JP2001097906A - Method for producing methanol - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing methanol, capable of effectively using an unreacted gas and carbon dioxide in a methanol synthesis process. SOLUTION: This method for producing methanol comprises a synthesis gas formation process, a 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. The methanol synthesis process is carried out by a first reaction process and a second reaction process. The synthesis gas supplied through a synthesis gas feed channel in the first reaction process is reacted on the methanol synthesis catalyst, the formed liquid crude methanol containing the unreacted gas is subjected to gas-liquid separation, the liquid crude methanol is recovered, the unreacted gas is compressed, circulated through the synthesis gas feed channel, a part of the unreacted gas is mixed with carbon dioxide, is introduced to the second reaction process and the mixed gas is reacted on the methanol synthesis catalyst to form the crude methanol.

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]

SUMMARY OF THE INVENTION The present invention aims to further increase the production of methanol by effectively utilizing the unreacted gas in the methanol synthesis step, and to reduce the emission of carbon dioxide by effectively utilizing carbon dioxide. It is an object of the present invention to provide a method for producing methanol, which is possible.

[0015]

According to the method for producing methanol according to the present invention, a raw material gas mainly composed of hydrocarbons and steam are supplied into a reformer, and these gases are reacted to produce hydrogen and monoxide. A synthesis gas generation step of generating a synthesis gas mainly containing carbon and carbon dioxide, a methanol synthesis step of reacting the synthesis gas on a methanol synthesis catalyst to synthesize crude methanol, and a liquid recovered from the synthesis step. A distillation step of distilling the crude methanol into wastewater containing a low-boiling organic compound and a high-boiling organic compound and purified methanol.
And a second reaction step, wherein the synthesis gas supplied through the synthesis gas supply passage in the first reaction step is reacted on a methanol synthesis catalyst, and a liquid crude containing the unreacted gas generated is produced. Methanol is gas-liquid separated, the liquid crude methanol is recovered, and the unreacted gas is compressed and circulated through the synthesis gas supply channel,
Part of the mixture is mixed with carbon dioxide and introduced into the second reaction step, and the mixed gas is reacted on a methanol synthesis catalyst to produce crude methanol.

In the method for producing methanol according to the present invention, it is permitted to further supply carbon dioxide to the inlet of the first reaction step.

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 generating boiler. Preferably, there is.

In the method for producing methanol according to the present invention, at least one of the first and second reaction steps is carried out vertically by using two separators, a synthesis gas supply chamber, a cooling medium flow chamber, and methanol. A reactor partitioned into three chambers of a containing gas storage chamber, and a triple pipe supported through the two separators and having an outer pipe, an intermediate pipe, and an inner pipe arranged concentrically; The upper end of the intermediate pipe is located below the upper end of the outer pipe, the lower end of the inner pipe is located near the center of the intermediate pipe, only the inner pipe is open at the upper end of the triple pipe, and the triple pipe It is preferable that an annular space formed by the intermediate tube and the outer tube be opened at the lower end of the tube, and that the reaction be performed using a reactor filled with the methanol synthesis catalyst in the annular space.

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.

[0020]

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.

FIG. 1 is a flow chart showing a process for producing methanol used in this embodiment.

The method for producing methanol is shown in FIG.
, 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 desulfurization unit, where a small amount of sulfur compounds 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
Steam is added at ~ 250 ° C to near saturation pressure.

The humidified raw material gas is supplied to a reformer after being supplied with superheated steam generated 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.

The raw material gas introduced into the reformer is supplied, for example, under a nickel-based catalyst filled in the reformer, for 800 hours.
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. This synthesis gas has a concentration higher than that required for hydrogen to react with these gases against carbon monoxide to produce methanol.

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 the second reaction in the methanol synthesis step described later is performed. Used in the process. 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 synthesis gas cooled to room temperature is pressurized to, for example, 50 to 150 atm by a compressor,
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) Further, 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.

The synthesis gas has a higher concentration than that required for producing methanol by reacting hydrogen with carbon monoxide with respect to carbon monoxide. In other words, by using a hydrogen-rich synthesis gas, the rate of heat generation accompanying the reaction is reduced, and a decrease in the activity of the catalyst is suppressed.

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.

