A dichloroethane refining apparatus and process

Abstract

The application discloses a dichloroethane refining device, which comprises a light component tower (1), a heavy component tower (2), a vacuum recovery tower (3), a first dichloroethane feeding pipeline (10), a second dichloroethane feeding pipeline (30) and a third dichloroethane feeding pipeline (50), and is characterized in that: the device further comprises a first polymerization inhibitor supply pipeline (60) for supplying an aromatic hydrocarbon nitro polymerization inhibitor, an outlet end of which is connected with the second dichloroethane feeding pipeline (30); a second polymerization inhibitor supply pipeline (70) for supplying an aromatic hydrocarbon nitro polymerization inhibitor, an outlet end of which is connected with the third dichloroethane feeding pipeline (50); and a third polymerization inhibitor supply pipeline (80) for supplying a phenolic polymerization inhibitor, an outlet end of which is connected with the vacuum recovery tower (3). The application further discloses a dichloroethane refining process using the dichloroethane refining device. Compared with the prior art, the application can reduce heavy component polymerization and improve the yield and purity of dichloroethane.

Description

Technical Field

[0001] This invention relates to the field of dichloroethane production technology, specifically to a dichloroethane refining apparatus and process. Background Technology

[0002] The ethylene-based vinyl chloride plant obtains vinyl chloride by cracking dichloroethane. To ensure the purity of dichloroethane, the ethylene-based vinyl chloride plant usually includes a dichloroethane refining process. The dichloroethane refining process usually includes a light component tower, a heavy component tower, and a dichloroethane vacuum recovery tower. The dichloroethane sent to the dichloroethane refining process usually comes from the following three sources: (1) generated by oxychlorination reaction; (2) generated by direct chlorination reaction; and (3) unreacted dichloroethane recovered from cracking reaction.

[0003] Dichloroethane produced by the oxychlorination reaction is passed through a light component tower to remove light components such as water, then through a heavy component tower for distillation to obtain most of the dichloroethane. Finally, it is sent to a dichloroethane vacuum recovery tower for further recovery of a small amount of dichloroethane, while heavy components such as chloroprene are concentrated and removed. Dichloroethane produced by the direct chlorination reaction contains virtually no light components, so it only needs to be sent to the heavy component tower and the dichloroethane vacuum recovery tower. Dichloroethane recovered from the cracking reaction has lower purity and is sent directly to the dichloroethane vacuum recovery tower. Most of the heavy components sent to the dichloroethane vacuum recovery tower come from dichloroethane produced by the direct chlorination reaction, a small portion comes from unreacted dichloroethane recovered from the cracking reaction, and a very small portion comes from dichloroethane produced by the oxychlorination reaction. During the heavy component concentration process in the dichloroethane vacuum recovery tower, some heavy components, especially chloroprene and styrene, are highly prone to polymerization to form heavy component tar, which causes coking in the reboiler of the dichloroethane vacuum recovery tower, significantly reducing its service life and increasing replacement frequency. Meanwhile, heavy components, along with solids and iron, will enter the dichloroethane product, causing coking in the evaporator and cracking furnace tubes of the dichloroethane cracking furnace, affecting the stable operation of the entire VCM unit.

[0004] Therefore, how to prevent the polymerization of heavy components and improve the yield and purity of dichloroethane during the purification process is a technical problem that urgently needs to be solved in the industry.

[0005] Chinese patent application number CN202320009293.4 discloses a negative pressure distillation and purification device for dichloroethane, comprising a tar kettle, a distillation column, a reboiler, a distillation column top cooler, a reflux tank, a reflux pump, a liquid ring vacuum pump, a gas-liquid separator, and a circulating liquid cooler connected in sequence. The tar kettle operates under controlled liquid level, pressure, and temperature, and is automatically controlled by an interlocking module in the DCS system. Dichloroethane in the distillation residue in the tar kettle is vaporized and recovered to the distillation column for separation and purification. The uncondensed gas is sent to an incineration unit for further treatment. The outlet pipe of the liquid ring vacuum pump is equipped with a pressure regulation and control loop for the distillation system, so that the entire distillation system operates under a relatively stable micro-negative pressure condition. This device reduces the polymerization of heavy components by controlling the negative pressure and the column bottom temperature.

[0006] Chinese patent application CN202122959772.6 discloses a method for recovering dichloroethane using a two-stage vacuum distillation process that is less prone to coking. The method includes the following steps: material from the bottom of a high-boiling-point distillation column is passed through the middle of a single-stage vacuum distillation column; when using both a single-stage and a two-stage vacuum distillation column: material with a dichloroethane content of 25%–35% is collected from the bottom of the single-stage vacuum distillation column and fed into the middle of the two-stage vacuum distillation column; material with a dichloroethane content of 10%–15% is collected from the bottom of the two-stage vacuum distillation column and stored as a byproduct in a storage tank; dichloroethane product is collected from the top of both the single-stage and two-stage vacuum distillation columns; when using only a single-stage vacuum distillation column: material with a dichloroethane content of 10%–15% is collected from the bottom of the single-stage vacuum distillation column and stored as a byproduct in a storage tank; dichloroethane product is collected from the top of the single-stage vacuum distillation column.

[0007] It is evident that existing technologies for preventing the polymerization of heavy components in the dichloroethane refining process only involve the dichloroethane vacuum recovery process, and the technical means employed are limited to indirect methods such as temperature control and adding backup distillation columns. They lack comprehensive, systematic, efficient, and direct methods for inhibiting polymerization, and therefore often prove ineffective in actual implementation.

