JP7461679B2 - System and method for VOCs recovery that integrates absorption, desorption and recovery - Google Patents

Description

The present invention relates to a VOCs recovery process, and more specifically to a VOCs recovery system and method that integrates absorption, desorption, and recovery.

In various industrial production and related processes, volatile organic compounds (VOCs) are often generated, whose molecular structure contains oxygen, nitrogen, sulfur, and chlorine in addition to carbon and hydrogen. If they are discharged, they will cause many serious harms to society and enterprises. For example, when a large amount of VOCs is evaporated and discharged, they have a high density and float and concentrate in the ground surface space, which not only easily causes fires and explosions, but also irritates the human respiratory tract and causes cancer and other risks. Moreover, they are the main reactants that generate photochemical smog, which causes serious harm to the ecology and environment. China has limited oil resources and is also a country that consumes and imports a lot of oil, so it is necessary to effectively recover VOCs. Existing recovery methods mainly adopt single recovery methods such as adsorption, absorption, condensation, and membrane methods, but in actual operation, the single use of these methods will cause a series of problems and the recovery efficiency is low. For example, the absorption method requires high performance of the absorbent, consumes a large amount of absorbent, and occupies a large space of the device, resulting in low process recovery rate. In practical application, the adsorption method generally selects an adsorbent with relatively desirable adsorption performance and reasonable price, such as activated carbon, but the heat of adsorption of activated carbon is high and the adsorption temperature rises rapidly, which not only leads to a decrease in adsorption performance and service life, but also increases safety issues such as fire and explosion. The condensation method requires high temperature, and needs to condense gas at extremely low temperatures to achieve the desired condensation effect, so it has high requirements for materials and processes, and the recovery and operation costs are relatively high. Oil and gas recovery by membrane method is a modern oil and gas separation technology that emerged in the second half of the last century. It can achieve separation by various molecular sizes, occupy a small space area, operate stably, and are easy to maintain, but it generally needs to be combined with other processes to achieve the desired separation efficiency.

The technical problem that this invention aims to solve is how to further improve the absorption efficiency of VOCs recovery and treatment systems and further reduce energy consumption and operating costs.

To solve the above technical problems, the present invention is realized by the following technical solutions.

a water washing unit connected to the automatic coupling pre-cooling unit and used for washing the VOCs-introducing gas;
an automatic combined pre-cooling unit connected to the low temperature absorption unit and used for condensing the VOCs gas after washing;
a low-temperature absorption unit connected to the high-temperature desorption unit via a heat exchanger 220 and used to absorb the condensed VOCs gas;
a high-temperature desorption unit connected to the low-temperature recovery unit via a heat exchanger 3 24 and used to desorb the VOCs gas after low-temperature absorption;
This is a VOC recovery system that integrates absorption, desorption and recovery, and includes a low-temperature recovery unit that is connected to the low-temperature absorption unit and is used to recover liquefied VOCs and transport unliquefied VOCs back to the low-temperature absorption unit for treatment.

The water washing unit is a multi-stage spray tower, and includes a water washing tower 3 equipped with two tower plates and two nozzles, the two nozzles being the first water washing tower nozzle 501 and the second water washing tower nozzle 502, which are respectively supplied with water by the first water washing tower circulation spray pump 601 and the second water washing tower circulation spray pump 602, and a small overflow pipe 14 is installed on the second tower plate. This achieves sufficient water washing of more than 80% of the VOCs gas introduced into the water washing tower.

The automatic coupling pre-cooling unit is an internal automatic coupling one-driven two-type defrosting system, which includes a two-stage condensing device A9, a two-stage condensing device B10 and a single-stage condensing device 7. There are two types of connection between the two-stage condensing device A, the two-stage condensing device B and the single-stage condensing device, namely, a first condensing circuit 2801 and a second condensing circuit 2802.
The connection manner of the first condensation circuit is as follows: an inlet end of the two-stage condenser B is connected to an outlet end of the water washing tower of the water washing unit, an outlet end of the two-stage condenser B is connected to an inlet end of the single-stage condenser, an outlet end of the single-stage condenser is connected to an inlet end of the two-stage condenser A, and an outlet end of the two-stage condenser A is connected to the low-temperature absorption unit;
The connection method of the second condensation circuit is such that the inlet end of the two-stage condenser A is connected to the outlet end of the water washing tower of the water washing unit, the outlet end of the two-stage condenser A is connected to the inlet end of the single-stage condenser, the outlet end of the single-stage condenser is connected to the inlet end of the two-stage condenser B, and the outlet end of the two-stage condenser B is connected to the low-temperature absorption unit.

The single-stage condenser, two-stage condenser A, and two-stage condenser B of the automatic combined pre-cooling unit are all connected to a liquid separation tank 111, and the liquid separation tank 1 is divided based on density, with the middle being a buffer region, the left side being an organic matter region, and the right side being a condensed water region.

The single-stage condenser performs primary condensation, and the two-stage condenser A and the two-stage condenser B perform advanced condensation. The VOCs gas undergoes advanced condensation first, and then primary condensation, thereby preventing the primary condenser from frosting, and then undergoes further advanced condensation. The second highly condensed gas outlet becomes the outlet of the automatically coupled pre-cooling unit, which is connected to the inlet of the low-temperature absorption unit.

When frost has formed on the two-stage condenser B and defrosting is required, the first condensation circuit is operated and the VOCs gas condenses by passing through the two-stage condenser B, the single-stage condenser, and the two-stage condenser A in that order. When frost has formed on the two-stage condenser A and defrosting is required, the second condensation circuit is operated and the VOCs gas condenses by first passing through the two-stage condenser A, and then condenses by passing through the single-stage condenser and the two-stage condenser B in that order.

The low-temperature absorption unit is a multi-stage spray tower, and includes an absorption tower 13 equipped with two tower plates and two nozzles. The gas inlet end of the absorption tower is installed above the liquid level of the absorbing liquid in the first layer of the absorption tower. The second layer tower plate of the absorption tower is equipped with a number of overflow pipes 2 14 for the transmission of VOCs gas and the overflow transmission of the second layer absorbing liquid. After the VOCs gas is sprayed by the nozzle 1501 of the first layer of the absorption tower, it enters the second layer of the absorption tower through the overflow pipe 2, and is further sprayed by the nozzle 1502 of the second layer of the absorption tower, thereby achieving sufficient absorption of the VOCs gas. An approved gas outlet is also installed at the top of the absorption tower.

