JP2022140290A - Removal method of sulfur oxide in gas with carbon dioxide as main component - Google Patents

Abstract

To establish a technology which uses carbon dioxide contained in fuel gas and economically removes sulfur dioxide that is contained in fuel gas and becomes catalytic poison of the methanation catalyst or methanol synthesis catalyst while suppressing methanation of carbon dioxide when obtaining methane or methanol by reacting carbon dioxide with hydrogen.SOLUTION: A method for removing sulfur oxide in gas to be treated containing sulfur oxide with carbon dioxide as a main component fixes sulfur to a desulfurizing agent as a sulfide and removes it by adding hydrogen to the gas to be treated, obtaining hydrogen added gas to be treated, and then bringing the hydrogen added gas to be treated into contact with the desulfurizing agent containing Ni, Cu, and Zn.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for removing sulfur oxides in gas containing carbon dioxide as a main component.

BACKGROUND ART In recent years, from the viewpoint of global warming countermeasures, it is required to suppress the emission of carbon dioxide. As technologies for recovering carbon dioxide from flue gas generated in thermal power generation and industrial processes, there are already industrially established techniques such as the amine absorption method and the physical absorption method. Investigations are underway to store the recovered carbon dioxide by injecting it into the ground, and a series of processes from recovery to storage is called carbon dioxide capture and storage (CCS) technology. Under certain preconditions, CCS is expected to be cost competitive as a low-carbon technology.

Instead of storing the recovered carbon dioxide, it is being considered to use it for producing valuable materials, and the development of carbon dioxide recovery and utilization (CCU) technology is also underway. Examples of valuables are methane and methanol. Since a large market has been formed for these as fuels, etc., it can be said that they are promising applications for the recovered carbon dioxide. Methane and methanol can be obtained by recovering carbon dioxide from flue gas and reacting it with hydrogen obtained by electrolysis using electricity from renewable energy sources such as solar power and wind power. Methane and methanol obtained by this method do not generate additional carbon dioxide even if they are used for combustion, so they can be considered as fuels that do not affect global warming.

The reaction (equation 1) to obtain methane from carbon dioxide and hydrogen is known.
_CO2 + _4H2- >CH4 _{+ 2H2O} (formula 1)

In Patent Document 1, when a gas containing CO and H ₂ is methanated, a methanation reactor in which a Cu—Zn-based low temperature shift catalyst is arranged on the upstream side and a methanation catalyst is arranged on the downstream side is used. A method for the methanation of gases containing CO and H ₂ is disclosed, characterized by: Since the CO shift reaction (equation 2) proceeds in the upstream low temperature shift reactor, most of the carbon monoxide reacts with water vapor and is converted to carbon dioxide by the low temperature shift catalyst. It is considered that the methanation reaction is progressing.
CO+ _H2O → _CO2 +H2 (formula ₂ )

The methanation reaction has long been used for the purpose of removing carbon monoxide and carbon dioxide from hydrogen for ammonia synthesis, and it is known that catalysts supporting Ni or Ru exhibit high activity (non-patent literature 1, 2).

Also known is a process for obtaining methane by reaction of carbon dioxide recovered from flue gas with hydrogen.

US Pat. No. 5,300,003 discloses a carbon-fuel-burning power station, more particularly a carbon-gas-burning power station, with an associated water/steam circuit, resulting from, more particularly diversion from, the power station flue gas. in a methanation process comprising the conversion of carbon dioxide produced or obtained, more particularly carbon dioxide gas, to methane in a methanation plant as waste heat in the conversion of carbon dioxide to methane in said methanation plant The resulting thermal energy is at least partially extracted into at least one material stream and/or thermal energy stream, which is fed into the steam generator of said power station on the burner side. Carbon dioxide off-gas treatment or carbon dioxide treatment connected to at least one medium flowing into the combustion chamber, to the water/steam circuit of the power station, upstream of the methanation plant in terms of process engineering, more particularly: A methanation process is disclosed which is characterized by being supplied, at least in part, to a power station flue gas treatment plant and/or to one or more stages of operation of an attached industrial plant.

Patent Document 3 discloses a first methanation reaction step for producing methane from a gas containing CO ₂ and H ₂ using a methanation catalyst, and a second methanation reaction step for producing methane from substances remaining in the first methanation reaction step. a two-methanation reaction step, and a change in the reactant gas flowing into the first methanation reaction step so that the first methanation reaction step approaches a chemical equilibrium state according to fluctuations in the reactant gas flowing into the first reaction step; a bypass step for partially bypassing and flowing into the second methanation reaction step.

These are attempts to improve the energy efficiency and controllability in the process of obtaining methane through the reaction of carbon dioxide recovered from flue gas with hydrogen.

Methanol is generally produced by the reaction of carbon monoxide and hydrogen (Equation 3), but from the perspective of CCU, attempts have also been made to obtain methanol by the reaction of carbon dioxide and hydrogen, and some catalysts have It has been shown to be highly active in reactions (Patent Documents 4 and 5).
CO+2H2→ _CH3OH (Equation ₃ )
_CO2 +3H2-> _{CH3OH + H2O} (equation 4)

As described above, catalysts and reaction conditions for synthesizing methane and methanol by reaction of carbon dioxide and hydrogen are known. On the other hand, the effects of trace components contained in carbon dioxide recovered from flue gas and how to avoid them have not been clarified sufficiently.

Carbon-containing fuels such as coal and biomass usually contain sulfur. This sulfur content changes into sulfur oxides (sulfur dioxide and sulfur trioxide) as it burns. In the chemical absorption method and the solid absorption method, sulfur oxides are also absorbed by the absorbing liquid or absorbent, but part of it is released when the carbon dioxide is released from the absorbing liquid or absorbent. Therefore, the separated carbon dioxide contains a small amount of sulfur oxides. In Non-Patent Document 3, in the separation of carbon dioxide from the exhaust gas of a coal-fired power plant, when carbon dioxide is separated by a chemical absorption method using an amine from the exhaust gas after desulfurization of the exhaust gas to reduce the sulfur dioxide concentration to 10 ppm. , the concentration of sulfur dioxide contained in the separated carbon dioxide is estimated to be 34-135 ppm.

As described above, catalysts containing Ni or Ru as active components are used as methanation catalysts, but they have the problem of being very susceptible to sulfur poisoning. A catalyst containing copper as a main active component is mainly used as a methanol synthesis catalyst, but it is also strongly poisoned by sulfur.

Catalysts containing Ni or Ru as active components are widely used not only for methanation, but also for steam reforming reaction, which is the reverse reaction of methanation. Sulfur poisoning is a serious problem even in steam reforming reactions, and various methods for desulfurization of hydrocarbons are therefore being investigated.

For example, in Patent Document 6, a high-order desulfurization agent obtained by hydrogen reduction of a copper oxide-zinc oxide-aluminum oxide mixture prepared by a coprecipitation method using a copper compound, a zinc compound, and an aluminum compound as raw materials is used. It is indicated that the sulfur content in the hydrocarbon can be reduced to 5 ppb or less by this.

In Patent Document 7, regarding the desulfurization of a hydrocarbon raw material, a mixture containing a copper compound and a zinc compound is mixed with an aqueous solution of an alkaline substance to produce a precipitate, the obtained precipitate is calcined, and a copper oxide-zinc oxide mixture is prepared. After obtaining the molded article, the molded article is impregnated with iron and / or nickel, and further baked. It has been shown to have excellent desulfurization performance.

