Method for co-producing methanol and methane and equipment for co-producing methanol and methane

Abstract

To provide a method of manufacturing methane and methanol improved in a conversion efficiency in combination while suppressing equipment cost, when manufacturing methane and methanol from hydrogen and carbon dioxide.SOLUTION: A method for producing methanol and methane from hydrogen and carbon dioxide, comprising: a step of obtaining a synthetic gas containing hydrogen, carbon monoxide, carbon dioxide and water vapor by reverse shift reaction from a source gas containing hydrogen and carbon dioxide; a step of separating water by cooling the synthetic gas; a step of flowing the synthetic gas from which water has been separated to a methanol synthesis catalyst to synthesize methanol; a step of separating methanol; and a step of synthesizing methane by flowing the source gas containing hydrogen and carbon dioxide to a methanation catalyst to synthesize methane, and a reaction heat generated in the methanation reaction is used as a heat source of the reverse shift reaction.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method and equipment for co-producing methanol and methane using hydrogen and carbon dioxide as raw materials. [Background technology]

[0002] In recent years, from the perspective of global warming countermeasures, attention has been focused on carbon-neutral fuels, which do not substantially increase the carbon dioxide concentration in the atmosphere even when burned.

[0003] Methane or methanol can be obtained by recovering carbon dioxide from exhaust gases generated in industrial processes and thermal power plants, and reacting it with hydrogen obtained by electrolysis using electricity from renewable energy sources such as solar power and wind power. Methane or methanol obtained by this method can be considered a carbon-neutral fuel that does not contribute to global warming, because no additional carbon dioxide is produced when it is burned.

[0004] The methanation reaction (formula 1) in which carbon dioxide and hydrogen are reacted to obtain methane is known. (Formula 1) CO 2 +4H 2 → CH 4 +2H 2 O

[0005] In Patent Document 1, CO and H 2 A methanation reactor having a Cu-Zn-based low-temperature shift catalyst arranged upstream and a methanation catalyst arranged downstream is used for methanation of a gas containing CO and H. 2 This paper discloses a method for methanating a gas containing CO. In the upstream low-temperature shift reactor, the CO shift reaction (formula 2) proceeds, so most of the carbon monoxide contained in the raw gas reacts with water vapor and is converted to carbon dioxide, and it is believed that the methanation reaction of carbon dioxide proceeds on the downstream methanation catalyst. (Formula 2) CO+H 2O → CO 2 +H 2

[0006] Methanation reactions have long been used to remove carbon monoxide and carbon dioxide from hydrogen for ammonia synthesis, and catalysts supporting Ni, Ru, etc. are known to exhibit high activity (Non-Patent Documents 1 and 2).

[0007] The methanation reaction in which carbon dioxide is reacted with hydrogen to obtain methane is an industrially established technology (for example, Non-Patent Document 3). However, from the viewpoint of producing carbon-neutral fuels, there is still room for improvement.

[0008] The methanation reaction, in which carbon dioxide reacts with hydrogen to obtain methane, is a reaction that produces 1 mol of methane from 4 mol of hydrogen, as shown in formula 1. The calorific value (higher heating value, the same below) of 4 mol of hydrogen is 1143.3 kJ, and the calorific value of 1 mol of methane is 890.3 kJ, so even if the reaction proceeds with a 100% yield as per the theoretical formula, the calorific value of the methane obtained is only 77.9% of the calorific value of the hydrogen used as the raw material. The remainder is released as reaction heat and cannot normally be used, so approximately 22% of the energy is lost in the process of converting hydrogen to methane.

[0009] The reaction (formula 3) in which carbon dioxide and hydrogen are reacted to obtain methanol is also known (for example, Patent Document 2). (Formula 3) CO 2 +3H 2 → CH 3 OH+H 2 O

[0010] In this reaction, 1 mol of methanol is produced from 3 mol of hydrogen. The calorific value (higher heating value, the same below) of 3 mol of hydrogen is 857.5 kJ, and the calorific value of 1 mol of methanol is 726.1 kJ. Therefore, if the reaction proceeds with a 100% yield according to the theoretical formula, the calorific value of the resulting methanol will be 84.7% of the calorific value of the raw material hydrogen, making it more efficient than converting it into methane.

[0011] This high thermal efficiency of conversion also means that the heat of reaction (enthalpy change) of the reaction between carbon dioxide and hydrogen to obtain methanol is small, which means that the Gibbs energy change of the reaction is small, i.e., the reaction is unlikely to proceed in an equilibrium state.

[0012] For example, at 250°C and 5 MPa, CO 2 :H 2 When the equilibrium composition is reached by methanation of the gas with a ratio of 1:4, CO 2 In contrast, under the same conditions of 250°C and 5 MPa, 99.5% of CO 2 :H 2 When the equilibrium composition is reached by the methanol synthesis reaction of the gas with a CO ratio of 1:3, 2 Only about 20% of the carbon dioxide is converted to methanol.

[0013] As described above, since it is difficult to obtain a high equilibrium conversion rate in the reaction of synthesizing methanol by the reaction of carbon dioxide with hydrogen, a method for synthesizing methanol has been proposed in which at least a portion of the carbon dioxide is converted into carbon monoxide in advance by a reverse shift reaction (Equation 4), and the generated water is then removed before passing the resulting mixture through a methanol synthesis catalyst (Non-Patent Document 4, Patent Document 3). (Formula 4) CO 2 +H 2 → CO+H 2 O

[0014] The reaction (equation 5) of obtaining methanol from carbon monoxide and hydrogen generates a larger amount of heat than the reaction of obtaining methanol from carbon dioxide and hydrogen, due to the endothermic heat of the reverse shift reaction. Accordingly, the equilibrium conversion rate of carbon monoxide to methanol is higher than that of the reaction of synthesizing methanol from carbon dioxide. For example, under conditions of 250°C and 5 MPa, the CO:H 2 When the gas with a CO / CO ratio of 1:2 is subjected to a methanol synthesis reaction to achieve an equilibrium composition, 58% of the CO is converted to methanol. (Formula 5) CO+2H 2 → CH 3 OH

[0015] The reverse shift reaction is an endothermic reaction, and the higher the temperature, the higher the conversion of carbon dioxide to carbon monoxide. For example, 2 :H 2 When a reverse shift reaction is performed on gas with a carbon dioxide to carbon monoxide ratio of 1:3, the conversion rate of carbon dioxide to carbon monoxide is only 16% at 250°C, but increases to 29% at 350°C and 43% at 450°C. Therefore, in order to sufficiently advance the reverse shift reaction, the reaction must be carried out at high temperatures, which requires a high-temperature heat source.