The low temperature absorption unit is
A first self-circulating absorbing liquid circuit 2803 in which an outlet of the absorbing liquid in the first layer of the absorption tower is connected to a nozzle of the first layer of the absorption tower via an absorption tower first-stage circulation spray pump 1601, thereby realizing spraying of VOCs gas;
The second layer absorbent outlet of the absorber is connected to the second layer nozzle of the absorber via the absorber two-stage circulation spray pump 1602, and a second self-circulating absorbent circuit 2804 is included to realize further spraying of VOCs gas.

The high-temperature desorption unit includes a desorption tower 21, and the connection manner between the desorption tower and the absorption tower in the low-temperature absorption unit is as follows:
a first desorption circuit 2805 in which a bottom absorbing liquid outlet of the absorption tower in the low temperature absorption unit is connected to an absorbing liquid inlet end at an upper part of the tower body of the desorption tower in the high temperature desorption unit through a tube layer of a heat exchanger 2;
a second desorption circuit 2806 in which the bottom lower absorbent outlet of the desorption column in the high temperature desorption unit is connected to the inlet of the second self-circulating absorbent circuit in the low temperature absorption unit through the shell of the heat exchanger 2;
The absorbing liquid in the first self-circulating absorbing liquid circuit, the second self-circulating absorbing liquid circuit, the first desorption circuit and the second desorption circuit of the absorber and the absorbing liquid in the absorber and desorption tower form a flow rate balance.

The desorption tower in the high-temperature desorption unit is connected to the absorption tower in the low-temperature absorption unit via a recovery circuit 2807, and the recovery circuit is configured so that the top outlet of the desorption tower is connected to the horizontal recovery tank 18 via a heat exchanger 3 and a vacuum pump 25, and the top outlet of the horizontal recovery tank is connected to the inlet end of the absorption tower.

The outlet end of the heat source 23 of the desorption tower in the high-temperature desorption unit is connected to the trap 22.

The horizontal recovery tank of the low-temperature recovery unit is connected to liquid separation tank 2 19, which is divided by density, with a buffer zone in the middle, an organic matter zone on the left, and a condensed water zone on the right.

The inlet end of the water washing unit is connected to the VOCs gas introduced into the site via a flame arrester 1, and each unit and each pipeline is equipped with a brake valve 2 or automatic control valve 8 or ball valve 12 and a flow meter.

The VOCs gas undergoes heat exchange with the cold source 27 and the heat source, recovering excess cold and condensing or vaporizing the VOCs.

A heat exchanger 1 17 is installed between the absorption tower of the low-temperature absorption unit and the safety outlet, and the heat exchanger 1 recovers the surplus cold amount using the low-temperature gas discharged from the absorption tower of the low-temperature absorption unit, and supplements the cold amount to the cold source after the automatic coupling pre-cooling unit;
A heat exchanger 2 is installed between the absorption tower of the low-temperature absorption unit and the high-temperature desorption unit, which recovers heat from the low-temperature absorption liquid discharged from the low-temperature absorption unit and the high-temperature absorption liquid desorbed from the high-temperature desorption unit.

The single-stage condenser, the two-stage condenser A, the two-stage condenser B, heat exchanger 1, the built-in heat exchanger in the absorption tower, and the built-in heat exchanger in the horizontal recovery tank are all connected to a cold source via a recovery pump, the built-in heat exchanger in the desorption tower is connected to a heat source, and the heat exchanger 3 is a circulating water heat exchanger.

Step (1) of introducing VOCs gas into the site through a flame arrester and a water washing unit to remove ammonia, and then introducing the gas into an automatic combination pre-cooling unit;
(2) the VOCs gas is dehydrated in an automatic combined pre-cooling unit and then introduced into a low-temperature absorption unit;
Step (3) in which the low-temperature absorption unit operates the first self-circulating absorption liquid circuit and the second self-circulating absorption liquid circuit to absorb, the rich absorption liquid in the first layer of the absorption tower passes through the first desorption circuit, the cold amount is recovered by the tube layer of the heat exchanger 2, and then the rich absorption liquid is introduced into the desorption tower in the high-temperature desorption unit for desorption, the desorbed fresh absorption liquid passes through the second desorption circuit, the heat amount is recovered by the shell layer of the heat exchanger 2, and then the lean absorption liquid in the second layer of the absorption tower is preferentially supplemented;
The VOC recovery method utilizing the VOC recovery processing system includes a step (4) in which the desorbed VOC gas passes through a recovery circuit and is introduced into a horizontal recovery tank where it is condensed, liquefied and recovered, and the unliquefied VOC gas is transported again to the low-temperature absorption unit for absorption.

The present invention achieved the following useful effects:

In this invention, a VOCs recovery method is adopted that integrates water washing + automatic binding pre-cooling + low-temperature absorption + high-temperature desorption + low-temperature recovery. By combining the advantages of several methods and complementing each other's disadvantages, energy conservation is increased, and the absorption liquid can be recycled and reused, resulting in a significant reduction in energy consumption costs.

In this invention, a multi-stage washing tower and a multi-stage absorption tower are used to thoroughly wash and absorb VOCs, respectively, and a few overflow pipes installed in the second tower plate allow the VOCs to be transported upward and the liquid to overflow downward. Furthermore, by utilizing the self-circulating spray in the two tower layers, not only is the absorption efficiency and the efficiency of the absorbent used improved, but energy consumption and operating costs are also reduced.

In this invention, an internal automatic combined defrosting system is adopted, and the three condensers are one-driven two-type, and the internal circulation piping unit operates alternately according to the demand for defrosting, that is, the two advanced condensers are used alternately, which not only improves the pre-cooling efficiency, but also uses the heat of the VOCs themselves to defrost the advanced condensers alternately, greatly reducing the energy consumption and avoiding energy waste.

Heat exchanger 1 and heat exchanger 2 in the present invention recover excess cold from the low-temperature gas and low-temperature liquid in the absorption tower, respectively, improving the efficiency of heat utilization and reducing energy consumption.

Both the automatic combined pre-cooling unit and the low-temperature recovery unit in this invention are equipped with liquid separation tanks that separate the liquids based on density, with a buffer zone in the middle, an organic matter zone on the left, and a condensed water zone on the right, greatly improving the VOCs recovery rate and safety of use.

