Adsorption purification method for volatile organic compounds in the production of antibiotics

Abstract

The present invention discloses a method for adsorption and purification of volatile organic compounds in the production of antibiotic drugs, which belongs to the technical field of pharmaceutical and chemical waste gas treatment. The method comprises: (1) passing the waste gas from the production of antibiotics into a pretreatment unit, treating it with an alkaline solution spray tower, and then dehumidifying it by condensation to make the dew point ≤8°C; (2) passing the pretreated waste gas into a three-stage adsorption system at a flow rate of 0.8 to 1.2 m / s to adsorb xylene and sulfide in the waste gas; (3) when the outlet VOCs concentration is ≥30 mg / m 3 If the sulfide concentration at the secondary adsorption inlet is ≥1 ppm for two consecutive measurements, regeneration is initiated: the primary silica gel is regenerated with 110-120°C hot air, the secondary activated carbon is regenerated with 120-130°C nitrogen, and the tertiary molecular sieve is regenerated with 130-150°C superheated steam. The regenerated exhaust gas is returned to the inlet of the alkali spray tower in the pretreatment unit. This invention designs a multi-component VOCs high-efficiency gradient adsorption system that reduces dynamic capacity fluctuations, extends adsorbent life, and achieves a decay rate of less than 5% per cycle, significantly reducing regeneration energy consumption by over 35%.

Description

Technical Field

[0001] The present invention relates to the technical field of pharmaceutical and chemical waste gas treatment, and in particular to a method for adsorbing and purifying volatile organic compounds in the production of antibiotics. Background Art

[0002] During the production process of antibiotic drugs such as penicillin and cephalosporin, waste gas containing characteristic VOCs components (such as chloroform, acetone, methanol, ethanol, ethyl acetate, xylene, etc.) and trace sulfides (such as hydrogen sulfide) produced by fermentation metabolism or sulfur-containing raw materials will be released during the fermentation tank exhaust, extraction and separation process, and solvent (such as butyl acetate, butanol) recovery process. These pollutants not only pose a potential threat to the atmospheric environment and human health, but the direct emission of organic solvents also means a loss of production costs, so efficient treatment technology is needed. Traditional adsorption methods generally use a single activated carbon fixed bed for treatment. This method uses the porous structure of activated carbon to capture VOCs molecules in the waste gas. Although activated carbon has a large specific surface area and a certain adsorption capacity, it has the following shortcomings when treating antibiotic production waste gas with complex components and rich in sulfides:

[0003] Low adsorption efficiency: Activated carbon has low selectivity for VOCs components with significant polarity differences in antibiotic waste gas (such as non-polar chloroform and polar acetone / ethanol). This is due to the uneven affinity of its surface chemical properties for different molecules, resulting in large fluctuations in dynamic adsorption capacity. When treating the actual fluctuating mixed waste gas of antibiotic production, the adsorption efficiency may drop by more than 30%, resulting in unstable performance.

[0004] High regeneration energy consumption: Hot nitrogen desorption requires continuous high temperature to destroy the binding force between the adsorbed molecules and the activated carbon surface. This process involves a large amount of heat energy input, resulting in a high proportion of energy consumption in the treatment cost, usually exceeding 65%, which increases the economic burden of the overall operation;

[0005] Rapid lifespan degradation: Trace sulfides (such as H2S) commonly found in waste gas from antibiotic production can easily react chemically with activated carbon, leading to poisoning of the activated carbon, clogging its pore structure or inactivating its surface active sites. The adsorption efficiency is significantly reduced in a relatively short period of time, typically dropping by more than 50% within three months. Frequent replacement of adsorbents further increases maintenance costs.

[0006] It can be seen that the existing technology has seriously restricted the improvement of the green manufacturing level of the antibiotic industry and the effective recovery of solvents because it has not fully solved the problem of gradient adsorption matching of multi-component VOCs (especially the coexistence of oxygen-containing and non-polar components) in antibiotic production waste gas (that is, the coordination of adsorption rate and capacity of different components) and the problem of anti-poisoning and efficient regeneration of adsorbents for characteristic sulfide poisoning. Summary of the Invention

[0007] In view of the above-mentioned deficiencies of the prior art in treating waste gas from the production of antibiotic drugs, the present invention provides a method for adsorption and purification of volatile organic compounds in the production of antibiotic drugs.

[0008] The technical solution adopted in the present invention is as follows:

[0009] A method for adsorption purification of volatile organic compounds in the production of antibiotic drugs comprises the following steps:

[0010] (1) The waste gas from antibiotic production is passed through a pretreatment unit, treated in an alkali spray tower, and then subjected to condensation and dehumidification to a dew point of ≤8°C;

[0011] (2) The pre-treated exhaust gas is passed into the three-stage adsorption system at a flow rate of 0.8-1.2 m / s:

[0012] The first-stage adsorption uses silica gel adsorbent, controls the temperature at 40-60°C, and utilizes the 2.5-3.5 nm mesoporous structure to accelerate the diffusion of chloroform molecules and achieve the capture of non-polar VOCs.

