram which shows the off gas processing unit in the fertilizer manufacturing plant which concerns on 3rd Embodiment of this invention. It is a systematic diagram of the fertilizer manufacturing plant which concerns on 4th Embodiment of this invention. It is a figure which shows the component contained in each of a gaseous phase and a liquid phase in the internal space of the scrubber in FIG. It is a systematic diagram of the fertilizer manufacturing plant which concerns on 5th Embodiment of this invention.

Hereinafter, some embodiments of the present invention will be described with reference to the accompanying drawings. However, the contents described in the following embodiments or the contents described in the drawings are merely examples, and can be arbitrarily changed and implemented without departing from the gist of the present invention. Moreover, each embodiment can be implemented in any combination of two or more. Furthermore, in each embodiment, the same code | symbol shall be attached | subjected about a common member, and the overlapping description is abbreviate | omitted for the simplification of description.

In addition, the dimensions, materials, shapes, relative arrangements, and the like of the components described in the embodiments or shown in the drawings are not intended to limit the scope of the present invention, but are merely illustrative examples. Absent.
For example, expressions expressing relative or absolute arrangements such as “in a certain direction”, “along a certain direction”, “parallel”, “orthogonal”, “center”, “concentric” or “coaxial” are strictly In addition to such an arrangement, it is also possible to represent a state of relative displacement with an angle or a distance such that tolerance or the same function can be obtained.
For example, an expression indicating that things such as “identical”, “equal”, and “homogeneous” are in an equal state not only represents an exactly equal state, but also has a tolerance or a difference that can provide the same function. It also represents the existing state.
For example, expressions representing shapes such as quadrangular shapes and cylindrical shapes represent not only geometrically strict shapes such as quadrangular shapes and cylindrical shapes, but also irregularities and chamfers as long as the same effects can be obtained. A shape including a part or the like is also expressed.
On the other hand, the expressions “comprising”, “comprising”, “comprising”, “including”, or “having” one constituent element are not exclusive expressions for excluding the existence of the other constituent elements.

FIG. 1 is a system diagram of a fertilizer production plant 100 according to the first embodiment of the present invention. The fertilizer manufacturing plant 100 is for manufacturing a fertilizer containing urea (urea fertilizer) from a hydrocarbon source such as methane-containing gas (natural gas or the like) or coal. In FIG. 1, methane containing gas is illustrated as a hydrocarbon source. The fertilizer production plant 100 includes a reformer 1, an ammonia production unit 10, a urea production unit 20, a granulator 61, and an off-gas treatment unit 80. In one embodiment of the present invention, a reformer 2, a carbon dioxide recovery device 3, and a methanation device 4 are provided in the subsequent stage of the reformer 1.

The reformer 1 is for reforming methane-containing gas. In one embodiment of the present 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.

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. 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 reformer (partial oxidation reforming reaction and steam reforming reaction)
CH ₄ + 0.5O ₂ → CO + 2H ₂ Formula (3)
CO + H ₂ O → CO ₂ + H ₂ Formula (2)

Therefore, in the reformer 1, carbon dioxide is generated from the methane-containing gas. However, about a part of carbon monoxide produced | generated from reaction of Formula (1) and Formula (3), reaction of Formula (2) does not advance but it remains as carbon monoxide. The remaining carbon monoxide is converted into carbon dioxide in the subsequent denaturing device 2.

The reaction represented by the formulas (1) and (2) can be carried out using any reforming catalyst. As the reforming catalyst, for example, an oxide of a transition metal such as nickel or platinum can be used. The reaction conditions may be, for example, about 900 ° C. to 1000 ° C. and about 2.5 MPa to 3.5 MPa at the outlet of the catalyst layer accommodated in the secondary reformer.

As described above, the reformer 1 also takes in air. For this reason, the gas discharged from the reforming apparatus 1 and supplied to the subsequent denaturing device 2 includes components derived from air. Specifically, the gas discharged from the reformer 1 includes nitrogen and the like.

The reformer 2 denatures carbon monoxide and water vapor in the gas supplied from the reformer 1 to obtain carbon dioxide and hydrogen. Therefore, in the denaturing device 2, the carbon monoxide concentration in the gas decreases, and instead, the carbon dioxide concentration increases. By changing carbon monoxide to carbon dioxide, carbon derived from carbon monoxide can be removed as carbon dioxide by the carbon dioxide collector 3 at the subsequent stage.

In the denaturing device 2, a chemical reaction represented by the following formula (4) occurs.
CO + H ₂ O → CO ₂ + H ₂ Formula (4)
As a catalyst for modifying carbon monoxide (modified catalyst), any modified catalyst can be used. Examples of the modification catalyst include a copper-zinc catalyst. The reaction conditions may be, for example, about 200 ° C. to 450 ° C. and about 2.5 MPa to 3.5 MPa at the outlet of the catalyst layer accommodated in the modifier 2.

The carbon dioxide recovery unit 3 is for recovering the carbon dioxide generated in the reformer 1. By collecting the carbon dioxide in the gas, it is possible to suppress the introduction of carbon dioxide into the ammonia production apparatus 12 at the subsequent stage and to suppress the influence on the ammonia generation 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 the 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.

