Patent Application
20240400907
The present invention relates to a hydrocarbon producing apparatus and a hydrocarbon producing method for obtaining a product containing hydrocarbons from a raw material gas by a Fischer-Tropsch synthesis reaction.
Recently, exhaust gas regulations of automobiles have been further advanced for the purpose of mitigating climate change or reducing the influence thereof, and as a part of this, research and development on effective use of carbon dioxide (CO2) have been conducted. For example, a technique has been developed to synthesize hydrocarbons that can be used as fuels using carbon dioxide as a raw material by combining a reverse shift reaction in which carbon monoxide (CO) and water (H2O) are produced by reacting carbon dioxide and hydrogen (H2) with a Fischer-Tropsch synthesis reaction (hereinafter, referred to as “FT synthesis reaction”) in which hydrocarbons (HCs) are synthesized from a synthesis gas of carbon monoxide and hydrogen using a catalytic reaction. In addition, in recent years, a direct FT synthesis reaction in which carbon dioxide and hydrogen are directly reacted to obtain hydrocarbons by performing a reverse shift reaction and an FT synthesis reaction in one reactor has also been studied.
In the FT synthesis reaction, hydrocarbons having a wide range of carbon numbers including light hydrocarbons having about 5 to 8 carbon atoms, heavy hydrocarbons having about 9 to 20 carbon atoms, and super-heavy hydrocarbons having 21 or more carbon atoms are produced. Therefore, in order to produce various fuel products such as gasoline, kerosene, and light oil therefrom, for example, a process of separating products according to a difference in boiling point using a fractionator or the like is required. When fractionation of hydrocarbons is performed as described above, a part of heavy or higher hydrocarbons is precipitated as a solid and adheres in a gas-liquid separator, a cooler, or a pipe, such that problems such as a decrease in yield of the FT synthesis reaction and pipe blockage may occur. Therefore, measures for recovering the adhered heavy or super-heavy hydrocarbons are required.
For example, JP 2014-196433 A discloses a technique in which a second gas-liquid separation tank having a temperature range different from that of a first gas-liquid separation tank for separating light hydrocarbons is provided at a front stage (upstream side) of the first gas-liquid separation tank in a hydrocarbon producing apparatus for producing hydrocarbons by an FT synthesis reaction, and heavy hydrocarbons are recovered by the second gas-liquid separation tank, such that the heavy hydrocarbons are prevented from flowing into the first gas-liquid separation tank, and the heavy hydrocarbons are prevented from being concentrated and adhering in the first gas-liquid separation tank.
When the reactor performing the FT synthesis reaction terminates the reaction by a predetermined operation such as stopping the supply of the raw material gas, the inside of the reactor is rapidly cooled along with the termination of the FT synthesis reaction which is an exothermic reaction, such that the super-heavy hydrocarbons remaining in the reactor may be precipitated as a solid and remain, or may adhere to the catalyst in the reactor. Such adhesion of the super-heavy hydrocarbons to the catalyst causes deterioration of the performance of the catalyst and causes a decrease in yield of the FT synthesis reaction.
In addition, in order to eliminate such adhesion to the catalyst, when the super-heavy hydrocarbons adhering to the catalyst are desorbed as gas from the catalyst by a purge treatment with an inert gas such as a high-temperature nitrogen (N2) gas after the termination of the FT synthesis reaction, the desorbed super-heavy hydrocarbons are cooled when flowing downstream and being precipitated as a solid in a valve or pipe, which may cause clogging of a flow path.
An object of the present invention is to provide a hydrocarbon producing apparatus and a hydrocarbon producing method that can eliminate adhesion of hydrocarbons to a catalyst and efficiently recover hydrocarbons while suppressing adhesion of the hydrocarbons to a downstream pipe or the like. In addition, another object of the present invention is to contribute to mitigating climate change or reducing the influence thereof.
