JPWO2007114279A1 - Liquid fuel synthesis system - Google Patents

Abstract

This liquid fuel synthesizing system 1 includes a reformer 12 for reforming a hydrocarbon raw material to generate a syngas mainly composed of carbon monoxide gas and hydrogen gas, and a synthesis gas discharged from the reformer 12. An exhaust heat boiler 14 that recovers exhaust heat, a bubble column reactor 30 that performs synthesis reaction of liquid fuel by reacting synthesis gas, and a reaction heat of the synthesis reaction of liquid fuel that is provided in the bubble column reactor 30 The heat transfer tube 32 to be recovered, and heat treatment devices 24, 40, and 70 for performing a predetermined heat treatment using the steam generated from the exhaust heat boiler 14 or the heat transfer tube 32 are provided.

Description

The present invention relates to a liquid fuel synthesis system for synthesizing a liquid fuel from a hydrocarbon raw material such as natural gas.
This application claims priority about the Japan patent application 2006-95534 for which it applied on March 30, 2006, and uses the content here.

In recent years, as one of the methods for synthesizing liquid fuel from natural gas, natural gas is reformed to produce synthesis gas mainly composed of carbon monoxide gas (CO) and hydrogen gas (H ₂ ). By synthesizing liquid hydrocarbons by Fischer-Tropsch synthesis reaction (hereinafter referred to as “FT synthesis reaction”) using this synthesis gas as raw material gas, and further hydrogenating and purifying this liquid hydrocarbon, naphtha (crude gasoline) ), GTL (Gas To Liquid) technology for producing liquid fuel products such as kerosene, light oil and wax has been developed.

  In a conventional liquid fuel synthesis system using GTL technology, heat of exhaust gas discharged from a reformer that reforms natural gas to produce synthesis gas mainly composed of carbon monoxide gas and hydrogen gas, for example, When recovering reaction heat generated in a reactor in which a liquid fuel synthesis reaction such as an FT synthesis reaction is performed, the heat is recovered as steam using an apparatus such as a heat exchanger.

  However, steam generated from a device for recovering exhaust heat of the reformer (for example, exhaust heat boiler) or a device for recovering reaction heat of the reactor (for example, heat transfer tube) is compared with, for example, a pressure of about 1.2 MPaG. Due to low steam pressure (hereinafter referred to as “medium pressure steam”), it is not used effectively and most of it is cooled and discarded as condensed drain.

  Therefore, the present invention has been made in view of such problems, and in a liquid fuel synthesis system for synthesizing liquid fuel from a hydrocarbon raw material such as natural gas, an apparatus and a reactor for recovering exhaust heat of a reformer It is an object of the present invention to improve the thermal efficiency of the entire liquid fuel synthesizing system by effectively utilizing the medium pressure steam generated from the reaction heat recovery apparatus.

  A first aspect of the liquid fuel synthesizing system of the present invention includes a reformer that reforms a hydrocarbon raw material to generate a syngas mainly composed of carbon monoxide gas and hydrogen gas; and discharges from the reformer An exhaust heat recovery device for recovering exhaust heat of the synthesized gas; a reactor for synthesizing liquid hydrocarbons from carbon monoxide gas and hydrogen gas contained in the synthesis gas; and water vapor generated in the exhaust heat recovery device A heat treatment apparatus for performing a predetermined heat treatment using

  In the first aspect of the liquid fuel synthesizing system of the present invention, the exhaust heat recovery device such as the exhaust heat boiler is configured to recover high pressure steam (high pressure steam) when recovering the exhaust heat of the synthesis gas exhausted from the reformer. Is generated. According to the present invention, this high-pressure steam can be used as a heating source for a predetermined heat treatment apparatus in the liquid fuel synthesizing system to improve the thermal efficiency of the entire liquid fuel synthesizing system.

  A first aspect of the liquid fuel synthesizing system of the present invention includes an absorption tower that separates carbon dioxide gas from the synthesis gas discharged from the exhaust heat recovery apparatus using an absorption liquid, and carbon dioxide separated by the absorption tower. And a regeneration tower having a regeneration tower that dissipates carbon dioxide gas by heating the absorbing liquid. The heat treatment apparatus may be the regeneration tower. According to the present invention, the high-pressure steam from the exhaust heat recovery apparatus can be used as a heating source when heating the absorbing liquid in the regeneration tower.

  The first aspect of the liquid fuel synthesizing system of the present invention further comprises a rectifying tower for fractionating a plurality of types of liquid fuels having different boiling points by heating the liquid hydrocarbon synthesized in the reactor. The heat treatment apparatus may be the rectification tower. According to the present invention, the high-pressure steam from the exhaust heat recovery apparatus can be used as a heating source when heating the liquid hydrocarbon in the rectification column.

  A second aspect of the liquid fuel synthesizing system of the present invention includes a reformer that reforms a hydrocarbon raw material to generate a syngas mainly composed of carbon monoxide gas and hydrogen gas; and is included in the syngas A reactor that synthesizes liquid hydrocarbons from carbon monoxide gas and hydrogen gas; a reaction heat recovery device that is provided in the reactor and recovers reaction heat of the synthesis reaction of the liquid hydrocarbon; and in the reaction heat recovery device A heat treatment apparatus for performing a predetermined heat treatment using the generated water vapor.

  In the second aspect of the liquid fuel synthesizing system of the present invention, the reaction heat recovery device such as the heat transfer tube generates steam having a relatively low pressure (medium pressure steam) when recovering the reaction heat of the reactor. According to the present invention, this intermediate pressure steam can be used as a heating source for a predetermined heat treatment apparatus in the liquid fuel synthesizing system to improve the thermal efficiency of the entire liquid fuel synthesizing system.

