A VOCs desorption condensation system and its use method

Abstract

The present invention provides a VOCs desorption and condensation system and a method for using the same, comprising: an adsorption unit, a condenser, a desorption fan, a heater and an air charging valve N1, wherein the adsorption unit, condenser, desorption fan and heater are connected end to end through pipelines in sequence to form a closed loop, an inert gas replenishment node is provided on the pipeline between the condenser and the desorption fan, and the inert gas replenishment node is connected to an inert gas generating source through the air charging valve N1, an inert gas discharge node is provided on the dry pipe connecting the adsorption unit and the heater, a pressure monitoring point is provided on the pipeline between the desorption fan and the condenser, and a pressure sensing controller is installed; by enabling pressure monitoring and control during the desorption process, sudden pressure changes caused by expansion and contraction of heating and condensed gas can be avoided, so that the system can operate at normal pressure, so that normal pressure containers and normal pressure pipelines can be selected for the system, which greatly reduces the initial investment cost and improves operation safety.

Description

Technical Field

[0001] The present invention relates to the technical field of industrial emission VOCs treatment, and in particular to a normal pressure VOCs desorption and condensation system and a method for using the system. Background Art

[0002] The common treatment methods for existing VOCs include: adsorption and desorption + condensation / combustion, which are convenient and simple to treat and have high economic benefits.

[0003] Patent CN201910779667 proposes a VOCs gas radial adsorption and desorption recovery device and system, including an adsorption and desorption recovery device, a heat exchange device and a pressure-bearing shell. The device takes into account that the volume of exhaust gas increases after heating and expansion, thereby increasing the pressure, so a pressure-bearing shell is used to ensure the airtightness and safety of the device.

[0004] Patent CN201810564537 proposes a condensation + adsorption integrated VOCs emission control system with thermal purge desorption and its treatment method. For components that cannot be desorbed by vacuum, it proposes the use of heated inert gas (such as nitrogen) for purge desorption and thermal desorption. After the purge gas is condensed and adsorbed, it meets the emission standards. This technology chooses to use inert gas for thermal desorption. Patent CN201821190102 proposes an organic waste gas recovery system using hot nitrogen as the desorption medium. It forms a closed desorption cycle through a combination of an adsorption concentration mechanism, a desorption mechanism, a cooling mechanism, and a condensation recovery mechanism. Similarly, patent CN2019112971875 proposes a system and method for treating VOCs at room temperature by using activated carbon statically activated VOCs condensation, including a VOCs pretreatment system, a desorption condensation system, and an auxiliary adsorption bed. During the nitrogen purge desorption and VOCs condensation recovery process, the pressure in the system will change over a large range, and the use of pressure-bearing equipment and devices must be considered.

[0005] Therefore, at present, the method of using inert gas for desorption treatment of VOCs generally faces the following problems: heating or condensation will cause huge gas expansion and contraction, causing pressure mutations, leading to positive overpressure and negative pressure differentials in equipment and pipeline systems, causing overpressure damage at equipment and pipeline connections, positive pressure leakage of extremely high concentrations of VOCs causing the risk of local environmental explosion, and oxygen inhalation during differential pressure causing the risk of internal explosion in closed systems.

[0006] To address the above issues, common measures are to use pressure-bearing equipment and pipeline valves, or to use an open system. The former measure significantly increases system investment, and there is still a risk of leakage during system operation, which increases maintenance and management costs; the latter increases the use of inert gases (such as nitrogen), significantly increasing system operating costs. Summary of the Invention

[0007] The purpose of the present invention is to provide a VOCs desorption and condensation system to solve the problems existing in the above-mentioned prior art. By maintaining the system pressure during VOCs desorption and condensation, the system is ensured to operate at normal pressure. The system equipment can be replaced with a common type, which greatly reduces the processing energy consumption and equipment cost.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] A VOCs desorption and condensation system comprises: an adsorption unit, a condenser, a desorption fan, a heater, and an air charging valve N1. The adsorption unit, condenser, desorption fan, and heater are sequentially connected end to end via pipelines to form a closed loop. An inert gas replenishment node is provided on the pipeline between the condenser and the desorption fan. The inert gas replenishment node is connected to an inert gas generation source via the air charging valve N1. An inert gas discharge node is provided on the main pipe connecting the adsorption unit and the heater. A pressure monitoring point is provided on the pipeline between the desorption fan and the condenser, and a pressure sensor controller is installed.

