AU2007232922B2 - Liquid fuel synthesis system - Google Patents

Description

OSP-27784AU SPECIFICATION LIQUID FUEL SYNTHESIZING SYSTEM 5 TECHNICAL FIELD [0001] The present invention relates to a liquid fuel synthesizing system. Priority is claimed on Japanese Patent Application No. 2006-95516, filed March 30, 2006, the content of which is incorporated herein by reference. 10 BACKGROUND ART OF THE INVENTION [0002] As one of the methods for synthesizing liquid fuel from natural gas, a GTL (Gas-To-Liquid: liquid fuel synthesis) technique of reforming natural gas to produce synthesis gas including carbon monoxide gas (CO) and hydrogen gas (H 2 ) as main components, synthesizing liquid hydrocarbons using this synthesis gas as a source gas by 15 the Fischer-Tropsch synthesis reaction (hereinafter referred to as "FT synthesis reaction"), and further hydrogenating and hydrocracking the liquid hydrocarbons to manufacture liquid fuel products, such as naphtha (rough gasoline), kerosene, gas oil, and wax, has recently been developed. [0003] In a liquid fuel synthesizing system using such a GTL technique, it is necessary 20 to heat an intermediate product oil produced by the FT synthesis reaction to a predetermined temperature (for example, about 320*C) before the intermediate product is introduced into a rectifying column on the downstream side of the liquid fuel synthesizing system. Further, the above intermediate product separated for every boiling point by this 25 rectifying column is made into a product after being hydrogenated and refined, but it is 2 necessary to heat the separated intermediate product to a predetermined temperature range (for example, 100 to 400*C) even before being introduced into a hydrogenation reactor. [0004] In the conventional liquid fuel synthesizing system using the GTL technique, in order to heat the intermediate product to the above temperature range, heat-medium oil 5 is used as a heating medium. Disclosure of the Invention Problems to be solved by the Invention [0005] However, in order to use heat-medium oil as a heating medium, it is necessary to install an apparatus for storing the heat-medium oil into the liquid fuel synthesizing 10 system, an apparatus for heating the heat-medium oil, etc. Further, the heat utilization efficiency of the whole liquid fuel synthesizing system does not improve. [0006] The present invention has been made in view of such a problem, and aims at providing a liquid fuel synthesizing system capable of improving the thermal efficiency of the whole liquid fuel synthesizing system. 15 Means for Solving the Problems [0007] A liquid fuel synthesizing system of the present invention includes: a reformer that reforms a hydrocarbon raw material to generate synthesis gas including carbon monoxide gas and hydrogen gas as main components; a reactor that synthesizes liquid hydrocarbons from the carbon monoxide gas and hydrogen gas included in the synthesis 20 gas by a Fischer-Tropsch synthesis reaction; a refining treatment apparatus that performs a predetermined refining treatment on the liquid hydrocarbons synthesized in the reactor; and a heating device that heats the liquid hydrocarbons introduced into the refining treatment apparatus, using emission gas produced by combustion of fuel gas in a burner of the reformer and discharged from the reformer as a heating medium, wherein the 25 emission gas is directly supplied to the refining treatment apparatus.

