A renewable SF6 drying device based on nanomaterials with high thermal conductivity and its implementation method

Abstract

The application relates to a renewable SF6 drying device based on nanometer high-thermal-conductivity material and an implementation method thereof, wherein the renewable SF6 drying device based on nanometer high-thermal-conductivity material comprises a composite drying agent module for drying SF6, the composite drying agent module comprises a drying tower with an SF6 inlet and an SF6 outlet, one side of the drying tower close to the SF6 inlet is a pretreatment zone, the pretreatment zone is filled with lower-layer drying agents, one side of the drying tower close to the SF6 outlet is a deep drying zone, the deep drying zone is filled with upper-layer drying agents, the lower-layer drying agents are composed of active alumina and 5% nanometer boron nitride in mass ratio, and the upper-layer drying agents are composed of 4A molecular sieve and 3% nanometer silicon carbide in mass ratio. The application solves the technical bottlenecks of slow regeneration, high energy consumption and uneven heating of a traditional SF6 drying device, and is particularly suitable for the fields of power equipment maintenance and SF6 gas recovery and purification.

Description

Technical Field

[0001] This invention relates to the field of high-voltage electrical equipment maintenance and special gas treatment technology, specifically to a regenerative drying device for SF6 gas and its implementation method that utilizes nano-high thermal conductivity materials to significantly improve regeneration efficiency and energy efficiency. Background Technology

[0002] SF6 gas is an indispensable insulating and arc-extinguishing medium in high-voltage switchgear. The moisture content of SF6 gas must be strictly controlled, usually requiring a dew point of ≤-40℃ to -60℃, to prevent the equipment insulation from deteriorating and the generation of toxic byproducts.

[0003] Currently, the following methods are mainly used in industry to dry SF6 gas:

[0004] Molecular sieve / alumina fixed bed adsorption: This is the most commonly used method. However, traditional desiccants, such as ordinary 4A molecular sieves and activated alumina, have extremely low thermal conductivity, usually only <0.5 W / (m·K), resulting in serious technical bottlenecks in the regeneration process: a) Long regeneration time, usually requiring more than 8-12 hours, resulting in high energy consumption; b) Uneven heating, which easily causes local overheating (hot spots) in the desiccant bed and permanent deactivation, while some areas are not completely regenerated (cold spots); c) Regeneration energy consumption accounts for more than 60% of the total equipment operating cost.

[0005] Freeze-drying: extremely energy-intensive and cannot achieve the requirements of deep drying; it is usually only used as a pretreatment.

[0006] Membrane separation: It has low separation efficiency for high-boiling-point gases such as SF6, and the equipment is expensive.

[0007] The above-mentioned problems with existing technologies can be summarized as follows: The core contradiction of traditional adsorption drying devices lies in the low thermal conductivity caused by the desiccant itself and the bed structure, which seriously restricts regeneration efficiency and energy consumption, and affects the long-term operational stability of the system and the lifespan of the desiccant. Summary of the Invention

[0008] In view of the shortcomings of the prior art, the purpose of this invention is to provide a renewable SF6 drying device and its implementation method based on nano-high thermal conductivity materials. This renewable SF6 drying device and its implementation method based on nano-high thermal conductivity materials can improve the thermal conductivity, adsorption efficiency and stability of the desiccant.

[0009] The technical solution of this invention:

[0010] A renewable SF6 drying device based on nanomaterials with high thermal conductivity is characterized by comprising a composite desiccant module for drying SF6. The composite desiccant module includes a drying tower with an SF6 inlet and an SF6 outlet. The side of the drying tower near the SF6 inlet is a pretreatment zone filled with a lower layer of desiccant. The side of the drying tower near the SF6 outlet is a deep drying zone filled with an upper layer of desiccant. The lower layer of desiccant is composed of activated alumina and 5% by mass of nano-sized boron nitride (BN), with a thermal conductivity of not less than 400 W / (m·K). The upper layer of desiccant is composed of 4A molecular sieve and 3% by mass of nano-sized silicon carbide (SiC), with a thermal conductivity of not less than 120 W / (m·K).

