JPWO2018173143A1 - Natural gas processing equipment - Google Patents

Abstract

An object of the present invention is to simplify the equipment, extend the life of the methanation catalyst, and reduce the amount of carbon dioxide used in methanation of natural gas. SOLUTION: A hydrogenation reactor 1 in which a catalyst layer 11 of a hydrogenation catalyst is arranged, an adsorption desulfurization reactor 2 in which an adsorbent layer 21 for adsorbing hydrogen sulfide is arranged, a catalyst layer 31, 41 of a methanation catalyst, The methanation reactors 3, 4, 5 in which 51 are respectively arranged are provided in this order from the upstream side. By mixing hydrogen gas with natural gas and supplying the heated mixed gas to the hydrogenation reactor 1, the organic sulfur in natural gas is hydrogenated by the hydrogenation catalyst to be converted to hydrogen sulfide, and the methanation reaction is performed. Also happens. Hydrogen is supplied to the desulfurized natural gas in the methanation reactors 3 and 4, respectively, where methanation occurs, and the hydrogen concentration in the gas is adjusted in the latter-stage reactor 5. Since hydrogenation and methanation are performed as pretreatments, the sulfur concentration can be kept very small and the amount of methanation catalyst used can be reduced. [Selection diagram] Fig. 1

Description

  The present invention relates to the technical field of methanating carbon dioxide in natural gas using hydrogen.

  Natural gas is produced in most cases containing carbon dioxide in addition to the main component methane, and is removed to obtain product gas as a raw material for pipeline gas (city gas) and liquefied natural gas There is a need to. Generally, carbon dioxide in natural gas is separated and removed by an AGRU (Acid Gas Removal Unit) mainly using amines and released to the atmosphere. Therefore, emission reduction is required.

  On the other hand, good gas fields with low carbon dioxide content, which have been developed preferentially from the viewpoint of profitability, are depleting, and it is necessary to develop natural gas wells containing higher concentrations of carbon dioxide in the future. For this reason, it is conceivable to use methanation as one of the effective uses of carbon dioxide in natural gas. However, when high-concentration carbon dioxide separated by a carbon dioxide separation device such as AGRU is used as a raw material, Causes a sharp rise in the temperature of the reactor. In addition, an increase in temperature is disadvantageous for the progress of methanation, which is an equilibrium reaction.

  In order to suppress the temperature rise in the reactor, generally, a method of dividing the reactor and arranging a cooler between the reactors, a method of returning the product gas generated by the reaction to the inlet of the reactor (recycling), a method of diluting steam A method of adding the agent to the raw material gas is used. However, these methods have problems in that the number of reactors is increased, a large amount of product gas needs to be recycled, or a large amount of steam needs to be accompanied by the raw material gas.

Patent Document 1 discloses that methane is produced by reacting hydrogen obtained by supplying natural gas to a hydrogen separation reactor with carbon dioxide in natural gas in the presence of a catalyst in a methanation reactor. And reduce carbon dioxide in natural gas.
Patent Document 2 discloses that a raw material gas containing carbon dioxide is mixed with hydrogen from a hydrogen gas supply line, the mixed gas is supplied to a first reactor, and then the mixed gas is supplied with hydrogen from a hydrogen gas supply line. A technique for mixing and supplying the mixed gas to a second reactor, further supplying the mixed gas to a third reactor for adjusting the composition of a product gas, and changing carbon dioxide in the raw material gas to methane is described. Have been.

  Patent Literatures 1 and 2 describe how to extend the service life of a methanation catalyst by extremely reducing the allowable amount of sulfur contained in natural gas, and how to reduce the amount of methanation catalyst used. It has not been. According to the description of the fifth and subsequent lines in paragraph 0037 of Patent Document 2, it is excluded that hydrogen for pretreatment is used in the preceding stage of the reactor.

US Patent 6,419,888 JP 2013-136538A

  An object of the present invention is to provide a natural gas processing apparatus capable of simplifying a facility for methanating carbon dioxide in natural gas and extending the life of a methanation catalyst and reducing the amount of use. It is in.

The processing apparatus for natural gas of the present invention comprises:
A natural gas and hydrogen are supplied as raw material gases, and a pre-stage reactor for producing methane by reacting carbon dioxide and hydrogen in the natural gas,
A second-stage reactor for adjusting the hydrogen concentration by reacting hydrogen and carbon dioxide remaining in the product gas discharged from the first-stage reactor,
A catalyst layer of a methanation catalyst provided in each of the first-stage reactor and the second-stage reactor,
A catalyst layer of a hydrogenation catalyst that is provided on the upstream side of the former-stage reactor and has a methanation catalytic action together with a main hydrogenation catalytic action for hydrogenating organic sulfur in natural gas to convert it to hydrogen sulfide,
An adsorbent layer of an adsorbent for adsorbing hydrogen sulfide, which is located on the upstream side of the first-stage reactor and downstream of the catalyst layer of the hydrogenation catalyst.

