JP2022136403A - Adsorbent for gas drying, gas drier and carbon dioxide circulation system - Google Patents

Abstract

To provide a technique that suppresses gas from decreasing in carbon dioxide content with respect to an adsorbent for gas drying which adsorbs moisture included in the gas to dry the gas.SOLUTION: A adsorbent for gas drying has zeolite which includes a magnesium ion as a cation.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to an adsorbent for gas drying, a gas dryer, and a carbon dioxide circulation system.

2. Description of the Related Art Gas-drying adsorbents that dry gas by adsorbing moisture contained in the gas have been conventionally known. For example, in Patent Document 1, a gas drying adsorbent for drying methane (CH ₄ ) combustion exhaust gas is provided, and methane is produced using carbon dioxide in the exhaust gas from which water vapor has been removed by the gas drying adsorbent. A methane production system is disclosed.

JP 2019-142806 A

In the methane production apparatus of Patent Document 1, a carbon dioxide recovery vessel filled with zeolite 13X is used to recover carbon dioxide from exhaust gas from which water vapor has been removed. Since zeolite 13X adsorbs water vapor, it is necessary to sufficiently dry the exhaust gas. installed in the front. However, since NaY-type zeolite adsorbs a certain amount of carbon dioxide in the exhaust gas as well as water vapor, drying the exhaust gas reduces the carbon dioxide content of the exhaust gas. As the carbon dioxide content in the exhaust gas decreases, so does the efficiency of methane production in the methane production plant.

The present invention has been made to solve the above-described problems, and provides a technique for suppressing a decrease in the carbon dioxide content of a gas in a gas drying adsorbent for drying a gas containing carbon dioxide. for the purpose.

The present invention has been made to solve at least part of the above problems, and can be implemented as the following modes.

(1) According to one aspect of the present invention, there is provided an adsorbent for drying a gas that dries the gas by adsorbing moisture contained in the gas. This gas drying adsorbent comprises a zeolite containing magnesium ions as cations.

According to this configuration, the gas drying adsorbent includes zeolite containing magnesium ions as cations. A zeolite containing magnesium ions has almost the same moisture storage capacity as a zeolite containing sodium ions as a cation, but has a lower carbon dioxide storage capacity. As a result, adsorption of carbon dioxide is suppressed when the gas containing carbon dioxide is dried, so that a decrease in the carbon dioxide content of the gas to be dried can be suppressed.

(2) In the gas drying adsorbent of the above aspect, the molar ratio of magnesium ions to cations contained in the zeolite may be 0.8 or more. According to this configuration, the molar ratio of magnesium ions to cations contained in the zeolite is 0.8 or more. By setting the proportion of magnesium ions in the cations to 0.8 or more, the carbon dioxide storage performance of the gas drying adsorbent can be further reduced. Therefore, when drying a gas containing carbon dioxide, it is possible to further suppress a decrease in the carbon dioxide content of the gas to be dried.

(3) In the adsorbent for gas drying of the above aspect, the zeolite contains a composite oxide of aluminum and silicon, and the composition ratio of silicon to aluminum in the composite oxide is 2 or more and 5 or less. good too. According to this configuration, the zeolite contains a composite oxide of aluminum and silicon, and the composition ratio of silicon to aluminum in this composite oxide is 2 or more and 5 or less. This increases the ion exchange capacity of the zeolite, so that the zeolite can contain more magnesium ions. Therefore, when the gas containing carbon dioxide is dried, the adsorption of carbon dioxide is further suppressed, so that the decrease in the carbon dioxide content of the gas to be dried can be further suppressed.

(4) In the adsorbent for gas drying of the above aspect, the zeolite may be Y-type zeolite, and the composition ratio of silicon to aluminum in the composite oxide may be 2.75. According to this configuration, since the zeolite is a Y-type zeolite having pores large enough for magnesium ions to pass through, the zeolite tends to contain magnesium ions as cations. This further suppresses the adsorption of carbon dioxide when drying the gas containing carbon dioxide, thereby further suppressing a decrease in the carbon dioxide content of the gas to be dried.

(5) In the adsorbent for gas drying of the above aspect, the zeolite is a Y-type zeolite having a composition of Mg _y Na _(6.4-2y) Al _6.4 Si _17.6 O ₄₈ , and y is greater than 2.23. good too. According to this configuration, the Y-type zeolite in which the composition ratio of silicon to aluminum is 2.75 has pores large enough for magnesium ions to pass through, and magnesium ions are used as cations. Contains more than ions. As a result, compared to zeolite containing sodium ions as cations, it is possible to further reduce the carbon dioxide storage performance without substantially changing the moisture storage performance. Therefore, when drying a gas containing carbon dioxide, it is possible to suppress a decrease in the carbon dioxide content of the gas to be dried.

(6) According to another aspect of the invention, a gas dryer is provided. This gas dryer includes the above-described gas drying adsorbent and a container that houses the gas drying adsorbent. According to this configuration, the gas dryer includes the gas drying adsorbent described above. As a result, the gas dried by this gas dryer contains a relatively large amount of carbon dioxide, so carbon dioxide can be used efficiently in a system that uses carbon dioxide.

