CN110862842A - Process for preparing LNG (liquefied Natural gas) from synthesis gas - Google Patents
Process for preparing LNG (liquefied Natural gas) from synthesis gas Download PDFInfo
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- 239000007789 gas Substances 0.000 title claims abstract description 253
- 238000003786 synthesis reaction Methods 0.000 title claims abstract description 116
- 230000015572 biosynthetic process Effects 0.000 title claims abstract description 113
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 21
- 239000003949 liquefied natural gas Substances 0.000 title abstract description 56
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims abstract description 645
- 239000003245 coal Substances 0.000 claims abstract description 165
- 238000000034 method Methods 0.000 claims abstract description 125
- 230000008569 process Effects 0.000 claims abstract description 106
- 229910052739 hydrogen Inorganic materials 0.000 claims abstract description 45
- 229910002091 carbon monoxide Inorganic materials 0.000 claims abstract description 44
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 44
- 238000006477 desulfuration reaction Methods 0.000 claims abstract description 37
- 230000023556 desulfurization Effects 0.000 claims abstract description 37
- 238000002309 gasification Methods 0.000 claims abstract description 33
- 238000011946 reduction process Methods 0.000 claims abstract description 24
- 238000005984 hydrogenation reaction Methods 0.000 claims abstract description 20
- 238000005261 decarburization Methods 0.000 claims abstract description 13
- 239000002002 slurry Substances 0.000 claims abstract description 12
- 230000009466 transformation Effects 0.000 claims abstract description 5
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims description 84
- 239000000463 material Substances 0.000 claims description 77
- 229910002092 carbon dioxide Inorganic materials 0.000 claims description 54
- 239000003054 catalyst Substances 0.000 claims description 47
- 238000006243 chemical reaction Methods 0.000 claims description 47
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 claims description 41
- 239000001257 hydrogen Substances 0.000 claims description 40
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 38
- 239000001569 carbon dioxide Substances 0.000 claims description 37
- 238000000926 separation method Methods 0.000 claims description 23
- 229910052799 carbon Inorganic materials 0.000 claims description 15
- 238000005262 decarbonization Methods 0.000 claims description 9
- 238000002360 preparation method Methods 0.000 claims description 2
- 239000003345 natural gas Substances 0.000 abstract description 55
- 239000002994 raw material Substances 0.000 abstract description 30
- 239000012535 impurity Substances 0.000 abstract description 6
- 239000000047 product Substances 0.000 description 61
- 238000001035 drying Methods 0.000 description 24
- 238000005265 energy consumption Methods 0.000 description 19
- 238000010438 heat treatment Methods 0.000 description 17
- 239000011280 coal tar Substances 0.000 description 11
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 10
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 9
- 230000000052 comparative effect Effects 0.000 description 9
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 8
- RHZUVFJBSILHOK-UHFFFAOYSA-N anthracen-1-ylmethanolate Chemical compound C1=CC=C2C=C3C(C[O-])=CC=CC3=CC2=C1 RHZUVFJBSILHOK-UHFFFAOYSA-N 0.000 description 8
- 239000003830 anthracite Substances 0.000 description 8
- 229920002994 synthetic fiber Polymers 0.000 description 8
- 239000003034 coal gas Substances 0.000 description 7
- 239000000126 substance Substances 0.000 description 7
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 6
- 229910052760 oxygen Inorganic materials 0.000 description 6
- 239000001301 oxygen Substances 0.000 description 6
- 238000010926 purge Methods 0.000 description 6
- 229910052757 nitrogen Inorganic materials 0.000 description 5
- 238000006722 reduction reaction Methods 0.000 description 5
- 239000007787 solid Substances 0.000 description 5
- 239000004215 Carbon black (E152) Substances 0.000 description 4
- UFWIBTONFRDIAS-UHFFFAOYSA-N Naphthalene Chemical compound C1=CC=CC2=CC=CC=C21 UFWIBTONFRDIAS-UHFFFAOYSA-N 0.000 description 4
- 238000001816 cooling Methods 0.000 description 4
- 229930195733 hydrocarbon Natural products 0.000 description 4
- 150000002430 hydrocarbons Chemical class 0.000 description 4
- 229910052759 nickel Inorganic materials 0.000 description 4
- 239000002245 particle Substances 0.000 description 4
- 238000011084 recovery Methods 0.000 description 4
- 238000002407 reforming Methods 0.000 description 4
- 238000005057 refrigeration Methods 0.000 description 4
- 230000002194 synthesizing effect Effects 0.000 description 4
- 239000002699 waste material Substances 0.000 description 4
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 3
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 3
- 238000004458 analytical method Methods 0.000 description 3
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- 238000000746 purification Methods 0.000 description 3
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- 239000000571 coke Substances 0.000 description 2
- 238000002485 combustion reaction Methods 0.000 description 2
- 229910052593 corundum Inorganic materials 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000003546 flue gas Substances 0.000 description 2
- 239000010439 graphite Substances 0.000 description 2
- 229910002804 graphite Inorganic materials 0.000 description 2
- 150000004820 halides Chemical class 0.000 description 2
- 150000002431 hydrogen Chemical class 0.000 description 2
- 238000009776 industrial production Methods 0.000 description 2
- MRELNEQAGSRDBK-UHFFFAOYSA-N lanthanum oxide Inorganic materials [O-2].[O-2].[O-2].[La+3].[La+3] MRELNEQAGSRDBK-UHFFFAOYSA-N 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 229910000480 nickel oxide Inorganic materials 0.000 description 2
- 238000005457 optimization Methods 0.000 description 2
- KTUFCUMIWABKDW-UHFFFAOYSA-N oxo(oxolanthaniooxy)lanthanum Chemical compound O=[La]O[La]=O KTUFCUMIWABKDW-UHFFFAOYSA-N 0.000 description 2
- GNRSAWUEBMWBQH-UHFFFAOYSA-N oxonickel Chemical compound [Ni]=O GNRSAWUEBMWBQH-UHFFFAOYSA-N 0.000 description 2
- 238000000197 pyrolysis Methods 0.000 description 2
- 238000004064 recycling Methods 0.000 description 2
- 238000012216 screening Methods 0.000 description 2
- 238000001179 sorption measurement Methods 0.000 description 2
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- 229910001845 yogo sapphire Inorganic materials 0.000 description 2
- 229910052688 Gadolinium Inorganic materials 0.000 description 1
- 229910052779 Neodymium Inorganic materials 0.000 description 1
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 description 1
- 229910052784 alkaline earth metal Inorganic materials 0.000 description 1
- 229910000287 alkaline earth metal oxide Inorganic materials 0.000 description 1
- 150000001342 alkaline earth metals Chemical class 0.000 description 1
- 150000004945 aromatic hydrocarbons Chemical class 0.000 description 1
- 239000010426 asphalt Substances 0.000 description 1
- 229910052790 beryllium Inorganic materials 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000002737 fuel gas Substances 0.000 description 1
- 230000008676 import Effects 0.000 description 1
- 229910052746 lanthanum Inorganic materials 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 229910000069 nitrogen hydride Inorganic materials 0.000 description 1
- 125000001741 organic sulfur group Chemical group 0.000 description 1
- 150000002989 phenols Chemical class 0.000 description 1
- 238000006068 polycondensation reaction Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
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- 229910052761 rare earth metal Inorganic materials 0.000 description 1
- 229910001404 rare earth metal oxide Inorganic materials 0.000 description 1
- 150000002910 rare earth metals Chemical class 0.000 description 1
- 230000035484 reaction time Effects 0.000 description 1
- 238000010992 reflux Methods 0.000 description 1
- 229930195734 saturated hydrocarbon Natural products 0.000 description 1
- 238000007086 side reaction Methods 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
- 229910052712 strontium Inorganic materials 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 239000011269 tar Substances 0.000 description 1
- 229930195735 unsaturated hydrocarbon Natural products 0.000 description 1
- 239000002912 waste gas Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10J—PRODUCTION OF PRODUCER GAS, WATER-GAS, SYNTHESIS GAS FROM SOLID CARBONACEOUS MATERIAL, OR MIXTURES CONTAINING THESE GASES; CARBURETTING AIR OR OTHER GASES
- C10J3/00—Production of combustible gases containing carbon monoxide from solid carbonaceous fuels
- C10J3/46—Gasification of granular or pulverulent flues in suspension
-
- 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
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- Chemical & Material Sciences (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Engineering & Computer Science (AREA)
- Organic Chemistry (AREA)
- Combustion & Propulsion (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Industrial Gases (AREA)
Abstract
The invention discloses a process for preparing LNG (liquefied natural gas) by using synthesis gas, which comprises the following steps: (1) preparing upgraded coal and rich gas from low-rank coal through a gasification reduction process, wherein the upgraded coal and the low-rank coal are at least one of prepared coal water slurry, prepared first synthesis gas from the upgraded coal, prepared second synthesis gas from the coal water slurry, and prepared third synthesis gas from the rich gas, wherein the third synthesis gas comprises at least one of the first synthesis gas, the second synthesis gas and the third synthesis gas, and the purified gas is obtained through a pre-desulfurization process, a hydrogenation process, a desulfurization process, a transformation process and a decarburization process, and is introduced into a first reactor and preheated to 150-; according to the method, CO and H required by natural gas synthesis raw materials are obtained through low-rank coal2The prepared natural gas has less impurities and high quality, fully and effectively utilizes the coal quality and volatile components in the low-rank coal, has lower cost and accords with the national comprehensive utilization direction of coal.
