A multi-stage purification and reuse device for nitrogen-sealed VOCs

Abstract

This application discloses a multi-stage purification and reuse device for nitrogen-sealed VOCs, relating to the field of VOCs recovery and treatment technology. The VOCs recovery and treatment device includes multiple condensers, each comprising at least a first-stage condenser and a final-stage condenser. The tube-side inlet of the first-stage condenser is connected to the VOCs inlet, and the shell-side outlet of the first-stage condenser is connected to the purified gas outlet. The shell-side inlet of the final-stage condenser is connected to the liquid nitrogen inlet. The heat exchange tubes of the multiple condensers are sequentially connected via tube-side connecting pipelines, and the shells of the multiple condensers are also sequentially connected via shell-side connecting pipelines. This multi-stage purification and reuse device for nitrogen-sealed VOCs solves the problems of low purification efficiency and inability to reuse nitrogen in the purified gas when traditional VOCs recovery and treatment equipment is used for low-oxygen VOCs.

Description

Technical Field

[0001] This application relates to the field of VOCs recovery and treatment technology, and in particular to a multi-stage purification and reuse device for nitrogen-sealed VOCs. Background Technology

[0002] In the production and storage processes of petrochemicals, coal chemicals, and organic chemicals, atmospheric pressure storage of organic liquids is very common, typically using vertical tanks or small horizontal tanks / silos. Due to the volatility of organic liquids, VOCs will evaporate during storage. Therefore, breather valves are installed on the top of the tank to prevent VOCs from being easily released. However, with temperature and pressure changes during storage, the tank's breathing action can cause internal oxygen to mix with VOCs, posing a safety hazard. Furthermore, the release of VOCs can cause environmental pollution and oil loss.

[0003] Currently, the commonly used explosion-proof and flame-retardant technology for atmospheric pressure storage tanks of organic liquids is inerting technology. This typically involves using a nitrogen blanketing system to inertate the oil storage tank, which involves injecting high-purity nitrogen to create a low-oxygen environment (e.g., 8% oxygen content), thereby inhibiting combustion and improving tank safety. However, purifying the low-oxygen VOCs emitted by the nitrogen blanketing system remains a challenge.

[0004] Currently, the main method used is to treat the low-oxygen VOCs emitted from the nitrogen blanketing system using oil and gas recovery equipment before emission. This method has several drawbacks. First, the containers and breather valves may not be airtight, potentially resulting in nitrogen purity below the requirements for nitrogen blanketing. Therefore, nitrogen from the low-oxygen VOCs cannot be reused, requiring the use of fresh nitrogen, which increases the operating cost and energy consumption of the nitrogen blanketing system. Second, malfunctions in the oil and gas recovery equipment can lead to substandard emissions and environmental pollution. Furthermore, unsafe conditions such as oil and gas leaks, spontaneous combustion of activated carbon layers, and electrostatic discharge within the equipment itself can increase the risk of fire and explosion.

[0005] Patent CN110143378 discloses a method for the safe collection and zero-emission of VOCs from storage tanks. This method connects VOCs pipelines in storage tanks containing the same or similar materials, collecting VOCs from multiple tank groups into a main oil and gas pipeline. The collected VOCs are then sent to a pressurized oil and gas recovery device via a controlled nitrogen generator. The recovered nitrogen is then circulated by controlling the opening and closing of a nitrogen sealing valve on the tank using a pressure monitoring signal. This method achieves safe collection, zero emissions, and nitrogen recycling, meeting increasingly stringent environmental standards. However, the pressurized recovery device described in this patent uses a combination of pressurized absorption, pressurized adsorption, membrane separation, and condensation for VOCs treatment and nitrogen recovery. Nitrogen recycling is shut off when the total hydrocarbon concentration at the outlet of the pressurized oil and gas recovery device exceeds the limit for VOCs concentration in the circulating nitrogen. Therefore, there is a risk of air pollution and fire / explosion due to device malfunction. Furthermore, high-pressure, high-concentration oil and gas leaks into the air are more likely to cause fires and explosions.

[0006] To address the problems of low VOCs recovery rates, substandard exhaust emissions, and fire and explosion risks associated with conventional oil and gas recovery technologies, patent CN109550350A discloses a liquid nitrogen cryogenic condensation VOCs recovery and treatment device. Volatile oil and gas are pressurized by a booster blower and then enter a cold insulation box for three-stage condensation and heat exchange with liquid nitrogen. The condensed liquid is then recovered through a pipeline separator and a gas-liquid separator. Non-condensable gases are vented, and the nitrogen gas from the vaporization of liquid nitrogen is de-nitrogenated into the nitrogen sealing system. Its advantages include: a VOCs recovery rate of up to 99.999%, reduced emissions of volatile organic compounds and ozone-depleting substances, thorough recovery, and no secondary pollution. However, this technology has two problems: 1) Due to the low cooling temperature, the equipment is prone to freezing and defrosting is difficult, making it impossible to operate continuously and stably for a long period of time. Two independent condensation systems need to be set up to maintain long-term operational reliability; 2) The low-temperature non-condensable gas and low-temperature nitrogen cooling capacity generated after liquid nitrogen heat exchange are not fully utilized, and a large amount of nitrogen in low-oxygen VOCs cannot be recycled and reused, resulting in high liquid nitrogen consumption and high energy consumption.

[0007] Therefore, how to efficiently, safely, and environmentally friendly recover and reuse low-oxygen VOCs gas in nitrogen sealing systems, improve the recovery efficiency of liquid nitrogen cryogenic purification, and solve the defrosting difficulties to maintain long-term equipment operation is a technical problem that urgently needs to be solved by those skilled in the art. Utility Model Content

[0008] The purpose of this application is to provide a multi-stage purification and reuse device for nitrogen-sealed VOCs, which solves the problems of low purification efficiency and inability to reuse nitrogen in the purified gas when traditional VOCs recovery and treatment equipment is used to recover and treat low-oxygen VOCs.

