JPS61188492A - Production of fuel oil - Google Patents

Abstract

PURPOSE:To produce a fuel gas with high efficiency by combining a process for removing a tar oil, a gun substance, dienes, oxygen, olefins and a sulfur compound and a process for synthesizing a methane. CONSTITUTION:A coke oven gas is brought into contact with a porous material to adsorb and remove a tar oil and a gummy substance contained therein. Dienes, oxygen and olefins contained in the treated gas are hydrogenated. The coke oven gas from the above step is mixed with a hydrocarbon to prepare a mixture, and the sulfur compound contained in the mixture is hydrogenated. The hydrogen sulfide contained in the treated gas from the above step is removed by adsorption. Steam is added to the gas from the above step comprising a mixture of a coke oven gas and a hydrocarbon to synthesize methane. The gas formed in the above step is mixed with a part of the coke oven gas and hydrocarbon to synthesize methane. Methane is synthesized from the gas formed in the above step. Steam and carbonic acid gas are removed from the gas formed in the above step to obtain an intended fuel gas.

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]

As a conventional method for producing fuel gas from a mixture of coke oven gas and hydrocarbons, for example, a method for synthesizing methane by mixing nickel hydrocarbons is known. For example r
PROcEssEs FORTHEMANUFACTU
RE OF NATURAL-G 5SUBSTI
TUTES J pages 14-15 Qas Council
Research Corymunication GC
155, November.

1968. In addition, in the two steps of hydrodesulfurization, dienes, oxygen,
Hydrogenating olefins and sulfur compounds, and in another step hydrogenating olefins and sulfur compounds in hydrocarbons, mixing purified coke oven gas and hydrocarbons, adding steam to the mixture, Methods of synthesizing methane by steam reforming and methanation using catalyst systems containing nickel are known. 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. In addition, there is a problem in that the dienes in the coke oven gas react with oxygen and nitrogen oxides, producing a gum-like substance and clogging 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 heat balance against fluctuations in the supply of feedstock coke oven gas and hydrocarbon mixture, and fluctuations in the ratio of 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 purpose 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 method.

[Summary of the invention]

To summarize the present invention, the present invention relates to tar oil, gum substances, and dienes 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. In the first method, the coke oven gas is brought into contact with a porous material to adsorb and remove the tar oil and gum material. a second adsorption step, a first step in which dienes, oxygen, and olefins remaining in the coke oven gas from the adsorption step are mainly hydrogenated;
a hydrogenation step, a second hydrogenation step of mixing the coke oven gas from the first hydrogenation step with the hydrocarbon and hydrogenating sulfur compounds in the mixture, and sulfurization in the mixture from the second hydrogenation step. A hydrogen sulfide removal step in which hydrogen is absorbed and removed, a step in which the mixture from the hydrogen sulfide removal step is divided into a first methane synthesis step and a second methane synthesis step, and a step in which water vapor is added to the mixture obtained from the separation step to produce methane. A first methane synthesis step for producing methane, a second methane synthesis step for producing methane from the mixture of the produced gas from the first methane synthesis step and the separation step, and a second methane synthesis step for producing methane from the mixture of the produced gas from the first methane synthesis step; a third methane synthesis step to increase methane concentration;
It is characterized by including a step of removing water vapor and carbon dioxide from the gas produced from the third methane synthesis step.

The first step is the 1st step. Examples of porous materials (hereinafter abbreviated as adsorbents) used in the second adsorption step include alumina, silica, zeolite, iron oxide, and titania.

Magnesia, diatomaceous earth, calcium oxide, zirconia,
There is one selected from the group consisting of activated carbon and mixtures thereof. Especially alumina, glue strength.

Activated carbon is preferred.

The adsorbent has a BET surface area of 10 m"/g or more, preferably in the range of 20 rr? to 1000 nI/g.

