Ethylene oxide sterilization tail gas treatment method and system

Abstract

The invention belongs to the technical field of ethylene oxide sterilization, and particularly relates to an ethylene oxide sterilization tail gas treatment method and system.The system comprises the steps that (a) tail gas containing ethylene oxide is introduced into a spray tower and makes countercurrent contact with an ethylene glycol solution containing an acid catalyst for catalytic hydrolysis; (b) the hydrolysate enters a neutralization kettle, alkali liquor is added to adjust the pH to be neutral, and an ethylene glycol solution is obtained through separation; and (c) carrying out vacuum evaporation and rectification purification on the ethylene glycol solution, and circulating part of the recovery liquid to the step (a) as the absorption liquid, (d) unreacted ethylene oxide enters a catalytic combustion chamber to be decomposed into carbon dioxide and water; and (e) adjusting the temperature, the pressure and the catalyst concentration in real time through a PLC control system, and maintaining reaction kinetics matching. Spraying absorption, catalytic combustion and recovery processes are integrated, efficient tail gas treatment is achieved, the PLC system monitors the EO concentration and reaction parameters in real time, stability is guaranteed, and the explosion risk is prevented.

Description

Technical Field

[0001] The present invention relates to the technical field of ethylene oxide sterilization, and in particular to a method and system for treating ethylene oxide sterilization tail gas. Background Art

[0002] Ethylene oxide sterilization is a low-temperature sterilization method widely used in the medical device, pharmaceutical, food, and daily chemical industries. Ethylene oxide (EO) is a colorless, flammable compound with an ether-like odor. It is broad-spectrum, low-toxic, and highly penetrating. Ethylene oxide sterilization utilizes EO gas to sterilize medical devices and other products difficult to sterilize using high-temperature or high-pressure methods. Ethylene oxide is a highly effective chemical sterilant, capable of killing a wide range of microorganisms, including bacterial spores.

[0003] Ethylene oxide (EO) sterilization processes for medical devices present challenges in treating the exhaust gas. Traditionally, the exhaust gas is diluted once before being directly ignited in a high-temperature device. However, this single dilution and ignition alone cannot guarantee complete combustion of the EO, resulting in an incomplete treatment process and a certain amount of EO remaining in the exhaust gas.

[0004] Therefore, it is necessary to propose a new solution for treating ethylene oxide sterilization tail gas. Summary of the Invention

[0005] The object of the present invention is to provide a method and system for treating ethylene oxide sterilization tail gas to solve the problems raised in the background technology.

[0006] To achieve the above object, the present invention provides the following technical solution: a method for treating ethylene oxide sterilization tail gas, comprising the following steps:

[0007] (a) passing the tail gas containing ethylene oxide into a spray tower, and contacting it with an ethylene glycol solution containing an acidic catalyst in countercurrent flow to cause catalytic hydrolysis;

[0008] (b) the hydrolyzed liquid enters a neutralization kettle, alkali solution is added to adjust the pH to neutral, and ethylene glycol solution is separated;

[0009] (c) the ethylene glycol solution is purified by vacuum evaporation and rectification, and part of the recovered liquid is recycled to step (a) as an absorption liquid;

[0010] (d) Unreacted ethylene oxide enters the catalytic combustion chamber and is decomposed into carbon dioxide and water;

[0011] (e) The temperature, pressure, and catalyst concentration are adjusted in real time through the PLC control system to maintain the reaction kinetics matching.

[0012] In the ethylene oxide sterilization tail gas treatment method of the present invention, the acidic catalyst in step (a) is sulfuric acid with a concentration of 0.5-1.2wt%, the spray tower operating temperature is 60-70°C, and the pressure is 10-20kPa.

[0013] In the method for treating tail gas from ethylene oxide sterilization of the present invention, in step (a), the reaction kinetics matching is optimized by:

[0014] (a1) adding 0.1-0.3 wt% sodium bromide as a co-catalyst to the ethylene glycol solution to accelerate the EO hydrolysis reaction;

[0015] (a2) Control the liquid-to-gas ratio of the spray tower to 2.5-3.5:1 and the gas velocity to 0.8-1.2 m / s.