OSP-27784AU 3 [0008] According to the liquid fuel synthesizing system of the present invention, the reformer reforms a hydrocarbon raw material to produce synthesis gas including carbon monoxide gas and hydrogen gas as main components, the reactor synthesizes liquid fuel using the synthesis gas as a raw material, the refmning treatment apparatus performs 5 predetermined refining treatment on a mixture of a plurality of kinds of the liquid fuels, and the heating device heats the liquid fuel introduced into the refining treatment apparatus. By supplying high-temperature gas discharged from the reformer to the heating device, this high-temperature gas can be utilized as a heating medium, just as it is. As a result, the thermal efficiency of the whole liquid fuel synthesizing system can be 10 improved. [0009] In the liquid fuel synthesizing system of the present invention, the refining treatment apparatus may be at least one of a rectifying column that fractionally distills the liquid hydrocarbons into a plurality of kinds of liquid fuels having different boiling points, and a hydrogenation reactor that hydrogenates the liquid hydrocarbons. 15 [0010] In addition, the heating device may be, for example, a heat exchanger which can perform exchange of heat between gas and liquid. Further, a liquid fuel synthesized in the reactor may be a mixture of a plurality of kinds of liquid fuels having different boiling points. 20 ADVANTAGEOUS EFFECTS OF THE INVENTION [0011] According to the present invention, the thermal efficiency of the whole liquid fuel synthesizing system can be improved by using the gas discharged from the reformer as a heat source. 25 BRIEF DESCRIPTION OF THE DRAWINGS OSP-27784AU 4 [0012] [FIG 1] FIG 1 is a schematic diagram showing the overall configuration of a liquid fuel synthesizing system according to an embodiment of the present invention. [FIG 2] FIG 2 is a schematic diagram showing a heating device of the liquid fuel synthesizing system according to the embodiment of the present invention. 5 DESCRIPTION OF THE REFERENCE SYMBOLS [0013] 1: LIQUID FUEL SYNTHESIZING SYSTEM 3: SYNTHESIS GAS PRODUCTION UNIT 5: FT SYNTHESIS UNIT 10 7: UPGRADING UNIT 9: REFINING TREATMENT APPARATUS 10: DESULFURIZING REACTOR 12: REFORMER 14: WASTE HEAT BOILER 15 16 and18: GAS-LIQUID SEPARATORS 20: CO 2 REMOVAL UNIT 22: ABSORPTION COLUMN 24: REGENERATION COLUMN 26: HYDROGEN SEPARATING APPARATUS 20 30: BUBBLE COLUMN REACTOR 32: HEAT TRANSFER PIPE 34 and 38: GAS-LIQUID SEPARATORS 36: SEPARATOR 40: FIRST RECTIFYING COLUMN 25 50: WAX COMPONENT HYDROCRACKING REACTOR OSP-27784AU 5 52: KEROSENE AND GAS OIL FRACTION HYDROTREATING REACTOR 54: NAPHTHA FRACTION HYDROTREATING REACTOR 56,58 and 60: GAS-LIQUID SEPARATERS 5 70: SECOND RECTIFYING COLUMN 72: NAPHTHA STABILIZER 100, 102 and 104: HEAT EXCHANGERS DESCRIPTION OF THE PREFERRED EMBODIMENTS 10 [0014] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, in the present specification and drawings, duplicate description is omitted by giving the same reference numerals to constituent parts having substantially the same functional configurations. [001 5] First, with reference to FIG. 1, the overall configuration and operation of a liquid 15 fuel synthesizing system 1 which carries out a GTL (Gas-To-Liquid) process according to an embodiment of the present invention will be described. FIG 1 is a schematic diagram showing the overall configuration of the liquid fuel synthesizing system 1 according to the present embodiment. [0016] As shown in FIG 1, the liquid fuel synthesizing system 1 according to the 20 present embodiment is a plant facility which carries out the GTL process which converts a hydrocarbon raw material, such as natural gas, into liquid fuels. This liquid fuel synthesizing system 1 includes a synthesis gas production unit 3, an FT synthesis unit 5, and an upgrading unit 7. The synthesis gas production unit 3 reforms natural gas, which is a hydrocarbon raw material, to produce synthesis gas including carbon monoxide gas 25 and hydrogen gas. The FT synthesis unit 5 produces liquid hydrocarbons from the OSP-27784AU 6 above synthesis gas by the Fischer-Tropsch synthesis reaction (hereinafter referred to as "FT synthesis reaction"). The upgrading unit 7 hydrogenates and hydrocracks the liquid hydrocarbons produced by the FT synthesis reaction to manufacture liquid fuel products (naphtha, kerosene, gas oil, wax, etc.). Hereinafter, constituent parts of each of these 5 units will be described. [0017] First, the synthesis gas production unit 3 will be described. The synthesis gas production unit 3 mainly includes, for example, a desulfurizing reactor 10, a reformer 12, a waste heat boiler 14, gas-liquid separators 16 and 18, a CO 2 removal unit 20, and a hydrogen separating apparatus 26. The desulfurizing reactor 10 is composed of a 10 hydrogenation desulfurizer, etc., and removes a sulfur component from natural gas as a raw material. The reformer 12 reforms the natural gas supplied from the desulfurizing reactor 10, to produce synthesis gas including carbon monoxide gas (CO) and hydrogen gas (H 2 ) as main components. The waste heat boiler 14 recovers heat duty of the synthesis gas produced by the reformer 12, to manufacture high-pressure steam. The 15 gas-liquid separator 16 separates the water heated by heat exchange with the synthesis gas in the waste heat boiler 14 into gas (high-pressure steam) and liquid. The gas-liquid separator 18 removes condensate components from the synthesis gas cooled down in the waste heat boiler 14, and supplies a gas component to the CO 2 removal unit 20. The

CO

2 removal unit 20 has an absorption column 22 which removes carbon dioxide gas 20 from the synthesis gas supplied from the gas-liquid separator 18 by absorption, and a regeneration column 24 which performs stripping treatment on the carbon dioxide gas from the absorbent including the carbon dioxide gas to diffuses and regenerate the carbon dioxide gas. The hydrogen separating apparatus 26 separates a part of the hydrogen gas included in the synthesis gas, from the synthesis gas the carbon dioxide gas of which has 25 been separated by the CO 2 removal unit 20.

