A method for removing hydrogen sulfide from a sucralose tail gas

Abstract

The application discloses a method for removing hydrogen sulfide in trichlorogalactose tail gas, and belongs to the technical field of tail gas treatment. The method is characterized by adopting a composite adsorbent to adsorb hydrogen sulfide gas in trichlorogalactose tail gas, so that the trichlorogalactose tail gas reaches the emission standard. N,N-dimethylethanolamine in the composite adsorbent has specificity for hydrogen sulfide. After the adsorption of hydrogen sulfide, the N,N-dimethylethanolamine is replaced by sodium hydroxide to generate sodium sulfide, and the N,N-dimethylethanolamine is supplemented. The sodium sulfide can be oxidized by oxygen in the air to generate sodium sulfate. The application solves the function of traditional adsorbents, i.e., only adsorption without conversion or only conversion without adsorption, ensures that the S element is converted into a stable state after adsorption, avoids secondary pollution, significantly reduces the content of hydrogen sulfide in the tail gas treated by the composite adsorbent, and generates less by-products. Therefore, the method is a relatively ideal green process for treating hydrogen sulfide tail gas.

Description

Technical Field

[0001] This invention belongs to the field of exhaust gas treatment technology, specifically relating to a method for removing hydrogen sulfide from sucralose exhaust gas. Background Technology

[0002] Sucralose (TGS), a novel sweetener jointly developed by Tate & Lyle and University College London and patented in 1976, is the only functional sweetener made from sucrose. Originally branded as Splenda, it is up to 600 times sweeter than sucrose. This sweetener is characterized by being calorie-free, highly sweet, pure in taste, and extremely safe, making it one of the best functional sweeteners available today.

[0003] The synthesis process of sucralose can be divided into three main steps: acylation, chlorination, and deacylation. The chlorination process generates tail gases such as sulfur dioxide, hydrogen chloride, trichloroethane, and hydrogen sulfide. Hydrogen sulfide is a highly toxic gas with a rotten egg smell and strong irritant properties. Exposure to certain concentrations of hydrogen sulfide can lead to poisoning, causing numerous health problems. Inhaling large amounts of hydrogen sulfide in a short period can damage the central nervous system. Furthermore, hydrogen sulfide corrodes pipes and equipment, leading to catalyst poisoning. Removing low concentrations of hydrogen sulfide from industrial tail gases is beneficial to human health and safe production. However, conventional ambient temperature desulfurization methods mostly rely on acid-base reactions to remove hydrogen sulfide. Since both carbon dioxide and hydrogen sulfide are acidic gases, the inhibitory effect of carbon dioxide during the desulfurization process cannot be avoided, resulting in poor desulfurization selectivity.

[0004] Industrially used ambient temperature desulfurization methods are mainly divided into two categories: adsorption and absorption. Adsorption methods primarily utilize molecular sieves and activated carbon to adsorb hydrogen sulfide, overcoming the low precision of absorption methods and being one of the common fine desulfurization technologies. Among these, activated carbon adsorbents are widely used due to their low cost and ease of regeneration. For example, Chinese patent application 202110555695.X discloses a solid amine adsorbent for removing trace amounts of hydrogen sulfide and its preparation method. The method is characterized by using oxidized activated carbon as a carrier, and tert-butylaminopropyltrimethoxysilane and a tertiary amine as active components. The carrier is oxidized and modified through oxidant treatment and plasma treatment. Then, tert-butylaminopropyltrimethoxysilane is immobilized on the oxidized activated carbon using a grafting method. Finally, the tertiary amine is loaded onto the immobilized activated carbon to prepare the adsorbent. The solid amine adsorbent described in this invention has advantages such as high hydrogen sulfide adsorption capacity and strong selectivity. However, the processing capacity of solid adsorbents is relatively small, which limits their application in industrial settings. Absorption methods mainly utilize alcohol amine solutions to absorb hydrogen sulfide into the liquid phase. For example, Chinese patent application 200810151911.9 discloses an extractant and removal method for removing sulfides from C9 fuel oil. The extractant includes a single-component solvent, a two-component mixed solvent, or a three-component mixed solvent of N,N-dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, triethylene glycol, diethylene glycol, acetonitrile, methanol, ethanol, or water. The mass percentage of each component is as follows: Group 1: 70-100%, Group 2: 0-30%, Group 3: 0-20%. The process involves preparing C9 fuel oil and an extractant at a mass ratio of 2:1 to 1:2, extracting at 20-70℃ for 10-60 minutes, followed by a constant-temperature settling time of 20-40 minutes. After extraction, the C9 fuel oil phase is washed with water to remove the solvent, yielding desulfurized fuel oil. The extractant used achieves a balance between C9 fuel oil yield and desulfurization rate, reaching up to 58%. While absorption methods offer larger processing capacities, their desulfurization precision is low, resulting in a high hydrogen sulfide content in the treated gas and potential equipment corrosion. Therefore, developing an effective and convenient process for treating hydrogen sulfide tail gas generated during the chlorination stage of sucralose synthesis is crucial. Summary of the Invention