[0016] On the other hand, since the methanol synthesis reaction is an exothermic reaction and the higher the temperature, the lower the conversion rate, it is common to carry out the reaction at around 250°C using a heat exchange reactor, and it is usually impossible to recover waste heat above 350°C. It is possible to cover the endothermic heat of the reverse shift reaction by burning hydrogen, but this inevitably reduces the efficiency of converting hydrogen to methanol. [Prior art documents] [Patent documents]

[0017] [Patent Document 1] Japanese Patent Application Publication No. 60-235893 [Patent Document 2] Japanese Patent Application Publication No. 7-39755 [Patent Document 3] U.S. Patent No. 8,198,338 [Non-patent literature]

[0018] [Non-Patent Document 1] Chemical Process Journal, edited by the Society of Chemical Engineers, 1970, p.153 [Non-Patent Document 2] Catalysis Society of Japan, Catalyst Handbook, 2008, p.535 [Non-Patent Document 3] Kawagoe, Matsuda, Matsushima and Uematsu, Hitachi Review, Vol. 68, No. 10, 1986, p. 73 [Non-Patent Document 4] S.-J. Uhm et al., Industrial and Engineering Chemistry Research, vol. 38, 1999, p. 1808. Summary of the Invention [Problem to be solved by the invention]

[0019] In view of the above problems, an object of the present invention is to provide a method and equipment for co-producing methane and methanol with improved conversion efficiency while suppressing equipment costs when producing methane and methanol from hydrogen and carbon dioxide. [Means for solving the problem]

[0020] The characteristic configuration of the method for producing methanol and methane according to the present invention is as follows: A process for co-producing methanol and methane from hydrogen and carbon dioxide, comprising the steps of: (a) obtaining a synthesis gas containing hydrogen, carbon monoxide, carbon dioxide and water vapor from a feed gas containing hydrogen and carbon dioxide by a reverse shift reaction; (b) cooling the synthesis gas to separate water; (c) synthesizing methanol by passing the synthesis gas from which water has been separated through a methanol synthesis catalyst; (d) cooling the gas obtained in step (c) to separate the methanol; (e) passing a raw material gas containing hydrogen and carbon dioxide through a methanation catalyst to synthesize methane; At least a part of the synthesis gas from which methanol has been separated in the step (d) is used as a raw material gas for the methanation reaction in the step (e); Step (e) is carried out only after step (d); The reaction heat generated in step (e) is used as a heat source for step (a) via a heat exchanger. The methanol and methane co-production equipment according to the present invention has the following characteristic configuration: A facility for co-producing methanol and methane from hydrogen and carbon dioxide, comprising: a reverse shift reaction section for obtaining a synthesis gas containing hydrogen, carbon monoxide, carbon dioxide and water vapor from a raw material gas containing hydrogen and carbon dioxide by a reverse shift reaction; a water separation section that cools the synthesis gas and separates water from it; a methanol synthesis unit that synthesizes methanol by passing the synthesis gas from which water has been separated through a methanol synthesis catalyst; a methanol separation section for cooling the gas sent from the methanol synthesis section and separating methanol; a methanation reaction section that synthesizes methane by passing a raw material gas containing hydrogen and carbon dioxide through a methanation catalyst; a heat supply section that supplies reaction heat generated in the methanation reaction section to the reverse shift reaction section via a heat exchanger; At least a part of the synthesis gas sent from the methanol separation section is supplied to the methanation reaction section as a raw material gas. The methanation reaction section is located only after the methanol separation section. The point is that...

[0021] According to this characteristic configuration, when obtaining methanol from a raw material gas containing hydrogen and carbon dioxide, a part of carbon dioxide is converted to carbon monoxide in advance by the reverse shift reaction, so that the yield of methanol is improved. Furthermore, the reverse shift reaction is usually carried out at 350°C or higher, preferably 450°C or higher, but in the methanol synthesis, exhaust heat at this temperature cannot be obtained. In the method and equipment for co-production of methane and methanol of the present invention, The process of synthesizing methane is configured to be performed only after the process of separating methanol, The heat generated by methanation is utilized as a heat source for the reverse shift reaction via a heat exchanger, increasing the efficiency of conversion of hydrogen to products (methane and methanol). According to this characteristic configuration, when obtaining methanol from a raw material gas containing hydrogen and carbon dioxide, at least a part of the synthesis gas from which methanol is separated is used as the raw material gas for the methanation reaction, so that the amount of unreacted gas that is usually required in the methanol synthesis process to be recycled to the raw material gas is reduced, and the synthesis gas from which methanol is separated can be effectively used as the raw material gas for the methanation reaction. When the entire amount of the synthesis gas from which methanol is separated is used as the raw material gas for the methanation reaction, it is not necessary to recycle the unreacted gas to the raw material gas for the methanol synthesis, and therefore the equipment cost can be significantly reduced.

[0022] Ma Further, the methanol and methane co-production equipment according to the present invention has the following characteristic configuration: , Me The advantage of this embodiment is that it includes a flow rate adjusting section that adjusts the flow rate of the synthesis gas supplied from the ethanol separation section to the methanation reaction section.

[0024] A further characteristic feature of the method for co-producing methanol and methane according to the present invention is that at least a part of the synthesis gas from which methanol has been separated in the step (d) is mixed with the feed gas for the reverse shift reaction in the step (a). In addition, a further characteristic configuration of the methanol and methane co-production equipment according to the present invention is configured to return at least a part of the synthesis gas sent from the methanol separation section to the reverse shift reaction section as a raw material gas, The flow rate adjusting section adjusts the flow rate of the synthesis gas supplied from the methanol separation section to the reverse shift reaction section.

[0025] According to this characteristic configuration, the amounts of methanol and methane produced can be arbitrarily selected within a range in which the heat generated in the methanation reaction step can cover the heat absorbed in the reverse shift reaction step, and methanol and methane can be co-produced in an economically advantageous manner. [Brief description of the drawings]

[0026] [Figure 1] FIG. 1 is a block flow diagram showing one embodiment of a method and equipment for co-producing methanol and methane according to the present invention. [Diagram 2] FIG. 2 is a block flow diagram showing another embodiment of the method and facility for co-producing methanol and methane according to the present invention. [Diagram 3] FIG. 1 is a process flow diagram showing one embodiment of a method and equipment for co-producing methanol and methane according to the present invention. [Figure 4] FIG. 1 is a process flow diagram showing a method and facility for co-producing methanol and methane other than the method of the present invention. [Diagram 5]FIG. 1 is a process flow diagram showing one embodiment of a method and equipment for co-producing methanol and methane according to the present invention. [Figure 6] FIG. 1 is a process flow diagram showing a method and facility for co-producing methanol and methane other than the method of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] [Embodiment] Hereinafter, an embodiment of the method and equipment for co-producing methanol and methane will be described. FIG. 1 is a block flow diagram showing the method and equipment for co-producing methanol and methane of the present invention. The method for co-producing methanol and methane according to this embodiment includes a step of obtaining a synthesis gas containing hydrogen, carbon monoxide, carbon dioxide and steam from a raw material gas containing hydrogen and carbon dioxide by a reverse shift reaction (reverse shift reaction step), a step of cooling the synthesis gas and separating water (water separation step), a step of synthesizing methanol by passing the synthesis gas from which water has been separated through a methanol synthesis catalyst (methanol synthesis step), a step of cooling the gas obtained in the methanol synthesis step and separating methanol (methanol separation step), and a step of synthesizing methane by passing the raw material gas containing hydrogen and carbon dioxide through a methanation catalyst (methanation reaction step), and the reaction heat generated in the methanation reaction step is used as a heat source for the reverse shift reaction step. The methanol and methane co-production facility according to this embodiment includes a reverse shift reaction section 1, a water separation section 2, a methanol synthesis section 3, a methanol separation section 4, and a methanation reaction section 5 which correspond to each step in the above-mentioned co-production method, and also includes a heat supply section 6 which supplies reaction heat generated in the methanation reaction section 5 to the reverse shift reaction section 1.

