WO2019019034A1

WO2019019034A1 - Gas fractionation device

Info

Publication number: WO2019019034A1
Application number: PCT/CN2017/094415
Authority: WO
Inventors: 张瑶; 李艳兵
Original assignee: 深圳市宏事达能源科技有限公司; 辽宁识微科技有限公司
Priority date: 2017-07-26
Filing date: 2017-07-26
Publication date: 2019-01-31
Also published as: CN108883343A

Abstract

A gas fractionation device, comprising a propane-removing column (10), an ethane-removing column (2), a first reboiler (2), a second reboiler (4) and a propylene recovery column (12). The propane-removing column (10) is provided with a first feed port, a first overhead discharge port and a first bottom discharge port. The ethane-removing column (11) is provided with a second feed port, a second overhead discharge port and a second bottom discharge port. The propylene recovery column (12) is provided with a third feed port, a third overhead discharge port and a third bottom discharge port.

Description

Gas fractionation device

Technical field

The invention relates to a gas fractionation device.

Background technique

The petrochemical plant of Sinopec Zhongyuan Oilfield Company has a gas fractionation unit. The feed of the gas fractionation unit comes from the liquefied gas produced by the catalytic cracking unit of the plant. In order to further increase the yield of propylene, in the existing equipment, the non-condensable gas at the top of the deethanizer tower is added to the outlet of the catalytic cracking unit air compressor to add a pipeline, so that the non-condensable gas of the portion is returned to the catalytic cracking device. To recover the propylene. According to the relevant literature, 78.75% of the propylene content in the carbon tail gas at the top of the deethanizer tower can be reduced to 72.28%.

According to the conventional four-tower process, the volume fraction of propylene products in the top of the propylene tower can reach 99.6%, and the volume fraction of propane in the bottom can reach 95.0%. In 2013, it was modified to add an absorption tower. The process is shown in Figure 1. The volume fraction of the propylene product at the top of the propylene tower can reach 99.8%, which is the highest yield of domestic propylene products. The device mixes the non-condensable gas at the top of the deethanizer into the diesel hydrogenated liquefied gas, and the propylene content in the diesel hydrogenated liquefied gas increases from 0% before the reform to 3.83% to 1.4 million tons. The annual processing capacity, 330 days a year, can recover 1,000 tons of propylene, the market price is about 5 million yuan, and the efficiency of consumption reduction is remarkable. Disadvantages: During the operation, the discharge pressure flow of the top of the deethanizer tower fluctuates greatly or the phenomenon of oiling occurs, which needs to be adjusted frequently.

Summary of the invention

The present invention proposes a gas fractionation apparatus that solves the above drawbacks existing in the prior art.

The technical scheme of the present invention is realized as follows: a gas fractionation apparatus comprising a depropanizer, a deethanizer, a reboiler 1, a reboiler 2, and a propylene recovery tower, wherein the depropanizer is provided with a feed port 1. The top discharge port of the column and the outlet port of the bottom of the column, the deethanizer tower is provided with a feed port 2, a top discharge port 2 and a bottom outlet port 2. The propylene recovery tower is provided The feed port 3, the top inlet, the top outlet 3 and the bottom outlet 3, the inlet 3 is disposed at the bottom of the propylene recovery tower; the depropanizer is passed through the pipeline The reboiler is connected in communication, and the deethanizer is connected to the reboiler through a pipeline; The feed port of the depropanizer tower is connected to the raw material inlet through a pipeline, and the top discharge port of the tower is connected to the feed port through the pipeline; the top discharge port of the tower is connected to the feed port through the pipeline. The bottom discharge port 3 is connected to the feed port through a pipe; the bottom discharge port of the bottom is connected to the first three-way pipe through a pipe, and the first three-way pipe has an outlet device, the first Another outlet of a tee is in communication with the top feed port.

Preferably, the top discharge port of the column is connected to the condenser one, the reflux tank one and the second three-way pipe through a pipeline, and one of the outlets of the second three-way pipe is connected to the top of the depropanizer The other outlet of the second tee is in communication with the feed port.