OSP-27784AU 7 [0018] Among them, the reformer 12 reforms natural gas by using carbon dioxide and steam to produce high-temperature synthesis gas including carbon monoxide gas and hydrogen gas as main components, by a steam and carbon-dioxide-gas reforming method expressed by the following chemical reaction formulas (1) and (2). In addition, the 5 reforming method in this reformer 12 is not limited to the example of above the steam and carbon-dioxide-gas reforming method. For example, a steam reforming method, a partial oxidation method (POX) using oxygen, an autothermal reforming method (ATR) that is a combination of the partial oxidation method and the steam reforming method, a carbon-dioxide-gas reforming method, and the like can also be utilized. 10 [0019] CH 4

+H

2 0-+CO+3H 2 (1)

CH

4 +C0 2 ->2CO+2H 2 '-- (2) [0020] Further, the hydrogen separating apparatus 26 is provided on a line branched from a main pipe which connects the CO 2 removal unit 20 or gas-liquid separator 18 with the bubble column reactor 30. This hydrogen separating apparatus 26 can be composed 15 of, for example, a hydrogen PSA (Pressure Swing Adsorption) device which performs adsorption and desorption of hydrogen by using a pressure difference. This hydrogen PSA device has adsorbents (zeolitic adsorbent, activated carbon, alumina, silica gel, etc.) within a plurality of adsorption columns (not shown) which are arranged in parallel. By sequentially repeating processes including pressurizing, adsorption, desorption (pressure 20 reduction), and purging in each of the adsorption columns, high-purity (for example, about 99.999%) hydrogen gas can be continuously supplied to a reactor. [0021] In addition, the hydrogen gas separating method in the hydrogen separating apparatus 26 is not limited to the example of the pressure swing adsorption method as in the above hydrogen PSA device. For example, there may be a hydrogen storing alloy 25 adsorption method, a membrane separation method, or a combination thereof.

OSP-27784AU 8 [0022] The hydrogen storing alloy method is, for example, a technique of separating hydrogen gas using a hydrogen storing alloy (TiFe, LaNiS, TiFeo.

7 to 0.9, Mno.

3 to 0.1, TiMnI.

