JPH0441197B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method for synthesizing methane from coke oven gas and hydrocarbons.

[Background of the invention]

Conventional methods for producing fuel gas from a mixture of coke oven gas and hydrocarbons include, for example, hydrodesulfurizing coke oven gas using a catalyst system containing nickel and/or cobalt and molybdenum, and then mixing hydrocarbons. A method for synthesizing methane is known. For example, "Processes before the
Manufacturer of Natural Lugus
PROCESSES FOR
THE MANUFACTURE OF NATURAL−
GAS SUBSTITUTES) pp. 14-15, Gas Council Research Communication GC 155
GC155) Listed in November 1968. In addition, through two steps of hydrodesulfurization, one step hydrogenates dienes, oxygen, olefins, and sulfur compounds in coke oven gas, and the other step hydrogenates olefins and sulfur compounds in hydrocarbons. However, a method is known in which methane is synthesized by mixing purified coke oven gas and hydrocarbons, adding steam to the mixture, and performing steam reforming and methanation using a catalyst system containing nickel. However, these conventional methods have a problem in that the tar oil contained in the coke oven gas covers the catalytic active sites, significantly reducing the catalytic activity. Furthermore, there is a problem in that the dienes in the coke oven gas react with oxygen and nitrogen oxides, producing gummy substances that clog the inside of the catalyst layer and the piping system. Furthermore, since the inlet temperature in the methane synthesis process is low, it is difficult to maintain a thermal balance with respect to fluctuations in the supply of feedstock coke oven gas and hydrocarbon mixture, and comparative fluctuations in coke oven gas and hydrocarbon mixture, resulting in decreased catalyst activity and carbon precipitation. There were drawbacks that caused problems such as:

[Purpose of the invention]

The object of the present invention is to efficiently produce fuel gas by combining a process for removing tar oil, gum substances, dienes, oxygen, olefins, and sulfur compounds contained in coke oven gas and a methane synthesis process for synthesizing methane. The purpose is to provide a manufacturing method.

[Summary of the invention]

To summarize the present invention, the present invention deals with tar oil, gum substances, dienes, etc. contained in coke oven gas,
Oxygen, olefins, and sulfur compounds contained in hydrocarbons such as LPG or naphtha are removed, and methane-rich fuel gas is produced from a mixture of refined coke oven gas and hydrocarbons. a first and second adsorption step of bringing the coke oven gas into contact with a porous material to adsorb and remove the tar oil and gum materials; dienes remaining in the coke oven gas from the adsorption step; A first hydrogenation step in which oxygen and olefins are mainly hydrogenated, a second hydrogenation step in which the coke oven gas from the first hydrogenation step and the hydrogen carbonate are mixed and sulfur compounds in the mixture are hydrogenated; A hydrogen sulfide removal step of absorbing and removing hydrogen sulfide in the mixture from the second hydrogenation step, a step of dividing the mixture from the hydrogen sulfide removal step into a first methane synthesis step and a second methane synthesis step, and the separation step. A first methane synthesis step of producing methane by adding steam to the mixture obtained from the first methane synthesis step, a second methane synthesis step of producing methane from the product gas from the first methane synthesis step and the mixture from the branching step; A third methane synthesis step for increasing the methane concentration in the gas produced from the second methane synthesis step, and a step of removing water vapor and carbon dioxide from the gas produced from the third methane synthesis step. shall be.

Examples of porous materials (hereinafter abbreviated as adsorbents) used in the first and second adsorption steps include alumina, silica, zeolite, iron oxide, titania, magnesia, diatomaceous earth, calcium oxide, and zirconia. , activated carbon, and mixtures thereof. Particularly preferred are alumina, silica, and activated carbon.

The adsorbent has a BET surface area of 10 m ² /g or more,
Preferably it is in the range of 20m ² to 1000m ² /g. Pore volume is 0.10ml/g or more, preferably 0.15~
It is in the range of 0.60ml/g. The adsorbent is highly hygroscopic and adsorbs moisture in the air, reducing its adsorption performance. Therefore, before use, keep it at an appropriate temperature, preferably 300~300°C.
Drying at a temperature of 400°C is preferred. The temperature of adsorption performed using an adsorbent is in the range of room temperature to 300°C, preferably in the range of room temperature to 200°C.
Adsorption performance decreases when the temperature exceeds 300℃. The feed rate of coke oven gas to this adsorbent is preferably 100 to 10,000 h ^-1 in terms of space velocity. space velocity
If it is less than 100 h ^-1 , the amount of adsorbent used becomes large and it is not economical, and if it exceeds 10000 h ^-1 , the adsorption capacity decreases. The adsorption pressure may be 2 to 100 atmospheres, but is not particularly limited.

