阅读说明：本技术 对二甲苯的生产装置及生产工艺 (Production device and production process of p-xylene ) 是由 胡珺 薄德臣 高明 张英 于 2020-03-30 设计创作，主要内容包括：本发明公开了对二甲苯的生产装置及生产工艺。本发明的生产装置,包括二甲苯分馏单元,吸附分离单元和异构化反应单元；所述的异构化反应单元,包括异构化膜反应器、异构化产物分馏塔、加氢反应器、异构化反应加热炉、换热器Ⅳ、换热器Ⅴ和压缩机。本发明同时提供了对二甲苯的生产工艺。本发明降低了二甲苯塔操作负荷,节约了二甲苯再沸炉燃料气用量,避免了物料先冷却再加热的用能不合理现象,优化换热网络,降低了异构化反应加热炉燃料气的用量,取消气液分离罐和空冷器的使用,同时提高了异构化产物脱除烯烃和羰基等不饱和烃的效率,解决了频繁更换废白土和污染环境的问题。(The invention discloses a production device and a production process of paraxylene. The production device comprises a xylene fractionation unit, an adsorption separation unit and an isomerization reaction unit; the isomerization reaction unit comprises an isomerization membrane reactor, an isomerization product fractionating tower, a hydrogenation reactor, an isomerization reaction heating furnace, a heat exchanger IV, a heat exchanger V and a compressor. The invention also provides a production process of the paraxylene. The invention reduces the operation load of the xylene tower, saves the fuel gas consumption of the xylene reboiling furnace, avoids the unreasonable energy consumption phenomenon of cooling and heating materials, optimizes a heat exchange network, reduces the fuel gas consumption of the isomerization reaction heating furnace, cancels a gas-liquid separation tank and an air cooler, improves the efficiency of removing unsaturated hydrocarbons such as olefin, carbonyl and the like from an isomerization product, and solves the problems of frequent replacement of waste argil and environmental pollution.)

1. The production device of the paraxylene is characterized by comprising 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; also comprises that C is added₈The 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 part of the discharged material at the top of the tower after heat exchange by the heat exchanger I is circulated to a pipeline of 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 xylene 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 C₈Aromatic hydrocarbon, the material at the bottom of the tower is C₉ ⁺Aromatic hydrocarbons;

the adsorption separation unit comprises an adsorption separation tower, an extract tower, a finished product tower, a raffinate tower, a finished product tower reboiler I and a finished product tower reboiler II; the method comprises the following steps of feeding the discharged material at the top of the xylene fractionation unit after heat exchange into an adsorption separation feeding pipeline of an adsorption separation tower, wherein the feeding pipeline is connected with a finished product tower reboiler II, a heat exchanger IV, a heat exchanger II and a heat exchanger III in sequence before the adsorption separation tower, and respectively exchanges heat with the material at the bottom of the finished product tower, the isomerization reaction feeding material, the extract liquid tower feeding material and the finished product tower feeding material; the separated paraxylene-rich extract is sent to a pipeline of an extract tower, a feed pipeline is connected with a pipeline of a heat exchanger II before being connected with the extract tower, and the paraxylene-poor raffinate obtained by adsorption separation of the adsorption separation tower is sent to a pipeline of a raffinate tower; the material at the top of the extract tower is sent to a feeding pipeline of a finished product tower, the feeding pipeline is connected with a pipeline of a heat exchanger III before being connected with the finished product tower, the material at the top of the finished product tower is sent to a toluene discharging pipeline, and the material at the bottom of the tower is sent to a p-xylene discharging pipeline; connecting a material pipeline at the bottom of the extraction liquid tower and a material pipeline at the bottom of the raffinate tower after heat exchange with a pipeline of a reboiler I of a finished product 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 membrane reactor, an isomerization product fractionating tower, a hydrogenation reactor, an isomerization reaction heating furnace, a heat exchanger IV, a heat exchanger V and a compressor; the method also comprises the steps that the isomerization reaction is fed into a feeding pipeline of the isomerization membrane reactor, and the pipeline of the heat exchanger IV, the heat exchanger V and the isomerization reaction heating furnace is connected in sequence before the isomerization reaction is connected with the isomerization membrane reactor; a feed line for feeding the isomerized product to the isomerized product fractionation column, the line connecting the heat exchanger V before connecting the isomerized product fractionation column; a purge gas feed line of the isomerization membrane reactor, a hydrogen gas discharge line of the isomerization membrane reactor, which are connected to a feed line for make-up hydrogen and a discharge line for discharging a part of the hydrogen gas, respectively; a compressor is connected to a feed pipeline for supplementing hydrogen, the pressure of the hydrogen is increased, part of outlet pipelines of the compressor are merged into a feed pipeline of the isomerization membrane reactor, and part of outlet pipelines of the compressor are merged into a feed pipeline of the hydrogenation reactor; a discharge line for discharging the overhead material of the isomerized product fractionating tower; a discharge line for discharging the isomerized product fractionation column bottoms; and feeding the side line material of the isomerization product fractionating tower into a pipeline of the hydrogenation reactor, merging the hydrogenation product of the hydrogenation reactor into a pipeline of the feeding of the adsorption separation tower, and connecting a pipeline of the heat exchanger IV before merging the side line material of the isomerization product fractionating tower into the feeding of the adsorption separation tower.

