Synthetic fuel production apparatus and synthetic fuel production method

Abstract

To provide a synthetic fuel manufacturing apparatus and a synthetic fuel manufacturing method capable of determining the type of synthetic fuel to be manufactured according to the generation state of hydrocarbons by FT synthesis reaction and efficiently operating a fractionator at a fractionation temperature suitable for fractionation of hydrocarbons to be used therefor.SOLUTION: A synthetic fuel manufacturing apparatus of the present invention comprises: a reactor having a catalyst active in Fischer-Tropsch reaction and generating FT crude oil containing hydrocarbons from a raw material gas; a fractionator provided on the downstream side of the reactor to fractionate FT crude oil and separate hydrocarbons having a predetermined number of carbons; and a reformer provided on the downstream side of the fractionator to generate a fuel product from hydrocarbons separated by the fractionator. The apparatus further comprises aromatic detection means provided between the reactor and the fractionator to detect the concentration CA of aromatic hydrocarbons contained in the FT crude oil and is configured to vary the fractionation temperature Tfra of the fractionator according to the detected concentration CA of aromatic hydrocarbons.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a synthetic fuel production apparatus and a synthetic fuel production method for producing synthetic fuel by reforming crude oil obtained from a feed gas by a Fischer-Tropsch 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, in addition to hydrocarbons with a carbon number of about 5 to 10 that are used as raw materials for gasoline and hydrocarbons with a carbon number of about 8 to 16 that are used as raw materials for jet fuel (aviation turbine oil), heavy hydrocarbons with a higher carbon number and light hydrocarbons containing methane (CH4) are produced. Therefore, the crude oil with a wide hydrocarbon distribution produced by the FT synthesis reaction (hereinafter referred to as "FT crude oil") can be fractionated using a fractionation device such as a distillation column, and then passed through a hydrorefining reactor to obtain a synthetic fuel product according to the carbon number.

[0004] For example, Patent Document 1 discloses a technology for producing liquid fuels such as naphtha, kerosene, and diesel by fractionating various liquid hydrocarbon compounds produced in a reactor of an FT synthesis unit into each fraction in a fractionator, and reforming the fractions in a hydrotreating reactor provided for each fraction in an upgrading unit. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2014-189603 A Summary of the Invention [Problem to be solved by the invention]

[0006] The carbon number distribution of the hydrocarbons produced by the FT synthesis reaction varies depending on the composition of the catalyst used. Even if the same catalyst is used, the composition ratio of the produced hydrocarbons changes due to changes in the reaction characteristics caused by the number of times the catalyst has been used and the length of the reaction time that has elapsed, and as a result, the production volume of the final synthetic fuel product can vary greatly by type.

[0007] In the technology described in Patent Document 1, even if the obtained hydrocarbon components change due to deterioration of the catalyst or the like, the fractionation and reforming process for each fuel type in the process after the FT synthesis reaction is always in steady operation. Therefore, even if the production volume of a specific type of fuel is low, energy is continuously consumed to operate the fractionator and reformer for producing it, and there is room for improvement in terms of production costs and efficiency.

[0008] The present invention has been made to solve the above problems, and aims to provide a synthetic fuel production apparatus and a synthetic fuel production method that can determine the type of synthetic fuel suitable for production depending on the state of hydrocarbon production by the FT synthesis reaction, and can efficiently operate a fractionator at a fractional distillation temperature suitable for the fractional distillation of the hydrocarbons used to produce the synthetic fuel, thereby contributing 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 synthetic fuel production device comprising a reactor 6 having an FT reaction catalyst active in the Fischer-Tropsch synthesis reaction (FT synthesis reaction) and producing FT crude oil containing hydrocarbons from a raw material gas, a fractionator (fractionator 9 in the embodiment (hereinafter the same in this section), first fractionator 91, second fractionator 92) provided downstream of the reactor 6 and fractionating the FT crude oil and separating hydrocarbons having a predetermined range of carbon numbers, and a reformer (first reformer 10, second reformer 11) provided downstream of the fractionator and producing a fuel product from the hydrocarbons separated by the fractionator, further comprising an aromatic detection means (aromatic detector 8) provided between the reactor 6 and the fractionator for detecting the concentration CA of aromatic hydrocarbons contained in the FT crude oil, and changing the fractionation temperature Tfra of the fractionator according to the detected concentration CA of aromatic hydrocarbons.

[0010] As a result of intensive research, the present inventors have found that the carbon number distribution of the hydrocarbons produced by a certain FT synthesis reaction has a correlation with the concentration of aromatic hydrocarbons in the produced hydrocarbons. That is, the higher the ratio of aromatic hydrocarbons in the produced hydrocarbons, the more hydrocarbons with a smaller carbon number are produced, and conversely, the lower the ratio of aromatic hydrocarbons, the more hydrocarbons with a larger carbon number are produced. Furthermore, it has been confirmed that with certain catalysts, when the catalytic activity is high in the early stage of the reaction, a relatively large amount of aromatic hydrocarbons are produced, and when the catalyst is deteriorated and its activity is reduced, the amount of aromatic hydrocarbons produced is relatively small. In other words, when the catalytic activity is high, a large amount of hydrocarbons with a small carbon number are produced, and when the catalytic activity is reduced, a large amount of hydrocarbons with a large carbon number are produced.

