Device and method for producing hydrocarbon

Abstract

To provide a device and method for producing a hydrocarbon, capable of efficiently recovering the hydrocarbon while preventing it from adhering to a catalyst and also preventing it from adhering to downstream piping and the like.SOLUTION: A device for producing a hydrocarbon obtains a product containing the hydrocarbon from a raw material gas by means of a Fischer-Tropsch synthesis reaction using a reactor 7 having an FT reaction catalyst that is active in the Fischer-Tropsch synthesis reaction. The device for producing the hydrocarbon includes: a purge section for vaporizing the hydrocarbon that has adhered to the FT reaction catalyst by supplying a high-temperature inert gas to the reactor 7, maintaining a temperature inside the reactor 7 at a temperature range during the FT synthesis reaction, and executing inert gas purging to reduce a pressure inside the reactor 7; and a recovery section provided downstream of the reactor 7 for condensing the vaporized hydrocarbon and recovering it in a liquid state.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a hydrocarbon production apparatus and a hydrocarbon production method for obtaining a product containing hydrocarbons from a feed gas by a Fischer-Tropsch synthesis reaction. [Background technology]

[0002] Conventionally, regulations on automobile exhaust gas have been further advanced in order to alleviate or reduce the impact of climate change, and as part of this, research and development on the effective use of carbon dioxide (CO2) has been conducted. For example, a technology has been developed to synthesize hydrocarbons that can be used as fuel using carbon dioxide as a raw material by combining the reverse shift reaction, which reacts carbon dioxide and hydrogen (H2) to produce carbon monoxide (CO) and water (H2O), and the Fischer-Tropsch synthesis reaction (hereinafter referred to as the "FT synthesis reaction"), which synthesizes hydrocarbons (HC) from a synthesis gas of carbon monoxide and hydrogen using a catalytic reaction. In recent years, research has also been conducted on the direct FT synthesis reaction, which directly reacts carbon dioxide and hydrogen to obtain hydrocarbons by performing the reverse shift reaction and the FT synthesis reaction in a single reactor.

[0003] In the FT synthesis reaction, a wide range of hydrocarbons with carbon numbers are produced, including light hydrocarbons with carbon numbers of about 5 to 8, heavy hydrocarbons with carbon numbers of about 9 to 20, and even extra-heavy hydrocarbons with carbon numbers of 21 or more. Therefore, in order to produce various fuel products such as gasoline, kerosene, and diesel from the reaction, a process of separating the products according to the difference in boiling point using, for example, a fractionator is required. When fractionating hydrocarbons in this way, some of the heavy or heavier hydrocarbons may precipitate and adhere as solids in the gas-liquid separator, cooler, or piping, which may cause problems such as a decrease in the yield of the FT synthesis reaction or clogging of the piping, and therefore measures are required to recover the adhered heavy or extra-heavy hydrocarbons.

[0004] For example, Patent Document 1 discloses a technology in which, in a hydrocarbon production apparatus which produces hydrocarbons by an FT synthesis reaction, a second gas-liquid separation tank having a temperature range different from that of the first gas-liquid separation tank is provided upstream of (on the upstream side of) a first gas-liquid separation tank which separates light hydrocarbons, and heavy hydrocarbons are recovered in the second gas-liquid separation tank, thereby inhibiting the heavy hydrocarbons from flowing into the first gas-liquid separation tank and preventing the heavy hydrocarbons from concentrating and solidifying in the first gas-liquid separation tank. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2014-196433 A Summary of the Invention [Problem to be solved by the invention]

[0006] When a reactor in which the FT synthesis reaction is being carried out is terminated by a prescribed operation such as stopping the supply of raw material gas, the reactor interior is rapidly cooled with the end of the exothermic FT synthesis reaction, and the extra-heavy hydrocarbons remaining in the reactor may precipitate and remain as solids or adhere to the catalyst in the reactor. The adhesion of the extra-heavy hydrocarbons to the catalyst deteriorates the performance of the catalyst and causes a decrease in the yield of the FT synthesis reaction.

[0007] In addition, in order to eliminate adhesion to the catalyst, if a purging process is performed after the completion of the FT synthesis reaction using an inert gas such as high-temperature nitrogen (N2) gas to remove the extra-heavy hydrocarbons that have adhered to the catalyst as gas, the removed extra-heavy hydrocarbons will cool as they flow downstream and precipitate as a solid inside valves and piping, which may cause the flow paths to be clogged.

