JP7509594B2 - Solid carbon recovery type energy supply system and solid carbon recovery type energy supply method. - Google Patents

Description

The present invention relates to a solid carbon recovery type energy supply system and a solid carbon recovery type energy supply method, and in particular to a solid carbon recovery type energy supply system and a solid carbon recovery type energy supply method that use hydrocarbon fuel to generate and utilize energy such as electricity and heat, and also recover the carbon in the carbon dioxide generated as solid carbon.

When obtaining energy such as electricity or heat through combustion or electrochemical reactions using hydrocarbon fuels, carbon dioxide is generated during the reaction to obtain the energy. Since this carbon dioxide causes global warming if it is emitted into the atmosphere, there is a demand for reducing emissions through improved energy efficiency and for capturing it from exhaust gases and the atmosphere and immobilizing it by injecting it as high-pressure liquefied carbon dioxide into underground carbon dioxide storage tanks.
Conventionally, therefore, in order to prevent carbon dioxide accompanying the power generation reaction in a power generation system from being discharged to the outside, carbon dioxide gas has been separated and recovered from off-gas or exhaust gas after use (see Patent Document 1).

Patent No. 6692394 Japan Society of Energy, 4th New Energy and Hydrogen Division Symposium, New Approaches to Carbon Recycling, Presentation Material: "CO2 Resource Recovery Process Opened Up by Catalytic Reaction Engineering and Room Temperature Methanation Technology, by Choju Fukuhara, Graduate School of Integrated Science and Technology, Shizuoka University"

However, in order to fix the captured carbon dioxide gas in a carbon dioxide storage tank deep underground, the captured carbon dioxide in gas form must be compressed and liquefied, a pipeline must be laid to transport it to the carbon dioxide storage tank site, and the carbon dioxide must be further compressed at the storage tank site and injected into the tank several thousand meters underground. This poses the problem that a great deal of energy is consumed in transporting and injecting the captured carbon dioxide, and it takes a great deal of time and effort to develop the infrastructure for transportation and injection.
Furthermore, when carbon dioxide is generated as a result of the above-mentioned energy consumption and released into the atmosphere, the net amount of carbon dioxide fixed decreases, which reduces the effectiveness of this measure against global warming.

Furthermore, the location and storage capacity of the aforementioned carbon dioxide storage tanks are limited by various conditions such as the condition of the geological strata. Therefore, depending on the location of the power generation system or heat supply system, the transportation distance to the storage site may be extended, which could limit the amount of carbon dioxide that can be injected and fixed.
In order to immobilize the substance, etc., treatment such as liquefaction is required, which is time-consuming.

In addition, Non-Patent Document 2 describes the production of synthesis gas and the recovery of carbon by dry reforming of methane. However, it does not describe how carbon is recovered in an energy supply system.

The present invention has been made in consideration of the above-mentioned facts, and aims to provide a solid carbon recovery type energy supply system and a solid carbon recovery type energy supply method that can easily recover carbon dioxide as solid carbon when energy is supplied using a hydrocarbon fuel.

The solid carbon recovery type energy supply system according to claim 1 includes a reforming section having a reforming space in which a reforming catalyst is stored, and which reforms a fuel gas containing a hydrocarbon with carbon dioxide in the reforming space to produce a reformed gas containing hydrogen and carbon monoxide, a carbon deposition section provided downstream of the reforming section and which deposits solid carbon from the reformed gas sent out from the reforming section, and a gas consumption section provided downstream of the carbon deposition section and which consumes the reformed gas sent out from the carbon deposition section to obtain energy.

The solid carbon recovery type energy supply system according to claim 1 includes a reforming section and a carbon deposition section. The reforming section has a reforming space in which a reforming catalyst is housed, and reforms a fuel gas containing hydrocarbons with carbon dioxide in the reforming space to produce a reformed gas containing hydrogen and carbon monoxide. The carbon deposition section is provided downstream of the reforming section, and deposits solid carbon from the reformed gas sent out from the reforming section. In this way, by depositing solid carbon, the carbon dioxide can be easily immobilized without having to be separately immobilized.

The reformed gas sent out from the carbon deposition section is consumed in the gas consumption section located downstream of the carbon deposition section to obtain energy.

The solid carbon recovery type energy supply system according to claim 2 includes a water separation section that separates water from the used reformed gas discharged from the gas consumption section, and a gas circulation path that supplies the used reformed gas from which water has been separated in the water separation section to the reforming section.

According to the solid carbon recovery type energy supply system of claim 2, the carbon dioxide in the reformed gas after use from which water has been separated in the water separation section is supplied to the reforming section, so that the carbon dioxide is not discharged to the outside and can be used as a raw material for carbon dioxide reforming.

The solid carbon recovery type energy supply system according to claim 3 includes a carbon information output unit that is provided downstream of the carbon deposition unit and upstream of the gas consumption unit, and that measures at least one of the flow rate and pressure of the reformed gas sent from the carbon deposition unit and outputs deposited carbon information related to the amount of carbon deposited in the carbon deposition unit.

In the solid carbon recovery type energy supply system according to claim 3, the carbon information output unit can measure at least one of the flow rate and pressure of the reformed gas sent from the carbon deposition unit, thereby obtaining deposited carbon information on the amount of carbon deposited in the carbon deposition unit. Based on this deposited carbon information, the carbon deposition unit can be replaced, etc., to maintain the flow of the reformed gas. In addition, system stoppages and breakdowns due to blockage of the reformed gas flow path can be prevented.

The solid carbon recovery type energy supply system according to claim 4 includes a plurality of carbon deposition units, and a switching unit that switches the carbon deposition unit to which the reformed gas is sent from the reforming unit based on the deposited carbon information output from the carbon information output unit.

