Dichloroethane refining device and process

Abstract

The invention 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 by further comprising a first polymerization inhibitor supply pipeline (60) for supplying aromatic nitryl polymerization inhibitors, the outlet end is connected with a second dichloroethane feeding pipeline (30); the second polymerization inhibitor supply pipeline (70) is used for supplying an aromatic nitryl polymerization inhibitor, and the outlet end of the second polymerization inhibitor supply pipeline (70) is connected with the third dichloroethane feeding pipeline (50); and the third polymerization inhibitor supply pipeline (80) is used for supplying a phenol polymerization inhibitor, and the outlet end of the third polymerization inhibitor supply pipeline (80) is connected with the vacuum recovery tower (3). The invention also discloses a dichloroethane refining process applying the dichloroethane refining device. Compared with the prior art, the method has the advantages that heavy component polymerization can be reduced, and the yield and purity of dichloroethane can be improved.

Description

Technical Field

[0001] The invention relates to the technical field of ethylene dichloride production, and in particular to a device and process for refining ethylene dichloride. Background Art

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

[0003] The dichloroethane generated by the oxychlorination reaction is passed through a light component tower to remove light components such as water, and then the heavy component tower is rectified to obtain most of the dichloroethane, and finally sent to a dichloroethane vacuum recovery tower to further recover a small amount of dichloroethane, and the heavy components such as chloroprene are concentrated and removed. Since the dichloroethane generated by the direct chlorination reaction basically does not contain light components, it only needs to be sent to the heavy component tower and the dichloroethane vacuum recovery tower. The dichloroethane recovered by the cracking reaction is directly sent to the dichloroethane vacuum recovery tower because of its low purity. Among them, most of the heavy components sent to the dichloroethane vacuum recovery tower come from the dichloroethane generated by the direct chlorination reaction, a small part comes from the unreacted dichloroethane recovered by the cracking reaction, and a very small part comes from the dichloroethane generated by the oxychlorination reaction. In the process of concentrating the heavy components of the dichloroethane vacuum recovery tower, some heavy components, especially chloroprene, styrene, etc., are very easy to polymerize to form heavy component tar, which leads to coking of the reboiler of the dichloroethane vacuum recovery tower, which will greatly reduce the service life of the reboiler and increase the replacement frequency. At the same time, the heavy components together with solids and iron will enter the ethylene dichloride product, causing coking of the evaporator and cracking furnace tubes of the ethylene dichloride 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 ethylene dichloride during the refining process of ethylene dichloride is a technical problem that needs to be solved urgently in the industry.

[0005] A Chinese patent with application number CN202320009293.4 discloses a negative pressure dichloroethane distillation and purification device, comprising a tar kettle, a distillation tower, a reboiler, a distillation tower top cooler, a reflux tank, a reflux pump, a liquid ring vacuum pump, a gas-liquid separation tank, and a circulating liquid cooler connected in sequence. The tar kettle controls a certain liquid level, pressure and temperature to operate and an interlocking module is set in the DCS system for automatic control. The dichloroethane in the distillation residue in the tar kettle is vaporized and recovered to the distillation tower for separation and purification, and the uncondensed gas is sent to an incineration device for further disposal. The outlet pipe of the liquid ring vacuum pump is provided with a distillation system pressure regulating control loop, so that the entire distillation system is operated in a relatively stable micro-negative pressure condition. The device reduces the polymerization of heavy components by controlling the negative pressure and the tower kettle temperature.

[0006] A Chinese patent application with application number CN202122959772.6 discloses a method for recovering dichloroethane by two-stage vacuum distillation that is not prone to coking, comprising the following steps: passing the material from the bottom of a high boiling tower through the middle of a first-stage vacuum distillation tower; when a first-stage vacuum distillation tower and a second-stage vacuum distillation tower are used at the same time: a material with a dichloroethane content of 25% to 35% is extracted from the bottom of the first-stage vacuum distillation tower and sent to the middle of the second-stage vacuum distillation tower, a material with a dichloroethane content of 10% to 15% is extracted from the bottom of the second-stage vacuum distillation tower, and is sent to a storage tank for storage as a by-product, and a dichloroethane product is extracted from the top of the first-stage vacuum distillation tower and the top of the second-stage vacuum distillation tower; when only a first-stage vacuum distillation tower is used: a material with a dichloroethane content of 10% to 15% is extracted from the bottom of the first-stage vacuum distillation tower, and is sent to a storage tank for storage as a by-product, and a dichloroethane product is extracted from the top of the first-stage vacuum distillation tower.

