CN112961711A - System and method for preparing LNG (liquefied Natural gas) and coproducing methanol, liquid ammonia and hydrogen through coke oven gas purification - Google Patents

System and method for preparing LNG (liquefied Natural gas) and coproducing methanol, liquid ammonia and hydrogen through coke oven gas purification Download PDF

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CN112961711A
CN112961711A CN202110170244.4A CN202110170244A CN112961711A CN 112961711 A CN112961711 A CN 112961711A CN 202110170244 A CN202110170244 A CN 202110170244A CN 112961711 A CN112961711 A CN 112961711A
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gas
tower
liquid
coke oven
outlet
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CN112961711B (en
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王贵
关杰
郝成浩
左永飞
范辉
张超
张焘
赵普生
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Sedin Engineering Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10K—PURIFYING OR MODIFYING THE CHEMICAL COMPOSITION OF COMBUSTIBLE GASES CONTAINING CARBON MONOXIDE
    • C10K1/00—Purifying combustible gases containing carbon monoxide
    • C10K1/08—Purifying combustible gases containing carbon monoxide by washing with liquids; Reviving the used wash liquors
    • C10K1/16—Purifying combustible gases containing carbon monoxide by washing with liquids; Reviving the used wash liquors with non-aqueous liquids
    • 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
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
    • C07C29/15—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively
    • C07C29/151—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively with hydrogen or hydrogen-containing gases
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10K—PURIFYING OR MODIFYING THE CHEMICAL COMPOSITION OF COMBUSTIBLE GASES CONTAINING CARBON MONOXIDE
    • C10K1/00—Purifying combustible gases containing carbon monoxide
    • C10K1/002—Removal of contaminants
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10K—PURIFYING OR MODIFYING THE CHEMICAL COMPOSITION OF COMBUSTIBLE GASES CONTAINING CARBON MONOXIDE
    • C10K1/00—Purifying combustible gases containing carbon monoxide
    • C10K1/002—Removal of contaminants
    • C10K1/003—Removal of contaminants of acid contaminants, e.g. acid gas removal
    • C10K1/004—Sulfur containing contaminants, e.g. hydrogen sulfide
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10K—PURIFYING OR MODIFYING THE CHEMICAL COMPOSITION OF COMBUSTIBLE GASES CONTAINING CARBON MONOXIDE
    • C10K1/00—Purifying combustible gases containing carbon monoxide
    • C10K1/002—Removal of contaminants
    • C10K1/003—Removal of contaminants of acid contaminants, e.g. acid gas removal
    • C10K1/005—Carbon dioxide
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10K—PURIFYING OR MODIFYING THE CHEMICAL COMPOSITION OF COMBUSTIBLE GASES CONTAINING CARBON MONOXIDE
    • C10K1/00—Purifying combustible gases containing carbon monoxide
    • C10K1/32—Purifying combustible gases containing carbon monoxide with selectively adsorptive solids, e.g. active carbon
    • 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
    • Y02P20/50—Improvements relating to the production of bulk chemicals

Abstract

The invention provides a system and a method for preparing LNG (liquefied natural gas) and coproducing methanol, liquid ammonia and hydrogen by coke oven gas purification, and belongs to the field of coke oven gas purification. The pre-washing tower is a supergravity rotating device, so that the debenzolized coke oven gas can be subjected to primary impurity removal in the pre-washing tower by a supergravity rotating technology to deeply remove harmful substances such as dust, benzene, tar, naphthalene, ammonia, sulfur and the like in the debenzolized coke oven gas, and the problem that sulfur and ammonia in the coke oven gas exceed standards and can shadow is solvedThe system stably operates after the noise, solves the problem that the tar and naphthalene in the coke oven gas can cause the blockage of a compression system, and solves the problem that the desulfurization adsorbent for fine desulfurization fails in advance to increase the operation cost due to abnormal coarse desulfurization. The coke oven gas is returned to the coke oven through pretreatment without desulfurization, so that the investment and the generation of desulfurization waste liquid can be reduced. Separation of CH by cryogenic separation of coke oven gas4、CO、H2The product can be used as raw material gas to synthesize methanol and liquid ammonia and output hydrogen, thereby achieving the effect of separate utilization of coke oven gas.

Description

System and method for preparing LNG (liquefied Natural gas) and coproducing methanol, liquid ammonia and hydrogen through coke oven gas purification
Technical Field
The invention relates to the technical field of coke oven gas purification, in particular to a system and a method for preparing LNG (liquefied natural gas) and coproducing methanol, liquid ammonia and hydrogen through coke oven gas purification.
Background
Coke oven gas is an important byproduct obtained in the coking process, and the research on the composition of coke oven gas has become quite mature in recent years. The coke oven gas belongs to medium-heat value natural gas, the hydrogen content is 50-60%, and the methane content is 22-24%, wherein the coke oven gas has great utilization value. A large amount of coke oven gas can be generated while producing coke, if the generation amount of the coke oven gas in China is basically maintained at 1800 billions of cubic meters according to the calculation of producing 430 cubic meters of coke oven gas by producing 1 ton of coke, wherein about 45-50% of the coke oven gas returns to the coke oven, and the residual coke oven gas is considerable. Therefore, how to recycle the coke oven gas has important significance for realizing the cyclic utilization of resources and the sustainable development of economy. The purification of the coke oven gas becomes the most important thing before the coke oven gas is comprehensively utilized.
The hydrogen content of the coke oven gas is about 55-60%. The hydrogen has the advantages of high heat value, pure quality and the like, and is popular among people. As a clean energy with the most development potential, hydrogen has wide development and application prospects, and can be widely applied to the fields of energy, industry, transportation, buildings and the like. Raw materials, reducing agents and high-quality heat sources are provided for the industries of refining, steel, metallurgy and the like, and carbon emission can be effectively reduced; the fuel cell can also be applied to the fields of automobiles, rail transit, ships and the like through the fuel cell technology, so that the dependence of transportation on petroleum and natural gas is reduced; the system can also be applied to distributed power generation and power supply and heating for family houses, commercial buildings and the like. Therefore, as a link of multi-energy transmission and fusion interaction, hydrogen energy is known as the secondary energy with the greatest development prospect in the 21 st century, and is one of the cores of future clean low-carbon energy systems.
The Liquefied Natural Gas (LNG) mainly contains 80-99% of methane, is colorless, odorless and noncorrosive, and has high heat value (more than 31 MJ/Nm)3) And the fuel has the characteristic of convenient storage and transportation, and is generally used as main fuel for industrial enterprises such as power plants, heat energy, heating and air conditioning, catering industry and civil fuel, chemical raw materials and the like. The hydrogen is used as fuel, is the highest of all fossil fuels, chemical raw materials and biological fuels, is 142351kJ/kg, is 3 times of the calorific value of gasoline, and the combustion product of the hydrogen is water, has no ash residue and waste gas, and does not pollute the environment. In recent years, with the continuous development of the hydrogen energy industry, the market demand is increasing, and the hydrogen energy industry has a wide market.
The high-content hydrogen in the coke oven gas is taken as an ideal raw material for hydrogen production, and the hydrogen is gradually an important way for promoting the industrial upgrading of the coking industry and developing hydrogen energy sources in China. Meanwhile, the coke oven gas is also rich in raw materials for preparing LNG, methanol and synthetic ammonia. Therefore, how to comprehensively utilize the coke oven gas is widely concerned. However, because the coke oven gas contains impurities such as benzene, naphthalene, ammonia, tar, dust, sulfur and the like, the purification process of the coke oven gas in comprehensive utilization faces significant examination. The main manifestations are as follows:
(1) the coke oven gas contains excessive sulfur and ammonia, and the normal operation of subsequent purification and synthesis is influenced.
When the coke oven gas is used as fuel gas, the requirement is H2S is less than 500mg/Nm3Ammonia content of less than 100mg/Nm3However, the acid gas and ammonia in actual operation exceed the standards, which affects the stable operation of the system. Along with the expansion of coking scale and industrial aggregation, the coke oven gas becomes an important chemical raw material gas for use, and the change of the application of the coke oven gas causes that the design index of the deep purification of the original coke oven gas can not meet the requirement of the current use index.
(2) The coke oven gas contains tar and naphthalene, which seriously affect the normal operation of the compressor, mainly because the coke oven gas contains the tar and the naphthalene is high in content, and the gas temperature is increased during compression to gasify and coke the tar; and naphthalene is condensed and crystallized to cause naphthalene blockage of the compressor, so that the compressor cannot normally run and is forced to stop repairing, and the compressor is stopped for repairing only by opening for 1-2 days, so that the production is quite passive and is usually the situation of 1 opening for 2 spare or 1 opening for 3 spare.
(3) The desulfurization agent of the fine desulfurization is failed in advance due to abnormal rough desulfurization, which affects the production operation, mainly sulfur penetrates, and the desulfurization agent is forced to be replaced in advance, so that the desulfurization agent is replaced frequently, and the operating cost is increased.
(4) The sulfur content in the coke oven gas returned to the furnace is high, a flue gas desulfurization device needs to be built to remove sulfur oxide in the flue gas, and meanwhile, the desulfurization process can generate refractory desulfurization waste liquid.
(5) The traditional decarburization process for hydrogen production adopts a methanation process, consumes a certain amount of hydrogen in the decarburization process, reduces the yield of the hydrogen and influences the yield of byproducts.