FIG. 2 is a structural connection schematic diagram of an apparatus according to an embodiment of the present invention. FIG. 2 is a structural connection schematic diagram of an apparatus according to an embodiment of the present invention. FIG. 2 is a detailed structural connection schematic diagram of the automatic combination pre-cooling unit in the apparatus of the embodiment according to the present invention; FIG. 2 is a schematic cross-sectional view of an overflow tube in the second layer of a water washing tower or an absorption tower in an embodiment of the present invention. FIG. 2 is a schematic diagram showing the process in which VOCs in an embodiment of the present invention pass through the overflow pipe of the second layer of a water washing tower or an absorption tower. FIG. 2 is a schematic diagram showing a process in which VOCs in an embodiment of the present invention pass through the overflow tube of the second layer of the absorption tower.

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be described in more detail with reference to the following examples. It should be understood that the specific examples described herein are merely for the purpose of illustrating the present invention, and are not intended to limit the present invention.

The application principle of this invention will be explained in detail below with reference to the drawings.

The VOCs treatment system of the present invention shown in FIG.
a water washing unit connected to the automatic coupling pre-cooling unit and used for washing the VOCs-introducing gas;
an automatic combined pre-cooling unit connected to the low temperature absorption unit and used for condensing the VOCs gas after washing;
a low-temperature absorption unit connected to the high-temperature desorption unit via a heat exchanger 220 and used to absorb the condensed VOCs gas;
a high-temperature desorption unit connected to the low-temperature recovery unit via a heat exchanger 3 24 and used to desorb the VOCs gas after low-temperature absorption;
and a low-temperature recovery unit connected to the low-temperature absorption unit for recovering the liquefied VOCs and transporting the unliquefied VOCs back to the low-temperature absorption unit for treatment.

The water washing unit shown in Figures 3 and 4 is a multi-stage spray tower, and includes a water washing tower 3 equipped with two tower plates and two nozzles, the two nozzles being the first water washing tower nozzle 501 and the second water washing tower nozzle 502, which are respectively supplied with water by the first water washing tower circulation spray pump 601 and the second water washing tower circulation spray pump 602, and a small overflow pipe 14 is installed on the second tower plate. This achieves sufficient washing of more than 80% of the VOCs gas introduced into the water washing tower.

The automatic coupling pre-cooling unit shown in FIG. 2 adopts an internal automatic coupling one-driven two-type defrosting system, which includes a two-stage condensing device A9, a two-stage condensing device B10 and a single-stage condensing device 7, and there are two types of connection between the two-stage condensing device A, the two-stage condensing device B and the single-stage condensing device, namely a first condensing circuit 2801 and a second condensing circuit 2802;
The connection manner of the first condensation circuit is as follows: an inlet end of the two-stage condenser B is connected to an outlet end of the water washing tower of the water washing unit, an outlet end of the two-stage condenser B is connected to an inlet end of the single-stage condenser, an outlet end of the single-stage condenser is connected to an inlet end of the two-stage condenser A, and an outlet end of the two-stage condenser A is connected to the low-temperature absorption unit;
The connection method of the second condensation circuit is such that the inlet end of the two-stage condenser A is connected to the outlet end of the water washing tower of the water washing unit, the outlet end of the two-stage condenser A is connected to the inlet end of the single-stage condenser, the outlet end of the single-stage condenser is connected to the inlet end of the two-stage condenser B, and the outlet end of the two-stage condenser B is connected to the low-temperature absorption unit.

The single-stage condenser, two-stage condenser A, and two-stage condenser B of the automatic combined pre-cooling unit are each connected to a liquid separation tank 111, and the liquid separation tank 1 is divided based on density, with the middle being a buffer region, the left side being an organic matter region, and the right side being a condensed water region.

The single-stage condenser performs primary condensation, and the two-stage condenser A and the two-stage condenser B perform advanced condensation. The VOCs gas undergoes advanced condensation first, and then primary condensation, thereby preventing the primary condenser from frosting, and then undergoes further advanced condensation. The second highly condensed gas outlet becomes the outlet of the automatically coupled pre-cooling unit, which is connected to the inlet of the low-temperature absorption unit.

When frost has formed on the two-stage condenser B and defrosting is required, the first condensation circuit is operated and the VOCs gas condenses by passing through the two-stage condenser B, the single-stage condenser, and the two-stage condenser A in that order. When frost has formed on the two-stage condenser A and defrosting is required, the second condensation circuit is operated and the VOCs gas condenses by first passing through the two-stage condenser A, and then condenses by passing through the single-stage condenser and the two-stage condenser B in that order.

The low-temperature absorption unit shown in Figures 3, 4, and 5 is a multi-stage spray tower, and includes an absorption tower 13 equipped with two tower plates and two nozzles. The gas inlet end of the absorption tower is installed above the liquid level of the absorbing liquid in the first layer of the absorption tower, and a number of overflow pipes 2 14 are installed on the tower plate of the second layer of the absorption tower for the transmission of VOCs gas and the overflow transmission of the second layer absorbing liquid. After the VOCs gas is sprayed by the nozzle 1501 of the first layer of the absorption tower, it enters the second layer of the absorption tower through the overflow pipe 2, and then sprayed by the nozzle 1502 of the second layer of the absorption tower, thereby achieving sufficient absorption of the VOCs gas. An approved gas outlet is also installed at the top of the absorption tower.

The low temperature absorption unit is
A first self-circulating absorbing liquid circuit 2803 in which an outlet of the absorbing liquid in the first layer of the absorption tower is connected to a nozzle of the first layer of the absorption tower via an absorption tower first-stage circulation spray pump 1601, thereby realizing spraying of VOCs gas;
The second layer absorbent outlet of the absorber is connected to the second layer nozzle of the absorber via the absorber two-stage circulation spray pump 1602, and a second self-circulating absorbent circuit 2804 is included to realize further spraying of VOCs gas.

The high-temperature desorption unit includes a desorption tower 21, and the connection manner between the desorption tower and the absorption tower in the low-temperature absorption unit is as follows:
a first desorption circuit 2805 in which the bottom absorption liquid outlet of the absorption tower in the low temperature absorption unit is connected to the absorption liquid inlet end at the top of the tower body of the desorption tower in the high temperature desorption unit through a tube layer of a heat exchanger 2;
a second desorption circuit 2806, in which the bottom lower absorption liquid outlet of the desorption column in the high temperature desorption unit is connected to the inlet of the second self-circulating absorption liquid circuit in the low temperature absorption unit through the shell of the heat exchanger 2;
The absorbing liquid in the first self-circulating absorbing liquid circuit, the second self-circulating absorbing liquid circuit, the first desorption circuit and the second desorption circuit of the absorber and the absorbing liquid in the absorber and desorption tower form a flow rate balance.