[0008] The present invention has been made to solve the above-mentioned problems, and has an object to provide a hydrocarbon production apparatus and a hydrocarbon production method that can eliminate adhesion of hydrocarbons to a catalyst and efficiently recover hydrocarbons while suppressing adhesion to downstream piping, etc., and that ultimately contributes to mitigating or reducing the impact of climate change. [Means for solving the problem]

[0009] In order to achieve this object, the invention according to claim 1 is a hydrocarbon production apparatus for obtaining a product containing hydrocarbons from a feed gas by an FT synthesis reaction using a reactor 7 having an FT reaction catalyst active in a Fischer-Tropsch synthesis reaction (FT synthesis reaction), and is characterized in that the apparatus comprises a purge unit (control unit 17, nitrogen supply unit 4, heater 6, flow rate control valve 12) that vaporizes the hydrocarbons adhered to the FT reaction catalyst by supplying a high-temperature inert gas to the reactor 7 when terminating the FT synthesis reaction, maintaining the temperature inside the reactor 7 within the temperature range during the FT synthesis reaction, and performing an inert gas purging process that reduces the pressure inside the reactor 7, and a recovery unit (first gas-liquid separator 9, heat insulator 8) that is provided downstream of the reactor 7 and condenses the vaporized hydrocarbons to recover them in liquid form.

[0010] The temperature in the reactor in which the FT reaction is carried out drops when the supply of the raw material gas is stopped and the FT synthesis reaction, which is an exothermic reaction, is terminated. When the temperature in the reactor drops, among the liquid or gaseous hydrocarbons remaining in the reactor, those with a high freezing point under high pressure may precipitate as a solid and adhere to the catalyst. In the hydrocarbon production apparatus of the present invention, when the FT synthesis reaction is terminated, a high-temperature inert gas is supplied to the reactor, the temperature in the reactor is maintained in a temperature range similar to that during the FT synthesis reaction, and an inert gas purging process is performed to reduce the pressure in the reactor, thereby vaporizing the hydrocarbons adhered to the catalyst and desorbing them as gas. Therefore, the adhesion of the hydrocarbons to the catalyst can be eliminated. Furthermore, by desorbing the hydrocarbons adhered to the catalyst while the catalyst is contained in the reactor, it is possible to simply reactivate the catalyst, and the operating efficiency when the reactor is restarted can be improved.

[0011] In addition, the hydrocarbons desorbed from the catalyst as a gas inside the reactor are condensed by a recovery section provided downstream of the reactor and recovered in liquid form. This makes it possible to efficiently recover the hydrocarbons and improve the yield, while also preventing the hydrocarbons from adhering to piping, etc. downstream of the recovery section.

[0012] The invention according to claim 2 is characterized in that, in the hydrocarbon production apparatus according to claim 1, the recovery section is provided downstream of the reactor 7 and has a first gas-liquid separation section 9 that condenses gaseous hydrocarbons mixed in with the inert gas and separates them in a liquid state when the FT synthesis reaction is terminated.

[0013] According to this configuration, the first gas-liquid separation section is provided downstream of the reactor as a recovery section for condensing gaseous hydrocarbons mixed in the inert gas and separating them in liquid form, so that when the FT synthesis reaction is terminated, the hydrocarbons desorbed from the catalyst as gases in the reactor by the inert gas purging process can be recovered in liquid form by the first gas-liquid separation section. Therefore, the hydrocarbons can be recovered efficiently to improve the yield, and the adhesion of the hydrocarbons to piping and the like downstream of the recovery section can be suppressed.

[0014] The invention of claim 3 is characterized in that, in the hydrocarbon production apparatus described in claim 2, the recovery section has a second gas-liquid separation section 13 downstream of the first gas-liquid separation section 9, which condenses gaseous hydrocarbons at a lower temperature than the first gas-liquid separation section 9 and separates them in liquid form.

[0015] According to this configuration, the second gas-liquid separation section is provided downstream of the first gas-liquid separation section as a recovery section which condenses gaseous hydrocarbons at a lower temperature than the first gas-liquid separation section and separates them in liquid form, so that lower hydrocarbons which could not be recovered in the first gas-liquid separation section can be recovered by the second gas-liquid separation section, thereby further improving the yield of hydrocarbons.

[0016] The invention of claim 4 is characterized in that, in the hydrocarbon production apparatus described in claim 2, the recovery section has a third gas-liquid separation section (second gas-liquid separator 130) downstream of the first gas-liquid separation section 9, which is capable of condensing gaseous hydrocarbons at a lower temperature than the first gas-liquid separation section 9 and separating them into liquid form, and which is capable of separating the gaseous hydrocarbons according to their carbon number by changing the internal temperature.

[0017] According to this configuration, the third gas-liquid separation section is provided downstream of the first gas-liquid separation section as a recovery section, which can condense gaseous hydrocarbons at a lower temperature than the first gas-liquid separation section and separate the hydrocarbons according to their carbon number by changing the internal temperature, so that lower hydrocarbons that could not be recovered in the first gas-liquid separation section can be recovered by the third gas-liquid separation section. In addition, by changing the temperature of the third gas-liquid separation section to a higher temperature, higher hydrocarbons that could not be recovered in the first gas-liquid separation section and flowed downstream can be recovered again by the third gas-liquid separation section. This can further improve the yield of hydrocarbons.