[0008] In addition, because the vacuum recovery process of dichloroethane uses negative pressure, although it reduces the distillation temperature, saves energy, and slows down the polymerization of heavy components, air will inevitably enter the vacuum distillation column under negative pressure. The reaction of oxygen with heavy components will form tar with higher viscosity or even solid particles, which will lead to increased blockage of the reboiler. Summary of the Invention

[0009] The first technical problem to be solved by the present invention is to provide a dichloroethane purification apparatus that can reduce the polymerization of heavy components and improve the yield and purity of dichloroethane, in light of the current state of the prior art.

[0010] The second technical problem to be solved by the present invention is to provide a dichloroethane refining process using the above-mentioned dichloroethane refining apparatus.

[0011] The technical solution adopted by this invention to solve the first technical problem is: a dichloroethane refining apparatus, comprising:

[0012] The light component tower has a first material outlet at the top for discharging the light component and a second material outlet at the bottom for discharging the remaining component.

[0013] The recombining column has a first material outlet at the top for discharging dichloroethane and a second material outlet at the bottom for discharging the remaining components.

[0014] The vacuum recovery tower has a first material outlet at the top for discharging dichloroethane and a second material outlet at the bottom for discharging heavy by-products.

[0015] A first dichloroethane feed line is used to supply dichloroethane generated from the oxychlorination reaction, and the outlet end of the first dichloroethane feed line is connected to the light component tower.

[0016] The first conveying pipeline has its inlet end connected to the second material outlet of the light component tower and its outlet end connected to the heavy component tower.

[0017] A second dichloroethane feed line is used to supply dichloroethane from a direct chlorination reaction, and the outlet end of the second dichloroethane feed line is connected to the heavy fraction tower.

[0018] The second conveying pipeline has its inlet end connected to the second material outlet of the recombining tower and its outlet end connected to the vacuum recovery tower; and

[0019] The third dichloroethane feed line is used to supply unreacted dichloroethane recovered from the cracking reaction, and the outlet end of the third dichloroethane feed line is connected to the vacuum recovery tower.

[0020] Its characteristic is that it also includes:

[0021] The first polymerization inhibitor supply line is used to supply aromatic nitro polymerization inhibitors, and the outlet end of the first polymerization inhibitor supply line is connected to the second dichloroethane feed line.

[0022] A second polymerization inhibitor supply line is used to supply aromatic nitro polymerization inhibitors, and the outlet end of the second polymerization inhibitor supply line is connected to the third dichloroethane feed line; and

[0023] A third polymerization inhibitor supply line is used to supply phenolic polymerization inhibitors, and the outlet end of the third polymerization inhibitor supply line is connected to the vacuum recovery tower.

[0024] To ensure the distillation effect of the light component column, a first condenser is installed at the top of the light component column, and a first reboiler is installed at the bottom of the light component column.

[0025] To ensure the distillation effect of the heavy fraction column, a second condenser is installed at the top of the heavy fraction column, and a second reboiler is installed at the bottom of the heavy fraction column.

[0026] To ensure the distillation effect of the vacuum recovery tower, a third condenser and a vacuum pump negative pressure system are installed at the top of the vacuum recovery tower, and a third reboiler is installed at the bottom of the vacuum recovery tower.

[0027] In order to realize the automatic conveying of materials in the first conveying pipeline, a first conveying pump is installed on the first conveying pipeline for conveying materials from the inlet end to the outlet end of the first conveying pipeline.

[0028] In order to realize the automatic conveying of materials in the second conveying pipeline, a second conveying pump is installed on the second conveying pipeline for conveying materials from the inlet end to the outlet end of the second conveying pipeline.

[0029] To simplify the piping, the first and second inhibitor supply lines share the same upstream section.

[0030] The technical solution adopted by the present invention to solve the second technical problem is: a dichloroethane refining process using the above-mentioned dichloroethane refining apparatus, comprising the following steps:

[0031] (1) Light component removal process: The first dichloroethane feed pipeline supplies dichloroethane generated from the oxychlorination reaction to the light component tower. The light component is removed at the top of the light component tower by distillation, and the remaining component is sent to the heavy component tower through the first conveying pipeline in the bottom of the tower.

[0032] (2) Heavy component removal process: The second dichloroethane feed line supplies dichloroethane from the direct chlorination reaction to the heavy component tower. The dichloroethane product is collected at the top of the heavy component tower by distillation, and the remaining components are sent to the vacuum recovery tower through the second conveying line in the bottom of the tower. At the same time, the first polymerization inhibitor supply line adds aromatic nitro polymerization inhibitor to the second dichloroethane feed line.

[0033] (3) Dichloroethane vacuum recovery process: The third dichloroethane feed line supplies unreacted dichloroethane recovered from the cracking reaction to the vacuum recovery tower. The dichloroethane product is recovered at the top of the tower by distillation in the vacuum recovery tower. The remaining components are sent out as heavy by-products in the bottom of the tower. At the same time, the second polymerization inhibitor supply line adds aromatic nitro polymerization inhibitors to the third dichloroethane feed line, and the third polymerization inhibitor supply line adds phenolic polymerization inhibitors to the vacuum recovery tower.

[0034] Preferably, the pressure at the top of the light component column is 0.02–0.1 MPaG, the temperature at the top is 74–80°C, the pressure at the bottom is 0.08–0.16 MPaG, and the temperature at the bottom is 108–114°C. Using these temperatures and pressures effectively removes moisture and light components from the light component column, preventing excessive moisture and light component content from affecting the polymerization inhibitor's effectiveness.

[0035] Preferably, the top pressure of the heavy component column is 0.02–0.1 MPaG, the top temperature is 96–105°C, the bottom pressure is 0.05–0.13 MPaG, and the bottom temperature is 103–112°C. Using these temperatures and pressures ensures that the purity of the extracted dichloroethane is above 99.5% and delays the polymerization of heavy components at the bottom of the heavy component column.