[0013] The secondary adsorption uses phosphoric acid wood activated carbon, controlled at 30-35°C, to target the adsorption of acetone and ethanol through the directional action of surface hydroxyl hydrogen bonds;

[0014] The third-stage adsorption uses CuO-modified 13X molecular sieve to adsorb xylene and sulfide in the exhaust gas at 50-70°C;

[0015] (3) When the outlet VOCs concentration is ≥30 mg / m3 or the sulfide concentration at the secondary adsorption inlet is ≥1 ppm for two consecutive times, the regeneration operation is started: the silica gel adsorbent is regenerated with 110-120°C hot air, the phosphoric acid method wood activated carbon is regenerated with 120-130°C nitrogen, and the CuO modified 13X molecular sieve is regenerated with 130-150°C superheated steam. The regenerated tail gas is returned to the inlet of the alkali solution spray tower of the pretreatment unit.

[0016] Specifically, in step (1), the circulating spray liquid in the alkali liquid spray tower is initially 10wt% sodium hydroxide solution to neutralize the acidic substances in the waste gas, and the pH of the circulating spray liquid is dynamically adjusted to maintain at 6.5-7.0; the circulating spray liquid flow rate is set at 5%-8% of the waste gas working volume flow rate, and when the pH is <6.5, the circulating spray liquid is replenished, and when the pH is >7.0, part of the circulating spray liquid is discharged. This design ensures the gas-liquid mass transfer efficiency, effectively neutralizes the common weak acidic substances in the waste gas (such as residual fermentation acid), and through the pH-humidity-adsorbent surface chemical properties ternary balance control, prevents the CuO molecular sieve from dissolving Cu due to the acidic environment under normal operating conditions (pH is 6.5-7.0). 2+ (If pH=5.5, the sulfur capacity decay can reach 23%, while after optimization the decay rate is <3%).

[0017] Preferably, the specific surface area of ​​the silica gel adsorbent in step (2) is 550 to 650 m 2 / g, with an average pore size of 2.5-3.5nm. This pore size range (approximately 7.5-10.6 times the molecular dynamics diameter of chloroform, 0.33nm) is particularly conducive to rapid adsorption, and a high temperature environment of 40-60°C can reduce the viscosity of chloroform and accelerate its diffusion into the mesoporous structure.

[0018] Furthermore, the iodine value of the phosphoric acid-activated wood-based activated carbon in step (2) is ≥950 mg / g. The high iodine value and phosphoric acid activation ensure its high saturated adsorption capacity (>350 mg / g) and acid resistance for oxygen-containing VOCs such as acetone, and retain the strength of hydroxyl hydrogen bonds in an environment of 30-35°C, thereby enhancing the targeted adsorption capacity for acetone / ethanol.

[0019] Furthermore, in step (2), the CuO-modified 13X molecular sieve is loaded with 3-5 wt% CuO by an impregnation method, the impregnation solution is a 0.4-0.6 mol / L copper nitrate solution, the impregnation time is 2±0.5 hours, the drying temperature is 100-130°C, the calcination temperature is 400-500°C, and the calcination time is 3-5 hours; the SiO2 / Al2O3 molar ratio of the 13X molecular sieve is 2.3-2.6. The optimized SiO2 / Al2O3 molar ratio and CuO loading enhance the π-complex adsorption of p-xylene and the chemical fixation ability of sulfides, and the melting point of CuO is 1326°C. The crystal phase structure is stable under the conditions of calcination at 400-500°C and regeneration at ≤150°C.

[0020] Furthermore, in step (2), the ratio of the filling volume of the primary adsorption, the secondary adsorption, and the tertiary adsorption is 1:(1.2-1.5):(0.8-1.0). This ratio design fully considers the concentration distribution of typical VOCs components in antibiotic waste gas (usually oxygen-containing VOCs such as acetone / ethanol have a higher concentration) and adsorption kinetics, and when the concentration of polar VOCs (such as acetone, ethanol, ethyl acetate) in the waste gas is greater than 200 mg / m 3 When the secondary activated carbon filling volume is taken as the upper limit of the ratio 1.55.

[0021] Preferably, the oxygen concentration of the regenerated hot air in step (3) is ≤7 vol%. This concentration is much lower than the lower explosion limit of non-polar solvents such as chloroform, ensuring the safety of the first-stage regeneration, and the temperature of 110-120°C matches the van der Waals fracture temperature of the C-Cl bond (avoiding bond dissociation at >200°C).

[0022] Furthermore, in step (3), the dew point of the regenerated nitrogen is ≤-40°C, and the flow rate is 25% to 35% of the waste gas flow rate during the adsorption stage. Ultra-dry nitrogen can effectively prevent oxidation and hydrolysis of the activated carbon during the regeneration process, protect the carboxyl groups on the surface of the activated carbon, and extend its life in treating oxygen-containing solvent waste gas.

[0023] Furthermore, in step (3), the superheated steam pressure is 0.15-0.25 MPa, and the superheat degree is ≥30° C. This ensures efficient desorption of xylene and adsorbed sulfides, and the hydrogen bonds of steam molecules can destroy the π complexation of xylene.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) The present invention designs a gradient adsorption system (silica gel high-temperature adsorption of chloroform; activated carbon targeted adsorption of oxygenated VOCs; CuO modified molecular sieve enhanced adsorption of xylene and chemical sulfur fixation) for the characteristic components of antibiotic waste gas (non-polar chloroform / solvent, oxygenated acetone / ethanol, aromatic hydrocarbon xylene and sulfide). Experiments show that the decay rate of acetone concentration at the outlet of the three-stage adsorption is greater than 95% (in situ infrared C=O bond strength verification), and the penetration time is extended by 180%, that is, a cascade protection is formed: CuO modified molecular sieve preferentially chemically fixes sulfur (Cu-S bonding), avoids sulfide poisoning of the activated carbon hydroxyl sites, maintains the adsorption efficiency of oxygenated VOCs, and further prevents oxygenated VOCs from competitively inhibiting the molecular sieve's adsorption of xylene. Therefore, the present invention solves the problem of reducing the dynamic adsorption capacity fluctuation from >30% to <15% when treating antibiotic waste gas, achieves a significant improvement in adsorption performance, ensures that the outlet concentration is stable and meets the standard, and creates conditions for solvent recovery.

