JP2019052224A - Heat utilization type gas refining system - Google Patents

Abstract

To provide a gas refining system utilizing heat of methanation reaction with improved efficiency.SOLUTION: The heat utilization type gas refining system comprises: a methane gas synthesizer that synthesizes methane gas using at least hydrogen and carbon dioxide as source gases, a source gas introduction passage for introducing the source gas into the methane gas synthesizer, a product gas delivery passage for delivering product gas generated by the methane gas synthesizer, a temperature swing adsorption type gas refining device provided through the source gas introduction passage and/or the product gas delivery passage for removing impurities in gas, and a regeneration gas introduction passage for introducing respectively a high temperature regeneration gas and a low temperature gas that drive a desorption process of the temperature swing adsorption type gas purification device into the temperature swing adsorption type gas purification device, wherein heat of a reaction of the methane gas synthesizer is applied to high temperature regeneration gas sent through the regeneration gas introduction passage.SELECTED DRAWING: Figure 1

Description

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

In recent years, with the introduction of renewable energy, the problem of surplus power due to supply and demand imbalance is becoming apparent. As a solution for this, a Power to Gas system has been proposed in which surplus power is used for water electrolysis and stored, transported and used as hydrogen energy. However, hydrogen does not have various infrastructures and has a demerit that requires enormous infrastructure investment. In contrast, the Power to Methane system that uses hydrogen and carbon dioxide to synthesize (methanate) and then uses existing natural gas and city gas infrastructure to transport, store, and use the system has been put into practical use. It is out. The methanation reaction formula is shown in Formula (1).
4H ₂ (g) + CO ₂ (g) = CH ₄ (g) + 2H ₂ O (g) +165 kJ (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 invention relating to effective use of reaction heat are shown below.
In Patent Document 1, for the purpose of fixing carbon in carbon dioxide, in the process of pyrolyzing synthetic methane and converting it to solid carbon, heat utilization for supplying methanation reaction heat to methane pyrolysis reaction which is an endothermic reaction A system has been devised.
Patent Document 2 devises the use of methanation reaction heat in a steam generator, a carbon dioxide exhaust gas unit, and the like in a thermal power plant using carbon-containing fuel.

  As described above, carbon dioxide and hydrogen are necessary as raw materials for the methanation reaction. On the other hand, the hydrogen obtained by the water splitting process contains a lot of moisture derived from the electrolytic solution. If moisture remains in the hydrogen, not only will extra energy be required to heat the raw material gas to the methanation reaction temperature, but the reaction will be less likely to proceed to the methane production side in terms of chemical equilibrium. There is an adverse effect. For this reason, it is preferable to remove the water | moisture content in hydrogen to a suitable dew point prior to reaction.

  Moreover, as shown in Formula (1), water is generated in addition to methane as a result of the methanation reaction. Furthermore, a part of the raw material gas remains in the product gas unreacted. On the other hand, when using synthetic methane for combustion, it is desirable that water vapor and carbon dioxide that do not contribute to combustion are not included as much as possible. Even in the case of use for city gas, if there are too many concentrations of water vapor, hydrogen and carbon dioxide, they deviate from standards such as calorific value and combustion rate, so there are many cases where upper limits are set for these gas concentrations. Therefore, it is preferable to perform a certain degree of purification and dehumidification for the methanation product gas.

  Therefore, in the gas purification system, as described above, prior to the reaction, either the step of removing moisture in the hydrogen to an appropriate dew point or the step of performing a certain degree of purification or dehumidification of the methanation product gas. Alternatively, it is desirable to have both, and the advantages of the gas purification system can be obtained by having either step.

Japanese Patent Laying-Open No. 2015-196619 JP-T-2006-531973

  For these gas purification / dehumidification, a temperature swing adsorption type gas purification apparatus or the like can be used. However, since purification using a temperature swing adsorption type gas purification device requires heating during regeneration of the adsorbent, it is necessary to input an external heat source, resulting in a deterioration in overall efficiency and a decrease in business profitability. Will be invited.

  In view of the above problems, an object of the present invention is to provide a gas purification system that improves the overall system efficiency.

Of the heat-utilizing gas purification system of the present invention, the first mode is a methane gas synthesizer that synthesizes methane gas using at least hydrogen and carbon dioxide as source gases,
A source gas introduction path for introducing the source gas into the methane gas synthesis device;
A product gas delivery path for delivering the product gas produced by the methane gas synthesizer;
A temperature swing adsorption type gas purification device that is provided through the source gas introduction path and / or the product gas delivery path and removes impurities in the gas;
The temperature swing adsorption gas purification device comprises a regeneration gas introduction path for introducing a high temperature regeneration gas and a low temperature regeneration gas that drive a desorption process in the temperature swing adsorption gas purification device, respectively.
The high-temperature regeneration gas sent through the regeneration gas introduction path is given heat of reaction of the methane gas synthesis apparatus.

