Method and system for recycling hydrogen in mixed gas by using pressure swing adsorption

Abstract

The invention relates to the technical field of gas separation and purification, in particular to a method and system for recycling hydrogen in mixed gas through pressure swing adsorption. The method comprises the following steps: performing multi-layer adsorption impurity removal on mixed gas containing 20-25% of silane, 10-15% of disilane and 60-70% of hydrogen, and cooling to 22-28 DEG C; the mixed gas subjected to primary impurity removal enters a pressure swing adsorption device, and an adsorbent in the adsorption device is modified activated carbon. The system comprises a mixed gas cylinder, a pretreatment unit, a pressure swing adsorption unit and a hydrogen collection unit which are connected in sequence. By adopting the pressure swing adsorption method, the hydrogen recovery rate is remarkably increased and can reach 93%, the purity can reach 99.2% or above, and the strict requirement of high-end industrial production for high-purity hydrogen can be met.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of gas separation and purification, in particular to a method and system for recovering hydrogen from mixed gas by pressure swing adsorption. BACKGROUND

[0002] In the fields of cutting-edge technologies such as semiconductor manufacturing, photovoltaic material production, and special gas preparation, silane (SiH4) and disilane (Si2H6) are important silicon source gases, which are often used in key process steps such as chemical vapor deposition (CVD) and epitaxial growth. Their usage is growing exponentially with the rapid development of new energy and electronic industries. At the same time, a large amount of mixed gas containing silane, disilane, and hydrogen (H2) is inevitably produced during the production process. Hydrogen is not only the core carrier of hydrogen energy economy, but also an indispensable reducing gas in fields such as chemical synthesis, metal smelting, and electronic device manufacturing. Silane and disilane can be reused after recovery, significantly reducing the cost of raw materials for enterprises. Therefore, efficient separation and recovery of each component in this type of mixed gas not only conforms to the concept of circular economy, but also effectively alleviates China's dependence on imported high-purity gases, which has important strategic significance for promoting the green and high-quality development of related industries.

[0003] Currently, the main methods for separating hydrogen from mixed gas in industry include pressure swing adsorption (PSA), membrane separation, cryogenic separation, and metal hydride adsorption. Although the pressure swing adsorption method has the characteristics of flexible operation and low energy consumption, the selective adsorption capacity of traditional adsorbents for silane and disilane is limited, and the hydrogen recovery rate is easily affected in the presence of high-concentration silane and disilane. Although the metal hydride adsorption method can achieve high-purity separation of hydrogen, the adsorption-desorption cycle time is long, and the cost of metal materials is high, which limits its industrial application.

[0004] In actual production, the composition and operating conditions of mixed gas have significant volatility. When the composition of mixed gas approaches the limit value, or the operating parameters are in the boundary condition, the limitations of existing separation technologies are more prominent. The traditional pressure swing adsorption process may cause a sharp drop in hydrogen purity due to adsorbent overload. In addition, the equipment failure rate increases significantly under extreme conditions, and the maintenance cost increases substantially, making it difficult for existing technologies to meet the needs of continuous and stable production.

[0005] Therefore, developing a new process that can adapt to complex conditions and achieve efficient separation and recovery of hydrogen, while solving the technical bottlenecks of existing technologies under extreme conditions, has become a key problem that needs to be overcome in this field. SUMMARY

[0006] In view of the problems that the existing industrial production method cannot adapt to complex working conditions, the separation efficiency is low, and the production cost is high, the application provides a new process which can adapt to complex working conditions and realize efficient separation and recovery of hydrogen, and solves the technical bottleneck of the prior art under extreme conditions. The technical scheme of the application is as follows:

[0007] In one aspect, the application provides a method for recovering hydrogen from a mixed gas by using pressure swing adsorption, comprising the following steps:

[0008] Step S1. Preliminary impurity removal: the mixed gas containing 20%-25% silane, 10%-15% disilane and 60-70% hydrogen is subjected to multi-layer adsorption impurity removal and cooled to 22-28℃;

[0009] Step S2. Pressure swing adsorption: the mixed gas subjected to preliminary impurity removal is introduced into a pressure swing adsorption device for pressure swing adsorption to recover hydrogen, and the adsorbent in the adsorption device is modified activated carbon.