Disclosure of Invention
The invention provides a system and a method for preparing LNG (liquefied natural gas) and co-producing methanol, liquid ammonia and hydrogen by purifying coke oven gas, aiming at solving the technical problems that the operation stability of a rear system is influenced, a compressor is blocked, a desulfurizing agent for fine desulfurization fails in advance to increase the operation cost, the sulfur content in the coke oven gas returned to a coke oven is high, and the yield of hydrogen is low to influence the yield of byproducts in the prior art when the coke oven gas is comprehensively utilized.
In order to solve the technical problems, the invention adopts the technical scheme that:
the utility model provides a system for coke oven gas purifies system LNG coproduction methyl alcohol, liquid ammonia and hydrogen, it includes prewashing tower, desulfurizing tower, decarbonization tower, first adsorption tower, second adsorption tower, strip tower, first reboiler, first vapour and liquid separator, second vapour and liquid separator, first cold box, second reboiler, third vapour and liquid separator, knockout tower, methyl alcohol synthetic tower, steam pocket and synthetic ammonia tower, wherein: the prewashing tower is a supergravity rotating device, wherein: the gas holder is connected with the gas phase inlet at the lower part of the prewashing tower through the first heat exchanger, the liquid phase outlet at the bottom of the prewashing tower is connected with the gas-liquid separation device, the gas outlet at the top of the prewashing tower is connected with the gas inlet at the lower part of the desulfurizing tower through the first compressor, the second heat exchanger and the third heat exchanger, the gas outlet at the top of the desulfurizing tower is connected with the coke oven through the fourth heat exchanger and the second compressor, the gas outlet at the top of the desulfurizing tower is also connected with the gas inlet at the lower part of the decarbonizing tower, the liquid outlet at the bottom of the desulfurizing tower is connected with the liquid phase inlet at the upper part of the prewashing tower through the fifth heat exchanger and the third compressor, the gas outlet at the top of the decarbonizing tower is connected with the gas inlet of the first adsorption tower and the gas inlet of the second adsorption tower, the gas outlet of the, the gas outlet of the first adsorption tower and the gas outlet of the second adsorption tower are connected with a gas inlet at the top of the first cold box, the gas outlet at the bottom of the first cold box is also connected with a gas inlet at the upper part of the first reboiler, the gas outlet at the lower part of the first reboiler and the gas outlet at the bottom of the first cold box are both connected with a gas inlet at the top of the second cold box, a material outlet at the bottom of the second cold box is connected with a material inlet at the top of the third gas-liquid separator, a hydrogen-rich gas outlet at the top of the third gas-liquid separator is connected with a hydrogen-rich gas inlet at the bottom of the second cold box, a hydrogen-rich gas outlet at the top of the second cold box is connected with a hydrogen-rich gas inlet at the bottom of the first cold box, a hydrogen-rich gas outlet at the top of the first cold box is connected with a PSA hydrogen purification system, a hydrogen-rich gas outlet at the top of the first cold box is also connected with a gas inlet of the synthetic ammonia tower, a liquid outlet at the bottom of the second gas-liquid separator is connected with a liquid inlet at the side of the second cooling box, a gas outlet at the side of the second cooling box and a gas outlet at the top of the second gas-liquid separator are both connected with a material inlet of the first gas-liquid separator, a liquid outlet and a gas outlet of the first gas-liquid separator are respectively connected with a liquid inlet and a gas inlet at the middle part of the stripping tower, a liquid outlet at the bottom of the third gas-liquid separator is also connected with a liquid inlet at the upper part of the stripping tower, a hydrogen-rich gas outlet at the top of the stripping tower is connected with a hydrogen-rich gas inlet at the side of the second cooling box, a liquid outlet at the bottom of the stripping tower is connected with a liquid inlet at the side of the second cooling box, a liquid outlet at the bottom of the second cooling box is connected with a liquid inlet at the middle part of the separating tower, a CH-rich liquid outlet at the bottom of the separating, a CH-rich liquid outlet at the top of the second cold box is connected with a CH-rich liquid inlet at the bottom of the first cold box, a CH-rich liquid outlet at the top of the first cold box is an LNG outlet, a CO outlet at the top of the separation tower is connected with a CO inlet at the bottom of the second cold box, a CO outlet at the top of the second cold box is connected with a CO inlet at the bottom of the first cold box, a CO outlet at the top of the first cold box is connected with an air inlet at the bottom of the methanol synthesis tower through a fourth compressor, a hydrogen-rich gas outlet at the top of the first cold box is also connected with an air inlet at the bottom of the methanol synthesis tower, a heat exchange tube of the methanol synthesis tower is connected with a steam drum, an air outlet at the top of the methanol synthesis tower is connected with an eighth heat exchanger, a CO outlet of the fourth compressor is connected with a CO inlet at the top of the first cold box, a CO outlet at the bottom of the first cold box is connected with a CO inlet at, the CO outlet of the bottom of the first cold box is also connected with the CO inlet of the upper part of the second reboiler, the CO outlet of the top of the second reboiler is connected with the CO inlet of the lower part of the separation tower, the liquid outlet of the bottom of the separation tower is connected with the liquid inlet of the bottom of the second reboiler, and the liquid outlet of the lower part of the second reboiler is connected with the liquid inlet of the side surface of the second cold box.
Optionally, the prewashing tower comprises a transmission device, a rotating shaft and a prewashing shell, the transmission device is connected with one end of the rotating shaft, the other end of the rotating shaft is connected with a rotor, the rotor is arranged at the middle lower part of an inner cavity of the prewashing shell, a gas outlet is connected in the middle of the top of the prewashing shell, a liquid outlet is connected at the bottom of the prewashing shell, a gas inlet is connected at the bottom of one side of the prewashing shell, a liquid inlet is connected at the middle upper part of the other side of the prewashing shell, an L-shaped liquid pipeline is connected to the liquid inlet, a vertical pipe of the L-shaped liquid pipeline extends to the middle part of the rotor, a plurality of liquid nozzles are installed on the vertical pipe of the L-shaped liquid pipeline, a demister is arranged at the top of the inner cavity of the prewashing shell, a separation plate is installed between the bottom of the demister and the top, the rotor is filled with a filler layer.
A method for preparing LNG and coproducing methanol, liquid ammonia and hydrogen by coke oven gas purification adopts the system for preparing LNG and coproducing methanol, liquid ammonia and hydrogen by coke oven gas purification, and comprises the following steps:
s1, the coke oven gas after benzene elution is sent into the prewashing tower from the lower part of the prewashing tower after the heat exchange of the coke oven gas is carried out to 20-25 ℃ through the first heat exchanger, and meanwhile, a gas detergent from the bottom of the decarbonizing tower is sent into the prewashing tower from the upper part of the prewashing tower after the heat exchange of a fifth heat exchanger and the pressurization of a third compressor; wherein, the prewashing tower is a supergravity rotating device;
s2, performing pretreatment by the countercurrent or cross-flow contact of the coke oven gas after heat exchange and a gas detergent in a prewashing tower, and discharging the pretreated gas detergent to a gas-liquid separation device after gathering on the inner wall of the prewashing tower under the supergravity action of the prewashing tower;
s3, pressurizing the pretreated coke oven gas to 0.3-1.0MPa by a first compressor, then performing heat exchange by a second heat exchanger, performing deep cooling by a third heat exchanger to-22-28 ℃, then entering a desulfurizing tower, performing low-temperature methanol washing operation on the lean methanol introduced into the desulfurizing tower and the lean methanol introduced into the desulfurizing tower in the desulfurizing tower to remove impurities in the coke oven gas to obtain deeply purified coke oven gas, reheating 42-50% of the deeply purified coke oven gas by a fourth heat exchanger, decompressing to 8-10kPa by the second compressor to serve as return gas for heating the coke oven, and introducing the rest of the deeply purified coke oven gas into a decarbonizing tower for decarbonization;
s4, decarbonizing towerThe decarbonized coke oven gas enters a first adsorption tower or a second adsorption tower to adsorb residual methanol and CO2To make their content less than 0.1ml/m3；
S5, the coke oven gas after adsorption is divided into two strands after heat exchange of a first cold box is carried out to-130 to-140 ℃, wherein one strand is mixed with the coke oven gas after adsorption and then enters a first reboiler for vaporization to be used as a heat source of a stripping tower; mixing the coke oven gas from the first reboiler with the other adsorbed coke oven gas from the first cold box, introducing the mixture into a second cold box, and further cooling the mixture in the second cold box to-180 to-185 ℃;
s6, feeding the material from the second cold box into a third gas-liquid separator, and performing gas-liquid separation in the third gas-liquid separator, wherein most of CO and CH4After the condensation, the gas-phase hydrogen-rich gas separated by the third gas-liquid separator is reheated to normal temperature by the first cooling box and the second cooling box, and then is divided into three parts: one part of the PSA hydrogen purification system is used for extracting hydrogen; the other part of the mixed gas and CO enter a methanol synthesis tower to synthesize methanol; a part of the ammonia enters a synthetic ammonia tower to be synthesized with the nitrogen introduced into the synthetic ammonia tower to obtain ammonia gas, and the ammonia gas is subjected to the action of a seventh heat exchanger to obtain liquid ammonia;
s7, dividing the liquid-phase material separated by the third gas-liquid separator into two materials, wherein: reducing the temperature of a strand of material to-180 to-185 after decompression and expansion, changing the pressure to 1.0 to 1.5MPa, allowing the strand of material to enter a second gas-liquid separator for gas-liquid separation, allowing a liquid phase separated by the second gas-liquid separator to enter a second cold box for heat exchange, mixing with a gas phase material separated by the second gas-liquid separator, allowing the temperature of the material to rise to-170 to-175 ℃, allowing the strand of material to enter a first gas-liquid separator for gas-liquid separation, and allowing a gas phase and a liquid phase obtained by separation of the first gas-liquid separator to enter a space between two layers of fillers in a stripping tower for hydrogen extraction; the other material in the liquid phase material separated by the third gas-liquid separator is decompressed and expanded, the temperature is reduced to-180 to-185, the pressure is 1.0 to 1.5MPa, and the other material enters a stripping tower from the upper part of the stripping tower to extract hydrogen; after steam stripping of the stripping tower, hydrogen-rich gas is analyzed from the top of the stripping tower, and is reheated to 35-45 ℃ by the first cooling box and the second cooling box, and then the hydrogen is extracted from a PSA hydrogen purification system, or methanol is synthesized in a methanol synthesis tower, or ammonia is synthesized in an ammonia synthesis tower;
s8, the liquid phase at the bottom of the stripping tower is subjected to heat exchange through a second cooling box to-180 to-185 ℃, the pressure is changed to 0.25 to 0.50MPa, and the liquid phase is divided into two parts: wherein one part of the waste water directly enters the middle part of the packing at the upper part of the separation tower; the other part is vaporized into gas phase in a second cold box, the temperature is raised to-170 to-175 ℃, and the gas phase is used as a heat source to enter a separation tower after the pressure is kept at 0.25 to 0.50 MPa;
s9, separating the material in the separating tower by the separating tower, and enriching CH at the bottom4The temperature of the liquid is-170 to-180 ℃, the pressure is 0.3 to 0.4MPa, and the bottom is rich in CH4After decompression and expansion, the liquid is subjected to heat exchange through a first cold box and a second cold box to normal temperature to obtain LNG;
s10, after the gas CO at the top of the separation tower is subjected to heat exchange to normal temperature through the first cold box 10 and the second cold box, the gas CO enters the fourth compressor to be compressed and then is divided into two parts, and the pressure of the compressed CO is 0.7-0.8 MPa, wherein: one part of the reflux liquid enters the top of the separation tower to be used as reflux liquid of the separation tower, the reflux liquid is subjected to heat exchange by a first cooling box to-150 to-155 ℃, then a material is shunted to a second reboiler to be vaporized to be used as a heat source of the separation tower, and the material cooled in the separation tower enters a second cooling box to be subjected to heat exchange to 180 to-185 ℃ and then enters the top of the separation tower to be used as reflux liquid; the other part of the mixed gas enters a methanol synthesis tower for methanol synthesis after being mixed with the hydrogen-rich gas, and the methanol is obtained from the methane synthesized by the methanol synthesis tower under the action of an eighth heat exchanger.
