CN110937974B - Production device and process of p-xylene - Google Patents
Production device and process of p-xylene Download PDFInfo
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- CN110937974B CN110937974B CN201811113925.1A CN201811113925A CN110937974B CN 110937974 B CN110937974 B CN 110937974B CN 201811113925 A CN201811113925 A CN 201811113925A CN 110937974 B CN110937974 B CN 110937974B
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- URLKBWYHVLBVBO-UHFFFAOYSA-N Para-Xylene Chemical group CC1=CC=C(C)C=C1 URLKBWYHVLBVBO-UHFFFAOYSA-N 0.000 title claims abstract description 142
- 238000000034 method Methods 0.000 title claims abstract description 37
- 238000004519 manufacturing process Methods 0.000 title claims description 13
- 238000006317 isomerization reaction Methods 0.000 claims abstract description 181
- 238000000926 separation method Methods 0.000 claims abstract description 134
- 238000001179 sorption measurement Methods 0.000 claims abstract description 92
- CTQNGGLPUBDAKN-UHFFFAOYSA-N O-Xylene Chemical compound CC1=CC=CC=C1C CTQNGGLPUBDAKN-UHFFFAOYSA-N 0.000 claims abstract description 88
- 239000008096 xylene Substances 0.000 claims abstract description 82
- 238000005194 fractionation Methods 0.000 claims abstract description 36
- 239000004927 clay Substances 0.000 claims abstract description 33
- 238000010438 heat treatment Methods 0.000 claims abstract description 28
- 239000000463 material Substances 0.000 claims description 159
- 239000000047 product Substances 0.000 claims description 107
- 239000007788 liquid Substances 0.000 claims description 43
- 150000004945 aromatic hydrocarbons Chemical class 0.000 claims description 37
- 229910052739 hydrogen Inorganic materials 0.000 claims description 34
- 239000001257 hydrogen Substances 0.000 claims description 34
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 31
- 229930195733 hydrocarbon Natural products 0.000 claims description 28
- 150000002430 hydrocarbons Chemical class 0.000 claims description 28
- 238000007599 discharging Methods 0.000 claims description 25
- 239000004215 Carbon black (E152) Substances 0.000 claims description 22
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Natural products CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 claims description 19
- 239000007795 chemical reaction product Substances 0.000 claims description 16
- 239000007791 liquid phase Substances 0.000 claims description 15
- 239000012071 phase Substances 0.000 claims description 15
- 239000007789 gas Substances 0.000 claims description 12
- 239000000203 mixture Substances 0.000 claims description 12
- 239000002994 raw material Substances 0.000 claims description 11
- 238000006243 chemical reaction Methods 0.000 claims description 7
- 238000010992 reflux Methods 0.000 claims description 6
- 125000003118 aryl group Chemical group 0.000 claims description 5
- 229930195735 unsaturated hydrocarbon Natural products 0.000 claims description 5
- 150000002431 hydrogen Chemical class 0.000 claims description 3
- 238000004064 recycling Methods 0.000 claims description 3
- 125000003944 tolyl group Chemical group 0.000 claims description 3
- 238000000605 extraction Methods 0.000 claims 1
- 238000005265 energy consumption Methods 0.000 abstract description 9
- 239000002737 fuel gas Substances 0.000 abstract description 9
- 238000001816 cooling Methods 0.000 description 9
- 239000002808 molecular sieve Substances 0.000 description 6
- URGAHOPLAPQHLN-UHFFFAOYSA-N sodium aluminosilicate Chemical compound [Na+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O URGAHOPLAPQHLN-UHFFFAOYSA-N 0.000 description 6
- YNQLUTRBYVCPMQ-UHFFFAOYSA-N Ethylbenzene Chemical compound CCC1=CC=CC=C1 YNQLUTRBYVCPMQ-UHFFFAOYSA-N 0.000 description 4
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 4
- 239000003463 adsorbent Substances 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 4
- WOZVHXUHUFLZGK-UHFFFAOYSA-N dimethyl terephthalate Chemical compound COC(=O)C1=CC=C(C(=O)OC)C=C1 WOZVHXUHUFLZGK-UHFFFAOYSA-N 0.000 description 4
- KKEYFWRCBNTPAC-UHFFFAOYSA-N Terephthalic acid Chemical compound OC(=O)C1=CC=C(C(O)=O)C=C1 KKEYFWRCBNTPAC-UHFFFAOYSA-N 0.000 description 3
- 230000000274 adsorptive effect Effects 0.000 description 3
- 150000001336 alkenes Chemical class 0.000 description 3
- 239000003054 catalyst Substances 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- JRZJOMJEPLMPRA-UHFFFAOYSA-N olefin Natural products CCCCCCCC=C JRZJOMJEPLMPRA-UHFFFAOYSA-N 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- DSNHSQKRULAAEI-UHFFFAOYSA-N 1,4-Diethylbenzene Chemical compound CCC1=CC=C(CC)C=C1 DSNHSQKRULAAEI-UHFFFAOYSA-N 0.000 description 2
- 150000001335 aliphatic alkanes Chemical class 0.000 description 2
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 125000004432 carbon atom Chemical group C* 0.000 description 2
- 238000009833 condensation Methods 0.000 description 2
- 230000005494 condensation Effects 0.000 description 2
- 150000001924 cycloalkanes Chemical class 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000005984 hydrogenation reaction Methods 0.000 description 2
- 229910052809 inorganic oxide Inorganic materials 0.000 description 2
- IVSZLXZYQVIEFR-UHFFFAOYSA-N m-xylene Chemical group CC1=CC=CC(C)=C1 IVSZLXZYQVIEFR-UHFFFAOYSA-N 0.000 description 2
- 238000005192 partition Methods 0.000 description 2
- 239000000377 silicon dioxide Substances 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- OCJBOOLMMGQPQU-UHFFFAOYSA-N 1,4-dichlorobenzene Chemical compound ClC1=CC=C(Cl)C=C1 OCJBOOLMMGQPQU-UHFFFAOYSA-N 0.000 description 1
- 239000005995 Aluminium silicate Substances 0.000 description 1
- 229910021536 Zeolite Inorganic materials 0.000 description 1
- 235000012211 aluminium silicate Nutrition 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 125000002915 carbonyl group Chemical group [*:2]C([*:1])=O 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- HNPSIPDUKPIQMN-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Al]O[Al]=O HNPSIPDUKPIQMN-UHFFFAOYSA-N 0.000 description 1
- GMSCBRSQMRDRCD-UHFFFAOYSA-N dodecyl 2-methylprop-2-enoate Chemical compound CCCCCCCCCCCCOC(=O)C(C)=C GMSCBRSQMRDRCD-UHFFFAOYSA-N 0.000 description 1
- 239000003814 drug Substances 0.000 description 1
- 229940079593 drug Drugs 0.000 description 1
- 239000000835 fiber Substances 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- NLYAJNPCOHFWQQ-UHFFFAOYSA-N kaolin Chemical group O.O.O=[Al]O[Si](=O)O[Si](=O)O[Al]=O NLYAJNPCOHFWQQ-UHFFFAOYSA-N 0.000 description 1
- 229910052745 lead Inorganic materials 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 229910052750 molybdenum Inorganic materials 0.000 description 1
- 229910052680 mordenite Inorganic materials 0.000 description 1
- -1 olefin Natural products 0.000 description 1
- 229910052763 palladium Inorganic materials 0.000 description 1
- 239000000575 pesticide Substances 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 229920003023 plastic Polymers 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 229910052761 rare earth metal Inorganic materials 0.000 description 1
- 150000002910 rare earth metals Chemical class 0.000 description 1
- 238000002407 reforming Methods 0.000 description 1
- 229910052702 rhenium Inorganic materials 0.000 description 1
- 235000012239 silicon dioxide Nutrition 0.000 description 1
- 229920003002 synthetic resin Polymers 0.000 description 1
- 239000000057 synthetic resin Substances 0.000 description 1