  In the present invention, when carbon dioxide in natural gas is methanated, natural gas is supplied to the reactor as a raw material gas, so that components other than carbon dioxide in natural gas can be used as a diluent for the methanation reaction. . For this reason, the temperature rise of the methanation reaction can be suppressed, and the equipment can be simplified. In addition, since the organic sulfur in natural gas is converted to hydrogen sulfide and adsorbed and removed by an adsorbent on the upstream side of the methanation reactor, the service life of the methanation catalyst can be extended and the hydrogenation catalyst can be extended. As a result, methanation proceeds, so that it is possible to reduce the amount of use of the subsequent stage methanation catalyst.

BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram which shows 1st Embodiment of the natural gas processing apparatus of this invention. FIG. 2 is a configuration diagram illustrating an example of a device configuration for effectively utilizing wastewater obtained in the first embodiment. FIG. 4 is a configuration diagram illustrating another example of a device configuration for effectively using wastewater obtained in the first embodiment. FIG. 9 is an explanatory diagram illustrating an application example of the first embodiment. 4 is a graph showing the relationship between the concentration of carbon dioxide in natural gas and the concentration of COS (carbonyl sulfide) after a hydrogenation reaction. It is a block diagram which shows 2nd Embodiment of the processing apparatus of the natural gas of this invention. It is a block diagram which shows the modification of 2nd Embodiment of the natural gas processing apparatus of this invention. FIG. 3 is an explanatory diagram illustrating an aspect of Example 1 corresponding to the first embodiment of the present invention. FIG. 13 is an explanatory diagram showing an aspect of Example 2 corresponding to the second embodiment of the present invention. FIG. 14 is an explanatory diagram showing an aspect of Example 3 corresponding to a modification of the second embodiment of the present invention. FIG. 4 is an explanatory diagram showing an aspect of Comparative Example 1 for comparison with the present invention. FIG. 9 is an explanatory diagram showing an aspect of Comparative Example 2 for comparison with the present invention.

[First Embodiment]
As shown in FIG. 1, the natural gas processing apparatus according to the first embodiment of the present invention includes a hydrogenation reactor 1, an adsorption desulfurization reactor 2 for absorbing hydrogen sulfide, and a pre-stage reactor. The 1st methanation reactor 3 and the 2nd methanation reactor 4 which comprise, and the latter-stage reactor 5 which is a methanation reactor are arranged in this order from the upstream side. Each of the reactors 1 to 5 is configured as an adiabatic reactor. In the following description, for convenience, the flow path of the natural gas connected to the upstream side of the hydrogenation reactor 1 is referred to as a “raw gas supply path”, and the flow path of the gas from the hydrogenation reactor 1 to the post-reactor 5 is referred to as “natural gas supply path”. The “gas flow path” and the flow path of the gas taken out from the latter-stage reactor 5 are referred to as “product gas outflow paths”.

The source gas supply path 101 is connected to the top of the hydrogenation reactor 1 via a heater 102, and a pretreatment hydrogen supply path 200 is connected upstream of the heater 102. AGRU (103) indicated by a dotted line will be described later.
In the row of each of the reactors 1 to 5, when viewed from the gas flow path, the tower bottom part and the downstream tower top part of the upstream reactor among the two reactors adjacent to each other are respectively gas passages. They are connected by 10, 20, 30, and 40.

  In the hydrogenation reactor 1, a catalyst layer 11 of a hydrogenation catalyst for converting organic sulfur contained in natural gas into hydrogen sulfide is disposed. The hydrogenation catalyst includes, for example, an inorganic oxide support containing aluminum, a first metal component selected from molybdenum and tungsten, and a second metal component selected from cobalt, nickel and chromium. Used with sulfurized components. Further, the hydrogenation catalyst has not only a main hydrogenation catalytic action for hydrogenating organic sulfur in natural gas to hydrogen sulfide but also a methanation catalytic action.

  In the adsorptive desulfurization reactor 2, an adsorbent layer 21 of an adsorbent for adsorbing hydrogen sulfide is arranged. As the adsorbent, for example, zinc oxide particles can be used. The adsorbent may be a carrier made of an inorganic oxide such as alumina or silica, on which a metal such as iron or copper is supported.