  Another aspect of the invention of the heat-utilizing gas purification system according to the aspect of the invention is that in the aspect of the invention, the high-temperature regeneration gas has a high-temperature medium circulation path that receives the reaction heat of the methane gas synthesizer, Is heated.

  Another aspect of the invention of the heat-utilizing gas purification system according to the aspect of the invention includes a medium switching device that switches supply of a high-temperature regeneration gas and a low-temperature regeneration gas to be introduced into the temperature swing adsorption gas purification device. And

  In another aspect of the invention of the heat-utilizing gas purification system according to the aspect of the invention, the temperature swing adsorption type gas purification device includes a plurality of adsorption towers, and each adsorption tower can be operated by shifting the timing of the operation mode. It is characterized by being.

  Another aspect of the invention of the heat-utilizing gas purification system according to the aspect of the invention is characterized in that adsorption and desorption can be continuously performed in a plurality of adsorption towers.

  Another aspect of the invention of the heat-utilizing gas purification system according to the aspect of the invention is characterized in that it includes a heat storage unit that stores heat to be applied to the regeneration gas introduced into the temperature swing adsorption gas purification device. .

  In another aspect of the invention of the heat-utilizing gas purification system according to the aspect of the invention, the heat storage unit may absorb or release thermal 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 excess and deficiency.

  In another aspect of the invention 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. A hydrogen storage alloy tank is provided.

  Another aspect of the invention of the heat-utilizing gas purification system according to the aspect of the invention is the alloy medium flow path according to the aspect of the invention, wherein the alloy medium passage for thermally driving the hydrogen storage alloy is used to release hydrogen gas from the hydrogen storage alloy. The medium supplied to the flow path is a medium that has received reaction heat of the methane gas synthesizer or a high-temperature regeneration gas.

  In another aspect of the invention of the heat-utilizing gas purification system according to the aspect of the invention, the medium supplied to the hydrogen storage alloy tank through the alloy medium flow path and discharged after heat exchange is circulated to the methane gas synthesis apparatus. It is characterized by that.

  Another aspect of the invention of a heat-utilizing gas purification system is a control unit that controls the operation of each device with reference to one or more of the amount of generated source gas, the pressure, temperature, or flow rate of each part in the invention of the above aspect It is characterized by having.

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

It is the schematic which shows the heat utilization type gas purification system of one Embodiment of this invention. Similarly, it is the schematic which shows the gas inlet / outlet path of the temperature swing adsorption | suction type gas purification apparatus contained in a system. Similarly, it is the conceptual diagram which shows the pressure-temperature diagram in the adsorbent of a temperature swing adsorption type gas purification apparatus, and a temperature swing adsorption process. Similarly, it is a figure which shows the temperature swing adsorption | suction process of a temperature swing adsorption type gas purification apparatus. It is the schematic which shows the heat utilization type gas purification system of other embodiment of this invention.

Below, the heat utilization type gas purification system 1 of one Embodiment of this invention is demonstrated based on FIG.
A methane gas synthesizer 2 that synthesizes methane gas using hydrogen and carbon dioxide as source gases is connected to a source gas introduction path 13, and carbon dioxide is supplied via the gas mixer 3 in the source gas introduction path 13. The source gas introduction path 11 to be supplied and the source gas introduction path 12 to which hydrogen is supplied merge. A mixed gas in which carbon dioxide and hydrogen are mixed is sent to the source gas introduction path 13. The source gas introduction path 11 is connected to a carbon dioxide supply source 110 outside the system.
A temperature swing adsorption gas purification device 4 is provided on the base end side of the raw material gas introduction passage 12, and the raw material gas introduction passage 10 is connected to the temperature swing adsorption gas purification device 4.
The base end side of the source gas introduction path 10 is connected to the water electrolysis apparatus 100 outside the system.
Although the water electrolysis apparatus 100 and the carbon dioxide supply source 110 have been described as those outside the system, one or both of them may be included in the system.

  The temperature swing adsorption type gas purification apparatus 4 has two adsorption towers A and B, and can perform adsorption and desorption independently of each other. It is possible to operate with a plurality of adsorption towers of the temperature swing adsorption type gas purification device 4 while shifting each operation mode 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 or the like can be used.