Optionally, the amount of the coal gas washing agent is 0.20-0.32 kg/m3The dosage of the poor methanol in the desulfurizing tower of the coke oven gas is 1.30-1.50kg/m3Coke oven gas.
Optionally, the temperature of the low-temperature methanol washing operation is-20 ℃ to-40 ℃, and the pressure is 0.3 MPa to 1.5 MPa.
Optionally, the adsorption operation temperature of the first adsorption tower or the second adsorption tower is-60 to-50 ℃, and the operation pressure is 5 to 6 MPa; the desorption operation temperature is 180-350 ℃, the operation pressure is 50-200 kPa, and nitrogen is used for desorption.
Optionally, the operating pressure of the stripping tower is 1.0-1.5 MPa, and the temperature is-196-40 ℃.
Optionally, the separation tower has an operating pressure of 0.1 to 0.5MPa and a temperature of-196 to 40 ℃.
Optionally, the methanol synthesis temperature of the methanol synthesis tower is 230-270 ℃, the pressure is 5-8 MPa, the hydrogen-carbon ratio is 2.05-2.15, and the catalyst is a copper-based catalyst.
Optionally, the temperature of the ammonia synthesized by the ammonia synthesis tower is 470-490 ℃, the pressure is 13-14 MPa, the hydrogen-nitrogen ratio is 2.7-3.0, and the catalyst is an iron-based catalyst.
The invention has the beneficial effects that:
the pre-washing tower is arranged and is a super-gravity rotating device, so that the debenzolized coke oven gas can be subjected to primary impurity removal in the pre-washing tower through a super-gravity rotating technology, and harmful substances such as dust, benzene, tar, naphthalene, ammonia, sulfur and the like in the debenzolized coke oven gas can be deeply removed through pretreatment of the pre-washing tower, so that the problem that the stable operation of a rear system is influenced by the over-standard sulfur and ammonia in the coke oven gas is solved, and the stability of the operation of the system can be improved; the problem that the compression system is blocked due to tar and naphthalene in the coke oven gas is solved, and possible blocking abnormity in the subsequent working section is avoided; the problem that the operation cost is increased due to the fact that the desulfurization adsorbent for fine desulfurization fails in advance due to abnormal coarse desulfurization is solved, and the fine desulfurization catalysis and the service life of chemical products produced subsequently are prolonged by at least more than one year. In addition, through pretreatment, the coke oven gas does not need to be desulfurized again after being returned to the coke oven, so that the investment of a flue gas desulfurization device and the generation of desulfurization waste liquid can be reduced. Further, carry out desulfurization and decarbonization operation through low temperature methanol washing operation, further the impurity in the coke oven gas of deep purification, the cleanliness factor of coke oven gas has been improved, not only avoid the consumption of doctor solution and the treatment cost of desulfurization waste liquid among the traditional handicraft, further reduce purification cost, the sour is sent to the system to the desulfurization waste gas simultaneously, system acid concentration is high and the quality is good, and the decarbonization precision has been improved, therefore can improve the yield of hydrogen to the decarbonization process does not consume hydrogen, and then can improve the output of by-product hydrogen, liquid ammonia and methyl alcohol. By adopting the process flow combining low-temperature methanol washing and PSA adsorption, the impurities such as sulfur in the coke oven gas are fully purified, the consumption of hydrogen in the decarbonization process of the coke oven gas is reduced, the purity and the utilization rate of the hydrogen are improved, and the yield of liquid ammonia and methanol is improved.
The invention separates CH by coke oven gas cryogenic separation4、CO、H2In which H is2And CO are respectively used as raw materials for methanol synthesis and ammonia synthesis, so that the effect of utilizing coke oven gas according to quality is achieved, and the comprehensive utilization efficiency and the economic benefit of the coke oven gas are improved. The system and the method realize the deep purification of the coke oven gas, and the LNG is prepared by cryogenic separation and methanation, and the high-quality hydrogen, methanol and liquid ammonia are byproducts, thereby realizing the cascade utilization of the coke oven gas and improving the economic benefit. The system and the method provided by the embodiment of the invention meet the requirements of pressurized conveying and subsequent deep purification of the coke oven gas, achieve the aim of purifying the produced chemical synthesis system, prepare the LNG and improve the yield of by-product hydrogen, methanol and liquid ammonia. The invention has the advantages of low investment, small equipment volume and occupied area, high efficiency of removing impurities such as tar dust, naphthalene and the like in the coke oven gas, low energy consumption, high washing efficiency and the like.
Drawings
FIG. 1 is a schematic diagram of the system components of the present invention.
FIG. 2 is a schematic view of the structure of the preliminary washing column in FIG. 1.
FIG. 3 is a schematic view of the structure of a gas-liquid separator used in the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples.
