CN114149837A - Process for preparing liquefied natural gas and co-producing liquid ammonia or hydrogen by coke oven gas with conversion decarburization - Google Patents

Process for preparing liquefied natural gas and co-producing liquid ammonia or hydrogen by coke oven gas with conversion decarburization Download PDF

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CN114149837A
CN114149837A CN202111272968.6A CN202111272968A CN114149837A CN 114149837 A CN114149837 A CN 114149837A CN 202111272968 A CN202111272968 A CN 202111272968A CN 114149837 A CN114149837 A CN 114149837A
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gas
coke oven
oven gas
hydrogen
coke
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CN114149837B (en
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汪涛
蹇守华
胡瑜飞
吴路平
刘琴
袁家均
杨柱荣
龙雨谦
葛得翠
杨运超
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Southwest Research and Desigin Institute of Chemical Industry
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Southwest Research and Desigin Institute of Chemical Industry
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    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
    • C10L3/00—Gaseous fuels; Natural gas; Synthetic natural gas obtained by processes not covered by subclass C10G, C10K; Liquefied petroleum gas
    • C10L3/06—Natural gas; Synthetic natural gas obtained by processes not covered by C10G, C10K3/02 or C10K3/04
    • C10L3/08—Production of synthetic natural gas
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B3/00—Hydrogen; Gaseous mixtures containing hydrogen; Separation of hydrogen from mixtures containing it; Purification of hydrogen
    • C01B3/50—Separation of hydrogen or hydrogen containing gases from gaseous mixtures, e.g. purification
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01C—AMMONIA; CYANOGEN; COMPOUNDS THEREOF
    • C01C1/00—Ammonia; Compounds thereof
    • C01C1/02—Preparation, purification or separation of ammonia
    • C01C1/04—Preparation of ammonia by synthesis in the gas phase
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
    • C10L3/00—Gaseous fuels; Natural gas; Synthetic natural gas obtained by processes not covered by subclass C10G, C10K; Liquefied petroleum gas
    • C10L3/06—Natural gas; Synthetic natural gas obtained by processes not covered by C10G, C10K3/02 or C10K3/04
    • C10L3/10—Working-up natural gas or synthetic natural gas
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00—Technologies relating to chemical industry
    • Y02P20/10—Process efficiency
    • Y02P20/129—Energy recovery, e.g. by cogeneration, H2recovery or pressure recovery turbines

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Abstract

The invention discloses a process for preparing liquefied natural gas and co-producing liquid ammonia or hydrogen by using transformed decarbonized coke oven gas, which comprises the following steps: the coke-oven gas is subjected to process units such as compression purification, hydrodesulfurization, conversion, decarburization, methanation, cryogenic separation and the like, liquid obtained after cryogenic separation is an LNG product, and the gas can be used as a hydrogen-nitrogen raw material of a downstream ammonia synthesis device to produce a liquid ammonia product or as a raw material of a PSA hydrogen extraction device to produce pure hydrogen after reheating. The process has the advantages of high utilization rate of effective components in the coke oven gas, good process reliability, low comprehensive energy consumption, large operation flexibility and the like.

Description

Process for preparing liquefied natural gas and co-producing liquid ammonia or hydrogen by coke oven gas with conversion decarburization
Technical Field
The invention belongs to the field of efficient clean utilization of coke oven gas, and particularly relates to a process for preparing liquefied natural gas and co-producing liquid ammonia or hydrogen by using coke oven gas with shift decarburization.
Background
1. Technology for preparing liquefied natural gas and co-producing liquid ammonia from coke oven gas
The method adopts the prior technology of preparing liquefied natural gas and liquid ammonia by coke oven gas, and mainly produces methane by the synthetic reaction of all non-methane carbon-containing compounds in the coke oven gas and hydrogen. The main purpose of the technology is to produce liquefied natural gas, and liquid ammonia is only a byproduct with small yield. Because the coke oven gas contains a large amount of CO and CO2The total amount of the ammonia gas accounts for-12% of the raw material coke oven gas, if the methane is completely synthesized, a large amount of hydrogen is consumed, and the consumed hydrogen accounts for about-80% of the total amount of the hydrogen in the coke oven gas, so that the yield of the product liquid ammonia is greatly reduced.
2. Technology for preparing liquefied natural gas from coke oven gas
By adopting the prior technology for preparing liquefied natural gas by coke oven gas, hydrogen and nitrogen which account for about 15 percent of the total amount of the coke oven gas are abundant, and if the hydrogen and the nitrogen are not well utilized, the part of gas can only be returned to the coke oven to be used as fuel. From the investment perspective, gas accounting for about 15 percent of the total gas amount of the coke oven gas is useless in the whole process, and the investment of the device is increased; from the energy consumption perspective, about 15% of the total gas amount of the coke oven gas is compressed from the normal pressure to 2.4MPaG, and finally, the gas is reduced to the normal pressure to be used as fuel, so that the compression work is wasted. Therefore, if the coke oven gas only produces liquefied natural gas without considering the comprehensive utilization of the tail gas, the method is not economical, and particularly, the method is not reasonable for a large-scale device for preparing the liquefied natural gas by the coke oven gas.
