阅读说明：本技术 一种芳烃产品的生产装置及工艺 (Production device and process of aromatic hydrocarbon product ) 是由 胡珺 高明 薄德臣 张英 于 2019-08-27 设计创作，主要内容包括：本发明公开了一种芳烃产品的生产装置及工艺。该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；所述的吸附分离单元,包括吸附分离塔、抽出液分馏塔、抽余液塔和换热器II；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、白土塔、异构化反应加热炉、换热器III、换热器IV、换热器V和压缩机。本发明同时提供了一种芳烃产品的生产工艺。本发明减少了设备投资,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,同时优化换热网络,降低了异构化反应加热炉燃料气的用量,大幅降低能耗,提高经济效益和社会效益。(The invention discloses a production device and a production process of aromatic hydrocarbon products. The device comprises a xylene fractionation unit, an adsorption separation unit and an isomerization reaction unit; the adsorption separation unit comprises an adsorption separation tower, an extract liquid fractionating tower, a raffinate tower and a heat exchanger II; the isomerization reaction unit comprises an isomerization membrane reactor, an isomerization product fractionating tower, a clay tower, an isomerization reaction heating furnace, a heat exchanger III, a heat exchanger IV, a heat exchanger V and a compressor. The invention also provides a production process of the aromatic hydrocarbon product. The invention reduces the equipment investment, reduces the operation load of the xylene tower, saves the fuel gas consumption of the xylene reboiling furnace, avoids the unreasonable energy consumption of the material which is firstly cooled and then heated, optimizes the heat exchange network, reduces the fuel gas consumption of the isomerization reaction heating furnace, greatly reduces the energy consumption and improves the economic benefit and the social benefit.)

1. The production device of the aromatic hydrocarbon product comprises a xylene fractionation unit, an adsorption separation unit and an isomerization reaction unit; the method is characterized in that: the xylene fractionation unit comprises a xylene tower, a heat exchanger I and a xylene reboiling furnace;

the xylene fractionation unit further comprises a unit for fractionating C₈The 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; circulating a part of the discharged material at the top of the tower after heat exchange by the heat exchanger I back to a pipeline of the xylene tower; the other part of the tower top discharge after heat exchange by the heat exchanger I is sent to a pipeline of the adsorption separation unit; a feed line for feeding a portion of the bottoms to a bottom reboiling furnace; a line for recycling the bottom material heated by the bottom reboiling furnace to the xylene column; the other part of the tower bottom material is discharged out of a pipeline of the xylene tower; wherein the top discharge of the tower is 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 liquid fractionating tower, a raffinate tower and a heat exchanger II; the extract fractionating tower adopts a dividing wall tower; the adsorption separation unit also comprises a pipeline for feeding the tower top discharge of the xylene fractionation unit after heat exchange to an adsorption separation tower, a pipeline for delivering the separated p-xylene-rich extract to an extract fractionation tower, and a pipeline for delivering the p-xylene-poor raffinate obtained by adsorption separation of the adsorption separation tower to a raffinate tower; a pipeline for 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 method comprises the following steps of (1) sending an extract fractionating tower bottom material to a pipeline of a heat exchanger II, sending a raffinate tower bottom material to a pipeline of the heat exchanger II, and sending the extract fractionating tower bottom material and the raffinate tower bottom material subjected to heat exchange to a pipeline of an adsorption separation tower; feeding the side line discharge at the upper part of the raffinate tower into a pipeline of an isomerization reaction unit after heat exchange of a heat exchanger II;