[0007] It can be seen that the existing technology for preventing the polymerization of heavy components in the dichloroethane refining process only involves the dichloroethane vacuum recovery process, and the technical means adopted are limited to indirect means such as controlling the temperature and adding spare distillation towers. It lacks a comprehensive system and efficient and direct means of preventing polymerization. Therefore, the effect is often not good in the actual implementation process.

[0008] In addition, because the vacuum recovery process of ethylene dichloride uses negative pressure, although it reduces the distillation temperature, saves energy, and delays the polymerization of heavy components, under negative pressure, air will inevitably enter the vacuum distillation tower, and the reaction of oxygen and heavy components will form tar with higher viscosity or even solid particles, thereby causing the reboiler to become more blocked. Summary of the invention

[0009] The first technical problem to be solved by the present invention is to provide an ethylene dichloride refining device capable of reducing the polymerization of heavy components and improving the yield and purity of ethylene dichloride in view of the current status of the prior art.

[0010] The second technical problem to be solved by the present invention is to provide an ethylene dichloride refining process using the above-mentioned ethylene dichloride refining device.

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

[0012] A light component tower, wherein the top of the tower has a first material outlet for discharging the light component, and the bottom of the tower has a second material outlet for discharging the remaining component;

[0013] A heavy component tower, wherein the top of the tower has a first material outlet for discharging ethylene dichloride, and the bottom of the tower has a second material outlet for discharging remaining components;

[0014] A vacuum recovery tower, wherein the top of the tower has a first material outlet for discharging ethylene dichloride, and the bottom of the tower has a second material outlet for discharging heavy by-products;

[0015] A first ethylene dichloride feed pipeline, used for supplying ethylene dichloride generated from the oxychlorination reaction, wherein the outlet end of the first ethylene dichloride feed pipeline is connected to the light component tower;

[0016] A first delivery pipeline, the inlet end of which is connected to the second material outlet of the light component tower, and the outlet end of which is connected to the heavy component tower;

[0017] A second ethylene dichloride feed pipeline, used for supplying ethylene dichloride from the direct chlorination reaction, wherein the outlet end of the second ethylene dichloride feed pipeline is connected to the heavy component tower;

[0018] A second conveying pipeline, the inlet end of which is connected to the second material outlet of the heavy component tower, and the outlet end of which is connected to the vacuum recovery tower; and

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

[0020] It is characterized by: it also includes

[0021] A first polymerization inhibitor supply pipeline, used for supplying aromatic nitro polymerization inhibitor, wherein the outlet end of the first polymerization inhibitor supply pipeline is connected to the second ethylene dichloride feed pipeline;

[0022] A second polymerization inhibitor supply pipeline, used for supplying aromatic nitro polymerization inhibitor, wherein the outlet end of the second polymerization inhibitor supply pipeline is connected to the third ethylene dichloride feed pipeline; and

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

[0024] In order to ensure the distillation effect of the light component tower, a first condenser is installed at the top of the light component tower, and a first reboiler is installed at the bottom of the light component tower.

[0025] In order to ensure the distillation effect of the heavy component tower, a second condenser is installed at the top of the heavy component tower, and a second reboiler is installed at the bottom of the heavy component tower.

[0026] In order to ensure the distillation effect of the vacuum recovery tower, a third condenser and a vacuum pump negative pressure system are installed on the top of the vacuum recovery tower, and a third reboiler is installed in the bottom of the vacuum recovery tower.

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

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

[0029] In order to simplify the pipeline, the first polymerization inhibitor supply pipeline and the second polymerization inhibitor supply pipeline 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 device comprises the following steps:

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

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

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

[0034] Preferably, the top pressure of the light component tower is 0.02-0.1 MPaG, the top temperature is 74-80° C., the bottom pressure is 0.08-0.16 MPaG, and the bottom temperature is 108-114° C. By adopting the above temperature and pressure, moisture and light components can be effectively removed in the light component tower, avoiding the influence of the inhibitor effect of the inhibitor due to excessive moisture and light component content.

