CN112410056A

CN112410056A - Purging system of catalytic cracking unit

Info

Publication number: CN112410056A
Application number: CN201910769932.5A
Authority: CN
Inventors: 杨元彬; 相养冬; 李健; 段伟峰; 杨永生; 盖永强; 周定一; 杨晓柯; 金刚; 刘明; 程文嘉; 刘呈军; 刘小行; 任刚; 王建波; 韩鸿浩
Original assignee: Petrochina Co Ltd
Current assignee: Petrochina Co Ltd
Priority date: 2019-08-20
Filing date: 2019-08-20
Publication date: 2021-02-26

Abstract

The invention provides a purging system of a catalytic cracking unit, which comprises: the gas and the steam in the first tower can be swept into the second tower, and the gas and the steam in the second tower can be swept into the cooler; and the inlet of the reflux tank is communicated with the outlet of the cooler, one outlet of the reflux tank is communicated with a gas pipe network arranged outside the catalytic cracking device, and the other outlet of the reflux tank is communicated with a purification device arranged outside the catalytic cracking device. The technical scheme of this application has effectively solved the poor problem of industrial waste gas treatment effect that carries in the steam among the prior art.

Description

Purging system of catalytic cracking unit

Technical Field

The invention relates to the field of petroleum refining processes, in particular to a purging system of a catalytic cracking device.

Background

In the prior art, the shutdown purging method of the domestic catalytic device stabilization system is mainly that steam is supplied to the tower bottom, and the tower top is emptied and directly discharged to atmosphere. Also known as a distillation tower, the method can bring media such as oil and non-condensable gas in the tower into the atmosphere to cause pollution.

In the blowing process in the prior art, the stable absorption and desulfurization unit stops working, is sealed and relayed, comprises an analytical tower, an absorption tower, a reabsorption tower and a stabilization tower, and comprises a dry gas desulfurization tower, a liquefied gas desulfurization tower, an amine liquid regeneration tower and a fractionating tower. In the purging process, purging steam of the four towers with stable absorption enters a low-pressure flare discharging pipeline, purging steam in the dry gas desulfurization tower, the liquefied gas desulfurization tower and the amine liquid regeneration tower enters a fractionating tower, the fractionating tower is communicated with an oil-gas separator, a low-pressure flare discharging pipeline outside the device is required to be added on the oil-gas separator in front of the gas compressor, and non-condensable gas behind the oil-gas separator is conveyed to the low-pressure flare discharging pipeline outside the device. The purging process has the following defects:

1) the line sweeping steam of the stabilizing system enters a low-pressure gas flare pipe network, a large amount of steam enters the flare pipe network, flare combustion is influenced or a flare cannot be combusted, and industrial waste gas carried in the steam is discharged into the atmosphere without being treated; 2) the flare pipe network is used by a plurality of devices together, and the risk of mutual channeling exists; 3) if a plurality of devices are stopped and overhauled simultaneously, the load of a flare pipe network is increased, the situation that waste gas containing steam cannot be treated is more likely to occur, and the possibility of medium channeling among the devices is increased; 4) the fractionation system overlaps less time with the stabilization system shutdown, and the fractionation system will end up shutting down earlier than the stabilization system, and the introduction of steam into the fractionation column will extend the fractionation system shutdown time. And the fractionating and stabilizing systems are linked by a torch line, so that the risk of channeling exists; 5) the process is complex and the operation is difficult.

Disclosure of Invention

The invention aims to provide a purging system of a catalytic cracking device, which aims to solve the problem of poor treatment effect of industrial waste gas carried in steam in the prior art.

In order to achieve the above object, the present invention provides a purge system of a catalytic cracking unit, comprising: the gas and the steam in the first tower can be swept into the second tower, and the gas and the steam in the second tower can be swept into the cooler; and the inlet of the reflux tank is communicated with the outlet of the cooler, one outlet of the reflux tank is communicated with a gas pipe network arranged outside the catalytic cracking device, and the other outlet of the reflux tank is communicated with a purification device arranged outside the catalytic cracking device.

Further, the purging system also includes a third column in communication with the inlet of the cooler.

Further, the purging system comprises a first pipeline connected between the second tower and the third tower, the first pipeline is located between the cooler and the second tower, and a first valve is arranged on the first pipeline.