[0036] Preferably, the pressure at the top of the vacuum recovery tower is -0.09 to -0.05 MPaG, the temperature at the top is 47 to 55°C, the pressure at the bottom is -0.07 to -0.03 MPaG, and the temperature at the bottom is 90 to 100°C. Using these temperatures and pressures allows for the recovery of dichloroethane as much as possible while ensuring a purity of over 99%, and also slows down the polymerization of heavy components at the bottom of the dichloroethane vacuum recovery tower.

[0037] Preferably, the amount of aromatic nitro polymerization inhibitor added to the second dichloroethane feed line is 50–150 ppm. The heavy component content in the direct chlorination reaction to heavy component removal process line is relatively high, requiring an appropriate increase in the amount of aromatic nitro compounds added.

[0038] Preferably, the amount of aromatic nitro polymerization inhibitor added to the third dichloroethane feed line is 20–60 ppm. The content of heavy components in the dichloroethane vacuum recovery process line from the cracking reaction is relatively low, so only a small amount of aromatic nitro compound needs to be added.

[0039] Preferably, the amount of phenolic polymerization inhibitor added to the vacuum recovery tower is 100–200 ppm. This amount effectively consumes the oxygen introduced during the dichloroethane vacuum recovery process and achieves a good polymerization inhibition effect.

[0040] Preferably, the aromatic nitro polymerization inhibitor is at least one of nitrobenzene or nitronaphthalene.

[0041] Preferably, the phenolic polymerization inhibitor is at least one of 2-tert-butylhydroquinone or 2,5-di-tert-butylhydroquinone.

[0042] Compared with the prior art, the advantages of the present invention are as follows:

[0043] (1) Based on the existing technology, by adding a high-efficiency polymerization inhibitor, the polymerization of heavy components is prevented more directly, efficiently and specifically, the service life of the equipment is extended and the stability of the equipment operation is improved.

[0044] First, aromatic nitro polymerization inhibitors are highly effective at inhibiting the polymerization of conjugated dienes such as chloroprene;

[0045] Secondly, phenolic polymerization inhibitors are also commonly used as antioxidants. Under aerobic conditions, they can react with oxygen, consuming it to generate quinone polymerization inhibitors. Quinone polymerization inhibitors are highly effective at inhibiting the polymerization of aromatic olefins such as styrene. Therefore, in the vacuum recovery process of dichloroethane, phenolic polymerization inhibitors, on the one hand, react with oxygen to continuously consume oxygen, thus avoiding the formation of more viscous tar or even solid particles from the reaction of oxygen with heavy components; on the other hand, they react with oxygen to generate quinone compounds, which can act as polymerization inhibitors.

[0046] Third, the aromatic nitro polymerization inhibitors and phenolic polymerization inhibitors ultimately converge in the dichloroethane vacuum recovery process, which can play a synergistic role and effectively inhibit the polymerization of conjugated dienes such as chloroprene and aromatic olefins such as styrene, thus significantly reducing the generation of heavy tar.

[0047] (2) Not limited to the vacuum recovery process of dichloroethane, but starting from the source of heavy components such as direct chlorination reaction and cracking reaction, the polymerization inhibition measures can be fully implemented to prevent the polymerization of heavy components.

[0048] (3) Existing technologies usually control the content of heavy components in the reboiler based on the reboiler temperature. If the polymerization of heavy components intensifies, the reboiler temperature will gradually rise, requiring a large amount of heavy components to be discharged from the reboiler to avoid polymerization. Heavy components usually contain about 20% dichloroethane. This method can reduce the discharge of heavy components, thereby increasing the yield of dichloroethane and reducing the overall unit consumption of the equipment, achieving cost reduction and efficiency improvement. On the other hand, it reduces the amount of waste liquid generated, which is conducive to reducing the cost of waste treatment and reducing emissions to the environment. Attached Figure Description

[0049] Figure 1 This is a schematic diagram of an embodiment of the dichloroethane purification apparatus of the present invention. Detailed Implementation

[0050] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0051] like Figure 1The diagram shows a preferred embodiment of the dichloroethane refining apparatus of the present invention. This dichloroethane refining apparatus includes a light component tower 1, a heavy component tower 2, a vacuum recovery tower 3, a first dichloroethane feed line 10, a first conveying line 20, a second dichloroethane feed line 30, a second conveying line 40, a third dichloroethane feed line 50, a first polymerization inhibitor supply line 60, a second polymerization inhibitor supply line 70, and a third polymerization inhibitor supply line 80.

[0052] The light component tower 1 is equipped with a first condenser 11 at the top and has a first material outlet for discharging the light component. The bottom of the light component tower 1 is equipped with a first reboiler 12 and has a second material outlet for discharging the remaining component.

[0053] The top of the heavy fraction column 2 is equipped with a second condenser 21 and has a first material outlet for discharging dichloroethane. The bottom of the heavy fraction column 2 is equipped with a second reboiler 22 and has a second material outlet for discharging the remaining components.

[0054] The top of the vacuum recovery tower 3 is equipped with a third condenser 31 and a vacuum pump negative pressure system 32, and has a first material outlet for discharging dichloroethane. The bottom of the vacuum recovery tower 3 is equipped with a third reboiler 33 and has a second material outlet for discharging heavy by-products.

[0055] The first dichloroethane feed line 10 is used to supply dichloroethane generated from the oxychlorination reaction, and the outlet end of the first dichloroethane feed line 10 is connected to the light component tower 1.

