阅读说明：本技术 一种气化焦尾气变换、脱碳制lng的方法 (Method for preparing LNG (liquefied Natural gas) by transforming and decarbonizing tail gas of gasified coke ) 是由 冉世红 龙雨谦 杨先忠 蹇守华 刘艳艳 肖云山 游林 魏素兰 于 2021-08-02 设计创作，主要内容包括：本发明属于气化焦尾气制LNG(液化天然气)技术领域,尤其涉及一种气化焦尾气变换、脱碳制LNG的方法,所述气化焦尾气依次经预处理单元、压缩单元、脱油脱萘单元和脱苯脱氨单元后,一部份气体依次进入耐硫变换单元、变换气脱硫单元和变换气湿法脱碳单元处理,处理后的脱碳气与另一部份气体混合再进入混合气精脱硫单元、混合气甲烷化单元和甲烷化气深冷分离单元,生成LNG产品。本发明中满足甲烷化反应对氢碳比的要求；混合气经过精脱硫后进行甲烷化反应,使其中的CO、CO-2和H-2反应生成CH-4,再通过深冷分离得到LNG产品。结构简单,成体低,以及效率高。(The invention belongs to the technical field of LNG (liquefied natural gas) preparation from gasification coke tail gas, and particularly relates to a method for preparing LNG through conversion and decarburization of the gasification coke tail gas. The invention meets the requirement of methanation reaction on hydrogen-carbon ratio; the mixed gas is subjected to fine desulfurization and then methanation reaction to ensure that CO and CO in the mixed gas are 2 And H 2 Reaction to form CH 4 And then the LNG product is obtained through cryogenic separation. Simple structure, low cost and high efficiency.)

1. A method for preparing LNG by transforming and decarbonizing tail gas of gasified coke is characterized by comprising the following steps: after the gasified coke tail gas sequentially passes through the pretreatment unit, the compression unit, the deoiling and decalcification unit and the debenzolization and deamination unit, one part of gas sequentially enters the sulfur-tolerant shift unit, the shift gas desulfurization unit and the shift gas wet decarburization unit for treatment, the treated decarbonized gas is mixed with the other part of gas and then enters the mixed gas fine desulfurization unit, the mixed gas methanation unit and the methanated gas deep cooling separation unit, and an LNG product is generated.

2. The method for preparing LNG by shift conversion and decarburization of the gasification coke tail gas as claimed in claim 1, wherein the method comprises the following steps: the gasification coke tail gas pretreatment unit adopts a carbon-based adsorbent to primarily remove tar and naphthalene in the gasification coke tail gas and adopts steam for regeneration.

3. The method for preparing LNG by shift conversion and decarburization of the gasification coke tail gas as claimed in claim 1, wherein the method comprises the following steps: and the pressure of the gasified coke tail gas after compression in the compression unit is 0.8-6.0 MPa.

4. According to claimThe method for preparing LNG by transforming and decarbonizing the tail gas of the gasified coke and the method are characterized by comprising the following steps of: the sulfur-tolerant shift unit of the gasified coke tail gas divides the gasified coke tail gas after compression, deoiling, decalcification, debenzolization and deamination into a part, heats the part to 220 ℃, mixes the part with supplemented water vapor and then enters the upper layer of a shift reactor to remove harmful impurities such as oxygen, olefin and the like in the gasified coke tail gas, simultaneously raises the temperature of the gasified coke tail gas, sprays water to cool the temperature to 210 ℃, then enters the lower layer of the shift reactor, and CO in the gasified coke tail gas is subjected to shift reaction to generate CO₂And H₂The CO dry basis concentration was reduced to 3.0% v.

5. The method for preparing LNG by shift conversion and decarburization of the coke gasification tail gas as claimed in claim 1 or 2, wherein: the outlet temperature of the sulfur-resistant transformation unit is less than or equal to 40 ℃.

