JP7572919B2 - Steam Boiler System - Google Patents

Description

The present invention relates to a steam boiler system.

In order to prevent global warming, development of technologies to reduce carbon dioxide (hereinafter referred to as " _CO2 ") emissions is underway. Such technologies include technologies to capture _CO2 , technologies to store _CO2 , technologies to convert _CO2 and make effective use of it, etc.

One technique for capturing _CO2 is the chemical absorption method. An amine aqueous solution is used to absorb _CO2 in exhaust gas, and the absorbed _CO2 is released from the aqueous solution, and the _CO2 is captured in a tank or the like. The amine aqueous solution generates heat when absorbing _CO2 , and heating is required when releasing _CO2 . Therefore, energy is required to cool and heat the amine aqueous solution, and reducing this energy is a challenge.

There is also technology to store the captured _CO2 . The captured _CO2 is transported to a storage location, a storage hole is dug deep underground, and the _CO2 is compressed and stored. Issues include reducing costs, maintaining the storage state after storage, and safety.

CCS (Carbon Dioxide Capture and Storage) is a combination of technology for capturing CO ₂ and technology for storing the captured CO _2. Due to the above-mentioned issues with CCS, development of CCU (Carbon Capture and Utilization), a technology for converting and effectively utilizing the captured CO ₂ , is underway.

For example, there is a method of converting _CO2 into methane (hereinafter referred to as " _CH4 "). The chemical reaction in this case is represented by the following reaction formula (1).

CO ₂ +4H ₂ → CH ₄ +2H ₂ O...Reaction formula (1)
Hydrogen (hereinafter referred to as "H ₂ ") required in the above reaction formula (1) can be obtained by the electrolysis of water represented by the following reaction formula (2).

2H ₂ O → 2H ₂ +O ₂ ... Reaction formula (2)
_CH4 is the main component of liquefied natural gas (hereinafter referred to as "LNG") and can be effectively used as a substitute for LNG. The challenge for obtaining _CH4 is to reduce the cost, and there is a demand for it to be at the same level as LNG.

In the electricity sector, efforts are underway to reduce _CO2 emissions by reducing the proportion of thermal power generation that burns fossil fuels and increasing the proportion of renewable energy sources such as solar and wind power generation.

In recent years, the introduction of renewable energy sources such as solar and wind power has increased, and the amount of electricity generated varies depending on the day and time of day. In cases where an excess supply of electricity is predicted, the acceptance of renewable energy sources is curtailed in advance.

If electricity is generated during the suspension of renewable energy use, surplus electricity will be generated, and one way to utilize this electricity is to produce _H2 through the electrolysis of water, as shown in the above reaction formula (2). If _H2 can be produced, _CO2 can be converted to _CH4, as shown in the above reaction formula (1), and reused as fuel.

Patent document 1 discloses a system and method for producing hydrocarbon compounds, comprising an electrolytic cell, a reverse water gas shift reactor, and a Fischer-Tropsch reactor.

Here, the reaction in the reverse water gas shift reactor is a reaction of converting _CO2 into CO (carbon monoxide), and is represented by the following reaction formula (3).

CO ₂ + H ₂ → CO + H ₂ O ... reaction formula (3)
The reaction in the Fischer-Tropsch reactor produces hydrocarbons such as _CH4 and is represented by the following reaction formula (4). This reaction is known as the Fischer-Tropsch process.

nCO+(2n+1)H ₂ → C _n H _2n+2 +nH ₂ O...Reaction formula (4)
There are two methods for capturing _CO2 : the pressure swing method, in which _CO2 is absorbed from fossil fuel combustion gas at high _pressure and then released and captured at low pressure; and the membrane separation method, in which only _CO2 is captured by passing it through a membrane. There are processes that use an aqueous amine solution to absorb and then release _CO2 for capture. _H2 can be produced by electrolyzing water using electrical energy obtained from renewable energy or nuclear fuel. .

