JP6994331B2 - Heat utilization type gas refining system - Google Patents

Description

The present invention relates to a gas purification system utilizing the heat of methanation reaction.

In recent years, with the expansion of the introduction of renewable energy, the problem of surplus electricity due to the imbalance between supply and demand is becoming apparent. As a solution to this problem, a Power to Gas system has been proposed in which water is electrolyzed using surplus electric power and stored, transported, and used as hydrogen energy. However, hydrogen does not have various infrastructures and has the disadvantage of requiring huge infrastructure investment. On the other hand, the Power to Methane system, which uses existing natural gas and urban gas infrastructure to transport, store, and utilize methane by reacting hydrogen and carbon dioxide, is being put into practical use. I'm out. The methanation reaction formula is shown in the formula (1).
4H ₂ (g) + CO ₂ (g) = CH ₄ (g) + 2H ₂ O (g) + 165kJ ... (1)

Since methanation is an exothermic reaction that proceeds at a high temperature of 200 ° C. or higher, the reaction heat can be used in heating, industrial processes, and the like. Examples of prior inventions relating to effective utilization of heat of reaction are shown below.
In Patent Document 1, for the purpose of immobilizing carbon in carbon dioxide, in the process of thermally decomposing synthetic methane into solid carbon, heat utilization that supplies the heat of metanation reaction to the endothermic methane pyrolysis reaction. The system has been devised.
Further, Patent Document 2 devises to utilize the metanation reaction heat in a steam generator, a carbon dioxide exhaust gas unit, or the like in a thermal power plant using a fuel containing carbon.

As described above, carbon dioxide and hydrogen are required as raw materials for the methanation reaction. On the other hand, the hydrogen obtained in the water splitting process contains a large amount of water derived from the electrolytic solution. If water remains contained in hydrogen, not only does it require extra energy to heat the raw material gas to the metanation reaction temperature, but it also makes it difficult for the reaction to proceed to the methane production side in terms of chemical equilibrium. There is an adverse effect. Therefore, it is preferable to remove the water content in hydrogen to an appropriate dew point prior to the reaction.

Further, as shown in the formula (1), water is produced in addition to methane as a result of the methanation reaction. Further, a part of the raw material gas remains unreacted in the generated gas. On the other hand, when synthetic methane is used for combustion, it is desirable that it does not contain water vapor or carbon dioxide that does not contribute to combustion as much as possible. Even in the case of using it for city gas, if the concentration of water vapor, hydrogen and carbon dioxide is too high, it deviates from the standards such as calorific value and combustion rate, so an upper limit is often set for these gas concentrations. Therefore, it is preferable to purify and dehumidify the metanation-producing gas to a certain extent.

Therefore, in the gas purification system, as described above, either a step of removing water in hydrogen to an appropriate dew point or a step of purifying or dehumidifying the metanation-producing gas to a certain degree prior to the reaction. Alternatively, it is desirable to have both, and the superiority of the gas refining system can be obtained by having either one of the steps.

Japanese Unexamined Patent Publication No. 2015-196619 Special Table 2016-531973

A temperature swing adsorption type gas purification device or the like can be used for these gas purification / dehumidification. However, since purification by the temperature swing adsorption type gas purification device needs to be heated at the time of adsorbent regeneration, it is necessary to input an external heat source, which results in deterioration of overall efficiency and deterioration of business profitability. It will be invited.

It is an object of the present invention to provide a gas refining system that improves the overall efficiency of the system in consideration of the above problems.

Among the heat-utilizing gas refining systems of the present invention, the first embodiment is a methane gas synthesizer that synthesizes methane gas using at least hydrogen and carbon dioxide as raw materials.
A raw material gas introduction path for introducing the raw material gas into the methane gas synthesizer,
A production gas delivery path for transmitting the production gas generated by the methane gas synthesizer, and
A temperature swing adsorption type gas purification device provided through the raw material gas introduction path and / or the generated gas delivery path to remove impurities in the gas.
The temperature swing adsorption type gas purification device is provided with a regenerated gas introduction path for introducing a high temperature regenerated gas and a low temperature regenerated gas that drive the desorption process in the temperature swing adsorption type gas purification device.
It is characterized in that the reaction heat of the methane gas synthesizer is applied to the high temperature regenerated gas sent through the regenerated gas introduction path.

The invention of another form of the heat utilization type gas purification system has the high temperature medium circulation path for receiving the reaction heat of the methane gas synthesizer in the invention of the above form, and the high temperature regenerated gas by heat exchange in the high temperature medium circulation path. It is characterized by heating.

The invention of another form of the heat-utilizing gas refining system is characterized in that, in the invention of the above-mentioned embodiment, there is a medium switching device for switching the supply of the high-temperature regenerated gas and the low-temperature regenerated gas to be introduced into the temperature swing adsorption type gas purification device. And.

In the invention of the other form of the heat utilization type gas refining system, in the invention of the said embodiment, the temperature swing adsorption type gas refining apparatus is provided with a plurality of adsorption towers, and each adsorption tower can be operated at different times of the operation mode. It is characterized by being.

The invention of another form of the heat-utilizing gas purification system is characterized in that, in the invention of the above-mentioned form, adsorption and desorption are possible in succession by a plurality of adsorption towers.