Further, the first valve is a plurality of.

Further, the purging system further comprises a water pump disposed between the purification device and the reflux drum.

Further, the purging system comprises a second pipeline connected between the return tank and the water pump, and a second valve is arranged on the second pipeline.

Further, the second valve is a plurality of.

Further, the purging system comprises a third pipeline connected to the first pipeline, one end of the third pipeline and a connection point of the first pipeline are located between the first valve and the second tower, the other end of the third pipeline is communicated with the torch system, and a first control valve group is arranged on the third pipeline.

Further, the purging system comprises a fourth pipeline connected between the first pipeline and the inlet of the cooler, a connection point of the fourth pipeline and the first pipeline is located between the first valve and the third tower, and a second control valve group is arranged on the fourth pipeline.

Further, the purging system further comprises a fourth tower arranged between the outlet of the first tower and the inlet of the second tower, wherein the first tower is a desorption tower, the second tower is a reabsorption tower, the third tower is a stabilization tower, and the fourth tower is an absorption tower.

By applying the technical scheme of the invention, the purging system of the catalytic cracking unit is used after the catalytic cracking unit stops working. The purging system comprises a first tower, a second tower, a cooler and a reflux tank which are sequentially communicated. The gas and steam in the first column can be purged into the second column, and the gas and steam in the second column can be purged into the cooler. The cooler processes the gas and steam and produces non-condensable gases and condensed water. The inlet of the reflux tank is communicated with the outlet of the cooler, one outlet of the reflux tank is communicated with a gas pipe network arranged outside the catalytic cracking device, the reflux tank receives the non-condensable gas and the condensed water, the non-condensable gas is sent into the gas pipe network of the catalytic cracking device, and then the non-condensable gas is sent to the torch system for combustion. Therefore, the gas and the steam are not directly discharged into the flare system, the gas and the steam are prevented from influencing the flare to be burnt, and the gas and the steam are also prevented from being directly discharged into the atmosphere. The other outlet of the reflux tank is communicated with a purification device arranged outside the catalytic cracking device. The condensed water is sent into a purification device for purification treatment, and the condensed water is not directly discharged. In this way, the purging system can significantly improve the effectiveness of treating the industrial waste gas entrained in the steam. Therefore, the technical scheme of this application has effectively solved the poor problem of industrial waste gas treatment effect that carries in the steam among the prior art.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:

FIG. 1 shows a schematic block diagram of an embodiment of a purge system of a catalytic cracking unit according to the present invention.

Wherein the figures include the following reference numerals:

11. a first tower; 12. a second tower; 13. a reflux tank; 14. a cooler; 15. a third tower; 16. a fourth column; 21. a first pipeline; 22. a second pipeline; 23. a third pipeline; 24. a fourth pipeline; 31. a first valve; 32. a second valve; 41. a water pump; 42. a dry air cooler; 43. a wet air cooler; 44. an oil-gas separator; 45. a pressure control valve; 51. a first control valve group; 511. a first main valve; 512. a first secondary valve; 52. a second control valve group; 521. a second main valve; 522. a second set of valves.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.

The relative arrangement of the components and steps, the numerical expressions and numerical values set forth in these embodiments do not limit the scope of the present invention unless specifically stated otherwise. Meanwhile, it should be understood that the sizes of the respective portions shown in the drawings are not drawn in an actual proportional relationship for the convenience of description. Techniques, methods, and apparatus known to those of ordinary skill in the relevant art may not be discussed in detail, but are intended to be part of the specification where appropriate. In all examples shown and discussed herein, any particular value should be construed as merely illustrative, and not limiting. Thus, other examples of the exemplary embodiments may have different values. It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, further discussion thereof is not required in subsequent figures.

As shown in fig. 1, the purge system of the catalytic cracking apparatus of the present embodiment includes: a first tower 11, a second tower 12 and a cooler 14 which are communicated in sequence. The gas and steam in the first column 11 can be purged into the second column 12, and the gas and steam in the second column 12 can be purged into the cooler 14. The inlet of the reflux tank 13 is communicated with the outlet of the cooler 14, one outlet of the reflux tank 13 is communicated with a gas pipe network A arranged outside the catalytic cracking device, and the other outlet of the reflux tank 13 is communicated with a purification device B arranged outside the catalytic cracking device.