(7) According to still another aspect of the present invention, a carbon dioxide circulation system is provided. This carbon dioxide circulation system is the above-mentioned gas dryer, and the moisture in the mixed gas containing carbon dioxide and moisture supplied from the external gas generation unit is adsorbed on the gas drying adsorbent. A gas dryer for drying the mixed gas, a carbon dioxide recovery unit for recovering carbon dioxide from the mixed gas dried in the gas dryer, and carbon dioxide recovered in the carbon dioxide recovery unit a hydrocarbon generator that generates a hydrocarbon compound and supplies it to the external gas generator. According to this configuration, in the carbon dioxide circulation system, the mixed gas supplied from the gas generator is dried in the gas dryer. At this time, the gas drying adsorbent provided in the gas dryer adsorbs moisture but does not adsorb much carbon dioxide. of carbon dioxide will be included. Carbon dioxide recovered from the mixed gas sent to the carbon dioxide recovery section serves as a raw material for hydrocarbon compounds to be produced in the hydrocarbon production section. The produced hydrocarbon compound is supplied to an external gas generating section. In the gas generating section, for example, thermal energy is extracted by combustion of hydrocarbon compounds, and a mixed gas containing carbon dioxide and moisture is generated. The generated mixed gas is dried again in the gas dryer, and then carbon dioxide is recovered as a raw material for hydrocarbon compounds in the carbon dioxide recovery section. In this manner, the carbon dioxide circulation system having the above-described configuration can take out energy such as combustion heat while circulating carbon with the gas generation section. In this carbon dioxide circulation system, in the gas dryer, a regeneration process is performed in which moisture adsorbed by the gas drying adsorbent is desorbed from the gas drying adsorbent by heating or the like and discharged out of the system. Compared with, for example, zeolite containing sodium ions as cations, the gas drying adsorbent described above does not easily adsorb carbon dioxide, so less carbon dioxide is discharged out of the system together with moisture in the regeneration process. Thereby, in the carbon circulation between the gas generating part and the carbon dioxide circulation system, the carbon circulation rate in the entire system can be improved.

The present invention can be implemented in various aspects, for example, a method for controlling a gas dryer and a carbon dioxide circulation system, a computer for executing moisture adsorption and recovery in a gas dryer and a carbon dioxide circulation system. It can be implemented in the form of a program, a server device for distributing the computer program, a non-temporary storage medium storing the computer program, or the like.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram which shows schematic structure of the carbon-dioxide circulation system of 1st Embodiment. FIG. 2 is a conceptual diagram illustrating the distribution of adsorbed H ₂ O within a gas dryer. It is a figure explaining the _CO2 loss rate in a gas dryer. FIG. 4 is a diagram showing the relationship between the percentage of unused adsorbent and the amount of CO ₂ loss.

<First embodiment>
FIG. 1 is an explanatory diagram showing a schematic configuration of a carbon dioxide circulation system 1 of the first embodiment. The carbon dioxide circulation system 1 includes a gas dryer 10, a carbon dioxide separator 20, a mixed gas supply channel 30, a hydrogen supply source 41, a hydrogen supply channel 42, a reactor 50, and a source gas channel. 60 , reaction gas flow paths 70 , heat medium flow paths 80 , and control section 90 . The carbon dioxide circulation system 1 is used in conjunction with a mixed gas supply source 5 that supplies a mixed gas containing carbon dioxide (CO ₂ ). The mixed gas supply source 5 is, for example, a combustion furnace in a factory, and the mixed gas contains oxygen (O ₂ ), nitrogen (N ₂ ), moisture (H ₂ O), etc. in addition to CO ₂ . there is Here, the moisture contained in the mixed gas includes gaseous moisture (water vapor) and liquid moisture (for example, liquid droplets). The carbon dioxide circulation system 1 uses CO ₂ contained in the mixed gas supplied from the mixed gas supply source 5 to generate methane (CH ₄ ) used for combustion by the mixed gas supply source 5, thereby circulating carbon. It is a system that allows _In this embodiment, the carbon dioxide circulation system ₁ is assumed to generate CH4, but it is also possible to generate hydrocarbon compounds other than CH4. The carbon dioxide circulation system 1 includes, for example, hydrocarbon compounds composed of carbon and hydrogen such as ethane (C ₂ H ₆ ) and propane (C ₃ H ₈ ), and mainly carbon compounds such as methanol (CH ₃ OH). and hydrogen. The mixed gas supply source 5 corresponds to the "gas generator" in the claims.

A gas dryer 10 is a device for separating H ₂ O from a mixed gas, and includes a storage container 12 in which an adsorbent 11 for gas drying is stored. The gas drying adsorbent 11 is a material having H ₂ O storage performance, and in this embodiment, Y-type zeolite containing magnesium ions as cations is used. The gas-drying adsorbent 11 desorbs and regenerates the adsorbed H ₂ O by utilizing the heat of a heat medium flowing through a heat medium flow path 80 to be described later, the heat of a heater (not shown), or the like. is possible. The H ₂ O desorbed from the gas drying adsorbent 11 is discharged out of the system from the discharge passage 13 via the discharge valve 14 by the purge gas supplied by the purge gas supply unit (not shown). Features of the gas drying adsorbent 11 will be described later.

The carbon dioxide separation section 20 includes a first CO ₂ separator 21 and a second CO ₂ separator 22 . The carbon dioxide separator 20 is a device for separating and recovering CO ₂ from the mixed gas. The carbon dioxide separation section 20 corresponds to the "carbon dioxide recovery section" in the claims.

The first CO ₂ separator 21 accommodates therein a CO ₂ adsorbent 21a having CO ₂ storage performance, such as zeolite, activated carbon, or silica gel. Inside the first CO ₂ separator 21 , a hydrogen injection part 21 b is provided for injecting hydrogen supplied from the hydrogen supply channel 42 into the first CO ₂ separator 21 . The first CO ₂ separator 21 is connected to the mixed gas supply channel 30, the source gas channel 60, and the first discharge channel 21c. The CO ₂ contained in the mixed gas supplied from the mixed gas supply channel 30 is occluded by the CO ₂ adsorbent 21a, and the remaining components in the mixed gas are discharged from the first discharge channel 21c via the first discharge valve 21d. and released outside the system. The CO ₂ desorbed from the CO ₂ adsorbent 21a is purged by H ₂ injected from the hydrogen injection section 21b and sent to the source gas flow path 60 together with H ₂ .

