JP2001097905A - Method for producing methanol - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing methanol capable of increasing production of methanol by effectively using excessive hydrogen in a gas formed in a reformer, capable of reducing discharge of carbon dioxide by effectively utilizing carbon dioxide and capable of decreasing an amount of steam to be fed to the reformer. SOLUTION: This method for producing methanol comprises a synthesis gas formation process for feeding a raw material gas comprising a hydrocarbon as a main component through a humidifier to the reformer, supplying steam to the humidifier and reacting the hydrocarbon with the steam to form a synthesis gas consisting essentially of hydrogen, carbon monoxide and carbon dioxide, a crude methanol synthesis process for reacting the synthesis gas on a methanol synthesis catalyst to synthesize crude methanol and a distillation process for distilling liquid crude methanol recovered from the synthesis process and separating liquid waste containing a low-boiling organic compound and a high-boiling organic compound from purified methanol. Carbon dioxide is supplied to at least one channel of a channel at the upstream side of the humidifier and a channel between the humidifier and the reformer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing methanol, and more particularly, to a method for producing methanol using carbon dioxide to increase the production of methanol.

[0002]

BACKGROUND OF THE INVENTION The present invention relates to a method for producing methanol,
In particular, the present invention relates to a method for producing methanol in which the production of methanol is increased using carbon dioxide.

[0003] Japanese Patent Application Laid-Open No. 1-180841 discloses a method for producing methanol (CH ₃ OH) from hydrocarbons such as natural gas by the steps described below.

(Syngas Generation Step) First, a gaseous hydrocarbon or a gaseous hydrocarbon which has been vaporized from a liquid hydrocarbon is reacted with steam in a reformer at a predetermined temperature under a nickel-based catalyst to obtain hydrogen ( H ₂ ), a synthesis gas containing carbon monoxide (CO) and carbon dioxide (CO ₂ ) as main components is generated.

[0005] The hydrocarbon is added with steam in a humidifier arranged on the upstream side of the reformer, and further supplied with superheated steam produced by a boiler or the like, and is converted into a gas containing hydrocarbons and steam. Introduced into the genitalia.

[0006] Since the steam reforming reaction is an endothermic reaction, the reformer is heated from the outside in the process of producing synthesis gas.

(Crude Methanol Synthesis Step) On the methanol synthesis catalyst, the synthesis gas is reacted at predetermined pressure and temperature with carbon monoxide and hydrogen or carbon dioxide and hydrogen to synthesize crude methanol.

(Distillation step) The liquid crude methanol recovered in the above synthesis step is distilled in one or more distillation columns, and an organic compound having a boiling point lower than that of methanol (hereinafter referred to as a low boiling organic compound), Waste water containing an organic compound having an boiling point higher than that of the organic acid and methanol (hereinafter, referred to as a high boiling point organic compound) is separated into purified methanol.

[0009] Methanol is produced through the above-described steps.

By the way, recently, as one of the measures against global warming,
And carbon dioxide from the factory (CO _Two) Reduce emissions
There is a growing need to do so.

In a plant for producing methanol from a natural gas such as the hydrocarbon, a reaction tube filled with a steam reforming catalyst is heated from the surroundings with a combustion gas in the reformer, thereby producing carbon monoxide and hydrogen. The heat required for the reaction (endothermic reaction) is supplied. In addition, a steam generator boiler is used to supplement the required amount of high-pressure steam consumed in the plant. Therefore, large amounts of carbon dioxide are contained in the combustion exhaust gas from reformers and steam generator boilers. In the future, the introduction of a carbon dioxide emission tax and the commencement of regulations on carbon dioxide emissions may reduce the economics of the plant.

On the other hand, in the method for producing methanol from natural gas, the concentration of hydrogen in the synthesis gas generated by the steam reforming reaction is necessary for reacting carbon monoxide and carbon dioxide in the synthesis gas to synthesize methanol. About 1.5 times the concentration to be used. Therefore, in the methanol synthesis step, in order to improve the reaction efficiency of the synthesis reactor, the unreacted gas after separating the synthesized methanol is circulated to the synthesis reactor, and a part of the unreacted gas is removed from the system. To release excess hydrogen. The circulation amount of the unreacted gas is set to a value that can reduce the heat generation rate during the reaction in the catalyst layer filled in the synthesis reactor.

[0013] For this reason, "INCREASED PRODUC
TION FROM EXISTING METHANOL PLANTS ”BY A. Englis
h, IA Forbes, MN Islam, JD Korchnak PRESE
NTEDTO: WORLD METHANOL CONFERENCE DECEMBER 2-4, 19
91 HYATT REGENCY HOTEL VANCOUVER, BC, CANADA, p.1-
FIG. 5 in the document of p12 discloses that carbon dioxide is supplied to a flow path for sending synthesis gas generated in a reformer to a methanol synthesis reactor in order to effectively use excess hydrogen in the synthesis gas. Have been.

[0014]

However, when a synthesis gas containing a large amount of carbon dioxide is supplied to the reactor in the crude methanol synthesis step, the activity of the methanol synthesis catalyst filled in the reactor may be reduced.

The present invention aims to increase the production of methanol by effectively utilizing the excess hydrogen in the gas generated in the reformer without causing a decrease in the activity of the methanol synthesis catalyst in the methanol synthesis step. An object of the present invention is to provide a method for producing methanol which can reduce carbon dioxide emissions by effectively utilizing carbon dioxide and reduce the amount of steam supplied to a reformer.