5 , etc.) having a property which adsorbs or diffuses hydrogen by being cooled or heated. By providing a plurality of adsorption columns in which a hydrogen storing 5 alloy is accommodated, and alternately repeating, in each of the adsorption columns, adsorption of hydrogen by cooling of the hydrogen storing alloy and diffusion of hydrogen by heating of the hydrogen storing alloy, hydrogen gas in synthesis gas can be separated and recovered. [0023] Further, the membrane separation method is a technique of separating hydrogen 10 gas having excellent membrane permeability out of a mixed gas, using a membrane made of a polymeric material, such as aromatic polyimide. Since this membrane separation method is not accompanied with a phase change, less energy for running is required, and its running cost is reduced. Further, since the structure of a membrane separation device is simple and compact, a low facility cost is required and the area of a required facility is 15 also less. Moreover, since there is no driving device in a separation membrane, and a stable running range is wide, there is an advantage in that maintenance and management is easy. [0024] Next, the FT synthesis unit 5 will be described. The FT synthesis unit 5 mainly includes, for example, the bubble column reactor 30, a gas-liquid separator 34, a 20 separator 36, a gas-liquid separator 38, and a first rectifying column 40. The bubble column reactor 30 carries out the FT synthesis reaction of the synthesis gas generated in the above synthesis gas production unit 3, i.e., carbon monoxide gas and hydrogen gas, to produce liquid hydrocarbons. The gas-liquid separator 34 separates the water circulated and heated through a heat transfer pipe 32 disposed in the bubble column reactor 30 into 25 steam (medium-pressure steam) and liquid. The separator 36 is connected to a central OSP-27784AU 9 part of the bubble column reactor 30, and separates a catalyst and a liquid hydrocarbon product. The gas-liquid separator 38 is connected to an upper part of the bubble column reactor 30, and cools down unreacted synthesis gas and gaseous hydrocarbon product. The first rectifying column 40 distills the liquid hydrocarbons supplied via the separator 5 36 and the gas-liquid separator 38 from the bubble column reactor 30, and separates and refines the liquid hydrocarbons into individual product fractions according to boiling points. [0025] Among them, the bubble column reactor 30, which is an example of a reactor which converts synthesis gas to liquid hydrocarbons, functions as a reactor which 10 produces liquid hydrocarbons from synthesis gas by the FT synthesis reaction. This bubble column reactor 30 is composed of, for example, a slurry bubble column reactor in which slurry consisting of a catalyst and medium oil is reserved inside a column. This bubble column reactor 30 produces liquid hydrocarbons from synthesis gas by the FT synthesis reaction. In detail, in this bubble column reactor 30, the synthesis gas as a 15 source gas is supplied as bubbles from a dispersing plate at the bottom of the bubble column reactor 30, and passes through the slurry consisting of a catalyst and medium oil, and in a suspend state, hydrogen gas and carbon monoxide gas cause a synthesis reaction with catalyst, as shown in the following chemical reaction formula (3). [0026] 2nH 2 + nCO -+ (-CH 2 -)n + nH 2 0 ... (3) 20 [0027] Since this FT synthesis reaction is an exothermic reaction, the bubble column reactor 30, which is a heat exchanger-type reactor within which the heat transfer pipe 32 is disposed, is adapted such that, for example, water (BFW: Boiler Feed Water) is supplied as a refrigerant so that reaction heat of the above FT synthesis reaction can be recovered as medium-pressure steam by heat exchange between slurry and water. 25 [0028] Finally, the upgrading unit 7 will be described. The upgrading unit 7 includes, OSP-27784AU 10 for example, a WAX component hydrocracking reactor 50, a kerosene and gas oil fraction hydrotreating reactor 52, a naphtha fraction hydrotreating reactor 54, gas-liquid separators 56, 58 and 60, a second rectifying column 70, and a naphtha stabilizer 72. The WAX component hydrocracking reactor 50 is connected to a lower part of the first 5 rectifying column 40. The kerosene and gas oil fraction hydrotreating reactor 52 is connected to a central part of the first rectifying column 40. The naphtha fraction hydrotreating reactor 54 is connected to an upper part of the first rectifying column 40. The gas-liquid separators 56, 58 and 60 are provided so as to correspond to the hydrogenation reactors 50, 52 and 54, respectively. The second rectifying column 70 10 separates and refines the liquid hydrocarbons supplied from the gas-liquid separators 56 and 58 according to boiling points. The naphtha stabilizer 72 rectifies liquid hydrocarbons of a naphtha fraction supplied from the gas-liquid separator 60 and the second rectifying column 70. Then, the naphtha stabilizer 72 discharges components lighter than butane towards flare gas, and to separate and recover components having a 15 carbon number of five or more as a naphtha product. [0029] Next, a process (GTL process) of synthesizing liquid fuel from natural gas by the liquid fuel synthesizing system 1 configured as above will be described. [0030] Natural gas (whose main component is CH 4 ) as a hydrocarbon raw material is supplied to the liquid fuel synthesizing system 1 from an external natural gas supply 20 source (not shown), such as a natural gas field or a natural gas plant. The above synthesis gas production unit 3 reforms this natural gas to manufacture synthesis gas (mixed gas including carbon monoxide gas and hydrogen gas as main components). [0031] Specifically, first, the above natural gas is supplied to the desulfurizing reactor 10 along with the hydrogen gas separated by the hydrogen separating apparatus 26. The 25 desulfurizing reactor 10 hydrogenates and desulfurizes a sulfur component included in OSP-27784AU 11 the natural gas using the hydrogen gas, with a ZnO catalyst. By desulfurizing natural gas in advance in this way, it is possible to prevent from decreasing activity of a catalyst used in the reformer 12, the bubble column reactor 30, etc. because of sulfur. [0032] The natural gas (may also contain carbon dioxide) desulfurized in this way is 5 supplied to the reformer 12 after the carbon dioxide (C0 2 ) gas supplied from a carbon-dioxide supply source (not shown) and the steam generated in the waste heat boiler 14 are mixed to the desulfurized natural gas. The reformer 12 reforms natural gas by using carbon dioxide and steam to produce high-temperature synthesis gas including carbon monoxide gas and hydrogen gas as main components, by the above steam and 10 carbon-dioxide-gas reforming method. At this time, the reformer 12 is supplied with, for example, fuel gas for a burner dispose in the reformer 12 and air, and reaction heat required for the above steam and carbon-dioxide-gas reforming reaction is provided by the heat of combustion of the fuel gas in the burner. The liquid fuel synthesizing system 1 according to the present embodiment has a feature in that emission gas of about 1000 to 15 1200*C produced by the combustion heat of combustion gas in this burner is utilized. This point will be described in detail below. [0033] The high-temperature synthesis gas (for example, 900*C, 2.0 MPaG) produced in the reformer 12 in this way is supplied to the waste heat boiler 14, and is cooled down by the heat exchange with the water which circulates through the waste heat boiler 14 20 (for example, 400*C), thereby exhausting and recovering heat. At this time, the water heated by the synthesis gas in the waste heat boiler 14 is supplied to the gas-liquid separator 16. From this gas-liquid separator 16, a gas component is supplied to the reformer 12 or other external devices as high-pressure steam (for example, 3.4 to 10.0 MPaG), and water as a liquid component is returned to the waste heat boiler 14. 25 [0034] Meanwhile, the synthesis gas cooled down in the waste heat boiler 14 is OSP-27784AU 12 supplied to the absorption column 22 of the CO 2 removal unit 20, or the bubble column reactor 30, after condensate components are separated and removed from the synthesis gas in the gas-liquid separator 18. The absorption column 22 absorbs carbon dioxide gas included in the synthesis gas into the circulated absorbent, to remove the carbon 5 dioxide gas from the synthesis gas. The absorbent including the carbon dioxide gas within this absorption column 22 is introduced into the regeneration column 24, the absorbent including the carbon dioxide gas is heated and subjected to stripping treatment with, for example, steam, and the resulting diffused carbon dioxide gas is delivered to the reformer 12 from the regeneration column 24, and is reused for the above reforming 10 reaction. [0035] The synthesis gas produced in the synthesis gas production unit 3 in this way is supplied to the bubble column reactor 30 of the above FT synthesis unit 5. At this time, the composition ratio of the synthesis gas supplied to the bubble column reactor 30 is adjusted to a composition ratio (for example, H 2 : CO = 2:1 (molar ratio)) suitable for the 15 FT synthesis reaction. In addition, the pressure of the synthesis gas supplied to the bubble column reactor 30 is raised to be suitable (for example, 3.6 MPaG) for the FT synthesis reaction by a compressor (not shown) provided in a pipe which connects the