2. The production apparatus of claim 1 wherein the isomerization membrane reactor has a catalyst-packed region in the middle, and a membrane module is disposed outside the catalyst-packed region, the membrane module and the wall of the isomerization membrane reactor forming a gas flow passage.

3. The apparatus of claim 1, wherein: the separation membrane adopted in the membrane component is a Pd-Ag alloy membrane; the content of Ag in the separation membrane is 20% -25%.

4. The production device according to claim 1, wherein the xylene column is a plate rectifier.

5. The production device according to claim 1, wherein the finished product tower has two reboilers for providing heat, and the heat source of the reboiler I of the finished product tower is used for providing desorbent at the bottoms of the extract tower and the raffinate tower, and reducing the temperature of the desorbent to the proper temperature for returning to the adsorption separation tower; and the heat source of the reboiler II of the finished product tower is adsorption separation feeding which enters the adsorption separation tower after further exchanging heat with isomerization reaction feeding.

6. The apparatus as claimed in claim 1, wherein the isomerized product fractionating column is in the form of a dividing wall column, and a vertical partition is disposed at the middle position of a conventional rectifying column to divide the rectifying column into an upper common rectifying section, a lower common stripping section, and a rectifying feed section and a side draw section separated by the partition.

7. Production of para-di using the production apparatus of any one of claims 1 to 6The production process of toluene comprises the following steps: containing C₈The method comprises the following steps that an 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 after heat exchange is carried out on the tower top material and the tower bottom material of a finished product tower, isomerization reaction feeding material, extract liquid tower feeding material and finished product tower feeding material by a finished product tower reboiler I, a heat exchanger IV, a heat exchanger II and a heat exchanger III, the raw material is sent to an adsorption separation tower after heat exchange is carried out on the tower bottom material, the isomerization reaction feeding material, the extract liquid tower feeding material and the finished product tower feeding material respectively; 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 C₉ ⁺Aromatic hydrocarbons; the adsorption separation feeding is subjected to adsorption separation by an adsorption separation tower, the obtained paraxylene-rich extract is subjected to heat exchange with the adsorption separation feeding by a heat exchanger II and then enters an extract tower for fractionation, the tower bottom material is a desorbent and is mixed with the raffinate tower bottom material to serve as a heat source of a finished product tower reboiler I, and the heat exchange is carried out and then the mixture returns to the adsorption separation tower; the material at the top of the extract tower is rich in p-xylene C₈The discharge at the bottom of the tower is a desorbent; enriched para-xylene C₈The components are subjected to heat exchange with the adsorption separation feed material through a heat exchanger III and then 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 lean p-xylene raffinate obtained by adsorption separation in the adsorption separation tower enters a raffinate tower for fractionation, the material at the upper side line passes through a heat exchanger IV and a heat exchanger V in sequence, exchanges heat with adsorption separation feed and an isomerization reaction product respectively, then enters an isomerization film reactor for isomerization reaction after being heated by an isomerization reaction heating furnace, and enters an isomerization product fractionation tower after being exchanged heat by the heat exchanger V; hydrogen which does not participate in the reaction in the isomerization membrane reactor passes through a membrane module and leaves the reactor under the action of a purge gas; mixing part of hydrogen with make-up hydrogen, pressurizing by a compressor, and mixing with reaction feed; when the hydrogen partial pressure is reduced, a part of the hydrogen gas is discharged from the discharge line; discharging the material at the top of the isomerized product fractionating tower, feeding the material at the side line of the isomerized product fractionating tower into a hydrogenation reactor to remove unsaturated hydrocarbon, taking the hydrogenated product as an adsorption separation feed, and discharging the material at the bottom of the isomerized product fractionating tower to C₉ ⁺An aromatic hydrocarbon.

8. The production process according to claim 7, characterized in that: said C containing₈The aromatic hydrocarbon raw material mainly comprises mixed hydrocarbon containing ethylbenzene, paraxylene, ortho-xylene and meta-xylene, and also comprises C₇Light hydrocarbons and C₉The above heavy hydrocarbons.

9. The production process according to claim 7, characterized in that: the top pressure of the xylene tower is 0.3-2.5 MPa, preferably 0.5-1.8 MPa, the temperature of the top of the xylene tower is 50-300 ℃, and preferably 110-280 ℃; the xylene tower is a plate tower, and the number of plates is 150-200.