The desorption tower in the high-temperature desorption unit is connected to the absorption tower in the low-temperature absorption unit via a recovery circuit 2807, and the recovery circuit is configured so that the top outlet of the desorption tower is connected to the horizontal recovery tank 18 via a heat exchanger 3 and a vacuum pump 25, and the top outlet of the horizontal recovery tank is connected to the inlet end of the absorption tower.

The horizontal recovery tank of the low-temperature recovery unit is connected to liquid separation tank 2 19, which is divided by density, with a buffer zone in the middle, an organic matter zone on the left, and a condensed water zone on the right.

The inlet end of the water washing unit is connected to the VOCs gas introduced on-site via a flame arrester 1, and each unit and each pipeline is equipped with a brake valve 2 or an automatic control valve 8 or a ball valve 12 and a flow meter, and the outlet end of the heat source 23 of the desorption tower in the high-temperature desorption unit is connected to a trap 22.

The VOCs gas undergoes heat exchange with the cold source 27 and the heat source, recovering excess cold and condensing or vaporizing the VOCs.

Step (1) of introducing VOCs gas into the site through a flame arrester and a water washing unit to remove ammonia, and then introducing the gas into an automatic combination pre-cooling unit;
(2) the VOCs gas is dehydrated in an automatic combined pre-cooling unit and then introduced into a low-temperature absorption unit;
Step (3) in which the low-temperature absorption unit operates the first self-circulating absorption liquid circuit and the second self-circulating absorption liquid circuit to absorb, the rich absorption liquid in the first layer of the absorption tower passes through the first desorption circuit, the cold amount is recovered by the tube layer of the heat exchanger 2, and then the rich absorption liquid is introduced into the desorption tower in the high-temperature desorption unit for desorption, the desorbed fresh absorption liquid passes through the second desorption circuit, the heat amount is recovered by the shell layer of the heat exchanger 2, and then the lean absorption liquid in the second layer of the absorption tower is preferentially supplemented;
The desorbed VOCs gas passes through a recovery circuit and is introduced into a horizontal recovery tank where it is condensed, liquefied and recovered, and the unliquefied VOCs gas is transported again to the low-temperature absorption unit for absorption (4). This is a VOCs recovery method that integrates absorption, desorption and recovery.

In step (2), the VOCs gas is introduced into the two-stage condenser B, and then the VOCs are condensed and dehydrated in the single-stage condenser 7 and the two-stage condenser A, respectively, and the uncondensed VOCs gas is then introduced into the absorption tower of the low-temperature absorption unit.

In step (3), the VOCs gas is first sprayed and absorbed in the first layer of the absorption tower, at which point a large amount of VOCs is absorbed in the absorbing liquid, and the remaining VOCs gas passes through the overflow pipe 2 and is introduced into the second layer of the absorption tower, where it is highly absorbed through the spray of fresh absorbing liquid, and the gas that passes is discharged from the safety outlet via the heat exchanger 1.

In step (3), in addition to being used for its own spray, when the liquid level exceeds the overflow port of small tube 2, the absorbing liquid overflows and enters the rich absorbing liquid in the first layer of the absorbing tower.

In step (4), the high-temperature VOC gas is recovered from the top outlet of the desorption tower 21 via a recovery circuit; that is, the temperature is initially lowered with circulating water by the heat exchanger 3, and then the gaseous VOCs are introduced into the low-temperature horizontal recovery tank by the vacuum pump 25, where the gaseous VOCs are liquefied, the liquefied VOCs are recovered, and the unliquefied VOCs are introduced back into the absorption tower to continue the process.

In order to realize the conversion of the VOCs in the absorbent into two gas-liquid states and the separation by gas-liquid conversion, and to improve the separation efficiency, the heat exchange device includes:
A heat exchanger 117 is installed between the low-temperature absorption unit and the safety outlet, connected to a cold source via a recovery pump 26, and used for recovering surplus cold from the discharged low-temperature gas to supplement the cold source cold discharged from the automatic coupling pre-cooling unit;
The heat exchanger 2 is installed between the absorption tower of the low-temperature absorption unit and the high-temperature desorption unit, and one end of one of the heat exchange pipes is connected to the low-temperature absorption unit and the other end is connected to the high-temperature desorption unit.
The heat exchanger 2 recovers heat from the low temperature absorption liquid discharged from the low temperature absorption unit and from the high temperature absorption liquid desorbed from the high temperature desorption unit.
A heat exchanger 3 is provided between the high-temperature desorption unit and the low-temperature recovery unit;
The heat exchanger 3 is a circulating water heat exchanger, and is intended to prevent high-temperature VOCs from damaging the vacuum pump. The low-temperature VOCs that have been cooled by the heat exchanger 3 are transported by the vacuum pump to the horizontal recovery tank, where they are further condensed, and the VOCs that have turned into liquid are stored in the liquid separation tank 2 of the low-temperature recovery unit.
The automatic combined pre-cooling unit includes a single-stage condenser, a two-stage condenser A, and a two-stage condenser B, and the single-stage condenser, the two-stage condenser A, and the two-stage condenser B are connected to a cold source via a recovery pump.
The heat exchange unit further includes built-in heat exchangers built into the absorption tower, desorption tower and horizontal recovery tank, respectively, and a heat exchange circulation line in the heat exchange unit, of which the built-in heat exchangers in the absorption tower and horizontal recovery tank are connected to a cold source via a recovery pump, and the built-in heat exchanger in the desorption tower is connected to a heat source.

In one embodiment of the present invention, the cold source is a secondary refrigerant and the heat source is water vapor at a temperature greater than 100°C.

In an embodiment of the present invention, the VOCs recovery system specifically comprises:
The system includes a water washing unit consisting of a brake valve, a water washing tower, a first layer nozzle of the water washing tower, a second layer nozzle of the water washing tower, a water storage tank, a first stage circulation spray pump of the water washing tower, and a second stage circulation spray pump of the water washing tower. The VOCs that have passed through the flame arrester must pass through the water washing device, and the purpose of this is to remove ammonia by water washing and to remove large amounts of impurities that dissolve in water.