[0009] To achieve the above objectives, this application provides a multi-stage purification and reuse device for nitrogen-sealed VOCs, comprising multiple condensers. Each condenser is provided with a tube-side inlet, a tube-side outlet, a shell-side inlet, and a shell-side outlet. The multiple condensers include at least a first-stage condenser and a last-stage condenser. The tube-side inlet of the first-stage condenser is used to connect to the VOCs inlet, the shell-side outlet of the first-stage condenser is used to connect to the purified gas outlet, and the shell-side inlet of the last-stage condenser is used to connect to the liquid nitrogen inlet.

[0010] The heat exchange tubes of multiple condensers are connected sequentially through tube-side connecting pipelines, and the shells of multiple condensers are also connected sequentially through shell-side connecting pipelines. This allows VOCs introduced through the VOCs inlet to flow out of the final condenser through the tube-side connecting pipelines, and liquid nitrogen introduced through the liquid nitrogen inlet to enter the final condenser and undergo heat exchange in the final condenser. After heat exchange, liquid nitrogen and VOCs flowing out of the final condenser undergo multi-stage heat exchange together through the shell-side connecting pipelines towards the first condenser and flow out from the purified gas outlet.

[0011] In some embodiments, the first-stage condenser includes a primary condenser, and a secondary primary condenser and a tertiary condenser are provided between the first-stage condenser and the final-stage condenser. Specifically, the final-stage condenser is a quaternary condenser.

[0012] The tube-side inlet of the first-stage main condenser is connected to the VOCs inlet; the tube-side outlet of the first-stage main condenser is connected to the tube-side inlet of the second-stage main condenser; the tube-side outlet of the second-stage main condenser is connected to the tube-side inlet of the third-stage condenser; the tube-side outlet of the third-stage condenser is connected to the tube-side inlet of the fourth-stage condenser; the tube-side outlet of the fourth-stage condenser is connected to the shell-side inlet of the third-stage condenser; the shell-side outlet of the third-stage condenser is connected to the shell-side inlet of the second-stage main condenser; the shell-side outlet of the second-stage main condenser is connected to the shell-side inlet of the first-stage main condenser; and the shell-side outlet of the first-stage main condenser is connected to the purified gas outlet.

[0013] In some embodiments, the first-stage condenser further includes a primary secondary condenser, and the plurality of condensers further includes a secondary secondary condenser;

[0014] The tube-side inlet of the primary condenser is connected to the VOCs inlet. The tube-side outlet of the primary condenser is connected to the tube-side inlets of the secondary main condenser and the secondary condenser, respectively. The tube-side inlet of the secondary condenser is connected to the tube-side outlet of the primary main condenser. The tube-side outlet of the secondary condenser is connected to the tube-side inlet of the tertiary condenser. The shell-side outlet of the tertiary condenser is connected to the shell-side inlet of the secondary condenser. The shell-side outlet of the secondary condenser is connected to the shell-side inlet of the primary main condenser and the primary condenser. The shell-side outlet of the primary condenser is connected to the purified gas outlet.

[0015] In some embodiments, the multi-stage purification and reuse device for nitrogen-sealed VOCs further includes a first programmable valve, a second programmable valve, a third programmable valve, a fourth programmable valve, a fifth programmable valve, a sixth programmable valve, a seventh programmable valve, an eighth programmable valve, a ninth programmable valve, a tenth programmable valve, an eleventh programmable valve, a twelfth programmable valve, a thirteenth programmable valve, and a fourteenth programmable valve.

[0016] The inlet of the first programmable valve is connected to the VOCs inlet, the outlet of the first programmable valve is connected to the tube-side inlet of the primary condenser, the inlet of the second programmable valve is connected to the VOCs inlet, and the outlet of the second programmable valve is connected to the tube-side inlet of the primary secondary condenser.

[0017] The inlet of the fifth programmable valve is connected to the tube-side outlet of the first-stage main condenser. The outlet of the fifth programmable valve is connected to the inlet of the seventh programmable valve and the inlet of the eighth programmable valve. The inlet of the sixth programmable valve is connected to the tube-side outlet of the first-stage secondary condenser. The outlet of the sixth programmable valve is connected to the inlet of the seventh programmable valve and the inlet of the eighth programmable valve. The outlet of the seventh programmable valve is connected to the tube-side inlet of the second-stage main condenser. The outlet of the eighth programmable valve is connected to the tube-side inlet of the second-stage secondary condenser.

[0018] The inlet of the thirteenth programmable valve is connected to the tube-side outlet of the secondary main condenser, the outlet of the thirteenth programmable valve is connected to the tube-side inlet of the tertiary condenser, the inlet of the fourteenth programmable valve is connected to the tube-side outlet of the secondary condenser, and the outlet of the fourteenth programmable valve is connected to the tube-side inlet of the tertiary condenser.

[0019] The inlet of the eleventh programmable valve is connected to the shell-side outlet of the third-stage condenser, the outlet of the eleventh programmable valve is connected to the shell-side inlet of the second-stage main condenser, the inlet of the twelfth programmable valve is connected to the shell-side outlet of the third-stage condenser, and the outlet of the twelfth programmable valve is connected to the shell-side inlet of the second-stage secondary condenser.

[0020] The inlet of the tenth programmable valve is connected to the shell-side outlet of the secondary main condenser. The outlet of the tenth programmable valve is connected to the inlet of the third programmable valve and the inlet of the fourth programmable valve. The inlet of the ninth programmable valve is connected to the shell-side outlet of the secondary condenser. The outlet of the ninth programmable valve is connected to the inlet of the third programmable valve and the inlet of the fourth programmable valve. The outlet of the fourth programmable valve is connected to the shell-side inlet of the primary main condenser. The outlet of the third programmable valve is connected to the shell-side inlet of the primary secondary condenser.

[0021] In some embodiments, a demister is provided below the tube outlet of each of the primary condenser, secondary condenser, tertiary condenser, quaternary condenser, primary secondary condenser, and secondary secondary condenser.

[0022] In some embodiments, the primary condenser, secondary condenser, tertiary condenser, quaternary condenser, primary secondary condenser, and secondary secondary condenser are all provided with drain ports, and each drain port is connected to an oil collection tank.

[0023] In some embodiments, temperature detection instruments are provided at the tube outlets of the primary condenser, secondary condenser, tertiary condenser, quaternary condenser, primary secondary condenser, and secondary secondary condenser.

