Resource utilization method of 1, 1, 2-trichloroethane waste liquid

Abstract

The invention discloses a resource utilization method of 1, 1, 2-trichloroethane waste liquid, which comprises the following steps: 1) feeding the 1, 1, 2-trichloroethane waste liquid into a scraper device to remove heavy components, and extracting gas-phase light components from the top; (2) condensing the gas-phase light component, feeding into a chlorination reactor, and carrying out chlorination reaction; and 3) carrying out reactive distillation on the material at the outlet of the chlorination reactor to remove light components and heavy components to obtain 1, 1, 2-trichloroethane. According to the method, on one hand, impurities which influence the purity of 1, 1, 2-trichloroethane and are difficult to separate react with chlorine under specific conditions to generate heavier components, and on the other hand, it is ensured that light components cannot be chlorinated into the impurities which are difficult to separate, and 1, 1, 2-trichloroethane with the purity being 99% or above can be recycled; on the other hand, 5-20 wt% of 1, 1, 2-trichloroethane is additionally generated in the reactive distillation process, waste liquid recycling is achieved, and the method has the advantages of being simple in technological process, low in energy consumption and high in product yield.

Description

Technical Field

[0001] The present invention relates to the field of waste liquid utilization, and particularly to a method for resource utilization of 1,1,2-trichloroethane waste liquid. Background Art

[0002] 1,1,2-Trichloroethane is an important organic intermediate and can be used to produce vinylidene chloride (VDC) monomer. The industrial methods for preparing 1,1,2-trichloroethane mainly include vinyl chloride (VCM) chlorination method and dichloroethane (EDC) chlorination method. Since the VCM chlorination method has mild conditions and a relatively mature process, almost all domestic manufacturers adopt this route, such as CN110511110B, CN109651067A, etc., which are obtained by carrying out a chlorination reaction with vinyl chloride and chlorine as raw materials.

[0003] As a polymerization raw material for the general resin polyvinyl chloride, the synthesis process of vinyl chloride mostly adopts the ethylene method. In the ethylene method production process, ethylene is first subjected to a chlorination or oxychlorination reaction to generate 1,2-dichloroethane (EDC), and then 1,2-dichloroethane (EDC) is pyrolyzed at high temperature to generate vinyl chloride (VCM). We found that 1,1,2-trichloroethane is generated during the preparation of vinyl chloride and exists in the production waste liquid with a relatively high concentration. If it is incinerated after passing through the refining unit, such a treatment method has great disadvantages. One is that the cost of treating the waste liquid is expensive, increasing the production cost of the enterprise; the other is that simply adopting the incineration method not only cannot reduce environmental pollution, but also causes waste of resources, which does not conform to the principles of waste resource utilization and reduction. Therefore, it has become an urgent problem to provide a method for resource utilization of 1,1,2-trichloroethane waste liquid based on a vinyl chloride production device. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention proposes a method for resource utilization of 1,1,2-trichloroethane waste liquid.

[0005] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A method for resource utilization of 1,1,2-trichloroethane waste liquid, comprising the following steps:

[0007] 1) Feeding the 1,1,2-trichloroethane waste liquid into a scraper to remove heavy components, and taking out the gas-phase light components from the top;

[0008] 2) Condensing the gas-phase light components and feeding them into a chlorination reactor for chlorination reaction;

[0009] 3) Removing light components and heavy components from the material at the outlet of the chlorination reactor through reactive distillation to obtain 1,1,2-trichloroethane.

[0010] The 1,1,2-trichloroethane waste liquid described in the present invention comes from the process of preparing vinyl chloride by the ethylene method. It mainly comes from the process of generating 1,2-dichloroethane in the ethylene chlorination or oxychlorination reaction. In addition, the process of preparing vinyl chloride by the ethylene method is a conventional process in the art, and reference can be made to patents such as CN118594405A, CN118253267A, CN222368368U, etc.