[0028] In the reverse shift reaction step (reverse shift reaction section 1), a raw material gas containing carbon dioxide and hydrogen is preheated by supplying reaction heat generated in a methanation reaction step described later from a heat supply section 6, and is brought into contact with a reverse shift catalyst to generate carbon monoxide and water vapor by a reverse shift reaction of carbon dioxide and hydrogen. The heat supply section 6 is, for example, a heat exchanger that exchanges heat between the raw material gas and a gas whose temperature has been increased by the methanation reaction.

[0029] The carbon dioxide and hydrogen used as the raw materials may be produced by any method as long as they have a purity and properties that do not interfere with the reverse shift reaction. The hydrogen may be electrolytic hydrogen obtained by electrolyzing water. The carbon dioxide may be recovered from combustion exhaust gas by a known carbon dioxide recovery method such as an amine absorption method, or may be carbon dioxide recovered from biogas obtained by methane fermentation of organic matter.

[0030] When carbon dioxide or hydrogen contains sulfur, halogen compounds, siloxane compounds, heavy hydrocarbons, etc., these may cause deterioration of the reverse shift catalyst or the downstream methanol synthesis catalyst, so it is preferable to remove these, if necessary, before subjecting them to the reaction.

[0031] As the reverse shift catalyst, known CO shift catalysts such as copper-zinc catalyst and iron-chromium catalyst can be used.

[0032] The preheating temperature is restricted by the balance with the heat generated in the methanation reaction step, but is usually set to 300° C. or higher and 550° C. or lower, preferably 350° C. or higher and 500° C. or lower. Within this range, the conversion rate of carbon dioxide to carbon monoxide is ensured, and the heat required for preheating can easily be provided by the heat generated in the methanation reaction step.

[0033] When the reverse shift reaction is carried out in an adiabatic reactor, the temperature decreases as the reaction proceeds, and the conversion rate of carbon dioxide to carbon monoxide decreases accordingly. Therefore, preheating and reaction may be repeated in multiple stages as necessary.

[0034] In the water separation step (water separation section 2), the gas containing hydrogen, carbon monoxide, carbon dioxide and water vapor obtained by the reverse shift reaction is cooled to separate the water vapor into water. Since the gas after the reverse shift reaction is at a sufficiently high temperature, it is preferable to recover its sensible heat and use it, for example, for heat exchange with a raw material gas containing carbon dioxide and hydrogen to be subjected to the reverse shift reaction, for preheating the raw material gas.

[0035] When the temperature is not sufficiently decreased by only the heat exchange with the raw material gas containing carbon dioxide and hydrogen to be subjected to the reverse shift reaction, the gas is further cooled by means of cooling water, air cooling, or the like, preferably to 50° C. or less, more preferably to 40° C. or less, and condensed water is separated. For example, if the amount of water vapor remaining in the gas is reduced by cooling to a lower temperature using a refrigerator or the like and then separating the water, the amount of methanol obtained in the subsequent methanol synthesis step increases to some extent, but usually cooling with cooling water or the like is sufficient.

[0036] In the methanol synthesis step (methanol synthesis section 3), the hydrogen, carbon monoxide, and carbon dioxide from which water has been separated, and a gas containing a trace amount of water vapor are brought into contact with a methanol synthesis catalyst to produce methanol.

[0037] As the methanol synthesis catalyst, known copper-zinc catalysts, chromium-zinc catalysts, copper-chromium-zinc catalysts, etc. can be used.

[0038] The temperature at which the reaction mixture is contacted with the methanol synthesis catalyst is preferably from 200° C. to 350° C., more preferably from 220° C. to 280° C. Within the above range, a sufficient reaction rate and conversion rate to methanol can be ensured, and therefore, the amount of methanol produced can be ensured without using an excessive amount of catalyst.

[0039] Since the methanol synthesis reaction is accompanied by a certain amount of heat generation, it is preferable to use, as the methanol synthesis reactor, a heat exchange type reactor in which the reaction proceeds while removing the generated heat.

[0040] In the methanol separation step (methanol separation section 4), the gas containing methanol and unreacted hydrogen, carbon monoxide, and carbon dioxide obtained in the methanol synthesis step is cooled to separate and recover methanol as a liquid. Since the gas after the methanol synthesis step is at a sufficiently high temperature, it is preferable to recover its sensible heat and use it, for example, for heat exchange with the gas to be used for methanol synthesis, for preheating it.

[0041] Since methanol has a certain vapor pressure even at room temperature, the amount of methanol recovered can be increased by cooling it to room temperature or below using a refrigerator and a heat exchanger, in addition to cooling it by heat exchange, water cooling, or air cooling. Methanol is separated by cooling it to preferably 20°C or below, more preferably 10°C or below.

[0042] In the methanation reaction step (methanation reaction section 5), the gas containing unreacted hydrogen, carbon monoxide and carbon dioxide after separation of the methanol is contacted with a methanation catalyst to produce methane.

[0043] As the methanation catalyst used in the methanation reaction step, a known methanation catalyst containing Ni, Ru or the like can be used.

[0044] The inlet temperature when contacting with the methanation catalyst is preferably 200° C. or higher and 350° C. or lower, and more preferably 225° C. or higher and 275° C. or lower. When the temperature is within the above range, a sufficient reaction rate is likely to be obtained, making it easy to proceed with the methanation reaction without using an excessive amount of catalyst, and since the outlet temperature of the methanation reaction does not become too high, it is easy to ensure the durability of the catalyst.

[0045] Since the methanation reaction generates a relatively large amount of heat, the temperature of the gas rises as the reaction proceeds, and the equilibrium conversion rate decreases accordingly. Therefore, it is usually difficult to obtain a desired conversion rate in a single-stage reaction. On the other hand, if a heat exchange type reactor is used, it becomes difficult to extract the high-temperature heat required for the reverse shift reaction. Therefore, it is preferable to use an adiabatic reactor on the inlet side, and cool the outlet gas whose temperature has risen due to the reaction heat by heat exchange with the gas to be used for the reverse shift reaction (i.e., use the reaction heat generated in the methanation reaction step as a heat source for the reverse shift reaction step), and then introduce the cooled gas into the next-stage reactor. Adiabatic reactors may be connected in multiple stages via a heat exchanger for cooling, and at least one adiabatic reactor on the inlet side and at least one heat exchange type reactor on the outlet side may be connected via a heat exchanger for cooling.