In the present invention, in the above-mentioned production of methanol, the methanol synthesis step is carried out by a first reaction step and a second reaction step. That is, in the first reaction step, the synthesis gas supplied through the synthesis gas supply channel is caused to react on the methanol synthesis catalyst, and the liquid crude methanol containing the generated unreacted gas is subjected to gas-liquid separation. The liquid crude methanol obtained by this gas-liquid separation is recovered. On the other hand, the unreacted gas is compressed and circulated through the synthesis gas supply channel. At the same time, the unreacted part of carbon dioxide, if necessary, compressed and pressurized carbon dioxide,
And the mixture is introduced into the second reaction step, and the mixed gas is reacted on a methanol synthesis catalyst to produce crude methanol.

The carbon dioxide is allowed to be further supplied to the inlet of the first reaction step.

As the carbon dioxide to be supplied, for example, carbon dioxide recovered from the combustion exhaust gas discharged from the boiler or the combustor of the reformer during the production process of methanol can be used. However, carbon dioxide discarded at another factory or the like can also be used. That is, by effectively utilizing carbon dioxide that has been conventionally discarded from factories and the like as a raw material for the methanol production method 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 present invention described above, by performing the methanol synthesis step by the first reaction step and the second reaction step, the second reaction step can be performed without largely changing the equipment for producing methanol. Methanol can be increased simply by adding it.

That is, in the first reaction step, the hydrogen supplied through the synthesis gas supply channel is higher than the concentration required for reacting carbon monoxide with hydrogen and carbon monoxide to produce methanol. By reacting a synthesis gas having a concentration, that is, a hydrogen-rich synthesis gas on a methanol synthesis catalyst, while suppressing the heat generated by the reaction, reducing the activity decrease of the catalyst and forming a liquid crude methanol containing an unreacted gas is produced. After that, gas-liquid separation is further performed. By this gas-liquid separation, liquid crude methanol can be recovered.

On the other hand, the unreacted gas has a ぃ concentration higher than that required for producing methanol by reacting hydrogen with carbon monoxide with respect to carbon monoxide.
The unreacted gas is compressed and circulated through the synthesis gas supply channel, and a part of the unreacted gas is mixed with carbon dioxide and introduced into the second reaction step. As a result, hydrogen in the unreacted gas and the supplied carbon dioxide can be reacted on the methanol synthesis catalyst, so that crude methanol can be generated in the second reaction step. As a result, it is possible to increase the production of methanol by effectively utilizing the hydrogen in the unreacted gas.

Further, by circulating the unreacted gas through the synthesis gas to dilute the synthesis gas, it is possible to slow down the heat generation rate during the above-mentioned methanol synthesis, thereby suppressing a decrease in the activity of the methanol synthesis catalyst.

Further, by utilizing carbon dioxide recovered from flue gas discharged from a boiler or a combustor of a reformer as carbon dioxide supplied together with unreacted gas to the second reaction step, methanol can be produced. The amount of carbon dioxide emitted 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.

[0042]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments will be described below in detail with reference to the drawings.

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

Reference numeral 10 in FIG. 2 denotes a one-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.

The first reactor 40 ₁ for methanol synthesis comprises:
Wherein disposed on the downstream side of the reformer 20 is connected to the reformer 20 through the passage 30 _3. The first reactor 40 ₁ includes a first preheater 41 ₁ and the first preheater 41 ₁
Synthesis gas is provided with a first reactor 43 ₁ for methanol synthesis, which is supplied through the first circulation passage 42 ₁ from. This first reactor 43 _1, an oxide containing methanol synthesis catalyst, for example Cu, Zn, Al, Ga and M (at least one element selected from alkaline earth metal elements and rare earth elements), wherein Cu, 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
A catalyst having a composition of 20 was packed. Heat exchanger 51, heat recovery unit 52 and first compressor 5
3, the channel said reformer from said 20 side first 30 ₃
It is successively interposed toward the preheater 41 _1. The flow path 30 between the heat exchanger 51 and the heat recovery unit 52
_{The three} parts pass through the tube 12 of the humidifier 10.

The distillation column 60, the disposed first downstream reactor 40 ₁ is connected to the first reactor 40 ₁ through the passage 30 _4. Incidentally, the channel 30 ₄ whose one end is connected to the bottom of the first reactor 43 _1.
The first preheater 41 ₁ , the cooler 71 and the gas-liquid separator 7
2 is sequentially interposed from the first reactor 43 ₁ side of the channel 30 the _four first reactor 40 ₁ towards the distillation column 60.