- 229910052718 tin Inorganic materials 0.000 description 1
- 229910052721 tungsten Inorganic materials 0.000 description 1
- 229910052720 vanadium Inorganic materials 0.000 description 1
- 239000010457 zeolite Substances 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
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C5/00—Preparation of hydrocarbons from hydrocarbons containing the same number of carbon atoms
- C07C5/22—Preparation of hydrocarbons from hydrocarbons containing the same number of carbon atoms by isomerisation
- C07C5/27—Rearrangement of carbon atoms in the hydrocarbon skeleton
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C7/00—Purification; Separation; Use of additives
- C07C7/04—Purification; Separation; Use of additives by distillation
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/50—Improvements relating to the production of bulk chemicals
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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)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
The invention discloses a device and a process for producing paraxylene. The device comprises a xylene fractionation unit, an adsorption separation unit and an isomerization reaction unit; the adsorption separation unit comprises an adsorption separation tower, an extract tower, a raffinate tower, a finished product tower reboiler I and a finished product tower reboiler II; the isomerization reaction unit comprises an isomerization reactor, an isomerization product fractionating tower, a clay tower, an isomerization reaction heating furnace, a heat exchanger II, a heat exchanger III, a heat exchanger IV, a heat exchanger VI and a compressor. The process reduces the operation load of the xylene tower, saves the fuel gas consumption of the xylene reboiling furnace, optimizes the heat exchange network, reduces the fuel gas consumption of the isomerization reaction heating furnace, greatly reduces the energy consumption, and improves the economic benefit and the social benefit.
Description
Technical Field
The invention relates to a device and a process for producing paraxylene.
Background
Paraxylene is one of important basic organic raw materials in petrochemical industry, is mainly used for Preparing Terephthalic Acid (PTA) and dimethyl terephthalate (DMT), and is widely applied to the production fields of chemical fibers, synthetic resins, pesticides, medicines, plastics and the like. The apparent consumption of p-xylene in 2017 will reach 2400 x 10 4 t, the productivity of the p-xylene device reaches 816 multiplied by 10 4 t, the production capacity of the world is about 20 percent, and China is the biggest paraxylene producing country in the world.
C 8 Aromatic hydrocarbons include the four isomers of ortho-, para-, meta-and ethylbenzene, with para-xylene being the largest in the marketplace, and so it is generally more desirable in the industry to enhance the conversion of the aromatic hydrocarbon to the specified C 8 The aromatic feedstock source even maximizes the production of para-xylene. Due to their similar chemical structure and physical properties and molecular weightSimilarly, para-xylene depleted C is generally obtained by isomerization 8 Conversion of aromatics to equilibrium concentration C 8 Aromatic hydrocarbon mixture is rectified, adsorbed and separated to obtain high purity p-xylene product and lean p-xylene C 8 The aromatic hydrocarbon is recycled in the system to carry out isomerization reaction again.
The separation of paraxylene is generally carried out industrially by crystallization and adsorption separation, and the adsorption separation is used in many cases. The raw material for adsorption separation is mixed C 8 Aromatic hydrocarbons, using para-C 8 The selectivity of four isomers of aromatic hydrocarbon is different, para-xylene is preferentially adsorbed, and then the para-xylene on the adsorbent is desorbed by a desorbent. The extract is a material rich in p-xylene, and a high-purity p-xylene product is obtained by rectification; the raffinate is a material poor in p-xylene, and after a desorbent is separated out by a raffinate tower, the C with the equilibrium concentration is obtained through isomerization reaction 8 The aromatic mixture is then recycled back to the xylene for fractionation. In the process, the isomerized product is subjected to a deheptanizer to remove C 7 After the light hydrocarbon is discharged, most of the light hydrocarbon is circulated back to the xylene tower, so that the operation load of the xylene tower is increased, and the fuel consumption of the xylene reboiling furnace is increased. Meanwhile, the isomerization product and the feeding material are cooled completely after heat exchange, and are reheated after hydrogen is separated, so that the phenomenon of unreasonable energy utilization exists.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a device and a process for producing paraxylene, which reduce equipment investment and floor area, reduce the operating load of a xylene tower, save the fuel gas consumption of a xylene reboiling furnace, optimize a heat exchange network, improve the furnace entering temperature of an isomerization reaction heating furnace, reduce the fuel gas consumption of the isomerization reaction heating furnace, and solve the phenomenon of unreasonable energy utilization of the conventional process of cooling before heating, thereby greatly reducing energy consumption and improving economic and social benefits.
The device for producing the paraxylene comprises a xylene fractionation unit, an adsorption separation unit and an isomerization reaction unit;
the xylene fractionation unit comprises a xylene tower, a heat exchanger I and a xylene reboiling furnace.
The xylene column is used for separating C 8 Component (A) and (C) 9 + The component is generally a plate-type rectifying tower.
The heat exchanger I is used for taking the xylene overhead material flow as a heat source of a reboiler of a raffinate tower and a reboiler of a draw-out liquid tower, one part of the condensate after heat exchange is used as reflux to return to the xylene tower, and the other part of the condensate after heat exchange is used as adsorption separation feeding.
The xylene reboiling furnace is used for heating materials which are circulated to the bottom of the xylene reboiling furnace so as to provide reboiling heat for the xylene reboiling tower.
The xylene fractionation unit further comprises a unit for fractionating C 8 The aromatic hydrocarbon mixture raw material is fed into a feed pipeline of the xylene tower; a pipeline for sending the tower top discharge to a heat exchanger I; a pipeline for circulating a part of the discharged material at the top of the tower after the heat exchange of the heat exchanger I back to the xylene tower; the other part of the tower top discharge after heat exchange by the heat exchanger I is sent to a pipeline of the adsorption separation unit; a feed line for feeding a portion of the bottoms to a bottom reboiling furnace; a line for recycling the bottom material heated by the bottom reboiling furnace to the xylene column; the other part of the tower bottom material is discharged out of a pipeline of the xylene tower; wherein the top discharge of the tower is C 8 Aromatic hydrocarbon, the material at the bottom of the tower is C 9 + An aromatic hydrocarbon.
