Method for separating so2 and hcl mixed acid gas and application of the method

Abstract

The application provides a method for separating SO2 and HCl mixed acid gas, which has the advantages of simple process flow, simple operation, few investment equipment, low cost, few types of raw materials, and the like, the absorption liquid can be reused, the complete separation and reuse of sulfur dioxide and hydrogen chloride gas can be realized, and the environmental protection pressure is effectively reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of efficient separation and utilization of mixed acid gas, C01B7 / 00, and in particular to a method for separating SO2 and HCl mixed acid gas and application of the method. BACKGROUND

[0002] In the chemical industry, chlorination and sulfonation are commonly used reactions, such as sulfoxide chlorination, chloroformic acid chlorination, etc. The tail gas contains a large amount of hydrogen chloride and sulfur dioxide. At present, the absorption of these tail gases in industry is generally carried out by using multi-stage water absorption hydrochloric acid, which is then sold to other enterprises as a neutralizing agent or acidifying agent, thereby generating a large amount of wastewater and waste salt. Moreover, the solubility of sulfur dioxide in water leads to the fact that the method cannot completely separate sulfur dioxide and hydrogen chloride in the tail gas, so that at least about 4% of sulfur dioxide remains in the hydrochloric acid by-product, which causes damage to the health of the workers and the environment and limits the application of the hydrochloric acid by-product. Therefore, it is of great practical significance to completely separate sulfur dioxide and hydrogen chloride in the mixed acid gas and utilize them.

[0003] Chinese patent CN 102343197A discloses a method for separating and recovering hydrogen chloride and sulfur dioxide mixed gas, which separates the two by using the difference in solubility through a one-stage falling film absorption, a two-stage packing absorption, a sulfur dioxide packing absorption and a tail gas treatment process. However, this method has many devices and a complex absorption process, and the separation of sulfur dioxide and hydrogen chloride is not complete. Chinese patent CN 103908870A discloses a method for treating acyl chloride reaction tail gas, in which the reaction tail gas enters a three-stage series hydrogen chloride absorption tower and a two-stage series ammonia water absorption tower in sequence. Chloroaniline and hydrochloric acid are used as raw materials to generate diazonium salt. Ammonium sulfite is used as a reducing agent to reduce the diazonium salt to recover hydrochloric acid, and the acidification and hydrolysis are used to prepare p-chlorophenylhydrazine hydrochloride. This method is complicated, cannot completely separate sulfur dioxide and hydrogen chloride, cannot completely recover hydrogen chloride, introduces many other raw materials or additives in the process, has high cost and is not environmentally friendly.

[0004] Therefore, a method for completely separating and utilizing sulfur dioxide and hydrogen chloride in mixed acid gas with simple process and low cost needs to be designed. SUMMARY

[0005] To solve the above technical problems, the present application first provides a method for separating SO2 and HCl mixed acid gas, which comprises:

[0006] a step of completely absorbing hydrogen chloride in the mixed acid gas to generate a hydrochloride solution;

[0007] a step of completely absorbing the discharged sulfur dioxide to generate a sodium sulfite by-product;

[0008] The step of treating the hydrochloride solution, completely removing the residual sulfur dioxide to obtain a hydrochloride suspension;

[0009] The step of pyrolyzing or replacement reaction of the hydrochloride suspension, releasing and absorbing hydrogen chloride to obtain 30wt% hydrochloric acid by-product.

[0010] In the present application, hydrogen chloride is first absorbed specifically, so that hydrogen chloride in the mixed acid gas is completely absorbed, then the discharged sulfur dioxide is absorbed to generate sodium sulfite by-product, realizing the preliminary separation of hydrogen chloride and sulfur dioxide; in addition, a small amount of sulfur dioxide existing in the hydrogen chloride absorption product is further distilled out, realizing the complete separation of sulfur dioxide and hydrogen chloride; then the hydrogen chloride absorption product is treated by pyrolysis or replacement reaction, completely releasing hydrogen chloride and obtaining 30wt% hydrochloric acid by-product; the method of the present application has simple process flow, simple operation, less equipment investment, and can realize the complete separation and reuse of sulfur dioxide and hydrogen chloride gas, effectively reducing the environmental pressure.

