CN106608800B - Processing method of light product of preparing aromatic hydrocarbon from methanol - Google Patents
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- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 title claims abstract description 141
- 150000004945 aromatic hydrocarbons Chemical class 0.000 title abstract description 31
- 238000003672 processing method Methods 0.000 title description 4
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims abstract description 214
- 239000007789 gas Substances 0.000 claims abstract description 166
- 229930195733 hydrocarbon Natural products 0.000 claims abstract description 71
- 150000002430 hydrocarbons Chemical class 0.000 claims abstract description 66
- 239000007788 liquid Substances 0.000 claims abstract description 66
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims abstract description 60
- 239000001257 hydrogen Substances 0.000 claims abstract description 58
- 229910052739 hydrogen Inorganic materials 0.000 claims abstract description 58
- 238000000926 separation method Methods 0.000 claims abstract description 56
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims abstract description 50
- 239000004215 Carbon black (E152) Substances 0.000 claims abstract description 43
- 238000005899 aromatization reaction Methods 0.000 claims abstract description 34
- 239000001569 carbon dioxide Substances 0.000 claims abstract description 30
- 229910002092 carbon dioxide Inorganic materials 0.000 claims abstract description 30
- 239000012528 membrane Substances 0.000 claims abstract description 30
- 238000000034 method Methods 0.000 claims abstract description 29
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 20
- 238000005191 phase separation Methods 0.000 claims abstract description 14
- 239000000463 material Substances 0.000 claims abstract description 9
- 238000001816 cooling Methods 0.000 claims abstract description 8
- 239000002253 acid Substances 0.000 claims description 7
- 125000003118 aryl group Chemical group 0.000 claims description 4
- 239000012510 hollow fiber Substances 0.000 claims description 3
- 239000003518 caustics Substances 0.000 claims description 2
- 238000002360 preparation method Methods 0.000 claims 1
- 238000005265 energy consumption Methods 0.000 abstract description 25
- 238000009776 industrial production Methods 0.000 abstract 1
- 239000012071 phase Substances 0.000 description 51
- 239000000047 product Substances 0.000 description 35
- UHOVQNZJYSORNB-UHFFFAOYSA-N Benzene Chemical compound C1=CC=CC=C1 UHOVQNZJYSORNB-UHFFFAOYSA-N 0.000 description 21
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 21
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 description 10
- 239000005977 Ethylene Substances 0.000 description 10
- 229910052799 carbon Inorganic materials 0.000 description 10
- ATUOYWHBWRKTHZ-UHFFFAOYSA-N Propane Chemical compound CCC ATUOYWHBWRKTHZ-UHFFFAOYSA-N 0.000 description 8
- 239000007795 chemical reaction product Substances 0.000 description 7
- 150000002431 hydrogen Chemical class 0.000 description 6
- CTQNGGLPUBDAKN-UHFFFAOYSA-N O-Xylene Chemical compound CC1=CC=CC=C1C CTQNGGLPUBDAKN-UHFFFAOYSA-N 0.000 description 5
- 239000000203 mixture Substances 0.000 description 5
- QQONPFPTGQHPMA-UHFFFAOYSA-N propylene Natural products CC=C QQONPFPTGQHPMA-UHFFFAOYSA-N 0.000 description 5
- 125000004805 propylene group Chemical group [H]C([H])([H])C([H])([*:1])C([H])([H])[*:2] 0.000 description 5
- 239000002994 raw material Substances 0.000 description 5
- 239000012465 retentate Substances 0.000 description 5
- 239000008096 xylene Substances 0.000 description 5
- LCGLNKUTAGEVQW-UHFFFAOYSA-N Dimethyl ether Chemical compound COC LCGLNKUTAGEVQW-UHFFFAOYSA-N 0.000 description 4
- OTMSDBZUPAUEDD-UHFFFAOYSA-N Ethane Chemical compound CC OTMSDBZUPAUEDD-UHFFFAOYSA-N 0.000 description 4
- 238000005516 engineering process Methods 0.000 description 4
- 239000001294 propane Substances 0.000 description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 3
- 239000008346 aqueous phase Substances 0.000 description 3
- 239000003245 coal Substances 0.000 description 3
- 239000002737 fuel gas Substances 0.000 description 3
- 239000012466 permeate Substances 0.000 description 3
- 238000010521 absorption reaction Methods 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 238000006356 dehydrogenation reaction Methods 0.000 description 2
- 238000003795 desorption Methods 0.000 description 2
- 238000007323 disproportionation reaction Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- -1 hydrocarbon arene Chemical class 0.000 description 2
