阅读说明：本技术 一种向脱乙烷塔尾气中注入甲醇提高丙烯收率的方法 (Method for improving propylene yield by injecting methanol into tail gas of deethanizer ) 是由 叶绿生 陈波 刘飞 葛正坤 张宝君 于 2021-06-29 设计创作，主要内容包括：本发明公开了一种向脱乙烷塔尾气中注入甲醇提高丙烯收率的方法,属于低碳烯烃精制领技术领域。本发明提高丙烯收率的方法包括向脱乙烷塔尾气中注入甲醇提高丙烯收率和控制循环丙烷中丙烯含量以提高丙烯收率,在向脱乙烷塔尾气中注入甲醇提高丙烯收率的方法中增加一套注甲醇系统和相关的附属管线,将甲醇通过管线注入脱乙烷塔巴氏精馏段的不同部位,本发明解决了之前工艺脱乙烷塔尾气中丙烯含量高,丙烯收率低的问题；通过合理的控制循环丙烷中丙烯的含量,使更少的丙烯进入循环丙烷,从而提高丙烯收率,解决过去增加丙烯收率方法中能耗高、操作复杂、回收率不高的的缺点,降低了装置的能耗,精简了操作,节省了人力物力。(The invention discloses a method for improving propylene yield by injecting methanol into the tail gas of a deethanizer, belonging to the technical field of low-carbon olefin refining. The method for improving the propylene yield comprises the steps of injecting methanol into the tail gas of a deethanizer to improve the propylene yield and controlling the propylene content in the circulating propane to improve the propylene yield, adding a methanol injection system and related auxiliary pipelines in the method for improving the propylene yield by injecting methanol into the tail gas of the deethanizer, and injecting methanol into different parts of a pasteurisation section of the deethanizer through the pipelines, so that the problems of high propylene content and low propylene yield in the tail gas of the deethanizer in the prior art are solved; by reasonably controlling the content of propylene in the circulating propane, less propylene enters the circulating propane, so that the propylene yield is improved, the defects of high energy consumption, complex operation and low recovery rate in the conventional method for increasing the propylene yield are overcome, the energy consumption of a device is reduced, the operation is simplified, and manpower and material resources are saved.)

1. A method for improving the yield of propylene by injecting methanol into the tail gas of a deethanizer is characterized in that: the method for improving the yield of the propylene by injecting the methanol into the tail gas of the deethanizer comprises the following steps:

step 1: introducing nitrogen into the methanol storage tank (1) through a self-operated regulating valve I (2) before the methanol unloading, and setting the oxygen content in the methanol storage tank (1) below 0.5 percent through the injected nitrogen;

step 2: connecting the methanol storage tank (1) with the tank car by using a metal hose, and checking whether the on-site buckle connection is clamped tightly without leakage;

step 3: opening a hand brake on the tank car after checking that no error exists, unloading the methanol into the methanol storage tank (1), and checking whether the liquid levels of the on-site liquid level meter (4) and the remote transmission liquid level meter (5) are consistent or not in the unloading process;

step 4: when the liquid level is about 90%, closing a tank car hand valve, replacing a pipeline, and disconnecting the metal hose from a buckle connected with the tank car;

step 5: adjusting the pressure of the self-operated regulating valve I (2) to 50Kpa, injecting low-pressure nitrogen into the methanol storage tank (1) through the self-operated regulating valve I (2) for nitrogen sealing, isolating air, opening the self-operated regulating valve II (3) when the pressure in the methanol storage tank (1) exceeds 55Kpa, and discharging the pressure in the methanol storage tank (1) to a torch system;

step 6: analyzing the content of propylene in the tail gas of the deethanizer by an online analyzer (9);

step 7: adjusting the stroke of the methanol injection pump (6) according to the concentration of propane and propylene in the tail gas of the deethanizer;

step 8: the stroke and flow rate of the methanol injection pump (6) are recorded as the propylene and propane recovery in the deethanizer tail gas is minimized.

2. The method for improving the yield of the propylene by injecting the methanol into the tail gas of the deethanizer according to claim 1, wherein: the method for controlling the content of propylene in the circulating propane to improve the yield of the propylene comprises the following steps:

the method comprises the following steps: injecting propane propylene from the feed inlet into a product separation column (11);

step two: continuously increasing guide vanes of the heat pump compressor (10);

step three: monitoring MAPD content in a 168 th tray of the product separation tower (11) and propylene content in a propylene content monitoring device (13) in the circulating propane at the bottom of the tower on line;

step four: various data of the device at the time of the optimal operation are recorded.