The gas-liquid separator 72 includes a gas circulation passage 73
It is connected to the first preheater 41 ₁ inlet of the channel 30 ₃ through. The second gas compressor 74 is interposed in the gas circulation channel 73. The gas circulation flow path 73 is connected to _two second reactor for methanol synthesis 40 through flow path 30 _5, which is branched. The carbon dioxide recovery device 24 is connected to the channel 30 ₅ through the flow channel 30 _6. Third gas compressor 75 is interposed in the flow path 30 _6.

[0049] The second reactor 40 _2, second preheater 4
And 1 _2, and a non-reacted gas and the second reactor 43 ₂ for methanol synthesis, which is supplied the mixed gas through the second circulation passage 42 ₂ of carbon dioxide from the second preheater 41 _2. This second reactor 43 _2, an oxide containing methanol synthesis catalyst, for example Cu, Zn, Al, Ga and M (at least one element selected from alkaline earth metal elements and rare earth elements), wherein Cu, 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
A catalyst having a composition of 20 was packed. The second bottom of the reactor 43 _2, the first preheater through passage 30 ₇ passing through the second preheater 41 ₂ 41
It is connected to the channel 30 ₄ portions between ₁ and the cooler 71.

The first of the methanol synthesis reactor, the second reactor 43 _1, 43 at least one of the reactors of the _two, for example have a structure incorporating a triple pipe shown in FIG. 3, described below Is preferred.

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. When applied to the reactor, for example, the first reactor 43 ₁ having the structure shown in FIG. 3, is connected, for example the first circulation passage 42 ₁ to the supply port 116. At the lower portion of the reactor body 101, the triple tube 11
A discharge port 117 for discharging a generated gas containing methanol generated in step 0 is attached. When applied to the reactor, for example, the first reactor 43 ₁ having the structure shown in FIG. 3, 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.

The gas is desulfurized by the desulfurization unit 76 and is further preheated.
Raw material gas composed mainly of hydrocarbons (eg natural gas)
Is the channel 30₈Through the packed bed at the top of the heat exchange humidifier 10
11 is supplied. In this humidifier 10,
The pump 14 disposed in the humidifier 10 is operated in advance.
Water from the humidifier 10 via the circulating water flow path 13
Circulated to the top, before being fed to the top
Humidify the raw material gas. That is, the source gas is
Contact with water supplied from circulating water channel 13 in packed bed 11
Then, after being humidified, a reformer described below is connected to the tube 12.
20 to flow path 30 _ThreeHot syngas fed through
Is exchanged and heated, and further humidified.

[0056] humidified the mixed gas is supplied to the reformer 20 steam reforming reaction tube 21 through the passage 30 _1. The humidified source gas is supplied to the flow path 30 ₁
The required amount of process steam flow path in the course of flowing through the 30 ₉
Is supplied to the reaction tube 21 through a preheating section 22 at a convection section of the reformer 20. The raw material gas and steam mainly containing hydrocarbons supplied to the reaction tube 21 of the reformer 20 are mainly subjected to steam reforming of hydrocarbons, for example, methane in the presence of a catalyst in the reaction tube 21, It is converted to a synthesis gas containing carbon monoxide, carbon dioxide and hydrogen. Since this reaction is an endothermic reaction, the fuel gas and air are burned in the combustor 23 of the reformer 20 to heat the inside of 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.

[0057] The resulting synthesis gas is fed through a passage 30 ₃ in the heat exchanger 51, is heated here boiler water flowing through the flow path 30 _10, after generating a high-pressure steam, the humidifier 10 Is supplied to the outer flow path of the tube 12. Here, part of the heat of the synthesis gas is recovered and the humidifier 10
Is used as a heat source.

The synthesis gas that has exited 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 ₁₁
3 and is used for humidifying the raw material gas introduced into the humidifier 10. Other condensed water is available through the channel 30 _12, for example, as process water.