[0024] In some embodiments, a first differential pressure detector is provided on the pipeline between the inlet of the first programmable valve and the outlet of the fifth programmable valve, and on the pipeline between the inlet of the second programmable valve and the outlet of the sixth programmable valve.

[0025] A second differential pressure detector is installed on the pipeline between the air inlet of the seventh programmable valve and the air outlet of the thirteenth programmable valve, and on the pipeline between the air inlet of the eighth programmable valve and the air outlet of the fourteenth programmable valve.

[0026] In some embodiments, the condensing temperatures of the primary main condenser, secondary main condenser, tertiary condenser, and quaternary condenser decrease sequentially. The condensing temperature range of the primary main condenser is 0 to -5 degrees Celsius, the condensing temperature range of the secondary main condenser is -35 to -45 degrees Celsius, the condensing temperature range of the tertiary condenser is -75 to -85 degrees Celsius, and the condensing temperature range of the quaternary condenser is -115 to -125 degrees Celsius.

[0027] In some embodiments, the multi-stage purification and reuse device for nitrogen-sealed VOCs further includes a fan, the fan's inlet being connected to the VOCs inlet, and the fan's outlet being connected to the tube-side inlet of the first-stage condenser.

[0028] The shell-side inlet of the final condenser is connected to a liquid nitrogen flow regulating valve, and a VOCs concentration sensor is installed at the shell-side outlet of the first condenser. The liquid nitrogen flow regulating valve is configured to regulate the liquid nitrogen input based on the data from the VOCs concentration sensor.

[0029] Compared to the background technology described above, the multi-stage purification and reuse device for nitrogen-sealed VOCs provided in this application includes multiple condensers, including a first-stage condenser and a final-stage condenser. The tube-side inlet of the first-stage condenser is used to connect to the VOCs inlet, the shell-side outlet of the first-stage condenser is used to connect to the purified gas outlet, and the shell-side inlet of the final-stage condenser is used to connect to the liquid nitrogen inlet. The heat exchange tubes of the multiple condensers are connected sequentially through tube-side connecting pipelines, and the shells of the multiple condensers are also connected sequentially through shell-side connecting pipelines. In this way, VOCs introduced through the VOCs inlet flow out of the final-stage condenser from the first-stage condenser through the tube-side connecting pipelines, and liquid nitrogen introduced through the liquid nitrogen inlet enters the final-stage condenser and undergoes heat exchange in the final-stage condenser. After heat exchange, liquid nitrogen and VOCs flowing out of the final-stage condenser undergo multi-stage heat exchange together through the shell-side connecting pipelines towards the first-stage condenser and flow out from the purified gas outlet.

[0030] It can be seen that, on the one hand, VOCs are condensed and purified sequentially by each condenser along the direction from the first condenser to the last condenser. On the other hand, liquid nitrogen enters the last condenser and undergoes heat exchange there. Then, it undergoes multi-stage heat exchange with the VOCs flowing out of the last condenser through the shell-side connecting pipeline towards the first condenser, resulting in nitrogen with extremely low oxygen content, which finally flows out from the purified gas outlet.

[0031] The beneficial effects of this multi-stage purification and reuse device for nitrogen-sealed VOCs mainly include:

[0032] After VOCs are condensed and purified by multi-stage condensers along the tube-side connecting pipeline, liquid nitrogen vaporized gas is mixed with non-condensable VOCs gas after heat exchange, and then further mixed by heat exchange along the shell-side connecting pipeline through multi-stage condensers to obtain high-purity nitrogen gas. Finally, the high-purity nitrogen gas is introduced into the nitrogen sealing system. This not only makes full use of the cooling capacity of liquid nitrogen, effectively removes VOCs components from low-oxygen VOCs, improves the purification efficiency of VOCs, and solves the problem of environmental pollution caused by substandard emissions, but also improves the purity of nitrogen in the purified gas, allowing the purified gas to return to the nitrogen sealing system. This achieves the recycling and reuse of nitrogen in nitrogen-sealed VOCs, saves resources, reduces costs, and ensures the safety of the nitrogen sealing system. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of this application or related technologies, the drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0034] Figure 1This is a schematic diagram of the connection of the multi-stage purification and reuse device for nitrogen-sealed VOCs in the embodiments of this application.

[0035] in:

[0036] 1-Fan, 201-First control valve, 202-Second control valve, 203-Third control valve, 204-Fourth control valve, 205-Fifth control valve, 206-Sixth control valve, 207-Seventh control valve, 208-Eighth control valve, 209-Ninth control valve, 210-Tenth control valve, 211-Eleventh control valve, 212-Twelfth control valve, 213-Thirteenth control valve, 214-Fourteenth control valve Programmable valve, 301-primary main condenser, 302-primary secondary condenser, 401-secondary main condenser, 402-secondary secondary condenser, 5-tertiary condenser, 6-quadrant condenser, 7-oil collection tank, 8-demister, 9-temperature detection instrument, 1001-first differential pressure detector, 1002-second differential pressure detector, 1101-VOCs inlet, 1102-liquid nitrogen inlet, 1103-purified gas outlet. Detailed Implementation

[0037] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0038] To enable those skilled in the art to better understand the present application, the present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0039] Please see Figure 1 The multi-stage purification and reuse device for nitrogen-sealed VOCs provided in this application includes multiple condensers. Each condenser is provided with a tube-side inlet, a tube-side outlet, a shell-side inlet, and a shell-side outlet. The multiple condensers include at least a first-stage condenser and a last-stage condenser. The tube-side inlet of the first-stage condenser is used to connect to the VOCs inlet 1101, and the shell-side outlet of the first-stage condenser is used to connect to the purified gas outlet 1103. The purified gas outlet 1103 is used to connect to the nitrogen-sealing system, and the shell-side inlet of the last-stage condenser is used to connect to the liquid nitrogen inlet 1102.

[0040] Furthermore, a multi-stage purification and reuse device for nitrogen-sealed VOCs also includes tube-side connecting pipelines and shell-side connecting pipelines. The heat exchange tubes of multiple condensers are connected sequentially through the tube-side connecting pipelines, and the shells of multiple condensers are also connected sequentially through the shell-side connecting pipelines.

