Method and system for recovering electronic grade dichlorodihydrogen silicon and helium gas

Abstract

The application provides a recovery method and recovery system of electronic-grade dichlorodihydrogen silicon and helium, and belongs to the field of tail gas treatment.The recovery method comprises the following steps: removing solid particle impurities from tail gas containing dichlorodihydrogen silicon and helium after filtration; using the difference between the boiling points of dichlorodihydrogen silicon and helium, condensing the tail gas after removal of solid particle impurities through multi-stage gas-liquid separation to obtain liquid dichlorodihydrogen silicon and preliminarily separated gaseous helium; removing residual organic impurities and inorganic impurities in the gaseous helium after preliminary separation through multi-stage adsorption; removing residual impurities from the impurity-removed helium through multi-stage membrane separation and purification to obtain high-purity helium.The application can realize harmless treatment of tail gas, maximally reduce tail gas emission, reduce energy consumption and environmental pollution; meanwhile, useful substances in the tail gas are recovered, the helium is purified to the purity standard that can be used for electronic-grade product production again, the purpose of resource recycling is achieved, the production cost is reduced, and the economic benefit of enterprises is improved.

Description

Technical Field

[0001] This invention belongs to the field of exhaust gas treatment technology, specifically relating to a method and system for recovering electronic-grade dichlorosilane and helium. Background Technology

[0002] In semiconductor manufacturing and related fields, electronic-grade dichlorosilane is an important silicon source gas in semiconductor manufacturing, commonly used in core processes such as thin film deposition and silicon epitaxial growth. During production and filling, helium is typically used as a replacement or protective gas to ensure process stability and product quality. However, the used helium is often directly emitted, resulting in resource waste and increased costs. Helium is a rare gas with limited reserves on Earth and high acquisition costs. Furthermore, directly emitting helium containing small amounts of impurities (such as trace amounts of dichlorosilane) is not environmentally friendly. Therefore, how to effectively recycle and utilize this displaced helium has become an urgent problem to be solved in this field.

[0003] Currently, although some helium recovery technologies exist, recovering helium containing impurities such as electronic-grade dichlorosilane still faces challenges, including low recovery rates, difficulty in guaranteeing purity, and high recovery costs. Traditional exhaust gas treatment processes have numerous drawbacks:

[0004] (1) Some traditional processes use simple combustion to treat exhaust gas. Although they can decompose some harmful substances, they will produce a large amount of high-temperature exhaust gas, which not only consumes a lot of energy, but may also produce new pollutants, such as chlorinated organic compounds, due to incomplete combustion. Furthermore, the useful resources in the exhaust gas cannot be recovered.

[0005] (2) Some wet treatment processes absorb tail gas through water or alkaline solution. However, this can easily lead to the generation of a large amount of wastewater containing high concentrations of silicides and chlorides. The wastewater is difficult to treat and costly. If not treated properly, it can cause serious pollution to water bodies and soil.

[0006] (3) In addition, since electronic products have extremely high purity requirements, traditional processing technology is difficult to meet the high purity requirements of the recovered materials while effectively treating the exhaust gas, and thus cannot achieve efficient recycling of resources.

[0007] With increasingly stringent environmental regulations and the electronics industry's pursuit of efficient resource utilization, the development of an efficient, environmentally friendly exhaust gas treatment process that enables resource recycling is urgently needed. Summary of the Invention

[0008] This invention provides a method and system for recovering electronic-grade dichlorosilane and helium, aiming to solve the problems of high energy consumption, low recycling rate, and secondary pollution to the environment caused by traditional processing techniques.

[0009] Firstly, to achieve the above objectives, the technical solution adopted by the present invention is: to provide a method for recovering electronic-grade dichlorosilane and helium, the recovery method comprising:

[0010] The exhaust gas containing dichlorosilane and helium is filtered to remove solid particulate impurities.

[0011] By taking advantage of the difference in boiling points between dichlorosilane and helium, the tail gas after removing solid particulate impurities is condensed through multi-stage gas-liquid separation to obtain liquid dichlorosilane and preliminarily separated gaseous helium.

[0012] After initial separation, the gaseous helium undergoes multi-stage adsorption to remove residual organic and inorganic impurities.

[0013] The helium gas, after impurities have been removed, is purified through multi-stage membrane separation to remove residual impurities and obtain high-purity helium gas.

[0014] In conjunction with the first aspect, in one feasible manner, the removal of solid particulate impurities from the tail gas containing dichlorosilane and helium by filtration includes:

[0015] The exhaust gas containing dichlorosilane and helium is introduced into a buffer tank, pressurized to 0.2-1.0 MPa by a pressurizer, and then enters a 0.1 μm filter to remove solid particulate impurities.

