Treatment process of aldehyde waste gas in vitamin B6 production

Abstract

The invention aims to provide a treatment process of aldehyde waste gas in vitamin B6 production, and belongs to the technical field of waste gas treatment in pharmaceutical synthesis. Vitamin B6 aldehyde waste gas which is collected in a centralized and sealed manner is subjected to oxidation absorption by adopting a common oxidizing agent by adopting a simple combination of a chemical method and an adsorption method; the aldehyde waste gas is converted into harmless or low-toxicity substances, and the tail gas is treated to be qualified through four procedures of alkali washing, water washing and activated carbon adsorption. And after the treatment facility is put into operation, the concentration of the aldehyde waste gas at the outlet is reduced to be below 10mg / m < 3 >, and the total VOCs removal rate reaches 99% or above. According to the invention, the investment cost of equipment and facilities is greatly saved, the operation cost is reduced, and the operation is more convenient and simpler. And the method has good applicability and economical efficiency.

Description

Technical Field

[0001] This invention belongs to the field of waste gas treatment technology in drug synthesis, specifically relating to a treatment process for aldehyde waste gas in vitamin B6 production. Background Technology

[0002] Aldehydes are a common type of organic pollutant in industrial production, primarily originating from production processes across multiple industries. Aldehydes share several significant common characteristics. These substances typically have an irritating odor, detectable even at low concentrations. Most aldehydes are highly volatile, readily transforming from liquid to gaseous state and entering the atmosphere. The health hazards of these aldehydes manifest in several ways. Short-term exposure to high concentrations of aldehydes can cause eye and respiratory irritation symptoms such as tearing, coughing, and chest tightness. Long-term exposure may lead to chronic respiratory diseases, nervous system damage, and an increased risk of cancer. From an environmental perspective, aldehydes participate in atmospheric photochemical reactions, serving as important precursors to photochemical smog, and also contributing to environmental problems such as acid rain and ozone layer depletion.

[0003] The implementation of laws and regulations such as the Environmental Protection Law of the People's Republic of China, the Air Pollution Prevention and Control Law of the People's Republic of China, and the Technical Policy for the Prevention and Control of Volatile Organic Compounds (VOCs) Pollution has led to increasingly stringent emission standards for volatile organic compounds, and the emission treatment technology for aldehyde waste gas in vitamin B6 production has also improved accordingly.

[0004] For the treatment of aldehyde waste gas, a variety of mature process routes have been developed, which can be divided into three main categories according to different principles: physical methods, chemical methods, and biological methods.

[0005] Absorption is a typical physical method, utilizing the water solubility of aldehydes to purify waste gas using water or a specific absorbent. It involves simple equipment and low investment, but its effectiveness is limited for insoluble aldehydes. Adsorption uses activated carbon, molecular sieves, and other adsorbent materials to capture aldehyde molecules in waste gas. It is suitable for treating low-concentration, high-volume waste gas, but the adsorbent needs regular replacement or regeneration. Furthermore, the pore size distribution and surface chemical properties of activated carbon significantly affect its adsorption efficiency for different types of aldehydes.

[0006] Chemical methods mainly include catalytic combustion and photocatalytic oxidation. Catalytic combustion completely oxidizes aldehydes into CO2 and water under the action of a catalyst, resulting in high purification efficiency and suitability for medium- to high-concentration waste gases, but it consumes a large amount of energy. Photocatalytic oxidation uses ultraviolet light to excite a catalyst to generate highly oxidizing free radicals that decompose aldehyde molecules. The reaction conditions are mild and there is no secondary pollution, but the equipment requires high maintenance. The type of catalyst plays a decisive role in the treatment effect. Noble metal catalysts have low activation temperatures but are expensive, while transition metal oxide catalysts are moderately priced but have poor resistance to toxicity.

[0007] The biological method utilizes the metabolic processes of microorganisms to degrade aldehyde pollutants, making it suitable for treating water-soluble aldehydes. However, its treatment efficiency is significantly affected by environmental conditions. Strict control of humidity, pH, and nutrient concentrations is required during operation to ensure microbial activity, resulting in high management costs and a large footprint.

