Method and system for increasing yield of ethylene by using refinery dry gas

文档序号:931647 发布日期:2021-03-05 浏览:17次 中文

阅读说明:本技术 一种利用炼厂干气增产乙烯的方法及系统 (Method and system for increasing yield of ethylene by using refinery dry gas ) 是由 彭光勤 杨书显 汪文强 洪成龙 徐庆辉 李涛 温建成 尚纪兵 窦志俊 王晓猛 胡 于 2020-12-02 设计创作,主要内容包括:本发明提供了一种利用炼厂干气增产乙烯的方法及其系统,包括以下步骤:(1)将轻石脑油送至正异构分离单元以产生正构组分和非正构组分;(2)将非正构组分送至加氢裂化单元并经分离得到炼厂干气、丙烷、正丁烷和异丁烷;将非正构组分也可送至芳构化单元,经分离别得到炼厂干气、丙烷、正丁烷和异丁烷和C5+组分;(3)将炼厂干气经深冷分离装置得到乙烷,将乙烷经蒸汽裂解装置得到乙烯。本发明提供的制备方法大大提高低乙烯的收率,显著提高石脑油的利用效率,实现资源的合理配置。(The invention provides a method and a system for increasing the yield of ethylene by using refinery dry gas, which comprises the following steps: (1) passing the light naphtha to an orthoisomerization separation unit to produce normal components and non-normal components; (2) sending the non-normal components to a hydrocracking unit and separating to obtain refinery dry gas, propane, normal butane and isobutane; sending the non-normal components to an aromatization unit, and separating to obtain refinery dry gas, propane, normal butane, isobutane and C5+ components; (3) the refinery dry gas is processed by a cryogenic separation device to obtain ethane, and the ethane is processed by a steam cracking device to obtain ethylene. The preparation method provided by the invention greatly improves the yield of low ethylene, obviously improves the utilization efficiency of naphtha and realizes reasonable allocation of resources.)

1. A preparation method of low-carbon olefin is characterized by comprising the following steps:

(1) passing the light naphtha to an orthoisomerization separation unit to produce normal components and non-normal components;

(2) sending the non-normal components to a hydrocracking unit, and further separating the hydrocracking product to obtain refinery dry gas; and/or sending the non-normal components to an aromatization unit, and further separating aromatization products to obtain refinery dry gas;

(3) sending the refinery dry gas produced in step (2) and the dry gases produced in other units of the refinery, except the hydrocracking unit and the aromatization unit, to a cryogenic separation unit to produce ethane and a fuel gas comprising C1, and sending the produced ethane to a steam cracking unit to produce ethylene.

2. The method of claim 1, wherein the light naphtha comprises C5-C6 alkanes; the normal component comprises normal C5-C6 alkane; the non-normal component comprises isomeric C5-C6 alkane.

3. The method of claim 1, wherein the normal components produced in step (1) are sent to a steam cracking unit to produce ethylene and propylene.

4. The method of claim 1, wherein the refinery-related dry gas comprises C1-C2 components.

5. The method according to claim 1, wherein the light naphtha is subjected to normal isomerization separation by distillation or adsorption.

6. The method of claim 1, wherein the refinery other units include a aviation kerosene hydrogenation unit, a wax oil hydrocracking unit, a diesel oil hydrocracking unit, a residue hydrocracking unit, a reforming unit, a disproportionation unit, an alkylation unit, and an MTBE unit.

7. A system for use in the process of claim 1, wherein the system comprises a normal isomerization separation unit, a hydrocracking unit, an aromatization unit, a steam cracking unit, and a cryogenic separation unit;

the normal and heterogeneous separation device comprises a light naphtha feeding hole, a normal component outlet and a heterogeneous component outlet; the isomeric component outlet is respectively communicated with the feed inlets of the hydrocracking device and the aromatization device;

the hydrocracking device comprises a hydrocracking unit and a cracked product separation unit which are sequentially communicated; the pyrolysis product separation unit comprises a refinery dry gas outlet I;

the aromatization device comprises an aromatization unit and an aromatization product separation unit which are sequentially communicated; the aromatization product separation unit comprises a refinery dry gas outlet II;

the first refinery dry gas outlet and the second refinery dry gas outlet are communicated with a feed inlet of the cryogenic separation device; the cryogenic separation device further comprises a fuel gas outlet and an ethane outlet; the ethane outlet is communicated with the feed inlet of the steam cracking device.