[0056] The inlet end of the first conveying pipeline 20 is connected to the second material outlet of the light component tower 1, and the outlet end of the first conveying pipeline 20 is connected to the heavy component tower 2. A first conveying pump 201 for conveying material from the inlet end to the outlet end of the first conveying pipeline 20 is installed on the first conveying pipeline 20.

[0057] The second dichloroethane feed line 30 is used to supply dichloroethane from the direct chlorination reaction, and the outlet end of the second dichloroethane feed line 30 is connected to the heavy fraction tower 2.

[0058] The inlet end of the second conveying pipeline 40 is connected to the second material outlet of the heavy separation tower 2, the outlet end of the second conveying pipeline 40 is connected to the vacuum recovery tower 3, and a second conveying pump 401 for conveying materials from the inlet end to the outlet end of the second conveying pipeline 40 is installed on the second conveying pipeline 40.

[0059] The third dichloroethane feed line 50 is used to supply unreacted dichloroethane recovered from the cracking reaction, and the outlet end of the third dichloroethane feed line 50 is connected to the vacuum recovery tower 3.

[0060] The first inhibitor supply line 60 is used to supply aromatic nitro inhibitors, and the outlet end of the first inhibitor supply line 60 is connected to the second dichloroethane feed line 30.

[0061] The second inhibitor supply line 70 is used to supply aromatic nitro-based inhibitors, and its outlet is connected to the third dichloroethane feed line 50. In this embodiment, the first inhibitor supply line 60 and the second inhibitor supply line 70 share the same upstream section.

[0062] The third polymerization inhibitor supply line 80 is used to supply phenolic polymerization inhibitors, and the outlet end of the third polymerization inhibitor supply line 80 is connected to the vacuum recovery tower 3.

[0063] Example 1:

[0064] (1) Light component removal process: The first dichloroethane feed line 10 supplies dichloroethane generated from the oxychlorination reaction to the light component tower 1. The light component is removed at the top of the light component tower 1 by distillation, and the remaining component is sent to the heavy component tower 2 through the first conveying line 20 in the bottom of the tower.

[0065] Among them, the pressure at the top of the light component tower 1 is controlled at 0.06 MPaG, the temperature at the top of the tower is 77℃, the pressure at the bottom of the tower is 0.12 MPaG, and the temperature at the bottom of the tower is 111℃;

[0066] (2) Heavy component removal process: The second dichloroethane feed line 30 supplies dichloroethane from the direct chlorination reaction to the heavy component tower 2. The dichloroethane product is collected at the top of the heavy component tower 2 through distillation, and the remaining components are sent to the vacuum recovery tower 3 through the second conveying line 40 in the bottom of the tower. At the same time, the first polymerization inhibitor supply line 60 adds nitrobenzene as a polymerization inhibitor to the second dichloroethane feed line 30.

[0067] The initial heavy component content of the dichloroethane supplied to the heavy component tower 2 from the direct chlorination reaction is 5%.

[0068] The pressure at the top of the recombining column 1 is controlled at 0.06 MPaG, the temperature at the top of the column is 100℃, the pressure at the bottom of the column is 0.09 MPaG, and the temperature at the bottom of the column is 108℃.

[0069] The amount of nitrobenzene added to the second dichloroethane feed line 30 is 150 ppm;

[0070] (3) Dichloroethane vacuum recovery process: The third dichloroethane feed line 50 supplies unreacted dichloroethane recovered from the cracking reaction to the vacuum recovery tower 3. The dichloroethane product is recovered at the top of the tower by distillation in the vacuum recovery tower 3. The remaining components are sent out as heavy by-products in the bottom of the tower. At the same time, the second polymerization inhibitor supply line 70 adds nitrobenzene as a polymerization inhibitor to the third dichloroethane feed line 50, and the third polymerization inhibitor supply line 80 adds 2-tert-butylhydroquinone as a polymerization inhibitor to the vacuum recovery tower 3.

[0071] The initial heavy component content of the unreacted dichloroethane recovered from the cracking reaction supplied to vacuum recovery tower 3 is 2.5%;

[0072] The vacuum recovery tower 3 is controlled with a top pressure of -0.07 MPaG, a top temperature of 51℃, a bottom pressure of -0.05 MPaG, and a bottom temperature of 95℃.

[0073] The amount of nitrobenzene added to the third dichloroethane feed line 50 is 60 ppm;

[0074] The amount of 2-tert-butylhydroquinone added to vacuum recovery tower 3 is 200 ppm;

[0075] The final dichloroethane refining process produces 100 tons / hour of refined dichloroethane, while the vacuum recovery process for dichloroethane emits 0.5 tons / hour of heavy components.

[0076] Sampling and analysis of the heavy components in the vacuum recovery process of dichloroethane showed that the dynamic viscosity at 25°C was 1.1 mPa·s, the solid particulate matter content was 0.12%, the reboiler flow rate decrease was 0.49% after one week of operation, and the reboiler is expected to be usable for 1.57 years.

[0077] Example 2:

[0078] (1) Light component removal process: The first dichloroethane feed line 10 supplies dichloroethane generated from the oxychlorination reaction to the light component tower 1. The light component is removed at the top of the light component tower 1 by distillation, and the remaining component is sent to the heavy component tower 2 through the first conveying line 20 in the bottom of the tower.

[0079] Among them, the pressure at the top of the light component tower 1 is controlled at 0.06 MPaG, the temperature at the top of the tower is 77℃, the pressure at the bottom of the tower is 0.12 MPaG, and the temperature at the bottom of the tower is 111℃;

[0080] (2) Heavy component removal process: The second dichloroethane feed line 30 supplies dichloroethane from the direct chlorination reaction to the heavy component tower 2. The dichloroethane product is collected at the top of the heavy component tower 2 through distillation, and the remaining components are sent to the vacuum recovery tower 3 through the second conveying line 40 in the bottom of the tower. At the same time, the first polymerization inhibitor supply line 60 adds nitrobenzene as a polymerization inhibitor to the second dichloroethane feed line 30.