In Patent Document 8, regarding desulfurization of hydrocarbon raw materials, a gas desulfurization agent containing zinc oxide, aluminum oxide and copper, and further containing cobalt and ruthenium, has better desulfurization performance than the desulfurization agent described in Patent Document 6. It has been shown to be superior to Patent Document 9 discloses desulfurization of a gas containing zinc oxide, aluminum oxide and copper, and further containing 1.0% to 10% by mass of nickel and 0.1% to 1.0% by mass of ruthenium. It is shown that the desulfurization agent is superior in desulfurization performance to the desulfurization agent described in Patent Document 6.

Sulfur components contained in hydrocarbons are hydrogen sulfide and organic sulfur compounds such as thiols and sulfides, and generally do not contain sulfur dioxide. In some cases, carbon dioxide is separated from methane fermentation gas and coal and biomass gasification gas, but the sulfur compounds contained in such gases are also hydrogen sulfide, COS, and organic sulfur compounds, and sulfur dioxide is Not usually included.

Patent Document 10 describes a method for producing methane from carbon dioxide containing sulfur oxides (SOx), in which a mixed gas generating step of mixing carbon dioxide containing 20 ppm or less of sulfur oxides and hydrogen as a reducing agent; and a methane generation step of reducing the mixed gas obtained in the mixed gas generation step at a low temperature using a hydrogen reduction catalyst in which nanoparticles are dispersedly supported on the surface of a powdery carrier. , a method for producing methane from carbon dioxide containing sulfur oxides is shown.

In this document, when carbon dioxide is reacted with hydrogen using a catalyst to produce methane, sulfur oxides contained in carbon dioxide significantly lower the catalytic activity, specifically the SOx concentration of carbon dioxide. It has been shown that the catalyst deactivates in a few hours in the region where is above 20 ppm, for example when carbon dioxide contains 60 ppm SOx.

Patent Document 11 describes a process of contacting combustion exhaust gas with a carbon dioxide absorbent to absorb carbon dioxide in the combustion exhaust gas, and heating the carbon dioxide absorbent that has absorbed carbon dioxide to produce a gas mainly composed of carbon dioxide. and a step of removing sulfur compounds in the gas by passing a gas obtained by adding a first amount of hydrogen to a gas containing carbon dioxide as a main component through a desulfurizer filled with a desulfurizing agent, and sulfur compounds A process for the methanation of carbon dioxide in flue gas is presented by adding a second amount of hydrogen to the gas that has undergone the step of removing the carbon dioxide, passing it through a methanation catalyst and converting it to methane by a methanation reaction.

This document describes that a desulfurization agent containing at least one component metal or oxide of iron, nickel, cobalt and copper and zinc oxide is preferable, and that when desulfurizing carbon dioxide, hydrogen is used for carbon dioxide. is divided and added, first a small amount of hydrogen is added to perform desulfurization, and hydrogen necessary to complete the methanation reaction is added to the desulfurized carbon dioxide to perform the methanation reaction, It is described that an unexpected methanation progress on the desulfurization agent can be avoided. However, specific desulfurization performance of each desulfurization agent is not specified.

A cobalt-molybdenum/alumina catalyst used in petroleum hydrodesulfurization has also been reported to reduce sulfur dioxide with hydrogen to obtain sulfur (Non-Patent Document 3). It has been shown that sulfur oxides can be reduced to sulfur and hydrogen sulfide at a relatively low temperature of about 300°C. There is a need. In addition, the performance of reducing sulfur oxides in a gas containing carbon dioxide as a main component is also unclear.

Patent Document 12 discloses a method for desulfurizing carbon dioxide containing sulfur oxides, in which hydrogen is added to a gas to be treated containing carbon dioxide as a main component and containing sulfur oxides, and then the gas is brought into contact with a desulfurizing agent containing copper. there is As the desulfurizing agent, a desulfurizing agent containing copper and alumina and a desulfurizing agent containing copper, alumina and zinc oxide are disclosed, including cobalt-molybdenum/alumina catalysts and nickel-molybdenum/alumina catalysts used for hydrodesulfurization of petroleum. It has been shown to have desulfurization performance even under conditions where it exhibits little significant desulfurization performance.

When the desulfurizing agent described in Patent Document 12 is used, sulfur oxides in carbon dioxide can be reduced to the ppb level. However, at a lower temperature, for example, a temperature lower than 300 ° C., the desulfurization performance decreases and the sulfur adsorption capacity is limited, so replacement is required after a certain operating time. A high-performance desulfurization agent that exhibits sufficient desulfurization performance and can adsorb a larger amount of sulfur has been desired.

As described above, with regard to desulfurization of hydrocarbon raw materials, it is known that adding ruthenium, nickel, cobalt, iron, etc. to a copper-zinc desulfurizing agent improves the desulfurization performance. Cobalt and iron have a relatively high activity for hydrogenation (methanation) of carbon oxides (carbon monoxide and carbon dioxide) (Non-Patent Documents 4 and 5), so hydrogen is added to the gas to be treated to produce dioxide. When removing sulfur, if the gas to be treated contains a large amount of carbon dioxide, there is a concern that the hydrogenation of carbon dioxide will rapidly progress.

JP-A-60-235893 Japanese Patent Publication No. 2016-531973 JP 2018-135283 A JP-A-3-258738 JP-A-7-39755 JP-A-1-123628 JP-A-11-61154 JP 2018-199126 A WO2018/216555 JP 2020-19751 A JP 2019-172595 A JP 2020-127935 A

Edited by the Japan Society of Chemical Engineers, Chemical Process Collection, 1970, p. 153 Catalysis Society of Japan, Catalysis Handbook, 2008, p. 535 Paik and Chung, Applied Catalysis B: Environmental, Vol. 5, 1995, p. 233-243 Seglin, Geosits, Franko and Gruber, Methanation of Synthesis Gas, 1975, p. 1-30 Younas, Kong, Bashir, Nadeem, Shehzad and Sethupathi, Energy and Fuels, Vol. 30, 2016, p. 8815-8831

In view of the above problems, the problem to be solved by the present invention is to use the carbon dioxide contained in the flue gas to react with hydrogen to obtain methane or methanol. It is to establish a technology for economically removing sulfur oxides, which are poisonous to methanation catalysts or methanol synthesis catalysts, while suppressing the methanation of carbon dioxide.

In order to solve the above problems, the present invention provides a method for removing sulfur oxides from a gas to be treated containing carbon dioxide as a main component and containing sulfur oxides, comprising adding hydrogen to the gas to be treated. and a desulfurization step of contacting the hydrogenated gas with a desulfurizing agent containing nickel, copper and zinc.

According to this configuration, the sulfur oxides in the gas containing carbon dioxide as a main component and containing sulfur oxides separated from the combustion exhaust gas are treated with the desulfurizing agent, and carbon dioxide substantially free of sulfur compounds is obtained. , sulfur poisoning of the methanation catalyst is likely to be prevented. Since the input of energy to the desulfurization reaction is substantially unnecessary, methanation with excellent efficiency and economy is possible.

In the above invention, it is preferable that the nickel content of the desulfurizing agent is 4.5% by mass or more and 9% by mass or less, because particularly high desulfurization performance can be ensured while suppressing methanation, which is a side reaction.

In the above invention, when the hydrogen concentration in the gas to be hydrogenated is 0.5% by volume or more and 2% by volume or less, it is preferable because sufficient desulfurization performance can be secured and methanation, which is a side reaction, can be suppressed. .