  The second aspect of the liquid fuel synthesizing system of the present invention further includes a rectifying tower for heating the liquid hydrocarbon synthesized in the reactor to fractionate into a plurality of types of liquid fuels having different boiling points. The heat treatment apparatus may be the rectification tower. According to the present invention, the medium-pressure steam from the reaction heat recovery apparatus can be used as a heating source when heating the liquid hydrocarbon in the rectification column.

  In the second aspect of the liquid fuel synthesizing system of the present invention, the rectification column includes a rectification column decompression device (for example, a vacuum pump) for reducing the pressure in the rectification column, that is, the pressure. Also good. Thereby, the boiling point of the liquid fuel in the rectification column can be lowered, and even steam having low energy such as medium pressure steam can be used as a heating source. Furthermore, since the boiling point of the liquid fuel can be lowered, the liquid fuel can be fractionated with less heat, and the liquid fuel does not receive much heat history. Therefore, the quality of the liquid fuel product to be refined can be improved.

  A second aspect of the liquid fuel synthesizing system of the present invention includes an exhaust heat recovery device that recovers exhaust heat of the synthesis gas exhausted from the reformer, and the synthesis gas that is exhausted from the exhaust heat recovery device. The apparatus further comprises a decarbonation device having an absorption tower that separates carbon dioxide gas using an absorption liquid, and a regeneration tower that heats the absorption liquid containing the carbon dioxide gas separated by the absorption tower to dissipate the carbon dioxide gas. The heat treatment apparatus may be the regeneration tower. According to the present invention, the medium pressure steam from the reaction heat recovery apparatus can be used as a heating source when heating the absorbent in the regeneration tower.

  In the second aspect of the liquid fuel synthesizing system of the present invention, the regeneration tower may include a regeneration tower decompression device (for example, a vacuum pump) that reduces the atmospheric pressure in the regeneration tower. Thereby, the boiling point of the absorbing liquid can be lowered, and steam with low energy such as medium pressure steam can be used as a heating source.

  Further, a steam decompression device that decompresses water vapor generated from the exhaust heat recovery device may be disposed between the exhaust heat recovery device and the heat treatment device.

  According to the present invention, in a liquid fuel synthesis system for synthesizing liquid fuel from a hydrocarbon raw material such as natural gas, steam generated from an apparatus for recovering exhaust heat of a reformer or an apparatus for recovering reaction heat of a reactor Can be used as a heating source for a predetermined heat treatment apparatus in the liquid fuel synthesis system. Therefore, according to the present invention, it is possible to improve the thermal efficiency of the entire liquid fuel synthesizing system by effectively utilizing the intermediate pressure steam.

FIG. 1 is a schematic diagram showing the overall configuration of a liquid hydrocarbon synthesis system according to an embodiment of the present invention. FIG. 2 is a block diagram showing an outline of the use of water vapor in the liquid hydrocarbon synthesis system according to the embodiment of the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Liquid fuel synthesis system, 3 ... Syngas production unit, 5 ... FT synthesis unit, 7 ... Product refinement unit, 10 ... Desulfurization reactor, 12 ... Reformer, 14 ... Exhaust heat boiler, 16, 18 ... Gas-liquid Separator, 20 ... decarbonation device, 22 ... absorption tower, 24 ... regeneration tower, 26 ... hydrogen separator, 30 ... bubble column reactor, 32 ... heat transfer tube, 34, 38 ... gas-liquid separator, 36 ... separation 40 ... 1st rectification column, 50 ... WAX fraction hydrocracking reactor, 52 ... Kerosene / light oil fraction hydrotreating reactor, 54 ... Naphtha fraction hydrocracking reactor, 56, 58, 60 ... Gas-liquid separator, 70 ... second rectification column, 72 ... naphtha stabilizer, 144 ... steam decompression device, 242,402,702 ... heat exchanger, 244 ... regeneration tower decompression device, 404 ... first rectification column Decompression device, 704 ... second decompression column decompression device

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

  First, an overall configuration and operation of a liquid fuel synthesizing system 1 that executes a GTL (Gas To Liquid) process according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a schematic diagram showing the overall configuration of a liquid fuel synthesis system 1 according to the present embodiment.

  As shown in FIG. 1, a liquid fuel synthesis system 1 according to the present embodiment is a plant facility that executes a GTL process for converting a hydrocarbon raw material such as natural gas into liquid fuel. The liquid fuel synthesis system 1 includes a synthesis gas generation unit 3, an FT synthesis unit 5, and a product purification unit 7. The synthesis gas generation unit 3 reforms natural gas that is a hydrocarbon raw material to generate synthesis gas containing carbon monoxide gas and hydrogen gas. The FT synthesis unit 5 generates liquid hydrocarbons from the generated synthesis gas by a Fischer-Tropsch synthesis reaction (hereinafter referred to as “FT synthesis reaction”). The product refining unit 7 produces liquid fuel products (naphtha, kerosene, light oil, wax, etc.) by hydrogenating and refining the liquid hydrocarbons produced by the FT synthesis reaction. Hereinafter, components of each unit will be described.

First, the synthesis gas generation unit 3 will be described. The synthesis gas generation unit 3 includes, for example, a desulfurization reactor 10, a reformer 12, an exhaust heat boiler 14 as an example of an exhaust heat recovery device, gas-liquid separators 16 and 18, a decarboxylation device 20, A hydrogen separator 26 is mainly provided.
The desulfurization reactor 10 is composed of a hydrodesulfurization device or the like, and removes sulfur components from natural gas as a raw material. The reformer 12 reforms the natural gas supplied from the desulfurization reactor 10 to generate a synthesis gas containing carbon monoxide gas (CO) and hydrogen gas (H ₂ ) as main components. The exhaust heat boiler 14 recovers the exhaust heat of the synthesis gas generated in the reformer 12 and generates high-pressure steam. The gas-liquid separator 16 separates water heated by heat exchange with the synthesis gas in the exhaust heat boiler 14 into a gas (high-pressure steam) and a liquid. The gas-liquid separator 18 removes the condensate from the synthesis gas cooled by the exhaust heat boiler 14 and supplies the gas to the decarboxylation device 20. The decarboxylation device 20 uses an absorption liquid to separate carbon dioxide from the synthesis gas supplied from the gas-liquid separator 18 and heats the absorption liquid containing the carbon dioxide with steam, for example, to generate carbon dioxide. And a regeneration tower 24 for regenerating and regenerating. The hydrogen separation device 26 separates a part of the hydrogen gas contained in the synthesis gas from the synthesis gas from which the carbon dioxide gas has been separated by the decarbonation device 20.