[0016] In conjunction with the first aspect, in one feasible manner, the process of condensing the exhaust gas after removing solid particulate impurities through multi-stage gas-liquid separation to obtain liquid dichlorosilane and preliminarily separated gaseous helium includes:

[0017] After removing solid particulate impurities, the exhaust gas is sent to a primary gas-liquid separator and cooled to -30°C to obtain liquid dichlorosilane, which is then sent to the first collection tank for storage.

[0018] The exhaust gas after separation by the primary gas-liquid separator enters the secondary gas-liquid separator, where it is cooled to -50°C and separated again. The resulting liquid dichlorosilane is then sent to the second collection tank for storage.

[0019] In conjunction with the first aspect, in one feasible manner, the initially separated gaseous helium undergoes multi-stage adsorption, including:

[0020] Helium gas, kept in a gaseous state, is introduced into a multi-stage adsorption tower to remove organic and inorganic impurities in stages.

[0021] The multi-stage adsorption tower is filled from bottom to top with a 3A molecular sieve, a modified activated carbon layer, and an activated carbon fiber layer. The activated carbon fiber is used to adsorb residual organic impurities in helium; the modified activated carbon is used to adsorb some inorganic impurities in helium; and the 3A molecular sieve is used to remove small molecule impurities such as carbon and water from inorganic impurities, thereby reducing the carbon dioxide and water content in helium to <0.5 ppm.

[0022] In conjunction with the first aspect, in one feasible manner, the adsorption temperature within the multi-stage adsorption tower is 25-50°C, and the gas flow rate is 0.3-0.8 m / s.

[0023] In conjunction with the first aspect, in one feasible manner, the removal of impurities from the helium gas via multi-stage membrane separation includes:

[0024] The helium gas, after impurities have been removed, enters the first-stage membrane separator for coarse separation, separating most of the nitrogen in the helium gas and hydrocarbons from the organic impurities.

[0025] The helium gas separated by the first-stage membrane separator is pressurized by a compressor and then enters the second-stage membrane separator for further purification, separating out the residual impurities in the helium gas to obtain high-purity helium gas.

[0026] In conjunction with the first aspect, in one feasible manner, the primary membrane separator is provided with a hollow fiber membrane module, and the secondary membrane separator is provided with a high-performance composite membrane module.

[0027] Secondly, embodiments of the present invention also provide an electronic-grade dichlorosilane and helium recovery system for the aforementioned electronic-grade dichlorosilane and helium recovery method, comprising a buffer tank, a compressor, a filter, a multi-stage gas-liquid separator, a multi-stage adsorption tower, a primary membrane separator, a compressor, a secondary membrane separator, and a helium storage tank connected in sequence via pipelines; the multi-stage gas-liquid separator is connected to a liquid dichlorosilane collection tank.

[0028] Secondly, embodiments of the present invention also provide a multi-stage gas-liquid separator comprising a primary gas-liquid separator and a secondary gas-liquid separator connected in series. The primary gas-liquid separator is connected to a first collection tank via a pipeline, and the secondary gas-liquid separator is connected to a second collection tank via a pipeline. The first collection tank and the second collection tank are connected to the liquid dichlorosilane collection tank via pipelines. Liquid dichlorosilane condensed to different temperatures is stabilized in its respective collection tank and then flows into the liquid dichlorosilane collection tank.

[0029] Secondly, embodiments of the present invention also provide a recovery system that further includes a regeneration adsorption tower, wherein the regeneration adsorption tower is connected in parallel with the multi-stage adsorption tower between the multi-stage gas-liquid separator and the primary membrane separator, so that the recovery system switches between the regeneration adsorption tower and the multi-stage adsorption tower.

[0030] The method for recovering electronic-grade dichlorosilane and helium provided by this invention has the following advantages compared with the prior art:

[0031] (1) In view of the problems that traditional high-temperature combustion is used to treat exhaust gas, which not only consumes a lot of energy and generates a lot of high-temperature waste gas, but also cannot recover useful resources such as helium and dichlorosilane, this invention replaces chemical combustion with physical separation to solve the problems of energy consumption and resource waste:

[0032] By utilizing the significant boiling point difference between dichlorosilane (boiling point 8.2℃) and helium (boiling point -268.94℃), a multi-stage gas-liquid separation and condensation technology can achieve highly efficient separation of the two. This process does not require high-temperature combustion, does not produce high-temperature waste gas, does not consume a large amount of heat source, does not generate new pollutants due to incomplete combustion, and does not affect the recovery of helium and dichlorosilane.

[0033] After the exhaust gas is condensed by a gas-liquid separator, liquid dichlorosilane is obtained directly, avoiding the loss of silicon source in the combustion method. Combined with subsequent purification processes, the purity of the recovered helium can reach electronic grade of 99.999% or higher, and can be directly reused in processes such as thin film deposition and silicon epitaxial growth, realizing a closed-loop cycle of helium.