The second CO ₂ separator 22 has the same shape and capacity as the first CO ₂ separator 21, and accommodates a CO ₂ adsorbent 22a therein. The CO ₂ adsorbent 22a, like the CO ₂ adsorbent 21a, is a material capable of absorbing CO 2 and has the same degree of occluding performance as the CO ₂ adsorbent 21a. Inside the second CO ₂ separator 22 , a hydrogen injection part 22 b is provided for injecting hydrogen supplied from the hydrogen supply channel 42 into the second CO ₂ separator 22 . The second CO ₂ separator 22 is connected to the mixed gas supply channel 30, the source gas channel 60, and the second discharge channel 22c. The CO ₂ contained in the mixed gas supplied from the mixed gas supply channel 30 is occluded by the CO ₂ adsorbent 22a, and the remaining components in the mixed gas are discharged from the second discharge channel 22c via the second discharge valve 22d. and released outside the system. The CO ₂ desorbed from the CO ₂ adsorbent 22a is purged by H ₂ injected from the hydrogen injection section 22b and sent to the source gas flow path 60 together with H ₂ .

The mixed gas supply channel 30 is a gas channel for supplying the mixed gas supplied from the mixed gas supply source 5 to the carbon dioxide separator 20 via the gas dryer 10, and includes a plurality of gas pipes. is composed of The mixed gas supply passage 30 is provided with a first mixed gas supply valve 31 and a second mixed gas supply valve 32 . The mixed gas supplied from the mixed gas supply source 5 is dried in the gas dryer 10 and then supplied to the first CO ₂ separator 21 via the first mixed gas supply valve 31 . Also, the mixed gas supplied from the mixed gas supply source 5 is supplied to the second CO ₂ separator 22 via the second mixed gas supply valve 32 . The opening and closing of the first mixed gas supply valve 31 and the second mixed gas supply valve 32 are controlled by the controller 90 . The mixed gas supply channel 30 includes a temperature sensor and a flow rate sensor (not shown) for measuring the temperature, flow rate, and CO ₂ concentration of the mixed gas supplied to the first CO ₂ separator 21 and the second CO ₂ separator 22. , and a CO ₂ concentration sensor.

The hydrogen supply source 41 is, for example, a water electrolysis device, a hydrogen tank, etc. Here, the water electrolysis device will be described. A hydrogen supply source 41 produces H ₂ that is supplied to the first CO ₂ separator 21 and the second CO ₂ separator 22 .

The hydrogen supply channel 42 is a gas channel for supplying H ₂ generated in the hydrogen supply source 41 to the first CO ₂ separator 21, the second CO ₂ separator 22, and the source gas channel 60. , including a plurality of gas pipes. A first hydrogen supply valve 43 , a second hydrogen supply valve 44 , and a third hydrogen supply valve 45 are provided in the hydrogen supply channel 42 . H ₂ produced by the hydrogen supply source 41 is injected into the first CO ₂ separator 21 when the first hydrogen supply valve 43 is opened. Further, H ₂ produced by the hydrogen supply source 41 is injected into the second CO ₂ separator 22 when the second hydrogen supply valve 44 is opened. Further, when the third hydrogen supply valve 45 is opened, H ₂ is added from the hydrogen adding section 46 to the raw material gas flowing through the raw material gas flow path 60 . Opening and closing of the first hydrogen supply valve 43 , the second hydrogen supply valve 44 , and the third hydrogen supply valve 45 are controlled by the controller 90 . The hydrogen supply channel 42 includes the first CO ₂ separator 21, the second CO ₂ separator 22, and a temperature sensor (not shown) for measuring the temperature and flow rate of the H ₂ gas supplied to the source gas channel 60. A flow sensor is provided.

The reactor 50 is a vessel for generating CH ₄ by a methanation reaction inside, and accommodates a catalyst 51 . The catalyst 51 contains a metal having methanation performance, such as Ru or Ni. A source gas channel 60 and a reaction gas channel 70 are connected to the reactor 50 . The reactor 50 uses a raw material gas containing CO ₂ and H ₂ supplied through the raw material gas flow path 60 to produce CH ₄ through a methanation reaction. The reactor 50 corresponds to the "hydrocarbon production section" in the claims.

The raw material gas channel 60 is a gas channel for supplying the raw material gas containing H ₂ and CO ₂ sent out from the first CO ₂ separator 21 and the second CO ₂ separator 22 to the reactor 50, It is configured including a plurality of gas pipes. A first source gas valve 61 and a second source gas valve 62 are provided in the source gas flow path 60 . The opening and closing of the first raw material gas valve 61 and the second raw material gas valve 62 are respectively controlled by the controller 90 . Specifically, when the source gas inside the first CO ₂ separator 21 is supplied to the reactor 50, the first source gas valve 61 is opened and the second source gas valve 62 is closed. controlled by When the raw material gas inside the second CO ₂ separator 22 is supplied to the reactor 50, control is performed so that the first raw material gas valve 61 is closed and the second raw material gas valve 62 is open. The raw material gas flow path 60 is provided with a temperature sensor, a flow rate sensor, and a CO ₂ concentration sensor (not shown) for measuring the temperature, flow rate, and CO ₂ concentration of the flowing raw material gas.

