阅读说明：本技术 一种富乙烯气制乙苯的闪蒸分离工艺与装置 (Flash separation process and device for preparing ethylbenzene from ethylene-rich gas ) 是由 陈晓宇 朱炜玄 刘宏 韩志忠 董宏光 李香琴 于 2021-07-02 设计创作，主要内容包括：本发明提供了一种富乙烯气制乙苯的闪蒸分离装置及其分离方法,属于属于烃类裂解装置下游的富乙烯气与苯烷基化生产乙苯的技术领域。本分离装置经过上游预处理的原料气,溶解于原料苯后进入烷基化反应器；烷基化反应产物首先进入多级闪蒸系统,经过一级或多级闪蒸后,液相物料进入苯塔进行分离,气相物料进入脱轻组分塔脱除轻组分；苯塔塔底物料进入乙苯塔进一步分离,乙苯塔塔底物料进入多乙苯塔进一步分离,多乙苯塔塔顶为循环多乙苯产品,塔底物料为乙苯单元残油。与传统分离方法相比,本发明中取消了脱乙烷塔,改为多级闪蒸系统,具有设备投资小、装置能耗低等优势。(The invention provides a flash separation device and a flash separation method for preparing ethylbenzene from ethylene-rich gas, belonging to the technical field of production of ethylbenzene by alkylation of ethylene-rich gas and benzene at the downstream of a hydrocarbon cracking device. The raw material gas pretreated by the upstream of the separation device is dissolved in the raw material benzene and then enters an alkylation reactor; the alkylation reaction product firstly enters a multi-stage flash system, after one-stage or multi-stage flash evaporation, liquid-phase material enters a benzene tower for separation, and gas-phase material enters a light component removal tower for removing light components; the material at the bottom of the benzene tower enters an ethylbenzene tower for further separation, the material at the bottom of the ethylbenzene tower enters a polyethylbenzene tower for further separation, a circulating polyethylbenzene product is arranged at the top of the polyethylbenzene tower, and the material at the bottom of the ethylbenzene tower is ethylbenzene unit residual oil. Compared with the traditional separation method, the method cancels the deethanizer and changes the deethanizer into a multi-stage flash evaporation system, and has the advantages of small equipment investment, low energy consumption of the device and the like.)

1. The flash separation device for preparing ethylbenzene from ethylene-rich gas is characterized by comprising an alkylation reactor (1), a transalkylation reactor (2), a multistage flash system (3), a benzene tower (4), a benzene tower condenser (5), a light component removal tower (6), a light component removal tower condenser (7), a tail gas cooler (8), a light component removal tower reflux tank (9), a recycle benzene tank (10), a benzene tower reflux tank (11), an ethylbenzene tower (12), an ethylbenzene tower condenser (13), an ethylbenzene tower reflux tank (14), a polyethylbenzene tower (15), a polyethylbenzene tower condenser (16) and a polyethylbenzene tower reflux tank (17);