[0010] Preferably, the modified activated carbon is modified activated carbon activated at high temperature and loaded with 3%-5% copper oxide on the surface.

[0011] Preferably, the high-temperature activation process is as follows: the activated carbon is placed in a high-temperature furnace protected by inert gas or nitrogen, heated to 820-900℃ at a heating rate of 5-10℃ / min, and held for 2-3 hours; copper oxide is loaded by using an equal-volume impregnation method, copper nitrate solution is uniformly impregnated on the activated activated carbon, dried at 80-100℃ for 12-16 hours, and then calcined at 320-400℃ for 3.2-4 hours to obtain modified activated carbon adsorbent. The specific surface area of the modified activated carbon adsorbent reaches 1500m 2 / g or more, and the pore size is concentrated in the range of 0.8-1.5nm.

[0012] Preferably, in step S1, the multi-layer adsorption includes a first rough filtration layer and a second fine filtration layer, the filtration precision of the first rough filtration layer is 1μm, and the precision of the second fine filtration layer is 0.05μm.

[0013] Preferably, in step S2, the flow rate of the mixed gas is controlled at 10-20L / min, and the composition of the mixed gas is monitored in real time to ensure that the proportion of each component fluctuates within ±0.5%;

[0014] Preferably, in step S2, the pressure swing adsorption controls the adsorption pressure at 0.6-0.8MPa, and the pressure rise rate is maintained at 0.06-0.08MPa / min; the desorption pressure is 0.05-0.1MPa, and the pressure drop rate is 0.12-0.15MPa / min.

[0015] Preferably, in step S2, the purity of hydrogen output from the pressure swing adsorption device is monitored in real time during the pressure swing adsorption process, and when the purity is lower than 99%, the system automatically fine-tunes the adsorption time by 1-3 minutes.

[0016] In another aspect, the application provides a system for recovering hydrogen from mixed gas by pressure swing adsorption, comprising a mixed gas cylinder, a pretreatment unit, a pressure swing adsorption unit, and a hydrogen collection unit connected in sequence, wherein the pretreatment unit comprises a first filter and a second filter connected in series, and a cooler is arranged outside the first filter and the second filter; the pressure swing adsorption unit comprises at least three adsorption towers arranged in parallel; and the hydrogen collection unit comprises a primary buffer tank and a secondary buffer tank connected in series, and the secondary buffer tank is connected to a hydrogen storage device.

[0017] The application has the following beneficial effects:

[0018] The application can significantly improve the hydrogen recovery rate to more than 93% and the purity to 99.2%, which can meet the strict demand for high-purity hydrogen in high-end industrial production. The special modified activated carbon adsorbent of the application is activated at high temperature and loaded with copper oxide, which optimizes the physical and chemical properties of the adsorbent, and the high specific surface area and specific pore size distribution, as well as the interaction between copper oxide and silane and disilane, greatly enhance the adsorption capacity of silane and disilane. Meanwhile, precise control of the pressure swing adsorption parameters further improves the adsorption and desorption efficiency.

[0019] The application can reduce the energy consumption by about compared with the traditional technology through precise pressure control and optimized design of the equipment, thereby effectively saving the production cost.

[0020] The application has greatly improved equipment stability, prolonged mean time between failures, reduced equipment maintenance frequency and downtime, and improved production efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0021] ATTACHMENT Figure 1 FIG. 1 is a diagram of a system for recovering hydrogen from mixed gas by pressure swing adsorption according to the application.

[0022] FIG. 1 is a diagram of a system for recovering hydrogen from mixed gas by pressure swing adsorption according to the application. DETAILED DESCRIPTION

[0023] For further elaboration of the technical means and effects taken by the present application to achieve the predetermined invention purposes, the specific embodiments, structures, features and effects thereof according to the present application are described in detail as follows in combination with the drawings and preferred embodiments.