The coke oven gas contains more sulfides with complex forms, and if the hydrolysis mode is adopted for desulfurization, the total sulfur is difficult to remove the precision required by the downstream methanation process, so that the performance and the service life of the methanation catalyst are influenced. Therefore, the liquefied natural gas prepared by methanation of the coke-oven gas basically adopts a fine desulfurization process after hydroconversion.
3. Technology for preparing LNG and co-producing liquid ammonia by taking coal gas and semi-coke tail gas as raw materials or mixing coal gas and coke oven gas as raw materials
At present, in the prior art, the liquefied natural gas is produced by adopting coke oven gas as a raw material and adopting coal gas and semi-coke tail gas as raw materials. Although the general composition of these gases is almost the same, the main components, such as the content of hydrogen and the content of CO, are greatly different, and the forms and the contents of impurities in the gases are also greatly different, so the adopted process method is different and is not strong in comparison with the process of the application.
Disclosure of Invention
The invention aims to provide a process for preparing liquefied natural gas and co-producing liquid ammonia or hydrogen by using coke oven gas with shift decarburization. In the process, coke oven gas is subjected to process units such as compression purification, hydrodesulfurization, conversion, decarburization, methanation, cryogenic separation and the like, liquid obtained after cryogenic separation is an LNG product, and the gas can be used as a hydrogen and nitrogen raw material of a downstream ammonia synthesis device to produce a liquid ammonia product or used as a raw material of a PSA hydrogen extraction device to produce pure hydrogen after reheating. The process has the advantages of high utilization rate of effective components in the coke oven gas, good process reliability, low comprehensive energy consumption, large operation flexibility and the like.
In order to achieve the above purpose, the purpose of the invention is achieved by the following specific technical scheme:
a process for preparing liquefied natural gas and co-producing liquid ammonia or hydrogen by using coke oven gas with conversion decarburization comprises the following steps:
1) purifying: pretreating the coke-oven gas to obtain primarily purified coke-oven gas;
2) hydrodesulfurization: carrying out hydrodesulfurization treatment on the primarily purified coke oven gas to remove sulfides in the coke oven gas;
3) and (3) transformation: setting a conversion and waste heat recovery unit to adjust H in the coke oven gas2、CO、CO2Obtaining the transformed gas according to the proportion;
4) decarbonization: most of carbon dioxide in the shift gas is removed, and the obtained decarbonized gas is sent to a methanation unit;
5) methanation: carrying out methanation on the decarbonized gas to obtain a methane-rich gas;
6) cryogenic separation: and (3) performing a refrigeration separation process on the methane-rich gas by using a mixed refrigerant to obtain an LNG product.
The method comprises the following specific steps:
1) compression purification
The coke oven gas from coking is pretreated, macromolecular impurities in the coke oven gas are primarily removed by adopting a gas-liquid separation or adsorption mode, and the coke oven gas enters a gas holder for buffering and storage, then enters a compressor for compression and then is sent to a purification process unit. The purification process unit mainly removes impurities such as tar, naphthalene, ammonia, hydrogen cyanide and the like in the coke oven gas to the process requirement indexes in the modes of washing, gas-liquid separation, adsorption and the like. And feeding the purified coke-oven gas into a hydrodesulfurization unit.
As a better implementation mode in the application, the coke oven gas is compressed to 1.0-4.5 MPaG from normal pressure through the compression of a compressor.
2) Hydrodesulfurization of hydrocarbons
Preheating purified coke-oven gas, sequentially entering a pre-hydrogenation reactor and a primary hydrogenation reactor, removing oxygen in the coke-oven gas, simultaneously converting 90% of organic sulfur into inorganic sulfur, and then entering a primary medium-temperature zinc oxide tank to remove hydrogen sulfide in the coke-oven gas. The coke-oven gas from the first-stage medium-temperature zinc oxide tank enters a second-stage hydrogenation reactor to further convert organic sulfur into inorganic sulfur, and then passes through a second-stage medium-temperature zinc oxide tank. The desulfurized gas is sent to a shift unit.
As a preferred embodiment in this application, the sulfur content of the coke oven gas is removed to below 0.1ppmv after the hydrodesulfurization step.
3) Transformation of
The desulfurized gas enters a shift reactor after waste heat recovery and proper steam addition, and the shifted gas is sent to a decarburization unit after byproduct steam and heat recovery.
In a preferred embodiment of the present invention, the carbon monoxide dry basis content of the shifted gas is from 0.2V% to 1.5V%.
4) Decarburization of carbon
The shift gas is decarbonized with MDEA solution.
In a preferred embodiment of the present invention, the dry content of carbon dioxide in the decarbonated gas is 0.1 to 1.5V%.
5) Methanation
The decarbonized gas enters a methanation reactor after being preheated, the methane-rich gas at the outlet of the methanation reactor enters a second-stage methanation reactor after byproduct steam and waste heat are recovered, and CO + CO at the outlet of the second-stage methanation reactor2Less than or equal to 20 ppm. After waste heat recovery, the waste heat is cooled to 40 ℃ by using circulating water to obtain methane-rich gas, and the main components of the methane-rich gas are hydrogen, methane and nitrogen.
In a preferred embodiment of the present invention, the methane-rich gas comprises hydrogen, methane and nitrogen as main components, wherein the hydrogen is 30-80V%, the methane is 20-60V%, and the nitrogen is 3-8V%.