3. The method for improving the yield of the propylene by injecting the methanol into the tail gas of the deethanizer according to claim 1, wherein: the methanol injection system comprises a methanol storage tank (1), a self-operated regulating valve I (2), a self-operated regulating valve II (3), an on-site liquid level meter (4), a remote transmission liquid level meter (5), a methanol injection pump (6) and a methanol conveying pipeline (7);

the input end of the methanol storage tank (1) is provided with a self-operated regulating valve I (2) and a self-operated regulating valve II (3), the two sides of the methanol storage tank (1) are provided with an on-site liquid level meter (4) and a remote transmission liquid level meter (5), the output end of the methanol storage tank (1) is provided with a methanol injection pump (6) through a methanol conveying pipeline (7), the input end of the methanol storage tank (1) is connected with a safety valve I (111), the other end of the safety valve I (111) is connected with the self-operated regulating valve II (3), and the safety valve I (111) is used for performing overpressure protection on the self-operated regulating valve II (3);

the methanol injection pump (6) is connected with the methanol storage tank (1) and the deethanizer (8) through a methanol conveying pipeline (7), and the methanol injection pump (6) is used for adjusting the flow of methanol injected into the deethanizer (8).

4. The method for improving the yield of the propylene by injecting the methanol into the tail gas of the deethanizer according to claim 1, wherein: and a small buffer tank and a safety valve II for preventing the pipeline from being over-pressurized are added on the outlet pipeline of the methanol injection pump (6), and the setting pressure of the safety valve II is up to 1.8 Mpa.

5. The method for improving the yield of propylene by injecting methanol into the tail gas of the deethanizer according to claim 3, wherein: the self-operated regulating valve I (2) is used for reducing the pressure of low-pressure nitrogen and then enabling the low-pressure nitrogen to enter the methanol storage tank (1) for nitrogen sealing, the self-operated regulating valve II (3) is used for discharging the pressure to a torch system after the pressure of the methanol storage tank (1) is increased, and the setting pressure of the safety valve I (111) is 1.0 Mpa.

6. The method for improving the yield of the propylene by injecting the methanol into the tail gas of the deethanizer according to claim 1, wherein: the volume of the methanol storage tank (1) is 5m³The pressure in the tank is set to be 0.5Mpa, the temperature in the tank is designed to be 90 ℃, and the methanol storage tank (1) is made of Q345R steel.

7. The method for improving the yield of propylene by injecting methanol into the tail gas of the deethanizer according to claim 3, wherein: the design flow rate of the methanol injection pump (6) is 0.565m³The pressure of the outlet of the pump is 1.6Mpa, the methanol injection pump (6) is made of molybdenum-containing stainless steel materials, the methanol injection pump (6) can be started on site, and methanol is injected into a pasteurization rectification section of the deethanizer (8) through a methanol conveying pipeline (7) as required.

8. The method for improving the yield of propylene by injecting methanol into the tail gas of the deethanizer according to claim 3, wherein: the methanol conveying pipeline (7) is composed of a metal hose, a carbon steel pipeline and a stainless steel pipeline, the carbon steel pipeline is used for conveying methanol from the methanol storage tank (1) to the metal hose, and the stainless steel pipeline is used for being matched with the metal hose to convey the methanol to the deethanizer (8).

9. The method for improving the yield of propylene by injecting methanol into the tail gas of the deethanizer according to claim 3, wherein: and the metal hose, the carbon steel pipeline and the stainless steel pipeline in the methanol conveying pipeline (7) are connected and installed in a flange connection mode.

10. The method for improving the yield of the propylene by injecting the methanol into the tail gas of the deethanizer according to claim 1, wherein: the ideal value of the propylene content in the circulating propane is controlled between 0.5 and 0.8 percent.

Technical Field

The invention relates to the technical field of low-carbon olefin refining, in particular to a method for improving the yield of propylene by injecting methanol into the tail gas of a deethanizer.

Background

The current PDH plant has a propane consumption of 1.18 (i.e. 1 tonne of propylene is produced, and 1.18 tonnes of propane is required to be charged to the reaction), corresponding to a propylene yield of 84.7%.

