WO2018173143A1

WO2018173143A1 - Treatment device for natural gas

Info

Publication number: WO2018173143A1
Application number: PCT/JP2017/011404
Authority: WO
Inventors: 恵里杉; 嘉之渡邉; 近松　伸康
Original assignee: 日揮株式会社
Priority date: 2017-03-22
Filing date: 2017-03-22
Publication date: 2018-09-27
Also published as: JP6740458B2; AU2017404979B2; JPWO2018173143A1; AU2017404979A1

Abstract

[Problem] To simplify equipment for converting carbon dioxide contained in natural gas into methane, to prolong the life of a methane formation catalyst, and to reduce the use amount thereof. [Solution] Reactors are installed in the following order from the upstream side: a hydrogenation reactor 1 in which a layer 11 of a hydrogenation catalyst has been disposed; an adsorptive desulfurization reactor 2 in which an adsorbent layer 21 for adsorbing hydrogen sulfide has been disposed; and methane formation reactors 3, 4, and 5 in which methane-formation catalyst layers 31, 41, and 51 have been disposed respectively. Hydrogen gas is mixed with natural gas, and the mixed gas is heated and fed to the hydrogenation reactor 1. Thus, the organic sulfur compounds contained in the natural gas are hydrogenated by means of the hydrogenation catalyst to become hydrogen sulfide, and a methane formation reaction takes place. In the methane formation reactors 3 and 4, hydrogen is fed to the desulfurized natural gas to cause a methane formation reaction. Furthermore, in the succeeding-stage reactor 5, the hydrogen concentration in the gas is regulated. Since hydrogenation and methane formation are conducted as pretreatments, the sulfur concentration can be kept extremely low and the amount of the methane formation catalyst to be used can be reduced.

Description

Natural gas processing equipment

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

Natural gas is often produced in a state containing carbon dioxide in addition to the main component methane, and carbon dioxide 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 mainly by AGRU (Acid Gas Removal Unit) using amines and released into the atmosphere, but carbon dioxide has the greatest impact on global warming. Therefore, emission reduction is required.

On the other hand, excellent gas fields with low carbon dioxide content, which have been preferentially developed from the viewpoint of profitability, are heading for depletion, and in the future, it will be necessary to develop natural gas wells containing higher concentrations of carbon dioxide. For this reason, it is conceivable to perform methanation as one of the effective uses of carbon dioxide in natural gas. However, when high-concentration carbon dioxide separated by a carbon dioxide separator such as AGRU is used as a raw material, the heat of methanation reaction Causes a rapid temperature rise in the reactor. Also, the temperature rise is disadvantageous for the progress of methanation, which is an equilibrium reaction.

In order to suppress the temperature rise of the reactor, in general, 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), diluting water vapor A method of adding to the source gas as an agent is employed. However, these methods have a problem that the number of reactors increases, a large amount of product gas needs to be recycled, or a large amount of water vapor needs to be entrained in the raw material gas.

In Patent Document 1, hydrogen obtained by supplying natural gas to a hydrogen separation reactor is reacted with carbon dioxide in natural gas in the presence of a catalyst in a methanation reactor to produce methane. And reducing carbon dioxide in natural gas.
In Patent Document 2, hydrogen from a hydrogen gas supply line is mixed with a raw material gas containing carbon dioxide, the mixed gas is supplied to the first reactor, and then hydrogen from the hydrogen gas supply line is supplied to the mixed gas. A technique is described in which the mixed gas is supplied to the second reactor, the mixed gas is further supplied to the third reactor for adjusting the composition of the product gas, and the carbon dioxide in the raw material gas is changed to methane. Has been.

Patent Documents

1 and 2 describe a technique for extending the service life of the methanation catalyst by extremely reducing the allowable content of sulfur contained in natural gas, and a device for reducing the amount of methanation catalyst used. It has not been. In addition, according to the description after the 5th line of Paragraph 0037 of patent document 2, using the hydrogen for pretreatment in the front | former stage of a reactor is excluded.

US Pat. No. 6,419,888 JP 2013-136538 A

The present invention provides a natural gas processing apparatus capable of simplifying equipment for methanating carbon dioxide in natural gas, extending the life of the methanation catalyst, and reducing the amount used. It is in.