the isomerization reaction unit comprises an isomerization membrane reactor, an isomerization product fractionating tower, a clay tower, an isomerization reaction heating furnace, a heat exchanger III, a heat exchanger IV, a heat exchanger V and a compressor; the isomerization membrane reactor is internally provided with a membrane component and a catalyst filling area, the membrane component is positioned on the outer layer of the catalyst filling area, and the membrane component and the wall of the reactor form a gas circulation channel; the separation membrane adopted in the membrane component is a Pd-Ag alloy membrane; the isomerization product fractionating tower adopts a dividing wall tower form; the isomerization reaction unit also comprises a feed pipeline for feeding the isomerization reaction into the isomerization membrane reactor, and the feed pipeline is sequentially connected with a heat exchanger III, a heat exchanger IV and an isomerization reaction heating furnace before being connected with the isomerization membrane reactor; a feed line for feeding the isomerized product to the isomerized product fractionation column, the feed line being connected to the heat exchanger IV before being connected to the isomerized product fractionation column; a purge gas feed line for feeding a purge gas to the reactor, a hydrogen gas discharge line for the isomerization membrane reactor, and an exhaust line for discharging a part of the hydrogen gas when the hydrogen partial pressure is reduced; the hydrogen feeding pipeline is connected with the compressor, and the pipeline is connected with the isomerization feeding pipeline after the pressure is increased; a discharge line for discharging the overhead material of the isomerized product fractionating tower; feeding the side-line material of the isomerization product fractionating tower into a feeding pipeline of the clay tower, wherein the feeding pipeline is connected with a heat exchanger V in front of the clay tower; connecting a discharging pipeline at the bottom of the argil tower with a heat exchanger V, and connecting a pipeline after heat exchange with an adsorption separation feeding pipeline; a vent line for venting the isomerate fractionator bottoms.

2. The production device according to claim 1, wherein: the heat exchanger I is used for taking the xylene overhead material flow as a heat source of a reboiler of a raffinate tower and a reboiler of a draw-out liquid tower, one part of condensed liquid after heat exchange is used as reflux to return to the xylene tower, and the other part of condensed liquid is used as adsorption separation feeding.

3. The production device according to claim 1, wherein: the heat exchanger II 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.

4. The production device according to claim 1, wherein: the heat exchanger III is used for feeding the adsorption separation tower and the isomerization reaction, improving the isomerization feeding temperature and reducing the feeding temperature of the adsorption separation tower to a proper temperature.

5. The production device according to claim 1, wherein: the heat exchanger IV is used for isomerizing the feed and the isomerization reaction product (rich in p-xylene C)₈Component) heat exchange.

6. The production device according to claim 1, wherein: the heat exchanger V is used for exchanging heat between the side line material of the isomerization product fractionating tower and the clay tower discharging material, and improving the clay tower discharging temperature; the clay tower discharging after heat exchange is the feeding of the adsorption separation tower.

7. The production process of the aromatic hydrocarbon product is characterized by comprising the following steps of: containing C₈The aromatic hydrocarbon mixture raw material enters a xylene tower for fractionation, after heat exchange is carried out on the tower top material by a heat exchanger I, one part of the tower top material is returned to the xylene tower as reflux, the other part of the tower top material is used as adsorption separation feeding material, and then the tower top material is sent to the adsorption separation tower after heat exchange with isomerization reaction feeding material by a heat exchanger III; the bottom material of the tower returns to the xylene tower after passing through the xylene reboiling furnace and being heated, and the other part of the bottom material of the tower is C₉ ⁺Aromatic hydrocarbons; the adsorption separation feeding is subjected to adsorption separation by an adsorption separation tower, the obtained p-xylene-rich extract enters an extract fractionating tower for fractionation, the tower bottom material is a desorbent, and after being mixed with the raffinate tower bottom material, the desorbent exchanges heat with the isomerization reaction feeding by a heat exchanger II 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 material on the upper side line sequentially flows through a heat exchanger II, a heat exchanger III and a heat exchanger IV to exchange heat with a desorbent, an adsorption separation feed and an isomerization reaction product respectively, then the material enters an isomerization film reactor for isomerization reaction after being heated by an isomerization reaction heating furnace, and the reaction product enters an isomerization product fractionation tower after being subjected to heat exchange in the heat exchanger IV; hydrogen which does not participate in the reaction in the isomerization membrane reactor passes through the membrane and leaves the reactor under the action of a purge gas; mixing hydrogen and make-up hydrogen, then pressurizing by a compressor, and mixing with reaction feed; discharging the overhead material of the isomerization product fractionating tower, exchanging heat between the side line material of the isomerization product fractionating tower and a heat exchanger V, removing unsaturated hydrocarbon in a clay tower, exchanging heat with the side line material of the isomerization product fractionating tower by the heat exchanger V, and then taking the side line material as adsorption separation feeding material, and discharging the bottom material of the isomerization product fractionating tower C₉ ⁺An aromatic hydrocarbon.