[0046] Since the methanation reaction generates a relatively large amount of heat, thermal degradation of the catalyst may be a problem. The gas from the reactor outlet side can be returned to the reactor inlet side to dilute the gas to be used in the reaction. When this reactor configuration is used, the dilution effect suppresses temperature rise, improving the durability of the catalyst. In addition, the lower reactor outlet temperature has the effect of increasing the equilibrium conversion rate, so that the number of reactor stages may be reduced compared to a simple multi-stage reactor configuration.

[0047] The gas after the methanation reaction is cooled and the water is separated to obtain a gas mainly composed of methane.

[0048] The reaction pressure is preferably 3 MPa to 10 MPa, more preferably 4 MPa to 7 MPa. When the reaction pressure is in this range, it is possible to obtain methanol at a molar ratio to methane of about 0.5 to 1 while suppressing equipment costs.

[0049] In the method and facility for co-producing methanol and methane shown in Fig. 1, methanol is first synthesized based on synthesis gas obtained from a feed gas containing carbon dioxide and hydrogen supplied to a reverse shift reaction section 1, and methane is synthesized using the unreacted synthesis gas remaining after separation as a feedstock. The molar ratio of methanol to methane produced is determined by the reaction pressure, the degree of progress of the reverse shift reaction, and the like, and is usually in the range of 3:7 to 5:5.

[0050] In the method of this embodiment, the entire amount of unreacted synthesis gas remaining after the methanol synthesis reaction is used as a raw material for the methanation reaction. Therefore, it is not necessary to select an extremely high pressure, for example, 20 MPa, as employed in conventional methanol synthesis in order to increase the methanol conversion rate, and there is also no need for expensive equipment such as a recycle compressor that returns the unreacted synthesis gas to the inlet side of the methanol synthesis reaction.

[0051] In the method and equipment for co-producing methanol and methane according to the present embodiment, the molar ratio of methanol to methane produced varies depending on the reaction conditions. When methanol is obtained by the reaction of carbon dioxide with hydrogen, three times the molar ratio of hydrogen is required relative to carbon dioxide, and when methane is obtained, four times the molar ratio of hydrogen is required relative to carbon dioxide. Therefore, in the method for co-producing methanol and methane according to the present embodiment, the ratio of carbon dioxide and hydrogen supplied to the reverse shift reaction is set to a molar ratio of hydrogen to carbon dioxide of 3 to 4, but when methane is used as a raw material for city gas, it is not preferable for a large amount of hydrogen or carbon dioxide to remain. For example, when the molar ratio of methanol and methane produced is 4:6, the concentration of gases other than methane contained in the gas after the methanation reaction can be reduced by supplying a mixed gas to the reverse shift reaction section 1 so that the molar ratio of hydrogen to carbon dioxide is 3.6.

[0052] FIG. 2 is a block flow diagram showing a method and equipment for co-producing methanol and methane according to another embodiment of the present invention. The method and equipment for co-producing methanol and methane according to this embodiment also have a reverse shift reaction step (reverse shift reaction section 1), a water separation step (water separation section 2), a methanol synthesis step (methanol synthesis section 3), a methanol separation step (methanol separation section 4), and a methanation reaction step (methanation reaction section 5). However, unlike the embodiment shown in FIG. 1, the synthesis gas after separation of methanol in the methanol separation step (methanol separation section 4) passes through a flow rate adjustment section 7, and most of the synthesis gas is returned to the inlet of the reverse shift reaction section 1, and the remainder is mixed with a separately prepared raw material gas containing hydrogen and carbon dioxide and used as a raw material for the methanation reaction step. The flow rate adjustment section 7 is configured to be able to arbitrarily adjust the amount of synthesis gas returned to the reverse shift reaction section 1 and the amount of synthesis gas supplied to the methanation reaction section 5.

[0053] In this embodiment, the production ratio of methanol and methane can be set arbitrarily within a range in which the heat generated in the methanation reaction step can cover the heat absorbed in the reverse shift reaction.

[0054] In the method of this embodiment, a part of carbon dioxide is converted to carbon monoxide by the reverse shift reaction, so that the methanol conversion rate in a single pass is high. Therefore, the scale of equipment such as a recycle compressor that returns the unreacted synthesis gas to the inlet side is smaller than that of conventionally known methods and equipment. In addition, since the methanol conversion rate in a single pass is high, the proportion of the unreacted gas to be recycled is reduced, and the flow rate of the synthesis gas introduced into the methanol synthesis catalyst is reduced, so that the amount of the methanol synthesis catalyst can be reduced, and the cost of the catalyst and the reactor can be reduced.

[0055] In a methanol synthesis facility with recycling of unreacted gas, a part of the unreacted synthesis gas is usually extracted from the system as a purge gas to prevent accumulation of inert components. This may include light hydrocarbons such as methane, which can be used as a methanation feedstock. In the methanol and methane co-production method and facility of this embodiment, the unreacted synthesis gas can be mixed with a feedstock gas containing hydrogen and carbon dioxide prepared separately from the feedstock to be used in the reverse shift reaction, and used as a feedstock to be used in the methanation reaction step, thereby increasing the conversion efficiency from hydrogen to the products methanol and methane.

[0056] [Examples and Comparative Examples] An example of a trial calculation based on process calculation is shown below. The pressure is 5 MPa, and pressure loss and heat loss in each device and piping are not taken into consideration. Figure 3 is a process flow diagram showing one embodiment of the method and equipment for co-producing methanol and methane according to the present invention.

[0057] The raw material gas is supplied to the reverse shift reactor 1 at a temperature of 25° C. and a flow rate of carbon dioxide 1 mol / s and hydrogen 3.6 mol / s. In the reverse shift reactor 1, the raw material gas is heated to 350° C. in the heat exchanger 311 by heat exchange with gas after the reverse shift reaction described below. Then, the raw material gas is sent to the reverse shift reactor 312, where a part of the carbon dioxide is converted to carbon monoxide by the reverse shift reaction. The gas whose temperature has been reduced by the reverse shift reaction is heated to 520° C. in the heat exchanger 313 (corresponding to the heat supply unit) by heat exchange with gas after the methanation reaction. Then, the raw material gas is sent to the reverse shift reactor 314, where the reverse shift reaction is further advanced to further increase the proportion of carbon monoxide (reverse shift reaction step). The outlet gas of the reverse shift reactor 314 is cooled to 150° C. by heat exchange with the raw material gas in the heat exchanger 315 (= the high temperature side of the heat exchanger 311), and sent to the water separation unit 2.