  Among these, the reformer 12 reforms natural gas using carbon dioxide and steam by, for example, the steam / carbon dioxide reforming method represented by the following chemical reaction formulas (1) and (2). Thus, a high-temperature synthesis gas mainly composed of carbon monoxide gas and hydrogen gas is generated. The reforming method in the reformer 12 is not limited to the steam / carbon dioxide reforming method described above, but includes, for example, a steam reforming method, a partial oxidation reforming method (POX) using oxygen, and a partial oxidation method. An autothermal reforming method (ATR), a carbon dioxide gas reforming method, or the like, which is a combination of the reforming method and the steam reforming method, can also be used.

CH ₄ + H ₂ O → CO + 3H ₂ (1)
CH ₄ + CO ₂ → 2CO + 2H ₂ (2)

  A steam pressure reducing device 144 is provided at the tip of the gas-liquid separator 16. For example, the high-pressure steam generated from the exhaust heat boiler 14 has a pressure of about 3.4 to 10 MPaG, and the high-pressure steam is reduced to a medium-pressure steam having a pressure of about 1.2 to 2.5 MPaG, for example. A steam decompression device 144 is provided for this purpose.

  Further, as the absorbing liquid used for absorbing / removing carbon dioxide gas in the decarboxylation device 20, a basic organic solvent is generally used, and as such a basic organic solvent, for example, monoethanol Examples include amine solvents such as amine, catecholamine, tryptamine, arylamine, alkanolamine. The decarboxylation device 20 uses, for example, the amine solvent as an absorbing solution, and generates carbamic acid by absorbing carbon dioxide gas by a reaction represented by the following chemical reaction formula (3). The reaction represented by the following chemical reaction formula (3) is an equilibrium reaction.

RNH ₂ + CO ₂ → RNHCOOH (3)

  Further, the hydrogen separator 26 is provided in a branch line branched from a main pipe connecting the decarbonator 20 or the gas-liquid separator 18 and the bubble column reactor 30. The hydrogen separator 26 can be constituted by, for example, a hydrogen PSA (Pressure Swing Adsorption) device that performs adsorption and desorption of hydrogen using a pressure difference. This hydrogen PSA apparatus has an adsorbent (zeolite adsorbent, activated carbon, alumina, silica gel, etc.) in a plurality of adsorption towers (not shown) arranged in parallel, and hydrogen is added to each adsorption tower. High-purity hydrogen gas (for example, about 99.999%) separated from the synthesis gas can be continuously supplied to the reactor by sequentially repeating the pressure, adsorption, desorption (decompression), and purge steps. it can.

  Next, the FT synthesis unit 5 will be described. The FT synthesis unit 5 mainly includes, for example, a bubble column reactor 30, a gas-liquid separator 34, a separator 36, a gas-liquid separator 38, and a first rectifying column 40. The bubble column reactor 30 generates a liquid hydrocarbon by performing an FT synthesis reaction of the synthesis gas produced by the synthesis gas production unit 3, that is, carbon monoxide gas and hydrogen gas. The gas-liquid separator 34 circulates water heated in a heat transfer tube 32 as an example of a reaction heat recovery device disposed in the bubble column reactor 30, steam (medium pressure steam), liquid, To separate. The separator 36 is connected to the center of the bubble column reactor 30 and separates the catalyst and the liquid hydrocarbon product. The gas-liquid separator 38 is connected to the upper part of the bubble column reactor 30 and cools the unreacted synthesis gas and the gaseous hydrocarbon product. The first fractionator 40 distills the liquid hydrocarbons supplied from the bubble column reactor 30 via the separator 36 and the gas-liquid separator 38, and separates and purifies each product fraction according to the boiling point. .

  Among these, the bubble column reactor 30 is an example of a reactor that synthesizes synthesis gas into liquid hydrocarbons, and functions as a reactor for FT synthesis that synthesizes liquid hydrocarbons from synthesis gas by an FT synthesis reaction. The bubble column reactor 30 is constituted by, for example, a bubble column type slurry bed type reactor in which a slurry composed of a catalyst and a medium oil is stored inside a column type container. The bubble column reactor 30 generates liquid hydrocarbons from synthesis gas by an FT synthesis reaction. More specifically, in this bubble column reactor 30, the synthesis gas, which is a raw material gas, is supplied as bubbles from the dispersion plate at the bottom of the bubble column reactor 30, and rises in the slurry composed of the catalyst and the medium oil. During the rising, the synthesis gas contained in the bubbles is dissolved in the slurry, and hydrogen gas and carbon monoxide gas cause a synthesis reaction as shown in the following chemical reaction formula (4).

2nH ₂ + nCO → − (CH ₂ ) _n − + nH ₂ O (4)

  Since this FT synthesis reaction is an exothermic reaction, the bubble column reactor 30 has a heat exchanger type in which a heat transfer tube 32 is disposed, and water (BFW: Boiler Feed Water) or the like is used as a refrigerant. The reaction heat of the above FT synthesis reaction can be recovered as intermediate pressure steam by heat exchange between the slurry and water.