[0011] Based on this knowledge, in the synthetic fuel production device of the present invention, the concentration of aromatic hydrocarbons contained in the FT crude oil produced by the FT synthesis reaction is detected, and the fractionation temperature of the fractionator is changed accordingly. As described above, the carbon number distribution in the produced hydrocarbons can be estimated from the concentration of aromatic hydrocarbons in the produced hydrocarbons, so that the type of synthetic fuel suitable for production is determined based on that, and the fractionation temperature is changed to a temperature suitable for the fractionation of the hydrocarbons used to produce that synthetic fuel, thereby making it possible to operate the fractionator efficiently and to produce synthetic fuel efficiently.

[0012] The invention according to claim 2 is characterized in that in the synthetic fuel production apparatus according to claim 1, the fractionator is a variable-temperature fractionator 9 capable of switching the fractionation temperature.

[0013] According to this configuration, since the fractionator is a variable temperature fractionator that can switch the fractionation temperature, the fractionation temperature can be changed to a temperature at which synthetic fuel can be efficiently produced according to the detected concentration of aromatic hydrocarbons. Therefore, the fractionator can be operated efficiently while suppressing unnecessary energy consumption, and synthetic fuel can be efficiently produced.

[0014] The invention of claim 3 is characterized in that, in the synthetic fuel production apparatus described in claim 1, the fractionator is a plurality of fractionators (first fractionator 91, second fractionator 92) each set to a different fractionation temperature, and each of the plurality of fractionators is connected to a branch pipe having a branch section branching off from the downstream side of the reactor 6, and the branch section has a switching valve 101 that switches which of the branch pipes is connected to the reactor based on the detected aromatic hydrocarbon concentration CA.

[0015] According to this configuration, a plurality of fractionators set to different distillation temperatures are used as the fractionator, and the pipes connected to the reactor are switched by a switching valve depending on the concentration of the detected aromatic hydrocarbons, thereby changing the fractionator used and the temperature at which the fractionation is performed. This allows the fractionation to be performed at a fractionation temperature at which the synthetic fuel can be produced efficiently. Therefore, the fractionator can be operated efficiently while suppressing unnecessary energy consumption, and the synthetic fuel can be produced efficiently.

[0016] The invention of claim 4 is a synthetic fuel production apparatus as described in claim 1, further comprising a heat exchange type gas-liquid separation device (gas-liquid separator 7) provided between the reactor 6 and the aromatic detection means 8.

[0017] According to this configuration, since a heat exchange type gas-liquid separator is provided between the reactor and the aromatic detection means, it is possible to recover light hydrocarbons and unreacted gases that are mainly generated in gas form together with the FT crude oil by the FT synthesis reaction, and separate them from the hydrocarbons that are the raw material for the synthetic fuel. In addition, the recovered light hydrocarbons and unreacted gases can be recycled by returning them to the upstream of the reactor, thereby improving the yield of hydrocarbons that can be used as synthetic fuel.

[0018] The invention of claim 5 is a synthetic fuel production device according to any one of claims 1 to 4, further comprising an alarm means (alarm unit 13) that notifies the user that regeneration or replacement of the FT reaction catalyst is necessary when the concentration CA of the detected aromatic hydrocarbons falls below a predetermined threshold value CAref2.

[0019] According to this configuration, the detected concentration of aromatic hydrocarbons is regarded as an index showing the degree of deterioration of the FT reaction catalyst, and when the concentration of aromatic hydrocarbons falls below a predetermined threshold, it is notified that it is time to perform regeneration treatment or replacement of the FT reaction catalyst. Therefore, the aromatic detection means can be used to know the time to regenerate / replace the FT reaction catalyst.

[0020] The invention according to claim 6 is a synthetic fuel production method comprising: an FT crude oil production step of producing FT crude oil containing hydrocarbons from a feed gas using a reactor 6 having an FT reaction catalyst active in the Fischer-Tropsch synthesis reaction (FT synthesis reaction); a fractionation step of fractionating the FT crude oil and separating hydrocarbons having a predetermined range of carbon numbers using fractionators (fractionator 9, first fractionator 91, second fractionator 92) provided downstream of the reactor 6; and a reforming step of producing a fuel product from the separated hydrocarbons using reformers (first reformer 10, second reformer 11) provided downstream of the fractionators, the method further comprising an aromatic detection step of detecting a concentration CA of aromatic hydrocarbons contained in the FT crude oil using aromatic detection means (aromatic detector 8) provided between the reactor 6 and the fractionator, and changing the fractionation temperature Tfra in the fractionation step according to the detected concentration CA of aromatic hydrocarbons.