The washing tower adopts a vertical washing tower, with a height of 3m-15m and a diameter of 0.5m-3m. The washing tower is designed as a multi-stage spray type, with a few overflow pipes 1 installed on the second layer of tower plate, with the diameter of the overflow pipes 1 being φ10mm-φ30mm, the height being 5mm-10mm, and the total cross-sectional area being 5%-15% of the cross-sectional area of the tower plate, a water storage tank with a water storage capacity of 0.5 tons-10 tons is installed on the first layer of the washing tower, and the spray amount is 5m ³ /h-50m ³ /h, the water source of the second layer of the washing tower is supplied from a water replenishment port, with the water replenishment amount being 1m ³ /h-5m ³ /h, the spray amount being 5m ³ /h-50m ³ /h, and the ammonia (water) recovery amount by the washing tower is 5kg/h-100kg/h.

A VOCs outlet is installed at the top of the absorption tower, and a VOCs inlet is installed at the bottom of the tower body above the highest liquid level of the absorbing liquid, so that gas is introduced from below and comes into contact with the sprayed absorbing liquid in the opposite direction to achieve sufficient absorption. The absorption tower is also designed as a multi-stage spray type, and a number of overflow pipes 2 are installed on the second layer of tower plates, with a diameter of φ10mm to φ30mm, a height of 5mm to 10mm, and a total cross-sectional area of 5% to 15% of the tower plate cross-sectional area. The diameter of the tower body is generally determined according to the amount of oil gas to be treated. Generally, the height of the tower body is 3m to 15m, the diameter is 0.5m to 3m, the storage height is 0.3m to 4m, the operation temperature of the tower is designed to be -25℃ to -5℃, the cold source flow rate in the built-in heat exchanger is 0.5m ³ /h ² to 3m ³ /h ² , and the spray rate of the first layer and the second layer is 5m ³ /h to 50m ³ /h.

The desorption tower uses high-temperature steam as the heat medium, has a tower diameter of 0.1m to 3m, a height of 0.5m to 5m, a high-temperature steam temperature of 120℃ to 150℃, a steam consumption rate of 1kg/h to 5kg/h, and a desorption rate of 0.5kg/h to 50kg/h.

The horizontal recovery tank has a diameter of 0.2m to 3m, a length of 0.5m to 5m, and a recovery liquid rate of 0.5kg/h to 50kg/h.

The temperature of the circulating water in the heat exchanger 3 is 10° C. to 100° C., and the flow rate is 0.01 m ³ /h to 2 m ³ /h.

In the VOCs recovery system of the present invention, the secondary refrigerant pipe connected to the cold source generally uses DN10 to DN20, the secondary refrigerant temperature is -25°C to -10°C, and the secondary refrigerant flow rate is 1 m ³ /h to 20 m ³ /h.

The above shows and describes the basic principles, main features and advantages of the present invention. The present invention is not limited to the above embodiments, and the above embodiments and specification are merely intended to describe the principles of the present invention. As long as they do not deviate from the spirit and scope of the present invention, various changes and improvements are possible in the present invention, and it is obvious to those skilled in the art that all such changes and improvements are included in the scope of the present invention, which is protected by the present invention. The scope of protection of the present invention is limited by the appended claims and their equivalents.

(Additional Note)
(Appendix 1)
a water washing unit connected to the automatic coupling pre-cooling unit and used for washing the VOCs-introducing gas;
an automatic combined pre-cooling unit connected to the low temperature absorption unit and used for condensing the VOCs gas after washing;
a low-temperature absorption unit connected to the high-temperature desorption unit via a heat exchanger 2 and used to absorb the condensed VOCs gas;
a high-temperature desorption unit connected to the low-temperature recovery unit via a heat exchanger 3 and used for desorbing the VOCs gas after low-temperature absorption;
a low-temperature recovery unit connected to the low-temperature absorption unit for recovering the liquefied VOCs and transporting the unliquefied VOCs back to the low-temperature absorption unit for treatment;
A VOCs recovery system that integrates absorption, desorption and recovery.

(Appendix 2)
The water washing unit is a multi-stage spray tower, and includes a water washing tower having two tower plates and two nozzles.
2. A VOCs recovery system that integrates absorption, desorption and recovery, as described in claim 1.

(Appendix 3)
The automatic combined pre-cooling unit includes a two-stage condensing device A, a two-stage condensing device B and a single-stage condensing device, and the two-stage condensing device A, the two-stage condensing device B and the single-stage condensing device are connected in two ways, namely, a first condensing circuit and a second condensing circuit;
The connection manner of the first condensation circuit is as follows: an inlet end of the two-stage condenser B is connected to an outlet end of the water washing tower of the water washing unit, an outlet end of the two-stage condenser B is connected to an inlet end of the single-stage condenser, an outlet end of the single-stage condenser is connected to an inlet end of the two-stage condenser A, and an outlet end of the two-stage condenser A is connected to the low-temperature absorption unit;
The connection manner of the second condensation circuit is such that an inlet end of the two-stage condenser A is connected to an outlet end of the water washing tower of the water washing unit, an outlet end of the two-stage condenser A is connected to an inlet end of the single-stage condenser, an outlet end of the single-stage condenser is connected to an inlet end of the two-stage condenser B, and an outlet end of the two-stage condenser B is connected to the low-temperature absorption unit.
2. A VOCs recovery system that integrates absorption, desorption and recovery, as described in claim 1.

(Appendix 4)
The single-stage condenser, the two-stage condenser A and the two-stage condenser B of the automatic combination pre-cooling unit are all connected to a liquid separation tank 1;
4. A VOCs recovery system that integrates absorption, desorption and recovery, as described in appendix 3.

(Appendix 5)
The low-temperature absorption unit is a multi-stage spray tower, including an absorption tower with two tower plates and two nozzles, the gas inlet end of the absorption tower is installed above the liquid level of the absorbing liquid in the first layer of the absorption tower, and the tower plate of the second layer of the absorption tower is installed with a number of overflow pipes 2 for the transmission of VOCs gas and the overflow transmission of the absorbing liquid in the second layer, the VOCs gas is sprayed by the nozzles of the first layer of the absorption tower, and then enters the second layer of the absorption tower through the overflow pipes 2, and is further sprayed by the nozzles of the second layer of the absorption tower, thereby achieving sufficient absorption of the VOCs gas.
2. A VOCs recovery system that integrates absorption, desorption and recovery, as described in claim 1.