Description
Technical Field
The invention relates to the technical field of low-rank coal quality-based utilization, in particular to a process for preparing LNG (liquefied natural gas) by using synthesis gas.
Background
China is a country rich in coal, poor in oil and less in gas, and the coal consumption accounts for more than 60% of the primary energy consumption, so that the energy structure mainly based on coal is difficult to change in a long period of time. From the ascertained coal mine quality, the proportion of low-rank coal in the coal in China is very large, so that the reasonable and efficient utilization of the low-and-medium-rank coal to produce high-quality chemical products is very important. In recent years, the continuous development of technologies such as coal gasification, coal pyrolysis, coal gas purification, coal gas separation and the like makes the clean and efficient utilization of medium-low-grade coal more and more important.
Natural gas is a highly efficient clean energy source. In recent years, with the successive construction and use of national grade fuel gas transportation projects such as Shanxi gas import Jing and Xiqidong gas transportation, the demand of natural gas is increased explosively. According to prediction, in 2015, the demand of Chinese natural gas reaches 1700 hundred million Nm 3-2100 hundred million Nm3, while the yield of the natural gas at the same time can only reach 1400 hundred million Nm3, and the supply and demand gaps are about 300 hundred million Nm 3-700 hundred million Nm 3. In order to solve the problem of contradiction between supply and demand of natural gas in China, other alternative ways are required to be found besides the domestic resources are established and natural gas resources in other countries in the world are actively utilized.
The natural gas is prepared by adopting high-quality coal such as anthracite, and the production cost is high although the yield of the natural gas is high. And many middle-low rank coals in China have poor quality, high ash content and high water content, and the production cost of natural gas can be reduced by preparing the natural gas from the low rank coals. The raw coal gas is obtained by pyrolyzing low rank coal, which is generally carried out in the presence of a large amount of oxygen (or air), wherein a part of low rank coal is reacted with oxygen to supply heat and produce a large amount of CO2. Due to CO2Can not be combusted, belongs to ineffective gas, and has over high nitrogen content due to aerobic combustion, thereby reducing H in the crude gas2And CO energy density, so that the calorific value of the crude gas is reduced, and the crude gas produced by pyrolysis has other economic values except for return combustion. The biggest problem of the coal gasification process is that the chemical components contained in coal are not fully utilized, and the molecules of the chemical components cannot be separatedComplete interruption of CO and H production2And then chemically synthesizing the natural gas. The low-rank coal gasification reduction, reforming technology and natural gas synthesis technology can reserve chemical components in coal to the maximum extent in the form of natural gas.
Disclosure of Invention
In view of the above, the present invention provides a process for preparing LNG from synthesis gas, in which natural gas is synthesized from upgraded coal and rich gas, which are used by low-rank coal, and then the natural gas product is obtained by combining a liquefaction process, so that the process has the advantages of low raw material cost, substantial production cost saving, less impurities in the prepared natural gas, high quality, full and effective utilization of volatile components and coal quality in the low-rank coal, and energy can be provided for the corresponding process by coupling a methane synthesis process and a liquefaction process, coupling of specific steps of the methane synthesis process, coupling of the methane synthesis process and other coal processing processes.
In order to solve the technical problems, the invention provides the following technical scheme:
a process for preparing LNG from synthesis gas comprises the following steps:
(1) preparing upgraded coal and rich gas from low-rank coal through a gasification reduction process, wherein the upgraded coal and the low-rank coal are prepared to obtain coal water slurry, the upgraded coal is prepared to obtain first synthesis gas, the coal water slurry is prepared to obtain second synthesis gas, the rich gas is prepared to obtain third synthesis gas, the third synthesis gas comprises at least one of the first synthesis gas, the second synthesis gas and the third synthesis gas, and the purified gas is obtained through a pre-desulfurization process, a hydrogenation process, a desulfurization process, a transformation process and a decarburization process, is introduced into a first reactor and is preheated to 150-fold 500 ℃ to obtain preheated purified gas;
(2) introducing the preheated purified gas into a second reactor, wherein in the second reactor, in the environment with a first high-temperature-resistant methane catalyst, carbon monoxide, carbon dioxide and hydrogen of the preheated purified gas react to synthesize methane, so as to obtain a first methane material flow, and further obtain a first methane product material flow;
(3) separating the first methane product material flow obtained in the step (2) by a first gas-water separation device to obtain a second methane product material flow;
(4) introducing the second methane product material flow into a third reactor, wherein in the third reactor, in the environment with a second high-temperature-resistant methane catalyst, carbon monoxide, carbon dioxide and hydrogen of the second methane product material flow react to synthesize methane, so that a second methane material flow is obtained, and a third methane product material flow is obtained;
(5) separating the third methane product flow obtained in the step (4) by a second gas-water separation device to obtain a raw LNG flow;
(6) and introducing the original LNG material flow into a liquefaction process, and producing methane with volume percentage not less than 90% by using a cryogenic liquefaction process to obtain the product LNG.
The raw material low-rank coal can be pulverized coal or lump coal, and when the low-rank coal adopts the lump coal, the pulverized coal with smaller granularity can be obtained by crushing and screening the oversize lump coal. The pulverized coal is preferably used as a raw material, on one hand, the pulverized coal does not need to be crushed and screened, so that the process steps are saved, the heating area is large during drying, the drying efficiency is high, and on the other hand, the pulverized coal is low in price compared with lump coal. Pulverized coal having a particle size of less than 20mm is preferably used, and pulverized coal having a particle size of less than 6mm is still more preferably used.
The low-rank coal dried by the drying process enters the gasification reduction process for reaction, and for one-step optimization process, a gasification feeding process can be added before the dried low-rank coal enters the gasification reduction process, so that the dried low-rank coal can rapidly enter the gasification reduction process, the surface area of the material is increased, and the gasification reduction reaction can be accelerated.
Wherein, the gasification reduction process is a chemical reaction process for heating the dried low-rank coal under the condition of no oxygen or micro oxygen. The dried low-rank coal enters a gasification reduction process, under the heating of heating media such as flue gas and the like, additives and other substances are not required to be added in the reaction process, the temperature is generally 350-800 ℃, and the pressure is less than or equal to 30KpaAnd obtaining solid carbon and high-temperature rich gas, wherein the solid carbon is upgraded coal, and the volatile components in the upgraded coal are 8-15 wt%. The high-temperature rich gas comprises CO and H2、CO2Hydrocarbon, coal tar, naphthalene, halide, dust, sulfur compounds, and the like.