The invention of another form of the heat utilization type gas refining system is characterized in that, in the invention of the said form, it is provided with a heat storage unit that stores heat to be applied to the regenerated gas to be introduced into the temperature swing adsorption type gas refining apparatus. ..

In the invention of another form of the heat utilization type gas refining system, in the invention of the above-mentioned embodiment, the heat storage unit absorbs and releases heat energy even if there is a time lag between the high-temperature heat supply and the high-temperature heat demand. It is characterized by adjusting the excess and deficiency.

In the invention of the other form of the heat utilization type gas purification system, the hydrogen gas purified by the temperature swing adsorption type gas purification device can be stored, and the stored hydrogen gas can be supplied to the methane gas synthesis device. It is characterized by being equipped with a hydrogen storage alloy tank.

The invention of another form of the heat utilization type gas purification system is an alloy medium for thermally driving a hydrogen storage alloy contained in a hydrogen storage alloy tank capable of supplying the stored hydrogen gas to the methane gas synthesizer in the invention of the above form. A medium or a high-temperature regenerated gas that has received the reaction heat of the methane gas synthesizer is used as the medium that has a flow path and is supplied to the alloy medium flow path in order to release hydrogen gas from the hydrogen storage alloy. It is characterized by that.

In the invention of the other form of the heat utilization type gas purification system, in the invention of the above-mentioned embodiment, the medium supplied to the hydrogen storage alloy tank in the alloy medium flow path and discharged after heat exchange is recirculated to the methane gas synthesizer. It is characterized by that.

In the invention of the other form of the heat utilization type gas purification system, in the invention of the above-mentioned embodiment, the control unit that controls the operation of each device by referring to one or more of the generated amount of the raw material gas, the pressure of each part, the temperature or the flow rate. It is characterized by having.

According to the present invention, by effectively utilizing the heat of the metanation reaction in the temperature swing adsorption type gas purification process, there is an effect that the total energy efficiency of the system can be effectively improved.

It is a schematic diagram which shows the heat utilization type gas purification system of one Embodiment of this invention. Similarly, it is a schematic diagram which shows the gas entry / exit path of the temperature swing adsorption type gas purification apparatus included in the system. Similarly, it is a pressure-temperature diagram in the adsorbent of the temperature swing adsorption type gas purification apparatus, and a conceptual diagram showing the temperature swing adsorption process. Similarly, it is a figure which shows the temperature swing adsorption process of the temperature swing adsorption type gas purification apparatus. It is a schematic diagram which shows the heat utilization type gas purification system of another embodiment of this invention.

Hereinafter, the heat-utilizing gas purification system 1 according to the embodiment of the present invention will be described with reference to FIG.
A raw material gas introduction path 13 is connected to a methane gas synthesizer 2 that synthesizes methane gas using hydrogen and carbon dioxide as raw materials, and carbon dioxide is supplied through the gas mixer 3 in the raw material gas introduction path 13. The raw material gas introduction path 11 to be supplied and the raw material gas introduction path 12 to which hydrogen is supplied are merged. A mixed gas in which carbon dioxide and hydrogen are mixed is sent to the raw material gas introduction path 13. The raw material gas introduction path 11 is connected to a carbon dioxide supply source 110 outside the system.
A temperature swing adsorption type gas purification device 4 is provided on the base end side of the raw material gas introduction path 12, and the raw material gas introduction path 10 is connected to the temperature swing adsorption type gas purification device 4.
The base end side of the raw material gas introduction path 10 is connected to the water electrolyzer 100 outside the system.
Although the water electrolyzer 100 and the carbon dioxide supply source 110 have been described as being outside the system, one or both of them may be included in the system.

The temperature swing adsorption type gas purification device 4 has two adsorption towers A and B, each of which can independently perform adsorption and desorption. After providing a plurality of adsorption towers of the temperature swing adsorption type gas purification apparatus 4, each operation mode can be staggered in time. In the temperature swing adsorption type gas purification apparatus 4, an appropriate adsorbent that adsorbs water is used. For example, activated alumina, zeolite, silica gel and the like can be used.

In the temperature swing adsorption type gas purification device 4, the introduction of the high temperature regenerated gas and the introduction of the low temperature regenerated gas to the adsorption towers A and B can be switched by the high temperature regenerated gas introduction path 21 and the low temperature regenerated gas introduction path 22. ing. In this embodiment, the high temperature regenerated gas introduction path 21 and the low temperature regenerated gas introduction path 22 are merged and connected to the temperature swing adsorption type gas purification device 4, and the high temperature regenerated gas and the low temperature regenerated gas for the adsorption towers A and B are connected. Introduce. The base end side of the high temperature regenerated gas introduction path 21 and the low temperature regenerated gas introduction path 22 is connected to the medium switching device 25, and the regenerated gas introduction path 20 is connected to the medium switching device 25. The regenerated gas introduction path 20 is connected to the raw material gas introduction path 12, and the regenerated gas accompanied by the raw material gas introduction path 12 is taken out and sent to the regenerated gas introduction path 20. The method of taking out the regenerated gas from the raw material gas introduction path 12 is not particularly limited, and even if a pipeline for transporting the regenerated gas to the inside or the outside of the raw material gas introduction path 12 is separately provided. good.
The medium switching device 25 may have a specific structure as long as it can selectively switch the regenerated gas conveyed by the regenerated gas introduction path 20 and transfer it to the high temperature regenerated gas introduction path 21 and the low temperature regenerated gas introduction path 22. Not limited to. For example, a three-way valve or the like can be used. Further, in this embodiment, the regenerated gas is transported by switching between the high temperature regenerated gas introduction path 21 and the low temperature regenerated gas introduction path 22 via the regenerated gas introduction path 20, but the regenerated gas is used for the high temperature regenerated gas. And the regenerated gas for low-temperature regenerated gas are separately connected to the temperature swing adsorption type gas purification device 4, and the regenerated gas is introduced into the temperature swing adsorption type gas purification device 4 by an on-off valve or the like provided in each introduction path. May be switched.

