JP2023112984A - Fuel synthesizing system - Google Patents

Abstract

To provide a fuel synthesizing system that, when power stop or shortage has occurred, can prevent the system from stopping by quickly compensating for the power shortage, or can stop the system safely.SOLUTION: A fuel synthesizing system comprises: supply means 11, 12 for supplying carbon dioxide and hydrogen respectively that are disposed upstream in a main passage; a catalyst reactor 6 for synthesizing fuel using a fuel synthesizing catalyst that is disposed downstream of the supply means; first power supply means for performing power supply using renewable energy at the normal time; second power supply means 14 for performing power supply using a fuel battery; and power measurement means for measuring the supplied power. The fuel synthesizing system comprises power control means that, when the power supplied by the first power supply means is reduced, supplies hydrogen to the second power supply means 14 using the means 12 for supplying hydrogen to generate power and makes the fuel synthesizing system operate by power supply by the second power supply means 14.SELECTED DRAWING: Figure 3

Description

The present invention relates to a fuel synthesizing system capable of coping with power outages and power shortages.

In order to reduce the negative impact on the global environment, we collect carbon dioxide from the exhaust gas of automobiles, etc., and then synthesize fuel such as methanol from carbon dioxide using renewable energy. technology is being considered.

When operating a system that synthesizes fuel using carbon dioxide as a raw material gas, if the power of the solar power generation device is used as renewable energy, power generation will stop after sunset, and during the daytime in bad weather. Even if there is, it is assumed that power generation will stop or run short.

For example, if the power supply is interrupted while a methanol synthesis system is in operation, the purity of the methanol being synthesized may drop, or the residual methanol gas in the pipes may cause some kind of abnormal situation. There is concern that it will occur. Methanol is a class 4 alcohol that is flammable and toxic.

An emergency stop system that causes an emergency stop of the system each time the power supply is stopped cannot stably and continuously operate a system that synthesizes methanol using carbon dioxide as a raw material. Therefore, there has been a demand for a system that can solve the above problems without relying on the emergency stop system.

As methods related to system shutdown, for example, Patent Literature 1 and Patent Literature 2 disclose methods for stopping the supply of fuel and oxidant, or using inert A method for supplying gas, etc. is disclosed.

Japanese Patent No. 5264040 Japanese Patent No. 6138378

The present invention has been made in view of the circumstances as described above. SUMMARY OF THE INVENTION It is an object of the present invention to provide a fuel synthesizing system that can quickly make up for the power shortage or prevent the system from stopping or can safely stop the system when power stops or runs short. do.

The inventors of the present invention have completed a system that can continue to operate even when electric power is stopped or when electric power is insufficient, by utilizing a fuel cell in a fuel synthesizing system. Also, the present inventors have completed a system that can be stopped without using external energy or external resources by using by-product gas generated from the fuel synthesis system. That is, the present invention has the following configurations.

(1) The fuel synthesis system of the present invention uses a supply means for supplying carbon dioxide and a supply means for supplying hydrogen, which are arranged upstream of the main passage, and a fuel synthesis catalyst, which is arranged downstream of the supply means. a catalytic reactor for synthesizing fuel using renewable energy; a first power supply means for normally supplying power using renewable energy; a second power supply means for supplying power by a fuel cell; wherein, when the power supplied by the first power supply means is reduced, the supply means for supplying hydrogen supplies hydrogen to the second power supply means to generate power, It is characterized by comprising power control means for operating the fuel synthesizing system by power supply from the second power supply means.

(2) In the fuel synthesizing system of the present invention, it is preferable that the first power supply means is a solar power generation device.

(3) The fuel synthesizing system of the present invention includes detection means for detecting whether or not the power supplied by the first power supply means has been restored, and exhaust gas bypassed from the main passage downstream of the catalytic reactor and exhausted. A passage and a control valve installed in the exhaust passage, wherein the control valve is opened when the detection means does not detect the return of the supplied power after the second power supply means supplies power. The valve is characterized by exhausting the fuel in the main passage.

(4) The fuel synthesizing system of the present invention includes inert gas separation means disposed downstream of the catalytic reactor, a reflux passage for refluxing from the inert gas separation means upstream of the catalytic reactor, and an inert gas storage tank arranged downstream of the inert gas separation means; an inert gas recirculation passage introduced from the inert gas storage tank into the recirculation passage; and installed in the inert gas recirculation passage. A second control valve is provided, and when the detection means does not detect the return of the supplied power after the power is supplied by the second power supply means, the control valve is opened and the fuel in the main passage is discharged. is exhausted and the second control valve is opened to recirculate the inert gas upstream of the main passage.