As shown in fig. 1, an embodiment of the present invention provides a system for preparing LNG and co-producing methanol, liquid ammonia and hydrogen by purifying coke oven gas, which includes a prewashing tower 1, a desulfurizing tower 2, a decarbonizing tower 3, a first adsorption tower 4, a second adsorption tower 5, a stripping tower 6, a first reboiler 7, a first gas-liquid separator 8, a second gas-liquid separator 9, a first cold box 10, a second cold box 11, a second reboiler 12, a third gas-liquid separator 13, a separation tower 14, a methanol synthesis tower 15, a steam drum 16 and an ammonia synthesis tower 17, wherein: prewashing tower 1 is hypergravity rotary device, wherein: the gas holder is connected with a gas phase inlet 103 at the lower part of the prewashing tower 1 through a first heat exchanger 18, a liquid phase outlet 102 at the bottom of the prewashing tower 1 is connected with a gas-liquid separation device 20, a gas outlet 107 at the top of the prewashing tower 1 is connected with a gas inlet at the lower part of the desulfurizing tower 2 through a first compressor 19, a second heat exchanger 26 and a third heat exchanger 21, a gas outlet at the top of the desulfurizing tower 2 is connected with a coke oven through a fourth heat exchanger 22 and a second compressor 23, a gas outlet at the top of the desulfurizing tower 2 is also connected with a gas inlet at the lower part of the decarbonizing tower 3, a liquid outlet at the bottom of the desulfurizing tower 2 is connected with a liquid phase inlet 109 at the upper part of the decarbonizing tower 3 through a fifth heat exchanger 24 and a third compressor 25, a gas outlet at the top of the decarbonizing tower 3 is connected with a gas inlet of the first adsorption tower 4 and a gas inlet of the second adsorption tower 5, a gas outlet of the first adsorption tower 4 and a gas outlet of Then, the gas outlet of the first adsorption tower 4 and the gas outlet of the second adsorption tower 5 are both connected with the gas inlet at the top of the first cold box 10, the gas outlet at the bottom of the first cold box 10 is also connected with the gas inlet at the upper part of the first reboiler 7, the gas outlet at the lower part of the first reboiler 7 and the gas outlet at the bottom of the first cold box 10 are both connected with the gas inlet at the top of the second cold box 11, the material outlet at the bottom of the second cold box 11 is connected with the material inlet at the top of the third gas-liquid separator 13, the hydrogen-rich gas outlet at the top of the third gas-liquid separator 13 is connected with the hydrogen-rich gas inlet at the bottom of the second cold box 11, the hydrogen-rich gas outlet at the top of the second cold box 11 is connected with the hydrogen-rich gas inlet at the bottom of the first cold box 10, the hydrogen-rich gas outlet at the top of the first cold box 10 is connected with the hydrogen purification system, the hydrogen-rich gas outlet at the top of the first cold, a liquid outlet at the bottom of a third gas-liquid separator 13 is connected with a material inlet at the lower part of the second gas-liquid separator 9, a liquid outlet at the bottom of the second gas-liquid separator 9 is connected with a liquid inlet at the side of a second cold box 11, a gas outlet at the side of the second cold box 11 and a gas outlet at the top of the second gas-liquid separator 9 are both connected with a material inlet of a first gas-liquid separator 8, a liquid outlet and a gas outlet of the first gas-liquid separator 8 are respectively connected with a liquid inlet and a gas inlet at the middle part of a stripping tower 6, a liquid outlet at the bottom of the third gas-liquid separator 13 is also connected with a liquid inlet at the upper part of the stripping tower 6, a hydrogen-enriched gas outlet at the top of the stripping tower 6 is connected with a hydrogen-enriched gas inlet at the side of the second cold box 11, a liquid outlet at the bottom of the stripping tower 6 is connected with a liquid inlet at the side, an air outlet at the side of the second cold box 11 is connected with an air inlet at the middle part of the separation tower 14, an outlet of a CH-rich 4 liquid at the bottom of the separation tower 14 is connected with an inlet of a CH-rich 4 liquid at the bottom of the second cold box 11, an outlet of a CH-rich 4 liquid at the top of the second cold box 11 is connected with an inlet of a CH-rich 4 liquid at the bottom of the first cold box 10, an outlet of the CH-rich 4 liquid at the top of the first cold box 10 is an LNG outlet, an outlet of CO at the top of the separation tower 14 is connected with an inlet of CO at the bottom of the second cold box 11, an outlet of CO at the top of the second cold box 11 is connected with an inlet of CO at the bottom of the first cold box 10, an outlet of CO at the top of the first cold box 10 is connected with an air inlet at the bottom of the methanol synthesis tower 15 through a fourth compressor 29, an outlet of hydrogen-rich gas at the top of the first cold box 10 is also connected with an air inlet at, the CO outlet of the fourth compressor 16 is connected with the CO inlet at the top of the first cold box 10, the CO outlet at the bottom of the first cold box 10 is connected with the CO inlet at the top of the second cold box 11, the CO outlet at the bottom of the second cold box 11 is connected with the CO inlet at the top of the separation tower 14, the CO outlet at the bottom of the first cold box 10 is further connected with the CO inlet at the upper part of the second reboiler 12, the CO outlet at the top of the second reboiler 12 is connected with the CO inlet at the lower part of the separation tower 14, the liquid outlet at the bottom of the separation tower 14 is connected with the liquid inlet at the bottom of the second reboiler 12, and the liquid outlet at the lower part of the second reboiler 12 is connected with the liquid inlet.
The system is applied to the initial cooling, electric tar capturing, precooling, intermediate cooling, ammonia removal, final cooling and benzene elution of the coke oven gas, is used for removing impurities such as dust, benzene, tar, naphthalene, ammonia, sulfur in various forms and the like in the coke oven gas, and is used for preparing LNG, methanol, liquid ammonia and hydrogen. The system for preparing LNG and coproducing methanol, liquid ammonia and hydrogen by coke oven gas purification relates to treatment procedures including prewashing, desulfurization, decarburization, cryogenic separation and synthesis.
Optionally, as shown in fig. 2, the prewashing tower 1 includes a transmission device 101, a rotating shaft 115 and a prewashing housing 108, the transmission device 101 is connected to one end of the rotating shaft 115, the other end of the rotating shaft 115 is connected to a rotor 104, the rotor 104 is disposed at the middle lower part of the inner cavity of the prewashing housing 108, a gas outlet 107 is connected to the middle of the top of the prewashing housing 108, a liquid outlet 102 is connected to the bottom of the prewashing housing 108, a gas inlet 103 is connected to the bottom of one side of the prewashing housing 108, a liquid inlet 109 is connected to the middle upper part of the other side of the prewashing housing 108, an L-shaped liquid pipeline is connected to the liquid inlet 109, a vertical pipe of the L-shaped liquid pipeline extends to the middle of the rotor 104, a plurality of liquid nozzles 111 are mounted on the vertical pipe of the L-shaped liquid pipeline, a demister 106 is disposed at the top of the inner cavity of the prewashing housing 108, a, the two sides of the middle of the bottom of the rotor 104 are sealed with the rotating shaft 115 through a second sealing gasket 112 and a third sealing gasket 113 respectively, and the interior of the rotor 104 is filled with a packing layer 114.
Optionally, the porosity of the filler layer 114 is 80% to 99%; the filler of the filler layer 114 adopts large corrugated wire mesh filler and small corrugated wire mesh filler. The small corrugated filler with the length accounting for 5% -10% of the radius of the prewashing shell 108 is arranged near the rotating shaft 115, preferably 5% -8%. The average pore diameter of the large corrugated wire mesh packing is 5-10 mm, and preferably 4-8 mm; the average pore diameter of the small corrugated wire mesh packing is 1-5 mm, preferably 2-4 mm. The packing mode is beneficial to uniform atomization of liquid-phase washing liquid, the impurity trapping effect is improved, the large-ripple packing can reduce the gas-liquid phase resistance, and the anti-blocking capacity of the packing is improved.
Alternatively, as shown in fig. 3, the gas-liquid separation device 20 is a horizontal three-weir type gas-liquid four-phase separator, the four-phase separator includes a separation shell 218, and an inner cavity of the separation shell 218 is divided into an inlet section i, a settling separation section ii and a collection section iii from left to right; the inlet section I is provided with a gas-liquid separation device 206, a baffle 207 and a calming plate 208, the feed inlet 201 is arranged outside the separation shell 218 and is connected with the top of the separation shell 218, the gas-liquid separation device 206 is arranged below the feed inlet 201, the bottom end of the calming plate 208 is connected with the bottom of the separation shell 218, and the top end of the baffle 207 is connected with the top of the separation shell 218 and is positioned between the gas-liquid separation device 206 and the calming plate 208; the sedimentation separation section II is provided with a coalescer 209; the collection section III is provided with a heavy phase fluid overflow weir 217, a heavy phase fluid collection groove 219, a light phase fluid collection groove 220 and an intermediate phase fluid overflow weir 216, the heavy phase fluid overflow weir 217 is arranged on one side of the coalescer 209 and is connected with the bottom of the separation shell 218, the top end of the heavy phase fluid collection groove 219 is connected with the bottom of the separation shell 218 and is positioned between the coalescer 209 and the heavy phase fluid overflow weir 217, the top and the bottom of the side wall of the heavy phase fluid collection groove 219 are respectively provided with a first liquid level meter 213, the bottom of the heavy phase fluid collection groove 219 is connected with a heavy phase fluid outlet 203, the top and the bottom of the separation shell 218 above the heavy phase fluid collection groove 219 are respectively provided with a second liquid level meter 212, the light phase fluid collection groove 220 is arranged on one side of the heavy phase fluid overflow weir 217, the front wall of the light phase fluid collection groove 220 is a light phase fluid overflow weir 214, and the height of the light phase fluid overflow weir, a third liquid level meter 210 is respectively arranged at the top and the bottom in the light phase fluid collecting tank 220, a light phase fluid outlet 204 is connected to the bottom of the light phase fluid collecting tank 220, the light phase fluid outlet 204 is positioned outside the separating shell 218, a demister 222 is arranged above the light phase fluid collecting tank 220, the gas phase outlet 202 is arranged outside the separating shell 218 and is connected with the demister 222, an intermediate phase fluid overflow weir 216 is arranged at one side of the light phase fluid collecting tank 220 and is connected with the bottom of the separating shell 218, the intermediate phase fluid overflow weir 216 and the space at the tail part of the separating shell 218 form an intermediate phase fluid collecting tank 221, a fourth liquid level meter 211 is respectively arranged at the top and the bottom at one side of the intermediate phase fluid overflow weir 216, and the intermediate phase fluid outlet 205 is connected to the bottom of the separating shell 218 at one.
Wherein the gas-liquid separation device 206 and the calming plate 208 are conventional components of the inlet section i, wherein the gas-liquid separation device 206 has a main function of realizing gas-liquid pre-separation, and can be in various forms in practical application, and the function of the device is to perform uniform initial distribution or redistribution on the top of the packing or on a certain height of the packing, so as to improve effective surfaces of mass transfer and heat transfer, improve phase-to-phase contact and further improve the separation efficiency of the tower. The main function of the static plate 208 is to slow down the two-phase fluctuation of the liquid phase region of the inlet section I, and also to have the function of liquid-liquid pre-separation, but mainly to inhibit the fluctuation to provide stable operation conditions for the sedimentation separation section II. The coalescer 209 is primarily intended to enhance the separation efficiency by promoting coalescence of the light phase (e.g., oil droplets) on the plate surface, and also has the function of suppressing fluctuation of the liquid phase region in the settling section ii.
Optionally, the length ratio of the inlet section i, the settling separation section ii and the collection section iii is 1: 3.2-4.2: 2.