[0018] The invention according to claim 5 is a hydrocarbon production method for obtaining a product containing hydrocarbons from a feed gas by an FT synthesis reaction using a reactor 7 having an FT reaction catalyst active in a Fischer-Tropsch synthesis reaction (FT synthesis reaction), characterized in that, when terminating the FT synthesis reaction, an inert gas is supplied to the reactor 7 to maintain the temperature inside the reactor 7 within the temperature range during the FT synthesis reaction, and an inert gas purging process is performed to reduce the pressure inside the reactor 7, thereby vaporizing the hydrocarbons adhered to the FT reaction catalyst, and condensing the vaporized hydrocarbons to recover them in liquid form.

[0019] In the hydrocarbon production method of the present invention, when the FT synthesis reaction is terminated, a high-temperature inert gas is supplied to the reactor, the temperature in the reactor is maintained in a temperature range similar to that during the FT synthesis reaction, and an inert gas purging process is performed to reduce the pressure in the reactor, thereby vaporizing the hydrocarbons adhering to the catalyst and desorbing them as gas. Therefore, the adhesion of the hydrocarbons to the catalyst can be eliminated. Furthermore, by desorbing the adhering hydrocarbons while the FT reaction catalyst is contained in the reactor, it is possible to easily reactivate the FT reaction catalyst, and the operating efficiency when the reactor is restarted can be improved. In addition, the hydrocarbons desorbed from the catalyst as a gas in the reactor are condensed and recovered in liquid form, so that the yield can be improved by efficiently recovering the hydrocarbons, and the adhesion of the hydrocarbons to downstream piping and the like can be suppressed. [Brief description of the drawings]

[0020] [Figure 1] 1 is a diagram showing an overall structure of a hydrocarbon production apparatus according to an embodiment of the present invention. [Diagram 2] 4 is a flowchart showing a process during an FT synthesis reaction in a hydrocarbon production apparatus according to one embodiment of the present invention. [Diagram 3] 4 is a flowchart showing a process for terminating the FT synthesis reaction in the hydrocarbon production apparatus according to one embodiment of the present invention. [Figure 4] 1 is a phase diagram showing the relationship between pressure and temperature and phase changes of heavy hydrocarbons. [Diagram 5] FIG. 1 is a phase diagram showing the relationship between pressure and temperature and phase changes of extra heavy hydrocarbons. [Figure 6] FIG. 2 is a diagram showing an overall structure of a hydrocarbon production apparatus according to another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, a preferred embodiment of the hydrocarbon production apparatus of the present invention will be described in detail with reference to the drawings. The configuration described below is an example of the present invention, and the present invention is not limited thereto. In the following description, the terms upstream side and downstream side refer to the upstream side and downstream side in the direction in which the fluid flows in each part to be described.

[0022] FIG. 1 shows an example of the overall structure of a hydrocarbon production apparatus 1 according to this embodiment. The hydrocarbon production apparatus 1 includes a carbon dioxide supply unit 2, a hydrogen supply unit 3, a nitrogen supply unit 4, a compressor 5, a heater 6, a reactor 7, a heat insulator 8, a first gas-liquid separator 9, a cooler 10, a back pressure control valve 11, a flow rate control valve 12, a second gas-liquid separator 13, a heavy hydrocarbon recovery tank 14, an extra-heavy hydrocarbon recovery tank 15, a light hydrocarbon recovery tank 16, and a control unit 17. The operation of each of the above-mentioned units of the hydrocarbon production apparatus 1 is controlled by the control unit 17. With this configuration, the hydrocarbon production apparatus 1 uses carbon dioxide gas and hydrogen gas as raw materials to generate various hydrocarbons with different carbon numbers through the FT synthesis reaction, and separates and recovers the generated hydrocarbons into light hydrocarbons with a carbon number of about 5 to 8 (hereinafter also referred to as "light HCs"), heavy hydrocarbons with a carbon number of about 9 to 20 (hereinafter also referred to as "heavy HCs"), and extra-heavy hydrocarbons with a carbon number of 21 or more (hereinafter also referred to as "extra-heavy HCs"). The configuration of each part will be described in detail below.

[0023] The carbon dioxide supply unit 2 and the hydrogen supply unit 3 respectively supply carbon dioxide gas and hydrogen gas to piping connected to the compressor 5. The supply amounts of carbon dioxide gas and hydrogen gas, which are the raw material gases for the FT synthesis reaction in the reactor 7, are detected by a flow rate sensor (not shown) or the like, and the detected value is transmitted to the control unit 17. The control unit 17 controls the supply amounts so that the carbon dioxide and hydrogen are in a predetermined ratio suitable for the FT synthesis reaction. In this embodiment, the supply amounts are controlled to a molar ratio of H2 / CO2=3.