[0008] In practical engineering applications, combined processes are often adopted based on the characteristics of the waste gas. Common combinations include "pretreatment + adsorption concentration + catalytic combustion", "alkaline scrubbing + biological filter", and "photocatalysis + activated carbon adsorption" to achieve the best treatment effect. When selecting a process, it is necessary to comprehensively consider factors such as waste gas concentration, composition complexity, treatment scale, investment and operating costs.

[0009] Chinese patents have disclosed several methods and devices for treating aldehyde-containing waste gases. Examples include: CN120733504A "A circulating formaldehyde adsorption and regeneration system for plywood gluing"; CN221808456U "A furfural production waste gas treatment device"; CN218741137U "A concentrated formaldehyde waste gas treatment device"; CN114849426A "A novel formaldehyde waste gas treatment system"; CN214764267U "A polyoxymethylene waste gas treatment device"; CN209885549U "A formaldehyde waste gas treatment device"; and CN108870422A "A formaldehyde waste gas treatment system," etc.

[0010] Chinese patents CN219441199U ("A Butyraldehyde Storage Tank Top Tail Gas Treatment System"), CN223213028U ("A Tank Farm Waste Gas Recovery Device"), and CN202355996U ("A Device for Recovering and Treating Isobutyraldehyde Tail Gas from Storage Tanks") all involve pre-treating the collected butyraldehyde tail gas before incinerating it in an RTO incinerator. This method can efficiently treat butyraldehyde tail gas, but the incinerator requires a large investment and occupies a large area.

[0011] In vitamin B6 production, butyraldehyde and isobutyraldehyde are important reactants, and their storage, production, use, and recycling all generate waste gas emissions. Taking butyraldehyde as a raw material for synthesis as an example, aldehyde waste gases in vitamin B6 production originate from the following sources: (1) Seven-ring synthesis position: ; (2) Vitamin B6 hydrolysis site: ; (3) Butyraldehyde recovery post; (4) Butyraldehyde storage position.

[0012] Existing technologies for aldehyde treatment have many drawbacks in treating aldehyde exhaust gases. However, there are few reports of economical and compliant treatment methods for aldehyde waste gases generated during vitamin B6 production. Summary of the Invention

[0013] This invention addresses the problems of high cost, complex processes, and poor efficiency in existing aldehyde waste gas treatment methods by providing a treatment process for aldehyde waste gas generated during vitamin B6 production. From a chemical structure and property perspective, aldehydes have strong reducing properties and are easily oxidized to their corresponding carboxylic acids. While n-butyraldehyde and isobutyraldehyde gases have limited solubility in water, their conversion to n-butyric acid and isobutyric acid allows for greater dissolution in water, thus reducing the emission of gaseous pollutants.

[0014] To achieve the above objectives, the present invention adopts the following technical solution: A process for treating aldehyde waste gas in vitamin B6 production includes the following steps: S1 is used for pipeline collection of volatile aldehyde gases and distilled non-condensable gases generated by reaction vessels, concentration vessels, condensate tanks, vacuum pumps and storage tanks used in the production of vitamin B6. S2, a certain amount of sodium hypochlorite solution or hydrogen peroxide solution is added to the oxidation washing tower in advance; S3, the collected volatile aldehyde gases are collected to the oxidation scrubbing tower by an induced draft fan; the oxidation scrubbing tower circulation pump is turned on to circulate and spray for oxidation reaction; S4, after oxidation, the volatile aldehyde gases are then sequentially fed by an induced draft fan into a primary alkaline scrubbing tower, a secondary water scrubbing tower, and an activated carbon adsorption box before being discharged in compliance with standards.

[0015] Furthermore, the sodium hypochlorite solution in S2 has a mass concentration of 8-15%; the hydrogen peroxide solution has a mass concentration of 27-35%.

[0016] Furthermore, the amount of sodium hypochlorite solution or hydrogen peroxide solution added is 1 mg / L. 3 .

