JP7816062B2 - Hydrocarbon Production Systems - Google Patents

Description

The present invention relates to a hydrocarbon production system having a hydrocarbon production device and an electrolysis device.

Methanation, which uses the Sabatier reaction to produce methane from carbon dioxide and hydrogen, is a known method of producing hydrocarbons. Another known method of producing hydrogen is the electrolysis of water vapor.

Patent Document 1 proposes a technology that uses hydrogen obtained by electrolysis for methanation. According to Patent Document 1, since methanation is an exothermic reaction, thermal energy efficiency can be improved by utilizing the reaction heat to generate hydrogen.

Japanese Patent Application Laid-Open No. 2019-108238

In hydrogen production, heat is required not only for the endothermic reaction in the electrolysis of water vapor, but also to obtain water vapor, so the reaction heat from the Sabatier reaction is insufficient to provide the required thermal energy.

Specifically, as shown in the following (1) to (3), in order to obtain 1 mol of methane by the Sabatier reaction, 4 mol of hydrogen must be supplied, and therefore 4 mol of water must be converted into steam.
4H ₂ O (liquid) → 4H ₂ O (gas) ... (1)
4H ₂ O (gas) → 4H ₂ +2O ₂ ...(2)
CO ₂ +4H ₂ →CH ₄ +2H ₂ O...(3)

For example, to heat 4 mol of water at 25°C to 100°C and boil it, the amount of heat required to produce 100°C steam (i.e., the amount of heat required for the reaction in equation (1)) is 185 kJ, which is greater than the 165 kJ of heat generated in the Sabatier reaction (i.e., the amount of reaction heat generated in equation (3)). In other words, in principle, the heat of reaction cannot cover the heat required to produce steam from water. Furthermore, when heat dissipation is taken into account, it is difficult to recover 100% of the heat of reaction, so the difference in heat amount becomes even greater. As a result, thermal energy must be supplied from an external source. Conventional systems are unable to recover all heat other than the heat of reaction, resulting in poor heat balance.

The present invention was made in consideration of these issues, and aims to provide a hydrocarbon production system that can efficiently use thermal energy to produce hydrocarbons.

One aspect of the present invention is a hydrocarbon production device (2) that produces hydrocarbons and water vapor by an exothermic reaction between carbon dioxide gas and hydrogen;
an electrolysis device (3) that generates hydrogen from raw steam to be supplied to the hydrocarbon generation device;
a steam supply line (4) for evaporating the raw material liquid water to generate the raw material steam and supplying the raw material steam to the electrolysis device;
a heat exchanger (51) for exchanging heat of the produced gas containing the water vapor discharged from the hydrocarbon production apparatus with the raw material liquid water or the raw material water vapor in the water vapor supply line,
In the hydrocarbon production system (1), the steam partial pressure P1 of the produced gas in the heat exchanger is higher than the pressure P2 of the raw steam supplied to the electrolysis device.

As described above, the hydrocarbon production system includes a hydrocarbon production device, an electrolysis device, a steam supply line, and a heat exchanger. The heat exchanger exchanges heat from the produced gas with the raw liquid water or raw steam in the steam supply line. In other words, the heat from the produced gas is recovered by the heat exchanger and can be used to generate raw steam to be supplied to the electrolysis device. This increases the thermal efficiency of the hydrocarbon production system.

In addition, in the above-mentioned hydrocarbon production system, the water vapor partial pressure P1 of the product gas in the heat exchanger is higher than the pressure P2 of the raw water vapor supplied to the electrolysis device. In other words, P1 - P2 > 0 (kPa). This makes the condensation temperature of the water vapor contained in the product gas higher than the evaporation temperature of the raw water vapor supplied to the electrolysis device. Therefore, the condensation heat of the water vapor in the product gas generated by the hydrocarbon production reaction in the hydrocarbon production device can be recovered as the evaporation heat of the water supplied to the electrolysis device. From this perspective, too, the thermal efficiency of the hydrocarbon production system can be improved.

As described above, according to the above-described embodiment, it is possible to efficiently utilize thermal energy to produce hydrocarbons.
In addition, the symbols in parentheses in the claims and the means for solving the problems indicate the correspondence with the specific means described in the embodiments described below, and do not limit the technical scope of the present invention.