The existing method for improving the yield of propylene by using a propane dehydrogenation propylene preparation device mainly comprises the following steps:

injecting methanol into the product gas in the cold box, removing moisture carried in the product gas through two product gas dryers before the product gas enters the cold box, and freezing the product gas in a flow channel with a lower temperature grade to block the product gas flow channel if the moisture is not removed; on the other hand, if the drying effect of the product gas dryer is poor, trace moisture can enter the cold box along with the product gas to cause the freezing blockage of a product gas flow channel, so that 6 different positions are arranged in the product gas flow channel of EA-2011X, EA-2012X, EA-2013X, EA-2016X (3) to inject methanol, thereby preventing the freezing blockage of the cold box flow channel caused by the moisture entering the cold box to cause the propylene to be discharged out of a torch, and causing the propylene to have a large loss.

The temperature of an ethylene system is reduced, the temperature of a cold box is reduced to condense more propylene in product gas, the product gas contains a small amount of H2 and CH4 which are gases difficult to condense, hydrogen-rich tail gas (mainly comprising H2 and CH4) in the product gas must be separated before the product gas enters a deethanizer, a small amount of propane propylene enters a fuel gas system along with the hydrogen-rich tail gas in the separation process, and finally the propane propylene can only be burnt as fuel, the temperature of ethylene refrigerant is reduced, the temperature of the cold box is reduced, the propane propylene can be condensed more, the content of the propane propylene in the hydrogen-rich tail gas is reduced, and the yield of the propylene is improved.

The pressure of the cold box is increased, the condensation of propylene is increased, the yield of the propylene is improved, the pressure of the cold box is increased, equivalently, the condensation point of propane propylene is increased, and the propylene in the product gas is more easily condensed, so that the purpose of increasing the yield of the propylene is achieved.

The content of propylene in the circulating propane is reduced, more propylene can be separated from a product separation tower by reducing the content of propylene in the circulating propane, but the LUMMUS process requires that the content of propylene in the circulating propane is controlled to be 1.5-3% and cannot be too low, too low propylene can have MAPD to accumulate in the product separation tower, and after long-term operation, the MAPD accumulated in the product separation tower can quickly release heat and explode.

The above methods all have many disadvantages, such as: the amount of methanol is increased, and more methanol affects downstream systems; the power of the ethylene machine is increased, the consumption of steam is increased, the energy consumption of the whole device is increased, the power of the product gas compressor is increased, the energy consumption of the whole device is increased, and the loss of propylene in the tail gas of the deethanizer is not considered, so that the loss of propylene in the tail gas is greatly reduced.

Disclosure of Invention

The invention aims to provide a method for improving the yield of propylene by injecting methanol into the tail gas of a deethanizer so as to solve the problems in the background technology.

In order to solve the technical problems, the invention provides the following technical scheme: the method for improving the yield of the propylene by injecting the methanol into the tail gas of the deethanizer comprises the following steps:

step 1: introducing nitrogen into a methanol storage tank through a self-operated regulating valve before unloading the methanol, and setting the oxygen content in the methanol storage tank to be below 0.5 percent through the injected nitrogen;

step 2: the method comprises the following steps of connecting a methanol storage tank and a tank car by using a metal hose, checking whether field buckle connection is clamped or not and leakage does not exist, connecting the methanol storage tank and the tank car by using the metal hose so as to facilitate the methanol to be unloaded more conveniently and more quickly, wherein the connection mode among the metal hose, the methanol storage tank and the tank car is a wrench type quick connector, and the quick connector can ensure that the methanol can be unloaded into the methanol storage tank quickly, safely and effectively;

step 3: opening a hand brake on the tank car after checking that no error exists, unloading the methanol into a methanol storage tank, checking whether the liquid levels of the on-site liquid level meter and the remote transmission liquid level meter are consistent or not in the unloading process, controlling the liquid level to be about 90%, and if the liquid levels of the on-site liquid level meter and the remote transmission liquid level meter are not consistent, needing to contact instrument personnel to calibrate the instrument;

step 4: when the liquid level is about 90%, closing a tank car hand valve, replacing a pipeline, and disconnecting the metal hose from a buckle connected with the tank car;

