Treatment methods for chlorinated tail gas

Abstract

The present invention relates to a method for treating chlorinated tail gas, comprising: providing chlorinated tail gas, the chlorinated tail gas comprising sulfur dioxide gas and hydrogen chloride gas; subjecting the chlorinated tail gas and chlorine gas to an acyl chloride synthesis reaction under the action of a catalyst to obtain sulfuryl chloride and a first tail gas; subjecting the first tail gas to a sulfuryl chloride decomposition reaction under the action of a catalyst to obtain a second tail gas; subjecting the second tail gas to a heating and absorption treatment using a saturated hydrochloric acid aqueous solution to obtain a third tail gas; and drying the third tail gas to obtain hydrogen chloride gas. The treatment method of the present invention can not only obtain high-purity hydrogen chloride gas and improve the recycling value of hydrogen chloride, but also has mild reaction conditions, simple operation, and is easy to industrialize.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical tail gas treatment, in particular to a method for treating chlorinated tail gas. Background Art

[0002] Sulfuryl chloride (SO2Cl2) is often used as a chlorinating agent due to its low price, mild reaction conditions, high reaction yield, and the fact that it does not introduce impurities. It is used for chlorination of aromatic compounds, carboxylic acids, and various other organic compounds. The main reaction formula when sulfuryl chloride is used as a chlorinating agent is as follows:

[0003] RH+SO2Cl2→RCl+SO2+HCl

[0004] From reaction formula, sulfuryl chloride can produce sulphur dioxide gas and hydrogen chloride gas of equimolar amount after reaction, and these acid gases all can produce serious harm to human body and environment, so the processing of chlorinated tail gas becomes one of difficulty of this type of reaction in industry.Usually the sulphur dioxide in industrial chlorinated tail gas can be converted into materials such as sulfuryl chloride by acyl chloride synthesis reaction and recycled again, but there are more problems in the purification and recovery of hydrogen chloride.Hydrogen chloride, as important industrial chemicals, can be used as various chlorides (chloroalkanes, chlorohydrins, chloric acids, chloromethyl group-related products and various pharmaceutical intermediates) for synthesis, and is widely used in fields such as dyestuff, spices, medicine, anti-corrosion.Therefore, the recycling of hydrogen chloride can not only alleviate environmental pressure, but also bring higher economic benefits.

[0005] Currently, there are two main methods for recovering hydrogen chloride from chlorinated tail gas. The first is a physical recovery method, in which sulfur dioxide and hydrogen chloride in the chlorinated tail gas are first separated by physical means, and the separated hydrogen chloride is then converted into hydrochloric acid by absorption. However, this method consumes a lot of energy and has high requirements for equipment materials, so its industrial application value is not high. For example, patents CN103752125A and CN109205573A utilize the difference in boiling points between sulfur dioxide and hydrogen chloride to separate sulfur dioxide and hydrogen chloride through cooling and pressurized distillation. Second, there is the chemical recovery method, which involves first converting the sulfur dioxide in the chlorinated tail gas into sulfuryl chloride and other substances for reuse, and then converting the remaining hydrogen chloride into hydrochloric acid through absorption. This method is currently the most widely used process in industry, but the resulting hydrochloric acid is of low quality and has significant limitations in downstream applications. For example, patent CN1408463A mentions using industrial-grade phosphorus trichloride and chlorine as raw materials, first converting the sulfur dioxide into thionyl chloride and phosphorus oxychloride, and then absorbing the remaining chlorinated tail gas into industrial hydrochloric acid through water. However, the hydrochloric acid prepared by this method not only contains sulfur dioxide gas but also introduces large amounts of sulfuryl chloride and chlorine, resulting in the hydrochloric acid being high in impurities, making it unsaleable or difficult to use as raw materials for reactions, and thus difficult to handle. Summary of the Invention

[0006] Based on this, it is necessary to provide a method for treating chlorinated tail gas to address the above problems. The treatment method can not only obtain high-purity hydrogen chloride gas and improve the recovery and utilization value of hydrogen chloride, but also has mild reaction conditions, simple operation, and is easy to industrialize.

[0007] A method for treating chlorinated tail gas, comprising:

[0008] Providing chlorinated tail gas, wherein the chlorinated tail gas includes sulfur dioxide gas and hydrogen chloride gas;

[0009] The chlorinated tail gas and chlorine are subjected to an acyl chloride synthesis reaction under the action of a catalyst to obtain sulfuryl chloride and a first tail gas;

[0010] Decomposing the first tail gas with sulfuryl chloride under the action of a catalyst to obtain a second tail gas;

[0011] using a saturated hydrochloric acid aqueous solution to heat and absorb the second tail gas to obtain a third tail gas;

[0012] The third tail gas is dried to obtain hydrogen chloride gas.

[0013] In one embodiment, in the step of subjecting the chlorinated tail gas and chlorine to an acyl chloride synthesis reaction under the action of a catalyst, the flow ratio of the chlorinated tail gas to the chlorine is 1.80:1-1.99:1.

[0014] In one embodiment, in the step of reacting the chlorinated tail gas and chlorine under the action of a catalyst, the catalyst is selected from activated carbon, and the temperature is 10° C.-20° C.;

[0015] And / or, in the step of subjecting the first tail gas to a sulfuryl chloride decomposition reaction under the action of a catalyst, the catalyst is selected from activated carbon, and the temperature is 90° C.-180° C.

[0016] In one embodiment, in the step of heating and absorbing the second tail gas using a saturated hydrochloric acid aqueous solution, at least two stages of heating and absorption treatment are performed.

[0017] In one embodiment, in the step of heating and absorbing the second tail gas with a saturated hydrochloric acid aqueous solution, a two-stage heating and absorption treatment is performed, and the temperature of the first-stage heating and absorption treatment is 50°C-90°C, and the temperature of the second-stage heating and absorption treatment is 50°C-90°C.

[0018] In one embodiment, in the step of drying the third tail gas, concentrated sulfuric acid is used for absorption treatment.

[0019] In one embodiment, before the step of using concentrated sulfuric acid for absorption treatment, the third tail gas is first condensed.

[0020] In one embodiment, the temperature of the condensation treatment is 1°C-5°C.

[0021] In one embodiment, the chlorinated tail gas is a reaction tail gas generated by a chlorination reaction using sulfuryl chloride as a chlorinating agent.