10. The production process according to claim 7, 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.

11. The production process according to claim 7, characterized in that: the adsorption separation tower adopts a fixed bed, and the effect that the adsorbent continuously moves downwards and the material continuously moves upwards is generated by changing the positions of the material inlet and the material outlet of the adsorption equipment of the fixed bed.

12. The production process according to claim 7, characterized in that: the operation conditions of the extract 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 ℃.

13. The production process according to claim 7, 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 ℃.

14. The production process according to claim 7, 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 ℃.

15. The production process according to claim 7, characterized in that: in the isomerization unit, an isomerization catalyst is filled in an isomerization membrane reactor, and a selective hydrogenation and olefin removal catalyst is filled in a hydrogenation reactor.

16. The production process according to claim 7, characterized in that: the operation conditions of the isomerization membrane 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^-1The molar ratio of the reaction hydrogen to the hydrocarbon is 2 to 8.

17. The production process according to claim 7, 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 ℃.

18. The production process according to claim 7, characterized in that: the operating conditions of the hydrogenation reactor are as follows: the reaction temperature is 120-250 ℃, the pressure is 0.2-2.0 MPa, and the mass space velocity is 2-8 h^-1The volume ratio of reaction hydrogen to hydrocarbon is 200-500: 1.

Technical Field

The invention relates to a production device and a production process of paraxylene.

Background

C₈Aromatic hydrocarbons include four isomers of ortho-xylene, para-xylene, meta-xylene and ethylbenzene, and since they have similar chemical structures and physical properties and the same molecular weight, para-xylene depleted C is generally obtained by isomerization₈Conversion of aromatics to equilibrium concentration C₈Aromatic hydrocarbon mixture is rectified, adsorbed and separated to obtain high purity p-xylene product and low p-xylene C₈The aromatic hydrocarbon is circulated in the system to carry out isomerization reaction again.

The separation of paraxylene is generally carried out industrially by crystallization and adsorption separation, among which adsorption separation is used in many cases. The raw material for adsorption separation is mixed C₈Aromatic hydrocarbons, using para-C₈The 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 reaction₈The aromatic mixture is then recycled back to the xylene for fractionation. In the process, the isomerized product is subjected to a deheptanizer to remove C₇After 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; in addition, clay is generally used in industry to treat unsaturated hydrocarbons such as olefin and carbonyl in isomerization reaction products, wherein clay has short service cycle, rapid deactivation and limited adsorption capacity to cause adsorptionThe attached efficiency is poor, and the waste argil needs to be frequently replaced and causes pollution to the environment.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide a production device and a production process of paraxylene, which reduce the operation load of a xylene tower, save the fuel gas consumption of a xylene reboiling furnace, improve the removal efficiency of unsaturated hydrocarbons such as olefin, carbonyl and the like in an isomerization reaction product, solve the problems of waste clay replacement and environmental pollution, optimize a heat exchange network, improve the heat exchange efficiency of an isomerization reaction feed and discharge heat exchanger and the furnace inlet temperature of an isomerization reaction heating furnace, reduce the fuel gas consumption of the isomerization reaction heating furnace and the supplement consumption of hydrogen, greatly reduce the energy consumption, reduce the equipment investment and the occupied area, and improve the economic benefit and the social benefit.

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; also comprises that C is added₈The 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 part of the discharged material at the top of the tower after heat exchange by the heat exchanger I is circulated to a pipeline of 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 xylene 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 C₈Aromatic hydrocarbon, the material at the bottom of the tower is C₉ ⁺Aromatic hydrocarbons;