[0024] Device embodiment

[0025] The present embodiment provides a device, referring to Figure 1 , specifically as follows: comprising sequentially connected mixed gas bottle 1, pretreatment unit 2, pressure swing adsorption unit 5 and hydrogen collection unit 6, the pretreatment unit 2 is connected in series between first filter 21 and second filter 22, and a cooler 23 is arranged outside the first filter 21 and the second filter 22; the pressure swing adsorption unit 5 at least comprises three adsorption towers 51 arranged in parallel; the hydrogen collection unit 6 comprises a first-stage buffer tank 61 and a second-stage buffer tank 62 connected in series, and the second-stage buffer tank 62 is communicated with a hydrogen storage device 7.

[0026] The device implementation principle is as follows:

[0027] Step S1. A mixed gas containing 20%-25% silane, 10%-15% disilane and 60-70% hydrogen is introduced into the pretreatment unit 2, wherein the pretreatment unit 2 is provided with a first filter 21 and a second filter 22, wherein the first filter 21 is provided with a first rough filtration layer and the second filter 22 is provided with a second fine filtration layer, the filtration accuracy of the first rough filtration layer is 1 μm, and the filtration accuracy of the second fine filtration layer is 0.05 μm; at the same time, a cooler 23 is used to cool the mixed gas, the cooler 23 is a air-cooled cooler 23, the temperature of the mixed gas is maintained at 22-28℃, the cooler 23 is equipped with a temperature self-adaptive control system, which automatically adjusts the flow and temperature of the cooling medium according to the real-time temperature and flow of the mixed gas, to ensure the cooling effect of the mixed gas; the cooler 23 is made of corrosion-resistant aluminum alloy material, and the surface is treated with a corrosion-resistant coating to prolong the service life of the equipment; the pretreatment unit 2 is provided with an automatic backflushing system for impurities, when the pressure difference before and after the filter reaches a set threshold, the backflushing program is automatically started to remove impurities in the filter core by using compressed nitrogen, so as to ensure the stability of the filtration performance.

[0028] Step S2. The mixed gas is then introduced into the pressure swing adsorption unit 5, and the mixed gas flow is stably controlled at 10-20 L / min by means of the high-precision gas mass flow meter 3, while the composition of the mixed gas is monitored in real time to ensure that the proportion of each component fluctuates within ±0.5%. The pressure swing adsorption unit 5 includes at least three parallel adsorption towers 51, which are connected by an automatic valve group. According to the mixed gas flow, the composition change, and the adsorbent saturation degree, the self-control system is used to dynamically adjust the switching time of the adsorption tower 51, with a range of 1.5-4 minutes, to ensure continuous and efficient operation of the device. A built-in rotary gas agitator is used in each adsorption tower 51, and the stirring rate is dynamically adjusted according to the mixed gas flow and the pressure in the adsorption tower 51, with a range of 60-90 r / min. The agitator blades are designed with a curved surface to enhance the gas mixing effect, promote the full contact between the mixed gas and the adsorbent, and improve the adsorption efficiency. The adsorption tower 51 is made of high-strength stainless steel 316L, and the inner wall is electrolytically polished to a roughness of Ra0.5 μm.

[0029] Step S3. The hydrogen gas from the pressure swing adsorption unit 5 enters the hydrogen gas collection unit 6, which includes a first-stage buffer tank 61 and a second-stage buffer tank 62 connected in series. The first-stage buffer tank 61 has a volume of 60 L, and the second-stage buffer tank 62 has a volume of 80 L, and is equipped with a pressure stabilizing valve to stabilize the output hydrogen gas pressure at 0.5-0.6 MPa. At the same time, a hydrogen gas online analyzer 4 is used to detect the purity of the hydrogen gas.