A cooler 22 is provided in a gas flow path 20 for supplying the gas flowing out of the adsorption desulfurization reactor 2 to the first methanation reactor 3. When the apparatus is operated under operating conditions in which the inlet temperature of the first methanation reactor 3 is lower than the outlet temperature of the adsorptive desulfurization reactor 2, the cooler 22 is required, but the first methanation reactor is required. When the apparatus is operated under the operating conditions in which the inlet temperature of the reactor 3 is the same as the outlet temperature of the adsorption desulfurization reactor 2, the cooler 22 is not necessary.
As an example of operating conditions, the inlet temperatures of the first-stage methanation reactor (first methanation reactor 3, second methanation reactor 4) and the second-stage methanation reactor 5 are, for example, 200 to 300 ° C. And the temperature in the adsorption desulfurization reactor 2 is 300 to 350 ° C. In this example, since the inlet temperature of the first methanation reactor 3 is 250 ° C. and the temperature in the adsorption desulfurization reactor 2 is 300 ° C., the gas flowing out of the adsorption desulfurization reactor 2 is cooled by the cooler 22. ing.

A first hydrogen supply path 201 and a steam supply path 203 are connected between the cooler 22 in the gas flow path 20 and the top of the first methanation reactor 3. In the first methanation reactor 3, a catalyst layer 31 of a methanation catalyst is arranged. As the methanation catalyst, a particulate catalyst containing nickel as a main component (for example, 40 to 60% by mass based on the entire catalyst) can be used. As the methanation catalyst, a catalyst in which ruthenium is supported on an inorganic oxide such as alumina or silica can also be used.
Catalyst layers 41 and 51 using the same methanation catalyst are also arranged inside each of the second methanation reactor 4 and the latter-stage methanation reactor 5.

A cooler 32 is provided in a gas flow path 30 for supplying a gas flowing out of the first methanation reactor 3 to the second methanation reactor 4, and a second cooler is provided downstream of the cooler 32. Are connected. Further, a cooler 42 is also provided in a gas flow path 40 for supplying the gas flowing out of the second methanation reactor 4 to the latter-stage methanation reactor 5. In the first methanation reactor 3 and the second methanation reactor 4, a methanation reaction occurs in which carbon dioxide (carbon dioxide gas) and hydrogen (hydrogen gas) react to produce methane, Since this reaction is an exothermic reaction, each outlet temperature is higher than each inlet temperature of the methanation reactors 3 and 4. Therefore, the gas flowing out of each of the methanation reactors 3 and 4 is cooled by these coolers 32 (42).
The pretreatment hydrogen supply path 200, the first hydrogen supply path 201, and the second hydrogen supply path 202 described above are connected to, for example, a common hydrogen supply source, and flow control valves V0, V1, and V2, respectively. Is provided. The steam supply path 203 is provided with a valve V3 for adjusting a flow rate.

  The latter-stage methanation reactor 5 is provided to allow excess hydrogen contained in the gas to react with carbon dioxide so that the hydrogen concentration in the product gas after treatment falls within a preset concentration range. One end of a product gas outlet 50 is connected to the bottom of the latter stage methanation reactor 5, and the other end of the product gas outlet 50 is connected to a gas-liquid separation drum 53 via a cooler 52. . The gas-liquid separation drum 53 flows out of the latter-stage methanation reactor 5, separates and removes water (drainage) from the cooled product gas, and the product gas from which the water has been separated is taken out as, for example, a product gas.

  Next, the operation of the first embodiment will be described. First, natural gas, which is a source gas, passes through a source gas supply path 101 and is mixed with a pretreatment hydrogen gas sent from a pretreatment hydrogen supply path 200. Heated. The heated mixed gas is supplied into the hydrogenation reactor 1, and the hydrogenation reaction mainly occurs. That is, the organic sulfur contained in the natural gas is changed to hydrogen sulfide by the hydrogenation catalyst constituting the catalyst layer 11. As described above, the hydrogenation catalyst has a methanation catalytic action in addition to the hydrogenation catalytic action, so that the methanation reaction proceeds in the hydrogenation reactor 1 and the carbon dioxide contained in the natural gas. Some of the carbon reacts with hydrogen to produce methane.

