JP2023180568A - Synthetic gas manufacturing system and synthetic gas manufacturing method - Google Patents

Abstract

To provide a synthetic gas manufacturing system capable of efficiently manufacturing a synthetic gas having a small content of CO2.SOLUTION: A system for manufacturing a synthetic gas comprising CO and H2 comprises: a reverse shift reaction device for generating gas containing CO by a reverse shift reaction from a raw material gas containing CO2 and H2; a separation device for separating gas generated by the reverse shift reaction device into CO and PSA off gas by a pressure swing adsorption method (PSA method); a merging flow path for merging the PSA off gas separated by the separation device with the raw material gas introduced into the reverse shift reaction device; and a mixing flow path for mixing H2 with the CO separated by the separation device.SELECTED DRAWING: Figure 1

Description

The present invention relates to a synthesis gas production system and a synthesis gas production method.

Currently, industry is actively conducting research and development on reducing carbon dioxide (CO ₂ ) emissions in order to achieve carbon neutrality (CN) as a countermeasure to climate change caused by global warming. .

As a specific method for reducing _CO2 emissions, processes and methods for separating and recovering _CO2 from waste gas emitted from equipment that generates _CO2 , such as steel mills and thermal power plants, are already being considered. ing. Research and development has been progressing on various CO ₂ separation and recovery methods, including adsorption methods, absorption methods, and membrane separation methods.

However, with regard to the use of recovered _CO2 , currently there is a method called EOR (Enhanced Oil Recovery), in which _CO2 is injected into oil fields to increase the recovery rate of crude oil in oil fields where production efficiency has decreased, or for use in agricultural crops. There are only limited uses for this, such as farming methods that supply _CO2 to greenhouses to increase production.

Therefore, by adding hydrogen (H ₂ ) to the recovered CO ₂ or using electrical energy, CO 2 can be used to produce valuables such as fuels and raw materials for chemical products, such as methanol, methane, and _synthetic gas. Research and development is also actively underway regarding the utilization technology. At this time, by using hydrogen gas produced using renewable energy, it is also possible to reduce CO ₂ generated along with the production of H ₂ .

As a method for producing synthesis gas from a mixed gas of CO ₂ and H ₂ , there is a method of mixing H ₂ with carbon monoxide (CO) produced by a reverse shift reaction, as described below.

The reverse shift reaction is a chemical reaction represented by the following formula (1), and CO can be generated from a mixed gas of CO ₂ and H ₂ by the reverse shift reaction.
CO ₂ + H ₂ → CO + H ₂ O…(1)

The reverse shift reaction is an endothermic reaction that proceeds without being affected by pressure. For the reverse shift reaction, for example, a Mn-Pd/Al ₂ O ₃ based catalyst in which an Mn-Pd alloy is supported on Al ₂ O ₃ can be used, and Patent Document 1 describes a catalyst that can be used for the reverse shift reaction. is proposed. By mixing H ₂ with CO generated by the reverse shift reaction, synthesis gas, which is a mixed gas containing CO and H ₂ as main components, can be produced.

A wide variety of chemical products such as methanol, gasoline, light oil, dimethyl ether (DME), etc. can be produced from synthesis gas. Methanol can be produced from synthesis gas by the chemical reaction of formula (2) below.
CO+ _2H2 → _CH3OH ...(2)

DME can be produced by indirect synthesis via methanol, or directly from synthesis gas by direct methods. In the direct method, DME can be produced by the chemical reaction of formula (3) or formula (4) below. When the H ₂ /CO ratio of the synthesis gas is 1, the reaction of formula (3) proceeds with the generation of CO ₂ . When the H ₂ /CO ratio of the synthesis gas is 2, the reaction of formula (4) proceeds, and the generation of CO ₂ is theoretically suppressed. In the actual DME manufacturing process, the H ₂ /CO ratio of the synthesis gas is adjusted to 2 or more.
3CO+ _{3H2 → CH3OCH3} + _CO2 ...(3)
2CO+4H ₂ →CH ₃ OCH ₃ +H ₂ O…(4)

Further, GTL (Gas to liquid) products such as linear hydrocarbons can be produced from synthesis gas by FT (Fischer-Tropsch) synthesis of the following formula (5). Generally, in FT synthesis, the H ₂ /CO ratio of the synthesis gas is adjusted to 2-3. In FT synthesis, olefins, alcohols, etc. are produced as side reaction products.
nCO+(2n+1)H ₂ →C _n H _2n+2 +nH ₂ O…(5)

The chemical reactions represented by the above formulas (2) to (5) are all reactions in which the number of molecules decreases, and are high-pressure processes that advantageously proceed under high pressure in terms of equilibrium theory. Therefore, it is necessary to pressurize the synthesis gas.