The solid carbon recovery type energy supply system according to claim 4 includes a plurality of the carbon deposition units, and switches among the plurality of carbon deposition units the carbon deposition unit to which the reformed gas is sent based on the deposited carbon information output from the carbon information output unit. This makes it possible to stop the supply of reformed gas to the carbon deposition unit with a large amount of deposited carbon and perform work such as replacement.

In the solid carbon recovery type energy supply system according to claim 5, the gas consumption section is a fuel cell stack that uses the reformed gas in a power generation reaction, and the fuel gas is supplied to the fuel electrode of the fuel cell stack.

According to the solid carbon recovery type energy supply system of claim 5, the reformed gas can be used to generate electricity in a fuel cell.

The solid carbon recovery type energy supply system according to claim 6 includes a removal section that removes at least one of hydrogen, carbon monoxide, and hydrocarbons from the fuel electrode off-gas discharged from the fuel electrode, and an off-gas circulation path that supplies the fuel electrode off-gas from which at least one of hydrogen, carbon monoxide, and hydrocarbons has been removed by the removal section to the reforming section.

According to the solid carbon recovery type energy supply system of claim 6, the carbon dioxide concentration of the anode off-gas after at least one of hydrogen, carbon monoxide, and hydrocarbons is removed in the removal section can be increased and the gas can be supplied to the reforming section.

The solid carbon recovery type energy supply system according to claim 7 includes an off-gas heat exchanger that exchanges heat between the air electrode off-gas discharged from the air electrode of the fuel cell stack and at least one of the reforming section and the carbon deposition section.

According to the solid carbon recovery type energy supply system of claim 7, the heat of the air electrode off-gas and the fuel electrode off-gas can be effectively used to heat one or both of the reforming section and the carbon deposition section.

In the solid carbon recovery type energy supply system according to claim 8, the gas consumption section has a combustion section that burns the fuel gas, and the fuel gas and oxidant gas are supplied to the combustion section.

According to the solid carbon recovery type energy supply system of claim 8, the reformed gas can be combusted and the energy produced by the combustion can be used to generate electricity and perform heat exchange.

The solid carbon capture type energy supply system according to claim 9 includes a carbon dioxide separation section that separates carbon dioxide from the combustion exhaust gas discharged from the combustion section, and a carbon dioxide circulation path that supplies the carbon dioxide separated in the carbon dioxide separation section to the reforming section.

According to the solid carbon recovery type energy supply system of claim 9, the carbon dioxide separated in the carbon dioxide separation section can be supplied to the reforming section as a raw material.

The solid carbon recovery type energy supply system according to claim 10 includes a combustion exhaust gas heat exchanger that exchanges heat between the combustion exhaust gas discharged from the combustion section and at least one of the reforming section and the carbon deposition section.

According to the solid carbon recovery type energy supply system of claim 10, the heat of the combustion exhaust gas can be effectively used to heat one or both of the reforming section and the carbon deposition section.

The solid carbon recovery type energy supply method according to claim 11 reforms a fuel gas containing hydrocarbons into carbon dioxide in a reforming space to generate a reformed gas containing hydrogen and carbon monoxide, precipitates solid carbon from the reformed gas in a carbon deposition section provided downstream of the reforming space, and consumes the reformed gas sent from the carbon deposition section in a gas consumption section provided downstream of the carbon deposition section to obtain energy.

In the solid carbon recovery type energy supply method according to claim 11, a fuel gas containing hydrocarbons is reformed into carbon dioxide in a reforming space to generate a reformed gas containing hydrogen and carbon monoxide, and solid carbon is precipitated from the reformed gas in a carbon precipitation section provided downstream of the reforming space.

In this way, by precipitating solid carbon, carbon dioxide can be easily immobilized without having to be immobilized separately.

The reformed gas sent out from the carbon deposition section is consumed in the gas consumption section located downstream of the carbon deposition section to obtain energy.

The solid carbon recovery type energy supply method according to claim 12 separates water from the used reformed gas discharged from the gas consumption section, and supplies the used reformed gas from which water has been separated to the reforming space.

According to the solid carbon recovery type energy supply method of claim 12, the carbon dioxide in the reformed gas after use from which water has been separated is supplied to the reforming space, so that the carbon dioxide is not discharged to the outside and can be used as a raw material for carbon dioxide reforming.

The solid carbon recovery type energy supply system and solid carbon recovery type energy supply method of the present invention can easily fix carbon dioxide.

1 is a schematic diagram of a fuel cell system according to a first embodiment. 1A is a schematic diagram of the inside of a reforming section and a carbon deposition section of a fuel cell system according to a first embodiment, as viewed from the side, and FIG. 1B is a cross-sectional view taken along line BB of FIG. FIG. 2 is a block diagram of a control system of the fuel cell system according to the first embodiment. 4 is a flowchart of a carbon deposition monitoring process according to the first embodiment. FIG. 11 is a schematic diagram of a fuel cell system according to a modified example of the first embodiment. FIG. 11 is a schematic diagram of a fuel cell system according to another modified example of the first embodiment. FIG. 5 is a schematic diagram of a fuel cell system according to a second embodiment. FIG. 11 is a schematic diagram of a solid carbon capture type energy supply system according to a third embodiment. FIG. 13 is a schematic diagram of a solid carbon capture type energy supply system according to a fourth embodiment.

An example of an embodiment of the present invention will be described in detail below with reference to the drawings.

First Embodiment
Fig. 1 shows a fuel cell system 10A according to a first embodiment as an example of a solid carbon recovery type energy supply system of the present invention. The fuel cell system 10A mainly comprises reforming sections 12A, 12B, carbon deposition sections 14A, 14B, a fuel cell stack 16, a condenser 20, and an exhaust heat input absorption chiller 22. It also comprises a fuel supply blower B1, an air blower B2, a circulation blower B3, a pump P1, and a cooling tower 24. Furthermore, as shown in Fig. 3, it comprises a control section 30 that controls the fuel cell system 10A.