6) Cryogenic separation
The methane-rich gas is subjected to cryogenic pretreatment, and enters a cold box after water, micro dust and other trace harmful impurities are removed. The cold energy of the cold box is provided by mixed refrigerant and a compressor, an LNG product is obtained after cryogenic separation, and the byproduct cryogenic tail gas enters a downstream production device after reheating.
Compared with the prior art, the invention has the following beneficial effects:
compared with other similar process flows for preparing liquefied natural gas and coproducing liquid ammonia from coke oven gas, the process mainly has the following main differences that the original effective gas components in the coke oven gas are reserved and utilized to a greater extent: hydrogen gas.
1) The process is provided with a conversion process unit, and converts the liquefied natural gas prepared from coke oven gas into liquid ammonia or useless carbon monoxide in the hydrogen preparation process into hydrogen.After the conversion, a decarburization process unit is arranged to remove useless carbon dioxide in the process of preparing liquefied natural gas and co-producing liquid ammonia or hydrogen from coke oven gas. Through the combination of the processes of conversion, decarburization and demethanization, the reaction of synthesizing methane from carbon monoxide, carbon dioxide and hydrogen is greatly reduced, so that more hydrogen is reserved and the yield of liquid ammonia or hydrogen is increased. From the viewpoint of material balance, 2.83kg of liquid ammonia can be produced or 5.6Nm can be produced per 1kg of methane synthesized3Hydrogen gas.
Taking a device of 50000Nm3/h for preparing LNG and co-producing liquid ammonia from coke oven gas as an example, if the patent technology 'a process (CN102517108A) for preparing liquefied natural gas and co-producing liquid ammonia from coke oven gas' is adopted, 11.2 ten thousand tons of LNG and 5.0 ten thousand tons of liquid ammonia can be obtained every year; if the method is adopted, 9.2 ten thousand tons of LNG and 10.6 ten thousand tons of liquid ammonia can be obtained every year.
2) The process flow of methanation matched with cryogenic separation is adopted and is arranged after transformation and decarburization, so that transformation reaction and CO are reduced2The requirement of the removal depth can save the steam consumption under the condition of meeting the impurity requirement of a downstream device.
Compared with other similar process flows for producing LNG by using coke-oven gas, the method mainly has the following main differences that the original effective gas components in the coke-oven gas are utilized to a greater extent: hydrogen, nitrogen.
1) The process flow of co-producing liquid ammonia or hydrogen by using the cryogenic tail gas increases the yield of liquid ammonia or hydrogen.
2) The process flow for preparing liquefied natural gas by using coke oven gas generally comprises that cryogenic tail gas accounts for 20-30V% of raw coke oven gas. If the gas can not be well utilized, the waste of the cost of compression power consumption, gas purification and the like can be caused, and once the gas is made into a chemical product, the economic value of the gas is considerable.
At 50000Nm3For example, if the patent technology of 'a method for producing liquefied natural gas from coke oven gas (CN 102115684B)' is adopted, there will be about 12500Nm3The deep cooling tail gas per hour is burned back without other purification cost, and the electricity wasted each year is about 1600 ten thousandAnd (4) degree.
Compared with other process flows of preparing liquefied natural gas and co-producing liquid ammonia or hydrogen by using similar coke oven gas, the method has the main difference that the LNG yield and the yield of the co-produced liquid ammonia or hydrogen can be adjusted according to market conditions, so that greater economic benefit is obtained. By adjusting the reaction depth of shift and decarburization, the variation range of 90-120% of LNG yield can be obtained under the same 100% of raw gas quantity, and at the moment, the corresponding yield of liquid ammonia or hydrogen can be varied within the range of 120-60%.
Drawings
FIG. 1 is a schematic view of a process flow of producing liquefied natural gas and liquid ammonia from coke oven gas with shift decarburization.
FIG. 2 is a schematic view of a process flow of producing liquefied natural gas and co-producing hydrogen gas from coke oven gas with shift decarburization.
FIG. 3 is a schematic view of the process flow of hydrodesulfurization according to example 1 of the present invention.
Detailed Description
A process for preparing liquefied natural gas and co-producing liquid ammonia or hydrogen by using transformed decarbonized coke oven gas comprises the following steps:
1) purifying: pretreating the coke-oven gas to obtain primarily purified coke-oven gas;
2) hydrodesulfurization: carrying out hydrodesulfurization treatment on the primarily purified coke oven gas to remove sulfides in the coke oven gas;
3) and (3) transformation: setting a conversion and waste heat recovery unit to adjust H in the coke oven gas2、CO、CO2Obtaining the transformed gas according to the proportion;
4) decarbonization: most of carbon dioxide in the shift gas is removed, and the obtained decarbonized gas is sent to a methanation unit;
5) methanation: carrying out methanation on the decarbonized gas to obtain a methane-rich gas;
6) cryogenic separation: and (3) performing a refrigeration separation process on the methane-rich gas by using a mixed refrigerant to obtain an LNG product.