Finally, the product purification unit 7 will be described. The product refining unit 7 includes, for example, a WAX fraction hydrocracking reactor 50, a kerosene / light oil fraction hydrotreating reactor 52, a naphtha fraction hydrotreating reactor 54, and gas-liquid separators 56, 58, 60, a second rectifying column 70, and a naphtha stabilizer 72. The WAX fraction hydrocracking reactor 50 is connected to the lower part of the first fractionator 40. The kerosene / light oil fraction hydrotreating reactor 52 is connected to the center of the first fractionator 40. The naphtha fraction hydrotreating reactor 54 is connected to the upper part of the first fractionator 40. The gas-liquid separators 56, 58 and 60 are provided corresponding to the hydrogenation reactors 50, 52 and 54, respectively. The second rectification column 70 separates and purifies the liquid hydrocarbons supplied from the gas-liquid separators 56 and 58 according to the boiling point. The naphtha stabilizer 72 rectifies the liquid hydrocarbons of the naphtha fraction supplied from the gas-liquid separator 60 and the second rectifying column 70, and discharges components lighter than butane to the flare gas (exhaust gas) side. number C ₅ or more components are separated and recovered as a naphtha product.

  Next, a process (GTL process) of synthesizing liquid fuel from natural gas by the liquid fuel synthesizing system 1 having the above configuration will be described.

The liquid fuel synthesizing system 1 is supplied with natural gas (main component is CH ₄ ) as a hydrocarbon feedstock from an external natural gas supply source (not shown) such as a natural gas field or a natural gas plant. The synthesis gas generation unit 3 reforms the natural gas to produce a synthesis gas (a mixed gas containing carbon monoxide gas and hydrogen gas as main components).

  Specifically, first, the natural gas is supplied to the desulfurization reactor 10 together with the hydrogen gas separated by the hydrogen separator 26. The desulfurization reactor 10 hydrodesulfurizes sulfur contained in natural gas using the hydrogen gas, for example, with a ZnO catalyst. By desulfurizing the natural gas in advance in this way, it is possible to prevent the activity of the catalyst used in the reformer 12 and the bubble column reactor 30 or the like from being reduced by sulfur.

Natural gas (which may contain carbon dioxide) desulfurized in this way is generated in carbon dioxide (CO ₂ ) gas supplied from a carbon dioxide supply source (not shown) and in the exhaust heat boiler 14. After the steam is mixed, the reformer 12 is supplied. For example, the reformer 12 reforms the natural gas using carbon dioxide and steam by the steam / carbon dioxide reforming method described above, so that the reformer 12 has a high temperature mainly composed of carbon monoxide gas and hydrogen gas. Generate synthesis gas. At this time, for example, the fuel gas and air for the burner included in the reformer 12 are supplied to the reformer 12, and the steam / carbon dioxide gas which is an endothermic reaction by the combustion heat of the fuel gas in the burner. The reaction heat necessary for the reforming reaction is covered.

  The high-temperature synthesis gas (for example, 900 ° C., 2.0 MPaG) generated in the reformer 12 in this manner is supplied to the exhaust heat boiler 14 and is exchanged by heat exchange with the water flowing in the exhaust heat boiler 14. It is cooled (for example, 400 ° C.) and the exhaust heat is recovered. At this time, water heated by the synthesis gas in the exhaust heat boiler 14 is supplied to the gas-liquid separator 16, and the gas component is reformed as high-pressure steam (for example, 3.4 to 10.0 MPaG) from the gas-liquid separator 16. The water in the liquid is returned to the exhaust heat boiler 14 after being supplied to the vessel 12 or other external device.

  On the other hand, the synthesis gas cooled in the exhaust heat boiler 14 is supplied to the absorption tower 22 or the bubble column reactor 30 of the decarboxylation device 20 after the condensed liquid is separated and removed in the gas-liquid separator 18. The The absorption tower 22 removes carbon dioxide from the synthesis gas by absorbing the carbon dioxide contained in the synthesis gas in the stored absorption liquid. The absorption liquid containing carbon dioxide gas in the absorption tower 22 is introduced into the regeneration tower 24, and the absorption liquid containing carbon dioxide gas is heated and stripped by, for example, steam, and the released carbon dioxide gas is removed from the regeneration tower 24. To the reformer 12 and reused in the reforming reaction. In addition, the absorption liquid that has been extracted and regenerated by extracting carbon dioxide is sent to the absorption tower 22 and reused for removing the carbon dioxide.

In this way, the synthesis gas produced by the synthesis gas production unit 3 is supplied to the bubble column reactor 30 of the 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 suitable for the FT synthesis reaction (for example, H ₂ : CO = 2: 1 (molar ratio)). The synthesis gas supplied to the bubble column reactor 30 is subjected to an FT synthesis reaction by a compressor (not shown) provided in a pipe connecting the decarboxylation device 20 and the bubble column reactor 30. The pressure is increased to an appropriate pressure (for example, 3.6 MPaG).

  A part of the synthesis gas from which the carbon dioxide gas has been separated by the decarbonation device 20 is also supplied to the hydrogen separation device 26. The hydrogen separator 26 separates the hydrogen gas contained in the synthesis gas by adsorption and desorption (hydrogen PSA) using the pressure difference as described above. The separated hydrogen is subjected to various hydrogen utilization reactions in which a predetermined reaction is performed using hydrogen in the liquid fuel synthesizing system 1 from a gas holder (not shown) or the like via a compressor (not shown). It is continuously supplied to the apparatus (for example, desulfurization reactor 10, WAX fraction hydrocracking reactor 50, kerosene / light oil fraction hydrotreating reactor 52, naphtha fraction hydrotreating reactor 54, etc.).