(Appendix 6)
Between the absorption tower of the low-temperature absorption unit and the safety outlet, a heat exchanger 1 is installed, which recovers surplus cold using the low-temperature gas discharged from the absorption tower of the low-temperature absorption unit, and replenishes the cold source after the automatic coupling pre-cooling unit.
6. A VOCs recovery system that integrates absorption, desorption and recovery, as described in appendix 5.

(Appendix 7)
The low temperature absorption unit is
a first self-circulating absorbing liquid circuit in which an outlet of the absorbing liquid in the first layer of the absorber is connected to a nozzle of the first layer of the absorber via a first-stage circulating spray pump of the absorber, thereby realizing spraying of the VOCs gas;
and a second self-circulating absorbing liquid circuit in which the outlet of the absorbing liquid in the second layer of the absorber is connected to a nozzle of the second layer of the absorber via a two-stage circulating spray pump in the absorber, thereby realizing further spraying of the VOCs gas.
2. A VOCs recovery system that integrates absorption, desorption and recovery, as described in claim 1.

(Appendix 8)
The high temperature desorption unit includes a desorption tower, and the connection manner between the desorption tower and the absorption tower in the low temperature absorption unit is:
a first desorption circuit in which a bottom absorption liquid outlet of an absorption tower in the low temperature absorption unit is connected to an absorption liquid inlet end at an upper part of a tower body of a desorption tower in the high temperature desorption unit through a tube layer of a heat exchanger;
a second desorption circuit in which the bottom lower absorbent outlet of the desorption column in the high temperature desorption unit is connected to the inlet of the second self-circulating absorbent circuit in the low temperature absorption unit through the shell of the heat exchanger 2;
the absorption liquid in the first self-circulating absorption liquid circuit, the second self-circulating absorption liquid circuit, the first desorption circuit and the second desorption circuit of the absorption tower and the absorption liquid in the absorption tower and the desorption tower form a flow rate balance;
2. A VOCs recovery system that integrates absorption, desorption and recovery as described in claim 1.

(Appendix 9)
The desorption tower in the high-temperature desorption unit is connected to the absorption tower in the low-temperature absorption unit through a recovery circuit, and the recovery circuit is configured such that the top outlet of the desorption tower is connected to a horizontal recovery tank through a heat exchanger 3 and a vacuum pump in this order, and the top outlet of the horizontal recovery tank is connected to an inlet end of the absorption tower.
2. A VOCs recovery system that integrates absorption, desorption and recovery as described in claim 1.

(Appendix 10)
The horizontal recovery tank of the low temperature recovery unit is connected to a liquid separation tank 2;
10. A VOCs recovery system that integrates absorption, desorption and recovery as described in appendix 9.

(Appendix 11)
Between the absorption tower of the low-temperature absorption unit and the high-temperature desorption unit, a heat exchanger 2 is installed to recover heat from each other using the low-temperature absorption liquid discharged from the low-temperature absorption unit and the high-temperature absorption liquid desorbed from the high-temperature desorption unit.
6. A VOCs recovery system that integrates absorption, desorption and recovery, as described in appendix 5.

(Appendix 12)
Step (1) of introducing VOCs gas into the site through a flame arrester and a water washing unit to remove ammonia, and then introducing the gas into an automatic combination pre-cooling unit;
(2) the VOCs gas is dehydrated in an automatic combined pre-cooling unit and then introduced into a low-temperature absorption unit;
Step (3) in which the low-temperature absorption unit operates the first self-circulating absorption liquid circuit and the second self-circulating absorption liquid circuit to absorb, the rich absorption liquid in the first layer of the absorption tower passes through the first desorption circuit, the cold amount is recovered by the tube layer of the heat exchanger 2, and then the rich absorption liquid is introduced into the desorption tower in the high-temperature desorption unit for desorption, the desorbed fresh absorption liquid passes through the second desorption circuit, the heat amount is recovered by the shell layer of the heat exchanger 2, and then the lean absorption liquid in the second layer of the absorption tower is preferentially supplemented;
The desorbed VOCs gas passes through a recovery circuit and is introduced into a horizontal recovery tank where it is condensed, liquefied and recovered, and the unliquefied VOCs gas is transported again to a low-temperature absorption unit for absorption.
A method for recovering VOCs using a VOCs recovery system.

(Appendix 13)
In the step (2), when the two-stage condenser B is frosted and defrosting is required, the first condensation circuit is operated, and the VOCs gas is condensed by passing through the two-stage condenser B, the single-stage condenser, and the two-stage condenser A in order; when the two-stage condenser A is frosted and defrosting is required, the second condensation circuit is operated, and the VOCs gas is first condensed by passing through the two-stage condenser A, and then condensed by passing through the single-stage condenser and the two-stage condenser B in order;
A method for recovering VOCs using the VOCs recovery system described in Appendix 12.

(Appendix 14)
In the step (2), when the VOCs gas passes through the first condensation circuit or the second condensation circuit, the single-stage condenser, the two-stage condenser B and the two-stage condenser A condense the VOCs and remove water, respectively, and then the uncondensed VOCs gas is introduced into the absorption tower of the low-temperature absorption unit;
A method for recovering VOCs using the VOCs recovery system described in Appendix 13.

(Appendix 15)
In the step (3), the VOCs gas is first sprayed and absorbed in the first layer of the absorption tower, a large amount of VOCs is absorbed in the absorbing liquid, and the remaining VOCs gas is introduced into the second layer of the absorption tower through the overflow pipe and is highly absorbed through the spray of fresh absorbing liquid, and the gas that passes the test is discharged from the safety outlet through the heat exchanger 1.
A method for recovering VOCs using the VOCs recovery system described in Appendix 12.

(Appendix 16)
In the step (3), in addition to being used for its own spray, when the liquid level exceeds the overflow port of the overflow pipe 2, the absorbing liquid overflows and enters the rich absorbing liquid of the first layer of the absorbing tower;
A method for recovering VOCs using the VOCs recovery system described in Appendix 12.

(Appendix 17)
In the step (4), the high-temperature VOC gas is recovered from the top outlet of the desorption tower via a recovery circuit, i.e., the temperature is initially lowered by circulating water in a heat exchanger 3, and then the gaseous VOCs are introduced into a low-temperature recovery horizontal tank by a vacuum pump, where the gaseous VOCs are liquefied, the liquefied VOCs are recovered, and the unliquefied VOCs are introduced back into the absorption tower to continue the treatment.
A method for recovering VOCs using the VOCs recovery system described in Appendix 12.