[0011] Furthermore, the pretreatment zone and deep drying zone of the aforementioned drying tower are also equipped with temperature sensors, semiconductor heat sinks, and heating coils. The temperature sensors are used to monitor the internal temperature of the desiccant; the semiconductor heat sinks are used to dissipate the adsorption heat generated during the desiccant adsorption process; and the heating coils are used to maintain a constant temperature of the desiccant bed during the adsorption stage and to assist in heating the bed during the regeneration stage.

[0012] Furthermore, the temperature of the pretreatment zone is maintained at 30℃±1℃ to maximize the adsorption rate of the desiccant under medium and high humidity conditions; the temperature of the deep drying zone is maintained at 20℃±1℃ to ensure deep dehydration capability under low humidity conditions.

[0013] Furthermore, it also includes a heating and regeneration module, which includes a heating element for heating and generating regenerating hot air and a conveying pipe for sending the regenerating hot air into the pretreatment zone and deep drying zone inside the drying tower. The conveying pipe is connected to the SF6 main gas line through a valve, and the SF6 main gas line is connected to the SF6 inlet. The surface of the heating element is coated with a nano boron nitride (BN) high thermal conductivity coating, which has a thermal conductivity ≥120 W / (m·K), to achieve rapid and uniform heat diffusion and reduce the contact thermal resistance between the heat source and the hot air.

[0014] Furthermore, it also includes a control system, in which the semiconductor heat sink and heating coil are controlled by PID intelligent cycle control to ensure that the temperature uniformity deviation in the pretreatment zone and the deep drying zone is ≤±1℃ and the volumetric efficiency deviation is ≤0.5%.

[0015] Furthermore, the aforementioned heating and regeneration module is connected to the control system to control the regeneration temperature at 170-250°C.

[0016] Furthermore, it also includes an intelligent monitoring and alarm module connected to the control system. The intelligent monitoring and alarm module includes a temperature sensor installed inside the composite desiccant module, an SF6 leak detection probe installed at the gas outlet of the device, an over-temperature alarm unit, and an SF6 leak audible and visual alarm unit.

[0017] The core innovation of this invention lies in the creative use of nano-boron nitride (BN) and silicon carbide (SiC) high thermal conductivity materials as functional engineering materials. By adding an external temperature control device to the existing "4A molecular sieve + activated alumina + nano-high thermal conductivity materials" structure, drying performance is significantly improved. The temperature control device eliminates the interference of ambient temperature fluctuations on adsorption, while the nano-high thermal conductivity materials enhance the uniformity of heat transfer within the bed. Together, they form a dual guarantee of "stable external temperature + uniform internal temperature," maximizing the adsorption efficiency and stability of the desiccant from a temperature control perspective. This invention solves the technical bottlenecks of traditional SF6 drying devices, such as slow regeneration, high energy consumption, and uneven heat distribution, and is particularly suitable for power equipment maintenance and SF6 gas recovery and purification.

[0018] This invention relates to a method for drying renewable SF6 based on nanomaterials with high thermal conductivity, comprising the following steps:

[0019] S1: Prepare an upper desiccant mixed with 3% by mass of nano-silicon carbide (SiC) and a lower desiccant mixed with 5% by mass of nano-boron nitride (BN), and fill them into the drying tower according to the layered structure of the lower pretreatment zone and the upper deep drying zone.

[0020] S2: Start the adsorption drying process, control the SF6 gas to enter from the SF6 inlet at the bottom of the drying tower, and pass through the lower pretreatment zone and the upper deep drying zone in sequence. At the same time, the temperature of the two desiccant beds is maintained at 30℃±1℃ and 20℃±1℃ respectively by semiconductor heat sink and heating coil to deeply dry the SF6 gas.

[0021] S3: Real-time monitoring of the SF6 gas dew point at the outlet of the drying unit. When the outlet dew point rises to -35℃ or the continuous operation time of the unit reaches the preset threshold, the adsorption drying process is stopped and the regeneration program is started.

[0022] S4: Close the SF6 main gas line, start the heating and regeneration module to generate high-temperature hot air of 170-250℃, purge and desorb the desiccant bed in the drying tower, control the regeneration temperature rise rate ≤10℃ / min, and the purging time is 4-6 hours;

[0023] S5: After the regeneration purging is completed, stop the heating regeneration module, start the semiconductor heat sink to cool the desiccant bed to room temperature, and switch the system to SF6 adsorption drying mode.