The natural gas processing apparatus of the present invention comprises:
A pre-stage reactor for supplying natural gas, which is a raw material gas, and hydrogen, and reacting carbon dioxide and hydrogen in the natural gas to produce methane,
A post-reactor for adjusting the hydrogen concentration by reacting hydrogen and carbon dioxide remaining in the product gas discharged from the pre-reactor;
A catalyst layer of a methanation catalyst provided in each of the former reactor and the latter reactor;
A catalyst layer of a hydrogenation catalyst provided on the upstream side of the preceding reactor and having methanation catalysis together with main hydrogenation catalysis that hydrogenates organic sulfur in natural gas to hydrogen sulfide;
And an adsorbent layer of an adsorbent disposed on the downstream side of the catalyst layer of the hydrogenation catalyst and adsorbing hydrogen sulfide.

In the present invention, when methanating carbon dioxide in natural gas, since natural gas is supplied to the reactor as a raw material gas, components other than carbon dioxide in natural gas can be used as a diluent for methanation reaction. . For this reason, since the temperature rise of the methanation reaction can be suppressed, the equipment can be simplified. Also, since the organic sulfur in natural gas is changed to hydrogen sulfide and adsorbed and removed at the upstream side of the methanation reactor, the service life of the methanation catalyst can be extended and the hydrogenation catalyst can be extended. Since the methanation proceeds by this, the amount of the methanation catalyst in the latter stage can be reduced.

It is a block diagram which shows 1st Embodiment of the processing apparatus of the natural gas of this invention. It is a block diagram which shows an example of the apparatus structure for aiming at the effective utilization of the waste_water | drain obtained in 1st Embodiment. It is a block diagram which shows the other example of the apparatus structure for aiming at the effective utilization of the waste_water | drain obtained in 1st Embodiment. It is explanatory drawing which shows the application example of 1st Embodiment. It is a graph which shows the relationship between the density | concentration of the carbon dioxide in natural gas, and the density | concentration of COS (carbonyl sulfide) after 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 processing apparatus of the natural gas of this invention. It is explanatory drawing which shows the aspect of Example 1 corresponding to the 1st Embodiment of this invention. It is explanatory drawing which shows the aspect of Example 2 corresponding to the 2nd Embodiment of this invention. It is explanatory drawing which shows the aspect of Example 3 corresponding to the modification of the 2nd Embodiment of this invention. It is explanatory drawing which shows the aspect of the comparative example 1 for comparing with this invention. It is explanatory drawing which shows the aspect of the comparative example 2 for comparing with this invention.

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

The source gas supply path 101 is connected to the tower top of the hydrogenation reactor 1 via a heater 102, and a pretreatment hydrogen supply path 200 is connected to the upstream side of the heater 102. The AGRU (103) indicated by the dotted line will be described later.
In the arrangement of the reactors 1 to 5, when the gas flow path is viewed, the tower bottom portion of the upstream reactor and the tower top portion of the downstream side of the two reactors adjacent to each other are respectively the gas flow paths. 10, 20, 30, 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. In this example, the metal Used in a sulfurized state. The hydrogenation catalyst also has methanation catalysis as well as main hydrogenation catalysis that converts organic sulfur in natural gas into hydrogen sulfide.

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

A cooler 22 is provided in the gas flow path 20 for supplying the gas flowing out from the adsorptive desulfurization reactor 2 to the first methanation reactor 3. When the apparatus is operated under an operating condition 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 necessary, but the first methanation reactor When the apparatus is operated under an operating condition in which the inlet temperature of 3 is the same as the outlet temperature of the adsorptive desulfurization reactor 2, the cooler 22 is not necessary.
As an example of operating conditions, the inlet temperature of each of the first-stage methanation reactor (first methanation reactor 3, second methanation reactor 4) and second-stage methanation reactor 5 is, for example, 200 to 300 ° C. The temperature in the adsorptive 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 adsorptive desulfurization reactor 2 is 300 ° C., the gas flowing out from the adsorptive 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. A catalyst layer 31 of a methanation catalyst is disposed in the first methanation reactor 3. As the methanation catalyst, a particulate catalyst containing nickel as a main component (for example, 40 to 60 mass% with respect to the whole 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.
Inside each of the second methanation reactor 4 and the post-stage methanation reactor 5, catalyst layers 41 and 51 using the same methanation catalyst are arranged.