[0010] The adsorption unit includes at least two sub-adsorption units arranged in parallel, a pressure relief valve N2 and an oxygen content detector. Each of the sub-adsorption units includes an adsorption bed, a first valve and a second valve. The inlet of the adsorption bed is connected to the heater through the first valve, and the outlet of the adsorption bed is connected to the condenser through the second valve. The first end of the oxygen content detector is connected to the inert gas discharge node through a pipeline, the second end of the oxygen content detector is connected to the first end of the pressure relief valve N2, and the second end of the pressure relief valve N2 is connected to the pipeline between the adsorption bed and the second valve.

[0011] In one embodiment, a VOCs concentration detector is provided at the inlet and outlet of the condenser respectively.

[0012] In one embodiment, the sub-adsorption unit further includes a chimney and a third valve, and the pipeline connecting the inlet of the adsorption bed and the first valve is provided with an atmospheric node, the atmospheric node is connected to the first end of the third valve, and the second end of the third valve is connected to the chimney.

[0013] In one embodiment, the sub-adsorption unit further includes a temperature measuring instrument, which is disposed on a pipe connecting the outlet of the adsorption bed and the second valve.

[0014] In one embodiment, the monitoring pressure value of the pressure sensor controller is P1-P2, and the residual pressure outside the desorption fan is P 风机 The pressure range of the VOCs desorption condensation system is (P1~P2)+P风机 .

[0015] In one embodiment, the inflation valve N1 and the pressure relief valve N2 are respectively automatic opening and closing valves, and their air tightness levels should be adapted to the pressure of the inert gas source used.

[0016] In one embodiment, the adsorption unit further includes a fourth valve, a first end of the fourth valve is connected to the pipeline between the adsorption bed and the second valve, and a second end of the fourth valve is connected to the pressure relief valve N2.

[0017] In one embodiment, the pressure sensor controller presets four control values, namely P1, P2, P3, and P4, and satisfies P1<P4<P3<P2. After detecting the pressure, it controls the opening and closing of the inflation valve N1 and the pressure relief valve N2 through analysis.

[0018] In one embodiment, during the desorption process, the pressure sensor controller continuously monitors the pressure at the pressure monitoring point. If the pressure is higher than a preset value P2, the pressure relief valve N2 is opened to discharge the inert gas. When the pressure drops to a preset value P3, the pressure relief valve N2 is closed. If the pressure is lower than a preset value P1, the charging valve N1 is opened to charge the inert gas. When the pressure rises to a preset value P4, the charging valve N1 is closed.

[0019] In one embodiment, the size of the pressure relief valve N2 should meet the following requirements:

[0020] System temperature rise rate calculation formula:

[0021]

[0022] Pressure relief flow calculation formula:

[0023]

[0024] The calculation formula for the maximum pressure difference between the inside and outside of the valve:

[0025] ΔP=P1+P 风机

[0026] Valve flow rate calculation formula:

[0027]

[0028] Valve diameter calculation formula:

[0029]

[0030] The diameter d of the selected valve should satisfy: d>d′,

[0031] Where: T1 is the temperature detected at the outlet of the desorbed adsorption bed after the system has been running for Δt, K; Δt is the time taken for the system pressure to reach P2, s; P2 is the maximum pressure controlled by the system pressure monitoring point, Pa; ΔT is the system temperature rise rate, K / s; ΔV is the system expansion rate, m 3 / s; V total system capacity, m 3 ; T is the temperature at system startup, K; ΔP is the maximum pressure difference when the system is depressurized, Pa; ρ is the density of the inert gas corresponding to the temperature T; ε is the resistance coefficient of the selected valve type; v is the calculated flow rate of the valve, m / s; d′ is the calculated diameter of the valve, m; d is the diameter of the selected valve, m.