[0022] In one embodiment, the chlorinated tail gas is a reaction tail gas generated by a chlorination reaction of 3,5-dimethylphenol and sulfuryl chloride;

[0023] And / or, the sulfuryl chloride obtained by reacting the chlorinated tail gas with chlorine in the presence of a catalyst is recycled for use in the chlorination reaction.

[0024] In the method for treating chlorinated tail gas of the present invention, chlorinated tail gas and chlorine are subjected to an acyl chloride synthesis reaction to obtain sulfuryl chloride and a first tail gas, so that sulfur dioxide gas in the chlorinated tail gas is converted into sulfuryl chloride, thereby achieving the purpose of recovering sulfur dioxide gas and the prepared sulfuryl chloride can be recycled. Then, the first tail gas is subjected to a sulfuryl chloride decomposition reaction to decompose sulfuryl chloride entrained in the first tail gas into sulfur dioxide gas and chlorine gas, thereby removing sulfuryl chloride in the first tail gas and effectively avoiding the influence of sulfuryl chloride on subsequent purification of hydrogen chloride gas. Then, the second tail gas is subjected to a heating absorption treatment using a saturated hydrochloric acid aqueous solution to remove sulfur dioxide gas and chlorine gas in the second tail gas. Finally, the third tail gas is dried to remove moisture, thereby obtaining high-purity hydrogen chloride gas, wherein the purity of the hydrogen chloride gas is ≥99% and the recovery rate of the hydrogen chloride gas is ≥95%.

[0025] Therefore, the present invention not only recovers hydrogen chloride gas in the chlorinated tail gas, but also can purify hydrogen chloride to obtain high-purity hydrogen chloride gas, which can be used for downstream synthesis, thereby realizing the recycling of hydrogen chloride gas. This not only reduces production costs, but also reduces the amount of halogen-containing compounds entering the three waste systems, greatly reduces environmental pressure, and can simultaneously bring higher economic and environmental benefits.

[0026] In addition, in the method for treating chlorinated tail gas of the present invention, the reaction conditions should be mild, the operation should be simple, and the industrialization should be easy. DETAILED DESCRIPTION

[0027] To facilitate understanding of the present invention, the present invention will be described in more detail below. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. On the contrary, the purpose of providing these embodiments or examples is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in this specification of the present invention are only for the purpose of describing specific embodiments or examples and are not intended to limit the present invention.

[0029] The method for treating chlorinated tail gas provided by the present invention is mainly used to treat chlorinated tail gas including sulfur dioxide gas and hydrogen chloride gas, wherein the chlorinated tail gas is mainly produced by a chlorination reaction. Optionally, the chlorinated tail gas is a reaction tail gas generated by a chlorination reaction using sulfuryl chloride as a chlorinating agent. For example, the chlorinated tail gas is a reaction tail gas generated by a chlorination reaction between 3,5-dimethylphenol and sulfuryl chloride.

[0030] Specifically, in the method for treating chlorinated tail gas of the present invention, the chlorinated tail gas and chlorine are first subjected to an acyl chloride synthesis reaction under the action of a catalyst, so that the sulfur dioxide gas in the chlorinated tail gas is converted into sulfuryl chloride. After separation, sulfuryl chloride and a first tail gas are obtained, thereby not only achieving the purpose of recovering the sulfur dioxide gas, but also the prepared sulfuryl chloride can be recycled. For example, when the chlorinated tail gas is a reaction tail gas generated by a chlorination reaction using sulfuryl chloride as a chlorinating agent, the separated sulfuryl chloride can be recycled for use in the chlorination reaction. Such an arrangement can further achieve the recycling of sulfuryl chloride and save costs.

[0031] After the acyl chloride synthesis reaction, most of the sulfur dioxide gas is recovered, so the first tail gas is mainly hydrogen chloride gas, and the impurity components are a small amount of entrained sulfuryl chloride, unreacted chlorine and sulfur dioxide gas.

[0032] Optionally, in the step of subjecting the chlorinated tail gas and chlorine to an acyl chloride synthesis reaction under the action of a catalyst, the flow ratio of the chlorinated tail gas to the chlorine is 1.80:1 to 1.99:1. This arrangement ensures that the amount of chlorine used is excessive relative to the sulfur dioxide gas in the chlorinated tail gas, thereby further ensuring that the sulfur dioxide gas is completely converted into sulfuryl chloride, that is, further improving the conversion rate of the sulfur dioxide gas, thereby better realizing the recovery and utilization of the sulfur dioxide gas.

[0033] In one embodiment, the flow rate of the chlorine gas is 150 mL / min-160 mL / min, and the flow rate of the chlorinated tail gas is 290 mL / min-300 mL / min.

[0034] Optionally, in the step of reacting the chlorinated tail gas and chlorine under the action of a catalyst, the catalyst is selected from activated carbon, and the temperature is 10°C-20°C. Preferably, the catalyst is activated carbon, and the temperature is 15°C. Such an arrangement enables the sulfur dioxide gas and chlorine in the chlorinated tail gas to more fully undergo the acyl chloride synthesis reaction. The specific reaction equation is as follows:

[0035]

[0036] Therefore, in the present invention, the chlorinated tail gas and chlorine gas are subjected to an acyl chloride synthesis reaction, so that the sulfur dioxide gas can be converted into sulfuryl chloride, thereby achieving the recycling of the sulfur dioxide gas and further realizing the cyclic utilization of sulfuryl chloride as a chlorinating agent in the chlorination reaction.

[0037] Sulfuryl chloride carried in the first tail gas can affect the quality of the final hydrogen chloride gas. Therefore, in the treatment method of the present invention, after obtaining the first tail gas, the first tail gas is subjected to a sulfuryl chloride decomposition reaction in the presence of a catalyst to produce a second tail gas. In this step, the sulfuryl chloride carried in the first tail gas can be decomposed into sulfur dioxide gas and chlorine gas, thereby effectively preventing the impact of sulfuryl chloride on the subsequent purification of the hydrogen chloride gas.

[0038] Therefore, the second tail gas is mainly hydrogen chloride gas, and the impurity components are a small amount of sulfur dioxide gas and chlorine gas. Of course, it is not ruled out that the second tail gas may also contain a small amount of sulfuryl chloride.

[0039] Optionally, in the step of subjecting the first tail gas to a sulfuryl chloride decomposition reaction in the presence of a catalyst, the catalyst is selected from activated carbon, and the temperature is 90° C. to 180° C. Preferably, the catalyst is activated carbon, and the temperature is 100° C. to 150° C. This configuration facilitates the complete decomposition of sulfuryl chloride in the first tail gas into sulfur dioxide gas and chlorine gas, further preventing the impact of sulfuryl chloride on the subsequent purification of hydrogen chloride gas.

