Hydrocarbon production system and carbon dioxide circulation system

Abstract

To provide a hydrocarbon generation system which can generate hydrocarbon while stably performing heat exchange, and a carbon dioxide circulation system utilizing the hydrocarbon generation system.SOLUTION: A hydrocarbon generation system 1 is provided, having a hydrocarbon generation device 2, an electrolytic device 3, a steam supply line 4, and a heat exchanger 51. The hydrocarbon generation device 2 generates hydrocarbon and steam by exothermic reaction of carbon oxide gas and hydrogen. The electrolytic device 3 generates from raw material steam, hydrogen supplied to the hydrocarbon generation device. The steam supply line 4 evaporates raw material liquid water to generate raw material steam, and also supplies the raw material steam to the electrolytic device. The heat exchanger 51 utilizes reaction heat generated in the hydrocarbon generation device, in evaporation of the raw material liquid water in the steam supply line, through heat medium oil.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a hydrocarbon production system having a hydrocarbon production device and an electrolysis device, and a carbon dioxide circulation system including the same. [Background technology]

[0002] Known methods for producing hydrocarbons include methanation, which uses the Sabatier reaction to produce methane from carbon dioxide and hydrogen, and hydrogen production through the electrolysis of steam.

[0003] 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, the heat of the reaction can be used to generate hydrogen, thereby improving thermal energy efficiency. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-108238 Summary of the Invention [Problem to be solved by the invention]

[0005] 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 of the Sabatier reaction is not enough to provide the necessary thermal energy.

[0006] 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. 4H2O (liquid) → 4H2O (gas) (1) 4H2O (gas) → 4H2 + 2O2 (2) CO2 + 4H2 → CH4 + 2H2O (3)

[0007] For example, if 4 moles of water at 25°C is heated to 100°C and boiled, 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 reaction heat, making the difference in heat even greater. Therefore, thermal energy must be supplied from an external source. Meanwhile, the amount of heat generated in hydrocarbon production reactions such as methanation varies depending on the amount of hydrocarbon produced. Therefore, the amount of heat supplied from an external source must be adjusted to match the amount of heat generated in the hydrocarbon production reaction, making it difficult to control the amount of heat supplied.

[0008] The present invention has been made in view of the above problems, and aims to provide a hydrocarbon production system capable of producing hydrocarbons while stably performing heat exchange, and a carbon dioxide circulation system utilizing the hydrocarbon production system. [Means for solving the problem]

[0009] One aspect of the present invention is a hydrocarbon production device (2, 21, 22) for producing hydrocarbons 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) that utilizes reaction heat generated in the hydrocarbon generation apparatus to evaporate the raw material liquid water in the steam supply line via heat transfer oil; and No water evaporation means is provided between the heat exchanger and the electrolysis device in the water vapor supply line, and the raw material liquid water supplied to the heat exchanger is entirely vaporized by receiving heat from the heat transfer oil. And, The system further includes a heater for heating the thermal oil and a temperature sensor for sensing the temperature of the thermal oil flowing into the heater, The heater is installed on the circulation path of the thermal oil, downstream of the heat exchanger, and upstream of the hydrocarbon production reaction device, and is configured to control the amount of heating based on the sensing value of the temperature sensor. , in hydrocarbon production systems (1).

[0010] Another aspect of the present invention is a hydrocarbon production system (1) as described above, a combustion furnace (71) that uses hydrocarbons as fuel and emits carbon dioxide; a carbon dioxide supply line (72) for supplying carbon dioxide discharged from the combustion furnace as the carbon oxide gas to the hydrocarbon production device of the hydrocarbon production system; a hydrocarbon supply line (73) for supplying hydrocarbons produced in the hydrocarbon production device to the combustion furnace; The carbon dioxide circulation system (7) is configured to adjust the amount of hydrocarbons produced in the hydrocarbon production device depending on the operating state of the combustion furnace. [Effects of the Invention]

[0011] As described above, the hydrocarbon production system includes a hydrocarbon production apparatus, an electrolysis apparatus, a steam supply line, and a heat exchanger. The heat exchanger utilizes the reaction heat generated in the hydrocarbon production apparatus to evaporate the raw material liquid water in the steam supply line. In the heat exchanger, the reaction heat is utilized to evaporate the raw material liquid water via heat transfer oil.

[0012] Because thermal oil has a large heat capacity, it can retain a large amount of heat after heat recovery in heat exchange. Therefore, when the amount of heat generated in the hydrocarbon production reaction is large, the thermal oil can recover sufficient reaction heat, and this reaction heat can be used to evaporate the raw material liquid water in the steam supply line. On the other hand, because the thermal oil can store sufficient reaction heat, even if the amount of reaction heat generated in the hydrocarbon production reaction fluctuates and the heat value becomes low or even zero, the heat retained in the thermal oil can be supplied to the raw material liquid water in the steam supply line and used to evaporate the raw material liquid water. In the above-mentioned hydrocarbon production system, heat exchange is performed stably even if the amount of reaction heat fluctuates.