8. The process according to claim 7, characterized in that: the separation membrane is a Pd-Ag alloy membrane, and the content of Ag in the membrane is 20% -25%.

9. The process according to claim 7, characterized in that: the top pressure of the xylene tower is 0.3-2.5 MPa, and the temperature of the top of the xylene tower is 50-300 ℃.

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

12. The 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 ℃.

13. The process according to claim 7, characterized in that: the operation conditions of the isomerization reactor are as follows: the reaction temperature is 300-450 ℃, the pressure is 0.1-2.0 MPa, and the mass space velocity is 2-10 h^-1The molar ratio of the reaction hydrogen to the hydrocarbon is 2 to 8.

14. The 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 ℃.

Technical Field

The invention relates to a production device and a production process of aromatic hydrocarbon products.

Background

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 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; the presence of hydrogen also reduces the heat exchange efficiency of the isomerization feed and discharge heat exchanger.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a device and a process for producing aromatic hydrocarbon products, which improve the heat exchange efficiency of an isomerization reaction charging and discharging heat exchanger and the charging furnace temperature of an isomerization reaction heating furnace, reduce the fuel gas consumption of the isomerization reaction heating furnace and the supplement consumption of hydrogen, and solve the problem of unreasonable energy utilization of the conventional process of cooling before heating, thereby greatly reducing the energy consumption, simultaneously reducing the equipment investment and the floor area, reducing the operation load of a xylene tower, saving the fuel gas consumption of the xylene reboiling furnace, and improving the economic benefit and the social benefit.

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

the xylene fractionation unit comprises a xylene tower, a heat exchanger I and a xylene reboiling furnace.

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

The heat exchanger I is used for taking the xylene overhead material flow as a heat source of a reboiler of a raffinate tower and a reboiler of a draw-out liquid tower, one part of condensed liquid after heat exchange is used as reflux to return to the xylene tower, and the other part of condensed liquid is used as adsorption separation feeding.

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 xylene fractionation unit further comprises a unit for fractionating C₈The 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; circulating a part of the discharged material at the top of the tower after heat exchange by the heat exchanger I back to a pipeline of the xylene tower; the other part of the tower top discharge after heat exchange by the heat exchanger I is sent to a pipeline of the adsorption separation unit; a feed line for feeding a portion of the bottoms to a bottom reboiling furnace; a line for recycling the bottom material heated by the bottom reboiling furnace to the xylene column; the other part of the tower bottom material is discharged out of a pipeline of the xylene tower; wherein the top discharge of the tower is C₈Aromatic hydrocarbon, the material at the bottom of the tower is C₉ ⁺An aromatic hydrocarbon.

The adsorption separation unit comprises an adsorption separation tower, an extract liquid fractionating tower, a raffinate tower and a heat exchanger II.

The adsorption separation tower is used for separating paraxylene and isomers thereof in materials from a xylene fractionation unit to obtain a paraxylene-rich extract and a paraxylene-poor raffinate.

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.