8. The system of claim 7, further comprising other refinery devices, wherein the discharge ports of the other refinery devices are communicated with the feed ports of the cryogenic separation device; the other devices of the refinery comprise an aviation kerosene hydrogenation device, a wax oil hydrocracking device, a diesel oil hydrocracking device, a residual oil hydrocracking device, a reforming device, a disproportionation device, an alkylation device and an MTBE device.

Technical Field

The invention belongs to the field of preparation of low-carbon olefins, and particularly relates to a method and a system for increasing ethylene yield by using refinery dry gas.

Background

As petroleum resources are exploited in large quantities, the petroleum resources become increasingly scarce, and therefore, how to optimally utilize the petroleum resources becomes a problem of increasing concern for many oil refining researchers. The capacity of an ethylene production plant and its production are among the most important indicators of the state of development of the petrochemical industry. With the development of national economy and the development of petrochemical industry, the demand for ethylene has also sharply increased.

At present, the raw material for industrially producing ethylene is mainly naphtha, naphtha is a mixture of normal alkane, isoparaffin, cycloparaffin and aromatic hydrocarbon, at present, the naphtha is processed by mixing a plurality of components with different properties, the product yield obtained by the method is low, the waste of energy and resources is caused, and simultaneously, all the components in the naphtha can not be fully utilized.

Disclosure of Invention

Aiming at the technical problems, the invention provides a method and a system for increasing the yield of low-carbon olefins such as ethylene, propylene and the like and aromatic hydrocarbons, which can realize the comprehensive utilization of light naphtha and maximize the production of ethylene and propylene products.

The technical scheme of the invention is as follows:

in one aspect, the invention provides a method for increasing yields of low-carbon olefins and aromatics, comprising the following steps:

(1) passing the light naphtha to an orthoisomerization separation unit to produce normal components and non-normal components;

(2) sending the non-normal components to a hydrocracking unit, and further separating the hydrocracking product to obtain refinery dry gas, propane, normal butane and isobutane respectively; and/or, sending non-normal components to an aromatization unit and further separating the aromatization products to obtain refinery dry gas, propane, n-butane and isobutane, and C5+ components, respectively;

(3) sending the propane to a propane dehydrogenation unit to produce propylene and the n-butane to a steam cracking unit to produce ethylene, propylene; sending the isobutane to a normal reforming unit to produce n-butane and the produced n-butane to a steam cracking unit to produce ethylene, propylene;

(4) the refinery-related dry gas is sent to a cryogenic separation unit to produce ethane and a fuel gas comprising C1, the ethane produced being sent to a steam cracking unit to produce ethylene.

The raw material of the cryogenic separation unit also comprises dry gas generated by other devices in a refinery; the feed to the normal isomerization unit also includes isomeric C4 produced by other units of the refinery; the feedstock to the propane dehydrogenation unit also includes propane produced by other refinery units, which refer to refinery units other than those used in the normal isomerization separation unit and the aromatization unit.

Based on the above scheme, preferably, the other refinery devices include: atmospheric and vacuum distillation unit, aviation kerosene hydrogenation unit, wax oil hydrogenation unit (containing cracking), diesel oil hydrogenation unit (containing cracking), residual oil hydrogenation unit (containing cracking), reforming unit, disproportionation unit, alkylation unit and MTBE unit.

Based on the scheme, preferably, the light naphtha comprises C5-C6 alkane; the normal component comprises normal C5-C6 alkane; the non-normal component comprises isomeric C5-C6 alkane.

Based on the above scheme, preferably, the normal components produced in step (1) are sent to a steam cracking unit to produce ethylene and propylene.

Based on the above scheme, preferably, the C5+ component comprises benzene, toluene and C8-C10 aromatic hydrocarbons.