[0016]

In a method for producing methanol according to the present invention, a raw material gas containing hydrocarbon as a main component is supplied to a reformer through a humidifier and steam is supplied.
Reacting the hydrocarbon with the steam to produce a synthesis gas containing hydrogen, carbon monoxide and carbon dioxide as main components; and reacting the synthesis gas on a methanol synthesis catalyst to produce crude methanol. A crude methanol synthesis step for synthesizing, comprising a distillation step of distilling the liquid crude methanol recovered from the synthesis step to separate wastewater containing purified low-boiling organic compounds and high-boiling organic compounds and purified methanol, Carbon dioxide is supplied to at least one of the flow path on the upstream side of the humidifier and the flow path between the humidifier and the reformer.

In the method for producing methanol according to the present invention, the humidifier includes a first-stage humidifier and a second humidifier disposed downstream of the first-stage humidifier and upstream of the reformer. A wastewater collected in the distillation step is supplied to a circulating water flow path of the first-stage humidifier, and a raw material mainly containing hydrocarbons is supplied to a flow path on the upstream side of the first-stage humidifier. Allow supply of gas and carbon dioxide.

[0018] Carbon dioxide may be further supplied to at least one of the flow path between the first and second humidifiers and the flow path between the second humidifier and the reformer. I do.

In the method for producing methanol according to the present invention, the carbon dioxide to be supplied is carbon dioxide recovered from at least one of a combustion gas for heating the reformer and a combustion exhaust gas from a steam generator boiler. Preferably, there is.

In the method for producing methanol according to the present invention, the crude methanol synthesizing step is vertically divided into three chambers of a synthesis gas supply chamber, a cooling medium flow chamber and a methanol-containing gas retention chamber by two separators. A reactor, and a triple tube supported through the two separators and having an outer tube, an intermediate tube, and an inner tube arranged concentrically, wherein the upper end of the intermediate tube is lower than the upper end of the outer tube , The lower end of the inner pipe is located near the center of the intermediate pipe, only the inner pipe is opened at the upper end of the triple pipe, and formed by the intermediate pipe and the outer pipe at the lower end of the triple pipe Preferably, the reaction is performed using a reactor in which the formed annular space is opened, and the annular space is filled with the methanol synthesis catalyst.

In the method for producing methanol according to the present invention, the methanol synthesis catalyst is Cu, Zn, Al, Ga.
And an oxide containing M and at least one element selected from the group consisting of an alkaline earth metal element and a rare earth element, wherein the Cu, Zn, Al, Ga and M have an atomic ratio of Cu: Zn: Al: Ga: M. = 100: 10-200:
It is preferable that the composition has a composition of 1 to 20: 1 to 20: 0.1 to 20.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method for producing methanol according to the present invention will be described in detail with reference to the drawings.

(First Embodiment) FIG. 1 is a flow chart showing a process for producing methanol used in the first embodiment.

The method for producing methanol includes a synthesis gas generation step indicated by 1 in FIG. 1, a methanol synthesis step indicated by 2 in FIG. 1, and a distillation step indicated by 3 in FIG.

(1) Synthesis Gas Generation Step First, a raw material gas mainly composed of hydrocarbons, such as natural gas, is supplied to a desulfurizer, where a small amount of a sulfur compound contained in the raw material gas is removed. Is made. The raw material gas after desulfurization is introduced into a humidifier, where, for example, 150 to
Steam is added at 250 ° C. to near saturation pressure.

The humidified raw material gas is introduced into a reformer after being supplied with superheated steam produced by a boiler or the like. It is preferable that the amount of water vapor in the gas introduced into the reformer is approximately two to three times the volume flow rate of the raw material gas.

[0027] The raw material gas introduced into the reformer is, for example, 800 N under a nickel-based catalyst filled in the reformer.
It is reformed by steam introduced together with the raw material gas at ~ 1000 ° C to generate a synthesis gas containing hydrogen (H ₂ ), carbon monoxide (CO) and carbon dioxide (CO ₂ ) as main components.

The steam reforming reaction is an endothermic reaction. For this reason, the reformer is constituted by a reaction tube filled with the catalyst and a combustor surrounding the outer periphery of the reaction tube, and a fuel gas and air are supplied to the combustor for combustion, and the inside of the reaction tube is formed. For example, by heating to 700 to 900 ° C. and supplying reaction heat, an efficient steam reforming reaction is performed.

In the syngas generation step, the combustion exhaust gas generated in the boiler for producing the steam and the carbon dioxide in the combustion exhaust gas generated in the combustor are recovered, and are upstream and downstream of a humidifier to be described later. Used to feed at least one of the sides. As a method for recovering carbon dioxide from the combustion exhaust gas, a chemical absorption method using a normal amine absorbing liquid is used, but is not particularly limited as long as it is a method capable of efficiently recovering carbon dioxide.

(2) Crude Methanol Synthesis Step The synthesis gas is sent from the synthesis gas generation step 1 of FIG. 1 to the methanol synthesis step 2. At this time, the heat retained in the synthesis gas is recovered by, for example, a waste heat boiler, a humidifier, or a heat exchanger and cooled to approximately room temperature. As the temperature of the synthesis gas decreases in the heat recovery process, the water vapor contained in the synthesis gas condenses and is collected as condensed water. This condensed water is used, for example, as humidifying water in a humidifier, boiler supply water, or the like.

The syngas cooled to room temperature is pressurized by a compressor to, for example, 50 to 150 atmospheres,
It is preheated to 00 to 300 ° C. and supplied to a reactor filled with a methanol synthesis catalyst. In this reactor, methanol is synthesized by the reactions shown in the following equations (1) and (2).

CO + 2H ₂ → CH ₃ OH (1) CO ₂ + 3H ₂ → CH ₃ OH + H ₂ O (2) Also, impurities such as dimethyl ether and ethanol are generated by a side reaction. These impurities and water are contained in the liquid crude methanol together with the methanol.