Preparing first synthesis gas from upgraded coal through a gas making process, preparing second synthesis gas from coal water slurry through a gas making process, and preparing third synthesis gas from rich gas; preferably, the first synthesis gas is subjected to the pre-desulfurization process, the hydrogenation process, the desulfurization process, the shift process, and the decarburization process to obtain a first purified gas, the second synthesis gas is subjected to the pre-desulfurization process, the hydrogenation process, the desulfurization process, the shift process, and the decarburization process to obtain a second purified gas, and the third synthesis gas is subjected to the pre-desulfurization process, the hydrogenation process, the desulfurization process, and the decarburization process to obtain a third purified gas.
The effective component in the methane synthesis gas required by natural gas synthesis is H2、CO、CO2The requirement for the hydrogen to carbon ratio in methane synthesis gas is expressed as follows: r ═ H2-CO2)/(CO+CO2) Wherein, the theoretical value of the hydrogen-carbon ratio R value of the methane synthetic gas is 3.0, and the optimal value is 2.95-3.05. And the R value of the hydrogen-carbon ratio in the prepared reformed gas can not just meet the condition that the R value is between 2.95 and 3.05, so the R value of the hydrogen-carbon ratio of the methane synthesis gas is adjusted to be 2.9 to 3.1, preferably the R value of the hydrogen-carbon ratio of the methane synthesis gas is adjusted to be 2.95 to 3.05, and the upgraded coal and the rich gas are prepared by the gasification reduction process from the low-rank coal, wherein the upgraded coal and/or the rich gas are prepared to contain CO and CO2And H2Thus entering the methane synthesis process to synthesize methane. Therefore, part of hydrocarbons in the hydrogenated rich gas or the hydrogenated pre-desulfurized synthesis gas are reformed and converted by using a conversion process to obtain the product containing CO and H2Reforming reformed gas of (1), CO and H in the reforming reformed gas after reforming2The total volume percentage is increased, which is beneficial to improving the quantity of the subsequent natural gas synthesis raw materials.
Preferably, the first methane stream is passed into a fourth reactor, and in the fourth reactor, in an environment where a third high temperature resistant methane catalyst exists, carbon monoxide, carbon dioxide and hydrogen of the first methane stream react to synthesize methane, so as to obtain a third methane stream, thereby obtaining the first methane product stream.
The method is further characterized in that the third methane material flow is introduced into a fifth reactor, in the environment with a fourth high-temperature resistant methane catalyst, carbon monoxide, carbon dioxide and hydrogen of the third methane material flow react to synthesize methane, and a fourth methane material flow is obtained, so that the first methane product flow is obtained.
Preferably, the second methane stream is introduced into a sixth reactor, in the sixth reactor, in an environment where a fifth high temperature resistant methane catalyst exists, carbon monoxide, carbon dioxide and hydrogen of the second methane stream react to synthesize methane, so as to obtain a fifth methane stream, and the volume percentage of carbon monoxide in the fifth methane stream is lower than 1%, so as to obtain the third methane product stream.
Preferably, a third purified gas is introduced into the second reactor, the third reactor and/or the fourth reactor, so that the reaction temperature is 200-500 ℃ when the methane is synthesized.
Preferably, a portion of the second methane stream is recycled back to the second reactor such that the reaction temperature is at 200-.
Further, part of the third methane stream is recycled to the second reactor and/or the fourth reactor, such that the reaction temperature is 200-500 ℃ when methane is synthesized.
Further, a portion of the fourth methane stream is recycled to the second reactor, the fourth reactor and/or the fifth reactor such that the reaction temperature is at 200-500 ℃ when methane is synthesized.
Preferably, carbon dioxide-rich gas is introduced into the second reactor, the fourth reactor and/or the fifth reactor, and the hydrogen-carbon ratio of the carbon dioxide-rich gas is (2.9-3.5): 1, and in the carbon dioxide-rich gas, the volume percentage of carbon dioxide is not less than 5%, and the reaction temperature is 200-500 ℃.
Preferably, the carbon monoxide-rich gas is introduced into the second reactor, the fourth reactor and/or the fifth reactor, so that the reaction temperature is 200-500 ℃.
Preferably, a hydrogen-rich gas is passed into the third reactor such that the volume percent concentration of carbon monoxide in the second methane stream is less than 1%.
Further, passing a hydrogen-rich gas into the sixth reactor such that the volume percent concentration of carbon monoxide in the second methane stream is less than 0.5%.
Further, in the first high temperature resistant methane catalyst, the second high temperature resistant methane catalyst, the third high temperature resistant methane catalyst, the fourth high temperature resistant methane catalyst and the fifth high temperature resistant methane catalyst, the content of nickel is 10-40% and increases in sequence.
And further, the first methane synthetic material enters a first heat exchanger for heating, and enters the second reactor after being heated.
Preferably, the first methane material flow flows out from the outlet of the second reactor, and after the first methane material flow passes through the first waste boiler to recover heat, the first methane material flow enters the first heat exchanger to exchange heat and reduce the temperature to 150-500 ℃, and the first heat exchanger is coupled with the second reactor to heat the first methane synthetic material.
Preferably, the second methane material flow flows out from the outlet of the third reactor, the second methane material flow enters a second heat exchanger for cooling after passing through a second waste boiler for heat exchange and heat recovery, and then enters a first gas-water separation device after passing through a third heat exchanger, a fourth heat exchanger or a first condenser for heat exchange, the second heat exchanger and the first condenser are coupled with the fourth reactor for heating the third methane synthetic material, the third heat exchanger is coupled with the first reactor for heating the purified gas, and the fourth heat exchanger is coupled with the second reactor for heating the first methane synthetic material.
Preferably, the methane product stream enters the second gas-water separation device after being cooled by the deoxygenated water preheater and the second condenser.
Wherein the component of the rich gas comprises CH according to the volume ratio428-40% of content, 5-20% of CO content and H225-40% of CO2Content of 5-20%, C2H6Content 2-8%, C2H4Content 1-4%, C3H60.5-3% of C3H8Content of 0.4-2.5%, C4H80.2-2% of H2S content 2000-3The content is less than 100 ppm;
further, in the desulfurization process, pressurized gas is introduced so that the pressure is 0.2 to 1.0MPa, and the temperature is maintained at 20 to 30 ℃.
Preferably, the decarbonization process comprises using a decarbonization solution, wherein the hydrogenation rich gas or the hydrogenation pre-desulfurization synthesis gas enters from the lower part of a decarbonization device and is in countercurrent contact with a decarbonization solution sprayed from the upper part of the decarbonization device, so that carbon dioxide in the hydrogenation rich gas or the hydrogenation pre-desulfurization synthesis gas is removed, and the decarbonization solution contains an NHD solvent.
Preferably, in the decarburization process, a pressurized gas is introduced so that the pressure is 0.3 to 1.0 MPa.
Finally, the methane product stream is liquefied to obtain crude natural gas and natural gas purge gas, and the natural gas purge gas is rich in hydrogen, so that the raw materials can be recycled, and the effective utilization rate of the raw materials is improved. Preferably, the liquefaction process comprises the steps that raw material gas obtained from a raw LNG material flow enters a refrigeration heat exchanger, flows into a low-pressure rectification device after precooling, is further cooled, then flows back to the refrigeration heat exchanger, is continuously cooled to-156 ℃ to-160 ℃, and then flows into the high-pressure rectification device for rectification, hydrogen components in the raw material gas are distilled out from the upper part of the high-pressure rectification device to form a hydrogen-rich material flow, first rectification gas containing carbon monoxide, nitrogen and methane flows out from the lower part of the high-pressure rectification device, the first rectification gas is subjected to throttling and pressure reduction and then enters the low-pressure rectification device, carbon monoxide and nitrogen in the first rectification gas form a carbon monoxide-rich material flow, the first rectification gas is distilled out from the upper part of the low-pressure rectification device, and the rest material forms second rectification gas and flows out from the lower part of the low-pressure rectification device.