[0016] In the ethylene oxide sterilization tail gas treatment method of the present invention, the molar ratio of the amount of sodium bromide added to the sulfuric acid concentration in step (a1) is 1:8-1:12, and an online conductivity sensor is integrated in the PLC control system to dynamically adjust the catalyst replenishment rate.

[0017] In the method for treating tail gas from ethylene oxide sterilization according to the present invention, the ethylene glycol solution after distillation and purification in step (c) is divided into two parts:

[0018] (c1) diluting the 60-70% solution to a concentration of 50-60% and adding sulfuric acid, and circulating to the spray tower;

[0019] (c2) The remaining part is used as the reducing agent in the catalytic combustion chamber and is atomized and mixed with the exhaust gas before entering the combustion chamber.

[0020] The ethylene oxide sterilization tail gas treatment method of the present invention, wherein the atomized particle size of the ethylene glycol solution in step (c2) is 20-50 μm, the combustion temperature is 280-320° C., the catalytic bed layer uses a palladium / alumina catalyst, and the palladium loading is 0.3-0.8 wt%.

[0021] In addition, the present invention also provides an ethylene oxide sterilization tail gas treatment system, which is applied to the above-mentioned ethylene oxide sterilization tail gas treatment method. Specifically, the system includes:

[0022] Spray tower with built-in PP packing layer and sulfuric acid spray device;

[0023] Catalytic hydration reactor with acid-resistant ceramic lining and temperature control module;

[0024] Neutralization kettle, integrated with pH meter and automatic alkali dosing valve;

[0025] The vacuum evaporator and distillation tower are connected to the ethylene glycol storage tank;

[0026] Catalytic combustion chamber with built-in platinum / alumina catalyst bed;

[0027] PLC control unit, connected to temperature sensor, pressure sensor and online EO detector.

[0028] The ethylene oxide sterilization tail gas treatment system of the present invention, wherein the packing layer height of the spray tower is 1.0-1.5m, the porosity is ≥85%, and the packing specific surface area is 200-300m 2 / m 3 ; The exhaust gas residence time in the catalytic combustion chamber is 0.8-1.5s.

[0029] In the ethylene oxide sterilization tail gas treatment system of the present invention, the PLC control unit implements closed-loop control according to the following parameters:

[0030] The target EO concentration at the spray tower outlet is less than or equal to 100ppm;

[0031] The target pH range of the neutralization kettle is 6.8-7.2;

[0032] The target value of ethylene glycol density in vacuum evaporator is 1.10-1.15 g / cm 3 .

[0033] The ethylene oxide sterilization tail gas treatment system of the present invention further includes an emergency treatment module, which automatically initiates the following operations when the online EO detector exceeds the limit:

[0034] (d) Close the tail gas input valve and switch to the standby spray tower;

[0035] (e) Injecting an excess of ethylene glycol solution with a concentration greater than 40% into the catalytic combustion chamber to force the combustion temperature to be lowered to below 250°C

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] Achieved full-process closed-loop control: integrated spray absorption, catalytic combustion and recovery processes to achieve efficient and thorough exhaust gas treatment;

[0038] Furthermore, the products in the process are used as resources: through the purification and recycling of ethylene glycol, the consumption of fresh chemicals is reduced;

[0039] Moreover, the system has a safety redundant design: the PLC system monitors EO concentration and reaction parameters in real time to prevent explosion risks. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0041] Figure 1 It is a flow chart of the process steps of the present invention. DETAILED DESCRIPTION

[0042] The terms "first," "second," "third," and "fourth," etc., in the specification, claims, and accompanying drawings of the present invention are used to distinguish between different items, not to describe a specific order. Furthermore, the terms "including," "having," and any variations thereof, are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or apparatus comprising a series of steps or elements is not limited to the listed steps or elements, but may optionally include steps or elements not listed, or may optionally include other steps or elements inherent to the process, method, product, or apparatus.