The gas flow path 30 for supplying the gas flowing out from the first methanation reactor 3 to the second methanation reactor 4 is provided with a cooler 32, and the second side is located downstream of the cooler 32. The hydrogen supply path 202 is connected. A cooler 42 is also provided in the gas flow path 40 for supplying the gas flowing out from the second methanation reactor 4 to the subsequent 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 generate methane, Since this reaction is an exothermic reaction, each outlet temperature becomes higher than each inlet temperature of the

methanation reactors

3 and 4. Therefore, the gas flowing out from 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 rate adjusting valves V0, V1, and V2, respectively. Is provided. Further, the water vapor supply path 203 is provided with a valve V3 for flow rate adjustment.

The post-stage methanation reactor 5 is provided for reacting excess hydrogen contained in the gas with carbon dioxide so that the hydrogen concentration in the product gas after the treatment falls within a preset concentration range. One end side of the product gas outflow passage 50 is connected to the tower bottom of the rear stage methanation reactor 5, and the other end side of the product gas outflow passage 50 is connected to the gas-liquid separation drum 53 via the cooler 52. . The gas-liquid separation drum 53 flows out from the post-stage methanation reactor 5, separates and removes moisture (drainage) from the cooled product gas, and the product gas from which the moisture 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 raw material gas, is mixed with the pretreatment hydrogen gas sent from the pretreatment hydrogen supply passage 200 through the raw material gas supply passage 101, and is heated at, for example, 250 ° C. to 350 ° C. in the heater 102. To be 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 methanation catalysis in addition to hydrogenation catalysis, so that the methanation reaction also proceeds in the hydrogenation reactor 1 and carbon dioxide in the natural gas. Part of the carbon reacts with hydrogen to produce methane.

Since the methanation reaction which is an exothermic reaction occurs, the temperature of the gas on the outlet side of the hydrogenation reactor 1 is, for example, 10 ° C. to 100 ° C. higher than the temperature of the gas on the inlet side. The amount of hydrogen supplied to the hydrogenation reactor 1 is not less than an amount sufficient for hydrogenation of organic sulfur (for example, 1 to 2 mol (mol)%) and, for example, 10 mol% in consideration of the heat resistant temperature of the hydrogenation catalyst. The following. The gas flowing out of the hydrogenation reactor 1 is sent into the adsorptive desulfurization reactor 2, and hydrogen sulfide in the gas is adsorbed by the adsorbent constituting the adsorbent layer 21 to perform desulfurization. Thereby, the sulfur concentration in the gas flowing out from the adsorptive desulfurization reactor 2 becomes 0.1 ppm or less. The concentration unit “ppm” in the present specification represents the mol concentration.
In order to reduce the load of the adsorbent in the adsorptive desulfurization reactor 2, when the sulfur concentration in the natural gas is high, an AGRU (Acid Gas Removal Unit) (103 is provided in the raw material gas supply path 101 as indicated by a dotted line in FIG. ) May be used. For example, the AGRU (103) supplies natural gas from the bottom side of the amine contact tower to flow out from the top of the tower, and supplies an amine liquid from the top side of the amine contact tower to make countercurrent contact with the natural gas. It is configured. When the natural gas comes into contact with the amine liquid, hydrogen sulfide in the natural gas is removed.

The gas that has been mainly desulfurized and that has undergone secondary methanation, that is, pretreated, flows out of the adsorption desulfurization reactor 2 and is then cooled to, for example, 250 ° C. by the cooler 22 to generate hydrogen and water vapor. 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 with each other in the catalyst layer 31 of the methanation catalyst to generate methane. The flow rate of hydrogen supplied from the first hydrogen supply channel 201 is the same as that of the methanation catalyst and methanation reaction when the methanation reaction occurs with the hydrogen remaining in the gas flowing out from the adsorptive desulfurization reactor 2. In consideration of the heat-resistant temperature of the equipment, the temperature on the outlet side of the first methanation reactor 3 is adjusted to be 540 ° C. or less, for example.

Steam is supplied to prevent activity degradation due to coking of the methanation catalyst, but also has a role of further suppressing the temperature in each of the

methanation reactors

3, 4 and 5. The supply amount of water vapor is such that the molar ratio of water vapor to the total of carbon dioxide and hydrogen is 0.6 [mol concentration of water vapor / mol concentration of carbon dioxide + mol of hydrogen at the inlet of the first methanation reactor 3. Density)]. Note that water vapor is not necessarily supplied and may not be used.