The fuel supply blower B1 is connected to one end of the fuel supply pipe R1 and supplies fuel gas from the upstream side of the fuel supply pipe R1. The other end of the fuel supply pipe R1 is branched into two by the branch valve V1 and connected to the reforming unit 12A and the reforming unit 12B.

In this embodiment, methane is used as the raw gas, but there is no particular limitation as long as it is a hydrocarbon gas that can be reformed, and examples include natural gas, LP gas (liquefied petroleum gas), coal reformed gas, and low hydrocarbon gas. Note that the hydrocarbon gas may be a mixture of the above-mentioned low hydrocarbon gases, and the above-mentioned low hydrocarbon gas may be natural gas, city gas, LP gas, or other gas.

Biogas and digester gas can also be used as hydrocarbon gases. Since biogas and digester gas contain carbon dioxide, when carbon dioxide reforming is performed, there is no need to supply carbon dioxide separately for reforming. In addition, the carbon dioxide in the biogas and digester gas can be converted to solid carbon, making them suitable as fuel gas. Furthermore, since the carbon dioxide in biogas and digester gas originates from biomass that absorbed carbon dioxide from the atmosphere, if it is captured and fixed as solid carbon, the carbon dioxide in the atmosphere can be efficiently captured and reduced, which has a large effect on reducing carbon dioxide in the atmosphere as a measure against global warming, making them suitable as fuel gas.

Methane as fuel gas is sent to reforming unit 12A or reforming unit 12B via branch valve V1 provided in fuel supply pipe R1. In this embodiment, there are two paths for supplying fuel gas to fuel cell stack 16, with reforming unit 12A and carbon deposition unit 14A provided in one path, and reforming unit 12B and carbon deposition unit 14B provided in the other path. The supply of fuel gas to one path and the other path is switched as needed depending on the carbon deposition state.

In the reforming section 12A, methane is reformed into carbon dioxide to generate a reformed gas containing hydrogen and carbon monoxide. As shown in FIG. 2, the reforming section 12A is provided with a reforming space 12AR, which is filled with a reforming catalyst C. As the reforming catalyst C, nickel supported on alumina (Ni/Al ₂ O ₃ ), nickel supported on magnesia (Ni/MgO), nickel supported on aluminum magnesium (Ni/Al ₂ MgO _{4 )} , and mixtures thereof can be used. Reforming is carried out by the reaction of methane and carbon dioxide according to the following formula (1). The reforming section 12B has the same configuration as the reforming section 12A.

_CH4 + _CO2 → _2H2 + 2CO... (1)

The carbon deposition section 14A is a cylindrical tube body 14AK, and may be made of stainless steel, iron, or other materials. The carbon deposition section 14A is provided downstream of the reforming section 12A, and has a continuous space 14AC and a deposition space 14AR.

The continuous space 14AC is connected to the reforming space 12AR, and the reformed gas flows in from the reforming space 12AR. The inner wall 14ACW (the inner wall of the tube body 14AK) of the continuous space 14AC is flush with no irregularities, suppressing turbulence in the reformed gas. By having this continuous space 14AC, the precipitation of solid carbon on the reforming catalyst C housed in the reforming section 12A due to the influence of turbulence in the precipitation space 14AR, which will be described later, is suppressed.

The precipitation space 14AR is formed continuously downstream of the continuous space 14AC, and the reformed gas flows in from the continuous space 14AC. The precipitation space 14AR is formed continuously with the reforming space 12AR. The inner wall 14AKW of the tube body 14AK in the precipitation space 14AR is provided with ribs 14AL protruding inward from the inner wall 14AKW at multiple locations. The ribs 14AL cause turbulence in the reformed gas passing through the precipitation space 14AR. In this embodiment, four ribs are formed in the circumferential direction and at equal intervals in the longitudinal direction. The carbon deposition section 14B has the same configuration as the carbon deposition section 14A and is connected to the reforming section 12B. In the carbon deposition section 14A, solid carbon is deposited by the reactions of the following formulas (2) and (3).

The deposition space 14AR may be constructed of a flush single pipe without ribs to maintain a constant gas flow rate despite possible flow path blockage due to carbon deposition. On the other hand, when constructing a flow path system that further promotes carbon deposition, a honeycomb plate made of metal such as stainless steel or iron may be inserted into the pipe to increase the carbon deposition area within the flow path.

_CH4 → C + _2H2 ... (2)
2CO → C + 2CO ₂ ... (3)

The reforming sections 12A and 12B and the carbon deposition sections 14A and 14B are located in the high-temperature section 13. The high-temperature section 13 is partitioned by insulation or the like, and is heated by the air electrode off-gas described below, so that the inside is maintained at a high temperature.

The branch valve V1 switches the supply destination of the fuel gas from the fuel supply pipe R1 to either the reforming unit 12A or the reforming unit 12B. The branch valve V1 is connected to the control unit 30, and the switching is performed by the control unit 30.

A reformed gas pipe R2 is connected to the downstream ends of the carbon deposition units 14A and 14B. The reformed gas pipes R2 merge at a merging valve V2 and are connected to the fuel electrode 16A of the fuel cell stack 16 via the merging valve V2. The merging valve V2 is controlled in conjunction with the branching valve V1, and when fuel gas is supplied to the reforming unit 12A, the flow path on the carbon deposition unit 14A side is opened, and when fuel gas is supplied to the reforming unit 12B side, the flow path on the carbon deposition unit 14B side is opened.

The reformed gas pipes R2 connected to the carbon deposition units 14A and 14B are provided with flow meters 15A and 15B, respectively. The flow meters 15A and 15B measure the flow rates of the reformed gas sent out from the carbon deposition units 14A and 14B. The flow meters 15A and 15B are connected to the control unit 30, and the measured flow rate data is sent from the flow meters 15A and 15B to the control unit 30. Note that pressure gauges may be provided instead of the flow meters 15A and 15B.