[0026] (2) The present invention adopts a graded regeneration strategy to match the physical and chemical properties of each characteristic component in the antibiotic waste gas: the first-level silica gel uses hot air with an oxygen concentration of ≤8% (110-120°C for safe desorption of chloroform and non-polar solvents, and the desorption energy consumption is reduced to 0.9kWh / kg); the second-level activated carbon uses nitrogen with a dew point of ≤-40°C (120-130°C for anti-oxidation and decomposition of oxygen-containing solvents such as acetone / ethanol, and the desorption energy consumption is only 1.2kWh / kg); the third-level molecular sieve uses 0.15-0.25MPa superheated steam (130-150°C for deep desorption of xylene and sulfide, and the desorption energy consumption is 1.5kWh / kg). Therefore, by adopting the scheme of the present invention, the total regeneration energy consumption is reduced by 35%-45% compared with the single nitrogen regeneration treatment of similar antibiotic waste gas, the heat source utilization rate is increased to 80%-85%, and the use of hot air instead of nitrogen to treat the main non-polar components can reduce the cost of inert gas use.

[0027] (3) In the present invention, the three-stage CuO-modified molecular sieve preferentially chemically adsorbs and fixes the characteristic sulfides in the antibiotic waste gas. Its loading amount is designed based on a sulfide adsorption capacity of ≥120 mg / g, so that the H2S penetration concentration is ≤0.7 ppm (the penetration concentration of the unmodified molecular sieve is 8.2 ppm). At the same time, the skeleton aluminum density is increased by a SiO2 / Al2O3 ratio of 2.3 to 2.6, and the CuO dispersion is enhanced (the acid-resistant sulfur capacity decay is <3% / 72h under pH 6.5 to 7.0). Therefore, the poisoning process of the secondary activated carbon can be greatly delayed (the sulfur capacity decay rate is reduced to 3% / 72h); combined with the enhanced acid resistance of the phosphoric acid wood activated carbon itself, the adsorbent life is extended from 2 months to about 4 months. Under the rated working conditions of antibiotic production, the capacity decay rate is <5% / regeneration cycle, effectively solving the problem of 40% adsorption efficiency decay caused by sulfide poisoning.

[0028] (4) In the present invention, the circulating spray liquid of the alkali spray tower is initially 10wt% NaOH and is dynamically maintained at pH 6.5-7.0, while condensing and dehumidifying (dew point ≤ 8°C, relative humidity of exhaust gas < 25%RH at an operating temperature of 30-35°C). In this control mechanism, pH 6.5-7.0 neutralizes weak acid and prevents Cu 2+ Dissolution (sulfur capacity decays 23% at pH 5.5 → <3% after optimization under normal operating conditions); while a dew point of ≤8°C reduces humidity to <25% RH, eliminating competitive adsorption by water molecules. This reduces adsorption capacity by less than 8.5% under the high-humidity exhaust conditions of antibiotic production, effectively eliminating acidic corrosion and competitive adsorption by water molecules (especially oxygenated VOCs), ensuring the stability of the adsorbent's dynamic capacity when treating complex antibiotic waste gas.

[0029] (5) In the present invention, the silica gel has a specific surface area of ​​550 to 650 m 2 / g, pore size of 2.5~3.5nm maximizes chloroform retention (high temperature of 40~60℃ reduces viscosity and increases diffusion rate by 2.3 times); activated carbon iodine value ≥950mg / g ensures acetone saturation adsorption capacity >350mg / g; CuO modified molecular sieve SiO2 / Al2O3 molar ratio of 2.3~2.6 optimizes xylene (solvent or intermediate) diffusion channel; filling volume ratio 1:(1.2~1.5):(0.8~1.0) matches the concentration ratio and adsorption kinetics of each typical component in antibiotic waste gas.

[0030] (6) The present invention uses low-oxygen hot air (oxygen concentration ≤ 7 vol%, which is lower than the lower explosion limit of non-polar solvents such as chloroform) to prevent combustion and explosion, uses ultra-dry nitrogen to prevent activated carbon from hydrolyzing during the regeneration of oxygen-containing solvents, and uses steam with a superheat of ≥ 30°C to prevent condensation; and after 100% of the regenerated tail gas is returned to the pretreatment, the VOCs concentration in the tail gas is less than 10 mg / m 3, achieving zero VOCs escape and recovery of high-value solvents for antibiotic production, with a recovery rate of over 95%. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of the process of the present invention. DETAILED DESCRIPTION

[0032] The present invention provides a method for adsorption and purification of volatile organic compounds in the production of antibiotic drugs. By designing a three-stage gradient adsorption system to match the physicochemical characteristics of different VOCs components, combined with a graded regeneration strategy and anti-sulfur poisoning modification, the technical problems of low adsorption efficiency of multi-component VOCs in antibiotic waste gas, short adsorbent life due to sulfide poisoning, and high energy consumption of a single regeneration method are solved, thereby achieving efficient purification and solvent recovery.

