Chlorinated paraffin tail gas treatment process

Abstract

The invention relates to a chlorinated paraffin tail gas treatment process, belongs to the technical field of chemical production, and aims to solve the problems of low chlorine recycling rate and limited product quality after byproduct hydrochloric acid gas is absorbed in the prior art. According to the technology, a modified glass membrane separation technology is adopted, chlorine and hydrochloric acid gas in chlorinated paraffin reaction tail gas are efficiently separated, the chlorine obtained through separation can return to a reaction system again to participate in a synthetic reaction of chlorinated paraffin, and the utilization rate of the chlorine is further increased; the hydrochloric acid gas is absorbed by pure water to generate a high-purity hydrochloric acid aqueous solution, other impurities are not contained, and the quality of a hydrochloric acid product is remarkably improved. After the tail gas is treated, the concentration of chlorine gas and hydrochloric acid gas is detected to be less than 5ppm at an exhaust port and reach the emission standard. The method not only realizes cyclic utilization of chlorine gas resources, but also reduces volatilization of hydrochloric acid gas and environmental pollution, has double advantages of economy and environmental protection, and is suitable for the field of tail gas treatment in chlorinated paraffin production.

Description

Technical Field

[0001] The invention relates to the technical field of chemical production, in particular to a chlorinated paraffin tail gas treatment process. Background Art

[0002] Chlorinated paraffin, also known as chlorocarbon, or chlorinated wax for short, is a chlorinated derivative of paraffin hydrocarbons with the advantages of low volatility, flame retardancy, good electrical insulation, and low price. Chlorinated paraffin is divided into varieties such as chlorinated wax-42, chlorinated wax-52, and chlorinated wax-70 according to the mass fraction of chlorine. Chlorinated wax produces tail gas during the chlorination and refining process. During the chlorination process, chlorine and wax oil react under the catalytic effect of ultraviolet light and at a certain temperature to generate chlorinated wax and hydrogen chloride. The unreacted chlorine and the generated hydrogen chloride in the chlorination reactor carry a small amount of wax oil and escape from the top of the reactor, entering the tail gas treatment process as the tail gas of the chlorination reaction; during the refining process, dry air is blown in from the bottom of the chlorinated wax refining reactor to blow out the residual hydrogen chloride in the wax oil in the refining reactor and escape from the top of the refining reactor. These air mixed with a small amount of hydrogen chloride constitute the tail gas of the chlorinated wax refining process. The chlorine and hydrogen chloride contained in the tail gas are harmful gases and cannot be discharged directly into the atmosphere. They must be comprehensively treated and meet national standards before they can be discharged.

[0003] At present, a Chinese invention patent application with publication number CN117463104A proposes a process for treating chlorinated paraffin and recovering by-products, wherein the device includes a hydrogenated paraffin reactor, an oxygen distribution table, a first treatment device, an exhaust gas condensing device, an exhaust gas capturing device, and an exhaust gas pressure stabilizing device, etc. The process for recovering by-product hydrochloric acid includes pretreatment before combustion, mixed combustion treatment, and recovery treatment after combustion.

[0004] The treatment principle is to burn chlorine and hydrogen in the reaction device. The combustion generates high temperature to make the chlorine in the tail chlorine undergo chlorination and oxidation reactions thoroughly to generate hydrogen chloride, carbon dioxide and water. The hydrogen chloride is absorbed by water as an absorption liquid to generate hydrochloric acid, which meets the quality requirements of industrial hydrochloric acid standards. However, after chlorine and hydrogen are mixed, when the volume fraction of hydrogen in chlorine is more than 5%, it may explode when exposed to strong light or open flames, which is somewhat dangerous.

[0005] The Chinese invention patent application with publication number CN104570197A proposes a tail gas treatment process for chlorinated paraffin. The treatment method is that the wax oil is pumped into a residual hydrogen absorption tower by an absorption pump to increase the temperature of the wax oil through heat exchange, and the slightly hot wax oil flowing out of the residual chlorine absorption tower enters the reaction device through a metering pump. When the liquid level of the reaction liquid in the reaction device reaches the overflow port height, the reaction liquid flows into the hydrogenated paraffin buffer tank through the overflow port of the reaction device. Finally, the reaction liquid in the oxidized paraffin buffer tank enters a continuous negative pressure degassing device through a delivery pump, and the hydrogen oxide and residual oxygen removed from the continuous negative pressure degassing device are pressed into the residual chlorine absorption tower through a blower to exchange heat with the raw wax oil.