According to an invention according to claim 1, there is provided a hydrocarbon producing apparatus for obtaining a product containing hydrocarbons from a raw material gas by a Fischer-Tropsch synthesis reaction (FT synthesis reaction) using a reactor 7 containing an FT reaction catalyst exhibiting activity in the FT synthesis reaction, the hydrocarbon producing apparatus including: a purge unit (a control unit 17, a nitrogen supply unit 4, a heater 6, and a flow rate regulating valve 12) that executes an inert gas purge process that supplies a high-temperature inert gas to the reactor 7, maintains a temperature in the reactor 7 in a temperature range during the FT synthesis reaction, and reduces a pressure in the reactor 7, when the FT synthesis reaction is terminated, so that the hydrocarbons adhering to the FT reaction catalyst are vaporized; and a recovery unit (a first gas-liquid separator 9 and a warmer 8) that is provided on a downstream side of the reactor 7, condenses the vaporized hydrocarbons, and recovers the condensed hydrocarbons in a liquid state.
The temperature in the reactor in which the FT reaction is performed decreases 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 decreases, among liquid or gas hydrocarbons remaining in the reactor, hydrocarbons having a high solidifying point at a high pressure are precipitated as a solid and adhere to the catalyst in some cases. In the hydrocarbon producing apparatus of the present invention, when the FT synthesis reaction is terminated, an inert gas purge process in which a high-temperature inert gas is supplied to the reactor, the temperature in the reactor is maintained in a temperature range similar to the temperature during the FT synthesis reaction, and the pressure in the reactor is reduced, is executed, such that the hydrocarbons adhering to the catalyst can be vaporized and desorbed as gas. Therefore, the adhesion of the hydrocarbons to the catalyst can be eliminated. Furthermore, the adhered hydrocarbons are desorbed in a state where the catalyst is contained in the reactor, such that the catalyst can be easily reactivated, and the operation efficiency at the time of restarting the reactor can be improved.
In addition, since the hydrocarbons desorbed from the catalyst as gas in the reactor are condensed by the recovery unit provided on the downstream side of the reactor and recovered in a liquid state, the hydrocarbons can be efficiently recovered to improve the yield, and the hydrocarbons can be suppressed from adhering to the pipe or the like on the downstream side of the recovery unit.
According to an invention according to claim 2, in the hydrocarbon producing apparatus according to claim 1, the recovery unit includes a first gas-liquid separator 9 that is provided on the downstream side of the reactor 7, condenses gaseous hydrocarbons mixed with the inert gas, and separates the condensed hydrocarbons in a liquid state, when the FT synthesis reaction is terminated.
According to the configuration, since the first gas-liquid separator that condenses the gaseous hydrocarbons mixed with the inert gas and separates the condensed hydrocarbons in a liquid state is provided as the recovery unit on the downstream side of the reactor, the hydrocarbons desorbed as gas from the catalyst in the reactor by the inert gas purge process can be recovered in a liquid state by the first gas-liquid separator when the FT synthesis reaction is terminated. Therefore, it is possible to efficiently recover the hydrocarbons to improve the yield and to suppress the hydrocarbons from adhering to the pipe or the like on the downstream side of the recovery unit.
According to an invention according to claim 3, in the hydrocarbon producing apparatus according to claim 2, the recovery unit includes a second gas-liquid separator 13 that is provided on a downstream side of the first gas-liquid separator 9, condenses the gaseous hydrocarbons at a lower temperature than the first gas-liquid separator 9, and separates the condensed hydrocarbons in a liquid state.
According to the configuration, since the second gas-liquid separator that condenses the gaseous hydrocarbons at a lower temperature than the first gas-liquid separator and separates the condensed hydrocarbons in a liquid state is provided as the recovery unit on the downstream side of the first gas-liquid separator, lower hydrocarbons that cannot be recovered by the first gas-liquid separator can be recovered by the second gas-liquid separator. Thus, the yield of hydrocarbons can be further improved.
According to an invention according to claim 4, in the hydrocarbon producing apparatus according to claim 2, the recovery unit includes a third gas-liquid separator (a second gas-liquid separator 130) that is provided on a downstream side of the first gas-liquid separator 9, can condense the gaseous hydrocarbons at a lower temperature than the first gas-liquid separator 9 and separate the condensed hydrocarbons in a liquid state, and can separate the gaseous hydrocarbons according to a carbon number by changing an internal temperature.