The adsorption separation unit comprises an adsorption separation tower, an extract tower, a raffinate tower, a finished product tower reboiler I and a finished product tower reboiler II.
The adsorption separation tower is used for separating paraxylene and isomers thereof in materials from a xylene fractionation unit.
The extract tower is used for separating C in the p-xylene-rich extract 8 The components and a desorbent are mixed, and the material at the top of the extract tower is rich in p-xylene C 8 The components, the discharge from the bottom of the tower is the desorbent.
The raffinate tower is used for separating C in the p-xylene-poor raffinate 8 The components and the desorbent are discharged from the upper side line of the raffinate tower as the lean p-xylene C 8 The components are discharged from the bottom of the tower and are desorbent.
The finished product tower is used for separating paraxylene and methylbenzene from paraxylene, the material at the top of the finished product tower is methylbenzene, and the material at the bottom of the finished product tower is paraxylene.
The finished product tower is provided with two reboilers for supplying heat, the heat source of the reboiler I of the finished product tower is a desorbent at the bottoms of the extract tower and the raffinate tower, and the temperature of the desorbent is reduced to be the proper temperature for returning to the adsorption separation tower; and the heat source of the reboiler II of the finished product tower is xylene tower bottom liquid (or medium-pressure steam), and the adsorption separation feed enters the adsorption separation tower after further exchanging heat with the isomerization reaction feed.
The adsorption separation unit also comprises a pipeline for feeding the tower top discharge of the xylene fractionation unit after heat exchange to an adsorption separation tower, a pipeline for delivering the separated p-xylene-rich extract to an extract tower, and a pipeline for delivering the p-xylene-poor raffinate obtained by adsorption separation of the adsorption separation tower to a raffinate tower; a pipeline for conveying the material at the top of the extract tower to a finished product tower; the method comprises the following steps of (1) sending a material at the bottom of an extract tower to a pipeline of a finished product tower reboiler I, sending a material (a desorbent) at the bottom of a raffinate tower to a pipeline of the finished product tower reboiler I, and sending the heat-exchanged material at the bottom of the extract tower and the raffinate tower to a pipeline of an adsorption separation tower; discharging the side line at the upper part of the raffinate tower to a pipeline of an isomerization reaction unit;
the isomerization reaction unit comprises an isomerization reactor, an isomerization product fractionating tower, a clay tower, an isomerization reaction heating furnace, a heat exchanger II, a heat exchanger III, a heat exchanger IV, a heat exchanger VI and a compressor.
The isomerization reactor is used for separating the lean p-xylene C from the adsorption separation unit 8 Conversion of the component into para-xylene-rich C 8 And (4) components.
The isomerization product fractionating tower is used for separating the isomerization reactor discharge rich in the paraxylene C 8 C in component (A) 7 Lower light hydrocarbon, C 8 Aromatic hydrocarbons and C 9 The aromatic hydrocarbon component and the isomerized product fractionating tower adopts a dividing wall tower form, wherein the material at the top of the tower is C 7 The material at the bottom of the tower is C 9 + Aromatic component, side streamIs C 8 An aromatic hydrocarbon.
The isomerization reaction unit and the hydrogen come from the reforming unit. The proper hydrogen to hydrocarbon ratio is beneficial to maintaining the activity and stability of the isomerization catalyst. The hydrogen can be recycled and can also be supplemented with new hydrogen. With the progress of isomerization reaction, the purity of the circulating hydrogen is gradually reduced, so that a part of low-purity hydrogen-containing gas needs to be discharged, and meanwhile, high-purity hydrogen is supplemented to maintain the purity of the circulating hydrogen. The clay tower is used for removing a small amount of unsaturated hydrocarbons such as olefin and carbonyl in the side line material of the isomerization product fractionating tower.
The isomerization heating furnace is used for controlling the isomerization feeding temperature.
The heat exchanger II is used for exchanging heat between the side line material of the isomerization product fractionating tower as the clay tower feeding material and the isomerization reaction feeding material, improving the isomerization feeding temperature and reducing the clay tower feeding temperature to the proper temperature.
The heat exchanger III is used for feeding the adsorption separation tower and the isomerization reaction, improving the isomerization feeding temperature and reducing the feeding temperature of the adsorption separation tower to a proper temperature.
The heat exchanger IV is used for isomerizing the feed and the isomerization reaction product (rich in p-xylene C) 8 Component) is used.
The heat exchanger VI is used for exchanging heat between the tower bottom material of the isomerization product fractionating tower and the clay tower discharging material, and improving the clay tower discharging temperature; the clay tower discharging after heat exchange is the feeding of the adsorption separation tower.
The compressor is used to pressurize the hydrogen and/or recycle hydrogen entering the isomerization reactor.
The isomerization reaction unit also comprises a feeding pipeline for feeding the isomerization reaction to the isomerization reactor, and the feeding pipeline is sequentially connected with a heat exchanger II, a heat exchanger III, a heat exchanger IV and an isomerization reaction heating furnace before being connected with the isomerization reactor; a feed line for feeding the isomerized product to the isomerized product fractionation column, the feed line being connected to the heat exchanger IV before being connected to the isomerized product fractionation column; a discharge line for discharging the overhead material of the isomerized product fractionating tower; feeding the side line material of the isomerization product fractionating tower into a feeding pipeline of the clay tower, wherein the feeding pipeline is connected with the front part of the clay tower and is connected with a heat exchanger II; connecting a discharging pipeline at the bottom of the carclazyte tower with a heat exchanger VI, and connecting a pipeline after heat exchange with an adsorption separation feeding pipeline; and a discharge pipeline for discharging the bottom product of the isomerization product fractionating tower is connected with a heat exchanger VI before discharging.
The isomerization reaction unit is preferably provided with a gas-liquid separation tank, an air cooler and a heat exchanger V; the gas-liquid separation tank is used for separating the overhead material C of the isomerization product fractionating tower 7 The hydrogen and other components in the lower light hydrocarbon are partially discharged outside, and part of the gas phase is pressurized, heat exchanged and/or heated and returns to the isomerization reactor; the liquid phase is subjected to heat exchange and then is taken out of the device as a light hydrocarbon product; the heat exchanger V is used for liquid-phase light hydrocarbon products of the gas-liquid separation tank and tower top materials (C) of the isomerization product fractionating tower 7 The following light hydrocarbons and hydrogen) heat exchange; the air cooler is used for further isomerizing the overhead material (C) of the product fractionating tower 7 The following light hydrocarbons and hydrogen); the isomerization product fractionating tower comprises a gas-liquid separation tank, a heat exchanger V and an air cooler, wherein the gas-liquid separation tank is connected with the top of the isomerization product fractionating tower; a discharge line for discharging at least a part of the gas phase separated by the gas-liquid separation tank to the outside, and a feed line for feeding the remaining part to the feed line of the isomerization reactor; the remaining part is first mixed with hydrogen passing through the hydrogen feed line before being fed to the feed line of the isomerization reactor and then enters the compressor feed line; and a discharge line for discharging the liquid phase separated in the gas-liquid separation tank.