[0034] (2) For wet treatment processes, which generate high-concentration silicide and chloride wastewater, there is a serious risk of water and soil pollution. This invention completely eliminates secondary pollution through a fully dry process design:

[0035] This invention removes impurities using dry methods such as filtration and adsorption. The multi-stage adsorption process efficiently captures residual organic and inorganic impurities, avoiding the high costs and pollution risks associated with wastewater treatment in wet processes.

[0036] After the dichlorodihydrosilicon in the exhaust gas is condensed and recovered, the concentration of residual impurities in the helium gas has been significantly reduced. The subsequent adsorption-membrane separation combination can further reduce the impurity content. The final exhaust gas contains only trace amounts of inert gas, which fully complies with the stringent environmental protection regulations and requires no additional exhaust gas treatment facilities.

[0037] (3) Electronic-grade products require helium purity of 99.999% or higher (GB / T4844-2011 standard), and traditional processes struggle to balance recovery rate and purity. This technical solution removes impurities from helium through multi-stage condensation, multi-stage adsorption, and multi-stage membrane separation, increasing helium purity to 99.9996%. Combined with a closed-loop reflux design, the total helium recovery rate can reach over 95%. While purifying helium, the dichlorosilane obtained from condensation can be further processed to meet electronic-grade standards, significantly improving the efficiency of resource recycling.

[0038] The method and system for recovering electronic-grade dichlorosilane and helium provided by this invention can achieve harmless treatment of exhaust gas, minimize exhaust gas emissions, and reduce energy consumption and environmental pollution. At the same time, it can efficiently recover useful substances in the exhaust gas and purify them to a purity standard that can be reused in the production of electronic-grade products, thereby achieving the purpose of resource recycling, reducing production costs, and improving the economic and environmental benefits of enterprises.

[0039] This invention is particularly effective in the efficient, energy-saving, and high-purity recovery of exhaust gases from electronic-grade dichlorosilane (SiH2Cl2) and helium, achieving harmless treatment and resource recycling of exhaust gases while meeting the environmental protection and cost control requirements of the electronics industry in the production process of high-purity products. Attached Figure Description

[0040] Figure 1 A schematic flowchart illustrating the method for recovering electronic-grade dichlorosilane and helium provided in an embodiment of the present invention;

[0041] Figure 2 A schematic diagram of the process for recovering electronic-grade dichlorosilane and helium provided in an embodiment of the present invention;

[0042] Explanation of reference numerals in the attached figures:

[0043] 1. Buffer tank; 2. Compressor; 3. Filter; 4. Primary gas-liquid separator; 5. Secondary gas-liquid separator; 6. Multistage adsorption tower; 7. Primary membrane separator; 8. Compressor; 9. Secondary membrane separator; 10. Helium storage tank; 11. First collection tank; 12. Second collection tank. Detailed Implementation

[0044] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0045] Please see Figure 1 and Figure 2 The present invention will now describe a method for recovering electronic-grade dichlorosilane and helium. The method for recovering electronic-grade dichlorosilane and helium includes the following steps:

[0046] S001, the tail gas containing dichlorosilane and helium is filtered to remove solid particulate impurities.

[0047] S002, utilizing the difference in boiling points between dichlorosilane and helium, the tail gas after removing solid particulate impurities is condensed through multi-stage gas-liquid separation to obtain liquid dichlorosilane and preliminarily separated gaseous helium.

[0048] S003, the initially separated gaseous helium is subjected to multi-stage adsorption to remove residual organic and inorganic impurities in the helium;

[0049] S004, the helium gas after removing impurities is purified by multi-stage membrane separation to remove residual impurities and obtain high-purity helium gas.

[0050] In some embodiments, see Figure 2 Before step S001, the exhaust gas containing dichlorosilane and helium needs to be introduced into buffer tank 1, pressurized to 0.2-1.0 MPa by pressurizer 2, and then enters 0.1μm high efficiency filter 3 to remove solid particulate impurities greater than or equal to 0.1μm, so as to avoid the risk of subsequent equipment blockage and contamination of semiconductor wafers.

[0051] In step S002, the difference in boiling points between dichlorosilane and helium is utilized to perform multi-stage gas-liquid separation on the filtered tail gas by gradually reducing the temperature to different ranges, thereby achieving the separation of dichlorosilane and helium.

[0052] Specifically, the boiling point of dichlorodihydrosilicon is 8.2℃, while that of helium is -268.94℃, a significant difference exists between the two. Therefore, in the first-stage gas-liquid separator 4, the exhaust gas is cooled to approximately -30℃, causing the dichlorodihydrosilicon to condense into a liquid state. This liquid substance is then separated out by the first-stage gas-liquid separator 4. The exhaust gas separated by the first-stage gas-liquid separator 4 enters the second-stage gas-liquid separator 5, where the temperature is further reduced to -50℃, causing the remaining dichlorodihydrosilicon to liquefy and undergo gas-liquid separation again.