The methanator 4 includes carbon dioxide that could not be recovered by the carbon dioxide collector 3 and carbon monoxide that was not converted to carbon dioxide by the denaturator 2 and was not recovered by the carbon dioxide collector 3. Are each converted to methane. In the methanator 4, the removal of carbon oxide such as carbon monoxide and carbon dioxide suppresses the introduction of carbon oxide into the subsequent ammonia production apparatus 12. Thereby, the influence on the ammonia production | generation catalyst (it mentions later) resulting from carbon oxide can be suppressed.

In the methanator 4, chemical reactions represented by the following formulas (5) and (6) occur.
CO ₂ + H ₂ → CO + H ₂ O Formula (5)
CO + 3H ₂ → CH ₄ + H ₂ O (6)
As a catalyst (methanation catalyst) for causing methanation, any methanation catalyst can be used. As a methanation catalyst, a nickel catalyst etc. can be mentioned, for example. The reaction conditions may be, for example, about 250 ° C. to 350 ° C. and about 2.0 MPa to 3.0 MPa at the outlet of the catalyst layer accommodated in the methanator 4.

The ammonia production unit 10 is for obtaining ammonia using at least the hydrogen obtained by the reformer 1 and the nitrogen in the air taken in by the reformer 1.

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.

The compressor 11 is for increasing the pressure of a raw material gas (including hydrogen and nitrogen and methane as an impurity) introduced into the ammonia production apparatus 12 at the subsequent stage. In the ammonia production apparatus 12, the ammonia generation reaction proceeds at a high pressure. Therefore, the ammonia generation reaction can be promoted by increasing the source gas to a high pressure by the compressor 11.

The ammonia production apparatus 12 is for obtaining ammonia by using at least hydrogen and nitrogen in the raw material gas. Among the generated ammonia, 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 an ammonia recovery apparatus 13 described later. In addition, the gas phase of the ammonia production apparatus 12 includes surplus hydrogen and nitrogen (unreacted nitrogen), and also includes unreacted methane.

In the ammonia production apparatus 12, a chemical reaction represented by the following formula (7) occurs.
N ₂ + 3H ₂ → 2NH ₃ Formula (7)
As the catalyst for generating ammonia (ammonia production catalyst), any ammonia production catalyst can be used. As an ammonia production | generation catalyst, the iron catalyst containing a triiron tetroxide etc. can be mentioned, for example. The reaction conditions may be, for example, about 400 ° C. to 480 ° C. and about 12 MPa to 20 MPa at the outlet of the catalyst layer accommodated in the ammonia production apparatus 12.

The ammonia recovery device 13 recovers 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. Thereby, 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 in the same manner as the ammonia in the liquid phase of the ammonia production apparatus 12 described above, and then supplied to the urea production unit 20 described later.

The hydrogen recovery device 14 is for recovering surplus hydrogen in the ammonia production device 12. Excess hydrogen recovered by the hydrogen recovery device 14 is returned to the space between the methanator 4 and the compressor 11 (the front stage of the compressor 11) through the hydrogen circulation system 72. On the other hand, hydrogen that could not be recovered and methane that was not recovered are supplied to the reformer 1 or a boiler (not shown) together with nitrogen that has not been recovered, and are combusted and used as fuel.

The hydrogen recovery device 14 can have any configuration as long as it can recover hydrogen. Specifically, for example, hydrogen in the gas can be recovered by using an arbitrary hydrogen separation membrane.

The urea production unit 20 is for obtaining urea using at least the carbon dioxide obtained by the reformer 1 and the ammonia obtained by the ammonia production unit 10. The carbon dioxide used in the urea production unit 20 is recovered by the carbon dioxide recovery unit 3 described above. The ammonia used in the urea production unit 20 is ammonia produced by the above ammonia production unit and is supplied through the ammonia supply system 71.

The urea production unit 20 includes a compressor 21 and a urea production apparatus 22.

The compressor 21 is for increasing the pressure of carbon dioxide recovered by the carbon dioxide recovery device 3 and supplied to the urea production apparatus 22 (described later). The pressurized 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 urea carbon dioxide boosted in the compressor 21 to the urea production apparatus 22.

Since the urea production reaction proceeds at a high pressure in the urea production apparatus 22, the urea production reaction can be promoted by increasing the raw material gas to a high pressure by the compressor 21. The produced urea is supplied to a granulator 61 which will be described later.

Further, the carbon dioxide boosted by the compressor 21 is also supplied to a microbubble generator 116 (a carbonic acid producing apparatus, which will be described later) through a second carbon dioxide supply system 118. The second carbon dioxide supply system 118 is for supplying the carbon dioxide boosted in the compressor 21 to the microbubble generator 116.

By providing the compressor 21, the first carbon dioxide supply system 121, and the second carbon dioxide supply system 118, the pressurized carbon dioxide is supplied to both the urea production apparatus 22 and the microbubble generator 116 (carbonic acid production apparatus). Can supply. Thereby, 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 pressure increase, the production amount of carbonic acid can be increased.