[0032] The present invention also provides a method for using the VOCs desorption and condensation system, comprising the following steps:

[0033] Step S1: Fill with inert gas, open the pressure relief valve N2 and the charging valve N1. During the charging process, the oxygen content detector continuously detects the oxygen concentration in the exhaust gas. When the concentration decreases to 5% of the set value, close the pressure relief valve N2 and the charging valve N1, and stop filling with inert gas;

[0034] Step S2: Start the desorption fan, heater and condenser to start desorption;

[0035] Step S3: During the desorption process, the pressure at the pressure monitoring point is continuously monitored. If the pressure is higher than the preset value P2, the pressure relief valve N2 is opened to discharge the inert gas. When the pressure drops to the preset value P3, the pressure relief valve N2 is closed. If the pressure is lower than the preset value P1, the charging valve N1 is opened to charge the inert gas. When the pressure rises to the preset value P4, the charging valve N1 is closed.

[0036] Step S4: When the desorption system operation time reaches the set time t, the heater is turned off and the outlet temperature of the desorbed adsorption bed is detected. When the outlet temperature drops to the set temperature T, the desorption fan is turned off and the desorption process ends.

[0037] In one embodiment, the values ​​of P1, P2, P3 and P4 satisfy P1<P4<P3<P2.

[0038] In one embodiment, the method for setting the operation time t of the desorption system is as follows: VOCs concentration detectors C1 and C2 are respectively set at the inlet and outlet of the condenser; during the system trial operation stage, the concentration of VOCs at the condenser outlet is detected, and the concentration values ​​c1 and c2 detected by the VOCs concentration detectors C1 and C2 are recorded, and c1 / c2 is calculated in real time. When c1 / c2=1.1, the system operation time t at this time is recorded. This time is the desorption time of each adsorption bed.

[0039] In one embodiment, the set temperature T at which the desorption system stops is determined by the outdoor ambient temperature. When the outdoor ambient temperature is T', the temperature is determined to be T'+10°C.

[0040] The above-mentioned VOCs desorption and condensation system enables pressure monitoring and control during the desorption process, which can avoid sudden pressure changes caused by heating and expansion and contraction of condensed gas, so that the system can operate at normal pressure. Therefore, the system can select normal pressure containers and normal pressure pipelines, greatly reducing the initial investment cost and improving operation safety; the size of the pressure relief valve N2 door is accurately calculated to ensure that the system can quickly release pressure after pressurization, thereby meeting the system's operation at normal pressure, and there will be no situation where the pressure relief speed is less than the system expansion speed, and the pressure relief valve N2 is always open, and the system is continuously pressurized. Dangerous state.

[0041] During the operation of the system, time is used to control the start and stop of the desorption system instead of concentration monitoring control, which can avoid errors caused by inaccurate values ​​after long-term operation of existing concentration monitoring instruments, and the control process is simple and reliable; keeping at least one adsorption bed in a non-desorption state ensures that during the nitrogen filling process and the pressure relief process, the waste gas with a small amount of VOCs pollution is not discharged directly into the atmosphere through the chimney, but is first adsorbed by the adsorption bed before being discharged into the atmosphere, so as to ensure the emission concentration of the treatment system and further improve the treatment efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the embodiments of the present application or the technical solutions of the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0043] Figure 1 This is the schematic diagram of the VOCs desorption and condensation system;

[0044] Description of the accompanying drawings: adsorption bed 1, heater 2, desorption fan 3, condenser 4, inert gas generating source 5, chimney 6, pressure sensor controller 7, oxygen content detector 11, temperature measuring instrument 12. DETAILED DESCRIPTION

[0045] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0046] The purpose of the present invention is to provide a VOCs desorption and condensation system to solve the problems existing in the above-mentioned prior art. By maintaining the system pressure during VOCs desorption and condensation, the system is ensured to operate at normal pressure. The system equipment can be replaced with a common type, which greatly reduces the processing energy consumption and equipment cost.