[0005] Based on the shortcomings of existing technologies, this application aims to provide a method for removing hydrogen sulfide from sucralose tail gas. This composite adsorption solvent can achieve the harmless treatment of hydrogen sulfide tail gas generated in the chlorination process during sucralose synthesis, and has the characteristics of low cost, significant effect, green and pollution-free.

[0006] To achieve the above objectives, this application adopts the following technical solution:

[0007] On the one hand, this application provides a method for removing hydrogen sulfide from sucralose tail gas, namely, using a composite adsorbent to adsorb hydrogen sulfide gas in sucralose tail gas so that it meets emission standards.

[0008] The composite adsorption solvent is a mixed solvent of N,N-dimethylethanolamine, sodium hydroxide, p-hydroxybenzoic acid, polydimethylsiloxane, 1-phenyl-3-methyl-5-pyrazolone and water;

[0009] In some preferred embodiments, the mass content of each component in the composite adsorption solvent is as follows: N,N-dimethylethanolamine 69-79%, sodium hydroxide 3-8%, p-hydroxybenzoic acid 0.1-1%, polydimethylsiloxane 0.05-0.1%, 1-phenyl-3-methyl-5-pyrazolone 0.5-1%, and water 10-25%.

[0010] Preferably, the mass content of each component in the composite adsorption solvent is as follows: N,N-dimethylethanolamine 70-78%, sodium hydroxide 4-7%, p-hydroxybenzoic acid 0.2-0.8%, polydimethylsiloxane 0.06-0.09%, 1-phenyl-3-methyl-5-pyrazolone 0.6-0.9%, and water 13-24%.

[0011] This application uses a mixed solvent of N,N-dimethylethanolamine and sodium hydroxide as a composite adsorption solvent for removing hydrogen sulfide. On one hand, N,N-dimethylethanolamine can accurately capture hydrogen sulfide; on the other hand, sodium hydroxide can displace the hydrogen sulfide to generate sodium sulfide and water, and also replenish the N,N-dimethylethanolamine. Furthermore, oxygen in the exhaust gas will further oxidize the sodium sulfide to generate sodium sulfate. Sodium sulfate, also known as Glauber's salt, has certain industrial value.

[0012] On the other hand, this application also provides a method for preparing a composite adsorption solvent, specifically: mixing N,N-dimethylethanolamine, sodium hydroxide, water, p-hydroxybenzoic acid, polydimethylsiloxane, and 1-phenyl-3-methyl-5-pyrazolone in the amounts specified in the formulation to obtain the composite adsorption solvent.

[0013] N,N-Dimethylethanolamine is the main adsorbent, used to capture hydrogen sulfide gas in the tail gas of the sucralose chlorination process; sodium hydroxide is a functional conversion agent, used to convert the hydrogen sulfide captured by N,N-dimethylethanolamine into sodium sulfide, thereby improving the adsorption capacity of the composite adsorbent and facilitating the conversion of hydrogen sulfide into sodium sulfate; water, as a good solvent for sodium hydroxide, is mainly used to dissolve sodium hydroxide and sodium sulfide; p-hydroxybenzoic acid is an antioxidant, mainly used to prevent the oxidation of organic matter and increase the cycle number of the composite adsorbent; polydimethylsiloxane is an antifoaming agent to prevent the formation of mist entrainment during the use of the adsorbent; 1-phenyl-3-methyl-5-pyrazolone is a corrosion inhibitor, mainly used to prevent corrosion of metal equipment and extend the service life of the equipment.