Since a methanation reaction which is an exothermic reaction occurs, the temperature of the gas on the outlet side of the hydrogenation reactor 1 becomes higher than the temperature of the gas on the inlet side by, for example, 10 ° C to 100 ° C. The amount of hydrogen supplied to the hydrogenation reactor 1 is an amount sufficient for hydrogenation of organic sulfur (for example, 1 to 2 mol (mol)%) or more, and is, for example, 10 mol% in consideration of the heat resistance temperature of the hydrogenation catalyst. The following is assumed. The gas flowing out of the hydrogenation reactor 1 is sent into the adsorptive desulfurization reactor 2, where the adsorbent constituting the adsorbent layer 21 adsorbs hydrogen sulfide in the gas to perform desulfurization. Thereby, the sulfur concentration in the gas flowing out of the adsorption desulfurization reactor 2 becomes 0.1 ppm or less. The concentration unit “ppm” in the specification of the present application represents a mol concentration.
When the sulfur concentration in the natural gas is high in order to reduce the load of the adsorbent in the adsorptive desulfurization reactor 2, an AGRU (Acid Gas Removal Unit) (103) is connected to the raw material gas supply path 101 as shown by a dotted line in FIG. ) May be used. The AGRU (103) supplies, for example, natural gas from the bottom side of the amine contact tower and causes it to flow out from the top, and supplies a liquid of amine from the upper side of the amine contact tower to make a countercurrent contact with the natural gas. It is configured. The contact of the natural gas with the amine liquid removes hydrogen sulfide in the natural gas.

  The gas, which has been subjected mainly to desulfurization and secondary methanation, that is, pretreated, flows out of the adsorptive desulfurization reactor 2 and is then cooled to, for example, 250 ° C. by the cooler 22 to obtain hydrogen and steam. And sent to the first methanation reactor 3. In the first methanation reactor 3, a methanation reaction occurs in which carbon dioxide and hydrogen react in the catalyst layer 31 of the methanation catalyst to produce methane. The flow rate of hydrogen supplied from the first hydrogen supply path 201 is determined by the amount of hydrogen remaining in the gas flowing out of the adsorption desulfurization reactor 2 and the methanation reaction and the methanation reaction. The temperature at the outlet side of the first methanation reactor 3 is adjusted to, for example, 540 ° C. or less in consideration of the heat-resistant temperature of the equipment.

  The steam is supplied to prevent the activity of the methanation catalyst from deteriorating due to coking, and also has a role of further suppressing the temperature in each of the methanation reactors 3, 4, and 5. At the inlet of the first methanation reactor 3, the molar ratio of water vapor to the total of carbon dioxide and hydrogen is, for example, 0.6 [mol concentration of water vapor / (mol concentration of carbon dioxide + mol of hydrogen) at the entrance of the first methanation reactor 3. Density)]. In addition, steam does not necessarily have to be supplied, and may not be used.

  The gas flowing out of the first methanation reactor 3 is cooled to, for example, 250 ° C. by the cooler 32 and sent to the second methanation reactor 4. Then, in the second methanation reactor 4, the hydrogen concentration is adjusted to a value corresponding to the concentration of carbon dioxide remaining in the gas, and the temperature at the outlet side of the second methanation reactor 4 is adjusted. For example, hydrogen is supplied from the second hydrogen supply path 202 to the second methanation reactor 4 via the gas flow path 30 so as to be 540 ° C. or lower. Then, a methanation reaction occurs in the catalyst layer 41, and the gas in which the concentration of carbon dioxide is reduced is cooled to, for example, 250 ° C. by the cooler 42, and is sent to the latter-stage reactor 5.

Since the gas heated in the second methanation reactor 4 is cooled and supplied to the subsequent reactor 5, the methanation reaction further proceeds in the methanation catalyst catalyst layer 51 of the latter reactor 5. Then, carbon dioxide and hydrogen are reduced, and the hydrogen concentration in the product gas is adjusted to an allowable concentration, for example, 3 mol% or less. The product gas flowing out of the latter reactor 5 is cooled by a cooler 52 to a temperature lower than the temperature at which water condenses, for example, to 50 ° C., and then gas and water are separated by a gas-liquid separation drum 53 which is a gas-liquid separation unit. Product gas is obtained.
In the above, the pressure in each of the reactors 1 to 5 is set to, for example, 1 MPa to 8 MPa. Further, the number of stages of the pre-stage reactor (the first methanation reactor 3 and the second methanation reactor 4 in the above example) is determined according to the concentration of carbon dioxide in natural gas. Assuming that steam is used as described above, one pre-reactor is used if the concentration of carbon dioxide is 25 mol% or less, two if the concentration is 40 mol% or less, and three if 70 mol% or less. Is done.