In the temperature swing adsorption type gas purification device 4, the regenerated gas discharge path 23 is connected to the side where the introduced high-temperature regenerated gas or the low-temperature regenerated gas is discharged, and the exhaust facility 24 is connected to the tip side of the regenerated gas discharge path 23. Has been done. The regenerated gas after leaving the temperature swing adsorption type gas purification device 4 is generally exhausted to the outside of the system as described above. However, when an expensive process gas is used as the regenerated gas, the regenerated gas is not exhausted, but is boosted by the pump 26 and then introduced into the raw material gas introduction path 10 described later through the regenerated gas return flow path 27. May be good.

The regenerated gas is positioned as a gas for regenerating the temperature swing adsorption type gas purification device as a gaseous low temperature medium. In the present invention, the regenerated gas is not limited to a special one. However, as the regenerated gas, an inert gas such as nitrogen or a process gas such as hydrogen can be preferably used. These gases can avoid adverse effects on the filling in the equipment due to contamination in the equipment system or active gas (eg oxygen in the air). However, when nitrogen, which is an inert gas, is used as the regenerated gas, a small amount of nitrogen gas remains in the system at the end of the regenerating process, and if the gas purification process is started as it is, the gas after purification is used. Nitrogen gas contaminates, which reduces the purity of the purified gas. When this point is emphasized, it is desirable to use a process gas as the regenerated gas.

Further, the temperature swing adsorption type gas purification device 4 is connected to a raw material gas introduction path 10 for introducing hydrogen for purification and a raw material gas introduction path 12 for delivering purified dry hydrogen.
The downstream end of the raw material gas introduction path 12 and the downstream end of the raw material gas introduction path 11 for delivering carbon dioxide are connected to the gas mixer 3. In the gas mixer 3, carbon dioxide and hydrogen can be mixed in a quantitative ratio for methane gas synthesis and sent to the downstream side as a mixed gas. A raw material gas introduction path 13 for sending a mixed gas is connected to the gas mixer 3 on the downstream side, and the raw material gas introduction path 13 is connected to the methane gas synthesizer 2.

The methane gas synthesizer 2 has a generated gas delivery path 30 for sending the produced gas to the outside of the methane gas synthesizer 2. The product gas delivery path 30 is connected to the temperature swing adsorption type gas purification device 5, and the temperature swing adsorption type gas purification device 5 purifies the product gas. The temperature swing adsorption type gas purification device 5 has a refined gas delivery path 31 for delivering the purified gas, and the refined gas delivery path 31 is connected to a methane utilization device 200 outside the system. In the temperature swing adsorption type gas purification apparatus 5, an appropriate adsorbent that adsorbs a part of water and unreacted gas is used.

The temperature swing adsorption type gas purification device 5 has two adsorption towers A and B, each of which can independently perform adsorption and desorption. A plurality of adsorption towers of the temperature swing adsorption type gas purification apparatus 5 can be provided, and the respective operation modes can be staggered in time. In the temperature swing adsorption type gas purification apparatus 5, an appropriate adsorbent that adsorbs a part of water and unreacted gas is used. For example, activated alumina, zeolite, silica gel and the like can be used. The temperature swing adsorption type gas purification device 5 may have the same structure as the temperature swing adsorption type gas purification device 4, or may use a device having a different structure.

The high temperature regenerated gas introduction path 41 and the low temperature regenerated gas introduction path 42 are connected to the temperature swing adsorption type gas purification device 5, and the introduction of the high temperature regenerated gas and the introduction of the low temperature regenerated gas to the adsorption towers A and B are performed. It can be switched. In this embodiment, the high temperature regenerated gas introduction path 41 and the low temperature regenerated gas introduction path 42 merge to introduce the high temperature regenerated gas and the low temperature regenerated gas into the adsorption towers A and B. The base end side of the high temperature regenerated gas introduction path 41 and the low temperature regenerated gas introduction path 42 is connected to the medium switching device 45, and the regenerated gas introduction path 40 is connected to the medium switching device 45. The reclaimed gas introduction path 40 is connected to the refined gas delivery path 31, and the regenerated gas accompanied by the refined gas delivery path 31 is taken out and sent to the reclaimed gas introduction path 40. The method for taking out the regenerated gas from the refined gas delivery path 31 is not particularly limited, and even if a pipeline for transporting the regenerated gas to the inside or the outside of the refined gas delivery path 31 is separately provided. good. A three-way valve or the like can be used for the medium switching device 45. Further, the regenerated gas for the high temperature regenerated gas and the regenerated gas for the low temperature regenerated gas are separately transported, and the introduction of the regenerated gas to the temperature swing adsorption type gas purification device 5 is switched by an on-off valve or the like. May be good.
In the temperature swing adsorption type gas purification device 5, the regenerated gas discharge path 43 is connected to the side where the introduced regenerated gas is discharged, and the exhaust facility 44 is connected to the tip side of the regenerated gas discharge path 43. When an expensive process gas is used as the regenerated gas, the regenerated gas can be introduced into the generated gas delivery path 30 through the regenerated gas return flow path 47 after being boosted by the pump 46 without exhausting the regenerated gas.