In the first hydrogenation step after adsorbing tar oil and gum substances, platinum metals such as platinum, ruthenium, rhodium, palladium,
It is preferable to use a catalyst containing at least one of osmium and iridium. These catalysts almost completely hydrogenate impurities such as dienes, oxygen, and olefins in coke oven gas.

The present inventors have confirmed through experiments that dienes contained in coke oven gas react with oxygen and nitrogen compounds to produce gum substances, which clog the catalyst layer and piping system and reduce catalyst activity. did.
In order to prevent the formation of this polymer, a first hydrogenation step was provided to hydrogenate dienes and oxygen, which cause clogging at low temperatures, before the step of mainly hydrogenating sulfur compounds. It was confirmed that the decrease in activity of the catalyst in the second hydrogenation step for hydrogenating sulfur compounds was also very small.

In the second hydrogenation step after the first hydrogenation step, nickel and/or cobalt and molybdenum are used as catalysts to hydrogenate the sulfur compounds in the coke oven gas and hydrocarbon mixture and the olefins remaining in the first hydrogenation step. It is preferred to use a catalyst containing. For example, catalysts having the _form NiO- _MoO3 - _Al2O3 , _CoO - _MoO3 - _Al2O3 are used. In normal use, it is preferable to use it after reducing it with hydrogen and sulfiding it with hydrogen sulfide, carbon disulfide, thiophene, etc. in order to increase the hydrodesulfurization activity and suppress the methanation reaction. A known method is used to remove hydrogen sulfide after the second hydrogenation step. for example
Solid adsorbents such as ZnO, Fe ₂ O ₃ and CuO are used.

In the first and second methane synthesis steps after the hydrogen sulfide removal step, nickel and/or cobalt-based catalysts are suitable as catalysts for adding steam to the coke oven gas and hydrocarbon mixture to produce methane-rich gas. These catalysts include, for example, Ni-Al ₂ O ₃ ,
There are Ni−MgO and NiO−La ₂ O ₃ −Al ₂ O ₃ . The purpose of the third methane synthesis step after the first and second methane synthesis steps is to further increase the methane concentration in the gas produced from the first and second methane synthesis steps, and the first catalyst for this purpose is , may be the same as that used in the second methane synthesis step.

The temperature of the hydrogenation reaction in the first hydrogenation step is 100~
350°C, preferably in the range of 150-300°C.

If the reaction temperature in the first hydrogenation step is less than 100° C., hydrogenation activity will not be sufficient and dienes and oxygen will flow from the first hydrogenation step to the second hydrogenation step.

The temperature of the hydrogenation reaction in the second hydrogenation step is 250℃
-450°C, preferably 300-410°C.
When the temperature exceeds 450°C, the methanation reaction of carbon monoxide and carbon dioxide gas progresses rapidly, the temperature of the catalyst layer increases significantly, and the catalyst becomes half-melted. 500
If the temperature exceeds 250°C, hydrocarbon decomposition may lead to carbon precipitation, and if the temperature is lower than 250°C, the hydrodesulfurization activity is insufficient. In order to particularly increase the hydrogenation activity of thiophene among sulfur compounds, the temperature is in the range of 300 to 410°C, preferably 350 to 410°C.

Oxygen in coke oven gas is 0.1 to 2.0% by volume,
contains, and when 1.0% by volume of oxygen reacts,
There is a temperature rise of 150℃. In order to suppress this reaction heat, the temperature rise in the catalyst layer may be monitored and a portion of the purified gas may be recirculated to dilute the oxygen and olefin concentrations at the inlet.

The present invention may include a step of circulating a part of the coke oven gas and hydrocarbon mixture purified in this manner to a stage before or after the adsorption step. By circulating the purified gas, the temperature of the hydrogenation reaction in the first hydrogenation step can be easily controlled. The amount of gas circulated at this time is preferably in the range of 10 to 100% of the raw material coke oven gas and hydrocarbon mixture. The amount of gas to be circulated is selected and adjusted within a range such that the temperature in the first hydrogenation step is kept below 350°C and the temperature in the second hydrogenation step is kept below 450°C.