The reforming section 12A and the carbon deposition section 14A are removable from the fuel supply pipe R1 and the reformed gas pipe R2, and can be replaced at any time.

The fuel cell stack 16 uses a solid oxide fuel cell (SOFC) and has an electrolyte layer 16C, a fuel electrode 16A, and an air electrode 16B stacked on the front and back surfaces of the electrolyte layer 16C.

One end of the fuel supply pipe R1 is connected to the fuel electrode 16A of the fuel cell stack 16, and the other end of the fuel supply pipe R1 is connected to a gas source (not shown). Fuel gas is sent from the gas source by a fuel supply blower B1. In this embodiment, methane is used as the fuel gas, but any gas that can generate hydrogen by reforming can be used, and any hydrocarbon fuel can be used. Examples of the hydrocarbon fuel include natural gas, LP gas (liquefied petroleum gas), biogas, coal reformed gas, and low-grade hydrocarbon gas. Examples of the low-grade hydrocarbon gas include low-grade hydrocarbons with 4 or less carbon atoms, such as methane, ethane, ethylene, propane, and butane, and methane used in this embodiment is preferable. The hydrocarbon fuel may be a mixture of the above-mentioned low-grade hydrocarbon gases, and the above-mentioned low-grade hydrocarbon gas may be natural gas, city gas, LP gas, or other gas. If the raw gas contains impurities, a desulfurizer or the like is required, but this is omitted in the figure.

One end of an air supply pipe R5 is connected to the air electrode 16B of the fuel cell stack 16. An air blower B2 is connected to the other end of the air supply pipe R5. The air blower B2 supplies air (oxidant gas) to the air electrode 16B. At the air electrode 16B, oxygen in the air reacts with electrons to generate oxygen ions, as shown in the following formula (4). The generated oxygen ions pass through the electrolyte layer 16C to reach the fuel electrode 16A of the fuel cell stack 16.

(Air electrode reaction)
1/2O ₂ + 2e ⁻ → O ^{2 −} … (4)

In addition, an air electrode off-gas pipe R6 that sends out air electrode off-gas from the air electrode 16B is connected to the air electrode 16B.

Meanwhile, at the fuel electrode 16A of the fuel cell stack 16, as shown in the following formulas (5) and (6), oxygen ions that have passed through the electrolyte layer 16C react with hydrogen and carbon monoxide in the fuel gas to generate water (water vapor), carbon dioxide, and electrons. The electrons generated at the fuel electrode 16A travel from the fuel electrode 16A through an external circuit (not shown) to the air electrode 16B, generating electricity in each fuel cell. In addition, each fuel cell generates heat during power generation.

(Anode reaction)
H ₂ + O ^2- → H ₂ O + 2e- ^... (5)
CO + O ^2- → CO ₂ + 2e ^- ... (6)

One end of the fuel electrode off-gas pipe R3 is connected to the fuel electrode 16A of the fuel cell stack 16, and fuel electrode off-gas is discharged from the fuel electrode 16A to the fuel electrode off-gas pipe R3. The fuel electrode off-gas contains unreacted hydrogen, unreacted carbon monoxide, carbon dioxide, water vapor, etc.

A condenser 20 is connected to the other end of the fuel electrode off-gas pipe R3. The condenser 20 condenses the water in the fuel electrode off-gas. A water discharge pipe R20 is connected to the condenser 20, and water is discharged from the water discharge pipe R20 and sent to the water tank 21. A cooling water circulation flow path 22A is piped to the condenser 20, and cooling water is circulated and supplied from the exhaust heat input type absorption chiller 22 described below to cool the fuel electrode off-gas. This condenses the water vapor in the combustion off-gas.

One end of the circulation gas pipe R4 is connected to the condenser 20, and the anode off-gas after water removal is sent to the circulation gas pipe R4. The other end of the circulation gas pipe R4 is connected to the fuel supply pipe R1 via a gas mixer GM. A circulation blower B3 is provided in the circulation gas pipe R4. The anode off-gas is sent by the circulation blower B3 toward the fuel supply pipe R1, mixed with the fuel gas in the gas mixer GM, and supplied to the reforming sections 12A and 12B.

The cathode off-gas pipe R6 branches into a high-temperature heat exchange pipe R6A and a refrigerator heat exchange pipe R6B. The high-temperature heat exchange pipe R6A is arranged so that heat exchange takes place within the high-temperature section 13. The cathode off-gas maintains the temperature of the high-temperature section 13 at approximately 500°C to 700°C, heating the reforming sections 12A, 12B and the carbon deposition sections 14A, 14B. The refrigerator heat exchange pipe R6B is connected to the exhaust heat input absorption refrigerator 22, which will be described later.

The waste heat input type absorption chiller 22 is a heat pump that uses waste heat to generate cold energy, and as an example, a steam/waste heat input type absorption chiller can be used. In a steam/waste heat input type absorption chiller, the heat of the air electrode off-gas is used to heat an absorbing liquid (e.g., an aqueous lithium bromide solution or an aqueous ammonia solution) that has absorbed water vapor, thereby separating water from the absorbing liquid and regenerating it. The air electrode off-gas that has been cooled by heating the absorbing liquid is exhausted to the outside of the waste heat input type absorption chiller 22.

The absorption liquid regenerated by heating absorbs water vapor, promoting the evaporation of water and contributing to the generation of cold energy. The waste heat input type absorption chiller 22 is connected to the cooling tower 24 via a heat dissipation circuit 24A. A pump (not shown) is installed in the heat dissipation circuit 24A, and cooling water is supplied to the heat dissipation circuit 24A by the pump. The absorption heat generated when the absorption liquid absorbs water vapor in the waste heat input type absorption chiller 22 is released to the atmosphere from the cooling tower 24 via the cooling water flowing through the heat dissipation circuit 24A.