Preferably, the top outlet 2 is connected to the condenser 2, the reflux tank 2 and the third tee through a pipeline, and an outlet of the third tee is connected to the top of the deethanizer. The other outlet of the third tee is in communication with the feed port three.

Preferably, the other outlet of the first tee is in communication with the top feed port through a heat exchanger and a pump.

Preferably, the other outlet of the first tee is in communication with the top inlet of the tower through a heat exchanger and a pump.

Preferably, a feed tank is arranged between the feed port and the raw material inlet.

Preferably, a fourth three-way pipe is disposed between the raw material inlet and the feed tank, the first end of the fourth three-way pipe is in communication with the raw material inlet, and the second end of the fourth three-way pipe Connected with the feed tank, the third end of the fourth tee is connected to the top discharge port.

The beneficial effects of the invention are:

The gas fractionation device of the invention adds a simple and easy-to-operate propylene recovery tower, and the C4 from the bottom of the depropanizer tower acts as an absorbent, so that it is no longer necessary to repurchase the absorbent, thereby saving cost.

C4 is fed as an absorbent from the top of the column, and C2 is not condensed from the bottom of the column. The two materials are in reverse contact, which is beneficial for absorption.

The pressure of the propylene recovery tower is the same as the pressure of the top reflux tank of the depropanizer, which is favorable for returning to the depropanizer by the self-pressure of the absorbed C4.

Propylene is a high-priced and demanding product on the market, and the current situation is in short supply. The invention further recovers the component of propylene in the liquefied gas by adding a propylene recovery tower, and then the propylene recovery tower tops The yield of propylene products increased to 99.99%, and the propylene content in the non-condensable gas at the top of the deethanizer tower was reduced to 65.9%, which is the yield and recovery rate that cannot be achieved by the existing propylene recovery technology on the market. The increased propylene recovery tower is not only simple to operate but also less expensive to invest.

DRAWINGS

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the embodiments or the description of the prior art will be briefly described below. Obviously, the drawings in the following description are only It is a certain embodiment of the present invention, and other drawings can be obtained from those skilled in the art without any inventive labor.

Figure 1 is a flow chart of a prior art fractionation apparatus;

2 is a schematic view showing the structure of a gas fractionation apparatus according to the present invention.

In the drawings: 1-return tank one; 2-reboiler one; 3-return tank two; 4-reboiler two; 5-heat exchanger; 6-pump; 7-feed tank; 8-condenser One; 9-condenser two; 10-depropanizer; 11-deethanizer; 12-propylene recovery tower.

Detailed ways

The technical solutions in the embodiments of the present invention are clearly and completely described in the following with reference to the accompanying drawings in the embodiments of the present invention. It is obvious that the described embodiments are only a part of the embodiments of the present invention, but not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative efforts are within the scope of the present invention.

As shown in FIG. 2, a gas fractionation apparatus includes a depropanizer 10, a deethanizer 11, a reboiler-2, a reboiler 2, and a propylene recovery tower 12, and the depropanizer 10 is provided with a material outlet 1, a top discharge port 1 and a bottom outlet port 1. The deethanizer column 11 is provided with a feed port 2, a top discharge port 2 and a bottom outlet port 2, and the propylene recovery The tower 12 is provided with a feed port 3, an overhead feed port, a top discharge port 3, and a bottom discharge port 3. The feed port 3 is disposed at the bottom of the propylene recovery column 12; The propane column 10 is connected to the reboiler 2 through a pipe, and the deethanizer 11 is connected to the reboiler 2 through a pipe; the feed port of the depropanizer 10 is connected to the raw material inlet through a pipe. The top outlet of the tower is connected to the inlet port through a pipeline; the outlet of the tower top is connected to the inlet port through the pipeline. The bottom discharge port 3 is connected to the feed port through a pipe; the bottom discharge port is connected to the first three-way pipe through a pipe, and the first three-way pipe is an outlet device, the first Another outlet of the tee is in communication with the top feed port.