- JRZJOMJEPLMPRA-UHFFFAOYSA-N olefin Natural products CCCCCCCC=C JRZJOMJEPLMPRA-UHFFFAOYSA-N 0.000 description 2
- 238000011084 recovery Methods 0.000 description 2
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 1
- 230000002745 absorbent Effects 0.000 description 1
- 239000002250 absorbent Substances 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 229910002091 carbon monoxide Inorganic materials 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 238000001833 catalytic reforming Methods 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000003208 petroleum Substances 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C7/00—Purification; Separation; Use of additives
- C07C7/005—Processes comprising at least two steps in series
-
- 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
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C1/00—Preparation of hydrocarbons from one or more compounds, none of them being a hydrocarbon
- C07C1/20—Preparation of hydrocarbons from one or more compounds, none of them being a hydrocarbon starting from organic compounds containing only oxygen atoms as heteroatoms
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C2/00—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Analytical Chemistry (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Water Supply & Treatment (AREA)
- Combustion & Propulsion (AREA)
- Inorganic Chemistry (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
The invention relates to a treatment method of a light product of aromatic hydrocarbon prepared from methanol, which mainly solves the problem of high energy consumption of gas separation in the process of utilizing the light product of aromatic hydrocarbon prepared from methanol in the prior art. The invention adopts the following steps: the methanol aromatization product is separated into a gas phase, an oil phase and a water phase in a three-phase separation unit; the gas phase is compressed and then sent into a membrane separation unit to be separated into hydrogen-rich gas and hydrogen-poor gas; cooling the hydrogen-poor gas, and then sending the cooled hydrogen-poor gas into a first gas-liquid separation unit to separate the hydrogen-poor gas into a first methane-rich gas and a first methane-poor liquid; separating the first methane-rich gas into a second methane-rich gas and a second methane-lean liquid; the second methane-rich gas is sent into a gas separation unit to be separated into methane gas, carbon dioxide and heavier hydrocarbon material flows; the technical scheme that the carbon dioxide and heavier hydrocarbon material flow, the first methane-depleted liquid and the second methane-depleted liquid are sent into a light hydrocarbon reactor to be converted into a light hydrocarbon aromatization product better solves the problems and can be used in the industrial production of aromatic hydrocarbon.
Description
Technical Field
The invention relates to a treatment method for preparing an aromatic hydrocarbon light product from methanol.
Technical Field
Aromatic hydrocarbons, in particular the light aromatic hydrocarbons BTX (benzene, toluene, xylene), are important basic organic chemicals, second only to ethylene and propylene in terms of yield and scale. The main source of aromatics is naphtha catalytic reforming. By combining the national conditions of rich coal resources and higher petroleum dependence of China, the development of the technology for preparing aromatic hydrocarbon from coal with the advantage of raw material price becomes a research hotspot of nearly ten years, and technical breakthroughs are made in recent years, and especially the technology for preparing aromatic hydrocarbon from coal-based methanol has already completed industrial demonstration tests.
The technology for preparing the aromatic hydrocarbon from the methanol has the great characteristics that reaction products are various, not only comprise target products such as the aromatic hydrocarbon, but also comprise low-carbon hydrocarbons such as methane, carbon dioxide and the like, and a large amount of hydrogen is generated as a byproduct. In order to increase the yield of aromatic hydrocarbons, it is necessary to recover and aromatize lower hydrocarbons and separate hydrogen as a high value-added product to improve the overall economy of the plant. Because the separation of light hydrocarbons, particularly the separation of methane and carbon dioxide, needs to consume a large amount of cold energy, the device has high energy consumption, long flow path and large investment, and the popularization and the industrial application of the technology for preparing aromatic hydrocarbon from methanol are restricted.