The natural gas produced in the industrial production at present is basically synthesized by anthracite coal gasification into synthesis gas and then is produced into natural gas, the unit cost price of the raw material anthracite coal is about 1200 plus 1500 yuan/t, about 0.294 ton of natural gas is produced from 1 ton of coal, the unit cost price of the raw material low-rank coal is 80-100 yuan/t, the volatile content in the low-rank coal is 20-55 wt%, and the yield of the natural gas produced by utilizing the volatile content in the low-rank coal is 15% based on 1 ton of low-rank coal. As shown in table 1 below, the unit cost price of the natural gas prepared by using low-rank coal as the raw material is much lower than that of the natural gas prepared by using anthracite coal as the raw material, so that the cost expenditure of the raw material is greatly reduced by preparing the natural gas by using the method of the present invention. In addition, in the process of preparing natural gas by using low-rank coal, byproduct upgraded coal and coal tar can be obtained, and the unit price of the upgraded coal is 500-; the unit price of the coal tar is 2000-2500 yuan/t, and the product value of the upgraded coal and the coal tar is high.
TABLE 1 comparison of the cost per unit of natural gas produced from anthracite and low rank coal
Based on the technical scheme, on one hand, the method obtains CO and H required by natural gas synthetic raw materials by gasifying and reducing low-rank coal2The natural gas is prepared by the method, the impurities in the natural gas are few, the quality is high, the volatile components and the coal quality in the low-rank coal are fully and effectively utilized, the raw materials for preparing the natural gas are rich, the cost is low, the production cost is greatly saved, high-value upgraded coal and coal tar are rich, and the method accords with the national comprehensive utilization direction of coal.
Detailed Description
The present invention is further illustrated by the following examples, which are not intended to limit the invention to these embodiments. It will be appreciated by those skilled in the art that the present invention encompasses all alternatives, modifications and equivalents as may be included within the scope of the claims.
In the present invention, the raw materials and equipment used are commercially available or commonly used in the art, unless otherwise specified. The methods in the following examples are conventional in the art unless otherwise specified. The terms "first," "second," and the like in the present disclosure are used for distinguishing between descriptions and not to imply or imply relative importance.
Preparation example
The invention discloses a process for preparing LNG (liquefied natural gas) by using synthesis gas, which comprises the following steps:
(1) preparing upgraded coal and rich gas from low-rank coal through a gasification reduction process, wherein the upgraded coal and the low-rank coal are prepared to obtain coal water slurry, the upgraded coal is prepared to obtain first synthesis gas, the coal water slurry is prepared to obtain second synthesis gas, the rich gas is prepared to obtain third synthesis gas, the third synthesis gas comprises at least one of the first synthesis gas, the second synthesis gas and the third synthesis gas, and the purified gas is obtained through a pre-desulfurization process, a hydrogenation process, a desulfurization process, a transformation process and a decarburization process, is introduced into a first reactor and is preheated to 150-fold 500 ℃ to obtain preheated purified gas;
(2) introducing the preheated purified gas into a second reactor, wherein in the second reactor, in the environment with a first high-temperature-resistant methane catalyst, carbon monoxide, carbon dioxide and hydrogen of the preheated purified gas react to synthesize methane, so as to obtain a first methane material flow, and further obtain a first methane product material flow;
(3) separating the first methane product material flow obtained in the step (2) by a first gas-water separation device to obtain a second methane product material flow;
(4) introducing the second methane product material flow into a third reactor, wherein in the third reactor, in the environment with a second high-temperature-resistant methane catalyst, carbon monoxide, carbon dioxide and hydrogen of the second methane product material flow react to synthesize methane, so that a second methane material flow is obtained, and a third methane product material flow is obtained;
(5) separating the third methane product flow obtained in the step (4) by a second gas-water separation device to obtain a raw LNG flow;
(6) and introducing the original LNG material flow into a liquefaction process, and producing methane with volume percentage not less than 90% by using a cryogenic liquefaction process to obtain the product LNG.
The raw material low-rank coal can be pulverized coal or lump coal, and when the low-rank coal adopts the lump coal, the pulverized coal with smaller granularity can be obtained by crushing and screening the oversize lump coal. The pulverized coal is preferably used as a raw material, on one hand, the pulverized coal does not need to be crushed and screened, so that the process steps are saved, the heating area is large during drying, the drying efficiency is high, and on the other hand, the pulverized coal is low in price compared with lump coal. Pulverized coal having a particle size of less than 20mm is preferably used, and pulverized coal having a particle size of less than 6mm is still more preferably used.
The low-rank coal generally has 20-55% of volatile components, about 3-15% of tar, 30-60% of fixed carbon, 10-40% of water and the balance of other impurities such as dust. The low-rank coal has low coalification degree but contains abundant oil and gas resources, and the volatile components in the low-rank coal are very beneficial to extracting the synthesis gas, so that the low-rank coal with the volatile components between 30% and 55% is preferred.
The drying process can only remove most of the free water in the low-rank coal, but not remove the bound water in the low-rank coal, so that the low-rank coal is treated by the drying process to obtain the dried low-rank coal and waste gas, the dried low-rank coal still contains a certain amount of moisture, and the residual moisture can be gasified to form steam in the subsequent gasification reduction process.
The drying process can be one-stage or multi-stage, because if the water content of the low-rank coal after the first-stage drying process still does not meet the process requirement, multi-stage drying such as secondary drying, tertiary drying and the like can be adopted to continue further drying until the water content of the dried low-rank coal meets the process condition. In addition, the multistage drying process can be arranged in series or in parallel, the drying effect can be enhanced when the multistage drying process is connected in series, and the treatment capacity of the drying process can be increased when the multistage drying process is connected in parallel, so that the design that the multistage drying process is connected in series or in parallel or in series and in parallel can be adjusted according to the actual situation according to the requirement of the actual production process as long as the same technical effect can be achieved, and specifically, for example, when the feeding capacity of the drying process is calculated by low-rank coal of 20-30t/h, a one-stage steam drying process can be adopted; when the feeding amount of the drying process is calculated by a low level of 50-70t/h, a secondary steam drying process can be adopted, so that the method is more economical and reasonable.
The low-rank coal dried by the drying process enters the gasification reduction process for reaction, and for one-step optimization process, a gasification feeding process can be added before the dried low-rank coal enters the gasification reduction process, so that the dried low-rank coal can rapidly enter the gasification reduction process, the surface area of the material is increased, and the gasification reduction reaction can be accelerated.
Wherein, the gasification reduction process is a chemical reaction process for heating the dried low-rank coal under the condition of no oxygen or micro oxygen. The dried low-rank coal enters a gasification reduction process, under the heating of heating media such as flue gas and the like, additives and other substances are not needed to be added in the reaction process, the temperature is generally 350-800 ℃, and the pressure is less than or equal to 30Kpa, a complex chemical reaction process is carried out, so that solid carbon and high-temperature rich gas are obtained, wherein the solid carbon is upgraded coal, and the volatile matter in the upgraded coal is 8-15 wt%. The high-temperature rich gas comprises CO and H2、CO2Hydrocarbon, coal tar, naphthalene, halide, dust, sulfur compounds, and the like.
Wherein, the gasification reduction process can be one-stage or multi-stage. When the primary gasification reduction process is adopted, the reaction temperature of the gasification reduction process is 350-800 ℃, the volatile content in the upgraded coal is 8-15 wt%, and the reaction temperature of the gasification reduction process is further preferably 400-750 ℃; still more preferably 450-700 ℃. When the multistage gasification reduction process is adopted, the multistage gasification reduction process mainly has the main function of continuously gasifying certain amount of high-boiling-point oily substances (such as similar asphalt and the like) which cannot be gasified in a certain retention time and cannot be separated out or the temperature cannot reach the polycondensation reaction conditions of phenolic compounds, aromatic hydrocarbon compounds and the like in the previous stage gasification reduction process, and continuously reacting and gasifying, so that the gas yield and the quality of upgraded coal are improved. The unit price of the upgraded coal is generally 500-.