  Next, the FT synthesis unit 5 synthesizes liquid hydrocarbons from the synthesis gas produced by the synthesis gas production unit 3 by an FT synthesis reaction.

  Specifically, the synthesis gas from which the carbon dioxide gas has been separated in the decarboxylation device 20 flows from the bottom of the bubble column reactor 30 and rises in the catalyst slurry stored in the bubble column reactor 30. To do. At this time, in the bubble column reactor 30, the carbon monoxide and hydrogen gas contained in the synthesis gas react with each other by the above-described FT synthesis reaction to generate hydrocarbons. Furthermore, at the time of this synthesis reaction, water is circulated through the heat transfer tube 32 of the bubble column reactor 30 to remove the reaction heat of the FT synthesis reaction. Become. As for this water vapor, the water liquefied by the gas-liquid separator 34 is returned to the heat transfer tube 32, and the gas component is supplied to the external device as medium pressure steam (for example, 1.0 to 2.5 MPaG).

Thus, the liquid hydrocarbon synthesized in the bubble column reactor 30 is taken out from the center of the bubble column reactor 30 and introduced into the separator 36. The separator 36 separates the catalyst (solid content) in the extracted slurry into a liquid content containing the liquid hydrocarbon product. A part of the separated catalyst is returned to the bubble column reactor 30, and the liquid is supplied to the first rectifying column 40. Further, unreacted synthesis gas and synthesized hydrocarbon gas are introduced into the gas-liquid separator 38 from the top of the bubble column reactor 30. The gas-liquid separator 38 cools these gases, separates some of the condensed liquid hydrocarbons, and introduces them into the first fractionator 40. On the other hand, with respect to the gas component separated by the gas-liquid separator 38, unreacted synthesis gas (CO and H ₂ ) is reintroduced into the bottom of the bubble column reactor 30 and reused for the FT synthesis reaction. In addition, exhaust gas (flare gas) mainly composed of hydrocarbon gas with a low carbon number (C ₄ or less) that is not subject to product is introduced into an external combustion facility (not shown) and burned. Released into the atmosphere.

Next, the first rectifying column 40 heats the liquid hydrocarbon (having various carbon numbers) supplied from the bubble column reactor 30 through the separator 36 and the gas-liquid separator 38 as described above. Fractionation using the difference in boiling point, naphtha fraction (boiling point is less than about 315 ° C), kerosene / light oil fraction (boiling point is about 315 to 800 ° C), WAX (boiling point is about 800 ° C or more) Large) and separated and purified. Wax liquid hydrocarbons (mainly C ₂₁ or more) taken out from the bottom of the first fractionator 40 are transferred to the WAX fraction hydrocracking reactor 50 and taken out from the center of the first fractionator 40. The liquid hydrocarbon (mainly C _{11 to} C ₂₀ ) of the kerosene / light oil fraction is transferred to the kerosene / light oil fraction hydrotreating reactor 52 and taken out from the upper part of the first rectifying tower 40. Hydrocarbons (mainly C ₅ -C ₁₀ ) are transferred to the naphtha fraction hydrotreating reactor 54.

The WAX fraction hydrocracking reactor 50 is a liquid fed from the lower part of the first rectifying column 40 and contains a liquid hydrocarbon having a large number of carbon atoms (generally C ₂₁ or more) supplied from the hydrogen separator 26. Hydrocracking using gas to reduce the carbon number to C ₂₀ or less. In this hydrocracking reaction, a C—C bond of a hydrocarbon having a large number of carbon atoms is cut using a catalyst and heat to generate a low molecular weight hydrocarbon having a small number of carbon atoms. A product containing liquid hydrocarbons hydrocracked by the WAX hydrocracking reactor 50 is separated into a gas and a liquid by a gas-liquid separator 56, and the liquid hydrocarbons are separated from the second fractionator. The gas component (including hydrogen gas) is transferred to a kerosene / light oil fraction hydrotreating reactor 52 and a naphtha fraction hydrotreating reactor 54.

The kerosene / light oil fraction hydrotreating reactor 52 is a liquid hydrocarbon (approximately C _{11 to} C ₂₀ ) of a kerosene / light oil fraction having a medium carbon number supplied from the center of the first fractionator 40. Is hydrorefined using the hydrogen gas supplied from the hydrogen separator 26 via the WAX fraction hydrocracking reactor 50. This hydrorefining reaction is a reaction in which hydrogen is added to the unsaturated bond of the liquid hydrocarbon to saturate to produce a linear saturated hydrocarbon. As a result, the hydrorefined liquid hydrocarbon-containing product is separated into a gas and a liquid by the gas-liquid separator 58, and the liquid hydrocarbon is transferred to the second rectifying column 70, where the gas component (hydrogen Gas is reused) in the hydrogenation reaction.

The naphtha fraction hydrotreating reactor 54 supplies the liquid hydrocarbon (approximately C ₁₀ or less) of the naphtha fraction having a small number of carbons supplied from the upper part of the first rectification column 40 to the WAX fraction hydrogen from the hydrogen separator 26. Hydrotreating is performed using the hydrogen gas supplied through the hydrocracking reactor 50. As a result, the hydrorefined liquid hydrocarbon-containing product is separated into a gas and a liquid by the gas-liquid separator 60, and the liquid hydrocarbon is transferred to a naphtha stabilizer 72, which is a kind of rectification column. The gas component (including hydrogen gas) is reused in the hydrogenation reaction.

Next, the second rectifying column 70 distills the liquid hydrocarbons supplied from the WAX fraction hydrocracking reactor 50 and the kerosene / light oil fraction hydrotreating reactor 52 as described above to obtain a carbon number. and _of C ₁₀ or less hydrocarbons (having a boiling point of approximately less than 315 ° C.), and kerosene (boiling point of about three hundred fifteen to four hundred fifty ° C.), separated and purified in the gas oil (boiling point of about 450 to 800 ° C.). Light oil is taken out from the lower part of the second fractionator 70, and kerosene is taken out from the center. On the other hand, a hydrocarbon gas having a carbon number of ₁₀ or less is taken out from the top of the second rectifying column 70 and supplied to the naphtha stabilizer 72.