Dissolving the feed gas subjected to upstream treatment in the raw material benzene, and then feeding the raw material benzene into an alkylation reactor (1), wherein the alkylation reactor (1) is communicated with a multistage flash evaporation system (3); the multistage flash system (3) comprises multistage flash tanks, wherein gas phase at the outlet of the previous flash tank enters the next flash tank, gas phase at the outlet of the last flash tank enters the light component removal tower (6), and liquid phase at the outlet of each flash tank enters the benzene tower (4); a lateral line outlet of the benzene tower (4) is communicated with an inlet of a circulating benzene tank (10), the raw material benzene is supplemented from the other inlet of the circulating benzene tank (10), and two outlets of the circulating benzene tank (10) are respectively communicated with the alkylation reactor (1) and the transalkylation reactor (2); a transalkylation reaction product generated by the transalkylation reactor (2) enters the benzene tower (4), and the outlet at the bottom of the benzene tower (4) is communicated with the inlet of the ethylbenzene tower (12); the gas phase of the benzene tower (4) enters a benzene tower reflux tank (11) through a benzene tower condenser (5), the liquid phase of the benzene tower reflux tank (11) flows in from the top of the benzene tower (4) through a reflux pump, and the gas phase of the benzene tower reflux tank (11) enters a light component removal tower (6); the gas phase of the light component removal tower (6) flows into a light component removal tower reflux tank (9) from the top of the tower through a light component removal tower condenser (7), the gas phase of the light component removal tower reflux tank (9) enters a tail gas cooler (8), the liquid phase cooled by the tail gas cooler (8) reflows to the light component removal tower reflux tank (9), and the liquid phase at the bottom of the light component removal tower reflux tank (9) reflows to the light component removal tower (6) through a reflux pump; the outlet of the tower bottom of the ethylbenzene tower (12) is communicated with the inlet of a polyethylbenzene tower (15), the gas phase of the ethylbenzene tower (12) enters an ethylbenzene tower reflux tank (14) through an ethylbenzene tower condenser (13), one part of the gas phase flows back to the ethylbenzene tower (12) through a reflux pump, and the other part of the gas phase is used as a high-purity ethylbenzene product; the gas phase of the polyethylbenzene tower (15) enters a reflux tank (17) of the polyethylbenzene tower through a condenser (16) of the polyethylbenzene tower, one part of reflux pump flows back to the polyethylbenzene tower (15), and the other part of reflux pump is used as circulating polyethylbenzene; the ethylbenzene unit residue in the polyethylbenzene tower (15) flows out from the outlet of the tower bottom.

2. The flash separation device for preparing ethylbenzene from the ethylene-rich gas as claimed in claim 1, wherein the flash evaporation system (3) comprises 1-5 stages.

3. The flash separation device for preparing ethylbenzene from the ethylene-rich gas as claimed in claim 1 or 2, wherein the number of theoretical plates of the light component removal tower (6) is 15-30.

4. A flash separation method for preparing ethylbenzene from ethylene-rich gas is characterized by comprising the following steps:

(1) raw material gas subjected to upstream pretreatment is dissolved in raw material benzene to form a feed stream, and the feed stream enters an alkylation reactor (1); in the alkylation reactor (1), benzene and ethylene are subjected to alkylation reaction; the alkylation reaction product firstly enters a multi-stage flash evaporation system (3), after one-stage or multi-stage flash evaporation, liquid-phase material enters a benzene tower (4) for separation, and gas-phase material enters a light component removal tower (6);

(2) the light component removal tower (6) is not provided with a reboiler, and the gas phase material at the top of the light component removal tower (6) is condensed in a light component removal tower condenser (7); the gas phase material in the light component removal tower reflux tank (9) is further condensed by circulating cooling water in a tail gas cooler (8), and tail gas enters a subsequent absorption device; the liquid phase material distilled from the light component removal tower reflux tank (9) is used as reflux and returned to the top of the light component removal tower (6) through a reflux pump;

(3) The feeding of the benzene tower (4) is liquid phase material of a multi-stage flash system (3), alkyl transfer reaction product and tower bottom material of a light component removal tower (6), circulating benzene extracted from the side line of the benzene tower (4) enters a circulating benzene tank (10) and is used as the feeding of an alkylation reactor (1) and an alkyl transfer reactor (2), and non-condensable gas of the benzene tower (4) returns to the tower bottom of the light component removal tower (6) and is used as a heat source;

(4) the material at the bottom of the benzene tower (4) enters an ethylbenzene tower (12) for further separation, the product at the top of the ethylbenzene tower (12) is high-purity ethylbenzene, the material at the bottom of the benzene tower (4) enters a polyethylbenzene tower (15) for further separation, the product at the top of the polyethylbenzene tower (15) is a circulating polyethylbenzene product, and the material at the bottom of the tower is ethylbenzene unit residual oil.

5. The flash distillation separation method for preparing ethylbenzene by using the ethylene-rich gas as claimed in claim 4, wherein the first stage flash distillation pressure is controlled to be 2.5 MPa-3.5 MPa according to the outlet pressure of the alkylation reactor (1), and the last stage flash distillation pressure is controlled to be 1 MPa-2 MPa according to the operation conditions of the subsequent separation device of the flash distillation system.