[0041] In this way, VOCs introduced through VOCs inlet 1101 flow out of the final condenser through the tube-side connecting pipeline from the first condenser. Liquid nitrogen introduced through liquid nitrogen inlet 1102 enters the final condenser and undergoes heat exchange in the final condenser. Then, together with the VOCs flowing out of the final condenser, they undergo multi-stage heat exchange with the first condenser through the shell-side connecting pipeline and flow out from the purified gas outlet 1103.

[0042] It can be seen that, on the one hand, VOCs are condensed and purified sequentially by each condenser along the direction from the first condenser to the last condenser. On the other hand, liquid nitrogen enters the last condenser and undergoes heat exchange there. Then, it undergoes multi-stage heat exchange with the VOCs flowing out of the last condenser through the shell-side connecting pipeline towards the first condenser, resulting in nitrogen with extremely low oxygen content. Finally, it flows out from the purified gas outlet 1103 to the nitrogen sealing system.

[0043] This multi-stage purification and reuse device for nitrogen-sealed VOCs, after condensing and purifying VOCs along the tube-side connecting pipelines through a multi-stage condenser, mixes liquid nitrogen vaporized gas with non-condensable VOCs gas through heat exchange, and then further exchanges heat along the shell-side connecting pipelines through a multi-stage condenser to obtain high-purity nitrogen gas. Finally, the high-purity nitrogen gas is introduced into the nitrogen-sealing system. This not only fully utilizes the cooling capacity of liquid nitrogen, effectively removes VOCs components from low-oxygen VOCs, improves VOCs purification efficiency, and solves the problem of environmental pollution caused by substandard emissions, but also improves the purity of nitrogen in the purified gas, allowing the purified gas to return to the nitrogen-sealing system. This achieves the recycling and reuse of nitrogen in nitrogen-sealed VOCs, saves resources, reduces costs, and ensures the safety of the nitrogen-sealing system.

[0044] To facilitate the provision of power for gas recovery and treatment, the multi-stage purification and reuse device for nitrogen-sealed VOCs also includes a fan 1. The inlet of the fan 1 is connected to the VOCs inlet 1101, and the outlet of the fan 1 is connected to the tube inlet of the first-stage condenser.

[0045] In some embodiments, the plurality of condensers are four-stage condensers. Specifically, the first stage condenser includes a primary main condenser 301, the plurality of condensers also include a secondary main condenser 401 and a tertiary condenser 5, and the last stage condenser is specifically a quaternary condenser 6, with the secondary main condenser 401 and the tertiary condenser 5 located between the primary main condenser 301 and the quaternary condenser 6.

[0046] Specifically, the tube-side inlet N1 of the primary main condenser 301 is connected to the VOCs inlet 1101; the tube-side outlet N2 of the primary main condenser 301 is connected to the tube-side inlet N1 of the secondary main condenser 401; the tube-side outlet N2 of the secondary main condenser 401 is connected to the tube-side inlet N1 of the tertiary condenser 5; the tube-side outlet N2 of the tertiary condenser 5 is connected to the tube-side inlet N1 of the quaternary condenser 6; the tube-side outlet N2 of the quaternary condenser 6 is connected to the shell-side inlet N3 of the tertiary condenser 5; the shell-side outlet N4 of the tertiary condenser 5 is connected to the shell-side inlet N3 of the secondary main condenser 401; the shell-side outlet N4 of the secondary main condenser 401 is connected to the shell-side inlet N3 of the primary main condenser 301; and the shell-side outlet N4 of the primary main condenser 301 is connected to the purified gas outlet 1103.

[0047] In this way, under the power of the fan 1, the VOCs introduced through the VOCs inlet 1101 can be condensed and purified sequentially through the primary main condenser 301, the secondary main condenser 401, the tertiary condenser 5, and the quaternary condenser 6 along the tube-side connecting pipeline. After the VOCs are purified by the quaternary condensation, the non-condensable gas is discharged from the tube-side outlet N2 of the quaternary condenser 6. Liquid nitrogen enters the shell-side inlet N3 of the quaternary condenser 6 through the liquid nitrogen inlet 1102 and the pipeline to exchange heat with the VOCs before being discharged from the shell-side outlet N4 of the quaternary condenser 6. Then, the nitrogen gas is combined with the non-condensable VOCs discharged from the tube-side outlet N2 of the quaternary condenser 6. The combined low-temperature mixed gas is then heat-exchanged through the tertiary condenser 5, the secondary main condenser 401, and the primary main condenser 301 before being discharged from the shell-side outlet N4 of the primary main condenser 301 to the purified gas outlet 1103, and then transported to the nitrogen sealing system for recycling.

[0048] It should be noted that in this embodiment, the tube-side air inlet of the first-stage condenser is the tube-side air inlet N1 of the first-stage main condenser 301, and the shell-side air outlet of the first-stage condenser is the shell-side air outlet N4 of the first-stage main condenser 301.

[0049] In some embodiments, the condensing temperatures of the primary main condenser 301, the secondary main condenser 401, the tertiary condenser 5, and the quaternary condenser 6 decrease sequentially. The condensing temperature range of the primary main condenser 301 is 0 to -5 degrees Celsius, the condensing temperature range of the secondary main condenser 401 is -35 to -45 degrees Celsius, the condensing temperature range of the tertiary condenser 5 is -75 to -85 degrees Celsius, and the condensing temperature range of the quaternary condenser 6 is -115 to -125 degrees Celsius.

[0050] Furthermore, the primary condenser also includes a first-stage secondary condenser 302, and the multiple condensers also include a second-stage secondary condenser 402. The condensing temperature ranges of the first-stage secondary condenser 302 and the second-stage secondary condenser 402 can be set to be the same as the condensing temperature ranges of the first-stage main condenser 301 and the second-stage main condenser 401, respectively. Moreover, the first-stage secondary condenser 302 and the first-stage main condenser 301 serve as backup condensers for each other, and the second-stage secondary condenser 402 and the second-stage main condenser 401 serve as backup condensers for each other.