[0053] This process allows dichlorosilane to fully condense, while the helium gas remains in a gaseous state. The condensed liquid dichlorosilane can be stored in a liquid collection tank for subsequent treatment or reuse. Thus, the recovery of dichlorosilane from the exhaust gas is achieved.

[0054] In step S003, see Figure 2 The main process involves drying, adsorbing, and purifying the initially separated helium through multi-stage adsorption, removing moisture and most impurities to achieve preliminary purification of the helium.

[0055] The multi-stage adsorption tower 6 is filled from bottom to top with a 3A molecular sieve, a modified activated carbon layer, and an activated carbon fiber layer. Preliminarily purified helium enters the multi-stage adsorption tower 6, first passing through the activated carbon fiber to adsorb residual dichlorosilane and some hydrocarbon organic impurities, such as methane and ethane; then passing through the middle modified activated carbon layer to remove some inorganic impurities such as CO2 and CO; finally, passing through the 3A molecular sieve to further remove small molecule impurities such as carbon and water from the helium. Because the moisture content of the helium needs to be reduced to below 0.5 ppm before entering the subsequent membrane separation process, it is necessary to protect downstream equipment or pipelines from ice blockage.

[0056] To explain, 3A molecular sieve, also known as 3A zeolite molecular sieve, is an alkali metal aluminosilicate with the chemical formula 2 / 3K₂O·1 / 3Na₂O·Al₂O₃·2SiO₂·9 / 2H₂O. Its effective pore size is 3 Å (0.3 nanometers), specifically designed to adsorb water molecules with a diameter smaller than 3 Å. It repels large molecules such as ethane, thus effectively removing moisture from helium gas.

[0057] The adsorption temperature in the multi-stage adsorption tower 6 is 25-50℃, and the gas flow rate is 0.3-0.8m / s, achieving a good adsorption effect.

[0058] In this application, two parallel multi-stage adsorption towers 6 are provided, which can be periodically regenerated by switching between high-temperature desorption and low-pressure desorption to extend the service life of the adsorbent and ensure the continuity of the recovery process.

[0059] For example, the regeneration conditions using high-temperature desorption are as follows: purging with hot nitrogen gas at 150°C, with a regeneration cycle of 4-8 hours.

[0060] In step S004, see Figure 2 The main method utilizes the different affinities of helium and its impurities with the membrane material under pressure difference to purify and refine helium, obtaining 99.999% high-purity helium.

[0061] The working principle of membrane separation is as follows:

[0062] First, there's adsorption and dissolution: the mixed gas comes into contact with the membrane surface under pressure. Due to intermolecular forces between gas molecules and the membrane material, the gas is adsorbed onto the membrane surface and dissolves into the membrane material. Gases with small molecular sizes and high affinity for membrane materials dissolve more easily. Helium (He), because of its extremely small molecules and inert nature, has weak interactions with most polymer membranes, but due to its extremely small size, it can easily squeeze into the gaps between the molecular chains of the membrane material.

[0063] Secondly, there is diffusion: gas molecules dissolved within the membrane move from the high-pressure side to the low-pressure side, driven by the concentration difference across the membrane (driven by the pressure difference). The speed of this movement (diffusion rate) depends on the size and shape of the molecules. The smaller and lighter the molecules, the faster the diffusion rate. Helium is one of the smallest and lightest molecules of all gases, therefore its diffusion rate within the membrane is much faster than that of larger molecules such as nitrogen (N2) and methane (CH4).

[0064] Finally, desorption occurs: gas molecules that have diffused to the other side of the membrane (the low-pressure side) are released from the membrane material and become permeate gas.

[0065] After multi-stage adsorption, the impurities in helium mainly include small amounts of nitrogen and methane. Since the diameter of helium molecules (approximately 0.26 nm) is much smaller than that of common impurity gases such as nitrogen (0.364 nm) and methane (0.38 nm), helium molecules are more easily dissolved in the membrane material and diffuse through the membrane pores to the other side of the membrane under the drive of the concentration gradient, thereby achieving separation from other gases.

[0066] This invention employs a two-stage membrane separation process. After passing through the first-stage membrane separator 7, most of the nitrogen and hydrocarbon impurities in organic impurities such as methane and ethane are separated. The helium is then concentrated 7-10 times before entering the permeate gas stage, and then passes through the more selective second-stage membrane separator 9 to achieve the purification of the helium.

[0067] Selection of primary membrane separator 7: The helium gas after multi-stage adsorption has a high impurity gas content and high partial pressure. Therefore, primary membrane separator 7 needs to be a membrane with high permeation flux, good mechanical strength, and strong antifouling ability, such as hollow fiber membrane modules made of polyimide or polysulfone. It has moderate selectivity for helium but a large throughput.