[0021] In the synthetic fuel production method of the present invention, the concentration of aromatic hydrocarbons contained in the FT crude oil produced by FT synthesis is detected, and the fractionation temperature of the fractionator is changed accordingly. As described above, the carbon number distribution in the produced hydrocarbons can be estimated from the concentration of aromatic hydrocarbons in the produced hydrocarbons, so that the type of synthetic fuel suitable for production is determined based on that, and the fractionation temperature is changed to a temperature suitable for the fractionation of the hydrocarbons used to produce the synthetic fuel, thereby making it possible to operate the fractionator efficiently and to produce synthetic fuel efficiently. [Brief description of the drawings]

[0022] [Figure 1] 1 is a diagram showing an overall structure of a synthetic fuel production apparatus according to an embodiment of the present invention. [Diagram 2] 1 is a graph showing the relationship between the carbon number of produced hydrocarbons and the selectivity of hydrocarbon compounds due to differences in the configuration of the FT reaction catalyst. [Diagram 3] 1 is a graph showing the relationship between the proportion of aromatics in liquid components (hydrocarbons having 5 or more carbon atoms) of hydrocarbons produced by an FT synthesis reaction, the proportion of hydrocarbons having 5 to 7 carbon atoms, and the proportion of hydrocarbons having 8 to 16 carbon atoms. [Figure 4] 1 is a graph showing the relationship between the proportion of aromatics in hydrocarbons having 5 or more carbon atoms and the proportion of aromatics in hydrocarbons having 8 to 16 carbon atoms, among hydrocarbons produced by the FT synthesis reaction. [Diagram 5] 11 is a flowchart showing a fractional distillation temperature switching process. [Figure 6] FIG. 13 is a diagram showing the overall structure of a synthetic fuel production apparatus according to another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] A preferred embodiment of the synthetic fuel production apparatus of the present invention will be described in detail below 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.

[0024] FIG. 1 shows an example of the overall structure of a synthetic fuel production apparatus 1 according to this embodiment. The synthetic fuel production apparatus 1 includes, in order from the upstream side, a hydrogen supply unit 2, a carbon dioxide supply unit 3, a compressor 4, a heater 5, a reactor 6, a gas-liquid separator 7, an aromatic detector 8, a fractionator 9, a first reformer 10, and a second reformer 11. Each unit of the synthetic fuel production apparatus 1 is controlled by a control unit 12. With this configuration, the synthetic fuel production apparatus 1 uses carbon dioxide gas and hydrogen gas as raw material gases to produce FT crude oil through an FT synthesis reaction, and determines whether to produce gasoline or jet fuel depending on the carbon number of the hydrocarbons contained in the produced FT crude oil. After performing fractionation at a fractionation temperature appropriate for the purpose, gasoline or jet fuel is produced through a hydrorefining process using a reformer.

[0025] The hydrogen supply unit 2 and the carbon dioxide supply unit 3 supply hydrogen gas and carbon dioxide gas, respectively, to a pipe connected to the compressor 4. The supply amounts of hydrogen gas and carbon dioxide gas are detected by a flow rate sensor (not shown) or the like, and the detection value is transmitted to the control unit 12. The control unit 12 controls the supply amounts so that hydrogen and carbon dioxide have a predetermined ratio suitable for the FT synthesis reaction. In this embodiment, the supply amounts are controlled to, for example, a molar ratio of H2 / CO2=3. Although not shown, a separate inert gas supply unit for nitrogen, argon, helium, or the like is connected to a pipe upstream of the synthetic fuel production device 1 for purging treatment at the end of the FT synthesis reaction, and is configured to be able to be appropriately replaced with the raw material gas for the FT reaction.

[0026] The compressor 4 and the heater 5 are for creating a high pressure / high temperature state suitable for carrying out the FT synthesis reaction in this embodiment, as described later. The compressor 4 is not particularly limited in type as long as it can compress the raw material gas, which is a mixture of supplied hydrogen gas and carbon dioxide gas, and send it to the heater 5 on the downstream side, 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 4, and the detection value is transmitted to the control unit 12. The compressor 4 of this embodiment is controlled by the control unit 12 so as to pressurize the raw material gas to about 3 MPaG. The heater 5 may be any type as long as it can heat the compressed raw material gas and send it to the reactor 6 on the downstream side. A temperature sensor (not shown) is provided downstream of the heater, and the detection value is transmitted to the control unit 12. The heater 5 of this embodiment is controlled by the control unit 12 so as to heat the raw material gas to about 380°C.

[0027] The reactor 6 contains a catalyst (hereinafter referred to as "FT reaction catalyst") that exhibits activity in the FT synthesis reaction, and produces FT crude oil containing hydrocarbons by the FT synthesis reaction from the raw material gas passing through the reactor 6. The reaction that takes place in the reactor 6 in this embodiment is a direct FT synthesis reaction shown in the following formula (1), which produces hydrocarbons and water by directly reacting carbon dioxide and hydrogen. nCO2+mH2→HC+H2O …(1)

[0028] 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.