[0024] The nitrogen supply unit 4 supplies nitrogen (N2) gas, which is an inert gas, to a pipe connected to the compressor 5. The nitrogen gas is supplied to a synthesis path consisting of the compressor 5, heater 6, reactor 7, insulator 8, first gas-liquid separator 9, cooler 10, back pressure valve 11, flow rate control valve 12, and second gas-liquid separator and the pipes connecting them, in a form replacing the raw material gas consisting of carbon dioxide and hydrogen at the end of the FT synthesis reaction performed in the reactor 7.

[0025] The compressor 5 and the heater 6 are used to create a high pressure / high temperature state suitable for carrying out the FT synthesis reaction in this embodiment, as described later. The compressor 5 is not particularly limited in type as long as it can compress the raw material gas supplied from the carbon dioxide supply unit 2 and the hydrogen supply unit 3 and send it to the downstream heater 6, and for example, a centrifugal turbo compressor driven by an electric motor or an electric pump can be used. A pressure sensor (not shown) is provided downstream of the compressor 5, and the detection value is transmitted to the control unit 17. The compressor 5 of this embodiment is controlled by the control unit 17 so as to increase the pressure of the raw material gas in the synthesis path to about 3 MPaG. In addition, the heater 6 may be a known heater as long as it can increase the temperature of the compressed raw material gas and send it to the downstream reactor 7. A temperature sensor (not shown) is provided downstream of the heater 6, and the detection value is transmitted to the control unit 17. The heater 6 of this embodiment is controlled by the control unit 17 so as to increase the temperature of the raw material gas to about 380°C.

[0026] The reactor 7 contains a catalyst (hereinafter referred to as "FT reaction catalyst") that exhibits activity in the FT synthesis reaction, and generates hydrocarbons with various carbon numbers by the FT synthesis reaction from the raw material gas passing through the reactor 7. The reaction that takes place in the reactor 7 in this embodiment is a direct FT synthesis reaction, shown in the following formula (1), in which carbon dioxide and hydrogen are directly reacted to generate hydrocarbons and water. nCO2+mH2→HC+H2O …(1)

[0027] The FT reaction catalyst of this embodiment is a combination of a pellet-shaped sodium iron catalyst, which is made by adding sodium (Na) as a promoter to the catalytic metals iron (Fe), gallium (Ga), and zirconium (Zr), and a zeolite catalyst using aluminosilicate zeolite (ZSM-5), in a predetermined ratio. Both the sodium iron catalyst and the zeolite catalyst have a porous structure.

[0028] The direct FT synthesis reaction using the above-mentioned FT reaction catalyst produces light HCs with carbon numbers of about 5 to 8, heavy HCs with carbon numbers of about 9 to 20, and extra-heavy HCs with carbon numbers of 21 or more, which can all be used as raw materials for synthetic fuel, as well as hydrocarbons with carbon numbers of 2 to 4, including methane (CH4), and water as by-products.

[0029] The insulator 8 is a type of heater, and heats the effluent from the reactor 7 and maintains its temperature at an appropriately high level, thereby accelerating the separation of hydrocarbons in the first gas-liquid separator 9 downstream, which will be described later. In this embodiment, the insulator 8 is controlled by the control unit 17 to heat the effluent from the reactor 7 to a temperature at which heavy HCs having a carbon number of about 9 to 20 become liquid under high pressure (3 MPa) and normal pressure, and extra heavy HCs having a carbon number of 21 or more become liquid under normal pressure. In this embodiment, the insulator 8 is controlled ... fluid flowing into the first gas-liquid separator 9 so that the temperature of the fluid is maintained at approximately 100°C.

[0030] The first gas-liquid separator 9 can be composed of a known gas-liquid separator, and separates the effluent from the reactor 7 into a liquid component and a gas component. As described above, the first gas-liquid separator 9 is kept at a high temperature of about 100°C by the insulator 8. As described later, the pressure applied to the first gas-liquid separator 9 changes when the FT synthesis reaction is carried out and stopped, and the components to be separated also change accordingly. At the high pressure during the FT synthesis reaction, the first gas-liquid separator 9 functions to separate heavy HCs having a carbon number of about 9 to 20 as liquid components, and light HCs having a carbon number of 8 or less, water, and unreacted gas as gas components. The separated heavy HCs are sent to the heavy HC recovery tank 14, and the gas components including the light HCs, water, and unreacted gas are sent to the cooler 10. At normal pressure when the FT synthesis reaction is completed, the first gas-liquid separator 9 functions to separate extra-heavy HCs having a carbon number of 21 or more as liquid components in addition to heavy HCs. The separated heavy HC and extra heavy HC are separated by a fractionator (not shown) and then sent to a heavy HC recovery tank 14 and an extra heavy HC recovery tank 15, respectively. The recovered heavy HC and extra heavy HC are then hydrogenated and refined by a reformer (not shown) or the like, and are used as synthetic fuel products such as kerosene and diesel.