[0013] As described above, the carbon dioxide circulation system includes a hydrocarbon production system, a combustion furnace, a carbon dioxide supply line, and a hydrocarbon supply line. In the hydrocarbon production device of the hydrocarbon production system, hydrocarbons are produced by an exothermic reaction between carbon dioxide or other carbon oxide gases and hydrogen. The hydrocarbons are supplied to the combustion furnace via the hydrocarbon supply line. In the combustion furnace, carbon dioxide is emitted by combustion of the hydrocarbons. The carbon dioxide is supplied to the hydrocarbon production device of the hydrocarbon production system via the carbon dioxide supply line. In this way, in the carbon dioxide circulation system, carbon dioxide circulates between the hydrocarbon production system and the combustion furnace. This makes it possible to build a so-called carbon-neutral system in which greenhouse gas emissions are suppressed.

[0014] The carbon dioxide circulation system is configured to adjust the amount of hydrocarbons produced in the hydrocarbon production device according to the operating state of the combustion furnace. As a result, even if the required amount of hydrocarbons fluctuates depending on the operating state of the combustion furnace, the hydrocarbon production system can produce hydrocarbons according to the fluctuation and supply them to the combustion furnace.

[0015] As described above, according to the above-described aspects, it is possible to provide a hydrocarbon production system capable of producing hydrocarbons while stably performing heat exchange, and a carbon dioxide circulation system utilizing the hydrocarbon production system. In addition, the symbols in parentheses described 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. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a block diagram showing the main configuration of a hydrocarbon production system according to a first embodiment. [Figure 2] FIG. 1 is a block diagram showing a hydrocarbon production system that produces hydrocarbons using carbon dioxide and hydrogen in a first embodiment. [Figure 3] FIG. 1 is a block diagram showing a hydrocarbon production system that produces hydrocarbons using carbon monoxide and hydrogen in a first embodiment. [Figure 4] FIG. 2 is an operational flow diagram showing the start-up process of the hydrocarbon production system in the first embodiment. [Figure 5] FIG. 2 is an operational flow diagram of hydrogen production control in the hydrocarbon production system according to the first embodiment. [Figure 6] FIG. 2 is an operational flow diagram of hydrocarbon production in the hydrocarbon production system according to the first embodiment. [Figure 7] FIG. 3 is an operational flow diagram of temperature control in the hydrocarbon production system according to the first embodiment. [Figure 8] FIG. 10 is a block diagram showing a hydrocarbon production system according to a second embodiment. [Figure 9] FIG. 10 is a block diagram showing a hydrocarbon production system according to a third embodiment. [Figure 10] FIG. 10 is an explanatory diagram showing the heat balance in the hydrocarbon production system according to the third embodiment. [Figure 11] 10 is a graph showing the relationship between the water vapor partial pressure and the condensation temperature of water in the third embodiment. [Figure 12] 10 is a graph showing the relationship between the amount of recovered heat and the temperature of the produced gas in the third embodiment. [Figure 13] 11 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 third embodiment. [Figure 14] 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. [Figure 15] FIG. 10 is an operational flow diagram showing hydrogen production control of the hydrocarbon production system in the third embodiment. [Figure 16] FIG. 10 is an operational flow diagram of hydrocarbon production in the hydrocarbon production system according to the third embodiment. [Figure 17] FIG. 10 is a block diagram showing a hydrocarbon production system according to a fourth embodiment. [Figure 18] FIG. 10 is a block diagram showing a hydrocarbon production system according to a fifth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0017] (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 or physical values ​​written before and after it. Furthermore, when a numerical or physical value is written as an upper or lower limit, it is intended to include that value.

[0018] As shown in FIGS. 1 and 2, the hydrocarbon production system 1 of this embodiment includes a hydrocarbon production device 2, an electrolysis device 3, a steam supply line 4, and a heat exchanger 51.

[0019] The hydrocarbon producer 2 produces hydrocarbons and water vapor through an exothermic reaction between carbon dioxide gas and hydrogen. The hydrocarbon production reaction in the hydrocarbon producer 2 is usually carried out at 200 to 500°C, and a product gas at 200 to 500°C is produced.

[0020] Examples of carbon oxide gases include carbon monoxide and carbon dioxide. Carbon dioxide is preferred because it is easily available from factory combustion furnaces, the atmosphere, etc., and carbon monoxide is preferred because it has high reactivity in producing hydrocarbons. Carbon dioxide and carbon monoxide may be used in combination as carbon oxide gases. 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 by the Sabatier reaction shown in formula (I) below.

[0021] 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). Note that ΔH in formula (I) represents the enthalpy change before and after the reaction. CO2+4H2→CH4+2H2O (ΔH=-165kJ / mol)...(I)

[0022] As shown in FIG. 2, the hydrocarbon production device 2 specifically includes a production reactor 22 (hereinafter referred to as reactor 22 as appropriate) in which a hydrocarbon production reaction takes place, and mass flow controllers 26 and 27 that control the amount of gas supplied to the 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 capture device 61. The CO2 capture device 61 captures 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 produce carbon monoxide.