[0035] Preferably, the top pressure of the heavy component tower 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. The above temperature and pressure can ensure that the purity of the extracted ethylene dichloride is above 99.5% and delay the polymerization of the heavy components at the bottom of the heavy component tower.

[0036] Preferably, the top pressure of the vacuum recovery tower is -0.09 to -0.05 MPaG, the top temperature is 47 to 55° C., the bottom pressure is -0.07 to -0.03 MPaG, and the bottom temperature is 90 to 100° C. By adopting the above temperature and pressure, ethylene dichloride can be recovered as much as possible and the purity of ethylene dichloride can be ensured to be above 99%, and the polymerization of heavy components at the bottom of the ethylene dichloride vacuum recovery tower can be delayed.

[0037] Preferably, the amount of aromatic nitro inhibitor added to the second ethylene dichloride feed pipeline is 50-150 ppm. The heavy component content of the direct chlorination reaction to heavy component removal process pipeline is relatively high, and the amount of aromatic nitro compound added needs to be appropriately increased.

[0038] Preferably, the amount of aromatic nitro inhibitor added to the third dichloroethane feed pipeline is 20-60 ppm. The heavy component content of the pipeline from the cracking reaction to the dichloroethane vacuum recovery process is relatively low, so a small amount of aromatic nitro compound can be added.

[0039] Preferably, the amount of phenolic polymerization inhibitor added to the vacuum recovery tower is 100-200 ppm, which can effectively consume the oxygen mixed in the vacuum recovery process of ethylene dichloride and achieve 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:

[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 device operation is improved;

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

[0045] Second, phenolic inhibitors are also usually used as antioxidants. Under aerobic conditions, they can react with oxygen and consume oxygen to generate quinone inhibitors. Quinone inhibitors are highly targeted at inhibiting the polymerization of aromatic olefins such as styrene. Therefore, in the vacuum recovery process of ethylene dichloride, phenolic inhibitors react with oxygen to continuously consume oxygen, which to a certain extent avoids the reaction of oxygen with heavy components to form tar with higher viscosity or even solid particles. On the other hand, they react with oxygen to generate quinone compounds, which can act as inhibitors.

[0046] Third, aromatic nitro inhibitors and phenolic inhibitors are finally gathered in the vacuum recovery process of ethylene dichloride, which can play a synergistic role and effectively inhibit the polymerization of conjugated dienes such as chloroprene and aromatic olefins such as styrene, significantly reducing the production of heavy tar;

[0047] (2) Not limited to the vacuum recovery process of ethylene dichloride, the polymerization inhibition measures are implemented from the source of the heavy components such as direct chlorination reaction and cracking reaction, which can fully achieve the effect of preventing the polymerization of heavy components;

[0048] (3) The prior art usually controls the content of heavy components in the bottom of the tower according to the bottom temperature. If the polymerization of the heavy components intensifies, the bottom temperature will gradually rise, and a large amount of heavy components in the bottom of the tower will need to be discharged to avoid polymerization. The heavy components usually contain about 20% of ethylene dichloride. The present method can reduce the discharge of heavy components. On the one hand, it improves the yield of ethylene dichloride, thereby reducing the overall unit consumption of the device and 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 three waste treatment and reducing emissions to the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 It is a schematic structural diagram of an embodiment of a dichloroethane refining device of the present invention. DETAILED DESCRIPTION

[0050] The present invention is further described in detail below with reference to the accompanying drawings.

[0051] like Figure 1As shown in FIG. 1 , a preferred embodiment of the ethylene dichloride refining device of the present invention is shown. The ethylene dichloride refining device comprises a light component tower 1, a heavy component tower 2, a vacuum recovery tower 3, a first ethylene dichloride feed pipeline 10, a first conveying pipeline 20, a second ethylene dichloride feed pipeline 30, a second conveying pipeline 40, a third ethylene dichloride feed pipeline 50, a first inhibitor supply pipeline 60, a second inhibitor supply pipeline 70 and a third inhibitor supply pipeline 80.

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

[0053] The top of the heavy component tower 2 is provided with a second condenser 21 and has a first material outlet for discharging ethylene dichloride, and the bottom of the heavy component tower 2 is provided with a second reboiler 22 and has a second material outlet for discharging 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 ethylene dichloride feed pipeline 10 is used to supply ethylene dichloride generated by the oxychlorination reaction, and the outlet end of the first ethylene dichloride feed pipeline 10 is connected to the light component column 1 .