[0031] The cooler 10 is a heat exchanger that cools the gas components that flow into the cooler 10 by exchanging heat with a refrigerant. The amount of cooling for the gas components that flow in can be adjusted by the flow rate of the refrigerant flowing through the cooler 10, and the flow rate of the refrigerant is adjusted by the control unit 17 adjusting the opening of a flow rate control valve (not shown). In this embodiment, the flow rate of the refrigerant is controlled in the cooler 10 so that the gas components that flow in are cooled to a temperature at which light HCs having a carbon number of about 5 to 8 condense. In this embodiment, the gas components that flow into the cooler 10 are cooled to about 10°C.

[0032] A branch is provided in the pipe downstream of the cooler 10, and a back pressure valve 11 and a flow rate control valve 12 are provided at the end of each branch. A changeover valve 18 is provided at the branch, and by operating the changeover valve 18, it is possible to control the fluid from the upstream side to flow only to either the back pressure valve 11 side or the flow rate control valve 12 side. The operation of the changeover valve 18 is controlled by the control unit 17.

[0033] The back pressure valve (BPCV) 11 is connected to one of the pipings branched from the branch part downstream of the cooler 10, and functions to keep the pressure on the upstream side (primary side) of the back pressure valve 11 constant. A known back pressure valve can be used as the back pressure valve 11, and in this embodiment, a valve having a configuration in which a flow path connected to the front and rear of the back pressure valve 11 is partitioned by a diaphragm valve and the diaphragm valve is pressed down by a spring is used. Such a back pressure valve 11 can keep the pressure on the upstream side of the back pressure valve 11 at a predetermined pressure. The back pressure valve 11 is configured so that a fluid flows only during the FT synthesis reaction in the reactor 7 by controlling the switching valve 18, and the pressure on the upstream side of the back pressure valve 11 is kept at 3 MPa during the FT synthesis reaction.

[0034] The flow rate control valve 12 is connected to the other end of the piping branched from the branched portion downstream of the cooler 10, and functions to adjust the flow rate of the fluid flowing through the flow rate control valve 12. Any known valve can be used as the flow rate control valve 12, but in this embodiment, a known needle valve (NV) is used as the flow rate control valve 12. The needle valve controls the flow rate by adjusting the opening of an orifice-shaped flow path in the valve with a needle-shaped or rod-shaped needle. The flow rate control valve 12 is configured to allow the fluid to flow only when the FT synthesis reaction in the reactor 7 is stopped by controlling the switching valve 18, and particularly at the end of the FT synthesis reaction, the flow path is switched from the back pressure valve 11 side to the flow rate control valve 12 side, and functions to gradually reduce the pressure of the synthesis path that was kept at high pressure to normal pressure.

[0035] The second gas-liquid separator 13 can be constructed of a known gas-liquid separator, and separates the fluid flowing in from the upstream side at a lower temperature than the first gas-liquid separator 9 into a liquid component and a gas component. The fluid of the mixture of light HC, water, and unreacted gas flowing in the second gas-liquid separator 13 is cooled to about 10°C by the cooler 10 provided on the upstream side, so that light HC with a carbon number of about 5 to 8 and water are separated as liquid components, and hydrocarbons with a carbon number of 4 or less and unreacted gas are separated as gas components. The light HC with a carbon number of about 5 to 8 and water separated as liquid components are separated by a fractionator (not shown), and then the light HC is sent to a light HC recovery tank, and the water is discharged to the outside as it is. In addition, the hydrocarbons with a carbon number of 4 or less and the unreacted gas separated as gas components are returned to the upstream side of the reactor 7 and recycled. The recovered light HC are then hydrogenated and refined by a reformer (not shown) or the like, and are used as synthetic fuel products such as gasoline.

[0036] The control unit 17 is an ECU (Electronic Control Unit) that controls each part of the hydrocarbon production apparatus 1, and is configured with a microcomputer including a CPU, RAM, ROM, and an I / O interface (none of which are shown), etc. The control unit 17 in this embodiment controls the operations of at least the carbon dioxide supply unit 2, the hydrogen supply unit 3, the nitrogen supply unit 4, the compressor 5, the heater 6, the heat retainer 8, the cooler 10, and the switching valve 18.

[0037] Next, the processing of each part during the FT synthesis reaction will be described. Fig. 2 is a flowchart showing the processing during the FT synthesis reaction. The processing shown in the flowchart is executed by the processor of the control unit 17 releasing a program stored in a storage device such as a ROM to a memory such as a RAM.