step 5: adjusting the pressure of the first self-operated regulating valve to 50Kpa, injecting low-pressure nitrogen into the methanol storage tank through the first self-operated regulating valve for nitrogen sealing, isolating air, opening the second self-operated regulating valve when the pressure in the methanol storage tank exceeds 55Kpa, and discharging the pressure in the methanol storage tank to a torch system;

step 6: analyzing the content of propylene in the tail gas of the deethanizer by an online analyzer, confirming a methanol injection flow on site and starting a methanol injection pump when the concentration of propane and propylene in the tail gas of the deethanizer is more than 2.5%, and directly transporting methanol in a methanol storage tank to each part of the deethanizer by the methanol injection pump, so that the propylene in the tail gas of the deethanizer is quickly reduced, the continuity and stability of production are ensured, the yield of the propylene is improved, the capacity of the device is increased, and the material consumption and energy consumption are reduced;

step 7: adjusting the stroke of the methanol injection pump according to the concentration of propane and propylene in the tail gas of the deethanizer, and continuously injecting methanol until the pressure of the deethanizer is restored to the normal operation pressure, wherein the concentration of propane and propylene in the tail gas is less than 2.5%;

step 8: the stroke and flow rate of the methanol pump was recorded as the propylene and propane in the deethanizer tail gas recovered to a minimum.

Further, the method for controlling the content of propylene in the recycled propane to improve the yield of propylene comprises the following steps:

the method comprises the following steps: injecting propane propylene into the product separation column from the feed inlet;

step two: continuously increasing the guide vane degree of the heat pump compressor;

step three: monitoring the MAPD content in a 168 th tray of the product separation tower and the propylene content in a propylene content monitoring device in the circulating propane at the bottom of the tower on line, wherein the MAPD is a mixture of propyne and propadiene generated by a PDH device;

step four: various data of the device at the time of the optimal operation are recorded.

Further, the methanol injection system comprises a methanol storage tank, a self-operated regulating valve I, a self-operated regulating valve II, an on-site liquid level meter, a remote transmission liquid level meter, a methanol injection pump and a methanol conveying pipeline;

the input end of the methanol storage tank is provided with a first self-operated regulating valve and a second self-operated regulating valve, the two sides of the methanol storage tank are provided with an on-site liquid level meter and a remote-transmission liquid level meter, the output end of the methanol storage tank is provided with a methanol injection pump through a methanol conveying pipeline, the input end of the methanol storage tank is connected with a first safety valve, the other end of the first safety valve is connected with the second self-operated regulating valve, and the first safety valve is used for carrying out overpressure protection on the second self-operated regulating valve;

the methanol injection pump is connected with the methanol storage tank and the deethanizer through a methanol conveying pipeline, the methanol injection pump is used for adjusting the flow of methanol injected into the deethanizer, the methanol injection pump can be started or stopped on site, and remote operation can only be stopped.

Furthermore, a small buffer tank and a second safety valve for preventing pipeline overpressure are added on a pipeline of the outlet of the pump for injecting the methanol, the setting pressure of the second safety valve is 1.8Mpa, and the second safety valve is used for protecting the pipeline with overpressure nearby the pump for injecting the methanol.

Furthermore, the type of the first self-operated regulating valve is PCV-90201, the first self-operated regulating valve is used for reducing the pressure of low-pressure nitrogen and then enabling the nitrogen to enter a methanol storage tank for nitrogen sealing, the type of the second self-operated regulating valve is PCV-90202, the self-operated regulating valve is used for discharging the pressure to a torch system after the pressure of the methanol storage tank is increased, the setting pressure of the first safety valve is 1.0MPa, and the first safety valve is used for performing overpressure protection on the second self-operated regulating valve.

Further, the volume of the methanol storage tank is 5m³The pressure in the tank is set to be 0.5Mpa, the temperature in the tank is designed to be 90 ℃, the methanol storage tank is made of Q345R steel, the Q345R steel is adopted by the methanol storage tank to improve the comprehensive mechanical property and the process property of the methanol storage tank and improve the impact toughness of the methanol storage tank, and the model of the methanol storage tank is FA-9001X.

Further, the design flow rate of the methanol injection pump is 0.565m³The utility model discloses a methanol injection pump, including methanol injection pump, methanol delivery pump, methanol injection pump, and methanol injection pump, wherein, methanol injection pump, and methanol injection pump are respectively.