[0006] The processing principle is that the raw wax oil passes through the residual hydrogen absorption tower, which not only achieves the purpose of increasing its own temperature without consuming energy, but also allows the residual chlorine to react with the fresh wax oil, eliminating the emission of chlorine containing trace chlorine. The subsequent tail gas treatment process realizes the continuous and efficient removal of hydrogen hydride and hydrogen contained in hydrogenated paraffin, improving the product quality. However, the hydrogen chloride gas generated by the reaction eventually generates hydrochloric acid liquid. Due to the incomplete treatment of chlorine, some chlorine is mixed in the hydrochloric acid gas, which in turn causes the hydrochloric acid solution to be of low purity and cannot be sold on the market.

[0007] It can be seen that the existing chlorinated paraffin tail gas treatment process will recycle the generated chlorine and continue to use it in the production of chlorinated paraffin, and the excess hydrogen chloride is mainly used to prepare hydrochloric acid in an absorption tower. Due to the limitations of chlorine separation, the purity of the hydrochloric acid solution is low, and the chlorine concentration and hydrochloric acid gas concentration at the exhaust port after absorption are high, which does not meet the emission standards. The current process not only wastes resources but also causes environmental pollution. Therefore, an innovative chlorinated paraffin tail gas treatment process is urgently needed to overcome the defects in the prior art, achieve efficient utilization of resources, and reduce the impact on the environment. Summary of the invention

[0008] In order to reduce the limitations of a chlorinated paraffin tail gas treatment process, the present invention provides a chlorinated paraffin tail gas treatment process.

[0009] The present invention is achieved by adopting the following technical solutions: Modified glass membrane technology is used to separate chlorine and hydrochloric acid gas from the tail gas of chlorinated paraffin production; The separated chlorine gas is reintroduced into the reaction system for use in the paraffin chlorination reaction; The separated hydrochloric acid gas is subjected to a hydrochloric acid gas absorption process to generate a high-purity hydrochloric acid aqueous solution.

[0010] Furthermore, the modified glass membrane is a high-strength glass material that has been surface-treated and has high selectivity, corrosion resistance and a long service life.

[0011] Furthermore, the pore size of the modified glass membrane is 1-50 nm, and the thickness of the modified glass membrane is 1-10 cm, which is suitable for the separation of chlorine gas and hydrochloric acid gas to ensure efficient separation effect.

[0012] Furthermore, during separation of the modified glass membrane, the pressure is set to 0.5-2.5 MPa and the temperature is set to 30-50°C.

[0013] Furthermore, the absorption process of the hydrochloric acid gas is through continuous pure water circulation absorption, the absorption process temperature is 20-30°C, and the absorption equipment adopts a spray tower with high gas-liquid contact efficiency.

[0014] Furthermore, the concentration of the hydrochloric acid aqueous solution after the hydrochloric acid gas is absorbed by pure water is 28-32%, and the impurity content is less than 0.5%.

[0015] Furthermore, after the chlorinated paraffin tail gas is processed through the tail gas treatment process, the concentrations of chlorine and hydrochloric acid gas detected at the discharge port are both less than 5 ppm, thus meeting the emission standards.

[0016] Furthermore, the modified glass membrane device has a modular design, is easy to disassemble, replace and clean, and is suitable for large-scale industrial production.

[0017] The present invention is beneficial in that: Chlorinated paraffin tail gas contains chlorine and hydrochloric acid gas. The modified glass membrane is used to classify the chlorine and hydrochloric acid gas. The separated chlorine gas re-enters the reaction system for paraffin chlorination reaction. The hydrochloric acid gas is absorbed by pure water to prepare hydrochloric acid aqueous solution. This process can not only increase the utilization rate of chlorine to more than 90%, but also improve the quality of hydrochloric acid aqueous solution. After tail gas treatment, the content of chlorine and hydrochloric acid gas in the chlorinated paraffin tail gas is less than 5ppm, the content of hydrochloric acid solution is 28-32%, and the impurity content is less than 0.5%. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to explain the present invention more clearly, the drawings required for the description will be briefly introduced below. For ordinary technicians in this field, other drawings can be obtained based on the drawings without paying any creative work.

[0019] Figure 1 A process flow chart for treating chlorinated paraffin tail gas. DETAILED DESCRIPTION

[0020] In order to facilitate the understanding of the present invention, the present invention is further described below in conjunction with examples and comparative examples. The following examples and comparative examples are only for a better understanding of the present invention and do not mean that the present invention is limited to the following examples. The present invention is further described below in conjunction with examples and comparative examples.