[0038] First, in step 201 (illustrated as "S201"; the same applies below), the compressor 5, heater 6, insulator 8, and cooler 10 are operated while nitrogen gas, which is an inert gas, is circulated through the synthesis path, and the switching valve 18 is set to open to the back pressure valve 11 side. As a result, the synthesis path from the compressor 5 to the back pressure valve 11 is pressurized to 3 MPa, and the reactor 7 is heated to about 380°C.

[0039] Next, the supply of carbon dioxide gas and hydrogen gas, which are raw material gases, is started to the synthesis path filled with the inert gas (step 202). The supply amounts of carbon dioxide gas and hydrogen gas are controlled so that the molar ratio of H2 / CO2=3. As the replacement of the inert gas with the raw material gas progresses, the direct FT synthesis reaction is started via the catalyst in the reactor 7 (step 203).

[0040] As a result of the direct FT synthesis reaction being carried out, an effluent consisting of hydrocarbons including light HC, heavy HC, and extra heavy HC, as well as by-product hydrocarbons having 1 to 4 carbon atoms, water, and unreacted gases flows out downstream of the reactor 7, passes through an insulator 8, and flows into the first gas-liquid separator 9.

[0041] In the next step 204, heavy HCs having carbon numbers of about 9 to 20 are separated and collected by the first gas-liquid separator 9 maintained at about 100°C. FIG. 4 is a phase diagram showing the relationship between pressure and temperature and the phase change of heavy HCs. As shown in the figure, heavy HCs exist as a gas under high temperature (380°C) and high pressure (3 MPa) immediately after the FT synthesis reaction, but are easily liquefied by the temperature drop caused by moving downstream. If the temperature continues to drop, they will eventually solidify, but in the hydrocarbon production apparatus 1 of this embodiment, the flow path up to the first gas-liquid separator 9 is maintained at about 100°C by the insulator 8, so that the heavy HCs can be collected in liquid form in the first gas-liquid separator. This makes it possible to prevent heavy HCs from precipitating and adhering as a solid in downstream piping and equipment.

[0042] Thereafter, the fluid leaving the first gas-liquid separator 9 is cooled to about 10°C while passing through the cooler 10, and then passes through the back pressure valve 11 and flows into the second gas-liquid separator 13. In the second gas-liquid separator 13, light HCs having a carbon number of about 5 to 8 are separated and recovered (step 205).

[0043] In this way, heavy HC and light HC are separated and recovered by repeating steps 204 and 205 while the direct FT synthesis reaction is being carried out. Thereafter, for example, after a predetermined time has elapsed, the FT synthesis reaction is terminated by a predetermined operation (step 206). The operation at the end of the FT synthesis reaction will be described later.

[0044] Next, the processing of each part when the FT synthesis reaction is completed will be described. Fig. 3 is a flowchart showing the processing of the FT synthesis reaction completion. The processing shown in the flowchart is executed by the processor of the control part 17 releasing a program stored in a storage device such as a ROM to a memory such as a RAM.

[0045] First, in step 301, as an operation for terminating the FT synthesis reaction, the supply of nitrogen gas, which is an inert gas, to the synthesis path filled with the raw material gas is started, so that the raw material gas in the synthesis path is gradually replaced with nitrogen gas. Note that the temperature of the nitrogen gas is raised by passing through the heater 6 upstream of the reactor 7, so that a sudden drop in the temperature in the reactor can be suppressed.

[0046] On the other hand, the temperature in the reactor 7 is reduced to a certain extent by the gradual weakening of the exothermic reaction due to the FT synthesis reaction caused by the reduction in the raw material gas in the reactor 7. FIG. 5 is a phase diagram showing the relationship between pressure and temperature and the phase change of the extra-heavy HC. As shown in the figure, the extra-heavy HC exists in a liquid state under high temperature (380° C.) and high pressure (3 MPa) immediately after the FT synthesis reaction, but when the temperature drops as it flows downstream, or when the temperature drops due to the end of the exothermic reaction under high pressure at the end of the FT synthesis reaction, it solidifies relatively easily. The extra-heavy HC precipitated as a solid remains in the reactor 7 or downstream piping, and may cause deterioration of the catalyst performance, especially when it adheres to the FT reaction catalyst having a pore structure. In the hydrocarbon production apparatus 1 of this embodiment, the extra-heavy HC precipitated as a solid is vaporized by the subsequent processing, and the extra-heavy HC adhered to the catalyst in particular is desorbed, thereby efficiently recovering the extra-heavy HC as a liquid.

[0047] In the next step 302, after the replacement with the inert gas in step 301 is completed, the operation of the compressor 5 is stopped to stop the pressurization of the synthesis path. Next, in step 303, the switching valve 18 is controlled to switch the flow path set to the back pressure valve 11 side to the flow rate adjustment valve 12 side. As a result, the pressure in the synthesis path is gradually reduced from a high pressure state of 3 MPa to normal pressure.