Further, in the above invention, it is preferable that the temperature of the desulfurizing agent is 250° C. or more and 300° C. or less in the desulfurization step, because sufficient desulfurization performance can be ensured and methanation, which is a side reaction, can be suppressed. In addition, since the above-mentioned temperature range matches the temperature range suitable as the inlet temperature of the methanation or methanol synthesis reaction, the treated gas can be directly subjected to the methanation or methanol synthesis reaction without heating or cooling. can be done.

According to the above configuration, when carbon dioxide contained in the combustion exhaust gas is used to react with hydrogen to obtain methane or methanol, it is contained in the combustion exhaust gas and becomes a catalyst poison for the methanation catalyst or the methanol synthesis catalyst. Sulfur oxides can be economically removed while suppressing the methanation of carbon dioxide.

FIG. 2 is a diagram showing an example of a flow of producing methane using carbon dioxide recovered from flue gas using the method of removing sulfur oxides in the gas to be treated according to the present invention.

Hereinafter, an embodiment of a method (desulfurization method) for removing sulfur oxides in a gas to be treated containing carbon dioxide as a main component and containing sulfur oxides according to the present invention will be described. In the specification, claims, and abstract of the present application, the term "main component" refers to the component with the highest volume concentration in the mixed gas, and in particular, the mixed gas contains 50% by volume or more. It refers to the ingredients that can be

The gas to be treated, which is mainly composed of carbon dioxide and contains sulfur oxides, which is the object of the present invention, is not limited to this, but is a chemical absorption method using a solvent such as amine, which is a known carbon dioxide separation method. Carbon dioxide is a gas mainly composed of carbon dioxide separated from flue gas using a solid absorption method or a physical absorption method. In addition, it may be a gas after cooling the combustion exhaust gas obtained by the oxygen combustion method in which the fuel is burned with oxygen instead of air, and condensing and separating at least part of the water vapor. These carbon dioxide main component gases contain sulfur oxides of 0.1 ppm or more and 100 ppm or less (on a volume basis, the same shall apply hereinafter), although the degree varies depending on the combusted fuel and the carbon dioxide separation method. Sulfur oxides are mostly sulfur dioxide and may also include sulfur trioxide.

Nitrogen, oxygen, water vapor and nitrogen oxides may also be included in the carbon dioxide base gas. Of these, nitrogen does not affect the desulfurization method of the present invention. Oxygen and nitrogen oxides react with hydrogen on the desulfurization agent to generate water vapor and nitrogen. Since heat is generated, it is preferable to operate the carbon dioxide separation equipment so that the concentration is preferably 1% or less, more preferably 0.1% or less. If the concentration of water vapor is too high, it oxidizes and inactivates the desulfurizing agent. Therefore, it is preferable to operate the carbon dioxide separation facility so that the concentration is preferably 20% or less, more preferably 10% or less. On the other hand, when the water vapor concentration is low, hydrogen is consumed by the reverse shift reaction (Equation 5) to produce carbon monoxide, which may reduce the desulfurization performance.
_CO2 +H2→CO _{+ H2O} (equation 5)

The water vapor concentration is preferably 1% or more, more preferably 3% or more. A carbon dioxide main component gas obtained by a conventional carbon dioxide separation method contains several percent of water vapor unless it is cryogenically separated, but the desulfurization method of the present invention can suitably treat such gas.

In the desulfurization method of the present invention, hydrogen is added to the gas to be treated. Although the mechanism of sulfur removal in the desulfurization method of the present invention is not clear, it is presumed to be due to the following mechanism.
SO2+ _3H2- > _{H2S + 2H2O} (equation 6)
ZnO+ _H2S → ZnS+ _H2O (Formula 7)
2Cu _{+ H2S} →Cu2S+H2 ₍ equation 8)

First, sulfur dioxide is reduced to hydrogen sulfide on metal Cu, which serves as a catalytic active site (Equation 6). The produced hydrogen sulfide then reacts with zinc oxide and metallic Cu to form zinc sulfide and copper sulfide, respectively, and the sulfur is fixed in the desulfurizing agent (equations 7, 8). If the sulfur oxide is sulfur trioxide, more hydrogen is required, but basically the same mechanism is presumed. Although the action of nickel is not clear, it is presumed that it exists as metallic Ni on the desulfurizing agent and acts as a co-catalyst for Cu that reduces sulfur dioxide to hydrogen sulfide.

If the nickel content of the desulfurization agent is too low, the action as a co-catalyst may be insufficient, and sufficient desulfurization performance may not be obtained. On the other hand, if the nickel content of the desulfurizing agent is too high, it will cover Cu, which is an essential active site, and inhibit its action, so there is a possibility that sufficient desulfurization performance cannot be obtained. When the nickel content of the desulfurizing agent is 3% by mass or more and 12% by mass, it is easy to obtain high desulfurization performance while suppressing methanation, and when it is 4.5% by mass or more and 9% by mass or less, particularly high desulfurization This is more preferable because performance can be ensured.

If the copper content of the desulfurization agent is too low, the catalytic action may be insufficient, and sufficient desulfurization performance may not be obtained. On the other hand, if the copper content of the desulfurizing agent is too high, the degree of dispersion of copper in a reduction-treated state prior to use may decrease, and desulfurization performance commensurate with the copper content may not be obtained. When the copper content of the desulfurizing agent is 20% by mass or more and 50% by mass or less, the reduction of sulfur dioxide to hydrogen sulfide tends to proceed, so that desulfurization performance is easily obtained. If there is, it is more preferable because a particularly high desulfurization performance can be secured.

If the zinc content of the desulfurizing agent is too low, the effect of trapping hydrogen sulfide generated by the reduction of sulfur dioxide may be insufficient, and sufficient desulfurizing performance may not be obtained. On the other hand, if the zinc content of the desulfurizing agent is too high, the specific surface area of zinc oxide may decrease, and desulfurization performance commensurate with the zinc content may not be obtained. When the zinc content of the desulfurizing agent is 20% by mass or more and 50% by mass or less, it becomes easy to trap hydrogen sulfide generated by the reduction of sulfur dioxide, so that desulfurization performance is easily obtained. It is more preferable if it is less than or equal to, since particularly high desulfurization performance can be ensured.

From the reaction mechanism described above, the molar ratio of hydrogen to sulfur oxides needs to be at least twice, but in reality, in order to maintain the reaction rate and the preferable copper reduction state, hydrogen is required in a large excess over the stoichiometric amount. is required. On the other hand, when the hydrogen concentration in the gas to be treated which is brought into contact with the desulfurizing agent is high, methanation and methanol synthesis reactions may proceed rapidly on the desulfurizing agent. Since both reactions are accompanied by a large amount of heat, the temperature of the desulfurizing agent rises sharply, which may damage the desulfurizing agent or the container, or cause the sulfur content to scatter from the desulfurizing agent. From the above viewpoints, the hydrogen concentration in the gas to be treated that is brought into contact with the desulfurizing agent is preferably 0.1% by volume or more and 5% by volume or less, more preferably 0.5% by volume or more and 2% by volume or less. . Hydrogen is added to the gas to be treated containing carbon dioxide as a main component and containing sulfur oxides so that the concentration of hydrogen in the hydrogenated gas to be treated with the desulfurizing agent is within the above range. Excess hydrogen will remain in the gas after the treatment, but when methanation and methanol synthesis reactions are carried out, hydrogen is further added to the gas after desulfurization and these reactions are carried out. Therefore, it is sufficient to adjust the amount of hydrogen to be added in the latter stage, and residual hydrogen is not a problem.