CO

2 removal unit 20 with the bubble column reactor 30. [0036] Further, a part of the synthesis gas, the carbon dioxide gas of which has been 20 separated by the above CO 2 removal unit 20, is also supplied to the hydrogen separating apparatus 26. The hydrogen separating apparatus 26 separates the hydrogen gas included in the synthesis gas, by the adsorption and desorption (hydrogen PSA) utilizing a pressure difference as described above. This separated hydrogen is continuously supplied from a gas holder (not shown), etc. via a compressor (not shown) to various 25 hydrogen-utilizing reaction devices (for example, the desulfurizing reactor 10, the WAX OSP-27784AU 13 component hydrocracking reactor 50, the kerosene and gas oil fraction hydrotreating reactor 52, the naphtha fraction hydrotreating reactor 54, etc.) which perform predetermined reactions utilizing hydrogen within the liquid fuel synthesizing system 1. [0037] Next, the above FT synthesis unit 5 produces liquid hydrocarbons by the FT 5 synthesis reaction from the synthesis gas produced by the above synthesis gas production unit 3. [0038] Specifically, the synthesis gas from which carbon dioxide gas has been separated in the above CO 2 removal unit 20 flows into the bubble column reactor 30 from the bottom of the reactor 30, and flows up through the catalyst slurry reserved in the bubble 10 column reactor 30. At this time, within the bubble column reactor 30, the carbon monoxide and hydrogen gas which are included in the synthesis gas react with each other by the FT synthesis reaction, thereby producing hydrocarbons. Moreover, by circulating water through the heat transfer pipe 32 in the bubble column reactor 30 at the time of this synthesis reaction, the heat of the FT synthesis reaction is removed, and the 15 water heated by this heat exchange is vaporized into steam. As for this water vapor, the water separated in the gas-liquid separator 34 is returned to the heat transfer pipe 32, and the vapor is supplied to an external device as medium-pressure steam (for example, 1.0 to 2.5 MPaG). [0039] The liquid hydrocarbons synthesized in the bubble column reactor 30 in this way 20 are removed from the central part of the bubble column reactor 30, and are introduced into the separator 36. The separator 36 separates the introduced liquid hydrocarbons into a catalyst (solid component) in the extracted slurry, and a liquid component including a liquid hydrocarbon product. A part of the separated catalyst is supplied to the bubble column reactor 30, and a liquid component thereof is supplied to the first 25 rectifying column 40. From the top of the bubble column reactor 30, unreacted OSP-27784AU 14 synthesis gas, and a gas component of the synthesized hydrocarbons are introduced into the gas-liquid separator 38. The gas-liquid separator 38 cools down these gases, and then separates some condensed liquid hydrocarbons to introduce them into the first rectifying column 40. Meanwhile, as the gas component separated in the gas-liquid 5 separator 38, unreacted synthesis gases (CO and H 2 ) are put into the bottom of the bubble column reactor 30, and reused for the FT synthesis reaction. Further, generally, the emission gas (flare gas) other than products, which contains as a main component hydrocarbon gas having a low carbon number (C 4 or less), is introduced into an external combustion facility (not shown), is combusted therein, and is then discharged to the 10 atmosphere. [0040] Next, the first rectifying column 40 heats the liquid hydrocarbons (whose carbon numbers are various) supplied via the separator 36 and the gas-liquid separator 38 from the bubble column reactor 30 as described above, to fractionally distill the liquid hydrogen using a difference in boiling point. Thereby, the first rectifying column 40 15 separates and refines the liquid hydrogen into a naphtha fraction (whose boiling point is less than about 315*C), a kerosene and gas oil fraction (whose boiling point is about 315 to 800*C), and a WAX component (whose boiling point is greater than about 800*C). The liquid hydrocarbons (mainly C 2 1 or more) as the WAX component extracted from the bottom of the first rectifying column 40 are transferred to the WAX component 20 hydrocracking reactor 50, the liquid hydrocarbons (mainly CII to C 20 ) as the kerosene and gas oil fraction removed from the central part of the first rectifying column 40 are transferred to the kerosene and gas oil fraction hydrotreating reactor 52, and the liquid hydrocarbons (mainly C 5 to CIO) as the naphtha fraction extracted from the upper part of the first rectifying column 40 are transferred to the naphtha fraction hydrotreating reactor 25 54.