the adsorption separation unit comprises an adsorption separation tower, an extract tower, a finished product tower, a raffinate tower, a finished product tower reboiler I and a finished product tower reboiler II; the method comprises the following steps of feeding the discharged material at the top of the xylene fractionation unit after heat exchange into an adsorption separation feeding pipeline of an adsorption separation tower, wherein the feeding pipeline is connected with a finished product tower reboiler II, a heat exchanger IV, a heat exchanger II and a heat exchanger III in sequence before the adsorption separation tower, and respectively exchanges heat with the material at the bottom of the finished product tower, the isomerization reaction feeding material, the extract liquid tower feeding material and the finished product tower feeding material; the separated paraxylene-rich extract is sent to a pipeline of an extract tower, a feed pipeline is connected with a pipeline of a heat exchanger II before being connected with the extract tower, and the paraxylene-poor raffinate obtained by adsorption separation of the adsorption separation tower is sent to a pipeline of a raffinate tower; the material at the top of the extract tower is sent to a feeding pipeline of a finished product tower, the feeding pipeline is connected with a pipeline of a heat exchanger III before being connected with the finished product tower, the material at the top of the finished product tower is sent to a toluene discharging pipeline, and the material at the bottom of the tower is sent to a p-xylene discharging pipeline; connecting a material pipeline at the bottom of the extraction liquid tower and a material pipeline at the bottom of the raffinate tower after heat exchange with a pipeline of a reboiler I of a finished product 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 membrane reactor, an isomerization product fractionating tower, a hydrogenation reactor, an isomerization reaction heating furnace, a heat exchanger IV, a heat exchanger V and a compressor; the method also comprises the steps that the isomerization reaction is fed into a feeding pipeline of the isomerization membrane reactor, and the pipeline of the heat exchanger IV, the heat exchanger V and the isomerization reaction heating furnace is connected in sequence before the isomerization reaction is connected with the isomerization membrane reactor; a feed line for feeding the isomerized product to the isomerized product fractionation column, the line connecting the heat exchanger V before connecting the isomerized product fractionation column; a purge gas feed line of the isomerization membrane reactor, a hydrogen gas discharge line of the isomerization membrane reactor, which are connected to a feed line for make-up hydrogen and a discharge line for discharging a part of the hydrogen gas, respectively; a compressor is connected to a feed pipeline for supplementing hydrogen, the pressure of the hydrogen is increased, part of outlet pipelines of the compressor are merged into a feed pipeline of the isomerization membrane reactor, and part of outlet pipelines of the compressor are merged into a feed pipeline of the hydrogenation reactor; a discharge line for discharging the overhead material of the isomerized product fractionating tower; a discharge line for discharging the isomerized product fractionation column bottoms; and feeding the side line material of the isomerization product fractionating tower into a pipeline of the hydrogenation reactor, merging the hydrogenation product of the hydrogenation reactor into a pipeline of the feeding of the adsorption separation tower, and connecting a pipeline of the heat exchanger IV before merging the side line material of the isomerization product fractionating tower into the feeding of the adsorption separation tower.

The xylene column is used for separating C₈Component (A) and (C)₉ ⁺The component is a plate-type rectifying tower.

And the heat exchanger I is used for taking the tower top material flow of the xylene tower as a heat source of a reboiler of the raffinate tower and a reboiler of the extract tower.

The xylene reboiling furnace is used for heating materials which are recycled to the bottom of the tower, and provides reboiling heat for the xylene tower.

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 extract₈The components and a desorbent are mixed, and the material at the top of the extract tower is rich in p-xylene C₈The 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 raffinate₈The components and the desorbent are discharged from the upper side line of the raffinate tower as the lean p-xylene C₈The components, the discharge from the bottom of the tower is the 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 adsorption separation feeding which enters the adsorption separation tower after further exchanging heat with isomerization reaction feeding.

And the heat exchanger II is used for exchanging heat between adsorption separation feeding and extraction liquid tower feeding, improving the feeding temperature of the extraction liquid tower and reducing the heat load of the bottom of the extraction liquid tower.

And the heat exchanger III is used for exchanging heat between the adsorption separation feeding and the finished product tower feeding, improving the temperature of the different finished product tower feeding, reducing the heat load at the bottom of the finished product tower, and simultaneously reducing the temperature of the adsorption separation feeding to the proper temperature of the adsorption separation tower.

Said isomerizationMembrane reactor for the conversion of para-xylene lean C from an adsorptive separation unit₈Conversion of the component into para-xylene-rich C₈The components are separated, and meanwhile, hydrogen which does not participate in the reaction is separated out. The middle of the isomerization membrane reactor is a catalyst filling area, a membrane module is arranged outside the catalyst filling area, and the membrane module and the wall of the isomerization membrane reactor form a gas circulation channel; the separation membrane adopted in the membrane component is a Pd-Ag alloy membrane for H₂Has extremely high selectivity; preferably, the content of Ag in the film is 20% -25%, and H₂The permeability of (2) is higher. Conversion of lean p-xylene to rich p-xylene C over a catalyst₈And the hydrogen which does not participate in the reaction is separated by the membrane module in the reaction process, and the hydrogen leaves the reactor through the gas flow channel under the action of the purge gas through the membrane module. Mixing hydrogen and make-up hydrogen, then pressurizing by a compressor, and mixing with reaction feed; when the hydrogen partial pressure is reduced due to the excessively high concentration of the purge gas in the recycle hydrogen, a part of the recycle hydrogen may be discharged.

The isomerization product fractionating tower is used for separating the isomerization membrane reactor discharge rich in the paraxylene C₈C in component (A)₇Lower light hydrocarbon, C₈Aromatic hydrocarbons and C₉The isomerization product fractionating tower is in a dividing wall tower form, a vertical clapboard is generally placed in the middle of a traditional rectifying tower, and the rectifying tower is divided into four parts, namely 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. Wherein the material at the top of the tower is C₇Light hydrocarbon and hydrogen, the material at the bottom of the tower is C₉+ an aromatic component, a side stream C₈An 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 hydrogenation reactor is used for removing a small amount of unsaturated hydrocarbon impurities such as olefin, carbonyl and the like in the isomerization product, and meets the product quality requirement.