[0021] Embodiment 1: The tail gas generated during the production of chlorinated paraffin is introduced into a modified glass membrane separation device. A modified glass membrane with a pore size of 50nm is selected, and the thickness of the membrane is adjusted to 1cm, so that the chlorine and hydrochloric acid gas in the tail gas are effectively separated. The pressure is set to 0.5MPa and the temperature is set to 30℃ during separation. The separated chlorine enters the chlorinated paraffin reactor to prepare chlorinated paraffin. The chlorinated paraffin reactor is added with solvent carbon tetrachloride, heated to 90℃, and paraffin (C10-C20) preheated to 50℃ and a catalyst are added. The reaction is fully stirred under ultraviolet radiation. The reaction time is 10h. The chlorine content of the chlorinated paraffin is detected. The calculated chlorine cycle yield is 91.15%. The hydrochloric acid gas passes through a spray tower and is continuously absorbed by pure water circulation. The temperature of the absorption process is 20℃. The pure water absorbs to generate a hydrochloric acid solution. The concentration of the hydrochloric acid solution is 31.95%, the purity of the hydrochloric acid is 31.51%, and the impurity content is 0.44%. Sampling and testing at the exhaust port of the spray tower showed that the chlorine concentration was 4.25ppm and the hydrochloric acid gas concentration was 3.88ppm, both meeting the emission standards.

[0022] Embodiment 2: The tail gas generated during the production of chlorinated paraffin is introduced into a modified glass membrane separation device. A modified glass membrane with a pore size of 40nm is selected, and the thickness of the membrane is adjusted to 3cm, so that the chlorine gas and hydrochloric acid gas in the tail gas are effectively separated. The pressure is set to 0.9MPa and the temperature is set to 35℃ during separation. The separated chlorine gas enters the chlorinated paraffin reactor to prepare chlorinated paraffin. The chlorinated paraffin reactor is added with solvent carbon tetrachloride, heated to 90℃, and paraffin (C10-C20) preheated to 50℃ and catalyst are added. The reaction is fully stirred under ultraviolet radiation. The reaction time is 10h. The chlorine content of the chlorinated paraffin is detected. The calculated chlorine cycle yield is 93.84%. The hydrochloric acid gas passes through a spray tower and is continuously absorbed by pure water circulation. The temperature of the absorption process is 22℃. The pure water absorbs to generate a hydrochloric acid solution. The concentration of the hydrochloric acid solution is 30.64%, the purity of the hydrochloric acid is 31.05%, and the impurity content is 0.41%. Sampling and testing at the exhaust port of the spray tower showed that the chlorine concentration was 3.57ppm and the hydrochloric acid gas concentration was 4.12ppm, both meeting the emission standards.

[0023] Embodiment 3: The tail gas generated during the production of chlorinated paraffin is introduced into a modified glass membrane separation device. A modified glass membrane with a pore size of 35nm is selected, and the thickness of the membrane is adjusted to 5cm, so that the chlorine and hydrochloric acid gas in the tail gas are effectively separated. The pressure is set to 1.2MPa and the temperature is set to 35℃ during separation. The separated chlorine enters the chlorinated paraffin reactor to prepare chlorinated paraffin. The chlorinated paraffin reactor is added with solvent carbon tetrachloride, heated to 90℃, and paraffin (C10-C20) preheated to 50℃ and a catalyst are added. The reaction is fully stirred under ultraviolet radiation. The reaction time is 10h. The chlorine content of the chlorinated paraffin is detected. The calculated chlorine cycle yield is 96.17%. The hydrochloric acid gas passes through a spray tower and is continuously absorbed by pure water in a circulation process. The temperature of the absorption process is 25℃. The pure water absorbs to generate a hydrochloric acid solution. The concentration of the hydrochloric acid solution is 30.61%, the purity of the hydrochloric acid is 30.98%, and the impurity content is 0.37%. Sampling and testing at the exhaust port of the spray tower showed that the chlorine concentration was 3.67ppm and the hydrochloric acid gas concentration was 3.22ppm, both meeting the emission standards.