Optionally, the top end of the ballast plate 208 is at the same level as the second level gauge 212 at the top of the separation housing 218; the bottom end of the baffle 207 is 400 mm and 500mm higher than the top end of the sedation plate 208, and the bottom end of the baffle 207 is no less than 200mm lower than the bottom end of the gas-liquid separation device 206.
Alternatively, the height of the coalescer 209 is the same as the height of the light phase fluid weir 214 (H1), the height of the heavy phase fluid weir 217 is 500mm above the bottom end of the light phase fluid collection tank 220, the height of the light phase fluid weir 214 is 1/2-3/4 of the diameter of the four phase separator, the height of the back wall 215 of the light phase fluid collection tank 220 (H2) is 200mm above the bottom end of the demister 222, and the height of the intermediate phase fluid weir 216 (H3) is 20-100mm below the height of the light phase fluid weir 214.
The three overflow weir plates of the heavy phase fluid overflow weir 217, the light phase fluid overflow weir 214 and the middle phase fluid overflow weir 216, the three heavy phase fluid collecting tanks 219, the light phase fluid collecting tank 220 and the middle phase fluid collecting tank 221 are arranged in the collecting section III, so that the length of the collecting section III of the four-phase separator is greater than that of a common separator, but the liquid-liquid interface in the operation process is well controlled due to the arrangement, the stable operation of the separation process is ensured, and the influence of working condition fluctuation on the process of the sedimentation separation section II is reduced or avoided. The control of the liquid-liquid interface of the four-phase separator in the embodiments of the invention comes from two aspects: the three overflow weir plates and the three liquid phase collecting groove structures enable a liquid-liquid interface to be simultaneously controlled by hydrostatic pressure of light phase/intermediate phase and heavy phase, so that the liquid-liquid interface is relatively stable; the light phase fluid collecting tank 220 and the intermediate phase fluid collecting tank 221 provide buffer space for fluctuation of upstream and downstream (inlet and outlet) flow in the operation process, so that influence of fluctuation of working conditions on the separation process of the settling section is reduced or avoided. By arranging the components such as the static plate 208, the coalescer 209 and the like, the liquid-liquid sedimentation separation can be realized by ensuring the lower transverse flow velocity to ensure that the liquid in the liquid phase region has enough residence time, meanwhile, the sedimentation or the buoyancy lift of the dispersed phase is facilitated, the fluctuation of the liquid phase region is also reduced, the separation time is shortened, and the size of the equipment is reduced.
In all embodiments of the present invention, the four-phase separator shown in fig. 3 is used for gas-liquid separation, and the influence factors of the pressure distribution at the tail end of the descending separation section ii under the actual separation condition are comprehensively considered, including: the height of the light phase fluid weir 214 and the difference in height of the three weirs, the slice thickness at the weir crest and the slice flow rate at the weir crest and the flow resistance at the bottom of the light phase collection tank 220.
In the embodiment of the invention, the coal gas washing liquid pretreated by the prewashing tower 1 enters the four-phase separator, the coal gas washing liquid pretreated by the prewashing tower 1 contains impurities such as tar, dust, crude benzene, naphthalene, ammonia, organic sulfur and the like, and the residual gas, heavy oil, light oil and intermediate phase liquid in the coal gas washing liquid are recovered and treated by the four-phase separator. The gas separated by the four-phase separator is discharged from a gas phase outlet 202, the heavy oil separated by the four-phase separator is discharged from a heavy phase fluid outlet 203, the light oil separated by the four-phase separator is discharged from a light phase fluid outlet 204, and the intermediate phase liquid separated by the four-phase separator is discharged from an intermediate phase fluid outlet 205.
The embodiment of the invention also provides a method for preparing LNG and co-producing methanol, liquid ammonia and hydrogen by purifying coke oven gas, wherein the method for preparing LNG and co-producing methanol, liquid ammonia and hydrogen by purifying coke oven gas adopts the system for preparing LNG and co-producing methanol, liquid ammonia and hydrogen by purifying coke oven gas, which comprises the following steps:
s1, the coke oven gas after benzene elution is sent into the prewashing tower 1 from the lower part of the prewashing tower 1 after the heat exchange of the coke oven gas is carried out to 20-25 ℃ through the first heat exchanger 18, and meanwhile, the gas detergent from the bottom of the decarbonizing tower 3 is sent into the prewashing tower 1 from the upper part of the prewashing tower 1 after the heat exchange of the gas detergent through the fifth heat exchanger 24 and the pressurization of the third compressor 25; wherein, the prewashing tower 1 is a supergravity rotating device.
The coke oven gas after benzene elution contains impurities such as dust, benzene, tar, naphthalene, ammonia, sulfur in various forms, and the like. Generally, the coke oven gas after benzene elution contains 5-15mg/m of tar dust310-200mg/m of naphthalene3Ammonia 15-100mg/m3Sulfur less than 500mg/m3And other minor impurities.
S2, the coke oven gas after heat exchange and the gas detergent are in countercurrent or cross-current contact in the prewashing tower 1 for pretreatment, and the pretreated gas detergent is collected on the inner wall of the prewashing tower 1 under the supergravity action of the prewashing tower 1 and then discharged to the gas-liquid separation device 20.
Alternatively, the operating conditions of the prewash column 1 are: the operation temperature is 15-20 ℃, the operation pressure is 3-6 kPa, and the specific surface area of the filler is 500-4000 m2/m3The rotating frequency of the filler is 30-60 Hz, and the gas-liquid ratio is 1000-6000. The amount of the coal gas detergent is 0.20-0.32 kg/m3Coke oven gas.
Since the coke oven gas after benzene elution includes impurities such as dust, benzene, tar, naphthalene, ammonia, and various forms of sulfur, the embodiment of the present invention first pretreats the coke oven gas after benzene elution by using the pre-washing tower 1 adopting the supergravity rotation technology to primarily remove the impurities such as dust, benzene, tar, naphthalene, ammonia, and various forms of sulfur from the coke oven gas after benzene elution.
Specifically, in the prewashing tower 1, the gas washing agent enters the packing layer 114 after being uniformly distributed through the liquid phase nozzle 111 of the prewashing tower 1, and under the action of the transmission device 101, the rotating shaft 115 and the rotor 104, the gas washing agent is split into liquid microelements (liquid films, liquid threads and liquid drops) and is in countercurrent contact with the coke oven gas after benzene elution to remove impurities in the coke oven gas after benzene elution. Because the prewashing tower 1 is a supergravity rotating device, the embodiment of the invention utilizes the supergravity rotating technologyThe removal of impurities is performed. The cutting grain diameter of the super-gravity rotating technology reaches 10-8m, the particle diameter of the coal gas washing agent passing through the packing layer 114 almost reaches the molecular level, and the coal gas washing agent is gathered in the supergravity rotating device and then removed together with impurities. According to the embodiment of the invention, the coke oven gas after benzene elution is pretreated by using a supergravity rotation technology, so that the washing effect can be enhanced, the particle size cutting size of washing is reduced, and meanwhile, under the action of liquid phase spraying and supergravity, liquid drops are more uniformly distributed and have larger contact surface with impurities in the coke oven gas, so that the impurity elution effect is improved. The supergravity rotating device has the characteristics of good particle trapping effect, small gas phase pressure drop, difficult blockage of the rotating filler and the like, so that harmful substances such as dust, benzene, tar, naphthalene, ammonia, sulfur and the like in the coke oven gas are deeply removed, the pressurized conveying and the subsequent deep purification of the coke oven gas are met, and the purpose of purifying the production chemical synthesis system is achieved. The coke oven gas after impurity removal is defoamed by the demister 106 to obtain pretreated coke oven gas, and the gas detergent after impurity removal is thrown to the inner wall of the prewashing shell 108 and flows into the gas-liquid separation device 20 from the liquid phase outlet 102.
Furthermore, the embodiment of the invention determines the optimal temperature for pretreating the coke oven gas to be 20-25 ℃ through experiments, the gas washing agent at least comprises methanol and crude benzene, the gas washing agent also can comprise one or the combination of two or more of desalted water, ethanol, wash oil and tar, and the gas washing agent has good pretreatment effect when the temperature is lower than 20 ℃.
The coke oven gas pretreatment is that naphthalene in the coke oven gas is easy to crystallize and separate out at the temperature of less than 20 ℃ through tests under different temperatures, pressures and detergents. In order to avoid the blockage of equipment and pipelines caused by naphthalene crystallization at low temperature, the embodiment of the invention removes naphthalene in coke oven gas by adding a prewashing tower 1 and using prewashing methanol. Because the pre-washed methanol contains crude benzene, the benzene and the naphthalene belong to aromatic compounds, and the naphthalene is dissolved in the gas detergent according to the similar compatibility principle. After the coke oven gas after benzene elution is pretreated under the conditions, practice proves that the collection efficiency of tar ash reaches more than 99 percent, and particles with the particle size of more than 3 mu m can be completely removed; the removal rate of naphthalene is more than 80%; the removal rate of tar and dust reaches more than 60 percent; the removal rate of the organic sulfur reaches more than 85 percent; the removal rate of ammonia reaches more than 50 percent; the removal rate of the benzene reaches more than 50 percent; the removal rate enables the pretreated coke oven gas to meet the requirements of subsequent compression and deep purification.