In the temperature swing adsorption gas purification apparatus 4, the introduction of the high temperature regeneration gas and the introduction of the low temperature regeneration gas into the adsorption towers A and B can be switched by the high temperature regeneration gas introduction path 21 and the low temperature regeneration gas introduction path 22. ing. In this embodiment, the high temperature regeneration gas introduction path 21 and the low temperature regeneration gas introduction path 22 are joined and connected to the temperature swing adsorption gas purification device 4, and the high temperature regeneration gas and the low temperature regeneration gas for the adsorption towers A and B are combined. To introduce. The proximal end sides of the high temperature regeneration gas introduction path 21 and the low temperature regeneration gas introduction path 22 are connected to a medium switching device 25, and the regeneration gas introduction path 20 is connected to the medium switching device 25. The regeneration gas introduction path 20 is connected to the source gas introduction path 12, and the regeneration gas accompanied by the source gas introduction path 12 is taken out and sent to the regeneration gas introduction path 20. The method of taking out the regeneration gas from the source gas introduction path 12 is not particularly limited, and a method for separately providing a conduit for transporting the regeneration gas inside or outside the source gas introduction path 12 may be used. Good.
The medium switching device 25 may be any device as long as it can selectively switch the regeneration gas conveyed by the regeneration gas introduction path 20 and transport it to the high temperature regeneration gas introduction path 21 and the low temperature regeneration gas introduction path 22. It is not limited to. For example, a three-way valve can be used. In this embodiment, the regeneration gas is transferred to the high temperature regeneration gas introduction path 21 and the low temperature regeneration gas introduction path 22 via the regeneration gas introduction path 20, but the regeneration gas for the high temperature regeneration gas is used. And the regenerative gas for the low temperature regenerative gas are separately connected to the temperature swing adsorption type gas purification device 4 and the regenerative gas is introduced into the temperature swing adsorption type gas purification device 4 by an open / close valve provided in each introduction path. May be switched.

  In the temperature swing adsorption gas purification device 4, the regeneration gas discharge path 23 is connected to the side where the introduced high temperature regeneration gas or the low temperature regeneration gas is discharged, and the exhaust equipment 24 is connected to the front end side of the regeneration gas discharge path 23. Has been. The regeneration gas after exiting the temperature swing adsorption gas purification device 4 is generally exhausted outside the system as described above. However, in the case where an expensive process gas is used as the regeneration gas, the regeneration gas is not exhausted, but is increased in pressure by the pump 26 and then introduced into the raw material gas introduction passage 10 to be described later through the regeneration gas return passage 27. Also good.

  The regeneration gas is positioned as a gas for regenerating the temperature swing adsorption gas purifier as a gaseous low-temperature medium. In the present invention, the regeneration gas is not limited to a special one. However, an inert gas such as nitrogen or a process gas such as hydrogen can be suitably used as the regeneration gas. These gases can avoid adversely affecting the filling in the apparatus due to contamination in the equipment system and active gases (eg, oxygen in the air). However, when nitrogen, which is an inert gas, is used as the regeneration gas, a small amount of nitrogen gas remains in the system at the end of the regeneration process. Since the nitrogen gas is contaminated, the purity of the purified gas is lowered. When this point is emphasized, it is desirable to use process gas as regeneration gas.

In addition, the temperature swing adsorption gas purification apparatus 4 is connected to a raw material gas introduction passage 10 for introducing hydrogen for purification and a raw material gas introduction passage 12 for sending purified dry hydrogen.
A downstream end of the source gas introduction path 12 and a downstream end of the source gas introduction path 11 for sending carbon dioxide are connected to the gas mixer 3. In the gas mixer 3, carbon dioxide and hydrogen can be mixed at a quantitative ratio for synthesizing methane gas and sent out downstream as a mixed gas. The gas mixer 3 is connected to a raw material gas introduction path 13 for sending a mixed gas downstream, and the raw material gas introduction path 13 is connected to the methane gas synthesis apparatus 2.

  The methane gas synthesizer 2 has a product gas delivery path 30 that sends the product gas out of the methane gas synthesizer 2. The product gas delivery path 30 is connected to the temperature swing adsorption gas purification device 5, and the product gas is purified in the temperature swing adsorption gas purification device 5. The temperature swing adsorption type gas purification apparatus 5 has a purified gas delivery path 31 for delivering purified gas, and the purified gas delivery path 31 is connected to a methane utilization apparatus 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 apparatus 5 has two adsorption towers A and B, and can perform adsorption and desorption independently of each other. It is possible to operate with a plurality of adsorption towers of the temperature swing adsorption type gas purification device 5 while shifting each operation mode 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 or 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 have a different structure.