Patent CN101823929 discloses a system and a process for preparing aromatic hydrocarbon by converting methanol or dimethyl ether. The raw material methanol or dimethyl ether is firstly reacted in a raw material aromatization reactor, and the product after the reaction is separated into gas-phase light hydrocarbon, oil phase mainly containing aromatic hydrocarbon and water by a three-phase separation unit. In order to improve the selectivity and yield of aromatic hydrocarbon, the patent provides three technical schemes. In the first embodiment, C is separated from the reaction product2And the non-aromatic hydrocarbons are firstly subjected to aromatization reaction in the low-carbon olefin aromatization reactor, then the aromatic hydrocarbons and the light hydrocarbons are separated, hydrogen and methane mixed gas is separated from the light hydrocarbons, then the hydrogen products and the methane products are separated from the hydrogen and methane mixed gas, the rest light hydrocarbons are sent into the low-carbon hydrocarbon aromatization reactor, and the products return to the three-phase separation unit. In addition, benzene, toluene, and part C9+ hydrocarbons are sent to an aromatics disproportionation reactor to produce C8 aromatics, which are also returned to the three-phase separation unit. Hydrogen, methane, mixed C8Aromatic hydrocarbons and fraction C9+ hydrocarbons as product export system. The second technical scheme of the patent provides a simplified process flow, wherein hydrogen and methane mixed gas is firstly separated from light hydrocarbon, then a hydrogen product and a methane product are separated from the light hydrocarbon, the light hydrocarbon after methane hydrogen removal is sent to a low-carbon hydrocarbon aromatization reactor, and a reaction product returns to a three-phase separation unit, namely the low-carbon olefin aromatization reactor is not arranged. The third technical proposal of the patent is further simplified on the basis of the former technical proposal, and the benzene, the toluene and part C are separated from the oil phase aromatic hydrocarbon9The hydrocarbons are not sent into the aromatic disproportionation reactor, but directly returned to the raw material aromatization reactor. The technical proposal adopts the same processing method as the second technical proposal for light hydrocarbon. The three technical schemes of the patent adopt a processing method of firstly separating methane-hydrogen mixture from light hydrocarbon and then separating methane and hydrogen from the mixture. The method disclosed in this patentIt is recommended to separate methane-hydrogen mixture from light hydrocarbon by absorption, desorption or rectification. Because the hydrogen content in the light hydrocarbon is high, when an absorption desorption method is adopted, the concentration of ethylene in the light hydrocarbon is low, and a large amount of absorbent is needed to ensure the recovery rate of ethylene, so the energy consumption is high; when cryogenic separation is adopted, the temperature at the top of the tower is very low due to the high hydrogen content in the hydrocarbons, the cold consumption is large, and the energy consumption is high.
The invention aims to solve the problem of high energy consumption of gas separation in the process of utilizing light products of aromatic hydrocarbon prepared from methanol in the prior art.
Disclosure of Invention
The invention aims to solve the technical problem that the energy consumption of gas separation is high in the process of utilizing the light product of preparing aromatic hydrocarbon from methanol in the prior art, and provides a novel treatment method of the light product of preparing aromatic hydrocarbon from methanol. The device has the advantage of low energy consumption.
In order to solve the problems, the technical scheme adopted by the invention is as follows: a treatment method for preparing an aromatic light product from methanol comprises the following steps: 1) methanol is converted into a methanol aromatization product in a methanol reactor; 2) the methanol aromatization product is separated into a gas phase, an oil phase and a water phase in a three-phase separation unit; 3) the gas phase is compressed and then sent into a membrane separation unit to be separated into hydrogen-rich gas and hydrogen-poor gas; 4) cooling the hydrogen-poor gas, and then sending the cooled hydrogen-poor gas into a first gas-liquid separation unit to separate the hydrogen-poor gas into a first methane-rich gas and a first methane-poor liquid; 5) the first methane-rich gas is further compressed and cooled and then sent to a second gas-liquid separation unit to be separated into a second methane-rich gas and a second methane-poor liquid; 6) the second methane-rich gas is sent into a gas separation unit to be separated into methane gas, carbon dioxide and heavier hydrocarbon material flows; 7) feeding the carbon dioxide and heavier hydrocarbon material flow, the first methane-depleted liquid and the second methane-depleted liquid into a light hydrocarbon reactor to be converted into a light hydrocarbon aromatization product; 8) the light hydrocarbon aromatization product returns to the three-phase separation unit.