Patent No. 5105007

As described above, techniques for producing synthesis gas from a mixed gas of CO ₂ and H ₂ have been developed. In the reverse shift reaction used to produce synthesis gas, it is difficult to completely react CO ₂ due to reaction constraints, and currently the reaction rate (conversion rate) of CO ₂ is about 50%. Therefore, unreacted CO ₂ will remain in the synthesis gas as well.

As described above, the chemical reactions represented by formulas (2) to (5) for producing chemical products from synthesis gas are high-pressure processes, and therefore it is necessary to pressurize the synthesis gas. At this time, if unreacted CO ₂ remains in the synthesis gas, the power required for pressurization increases accordingly, resulting in a problem that energy efficiency decreases.

The present invention has been made in view of such problems, and an object of the present invention is to provide a synthesis gas production system that can efficiently produce synthesis gas with a low content of _CO2 . Another object of the present invention is to provide a method for producing such synthesis gas.

As a result of various studies, the present inventors have found that the above object can be achieved by the following invention.

A synthesis gas production system according to one aspect of the present invention includes:
A system for producing synthesis gas containing CO and _H2 ,
A reverse shift reaction device that generates a gas containing CO by a reverse shift reaction from a raw material gas containing CO ₂ and H ₂ ;
a separation device that separates the gas generated in the reverse shift reaction device into CO and PSA off-gas by a pressure swing adsorption method (PSA method);
a merging flow path for merging the PSA off-gas separated by the separation device with the raw material gas introduced into the reverse shift reaction device;
A mixing flow path for mixing H ₂ with the CO separated by the separation device.

A method for producing synthesis gas according to another aspect of the present invention includes:
A method for producing synthesis gas containing CO and _H2 , the method comprising:
a reverse shift reaction step of generating a gas containing CO from a raw material gas containing CO ₂ and H ₂ by a reverse shift reaction;
a separation step of separating the gas generated in the reverse shift reaction step into CO and PSA off-gas by a pressure swing adsorption method (PSA method);
a merging step in which the PSA off-gas separated in the separation step is merged with the raw material gas to be subjected to the reverse shift reaction step;
and a mixing step of mixing H ₂ with the CO separated in the separation step.

According to the present invention, it is possible to provide a synthesis gas production system that can efficiently produce synthesis gas with a low content of _CO2 . Furthermore, a method for producing such synthesis gas can be provided.

FIG. 1 is a block diagram showing an example of a synthesis gas production system according to a first embodiment of the present invention. FIG. 2 is a block diagram showing an example of a synthesis gas production system according to a second embodiment of the present invention.

[First embodiment]
EMBODIMENT OF THE INVENTION Hereinafter, a synthesis gas production system and a synthesis gas production method according to a first embodiment of the present invention will be described based on the drawings.

The synthesis gas production system according to the present embodiment is a production system for synthesis gas containing carbon monoxide (CO) and hydrogen (H ₂ ), and is produced from a raw material gas containing carbon dioxide (CO ₂ ) and H ₂ . A reverse shift reaction device that generates a gas containing CO by a reverse shift reaction, a separation device that separates the gas generated by the reverse shift reaction device into CO and PSA off-gas by a pressure swing adsorption method (PSA method), and a separation device The PSA off-gas separated by the PSA off-gas is combined with the raw material gas introduced into the reverse shift reaction device, and the CO separated by the separation device is mixed with _H2 .

The synthesis gas production method according to the present embodiment is a method for producing synthesis gas containing CO and H ₂ , in which a gas containing CO is produced by a reverse shift reaction from a raw material gas containing CO ₂ and H ₂ . a shift reaction step; a separation step of separating the gas produced in the reverse shift reaction step into CO and PSA off-gas by a pressure swing adsorption method (PSA method); and a separation step of separating the PSA off-gas separated in the separation step into the The method includes a merging step of merging the raw material gas to be subjected to the reverse shift reaction step, and a mixing step of mixing H ₂ with the CO separated in the separation step.