INDUSTRIAL APPLICABILITY The fuel synthesizing system of the present invention is capable of quickly compensating for the shortage of electric power, preventing the system from stopping, or safely stopping the system when the electric power stops or becomes insufficient.

1 is a schematic diagram of a configuration of a conventional fuel synthesizing system; FIG. 1 is a process flow diagram for a conventional fuel synthesizing system during sunset or severe weather; FIG. 1 is a schematic diagram of a configuration of a fuel synthesizing system according to an embodiment; FIG. FIG. 4 is a flow diagram of the process of the fuel synthesizing system of the present embodiment at sunset or sudden bad weather.

Hereinafter, embodiments of the present invention will be described in detail.

As an environmental measure, various attempts have been made to convert carbon dioxide recovered from exhaust gas or the atmosphere into other useful compounds for effective utilization.

There is known a technique for synthesizing a fuel such as methanol by mixing carbon dioxide and hydrogen and passing the mixture through a reactor having a catalyst. For example, there are the following synthesis techniques. After the carbon dioxide (CO ₂ ) in the exhaust gas discharged from the internal combustion engine is once adsorbed by the adsorbent, the carbon dioxide is desorbed. The desorbed carbon dioxide is mixed with separately supplied hydrogen, pressurized by a compressor, and then put into a catalytic reactor having a catalyst. Fuel can be extracted from the fluid that has passed through the catalytic reactor by gas-liquid separation.

(conventional fuel synthesis system)
A conventional fuel synthesis system synthesizes fuel using a supply means for supplying carbon dioxide and a supply means for supplying hydrogen, which are arranged upstream of the main passage, and a fuel synthesis catalyst, which is arranged downstream of the supply means. and a power supply means for supplying power using renewable energy.

The supply means for supplying carbon dioxide is, for example, a tank storing carbon dioxide. Carbon dioxide stored in a tank or the like is, for example, as described above, a recovery method in which the carbon dioxide in the exhaust gas emitted from the internal combustion engine is once adsorbed by the adsorbent and then the carbon dioxide is desorbed. can be obtained by Internal combustion engines include gasoline engines and diesel engines for automobiles and the like. Carbon dioxide in exhaust gas discharged from an internal combustion engine of an automobile or the like is recovered by the carbon dioxide recovery device described above and then stored in a recovered gas storage tank or the like.

The supply means for supplying hydrogen is, for example, a water electrolysis device or the like. Hydrogen gas generated by electrolyzing water using electric power can be temporarily stored in a hydrogen storage tank and supplied as needed. Oxygen is generated at the same time as hydrogen by the electrolysis of water. Similarly, oxygen can be temporarily stored in an oxygen storage tank and supplied as needed.

A fuel synthesis catalyst that synthesizes fuel is, for example, a catalyst that synthesizes methanol and water from carbon dioxide and hydrogen. Methods for synthesizing methanol and water from carbon dioxide and hydrogen are already widely known. The reaction formula is the following formula (1). Further, as a reaction via carbon monoxide, methanol may be synthesized via the following formulas (2) and (3).
_CO2 + _3H2- > _CH3OH + _H2O (1)
_CO2 + _H2- >CO+ _H2O (2)
CO+2H ₂ →CH ₃ OH (3)
A catalytic reactor for synthesizing a fuel using a fuel synthesis catalyst has the above fuel synthesis catalyst inside. Since the above reaction proceeds at high temperature, the catalytic reactor must be heated to a high temperature by an external heater or the like.

A photovoltaic power generation device is a typical example of power supply means that supplies power using renewable energy. Power can be supplied by installing solar cells (solar panels). As ancillary equipment, rechargeable batteries and power controllers are installed as necessary. In the case of automobiles, solar cells are installed on top of the vehicle body. The power supplied by the power supply means makes it possible to operate the water electrolysis device, the heater outside the catalytic reactor, various control devices, and the like.

FIG. 1 is a schematic diagram of the configuration of a conventional fuel synthesizing system.
It is intended for use in automobiles. The main passage of the conventional fuel synthesis system includes, from upstream to downstream, an onboard tank 1 for carbon dioxide and nitrogen, a recovered gas storage tank 2, a primary storage tank 3, a booster 4, a secondary storage tank 5, a catalyst A reactor 6, a gas-liquid separator 7, and a nitrogen separator 8 are installed. Separately from the main passage, a water electrolysis device 10, a hydrogen storage tank 12, and an oxygen storage tank 11 are installed as supply means for supplying hydrogen. Moreover, there is a photovoltaic power generation device (not shown) as a power supply means.