The isomerization heating furnace is used for controlling the isomerization feeding temperature.

The compressor is used for pressurizing hydrogen and circulating hydrogen entering the isomerization membrane reactor.

The invention also provides a process for producing the aromatic hydrocarbon product, which comprises the following steps: containing C₈The method comprises the following steps that an 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 after heat exchange is carried out on the tower top material and the tower bottom material of a finished product tower, isomerization reaction feeding material, extract liquid tower feeding material and finished product tower feeding material by a finished product tower reboiler I, a heat exchanger IV, a heat exchanger II and a heat exchanger III, the raw material is sent to an adsorption separation tower after heat exchange is carried out on the tower bottom material, the isomerization reaction feeding material, the extract liquid tower feeding material and the finished product tower feeding material respectively; 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 C₉ ⁺Aromatic hydrocarbons; the adsorption separation feeding is subjected to adsorption separation by an adsorption separation tower, the obtained paraxylene-rich extract is subjected to heat exchange with the adsorption separation feeding by a heat exchanger II and then enters an extract tower for fractionation, the tower bottom material is a desorbent and is mixed with the raffinate tower bottom material to serve as a heat source of a finished product tower reboiler I, and the heat exchange is carried out and then the mixture returns to the adsorption separation tower; the material at the top of the extract tower is rich in p-xylene C₈The discharge at the bottom of the tower is a desorbent; enriched para-xylene C₈The components are subjected to heat exchange with the adsorption separation feed material through a heat exchanger III and then 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 lean p-xylene raffinate obtained by adsorption separation in the adsorption separation tower enters a raffinate tower for fractionation, the material at the upper side line passes through a heat exchanger IV and a heat exchanger V in sequence, exchanges heat with adsorption separation feed and an isomerization reaction product respectively, then enters an isomerization film reactor for isomerization reaction after being heated by an isomerization reaction heating furnace, and enters an isomerization product fractionation tower after being exchanged heat by the heat exchanger V; hydrogen which does not participate in the reaction in the isomerization membrane reactor passes through a membrane module and leaves the reactor under the action of a purge gas; when the hydrogen partial pressure is reduced, a part of the hydrogen gas is discharged from the discharge line; a portion of the hydrogen andafter being mixed, the supplementary hydrogen is pressurized by a compressor and mixed with the isomerization reaction material to enter a heat exchanger; a part of hydrogen is mixed with the hydrogenation reaction feed after being pressurized by a compressor; discharging the material at the top of the isomerized product fractionating tower, feeding the material at the side line of the isomerized product fractionating tower into a hydrogenation reactor to remove unsaturated hydrocarbon, taking the hydrogenated product as an adsorption separation feed, and discharging the material at the bottom of the isomerized product fractionating tower to C₉ ⁺An aromatic hydrocarbon.

In the catalyst filling zone of the isomerization membrane reactor, the lean p-xylene is converted into rich p-xylene C under the action of the catalyst₈And the hydrogen which does not participate in the reaction is separated by the membrane module in the reaction process, and the hydrogen leaves the reactor through the gas flow channel under the action of the purge gas through the membrane module. Mixing hydrogen and make-up hydrogen, then pressurizing by a compressor, and mixing with reaction feed; when the hydrogen partial pressure is reduced due to the excessively high concentration of the purge gas in the recycle hydrogen, a part of the recycle hydrogen may be discharged. The separation membrane is a Pd-Ag alloy membrane for H₂Has extremely high selectivity; preferably, the content of Ag in the film is 20% -25%, and H₂The permeability of (2) is higher.

Said C containing₈The aromatic hydrocarbon raw material mainly comprises mixed hydrocarbon containing ethylbenzene, paraxylene, ortho-xylene and meta-xylene, and also comprises C₇Light hydrocarbons and C₉The above heavy hydrocarbons. Wherein C is₇ The light hydrocarbon below is an aromatic hydrocarbon, an alkane or a cycloalkane having 7 or less carbon atoms, C₉The heavy hydrocarbon refers to 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 continuous direction of the adsorbent is generated by changing the positions of a material inlet and a material outlet of the adsorption equipment of the fixed bedDownward movement and continuous upward movement of the materials. 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 C₈The 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 operation conditions of the isomerization membrane reactor are as follows: the reaction temperature is 300-450 ℃, the preferable temperature is 330-400 ℃, the pressure is 0.1-2.0 MPa, the preferable pressure is 0.4-1.5 MPa, and the mass space velocity is 2-10 h^-1Preferably 3 to 6 hours^-1The 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 membrane reactor, and the isomerization catalyst is an active component of one or more of Pt, Sn, Mg, Bi, Pb, Pd, Re, Mo, W, V and rare earth metals loaded 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 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 ℃.