Preparing first synthesis gas from upgraded coal through a gas making process, preparing second synthesis gas from coal water slurry through a gas making process, and preparing third synthesis gas from rich gas; preferably, the first synthesis gas is subjected to the pre-desulfurization process, the hydrogenation process, the desulfurization process, the shift process, and the decarburization process to obtain a first purified gas, the second synthesis gas is subjected to the pre-desulfurization process, the hydrogenation process, the desulfurization process, the shift process, and the decarburization process to obtain a second purified gas, and the third synthesis gas is subjected to the pre-desulfurization process, the hydrogenation process, the desulfurization process, and the decarburization process to obtain a third purified gas.
The effective component in the methane synthesis gas required by natural gas synthesis is H2、CO、CO2The requirement for the hydrogen to carbon ratio in methane synthesis gas is expressed as follows: r ═ H2-CO2)/(CO+CO2) Wherein the hydrogen-carbon ratio of the methane synthesis gas is R ═ (H)2-CO2)/(CO+CO2) The theoretical value is 3.0, and the optimal value is 2.9-3.1.
The main chemical reaction formula of the synthetic natural gas is as follows:
since natural gas synthesis is exothermic, there are many side reactions, preferably the first methane stream is passed to a fourth reactor where carbon monoxide, carbon dioxide and hydrogen of the first methane stream react in the presence of a third refractory methane catalyst to synthesize methane and obtain a third methane stream, thereby obtaining the first methane product stream.
The method is further characterized in that the third methane material flow is introduced into a fifth reactor, in the environment with a fourth high-temperature resistant methane catalyst, carbon monoxide, carbon dioxide and hydrogen of the third methane material flow react to synthesize methane, and a fourth methane material flow is obtained, so that the first methane product flow is obtained.
Preferably, the second methane stream is introduced into a sixth reactor, in the sixth reactor, in an environment where a fifth high temperature resistant methane catalyst exists, carbon monoxide, carbon dioxide and hydrogen of the second methane stream react to synthesize methane, so as to obtain a fifth methane stream, and the volume percentage of carbon monoxide in the fifth methane stream is lower than 1%, so as to obtain the third methane product stream.
Preferably, a third purified gas is introduced into the second reactor, the third reactor and/or the fourth reactor, so that the reaction temperature is 200-500 ℃ when the methane is synthesized. Preferably, a portion of the second methane stream is recycled back to the second reactor such that the reaction temperature is at 200-. Further, part of the third methane stream is recycled to the second reactor and/or the fourth reactor, such that the reaction temperature is 200-500 ℃ when methane is synthesized. Further, a portion of the fourth methane stream is recycled to the second reactor, the fourth reactor and/or the fifth reactor such that the reaction temperature is at 200-500 ℃ when methane is synthesized.
Preferably, carbon dioxide-rich gas is introduced into the second reactor, the fourth reactor and/or the fifth reactor, and the hydrogen-carbon ratio of the carbon dioxide-rich gas is (2.9-3.5): 1, and in the carbon dioxide-rich gas, the volume percentage of carbon dioxide is not less than 5%, and the reaction temperature is 200-500 ℃. Preferably, the carbon monoxide-rich gas is introduced into the second reactor, the fourth reactor and/or the fifth reactor, so that the reaction temperature is 200-500 ℃.
Preferably, a hydrogen-rich gas is passed into the third reactor such that the volume percent concentration of carbon monoxide in the second methane stream is less than 1%. Further, passing a hydrogen-rich gas into the sixth reactor such that the volume percent concentration of carbon monoxide in the second methane stream is less than 0.5%. Further, in the first high temperature resistant methane catalyst, the second high temperature resistant methane catalyst, the third high temperature resistant methane catalyst, the fourth high temperature resistant methane catalyst and the fifth high temperature resistant methane catalyst, the content of nickel is 10-40% and increases in sequence. And further, the first methane synthetic material enters a first heat exchanger for heating, and enters the second reactor after being heated.
The methanation catalyst comprises a first high-temperature-resistant methane catalyst, a second high-temperature-resistant methane catalyst, a third high-temperature-resistant methane catalyst, a fourth high-temperature-resistant methane catalyst and a fifth high-temperature-resistant methane catalyst, and comprises 20-75% by mass of alumina as a carrier, 10-90% by mass of nickel oxide as an active component, and 5-25% by mass of rare earth metal oxide and alkaline earth metal oxide, wherein the rare earth metal comprises Nd, La and Gd, and the alkaline earth metal comprises Be and Sr. Preferably, the content of nickel oxide of the active component is increased from the first high temperature resistant methane catalyst, the second high temperature resistant methane catalyst to the third high temperature resistant methane catalyst, and the La of the active component is increased from the fourth high temperature resistant methane catalyst to the fifth high temperature resistant methane catalyst2O3The content of (a) increases in turn.
Preferably, the first methane material flow flows out from the outlet of the second reactor, and after the first methane material flow passes through the first waste boiler to recover heat, the first methane material flow enters the first heat exchanger to exchange heat and reduce the temperature to 150-500 ℃, and the first heat exchanger is coupled with the second reactor to heat the first methane synthetic material.
Preferably, the second methane material flow flows out from the outlet of the third reactor, the second methane material flow enters a second heat exchanger for cooling after passing through a second waste boiler for heat exchange and heat recovery, and then enters a first gas-water separation device after passing through a third heat exchanger, a fourth heat exchanger or a first condenser for heat exchange, the second heat exchanger and the first condenser are coupled with the fourth reactor for heating the third methane synthetic material, the third heat exchanger is coupled with the first reactor for heating the purified gas, and the fourth heat exchanger is coupled with the second reactor for heating the first methane synthetic material. Preferably, the methane product stream enters the second gas-water separation device after being cooled by the deoxygenated water preheater and the second condenser.
In the process of synthesizing natural gas, the pressure is about 2.5MPa generally.
Finally, the methane product stream is liquefied to obtain crude natural gas and natural gas purge gas, and the natural gas purge gas is rich in hydrogen, so that the raw materials can be recycled, and the effective utilization rate of the raw materials is improved. Preferably, the liquefaction process comprises the steps that raw material gas obtained from a raw LNG material flow enters a refrigeration heat exchanger, flows into a low-pressure rectification device after precooling, is further cooled, then flows back to the refrigeration heat exchanger, is continuously cooled to-156 ℃ to-160 ℃, and then flows into the high-pressure rectification device for rectification, hydrogen components in the raw material gas are distilled out from the upper part of the high-pressure rectification device to form a hydrogen-rich material flow, first rectification gas containing carbon monoxide, nitrogen and methane flows out from the lower part of the high-pressure rectification device, the first rectification gas is subjected to throttling and pressure reduction and then enters the low-pressure rectification device, carbon monoxide and nitrogen in the first rectification gas form a carbon monoxide-rich material flow, the first rectification gas is distilled out from the upper part of the low-pressure rectification device, and the rest material forms second rectification gas and flows out from the lower part of the low-pressure rectification device.
The natural gas produced in the industrial production at present is basically synthesized by anthracite coal gasification into synthesis gas and then is reproduced, the unit cost of the anthracite coal is about 1500 yuan/t, 1 ton of coal restricts the taking of 0.294 ton of natural gas, the unit cost of the low-rank coal is 80-100 yuan/t, the volatile content in the low-rank coal is 20-55 wt%, and the yield of the natural gas produced by using the volatile components in the low-rank coal is 15% based on 1 ton of low-rank coal. As shown in table 1 below, the unit cost price of the natural gas prepared by using low-rank coal as the raw material is much lower than that of the natural gas prepared by using anthracite coal as the raw material, so that the cost expenditure of the raw material is greatly reduced by preparing the natural gas by using the method of the present invention. In addition, in the process for preparing the natural gas by using the low-rank coal, the byproduct upgraded coal and the coal tar can be obtained, the unit price of the upgraded coal is 500-600 yuan/t, the unit price of the coal tar is 2000-2500 yuan/t, and the value of the product rich in yield is high.
The technical progress of the process for preparing LNG by using the purified gas of the low-rank coal in different qualities is analyzed by analyzing the components of the obtained raw LNG material flow, the purity of methane in the product gas LNG and the energy consumption of each kilogram of natural gas through a comparison experiment.