The reaction gas flow path 70 is a gas flow path for supplying the CH ₄ produced in the reactor 50 to the mixed gas supply source 5, and includes a plurality of gas pipes. A heat exchange section 71 is provided in the reaction gas flow path 70 . The reaction gas mixture containing CH ₄ discharged from the reactor 50 is first supplied to the heat exchange section 71 . In the heat exchange section 71, H ₂ O is separated from the reaction gas mixture. The H ₂ O separated from the reaction mixture gas is discharged outside the system via the H ₂ O discharge channel 72 . The reactant gas containing CH ₄ from which H ₂ O has been separated is supplied to the mixed gas supply source 5 via the reactant gas flow path 70 .

The heat medium flow path 80 is a flow path through which a fluid heat medium (thermal fluid) such as oil flows, and supplies heat generated in the reactor 50 by the methanation reaction to the carbon dioxide separation section 20 . A first channel switching valve 81 and a second channel switching valve 82 are provided in the heat medium channel 80 . The heat medium flow path 80 includes three flow paths (first heat medium flow path 83, second heat medium flow path 84, third heat medium flow path 85) separated by these two valves. The first heat medium flow path 83 supplies the heat medium to the first CO ₂ separator 21 . A second heat medium flow path 84 supplies the heat medium to the second CO ₂ separator 22 . A pump 86 and a temperature adjuster 87 are provided in the third heat medium flow path 85 . The heat medium in the third heat medium flow path 85 flows through the first heat medium flow path 83 or the second heat medium flow path 84 by driving the pump 86, and then returns to the third heat medium flow path 85 again. circulated. The temperature adjustment unit 87 is a device that adjusts the temperature of the heat medium, and when the temperature of the heat medium heated in the reactor 50 or the heat exchange unit 71 is higher than the set temperature, the heat medium at room temperature is added. to adjust the temperature. Further, when the temperature of the heat medium is lower than the set temperature, it is heated to the set temperature by a heater or the like in addition to the flow rate adjustment. Pump 86 and temperature adjustment section 87 are controlled by control section 90 .

The first flow path switching valve 81 is a three-way valve for switching the destination (first heat medium flow path 83 or second heat medium flow path 84) of the heat medium sent out from the third heat medium flow path 85 by the pump 86. is. The second flow path switching valve 82 is interlocked with the switching of the first flow path switching valve 81, and is the source of the heat medium returning to the third heat medium flow path 85 (the first heat medium flow path 83 or the second heat medium flow path). It is a three-way valve for switching the medium flow path 84). Switching between the first flow path switching valve 81 and the second flow path switching valve 82 is controlled by the control unit 90 respectively.

The first heat medium flow path 83 includes a flow path passing through the interior of the first CO ₂ separator 21 and is configured to supply heat of the heat medium to the CO ₂ adsorbent 21a. The first CO ₂ separator 21 is composed of a double pipe, and a heat medium flow path is formed between the outer pipe and the inner pipe.

The second heat medium flow path 84 includes a flow path passing through the interior of the second CO ₂ separator 22, and is configured to supply heat of the heat medium to the CO2 adsorbent 22a. The second CO ₂ separator 22 is composed of a double pipe, and a heat medium flow path is formed between the outer pipe and the inner pipe.

The third heat medium flow path 85 includes a flow path passing through the interior of the reactor 50 and is configured to transfer heat generated by the methanation reaction inside the reactor 50 to the heat medium. Here, the reactor 50 is composed of a double tube, a catalyst 51 is arranged in the inner tube, and a heat medium flow path is formed between the outer tube and the inner tube.

The control unit 90 is a computer including a ROM, a RAM, and a CPU, and controls the carbon dioxide circulation system 1 as a whole. The control unit 90 is electrically connected to the valves and sensors (temperature sensor, flow rate sensor, concentration sensor, etc.) provided in each of the flow paths, as well as the pump 86 and the temperature adjustment unit 87. Various valves, a pump 86, a temperature control unit 87, and the like are controlled based on the values.

In the carbon dioxide circulation system 1 , the mixed gas supplied from the mixed gas supply source 5 is dried by removing H ₂ O by adsorption in the gas dryer 10 . The dried mixed gas is sent to the carbon dioxide separation section 20 . In the carbon dioxide separation section 20 , the dried mixed gas is supplied to either the first CO ₂ separator 21 or the second CO ₂ separator 22 . The CO ₂ separator supplied with the dried mixed gas adsorbs and recovers the CO ₂ in the mixed gas. At this time, H ₂ is supplied from the hydrogen supply source 41 to the other of the first CO ₂ separator 21 or the second CO ₂ separator 22, so that the CO ₂ adsorbed on the CO ₂ adsorbent becomes CO ₂ adsorbed. A source gas desorbed from the material and containing CO ₂ and H ₂ is sent to the reactor 50 . Thus, in the carbon dioxide separation unit 20, when either the first CO ₂ separator 21 or the second CO ₂ separator 22 is adsorbing CO ₂ from the mixed gas, the first CO ₂ separator 21 or the second CO 2 separator Either one of the _two separators 22 supplies the source gas to the reactor 50 . Thereby, the raw material gas containing CO ₂ and H ₂ can be continuously supplied to the reactor 50 .