The operating conditions of the hydrogenation reactor are as follows: the reaction temperature is 120-250 ℃, the pressure is 0.2-2.0 MPa, and the mass space velocity is 2-8 h-¹By reaction of hydrogenThe volume ratio of hydrocarbon is 200-500: 1.

compared with the prior art, the novel p-xylene production method provided by the invention has the following beneficial effects:

(1) in the device and the process, the isomerization fractionating tower with a dividing wall tower structure is arranged, the deheptanizer in the conventional process is omitted, the isomerization reaction product is skillfully pre-separated by the isomerization fractionating tower, and the tower bottom C in the isomerization reaction product₉ ⁺Aromatics and overhead C₇The lower light hydrocarbon is separated out from the device in advance, and the side stream material is C₈Aromatic hydrocarbon, directly mixed with the adsorption separation feed; in the conventional process, the C is not treated in the deheptanizer₉ ⁺Aromatic hydrocarbon is separated, so that the operation load of the clay tower is increased, and meanwhile, materials passing through the clay tower need to enter the xylene tower again, so that the operation load of xylene is greatly increased. The invention reduces the operation load of the xylene tower, saves the fuel gas consumption of the reboiling furnace of the xylene tower, saves the condensation and reboiling loads, reduces the equipment investment and the occupied area, reduces the back mixing of materials and improves the thermodynamic efficiency of separation;

(2) the isomerization membrane reactor realizes the separation of hydrogen and reaction products, does not need to cool and heat the reaction products, has higher purity of the hydrogen separated by the isomerization membrane reactor, reduces the consumption of supplementary hydrogen, and obtains the material C at the top of the isomerization reaction product tower₇The light hydrocarbon can be directly discharged from the device without a condensing system and gas-liquid separation equipment. The isomerization reaction product of the conventional process needs to be cooled by an air cooler and a water cooler, gas-phase components such as hydrogen and the like are separated out by a gas-liquid separation tank, the liquid-phase components are reheated, and C is separated out by a deheptanizer₇ ^-Light component, C₈ ⁺Returning the components to the xylene tower for further separation to obtain C₈The 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.

(3) In the conventional process, the heat load of the reboiling furnace of the finished product tower is provided by a resolving agent and xylene tower bottom liquid, adsorption separation feeding, namely xylene tower top liquid and deheptanizer feeding enter an adsorption separation tower after heat exchange, and the heat of the xylene tower top material is not fully utilized; the invention fully utilizes the heat of the material at the top of the xylene tower by optimizing the heat source of the reboiler of the finished product tower and the heat exchange network in the device, thereby reducing the load of the xylene reboiling furnace and saving the fuel gas consumption of the xylene tower reboiling furnace;

(4) by arranging the hydrogenation reactor, a clay tower in the conventional process is omitted, so that impurities such as olefin in an isomerization reaction product can be quickly subjected to hydrogenation saturation under the action of a selective hydrogenation olefin-removing catalyst, and reactions such as aromatic hydrocarbon saturation and hydrocracking are reduced; thereby solving the problems that the clay is inactivated quickly, the adsorption capacity is limited, the adsorption efficiency is poor, the waste clay needs to be replaced frequently, the environment is polluted and the like in the conventional process.

Drawings

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.

FIG. 1 is a schematic of the xylene fractionation unit of example 1;

FIG. 2 is a schematic view of an adsorption separation unit of example 1;

FIG. 3 is a schematic of an isomerization reaction unit of example 1;

the system comprises a xylene column, a xylene reboiler, a heat exchanger, and a heat exchanger, a heat exchanger;

FIG. 4 is a schematic of a xylene fractionation unit of comparative example 1;

FIG. 5 is a schematic view of an adsorption separation unit of comparative example 1;

FIG. 6 is a schematic of an isomerization reaction unit of comparative example 1;

the system comprises a xylene tower 401, a xylene tower 402, a heat exchanger I, a heat exchanger 403, a xylene reboiling furnace 501, an adsorption separation tower 502, a liquid extract tower 503, a raffinate tower 504, a finished product tower 505, a finished product reboiler I, a finished product reboiler 506, a finished product reboiler II, a finished product reboiler 601, an isomerization reactor 602, a deheptanizer tower 603, a clay tower 604, a gas-liquid separation tank 605, an isomerization reaction heating furnace 606, a heat exchanger III, a heat exchanger IV 607, a heat exchanger IV, a heat exchanger V, a heat exchanger 609, a heat exchanger VI, a compressor 610, an air cooler 611 and a water cooler 612.

Detailed Description

The paraxylene production process of the present invention will be described in more detail below with reference to the accompanying drawings.