Experimental example 1
A process for preparing LNG from synthesis gas comprises the following steps:
(1) preparing upgraded coal and rich gas from low-rank coal through a gasification reduction process, wherein the upgraded coal and the low-rank coal are prepared to obtain coal water slurry, the upgraded coal is prepared to obtain first synthesis gas, the coal water slurry is prepared to obtain second synthesis gas, the rich gas is prepared to obtain third synthesis gas, the third synthesis gas comprises at least one of the first synthesis gas, the second synthesis gas and the third synthesis gas, and the purified gas is obtained through a pre-desulfurization process, a hydrogenation process, a desulfurization process, a transformation process and a decarburization process, is introduced into a first reactor and is preheated to 150-fold 500 ℃ to obtain preheated purified gas; specifically, a first synthesis gas is prepared from upgraded coal, and a first purified gas is obtained through a pre-desulfurization process, a hydrogenation process, a desulfurization process, a shift process and a decarburization process to obtain the preheated purified gas of example 1;
(2) introducing the preheated purified gas into a second reactor, wherein in the second reactor, in the environment with a first high-temperature-resistant methane catalyst, carbon monoxide, carbon dioxide and hydrogen of the preheated purified gas react to synthesize methane, so as to obtain a first methane material flow, and further obtain a first methane product material flow;
(3) separating the first methane product material flow obtained in the step (2) by a first gas-water separation device to obtain a second methane product material flow;
(4) introducing the second methane product material flow into a third reactor, wherein in the third reactor, in the environment with a second high-temperature-resistant methane catalyst, carbon monoxide, carbon dioxide and hydrogen of the second methane product material flow react to synthesize methane, so that a second methane material flow is obtained, and a third methane product material flow is obtained;
(5) separating the third methane product flow obtained in the step (4) by a second gas-water separation device to obtain a raw LNG flow;
(6) and introducing the original LNG material flow into a liquefaction process, and producing methane with volume percentage not less than 90% by using a cryogenic liquefaction process to obtain the product LNG.
In experimental example 1, at least 3 adiabatic methane synthesis reactors, specifically 3 reactors (R1, R2 and R3, respectively) were used, the 3 reactors were connected in series, R1 preheated the purge gas so that the temperature of the purge gas was 150-: al (Al)2O3: 56.5 percent; MgO: 22.5 percent; ni: 18.5 percent; la: 1.0 percent; ce: 1.0 percent; ba: 0.5% of catalyst, in the stages of methane synthesis at R2 and R3, and in R3, also reduces the CO content in the product, so that the quality of the product is improved. The total gas amount of purified gas is 1000kmol/h, under the pressure condition of 3.0MPa, the temperature of R1 outlet gas is about 250 ℃, the purified gas enters R2, the heat of R2 outlet gas is recovered and cooled, the recovered heat is cooled to about 100 ℃ plus of heat and enters a first gas-water separation device, gas-liquid separation is carried out to obtain a gas phase material which is a second methane product material, the gas phase material is coupled with R2 or R1 and heated to 150 ℃ plus of heat of 500 ℃, particularly about 250 ℃, the purified gas enters R3, the temperature of R3 outlet gas is about 350 ℃, the heat of R3 outlet gas is recovered and cooled to about 100 ℃ plus of heat and enters a second gas-water separation device, and gas-liquid separation is carried out to obtain a gas phase material which is the original LNG material; and introducing the original LNG material flow into a liquefaction process, and producing methane with the volume percentage not less than 90% by a cryogenic liquefaction process to obtain the product LNG.
Experimental example 2
Experimental example 2 referring to experimental example 1, except that in experimental example 2, at least 4 adiabatic methane synthesis reactors, specifically 4 reactors (R1, R2, R3 and R4, respectively) were used, the 4 reactors were connected in series, the first methane stream was passed to a fourth reactor (R4), and in the fourth reactor (R4), in the presence of a third refractory methane catalyst, carbon monoxide, carbon dioxide and hydrogen of the first methane stream were reacted to synthesize methane, and a third methane stream was obtained, thereby obtaining the first methane product stream. Aim at increases reaction unit before first gas-water separation device to increase reaction time, also be convenient for control reaction temperature, improve reaction efficiency.
Experimental example 3
Experimental example 3 referring to experimental example 1, except that in experimental example 3, at least 4 adiabatic methane synthesis reactors, specifically 4 (R1, R2, R3 and R5, respectively) were used, the 4 reactors were connected in series, the third methane stream was passed to a fifth reactor (R5) in which carbon monoxide, carbon dioxide and hydrogen of the third methane stream were reacted in the presence of a fourth refractory methane catalyst to synthesize methane and obtain a fourth methane stream, thereby obtaining a first methane product stream; the purpose is to carry out the quality control of the methane synthesis reaction by arranging an additional reactor behind the first gas-water separation device, and reduce the CO content in the obtained original LNG material flow.
The outlet gas of R3, after heat recovery and cooling to about 200-500 ℃, flows into R5, and the R5 is filled with a fourth high temperature resistant methane catalyst, which comprises the following components: al (Al)2O3: 56.5 percent; MgO: 22.5 percent; ni: 18.5 percent; la: 1.0 percent; ce: 1.0 percent; ba: 0.5% of catalyst, R5 outlet gas, after heat recovery and cooling to about 100-120 ℃, entering a second gas-water separation device, and then carrying out gas-liquid separation to obtain the original LNG material flow; and introducing the original LNG material flow into a liquefaction process, and producing methane with the volume percentage not less than 90% by a cryogenic liquefaction process to obtain the product LNG.
Experimental example 4
Experimental example 4 referring to experimental example 1 and experimental example 2, except that in experimental example 4, at least 4 adiabatic methane synthesis reactors, specifically 4 reactors (R1, R2, R3 and R4, respectively) were used, the 4 reactors were connected in series, and a third purified gas was introduced into the second reactor (R2), the third reactor (R3) and/or the fourth reactor (R4) so that the reaction temperature was 200-; specifically, a third purified gas is introduced into the second reactor (R2) and the fourth reactor (R4); the method aims to control the reaction temperature and the water production by utilizing the characteristics of high methane content and high hydrogen content of a third purified gas prepared from rich gas, thereby improving the synthesis efficiency.
Experimental example 5
Experimental example 5 referring to experimental example 1 and experimental example 2, except that in experimental example 5, at least 4 adiabatic methane synthesis reactors, specifically 4 reactors (R1, R2, R3 and R4, respectively) were used, the 4 reactors were connected in series, and a portion of the third methane stream was recycled to the second reactor (R2) and/or the fourth reactor, such that the reaction temperature was 200-500 ℃ when methane was synthesized; in particular, the third methane stream is recycled to the second reactor (R2) and the fourth reactor. Aims to control the reaction temperature by the circulating reflux of the product in a reactor in front of the first gas-water separation device, thereby improving the synthesis efficiency.
Experimental example 6
Experimental example 6 referring to experimental example 1, experimental example 2 and experimental example 3, except that in experimental example 6, at least 4 adiabatic methane synthesis reactors, specifically 5 reactors (R1, R2, R3, R4 and R5, respectively) were used, and 5 reactors were connected in series, and carbon dioxide-rich gas was introduced into the second reactor (R2), the third reactor (R3), the fourth reactor (R4) and/or the fifth reactor (R5) so that the reaction temperature was 200-; specifically, carbon dioxide-rich gas is introduced into the second reactor (R2) and the fourth reactor (R4); aims to control the reaction temperature and improve the synthesis efficiency by utilizing the fact that the carbon dioxide-rich gas can generate more water when synthesizing methane.