In the reactor 50 , CH ₄ is produced using the raw material gas supplied from the carbon dioxide separation section 20 . The produced CH ₄ is discharged from the reactor 50 as a reaction mixture gas together with the by-product H ₂ O. H ₂ O contained in the reaction mixture gas is removed from the reaction mixture gas in the heat exchange section 71 . The reaction gas from which H ₂ O has been removed is supplied to the mixed gas supply source 5 via the reaction gas channel 70 . In this embodiment, the mixed gas supply source 5 burns CH ₄ to generate thermal energy, and the generated thermal energy is used to generate power and drive various devices. A mixed gas containing CO ₂ generated by combustion of CH ₄ in this mixed gas supply source 5 is supplied to a gas dryer 10 . As a result, by using the mixed gas supply source 5 and the carbon dioxide circulation system 1 together, thermal energy can be obtained in a circulated state without discharging carbon to the outside of the system.

In the carbon dioxide circulation system 1, the gas drying adsorbent 11 that adsorbs H ₂ O is heated in the gas dryer 10 to desorb the adsorbed H ₂ O and the gas drying adsorbent 11 is played. When the gas drying adsorbent 11 is regenerated, gas components other than H ₂ O adsorbed on the gas drying adsorbent 11 are also desorbed from the gas drying adsorbent 11 . The gas component containing H ₂ O desorbed from the gas drying adsorbent 11 is discharged out of the system by the purge gas. Note that the method for regenerating the gas drying adsorbent 11 that has adsorbed H ₂ O is not limited to the method described above, and may be performed using only a purge gas.

Next, the gas drying adsorbent 11 will be described. The gas drying adsorbent 11 is zeolite containing magnesium ions as cations. Specifically, the gas drying adsorbent 11 contains Y-type zeolite having a composition of Mg _2.8 Na _0.8 Al _6.4 Si _17.6 O ₄₈ . That is, the gas drying adsorbent 11 of the present embodiment contains a composite oxide of aluminum and silicon, and the composition ratio of silicon to aluminum in this composite oxide is 2.75. Furthermore, the molar ratio of magnesium ions to cations contained in Y-type zeolite is 0.78.

The proportion of magnesium ions in the cations contained in the gas drying adsorbent 11 is measured by inductively coupled plasma mass spectrometry (ICP-MS) or inductively coupled plasma atomic emission spectrometry (ICP-AES). Specifically, a solution is prepared by dissolving a certain amount of the gas drying adsorbent 11, and the amount of cations and the amount of magnesium contained in the certain amount of the gas drying adsorbent 11 are measured. Next, the ratio of the amount of magnesium to the measured amount of cations is calculated, and the molar ratio of magnesium ions to cations contained in Y-type zeolite is calculated. Moreover, the proportion of magnesium ions in the cations contained in the gas drying adsorbent 11 may be measured by energy dispersive X-ray spectroscopy (EDX). Specifically, by polishing the gas drying adsorbent 11, a sample with an exposed cross section is formed. A cross section of this sample is observed by EDX, and the total number of observed cation atoms and the total number of magnesium atoms are counted within a predetermined range. The ratio of the number of magnesium atoms to the total number of cation atoms counted at this time is taken as the molar ratio of magnesium ions to cations contained in the Y-type zeolite. Alternatively, atomic absorption spectrometry (AAS) may be used to measure the proportion of magnesium ions in the cations contained in the gas drying adsorbent 11 .

The composition ratio of silicon to aluminum in the composite oxide contained in the Y-type zeolite is measured using ICP-AES or AAS. Also, the type of zeolite contained in the gas drying adsorbent 11 is identified based on the measurement results by the X-ray diffraction method (XRD).

Next, a method for manufacturing the gas drying adsorbent 11 will be described. First, 10 g of zeolite pellets (NaY type zeolite, Tosoh HSZ-320NAD1C, Si/Al ratio = 2.75, composition Na: 6.4, Al: 6.4, Si: 17.6, O: 48) is immersed in 50 mL of a 2 mol/L magnesium nitrate solution and allowed to stand overnight at a temperature of 60° C. with occasional stirring. The sample left standing for one day and night is cooled to room temperature, filtered, and then washed three times with 500 mL of deionized water. The washed sample is again immersed in 50 mL of a new 2 mol/L magnesium nitrate solution, left at rest under a temperature condition of 60° C. for 1 day and night, and washed in the same manner. The zeolite of the adsorbent 11 for gas drying was obtained by performing a series of operations of immersion, standing, and washing once more and then drying. By this production method, the cations of the zeolite are exchanged from sodium ions to magnesium ions, so that the cation exchange rate based on the number of ion exchange sites in the zeolite can be 80% or more.

Next, the characteristics of the gas drying adsorbent 11 of this embodiment will be described using the performance of the gas dryer 10 provided with the gas drying adsorbent 11. FIG. Here, the performance of the gas dryer 10 of the present embodiment will be described while comparing with the performance of the gas dryer provided with the gas drying adsorbent of the comparative example. Here, the adsorbent for gas drying of the comparative example is Y-type zeolite containing sodium ions as cations, and is zeolite prepared before being immersed in the magnesium nitrate solution in the production method described above. Hereinafter, the gas drying adsorbent 11 of the present embodiment will be referred to as "MgY zeolite", and the gas drying adsorbent of the comparative example will be referred to as "NaY zeolite".

Prior to performance evaluation of the gas dryer, adsorption isotherms for CO ₂ and H ₂ O were created for each of MgY zeolite and NaY zeolite. The CO ₂ adsorption isotherm was measured by vacuum pretreatment of 1 g of the gas drying adsorbent at 150 ° C., followed by a volumetric fully automatic adsorption measurement device (BELSORP-MAX, manufactured by Microtrack Bell). It was prepared by measuring the adsorption amount of ₂ . Further, the adsorption isotherm of H ₂ O was obtained by subjecting 0.1 g of the adsorbent for gas drying to vacuum pretreatment at 150° C., and then using a volumetric fully automatic adsorption measuring device in the same manner as for CO ₂ . It was prepared by measuring the adsorption amount of H ₂ O at °C.