[0058] In the water separation section 2, the gas after the reverse shift reaction is further cooled to 40° C. using cooling water in a heat exchanger 321. Water condensed by cooling is separated from the synthesis gas in a gas-liquid separation drum 322 (water separation step).

[0059] In the methanol synthesis section 3, the synthesis gas from which water has been separated in the water separation section 2 is heated to 150°C in a heat exchanger 331 by heat exchange with gas after the methanol synthesis reaction described later, and further heated to 250°C in a heat exchanger 332 by heat exchange with recycled gas after the methanation reaction described later, and then passed to a methanol synthesis reactor 333 to synthesize methanol from the synthesis gas. It is not necessarily required to raise the temperature to 250°C by heat exchange with recycled gas after the methanation reaction. In a normal methanol synthesis reaction, it is common to preheat the inlet gas of the methanol synthesis reactor to a temperature required to start the methanol synthesis reaction, for example, about 200°C, by heat exchange between the outlet gas and inlet gas of the methanol synthesis reactor, and gradually raise the temperature to a temperature appropriate for the methanol synthesis reaction by reaction and heat exchange in the methanol synthesis reactor. However, it is advantageous to raise the temperature to 250°C by heat exchange with recycled gas after the methanation reaction, in that the reaction starts quickly at a temperature appropriate for the methanol synthesis reaction.

[0060] The methanol synthesis reactor 333 is a heat exchange type reactor in which the reaction proceeds while maintaining the temperature at approximately 250°C while removing the heat generated by the methanol synthesis reaction, and the methanol synthesis reaction proceeds until the equilibrium composition reaches 250°C (methanol synthesis step). The heat generated is recovered as high-pressure steam. The gas after the methanol synthesis reaction is heat-recovered to 150°C in the heat exchanger 334 (the high-temperature side of the heat exchanger 331) and sent to the methanol separation section 4.

[0061] In the methanol separation section 4, the gas after the methanol synthesis reaction is cooled to 40°C using cooling water in a heat exchanger 341, and further cooled to below room temperature using a refrigerator and a heat exchanger (not shown), and the produced methanol is separated in a gas-liquid separation drum 342 (methanol separation process).

[0062] In the methanation reaction section 5, the entire amount of the synthesis gas from which methanol has been separated in the methanol separation section 4 is mixed with gas branched from the outlet of a heat exchanger 352 (described later) and passed through a methanation reactor 351 at 250°C to carry out a methanation reaction of the synthesis gas (methanation reaction step). The methanation reactor 351 is an adiabatic reactor, and the temperature rises as methanation proceeds, and the methanation reaction proceeds up to an equilibrium composition of 600°C. The heat exchanger 352 is the high-temperature side (heat dissipation side) of the heat exchanger 313, and the gas after the methanation reaction is cooled to 479°C by heat exchange, and 72.3% is returned to the inlet side as recycled gas using a recycle compressor (not shown). The recycled gas is first cooled to 416°C by heat exchange with gas on the inlet side of the methanol synthesis catalyst in heat exchanger 353 (the high temperature side of heat exchanger 332), and then further cooled to 350°C while recovering heat as high pressure steam by heat exchange with water in heat exchanger 354, and mixed with the synthesis gas from which methanol has been separated. The remaining 27.7% is passed through heat exchanger 355, where it is cooled to 250°C while recovering heat as high pressure steam, and sent to methanation reactor 356. Methanation reactor 356 is a heat exchange type reactor, in which the reaction proceeds while maintaining the temperature at approximately 250°C while removing heat generated by the reaction, and the methanation reaction proceeds until the equilibrium composition reaches 250°C, and the heat is recovered as high pressure steam. The gas after the reaction is subjected to heat recovery up to 150°C in a heat exchanger 357 to obtain low-pressure steam, which is then further cooled with cooling water in a heat exchanger 358, and water is separated in a gas-liquid separation drum 359 to obtain a gas mainly composed of methane.

[0063] The temperatures and flow rates at key points in the process are shown in Table 1.

[0064] [Table 1]

[0065] The production rates of methanol and methane were 0.400 mol / s and 0.597 mol / s, respectively. The ratio of the calorific value of the products (methanol and methane) to the raw hydrogen was 79.9%. The composition of the main methane gas produced after dehydration was 97.66% methane, 1.86% hydrogen, and 0.48% carbon dioxide. As shown in Table 1, the inlet gas flow rate of the methanol synthesis catalyst was 4.118 mol / s. When the designed catalyst amount of the methanol synthesis catalyst is designed at a gas hourly space velocity (GHSV) of 2000 per hour, 166 liters of methanol synthesis catalyst are required, and the methanol production rate per unit volume of the methanol synthesis catalyst is 8.66 mol [methanol] / (h·L [catalyst]).

[0066] FIG. 4 is a process flow diagram of a configuration in which the reverse shift reaction section 1 and the water separation section 2 are omitted from the configuration of FIG. 3, and is a comparative example to FIG.

[0067] The raw material gas is directly introduced into the methanol synthesis section 3 at a temperature of 25°C and a flow rate of carbon dioxide 1 mol / s and hydrogen 3.778 mol / s. In the methanol synthesis section 3, the gas containing the raw materials carbon dioxide and hydrogen is heated to 150°C by heat exchange with the gas after the methanol synthesis reaction described later in the heat exchanger 431, and further heated to 250°C by heat exchange with the recycled gas after the methanation reaction described later in the heat exchanger 432, and then passed to the methanol synthesis reactor 433 to synthesize methanol from the synthesis gas. The methanol synthesis reactor 433 is a heat exchange type reactor, and the reaction proceeds while maintaining approximately 250°C while removing the heat generated by the methanol synthesis reaction, and the methanol synthesis reaction proceeds until the equilibrium composition of 250°C. The heat is recovered as high-pressure steam. The gas after the methanol synthesis reaction is heat recovered to 150°C in the heat exchanger 434 (the high-temperature side of the heat exchanger 431) and sent to the methanol separation section 4.

[0068] In the methanol separation section 4, the gas after the methanol synthesis reaction is cooled to 40°C using cooling water in a heat exchanger 441, and further cooled to below room temperature using a refrigerator and a heat exchanger (not shown), and the produced methanol is separated in a gas-liquid separation drum 442.