In the desulfurization method of the present invention, the gas to be treated to which hydrogen has been added as described above is brought into contact with a desulfurization agent containing nickel, copper and zinc. The desulfurizing agent may further contain aluminum.

The desulfurizing agent is, for example, a copper oxide-zinc oxide-aluminum oxide compact prepared by a coprecipitation method as described in Patent Document 6, and nickel by an impregnation method as described in Patent Document 7. It is obtained by carrying.

In the desulfurization agent containing nickel, copper and zinc prepared by the above method, copper is usually present as copper oxide (CuO or Cu ₂ O) and nickel is present as nickel oxide (NiO) at the stage of preparation. . In the desulfurization method of the present invention, in order for the desulfurization agent containing nickel, copper and zinc to exhibit its performance, copper and nickel must be in a metallic state. Therefore, desulfurizing agents must be reduced before use. Reduction of the desulfurizing agent is performed by maintaining the desulfurizing agent at a temperature of preferably 200° C. or higher and 400° C. or lower, more preferably 250° C. or higher and 350° C. or lower, and circulating a gas containing hydrogen. If the hydrogen concentration in the hydrogen-containing gas is too high, the copper will be reduced with a large amount of heat generation, which may promote the aggregation of copper. It is preferable to make it about 1 volume % or more and 10 volume % or less. The reduction time may be determined in consideration of the minimum amount of hydrogen required to reduce copper and nickel, but is preferably 1.5 times or more, preferably 3 times or more, the minimum amount of hydrogen required. It is preferable to carry out the heating over 1 hour or more and 3 hours or less.

(Example of application of the present invention)
An example of a methane production flow (FIG. 1) to which the method according to the present invention is applied will be described.

In the methane production flow shown in FIG. 1, methane is produced using combustion exhaust gas 101 containing carbon fuel, which is discharged from the thermal power plant 1, as a raw material. Flue gas 101 discharged from thermal power plant 1 is introduced into carbon dioxide separation facility 2 and separated into flue gas 201 from which carbon dioxide has been removed and gas 202 whose main component is carbon dioxide. The separated gas 202 mainly composed of carbon dioxide is introduced into the desulfurization equipment 3 .

In the desulfurization equipment 3, first, hydrogen 301 is added to a gas 202 mainly composed of carbon dioxide (example of gas to be treated), and gas 302 mainly composed of hydrogen-added carbon dioxide (hydrogenated (example of process gas) is obtained (example of hydrogenation step). A gas 302 containing carbon dioxide to which hydrogen has been added as a main component is preheated in the preheater 32 and then introduced into the desulfurizer 33 filled with a desulfurizing agent. In the desulfurizer 33, the hydrogen-added carbon dioxide-based gas 302 comes into contact with the desulfurizing agent containing nickel, copper, and zinc, and the sulfur is fixed to the desulfurizing agent as copper sulfide and zinc sulfide by the mechanism described above. (example of desulfurization process). Therefore, the desulfurizer 33 discharges a gas 303 mainly composed of carbon dioxide from which sulfur oxides have been removed. The gas 303 is introduced into the methanation facility 4 and subjected to a methanation reaction.

EXAMPLES The present invention will be described in more detail below based on examples and comparative examples, but the present invention is not limited to the following examples.

(Example 1)
45.0 g of a commercially available copper oxide-zinc oxide-aluminum oxide mixture molded body (manufactured by Süd-Chemie Catalysts, MDC-7, 3 mm tablet, CuO: 45% by mass, ZnO: 45% by mass, Al ₂ O ₃ : 6% by mass) 33 g of an aqueous solution in which nickel nitrate (containing 2.87 g of Ni) was dissolved was added dropwise, and impregnated for 3 hours.

After that, it was evaporated to dryness on a hot plate as a heater, dried overnight in a dryer set at 110°C, and then using a muffle furnace as a firing furnace at a heating rate of 2°C per minute in air. The temperature was raised to 300° C., sintered, and held at 300° C. for 1 hour. Then, a desulfurizing agent A containing 6% by mass of Ni was obtained.

Desulfurizing agent A (10 g) was filled in a glass tube with an inner diameter of 14 mm, maintained at 250 ° C., and a hydrogen-nitrogen mixed gas containing 2% hydrogen (by volume, the same applies hereinafter) was passed at a flow rate of 60 L per hour for 2 hours. made a refund. Next, while maintaining the desulfurizing agent temperature at 300 ° C., a gas consisting of 150 ppm sulfur dioxide-2% hydrogen-76% carbon dioxide-4% water vapor-balance nitrogen is circulated at a flow rate of 20 L per hour, and every 2 hours from the start of circulation. The desulfurization agent outlet gas was analyzed. Analysis was performed using a gas chromatograph with FPD detectors for hydrogen sulfide, sulfur dioxide, carbonyl sulfide (COS), methanethiol ₍ CH SH), FID detectors for methane, hydrogen, carbon monoxide and carbon dioxide. were detected with a TCD detector, respectively.

Table 1 shows the analysis results (analytical values on a dry base after removing moisture with an ice-cold trap, the same applies hereinafter). None of sulfur dioxide, hydrogen sulfide, carbonyl sulfide, and methanethiol was detected in the gas after desulfurization for 70 hours from the start of the flow of the sulfur dioxide-containing gas. Hydrogen was 1.0-1.1% and carbon monoxide was 0.7-0.8%. It is speculated that some of the hydrogen reacted with carbon dioxide to produce water and carbon monoxide due to the reverse shift reaction. In addition, the production of methane was also confirmed, but it was a very small amount (about 40 ppm).

－：検出されず（検出下限：硫黄化合物 ０．３ｐｐｂ、ＣＨ_４ ２ｐｐｍ）

-: Not detected (detection limit: sulfur compounds 0.3 ppb, CH ₄ 2 ppm)

(Example 2)
The desulfurization performance of the desulfurization agent A was evaluated in the same manner as in Example 1, except that the temperature of the desulfurization agent during the flow of the sulfur dioxide-containing gas was changed from 300°C to 275°C.

Table 2 shows the analysis results of the desulfurization agent outlet gas. None of sulfur dioxide, hydrogen sulfide, carbonyl sulfide, and methanethiol was detected in the desulfurized gas for 64 hours from the start of the flow of the sulfur dioxide-containing gas. Hydrogen was 1.4-1.5% and carbon monoxide was about 0.5%. It is presumed that part of the hydrogen reacted with carbon dioxide in the reverse shift reaction to produce water and carbon monoxide, but compared to Example 1, the reverse shift reaction was suppressed as the temperature decreased. . The production of methane was also confirmed, but the amount was very small (approximately 10 ppm).

－：検出されず（検出下限：硫黄化合物 ０．３ｐｐｂ、ＣＨ_４ ２ｐｐｍ）

-: Not detected (detection limit: sulfur compounds 0.3 ppb, CH ₄ 2 ppm)

(Example 3)
The desulfurization performance of the desulfurization agent A was evaluated in the same manner as in Example 1, except that the temperature of the desulfurization agent during the flow of the sulfur dioxide-containing gas was changed from 300°C to 250°C.