Patent document 2 discloses a method of supplying a CO2 stream to a solid oxide electrolysis cell (SOEC) unit to produce CO and feed the CO back into a first synthesis gas stream, thereby increasing the CO concentration in the first synthesis gas stream.

Non-Patent Document 1 discloses that a solid oxide electrolysis cell (SOEC) is used to simultaneously electrolyze carbon dioxide and water vapor (co-electrolysis) at high temperatures of 500°C or higher to convert them into hydrogen and carbon monoxide, and that the gas and heat obtained from this conversion are used to produce methane.

Special Publication No. 2008-533287 Special table 2019-507718 publication

Fuel Cell, Vol. 14, No. 4, pp. 81-86 (2015)

Patent documents 1 and 2 do not describe the oxidation of fuel and the reduction of combustion product gases in a closed space that does not contain nitrogen.

The object of the present invention is to improve energy efficiency in a steam boiler system that includes a steam boiler and a carbon dioxide fuel generator, and in which fuel, oxygen, etc. circulate in a closed loop, and to reduce the cost of introducing the carbon dioxide fuel generator by making the device smaller.

The steam boiler system of the present invention comprises a steam boiler, a carbon dioxide fuel generator, a combustion product gas flow path that sends combustion product gas from the steam boiler to the carbon dioxide fuel generator, a converted gas flow path that sends converted gas from the carbon dioxide fuel generator to the steam boiler, and an oxygen gas flow path that sends oxygen gas from the carbon dioxide fuel generator to the steam boiler. The steam boiler burns the converted gas with oxygen gas to generate combustion product gas, the carbon dioxide fuel generator reduces the combustion product gas and separates it into converted gas and oxygen gas, and the combustion product gas, converted gas, and oxygen gas circulate in a closed loop consisting of the steam boiler, the carbon dioxide fuel generator, the combustion product gas flow path, the converted gas flow path, and the oxygen gas flow path. A heat exchanger is installed in the water supply flow path of the steam boiler to provide at least one of the thermal energy of the converted gas and the oxygen gas to the water supply of the water supply flow path.

According to the present invention, in a steam boiler system having a steam boiler and a carbon dioxide fuel generator, in which fuel, oxygen, etc. circulate in a closed loop, it is possible to improve energy efficiency and reduce the size of the carbon dioxide fuel generator, thereby reducing the introduction cost of the carbon dioxide fuel generator.

1 is an overall configuration diagram showing a steam boiler system according to a first embodiment of the present invention; FIG. 1 is an overall configuration diagram showing a steam boiler system according to a second embodiment of the present invention.

This disclosure relates to a steam boiler system and to a technology for recovering combustion product gas (exhaust gas) generated in the combustor of a steam boiler and reusing the carbon dioxide contained in the combustion product gas as fuel.

The following examples are explained with reference to the drawings.

In the embodiment, a system that reuses carbon dioxide generated from a steam boiler used for steam sterilization of medical equipment and food containers will be described, but the present invention is not limited to this and can be applied to any system that generates carbon dioxide by burning fuel.

Figure 1 is an overall configuration diagram showing the steam boiler system of the first embodiment.

The steam boiler system shown in this diagram includes a steam boiler 1, a carbon dioxide fuel conversion device 2, a combustion catalyst unit 3, a conversion gas tank 6, an oxygen gas tank 7, and a control device 13.

The steam boiler 1 is connected to a water supply pipe 15 (water supply flow path), a steam pipe 16 (steam flow path), a fuel gas pipe 17 (fuel gas flow path), and an exhaust gas pipe 18 (combustion product gas flow path). The water supply pipe 15 is a pipe that supplies water to the steam boiler 1 from the outside. Heat exchangers 11-1 and 11-2 are installed in the water supply pipe 15. A gas flow rate control valve 10-4 is installed in the fuel gas pipe 17. A gas flow rate control valve 10-5 is installed in the exhaust gas pipe 18.