[0023] The electrolysis device 3 generates hydrogen from raw steam to be supplied to the hydrocarbon production device 2. The electrolysis device 3 is configured, for example, with an electrolysis reactor and a cell stack housed in the electrolysis reactor, although the configuration is not shown. The cell stack is configured with a plurality of solid oxide electrolysis cells (i.e., SOEC). The specific configuration of the electrolysis device 3 is not shown, but a configuration used in the electrolysis of steam using an SOEC or the co-electrolysis of steam and carbon dioxide, which will be described later, can be adopted. 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. H2O(g) → H2 + 1 / 2O2 (II)

[0024] 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. 3, 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, since highly reactive carbon monoxide is used as the carbon oxide gas, the hydrocarbon production reaction progresses more easily. 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, that is, water is steam. In formula (V), n is a natural number. Although FIG. 3 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 produced in the electrolysis device 3 in separate tanks. CO2+3H2O(g)→CO+3H2+2O2···(III) CO+3H2→CH4+H2O(g) ···(IV) nCO+(2n+1)H2→C n H 2n+2 +nH2O(g) (V)

[0025] The steam supply line 4 evaporates the raw water liquid to generate raw water vapor as shown in formula (VI), and supplies the raw water vapor to the electrolysis device 3. In the steam supply line 4, the raw water liquid is sent to the electrolysis device side by, for example, a pump 45. An evaporator 41 is provided inside the steam supply line 4, and supplies thermal energy to the raw water liquid to evaporate the raw water liquid to generate raw water vapor. The pump 45 transports the raw water vapor to the electrolysis device 3. The evaporator 41 is configured to exchange heat with a first heat exchanger 51. H2O(l) → H2O(g) (VI)

[0026] 1 and 2, the heat exchanger 51 (specifically, the first heat exchanger 51) utilizes the reaction heat generated in the hydrocarbon production apparatus 2 through heat exchange to evaporate the raw material liquid water in the steam supply line 4. The first heat exchanger 51 recovers the reaction heat via heat transfer oil, and allows the raw material liquid water to receive the heat.

[0027] Since thermal oil is used, for example, an oil heater 522 and an oil pump 521 are connected to the first heat exchanger 51. The oil pump 521 is also called a thermal oil pump 521. A cooler 523 (specifically, a second cooler 523) can be connected to the first heat exchanger 51 to compensate for insufficient cooling. The refrigerant is, for example, water. In Figures 1 and 2, the flow of the thermal oil is represented by a solid line, and the flow direction is counterclockwise. The same applies to the flow of the thermal oil illustrated in the subsequent figures.

[0028] It is preferable that no water evaporation means is provided between the first heat exchanger 51 and the electrolysis device 3 in the water vapor supply line 4. In this case, the raw material liquid water supplied to the first heat exchanger 51 is entirely vaporized by receiving heat from the thermal oil. Therefore, raw material steam can be produced from the raw material liquid water by receiving heat in the first heat exchanger 51, regardless of the amount of heat generated in the hydrocarbon production device 2. An example of the water evaporation means is an evaporator having a configuration similar to that of the first evaporator 41 that exchanges heat with the first heat exchanger 51. Since there is no need to add such an evaporator, the configuration of the hydrocarbon production system 1 is simplified and control is also facilitated.

[0029] The hydrocarbon production system 1 preferably includes a compressor 33 that compresses the hydrogen produced in the electrolysis device 3. In this case, hydrogen pressurized by compression can be supplied to the hydrocarbon production device 2, thereby improving the reaction efficiency of the hydrocarbon production reaction in the hydrocarbon production device 2.

[0030] Since the response speed of the electrolysis device 3 and the response speed of the hydrocarbon production device 2 generally differ, attempting to match the responsiveness of the two devices places a heavy load on one of the devices 2, 3. As a result, hydrogen production and hydrocarbon production become unstable, leading to unstable operation of the system. From the viewpoint of avoiding this, it is preferable that the hydrocarbon production system 1 further includes a buffer tank 35 (specifically, an H2 tank 35) for storing hydrogen, which is disposed between the hydrocarbon production device 2 and the electrolysis device 3. In this case, the buffer tank 35 can absorb the difference in the amount of hydrogen transferred due to the difference in response speed, thereby improving the stability of the system. From the viewpoint of further improving this effect, it is preferable to adjust the flow rate of the thermal oil to 50 to 150 times the flow rate of the raw liquid water or raw steam.

[0031] The operation of the hydrocarbon production system 1 of this embodiment will be described with reference to the operational flow diagrams shown in Figs. 4 to 7. In the following description, T1, T2, and T3 represent the temperature sensors shown in Fig. 2. The temperature sensors may be, for example, thermometers. The flow diagram is 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).

[0032] <Start-up process> 4, when the hydrocarbon production system 1 starts operating, 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).