[0011] Further, the method is specifically:

[0012] (1) passing the mixed acid gas into the HCl primary absorption kettle and the HCl secondary absorption kettle, completely absorbing HCl in two stages to obtain hydrochloride solutions in the primary absorption kettle and the secondary absorption kettle;

[0013] (2) passing the gas discharged in (1) into the SO2 primary absorption kettle and the SO2 secondary absorption kettle, completely absorbing SO2 in the mixed acid gas in two stages, then cooling, filtering and drying the absorption kettle product to obtain sodium sulfite by-product;

[0014] (3) warming the hydrochloride solution in (1) to reflux, releasing residual sulfur dioxide and treating it by the recovery process of step (2), then treating the remaining hydrochloride suspension by any one of steps (4) or (5);

[0015] (4) continuing to warm to decompose the hydrochloride in the hydrochloride suspension, releasing hydrogen chloride and absorbing it by the HCl tertiary absorption tower to obtain 30wt% hydrochloric acid by-product;

[0016] (5) reacting the hydrochloride suspension with acyl chloride to produce amide product and double hydrogen chloride, and absorbing the hydrogen chloride by the HCl tertiary absorption tower to obtain 30wt% hydrochloric acid by-product.

[0017] Further, the HCl primary absorption kettle and the HCl secondary absorption kettle are configured with organic amine absorption liquid.

[0018] Further, the structure of the organic amine is:

[0019] Structure formula I: R1-[N(R2)] n -R3;

[0020] or

[0021] Structure Formula II: R1-[N(R2) m ] y any one of the following.

[0022] In the structure formula I and II, R1 is any one of phenyl or substituted phenyl, heterocyclic group or its derivative, alkyl or substituted alkyl, alkoxy, alkylcarbonyl, R2 is C1-C10 alkyl or H, R3 is any one of H, phenyl or substituted phenyl, alkyl or substituted alkyl, alkylcarbonyl, n≤3, m≤2, y≤20, n, m and y are all positive integers.

[0023] Further, R1 is any one of phenyl or substituted phenyl, C3-C18 heterocyclic group or its derivative, C1-C20 alkyl or substituted alkyl, C1-C15 alkoxy.

[0024] Preferably, R1 is at least one of phenyl or substituted phenyl, C3-C18 heterocyclic group or its derivative, C1-C20 alkyl or substituted alkyl.

[0025] Further, R3 is at least one of H, phenyl or substituted phenyl, C1-C10 alkyl or C1-C10 substituted alkyl.

[0026] Preferably, for the molecular formula I, R2 and R3 are at least one of H.

[0027] Preferably, for the molecular formula II, R2 is H.

[0028] In a preferred embodiment, the structure of the organic amine is structure formula I, wherein R1 is C1-C20 alkyl, and R2 and R3 are both H.

[0029] In an embodiment, the structure of the organic amine is structure formula I, wherein R1 and R3 are both C1-C18 alkyl, and R2 is H.

[0030] In an embodiment, the structure of the organic amine is structure formula II, wherein R1 is phenyl, R2 is H, m=2, and y=1.

[0031] In an embodiment, the structure of the organic amine is structure formula II, wherein R1 is C1-C20 alkyl, R2 is H, m=2, and y=1-5.

[0032] Further, the substituents in the substituted phenyl or substituted alkyl include, but are not limited to, at least one of hydroxyl, carbonyl, ether bond, ester group, sulfhydryl, -Cl, -F, -Br, -I.

[0033] Further, the organic amine accounts for 5-70% and the solvent accounts for 30-95% in the absorption solution of the organic amine by total mass.

[0034] Further, the organic amine accounts for 16-35% and the solvent accounts for 65-84% in the absorption solution of the organic amine by total mass.

[0035] Further, the solvent is a non-water solvent selected from at least one of benzene, toluene, xylene, chlorobenzene, mesitylene, dichloromethane, trichloromethane and carbon tetrachloride.

[0036] Further, the temperature of the organic amine absorption solution in the HCl primary absorption kettle and the HCl secondary absorption kettle is 25-105℃, preferably 98-104℃.