By applying the technical scheme of the embodiment, the purging system of the catalytic cracking unit is used after the catalytic cracking unit is shut down. The purging system comprises a first tower 11, a second tower 12, a cooler 14 and a reflux tank 13 which are communicated in sequence. The gas and steam in the first column 11 can be purged into the second column 12, and the gas and steam in the second column 12 can be purged into the cooler 14. The cooler 14 processes the gas and steam and produces non-condensable gases and condensed water. The inlet of the reflux tank 13 is communicated with the outlet of the cooler, one outlet of the reflux tank 13 is communicated with a gas pipe network A arranged outside the catalytic cracking device, and the reflux tank 13 receives non-condensable gas and condensed water. The non-condensable gas is sent into a gas pipe network A of the catalytic cracking device and then sent to a torch system for combustion. Therefore, the gas and the steam are not directly discharged into the flare system, the gas and the steam are prevented from influencing the flare to be burnt, and the gas and the steam are also prevented from being directly discharged into the atmosphere. The other outlet of the reflux drum 13 communicates with a purification apparatus B provided outside the catalytic cracking apparatus. The condensed water is sent into the purification device B for purification treatment, and the condensed water is not directly discharged. In this way, the purging system can significantly improve the effectiveness of treating the industrial waste gas entrained in the steam. Therefore, the technical scheme of this embodiment has effectively solved the problem that the industrial waste gas treatment effect that carries in the steam is poor among the prior art. The return tank 13 of this embodiment can deposit the comdenstion water to utilize the pipeline of return tank 13 and gas pipe network A intercommunication, will not condensate gas and send to in the gas pipe network A.

It should be noted that the purge system of this embodiment is preferably used in a stabilization unit of a catalytic cracking unit. The purge is preferably a steam purge. The gas is preferably a hydrocarbon. The gas pipe network A is in the direction of introducing the gas pipe network, the purification device B is in the direction of introducing the purification device, the C direction is in the direction of introducing rich gas, the D direction is in the direction of communicating with the torch system, and the E direction is in the direction of introducing acidic water.

As shown in fig. 1, in this embodiment, the purging system further includes a third tower 15, and the third tower 15 is in communication with the inlet of the cooler 14. The steam and gas in the first, second and

third towers

11, 12 and 15 are purged into the cooler 14. Thus, the purging system can sequentially purge the first tower 11, the second tower 12 and the third tower 15 of the catalytic cracking unit, and the purpose of relay purging is achieved.

As shown in fig. 1, in the present embodiment, the purging system includes a first pipeline 21 connected between the second tower 12 and the third tower 15, the first pipeline 21 is located between the cooler 14 and the second tower 12, and a first valve 31 is provided on the first pipeline 21. When the purge system is purging, the first valve 31 is opened and gas and steam are passed through the first line 21. Therefore, gas and steam can not be directly discharged into the atmosphere, and the environment protection is considered while the purging quality is ensured.

As shown in fig. 1, in this embodiment, there are two first valves 31, one of the two first valves is disposed at the first end of the first pipeline 21, and the other is disposed at the second end of the first pipeline 21, so that when the first pipeline 21 is not operated, the two first valves are closed at the same time, the gas in the catalytic cracking apparatus does not enter the first pipeline 21, and the gas does not accumulate in the first pipeline 21. In other embodiments not shown, the first valves may be three, four, or more.

As shown in fig. 1, in the present embodiment, the purge system further includes a water pump 41 provided between the purification apparatus B and the reflux drum 13. Therefore, the water pump 41 in the prior art is fully beneficial to discharge the condensed water into the purifying device B, and thus, the change is small, the construction is simple, and the implementation is convenient.

As shown in fig. 1, in the present embodiment, the purge system includes a second line 22 connected between the reflux drum 13 and the water pump 41, and the second line 22 is provided with a second valve 32. When the purge system is purging, the second valve 32 is opened and gas and steam pass through the second line 22. This facilitates the operation.

As shown in fig. 1, in the present embodiment, the second valve 32 is two. One of the two second valves is disposed at a first end of the second pipeline 22 and the other is disposed at a second end of the second pipeline 22, so that when the second pipeline 22 is not operated, the two second valves are closed at the same time, gas in the catalytic cracking unit does not enter the second pipeline 22, and gas does not accumulate in the second pipeline 22. In other embodiments not shown, the second valves may be three, four, and more.