The regenerated gas is positioned as a gaseous low-temperature medium, and the same gas as the temperature swing adsorption type gas purification device 4 can be used. However, different types of regenerated gas may be used in the temperature swing adsorption type gas purification device 4 and the temperature swing adsorption type gas purification device 5.

Further, a high temperature medium circulation path 50 for recovering the waste heat generated by the methane gas synthesizer 2 is provided. In the high temperature medium circulation path 50, a heat storage tank 6 is interposed downstream of the position where the waste heat is recovered by the methane gas synthesizer 2, and the high temperature medium that has received the reaction heat in the methane gas synthesizer 2 is temporarily stored. Can be done. The heat storage tank 6 corresponds to the heat storage unit of the present invention. The heat storage unit is not limited to the heat storage tank as long as it can store heat. The heat storage tank 6 can function as a means for eliminating the time lag between the high temperature heat supply from the metanation equipment and the high temperature heat demand of the temperature swing adsorption type gas purification devices 4 and 5. In the present invention, the heat storage tank may not be provided.

A high-temperature medium pump 7 is interposed on the downstream side of the heat storage tank 6, and the high-temperature medium of the heat storage tank 6 can be sent to the high-temperature medium circulation path 50 on the downstream side. On the downstream side of the heat storage tank 6, the high temperature medium circulation path 50 is branched into two high temperature medium circulation paths 50A and 50B, and heat exchangers 52 and 53 are interposed in each of the two high temperature medium circulation paths 50A and 50B. In the heat exchanger 52, heat is transferred to the regenerated gas flowing through the high temperature regenerated gas introduction path 21 to raise the temperature of the regenerated gas, and in the heat exchanger 53, heat is transferred to the regenerated gas flowing through the high temperature regenerated gas introduction path 41. By raising the temperature of the regenerated gas, it is possible to introduce the high temperature regenerated gas into the temperature swing adsorption type gas purification device 4 and the temperature swing adsorption type gas purification device 5. The high temperature medium circulation paths 50A and 50B merge on the downstream side of the heat exchangers 52 and 53 and circulate on the upstream side of the methane gas synthesizer 2 as the high temperature medium circulation path 50.

In this embodiment, a temperature swing adsorption type gas purification device is installed for each of the introduction of the raw material hydrogen and the delivery of the generated gas, and the exhaust heat of the methane gas synthesis facility is used for each gas purification device. As the present invention, a temperature swing adsorption type gas purification device may be installed in either the introduction of the raw material hydrogen or the delivery of the generated gas, and the temperature swing adsorption type gas may be further installed in the introduction of the other raw material gas. A purification device may be installed.

Next, the detailed configuration of the temperature swing adsorption type gas purification device will be described with reference to FIGS. 2 and 3.
It should be noted that the temperature swing adsorption type gas refining device 4 and the temperature swing adsorption type gas refining device 5 have the same configuration. Will be explained with.

The temperature swing adsorption type gas purification device has an adsorption tower A and an adsorption tower B, and as shown in FIG. 2, each has an inlet / outlet path for gas. The adsorption tower A has a gas inlet / outlet passage IO1 and the adsorption tower B has a gas inlet / outlet passage IO2, and two common paths C1 and C2 are connected between them, and the common paths C1 and C2 are connected to each other. Two on-off valves V11 and V12 and on-off valves V21 and V22 are interposed, respectively. A raw material gas introduction path 10 is installed on the gas entry side, and is connected to a common path C1 between the on-off valves V11 and V12. Further, in the common path C2, the exhaust gas path E1 is connected between the on-off valves V21 and V22.

When introducing the raw material gas into the adsorption tower A by the temperature swing adsorption type gas purification device 4, the on-off valves V12 and V21 are closed, and the on-off valve V11 is opened to introduce the raw material gas into the adsorption tower A. When the gas is introduced into the adsorption tower B, the on-off valves V11 and V22 are closed, and the on-off valve V12 is opened to introduce the raw material gas into the adsorption tower B. In the temperature swing adsorption type gas purification device 5, the generated gas is sent from the methane gas synthesizer 2 instead of the raw material gas.
Further, when the regenerated gas introduced into the temperature swing adsorption type gas purification device is discharged from the adsorption tower as exhaust gas, when the regenerated gas is discharged from the adsorption tower A, the on-off valves V11 and V22 are closed, and the on-off valve V21 is opened to exhaust the exhaust gas. Is discharged from the suction tower A and discharged from the suction tower B, the on-off valves V12 and V21 are closed, the on-off valve V22 is opened, and the exhaust gas is discharged from the suction tower B.