[0040] In the treatment method of the present invention, after obtaining the second tail gas, the second tail gas is subjected to heating and absorption treatment using a saturated hydrochloric acid aqueous solution to obtain the third tail gas.

[0041] Specifically, the second tail gas passes through a saturated hydrochloric acid aqueous solution, and the sulfur dioxide gas in the second tail gas dissolves in water to form sulfurous acid. At the same time, the chlorine reacts with water to form hypochlorous acid and hydrogen chloride. Then, part of the generated hypochlorous acid reacts with the sulfurous acid to form sulfuric acid and hydrogen chloride, and the remaining part decomposes into hydrogen chloride and oxygen under heating conditions, thereby removing the chlorine and sulfur dioxide gas. Specifically, the chlorine and sulfur dioxide gas in the second tail gas undergo the following reactions during the process of passing through the saturated hydrochloric acid aqueous solution:

[0042] SO2+H2O→H2SO3, Cl2+H2O→HCl+HClO;

[0043] H2SO3+HClO→H2SO4+HCl, 2HClO→2HCl+O2.

[0044] It should be noted that if a small amount of sulfuryl chloride is mixed in the second tail gas, the sulfuryl chloride will also undergo a hydrolysis reaction with water in the saturated hydrochloric acid aqueous solution to generate sulfuric acid and hydrogen chloride. The specific reaction formula is as follows:

[0045] SO2Cl2+2H2O→2HCl+H2SO4.

[0046] Therefore, in the treatment method of the present invention, the second tail gas is subjected to heating and absorption treatment using a saturated hydrochloric acid aqueous solution, which can remove sulfur dioxide gas and chlorine gas in the second tail gas. At the same time, if there is a trace amount of sulfuryl chloride remaining, it can also be removed, thereby obtaining water-containing hydrogen chloride gas, i.e., the third tail gas.

[0047] Optionally, in the step of heating and absorbing the second tail gas with a saturated hydrochloric acid aqueous solution, a single heating and absorption treatment can be performed, or a two-stage heating and absorption treatment can be performed, or a three-stage heating and absorption treatment can be performed, or a four-stage heating and absorption treatment can be performed, etc., depending on the proportion of the impurity components sulfur dioxide and chlorine in the second tail gas. The present invention preferably performs at least two-stage heating and absorption treatment, which is conducive to obtaining high-purity hydrogen chloride gas.

[0048] In one embodiment, in the step of heating and absorbing the second tail gas with a saturated hydrochloric acid aqueous solution, a two-stage heating and absorption treatment is performed, and the temperature of the first-stage heating and absorption treatment is 50°C-90°C, and the temperature of the second-stage heating and absorption treatment is 50°C-90°C.

[0049] In one embodiment, the saturated hydrochloric acid aqueous solution is a hydrochloric acid aqueous solution with a mass concentration of 37% at room temperature. It should be noted that, during the entire process of heating and absorbing the second tail gas using the saturated hydrochloric acid aqueous solution, although the mass concentration of the saturated hydrochloric acid aqueous solution will change, the change has no effect on the absorption of the impurity components chlorine and sulfur dioxide gas by the saturated hydrochloric acid aqueous solution, and the hydrochloric acid aqueous solution is saturated throughout the entire process, which can ensure that hydrogen chloride gas is insoluble in the saturated hydrochloric acid aqueous solution.

[0050] In the treatment method of the present invention, after obtaining the third tail gas, it only needs to be dried to remove moisture to obtain high-purity hydrogen chloride gas. Specifically, the purity of the hydrogen chloride gas is ≥99%, and the recovery rate of the hydrogen chloride gas is ≥95%.

[0051] Optionally, in the step of drying the third tail gas, concentrated sulfuric acid is used for absorption treatment. This arrangement can remove water without affecting the quality of the hydrogen chloride gas.

[0052] Optionally, before the absorption treatment with concentrated sulfuric acid, the third tail gas may be condensed, wherein the condensation temperature is preferably 1-5° C. This arrangement can remove most of the water and reduce the amount of subsequent desiccant such as concentrated sulfuric acid.

[0053] Therefore, the present invention not only recovers hydrogen chloride gas in the chlorinated tail gas, but also can purify the hydrogen chloride to obtain high-purity hydrogen chloride gas, which can be used for downstream synthesis, such as the synthesis of trimethyl orthoformate. This realizes the recycling of hydrogen chloride gas, which not only reduces production costs but also reduces the amount of halogen-containing compounds entering the three-waste system, greatly reduces environmental pressure, and can simultaneously bring higher economic and environmental benefits.

[0054] At the same time, in the method for treating chlorinated tail gas of the present invention, the reaction conditions should be mild, the operation should be simple, and the industrialization should be easy.

[0055] Hereinafter, the method for treating the chlorinated tail gas will be further described through the following specific examples.

[0056] At the same time, it should be noted that the raw materials involved in the examples and comparative examples of the present invention can be purchased from the market.

[0057] In addition, the compositions of the first tail gas, the second tail gas, the remaining second tail gas, the third tail gas, and the remaining third tail gas involved in the embodiments and comparative examples of the present invention are all gas phase compositions measured by gas chromatography, wherein the gas chromatography analysis conditions are as follows:

[0058] Detector: thermal conductivity detector (TCD detector), sensitivity ST>1000;

[0059] Carrier gas: hydrogen, purity greater than 99.9%;

[0060] Chromatographic column: Model OV-101, capillary column 30m*0.25mm*0.25um;

[0061] Injector: micro syringe, minimum scale 0.1ul;

[0062] Analysis conditions: column temperature 80°C, detector temperature 100-150°C, bridge current 150 mA; carrier gas flow rate: hydrogen 10 ml / min.

[0063] Example 1

[0064] The chlorinated tail gas in this embodiment is the chlorinated tail gas produced by the chlorination reaction of 3,5-dimethylphenol and sulfuryl chloride, wherein the chlorinated tail gas includes hydrogen chloride and sulfur dioxide in an equal molar ratio.