[0081] The initial heavy component content of the dichloroethane supplied to the heavy component tower 2 from the direct chlorination reaction is 5%.

[0082] The pressure at the top of the recombining column 1 is controlled at 0.06 MPaG, the temperature at the top of the column is 100℃, the pressure at the bottom of the column is 0.09 MPaG, and the temperature at the bottom of the column is 108℃.

[0083] The amount of nitrobenzene added to the second dichloroethane feed line 30 is 100 ppm;

[0084] (3) Dichloroethane vacuum recovery process: The third dichloroethane feed line 50 supplies unreacted dichloroethane recovered from the cracking reaction to the vacuum recovery tower 3. The dichloroethane product is recovered at the top of the tower by distillation in the vacuum recovery tower 3. The remaining components are sent out as heavy by-products in the bottom of the tower. At the same time, the second polymerization inhibitor supply line 70 adds nitrobenzene as a polymerization inhibitor to the third dichloroethane feed line 50, and the third polymerization inhibitor supply line 80 adds 2-tert-butylhydroquinone as a polymerization inhibitor to the vacuum recovery tower 3.

[0085] The initial heavy component content of the unreacted dichloroethane recovered from the cracking reaction supplied to vacuum recovery tower 3 is 2.5%;

[0086] The vacuum recovery tower 3 is controlled with a top pressure of -0.07 MPaG, a top temperature of 51℃, a bottom pressure of -0.05 MPaG, and a bottom temperature of 95℃.

[0087] The amount of nitrobenzene added to the third dichloroethane feed line 50 is 40 ppm;

[0088] The amount of 2-tert-butylhydroquinone added to vacuum recovery tower 3 is 150 ppm;

[0089] The final dichloroethane refining process produces 100 tons / hour of refined dichloroethane, while the vacuum recovery process for dichloroethane emits 0.5 tons / hour of heavy components.

[0090] Sampling and analysis of the heavy components in the vacuum recovery process of dichloroethane showed that the dynamic viscosity at 25°C was 1.7 mPa·s, the solid particulate matter content was 0.19%, the reboiler flow rate decrease after one week of operation was 0.56%, and the expected service life of the reboiler was 1.37 years.

[0091] Example 3:

[0092] (1) Light component removal process: The first dichloroethane feed line 10 supplies dichloroethane generated from the oxychlorination reaction to the light component tower 1. The light component is removed at the top of the light component tower 1 by distillation, and the remaining component is sent to the heavy component tower 2 through the first conveying line 20 in the bottom of the tower.

[0093] Among them, the pressure at the top of the light component tower 1 is controlled at 0.06 MPaG, the temperature at the top of the tower is 77℃, the pressure at the bottom of the tower is 0.12 MPaG, and the temperature at the bottom of the tower is 111℃;

[0094] (2) Heavy component removal process: The second dichloroethane feed line 30 supplies dichloroethane from the direct chlorination reaction to the heavy component tower 2. The dichloroethane product is collected at the top of the heavy component tower 2 through distillation, and the remaining components are sent to the vacuum recovery tower 3 through the second conveying line 40 in the bottom of the tower. At the same time, the first polymerization inhibitor supply line 60 adds nitrobenzene as a polymerization inhibitor to the second dichloroethane feed line 30.

[0095] The initial heavy component content of the dichloroethane supplied to the heavy component tower 2 from the direct chlorination reaction is 5%.

[0096] The pressure at the top of the recombining column 1 is controlled at 0.06 MPaG, the temperature at the top of the column is 100℃, the pressure at the bottom of the column is 0.09 MPaG, and the temperature at the bottom of the column is 108℃.

[0097] The amount of nitrobenzene added to the second dichloroethane feed line 30 is 50 ppm;

[0098] (3) Dichloroethane vacuum recovery process: The third dichloroethane feed line 50 supplies unreacted dichloroethane recovered from the cracking reaction to the vacuum recovery tower 3. The dichloroethane product is recovered at the top of the tower by distillation in the vacuum recovery tower 3. The remaining components are sent out as heavy by-products in the bottom of the tower. At the same time, the second polymerization inhibitor supply line 70 adds nitrobenzene as a polymerization inhibitor to the third dichloroethane feed line 50, and the third polymerization inhibitor supply line 80 adds 2-tert-butylhydroquinone as a polymerization inhibitor to the vacuum recovery tower 3.

[0099] The initial heavy component content of the unreacted dichloroethane recovered from the cracking reaction supplied to vacuum recovery tower 3 is 2.5%;

[0100] The vacuum recovery tower 3 is controlled with a top pressure of -0.07 MPaG, a top temperature of 51℃, a bottom pressure of -0.05 MPaG, and a bottom temperature of 95℃.

[0101] The amount of nitrobenzene added to the third dichloroethane feed line 50 is 20 ppm;

[0102] The amount of 2-tert-butylhydroquinone added to vacuum recovery tower 3 is 100 ppm;

[0103] The final dichloroethane refining process produces 100 tons / hour of refined dichloroethane, while the vacuum recovery process for dichloroethane emits 0.5 tons / hour of heavy components.

[0104] Sampling and analysis of the heavy components in the dichloroethane vacuum recovery process were performed. The dynamic viscosity at 25°C was 2.8 mPa·s, the solid particulate matter content was 0.36%, the reboiler flow rate decrease after one week of operation was 0.73%, and the expected service life of the reboiler is 1.05 years.