The pore volume is 0.10 mg/g or more, preferably 0.10 mg/g or more.
It is in the range of 15 to 0.60 d/H. The adsorbent is highly hygroscopic and adsorbs moisture in the air, reducing its adsorption performance. Therefore, the adsorbent should be kept at an appropriate temperature, preferably 300 to 400 C, before use.
It is preferable to dry at a temperature of . The temperature of adsorption performed using an adsorbent is in the range of room temperature to 300C, preferably in the range of room temperature to 200C. When the temperature exceeds 300C, the adsorption performance decreases. The coke oven gas supply rate to this adsorbent is 100 to 10,000 h-'1 in space velocity.
is suitable. If the space velocity is less than 100 b-1, the amount of adsorbent used will be large and it will be uneconomical to use 10 ρ.
If the pressure exceeds 00 h'', the adsorption capacity decreases.The pressure for adsorption may be from 2 to 100 atm, but is not particularly limited.

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

The present inventors have experimentally demonstrated 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. Confirmed.

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, NiOMOO3h120s',
Coo Mo5s! A catalyst having the 'hlzoρ form is 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 zn
Solid adsorbents such as O, Fetos, cu'o, etc. are used.

The first step after the hydrogen sulfide removal process. In the second methane synthesis step, a nickel and/or cobalt-based catalyst is suitable as a catalyst for adding steam to the coke oven gas and hydrocarbon mixture to produce methane-rich gas. These catalysts include, for example, N1-AtzOs.

There are Ni-MgO and N1O-La20s-AtzOs. 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 catalyst for this purpose is the third methane synthesis step. 1. It 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 to 350.
C, preferably in the range of 150 to 300t:'.

If the reaction temperature in the first hydrogenation step is less than 100 C, hydrogenation activity is insufficient and dienes and oxygen flow out from the first hydrogenation step to the second hydrogenation step.

The temperature of the hydrogenation reaction in the second hydrogenation step is 250C to 45C.
0C, preferably in the range of 300-410G. 45
If the temperature exceeds 0C, the methanation reaction of carbon monoxide and carbon dioxide gas will progress rapidly, and the temperature of the catalyst layer will rise rapidly.
Causes the half-melting phenomenon of the catalyst. Exceeding 500C may cause decomposition of hydrocarbons and carbon precipitation; 250C
If it is less than that, the hydrodesulfurization activity will not be sufficient. In order to particularly increase the hydrogenation activity of thiophene among sulfur compounds, 300~
410C, preferably in the range of 350-410C.

Coke oven gas contains oxygen at a volume of 0.1 to λO, and when oxygen reacts at a volume of 1.0, 150 tons
There is a temperature rise of ll'. In order to suppress this reaction heat, it is sufficient to monitor the temperature rise of the catalyst layer and recirculate a portion of the gas after fI production 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 10% of the raw material coke oven gas and hydrocarbon mixture.
It is preferably in the range of ~100%. 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 350C and the temperature in the second hydrogenation step is kept below 450C.

The supply rate of the coke oven gas and hydrocarbon mixture in the first hydrogenation step and the second hydrogenation step is 500 to 5 in space velocity (SV).
0.000 h" is preferable. If the space velocity is less than 500 h", the amount of catalyst used becomes large and becomes uneconomical.
On the other hand, if it exceeds so, oooh-t, hydrogenation activity is insufficient.

The pressure is preferably 2 to 100 atmospheres; it is not particularly limited.

・The higher the pressure, the higher the proportion of methanation reactions of carbon monoxide and carbon dioxide in 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 water vapor added to the mixture of coke oven gas and hydrocarbons in the first methane synthesis step has an fi of 0.8 to 4.5 per weight of hydrocarbons in the mixture of coke oven gas and hydrocarbons. 0
．． If it is less than 8, the temperature rise at the reactor outlet becomes large, causing the catalyst to be half-melted, and furthermore, to cause 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 is 230
-550C, preferably in the range of 350-500C. If the methanation reaction temperature is below 230C, the methanation activity will not be sufficient, and if it exceeds 550C, it may lead to half-melting of the catalyst and carbon precipitation.