The synthesis gas from which the condensed water has been separated is supplied to the flow path 30 ₃
To the first compressor 53, where it is compressed to a pressure (for example, 50 to 150 atm) suitable for a methanol synthesis reaction. Boosted syngas flow path 30 ₃ first preheater 4 of the first reactor 40 ₁ for methanol synthesis through
It is supplied to the 1 _1, where it is preheated to a temperature (e.g. 200 to 300 [° C.) which is suitable for methanol synthesis reaction, further fed to the first reactor 43 ₁ methanol synthesis catalyst has been filled through the first circulation passage 42 ₁ Is done. The unreacted gas separated by the gas-liquid separator 72 described later is supplied to the gas circulation passage 7.
It is supplied to the flow passage 30 _third portion of the first preheater 41 ₁ front through 3, is mixed with the synthesis gas. Wherein the first reactor 43 _1, the formula (1), (2) shows the reaction is that it is methanol synthesis made. The first to the reactor 43 _1, it is preferable to use a reactor incorporating a triple pipe shown in FIG. 3 described above.

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 main 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.
That is, in the synthesis process of methanol, the catalyst layer 115 at the synthesis gas inlet where the temperature rises sharply during the exothermic reaction can be cooled by the cooling medium and the synthesis gas as described above. 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.

[0062] Then, the product gas from the first reactor 43 ₁ are respectively supplied through the passage 30 ₄ to the first preheater 41 ₁ and the cooler 71 are 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. The gas-liquid separator 72 separates the liquid crude methanol and unreacted gas.

[0063] The unreacted gas is fed to the second gas compressor 74 through the gas circulation flow path 73 is pressurized, yet the gas circulation flow path 73 the channel 30 of the first preheater 41 ₁ inlet through It is circulated to _3, supplied to the first reactor 43 ₁ together with synthesis gas. Some of the unreacted gas
It supplied through flow paths 30 ₅ branched from the gas circulating passage 73 to the second preheater 41 ₂ of the second reactor 40 ₂ for methanol synthesis. At the same time, carbon dioxide then through the passageway 30 ₆ from the carbon dioxide recovery apparatus 24, the flow path 30 ₆ third compressor interposed 75 is boosted is supplied to the flow path 30 _5, the unreacted supplied to ₂ the second preheater 41 as a mixed gas together with the gas. In the second preheater 41 _2, the mixed gas is preheated to a temperature suitable for methanol synthesis reaction and is further supplied through the second circulation passage 42 ₂ to the second reactor 43 ₂ methanol synthesis catalyst is filled . In the second reactor 43 ₂ mainly been the reaction of carbon dioxide and hydrogen methanol is synthesized. This second
The reactor 43 _2, it is preferable to use a reactor incorporating a triple pipe shown in FIG. 3 described above.

[0064] Incidentally, the portion of the unreacted gas via the flow path 30 ₁₃ as a purge gas from the circulating gas flow path 73 is used, for example, as a fuel for heating the reaction tube 21 of the reformer 20.

[0065] product gas from the second reactor 43 _2,
Flow path 30 ₇ via the flow path 30 ₇ the second interposed
Is cooled in the preheater 41 ₂ is supplied to the flow path 30 _4, it is merged with the generated gas produced in the first reactor 43 ₁ described above. The product gas is supplied to the cooler 71 through the passage 30 _4, it is cooled to approximately room temperature. 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. The gas-liquid separator 72 separates the liquid crude methanol and unreacted gas. The unreacted gas is in the same manner as described above, the first or is recycled to the synthesis gas fed to the reactor 43 _1, or supplied to the second reactor 43 _2, the fuel reformer 20 as a purge gas Used for

[0066] On the other hand, crude methanol separated by the gas-liquid separator 72 is fed to distillation column 60 through the channel 30 _4. In this distillation column 60, methanol is purified to high purity and is extracted as a product outside the system. Further, water containing a small amount of a high-boiling organic compound, an organic acid and a trace amount of an inorganic substance is discharged out of the system as wastewater.

[0067] above, Example 1 first methanol synthesis step in a second using a reactor 40 _1, 240 _2, first reactor 40 ₁ of the product gas (and the second reactor 40 ₂ of the product gas) by supplying the second reactor 43 ₂ of the second reactor 40 ₂ unreacted gas separated with the carbon dioxide recovered by the carbon dioxide recovery unit 24 for example for synthesizing methanol from the methanol manufacturing plant equipment Methanol can be increased simply by adding a second reactor without significant changes.