The heat exchanger II 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 adsorption separation unit also comprises a pipeline for feeding the tower top discharge of the xylene fractionation unit after heat exchange to an adsorption separation tower, a pipeline for delivering the separated p-xylene-rich extract to an extract fractionation tower, and a pipeline for delivering the p-xylene-poor raffinate obtained by adsorption separation of the adsorption separation tower to a raffinate tower; a pipeline for 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 method comprises the following steps of (1) sending an extract fractionating tower bottom material to a pipeline of a heat exchanger II, sending a raffinate tower bottom material (desorbent) to a pipeline of the heat exchanger II, and sending the extract fractionating tower bottom material and the raffinate tower bottom material subjected to heat exchange to a pipeline of an adsorption separation tower; and (3) feeding the side line discharge at the upper part of the raffinate tower to a pipeline of an isomerization reaction unit after heat exchange of a heat exchanger II.

The isomerization reaction unit comprises an isomerization membrane reactor, an isomerization product fractionating tower, a clay tower, an isomerization reaction heating furnace, a heat exchanger III, a heat exchanger IV, a heat exchanger V and a compressor.

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 C₈Separating out unreacted hydrogen simultaneously; hydrogen leaves the reactor through a membrane module of the reactor under the action of a purge gas; 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 aromatic hydrocarbon component and the isomerized product fractionating tower adopts a dividing wall tower form, wherein the material at the top of the tower is 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 clay tower is used for removing a small amount of unsaturated hydrocarbons such as olefin and carbonyl in the side line material of the isomerization product fractionating tower.

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

The heat exchanger III is used for feeding the adsorption separation tower and the isomerization reaction, improving the isomerization feeding temperature and reducing the feeding temperature of the adsorption separation tower to a proper temperature.

The heat exchanger IV is used for isomerizing the feed and the isomerization reaction product (rich in p-xylene C)₈Component) heat exchange.

The heat exchanger V is used for exchanging heat between the side line material of the isomerization product fractionating tower and the clay tower discharging material, and improving the clay tower discharging temperature; the clay tower discharging after heat exchange is the feeding of the adsorption separation tower.

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

The isomerization reaction unit also comprises a feed pipeline for feeding the isomerization reaction into the isomerization membrane reactor, and the feed pipeline is sequentially connected with a heat exchanger III, a heat exchanger IV and an isomerization reaction heating furnace before being connected with the isomerization membrane reactor; a feed line for feeding the isomerized product to the isomerized product fractionation column, the feed line being connected to the heat exchanger IV before being connected to the isomerized product fractionation column; a purge gas feed line for feeding a purge gas to the reactor, a hydrogen gas discharge line for the isomerization membrane reactor, and an exhaust line for discharging a part of the hydrogen gas when the hydrogen partial pressure is reduced; the hydrogen feeding pipeline is connected with the compressor, and the pipeline is connected with the isomerization feeding pipeline after the pressure is increased; a discharge line for discharging the overhead material of the isomerized product fractionating tower; feeding the side-line material of the isomerization product fractionating tower into a feeding pipeline of the clay tower, wherein the feeding pipeline is connected with a heat exchanger V in front of the clay tower; connecting a discharging pipeline at the bottom of the argil tower with a heat exchanger V, and connecting a pipeline after heat exchange with an adsorption separation feeding pipeline; a vent line for venting the isomerate fractionator bottoms.