[0047] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0048] See also Figure 1 The present invention provides a VOCs desorption and condensation system, comprising an adsorption bed 1, a heater 2, a desorption fan 3, a condenser 4, an inert gas generator 5, a chimney 6, a pressure sensor controller 7, a pipeline and a series of valves, and an oxygen content detector 11. There are at least two adsorption beds, A and B, connected in parallel. The adsorption bed outlet is connected to the condenser via a pipeline, the condenser outlet is connected to the desorption fan, the desorption fan outlet is connected to the heater, and the heater outlet is connected to the adsorption bed, forming a closed loop. A first valve Ad1 and a first valve Bd1 are provided on the parallel branches of the pipeline connecting the adsorption bed A and the adsorption bed B to the heater, respectively. A second valve Ad2 and a second valve Bd2 are provided on the parallel branches of the pipeline connecting the adsorption bed A and the adsorption bed B to the condenser, respectively. Temperature measuring instruments TA and TB are also provided. The inert gas generator is connected to a nitrogen replenishment point 9 via a pipeline. The nitrogen replenishment point is provided on the pipeline between the condenser and the desorption fan. A charging valve N1 is provided on the pipeline connecting the inert gas generator to the nitrogen replenishment point. A pressure monitoring point 8 is set on the pipeline between the desorption fan and the condenser, and a pressure sensor controller 7 is installed. A nitrogen discharge point 10 is set on the main pipe connecting the heater and the adsorption bed. The nitrogen discharge point is connected to the parallel pipe branch between the adsorption bed and the condenser. A pressure relief valve N2 is set on the main pipe connecting the nitrogen discharge point and the adsorption bed. Fourth valves Aa1 and Ba1 are set on the branch pipes connecting the nitrogen discharge point and each adsorption bed. Branch pipes are set on the pipeline between adsorption bed A and the first valve Ad1 and on the pipeline between adsorption bed B and the first valve Bd1, connected to the chimney, and third valves Aa2 and Ba2 are set on each branch pipe. Oxygen content detectors are set on the pipelines connecting adsorption bed A and adsorption bed B to the nitrogen discharge point; VOCs concentration detectors C1 and C2 are respectively set at the inlet and outlet of the condenser.

[0049] The VOCs desorption and condensation system in this embodiment uses atmospheric pressure piping and atmospheric pressure containers. The atmospheric pressure piping pressure range is P1-P2. The system atmospheric pressure range is (P1-P2) + ΔP, where ΔP is the residual pressure outside the desorption fan. In this embodiment, P1 = 500Pa, P2 = 1500Pa, and ΔP = 5000Pa.

[0050] In this embodiment, the inflation valve N1 and the pressure relief valve N2 should be electric valves. The minimum size of the pressure relief valve N2 in this embodiment is calculated as follows:

[0051] System temperature rise rate calculation:

[0052] ΔT=(T1×T) / t=(326-300) / 300=0.0867

[0053] Pressure relief flow calculation formula:

[0054] ΔV=(ΔT×V) / T=(0.0867×50) / 300=0.01445m^3 / s

[0055] The calculation formula for the maximum pressure difference between the inside and outside of the valve:

[0056] ΔP=P1+P_fan=1500+5000=6500Pa

[0057] Valve flow rate calculation formula:

[0058] v=√(2ΔP / (ρ×ε))=√((2×6500) / (1.1×0.1)=344)

[0059] Valve diameter calculation formula:

[0060] d^'=√(4ΔV / (π×v))=√((4×0.01445) / (π×344))=7×〖10〗^(-3)m

[0061] The diameter d of the pressure relief valve N2 selected in this embodiment is 5 cm, which should satisfy: d=5 cm>d'=7 mm. At this time, the system pressure relief time is 0.7 / 5=0.14 times the pressure rise time, which can ensure rapid pressure relief.

[0062] In this embodiment, a nitrogen source is used as the inert gas generating source.

[0063] In this embodiment, the valves N1 and N2 are electric valves, and their air tightness level should be adapted to the pressure of the inert gas source used.

[0064] In this embodiment, only one adsorption bed is desorbed each time.

[0065] After testing, the operating time t of the desorption condensation system of this embodiment is selected to be 12 hours.

[0066] When the outdoor temperature is T'=30°C, the judgment temperature T for stopping the desorption condensation system of this embodiment is T=T'+10°C=40°C.

[0067] In this embodiment of the atmospheric pressure VOCs desorption and condensation system, when desorption and condensation are performed on bed A, the operation process includes the following steps:

[0068] S1: Fill with inert gas, such as nitrogen, open the pressure relief valve N2 and the charging valve N1. During the charging process, the oxygen content detector 11 continuously detects the oxygen concentration in the exhaust gas. When the concentration is reduced to 5% of the set value, close the pressure relief valve N2 and the charging valve N1, and stop charging nitrogen.

[0069] S2: open the first valve Ad1, close the first valve Bd1, open the second valve Ad2, close the second valve Bd2, open the fourth valve Ba1 and the third valve Ba2, and close the fourth valve Aa1 and the third valve Aa2; that is, open all valves in the sub-adsorption unit.