Experimental example 7
Experimental example 7 referring to experimental example 1, experimental example 2 and experimental example 3, except that in experimental example 7, at least 4 adiabatic methane synthesis reactors, specifically 5 reactors (R1, R2, R3, R4 and R5, respectively) were used, and 5 reactors were connected in series, and hydrogen-rich gas was introduced into the second reactor (R2), the third reactor (R3), the fourth reactor (R4) and/or the fifth reactor (R5) so that the reaction temperature was 200-; specifically, hydrogen-rich gas is introduced into the third reactor (R3) and the fifth reactor (R5); the method aims to utilize the hydrogen-rich gas to generate more heat during methane synthesis so as to control the reaction temperature and improve the synthesis efficiency, and utilize the hydrogen-rich gas to reduce the content of CO in the original LNG material flow.
Experimental example 8
Experimental example 8 referring to Experimental example 1, Experimental example 2 and Experimental example 3, except that in Experimental example 8, at least 4 adiabatic methane synthesis reactors, specifically 5 reactors (R1, R2, R3, R4 and R5, respectively) were used, and 5 reactors were connected in series, and carbon monoxide-rich gas was introduced into the second reactor (R2), the third reactor (R3), the fourth reactor (R4) and/or the fifth reactor (R5) so that the reaction temperature was 200-; specifically, the second reactor (R2) and the fourth reactor (R3) are filled with carbon monoxide-rich gas; aims to utilize the carbon monoxide-rich gas to generate more heat when synthesizing methane, thereby controlling the reaction temperature and improving the synthesis efficiency.
Comparative example 1
The method for preparing natural gas and co-producing hydrogen by rich gas utilized by low-rank coal in a quality-divided manner comprises the following steps:
(1) heating low-rank coal at 600 ℃ by isolating air to obtain semi-coke, coal tar and rich gas as byproducts, wherein the components of the rich gas comprise 28-40% of CH4, 10-15% of CO, 25-40% of H2, 5-10% of CO2, 2-8% of C2H6, 1-4% of C2H4, 0.5-3% of C3H6, 0.4-2.5% of C3H8, 0.2-2% of C4H8, 6000ppm of H2S and 800ppm of NH3, wherein the contents of the semi-coke, coal tar and the rich gas are respectively 400-;
(2) through the spraying water washing purification process adopted by the water washing purification unit 2, the pretreated rich gas is further purified, and ammonia gas and sulfide in the rich gas are removed, so that the load of a subsequent desulfurization procedure is reduced, and the pre-desulfurized rich gas is obtained;
(3) all unsaturated hydrocarbons in the coal gas are converted into corresponding saturated hydrocarbons through the hydrogenation unit 3, and organic sulfur is converted into H2S at the same time, so that hydrogenated rich gas is obtained;
(4) the content of H2S in the raw material gas is reduced to less than 0.1ppm by adopting a dry desulfurization process through a fine desulfurization unit 4 and utilizing solid ZnO for desulfurization, so that desulfurized rich gas is obtained;
(5) passing the desulfurized gas through a pre-conversion unit 5, and pre-converting a catalyst by using hydrocarbon steam with high nickel content, wherein the catalyst contains 48-68% of NiO, 15-36% of Al2O3, 1.2-4.8% of MgO, 1.2-4.8% of La2O3, 5-12% of CaO, 0.5-1.2% of K2O and 1.5-4.5% of graphite; the unit leads higher hydrocarbon above C2 in the coal gas to carry out pre-conversion reaction to generate methane under the conditions of pressure of 1.5-3.5MPa, temperature of 400-; wherein the coal gas after the pre-conversion reaction comprises the following components: 30-50% of CH4, 13-18% of CO, 30-60% of H2, 10-15% of CO2 and a small amount of water vapor and other impurity gases;
(6) passing the pre-converted gas through a methanation unit 6, and adopting a methanation catalyst with low nickel content, wherein the components of the methanation catalyst comprise NiO content of 12-24%, Al2O3 content of 32-74%, MgO content of 1.2-4.8%, La2O3 content of 1.2-4.8%, CaO content of 5-12%, K2O content of 0.5-1.2%, and graphite content of 1.5-4.5%; the effective components in the raw material gas are: h2, CO and CO2 are subjected to methanation reaction, so that the concentration of the generated methane can reach 75-90%, and then the methane passes through a gas-water separation device to obtain the original LNG material flow;
(7) and introducing the gas after the methanation reaction into a pressure swing adsorption unit 7, and producing high-concentration methane, namely a product LNG and high-purity hydrogen through a pressure swing adsorption process.
Table 2 table of analysis of composition of raw LNG stream produced in test examples 1 to 8 and comparative example 1
Note that the raw LNG stream has a composition content in volume percent.
From the results in table 2, the components of the obtained raw LNG stream are analyzed, and we can obtain that, firstly, more than 3 methane synthesis reactors are connected in series to perform a methane synthesis reaction, so that the methane content in the product can be remarkably increased from 88.99% in comparative example 1 to 91.47% in experimental example 1, and secondly, the methane content in the product can be remarkably increased from 91.47% in experimental example 1 to 95.00% in experimental example 2 by introducing the first methane stream into a fourth reactor (R4); thirdly, the methane content in the product can be remarkably improved by introducing the third methane material flow into a fifth reactor (R5), and the methane content is increased from 91.47% in experimental example 1 to 95.40% in experimental example 3; fourthly, the methane content in the product can be remarkably improved by introducing a third purified gas into the second reactor (R2), the third reactor (R3) and/or the fourth reactor (R4), and is increased from 91.47% of experimental example 1 to 95.99% of experimental example 4; fifthly, recycling part of the third methane flow to the second reactor (R2) and/or the fourth reactor can remarkably improve the methane content in the product, and the methane content is increased from 91.47% of experimental example 1 to 95.60% of experimental example 5; sixthly, the methane content in the product can be remarkably improved by introducing carbon dioxide-rich gas into the second reactor (R2), the third reactor (R3), the fourth reactor (R4) and/or the fifth reactor (R5), and is increased from 91.47% of experimental example 1 to 95.35% of experimental example 6; seventhly, the hydrogen-rich gas is introduced into the second reactor (R2), the third reactor (R3), the fourth reactor (R4) and/or the fifth reactor (R5), so that the methane content in the product can be remarkably improved, the CO content in the original LNG material flow can be reduced, and the content is increased from 91.47% of experimental example 1 to 96.24% of experimental example 7; eighth, the introduction of carbon monoxide-rich gas into the second reactor (R2), the third reactor (R3), the fourth reactor (R4) and/or the fifth reactor (R5) can significantly increase the methane content in the product from 91.47% in experimental example 1 to 95.58% in experimental example 8.
Table 3 comparison of purity of methane in LNG as product gas produced in experimental examples 1 to 5 and comparative example 1
| Name (R) | Experimental example 1 | Experimental example 2 | Experimental example 3 | Experimental example 4 | Experimental example 5 | Experimental example 6 | Experimental example 7 | Experimental example 8 | Comparative example 1 |
| Methane | 99.083％ | 99.046％ | 99.049％ | 99.093％ | 99.011％ | 99.63％ | 99.132％ | 99.77％ | 96.72％ |
Note that the methane purity in LNG is the volume percent content of methane.
From the results in table 3, we can analyze the components of the methane purity in the obtained product gas LNG, and we can obtain that the quality of the finally obtained product gas LNG can be affected due to the component difference of the raw LNG stream in the methane synthesis stage, so that the purity of the LNG products of experimental examples 1-8 is higher than that of comparative example 1.
| Composition of | Experimental example 1 | Experimental example 2 | Experimental example 3 | Experimental example 4 | Experimental example 5 | Experimental example 6 | Experimental example 7 | Experimental example 8 | Comparative example 1 |
| Energy consumption/kJ | 1568 | 1488 | 1476 | 1426 | 1442 | 1406 | 1386 | 1415 | 1728 |
TABLE 4 analytical analysis table of energy consumption before cut-off methanation reaction in test examples 1 to 3 and comparative example 1
Note: the energy consumption analysis is the energy consumption of the methane synthesis gas which can produce 1 cubic meter of LNG before the methanation reaction is stopped.