Further, the naphtha stabilizer 72 distills hydrocarbons having a carbon number of C ₁₀ or less supplied from the naphtha fraction hydrotreating reactor 54 and the second rectifying tower 70 to obtain naphtha (C ₅ as a product). ~C ₁₀₎ are separated and purified. Thereby, high-purity naphtha is taken out from the lower part of the naphtha stabilizer 72. On the other hand, from the top of the naphtha stabilizer 72, exhaust gas (flare gas) mainly composed of hydrocarbons having a carbon number of not more than a predetermined number (C ₄ or less) is discharged. This exhaust gas is introduced into an external combustion facility (not shown), burned, and then released into the atmosphere.

The process of the liquid fuel synthesis system 1 (GTL process) has been described above. Such GTL process, natural gas, high-purity naphtha (C ₅ -C _10: crude gasoline), kerosene (C ₁₁ -C _15: kerosene), and light oil: clean the (C ₁₆ -C ₂₀ gas oil), etc. It can be easily and economically converted to liquid fuel. Furthermore, in this embodiment, since the steam / carbon dioxide reforming method is adopted in the reformer 12, carbon dioxide contained in natural gas as a raw material is effectively used, and the FT synthesis is performed. A composition ratio (for example, H ₂ : CO = 2: 1 (molar ratio)) of synthesis gas suitable for the reaction can be efficiently generated by one reaction of the reformer 12, and a hydrogen concentration adjusting device, etc. There is an advantage that is unnecessary.

  By the way, conventionally, the reaction heat of the FT synthesis reaction by the high-pressure steam generated in the exhaust heat recovery of the synthesis gas generated in the reformer 12 by the exhaust heat boiler 14 or the bubble column reactor 30 by the heat transfer tube 32. The medium-pressure steam generated during the recovery was not effectively used, and most of the steam was recovered and discarded as condensed drain. In particular, as described above, the medium pressure steam is water vapor having a relatively low pressure of, for example, about 1.2 MPaG, and therefore has low energy and low utility value as a heating source or the like. Further, the high-pressure steam generated by the heat recovery of the exhaust heat boiler 14 is often made into medium-pressure steam by using a pressure reducing valve, a temperature reducing device alone, or a steam pressure reducing device 144 using a combination thereof.

  Therefore, in the liquid fuel synthesizing system 1 according to the present embodiment, as shown in FIG. 1, high-pressure steam (circle A in the figure) generated when exhaust heat is recovered by the exhaust heat boiler 14, or a heat transfer tube 32. The intermediate pressure steam (B in the figure) generated during the recovery of the reaction heat by means of the regeneration column 24, the first rectifying column 40, the second rectifying column 70, the naphtha stabilizer 72, etc. By using the high-pressure steam and medium-pressure steam effectively in the liquid fuel synthesizing system 1 by using as a heat source of a heat treatment apparatus that performs predetermined heat treatment using steam, liquid fuel synthesis using GTL technology The thermal efficiency of the entire system 1 is improved.

  Hereinafter, based on FIG. 2, the high-pressure steam generated during exhaust heat recovery by the exhaust heat boiler 14 in the liquid fuel synthesizing system 1 according to the present embodiment and the medium generated during the recovery of reaction heat by the heat transfer tube 32 will be described. Details of the use of water vapor such as pressure steam will be described. FIG. 2 is a block diagram showing an outline of the use of water vapor in the liquid fuel synthesis system 1 according to the embodiment of the present invention.

  First, detailed configurations of the regeneration tower 24, the first rectifying tower 40, and the second rectifying tower 70 according to the present embodiment will be described. Other configurations are as described above.

  As shown in FIG. 2, the regeneration tower 24 includes a heat exchanger 242 as a heating means for performing heating when the carbon dioxide gas is diffused from the absorbing liquid containing a large amount of carbon dioxide gas. The heat exchanger 242 performs heat exchange in order to use the heat of the high-temperature steam for heating the absorption liquid in the regeneration tower, and the steam after the heat exchange is performed as a drain via a steam trap or the like. Discharged. In this embodiment, as steam serving as a heat source for the heat exchanger 242, medium pressure steam obtained by reducing the high pressure steam generated by the exhaust heat recovery of the exhaust heat boiler (WHB) 14 by the steam decompression device 144 or the heat transfer tube 32 is used. The medium pressure steam generated by the recovery of reaction heat is used. Using such intermediate pressure steam, the heat exchanger 242 can heat the absorbent in the regeneration tower 24 to about 100 to 140 ° C., for example.

  The regeneration tower 24 also includes a regeneration tower decompression device 244 that reduces the pressure in the regeneration tower 24. For example, a vacuum pump can be used as the decompression device 244 for the regeneration tower. As this vacuum pump, for example, a high-pressure liquid flow is generated by the pump, supplied to the nozzle, and the pressure drop due to the velocity energy of the liquid ejected from the nozzle at a high speed is used. Alternatively, an ejector pump that connects a conduit for sucking the condensed liquid can be used. In this way, by using the regeneration tower decompression device 244 to reduce the pressure in the regeneration tower 24 and lower the boiling point of the absorbing liquid, the steam having a small energy, such as the medium pressure steam, is used. Even so, it is possible to sufficiently regenerate the absorbing solution that has absorbed the carbon dioxide gas.