The supply speed of the coke oven gas and hydrocarbon mixture in the first hydrogenation step and the second hydrogenation step is the space velocity (SV).
500 to 50000h ^-1 is preferable. Space velocity is 500h ^-1
If it is less than 50,000 h -1, the amount of catalyst used becomes large and becomes uneconomical, while if it exceeds 50,000 h ^-1 , the hydrogenation activity is not sufficient.

The pressure may be 2 to 100 atmospheres, but is not particularly limited.
The higher the pressure is, the higher the proportion of methanation reactions of carbon monoxide and carbon dioxide gas in the coke oven gas as side reactions.

The mixture of coke oven and hydrocarbons purified as described above is subjected to a methanation reaction.

The raw material coke oven gas and hydrocarbons are divided into a first methane synthesis step and a second methane synthesis step. The proportion of branching in the first methane synthesis step is suitably in the range of 50 to 100%.

The amount of water vapor added to the mixture of coke oven gas and hydrocarbons in the first methane synthesis step is 0.8 to 0.8% per weight of hydrocarbons in the mixture of coke oven gas and hydrocarbons.
It is 4.5. If it is less than 0.8, the temperature rise at the reactor outlet becomes large, causing a half-melting phenomenon in the catalyst, which may further lead to carbon precipitation. If it is 4.5 or more, the amount of steam used increases, which is not economical, and the methane concentration in the reaction product gas decreases, resulting in a decrease in thermal efficiency.

The methanation reaction temperature in the first methane synthesis step should be 230-550°C, preferably in the range of 350-500°C. If the methanation reaction temperature is below 230℃, the methanation activity will not be sufficient, and if it exceeds 550℃,
This may lead to half-melting of the catalyst and carbon deposition.

The feed rate of the mixture of coke oven gas and hydrocarbons in the first methane synthesis step (the weight of hydrocarbons in the mixture of coke oven gas and hydrocarbons passing per unit cross-sectional area) is 400 to 2000 g/cm ² h. A range is preferred. If it is less than 400 g/cm ² ·h, the amount of catalyst used becomes large and it is not economical. On the other hand, 1000g/
If it exceeds cm ² ·h, the methanation activity will not be sufficient.
The reaction pressure is not particularly limited, although it is carried out at 2 to 100 atmospheres.

In the second methane synthesis step after the first methane synthesis step, the produced gas after the first methane synthesis step is mixed with a mixture of coke oven gas and hydrocarbons, a part of which was diverted from the first methane synthesis step, and further methane synthesis step is performed. Increase concentration.

The splitting ratio of the coke oven gas and hydrocarbon mixture in the second methane synthesis step is suitably in the range of 50% to 0%.

The amount of unreacted water vapor after the first methane synthesis step is suitable for the water vapor added to the mixture of coke oven gas and hydrocarbons in the second methane synthesis step and the gas produced after the first methane synthesis step.

Supply rate of the mixture of coke oven gas and hydrocarbons in the second methane synthesis step and the produced gas after the first methane synthesis step (per unit cross-sectional area, hydrocarbons in the mixture of coke oven gas and hydrocarbons passing per unit time) weight) is suitably in the range of 400 to 2000 g/cm ² ·h.

The methanation reaction temperature in the second methane synthesis step should be 230-550°C, preferably in the range of 350-500°C. When the methanation reaction temperature is below 230℃,
If the methanation activity is not sufficient and the temperature exceeds 550℃,
This may lead to half-melting of the catalyst and carbon deposition.
The reaction pressure is carried out at 2 to 100 atmospheres, but is not particularly limited.

In the third methane synthesis step after the second methane synthesis step, the amount of unreacted water vapor in the second methane synthesis step is appropriate.

The feed rate of the product gas after the second methane synthesis step in the third methane synthesis step (the weight of hydrocarbons in the product gas after the second methane synthesis step that passes per unit time per unit cross-sectional area) is 400 to 4000 g/ ^cm2・h
A range of is appropriate.

The methanation reaction temperature in the third methane synthesis step is preferably in the range of 200 to 500°C, preferably 300 to 500°C. If the methanation reaction temperature is below 200°C, the methanation activity will not be sufficient, and if it exceeds 550°C, it may lead to half-melting of the catalyst and carbon precipitation. The reaction pressure may be in the range of 2 to 100 atmospheres, but is not particularly limited.

The generated gas after the third methane synthesis step is H ₂ ,
Although it contains CO ₂ , CH ₄ , and H ₂ O, CO ₂ can be removed by providing a decarboxylation step and H ₂ O by providing a dehydration step. The product gas thus obtained is composed of H ₂ and CH ₄ and can be used as city gas by providing a calorific value adjustment step of mixing LPG into the product gas.