[0033] <Control of hydrogen generation> As shown in Fig. 5, when hydrogen generation starts, the pump 45 of the water vapor supply line 4 is activated (S211). The pump 45 sends a specified amount of water (specifically, raw liquid water) to the first heat exchanger 51 based on a command value for the amount of hydrogen generated (S221). In the first heat exchanger 51, the water evaporates to generate raw water vapor, which is then sent to the electrolysis device 3. In the electrolysis device 3, water is electrolyzed to generate hydrogen (S231). 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. 2).

[0034] <Control of hydrocarbon production> As shown in Fig. 6, when hydrocarbon production is started, hydrogen and CO2 are supplied to the reactor 22 based on a command value for the amount of hydrocarbon production (e.g., the amount of methane produced) (S311). Hydrogen is supplied from the H2 tank 35, and CO2 is supplied from the recovery machine 61. In the reactor 22, for example, a methanation reaction is carried out to produce methane and water (water vapor) (S321). The produced gas is supplied to the first heat exchanger 51 and cooled, condensing the water (S331). The condensed water is separated, for example, by the gas-liquid separator 65, and high-concentration methane is produced (S341).

[0035] <Thermal oil temperature control> As shown in FIG. 10, the temperature of the thermal oil is controlled by controlling the cooling steps S41 to S45 and the heating steps S46 to S49 while the thermal oil is circulated by the thermal oil pump 521. In the cooling steps S41 to 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, and if the T1 temperature exceeds, for example, 260°C, the second cooler 523 is operated and the thermal oil is cooled with the refrigerant (S43). In the T2 temperature determination S44, the T2 temperature is determined, and if the T2 temperature is less than, for example, 250°C, the second cooler 523 is stopped (S45). On the other hand, if the T1 temperature is equal to or lower than, for example, 260°C in the T1 temperature determination S42, the heating step is performed, and if the T2 temperature is equal to or higher than, 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, a T2 temperature determination S46 (during heating) and a T3 temperature determination S48 are performed. In the T2 temperature determination S46, the T2 temperature is determined, and if the T2 temperature is less than, 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 heater 522 is stopped (S49). After the oil heater 522 is stopped, the T1 temperature determination S42 in the cooling step is performed. On the other hand, if the T2 temperature is, for example, 240°C or higher in the T2 temperature determination S46, the T1 temperature determination S42 in the cooling step is performed, and if the T3 temperature is, for example, 250°C or lower in the T3 temperature determination S48, the thermal oil is heated by the oil heater 522 (S47). Although FIG. 10 shows a flow in which the cooling step is performed first, the order of the cooling step and the heating step can be reversed.

[0036] Also, with reference to FIG. 1, an image of temperature control of the heat transfer oil when the temperature of the production reactor 22 is controlled to, for example, 250° C. will be described. (a) When the temperature of T1 is 240 to 260°C (that is, when the amount of heat generated is equal to the amount of recovery), the cooler 523 is stopped, and the oil heater 522 is also stopped. (b) If the temperature of T1 is less than 240°C (that is, if the amount of heat generated is less than the amount of recovery), the cooler 523 is stopped and the heating by the oil heater 522 is controlled so that T3=250°C. (c) When the temperature of T1 exceeds 260°C (that is, when the amount of heat generated is greater than the amount of recovery), the oil heater 522 is stopped and the cooling by the cooler 523 is controlled so that T2=250°C.

[0037] In the Sabatier reaction, the case where the amount of methane produced in the hydrocarbon production device 2 is 1 / 4 mole per mole of hydrogen produced in the electrolysis device 3 corresponds to the case (b) above, but for example, if water evaporation is stopped for some reason, the case (c) above can also occur. Therefore, it is preferable to install a cooler 523 for cooling the heat transfer oil. When the heat generation amount is less than the recovery amount, the temperature of the thermal oil gradually decreases. However, by heating with the oil heater 522, the temperature of the thermal oil can be kept constant throughout the entire circulation path, and the temperature of the production reactor 22 can be maintained at a predetermined temperature, such as 250°C.

[0038] 1 to 7, the hydrocarbon production system 1 of this embodiment includes the hydrocarbon production apparatus 2, the electrolysis apparatus 3, the steam supply line 4, and the heat exchanger 51 (specifically, the first heat exchanger 51), as described above. The first heat exchanger 51 utilizes the reaction heat generated in the hydrocarbon production apparatus 2 for evaporating the raw material liquid water in the steam supply line 4. In the first heat exchanger 51, the reaction heat is utilized for evaporating the raw material liquid water via heat transfer oil.

[0039] The thermal oil has a larger heat capacity than gases such as steam. Therefore, the thermal oil has a large heat capacity after heat recovery. For example, when the amount of heat generated in the hydrocarbon generator 2 is large, the thermal oil can recover sufficient reaction heat, and this reaction heat can be used to evaporate the raw material liquid water in the steam supply line 4.