[0043] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present invention. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute a separate or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0044] "Multiple" refers to two or more. "And / or" describes the relationship between associated objects, indicating that three possible relationships exist. For example, "A and / or B" can mean: A exists alone, A and B exist simultaneously, or B exists alone. The character " / " generally indicates that the associated objects are in an "or" relationship.

[0045] Moreover, the terms "up, down, left, right, upper end, lower end, longitudinal" and the like indicating directions are all based on the posture and position of the device or apparatus described in this solution during normal use.

[0046] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the following will be a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work shall fall within the scope of protection of the present invention.

[0047] This embodiment discloses Figure 1 The ethylene oxide sterilization tail gas treatment method shown includes the following steps:

[0048] Step (a) passing the tail gas containing ethylene oxide into a spray tower, and contacting it with an ethylene glycol solution containing an acidic catalyst in countercurrent to cause catalytic hydrolysis;

[0049] The hydrolyzed liquid in step (b) enters a neutralization kettle, where an alkali solution is added to adjust the pH to neutral, and an ethylene glycol solution is obtained by separation;

[0050] In step (c), the ethylene glycol solution is purified by vacuum evaporation and rectification, and part of the recovered liquid is recycled to step (a) as an absorption liquid;

[0051] In step (d), unreacted ethylene oxide enters a catalytic combustion chamber and is decomposed into carbon dioxide and water;

[0052] Step (e) adjusting the temperature, pressure and catalyst concentration in real time through a PLC control system to maintain reaction kinetics matching;

[0053] Through the above process:

[0054] Achieved full-process closed-loop control: integrated spray absorption, catalytic combustion and recovery processes to achieve efficient and thorough exhaust gas treatment;

[0055] Furthermore, the products in the process are used as resources: through the purification and recycling of ethylene glycol, the consumption of fresh chemicals is reduced;

[0056] Moreover, the system has a safety redundant design: the PLC system monitors EO concentration and reaction parameters in real time to prevent explosion risks.

[0057] In this embodiment, the acidic catalyst in step (a) is sulfuric acid at a concentration of 0.5-1.2 wt % to balance catalytic activity and equipment corrosion resistance and improve the reaction rate. The lower limit of the concentration (0.5 wt %) ensures that the activation energy of the hydrolysis reaction can be maintained at ≤50 kJ / mol, while the upper limit (1.2 wt %) can prevent excessive corrosion of the equipment. In practice, the corrosion rate is generally required to be less than 0.1 mm / year. The operating temperature of the spray tower is 60-70° C. and the pressure is 10-20 kPa. This parameter configuration can reduce the thermal decomposition rate of ethylene glycol. The sodium sulfate remaining in the neutralization stage can be removed by centrifugation and membrane filtration to avoid salt accumulation in the circulating liquid.

[0058] In this embodiment, the reaction kinetics matching is optimized in step (a) by:

[0059] (a1) adding 0.1-0.3 wt% sodium bromide as a co-catalyst to the ethylene glycol solution to accelerate the EO hydrolysis reaction. The sodium bromide co-catalyst shortens the EO hydrolysis induction period, thereby reducing the activation energy of the SN2 reaction;

[0060] (a2) Controlling the liquid-to-gas ratio of the spray tower to 2.5-3.5:1 and the gas velocity to 0.8-1.2 m / s can further reduce the pressure drop of the absorption tower and improve the efficiency of the absorption tower.

[0061] In this embodiment, the molar ratio of the amount of sodium bromide added to the sulfuric acid concentration in step (a1) is 1:8-1:12. The specific molar ratio of sodium bromide to sulfuric acid balances catalytic activity and side reaction inhibition, thereby extending the catalyst life. In practice, the catalyst life can be extended to 1200 hours. An online conductivity sensor is integrated into the PLC control system to dynamically adjust the catalyst replenishment rate, thereby achieving high-precision fluctuation monitoring of the catalyst concentration, and basically ensuring fluctuation control of ±5%.