The invention also provides a production process of the aromatic hydrocarbon product, which comprises the following steps: containing C₈The aromatic hydrocarbon mixture raw material enters a xylene tower for fractionation, after heat exchange is carried out on the tower top material by a heat exchanger I, one part of the tower top material is returned to the xylene tower as reflux, the other part of the tower top material is used as adsorption separation feeding material, and then the tower top material is sent to the adsorption separation tower after heat exchange with isomerization reaction feeding material by a heat exchanger III; the bottom material of the tower returns to the xylene tower after passing through the xylene reboiling furnace and being heated, and the other part of the bottom material of the tower is C₉ ⁺Aromatic hydrocarbons; the adsorption separation feeding is subjected to adsorption separation by an adsorption separation tower, the obtained p-xylene-rich extract enters an extract fractionating tower for fractionation, the tower bottom material is a desorbent, and after being mixed with the raffinate tower bottom material, the desorbent exchanges heat with the isomerization reaction feeding by a heat exchanger II 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 material on the upper side line sequentially flows through a heat exchanger II, a heat exchanger III and a heat exchanger IV to exchange heat with a desorbent, an adsorption separation feed and an isomerization reaction product respectively, then the material enters an isomerization film reactor for isomerization reaction after being heated by an isomerization reaction heating furnace, and the reaction product enters an isomerization product fractionation tower after being subjected to heat exchange in the heat exchanger IV; hydrogen which does not participate in the reaction in the isomerization membrane reactor passes through the membrane and leaves the reactor under the action of a purge gas; mixing hydrogen and make-up hydrogen, then pressurizing by a compressor, and mixing with reaction feed; discharging the overhead material of the isomerized product fractionating tower, and exchanging the side material of the isomerized product fractionating towerHeat exchange is carried out by a heat exchanger V, unsaturated hydrocarbon is removed in a clay tower, the unsaturated hydrocarbon and the side line material of the isomerization product fractionating tower are used as adsorption separation feeding after heat exchange is carried out by the heat exchanger V, and the bottom discharging material of the isomerization product fractionating tower is C₉ ⁺An aromatic hydrocarbon.

The isomerization product fractionating tower is in a dividing wall tower form, a vertical partition plate is generally arranged in the middle of a traditional rectifying tower, and the rectifying tower is divided into an upper public rectifying section, a lower public stripping section, a rectifying feeding section and a side line extracting section which are separated by the partition plate.

The isomerization membrane reactor is in a membrane reactor form, the separation membrane is a Pd-Ag alloy membrane, and the separation membrane is 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 positions of a material inlet and a material outlet of the fixed bed adsorption equipment are changed to generate the effect that the adsorbent continuously moves downwards and the material continuously moves upwards. The bed is filled with an adsorbent with high selectivity to p-xylene. The active component of the adsorbent is X-type zeolite or Y-type molecular sieve of Ba or BaK, and the binder is selected from kaolin, silicon dioxide or alumina. The desorbent is mutually soluble with each component in the raw material and is also mutually soluble with 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 fractionating 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 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 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 ℃.

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

(1) 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-; 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;

(2) 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 hydrocarbons are directly mixed with the adsorptive separation feed, whereas 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 following light hydrocarbon can be directly discharged from the device without arranging 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 by a gas-liquid separation tank, the liquid phase components are reheated, and heptane removal is carried out on the liquid phase componentsColumn separation of C₇ ^-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. In the conventional process flow, the temperature of an isomerization reaction feed of an isomerization reaction unit entering an isomerization reaction heating furnace is about 280-300 ℃; the isomerization reaction unit of the invention cancels the deheptanizer, simultaneously, the isomerization reaction feeding does not undergo the process of cooling first and then heating through optimizing a heat exchange network, namely, the heat of the isomerization reaction feeding (the side line material on the upper part of the raffinate tower) is prevented from heating the cooled deheptanizer feeding, and the cold and hot material flows are reasonably matched, meanwhile, the components such as hydrogen and the like are treated in the isomerization film reactor, so that the heat transfer coefficient of the isomerization reaction feeding and discharging heat exchanger can be effectively improved, the heat exchange efficiency is improved, the temperature of the isomerization reaction feeding entering the isomerization reaction heating furnace is further improved, the temperature of the isomerization reaction feeding furnace can be improved to 310-330 ℃, the fuel gas consumption of the isomerization reaction heating furnace is reduced, the energy consumption is greatly reduced, and the economic benefit and the social benefit are improved.

Drawings

Fig. 1, 2 and 3 are schematic flow diagrams of a xylene fractionation unit, an adsorption separation unit and an isomerization unit of a xylene plant according to the present invention, respectively.