[0068] The primary membrane separation process is as follows:

[0069] Helium gas is pressurized to a certain pressure (e.g., 3.0 MPa) and enters the first-stage membrane separator 7. Under pressure, helium gas will preferentially permeate through the membrane and reach the low-pressure side; while most impurities such as nitrogen, methane and ethane cannot permeate through the membrane due to their extremely slow permeation rate and are discharged from the high-pressure side outlet of the first-stage membrane separator 7.

[0070] After passing through the first-stage membrane separator 7, the helium concentration in the permeate gas is concentrated by about 7-10 times, but it still contains a considerable proportion of impurities such as nitrogen and methane.

[0071] Selection of Secondary Membrane Separator 9: The goal of the secondary membrane separator 9 is to further purify the helium after primary concentration to 99.999% high-purity helium. At this point, the total gas volume has been reduced, the helium concentration is high, and the impurity partial pressure is low. Therefore, a highly selective membrane can be selected, such as a membrane based on polytrimethylsilylpropyne (PTMSP) or other high-performance composite materials, to further separate the helium from other residual impurity gases, thereby obtaining high-purity helium.

[0072] Secondary membrane separation process:

[0073] The permeate gas pressure in the first-stage membrane separator is relatively low. After being pressurized by the compressor 8 (e.g., to 2.0 MPa), it enters the second-stage membrane separator 9.

[0074] In highly selective secondary membranes, helium can pass through rapidly due to its extremely small molecular size, while residual impurities such as nitrogen and methane are strictly blocked.

[0075] After two-stage purification and separation, high-purity helium gas with a purity of 99.999% can be obtained from the low-pressure side of the membrane.

[0076] The exhaust gas from the recovery of electronic-grade dichlorosilane and helium in this invention contains total hydrocarbons, primarily organic impurities such as methane, ethane, and residual solvents; and inorganic impurities mainly consisting of carbon monoxide, carbon dioxide, nitrogen, and oxygen; among which carbon and water are small molecule impurities. This invention utilizes corresponding treatment methods tailored to the characteristics of different substances in the exhaust gas to remove impurities in a graded manner, and can efficiently recover dichlorosilane and helium.

[0077] After the exhaust gas is treated using the recovery method provided by this invention, the purified helium is monitored in real time by a mass flow controller (MFC) and a laser gas analyzer (detection accuracy 0.1ppm), and impurities in the helium are detected. The detection results are shown in Table 1 below:

[0078] Table 1

[0079]

[0080] In Table 1, GC represents gas chromatography; B indicates basic qualification, and G represents qualification; the moisture analyzer refers to a dew point meter and a Karl Fischer moisture analyzer; and the trace O2 is measured by an electrochemical sensor and a laser spectroscopy method.

[0081] The data in the table directly proves that the core quality and impurity control of the recovered products meet or even exceed the preset requirements, as detailed below:

[0082] (1) Helium purity meets and exceeds the standard: total purity ≥ 99.9997% (5.7N grade), which meets the stringent standards for industrial-grade high-purity materials. The fact that the target product is purified to meet the design expectations even without an upper limit setting indicates that the purification effect of the target product has met the design expectations.

[0083] (2) Extreme control of key impurities: The actual values ​​of key impurities such as water (≤0.02ppm) and oxygen (≤0.01ppm), which are most harmful to product stability and downstream applications, are all lower than the control limit and are marked as G, which proves the system's ability to remove impurities.

[0084] (3) Other impurities are fully compliant: Nitrogen (≤1.00ppm), total hydrocarbons (such as methane, ethane and solvent residues ≤0.10ppm), CO2+CO (≤0.10ppm) and other major impurities, although the control upper limit is slightly higher than that of key impurities (due to the higher difficulty of removal), the actual values ​​are all within the standard and the status is marked as B (generally qualified), achieving compliance control of all impurities without any risk of omission.

[0085] The structural rationality and operational effectiveness of the recycling system were verified:

[0086] Firstly, the adsorption and separation efficiency is excellent: the dual achievement of high purity and low impurities proves that the combination of multi-stage adsorption towers and regeneration adsorption towers can effectively intercept different types of impurities such as moisture, oxygen, and hydrocarbons, and the selectivity and adsorption capacity of the adsorbent meet the design requirements.

[0087] Secondly, the switching of regeneration mode is reliable: no indicators exceeded the standard (especially the core impurities were consistently within the standard), indicating that the "dual-tower alternating adsorption-regeneration" mode avoids impurity penetration caused by adsorption saturation, realizes continuous purification without downtime, and ensures the stability of product quality.

[0088] Third, the multi-stage gas-liquid separation + adsorption process effectively removes the vast majority of impurities, achieving high-purity helium recovery.

[0089] Fourth, the detection methods are highly adaptable: the combination of specialized instruments (moisture analyzer, trace O2 analyzer) and gas chromatography (GC) ensures accurate quantification of trace / ultra-micro impurities and verifies the reliability of the detection data, providing reliable support for quality conclusions.