The steam boiler 1 and the carbon dioxide fuel generator 2 are connected by a pipe. A combustion catalyst unit 3 is installed in the middle of this pipe. This pipe is a flow path branched off from the exhaust gas pipe 18 generated in the steam boiler 1. A pressure gauge 9-3, a gas flow meter 8-4, and a gas analyzer 12-2 are installed in the pipe between the combustion catalyst unit 3 and the carbon dioxide fuel generator 2.

The carbon dioxide fuel device 2 and the converted gas tank 6 are connected by piping (converted gas flow path). Along the way, a cooler 4-1, a pressure gauge 9-4, and a compressor 5-1 are installed in this order.

The carbon dioxide fuel device 2 and the oxygen gas tank 7 are connected by piping (oxygen gas flow path). Along the way, a cooler 4-2, a pressure gauge 9-5, and a compressor 5-2 are installed in this order.

The converted gas tank 6 and the steam boiler 1 are connected by piping (converted gas flow path). A gas flow control valve 10-2 and a gas flow meter 8-2 are installed in this order along the piping.

The oxygen gas tank 7 and the steam boiler 1 are connected by piping. A gas flow control valve 10-1 and a gas flow meter 8-1 are installed in this order along the piping.

A bypass pipe (converted gas bypass flow path) from the converted gas tank 6 is connected to the pipe connecting the steam boiler 1 and the combustion catalyst unit 3. In other words, a converted gas bypass flow path that joins a portion of the converted gas is connected to the flow path connecting the steam boiler 1 and the combustion catalyst unit 3. A gas flow control valve 10-3 and a gas flow meter 8-3 are installed in this order in the middle of this bypass pipe. The converted gas bypass flow path may be branched off from the converted gas flow path upstream of the converted gas tank 6.

The electrode material of the SOEC, which is a component of the carbon dioxide fuel production device 2, is deteriorated by _O2 . For this reason, a combustion catalyst unit 3 is provided in the piping from the steam boiler 1 to the carbon dioxide fuel production device 2 in case _O2 remains in the exhaust gas sent from the steam boiler 1 to the carbon dioxide fuel production device 2, but there are cases where the fuel components to react with the remaining _O2 are insufficient. In this case, a converted gas containing CO, _H2, etc. is supplied to the upstream side of the combustion catalyst unit 3 via a bypass piping from the converted gas tank 6, and the _O2 can be removed by reacting it with the remaining _O2 .

A pressure gauge 9-2 and a gas analyzer 12-1 are installed in the converted gas tank 6.

A pressure gauge 9-1 is installed in the oxygen gas tank 7. In addition, an oxygen supply pipe 19 for supplying oxygen from the outside is connected to the oxygen gas tank 7. A gas flow rate adjustment valve 10-6 is installed in the oxygen supply pipe 19.

The carbon dioxide fuel device 2, compressor 5-1, and compressor 5-2 are supplied with grid power 14 from an external source.

In the steam boiler system, the exhaust gas from the steam boiler 1 is converted into fuel by the carbon dioxide fuel conversion device 2. The converted gas is then cooled to a temperature that allows it to be sealed in the converted gas tank 6, and then compressed and sealed in the converted gas tank 6.

The gas sealed in the converted gas tank 6 is reused as fuel for the steam boiler 1. In other words, the steam boiler system is a circulation system that repeats combustion and reduction.

The steam boiler 1 is a device that burns fuel with oxygen and uses the heat of combustion to heat water and obtain steam. The gas (exhaust gas) produced after combustion is carbon dioxide and water, and its temperature is high, ranging from 200°C to 500°C. The ratio of fuel to oxygen is kept constant to generate a stable flame.

This combustion gas is introduced into the carbon dioxide fuel production device 2.

The carbon dioxide fuel apparatus 2 includes a solid oxide electrolysis cell (SOEC) that converts _CO2 into CO. The SOEC is an apparatus that generates CO and _H2 using _CO2 and _H2O as raw materials by supplying electric power. In other words, the carbon dioxide fuel apparatus 2 is an apparatus that reduces the exhaust gas generated in the steam boiler 1.