The invention also provides a production process of paraxylene, which comprises the following steps: containing C 8 The aromatic hydrocarbon mixture raw material enters a xylene tower for fractionation, after heat exchange is carried out on the tower top material through a heat exchanger I, one part of the tower top material is returned to the xylene tower as reflux, the other part of the tower top material is used as adsorption separation feeding material, and then the tower top material is sent to the adsorption separation tower after heat exchange is carried out on the tower top material and isomerization reaction feeding material through a heat exchanger III; the bottom material of the tower returns to the xylene tower after passing through the xylene reboiling furnace and being heated, and the other part of the bottom material of the tower is C 9 + Aromatic hydrocarbons; the adsorption separation feeding material is adsorbed and separated by an adsorption separation tower,the obtained paraxylene-rich extract enters an extract tower for fractionation, the tower bottom material is a desorbent, and is mixed with the raffinate tower bottom material to be used as a heat source of a finished product tower reboiler I, and the heat exchange is carried out and then the mixture returns to an adsorption separation tower; the material at the top of the extract tower is rich in p-xylene C 8 Component, the discharge material at the bottom of the tower is a desorbent; enriched para-xylene C 8 The components enter a finished product tower for further separation, wherein the material at the top of the tower is toluene, and the material at the bottom of the tower is p-xylene. The para-xylene depleted raffinate obtained by adsorption separation in the adsorption separation tower enters a raffinate tower for fractionation, the upper side line material sequentially flows through a heat exchanger II, a heat exchanger III and a heat exchanger IV, exchanges heat with the side line material, the adsorption separation feed and the isomerization reaction product of the isomerization product fractionating tower respectively, then enters an isomerization reactor for isomerization reaction after being heated by an isomerization reaction heating furnace, and enters the isomerization product fractionating tower after being exchanged heat by the heat exchanger IV; the reboiling heat of the isomerization product fractionating tower is provided by an isomerization reaction heating furnace, the materials at the top of the isomerization product fractionating tower are discharged, the materials at the side line of the isomerization product fractionating tower exchange heat through a heat exchanger II, enter a clay tower to remove unsaturated hydrocarbons such as olefin, exchange heat with the materials at the bottom of the isomerization product fractionating tower through a heat exchanger VI and then serve as adsorption separation feeding materials, and the discharging material at the bottom of the isomerization product fractionating tower is C 9 + An aromatic hydrocarbon.
In the process for producing the p-xylene, materials at the top of an isomerization product fractionating tower are preferably subjected to heat exchange by a heat exchanger V, cooled by an isomerization reaction product air cooler and enter a gas-liquid separation tank to be separated into a gas-liquid two-phase; the gas phase is discharged from the top of the gas-liquid separation tank and divided into two parts: one strand is discharged outside; the other strand is mixed with hydrogen, pressurized by a compressor and mixed with isomerization reaction feed; the liquid phase material obtained by the separation of the gas-liquid separation tank is used as C after heat exchange of the heat exchanger V 7 The following light hydrocarbons.
The isomerization product fractionating tower is in a dividing wall tower form, a vertical partition plate is generally arranged in the middle of a traditional rectifying tower, and the rectifying tower is divided into an upper public rectifying section, a lower public stripping section, a rectifying feeding section and a side line extracting section which are separated by the partition plate.
Said C containing 8 The aromatic hydrocarbon raw material mainly comprises mixed hydrocarbon containing ethylbenzene, paraxylene, ortho-xylene and meta-xylene, and also comprises C 7 Light hydrocarbon and C 9 The above heavy hydrocarbons. Wherein C is 7 The light hydrocarbon below is an aromatic hydrocarbon, an alkane or a cycloalkane having 7 or less carbon atoms, C 9 The heavy hydrocarbon means a hydrocarbon having 9 or more carbon atoms such as an aromatic hydrocarbon, an alkane, or a cycloalkane.
The top pressure of the xylene tower is 0.3-2.5 MPa, preferably 0.5-1.8 MPa, and the temperature of the top of the xylene tower is 50-300 ℃, preferably 110-280 ℃. The xylene tower is preferably a plate tower, and the number of plates is 150-200.
The operating conditions of the adsorption separation tower are as follows: the temperature is 100 to 300 ℃, preferably 150 to 200 ℃, and the pressure is 0.2 to 1.5MPa, preferably 0.6 to 1.0 MPa.
In the adsorption separation unit, the adsorption separation tower adopts a fixed bed, and the positions of a material inlet and a material outlet of the fixed bed adsorption equipment are changed to generate the effect that the adsorbent continuously moves downwards and the material continuously moves upwards. The bed is filled with an adsorbent with high selectivity to p-xylene. The active component of the adsorbent is X-type zeolite or Y-type molecular sieve of Ba or BaK, and the binder is selected from kaolin, silicon dioxide or alumina. The desorbent is mutually soluble with each component in the raw material and is also mutually soluble with C 8 The boiling points of the components in the aromatic hydrocarbon have larger difference, and the components are easy to recycle, preferably p-diethylbenzene or toluene.
The operation conditions of the extract tower are as follows: the pressure at the top of the tower is 0.1-0.5 MPa, the operation at normal pressure is preferred, and the temperature at the top of the tower is 100-220 ℃, and the temperature at 120-170 ℃ is preferred.
The operation conditions of the raffinate tower are as follows: the pressure at the top of the tower is 0.1-1.0 MPa, the operation at normal pressure is preferred, and the temperature at the top of the tower is 120-170 ℃.
The operating conditions of the finished product tower are as follows: the pressure at the top of the tower is 0.1-0.5 MPa, the operation at normal pressure is preferred, and the temperature at the top of the tower is 50-200 ℃, and the temperature is preferably 100-150 ℃.
The isomerization reactor operating conditions are as follows: the reaction temperature is 300-450 ℃, preferably 330-400 ℃, and the pressure is 0.1-2.0 MPa, preferably 0.4About 1.5MPa, and the mass airspeed of 2-10 h -1 Preferably 3 to 6 hours -1 The molar ratio of the reaction hydrogen to the hydrocarbon is 2 to 8, preferably 3 to 6.
In the isomerization unit, an isomerization catalyst is filled in an isomerization reactor, and the isomerization catalyst is an active component loaded with one or more of Pt, Sn, Mg, Bi, Pb, Pd, Re, Mo, W, V and rare earth metals on a molecular sieve and/or an inorganic oxide carrier. The molecular sieve is one or a mixture of more of five-membered ring molecular sieve, mordenite, EUO type molecular sieve and MFI molecular sieve. The inorganic oxide is alumina and/or silica.
The operating conditions of the gas-liquid separation tank are as follows: the operation temperature is 35-40 ℃, and the pressure is 0.5-1.1 MPa.
The operation conditions of the isomerization product fractionating tower are as follows: the pressure at the top of the tower is 0.2-2.0 MPa, preferably 0.5-1.5 MPa, and the temperature at the top of the tower is 50-250 ℃, preferably 130-170 ℃.