[0040] On the other hand, since the thermal oil can store sufficient heat of reaction, even if the amount of reaction heat generated in the hydrocarbon generator 2 fluctuates and the calorific value decreases or becomes zero, for example, the heat held by the thermal oil can be supplied to the raw material liquid water in the steam supply line 4 and used to evaporate the raw material liquid water. In other words, the hydrocarbon generator 2 is more robust against fluctuations in the calorific value.

[0041] The hydrocarbon production system 1 preferably has a temperature sensor T2 that senses the temperature of the thermal oil flowing into the oil heater 522, and the oil heater 522 is installed on the circulation path of the thermal oil and downstream of the first heat exchanger 51, and is configured to control the amount of heating based on the sensing value of the temperature sensor T2. In this case, the temperature control of the thermal oil becomes easy. In addition, the oil heater 522 is preferably also used to increase the temperature (i.e., warm up) of the hydrocarbon production device 2 when the hydrocarbon production system is started up. Therefore, when the oil heater 522 is provided, there is no need to provide a separate heating device for start-up.

[0042] The hydrocarbon production system 1 is preferably configured to include a cooler 23 (specifically, the second cooler 23) downstream of the first heat exchanger in the flow direction of the thermal oil, and a temperature sensor T1 that senses the temperature of the thermal oil flowing into the cooler 23, and to perform cooling based on the sensing value of the temperature sensor T1. In this case, as shown in Fig. 7, for example, the thermal oil is cooled by the cooler 23 based on the sensing value (i.e., temperature) of T1, making it easier to control the temperature of the thermal oil within a desired temperature range.

[0043] (Embodiment 2) Next, an embodiment of a hydrocarbon production system 1 including two hydrocarbon production devices 2 will be described with reference to Fig. 8. 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.

[0044] As shown in FIG. 8, the hydrocarbon production system 1 of this embodiment includes two hydrocarbon production apparatuses 21 and 22, which are connected in series. Specifically, the gas flow paths of the hydrocarbon production apparatuses 2 are connected in series. The two hydrocarbon production apparatuses 2 each include a hydrocarbon production reactor 22. In FIG. 8, 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 21 and 22 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 that is discharged from the second production reactor 222 and has been heat exchanged in the third heat exchanger, and liquefies the water vapor. The other configurations are the same as in embodiment 1, and the same effects as in embodiment 1 are achieved.

[0045] (Embodiment 3) Next, a hydrocarbon production system 1 including a second heat exchanger 52 will be described with reference to Fig. 9 to Fig. 16. As shown in Fig. 9, the second heat exchanger 52 exchanges heat energy of the produced gas containing water vapor discharged from the hydrocarbon production apparatus 2 with the raw material liquid water or raw material steam in the steam supply line 4.

[0046] In this embodiment, the steam supply line 4 includes, for example, evaporators 41 and 42 (specifically, a first evaporator 41 and a second evaporator 42) and a pump 45. The evaporators 41 and 42 supply thermal energy to the raw material liquid water and / or raw material steam. In the first evaporator 41, heat exchange is performed by the first heat exchanger 51 using thermal oil, and in the second evaporator 42, heat exchange is performed by the second heat exchanger 52 using the generated gas.

[0047] As shown in Fig. 9, the second heat exchanger 52 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 possessed by 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 in 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 for further cooling the product gas whose heat has been released in the first heat exchanger 51. The refrigerant is, for example, water.

[0048] The second heat exchanger 52 recovers the thermal energy of 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 water liquid or the feed steam. The second heat exchanger 52 preferably uses at least the water vapor in the product gas as a heat transfer medium and exchanges the heat of this heat transfer water vapor with the feed water liquid or the feed steam. In this case, the second heat exchanger 52 can use the condensation heat of the water vapor to evaporate the water in the water vapor supply line 4. Furthermore, when the second heat exchanger 52 exchanges the heat of the hydrocarbons, the heat balance in the hydrocarbon production system 1 is further improved, and the thermal efficiency is further enhanced. The hydrocarbon production reaction generates reaction heat and latent heat of vaporization, and the latent heat of vaporization is distributed to the water vapor of the product gas, and the reaction heat is distributed to the heat transfer oil and / or the product gas. Therefore, the heat of the product gas refers to the latent heat of vaporization and a portion of the heat of reaction, and the heat of the product gas can also be referred to as the heat retained by the product gas after it has been recovered by the heat transfer oil in the first heat exchanger 51.

[0049] 9, the steam supply line 4 can be provided 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 also possible to use a single evaporator that receives heat from both the first heat exchanger 51 and the second heat exchanger 52.

[0050] 9, the first heat exchanger 51 is preferably disposed downstream of the second heat exchanger 52 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 first heat exchanger 51, which is disposed downstream of the second heat exchanger 52, uses thermal oil with a large heat capacity, and efficient heat exchange is performed in this first heat exchanger 51.