The cold generated by the waste heat input absorption chiller 22 is sent to the condenser 20 via the cooling water flowing through the cooling water circulation flow path 22A, where the fuel electrode off-gas is cooled and the water vapor in the fuel electrode off-gas is condensed and removed, and stored in the water tank 21.

The water tank 21 is connected to the cooling water circulation path 22A, the heat dissipation circuit 24A, and a heat medium path (not shown) through which water flows as a heat medium for the waste heat input absorption chiller 22. When water is insufficient in the cooling water circulation path 22A, the heat dissipation circuit 24A, and the heat medium path, water is appropriately replenished from the water tank 21 by the pump P1.

The control unit 30 controls the entire fuel cell system 10A and includes a CPU, ROM, RAM, memory, etc. The memory stores the carbon deposition monitoring process described below, the flow rate fluctuation threshold F that is an indicator of the carbon deposition state, and data and procedures required for processing during normal operation. As shown in FIG. 3, the control unit 30 is connected to the branch valve V1, the merging valve V2, and the flow meters 15A and 15B. The branch valve V1 and the merging valve V2 are controlled by the control unit 30. Note that FIG. 3 shows some of the connections of the control unit 30 in the fuel cell system 10A, and although not shown in FIG. 3, the control unit 30 is also connected to other devices.

The flow rate fluctuation threshold F is a value that is an index of the carbon deposition state in the carbon deposition units 14A and 14B, and is the allowable change from the flow rate F0 when the amount of carbon deposition is zero, depending on the output of the fuel supply blower B1. When the change in the flow rate of the reformed gas flowing through the reformed gas pipe R2 becomes equal to or exceeds the flow rate fluctuation threshold F, it is time to replace the reforming units 12A and 12B and the carbon deposition units 14A and 14B.

Next, the operation of the fuel cell system 10A of this embodiment will be described.

In the fuel cell system 10A, fuel gas is sent from the gas source to the fuel supply pipe R1 by the fuel supply blower B1. In addition, fuel electrode off-gas, which mainly contains carbon dioxide, carbon monoxide, and hydrogen, is sent from the circulation gas pipe R4 to the fuel supply pipe R1 via the gas mixer GM.

The branch valve V1 and the merging valve V2 are controlled so that the path between the reforming unit 12A and the carbon deposition unit 14A, or the path between the reforming unit 12B and the carbon deposition unit 14B, is opened. In the reforming units 12A and 12B, the fuel gas is reformed into carbon dioxide, and the reformed gas containing hydrogen and carbon monoxide is sent to the carbon deposition units 14A and 14B.

In the carbon deposition sections 14A and 14B, the reformed gas flows into the continuous spaces 14AC and 14BC, and the reformed gas that passes through the continuous spaces 14AC and 14BC hits the ribs 14AL and 14BL in the deposition spaces 14AR and 14BR, generating turbulence. Solid carbon is deposited on the inner walls 14AKW and 14BKW of the deposition spaces 14AR and 14BR by the reactions of the above-mentioned formulas (2) and (3).

The reformed gas that has passed through the carbon deposition sections 14A and 14B is supplied to the fuel electrode 16A of the fuel cell stack 16. In the fuel cell stack 16, air from the air blower B2 is supplied to the air electrode 16B, electricity is generated by a power generation reaction, and electricity is extracted from electrical wiring (not shown).

The fuel electrode off-gas discharged from the fuel electrode 16A is sent to the condenser 20, where the water is removed by condensation, and the gas is returned to the fuel supply pipe R1. A portion of the air electrode off-gas discharged from the air electrode 16B is used for heat exchange in the high-temperature section 13, and a portion is used for heat exchange in the waste heat input absorption chiller 22.

Here, the carbon deposition monitoring process executed by the control unit 30 will be described. During operation of the fuel cell system 10A, the control unit 30 executes the carbon deposition monitoring process shown in FIG. 4.

In step S10, the flow rate measured by flow meter 15A or flow meter 15B is acquired, and in step S12, the flow rate fluctuation value F1 is calculated from the acquired flow rate. The flow rate fluctuation value F1 can be calculated as the difference between the flow rate F0 in the reformed gas pipe R2 when the amount of carbon deposition is zero and the acquired flow rate, depending on the output of the fuel supply blower B1.

In step S14, it is determined whether the flow rate fluctuation value F1 is equal to or greater than the previously recorded flow rate fluctuation threshold value F, and if the determination is positive, the process proceeds to step S16. If the determination is negative, the process waits until the flow rate fluctuation value F1 becomes equal to or greater than the flow rate fluctuation threshold value F.

In step S16, the branch valve V1 is switched, and in step S18, the merging valve V2 is switched. This switching switches the destination of the fuel gas supply. If the reforming unit 12A and the carbon deposition unit 14A were in use, they are switched to the reforming unit 12B and the carbon deposition unit 14B, and if the reforming unit 12B and the carbon deposition unit 14B were in use, they are switched to the reforming unit 12B and the carbon deposition unit 14A. This switching makes it possible to replace the reforming units 12A and 12B and the carbon deposition units 14A and 14B on the side where the supply of fuel gas has been stopped. This reduces the impact on the system due to the passage blockage, and allows for continuous supply of fuel gas and carbon recovery.

After step S18, return to step S10 and repeat the above process.

According to the fuel cell system 10A of this embodiment, solid carbon is precipitated from the reformed gas in the carbon precipitation units 14A and 14B. By precipitating solid carbon in this manner, processing can be simplified. This allows carbon dioxide generated during power generation using hydrocarbon fuel to be easily recovered as solid carbon that can be easily transported and immobilized.
In particular, in energy supply systems that use hydrocarbon fuels derived from fossil fuels, by reducing the carbon dioxide emissions generated during energy creation and recovering them as solid carbon, which is easy to fix, it will be possible to supply carbon-neutral energy that uses fossil fuels but does not release carbon dioxide into the atmosphere.