[0065] Chlorinated tail gas and chlorine are introduced together into an acyl chloride synthesis device containing a catalyst to carry out an acyl chloride synthesis reaction, wherein the catalyst is activated carbon, the flow rates of chlorine and chlorinated tail gas are 152 mL / min and 300 mL / min respectively (i.e., the flow ratio of chlorinated tail gas to chlorine is 1.97:1), and the temperature is 15° C. to obtain a first tail gas consisting of 90.7% hydrogen chloride gas, 1.1% sulfur dioxide gas, 2.3% chlorine gas, and 5.90% sulfuryl chloride.

[0066] The first tail gas obtained above is passed into a sulfuryl chloride decomposition reactor containing a catalyst to carry out a sulfuryl chloride decomposition reaction, wherein the catalyst is activated carbon and the temperature is 100° C. to obtain a second tail gas composed of 90.7% hydrogen chloride gas, 3.14% sulfur dioxide gas, 4.34% chlorine gas and 1.82% sulfuryl chloride.

[0067] The second tail gas obtained above is passed into an absorption device containing a saturated hydrochloric acid aqueous solution for a primary heating absorption treatment, wherein the mass fraction of hydrochloric acid in the saturated hydrochloric acid aqueous solution is 37% and the temperature is 50° C., thereby obtaining a remaining second tail gas, wherein the impurity components in the remaining second tail gas consist of 0.42% of sulfur dioxide gas and 0.91% of chlorine gas. The remaining second tail gas is then passed into an absorption device containing a saturated hydrochloric acid aqueous solution for a secondary heating absorption treatment, wherein the mass fraction of hydrochloric acid in the saturated hydrochloric acid aqueous solution is 37% and the temperature is 50° C., thereby obtaining a third tail gas, wherein the impurity components in the third tail gas consist of less than 0.16% of sulfur dioxide gas and 0.4% of chlorine gas.

[0068] Finally, the third tail gas obtained above was passed into a condenser for cooling and separation, wherein the condensation temperature was 5° C., to obtain a remaining third tail gas, wherein the mass fraction of water in the remaining third tail gas was 2.15%. The remaining third tail gas was then passed into concentrated sulfuric acid to absorb the remaining water. The gas discharged after the absorption was high-purity hydrogen chloride gas, specifically, with a purity of 99.57% and a recovery rate of 96.74%.

[0069] Example 2

[0070] Example 2 is different from Example 1 only in that, during the process of passing the obtained first tail gas into the sulfuryl chloride decomposition reactor containing the catalyst for decomposition reaction, the temperature is 110° C., and a second tail gas consisting of 90.7% hydrogen chloride gas, 3.23% sulfur dioxide gas, 4.43% chlorine gas and 1.64% sulfuryl chloride is obtained.

[0071] The second tail gas obtained above is passed into an absorption device containing a saturated hydrochloric acid aqueous solution for a primary heating absorption treatment to obtain a remaining second tail gas, and the impurity components in the remaining second tail gas are composed of 0.47% sulfur dioxide gas and 0.96% chlorine gas.

[0072] The remaining second tail gas is passed into an absorption device containing a saturated hydrochloric acid aqueous solution for secondary heating absorption treatment to obtain a third tail gas, wherein the impurity components in the third tail gas are composed of less than 0.05% sulfur dioxide gas and 0.1% chlorine gas.

[0073] Finally, the third tail gas obtained above is passed into a condenser for cooling and separation to obtain a remaining third tail gas, wherein the mass fraction of water in the remaining third tail gas is 2.10%. The remaining third tail gas is then passed into concentrated sulfuric acid to absorb the remaining water. The gas discharged after absorption is high-purity hydrogen chloride gas, specifically, the purity is 99.84%, and the recovery rate is 96.89%.

[0074] Example 3

[0075] Example 3 is different from Example 1 only in that, during the process of passing the obtained first tail gas into the sulfuryl chloride decomposition reactor containing a catalyst for decomposition reaction, the temperature is 120° C., and a second tail gas consisting of 90.7% hydrogen chloride gas, 3.24% sulfur dioxide gas, 4.44% chlorine gas and 1.62% sulfuryl chloride is obtained.

[0076] The second tail gas obtained above is passed into an absorption device containing a saturated hydrochloric acid aqueous solution for a primary heating absorption treatment to obtain a remaining second tail gas, and the impurity components in the remaining second tail gas are composed of 0.53% sulfur dioxide gas and 1.14% chlorine gas.

[0077] The remaining second tail gas is passed into an absorption device containing a saturated hydrochloric acid aqueous solution for secondary heating absorption treatment to obtain a third tail gas, and the impurity components in the third tail gas are composed of less than 0.07% sulfur dioxide gas and 0.14% chlorine gas.

[0078] Finally, the third tail gas obtained above is passed into a condenser for cooling and separation to obtain a remaining third tail gas, wherein the mass fraction of water in the remaining third tail gas is 2.14%. The remaining third tail gas is then passed into concentrated sulfuric acid to absorb the remaining water. The gas discharged after absorption is high-purity hydrogen chloride gas, specifically, the purity is 99.61%, and the recovery rate is 97.11%.

[0079] Example 4

[0080] Example 4 is different from Example 1 only in that, during the process of passing the obtained first tail gas into the sulfuryl chloride decomposition reactor containing a catalyst for decomposition reaction, the temperature is 130° C., and a second tail gas consisting of 90.70% hydrogen chloride gas, 3.48% sulfur dioxide gas, 4.72% chlorine gas and 1.05% sulfuryl chloride is obtained.

[0081] The second tail gas obtained above is passed into an absorption device containing a saturated hydrochloric acid aqueous solution for a primary heating absorption treatment to obtain a remaining second tail gas, and the impurity components in the remaining second tail gas are composed of 0.7% sulfur dioxide gas and 1.27% chlorine gas.

[0082] The remaining second tail gas is passed into an absorption device containing a saturated hydrochloric acid aqueous solution for secondary heating absorption treatment to obtain a third tail gas, and the impurity components in the third tail gas are composed of less than 0.11% sulfur dioxide gas and 0.16% chlorine gas.

[0083] Finally, the third tail gas obtained above is passed into a condenser for cooling and separation to obtain a remaining third tail gas, wherein the mass fraction of water in the remaining third tail gas is 2.03%. The remaining third tail gas is then passed into concentrated sulfuric acid to absorb the remaining water. The gas discharged after absorption is high-purity hydrogen chloride gas, specifically, the purity is 99.44%, and the recovery rate is 97.23%.

[0084] Example 5

[0085] Example 5 is different from Example 1 only in that, during the process of passing the obtained first tail gas into the sulfuryl chloride decomposition reactor containing the catalyst for decomposition reaction, the temperature is 140° C., and a second tail gas consisting of 90.69% hydrogen chloride gas, 3.74% sulfur dioxide gas, 4.94% chlorine gas and 0.63% sulfuryl chloride is obtained.