The carbon dioxide fuel production device 2 may also include a device that produces _CH4 and the like through a catalytic reaction from CO and _H2 produced by the SOEC.

Furthermore, the carbon dioxide fuel apparatus 2 may be an apparatus that uses a gas containing _CO2 as a raw material and directly produces _CH4 or the like through a catalytic reaction or the like. In this case, the carbon dioxide fuel apparatus 2 does not need to include an SOEC.

Therefore, the carbon dioxide fuel production device 2 is a device that produces gas containing CO, _CH4 , or the like.

The CO and _H2 or _CH4 , etc. (hereinafter referred to as "converted gas") produced in the carbon dioxide fuel production apparatus 2 are sent to and stored in a converted gas tank 6. On the other hand, the _O2 produced in the carbon dioxide fuel production apparatus 2 is sent to and stored in an oxygen gas tank 7. Thus, the CO, _H2 , _CH4 , etc. produced in the carbon dioxide fuel production apparatus 2 are reused as fuel for the steam boiler 1. Similarly, the _O2 produced in the carbon dioxide fuel production apparatus 2 is reused as an oxidizing agent for the steam boiler 1.

The SOEC is a device that electrolyzes water at high temperatures. The SOEC has a three-layer structure of an oxygen electrode, an electrolyte, and a hydrogen electrode, and produces _H2 from _H2O at the hydrogen electrode using grid power 14, and produces _O2 at the oxygen electrode. Furthermore, as shown in the above reaction formula (3), _H2O and CO are produced by the reverse water gas shift reaction of _CO2 and _H2 .

In the SOEC, the entire amount of _CO2 is not reacted, and some of it remains, so that the gas at the hydrogen electrode is a mixture of _H2O , CO, and unreacted _H2 and _CO2 .

Therefore, when the carbon dioxide fuel apparatus 2 is substantially composed of only an SOEC, the converted gas comprises the above-mentioned _H2O , CO, _H2 , and _CO2 . The _O2 produced in the carbon dioxide fuel apparatus 2 is discharged while being physically separated from the converted gas, so the converted gas does not contain _O2 .

The power required for the water electrolysis reaction in the carbon dioxide fuel production device 2 and the composition of the converted gas by the reverse water gas shift reaction vary depending on the gas temperature. Both the electrolysis reaction and the reverse water gas shift reaction in the carbon dioxide fuel production device 2 are endothermic reactions. For this reason, the carbon dioxide fuel production device 2 also requires heating to prevent the internal gas temperature from decreasing.

Furthermore, if the exhaust gas supplied to the carbon dioxide fuel production device 2 contains oxygen, the hydrogen electrode of the carbon dioxide fuel production device 2 will be oxidized and deteriorated. Therefore, it is desirable to install a combustion catalyst unit 3 upstream of the carbon dioxide fuel production device 2 to remove _O2 from the exhaust gas.

The converted gas produced in the carbon dioxide fuel production system 2 is cooled by a cooler 4-1 installed downstream of the carbon dioxide fuel production system 2, compressed by a compressor 5-1, and sent to a converted gas tank 6 where it is stored. On the other hand, the O ₂ produced in the carbon dioxide fuel production system 2 is cooled by a cooler 4-2 installed downstream of the carbon dioxide fuel production system 2, compressed by a compressor 5-2, and sent to an oxygen gas tank 7 where it is stored.

The flow path pressure of the converted gas cooled by the cooler 4-1 is measured by a pressure gauge 9-4. The flow path pressure of the _O2 cooled by the cooler 4-2 is measured by a pressure gauge 9-5. The measurement values of the pressure gauges 9-4, 9-5 are transmitted to the control device 13. The control device 13 controls the outputs of the compressors 5-1 and 5-2 based on the measurement values received from the pressure gauges 9-4, 9-5. This makes it possible to stabilize the flow path pressures of the converted gas and _O2 .