As the methanol synthesis catalyst, for example, a copper catalyst is used. In particular, it is made of an oxide containing Cu, Zn, Al, Ga and M (at least one element selected from an alkaline earth metal element and a rare earth element) having high durability in a high-concentration carbon dioxide atmosphere, , Zn, Al, Ga and M are composed of Cu:
Zn: Al: Ga: M = 100: 10 to 200: 1 to 2
A catalyst having a composition of 0: 1 to 20: 0.1 to 20 is preferable.

(3) Distillation Step The liquid crude methanol is sent to, for example, a distillation column in the distillation step 3 from the methanol synthesis step 2 shown in FIG. 1, and is distilled to produce purified methanol and low-boiling organic compounds as by-products. And wastewater containing high-boiling organic compounds. By-products in the wastewater are discharged out of the system.

According to the present invention, in the above-mentioned production of methanol, for example, carbon dioxide is recovered from flue gas discharged from a combustor of a boiler or a reformer, and after the carbon dioxide is pressurized to a predetermined pressure by a compressor, It is supplied to at least one of a flow path on the upstream side of the humidifier and a flow path between the humidifier and the reformer.

The carbon dioxide to be supplied is not limited to carbon dioxide recovered during the methanol production process, but carbon dioxide discarded at another factory or the like can also be used. That is, by effectively utilizing carbon dioxide conventionally discarded from factories and the like as a raw material for the method for producing methanol according to the present invention, the amount of carbon dioxide emitted to the atmosphere can be reduced, which can contribute to prevention of global warming.

According to the first embodiment described above, carbon dioxide is supplied to at least one of the flow path on the upstream side of the humidifier and the flow path between the humidifier and the reformer. When supplying the raw material gas mainly composed of hydrocarbons to the humidifier and humidifying the raw material gas, the humidified gas can be increased by an amount corresponding to the supply amount of the carbon dioxide. As a result, the humidified raw material gas containing carbon dioxide can be supplied to the reformer, so that the amount of superheated steam generated by a boiler or the like separately supplied to the humidified raw material gas can be reduced. Therefore, the running cost for producing methanol can be reduced.

In particular, by supplying carbon dioxide to the upstream flow path of the humidifier together with the raw material gas mainly composed of hydrocarbons, not only the raw material gas but also carbon dioxide is supplied while flowing through the humidifier. Humidified. As a result, a mixed gas of humidified raw material gas and carbon dioxide can be supplied to the reformer, so that the amount of superheated steam produced by a boiler or the like separately supplied to the humidified raw material gas can be further reduced. . Therefore, the running cost for producing methanol can be further reduced.

Further, the carbon dioxide is supplied to the flow path on the upstream side of the humidifier.
And less of the flow path between the humidifier and the reformer
By supplying at least one, hydrocarbons as the main component
Feed gas, carbon dioxide and steam to the reformer
Can be paid. Therefore, in the reformer, the hydrogen
(H_Two), Carbon monoxide (CO) and carbon dioxide (C
O _Two) As the main component,
Carbon dioxide and the source gas, for example, methane gas are as follows
Reacting according to equation (3) to produce carbon monoxide and hydrogen
Wear.

CO ₂ + CH ₄ → 2CO + 2H ₂ (3) Accordingly, the amount of carbon dioxide in the synthesis gas generated by the reformer is determined by the conventional method of supplying carbon dioxide to the synthesis gas generated by the reformer. Can be reduced. As a result, since the synthesis gas having a low carbon dioxide content can be transferred from the reformer to the methanol synthesis step, the methanol synthesis catalyst used in this methanol synthesis step is exposed to a high-concentration carbon dioxide atmosphere and its activity decreases. Can be prevented.

Further, carbon dioxide supplied to at least one of the flow path on the upstream side of the humidifier and the flow path between the humidifier and the reformer is discharged by a boiler or a combustor of a reformer. By utilizing the carbon dioxide recovered from the combustion exhaust gas thus collected, the amount of carbon dioxide emitted by the production of methanol can be reduced. As a result, when the introduction of the carbon dioxide emission tax and the regulation of carbon dioxide emission are started, the economic efficiency of the methanol production plant can be improved.

(Second Embodiment) In the flow chart of the methanol production shown in FIG. 1 described above, the humidifier is a first-stage humidifier, and a humidifier downstream of the first-stage humidifier and upstream of the reformer. And a second-stage humidifier disposed therebetween. The wastewater collected in the distillation step is supplied to the circulating water flow path of the first humidifier. From the upstream side of the first-stage humidifier, a mixed gas of a raw material gas mainly composed of hydrocarbons and carbon dioxide is supplied to the top of the first-stage humidifier.

Further, carbon dioxide is further supplied to at least one of a flow path for connecting the first and second humidifiers and a flow path between the second humidifier and the reformer. Allow to supply.

According to such a second embodiment, the first
By using the humidifier of the second stage and the second stage, a sufficiently humidified mixed gas can be supplied to the reformer, so that the amount of process steam can be further reduced as compared with the first embodiment.

By supplying a mixed gas of the raw material gas and carbon dioxide to the top of the first stage humidifier, the mixed gas is mixed with water supplied from a circulating water flow path in a packed bed at the top of the first stage humidifier. Adiabatic contact and humidification. At this time, the salt of the alkali metal or alkaline earth metal in the wastewater is neutralized by the carbon dioxide in the mixed gas by supplying the wastewater recovered in the distillation step to the circulating water channel. As a result, the pH of the wastewater can be shifted from the alkaline side to the neutral side or the acidic side. Therefore, even if the wastewater collected in the distillation step is supplied to the circulating water flow path of the first-stage humidifier, corrosion by the alkali in the first-stage humidifier can be prevented, and the wastewater can be used effectively.