  The first fractionator 40 includes a heat exchanger 402 as a heating means for performing fractional distillation of a mixture of a plurality of liquid hydrocarbons having different boiling points generated by the bubble column reactor 30; The second rectifying column 70 includes a heat exchanger 702 as a heating means for performing fractional distillation of the reaction products of the hydrogenation reactors 50, 52, and 54. The heat exchangers 402 and 702 perform heat exchange in order to use the heat of the high-temperature steam for heating the liquid hydrocarbons in the first rectification column 40 and the second rectification column 70, and the heat exchange is performed. After that, the water vapor is discharged as liquid water. In the present embodiment, as steam serving as a heating source for the heat exchangers 402 and 702, high-pressure steam generated by exhaust heat recovery of the exhaust heat boiler (WHB) 14 is reduced by the steam decompression device 144, The medium pressure steam generated by the reaction heat recovery of the heat pipe 32 is used. Using such intermediate pressure steam, the heat exchangers 402 and 702 can heat the liquid hydrocarbons in the first rectifying column 40 and the second rectifying column 70 to about 300 ° C., for example.

  The first rectifying column 40 and the second rectifying column 70 are, respectively, a first rectifying column decompression device 404 and a first rectifying column pressure reducing device 404 for reducing the pressure in the first rectifying column 40 and the second rectifying column 70. A rectifying column decompression device 704 is provided. As the first rectifying column decompression device 404 and the second rectifying column decompression device 704, for example, a vacuum pump can be used in the same manner as the regeneration tower decompressing device 244. As described above, the pressure in the first rectifying column 40 and the second rectifying column 70, that is, the pressure, is reduced by using the first rectifying column pressure reducing device 404 and the second rectifying column pressure reducing device 704. The liquid hydrocarbon components having different boiling points are fractionated even by using steam having a small energy, such as the above-mentioned intermediate pressure steam, by reducing the boiling point of the liquid hydrocarbon and performing vacuum distillation or the like. A sufficient amount of heat can be supplied. Moreover, since the boiling point of the liquid hydrocarbon is lowered, the amount of heat given to the liquid hydrocarbon to be heated can be reduced, and the heat history can be reduced as compared with the conventional case. Thereby, the quality of the liquid hydrocarbon product refine | purified can be improved.

  Next, a specific method for using water vapor such as high-pressure steam generated during exhaust heat recovery by the exhaust heat boiler 14 and medium-pressure steam generated during reaction heat recovery by the heat transfer tube 32 will be described.

  As shown in FIG. 2, the natural gas from which the sulfur component has been removed by the desulfurization reactor 10 is reformed by the reformer 12 to produce a synthesis gas mainly composed of carbon monoxide gas and hydrogen gas. The exhaust heat of the synthesis gas generated by the reformer 12 is recovered by the exhaust heat boiler 14. The water vapor (high pressure steam) generated by the exhaust heat recovery by the exhaust heat boiler 14 has a high pressure of, for example, about 3.8 MPaG, but is reduced to, for example, about 1.2 MPaG by the steam decompression device 144. On the other hand, the synthesis gas from which the exhaust heat has been recovered is sent to the absorption tower 22 of the decarbonation device 20, and the carbon dioxide gas is separated by the absorption liquid.

  The absorbent that has absorbed carbon dioxide and has a high carbon dioxide concentration is sent to the regeneration tower 24, where the absorbent is regenerated. In the regeneration tower 24, carbon dioxide gas is released from the absorption liquid while the regeneration tower 24 is made to be in a reduced pressure atmosphere by the regeneration tower decompression device 244 and the absorption liquid containing the carbon dioxide gas is heated using the heat exchanger 242. The absorption liquid regenerated by releasing the regeneration tower 244 carbon dioxide is sent to the absorption tower 22 and reused for removing the carbon dioxide.

  The synthesis gas from which the carbon dioxide gas has been removed is introduced into the bubble column reactor 30, and an FT synthesis reaction, that is, a liquid hydrocarbon synthesis reaction is performed. At this time, since the FT synthesis reaction is an exothermic reaction, the reaction heat of the FT synthesis reaction is recovered by the heat transfer tube 32, and the temperature of the liquid hydrocarbon in the bubble column reactor 30 is controlled so as not to rise too much. Is done. Steam (medium pressure steam) is generated by the recovery of the reaction heat of the heat transfer tube 32.

  The liquid hydrocarbon synthesized in the bubble column reactor 30 is a mixture containing various hydrocarbons having different numbers of carbon atoms (different boiling points). In the rectification column 40, fractional distillation is performed using the difference in boiling points. In the first rectifying column 40, the inside of the first rectifying column 40 is evacuated by the first rectifying column decompression device 404, and a mixture of liquid hydrocarbons having different boiling points is heated using the heat exchanger 402. The liquid hydrocarbon mixture is fractionated.

  The hydrocarbon components fractionated in the first rectification column 40 are still the final products of the liquid fuel synthesis system 1, such as naphtha, kerosene and light oil, and those having a higher carbon number and unsaturated bonds such as olefins. The thing which has is also included. For this reason, the hydrogenation reactors 50, 52, and 54 decompose the hydrocarbons into those having a small number of carbons by hydrocracking them, or convert them into saturated hydrocarbon components by hydrogenation.

  The reaction products in the hydrogenation reactors 50, 52, and 54 are further sent to the second rectification column 70, where final liquid hydrocarbon products (liquid fuel products) such as naphtha, kerosene, and light oil. Is fractionated. In the second rectifying column 70, the pressure in the second rectifying column 70 is reduced by the second rectifying column decompression device 704, and a mixture of liquid hydrocarbons having different boiling points is heated using the heat exchanger 702. The liquid hydrocarbon mixture is fractionated.