The converted gas stored in the converted gas tank 6 and _O2 stored in the oxygen gas tank 7 are re-supplied to the steam boiler 1. The converted gas in the converted gas tank 6 is also supplied to the combustion catalyst unit 3 and is used to remove _O2 contained in the exhaust gas from the steam boiler 1.

The flow rate of the converted gas supplied to the steam boiler 1 is measured by a gas flow meter 8-2. The flow rate of the converted gas supplied to the combustion catalyst unit 3 is measured by a gas flow meter 8-3. The flow rate of _O2 gas supplied to the steam boiler 1 is measured by a gas flow meter 8-1. The flow rates of these gases are controlled by adjusting the apertures of gas flow control valves 10-2, 10-3, and 10-1, respectively. This control is performed by a control device 13.

The means for transmitting various measurement data to the control device 13 and the means for transmitting various control signals from the control device 13 may be wireless or wired. In this diagram, they are indicated by dashed lines.

The converted gas and _O2 gas supplied to the steam boiler 1 are set at a flow rate ratio that allows stable combustion in the steam boiler 1. On the other hand, the converted gas supplied to the combustion catalyst unit 3 is set at a flow rate that prevents _O2 from remaining in the gas after catalytic combustion.

In this manner, the H ₂ O and CO ₂ produced in the steam boiler 1 are converted into fuel H ₂ and CO in the carbon dioxide fuel conversion device 2 and are supplied to the steam boiler 1 again.

In this way, during steady-state operation, the gas inside the system circulates in a closed loop.

By configuring in this way, carbon dioxide emissions from the system can be reduced to essentially zero (0).

In this embodiment, the symbol a of the heat exchanger 11-1 is connected to the symbol a of the converted gas flow path connected to the carbon dioxide fuel production device 2. The symbol b of the heat exchanger 11-1 is connected to the symbol b of the converted gas flow path connected to the carbon dioxide fuel production device 2.

Also, the reference symbol c of the heat exchanger 11-2 is connected to the reference symbol c of the _O2 gas flow path connected to the carbon dioxide fuel production device 2. The reference symbol d of the heat exchanger 11-2 is connected to the reference symbol d of the _O2 gas flow path connected to the carbon dioxide fuel production device 2.

In other words, the converted gas produced in the carbon dioxide fuel production system 2 passes through the heat exchanger 11-1 and heats the feed water of the steam boiler 1. Also, the _O2 gas produced in the carbon dioxide fuel production system 2 passes through the heat exchanger 11-2 and heats the feed water of the steam boiler 1.

The converted gas and _O2 gas produced in the carbon dioxide fuel production device 2 have a high temperature of 600°C to 1000°C.

By providing these thermal energies to the feed water pipe 15 of the steam boiler 1, it is possible to reduce the amount of heat exchanged in the converted gas cooler 4-1 and the _O2 gas cooler 4-2. Note that only one of the heat exchangers 11-1 and 11-2 may be used, and the heat exchanger 11-1 provides the thermal energy of the converted gas, and the heat exchanger 11-2 provides the thermal energy of the _O2 gas to the feed water pipe 15 of the steam boiler 1.

In this way, by providing the thermal energy of the converted gas and _O2 gas of the carbon dioxide fuel conversion device 2 to the water supply pipe 15 of the steam boiler 1, the steam flow rate obtained by the steam boiler 1 can be increased. In addition, when the same amount of steam flow rate is obtained by the steam boiler 1, the flow rates of the converted gas and _O2 gas supplied to the steam boiler 1 can be reduced. As a result, in a closed circulation system of gas in which _H2O and _CO2 generated by the steam boiler 1 are converted into fuel _H2 and CO by the carbon dioxide fuel conversion device 2 and then supplied to the steam boiler again, the gas flow rate supplied by the carbon dioxide fuel conversion device 2 can be reduced, and the size of the carbon dioxide fuel conversion device 2 and the power required for the electrolysis of water in the above reaction formula (2) can be reduced. This makes it possible to suppress the energy consumption of the entire system. In other words, the running costs can be reduced.