According to the configuration, since the third gas-liquid separator that can condense the gaseous hydrocarbons at a lower temperature than the first gas-liquid separator and separate the condensed hydrocarbons in a liquid state and can separate the hydrocarbons according to a carbon number by changing an internal temperature is provided as the recovery unit on the downstream side of the first gas-liquid separator, lower hydrocarbons that cannot be recovered by the first gas-liquid separator can be recovered by the third gas-liquid separator. In addition, the temperature of the third gas-liquid separator is changed to a higher temperature, such that it is possible to recover higher hydrocarbons that cannot be recovered by the first gas-liquid separator and flow to the downstream side again by the third gas-liquid separator. Thus, the yield of hydrocarbons can be further improved.
According to an invention according to claim 5, there is provided a hydrocarbon producing method for obtaining a product containing hydrocarbons from a raw material gas by a Fischer-Tropsch synthesis reaction (FT synthesis reaction) using a reactor 7 containing an FT reaction catalyst exhibiting activity in the FT synthesis reaction, the hydrocarbon producing method including vaporizing hydrocarbons adhering to the FT reaction catalyst by executing an inert gas purge process that supplies an inert gas to the reactor 7, maintains a temperature in the reactor 7 in a temperature range during the FT synthesis reaction, and reduces a pressure in the reactor 7, when the FT synthesis reaction is terminated; and condensing the vaporized hydrocarbons and recovering the condensed hydrocarbons in a liquid state.
In the hydrocarbon producing method of the present invention, when the FT synthesis reaction is terminated, an inert gas purge process in which a high-temperature inert gas is supplied to the reactor, the temperature in the reactor is maintained in a temperature range similar to the temperature during the FT synthesis reaction, and the pressure in the reactor is reduced is executed, such that the hydrocarbons adhering to the catalyst can be vaporized and desorbed as gas. Therefore, the adhesion of the hydrocarbons to the catalyst can be eliminated. Furthermore, the adhered hydrocarbons are desorbed in a state where the FT reaction catalyst is contained in the FT reactor, such that the FT reaction catalyst can be easily reactivated, and the operation efficiency at the time of restarting the reactor can be improved. In addition, since the hydrocarbons desorbed from the catalyst as gas in the reactor are condensed and recovered in a liquid state, the hydrocarbons can be efficiently recovered to improve the yield, and the hydrocarbons can be suppressed from adhering to the pipe or the like on the downstream side.
Hereinafter, preferred embodiments of a hydrocarbon producing 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. Note that, in the following description, the terms “upstream side” and “downstream side” refer to an upstream side and a downstream side in a fluid flow direction in each unit to be described.
The carbon dioxide supply unit 2 and the hydrogen supply unit 3 supply carbon dioxide gas and hydrogen gas to a pipe connected to the compressor 5, respectively. Supply amounts of the carbon dioxide gas and the hydrogen gas to be the raw material gas of the FT synthesis reaction in the reactor 7 are detected by flow rate sensors (not illustrated) or the like, and the detected values are transmitted to the control unit 17. The control unit 17 controls the supply amounts so that carbon dioxide and hydrogen have a predetermined ratio suitable for the FT synthesis reaction. In the present embodiment, the supply amounts are controlled so that a molar ratio H2/CO2 is 3.
The nitrogen supply unit 4 supplies nitrogen (N2) gas, which is an inert gas, to a pipe connected to the compressor 5. At the termination of the FT synthesis reaction performed in the reactor 7, the nitrogen gas is supplied to a synthesis path including the compressor 5, the heater 6, the reactor 7, the warmer 8, the first gas-liquid separator 9, the cooler 10, the back pressure control valve 11, the flow rate regulating valve 12, the second gas-liquid separator 13, and pipes connecting these units, by being replaced with the raw material gas formed of carbon dioxide and hydrogen.
As described below, the compressor 5 and the heater 6 are used to create a high-pressure and high-temperature state suitable for performing the FT synthesis reaction in the present embodiment. The type of the compressor 5 is not particularly limited as long as the compressor 5 can compress the raw material gas supplied from the carbon dioxide supply unit 2 and the hydrogen supply unit 3 and send the compressed raw material gas to the heater 6 on the downstream side. For example, a centrifugal turbocompressor, an electric pump, or the like using an electric motor as a drive source can be used. A pressure sensor (not illustrated) is provided on the downstream side of the compressor 5, and a detected value thereof is transmitted to the control unit 17. The compressor 5 of the present embodiment is controlled by the control unit 17 so as to increase the pressure of the raw material gas to about 3 MPaG in the synthesis path. In addition, the heater 6 may be any heater as long as it can raise the temperature of the compressed raw material gas and send the raw material gas to the reactor 7 on the downstream side, and a known heater can be used. A temperature sensor (not illustrated) is provided on the downstream side of the heater 6, and a detected value thereof is transmitted to the control unit 17. The heater 6 of the present embodiment is controlled by the control unit 17 so as to raise the temperature of the raw material gas to about 380° C.