[0033] like Figure 1 As shown, the implementation of the solution of the present invention includes the following steps:

[0034] Step S10: Waste gas generated during the production of antibiotics (such as penicillin and cephalosporins) containing components such as chloroform, acetone, ethanol, xylene, and sulfides is passed through a pretreatment unit, treated in an alkaline spray tower, and then subjected to condensation and dehumidification to a dew point ≤ 8°C (relative humidity < 25% RH at an operating temperature of 30-35°C). The circulating spray liquid in the alkaline spray tower is initially a 10wt% sodium hydroxide solution, and the pH of the circulating spray liquid is dynamically adjusted to maintain a pH of 6.5-7.0 (to neutralize acidic substances such as organic acids in the waste gas).

[0035] Step S20: Introduce the pretreated exhaust gas into the three-stage adsorption system at a flow rate of 0.8 to 1.2 meters per second:

[0036] The first-stage adsorption uses silica gel adsorbent to adsorb chloroform and non-polar VOCs above C6 (such as alkanes in the solvent) in the exhaust gas at 40 to 60°C;

[0037] The secondary adsorption uses phosphoric acid-processed wood activated carbon to adsorb oxygen-containing volatile organic compounds (VOCs) such as acetone, ethanol, and ethyl acetate in the exhaust gas at a temperature of 30 to 35°C.

[0038] The tertiary adsorption process uses CuO-modified 13X molecular sieves to adsorb xylene (which may be a solvent or intermediate) and sulfides (such as H2S, originating from fermentation or sulfur-containing raw materials) in the exhaust gas at 50 to 70°C. Modification method: 13X molecular sieves are immersed in a 0.4-0.6 mol / L copper nitrate solution at a liquid-to-solid ratio of 3:1, with an oscillation rate of 200-240 rpm for 2 hours. After drying at 100-130°C, the solution is calcined in an air atmosphere at 400-500°C (programmed to increase the temperature to 400-500°C at 5°C / min) for 3-5 hours to obtain a modified molecular sieve with a CuO loading of 3% to 5%.

[0039] Step S30: When the outlet VOCs concentration is ≥30mg / m 3 (Test standard: HJ 734-2014), or when the sulfide concentration at the secondary adsorption inlet is detected ≥1ppm for two consecutive times (test method: gas chromatography, sampling interval 30min), the regeneration operation is started: the primary silica gel adsorbent is regenerated with 110-120℃ hot air; the secondary activated carbon is regenerated with 120-130℃ nitrogen; the tertiary molecular sieve is regenerated with 130-150℃ superheated steam; the regenerated tail gas is returned to the inlet of the alkali solution spray tower of the pretreatment unit for reprocessing and enrichment and recovery of organic solvent.

[0040] According to the present invention, the circulating spray liquid in the alkali spray tower is initially a 10wt% sodium hydroxide solution, with a flow rate set at 5% to 8% of the exhaust gas volume flow rate. Dynamic adjustment maintains the pH between 6.5 and 7.0: 10wt% NaOH solution is added when the pH is <6.5, and a portion of the circulating spray liquid is discharged when the pH is >7.0. This step neutralizes the acidic components while simultaneously eliminating the potential impact of acidic corrosion on the subsequent adsorption system. Condensation dehumidification further removes moisture from the exhaust gas, reducing the possibility of competitive adsorption of water molecules, thereby improving the dynamic capacity stability of the adsorbent.

[0041] In some embodiments, the silica gel adsorbent in step S20 has a specific surface area of ​​550 to 650 square meters per gram and an average pore size of 2.5 to 3.5 nanometers. By optimizing these parameters, the silica gel's adsorption performance for chloroform is significantly improved, enabling efficient retention of chloroform molecules with a kinetic diameter of 0.33 nanometers while effectively reducing competitive adsorption interference from other components.

[0042] In some embodiments, the secondary activated carbon in step S20 is activated using phosphoric acid (the initial mass concentration of the phosphoric acid solution used to impregnate the wood raw material is controlled at 35% to 40%), with an iodine value of no less than 950 mg / g. Phosphoric acid-activated wood carbon exhibits high acid resistance and selectivity, ensuring a saturated adsorption capacity exceeding 350 mg / g for oxygenated VOCs such as acetone. This parameter design, combined with an adsorption temperature controlled between 30 and 35°C, preserves hydroxyl affinity and significantly enhances the selective adsorption capacity for oxygenated VOCs.

[0043] In some embodiments, the SiO2 / Al2O3 molar ratio of the tertiary molecular sieve in step S20 is 2.3 to 2.6. The CuO-modified molecular sieve preferentially chemically adsorbs sulfides, forming Cu-S bonds and preventing sulfide poisoning of the secondary activated carbon. This optimized SiO2 / Al2O3 molar ratio improves the efficiency of the xylene diffusion channel, enhances the π-complexation effect, and further enhances the capture capacity of xylene and sulfides.

[0044] In some embodiments, the ratio of the loading volumes of the primary, secondary, and tertiary adsorption stages in step S20 is 1:(1.2-1.5):(0.8-1.0). This ratio design comprehensively considers the adsorption kinetics of each component, matches the equilibrium points of different VOCs components in each stage of adsorbent, and avoids efficiency loss due to differences in adsorption rates.

[0045] In some embodiments, the oxygen concentration of the regenerated hot air in step S30 does not exceed 7 vol %. This condition prevents the risk of explosion during the regeneration of the primary silica gel at 110 to 120° C. while ensuring safe desorption.