[0024] The advantages of this invention are: 1. It can achieve deep dehydration of SF6 gas, with high dryness of the outlet gas, adapting to the stringent requirements of various high-voltage SF6 electrical equipment and strong operational stability; 2. Through the optimized application of high thermal conductivity materials, the thermal utilization efficiency of the regeneration process is greatly improved, the regeneration cycle is shortened, and the operating energy consumption and maintenance costs of the device throughout its entire life cycle are significantly reduced; 3. The temperature distribution of the desiccant bed is uniform, avoiding the problems of local overheating or insufficient temperature, effectively delaying the performance degradation of the desiccant, reducing the risk of equipment failure, and ensuring higher long-term operational reliability. Attached Figure Description

[0025] Figure 1 This is an integrated schematic diagram of the drying device of the present invention;

[0026] Figure 2 This is a schematic diagram of the composite desiccant module of the present invention;

[0027] Figure 3 This is a curve comparing the drying and regeneration performance of the present invention with that of existing technologies. Detailed Implementation

[0028] To explain in detail the technical content, objectives, and effects of the present invention, the following description is provided in conjunction with the embodiments and accompanying drawings.

[0029] The present invention relates to a renewable SF6 drying device based on nano-high thermal conductivity materials, comprising a composite desiccant module 1 for drying SF6, a heating and regeneration module 3, a control system 2, and an intelligent monitoring and alarm module 4.

[0030] The composite desiccant module 1 includes a drying tower 100 with an SF6 inlet and an SF6 outlet. The side of the drying tower near the SF6 inlet is a pretreatment zone, which is filled with a lower layer of desiccant 103. The side of the drying tower near the SF6 outlet is a deep drying zone, which is filled with an upper layer of desiccant 102. The lower layer of desiccant 103 is composed of activated alumina and 5% by mass of nano-sized boron nitride (BN), with a thermal conductivity of not less than 400 W / (m·K). The upper layer of desiccant 102 is composed of 4A molecular sieve and 3% by mass of nano-sized silicon carbide (SiC), with a thermal conductivity of not less than 120 W / (m·K).

[0031] The pretreatment zone and deep drying zone of the drying tower are equipped with a temperature sensor 101, a semiconductor heat sink 104, and a heating coil 105. The temperature sensor 101 is used to monitor the internal temperature of the desiccant; the semiconductor heat sink 104 is used to discharge the adsorption heat generated during the desiccant adsorption process; and the heating coil 105 is used to maintain a constant temperature of the desiccant bed during the adsorption stage and to assist in heating the bed during the regeneration stage.

[0032] The control system 2 controls the temperature sensor 101 and the semiconductor heat sink 104 to maintain the temperature of the pretreatment zone at 30℃±1℃, so as to maximize the adsorption rate of the desiccant under medium and high humidity at this temperature; and maintains the temperature of the deep drying zone at 20℃±1℃, so as to ensure the deep dehydration capability under low humidity environment at this temperature.

[0033] The heating and regeneration module 3 includes a heating element for generating regeneration hot air and a conveying pipe for delivering the regeneration hot air into the pretreatment zone and deep drying zone of the drying tower. The conveying pipe is connected to the SF6 main gas line through a valve. The SF6 main gas line is connected to the SF6 inlet (drawing omitted). The heating element (which can be a finned alloy heating tube or an explosion-proof duct electric heater, with a typical thickness of 30-50 μm for the nano boron nitride (BN) high thermal conductivity coating) is coated with a nano boron nitride (BN) high thermal conductivity coating. This high thermal conductivity coating has a thermal conductivity ≥120 W / (m·K) to achieve rapid and uniform heat diffusion and reduce the contact thermal resistance between the heat source and the hot air. The heating and regeneration module 3 is connected to the control system 2 to control the regeneration temperature at 170-250℃.

[0034] The semiconductor heat sink 104 and the heating coil 105 are controlled by PID intelligent cycle control through the control system 3 to ensure that the temperature uniformity deviation in the pretreatment zone and the deep drying zone is ≤±1℃ and the volumetric efficiency deviation is ≤0.5%.

[0035] The intelligent monitoring and alarm module includes a temperature sensor 101 installed inside the composite desiccant module 1, an SF6 leak detection probe installed at the gas outlet of the device, an over-temperature alarm unit, and an SF6 leak audible and visual alarm unit.