1 is a block diagram showing a hydrocarbon production system that produces hydrocarbons using carbon dioxide and hydrogen in a first embodiment. FIG. 1 is a block diagram showing a hydrocarbon production system that produces hydrocarbons using carbon monoxide and hydrogen in a first embodiment. FIG. FIG. 2 is an explanatory diagram showing the heat balance in the hydrocarbon production system according to the first embodiment. 1 is a graph showing the relationship between the water vapor partial pressure and the condensation temperature of water in the first embodiment. 4 is a graph showing the relationship between the amount of recovered heat and the temperature of the generated gas in the first embodiment. FIG. 3 is an operational flow diagram showing a start-up process of the hydrocarbon production system in the first embodiment. FIG. 3 is an operational flow diagram showing a start-up process of the hydrocarbon production system in the first embodiment. FIG. 2 is an operational flow diagram of hydrogen generation control in the first embodiment. FIG. 2 is an operational flow diagram of hydrocarbon production in the first embodiment. 1 is a graph showing the relationship between the heat exchange area and the amount of condensation heat recovered for each water vapor pressure difference in the first embodiment. 1 is a graph showing the relationship between the steam pressure difference and the heat exchange area required to recover all the heat of condensation. FIG. 10 is a block diagram showing a hydrocarbon production system according to a second embodiment.

(Embodiment 1)
An embodiment of a hydrocarbon production system 1 will be described with reference to FIGS.
In this specification, when the expression "to" is used, it is intended to include the numerical values or physical values written before and after it. Furthermore, when a numerical value or physical value is written as an upper or lower limit, it is intended to include that value.

As shown in Figure 1, the hydrocarbon production system 1 of this embodiment comprises a hydrocarbon production device 2, an electrolysis device 3, a steam supply line 4, and a heat exchanger 51.

The hydrocarbon generator 2 generates hydrocarbons and water vapor through an exothermic reaction between carbon dioxide gas and hydrogen. The hydrocarbon generation reaction in the hydrocarbon generator 2 typically occurs at 200 to 500°C, producing product gas at 200 to 500°C.

Examples of carbon oxide gases include carbon monoxide and carbon dioxide. Carbon dioxide is preferred because it is easily available from factory furnaces, the atmosphere, etc., and carbon monoxide is preferred because of its high reactivity in producing hydrocarbons. Carbon dioxide and carbon monoxide may be used in combination as carbon oxide gases. Examples of hydrocarbons include saturated hydrocarbons such as methane and ethane. When the hydrocarbon is methane, the hydrocarbon production reaction is called methanation. The carbon number of the hydrocarbon can be controlled by changing the catalyst. Methane is preferred because it can be used as city gas and can be directly synthesized from carbon dioxide and hydrogen using the Sabatier reaction shown in formula (I) below.

The hydrocarbon production reaction is an exothermic reaction. When the carbon oxide gas is carbon dioxide and the hydrocarbon is methane, the chemical reaction formula is expressed by the following formula (I): ΔH in formula (I) represents the enthalpy change before and after the reaction.
CO ₂ +4H ₂ →CH ₄ +2H ₂ O (ΔH=-165kJ/mol)...(I)

As shown in Figure 2, the hydrocarbon production device 2 specifically includes a production reactor 22 in which a hydrocarbon production reaction takes place, and mass flow controllers 26 and 27 that control the amount of gas supplied to the production reactor 22. The first mass flow controller 26 controls the amount of carbon oxide gas such as _CO2 supplied. The second mass flow controller 27 controls the amount of hydrogen supplied. The hydrocarbon production system 1 can further include a _CO2 recovery unit 61. The _CO2 recovery unit 61 recovers and stores carbon dioxide to be used as carbon oxide gas from the atmosphere, a combustion furnace, or the like. The carbon dioxide can also be supplied to the electrolysis device 3 and used to generate carbon monoxide.

The electrolysis device 3 generates hydrogen from raw steam to be supplied to the hydrocarbon production device 2. Although the specific configuration of the electrolysis device 3 is not shown, it is composed of, for example, an electrolysis reactor and a cell stack housed in the electrolysis reactor. The cell stack is composed of a plurality of solid oxide electrolysis cells (i.e., SOEC). Although the specific configuration of the electrolysis device 3 is not shown, the electrolysis device 3 may have a configuration used in the electrolysis of steam using an SOEC or in the co-electrolysis of steam and carbon dioxide. In the electrolysis device 3, a water electrolysis reaction occurs in the cell stack as shown in the following formula (II), and hydrogen is generated.
4H ₂ O (g) → 4H ₂ +2O ₂ ...(II)