In the above technical solution, preferably, the volume fraction of hydrogen in the gas phase in the step 2) is 40-70%.
In the above technical solution, preferably, the membrane separation unit in step 3) adopts one of a spiral-wound membrane, a hollow fiber membrane or a plate-and-frame membrane.
In the above technical scheme, preferably, the pressure range of the compressed gas phase in the step 3) is 2-3 MPa.
In the above technical scheme, preferably, the gas phase in the step 3) is firstly sent to a caustic washing tower and a dryer to remove acid gas and water before being sent to the membrane separation unit.
In the above technical solution, preferably, the hydrogen-rich gas in step 3) is pressurized and then sent to the PSA unit to obtain high-purity hydrogen.
In the above technical solution, preferably, the hydrogen-poor gas in the step 4) is cooled to below 50 ℃ by a heat exchanger and sent to the first gas-liquid separation unit.
In the above technical scheme, preferably, the first methane-rich gas in the step 5) is pressurized to 3-4 MPa, cooled to below 10 ℃ by a heat exchanger, and then sent to the second gas-liquid separation unit.
In the above technical solution, preferably, in the step 6), the gas separation unit uses cryogenic separation for methane and carbon dioxide and heavier hydrocarbon material flows.
By adopting the method, the high-temperature product from the reactor for preparing the aromatic hydrocarbon from the methanol is subjected to three-phase separation to obtain an aqueous phase, an oil phase containing heavy hydrocarbon such as benzene, toluene and xylene and a gas phase containing hydrogen and light hydrocarbon products such as methane, ethylene, ethane, propylene and propane. The gas phase contains more than 30% by volume of hydrogen, since a large amount of hydrogen accompanies the methanol aromatization reaction. Since the methanol aromatization reaction typically occurs at pressures below 0.5MPa, the gas phase from the three-phase separation unit typically first needs to be pressurized to above 2MPa via a compressor to facilitate membrane separation of the hydrogen. In addition, in order to avoid ensuring the efficiency of membrane separation and the service life of the membrane, the gas after pressure boosting is firstly sent to an alkaline tower and a dryer to respectively remove acid gas and water, then hydrogen-rich gas with the volume fraction of about 90 percent of hydrogen is separated in a membrane separation unit, and the hydrogen recovery rate is more than 85 percent. In a better scheme, the hydrogen-rich gas can be pressurized and then sent into a PSA device to prepare pure hydrogen products with the volume fraction of more than 99 percent, thereby improving the product value. The pressure drop of the retentate side of the membrane separation unit is small, and the pressure of the obtained hydrogen-poor gas is more than 1.5 MPa. After being cooled by a hydrogen-poor gas heat exchanger, the gas is separated into a first methane-rich gas and a first methane-poor liquid in a first gas-liquid separation tank. And the first methane-rich gas is pressurized and then sent to a second gas-liquid separation unit for further separation into a second methane-rich gas and a second methane-poor liquid. And separating the second methane-rich gas into methane and carbon dioxide and heavier components in the gas separation unit by adopting a rectification method.
In a preferred embodiment, the hydrogen-depleted gas is cooled to 40 ℃ and then separated in a first gas-liquid separator into a first methane-rich gas and a first methane-depleted liquid, wherein the first methane-rich gas comprises at least 80% of the methane in the hydrogen-depleted gas. Subsequently, the first methane-rich gas is pressurized to 3.5MPa, cooled to 10 ℃, and then sent to a second gas-liquid separator to be separated into a second methane-rich gas and a second methane-lean liquid, wherein the second methane-rich gas contains at least 80% of methane in the first methane-rich gas. The second methane-rich gas is sent to a demethanizer, separated by a cryogenic rectification method well known to those skilled in the art, and the obtained carbon dioxide and heavier hydrocarbon material flow is used as a raw material for light hydrocarbon aromatization and is sent to a light hydrocarbon aromatization reactor together with the methane-poor liquid from the gas-liquid separator, so that the yield of the aromatic hydrocarbon is further increased.