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 through a unit cross-sectional area vehicle) is 4
The range of 00 to 2000g10+1-h is preferable. 40
Below 0 g/-h, the amount of catalyst used increases,
Not economical. On the other hand, if it exceeds 1000 g/cii-h, the methanation activity will not be sufficient. The reaction pressure is carried out at 2 to 100 atmospheres, but is not particularly limited.

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

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

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 400~
A range of 2000 g/-h is appropriate.

The methanation reaction temperature in the second methane synthesis step is 230
-550C, preferably in the range of 350-500C. If the methanation reaction temperature is below 230C, the methanation activity will not be sufficient, and if it exceeds 550C, it may lead to half-melting of the catalyst and carbon precipitation. The reaction pressure is 2~
Although it is carried out at 100 atmospheres, there is no particular limitation.

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

The supply 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. A range of /cn·h is appropriate.

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

The generated gas after the third methane synthesis step is H21CO2*
Although it contains CH4+ HaO, COz can be removed by providing a decarboxylation step and H20 by providing a dehydration step.

The product gas thus obtained consists of H2*CH4, 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 process diagram showing an embodiment of the present invention.
is a bypass, 4 is a second adsorption tower, 5 is a first hydrogenation tower, 6 is a feedstock 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 process branch line, 12 is raw material steam, 13 is a second methane synthesis process branch line, 14 is a first methane synthesis process, 15 is a A second methane synthesis step, 16 a third methane synthesis step, 17 a decarboxylation step, 18 a dehydration step, 19 a hydrocarbon for controlling calorific value, and 20 city gas. Also, the second
The figure shows a process in the present invention in which a part of the purified gas is recirculated to the inlet or outlet of the adsorption process, 1 to 8 are the same as in Figure 1, and 9 is the recirculation process. means line. The drawings include only the main parts necessary for understanding the present invention, and other parts such as a circulator, a heating furnace, and a cooler.

Measuring instruments, control devices, 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 to 200
It is heated to a temperature of C and introduced into the adsorption tower 2. This adsorption tower 2 has a BET surface area of 320 i/g and an average pore volume of 0.
Filled with 18d/g alumina. The composition of the main components of coke oven gas is H22>H53, 25%, CO 5.894, CO2 Ka120, CHa 30.67, C2H4 1.60, Cs Ha 1.60, 0
2 is 0.5, C4Ha is 0.10, and sulfur compounds are 0.
．． Section 01, N2 was 4.18%, and tar oil and gum substances therein were 10 mg/Nm3. Adsorption tower 2
Alumina adsorbs and removes tar oil and gum substances from 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' or less, 1), 99.
Glue oil and gum substances of 01 or higher are adsorbed and removed.

The gas composition (volume %) at the outlet of adsorption tower 2 is 53.25 H2.
1, CO is 5.89 yen, CO□ is 20 yen, CH-a
is 30.67%, Cx H4 is 1.60t, C5Ha is 1.60t, 02 is 0.5t, C4H8 is 0.101.
The sulfur compounds are o, oi, and N2 is 4.18'16.

The gas leaving the adsorption tower 2 is introduced into the first hydrogenation tower 5 at a temperature of about 150-2001:. The catalyst in the first hydrogenation column was an alumina carrier with 0.5% by weight of palladium supported thereon. In the first hydrogenation tower, dienes, oxygen, and olefins in the coke oven gas are almost completely hydrogenated and removed. Hydrogenation tower 5
The gas composition (capacity qIJ) at the outlet is as follows: H2 is 51.37 mm, CO is 6.19 mm, Cozy>:1311, CH4 is 3125%, C2Ha is 1.68 mm, Cs Hs is 1.
68, C4Hto is 0.11, and sulfur compounds are 0.
011, Nz is 4.401.