In the electrolysis device 3, it is also possible to produce carbon monoxide together with hydrogen by co-electrolysis of water vapor and carbon dioxide, as shown in the following formula (III). In this case, as shown in FIG. 2 , CO2 recovered by the _CO2 recovery device 61 is supplied to the electrolysis device 3, _{and CO2} is electrolyzed in the electrolysis device 3 together with water vapor supplied from the water vapor supply line 4, producing carbon monoxide together with hydrogen. In co-electrolysis, carbon monoxide is supplied together with hydrogen to the production reactor 22 of the hydrocarbon production device 2, and as shown in the following formula (IV), methane can be produced by reacting carbon monoxide and hydrogen in the production reactor 22. In this case, highly reactive carbon monoxide is used as the carbon oxide gas, which facilitates the hydrocarbon production reaction. From this perspective, it is preferable to perform co-electrolysis of water vapor and carbon dioxide in the electrolysis device 3. Furthermore, hydrocarbons other than methane can also be produced by co-electrolysis, as shown in formula (V). Note that the "g" in parentheses in formulas (II) to (V) indicates that the substance is in a gaseous state, i.e., water is converted into steam. In formula (V), n is a natural number. Although Fig. 2 shows a configuration in which hydrogen and carbon monoxide are stored in the product gas tank 350, it is also possible to store the hydrogen and carbon monoxide generated in the electrolysis device in separate tanks.
CO ₂ +3H ₂ O (g) → CO + 3H ₂ +2O ₂ ...(III)
CO+3H ₂ →CH ₄ +H ₂ O(g) ...(IV)
nCO+(2n+1)H ₂ →C _n H _2n+2 +nH ₂ O(g) ...(V)

The steam supply line 4 evaporates the raw material liquid water to generate raw material steam as shown in formula (VI) and supplies the raw material steam to the electrolysis device 3. The steam supply line 4 includes, for example, an evaporator 41 (specifically, a first evaporator 41) and a pump 45. The evaporator 41 supplies thermal energy to the raw material liquid water to evaporate the raw material liquid water to generate raw material steam. The pump 45 transports the raw material steam to the electrolysis device 3.
H ₂ O (l) → H ₂ O (g) ... (VI)

As shown in FIG. 1, the heat exchanger (specifically, the first heat exchanger 51) exchanges heat energy of the product gas containing water vapor discharged from the hydrocarbon production apparatus 2 with the feed liquid water or feed steam in the water vapor supply line 4. The heat of the product gas refers to the thermal energy contained in the product gas discharged from the production reactor 22 of the hydrocarbon production apparatus 2, and is a different concept from the reaction heat generated in the hydrocarbon production reaction within the production reactor 22. A first cooler 513 can be provided downstream of the first heat exchanger 51 in the product gas discharge flow path to further cool the product gas that has released heat in the first heat exchanger 51. The refrigerant is, for example, water.

The first heat exchanger 51 recovers thermal energy from the product gas (specifically, hydrocarbons such as methane, and water vapor) discharged from the hydrocarbon production apparatus 2 and transfers the heat to the feed liquid water or feed steam. The first heat exchanger 51 preferably uses at least the water vapor in the product gas as a heat medium and exchanges heat from this heat medium steam with the feed liquid water or feed steam. In this case, the first heat exchanger 51 can use the condensation heat of the water vapor to evaporate the water in the steam supply line 4. Furthermore, when the first heat exchanger 51 exchanges heat from the hydrocarbons, the heat balance in the hydrocarbon production system 1 is further improved, resulting in greater thermal efficiency.

The hydrocarbon production system 1 preferably further includes a second heat exchanger 52 that recovers the reaction heat generated in the hydrocarbon production device 2 via thermal oil. In this case, not only the thermal energy of the produced gas but also the reaction heat can be recovered and used, for example, for evaporating water, thereby further improving the heat balance in the hydrocarbon production system 1. Furthermore, because thermal oil has a larger heat capacity than gases such as steam, using thermal oil as described above increases the robustness of the hydrocarbon production device 2 against fluctuations in heat generation. Because thermal oil is used, the second heat exchanger 52 is connected to, for example, an oil heater 522 and an oil pump 521. The oil pump 521 is also referred to as a thermal oil pump 521. A second cooler 523 can be connected to the second heat exchanger 52 to compensate for insufficient cooling. The refrigerant is, for example, water. In Figure 2, the flow of thermal oil is represented by a solid line and flows counterclockwise. The hydrocarbon production reaction generates reaction heat and latent heat of vaporization, with the latent heat of vaporization being distributed to the water vapor in the product gas and the reaction heat being distributed to the heat transfer oil and/or product gas. Therefore, the heat of the product gas refers to the latent heat of vaporization and a portion of the heat of reaction. If the hydrocarbon production system 1 has a second heat exchanger 52, the heat of the product gas can also be said to be the heat retained in the product gas after it has been recovered in the heat transfer oil in the second heat exchanger 52.