[0090] The stringency of the indicators suggests that the products of this recovery system can meet the requirements of scenarios with extremely high requirements for material purity and impurity control, proving that the system has practical application value.

[0091] With a total purity of 5.7N and impurity control below ppm, it meets the quality requirements of the electronics industry (such as semiconductor manufacturing), high-end chemicals (such as catalyst raw materials), and standard gas preparation, and can replace high-cost virgin high-purity materials, enabling resource recycling and reuse.

[0092] The following is an explanation of the impurity control parameters in Table 1:

[0093] Regarding moisture: Moisture content is expressed in ppm (parts per million) by volume, with an upper limit of ≤0.02ppm. If the actual value is lower than this upper limit, the state is G, and the detection method is a moisture meter (such as a dew point meter or Karl Fischer moisture meter).

[0094] Moisture is one of the most common and harmful impurities in industrial recycling. The strict limits on moisture content are due to: ① preventing moisture from reacting with the target product (e.g., hydrolysis, oxidation), leading to product deterioration; ② preventing moisture from condensing under low temperature or high pressure conditions, causing equipment corrosion and pipeline blockage (especially applicable to gas recovery systems); ③ meeting the requirements of downstream processes for an anhydrous environment (e.g., moisture in electronic component manufacturing can cause product defects, and moisture in chemical reactions can affect catalyst activity). Meeting this standard indicates that the adsorption unit (multi-stage adsorption tower + regeneration adsorption tower) of the recovery system has a strong adsorption capacity for trace amounts of moisture.

[0095] Regarding oxygen: The upper limit of oxygen content is ≤0.01ppm. The actual value is lower than the upper limit. The state is G. The detection method is trace O2 (such as electrochemical sensor, laser spectroscopy).

[0096] The presence of oxygen can cause two types of problems: ① Oxidation reaction risk (e.g., when the target product is an easily oxidized gas / solvent, oxygen can cause product deterioration, aging, or even safety hazards); ② Affect product performance (e.g., in semiconductor manufacturing, trace amounts of oxygen can cause chip oxidation defects; oxygen impurities in high-purity gases can reduce the purity level of materials).

[0097] The stringent upper limit of 0.01 ppm for oxygen content demonstrates the system's ability to deeply remove oxidizing impurities and verifies the effectiveness of the specialized adsorbent in the adsorption tower.

[0098] Regarding nitrogen: The upper limit of nitrogen content is ≤1.00ppm. If the actual value is lower than the upper limit, the status is Class B, and the detection method is GC (gas chromatography).

[0099] Nitrogen is usually an inert gas, but when it exists as an impurity, the consequences are: ① dilution of the purity of the target product (especially in scenarios requiring high purity, nitrogen is the main dilutive impurity); ② impact on process stability (for example, in some catalytic reactions, the accumulation of inert gases can reduce the reaction rate).

[0100] The upper limit of nitrogen index (1 ppm) is higher than that of oxygen, water and other indicators. This is because nitrogen molecules have a stable structure and it is difficult for adsorbents to selectively adsorb nitrogen. The control level of 1 ppm is already a routine and stringent standard for industrial high-purity recovery.

[0101] Regarding total hydrocarbons (THC): the upper limit of content is ≤0.10ppm. If the actual value is lower than the upper limit, the state is B, and the detection method is GC.

[0102] Hydrocarbons (such as methane, ethane, and solvent residues) are organic impurities that may remain during the recycling process. Their hazards include: ① contaminating the target product (e.g., hydrocarbons in high-purity gases can affect combustion efficiency and lead to carbon buildup); ② posing safety risks (some hydrocarbons are flammable and explosive, and may accumulate to the explosion limit in a closed system); ③ failing to meet environmental protection requirements (if the recycled product is used for emission or secondary utilization, excessive hydrocarbons will cause pollution).

[0103] The fact that this indicator meets the standard proves that the multi-stage adsorption tower has sufficient adsorption capacity for organic impurities, and that the desorption and regeneration process of the regeneration adsorption tower can effectively remove the adsorbed hydrocarbons and avoid the accumulation of impurities in the adsorption-regeneration cycle.

[0104] Regarding carbon dioxide + carbon monoxide: The upper limit of the total content of CO2 and CO is ≤0.10ppm. If the actual value is lower than the upper limit, the state is B, and the detection method is GC.

[0105] These two gases are acidic oxides / reducing impurities, and their hazards are manifested in the following ways: ① Corrosion of equipment (CO2 dissolves in water to form carbonic acid, which corrodes pipes and the inner walls of equipment); ② Affecting product quality; in the electronics industry, CO can cause oxidation of metal plating); ③ Environmental compliance risks (CO is a toxic gas, and exceeding emission standards will violate environmental standards).