1 Flame arrester 2 Brake valve 3 Water washing tower 4 Overflow pipe 1
501: First layer nozzle of water washing tower 502: Second layer nozzle of water washing tower 601: First stage circulation spray pump of water washing tower 602: Second stage circulation spray pump of water washing tower 7: First stage condenser 8: Automatic control valve 9: Second stage condenser A
10 Two-stage condenser B
11 Liquid separation tank 1
12 ball valve 13 absorption tower 14 overflow pipe 2
1501 Absorption tower first layer nozzle 1502 Absorption tower second layer nozzle 1601 Absorption tower first stage circulation spray pump 1602 Absorption tower second stage circulation spray pump 17 Heat exchanger 1
18 Horizontal recovery tank 19 Liquid separation tank 2
20 Heat exchanger 2
21 Desorption column 22 Trap 23 Heat source 24 Heat exchanger 3
25 Vacuum pump 26 Recovery pump 27 Cold source 2801 First condensation circuit 2802 Second condensation circuit 2803 First self-circulating absorbing liquid circuit 2804 Second self-circulating absorbing liquid circuit 2805 First desorption circuit 2806 Second desorption circuit 2807 Recovery circuit

Claims (16)

A water washing unit used for washing the VOCs-introducing gas with water;
an automatic combined pre-cooling unit connected to the water washing unit, used for cooling and condensing the VOCs gas after water washing;
a low-temperature absorption unit connected to the automatic combined pre-cooling unit, for absorbing the cooled VOCs gas that could not be condensed by the automatic combined pre-cooling unit into an absorption liquid;
a high-temperature desorption unit connected to the low-temperature absorption unit and used to heat the absorption liquid to desorb the VOCs gas absorbed in the absorption liquid;
a first heat exchanger provided between the low-temperature absorption unit and the high-temperature desorption unit for exchanging heat between the absorption liquid cooled in the low-temperature absorption unit before VOCs gas is desorbed and the absorption liquid heated in the high-temperature desorption unit from which VOCs gas has been desorbed;
a low-temperature recovery unit connected to the low-temperature absorption unit and the high-temperature desorption unit, for condensing and liquefying the VOCs gas desorbed in the high-temperature desorption unit and for transporting the unliquefied VOCs gas back to the low-temperature absorption unit for treatment;
a second heat exchanger provided between the high-temperature desorption unit and the low-temperature recovery unit for performing heat exchange between the VOCs gas desorbed in the high-temperature desorption unit before being condensed and liquefied and circulating water;
The automatic combined pre-cooling unit includes a single-stage condenser used for condensation, and a first two-stage condenser and a second two-stage condenser used for condensation at a higher level than that of the single-stage condenser,
the first two-stage condensation device, the second two-stage condensation device, and the single-stage condensation device,
an inlet end of the second two-stage condenser is connected to an outlet end of a water washing tower of the water washing unit;
an outlet end of the second two-stage condenser is connected to an inlet end of the single-stage condenser;
an outlet end of the first stage condenser is connected to an inlet end of the first two-stage condenser;
a first condensation circuit, an outlet end of the first two-stage condensation device being connected to the low temperature absorption unit;
an inlet end of the first two-stage condenser is connected to an outlet end of the water wash tower;
an outlet end of the first two-stage condenser is connected to an inlet end of the single-stage condenser;
an outlet end of the first stage condenser is connected to an inlet end of the second two stage condenser;
a second condensation circuit, the outlet end of the second two-stage condenser being connected to the low temperature absorption unit;
Forming
the first condensing circuit is used to defrost the second two-stage condensing device when frost forms;
A VOCs recovery system that integrates absorption, desorption and recovery, characterized in that, when frost forms on the first two-stage condenser, the second condensation circuit is used to defrost the frost. The water washing unit is a multi-stage spray tower, and includes a water washing tower having two tower plates and two nozzles.
2. The VOCs recovery system according to claim 1, which integrates absorption, desorption and recovery. The apparatus further includes a first liquid separation tank for separating the condensed water and the liquid containing the condensed VOCs based on the difference in density,
the single-stage condenser, the first two-stage condenser and the second two-stage condenser of the automatic combination pre-cooling unit are all connected to the first liquid separation tank;
2. The VOCs recovery system according to claim 1, which integrates absorption, desorption and recovery. The low-temperature absorption unit includes a multi-stage spray tower having two tower plates, a first-stage nozzle, and a second-stage nozzle;
The gas inlet end of the absorption tower is installed above the liquid level of the absorption liquid in the first layer of the absorption tower,
The second layer of the absorption tower is provided with an overflow pipe for the transmission of VOCs gas and the overflow of the second layer of the absorbing solution.
After the VOCs gas is sprayed with the absorbing liquid by the first layer nozzle, it passes through the overflow pipe and enters the second layer of the absorption tower, where the absorbing liquid is further sprayed by the second layer nozzle, so that the VOCs gas is further absorbed.
2. The VOCs recovery system according to claim 1, which integrates absorption, desorption and recovery. Between the absorption tower and the safety outlet, a third heat exchanger is installed, which recovers surplus cold energy using the cooled gas discharged from the absorption tower to supplement the cold energy of the cold source of the automatic combination pre-cooling unit.
5. The VOCs recovery system according to claim 4, which integrates absorption, desorption and recovery. The low-temperature absorption unit includes a multi-stage spray tower having two layers of tower plates;
the absorption tower has a first layer absorbing liquid outlet, a second layer absorbing liquid outlet, a first layer nozzle, a second layer nozzle, a first stage circulation spray pump, and a two stage circulation spray pump;
a first self-circulating absorbing liquid circuit in which the first layer absorbing liquid outlet is connected to the first layer nozzle via the single-stage circulating spray pump and which sprays absorbing liquid against the VOCs gas;
and a second self-circulating absorbing liquid circuit in which the second layer absorbing liquid outlet is connected to the second layer nozzle via the two-stage circulation spray pump and further sprays absorbing liquid against the VOCs gas.
2. The VOCs recovery system according to claim 1, which integrates absorption, desorption and recovery. The high temperature desorption unit includes a desorption column;
Between the desorption tower and the absorption tower,
a first desorption circuit in which a tower bottom absorption liquid outlet of the absorption tower is connected to an absorption liquid inlet end at an upper part of a tower body of the desorption tower via a tube layer of the first heat exchanger;
a second desorption circuit is formed in which a column bottom lower absorption liquid outlet of the desorption column is connected to an inlet of the second self-circulating absorption liquid circuit in the low temperature absorption unit through a shell of the first heat exchanger;