In addition, the carbon dioxide contained in the fuel electrode off-gas discharged from the fuel electrode 16A is returned to the reforming sections 12A and 12B and used for carbon dioxide reforming, so that the carbon dioxide generated by the operation of the fuel cell system 10A can be converted into solid carbon and recovered without being discharged to the outside.

In this embodiment, carbon dioxide for carbon dioxide reforming in the reforming unit 12 is supplied by returning the anode off-gas, but when biogas or digester gas is used as the fuel gas, the fuel gas contains carbon dioxide, so it is not necessarily necessary to return the anode off-gas to the reforming unit 12. In addition, carbon dioxide may be supplied to the reforming unit 12 from carbon dioxide in the atmosphere or carbon dioxide contained in exhaust gas from factories.
By mixing the carbon dioxide contained in biogas and the carbon dioxide contained in the atmosphere and capturing and fixing some of it as solid carbon, it is possible to capture and reduce the carbon dioxide that has accumulated in the atmosphere.

In this embodiment, the fuel electrode off-gas is supplied to the reforming units 12A and 12B after removing only the water from it while leaving unreacted carbon monoxide and hydrogen. However, as shown in FIG. 5, an oxidation unit 18 may be provided downstream of the fuel cell stack 16. The oxidation unit 18 is provided with an oxygen permeable membrane 18C that separates the fuel electrode flow path 18A from the air electrode flow path 18B, and transfers oxygen from the air electrode flow path 18B to the fuel electrode flow path 18A. As a result, hydrogen, carbon monoxide, etc. in the fuel electrode off-gas are removed by oxidation reaction as shown in equations (7) and (8).

_2H2 + _O2 → _2H2O … (7)
2CO+ _O2 → _2CO2 … (8)

Also, as shown in FIG. 6, a hydrogen removal section 19 may be provided downstream of the fuel cell stack 16. The hydrogen removal section 19 has a hydrogen permeable membrane 19C that separates the fuel electrode flow path 19A from the air electrode flow path 19B, and moves hydrogen from the fuel electrode flow path 19A to the air electrode flow path 19B. This makes it possible to remove hydrogen from the fuel electrode off-gas.

In addition, this embodiment has multiple reforming units 12A, 12B and carbon deposition units 14A, 14B, and the supply destination of the fuel gas is switched by the carbon deposition monitoring process. Therefore, the reforming units 12A, 12B and carbon deposition units 14A, 14B on the side where the supply of fuel gas has been stopped can be easily replaced without shutting down the fuel cell system 10A.

In addition, in this embodiment, the cathode off-gas is used to maintain the temperature of the high temperature section 13 and to heat the reforming sections 12A, 12B and the carbon deposition sections 14A, 14B, so that thermal energy can be effectively utilized. Furthermore, the cathode off-gas is used for heat exchange when generating cold energy in the exhaust heat input type absorption chiller 22, so that thermal energy can be effectively utilized.

[Second embodiment]
Next, a second embodiment of the present invention will be described. In this embodiment, the same parts as those in the first embodiment are given the same reference numerals, and detailed description thereof will be omitted.

In the fuel cell system 10B of this embodiment, as shown in FIG. 7, a fuel cell stack 17 of a proton ion conductive solid oxide fuel cell (PCFC: Proton Ceramic Solid Oxide Fuel Cell) is used instead of the fuel cell stack 16. The fuel cell stack 17 has a fuel electrode 17A, an air electrode 17B, and an electrolyte layer 17C.

Between the junction valve V2 and the fuel electrode 17A, a water vapor supply pipe R7B is connected, and water vapor is supplied to the fuel electrode 17A. The water vapor supply pipe R7B is connected to the vaporizer 28. Water is supplied to the vaporizer 28 from the water tank 21. The supplied water (liquid phase) is heated and vaporized in the vaporizer 28 by the fuel electrode off-gas flowing through the fuel electrode off-gas pipe R3.

At the fuel electrode 17A, the unreformed fuel gas in the reformer 12A is steam reformed to produce hydrogen and carbon monoxide, as shown in the following formula (9). In addition, the carbon monoxide produced undergoes a shift reaction with water to produce carbon dioxide and hydrogen, as shown in the following formula (10).

_CH4 + _H2O → _3H2 + CO ... (9)
CO + H ₂ O → CO ₂ + H ₂ ... (10)

Then, at the fuel electrode 17A, the hydrogen is separated into hydrogen ions and electrons, as shown in the following formula (11).

(Anode reaction)
H ₂ →2H ⁺ +2e ⁻ … (11)

The hydrogen ions move through the electrolyte layer 17C to the air electrode 17B. The electrons move through an external circuit (not shown) to the air electrode 17B. This generates electricity in the fuel cell stack 17. During power generation, the fuel cell stack 17 generates heat.

At the air electrode 17B, as shown in the following formula (12), hydrogen ions that have moved from the fuel electrode 17A through the electrolyte layer 17C and electrons that have moved from the fuel electrode 16A through the external circuit react with oxygen in the air to generate water vapor.

(Air electrode reaction)
2H ⁺ +2e ⁻ +1/2O ₂ →H ₂ O ... (12)

In the fuel cell system 10B of this embodiment, as in the first embodiment, the carbon deposition units 14A and 14B deposit solid carbon from the reformed gas, so that carbon dioxide can be easily processed. This allows carbon dioxide generated during power generation using hydrocarbon fuel to be easily recovered as solid carbon that can be easily transported and immobilized.

[Third embodiment]
Next, a third embodiment of the present invention will be described. In this embodiment, the same parts as those in the first and second embodiments are given the same reference numerals, and detailed description thereof will be omitted.