[0014] Furthermore, this application also provides the application of the aforementioned composite adsorption solvent in removing hydrogen sulfide from the tail gas generated in the chlorination process section during the synthesis of sucralose.

[0015] The exhaust gas is a mixture of carbon monoxide, carbon dioxide, nitrogen, oxygen, and hydrogen sulfide.

[0016] The mixed gas contains the following components in the following proportions: carbon monoxide 5-20%, carbon dioxide 10-30%, nitrogen 50-60%, oxygen 10-15%, and hydrogen sulfide 0.1-0.5%.

[0017] The exhaust gas must contain oxygen to further oxidize sodium sulfide into sodium sulfate.

[0018] The composite adsorption solvent adsorbs hydrogen sulfide at a temperature of 0-60℃. When the temperature exceeds 60℃, the hydrogen sulfide adsorbed by N,N-dimethylethanolamine will be released, thus affecting the adsorption effect.

[0019] The regeneration of the composite adsorbent involves introducing air into it after it becomes saturated, allowing the oxygen in the air to continue oxidizing sodium sulfide to produce sodium sulfate, until the sulfide ion content is less than 10 ppm. Then, moisture is removed by vacuum evaporation. At this point, sodium sulfate precipitates because it is insoluble in N,N-dimethylethanolamine solvent. This is separated by pressure filtration to obtain solid sodium sulfate and mother liquor. Adding a certain mass of liquid alkali to the mother liquor prepares the composite adsorbent for hydrogen sulfide tail gas treatment.

[0020] This invention uses a mixed solvent of N,N-dimethylethanolamine and sodium hydroxide as the adsorption solvent to adsorb hydrogen sulfide in the exhaust gas. It has good adsorption effect, is green and pollution-free, and can convert hydrogen sulfide into sodium sulfate, thereby realizing certain industrial value. It is a relatively ideal hydrogen sulfide exhaust gas treatment process.

[0021] Compared with the prior art, the beneficial effects of this application are as follows:

[0022] 1. This invention solves the current problem of difficult H2S treatment and can achieve H2S emission standards in exhaust gas;

[0023] 2. This invention develops a composite adsorption solvent for N,N-dimethylethanolamine and NaOH, which has a triple function of capture, conversion and oxidation.

[0024] 3. This invention solves the problem of traditional adsorbents only adsorbing without converting or only converting without adsorbing, ensuring that the S element is converted into a stable state after adsorption and avoiding secondary pollution.

[0025] 4. This invention ensures stable SO2 production;

[0026] 5. This invention solves the problems of high post-processing difficulty and high processing cost. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail. Specific examples herein are merely illustrative and do not limit the scope of the invention.

[0028] The present invention will be further described in detail below with reference to specific embodiments.

[0029] Basic Implementation

[0030] A conventional adsorption tower is used. The composite adsorption solvent is introduced into the scrubbing tower through the side inlet. The exhaust gas passes through the composite adsorption solvent from the bottom of the scrubbing tower and is then discharged from the top, thus absorbing hydrogen sulfide in the exhaust gas and meeting emission standards. After the adsorbent is saturated, a large amount of air is introduced, and the oxygen in the air oxidizes the sodium sulfide into sodium sulfate. The specific operation is as follows:

[0031] The composite adsorption solvent is placed in a scrubbing tower to allow the exhaust gas to be fully adsorbed until the solvent becomes saturated. The saturated solvent is then removed and oxidized by air, followed by evaporation, crystallization, filtration, and drying of the filter cake to obtain sodium sulfate. The mother liquor is replenished with sodium hydroxide solution and can then be reused as a composite adsorption solvent.