Furthermore, the metal hose, the carbon steel pipeline and the stainless steel pipeline in the methanol conveying pipeline are connected and installed in a flange connection mode, and the methanol conveying pipeline is prevented from falling off or leaking in the using process by installation in the flange connection mode.

Furthermore, the ideal value of the propylene content in the circulating propane is controlled to be 0.5-0.8%, and the propylene yield effect is best when the propylene content in the circulating propane is 0.5-0.8%.

Compared with the prior art, the invention has the following beneficial effects:

1. according to the invention, after methanol is injected into the tail gas of the deethanizer, the content of propylene in the tail gas is reduced from 19% to 0.2%, the propylene can be recovered by 0.34t/h according to the calculation of 1.8t/h of the tail gas, the content of propylene in the circulating propane is controlled to be about 0.5%, the propylene yield can be increased by 1.2t/h according to the calculation of 120t/h of the circulating propane, the overall propylene yield is improved by 1.54t/h compared with the previous propylene yield, the economic benefit of the device is greatly increased, and the problems of high propylene content and low propylene yield in the tail gas of the deethanizer in the prior art are solved.

2. The invention reasonably controls the content of propylene in the circulating propane, so that less propylene enters the circulating propane, thereby improving the yield of the propylene and solving the defects of high energy consumption, complex operation and low recovery rate in the traditional method for increasing the yield of the propylene.

3. The invention reduces the energy consumption of the device by reasonably controlling the content of propylene in the circulating propane, simplifies the operation and saves manpower and material resources.

Drawings

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

FIG. 1 is a schematic diagram of a methanol injection system for injecting methanol into the tail gas of a deethanizer to increase propylene yield according to the present invention;

FIG. 2 is a schematic diagram of the process flow of the deethanizer according to the present invention for improving propylene yield by injecting methanol into the deethanizer tail gas;

FIG. 3 is a schematic diagram of the structure of the work flow of propylene content in the recycled propane production by the method of the present invention for increasing the yield of propylene by injecting methanol into the tail gas of the deethanizer.

In the figure: 1. a methanol storage tank; 111. a first safety valve; 2. a self-supporting regulating valve I; 3. a second self-operated regulating valve; 4. an on-site level gauge; 5. a remote liquid level meter; 6. injecting a methanol pump; 7. a methanol delivery pipeline; 8. a deethanizer; 9. an on-line analyzer; 10. a heat pump compressor; 11. a product separation column; 12. a product splitter reboiler; 13. a device for monitoring the content of propylene in circulating propane in a tower bottom.

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. 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.

The implementation method comprises the following steps: the method for improving the yield of the propylene by injecting the methanol into the tail gas comprises the following steps:

step 1: introducing nitrogen into the methanol storage tank 1 through a self-operated regulating valve I2 before the methanol is unloaded, and setting the oxygen content in the methanol storage tank 1 to be below 0.5 percent through the injected nitrogen;

step 2: connecting the methanol storage tank 1 with the tank car by using a metal hose, and checking whether the on-site buckle connection is clamped tightly without leakage;

step 3: opening a hand brake on the tank car after checking that no error exists, unloading the methanol into the methanol storage tank 1, checking whether the liquid levels of the on-site liquid level meter 4 and the remote transmission liquid level meter 5 are consistent or not in the unloading process, controlling the liquid level to be about 90 percent, and if the liquid levels of the on-site liquid level meter 4 and the remote transmission liquid level meter 5 are not consistent, contacting instrument personnel to calibrate the instrument;

step 4: when the liquid level is about 90%, closing a tank car hand valve, replacing a pipeline, and disconnecting the metal hose from a buckle connected with the tank car;

step 5: adjusting the pressure of a self-operated regulating valve I2 to 50Kpa, injecting low-pressure nitrogen into a methanol storage tank 1 through the self-operated regulating valve I2 for nitrogen sealing, isolating air, wherein the temperature in the methanol storage tank 1 is 30 ℃, and when the pressure in the methanol storage tank 1 exceeds 55Kpa, opening a self-operated regulating valve II 3 and discharging the pressure in the methanol storage tank 1 to a torch system;

step 6: the content of propylene in the tail gas of the deethanizer is analyzed by the on-line analyzer 9, and the content of propylene in the tail gas of the deethanizer is analyzed to be 0.24%, at the moment, the yield of propylene is optimal, the pump pressure of the methanol injection pump 6 is 1.60Mpa, and the stroke of the methanol injection pump 6 is 50%.