The reactor 7 contains a catalyst (hereinafter, referred to as “FT reaction catalyst”) exhibiting activity in the FT synthesis reaction therein, and produces hydrocarbons having various carbon numbers from the raw material gas passing through the reactor 7 by the FT synthesis reaction. The reaction performed in the reactor 7 of the present embodiment is a direct FT synthesis reaction represented by the following Formula (1) in which carbon dioxide and hydrogen are directly reacted to produce hydrocarbons and water.
As the FT reaction catalyst of the present embodiment, a combination of a pellet-like sodium iron catalyst obtained by adding sodium (Na) as a co-catalyst to iron (Fe), gallium (Ga), and zirconium (Zr), which are catalytic metals, and a zeolite catalyst using aluminosilicate zeolite (ZSM-5) at a predetermined ratio is used. Both the sodium iron catalyst and the zeolite catalyst are catalysts having a pore structure.
By the direct FT synthesis reaction using the FT reaction catalyst described above, in addition to light HCs having about 5 to 8 carbon atoms, heavy HCs having about 9 to 20 carbon atoms, and super-heavy HCs having 21 or more carbon atoms that can be raw materials of a synthetic fuel, hydrocarbons having 2 to 4 carbon atoms including methane (CH4) and water as by-products are produced.
The warmer 8 is a type of heater, and heats a passing fluid from the reactor 7 and maintains the temperature at an appropriate high temperature, such that separation of hydrocarbons in the first gas-liquid separator 9 on the downstream side described below is promoted. In the present embodiment, the heating of the warmer 8 is controlled by the control unit 17 so that the passing fluid from the reactor 7 has a temperature at which the heavy HCs having about 9 to 20 carbon atoms become a liquid at a high pressure (3 MPa) and normal pressure, and the super-heavy HCs having 21 or more carbon atoms become a liquid at normal pressure. In the present embodiment, heating is controlled so that the temperature of the fluid flowing into the first gas-liquid separator 9 is maintained at about 100° C.
The first gas-liquid separator 9 can be configured by a known gas-liquid separator, and separates the passing fluid from the reactor 7 into a liquid component and a gas component. As described above, the first gas-liquid separator 9 is maintained at a high temperature of about 100° C. by the warmer 8. As described below, in the first gas-liquid separator 9, since the pressure applied at the time of performing and stopping the FT synthesis reaction changes, the components to be separated also change. The first gas-liquid separator 9 functions to separate heavy HCs having about 9 to 20 carbon atoms as liquid components and separate light HCs having 8 or fewer carbon atoms, water, and unreacted gas as gas components at a high pressure during the FT synthesis reaction. The separated heavy HCs are sent to the heavy HC recovery tank 14, and the gas components including the light HCs, the water, and the unreacted gas are sent to the cooler 10. In addition, at normal pressure at the termination of the FT synthesis reaction, the first gas-liquid separator 9 functions to separate not only heavy HCs but also super-heavy HCs having 21 or more carbon atoms as liquid components. The separated heavy HCs and super-heavy HCs are separated by a fractionator (not illustrated), and then sent to the heavy HC recovery tank 14 and the super-heavy HC recovery tank 15, respectively. The recovered heavy HCs and super-heavy HCs are then hydrogenated and purified by a reformer (not illustrated) or the like to be used as a synthetic fuel product such as kerosene or light oil.
The cooler 10 is a heat exchanger that cools the gas components flowing into the cooler 10 by exchanging heat with a refrigerant. The cooling amount with respect to the flowing gas components can be controlled by the flow rate of the refrigerant flowing in the cooler 10, and the flow rate of the refrigerant is controlled by the control unit 17 controlling an opening degree of a flow rate regulating valve (not illustrated). In the present embodiment, the flow rate of the refrigerant of the cooler 10 is controlled so that the flowing gas components are cooled to a temperature at which light HCs having about 5 to 8 carbon atoms are condensed. In the present embodiment, the gas components flowing into the cooler 10 are cooled to about 10° C.