As shown in FIG. 1, the steam supply line 4 can be equipped with a first evaporator 41 that uses the heat of the produced gas and receives heat from a first heat exchanger 51, and a second evaporator 42 that uses the reaction heat of hydrocarbon production and receives heat from a second heat exchanger 52. Also, instead of the first evaporator 41 and the second evaporator 42, it is possible to use a single evaporator that receives heat from both the first heat exchanger 51 and the second heat exchanger 52.

As shown in Figure 2, the second heat exchanger 52 is preferably located downstream of the first heat exchanger 51 in the gas flow path. In this case, stable heat exchange is possible even if the amount of thermal energy recovered in the first heat exchanger 51 fluctuates. This is because the second heat exchanger 52, located downstream of the first heat exchanger 51, uses thermal oil with a large heat capacity, allowing for efficient heat exchange in this second heat exchanger 52.

As shown in Figure 3, the generation of raw steam in the steam supply line 4 typically requires sensible heat to heat the raw liquid water up to 100°C, as well as latent heat associated with phase transition above 100°C. The heat of reaction from the hydrocarbon production reaction typically provides approximately 50 to 70 percent of the heat required for water evaporation. Meanwhile, the condensation temperature of water depends on its partial pressure. As shown in Figure 4, the condensation temperature is 100°C at atmospheric pressure (approximately 0.1 MPa). However, by performing the hydrocarbon production reaction at high pressure, the partial pressure of water also increases, allowing for a higher condensation temperature. For example, when the partial pressure of the steam produced along with the hydrocarbons in the hydrocarbon production reaction is 0.33 MPa, the condensation temperature is 135°C (see Figures 4 and 5). This increases the amount of heat that can be recovered from the product gas, and this recovered heat, combined with the reaction heat from the hydrocarbon production reaction, can provide almost all of the thermal energy required to generate the raw steam (see Figure 3).

In the hydrocarbon production system 1, the water vapor partial pressure P1 of the product gas in the first heat exchanger 51 is higher than the pressure P2 of the raw steam supplied to the electrolysis device 3. The water vapor partial pressure P1 of the product gas can be increased, for example, by compressing the hydrogen and/or carbon dioxide flowing into the hydrocarbon production device _2. As shown in FIG. 1 , hydrogen is compressed, for example, by a compressor 33 that compresses hydrogen produced in the electrolysis device 3. Although not shown, the water vapor partial pressure P1 can also be increased by providing a CO2 compressor that compresses carbon dioxide and pressurizing the carbon dioxide supplied to the hydrocarbon production device using this _CO2 compressor. In this way, by compressing hydrogen and/or carbon dioxide, the product gas is pressurized, and the water vapor partial pressure P1 can be increased. Preferably, hydrogen is compressed and pressurized by the compressor 33 located downstream of the electrolysis device 3 in the gas flow path. In this case, the water vapor partial pressure P1 of the product gas can be increased more efficiently than the raw steam P2. This is because the hydrogen produced in the electrolysis device 3 is at a low pressure.
When the produced gas is not pressurized (specifically, when the pressure of the produced gas is atmospheric pressure), the condensation temperature of water vapor is 100°C, so the condensation heat, which accounts for 70 to 80% of the heat content of the produced gas, may not be usable as latent heat of vaporization, but it can be used as sensible heat. In contrast, when the produced gas is pressurized (specifically, when the pressure of the produced gas is higher than atmospheric pressure), the water vapor partial pressure P1 of the produced gas becomes higher than the pressure P2 of the feed steam, and the condensation heat can also be used as latent heat of vaporization. This increases the amount of heat recovered and further improves the heat balance in the hydrocarbon production system 1. Furthermore, when the produced gas is pressurized, the pressure inside, for example, the production reactor 22 of the hydrocarbon production apparatus 2 usually increases, and the reaction rate of hydrocarbon production also increases.