Wherein, fig. 1 is a xylene fractionation unit, which comprises a xylene column 101, a heat exchanger I102 and a xylene reboiling furnace 103; FIG. 2 is an adsorptive separation unit comprising an adsorptive separation column 201, an extract fractionation column 202, a raffinate column 203, and a heat exchanger II 204; fig. 3 is an isomerization reaction unit in which an isomerization membrane reactor 301, an isomerization product fractionation column 302, a clay column 303, a compressor 304, an isomerization reaction heating furnace 305, a heat exchanger III306, a heat exchanger IV307, and a heat exchanger V308.

Fig. 4, 5 and 6 are schematic flow diagrams of a xylene fractionation unit, an adsorption separation unit and an isomerization reaction unit, respectively, of a conventional xylene plant.

Wherein, fig. 4 is a xylene fractionation unit, which comprises a xylene column 401, a heat exchanger I402 and a xylene reboiling furnace 403; FIG. 5 shows an adsorption separation unit comprising an adsorption separation column 501, an extract column 502, a raffinate column 503, a finished product column 504, a finished product reboiler I505, and a finished product reboiler II 506; fig. 6 is an isomerization reaction unit, which includes an isomerization reactor 601, a deheptanizer 602, a clay column 603, a gas-liquid separation tank 604, an isomerization reaction heating furnace 605, a heat exchanger III606, a heat exchanger IV607, a heat exchanger V608, a heat exchanger VI609, a compressor 610, an air cooler 611, and a water cooler 612.

FIG. 7 is a schematic diagram of the structure of an isomerization membrane reactor.

Wherein 301-a is a membrane reactor discharge port, 301-b is a purge gas inlet, 301-c is a flange, 301-d is a membrane module, 301-e is a shell, 301-f is a catalyst filling area, 301-g is a purge gas outlet, and 301-h is a membrane reactor feed port.

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention.

Detailed Description

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

The xylene fractionation unit comprises₈The aromatic hydrocarbon mixture raw material 104 is fed to a feed line 107 of the xylene column; line 108 feeding the overhead discharge to heat exchanger I102; a pipeline 109 for circulating a part of the discharged material at the top of the tower after heat exchange by the heat exchanger I102 back to the xylene tower; another part of the overhead discharge 105 after heat exchange in heat exchanger I102 is sent to line 110 of heat exchanger III306, and then the adsorptive separation feed 205 is connected to line 209 of heat exchanger II306 before being connected to line 211 of the feed to adsorptive separation column 201; 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, bottom of the columnMaterial 106 is C₉ ⁺Aromatic hydrocarbons;

the adsorption separation unit comprises a pipeline 209 for feeding the overhead discharge 205 of the xylene fractionation unit after heat exchange into an adsorption separation tower, a pipeline 210 for sending the p-xylene-rich extract separated from the adsorption separation tower 201 to an extract fractionation tower 202, and a pipeline 214 for sending the p-xylene-poor raffinate obtained by adsorption separation in the adsorption separation tower 201 to a raffinate column 203; a line 211 for withdrawing overhead 206 from the extract fractionator 202, and a line 212 for withdrawing side 207 from the extract fractionator 202; the material at the bottom of the extract fractionating tower 202 is sent to a pipeline 213 of a heat exchanger II204, the material at the bottom of the raffinate tower (desorbent) is sent to a pipeline 217 of the heat exchanger II204, and the material at the bottom of the extract fractionating tower 202 and the material at the bottom of the raffinate tower after heat exchange are sent to a pipeline 218 of the adsorption separation tower 201; the upper side draw 215 of the raffinate column 203 is heat exchanged in exchanger II204 and fed 208 to line 216 of the isomerization unit.