[0086] The second tail gas obtained above is passed into an absorption device containing a saturated hydrochloric acid aqueous solution for a primary heating absorption treatment to obtain a remaining second tail gas, and the impurity components in the remaining second tail gas are composed of 0.64% sulfur dioxide gas and 1.40% chlorine gas.

[0087] The remaining second tail gas is passed into an absorption device containing a saturated hydrochloric acid aqueous solution for secondary heating absorption treatment to obtain a third tail gas, wherein the impurity components in the third tail gas are composed of less than 0.07% sulfur dioxide gas and 0.2% chlorine gas.

[0088] Finally, the third tail gas obtained above is passed into a condenser for cooling and separation to obtain a remaining third tail gas, wherein the mass fraction of water in the remaining third tail gas is 2.16%. The remaining third tail gas is then passed into concentrated sulfuric acid to absorb the remaining water. The gas discharged after absorption is high-purity hydrogen chloride gas, specifically, the purity is 99.31%, and the recovery rate is 97.26%.

[0089] Example 6

[0090] Example 6 is different from Example 1 only in that, during the process of passing the obtained first tail gas into a sulfuryl chloride decomposition reactor containing a catalyst for decomposition reaction, the temperature is 150° C., and a second tail gas consisting of 90.69% hydrogen chloride gas, 3.95% sulfur dioxide gas, 5.15% chlorine gas and 0.21% sulfuryl chloride is obtained.

[0091] The second tail gas obtained above is passed into an absorption device containing a saturated hydrochloric acid aqueous solution for a primary heating absorption treatment to obtain a remaining second tail gas, and the impurity components in the remaining second tail gas are composed of 0.79% sulfur dioxide gas and 1.67% chlorine gas.

[0092] The remaining second tail gas is passed into an absorption device containing a saturated hydrochloric acid aqueous solution for secondary heating absorption treatment to obtain a third tail gas, wherein the impurity components in the third tail gas are composed of less than 0.14% sulfur dioxide gas and 0.23% chlorine gas.

[0093] Finally, the third tail gas obtained above is passed into a condenser for cooling and separation to obtain a remaining third tail gas, wherein the mass fraction of water in the remaining third tail gas is 2.01%. The remaining third tail gas is then passed into concentrated sulfuric acid to absorb the remaining water. The gas discharged after absorption is high-purity hydrogen chloride gas, specifically, the purity is 99.18%, and the recovery rate is 97.40%.

[0094] Example 7

[0095] Example 7 differs from Example 6 only in that the obtained second tail gas is passed through an absorption device containing a saturated aqueous hydrochloric acid solution for a primary heating absorption treatment at a temperature of 60° C., thereby obtaining a residual second tail gas, wherein the impurity components of the residual second tail gas are composed of 0.55% sulfur dioxide gas and 0.95% chlorine gas. The residual second tail gas is then passed through an absorption device containing a saturated aqueous hydrochloric acid solution for a secondary heating absorption treatment, thereby obtaining a third tail gas, wherein the impurity components of the third tail gas are composed of less than 0.08% sulfur dioxide gas and 0.16% chlorine gas.

[0096] Finally, the third tail gas obtained above is passed into a condenser for cooling and separation, and the remaining third tail gas is obtained. The mass fraction of water in the remaining third tail gas is 2.53%. Then, the remaining third tail gas is passed into concentrated sulfuric acid to absorb the remaining water. The gas discharged after absorption is high-purity hydrogen chloride gas, specifically, the purity is 99.23%, and the recovery rate is 97.43%.

[0097] Example 8

[0098] Example 8 differs from Example 6 only in that the obtained second tail gas is passed through an absorption device containing a saturated aqueous hydrochloric acid solution for a primary heating absorption treatment at a temperature of 70° C., thereby obtaining a residual second tail gas, wherein the impurity components of the residual second tail gas are composed of 0.40% sulfur dioxide gas and 0.78% chlorine gas. The residual second tail gas is then passed through an absorption device containing a saturated aqueous hydrochloric acid solution for a secondary heating absorption treatment, thereby obtaining a third tail gas, wherein the impurity components of the third tail gas are composed of less than 0.07% sulfur dioxide gas and 0.13% chlorine gas.

[0099] Finally, the third tail gas obtained above is passed into a condenser for cooling and separation to obtain a remaining third tail gas, wherein the mass fraction of water in the remaining third tail gas is 3.37%. The remaining third tail gas is then passed into concentrated sulfuric acid to absorb the remaining water. The gas discharged after absorption is high-purity hydrogen chloride gas, specifically, the purity is 99.26%, and the recovery rate is 97.56%.

[0100] Example 9

[0101] Example 9 differs from Example 6 only in that the obtained second tail gas is passed through an absorption device containing a saturated aqueous hydrochloric acid solution for a primary heating absorption treatment at a temperature of 80° C., thereby obtaining a residual second tail gas, wherein the impurity components of the residual second tail gas consist of less than 0.32% sulfur dioxide gas and 0.66% chlorine gas. The residual second tail gas is then passed through an absorption device containing a saturated aqueous hydrochloric acid solution for a secondary heating absorption treatment, thereby obtaining a third tail gas, wherein the impurity components of the third tail gas consist of less than 0.05% sulfur dioxide gas and 0.1% chlorine gas.

[0102] Finally, the third tail gas obtained above is passed into a condenser for cooling and separation to obtain a remaining third tail gas, wherein the mass fraction of water in the remaining third tail gas is 3.79%. The remaining third tail gas is then passed into concentrated sulfuric acid to absorb the remaining water. The gas discharged after absorption is high-purity hydrogen chloride gas, specifically, the purity is 99.31%, and the recovery rate is 97.71%.

[0103] Example 10

[0104] Example 10 differs from Example 6 only in that the obtained second tail gas is passed through an absorption device containing a saturated aqueous hydrochloric acid solution for a primary heating absorption treatment at a temperature of 90° C., thereby obtaining a residual second tail gas, wherein the impurity components of the residual second tail gas are composed of 0.43% sulfur dioxide gas and 0.6% chlorine gas. The residual second tail gas is then passed through an absorption device containing a saturated aqueous hydrochloric acid solution for a secondary heating absorption treatment, thereby obtaining a third tail gas, wherein the impurity components of the third tail gas are composed of less than 0.07% sulfur dioxide gas and 0.12% chlorine gas.