<Synthesis gas production system configuration>
FIG. 1 is a block diagram showing an example of a synthesis gas production system according to the first embodiment. A synthesis gas production system 1 shown in FIG. 1 is a production system for synthesis gas containing CO and _H2 , and includes a reverse shift reaction device 14, a separation device 20, a merging channel 22, and a mixing channel 24. , is provided.

The reverse shift reaction device 14 is a device that causes a reverse shift reaction represented by the following formula (1) on a raw material gas containing CO ₂ and H ₂ to generate a gas containing CO (CO-containing gas). . In the reverse shift reaction device 14 of this embodiment, the raw material gas is continuously introduced, and the generated CO-containing gas is continuously discharged. Note that a batch type reverse shift reaction apparatus may be used instead of the flow type reverse shift reaction apparatus.
CO ₂ + H ₂ → CO + H ₂ O…(1)

The reverse shift reaction is a reaction (catalytic reaction) whose progress is promoted by a catalyst, and the reverse shift reaction device 14 is provided with a catalyst suitable for the reverse shift reaction in the flow path of the raw material gas. In this embodiment, the catalyst provided in the reverse shift reaction device 14 is a catalyst in which Rh, Ba, K, Pt, Ag, Pd, etc. are supported on alumina (Al ₂ O ₃ ), or a catalyst in which Li and Rh are supported on NaY-type zeolite. Pt supported on titania (TiO 2 ), Pt supported on titania (TiO ₂ ), etc. can be used. The catalyst provided in the reverse shift reaction device 14 is preferably one that suppresses the production of methane as a by-product. In this embodiment, the production of methane in the reverse shift reactor 14 is not considered.

Further, the reverse shift reaction is an endothermic reaction, and the higher the temperature, the easier it is to proceed. Therefore, the reverse shift reaction device 14 is provided with a heating device (not shown) that heats the raw material gas. In the reverse shift reaction device 14, it is preferable to heat the raw material gas to 400 to 800° C. using a heating device.

When the reverse shift reaction proceeds for the entire amount of source gas, the H ₂ /CO ₂ ratio of the source gas is 1 in the stoichiometry based on equation (1). However, in the reverse shift reaction device 14, it is difficult to proceed with the reverse shift reaction for the entire amount of raw material gas, and the CO-containing gas generated in the reverse shift reaction device 14 contains CO and _H2 generated in the reverse shift reaction. In addition to O, unreacted raw material gas is included. Therefore, the H ₂ /CO ₂ ratio of the raw material gas may be adjusted depending on the characteristics of the reverse shift reaction device 14 or the characteristics of the catalyst used, and may be set to a value larger than 1 or a value smaller than 1. The composition and amount of unreacted raw material gas contained in the CO-containing gas generated in the reverse shift reactor 14 vary depending on the reverse shift reactor 14 used, the catalyst, or the H ₂ /CO ₂ ratio of the raw material gas.

The CO-containing gas discharged from the reverse shift reactor 14 has a high temperature of 400 to 800° C., and H ₂ O contained in the CO-containing gas is contained in the CO-containing gas in the form of water vapor, that is, gas.

Although the method of _introducing the raw material gas into the reverse shift _reaction device ₁₄ is not particularly limited, for example, as shown in _FIG. The mixed raw material gas can be supplied to the reverse shift reaction device 14 through the raw material gas flow path 13.

The CO ₂ storage unit 11 includes a container that can store CO ₂ and a flow rate adjustment unit that can adjust the discharge flow rate of CO ₂ , and can discharge the stored CO ₂ gas at an arbitrary flow rate. Although the CO 2 stored in the CO ₂ storage unit 11 may be generated by any method, in this embodiment, in order to reduce CO ₂ emissions, a facility having a _{CO 2 generation} source, such as a steel mill or a thermal power plant, is used. Preference is given to using CO ₂ recovered at . CO ₂ can be recovered by a recovery method such as an adsorption method, an absorption method, or a membrane separation method.

The H ₂ storage unit 12 includes a container that can store H ₂ and a flow rate adjustment unit that can adjust the discharge flow rate of H ₂ , and can discharge the stored H ₂ gas at an arbitrary flow rate. Further, the method for producing the stored H ₂ is not limited; for example, H ₂ produced by a water electrolysis type hydrogen generator can be used. In this embodiment, in order to reduce _CO2 emissions, it is preferable to use electric power derived from renewable energy such as sunlight and wind power in the water electrolysis type hydrogen generator.