[0048] After the pressure in the synthesis path has dropped to normal pressure, a purging process is continued for about 30 minutes in which high-temperature nitrogen gas is continued to be supplied to the synthesis path to replace the raw material gas in step 304. As shown in Fig. 5, the purging process at high temperature (380°C) and normal pressure can vaporize the extra-heavy HC that has remained as a solid in the reactor 7 and in the piping, and can also vaporize the extra-heavy HC that has adhered to the catalyst in the reactor 7 (step 305).

[0049] The gasified extra-heavy HC flows downstream, passes through insulator 8, and enters first gas-liquid separator 9. In the process, the extra-heavy HC, whose temperature drops from about 380° C. to about 100° C., condenses and liquefies, as shown in Fig. 5. The liquefied extra-heavy HC is separated as a liquid component in first gas-liquid separator 9 and sent to extra-heavy HC recovery tank 15 (step 306).

[0050] In this way, by repeating steps 305 and 306 during the purging process with nitrogen gas at the end of the FT synthesis reaction, the adhesion of extra-heavy HC to the FT reaction catalyst is eliminated, and the gasified extra-heavy HC can be condensed and recovered as liquid in the first gas-liquid separator 9.

[0051] As described above, according to the hydrocarbon production apparatus 1 of the present embodiment, high-temperature inert gas is supplied to the reactor 7 at the end of the FT synthesis reaction, the temperature in the reactor is maintained in the same temperature range as the temperature during the FT synthesis reaction, and a purging process is performed to reduce the pressure in the reactor and maintain normal pressure, so that the extra-heavy HCs adhering to the FT reaction catalyst in the reactor 7 can be vaporized and desorbed as gas, and the adhering of the extra-heavy HCs to the FT reaction catalyst can be eliminated. In addition, the extra-heavy HCs adhering to the catalyst can be desorbed while the catalyst is still installed in the reactor 7, and the catalyst can be reactivated easily. This can improve the operating efficiency when the reactor 7 is restarted.

[0052] Furthermore, when the extra-heavy HC remaining in reactor 7 and the piping is gasified and flows downstream, it is condensed by adjusting the temperature in insulator 8 and is separated and recovered in liquid form in first gas-liquid separator 9. This makes it possible to efficiently recover the extra-heavy HC and improve the yield, while also preventing the extra-heavy HC from adhering to the piping, etc. downstream of first gas-liquid separator 9.

[0053] Furthermore, since the second gas-liquid separator 13 is provided downstream of the first gas-liquid separator 9, which condenses gaseous light HC at a lower temperature than the first gas-liquid separator 9 and separates it in liquid form, the light HC that cannot be recovered by the first gas-liquid separator 9 can be recovered by the second gas-liquid separator 13. This makes it possible to further improve the yield of hydrocarbons.

[0054] Next, a hydrocarbon production apparatus 100 according to a second embodiment of the present invention will be described with reference to Fig. 6. In the following description of the embodiment, the same components as those described in the above embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

[0055] In the hydrocarbon production apparatus 1 according to the above-described embodiment, the second gas-liquid separator 13 capable of separating and recovering light HCs is provided downstream of the first gas-liquid separator 9 capable of separating and recovering heavy HCs and extra heavy HCs. However, the hydrocarbon production apparatus 100 according to the second embodiment is characterized in that, instead of the second gas-liquid separator 13, a second gas-liquid separator 130 is employed that can separate and recover light HCs and heavy HCs by changing the internal temperature to change the gas components and liquid components to be separated.

[0056] The second gas-liquid separator 130 is a known gas-liquid separator that includes, for example, a heat exchanger (not shown) in the front stage and can change the internal temperature by controlling a heat source. The second gas-liquid separator 130 is configured to be able to change the internal temperature between a low first temperature at which light HCs having a carbon number of about 5 to 8 can be condensed under normal pressure and a high second temperature at which heavy HCs having a carbon number of about 9 to 20 can be condensed under normal pressure. In this embodiment, the first temperature is set to 10°C and the second temperature is set to 100°C.

[0057] The temperature of the second gas-liquid separator 130 is set to a low first temperature during the FT synthesis reaction. During the FT synthesis reaction, the fluid flowing into the second gas-liquid separator 130 through the back pressure valve 11 may contain a small amount of heavy HC that could not be completely recovered by the first gas-liquid separator 9, in addition to light HC, water, and unreacted gas. The fluid containing these components is cooled to approximately 10°C by the cooler 10 provided upstream, and the second gas-liquid separator 130 itself is set to the first temperature of 10°C. As a result, the light HC and water are separated as liquid components in the second gas-liquid separator 130, and the hydrocarbons with a carbon number of 4 or less and the unreacted gas are separated as gas components. Meanwhile, the small amount of remaining heavy HC precipitates as a solid in the second gas-liquid separator 130. The light HCs having a carbon number of about 5 to 8 and water separated as liquid components are separated by a fractionator (not shown), after which the light HCs are sent to a light HC recovery tank and the water is directly discharged to the outside. Moreover, the hydrocarbons having a carbon number of 4 or less and the unreacted gas separated as gas components are returned to the upstream side of the reactor 7 and recycled. The recovered light HCs are then hydrogenated and refined by a reformer (not shown) or the like, and are used as synthetic fuel products such as gasoline.