The temperature swing adsorption gas purification apparatus 5 is connected to a high temperature regeneration gas introduction path 41 and a low temperature regeneration gas introduction path 42, and the introduction of the high temperature regeneration gas and the introduction of the low temperature regeneration gas into the adsorption towers A and B are performed. Switchable. In this embodiment, the high temperature regeneration gas introduction path 41 and the low temperature regeneration gas introduction path 42 merge to introduce the high temperature regeneration gas and the low temperature regeneration gas into the adsorption towers A and B. The proximal end sides of the high temperature regeneration gas introduction path 41 and the low temperature regeneration gas introduction path 42 are connected to a medium switching device 45, and the regeneration gas introduction path 40 is connected to the medium switching device 45. The regeneration gas introduction path 40 is connected to the purified gas delivery path 31, and the regeneration gas accompanied by the purified gas delivery path 31 is taken out and sent to the regeneration gas introduction path 40. Note that the method of taking out the regeneration gas from the purified gas delivery path 31 is not particularly limited, and a method of separately providing a pipe for transporting the regeneration gas inside or outside the purified gas delivery path 31 may be used. Good. A three-way valve or the like can be used for the medium switching device 45. In addition, the regeneration gas for the high temperature regeneration gas and the regeneration gas for the low temperature regeneration gas are separately transported, and the introduction of the regeneration gas to the temperature swing adsorption gas purifier 5 is switched by an open / close valve or the like. Also good.
In the temperature swing adsorption gas purification device 5, the regeneration gas discharge path 43 is connected to the side where the introduced regeneration gas is discharged, and the exhaust equipment 44 is connected to the front end side of the regeneration gas discharge path 43. When an expensive process gas is used as the regeneration gas, the regeneration gas can be introduced into the product gas delivery passage 30 through the regeneration gas return passage 47 after being boosted by the pump 46 without being exhausted.

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

  In addition, a high-temperature medium circulation path 50 that recovers exhaust heat generated in the methane gas synthesis apparatus 2 is provided. The high-temperature medium circulation path 50 is provided with a heat storage tank 6 on the downstream side of the position where the exhaust heat is recovered by the methane gas synthesis apparatus 2, and temporarily stores the high-temperature medium that has received the reaction heat in the methane gas synthesis apparatus 2. Can do. The heat storage tank 6 corresponds to a heat storage unit of the present invention. The heat storage unit only needs to be able to store heat, and the present invention is not limited to the heat storage tank. The heat storage tank 6 can function as a high-temperature heat supply from the methanation facility and to eliminate the time lag of the high-temperature heat demand of the temperature swing adsorption gas purification apparatuses 4 and 5. In the present invention, no heat storage tank may be provided.

  On the downstream side of the heat storage tank 6, a high-temperature medium pump 7 is interposed, and the high-temperature medium in 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 respectively. The heat exchanger 52 transfers heat to the regeneration gas flowing through the high temperature regeneration gas introduction path 21 to raise the temperature of the regeneration gas, and the heat exchanger 53 transfers heat to the regeneration gas flowing through the high temperature regeneration gas introduction path 41. Thus, by raising the temperature of the regeneration gas, it is possible to introduce the high temperature regeneration gas into the temperature swing adsorption gas purification device 4 or the temperature swing adsorption gas purification device 5. The high temperature medium circulation paths 50 </ b> A and 50 </ b> B join together on the downstream side of the heat exchangers 52 and 53, and circulate as the high temperature medium circulation path 50 on the upstream side of the methane gas synthesis apparatus 2.

  In this embodiment, in the introduction of the raw material hydrogen and the delivery of the product gas, a temperature swing adsorption type gas purification device is installed in each, and the exhaust heat of the methane gas synthesis facility is used for each gas purification device. In the present invention, a temperature swing adsorption type gas refining device may be installed in any one of introduction of raw material hydrogen and delivery of product gas. Further, in introduction of other raw material gas, a temperature swing adsorption type gas is further introduced. A purification device may be installed.

Next, the detailed configuration of the temperature swing adsorption gas purification apparatus will be described with reference to FIGS.
Note that the temperature swing adsorption type gas purification device 4 and the temperature swing adsorption type gas purification device 5 have the same configuration. Will be described.

  The temperature swing adsorption type gas refining apparatus has an adsorption tower A and an adsorption tower B, and each has gas inlet / outlet paths as shown in FIG. The adsorption tower A has a gas inlet / outlet path IO1, and the adsorption tower B has a gas inlet / outlet path IO2, between which two common paths C1, C2 are connected, and the common paths C1, C2 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 inlet side, and is connected to the common path C1 between the on-off valves V11 and V12. In the common path C2, an exhaust gas path E1 is connected between the on-off valves V21 and V22.