In the raw material gas flow path 13, CO ₂ discharged from the CO ₂ storage section 11 and H ₂ discharged from the H ₂ storage section 12 are mixed, and the raw material gas containing CO ₂ and H ₂ flows. The flow rate of the raw material gas and the content of CO ₂ and H ₂ in the raw gas are adjusted by adjusting the flow rate of CO ₂ discharged from the CO ₂ storage section 11 and the flow rate of H ₂ discharged from the H ₂ storage section 12. This can be done by

The CO-containing gas discharged from the reverse shift reactor 14 is cooled to room temperature to 80° C. and then introduced into the separator 20. This is because, due to the characteristics of the separator 20, the CO-containing gas introduced into the separator 20 must be at room temperature to 80°C. By cooling the CO-containing gas, most of the water vapor contained in the CO-containing gas is condensed into water and separated from the CO-containing gas. Therefore, the cooled CO-containing gas contains CO obtained by the reverse shift reaction and unreacted raw material gas.

Although the CO-containing gas discharged from the reverse shift reactor 14 may be naturally cooled in the pipe, it is preferably cooled by a cooling device 16 as shown in FIG. As the cooling device 16, for example, a shell and tube type cooling device or a plate stacked type cooling device can be used. As the cooling method, either an air-cooling method or a water-cooling method can be used, but the water-cooling method is preferable from the viewpoint of efficiency.

The separation device 20 includes a CO-PSA device 20a that separates cooled CO-containing gas into CO and PSA off-gas by the PSA method, and a PSA off-gas that stores the PSA off-gas separated from the CO-containing gas by the CO-PSA device 20a. It has a holder 20b and a CO guide path 20c that guides CO separated from the CO-containing gas by the CO-PSA device 20a to the mixing flow path 24. The separation device 20 can separate the CO-containing gas generated in the reverse shift reaction device 14 into high-purity CO with a low content of CO ₂ and PSA off-gas.

In the separation device 20 according to this embodiment, the CO recovery rate is, for example, about 80%. This is because a part of the CO contained in the CO-containing gas is not adsorbed by the CO adsorption material. The CO recovery rate differs depending on the adsorbent provided in the CO-PSA device 20a. The CO recovery rate refers to the amount of CO induced from the CO-PSA device 20a relative to the amount of CO (CO _in [mol/h] or [Nm ³ /h]) contained in the CO-containing gas introduced into the CO-PSA device 20a. This is the ratio (CO _out /CO _in ) of the amount of CO (CO _out [mol/h] or [Nm ³ /h]) discharged into the passage 20c. The remainder of the CO that is not discharged into the CO guideway 20c is included in the PSA off-gas.

A plurality of CO-PSA devices 20a are provided in parallel to the cooling device 16, and in this embodiment, four CO-PSA devices 20a are provided. The CO-PSA device 20a starts operating after the reverse shift reaction starts in the reverse shift reaction device 14 and the CO-containing gas starts to be discharged from the cooling device 16.

The CO-PSA device 20a is equipped with an adsorbent containing a CO adsorbent. A CO adsorbing substance is a substance that selectively adsorbs CO, and the higher the CO pressure, the more the amount of CO adsorbed increases. H ₂ and CO ₂ are not adsorbed on CO adsorbent materials. In this embodiment, as the CO adsorbing substance, for example, monovalent copper (Cu) supported on alumina (Al ₂ O ₃ ) or a porous polymer material can be used.

A PSA method using the CO-PSA device 20a will be explained. The CO-containing gas cooled by the cooling device 16 is introduced into the CO-PSA device 20a under pressure higher than atmospheric pressure. The pressure of the CO-containing gas introduced into the CO-PSA device 20a at this time can be determined depending on the composition of the adsorbent and the CO-containing gas, and is preferably 0.2 to 1.0 MPa.

Approximately 80% of the CO contained in the CO-containing gas introduced into the CO-PSA device 20a is adsorbed by the CO adsorption material. Gas other than CO contained in the CO-containing gas and CO not adsorbed by the CO-adsorbing material are discharged from the CO-PSA device 20a as PSA off-gas and stored in the PSA off-gas holder 20b. While the pressurized CO-containing gas is being introduced, the CO guide path 20c is closed and no PSA off-gas enters the CO guide path 20c. The introduction time of the pressurized CO-containing gas can be determined depending on the capacity of the CO-PSA device 20a, the type and amount of the adsorbent used, etc.