[0029] The FT crude oil produced by the direct FT synthesis reaction using the above-mentioned FT reaction catalyst contains heavy hydrocarbons with a carbon number of about 5 to 10, which are the raw material for gasoline, and hydrocarbons with a carbon number of about 8 to 16, which are the raw material for jet fuel (aviation turbine oil), as well as light hydrocarbons with a carbon number of 2 to 4, including methane (CH4). 2-4 ) is produced in gas form.

[0030] The gas-liquid separator 7 is a heat exchange type gas-liquid separator, and separates a two-phase gas-liquid product consisting of FT crude oil, light hydrocarbons, unreacted gas, etc., which leaves the reactor 6 and flows into the gas-liquid separator 7 into a liquid phase FT crude oil and a gas phase light hydrocarbons including methane (C 2-4 The separated liquid-phase FT crude oil is sent to the downstream fractionator 9. Meanwhile, the gas-phase light hydrocarbons and unreacted gas are returned to the upstream compressor 4 and recycled by being mixed with the feed gas.

[0031] The aromatics detector 8 is a device capable of detecting the concentration CA of aromatic hydrocarbons in the hydrocarbons in the FT crude oil sent from the gas-liquid separator 7 to the fractionator 9, and may be, for example, a commercially available gas chromatograph. The detected value of the aromatics concentration CA is sent to the control unit 12 and used in the fractionation temperature switching process described later.

[0032] The fractionator 9 separates hydrocarbons with a predetermined carbon number from the FT crude oil containing hydrocarbons with a carbon number of 5 or more by utilizing the difference in boiling point. In particular, the fractionator 9 in this embodiment is a temperature variable fractionator that can set the fractionation temperature Tfra by switching. The fractionator 9 is provided with a temperature sensor such as a thermocouple (not shown), and the detection value is transmitted to the control unit 12. The control unit 12 controls the output of a heat source unit (not shown) so that the detection value of the temperature sensor approaches the set fractionation temperature Tfra. Note that a control unit for the fractionator 9 different from the control unit 12 may be provided separately, and the fractionation temperature Tfra may be controlled by the control unit.

[0033] In the fractionator 9 of this embodiment, the fractionation temperature Tfra is switchable between a first fractionation temperature Tfra1 for separating hydrocarbons having 5 to 10 carbon atoms that can be used to produce gasoline, and a second fractionation temperature Tfra2 for separating hydrocarbons having 8 to 16 carbon atoms that can be used to produce jet fuel.

[0034] The first fractional distillation temperature Tfra1 is set to, for example, a temperature (for example, around 180°C) at which hydrocarbons having a carbon number of 10 or less vaporize. When the fractional distillation temperature Tfra of the fractionator 9 is set to the first fractional distillation temperature Tfra1, the gas component separated by the fractionator 9 is cooled by a cooler (not shown) or the like and then sent in liquid form to the first reformer 10 downstream, and the remaining liquid component is discarded or recycled after cracking.

[0035] Furthermore, the second fractional distillation temperature Tfra2 is set to, for example, a temperature (for example, around 100°C) at which hydrocarbons having a carbon number of 7 or less vaporize. When the fractional distillation temperature Tfra of the fractionator 9 is set to the second fractional distillation temperature Tfra2, the gas component separated by the fractionator 9 is discarded or reused as a heat source, and the remaining liquid component is sent to the second reformer 11 downstream.

[0036] The first reformer 10 performs hydrogenation treatment on the liquid hydrocarbons, mainly having 5 to 10 carbon atoms, supplied from the fractionator 9, using hydrogen gas supplied from the hydrogen supply unit 2, and then refines the hydrocarbons by distillation to extract gasoline as a synthetic fuel product.

[0037] The second reformer 11 performs hydrogenation treatment on the liquid hydrocarbons, mainly having a carbon number of 8 to 16, supplied from the fractionator 9, using hydrogen gas supplied from the hydrogen supply unit 2, and then refines the resulting mixture by distillation to extract jet fuel as a synthetic fuel product.

[0038] The control unit 12 is an ECU (Electronic Control Unit) that controls each part of the synthetic fuel production apparatus 1, and is configured with a microcomputer including a CPU, RAM, ROM, and an I / O interface (none of which are shown in the figures). The control unit 12 in this embodiment controls the operations of at least the hydrogen supply unit 2, the carbon dioxide supply unit 3, the compressor 4, the heater 5, the aromatic detector 8, and the fractionator 9. In addition, the control unit 12 controls the fractionation temperature in the fractionator 9, particularly by executing a fractionation temperature switching process described later.