Table 3 shows the analysis results of the desulfurization agent outlet gas. None of sulfur dioxide, hydrogen sulfide, carbonyl sulfide, and methanethiol was detected in the desulfurized gas for 62 hours from the start of the flow of the sulfur dioxide-containing gas. Hydrogen was 1.5-1.6% and carbon monoxide was about 0.4%. No methane production was confirmed. As compared with Example 1, it can be seen that both the reverse shift reaction and the methanation reaction were suppressed as the temperature decreased.

－：検出されず（検出下限：硫黄化合物 ０．３ｐｐｂ、ＣＨ_４ ２ｐｐｍ）

-: Not detected (detection limit: sulfur compounds 0.3 ppb, CH ₄ 2 ppm)

(Comparative example 1)
Example 1 except that instead of desulfurizing agent A, 10 g of a commercially available copper oxide-zinc oxide-aluminum oxide mixture molding (manufactured by Süd-Chemie Catalysts, MDC-7, 3 mm tablet) (referred to as desulfurizing agent B) was used. Desulfurization performance at 300° C. was evaluated in the same manner as above.

Table 4 shows the analysis results of the desulfurization agent outlet gas. None of sulfur dioxide, hydrogen sulfide, carbonyl sulfide, and methanethiol was detected in the gas after desulfurization for 18 hours after the start of circulation of the sulfur dioxide-containing gas, but 0.32 ppm of sulfur dioxide was detected at 20 hours. rice field. Hydrogen was 1.3-1.4%, carbon monoxide was 0.6-0.7%, and no methane production was confirmed. Compared with Example 1, the breakthrough of sulfur compounds was observed in a short time.

－：検出されず（検出下限：硫黄化合物 ０．３ｐｐｂ、ＣＨ_４ ２ｐｐｍ）

-: Not detected (detection limit: sulfur compounds 0.3 ppb, CH ₄ 2 ppm)

(Comparative example 2)
The desulfurization performance of the desulfurizing agent B at 275°C was evaluated in the same manner as in Comparative Example 1, except that the temperature of the desulfurizing agent during the flow of the sulfur dioxide-containing gas was changed from 300°C to 275°C.

Table 5 shows the analysis results of the desulfurizing agent outlet gas. None of sulfur dioxide, hydrogen sulfide, carbonyl sulfide, and methanethiol was detected in the gas after desulfurization for 14 hours after the start of circulation of the sulfur dioxide-containing gas, but 0.32 ppm of sulfur dioxide was detected at 16 hours. rice field. Hydrogen was about 1.5%, carbon monoxide was about 0.6%, and no methane production was confirmed. In Comparative Example 2, the breakthrough of the sulfur compound was observed in a shorter time than in Comparative Example 1, and it became clear that with the desulfurizing agent B, the desulfurizing agent temperature has a large effect on the breakthrough time.

－：検出されず（検出下限：硫黄化合物 ０．３ｐｐｂ、ＣＨ_４ ２ｐｐｍ）

-: Not detected (detection limit: sulfur compounds 0.3 ppb, CH ₄ 2 ppm)

(Comparative Example 3)
The desulfurization performance of the desulfurizing agent B at 250°C was evaluated in the same manner as in Comparative Example 1, except that the temperature of the desulfurizing agent during the flow of the sulfur dioxide-containing gas was changed from 300°C to 250°C.

Table 6 shows the analysis results of the desulfurization agent outlet gas. None of sulfur dioxide, hydrogen sulfide, carbonyl sulfide, and methanethiol was detected in the post-desulfurization gas for 12 hours from the start of circulation of the sulfur dioxide-containing gas, but 0.23 ppm of sulfur dioxide was detected at 14 hours. rice field. Hydrogen was about 1.5%, carbon monoxide was about 0.6%, and no methane production was confirmed. In Comparative Example 3, even in comparison with Comparative Example 2, the sulfur compound was found to break through in a shorter time.

－：検出されず（検出下限：硫黄化合物 ０．３ｐｐｂ、ＣＨ_４ ２ｐｐｍ）

-: Not detected (detection limit: sulfur compounds 0.3 ppb, CH ₄ 2 ppm)

(Comparative Example 4)
30 g of an aqueous solution of iron (III) nitrate (containing 2.23 g of Fe) was added dropwise to 35.0 g of a commercially available molded copper oxide-zinc oxide-aluminum oxide mixture (manufactured by Süd-Chemie Catalyst Co., Ltd., MDC-7). , impregnated for 3 hours.

After that, it was evaporated to dryness on a hot plate as a heater, dried overnight in a dryer set at 110°C, and then using a muffle furnace as a firing furnace at a heating rate of 2°C per minute in air. The temperature was raised to 300° C., sintered, and held at 300° C. for 1 hour. Then, a desulfurizing agent C containing 6% by mass of Fe was obtained.

A glass tube having an inner diameter of 14 mm was filled with the desulfurizing agent C (10 g), kept at 250° C., and a hydrogen-nitrogen mixed gas containing 2% hydrogen was passed through at a flow rate of 60 L/h for 2 hours for reduction. Next, while maintaining the temperature of the desulfurizing agent at 250° C., a gas consisting of 150 ppm of sulfur dioxide, 2% hydrogen, 76% carbon dioxide, 4% water vapor, and the balance nitrogen is circulated at a flow rate of 20 L per hour, and every 2 hours from the start of circulation. The desulfurizing agent outlet gas was analyzed.

Table 7 shows the analysis results of the desulfurization agent outlet gas. None of sulfur dioxide, hydrogen sulfide, carbonyl sulfide, and methanethiol was detected in the post-desulfurization gas for 12 hours from the start of circulation of the sulfur dioxide-containing gas, but 0.27 ppm of sulfur dioxide was detected at 14 hours. rice field. Hydrogen was 1.6-1.7%, carbon monoxide was 0.2-0.3%, and no methane production was confirmed. When Comparative Example 4 was used, compared with the case of Comparative Example 3, the time required for the sulfur compound to break through did not change. In addition, in Comparative Example 4 in which Fe was introduced into the catalyst, although promotion of the methanation reaction was not observed, the desulfurization performance improvement effect seen in Example 1 in which Ni was introduced into the catalyst was not observed. It became clear.

－：検出されず（検出下限：硫黄化合物 ０．３ｐｐｂ、ＣＨ_４ ２ｐｐｍ）

-: Not detected (detection limit: sulfur compounds 0.3 ppb, CH ₄ 2 ppm)

(Comparative Example 5)
32 g of an aqueous solution of cobalt (II) nitrate (containing 2.87 g of Co) dissolved in 45.0 g of a commercially available copper oxide-zinc oxide-aluminum oxide mixture molded product (manufactured by Süd-Chemie Catalysts, MDC-7, 3 mm tablet). was added dropwise and impregnated for 3 hours.

After that, it was evaporated to dryness on a hot plate as a heater, dried overnight in a dryer set at 110°C, and then using a muffle furnace as a firing furnace at a heating rate of 2°C per minute in air. The temperature was raised to 300° C., sintered, and held at 300° C. for 1 hour. Then, a desulfurizing agent D containing 6% by mass of Co was obtained.

A glass tube having an inner diameter of 14 mm was filled with the desulfurizing agent D (10 g), maintained at 250° C., and a hydrogen-nitrogen mixed gas containing 2% hydrogen was passed through at a flow rate of 60 L/h for 2 hours for reduction. Next, while maintaining the temperature of the desulfurizing agent at 250° C., a gas consisting of 150 ppm of sulfur dioxide, 2% hydrogen, 76% carbon dioxide, 4% water vapor, and the balance nitrogen is circulated at a flow rate of 20 L per hour, and every 2 hours from the start of circulation. The desulfurizing agent outlet gas was analyzed.