[0046] In some embodiments, the regeneration nitrogen gas in step S30 has a dew point no higher than -40°C and a flow rate of 30% to 40% of the exhaust gas flow rate during the adsorption phase. Ultra-dry nitrogen prevents hydrolysis of the secondary activated carbon during regeneration at temperatures between 120°C and 130°C, while also preventing oxidative decomposition and extending the life of the adsorbent.

[0047] In some embodiments, the superheated steam pressure in step S30 is 0.15-0.25 MPa, and the superheat degree is not less than 30° C. This condition ensures that the regeneration efficiency of the three-stage molecular sieve will not decrease due to condensation during the deep desulfurization process at 130-150° C.

[0048] In some embodiments, the regeneration cycle for each adsorbent stage is 72 to 120 hours, and when the initial pH of the exhaust gas is ≥5.0, the adsorption capacity decay rate after regeneration is less than 5%. This design, combined with a staged regeneration strategy, significantly extends the service life of the adsorbent.

[0049] The present invention is further described below with reference to specific embodiments.

[0050] Example 1

[0051] Step S10: The waste gas generated by the solvent recovery section of simulated penicillin production (typical component: chloroform 200mg / m 3 , acetone 150mg / m 3 , ethanol 50mg / m 3 , xylene 100mg / m 3 、H2S 30mg / m 3 The waste gas is then passed through a pretreatment unit (with a relative humidity of 70% RH) and treated in an alkali spray tower. The circulating spray liquid is initially a 10wt% NaOH solution, with a flow rate set at 6% of the waste gas volume flow rate. The pH is dynamically maintained at 6.8 through real-time liquid replenishment and drainage (to neutralize trace amounts of acidic substances such as acetic acid). Condensation and dehumidification are then performed to reduce the dew point to 7°C (at an operating temperature of 32°C, the relative humidity of the waste gas is approximately 20% RH, significantly reducing the impact of high humidity on the fermentation-derived waste gas).

[0052] Step S20: Introduce the exhaust gas into the three-stage adsorption system at a flow rate of 1.0 m / s:

[0053] The first stage uses a silica gel adsorbent with a specific surface area of ​​600 square meters per gram and an average pore size of 3.0 nanometers to adsorb chloroform and non-polar VOCs above C6 at 50°C (focusing on capturing chloroform and non-polar components in the solvent);

[0054] The second stage uses wood activated carbon with a phosphoric acid activation concentration of 38% (the initial mass concentration of the phosphoric acid solution) and an iodine value of 980 mg / g to adsorb oxygenated VOCs such as acetone and ethanol at 32°C (recovering the commonly used solvents acetone and ethanol);

[0055] The third stage uses 13X molecular sieve with a 4% CuO loading and a SiO2 / Al2O3 molar ratio of 2.5. It adsorbs xylene and sulfides at 60°C (enhancing the adsorption of byproduct xylene and solidifying H2S). The ratio of the adsorbent loading volume of each stage is 1:1.3:0.9; the third stage molecular sieve loading accounts for 28% of the total adsorbent volume. Tested according to GB / T 30202.3-2013, its sulfur capacity for H2S is 128 mg / g.

[0056] Step S30: When the outlet VOCs concentration is ≥30mg / m 3Or when the sulfide concentration at the secondary adsorption inlet is detected to be ≥1ppm for two consecutive times, the regeneration operation is started: the first-stage silica gel is regenerated with 115℃ hot air and an oxygen concentration of 6vol%; the second-stage activated carbon is regenerated with 125℃ nitrogen, with a nitrogen dew point of -45℃ and a flow rate of 32% of the exhaust flow rate; the third-stage molecular sieve is regenerated with 140℃ superheated steam, with a superheated steam pressure of 0.2MPa and a superheat degree of 35℃. The regenerated tail gas is returned to the inlet of the alkali solution spray tower of the pretreatment unit. GC-MS analysis shows that the average VOCs concentration in the regenerated tail gas is 8.5mg / m 3 , VOCs concentration at the outlet of the adsorption system is 26 mg / m 3 The enriched organic solvents (mainly chloroform, acetone, and ethanol) can be recovered by subsequent distillation with a recovery rate of >95%.

[0057] The results of the anti-fluctuation test of this example (simulating penicillin production load fluctuation) are as follows:

[0058] Reference conditions: Chloroform 200 mg / m 3 / Acetone 150mg / m 3 / Xylene 100mg / m 3 ;

[0059] Fluctuating working conditions: Simulating abnormal extraction process, acetone concentration suddenly increased to 225mg / m 3 (+50%);

[0060] The changes in outlet concentration are shown in Table 1 (verification of the filling volume ratio of 1:1.3:0.9):

[0061] Table 1

[0062]

[0063] Conclusion: The concentration increase after the fluctuation was <15%. This indicates that the aforementioned loading volume ratio effectively matches the concentration distribution and adsorption kinetics of the various VOCs components in antibiotic waste gas. Therefore, even with a sudden increase of 50% in the concentration of acetone, a key component in the waste gas, and 67% in H₂S, the outlet VOC concentration only increased slightly, demonstrating that the proposed solution effectively buffers input disturbances and maintains high purification performance.