When CO is sufficiently adsorbed by the CO-adsorbing material, the introduction of CO-containing gas to the CO-PSA device 20a is stopped, and the pressure inside the CO-PSA device 20a is reduced by the vacuum pump provided in the CO-PSA device 20a. to desorb CO from the CO adsorbing material. Thereby, highly purified CO with a low content of CO ₂ can be obtained. The content of the desorbed CO is, for example, 99% by volume or more. The desorbed high-purity CO is discharged into the CO guideway 20c. While the pressure inside the CO-PSA device 20a is being reduced, the PSA off-gas holder 20b is closed, and the desorbed CO does not flow into the PSA off-gas holder 20b. The time period for reducing the pressure inside the CO-PSA device 20a can be determined depending on the capacity of the CO-PSA device 20a, the type and amount of the adsorbent used, and the like.

Thus, according to the PSA method, cooled CO-containing gas can be separated into PSA off-gas and high-purity CO. Furthermore, by performing these operations in conjunction with a plurality of CO-PSA devices 20a and always introducing CO-containing gas into at least one CO-PSA device 20a, the separation device 20 can continuously CO-containing gas can be separated into PSA off-gas and high-purity CO.

The PSA offgas stored in the PSA offgas holder 20b is introduced into the raw material gas flow path 13 through the merging flow path 22, and is introduced into the reverse shift reaction device 14 together with the raw material gas. Since the PSA off-gas includes CO that has not been separated into high-purity CO by the separator 20, the combined flow path 22 allows the CO contained in the PSA off-gas to be supplied to the separator 20 again without being discharged outside the system. Can be done. Therefore, synthesis gas can be efficiently produced.

The confluence channel 22 is a pipe provided to connect the PSA off-gas holder 20b of the separation device 20 and the source gas channel 13. The confluence channel 22 is provided with a valve 22a (flow rate adjustment device) for adjusting the flow rate of the PSA off-gas. The flow rate of the PSA off-gas introduced into the source gas flow path 13 can be adjusted by the valve 22a according to the composition and flow rate of the source gas, the composition of the PSA off-gas, the processing capacity of the reverse shift reaction device 14, and the like. Thereby, the reverse shift reaction can proceed efficiently in the reverse shift reaction device 14. Further, the flow rate of CO 2 discharged from the CO ₂ storage unit 11 and the flow rate of H ₂ discharged from the H ₂ storage unit 12 may be adjusted depending on the composition and flow rate of the PSA off _- gas.

On the other hand, the high-purity CO discharged into the CO guiding path 20c is mixed with H ₂ supplied from the H ₂ storage section 12 in the mixing flow path 24 . Thereby, according to the synthesis gas production system according to the present embodiment, synthesis gas with a low content of CO ₂ can be produced.

The mixing flow path 24 is a pipe that connects the CO guiding path 20c of the separation device 20 and the pipe 12a through which H ₂ discharged from the H ₂ storage section 12 flows. Any composition ( _{H 2 /} CO ratio) can be obtained. The resulting synthesis gas is sent to subsequent processes depending on its use. The H ₂ supplied to the mixing channel 24 may be supplied from an H ₂ source other than the H ₂ storage section 12 .

<Synthesis gas production method>
The synthesis gas production method according to the present embodiment is a method for producing synthesis gas containing CO and H ₂ , in which a gas containing CO is produced by a reverse shift reaction from a raw material gas containing CO ₂ and H ₂ . a shift reaction step; a separation step of separating the gas produced in the reverse shift reaction step into CO and PSA off-gas by a pressure swing adsorption method (PSA method); and a separation step of separating the PSA off-gas separated in the separation step into the The method includes a merging step of merging the raw material gas to be subjected to the reverse shift reaction step, and a mixing step of mixing H ₂ with the CO separated in the separation step.

The synthesis gas production method according to the present embodiment is a synthesis gas production method containing CO and _H2 , and can be implemented, for example, by a synthesis gas production system 10 shown in FIG. 1.

The synthesis gas production method according to the present embodiment includes a reverse shift reaction step, a separation step, a merging step, and a mixing step.