[0037] The application uses the alkaline absorption of the organic amine to absorb hydrogen chloride in the mixed acid gas, and then pyrolyzes the product to release hydrogen chloride, so as to realize the separation of hydrogen chloride and sulfur dioxide; when the concentration of the organic amine is 16-35% and the absorption temperature is 98-104℃, the absorption rate of the organic amine to hydrogen chloride reaches the highest, and all the hydrogen chloride in the mixed acid gas can be fixed when passing through the HCl primary absorption tower, so that the use of the HCl secondary absorption tower can be omitted. However, in order to avoid the problem that the concentration of the organic amine in the HCl primary absorption tower decreases too much after long time use, and the hydrogen chloride cannot be completely absorbed, the application sets the HCl secondary absorption tower to supplement the absorption of the hydrogen chloride which is not completely absorbed in the HCl primary absorption tower. When the concentration of the organic amine and the absorption temperature are low, the absorption is incomplete; when the concentration is too high, the process cost is increased; and when the absorption reaction temperature is too high, the decomposition temperature of part of the organic amine hydrochloride can be reached, so that part of the hydrogen chloride is released and enters the next procedure with the sulfur dioxide, resulting in the appearance of sodium chloride salt in the sodium sulfite by-product, and the complete separation of the mixed acid gas cannot be realized, so it is necessary to control the concentration of the organic amine and the reaction temperature.

[0038] Further, in step (1), the passing speed or flow of the mixed acid gas is 1-1000 L / min; preferably 5-500 L / min; more preferably 10-100 L / min.

[0039] After the treatment in step (1), a small part of the sulfur dioxide in the mixed acid gas is dissolved into the organic amine absorption solution in the HCl primary absorption kettle and the HCl secondary absorption kettle, all the hydrogen chloride gas in the acid gas is completely absorbed by the absorption kettle, and only the sulfur dioxide gas is included in the gas flowing out of the absorption kettle, and this part of the sulfur dioxide is treated to obtain the sulfite by-product after being absorbed by the two-stage absorption tower.

[0040] Further, the residual amount of SO2 in the hydrochloride solution in step (1) accounts for 0.08-5.0% of the total mass of the hydrochloride solution; preferably 0.08-0.1%.

[0041] Further, in step (2), the SO2 primary absorption tank and the SO2 secondary absorption tank are equipped with alkali liquor; the alkali liquor is sodium hydroxide solution, wherein the concentration of sodium hydroxide is 8-16wt%, preferably 12.5-14.5wt%.

[0042] Further, the temperature of the alkali liquor in the SO2 primary absorption tank and the SO2 secondary absorption tank is 50-70℃, preferably 50-55℃.

[0043] When the next batch of mixed acid gas is subjected to SO2 absorption treatment, the SO2 primary absorption tank in step (2) can be replaced with new alkali liquor or switched with the SO2 secondary absorption tank.

[0044] Further, in step (3), the temperature of the reflux is 40-170℃, preferably 110-150℃.

[0045] Further, in step (4), the temperature is raised to evaporate part of the solvent in the organic amine suspension, and as the temperature rises, the system temperature rises to the decomposition temperature of the organic amine hydrochloride, so that hydrogen chloride is released. After the release, the residual organic amine can be subjected to the absorption of the next batch of mixed acid gas; further, the temperature is raised to 100-180℃, preferably 150-180℃.

[0046] In an embodiment, the organic amine is C1-C10 alkyl tertiary amine or C1-C10 alkyl primary amine, and the temperature in step (4) is raised to 150-170℃. In the process of absorbing hydrogen chloride by the organic amine, part of the sulfur dioxide is also fixed and absorbed by the organic amine through conjugation and electrostatic attraction, so the treatment method of the organic amine hydrochloride is to first heat to release the small amount of sulfur dioxide fixed, and then perform subsequent treatment. For the treatment process of recovering hydrogen chloride released after heating and pyrolyzing the organic amine hydrochloride, a suitable organic amine needs to be selected to form a layered interval between the release temperature of sulfur dioxide and the pyrolysis temperature of the organic amine hydrochloride, so as to avoid mixing of hydrogen chloride in the released gas. In addition, the pyrolysis temperature of the organic amine hydrochloride is different when the structure of the organic amine hydrochloride is different. If this treatment method is adopted, it is necessary to ensure that the organic amine hydrochloride can be fully pyrolyzed, and to reduce the process energy consumption. It is found that when the organic amine is C1-C10 alkyl tertiary amine or C1-C10 alkyl primary amine, the pyrolysis temperature of the prepared organic amine hydrochloride is in the range of 150-170℃, which not only forms an effective temperature layered interval, but also balances the pyrolysis time, low energy consumption and complete pyrolysis. When the temperature is too high, not only the energy consumption increases, but also the reaction risk increases. When the temperature is too low, the pyrolysis rate cannot meet the requirements.