Based on the scheme, the refinery dry gas preferably comprises components of C1-C2.

Based on the scheme, the light naphtha is preferably subjected to normal isomerization separation by a distillation method or an adsorption method.

In another aspect, the present invention provides a system for use in the above process, the system comprising an normal isomerization separation unit, a hydrocracking unit, an aromatization unit, a normal isomerization unit, a steam cracking unit, a propane dehydrogenation unit, and a cryogenic separation unit;

the normal and heterogeneous separation device comprises a light naphtha feeding hole, a normal component outlet and a heterogeneous component outlet; the isomeric component outlet is respectively communicated with the feed inlets of the hydrocracking device and the aromatization device;

the hydrocracking device comprises a hydrocracking unit and a cracked product separation unit which are sequentially communicated; the cracking product separation unit comprises a refinery dry gas outlet I, a propane outlet I, an n-butane outlet I and an isobutane outlet I;

the aromatization device comprises an aromatization unit and an aromatization product separation unit which are sequentially communicated; the aromatization product separation unit comprises a refinery dry gas outlet II, a propane outlet II, an n-butane outlet II, an isobutane outlet II and a C5+ component outlet;

the first propane outlet and the second propane outlet are communicated with a feed inlet of a propane dehydrogenation device;

the n-butane outlet I and the n-butane outlet II are communicated with a feed inlet of the steam cracking device;

the isobutane outlet I and the isobutane outlet II are communicated with a feed inlet of a normal structuring device, and a discharge hole of the normal structuring device is communicated with a feed inlet of a steam cracking device;

the first refinery dry gas outlet and the second refinery dry gas outlet are communicated with a feed inlet of the cryogenic separation device; the cryogenic separation device further comprises a fuel gas outlet and an ethane outlet; the ethane outlet is communicated with the feed inlet of the steam cracking device.

Based on the scheme, preferably, the system further comprises other devices of the refinery, and discharge ports of the other devices of the refinery are communicated with feed ports of one or more devices of the cryogenic separation device, the normal structuring device and the propane dehydrogenation device; the other devices of the refinery comprise an aviation kerosene hydrogenation device, a wax oil hydrocracking device, a diesel oil hydrocracking device, a residual oil hydrocracking device, a reforming device, a disproportionation device, an alkylation device and an MTBE device.

In the above device, the normal isomerization separation device can adopt a device used for realizing normal isomerization separation of light naphtha in the prior art; the hydrocracking device can adopt a device which is used for realizing hydrocracking of non-normal components in light naphtha and can further separate hydrocracking products in the prior art; the steam cracking device can adopt a device used for cracking the low-carbon hydrocarbon steam into ethylene in the prior art; the aromatization device can adopt a device used for aromatizing non-normal components and further separating aromatization products in the prior art; the normal structuring device can adopt a device used for normal structuring isobutane in the prior art; the propane dehydrogenation unit can adopt a unit used for dehydrogenating propane to produce propylene in the prior art; the cryogenic separation device can adopt a device which is used for separating dry gas generated by a refinery into ethane and fuel gas of C1 through a cryogenic separation process in the prior art. The other units of the refinery may be units of the prior art.

Advantageous effects

The invention firstly separates the light naphtha into normal alkane and non-normal alkane, and the normal alkane is directly used as the raw material for steam cracking, thus improving the yield of ethylene; meanwhile, the non-normal alkane component is further separated into refinery dry gas, propane, normal butane and isobutane through hydrocracking reaction; the yield of the propylene can be improved by preparing the propylene from the propane through dehydrogenation reaction, the isobutane is converted into the normal butane through normal structure, and the normal butane is used as a raw material for preparing low-carbon olefin, so that the yield of the ethylene and the propylene can be further improved; the refinery dry gas contains part of ethane, and the method separates the ethane by adopting a cryogenic separation process and takes the ethane as a raw material for preparing ethylene by steam cracking, so that the ethylene can be increased and the resources can be fully utilized.

The invention separates the C5-C6 isoparaffin in the light naphtha, aromatizes the isoparaffin, can produce C5+ products while further separating refinery dry gas, propane, n-butane and isobutane, fully and effectively utilizes various components in the naphtha, and improves the aromatic hydrocarbon yield of the light naphtha.