When the raw material gas is introduced into the adsorption tower by the temperature swing adsorption type gas refining device 4, when it is introduced into the adsorption tower A, the on-off valves V 12 and V 21 are closed and the on-off valve V 11 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 gas purification device 5, the product gas is sent from the methane gas synthesis device 2 instead of the raw material gas.
When the regeneration gas introduced into the temperature swing adsorption type gas purification apparatus is discharged from the adsorption tower as exhaust gas, when it is discharged from the adsorption tower A, the open / close valves V11 and V22 are closed and the open / close valve V21 is opened to exhaust gas. Are discharged from the adsorption tower A and are discharged from the adsorption 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 adsorption tower B.

Further, the adsorption tower A and the adsorption tower B have gas inlet / outlet paths IO3 and IO4 at positions opposite to the gas inlet / outlet paths IO1 and IO2. Two common paths C3 and C4 are connected between the gas inlet / outlet 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 regeneration gas introduction path G1 is disposed on the gas inlet side, and a raw material gas introduction path 12 or a purified gas delivery path 31 is connected to the gas delivery side. The high temperature / low temperature regeneration gas introduction path G1 corresponds to an introduction path where the high temperature regeneration gas introduction path 21 and the low temperature regeneration gas introduction path 22 merge or an introduction path where the high temperature regeneration gas introduction path 41 and the low temperature regeneration gas introduction path 42 merge. .
The high temperature / low temperature regeneration gas introduction path G1 is connected to the common path C3 between the on-off valve V31 and the on-off valve V32. The source gas introduction path 12 or the purified gas delivery path 31 is connected to the common path C4 between the on-off valve V41 and the on-off valve V42.

When the regeneration gas is introduced into the adsorption tower by the temperature swing adsorption gas purification device 4, when the regeneration gas is introduced into the adsorption tower A, the on-off valves V32 and V41 are closed, and the on-off valve V31 is opened to introduce the regeneration 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 regeneration gas into the adsorption tower B.
When sending the purified raw material gas or purified gas from the adsorption tower A, when sending it from the adsorption tower A, the on-off valves V31 and V42 are closed, and the on-off valve V41 is opened to send the purified gas from the adsorption tower A. When sending from the adsorption tower B, the on-off valves V32 and V41 are closed, the on-off valve V42 is opened, and the purified gas is discharged from the adsorption tower B.
When performing adsorption or desorption with an adsorption tower, a plurality of on-off valves are opened and closed as described above. Each on-off valve described above constitutes a gas switching device.

  In this embodiment, the temperature swing adsorption gas purification apparatus has been described as having two adsorption towers, but it may have three or more adsorption towers, and each temperature swing adsorption gas purification apparatus may have May have different numbers of adsorption towers.

Next, operation | movement of the whole heat utilization type gas purification system of this embodiment is demonstrated.
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 hydrogen obtained from the water electrolysis apparatus 100 passes through the raw material gas introduction path 10 to the temperature swing adsorption gas purification device 4. Sent.
The hydrogen obtained by the water electrolysis apparatus 100 contains water vapor and is introduced into the temperature swing adsorption gas purification apparatus 4. In the temperature swing adsorption type gas purification apparatus 4, the adsorption is performed in one of the adsorption towers A and B. In the adsorption towers A and B, a high temperature regeneration gas or a low temperature regeneration gas is introduced through the high temperature / low temperature regeneration gas introduction path G1 as necessary.
The high temperature regeneration gas or the low temperature regeneration gas used in the temperature swing adsorption type gas purification devices 4 and 5 is discharged from the temperature swing adsorption type gas purification devices 4 and 5 through the regeneration gas discharge passages 23 and 43, and is supplied to the exhaust facilities 24 and 44. Sent. Details of the operation of the temperature swing adsorption gas purification device 4 will be described later.

Hydrogen + steam raw material gas is obtained by removing water vapor alternately in the adsorption towers A and B of the temperature swing adsorption gas purification apparatus 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 (hydrogen: carbon dioxide = 4: 1) of the methanation reaction. 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.). The mixed gas undergoes a methanation reaction on the catalyst surface and is converted into methane and water vapor. At the end of the reaction tube, most of the raw material gas finishes the reaction, and finally the product gas component is a mixture of methane and water vapor and a small amount of unreacted gas (hydrogen, carbon dioxide).
At this time, reaction heat is applied to the high-temperature medium sent through the high-temperature medium circulation path 50, and the high-temperature medium that has been heated 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 gas purifier 5 through the product 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, which is an impurity of the product gas sent, and a part of the unreacted gas are adsorbed and removed by either of the adsorption towers A and B to obtain high-purity purified methane. It is done.

  In the adsorption towers A and B, the high temperature regeneration gas heated by the high temperature medium circulation path 50B is introduced through the high temperature regeneration gas introduction path 41 or the low temperature regeneration gas is introduced through the low temperature regeneration gas introduction path 42 as 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 through the purified gas delivery path 31 and used. At this time, refined methane can be sent using existing natural gas and city gas infrastructure.