  Here, as described above, as a heat source used in the heat exchanger 242 in the regeneration tower 24, the heat exchanger 402 in the first rectifying tower 40, and the heat exchanger 702 in the second rectifying tower 70, It is possible to use medium pressure steam obtained by reducing the high pressure steam generated by the exhaust heat recovery of the exhaust heat boiler 14 by the steam pressure reduction device 144 or medium pressure steam generated by the reaction heat recovery of the heat transfer tube 32. Therefore, it is possible to effectively use the medium-pressure steam, which has been rarely used effectively because the pressure of water vapor is relatively low, in the liquid hydrocarbon system 1, and thus the liquid hydrocarbon system. The overall thermal efficiency of 1 can be significantly improved. Further, by using low-pressure intermediate pressure steam for heating in the first rectifying column 40 and heating in the second rectifying column 70, the thermal history received by the liquid hydrocarbon can be reduced, and the final product It is also possible to improve the quality.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to this example. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

  For example, in the above embodiment, natural gas is used as the hydrocarbon raw material supplied to the liquid fuel synthesizing system 1. However, the present invention is not limited to this example, and other hydrocarbon raw materials such as asphalt and residual oil are used. May be.

Moreover, in the said embodiment, although the liquid hydrocarbon was synthesize | combined by FT synthesis reaction using the bubble column reactor 30 as a bubble column type reactor which concerns on this invention, this invention is not limited to this example. As the synthesis reaction in the bubble column reactor, for example, oxo synthesis (hydroformylation reaction) “R · CH═CH ₂ + CO + H ₂ → R · CH ₂ CH ₂ CHO”, methanol synthesis “CO + 2H ₂ → CH ₃ OH”, It can also be applied to dimethyl ether (DME) synthesis “3CO + 3H ₂ → CH ₃ OCH ₃ + CO ₂ ”.

  Moreover, in the said embodiment, although the example of the regeneration tower 24, the 1st rectification tower 40, and the 2nd rectification tower 70 of the decarbonation apparatus 20 was given as a heat processing apparatus, it is not limited to this example, Liquid fuel synthesis | combination Any apparatus other than those described above may be used as long as the apparatus performs predetermined heat treatment using water vapor in the system. For example, medium pressure steam can be used for heating the naphtha stabilizer 72 and the like.

  In the above embodiment, the bubble column type slurry bed type reactor is used as the reactor for synthesizing the synthesis gas into the liquid hydrocarbon. However, the present invention is not limited to this example, and for example, a fixed bed type reactor. The FT synthesis reaction may be performed using such as.

The present invention relates to a reformer for reforming a hydrocarbon raw material to generate a synthesis gas mainly composed of carbon monoxide gas and hydrogen gas; and recovering exhaust heat of the synthesis gas discharged from the reformer An exhaust heat recovery apparatus that performs; a reactor that synthesizes liquid hydrocarbons from carbon monoxide gas and hydrogen gas contained in the synthesis gas; and a heat treatment that performs a predetermined heat treatment using water vapor generated in the exhaust heat recovery apparatus And a liquid fuel synthesizing system.
According to the liquid fuel synthesizing system of the present invention, the thermal efficiency of the entire liquid fuel synthesizing system is obtained by effectively using the intermediate pressure steam generated from the apparatus for recovering the exhaust heat of the reformer and the apparatus for recovering the reaction heat of the reactor. Can be improved.

Claims (8)

A reformer for reforming a hydrocarbon raw material to generate a synthesis gas mainly composed of carbon monoxide gas and hydrogen gas;
An exhaust heat recovery device for recovering exhaust heat of the synthesis gas exhausted from the reformer;
A reactor for synthesizing liquid hydrocarbons from carbon monoxide gas and hydrogen gas contained in the synthesis gas;
And a heat treatment apparatus for performing a predetermined heat treatment using water vapor generated in the exhaust heat recovery apparatus. An absorption tower that separates carbon dioxide gas from the synthesis gas discharged from the exhaust heat recovery apparatus using an absorption liquid, and a regeneration that heats the absorption liquid containing the carbon dioxide gas separated by the absorption tower to dissipate the carbon dioxide gas. And a decarboxylation device having a tower,
The liquid fuel synthesis system according to claim 1, wherein the heat treatment apparatus is the regeneration tower. A rectifying tower for heating and fractionating the liquid hydrocarbon synthesized in the reactor into a plurality of types of liquid fuels having different boiling points;
The liquid fuel synthesis system according to claim 1, wherein the heat treatment apparatus is the rectification tower. A reformer for reforming a hydrocarbon raw material to generate a synthesis gas mainly composed of carbon monoxide gas and hydrogen gas;
A reactor for synthesizing liquid hydrocarbons from carbon monoxide gas and hydrogen gas contained in the synthesis gas;
A reaction heat recovery device provided in the reactor for recovering the reaction heat of the liquid hydrocarbon synthesis reaction;
And a heat treatment apparatus for performing a predetermined heat treatment using water vapor generated in the reaction heat recovery apparatus. A rectifying tower for heating the liquid hydrocarbon synthesized in the reactor to fractionate a plurality of types of liquid fuels having different boiling points;
The liquid fuel synthesis system according to claim 4, wherein the heat treatment apparatus is the rectification tower.   The liquid fuel synthesizing system according to claim 5, wherein the rectification column includes a rectification column decompression device that reduces the atmospheric pressure in the rectification column. An exhaust heat recovery device that recovers exhaust heat of the synthesis gas exhausted from the reformer; an absorption tower that separates carbon dioxide gas from the synthesis gas exhausted from the exhaust heat recovery device using an absorbent; Further comprising a decarbonation device having a regeneration tower that heats the absorption liquid containing carbon dioxide separated in the absorption tower to dissipate carbon dioxide.
The liquid fuel synthesis system according to claim 4, wherein the heat treatment apparatus is the regeneration tower.   The liquid fuel synthesizing system according to claim 7, wherein the regeneration tower includes a regeneration tower decompression device that reduces the atmospheric pressure in the regeneration tower.

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