[0069] In the methanation reaction section 5, the synthesis gas from which methanol has been separated in the methanol separation section 4 is mixed with gas branched from the outlet of the heat exchanger 452 described later, and is passed through the methanation reactor 451 at 250°C to carry out the methanation reaction of the synthesis gas. The methanation reactor 451 is an adiabatic reactor, and the temperature rises as the methanation proceeds, and the methanation reaction proceeds to an equilibrium composition of 579°C. In the heat exchanger 452, the gas is cooled to 489°C while recovering heat as high-pressure steam, and 72.3% is returned to the inlet side as recycled gas using a recycle compressor (not shown). The recycled gas is first cooled to 433°C by heat exchange with the gas at the inlet side of the methanol synthesis catalyst in the heat exchanger 453 (the high-temperature side of the heat exchanger 432), and then further cooled to 350°C while recovering heat as high-pressure steam by heat exchange with water in the heat exchanger 354, and mixed with the synthesis gas from which methanol has been separated. The remaining 27.7% is passed through a heat exchanger 455, where it is cooled to 250°C while recovering heat as high-pressure steam, and sent to a methanation reactor 456. The methanation reactor 456 is a heat exchange type reactor in which the reaction proceeds while maintaining the temperature at approximately 250°C while removing heat generated by the reaction, and the methanation reaction proceeds to an equilibrium composition of 250°C, and the heat is recovered as high-pressure steam. The gas after the reaction is cooled to 150°C by a heat exchanger 457 to recover heat and obtain low-pressure steam, and is further cooled with cooling water by a heat exchanger 458, and water is separated in a gas-liquid separation drum 459, thereby obtaining a gas mainly composed of methane.

[0070] The temperatures and flow rates at the main points of the process are shown in Table 2.

[0071] [Table 2]

[0072] The production rates of methanol and methane were 0.222 mol / s and 0.774 mol / s, respectively. The ratio of the calorific value of the products (methanol and methane) to the calorific value of the raw material hydrogen was 78.7%. The composition of the main methane gas produced after dehydration was 97.52% methane, 1.98% hydrogen, and 0.50% carbon dioxide. As shown in Table 2, the inlet gas flow rate of the methanol synthesis catalyst was 4.778 mol / s. When the designed catalyst amount of the methanol synthesis catalyst is designed at a gas hourly space velocity (GHSV) of 2000 per hour, 193 liters of methanol synthesis catalyst are required, and the methanol production rate per unit volume of the methanol synthesis catalyst is 4.15 mol [methanol] / (h·L [catalyst]).

[0073] In the configuration of Fig. 4, the methanol yield per unit volume of the methanol synthesis catalyst is smaller than that in the configuration of Fig. 3, and it is clear that the process is less economical as a process for simultaneously producing methanol and methane. In addition, the concentrations of hydrogen and carbon dioxide contained in the main component gas of methane produced by methanation are high, i.e., the purity of methane is low.

[0074] FIG. 5 is a process flow diagram showing another embodiment of the method and facility for co-producing methanol and methane according to the present invention.

[0075] The raw material gas for methanol synthesis is supplied to the reverse shift reactor 1 at a temperature of 25°C and a flow rate of 1 mol / s of carbon dioxide and 3 mol / s of hydrogen. In the reverse shift reactor 1, the raw material gas is heated to 350°C in the heat exchanger 511 by heat exchange with gas after the reverse shift reaction described below. Then, the raw material gas is sent to the reverse shift reactor 512, where a part of the carbon dioxide is converted to carbon monoxide by the reverse shift reaction. The gas whose temperature has been reduced by the reverse shift reaction is heated to 520°C in the heat exchanger 513 (corresponding to the heat supply unit) by heat exchange with gas after the methanation reaction. Then, the raw material gas is sent to the reverse shift reactor 514, where the reverse shift reaction is further advanced to further increase the proportion of carbon monoxide (reverse shift reaction step). The outlet gas of the reverse shift reactor 514 is cooled to 150°C by heat exchange with the raw material gas in the heat exchanger 515 (= the high temperature side of the heat exchanger 511), and sent to the water separation unit 2.

[0076] In the water separation section 2, the gas after the reverse shift reaction is further cooled to 40° C. using cooling water in a heat exchanger 521. Water condensed by cooling is separated from the synthesis gas in a gas-liquid separation drum 522 (water separation step).

[0077] In the methanol synthesis section 3, the synthesis gas from which water has been separated in the water separation section 2 is heated to 150°C in a heat exchanger 531 by heat exchange with gas after the methanol synthesis reaction described later, and further heated to 250°C in a heat exchanger 532 by heat exchange with recycled gas after the methanation reaction described later, and then passed to a methanol synthesis reactor 533 to synthesize methanol from the synthesis gas. The methanol synthesis reactor 533 is a heat exchange type reactor, and the reaction proceeds while maintaining approximately 250°C while removing heat generated by the methanol synthesis reaction, and the methanol synthesis reaction proceeds to an equilibrium composition of 250°C (methanol synthesis step). The heat is recovered as high-pressure steam. The gas after the methanol synthesis reaction is heat-recovered to 150°C in a heat exchanger 534 (the high-temperature side of the heat exchanger 531) and sent to the methanol separation section 4.

[0078] In the methanol separation section 4, the gas after the methanol synthesis reaction is cooled to 40°C in a heat exchanger 541 using cooling water, and then cooled to room temperature or below using a refrigerator and a heat exchanger (not shown), and the produced methanol is separated in a gas-liquid separation drum 542 (methanol separation step). Of the synthesis gas from which methanol has been separated in the methanol separation section 4, 1% by volume is extracted to the outside of the system as a purge gas in a flow rate adjustment section 543, and the remainder is returned to the inlet of the reverse shift reaction section using a recycle compressor (not shown).

[0079] The raw material gas for the methanation reaction is supplied to the methanation reaction section 5 at a temperature of 25°C and a flow rate of 1 mol / s carbon dioxide and 4 mol / s hydrogen. The raw material gas is heated to 250°C in the heat exchanger 551 by heat exchange with the gas after the methanation reaction described later, and is further mixed with the gas branched from the outlet of the heat exchanger 556 described later, and is introduced into the methanation reactor 552 at 250°C. The methanation reactor 552 is an adiabatic reactor, and the temperature increases as the methanation proceeds, and the methanation reaction proceeds to an equilibrium composition of 600°C (methanation reaction step). The heat exchanger 553 is the high-temperature side (heat dissipation side) of the heat exchanger 513, and the gas after the methanation reaction is cooled to 454°C by heat exchange. The heat exchanger 554 introduced next is the high-temperature side (heat dissipation side) of the heat exchanger 532, and the gas after the methanation is further cooled to 385°C by heat exchange. The next heat exchanger 555 is the high temperature side (heat dissipation side) of the heat exchanger 551, and is further cooled to 298°C by heat exchange with the raw material gas. In the next heat exchanger 556, the gas after methanation is cooled to 250°C while recovering heat as high pressure steam. 67.6% of the cooled gas is returned to the inlet side as recycled gas using a recycle compressor (not shown). The remaining 32.4% is sent to the methanation reactor 557. The methanation reactor 557 is a heat exchange type reactor, and the reaction proceeds while maintaining approximately 250°C while removing heat generated by the reaction, and the methanation reaction proceeds to an equilibrium composition of 250°C, and the heat is recovered as high pressure steam. The gas after the reaction is heat recovered to 150°C by the heat exchanger 558 to obtain low pressure steam, and is further cooled with cooling water by the heat exchanger 559, and water is separated in the gas-liquid separation drum 560 to obtain methane-based gas.