The gas flowing out from the first methanation reactor 3 is cooled to, for example, 250 ° C. by the cooler 32 and sent to the second methanation reactor 4. In the second methanation reactor 4, the temperature on the outlet side of the second methanation reactor 4 is adjusted so that the hydrogen concentration becomes a value corresponding to the concentration of carbon dioxide remaining in the gas. For example, hydrogen is replenished and supplied from the second hydrogen supply path 202 to the second methanation reactor 4 via the gas flow path 30 so that the temperature is 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 sent to the subsequent reactor 5.

Since the gas heated in the second methanation reactor 4 is cooled and supplied to the rear reactor 5, the methanation reaction further proceeds in the catalyst layer 51 of the methanation catalyst of the rear reactor 5. 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 from the rear reactor 5 is cooled to a temperature below the temperature at which water is condensed by the cooler 52, for example, 50 ° C., and then the gas and water are separated by the gas-liquid separation drum 53 as a gas-liquid separation unit, Product gas is obtained.
In the above, the pressure in each reactor 1 to 5 is set to 1 MPa to 8 MPa, for example. Further, the number of stages of the preceding 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 the natural gas. If steam is used as described above, the number of the first-stage reactors is 1 if the concentration of carbon dioxide is 25 mol% or less, 2 if the concentration is 40 mol% or less, and 3 if the concentration is 70 mol% or less. Is done.

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

According to the embodiment described above, methanation is performed using a gas other than carbon dioxide in natural gas as a diluent gas, and the reactor for methanation is divided into a plurality of stages, for example, two stages of

methanation reactors

3 and 4. Since hydrogen is supplied to each, the number of reactors for methanation can be reduced, and the apparatus can be simplified. And since the sulfur concentration in natural gas is reduced to 0.1 ppm or less using the hydrogenation catalyst and the adsorbent of hydrogen sulfide on the upstream side of the

methanation reactors

3 and 4, the methanation catalyst The service life can be extended. In addition, since a hydrogenation catalyst is used, a methanation reaction occurs in addition to the hydrogenation reaction, and therefore the amount of methanation catalyst used in the

methanation reactors

3 and 4 can be suppressed.

Here, in the above-described natural gas processing apparatus or a system including the processing apparatus, examples of configurations for effectively using energy or gas are listed.
The waste water 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. 2, and water vapor obtained by vaporization by the heat of the methanation reaction is used. It supplies to the 1st methanation reactor 3 from the water vapor | steam supply path 203 as stated above.
Similarly, the water vapor obtained by vaporization by the heat of the methanation reaction is provided in the hydrogen supply passage 300 upstream of the joining portions of the

hydrogen supply passages

200, 201, 202 described above as shown in FIG. The booster compressor 301 is supplied to a steam turbine 302 that drives it.
The waste water separated by the gas-liquid separation drum 53 is electrolyzed by an electrolysis device, and the obtained hydrogen is supplied into the treatment system via the

hydrogen supply paths

200, 201, 202 described above.

As shown in FIG. 4, in a system in which an LNG (Liquefied Natural Gas) manufacturing facility 400 is arranged at the subsequent stage of the above-described natural gas processing apparatus, waste water or other water separated by the gas-liquid separation drum 53 Water supplied from the supply source is vaporized by the heat of the methanation reaction to obtain water vapor, and this water vapor is used as a heat source for the AGRU diffusion tower reboiler in the LNG production facility 400. Further, as shown in FIG. 4, the carbon dioxide recovered from the AGRU in the LNG manufacturing facility 400 is recycled back to the upstream side of the first methanation reactor 3, thereby suppressing the emission of carbon dioxide and the product. Increase gas production.

[Second Embodiment]
When 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 uses carbonyl sulfide (COS). ) Has been adopted. FIG. 5 is a graph showing the relationship between the carbon dioxide concentration in natural gas and the carbonyl sulfide concentration 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 as very small as 0.095 ppm as shown by. On the other hand, when the sulfur in the natural gas is 10 ppm, as shown by Δ, the amount of carbonyl sulfide produced exceeds 0.1 ppm even if the carbon dioxide concentration in the natural gas is several percent, As the carbon concentration increases, it increases approximately proportionally, and the service life of the methanation catalyst is shortened by 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 predicted that the amount of carbonyl sulfide produced will be considerably increased.