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 generate urea. The urea produced is liquid here. In addition to the carbon dioxide compressed by the compressor 21, the urea production device 22 is supplied with ammonia that has been recovered by an ammonia recovery device 13 described later and whose pressure has been increased by a compressor (high pressure pump) 76. In the urea production apparatus 22, a chemical reaction represented by the following formula (8) occurs.
2NH ₃ + CO ₂ → (NH ₂ ) ₂ CO + H ₂ O (8)
The conditions for generating urea are not particularly limited. For example, the temperature can be set to about 170 to 200 ° C. and about 13 to 18 MPa at the outlet of the urea production apparatus 22.

The granulator 61 is for granulating the urea produced | generated in the urea manufacturing apparatus 22. FIG. In the granulator 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 granulation of urea is shipped and used as fertilizer.

The size of the granular urea is not particularly limited, but for example, the particle size can be about 2 mm to 6 mm.

The off gas processing unit 80 is for processing off gas of the fertilizer manufacturing plant 100. However, in one embodiment of the present invention, the offgas processed by the offgas processing unit 80 includes the offgas of the granulating device 61. Thereby, ammonia generated at the time of granulation of the urea aqueous solution in the granulator 61 can be removed from the off-gas by contact with the acidic absorbent.

The configuration of the off-gas processing unit 80 will be described with reference to FIG.

FIG. 2 is a system diagram showing an off-gas treatment unit 80 in the fertilizer manufacturing plant 100 shown in FIG. The off-gas processing unit 80 includes a solid content removing scrubber 80A and a scrubber 80B. That is, the fertilizer manufacturing plant 100 includes a solid content removing scrubber 80A and a scrubber 80B.

The solid content removal scrubber 80A is for removing the solid content in the off-gas. The solid content here is, for example, solid urea powder contained in the off-gas of the granulator 61. By providing the solid content removal scrubber 80A, it is possible to remove the solid content (for example, solid urea powder) contained in the off-gas of the fertilizer manufacturing plant 100. And the ammonia in the off gas after solid content removal can be removed from the off gas by the scrubber 80B.

The solid content removing scrubber 80A includes a casing 81 having an internal space 81a through which off-gas flows, a nozzle 83 for sprinkling water into the internal space 81a, and neutral water such as fresh water, medium water, and industrial water. (With a pH of about 7)). Since the inside of the solid content removing scrubber 80A is usually at a high temperature, liquid water evaporates. Therefore, water is sprayed by the nozzle 83 in order to replenish the evaporated liquid water.

In addition, since neutral water is sprinkled in the solid content removal scrubber 80A, some ammonia in the offgas 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 outside the solid content removing scrubber 80A through a drainage system (not shown), and the ammonia in the extracted liquid is processed. You may do it.

The solid content removing scrubber 80A includes an extraction system 86, a pump 82, and a nozzle 84. The extraction system 86 is for extracting the water remaining in the internal space 81 a by being sprayed by the nozzle 83 (including dissolved solids, the same applies to the remaining water below) to the outside of the housing 81. The pump 82 is for extracting water remaining in the internal space 81 a and flowing it to the system 86. The nozzle 84 is for sprinkling water that has flowed through the extraction system 86 into the internal space 81a.

A part of the water flowing through the extraction system 86 is extracted to the outside of the solid content removal scrubber 80A through a drainage system (not shown) from the viewpoint of suppressing the concentration of the solid content, and is drained. Moreover, the nozzle 84 is comprised so that water may be injected toward the tray 85 (for example, comprised with a perforated plate) installed in the middle of the off-gas flow. Thereby, the solid content deposited on the tray 85 is washed away (details will be described later).

The off gas supplied to the solid content removal scrubber 80A through the off gas supply system 111 flows upward in the internal space 81a of the casing 81. At this time, the off-gas is installed in the middle of the off-gas flow, and comes into contact with a tray 85 constituted by a perforated plate, for example. Thereby, 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. Thereby, excessive solid analysis is suppressed in the tray 85, and an increase in off-gas pressure loss is suppressed.

On the other hand, the off-gas from which the solid content has been removed by deposition 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 disposed downstream of the solid content removing scrubber 80A in the off gas flow direction.

The scrubber 80B has an internal space 91a for bringing the offgas containing ammonia and the offgas of the fertilizer manufacturing plant 100 into contact with the acidic absorbent. The acidic absorbent that is brought into contact with the offgas contains carbonic acid. The off-gas after removal of ammonia in the scrubber 80B is exhausted to the atmosphere through the exhaust system 113.

The scrubber 80B includes a casing 91 having an internal space 91a through which off-gas flows, a nozzle 93 for spraying water into 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 normally hot, liquid water evaporates. Therefore, water is sprayed by the nozzle 93 in order to replenish the evaporated liquid water.

The scrubber 80B includes an extraction system 96, a pump 92, and a nozzle 94. The extraction system 96 is for extracting the water retained in the internal space 91 a by being sprayed by the nozzle 93 to the outside of the housing 91. The pump 92 is for extracting water staying in the internal space 91 a and flowing it to the system 96. The nozzle 94 is for sprinkling water that has flowed through the extraction system 96 into the internal space 91a. The nozzle 94 injects water toward a tray 98 constituted by, for example, a perforated plate.