By adopting the technical scheme of the invention, the invention has the following advantages: 1) most of hydrogen is removed before the hydrogen-poor gas enters the gas separation unit, so that the energy consumption of the first methane-rich gas compressor is reduced, the energy consumption of the first methane-rich gas cooler is reduced, and the tower top temperature of the demethanizer is increased; 2) the methane-poor liquid is separated by the two stages of gas-liquid separation units, so that the feeding load of the gas separation unit is further reduced, particularly the concentration of carbon three and heavier components in the feeding of the gas separation unit is reduced, and the energy consumption for separation is reduced. Compared with the method for separating methane and hydrogen by pre-dehydrogenation and high-pressure deep cooling, which is widely adopted in the prior art, the method has the advantages that the energy consumption is reduced by at least 36 percent, and a better technical effect is achieved.
Drawings
FIG. 1 is a schematic flow diagram of the process of the present invention.
In FIG. 1, 1 is methanol; 2 is a methanol aromatization product; 3 is a gas phase; 4 is a gas phase compressor outlet stream; 5 is hydrogen-rich gas; 6 is a hydrogen-poor gas; 7 is a first methane-rich gas; 8 is a first methane lean liquid; 9 is a second methane-rich gas; 10 is a second methane lean liquid; 11 is methane; 12 is carbon dioxide and heavier hydrocarbons; 13 is a light hydrocarbon aromatization product; 14 is an oil phase; 15 is a non-aromatic hydrocarbon; 16 is an aromatic hydrocarbon; 17 is water; 100 is a methanol reactor; 101 is a three-phase separator; 102 is a gas phase compressor; 103 is a membrane separator; e1 is a hydrogen-depleted gas heat exchanger; 104 is a first gas-liquid separator; 105 is a first methane-rich gas compressor; e2 is a first methane-rich gas heat exchanger; 106 is a second gas-liquid separator; 107 is a demethanizer; 108 is a light hydrocarbon reactor; and 109 is an aromatic hydrocarbon extraction unit.
In figure 1, methanol is fed into a methanol reactor to perform aromatization reaction under the action of a catalyst to generate a high-temperature methanol aromatization product. After cooling, the mixture is separated into a water phase in a three-phase separator, an oil phase containing aromatic hydrocarbons such as benzene, toluene and xylene, and a gas phase containing hydrogen and hydrocarbons such as methane, ethylene, ethane, propylene and propane. After the pressure of the gas phase is increased by a compressor, the gas phase is sent to an alkaline tower and a dryer to respectively remove acid gas and water, and then hydrogen is separated in a membrane separation unit. The retentate side of the membrane separation unit is hydrogen-poor gas, and the hydrogen-poor gas is cooled by a hydrogen-poor gas heat exchanger and then is separated into first methane-rich gas and first methane-poor liquid in a first gas-liquid separation tank. And the first methane-rich gas is pressurized and cooled and then sent to a second gas-liquid separation unit for further separation into a second methane-rich gas and a second methane-poor liquid. The second methane-rich gas is separated in the demethanizer into methane and carbon dioxide and heavier components. Feeding the carbon dioxide and heavier hydrocarbon material flow, the first methane-poor liquid from the first gas-liquid separator and the second methane-poor liquid from the second gas-liquid separator into a light hydrocarbon aromatization reactor together to obtain a light hydrocarbon arene product, and returning the light hydrocarbon arene product to the three-phase separator.
The present invention will be further illustrated by the following examples, but is not limited to these examples.