[0106] The reason for combining the detection of CO2 and CO is that they often coexist in industrial exhaust gases (such as chemical reaction exhaust gases and combustion exhaust gases), and gas chromatography can achieve separation and quantification through the same detection channel. Combining the control of indicators simplifies the detection process and can comprehensively cover the control requirements of carbon oxide impurities.

[0107] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0108] Based on the same inventive concept, embodiments of this application also provide an electronic-grade dichlorosilane and helium recovery system, see [link to relevant documentation]. Figure 2 The method for recovering electronic-grade dichlorosilane and helium includes a buffer tank 1, a compressor 2, a filter 3, a multi-stage gas-liquid separator, a multi-stage adsorption tower 6, a primary membrane separator 7, a compressor 8, a secondary membrane separator 9, and a helium storage tank 10 connected in sequence by pipelines; the multi-stage gas-liquid separator is connected to a liquid dichlorosilane collection tank.

[0109] The system provided by this invention can recover the exhaust gas of electronic-grade dichlorosilane and helium, which can minimize exhaust gas emissions, reduce energy consumption and environmental pollution. At the same time, it can efficiently recover useful substances in the exhaust gas and purify them to a purity standard that can be reused in the production of electronic-grade products, thereby achieving the purpose of resource recycling, reducing production costs, and improving the economic and environmental benefits of enterprises.

[0110] In some embodiments, see Figure 2 The multi-stage gas-liquid separator includes a first-stage gas-liquid separator 4 and a second-stage gas-liquid separator 5 connected in series. The first-stage gas-liquid separator 4 is connected to a first collection tank 11 via a pipeline, and the second-stage gas-liquid separator 5 is connected to a second collection tank 12 via a pipeline. The first collection tank 11 and the second collection tank 12 are connected to a liquid dichlorosilane collection tank via pipelines. Liquid dichlorosilane condensed to different temperatures is stabilized in its respective collection tank and then flows into the liquid dichlorosilane collection tank for subsequent treatment or reuse.

[0111] In some embodiments, see Figure 2 The recovery system also includes a regeneration adsorption tower, which is connected in parallel with the multi-stage adsorption tower 6 between the multi-stage gas-liquid separator and the primary membrane separator 7, allowing the recovery system to switch between the regeneration adsorption tower and the multi-stage adsorption tower 6. The regeneration adsorption tower and the multi-stage adsorption tower 6 have the same internal structure and function, and are connected in parallel within the recovery system (see reference). Figure 2 However, no attached diagram of the regeneration adsorption tower was provided.

[0112] The recycling system provided by this invention is equipped with two adsorption towers, which can be periodically switched for regeneration to ensure the continuity of recycling and improve the recycling effect, as detailed below:

[0113] When a multi-stage adsorption tower needs to be regenerated due to adsorption saturation, it can be directly switched to the regeneration adsorption tower for operation without interrupting the feeding and separation process of the entire recovery system. This ensures the continuity of material recovery in industrial production and is especially suitable for continuous production scenarios with high requirements for operational stability, significantly reducing capacity loss and material waste caused by downtime.

[0114] This avoids the decrease in adsorption capacity caused by long-term saturation and lack of treatment of the adsorbent, and ensures that each set of towers is in the optimal adsorption state when put into use, thereby improving the adsorption selectivity and recovery rate of the target components.

[0115] In addition, the parallel design of the two towers can prevent the entire system from shutting down due to the failure of a single tower, thus improving the operational reliability of the recycling system and reducing production risks.

[0116] The recycling system provided by this invention is equipped with temperature sensors, pressure sensors, level gauges, and electrically controlled valves. It employs a DCS (Distributed Control System) automatic control system, enabling real-time monitoring and automatic adjustment of process parameters, reducing manual intervention, and improving system stability and reliability. This DCS automatic control system is a type of industrial automation control system based on a distributed architecture. It is a conventional technical means and is not the inventive point or scope of protection of this invention; therefore, it will not be described in detail herein.

[0117] The beneficial effects of the electronic-grade dichlorosilane and helium recovery system and method provided by this invention are as follows:

[0118] (1) High recovery rate: Through a series of steps such as condensation separation, adsorption purification and membrane separation, the helium recovery rate can reach more than 95%, which greatly improves the utilization rate of helium and reduces production costs.

[0119] (2) High purity: After being processed by the recycling system of the present invention, the purity of helium can reach more than 99.999%, which meets the strict requirements of high-end fields such as semiconductor manufacturing for helium purity, and ensures the stability of the process and product quality.

[0120] (3) Environmental protection and energy saving: It realizes the recycling of helium, reduces helium emissions, and conforms to the concept of environmental protection.

[0121] (4) Cost-effectiveness: It reduces the need for purchasing new helium, thereby lowering the company's operating costs. Furthermore, the equipment investment in the recycling system can be quickly recouped through the recycling of helium during long-term operation, demonstrating good cost-effectiveness.