[0105] Example 4:

[0106] (1) Light component removal process: The first dichloroethane feed line 10 supplies dichloroethane generated from the oxychlorination reaction to the light component tower 1. The light component is removed at the top of the light component tower 1 by distillation, and the remaining component is sent to the heavy component tower 2 through the first conveying line 20 in the bottom of the tower.

[0107] Among them, the pressure at the top of the light component tower 1 is controlled at 0.06 MPaG, the temperature at the top of the tower is 77℃, the pressure at the bottom of the tower is 0.12 MPaG, and the temperature at the bottom of the tower is 111℃;

[0108] (2) Heavy component removal process: The second dichloroethane feed line 30 supplies dichloroethane from the direct chlorination reaction to the heavy component tower 2. The dichloroethane product is collected at the top of the heavy component tower 2 through distillation, and the remaining components are sent to the vacuum recovery tower 3 through the second conveying line 40 in the bottom of the tower. At the same time, the first polymerization inhibitor supply line 60 adds nitronaphthalene as a polymerization inhibitor to the second dichloroethane feed line 30.

[0109] The initial heavy component content of the dichloroethane supplied to the heavy component tower 2 from the direct chlorination reaction is 5%.

[0110] The pressure at the top of the recombining column 1 is controlled at 0.06 MPaG, the temperature at the top of the column is 100℃, the pressure at the bottom of the column is 0.09 MPaG, and the temperature at the bottom of the column is 108℃.

[0111] The amount of nitronaphthalene added to the second dichloroethane feed line 30 is 150 ppm;

[0112] (3) Dichloroethane vacuum recovery process: The third dichloroethane feed line 50 supplies unreacted dichloroethane recovered from the cracking reaction to the vacuum recovery tower 3. The dichloroethane product is recovered at the top of the tower by distillation in the vacuum recovery tower 3, and the remaining components are sent out as heavy by-products in the bottom of the tower. At the same time, the second polymerization inhibitor supply line 70 adds nitronaphthalene as a polymerization inhibitor to the third dichloroethane feed line 50, and the third polymerization inhibitor supply line 80 uses 2,5-di-tert-butylhydroquinone as a polymerization inhibitor.

[0113] The heavy components of the dichloroethane vacuum recovery process were sampled and analyzed. The dynamic viscosity at 25°C was 1.2 mPa·s, and the solid particulate matter content was 0.14%. After running for 1 week, the reboiled components were added to the vacuum recovery tower 3 as a polymerization inhibitor.

[0114] The initial heavy component content of the unreacted dichloroethane recovered from the cracking reaction supplied to vacuum recovery tower 3 is 2.5%;

[0115] The vacuum recovery tower 3 is controlled with a top pressure of -0.07 MPaG, a top temperature of 51℃, a bottom pressure of -0.05 MPaG, and a bottom temperature of 95℃.

[0116] The amount of nitronaphthalene added to the third dichloroethane feed line 50 is 60 ppm;

[0117] The amount of 2,5-di-tert-butylhydroquinone added to vacuum recovery tower 3 is 200 ppm;

[0118] The final dichloroethane refining process produces 100 tons / hour of refined dichloroethane, while the vacuum recovery process for dichloroethane emits 0.5 tons / hour of heavy components.

[0119] Sampling and analysis of the heavy components in the vacuum recovery process of dichloroethane showed that the dynamic viscosity at 25°C was 1.2 mPa·s, the solid particulate matter content was 0.14%, the reboiler flow rate decrease was 0.51% after one week of operation, and the reboiler is expected to be usable for 1.50 years.

[0120] Example 5:

[0121] (1) Light component removal process: The first dichloroethane feed line 10 supplies dichloroethane generated from the oxychlorination reaction to the light component tower 1. The light component is removed at the top of the light component tower 1 by distillation, and the remaining component is sent to the heavy component tower 2 through the first conveying line 20 in the bottom of the tower.

[0122] Among them, the pressure at the top of the light component tower 1 is controlled at 0.06 MPaG, the temperature at the top of the tower is 77℃, the pressure at the bottom of the tower is 0.12 MPaG, and the temperature at the bottom of the tower is 111℃;

[0123] (2) Heavy component removal process: The second dichloroethane feed line 30 supplies dichloroethane from the direct chlorination reaction to the heavy component tower 2. The dichloroethane product is collected at the top of the heavy component tower 2 through distillation, and the remaining components are sent to the vacuum recovery tower 3 through the second conveying line 40 in the bottom of the tower. At the same time, the first polymerization inhibitor supply line 60 adds nitronaphthalene as a polymerization inhibitor to the second dichloroethane feed line 30.

[0124] The initial heavy component content of the dichloroethane supplied to the heavy component tower 2 from the direct chlorination reaction is 5%.

[0125] The pressure at the top of the recombining column 1 is controlled at 0.06 MPaG, the temperature at the top of the column is 100℃, the pressure at the bottom of the column is 0.09 MPaG, and the temperature at the bottom of the column is 108℃.

[0126] The amount of nitronaphthalene added to the second dichloroethane feed line 30 is 50 ppm;

[0127] (3) Dichloroethane vacuum recovery process: The third dichloroethane feed line 50 supplies unreacted dichloroethane recovered from the cracking reaction to the vacuum recovery tower 3. The dichloroethane product is recovered at the top of the tower by distillation in the vacuum recovery tower 3, and the remaining components are sent out as heavy by-products in the bottom of the tower. At the same time, the second polymerization inhibitor supply line 70 adds nitronaphthalene as a polymerization inhibitor to the third dichloroethane feed line 50, and the third polymerization inhibitor supply line 80 uses 2,5-di-tert-butylhydroquinone as a polymerization inhibitor.