[0017] Furthermore, the temperature at the bottom of the oxidation washing tower is 20-70℃.

[0018] Furthermore, the liquid alkali solution used in the primary alkali washing spray tower described in S3 has a mass concentration of 25-35%.

[0019] Furthermore, an online pH meter is installed at the bottom of the oxidative scrubbing tower. When the pH value is equal to 7, the absorbent in the scrubbing tower is discharged and replaced with fresh sodium hypochlorite solution or hydrogen peroxide solution.

[0020] Furthermore, the activated carbon adsorption box contains standard cube honeycomb activated carbon with an iodine value of 800 and a pore size of 1.5 mm.

[0021] Other gases carrying fugitive emissions, such as butene glycol and hydrochloric acid, collected by the pipeline are also treated through this process; the salt and acidic waste liquids after oxidation and absorption are discharged into the sewage treatment plant for comprehensive treatment.

[0022] The beneficial effects of this invention are as follows: For the centrally collected, sealed vitamin B6 aldehyde waste gas, a simple chemical and adsorption method is combined. Ordinary oxidants are used to oxidize and absorb the aldehydes, converting them into harmless or low-toxicity substances. The waste gas then undergoes four processes: alkaline washing, water washing, and activated carbon adsorption, to ensure the exhaust gas meets standards. After the treatment facility is operational, the concentration of aldehydes at the outlet is reduced to 10 mg / m³. 3 The total VOCs removal rate reaches over 99%. Compared to combined methods such as "pretreatment + adsorption concentration + catalytic combustion," "alkaline washing + biological filter," and "photocatalysis + activated carbon adsorption," this invention significantly reduces equipment and facility investment costs, lowers operating costs, and is more convenient and simpler to operate. It has excellent applicability and economic efficiency. Attached Figure Description

[0023] Figure 1 This is a process flow diagram of the present invention; Wherein: 1-Oxidation scrubbing tower; 2-Circulation pump one; 3-Absorbent storage tank; 4-First-stage alkaline scrubbing spray tower; 5-Circulation pump two; 6-Second-stage water scrubbing spray tower; 7-Circulation pump three; 8-Activated carbon adsorption box; 9-Fan; 10-Emission chimney.

[0024] Figure 2 This is a schematic diagram of the reaction principle of the present invention. Detailed Implementation

[0025] To more fully explain the implementation of the present invention, implementation examples are provided. These implementation examples are merely illustrative of the present invention and do not limit the scope of the present invention.

[0026] The detection methods and implementation standards involved in this invention include the following: GB 16297-1996 Integrated Emission Standard for Air Pollutants; GB 37822-2019 Standard for the Control of Fugitive Emissions of Volatile Organic Compounds; GB 37823-2019 "Emission Standard of Air Pollutants for Pharmaceutical Industry"; HJ 1013-2018 Technical Requirements and Testing Methods for Continuous Monitoring Systems of Non-Methane Total Hydrocarbons in Exhaust Gas from Stationary Sources; HJ 38-2017 Determination of total hydrocarbons, methane and non-methane total hydrocarbons in exhaust gas from stationary sources by gas chromatography.

[0027] Example 1 During vitamin B6 production, aldehyde exhaust gases generated at various work stations are collected through closed pipelines and transported to the oxidation scrubbing tower via an induced draft fan. The oxidation scrubbing tower is pre-filled with 1m³ of gas. 3 A 12% sodium hypochlorite solution was used. Circulation pump one was started for circulating oxidation washing. The temperature at the bottom of the oxidation washing tower was 45℃. The online pH meter readings were recorded every 8 hours. When the pH value was approximately 7, the sodium hypochlorite solution was replaced. After circulating oxidation absorption, the exhaust gas sequentially entered a primary alkaline scrubbing tower (containing a 30% sodium hydroxide solution), a secondary water scrubbing tower, and an activated carbon adsorption box before being discharged at high altitude. The NMHC concentration was measured at 7.96 mg / m³. 3 It complies with GB 37822-2019 "Standard for the Control of Unorganized Emissions of Volatile Organic Compounds".