Table 8 shows the analysis results of the desulfurizing agent outlet gas. None of sulfur dioxide, hydrogen sulfide, carbonyl sulfide, and methanethiol was detected in the desulfurized gas for 60 hours from the start of the flow of the sulfur dioxide-containing gas. Hydrogen was 1.6-1.7% and carbon monoxide was about 0.3%. Additionally, over 100 ppm of methane was identified.

Comparing Comparative Example 5 with Examples 3 and 3, in Comparative Example 5 in which Co was introduced into the catalyst, the effect of improving the desulfurization performance compared to Comparative Example 3 was the same as in Example 3 in which Ni was introduced into the catalyst. However, it was found that the methanation reaction was promoted more than in Example 3.

－：検出されず（検出下限：硫黄化合物 ０．３ｐｐｂ、ＣＨ_４ ２ｐｐｍ）

-: Not detected (detection limit: sulfur compounds 0.3 ppb, CH ₄ 2 ppm)

(Comparative Example 6)
14.2 g of hexaammineruthenium (III) chloride (containing 0.069 g of Ru) dissolved in 35.0 g of a commercially available copper oxide-zinc oxide-aluminum oxide mixture molding (manufactured by Süd-Chemie Catalysts, MDC-7). was added dropwise, and impregnated for 3 hours.

After that, it was evaporated to dryness on a hot plate as a heater, dried overnight in a dryer set at 110°C, and then using a muffle furnace as a firing furnace at a heating rate of 2°C per minute in air. The temperature was raised to 300° C., sintered, and held at 300° C. for 1 hour. Then, a desulfurizing agent E containing 0.2% by mass of Ru was obtained.

A glass tube having an inner diameter of 14 mm was filled with the desulfurizing agent E (10 g), maintained at 250° C., and a hydrogen-nitrogen mixed gas containing 2% hydrogen was passed through at a flow rate of 60 L/h for 2 hours for reduction. Next, while maintaining the temperature of the desulfurizing agent at 250° C., a gas consisting of 150 ppm of sulfur dioxide, 2% hydrogen, 76% carbon dioxide, 4% water vapor, and the balance nitrogen is circulated at a flow rate of 20 L per hour, and every 2 hours from the start of circulation. The desulfurizing agent outlet gas was analyzed.

Table 9 shows the analysis results of the desulfurization agent outlet gas. None of sulfur dioxide, hydrogen sulfide, carbonyl sulfide, and methanethiol was detected in the post-desulfurization gas for 16 hours from the start of circulation of the sulfur dioxide-containing gas, but 0.01 ppm of sulfur dioxide was detected at 18 hours. , the sulfur dioxide concentration continued to increase. Hydrogen was about 1.8% and carbon monoxide was about 0.3%. In the early stage after the sulfur dioxide-containing gas started to flow, about 10 ppm of methane was produced.

Comparing Comparative Example 6 with Example 3 and Comparative Example 3, in Comparative Example 6 in which Ru was introduced into the catalyst, the effect of improving the desulfurization performance compared to Comparative Example 3 was observed in the same manner as in Example 3. The effect was not as great as in Example 3 in which Ni was introduced into the catalyst. In addition, it was found that the methanation reaction was accelerated more than in Example 3.

－：検出されず（検出下限：硫黄化合物 ０．３ｐｐｂ、ＣＨ_４ ２ｐｐｍ）

-: Not detected (detection limit: sulfur compounds 0.3 ppb, CH ₄ 2 ppm)

(Example 4)
Desulfurizing agent A (10 g) was filled in a glass tube with an inner diameter of 14 mm, maintained at 250 ° C., and a hydrogen-nitrogen mixed gas containing 2% hydrogen (by volume, the same applies hereinafter) was passed at a flow rate of 60 L per hour for 2 hours. made a refund. Next, while maintaining the desulfurizing agent temperature at 250 ° C., a gas consisting of 250 ppm sulfur dioxide-2% hydrogen-76% carbon dioxide-4% water vapor-balance nitrogen is circulated at a flow rate of 20 L per hour, and every 2 hours from the start of circulation. The desulfurization agent outlet gas was analyzed.

Table 10 shows the analysis results of the desulfurization agent outlet gas. Neither sulfur dioxide, hydrogen sulfide, carbonyl sulfide, nor methanethiol was detected in the gas after desulfurization until 26 hours after the start of circulation of the sulfur dioxide-containing gas, but 0.01 ppm of sulfur dioxide was detected at 28 hours. and then the sulfur dioxide concentration gradually increased. Hydrogen was about 1.6% and carbon monoxide was 0.3%. About 10 ppm of methane was confirmed to be generated in the initial stage, but decreased with time.

－：検出されず（検出下限：硫黄化合物 ０．３ｐｐｂ、ＣＨ_４ ２ｐｐｍ）

-: Not detected (detection limit: sulfur compounds 0.3 ppb, CH ₄ 2 ppm)

(Comparative Example 7)
Desulfurization performance of desulfurization agent D at 250° C. was evaluated in the same manner as in Example 4, except that desulfurization agent D (10 g) was used instead of desulfurization agent A.

Table 11 shows the analysis results of the desulfurization agent outlet gas. None of sulfur dioxide, hydrogen sulfide, carbonyl sulfide, and methanethiol was detected in the post-desulfurization gas until 8 hours after the start of circulation of the sulfur dioxide-containing gas, but 0.01 ppm of sulfur dioxide was detected at 10 hours. and then the sulfur dioxide concentration gradually increased. Hydrogen was about 1.7% and carbon monoxide was 0.3%. Methane was generated in excess of 300 ppm in the initial stage, and was maintained at a high methanation activity of about 150 ppm even after 16 hours from the breakthrough of sulfur dioxide.

Comparing Comparative Example 7 with Example 4, in Example 4 in which Ni was supported on the molded copper oxide-zinc oxide-aluminum oxide mixture, the desulfurization performance could be significantly improved while suppressing methanation. On the other hand, in Comparative Example 7 in which Co was supported, the improvement in desulfurization performance was seen to some extent although inferior to Example 4, but the methanation activity was considerably high.

Since the progress of methanation on the desulfurization agent may cause irreversible deterioration of the desulfurization agent due to rapid heat generation on the desulfurization agent, the nickel, copper and zinc of the present invention, which have little risk of that, are included. It is clear that a desulfurization method using a desulfurization agent can more safely remove sulfur oxides in a carbon dioxide-based gas.

Incidentally, as shown in Non-Patent Documents 4 and 5, among Fe, Co, and Ni, Ni generally has the highest methanation activity. , the methanation activity of the desulfurizing agent containing nickel, copper and zinc of the present invention was significantly lower than that of the desulfurizing agent containing cobalt, copper and zinc. Although the reason is not necessarily clear, under the desulfurization conditions of the present invention, the methanation activity of Ni may be suppressed by the presence of Cu.

－：検出されず（検出下限：硫黄化合物 ０．３ｐｐｂ、ＣＨ_４ ２ｐｐｍ）

-: Not detected (detection limit: sulfur compounds 0.3 ppb, CH ₄ 2 ppm)

(Example 5)
45.0 g of a commercially available copper oxide-zinc oxide-aluminum oxide mixture molded body (manufactured by Süd-Chemie Catalysts, MDC-7, 3 mm tablet, CuO: 45% by mass, ZnO: 45% by mass, Al ₂ O ₃ : 6% by mass) 25 g of an aqueous solution in which nickel nitrate (containing 1.42 g of Ni) was dissolved was added dropwise, and impregnated for 3 hours.