In the performance evaluation test of the gas dryer, in the experiment of drying the mixed gas containing CO ₂ and H ₂ O, the conditions of the mixed gas and the gas dryer were set as follows.
・Mixed gas flow rate: 6 m ³ /h
Dew point: 25°C (H ₂ O concentration: 3%)
_CO2 concentration: 10%
This results in a weight of H ₂ O entering the gas dryer of 0.145 kg _H2O per hour. Also, the weight of _CO2 flowing into the gas dryer is 1.18 kg _CO2 per hour.
・Gas dryer Internal volume: 0.26 m ³
Filling weight of adsorbent for gas drying: 1.82 kg _ads (bulk density: 0.7 kg / L)

In the gas dryer, the gas drying adsorbent is brought into contact with the mixed gas for 2.5 hours (adsorption step), and then the gas drying adsorbent is regenerated (regeneration step). In this case, in order to adsorb all the H ₂ O flowing into the gas dryer, it is necessary to adsorb 0.08 kg of H ₂ O with the adsorbent for gas drying at 1 kg _ads per hour. Therefore, in one adsorption step, the H ₂ O adsorption amount required for the adsorbent is 0.2 kg _H 2 O /kg _ads .

From the H ₂ O adsorption isotherms of MgY-type zeolite and NaY-type zeolite, the saturated H ₂ O adsorption amounts of MgY-type zeolite and _NaY -type zeolite were both 0.3 kg H 2 O /kg _ads . Therefore, there is no difference in H ₂ O storage performance, ie, mixed gas drying performance, between MgY-type zeolite and NaY-type zeolite. From this, even if MgY type zeolite is used as a substitute for NaY type zeolite, the drying performance of the gas dryer does not change. In the performance evaluation test of the gas dryer described above, both the MgY zeolite and the NaY zeolite have a surplus capacity to adsorb H ₂ O, so the period (2.5 hours) for performing the regeneration process was set to Even longer (eg, 3.5 hours) are possible. However, in order to provide system redundancy, the regeneration timing of the gas drying adsorbent was left at 2.5 hours.

FIG. 2 is a conceptual diagram explaining the distribution of adsorbed H ₂ O within the gas dryer. Under the above conditions, about 30% of the adsorbent packed in the gas dryer is not used for _H2O adsorption. As shown in FIG. 2, when the mixed gas flows from one side of the gas dryer to the other side (the direction indicated by the white arrow in FIG. 2), H ₂ O contained in the mixed gas is It is adsorbed by the gas drying adsorbent filled upstream of the mixed gas in the gas dryer. Therefore, the gas drying adsorbent on the downstream side of the mixed gas in the gas dryer is not used for adsorbing _H2O . Since the mixed gas from which H ₂ O has been removed passes through this unused adsorbent (“H ₂ O unadsorbed portion” in FIG. 2), CO ₂ contained in the mixed gas is adsorbed. That is, in this evaluation test, CO ₂ is adsorbed by 0.61 kg of the gas drying adsorbent in one adsorption step.

FIG. 3 is a diagram explaining the CO ₂ loss rate in the gas dryer. As described above, when the CO ₂ concentration in the mixed gas is 10%, the total amount of CO ₂ flowing into the gas dryer is 2.95 kg in one adsorption step. From the CO ₂ adsorption isotherms of MgY zeolite and NaY zeolite, the “CO ₂ adsorption amount per unit weight” at a CO ₂ partial pressure of 10 kPa is 0.031 kg for MgY zeolite, and 0.031 kg for NaY zeolite. Then, it becomes 0.059 kg. Therefore, the "CO ₂ adsorption amount of the unused adsorbent" is 0.019 kg for MgY zeolite and 0.036 kg for NaY zeolite. The CO ₂ adsorbed by this "unused adsorbent" becomes the lost amount of CO ₂ discharged out of the system in the regeneration process. The ratio of CO ₂ released outside the system in the regeneration process (“CO ₂ loss rate”) to the total amount of CO ₂ flowing into the gas dryer in one adsorption step is MgY zeolite (0.65% ) is smaller than that of NaY zeolite (1.21%), MgY zeolite can reduce the amount of CO ₂ discharged outside the system. That is, the MgY zeolite can suppress the decrease in the carbon dioxide content of the mixed gas as compared with the NaY zeolite.

Further, the gas dryer provided in the carbon dioxide circulation system is repeatedly regenerated by operating the carbon dioxide circulation system for a long period of time. Therefore, in the regeneration process, the CO ₂ discharged outside the system cannot be used to generate hydrocarbon compounds in the carbon dioxide circulation system. As described above, MgY-type zeolite can suppress a decrease in the carbon dioxide content of the mixed gas, so more carbon dioxide is supplied to the subsequent carbon dioxide separation unit than NaY-type zeolite. be able to. Thereby, the carbon circulation rate in the entire carbon dioxide circulation system can be improved.

FIG. 4 is a diagram showing the relationship between the percentage of unused adsorbent and the amount of CO ₂ loss. As described above, the amount of CO ₂ discharged outside the system in the regeneration process of the adsorbent for gas drying, that is, the amount of CO ₂ loss, is determined by the amount of unused adsorbent in the gas dryer (“H ₂ O unused” in FIG. 2). determined by the ratio of "adsorption part"). Therefore, the relationship between the ratio of the unused adsorbent in the gas dryer (ratio to the total weight of the adsorbent for gas drying) and the CO ₂ loss rate was compared between MgY zeolite and NaY zeolite. The results are shown in FIG.