6. The method for preparing LNG by shift conversion and decarburization of the coke gasification tail gas as claimed in claim 1 or 2, wherein: the shift conversion gas wet decarburization unit uses the regenerated decarbonization liquid to convert CO in the shift conversion gas₂And removing the waste gas to achieve the aim of adjusting the hydrogen-carbon ratio after mixing with the part of the gasified coke tail gas which is not transformed.

7. The method for preparing LNG by shift conversion and decarburization of the gasification coke tail gas as claimed in claim 1, wherein the method comprises the following steps: the mixed gas methanation unit adopts a circulating three-stage methanation process, and the gasified coke tail gas or the mixed gas is subjected to three-stage methanation reaction to ensure that CO is obtained₂The concentration of the (B) reaches the requirement of less than or equal to 30 ppm.

8. The method for preparing LNG by shift conversion and decarburization of the gasification coke tail gas as claimed in claim 1, wherein the method comprises the following steps: nitrogen hydrogen tail gas that produces among the cryogenic separation unit returns and takes off benzene deamination unit as regenerated air supply, need heat nitrogen hydrogen tail gas at benzene deamination unit, heats 150 ~ 180 ℃.

Technical Field

The invention belongs to the technical field of LNG (liquefied natural gas) preparation from gasification coke tail gas, and particularly relates to a method for preparing LNG by transforming and decarbonizing gasification coke tail gas.

Background

A typical coking enterprise produces metallurgical coke, the typical composition of which is as follows:

components	CO	CO2	O2	CH4	H2	N2	CnHm	Total up to
									Content (%)	6.20	2.20	0.60	26.00	58.00	4.50	2.50	100.00

However, due to different market demands, some coking enterprises also produce gasified coke, and the tail gas of the gasified coke during the production of the gasified coke typically comprises the following components:

components	CO	CO2	O2	CH4	H2	N2	CnHm	Total up to
									Content (%)	15.03	5.13	0.46	20.84	52.86	2.71	2.97	100.00

In the production of metallurgical coke, CO and CO in coke oven gas₂Relatively low content of H₂In a relatively large amount, the so-called hydrogen-to-carbon ratio (3 molecules of H consumed per 1 molecule of CO)₂Per 1 molecule of CO₂Consumption of 4 molecules of H₂Per 1 molecule of O₂Consumption of 2 molecules of H₂) About 2, no matter for methanation catalyst, CO and CO₂The conversion effect of (2) and the like are advantageous. After the coke oven gas is compressed and harmful impurities in the coke oven gas are removed, methanation reaction can be directly carried out to ensure that CO and CO in the coke oven gas are₂And H₂Reaction to form CH₄And then the LNG product (liquefied natural gas) is obtained through cryogenic separation.

And CO in the tail gas of the gasified coke during the production of the gasified coke₂Much higher than that in metallurgical coke production, H₂And less than when producing metallurgical coke, the so-called hydrogen-to-carbon ratio (3 molecules of H consumed per 1 molecule of CO)₂Per 1 molecule of CO₂Consumption of 4 molecules of H₂Per 1 molecule of O₂Consumption of 2 molecules of H₂) Less than 80% of theory, whether for the use of methanation catalysts or for CO, CO₂The transformation effect of (b) is disadvantageous and infeasible in every respect.

SUMMARY OF THE PATENT FOR INVENTION

In order to solve the technical problems, the invention provides a method for preparing LNG (liquefied natural gas) by transforming and decarbonizing gasified coke tail gas, which comprises the steps of adding a transforming unit, a desulfurizing unit and a decarbonizing unit, carrying out methanation reaction after fine desulfurization, and carrying out cryogenic separation to produce an LNG product (liquefied natural gas). The process of preparing LNG from the gasified coke tail gas is opened after the gasified coke tail gas is transformed and decarbonized, so that the process becomes possible. The cost is reduced, and the economic benefit and the social benefit are increased.