Comparative example one:

step 1: introducing nitrogen into the methanol storage tank 1 through a self-operated regulating valve I2 before the methanol is unloaded, and setting the oxygen content in the methanol storage tank 1 to be below 0.5 percent through the injected nitrogen;

step 2: connecting the methanol storage tank 1 with the tank car by using a metal hose, and checking whether the on-site buckle connection is clamped tightly without leakage;

step 3: opening a hand brake on the tank car after checking that no error exists, unloading the methanol into the methanol storage tank 1, checking whether the liquid levels of the on-site liquid level meter 4 and the remote transmission liquid level meter 5 are consistent or not in the unloading process, controlling the liquid level to be about 90 percent, and if the liquid levels of the on-site liquid level meter 4 and the remote transmission liquid level meter 5 are not consistent, contacting instrument personnel to calibrate the instrument;

step 4: when the liquid level is about 90%, closing a tank car hand valve, replacing a pipeline, and disconnecting the metal hose from a buckle connected with the tank car;

step 5: adjusting the pressure of a self-operated regulating valve I2 to 48Kpa, injecting low-pressure nitrogen into a methanol storage tank 1 through the self-operated regulating valve I2 for nitrogen sealing, isolating air, keeping the temperature in the methanol storage tank 1 at 25 ℃, opening a self-operated regulating valve II 3 when the pressure in the methanol storage tank 1 exceeds 55Kpa, and discharging the pressure in the methanol storage tank 1 to a torch system;

step 6: analyzing the content of propylene in the tail gas of the deethanizer by an online analyzer 9, analyzing that the content of propylene in the tail gas of the deethanizer is 0.37 percent, determining the methanol injection process and starting the methanol injection pump 6 when the pump pressure of the methanol injection pump 6 is 1.50Mpa, and directly transporting methanol in the methanol storage tank 1 to each part of the deethanizer 8 by the methanol injection pump 6;

step 7: adjusting the stroke of the methanol injection pump 6 according to the concentration of propane and propylene in the tail gas of the deethanizer, and continuously injecting methanol until the pressure of the deethanizer 8 is restored to the normal operation pressure, wherein the concentration of propane and propylene in the tail gas is less than 2.5%;

step 8: when the propylene and propane in the deethanizer tail gas are recovered to a minimum, the stroke of the methanol injection pump 6 is 42.

The comparison column two:

step 1: introducing nitrogen into the methanol storage tank 1 through a self-operated regulating valve I2 before the methanol is unloaded, and setting the oxygen content in the methanol storage tank 1 to be below 0.5 percent through the injected nitrogen;

step 2: connecting the methanol storage tank 1 with the tank car by using a metal hose, and checking whether the on-site buckle connection is clamped tightly without leakage;

step 3: opening a hand brake on the tank car after checking that no error exists, unloading the methanol into the methanol storage tank 1, checking whether the liquid levels of the on-site liquid level meter 4 and the remote transmission liquid level meter 5 are consistent or not in the unloading process, controlling the liquid level to be about 90 percent, and if the liquid levels of the on-site liquid level meter 4 and the remote transmission liquid level meter 5 are not consistent, contacting instrument personnel to calibrate the instrument;

step 4: when the liquid level is about 90%, closing a tank car hand valve, replacing a pipeline, and disconnecting the metal hose from a buckle connected with the tank car;

step 5: adjusting the pressure of a self-operated regulating valve I2 to 53Kpa, injecting low-pressure nitrogen into a methanol storage tank 1 through the self-operated regulating valve I2 for nitrogen sealing, isolating air, wherein the temperature in the methanol storage tank 1 is 35 ℃, and when the pressure in the methanol storage tank 1 exceeds 55Kpa, opening a self-operated regulating valve II 3 and discharging the pressure in the methanol storage tank 1 to a torch system;

step 6: analyzing the content of propylene in the tail gas of the deethanizer by an online analyzer 9, analyzing that the content of propylene in the tail gas of the deethanizer is 0.42 percent, determining the methanol injection process and starting the methanol injection pump 6 when the pump pressure of the methanol injection pump 6 is 1.70Mpa, and directly transporting methanol in the methanol storage tank 1 to each part of the deethanizer 8 by the methanol injection pump 6;

step 7: adjusting the stroke of the methanol injection pump 6 according to the concentration of propane and propylene in the tail gas of the deethanizer, and continuously injecting methanol until the pressure of the deethanizer 8 is restored to the normal operation pressure, wherein the concentration of propane and propylene in the tail gas is less than 2.5%;

step 8: when the propylene and propane in the deethanizer tail gas are recovered to a minimum, the stroke of the methanol injection pump 6 is 55.