S3, pressurizing the pretreated coke oven gas to 0.3-1.0MPa by a first compressor 19, then exchanging heat by a second heat exchanger 26, carrying out deep cooling by a third heat exchanger 21 to-22-28 ℃, then entering a desulfurizing tower 2, carrying out low-temperature methanol washing operation on the lean methanol introduced into the desulfurizing tower 2 and the desulfurizing tower 2 to remove impurities in the coke oven gas, thus obtaining the deeply purified coke oven gas, reheating 42-50% of the deeply purified coke oven gas by a fourth heat exchanger 22, reducing the pressure by a second compressor 23 to 8-10kPa, then using the reheated gas as return gas for coke oven heating, and introducing the rest of the deeply purified coke oven gas into a decarbonizing tower 3 for decarbonization.
Optionally, the dosage of the poor methanol in the desulfurizing tower 2 is 1.30-1.50kg/m3Coke oven gas. The temperature of the low-temperature methanol washing operation is-20 ℃ to-40 ℃, and the pressure is 0.3 MPa to 1.5 MPa.
Methanol in the desulfurizing tower 2 absorbs NH in the process gas while absorbing acid gas3This has a certain influence on the low-temperature methanol washing system (the desulfurization tower 2 and the decarbonization tower 3). NH at low temperature3The solubility in methanol is much higher than that of CO2And H2Since acidic gases such as S have solubility in methanol, they are likely to accumulate in the methanol washing system. CO 22And H2After the acidic gases such as S and the like are dissolved in the methanol, the pH value of the methanol is reduced, and the corrosion of low-temperature methanol washing system equipment is caused. In order to reduce the corrosion of equipment and prolong the service life and the operation period of the equipment, the existing low-temperature methanol washing process allows a certain content of NH in the system3However, NH must be strictly controlled3Content in low-temperature methanol washing system, if NH3The low content can cause the aggravation of equipment corrosion; when NH is present3The content of sulfur in the process gas exceeds the standard to a certain extent. Therefore, it is necessary toWell-controlled NH in low-temperature methanol washing system3Content, therefore, the embodiment of the present invention needs to control the ammonia gas concentration in the purification within a range that maintains NH in the lean methanol (circulated in the desulfurization tower 2, the decarbonization tower 3 and the pre-washing tower 1) that is circulated3The content is less than 20 × 10－6ppm and pH value of 8-10.
According to H in the coke oven gas2The solubility of the S in methanol at 0.3-1.0MPa and-20-40 ℃ is 0.9-6 Nm3H2S/m3，CO2The solubility in methanol at 0.3-1.0MPa and-20-40 ℃ is 0.8-5 Nm3CO2/m3It can be determined that the amount of the lean methanol in the desulfurizing tower 2 (i.e., the amount of the lean methanol introduced into the desulfurizing tower 2) is 1.30 to 1.50kg/m3Coke oven gas.
The coke oven gas has complex components and a plurality of impurities, and the gas components comprise CO and H2、CO2、CH4、H2S, organic sulfur, C2H4、C2H6、C3H8、C4H10、HCN、N2Ar and tar, fatty acid, monophenol, polyphenol, naphtha, anthracene oil, naphthalene oil, fly ash, etc. Removing CO and H from these components2An active ingredient and CH4、 N2Ar and hydrocarbons other than inert gas, all other components including CO2And sulfides are harmful impurities to be removed, and the purification task is difficult. Along with the implementation of policies of going back to the city and entering the garden, upgrading and transforming and the like of coking enterprises, the large-scale and high-end coking industry is developed, the requirement for coke oven gas desulfurization is increased, and various harmful components such as CO in the coke oven gas can be cleanly removed by adopting a low-temperature methanol cleaning method2、H2S、COS、C4H4S、HCN、NH3、H2O、C2The above hydrocarbons (including light oil, aromatic hydrocarbon, naphtha, olefin, colloid substance, etc.) and other carbonyl compounds, etc., which cannot be achieved by any other purification process. In addition, the low-temperature methanol is adopted to elute and remove the sulfur impurities with complex components in the coke oven gas, thereby ensuring that the coke oven gas can not only be ensured to be purifiedThe indexes of the purified gas can be recycled by the regeneration of the methanol, so that the problem that the coking desulfurization waste liquid can not be treated radically is solved.
And (3) performing low-temperature methanol washing operation to remove almost all organic sulfur impurities in the deeply purified coke oven gas to remove the total sulfur content in the coke oven gas to be less than 10 ppm. The coke oven gas after deep purification is returned to the coke oven as fuel gas, so that the investment of a flue gas desulfurization device and the generation of desulfurization waste liquid can be reduced.
The coke oven gas after low-temperature methanol cleaning and decarburization is subjected to cryogenic separation to separate CH4And the purity of the CO is more than 99.5 percent, and the following steps are the specific implementation process of the cryogenic separation of the coke oven gas.
S4, the coke oven gas decarbonized by the decarbonization tower 3 enters the first adsorption tower 4 or the second adsorption tower 5 to adsorb residual methanol and CO2To make their content less than 0.1ml/m3。
Wherein, the first adsorption tower 4 and the second adsorption tower 5 adsorb residual methanol and CO2When the adsorption tower is used, the control valves are switched, and when the first adsorption tower 4 is used for adsorption, the second adsorption tower 5 is used for desorption; when the first adsorption tower 4 is desorbing, the second adsorption tower 5 is adsorbing.
Optionally, the adsorption operation temperature of the first adsorption tower 4 or the second adsorption tower 5 is-60 to-50 ℃, and the operation pressure is 5 to 6 MPa; the desorption operation temperature is 180-350 ℃, the operation pressure is 50-200 kPa, and nitrogen is used for desorption.
S5, the coke oven gas after adsorption is divided into two parts after heat exchange is carried out to-130 to-140 ℃ by the first cold box 10, wherein one part is mixed with the coke oven gas after adsorption and then enters the first reboiler 7 for vaporization to be used as a heat source of the stripping tower 6; the coke oven gas from the first reboiler 7 and the coke oven gas from the first cold box 10 after adsorption are mixed and enter the second cold box 11, and are further cooled to-180 to-185 ℃ in the second cold box 11.
S6, the material from the second cold box 11 enters a third gas-liquid separator 13, and gas-liquid separation is carried out in the third gas-liquid separator 13, wherein most of CO and CH4Condensed, separated by a third gas-liquid separator 13After being reheated to normal temperature by the first cooling box 10 and the second cooling box 11, the gas-phase hydrogen-rich gas is divided into three parts: one part of the PSA hydrogen purification system is used for extracting hydrogen; the other part is mixed with CO and enters a methanol synthesis tower 15 for methanol synthesis; and the other part of the ammonia enters the synthetic ammonia tower 17 to synthesize ammonia gas with the nitrogen introduced therein, and the ammonia gas obtains liquid ammonia under the action of the seventh heat exchanger 27.
S7, the liquid phase material separated by the third gas-liquid separator 13 is divided into two materials, wherein: a strand of material is decompressed and expanded, the temperature is reduced to-180 to-185, the pressure is changed to 1.0 to 1.5MPa, the strand of material enters a second gas-liquid separator 9 for gas-liquid separation, a liquid phase separated by the second gas-liquid separator 9 enters a second cold box 11 for heat exchange and then is mixed with a gas phase material separated by the second gas-liquid separator 9, the temperature of the material is raised to-170 to-175 ℃, the strand of material enters a first gas-liquid separator 8 for gas-liquid separation, and the gas phase and the liquid phase separated by the first gas-liquid separator 8 enter between two layers of fillers of a stripping tower 6 for hydrogen extraction; the other material in the liquid phase material separated by the third gas-liquid separator 13 is decompressed and expanded, the temperature is reduced to-180 to-185, the pressure is 1.0 to 1.5MPa, and the other material enters the stripping tower 6 from the upper part of the stripping tower 6 to extract hydrogen; the hydrogen-rich gas is desorbed from the top of the stripping tower 6 after being stripped by the stripping tower 6, and is reheated to 35-45 ℃ by the first cooling box 10 and the second cooling box 11 to be sent to a PSA hydrogen purification system for hydrogen extraction, or sent to a methanol synthesis tower 15 for methanol synthesis, or sent to an ammonia synthesis tower 17 for ammonia synthesis.
The process of extracting hydrogen by the PSA hydrogen purification process comprises pressure increase, adsorption, pressure equalization, forward release, reverse release, flushing and the like, and the specific process can refer to the existing PSA hydrogen purification process, and the embodiment of the invention does not explain the process in detail.
Optionally, the operation pressure of the stripping tower 6 is 1.0-1.5 MPa, and the temperature is-196-40 ℃.
Optionally, the temperature of the ammonia synthesis in the ammonia synthesis tower 17 is 470-490 ℃, the pressure is 13-14 MPa, the hydrogen-nitrogen ratio is 2.7-3.0, and the catalyst is an iron-based catalyst.
S8, exchanging heat of the liquid phase at the bottom of the stripping tower 6 to-180 to-185 ℃ through a second cooling box 11, changing the pressure to 0.25 to 0.50MPa, and dividing the liquid phase into two parts: one part of the waste water enters the middle part of the packing at the upper part of the separation tower 14 directly; the other part is vaporized into gas phase in a second cold box 11, the temperature is raised to-170 to-175 ℃, and the gas phase enters a separation tower 14 as a heat source after the pressure is maintained at 0.25 to 0.50 MPa.
S9, separating the material entering the separation tower 14 through the separation tower 14, and enriching CH at the bottom4The temperature of the liquid is-170 to-180 ℃, the pressure is 0.3 to 0.4MPa, and the bottom is rich in CH4The liquid is decompressed and expanded, and then is subjected to heat exchange through a first cold box 10 and a second cold box 11 to normal temperature, so that LNG is obtained.
Optionally, the separation column 14 is operated at a pressure of 0.1 to 0.5MPa and a temperature of-196 to 40 ℃.