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

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

FIG. 7 shows a modification of the second embodiment. In this example, a hydrolysis reactor for hydrolyzing and removing carbonyl sulfide instead of adsorbing carbonyl sulfide with an adsorbent. 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. Yes. As a catalyst which comprises the catalyst layer 71 provided in the hydrolysis reactor 7, what carried | supported chromium etc. on the support | carrier of an alumina or a titanium oxide can be used, for example. Since the operating temperature of the hydrolysis reactor 7 is lower than the operating temperature of each of the hydrogenation reactor 1 and the adsorptive desulfurization reactor 2, a cooler 72 is provided on the upstream side of the hydrolysis reactor 7, and a heater is provided on the downstream side. 73 is provided. Reference numeral 70 denotes a gas flow path.
According to the second embodiment, since the carbonyl sulfide by-produced by the hydrogenation catalyst is removed, poisoning of the methanation catalyst can be suppressed.

Examples (Examples and Comparative Examples) in which natural gas is processed by simulation will be described below.
[Example 1]
Example 1 is an example in which natural gas containing 40 mol% carbon dioxide and 1 ppm sulfur is processed according to the first embodiment to obtain a product gas having a carbon dioxide concentration of 2 mol%. FIG. 8 is an explanatory diagram showing a processing mode (concentration of component in gas, temperature, etc.) in the first embodiment.
Hydrogen was mixed with the raw material natural gas so as to be 10 mol% hydrogen at the inlet of the hydrogenation reactor 1, 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 rose to 340 ° C, and the carbon dioxide concentration became 35 mol%.
Sulfur in the form of hydrogen sulfide at the outlet of the hydrogenation reactor 1 was adsorbed and removed by the adsorptive desulfurization reactor 2, and the sulfur concentration at the outlet of the adsorptive desulfurization reactor 2 was confirmed to be 0.1 ppm or less. . This allows downstream methanation catalysts to be used for 2-4 years.

The gas that has passed through the adsorptive desulfurization reactor 2 is cooled so that the inlet temperature of the first methanation reactor 3 is 250 ° C., and hydrogen in an amount such 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 water vapor was set to an amount such that the molar ratio of water vapor 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 is 250 ° C., and an amount of hydrogen that can adjust the carbon dioxide concentration of the product gas to 2 mol% is mixed. 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 post-stage methanation reactor 5. After cooling as described above, the product 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 from 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, natural gas containing 40 mol% carbon dioxide and 10 ppm sulfur is processed 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 processing mode according to the second embodiment.
Hydrogen was mixed with the raw material natural gas so as to be 10 mol% hydrogen at the inlet of the hydrogenation reactor 1, 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 rose to 340 ° C, and the carbon dioxide concentration became 35 mol%. At the outlet of the hydrogenation reactor 1, sulfur was contained in the gas as carbonyl sulfide by-produced 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 carbonyl sulfide that was not adsorbed flowed out from the outlet of the adsorptive desulfurization reactor 2. By supplying the gas flowing out from 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 the first embodiment.

[Example 3]
In Example 3, natural gas containing 40 mol% carbon dioxide and 10 ppm sulfur was treated using the carbonyl sulfide hydrolysis reactor 7 in the second embodiment, and a product gas having a carbon dioxide concentration of 2 mol% was obtained. This is an example. FIG. 10 is an explanatory diagram illustrating a mode of processing in the second embodiment.
Hydrogen was mixed with the raw material natural gas so that the hydrogen concentration became 10 mol% at the inlet of the hydrogenation reactor 1, 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 rose to 340 ° C, and the carbon dioxide concentration became 35 mol%.

At the outlet of the hydrogenation reactor 1, sulfur was contained in the gas as carbonyl sulfide by-produced 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., water vapor is mixed so that the water vapor concentration becomes 5 mol%, and hydrolysis is performed. Feeded to 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 from the hydrolysis reactor 7 was heated to 350 ° C. by the heater 73 and supplied to the adsorptive desulfurization reactor 2. Hydrogen sulfide was adsorbed and removed, and the sulfur concentration at the outlet of the adsorptive desulfurization reactor 2 became 0.1 ppm or less.
The processing downstream of the adsorptive desulfurization reactor 2 is the same as in the first embodiment.