OSP-27784AU 15 [0041] The WAX component hydrocracking reactor 50 hydrocracks the liquid hydrocarbons as the WAX component with a large carbon number (approximately C 2 1 or more), which has been supplied from the lower part of the first rectifying column 40, by using the hydrogen gas supplied from the above hydrogen separating apparatus 26, to 5 reduce the carbon number to less than C 20 . In this hydrocracking reaction, hydrocarbons with a large carbon number and with low molecular weight are generated by cleaving C-C bonds of hydrocarbons with a large carbon number, using a catalyst and heat. A product including the liquid hydrocarbons hydrocracked by this WAX component hydrocracking reactor 50 is separated into gas and liquid in the gas-liquid 10 separator 56, the liquid hydrocarbons of which are transferred to the second rectifying column 70, and the gas component (including hydrogen gas) of which is transferred to the kerosene and gas oil fraction hydrotreating reactor 52 and the naphtha fraction hydrotreating reactor 54. [0042] The kerosene and gas oil fraction hydrotreating reactor 52 hydrotreats liquid 15 hydrocarbons (approximately CII to C 20 ) as the kerosene and gas oil fractions having an approximately middle carbon number, which have been supplied from the central part of the first rectifying column 40, by using the hydrogen gas supplied via the WAX component hydrocracking reactor 50 from the hydrogen separating apparatus 26. This hydrotreating reaction is a reaction which adds hydrogen to unsaturated bonds of the 20 above liquid hydrocarbons, to saturate the liquid hydrocarbons and to generate straight-chain saturated hydrocarbons. As a result, a product including the hydrotreated liquid hydrocarbons is separated into gas and liquid in the gas-liquid separator 58, the liquid hydrocarbons of which are transferred to the second rectifying column 70, and the gas component (including hydrogen gas) of which is reused for the above hydrogenation 25 reaction.

OSP-27784AU 16 [0043] The naphtha fraction hydrotreating reactor 54 hydrotreats liquid hydrocarbons (approximately C 10 or less) as the naphtha fraction with a low carbon number, which have been supplied from the upper part of the first rectifying column 40, by using the hydrogen gas supplied via the WAX component hydrocracking reactor 50 from the 5 hydrogen separating apparatus 26. As a result, a product including the hydrotreated liquid hydrocarbons is separated into gas and liquid in the gas-liquid separator 60, the liquid hydrocarbons of which are transferred to the naphtha stabilizer 72, which is a kind of rectifying column, and the gas component (including hydrogen gas) of which is reused for the above hydrogenation reaction. 10 [0044] Next, the second rectifying column 70 distills the liquid hydrocarbons supplied from the WAX component hydrocracking reactor 50 and the kerosene and gas oil fraction hydrotreating reactor 52 as described above. Thereby, the second rectifying column 70 separates and refines the liquid hydrogen into a naphtha fraction (whose boiling point is less than about 315*C) with a carbon number of 10 or less, kerosene (whose boiling point 15 is about 315 to 450*C), and gas oil (whose boiling point is about 450 to 800*C). The gas oil is extracted from a lower part of the second rectifying column 70, and the kerosene is extracted from a central part thereof. Meanwhile, a hydrocarbon gas with a carbon number of 10 or more is extracted from the top of the second rectifying column 70, and is supplied to the naphtha stabilizer 72. 20 [0045] Moreover, the naphtha stabilizer 72 distills the hydrocarbons with a carbon number of 10 or less, which have been supplied from the above naphtha fraction hydrotreating reactor 54 and second rectifying column 70. Thereby, the naphtha stabilizer 72 separates and refines naphtha (C 5 to CIO) as a product. Accordingly, high-purity naphtha is extracted from a lower part of the naphtha stabilizer 72. 25 Meanwhile, the emission gas (flare gas) other than products, which contains as a main OSP-27784AU 17 component hydrocarbons with a carbon number lower than or equal to a predetermined number or less (lower than or equal to C 4 ), is discharged from the top of the naphtha stabilizer 72. Further, the emission gas is delivered into an external combustion facility (not shown), is combusted therein, and is then discharged to the atmosphere. 5 [0046] The process (GTL process) of the liquid fuel synthesizing system 1 has been described hitherto. By the GTL process, natural gas can be easily and economically converted into clean liquid fuels, such as high-purity naphtha (C 5 to Cio: rough gasoline), kerosene (C 11 to C 15 : kerosene), and gas oil (C 16 to C 20 : gas oil). Moreover, in the present embodiment, the above steam and carbon-dioxide-gas reforming method is 10 adopted in the reformer 12. Thus, there are advantages in that carbon dioxide contained in natural gas to be used as a raw material can be effectively utilized, the composition ratio (for example, H 2 :CO = 2:1 (molar ratio)) of a synthesis gas suitable for the above FT synthesis reaction can be efficiently produced in one reaction of the reformer 12, and a hydrogen concentration adjustor, etc. is unnecessary. 15 [0047] Subsequently, a heating device which is used in the liquid fuel synthesizing system according to the present embodiment will be described in detail, referring to FIG 2. FIG 2 is a schematic diagram showing the heating device of the liquid fuel synthesizing system according to the present embodiment. [0048] As described above, the reformer 12 according to the present embodiment is an 20 apparatus which produces synthesis gas including, as main components, high-temperature carbon monoxide gas and hydrogen gas of about 1 000C from carbon dioxide gas and natural gas supplied as a raw material. In order to obtain reaction heat required for a generation reaction of the high-temperature synthesis gas, it is necessary to bum fuel gas introduced into the reformer 12 by a burner, etc. as described above. An 25 emission gas of about 1000 tol200*C is discharged from the reformer 12 by combustion OSP-27784AU 18 of this fuel gas. [0049] In a conventional liquid fuel synthesizing system using a reformer, the natural gas as a raw material, and the BFW (Boiler Feed Water) was heated by exchange of heat with the above high-temperature emission gas, which merely aims at effective use of 5 waste heat. [0050] Thus, in the liquid fuel synthesizing system according to the present embodiment, the thermal efficiency of the whole system can be further improved by directly utilizing the high-temperature emission gas discharged from the reformer 12 as a heating medium. 10 [0051] When a mixture of a plurality of kinds of intermediate liquid product having different boiling points, which have been produced in the bubble column reactor 30, is introduced into the first rectifying column 40 in the FT synthesis unit 5, the temperature of this liquid fuel mixture needs to be about 320*C. However, since the temperature of the intermediate liquid product extracted from the bubble column reactor 30 is about 15 240*C, it is necessary to further heat the mixture to the above temperature by about 80*C. Further, as shown in FIG. 1, a liquid hydrocarbon component of about 40*C separated as a liquid by the gas-liquid separator 38 is also supplied to the first rectifying column 40. It is also necessary to heat this liquid hydrocarbon component to about 320 0 C. [0052] Thus, in the liquid fuel synthesizing system according to the present 20 embodiment, a heating device such as the heat exchanger 100 is provided at the inlet of the first rectifying column 40 such that the hot emission gas discharged from the reformer 12 is supplied directly. [0053] As the above heat exchanger 100, a heat exchanger which can perform exchange of heat between gas and liquid can be used. As an example of such a heat exchanger, 25 there are, for example, a plate type heat exchanger, a fmned tube type heat exchanger, etc.