Next, a process for carrying out the present invention will be specifically explained with reference to the drawings. FIG. 1 is a process diagram showing an embodiment of the present invention, in which 1 is a coke oven gas, 2 is a first adsorption tower, 3 is a bypass, 4 is a second adsorption tower, 5 is a first hydrogenation tower, 6 is a raw material hydrocarbon, 7 is a mixture of coke oven gas and hydrocarbons, 8 is a second hydrogenation tower, 10 is a hydrogen sulfide absorption tower, 11 is a first methane synthesis step branch line, 12 is a raw material steam, 13
is the second methane synthesis process branch line, 14 is the first methane synthesis process, 15 is the second methane synthesis process, 16
is the third methane synthesis step, 17 is the decarboxylation step, 18
19 is a hydrocarbon for controlling calorific value, and 20 is city gas. Moreover, FIG. 2 shows a process in the present invention showing an embodiment in which a part of the purified gas is recirculated to the inlet or outlet of the adsorption step, and 1 to 8 are the same as in FIG. 1, 9 means a circulation line. The drawings include only the main parts necessary for understanding the present invention, and other devices such as a circulator, a heating furnace, a cooler, a measuring device, a control device, and other devices are omitted.

[Embodiments of the invention]

Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited thereto.

Example 1 In FIG. 1, the coke oven gas 1 is about 150~
It is heated to a temperature of 200°C and introduced into the adsorption tower 2.
This adsorption tower 2 is filled with alumina having a BET surface area of 320 m ² /g and an average pore volume of 0.18 ml/g.
The composition of the main components of coke oven gas is H ₂ 53.25
%, CO 5.89%, CO ₂ 2.20%, CH ₄ 30.67%,
_C2H4 1.60% _{, C3H6} 1.60% _{, O2 0.5} %, _C4H6
0.10%, sulfur compounds 0.01%, _N2 4.18%, of which tar oil and gum substances are 10mg/
It was Nm ³ . The alumina in the adsorption tower 2 adsorbs and removes tar oil and gum substances in the coke oven gas. The tar oil content and gum substances in the gas at the outlet of the adsorption tower are 0.1 mg/Nm ³ or less, and more than 99.0% of the tar oil content and gum substances are adsorbed and removed. Adsorption tower 2
The gas composition (volume %) at the outlet is 53.25% _H2 , CO
5.89%, _CO2 2.20%, _{CH4 30.67} %, _C2H4
1.60%, _C3H6 1.60%, _O2 0.5 _% , _{C4H6 0.10}
%, sulfur compounds are 0.01%, and _N2 is 4.18%.

The gas discharged from the adsorption tower 2 is introduced into the first hydrogenation tower 5 at a temperature of about 150-200°C. The catalyst in the first hydrogenation column was an alumina carrier with 0.5% by weight of palladium supported. In the first hydrogenation tower, dienes, oxygen, and olefins in the coke oven gas are almost completely hydrogenated and removed. The gas composition (volume %) at the exit of hydrogenation tower 5 is 51.37% _H2 , 6.19% CO2, and 2.31 _% CO2.
%, _CH4 32.25%, _{C2H6 1.68} %, _{C3H8 1.68}
%, C ₄ H ₁₀ 0.11%, sulfur compounds 0.01%, N ₂
It is 4.40%.

The purified coke oven gas leaves the first hydrogenation column at a temperature of 320-370°C. In addition, using the process shown in Figure 2, the circulating gas 9 is adjusted to the amount of raw material coke oven gas.
By 100% circulation, the oxygen and olefins at the entrance of the adsorption tower are diluted, and the temperature of the first hydrogenation tower is 240°C.
Temperature adjusted to ~290. Furthermore, according to the present invention,
Providing an adsorption tower dramatically improved catalyst life. For example, if no adsorbent was provided, the catalyst would become unusable after about 1,000 hours, but the example of the present invention could be operated without any trouble for more than 4,000 hours. A raw material hydrocarbon is mixed with the generated gas to obtain a mixture of coke oven gas and hydrocarbon. A mixture of coke oven gas and hydrocarbons is heated to 320-350℃, and a second
It is supplied to the hydrogenation tower 8. In the second hydrogenation tower, the sulfur compounds remaining in the coke oven gas, the sulfur compounds in the hydrocarbons, and the olefins discharged from the first hydrogenation tower are completely hydrogenated.