Further, the adsorption tower A and the adsorption tower B have gas inlet / outlet passages IO3 and IO4 at positions opposite to the gas inlet / outlet passages IO1 and IO2. Two common paths C3 and C4 are connected between the gas inlet / output paths IO3 and IO4, respectively, and two on-off valves V31 and V32 and on-off valves V41 and V42 are interposed in the common paths C3 and C4, respectively. .. A high-temperature / low-temperature regenerated gas introduction path G1 is arranged on the gas entry side, and a raw material gas introduction path 12 or a refined gas delivery path 31 is connected to the gas delivery side. The high-temperature / low-temperature regenerated gas introduction path G1 corresponds to an introduction path in which the high-temperature regenerated gas introduction path 21 and the low-temperature regenerated gas introduction path 22 merge, or an introduction path in which the high-temperature regenerated gas introduction path 41 and the low-temperature regenerated gas introduction path 42 merge. ..
The high-temperature / low-temperature regenerated gas introduction path G1 is connected to a common path C3 between the on-off valve V31 and the on-off valve V32. The raw material gas introduction path 12 or the refined gas delivery path 31 is connected to a common path C4 between the on-off valve V41 and the on-off valve V42.

When introducing the regenerated gas into the adsorption tower A by the temperature swing adsorption type gas purification device 4, the on-off valves V32 and V41 are closed, and the on-off valve V31 is opened to introduce the regenerated gas into the adsorption tower A. When the gas is introduced into the adsorption tower B, the on-off valves V31 and V42 are closed, and the on-off valve V32 is opened to introduce the regenerated gas into the adsorption tower B.
Further, when the purified raw material gas or the purified gas is sent out from the adsorption tower A, the on-off valves V31 and V42 are closed, the on-off valve V41 is opened, and the refined gas is sent out from the adsorption tower A. When the gas is sent from the adsorption tower B, the on-off valves V32 and V41 are closed, and the on-off valve V42 is opened to discharge the purified gas from the adsorption tower B.
When suction is performed by the suction tower or when desorption is performed, a plurality of on-off valves are opened and closed as described above. Each of the above-mentioned on-off valves constitutes a gas switching device.

In this embodiment, the temperature swing adsorption type gas purification device has been described as having two adsorption towers, but the temperature swing adsorption type gas purification device may have three or more adsorption towers, and each temperature swing adsorption type gas purification device may be provided. It may have different numbers of adsorption towers.

Next, the operation of the entire heat-utilizing gas refining system of the present embodiment will be described.
The carbon dioxide obtained from the carbon dioxide supply source 110 is sent to the gas mixer 3 through the raw material gas introduction path 11, and the hydrogen obtained from the water electrolyzer 100 is sent to the temperature swing adsorption type gas purification device 4 through the raw material gas introduction path 10. Sent.
The hydrogen obtained by the water electrolyzer 100 contains water vapor and is introduced into the temperature swing adsorption type gas purification device 4. In the temperature swing adsorption type gas purification apparatus 4, adsorption is performed by either the adsorption towers A or B. In the adsorption towers A and B, the high temperature regenerated gas or the low temperature regenerated gas is introduced through the high temperature / low temperature regenerated gas introduction path G1 as needed.
The high-temperature regenerated gas or low-temperature regenerated gas used in the temperature swing adsorption type gas refining devices 4 and 5 is discharged from the temperature swing adsorption type gas refining devices 4 and 5 by the regenerated gas discharge passages 23 and 43, and is discharged to the exhaust facilities 24 and 44. Sent. The details of the operation of the temperature swing adsorption type gas purification device 4 will be described later.

As the raw material gas of hydrogen + water vapor, the water vapor is alternately removed by the adsorption towers A and B of the temperature swing adsorption type gas purification device 4 to obtain purified hydrogen gas. The purified dry hydrogen is sent to the raw material gas introduction path 12 and sent to the gas mixer 3.
In the gas mixer 3, carbon dioxide is mixed from a separately provided carbon dioxide supply source 110 so as to be close to the stoichiometric ratio of the methane reaction (hydrogen: carbon dioxide = 4: 1), and the raw material gas introduction path 13 is used. It is introduced into the methane gas synthesizer 2.
In the methane gas synthesizer 2, a mixed gas of hydrogen and carbon dioxide is introduced into a reaction tube filled with a catalyst maintained at a predetermined temperature (150 to 400 ° C.). On the surface of the catalyst, the mixed gas undergoes a methanation reaction and is converted to methane and water vapor. At the end of the reaction tube, most of the raw material gas finishes the reaction, and finally the components of the produced gas are a mixture of methane and steam, as well as a trace amount of unreacted gas (hydrogen, carbon dioxide).
At this time, heat of reaction is applied to the high-temperature medium sent through the high-temperature medium circulation path 50, and the heated high-temperature medium is sent to the downstream side of the high-temperature medium circulation path 50 and temporarily stored in the heat storage tank 6. ..

The synthesized methane gas is sent to the temperature swing adsorption type gas purification device 5 through the generated gas delivery path 30. The methane gas synthesized by the methane gas synthesizer 2 contains water vapor and unreacted gas as impurities.
In the temperature swing adsorption type gas purification apparatus 5, water vapor and a part of the unreacted gas, which are impurities of the sent generated gas, are adsorbed and removed by either the adsorption tower A or B to obtain high-purity purified methane. Be done.