[0080] The temperatures and flow rates at the inlet and outlet of the methanol synthesis reactor 533 are shown in Table 3.

[0081] [Table 3]

[0082] The production rates of methanol and methane were 0.983 mol / s and 0.995 mol / s, respectively. The ratio of the calorific value of the products (methanol and methane) to the calorific value of the raw hydrogen was 79.9%. The composition of the main methane gas produced after dehydration was 97.44% methane, 2.05% hydrogen, and 0.51% carbon dioxide. As shown in Table 3, the inlet gas flow rate of the methanol synthesis catalyst was 9.261 mol / s. When the designed catalyst amount of the methanol synthesis catalyst is designed at a gas hourly space velocity (GHSV) of 2000 per hour, 374 liters of methanol synthesis catalyst are required, and the methanol production rate per unit volume of the methanol synthesis catalyst is 9.48 mol [methanol] / (h·L [catalyst]).

[0083] In the configuration of Figure 5, when the purge gas after methanol separation was mixed with the raw material for methanation, the composition of the methane-based gas after dehydration was the same, and the methane production rate increased to 1.011 mol / s. However, it was necessary to adjust the flow rate of the raw material gas for the methanation reaction to 4.017 mol / s. Under these conditions, the ratio of the calorific value of the products (methanol and methane) to the calorific value of the raw material hydrogen increased to 80.5%. This is because the purge gas was used as the raw material for methanation.

[0084] FIG. 6 is a process flow diagram of a configuration in which the reverse shift reaction section 1 and the water separation section 2 are omitted from the configuration of FIG. 5, and is a comparative example to FIG.

[0085] The raw material gas for methanol synthesis is supplied to the methanol synthesis section 3 at a temperature of 25° C. and a flow rate of carbon dioxide of 1 mol / s and hydrogen of 3 mol / s. In the methanol synthesis section 3, the gas is heated to 150°C by heat exchange with gas after the methanol synthesis reaction described later in a heat exchanger 631, and further heated to 250°C by heat exchange with recycled gas after the methanation reaction described later in a heat exchanger 632. The gas is then passed to a methanol synthesis reactor 633 to synthesize methanol from the synthesis gas. The methanol synthesis reactor 633 is a heat exchange type reactor, and the reaction proceeds while maintaining the temperature at approximately 250°C while removing the heat generated by the methanol synthesis reaction, and the methanol synthesis reaction proceeds until the equilibrium composition reaches 250°C. The heat generated is recovered as high-pressure steam. The gas after the methanol synthesis reaction is heat-recovered to 150°C in a heat exchanger 634 (the high-temperature side of the heat exchanger 531) and sent to the methanol separation section 4.

[0086] In the methanol separation section 4, the gas after the methanol synthesis reaction is cooled to 40°C in a heat exchanger 641 using cooling water, and then cooled to room temperature or below using a refrigerator and a heat exchanger (not shown), and the produced methanol is separated in a gas-liquid separation drum 642. Of the synthesis gas from which methanol has been separated in the methanol separation section 4, 1% by volume is extracted to the outside of the system as a purge gas in a flow rate adjustment section 643, and the remainder is returned to the inlet of the reverse shift reaction section using a recycle compressor (not shown).

[0087] The raw material gas for the methanation reaction is supplied to the methanation reaction section 5 at a temperature of 25°C and a flow rate of 1 mol / s carbon dioxide and 4 mol / s hydrogen. The raw material gas is heated to 250°C in the heat exchanger 651 by heat exchange with the gas after the methanation reaction described later, and is further mixed with the gas branched from the outlet of the heat exchanger 655 described later, and is introduced into the methanation reactor 652 at 250°C. The methanation reactor 652 is an adiabatic reactor, and the temperature rises as the methanation proceeds, and the methanation reaction proceeds up to the equilibrium composition of 600°C. The heat exchanger 653 is the high-temperature side (heat dissipation side) of the heat exchanger 632, and the gas after the methanation reaction is cooled to 470°C by heat exchange. The next heat exchanger 654 is the high-temperature side (heat dissipation side) of the heat exchanger 651, and is further cooled to 386°C by heat exchange with the raw material gas. In the next heat exchanger 655, the gas after methanation is cooled to 250°C while recovering heat as high-pressure steam. 67.6% of the cooled gas is returned to the inlet side as recycled gas using a recycle compressor (not shown). The remaining 32.4% is sent to the methanation reactor 656. The methanation reactor 656 is a heat exchange type reactor, in which the reaction proceeds while maintaining approximately 250°C while removing heat generated by the reaction, and the methanation reaction proceeds to an equilibrium composition of 250°C, and the heat is recovered as high-pressure steam. The gas after the reaction is cooled to 150°C by heat exchanger 657 to obtain low-pressure steam, and is further cooled with cooling water by heat exchanger 658, and water is separated in gas-liquid separation drum 659 to obtain methane-based gas.

[0088] The temperatures and flow rates at the inlet and outlet of the methanol synthesis reactor 633 are shown in Table 4.

[0089] [Table 4]

[0090] The production rates of methanol and methane were 0.964 mol / s and 0.995 mol / s, respectively. The ratio of the calorific value of the product (methanol and methane) to the calorific value of the raw hydrogen was 79.2%. The reason that it was lower than the ratio (79.9%) in the configuration of Figure 5 is thought to be that the single-pass conversion rate in the methanol synthesis process decreased, the proportion of recycled gas circulated increased, and the amount of purge gas increased. The composition of the generated methane main component gas after dehydration was 97.44% methane, 2.05% hydrogen, and 0.51% carbon dioxide. In addition, as shown in Table 4, the inlet gas volume of the methanol synthesis catalyst was 17.85 mol / s. When the designed catalyst volume of the methanol synthesis catalyst is designed at a gas hourly space velocity (GHSV) of 2000 per hour, 720 liters of methanol synthesis catalyst are required, and the methanol production volume per unit volume of the methanol synthesis catalyst is 4.82 mol [methanol] / (h·L [catalyst]). Compared with the configuration of Figure 5, the amount of methanol produced per unit volume of the methanol synthesis catalyst was reduced by half.

[0091] Comparing the single-pass conversion rate of methanol synthesis from the gas compositions at the inlet and outlet of the methanol synthesis catalyst in Tables 3 and 4, the results are 38% in the configuration of Figure 5 and 21% in the configuration of Figure 6. In the configuration of Figure 5, which includes a reverse shift reaction process, the composition ratio of carbon monoxide and carbon dioxide at the inlet of the methanol synthesis catalyst is approximately 1:1, which is thought to have led to a high single-pass conversion rate. On the other hand, in the configuration of Figure 6, the composition ratio of carbon monoxide and carbon dioxide at the inlet of the methanol synthesis catalyst is approximately 1:10, which leads to a high single-pass conversion rate. 2 :H 2 This is considered to be a low single-pass conversion rate, which is almost the same as the equilibrium conversion rate (about 20%) when a gas with a ratio of 1:3 was subjected to a methanol synthesis reaction.