[0062] In this embodiment, the ethylene glycol solution after distillation and purification in step (c) is divided into two parts:

[0063] (c1) diluting the 60-70% solution to a 50-60% concentration and adding sulfuric acid, which is then circulated to the spray tower. The ethylene glycol is then diluted and reused to reduce evaporation energy consumption;

[0064] (c2) The remaining portion is used as a reducing agent in the catalytic combustion chamber. After being atomized, it is mixed with the exhaust gas and enters the combustion chamber. Ethylene glycol is used as a reducing agent to participate in the catalytic combustion, which can reduce the fuel demand.

[0065] In this embodiment, the atomized particle size of the ethylene glycol solution in step (c2) is 20-50 μm, the combustion temperature is 280-320° C., the catalytic bed uses a palladium / alumina catalyst, and the palladium loading is 0.3-0.8 wt%, which can achieve the purpose of inhibiting carbon deposition and extending the regeneration cycle.

[0066] Example 2

[0067] This embodiment is basically the same as the first embodiment, and the similarities are not repeated here. The difference is that this embodiment provides an ethylene oxide sterilization tail gas treatment system, which is applied to the ethylene oxide sterilization tail gas treatment method of the first embodiment. The system includes:

[0068] Spray tower, with built-in PP packing layer and sulfuric acid spray device. Specifically, the PP packing layer can be combined with acid-resistant ceramic lining to extend the life of the equipment;

[0069] Catalytic hydration reactor with acid-resistant ceramic lining and temperature control module;

[0070] Neutralization kettle, integrated with pH meter and automatic alkali dosing valve;

[0071] The vacuum evaporator and distillation tower are connected to the ethylene glycol storage tank;

[0072] The catalytic combustion chamber has a built-in platinum / alumina catalyst bed. Specifically, the spray tower and the catalytic combustion chamber are connected in series to reduce pipeline pressure loss.

[0073] PLC control unit, connected to temperature sensor, pressure sensor and online EO detector.

[0074] In this embodiment, the packing layer height of the spray tower is 1.0-1.5m, the porosity is ≥85%, and the packing specific surface area is 200-300m 2 / m 3 The exhaust gas residence time in the catalytic combustion chamber is 0.8-1.5s. The configuration of this parameter can enhance gas-liquid contact, improve the mass transfer coefficient, and ensure sufficient EO decomposition.

[0075] In this embodiment, the PLC control unit implements closed-loop control according to the following parameters:

[0076] The target EO concentration at the spray tower outlet is less than or equal to 100 ppm;

[0077] The target pH range of the neutralization kettle is 6.8-7.2;

[0078] The target value of ethylene glycol density in vacuum evaporator is 1.10-1.15 g / cm 3 .

[0079] In this embodiment, the system also includes an emergency processing module. When the online EO detector exceeds the limit of ≥200ppm, the following operations are automatically initiated:

[0080] (d) Close the tail gas input valve and switch to the standby spray tower;

[0081] (e) Injecting an excess of ethylene glycol solution (concentration ≥ 40%) with a concentration greater than 40% into the catalytic combustion chamber to forcibly lower the combustion temperature to below 250°C to avoid high-temperature deflagration.

[0082] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all such improvements and changes should fall within the scope of protection of the appended claims of the present invention.

Claims

1. A method for treating tail gas from ethylene oxide sterilization, characterized in that: The following steps are involved: (a) passing the tail gas containing ethylene oxide into a spray tower, and contacting it with an ethylene glycol solution containing an acidic catalyst in countercurrent flow to cause catalytic hydrolysis; (b) the hydrolyzed liquid enters a neutralization kettle, alkali solution is added to adjust the pH to neutral, and ethylene glycol solution is separated; (c) the ethylene glycol solution is purified by vacuum evaporation and rectification, and part of the recovered liquid is recycled to step (a) as an absorption liquid; (d) Unreacted ethylene oxide enters the catalytic combustion chamber and is decomposed into carbon dioxide and water; (e) The temperature, pressure, and catalyst concentration are adjusted in real time through the PLC control system to maintain the reaction kinetics matching.