[0039] As described below, the notification unit 13 notifies that the catalyst should be regenerated or replaced when the concentration CA of aromatic hydrocarbons detected by the aromatic detector 8 falls below a predetermined threshold CAref2. The notification may take any form, and any form can be selected, such as displaying an icon on a control panel (not shown) of the synthetic fuel production apparatus 1, turning on an indicator, or providing audio guidance.

[0040] Next, the fractionation temperature switching process in this embodiment will be described. As described above, in this embodiment, the direct FT synthesis reaction is performed using a catalyst in which a sodium iron catalyst and a zeolite catalyst are mixed. When such a catalyst is used, the zeolite catalyst is more likely to deteriorate than the sodium iron catalyst due to factors such as the carbon generated by the FT synthesis reaction coking the pores of the zeolite, and the water (H2O) generated by the FT synthesis reaction promoting the dealumination (Al) of the zeolite, causing structural destruction. It has been confirmed that the carbon number distribution of the hydrocarbons generated by the direct FT synthesis reaction changes depending on the degree of deterioration of the zeolite catalyst.

[0041] Fig. 2 is a graph showing the relationship between the carbon number of the generated hydrocarbons and the selectivity of the hydrocarbon compounds due to the difference in the configuration of the FT reaction catalyst in this embodiment. In (1) to (6) of the figure, in order to simulate the gradually deteriorating state of the zeolite catalyst in the FT reaction catalyst, the FT synthesis reaction was carried out by changing the amount, quality, and arrangement of the zeolite catalyst mixed with the sodium iron catalyst. (1) of the figure simulates the state in which the activity of the zeolite catalyst is the highest, and (2) to (6) simulate the state in which the deterioration of the zeolite catalyst gradually progresses. Here, a two-stage catalyst divided into a front stage and a rear stage was used as the FT reaction catalyst.

[0042] In FIG. 2(1), a mixture of sodium iron catalyst and zeolite catalyst was used in both the front and rear stages, and the zeolite catalyst used was zeolite that had been surface-treated with sodium hydroxide at a molar concentration of 0.2 mol / L. In Fig. 2(2), a mixture of sodium iron catalyst and zeolite catalyst was used only in the front stage, and zeolite catalyst surface-treated with sodium hydroxide at a molar concentration of 0.2 mol / L was used as the zeolite catalyst. Only sodium iron catalyst was used in the rear stage. In Figure 2 (3), a mixture of sodium iron catalyst and zeolite catalyst was used only in the front stage, and the amount of zeolite catalyst mixed was reduced compared to Figure 2 (2). Zeolite surface-treated with sodium hydroxide at a molar concentration of 0.2 mol / L was used as the zeolite catalyst. Only sodium iron catalyst was used in the rear stage. In Figure 2 (4), a mixture of sodium iron catalyst and zeolite catalyst was used only in the front stage, and the amount of zeolite catalyst mixed was reduced compared to Figure 2 (2). Zeolite surface-treated with sodium hydroxide at a molar concentration of 0.1 mol / L was used as the zeolite catalyst. Only sodium iron catalyst was used in the rear stage. In Fig. 2(5), a mixture of sodium iron catalyst and zeolite catalyst was used only in the rear stage, and zeolite surface-treated with sodium hydroxide at a molar concentration of 0.2 mol / L was used as the zeolite catalyst. Only sodium iron catalyst was used in the front stage. In Fig. 2(6), a mixture of sodium iron catalyst and zeolite catalyst was used only in the rear stage, and zeolite surface-treated with sodium hydroxide at a molar concentration of 0.1 mol / L was used as the zeolite catalyst. Only sodium iron catalyst was used in the front stage.

[0043] As shown in Figure 2, from (1) to (6), as the activity of the zeolite catalyst decreases, the distribution of carbon numbers in the hydrocarbons produced by the FT synthesis reaction changes. It can be seen that the higher the activity, the more hydrocarbons with smaller carbon numbers are produced, and as the activity decreases, the more hydrocarbons with larger carbon numbers are produced.

[0044] In addition, when looking at the selectivity of hydrocarbon compounds in the produced hydrocarbons, (1), which has the highest activity of the zeolite catalyst, the production rate of aromatic hydrocarbons (aromas) is the highest at 32 wt%, while (6), which has the lowest activity of the zeolite catalyst, has the lowest production rate of aromatic hydrocarbons (aromas) at 3 wt%. The ratio of aromatic hydrocarbons was calculated from components with 5 or more carbon atoms. The reason why the production rate of aromatic hydrocarbons increases as the activity of the zeolite catalyst increases is thought to be because the cyclization reaction proceeds through the cracking and dehydrogenation reaction of higher hydrocarbons by the zeolite, and the oligomerization and dehydrogenation reaction of lower hydrocarbons.