[0028] Example 2 During vitamin B6 production, aldehyde exhaust gases generated at various work stations are collected through closed pipelines and transported to the oxidation scrubbing tower via an induced draft fan. The oxidation scrubbing tower is pre-filled with 1m³ of gas. 3 A 30% hydrogen peroxide solution was used to circulate the oxidation and washing process using the first circulation pump. The temperature at the bottom of the oxidation and washing tower was 45℃. The online pH meter readings were recorded every 8 hours. When the pH value reached approximately 7, the hydrogen peroxide solution was replaced. After oxidation and absorption, the exhaust gas sequentially entered a primary alkaline scrubbing tower (containing a 30% sodium hydroxide solution), a secondary water scrubbing tower, and an activated carbon adsorption tank before being discharged at high altitude. The NMHC concentration was measured at 6.97 mg / m³. 3 It complies with GB 37822-2019 "Standard for the Control of Unorganized Emissions of Volatile Organic Compounds".

[0029] Table 1. Test results of exhaust gas treatment in Examples 1 and 2 During the monitoring period, the NMHC emission concentration at the main exhaust outlet did not exceed the emission limits of the Unorganized Emission Control Standard for Volatile Organic Compounds (GB 37822-2019) and the special emission limits of air pollutants in the Emission Standard for Air Pollutants from the Pharmaceutical Industry (GB 37823-2019). The highest NMHC emission rate was 0.0176 kg / h. The NMHC removal rates for the two tests were 92.87% and 94.08%, respectively.

[0030] After a detailed description of the embodiments of the present invention, those skilled in the art will clearly understand that various changes and modifications can be made without departing from the scope and spirit of the above-mentioned patent applications. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention shall fall within the scope of the technical solution of the present invention, and the present invention is not limited to the embodiments of the examples given in the specification.

Claims

1. A process for the treatment of aldehyde waste gas in the production of vitamin B6, characterized by: The method comprises the following steps: S1, collecting aldehyde volatile gas and distillation non-condensable gas generated by reaction kettle, concentration kettle, condensate tank, vacuum pump and storage tank used in vitamin B6 production process through pipeline; S2, adding a certain amount of sodium hypochlorite solution or hydrogen peroxide solution into oxidation washing tower in advance; S3, collecting aldehyde volatile gas through air blower and collecting into oxidation washing tower; starting oxidation washing tower circulating pump to circulate and spray for oxidation reaction; S4, after oxidation reaction, aldehyde volatile gas is sequentially introduced into first-stage alkali washing spray tower, second-stage water washing spray tower and activated carbon adsorption box through air blower, and then discharged after reaching standard.

2. The process for treating aldehyde waste gas in the production of vitamin B6 according to claim 1, characterized in that: The mass concentration of sodium hypochlorite solution in S2 is 8-15%; the mass concentration of hydrogen peroxide solution is 27-35%.

3. The process for treatment of aldehyde waste gas in vitamin B6 production according to claim 1, characterized in that: The amount of the sodium hypochlorite solution or the hydrogen peroxide solution added is 1 m 3 .

4. The process for treatment of aldehyde waste gas in production of vitamin B6 according to claim 1, characterized in that: The temperature at the bottom of the oxidation washing tower is 20-70℃.

5. The process as claimed in claim 1, wherein the process for treatment of aldehyde waste gas in production of vitamin B6 is characterized by: The mass concentration of liquid alkali solution used in the first-stage alkali washing spray tower in S3 is 25-35%.

6. The process as claimed in claim 1, wherein the process for treatment of aldehyde waste gas in production of vitamin B6 is characterized by: The bottom of the oxidation washing tower is provided with an on-line pH meter; when the pH value is equal to 7, the absorption liquid in the washing tower is discharged, and fresh sodium hypochlorite solution or hydrogen peroxide solution is replaced.

7. The process as claimed in claim 1, wherein the process for treatment of aldehyde waste gas in production of vitamin B6 is characterized by: The activated carbon adsorption box is provided with standard square honeycomb activated carbon with 800 iodine value and 1.5mm pore size.

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