[0046]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments will be described below in detail.

Example 1 In Example 1, the production of methanol according to the first embodiment will be described more specifically with reference to a methanol production plant shown in FIG.

Reference numeral 10 in FIG. 2 is a single-stage heat exchange humidifier. In this humidifier 10, a filling layer 11 and a tube 12 for bringing gas and water into contact with each other in a wet wall manner are sequentially arranged from the top side downward. A pump 14 for circulating water from the bottom of the humidifier 10 to the top of the humidifier 10 via a circulating water flow path 13 is disposed below the humidifier 10.

The reformer 20 is disposed on the downstream side of the humidifier 10 is connected to the humidifier 10 through the passage 30 _1. The reformer 20 includes a steam reforming reaction tube 21.
And a combustor 23 disposed around the reaction tube 21 and having a preheating unit 22. The reaction tube 21 is filled with, for example, a nickel-based catalyst. Incidentally, the channel 30 ₁ the reaction tube 2 through the preheating section 22
1 connected. Carbon dioxide recovery apparatus 24 is connected through a passage 30 ₂ to the preheating unit 22.

[0050] for methanol synthesis reactor 40, the disposed downstream of the reformer 20 is connected to the reformer 20 through the passage 30 _3. The reactor 40 includes a preheater 41 and a reactor 43 for methanol synthesis to which synthesis gas from the preheater 41 is supplied through a circulation channel 42. The reactor 43 contains a methanol synthesis catalyst, for example, an oxide containing Cu, Zn, Al, Ga and M (at least one element selected from alkaline earth metal elements and rare earth elements). ,
Al, Ga and M are atomic ratios of Cu: Zn: Al: G
a: M = 100: 10 to 200: 1 to 1: 1 to 20:
A catalyst having a composition of 0.1 to 20 is packed. Heat exchanger 51, heat recovery unit 52 and first
Compressor 53 is interposed in order toward from the reformer 20 side to the channel 30 ₃ to the preheater 41. The channel 30 ₃ portion between the heat recovery unit 52 and the heat exchanger 51 through the tube 12 of the humidifier 10.

The first distillation column 60 _1, the disposed downstream of the methanol synthesis reactor 40 is connected to the a methanol synthesis reactor 40 through the passage 30 _4. First capacitor 61 ₁ is connected through a circulation passage 62 ₁ in the vicinity of the top of the first distillation column 60 _1. Incidentally, the channel 30 ₄ and one end thereof is connected to the reactor 43 bottom. The preheater 41, the cooler 71, the gas-liquid separator 72, and the crude methanol preheater 73
0 ₄ to the methanol synthesis reactor 40 reactor 43
It is successively interposed toward the first distillation column 60 ₁ from the side.
The gas-liquid separator 72 is connected to the channel 30 ₃ of the preheater 41 inlet through the gas circulation flow path 74. The gas compressor 75 is interposed in the gas circulation channel 74.

The second distillation column 60 ₂ is provided with the first distillation column 60 ₁
Of disposed downstream and connected to the first distillation column 60 ₁ through the passage 30 _5. The second capacitor 61 ₂ is connected through the circulation flow path 62 ₂ in the vicinity of the top of the second distillation column 60 _2.

The reactor of the reactor for methanol synthesis preferably has, for example, a structure incorporating a triple tube shown in FIG. 3 described below.

The reactor main body 101 shown in FIG. 3 is vertically arranged by two separators 102 and 103 in a synthesis gas supply chamber 104, a cooling medium flow chamber 105, and a methanol-containing gas retention chamber 1.
06 are divided into three rooms. A plurality of, for example, two, triple tubes 110 in which the outer tube 107, the intermediate tube 108, and the inner tube 109 are concentrically arranged, are connected to the two separators 102,
103 and is supported. An inner annular space 111 is formed between the inner pipe 109 and the intermediate pipe 108,
An outer annular space 1 is provided between the intermediate pipe 108 and the outer pipe 107.
12 are formed. The upper end of the intermediate pipe 108 is located below the upper end of the outer pipe 107. The lower end of the inner pipe 109 is located near the center of the intermediate pipe 108. The lower end position of the inner pipe 109 is set at a distance of 1/10 to 2/3 of the length of the triple pipe 110 from the upper end of the triple pipe 110 to suppress an increase in pressure loss, and to prevent the pressure loss from the inside of the catalyst described later. It is preferable to obtain a cooling effect.

The upper end of the triple tube 110 is connected to the upper shielding plate 1.
13, only the inner tube 109 is closed so as to be opened. The lower end of the triple tube 110 is
4, the intermediate tube 108 is closed, and the outer annular space 112 is opened. The outer annular space 112 between the intermediate pipe 108 and the outer pipe 107 is filled with a catalyst layer 115 made of, for example, a granular methanol synthesis catalyst from the lower end to the vicinity of the upper end. A mesh plate or a porous plate (not shown) is attached to a lower end of the outer annular space 112 to prevent the granular methanol synthesis catalyst from falling.

A supply port 116 for supplying the synthesis gas to the synthesis gas supply chamber 104 is attached to an upper portion of the reactor main body 101, and the circulation path 42 is connected to the supply port 116. . An outlet 117 is attached to a lower portion of the reactor main body 101 for discharging a generated gas including methanol generated in the triple tube 110,
The discharge port 117 is connected to the channel 30 _4.
The reactor body 1 in which the cooling medium flow chamber 105 is located
A cooling medium inlet 118 and an outlet 119 are attached to the side wall 01.