Here, in the scrubber 80B, the water staying in the internal space 91a is drawn out of the housing 91 as described above. In the scrubber 80B, as will be described in detail later, the acidic absorbing liquid sprayed from the nozzle 94 and the off gas containing ammonia are contacted. Therefore, the water staying in the internal space 91a includes ammonia absorbed in the acidic absorbent and the acidic absorbent after the off-gas contact. The water staying in the internal space 91a includes water sprinkled by the nozzle 93. And the ammonia in offgas may be absorbed to some extent by the sprinkled water. Further, the water staying in the internal space 91a includes an acidic absorbent supplied through a first acidic absorbent supply system 117 (described later).

Therefore, in one embodiment of the present invention, the water staying in the internal space 91a is uniformly referred to as an “acid absorbing solution” for convenience of explanation. In one embodiment of the present invention, the acidic absorbing liquid staying in the internal space 91 a is sprinkled from the nozzle 94 through the extraction system 96. Therefore, the acidic absorbing liquid circulates inside and outside the internal space 91a.

Note that in the water (acid absorbing liquid) staying in the internal space 91a, ammonia exists in the liquid as at least one form of ammonia molecules or ammonium ions.

The extraction system 96 for extracting the acidic absorbing liquid from the housing 91 includes an opening adjustment 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 is constant. Therefore, the amount of water sprayed through the nozzle 94 is constant.

A branch system 115 is connected to the extraction system 96. The branch system 115 includes, as an example of a carbonic acid production apparatus, a microbubble generator 116 for producing carbonic acid by dissolving carbon dioxide in water.

The microbubble generator 116 (an example of a carbonic acid production apparatus) is for producing carbonic acid using the carbon dioxide recovered by the carbon dioxide recovery device 3 (see FIG. 1). That is, the recovered carbon dioxide is dissolved in the acidic absorbing solution to generate carbonic acid in the acidic absorbing solution. The manufactured acidic absorbent is supplied to the casing 91 through the first acidic absorbent supply system 117.

A second carbon dioxide supply system 118 for supplying carbon dioxide from the compressor 21 is connected to the microbubble generator 116. By doing in this way, an acidic absorption liquid can be manufactured using the carbon dioxide produced | generated by modification | reformation of methane containing gas, such as natural gas.

The microbubble generator 116 is configured to generate, for example, bubbles having a size of about one hundred nanometers to several hundred micrometers in water. Specifically, for example, bubbles having a size of about 100 nm to about 500 μm are generated as the size of bubbles immediately after being generated by the microbubble generator 116. By providing such a microbubble generator 116, the existence time of carbonic acid in water can be extended.

The specific configuration of the microbubble generator 116 is not particularly limited, and for example, any method such as an ejector method, a cavitation method, a swirling flow method, and a pressure dissolution method can be adopted.

The second carbon dioxide supply system 118 includes an opening degree adjustment valve 119 for adjusting the supply amount of carbon dioxide. The opening degree of the opening degree adjusting valve 119 is controlled by the arithmetic and control unit 151 based on the pH measured by the pH meter 99a. That is, the pH of the acidic absorbent that stays in the internal space 91a due to ammonia absorption in the scrubber 80B gradually increases. Therefore, carbon dioxide is dissolved in the acidic absorbent such that the pH of the acidic absorbent that stays in the internal space 91a (that is, the acidic absorbent that flows 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 absorbent measured by the pH meter 99a (that is, the pH of the acidic absorbent sprayed by the nozzle 94) becomes small.

Specifically, the pH of the acidic absorbing solution measured by the pH meter 99a can be set to, for example, about 4 or more and 6.5 or less, and a smaller pH is preferable in this range. By controlling the amount of carbon dioxide dissolved so that the pH range is within this range, absorption of ammonia into the acidic absorbent can be promoted. Further, the absorbed ammonia is likely to be present as ammonium ions in the acidic absorbing solution, and re-scattering of ammonia into the gas phase can be suppressed.

Although not shown, the arithmetic and control unit 151 includes a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), a HDD (Hard Disk Drive), a control circuit, and the like. The stored predetermined control program is implemented by the CPU.

In the fertilizer manufacturing plant 100, the microbubble generator 116 generates microbubbles in the acidic absorbent flowing through the branch line 115, so that carbon dioxide is dissolved in the acidic absorbent flowing through the branch line 115. As a result, an acidic absorbent containing carbonic acid is generated, and the acidic absorbent produced by the microbubble generator 116 is supplied to the housing 91 through the first acidic absorbent supply system 117. The acidic absorbent supplied to the casing 91 is sprinkled into the internal space 91a of the casing 91 through the extraction system 96 and the nozzle 94. The sprinkled acidic absorbent absorbs ammonia in the off gas by coming into contact with the off gas and stays in the internal space 91 a of the housing 19.

The retained acidic absorbent contains ammonium carbonate produced by absorption of ammonia. Therefore, a part of the acidic absorbent 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 urea absorbent 22 with the acidic absorbent after the offgas contact in the scrubber 80B. By providing the ammonium carbonate supply system 114, ammonium carbonate contained in the acidic absorbent after contact with the off-gas can be used as a raw material for urea production.

According to the fertilizer manufacturing plant 100 having the above configuration, ammonia in off-gas can be absorbed using an acidic absorbent containing carbonic acid that is easy to handle without using an aqueous sulfuric acid solution. Thereby, ammonia in offgas can be removed without producing ammonium sulfate, and offgas generated in the fertilizer manufacturing plant 100 can be easily treated.