Preferably, the purification step in step 1) is: primarily removing macromolecular impurities in coke-oven gas from coking by adopting a gas-liquid separation or adsorption mode, then entering a gas holder for buffering and storage, then entering a compressor, compressing the coke-oven gas to 1.0-4.5 MPaG from normal pressure, and then sending the coke-oven gas to a purification process unit; the purification process unit mainly comprises the steps of washing, gas-liquid separation and adsorption, and impurities such as tar, naphthalene, ammonia, hydrogen cyanide and the like in the coke oven gas are removed to the process requirement index.
Preferably, the hydrodesulfurization in the step 2) comprises the specific steps of preheating purified coke-oven gas, sequentially entering a pre-hydrogenation reactor and a primary hydrogenation reactor to remove oxygen in the coke-oven gas, converting most organic sulfur into inorganic sulfur, and entering a primary medium-temperature zinc oxide tank to remove hydrogen sulfide in the coke-oven gas; the coke-oven gas from the first-stage medium-temperature zinc oxide tank enters a second-stage hydrogenation reactor to further convert organic sulfur into inorganic sulfur, and then the sulfur content in the coke-oven gas is removed through the second-stage medium-temperature zinc oxide tank.
Preferably, the total sulfur in the coke oven gas after desulfurization in the step 2) is reduced to less than or equal to 0.1 ppmv.
Preferably, the conversion specific step in the step 3) is that the desulfurized gas is subjected to waste heat recovery, proper water vapor is added, the desulfurized gas enters the conversion reactor, and the converted gas is sent to the decarburization unit after byproduct steam and heat are recovered.
Preferably, the dry basis index of carbon monoxide in the shifted gas obtained in step 3) is 0.2V% to 1.5V%.
Preferably, the gas in step 4) is decarbonized using an MDEA solution.
Preferably, the index of carbon dioxide in the decarbonated gas obtained in step 4) is 0.1 to 1.5V%.
Preferably, the methanation in the step 5) comprises the specific steps that the decarbonized gas is preheated and then enters a methanation reactor, the methane-rich gas at the outlet of the methanation reactor enters a second-stage methanation reactor after byproduct steam and waste heat are recovered, and CO + CO at the outlet of the second-stage methanation reactor2Less than or equal to 20 ppm; after waste heat recovery, the waste heat is cooled to 40 ℃ by using circulating water to obtain methane-rich gas, and the methane-rich gas mainly comprises 30-80V% of hydrogen, 20-60V% of methane and 3-8V% of nitrogen.
Preferably, the specific step of deep cooling separation in the step 6) is that the methane-rich gas enters a cooling box after being subjected to deep cooling pretreatment to remove moisture, dust and other trace harmful impurities; and carrying out cryogenic separation to obtain an LNG product.
In order to better explain the context of the invention, the invention is further described below by means of specific examples, which should not be construed as limiting the scope of the invention thereto, all features disclosed in the summary of the invention, or all steps of a method or process disclosed, may be combined in any way, except mutually exclusive features and/or steps. Any feature disclosed in this application may be replaced by alternative features serving equivalent or similar purposes, unless expressly stated otherwise. That is, unless expressly stated otherwise, each feature is only an example of a generic series of equivalent or similar features.
In the present application, all% refer to V% unless otherwise specified.
Example 1
Coke oven gas entering boundary region at 40 deg.c, 6kPaG pressure and 49724Nm gas amount3Dry basis, hydrogen 58.07%, carbon monoxide 6.45%, carbon dioxide 2.15%, methane 25.81%, oxygen 0.54%, CnHm 2.48%, and impurity composition (mg/Nm)3): 100 of tar, 200 of naphthalene, 50 of ammonia, 50 of hydrogen sulfide, 150 of organic sulfur, 150 of hydrogen cyanide, C6 and above hydrocarbons 2500.
1) Compression purification
Coke oven gas from coking is pretreated, and tar in the coke oven gas is removed to 5mg/Nm by gas-liquid separation or adsorption3Naphthalene is removed to 50mg/Nm3After the coke oven gas enters a gas holder for buffering and storage, the coke oven gas enters a plurality of parallel reciprocating compressors with the pressure of about 3-4 kPaG, the reciprocating compressors adopt four-stage compression, the coke oven gas can be compressed from normal pressure to 2.4MPaG, then the coke oven gas is sent to a purification unit, and the tar in the coke oven gas is further removed to 1mg/Nm3Following, naphthalene was removed to 5mg/Nm3The following.
2) Hydrodesulfurization of hydrocarbons
From pressureThe coke oven gas of the compressor is washed to remove the ammonia in the coke oven gas to 5mg/Nm3Hydrocyanic acid is removed to 1mg/Nm3The following. Then preheating to about 240 ℃, sequentially entering a pre-hydrogenation reactor and a primary hydrogenation reactor, removing oxygen in the coke-oven gas, simultaneously converting 90% of organic sulfur into inorganic sulfur, and then entering a primary medium-temperature zinc oxide tank to remove hydrogen sulfide in the coke-oven gas. The coke oven gas from the first-stage medium-temperature zinc oxide tank enters a second-stage hydrogenation reactor to further convert organic sulfur into inorganic sulfur, and then the total sulfur content in the coke oven gas is removed to be below 0.1ppm through the second-stage medium-temperature zinc oxide tank.