[0051] As shown in Figure 10, 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, and latent heat associated with phase transition above 100°C. The reaction heat from the hydrocarbon production reaction typically provides approximately 50 to 70% of the heat required for water evaporation. Meanwhile, the condensation temperature of water depends on the partial pressure. As shown in Figure 11, 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, making it possible to raise the condensation temperature. This increases the amount of heat that can be recovered from the product gas, and this recovered heat and the reaction heat from the hydrocarbon production reaction can provide almost all of the thermal energy required to generate raw steam (see Figure 10).

[0052] In the hydrocarbon production system 1, the water vapor partial pressure P1 of the product gas in the second heat exchanger 52 is preferably 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. 9, hydrogen is compressed, for example, by a compressor 33 that compresses the hydrogen produced in the electrolysis device 3. Although not shown in the figure, 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 the 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.

[0053] 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 percent 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 is 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 in, for example, the production reactor 22 of the hydrocarbon production apparatus 2 is usually higher, and the reaction rate of hydrocarbon production also increases.

[0054] Paradoxically, from the viewpoint of improving the heat balance in the hydrocarbon production system 1, it can be said that it is preferable that the second heat exchanger 52 is configured to evaporate part or all of the feed liquid water that receives heat in the second heat exchanger 52, and that the condensation heat of the water vapor in the produced gas is used as the latent heat of evaporation of the feed liquid water. A specific configuration for utilizing the condensation heat of the water vapor for the feed liquid water is the compressor for compressing hydrogen and / or carbon dioxide, as described above.

[0055] Equations (VII) to (IX) illustrate the main chemical reactions in the hydrocarbon production system 1. HO (liquid, 25 °C) → HO (gas, 100 °C) (ΔH = 46.3 kJ / mol) (VII) H2O → H2 + 1 / 2O2 (VIII) CO2+4H2→CH4+2H2O (ΔH=-165kJ / mol)...(IX)

[0056] As shown in equations (VII) to (IX), 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). On the other hand, 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. In addition, because heat is dissipated, 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.

[0057] 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 the water vapor generated in the methanation reaction depends on the pressure, but is generally around 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 will be in competition, and no temperature difference will occur. The heat exchange amount Q in the heat exchanger is expressed by the following formula (X). However, if there is no temperature difference (i.e., ΔT = 0), heat exchange will not occur 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 (X)

[0058] 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 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.

[0059] In contrast, by pressurizing the product gas, the condensation temperature of the water vapor contained in the product gas from methanation becomes higher than the evaporation temperature of the water supplied to the electrolysis device 3. Therefore, the condensation heat of the water vapor contained in the product gas from methanation can be recovered as the evaporation heat of the water supplied to the electrolysis device 3.

[0060] Figure 13 shows the relationship between the heat exchange area of ​​the second heat exchanger and the amount of condensation heat recovered. The vertical axis in Figure 13 shows the amount of heat that can be recovered from water vapor when methane is synthesized at 1 mol / sec. Note that the plots for 80 kW or more in Figure 13 represent the amount of heat recovered from liquid water after condensation.

[0061] As can be seen from Figure 13, 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 second heat exchanger can be made smaller.

[0062] FIG. 14 shows the relationship between the pressure difference of the steam and the heat exchange area required to recover all the condensation heat. As can be seen from FIG. 14, when the pressure difference is 50 kPa or more, the reduction in the required heat exchange area is small even if the pressure is increased. Furthermore, by setting the pressure difference P1-P2 between the steam partial pressure P1 of the generated gas in the second heat exchanger 52 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 FIG. 13 and FIG. 14 plot data calculated based on a steam pressure of 100 kPa (equivalent to atmospheric pressure) in the electrolysis device 3. However, even if the reference steam pressure of the electrolysis device 3 is changed, the same trends as those in FIG. 13 and FIG. 14 are observed. From the perspective of the pressure resistance of the heat exchanger, it is preferable that the pressure difference P1-P2 be 1000 kPa or less.

[0063] It is preferable that a portion of the heat of the product gas discharged from the hydrocarbon generator 2 is utilized to heat the carbon oxides 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 utilized for the hydrocarbon production reaction. This further improves the heat balance. A specific configuration for utilizing a portion of the heat of the product gas to heat the carbon oxides and hydrogen is a heat exchanger (specifically, a third heat exchanger 53) as shown in FIG. 9. The third heat exchanger 53 recovers a portion of the heat of the product gas and causes the carbon oxides and hydrogen to receive the recovered heat. Note that, for ease of illustration, two third heat exchangers are illustrated in the drawing, but in reality, they represent one heat exchanger. The other configurations are the same as those of the first embodiment, and the same effects as those of the first embodiment are achieved.

[0064] The operation of the hydrocarbon production system 1 of this embodiment will be described with reference to the operation flow diagrams shown in Figures 4, 7, 15, and 16. The flow diagrams show an example in which the thermal oil temperature is controlled within a range of 240 to 260°C, and the temperature is changeable. The operation flow is controlled, for example, by a control unit (not shown).

[0065] <Start-up process> The start-up process is the same as that in the first embodiment (see FIG. 4), for example.