[0024] Embodiment 4: The tail gas generated during the production of chlorinated paraffin is introduced into a modified glass membrane separation device. A modified glass membrane with a pore size of 20 nm is selected, and the thickness of the membrane is adjusted to 7 cm, so that the chlorine gas and hydrochloric acid gas in the tail gas are effectively separated. During separation, the pressure is set to 1.7 MPa and the temperature is set to 40°C. The separated chlorine gas enters the chlorinated paraffin reactor to prepare chlorinated paraffin. The chlorinated paraffin reactor is added with solvent carbon tetrachloride, heated to 90°C, and paraffin (C10-C20) preheated to 50°C and a catalyst are added. The reaction is fully stirred under ultraviolet radiation. The reaction time is 10 hours. The chlorine content of the chlorinated paraffin is detected, and the calculated chlorine cycle yield is 96.55%. The hydrochloric acid gas passes through a spray tower and is continuously absorbed by pure water in a circulation process. The temperature of the absorption process is 25°C. The pure water absorbs to generate a hydrochloric acid solution. The concentration of the hydrochloric acid solution is 30.43%, the purity of the hydrochloric acid is 30.66%, and the impurity content is 0.23%. Sampling and testing at the exhaust port of the spray tower showed that the chlorine concentration was 2.97ppm and the hydrochloric acid gas concentration was 4.13ppm, both meeting the emission standards.

[0025] Embodiment 5: The tail gas generated during the production of chlorinated paraffin is introduced into a modified glass membrane separation device. A modified glass membrane with a pore size of 10 nm is selected, and the thickness of the membrane is adjusted to 8 cm to effectively separate the chlorine and hydrochloric acid gas in the tail gas. The pressure is set to 2.0 MPa and the temperature is set to 40°C during separation. The separated chlorine enters the chlorinated paraffin reactor to prepare chlorinated paraffin. The chlorinated paraffin reactor is added with solvent carbon tetrachloride, heated to 90°C, and paraffin (C10-C20) preheated to 50°C and a catalyst are added. The reaction is fully stirred under ultraviolet radiation. The reaction time is 10 hours to detect the chlorine content of the chlorinated paraffin. The calculated chlorine cycle yield is 96.95%. The hydrochloric acid gas passes through a spray tower and is continuously absorbed by pure water in a circulation process. The temperature of the absorption process is 25°C. The pure water absorbs to generate a hydrochloric acid solution. The concentration of the hydrochloric acid solution is 29.97%, the purity of the hydrochloric acid is 30.14%, and the impurity content is 0.17%. Sampling and testing at the exhaust port of the spray tower showed a chlorine concentration of 3.55ppm and a hydrochloric acid concentration of 2.49ppm, both meeting the emission standards.

[0026] Embodiment 6: The tail gas generated during the production of chlorinated paraffin is introduced into a modified glass membrane separation device. A modified glass membrane with a pore size of 1 nm is selected, and the thickness of the membrane is adjusted to 10 cm, so that the chlorine and hydrochloric acid gas in the tail gas are effectively separated. The pressure is set to 2.5 MPa and the temperature is set to 40°C during separation. The separated chlorine enters the chlorinated paraffin reactor to prepare chlorinated paraffin. The chlorinated paraffin reactor is added with solvent carbon tetrachloride, heated to 90°C, and paraffin (C10-C20) preheated to 50°C and a catalyst are added. The reaction is fully stirred under ultraviolet radiation. The reaction time is 10 hours. The chlorine content of the chlorinated paraffin is detected, and the calculated chlorine cycle yield is 98.02%. The hydrochloric acid gas passes through a spray tower and is continuously absorbed by pure water in a circulation process. The temperature of the absorption process is 25°C. The pure water absorbs to generate a hydrochloric acid solution. The concentration of the hydrochloric acid solution is 29.17%, the purity of the hydrochloric acid is 29.21%, and the impurity content is 0.04%. Sampling and testing at the exhaust port of the spray tower showed that the chlorine concentration was 2.43ppm and the hydrochloric acid gas concentration was 2.15ppm, both meeting the emission standards.

[0027] Comparative Example 1: The tail gas generated during the production of chlorinated paraffin is introduced into a modified glass membrane separation device. A modified glass membrane with a pore size of 35nm is selected, and the thickness of the membrane is adjusted to 5cm, so that the chlorine and hydrochloric acid gas in the tail gas are effectively separated. The pressure is set to 1.2MPa and the temperature is set to 35℃ during separation. The separated chlorine enters the chlorinated paraffin reactor to prepare chlorinated paraffin. The chlorinated paraffin reactor is added with solvent carbon tetrachloride, heated to 90℃, and paraffin (C10-C20) preheated to 50℃ and a catalyst are added. The reaction is fully stirred under ultraviolet radiation. The reaction time is 10h. The chlorine content of the chlorinated paraffin is detected, and the calculated chlorine cycle yield is 96.17%. The hydrochloric acid gas passes through an ordinary absorption tower and is continuously absorbed by pure water in a circulation process. The temperature of the absorption process is 25℃. The pure water absorption generates a hydrochloric acid solution with a concentration of 31.47%, a hydrochloric acid purity of 31.96%, and an impurity content of 0.49%. Sampling was conducted at the exhaust port of the ordinary absorption tower, and the chlorine concentration was 153.67 ppm and the hydrochloric acid gas concentration was 104.22 ppm.