[0105] Finally, the third tail gas obtained above is passed into a condenser for cooling and separation to obtain a remaining third tail gas, wherein the mass fraction of water in the remaining third tail gas is 4.67%. The remaining third tail gas is then passed into concentrated sulfuric acid to absorb the remaining water. The gas discharged after absorption is high-purity hydrogen chloride gas, specifically, the purity is 99.42%, and the recovery rate is 97.75%.

[0106] Example 11

[0107] Example 11 differs from Example 6 only in that the obtained second tail gas is passed through an absorption device containing a saturated aqueous hydrochloric acid solution for a primary heating absorption treatment at a temperature of 60° C., thereby obtaining a remaining second tail gas, wherein the impurity components of the remaining second tail gas consist of 0.55% sulfur dioxide gas and 0.95% chlorine gas. The remaining second tail gas is then passed through an absorption device containing a saturated aqueous hydrochloric acid solution for a secondary heating absorption treatment at a temperature of 60° C., thereby obtaining a third tail gas, wherein the impurity components of the third tail gas consist of less than 0.06% sulfur dioxide gas and 0.09% chlorine gas.

[0108] Finally, the third tail gas obtained above is passed into a condenser for cooling and separation to obtain a remaining third tail gas, wherein the mass fraction of water in the remaining third tail gas is 3.01%. The remaining third tail gas is then passed into concentrated sulfuric acid to absorb the remaining water. The gas discharged after absorption is high-purity hydrogen chloride gas, specifically, the purity is 99.25%, and the recovery rate is 97.91%.

[0109] Example 12

[0110] The only difference between Example 12 and Example 11 is that the remaining second tail gas is passed into an absorption device containing a saturated hydrochloric acid aqueous solution for secondary heating absorption treatment, wherein the temperature is 70°C to obtain a third tail gas, and the impurity components in the third tail gas are composed of less than 0.03% sulfur dioxide gas and 0.08% chlorine gas.

[0111] Finally, the third tail gas obtained above is passed into a condenser for cooling and separation to obtain the remaining four-three tail gas, and the mass fraction of water in the remaining third tail gas is 3.66%. Then, the remaining third tail gas is passed into concentrated sulfuric acid to absorb the remaining water. The gas discharged after absorption is high-purity hydrogen chloride gas, specifically, the purity is 99.34%, and the recovery rate is 98.33%.

[0112] Example 13

[0113] The only difference between Example 13 and Example 11 is that the remaining second tail gas is passed into an absorption device containing a saturated hydrochloric acid aqueous solution for secondary heating absorption treatment. In the secondary heating absorption treatment, the temperature is 80°C to obtain a third tail gas, and the impurity component in the third tail gas is composed of 0.05% chlorine.

[0114] Finally, the third tail gas obtained above is passed into a condenser for cooling and separation to obtain a remaining third tail gas, wherein the mass fraction of water in the remaining third tail gas is 4.07%. The remaining third tail gas is then passed into concentrated sulfuric acid to absorb the remaining water. The gas discharged after absorption is high-purity hydrogen chloride gas, specifically, the purity is 99.53%, and the recovery rate is 98.59%.

[0115] Example 14

[0116] The only difference between Example 14 and Example 11 is that the remaining second tail gas is passed into an absorption device containing a saturated hydrochloric acid aqueous solution for secondary heating absorption treatment. In the secondary heating absorption treatment, the temperature is 90°C to obtain a third tail gas, and the impurity component in the third tail gas is composed of 0.01% chlorine.

[0117] Finally, the third tail gas obtained above was passed into a condenser for cooling and separation, wherein the condensation temperature was 5° C., to obtain a remaining third tail gas, wherein the mass fraction of water in the remaining third tail gas was 5.34%. The remaining third tail gas was then passed into concentrated sulfuric acid to absorb the remaining water. The gas discharged after the absorption was high-purity hydrogen chloride gas, specifically, with a purity of 99.61% and a recovery rate of 98.70%.

[0118] Example 15

[0119] Example 15 is different from Example 14 only in that the obtained third tail gas is passed into a condenser for cooling and separation, wherein the condensation temperature is 3°C to obtain a remaining third tail gas, and the mass fraction of water in the remaining third tail gas is 4.24%. Then, the remaining third tail gas is passed into concentrated sulfuric acid to absorb the remaining water. The gas discharged after absorption is high-purity hydrogen chloride gas, specifically, the purity is 99.77%, and the recovery rate is 96.51%.

[0120] Example 16

[0121] Example 16 is different from Example 14 only in that the obtained third tail gas is passed into a condenser for cooling and separation, wherein the condensation temperature is 1°C to obtain a remaining third tail gas, and the mass fraction of water in the remaining third tail gas is 3.56%. Then, the remaining third tail gas is passed into concentrated sulfuric acid to absorb the remaining water. The gas discharged after absorption is high-purity hydrogen chloride gas, specifically, the purity is 99.92%, and the recovery rate is 95.24%.

[0122] Example 17

[0123] Example 17 is compared with Example 1, except that the chlorinated tail gas and chlorine are introduced together into an acyl chloride synthesis device containing a catalyst to carry out an acyl chloride synthesis reaction, wherein the catalyst is activated carbon, the flow rates of chlorine and chlorinated tail gas are 151 mL / min and 300 mL / min, respectively (i.e., the flow ratio of chlorinated tail gas to chlorine is 1.99:1), the temperature is 10°C, and a first tail gas consisting of 90.56% hydrogen chloride gas, 1.17% sulfur dioxide gas, 2.47% chlorine and 5.80% sulfuryl chloride is obtained.

[0124] The first tail gas obtained above is passed into a sulfuryl chloride decomposition reactor containing a catalyst, wherein the catalyst is activated carbon and the temperature is 100° C. to obtain a second tail gas composed of 90.56% hydrogen chloride gas, 3.30% sulfur dioxide gas, 4.60% chlorine gas and 1.54% sulfuryl chloride.