The following table is compiled from the experimental data of example one, comparative example one and comparative example two:

watch 1

When the concentration of propane and propylene in the tail gas of the deethanizer is less than 2.5 percent and the propylene and propane in the tail gas of the deethanizer are recovered to the minimum, the propylene yield is optimal, the stroke of the methanol injection pump 6 is optimal at the moment, the optimal methanol injection amount is obtained when the stroke is 50 according to the data in the table I, the concentration of propylene and propane in the tail gas of the deethanizer is 0.24 percent when the stroke is recovered to the minimum, the pressure of the self-operated regulating valve is set to be 50Kpa at the moment, the pressure of the methanol injection pump 6 is 1.60Mpa, and the temperature in the methanol storage tank 1 is 30 ℃.

Example two: the method for controlling the content of propylene in the circulating propane to improve the yield of the propylene comprises the following steps:

the method comprises the following steps: injecting propane propylene from the feed inlet into the product separation column 11;

step two: increasing the guide vane of the heat pump compressor 10 to 69%, simultaneously increasing the outlet temperature of the heat pump compressor 10 to 55.5 ℃, and gradually increasing the temperature of the product separation tower reboiler 12 to 53.5 ℃;

step three: the MAPD content in the 168 th tray of the product separation tower 11 is monitored to be 0.49% on line, the propylene content in the circulating propane at the tower bottom is 0.51%, and the tower pressure in the deethanizer 8 is 1.097Mpa at the moment;

step four: and recording data of each device during operation.

Comparative example three:

the method for controlling the content of propylene in the circulating propane to improve the yield of the propylene comprises the following steps:

the method comprises the following steps: injecting propane propylene from the feed inlet into the product separation column 11;

step two: increasing the guide vanes of the heat pump compressor 10 to 67%, simultaneously increasing the outlet temperature of the heat pump compressor 10 to 54.1 ℃, and gradually increasing the temperature of the product separation tower reboiler 12 to 50.8 ℃;

step three: the MAPD content in the 168 th tray of the product separation tower 11 is monitored to be 0.43 percent on line, the propylene content in the circulating propane at the tower bottom is monitored to be 0.47 percent, and the tower pressure in the deethanizer 8 is 1.018Mpa at the moment;

step four: and recording data of each device during operation.

Comparative example four:

the method for controlling the content of propylene in the circulating propane to improve the yield of the propylene comprises the following steps:

the method comprises the following steps: injecting propane propylene from the feed inlet into the product separation column 11;

step two: increasing the guide vanes of the heat pump compressor 10 to 70.5%, simultaneously increasing the outlet temperature of the heat pump compressor 10 to 57.2 ℃, and gradually increasing the temperature of the product separation tower reboiler 12 to 55.4 ℃;

step three: the MAPD content in the 168 th tray of the product separation tower 11 is monitored to be 0.53 percent on line, the propylene content in the circulating propane at the tower bottom is 0.43 percent, and the tower pressure in the deethanizer 8 is 1.101Mpa at the moment;

step four: and recording data of each device during operation.

The following tables are compiled from the experimental data of example two, comparative example three and comparative example four:

watch two

As the ideal value of the propylene content in the circulating propane is 0.5-0.8%, the stationary blade angle of the heat pump compressor is slowly increased to 69%, the outlet temperature of the heat pump compressor is increased to 55.5 ℃, the reboiler temperature of the product separation tower is controlled to be 53.5 ℃, the tower pressure is increased to 1.097Mpa, the MAPD content in the 168 th layer tray of the online monitoring product separation tower is 0.49%, and the optimal operation is realized when the propylene content in the circulating propane at the bottom of the tower is 0.51%.

It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.

Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. 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.