[0064] Example 2

[0065] Step S10: exhaust the simulated cephalosporin fermentation tank (typical component: chloroform 80mg / m 3 , acetone 120mg / m 3 , methanol 100mg / m 3 、H2S 25mg / m 3, humidity 95% RH) is passed into the pretreatment unit and treated in an alkali spray tower: the circulating spray liquid is initially 10wt% NaOH solution, the flow rate is set at 7% of the exhaust gas volume flow rate, and the pH is maintained at 6.9 through real-time liquid replenishment / discharge; condensation and dehumidification are carried out to a dew point of 8°C (the relative humidity of the exhaust gas is about 22% RH at an operating temperature of 30°C);

[0066] Step S20: The exhaust gas is introduced into a three-stage adsorption system at a flow rate of 0.9 meters per second. The first stage uses a silica gel adsorbent with a specific surface area of ​​580 square meters per gram and an average pore size of 3.2 nanometers to adsorb chloroform and non-polar VOCs above C6 at 45°C. The second stage uses wood activated carbon with a phosphoric acid activation concentration of 36% (the initial mass concentration of the phosphoric acid solution) and an iodine value of 970 milligrams per gram to adsorb oxygenated VOCs such as acetone and ethanol at 30°C. The third stage uses 13X molecular sieve with a CuO loading of 3.5wt% and a SiO2 / Al2O3 molar ratio of 2.4 to adsorb xylene and sulfide at 55°C. The loading volume ratio of each adsorbent is 1:1.4:0.85.

[0067] Step S30: When the outlet VOCs concentration is ≥30mg / m 3 Or, if the sulfide concentration at the secondary adsorption inlet is ≥1ppm for two consecutive measurements, regeneration is initiated: the primary silica gel is regenerated with 118°C hot air and an oxygen concentration of 7 vol%. The secondary activated carbon is regenerated with 128°C nitrogen with a dew point of -42°C and a flow rate of 30% of the exhaust flow rate. The tertiary molecular sieve is regenerated with 135°C superheated steam with a superheated steam pressure of 0.22 MPa and a superheat of 33°C. The regenerated exhaust gas is returned to the pretreatment unit.

[0068] Results: Under high humidity (95%RH), the adsorption capacity of acetone by secondary activated carbon only decreased by 8.5%, H2S at the tertiary outlet was ≤0.5ppm, and the sulfur capacity decay rate of activated carbon was 2.9% / 72h.

[0069] Example 3

[0070] Step S10: antibiotic production waste gas (including solvent recovery tail gas and process exhaust, component: chloroform 150mg / m 3 , ethyl acetate 180mg / m 3 , xylene 80mg / m 3 、H2S 15mg / m 3 The waste gas is then passed through a pretreatment unit and treated using an alkali spray tower. The circulating spray liquid is initially a 10wt% NaOH solution, with a flow rate set at 5% of the waste gas volume flow rate. The pH is maintained at 6.7 through real-time alkali addition and drainage. Condensation dehumidification is then performed to reduce the dew point to 6°C (the relative humidity of the waste gas is approximately 18% RH at an operating temperature of 34°C).

[0071] Step S20: The exhaust gas is introduced into a three-stage adsorption system at a flow rate of 1.1 meters per second. The first stage uses a silica gel adsorbent with a specific surface area of ​​620 square meters per gram and an average pore size of 2.8 nanometers to adsorb chloroform and non-polar VOCs above C6 at 55°C. The second stage uses wood activated carbon with a phosphoric acid activation concentration of 39% (the initial mass concentration of the phosphoric acid solution) and an iodine value of 990 milligrams per gram to adsorb oxygenated VOCs such as acetone and ethanol at 34°C. The third stage uses a 13X molecular sieve with a CuO loading of 4.5 wt% and a SiO2 / Al2O3 molar ratio of 2.55 to adsorb xylene and sulfide at 65°C. The loading volume ratio of each adsorbent is 1:1.2:0.95.

[0072] Step S30: When the outlet VOCs concentration is ≥30mg / m 3 Or, if the sulfide concentration at the secondary adsorption inlet is ≥ 1 ppm for two consecutive measurements, regeneration is initiated: the primary silica gel is regenerated with 112°C hot air and an oxygen concentration of 5 vol%. The secondary activated carbon is regenerated with 122°C nitrogen with a dew point of -48°C and a flow rate of 28% of the exhaust flow. The tertiary molecular sieve is regenerated with 145°C superheated steam with a superheated steam pressure of 0.18 MPa and a superheat of 38°C. The regenerated exhaust gas is returned to the pretreatment unit.

[0073] Results: The saturated adsorption capacity of ethyl acetate reached 362 mg / g, and the CuO crystal phase of the molecular sieve was stable after regeneration.

[0074] Comparative Example 1

[0075] Step S10: Treating the same simulated penicillin waste gas as in Example 1;

[0076] Step S20: The exhaust gas is introduced into a two-stage adsorption system at a flow rate of 1.0 m / s: the first stage uses a silica gel adsorbent with a specific surface area of ​​600 m2 / g and an average pore size of 3.0 nm to adsorb chloroform and non-polar VOCs above C6 at 50°C; the second stage uses activated carbon with an iodine value of 980 mg / g to adsorb oxygenated VOCs such as acetone and ethanol at 30°C; no tertiary adsorption is provided;

[0077] Step S30: When the outlet VOCs concentration is ≥30mg / m 3 If the sulfide concentration at the secondary adsorption inlet is ≥ 1 ppm for two consecutive measurements, regeneration is initiated: the primary silica gel is regenerated with 115°C hot air and an oxygen concentration of 6 vol%. The secondary activated carbon is regenerated with 125°C nitrogen with a dew point of -45°C and a flow rate of 35% of the exhaust flow. The regenerated exhaust gas is returned to the pretreatment unit.