According to the invention, the C5-C6 isoparaffin in the light naphtha is separated out and subjected to hydrocracking, so that the saturation of the components is improved, the content of aromatic hydrocarbon is reduced, and the yield of low-carbon olefin in the steam cracking process is improved.

The process combination provided by the application comprehensively utilizes naphtha from the molecular perspective, and separates mixture components from the molecular perspective, namely from the specific requirements of different products on raw material molecules, so as to make the best use of the components, thereby greatly improving the yield of low-carbon olefins and aromatic hydrocarbons, remarkably improving the utilization efficiency of naphtha and realizing reasonable allocation of resources.

Drawings

FIG. 1 is a flow diagram of a general process for increasing the yields of lower olefins and aromatics provided by the present invention;

FIG. 2 is a flow chart of a process for increasing the yield of light olefins according to example 2 of the present invention;

FIG. 3 is a flow chart of a process for increasing the yields of light olefins and aromatics as provided in example 3 of the present invention;

FIG. 4 is a flow chart of a process for increasing the yields of light olefins and aromatics as provided in example 4 of the present invention;

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings.

In the following examples and comparative examples, the yield of lower olefins was calculated according to the following formula:

ethylene yield (wt%)/. wt. of ethylene in the steam cracking reaction product ÷ total weight of light naphtha × 100%;

the propylene yield (% by weight) is (weight of propylene in the steam cracking reaction product + weight of propylene in the propane dehydrogenation reaction product) ÷ total weight of light naphtha × 100%;

the yield (wt%) of each component of C5+ is the weight of each component of C5+ in the aromatization reaction product ÷ total weight of light naphtha × 100%.

Example 1

A method and a system for increasing the yield of low-carbon olefin are disclosed, as shown in figure 1, the system comprises a normal isomerization separation device, a hydrocracking device, an aromatization device, a normal formation device, a steam cracking device, a propane dehydrogenation device and a cryogenic separation device; the normal and heterogeneous separation device comprises a light naphtha feeding hole, a normal component outlet and a heterogeneous component outlet; the isomeric component outlet is respectively communicated with the feed inlets of the hydrocracking device and the aromatization device; the hydrocracking device comprises a hydrocracking unit and a cracked product separation unit which are sequentially communicated; the cracking product separation unit comprises a refinery dry gas outlet I, a propane outlet I, an n-butane outlet I and an isobutane outlet I; the aromatization device comprises an aromatization unit and an aromatization product separation unit which are sequentially communicated; the aromatization product separation unit comprises a refinery dry gas outlet II, a propane outlet II, an n-butane outlet II, an isobutane outlet II and a C5+ component outlet;

the first propane outlet and the second propane outlet are communicated with a feed inlet of a propane dehydrogenation device;

the n-butane outlet I and the n-butane outlet II are communicated with a feed inlet of the steam cracking device;

the isobutane outlet I and the isobutane outlet II are communicated with a feed inlet of a normal structuring device, and a discharge hole of the normal structuring device is communicated with a feed inlet of a steam cracking device; the first refinery dry gas outlet and the second refinery dry gas outlet are communicated with a feed inlet of the cryogenic separation device; the cryogenic separation device further comprises a fuel gas outlet and an ethane outlet; the ethane outlet is communicated with the feed inlet of the steam cracking device.

The method comprises the following steps:

(1) passing the light naphtha to an orthoisomerization separation unit to produce normal components and non-normal components;

(2) sending part of non-normal components to a hydrocracking unit, and further separating the hydrocracking product to obtain refinery dry gas, propane, normal butane and isobutane respectively; simultaneously sending the other part of non-normal components to an aromatization unit, and further separating aromatization products to respectively obtain refinery dry gas, propane, normal butane and isobutane and C5+ components;

(3) sending the propane to a propane dehydrogenation unit to produce propylene and the n-butane to a steam cracking unit to produce ethylene, propylene; sending the isobutane to a normal reforming unit to produce n-butane and the produced n-butane to a steam cracking unit to produce ethylene, propylene;

(4) sending the refinery-related dry gas to a cryogenic separation unit to produce ethane and a fuel gas comprising C1, the ethane produced being sent to a steam cracking unit to produce ethylene;

(5) sending the normal component produced in the step (1) to a steam cracking unit to produce ethylene and propylene.