Compared with the prior art, the novel p-xylene production method provided by the invention has the following beneficial effects: in the device and the process, the inventor sets the isomerization fractionating tower with a dividing wall tower structure, cancels the deheptanizer in the conventional process, skillfully separates the isomerization reaction products in advance through the isomerization fractionating tower, and separates the tower bottom C in the isomerization reaction products 9 + Aromatics and overhead C 7 The lower light hydrocarbon is separated out from the device in advance, and the side stream material is C 8 Aromatic hydrocarbons directly mixed with the adsorptive separation feed, whereas in conventional processes, the C is not added in the deheptanizer 9 + The aromatic hydrocarbon is separated, so that the operation load of the clay tower is increased, and meanwhile, the material passing through the clay tower needs to enter the xylene tower again, so that the operation load of xylene is greatly increased; overhead material C of isomerization reaction product in the invention 7 The lower light hydrocarbon can be directly discharged from the device without arranging a condensation systemAnd gas-liquid separation equipment, or a device for separating gas from liquid. Compared with the conventional process, the isomerization reaction product is cooled by an air cooler and a water cooler, gas-phase components such as hydrogen and the like are separated by a gas-liquid separation tank, the liquid-phase components are reheated, and C is separated by a deheptanizer 7 - Light component, C 8 + Returning the components to the xylene column for further separating out C 8 The cooling load is large in the process, and after gas-phase components such as hydrogen and the like are separated, the liquid-phase components are reheated; the invention solves the problem of unreasonable energy utilization of the conventional process of cooling before heating, and greatly reduces the cooling load. In the conventional process flow, the temperature of an isomerization reaction feed of an isomerization reaction unit entering an isomerization reaction heating furnace is about 280-300 ℃; the isomerization reaction unit of the invention cancels the deheptanizer, and simultaneously, through optimizing the heat exchange network, the isomerization reaction feeding does not undergo the process of cooling first and then heating, namely, the heat of the isomerization reaction feeding (the side line material at the upper part of the raffinate tower) is prevented from heating the cooled deheptanizer feeding, the cold and hot material flows are reasonably matched, the temperature of the isomerization reaction feeding in front of the furnace is increased to 310-330 ℃, thereby reducing the fuel gas consumption of the isomerization reaction heating furnace, greatly reducing the energy consumption and improving the economic benefit and the social benefit.
Drawings
Fig. 1, 2 and 3 (fig. 4) are schematic flow diagrams of a xylene fractionation unit, an adsorption separation unit and an isomerization reaction unit (an isomerization reaction unit including a gas-liquid separation flow) of the xylene plant of the present invention, respectively.
Wherein, fig. 1 is a xylene fractionation unit, which comprises a xylene column 101, a heat exchanger I102 and a xylene reboiling furnace 103; FIG. 2 is an adsorptive separation unit comprising an adsorptive separation column 201, an extract column 202, a finishing column 203, a raffinate column 204, a finishing column reboiler I205, and a finishing column reboiler II 206; fig. 3 is an isomerization reaction unit, and fig. 4 is an isomerization reaction unit including a gas-liquid separation flow path, in which an isomerization reactor 301, an isomerized product fractionating tower 302, a clay tower 303, a gas-liquid separation tank 304, an isomerization reaction heating furnace 305, a heat exchanger II306, a heat exchanger III307, a heat exchanger IV308, a heat exchanger V309, a heat exchanger VI310, an air cooler 311, and a compressor 312.
Fig. 5, 6 and 7 are schematic flow diagrams of a xylene fractionation unit, an adsorption separation unit and an isomerization reaction unit, respectively, of a conventional xylene plant.
Wherein, fig. 5 is a xylene fractionation unit, which comprises a xylene column 401, a heat exchanger I402 and a xylene reboiling furnace 403; FIG. 6 shows an adsorption separation unit comprising an adsorption separation column 501, an extract column 502, a raffinate column 503, a finished product column 504, a finished product reboiler I505, and a finished product reboiler II 506; fig. 7 is an isomerization reaction unit, which includes an isomerization reactor 601, a deheptanizer 602, a clay column 603, a gas-liquid separation tank 604, an isomerization reaction heating furnace 605, a heat exchanger III606, a heat exchanger IV607, a heat exchanger V608, a heat exchanger VI609, a compressor 610, an air cooler 611, and a water cooler 612.
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention.
Detailed Description
The paraxylene production process of the present invention will be described in more detail below with reference to the accompanying drawings.
The xylene fractionation unit comprises 8 The aromatic hydrocarbon mixture raw material 104 is fed to a feed line 107 of the xylene column; line 108 feeding the overhead discharge to heat exchanger I102; a pipeline 109 for circulating a part of the discharged material at the top of the tower after the heat exchange of the heat exchanger I102 back to the xylene tower; the other part of the overhead discharge 105 after heat exchange by the heat exchanger I102 is sent to a pipeline 110 of a heat exchanger III 307; a feed line 112 for feeding a portion of the bottoms 111 to the bottom reboiling furnace 103; a line 113 for recycling the bottom material heated by the bottom reboiling furnace 103 to the xylene column; a line 114 for withdrawing another portion of the bottoms 106 from the xylene column; wherein the overhead discharge 105 is C 8 Aromatic hydrocarbons, bottoms 106 being C 9 + Aromatic hydrocarbons;
the adsorption separation unit comprises a pipeline 211 for feeding the overhead discharge 207 of the xylene fractionation unit after heat exchange into the adsorption separation tower 201, a pipeline 212 for sending the separated p-xylene-rich extract to the extract tower 202, and a pipeline 217 for sending the p-xylene-poor raffinate obtained by adsorption separation in the adsorption separation tower to the raffinate tower 204; the material at the top of the extract tower 202 is sent to a feed line 213 of a finished product tower 203, the material toluene 208 at the top of the finished product tower 203 is sent to a discharge line 215, and the material p-xylene 209 at the bottom of the finished product tower 203 is sent to a discharge line 216; a material pipeline 214 at the bottom of the extract tower 202 and a material pipeline 218 at the bottom of the raffinate tower 204 after heat exchange are connected with a pipeline of a finished product tower reboiler I205, and the materials are conveyed to the adsorption separation tower 201 through a pipeline 219 after heat exchange; a side draw 210 from the upper portion of the raffinate column 204 to line 220 of the isomerization reaction unit;
the isomerization reaction unit comprises a feed pipeline 321 for feeding isomerization reaction feed 210 to the isomerization reactor 301, and the feed pipeline 220 is sequentially connected with a heat exchanger II306, a heat exchanger III307, a heat exchanger IV308 and an isomerization reaction heating furnace 305 through pipelines 318, 319, 320 and 321 before being connected with the isomerization reactor 301; a feed line 323 for feeding the isomerized reaction product to the isomerized product fractionation column 302, the feed line 322 connecting to the heat exchanger IV308 prior to connecting to the isomerized product fractionation column 302; the isomerization fractionator 302 overhead 340 exits the plant directly via line 324 and the hydrogen 315 required for the isomerization reaction passes via line 330 to compressor 312 and then to feed line 331 to feed line 319 of the isomerization reactor 301. Feeding the side line material of the isomerization product fractionating tower 302 into a feeding pipeline 335 of the clay tower 303, wherein the feeding pipeline 334 is connected with the front part of the clay tower 303 and is connected with a heat exchanger II306, and the pipeline 335 is connected with the clay tower 303 after heat exchange; a discharge pipeline 336 at the bottom of the clay tower 303 is connected with a heat exchanger VI310, and a pipeline 337 after heat exchange is connected with the adsorption separation feed pipeline 110; isomerate fractionation column 302 bottoms are withdrawn in lines 338 and 339 with heat exchanger VI310 between lines 338 and 339;
in addition, the overhead material from the isomerate fractionation column 302 can be fed to a feed line 326 of the knock-out drum 304, and lines 325, 326 can be connected to the heat exchanger V309 and the air cooler 311 in sequence before the feed line 324 is connected to the knock-out drum 304; a discharge line 328 for discharging at least a part of the gas phase separated by the knock-out drum 304 to the outside 314, and a feed line 331 for feeding the remaining part to the feed line 319 of the isomerization reactor; a line 330 connecting a feed line 329 for hydrogen 315 to the compressor 312; the liquid phase separated in the gas-liquid separation tank 304 is connected to a pipe 332 of the heat exchanger V309, and the liquid phase 316 after heat exchange passes through a discharge pipe 333.