6. The flash separation method for preparing ethylbenzene by rich ethylene gas as claimed in claim 4 or 5, wherein the non-condensable gas and the multi-stage flash vapor phase material in the benzene tower (4) enter from the bottom of the light component removal tower (6), and the condenser (7) of the light component removal tower is used for generating low-pressure steam or high-temperature heat medium water; the cooling temperature of the tail gas cooler is 40-60 ℃.

Technical Field

The invention belongs to the technical field of production of ethylbenzene by alkylation of ethylene-rich gas and benzene at the downstream of a hydrocarbon cracking device, and relates to a flash separation process and a flash separation device for preparing ethylbenzene from ethylene-rich gas.

Background

Ethylbenzene is one of the most commercially available derivatives of benzene and is an important chemical intermediate, and ethylene products at various concentrations in the ethylene industry can be used to produce ethylbenzene, while more than 90% of the world's ethylbenzene production is used to produce styrene, which is then polymerized to polystyrene, among other applications including paint solvents and pharmaceuticals. The method for producing ethylbenzene mainly comprises a gas phase method and a liquid phase method, wherein the gas phase method is mainly used as raw materials of various dry gases (catalytic cracking dry gases and the like) in a refinery, and the liquid phase method has high requirements on the concentration of raw material ethylene and is generally polymerization-grade ethylene. For some hydrocarbon cracking gases, the mass fraction of ethylene is more than 50%, and a liquid phase method can be used for producing the ethylbenzene process after the raw material gas is pretreated, so that the problems of high impurity content of the ethylbenzene product, high energy consumption of a device and the like in a gas phase method process are solved.

Patent CN102267859A discloses a method for producing ethylbenzene by using ethylene gas containing inert components, wherein an alkylation reactor is divided into a reaction section and an absorption section, raw material gas flows from top to bottom and is in countercurrent contact with an absorbent, so that the contact of gas-phase ethylene and a catalyst is avoided, and the coking and inactivation of the catalyst are relieved. But the absorption rate of the ethylene in the raw material gas is 90-95%, which causes the waste of a part of ethylene resources.

Patent CN107827692A discloses a method for producing ethylbenzene by using high-concentration ethylene gas, in which raw material concentrated ethylene dry gas is divided into multiple strands and correspondingly fed into multiple absorption towers, and the absorbent is a mixture of alkylation reaction raw material benzene and generated ethylbenzene and diethylbenzene, and is supplemented from the first-stage absorption tower. The gas phase material that comes out from the absorption tower gets into gas phase alkylation reactor and handles, and the liquid phase material gets into liquid phase alkylation reactor reaction, and this patent has increased a small-size gas phase method alkylation reactor, has guaranteed the make full use of ethylene resource, has increased a plurality of absorption towers and liquid phase alkylation reactor with, leads to the equipment investment increase.

Patent CN110055098A discloses a separation process for an ethylbenzene production device by ethylene-rich pyrolysis dry gas classification, which utilizes a coupling process of membrane separation, compression condensation and rectification to separate the pyrolysis dry gas into a low-concentration ethylene (less than 20 mol%) raw material and a high-concentration ethylene (greater than 60 mol%) raw material, and the raw materials are respectively used as raw materials of a dry gas ethylbenzene production device and a liquid-phase ethylbenzene production device to produce ethylbenzene. The problem of over-temperature of a dry gas ethylbenzene preparation reactor is avoided, reasonable utilization of high-concentration ethylene is realized, and practical industrial application is difficult due to the fact that downstream of the dry gas ethylbenzene preparation reactor needs to be respectively matched with a gas-phase method device and a liquid-phase ethylbenzene preparation device.

Patent US20060204410a1 discloses a technology for preparing ethylbenzene by catalytic distillation of ethylene, which requires less catalyst than the conventional process and achieves higher total conversion rate of ethylene. For unreacted ethylene gas in the catalytic distillation unit, a tail gas absorption tower and a post reactor are arranged in the process flow of the patent, and are used for recovering ethylene resources in the non-condensable gas, so that the ethylene resources are fully utilized.