[0066] <Control of hydrogen generation> As shown in FIG. 14, when hydrogen generation starts, the pump 45 of the water vapor supply line 4 is activated (S212). The pump 45 sends a specified amount of water (specifically, raw liquid water) to the second heat exchanger 52 and the first heat exchanger 51 based on a command value for the amount of hydrogen generated (S212). These heat exchangers 51 and 52 cause water evaporation, generating raw water vapor, which is then sent to the electrolysis device 3. In the electrolysis device 3, water is electrolyzed to generate hydrogen (S232). 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. 9).

[0067] <Control of hydrocarbon production> As shown in FIG. 16, when hydrocarbon production starts, hydrogen and CO2 are supplied to the reactor 22 based on a command value for the amount of hydrocarbon production (e.g., the amount of methane produced) (S312). Hydrogen is supplied from the H2 tank 35, and CO2 is supplied from the recovery machine 61. In the reactor 22, for example, a methanation reaction is carried out to produce methane and water (water vapor) (S322). The produced gas is supplied to the second heat exchanger 52 and cooled, and the water is condensed (S332). The amount that is not cooled is cooled by the first cooler 513, and the water is condensed (S342). The condensed water is separated, for example, by the gas-liquid separator 65, and high-concentration methane is produced (S352).

[0068] <Thermal oil temperature control> The temperature control of the thermal oil is the same as in the first embodiment (see FIG. 7), for example.

[0069] In the hydrocarbon production system 1 of this embodiment, the first heat exchanger 51 transfers heat from the heat transfer oil to the raw material liquid water in the steam supply line 4. Furthermore, the second heat exchanger 52 exchanges heat from the produced gas with the raw material liquid water or raw material steam in the steam supply line 4, so that, for example, the raw material steam can receive heat. This improves the thermal efficiency of the hydrocarbon production system 1.

[0070] (Embodiment 4) Next, an embodiment of a hydrocarbon production system 1 including two hydrocarbon production apparatuses 2 will be described with reference to Fig. 17. As shown in Fig. 17, the hydrocarbon production system 1 of this embodiment includes two hydrocarbon production apparatuses 2, which are connected in series in the same manner as in embodiment 2. The other configurations are the same as in embodiment 3.

[0071] The second heat exchanger 52 can exchange heat between the product gas discharged from each hydrocarbon production unit 2 and the feed water liquid or the feed water vapor in the steam supply line 4. Preferably, the second heat exchanger 52 exchanges heat between the product gas discharged from the hydrocarbon production unit 2 located most upstream (specifically, the first production reactor 221) and the feed water liquid or the feed water vapor 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 the product gas contains the most water vapor. The other configurations are the same as those of embodiment 3, and the same effects as those of embodiment 3 are achieved.

[0072] (Embodiment 5) Next, an embodiment of a carbon dioxide circulation system will be described with reference to FIG. 18, the carbon dioxide circulation system 7 includes a hydrocarbon production system 1, a combustion furnace 71, a carbon dioxide supply line 72, and a hydrocarbon supply line 73. As shown in FIG. 18, the hydrocarbon production system 1 can have a configuration similar to that of the first embodiment, for example, but can also have a configuration similar to that of the second to fourth embodiments.

[0073] The combustion furnace 71 is a facility that uses, for example, hydrocarbons as fuel and generates carbon dioxide through combustion. Examples of the combustion furnace 71 include incinerators found in factories and various melting furnaces such as aluminum melting furnaces. Carbon dioxide is emitted from the combustion furnace 71.

[0074] The carbon dioxide supply line 72 supplies the carbon dioxide discharged from the combustion furnace 71 to the hydrocarbon producer 2 of the hydrocarbon production system 1. In the hydrocarbon producer 2, the carbon dioxide is used as carbon oxide gas, and hydrocarbons are produced by a hydrocarbon production reaction.

[0075] The hydrocarbon supply line 73 supplies the hydrocarbons produced in the hydrocarbon production apparatus 2 to the combustion furnace 71. Then, as described above, combustion is carried out in the combustion furnace 71 using the hydrocarbons as fuel. In this way, in the carbon dioxide circulation system 7, carbon dioxide circulates between the hydrocarbon production system 1 and the combustion furnace 71. This makes it possible to build a so-called carbon-neutral system in which greenhouse gas emissions are suppressed.

[0076] The carbon dioxide circulation system 7 is configured so that the amount of hydrocarbons produced in the hydrocarbon production device 2 is adjusted according to the operating state of the combustion furnace 71. The adjustment of the amount of hydrocarbons produced is performed, for example, by a control unit (not shown). As a result, even if the required amount of hydrocarbons fluctuates according to the operating state of the combustion furnace 71, the hydrocarbon production system 1 can produce the required amount of hydrocarbons according to the fluctuation and supply it to the combustion furnace. The supply amount is adjusted, for example, by adjusting the amount of hydrogen produced and the amount of hydrocarbons in the hydrocarbon production system 1.