  In the case of using natural gas having a high concentration of carbon dioxide, in order to suppress the number of methanation reactors, a part of the carbon dioxide in the natural gas is removed upstream of the hydrogenation reactor 1. Unit may be provided. When the concentration of carbon dioxide in natural gas is lower than 3 mol%, the gas can be used as it is as a pipeline gas. Therefore, the natural gas used as a raw material gas has a carbon dioxide concentration of 3 mol% or more. Can be.

  According to the above embodiment, the methanation is performed using gas other than carbon dioxide in the natural gas as a diluting gas, and the reactor for methanation is divided into a plurality of stages, for example, two-stage methanation reactors 3 and 4. Since hydrogen is supplied to each, the number of reactors for performing methanation can be reduced, and the apparatus can be simplified. Then, on the upstream side of the methanation reactors 3 and 4, the sulfur concentration in natural gas is reduced to 0.1 ppm or less using a hydrogenation catalyst and a hydrogen sulfide adsorbent. The service life can be extended. In addition, since a hydrogenation catalyst is used, a methanation reaction occurs in addition to the hydrogenation reaction, so that the amount of the methanation catalyst used in the methanation reactors 3 and 4 can be reduced.

Here, a configuration example for achieving effective use of energy or gas in the above-described natural gas processing apparatus or a system including the processing apparatus will be listed.
The wastewater separated by the gas-liquid separation drum 53 is used as a cooling medium for the coolers 22, 32, 42, and 52 as shown in FIG. The water is supplied to the first methanation reactor 3 from the steam supply path 203 described above.
Similarly, as shown in FIG. 3, steam obtained by vaporization by the heat of the methanation reaction is provided in the hydrogen supply path 300 upstream of the junction of the hydrogen supply paths 200, 201, and 202 described above. Is supplied to the steam turbine 302 that drives the boosted compressor 301.
The wastewater separated by the gas-liquid separation drum 53 is electrolyzed by an electrolysis device, and the obtained hydrogen is supplied to the processing system via the hydrogen supply paths 200, 201, and 202 described above.

  As shown in FIG. 4, in a system in which a LNG (Liquefied Natural Gas) production facility 400 is arranged downstream of the above-described natural gas processing apparatus, the wastewater or other water separated by the gas-liquid separation drum 53 is used. Water supplied from the supply source is vaporized by the heat of the methanation reaction to obtain steam, and this steam is used as a heat source for the AGRU stripping tower reboiler in the LNG production facility 400. In addition, as shown in FIG. 4, the carbon dioxide recovered from the AGRU in the LNG production facility 400 is returned to the upstream side of the first methanation reactor 3 for recycling, thereby suppressing the emission of carbon dioxide and producing the product. Increase gas production.

[Second embodiment]
When a natural gas containing carbon dioxide and sulfur is supplied to the hydrogenation catalyst, carbonyl sulfide is generated as a by-product. Therefore, the natural gas processing apparatus according to the second embodiment of the present invention includes a carbonyl sulfide (COS) ) Is adopted. FIG. 5 is a graph showing the relationship between the concentration of carbon dioxide in natural gas and the concentration of carbonyl sulfide after the hydrogenation reaction. When the sulfur in the natural gas is 1 ppm and the carbon dioxide concentration in the natural gas is 64 mol%, the amount of carbonyl sulfide produced is extremely small at 0.095 ppm as indicated by ▲. On the other hand, when the sulfur in natural gas is 10 ppm, as shown by Δ, even if the concentration of carbon dioxide in natural gas is several percent, the amount of carbonyl sulfide generated exceeds 0.1 ppm, and As the carbon concentration increases, it increases roughly in proportion, and the service life of the methanation catalyst becomes shorter due to poisoning. Therefore, when natural gas having a high sulfur concentration is used as the raw material gas and the AGRU 103 is not provided on the upstream side of the hydrogenation reactor 1, it can be expected that the amount of carbonyl sulfide generated will be considerably large.

  Therefore, in the second embodiment, as shown in FIG. 6, carbonyl sulfide is adsorbed upstream of the first methanation reactor 3, for example, between the adsorption desulfurization reactor 2 and the first methanation reactor 3. There is provided a carbonyl sulfide adsorption reactor 6 which is a carbonyl sulfide removing section in which an adsorption layer 61 made of an adsorbent is disposed. Reference numeral 60 denotes a gas flow path. As the adsorbent for carbonyl sulfide, for example, an adsorbent in which copper is supported on a carrier made of an inorganic oxide such as alumina or silica, or a copper-based adsorbent such as a copper oxide particulate or molded article can be used.