As shown in fig. 1, in the present embodiment, the purging system includes a third pipeline 23 connected to the first pipeline 21, a connection point of one end of the third pipeline 23 and the first pipeline 21 is located between the first valve 31 and the second tower 12, the other end of the third pipeline 23 is communicated with the flare system, and a first control valve set 51 is disposed on the third pipeline 23. The first control valve group 51 can control on or off of the third pipeline 23. When the purge system is purging, the first control valve set 51 is closed, preventing the purged gas and steam from entering the flare system. In the present embodiment, the first control valve set 51 includes a first main valve 511 and a first sub-valve 512, so that the on/off of the first main valve 511 or the first sub-valve 512 can be controlled according to the need of purging. This facilitates the operation.

As shown in fig. 1, in the present embodiment, the purging system includes a fourth pipeline 24 connected between the first pipeline 21 and the inlet of the cooler 14, a connection point of the fourth pipeline 24 and the first pipeline 21 is located between the first valve 31 and the third tower 15, and a second control valve set 52 is disposed on the fourth pipeline 24. The second control valve group 52 can control the on or off of the fourth line 24. When the purge system is purging, the second control valve set 52 is opened to facilitate the entry of the purged gas and vapor into the cooler 14. The second control valve group 52 comprises a second main valve 521 and a second auxiliary valve 522, so that the on-off of the second main valve 521 or the second auxiliary valve 522 can be controlled according to the purging requirement.

As shown in fig. 1, in the present embodiment, the purging system further includes a fourth column 16 disposed between the outlet of the first column 11 and the inlet of the second column 12, the first column 11 is a desorption column, the second column 12 is a reabsorber, the third column 15 is a stabilizer, and the fourth column 16 is an absorption column. The reflux drum 13 is a stabilization overhead reflux drum. The first line 21 of this embodiment leads from the top of the reabsorber to the top cooler inlet of the stabilizer column. A second line 22 leads from the other outlet bottom acidic water line of the stabilizer overhead reflux drum to the inlet of a water pump 41, preferably a fractional acid water pump 41. Cooler 14 is preferably a stabilizer overhead cooler. In addition, the first pipeline 21 and the second pipeline 22 are respectively introduced into the purging system, so that the purging system is not easy to cause adverse effects on the normal production and public pipe network of the catalytic cracking unit, and the normal shutdown process of other systems in the catalytic cracking unit is not easy to be influenced.

In this embodiment, 42 is a dry air cooler, 43 is a wet air cooler, 44 is an oil-gas separator, and 45 is a pressure control valve. The above-mentioned devices are all devices of the prior art which stabilize the unit.

As shown in fig. 1, the specific working process of this embodiment is as follows:

the first 11, fourth 16, second 12 and third 15 columns of the stabilisation unit are steam purged by prior art cooling equipment in the catalytic cracking unit and the stabilisation overhead cooler condenses the steam and gas to a liquid state. And then sent to a purification device B, namely an acid water stripping device, for treatment through a water pump 41, namely an acid water pump 41.

Specifically, after the catalytic cracking unit is shut down, the pressure of the stabilizing unit is released to be below 0.1MPa to the torch system; the purging system introduces fresh water, the gasoline on the top of the fresh water enters a reflux tank area, and the topping oil is repeated for 3 times; putting an outlet of the reabsorption tower and a tower top communication line in front of the stabilizing tower top cooler, closing the flow from the outlet of the reabsorption tower to a dry gas pipe network, and realizing a purging flow from the desorption tower to the absorption tower through a desorption gas line and from a tower top lean gas line of the absorption tower to the tower top of the reabsorption tower to the stabilizing tower; firstly, feeding purge steam at the bottom of the desorption tower, driving gas in the tower into the desorption tower, feeding purge steam at the bottom of the absorption tower when the temperature at the top of the desorption tower is higher than 100 ℃, performing steam relay, and driving the gas in a purge system into the reabsorber; when the temperature of the top of the absorption tower is higher than 100 ℃, blowing steam at the bottom of the reabsorption tower, feeding gas of a blowing system into a stable top cooler through a top connecting line of the reabsorption tower for cooling, condensing the steam and the gas into a stable top reflux tank, and feeding the gas of the blowing system into a catalytic pipe network through a noncondensable gas line of the stable top reflux tank; when the temperature of the top of the reabsorption tower is higher than 100 ℃, putting the catalytic pipe network into use to purge steam, performing steam relay purging, driving the gas of a purging system into a flare line at the tail end of the catalytic pipe network, and enabling the system gas to pass through a flare line liquid separating tank of the catalytic pipe network and then to enter an overhead flare system of the catalytic cracking system for combustion; the sewage condensed in the reflux tank at the top of the stabilizing tower and the condensing tank at the outlet of the gas compressor is pumped out by a fractional acid water pump and sent to an acid water stripping device. After the blowing system of the embodiment is adopted for blowing, no oil is reserved and no peculiar smell is generated. The catalytic pipe network of this embodiment is a catalytic dry gas pipe network.