The method for preparing LNG by transforming and decarbonizing the tail gas of the gasified coke solves the technical problems and is characterized by comprising the following steps: after the gasified coke tail gas sequentially passes through the pretreatment unit, the compression unit, the deoiling and decalcification unit and the debenzolization and deamination unit, one part of gas sequentially enters the sulfur-tolerant shift unit, the shift gas desulfurization unit and the shift gas wet decarburization unit for treatment, the treated decarbonized gas is mixed with the other part of gas and then enters the mixed gas fine desulfurization unit, the mixed gas methanation unit and the methanated gas deep cooling separation unit, and an LNG product is generated. The decarbonized tail gas is output from the shift gas wet method decarbonization unit, and the cryogenic tail gas is output from the methanation gas cryogenic separation unit.

The gasified coke tail gas after the debenzolization and deamination of the debenzolization and deamination unit is divided into two paths, one path of the gasified coke tail gas is subjected to sulfur-tolerant shift unit, shift gas desulfurization unit and shift gas wet decarburization unit, and the decarbonized gas is obtained after shift, desulfurization and wet decarburization; the other path of the gasified coke tail gas is directly mixed with the decarbonization gas to form mixed gas, and the mixed gas enters a mixed gas fine desulfurization unit; the hydrogen-carbon ratio of the mixed gas can be adjusted by adjusting the relative gas amount of the two paths of gasified coke tail gas.

The reformed gasified coke tail gas in the two paths of gasified coke tail gases accounts for about 73 percent of the total gas amount (which can change along with the change of the composition of the gasified coke tail gas).

The two paths of gas flow are used for mainly adjusting the tail gas flow of the gasified coke subjected to the transformation, so that the hydrogen-carbon ratio of the mixed gas is adjusted.

The pretreatment unit adopts a carbon-based adsorbent with strong adsorption capacity to tar and naphthalene in the gasified coke tail gas, and after adsorbing the tar and the naphthalene in the gasified coke tail gas, the regeneration unit uses steam to purge and regenerate once every a period of time, and the regenerated wastewater is subjected to coking treatment. The carbon-based adsorbent has high tar and naphthalene removal rate and mild adsorption conditions (performed at normal temperature and normal pressure).

The carbon-based adsorbent comprises at least two kinds of carbon-based adsorbents, such as coke and activated carbon (the activated carbon can be divided into a plurality of combinations according to different pore diameters, is selected and used according to the properties of the carbon-based adsorbents, and is adsorbed at normal temperature and normal pressure (6-7 kPa).

The operation mode of the steam purging regeneration is as follows: introducing steam to gradually raise the temperature, after the temperature is raised to more than 150 ℃, closing the tank for a period of time, then releasing pressure and discharging waste liquid; the regeneration interval time is determined according to the content of tar and naphthalene in the gasified coke tail gas, namely the tar and naphthalene content at the outlet is detected and the regeneration is carried out when the tar and naphthalene content does not reach the standard. Generally 7-10 days.

In the invention, the adsorption is carried out at normal temperature and normal pressure (6-7 kPa); the regeneration is carried out with temperature and pressure, the temperature is mainly raised to be above 150 ℃, otherwise, the regeneration is not thorough, and the next adsorption effect can be influenced.

The compression unit can adopt a reciprocating compressor for compression treatment or a compression device combining a screw compressor and a centrifugal compressor, and the pressure of the compressed gasified coke tail gas is 0.8-6.0 MPa.

The deoiling and decalcification unit further removes the deoiling and decalcification unit by using a carbon-based complexing agent, a silicate complexing agent and the like so as to reduce the influence on the subsequent units. The carbon-based complexing agent is different from the carbon-based adsorbent, and mainly selects the active carbon with higher removal precision without coke. The silicate complexing agent has the characteristics of better deoiling effect (including tar and lubricating oil of a compressor), and can be purchased from the market by selecting a proper model.

The gas compressed by the gasification coke tail gas compressor still contains a small amount of impurities such as naphthalene, oil, water and the like and needs to be treated.