Example 1

The production device of the paraxylene comprises a xylene fractionation unit, an adsorption separation unit and an isomerization reaction unit;

the xylene fractionation unit is shown in figure 1, and comprises a xylene column 101, a heat exchanger I102, a xylene reboiling furnace 103 and a C-containing component₈The aromatic hydrocarbon mixture raw material 104 is fed to a feed line 107 of the xylene column; line 108 which delivers 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 heat exchange by 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 IV 306; 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 reboiler 103 to the xylene column; a line 114 for withdrawing another portion of the bottoms 106 from the xylene column; wherein the overhead output 105 is C₈Aromatic hydrocarbons, bottoms 106 being C₉ ⁺Aromatic hydrocarbons;

the adsorption separation unit is shown in fig. 2 and comprises an adsorption separation tower 201, an extract tower 202, a finished product tower 203, a raffinate tower 204, a finished product tower reboiler I205, a finished product tower reboiler II 206, a heat exchanger 207 and a heat exchanger III 208; the method further comprises the steps of feeding a tower top discharge 105 of the xylene fractionation unit subjected to heat exchange into a pipeline 110 of an adsorption separation tower, connecting the pipeline 110 with a finished product tower reboiler II 206 to exchange heat with a finished product tower bottom material feed, connecting an adsorption separation feed 212 subjected to heat exchange with a heat exchanger IV 305 through a pipeline 228 to exchange heat with an isomerization reaction feed, sequentially connecting an adsorption separation feed 213 subjected to heat exchange with a heat exchanger II 207 and a heat exchanger III 208 through pipelines 214, 215 and 216 to exchange heat with an extract liquid tower feed and a finished product tower feed respectively; a para-xylene-rich extract pipeline 217 separated by the adsorption separation tower 201 is connected with the heat exchanger II 207, and is sent to a pipeline 218 of the extract tower 202 after heat exchange, and a para-xylene-poor raffinate obtained by adsorption separation of the adsorption separation tower 201 is sent to a pipeline 224 of the raffinate tower 204; a feeding pipeline 219 for feeding the extract tower 202 overhead material to the finished product tower 203, wherein the feeding pipeline 219 is connected with a pipeline 220 of a heat exchanger III 208 before being connected with the finished product tower 203, and the finished product tower overhead material 209 is connected with a toluene discharging pipeline 221, and the tower bottom material 210 is connected with a p-xylene discharging pipeline 222; a material pipeline 223 at the bottom of the extract tower 202 and a material pipeline 225 at the bottom of the raffinate tower 204 after heat exchange are connected with a pipeline 226 of a finished product tower reboiler I205; the upper side stream 211 of raffinate column 204 is discharged to line 227 of the isomerization reaction unit.

The isomerization reaction unit is shown in fig. 3 and comprises an isomerization membrane reactor 301, an isomerization product fractionating tower 302, a hydrogenation reactor 303, an isomerization reaction heating furnace 305, a heat exchanger iv 306, a heat exchanger v 307 and a compressor 304; the method also comprises a feeding pipeline 315 for feeding the side line material 211 at the upper part of the raffinate tower 204 into the isomerization membrane reactor 301, and pipelines 313 and 314 for connecting a heat exchanger IV 306, a heat exchanger V307 and an isomerization reaction heating furnace 305 in sequence before connecting the isomerization membrane reactor 301; a feed line 316 for feeding the isomerized product to the isomerized product fractionation column 302, line 317 connecting heat exchanger v 307 prior to connecting the isomerized product fractionation column 302; a purge gas feed line 318 for feeding a purge gas 311 to the isomerization membrane reactor 301, an isomerization membrane reactor 301 hydrogen take-off line 319 connected to a make-up hydrogen feed line 322, and a discharge line 320 for discharging a portion of the hydrogen 312; the hydrogen 308 enters the compressor 304 through a feed line 322 to be pressurized, a compressor outlet line 323 is merged into a line 313 for feeding the isomerization membrane reactor 301, and a part of the hydrogen is merged into a feed line 324 for the hydrogenation reactor 303 through an outlet line of the compressor 304; a discharge line 325 for discharging the isomerate fractionator 302 overhead 309; line 326 feeding the isomerate fractionator 302 side stream to hydrogenation reactor 303, and the hydrogenation product feeding to adsorptive separation feed line 327; an effluent line 328 that discharges the isomerate fractionation column 302 bottoms 310.

The middle of the isomerization membrane reactor 301 is a catalyst filling area, a membrane module is arranged outside the catalyst filling area, and a gas circulation channel is formed by the membrane module and the wall of the isomerization membrane reactor; the separation membrane adopted in the membrane component is a Pd-Ag alloy membrane.

The isomerized product fractionating tower 302 is in a form of a dividing wall tower, wherein a vertical partition plate is 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.