FIG. 3 is a flowchart showing a method for manufacturing a fertilizer according to the first embodiment of the present invention. The fertilizer manufacturing method shown in FIG. 3 relates to a fertilizer manufacturing method for manufacturing a fertilizer containing urea. However, in FIG. 3, for simplification of description, the production of urea and the absorption removal of ammonia in the off-gas of the granulating apparatus 61 are mainly described.

3 can be implemented, for example, in the fertilizer manufacturing plant 100 shown in FIG. 1 described above. Therefore, in the following, FIG. 3 will be described with reference to FIG. 1 as appropriate.

In the fertilizer manufacturing plant 100, hydrogen is produced by reforming methane-containing gas such as natural gas. And ammonia and methanol are manufactured using the manufactured hydrogen. Further, carbon dioxide produced as a by-product during the reforming is recovered by the carbon dioxide recovery device 3 (step S1). And urea is manufactured using the collect | 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. And the fertilizer is manufactured using the manufactured urea, ammonia, and methanol.

Further, the microbubble generator 116 (see FIG. 2) uses the carbon dioxide collected by the carbon dioxide collector 3 to produce an acidic absorbent containing carbonic acid (step S2). The produced acidic absorbing liquid is brought into contact with offgas (for example, offgas of the granulating device 61) which is offgas generated during production of fertilizer and contains ammonia in the scrubber 80B (step S3, contact step). As a result, ammonia in the off-gas is absorbed by the acidic absorbent and ammonium carbonate is generated in the acidic absorbent.

Next, the acid absorbing liquid after contact with the off-gas is supplied through the ammonium carbonate supply system 114 (step S4). And in the urea manufacturing apparatus 22, urea is manufactured using the ammonium carbonate in the acidic absorbing liquid after the off-gas contact (step S5, urea manufacturing step).

According to the above production method, ammonia in off-gas can be absorbed using an acidic absorbent containing carbonic acid that is easy to handle without using an aqueous sulfuric acid solution. Thereby, ammonia in off-gas can be removed without producing ammonium sulfate, and off-gas generated during the production of fertilizer can be easily treated.

Here, the present inventors have shown in FIG. 2 in order to confirm the influence of the water spray amount of the acidic absorbent through the nozzle 94 and the water spray amount through the nozzle 93 on the ammonia removal rate in the scrubber 80B. The following tests were conducted using the scrubber 80B. In this test, the solid content removing scrubber 80A shown in FIG. 2 is not used to simplify the test. In this test, a small-scale test apparatus simulating the scrubber 80B was produced for the sake of simplicity. And the flow volume of the acidic absorption liquid at the time of the test shown below, and the off-gas flow volume were converted into the flow volume equivalent to the urea production amount (for example, 3500 tons / day scale) in the actual fertilizer manufacturing plant 100, and were shown. *

Off-gas having an ammonia concentration of 100 mg / Nm ³ (normal lube, hereinafter the same) at an off-gas supply port (not shown) in 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 absorbent 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 of water (flow rate) of the acidic absorbent through the nozzle 94. In addition, the pH was also measured with a pH meter 99a. These results are shown in Table 1 below (Examples 1 to 4).

 

As shown in Table 1, it was found that the ammonia removal rate was improved as the amount of water sprayed through the nozzle 94 increased, that is, as the flow rate of the acid absorbing solution with respect to the off-gas increased.

Next, in the same manner as in Examples 1 to 4, except that the amount of acidic absorbent extracted through the ammonium carbonate supply system 114 was changed to 15% by volume of the acidic absorbent flowing through the extraction system 96, the offgas was removed. The ammonia concentration and pH at the outlet were measured. These results are shown in Table 2 below (Examples 5 to 8).

As shown in Table 2, even if the extraction amount is increased, the amount of water sprayed through the nozzle 94 is larger, that is, as the flow rate of the acid absorbent relative to the off-gas is larger, as in Table 1 above. It was found that the ammonia removal rate was improved. Moreover, when Table 1 and Table 2 are compared, for example, if the extraction conditions are the same except that the extraction amount is different (Example 1 and Example 5), the ammonia removal rate is improved when the extraction amount is large. I understood.

From the results of Tables 1 and 2 above, the larger the amount of water sprayed through the nozzle 94 and the amount of water sprayed through the nozzle 93, the greater the ammonia removal rate in the scrubber 80B. I understood.

FIG. 4 is a system diagram of a fertilizer production plant according to the second embodiment of the present invention. The fertilizer manufacturing plant 100A shown in FIG. 4 includes a second acidic absorbent supply system 124 for supplying the acidic absorbent after the off-gas contact in the scrubber 80B to the solid content removing scrubber 80A. Moreover, the fertilizer manufacturing 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 manufactured by the urea manufacturing apparatus 22 to the solid content removing scrubber 80A. The urea aqueous solution returning system 122 is for returning the urea aqueous solution (solid content, including the acidic aqueous solution supplied from the scrubber 80B) after the off-gas contact in the solid content removing scrubber 80A to the urea manufacturing apparatus 22.