[0056] The inlet end of the first delivery pipeline 20 is connected to the second material outlet of the light component tower 1, and the outlet end of the first delivery pipeline 20 is connected to the heavy component tower 2. The first delivery pipeline 20 is installed with a first delivery pump 201 for delivering materials from the inlet end of the first delivery pipeline 20 to the outlet end.

[0057] The second ethylene dichloride feeding pipeline 30 is used to supply ethylene dichloride from the direct chlorination reaction, and an outlet end of the second ethylene dichloride feeding pipeline 30 is connected to the heavy component column 2 .

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

[0059] The third ethylene dichloride feeding pipeline 50 is used to supply unreacted ethylene dichloride recovered from the cracking reaction, and the outlet end of the third ethylene dichloride feeding pipeline 50 is connected to the vacuum recovery tower 3 .

[0060] The first polymerization inhibitor supply pipeline 60 is used to supply aromatic nitro polymerization inhibitor, and the outlet end of the first polymerization inhibitor supply pipeline 60 is connected to the second ethylene dichloride feeding pipeline 30 .

[0061] The second polymerization inhibitor supply pipeline 70 is used to supply aromatic nitro polymerization inhibitor, and the outlet end of the second polymerization inhibitor supply pipeline 70 is connected to the third ethylene dichloride feed pipeline 50. In this embodiment, the first polymerization inhibitor supply pipeline 60 and the second polymerization inhibitor supply pipeline 70 share the same upstream section.

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

[0063] Embodiment 1:

[0064] (1) Light component removal process: The first ethylene dichloride feed pipeline 10 supplies ethylene dichloride generated from the oxychlorination reaction to the light component tower 1, and the light components are removed at the top of the tower by distillation in the light component tower 1, and the remaining components are sent to the heavy component tower 2 through the first transfer pipeline 20 in the bottom of the tower;

[0065] Among them, the light component tower 1 controls the tower top pressure to 0.06MPaG, the tower top temperature to 77℃, the tower bottom pressure to 0.12MPaG, and the tower bottom temperature to 111℃;

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

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

[0068] The heavy component tower 1 controls the top pressure to 0.06MPaG, the top temperature to 100°C, the bottom pressure to 0.09MPaG, and the bottom temperature to 108°C;

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

[0070] (3) Ethylene dichloride vacuum recovery process: The third ethylene dichloride feed pipeline 50 supplies the unreacted ethylene dichloride recovered from the cracking reaction to the vacuum recovery tower 3, and the ethylene dichloride 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 pipeline 70 adds nitrobenzene as a polymerization inhibitor to the third ethylene dichloride feed pipeline 50, and the third polymerization inhibitor supply pipeline 80 adds 2-tert-butylhydroquinone as a polymerization inhibitor to the vacuum recovery tower 3;

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

[0072] The vacuum recovery tower 3 controls the top pressure to -0.07MPaG, the top temperature to 51°C, the bottom pressure to -0.05MPaG, and the bottom temperature to 95°C;

[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 the vacuum recovery tower 3 is 200 ppm;

[0075] The final output of refined ethylene dichloride in the ethylene dichloride refining process is 100 tons / hour, and the heavy component emission in the ethylene dichloride vacuum recovery process is 0.5 tons / hour;

[0076] Sampling and analysis of the heavy components in the dichloroethane vacuum recovery process revealed that the dynamic viscosity at 25°C was 1.1 mPa·s, the solid particle content was 0.12%, and the reboiler flow attenuation after one week of operation was 0.49%. The estimated service life of the reboiler is 1.57 years.

[0077] Embodiment 2:

[0078] (1) Light component removal process: The first ethylene dichloride feed pipeline 10 supplies ethylene dichloride generated from the oxychlorination reaction to the light component tower 1, and the light components are removed at the top of the tower by distillation in the light component tower 1, and the remaining components are sent to the heavy component tower 2 through the first transfer pipeline 20 in the bottom of the tower;

[0079] Among them, the light component tower 1 controls the tower top pressure to 0.06MPaG, the tower top temperature to 77℃, the tower bottom pressure to 0.12MPaG, and the tower bottom temperature to 111℃;

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

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

[0082] The heavy component tower 1 controls the top pressure to 0.06MPaG, the top temperature to 100°C, the bottom pressure to 0.09MPaG, and the bottom temperature to 108°C;