Next, a method for producing methanol will be described with reference to the methanol production plant shown in FIG.

[0058] raw material gas mainly composed of preheated hydrocarbon after desulfurization and supplies toward the filling layer 11 of the heat exchange type humidifier 10 top through the passage 30 _6. At the same time, the carbon dioxide recovered by the carbon dioxide recovery
0 ₇ is introduced into the compressor 25 from being boosted here. Boosted carbon dioxide, the flow path 3 through the flow path 30 ₈
0 ₆ is supplied to the flow path 3 is mixed with the raw material gas
0 ₆ is supplied to the packed bed 11 of the top of the humidifier 10. The pump 14 disposed below the humidifier 10 was previously operated to circulate water from the bottom of the humidifier 10 to the top of the humidifier 10 via the circulating water flow path 13, so that water was supplied to the top of the humidifier 10. The mixed gas of the raw material gas and carbon dioxide is humidified. That is, the mixed gas contacts the water supplied from the circulating water channel 13 in the packed bed 11,
After humidification, a reformer 20 described later is connected to the tube 12.
Passage 30 ₃ is syngas and heat exchange of the supplied high temperature through the heated, is further humidified. The gas after the recovery of carbon dioxide in the carbon dioxide recovery device 24 is discharged to the atmosphere through the passage 30 _9.

[0059] humidified the mixed gas is supplied to the reformer 20 steam reforming reaction tube 21 through the passage 30 _1. The humidified mixed gas is supplied to the flow path 30 ₁
The required amount of process steam flow path in the process of flowing 30 ₁₀
Is supplied to the reaction tube 21 through a preheating section 22 at a convection section of the reformer 20. The raw material gas, steam and carbon dioxide mainly containing hydrocarbons supplied to the reaction tube 21 of the reformer 20 mainly convert hydrocarbons, for example, methane, into steam in the presence of a catalyst in the reaction tube 21. And converted to a synthesis gas containing carbon monoxide, carbon dioxide and hydrogen. At the same time, carbon dioxide and methane react to be converted to synthesis gas containing carbon monoxide and hydrogen.

Since the reforming reaction is an endothermic reaction, fuel gas and air are burned in the combustor 23 of the reformer 20 to heat the reaction tube 21 to, for example, 800 to 1000 ° C. Flue gas preheating section 22 is supplied to the carbon dioxide recovery apparatus 24 through the passage 30 _2, where carbon dioxide is recovered, it is further supplied to the humidifier 10 as described above.

[0061] The resulting synthesis gas is fed through a passage 30 ₃ in the heat exchanger 51, wherein heating the boiler water flowing through the flow path 30 _11, after generating a high-pressure steam, the humidifier It is supplied to the outer channel of the tube 12. Here, a part of the heat of the synthesis gas is recovered and the humidifier 1
0 is used as a heat source.

The synthesis gas exiting the tube 12 is supplied to a heat recovery unit 52 and cooled to room temperature. At this time,
Circulation water passage 1 of the humidifier 10 the water vapor contained in the synthesis gas becomes condensed water partially through the channel 30 ₁₂
3 and used for humidification of the mixed gas of the raw material gas and carbon dioxide introduced into the humidifier 10. Other condensed water is available through the channel 30 _13, for example, as process water.

The synthesis gas from which the condensed water has been separated is supplied to the flow path 30_Three
To the first compressor 53, where methanol
To a pressure suitable for the synthesis reaction (for example, 50 to 150 atm)
Compressed. The pressurized synthesis gas is supplied to the flow path 30_ThreeThrough
Supplied to the preheater 41 of the reactor 40 for methanol synthesis.
Here, the temperature suitable for the methanol synthesis reaction (for example, 2
100 to 300 ° C.) and further circulates through the circulation channel 42.
To a reactor 43 filled with a methanol synthesis catalyst.
Paid. In addition, it was separated by a gas-liquid separator 72 described later.
The unreacted gas passes through the gas circulation passage 74 to the preheater 41.
The front channel 30 _ThreeSupplied to the part and mixed with the synthesis gas
Is done. In the reactor 43, the above formulas (1) and (2)
The following reaction is performed to synthesize methanol. This reaction
The reactor 43 incorporates the triple tube shown in FIG.
It is preferable to use a vessel.

That is, the synthesis gas is supplied from the supply port 116 shown in FIG.
Supplied to The synthesis gas in the supply chamber 104 passes through the inlet at the upper end of the inner pipe 109 of the triple pipe 110,
9 flows from above to below, and from the lower end outlet to the inner pipe 109
And into the inner annular space 111 between the and the intermediate pipe 108. The synthesis gas further flows upward through the inner annular space 111, and the outer annular space 1 between the intermediate pipe 108 and the outer pipe 107.
12 flows into the catalyst layer 115 filled in the outer annular space 112 from the upper end. The synthesis gas is supplied to the catalyst layer 115.
During the reaction, the reactions shown in the above formulas (1) and (2) are performed to synthesize methanol.

In the synthesis of methanol, a cooling medium such as boiler water is supplied from the cooling medium inlet 118 to the cooling medium flow chamber 105 of the reactor body 101,
The catalyst layer 115 is cooled through the outer tube 107 by discharging from the outlet 119 of the cooling medium. Further, a reaction part involved in the reaction of methanol is constituted by a triple tube 110, and the synthesis gas is supplied to the inner tube 109 and the inner annular space 111.
Outer annular space 11 filled with catalyst layer 115 via
By flowing the catalyst gas to the upper end of the catalyst layer 2, the catalyst layer 115 can be cooled from the inside by the synthesis gas.
As a result, it is possible to effectively suppress the heat generated by the methanol synthesis reaction and the decrease in the activity of the catalyst due to the heat generated.