Paradoxically, from the perspective of improving the heat balance in the hydrocarbon production system 1, it is preferable that the first heat exchanger 51 be configured to evaporate some or all of the feed liquid water that receives heat in the first heat exchanger 51, and that the condensation heat of the water vapor in the produced gas be used as the latent heat of evaporation of the feed liquid water. A specific example of a configuration for utilizing the condensation heat of water vapor for the feed liquid water is a compressor for compressing hydrogen and/or carbon dioxide, as described above.

Equations (VI) through (VIII) illustrate the main chemical reactions in hydrocarbon production system 1.
H ₂ O (liquid, 25° C.) → H ₂ O (gas, 100° C.) (ΔH=46.3 kJ/mol) (VI)
_H2O → _H2 +1/2O2 _... (VII)
CO ₂ +4H ₂ →CH ₄ +2H ₂ O (ΔH=-165kJ/mol)...(VIII)

As shown in equations (VI) to (VIII), for example, to synthesize _CH4 at a rate of 1 mol/sec, water must be evaporated at a rate of 4 mol/sec. The amount of heat generated when _CH4 is synthesized at 1 mol/sec is 165 kW (= 165 kJ/sec). Meanwhile, the amount of heat required to evaporate water is 185 kW (= 46.3 × 4 kW = 185 kJ/sec). Therefore, the heat generated by the hydrocarbon production reaction (specifically, methanation) alone cannot cover all of the heat required to evaporate water. Furthermore, because heat dissipation occurs, it is usually difficult to recover all of the heat generated; the amount of heat that can actually be recovered is approximately 70% of the 165 kW generated by the hydrocarbon production reaction.

Because water vapor is generated in the hydrocarbon production reaction, the condensation heat of the water vapor can also be utilized. The condensation heat of water vapor generated in the methanation reaction depends on the pressure, but is approximately 80 kW when synthesizing 1 mol/sec of methane. However, if there is no difference between the pressure of the water vapor generated by methanation and the pressure of the raw water vapor supplied to the electrolysis device, the condensation temperature of the water vapor generated by methanation and the evaporation temperature of the water supplied to the electrolysis device 3 are in competition, so no temperature difference occurs. The heat exchange amount Q in the heat exchanger is expressed by the following formula (IX). However, if no temperature difference occurs (i.e., when ΔT = 0), heat exchange cannot be performed even if the heat exchange area is large. In formula (IX), A represents the heat exchange area, U represents the overall heat transfer coefficient, and ΔT represents the logarithmic mean temperature difference.
Q=A×U×ΔT...(IX)

In other words, the condensation heat of the water vapor generated by methanation can be used to preheat the water supplied to the electrolysis device 3 up to its boiling point, but it cannot be used as evaporation heat. As a result, the amount of heat that can be recovered is approximately 20% of the total condensation heat.

In contrast, by pressurizing the product gas, the condensation temperature of the water vapor contained in the methanation product gas becomes higher than the evaporation temperature of the water supplied to the electrolysis device 3. As a result, the condensation heat of the water vapor contained in the methanation product gas can be recovered as the evaporation heat of the water supplied to the electrolysis device 3.

Figure 10 shows the relationship between the heat exchange area of the heat exchanger and the amount of heat recovered from condensation. The vertical axis of Figure 10 shows the amount of heat that can be recovered from water vapor when methane is synthesized at 1 mol/sec. Note that plots above 80 kW in Figure 10 represent the amount of heat recovered from liquid water after condensation.

As can be seen from Figure 10, when the pressure difference of the water vapor is 0, even if the heat exchange area is increased, only about 20% of the condensation heat of the water vapor can be exchanged. On the other hand, as the pressure difference increases, the temperature difference between the condensation temperature and the evaporation temperature also increases, and therefore, for example, the amount of heat exchanged per unit heat exchange area increases. As a result, the heat exchanger can be made smaller.