FIG. 5 is a system diagram showing the off-gas treatment unit 80 in the fertilizer manufacturing plant 100A shown in FIG. In the scrubber 80B of the fertilizer manufacturing plant 100A, a part of the acidic absorbent extracted from the housing 91 and flowing through the extraction system 96 is removed through the second acidic absorbent supply system 124 (acid absorbent supply system). It is supplied to the water supply system 87 of the scrubber 80A. The adjustment of the supply amount is performed by adjusting the opening degree of the opening degree adjustment valve 120 provided in the second acidic absorbent supply system 124. By supplying to the water supply system 87, the acidic absorbent after the off-gas contact in the scrubber 80B is sprinkled into the internal space 81a of the solid content removing scrubber 80A.

By providing the second acidic absorbent supply system 124, the acidic absorbent after the off-gas contact can be supplied to the solid content removing scrubber 80A. Thereby, even if water content decreases in the solid content removal scrubber 80A due to evaporation, the water content of the solid content removal scrubber 80A can be recovered. As a result, it is possible to reduce the amount of new water used from the outside for recovering the amount of water in the solid content removing scrubber 80A.

The off-gas treatment unit 80 in the fertilizer manufacturing 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 manufactured by the urea manufacturing apparatus 22 to the solid content removing scrubber 80A. The urea aqueous solution return system 122 is for returning the urea aqueous solution after the off-gas contact in the solid content removing scrubber 80 </ b> A to the urea production apparatus 22.

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 using the urea aqueous solution manufactured by the urea manufacturing apparatus 22. Thereby, the usage-amount of the new water from the outside for solid content removal can be reduced. Moreover, the fertilizer manufacturing plant 100A can manufacture the fertilizer using the urea aqueous solution returned from the solid content removing scrubber 80A.

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. Thereby, the discharge | release to the exterior of urea can be suppressed and the yield of urea can be improved.

Furthermore, as described above, the acidic absorbent after absorption of ammonia is supplied to the solid content removal scrubber 80A of the fertilizer manufacturing plant 100A through the second acidic absorbent supply system 124. Here, ammonium carbonate is contained in the acidic absorbent after absorption of ammonia. For this reason, 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. Thereby, the urea manufacturing apparatus 22 can manufacture urea using the ammonium carbonate produced | generated by ammonia absorption.

Here, the present inventors have shown in FIG. 5 in order to confirm the influence on the ammonia removal rate in the offgas by the supply of the solid content removal scrubber 80A of the acidic absorbent through the second acidic absorbent supply system 124. The following tests were performed using the off-gas treatment unit 80. However, for the sake of 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 described above, for the sake of simplicity, a small-scale test apparatus simulating the off-gas treatment unit 80 shown in FIG. 5 was produced in this test. And 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 manufacturing plant 100A and shown.

First, as Example 9, the second acidic absorbent supply system 124 is not provided, and 10.0 ton / h of fresh water (fresh water) is supplied to the solid content removal scrubber 80A through the water supply system 87, and the water supply system 97, 7.5 ton / h of fresh water (fresh water) was supplied to the scrubber 80B. Therefore, in Example 9, the total new water supply is 17.5 ton / h.

Then, a gas containing a predetermined amount of ammonia (simulated offgas) was flowed through the solid content removal scrubber 80A and the scrubber 80B in this order as a gas imitating offgas. At this time, the simulated off gas was continuously flowed at a predetermined flow rate. Then, the respective ammonia concentrations at the off-gas supply port and off-gas discharge port (both not shown) of the scrubber 80B were measured, and the ammonia removal rate at the scrubber 80B was calculated. As a result, the ammonia removal rate was 55% (Example 9).

Next, as Example 10, the supply amount of new water to the solid content removal scrubber 80A was set to 2.5 ton / h, the supply amount of new water to the scrubber 80B was set to 7.5 ton / h, and The test was conducted in the same manner as in Example 9 except that the supply amount of the acidic absorbent from the scrubber 80B to the solid content removing scrubber 80A through the second acidic absorbent supply system 124 was 7.5 ton / h. Therefore, in Example 10, the total new water supply is 10.0 ton / h.

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).

Further, as Example 11, the supply of new water to the scrubber 80B was set to 17.5 ton / h without supplying new water to the solid content removing scrubber 80A, and the second acidic absorbent was supplied. The test was performed in the same manner as in Example 9 except that the supply amount of the acidic absorbing liquid from the scrubber 80B through the system 124 to the solid content removing scrubber 80A was 17.5 ton / h. Therefore, in Example 11, the total new water supply is 17.5 ton / h.

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).

The results of Examples 9 to 11 are shown in Table 3 below.

When comparing Example 9 and Example 10, the ammonia removal rate was the same. However, the total supply amount of new water in Example 10 is smaller than that in Example 9. Specifically, the total supply amount of new water 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 absorbent from the scrubber 80B to the solid content removing scrubber 80A through the second acidic absorbent supply system 124, it is possible to reduce the amount of new water used while maintaining the ammonia removal rate.