From the results in table 4, we can obtain that energy consumption of methane synthesis gas capable of producing 1 cubic meter of LNG before stopping methanation reaction is firstly reduced to 1568kJ of experimental example 1 from 1728kJ of comparative example 1 by connecting more than 3 methane synthesis reactors in series to perform methane synthesis reaction, and secondly energy consumption of methane synthesis gas capable of reducing 1 cubic meter of LNG to 1488kJ of experimental example 2 by introducing the first methane stream into the fourth reactor (R4); thirdly, the energy consumption of methane synthesis gas of 1 cubic meter of LNG can be obviously reduced by introducing the third methane material flow into a fifth reactor (R5), and the energy consumption is reduced from 1568kJ of experimental example 1 to 1476kJ of experimental example 3; fourthly, the energy consumption of the methane synthesis gas of 1 cubic meter of LNG can be remarkably reduced by introducing a third purified gas into the second reactor (R2), the third reactor (R3) and/or the fourth reactor (R4), and the energy consumption is reduced from 1568kJ of experimental example 1 to 1426kJ of experimental example 4; fifthly, recycling part of the third methane stream to the second reactor (R2) and/or the fourth reactor can remarkably reduce the energy consumption of methane synthesis gas of 1 cubic meter of LNG, and the energy consumption is reduced from 1568kJ of experimental example 1 to 1442kJ of experimental example 5; sixthly, the energy consumption of the methane synthesis gas of 1 cubic meter of LNG can be remarkably reduced by introducing the carbon dioxide-rich gas into the second reactor (R2), the third reactor (R3), the fourth reactor (R4) and/or the fifth reactor (R5), and the energy consumption is reduced from 1568kJ of experimental example 1 to 1406kJ of experimental example 6; seventhly, the energy consumption of the methane synthesis gas of 1 cubic meter of LNG can be remarkably reduced by introducing hydrogen-rich gas into the second reactor (R2), the third reactor (R3), the fourth reactor (R4) and/or the fifth reactor (R5), and the energy consumption is reduced from 1568kJ of experimental example 1 to 1386kJ of experimental example 7; eighth, the carbon monoxide-rich gas introduced into the second reactor (R2), the third reactor (R3), the fourth reactor (R4) and/or the fifth reactor (R5) can significantly reduce the energy consumption of the methane synthesis gas of 1 cubic meter LNG, which is 1415kJ of experimental example 8 from 1568kJ of experimental example 1.
In summary, the method of the invention obtains rich gas and upgraded coal by gasifying and reducing low-rank coal, and then reforms and converts hydrocarbons and the like in the rich gas, or obtains CO and H required by natural gas synthetic raw materials by gasifying and converting the upgraded coal2The natural gas is prepared by the method, the impurities in the natural gas are few, the quality is high, the volatile components and the coal quality in the low-rank coal are fully and effectively utilized, the raw materials for preparing the natural gas are rich, the cost is low, the production cost is greatly saved, high-value upgraded coal and coal tar are rich, and the method accords with the national comprehensive utilization direction of coal.
The above-mentioned embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the same; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (10)
1. The process for preparing LNG from synthesis gas is characterized by comprising the following steps:
(1) preparing upgraded coal and rich gas from low-rank coal through a gasification reduction process, wherein the upgraded coal and the low-rank coal are prepared to obtain coal water slurry, the upgraded coal is prepared to obtain first synthesis gas, the coal water slurry is prepared to obtain second synthesis gas, the rich gas is prepared to obtain third synthesis gas, the third synthesis gas comprises at least one of the first synthesis gas, the second synthesis gas and the third synthesis gas, and the purified gas is obtained through a pre-desulfurization process, a hydrogenation process, a desulfurization process, a transformation process and a decarburization process, is introduced into a first reactor and is preheated to 150-fold 500 ℃ to obtain preheated purified gas;
(2) introducing the preheated purified gas into a second reactor, wherein in the second reactor, in the environment with a first high-temperature-resistant methane catalyst, carbon monoxide, carbon dioxide and hydrogen of the preheated purified gas react to synthesize methane, so as to obtain a first methane material flow, and further obtain a first methane product material flow;
(3) separating the first methane product material flow obtained in the step (2) by a first gas-water separation device to obtain a second methane product material flow;
(4) introducing the second methane product material flow into a third reactor, wherein in the third reactor, in the environment with a second high-temperature-resistant methane catalyst, carbon monoxide, carbon dioxide and hydrogen of the second methane product material flow react to synthesize methane, so that a second methane material flow is obtained, and a third methane product material flow is obtained;
(5) separating the third methane product flow obtained in the step (4) by a second gas-water separation device to obtain a raw LNG flow;
(6) and introducing the original LNG material flow into a liquefaction process, and producing methane with volume percentage not less than 90% by using a cryogenic liquefaction process to obtain the product LNG.
2. The process of claim 1, wherein the first methane stream is passed to a fourth reactor, wherein carbon monoxide, carbon dioxide and hydrogen of the first methane stream are reacted in the presence of a third refractory methane catalyst in the fourth reactor to synthesize methane and produce a third methane stream, thereby producing the first methane product stream.
3. The syngas to LNG process of claim 1 or 2 wherein the third methane stream is passed to a fifth reactor wherein carbon monoxide, carbon dioxide and hydrogen of the third methane stream are reacted in the presence of a fourth refractory methane catalyst in the fifth reactor to synthesize methane to obtain a fourth methane stream, thereby obtaining the first methane product stream.
4. The process of claim 1, wherein the second methane stream is passed to a sixth reactor, wherein carbon monoxide, carbon dioxide and hydrogen of the second methane stream are reacted in the presence of a fifth refractory methane catalyst in the sixth reactor to synthesize methane, resulting in a fifth methane stream, such that the volume percentage of carbon monoxide in the fifth methane stream is less than 1%, resulting in the third methane product stream.
5. The process of claim 1, wherein the first syngas is passed through the pre-desulfurization process, the hydrogenation process, the desulfurization process, the shift process, and the decarbonization process to obtain a first purified gas, the second syngas is passed through the pre-desulfurization process, the hydrogenation process, the desulfurization process, the shift process, and the decarbonization process to obtain a second purified gas, and the third syngas is passed through the pre-desulfurization process, the hydrogenation process, the desulfurization process, and the decarbonization process to obtain a third purified gas, and the purified gas comprises at least one of the first purified gas, the second purified gas, and the third purified gas.
6. The process for preparing LNG from synthesis gas as claimed in claim 1, wherein a third purified gas is introduced into the second reactor, the third reactor and/or the fourth reactor, so that the reaction temperature is 200-500 ℃ when methane is synthesized.
7. The process for the preparation of LNG as claimed in claim 1, wherein part of the second methane stream is recycled to the second reactor such that the reaction temperature for the synthesis of methane is at 200-500 ℃.
8. The process for synthesis gas to LNG as claimed in claim 2, characterised in that part of the third methane stream is recycled to the second reactor and/or the fourth reactor, such that the reaction temperature for methane synthesis is at 200-500 ℃.
9. The process of claim 3, wherein a portion of the fourth methane stream is recycled to the second reactor, the fourth reactor, and/or the fifth reactor such that the reaction temperature for methane synthesis is at 200-500 ℃.
10. The process for preparing LNG from synthesis gas according to claim 1, wherein carbon dioxide-rich gas is introduced into the second reactor, the fourth reactor and/or the fifth reactor, and the hydrogen-carbon ratio of the carbon dioxide-rich gas is (2.9-3.5): 1, and in the carbon dioxide-rich gas, the volume percentage of carbon dioxide is not less than 5%, and the reaction temperature is 200-500 ℃.
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| CN110055104A (en) * | 2019-04-01 | 2019-07-26 | 浙江天禄环境科技有限公司 | A kind of method that the utilization of low-order coal sub-prime prepares natural gas |
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| US20100313597A1 (en) * | 2007-07-09 | 2010-12-16 | Lng Technology Pty Ltd | Method and system for production of liquid natural gas |
| CN110055104A (en) * | 2019-04-01 | 2019-07-26 | 浙江天禄环境科技有限公司 | A kind of method that the utilization of low-order coal sub-prime prepares natural gas |
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