Water is electrolyzed by the water electrolysis device 10 using the power supplied by the solar power generation device to produce hydrogen and oxygen. After being temporarily stored in the hydrogen storage tank 12, the hydrogen is put into the primary storage tank 3 as a raw material for the fuel synthesis reaction. Oxygen is temporarily stored in the oxygen storage tank 11 and then released to the outside as appropriate.

After carbon dioxide is recovered from the exhaust gas by a carbon dioxide recovery device (not shown), the carbon dioxide is temporarily stored in the vehicle-mounted tank 1 for carbon dioxide and nitrogen, and then put into the recovered gas storage tank 2 . After that, the carbon dioxide and nitrogen stored in the recovered gas storage tank 2 are put into the primary storage tank 3 . A mixed gas of carbon dioxide, nitrogen and hydrogen introduced into the primary storage tank 3 is compressed to a high pressure by the booster 4 . After that, it is temporarily stored in the secondary storage tank 5 and then put into the catalytic reactor 6 .

The catalytic reactor 6 is heated to a high temperature by a heater using power supplied by the photovoltaic generator. Methanol and water synthesized at a high temperature in the catalytic reactor 6 are discharged from the catalytic reactor 6 as gases together with unreacted carbon dioxide, hydrogen and nitrogen. The discharged mixed gas of methanol, water, carbon dioxide, hydrogen and nitrogen is cooled in the gas-liquid separator 7 to separate methanol and water as liquids and carbon dioxide, hydrogen and nitrogen as gases. The mixed liquid of methanol and water is then dehydrated in the dehydrator 9 to obtain methanol. Water is appropriately discharged to the outside. On the other hand, nitrogen is separated from the mixed gas of carbon dioxide, hydrogen and nitrogen by the nitrogen separation device 8, and the nitrogen is then appropriately released to the outside. The separated carbon dioxide and hydrogen are recirculated to the primary storage tank 3 via the recirculation passage 13 as unreacted raw materials.

FIG. 2 is a process flow diagram for a conventional fuel synthesis system during sunset or severe weather.
The photovoltaic power generation device normally stops generating power at sunset. Also, in case of sudden bad weather, the power generation will be stopped urgently. As a result, the power supplied to the fuel synthesizing system is reduced. Since power cannot be supplied to boosters, heaters, coolers, etc., the drive of these devices gradually declines. Due to the decrease in pressure and temperature, the accuracy of synthesizing methanol in the fuel synthesizing system decreases, and the purity of recovered methanol decreases.
After that, if the sunshine does not return or it takes time to recover the sunshine, the device stops. As a result, methanol or the like will remain in the pipes of the apparatus, causing a problem with the safety of the apparatus. On the other hand, when the weather improves and the sunshine returns, the power supply will be restored and the fuel synthesis system will resume operation.

Thus, conventional fuel synthesizing systems are difficult to operate stably and continuously, and the purity and yield of the produced methanol may decrease, which poses a safety problem. .

(Fuel synthesizing system of this embodiment)
The fuel synthesizing system of this embodiment includes a supply means for supplying carbon dioxide and a supply means for supplying hydrogen, which are arranged upstream of the main passage, and a fuel synthesis catalyst, which is arranged downstream of the supply means, to produce fuel by using a fuel synthesis catalyst. a catalytic reactor for synthesizing, a first power supply means for normally supplying power by renewable energy, a second power supply means for supplying power by a fuel cell, and a power measuring means for measuring the power supplied It has

The supply means for supplying carbon dioxide, the supply means for supplying hydrogen, and the catalytic reactor for synthesizing fuel using the fuel synthesis catalyst are as described above. The first power supply means that normally supplies power using renewable energy is the same as the above-described power supply means that supplies power using renewable energy, and a representative means is a solar power generation device.

A fuel cell as a second power supply means for supplying power by a fuel cell is a power generator capable of supplying power using hydrogen and oxygen as fuel. Power can be supplied complementarily when the photovoltaic power generation device cannot supply power.

A power measuring means (not shown) for measuring the supplied power detects when the power supply from the photovoltaic power generation device, which is the first power supply means, stops or decreases at sunset, sudden bad weather, or the like. A device, usually a wattmeter, that can detect when a

In the fuel synthesizing system of the present embodiment, when the power supplied by the first power supply means is lowered, the supply means for supplying hydrogen supplies hydrogen to the second power supply means to generate power, A power control means (not shown) is provided for operating the fuel synthesizing system by power supply from the power supply means. The power control means switches the hydrogen supply passage to supply hydrogen to the second power supply when the power supplied by the first power supply means measured by the power measurement means becomes equal to or less than a predetermined value set in advance. means to operate the second power supply means to supply power and continue to operate the fuel synthesis system.