[0125] The second tail gas obtained above is passed through an absorption device containing a saturated hydrochloric acid aqueous solution for a primary heating absorption treatment, wherein the mass fraction of hydrochloric acid in the saturated hydrochloric acid aqueous solution is 37% and the temperature is 50° C., thereby obtaining a remaining second tail gas, wherein the impurity components in the remaining second tail gas consist of 0.47% of sulfur dioxide gas and 0.94% of chlorine gas. Then, the remaining second tail gas is passed through an absorption device containing a saturated hydrochloric acid aqueous solution for a secondary heating absorption treatment, wherein the mass fraction of hydrochloric acid in the saturated hydrochloric acid aqueous solution is 37% and the temperature is 50° C., thereby obtaining a third tail gas, wherein the impurity components in the third tail gas consist of less than 0.10% of sulfur dioxide gas and 0.13% of chlorine gas.

[0126] Finally, the third tail gas obtained above was passed into a condenser for cooling and separation, wherein the condensation temperature was 5° C., to obtain a remaining third tail gas, wherein the mass fraction of water in the remaining third tail gas was 2.14%. The remaining third tail gas was then passed into concentrated sulfuric acid to absorb the remaining water. The gas discharged after the absorption was high-purity hydrogen chloride gas, specifically, with a purity of 99.56% and a recovery rate of 96.87%.

[0127] Example 18

[0128] Example 18 is compared with Example 1, except that the chlorinated tail gas and chlorine are introduced together into an acyl chloride synthesis device containing a catalyst to carry out an acyl chloride synthesis reaction, wherein the catalyst is activated carbon, the flow rates of chlorine and chlorinated tail gas are 167 mL / min and 300 mL / min, respectively (i.e., the flow ratio of chlorinated tail gas to chlorine is 1.80:1), the temperature is 20°C, and a first tail gas consisting of 85.47% hydrogen chloride gas, 0.95% sulfur dioxide gas, 8.69% chlorine and 4.89% sulfuryl chloride is obtained.

[0129] The first tail gas obtained above is passed into a sulfuryl chloride decomposition reactor containing a catalyst, wherein the catalyst is activated carbon and the temperature is 100° C. to obtain the first tail gas composed of 85.47% hydrogen chloride gas, 2.58% sulfur dioxide gas, 10.32% chlorine gas and 1.63% sulfuryl chloride.

[0130] The second tail gas obtained above is passed through an absorption device containing a saturated hydrochloric acid aqueous solution for a primary heating absorption treatment, wherein the mass fraction of hydrochloric acid in the saturated hydrochloric acid aqueous solution is 37% and the temperature is 50° C., thereby obtaining a remaining second tail gas, wherein the impurity components in the remaining second tail gas are composed of 0.79% sulfur dioxide gas and 2.33% chlorine gas. Then, the remaining second tail gas is passed through an absorption device containing a saturated hydrochloric acid aqueous solution for a secondary heating absorption treatment, wherein the mass fraction of hydrochloric acid in the saturated hydrochloric acid aqueous solution is 37% and the temperature is 50° C., thereby obtaining a third tail gas, wherein the impurity components in the third tail gas are composed of less than 0.06% sulfur dioxide gas and 0.23% chlorine gas.

[0131] Finally, the third tail gas obtained above was passed into a condenser for cooling and separation, wherein the condensation temperature was 5° C., to obtain a remaining third tail gas, wherein the mass fraction of water in the remaining third tail gas was 2.46%. The remaining third tail gas was then passed into concentrated sulfuric acid to absorb the remaining water. The gas discharged after the absorption was high-purity hydrogen chloride gas, specifically, with a purity of 99.34% and a recovery rate of 97.21%.

[0132] Comparative Example 1

[0133] Comparative Example 1 is compared with Example 1, difference is only, there is not the first tail gas being passed into and carry out sulfuryl chloride decomposition reactor containing catalyzer in sulfuryl chloride decomposition this step, that is, directly the first tail gas is passed into and carries out one-level heating absorption process in the absorption unit containing saturated hydrochloric acid aqueous solution, in carrying out one-level heating absorption process, the massfraction of hydrochloric acid in the saturated hydrochloric acid aqueous solution is 37%, and temperature is 50 ℃, obtain the second tail gas, and in the second tail gas, foreign matter component is made up of 0.44% sulfur dioxide gas, 0.78% chlorine and 3.43% sulfuryl chloride.Then, the second tail gas is passed into and carries out secondary heating absorption process in the absorption unit containing saturated hydrochloric acid aqueous solution, in secondary heating absorption process, the massfraction of hydrochloric acid in the saturated hydrochloric acid aqueous solution is 37%, and temperature is 50 ℃, obtain the 3rd tail gas, and in the 3rd tail gas, foreign matter component is made up of 0.09% sulfur dioxide gas below, 0.13% chlorine and 1.87% sulfuryl chloride.

[0134] Finally, the third tail gas obtained above was passed into a condenser for cooling and separation, wherein the condensation temperature was 5° C., to obtain a remaining third tail gas, wherein the mass fraction of water in the remaining third tail gas was 2.30%. The remaining third tail gas was then passed into concentrated sulfuric acid to absorb the remaining water. The gas discharged after the absorption was hydrogen chloride gas. Specifically, the impurity components in the hydrogen chloride gas were mainly composed of 1.36% sulfuryl chloride and a small amount of sulfur dioxide and chlorine. The recovery rate of the hydrogen chloride was 96.52%, and the purity was 98.38%.

[0135] Comparative Example 2

[0136] Comparative Example 2 Compared with Example 1, there is no step of passing the second tail gas into an absorption device containing a saturated aqueous hydrochloric acid solution for heating and absorbing the treatment. That is, the obtained second tail gas is directly passed into a condenser for cooling and separation, wherein the condensation temperature is 5 ° C., and the mass fraction of water in the remaining second tail gas after the condensation treatment is 2.15%. Then, the remaining second tail gas after the condensation treatment is passed into concentrated sulfuric acid to absorb the remaining water. The gas discharged after absorption is hydrogen chloride gas. Specifically, the impurity components in the hydrogen chloride gas are mainly composed of 3.14% of sulfur dioxide gas, 4.34% of chlorine and 1.21% of sulfuryl chloride. At the same time, the recovery rate of the hydrogen chloride is 96.68% and the purity is 91.30%.

[0137] Comparative Example 3

[0138] Comparative Example 3 Compared with Example 1, in the step of heating and absorbing the second tail gas using a saturated hydrochloric acid aqueous solution, there is no heat treatment, that is, the second tail gas obtained above is passed into an absorption device containing a saturated hydrochloric acid aqueous solution for a first-level absorption treatment, in which the mass fraction of hydrochloric acid in the saturated hydrochloric acid aqueous solution is 37%, and the temperature is 25°C, to obtain a remaining second tail gas, and the impurity components in the remaining second tail gas are 1.56% of sulfur dioxide gas and 2.46% of chlorine. Then, the remaining second tail gas is passed into an absorption device containing a saturated hydrochloric acid aqueous solution for a second-level absorption treatment, in which the mass fraction of hydrochloric acid in the saturated hydrochloric acid aqueous solution is 37%, and the temperature is 25°C, to obtain a third tail gas, and the impurity components in the third tail gas are 0.78% of sulfur dioxide gas and 1.22% of chlorine.