[0036] This invention relates to a method for drying renewable SF6 based on nanomaterials with high thermal conductivity, comprising the following steps:

[0037] S1: Prepare an upper desiccant 102 containing 3% by mass of nano-silicon carbide (SiC) and a lower desiccant 103 containing 5% by mass of nano-boron nitride (BN), and fill them into the drying tower according to the layered structure of the lower pretreatment zone and the upper deep drying zone.

[0038] S2: Start the adsorption drying process, control the SF6 gas to enter from the SF6 inlet at the bottom of the drying tower, and pass through the lower pretreatment zone and the upper deep drying zone in sequence. At the same time, the temperature of the two desiccant beds is maintained at 30℃±1℃ and 20℃±1℃ respectively by the semiconductor heat sink 104 and the heating coil 105 to deeply dry the SF6 gas.

[0039] S3: Real-time monitoring of the SF6 gas dew point at the outlet of the drying unit. When the outlet dew point rises to -35℃ or the continuous operation time of the unit reaches the preset threshold, the adsorption drying process is stopped and the regeneration program is started.

[0040] S4: Close the SF6 main gas path, start the heating and regeneration module 3 to generate high-temperature hot air of 170-250℃, purge and desorb the desiccant bed in the drying tower, control the regeneration temperature rise rate ≤10℃ / min, and the purging time is 4-6 hours;

[0041] S5: After the regeneration purging is completed, stop heating the regeneration module 3, start the semiconductor heat sink 104 to cool the desiccant bed to room temperature, and switch the system to SF6 adsorption drying mode.

[0042] One of the significant innovations of this invention is that the composite desiccant module 1 adopts a counter-current layered structure with specific function guidance. The wet SF6 gas first enters the lower pretreatment zone from the SF6 inlet at the bottom of the drying tower to remove most of the moisture and possible large molecular impurities such as oil. Then the gas flows upward through the upper deep drying zone to achieve the ultimate removal of moisture. Each layer is matched with the optimal combination of desiccant and high thermal conductivity additives for its function.

[0043] The specific preparation of the lower and upper desiccants is shown in Example 1.

[0044] Example 1:

[0045] Preparation of lower layer desiccant (for pretreatment zone):

[0046] Substrate: Industrial grade activated alumina (γ-Al2O3, specific surface area 260-300 m² / g, static adsorption capacity ≥0.30g / g).

[0047] Additives: Add 5% by weight of nano boron nitride (BN) powder (average particle size <100 nm, thermal conductivity ≥400 W / (m·K)).

[0048] Process: A dry high-speed shear mixing process is adopted to highly disperse and tightly adhere the nano-BN particles to the surface of the activated alumina particles and the micropore inlets, forming a pre-treated composite desiccant (103) with high thermal conductivity and large capacity. The core function of this layer is to utilize the rapid and high-capacity adsorption of moisture by activated alumina and the excellent thermal conductivity of BN to efficiently remove most of the moisture load and quickly dissipate the adsorption heat, creating mild air intake conditions for the upper layer.

[0049] Preparation of upper desiccant (for deep drying zone):

[0050] Substrate: Industrial grade 4A molecular sieve (specific surface area 700-800 m² / g, static adsorption capacity ≥0.22 g / g).

[0051] Additives: 3% by weight of nano-silicon carbide (SiC) powder (average particle size <50 nm, thermal conductivity ≥120 W / (m·K)).

[0052] Process: By combining solution impregnation with fluidized bed drying, nano-SiC is uniformly loaded onto the internal pores and outer surface of molecular sieve particles, forming a highly thermally conductive and highly selective deep-drying composite desiccant (102). The core function of this layer is to utilize the precise sieving capability of 4A molecular sieve for water molecules (0.28 nm in diameter) and its extremely low equilibrium water vapor partial pressure, with the assistance of SiC, to reduce the gas dew point depth to below -60℃ and ensure uniform heat distribution during regeneration.

[0053] Comparison test of intrinsic properties of materials:

[0054] To verify the effectiveness of the additives, the two composite desiccants mentioned above were prepared and compared with traditional samples without added thermally conductive materials.