[0011] The applicant has found that in the process of preparing vinyl chloride by the ethylene method, in addition to 1,1,2-trichloroethane, the 1,1,2-trichloroethane waste liquid also contains 1,2-dichloroethane and some impurities. After analysis of the impurities, it is found that they include a class of substances with the molecular formula C 4 H 6 Cl 2 , which are dichlorides of 4-carbon olefins. Specifically, they include cis and trans structures and other isomers such as 3,4-dichloro-1-butene, 1,4-dichloro-1-butene, 1,3-dichloro-2-butene, etc. Through continuous research, it has been found that substances with the molecular formula C 4 H 6 Cl 2 have a boiling point close to that of 1,1,2-trichloroethane and form an azeotrope, resulting in the inability to increase the purity of the recovered 1,1,2-trichloroethane to more than 95% by traditional separation methods such as distillation, thus affecting the recycling of 1,1,2-trichloroethane.

[0012] The technical solution described in the present application first removes the heavy components from the 1,1,2-trichloroethane waste liquid to obtain light components. The light components contain 1,1,2-trichloroethane, 1,2-dichloroethane, substances with the molecular formula C 4 H 6 Cl 2 , etc. After condensation, they are sent to a chlorination reactor for chlorination reaction, so that substances such as those with the molecular formula C 4 H 6 Cl 2 react to form heavier components, and at the same time, the light component 1,1,2-trichloroethane is difficult to be further chlorinated during this process, thereby realizing the separation of the two.

[0013] As a preferred embodiment of the present invention, in step 1), the 1,1,2-trichloroethane waste liquid includes 30-50 wt% of 1,1,2-trichloroethane, 10-30 wt% of 1,2-dichloroethane, and 0.1-20 wt% of substances with the molecular formula C 4 H 6 Cl 2 , etc.

[0014] As a preferred embodiment of the present invention, in step 1), the pressure in the scraper is 10 - 100 kPaA, preferably 20 - 80 kPaA, the temperature is 30 - 200 °C, preferably 40 - 100 °C, and the residence time is 2 - 60 s, preferably 10 - 40 s.

[0015] As a preferred embodiment of the present invention, in step 2), the outlet temperature of the condenser is 30 - 90 °C, preferably 40 - 80 °C.

[0016] As a preferred embodiment of the present invention, in step 2), the pressure in the chlorination reactor is 0.1 - 1 MPaA, preferably 0.2 - 0.8 MPaA, the temperature is 30 - 200 °C, preferably 40 - 150 °C, and the residence time is 10 - 200 min, preferably 80 - 150 min.

[0017] As a preferred embodiment of the present invention, in step 2), the chlorine dosage in the chlorination reactor is 1 - 50 wt% of the mass of the 1,1,2 - trichloroethane waste liquid, preferably 10 - 40 wt%.

[0018] As a preferred embodiment of the present invention, the chlorination reactor is a tubular reactor. Preferably, the chlorination reactor is single, multiple in series or multiple in parallel, and is internally equipped with mixing elements. Preferably, the type of the mixing elements is random packing, structured packing or static mixer.

[0019] As a preferred embodiment of the present invention, in step 3), the reactive distillation uses a packed column with 30 - 120 trays, preferably 40 - 60 trays. Among them, the material at the outlet of the chlorination reactor is fed at the 10 - 45th tray from top to bottom, and 1,1,2 - trichloroethane is discharged at the 5 - 35th tray from top to bottom, and the discharge port is above the feed port.

[0020] As a preferred embodiment of the present invention, in step 3), the operating pressure at the top of the distillation column for the reactive distillation is 10 - 100 kPaA, preferably 20 - 80 kPaA, the temperature at the bottom of the column is 70 - 180 °C, preferably 80 - 150 °C, and the reflux ratio is 1 - 40, preferably 2 - 10.