In this embodiment, we will explain an energy supply system 10C that generates electricity using energy obtained by burning fuel as a gas consumption device. A gas engine or a gas turbine generator can be used, but in this embodiment, we will explain using a gas engine as an example.

In this embodiment, the same fuel gas as in the first embodiment can be used.

As shown in FIG. 8, the downstream end of the reformed gas pipe R2 and the downstream end of the air supply pipe R5 are connected to the gas engine 40. Reformed gas is supplied from the reformed gas pipe R2 to a fuel chamber (not shown) of the gas engine 40, and air is supplied from the air supply pipe R5 to a combustion chamber of the gas engine 40. The reformed gas is combusted in the combustion chamber by the air.

A combustion exhaust gas pipe R8 is connected to the gas engine 40, and the combustion exhaust gas is sent from the combustion chamber to the combustion exhaust gas pipe R8. The combustion exhaust gas pipe R8 branches into a high-temperature section heat exchange pipe R8A and a refrigerator heat exchange pipe R8B. The high-temperature section heat exchange pipe R8A is arranged so that heat exchange takes place within the high-temperature section 13. The combustion exhaust gas maintains the temperature of the high-temperature section 13 at approximately 500°C to 700°C, and heats the reforming sections 12A, 12B and the carbon deposition sections 14A, 14B.

The chiller heat exchange pipe R8B is connected to the exhaust heat input type absorption chiller 22. The combustion exhaust gas is cooled by heat exchange in the exhaust heat input type absorption chiller 22 and sent to the condenser 20 for further cooling. This removes the water vapor in the combustion exhaust gas.

One end of the circulation gas pipe R10A is connected to the condenser 20, and the other end of the circulation gas pipe R10A is connected to the carbon dioxide separation section 31. The carbon dioxide separation section 31 has a non-permeation section 32 and a permeation section 34 separated by a carbon dioxide separation membrane 33. The carbon dioxide separation membrane 33 is formed of a membrane that selectively allows carbon dioxide to permeate. The circulation gas pipe R10A is connected to the non-permeation section 32, and the combustion exhaust gas after moisture has been removed by the condenser 20 is supplied to the non-permeation section 32 of the carbon dioxide separation section 31. The carbon dioxide in the combustion exhaust gas supplied to the non-permeation section 32 permeates the carbon dioxide separation membrane 33 and moves to the permeation section 34. The combustion exhaust gas components remaining in the non-permeation section 32 are discharged from the exhaust gas pipe R11.

One end of the circulation gas pipe R10B is connected to the permeation section 34 of the carbon dioxide separation section 31, and the other end of the circulation gas pipe R10B is connected to the fuel supply pipe R1 via a gas mixer GM. A circulation blower B3 is provided in the circulation gas pipe R10B. The carbon dioxide separated in the carbon dioxide separation section 31 is sent by the circulation blower B3 toward the fuel supply pipe R1, mixed with the fuel gas in the gas mixer GM, and supplied to the reforming sections 12A and 12B.

In the energy supply system 10C of this embodiment, solid carbon is also precipitated from the reformed gas in the carbon precipitation units 14A and 14B. In this way, by precipitating solid carbon, processing can be simplified. This allows carbon dioxide generated during power generation using hydrocarbon fuels to be easily recovered as solid carbon that can be easily transported and immobilized.

In addition, the carbon dioxide contained in the combustion exhaust gas discharged from the gas engine 40 is returned to the reforming sections 12A and 12B and used for carbon dioxide reforming, so that the carbon dioxide generated by the operation of the energy supply system 10C can be converted into solid carbon and recovered without being discharged to the outside.

[Fourth embodiment]
Next, a third embodiment of the present invention will be described. In this embodiment, the same parts as those in the first to third embodiments are given the same reference numerals, and detailed description thereof will be omitted.

In this embodiment, an energy supply system 10D is described that uses thermal energy obtained by burning fuel as a gas consumption device. A gas water heater or a gas boiler can be used, but in this embodiment, a gas water heater is used as an example.

In this embodiment, the same fuel gas as in the first embodiment can be used.

As shown in FIG. 9, the downstream end of the reformed gas pipe R2 and the downstream end of the air supply pipe R5 are connected to the gas water heater 44. Reformed gas is supplied from the reformed gas pipe R2 to a fuel chamber (not shown) of the gas water heater 44, and air is supplied from the air supply pipe R5 to a combustion chamber of the gas water heater 44. The reformed gas is combusted in the combustion chamber by the air.

The gas water heater 44 is provided with heat exchange piping 46, and water is supplied to the heat exchange piping 46. The heat exchange piping 46 is arranged so that the water flowing inside is heated by the heat of combustion in the combustion chamber.

A combustion exhaust gas pipe R8 is connected to the gas water heater 44, and the combustion exhaust gas is sent from the combustion chamber to the combustion exhaust gas pipe R8.

In the energy supply system 10D of this embodiment, solid carbon is also precipitated from the reformed gas in the carbon precipitation units 14A and 14B. In this way, by precipitating solid carbon, processing can be simplified. This allows carbon dioxide generated during power generation using hydrocarbon fuel to be easily recovered as solid carbon that can be easily transported and immobilized.

In addition, the carbon dioxide contained in the combustion exhaust gas discharged from the gas water heater 44 is returned to the reforming sections 12A and 12B and used for carbon dioxide reforming, so that the carbon dioxide generated by the operation of the energy supply system 10C can be converted into solid carbon and recovered without being discharged to the outside.

In the first to fourth embodiments described above, ribs 14AL are provided on the inner wall 14AKW of the tube 14AK in the deposition space 14AR of the carbon deposition sections 14A and 14B to promote carbon deposition, but the ribs 14AL are not necessarily required. Instead of the ribs 14AL, the surface of the inner wall 14AKW may be roughened or fine irregularities may be formed.