[0055]

[0056] Conclusion: Test data show that, while maintaining the original adsorption kinetics and saturation capacity of the desiccant, this invention, through the functionalization of high thermal conductivity nanomaterials, increases the thermal conductivity of the pretreatment layer (lower layer) and the deep drying layer (upper layer) by approximately 375% and 233%, respectively. The extremely high thermal conductivity of the lower layer facilitates rapid heat dissipation and protects the upper layer; the moderate increase in thermal conductivity of the upper layer significantly improves regeneration uniformity while ensuring deep drying performance.

[0057] Example 2: Testing of the entire process of device integration, drying, and regeneration in this invention

[0058] in accordance with Figure 2 The structure shown describes the filling of desiccants according to their functions: the bottom of the drying tower is the lower pretreatment zone, filled with activated alumina + BN composite desiccant 103; above it is the upper deep drying zone, filled with 4A molecular sieve + SiC composite desiccant 102, with a total filling height ≥350 mm. An experimental prototype of this invention was built and paralleled with a control prototype using the same structure but with conventional desiccants. The results are as follows. Figure 3 As shown.

[0059] Test conditions:

[0060] Processing capacity: 60 NL / min wet SF6 gas (inlet dew point +20℃).

[0061] Performance target: Outlet dew point stable ≤-60℃.

[0062] Regeneration trigger: The outlet dew point rises to -35°C or the running time reaches the set value.

[0063] Regeneration parameters: Hot air temperature, set to 220℃ for the lower zone and 200℃ for the upper zone.

[0064] Overall performance comparison data:

[0065]

[0066] In summary, the significant advantages of this invention are as follows:

[0067] 1. Significantly improved drying performance and operating efficiency

[0068] Compared to traditional SF6 drying units of the same specifications, this unit extends the effective drying cycle to 28 hours under rated operating conditions, an improvement of over 55% compared to traditional solutions; the outlet SF6 gas dew point is consistently ≤-60℃, far exceeding the requirements of GB / T 8905-2012 standard, making it directly adaptable to harsh application scenarios such as ultra-high voltage and high-altitude cold regions; at the same time, the unit's start-up time is shortened to 2.2 hours, only 49% of the traditional solution, significantly reducing the pretreatment waiting time before equipment commissioning.

[0069] 2. Significantly reduced energy consumption and operation and maintenance costs of renewable energy.

[0070] Thanks to the several-fold increase in the thermal conductivity of the desiccant bed and the application of a high thermal conductivity coating on the heating element, the single regeneration time of this device is shortened to 4-6 hours, and the regeneration energy consumption is reduced by 20%-25% compared with the traditional solution. With a desiccant adsorption capacity recovery rate of ≥90%, the desiccant service life is extended to more than 3 years, which is twice that of the traditional solution. This significantly reduces the cost of desiccant replacement and the frequency of equipment downtime maintenance, and the total life cycle operating cost can be reduced by more than 35%.

[0071] 3. Comprehensive upgrade in operational stability and security redundancy.

[0072] The device adopts a layered temperature precision control design, with the bed temperature uniformity deviation in the adsorption stage ≤ ±1℃, avoiding the impact of ambient temperature fluctuations on drying efficiency; the maximum temperature difference in the bed during the regeneration stage is <10℃, completely solving the common problems of local overheating leading to desiccant sintering and deactivation, and local insufficient temperature leading to incomplete regeneration in traditional solutions; combined with real-time dew point monitoring, over-temperature alarm and SF6 leakage alarm functions, it can achieve unattended stable operation and eliminate the SF6 electrical equipment insulation safety hazards caused by drying unit failures.

[0073] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent modifications made based on the content of the present invention specification and drawings, or direct or indirect applications in related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A renewable SF6 drying device based on nanomaterials with high thermal conductivity, characterized in that: The system includes a composite desiccant module (1) for drying SF6. The composite desiccant module (1) includes a drying tower with an SF6 inlet and an SF6 outlet. The side of the drying tower near the SF6 inlet is a pretreatment zone, which is filled with a lower layer of desiccant (103). The side of the drying tower near the SF6 outlet is a deep drying zone, which is filled with an upper layer of desiccant (102). The lower layer of desiccant (103) is composed of activated alumina and 5% by mass of nano-sized boron nitride (BN), and its thermal conductivity is not less than 400 W / (m·K). The upper layer of desiccant (102) is composed of 4A molecular sieve and 3% by mass of nano-sized silicon carbide (SiC), and its thermal conductivity is not less than 120 W / (m·K).