Instead of providing the adsorption desulfurization reactor 2 and the carbonyl sulfide adsorption reactor 6 separately, only a copper-based adsorbent is used as the adsorption desulfurization agent used in the adsorption desulfurization reactor 2, and hydrogen sulfide is used. And carbonyl sulfide may be adsorbed to the adsorbent. However, since the cost of the copper-based adsorbent is high, from the viewpoint of cost, the configuration shown in FIG. 6 is employed, and the adsorptive desulfurization reactor 2 has a zinc-based adsorbent such as zinc oxide. It is advantageous to use, for example, a copper-based adsorbent in the carbonyl sulfide adsorption reactor 6 while using the adsorbent, and in this case, the amount of the copper-based adsorbent used can be reduced. Instead of providing the carbonyl sulfide adsorption reactor 6, a zinc-based adsorbent and a copper-based adsorbent may be arranged in the adsorption desulfurization reactor 2 in this order from the upstream side.
Further, instead of the configuration shown in FIG. 6, a carbonyl sulfide adsorbent may be provided above the catalyst layer 31 in the first methanation reactor 3.

FIG. 7 shows a modification of the second embodiment. In this example, instead of adsorbing carbonyl sulfide with an adsorbent, a hydrolysis reactor for hydrolyzing and removing carbonyl sulfide is used. 7 is provided on the upstream side of the first methanation reactor 3, for example, between the hydrogenation reactor 1 and the adsorptive desulfurization reactor 2, and steam is supplied to the hydrolysis reactor 7 through the steam supply path 204. I have. As a catalyst constituting the catalyst layer 71 provided in the hydrolysis reactor 7, for example, a catalyst in which chromium or the like is supported on a carrier of alumina or titanium oxide can be used. Since the operating temperature of the hydrolysis reactor 7 is lower than the operating temperature of each of the hydrogenation reactor 1 and the adsorption desulfurization reactor 2, a cooler 72 is provided upstream of the hydrolysis reactor 7 and a heater 72 is provided downstream. 73 are provided. 70 is a gas flow path.
According to the second embodiment, poisoning of the methanation catalyst is suppressed because carbonyl sulfide by-produced by the hydrogenation catalyst is removed.

Hereinafter, examples (examples and comparative examples) of processing natural gas by simulation will be described.
[Example 1]
Example 1 is an example in which a natural gas containing 40 mol% of carbon dioxide and 1 ppm of sulfur is treated according to the first embodiment to obtain a product gas having a carbon dioxide concentration of 2 mol%. FIG. 8 is an explanatory diagram illustrating a mode of processing (concentration of components in gas, temperature, and the like) in Example 1.
Hydrogen was mixed with the raw natural gas at the inlet of the hydrogenation reactor 1 so as to be 10 mol% hydrogen, heated to 250 ° C. by the heater 102, and supplied to the hydrogenation reactor 1. As a result of the methanation reaction occurring in the hydrogenation reactor 1, the outlet temperature of the hydrogenation reactor 1 increased to 340 ° C., and the carbon dioxide concentration became 35 mol%.
Sulfur was in the form of hydrogen sulfide at the outlet of the hydrogenation reactor 1 and was adsorbed and removed by the adsorption desulfurization reactor 2, and it was confirmed that the sulfur concentration at the outlet of the adsorption desulfurization reactor 2 was 0.1 ppm or less. . This allows the downstream methanation catalyst to be used for 2-4 years.

The gas that has passed through the adsorption desulfurization reactor 2 is cooled so that the inlet temperature of the first methanation reactor 3 becomes 250 ° C., and hydrogen is added in such an amount that the outlet temperature of the first methanation reactor 3 becomes 540 ° C. , And steam were mixed and supplied to the first methanation reactor 3. The supply amount (mixing amount) of steam was set to an amount such that the mole ratio of steam to the total of carbon dioxide and hydrogen at the inlet of the first methanation reactor 3 was 0.6.
The gas that has passed through the first methanation reactor 3 is cooled so that the inlet temperature of the second methanation reactor 4 becomes 250 ° C., and hydrogen is mixed in such an amount that the carbon dioxide concentration of the product gas can be adjusted to 2 mol%. And supplied to the second methanation reactor 4. The outlet temperature of the second methanation reactor 4 rises to 464 ° C. due to the methanation reaction, and the gas flowing out of the second methanation reactor 4 becomes 250 ° C. at the inlet temperature of the latter methanation reactor 5. After cooling as described above, the mixture was supplied to the latter-stage methanation reactor 5.
In the latter-stage methanation reactor 5, the remaining hydrogen and carbon dioxide reacted, and the outlet temperature rose to 304 ° C. After the gas flowing out of the latter-stage methanation reactor 5 is cooled to 50 ° C. by the cooler 502, water is separated by the gas-liquid separation drum 53 to obtain a product gas having a carbon dioxide concentration of 2 mol% and a hydrogen concentration of 3 mol%. did it.