[0139] Finally, the obtained third tail gas is passed into a condenser for cooling and separation, wherein the condensation temperature is 5° C., to obtain a remaining third tail gas, wherein the mass fraction of water in the remaining third tail gas is 2.63%. The remaining third tail gas is then passed into concentrated sulfuric acid to absorb the remaining water. The gas discharged after the absorption is hydrogen chloride gas. Specifically, the impurity components in the hydrogen chloride gas are mainly composed of 0.77% sulfur dioxide gas, 1.21% chlorine gas, and 0.11% sulfuryl chloride. The recovery rate of the hydrogen chloride is 96.70%, and the purity is 97.85%.

[0140] Comparative Example 4

[0141] Comparative Example 4 differs from Example 1 only in that an aqueous solution is used instead of a saturated hydrochloric acid aqueous solution. Specifically, the obtained second tail gas is passed through an absorption device containing an aqueous solution to perform a primary absorption and heating treatment. The primary absorption and heating treatment is performed at a temperature of 50° C., yielding a remaining second tail gas whose impurity components consist of 0.52% sulfur dioxide gas and 0.96% chlorine gas. Subsequently, the remaining second tail gas is passed through an absorption device containing an aqueous solution to perform a secondary heating and absorption treatment. The secondary heating and absorption treatment is performed at a temperature of 50° C., yielding a third tail gas whose impurity components consist of less than 0.09% sulfur dioxide gas and 0.15% chlorine gas.

[0142] Finally, the third tail gas obtained above was passed into a condenser for cooling and separation, wherein the condensation temperature was 5° C., and the mass fraction of water in the remaining third tail gas was 2.89%. The remaining third tail gas was then passed into concentrated sulfuric acid to absorb the remaining water. The gas discharged after absorption was hydrogen chloride gas. Specifically, the impurity components in the hydrogen chloride gas were mainly composed of trace amounts of sulfur dioxide and chlorine. At the same time, the recovery rate of the hydrogen chloride was 87.26%, and the purity was 99.56%.

[0143] The hydrogen chloride gas prepared in Example 1, Example 6, Example 11, Example 14, and Comparative Examples 1-4, as well as purchased hydrogen chloride gas (with a purity of 99.5%), was used as raw materials for the preparation of trimethyl orthoformate. The specific steps were as follows: the hydrogen chloride gas obtained above was dissolved in methanol, and then hydrocyanic acid was added and stirred at 10° C. to form a salt. The temperature was then raised to 30° C. and an excess of methanol was added dropwise to carry out an alcoholysis reaction to obtain the corresponding trimethyl orthoformate. The corresponding hydrogen chloride conversion rate and the corresponding trimethyl orthoformate yield were calculated. The specific calculation results are shown in Table 1.

[0144] Table 1

[0145]

[0146] As can be seen from the data in Table 1, the hydrogen chloride gas prepared by the method for treating chlorinated tail gas of the present invention has a purity of ≥99%, so that it can be used as a raw material for the synthesis of downstream products, such as the synthesis of trimethyl orthoformate, thereby improving the recycling value of hydrogen chloride.

[0147] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0148] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A method for treating chlorinated tail gas, characterized in that: include: Providing chlorinated tail gas, wherein the chlorinated tail gas includes sulfur dioxide gas and hydrogen chloride gas; The chlorinated tail gas and chlorine are subjected to an acyl chloride synthesis reaction under the action of a catalyst to obtain sulfuryl chloride and a first tail gas; Decomposing the first tail gas with sulfuryl chloride under the action of a catalyst to obtain a second tail gas; using a saturated hydrochloric acid aqueous solution to heat and absorb the second tail gas to obtain a third tail gas; The third tail gas is dried to obtain hydrogen chloride gas.

2. The method for treating chlorinated tail gas according to claim 1, wherein: In the step of subjecting the chlorinated tail gas and chlorine to an acyl chloride synthesis reaction under the action of a catalyst, the flow ratio of the chlorinated tail gas to the chlorine is 1.80:1-1.99:

1.

3. The method for treating chlorinated tail gas according to claim 1, wherein: In the step of reacting the chlorinated tail gas and chlorine under the action of a catalyst, the catalyst is selected from activated carbon and the temperature is 10° C.-20° C.; And / or, in the step of subjecting the first tail gas to a sulfuryl chloride decomposition reaction under the action of a catalyst, the catalyst is selected from activated carbon, and the temperature is 90° C.-180° C.

4. The method for treating chlorinated tail gas according to claim 1, wherein: In the step of using saturated hydrochloric acid aqueous solution to heat and absorb the second tail gas, at least two stages of heating and absorption treatment are performed.

5. The method for treating chlorinated tail gas according to claim 4, wherein: In the step of heating and absorbing the second tail gas with saturated hydrochloric acid aqueous solution, two-stage heating and absorption treatment is performed, and the temperature of the first-stage heating and absorption treatment is 50℃-90℃, and the temperature of the second-stage heating and absorption treatment is 50℃-90℃.

6. The method for treating chlorinated tail gas according to claim 1, wherein: In the step of drying the third tail gas, concentrated sulfuric acid is used for absorption treatment.

7. The method for treating chlorinated tail gas according to claim 6, wherein: Before the step of using concentrated sulfuric acid for absorption treatment, the third tail gas is first condensed.

8. The method for treating chlorinated tail gas according to claim 7, wherein: The temperature of the condensation treatment is 1°C-5°C.

9. The method for treating chlorinated tail gas according to any one of claims 1 to 8, characterized in that: The chlorinated tail gas is a reaction tail gas generated by a chlorination reaction using sulfuryl chloride as a chlorinating agent.

10. The method for treating chlorinated tail gas according to claim 9, wherein: The chlorinated tail gas is a reaction tail gas generated by the chlorination reaction of 3,5-dimethylphenol and sulfuryl chloride; And / or, the sulfuryl chloride obtained by reacting the chlorinated tail gas with chlorine in the presence of a catalyst is recycled for use in the chlorination reaction.

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