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

[0084] (3) Ethylene dichloride vacuum recovery process: The third ethylene dichloride feed pipeline 50 supplies the unreacted ethylene dichloride recovered from the cracking reaction to the vacuum recovery tower 3, and the ethylene dichloride 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 pipeline 70 adds nitrobenzene as a polymerization inhibitor to the third ethylene dichloride feed pipeline 50, and the third polymerization inhibitor supply pipeline 80 adds 2-tert-butylhydroquinone as a polymerization inhibitor to the vacuum recovery tower 3;

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

[0086] The vacuum recovery tower 3 controls the top pressure to -0.07MPaG, the top temperature to 51°C, the bottom pressure to -0.05MPaG, and the bottom temperature to 95°C;

[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 the vacuum recovery tower 3 is 150 ppm;

[0089] The final output of refined ethylene dichloride in the ethylene dichloride refining process is 100 tons / hour, and the heavy component emission in the ethylene dichloride vacuum recovery process is 0.5 tons / hour;

[0090] Sampling and analysis of the heavy components in the dichloroethane vacuum recovery process revealed that the dynamic viscosity at 25°C was 1.7 mPa·s, the solid particle content was 0.19%, and the reboiler flow attenuation after one week of operation was 0.56%. The estimated service life of the reboiler is 1.37 years.

[0091] Embodiment 3:

[0092] (1) Light component removal process: The first ethylene dichloride feed pipeline 10 supplies ethylene dichloride generated from the oxychlorination reaction to the light component tower 1, and the light components are removed at the top of the tower by distillation in the light component tower 1, and the remaining components are sent to the heavy component tower 2 through the first transfer pipeline 20 in the bottom of the tower;

[0093] Among them, the light component tower 1 controls the tower top pressure to 0.06MPaG, the tower top temperature to 77℃, the tower bottom pressure to 0.12MPaG, and the tower bottom temperature to 111℃;

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

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

[0096] The heavy component tower 1 controls the top pressure to 0.06MPaG, the top temperature to 100°C, the bottom pressure to 0.09MPaG, and the bottom temperature to 108°C;

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

[0098] (3) Ethylene dichloride vacuum recovery process: The third ethylene dichloride feed pipeline 50 supplies the unreacted ethylene dichloride recovered from the cracking reaction to the vacuum recovery tower 3, and the ethylene dichloride 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 pipeline 70 adds nitrobenzene as a polymerization inhibitor to the third ethylene dichloride feed pipeline 50, and the third polymerization inhibitor supply pipeline 80 adds 2-tert-butylhydroquinone as a polymerization inhibitor to the vacuum recovery tower 3;

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

[0100] The vacuum recovery tower 3 controls the top pressure to -0.07MPaG, the top temperature to 51°C, the bottom pressure to -0.05MPaG, and the bottom temperature to 95°C;

[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 the vacuum recovery tower 3 is 100 ppm;

[0103] The final output of refined ethylene dichloride in the ethylene dichloride refining process is 100 tons / hour, and the heavy component emission in the ethylene dichloride vacuum recovery process is 0.5 tons / hour;

[0104] Sampling and analysis of the heavy components in the dichloroethane vacuum recovery process revealed that the dynamic viscosity at 25°C was 2.8 mPa·s, the solid particle content was 0.36%, and the reboiler flow attenuation after one week of operation was 0.73%. The estimated service life of the reboiler is 1.05 years.

[0105] Embodiment 4:

[0106] (1) Light component removal process: The first ethylene dichloride feed pipeline 10 supplies ethylene dichloride generated from the oxychlorination reaction to the light component tower 1, and the light components are removed at the top of the tower by distillation in the light component tower 1, and the remaining components are sent to the heavy component tower 2 through the first transfer pipeline 20 in the bottom of the tower;

[0107] Among them, the light component tower 1 controls the tower top pressure to 0.06MPaG, the tower top temperature to 77℃, the tower bottom pressure to 0.12MPaG, and the tower bottom temperature to 111℃;

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

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

[0110] The heavy component tower 1 controls the top pressure to 0.06MPaG, the top temperature to 100°C, the bottom pressure to 0.09MPaG, and the bottom temperature to 108°C;

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

[0112] (3) Ethylene dichloride vacuum recovery process: The third ethylene dichloride feed line 50 supplies the unreacted ethylene dichloride recovered from the cracking reaction to the vacuum recovery tower 3, and the ethylene dichloride 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 ethylene dichloride feed line 50, and the third polymerization inhibitor supply line 80 adds 2,5-di-tert-butylhydroquinone as a polymerization inhibitor.