The production process flow of the xylene device comprises the following steps:

containing C₈The method comprises the following steps that an aromatic hydrocarbon mixture raw material 104 enters a xylene tower 101 for fractionation, after heat exchange is carried out on a tower top material flowing through a heat exchanger I102, one part of the tower top material returns to the xylene tower 101 as reflux, the other part of the tower top material serves as adsorption separation feeding 105, and after heat exchange is respectively carried out on the tower top material, the isomerization reaction feeding, the extraction liquid tower feeding and the finished product tower feeding through a finished product tower reboiler I205, a heat exchanger IV 306, a heat exchanger II 207 and a heat exchanger III 208, the tower bottom material, the isomerization reaction feeding, the extraction liquid tower feeding and the finished product tower feeding, the raw material is sent to an adsorption separation tower 201; 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 C₉ ⁺An aromatic hydrocarbon. The adsorption separation feed 206 is subjected to adsorption separation by the adsorption separation tower 201, the obtained paraxylene-rich extract is subjected to heat exchange with the adsorption separation feed by a heat exchanger II 205 and then enters an extract tower 202 for fractionation, the tower bottom material is a desorbent and is mixed with the 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 returns to the adsorption separation tower 201; the material at the top of the extract tower 202 is rich in paraxylene C₈The discharge at the bottom of the tower is a desorbent; enriched para-xylene C₈The components pass through a heat exchanger III 208 to exchange heat with the adsorption separation feeding material and then enter into the reactorThe product tower 203 is further separated, the material at the top of the tower is toluene 209, and the material at the bottom of the tower is p-xylene 210. The lean p-xylene raffinate obtained by adsorption separation in the adsorption separation tower 201 enters a raffinate tower 204 for fractionation, the upper side line material 211 sequentially passes through a heat exchanger IV 306 and a heat exchanger V307, is respectively subjected to heat exchange with adsorption separation feed and an isomerization reaction product, is heated in an isomerization reaction heating furnace 305 and then enters an isomerization film reactor 301 for isomerization reaction, and the reaction product enters an isomerization product fractionation tower 302 after being subjected to heat exchange in the heat exchanger V307; hydrogen which does not participate in the reaction in the isomerization membrane reactor 301 passes through the membrane and leaves the reactor under the action of the purge gas 311; after the pressure of hydrogen 308 is increased by a compressor 304, the hydrogen is mixed with the isomerization reaction material 212 and enters a heat exchanger V307, and one part of the hydrogen is mixed with the hydrogenation reaction feed; discharging the top material 309 of the isomerization product fractionating tower 302, feeding the side material of the isomerization product fractionating tower 302 into a hydrogenation reactor 303 to remove unsaturated hydrocarbon, taking the hydrogenation reaction product as adsorption separation feed, and discharging the bottom material 310 of the isomerization product fractionating tower 302 as C₉ ⁺An aromatic hydrocarbon.

Comparative example 1

The process flow of the conventional xylene plant is as follows: containing C₈The 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 feeding material 405, and after heat exchange is carried out on the overhead material and the feeding material of a deheptanizer 602 by a heat exchanger VI 609, the overhead material is sent to an adsorption separation column 501; one part of the bottom material flow 406 is heated by a dimethylbenzene reboiling furnace 403 and then returns to the dimethylbenzene tower 401, and the other part is C₉ ⁺And (5) discharging 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 material at the top of the tower is toluene 508. 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 III 606 and a heat exchanger IV 607 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 IV 607, 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 externally 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 by the heat exchanger III 606, the heat exchanger V608 and the heat exchanger VI 609. The material at the top of the deheptanizer 602 is C₇The bottom material of the light hydrocarbon 615 is returned to the xylene tower 401 after passing through a heat exchanger V608 and unsaturated hydrocarbons such as olefin are removed by a clay tower 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 equipment used is shown in Table 1, and the energy consumption of the apparatus is shown in Table 2.

Example 1

Example 1 illustrates the process and energy consumption of the novel para-xylene production process provided by the present invention. The equipment used is shown in Table 1, and the energy consumption of the apparatus is shown in Table 2.

TABLE 1

TABLE 2

As can be seen from Table 1, the process for producing paraxylene of the present invention can save the investment in the number of 1 gas-liquid separation tank, air cooler and water cooler, compared with comparative example 1. The method provided by the invention not only reduces the number of equipment, but also reduces the energy consumption by 19.1%. Therefore, the novel method for producing p-xylene provided by the invention saves the condensation and reboiling loads, reduces the equipment investment and the occupied area, reduces the back mixing of materials and improves the thermodynamic efficiency of separation; the phenomenon of unreasonable energy utilization of cooling and heating in the conventional process is solved, the cooling load is greatly reduced, the heat exchange efficiency of the isomerization reaction feeding and discharging heat exchanger is improved, and the consumption of supplementary hydrogen and the power consumption of a compressor are reduced; the efficiency of removing unsaturated hydrocarbons such as olefin, carbonyl and the like from the isomerization product is improved, and the problems of frequent replacement of waste argil and environmental pollution are solved; by optimizing the heat exchange network, the condition that heat is used for heating and cooling the feed of the deheptanizer is avoided, cold and hot material flows are reasonably matched, and the energy consumption is greatly reduced.