The carbon-based complexing agent and the silicate complexing agent after adsorbing the oil and the naphthalene are blown and regenerated once by steam at intervals according to the operation working conditions, and the regenerated wastewater is subjected to coking treatment. The method is characterized in that the regeneration is carried out once by steam blowing at intervals, the regeneration interval time is different as the mode of steam regeneration, and the regeneration is carried out when the content of tar and naphthalene in the gasified coke tail gas is not up to the standard, namely the content of tar and naphthalene at the detection outlet is determined. Generally 10-15 days.

The benzene and ammonia removal unit removes benzene and ammonia in the gasified coke tail gas by adopting a Temperature Swing Adsorption (TSA) method so as to reduce the influence on a subsequent unit. The regeneration gas of the Temperature Swing Adsorption (TSA) is tail gas or self-purified gas which is subjected to cryogenic separation, and the adsorbent is regenerated by purging the adsorption tower after the regeneration gas is heated by steam. After benzene and ammonia are removed, benzene in the gasification coke tail gas is less than or equal to 10PPm, and ammonia is less than or equal to 10 PPm.

The structure and operation steps of the Temperature Swing Adsorption (TSA) device are conventional operation, and the selected adsorbent has better selective adsorption to benzene and ammonia. The adsorption is at normal temperature, and the regeneration temperature is 150-180 ℃; the regeneration pressure is not particularly limited, and may be set by sending it out.

The temperature of the regenerated gas after steam heating is about 180-200 ℃, so that the adsorption parasitic bed layer can be heated to 150-180 ℃.

The sulfur-tolerant shift unit of the gasified coke tail gas is characterized in that a part of the gasified coke tail gas after compression, deoiling, decalcification, debenzolization and deamination is separated, the gasified coke tail gas is heated to 220 ℃ and mixed with supplemented water vapor and then enters the upper layer of a shift reactor to remove harmful impurities such as oxygen, olefin and the like in the gasified coke tail gas, meanwhile, the temperature of the gasified coke tail gas is increased, water is sprayed to cool to 210 ℃ and then enters the lower layer of the shift reactor, CO in the gasified coke tail gas is subjected to shift reaction to generate CO₂And H₂The CO dry basis concentration was reduced to 3.0% v.

The sulfur-tolerant shift unit supplements a proper amount of water vapor into the compressed gasified coke tail gas, and shifts most of CO to generate CO under the action of a sulfur-tolerant shift catalyst₂And H₂The process of (1). The shift reaction is exothermic reaction, proper measures (intermediate heat exchange and/or cold shock) are taken in the reactor, the temperature of the catalyst bed layer is well controlled, and accidents such as sintering inactivation and even equipment damage caused by overheating of the catalyst are prevented.

The sulfur tolerant shift unit includes 10 or more facilities such as shift reactors, and the shift reaction is performed in the shift reactors.

The temperature entering the shift reactor is 210-220 ℃ (the initial stage and the final stage of the catalyst are slightly different), and the heat release reason of the reaction is caused when the temperature is increased to 310 ℃; the intermediate extraction is used for heat exchange and/or cold shock to 210-220 ℃, and then enters the shift reactor for better shift reaction. The temperature of the outlet of the second-stage outlet transformed gas is 320 ℃, and the supplemented water vapor comes from the outside and is mixed in a device called a gas-vapor mixer. Make-up steam is about 21% (V/V) of the gasification coke tail gas entering the shift.

The conversion gas desulfurization unit converts H converted from organic sulfur in the conversion process₂S, under the condition of the temperature of the shift gas outlet, the sulfur content in the decarbonized tail gas of the shift gas wet-process decarbonization unit can reach the standard and be discharged or can be conveniently utilized.

The shift gas wet decarburization unit uses the regenerated decarbonization liquid to convert CO in the gas₂And (4) removing the carbon and hydrogen to achieve the purpose of adjusting the hydrogen-carbon ratio after mixing with the part of the gasification coke tail gas which is not transformed, and the loss of effective components in wet decarburization is less. Absorb CO₂The decarbonization solution is recycled by heating and regeneration, and the decarbonization tail gas generated by regeneration can be directly discharged or utilized.