[0032] Example 1: A method for removing hydrogen sulfide from sucralose tail gas

[0033] The composite adsorption solvent is 69% N,N-dimethylethanolamine, 8% sodium hydroxide, 21.45% water, 1% p-hydroxybenzoic acid, 0.05% polydimethylsiloxane, and 0.5% 1-phenyl-3-methyl-5-pyrazolone.

[0034] The exhaust gas contained 9.5% carbon monoxide, 30% carbon dioxide, 50% nitrogen, 10% oxygen, and 0.5% hydrogen sulfide. The reaction temperature was 0°C. After the reaction, the concentration of hydrogen sulfide in the exhaust gas was 10 ppm.

[0035] Example 2: A method for removing hydrogen sulfide from sucralose tail gas

[0036] The composite adsorption solvent consists of 79% N,N-dimethylethanolamine, 3% sodium hydroxide, 17.7% water, 0.1% p-hydroxybenzoic acid, 0.1% polydimethylsiloxane, and 0.1% 1-phenyl-3-methyl-5-pyrazolone.

[0037] The exhaust gas contained 10% carbon monoxide, 14.9% carbon dioxide, 60% nitrogen, 15% oxygen, and 0.1% hydrogen sulfide. The reaction temperature was 60℃. After the reaction, the concentration of hydrogen sulfide in the exhaust gas was 25 ppm.

[0038] Example 3: A method for removing hydrogen sulfide from sucralose tail gas

[0039] The composite adsorption solvent consists of 70% N,N-dimethylethanolamine, 5% sodium hydroxide, 23.73% water, 0.5% p-hydroxybenzoic acid, 0.07% polydimethylsiloxane, and 0.7% 1-phenyl-3-methyl-5-pyrazolone.

[0040] The exhaust gas contained 11.7% carbon monoxide, 20% carbon dioxide, 55% nitrogen, 13% oxygen, and 0.3% hydrogen sulfide. The reaction temperature was 30°C. After the reaction, the concentration of hydrogen sulfide in the exhaust gas was 17 ppm.

[0041] Example 4: A method for removing hydrogen sulfide from sucralose tail gas

[0042] The composite adsorption solvent consists of 73% N,N-dimethylethanolamine, 4% sodium hydroxide, 21.84% water, 0.2% p-hydroxybenzoic acid, 0.06% polydimethylsiloxane, and 0.9% 1-phenyl-3-methyl-5-pyrazolone.

[0043] The exhaust gas contained 5% carbon monoxide, 22.6% carbon dioxide, 58% nitrogen, 14% oxygen, and 0.4% hydrogen sulfide. The reaction temperature was 20°C. After the reaction, the concentration of hydrogen sulfide in the exhaust gas was 28 ppm.

[0044] Example 5: A method for removing hydrogen sulfide from sucralose tail gas

[0045] The composite adsorption solvent consists of 78% N,N-dimethylethanolamine, 7% sodium hydroxide, 13.71% water, 0.6% p-hydroxybenzoic acid, 0.09% polydimethylsiloxane, and 0.6% 1-phenyl-3-methyl-5-pyrazolone.

[0046] The exhaust gas contained 14.8% carbon monoxide, 17% carbon dioxide, 56% nitrogen, 12% oxygen, and 0.2% hydrogen sulfide. The reaction temperature was 5°C. After the reaction, the concentration of hydrogen sulfide in the exhaust gas was 25 ppm.

[0047] Example 6: A method for removing hydrogen sulfide from sucralose tail gas

[0048] The composite adsorption solvent consists of 77% N,N-dimethylethanolamine, 6% sodium hydroxide, 15.33% water, 0.8% p-hydroxybenzoic acid, 0.07% polydimethylsiloxane, and 0.8% 1-phenyl-3-methyl-5-pyrazolone.

[0049] The exhaust gas contained 13.8% carbon monoxide, 14% carbon dioxide, 57% nitrogen, 15% oxygen, and 0.2% hydrogen sulfide. The reaction temperature was 55℃. After the reaction, the concentration of hydrogen sulfide in the exhaust gas was 21 ppm.