Moreover, when Example 9 and Example 10 were compared, the new total supply amount of water was the same. However, in Example 11, the ammonia removal rate is improved compared to Example 9. Specifically, the ammonia removal rate was 55% in Example 9, but improved to 58% in Example 11. Therefore, by supplying the acidic absorbent from the scrubber 80B to the solid content removing scrubber 80A through the second acidic absorbent supply system 124, it is possible to improve the ammonia removal rate while keeping the new total water supply amount the same.

FIG. 6 is a system diagram showing an off-gas treatment unit 80 in a fertilizer production plant 100B according to the third embodiment of the present invention. The fertilizer manufacturing plant 100B includes, as the off-gas treatment unit 80, an integrated scrubber 80C including a solid content removal scrubber 80A and a scrubber 80B integrally formed with the solid content removal scrubber 80A above the solid content removal scrubber 80A. .

In the solid content removal scrubber 80A, an off-gas discharge port 181 is formed on the upper surface of the internal space 81a. Further, a member 191 that is constricted upward is provided above the off-gas discharge port 181. The lower end of the member 191 is open, and an offgas 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 cylindrical member 193 is connected to the upper end of the member 191. An umbrella member 192 is disposed above the tubular member 193, and the penetration of the acidic absorbent into the tubular member 193 is suppressed.

The umbrella member 192 is fixed to the tubular member 193 by a support member 194 that is disposed with a gap 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.

Off gas supplied through an off gas supply port (not shown) formed below the solid content removal scrubber 80A flows upward in the internal space 81a of the solid content removal scrubber 80A. At this time, for example, when the off gas comes into contact with the tray 85 formed 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.

The off gas that has flowed upward from the internal space 81a flows into the member 191 through the off gas discharge port 181. And the off gas which flowed in the inside of the member 191 flows through the inside of the cylindrical member 193 and the off gas supply port 195 as shown by a thick arrow in FIG. Thereby, off-gas is supplied to the internal space 91a of the scrubber 80B. Then, in the scrubber 80B, ammonia in the off gas is absorbed by the acidic absorbent. 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.

Since the integrated scrubber 80C is provided, the scrubber 80B can be integrally formed with the solid content removal scrubber 80A above the solid content removal scrubber 80A, so that the installation area of the scrubber (specifically, the off-gas treatment unit 80) is increased. Can be reduced.

FIG. 7 is a system diagram of a fertilizer manufacturing plant 100C according to the fourth embodiment of the present invention. The fertilizer manufacturing plant 100C includes a reformer 1 for reforming a methane-containing gas and a combustor 131 for burning fuel (heavy oil, kerosene, methane-containing gas, etc.). The reformer 1 is configured to reform the methane-containing gas using heat generated by the combustion of fuel in the combustor 131. By doing in this way, modification | reformation of methane containing gas, such as natural gas, can be performed using the heat | fever produced by combustion of fuel.

Further, the fertilizer manufacturing 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.

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. 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. Both ammonia (NH ₃ ) and carbon dioxide (CO ₂ ) in the gas phase exist as molecules.

On the other hand, carbon dioxide dissolved in the microbubble generator 116 (see FIG. 2) is present in the acidic absorbent as the liquid phase. Although carbon dioxide varies depending on the pH of the acidic absorbent, it exists in the acidic absorbent in the form of at least one of carbon dioxide molecules (CO ₂ ) or carbonate ions (HCO ₃ ⁻ ). In particular, carbon dioxide molecules are present as bubbles in the acidic absorbent, and carbonate ions are dissolved as ions in the acidic absorbent. In an embodiment of the present invention, for convenience of explanation, carbon dioxide molecules and carbonate ions are collectively referred to as “carbonic acid”.

When ammonia in the gas phase is absorbed by the acidic absorbent through the gas-liquid interface L, the absorbed ammonia is likely to exist as ammonium ions (NH ₄ ⁺ ) in the acidic absorbent. Ammonium ions have a high affinity for water molecules. Therefore, when ammonia exists as ammonium ions in the acidic absorbing liquid, re-release to the gas phase via the gas-liquid interface L is suppressed.

Also, carbonate ions in the acidic absorbent are suppressed from being released into the gas phase through the gas-liquid interface L due to the high affinity between carbonate ions and water. However, the carbon dioxide molecules in the acidic absorbing liquid are not easily so high in affinity between the carbon dioxide molecules and water that they are easily released into the gas phase through the gas-liquid interface L. When carbon dioxide molecules are released from the acidic absorbent into the gas phase, the pH of the acidic absorbent increases and ammonia is not easily absorbed.

Therefore, in the fertilizer manufacturing plant 100C, carbon dioxide is supplied to the gas phase of the internal space 91a. By doing in this way, the carbon dioxide partial pressure of the gaseous phase in the internal space 91a for making off gas contact an acidic absorption liquid can be raised. Thereby, it can suppress that a carbon dioxide molecule is discharge | released to a gaseous phase from an acidic absorption liquid, and the existence time of the carbonic acid in an acidic absorption liquid can be lengthened.

FIG. 9 is a system diagram of a fertilizer production plant 100D according to the fifth embodiment of the present invention. The fertilizer manufacturing plant 100D includes a reformer 1 for reforming a methane-containing gas. The fertilizer manufacturing plant 100D includes a boiler 141 for generating water vapor by combustion as an example of a combustor for burning fuel (heavy oil, kerosene, methane-containing gas, etc.).