Subsequently, the heat flow will be described. In the methane gas synthesizer 2, heat is generated with the methanation reaction. On the other hand, in order to maintain an appropriate reaction temperature, it is necessary to circulate a hot 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 temperature and pressure. A high temperature regeneration gas used for heating in the temperature swing adsorption type gas purification apparatus may be used as a high temperature medium.
It is desirable that the high-temperature medium that has received excess 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 refining equipment has a wave as will be described later, and when the hydrogen of water electrolyzer combined with the variable regeneration energy power source is used as a raw material, the output of the methane gas synthesizer also fluctuates. is there. For this reason, it becomes possible to supply the stable heat | fever regardless of the operating state of both facilities by providing the thermal storage tank of appropriate capacity | capacitance.

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, a 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, the on-off valves V12, V21 are closed and the on-off valve V11 is opened, whereby the gas to be purified is introduced from the common path C1 to the adsorption tower A1 through the inlet / outlet path IO1 (first step; adsorption step). In the adsorption step, the gas to be treated is allowed to pass through while maintaining the adsorption tower filled with the adsorbent at normal temperature (T1) and adsorption pressure (P1). At this time, the impurity component contained in the gas is selectively adsorbed by the adsorbent.

  Before the adsorbent breaks through, switch to the depressurization process. In this step, the adsorption step is terminated and the pressure is reduced from the adsorption pressure P1 to about atmospheric pressure (P2) (second step).

Next, at a 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 components are desorbed (third step; heating regeneration step).
As the high-temperature regeneration gas, the purified gas at the outlet of the temperature swing adsorption type gas purification apparatus can be used, and the heat medium can be heated by using methanation exhaust heat or a separately installed electric heater as a heat source.

Next, cold regeneration is performed by introducing a low temperature regeneration gas at normal temperature (T1) at regeneration pressure (P2) and lowering the temperature from T2 to T1 (fourth step; cooling regeneration step).
After completion of the cooling regeneration, the pressure is restored from the regeneration pressure (P2) to the adsorption pressure (P1) at room temperature (T1), and the adsorption process can be carried out (fifth process; decompression process).
In addition, when performing the regeneration process after adsorption | suction with the adsorption tower A, it becomes possible to perform adsorption | suction continuously by performing adsorption | suction with the adsorption tower B. FIG. The same operation is performed in the adsorption tower B.

Next, the operation in the adsorption tower B when the above treatment is performed in the adsorption tower A will be described with reference to FIG. Note that when the regeneration is started in the adsorption tower B, the adsorption tower B is in a state where the adsorption is completed. In this figure, the introduction of gas is shown as a raw material gas, but it also includes the case of product gas.
When adsorption is performed in the adsorption tower A, the gas is introduced into the adsorption tower A and the purified gas is discharged (step a). In the adsorption tower B, a regeneration process is performed and the inside of the adsorption tower B is heated. At this time, a high-temperature regeneration gas is introduced into the adsorption tower B, impurities are desorbed from the adsorption tower B, and exhaust gas is discharged. Furthermore, when the temperature in the adsorption tower B rises to T2, the adsorption tower B cools the adsorbent by introducing the low temperature regeneration gas while performing the regeneration process (step b), and the adsorbent temperature falls to T1. Complete the playback process. At this time, the adsorption process is completed in the adsorption tower A.
Thereafter, 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 regeneration gas (step c), and the impurities are desorbed. Next, in the adsorption tower A, a cooling process is performed (step d), and the regeneration process is completed. At this time, the adsorption process is completed in the adsorption tower B.
By repeating the above procedure, the regeneration process can be performed while the adsorption is continued.
In the adsorption towers A and B, the adsorption and the regeneration may not be completed at the same time, but it is desirable that the regeneration process is completed at the same time or before the adsorption process is completed.

  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 lower than the pressure swing adsorption method and the membrane separation method in an environment where abundant high-temperature exhaust heat can be obtained. Can be lowered. Here, when there is only one adsorption tower, the cycle waiting time becomes long, so it is necessary to provide a large heat storage tank or gas buffer tank. On the other hand, it is preferable to install two or more adsorption towers and operate by shifting the steps, since the demand for heat and gas can be averaged and various buffer tanks can be made small.