A branch portion is provided in the pipe on the downstream side of the cooler 10, and the back pressure control valve 11 and the flow rate regulating valve 12 are provided at the tip of the branched pipe, respectively. A switching valve 18 is provided in the branch portion, and the fluid from the upstream side can be controlled to flow into only one of the back pressure control valve 11 and the flow rate regulating valve 12 by the operation of the switching valve 18. The operation of the switching valve 18 is controlled by the control unit 17.
The back pressure control valve (BPCV) 11 is connected to one of the pipes branching from the branching portion on the downstream side of the cooler 10, and functions to keep the pressure on the upstream side (primary side) of the back pressure control valve 11 constant. As the back pressure control valve 11, a known back pressure control valve can be used, and in the present embodiment, a configuration in which a flow path leading to the front and rear of the back pressure control valve 11 is partitioned by a diaphragm valve and the diaphragm valve is pressed by a spring is adopted. With such a back pressure control valve 11, the pressure on the upstream side of the back pressure control valve 11 can be maintained at a predetermined pressure. The back pressure control valve 11 is configured so that the fluid flows only during the execution of the FT synthesis reaction in the reactor 7 by the control of the switching valve 18, and the pressure upstream of the back pressure control valve 11 is maintained at 3 MPa during the execution of the FT synthesis reaction.
The flow rate regulating valve 12 is connected to another pipe branching from the branching portion on the downstream side of the cooler 10, and functions to regulate the flow rate of the fluid flowing through the flow rate regulating valve 12. As the flow rate regulating valve 12, any known flow rate regulation valve can be adopted, and in the present embodiment, a known needle valve (NV) is used as the flow rate regulating valve 12. The needle valve controls a flow rate by regulating an opening degree of an orifice flow path in the valve with a needle or a rod needle. The flow rate regulating valve 12 is configured so that the fluid flows only while the FT synthesis reaction in the reactor 7 is stopped by the control of the switching valve 18, and in particular, at the termination of the FT synthesis reaction, the flow path is switched from the back pressure control valve 11 to the flow rate regulating valve 12, such that the synthesis path kept at a high pressure is gradually reduced to normal pressure.
The second gas-liquid separator 13 can be configured with a known gas-liquid separator, and separates the fluid flowing from the upstream side into a liquid component and a gas component at a lower temperature than the first gas-liquid separator 9. The fluid in which the light HCs, the water, and the unreacted gas flowing into the second gas-liquid separator 13 are mixed is cooled to about 10° C. by the cooler 10 provided on the upstream side, such that the light HCs having about 5 to 8 carbon atoms and the water are separated as liquid components, and the hydrocarbons having 4 or fewer carbon atoms and the unreacted gas are separated as gas components. The light HCs having about 5 to 8 carbon atoms and water separated as liquid components are separated by a fractionator (not illustrated), then the light HCs are sent to the light HC recovery tank, and the water is discharged to the outside as it is. In addition, the hydrocarbons having 4 or fewer carbon atoms 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 purified by a reformer (not illustrated) or the like to be used as a synthetic fuel product such as gasoline.
The control unit 17 is an electronic control unit (ECU) that controls each unit of the hydrocarbon producing apparatus 1, and includes a microcomputer including a CPU, a RAM, a ROM, an I/O interface (all not illustrated), and the like. The control unit 17 in the present embodiment controls at least the operations of the carbon dioxide supply unit 2, the hydrogen supply unit 3, the nitrogen supply unit 4, the compressor 5, the heater 6, the warmer 8, the cooler 10, and the switching valve 18.
Next, a process of each unit during the execution of the FT synthesis reaction will be described.
First, in step 201 (Illustrated as “S201”, the same applies hereinafter), the compressor 5, the heater 6, the warmer 8, and the cooler 10 are operated in a state where the nitrogen gas as the inert gas flows through the synthesis path, and the switching valve 18 is set to be opened to the back pressure control valve 11 side. As a result, the synthesis path from the compressor 5 to the back pressure control valve 11 is pressurized to 3 MPa, and the temperature of the reactor 7 is raised to about 380° C.