[0051] Specifically, the tube-side inlet N1 of the primary secondary condenser 302 is connected to the VOCs inlet 1101, and the tube-side outlet N2 of the primary secondary condenser 302 is connected to both the tube-side inlet N1 of the secondary main condenser 401 and the tube-side inlet N1 of the secondary secondary condenser 402. The tube-side inlet N1 of the secondary secondary condenser 402 is also connected to the tube-side outlet N2 of the primary main condenser 301. The tube-side outlet of the secondary secondary condenser 402... The outlet N2 is connected to the tube-side inlet N1 of the tertiary condenser 5. The shell-side outlet N4 of the tertiary condenser 5 is connected to the shell-side inlet N3 of the secondary condenser 402. The shell-side outlet N4 of the secondary condenser 402 is connected to the shell-side inlet N3 of the primary condenser 301 and the shell-side inlet N3 of the primary condenser 302. The shell-side outlet N4 of the primary condenser 302 is connected to the purified gas outlet 1103.

[0052] It should be noted that, in this embodiment, the tube-side air inlet of the first-stage condenser includes the tube-side air inlet N1 of the first-stage main condenser 301 and the tube-side air inlet N1 of the first-stage secondary condenser 302, and the shell-side air outlet of the first-stage condenser includes the shell-side air outlet N4 of the first-stage main condenser 301 and the shell-side air outlet N4 of the first-stage secondary condenser 302.

[0053] In some embodiments, a demister 8 is provided below the tube outlet N2 of the primary condenser 301, the secondary condenser 401, the tertiary condenser 5, the quaternary condenser 6, the primary secondary condenser 302, and the secondary secondary condenser 402; each of the primary condenser 301, the secondary condenser 401, the tertiary condenser 5, the quaternary condenser 6, the primary secondary condenser 302, and the secondary secondary condenser 402 is provided with a drain port D, and each drain port D is connected to an oil collection tank 7.

[0054] In addition, a multi-stage purification and reuse device for nitrogen-sealed VOCs further includes a first programmable valve 201, a second programmable valve 202, a third programmable valve 203, a fourth programmable valve 204, a fifth programmable valve 205, a sixth programmable valve 206, a seventh programmable valve 207, an eighth programmable valve 208, a ninth programmable valve 209, a tenth programmable valve 210, an eleventh programmable valve 211, a twelfth programmable valve 212, a thirteenth programmable valve 213, and a fourteenth programmable valve 214. Wherein:

[0055] The inlet of the first programmable valve 201 is connected to the outlet of the fan 1, and the outlet of the first programmable valve 201 is connected to the tube-side inlet N1 of the primary condenser 301. The inlet of the second programmable valve 202 is connected to the outlet of the fan 1, and the outlet of the second programmable valve 202 is connected to the tube-side inlet N1 of the secondary condenser 302. In this way, the outlet of the fan 1 is connected to the tube-side inlet N1 of the primary condenser 301 via the first programmable valve 201, and to the tube-side inlet N1 of the secondary condenser 302 via the second programmable valve 202. After being pressurized by the fan 1, VOCs can enter the primary condenser 301 and the secondary condenser 302 for heat exchange, reducing the temperature of the VOCs gas to about 0 to -5 degrees Celsius, thereby liquefying the water vapor in the VOCs. The gas and liquid are separated by the demister 8 installed inside the primary condenser 301 and the secondary condenser 302. The non-condensable gas is discharged from the tube outlet N2 of the primary condenser 301 and the secondary condenser 302, and the condensate is discharged into the oil collection tank 7 through the drain outlet D of the primary condenser 301 and the secondary condenser 302.

[0056] The inlet of the fifth programmable valve 205 is connected to the tube-side outlet N2 of the primary condenser 301. The outlet of the fifth programmable valve 205 is connected to the inlet of the seventh programmable valve 207 and the inlet of the eighth programmable valve 208. The inlet of the sixth programmable valve 206 is connected to the tube-side outlet N2 of the primary secondary condenser 302. The outlet of the sixth programmable valve 206 is connected to the inlet of the seventh programmable valve 207 and the inlet of the eighth programmable valve 208. The outlet of the seventh programmable valve 207 is connected to the tube-side inlet N1 of the secondary condenser 401. The outlet of the eighth programmable valve 208 is connected to the tube-side inlet N1 of the secondary secondary condenser 402. In this way, the VOCs after primary condensation can enter the secondary main condenser 401 and the secondary secondary condenser 402 for heat exchange, further reducing the temperature of the VOCs to about -40 degrees Celsius. This allows some of the heavy components in the VOCs (such as butane and pentane) to be liquefied. The gas and liquid are separated by the demister 8 installed inside the secondary main condenser 401 and the secondary secondary condenser 402. The non-condensable gas is discharged from the tube outlet N2 of the secondary main condenser 401 and the secondary secondary condenser 402, and the condensate is discharged into the oil collection tank 7 through the drain outlet D of the secondary main condenser 401 and the secondary secondary condenser 402.

[0057] The inlet of the thirteenth programmable valve 213 is connected to the tube-side outlet N2 of the secondary main condenser 401, the outlet of the thirteenth programmable valve 213 is connected to the tube-side inlet N1 of the tertiary condenser 5, the inlet of the fourteenth programmable valve 214 is connected to the tube-side outlet N2 of the secondary condenser 402, and the outlet of the fourteenth programmable valve 214 is connected to the tube-side inlet N1 of the tertiary condenser 5. In this way, the VOCs treated by the secondary main condenser 401 and the secondary secondary condenser 402 can enter the tertiary condenser 5 for heat exchange, further reducing the temperature of the VOCs to about -80 degrees Celsius, and liquefying some of the gases in the VOCs (such as butane, propane, etc.). The gas and liquid are separated by the demister 8 installed inside the tertiary condenser 5. The non-condensable gas is discharged from the tube outlet N2 of the tertiary condenser 5, and the condensate is discharged into the oil collection tank 7 through the drain outlet D of the tertiary condenser 5.

[0058] The tube-side outlet N2 of the third-stage condenser 5 is directly connected to the tube-side inlet N1 of the fourth-stage condenser 6, allowing the gas purified by the third-stage condenser to exchange heat again with the liquid nitrogen entering through the shell-side inlet N3 of the fourth-stage condenser. This further reduces the VOCs temperature to about -120 degrees Celsius, and then liquefies and condenses more than 97% of the VOCs again. The non-condensable gas is discharged from the tube-side outlet N2 of the fourth-stage condenser 6 and mixes with the partially vaporized low-temperature nitrogen discharged from the shell-side outlet N4 of the fourth-stage condenser 6, flowing to the shell-side inlet N3 of the third-stage condenser 5.