[0021] The method for resource utilization of 1,1,2 - trichloroethane waste liquid provided by the present invention can not only recover 1,1,2 - trichloroethane with a purity of more than 99% from the waste liquid, but also convert part of 1,2 - dichloroethane into 1,1,2 - trichloroethane through reactive distillation, additionally generating 5 - 20 wt% of 1,1,2 - trichloroethane, realizing the resource utilization of the waste liquid. The process flow is simple, the energy consumption is low, and the product yield is high. Description of the Drawings

[0022] Figure 1 It is the gas chromatogram of waste liquid A in Example 1 of the present invention. Detailed implementation mode

[0023] The present invention will be further described below through specific embodiments. The embodiments of the present invention are only used to illustrate the present invention and do not limit the scope of the present invention.

[0024]

Raw materials

[0025] Waste liquid A: containing 50 wt% 1,1,2-trichloroethane, 10 wt% 1,2-dichloroethane, 0.1 wt% of a substance with the molecular formula C 4 H 6 Cl 2 from the vinyl chloride production unit of Wanhua Chemical;

[0026] Waste liquid B: containing 40 wt% 1,1,2-trichloroethane, 20 wt% 1,2-dichloroethane, 15 wt% of a substance with the molecular formula C 4 H 6 Cl 2 from the vinyl chloride production unit of Wanhua Chemical;

[0027] Waste liquid C: containing 30 wt% 1,1,2-trichloroethane, 30 wt% 1,2-dichloroethane, 18 wt% of a substance with the molecular formula C 4 H 6 Cl 2 from the vinyl chloride production unit of Wanhua Chemical;

[0028] Waste liquid D: containing 35 wt% 1,1,2-trichloroethane, 25 wt% 1,2-dichloroethane, 20 wt% of a substance with the molecular formula C 4 H 6 Cl 2 from the vinyl chloride production unit of Wanhua Chemical;

[0029] Other raw materials, if not otherwise specified, are obtained through commercial channels on the market.

[0030]

Testing instruments and methods

[0031] For the examples and comparative examples, a 7890B gas chromatograph from Agilent Technologies, USA was used to quantitatively analyze the composition of the 1,1,2-trichloroethane product taken from the side line. An FID detector and a DB-1 chromatographic column were used. The feed volume was 0.5 μL, the inlet temperature was 250 °C, the detector temperature was 280 °C, the carrier gas (nitrogen) flow rate was 3 ml / min, the air flow rate was 300 ml / min, and the hydrogen flow rate was 30 ml / min.

[0032] Conditions for gas chromatography - mass spectrometry analysis: An Agilent gas chromatography - mass spectrometry instrument produced by Agilent Technologies, Inc. of the United States is used. For the Agilent 7697A chromatograph, an Agilent 19091S - 433UI HP - 5ms Ultra Inert chromatographic column is used. The mass spectrometer scans once per second and records the mass spectrum under the conditions of an ionization energy of 70 eV and a scanning range of 29 - 450 m / z. The structure of impurities is determined through ionization and mass analysis, and the waste liquid A is analyzed to obtain Figure 1 。

[0033]

Example 1

[0034] A method for resource utilization of 1,1,2 - trichloroethane waste liquid includes the following steps:

[0035] 1) Feed 1000 kg of waste liquid A into a scraper to remove heavy components. The gaseous light components are condensed and then mixed with chlorine gas and fed into a chlorination reactor for chlorination reaction. Among them, the temperature of the scraper is 50 °C, the pressure is 15 kPaA, and the residence time is 10 s; the outlet temperature of the condenser is 30 °C, the feeding amount of chlorine gas in the chlorination reactor is 200 kg, the reaction pressure is 1 MPaA, the reaction temperature is 200 °C, and the residence time is 80 min.