In the present invention, regeneration is carried out to absorb CO₂Heating the decarbonizing solution to drive out CO₂The regenerated decarbonizing solution is recycled.

The shift gas wet decarburization mainly comprises more than 10 devices such as an absorption tower, a regeneration tower, a reboiler, a circulating pump and the like, and is connected for recycling.

The mixed gas fine desulfurization unit is used for removing inorganic sulfur (H) from the tail gas (or the mixed gas) of the gasified coke₂S) is mostly removed, but the content of organic sulfur (sulfur oxygen carbon, carbon disulfide, mercaptan, thioether, thiophene and the like) is more, and the organic sulfur is subjected to pre-hydrogenation and primary hydrogenation by a solid catalyst to be converted into inorganic sulfur (H)₂S), removing the generated inorganic sulfur (H) by a solid desulfurizing agent₂S), and then carrying out secondary hydrogenation to convert the residual organic sulfur into inorganic sulfur (H)₂S) and removing the sulfur by a solid desulfurizer, wherein the total sulfur in the gasified coke tail gas (or the mixed gas) is removed to be less than or equal to 0.1 ppm. And further processing by using a super-fine purifying agent to remove the total sulfur in the gasified coke tail gas (or the mixed gas) at the outlet to less than 0.05 ppm. The shift gas after the desulfurization of the solid desulfurizing agent is heated to feed the coke tail gas to be cooled, and then the shift gas is sent to a regeneration tower of a wet decarburization unit to be used as a part of heat source.

The mixed gas fine desulfurization unit is used for pre-converting the mixed gas by organic sulfur, performing primary conversion, performing primary fine desulfurization, performing secondary conversion and performing secondary fine desulfurization. The solid catalysts for pre-conversion, primary conversion and secondary conversion are Co-Mo, Fe-Mo and Ni-Mo catalysts which are selected for purchase and have good effect on organic sulfur conversion; the solid catalyst for the first-stage fine desulfurization and the second-stage fine desulfurization is a zinc oxide desulfurizer which is selected for purchase and has good desulfurization effect. Mainly adopts a pre-conversion tank, a first-stage fine desulfurization tank, a second-stage conversion tank and a second-stage fine desulfurization tank which are connected for use.

The mixed gas methanation unit leads CO and CO in the gasification coke tail gas (or the mixed gas)₂And H₂Reaction to form CH₄。

On the one hand increase CH₄While removing CO and CO from the gasification coke tail gas₂And the subsequent separation difficulty and toxicity hazard are reduced. Because the methanation reaction is a strong exothermic reaction, a circulating three-stage methanation process (the technology in the applied patent) is adopted in the process setting, the temperature of each stage of catalyst bed is well controlled, and accidents such as sintering inactivation and even equipment damage caused by overheating of the catalyst are prevented. The gasification coke tail gas (or mixed gas) can be subjected to three-stage methanation reaction to enable CO₂The concentration of the LNG meets the requirement that the concentration of the LNG is less than or equal to 30ppm when the LNG is subjected to low-temperature separation, and a decarburization device is not required to be additionally arranged.

The methane-rich gas obtained by the methanation unit is subjected to cryogenic separation to obtain an LNG product and cryogenic tail gas. Before cryogenic separation, precise filtration and drying dehydration (which is necessary when the methanolic gas is subjected to precise filtration and drying dehydration before being subjected to cryogenic separation, or is blocked, and can be regarded as equipment in a cryogenic unit) are required to be carried out so as to separate impurities with the particle size of more than 1 mu m and ensure that the water content is less than or equal to 1 ppm.

The cryogenic separation unit can adopt processes such as stepped refrigeration liquefaction, Mixed Refrigerant (MRC) refrigeration liquefaction or expander refrigeration liquefaction and the like. These processes are conventional techniques.