3) Transformation of
After waste heat recovery and addition of proper amount of water vapor, the desulfurized gas enters a wide temperature shift reactor after the temperature is reduced to 230 ℃. The converted gas is about 280 ℃, and is sent to a downstream process after byproduct steam and heat are recovered. The main gas components of the time-varying ventilation gas are 59.52% of hydrogen, 0.60% of carbon monoxide, 7.82% of carbon dioxide and 25.25% of methane.
4) Decarburization of carbon
The scrubbing gas is decarbonized by adopting an MDEA solution, and the main gas components of the decarbonized process gas are 64.44% of hydrogen, 0.65% of carbon monoxide, 0.20% of carbon dioxide and 27.33% of methane.
5) Methanation
The decarbonization gas is preheated to the temperature of 360-plus-385 ℃ and then enters a methanation reactor, the outlet of the methanation reactor is 485-plus-515 ℃, the decarbonization gas enters a second-stage methanation reactor after byproduct steam and waste heat recovery, and CO + CO at the outlet of the second-stage methanation reactor2Less than or equal to 20 ppm. After waste heat recovery, the waste heat is cooled to 40 ℃ by using circulating water to obtain methane-rich gas, and the methane-rich gas mainly comprises 60.51% of hydrogen and 34.60% of methane. The amount of methane-rich gas is about 45752Nm3/h。
6) Cryogenic separation
The methane-rich gas enters a drying tower from the lower part, and the water in the dried gas from the upper part is removed to below 1ppm for cryogenic separation. The regeneration gas of the drying tower adopts nitrogen-rich gas of cryogenic separation and nitrogen gas from air separation. Then a mixed refrigerant refrigeration separation process is adopted to obtain an LNG product of 11.31t/h, the cryogenic tail gas of the byproduct is divided into two streams, one stream of hydrogen-rich gas is directly sent to an ammonia synthesis unit to be used as raw material gas, and the other stream of nitrogen-rich gas is used as regeneration gas of a drying unit.
7) Ammonia synthesis
After being pressurized by a nitrogen compressor, the nitrogen-rich gas from the dry regenerated gas is mixed with the hydrogen-rich gas from the cryogenic separation, and then the mixture enters an ammonia synthesis gas compressor, and enters an ammonia synthesis unit after being pressurized, so that a liquid ammonia product is obtained at 13.71 t/h.
Example 2
Coke oven gas entering boundary region at 40 deg.c, 6kPaG pressure and 49724Nm gas amount3Dry basis, hydrogen 58.07%, carbon monoxide 6.45%, carbon dioxide 2.15%, methane 25.81%, oxygen 0.54%, CnHm 2.48%, and impurity composition (mg/Nm)3): 100 of tar, 200 of naphthalene, 50 of ammonia, 50 of hydrogen sulfide, 150 of organic sulfur, 150 of hydrogen cyanide, C6 and above hydrocarbons 2500.
1) Compressed purification (same as example 1)
Coke oven gas from coking is pretreated, and tar in the coke oven gas is removed to 5mg/Nm by gas-liquid separation or adsorption3Naphthalene is removed to 50mg/Nm3After the coke oven gas enters a gas holder for buffering and storage, the coke oven gas enters a plurality of parallel reciprocating compressors with the pressure of about 3-4 kPaG, the reciprocating compressors adopt four-stage compression, the coke oven gas can be compressed from normal pressure to 2.4MPaG, then the coke oven gas is sent to a purification unit, and the tar in the coke oven gas is further removed to 1mg/Nm3Following, naphthalene was removed to 5mg/Nm3The following.
2) Hydrodesulfurization (same as in example 1)
Removing ammonia in coke oven gas from a compressor to 5mg/Nm through water washing3Hydrocyanic acid is removed to 1mg/Nm3The following. Then preheating to about 240 ℃, sequentially entering a pre-hydrogenation reactor and a primary hydrogenation reactor, removing oxygen in the coke-oven gas, simultaneously converting 90% of organic sulfur into inorganic sulfur, and then entering a primary medium-temperature zinc oxide tank to remove hydrogen sulfide in the coke-oven gas. The coke-oven gas from the first-stage medium-temperature zinc oxide tank enters a second-stage hydrogenation reactor to further convert organic sulfur into inorganic sulfur, and then the inorganic sulfur is oxidized by the second-stage medium-temperature zinc oxide tankAnd the zinc tank is used for removing the total sulfur content in the coke oven gas to be below 0.1 ppm.
3) The main gas components of the converted gas are 58.18% of hydrogen, 3.93% of carbon monoxide, 4.76% of carbon dioxide and 26.08% of methane by adjusting the steam-water ratio of the conversion.
4) The decarburization is carried out by adopting MDEA solution, and the main gas components in the decarburization gas are 60.48% of hydrogen, 4.08% of carbon monoxide, 0.99% of carbon dioxide and 27.11% of methane.