2. The renewable SF6 drying device based on nanomaterials with high thermal conductivity according to claim 1, characterized in that: The pretreatment zone and deep drying zone of the drying tower are also equipped with a temperature sensor (101), a semiconductor heat sink (104), and a heating coil (105). The temperature sensor (101) is used to monitor the internal temperature of the desiccant; the semiconductor heat sink (104) is used to remove the adsorption heat generated during the desiccant adsorption process; and the heating coil (105) is used to maintain a constant temperature of the desiccant bed during the adsorption stage and to assist in heating the bed during the regeneration stage.

3. The renewable SF6 drying device based on nano-high thermal conductivity materials according to claim 2, characterized in that: The temperature of the pretreatment zone is maintained at 30℃±1℃ to maximize the adsorption rate of the desiccant under medium and high humidity conditions; the temperature of the deep drying zone is maintained at 20℃±1℃ to ensure deep dehydration capability under low humidity conditions.

4. The renewable SF6 drying device based on nanomaterials with high thermal conductivity as described in claim 2 or 3, characterized in that: It also includes a heating and regeneration module (3), which includes a heating element for heating and generating regenerated hot air and a conveying pipe for sending the regenerated hot air into the pretreatment zone and deep drying zone of the drying tower. The conveying pipe is connected to the SF6 main gas line through a valve. The SF6 main gas line is connected to the SF6 inlet. The surface of the heating element is coated with a nano boron nitride (BN) high thermal conductivity coating. The high thermal conductivity coating has a thermal conductivity ≥120 W / (m·K) to achieve rapid and uniform heat diffusion and reduce the contact thermal resistance between the heat source and the hot air.

5. The renewable SF6 drying device based on nanomaterials with high thermal conductivity according to claim 4, characterized in that: It also includes a control system (2), in which the semiconductor heat sink (104) and heating coil (105) are controlled by PID intelligent cycle control to ensure that the temperature uniformity deviation in the pretreatment zone and the deep drying zone is ≤ ±1℃ and the volumetric efficiency deviation is ≤ 0.5%.

6. The renewable SF6 drying device based on nanomaterials with high thermal conductivity according to claim 5, characterized in that: The heating regeneration module (3) is connected to the control system (2) to control the regeneration temperature to 170-250℃.

7. The renewable SF6 drying device based on nanomaterials with high thermal conductivity according to claim 5, characterized in that: It also includes an intelligent monitoring and alarm module (4) connected to the control system (2). The intelligent monitoring and alarm module includes a temperature sensor (101) installed inside the composite desiccant module (1), an SF6 leak detection probe installed at the gas outlet of the device, an over-temperature alarm unit, and an SF6 leak audible and visual alarm unit.

8. A method for drying renewable SF6 based on nanomaterials with high thermal conductivity, employing the apparatus described in any one of claims 1-7, characterized in that, Includes the following steps: S1: Prepare an upper desiccant (102) mixed with 3% by mass of nano-silicon carbide (SiC) and a lower desiccant (103) mixed with 5% by mass of nano-boron nitride (BN), and fill them into the drying tower according to the layered structure of the lower pretreatment zone and the upper deep drying zone. S2: Start the adsorption drying process, control the SF6 gas to enter from the SF6 inlet at the bottom of the drying tower, pass through the lower pretreatment zone and the upper deep drying zone in sequence, and at the same time maintain the temperature of the two desiccant beds at 30℃±1℃ and 20℃±1℃ respectively through the semiconductor heat sink (104) and heating coil (105) to deeply dry the SF6 gas. S3: Real-time monitoring of the SF6 gas dew point at the outlet of the drying unit. When the outlet dew point rises to -35℃ or the continuous operation time of the unit reaches the preset threshold, the adsorption drying process is stopped and the regeneration program is started. S4: Close the SF6 main gas path and start the heating regeneration module (3) to generate high-temperature hot air of 170-250℃ to purge and desorb the desiccant bed in the drying tower. Control the regeneration temperature rise rate to ≤10℃ / min and the purging time to 4-6 hours. S5: After the regeneration purging is completed, stop heating the regeneration module (3), start the semiconductor heat sink (104) to cool the desiccant bed to room temperature, and switch the system to SF6 adsorption drying mode.

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