Patent WO2018052804a1 discloses a technology for preparing ethylbenzene from ethylene with an ethane recovery system, wherein a raw material rich in ethylene containing inert gas is passed through a reboiling absorption tower to remove light-end components such as hydrogen and methane, a set of ethane recovery system is arranged in the process flow, ethane is almost completely recovered from tail gas, and the ethane gas can be injected into an ethane cracking furnace to produce additional ethylene and improve economic benefits.

Disclosure of Invention

The invention aims to provide a separation method and a separation device for producing ethylbenzene by alkylating ethylene-rich gas and benzene.

The technical scheme of the invention is as follows:

the utility model provides a flash distillation separator of rich ethylene gas system ethylbenzene, includes alkylation reactor 1, transalkylation reactor 2, multistage flash system 3, benzene tower 4, benzene tower condenser 5, takes off light component tower 6, takes off light component tower condenser 7, tail gas cooler 8, takes off light component tower reflux tank 9, circulation benzene jar 10, benzene tower reflux tank 11, ethylbenzene tower 12, ethylbenzene tower condenser 13, ethylbenzene tower reflux tank 14, polyethyl benzene tower 15, polyethyl benzene tower condenser 16, polyethyl benzene tower reflux tank 17.

Dissolving the feed gas subjected to upstream treatment in the raw material benzene, and then feeding the raw material benzene into an alkylation reactor 1, wherein the alkylation reactor 1 is communicated with a multistage flash evaporation system 3; the multistage flash system 3 comprises multistage flash tanks, wherein gas phase at the outlet of the previous flash tank enters the next flash tank, gas phase at the outlet of the last flash tank enters the light component removal tower 6, and liquid phase at the outlet of each flash tank enters the benzene tower 4; the outlet of the side line of the benzene tower 4 is communicated with the inlet of a circulating benzene tank 10, the raw material benzene is supplemented from the other inlet of the circulating benzene tank 10, and two outlets of the circulating benzene tank 10 are respectively communicated with an alkylation reactor 1 and a transalkylation reactor 2; the transalkylation reaction product generated by the transalkylation reactor 2 enters a benzene tower 4, and the outlet at the bottom of the benzene tower 4 is communicated with the inlet of an ethylbenzene tower 12; the gas phase of the benzene tower 4 enters a benzene tower reflux tank 11 through a benzene tower condenser 5, the liquid phase of the benzene tower reflux tank 11 flows in from the top of the benzene tower 4 through a reflux pump, and the gas phase of the benzene tower reflux tank 11 enters a light component removal tower 6; the gas phase of the light component removal tower 6 flows into a light component removal tower reflux tank 9 from the top of the tower through a light component removal tower condenser 7, the gas phase of the light component removal tower reflux tank 9 enters a tail gas cooler 8, the liquid phase cooled by the tail gas cooler 8 reflows to the light component removal tower reflux tank 9, and the liquid phase at the bottom of the light component removal tower reflux tank 9 reflows to the light component removal tower 6 through a reflux pump; the outlet of the tower bottom of the ethylbenzene tower 12 is communicated with the inlet of a polyethylbenzene tower 15, the gas phase of the ethylbenzene tower 12 enters an ethylbenzene tower reflux tank 14 through an ethylbenzene tower condenser 13, one part of the gas phase flows back to the ethylbenzene tower 12 through a reflux pump, and the other part of the gas phase is used as a high-purity ethylbenzene product; the gas phase of the polyethylbenzene tower 15 enters a polyethylbenzene tower reflux tank 17 through a polyethylbenzene tower condenser 16, one part of reflux pump flows back to the polyethylbenzene tower 15, and the other part of reflux pump is used as circulating polyethylbenzene; the ethylbenzene unit residue in the polyethylbenzene column 15 flows out from the bottom outlet.

A flash separation device for preparing ethylbenzene from ethylene-rich gas comprises a first-stage flash tank V101, a second-stage flash tank V102, a third-stage flash tank V103, a fourth-stage flash tank V104 and a fifth-stage flash tank V105.