[0070] S2: Start the desorption fan, heater and condenser to start desorption;

[0071] S3: During the desorption process, the pressure at the pressure monitoring point 8 is continuously monitored by the pressure sensor controller 7. If the pressure is higher than 1500Pa, the pressure relief valve N2 is opened to discharge nitrogen. When the pressure drops to 1000Pa, the pressure relief valve N2 is closed. If the pressure is lower than 500Pa, the charging valve N1 is opened to charge nitrogen. When the pressure rises to 800Pa, the charging valve N1 is closed.

[0072] S4: After the desorption system has been running for 12 hours, the heater is turned off and the outlet temperature of bed A is continuously monitored. When the outlet temperature drops to 40°C, the desorption fan is turned off and the desorption of bed A is completed.

[0073] In this embodiment of the atmospheric pressure VOCs desorption and condensation system, when desorption and condensation are performed on the B bed, the operation process includes the following steps:

[0074] S1: Nitrogen charging. Open the charging valve N1 and the pressure relief valve N2. During the nitrogen charging process, the oxygen content detector 11 continuously detects the oxygen concentration in the exhaust gas. When the concentration is reduced to 5%, close the charging valve N1 and the pressure relief valve N2 and stop nitrogen charging.

[0075] S2: open the first valve Bd1, close the first valve Ad1, open the second valve Bd2, close the second valve Ad2, open the fourth valve Aa1 and the third valve Aa2, and close the fourth valve Ba1 and the third valve Ba2;

[0076] S2: Start the desorption fan, heater and condenser to start desorption;

[0077] S3: During the desorption process, the pressure at the pressure monitoring point 8 is continuously monitored by the pressure sensor controller 7. If the pressure is higher than 1500Pa, the pressure relief valve N2 is opened to discharge nitrogen. When the pressure drops to 1000Pa, the pressure relief valve N2 is closed. If the pressure is lower than 500Pa, the charging valve N1 is opened to charge nitrogen. When the pressure rises to 800Pa, the charging valve N1 is closed.

[0078] S4: After the desorption system has been running for 12 hours, the heater is turned off and the outlet temperature of bed B is continuously detected. When the outlet temperature drops to 40°C, the desorption fan is turned off and the desorption of bed B is completed.

[0079] The above description of the embodiments is intended to facilitate understanding and application of the present invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A VOCs desorption and condensation system, characterized in that: include: An adsorption unit, a condenser, a desorption fan, a heater, and an air charging valve are provided. The adsorption unit, the condenser, the desorption fan, and the heater are sequentially connected end to end through pipelines to form a closed loop. An inert gas replenishment node is provided on the pipeline between the condenser and the desorption fan. The inert gas replenishment node is connected to an inert gas generating source through the air charging valve. An inert gas discharge node is provided on the main pipe connecting the adsorption unit and the heater. A pressure monitoring point is provided on the pipeline between the desorption fan and the condenser, and a pressure sensor controller is installed. The adsorption unit includes at least two sub-adsorption units arranged in parallel, a pressure relief valve and an oxygen content detector. Each of the sub-adsorption units includes an adsorption bed, a first valve and a second valve. The inlet of the adsorption bed is connected to the heater through the first valve, and the outlet of the adsorption bed is connected to the condenser through the second valve. The first end of the oxygen content detector is connected to the inert gas discharge node through a pipeline, the second end of the oxygen content detector is connected to the first end of the pressure relief valve, and the second end of the pressure relief valve is connected to the pipeline between the adsorption bed and the second valve. The monitoring pressure value of the pressure sensor controller is P1~P2, and the residual pressure outside the desorption fan is P 风 The pressure range of the VOCs desorption condensation system is (P1~P2)+P fan; the pressure sensor controller presets four control values, namely P1, P2, P3, and P4, and satisfies P1<P4<P3<P2. After detecting the pressure, it controls the opening and closing of the inflation valve and the pressure relief valve through analysis; during the desorption process, the pressure sensor controller continuously monitors the pressure of the pressure monitoring point. If the pressure is higher than the preset value P2, the pressure relief valve is opened to discharge the inert gas, and when the pressure drops to the preset value P3, the pressure relief valve is closed; if the pressure is lower than the preset value P1, the inflation valve is opened to fill in the inert gas, and when the pressure rises to the preset value P4, the inflation valve is closed.