[0045] Fig. 3 is a graph showing the relationship between the proportion of aromatics in the liquid component of the hydrocarbons produced by the FT synthesis reaction (i.e., FT crude oil containing hydrocarbons with 5 or more carbon atoms) and the proportion of hydrocarbons with 5 to 7 carbon atoms and the proportion of hydrocarbons with 8 to 16 carbon atoms, calculated based on (1) to (6) in Fig. 2. As can be seen from the figure, the smaller the proportion of aromatic hydrocarbons in the FT crude oil (i.e., the more the deterioration of the zeolite catalyst progresses), the higher the production proportion of hydrocarbons with 8 to 16 carbon atoms, which are suitable for jet fuel production.

[0046] Therefore, when the aromatic concentration in FT crude oil is high (i.e., when the activity of the zeolite catalyst is high), it is considered efficient to separate hydrocarbons with a carbon number suitable for producing gasoline (approximately 5 to 10 carbon atoms) and produce gasoline, and when the aromatic concentration in FT crude oil is low (i.e., when the activity of the zeolite catalyst is low), it is considered efficient to separate hydrocarbons with a carbon number suitable for producing jet fuel (approximately 8 to 16 carbon atoms) and produce jet fuel.

[0047] FIG. 4 is a graph showing the relationship between the proportion of aromatic hydrocarbons in FT crude oil and the proportion of aromatic hydrocarbons in hydrocarbons with carbon numbers of 8 to 16, calculated based on (1) to (6) in FIG. 2. The slope of the regression line is 2.1804, and the coefficient of determination R 2 showed an extremely high value of 0.9991. Therefore, by measuring the aromatic hydrocarbon concentration CA in FT crude oil, it is possible to estimate with high accuracy the aromatic hydrocarbon concentration in the hydrocarbons with carbon numbers of 8 to 16 used in the production of jet fuel.

[0048] Currently, the components of biojet fuel are required to comply with the international standard ASTM D7566. According to this standard, the aromatic components must be 8wt% or more and 25wt% or less among the hydrocarbons with carbon numbers 8-16 used in jet fuel. When these values ​​are converted into the aromatic ratio in FT crude oil using the graph in Figure 4, the values ​​are 3.7wt% or more and 11.5wt% or less, as shown in the graph.

[0049] The aromatic content of jet fuel currently on the market is about 20 wt%. When this is converted into the aromatic content in FT crude oil using the graph in Figure 4, it becomes 9.2 wt%. Therefore, it can be said that for the production of jet fuel, it is most preferable for the aromatic content in FT crude oil to be within the range of about 9.2 ± 1 wt%.

[0050] Based on these experimental data, it is found that it is efficient to obtain hydrocarbons with a carbon number suitable for producing gasoline while the concentration CA of aromatic hydrocarbons in the FT crude oil produced by the FT synthesis reaction is above 11.5 wt%, and to obtain hydrocarbons with a carbon number suitable for producing jet fuel when the concentration CA of aromatic hydrocarbons in the FT crude oil falls below 11.5 wt%. In addition, when the concentration CA of aromatic hydrocarbons in the FT crude oil falls below 3.7 wt%, it is not possible to produce jet fuel conforming to ASTM D7566, so it can be determined that regeneration or replacement of the zeolite catalyst is necessary.

[0051] Based on this knowledge, the synthetic fuel production apparatus 1 of this embodiment executes a fractionation temperature switching process for switching the fractionation temperature Tfra in the fractionator 9. Fig. 5 is a flowchart showing the fractionation temperature switching process in this embodiment. The process shown in the flowchart is executed by the processor of the control unit 12 releasing a program stored in a storage device such as a ROM to a memory such as a RAM. This process is executed repeatedly during normal operation of the synthetic fuel production apparatus 1, for example at predetermined time intervals.

[0052] First, in step 501 (depicted as "S501"; the same applies below), the aromatic hydrocarbon concentration CA in the FT crude oil produced by the FT synthesis reaction is detected by the aromatic detector 8. Next, in step 502, it is determined whether the detected aromatic hydrocarbon concentration CA exceeds a predetermined first threshold concentration CAref1.

[0053] The first threshold concentration CAref1 is set as an aromatic concentration suitable for switching the type of synthetic fuel to be produced from gasoline to jet fuel, based on the hydrocarbon distribution when the aromatic hydrocarbons in the FT crude oil have that concentration and the aromatic component concentration in the jet fuel obtained by ASTM D7566. In this embodiment, the first threshold concentration CAref1 is set within the range of 11.5±1 wt% based on the above-mentioned experimental data. It is most preferable to set the first threshold concentration CAref1 to 11.5 wt%.

[0054] If the determination result in step 502 is YES and the aromatic concentration CA detected from the FT crude oil exceeds the first threshold concentration CAref1, it is determined that the hydrocarbon distribution and aromatic concentration CA in the FT crude oil are suitable for producing gasoline, and the process proceeds to step 503. In step 503, the fractionation temperature Tfra of the fractionator 9 is set to the first fractionation temperature Tfra1 for separating hydrocarbons with carbon numbers of 5 to 10 that can be used to produce gasoline, and this process ends.