[0050] Experimental example: Based on the formulation of Example 1, a stability test was conducted, in which the exhaust gas velocity was 100m. 3 The rate of operation was 1 t of composite adsorbent per hour. Specific operational results are shown in Table 1.

[0051] Table 1. Hydrogen sulfide content in exhaust gas

[0052] 1 2 10 2 4 13 3 6 18 4 8 25 5 10 44 6 12 60 7 14 80 8 16 101 9 18 120 10 20 162

[0053] As shown in the table, the formulated adsorbent can achieve compliant operation for 18 days (the emission standard stipulates that the hydrogen sulfide content in the exhaust gas is ≤120PPM).

[0054] Comparative Example 1

[0055] Referring to the example, the formulation was 77% N,N-dimethylethanolamine and 23% water. Stability tests were conducted, with the exhaust gas velocity at 100 m / s². 3 The rate of operation was 1 t of composite adsorbent per hour. Specific operational results are shown in Table 2.

[0056] Table 2 Hydrogen sulfide content in exhaust gas

[0057] 1 2 15 2 4 19 3 6 28 4 8 40 5 10 57 6 12 75 7 14 99 8 16 127 9 18 152 10 20 198

[0058] As shown in Table 2, the adsorption of N,N-dimethylethanolamine aqueous solution alone can only maintain the target adsorption for 15 days, which is slightly lower than the formulation of this invention.

[0059] The above description is only a partial embodiment of the present invention and does not limit the implementation and protection scope of the present invention. Any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the protection scope of the present invention.

Claims

1. A method for removing hydrogen sulfide from sucralose tail gas, characterized in that: A composite adsorption solvent is used to adsorb hydrogen sulfide gas from sucralose tail gas. The composite adsorption solvent contains the following components by mass: N,N-dimethylethanolamine 69-79%, sodium hydroxide 3-8%, p-hydroxybenzoic acid 0.1-1%, polydimethylsiloxane 0.05-0.1%, 1-phenyl-3-methyl-5-pyrazolone 0.5-1%, and water 10-25%, with the sum of the mass contents of the above six components being 100%. The regeneration method of the composite adsorption solvent is as follows: air is introduced into the adsorbent at room temperature and pressure to convert sodium sulfide into sodium sulfate; then, the water is removed by evaporation and concentration, and sodium sulfate is precipitated and separated by centrifugation; then, NaOH aqueous solution is added, and the adsorbent can be reused.

2. The removal method according to claim 1, characterized in that: The mass content of each component in the composite adsorption solvent is as follows: N,N-dimethylethanolamine 70-78%, sodium hydroxide 4-7%, p-hydroxybenzoic acid 0.2-0.8%, polydimethylsiloxane 0.06-0.09%, 1-phenyl-3-methyl-5-pyrazolone 0.6-0.9%, and water 13-24%, and the sum of the mass contents of the above six components is 100%.

3. The removal method according to claim 1, characterized in that: The composite adsorption solvent is prepared by mixing N,N-dimethylethanolamine, sodium hydroxide, water, p-hydroxybenzoic acid, polydimethylsiloxane, and 1-phenyl-3-methyl-5-pyrazolone to obtain the composite adsorption solvent.

4. The removal method according to claim 1, characterized in that: The hydrogen sulfide mentioned is the hydrogen sulfide produced in the tail gas of the chlorination process during the synthesis of sucralose.

5. The removal method according to claim 4, characterized in that: The exhaust gas is a mixture of carbon monoxide, carbon dioxide, nitrogen, oxygen, and hydrogen sulfide.

6. The removal method according to claim 5, characterized in that: The mass content of each component in the mixed gas is as follows: carbon monoxide 5-20%, carbon dioxide 10-15%, nitrogen 50-60%, oxygen 10-15%, and hydrogen sulfide 0.1-0.5%, and the sum of the mass contents of the above five components is 100%.

7. The removal method according to claim 1, characterized in that: The temperature at which the composite adsorption solvent removes hydrogen sulfide is 0-60℃.

8. The removal method according to claim 1, characterized in that: Sodium sulfide is converted into sodium sulfate until the sulfide ion content is less than 10 ppm.