[Comparative Example 1]
In Comparative Example 1, the same raw material natural gas containing 40 mol% carbon dioxide and 1 ppm sulfur as in Example 1 was applied without using the hydrogenation reactor 1 and the adsorptive desulfurization reactor 2, and the carbon dioxide concentration was 2 mol%. This is an example of obtaining the product gas. FIG. 11 is an explanatory diagram showing a processing mode in Comparative Example 1 using an apparatus in which the hydrogenation reactor 1 and the adsorptive desulfurization reactor 2 are removed from the configuration shown in FIG.
Compared with Example 1, a gas containing carbon dioxide at a high concentration is supplied to the methanation reaction section, so that heat is generated due to the methanation reaction, and the outlet temperature of the second methanation reactor 4 is 487 ° C. The outlet temperature of the methanation reactor 5 was 316 ° C.
The methanation reaction, which is an equilibrium reaction, is inhibited by the temperature rise, and in order to obtain a product gas having a carbon dioxide concentration of 2 mol%, it is necessary to supply excess hydrogen, and the hydrogen concentration of the product gas is higher than that in Example 1. It became 4 mol%. In order to achieve the hydrogen concentration of the product gas of Example 1, it was necessary to add a third methanation reactor.
In addition, since the raw natural gas was not desulfurized, the methanation catalyst was deactivated by sulfur, and it was necessary to replace it every several months.

[Comparative Example 2]
In Comparative Example 1, instead of adding a methanation reactor, an example in which the hydrogen concentration equivalent to that in Example 1 is achieved by diluting the raw natural gas with water vapor is referred to as Comparative Example 2. FIG. 12 is an explanatory diagram showing a mode of processing in Comparative Example 2.
At the inlet of the first methanation reactor 3, raw material natural gas is mixed with water vapor in an amount such that the molar ratio of water vapor to the total of carbon dioxide and hydrogen is 0.76 higher than in Example 1, and the gas to be treated is diluted. As a result, a hydrogen concentration of 2.9 mol% in the product gas could be achieved.
Comparative Example 2 required more water vapor than Example 1. In addition, since the raw natural gas was not desulfurized, the methanation catalyst was deactivated by sulfur, and it was necessary to replace it every several 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 arranged on the upstream side of the methanation reactor 3, natural gas containing high-concentration carbon dioxide is used. As a raw material, compared with the case where the hydrogenation reactor 1 is not used, the number of installation stages of the methanation reactor can be reduced, and the amount of steam used can also be suppressed. As described in the section of the background art, since it will be necessary to develop a natural gas well containing carbon dioxide at a high concentration in the future, it is understood that the present invention is a very useful technique. By using a hydrogenation catalyst, a methanation reaction occurs in addition to the hydrogenation reaction, and a reduction in the amount of methanation catalyst used in the methanation reactor can be expected. Also, since a carbonyl sulfide is by-produced by using a hydrogenation catalyst, it is effective to provide a carbonyl sulfide removal part.

Claims

A pre-stage reactor for supplying natural gas, which is a raw material gas, and hydrogen, and reacting carbon dioxide and hydrogen in the natural gas to produce methane,
A post-reactor for adjusting the hydrogen concentration by reacting hydrogen and carbon dioxide remaining in the product gas discharged from the pre-reactor;
A catalyst layer of a methanation catalyst provided in each of the former reactor and the latter reactor;
A catalyst layer of a hydrogenation catalyst provided on the upstream side of the preceding reactor and having methanation catalysis together with main hydrogenation catalysis that hydrogenates organic sulfur in natural gas to hydrogen sulfide;
An adsorbent layer of an adsorbent for adsorbing hydrogen sulfide, disposed on the upstream side of the preceding reactor and disposed on the downstream side of the catalyst layer of the hydrogenation catalyst. Gas processing equipment.
The pre-stage reactor includes a first methanation reactor and a second methanation reactor provided on the downstream side of the first methanation reactor,
A first hydrogen supply path for supplying hydrogen to the inlet side of the first methanation reactor; and a second hydrogen supply path for supplying hydrogen to the 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 preceding reactor,
2. The natural gas processing apparatus according to claim 1, further comprising a pretreatment hydrogen supply passage for supplying hydrogen to an inlet side of the pretreatment reactor.
The pretreatment reactor includes a hydrogenation reactor in which a catalyst layer of the hydrogenation catalyst is disposed, and an adsorptive desulfurization reactor in which the adsorbent layer is disposed on the downstream side of the hydrogenation reactor. The natural gas processing apparatus according to claim 1, comprising:
The carbonyl sulfide removal portion 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.