[0068] Also, by diluting the synthesis gas flowing through the channel 30 ₃ by circulating the unreacted gas to the first reactor 40 of the _first preheater 41 ₁ before the flow path 30 _3, the first it is possible to suppress the slow a manner reduced activity of methanol synthesis catalyst was charged to the first reactor 43 ₁ heat generation rate during the methanol synthesis in 1 reactor 40 _1.

[0069] Further, the combustor 23 of the second reactor 40 of the _second reactor 43 ₂ to the reformer 20 as the carbon dioxide is supplied together with the unreacted gas (and / or boiler)
By using the carbon dioxide recovered from the combustion exhaust gas discharged by the method, the amount of carbon dioxide discharged 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.

Further, the first and second reactors 43 ₁ , 43 ₁ ,
By the structure with a built-in triple pipe 110 shown in FIG. 3 at least one of the reactor of 43 _2, it can reduce the temperature of the synthesis gas inlet of the catalyst layer filled therein. As a result, the active state of the catalyst layer can be maintained for a long time.

Further, the first and second reactors 43 ₁ , 43 ₁ ,
Cu as a catalyst to be filled in 43 _2, 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:
If a catalyst having a composition of 1 to 20: 1 to 20: 0.1 to 20 and having a high durability against a synthesis gas containing 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.

[0072] Incidentally, the combustor 23 (and / or boiler) further first preheating of the first reactor 40 ₁ of carbon dioxide recovered from the exhaust flue gas by the embodiment example reformer 20 in 1 vessel 41 ₁ before the flow path 30
₃ may be supplied.

Example 2 In Example 2, another example of the methanol production according to the above-described embodiment will be described more specifically with reference to the methanol synthesizing apparatus of the main part of the 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.

The first reactor 40 for methanol synthesis shown in FIG.
_A distillation column (not shown) is disposed downstream of
Through ₁₄ is connected to the distillation column. The first reactor 40 ₁ includes a first preheater 41 ₁ and the first preheater 41 1.
Syngas from ₁ includes a first reactor 43 ₁ for methanol synthesis, which is supplied through the first circulation passage 42 _1. This first reactor 43 _1, such as methanol synthesis catalyst in the same composition as in Example 1 is filled. In addition,
The channel 30 ₁₄ is connected to the first reactor 43 ₁ bottom. The first preheater 41 _1, the first heat recovery unit 77 _1, the first cooler 71 ₁ and the first gas-liquid separator 72 _1, the first reaction of the channel 30 the ₁₄ first reactor 40 ₁ It is successively interposed towards the distillation column (not shown) from vessel 43 ₁ side.

[0075] The first gas-liquid separator 72 _1, the synthesis gas in the first preheater 41 ₁ inlet through the gas circulation flow path 73 is connected to the flow path 30 ₃ flowing. The second gas compressor 74 is interposed in the gas circulation channel 73. The gas circulation flow path 73 is connected to _two second reactor for methanol synthesis 40 through flow path 30 _5, which is branched.
Carbon dioxide recovery device (not shown) is connected to the channel 30 ₅ through the flow channel 30 _6. The third gas compressor (not shown) is interposed in the flow path 30 _6.

[0076] downstream of the second reactor 40 _2, the distillation column is disposed, it is connected to the distillation column through the flow passage 30 _{1 5.} The second reactor 40 _2, second
A preheater 41 _2, and a non-reacted gas and the second reactor 43 ₂ for methanol synthesis, which is supplied the mixed gas through the second circulation passage 42 ₂ of carbon dioxide from the second preheater 41 _2. This second reactor 43 _2, for example methanol synthesis catalyst having the same composition as in Example 1 is filled. Incidentally, the channel 30 ₁₅ is connected to the second reactor 43 ₂ bottom. The second preheater 41 ₂ , the second heat recovery unit 77 ₂ , the second cooler 71 ₂ and the second gas-liquid separator 72 ₂
It is successively interposed toward the distillation column from the second reactor 43 ₂ side of the channel 30 the ₁₅ second reactor 40 _2.