[0128] The heavy components of the dichloroethane vacuum recovery process were sampled and analyzed. The dynamic viscosity at 25°C was 1.2 mPa·s, and the solid particulate matter content was 0.14%. After running for 1 week, the reboiled components were added to the vacuum recovery tower 3 as a polymerization inhibitor.

[0129] The initial heavy component content of the unreacted dichloroethane recovered from the cracking reaction supplied to vacuum recovery tower 3 is 2.5%;

[0130] The vacuum recovery tower 3 is controlled with a top pressure of -0.07 MPaG, a top temperature of 51℃, a bottom pressure of -0.05 MPaG, and a bottom temperature of 95℃.

[0131] The amount of nitronaphthalene added to the third dichloroethane feed line 50 is 20 ppm;

[0132] The amount of 2,5-di-tert-butylhydroquinone added to vacuum recovery tower 3 is 100 ppm;

[0133] The final dichloroethane refining process produces 100 tons / hour of refined dichloroethane, while the vacuum recovery process for dichloroethane emits 0.5 tons / hour of heavy components.

[0134] Sampling and analysis of the heavy components in the vacuum recovery process of dichloroethane were conducted. The dynamic viscosity at 25°C was 3.0 mPa·s, the solid particulate matter content was 0.38%, the reboiler flow rate decrease after one week of operation was 0.75%, and the expected service life of the reboiler is 1.02 years.

[0135] Comparative Example 1:

[0136] Based on Example 1, 2-tert-butylhydroquinone was replaced with an equal amount of 2-tert-butylhydroquinone, while other processes remained unchanged and the process conditions were kept the same.

[0137] Sampling and analysis of the heavy components in the dichloroethane vacuum recovery process were performed. The dynamic viscosity at 25°C was 1.5 mPa·s, the solid particulate matter content was 0.18%, the reboiler flow rate decrease was 0.54% after one week of operation, and the expected service life of the reboiler is 1.42 years.

[0138] Comparative Example 2:

[0139] Based on Example 1, 2-tert-butylhydroquinone was replaced with an equal amount of nitrobenzene, while other processes remained unchanged and the process conditions were kept the same.

[0140] Sampling and analysis of the heavy components in the vacuum recovery process of dichloroethane showed that the dynamic viscosity at 25°C was 3.4 mPa·s, the solid particulate matter content was 0.42%, the reboiler flow rate decrease was 0.84% ​​after one week of operation, and the expected service life of the reboiler is 0.91 years.

[0141] Comparative Example 3:

[0142] Based on Example 1, the amount of nitrobenzene and 2-tert-butylhydroquinone added was changed to 0, that is, no polymerization inhibitor was added, while other processes remained unchanged and the process conditions were kept the same.

[0143] Sampling and analysis of the heavy components in the vacuum recovery process of dichloroethane showed that the dynamic viscosity at 25°C was 4.6 mPa·s, the solid particulate matter content was 0.61%, the reboiler flow rate decrease after one week of operation was 2.95%, and the expected service life of the reboiler is 0.26 years.

[0144] The performance testing steps are as follows:

[0145] (1) Dynamic viscosity: Dynamic viscosity was measured and calculated using a viscometer conforming to the Engler viscosity test method for petroleum products in GB / T 266-1988.

[0146] (2) Solid particulate matter content: The solid particulate matter content was determined by the laboratory filtration method of GB / T 21452-2008 "Determination of particulate matter content of middle distillate fuels".

[0147] (3) Reboiler flow rate attenuation: An online flow meter is installed on the pipeline from the distillation column to the reboiler, and the flow rate is monitored in real time through the DCS system. Before each embodiment, the reboiler is thoroughly cleaned to ensure that the initial flow rate difference does not exceed 1% and that the column operating parameters are consistent. The average flow rate of the first day (24 hours) is taken as the initial value X, and the average flow rate of the eighth day (24 hours) is taken as the final value Y. The weekly reboiler flow rate attenuation is calculated as (YX) / X*100%. If the reboiler flow rate attenuation exceeds 40%, the reboiler is considered to need maintenance and cleaning, and the usable life of the reboiler is calculated accordingly.

[0148] The experimental results above show that:

[0149] (1) Under the existing technical conditions, the emission of heavy components in the vacuum recovery process of dichloroethane must be more than 1 t / h to ensure that the reboiler can be used for 3 months. The method provided by the present invention reduces the emission of heavy components by more than 50% and at the same time ensures that the reboiler can be used for more than 1 year. On the one hand, it improves the yield of dichloroethane and reduces the overall unit consumption of the device; on the other hand, it reduces the amount of waste liquid generated, which is conducive to reducing the cost of waste treatment and reducing the emission to the environment.

[0150] In addition, the method of adding the polymerization inhibitor according to this method can ensure that the reboiler can be used for more than 1 year, while the maintenance cycle of the production unit is usually 1 year. This can ensure that the reboiler does not need to be repaired many times during the maintenance cycle, which can improve the stability of the unit operation.

[0151] (2) In Comparative Example 1, after replacing 2-tert-butylhydroquinone with the corresponding equal amount of quinone inhibitor, the polymerization inhibition effect was significantly reduced. It can be seen that phenolic inhibitors can achieve two effects at once. In addition to reacting with oxygen to generate quinone compounds and acting as a polymerization inhibitor, they can also react with oxygen to continuously consume oxygen, which to a certain extent avoids the formation of tar with higher viscosity or even solid particles when oxygen reacts with heavy components.

[0152] (3) In Comparative Example 2, after replacing 2-tert-butylhydroquinone with an equal amount of nitrobenzene, the polymerization inhibition effect decreased significantly. This shows that 2-tert-butylhydroquinone and nitrobenzene can play a good synergistic role and can achieve a better polymerization inhibition effect when used together.