[0122] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for recovering electronic-grade dichlorosilane and helium, characterized in that, The recycling method includes: The exhaust gas containing dichlorosilane and helium is filtered to remove solid particulate impurities. By taking advantage of the difference in boiling points between dichlorosilane and helium, the tail gas after removing solid particulate impurities is condensed through multi-stage gas-liquid separation to obtain liquid dichlorosilane and preliminarily separated gaseous helium. After initial separation, the gaseous helium undergoes multi-stage adsorption to remove residual organic and inorganic impurities. The helium gas, after impurities have been removed, is then separated through a multi-stage membrane process to remove any remaining impurities, yielding high-purity helium gas. The process of removing solid particulate impurities from the exhaust gas and then condensing it through multi-stage gas-liquid separation to obtain liquid dichlorosilane and preliminarily separated gaseous helium includes: The exhaust gas after removing solid particulate impurities is sent to the first-stage gas-liquid separator (4) and cooled to -30°C to obtain liquid dichlorosilane, which is then sent to the first collection tank (11) for storage. The tail gas separated by the first-stage gas-liquid separator (4) enters the second-stage gas-liquid separator (5), is cooled to -50℃, and is separated into gas and liquid again. The resulting liquid dichlorosilane is sent to the second collection tank (12) for storage. The initially separated gaseous helium undergoes multi-stage adsorption, including: Helium gas in a gaseous state is introduced into a multi-stage adsorption tower (6) to remove organic and inorganic impurities in stages. The multi-stage adsorption tower (6) is filled from bottom to top with 3A molecular sieve, modified activated carbon layer and activated carbon fiber. The activated carbon fiber is used to adsorb residual organic impurities in helium; the modified activated carbon is used to adsorb some inorganic impurities in helium; the 3A molecular sieve is used to remove small molecule impurities of carbon and water from inorganic impurities, so as to treat carbon dioxide and water in helium to <0.5ppm. The process of removing impurities from helium gas through multi-stage membrane separation includes: The helium gas, after impurities have been removed, enters the primary membrane separator (7) for coarse separation, separating most of the nitrogen gas and hydrocarbons from the organic impurities in the helium gas; The helium separated by the primary membrane separator (7) is pressurized by the compressor (8) and then enters the secondary membrane separator (9) for purification, separating the residual impurity gas in the helium and obtaining high-purity helium.

2. The method for recovering electronic-grade dichlorosilane and helium as described in claim 1, characterized in that, The process of removing solid particulate impurities from the tail gas containing dichlorosilane and helium by filtration includes: The tail gas containing dichlorosilane and helium is introduced into the buffer tank (1), pressurized to 0.2-1.0 MPa by the pressurizer (2), and then enters the 0.1 μm filter (3) to remove solid particulate impurities.

3. The method for recovering electronic-grade dichlorosilane and helium as described in claim 1, characterized in that, The adsorption temperature in the multi-stage adsorption tower (6) is 25-50℃, and the gas flow rate is 0.3-0.8m / s.

4. The method for recovering electronic-grade dichlorosilane and helium as described in claim 1, characterized in that, The primary membrane separator (7) is equipped with a hollow fiber membrane module, and the secondary membrane separator (9) is equipped with a high-performance composite membrane module.

5. A system for recovering electronic-grade dichlorosilane and helium, used in the method for recovering electronic-grade dichlorosilane and helium as described in any one of claims 1-4, characterized in that, It includes a buffer tank (1), a compressor (2), a filter (3), a multi-stage gas-liquid separator, a multi-stage adsorption tower (6), a primary membrane separator (7), a compressor (8), a secondary membrane separator (9), and a helium storage tank (10) connected in sequence by pipelines; the multi-stage gas-liquid separator is connected to a liquid dichlorosilane collection tank.

6. The electronic-grade dichlorosilane and helium recovery system as described in claim 5, characterized in that, The multi-stage gas-liquid separator includes a first-stage gas-liquid separator (4) and a second-stage gas-liquid separator (5) connected in series. The first-stage gas-liquid separator (4) is connected to a first collection tank (11) via a pipeline, and the second-stage gas-liquid separator (5) is connected to a second collection tank (12) via a pipeline. The first collection tank (11) and the second collection tank (12) are connected to the liquid dichlorosilane collection tank via pipelines. Liquid dichlorosilane condensed to different temperatures is stabilized in its respective collection tank and then flows into the liquid dichlorosilane collection tank.

7. The electronic-grade dichlorosilane and helium recovery system as described in claim 6, characterized in that, The recovery system also includes a regeneration adsorption tower, which is connected in parallel with the multi-stage adsorption tower (6) between the multi-stage gas-liquid separator and the primary membrane separator (7) so that the recovery system can switch between the regeneration adsorption tower and the multi-stage adsorption tower (6).

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