The temperature of the second hydrogenation tower is about 350 to 380°C due to the methanation reaction of carbon monoxide and carbon dioxide, which is introduced into the hydrogen sulfide removal tower 10, where hydrogen sulfide in the mixture of coke oven gas and hydrocarbons is absorbed and removed. be done. The composition of the main components of the purified gas thus purified is 51.37% _H2 , 6.19% CO2, 2.31% _CO2 ,
_CH4 is 32.25%, _C2H6 is _1.68 %, _C3H8 is _1.68 %,
C ₄ H ₁₀ is 0.11% and N ₂ is 4.40%.

The mixture of purified coke oven gas and hydrocarbons is divided into a first distribution line 11 and a second distribution line 13 . The dividing ratio of the mixture of coke oven gas and hydrocarbons supplied to the first dividing line 11 is 70/30 between the first dividing line and the second dividing line. Raw material steam 12 is added to the thus divided mixture of coke oven gas and hydrocarbons. The steam addition ratio is such that the weight of _C4 hydrocarbons in the first branch coke oven gas and hydrocarbon mixture is 0.8-4.5. The mixture of coke oven gas, hydrocarbon mixture and steam is heated to a temperature of 350-400°C and introduced into the first methane synthesis stage 14. In the first methane synthesis step 14, a steam reforming reaction of CH ₄ , C ₄ H ₁₀ , C ₃ H ₈ , C ₂ H ₆ and other hydrocarbons in the coke oven gas and hydrocarbon mixture, and CO and CO ₂ The methanation reaction of H ₂ , CO , CO ₂ ,
_CH4 is produced. The composition of the generated gas (volume %) is
_H2 is 19.94%, CO is 0.32%, _CH4 is 64.87%, _CO2
is 12.05%, and _N2 is 2.82%.

The produced gas contains residual steam and produced steam and exits the first methane synthesis step 14 at a temperature of about 460-500°C. The gas exiting the first methane synthesis step 14 contains residual steam and produced steam, and is further mixed with the coke oven gas and hydrocarbon mixture from the second branch line, heated to a temperature of about 350 to 400°C, and then It is introduced into the methane synthesis step 15. In the second methane synthesis step 15, CH ₄ , C ₄ H ₁₀ , C ₃ H ₈ , C ₂ H ₆ , Steam reforming reactions of other hydrocarbons and CO and _CO2
The methanation reaction of H ₂ , CO,
CO ₂ and CH ₄ are generated. The composition of the produced gas is H ₂
is 14.1%, CO is 0.26%, _CO2 is 11.8%, _CH4 is
70.9%, _N2 is 3.0%. The produced gas contains residual steam and produced steam and exits the second methane synthesis step 15 at a temperature of about 460 to 500°C. The gas leaving the second methane synthesis step 15 contains residual steam and generated steam, and is introduced into the third methane synthesis step 16 at a temperature of about 250 to 320°C. In the third methane synthesis step 16, the methanation reaction of CO ₂ and CO in the produced gas containing the generated steam and residual steam from the second methane synthesis step proceeds, and the H ₂ , CO and CO ₂ concentrations decrease. Methane concentration increases. The composition of the produced gas is _H2
6.7%, CO 0.04%, CO ₂ 10.82%, CH ₄ 79.2
%, _N2 is 3.2%. The generated gas contains generated steam and residual steam, and is heated to a temperature of about 350 to 400℃.
Exit methane synthesis step 16. The generated gas is approximately 150 ~
It is cooled to a temperature of 100° C. and introduced into a decarboxylation step 17 to absorb and remove CO ₂ in the generated gas. The composition of the generated gas after removing _CO2 is 7.41% _H2 , 0.05% CO,
_CO2 is 1.0%, _CH4 is 87.9%, and _N2 is 3.2%.
The product gas after absorption and removal is introduced into a dehydration step 18 at a temperature of about 30° C. to completely remove moisture in the product gas. The gas after dehydration is used for heating at a temperature of approximately 150℃.
It is mixed with LPG 19 and becomes city gas 20.

〔Effect of the invention〕

As is clear from the above detailed description, according to the present invention, tar oil and gum substances in coke oven gas can be efficiently removed, and dienes, oxygen, olefins, and sulfur compounds contained in coke oven gas can be efficiently removed. First, the first hydrogenation catalyst can hydrogenate mainly dienes and oxygen at low temperature, and the second hydrogenation catalyst can hydrogenate the olefins and sulfur compounds remaining from the first hydrogenation catalyst, so diene polymerization is possible. This has the effect of suppressing the formation of gummy substances caused by methane synthesis and efficiently producing methane-rich fuel gas without poisoning the catalyst in the methane synthesis process after purification.