[0047] Further, the C1-C10 alkyl tertiary amine includes, but is not limited to, at least one of tri-n-octylamine, tri-isooctylamine, tri-n-pentylamine, tri-n-decylamine, octyl dimethyl tertiary amine, decyl dimethyl tertiary amine.

[0048] Further, the C1-C10 alkyl primary amine includes, but is not limited to, at least one of ethylamine, ethylenediamine, pentylamine, pentanediamine, hexylamine, hexanediamine, octylamine, decylamine, decanediamine.

[0049] Further, the acyl chloride in step (5) is not strictly regulated in the present application, and can be selected and adjusted according to the requirements of the amide product.

[0050] Further, the method of the present application is used for the separation and recovery of SO2 and HCl mixed acid gas discharged by a pesticide factory.

[0051] Further, the mixed acid gas discharged by the pesticide factory is tail gas discharged by thionyl chloride acylation and xanthic acid chloride chlorination reaction.

[0052] Advantages

[0053] The present application first absorbs hydrogen chloride specifically, so that the hydrogen chloride in the mixed acid gas is completely absorbed, and then the discharged sulfur dioxide is absorbed to generate sodium sulfite as a by-product, thereby realizing the preliminary separation of hydrogen chloride and sulfur dioxide; in addition, a small amount of sulfur dioxide existing in the hydrogen chloride absorption product is distilled out, thereby realizing the complete separation of sulfur dioxide and hydrogen chloride; then the hydrogen chloride absorption product is treated by pyrolysis or replacement reaction, so that the hydrogen chloride is completely released and 30wt% hydrochloric acid by-product is obtained; the process flow is simple and easy to operate, the investment equipment is less, the types of raw materials used are less, the cost is low, the absorption liquid used can be reused, and the method can realize the complete separation and reuse of sulfur dioxide and hydrogen chloride gas, thereby effectively reducing the environmental pressure. DETAILED DESCRIPTION

[0054] EMBODIMENT

[0055] EMBODIMENT 1

[0056] The present embodiment provides a method for separating SO2 and HCl mixed acid gas:

[0057] (1) A mixed solution of hexanediamine and dichloromethane is prepared at 25°C and is added to the HCl primary absorption kettle and the HCl secondary absorption kettle; the mixed acid gas is introduced into the HCl primary absorption kettle and the HCl secondary absorption kettle at a flow rate of 25L / min, and the HCl is completely absorbed in two stages to obtain a hexanediamine hydrochloride solution in the primary absorption kettle and the secondary absorption kettle;

[0058] The mass concentration of hexanediamine in the mixed solution is 26%, and the temperature of the mixed solution in the primary absorption kettle and the secondary absorption kettle is 100°C;

[0059] (2) configuring an aqueous solution of sodium hydroxide (i.e. lye) at 30°C and adding it into the SO2 primary absorption kettle and the SO2 secondary absorption kettle; passing the gas discharged from the HCl secondary absorption kettle into the SO2 primary absorption kettle and the SO2 secondary absorption kettle, completely absorbing SO2 in the mixed acid gas in two stages, and then cooling, filtering and drying the product of the absorption kettle to obtain sodium sulfite by-product 1; wherein the concentration of sodium hydroxide in the lye is 13wt%, the temperature of the lye in the SO2 primary absorption kettle and the SO2 secondary absorption kettle is 55°C, the filtering temperature is 2°C, and the drying temperature is 115°C;

[0060] (3) heating the hydrochloride salt solution in (1) to 120°C to release the residual sulfur dioxide therein, and passing the released sulfur dioxide into step (2) for absorption and recovery treatment to obtain sodium sulfite by-product 2;

[0061] (4) after the release of sulfur dioxide, continuing to heat the residual hydrochloride salt suspension to 160°C to decompose the hydrochloride salt therein, release hydrogen chloride, and absorb the hydrogen chloride by the HCl tertiary absorption tower as a 30wt% hydrochloric acid by-product.