[0030] Methods Examples 1-4 are based on the device provided in Device Example 1, and the specific operations are as follows:

[0031] Example 1

[0032] Step S1. Preliminary impurity removal: The mixed gas containing 20% silane, 10% disilane, and 70% hydrogen is sequentially filtered through a multi-layer composite filter and an air-cooled cooler. The coarse filter layer and the fine filter layer of the filter work together to effectively remove impurities. The first coarse filter layer has a filtration accuracy of 1 μm, and the second fine filter layer has an accuracy of 0.05 μm. The cooler reduces the temperature of the mixed gas to 25°C, and the dynamic flow distributor ensures uniform flow in each branch to ensure consistency in pretreatment effect. The proportion of each component is then controlled within ±0.5% by means of a high-precision gas mass flow meter and a gas composition analyzer, and the flow is stabilized at 15 L / min.

[0033] Step S2. Pressure swing adsorption: the pretreated mixed gas is introduced into the pressure swing adsorption device, which uses three adsorption towers to operate alternately. The adsorption pressure is set to 0.7 MPa, the pressure rise rate is controlled at 0.07 MPa / min, the desorption pressure is 0.08 MPa, and the pressure drop rate is 0.13 MPa / min. The adsorption tower switching time is adjusted to 2.5 minutes according to the fuzzy control algorithm, and at the same time, the built-in rotary gas stirrer is operated at an appropriate speed to improve the contact efficiency of the mixed gas and the adsorbent, enhance the adsorption effect, and realize efficient and stable adsorption and desorption process. After stabilizing the pressure by double-stage buffer tank, the purity of the collected hydrogen gas reaches 99.2%, and the recovery rate is 93%.

[0034] The adsorbent in the pressure swing adsorption device is modified activated carbon with 3% copper oxide loaded on the surface after high-temperature activation, with a specific surface area of 1550 m 2 / g, and pore size concentrated in 0.8-1.2 nm; the high-temperature activation process is: placing the activated carbon in a high-temperature furnace under nitrogen protection, heating to 850°C at a rate of 6°C / min, and holding for 2.5 hours; loading copper oxide uses the equal volume impregnation method, evenly impregnating the calculated copper nitrate solution (mass fraction of 8%) on the activated activated carbon, drying at 90°C for 14 hours, and then calcining at 350°C for 3.5 hours.

[0035] Example 2

[0036] Step S1. Preliminary impurity removal: the mixed gas containing 22% silane, 10% disilane, and 68% hydrogen is filtered through a multi-layer composite filter and an air-cooled cooler in sequence. The coarse filter layer and the fine filter layer of the filter work together to effectively remove impurities, with a filtration accuracy of 1 μm for the first coarse filter layer and 0.05 μm for the second fine filter layer. The cooler stabilizes the temperature of the mixed gas at 23°C, ensuring the smooth progress of the subsequent pressure swing adsorption process. Then, through a high-precision gas mass flowmeter and a gas component analyzer, the proportion deviation of each component is controlled within ±0.8%, and the flow rate is stabilized at 12 L / min.

[0037] Step S2. Pressure swing adsorption: the adsorption pressure is set to 0.65 MPa, the desorption pressure is 0.06 MPa, and the adsorption tower switching time is 3 minutes. At the same time, the built-in rotary gas stirrer is operated at an appropriate speed to improve the contact efficiency of the mixed gas and the adsorbent, enhance the adsorption effect, and the purity of the collected hydrogen gas is 99.1%, and the recovery rate is 92%.

[0038] The adsorbent in the pressure swing adsorption device is modified activated carbon with 3% copper oxide loaded on the surface after high-temperature activation, with a specific surface area of 1550 m 2The activated carbon is heated to 880 °C at a heating rate of 8 °C / min under argon protection, and is kept for 2.8 hours; when the copper oxide is loaded, the activated carbon is immersed in a copper nitrate solution (8% by mass fraction), dried at 95 °C for 15 hours, and calcined at 400 °C for 4 hours.

[0039] Example 3 (extreme mixed gas composition working condition)

[0040] Step S1. Preliminary impurity removal: the mixed gas containing 25% silane, 15% disilane and 60% hydrogen is filtered through a multi-layer composite filter and an air-cooled cooler in sequence. The coarse filter layer and the fine filter layer of the filter work together to effectively remove impurities. The filtering precision of the first coarse filter layer is 1 μm, and the precision of the second fine filter layer is 0.05 μm. The air-cooled cooler is operated at full capacity to regulate the temperature of the mixed gas to 22 °C. The dynamic flow distributor finely adjusts the flow of each branch according to the low temperature and low flow state to maintain the uniformity of the pretreatment. Then, the proportion deviation of each component is controlled within ±0.5% by a high-precision gas mass flow meter and a gas composition analyzer, and the flow is stabilized at 10 L / min.