In the adsorption towers A and B, the high-temperature regenerated gas heated by the high-temperature medium circulation path 50B is introduced through the high-temperature regenerated gas introduction path 41, or the low-temperature regenerated gas is introduced through the low-temperature regenerated gas introduction path 42, if necessary. .. The purified methane discharged from the temperature swing adsorption type gas purification device 5 is sent to the methane utilization device 200 outside the system for use through the refined gas delivery path 31. At this time, refined methane can be sent by utilizing the existing natural gas and city gas infrastructure.

Next, the heat flow will be described. In the methane gas synthesizer 2, heat is generated along with the methanation reaction. On the other hand, in order to maintain an appropriate reaction temperature, it is necessary to circulate a high temperature medium to remove heat. Here, as the high-temperature medium, an appropriate high-temperature medium is selected from steam, oil, and the like according to the temperature and pressure. The high-temperature regenerated gas used for heating the temperature swing adsorption type gas purification device may be used as the high-temperature medium.
It is desirable that the high temperature medium that has received the surplus heat from the methane gas synthesizer is temporarily stored in the heat storage tank 6. The heat demand of the temperature swing adsorption type gas refiner has waves as described later, and when hydrogen of the water electrolyzer combined with the variable renewable energy power source is used as the raw material, the output of the methane gas synthesizer also fluctuates. be. Therefore, by providing a heat storage tank having an appropriate capacity, it is possible to supply stable heat regardless of the operating state of both facilities.

Next, the operation of the temperature swing adsorption type gas purification apparatus will be described with reference to the temperature swing adsorption conceptual diagram of FIG.
Here, the process from adsorption to regeneration in the adsorption tower A will be described. In the adsorption tower B, the same operation is performed at different times.
First, by closing the on-off valves V12 and V21 and opening the on-off valve V11, a gas for purification is introduced from the common path C1 to the adsorption tower A through the inlet / output path IO1 (first step; suction step). In the adsorption step, the gas to be treated is passed while keeping the adsorption tower filled with the adsorbent at room temperature (T1) and adsorption pressure (P1). At this time, the impurity component contained in the gas is selectively adsorbed by the adsorbent.

Switch to the depressurization step before the adsorbent breaks through. In this step, the adsorption step is completed and the pressure is reduced from the adsorption pressure P1 to about atmospheric pressure (P2) (second step).

Next, at the regeneration pressure (P2), a high-temperature regeneration gas is introduced to raise the temperature of the adsorbent to the heating regeneration temperature (T2). As a result, the adsorption capacity of the adsorbent is reduced, and the adsorbed impurity component is desorbed (third step; heat regeneration step).
As the high-temperature regenerated gas, the gas after purification at the outlet of the temperature swing adsorption type gas purification device is used, and the heat medium can be heated by using the waste heat of methanation or a separately installed electric heater as a heat source.

Next, at the regeneration pressure (P2), a low temperature regeneration gas at room temperature (T1) is introduced, and the temperature is lowered from T2 to T1 to perform cooling regeneration (fourth step; cooling regeneration step).
After the completion of the cooling regeneration, the pressure is restored from the regeneration pressure (P2) to the adsorption pressure (P1) at room temperature (T1) to enable the implementation in the adsorption step (fifth step; restoration step).
In addition, when the regeneration process after adsorption is performed in the adsorption tower A, the adsorption can be continuously performed by the adsorption in the adsorption tower B. The same operation is performed in the adsorption tower B.

Next, the operation in the adsorption tower B when the above processing is performed in the adsorption tower A will be described with reference to FIG. When the adsorption tower B starts the regeneration, it is assumed that the adsorption tower B is in a state where the adsorption is completed. In this figure, the introduction of gas is shown as raw material gas, but it also includes the case of generated gas.
During adsorption in the adsorption tower A, gas is introduced in the adsorption tower A and the purified gas is discharged (step a). In the adsorption tower B, a regeneration process is performed to heat the inside of the adsorption tower B. At this time, a high-temperature regenerated gas is introduced into the adsorption tower B, impurities are desorbed from the adsorption tower B, and the exhaust gas is discharged. Further, when the temperature inside the adsorption tower B rises to T2, the adsorbent is cooled by introducing the low-temperature regenerated gas while performing the regeneration process in the adsorption tower B (step b), and the temperature of the adsorbent drops to T1. Completes the playback process with. Around this time, the adsorption process is completed in the adsorption tower A.
After that, the adsorption treatment is started in the adsorption tower B, the regeneration treatment is started in the adsorption tower A, the heat treatment is performed by introducing the high temperature regenerated gas (step c), and the impurities are desorbed. Next, in the adsorption tower A, a cooling process is performed (step d) to complete the regeneration process. Around this time, the adsorption process is completed in the adsorption tower B.
By repeating the above procedure, the regeneration process can be performed while continuing the adsorption.
It should be noted that the adsorption towers A and B do not have to complete the adsorption and regeneration at the same time, but it is desirable that the regeneration process is completed at the same time as or by the completion of the adsorption process.

As described above, since the temperature swing adsorption method is a gas purification method using a temperature difference as a driving source, the operating cost is higher than that of the pressure swing adsorption method or the membrane separation method in an environment where abundant high-temperature waste heat can be obtained. Can be lowered. Here, if there is only one adsorption tower, the waiting time for the cycle becomes long, so it is necessary to provide a large heat storage tank or gas buffer tank. On the other hand, if two or more adsorption towers are installed and the processes are staggered, the demand for heat and gas can be averaged and various buffer tanks can be made smaller, which is preferable.