In particular, when carbon dioxide is supplied to the reformer 20 and a synthesis gas having a relatively high concentration of carbon monoxide is used as in the present invention, the rate of methanol synthesis reaction increases,
As a result, the heat generation rate may increase, and the temperature of the catalyst may increase, leading to a decrease in activity. In the use of such a synthesis gas, the reactor 43 incorporating the triple tube 110 described above is used.
By using the cooling medium and the synthesis gas to cool the catalyst layer 115 at the synthesis gas inlet where the temperature rises sharply during the exothermic reaction as described above, it is possible to maintain good catalytic activity for a long period of time. .

In the use of a synthesis gas having a high carbon monoxide concentration, the above-described unreacted gas is circulated through the synthesis gas to reduce the carbon monoxide concentration in the synthesis gas, thereby increasing the heat generation rate during the methanol synthesis. It is possible to suppress.

[0068] Then, the product gas from the reactor 43 are respectively supplied to the preheater 41 and the cooler 71 through the passage 30 _4, as shown in FIG. 2, is cooled to approximately room temperature by these members. At this time, most of the methanol and water in the produced gas are condensed, become liquid, and flow into the gas-liquid separator 72. In this gas-liquid separator 72,
It is separated into crude liquid methanol and unreacted gas.

The unreacted gas is sent to a gas compressor 75 through a gas circulation passage 74, where the gas is pressurized and then passed through the gas circulation passage 74 to the passage 3 at the inlet of the preheater 41.
Is circulated to 0 _3, it is fed to the reactor 43 together with the synthesis gas. Some of the unreacted gas is passed through the flow path 30 ₁₄ as a purge gas is used, for example, as a fuel in the reformer 20.

On the other hand, the crude methanol is_FourTo
The first distillation column 60 passes through the crude methanol preheater 73
₁Supplied to If necessary, the first distillation column 60₁Flow
Road 30_FifteenA small amount of water is supplied through the system. Low boiling organic
The compound is mixed with the first distillation column 60 ₁Concentrated at the top of the tower
And the first capacitor 61₁Is partially condensed and refluxed,
The remainder is discharged out of the system together with the dissolved gas. The first distillation
Tower 60₁Is mainly methanol and water at the bottom of
0_FiveThrough the second distillation column 60_TwoSupplied to

[0071] In the second column top of the distillation column 60 _2,
Methanol fraction resulting condensed is cooled by a ₂ second capacitor 61, methanol is highly purified, it is withdrawn from the flow channel 30 ₁₆ out of the system as a product by refluxing. The bottom of the second distillation column 60 ₂ is mainly made of water, a small amount of high boiling point organic compounds, organic acid, and inorganic trace caused by the device. The waste water is discharged outside the system through a flow path 30 ₁₇ from the second distillation column 60 ₂ of the bottom.

As described above, in the first embodiment, the combustor 2 of the reformer 20
Combustion exhaust gas discharged from the fuel cell 3
Was introduced, after compressing here recovered carbon dioxide compressor 25, and supplied to the flow path 30 ₆ through the flow path 30 ₈ upstream of the humidifier 10, and mixed with the supplied raw material gas here, This mixed gas is supplied to the top of the humidifier 10. For this reason, the gas flow rate supplied to the humidifier 10 can be increased as compared with the case where carbon dioxide is not mixed. As a result, the amount of humidification in the humidifier 10 can be increased. Therefore, it is possible to reduce the supply process water vapor from the flow path 30 _10.

For example, carbon dioxide is supplied at a raw material gas flow rate of 30%.
%, The humidification amount can be increased by about 30%. The amount of process steam can be reduced by this increased amount.

The flow path 30 on the upstream side of the humidifier 10
By utilizing the carbon dioxide recovered from the combustion exhaust gas discharged by the combustor 23 of the reformer 20 of carbon dioxide supplied to ₆ (and / or steam generation boiler), carbon dioxide emitted by the production of methanol The amount can be reduced. As a result, when the introduction of the carbon dioxide emission tax and the regulation of carbon dioxide emission are started, the economic efficiency of the methanol production plant can be improved.

The catalyst filled in the reactor 43 is an oxide containing Cu, Zn, Al, Ga and M (at least one element selected from alkaline earth metal elements and rare earth elements). Zn, Al, G
a and M are atomic ratios of Cu: Zn: Al: Ga: M =
100: 10 to 200: 1 to 20: 1 to 20: 0.1 to
If a catalyst having a composition of 20 and having a high durability against a synthesis gas containing a high concentration of carbon dioxide is used, deterioration of the activity of the catalyst can be suppressed. As a result, the amount of the catalyst can be reduced.

Further, by using the methanol synthesis reactor 43 having a structure incorporating the triple tube 110 as shown in FIG. 3, the temperature of the synthesis gas inlet of the catalyst layer can be reduced.
Therefore, when circulating the gas-liquid separator 72 in stream of synthesis gas separated unreacted gas is flow passage 30 ₃ in order to reduce the concentration of carbon monoxide in the synthesis gas, the circulating unreacted gas The amount can be reduced. As a result, circulating power can be reduced.

In the first embodiment, the case where the carbon dioxide recovered in the combustor 23 of the reformer 20 is compressed and then supplied to the upstream side (flow path 30 ₈ ) of the humidifier has been described.
It is not limited to this. For example, reduction of substantially similar process steam amount as in Example 1 was fed through the channel 30 ₁₈ 30 ₁ downstream of the humidifier 10 the carbon dioxide is obtained as shown in FIG.