In the above steps, the temperature of the hydrocracking device is 330-360 ℃, and the pressure is 6-8 MPa (gauge pressure); the temperature of the aromatization device is 380-400 ℃, and the pressure is 0.4-1.0 MPa (gauge pressure).

In the above steps, the contents of each component are as follows: the proportion of C5-C6 alkane in the light naphtha is 99%, after normal isomerization separation, the proportion of normal C5-C6 and non-normal C5-C6 in C5-C6 alkane is 35% and 65%, wherein 30% of non-normal C5-C6 hydrocracking unit and 35% of non-normal C5-C6 entering the aromatization unit.

After passing through a hydrocracking unit and separation, the proportion of refinery dry gas, propane, n-butane and isobutane in non-normal C5-C6 entering a hydrocracking unit is respectively 6%, 31%, 29% and 34%, and the proportion of ethane separated by cryogenic separation in refinery dry gas is 82%.

After the separation by an aromatization unit, the proportion of refinery dry gas, propane, n-butane, isobutane and C5+ components in non-normal C5-C6 is 5%, 49%, 11% and 24%, and the proportion of ethane separated by cryogenic cooling in refinery dry gas is 80%.

The total yield of ethylene in the obtained product is 35%, wherein the yield of ethylene from normal C5-C6 is about 18%, the yield of ethylene from isomeric C5-C6 is about 17%, and the yield of ethylene from refinery dry gas generated by a hydrocracking unit and an aromatization unit is about 3.5%.

In the obtained product, the total yield of the propylene is 40 percent, wherein the yield of the propylene derived from normal C5-C6 is about 9 percent, and the yield of the propylene derived from isomeric C5-C6 is about 31 percent.

In the obtained product, the total yield of propylene is 43 percent, wherein the yield of propylene generated by steam cracking of normal C5-C6 is about 9 percent, the yield of propylene generated by propane dehydrogenation is about 30.5 percent, and the yield of propylene generated by steam cracking of normal butane and iso-butane after normal structuring is about 3.5 percent.

In the obtained product, the total yield of C5+ components is 14%, wherein the total yield of benzene and toluene is 8.4%, and the total yield of C8-C10 aromatic hydrocarbons is 2.8%.

Example 2

A method and system for increasing the yield of low-carbon olefin is disclosed, as shown in figure 2, the system comprises a normal isomerization separation device, a hydrocracking device, a normal structuring device, a steam cracking device, a propane dehydrogenation device and a cryogenic separation device; the normal and heterogeneous separation device comprises a light naphtha feeding hole, a normal component outlet and a heterogeneous component outlet; the heterogeneous component outlet is communicated with a feed inlet of the hydrocracking device; the hydrocracking device comprises a hydrocracking unit and a cracked product separation unit which are sequentially communicated; the cracking product separation unit comprises a refinery dry gas outlet I, a propane outlet I, an n-butane outlet I and an isobutane outlet I; the first propane outlet is communicated with a feed inlet of a propane dehydrogenation device; the first n-butane outlet is communicated with a feed inlet of the steam cracking device; and the first isobutane outlet is communicated with the feeding hole of the normal structuring device, and the discharge hole of the normal structuring device is communicated with the feeding hole of the steam cracking device. The first refinery dry gas outlet is communicated with a feed inlet of the cryogenic separation device; the cryogenic separation device further comprises a fuel gas outlet and an ethane outlet; the ethane outlet is communicated with the feed inlet of the steam cracking device.