The heat balance of temperature swing adsorption type gas refining is calculated below. Considering only dehumidification for simplicity, when a saturated water vapor pressure of 7.4 kPa at 40 ° C is applied, 7.4 vol% of water vapor is contained in each of the electrolyzed hydrogen and the produced methane at 40 ° C and atmospheric pressure. Become. Considering that 4 mol of hydrogen is required to produce 1 mol of methane, the number of moles of water to be dehumidified per 1 mol of methane synthesis is 0.37 mol as shown in the following formula.
(4 mol + 1 mol) × 7.4 vol% = 0.37 molH ₂ O (3)

If the heat of desorption of water from the adsorbent is 44 kJ / mol H ₂ O, which is the same as the heat of vaporization of water, the required amount of heat is 16 kJ. On the other hand, since the calorific value when 1 mol of methane is synthesized by hydrogen and carbon dioxide is 165 kJ, dehumidification can be realized by supplying 10% of the heat to the gas purification apparatus. Of course, it is necessary to consider various heat exchange losses and sensible heat loss of the adsorption tower, but it is considered that the heat balance is sufficiently balanced even in the actual process.
As described above, the high-temperature medium after heat supply in the heating / desorption process of the temperature swing adsorption type gas purification device is additionally cooled by an auxiliary cooling facility (not shown) as necessary and then returned to the methane gas synthesizer. can do.

In addition, a regenerated gas line can be connected to the temperature swing adsorption type gas purification device to remove heat in the cooling / adsorption process and to release heat to the outside by a separately installed cooling facility.
This gas refining system does not have any problem even with simple control if it is premised on constant load operation, but when it is operated as a part of the Feedback to Gas system combined with a variable renewable energy power supply, heat and gas that fluctuate with time In order to balance the balance, it is desirable to introduce feedback control using multiple parameters. Possible parameters include the output of the water electrolyzer, the gas / medium pressure of each part, the temperature of each facility / gas / medium, and the flow rate of various gases / media. Examples of the controlled device include a water electrolyzer, a temperature swing adsorption type gas purifier, a methane synthesizer, a heat medium pump, a gas compressor, and valves.

Next, the operation control of the heat utilization type gas refining system will be described.
The entire heat-utilizing gas refining system 1 is controlled by the control unit. The control unit is composed of a CPU, a program executed on the CPU, a non-volatile memory that stores operation parameters, a storage unit such as a RAM that serves as a work area, and the like. The control unit may be installed in the main body of the heat-utilizing gas refining system, or may be connected to the main body of the heat-utilizing gas refining system via a network or the like.
The control unit can dynamically control the output of the methane synthesizer or the temperature swing adsorption type gas purification device by referring to the amount of unrefined gas, various gas pressures, and the temperature of the high temperature medium.

In order to acquire the state information of the heat utilization type gas refining system, various data are acquired in the control unit. One is to acquire the output state of the water electrolyzer 100. In addition, state information such as the pressure of the gas or medium of each part, the temperature of the gas or medium of each device, and the flow rate of the gas or medium is acquired.

Each part and each device is controlled from these state information. As one of them, the opening and closing and switching of various valves are controlled. Further, the operation control of the temperature swing adsorption type gas purification devices 4 and 5, the synthesis control of the methane gas synthesis device 2, the operation control of the medium pump, the control of the gas compressor in each device, and the like are executed.

Next, the heat utilization type gas purification system 1A of another embodiment will be described with reference to FIG.
In this embodiment, a part of hydrogen used in the reaction is temporarily stored in a hydrogen storage alloy and used for the reaction. The same components as those in the above embodiment are designated by the same reference numerals, and the description thereof will be omitted or simplified.
In the gas refining system of this embodiment, a hydrogen storage alloy tank 60 is added for a buffer of hydrogen gas after dehumidification.

A hydrogen supply path 61 is connected to the hydrogen storage alloy tank 60, the other end of the hydrogen supply path 61 is branched and connected to the raw material gas introduction path 12, and the hydrogen supply path 61 and the hydrogen supply path 61 and the hydrogen supply path 61 are connected from the upstream side of the branch point of the raw material gas introduction path 12. It is possible to transfer hydrogen into the hydrogen storage alloy tank 60 or from the hydrogen storage alloy tank 60 to the downstream side of the branch point of the raw material gas introduction path 12 through the hydrogen supply path 61. Further, the connection between the raw material gas introduction path 12 and the hydrogen supply path 61 may be selectively made.

Further, the alloy heat medium introduction path of the hydrogen storage alloy tank is connected to the high temperature medium circulation path 50, and the high temperature medium flowing through the high temperature medium circulation path 50 is introduced into the alloy heat medium introduction path by an on-off valve or the like (not shown). be able to. The hydrogen storage alloy can be thermally driven using this high temperature medium. Further, a bypass path for the alloy heat medium introduction path is provided, and when it is not necessary to introduce the high temperature medium into the hydrogen storage alloy tank 60, the alloy heat medium introduction path is bypassed by the bypass path.