2. The VOCs desorption and condensation system according to claim 1, characterized in that: The inlet and outlet of the condenser are respectively provided with VOCs concentration detectors.

3. The VOCs desorption and condensation system according to claim 1, characterized in that: The sub-adsorption unit also includes a chimney and a third valve. The pipeline connecting the inlet of the adsorption bed and the first valve is provided with an atmospheric node. The atmospheric node is connected to the first end of the third valve, and the second end of the third valve is connected to the chimney.

4. The VOCs desorption and condensation system according to claim 1, characterized in that: The sub-adsorption unit further includes a temperature measuring instrument, which is arranged on a pipeline connecting the outlet of the adsorption bed and the second valve.

5. The VOCs desorption and condensation system according to claim 1, characterized in that: The inflation valve and the pressure relief valve are respectively automatic opening and closing valves, and their air tightness levels should be adapted to the pressure of the inert gas generating source used.

6. The VOCs desorption and condensation system according to claim 1, characterized in that: The dimensions of the pressure relief valve shall meet the following requirements: System temperature rise rate calculation formula: Pressure relief flow calculation formula: The calculation formula for the maximum pressure difference between the inside and outside of the valve: ΔP=P1+P 风机 Valve flow rate calculation formula: Valve diameter calculation formula: The diameter d of the selected valve should satisfy: d>d′, Where: T1 is the temperature detected at the outlet of the desorbed adsorption bed after the system has been running for a period of time Δt, in K; Δt is the time taken for the system pressure to reach P2, in seconds; P1-the lowest pressure controlled by the system pressure monitoring point, in Pa; 风机 -External residual pressure of the desorption fan, in Pa; P2-the highest pressure controlled by the system pressure monitoring point, in Pa; ΔT-system temperature rise rate, unit is K / s; ΔV-system expansion rate, unit is m 3 / s; V-total system capacity, unit is m 3 ; T-system startup temperature, unit is K; ΔP-maximum pressure difference when the system is depressurized, unit is Pa; ρ-inert gas density corresponding to temperature T, unit is kg / m 3 ;ε-resistance coefficient of the selected valve type;v-calculated flow rate of the valve, in m / s;d′-calculated diameter of the valve, in m;d-diameter of the selected valve, in m.

7. A method for using the VOCs desorption and condensation system according to any one of claims 1 to 6, characterized in that: The following steps are involved: Step S1: Fill with inert gas, open the pressure relief valve and the inflation valve. During the inflation process, the oxygen content detector continuously detects the oxygen concentration in the exhaust gas. When the concentration decreases to 5% of the set value, close the pressure relief valve and the inflation valve, and stop filling with inert gas; Step S2: Start the desorption fan, heater and condenser to start desorption; Step S3: During the desorption process, the pressure at the pressure monitoring point is continuously monitored. If the pressure is higher than the preset value P2, the pressure relief valve is opened to discharge the inert gas. When the pressure drops to the preset value P3, the pressure relief valve is closed. If the pressure is lower than the preset value P1, the charging valve is opened to charge the inert gas. When the pressure rises to the preset value P4, the charging valve is closed. The values ​​of P1, P2, P3 and P4 satisfy P1<P4<P3<P2. Step S4: When the desorption system operation time reaches the set time t, the heater is turned off and the outlet temperature of the desorbed adsorption bed is detected. When the outlet temperature drops to the set temperature T, the desorption fan is turned off and the desorption process ends.

8. The method for using the VOCs desorption and condensation system according to claim 7, characterized in that: The method for setting the operation time t of the desorption system is as follows: VOCs concentration detectors C1 and C2 are respectively set at the inlet and outlet of the condenser; during the system trial operation stage, the concentration of VOCs at the condenser outlet is detected, the concentration values ​​c1 and c2 detected by the VOCs concentration detectors C1 and C2 are recorded, and c1 / c2 is calculated in real time. When c1 / c2=1.1, the system operation time t at this time is recorded. This time is the desorption time of each adsorption bed.

9. The method for using the VOCs desorption and condensation system according to claim 7, characterized in that: The set temperature T at which the desorption system stops is determined by the outdoor ambient temperature. When the outdoor ambient temperature is T', the temperature is determined to be T'+10°C.

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