Therefore, during normal times when power generation by renewable energy such as a solar power generation device is possible, electric power is supplied by renewable energy, and fuel synthesis can be performed without emitting carbon dioxide. In addition, when it becomes difficult to generate electricity using renewable energy, hydrogen, which is supplied as a raw material for fuel synthesis, is supplied to the fuel cell to generate electricity, and to cover the power required for the fuel synthesis system. It is possible to maximize the fuel synthesis by

FIG. 3 is a schematic diagram of the configuration of the fuel synthesizing system of this embodiment.
It is intended for use in automobiles. In the main passage of the fuel synthesizing system of this embodiment, as in the conventional fuel synthesizing system, there are, from upstream to downstream, a vehicle-mounted tank 1 for carbon dioxide and nitrogen, a recovered gas storage tank 2, a primary storage tank 3, A booster 4, a secondary storage tank 5, a catalytic reactor 6, a gas-liquid separator 7, and a nitrogen separator 8 are installed. Separately from the main passage, a water electrolysis device 10, a hydrogen storage tank 12, and an oxygen storage tank 11 are installed as means for supplying hydrogen. In addition, a solar power generation device (not shown) and a fuel cell 14 are provided as power supply means.

The parts that differ from the schematic diagram of the configuration of the conventional fuel synthesizing system shown in FIG. 1 will be described below.
Water is electrolyzed by the water electrolyzer 10 to produce hydrogen and oxygen. After the hydrogen is temporarily stored in the hydrogen storage tank 12, it is supplied to the primary storage tank 3 by the switching device 16 during normal operation (OFF). However, when the fuel cell 14 is operated, the switching device 16 is switched ON and hydrogen is supplied to the fuel cell 14 . Oxygen is temporarily stored in the oxygen storage tank 11 and then released to the outside by the switching device 15 during normal operation (OFF). However, when the fuel cell 14 is operated, the switching device 15 is switched ON and oxygen is supplied to the fuel cell 14 . The operation of these fuel cells and the control of the switching device 15 and the switching device 16 are performed by power control means (not shown).

The fuel synthesizing system of the present embodiment further includes detection means (not shown) for detecting whether or not the power supplied by the power supply means has been restored, bypassing the main passage downstream of the catalytic reactor 6, and exhausting An exhaust passage 20 and a control valve 18 installed in the exhaust passage 20 are provided.

After the power supply by the second power supply means, if the detection means does not detect the return of the supplied power even after a predetermined time has passed, the control valve 18 is opened and the downstream of the catalytic reactor 6 is opened. The fuel in the main passage of the can be exhausted to the outside.

Although fuel synthesis continues temporarily by the power supply from the fuel cell 14, if the power does not return after a certain period of time has passed, flammable synthetic fuel remains in the system and an abnormal situation occurs. There is concern that it will occur. Therefore, by forcibly discharging the fuel in the main passage to the outside, the system can be maintained in a safe state.

The fuel synthesizing system of the present embodiment further includes an inert gas separation means disposed downstream of the catalytic reactor 6, a reflux passage 13 that flows back from the inert gas separation means to the upstream of the catalytic reactor 6, and inert gas. an inert gas storage tank disposed downstream of the active gas separation means; an inert gas recirculation passage 21 introduced from the inert gas storage tank into the recirculation passage 13; A valve 19 is provided. If the detection means (not shown) does not detect the return of the supplied power even after a predetermined time has elapsed after the second power supply means supplies power, the control valve 18 is opened to restore the power supply to the main passage. While exhausting the fuel, the second control valve 19 can be opened to recirculate the inert gas upstream of the main passage. Here, in FIG. 3, the nitrogen separator 8 corresponds to the inert gas separating means, and the nitrogen storage tank 17 corresponds to the inert gas storage tank. The inert gas is not particularly limited, but nitrogen is preferred because it is the most readily available.

When the fuel is discharged from the main passage, the fuel in the main passage downstream of the catalytic reactor 6 can be discharged to the outside by opening the control valve 18 . However, the inert gas (nitrogen) stored in the inert gas storage tank is used as the sweep gas, and passes through the inert gas recirculation passage 21 and the recirculation passage 13 from the primary storage tank 3 to the gas-liquid separation device 7. By flowing it into the main passage and replacing the inside with an inert gas, the system can be brought to a safe state more thoroughly. Also, the pressure in the inert gas storage tank allows the interior of the main passage to be evacuated early and in a short period of time.

