阅读说明：本技术 一种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：本发明公开了一种对二甲苯的生产装置及生产工艺。本发明的装置,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,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。(The invention discloses a production device and a production process of paraxylene. The 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 cancels a gas-liquid separation tank and an air cooler, simultaneously improves the efficiency of removing unsaturated hydrocarbons such as olefin, carbonyl and the like from the isomerization product, solves the problems of frequent replacement of waste argil and environmental pollution, 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 the materials, optimizes a heat exchange network and reduces the fuel gas consumption of the isomerization reaction heating furnace.)

1. A production device of 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 a heat exchanger IV; 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 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 fractionating tower, a raffinate tower, a heat exchanger II and a heat exchanger III; also comprises C after heat exchange₈The top discharge of the aromatic hydrocarbon fractionation unit is fed into a pipeline of the adsorption separation tower and is connected with a pipeline of a heat exchanger II before entering the adsorption separation tower; connecting the separated p-xylene-rich extract to a pipeline of a heat exchanger II, transferring the extract to a pipeline of an extract fractionating tower after heat exchange, and transferring the p-xylene-poor raffinate obtained by adsorption separation of the adsorption separation tower to a pipeline of a raffinate tower; a pipeline for discharging the materials at the top of the extract fractionating tower and a pipeline for discharging the materials at the side line of the extract fractionating tower; the bottom material of the extract fractionating tower is sent to a pipeline of a heat exchanger III, the bottom material (desorbent) of the raffinate tower is sent to a pipeline of the heat exchanger III, and the bottom material of the extract fractionating tower and the bottom material of the raffinate tower after heat exchange are sent to a pipeline of an adsorption separation tower; feeding the side line discharged material at the upper part of the raffinate tower into a pipeline of an isomerization reaction unit after heat exchange of a heat exchanger III;

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 apparatus as claimed in claim 1, wherein the extract fractionating tower is a dividing wall tower, and a vertical partition is arranged in the middle of a conventional rectifying tower to divide the rectifying tower into an upper common rectifying section, a lower common stripping section, and a rectifying feed section and a side draw section which are separated by the partition.

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. The production process for producing paraxylene by using the production apparatus according to any one of claims 1 to 6, comprising: containing C₈The aromatic hydrocarbon raw material enters a xylene tower for fractionation, after the tower top material flows through a heat exchanger I for heat exchange, one part of the tower top material returns to the xylene tower as reflux, the other part of the tower top material is used as adsorption separation feeding material, and after the tower top material passes through a heat exchanger IV and a heat exchanger II, the tower top material exchanges heat with isomerization reaction feeding material and extract fractionating tower feeding material respectively, and then the obtained product is sent to an adsorption separation tower; 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 exchanges heat with the adsorption separation feeding by a heat exchanger II and then enters an extract fractionating tower for fractionation, the extract fractionating tower is in a dividing wall tower form, the tower bottom material is a desorbent and is mixed with the raffinate tower bottom material, and then the mixture exchanges heat with the isomerization reaction feeding by a heat exchanger III and returns to the adsorption separation tower; toluene is taken as a material at the top of the extract fractionating tower, and paraxylene is taken as a material at the side line; the lean p-xylene raffinate obtained by the adsorption separation in the adsorption separation tower enters a raffinate tower for fractionation, the upper side line material sequentially passes through a heat exchanger III, a heat exchanger IV and a heat exchanger V to respectively exchange heat with the resolving agent, the adsorption separation feed and the isomerization reaction product, then enters an isomerization film reactor for isomerization reaction after being heated by an isomerization reaction heating furnace, and the reaction productThe product enters an isomerization product fractionating tower after heat exchange by a 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; after being pressurized by a compressor, a part of hydrogen is mixed with the isomerization reaction material and enters a heat exchanger, and a part of hydrogen is pressurized by the compressor and then is mixed with the hydrogenation reaction feed; 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 process according to claim 7, wherein said C is contained₈The 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, wherein the top pressure of the xylene column is 0.3 to 2.5 MPa, preferably 0.5 to 1.8 MPa, and the temperature at the top of the xylene column is 50 to 300 ℃, preferably 110 to 280 ℃; the xylene tower is a plate tower, and the number of plates is 150-200.