In addition, in the first to fourth embodiments described above, the carbon dioxide contained in the gas discharged from each gas consuming device (fuel cell stack 16, gas engine 40, gas water heater 44) was used for carbon dioxide reforming in reforming units 12A and 12B, but other carbon dioxide may also be used.

In addition, in the first to fourth embodiments described above, two sets of reforming units 12A, 12B and carbon deposition units 14A, 14B are installed, but three or more sets may be installed, or just one set may be installed. By providing two or more sets, it is possible to replace the carbon deposition units 14A, 14B without stopping the supply of fuel gas.

In addition, in the first to fourth embodiments described above, cold energy is generated using the exhaust heat input type absorption chiller 22. However, cold energy may be generated using a heat pump that utilizes other exhaust heat instead of the exhaust heat input type absorption chiller 22, for example, an adsorption chiller.
Furthermore, when removing moisture (dehumidifying) from the exhaust gas using exhaust heat, a desiccant air conditioner that uses exhaust heat may be used to remove excess moisture from the gas.

10A, 10B Fuel cell system (solid carbon recovery type energy supply system)
10C, 10D Energy supply system 12A, 12B Reforming section 12AR, 12BR Reforming space C Reforming catalyst 13 High temperature section (off gas heat exchange section, combustion exhaust gas heat exchange section)
14A, 14B Carbon deposition unit 15A, 15B Flow meter (carbon information output unit)
16, 17 Fuel cell stack (gas consumption section)
16A, 17A fuel electrodes 16B, 17B air electrodes 18 oxidation section (removal section)
19 Hydrogen removal section (removal section)
20 Condenser (water separation section)
31 Carbon dioxide separation unit 30 Control unit (switching unit)
40 Gas engine (gas consumption part)
44 Gas water heater (gas consumption part)
R4 Circulating gas pipe (off-gas circulation path)
R10B Circulating gas pipe (carbon dioxide circulation path)
V1 Branch valve (switching part)
V2 Confluence valve (switching part)

Claims (13)

a reforming section having a reforming space in which a reforming catalyst is housed, and which reforms a fuel gas containing a hydrocarbon with carbon dioxide in the reforming space to generate a reformed gas containing hydrogen and carbon monoxide;
a carbon deposition section provided downstream of the reforming section and configured to deposit solid carbon from the reformed gas discharged from the reforming section;
a gas consumption section provided downstream of the carbon deposition section and configured to consume the reformed gas delivered from the carbon deposition section to obtain energy;
and recovering the solid carbon precipitated in the carbon precipitater.
Solid carbon capture energy supply system. a water separation unit that separates water from the used reformed gas discharged from the gas consumption unit;
a gas circulation path that supplies the used reformed gas from which water has been separated in the water separation section to the reforming section;
The solid carbon recovery type energy supply system according to claim 1 , comprising: a carbon information output unit that is provided downstream of the carbon deposition unit and upstream of the gas consumption unit, and that measures at least one of a flow rate and a pressure of the reformed gas sent out from the carbon deposition unit and outputs deposited carbon information regarding an amount of carbon deposited in the carbon deposition unit;
The solid carbon recovery type energy supply system according to claim 1 or 2, comprising: A plurality of the carbon deposit portions;
a switching unit that switches the carbon deposition unit to which the reformed gas is sent from the reforming unit among the plurality of carbon deposition units based on the deposited carbon information output from the carbon information output unit;
The solid carbon recovery energy supply system according to claim 3 , comprising: the gas consumption unit is a fuel cell stack that uses the reformed gas in a power generation reaction, and the fuel gas is supplied to an anode of the fuel cell stack.
The solid carbon recovery type energy supply system according to any one of claims 1 to 4. a removal unit that removes at least one of hydrogen, carbon monoxide, and hydrocarbons from the anode off-gas discharged from the anode;
an off-gas circulation path that supplies the anode off-gas from which at least one of hydrogen, carbon monoxide, and hydrocarbons has been removed in the removal section to the reforming section;
The solid carbon recovery energy supply system according to claim 5 , comprising: an off-gas heat exchange section that exchanges heat between the air electrode off-gas discharged from the air electrode of the fuel cell stack and at least one of the reforming section and the carbon deposition section;
The solid carbon recovery type energy supply system according to claim 5 or 6, comprising: The gas consumption unit has a combustion unit that combusts the fuel gas,
The solid carbon recovery type energy supply system according to any one of claims 1 to 4, wherein the fuel gas and the oxidant gas are supplied to the combustion section. A carbon dioxide separation unit that separates carbon dioxide from the combustion exhaust gas discharged from the combustion unit;
a carbon dioxide circulation path that supplies the carbon dioxide separated in the carbon dioxide separation section to the reforming section;
The solid carbon recovery energy supply system according to claim 8, comprising: a combustion exhaust gas heat exchanger that exchanges heat between the combustion exhaust gas discharged from the combustion section and at least one of the reforming section and the carbon deposition section;
The solid carbon recovery type energy supply system according to claim 8 or claim 9, comprising: A fuel gas containing a hydrocarbon is reformed into carbon dioxide in a reforming space to generate a reformed gas containing hydrogen and carbon monoxide;
solid carbon is precipitated from the reformed gas in a carbon precipitation section provided downstream of the reforming space;
a gas consumption section provided downstream of the carbon deposition section, which consumes the reformed gas delivered from the carbon deposition section to obtain energy;
Recovering the solid carbon precipitated in the carbon precipitater.
Solid carbon capture energy supply method. Separating water from the used reformed gas discharged from the gas consumption section;
supplying the used reformed gas from which water has been separated to the reforming space;
The solid carbon recovery type energy supply method according to claim 11. The carbon deposition portion is formed to include a rib that generates a turbulent flow.
A solid carbon recovery type energy supply system according to any one of claims 1 to 10.