[Brief explanation of drawings]

FIG. 1 is a process diagram showing an embodiment of the present invention;
FIG. 2 is a process diagram showing an embodiment of the present invention in which a part of the purified gas is recirculated to the inlet and outlet of the adsorption step. 1... Coke oven gas, 2... First adsorption tower, 3
...Bypass, 4...Second adsorption tower, 5...First hydrogenation tower, 6...Hydrocarbon, 7...Coke oven gas and hydrocarbon mixture, 8...Second hydrogenation tower, 9... Circulation line, 10...Hydrogen sulfide absorption tower, 11...1st
Methane synthesis process branch line, 12... Raw material steam, 13... Second methane synthesis process branch line, 1
4...First methane synthesis step, 15...Second methane synthesis step, 16...Third methane synthesis step, 17...
...Decarboxylation process, 18...Dehydration process, 19...Hydrocarbon for adjusting calorific value, 20...Product gas.

Claims (1)

[Scope of Claims] 1. A method for producing fuel gas from coke oven gas and hydrocarbons containing at least tar oil, gum substances, dienes, oxygen, olefins, and sulfur compounds as impurities, an adsorption step in which the tar oil and the gum substance are adsorbed and removed by contact with a porous substance; a first hydrogenation step in which dienes, oxygen, and olefins in the gas that has passed through the adsorption step are hydrogenated; and the first water a second hydrogenation step of mixing the coke oven gas from the addition step with hydrocarbons and hydrogenating sulfur compounds in the mixture;
A hydrogen sulfide removal step in which hydrogen sulfide in the coke oven gas from the hydrogenation step is adsorbed and removed; a first methane synthesis step in which water vapor is added to the mixture of coke oven gas and hydrocarbons from the hydrogen sulfide removal step to synthesize methane; step, to the generated gas from the first methane synthesis step,
a second methane synthesis step in which methane is synthesized by splitting and mixing a portion of the coke oven gas and hydrocarbons; a third methane synthesis step in which methane is synthesized from the gas produced from the second methane synthesis step; A method for producing fuel gas, comprising the step of removing water vapor and carbon dioxide from the gas produced in the third methane synthesis step. 2 A part of the mixture of coke oven gas and hydrocarbons from the second hydrogenation step is recycled to the previous stage of the adsorption step, and the temperature in the first hydrogenation step is 350°C or higher and the temperature in the second hydrogenation step is The method for producing fuel gas according to claim 1, wherein the temperature is adjusted so as not to exceed 450°C. 3 A part of the mixture of coke oven gas and hydrocarbons from the second hydrogenation step is recirculated to the latter stage of the adsorption step so that the temperature in the first hydrogenation step is 350°C or less and the temperature in the second hydrogenation step. The method for producing fuel gas according to claim 1, characterized in that the temperature is adjusted so that the temperature does not exceed 450°C. 4. The fuel gas production method according to claim 2 or 3, wherein the amount of gas circulated is 10 to 100% of the amount of feedstock coke oven gas. 5. The method for producing fuel gas according to claim 1, wherein the inlet temperature of the first hydrogenation step is adjusted to a temperature within a range of 100 to 230°C. 6. The method for producing fuel gas according to claim 1, characterized in that the temperature in the adsorption step is adjusted to 300° C. or lower. 7. The feed ratio of raw material coke oven gas entering the first methane synthesis step and LPG or naphtha is 0.23 Kg/Nm ³ or more for coke oven to LPG, and 0.05 Kg/Nm ³ or more to naphtha. A method for producing fuel gas according to claim 1, characterized in that: 8. Claim 1, characterized in that the mixture of raw material coke oven gas and hydrocarbons entering the first methane synthesis step is 50% to 100% of the feed amount of raw material coke oven gas and hydrocarbons. The method for producing the fuel gas described. 9. Claim 1, characterized in that the mixture of raw material coke oven gas and hydrocarbons entering the second methane synthesis step is 0 to 50% of the feed amount of raw material coke oven gas and hydrocarbons. Method for producing fuel gas as described in section. 10. The method for producing fuel gas according to claim 1, characterized in that the inlet temperatures of the first methane synthesis step and the second methane synthesis step are adjusted to a range of 230 to 500°C.