The process flow of the device for producing the paraxylene comprises the following steps:
containing C 8 The aromatic hydrocarbon mixture raw material 104 enters a xylene column 101 for fractionation, after the heat exchange of the overhead material is carried out by a heat exchanger I102, one part of the overhead material is returned to the xylene column 101 as reflux, and the other part of the overhead material is used as an adsorption separation feed 105, and then the overhead material is sent to an adsorption separation column 201 after heat exchange with an isomerization reaction feed by a heat exchanger II 306; the bottom material of the tower returns to the xylene tower 101 after passing through the xylene reboiling furnace 103 and the temperature is raised, and the other part of the bottom material 106 is C 9 + An aromatic hydrocarbon.
The adsorption separation feed 207 is subjected to adsorption separation by an adsorption separation tower 201, the obtained paraxylene-rich extract enters an extract tower 202 for fractionation, a tower bottom material is a desorbent and is mixed with a tower bottom material of a raffinate tower 204 to be used as a heat source of a finished product tower reboiler I205, and the heat exchange is carried out and then the mixture returns to the adsorption separation tower 201; the material at the top of the extract tower 202 is rich in paraxylene C 8 The discharge at the bottom of the tower is a desorbent; enriched para-xylene C 8 The components enter a finished product tower 203 for further separation, the material at the top of the tower is toluene 208, and the material at the bottom of the tower is p-xylene 209. The p-xylene depleted raffinate obtained by adsorption separation in the adsorption separation tower enters a raffinate tower 204 for fractionation, the upper side line material passes through a heat exchanger II306, a heat exchanger III307 and a heat exchanger IV308 in sequence, exchanges heat with the side line material, the adsorption separation feed and the isomerization reaction product in an isomerization product fractionating tower 302 respectively, is heated by an isomerization reaction heating furnace 305 and then enters an isomerization reactor 301 for isomerization reaction, and the reaction product enters an isomerization product fractionating tower 302 after exchanging heat by the heat exchanger IV 308; the isomerization fractionator 302 overhead 340 exits the plant directly and the hydrogen 315 needed for the isomerization reaction is mixed with the isomerization feed 210 after being pressurized by compressor 312. The side stream material of the isomerization product fractionating tower 302 exchanges heat through a heat exchanger II306 and enters a carclazyte tower 303 to remove olefinWhen unsaturated hydrocarbon is contained, the material discharged from the clay tower 303 exchanges heat with the material at the bottom of the isomerization product fractionating tower 302 and is mixed with the adsorption separation feed 105. The tower bottom material of the isomerization product fractionating tower 302 exchanges heat with the clay tower discharge material through a heat exchanger VI310, and the material 313 after heat exchange is taken as C 9 + And (5) discharging aromatic hydrocarbon.
In addition, the material at the top of the isomerization product fractionating tower 302 can be subjected to heat exchange by a heat exchanger V308, then is cooled by an isomerization reaction product air cooler 311, enters a gas-liquid separation tank 304, and is separated into a gas-liquid two-phase; the gas phase is discharged from the top of the gas-liquid separation tank 304 into two streams: one stream of the discharged hydrogen 314 is sent to a TSA unit (temperature swing adsorption unit) or a hydrogenation plant, and can also be sent to a fuel gas system; the other is mixed with hydrogen 315, pressurized by compressor 312, and mixed with isomerization feed 210; after the liquid-phase material separated by the gas-liquid separation tank 304 is subjected to heat exchange by a heat exchanger V309, the heat-exchanged material 316 is used as C 7 Discharging the following light hydrocarbons;
the process flow of the conventional xylene plant is as follows: containing C 8 The aromatic hydrocarbon mixture raw material 404 enters a xylene column 401 for fractionation, after heat exchange is carried out on the overhead material by a heat exchanger I402, one part of the overhead material is returned to the xylene column 401 as reflux, and the other part of the overhead material is used as adsorption separation feed 405, and after heat exchange is carried out on the overhead material and the feed of a deheptanizer 602 by a heat exchanger VI609, the overhead material is sent to an adsorption separation column 501; the bottom material of the tower flows through a dimethylbenzene reboiling furnace 403 and returns to the dimethylbenzene tower 401 after being heated, and the other part of the bottom material 406 is C 9 + An aromatic hydrocarbon. The tower top material flow is mainly used as a heat source of a reboiler of the raffinate tower 503 and a reboiler of the extract tower 502; the bottoms stream serves primarily as the heat source for the finishing column reboiler 506 and the deheptanizer 602 reboilers.
The adsorption separation feeding 507 is subjected to adsorption separation by an adsorption separation tower 501, the obtained p-xylene-rich extract enters an extract tower 502 for fractionation, the tower bottom material is a desorbent, and is mixed with the tower bottom material of a raffinate tower 503 to be used as a heat source of a finished product tower reboiler 505 and then returns to the adsorption separation tower 501; the material at the top of the extract tower 502 enters a finished product tower 504, the material at the bottom of the finished product tower is p-xylene 509, and the toluene 508 is at the top of the tower. The p-xylene depleted raffinate obtained by adsorption separation in the adsorption separation tower enters a raffinate tower 503, the upper side line material 510 passes through a heat exchanger III606 and a heat exchanger IV607 in sequence, exchanges heat with the deheptanizer feed and the isomerization reaction product respectively, then enters an isomerization reactor 601 for isomerization reaction after being heated by an isomerization reaction heating furnace 605, and the reaction product enters a gas-liquid separation tank 604 after being exchanged heat by the heat exchanger IV607, cooled by an air cooler 611 and a water cooler 612 and separated into a gas-liquid two phase;
the gas phase is discharged from the top of the knock-out pot 604 to be divided into two streams: one stream of the discharged hydrogen 613 is sent to a TSA unit (temperature swing adsorption unit) or a hydrogenation plant, and can also be sent to a fuel gas system; the other stream is mixed with hydrogen 614, pressurized by a compressor 610 and mixed with the isomerization feed; the liquid phase material obtained by the separation of the gas-liquid separation tank 604 enters the deheptanizer 602 after heat exchange in the heat exchanger III606, the heat exchanger V608 and the heat exchanger VI 609. The material at the top of the deheptanizer 602 is C 7 The bottom material of the light hydrocarbon 615 is returned to the xylene column 401 after passing through a heat exchanger V608 and unsaturated hydrocarbons such as olefin are removed by a clay column 603.