[0059] The inlet of the eleventh-stage control valve 211 is connected to the shell-side outlet N4 of the tertiary condenser 5, and the outlet of the eleventh-stage control valve 211 is connected to the shell-side inlet N3 of the secondary main condenser 401. The inlet of the twelfth-stage control valve 212 is connected to the shell-side outlet N4 of the tertiary condenser 5, and the outlet of the twelfth-stage control valve 212 is connected to the shell-side inlet N3 of the secondary condenser 402. In this way, the low-temperature mixed gas discharged from the quaternary condenser 6, after heat exchange in the tertiary condenser 5, can enter the secondary main condenser 401 or the secondary condenser 402 for heat exchange, respectively.

[0060] The inlet of the tenth programmable valve 210 is connected to the shell-side outlet N4 of the secondary main condenser 401. The outlet of the tenth programmable valve 210 is connected to the inlet of the third programmable valve 203 and the inlet of the fourth programmable valve 204. The inlet of the ninth programmable valve 209 is connected to the shell-side outlet N4 of the secondary condenser 402. The outlet of the ninth programmable valve 209 is connected to the inlet of the third programmable valve 203 and the inlet of the fourth programmable valve 204. The outlet of the fourth programmable valve 204 is connected to the shell-side inlet N3 of the primary main condenser 301. The outlet of the third programmable valve 203 is connected to the shell-side inlet N3 of the primary secondary condenser 302. In this way, the low-temperature mixed gas discharged from the secondary main condenser 401 or the secondary condenser 402 can be heat-exchanged by the primary main condenser 301 and the primary secondary condenser 302, respectively.

[0061] The shell-side outlet N4 of the primary condenser 301 and the shell-side outlet N4 of the secondary condenser 302 are both connected to the purified gas outlet 1103. Finally, the nitrogen gas with extremely low oxygen content flows from the purified gas outlet 1103 to the nitrogen sealing system.

[0062] In some embodiments, temperature detection instruments 9 are provided at the tube outlet N2 of the primary condenser 301, the secondary condenser 401, the tertiary condenser 5, the quaternary condenser 6, the primary secondary condenser 302, and the secondary secondary condenser 402.

[0063] In some embodiments, a first differential pressure detector 1001 is provided on the pipeline between the inlet of the first programmable valve 201 and the outlet of the fifth programmable valve 205, and on the pipeline between the inlet of the second programmable valve 202 and the outlet of the sixth programmable valve 206; a second differential pressure detector 1002 is provided on the pipeline between the inlet of the seventh programmable valve 207 and the outlet of the thirteenth programmable valve 213, and on the pipeline between the inlet of the eighth programmable valve 208 and the outlet of the fourteenth programmable valve 214.

[0064] The following details the working process or usage of a multi-stage purification and reuse device for nitrogen-sealed VOCs according to this application:

[0065] After VOCs enter the device, they are first pressurized by fan 1. The first control valve 201, the fourth control valve 204, the fifth control valve 205, the seventh control valve 207, the tenth control valve 210, the eleventh control valve 211, and the thirteenth control valve 213 are opened first. VOCs first enter the heat exchange tubes of the primary main condenser 301, and then pass through the demister 8 of the primary main condenser 301 for gas-liquid separation before being discharged from the tube side outlet N2 (this process is hereinafter referred to as: tube side). VOCs then re-enter the tube side of the secondary main condenser 401, the tube side of the tertiary condenser 5, and the tube side of the quaternary condenser 6, respectively, to achieve graded condensation and purification.

[0066] After entering the device, liquid nitrogen flows to the outside of the heat exchange tubes of the fourth-stage condenser 6, where it exchanges heat with VOCs and is then discharged from the shell-side outlet N4 of the fourth-stage condenser 6 (this process is referred to as the shell side). The purified VOCs discharged from the tube side of the fourth-stage condenser 6 and the low-temperature nitrogen discharged from the shell side are mixed and then pass through the tube side of the third-stage condenser 5, the tube side of the second-stage main condenser 401, and the tube side of the first-stage main condenser 301 as cold sources to conduct staged heat exchange with VOCs. Finally, it is discharged into the nitrogen sealing system through the purified gas outlet 1103, so that the nitrogen in the low-oxygen VOCs and the nitrogen after liquid nitrogen vaporization can be recycled and reused.

[0067] If the primary condenser 301 experiences frosting during operation, it may lead to blockage of the heat exchange tubes or reduced heat exchange efficiency. Specifically, when the first differential pressure detector 1001 or temperature detector 9 reaches the alarm threshold, the device will automatically open the second control valve 202, the third control valve 203, and the sixth control valve 206, while simultaneously closing the first control valve 201, the fourth control valve 204, and the fifth control valve 205. VOCs will then enter the primary secondary condenser 302, and the low-temperature mixed gas returning from the secondary condenser 402 will also enter the primary secondary condenser 302, where heat exchange and condensation will be performed. At this time, manual defrosting of the primary condenser 301 can be performed to resolve the fault. Similarly, when the primary secondary condenser 302 also experiences frosting, the device will automatically switch to the primary condenser 301 for heat exchange, ensuring long-term stable operation of the equipment.

[0068] If the secondary main condenser 401 experiences frosting during operation, it may lead to blockage of the heat exchange tubes or reduced heat exchange efficiency. Specifically, when the second differential pressure detector 1002 or temperature detector 9 reaches the alarm threshold, the device will automatically open the eighth control valve 208, the ninth control valve 209, the twelfth control valve 212, and the fourteenth control valve 214, while simultaneously closing the seventh control valve 207, the tenth control valve 210, the eleventh control valve 211, and the thirteenth control valve 213. VOCs gas will then enter the secondary secondary condenser 402, and the low-temperature mixed gas returning from the tertiary condenser 5 will also enter the secondary secondary condenser 402, where heat exchange and condensation will be performed. At this time, manual defrosting of the secondary main condenser 401 can be performed to resolve the fault. Similarly, when the secondary secondary condenser 402 also experiences frosting, the device will automatically switch to the secondary main condenser 401 for heat exchange, ensuring long-term stable operation of the equipment.