The alkylation reaction product B firstly enters a first-stage flash tank V101, the outlet gas phase of the first-stage flash tank V101 is communicated with the inlet of a second-stage flash tank V102, the outlet gas phase of the second-stage flash tank V102 is communicated with the inlet of a third-stage flash tank V103, the outlet gas phase of the third-stage flash tank V103 is communicated with the inlet of a fourth-stage flash tank V104, the outlet gas phase of the fourth-stage flash tank V104 is communicated with the inlet of a fifth-stage flash tank V105, and the outlet liquid phase of the first-stage flash tank V101, the outlet liquid phase of the second-stage flash tank V102, the outlet liquid phase of the third-stage flash tank V103, the outlet liquid phase of the fourth-stage flash tank V104 and the outlet liquid phase of the fifth-stage flash tank V105 are mixed and then communicated with the inlet of the benzene tower 4.

The number of theoretical plates of the light component removing tower 6 is 15-30.

In the device of the present invention, the communication and connection between the equipments and between the pipelines and the equipments can be set according to the requirement, and the equipments are not limited to the connection described above.

The multistage flash system 3 is provided with a plurality of flash systems according to requirements and is connected in series in sequence.

A flash separation method for preparing ethylbenzene from ethylene-rich gas uses the device and comprises the following steps:

(1) dissolving the raw material gas subjected to upstream pretreatment in the raw material benzene to form a feed stream, and feeding the feed stream into an alkylation reactor 1; in the alkylation reactor 1, benzene and ethylene are subjected to alkylation reaction; the alkylation reaction product firstly enters a multi-stage flash evaporation system 3, after one-stage or multi-stage flash evaporation, liquid-phase materials enter a benzene tower 4 for separation, and gas-phase materials enter a light component removal tower 6;

(2) the light component removal tower 6 is not provided with a reboiler, and the gas phase material at the top of the light component removal tower 6 is condensed in a light component removal tower condenser 7; the gas phase material in the light component removal tower reflux tank 9 is further condensed by circulating cooling water in a tail gas cooler 8, and tail gas enters a subsequent absorption device; the liquid phase material distilled from the light component removal tower reflux tank 9 is used as reflux and returned to the top of the light component removal tower 6 through a reflux pump;

(3) the feeding of the benzene tower 4 is liquid phase material of the multi-stage flash system 3, alkyl transfer reaction product and material at the bottom of the light component removing tower 6, the circulating benzene extracted from the side line of the benzene tower 4 enters a circulating benzene tank 10 to be used as the feeding of the alkylation reactor 1 and the alkyl transfer reactor 2, and the non-condensable gas of the benzene tower 4 returns to the bottom of the light component removing tower 6 to be used as a heat source;

(4) The material at the bottom of the benzene tower 4 enters an ethylbenzene tower 12 for further separation, the product at the top of the ethylbenzene tower 12 is high-purity ethylbenzene, the material at the bottom of the benzene tower enters a polyethylbenzene tower 15 for further separation, the product at the top of the polyethylbenzene tower 15 is a circulating polyethylbenzene product, and the material at the bottom of the tower is ethylbenzene unit residual oil.

According to the difference of the outlet pressure of the alkylation reactor 1, the first stage flash evaporation pressure is controlled to be 2.5 MPa-3.5 MPa, and according to the operation condition of the subsequent separation device of the flash evaporation system, the last stage flash evaporation pressure is controlled to be 1 MPa-2 MPa.

The non-condensable gas and the multi-stage flash vapor phase material of the benzene tower 4 enter from the bottom of the light component removal tower 6, and a condenser 7 of the light component removal tower is used for generating low-pressure steam or high-temperature heating medium water; the cooling temperature of the tail gas cooler is 40-60 ℃.

The invention has the beneficial effects that: compared with the traditional separation method, the method cancels the deethanizer and changes the deethanizer into a multi-stage flash evaporation system, and has the advantages of small equipment investment, low energy consumption of the device and the like.

Drawings

FIG. 1 is a process flow diagram of the present invention (with a portion of the separation section omitted).

In the figure: 1 alkylation reactor, 2 transalkylation reactor, 3 multistage flash systems, 4 benzene towers, 5 benzene tower condensers, 6 light component removal towers, 7 light component removal tower condensers, 8 tail gas coolers, 9 light component removal tower reflux tanks, 10 circulating benzene tanks, 11 benzene tower reflux tanks, 12 ethylbenzene towers, 13 ethylbenzene tower condensers, 14 ethylbenzene tower reflux tanks, 15 polyethylbenzene towers, 16 polyethylbenzene tower condensers and 17 polyethylbenzene tower reflux tanks.