FIG. 4 is a flow diagram of the process of the fuel synthesizing system of this embodiment at sunset or sudden bad weather.
The photovoltaic power generation device normally stops generating power at sunset. Also, in case of sudden bad weather, the power generation will be stopped urgently. As a result, the power supplied to the fuel synthesizing system is reduced. When the degree of decrease in power supply falls below a certain level, the power control means detects it and turns on the switching devices 15 and 16 to switch the power supply to the second power supply means, and hydrogen and oxygen are supplied to the fuel cell. 14, and the fuel cell 14 operates. As a result, power is supplied to the booster, heater, cooler, etc., and the fuel synthesis system can continue to operate.

After that, if the detection means does not detect the restoration of the power supply from the photovoltaic power generation device even after a predetermined period of time has passed due to reasons such as the weather not recovering, the control valve 18 is turned ON, and the control valve 18 is closed. The valve is opened to exhaust the methanol in the main passage. Further, the second control valve 19 is turned ON, the second control valve 19 is opened, nitrogen is purged into the main passage, and methanol is exhausted.
Normal methanol is then recovered and the fuel synthesis system shuts down. The control valve 18 and the second control valve 19 are turned off and closed.

When the weather improves and a predetermined period of time elapses, the detection means detects that the power supply from the photovoltaic power generation device is restored. The switching devices 15 and 16 are turned off, hydrogen and oxygen are no longer supplied to the fuel cell 14, and the fuel cell 14 stops.
The power supply from the photovoltaic power plant will be restored, and the fuel synthesis system will be restarted.

As described above, the fuel synthesizing system of the present embodiment has a smaller number of parts and can improve safety compared to the fuel synthesizing system disclosed in the prior art or the like.
In the fuel synthesizing system of the present embodiment, by utilizing the fuel cell, it is possible to quickly compensate for the shortage of electric power even when the electric power is stopped or insufficient, and the system can be operated continuously.
Moreover, in this embodiment, by using the by-product gas generated from the fuel synthesizing system, the system can be stopped safely without using external energy or external resources. That is, the hydrogen and oxygen produced by the fuel synthesis system are used to operate the fuel cell, and the nitrogen is used to exhaust the fuel in the main passage.
Moreover, in this embodiment, when stopping the fuel synthesizing system, the system can be normally stopped using almost no electric power.

1 On-vehicle tank for carbon dioxide and nitrogen 2 Recovered gas storage tank 3 Primary storage tank 4 Booster 5 Secondary storage tank 6 Catalytic reactor 7 Gas-liquid separator 8 Nitrogen separator (inert gas separation means)
9 dehydration device 10 water electrolysis device 11 oxygen storage tank 12 hydrogen storage tank 13 reflux path 14 fuel cell (second power supply means)
15 switching device 16 switching device 17 nitrogen storage tank (inert gas storage tank)
18 control valve 19 second control valve 20 exhaust passage 21 inert gas recirculation passage

Claims (4)

a supply means for supplying carbon dioxide and a supply means for supplying hydrogen, which are arranged upstream of the main passage;
a catalytic reactor arranged downstream of the supply means for synthesizing fuel using a fuel synthesis catalyst;
a first power supply means for normally supplying power using renewable energy;
a second power supply means for supplying power from the fuel cell;
and a power measuring means for measuring the power supplied,
When the power supplied by the first power supply means decreases, the supply means for supplying hydrogen supplies hydrogen to the second power supply means to generate power, and the power supply by the second power supply means fuels A fuel synthesis system comprising power control means for operating the synthesis system. 2. The fuel synthesizing system according to claim 1, wherein said first power supply means is a solar power generator. a detection means for detecting whether or not the power supplied by the first power supply means has been restored;
an exhaust passage that bypasses the main passage downstream of the catalytic reactor and is exhausted;
a control valve installed in the exhaust passage,
The control valve is opened to exhaust the fuel in the main passage when the detection means does not detect the return of the supplied power after the second power supply means supplies power. 3. A fuel synthesizing system according to claim 1 or claim 2. inert gas separation means arranged downstream of the catalytic reactor;
a reflux passage for refluxing from the inert gas separation means to the upstream of the catalytic reactor;
an inert gas storage tank located downstream of the inert gas separation means;
an inert gas recirculation passage introduced into the recirculation passage from the inert gas storage tank;
a second control valve installed in the inert gas recirculation passage;
If the detection means does not detect the return of the supplied power after the second power supply means supplies power, the control valve is opened to exhaust the fuel in the main passage, and the second power supply means discharges the fuel. 4. The fuel synthesizing system according to claim 3, wherein the control valve is opened to recirculate the inert gas upstream of the main passage.

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