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

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

[0115] The vacuum recovery tower 3 controls the top pressure to -0.07MPaG, the top temperature to 51°C, the bottom pressure to -0.05MPaG, and the bottom temperature to 95°C;

[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 the vacuum recovery tower 3 is 200 ppm;

[0118] The final output of refined ethylene dichloride in the ethylene dichloride refining process is 100 tons / hour, and the heavy component emission in the ethylene dichloride vacuum recovery process is 0.5 tons / hour;

[0119] Sampling and analysis of the heavy components in the dichloroethane vacuum recovery process revealed that the dynamic viscosity at 25°C was 1.2 mPa·s, the solid particle content was 0.14%, and the reboiler flow attenuation after one week of operation was 0.51%. The estimated service life of the reboiler is 1.50 years.

[0120] Embodiment 5:

[0121] (1) Light component removal process: The first ethylene dichloride feed pipeline 10 supplies ethylene dichloride generated from the oxychlorination reaction to the light component tower 1, and the light components are removed at the top of the tower by distillation in the light component tower 1, and the remaining components are sent to the heavy component tower 2 through the first transfer pipeline 20 in the bottom of the tower;

[0122] Among them, the light component tower 1 controls the tower top pressure to 0.06MPaG, the tower top temperature to 77℃, the tower bottom pressure to 0.12MPaG, and the tower bottom temperature to 111℃;

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

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

[0125] The heavy component tower 1 controls the top pressure to 0.06MPaG, the top temperature to 100°C, the bottom pressure to 0.09MPaG, and the bottom temperature to 108°C;

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

[0127] (3) Ethylene dichloride vacuum recovery process: The third ethylene dichloride feed line 50 supplies the unreacted ethylene dichloride recovered from the cracking reaction to the vacuum recovery tower 3, and the ethylene dichloride 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 ethylene dichloride feed line 50, and the third polymerization inhibitor supply line 80 adds 2,5-di-tert-butylhydroquinone as a polymerization inhibitor.

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

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

[0130] The vacuum recovery tower 3 controls the top pressure to -0.07MPaG, the top temperature to 51°C, the bottom pressure to -0.05MPaG, and the bottom temperature to 95°C;

[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 the vacuum recovery tower 3 is 100 ppm;

[0133] The final output of refined ethylene dichloride in the ethylene dichloride refining process is 100 tons / hour, and the heavy component emission in the ethylene dichloride vacuum recovery process is 0.5 tons / hour;

[0134] Sampling and analysis of the heavy components in the dichloroethane vacuum recovery process revealed that the dynamic viscosity at 25°C was 3.0 mPa·s, the solid particle content was 0.38%, and the reboiler flow attenuation after one week of operation was 0.75%. The estimated service life of the reboiler is 1.02 years.

[0135] Comparative Example 1:

[0136] On the basis of Example 1, 2-tert-butylhydroquinone was replaced with an equal amount of 2-tert-butyl-p-benzoquinone, and 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 revealed that the dynamic viscosity at 25°C was 1.5 mPa·s, the solid particle content was 0.18%, and the reboiler flow attenuation after one week of operation was 0.54%. The estimated service life of the reboiler is 1.42 years.

[0138] Comparative Example 2:

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

[0140] Sampling and analysis of the heavy components in the dichloroethane vacuum recovery process revealed that the dynamic viscosity at 25°C was 3.4 mPa·s, the solid particle content was 0.42%, and the reboiler flow attenuation after one week of operation was 0.84%. The estimated service life of the reboiler is 0.91 years.