5) Methanation
Preheating the decarbonization gas to the temperature of between 270 and 305 ℃, then feeding the decarbonization gas into a methanation reactor, wherein the temperature of the outlet of the methanation reactor is between 510 and 540 ℃, recycling byproduct steam and waste heat, then feeding the byproduct steam into a second-stage methanation reactor, and feeding CO + CO at the outlet of the second-stage methanation reactor2Less than or equal to 20 ppm. After waste heat recovery, the waste heat is cooled to 40 ℃ by using circulating water to obtain methane-rich gas, and the methane-rich gas mainly comprises 49.47% of hydrogen and 44.90% of methane. The amount of methane-rich gas is about 39731Nm3/h。
6) The LNG product is obtained at 12.74t/h by adopting a mixed refrigerant refrigeration separation process, the cryogenic tail gas of the byproduct is divided into two streams, one stream of hydrogen-rich gas is directly sent to an ammonia synthesis unit to be used as raw material gas, and the other stream of nitrogen-rich gas is used as regeneration gas of a drying unit.
7) After being pressurized by a nitrogen compressor, the nitrogen-rich gas from the dry regenerated gas is mixed with the hydrogen-rich gas from the cryogenic separation, and then the mixture enters an ammonia synthesis gas compressor, and enters an ammonia synthesis unit after being pressurized, so that a liquid ammonia product of 9.73t/h is obtained.
Example 3
Coke oven gas entering boundary region at 40 deg.c, 6kPaG pressure and 49724Nm gas amount3Dry basis, hydrogen 58.07%, carbon monoxide 6.45%, carbon dioxide 2.15%, methane 25.81%, oxygen 0.54%, CnHm 2.48%, and impurity composition (mg/Nm)3): 100 of tar, 200 of naphthalene, 50 of ammonia, 50 of hydrogen sulfide, 150 of organic sulfur, 150 of hydrogen cyanide, C6 and above hydrocarbons 2500.
1) Compressed purification (same example 1)
Coke oven gas from coking is pretreated, and tar in the coke oven gas is removed to 5mg/Nm by gas-liquid separation or adsorption3In the following, the following description is given,naphthalene is removed to 50mg/Nm3After the coke oven gas enters a gas holder for buffering and storage, the coke oven gas enters a plurality of parallel reciprocating compressors with the pressure of about 3-4 kPaG, the reciprocating compressors adopt four-stage compression, the coke oven gas can be compressed from normal pressure to 2.4MPaG, then the coke oven gas is sent to a purification unit, and the tar in the coke oven gas is further removed to 1mg/Nm3Following, naphthalene was removed to 5mg/Nm3The following.
2) Hydrodesulfurization (same as in example 1)
Removing ammonia in coke oven gas from a compressor to 5mg/Nm through water washing3Hydrocyanic acid is removed to 1mg/Nm3The following. Then preheating to about 240 ℃, sequentially entering a pre-hydrogenation reactor and a primary hydrogenation reactor, removing oxygen in the coke-oven gas, simultaneously converting 90% of organic sulfur into inorganic sulfur, and then entering a primary medium-temperature zinc oxide tank to remove hydrogen sulfide in the coke-oven gas. The coke oven gas from the first-stage medium-temperature zinc oxide tank enters a second-stage hydrogenation reactor to further convert organic sulfur into inorganic sulfur, and then the total sulfur content in the coke oven gas is removed to be below 0.1ppm through the second-stage medium-temperature zinc oxide tank.
3) Conversion (same example 1)
After waste heat recovery and addition of proper amount of water vapor, the desulfurized gas enters a wide temperature shift reactor after the temperature is reduced to 230 ℃. The converted gas is about 280 ℃, and is sent to a downstream process after byproduct steam and heat are recovered. The main gas components of the time-varying ventilation gas are 59.52% of hydrogen, 0.60% of carbon monoxide, 7.82% of carbon dioxide and 25.25% of methane.
4) Decarbonization (same as example 1)
The scrubbing gas is decarbonized by adopting an MDEA solution, and the main gas components of the decarbonized process gas are 64.44% of hydrogen, 0.65% of carbon monoxide, 0.20% of carbon dioxide and 27.33% of methane.
5) Methanation (as in example 1)
The decarbonization gas is preheated to the temperature of 360-plus-385 ℃ and then enters a methanation reactor, the outlet of the methanation reactor is 485-plus-515 ℃, the decarbonization gas enters a second-stage methanation reactor after byproduct steam and waste heat recovery, and CO + CO at the outlet of the second-stage methanation reactor2Less than or equal to 20 ppm. After waste heat recovery, the waste heat is cooled by circulating waterAnd (3) obtaining methane-rich gas with main components of 60.51% of hydrogen and 34.60% of methane at 40 ℃. The amount of methane-rich gas is about 45752Nm3/h。
6) Cryogenic separation (same example 1)
The methane-rich gas enters a drying tower from the lower part, and the water in the dried gas from the upper part is removed to below 1ppm for cryogenic separation. The regeneration gas of the drying tower adopts nitrogen-rich gas of cryogenic separation and nitrogen gas from air separation. Then, a mixed refrigerant refrigeration separation process is adopted to obtain 11.31t/h LNG product, the by-product cryogenic tail gas is reheated and then sent to a PSA hydrogen extraction device, the total amount is 30241Nm3/h, and the main gas components are 91.54% of hydrogen, 7.40% of nitrogen and 1.06% of methane. .
7) The tail gas from the cryogenic separation enters a PSA hydrogen extraction adsorption tower, and a hydrogen product (99.99%) 25705Nm3/h can be obtained. The desorbed gas is about 4536Nm3/h and is used as dry regenerated gas which is returned to the coke oven for fuel.