The effect of the novel p-xylene production process provided by the present invention is specifically illustrated by the following examples.
Comparative example 1
Comparative example 1 illustrates the process and energy consumption of a conventional para-xylene production process. The plant operating parameters and energy consumption are shown in table 1.
Example 1
Example 1 illustrates the process and energy consumption of the novel para-xylene production process provided by the present invention, wherein the overhead product of the isomerization fractionator is directly removed from the apparatus without separation, and the hydrogen required for the isomerization reaction is mixed with the isomerization feed after the pressure of the compressor has been increased. The energy consumption of the apparatus is shown in Table 1.
TABLE 1
| Examples | Comparative example 1 | Example 1 |
| Process flow | General procedure | Flow of the invention |
| Condensing cooling load/MW | 109.2 | 88.2 |
| Reboiler duty/MW | 97.3 | 79.8 |
As can be seen from Table 1, the process for producing p-xylene according to the present invention has an energy consumption reduced by 18.2% as compared with comparative example 1. Therefore, the novel p-xylene production method provided by the invention can reduce the operation load of the clay tower and the xylene tower (the operation load of the xylene tower can be reduced by 40%), save the fuel gas consumption of a reboiling furnace of the xylene tower, simultaneously save the condensation and reboiling loads, reduce the equipment investment and the occupied area, reduce the back mixing of materials and improve the thermodynamic efficiency of separation; the phenomenon of unreasonable energy utilization of cooling before heating in the conventional process is solved, and the cooling load is greatly reduced; by optimizing the heat exchange network, the feeding heating of the deheptanizer after the heat is used for heating and cooling is avoided, cold and hot material flows are reasonably matched, and the temperature in front of the feeding furnace of the isomerization reaction is increased, so that the use amount of fuel gas of the isomerization reaction heating furnace is reduced, the energy consumption is greatly reduced, and the economic benefit and the social benefit are improved.
Claims (18)
1. A production device of paraxylene comprises a xylene fractionation unit, an adsorption separation unit and an isomerization reaction unit; the method is characterized in that: the xylene fractionation unit comprises a xylene tower, a heat exchanger I and a xylene reboiling furnace; the adsorption separation unit comprises an adsorption separation tower, an extract tower, a raffinate tower, a finished product tower reboiler I and a finished product tower reboiler II; the isomerization reaction unit comprises an isomerization reactor, an isomerization product fractionating tower, a clay tower, an isomerization reaction heating furnace, a heat exchanger II, a heat exchanger III, a heat exchanger IV, a heat exchanger VI and a compressor; the isomerization product fractionating tower is in a dividing wall tower form, namely a vertical clapboard is arranged in the middle of the traditional rectifying tower, and the rectifying tower is divided into an upper public rectifying section, a lower public stripping section, a rectifying feeding section and a side line extracting section which are separated by the clapboard;
the xylene fractionation unit further comprises a unit for fractionating C 8 The feed line feeds the aromatic hydrocarbon mixture raw material to the xylene tower; a pipeline for sending the tower top discharge to a heat exchanger I; circulating a part of the discharged material at the top of the tower after heat exchange by the heat exchanger I back to a pipeline of the xylene tower; the other part of the discharged material at the top of the tower after the heat exchange of the heat exchanger I is sent to a pipeline of the adsorption separation unit; a feed line for feeding a portion of the bottoms to a bottom reboiling furnace; a line for recycling the bottom material heated by the bottom reboiling furnace to the xylene column; the other part of the tower bottom material is discharged out of a pipeline of the xylene tower; wherein the top discharge of the tower is C 8 Aromatic hydrocarbon, the material at the bottom of the tower is C 9 + An aromatic hydrocarbon;
the adsorption separation unit also comprises a pipeline for feeding the top discharge of the xylene fractionation unit after heat exchange to an adsorption separation tower, a pipeline for delivering the separated p-xylene-rich extract to an extract tower, and a pipeline for delivering the p-xylene-poor raffinate obtained by adsorption separation in the adsorption separation tower to a raffinate tower; a pipeline for delivering the material at the top of the extract tower to a finished product tower; the method comprises the following steps of (1) sending a material at the bottom of an extract tower to a pipeline of a finished product tower reboiler I, sending a material at the bottom of a raffinate tower to a pipeline of the finished product tower reboiler I, and sending the heat-exchanged material at the bottom of the extract tower and the raffinate tower to a pipeline of an adsorption separation tower; discharging the side line at the upper part of the raffinate tower to a pipeline of an isomerization reaction unit;
the isomerization reaction unit also comprises a feeding pipeline for feeding the isomerization reaction to the isomerization reactor, and the feeding pipeline is sequentially connected with a heat exchanger II, a heat exchanger III, a heat exchanger IV and an isomerization reaction heating furnace before being connected with the isomerization reactor; a feed line for feeding the isomerized product to the isomerized product fractionation column, the feed line being connected to the heat exchanger IV before being connected to the isomerized product fractionation column; a discharge line for discharging the overhead material of the isomerized product fractionating tower; feeding the side line material of the isomerization product fractionating tower into a feeding pipeline of the clay tower, wherein the feeding pipeline is connected with the front part of the clay tower and is connected with a heat exchanger II; connecting a discharging pipeline at the bottom of the clay tower with a heat exchanger VI, and connecting a pipeline after heat exchange with an adsorption separation feeding pipeline; and a discharge pipeline for discharging the bottom product of the isomerization product fractionating tower is connected with a heat exchanger VI before discharging.
2. The apparatus of claim 1, wherein: the heat exchanger I is used for taking the xylene overhead material flow as a heat source of a reboiler of a raffinate tower and a reboiler of a draw-out liquid tower, one part of condensed liquid after heat exchange is used as reflux to return to the xylene tower, and the other part of condensed liquid is used as adsorption separation feeding.
3. The apparatus of claim 1, wherein: the isomerization product fractionating tower is used for separating the isomerization reactor discharge rich in the paraxylene C 8 C in component (A) 7 Lower light hydrocarbon, C 8 Aromatic hydrocarbons and C 9 + an aromatic component, wherein the overhead material is C 7 Light hydrocarbon and hydrogen, the material at the bottom of the tower is C 9 + an aromatic component, a side stream C 8 An aromatic hydrocarbon.