[Example 2]
In Example 2, a natural gas containing 40 mol% of carbon dioxide and 10 ppm of sulfur is treated using the carbonyl sulfide adsorption reactor 6 in the second embodiment to obtain a product gas having a carbon dioxide concentration of 2 mol%. It is an example. FIG. 9 is an explanatory diagram illustrating a mode of processing according to the second embodiment.
Hydrogen was mixed with the raw natural gas at the inlet of the hydrogenation reactor 1 so as to be 10 mol% hydrogen, heated to 250 ° C. by the heater 102, and supplied to the hydrogenation reactor 1. As a result of the methanation reaction occurring in the hydrogenation reactor 1, the outlet temperature of the hydrogenation reactor 1 increased to 340 ° C., and the carbon dioxide concentration became 35 mol%. At the outlet of the hydrogenation reactor 1, sulfur was contained in gas as by-product carbonyl sulfide in addition to the form of hydrogen sulfide, and the concentration of carbonyl sulfide in the gas was 0.7 ppm.
Hydrogen sulfide was adsorbed and removed by the adsorptive desulfurization reactor 2, but unadsorbed carbonyl sulfide flowed out of the outlet of the adsorptive desulfurization reactor 2. By supplying the gas flowing out of the adsorption desulfurization reactor 2 to the downstream carbonyl sulfide adsorption reactor 6, the sulfur concentration at the outlet of the carbonyl sulfide adsorption reactor 6 became 0.1 ppm or less.
The processing downstream of the carbonyl sulfide adsorption reactor 6 is the same as in Example 1.

[Example 3]
In Example 3, a natural gas containing 40 mol% of carbon dioxide and 10 ppm of sulfur was treated using the carbonyl sulfide hydrolysis reactor 7 in the second embodiment, and the product gas having a carbon dioxide concentration of 2 mol% was used. This is an example of obtaining. FIG. 10 is an explanatory diagram illustrating a mode of processing according to the second embodiment.
Hydrogen was mixed with the raw material natural gas at the inlet of the hydrogenation reactor 1 so that the hydrogen concentration became 10 mol%, heated to 250 ° C. by the heater 102, and supplied to the hydrogenation reactor 1. As a result of the methanation reaction occurring in the hydrogenation reactor 1, the outlet temperature of the hydrogenation reactor 1 increased to 340 ° C., and the carbon dioxide concentration became 35 mol%.

At the outlet of the hydrogenation reactor 1, sulfur was contained in gas as by-product carbonyl sulfide in addition to the form of hydrogen sulfide, and the concentration of carbonyl sulfide in the gas was 0.7 ppm.
After the gas flowing out of the hydrogenation reactor 1 is cooled by the cooler 72 so that the inlet temperature of the hydrolysis reactor 7 becomes 150 ° C., steam is mixed so that the steam concentration becomes 5 mol%, and hydrolysis is performed. It was supplied to the reactor 7. As the carbonyl sulfide was hydrolyzed (converted to hydrogen sulfide), the carbonyl sulfide concentration at the outlet of the hydrolysis reactor 7 became 0.1 ppm or less.
The gas flowing out of the hydrolysis reactor 7 was heated to 350 ° C. by the heater 73 and supplied to the adsorption desulfurization reactor 2. Hydrogen sulfide was adsorbed and removed, and the sulfur concentration at the outlet of the adsorption desulfurization reactor 2 became 0.1 ppm or less.
The processing downstream of the adsorption desulfurization reactor 2 is the same as in Example 1.