Then, it is evaporated to dryness on a hot plate as a heater, dried for 1 hour in a dryer set at 110°C, and then using a muffle furnace as a firing furnace at a heating rate of 2°C per minute in air. The temperature was raised to 300° C., sintered, and held at 300° C. for 1 hour. Then, a desulfurizing agent F containing 3% by mass of Ni was obtained.

Desulfurization agent F (10 g) was filled in a glass tube with an inner diameter of 14 mm, maintained at 250 ° C., and a hydrogen-nitrogen mixed gas containing 2% hydrogen (by volume, the same applies hereinafter) was passed at a flow rate of 60 L per hour for 2 hours. made a refund. Next, while maintaining the temperature of the desulfurizing agent at 250° C., a gas consisting of 150 ppm of sulfur dioxide, 2% hydrogen, 76% carbon dioxide, 4% water vapor, and the balance nitrogen is circulated at a flow rate of 20 L per hour, and every 2 hours from the start of circulation. The desulfurizing agent outlet gas was analyzed.

Table 12 shows the analysis results of the desulfurization agent outlet gas. None of sulfur dioxide, hydrogen sulfide, carbonyl sulfide, and methanethiol was detected in the desulfurized gas for 8 hours after the start of the flow of the sulfur dioxide-containing gas. 0.02 ppm of sulfur dioxide was detected 10 hours after the start of the flow of the sulfur dioxide-containing gas. After that, the sulfur dioxide concentration gradually increased to 0.15 ppm after 20 hours. Hydrogen was about 1.7% and carbon monoxide was 0.30-0.35%. No methane production was confirmed.

Comparing Example 5 with Example 3, in Example 5, in which the desulfurizing agent had a low Ni content, sulfur compound breakthrough was observed in a relatively short time (10 hours), and desulfurization was performed stably for a long period of time. Therefore, it is preferable to set the Ni content of the desulfurizing agent to a certain level or more. On the other hand, when Example 5 is compared with Comparative Example 3, although a trace amount of sulfur compound breakthrough is slightly faster in Example 5, in Example 5, even 20 hours after the start of circulation of the sulfur dioxide-containing gas, The sulfur dioxide concentration in the gas after desulfurization is kept as low as 0.15 ppm, and the effect of Ni is clear.

－：検出されず（検出下限：硫黄化合物 ０．３ｐｐｂ、ＣＨ_４ ２ｐｐｍ）

-: Not detected (detection limit: sulfur compounds 0.3 ppb, CH ₄ 2 ppm)

(Example 6)
45.0 g of a commercially available copper oxide-zinc oxide-aluminum oxide mixture molded body (manufactured by Süd-Chemie Catalysts, MDC-7, 3 mm tablet, CuO: 45% by mass, ZnO: 45% by mass, Al ₂ O ₃ : 6% by mass) 29 g of an aqueous solution in which nickel nitrate (containing 2.18 g of Ni) was dissolved was added dropwise, and impregnated for 3 hours.

Then, it is evaporated to dryness on a hot plate as a heater, dried for 1 hour in a dryer set at 110°C, and then using a muffle furnace as a firing furnace at a heating rate of 2°C per minute in air. The temperature was raised to 300° C., sintered, and held at 300° C. for 1 hour. Then, a desulfurizing agent G containing 4.6% by mass of Ni was obtained.

Desulfurizing agent G (10 g) was filled in a glass tube with an inner diameter of 14 mm, maintained at 250 ° C., and a hydrogen-nitrogen mixed gas containing 2% hydrogen (by volume, the same applies hereinafter) was passed at a flow rate of 60 L per hour for 2 hours. made a refund. Next, while maintaining the temperature of the desulfurizing agent at 250° C., a gas consisting of 150 ppm of sulfur dioxide, 2% hydrogen, 76% carbon dioxide, 4% water vapor, and the balance nitrogen is circulated at a flow rate of 20 L per hour, and every 2 hours from the start of circulation. The desulfurizing agent outlet gas was analyzed.

Table 13 shows the analysis results of the desulfurization agent outlet gas. None of sulfur dioxide, hydrogen sulfide, carbonyl sulfide, and methanethiol was detected in the desulfurized gas for 60 hours from the start of the flow of the sulfur dioxide-containing gas. Hydrogen was 1.6-1.7% and carbon monoxide was about 0.3%. No methane production was confirmed. About 10 ppm of methane was confirmed to be generated in the initial stage, but decreased with time.

－：検出されず（検出下限：硫黄化合物 ０．３ｐｐｂ、ＣＨ_４ ２ｐｐｍ）

-: Not detected (detection limit: sulfur compounds 0.3 ppb, CH ₄ 2 ppm)

(Example 7)
Commercially available copper oxide-zinc oxide-aluminum oxide mixture molded body (MDC-7, 3 mm tablet, manufactured by Süd-Chemie Catalyst Co., Ltd., CuO: 45% by mass, ZnO: 45% by mass, Al ₂ O ₃ : 6% by mass) 45.1 g 41 g of an aqueous solution in which nickel nitrate (containing 4.57 as Ni) was dissolved was added dropwise, and impregnated for 3 hours.

Then, it is evaporated to dryness on a hot plate as a heater, dried for 1 hour in a dryer set at 110°C, and then using a muffle furnace as a firing furnace at a heating rate of 2°C per minute in air. The temperature was raised to 300° C., sintered, and held at 300° C. for 1 hour. Then, a desulfurizing agent H containing 9% by mass of Ni was obtained.

Desulfurization agent H (10 g) was filled in a glass tube with an inner diameter of 14 mm, maintained at 250 ° C., and a hydrogen-nitrogen mixed gas containing 2% hydrogen (by volume, the same applies hereinafter) was passed at a flow rate of 60 L per hour for 2 hours. made a refund. Next, while maintaining the temperature of the desulfurizing agent at 250° C., a gas consisting of 150 ppm of sulfur dioxide, 2% hydrogen, 76% carbon dioxide, 4% water vapor, and the balance nitrogen is circulated at a flow rate of 20 L per hour, and every 2 hours from the start of circulation. The desulfurization agent outlet gas was analyzed.

Table 14 shows the analysis results of the desulfurization agent outlet gas. None of sulfur dioxide, hydrogen sulfide, carbonyl sulfide, and methanethiol was detected in the desulfurized gas for 62 hours from the start of the flow of the sulfur dioxide-containing gas. Hydrogen was 1.7-1.8% and carbon monoxide was 0.29-0.35%. Methane was confirmed to be produced at 6 ppm in the beginning, but decreased over time.

－：検出されず（検出下限：硫黄化合物 ０．３ｐｐｂ、ＣＨ_４ ２ｐｐｍ）

-: Not detected (detection limit: sulfur compounds 0.3 ppb, CH ₄ 2 ppm)

(Example 8)
45.0 g of a commercially available copper oxide-zinc oxide-aluminum oxide mixture molded body (manufactured by Süd-Chemie Catalysts, MDC-7, 3 mm tablet, CuO: 45% by mass, ZnO: 45% by mass, Al ₂ O ₃ : 6% by mass) 49 g of an aqueous solution in which nickel nitrate (containing 6.28 g of Ni) was dissolved was added dropwise to the substrate, and impregnated for 3 hours.