4. The apparatus of claim 1, wherein: the heat exchanger II is used for exchanging heat between the side line material of the isomerization product fractionating tower as the clay tower feeding material and the isomerization feeding material, improving the isomerization feeding temperature and reducing the clay tower feeding temperature to the proper temperature.
5. The apparatus of claim 1, wherein: the heat exchanger III is used for feeding the adsorption separation tower and the isomerization reaction, improving the isomerization feeding temperature and reducing the feeding temperature of the adsorption separation tower to a proper temperature.
6. The apparatus of claim 1, wherein: the heat exchanger IV is used for isomerizing the feed and isomerizing the reaction product to be rich in the paraxylene C 8 And (4) heat exchange of the components.
7. The apparatus of claim 1, wherein: and the heat exchanger VI is used for exchanging heat between the side line material of the isomerization product fractionating tower as the clay tower feeding material and the clay tower discharging material, and improving the clay tower discharging temperature.
8. The apparatus of claim 1, wherein: the isomerization reaction unit is provided with a gas-liquid separation tank, an air cooler and a heat exchanger V; the gas-liquid separation tank is used for separating the overhead material C of the isomerization product fractionating tower 7 The hydrogen components in the following light hydrocarbon are discharged outside the gas phase part, and the part is pressurized, heat exchanged and/or heated and returns to the isomerization reactor; the liquid phase is subjected to heat exchange and then is taken out of the device as a light hydrocarbon product; the heat exchanger V is used for exchanging heat between the liquid-phase light hydrocarbon product of the gas-liquid separation tank and the material at the top of the isomerization product fractionating tower; the air cooler is used for further isomerizing the temperature of the overhead material of the product fractionating tower.
9. The apparatus of claim 1, wherein: the isomerization reaction unit also comprises a feeding pipeline for feeding the material at the top of the isomerization product fractionating tower into the gas-liquid separation tank, and the feeding pipeline is sequentially connected with a heat exchanger V and an air cooler before being connected with the gas-liquid separation tank; a discharge line for discharging at least a part of the gas phase separated by the gas-liquid separation tank to the outside, and a feed line for feeding the remaining part to the feed line of the isomerization reactor; the rest part is firstly mixed with hydrogen passing through a hydrogen feeding pipeline before being fed into a feeding pipeline of the isomerization reactor, and then enters a compressor feeding pipeline; and a discharge line for discharging the liquid phase separated in the gas-liquid separation tank.
10. A process for producing paraxylene by using the apparatus for producing paraxylene according to any one of claims 1 to 9, characterized by comprising: containing C 8 The aromatic hydrocarbon mixture raw material enters a xylene tower for fractionation, after heat exchange is carried out on the tower top material by a heat exchanger I, one part of the tower top material is returned to the xylene tower as reflux, the other part of the tower top material is used as adsorption separation feeding material, and then the tower top material is sent to the adsorption separation tower after heat exchange with isomerization reaction feeding material by a heat exchanger III; the bottom material of the tower returns to the xylene tower after passing through the xylene reboiling furnace and being heated, and the other part of the bottom material of the tower is C 9 + Aromatic hydrocarbons; the adsorption separation feeding is subjected to adsorption separation by an adsorption separation tower, the obtained paraxylene-rich extract enters an extract tower for fractionation, the tower bottom material is a desorbent, and is mixed with the tower bottom material of the raffinate tower to be used as a heat source of a finished product tower reboiler I, and the heat exchange is carried out and then the extract returns to the adsorption separation tower; the material at the top of the extract tower is rich in p-xylene C 8 The discharge at the bottom of the tower is a desorbent; enriched para-xylene C 8 The components enter a finished product tower for further separation, wherein the material at the top of the tower is toluene, and the material at the bottom of the tower is p-xylene; the p-xylene depleted raffinate obtained by adsorption separation in the adsorption separation tower enters a raffinate tower for fractionation, the upper side line material sequentially flows through a heat exchanger II, a heat exchanger III and a heat exchanger IV to respectively exchange heat with the side line material of the isomerization product fractionating tower, the adsorption separation feed and the isomerization reaction product, then the side line material is heated in an isomerization reaction heating furnace and enters an isomerization reactor for isomerization reaction, and the reaction product enters the isomerization product fractionating tower after being subjected to heat exchange in the heat exchanger IV; discharging the overhead material of the isomerization product fractionating tower, exchanging heat of the side line material of the isomerization product fractionating tower by a heat exchanger II, entering a clay tower to remove unsaturated hydrocarbon, exchanging heat with the bottom material of the isomerization product fractionating tower by a heat exchanger VI to be used as adsorption separation feeding, and discharging the bottom material of the isomerization product fractionating tower to be C 9 + An aromatic hydrocarbon.
11. The process according to claim 10, characterized in that: the tower top material of the isomerization product fractionating tower exchanges heat by a heat exchanger V and then undergoes isomerization reactionCooling the product by an air cooler, and separating the product into a gas phase and a liquid phase in a gas-liquid separation tank; the gas phase is discharged from the top of the gas-liquid separation tank and divided into two parts: one strand is discharged outside; the other strand is mixed with hydrogen, pressurized by a compressor and mixed with an isomerization reaction feed; the liquid phase material obtained by the separation of the gas-liquid separation tank is used as C after heat exchange of the heat exchanger V 7 The following light hydrocarbons.
12. The process according to claim 10, characterized in that: the top pressure of the xylene tower is 0.3-2.5 MPa, and the temperature of the top of the xylene tower is 50-300 ℃.
13. The process according to claim 10, characterized in that: the operating conditions of the adsorption separation tower are as follows: the temperature is 100-300 ℃, and the pressure is 0.2-1.5 MPa.
14. The process according to claim 10, characterized in that: the operation conditions of the extraction liquid tower are as follows: the pressure at the top of the tower is 0.1-0.5 MPa, and the temperature at the top of the tower is 100-220 ℃.
15. The process according to claim 10, characterized in that: the operation conditions of the raffinate tower are as follows: the pressure at the top of the tower is 0.1-1.0 MPa, and the temperature at the top of the tower is 120-170 ℃.
16. The process according to claim 10, characterized in that: the operating conditions of the finished product tower are as follows: the pressure at the top of the tower is 0.1-0.5 MPa, and the temperature at the top of the tower is 50-200 ℃.
17. The process according to claim 10, characterized in that: the operation conditions of the isomerization reactor are as follows: the reaction temperature is 300-450 ℃, the pressure is 0.1-2.0 MPa, and the mass space velocity is 2-10 h -1 The molar ratio of the reaction hydrogen to the hydrocarbon is 2 to 8.
18. The process according to claim 10, characterized in that: the operation conditions of the isomerization product fractionating tower are as follows: the pressure at the top of the tower is 0.2-2.0 MPa, and the temperature at the top of the tower is 50-250 ℃.
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