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

[0078] Synthesis gas is boosted by the Example 1 and the same processing is supplied to the first preheater 41 ₁ of the first reactor 40 ₁ for methanol synthesis through flow path 30 _3, wherein the methanol synthesis reaction Suitable temperature (e.g. 200-30
0 ° C.) is preheated to, and is further supplied through the first circulation passage 42 ₁ to the first reactor 43 ₁ methanol synthesis catalyst has been filled. Incidentally, the unreacted gas separated in the first gas-liquid separator 72 ₁ to be described later is supplied to the flow passage 30 _third portion of the first preheater 41 ₁ front through the gas circulation flow path 73, is mixed with the synthesis gas You. Wherein the first reactor 43 _1, the formula (1), (2) shows the reaction is that it is methanol synthesis made.

[0079] product gas from the first reactor 43 _1,
The first preheater 41 _{1 ,} the first heat recovery unit 7 through the flow path 30 ₁₄
7 is respectively supplied ₁ and the first cooler 71 _1, is cooled to approximately room temperature by these members. At this time, methanol and water in the product gas mostly condensed, is introduced into the first gas-liquid separator 72 ₁ becomes liquid. This first
In the gas-liquid separator 72 _1, it is separated into a coarse methanol and unreacted gas liquid.

[0080] The unreacted gas is fed to the second gas compressor 74 through the gas circulation flow path 73 is pressurized, yet the gas circulation flow path 73 the channel 30 of the first preheater 41 ₁ inlet through It is circulated to _3, supplied to the first reactor 43 ₁ together with synthesis gas.

A part of the unreacted gas is supplied to the gas circulation passage 7
3 as a purge first reactor 43 ₁ is set lower than the pressure supplied to the second preheater 41 ₂ of the second reactor 40 ₂ for methanol synthesis through flow paths 30 ₅ branched from. At the same time, carbon dioxide then through the passageway 30 ₆ from the carbon dioxide recovery apparatus, not shown, the flow paths 30 ₆ (not shown) is interposed is boosted by the third compressor is supplied to the flow path 30 _5, the non together with the reaction gas supplied to the second preheater 41 ₂ as a mixed gas. In the second preheater 41 _2, the mixed gas is preheated to a temperature suitable for methanol synthesis reaction and is further supplied through the second circulation passage 42 ₂ to the second reactor 43 ₂ methanol synthesis catalyst is filled . In the second reactor 43 ₂ mainly been the reaction of carbon dioxide and hydrogen methanol is synthesized.

[0082] product gas from the second reactor 43 _2,
Passage 30 ₁₅ second preheater 41 ₂ interposed the flow path 30 ₁₅ via the _second heat recovery unit 77 ₂ and the second cooler 71 ₂
And cooled to almost room temperature by these members. At this time, most of the methanol and water in the produced gas are condensed, become liquid, and become second liquid-liquid separator 7.
It flows into the 2 _2. In the second gas-liquid separator 72 _2, it is separated into a coarse methanol and unreacted gas liquid. The unreacted gas is passed through the channel 30 ₁₆ as a purge gas is used, for example, as a fuel for heating the reformer.

On the other hand, the first and second gas-liquid separators 7
2 _1, 72 ₂ in an isolated crude methanol the respective flow paths 30
_14, 30 ₁₅ via being fed to the distillation column (not shown). In this distillation column, methanol is purified to high purity, and is extracted as a product outside the system. Also, a small amount of high boiling organic compounds,
Water containing organic acids and trace amounts of inorganic substances is discharged out of the system as wastewater.

As described above, according to the second embodiment, the first embodiment described above is used.
A similar effect is achieved.

[0085] The second reactor 4 for methanol synthesis through the first gas-liquid separator 72 _first gas circulation flow path 73 from
By setting lower than the purge gas pressure of the unreacted gas supplied to the 0 ₂ the first pressure reactor 43 _1, the carbon dioxide recovered by the carbon dioxide recovery unit and through the passageway 30 _6, the flow path 30 boost to when supplying to the channel 30 ₅ in the third compressor (not shown) which is interposed ₆ can be suppressed lower than the first pressure reactor 43 ₁ compression pressure of the carbon dioxide. As a result, the compression power was reduced to
It becomes possible to reduce compared with.

[0086] Incidentally, the combustor (and / or steam generation boiler) further first preheating of the first reactor 40 ₁ of carbon dioxide recovered from the exhaust flue gas by, for example, a reformer in Example 2 vessel 41 ₁ before the flow path 30
₃ may be supplied.