[0036] 2) Feed the material at the outlet of the chlorination reactor into a distillation column with 50 trays. The feeding position is at the 10th tray from the top downwards. Control the top pressure of the column to be 20 KPaA, the bottom temperature of the column to be 80 °C, and the reflux ratio to be 20. During the distillation process, the product 1,1,2 - trichloroethane is taken out from the side line, that is, the 5th tray from the top downwards. The light components are taken out from the top of the column, and the heavy components are taken out from the bottom of the column.

[0037] After analysis, in the product taken out from the side line, the content of 1,1,2 - trichloroethane is 99.58 wt%, and the recovery amount / original liquid target product amount = 96% (where the recovery amount is the actual recovery amount of 1,1,2 - trichloroethane, and the original liquid target product amount is the initial content of 1,1,2 - trichloroethane in the waste liquid, the same below). The content of 1,2 - dichloroethane is not detected, and the content of the substance with the molecular formula C 4 H 6 Cl 2 is 0.02 wt%.

[0038]

Example 2

[0039] A method for resource utilization of 1,1,2 - trichloroethane waste liquid includes the following steps:

[0040] 1) Feed 1000 kg of waste liquid B into a scraper to remove heavy components. The gaseous light components are condensed and then mixed with chlorine gas and fed into a chlorination reactor for chlorination reaction. Among them, the temperature of the scraper is 200 °C, the pressure is 100 kPaA, and the residence time is 40 s; the temperature at the condenser outlet is 60 °C, the feeding amount of chlorine gas in the chlorination reactor is 500 kg, the reaction pressure is 0.1 MPaA, the reaction temperature is 30 °C, and the residence time is 150 min.

[0041] 2) Feed the material at the outlet of the chlorination reactor into a distillation column with 60 trays. The feeding position is at the 20th tray from the top down. Control the top pressure of the column to be 10 KPaA, the bottom temperature of the column to be 180 °C, and the reflux ratio to be 2. During the distillation process, the product 1,1,2-trichloroethane is taken out from the side line, that is, at the 14th tray from the top down. The light components are taken out from the top of the column, and the heavy components are taken out from the bottom of the column.

[0042] After analysis, in the product taken out from the side line, the content of 1,1,2-trichloroethane is 99.84 wt%, the recovery amount / the target product amount of the original liquid = 108.75%, the content of 1,2-dichloroethane is not detected, and the content of the substance with the molecular formula C 4 H 6 Cl 2 is 0.12 wt%.

[0043]

Example 3

[0044] A method for resource utilization of 1,1,2-trichloroethane waste liquid includes the following steps:

[0045] 1) Feed 1000 kg of waste liquid B into a scraper to remove heavy components. The gaseous light components are condensed and then mixed with chlorine gas and fed into a chlorination reactor for chlorination reaction. Among them, the temperature of the scraper is 60 °C, the pressure is 20 kPaA, and the residence time is 60 s; the temperature at the condenser outlet is 30 °C, the feeding amount of chlorine gas in the chlorination reactor is 100 kg, the reaction pressure is 0.2 MPaA, the reaction temperature is 40 °C, and the residence time is 120 min.

[0046] 2) Feed the material at the outlet of the chlorination reactor into a distillation column with 30 trays. The feeding position is at the 16th tray from the top down. Control the top pressure of the column to be 80 KPaA, the bottom temperature of the column to be 160 °C, and the reflux ratio to be 10. During the distillation process, the product 1,1,2-trichloroethane is taken out from the side line, that is, at the 10th tray from the top down. The light components are taken out from the top of the column, and the heavy components are taken out from the bottom of the column.

[0047] After analysis, in the product taken out from the side line, the content of 1,1,2-trichloroethane is 99.61 wt%, the recovery amount / the target product amount of the original liquid = 93.75%, the content of 1,2-dichloroethane is not detected, and the content of the substance with the molecular formula C 4 H 6 Cl2 The content of the substance is 0.34 wt%.