In addition, by reducing the amount of combustion gas produced, the carbon dioxide fuel production device can be made smaller, which reduces the introduction cost when adding a carbon dioxide fuel production device including an SOEC to an existing steam boiler.

Figure 2 is an overall configuration diagram showing the steam boiler system of Example 2.

In the explanation of this diagram, configurations that are the same as in Example 1 will be omitted.

In this diagram, a bypass pipe 20 (combustion product gas bypass flow path) is installed as a branch pipe in the middle of the pipe connecting the steam boiler 1 and the combustion catalyst unit 3. The bypass pipe 20 is connected to the pipe between the cooler 4-1 and the compressor 5-1. In other words, the bypass pipe 20 is connected to the upstream side of the compressor 5-1. In other words, a combustion product gas bypass flow path that merges a part of the combustion product gas of the steam boiler 1 is connected to the converted gas flow path. This allows the exhaust gas of the steam boiler 1 to be mixed with the converted gas generated in the carbon dioxide fuel conversion device 2. The combustion product gas bypass flow path may branch off from the middle of the pipe connecting the combustion catalyst unit 3 and the carbon dioxide fuel conversion device 2 and be connected to the pipe between the cooler 4-1 and the compressor 5-1.

A gas flow meter 8-5, a pressure gauge 9-6, a cooler 4-3, and a gas flow control valve 10-7 are installed in this order in the bypass piping 20.

By providing the bypass piping 20, the gas flow rate supplied to the carbon dioxide fuel production device 2 can be reduced, and the carbon dioxide fuel production device 2 can be made smaller.

In addition, when fuel is burned with oxygen in a closed space, the temperature of the combustion product gas becomes high because there is no nitrogen. Therefore, if complete combustion occurs using only fuel and oxygen, there is a risk that the heat resistance temperature of the material that makes up the combustor of the steam boiler 1 will be exceeded.

By providing the bypass piping 20, the combustion product gas containing carbon dioxide and the like is mixed with the converted gas, so the combustion temperature in the steam boiler 1 can be lowered and the steam boiler 1 can be operated at or below the heat resistance temperature of the material that constitutes the combustor.

The gas flow rate in the bypass pipe 20 is controlled by the control device 13 by adjusting the opening of the gas flow control valve 10-7 based on the measurement values of the gas flow meters 8-4 and 8-5. The control device 13 may also adjust the opening of the gas flow control valve 10-7 based on the measurement values of the pressure gauges 9-3 and 9-6.

The exhaust gas components of the steam boiler 1 are _H2O and _CO2 , and the flow rates of _H2O and _CO2 supplied to the carbon dioxide fuel production device 2 are also reduced by the bypass. The carbon dioxide fuel production device 2 needs to produce _H2 and CO through the above reaction formula (2) and the electrolysis reaction of _CO2 , but there is a shortage of the raw materials _H2O and _CO2 .

Therefore, it is desirable to have a configuration in which water is supplied to the combustion product gas flow path between the combustion catalyst unit 3 and the carbon dioxide fuel conversion device 2.

In this embodiment, the condensed water (drain) recovered by the cooler 4-1 that cools the converted gas downstream of the carbon dioxide fuel conversion device 2 is effectively used as the water supplied to the combustion product gas flow path. The recovery path is indicated by a thick dashed line in the figure.

The condensed water collected by the cooler 4-1 is stored in a drain tank 21 and supplied downstream of the gas flow meter 8-4 by a water supply pump 22. The water flow is measured by a water flow meter 25, and the control device 13 adjusts the opening of the water flow control valve 24 based on the measured value.

In addition, the condensed water (drain) recovered by the cooler 4-3 in the bypass piping 20 can also be used effectively. Similarly, the condensed water recovered by the cooler 4-3 is stored in the drain tank 21. The recovery path in this case is also shown by a thick dashed line in the figure.