[0069] After VOCs are purified by the first stage of condensation at 0 to -5 degrees Celsius and the second stage at -40 degrees Celsius, almost no solid particles will form in the residual gas, thus preventing equipment frost malfunctions. Therefore, differential pressure detection is not required for the third-stage condenser 5 and the fourth-stage condenser 6. The operating status of the equipment is monitored only by temperature sensors 9 located at the tube-side outlet N2 of the third-stage condenser and the tube-side outlet N2 of the fourth-stage condenser 6. When the temperature sensors 9 detect excessively high or low temperatures at the tube-side outlets N2 of the third-stage condenser and N2 of the fourth-stage condenser 6, the long-term stable operation of the equipment can be ensured by adjusting the liquid nitrogen flow rate.

[0070] In some embodiments, the shell-side inlet N3 of the fourth-stage condenser 6 can also be connected to a liquid nitrogen flow regulating valve, and VOCs concentration sensors are provided at the shell-side outlet N4 of the first-stage main condenser 301 and the shell-side outlet N4 of the first-stage secondary condenser 302. The liquid nitrogen flow regulating valve is configured to regulate the liquid nitrogen input based on the data from the VOCs concentration sensors.

[0071] In this way, when the VOCs concentration sensor monitors in real time the residual VOCs at the shell-side outlet N4 of the primary condenser 301 and the shell-side outlet N4 of the secondary condenser 302, the liquid nitrogen flow regulating valve automatically increases the liquid nitrogen input to enhance condensation when the concentration is detected to increase, and reduces the liquid nitrogen supply when the concentration is decreased. The liquid nitrogen flow regulating valve (such as a cryogenic proportional regulating valve) achieves fine regulation of the liquid nitrogen flow rate through a PID algorithm combined with temperature feedback and concentration data.

[0072] Considering that excessive liquid nitrogen can cause the condenser to freeze and become blocked (increasing resistance), while insufficient liquid nitrogen will result in incomplete condensation of VOCs, the above-mentioned dynamic adjustment method can ensure that the condensation temperature of the device is always within the optimal condensation range.

[0073] In summary, the multi-stage purification and reuse device for nitrogen-sealed VOCs provided in this application avoids the inherent safety and environmental hazards of traditional oil and gas recovery and treatment equipment through a multi-stage liquid nitrogen condensation purification process. It achieves nitrogen recycling and reuse, and also avoids the risk of high-pressure, high-concentration oil and gas leakage present in traditional recovery and treatment devices. Specifically, six condensers and fourteen programmable valves achieve four-stage cooling capacity distribution and redundant switching for condenser frosting, solving the problems of low cooling capacity utilization, high heat exchanger failure rate, high liquid nitrogen consumption, high energy consumption, and high cost of redundant systems inherent in existing liquid nitrogen condensation and recovery technologies. Furthermore, this device employs a novel process where liquid nitrogen vaporized gas is mixed with non-condensable VOCs gas as a low-temperature cold source for heat exchange in the tertiary, secondary, and tertiary condensers. This not only fully utilizes the cooling capacity of liquid nitrogen and effectively removes VOCs components from low-oxygen VOCs gas, but also improves the purity of nitrogen in the purified gas, achieving nitrogen recycling and reuse in low-oxygen VOCs and ensuring the safety of the nitrogen-sealing system.

[0074] It should be noted that in this specification, relational terms such as first and second are used only to distinguish one entity from several other entities, and do not necessarily require or imply any such actual relationship or order between these entities.

[0075] The above provides a detailed description of a multi-stage purification and reuse device for nitrogen-sealed VOCs provided in this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the embodiments above are merely for the purpose of helping to understand the solution and core ideas of this application. It should be noted that those skilled in the art can make various improvements and modifications to this application without departing from its principles, and these improvements and modifications also fall within the protection scope of this application.

Claims

1. A multi-stage purification and reuse device for nitrogen-sealed VOCs, characterized in that, It includes multiple condensers, which include at least a first-stage condenser and a last-stage condenser. The tube-side inlet of the first-stage condenser is used to connect to the VOCs inlet, and the shell-side outlet of the first-stage condenser is used to connect to the purified gas outlet. The shell-side inlet of the last-stage condenser is used to connect to the liquid nitrogen inlet. The heat exchange tubes of the multiple condensers are connected sequentially via tube-side connecting pipelines, and the shells of the multiple condensers are also connected sequentially via shell-side connecting pipelines, such that: VOCs introduced through the VOCs inlet flow out of the final condenser from the first condenser via the tube-side connecting pipelines; and liquid nitrogen introduced through the liquid nitrogen inlet enters the final condenser and undergoes heat exchange in the final condenser, and then, together with the VOCs flowing out of the final condenser, undergoes multi-stage heat exchange with the VOCs flowing out of the final condenser via the shell-side connecting pipelines towards the first condenser and flows out from the purified gas outlet.

2. The multi-stage purification and reuse device for nitrogen-sealed VOCs as described in claim 1, characterized in that, The first-stage condenser includes a primary condenser, and a secondary primary condenser and a tertiary condenser are provided between the first-stage condenser and the final-stage condenser. Specifically, the final-stage condenser is a quaternary condenser. The tube-side inlet of the first-stage main condenser is connected to the VOCs inlet; the tube-side outlet of the first-stage main condenser is connected to the tube-side inlet of the second-stage main condenser; the tube-side outlet of the second-stage main condenser is connected to the tube-side inlet of the third-stage condenser; the tube-side outlet of the third-stage condenser is connected to the tube-side inlet of the fourth-stage condenser; the tube-side outlet of the fourth-stage condenser is connected to the shell-side inlet of the third-stage condenser; the shell-side outlet of the third-stage condenser is connected to the shell-side inlet of the second-stage main condenser; the shell-side outlet of the second-stage main condenser is connected to the shell-side inlet of the first-stage main condenser; and the shell-side outlet of the first-stage main condenser is connected to the purified gas outlet.