The horizontal axis of FIG. 4 indicates the percentage of unused adsorbent in the gas dryer. Specifically, the ratio of unused adsorbents is the ratio of the total weight of H ₂ O flowing into the gas dryer to the weight of H ₂ O that can be adsorbed by the adsorbents filled in the gas dryer. is represented by The total weight of H ₂ O flowing into the gas dryer is given by α (kg/hour) being the weight of H ₂ O flowing into the gas dryer per unit time and β (hour) being the time of one cycle. It can be expressed as α×β (kg). Further, the weight of H ₂ O that can be adsorbed by the gas drying adsorbent filled in the gas dryer is given by the unit weight, where the weight of the gas drying adsorbent filled in the gas dryer is γ (kg). Assuming that the weight of H ₂ O that can be adsorbed by the gas drying adsorbent is Wsat (kg/kg), it can be expressed as γ×Wsat (kg). α×β for γ×Wsat, that is, (α×β)/(γ×Wsat) is the H ₂ O flowing into the gas dryer with respect to the total weight of the gas drying adsorbent packed in the gas dryer. is the ratio of the weight of the gas drying adsorbent used when all are adsorbed on the gas drying adsorbent, so {1-(α × β) / (γ × Wsat)} is the gas dryer It is the ratio of the adsorbent for gas drying that is not used for adsorbing H ₂ O to the packed adsorbent for gas drying. That is, the larger {1−(α×β)/(γ×Wsat)}, the larger the ratio of the unused adsorbent filled in the gas dryer. It should be noted that α×β/γ< _Wsat is required for a gas dryer in actual use. material will not exist. The vertical axis in FIG. 4 indicates the "CO ₂ loss rate" shown in FIG.

As shown in FIG. 4, when comparing MgY zeolite (solid line L1 in FIG. 4) and NaY zeolite (one-dot chain line L2 in FIG. 4), CO ₂ It became clear that the difference in the loss rate becomes large. Here, if the ratio of the unused adsorbent is less than 0.3, the difference in CO ₂ loss rate between the MgY zeolite and the NaY zeolite becomes small, but the H ₂ O storage performance of the gas dryer decreases. redundancy is reduced, and H ₂ O may leak from the gas dryer due to abrupt fluctuations in the gas flow rate or the like. In addition, when the ratio of the unused adsorbent is greater than 0.6, the CO ₂ loss rate of MgY-type zeolite is less than 1/2 of the CO ₂ loss rate of NaY-type zeolite, so the effect of reducing the CO ₂ loss rate becomes larger. However, since the ratio of the unused adsorbent increases, the utilization rate of the gas drying adsorbent decreases when H ₂ O is adsorbed from the mixed gas. Furthermore, if the ratio of the unused adsorbent is greater _than 0.6, there will be excess adsorbent for gas drying. sensible heat loss, etc.). Therefore, the range of the ratio of the unused adsorbent is desirably 0.3 ≤ {1-(α × β) / (γ × Wsat)} ≤ 0.6 (the range indicated by the double-ended arrow A1 in FIG. 4 ).

According to the gas drying adsorbent 11 of the present embodiment described above, the gas drying adsorbent 11 includes zeolite containing magnesium ions as cations. A zeolite containing magnesium ions has almost the same H ₂ O storage capacity as a zeolite containing sodium ions as cations, but has a lower CO ₂ storage capacity. As a result, adsorption of CO ₂ is suppressed when the mixed gas containing CO ₂ is dried, so that a decrease in the carbon dioxide content of the mixed gas discharged from the gas dryer 10 can be suppressed.

Further, according to the gas drying adsorbent 11 of the present embodiment, the gas drying adsorbent 11 contains Y-type zeolite having a composition of Mg _2.8 Na _0.8 Al _6.4 Si _17.6 O ₄₈ . That is, the composition ratio of silicon to aluminum in the composite oxide of aluminum and silicon is 2.75. As a result, the ion exchange capacity of the zeolite can be increased, and since the zeolite has pores large enough to allow magnesium ions to pass through, the zeolite can contain more magnesium ions. Therefore, compared with zeolite containing sodium ions as cations, the gas drying adsorbent ₁₁ can reduce the CO ₂ storage performance while hardly changing the H ₂ O storage performance. When the mixed gas is dried, it is possible to prevent the carbon dioxide content of the mixed gas from decreasing.

Further, according to the gas drying adsorbent 11 of the present embodiment, the composition ratio of silicon to aluminum in the composite oxide of aluminum and silicon is 2 or more and 5 or less, and aluminum is relatively large. This improves the hydrophilicity of the zeolite, making it easier to adsorb moisture. Therefore, the dryness of the mixed gas discharged from the gas dryer 10 can be improved.

Moreover, according to the carbon dioxide circulation system 1 of the present embodiment, the mixed gas discharged from the mixed gas supply source 5 is dried in the gas dryer 10 . At this time, the gas drying adsorbent 11 provided in the gas dryer 10 adsorbs H ₂ O but does not adsorb much CO ₂ , so the mixed gas sent from the gas dryer 10 to the carbon dioxide separation unit 20 contains , contains a relatively large amount of CO ₂ . CO ₂ recovered from the mixed gas sent to the carbon dioxide separation section 20 serves as a raw material for CH ₄ produced in the reactor 50 . This generated CH ₄ is supplied to the mixed gas supply source 5 . In the mixed gas supply source ₅ , heat energy is taken out by combustion of CH4, and mixed gas containing _CO2 and _H2O is generated. The generated mixed gas is dried in the gas dryer 10 again, and then CO ₂ is recovered as a raw material of CH ₄ in the carbon dioxide separator 20 . Thus, the carbon dioxide circulation system 1 can take out energy such as combustion heat while circulating carbon between the mixed gas supply source 5 and the mixed gas supply source 5 . In the carbon dioxide circulation system 1, when the gas drying adsorbent 11 adsorbs H _{2 O in the gas dryer 10, the H 2 O} is desorbed from the gas drying adsorbent 11 by heating or the like and is discharged outside the system. Carry out the regeneration process. Compared with, for example, zeolite containing sodium ions as cations, the gas drying adsorbent 11 is less likely to adsorb CO ₂ , so less CO ₂ is discharged out of the system together with H ₂ O in the regeneration process. Thereby, in the carbon circulation between the mixed gas supply source 5 and the carbon dioxide circulation system 1, the carbon circulation rate in the entire system can be improved.