[0055] On the other hand, if the determination result in step 502 is NO and the aromatic concentration CA detected from the FT crude oil is equal to or lower than the first threshold concentration CAref1, it is determined that the hydrocarbon distribution and aromatic concentration CA in the FT crude oil are suitable for producing jet fuel, and the process proceeds to step 504. In step 504, the fractionation temperature Tfra of the fractionator 9 is set to a second fractionation temperature Tfra2 for separating hydrocarbons with carbon numbers of 8 to 16 that can be used to produce jet fuel, and the process proceeds to step 505.

[0056] In step 505, it is determined whether the detected aromatic concentration CA is below a predetermined second threshold concentration CAref2. The second threshold concentration CAref2 is set as an aromatic concentration below which the aromatic components in the produced jet fuel will fall below the minimum aromatic component concentration in the jet fuel required by ASTM D7566 if the aromatic hydrocarbons in the FT crude oil fall below this concentration. In this embodiment, the second threshold concentration CAref2 is set in the range of 3.7±1 wt% based on the above-mentioned experimental data. It is most preferable to set the second threshold concentration CAref2=3.7 wt%.

[0057] If the judgment result in step 505 is NO, that is, the aromatic concentration CA detected from the FT crude oil is equal to or greater than the second threshold concentration CAref2, it is determined that the aromatic concentration in the produced jet fuel is within the range required by ASTM D7566, and this process is terminated.

[0058] On the other hand, if the judgment result in step 505 is YES, and the aromatic concentration CA detected from the FT crude oil is below the second threshold concentration CAref2, it is determined that the aromatic concentration in the produced jet fuel does not satisfy the requirements of ASTM D7566, and the notification unit 13 notifies that the zeolite catalyst needs to be regenerated or replaced, and this process is terminated.

[0059] In this way, the synthetic fuel production device 1 of this embodiment detects the concentration CA of aromatic hydrocarbons contained in the FT crude oil produced by the FT synthesis reaction, and changes the fractionation temperature Tfra of the fractionator 9 accordingly. With this configuration, the type of synthetic fuel suitable for production is determined based on the concentration CA of aromatic hydrocarbons, and the fractionation temperature Tfra is changed to a temperature suitable for the fractionation of the hydrocarbons used to produce that synthetic fuel, thereby making it possible to operate the fractionator efficiently and to produce synthetic fuel efficiently.

[0060] In particular, since the fractionator 9 is a variable-temperature fractionator capable of switching the fractionation temperature, the fractionation temperature Tfra can be changed to a temperature at which synthetic fuel can be efficiently produced according to the detected aromatic hydrocarbon concentration CA. This makes it possible to operate the fractionator efficiently while suppressing unnecessary energy consumption, and to efficiently produce synthetic fuel.

[0061] In addition, since a gas-liquid separator 7 is provided between the reactor 6 and the aromatics detector 8, it is possible to recover and separate the light hydrocarbons and unreacted gases that are generated mainly in gas form together with the FT crude oil by the FT synthesis reaction from the FT crude oil. In addition, the recovered light hydrocarbons and unreacted gases can be recycled by returning them upstream of the reactor 6, thereby improving the yield of hydrocarbons that can be used as synthetic fuel.

[0062] Furthermore, the detected aromatic hydrocarbon concentration CA is regarded as an index showing the degree of deterioration of the zeolite catalyst, and when the concentration CA falls below the second threshold concentration CAref2, it is notified that the FT reaction catalyst needs to be regenerated or replaced. Therefore, the aromatic hydrocarbon detector 7 can be used to know when to regenerate / replace the zeolite catalyst.

[0063] Next, a synthetic fuel 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.

[0064] In the synthetic fuel production apparatus 1 according to the embodiment described above, a variable-temperature fractionator 9 capable of switching between a plurality of fractional distillation temperatures Tfra1, Tfra2 was employed as a configuration for changing the fractional distillation temperature Tfra of the fractionator in accordance with the concentration CA of the detected aromatic hydrocarbons. However, the synthetic fuel production apparatus 100 according to the second embodiment is characterized in that, instead of the fractionator 9, a plurality of fractionators 91, 92 each set to a different fractional distillation temperature Tfra1, Tfra2 is employed.

[0065] The first fractionator 91 has a fractionation temperature Tfra set to the above-mentioned first fractionation temperature Tfra1 suitable for producing gasoline, and the gas components separated by the first fractionator 91, mainly consisting of hydrocarbons having a carbon number of 5 to 10, are cooled by a cooler (not shown) or the like, and then sent in liquid form to the downstream first reformer 10, and the remaining liquid components are discarded or recycled after cracking.

[0066] On the other hand, the second fractionator 92 has a fractionation temperature Tfra set to the above-mentioned second fractionation temperature Tfra2 suitable for producing jet fuel, and the gas components separated by the second fractionator 92, mainly consisting of hydrocarbons having a carbon number of 5 to 7, are discarded or reused as a heat source, and the remaining liquid components are sent to the second reformer 11 downstream.