After that, it was evaporated to dryness on a hot plate as a heater, dried overnight in a dryer set at 110°C, and then using a muffle furnace as a firing furnace at a heating rate of 2°C per minute in air. The temperature was raised to 300° C., sintered, and held at 300° C. for 1 hour. Then, a desulfurizing agent I containing 12% by mass of Ni was obtained.

Desulfurizing agent I (10 g) was filled in a glass tube with an inner diameter of 14 mm, maintained at 250 ° C., and a hydrogen-nitrogen mixed gas containing 2% hydrogen (by volume, the same applies hereinafter) was passed at a flow rate of 60 L per hour for 2 hours. made a refund. Next, while maintaining the temperature of the desulfurizing agent at 250° C., a gas consisting of 150 ppm of sulfur dioxide, 2% hydrogen, 76% carbon dioxide, 4% water vapor, and the balance nitrogen is circulated at a flow rate of 20 L per hour, and every 2 hours from the start of circulation. The desulfurization agent outlet gas was analyzed.

Table 15 shows the analysis results of the desulfurization agent outlet gas. None of sulfur dioxide, hydrogen sulfide, carbonyl sulfide, or methanethiol was detected in the gas after desulfurization until 18 hours after the start of circulation of the sulfur dioxide-containing gas, but 0.02 ppm of sulfur dioxide was detected at 20 hours. and then the sulfur dioxide concentration gradually increased. Hydrogen was 1.6-1.7% and carbon monoxide was about 0.3%. No methane production was confirmed.

－：検出されず（検出下限：硫黄化合物 ０．３ｐｐｂ、ＣＨ_４ ２ｐｐｍ）

-: Not detected (detection limit: sulfur compounds 0.3 ppb, CH ₄ 2 ppm)

Comparing the results of Examples 3 and 5 to 8, it can be seen that desulfurization performance is particularly high when the Ni content of the desulfurizing agent is in the range of 4.5 mass % to 9 mass %. When the Ni content of the desulfurizing agent was 3% by mass, the sulfur compound was found to break through in a shorter time than when it was in the range of 4.5% by mass to 9% by mass. It is presumed that the effect of Ni as a co-catalyst was lowered. On the other hand, even when the Ni content of the desulfurizing agent was 12% by mass, sulfur compounds were found to break through in a shorter time than when the content was within the range of 4.5% by mass to 9% by mass. It is presumed that this is because nickel covered Cu, which is an essential active site, and inhibited its action to some extent. From the above results, it is understood that there is a suitable range for the Ni content of the desulfurizing agent, and that 4.5% by mass to 9% by mass is particularly preferable.

(Comparative Example 8)
45.0 g of a commercially available copper oxide-zinc oxide-aluminum oxide mixture molded body (manufactured by Süd-Chemie Catalysts, MDC-7, 3 mm tablet, CuO: 45% by mass, ZnO: 45% by mass, Al ₂ O ₃ : 6% by mass) 25 g of an aqueous solution in which cobalt nitrate (containing 1.42 g of Co) was dissolved was added dropwise to the substrate, and impregnated for 3 hours.

After that, it was evaporated to dryness on a hot plate as a heater, dried overnight in a dryer set at 110°C, and then using a muffle furnace as a firing furnace at a heating rate of 2°C per minute in air. The temperature was raised to 300° C., sintered, and held at 300° C. for 1 hour. Then, a desulfurizing agent J containing 3% by mass of Co was obtained.

Desulfurization agent J (10 g) was filled in a glass tube with an inner diameter of 14 mm, maintained at 250 ° C., and a hydrogen-nitrogen mixed gas containing 2% hydrogen (by volume, the same applies hereinafter) was passed at a flow rate of 60 L per hour for 2 hours. made a refund. Next, while maintaining the temperature of the desulfurizing agent at 250° C., a gas consisting of 150 ppm of sulfur dioxide, 2% hydrogen, 76% carbon dioxide, 4% water vapor, and the balance nitrogen is circulated at a flow rate of 20 L per hour, and every 2 hours from the start of circulation. The desulfurizing agent outlet gas was analyzed.

Table 16 shows the analysis results of the desulfurizing agent outlet gas. None of sulfur dioxide, hydrogen sulfide, carbonyl sulfide, and methanethiol was detected in the desulfurized gas for 10 hours from the start of the flow of the sulfur dioxide-containing gas. 0.01 ppm of sulfur dioxide was detected 12 hours after the start of the flow of the sulfur dioxide-containing gas. The sulfur dioxide concentration gradually increased and reached 0.49 ppm after 18 hours. Hydrogen was about 1.5-1.8% and carbon monoxide was 0.2-0.7%. The methane concentration was 42 ppm at the initial stage and became 13 ppm after 18 hours.

Comparing Comparative Example 8 with Example 5, although a small amount of sulfur compound breakthrough was slightly faster in Example 5, in Example 5, even after 20 hours from the start of circulation of the sulfur dioxide-containing gas, the desulfurized gas was only 0.15 ppm, in Comparative Example 8, the sulfur dioxide concentration of the gas after desulfurization reached 0.49 ppm 18 hours after the start of circulation of the sulfur dioxide-containing gas, and Ni changed to Co It is clear that the same desulfurization performance cannot be obtained even if it is replaced with
Moreover, when the methane concentration of the gas after desulfurization is compared, the Co-containing desulfurizing agent J shows significant methane formation, and there is concern that the methanation reaction proceeds on the desulfurizing agent.

－：検出されず（検出下限：硫黄化合物 ０．３ｐｐｂ、ＣＨ_４ ２ｐｐｍ）

-: Not detected (detection limit: sulfur compounds 0.3 ppb, CH ₄ 2 ppm)

It should be noted that the configurations disclosed in the above embodiments (including other embodiments, the same shall apply hereinafter) can be applied in combination with configurations disclosed in other embodiments as long as there is no contradiction. The embodiments disclosed in this specification are exemplifications, and the embodiments of the present invention are not limited thereto, and can be modified as appropriate without departing from the scope of the present invention.

1: thermal power plant 2: carbon dioxide separation equipment 3: desulfurization equipment 4: methanation equipment 31: flow control valve 32: preheater 33: desulfurizer filled with desulfurizing agent 101: combustion exhaust gas of carbon-containing fuel 201: carbon dioxide 202: Gas mainly composed of carbon dioxide separated from flue gas 301: Hydrogen 302: Gas mainly composed of hydrogen-added carbon dioxide 303: Carbon dioxide from which sulfur oxides have been removed gas whose main component is

Claims (4)

A method for removing sulfur oxides in a gas to be treated containing carbon dioxide as a main component and containing sulfur oxides,
a hydrogenation step of adding hydrogen to the gas to be treated to obtain a hydrogenated gas to be treated;
and a desulfurization step of contacting the hydrogenated gas to be treated with a desulfurization agent containing nickel, copper and zinc. 2. The method according to claim 1, wherein the desulfurizing agent has a nickel content of 4.5% by mass or more and 9% by mass or less. 3. The method according to claim 1, wherein the hydrogen concentration in the gas to be hydrogenated is 0.5% by volume or more and 2% by volume or less. The method according to any one of claims 1 to 3, wherein in the desulfurization step, the temperature of the desulfurization agent is 250°C or higher and 300°C or lower.

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