Example 2 In Example 2, the production of methanol according to the second embodiment described above will be described more specifically with reference to a main part of a methanol production plant shown in FIG. In FIG. 4, the same members as those in FIG. 2 described above are denoted by the same reference numerals, and description thereof will be omitted.

[0079] 10 ₁ of FIG. 4, the first heat exchange of single stage
It is a stage humidifier. The first stage humidifier 10 _1, tube 12 ₁ contacting a gas and water from the top side with a filling layer 11 ₁ and the wet wall type downward are sequentially arranged.
The first stage humidifier 10 ₁ water is supplied from the bottom to the first circulating water passage 1
_First circulating to the top of said humidifier 10 ₁ via 31
Pump 14 ₁ is disposed below the humidifier 10 _1. Wastewater discharged from the second distillation column is fed to the first circulation flow passage 13 ₁ through the flow path 30 _17.

One-stage heat exchange type second-stage humidifier 10
₂ is disposed on the first stage downstream of the humidifier 10 ₁ are connected by a flow path 30 _19. This second stage humidifier 10 ₂
The tube 12 ₂ contacting a gas and water from the top side with a filling layer 11 ₂ and wetted wall method downwardly are sequentially arranged. Incidentally, the flow path 30 ₁₉ has one end connected to the side wall of the tube 12 ₁ under the first stage humidifier, the other end is connected to the top of the second stage humidifier 10 _2. The second
Stage humidifier 10 ₂ second pump 14 the water from the bottom via the second circulation flow path 13 ₂ is recycled to the second stage humidifier 10 ₂ of the top portion _2, the second stage humidifier 10 ₂ lower Are located in The second stage humidifier 10 ₂ is connected to the reformer to be placed through the passage 30 ₁ to the second stage downstream of the humidifier 10 _2. Further, the synthesis gas of the reformer is supplied to the flow path 3
0 ₃ through is introduced into the tube 12 ₂ of the second stage humidifier 10 ₂ is heat exchanged.

The methanol production process shown in FIG.
In the runt, the desulfurization unit 8 is used in the same manner as in the first embodiment.
1. Hydrocarbons desulfurized in step 1 and preheated mainly
Source gas is supplied to the flow path 30₆Through the first stage of the heat exchange type
Humidifier 10₁Top packed bed 11 ₁Supplied to. same
Sometimes, for example, it is captured by a carbon dioxide capture device and then lifted by a compressor.
The pressurized carbon dioxide flows through the channel 30₈Through the channel 30₆
Mixed with the carbon dioxide and the raw material gas
The gas passes through the flow path 30₆From the first stage humidifier 10₁Top of
Packed bed 11₁Supplied to The humidifier 10₁Below
First pump 14 arranged₁To operate the humidifier 1 in advance.
0₁The water is supplied from the bottom to the first circulating water flow path 13₁Via the
Humidifier 10₁Of the second distillation column
Waste water discharged from the₁₇Through the first circulating water
Channel 13₁To supply. Due to such water circulation,
First stage humidifier 10₁The mixed gas supplied to the top of
The packed layer 11₁And the first circulating water flow path 13₁Supplied by
The tube 12 that comes in contact with water and further below it₁With water in
Humidified on contact. At this time, the first circulating water flow path 13
₁Metals and alkali contained in wastewater supplied to
Lithium metal salt is mixed with carbon dioxide in the mixed gas.
Be summed up. Therefore, the wastewater collected in the distillation process is
Humidifier 10₁First circulating water channel 13₁To supply
First stage humidifier 10₁Can prevent corrosion by alkali
You.

The first stage humidifier 10₁Humidified mixing
The gas passes through the flow path 30₁₉Through the second stage humidifier 10_TwoAt the top
Packed bed 11_TwoSupplied to This second stage humidifier 10_TwoUnder
Second pump 14 arranged on the side_TwoTo operate the second
Step humidifier 10_TwoWater is supplied from the bottom to the second circulating water flow path 13_TwoVia
And the second stage humidifier 10_TwoCirculating at the top of the
Thus, the mixed gas supplied to the top is humidified.
That is, the mixed gas is filled in the packed bed 11._TwoIn the second circulation
Water channel 13_TwoHumidified by contact with water supplied from
Later, the tube 12_TwoAnd the flow path 30 from the reformer_ThreeThrough
Heat is exchanged with the supplied high-temperature syngas and heated,
Is humidified. The second circulating water flow path 13 _TwoImplemented in
As described in Example 1, the condensed water discharged from the heat recovery
Road 30₁₂May be supplied through

[0083] mixed gas is humidified in the second stage humidifier 10 ₂ is supplied to the reformer through the channel 30 ₁ in the same manner as in Example 1 described above, the generation of synthesis gas, the synthesis of methanol is made The purified methanol is recovered through a distillation column.

As described above, in the second embodiment, the same effects as those of the first embodiment can be obtained. Of course, the humidifiers 10 ₁ and 10 ₂ of the _first and second stages are used to sufficiently humidify. Since the mixed gas can be supplied to the reformer, the amount of process steam can be reduced as compared with the first embodiment.

[0085] Moreover, by supplying carbon dioxide to the first stage upstream of the humidifier 10 _1, containing an alkali metal or an alkaline earth metal salt discharged from the distillation step to a first circulation flow passage 13 ₁ Even when the wastewater is supplied, the pH can be lowered to shift from the neutral side to the acidic side. Therefore, it is possible to prevent the alkali due to corrosion in the first stage humidifier 10 _1, it can be effectively utilized the waste water.