Drawings

FIG. 1 and FIG. 2 are schematic views of the preparation process of the present invention

Detailed Description

The invention is described in detail below with reference to the following figures and specific examples:

example 1

The method for preparing LNG by transforming and decarbonizing the tail gas of the gasified coke comprises the following steps:

at 38000Nm³For example, the LNG preparation device is prepared from the/h gasified coke tail gas, the pressure of the gasified coke tail gas is 6-7 kPa, and the normal temperature is 38000Nm³Composition is shown in the following table:

components	CO	CO2	O2	CH4	H2	N2	CnHm	Total up to
									Content (%)	15.03	5.13	0.46	20.84	52.86	2.71	2.97	100.00

The impurity levels are shown in the following table:

components

H2S

Organic sulfur

Naphthalene

Tar plus dust

NH3

B.T.X (benzene)

HCN

Content (mg/Nm)3)

≤20

≤150

≤300

≤50

≤50

≤3000

≤100

First pass throughThe over-gasification coke tail gas pretreatment unit adopts a carbon-based adsorbent to adsorb tar and naphthalene in the gasification coke tail gas, and the pretreatment is carried out on the gasification coke tail gas: tar plus dust less than or equal to 10mg/Nm³Naphthalene is less than or equal to 20mg/Nm³。

Then two reciprocating compressors are adopted for four-stage compression, and the pretreated gasified coke tail gas is compressed to 2.4 MPa. Then adopting carbon-based complexing agent and silicate complexing agent to further deoil and decalcify, and gasifying coke tail gas after deoiling and decalcifying: tar plus dust less than or equal to 1mg/Nm³Naphthalene is less than or equal to 2mg/Nm³。

Benzene and ammonia in the gasified coke tail gas are removed by adopting Temperature Swing Adsorption (TSA), and benzene and ammonia in the gasified coke tail gas after benzene and ammonia removal are less than or equal to 10PPm and less than or equal to 10 PPm; the Temperature Swing Adsorption (TSA) adopts a three-tower process, namely, one-tower adsorption, one-tower heating regeneration and one-tower cold blowing cooling, nitrogen-hydrogen tail gas separated by deep cooling is used as a regenerated gas source, the regenerated gas is used for purging and heating the adsorption tower after being heated by steam to regenerate an adsorbent, then the cold blowing cooling is used for recovering the adsorption capacity of the adsorbent, three tower streams are recycled in sequence, and the whole process is continuously carried out.

28000Nm & lt/EN & gt are separated from gasification coke tail gas after benzene removal and deamination³Firstly heating the gasified coke tail gas to 220 ℃ by hot conversion gas, mixing the gasified coke tail gas with supplemented 4700kg/h of water vapor, then feeding the mixture into the upper layer of a conversion reactor to remove harmful impurities such as oxygen, olefin and the like in the gasified coke tail gas, reacting the oxygen, olefin and hydrogen to release a large amount of heat, heating the gasified coke tail gas to 310 ℃, feeding the gasified coke tail gas into a water spray cooler to spray water and cool the gasified coke tail gas to 210 ℃, then feeding the gasified coke tail gas into the lower layer of the conversion reactor, and carrying out conversion reaction on CO in the gasified coke tail gas to generate CO₂And H₂The concentration of CO on a dry basis is reduced to 3.0% v and the temperature is reduced to 320 ℃. At the temperature, the shift gas enters a fine desulfurization tank, and H in the shift gas is removed by a solid desulfurizing agent₂S is less than or equal to 1PPm, the raw material gasification coke tail gas is heated to be cooled, then the raw material gasification coke tail gas is removed to be cooled, and then the raw material gasification coke tail gas is removed to be used as a part of heat source, and then the raw material gasification coke tail gas enters a water cooler to be cooled to be less than or equal to 40 ℃ (the water cooler is equipment in a conversion unit, and is arranged after a fine desulfurization tank, a raw material gas heater and a wet decarburization reboiler and before wet decarburization), condensed water is separated, and then the raw material gasification coke tail gas is cooled to be less than or equal to 40 ℃ (the water cooler is arranged in the conversion unit, and the condensed water is separatedSending to a shift gas wet decarburization unit.