[0078] Comparative Example 2

[0079] Step S10: Treating the same simulated cephalosporin waste gas as in Example 2;

[0080] Step S20: The exhaust gas is introduced into a three-stage adsorption system at a flow rate of 1.0 m / s: the first stage uses a silica gel adsorbent with a specific surface area of ​​600 m2 / g and an average pore size of 3.0 nm to adsorb chloroform and non-polar VOCs above C6 at 50°C; the second stage uses wood activated carbon with a phosphoric acid activation concentration of 38% and an iodine value of 980 mg / g to adsorb oxygenated VOCs such as acetone and ethanol at 30°C; the third stage uses a silica gel adsorbent with a specific surface area of ​​≥550 m 2 / g, SiO2 / Al2O3=2.4 unmodified 13X molecular sieve (specific surface area 580m 2 / g, average pore size 1.0nm), adsorbed xylene and sulfide at 60°C. The loading volume ratio of each adsorbent level was set at 1:1.3:0.9.

[0081] Step S30: Same as Example 2.

[0082] The performance comparison of antibiotic production waste gas treatment is shown in Table 2:

[0083] Table 2

[0084]

[0085] As shown in Table 2, the embodiments of the present invention have significant advantages over the comparative examples in the following aspects:

[0086] (1) Adsorption efficiency: The VOCs concentration at the outlet of the present invention (23-28 mg / m 3 ) is much lower than that of comparative example 1 (45 mg / m 3 , -40%) and Comparative Example 2 (40mg / m 3 , -30%), indicating the efficient synergistic effect of the three-stage gradient adsorption technology of the present invention in capturing multi-component VOCs;

[0087] (2) Energy consumption and economy: Graded renewable energy consumption (0.11~0.13 kWh / m 3 ) The regeneration energy consumption is reduced by 35% to 45% compared with Comparative Example 1, indicating that the hierarchical regeneration strategy (precise matching of hot air / nitrogen / steam) significantly improves energy utilization;

[0088] (3) Enhanced long-term stability: The adsorption capacity decay rate is stable at 4.0% to 4.5% per cycle, which is much lower than that of the comparative example (7.8%, 8.5% per cycle). This indicates that the sulfide preferential adsorption mechanism of the CuO-modified molecular sieve (compared with the unmodified comparative example 2) effectively delays activated carbon poisoning and prolongs the life of the adsorbent.

[0089] (4) Solvent recovery value: VOCs concentration in regenerated tail gas <10mg / m 3 After pretreatment and enrichment, the recovery rate of solvents used in antibiotic production, such as acetone and chloroform, is >94%, significantly reducing production costs.

[0090] In summary, the scheme of the present invention shows better performance in terms of adsorbent service life, regeneration energy consumption, outlet VOCs concentration and adsorption capacity attenuation rate through the three-level precise matching of "component-adsorbent-regeneration".

[0091] In addition, to further highlight the advantages of the solution of the present invention, the following experimental comparisons were conducted, as shown in Tables 3 to 8:

[0092] Table 3: Performance comparison of different desulfurizers (test conditions: simulated penicillin waste gas, chloroform 200mg / m 3 , temperature 60°C, flow rate 1.0m / s)

[0093]

[0094] Table 4: Comparison of penetration time (simulated penicillin waste gas, penetration test conditions: initial chloroform concentration 200 mg / m 3 , flow rate 1.0m / s)

[0095]

[0096] Table 5: Sulfide control effect (cephalosporin waste gas, H2S initial 25mg / m 3 )

[0097]

[0098] Table 6: Energy consumption of solvent desorption (kWh / m 3 , detection conditions: 120℃ nitrogen regeneration)

[0099]

[0100] Table 7: Comparison of adsorption capacity changes and adsorbent life cycle changes when exhaust gas humidity fluctuates to 95% RH

[0101]

[0102] Note: The reduction is based on the adsorption capacity / cycle data of the standard working conditions (pH=6.8, dew point 7°C) in Example 1.

[0103] Table 8: Pretreatment pH fluctuations to 5.5 and 7.5, comparing the changes in adsorption capacity and the changes in adsorbent usage cycle

[0104]

[0105] Note: The reduction is based on the adsorption capacity / cycle data of the standard working conditions (pH=6.8, dew point 7°C) in Example 1.

[0106] According to Table 3, the sulfur capacity decay rate of the traditional desulfurizer (ZnO / Al2O3) in acidic waste gas is greater than 20% / 72h, and the structure is destroyed after regeneration (partially converted into ZnS); the sulfur capacity decay rate of the unmodified CuO molecular sieve in acidic waste gas is greater than 15% / 72h, and the micropores collapse after regeneration. 2+ The d-orbital electrons form a strong coordination bond (Cu-S bond) with the lone pair electrons of H2S. The acidic sulfur capacity attenuation rate is less than 3% / 72h under pH 6.5-7.0 conditions, and the crystal phase is stable after regeneration.

[0107] As can be seen from Table 4, the penetration time of each component in the three-stage system is extended by more than 180%, demonstrating that the synergistic effect of gradient adsorption significantly delays the competitive inhibition of highly active components (such as chloroform) on subsequent adsorbents, thereby avoiding the problem of dynamic adsorption capacity fluctuation of >30% in the prior art (calculated by the formula: (maximum adsorption capacity - minimum adsorption capacity) / average adsorption capacity × 100%, the dynamic adsorption capacity fluctuation in Example 1 was 22%).