The reformer 1 is configured to reform the methane-containing gas using water vapor generated by the combustion of fuel in the boiler 141, and the carbon dioxide generated by the combustion of fuel in the boiler 141 is 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.

By doing so, reforming of a methane-containing gas such as natural gas can be performed using the steam generated in the boiler 141. Further, the partial pressure of carbon dioxide in the gas phase in the internal space 91a of the scrubber 80B can be increased, and the duration of carbon dioxide in the acidic absorbent can be increased.

DESCRIPTION OF SYMBOLS 1 Reformer 2 Denaturer 3 Carbon dioxide collector 4 Methanator 10 Ammonia production unit 11, 21, 76 Compressor 12 Ammonia production device 13 Ammonia collection device 14 Hydrogen collection device 19, 81, 91 Housing 20 Urea production unit 22 Urea production apparatus 61 Granulator 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 Line 114 charcoal Ammonium supply system 115 Branch system 116 Microbubble generator 117 First acidic absorbent supply system 118 Second carbon dioxide supply system 121 First carbon dioxide supply system 123 Urea aqueous solution supply system 124 Second acidic absorbent supply system 131 Combustor 133 , 142 Third carbon dioxide supply system 141 Boiler 151 Arithmetic controller 181 Off gas discharge port 191 Member 192 Umbrella member 193 Cylindrical member 194 Support member 195 Off gas supply port L Gas-liquid interface

Claims (14)

1. A fertilizer production plant for producing fertilizers containing urea,
   A urea production apparatus for producing the urea using ammonia;
   A scrubber having an internal space for contacting the offgas containing the ammonia, which is an offgas of the fertilizer production plant, with the acidic absorbent,
   The fertilizer manufacturing plant, wherein the acidic absorbent includes carbonic acid.
2. A reformer for reforming methane-containing gas;
   A carbon dioxide recovery device for recovering carbon dioxide produced in the reformer;
   A carbonic acid producing apparatus for producing the carbonic acid using the recovered carbon dioxide,
   The fertilizer manufacturing plant of Claim 1 characterized by the above-mentioned.
3. A compressor for increasing the pressure of the carbon dioxide recovered and supplied to the urea production apparatus;
   A first carbon dioxide supply system for supplying the carbon dioxide boosted in the compressor to the urea production apparatus;
   A second carbon dioxide supply system for supplying the carbon dioxide boosted in the compressor to the carbonic acid production apparatus;
   The fertilizer manufacturing plant of Claim 2 characterized by the above-mentioned.
4. The fertilizer manufacturing plant according to claim 2 or 3, wherein the carbonic acid production device includes a microbubble generator for producing the carbonic acid by dissolving carbon dioxide in water.
5. The fertilizer production plant according to any one of claims 1 to 4, further comprising an ammonium carbonate supply system for supplying the urea-producing apparatus with the acidic absorbent after the off-gas contact in the scrubber. .
6. The fertilizer production plant includes a solid content removal scrubber for removing solid content in the off gas,
   The fertilizer production plant according to any one of claims 1 to 5, wherein the scrubber is disposed downstream of the solid content removal scrubber in the flow direction of the off-gas.
7. The fertilizer manufacturing plant according to claim 6, further comprising an acidic absorbent supply system for supplying the acidic absorbent after the off-gas contact in the scrubber to the solid content removing scrubber.
8. The fertilizer production plant is
   A urea aqueous solution supply system for supplying the urea aqueous solution produced by the urea production apparatus to the solid content removing scrubber;
   A fertilizer production plant according to claim 6 or 7, comprising a urea aqueous solution return system for returning the urea aqueous solution after the off-gas contact in the solid content scrubber to the urea production apparatus.
9. 9. An integrated scrubber comprising: the solid content removing scrubber; and the scrubber integrally formed with the solid content removing scrubber above the solid content removing scrubber. The fertilizer manufacturing plant of Claim 1.
10. A combustor for burning fuel;
    The fertilizer production plant according to any one of claims 1 to 9, further comprising a third carbon dioxide supply system for supplying carbon dioxide generated in the combustor to the internal space.
11. The fertilizer manufacturing plant includes a reforming device for reforming methane-containing gas,
    11. The fertilizer production according to claim 10, wherein the reformer is configured to reform the methane-containing gas using heat generated by combustion of the fuel in the combustor. plant.
12. The fertilizer manufacturing plant includes a reforming device for reforming methane-containing gas,
    The combustor includes a boiler,
    The fertilizer according to claim 10 or 11, wherein the reformer is configured to reform the methane-containing gas using water vapor generated by combustion of the fuel in the boiler. Production plant.
13. The fertilizer production plant includes a granulation device for granulating urea produced in the urea production device,
    The fertilizer manufacturing plant according to any one of claims 1 to 12, wherein the offgas of the fertilizer manufacturing plant includes the offgas of the granulating device.
14. A method for producing a fertilizer for producing a fertilizer containing urea,
    A urea production step of producing the urea using ammonia;
    A contact step of contacting offgas generated during the manufacture of the fertilizer and containing ammonia with an acidic absorbent.
    The method for producing a fertilizer, wherein the acidic absorbent includes carbonic acid.

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