[0141] Comparative Example 3:

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

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

[0144] The performance test steps are as follows:

[0145] (1) Dynamic viscosity: The dynamic viscosity is measured and calculated using a viscometer that complies with GB / T 266-1988 Engler Viscosity Determination of Petroleum Products;

[0146] (2) Solid particulate matter content: The solid particulate matter content is determined using the "GB / T 21452-2008 Laboratory filtration method for determination of particulate matter content of middle distillate fuels";

[0147] (3) Reboiler flow attenuation: Install an online flow meter on the pipeline from the distillation tower to the reboiler, and monitor the flow in real time through the DCS system. Before carrying out each embodiment, the reboiler is fully cleaned to ensure that the initial flow rate does not differ by more than 1%, and the tower operation parameters are consistent. The average flow rate of 24 hours on the first day is taken as the initial value X, and the average flow rate of 24 hours on the eighth day is taken as the final value Y. The reboiler flow weekly attenuation is calculated as (YX) / X*100%. If the reboiler flow attenuation exceeds 40%, it is considered that the reboiler needs to be repaired and cleaned, so as to calculate the usable time of the reboiler.

[0148] From the above experimental results, we can see that:

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

[0150] In addition, the method of adding the polymerization inhibitor according to the present invention can ensure that the reboiler can be used for more than 1 year, while the maintenance cycle of the production device is usually 1 year, which can ensure that the reboiler does not need to be overhauled multiple times during the maintenance cycle, and can improve the stability of the device operation;

[0151] (2) In comparative example 1, after 2-tert-butylhydroquinone was replaced with a corresponding equivalent amount of quinone inhibitor, the inhibitory effect was significantly reduced. It can be seen that the phenolic inhibitor can achieve two effects at one stroke. In addition to reacting with oxygen to form quinone compounds that act as inhibitors, it can also react with oxygen to continuously consume oxygen, thus avoiding to a certain extent the reaction of oxygen with heavy components to form tar with higher viscosity or even solid particles.

[0152] (3) In Comparative Example 2, after replacing 2-tert-butylhydroquinone with an equal amount of nitrobenzene, the inhibition effect was significantly reduced. It can be seen that 2-tert-butylhydroquinone and nitrobenzene can play a good synergistic role, and their combined use can achieve a better inhibition effect;

[0153] (4) In comparative example 3, after no polymerization inhibitor was added, the polymerization inhibition effect was significantly reduced, and the reboiler needed to be overhauled in only three months. It can be seen that in the dichloroethane refining process, the present method can well prevent the polymerization of heavy components and extend the service life of the reboiler.

Claims

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

2. The ethylene dichloride refining device according to claim 1, characterized in that: The first polymerization inhibitor supply pipeline (60) and the second polymerization inhibitor supply pipeline (70) share the same upstream section.

3. A process for refining ethylene dichloride using the ethylene dichloride refining device according to any one of claims 1 to 2, comprising the following steps: (1) Light component removal process: The first ethylene dichloride feed pipeline (10) supplies ethylene dichloride generated from the oxychlorination reaction to the light component tower (1), the light component is removed at the top of the tower by distillation in the light component tower (1), and the remaining components are sent to the heavy component tower (2) through the first transfer pipeline (20) in the bottom of the tower; (2) Heavy component removal process: The second ethylene dichloride feed pipeline (30) supplies ethylene dichloride from the direct chlorination reaction to the heavy component tower (2), and the ethylene dichloride product is extracted at the top of the tower through distillation in the heavy component tower (2), and the remaining components are sent to the vacuum recovery tower (3) through the second transfer pipeline (40) in the bottom of the tower. At the same time, the first inhibitor supply pipeline (60) adds the aromatic nitro inhibitor to the second ethylene dichloride feed pipeline (30); (3) Ethylene dichloride vacuum recovery process: The third ethylene dichloride feed line (50) supplies the unreacted ethylene dichloride recovered from the cracking reaction to the vacuum recovery tower (3), and the ethylene dichloride product is recovered at the top of the vacuum recovery tower (3) through distillation, 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 the aromatic nitro polymerization inhibitor to the third ethylene dichloride feed line (50), and the third polymerization inhibitor supply line (80) adds the phenol polymerization inhibitor to the vacuum recovery tower (3).

4. The process for refining ethylene dichloride 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°C, a bottom pressure of 0.08-0.16 MPaG, and a bottom temperature of 108-114°C.

5. The process for refining ethylene dichloride according to claim 3, characterized in that: The top pressure of the heavy component tower (2) 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.

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

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

8. The process for refining ethylene dichloride 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 process for refining ethylene dichloride according to any one of claims 3 to 8, characterized in that: The aromatic nitro polymerization inhibitor is at least one of nitrobenzene and nitronaphthalene.

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

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