[0041] Step S2. Pressure swing adsorption: the pressure swing adsorption device is introduced, and the adsorption tower switching time is shortened to 1.5 minutes to meet the adsorption needs of high-concentration impurity gas. The adsorption pressure is increased to 0.8 MPa, and the pressure rise rate is accelerated to 0.08 MPa / min to promote the rapid adsorption of silane and disilane by the adsorbent. The desorption pressure is reduced to 0.05 MPa, and the pressure drop rate is increased to 0.15 MPa / min to enhance the desorption effect. The rotation speed of the built-in rotary gas stirrer is increased to 90 r / min to strengthen the contact between the mixed gas and the adsorbent. After pressure stabilization by the double-stage buffer tank, the purity of the collected hydrogen gas reaches 99%, and the recovery rate is 90%. Although in the extreme mixed gas composition working condition, the method and system of the present application can still realize the recovery of high-purity hydrogen gas, showing good adaptability.

[0042] The adsorbent in the pressure swing adsorption device is modified activated carbon with high-temperature activation and 5% copper oxide loaded on the surface, with a specific surface area of 1580 m 2 / g, and pore size concentrated in 1.0-1.5 nm; the high-temperature activation is to heat the activated carbon to 860 °C at a heating rate of 7 °C / min under helium protection, and keep for 2.2 hours; in the operation of loading copper oxide, the immersion is dried at 85 °C for 13 hours, and calcined at 380 °C for 3.8 hours.

[0043] Example 4 (extreme temperature and pressure working condition)

[0044] Step S1. Preliminary impurity removal: the mixed gas containing silane 21%, disilane 11%, hydrogen 68% is rapidly cooled from 40°C to 28°C under the influence of extreme ambient temperature, which puts a huge load on the air-cooled cooler. The automatic backflushing system for impurities is frequently started to ensure that the performance of the filter is not affected. The control component ratio deviation is within ±0.5%, and the flow rate is stabilized at 20 L / min.

[0045] Step S2. Pressure swing adsorption: the pressure control unit of the pressure swing adsorption unit quickly responds to the severe fluctuations in external pressure. The adsorption pressure is frequently adjusted between 0.6-0.8 MPa, and the pressure rise rate dynamically changes between 0.06-0.08 MPa / min according to the real-time pressure fluctuations; the desorption pressure is flexibly adjusted between 0.05-0.1 MPa, and the pressure drop rate changes between 0.12-0.15 MPa / min accordingly. The intelligent valve group accurately controls the switching time of the adsorption tower according to the pressure changes and the conditions inside the adsorption tower, and dynamically adjusts it between 1.5-3 minutes. The output pressure is stabilized by the double-stage buffer tank and pressure stabilizing valve, the hydrogen purity is maintained at 99.1%, and the recovery rate reaches 91%. Under extreme temperature and pressure conditions, the system can still operate stably and achieve good hydrogen recovery effect, verifying the reliability and stability of the system.

[0046] The adsorbent in the pressure swing adsorption device is modified activated carbon with 3.5% copper oxide loaded on the surface after high-temperature activation, with a specific surface area of 1560 m 2 / g, and pore size concentrated in 0.8-1.3 nm; during high-temperature activation, the activated carbon is heated to 820°C at a rate of 5°C / min under nitrogen protection, and kept for 3 hours; the copper oxide is loaded by the equal-volume impregnation method, the copper nitrate solution (mass fraction 8%) is impregnated, dried at 80°C for 16 hours, and calcined at 320°C for 3.2 hours.