Figure 11 shows the relationship between the pressure difference of the steam and the heat exchange area required to recover all of the condensation heat. As can be seen from Figure 11, when the pressure difference is 50 kPa or more, increasing the pressure reduces the required heat exchange area. Furthermore, by setting the pressure difference P1-P2 between the steam partial pressure P1 of the generated gas in the heat exchanger 51 and the pressure P2 of the raw steam supplied to the electrolysis device to 50 kPa or more, the heat exchange amount per unit heat exchange area can be sufficiently increased. Both Figures 10 and 11 plot data calculated based on a steam pressure of 100 kPa (equivalent to atmospheric pressure) in the electrolysis device 3. However, even if the base steam pressure of the electrolysis device 3 changes, the same trends as Figures 10 and 11 are observed. From the perspective of the pressure resistance of the heat exchanger, it is preferable that the pressure difference P1-P2 be 1,000 kPa or less.

It is preferable that a portion of the heat of the product gas discharged from the hydrocarbon generator 2 be used to heat the carbon oxide gas and hydrogen supplied to the hydrocarbon generator 2. In this case, the excess thermal energy of the product gas that is not used in the steam supply line 4 can be used for the hydrocarbon production reaction, further improving the heat balance. A specific configuration for using a portion of the heat of the product gas to heat the carbon oxide gas and hydrogen is a heat exchanger (specifically, the third heat exchanger 53), as shown in Figure 1. The third heat exchanger 53 recovers a portion of the heat of the product gas and allows the carbon oxide gas and hydrogen to receive the recovered heat. Note that, for ease of illustration, two third heat exchangers are shown in Figure 1, but in reality, they represent a single heat exchanger.

The hydrocarbon production system 1 preferably has a compressor 33 that compresses the hydrogen produced in the electrolysis device 3. In this case, pressurized hydrogen can be supplied to the hydrocarbon production device 2, improving the reaction efficiency of the hydrocarbon production reaction in the hydrocarbon production device 2. In addition, in this case, the water vapor partial pressure P1 of the produced gas can be made higher than the pressure P2 of the feed water vapor.

The operation of the hydrocarbon production system 1 of this embodiment will be explained using the operational flow diagrams shown in Figures 6 to 9. In the following explanation, T1, T2, and T3 represent the temperature sensors shown in Figure 1. The temperature sensors may be thermometers, for example. The flow diagram shows an example in which the thermal oil temperature is controlled in the range of 240 to 260°C, and the temperature is changeable. The operational flow is controlled, for example, by a control unit (not shown).

<Start-up process>
6, when the hydrocarbon production system 1 starts operation, the thermal oil pump 521 starts to circulate the thermal oil (S11). The oil heater 522 starts to heat the thermal oil (S12), and when the temperature of T2 exceeds 250°C, the oil heater 522 stops heating (S13, S14).

<Control of hydrogen generation>
As shown in Fig. 7, when hydrogen generation starts, the pump 45 of the steam supply line 4 is activated (S21). The pump 45 sends a designated amount of water (specifically, raw liquid water) to the first heat exchanger 51 and the second heat exchanger 52 based on a command value for the amount of hydrogen generated (S22). The water evaporates in the first heat exchanger 51 and the second heat exchanger 52, generating raw steam, and the raw liquid water is sent to the electrolysis device 3. In the electrolysis device 3, water is electrolyzed to generate hydrogen (S23). The hydrogen is dehydrated in the post-treatment device 37, compressed and pressurized by the compressor 33, and stored in the _H2 tank 35 (see Fig. 1).

Control of hydrocarbon production
As shown in Fig. 8, when hydrocarbon production is started, hydrogen and _CO2 are supplied to the production reactor 22 based on a command value for the amount of hydrocarbon production (e.g., the amount of methane produced) (S31). Hydrogen is supplied from the _H2 tank 35, and _CO2 is supplied from the recovery device 61. In the production reactor 22, for example, a methanation reaction is carried out to produce methane and water (water vapor) (S32). The produced gas is supplied to the first heat exchanger 51 and cooled, condensing the water (S33). The insufficient cooling is made up by cooling the first cooler 513, condensing the water (S34). The condensed water is separated, for example, by the gas-liquid separator 65, and high-concentration methane is produced (S35).