The transformed gas consists of:

components	CO	CO2	O2	CH4	H2	N2	CnHm	Total up to
									Content (%)	3.00	15.26	-	18.90	57.68	2.46	2.70	100.00

The variable gas volume is: 30940Nm³/h。

The desulfurized and cooled conversion gas enters an absorption tower and is washed by decarburization solution, and CO in the gas after the conversion gas is washed by semi-barren solution and barren solution₂The content is reduced to below 0.5% v, cooled, separated to remove trace decarbonization solution in gas, and mixed with another stream of 10000Nm³And/h, mixing the gasification coke tail gas after benzene and ammonia removal to form mixed gas. The hydrogen-carbon ratio of the mixed gas can be adjusted by adjusting the relative gas amount of the two paths of gasified coke tail gas.

The rich liquid from the bottom of the absorption tower enters the top of a regeneration tower and is decompressed to 0.1MPa, and is stripped by steam from the lower part of the tower. Cooling the gas stripped from the top of the regeneration tower to below 40 ℃, returning the separated condensate to the top of the regeneration tower as reflux, and cooling the cooled CO₂Discharging after reaching the standard or utilizing outside the boundary.

The decarbonized solution coming out from the bottom of the upper section of the regeneration tower is a semi-barren solution and is divided into two parts. Most of the semi-barren solution is pressurized and then circulated to the middle part of the absorption tower; the rest semi-barren solution is preheated and then sent to the lower section of the regeneration tower for continuous regeneration, the decarbonized solution from the bottom of the lower section of the regeneration tower is barren solution, and the barren solution is cooled and then sent to the upper part of the absorption tower for cyclic absorption. Part of the heat of the reboiler of the regeneration tower is provided by the shift gas, and the rest is supplemented by steam.

The decarbonization gas composition was as follows:

components	CO	CO2	O2	CH4	H2	N2	CnHm	Total up to
									Content (%)	3.53	0.50	-	22.20	67.75	2.89	3.13	100.00

The decarbonizing gas amount is: 26350Nm³/h。

The composition of the mixed gas is as follows:

components	CO	CO2	O2	CH4	H2	N2	CnHm	Total up to
									Content (%)	6.89	1.85	0.13	21.81	63.39	2.84	3.09	100.00

The gas mixing amount is as follows: 36350Nm³/h。

And (3) mixed gas formed by the gasification coke tail gas after the benzene and ammonia removal and the decarbonization gas enters a mixed gas fine desulfurization unit for fine desulfurization. The mixed gas and the gas after fine desulfurization exchange heat and rise in temperature, then enter two pre-hydrogenation tanks which can be connected in parallel or used independently, mainly carry out hydrogenation saturation on unsaturated hydrocarbon in the mixed gas, react to remove oxygen in the mixed gas, and simultaneously, a small amount of organic desulfurization and hydrogenation are carried out to convert the mixed gas into inorganic sulfur (H)₂S)。

The pre-hydrogenated mixed gas enters a first-stage hydrogenation tank to further carry out hydrogenation conversion on organic desulfurization in the mixed gas, and then enters a first-stage fine desulfurization tank with two series connection, parallel connection or independent use to remove H generated by hydrogenation conversion₂And S. In order to further reduce organic sulfur and inorganic sulfur in the mixed gas, the mixed gas enters a secondary hydrogenation tank and two secondary fine desulfurization tanks. When the prior hydrodesulfurization can meet the total sulfur requirement of the process, the purified mixed gas is bypassed (without passing throughSecond stage hydrodesulfurization). The purified gas is cooled and then enters a super-fine purifier, so that the total sulfur content in the purified gas at the outlet is ensured to be less than 0.05 ppm.

The ultra-fine purified gas is divided into two paths according to a proportion, and the two paths are respectively a demethanization first-stage reactor and a methanation second-stage reactor.