3. The multi-stage purification and reuse device for nitrogen-sealed VOCs as described in claim 2, characterized in that, The first-stage condenser also includes a primary secondary condenser, and the plurality of condensers also include a secondary secondary condenser; The tube-side inlet of the first-stage secondary condenser is connected to the VOCs inlet. The tube-side outlet of the first-stage secondary condenser is connected to both the tube-side inlet of the second-stage main condenser and the tube-side inlet of the second-stage secondary condenser. The tube-side inlet of the second-stage secondary condenser is connected to the tube-side outlet of the first-stage main condenser. The tube-side outlet of the second-stage secondary condenser is connected to the tube-side inlet of the third-stage condenser. The shell-side outlet of the third-stage condenser is connected to the shell-side inlet of the second-stage secondary condenser. The shell-side outlet of the second-stage secondary condenser is connected to both the shell-side inlet of the first-stage main condenser and the shell-side inlet of the first-stage secondary condenser. The shell-side outlet of the first-stage secondary condenser is connected to the purified gas outlet.

4. The multi-stage purification and reuse device for nitrogen-sealed VOCs as described in claim 3, characterized in that, The multi-stage purification and reuse device for nitrogen-sealed VOCs also includes a first programmable valve, a second programmable valve, a third programmable valve, a fourth programmable valve, a fifth programmable valve, a sixth programmable valve, a seventh programmable valve, an eighth programmable valve, a ninth programmable valve, a tenth programmable valve, an eleventh programmable valve, a twelfth programmable valve, a thirteenth programmable valve, and a fourteenth programmable valve. The inlet of the first programmable valve is connected to the VOCs inlet, the outlet of the first programmable valve is connected to the tube-side inlet of the primary condenser, the inlet of the second programmable valve is connected to the VOCs inlet, and the outlet of the second programmable valve is connected to the tube-side inlet of the primary secondary condenser. The inlet of the fifth programmable valve is connected to the tube-side outlet of the first-stage main condenser; the outlet of the fifth programmable valve is connected to the inlet of the seventh programmable valve and the inlet of the eighth programmable valve; the inlet of the sixth programmable valve is connected to the tube-side outlet of the first-stage secondary condenser; the outlet of the sixth programmable valve is connected to the inlet of the seventh programmable valve and the inlet of the eighth programmable valve; the outlet of the seventh programmable valve is connected to the tube-side inlet of the second-stage main condenser; and the outlet of the eighth programmable valve is connected to the tube-side inlet of the second-stage secondary condenser. The inlet of the thirteenth programmable valve is connected to the tube-side outlet of the secondary main condenser, the outlet of the thirteenth programmable valve is connected to the tube-side inlet of the tertiary condenser, the inlet of the fourteenth programmable valve is connected to the tube-side outlet of the secondary condenser, and the outlet of the fourteenth programmable valve is connected to the tube-side inlet of the tertiary condenser. The inlet of the eleventh programmable valve is connected to the shell-side outlet of the third-stage condenser, the outlet of the eleventh programmable valve is connected to the shell-side inlet of the second-stage main condenser, the inlet of the twelfth programmable valve is connected to the shell-side outlet of the third-stage condenser, and the outlet of the twelfth programmable valve is connected to the shell-side inlet of the second-stage secondary condenser. The inlet of the tenth programmable valve is connected to the shell-side outlet of the secondary main condenser. The outlet of the tenth programmable valve is connected to the inlet of the third programmable valve and the inlet of the fourth programmable valve. The inlet of the ninth programmable valve is connected to the shell-side outlet of the secondary secondary condenser. The outlet of the ninth programmable valve is connected to the inlet of the third programmable valve and the inlet of the fourth programmable valve. The outlet of the fourth programmable valve is connected to the shell-side inlet of the primary main condenser. The outlet of the third programmable valve is connected to the shell-side inlet of the primary secondary condenser.

5. The multi-stage purification and reuse device for nitrogen-sealed VOCs as described in claim 3, characterized in that, Demisters are installed below the tube outlets of the primary condenser, the secondary condenser, the tertiary condenser, the quaternary condenser, the primary secondary condenser, and the secondary secondary condenser.

6. The multi-stage purification and reuse device for nitrogen-sealed VOCs as described in claim 3, characterized in that, The primary condenser, the secondary condenser, the tertiary condenser, the quaternary condenser, the primary secondary condenser, and the secondary secondary condenser are all equipped with drain ports, and each drain port is connected to an oil collection tank.

7. The multi-stage purification and reuse device for nitrogen-sealed VOCs as described in claim 3, characterized in that, Temperature detection instruments are installed at the tube outlets of the primary condenser, the secondary condenser, the tertiary condenser, the quaternary condenser, the primary secondary condenser, and the secondary secondary condenser.

8. The multi-stage purification and reuse device for nitrogen-sealed VOCs as described in claim 4, characterized in that, A first differential pressure detector is installed on the pipeline between the air inlet of the first programmable valve and the air outlet of the fifth programmable valve, and on the pipeline between the air inlet of the second programmable valve and the air outlet of the sixth programmable valve. A second differential pressure detector is installed on the pipeline between the air inlet of the seventh programmable valve and the air outlet of the thirteenth programmable valve, and on the pipeline between the air inlet of the eighth programmable valve and the air outlet of the fourteenth programmable valve.

9. The multi-stage purification and reuse device for nitrogen-sealed VOCs as described in claim 2, characterized in that, The condensing temperatures of the primary main condenser, the secondary main condenser, the tertiary condenser, and the quaternary condenser decrease sequentially. The condensing temperature range of the primary main condenser is 0 to -5 degrees Celsius, the condensing temperature range of the secondary main condenser is -35 to -45 degrees Celsius, the condensing temperature range of the tertiary condenser is -75 to -85 degrees Celsius, and the condensing temperature range of the quaternary condenser is -115 to -125 degrees Celsius.

10. The multi-stage purification and reuse device for nitrogen-sealed VOCs as described in any one of claims 1-9, characterized in that, The multi-stage purification and reuse device for nitrogen-sealed VOCs also includes a fan, the inlet of which is connected to the VOCs inlet, and the outlet of which is connected to the tube inlet of the first-stage condenser. The shell-side inlet of the final stage condenser is connected to a liquid nitrogen flow regulating valve, and a VOCs concentration sensor is provided at the shell-side outlet of the first stage condenser. The liquid nitrogen flow regulating valve is configured to adjust the liquid nitrogen input based on the data from the VOCs concentration sensor.

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