[0047] The above is only a preferred embodiment of the present application, and does not limit the present application in any form. Although the preferred embodiment has been disclosed as above, it is not intended to limit the present application. Any person skilled in the art can make some changes or modifications to the above disclosed technical content without departing from the scope of the technical solution of the present application, and any equivalent embodiments with equivalent changes and modifications are equivalent to the above embodiments. Any modification, change, equivalent change and modification of the above embodiments made in accordance with the technical essence of the present application are still within the scope of the technical solution of the present application.

Claims

1. A method for recovering hydrogen from a mixed gas by pressure swing adsorption, characterized by, It comprises the following steps: Step S1. Preliminary impurity removal: the mixed gas containing 20-25% silane, 10-15% disilane and 60-70% hydrogen is subjected to multi-layer adsorption impurity removal and cooled to 22-28℃; Step S2. Pressure swing adsorption: the mixed gas subjected to preliminary impurity removal is introduced into a pressure swing adsorption device for pressure swing adsorption to recover hydrogen, and the adsorbent in the adsorption device is modified activated carbon.

2. The method for recovering hydrogen from a mixed gas by pressure swing adsorption according to claim 1, wherein The modified activated carbon is modified activated carbon activated at high temperature and loaded with 3-5% copper oxide on the surface.

3. The method for recovering hydrogen from a mixed gas by pressure swing adsorption according to claim 2, characterized by, The high-temperature activation process is: placing the activated carbon in an inert gas or nitrogen-protected high-temperature furnace, heating to 820-900℃ at a heating rate of 5-10℃ / min, and keeping the temperature for 2-3 hours; the copper oxide loading uses an equal-volume impregnation method, uniformly impregnating a copper nitrate solution on the activated activated carbon, drying at 80-100℃ for 12-16 hours, and then calcining at 320-400℃ for 3.2-4 hours to obtain the modified activated carbon adsorbent, the specific surface area of the modified activated carbon adsorbent reaching 1500m 2 / g or more, and the pore size is concentrated in the range of 0.8-1.5nm.

4. The method for recovering hydrogen from a mixed gas by pressure swing adsorption according to claim 1, characterized by, In step S1, the multi-layer adsorption includes a first rough filtration layer and a second fine filtration layer, the filtration precision of the first rough filtration layer is 1 μm, and the precision of the second fine filtration layer is 0.05 μm.

5. The method for recovering hydrogen from a mixed gas by pressure swing adsorption according to claim 1, characterized by, In step S2, the flow rate of the mixed gas is controlled to be 10-20 L / min, and the composition of the mixed gas is monitored in real time to ensure that the fluctuation of the proportion of each component is within ±0.5%.

6. The method for recovering hydrogen from a mixed gas by pressure swing adsorption according to claim 1, wherein In step S2, the adsorption pressure of the pressure swing adsorption is controlled to be 0.6-0.8 MPa, and the pressure rise rate is maintained at 0.06-0.08 MPa / min; the desorption pressure is 0.05-0.1 MPa, and the pressure drop rate is 0.12-0.15 MPa / min.

7. The method for recovering hydrogen from a mixed gas by pressure swing adsorption according to claim 1, wherein In step S2, during the pressure swing adsorption process, the purity of the hydrogen gas output from the pressure swing adsorption device is monitored in real time, and when the purity is lower than 99%, the system automatically adjusts the adsorption time by 1-3 minutes.

8. A system for recovering hydrogen from a mixed gas by pressure swing adsorption, for the method for recovering hydrogen from a mixed gas by pressure swing adsorption according to any one of claims 1 to 7, characterized by It comprises a mixed gas cylinder, a pretreatment unit (2), a pressure swing adsorption unit (5) and a hydrogen gas collection unit (6) connected in sequence, the pretreatment unit (2) comprises a first filter (21) and a second filter (22) connected in series, and a cooler (23) is arranged outside the first filter (21) and the second filter (22); the pressure swing adsorption unit (5) comprises at least three adsorption towers (51) arranged in parallel; the hydrogen gas collection unit (6) comprises a first-stage buffer tank (61) and a second-stage buffer tank (62) connected in series, and the second-stage buffer tank (62) is connected to a hydrogen gas storage device (7).

Images