10. The process according to claim 7, wherein the operating conditions of the adsorption separation column are: the temperature is 100-300 ℃ and the pressure is 0.2-1.5 MPa.

11. The process of claim 7 wherein the draw fractionation column is operated under the following conditions: 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 ℃.

12. The process of claim 7, wherein the raffinate column is operated at: 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 ℃.

13. The process of claim 7 wherein the isomerization unit comprises an isomerization membrane reactor loaded with an isomerization catalyst and a hydrogenation reactor loaded with a selective hydrodeolefination catalyst.

14. The process of claim 7 wherein the isomerization membrane reactor is operated under the following conditions: 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.

15. The process of claim 7 wherein the isomerate fractionation column is operated under the conditions: 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 ℃.

16. The process of claim 7 wherein the hydrogenation reactor is operated under the following conditions: 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 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 extract is rectified into an extract tower and a finished product tower double-tower flow, the energy consumption is large, and C in the isomerized product is removed by a deheptanizer₇After 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, unsaturated hydrocarbons such as olefin and carbonyl in isomerization reaction products are generally treated by clay in industry, wherein clay has short service cycle, fast deactivation, limited adsorption capacity and poor adsorption efficiency, and the waste clay needs to be replaced frequently and causes environmental pollutionAnd pollution is caused.

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 feeding temperature of an isomerization reaction heating furnace, reduce the fuel gas consumption and the hydrogen supplement consumption of the isomerization reaction heating furnace, reduce the equipment investment and the floor area and greatly reduce the energy consumption.

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 a heat exchanger IV; 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 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 fractionating tower, a raffinate tower, a heat exchanger II and a heat exchanger III; also comprises C after heat exchange₈The top discharge of the aromatic hydrocarbon fractionation unit is fed into a pipeline of the adsorption separation tower and is connected with a pipeline of a heat exchanger II before entering the adsorption separation tower; connecting the separated paraxylene-rich extract to a pipeline of a heat exchanger II, transferring the heat-exchanged extract to a pipeline of an extract fractionating tower, and extracting the residual of the low-grade paraxylene obtained by adsorption separation in an adsorption separation towerA line for liquid to the raffinate column; a pipeline for discharging the materials at the top of the extract fractionating tower and a pipeline for discharging the materials at the side line of the extract fractionating tower; the bottom material of the extract fractionating tower is sent to a pipeline of a heat exchanger III, the bottom material (desorbent) of the raffinate tower is sent to a pipeline of the heat exchanger III, and the bottom material of the extract fractionating tower and the bottom material of the raffinate tower after heat exchange are sent to a pipeline of an adsorption separation tower; feeding the side line discharged material at the upper part of the raffinate tower into a pipeline of an isomerization reaction unit after heat exchange of a heat exchanger III;

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 fractionating tower is used for separating toluene, paraxylene and desorbent in the extract rich in paraxylene to obtain a high-purity paraxylene product. The extract fractionating tower adopts a dividing wall tower, a vertical clapboard is generally arranged in the middle of the 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. The material at the bottom of the tower is a desorbent, the material at the top of the tower is toluene, and the material at the side line is a paraxylene product.

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.

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

The heat exchanger III is used for exchanging heat between a desorbent and an isomerization feed, improving the temperature of the isomerization feed and reducing the load of an isomerization reaction heating furnace; and simultaneously reducing the temperature of the desorbent to the proper temperature of the desorbent returning to the adsorption separation tower.