[0153] (4) In Comparative Example 3, without the addition of any polymerization inhibitor, the polymerization inhibition effect decreased significantly, and the reboiler needed to be repaired after only three months. It can be seen that this method can effectively prevent the polymerization of heavy components and extend the service life of the reboiler in the dichloroethane refining process.

Claims

1. A dichloroethane refining apparatus, comprising: The light component tower (1) has a first material outlet at the top for discharging the light component and a second material outlet at the bottom for discharging the remaining component. The recombining column (2) has a first material outlet at the top for discharging dichloroethane and a second material outlet at the bottom for discharging the remaining components. The vacuum recovery tower (3) has a first material outlet at the top for discharging dichloroethane and a second material outlet at the bottom for discharging heavy by-products. A first dichloroethane feed line (10) is used to supply dichloroethane generated from the oxychlorination reaction, and the outlet end of the first dichloroethane feed line (10) is connected to the light component tower (1); The first conveying pipeline (20) is connected at its inlet end to the second material outlet of the light component tower (1) and at its outlet end to the heavy component tower (2). A second dichloroethane feed line (30) is used to supply dichloroethane from a direct chlorination reaction, and the outlet end of the second dichloroethane feed line (30) is connected to the heavy fraction tower (2); The second conveying pipeline (40) is connected at its inlet end to the second material outlet of the recombining tower (2) and at its outlet end to the vacuum recovery tower (3). as well as The third dichloroethane feed line (50) is used to supply unreacted dichloroethane recovered from the cracking reaction, and the outlet end of the third dichloroethane feed line (50) is connected to the vacuum recovery tower (3). Its characteristic is that it also includes: A first polymerization inhibitor supply line (60) is used to supply aromatic nitro polymerization inhibitors, and the outlet end of the first polymerization inhibitor supply line (60) is connected to the second dichloroethane feed line (30). A second polymerization inhibitor supply line (70) for supplying aromatic nitro polymerization inhibitors, the outlet of which is connected to the third dichloroethane feed line (50); and A third polymerization inhibitor supply line (80) is used to supply phenolic polymerization inhibitors, and the outlet end of the third polymerization inhibitor supply line (80) is connected to the vacuum recovery tower (3).

2. The dichloroethane refining apparatus according to claim 1, characterized in that: The first inhibitor supply line (60) and the second inhibitor supply line (70) share the same upstream section.

3. A dichloroethane refining process using the dichloroethane refining apparatus according to any one of claims 1 to 2, comprising the following steps: (1) Light component removal process: The first dichloroethane feed line (10) supplies dichloroethane generated from the oxychlorination reaction to the light component tower (1). The light components are removed at the top of the light component tower (1) by distillation, and the remaining components are sent to the heavy component tower (2) through the first conveying line (20) in the bottom of the tower. (2) Heavy component removal process: The second dichloroethane feed line (30) supplies dichloroethane from the direct chlorination reaction to the heavy component tower (2). The dichloroethane product is collected at the top of the heavy component tower (2) through distillation, and the remaining components are sent to the vacuum recovery tower (3) through the second conveying line (40) in the bottom of the tower. At the same time, the first polymerization inhibitor supply line (60) adds aromatic nitro polymerization inhibitor to the second dichloroethane feed line (30). (3) Dichloroethane vacuum recovery process: The third dichloroethane feed line (50) supplies unreacted dichloroethane recovered from the cracking reaction to the vacuum recovery tower (3). The dichloroethane product is recovered at the top of the tower by distillation in the vacuum recovery tower (3). The remaining components are sent out as heavy by-products in the bottom of the tower. At the same time, the second polymerization inhibitor supply line (70) adds aromatic nitro polymerization inhibitors to the third dichloroethane feed line (50), and the third polymerization inhibitor supply line (80) adds phenolic polymerization inhibitors to the vacuum recovery tower (3).

4. The dichloroethane refining process according to claim 3, characterized in that: The light component tower (1) has a top pressure of 0.02-0.1 MPaG, a top temperature of 74-80℃, a bottom pressure of 0.08-0.16 MPaG, and a bottom temperature of 108-114℃.

5. The dichloroethane refining process according to claim 3, characterized in that: The top pressure of the recombinant column (2) is 0.02-0.1 MPaG, the top temperature is 96-105℃, the bottom pressure is 0.05-0.13 MPaG, and the bottom temperature is 103-112℃.

6. The dichloroethane refining process according to claim 3, characterized in that: The vacuum recovery tower (3) has a top pressure of -0.09 to -0.05 MPaG, a top temperature of 47 to 55°C, a bottom pressure of -0.07 to -0.03 MPaG, and a bottom temperature of 90 to 100°C.

7. The dichloroethane refining process according to claim 3, characterized in that: The amount of aromatic nitro polymerization inhibitor added to the second dichloroethane feed line (30) is 50-150 ppm; The amount of aromatic nitro polymerization inhibitor added to the third dichloroethane feed line (50) is 20-60 ppm.

8. The dichloroethane refining process according to claim 3, characterized in that: The amount of phenolic polymerization inhibitor added to the vacuum recovery tower (3) is 100-200 ppm.

9. The dichloroethane refining process according to any one of claims 3 to 8, characterized in that: The aromatic nitro polymerization inhibitor is at least one of nitrobenzene or nitronaphthalene.

10. The dichloroethane refining process according to any one of claims 3 to 8, characterized in that: The phenolic polymerization inhibitor is at least one of 2-tert-butylhydroquinone or 2,5-di-tert-butylhydroquinone.

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