The isomerization reaction unit comprises a feed line 316 for feeding the isomerization reaction feed 208 to the isomerization reactor 301, wherein the feed line 216 is connected with a heat exchanger III306, a heat exchanger IV307 and an isomerization reaction heating furnace 305 in sequence through lines 314, 315 and 316 before being connected with the isomerization reactor 301; a feed line 318 for feeding the isomerized reaction product to the isomerized product fractionation column 302, the feed line 317 connecting to the heat exchanger IV307 prior to connecting to the isomerized product fractionation column 302; a purge gas 312 to a purge gas feed line 319, an isomerization reactor 301 hydrogen take-off line 320, a line 322 connected to make-up hydrogen 309 feed line 323, a vent line 321 for venting a portion of the hydrogen 313 as the hydrogen partial pressure is reduced; a hydrogen feed line 323 connects to compressor 304 and a post-pressurization line 324 connects to isomerization feed line 314. The isomerization fractionator 302 overhead 310 exits the plant directly via line 325; the side material of the isomerization product fractionating tower 302 is fed into a feeding pipeline 327 of the clay tower 303, the feeding pipeline 326 is connected with the front of the clay tower 303 and is connected with a heat exchanger V308, and a pipeline 327 after heat exchange is connected with the clay tower 303; a discharge pipeline 328 at the bottom of the clay tower 303 is connected with a heat exchanger V308, and a pipeline 329 after heat exchange is connected with the adsorption separation feed pipeline 110; the isomerate fractionation column 302 bottoms 311 exits the unit via line 330.

The process flow of the device for producing the aromatic hydrocarbon product comprises the following steps:

containing C₈The aromatic hydrocarbon mixture raw material 104 enters a xylene column 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 column 101 as reflux, the other part of the tower top material serves as adsorption separation feed 105, and then the tower top material is sent to an adsorption separation column 201 after heat exchange with isomerization reaction feed through a heat exchanger III 306; the bottom material of the tower returns to the xylene tower 101 after passing through the xylene reboiling furnace 103 and the temperature is raised, and the other part of the bottom material 106 is C₉ ⁺An aromatic hydrocarbon.

The adsorption separation feed 205 is subjected to adsorption separation by an adsorption separation tower 201, the obtained paraxylene-rich extract enters an extract fractionating tower 202 for fractionation, a tower bottom material is a desorbent, and after being mixed with a tower bottom material of a raffinate tower 203, the desorbent exchanges heat with the isomerization reaction feed by a heat exchanger II204 and returns to the adsorption separation tower 201; the material at the top of the extract fractionating tower 202 is toluene 206; the side stream material is p-xylene 207; the p-xylene depleted raffinate obtained by adsorption separation in the adsorption separation tower 201 enters a raffinate tower 203 for fractionation, and the upper side line material passes through a heat exchanger II204, a heat exchanger III306 and a heat exchanger IV307 in sequence to exchange heat with a desorbent, an adsorption separation feed and an isomerization reaction product respectively; then the reaction product is heated by an isomerization heating furnace 305 and enters an isomerization membrane reactor 301 for isomerization reaction, and the reaction product enters an isomerization product fractionating tower 302 after heat exchange by a heat exchanger IV 307; hydrogen which does not participate in the reaction in the isomerization membrane reactor passes through the membrane and leaves the reactor 301 under the action of the purge gas; the hydrogen is mixed with make-up hydrogen 309 and then pressurized by compressor 304 and mixed with reaction feed 208. The isomerization fractionator 302 overhead 310 exits the plant directly; the side stream material of the isomerization product fractionating tower 302 exchanges heat through a heat exchanger V308, enters a clay tower 303 to remove unsaturated hydrocarbons such as olefin and the like, and the material discharged from the clay tower 303 exchanges heat with the side stream material of the isomerization product fractionating tower 302 and is mixed with the adsorption separation feed 105; the bottoms 311 of the isomerate fractionation column 302 is taken as C₉ ⁺And (5) discharging aromatic hydrocarbon.