<Thermal oil temperature control>
As shown in FIG. 9 , the thermal oil temperature is controlled by controlling the cooling steps S41-S45 and the heating steps S46-S49 while the thermal oil is circulated by the thermal oil pump 521. During the cooling steps S41-S45, the T1 temperature determination S42 and the T2 temperature determination S44 (only during cooling) are performed. In the T1 temperature determination S42, the T1 temperature is determined. If the T1 temperature exceeds, for example, 260°C, the second cooler 523 is activated and the thermal oil is cooled with the refrigerant (S43). In the T2 temperature determination S44, the T2 temperature is determined. If the T2 temperature is below, for example, 250°C, the second cooler 523 is stopped (S45). On the other hand, if the T1 temperature is below, for example, 260°C in the T1 temperature determination S42, the heating step is performed. If the T2 temperature is above, for example, 250°C in the T2 temperature determination S44, the thermal oil is cooled with the refrigerant of the second cooler 523.
Next, in the heating steps S46 to S49, the T2 temperature determination S46 (during heating) and the T3 temperature determination S48 are performed. In the T2 temperature determination S46, the T2 temperature is determined. If the T2 temperature is below, for example, 240°C, the oil heater 522 is activated to heat the thermal oil (S47). In the T3 temperature determination S48, if the T3 temperature exceeds, for example, 250°C, the oil heater 522 is stopped (S49). After the oil heater 522 is stopped, the T1 temperature determination S42 for the cooling step is performed. On the other hand, if the T2 temperature is above, for example, 240°C in the T2 temperature determination S46, the T1 temperature determination S42 for the cooling step is performed. If the T3 temperature is below, for example, 250°C in the T3 temperature determination S48, the thermal oil is heated by the oil heater 522 (S47).
Although FIG. 9 shows a flow in which the cooling step is performed first, the order of the cooling step and the heating step can be reversed.

In this embodiment of the hydrocarbon production system 1, the first heat exchanger 51 exchanges heat from the produced gas with the raw liquid water or raw steam in the steam supply line 4. This allows the first heat exchanger 51 to recover heat from the produced gas and use it to generate raw steam that is supplied to the electrolysis device 3. This increases the thermal efficiency of the hydrocarbon production system 1.

(Embodiment 2)
Next, an embodiment of a hydrocarbon production system 1 including two hydrocarbon production devices 2 will be described with reference to Fig. 12. Note that, among the symbols used in the second and subsequent embodiments, the same symbols as those used in the previous embodiments represent the same components as those in the previous embodiments, unless otherwise specified.

As shown in FIG. 12, the hydrocarbon production system 1 of this embodiment includes two hydrocarbon production apparatuses 2, which are connected in series. Specifically, the gas flow paths of each hydrocarbon production apparatus 2 are connected in series. Each of the two hydrocarbon production apparatuses 2 includes a hydrocarbon production reactor 22. In FIG. 12, a first production reactor 221 is provided upstream of the gas flow path, and a second production reactor 222 is provided downstream of the first production reactor 221. The two hydrocarbon production apparatuses 2 have the same configuration as each other, and each has the same configuration as in embodiment 1. The third cooler 543 cools the production gas discharged from the second production reactor 222 and heat exchanged in the third heat exchanger 53, and liquefies the water vapor. The other configurations are the same as in embodiment 1.

The first heat exchanger 51 can exchange heat from the product gas discharged from each hydrocarbon production unit 2 with the feed liquid water or feed steam in the steam supply line 4. Preferably, the first heat exchanger 51 exchanges heat from the product gas discharged from the hydrocarbon production unit 2 located most upstream (specifically, the first production reactor 221) with the feed liquid water or feed steam in the steam supply line 4. In this case, the thermal efficiency of the hydrocarbon production system 1 is further improved. This is because the first production reactor 221 has the highest reaction rate and contains the most water vapor in the product gas. The rest of the configuration can be the same as in embodiment 1, and the same effects as embodiment 1 are achieved.

The present invention is not limited to the above-described embodiments and can be applied to various embodiments without departing from the spirit of the present invention. For example, the hydrocarbon production system 1 can achieve carbon neutrality in factories such as aluminum melting furnaces. Specifically, the _CO2 capture device 61 in the hydrocarbon production system 1 captures carbon dioxide emitted from the aluminum melting furnace and uses it to produce hydrocarbons such as methane in the hydrocarbon production device 2. The hydrocarbons are then used as combustion heat for the aluminum melting furnace. In this way, a carbon neutral environment can be achieved. The aluminum melting furnace is one example, and the present invention can be used in various factories, facilities, devices, and the like that use combustion.