[0062] Example 2

[0063] The present embodiment provides a method for separating SO2 and HCl mixed acid gas:

[0064] (1)-(3) are the same as in Example 1,

[0065] (4) after the release of sulfur dioxide, the residual hydrochloride salt suspension is reacted with acyl chloride as a production raw material to produce amide product and double chlorine, and the chlorine is absorbed by the HCl tertiary absorption tower as a 30wt% hydrochloric acid by-product;

[0066] Example 3

[0067] The present embodiment provides a method for separating SO2 and HCl mixed acid gas:

[0068] (1) configuring a mixed solution of aniline and carbon tetrachloride at 30°C and adding it into the HCl primary absorption kettle and the HCl secondary absorption kettle; passing the mixed acid gas into the HCl primary absorption kettle and the HCl secondary absorption kettle at a flow rate of 15L / min, completely absorbing HCl in two stages, and obtaining aniline hydrochloride salt solution in the primary absorption kettle and the secondary absorption kettle;

[0069] wherein the mass concentration of aniline in the mixed solution is 35%, and the temperature of the mixed solution in the primary absorption kettle and the secondary absorption kettle is 98°C;

[0070] (2) configuring an aqueous solution of sodium hydroxide (i.e. lye) at 45°C and adding it into the SO2 primary absorption tower and the SO2 secondary absorption tower; passing the gas discharged from the HCl secondary absorption tower into the SO2 primary absorption tower and the SO2 secondary absorption tower, completely absorbing SO2 in the mixed acid gas in two stages, and then cooling, filtering and drying the absorption tower product to obtain sodium sulfite by-product 1; wherein the concentration of sodium hydroxide in the lye is 12.5wt%, the temperature of the lye in the SO2 primary absorption tower and the SO2 secondary absorption tower is 70°C, the filtering temperature is 0°C, and the drying temperature is 110°C;

[0071] (3) heating the hydrochloride salt solution in (1) to 150°C to release the residual sulfur dioxide therein, and passing the released sulfur dioxide into step (2) for absorption and recovery treatment to obtain sodium sulfite by-product 2;

[0072] (4) after the release of sulfur dioxide, continuing to heat the residual hydrochloride salt suspension to 170°C to decompose the hydrochloride salt therein, release hydrogen chloride, and absorb the hydrogen chloride by the HCl tertiary absorption tower as a 30wt% hydrochloric acid by-product.

[0073] Example 4

[0074] The present embodiment provides a method for separating SO2 and HCl mixed acid gas:

[0075] (1) configuring a mixed solution of decylamine and carbon tetrachloride at 25°C and adding it into the HCl primary absorption tower and the HCl secondary absorption tower; passing the mixed acid gas into the HCl primary absorption tower and the HCl secondary absorption tower at a flow rate of 18L / min, completely absorbing HCl in two stages, and obtaining a decylamine hydrochloride salt solution in the primary absorption tower and the secondary absorption tower;

[0076] wherein the mass concentration of decylamine in the mixed solution is 16%, and the temperature of the mixed solution in the primary absorption tower and the secondary absorption tower is 104°C;

[0077] (2) configuring an aqueous solution of sodium hydroxide (i.e. lye) at 25°C and adding it into the SO2 primary absorption tower and the SO2 secondary absorption tower; passing the gas discharged from the HCl secondary absorption tower into the SO2 primary absorption tower and the SO2 secondary absorption tower, completely absorbing SO2 in the mixed acid gas in two stages, and then cooling, filtering and drying the absorption tower product to obtain sodium sulfite by-product 1; wherein the concentration of sodium hydroxide in the lye is 14.5wt%, the temperature of the lye in the SO2 primary absorption tower and the SO2 secondary absorption tower is 50°C, the filtering temperature is 5°C, and the drying temperature is 120°C;

[0078] (3) The hydrochloride solution in (1) is heated to 110°C to warm reflow, to release the residual sulfur dioxide therein, and the released sulfur dioxide is passed into step (2) for absorption and recovery treatment to obtain sodium sulfite by-product 2;

[0079] (4) After the release of sulfur dioxide, the remaining hydrochloride suspension in the reaction is continuously warmed to 150°C to decompose the hydrochloride therein, release hydrogen chloride, and absorb it into the HCl tertiary absorption tower as a 30wt% hydrochloric acid by-product.