Next, supply of carbon dioxide gas and hydrogen gas as raw material gases to the synthesis path filled with the inert gas is started (step 202). The supply amounts of the carbon dioxide gas and the hydrogen gas are controlled so that a molar ratio H2/CO2 is 3. As the inert gas is replaced with the raw material gas, the direct FT synthesis reaction is started via the catalyst of the reactor 7 (step 203).
When the direct FT synthesis reaction is performed, a passing fluid containing hydrocarbons including light HCs, heavy HCs, and super-heavy HCs, and hydrocarbons having 1 to 4 carbon atoms as by-products, water, and unreacted gas flows out to the downstream side of the reactor 7, and flows into the first gas-liquid separator 9 through the warmer 8.
Next, in step 204, heavy HCs having about 9 to 20 carbon atoms are separated and recovered by the first gas-liquid separator 9 maintained at about 100° C.
Thereafter, the fluid that exits the first gas-liquid separator 9 is cooled to about 10° C. when passing through the cooler 10, and then flows into the second gas-liquid separator 13 through the back pressure control valve 11. In the second gas-liquid separator 13, light HCs having about 5 to 8 carbon atoms are recovered (step 205).
In this way, heavy HCs and light HCs are separated and recovered by repeating steps 204 and 205 while performing the direct FT synthesis reaction. 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 termination of the FT synthesis reaction will be described below.
Next, a process of each unit at the termination of the FT synthesis reaction will be described.
First, in step 301, as an operation for terminating the FT synthesis reaction, supply of nitrogen gas as an inert gas to the synthesis path filled with the raw material gas is started, such that the raw material gas in the synthesis path is gradually replaced with nitrogen gas. Note that since the nitrogen gas is heated by passing through the heater 6 on the upstream side of the reactor 7, it is possible to suppress a rapid decrease in the temperature in the reactor 7.
On the other hand, the exothermic reaction caused by the FT synthesis reaction is gradually weakened due to the decrease in the raw material gas in the reactor 7, such that the temperature in the reactor 7 decreases to some extent.
Subsequently, in step 302, after the replacement with the inert gas in step 301 is terminated, the pressurization of the synthesis path is stopped by stopping the operation of the compressor 5. Next, in step 303, the flow path set on the back pressure control valve 11 is switched to the flow rate regulating valve 12 by controlling the switching valve 18. As a result, the pressure in the synthesis path is gradually reduced from a high pressure state of 3 MPa to normal pressure.
After the pressure in the synthesis path decreases to normal pressure, in subsequent step 304, a purge process of supplying high-temperature nitrogen gas to the synthesis path to replace the raw material gas is continued for about 30 minutes. As illustrated in
The vaporized super-heavy HCs flow downstream and enter the first gas-liquid separator 9 through the warmer 8. The super-heavy HCs whose temperatures decrease from about 380° C. to about 100° C. in the process are condensed and liquefied as illustrated in
In this way, when the FT synthesis reaction is terminated, steps 305 and 306 are repeated during the purge process with the nitrogen gas, such that the adhesion of the super-heavy HCs to the FT reaction catalyst is eliminated, and the vaporized super-heavy HCs are condensed and can be recovered as a liquid in the first gas-liquid separator 9.
As described above, according to the hydrocarbon producing apparatus 1 of the present embodiment, at the termination of the FT synthesis reaction, the purge process in which a high-temperature inert gas is supplied to the reactor 7, the temperature in the reactor 7 is maintained in a temperature range similar to the temperature during the FT synthesis reaction, and the pressure in the reactor 7 is reduced to maintain normal pressure, is performed, such that the super-heavy HCs adhering to the FT reaction catalyst in the reactor 7 can be vaporized and desorbed as gas. As a result, the adhesion of the super-heavy HCs to the FT reaction catalyst can be eliminated. In addition, the super-heavy HCs adhering to such a catalyst can be desorbed in a state where the catalyst remains installed in the reactor 7, and the catalyst can be easily reactivated. As a result, the operating efficiency of the reactor 7 when it is restarted can be improved.