The reverse shift reaction process is a process in which a gas containing CO is generated from a raw material gas containing CO ₂ and H ₂ by a reverse shift reaction, and is performed in the reverse shift reaction device 14 in the synthesis gas production system shown in FIG. .

The separation step is a step of separating the gas generated in the reverse shift reaction step into CO and PSA off-gas by the PSA method, and is performed in the separation device 20 in the synthesis gas production system shown in FIG.

The merging process is a process in which the PSA off-gas separated in the separation process is merged with the raw material gas to be subjected to the reverse shift reaction process. In the synthesis gas production system shown in FIG. This is performed by merging the PSA off-gas from the merging channel 22 with the gas.

The mixing step is a step in which H ₂ is mixed with CO separated in the separation step, and in the synthesis gas production system shown in FIG. This is done by mixing the collected CO with H ₂ supplied from the H ₂ storage 12 in the mixing channel 24 .

[Second embodiment]
Next, a second embodiment of the present invention will be described.

FIG. 2 is a block diagram showing an example of a synthesis gas production system according to the second embodiment. The synthesis gas production system 30 according to the present embodiment is the same as the first embodiment except that it includes a discharge flow path 31 for discharging a part of the PSA off-gas separated by the separation device 20 to the outside of the synthesis gas production system 30. It has the same configuration as the synthesis gas production system according to the above embodiment, is given the same reference numeral, and a description thereof will be omitted.

The discharge channel 31 is provided so as to branch from the confluence channel 22 for introducing the PSA off-gas from the PSA off-gas holder 20b into the raw material gas channel 13. The discharge channel 31 is provided with a valve 31a that can be opened and closed.

In the reverse shift reaction device 14, depending on the catalyst used, methane (CH ₄ ) may be produced as a byproduct of the reverse shift reaction. In the first embodiment, the generation of CH ₄ in the reverse shift reactor 14 was not considered, but in the second embodiment, the generation of CH ₄ in the reverse shift reactor 14 is considered.

When CH ₄ is generated in the reverse shift reactor 14, the PSA off-gas contains CH ₄ . When the PSA off-gas containing CH ₄ continues to be introduced into the reverse shift reactor 14 together with the raw material gas, the CH ₄ content of the PSA off-gas gradually increases. Since CH ₄ is an impurity that does not contribute to the reverse shift reaction, the CH ₄ content of the PSA off-gas must be as low as possible in order to allow the reverse shift reaction to proceed efficiently and to efficiently obtain CO, the target component in this reaction. preferable.

In this embodiment, by discharging the PSA off-gas to the outside of the synthesis gas production system 30 from the discharge flow path 31, it is possible to suppress the CH ₄ content of the PSA off-gas from increasing excessively. When the syngas production system 30 is operated for a predetermined time, when a predetermined amount of syngas is produced in the syngas production system 30, the PSA off gas is discharged from the PSA off gas introduced into the PSA off gas holder 20b or from the PSA off gas holder 20b. This can be performed when a predetermined condition that is assumed to have an adverse effect on the CO production efficiency of the reverse shift reaction device 14 is satisfied, such as when the CH ₄ content of the discharged PSA off-gas exceeds a predetermined value. Furthermore, even if the predetermined conditions are not met, the PSA off-gas may be discharged at any timing. The CH ₄ content of the PSA off-gas can be measured, for example, by a sensor provided in the flow path of the PSA off-gas.

Since the PSA off-gas discharged from the discharge flow path 31 contains H ₂ and CH ₄ and has a calorific value, it may be used as fuel as it is. In addition, since the PSA off-gas discharged from the discharge channel 31 contains CO ₂ , it is introduced into a recovery device (CO ₂ recovery device) for recovering CO ₂ stored in the CO ₂ storage section 11 to collect CO 2 . ₂ and H ₂ and CH ₄ having a calorific value. The CO ₂ recovered by the CO ₂ recovery device can be stored in the CO ₂ storage unit 11 and used as a raw material gas, and the separated H ₂ and CH ₄ can be used as fuel.

[Modified example]
Note that in the first embodiment and the second embodiment described above, the separation device 20 is provided with the PSA off-gas holder 20b for storing the PSA off-gas separated by the CO-PSA device 20a, and the confluence flow path 22 is provided with the valve 22a. However, both or one of the PSA off-gas holder 20b and the valve 22a may not be provided. However, in order to facilitate adjustment of the amount of PSA offgas supplied to the reverse shift reaction device 14, it is preferable to provide a PSA offgas holder 20b and a valve 22a.