OSP-27784AU 19 These heat exchangers are apparatuses which perform transfer of heat between gas and liquid through plates, tubes, etc. [0054] That is, the intermediate liquid product produced in the bubble column reactor 30 is supplied to the first rectifying column 40 through the heat exchanger 100 provided 5 between the bubble column reactor 30 and the first rectifying column 40. In this case, when the liquid fuel mixture passes through the heat exchanger 100, the mixture is heated to about 320*C by the high-temperature emission gas discharged by the heat exchanger 100 from the reformer 12. The emission gas from the reformer 12 which has passed through the heat exchanger 100 is discarded after being subjected to a 10 predetermined treatment. [0055] As such, the liquid fuel synthesizing system according to the present embodiment heats a mixture of a plurality of kinds of liquid fuels introduced into the first rectifying column 40, directly using high-temperature emission gas. Therefore, compared with a conventional heating method using heat-medium oil, the thermal 15 efficiency can be improved, and a facility which generates heat-medium oil does not need to be newly provided. [0056] As shown in FIG. 1, a mixture of a plurality of kinds of liquid fuels is fractionally distilled and refined into three kinds of liquid fuels on the basis of differences in boiling point by the first rectifying column 40. Next, the three kinds of 20 fractionally distilled liquid fuels are respectively supplied to the hydrogenation reactors 50, 52 and 54 in the upgrading unit 7 where a liquid fuel including unsaturated bonds, such as C=C double bonds or C=C triple bonds is hydrogenated into a liquid fuel including only C-C single bonds. These three kinds of liquid fuels need to be heated to about 300*C, when they are supplied to the hydrogenation reactors 50, 52 and 54. Even 25 in this case, in the manner similar to the above, the heat exchanger 102 is provided as a OSP-27784AU 20 heating device between the first rectifying column 40 and each of the hydrogenation reactors 50, 52 and 54, and the emission gas discharged from the reformer 12 is supplied to this heat exchanger 102, so that each liquid fuel can be heated efficiently. [0057] As shown in FIG 1, each of the hydrogenated liquid fuels is introduced into the 5 second rectifying column 70, and is separated and refined therein. Even at this time, each fuel needs to be heated to about 110 to 400*C before being supplied to the second rectifying column 70. Even in this case, as shown in FIG 2, the heat exchanger 104, for example, is provided as a heating device between each of the hydrogenation reactors 50, 52 and 54 and the second rectifying column 70, and the emission gas discharged from the 10 reformer 12 is supplied to this heat exchanger 102, so that each liquid fuel can be heated efficiently. [0058] As the above heat exchangers 102 and 104, the same heat exchangers as the above heat exchanger 100 can also be used. The emission gas from the reformer 12 which has passed through these heat exchangers 102 and 104 is discarded after being 15 subjected to predetermined treatment. [0059] In addition, although FIG. 2 shows the case where the emission gas discharged from the reformer 12 is supplied to each of the heat exchangers 100, 102 and 104, using a common emission gas supply path, the supply path of the emission gas is not limited to such an example. For example, a path exclusively for each of the heat exchangers 100, 20 102 and 104 may be provided separately. [0060] As such, since the liquid fuel synthesizing system I according to the present embodiment directly uses the emission gas discharged from the reformer 12 as a heating medium, the size of the heat exchangers 100, 102 and 104 provided in the system I can be made small, and liquid fuels can be heated efficiently. Further, compared with a 25 conventional heating method using heat-medium oil, etc., the thermal efficiency of the OSP-27784AU 21 whole liquid fuel synthesizing system can be improved as much as about 5 to 10%. Moreover, since a facility which generates a new heat source does not need to be provided, such as heat-medium oil, the whole liquid fuel synthesizing system 1 can also be miniaturized. 5 [0061] Although the preferred embodiments of the present invention have been described with reference to the accompanying drawings, it is needless to say that the present invention is not limited to such embodiments. It is apparent to those skilled in the art that various alternations or modifications can be made in the scope as set forth in the claims, and it will be understood that these alternations or modifications naturally 10 belong to the technical scope of the present invention. [0062] For example, in the above embodiments, natural gas is used as a hydrocarbon raw material to be supplied to the liquid fuel synthesizing system 1. However, the present invention is not limited to such an example. For example, other hydrocarbon raw materials, such as asphalt and residual oil, may be used. 15 [0063] Further, in the above embodiment, the case where the liquid fuel synthesizing system 1 is provided with the CO 2 removal unit 20 has been described. However, depending on circumstances, the CO 2 removal unit 20 may not be provided in the liquid fuel synthesizing system 1. [0064] Further, in the above embodiments, the slurry bubble column reactor is used as 20 the reactor which synthesizes synthesis gas into liquid hydrocarbons. However, the present invention is not limited to such an example. For example, an FT synthesis reaction using a fixed bed type reactor, etc. may be performed. INDUSTRIAL APPLICABILITY 25 [0065] The present invention relates to a liquid fuel synthesizing system including: a OSP-27784AU 22 reformer that reforms a hydrocarbon raw material to prouce synthesis gas including carbon monoxide gas and hydrogen gas as main components; a reactor that synthesizes liquid hydrocarbons from the carbon monoxide gas and hydrogen gas included in the synthesis gas; a refining treatment apparatus that performs predetermined refining 5 treatment on the liquid hydrocarbons synthesized in the reactor; and a heating device that heats the liquid hydrocarbons introduced into the refining treatment apparatus, using the gas discharged from the reformer as a heat source. According to the liquid fuel synthesizing system of the present invention, the thermal efficiency of the whole liquid fuel synthesizing system can be improved.