FIG. 2 is a schematic of a multi-stage flash system of the present invention.

In the figure, V101 is a first-stage flash tank, V102 is a second-stage flash tank, V103 is a third-stage flash tank, V104 is a fourth-stage flash tank, and V105 is a fifth-stage flash tank.

Detailed Description

The technical solution of the present invention will be clearly and completely described below. It is to be understood that the described embodiments are merely a few embodiments of the invention, and not all embodiments. All other embodiments that can be modified or adapted by one of ordinary skill in the art based on the embodiments of the present invention are within the scope of the present invention.

The utility model provides a flash distillation separator of rich ethylene gas system ethylbenzene, includes alkylation reactor 1, transalkylation reactor 2, multistage flash system 3, benzene tower 4, benzene tower condenser 5, takes off light component tower 6, takes off light component tower condenser 7, tail gas cooler 8, takes off light component tower reflux tank 9, circulation benzene jar 10, benzene tower reflux tank 11, ethylbenzene tower 12, ethylbenzene tower condenser 13, ethylbenzene tower reflux tank 14, polyethyl benzene tower 15, polyethyl benzene tower condenser 16, polyethyl benzene tower reflux tank 17.

Dissolving the feed gas subjected to upstream treatment in the raw material benzene, and then feeding the raw material benzene into an alkylation reactor 1, wherein the alkylation reactor 1 is communicated with a multistage flash evaporation system 3; the multistage flash system 3 comprises multistage flash tanks, wherein gas phase at the outlet of the previous flash tank enters the next flash tank, gas phase at the outlet of the last flash tank enters the light component removal tower 6, and liquid phase at the outlet of each flash tank enters the benzene tower 4; the outlet of the side line of the benzene tower 4 is communicated with the inlet of a circulating benzene tank 10, the raw material benzene is supplemented from the other inlet of the circulating benzene tank 10, and two outlets of the circulating benzene tank 10 are respectively communicated with an alkylation reactor 1 and a transalkylation reactor 2; the transalkylation reaction product generated by the transalkylation reactor 2 enters a benzene tower 4, and the outlet at the bottom of the benzene tower 4 is communicated with the inlet of an ethylbenzene tower 12; the gas phase of the benzene tower 4 enters a benzene tower reflux tank 11 through a benzene tower condenser 5, the liquid phase of the benzene tower reflux tank 11 flows in from the top of the benzene tower 4 through a reflux pump, and the gas phase of the benzene tower reflux tank 11 enters a light component removal tower 6; the gas phase of the light component removal tower 6 flows into a light component removal tower reflux tank 9 from the top of the tower through a light component removal tower condenser 7, the gas phase of the light component removal tower reflux tank 9 enters a tail gas cooler 8, the liquid phase cooled by the tail gas cooler 8 reflows to the light component removal tower reflux tank 9, and the liquid phase at the bottom of the light component removal tower reflux tank 9 reflows to the light component removal tower 6 through a reflux pump; the outlet of the tower bottom of the ethylbenzene tower 12 is communicated with the inlet of a polyethylbenzene tower 15, the gas phase of the ethylbenzene tower 12 enters an ethylbenzene tower reflux tank 14 through an ethylbenzene tower condenser 13, one part of the gas phase flows back to the ethylbenzene tower 12 through a reflux pump, and the other part of the gas phase is used as a high-purity ethylbenzene product; the gas phase of the polyethylbenzene tower 15 enters a polyethylbenzene tower reflux tank 17 through a polyethylbenzene tower condenser 16, one part of reflux pump flows back to the polyethylbenzene tower 15, and the other part of reflux pump is used as circulating polyethylbenzene; the ethylbenzene unit residue in the polyethylbenzene column 15 flows out from the bottom outlet.

Example 1:

by taking a certain device for preparing ethylbenzene from ethylene-rich gas as an example, by adopting the device and the process method, a plurality of flash tanks in the multistage flash system 3 can be arranged as required, two flash tanks are arranged in the embodiment, and the flow chart is shown in fig. 1.