[0080] Comparative Example 1

[0081] Basically the same as Example 1, except that the hexanediamine is replaced by trioctylamine.

[0082] Comparative Example 2

[0083] Basically the same as Example 1, except that the hexanediamine is replaced by octadecylamine.

[0084] Comparative Example 3

[0085] Basically the same as Example 1, except that the temperature of the mixed solution in the primary absorption kettle and the secondary absorption kettle in step (1) is 85°C.

[0086] Comparative Example 4

[0087] Basically the same as Example 1, except that the mass concentration of hexanediamine in the mixed solution in step (1) is 10%.

[0088] Comparative Example 5

[0089] Basically the same as Example 1, except that the dichloromethane in the mixed solution in step (1) is replaced by isopropyl alcohol.

[0090] Performance test method:

[0091] 1. The residual content of chloride ions in the sodium sulfite by-product (sodium sulfite by-product 1 + sodium sulfite by-product 2) is tested by the method of titrating sulfurous acid with sodium thiosulfate, in terms of mass percentage of sodium sulfite by-product;

[0092] 2. The residual content of sulfurous acid in the 30wt% hydrochloric acid by-product is tested by the method of titrating chloride ions with silver nitrate, in terms of mass percentage of 30wt% hydrochloric acid by-product.

[0093] Performance test results:

[0094] The test results are shown in Table 1.

[0095] Table 1

[0096]

[0097]

Claims

1. A method for separating a mixture of SO2 and HCl acid gases, characterized in that, The method is specifically as follows: (1) The mixed acid gas is passed into the HCl primary absorption vessel and the HCl secondary absorption vessel to completely absorb the HCl in both stages, and the hydrochloric acid solution in the primary absorption vessel and the secondary absorption vessel is obtained. (2) The gas discharged in (1) is passed into the SO2 primary absorption vessel and the SO2 secondary absorption vessel. After the SO2 in the mixed acid gas is completely absorbed in both stages, the product in the absorption vessel is cooled, filtered and dried to obtain sodium sulfite by-product. (3) Heat the hydrochloric acid solution in (1) and reflux it to release the residual sulfur dioxide and perform the recovery treatment in step (2). Then, perform any one of the treatments in step (4) or step (5) on the remaining hydrochloric acid suspension. (4) Continue to heat up to decompose the hydrochloric acid in the hydrochloric acid suspension, release hydrogen chloride and absorb it through the HCl three-stage absorption tower to produce 30wt% hydrochloric acid by-product. (5) The hydrochloric acid suspension is reacted with acyl chloride to produce an amide product and double hydrogen chloride. The hydrogen chloride is absorbed by the HCl three-stage absorption tower as a 30wt% hydrochloric acid byproduct. The HCl primary absorption tank and the HCl secondary absorption tank are equipped with organic amine absorption liquid. In the organic amine absorption liquid, the organic amine accounts for 5-70% and the solvent accounts for 30-95%. The solvent is a non-aqueous solvent and is selected from at least one of benzene, toluene, xylene, chlorobenzene, mesitylene, dichloromethane, trichloromethane, and carbon tetrachloride. The organic amine is a C1-C10 alkyl tertiary amine or a C1-C10 alkyl primary amine. In step (4), the temperature is raised to 150-170℃.

2. The method according to claim 1, characterized in that, The temperature of the organic amine absorption liquid in the HCl primary absorption vessel and the HCl secondary absorption vessel is 25-105℃.

3. The method according to claim 1, characterized in that, The SO2 primary absorption vessel and the SO2 secondary absorption vessel are equipped with alkaline solution; the concentration of the alkaline solution is 8-16 wt%, and the temperature of the alkaline solution is 50-70℃.

4. The method according to claim 1, characterized in that, In step (3), the reflux temperature is 40-170℃.

5. The application of the method according to any one of claims 1-4, characterized in that, The method is used for the separation and recovery of mixed SO2 and HCl acid gas emitted from pesticide plants.

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