Claims (7)

1. A liquid fuel synthesizing system comprising: a reformer that reforms a hydrocarbon raw material to produce synthesis gas including carbon monoxide gas and hydrogen gas as main components; 5 a reactor that synthesizes liquid hydrocarbons from the carbon monoxide gas and hydrogen gas included in the synthesis gas by a Fischer-Tropsch synthesis reaction; a refining treatment apparatus that performs a predetermined refining treatment on the liquid hydrocarbons synthesized in the reactor; and a heating device that heats the liquid hydrocarbons introduced into the refining 10 treatment apparatus, using emission gas produced by combustion of fuel gas in a burner of the reformer and discharged from the reformer as a heating medium, wherein the emission gas is directly supplied to the refining treatment apparatus.

2. The liquid fuel synthesizing system according to claim 1, wherein the refining treatment apparatus is at least one of a rectifying column that 15 fractionally distills the liquid hydrocarbons into a plurality of kinds of liquid fuels having different boiling points, and a hydrogenation reactor that hydrogenates the liquid hydrocarbons.

3. The liquid fuel synthesizing system according to claim 1, further comprising a waste heat boiler that heats water by heat exchange with the synthesis gas 20 discharged from the reformer to produce high-pressure steam.

4. A liquid fuel synthesizing system as defined in claim I and substantially as herein described with reference to Fig. I or Figs. I and 2.

5. A liquid fuel synthesizing system as defined in claim 1, wherein said heating device is substantially as herein described with reference to Fig. 2. 25

6. Use of the liquid fuel synthesizing system according to any one of claims I to 5 for preparing a liquid fuel.

7. A liquid fuel prepared in accordance with the use of claim 6. Dated 2 November, 2010 Nippon Steel Engineering Co., Ltd. 30 Patent Attorneys for the Applicant/Nominated Person SPRUSON & FERGUSON