The top outlet of the tower is connected to the condenser 8 , the reflux tank 1 and the second tee through a pipeline, and one of the outlets of the second tee is connected to the top of the depropanizer 10 . The other outlet of the second tee is in communication with the feed port.

The top outlet 2 is connected to the condenser 2, the reflux tank 2, and the third tee through a pipeline, and an outlet of the third tee is connected to the top of the deethanizer 11 The other outlet of the third tee is in communication with the feed port three.

The other outlet of the first tee is in communication with the top feed port through a heat exchanger 5 and a pump 6.

The other outlet of the first tee is in turn connected to the top feed port through the heat exchanger 5 and the pump 6.

A feed tank 7 is disposed between the feed port and the raw material inlet.

a fourth three-way pipe is disposed between the raw material inlet and the feed tank 7, the first end of the fourth three-way pipe is in communication with the raw material inlet, and the second end of the fourth three-way pipe is The tank is connected, and the third end of the fourth tee is connected to the top outlet of the tower.

In the examples of the present invention, the raw materials are mainly carbon di(C2H6), carbon tris(C3H6, C3H8) carbon tetra (C4H10, C4H8, C5H12, CCL2O (carbon oxychloride, a component in liquefied gas)). The constituents of C. chinensis also include their isomers.

Feed tank 7: The raw material enters the tank before entering the tower equipment, and then flows into the tower through the pipeline;

The condenser reboilers are heat exchangers connected to the tower. The depropanizer and deethanizer are functionally all rectification towers. The general rectification towers are equipped with condensers and reboilers. of. The propylene recovery tower is functionally an absorption tower.

Flow of non-condensable gas: When the raw materials in the flow chart enter the tower, they are all liquid. The bottom reboiler supplies heat to the tower through different ways of heat exchange, so the light components and heavy components after the raw materials enter the depropanizer Separated, the carbon dioxide is vaporized in the material coming out of the tower due to the increase in temperature. This is the location where the first condensation does not occur.

The gas-liquid mixture at the top of the depropanizer column enters the deethanizer column. After a series of reactions, the light components are finally withdrawn from the top of the column. Because the bottom reboiler provides heat, a portion of the propylene is vaporized. The main part of the tower is the non-condensable carbon, which contains some of our target products. (Now the average company chooses to directly mix the non-condensable gas into the civil liquefied gas and sell it directly as fuel. It will not be disposed of. There are very few companies that use this part of the non-condensable gas to be mixed into other workshops for use. In the previous report, there is a detailed description.)

The non-condensable gas coming out from the top of the deethanizer tower entrains part of the desired product propylene, so the present invention designs a propylene recovery tower for recovery. The non-condensable gas enters from the bottom of the propylene recovery tower, the gas rises from the bottom, and the heavy component liquid from the bottom of the first tower depropanizer tower enters from the top of the propylene recovery tower, and the liquid flows from top to bottom, resulting in Reverse contact absorption. The heavy component absorbs the propylene in the non-condensable gas, and the non-condensed gas hardly entrains the propylene, and then discharges the non-condensable gas from the top of the propylene recovery tower, which is the last destination after the non-condensable gas is absorbed. The heavy component liquid that has absorbed propylene in the non-condensable gas is returned to the feed tank and mixed with the first raw material, so that more propylene enters the depropanizer column for a new round of rectification reaction to reach the propylene recovery tower. At that time, there will be more quality propylene.