The isomerization membrane reactor is used for separating the lean p-xylene C from the adsorption 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. Effect of lean p-xylene on catalystConversion to para-xylene-rich C₈And 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 production process of paraxylene, which comprises the following steps: containing C₈The aromatic hydrocarbon raw material enters a xylene tower for fractionation, and after heat exchange is carried out on the tower top material by a heat exchanger I, a part of the tower top material is returned as refluxThe other part of the xylene tower is used as adsorption separation feeding, and is respectively subjected to heat exchange with isomerization reaction feeding and extract fractionating tower feeding through a heat exchanger IV and a heat exchanger II, and then is sent to the adsorption separation tower; 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 exchanges heat with the adsorption separation feeding by a heat exchanger II and then enters an extract fractionating tower for fractionation, the extract fractionating tower is in a dividing wall tower form, the tower bottom material is a desorbent and is mixed with the raffinate tower bottom material, and then the mixture exchanges heat with the isomerization reaction feeding by a heat exchanger III and returns to the adsorption separation tower; toluene is taken as a material at the top of the extract fractionating tower, and paraxylene is taken as a material at the side line; the lean p-xylene raffinate obtained by adsorption separation in the adsorption separation tower enters a raffinate tower for fractionation, the materials at the side line at the upper part respectively exchange heat with the resolving agent, the adsorption separation feed and the isomerization reaction product through a heat exchanger III, a heat exchanger IV and a heat exchanger V, then enter an isomerization film reactor for isomerization reaction after being heated by an isomerization reaction heating furnace, and enter an isomerization product fractionation tower after the reaction product exchanges heat through a 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; after being pressurized by a compressor, a part of hydrogen is mixed with the isomerization reaction material and enters a heat exchanger, and a part of hydrogen is pressurized by the compressor and then is mixed with the hydrogenation reaction feed; 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. Hydrogen andafter being mixed, the make-up hydrogen is pressurized by a compressor and is mixed with the 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 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. 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, and the temperature at the top of the tower is 50-200 ℃.

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 above-mentionedThe 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-¹The volume ratio of reaction hydrogen to hydrocarbon is 200-500: 1.

compared with the prior art, the invention provides C₈The device and the process for converting and separating the aromatic hydrocarbon have the following beneficial effects:

the extraction liquid fractionating tower with a dividing wall tower structure is arranged in the adsorption separation unit, and an extraction liquid tower and a finished product tower in the conventional process are omitted, so that the back mixing degree of p-xylene in the separated components is reduced, the thermodynamic efficiency of separation is improved, and meanwhile, the phenomenon that the extraction liquid tower cools the toluene and the p-xylene components in the conventional process, and the heat entering the finished product tower for separation is unreasonably utilized after being heated is avoided; in the conventional process, reboiling loads of an extract tower and a finished product tower are respectively provided by materials at the top and the bottom of a dimethylbenzene tower and a desorbent, the extract fractionating tower with a dividing wall tower structure is arranged, the reboiling loads can be completely provided by the materials at the top of the dimethylbenzene tower, the heat of the materials at the top of the dimethylbenzene tower is fully recovered, and the use of the heat of the materials at the bottom of the dimethylbenzene tower is reduced, so that the fuel gas consumption of a reboiling furnace of the dimethylbenzene tower is saved, meanwhile, the top of the extract fractionating tower only needs to cool methylbenzene and part of p-dimethylbenzene components, and the condensation load is reduced; desorbent materials at the bottoms of the extract fractionating tower and the raffinate tower are not used as heat sources of a reboiler of a finished product tower, but used for preheating isomerization reaction feeding, so that the temperature of the reaction feeding into an isomerization heating furnace is increased, and the fuel gas consumption of the isomerization heating furnace is reduced;

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 pre-separates the isomerization reaction product by the isomerization fractionating tower, and pre-separates 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;

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 isThe phenomenon of unreasonable energy utilization of cooling before heating in the conventional process is solved, and the cooling load is greatly reduced;