Example 4
Coke oven gas entering boundary region at 40 deg.c, 6kPaG pressure and 49724Nm gas amount3Dry basis, hydrogen 58.07%, carbon monoxide 6.45%, carbon dioxide 2.15%, methane 25.81%, oxygen 0.54%, CnHm 2.48%, and impurity composition (mg/Nm)3): 100 of tar, 200 of naphthalene, 50 of ammonia, 50 of hydrogen sulfide, 150 of organic sulfur, 150 of hydrogen cyanide, C6 and above hydrocarbons 2500.
1) Compressed purification (same as example 2)
Coke oven gas from coking is pretreated, and tar in the coke oven gas is removed to 5mg/Nm by gas-liquid separation or adsorption3Naphthalene is removed to 50mg/Nm3After the coke oven gas enters a gas holder for buffering and storage, the coke oven gas enters a plurality of parallel reciprocating compressors with the pressure of about 3-4 kPaG, the reciprocating compressors adopt four-stage compression, the coke oven gas can be compressed from normal pressure to 2.4MPaG, then the coke oven gas is sent to a purification unit, and the tar in the coke oven gas is further removed to 1mg/Nm3Following, naphthalene was removed to 5mg/Nm3The following.
2) Hydrodesulfurization (same as in example 2)
The coke-oven gas from the compressor is washed to remove ammonia in the coke-oven gas to 5mg/Nm3Hydrocyanic acid is removed to 1mg/Nm3The following. Then preheating to about 240 ℃, sequentially entering a pre-hydrogenation reactor and a primary hydrogenation reactor, removing oxygen in the coke-oven gas, simultaneously converting 90% of organic sulfur into inorganic sulfur, and then entering a primary medium-temperature zinc oxide tank to remove hydrogen sulfide in the coke-oven gas. The coke oven gas from the first-stage medium-temperature zinc oxide tank enters a second-stage hydrogenation reactor to further convert organic sulfur into inorganic sulfur, and then the total sulfur content in the coke oven gas is removed to be below 0.1ppm through the second-stage medium-temperature zinc oxide tank.
3) Alternative (same as embodiment 2)
The main gas components of the converted gas are 58.18% of hydrogen, 3.93% of carbon monoxide, 4.76% of carbon dioxide and 26.08% of methane by adjusting the steam-water ratio of the conversion.
4) Decarburization (same as example 2)
The decarburization is carried out by adopting MDEA solution, and the main gas components in the decarburization gas are 60.48% of hydrogen, 4.08% of carbon monoxide, 0.99% of carbon dioxide and 27.11% of methane.
5) Methanation (as in example 2)
Preheating the decarbonization gas to the temperature of between 270 and 305 ℃, then feeding the decarbonization gas into a methanation reactor, wherein the temperature of the outlet of the methanation reactor is between 510 and 540 ℃, recycling byproduct steam and waste heat, then feeding the byproduct steam into a second-stage methanation reactor, and feeding CO + CO at the outlet of the second-stage methanation reactor2Less than or equal to 20 ppm. After waste heat recovery, the waste heat is cooled to 40 ℃ by using circulating water to obtain methane-rich gas, and the methane-rich gas mainly comprises 49.47% of hydrogen and 44.90% of methane. The amount of methane-rich gas is about 39731Nm3/h。
6) Cryogenic separation (same as example 2)
The LNG product is 12.74t/h by adopting a mixed refrigerant refrigeration separation process, the by-product cryogenic tail gas is reheated and then sent to a PSA hydrogen extraction device, and the total amount is 22123Nm3The main gas components are 88.85 percent of hydrogen, 10.11 percent of nitrogen and 1.04 percent of methane. .
7) The tail gas from the cryogenic separation enters a PSA hydrogen extraction adsorption tower to obtain a hydrogen product (99.99 percent) 18804Nm3H is used as the reference value. The desorbed gas is about 3319Nm3/h, and is used as dry regenerated gas, which is returned to the coke oven for fuel.
The invention is not limited to the foregoing embodiments. The invention extends to any novel feature or any novel combination of features disclosed in this specification and any novel method or process steps or any novel combination of features disclosed.

Claims (10)

1. A technology for preparing liquefied natural gas and co-producing liquid ammonia or hydrogen by using coke oven gas with shift decarburization is characterized by comprising the following steps:
1) purifying: pretreating the coke-oven gas to obtain primarily purified coke-oven gas;
2) hydrodesulfurization: carrying out hydrodesulfurization treatment on the primarily purified coke oven gas to remove sulfides in the coke oven gas;
3) and (3) transformation: setting a conversion and waste heat recovery unit to adjust H in the coke oven gas2、CO、CO2Obtaining the transformed gas according to the proportion;
4) decarbonization: most of carbon dioxide in the shift gas is removed, and the obtained decarbonized gas is sent to a methanation unit;
5) methanation: carrying out methanation on the decarbonized gas to obtain a methane-rich gas;
6) cryogenic separation: and (3) performing a refrigeration separation process on the methane-rich gas by using a mixed refrigerant to obtain an LNG product.