The mixed gas fine desulfurization unit mainly comprises a pre-conversion tank, a primary fine desulfurization tank, a secondary conversion tank and a secondary fine desulfurization tank which are connected in series. And a conversion unit and a decarburization unit are arranged, so that the gasification coke tail gas can be utilized to produce LNG.

The purified gas of the demethanization first-stage reactor is mixed with the circulating gas pressurized by the circulating compressor, heated to a temperature of more than or equal to 250 ℃, and enters the methanation first-stage reactor for methanation reaction. And (3) allowing high-temperature reaction gas discharged from the methanation first-stage reactor to reach 505 ℃, allowing the temperature of the byproduct 2.5MPa steam to be reduced to 360-400 ℃, performing heat exchange and cooling, mixing the mixture with purified gas of a demethanization second-stage reactor, allowing the mixed gas to reach 250-300 ℃, and allowing the mixed gas to enter the methanation second-stage reactor for continuous methanation reaction.

The high-temperature reaction gas at the outlet of the methanation second-stage reactor is 505 ℃, the temperature is reduced to 360 ℃ after 2.5MPa steam is byproduct, and the process gas and the first-stage raw gas which are preheated and enter the methanation third-stage reactor are divided into two paths after heat is recovered. Cooling one path to be less than or equal to 40 ℃, separating condensed water, heating, then feeding the condensed water into a methanation three-section reactor, and discharging reaction gas CO from the methanation three-section reactor₂The concentration of the LNG is less than or equal to 30ppm, the LNG is cooled to be less than or equal to 40 ℃, and the LNG product is prepared by a cryogenic separation unit after condensed water is separated.

And the other path is cooled to be less than or equal to 60 ℃, condensed water is separated, and the condensed water is pressurized by a circulating gas compressor and then returns to an inlet of the methanation unit to dilute the raw gas.

The methanated gas had the following composition:

components	CO	CO2	O2	CH4	H2	N2	CnHm	Total up to
									Content (%)	-	-	-	53.47	42.17	4.11	0.25	100.00

The methane gasification gas amount is as follows: 25050Nm³/h。

The methanated gas enters a cryogenic separation unit, and an LNG product and cryogenic tail gas are prepared through cryogenic separation. Before cryogenic separation, precise filtration and drying dehydration are carried out to separate impurities with the particle size of more than 1 mu m and ensure that the water content is less than or equal to 1 ppm.

The methanation gas enters a liquefaction cold box, is cooled to a certain temperature by mixed refrigerant, is pumped out from a heat exchanger to a reboiler at the bottom of a rectifying tower to be used as a heat source, then returns to the liquefaction heat exchanger to be cooled and condensed by the mixed refrigerant, and then enters a flash tank after throttling, hydrogen-rich tail gas discharged from the flash tank returns to the liquefaction heat exchanger to be reheated and then is discharged from the cold box, liquid discharged from the flash tank enters a rectifying tower, nitrogen-rich tail gas obtained at the tower top is rectified to be throttled and reheated and then discharged from the cold box, LNG is obtained at the tower bottom and enters the liquefaction heat exchanger to be subcooled, and the LNG is throttled by a throttle valve to be reduced to normal pressure and then is discharged from the cold box to enter an LNG storage tank.

The hydrogen-rich tail gas and the nitrogen-rich tail gas (namely the cryogenic tail gas) discharged from the cooling box are partially used as the regeneration gas for drying and dehydrating in the unit, and then are used as the gas source for regenerating the debenzolization and deamination together with the residual cryogenic tail gas.

The LNG composition was as follows:

components	CO	CO2	O2	CH4	H2	N2	CnHm	Total up to
									Content (%)	-	-	-	98.54	-	0.99	0.47	100.00

The LNG production is: 13200Nm³/h。

The composition of the cryogenic tail gas is as follows:

components	CO	CO2	O2	CH4	H2	N2	CnHm	Total up to
									Content (%)	-	-	-	3.27	89.14	7.59	-	100.00

The amount of the cryogenic tail gas is as follows: 11850Nm³/h。

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.