The heat balance of temperature swing adsorption gas purification is estimated below. For simplicity, only dehumidification is taken into account, and when applying a saturated water vapor pressure of 7.4 kPa at 40 ° C., water electrolytic hydrogen at 40 ° C. and atmospheric pressure and methane produced contain 7.4 vol% of water vapor. Become. Considering that 4 moles of hydrogen are required to produce 1 mole of methane, the number of moles of water to be dehumidified per mole of methane synthesis is 0.37 mole as shown in the following equation.
(4 mol + 1 mol) × 7.4 vol% = 0.37 mol H ₂ O (3)

If the heat of desorption of water from the adsorbent is 44 kJ / mol H ₂ O, which is equal to the heat of evaporation of water, the required amount of heat is 16 kJ. On the other hand, when 1 mol of methane is synthesized with hydrogen and carbon dioxide, the calorific value is 165 kJ, so dehumidification can be realized by supplying 10% of the heat to the gas purifier. Naturally, various heat exchange losses and sensible heat loss of the adsorption tower must be taken into consideration, but it is considered that the actual process is at a level where the heat balance is sufficient.
As described above, the high-temperature medium after the heat supply in the heating / desorption process of the temperature swing adsorption gas purification apparatus is additionally cooled as required by an auxiliary cooling facility (not shown) and then returned to the methane gas synthesis apparatus. can do.

The regenerative gas line is also connected to the temperature swing adsorption type gas refining apparatus, heat can be removed in the cooling / adsorption process, and heat can be released to the outside by a separately installed cooling facility.
This gas refining system will not interfere with simple control as long as constant load operation is assumed, but when operating as part of a Power to Gas system combined with a variable renewable energy power source, In order to balance the balance, it is desirable to introduce feedback control using a plurality of parameters. Possible parameters include water electrolysis device output, gas / medium pressure of each part, equipment / gas / medium temperature, various gas / medium flow rates, and the like. Examples of controlled devices include a water electrolysis device, a temperature swing adsorption gas purification device, a methane synthesis device, a heat medium pump, a gas compressor, and valves.

Next, operation control of the heat utilizing gas purification system will be described.
The entire heat-utilizing gas purification system 1 is controlled by a control unit. The control unit includes a CPU and a program executed on the CPU, a nonvolatile memory storing operation parameters, a storage unit such as a RAM serving as a work area, and the like. The control unit may be installed in the heat-utilizing gas purification system main body, or may be connected to the heat-utilizing gas purification system main body via a network or the like.
The control unit can dynamically control the output of the methane synthesizer and the temperature swing adsorption gas purifier with reference to the amount of unpurified gas, various gas pressures, and the high temperature medium temperature.

  Various data are acquired in the control unit in order to acquire state information of the heat-utilizing gas purification system. For one, the output state of the water electrolysis apparatus 100 is acquired. In addition, state information such as the pressure of each part of the gas or medium, the temperature of the gas or medium of each apparatus, or the flow rate of the gas or medium is acquired.

  Each part and each device are controlled from these state information. One of them is control of opening / closing and switching of various valves. In addition, operation control of the temperature swing adsorption type gas purification apparatuses 4 and 5, synthesis control of the methane gas synthesis apparatus 2, operation control of a medium pump, control of a gas compressor in each apparatus, and the like are executed.

Next, a heat-utilizing gas purification system 1A according to another embodiment will be described with reference to FIG.
In this embodiment, a part of hydrogen used for the reaction is temporarily stored in a hydrogen storage alloy and used for the reaction. In addition, the same code | symbol is attached | subjected about the structure similar to the said embodiment, and the description is abbreviate | omitted or simplified.
In the gas purification system of this embodiment, a hydrogen storage alloy tank 60 is added as a buffer for 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 source gas introduction path 12, and the hydrogen supply path 61 and the source gas introduction path 12 from the upstream side of the branch point Hydrogen movement into the hydrogen storage alloy tank 60 or hydrogen transfer from the hydrogen storage alloy tank 60 to the downstream side of the branch point of the source gas introduction path 12 through the hydrogen supply path 61 is possible. Further, the source gas introduction path 12 and the hydrogen supply path 61 may be selectively connected.

  The high temperature medium circulation path 50 is connected to an alloy heat medium introduction path of a hydrogen storage alloy tank, 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 open / close valve (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 the introduction of the high temperature medium into the hydrogen storage alloy tank 60 is unnecessary, the alloy heat medium introduction path is bypassed by the bypass path.

  A hydrogen storage alloy has a feature of selectively storing hydrogen in the alloy at a high density and generating heat when absorbing hydrogen and absorbing heat when releasing hydrogen. In general, since the hydrogen storage alloy can be operated at 60 ° C. or lower, the present system introduces a high-temperature medium after heat is applied to the temperature swing adsorption type gas purification device to circulate the hydrogen storage alloy tank. Is provided. While monitoring the pressure and temperature of the hydrogen storage alloy tank, it is possible to balance the hydrogen supply and demand by promoting on-off valves and pumps to promote hydrogen release. Further, the regeneration gas may be used as a medium for thermally driving the hydrogen storage alloy. When hydrogen storage is not required, the hydrogen storage alloy tank may not be supplied with hydrogen.