Process flow of conventional xylene plantComprises the following steps: 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 feed 405, and after heat exchange is carried out on the overhead material and the feed of a deheptanizer 602 by a heat exchanger VI609, the overhead material is sent to an adsorption separation column 501; the bottom material of the tower returns to the xylene tower 401 after passing through the xylene reboiling furnace 403 and the temperature is raised, and the other part of the bottom material 406 is C₉ ⁺An aromatic hydrocarbon. The tower top material flow is mainly used as a heat source of a reboiler of the raffinate tower 503 and a reboiler of the extract tower 502; the bottoms stream serves primarily as the heat source for the finishing column reboiler 506 and the deheptanizer 602 reboilers.

The adsorption separation feeding 507 is subjected to adsorption separation by an adsorption separation tower 501, the obtained p-xylene-rich extract enters an extract tower 502 for fractionation, the tower bottom material is a desorbent, and is mixed with the tower bottom material of a raffinate tower 503 to be used as a heat source of a finished product tower reboiler 505 and then returns to the adsorption separation tower 501; the material at the top of the extract tower 502 enters a finished product tower 504, the material at the bottom of the finished product tower is p-xylene 509, and the 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 III606 and a heat exchanger IV607 in sequence, is respectively subjected to heat exchange with the feed of the deheptanizer and the isomerization reaction product, then enters an isomerization reactor 601 for isomerization reaction after being heated by an isomerization reaction heating furnace 605, and enters a gas-liquid separation tank 604 after being subjected to heat exchange by the heat exchanger IV607, and is cooled by an air cooler 611 and a water cooler 612 to be 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 separation in the gas-liquid separation tank 604 enters the deheptanizer 602 after heat exchange in the heat exchanger III606, the heat exchanger V608 and the heat exchanger VI 609. The material at the top of the deheptanizer 602 is C₇The bottom material of the light hydrocarbon 615 is returned to the xylene column 401 after passing through a heat exchanger V608 and unsaturated hydrocarbons such as olefin are removed by a clay column 603.

The effect of the novel p-xylene production process provided by the present invention is specifically illustrated by the following examples.

Comparative example 1

Comparative example 1 illustrates the process and energy consumption of a conventional para-xylene production process. The equipment used is shown in Table 1, some key operating parameters are shown in Table 2, and the energy consumption of the apparatus is shown in Table 3.

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, some key operating parameters are shown in Table 2, and the energy consumption of the apparatus is shown in Table 3.

TABLE 1

TABLE 2

TABLE 3

As can be seen from table 1, the process for producing paraxylene according to the present invention can save investment in 1 set of rectifying column, cooler and reboiler equipment, and the number of 1 heat exchanger, gas-liquid separation tank, air cooler and water cooler, compared to comparative example 1. The temperature of the isomerization reaction heating furnace is increased, the inlet pressure of the compressor is increased, and the purity of the circulating hydrogen is improved, so that the fuel gas consumption of the heating furnace is reduced, the power consumption of the compressor is reduced, and the hydrogen supplement consumption is reduced. The method provided by the invention not only reduces the number of equipment, but also reduces the fuel gas consumption of the heating furnace, the power consumption of the compressor and the hydrogen supplement consumption, and the energy consumption is reduced by 19.5%. Therefore, the novel p-xylene production method provided by the invention can reduce the operation loads of the clay tower and the xylene tower, save the fuel gas consumption of the reboiling furnace of the xylene tower, simultaneously save the condensation and reboiling loads, reduce the equipment investment and the occupied area, reduce the back mixing of materials and improve the thermodynamic efficiency of separation; the phenomenon of unreasonable energy utilization of cooling 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; by optimizing the heat exchange network, the feeding heating of the deheptanizer after the heat is used for heating and cooling is avoided, cold and hot material flows are reasonably matched, and the temperature in front of the feeding furnace of the isomerization reaction is increased, so that the use amount of fuel gas of the isomerization reaction heating furnace is reduced, the energy consumption is greatly reduced, and the economic benefit and the social benefit are improved.