In this embodiment, after the depropanizer bottom C4 is cooled, the temperature is lowered to 35 ° C, and after the pressure of the pressure pump is increased to 2.6 MPa, one device is discharged, and the other channel is about 10 tons per hour into the top of the propylene recovery tower as an absorbent. The propylene in the non-condensable gas C2 discharged from the top of the deethanizer is absorbed. The non-condensable gas C2 in the top reflux tank of the deethanizer tower enters the bottom of the propylene recovery tower through the pipeline from the gas phase outlet of the reflux tank, and is in reverse contact with the C4 absorbent. The propylene and propane in the non-condensable gas C2 are absorbed by the C4 absorbent. A small amount of C4 enters C2 and is not condensed by the propylene recovery tower overhead discharge unit. The propylene recovery tower bottom can obtain a heavy component mixture containing a higher content of propylene, and the material is directly returned to the feed of the depropanizer, and mixed with the catalytic cracked product as a gas. The sub-plant feeds into the depropanizer. The high pressure and low temperature of the depropanizer tower is favorable for absorption, so the column pressure is set to 2.0 MPa, and the bottom of the propylene recovery tower is returned to the depropanizer column. Therefore, the propylene recovery tower pressure should be similar to that of the depropanizer reflux tank, and the propylene recovery tower. When the column pressure is set to 2.4 MPa, it can be self-pressurized without adding a pump. Low temperature and high pressure not only ensure the complete recovery of propylene and propane, but also reduce the emission loss of C4 fraction. After calculating the cycle through the simulation software, the content of propylene in the non-condensable gas at the top of the deethanizer column was 65.9%, and the purity of the propylene product distilled from the top of the propylene column was 99.99%.

The role of heat exchanger 5: Because the temperature of the pipeline is too high, propylene is volatile. If it enters the propylene recovery tower directly, the propylene in the non-condensable gas will always be in a gaseous state because of the high temperature, which will not achieve good absorption. .

Pressurized pump 6: The pressure of the material from the depropanizer is 18.5, and the pressure at the top of the propylene recovery tower is 2.4. It needs to be pressurized by the pump before entering the propylene recovery tower. The pressure of the pump can be above 2.4, the pressure pump of 2.6 has more contact, and the actual situation may be floating, so the pump of 2.6 is selected.

According to the actual situation, at the time of operation, a pressure difference of 0.5 is set at the bottom of each tower, and the pressure at the top of the tower is 0.5 MPa less than the pressure at the bottom of the tower.

The function of the top condenser: For the depropanizer and deethanizer, the components in the tower are all components that are easily vaporized. When the temperature inside the tower is high, when the top of the tower is transported from the pipeline, it belongs to the gas and liquid. The mixture, after cooling by the overhead condenser, all became liquid and entered the reflux tank at the top. After turning into a liquid, it is beneficial to return to the reflux and transport to the next tower. Second, if there is gas, it may be partially evaporated and waste. The third is to recover heat. Therefore, one thing at the top of the material is to go to the top condenser and turn it into a liquid. (Condenser is a type of heat exchanger) The data and phase states listed in the table are cooled by the overhead condenser.

The propylene recovery tower can be used because the discharged material is in the gas phase, so no overhead condenser is added.

In the case of 1.8 MPa, the liquefied gas is all in the liquid phase due to the pressurization, and the normal temperature and normal pressure are the gas phase. Total feed The amount is 300,000 tons / year.

When the propylene recovery column is not added, the gas fractionation unit directly discharges the mixed non-condensable gas containing C2H6 (0.09), C3H6 (0.3), and C3H8 (0.01) from the line B1. After the addition of the propylene recovery column, the propylene recovery column overhead D1 line discharges C2H6 (0.05) C3H6 (0.00006) and other components in the feed. It can be seen that the flow of propylene in the discharged non-condensable gas is significantly reduced.

As can be seen from the composition of the bottom line A2 of the column 201, there is almost no propylene C3H6 (0.00001), all of which are heavier components in the raw materials. Divided into two groups by A2, a group of A4 directly out of the device, into other equipment areas. One group is A3 (flow rate 100,000 tons/year) entering the propylene recovery tower, reacting and absorbing the non-condensable mixture containing propylene in B1, absorbing propylene into the mixed liquid entering from the A3 line, and then propylene. The recovery tower bottom C3 line is delivered to the feed and mixed with the feed. Among them, the pipeline C3 contains C3H6 (0.3) and C3H8, C4H10, C4H8, C5H12, C5H10, CCL2O (total 10.01), it can be seen that for the propylene recovery tower, the feed in the A3 pipeline absorbs the B1 pipeline feed. The propylene, after absorption, is partially returned from the bottom line D3 with absorbed propylene and mixed with the raw material, so that about 0.3 million tons/year of propylene is recovered.