In the second embodiment, the first carbon dioxide is used.
It has dealt with the case of supplying to the upstream side of the stage humidifier 10 _1, but is not limited thereto. For example, the first stage through the further passage 30 ₂₀ carbon dioxide as shown in FIG. 4, the second
The humidifiers 10 ₁ and 10 ₂ of the stages may be supplied to the flow path 30 ₁₉ or the flow path 30 ₁ through the flow path 30 ₂₁ , that is, the flow path 30 ₁ for supplying the mixed gas to the reformer. It may also be fed directly to the distillation wastewater flow paths 30 ₁₇ further through the channel 30 ₂₂ carbon dioxide as shown in FIG.

As described above, carbon dioxide is supplied to the first stage humidifier 10.
_By supplying the gas to a specific location in addition to the upstream side, the flow rate of the humidified mixed gas can be increased, so that the process steam amount can be further reduced as compared with the first embodiment.

[0088]

As described above, according to the present invention, the excess hydrogen in the gas generated in the reformer can be effectively used without causing a decrease in the activity of the methanol synthesis catalyst in the methanol synthesis step. To increase methanol production,
It is possible to provide a method for producing methanol capable of reducing carbon dioxide emission by effectively utilizing carbon dioxide and reducing the amount of steam supplied to the reformer from outside the system.

Further, the humidifier is constituted by a first-stage humidifier and a second-stage humidifier, and the distillation wastewater is supplied to the circulating water of the first-stage humidifier to which the raw material gas and the carbon dioxide are supplied. Can be shifted to a neutral side or an acidic side to prevent corrosion of the metal member of the first stage humidifier due to alkali in the distillation wastewater, whereby the distillation wastewater can be used effectively.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a methanol production process according to the present invention.

FIG. 2 is a schematic diagram illustrating an example of a methanol production plant according to the first embodiment of the present invention.

FIG. 3 is a sectional view showing one embodiment of a reactor for methanol synthesis incorporated in the plant of FIG. 2;

FIG. 4 is a main part schematic diagram showing another example of the methanol production plant in Embodiment 2 of the present invention.

[Explanation of symbols]

10, 10 _1, 10 ₂ ... humidifier, 20 ... reformer, 24 ... carbon dioxide recovery device, 40 ... methanol synthesis reactor, 43 ... reactor, 60 _1, 60 ₂ ... distillation column, 101 ... reactor Main body, 107: outer tube, 108: intermediate tube, 109: inner tube, 110: triple tube.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C07C 31/04 C07B 61/00 300 // C07B 61/00 300 B01J 23/82 X (72) Inventor Ozora Hiroyuki Hiroshima Pref. Hiroshima Pref. Hiroshima 4-6-22 Kannon Shinmachi Inside the Hiroshima Research Laboratory, Mitsubishi Heavy Industries, Ltd. (Reference) 4H006 AA02 AC29 AC41 AD11 BA05 BA06 BA07 BA08 BA09 BD80 BD81 BE40 BE41 BE60 FE11 4H039 CA60 CL35

Claims (6)

[Claims] A raw material gas containing hydrocarbon as a main component is supplied to a reformer through a humidifier, and steam is supplied.
Reacting the hydrocarbon with the steam to produce a synthesis gas containing hydrogen, carbon monoxide and carbon dioxide as main components; and reacting the synthesis gas on a methanol synthesis catalyst to produce crude methanol. A crude methanol synthesis step of synthesizing, and a distillation step of distilling liquid crude methanol recovered from the synthesis step to separate wastewater containing low-boiling organic compounds and high-boiling organic compounds into purified methanol, and A method for producing methanol, comprising supplying carbon dioxide to at least one of a flow path on an upstream side of a humidifier and a flow path between the humidifier and the reformer. 2. The humidifier comprises a first-stage humidifier, and a second-stage humidifier disposed downstream of the first-stage humidifier and upstream of the reformer. Supplying the wastewater recovered in the distillation step to the circulating water flow path of the first-stage humidifier, and supplying the raw material gas mainly composed of hydrocarbons and carbon dioxide to the upstream-side flow path of the first-stage humidifier The method for producing methanol according to claim 1, wherein: 3. Carbon dioxide is further supplied to at least one of a flow path for connecting the first and second humidifiers and a flow path between the second humidifier and the reformer. The method for producing methanol according to claim 2, wherein the methanol is supplied. 4. The reactor for synthesizing crude methanol is divided into three chambers, a synthesis gas supply chamber, a cooling medium flow chamber, and a methanol-containing gas retention chamber, vertically by two separators; Supported through the two separators, the outer tube,
A triple pipe in which the intermediate pipe and the inner pipe are arranged concentrically, wherein the upper end of the intermediate pipe is located below the upper end of the outer pipe, and the lower end of the inner pipe is located near the center of the intermediate pipe;
Only the inner tube was opened at the upper end of the triple tube, and the annular space formed by the intermediate tube and the outer tube was opened at the lower end of the triple tube, and the methanol synthesis catalyst was filled in the annular space. The method for producing methanol according to claim 1, wherein the method is performed using a reactor. 5. The method according to claim 1, wherein the methanol synthesis catalyst comprises Cu, Z
an oxide containing n, Al, Ga and M (at least one element selected from an alkaline earth metal element and a rare earth element), wherein the Cu, Zn, Al, Ga and M
Is in atomic ratio Cu: Zn: Al: Ga: M = 100: 1
The method for producing methanol according to claim 1, wherein the composition has a composition of 0 to 200: 1 to 20: 1 to 20: 0.1 to 20. 6. The carbon dioxide to be supplied is carbon dioxide recovered from at least one of a combustion gas for heating the reformer and a combustion gas of a steam generating boiler. Item 6. The method for producing methanol according to any one of Items 1 to 5.