In addition, when the super-heavy HCs remaining in the reactor 7 and the pipe are gasified and flow to the downstream side, the super-heavy HCs are condensed by being temperature-controlled by the warmer 8, and are separated and recovered in a liquid state in the first gas-liquid separator 9. Therefore, the super-heavy HCs can be efficiently recovered to improve the yield, and the super-heavy HCs can be prevented from adhering to the pipe or the like on the downstream side of the first gas-liquid separator 9.
Further, the second gas-liquid separator 13 that condenses gaseous light HCs at a lower temperature than the first gas-liquid separator 9 and separates the condensed light HCs in a liquid state is provided on the downstream side of the first gas-liquid separator 9, such that light HCs that cannot be recovered by the first gas-liquid separator 9 can be recovered by the second gas-liquid separator 13. Thus, the yield of hydrocarbons can be further improved.
Next, a hydrocarbon producing apparatus 100 according to a second embodiment of the present invention will be described with reference to
In the hydrocarbon producing apparatus 1 according to the embodiment described above, the second gas-liquid separator 13 capable of separating and recovering light HCs is provided on the downstream side of the first gas-liquid separator 9 capable of separating and recovering heavy HCs and super-heavy HCs. On the other hand, in the hydrocarbon producing apparatus 100 according to the second embodiment, instead of the second gas-liquid separator 13, a second gas-liquid separator 130 that can separate and recover light HCs and heavy HCs by changing gas and liquid components to be separated by changing an internal temperature is adopted.
The second gas-liquid separator 130 is, for example, a known gas-liquid separator that includes a heat exchange unit (not illustrated) at a front stage and is capable of changing the internal temperature by controlling a heat source. The second gas-liquid separator 130 is configured to be capable of changing the internal temperature between a low first temperature at which light HCs having about 5 to 8 carbon atoms can be condensed at normal pressure and a high second temperature at which heavy HCs having about 9 to 20 carbon atoms can be condensed at normal pressure. In the present embodiment, the first temperature is set to 10° C., and the second temperature is set to 100° C.
The temperature of the second gas-liquid separator 130 is set to the low first temperature during the execution of the FT synthesis reaction. During the execution of the FT synthesis reaction, the fluid flowing into the second gas-liquid separator 130 through the back pressure control valve 11 may contain light HCs, water, unreacted gas, and a small amount of heavy HCs that cannot be completely recovered by the first gas-liquid separator 9. The mixed fluid is cooled to about 10° C. by the cooler 10 provided on the upstream side, and the second gas-liquid separator 130 itself is also set to the first temperature of 10° C., and therefore, in the second gas-liquid separator 130, light HCs and water are separated as liquid components, and hydrocarbons having 4 or fewer carbon atoms and unreacted gas are separated as gas components. On the other hand, a small amount of remaining heavy HCs is precipitated as a solid in the second gas-liquid separator 130. The light HCs having about 5 to 8 carbon atoms and water separated as liquid components are separated by a fractionator (not illustrated), then the light HCs are sent to the light HC recovery tank, and the water is discharged to the outside as it is. In addition, the hydrocarbons having 4 or fewer carbon atoms 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 purified by a reformer (not illustrated) or the like to be used as a synthetic fuel product such as gasoline.
The temperature of the second gas-liquid separator 130 is switched to the high second temperature at the termination of the FT synthesis reaction, for example, after the separation and recovery of light HCs by the second gas-liquid separator 130 are terminated. As a result, since the heavy HCs precipitated as a solid in the second gas-liquid separator 130 are melted, the liquefied heavy HCs can be recovered by the second gas-liquid separator 130. The recovered heavy HCs are sent to the heavy HC recovery tank 14.
As described above, according to the hydrocarbon producing apparatus 100 according to the second embodiment, the light HCs can be separated and recovered by setting the temperature of the second gas-liquid separator 130 to the first temperature that is low during the execution of the FT synthesis reaction, and the heavy HCs that cannot be recovered by the first gas-liquid separator 9 and flowing to the downstream side can be separated and recovered by setting the temperature of the second gas-liquid separator 130 to the second temperature that is high at the termination of the FT synthesis reaction. Thus, the yield of hydrocarbons can be further improved.
Note that the present invention is not limited to the described embodiments, and can be implemented in various modes. In addition, the detailed configuration can be changed appropriately within the scope of the gist of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023-089416 | May 2023 | JP | national |