2. The method for treating ethylene oxide sterilization tail gas according to claim 1, wherein: The acidic catalyst in step (a) is sulfuric acid with a concentration of 0.5-1.2 wt %. The operating temperature of the spray tower is 60-70° C. and the pressure is 10-20 kPa.

3. The method for treating tail gas from ethylene oxide sterilization according to claim 2, wherein: In step (a), the reaction kinetics matching is optimized by: (a1) adding 0.1-0.3 wt% sodium bromide as a co-catalyst to the ethylene glycol solution to accelerate the EO hydrolysis reaction; (a2) Control the liquid-to-gas ratio of the spray tower to 2.5-3.5:1 and the gas velocity to 0.8-1.2 m / s.

4. The method for treating tail gas from ethylene oxide sterilization according to claim 3, wherein: The molar ratio of the amount of sodium bromide added to the sulfuric acid concentration in step (a1) is 1:8-1:12, and an online conductivity sensor is integrated in the PLC control system to dynamically adjust the catalyst replenishment rate.

5. The method for treating tail gas from ethylene oxide sterilization according to claim 1, wherein: The ethylene glycol solution after distillation and purification in step (c) is divided into two parts: (c1) diluting the 60-70% solution to a concentration of 50-60% and adding sulfuric acid, and circulating to the spray tower; (c2) The remaining part is used as the reducing agent in the catalytic combustion chamber and is atomized and mixed with the exhaust gas before entering the combustion chamber.

6. The method for treating tail gas from ethylene oxide sterilization according to claim 5, wherein: In step (c2), the atomized particle size of the ethylene glycol solution is 20-50 μm, the combustion temperature is 280-320° C., the catalytic bed layer uses a palladium / alumina catalyst, and the palladium loading is 0.3-0.8 wt %.

7. An ethylene oxide sterilization tail gas treatment system, applied to the ethylene oxide sterilization tail gas treatment method according to any one of claims 1 to 6, characterized in that: The system includes: Spray tower with built-in PP packing layer and sulfuric acid spray device; Catalytic hydration reactor with acid-resistant ceramic lining and temperature control module; Neutralization kettle, integrated with pH meter and automatic alkali dosing valve; The vacuum evaporator and distillation tower are connected to the ethylene glycol storage tank; Catalytic combustion chamber with built-in platinum / alumina catalyst bed; PLC control unit, connected to temperature sensor, pressure sensor and online EO detector.

8. The ethylene oxide sterilization tail gas treatment system according to claim 7, characterized in that: The packing layer height of the spray tower is 1.0-1.5m, the porosity is ≥85%, and the packing specific surface area is 200-300m 2 / m 3 ; The exhaust gas residence time in the catalytic combustion chamber is 0.8-1.5s.

9. The ethylene oxide sterilization tail gas treatment system according to claim 8, characterized in that: The PLC control unit implements closed-loop control according to the following parameters: The target EO concentration at the spray tower outlet is less than or equal to 100 ppm; The target pH range of the neutralization kettle is 6.8-7.2; The target value of ethylene glycol density in vacuum evaporator is 1.10-1.15 g / cm 3 .

10. The ethylene oxide sterilization tail gas treatment system according to claim 9, characterized in that: The system also includes an emergency processing module that automatically initiates the following operations when the online EO detector exceeds the limit: (d) Close the tail gas input valve and switch to the standby spray tower; (e) Injecting an excess of ethylene glycol solution with a concentration greater than 40% into the catalytic combustion chamber to forcibly lower the combustion temperature to below 250°C.

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