[Comparative Example 1]
Comparative Example 1 uses the same raw natural gas as in Example 1 containing 40 mol% of carbon dioxide and 1 ppm of sulfur, and has a carbon dioxide concentration of 2 mol% without using the hydrogenation reactor 1 and the adsorption desulfurization reactor 2. This is an example of obtaining the product gas of Example 1. FIG. 11 is an explanatory diagram showing a mode of processing in Comparative Example 1 using an apparatus in which the hydrogenation reactor 1 and the adsorption desulfurization reactor 2 are removed from the configuration shown in FIG.
Since a gas containing carbon dioxide at a high concentration is supplied to the methanation reaction section as compared with Example 1, a large amount of heat is generated by the methanation reaction, and the outlet temperature of the second methanation reactor 4 is 487 ° C. The outlet temperature of the methanation reactor 5 became 316 ° C.
The methanation reaction, which is an equilibrium reaction, is inhibited by the temperature rise, and it is necessary to supply an excessive amount of hydrogen to obtain a product gas having a carbon dioxide concentration of 2 mol%, and the hydrogen concentration of the product gas is higher than that in Example 1. It became 4 mol%. To achieve the hydrogen concentration of the product gas of Example 1, an additional third methanation reactor was required.
Also, since the raw natural gas has not been desulfurized, the methanation catalyst has been deactivated by sulfur, necessitating replacement every few months.

[Comparative Example 2]
In Comparative Example 1, an example in which the raw material natural gas is diluted with steam to achieve a hydrogen concentration equivalent to that in Example 1 instead of adding a methanation reactor is referred to as Comparative Example 2. FIG. 12 is an explanatory diagram illustrating a mode of processing in Comparative Example 2.
At the inlet of the first methanation reactor 3, the raw natural gas is mixed with water vapor in such an amount that the molar ratio of water vapor to the total of carbon dioxide and hydrogen becomes 0.76, which is higher than that in Example 1, to dilute the gas to be treated. As a result, a hydrogen concentration of 2.9 mol% of the product gas was achieved.
Comparative Example 2 required more water vapor than Example 1. Also, since the raw natural gas has not been desulfurized, the methanation catalyst has been deactivated by sulfur, necessitating replacement every few months.

[Evaluation of Examples and Comparative Examples]
As can be seen from the examples and comparative examples, by using the hydrogenation reactor 1 in which the catalyst layer 11 of the hydrogenation catalyst is disposed on the upstream side of the methanation reactor 3, natural gas containing high-concentration carbon dioxide is used. When is used as the raw material, the number of stages of the methanation reactor can be reduced and the amount of steam used can be reduced as compared with the case where the hydrogenation reactor 1 is not used. As described in the section of the background art, since it is necessary to develop a natural gas well containing a high concentration of carbon dioxide in the future, it is understood that the present invention is an extremely useful technique. By using the hydrogenation catalyst, a methanation reaction occurs in addition to the hydrogenation reaction, and it is expected that the amount of the methanation catalyst used in the methanation reactor can be reduced. Since carbonyl sulfide is by-produced by using a hydrogenation catalyst, it is effective to provide a carbonyl sulfide removing section.

Claims (5)

A natural gas and hydrogen are supplied as raw material gases, and a pre-stage reactor for producing methane by reacting carbon dioxide and hydrogen in the natural gas,
A second-stage reactor for adjusting the hydrogen concentration by reacting hydrogen and carbon dioxide remaining in the product gas discharged from the first-stage reactor,
A catalyst layer of a methanation catalyst provided in each of the first-stage reactor and the second-stage reactor,
A catalyst layer of a hydrogenation catalyst that is provided on the upstream side of the former-stage reactor and has a methanation catalytic action together with a main hydrogenation catalytic action for hydrogenating organic sulfur in natural gas to convert it to hydrogen sulfide,
An adsorbent layer of an adsorbent for adsorbing hydrogen sulfide, which is located on the upstream side of the first-stage reactor and on the downstream side of the catalyst layer of the hydrogenation catalyst. Gas treatment equipment. The first-stage reactor includes a first methanation reactor, and a second methanation reactor provided downstream of the first methanation reactor,
A first hydrogen supply path for supplying hydrogen to an inlet side of the first methanation reactor; and a second hydrogen supply path for supplying hydrogen to an inlet side of the second methanation reactor. The natural gas processing apparatus according to claim 1, wherein: The catalyst layer of the hydrogenation catalyst and the adsorbent layer are disposed in a pretreatment reactor provided on the upstream side of the pre-stage reactor,
2. The natural gas processing apparatus according to claim 1, further comprising a pretreatment hydrogen supply path for supplying hydrogen to an inlet side of the pretreatment reactor.   The pretreatment reactor is a hydrogenation reactor in which a catalyst layer of the hydrogenation catalyst is disposed, and an adsorption desulfurization reactor provided downstream of the hydrogenation reactor and in which the adsorbent layer is disposed. The natural gas processing apparatus according to claim 1, comprising: The carbonyl sulfide removing section for removing carbonyl sulfide by-produced in the catalyst layer of the hydrogenation catalyst is provided upstream of the catalyst layer of the methanation catalyst. Natural gas processing equipment.

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