[0048]

Example 4

[0049] A method for resource utilization of 1,1,2-trichloroethane waste liquid comprises the following steps:

[0050] 1) Feed 1000 kg of waste liquid C into a scraper to remove heavy components. The gaseous light components are condensed and then mixed with chlorine gas and fed into a chlorination reactor for chlorination reaction. Among them, the temperature of the scraper is 100 °C, the pressure is 30 kPaA, and the residence time is 30 s; the temperature at the outlet of condensation is 40 °C. The feeding amount of chlorine gas in the chlorination reactor is 400 kg, the reaction pressure is 0.2 MPaA, the reaction temperature is 40 °C, and the residence time is 120 min.

[0051] 2) Feed the material at the outlet of the chlorination reactor into a distillation column with 80 trays. The feeding position is at the 40th tray from top to bottom. Control the pressure at the top of the column to be 100 KPaA, the temperature at the bottom of the column to be 150 °C, and the reflux ratio to be 8. During the distillation process, product 1,1,2-trichloroethane is taken out from the side line, i.e., at the 20th tray from top to bottom. Light components are taken out from the top of the column, and heavy components are taken out from the bottom of the column.

[0052] After analysis, in the product taken out from the side line, the content of 1,1,2-trichloroethane is 99.66 wt%, the recovery amount / the amount of the target product in the original liquid = 106.67%, the content of 1,2-dichloroethane is not detected, and the content of the substance with the molecular formula C 4 H 6 Cl 2 is 0.06 wt%.

[0053]

Example 5

[0054] A method for resource utilization of 1,1,2-trichloroethane waste liquid comprises the following steps:

[0055] 1) Feed 1000 kg of waste liquid D into a scraper to remove heavy components. The gaseous light components are condensed and then mixed with chlorine gas and fed into a chlorination reactor for chlorination reaction. Among them, the temperature of the scraper is 160 °C, the pressure is 80 kPaA, and the residence time is 20 s; the temperature at the outlet of condensation is 80 °C. The feeding amount of chlorine gas in the chlorination reactor is 300 kg, the reaction pressure is 0.8 MPaA, the reaction temperature is 150 °C, and the residence time is 200 min.

[0056] 2) Feed the material from the outlet of the chlorination reactor into a distillation column with 80 trays. The feeding position is at the 40th tray from the top downwards. Control the top pressure of the column at 40 KPaA, the bottom temperature at 100 °C, and the reflux ratio at 35. During the distillation process, product 1,1,2-trichloroethane is withdrawn from the side line, i.e., at the 24th tray from the top downwards. Light components are withdrawn from the top of the column, and heavy components are withdrawn from the bottom of the column.

[0057] Upon analysis, in the product withdrawn from the side line, the content of 1,1,2-trichloroethane is 99.89 wt%, the recovery amount / the target product amount of the original solution = 107.14%, the content of 1,2-dichloroethane is not detected, and the content of the substance with the molecular formula C 4 H 6 Cl 2 is 0.068 wt%.

[0058]

Comparative Example 1

[0059] A method for resource utilization of 1,1,2-trichloroethane waste liquid includes the following steps:

[0060] 1) Mix 1000 kg of waste liquid D with chlorine and feed it into a chlorination reactor for chlorination reaction. The feeding amount of chlorine in the chlorination reactor is 300 kg, the reaction pressure is 0.8 MPaA, the reaction temperature is 150 °C, and the residence time is 200 min.

[0061] 2) Feed the material from the outlet of the chlorination reactor into a distillation column with 80 trays. The feeding position is at the 40th tray from the top downwards. Control the top pressure of the column at 40 KPaA, the bottom temperature at 100 °C, and the reflux ratio at 35. During the distillation process, product 1,1,2-trichloroethane is withdrawn from the side line, i.e., at the 24th tray from the top downwards. Light components are withdrawn from the top of the column, and heavy components are withdrawn from the bottom of the column.