The method comprises the following steps:

(1) passing the light naphtha to an orthoisomerization separation unit to produce normal components and non-normal components;

(2) sending the non-normal components to a hydrocracking unit, and further separating the hydrocracking product to obtain refinery dry gas, propane, normal butane and isobutane respectively;

(3) sending the propane to a propane dehydrogenation unit to produce propylene and the n-butane to a steam cracking unit to produce ethylene, propylene; sending the isobutane to a normal reforming unit to produce n-butane and the produced n-butane to a steam cracking unit to produce ethylene, propylene;

(4) sending the normal components produced in the step (1) to a steam cracking unit to produce ethylene and propylene;

(5) sending the refinery-related dry gas produced in step (2) to a cryogenic separation unit to produce ethane and a fuel gas comprising C1, the ethane being sent to a steam cracking unit to produce ethylene.

In the above step, the temperature of the hydrocracking device is 330 to 360 ℃, and the pressure is 6 to 8MPa (gauge pressure).

In the above steps, the contents of each component are as follows: the proportion of C5-C6 alkane in the light naphtha is 98 percent, and after normal isomerization separation, the proportion of normal C5-C6 and non-normal C5-C6 in C5-C6 alkane is 34 percent and 66 percent respectively; after being separated by a hydrocracking unit, the proportion of refinery dry gas, propane, n-butane and isobutane in non-normal C5-C6 is respectively 6%, 30% and 34%, and the proportion of ethane separated by cryogenic separation in refinery dry gas is 80%.

In the obtained product, the total yield of the ethylene is 44.5 percent, wherein the yield of the ethylene generated by steam cracking of normal C5-C6 is about 18 percent, the yield of the ethane generated by steam cracking of refinery dry gas cryogenically separated is about 3.5 percent, and the yield of the ethylene generated by steam cracking of normal butane and iso-butane after normal structuring is about 23 percent.

In the obtained product, the total yield of the propylene is 36.5 percent, wherein the yield of the propylene generated by steam cracking of normal C5-C6 is about 9.5 percent, the yield of the propylene generated by propane dehydrogenation is about 19 percent, and the yield of the propylene generated by steam cracking of n-butane and isobutane is about 8 percent.

Example 3

A method and system for increasing the yield of light olefins and aromatics, as shown in fig. 3, the system used is as follows:

the system comprises a normal isomerization separation device, an aromatization device, a normal structuring device, a steam cracking device, a propane dehydrogenation device and a cryogenic separation device; the normal and heterogeneous separation device comprises a light naphtha feeding hole, a normal component outlet and a heterogeneous component outlet; the isomeric component outlet is communicated with a feed inlet of the aromatization device; the aromatization device comprises an aromatization unit and an aromatization product separation unit which are sequentially communicated; the aromatization product separation unit comprises a refinery dry gas outlet II, a propane outlet II, an n-butane outlet II, an isobutane outlet II and a C5+ component outlet; the second propane outlet is communicated with a feed inlet of the propane dehydrogenation device; the second n-butane outlet is communicated with a feed inlet of the steam cracking device; and the second isobutane outlet is communicated with a feed inlet of the normal structuring device, and a discharge hole of the normal structuring device is communicated with a feed inlet of the steam cracking device.

The second refinery dry gas outlet is communicated with a feed inlet of the cryogenic separation device; the cryogenic separation device further comprises a fuel gas outlet and an ethane outlet; the ethane outlet is communicated with the feed inlet of the steam cracking device.

The method comprises the following steps:

(1) passing the light naphtha to an orthoisomerization separation unit to produce normal components and non-normal components;

(2) sending the non-normal components to an aromatization unit, and further separating aromatization products to respectively obtain refinery dry gas, propane, normal butane, isobutane and C5+ components;

(3) sending the propane to a propane dehydrogenation unit to produce propylene and the n-butane to a steam cracking unit to produce ethylene, propylene; sending the isobutane to a normal reforming unit to produce n-butane and the produced n-butane to a steam cracking unit to produce ethylene, propylene;

(4) sending the normal components produced in the step (1) to a steam cracking unit to produce ethylene and propylene;

(5) sending the refinery-related dry gas produced in step (2) to a cryogenic separation unit to produce ethane and a fuel gas comprising C1, the ethane being sent to a steam cracking unit to produce ethylene.