Detailed Description
[ example 1 ]
The process flow shown in figure 1 is followed. Methanol with the scale of 225 tons/hour reacts through a methanol reactor to generate methanol aromatization products containing 1.2 wt% of hydrogen, 1.3 wt% of methane, 0.2 wt% of carbon dioxide, 55.4 wt% of water, 16.5 wt% of carbon-to-carbon pentahydrocarbons and 23.6 wt% of other hydrocarbons, and water phase, oil phase and gas phase are obtained through heat exchange cooling and three-phase separation, wherein the gas phase has the mass flow rate of 45.6 tons/hour and contains 53% of hydrogen, 8% of methane, 0.5% of carbon dioxide, 1.5% of carbon monoxide and 34% of carbon dioxide and the hydrocarbons thereof. And after the gas phase is pressurized to 2.8MPa by a compressor, acid gas is removed by an alkaline tower to ensure that the mass content of carbon dioxide in the gas phase is less than 5wppm, water is removed by a dryer to ensure that the mass content of water in the gas phase is less than 3wppm, and then the gas phase is sent to a membrane separation unit. The hollow fiber membrane is adopted to obtain the permeating gas with the hydrogen volume fraction of 89.7 percent, and the pressure is 2.1 MPa. The permeate gas is directly sent to a PSA device to prepare 99.9 percent high-purity hydrogen. The pressure of the hydrogen poor gas on the retentate side of the membrane separation unit is 2.7MPa, the temperature is 60 ℃, the mass flow rate is 38.9 tons/hour, the hydrogen poor gas is cooled to 40 ℃ by a hydrogen poor gas heat exchanger and then sent into a first gas-liquid separator, and a first methane-rich gas with the mass flow rate of 28.9 tons/hour and a first methane-poor liquid with the mass flow rate of 10 tons/hour are obtained. The first methane-rich gas is pressurized to 3.8MPa by a compressor and then sent to a first methane-rich gas cooler to be cooled to 9 ℃, and then is separated into a second methane-rich gas and a second methane-poor liquid in a second gas-liquid separator, wherein the mass fraction of methane in the second methane-poor liquid is 2.4%. The methane-rich gas is sent to a demethanizer, and cryogenic separation well known to those skilled in the art is adopted, the operating pressure is 3.6MPa, the temperature of the tower top is-118.8 ℃, and the temperature of the tower bottom is 21.4 ℃, so that methane, carbon dioxide and heavier hydrocarbons are obtained. The demethanizer has less than 0.2% ethylene loss. Wherein methane can be used as fuel gas. And the carbon dioxide and heavier hydrocarbons, the first methane-depleted liquid and the second methane-depleted liquid are sent into a light hydrocarbon reactor to carry out aromatization reaction to further increase the yield of the aromatic hydrocarbon, and reaction products return to the three-phase separator.
In this example, the energy consumption of the second methane-rich gas compressor is 0.24MW, the energy consumption of the compressor aftercooler is 2.88MW, the mass flow of the demethanizer feed is 12.1 ton/hour, and the energy consumption of the demethanizer is 1.69 MW.
[ COMPARATIVE EXAMPLE 1 ]
Using the reaction product composition of example 1, the most widely used prior dehydrogenation high pressure cryogenic techniques in the art were used to separate methane, hydrogen and carbon dioxide and heavier hydrocarbons. The energy consumption of the four-stage compressor is 0.79MW, the energy consumption of the aftercooler of the compressor is 4.1MW, the mass flow of the feed of the demethanizer is 39.6 tons/hour, and the energy consumption of the demethanizer is 2.5 MW.