[0028] Comparative Example 2: The tail gas generated during the production of chlorinated paraffin is introduced into a common gas separation membrane. A common gas separation membrane with a pore size of 35nm is selected, and the thickness of the membrane is adjusted to 5cm. The chlorine and hydrochloric acid gas in the tail gas are separated. The pressure is set to 1.2MPa and the temperature is set to 35℃ during separation. The separated chlorine enters the chlorinated paraffin reactor to prepare chlorinated paraffin. The chlorinated paraffin reactor is added with solvent carbon tetrachloride, heated to 90℃, and paraffin (C10-C20) preheated to 50℃ and catalyst are added. The reaction is fully stirred under ultraviolet radiation. The reaction time is 10h. The chlorine content of the chlorinated paraffin is detected. The calculated chlorine cycle yield is 65.17%. The hydrochloric acid gas passes through the spray tower and is continuously absorbed by pure water circulation. The temperature of the absorption process is 22℃. The pure water absorbs to generate hydrochloric acid solution. The concentration of the hydrochloric acid solution is 30.79% after testing, the purity of the hydrochloric acid is 33.44%, and the impurity content is 2.65%. Sampling was conducted at the exhaust port of the spray tower, and the chlorine concentration was 29.73 ppm and the hydrochloric acid concentration was 25.44 ppm.

[0029] Comparative Example 3: The tail gas generated during the production of chlorinated paraffin is directly fed into a common absorption tower and continuously absorbed by pure water circulation. The absorption process temperature is 22°C. The pure water absorbs and generates hydrochloric acid solution. The concentration of the hydrochloric acid solution is 29.97%, the purity of hydrochloric acid is 33.05%, and the impurity content is 3.08%. Samples are taken from the exhaust port of the common absorption tower for testing. The chlorine concentration is 1009.97ppm and the hydrochloric acid concentration is 851.44ppm.

Claims

1. A chlorinated paraffin tail gas treatment process, characterized in that: The following steps are involved: Modified glass membrane technology is used to separate chlorine and hydrochloric acid gas from the tail gas of chlorinated paraffin production; The separated chlorine gas is reintroduced into the reaction system for use in the paraffin chlorination reaction; The separated hydrochloric acid gas is subjected to a hydrochloric acid gas absorption process to generate a high-purity hydrochloric acid aqueous solution.

2. A chlorinated paraffin tail gas treatment process according to claim 1, characterized in that: The modified glass membrane is a high-strength glass material that has been surface-treated and has high selectivity, corrosion resistance and a long service life.

3. A chlorinated paraffin tail gas treatment process according to claim 2, characterized in that: The pore size of the modified glass membrane is 1-50 nm, and the thickness of the modified glass membrane is 1-10 cm.

4. A chlorinated paraffin tail gas treatment process according to claim 3, characterized in that: During the separation of the modified glass membrane, the pressure is set to 0.5-2.5 MPa and the temperature is set to 30-50°C.

5. A chlorinated paraffin tail gas treatment process according to claim 1, characterized in that: The absorption process of the hydrochloric acid gas is absorption through continuous pure water circulation, the absorption process temperature is 20-30° C., and the absorption equipment adopts a spray tower with high gas-liquid contact efficiency.

6. A chlorinated paraffin tail gas treatment process according to claim 5, characterized in that: The concentration of the hydrochloric acid aqueous solution after the hydrochloric acid gas is absorbed by pure water is 28-32%, and the impurity content is less than 0.5%.

7. A chlorinated paraffin tail gas treatment process according to claims 1-6, characterized in that: After the chlorinated paraffin tail gas is processed through the tail gas treatment process, the concentrations of chlorine and hydrochloric acid gas detected at the discharge port are both less than 5 ppm.

8. The chlorinated paraffin tail gas treatment process according to claim 1, characterized in that: The modified glass membrane device has a modular design, is easy to disassemble, replace and clean, and is suitable for large-scale industrial production.

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