Most of light-end components (hydrogen, nitrogen, methane and the like) are removed from the feed gas after upstream treatment, the feed gas is dissolved in the raw material benzene and then enters an alkylation reactor 1, and the alkylation reaction product enters the process of the invention: the alkylation reaction product firstly enters a multistage flash system 3, the outlet pressure of a first-stage flash tank is 2.5MPa, the outlet pressure of a second-stage flash tank is 1.5MPa, and the outlet gas phase of the second-stage flash tank enters the bottom of a light component removal tower 6 to recover benzene, ethylbenzene, polyethylbenzene and the like. The condenser 7 of the light component removal tower is used for generating low-pressure steam, and the gas phase at the outlet of the reflux tank 9 of the light component removal tower is sent to a subsequent absorption device after being condensed by the tail gas cooler 8. The feeding material of the benzene tower 4 is a transalkylation reaction product, a light component removing tower 6 tower bottom material and a multi-stage flash system 3 liquid phase material, the benzene tower condenser 5 is used for generating low pressure steam, the benzene tower non-condensable gas contains a small amount of light components such as ethane and the like, the light components are removed from the bottom of the light component removing tower 6, and the light components are used as a heat source of the light component removing tower 6. The recycle benzene is extracted from the side line of the benzene tower 4 to the recycle benzene tank 10, meanwhile, the fresh benzene is also supplemented to the recycle benzene tank 10, the recycle benzene is divided into two branches and is respectively used as raw materials of alkylation reaction and transalkylation reaction. Crude ethylbenzene in the tower bottom of the benzene tower 4 enters an ethylbenzene tower 12 for separation, low-pressure steam is generated in an ethylbenzene tower condenser 13, a high-purity ethylbenzene product is extracted from the tower top, tower bottom materials are sent to a polyethylbenzene tower 15, low-pressure steam is generated in a polyethylbenzene tower condenser 16, a polyethylbenzene product M is extracted from the tower top, ethylbenzene residual oil O is extracted from the tower bottom, and data results are shown in tables 1 and 2.

Table 1 main logistics data sheet

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TABLE 2 comparison of major energy consumption

In the embodiment, compared with the traditional separation method, the invention cancels the deethanizer, changes the deethanizer into a multi-stage flash evaporation system, saves part of equipment investment, only increases 399kW of load of the reboiler of the benzene tower, does not set a reboiler of the light component removal tower, and uses the uncondensed gas of the benzene tower as a heat source, so that the load of the reboiler of the light component removal tower is reduced by 3862kW, and the operation cost is greatly reduced.

Example 2

The device and method of example 2 are the same as those of example 1, and the process parameters are different. By adopting the device and the process method, a plurality of flash tanks in the multi-stage flash system can be arranged as required, two flash tanks are arranged in the embodiment, and the flow chart is shown in figure 1.

Most of light-end components (hydrogen, nitrogen, methane and the like) are removed from the feed gas after upstream treatment, the feed gas is dissolved in the raw material benzene and then enters an alkylation reactor 1, and the alkylation reaction product enters the process of the invention: the alkylation reaction product firstly enters a multistage flash system 3, the outlet pressure of a first-stage flash tank is 3MPa, the outlet pressure of a second-stage flash tank is 2MPa, the subsequent flow is consistent with that of example 1, and the data results are shown in tables 3 and 4.

TABLE 3 Main Logistics data sheet

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TABLE 4 comparison of major energy consumptions

In the embodiment, compared with the traditional separation method, the invention cancels the deethanizer, changes the deethanizer into the multi-stage flash system 3, saves part of equipment investment, increases the load of the reboiler of the benzene tower 4 by only 202kW, does not set a reboiler for the light component removal tower 6, and uses the non-condensed gas of the benzene tower 4 as a heat source, so that the load of the reboiler of the light component removal tower 6 is reduced by 3862kW, and the operation cost is greatly reduced.

This description is intended to be exemplary rather than a complete description, and all other embodiments which may be modified or adapted by those skilled in the art are intended to be within the scope of the present invention.