[0108] According to Table 5, it can be seen that the CuO-modified molecular sieve reduces the sulfide penetration concentration by 92% and the sulfur capacity decay rate of the secondary activated carbon by 80%, which confirms that the protective effect of the preferential chemical adsorption mechanism (Cu-S bonding) on ​​the activated carbon far exceeds that of physical adsorption (Comparative Example 2).

[0109] As can be seen from Table 6, the graded regeneration matches the optimal medium for different VOCs polarity and boiling points, and the comprehensive desorption energy consumption is reduced by 45% to 50% (compared with the existing technology). In addition, hot air replaces nitrogen to treat the main non-polar components, which can reduce the cost of inert gas.

[0110] As can be seen from Table 7, condensation dehumidification (dew point ≤ 8°C) reduces the competitive adsorption effect of water molecules and the damage to the adsorbent to less than 10%, verifying the adaptability of the present invention to complex working conditions and solving the problems of sudden drop in efficiency and adsorbent water poisoning in high humidity environments in traditional processes.

[0111] It can be seen from Table 8 that pH adjustment has a stable regulating capability for subsequent waste gas treatment, forming a closed loop of "pretreatment-adsorption-regeneration", reducing the risk of adsorption efficiency decline or system failure caused by pH abnormality.

[0112] The above embodiments are only preferred implementation modes of the present invention and should not be used to limit the scope of protection of the present invention. Any changes or modifications that are made to the main design concept and spirit of the present invention and have no substantive significance, as long as the technical problems they solve are still consistent with the present invention, should be included in the scope of protection of the present invention.

Claims

1. A method for purifying volatile organic compounds by adsorption in the production of antibiotics, characterized in that: The following steps are involved: (1) The waste gas from antibiotic production is passed through a pretreatment unit, treated in an alkali spray tower, and then subjected to condensation and dehumidification to a dew point of ≤8°C; (2) The pre-treated exhaust gas is passed into the three-stage adsorption system at a flow rate of 0.8-1.2 m / s: The first-stage adsorption uses silica gel adsorbent, controls the temperature at 40-60°C, and utilizes the 2.5-3.5 nm mesoporous structure to accelerate the diffusion of chloroform molecules and achieve the capture of non-polar VOCs. The secondary adsorption uses phosphoric acid wood activated carbon, controlled at 30-35°C, to target the adsorption of acetone and ethanol through the directional action of surface hydroxyl hydrogen bonds; The third-stage adsorption uses CuO-modified 13X molecular sieve to adsorb xylene and sulfide in the exhaust gas at 50-70°C; (3) When the outlet VOCs concentration is ≥30mg / m 3 Or when the sulfide concentration at the secondary adsorption inlet is detected ≥1ppm for two consecutive times, the regeneration operation is started: the silica gel adsorbent is regenerated with 110-120℃ hot air, the phosphoric acid method wood activated carbon is regenerated with 120-130℃ nitrogen, and the CuO modified 13X molecular sieve is regenerated with 130-150℃ superheated steam. The regenerated tail gas is returned to the inlet of the alkali solution spray tower of the pretreatment unit.

2. The method for adsorption and purification of volatile organic compounds in the production of antibiotic drugs according to claim 1, characterized in that: In step (1), the circulating spray liquid in the alkali liquid spray tower is initially 10wt% sodium hydroxide solution to neutralize the acidic substances in the exhaust gas, and the pH of the circulating spray liquid is dynamically adjusted to maintain at 6.5-7.0; the flow rate of the circulating spray liquid is set at 5%-8% of the exhaust gas working volume flow rate, and the circulating spray liquid is supplemented when the pH is <6.5, and part of the circulating spray liquid is discharged when the pH is >7.

0.

3. The method for adsorption and purification of volatile organic compounds in the production of antibiotics according to claim 2, characterized in that: The specific surface area of ​​the silica gel adsorbent in step (2) is 550 to 650 m 2 / g, average pore size 2.5~3.5nm.

4. The method for adsorption and purification of volatile organic compounds in the production of antibiotic drugs according to claim 3, characterized in that: The iodine value of the phosphoric acid-processed wood activated carbon in step (2) is ≥950 mg / g.

5. The method for adsorption and purification of volatile organic compounds in the production of antibiotics according to claim 4, characterized in that: In step (2), the CuO-modified 13X molecular sieve is loaded with CuO 3-5wt% by impregnation, the impregnation solution is 0.4-0.6mol / L copper nitrate solution, the impregnation time is 2±0.5 hours, the drying temperature is 100-130°C, the calcination temperature is 400-500°C, and the calcination time is 3-5 hours; the SiO2 / Al2O3 molar ratio of the 13X molecular sieve is 2.3-2.

6.

6. The method for adsorption and purification of volatile organic compounds in the production of antibiotics according to claim 5, characterized in that: In step (2), the ratio of the filling volumes of the primary adsorption, the secondary adsorption, and the tertiary adsorption is 1:(1.2-1.5):(0.8-1.0).

7. The method for volatile organic compound adsorption purification in the production of antibiotics according to any one of claims 1 to 6, characterized in that: The oxygen concentration of the regenerated hot air in step (3) is ≤7 vol%.

8. The method for adsorption and purification of volatile organic compounds in the production of antibiotics according to claim 7, characterized in that: The dew point of the regenerated nitrogen in step (3) is ≤-40°C, and the flow rate is 25% to 35% of the exhaust flow rate in the adsorption stage.

9. The method for adsorption and purification of volatile organic compounds in the production of antibiotics according to claim 8, characterized in that: In step (3), the superheated steam pressure is 0.15-0.25 MPa, and the superheat degree is ≥30°C.

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