S10, after heat exchange of gas CO at the top of the separation tower 14 to normal temperature through the first cold box 10 and the second cold box 11, the gas CO enters the fourth compressor 29 to be compressed and then is divided into two parts, and the pressure of the compressed CO is 0.7-0.8 MPa, wherein: a part of the reflux liquid enters the top of the separation tower 14 to be used as reflux liquid of the separation tower 14, a part of the reflux liquid is subjected to heat exchange through a first cold box 10 to-150 to-155 ℃, then a part of the reflux liquid is shunted to a second reboiler 12 to be vaporized to be used as a heat source of the separation tower 14, and the material cooled in the separation tower 14 enters a second cold box 11 to be subjected to heat exchange to 180 to-185 ℃ and then enters the top of the separation tower 14 to be used as reflux liquid; the other part of the methanol is mixed with the hydrogen-rich gas and then enters the methanol synthesis tower 15 for methanol synthesis, and the methanol is obtained from the methane synthesized in the methanol synthesis tower 15 under the action of the eighth heat exchanger 28.
Separating CH from the purified coke oven gas by deep cooling4And purifying the cryogenic hydrogen by PSA, synthesizing part of the cryogenic hydrogen and cryogenically separated CO as synthesis gas methanol, mixing part of the cryogenic hydrogen and nitrogen to synthesize ammonia, and outputting the other part of the cryogenic hydrogen and the ammonia as a hydrogen product with the purity of 99.999%.
The embodiment of the invention carries out deep purification pretreatment on the coke oven gas to solve the problems that the content of dust, benzene, tar, naphthalene, ammonia, sulfur in various forms and the like is high during the compression of the coke oven gas, and the requirements of pressurization conveying and subsequent deep purification of the coke oven gas cannot be met. Coke oven gas compression after deep purification of coke oven gasThe invention has the advantages of high desulfurization precision, short process flow, less equipment investment, low operation and maintenance cost, no generation of desulfurization waste liquid and no need of desulfurization after the coke oven gas is returned to the furnace for combustion. Separating CH in the purified coke oven gas by cryogenic cooling4、CO、H2The methanol and liquid ammonia can be synthesized and the hydrogen can be output as raw material gas, thereby achieving the effect of utilizing coke oven gas according to quality and improving economic benefit.
It will be understood that the above embodiments are merely exemplary embodiments taken to illustrate the principles of the present invention, which is not limited thereto. It will be apparent to those skilled in the art that various modifications and improvements can be made without departing from the spirit and substance of the invention, and these modifications and improvements are also considered to be within the scope of the invention.

Claims (10)

1. The utility model provides a system for coke oven gas purifies system LNG coproduction methyl alcohol, liquid ammonia and hydrogen, a serial communication port, including prewashing tower (1), desulfurizing tower (2), decarbonization tower (3), first adsorption tower (4), second adsorption tower (5), strip tower (6), first reboiler (7), first vapour and liquid separator (8), second vapour and liquid separator (9), first cold box (10), second cold box (11), second reboiler (12), third vapour and liquid separator (13), knockout tower (14), methyl alcohol synthetic tower (15), steam pocket (16) and synthetic ammonia tower (17), wherein: the prewashing tower (1) is a supergravity rotating device, wherein: the gas holder is connected with a gas phase inlet (103) at the lower part of the prewashing tower (1) through a first heat exchanger (18), a liquid phase outlet (102) at the bottom of the prewashing tower (1) is connected with a gas-liquid separation device (20), a gas outlet (107) at the top of the prewashing tower (1) is connected with a gas inlet at the lower part of the desulfurizing tower (2) through a first compressor (19), a second heat exchanger (26) and a third heat exchanger (21), a gas outlet at the top of the desulfurizing tower (2) is connected with a coke oven through a fourth heat exchanger (22) and a second compressor (23), a gas outlet at the top of the desulfurizing tower (2) is also connected with a gas inlet at the lower part of the decarbonizing tower (3), a liquid outlet at the bottom of the desulfurizing tower (2) is connected with a liquid inlet at the upper part of the decarbonizing tower (3), and a liquid outlet at the bottom of the decarbonizing tower (3) is connected with a liquid phaseAn inlet (109) is connected, an air outlet at the top of the decarbonization tower (3) is connected with an air inlet of the first adsorption tower (4) and an air inlet of the second adsorption tower (5), an air outlet of the first adsorption tower (4) and an air outlet of the second adsorption tower (5) are connected with an air inlet at the upper part of the first reboiler (7), an air outlet of the first adsorption tower (4) and an air outlet of the second adsorption tower (5) are also connected with an air inlet at the top of the first cooling box (10), an air outlet at the bottom of the first cooling box (10) is also connected with an air inlet at the upper part of the first reboiler (7), an air outlet at the lower part of the first reboiler (7) and an air outlet at the bottom of the first cooling box (10) are connected with an air inlet at the top of the second cooling box (11), a material outlet at the bottom of the second cooling box (11) is connected with a material inlet at the top of the third gas-liquid separator (13), a hydrogen-rich gas outlet at the top of the third gas-liquid separator (13) is connected with a hydrogen, a hydrogen-rich gas outlet at the top of the second cold box (11) is connected with a hydrogen-rich gas inlet at the bottom of the first cold box (10), a hydrogen-rich gas outlet at the top of the first cold box (10) is connected with a PSA hydrogen purification system, a hydrogen-rich gas outlet at the top of the first cold box (10) is also connected with a gas inlet of a synthetic ammonia tower (17), a gas outlet of the synthetic ammonia tower (17) is connected with a seventh heat exchanger (27), a liquid outlet at the bottom of the third gas-liquid separator (13) is connected with a material inlet at the lower part of the second gas-liquid separator (9), a liquid outlet at the bottom of the second gas-liquid separator (9) is connected with a liquid inlet at the side of the second cold box (11), a gas outlet at the side of the second cold box (11) and a gas outlet at the top of the second gas-liquid separator (9) are both connected with a material inlet of the first gas-liquid separator (8), and the liquid outlet and gas outlet of, the liquid outlet of the bottom of the third gas-liquid separator (13) is also connected with the liquid inlet of the upper part of the stripping tower (6), the hydrogen-rich gas outlet of the top of the stripping tower (6) is connected with the hydrogen-rich gas inlet of the side of the second cooling box (11), the liquid outlet of the bottom of the stripping tower (6) is connected with the liquid inlet of the side of the second cooling box (11), the liquid outlet of the bottom of the second cooling box (11) is connected with the middle part of the upper filler of the separation tower (14), the liquid outlet of the bottom of the second cooling box (11) is also connected with the liquid inlet of the bottom of the second cooling box (11), the gas outlet of the side of the second cooling box (11) is connected with the gas inlet of the middle part of the separation tower4Liquid outlet and secondary coolingRich CH in the bottom of the tank (11)4Liquid inlet connection, rich CH at the top of the second cooling box (11)4Rich CH at the liquid outlet and the bottom of the first cooling box (10)4Liquid inlet connection, rich CH at the top of the first cold box (10)4The liquid outlet is an LNG outlet, the CO outlet at the top of the separation tower (14) is connected with the CO inlet at the bottom of the second cold box (11), the CO outlet at the top of the second cold box (11) is connected with the CO inlet at the bottom of the first cold box (10), the CO outlet at the top of the first cold box (10) is connected with the air inlet at the bottom of the methanol synthesis tower (15) through a fourth compressor (29), the hydrogen-rich gas outlet at the top of the first cold box (10) is also connected with the air inlet at the bottom of the methanol synthesis tower (15), the heat exchange tube of the methanol synthesis tower (15) is connected with a steam drum (16), the air outlet at the top of the methanol synthesis tower (15) is connected with an eighth heat exchanger (28), the CO outlet of the fourth compressor (16) is connected with the CO inlet at the top of the first cold box (10), the CO outlet at the bottom of the first cold box (10) is connected with the CO inlet at the top of the second cold box (11), the CO outlet at the bottom of the second cold box (11) is connected with the CO inlet, the CO outlet at the bottom of the first cooling box (10) is also connected with the CO inlet at the upper part of the second reboiler (12), the CO outlet at the top of the second reboiler (12) is connected with the CO inlet at the lower part of the separation tower (14), the liquid outlet at the bottom of the separation tower (14) is connected with the liquid inlet at the bottom of the second reboiler (12), and the liquid outlet at the lower part of the second reboiler (12) is connected with the liquid inlet at the side surface of the second cooling box (11).
2. The system for preparing LNG and coproducing methanol, liquid ammonia and hydrogen through coke oven gas purification according to claim 1, wherein the prewashing tower (1) comprises a transmission device (101), a rotating shaft (115) and a prewashing shell (108), the transmission device (101) is connected with one end of the rotating shaft (115), the other end of the rotating shaft (115) is connected with a rotor (104), the rotor (104) is arranged at the middle lower part of an inner cavity of the prewashing shell (108), a gas outlet (107) is connected with the middle of the top of the prewashing shell (108), a liquid phase outlet (102) is connected with the bottom of the prewashing shell (108), a gas phase inlet (103) is connected with the bottom of one side of the prewashing shell (108), a liquid phase inlet (109) is connected with the middle upper part of the other side of the prewashing shell (108), an L-shaped liquid pipeline is connected with the liquid phase inlet (109), and a vertical pipe, install a plurality of liquid phase nozzle (111) on L shape liquid pipeline's the vertical pipe, the top of prewashing casing (108) inner chamber is equipped with demister (106), install division board (105) between demister (106) bottom and rotor (104) top, it is sealed through first sealed pad (110) between rotor (104) top middle and division board (105), it is sealed through second sealed pad (112) and third sealed pad (113) respectively between both sides and pivot (115) in the middle of rotor (104) bottom, rotor (104) inside packing has packing layer (114).