[0077] In the carbon dioxide circulation system 7, from the viewpoint of system simplification, it is preferable that all of the hydrogen supplied to the hydrocarbon production device 2 is supplied from the electrolysis device 3. In this case, the amount of heat used for evaporating water in the steam supply line 4 is greater on average than the reaction heat generated in hydrocarbon production, and therefore thermal energy needs to be supplied, but in this embodiment, since the first heat exchanger 51 is provided, thermal energy can be additionally supplied from thermal oil.

[0078] The present invention is not limited to the above-described embodiments, and can be applied to various embodiments within the scope of the present invention.

[0079] The features of the present invention are as follows. [1] A hydrocarbon generator (2, 21, 22) for generating hydrocarbons 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) that utilizes reaction heat generated in the hydrocarbon generation apparatus to evaporate the raw material liquid water in the steam supply line via heat transfer oil; A hydrocarbon production system (1) comprising: [2] The hydrocarbon production system according to [1], wherein no water evaporation means is provided in the steam supply line between the heat exchanger and the electrolysis device. [3] Further, the system has a heater for heating the thermal oil and a temperature sensor for sensing the temperature of the thermal oil flowing into the heater, The heater is installed on the circulation path of the thermal oil and downstream of the heat exchanger, and is configured to control the amount of heating based on the sensing value of the temperature sensor. [1] or [2] A hydrocarbon production system described in [1] or [2]. [4] The hydrocarbon production system according to [3], wherein the heater is configured to warm up the hydrocarbon production device at startup. [5] The heat exchanger is a first heat exchanger, The hydrocarbon production system according to any one of [1] to [4], further comprising a second heat exchanger that exchanges heat of the produced gas containing the steam discharged from the hydrocarbon production apparatus with the raw liquid water or the raw steam in the steam supply line. [6] The hydrocarbon production system according to [5], wherein the steam partial pressure P1 of the produced gas in the second heat exchanger is higher than the pressure P2 of the raw steam supplied to the electrolysis device. [7] The hydrocarbon production system according to any one of [1] to [6], further comprising a buffer tank (35) for storing hydrogen, disposed between the hydrocarbon production device and the electrolysis device. [8] A hydrocarbon production system (1) according to any one of [1] to [7]; a combustion furnace (71) that uses hydrocarbons as fuel and emits carbon dioxide; a carbon dioxide supply line (72) for supplying carbon dioxide discharged from the combustion furnace as the carbon oxide gas to the hydrocarbon production device of the hydrocarbon production system; a hydrocarbon supply line (73) for supplying hydrocarbons produced in the hydrocarbon production device to the combustion furnace; a carbon dioxide circulation system (7) configured to adjust the amount of hydrocarbons produced in the hydrocarbon production device according to the operating state of the combustion furnace; [Explanation of symbols]

[0080] 1. Hydrocarbon Production System 2. Hydrocarbon Generation Unit 3 Electrolyzer 4. Steam supply line 51 Heat exchanger 7 Carbon dioxide circulation system

Claims

1. a hydrocarbon generator (2, 21, 22) for generating hydrocarbons 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) that utilizes reaction heat generated in the hydrocarbon production apparatus to evaporate the raw material liquid water in the steam supply line via heat transfer oil; and no water evaporation means is provided between the heat exchanger and the electrolysis device in the water vapor supply line, and the raw material liquid water supplied to the heat exchanger is entirely vaporized by receiving heat from the thermal oil; The system further includes a heater for heating the thermal oil and a temperature sensor for sensing the temperature of the thermal oil flowing into the heater, the heater is installed on the circulation path of the thermal oil, downstream of the heat exchanger and upstream of the hydrocarbon production reaction device, and is configured to control the amount of heating based on the sensing value of the temperature sensor.

2. The hydrocarbon production system of claim 1 , wherein the heater is configured to provide start-up warm-up of the hydrocarbon production device.

3. the heat exchanger is a first heat exchanger, 2. The hydrocarbon production system according to claim 1, further comprising a second heat exchanger that exchanges heat of a produced gas containing steam discharged from the hydrocarbon production device with the raw liquid water or the raw steam in the steam supply line.

4. 4. The hydrocarbon production system according to claim 3, wherein a partial pressure P1 of the steam in the produced gas in the second heat exchanger is higher than a pressure P2 of the raw steam supplied to the electrolysis device.

5. 3. The hydrocarbon production system according to claim 1 or 2, further comprising a buffer tank (35) for storing hydrogen, disposed between the hydrocarbon production device and the electrolysis device.

6. A hydrocarbon production system (1) according to claim 1 or 2; a combustion furnace (71) that uses hydrocarbons as fuel and emits carbon dioxide; a carbon dioxide supply line (72) for supplying the carbon dioxide discharged from the combustion furnace as the carbon oxide gas to the hydrocarbon production device of the hydrocarbon production system; a hydrocarbon supply line (73) that supplies hydrocarbons produced in the hydrocarbon production device to the combustion furnace; a carbon dioxide circulation system (7) configured to adjust the amount of hydrocarbons produced in the hydrocarbon production device according to the operating state of the combustion furnace;

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