[Summary of disclosed technologies]
This specification discloses various techniques as described above, and the main techniques are summarized below.

As described above, the synthesis gas production system according to one aspect of the present invention is a synthesis gas production system containing CO and H ₂ , in which CO 2 is produced from a raw material gas containing CO ₂ and H ₂ by a reverse shift reaction. a reverse shift reaction device that generates a gas containing CO; a separation device that separates the gas generated in the reverse shift reaction device into CO and PSA off-gas by a pressure swing adsorption method (PSA method); The present invention includes a merging flow path that causes the PSA off-gas to be combined with the raw material gas introduced into the reverse shift reaction device, and a mixing flow path that mixes H ₂ with the CO separated by the separation device.

According to this configuration, synthesis gas with a low content of CO ₂ can be efficiently produced.

In the synthesis gas production system configured as described above, the merging channel may include a flow rate adjustment device for adjusting the flow rate of the PSA off-gas to be merged with the raw material gas.

According to this configuration, it is possible to adjust the flow rate of the PSA off-gas to be combined with the raw material gas, and it is possible to efficiently advance the reverse shift reaction in the reverse shift reaction device. Therefore, synthesis gas with low CO ₂ content can be produced more efficiently.

The syngas production system configured as described above may have an exhaust flow path for discharging a part of the PSA off-gas separated by the separation device to the outside of the syngas production system.

According to this configuration, when CH ₄ is generated as a byproduct of the reverse shift reaction in the reverse shift reaction device, the PSA off gas can be appropriately discharged to the outside of the synthesis gas production system through the discharge flow path. It is possible to suppress an excessive increase in the content of CH ₄ contained in the . Thereby, the reverse shift reaction can proceed efficiently in the reverse shift reaction device, and synthesis gas with a low CO ₂ content can be produced more efficiently.

Further, as described above, the method for producing synthesis gas according to another aspect of the present invention is a method for producing synthesis gas containing O and H ₂ , wherein reverse shift from the raw material gas containing CO ₂ and H ₂ is performed. a reverse shift reaction step in which a gas containing CO is produced by reaction; a separation step in which the gas produced in the reverse shift reaction step is separated into CO and PSA off-gas by a pressure swing adsorption method (PSA method); and the separation step. a merging step in which the PSA off-gas separated in the step is combined with the raw material gas to be subjected to the reverse shift reaction step, and a mixing step in which H ₂ is mixed into the CO separated in the separation step. .

According to this configuration, synthesis gas with a low content of CO ₂ can be efficiently produced.

10, 30 Synthesis gas production system 14 Reverse shift reaction device 20 Separation device 22 Merging channel 22a Valve (flow rate adjustment device)
24 Mixing channel 31 Discharge channel

Claims (4)

A system for producing synthesis gas containing CO and _H2 ,
A reverse shift reaction device that generates a gas containing CO by a reverse shift reaction from a raw material gas containing CO ₂ and H ₂ ;
a separation device that separates the gas generated in the reverse shift reaction device into CO and PSA off-gas by a pressure swing adsorption method (PSA method);
a merging flow path for merging the PSA off-gas separated by the separation device with the raw material gas introduced into the reverse shift reaction device;
A synthesis gas production system comprising: a mixing flow path for mixing H ₂ with the CO separated by the separation device. The synthesis gas production system according to claim 1, wherein the merging channel includes a flow rate adjustment device for adjusting the flow rate of the PSA off-gas to be merged with the raw material gas. The synthesis gas production system according to claim 1 or 2, further comprising an exhaust flow path for discharging a part of the PSA off-gas separated by the separation device to the outside of the synthesis gas production system. A method for producing synthesis gas containing CO and _H2 , the method comprising:
a reverse shift reaction step of generating a gas containing CO from a raw material gas containing CO ₂ and H ₂ by a reverse shift reaction;
a separation step of separating the gas generated in the reverse shift reaction step into CO and PSA off-gas by a pressure swing adsorption method (PSA method);
a merging step in which the PSA off-gas separated in the separation step is merged with the raw material gas to be subjected to the reverse shift reaction step;
A method for producing synthesis gas, comprising: a mixing step of mixing H ₂ with the CO separated in the separation step.

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