[0087] Further, the unreacted gas separated from the second gas-liquid separator 72 ₂ as indicated by a dotted line in FIG. 4 the fourth compressor 78
In boosting, a mixed gas of unreacted gas and carbon dioxide introduced from the first gas-liquid separator 72 ₁ may be circulated in the channel 30 ₅ is circulated.

[0088]

As described above, according to the present invention, by performing the methanol synthesis step by the first reaction step and the second reaction step, the methanol production step can be performed without greatly changing the equipment for producing methanol. It is possible to provide a method for producing methanol capable of increasing the production of methanol only by adding two reaction steps.

Further, the second process is performed by using the recovered carbon dioxide.
Since methanol can be synthesized at a low pressure in the reaction step, the compression power of carbon dioxide can be reduced.

[Brief description of the drawings]

FIG. 1 is a flowchart showing another 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 schematic diagram illustrating a main part of another example of the methanol production plant according to the second embodiment of the present invention.

[Explanation of symbols]

10 ... Humidifier, 20 ... reformer, 24 ... carbon dioxide recovery device 40 _1, 40 ₂ ... for methanol synthesis reactor, 43 _1, 43 ₂ ... reactor, 60 ... distillation column, 72 _1, 72 ₂ ... gas-liquid separator, 101 ... reactor main body, 107 ... outer tube, 108 ... intermediate tube, 109 ... inner tube, 110 ... triple tube.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) // C07B 61/00 300 B01J 23/82 X (72) Inventor Tetsuya Imai 4-chome, Kannonshinmachi, Nishi-ku, Hiroshima-shi, Hiroshima, Japan No. 22 Inside Hiroshima Research Laboratory of Mitsubishi Heavy Industries, Ltd. (72) Inventor Hiroyuki Ozora 4-6-22 Kannon Shinmachi, Nishi-ku, Hiroshima-shi, Hiroshima F-term in Hiroshima Research Laboratory Mitsubishi Heavy Industries, Ltd. 4H006 AA02 AC41 AD13 BA05 BA06 BA07 BA08 BA09 BA21 BA30 BA61 BB62 BC10 BC11 BC32 BD10 BD33 BD52 BE20 BE40 BE41 4H039 CA60 CB20 CL35

Claims (6)

[Claims] 1. A raw material gas mainly composed of hydrocarbons and steam are supplied into a reformer, and these gases are reacted to generate a synthesis gas mainly composed of hydrogen, carbon monoxide and carbon dioxide. A synthesis gas generation step; a methanol synthesis step of reacting the synthesis gas on a methanol synthesis catalyst to synthesize crude methanol; and a low boiling organic compound and a high boiling point by distilling the liquid crude methanol recovered from the synthesis step. A distillation step of separating wastewater containing an organic compound and purified methanol, wherein the methanol synthesis step is performed by a first reaction step and a second reaction step, and the synthesis gas supply flow is performed in the first reaction step. The synthesis gas supplied through the passage is reacted on a methanol synthesis catalyst, and the liquid crude methanol containing the unreacted gas generated is subjected to gas-liquid separation. While the unreacted gas is compressed and circulated through the synthesis gas supply channel, a part of which is mixed with carbon dioxide and introduced into the second reaction step. A method for producing methanol, comprising reacting the mixed gas to produce crude methanol. 2. The synthesis gas of claim 1, wherein the synthesis gas has a concentration higher than that required to produce methanol by reacting hydrogen with carbon monoxide with respect to carbon monoxide. For producing methanol. 3. The method for producing methanol according to claim 1, wherein carbon dioxide is further supplied to an inlet of the first reaction step. 4. The reaction step of at least one of the first and second reaction steps is performed by two separators vertically above and below a synthesis gas supply chamber, a cooling medium flow chamber, and a methanol-containing gas retention chamber. A reactor body partitioned into a chamber,
And a triple pipe in which the outer pipe, the intermediate pipe, and the inner pipe are concentrically arranged, the upper end of the intermediate pipe being located below the upper end of the outer pipe, The lower end of the pipe is located near the center of the intermediate pipe, only the inner pipe is open at the upper end of the triple pipe, and the annular space formed by the intermediate pipe and the outer pipe is open at the lower end of the triple pipe. The method for producing methanol according to claim 1, wherein the method is performed using a reactor in which the annular space is filled with the methanol synthesis catalyst. 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.