2. The process for preparing liquefied natural gas and co-producing liquid ammonia or hydrogen gas by using coke oven gas with shift decarburization as claimed in claim 1, wherein the purification step in step 1) is: primarily removing macromolecular impurities in coke-oven gas from coking by adopting a gas-liquid separation or adsorption mode, then entering a gas holder for buffering and storage, then entering a compressor, compressing the coke-oven gas to 1.0-4.5 MPaG from normal pressure, and then sending the coke-oven gas to a purification process unit; the purification process unit mainly comprises the steps of washing, gas-liquid separation and adsorption, and impurities such as tar, naphthalene, ammonia, hydrogen cyanide and the like in the coke oven gas are removed to the process requirement index.
3. The process for preparing liquefied natural gas and co-producing liquid ammonia or hydrogen gas by using the coke oven gas with shift decarburization as claimed in claim 1, wherein the hydrodesulfurization in step 2) comprises preheating purified coke oven gas, sequentially feeding the preheated coke oven gas into a pre-hydrogenation reactor and a primary hydrogenation reactor to remove oxygen in the coke oven gas, converting most organic sulfur into inorganic sulfur, and feeding the inorganic sulfur into a primary medium-temperature zinc oxide tank to remove hydrogen sulfide in the coke oven gas; the coke-oven gas from the first-stage medium-temperature zinc oxide tank enters a second-stage hydrogenation reactor to further convert organic sulfur into inorganic sulfur, and then the sulfur content in the coke-oven gas is removed through the second-stage medium-temperature zinc oxide tank.
4. The process for preparing liquefied natural gas and co-producing liquid ammonia or hydrogen gas by using the coke oven gas with shift decarburization as claimed in claim 1 or 3, wherein the total sulfur in the coke oven gas after desulfurization in step 2) is reduced to less than or equal to 0.1 ppmv.
5. The process for preparing liquefied natural gas and co-producing liquid ammonia or hydrogen gas by using coke oven gas with shift decarburization as claimed in claim 1, wherein the shift in step 3) comprises the specific steps of recovering waste heat of the desulfurized gas, adding appropriate amount of water vapor, entering a shift reactor, and sending the shifted gas to the decarburization unit after byproduct steam and heat are recovered.
6. The process for preparing liquefied natural gas and co-producing liquid ammonia or hydrogen gas by using the coke oven gas with shift decarburization as claimed in claim 1 or 5, wherein the dry basis index of carbon monoxide in the shift gas obtained in step 3) is 0.2V% -1.5V%.
7. The process for preparing liquefied natural gas and co-producing liquid ammonia or hydrogen gas by using coke oven gas with shift decarburization as claimed in claim 1, wherein the shift gas in step 4) is decarbonized by using MDEA solution.
8. The process for preparing liquefied natural gas and co-producing liquid ammonia or hydrogen gas by using coke oven gas with shift decarburization as claimed in claim 1 or 7, wherein the index of carbon dioxide in the decarbonized gas obtained in step 4) is 0.1V% -1.5V%.
9. The process for preparing liquefied natural gas and CO-producing liquid ammonia or hydrogen gas by using the coke oven gas with shift decarburization as claimed in claim 1, wherein the methanation in step 5) comprises the specific steps of preheating the decarbonized gas and then feeding the decarbonized gas into a methanation reactor, recycling the byproduct steam and waste heat of the methane-rich gas at the outlet of the methanation reactor and then feeding the methane-rich gas into a second-stage methanation reactor, and recycling CO + CO at the outlet of the second-stage methanation reactor2Less than or equal to 20 ppm; after waste heat recovery, the waste heat is cooled to 40 ℃ by using circulating water to obtain methane-rich gas, and the methane-rich gas mainly comprises 30-80V% of hydrogen, 20-60V% of methane and 3-8V% of nitrogen.
10. The process for preparing liquefied natural gas and co-producing liquid ammonia or hydrogen gas by using the coke oven gas with shift decarburization as claimed in claim 1, wherein the specific step of deep cooling separation in step 6) is that the methane-rich gas is subjected to deep cooling pretreatment, and enters a cooling box after moisture, micro dust and other trace harmful impurities are removed; and carrying out cryogenic separation to obtain an LNG product.
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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113955716A (en) * 2020-06-29 2022-01-21 杨皓 Process for preparing synthetic gas and CNG (compressed natural gas) from coke-oven gas submerged arc furnace gas
CN115572213A (en) * 2022-11-08 2023-01-06 中国平煤神马控股集团有限公司 Process for coproduction of 1, 4-butanediol and liquid ammonia by coal gasification coupled with coal coking

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CN112897464A (en) * 2021-01-18 2021-06-04 西南化工研究设计院有限公司 Process for producing hydrogen and coproducing LNG (liquefied Natural gas) by using raw gas with methanation

Patent Citations (1)

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CN112897464A (en) * 2021-01-18 2021-06-04 西南化工研究设计院有限公司 Process for producing hydrogen and coproducing LNG (liquefied Natural gas) by using raw gas with methanation

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113955716A (en) * 2020-06-29 2022-01-21 杨皓 Process for preparing synthetic gas and CNG (compressed natural gas) from coke-oven gas submerged arc furnace gas
CN115572213A (en) * 2022-11-08 2023-01-06 中国平煤神马控股集团有限公司 Process for coproduction of 1, 4-butanediol and liquid ammonia by coal gasification coupled with coal coking

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