<Modification of this embodiment>
The present invention is not limited to the above-described embodiments, and can be implemented in various aspects without departing from the scope of the invention. For example, the following modifications are possible.

[Modification 1]
In the above-described embodiment, the gas drying adsorbent 11 is used in the gas dryer 10 included in the carbon dioxide circulation system 1 . However, the field to which the gas drying adsorbent 11 is applied is not limited to this. For example, since a gas containing CO ₂ and H ₂ O can be separated into CO ₂ and H ₂ O with high accuracy, the separated CO ₂ and H ₂ O can be used for different purposes. can do.

[Modification 2]
In the above-described embodiment, the gas drying adsorbent 11 contains Y-type zeolite having a composition of Mg _2.8 Na _0.8 Al _6.4 Si _17.6 O ₄₈ in which the molar ratio of magnesium ions to cations contained in the zeolite is 0.78. I thought I was there. In this Y-type zeolite, the molar ratio of magnesium ions to cations is 0.78, and the molar ratio of magnesium ions to cations is preferably 0.8 or more. As a result, the CO ₂ storage performance of the gas drying adsorbent can be further reduced. Therefore, when drying the gas containing carbon dioxide, it is possible to further suppress the decrease in the carbon dioxide content of the gas. In the production method described above, a zeolite having a molar ratio of magnesium ions to cations of 0.8 or more can be obtained by further repeating a series of operations of immersion, standing, and washing.

[Modification 3]
In the above-described embodiment, the zeolite contained in the gas drying adsorbent 11 is Y-type zeolite having a composition ratio of silicon to aluminum of 2.75 in the composite oxide. However, the composition ratio of silicon to aluminum is not limited to this. 2 or more and 5 or less may be sufficient. Since the ion exchange capacity of the zeolite can be increased by setting the composition ratio of silicon to aluminum to 2 or more and 5 or less, the zeolite can contain more magnesium ions.

[Modification 4]
In the above-described embodiment, the carbon dioxide circulation system 1 includes the gas dryer 10, the carbon dioxide separator 20, the hydrogen supply source 41, the reactor 50, and the like. However, the configuration of the carbon dioxide circulation system 1 is not limited to this. For example, the carbon dioxide separation unit 20 does not have to have two CO ₂ separators, and even if there is only one, the CO ₂ adsorption process and the CO ₂ desorption process can be switched so that A source gas containing CO ₂ and H ₂ can be supplied.

The present aspect has been described above based on the embodiments and modifications, but the above-described embodiments are intended to facilitate understanding of the present aspect, and do not limit the present aspect. This aspect may be modified and modified without departing from its spirit and scope of the claims, and this aspect includes equivalents thereof. Also, if the technical features are not described as essential in this specification, they can be deleted as appropriate.

DESCRIPTION OF SYMBOLS 1... Carbon dioxide circulation system 5... Mixed gas supply source 10... Gas dryer 11... Adsorbent for gas drying 12... Container 20... Carbon dioxide separator 41... Hydrogen supply source 50... Reactor

Claims (7)

A gas drying adsorbent that dries the gas by adsorbing moisture contained in the gas,
comprising a zeolite containing magnesium ions as cations,
Adsorbent for gas drying. The adsorbent for gas drying according to claim 1,
The molar ratio of magnesium ions to cations contained in the zeolite is 0.8 or more.
Adsorbent for gas drying. The gas drying adsorbent according to claim 1 or 2,
The zeolite contains a composite oxide of aluminum and silicon,
The composition ratio of silicon to aluminum in the composite oxide is 2 or more and 5 or less.
Adsorbent for gas drying. The adsorbent for gas drying according to claim 3,
The zeolite is a Y-type zeolite,
The composition ratio of silicon to aluminum in the composite oxide is 2.75.
Adsorbent for gas drying. The adsorbent for gas drying according to claim 1,
The zeolite is a Y-type zeolite having a composition of Mg _y Na _(6.4-2y) Al _6.4 Si _17.6 O ₄₈ ,
y is 2.23 or greater;
Adsorbent for gas drying. A gas dryer,
The gas drying adsorbent according to any one of claims 1 to 5,
A storage container that stores the gas drying adsorbent,
gas dryer. A carbon dioxide circulation system,
7. The gas dryer according to claim 6, wherein moisture in a mixed gas containing carbon dioxide and moisture supplied from an external gas generating unit is adsorbed by the gas drying adsorbent, so that the mixture is a gas dryer for drying gas;
a carbon dioxide recovery unit for recovering carbon dioxide from the mixed gas dried in the gas dryer;
a hydrocarbon generation unit that generates a hydrocarbon compound using the carbon dioxide recovered in the carbon dioxide recovery unit and supplies the hydrocarbon compound to the external gas generation unit;
Carbon dioxide circulation system.

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