[ example 2 ]
The process flow shown in figure 1 is followed. Methanol with the scale of 180 ten thousand tons/year is reacted by a methanol reactor to generate methanol aromatization products containing 0.7wt percent of hydrogen, 1.5wt percent of methane, 0.2wt percent of carbon dioxide, 56.3wt percent of water, 16.8wt percent of C to C five hydrocarbons and 24.5wt percent of other hydrocarbons, and the methanol aromatization products are subjected to heat exchange cooling and three-phase separation to obtain an aqueous phase, an oil phase containing heavy hydrocarbons such as benzene, toluene and xylene and a gas phase containing hydrogen and light hydrocarbon products such as methane, ethylene, ethane, propylene and propane, wherein the gas phase contains 40.4 percent of hydrogen by volume fraction. And after the gas phase is pressurized to 2.1MPa by a compressor, acid gas is removed by an alkaline tower to ensure that the mass content of carbon dioxide in the gas phase is less than 10wppm, water is removed by a dryer to ensure that the mass content of water in the gas phase is less than 8wppm, and then the gas phase is sent to a membrane separation unit. The spiral wound membrane is adopted to obtain the permeating gas with the hydrogen volume fraction of 90.3 percent, and the pressure is 1.3 MPa. The permeate gas is directly sent to a PSA device to prepare 99.9 percent high-purity hydrogen. The pressure of the hydrogen-poor gas on the retentate side of the membrane separation unit is 2.0MPa, the mass flow rate is 38.9 tons/hour, the hydrogen-poor gas is cooled to 30 ℃ by a hydrogen-poor gas heat exchanger and then sent into a first gas-liquid separator, and a first methane-rich gas with the mass flow rate of 23.5 tons/hour and a first methane-poor liquid with the mass flow rate of 15.4 tons/hour are obtained. The first methane-rich gas is pressurized to 3.2MPa by a compressor and then sent to a first methane-rich gas cooler to be cooled to 5 ℃, and then is separated into a second methane-rich gas and a second methane-poor liquid in a second gas-liquid separator, wherein the mass fraction of methane in the second methane-poor liquid is 2.1%. The methane-rich gas is sent to a demethanizer, and cryogenic separation well known to those skilled in the art is adopted, the operating pressure is 3.12MPa, the temperature of the tower top is-119.5 ℃, and the temperature of the tower bottom is 14 ℃, so that methane, carbon dioxide and heavier hydrocarbons are obtained. The demethanizer has less than 0.2% ethylene loss. Wherein methane can be used as fuel gas. And the carbon dioxide and heavier hydrocarbons, the first methane-depleted liquid and the second methane-depleted liquid are sent into a light hydrocarbon reactor to carry out aromatization reaction to further increase the yield of the aromatic hydrocarbon, and reaction products return to the three-phase separator.
In this example, the energy consumption of the second methane-rich gas compressor is 0.32MW, the energy consumption of the aftercooler of the compressor is 3.048MW, the mass flow of the feed to the demethanizer is 12.6 ton/hour, and the energy consumption of the demethanizer is 1.7 MW.
[ example 3 ]
The process flow shown in figure 1 is followed. Methanol with the scale of 180 ten thousand tons/year is reacted by a methanol reactor to generate methanol aromatization products containing 2.5wt percent of hydrogen, 1.2wt percent of methane, 0.2wt percent of carbon dioxide, 55.5wt percent of water, 16.6wt percent of carbon two to carbon five hydrocarbons and 24.0wt percent of other hydrocarbons, and the methanol aromatization products are subjected to heat exchange cooling and three-phase separation to obtain an aqueous phase, an oil phase containing heavy hydrocarbons such as benzene, toluene and xylene and a gas phase containing hydrogen and light hydrocarbon products such as methane, ethylene, ethane, propylene and propane, wherein the gas phase contains 69.5 percent of hydrogen by volume fraction. And after the gas phase is pressurized to 2.5MPa by a compressor, acid gas is removed by an alkaline tower to ensure that the mass content of carbon dioxide in the gas phase is less than 6wppm, water is removed by a dryer to ensure that the mass content of water in the gas phase is less than 3wppm, and then the gas phase is sent to a membrane separation unit. The permeation gas with the hydrogen volume fraction of 92.3 percent is obtained by adopting a plate-frame type membrane, and the pressure is 1.8 MPa. The permeate gas is directly sent to a PSA device to prepare 99.9 percent high-purity hydrogen. The pressure of the hydrogen-poor gas on the retentate side of the membrane separation unit is 2.3MPa, the mass flow rate is 38.1 tons/hour, the hydrogen-poor gas is cooled to 45 ℃ by a hydrogen-poor gas heat exchanger and then sent into a first gas-liquid separator, and a first methane-rich gas with the mass flow rate of 28 tons/hour and a first methane-poor liquid with the mass flow rate of 10.1 tons/hour are obtained. The first methane-rich gas is pressurized to 3.5MPa by a compressor and then sent to a first methane-rich gas cooler to be cooled to 5 ℃, and then is separated into a second methane-rich gas and a second methane-poor liquid in a second gas-liquid separator, wherein the mass fraction of methane in the second methane-poor liquid is 2.3%. The methane-rich gas is sent to a demethanizer, and cryogenic separation well known to those skilled in the art is adopted, the operating pressure is 3.44MPa, the temperature at the top of the tower is-119.9 ℃, and the temperature at the bottom of the tower is 18.3 ℃, so that methane, carbon dioxide and heavier hydrocarbons are obtained. The demethanizer has less than 0.2% ethylene loss. Wherein methane can be used as fuel gas. And the carbon dioxide and heavier hydrocarbons, the first methane-depleted liquid and the second methane-depleted liquid are sent into a light hydrocarbon reactor to carry out aromatization reaction to further increase the yield of the aromatic hydrocarbon, and reaction products return to the three-phase separator.