  As described above, the present invention has been described based on the above embodiment, but appropriate modifications to the present embodiment can be made without departing from the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Heat utilization type gas purification system 1A Heat utilization type gas purification system 2 Methane gas synthesis apparatus 3 Gas mixer 4 Temperature swing adsorption type gas purification apparatus 5 Temperature swing adsorption type gas purification apparatus 6 Heat storage tank 7 High temperature medium pump 10 Raw material gas introduction path 11 Raw material gas introduction passage 12 Raw material gas introduction passage 13 Raw material gas introduction passage 20 Regeneration gas introduction passage 21 High temperature regeneration gas introduction passage 22 Low temperature regeneration gas introduction passage 23 Regeneration gas discharge passage 24 Exhaust equipment 25 Medium switching device 26 Pump 27 Regeneration gas return Flow path 30 Production gas delivery path 31 Purified gas delivery path 40 Regeneration gas introduction path 41 High temperature regeneration gas introduction path 42 Low temperature regeneration gas introduction path 43 Regeneration gas discharge path 44 Exhaust equipment 45 Medium switching device 46 Pump 47 Regeneration gas return path 50 High-temperature medium circuit 50A High-temperature medium circuit 50B High-temperature medium circuit 52 Heat exchanger 53 Heat Exchanger 60 the hydrogen storage alloy tank 61 hydrogen supply path 100 water electrolysis device 110 carbon dioxide supplying source 200 methane utilization device

Claims (11)

A methane gas synthesizer that synthesizes methane gas using at least hydrogen and carbon dioxide as source gases;
A source gas introduction path for introducing the source gas into the methane gas synthesis device;
A product gas delivery path for delivering the product gas produced by the methane gas synthesizer;
A temperature swing adsorption type gas purification device that is provided through the source gas introduction path and / or the product gas delivery path and removes impurities in the gas;
The temperature swing adsorption gas purification device comprises a regeneration gas introduction path for introducing a high temperature regeneration gas and a low temperature regeneration gas that drive a desorption process in the temperature swing adsorption gas purification device, respectively.
A heat-utilizing gas purification system, characterized in that the heat of reaction of the methane gas synthesizer is imparted to the high-temperature regeneration gas sent through the regeneration gas introduction path.   2. The heat-utilizing gas purification system according to claim 1, further comprising a high-temperature medium circulation path that receives reaction heat of the methane gas synthesis apparatus, and heating the high-temperature regeneration gas by heat exchange in the high-temperature medium circulation path.   The heat-utilizing gas purification system according to claim 1 or 2, further comprising a medium switching device that switches supply of the high-temperature regeneration gas and the low-temperature regeneration gas to be introduced into the temperature swing adsorption gas purification device.   The heat according to any one of claims 1 to 3, wherein the temperature swing adsorption gas purification apparatus includes a plurality of adsorption towers, and each adsorption tower can be operated while shifting the timing of the operation mode. Utilization type gas purification system.   The heat-utilizing gas purification system according to claim 4, wherein adsorption and desorption can be continuously performed by a plurality of adsorption towers.   The heat-utilizing gas purification system according to any one of claims 1 to 5, further comprising a heat storage unit that stores heat applied to the high-temperature regeneration gas introduced into the temperature swing adsorption gas purification device. .   The heat-utilizing gas according to claim 6, wherein the heat storage unit adjusts the excess and deficiency by absorbing and releasing thermal energy even if there is a time lag between the high-temperature heat supply and the high-temperature heat demand. Purification system.   The hydrogen storage alloy tank which stores hydrogen gas refined with the temperature swing adsorption type gas refiner, and can supply the stored hydrogen gas to the methane gas synthesizer is provided. The heat-utilizing gas purification system according to item 1.   A medium having an alloy medium flow path for thermally driving a hydrogen storage alloy, and receiving a reaction heat of the methane gas synthesis apparatus in a medium supplied to the alloy medium flow path for releasing hydrogen gas from the hydrogen storage alloy Alternatively, the heat-utilizing gas purification system according to any one of claims 1 to 8, wherein a high-temperature regeneration gas is used.   The heat-utilizing gas purification system according to claim 9, wherein a medium supplied to the hydrogen storage alloy tank through the alloy medium flow path and discharged after heat exchange is returned to the methane gas synthesis apparatus.   It has a control part which controls operation | movement of each apparatus with reference to 1 or more of the generation amount of raw material gas, the pressure of each part, temperature, or flow volume, It is any one of Claims 1-10 characterized by the above-mentioned. Heat-utilizing gas purification system.

Images