The features of the present invention are as follows.
[1] A hydrocarbon generator (2) for generating hydrocarbons and water vapor by an exothermic reaction between carbon dioxide gas and hydrogen;
an electrolysis device (3) that generates hydrogen from raw steam to be supplied to the hydrocarbon generation device;
a steam supply line (4) for evaporating the raw material liquid water to generate the raw material steam and supplying the raw material steam to the electrolysis device;
a heat exchanger (51) for exchanging heat of the produced gas containing the water vapor discharged from the hydrocarbon production apparatus with the raw material liquid water or the raw material water vapor in the water vapor supply line,
A hydrocarbon production system (1), wherein a steam partial pressure P1 of the produced gas in the heat exchanger is higher than a pressure P2 of the raw steam supplied to the electrolysis device.
[2] The hydrocarbon production system according to [1], wherein the pressure difference P1-P2 between the steam partial pressure P1 and the raw steam pressure P2 is 50 kPa or more.
[3] A hydrocarbon production system described in [1] or [2], wherein the heat exchanger is configured to evaporate part or all of the raw material liquid water received in the heat exchanger, and the condensation heat of the water vapor in the produced gas is utilized as the latent heat of evaporation of the raw material liquid water.
[4] The hydrocarbon production system according to any one of [1] to [3], further comprising a compressor (33) for compressing hydrogen produced in the electrolysis device.
[5] The hydrocarbon production system according to any one of [1] to [4], wherein the heat exchanger is a first heat exchanger (51), and the hydrocarbon production system further includes a second heat exchanger (52) that recovers reaction heat generated in the hydrocarbon production device via thermal oil, and the second heat exchanger is disposed downstream of the first heat exchanger in the gas flow path.
[6] A hydrocarbon production system according to any one of [1] to [5], configured to utilize a portion of the heat of the produced gas discharged from the hydrocarbon production device to heat carbon dioxide gas and hydrogen supplied to the hydrocarbon production device.
[7] A hydrocarbon production system according to any one of [1] to [6], which has a plurality of the hydrocarbon production apparatuses connected in series with each other, and the heat exchanger exchanges heat of the produced gas discharged from the hydrocarbon production apparatus that is the most upstream of the plurality of the hydrocarbon production apparatuses in the gas flow path with the raw material liquid water or the raw material steam in the steam supply line.

1 Hydrocarbon production system 2 Hydrocarbon production device 3 Electrolysis device 4 Steam supply line 5 Heat exchanger

Claims (7)

a hydrocarbon generator (2) for generating hydrocarbons and water vapor by an exothermic reaction between carbon dioxide gas and hydrogen;
an electrolysis device (3) that generates hydrogen from raw steam to be supplied to the hydrocarbon generation device;
a steam supply line (4) for evaporating the raw material liquid water to generate the raw material steam and supplying the raw material steam to the electrolysis device;
a heat exchanger (51) for exchanging heat of the produced gas containing the water vapor discharged from the hydrocarbon production apparatus with the raw material liquid water or the raw material water vapor in the water vapor supply line,
A hydrocarbon production system (1), wherein a steam partial pressure P1 of the produced gas in the heat exchanger is higher than a pressure P2 of the raw steam supplied to the electrolysis device. The hydrocarbon production system described in claim 1, wherein the pressure difference P1-P2 between the steam partial pressure P1 and the feed steam pressure P2 is 50 kPa or more. The hydrocarbon production system described in claim 1 or 2, wherein the heat exchanger is configured to evaporate some or all of the feed liquid water received in the heat exchanger, and the heat of condensation of the water vapor in the produced gas is used as the latent heat of vaporization of the feed liquid water. The hydrocarbon production system according to claim 1 or 2, further comprising a compressor (33) for compressing the hydrogen produced in the electrolysis device. The hydrocarbon production system according to claim 1 or 2, wherein the heat exchanger is a first heat exchanger (51), and the hydrocarbon production system further includes a second heat exchanger (52) that recovers reaction heat generated in the hydrocarbon production device via thermal oil, the second heat exchanger being arranged downstream of the first heat exchanger in the gas flow path. The hydrocarbon production system described in claim 1 or 2, configured to utilize a portion of the heat of the product gas discharged from the hydrocarbon production device to heat the carbon dioxide gas and hydrogen supplied to the hydrocarbon production device. The hydrocarbon production system according to claim 1 or 2, which has a plurality of hydrocarbon production apparatuses connected in series, and the heat exchanger exchanges heat from the produced gas discharged from the hydrocarbon production apparatus furthest upstream in the gas flow path among the plurality of hydrocarbon production apparatuses with the raw liquid water or raw steam in the steam supply line.