Hydrogen storage alloys have the characteristics of selectively storing hydrogen in the alloy at high density, generating heat when absorbing hydrogen, and absorbing heat when releasing hydrogen. In general, hydrogen storage alloys can be operated at 60 ° C or lower, so in this system, a high-temperature medium after heat is applied to the temperature swing adsorption type gas purification device is introduced into the hydrogen storage alloy tank and circulated. Is provided. While monitoring the pressure and temperature of the hydrogen storage alloy tank, the on-off valve and pump can be driven to promote hydrogen release and balance the supply and demand of hydrogen. Further, the recycled gas may be used as a medium for thermally driving the hydrogen storage alloy. If hydrogen storage is not required, the hydrogen storage alloy tank may not be supplied with hydrogen.

Although the present invention has been described above based on the above-described embodiment, appropriate modifications to the present embodiment can be made as long as the present invention is not deviated from the scope of the present invention.

1 Heat utilization type gas purification system 1A Heat utilization type gas purification system 2 methane gas synthesizer 3 Gas mixer 4 Temperature swing adsorption type gas purification device 5 Temperature swing adsorption type gas purification device 6 Heat storage tank 7 High temperature medium pump 10 Raw material gas introduction path 11 Raw material gas introduction path 12 Raw material gas introduction path 13 Raw material gas introduction path 20 Recycled gas introduction path 21 High temperature recycled gas introduction path 22 Low temperature recycled gas introduction path 23 Regenerated gas discharge path 24 Exhaust equipment 25 Medium switching device 26 Pump 27 Recycled gas return Flow path 30 Generated gas delivery path 31 Purified gas delivery path 40 Regenerated gas introduction path 41 High temperature recycled gas introduction path 42 Low temperature recycled gas introduction path 43 Regenerated gas discharge path 44 Exhaust equipment 45 Medium switching device 46 Pump 47 Regenerated gas return channel 50 High temperature medium circulation path 50A High temperature medium circulation path 50B High temperature medium circulation path 52 Heat exchanger 53 Heat exchanger 60 Hydrogen storage alloy tank 61 Hydrogen supply path 100 Water electrolytic device 110 Carbon dioxide supply source 200 methane utilization device

Claims (11)

At least a methane gas synthesizer that synthesizes methane gas using hydrogen and carbon dioxide as raw material gases,
A raw material gas introduction path for introducing the raw material gas into the methane gas synthesizer,
A production gas delivery path for transmitting the production gas generated by the methane gas synthesizer, and
A temperature swing adsorption type gas purification device provided through the raw material gas introduction path and / or the generated gas delivery path to remove impurities in the gas.
The temperature swing adsorption type gas purification device is provided with a regenerated gas introduction path for introducing a high temperature regenerated gas and a low temperature regenerated gas that drive the desorption process in the temperature swing adsorption type gas purification device.
A heat-utilizing gas refining system characterized in that the reaction heat of the methane gas synthesizer is applied to the high-temperature regenerated gas sent through the regenerated gas introduction path. The heat-utilizing gas refining system according to claim 1, further comprising a high-temperature medium circulation path that receives the reaction heat of the methane gas synthesizer, and heating the high-temperature regenerated gas by heat exchange in the high-temperature medium circulation path. The heat utilization type gas purification system according to claim 1 or 2, further comprising a medium switching device for switching between supply of high temperature regenerated gas and low temperature regenerated gas to be introduced into the temperature swing adsorption type gas purification device. The heat according to any one of claims 1 to 3, wherein the temperature swing adsorption type gas purification apparatus is provided with a plurality of adsorption towers, and each adsorption tower can be operated at different times of the operation mode. Utilization type gas refining system. The heat-utilizing gas purification system according to claim 4, wherein adsorption and desorption are possible in succession in a plurality of adsorption towers. The heat utilization type gas refining system according to any one of claims 1 to 5, further comprising a heat storage unit for storing heat applied to the high temperature regenerated gas to be introduced into the temperature swing adsorption type gas refining apparatus. .. The heat utilization type gas according to claim 6, wherein the heat storage unit adjusts an excess or deficiency by absorbing and releasing heat energy even if there is a time lag between high temperature heat supply and high temperature heat demand. Purification system. One of claims 1 to 7, wherein the hydrogen gas purified by the temperature swing adsorption type gas purification apparatus is stored, and the stored hydrogen gas is provided with a hydrogen storage alloy tank capable of supplying the stored hydrogen gas to the methane gas synthesizer. The heat-utilizing gas purification system according to item 1. The alloy has an alloy medium flow path for thermally driving the hydrogen storage alloy contained in the hydrogen storage alloy tank capable of supplying the stored hydrogen gas to the methane gas synthesizer, and the alloy for releasing hydrogen gas from the hydrogen storage alloy. The heat utilization according to any one of claims 1 to 8, wherein a medium that has received the reaction heat of the methane gas synthesizer or a high-temperature regenerated gas is used as the medium supplied to the medium flow path. Type gas purification system. The heat utilization type gas refining system according to claim 9, wherein the medium supplied to the hydrogen storage alloy tank in the alloy medium flow path and discharged after heat exchange is recirculated to the methane gas synthesizer. The invention according to any one of claims 1 to 10, further comprising a control unit that controls the operation of each device with reference to one or more of the amount of raw material gas generated, the pressure of each unit, the temperature, or the flow rate. Heat utilization type gas refining system.

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