In the description of the present invention, it is to be understood that the orientation or positional relationship indicated by the orientation words such as "front, rear, upper, lower, left, right", "lateral, vertical, horizontal" and "top, bottom", etc. are usually based on the orientation or positional relationship shown in the drawings, and are only for convenience of description and simplicity of description, and in the case of not making a reverse description, these orientation words do not indicate and imply that the device or element being referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore, should not be considered as limiting the scope of the present invention; the terms "inner and outer" refer to the inner and outer relative to the profile of the respective component itself.

Spatially relative terms, such as "above … …," "above … …," "above … …," "above," and the like, may be used herein for ease of description to describe one device or feature's spatial relationship to another device or feature as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if a device in the figures is turned over, devices described as "above" or "on" other devices or configurations would then be oriented "below" or "under" the other devices or configurations. Thus, the exemplary term "above … …" can include both an orientation of "above … …" and "below … …". The device may be otherwise variously oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

It should be noted that the terms "first", "second", and the like are used to define the components, and are only used for convenience of distinguishing the corresponding components, and the terms have no special meanings unless otherwise stated, and therefore, the scope of the present invention should not be construed as being limited.

The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes will occur to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A purge system for a catalytic cracking unit, comprising:

a first tower (11), a second tower (12) and a cooler (14) which are communicated in sequence, wherein gas and steam in the first tower (11) can be swept into the second tower (12), and gas and steam in the second tower (12) can be swept into the cooler (14);

the inlet of the reflux tank (13) is communicated with the outlet of the cooler (14), one outlet of the reflux tank (13) is communicated with a gas pipe network (A) arranged outside the catalytic cracking device, and the other outlet of the reflux tank (13) is communicated with a purification device (B) arranged outside the catalytic cracking device.

2. A purge system according to claim 1, further comprising a third column (15), the third column (15) being in communication with an inlet of the cooler (14).

3. A purge system according to claim 2, comprising a first line (21) connected between the second column (12) and the third column (15), the first line (21) being located between the cooler (14) and the second column (12), the first line (21) being provided with a first valve (31).

4. A purge system according to claim 3, wherein the first valve (31) is plural.

5. A purge system according to claim 1, further comprising a water pump (41) arranged between the purification device (B) and the return tank (13).

6. A purge system according to claim 5, comprising a second line (22) connected between the return tank (13) and the water pump (41), the second line (22) being provided with a second valve (32).

7. A purge system according to claim 6, wherein the second valve (32) is plural.

8. A purge system according to claim 4, comprising a third line (23) connected to the first line (21), the connection point of one end of the third line (23) to the first line (21) being located between the first valve (31) and the second column (12), the other end of the third line (23) being in communication with a flare system, the third line (23) being provided with a first control valve set (51).

9. A purge system according to claim 4, comprising a fourth line (24) connected between the first line (21) and the inlet of the cooler (14), the connection point of the fourth line (24) to the first line (21) being located between the first valve (31) and the third column (15), a second set of control valves (52) being provided on the fourth line (24).

10. A purge system according to claim 3, further comprising a fourth column (16) arranged between the outlet of the first column (11) and the inlet of the second column (12), the first column (11) being a desorption column, the second column (12) being a reabsorber column, the third column (15) being a stabilizer column, the fourth column (16) being an absorber column.