3. A method for preparing LNG and co-producing methanol, liquid ammonia and hydrogen by coke oven gas purification, wherein the method for preparing LNG and co-producing methanol, liquid ammonia and hydrogen by coke oven gas purification adopts the system for preparing LNG and co-producing methanol, liquid ammonia and hydrogen by coke oven gas purification as claimed in claim 1 or 2, and is characterized by comprising the following steps:
s1, the coke oven gas after benzene elution is subjected to heat exchange by a first heat exchanger (18) to 20-25 ℃, and then is sent into the prewashing tower (1) from the lower part of the prewashing tower (1), and meanwhile, a gas washing agent from the bottom of the decarbonizing tower (3) is subjected to heat exchange by a fifth heat exchanger (24) and pressurization by a third compressor (25) and then is sent into the prewashing tower (1) from the upper part of the prewashing tower (1); wherein, the prewashing tower (1) is a supergravity rotating device;
s2, performing pretreatment by the countercurrent or cross-flow contact of the coke oven gas after heat exchange and a gas detergent in the prewashing tower (1), and discharging the pretreated gas detergent to a gas-liquid separation device (20) after gathering on the inner wall of the prewashing tower (1) under the supergravity action of the prewashing tower (1);
s3, pressurizing the pretreated coke oven gas to 0.3-1.0MPa by a first compressor (19), performing heat exchange by a second heat exchanger (26), performing deep cooling by a third heat exchanger (21) to-22-28 ℃, then feeding the coke oven gas into a desulfurizing tower (2), performing low-temperature methanol washing operation on the lean methanol introduced into the desulfurizing tower (2) in the desulfurizing tower (2) to remove impurities in the coke oven gas to obtain the deeply purified coke oven gas, reheating 42-50% of the deeply purified coke oven gas by a fourth heat exchanger (22), reducing the pressure to 8-10kPa by the second compressor (23), and then using the reheated coke oven gas as return gas for coke oven heating, and feeding the rest of the deeply purified coke oven gas into a decarburization tower (3) for decarburization;
s4, feeding the coke oven gas subjected to decarburization in the decarburization tower (3)Adsorbing residual methanol and CO in a first adsorption tower (4) or a second adsorption tower (5)2To make their content less than 0.1ml/m3；
S5, the coke oven gas after adsorption is divided into two parts after heat exchange is carried out on the coke oven gas to-130 to-140 ℃ through a first cold box (10), wherein one part is mixed with the coke oven gas after adsorption and then enters a first reboiler (7) for vaporization to be used as a heat source of a stripping tower (6); mixing the coke oven gas from the first reboiler (7) with another adsorbed coke oven gas from the first cold box (10), introducing the mixture into a second cold box (11), and further cooling the mixture in the second cold box (11) to-180 to-185 ℃;
s6, feeding the material from the second cooling box (11) into a third gas-liquid separator (13), and performing gas-liquid separation in the third gas-liquid separator (13), wherein most of CO and CH4After being condensed, the gas-phase hydrogen-rich gas separated by the third gas-liquid separator (13) is reheated to normal temperature by the first cooling box (10) and the second cooling box (11), and then is divided into three parts: one part of the PSA hydrogen purification system is used for extracting hydrogen; the other part is mixed with CO and enters a methanol synthesis tower (15) for methanol synthesis; a part of the ammonia enters a synthetic ammonia tower (17) to be synthesized with the nitrogen introduced into the synthetic ammonia tower to obtain ammonia gas, and the ammonia gas obtains liquid ammonia under the action of a seventh heat exchanger (27);
s7, dividing the liquid-phase material separated by the third gas-liquid separator (13) into two materials, wherein: a strand of material is decompressed and expanded, the temperature is reduced to-180 to-185, the pressure is changed to 1.0 to 1.5MPa, the strand of material enters a second gas-liquid separator (9) for gas-liquid separation, a liquid phase separated by the second gas-liquid separator (9) enters a second cooling box (11) for heat exchange and then is mixed with a gas-phase material separated by the second gas-liquid separator (9), the temperature of the material is increased to-170 to-175 ℃, the strand of material enters a first gas-liquid separator (8) for gas-liquid separation, and a gas phase and a liquid phase separated by the first gas-liquid separator (8) enter between two layers of fillers of a stripping tower (6) for hydrogen extraction; the other material in the liquid phase material separated by the third gas-liquid separator (13) is decompressed and expanded, the temperature is reduced to-180 to-185, the pressure is 1.0 to 1.5MPa, and the other material enters the stripping tower (6) from the upper part of the stripping tower (6) to extract hydrogen; after being stripped by the stripping tower (6), the hydrogen-rich gas is resolved from the top of the stripping tower (6), and is reheated to 35-45 ℃ by the first cooling box (10) and the second cooling box (11) to go to a PSA hydrogen purification system for hydrogen extraction, or go to a methanol synthesis tower (15) for methanol synthesis, or go to an ammonia synthesis tower (17) for ammonia synthesis;
s8, exchanging heat of the liquid phase at the bottom of the stripping tower (6) to-180 to-185 ℃ through a second cooling box (11), wherein the pressure is changed to 0.25 to 0.50MPa, and the liquid phase is divided into two parts: one part of the waste water enters the middle part of the packing at the upper part of the separation tower (14); the other part is vaporized into gas phase in a second cold box (11), the temperature is raised to-170 to-175 ℃, and the gas phase enters a separation tower (14) as a heat source after the pressure is kept at 0.25 to 0.50 MPa;
s9, separating the material entering the separation tower (14) by the separation tower (14) and enriching CH at the bottom4The temperature of the liquid is-170 to-180 ℃, the pressure is 0.3 to 0.4MPa, and the bottom is rich in CH4After decompression and expansion, the liquid is subjected to heat exchange through a first cold box (10) and a second cold box (11) to normal temperature to obtain LNG;
s10, after heat exchange of gas CO at the top of the separation tower (14) is carried out to normal temperature through the first cold box (10) and the second cold box (11), the gas CO enters the fourth compressor (29) to be compressed and then is divided into two parts, and the pressure of the compressed CO is 0.7-0.8 MPa, wherein: one part of the reflux liquid enters the top of the separation tower (14) to be used as reflux liquid of the separation tower (14), the reflux liquid is subjected to heat exchange through a first cooling box (10) to-150 to-155 ℃, then a material is shunted to a second reboiler (12) to be vaporized to be used as a heat source of the separation tower (14), and the material cooled in the separation tower (14) enters a second cooling box (11) to be subjected to heat exchange to 180 to-185 ℃, and then enters the top of the separation tower (14) to be used as reflux liquid; the other part of the mixed gas enters a methanol synthesis tower (15) for methanol synthesis after being mixed with the hydrogen-rich gas, and the methanol is obtained from the methane synthesized by the methanol synthesis tower (15) under the action of an eighth heat exchanger (28).
4. The method for preparing LNG and co-producing methanol, liquid ammonia and hydrogen through coke oven gas purification according to claim 3, wherein the amount of the gas washing agent is 0.20-0.32 kg/m3The dosage of the poor methanol in the desulfurizing tower (2) of the coke oven gas is 1.30-1.50kg/m3Coke oven gas.
5. The method for preparing LNG and coproducing methanol, liquid ammonia and hydrogen through coke oven gas purification according to claim 3, wherein the low-temperature methanol washing operation is carried out at a temperature of-20 ℃ to-40 ℃ and at a pressure of 0.3 MPa to 1.5 MPa.
6. The method for preparing LNG and co-producing methanol, liquid ammonia and hydrogen through coke oven gas purification according to claim 3, wherein the adsorption operation temperature of the first adsorption tower (4) or the second adsorption tower (5) is-60 to-50 ℃, and the operation pressure is 5 to 6 MPa; the desorption operation temperature is 180-350 ℃, the operation pressure is 50-200 kPa, and nitrogen is used for desorption.
7. The method for preparing LNG and co-producing methanol, liquid ammonia and hydrogen through coke oven gas purification according to claim 3, wherein the operating pressure of the stripping tower (6) is 1.0-1.5 MPa, and the temperature is-196-40 ℃.
8. The method for preparing LNG and co-producing methanol, liquid ammonia and hydrogen through coke oven gas purification according to claim 3, wherein the operating pressure of the separation tower (14) is 0.1-0.5 MPa, and the temperature is-196-40 ℃.
9. The method for preparing LNG and coproducing methanol, liquid ammonia and hydrogen through coke oven gas purification according to claim 3, wherein the methanol synthesis temperature of the methanol synthesis tower (15) is 230-270 ℃, the pressure is 5-8 MPa, the hydrogen-carbon ratio is 2.05-2.15, and the catalyst is a copper-based catalyst.
10. The method for preparing LNG and coproducing methanol, liquid ammonia and hydrogen through coke oven gas purification according to claim 3, wherein the temperature of the ammonia synthesized by the ammonia synthesis tower (17) is 470-490 ℃, the pressure is 13-14 MPa, the hydrogen-nitrogen ratio is 2.7-3.0, and the catalyst is an iron-based catalyst.
CN202110170244.4A 2021-02-08 2021-02-08 System and method for preparing LNG (liquefied Natural gas) and coproducing methanol, liquid ammonia and hydrogen through coke oven gas purification Active CN112961711B (en)

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