The purified coke oven gas leaves the first hydrogenation column at a temperature of 320-370C. By using the process shown in FIG. 2 and circulating the circulating gas 9 100 times per amount of raw material coke oven gas, the oxygen and olefins at the entrance of the adsorption tower are diluted, and the temperature of the first hydrogenation tower is 240°C. The temperature was adjusted to ~290°C. Furthermore, when an adsorption tower was provided according to the present invention, the catalyst life was dramatically improved. For example, if an adsorption tower is not installed, approximately 1
Although the catalyst became unusable after 1,000 hours, 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.

Mixture of coke oven gas and hydrocarbons at 320-350C
and is supplied to the second hydrogenation tower 8.

In the second hydrogenation tower, the sulfur compounds remaining in the coke oven gas and 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 380C due to the methanation reaction of carbon monoxide and carbon dioxide, and the hydrogen sulfide in the mixture of coke oven gas and hydrocarbons is introduced into the hydrogen sulfide removal tower 10. Absorbed and removed. The composition of the main components of the purified gas thus purified is 51.37% H2,
CO 6.19, COz 2.31%, CHa 3
2. ．． 25%, C2H6 is 1, 68%, C1Hs is 1
．． 684, C4HIG is 0.11, N2 is 464
It is 0 yen.

The mixture of coke oven gas and hydrocarbons is split into a first split line 11 and a second split line/13. 1st
The distribution ratio of the mixture of coke oven gas and hydrocarbons supplied to the distribution line 11 is 7 between the first distribution line and the second distribution line.
It is 0730. 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 mixture of first branch coke oven gas and hydrocarbons is 0.8 to 4.
It is 5. The mixture of coke oven gas, hydrocarbon mixture and steam is heated to a temperature of 350-400C and introduced into the first methane synthesis stage 14. In the first methane synthesis step 14, CH in the coke oven gas and hydrocarbon mixture is
4*C4H10*C5Hs +C2H6, the steam reforming reaction of other hydrocarbons and the methanation reaction of CO and CO2 proceed simultaneously to produce 1-I2, Co, COz
, CH4 is generated. The composition of the generated gas (capacity) is H
2 is 1.9.94, CO is 0.32, CH4 is 6
4871, Cot 2>flZO59K.

Nz is in charge of 182.

The produced gas includes residual steam and produced steam, and is approximately 460%
Exit the first methane synthesis step 14 at a temperature of ~5ooc. 5
gl methane, the gas exiting the synthesis step 14 contains residual steam, produced steam, and is further mixed with coke oven gas and hydrocarbon mixture from the second branch line to approximately 350-400 gl methane.
It is heated to a temperature of C and introduced into the second methane synthesis step 15. In the second methane synthesis step 15, the produced gas from the first methane synthesis step, the coke oven gas from the second branch line, and CH4, C4HIO in the hydrocarbon mixture.

A steam reforming reaction of C5Hs, CzHa, and other hydrocarbons and a methanation reaction of CO and Cow proceed simultaneously to produce Hz, CO, .CO2, and CH4.

The composition of the generated gas is 14.1% H2, 0.26% CO, 11.8% CO11, 70.9% CH4, and 3.0% N2. The produced gas contains residual steam and produced steam and exits the second methane synthesis step 15 at a temperature of about 460 to 5 car. The gas leaving the second methane synthesis step 15 contains residual steam and produced steam, and is introduced into the third methane synthesis step 16 at a temperature of about 250 to 320C. In the third methane synthesis step 16, the methanation reaction of COz and Co in the generated gas including the generated steam and residual steam from the second methane synthesis step progresses, N2, CO, and CO2 decrease by 111 degrees, and the methane concentration decreases. To increase. The composition of the generated gas is N
2 is 6.7, CO is 0.04, and CO2 is 10.82.
%, CH4 cuff 9.2 L N! “I)N3.2
* There is a chance. The generated gas contains generated steam and residual steam and is heated to a temperature of about 350 to 400 C in the third methane synthesis step 16.
exit. The product gas is cooled to a temperature of about 150-100C and introduced into a decarboxylation step 17 to absorb and remove CO2 in the product gas. The composition of the generated gas after CO2 removal is N2: 7
．． 41 section, co 0.05%, Cow 1.0 section, CH
4 is 87.9 times, and N2 is 12 times. The generated gas after absorption and removal is introduced into a dehydrator 818 at a temperature of about 3 Orr,
Completely removes moisture from generated gas. The dehydrated gas is mixed with heat-increasing LPG 19 at a temperature of about 150C to become city gas 20.