[0062] Upon analysis, in the product withdrawn from the side line, the content of 1,1,2-trichloroethane is 84.52 wt%, the recovery amount / the target product amount of the original solution = 71.43%, the content of 1,2-dichloroethane is not detected, and the content of the substance with the molecular formula C 4 H 6 Cl 2 is 15.38 wt%.

[0063]

Comparative Example 2

[0064] A method for resource utilization of 1,1,2-trichloroethane waste liquid includes the following steps:

[0065] 1) Feed 1000 kg of waste liquid D into a scraper to remove heavy components. The temperature of the scraper is 160 °C, the pressure is 80 kPaA, the residence time is 20 s; the condensation outlet temperature is 80 °C.

[0066] 2) It is sent into a distillation column with 80 trays through a condenser. The feeding position is at the 40th tray from the top downwards. The top pressure of the column is controlled at 40 KPaA, the bottom temperature of the column is 100 °C, and the reflux ratio is 35. During the distillation process, the product 1,1,2-trichloroethane is withdrawn from the side line, i.e., at the 24th tray from the top downwards. The light components are withdrawn from the top of the column, and the heavy components are withdrawn from the bottom of the column.

[0067] Upon analysis, in the product withdrawn from the side line, the content of 1,1,2-trichloroethane is 76.34 wt%, the recovery amount / the target product amount of the original solution = 81.43%, the content of 1,2-dichloroethane is not detected, and the content of the substance with the molecular formula C 4 H 6 Cl 2 is 23.55 wt%.

[0068] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the method of the present invention, several improvements and supplements can be made, and these improvements and supplements should also be regarded as the protection scope of the present invention.

Claims

1. A method for resource utilization of 1,1,2-trichloroethane waste liquid, characterized in that: The following steps are involved: 1) Removing heavy components from 1,1,2-trichloroethane waste liquid and extracting light components in gas phase; 2) The light components in the gas phase are condensed and sent to the chlorination reactor for chlorination reaction; 3) The material at the outlet of the chlorination reactor is subjected to reactive distillation to remove light components and heavy components to obtain 1,1,2-trichloroethane.

2. The method according to claim 1, characterized in that In step 1), the 1,1,2-trichloroethane waste liquid contains 30-50wt% of 1,1,2-trichloroethane, 10-30wt% of 1,2-dichloroethane, and 0.1-20wt% of a substance with a molecular formula of C4H6Cl2.

3. The method according to claim 1 or 2, characterized in that: In step 1), the heavy components are removed by a scraper, the scraper pressure is 10-100 kPaA, preferably 20-80 kPaA, the temperature is 30-200°C, preferably 40-100°C, and the residence time is 2-60s, preferably 10-40s.

4. The method according to claim 1, characterized in that In step 2), the condenser outlet temperature is 30-90°C, preferably 40-80°C.

5. The method according to claim 1 or 4, characterized in that: In step 2), the pressure in the chlorination reactor is 0.1-1 MPaA, preferably 0.2-0.8 MPaA, the temperature is 30-200° C., preferably 40-150° C., and the residence time is 10-200 min, preferably 80-150 min.

6. The method according to claim 5, characterized in that In step 2), the amount of chlorine used in the chlorination reactor is 1-50wt% of the mass of the 1,1,2-trichloroethane waste liquid, preferably 10-40wt%.

7. The method according to claim 1, characterized in that In step 3), the reactive distillation adopts a packed tower with a plate number of 30-120, preferably 40-60, an operating pressure at the top of the tower of 10-100 kPaA, preferably 20-80 kPaA, a bottom temperature of 70-180°C, preferably 80-150°C, and a reflux ratio of 1-40, preferably 2-10.

8. The method according to claim 7, characterized in that Step 3) the outlet material of the chlorination reactor is fed from the 10th to the 45th plate number from the top to the bottom, and 1,1,2-trichloroethane is discharged from the 5th to the 35th plate number from the top to the bottom, and the discharge port is above the feed port.

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