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;

wherein, 101, a xylene column, 102, a heat exchanger I, 103, a xylene reboiling furnace, 201, an adsorption separation column, 202, an extract fractionating column, 203, a raffinate column, 204, a heat exchanger II, 205, a heat exchanger III, 301, an isomerization membrane reactor, 302, an isomerization product fractionating column, 303, a hydrogenation reactor, 304, a compressor, 305, an isomerization reaction heating furnace, 306, a heat exchanger IV, 307, a heat exchanger V;

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 unit₈The aromatic hydrocarbon mixture raw material 104 is fed to a feed line 107 of the xylene column 101; 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 fractionating tower 202, a raffinate tower 203, a heat exchanger ii 204 and a heat exchanger iii 205; also comprises C after heat exchange₈The overhead discharge 206 of the aromatic hydrocarbon fractionation unit is fed to a pipeline 210 of the adsorption separation tower, and the pipeline 210 is connected with a heat exchanger II 204 through a pipeline 211 before entering the adsorption separation tower 201; a para-xylene-rich extract pipeline 212 separated by the adsorption separation tower 201 is connected with a heat exchanger II 204, and is sent to a pipeline 213 of the extract fractionating 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 217 of the raffinate tower 203; a line 214 for withdrawing overhead 207 from the extract fractionator 202, and a line 215 for withdrawing side 208 from the extract fractionator 202; fractionating the extract in a column 202The tower bottom material is sent to a pipeline 216 of the heat exchanger III 205, the raffinate tower bottom material (desorbent) is sent to a pipeline 220 of the heat exchanger III 205, and the extract fractionating tower 202 tower bottom material and the raffinate tower 203 tower bottom material after heat exchange are sent to a pipeline 221 of the adsorption separation tower 201 after heat exchange through the heat exchanger III 205; the upper side draw 218 of raffinate column 203 is fed 209 to isomerization unit line 219 after heat exchange in exchanger III 205.

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 209 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 aromatic hydrocarbon mixture raw material 104 enters a xylene tower 101 for fractionation, after heat exchange is carried out on tower top materials through a heat exchanger I102, one part of the tower top materials are returned to the xylene tower 101 as reflux, the other part of the tower top materials are used as adsorption separation feeding materials 105, and after heat exchange is carried out on the tower top materials and isomerization reaction feeding materials and feeding materials of an extract fractionating tower through a heat exchanger IV 306 and a heat exchanger II 204 respectively, the tower top materials are 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 exchanges heat with the adsorption separation feed by a heat exchanger II 204 and then enters an extract fractionating tower 202, the tower bottom material is a desorbent and is mixed with the tower bottom material of the raffinate tower 203, and then the mixture exchanges heat with the isomerization reaction feed by a heat exchanger III 205 and returns to the adsorption separation tower 201; the material at the top of the extract fractionating tower 202 is toluene 207; the side stream material is p-xylene 208; the lean p-xylene raffinate obtained by adsorption separation in the adsorption separation tower 201 enters a raffinate tower 203 for fractionation, the upper side line material sequentially passes through a heat exchanger IV 306 and a heat exchanger V307, respectively exchanges heat with adsorption separation feed and an isomerization reaction product, then enters an isomerization film reactor 301 for isomerization reaction after being heated by an isomerization reaction heating furnace 305, and enters an isomerization product fractionation tower 302 after being exchanged heat by 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, and separating the hydrogenation reaction product as adsorptionThe bottoms 310 of the isomerization product fractionation column 302 is 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 is exchanged by a heat exchanger III 606, a heat exchanger V608 and a heat exchanger VI 609 in sequenceAfter being heated, it enters the deheptanizer 602. 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, compared with comparative example 1, the method for producing p-xylene provided by the invention can save the investment of 1 set of rectifying tower, cooler reboiler equipment, 1 gas-liquid separation tank, air cooler and water cooler, cancel the clay tower and add one reactor. The method provided by the invention not only reduces the number of equipment, but also reduces the energy consumption by 19.3%. Therefore, the novel p-xylene production method provided by the invention saves the condensation and reboiling loads, reduces the back mixing of materials and improves 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; 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.