[Invention rho effect]

As is clear from the above detailed description, according to the present invention,
The tar oil and gum substances in the coke oven gas are efficiently removed, and the dienes, oxygen, olefins, and sulfur compounds contained in the coke oven gas are first removed by the first hydrogenation catalyst at a low temperature. Dienes and oxygen can be hydrogenated, and the second hydrogenation catalyst can hydrogenate the olefins and sulfur compounds remaining from the first hydrogenation catalyst, suppressing the formation of gummy substances due to diene polymerization and reducing the It has the effect of efficiently producing methane-rich fuel gas without poisoning the catalyst in the methane synthesis process.

[Brief explanation of drawings]

Fig. 1 is a process diagram showing an embodiment of the present invention, and Fig. 2 is a process diagram showing an embodiment in which a part of the purified gas is recirculated to the inlet and outlet of the adsorption process in the present invention. It is. 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, Death... Second hydrogenation tower, 9...Circulation line, 1
0... Hydrogen sulfide absorption tower, 11... First methane synthesis step branch line, 12... Raw material steam, 13... Second methane synthesis step branch line, 14... First methane synthesis step, 15... Second methane synthesis step, 16... Third methane synthesis step, 17... Decarboxylation step, 18...
Dehydration step, 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, the method comprising: an adsorption step of contacting with a porous material to adsorb and remove the tar oil and the gum substance; a first hydrogenation step of hydrogenating dienes, oxygen, and olefins in the gas that has passed through the adsorption step; A second hydrogenation step in which coke oven gas from the hydrogenation step and hydrocarbons are mixed to hydrogenate sulfur compounds in the mixture, and hydrogen sulfide in the coke oven gas from the second hydrogenation step is adsorbed and removed. a hydrogen sulfide removal step, a first methane synthesis step of adding steam to a mixture of coke oven gas and hydrocarbons from the hydrogen sulfide removal step to synthesize methane; a second methane synthesis step in which coke oven gas and a portion of hydrocarbons are separated and mixed to synthesize methane; a third methane synthesis step in which methane is synthesized from the gas produced from the second methane synthesis step; 3. A method for producing fuel gas, comprising the step of removing water vapor and carbon dioxide from the gas produced from the methane synthesis step. 2. 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 of the first hydrogenation step is 350°C or higher and the second hydrogenation step The method for producing fuel gas according to claim 1, wherein the temperature of the fuel gas is adjusted so as not to exceed 450°C. 3. Part of the mixture of coke oven gas and hydrocarbons from the second hydrogenation step is recycled to the latter stage of the adsorption step.
2. The method for producing fuel gas according to claim 1, wherein the temperature in the hydrogenation step is adjusted to be 350° C. or less and the temperature in the second hydrogenation step is adjusted not to exceed 450° C. 4. The method for producing fuel gas according to claim 2 or 3, wherein the amount of gas circulated is 10 to 100% of the amount of feedstock coke oven gas supplied. 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 of 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 to naphtha. 3. The method for producing fuel gas according to claim 1, wherein the fuel gas is ^3 or more. 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. Method for producing fuel gas as described in section. 9. Claim No. 9, 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. The method for producing fuel gas according to item 1. 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.