In the above step, the temperature of the aromatization device is 380-400 ℃, and the pressure is 0.4-1.0 MPa (gauge pressure).

In the above steps, the contents of each component are as follows: the proportion of C5-C6 alkane in the light naphtha is 98 percent, and after normal isomerization separation, the proportion of normal C5-C6 and non-normal C5-C6 in C5-C6 alkane is 34 percent and 66 percent respectively; after the separation by an aromatization unit, the proportion of refinery dry gas, propane, n-butane, isobutane and C5+ components in non-normal C5-C6 is 5%, 50%, 10% and 25%, and the proportion of ethane separated by deep cooling in refinery dry gas is 80%.

In the obtained product, the total yield of the ethylene is 27 percent, wherein the yield of the ethylene generated by steam cracking of normal C5-C6 is about 18 percent, the yield of the ethane generated by steam cracking of refinery dry gas cryogenically separated is about 3 percent, and the yield of the ethylene generated by steam cracking of normal butane and normal isobutane is about 6 percent.

In the obtained product, the total yield of propylene is 43 percent, wherein the yield of propylene generated by steam cracking of normal C5-C6 is about 9 percent, the yield of propylene generated by propane dehydrogenation is about 30.5 percent, and the yield of propylene generated by steam cracking of normal butane and iso-butane after normal structuring is about 3.5 percent.

In the obtained product, the total yield of C5+ components is 25%, wherein the total yield of benzene and toluene is 15%, and the total yield of C8-C10 aromatic hydrocarbons is 5%.

Example 4

A method for increasing the yield of ethylene by using refinery dry gas and a system thereof are disclosed, as shown in figure 4, the system is as follows:

the system comprises an orthoisomerization separation device, a hydrocracking device, an aromatization device, a steam cracking device and a cryogenic separation device; the normal and heterogeneous separation device comprises a light naphtha feeding hole, a normal component outlet and a heterogeneous component outlet; the isomeric component outlet is respectively communicated with the feed inlets of the hydrocracking device and the aromatization device; the hydrocracking device comprises a hydrocracking unit and a cracked product separation unit which are sequentially communicated; the pyrolysis product separation unit comprises a refinery dry gas outlet I; the aromatization device comprises an aromatization unit and an aromatization product separation unit which are sequentially communicated; the aromatization product separation unit comprises a refinery dry gas outlet II;

the first refinery dry gas outlet and the second refinery dry gas outlet are communicated with a feed inlet of the cryogenic separation device; the cryogenic separation device further comprises a fuel gas outlet and an ethane outlet; the ethane outlet is communicated with the feed inlet of the steam cracking device.

The system also comprises other devices of the refinery, and discharge ports of the other devices of the refinery are communicated with a feed port of the cryogenic separation device; the other devices of the refinery comprise a aviation kerosene hydrogenation device, a wax oil hydrocracking device, a diesel oil hydrocracking device and a residual oil hydrocracking device.

The working process of the method is as follows:

(1) passing the light naphtha to an orthoisomerization separation unit to produce normal components and non-normal components;

(2) sending part of non-normal components to a hydrocracking unit, and further separating hydrocracking products to obtain refinery dry gas; sending the other part of non-normal components to an aromatization unit, and further separating aromatization products to obtain refinery dry gas;

(3) sending the refinery dry gas produced in step (2) and the dry gas produced by other units in the refinery, except the hydrocracking unit and the aromatization unit, to a cryogenic separation unit to produce ethane and a fuel gas comprising C1, and sending the produced ethane to a steam cracking unit to produce ethylene.

In the above steps, the dry gas produced by other units of the refinery accounts for 85% of the feed of the cryogenic separation unit, the dry gas produced by the hydrocracking unit and the aromatization unit accounts for 15% of the feed of the cryogenic separation unit, the ethane separated by cryogenic separation accounts for 78% of the feed of the cryogenic separation unit, the yield of the produced ethylene is 63%, and the calculation mode of the ethylene yield here is as follows: ethylene yield (% by weight) is the weight of ethylene produced by steam cracking of ethane separated cryogenically ÷ total weight of cryogenic separation unit feed x 100%.

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