The role of heat exchanger 5: Because the temperature of the pipeline A2 is too high, propylene is volatile. If it enters the propylene recovery tower directly, the propylene in the non-condensable gas will always be in a gaseous state because of the high temperature, which will not achieve good absorption. effect.

Pressurized pump 6: The pressure of the material from T-201 is 18.5, and the pressure at the top of the propylene recovery tower is 2.4. It needs to be pressurized by the pump before entering the propylene recovery tower. The pressure of the pump can be above 2.4, the pressure pump of 2.6 has more contact, and the actual situation may be floating, so the pump of 2.6 is selected.

The role of the top condenser: For T-201 and T-202, the components in the tower are components that are easily vaporized. When the temperature inside the tower is high, when the top of the tower is transported outward by the Q1 and Q2 pipelines, it belongs to Gas-liquid mixture, tower After the top condensers 8, 9 are cooled, they all become liquid, and enter the top reflux tanks 1 and 2, respectively. After turning into a liquid, it is beneficial to return to the reflux and transport to the next tower. Second, if there is gas, it may be partially evaporated and waste. The third is to recover heat. Therefore, one thing at the top of the material is to go to the top condenser and turn it into a liquid. (Condenser is a type of heat exchanger) The data and phase states listed in the table are cooled by the overhead condenser.

The above is only the preferred embodiment of the present invention, and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., which are included in the spirit and scope of the present invention, should be included in the present invention. Within the scope of protection.

Claims

A gas fractionation device, comprising: a depropanizer, a deethanizer, a reboiler, a reboiler, and a propylene recovery tower, wherein the depropanizer is provided with a feed port and a top discharge The first and the bottom outlet of the tower, the deethanizer is provided with a feed port 2, a top discharge port 2 and a bottom outlet port 2. The propylene recovery tower is provided with a feed port 3 and a tower. a top feed port, a top discharge port 3 and a bottom outlet 3, the feed port 3 is disposed at the bottom of the propylene recovery column; the depropanizer is passed through the pipe and the reboiler Unicom, the deethanizer is connected to the reboiler through a pipeline; the feed port of the depropanizer is connected to the raw material inlet through a pipeline, and the outlet of the tower is connected to the inlet through the pipeline. The top discharge port 2 is connected to the feed port through the pipeline, and the bottom discharge port 3 is connected to the feed port through the pipeline; the bottom discharge port of the tower passes through the pipeline and the first three-way Pipe communication, the first tee is an outlet device, and the other outlet of the first tee is connected to the top inlet .
The gas fractionation device according to claim 1, wherein the top discharge port of the column is connected to the condenser one, the reflux tank one and the second three-way pipe through a pipe, wherein the second three-way pipe is One outlet is in communication with the top of the depropanizer, and the other outlet of the second tee is in communication with the feed port.
The gas fractionation device according to claim 1, wherein the top outlet 2 is connected to the condenser 2, the reflux tank 2 and the third tee through a pipe, and one of the third tees The outlet is in communication with the top of the deethanizer, and the other outlet of the third tee is in communication with the feed port three.
A gas fractionation apparatus according to claim 1, wherein the other outlet of said first tee is in communication with said top feed port through a heat exchanger and a pump.
A gas fractionation apparatus according to claim 4, wherein the other outlet of said first tee is in communication with said top feed port through a heat exchanger and a pump.
A gas fractionation apparatus according to claim 1, wherein a feed tank is provided between said feed port and said material inlet.
The gas fractionation device according to claim 6, wherein a fourth tee is disposed between the raw material inlet and the feed tank, and the first end of the fourth tee is connected to the raw material inlet. , said The second end of the fourth three-way pipe is connected to the feed tank, and the third end of the fourth three-way pipe is connected to the top discharge port of the tower.