[0067] These multiple fractionators 91, 92 are each connected to a branch pipe having a branch section branching off from the downstream side of the gas-liquid separator 7, and the branch section is provided with a switching valve 101. The switching valve 101 is configured to be switchable so as to selectively connect only one of the branch pipes connected to the first fractionator 91 or the branch pipe connected to the second fractionator 92 to the gas-liquid separator 7.

[0068] The flow path switching operation of the switching valve 101 is controlled by the control unit 12. The fractionation temperature switching process in the synthetic fuel production apparatus 100 is almost the same as the control described in Fig. 5, but only the processes in steps 503 and 504 are different. That is, if the determination result in step 502 is YES and the aromatic concentration CA detected from the FT crude oil is higher than the first threshold concentration CAref1, a process of switching the switching valve 101 to the first fractionator 91 side is performed in the subsequent step. On the other hand, if the determination result in step 502 is NO and the aromatic concentration CA detected from the FT crude oil is equal to or lower than the first threshold concentration CAref1, a process of switching the switching valve 101 to the second fractionator 92 side is performed in the subsequent step.

[0069] In this way, according to the synthetic fuel production apparatus 100, a plurality of fractionators 91, 92 set to different fractional distillation temperatures Tfra1, Tfra2 are used, and the fractionator used is changed and the fractional distillation temperature is changed by switching the pipes connected to the upstream gas-liquid separator 7 and reactor 6 by the switching valve 101 according to the detected aromatic hydrocarbon concentration CA. This makes it possible to perform fractional distillation at a fractional distillation temperature at which the synthetic fuel can be efficiently produced. Therefore, the fractionator can be operated efficiently while suppressing unnecessary energy consumption, and the synthetic fuel can be efficiently produced.

[0070] 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]

[0071] 1…Synthetic fuel production equipment 6. Reactor 7... Gas-liquid separator (heat exchange type gas-liquid separator) 8...Aromatic detector (aromatic detection means) 9...Fractionator 10...First reformer (reformer) 11...Second reformer (reformer) 13…Information Department 91...1st fractionator (fractionator) 92…Second fractionator (fractionator) 101...Switch valve CA: Concentration of aromatic hydrocarbons Tfra…Fractional temperature Tfra1…1st fractionation temperature Tfra2…Second fractional distillation temperature

Claims

1. a reactor having an FT reaction catalyst exhibiting activity in a Fischer-Tropsch synthesis reaction (FT synthesis reaction) and producing an FT crude oil containing hydrocarbons from a feed gas; a fractionator provided downstream of the reactor for fractionating the FT crude oil and separating hydrocarbons having a carbon number in a predetermined range; a reformer disposed downstream of the fractionator for producing a fuel product from the hydrocarbons separated by the fractionator, The apparatus further includes an aromatic hydrocarbon detection means provided between the reactor and the fractionator for detecting a concentration of aromatic hydrocarbons contained in the FT crude oil, A synthetic fuel production apparatus comprising: a distillation temperature of the fractionator being changed in response to the detected concentration of the aromatic hydrocarbons.

2. 2. The synthetic fuel production apparatus according to claim 1, wherein the fractionator is a variable-temperature fractionator capable of switching the fractionation temperature.

3. The fractionator is a plurality of fractionators each set at a different fractionation temperature, a branch pipe having a branch portion branching from a downstream side of the reactor is connected to each of the plurality of fractionators, 2. The synthetic fuel production apparatus according to claim 1, wherein the branching section has a switching valve that switches one of the branch pipes to be connected to the reactor based on the detected concentration of the aromatic hydrocarbons.

4. 2. The synthetic fuel production system according to claim 1, further comprising a heat exchange type gas-liquid separator provided between said reactor and said aromatic detection means.

5. The synthetic fuel production device according to any one of claims 1 to 4, further comprising a notification means for notifying that regeneration treatment or replacement of the FT reaction catalyst is necessary when the detected concentration of the aromatic hydrocarbons falls below a predetermined threshold value.

6. an FT crude oil production step of producing an FT crude oil containing hydrocarbons from a feed gas using a reactor having an FT reaction catalyst active in a Fischer-Tropsch synthesis reaction (FT synthesis reaction); a fractionation step of fractionating the FT crude oil by a fractionator provided downstream of the reactor to separate hydrocarbons having a carbon number in a predetermined range; a reforming step of producing a fuel product from the separated hydrocarbons by a reformer provided downstream of the fractionator, The method further includes an aromatic hydrocarbon detection step of detecting a concentration of aromatic hydrocarbons contained in the FT crude oil by an aromatic hydrocarbon detection means provided between the reactor and the fractionator, A method for producing a synthetic fuel, comprising changing a fractionation temperature in the fractionation step depending on the detected concentration of the aromatic hydrocarbons.

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