In this example, the energy consumption of the second methane-rich gas compressor is 0.29MW, the energy consumption of the compressor aftercooler is 3.31MW, the mass flow of the demethanizer feed is 11.1 ton/hour, and the energy consumption of the demethanizer is 1.62 MW.
Comparison of the energy consumption of comparative example 1 and example 1 shows that the total energy consumption is reduced by 34.9% compared with the prior art by the method of the present invention, and a better technical effect is achieved.
Claims (8)
1. A treatment method for preparing an aromatic light product from methanol comprises the following steps: 1) methanol is converted into a methanol aromatization product in a methanol reactor; 2) the methanol aromatization product is separated into a gas phase, an oil phase and a water phase in a three-phase separation unit; 3) the gas phase is compressed and then sent into a membrane separation unit to be separated into hydrogen-rich gas and hydrogen-poor gas; 4) cooling the hydrogen-poor gas, and then sending the cooled hydrogen-poor gas into a first gas-liquid separation unit to separate the hydrogen-poor gas into a first methane-rich gas and a first methane-poor liquid; 5) the first methane-rich gas is further compressed and cooled and then sent to a second gas-liquid separation unit to be separated into a second methane-rich gas and a second methane-poor liquid; 6) the second methane-rich gas is sent into a gas separation unit to be separated into methane gas, carbon dioxide and heavier hydrocarbon material flows; 7) feeding the carbon dioxide and heavier hydrocarbon material flow, the first methane-depleted liquid and the second methane-depleted liquid into a light hydrocarbon reactor to be converted into a light hydrocarbon aromatization product; 8) and (3) returning the light hydrocarbon aromatization product to the three-phase separation unit, wherein the volume fraction of hydrogen in the gas phase in the step 2) is 40-70%.
2. The method for processing light methanol to aromatics products according to claim 1, wherein the membrane separation unit in step 3) is one of a spiral-wound membrane, a hollow fiber membrane or a plate-and-frame membrane.
3. The method for processing the light methanol-to-aromatics product as recited in claim 1, wherein the pressure of the compressed gas phase in step 3) is in the range of 2-3 MPa.
4. The method for processing light products of aromatics preparation from methanol as claimed in claim 1, wherein in step 3), the gas phase is first sent to a caustic tower and a drier to remove acid gases and water, respectively, before being sent to the membrane separation unit.
5. The method for processing the light methanol-to-aromatics product as recited in claim 1, wherein the hydrogen-rich gas in step 3) is pressurized and then sent to a PSA unit to obtain high-purity hydrogen.
6. The method for processing the light methanol-to-aromatics product according to claim 1, wherein the hydrogen-poor gas in step 4) is cooled to below 50 ℃ by a heat exchanger and sent to the first gas-liquid separation unit.
7. The method for treating the light methanol-to-aromatics product according to claim 1, wherein the first methane-rich gas in step 5) is pressurized to 3-4 MPa, cooled to a temperature below 10 ℃ by a heat exchanger, and then sent to the second gas-liquid separation unit.
8. The method for processing light products of aromatics from methanol as claimed in claim 1, wherein the gas separation unit in step 6) uses cryogenic separation to separate methane and carbon dioxide and heavier hydrocarbons.
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