In addition, by providing a circulation path 23 in the piping before and after the water supply pump 22, the flow rate can be adjusted even if the water supply pump 22 is not an inverter type.

It is desirable to supply water in the form of steam from the drain tank 21 to the carbon dioxide fuel production system 2. Using external electricity to produce steam does not result in a reduction in energy consumption, so the water is heated using the thermal energy of the high-temperature converted gas or _O2 gas from the carbon dioxide fuel production system 2, or the high-temperature gas in the bypass piping 20.

In this embodiment, the symbol p of the heat exchanger 11-4 is connected to the symbol p of the converted gas flow path connected to the carbon dioxide fuel production device 2. The symbol q of the heat exchanger 11-1 is connected to the symbol q of the converted gas flow path connected to the carbon dioxide fuel production device 2.

Also, the reference symbol r of the heat exchanger 11-5 is connected to the reference symbol r of the _O2 gas flow path connected to the carbon dioxide fuel production device 2. The reference symbol s of the heat exchanger 11-5 is connected to the reference symbol s of the _O2 gas flow path connected to the carbon dioxide fuel production device 2.

The symbol t of the heat exchanger 11-6 is connected to the symbol t of the bypass pipe 20. The symbol u of the heat exchanger 11-6 is connected to the symbol u of the bypass pipe 20.

In other words, the water supplied from the drain tank 21 to the carbon dioxide fuel conversion device 2 is heated by the heat exchangers 11-4, 11-5, and 11-6 and becomes water vapor.

With this configuration, it is possible to recover thermal energy from the high-temperature converted gas and _O2 gas downstream of the carbon dioxide fuel production system 2, and use this energy to heat the condensed water (drain) recovered in the coolers 4-1 and 4-3 to produce water vapor.

From a performance standpoint, it is desirable to install all of the heat exchangers 11-4, 11-5, and 11-6, but it is also possible to install just one or two of them.

Furthermore, a heat exchanger 11-3 is installed in the water supply pipe 15. Symbol e of the heat exchanger 11-3 is connected to symbol e of the bypass pipe 20. Symbol f of the heat exchanger 11-3 is connected to symbol f of the bypass pipe 20. This allows the heat exchanger 11-3 to heat the water supply to the steam boiler 1 with the heat of the exhaust gas from the steam boiler 1.

The gas flow rate of the gas supplied to the carbon dioxide fuel production device 2 increases when water or steam is supplied, but the gas flow rate is less than when the bypass piping 20 is not installed as in Example 1, and the carbon dioxide fuel production device 2 can be made even smaller.

As in Example 1, heat exchangers 11-1 and 11-2 are installed in the water supply pipe 15 of the steam boiler 1.

The symbol a of the heat exchanger 11-1 is connected to the symbol a downstream of the symbol q of the converted gas flow path connected to the carbon dioxide fuel conversion device 2. The symbol b of the heat exchanger 11-1 is connected to the symbol b of the converted gas flow path connected to the carbon dioxide fuel conversion device 2.

The reference symbol c of the heat exchanger 11-2 is connected to the reference symbol c downstream of the reference symbol s of the _O2 gas flow passage connected to the carbon dioxide fuel production device 2. The reference symbol d of the heat exchanger 11-2 is connected to the reference symbol d of the _O2 gas flow passage connected to the carbon dioxide fuel production device 2.

From a performance standpoint, it is desirable to install all of the heat exchangers 11-1, 11-2, and 11-3, but it is also possible to install just one or two of them. In other words, a heat exchanger is installed in the feedwater passage of the steam boiler 1 to provide at least one of the thermal energies of the converted gas flowing through the converted gas passage, the oxygen gas flowing through the oxygen gas passage, and the combustion product gas flowing through the combustion product gas bypass passage to the feedwater in the feedwater passage.