[0058] The temperature of the second gas-liquid separator 130 is switched to a higher second temperature when the FT synthesis reaction is completed, for example, after separation and recovery of light HC by the second gas-liquid separator 130 is completed. This causes the heavy HC that has precipitated as a solid in the second gas-liquid separator 130 to melt, and the liquefied heavy HC can be recovered by the second gas-liquid separator 130. The recovered heavy HC is sent to the heavy HC recovery tank 14.

[0059] Thus, according to the hydrocarbon production apparatus 100 according to the second embodiment, the temperature of the second gas-liquid separator 130 is set to a low first temperature during the FT synthesis reaction, thereby separating and recovering light HC, and by setting it to a high second temperature at the end of the FT synthesis reaction, it is possible to separate and recover heavy HC that was not completely recovered in the first gas-liquid separator 9 and has flowed downstream. This makes it possible to further improve the yield of hydrocarbons.

[0060] The present invention is not limited to the embodiment described above, but can be embodied in various forms. Furthermore, the detailed configuration can be appropriately changed within the scope of the spirit of the present invention. [Explanation of symbols]

[0061] 1...Hydrocarbon production equipment 2…Carbon dioxide supply unit 3. Hydrogen supply unit 4...Nitrogen supply section (purge section) 5…Compressor 6...Heater (purge section) 7. Reactor 8…Warming device (collection section) 9...First gas-liquid separator (recovery section, first gas-liquid separation section) 10...Cooler 11…Back pressure valve 12...Flow rate control valve (purge section) 13...Second gas-liquid separator (recovery section, second gas-liquid separation section) 14...Heavy Hydrocarbon Recovery Tank 15...Extra heavy hydrocarbon recovery tank 16...Light hydrocarbon recovery tank 17...Control section (purge section, recovery section) 130...Second gas-liquid separator (recovery section, third gas-liquid separation section)

Claims

1. A hydrocarbon production apparatus for obtaining a product containing hydrocarbons from a feed gas by a Fischer-Tropsch synthesis reaction using a reactor having an FT reaction catalyst active in the FT synthesis reaction, comprising: a purge unit that, when terminating the FT synthesis reaction, supplies a high-temperature inert gas to the reactor, maintains the temperature inside the reactor within the temperature range during the FT synthesis reaction, and performs an inert gas purging process to reduce the pressure inside the reactor, thereby vaporizing hydrocarbons that have adhered to the FT reaction catalyst; a recovery section provided downstream of the reactor for condensing the vaporized hydrocarbons and recovering them in a liquid state; A hydrocarbon production apparatus comprising:

2. 2. The hydrocarbon production apparatus according to claim 1, characterized in that the recovery section has a first gas-liquid separation section that is provided downstream of the reactor and that condenses gaseous hydrocarbons mixed in the inert gas and separates them in a liquid state when the FT synthesis reaction is terminated.

3. 3. The hydrocarbon production apparatus according to claim 2, characterized in that the recovery section has a second gas-liquid separation section downstream of the first gas-liquid separation section which condenses the gaseous hydrocarbons at a lower temperature than the first gas-liquid separation section and separates them in a liquid state.

4. 3. The hydrocarbon production apparatus according to claim 2, wherein the recovery section has a third gas-liquid separation section downstream of the first gas-liquid separation section, the third gas-liquid separation section being capable of condensing the gaseous hydrocarbons at a temperature lower than that of the first gas-liquid separation section and separating the gaseous hydrocarbons in a liquid state at a temperature lower than that of the first gas-liquid separation section, and capable of separating the gaseous hydrocarbons according to their carbon number by changing an internal temperature.

5. A hydrocarbon production method for obtaining a product containing hydrocarbons from a feed gas by a Fischer-Tropsch synthesis reaction using a reactor having an FT reaction catalyst active in the FT synthesis reaction, comprising the steps of: when terminating the FT synthesis reaction, an inert gas is supplied to the reactor, the temperature inside the reactor is maintained within a temperature range during the FT synthesis reaction, and an inert gas purging process is performed to reduce the pressure inside the reactor, thereby vaporizing hydrocarbons adhering to the FT reaction catalyst; condensing the vaporized hydrocarbons to recover them in liquid form; A method for producing hydrocarbons, comprising:

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