[0092] Furthermore, by providing the reverse shift reaction step, the single-pass conversion rate in the methanol synthesis step was significantly improved, which resulted in an increase in the amount of methanol produced per unit volume of the methanol synthesis catalyst, a reduction in the amount of unreacted gas recycled, and a reduction in the amount of purge gas. This is believed to have improved the ratio of the calorific value of the products (methanol and methane) to the calorific value of the feed hydrogen.

[0093] [Another embodiment] [1] In the above embodiment, the reaction pressure in the methanol synthesis step and the reaction pressure in the methanation step are the same (5 MPa). However, in the methanol synthesis step and the methanation step according to the present invention, the pressures may be the same or different.

[0094] 1 and 3, a flow rate adjusting unit is not provided, and the entire amount of the synthesis gas from which methanol has been separated in the methanol separation unit 4 is supplied to the methanation reaction unit 5. However, the present invention is not limited to this. A flow rate adjusting unit may be provided, and a part of the synthesis gas from which methanol has been separated in the methanol separation unit 4 may be extracted to the outside of the system as a purge gas, and the remainder may be supplied to the methanation reaction unit 5. Alternatively, the entire amount of the synthesis gas may be supplied to the methanation reaction unit 5.

[0095] [3] In the embodiment shown in Fig. 2, the flow rate adjusting unit 7 is configured to be able to arbitrarily adjust the amount of synthesis gas returned to the reverse shift reaction unit 1 and the amount of synthesis gas supplied to the methanation reaction unit 5, and the synthesis gas after methanol separation in the methanol separation unit 4 passes through the flow rate adjusting unit 7, and most of the synthesis gas is returned to the inlet of the reverse shift reaction unit 1, and the remainder is mixed with a separately prepared raw material gas (hydrogen and carbon dioxide) and used as a raw material for the methanation reaction step, but this is not limited to this. The flow rate adjusting unit 7 may be configured to arbitrarily adjust the amount of synthesis gas returned to the reverse shift reaction unit 1, the amount of synthesis gas supplied to the methanation reaction unit 5, and the amount of synthesis gas discharged outside the system as a purge gas. In this case, for example, a predetermined amount of the synthesis gas after methanol separation may be returned to the inlet of the reverse shift reaction unit 1, a predetermined amount may be supplied to the methanation reaction unit 5, and a predetermined amount may be discharged outside the system as a purge gas.

[0096] 5, a flow rate adjusting unit 543 is provided, and part of the synthesis gas from which methanol has been separated in the methanol separation unit 4 is extracted to the outside of the system as a purge gas, and the remainder is returned to the inlet of the reverse shift reaction unit 1. However, the present invention is not limited to this. For example, the entire amount of the synthesis gas from which methanol has been separated may be returned to the inlet of the reverse shift reaction unit 1, or a configuration without a flow rate adjusting unit may be adopted in which the entire amount of the synthesis gas is returned to the inlet of the reverse shift reaction unit 1.

[0097] The configurations disclosed in the above embodiments (including other embodiments) can be applied in combination with configurations disclosed in other embodiments, provided that no contradiction arises. Furthermore, the embodiments disclosed in this specification are illustrative, and the embodiments of the present invention are not limited thereto, and can be appropriately modified within the scope that does not deviate from the purpose of the present invention. [Industrial Applicability]

[0098] The present invention can be used, for example, as a method and equipment for producing methane-based gas that is a raw material for city gas and methanol that can be used as a chemical product or liquid fuel. [Explanation of symbols]

[0099] 1 Reverse shift reaction section 2 Water separation section 3. Methanol synthesis section 4. Methanol Separation Section 5. Methanation reaction section 6 Heat supply section 7 Flow rate adjustment section 312,314,512,514 Reverse shift reactor 333,533 Methanol synthesis reactor 351,552 Methanation reactor (insulated type) 356,557 Methanation reactor (heat exchange type)

Claims

1. A process for co-producing methanol and methane from hydrogen and carbon dioxide, comprising the steps of: (a) obtaining a synthesis gas containing hydrogen, carbon monoxide, carbon dioxide and water vapor from a raw material gas containing hydrogen and carbon dioxide by a reverse shift reaction; (b) cooling the synthesis gas to separate water; (c) passing the synthesis gas from which water has been separated through a methanol synthesis catalyst to synthesize methanol; (d) cooling the gas obtained in step (c) to separate methanol; (e) passing a raw material gas containing hydrogen and carbon dioxide through a methanation catalyst to synthesize methane; At least a part of the synthesis gas from which methanol has been separated in the step (d) is used as a raw material gas for the methanation reaction in the step (e); Step (e) is carried out only after step (d); A method for co-producing methanol and methane, comprising using the reaction heat generated in step (e) as a heat source for step (a) via a heat exchanger.

2. 2. The process for co-producing methanol and methane according to claim 1, wherein at least a part of the synthesis gas obtained in step (d) from which methanol has been separated is mixed with the feed gas for the reverse shift reaction in step (a).

3. A facility for co-producing methanol and methane from hydrogen and carbon dioxide, comprising: a reverse shift reaction section for obtaining a synthesis gas containing hydrogen, carbon monoxide, carbon dioxide and water vapor from a raw material gas containing hydrogen and carbon dioxide by a reverse shift reaction; a water separation section that cools the synthesis gas and separates water from it; a methanol synthesis unit that synthesizes methanol by passing the synthesis gas from which water has been separated through a methanol synthesis catalyst; a methanol separation section for cooling the gas sent from the methanol synthesis section and separating methanol; a methanation reaction section that synthesizes methane by passing a raw material gas containing hydrogen and carbon dioxide through a methanation catalyst; a heat supply section that supplies reaction heat generated in the methanation reaction section to the reverse shift reaction section via a heat exchanger; A methanol and methane co-production facility configured to supply at least a portion of the synthesis gas sent out from the methanol separation section as a raw material gas to the methanation reaction section, the methanation reaction section being disposed only downstream of the methanol separation section.

4. 4. The methanol and methane co-production facility according to claim 3, further comprising a flow rate adjusting section for adjusting a flow rate of the synthesis gas supplied from the methanol separation section to the methanation reaction section.

5. At least a part of the synthesis gas sent from the methanol separation section is returned to the reverse shift reaction section as a raw material gas, 5. The methanol and methane co-production facility according to claim 4, wherein the flow rate adjusting section adjusts the flow rate of the synthesis gas supplied from the methanol separation section to the reverse shift reaction section.

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