In this embodiment, the gas flow rate supplied by the carbon dioxide fuel production device 2 can be further reduced compared to the system of embodiment 1, and the carbon dioxide fuel production device 2 can be further miniaturized compared to the system of embodiment 1. This allows the electrical energy consumed by the carbon dioxide fuel production device 2 to be further reduced.

1: Steam boiler, 2: Carbon dioxide fuel conversion device, 3: Combustion catalyst unit, 4-1, 4-2, 4-3: Cooler, 5-1, 5-2: Compressor, 6: Conversion gas tank, 7: Oxygen gas tank, 8-1, 8-2, 8-3, 8-4, 8-5: Gas flow meter, 9-1, 9-2, 9-3, 9-4, 9-5, 9-6: Pressure gauge, 10-1, 10-2, 10-3, 10-4, 10-5, 10-6, 10-7: Gas flow Flow control valve, 11-1, 11-2, 11-3, 11-4, 11-5, 11-6: heat exchanger, 12-1, 12-2: gas analyzer, 13: control device, 14: system power, 15: water supply pipe, 16: steam pipe, 17: fuel gas pipe, 18: exhaust gas pipe, 19: oxygen supply pipe, 20: bypass pipe, 21: drain tank, 22: water supply pump, 23: circulation path, 24: water flow control valve, 25: water flow meter.

Claims (7)

A steam boiler;
A carbon dioxide fuel generator;
a combustion product gas flow path for transmitting a combustion product gas from the steam boiler to the carbon dioxide fuel production device;
a converted gas flow path for transmitting a converted gas from the carbon dioxide fuel production device to the steam boiler;
an oxygen gas flow path for transmitting oxygen gas from the carbon dioxide fuel production device to the steam boiler;
The steam boiler combusts the converted gas with the oxygen gas to generate the combustion product gas;
The carbon dioxide fuel production device reduces the combustion product gas and separates it into the converted gas and the oxygen gas,
the combustion product gas, the converted gas, and the oxygen gas are configured to circulate through a closed loop formed by the steam boiler, the carbon dioxide fuel conversion device, the combustion product gas flow path, the converted gas flow path, and the oxygen gas flow path;
A heat exchanger is installed in the feedwater passage of the steam boiler to give at least one of the thermal energy of the converted gas and the thermal energy of the oxygen gas to the feedwater of the feedwater passage ;
a combustion catalyst unit is installed in the combustion product gas flow path between the steam boiler and the carbon dioxide fuel production device;
A steam boiler system , wherein a converted gas bypass flow path for joining a portion of the converted gas is connected to a flow path connecting the steam boiler and the combustion catalyst unit . The steam boiler system according to claim 1, wherein the converted gas flow path is connected to a combustion product gas bypass flow path that merges a portion of the combustion product gas of the steam boiler. The steam boiler system according to claim 1 , further comprising a configuration for supplying water to the combustion product gas flow path between the combustion catalyst unit and the carbon dioxide fuel production device. a combustion product gas bypass flow path that merges a portion of the combustion product gas of the steam boiler with the converted gas flow path is connected to the converted gas flow path;
a configuration in which water is supplied to the combustion product gas flow path between the combustion catalyst unit and the carbon dioxide fuel production device;
a cooler is provided in each of the converted gas flow passage and the combustion product gas bypass flow passage;
The steam boiler system according to claim 1 , further comprising a configuration in which condensed water produced in the cooler is used as the water. 5. The steam boiler system according to claim 4, wherein a heat exchanger is provided in the condensate flow path to provide at least one of the thermal energy of the converted gas and the oxygen gas, and the thermal energy of the combustion product gas flowing through the combustion product gas bypass flow path. 3. The steam boiler system according to claim 2 , further comprising a heat exchanger disposed in the feedwater passage of the steam boiler for imparting thermal energy of the combustion product gas flowing through the combustion product gas bypass passage to the feedwater. A compressor is installed in the converted gas flow path,
The steam boiler system of claim 2 , wherein the combustion product gas bypass passage is connected upstream of the compressor.

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