the absorption liquid in the first self-circulating absorption liquid circuit, the second self-circulating absorption liquid circuit, the first desorption circuit and the second desorption circuit of the absorption tower and the absorption liquid in the absorption tower and the desorption tower form a flow rate balance;
7. The VOCs recovery system according to claim 6, which integrates absorption, desorption and recovery. a recovery horizontal tank; and a recovery circuit in which a top outlet of a desorption column in the high temperature desorption unit is connected to the recovery horizontal tank via the second heat exchanger and a vacuum pump in this order,
the desorption column is connected to an absorption column in the low temperature absorption unit via the recovery circuit;
The top end outlet of the horizontal recovery tank is connected to the inlet end of the absorption tower.
2. The VOCs recovery system according to claim 1, which integrates absorption, desorption and recovery. The second liquid separation tank separates the condensed water and the liquid containing the condensed VOCs based on the difference in density.
The recovery horizontal tank is connected to the second liquid separation tank.
9. The VOCs recovery system according to claim 8, wherein the VOCs recovery system is an integrated system for absorption, desorption and recovery. Between the absorption tower and the high-temperature desorption unit, the first heat exchanger is installed, which recovers heat from the cooled absorption liquid discharged from the low-temperature absorption unit and the absorption liquid desorbed and heated in the high-temperature desorption unit.
5. The VOCs recovery system according to claim 4, which integrates absorption, desorption and recovery. A first step of passing the VOCs on-site gas through a flame arrester and a water washing unit spraying water in order to remove ammonia, and then introducing the gas into an automatic combined pre-cooling unit connected to the water washing unit;
A second step of cooling the VOCs gas in the automatic combined pre-cooling unit to dehydrate and condense the gas, and then introducing the gas into a low-temperature absorption unit connected to the automatic combined pre-cooling unit;
A third step,
the low-temperature absorption unit includes an absorption tower having two tower plates each containing an absorbing liquid, and a first self-circulating absorbing liquid circuit is operated to spray the absorbing liquid of the first layer of the absorption tower against the VOCs gas of the first layer of the absorption tower, and a second self-circulating absorbing liquid circuit is operated to further spray the absorbing liquid of the second layer of the absorption tower against the VOCs gas of the second layer of the absorption tower, thereby absorbing the VOCs gas into the absorbing liquid,
The absorption liquid in the first layer of the absorption tower is passed through a first desorption circuit connecting the bottom of the absorption tower and an upper part of a tower body of a desorption tower in a high-temperature desorption unit connected to the low-temperature absorption unit;
During the process of passing through the first desorption circuit, the absorption liquid is cooled by a tube layer of a first heat exchanger provided between the absorption tower and the desorption tower, and then introduced into the desorption tower to heat the absorption liquid and desorb VOCs gas;
The desorbed fresh absorption liquid is passed through a second desorption circuit connecting the bottom of the desorption tower and an inlet of the second self-circulating absorption liquid circuit;
a third step of recovering heat from the absorbing liquid by a shell layer of the first heat exchanger during the process of passing through the second desorption circuit, and then preferentially replenishing the absorbing liquid in a second layer of the absorption tower;
and a fourth step of introducing the desorbed VOCs gas into a horizontal recovery tank, condensing and liquefying the desorbed VOCs gas, and recovering the desorbed VOCs gas, and transporting the unliquefied VOCs gas back to the low-temperature absorption unit for absorption.
The automatic combined pre-cooling unit includes a single-stage condenser used for condensation, and a first two-stage condenser and a second two-stage condenser used for condensation at a higher level than that of the single-stage condenser,
the first two-stage condensation device, the second two-stage condensation device, and the single-stage condensation device,
an inlet end of the second two-stage condenser is connected to an outlet end of a water washing tower of the water washing unit;
an outlet end of the second two-stage condenser is connected to an inlet end of the single-stage condenser;
an outlet end of the first stage condenser is connected to an inlet end of the first two-stage condenser;
a first condensation circuit, an outlet end of the first two-stage condensation device being connected to the low temperature absorption unit;
an inlet end of the first two-stage condenser is connected to an outlet end of the water wash tower;
an outlet end of the first two-stage condenser is connected to an inlet end of the single-stage condenser;
an outlet end of the first stage condenser is connected to an inlet end of the second two stage condenser;
a second condensation circuit, the outlet end of the second two-stage condenser being connected to the low temperature absorption unit;
Forming
the first condensing circuit is used to defrost the second two-stage condensing device when frost forms;
When the first two-stage condensing device frosts, the second condensing circuit is used to defrost the device.
A method for recovering VOCs using a VOCs recovery system. In the second step,
When frost forms on the second two-stage condenser, in order to defrost the frost, the first condensation circuit in which the water washing unit, the second two-stage condenser, the single-stage condenser, the first two-stage condenser, and the low-temperature absorption unit are connected in this order is operated, and VOCs gas is condensed by passing it through the second two-stage condenser, the single-stage condenser, and the first two-stage condenser in this order;
When frost forms on the first two-stage condenser, in order to defrost the frost, the second condensation circuit in which the water washing tower, the first two-stage condenser, the single-stage condenser, the second two-stage condenser, and the low-temperature absorption unit are connected in this order is operated, and the VOCs gas is condensed by passing it through the first two-stage condenser, the single-stage condenser, and the second two-stage condenser in this order.
A method for recovering VOCs using the VOCs recovery system according to claim 11. In the second step, when the VOCs gas is passed through the first condensation circuit or the second condensation circuit, the VOCs gas is condensed and dehydrated by the single-stage condenser, the second two-stage condenser and the first two-stage condenser, respectively, and then the uncondensed VOCs gas is introduced into the absorption tower.
A method for recovering VOCs using the VOCs recovery system according to claim 12. In the third step, the VOCs gas is sprayed with an absorbing liquid in the first layer of the absorption tower to be absorbed in the absorbing liquid, and the VOCs gas that has not been absorbed is introduced into the second layer of the absorption tower via an overflow small pipe, where fresh absorbing liquid is sprayed therein to absorb the VOCs gas to a higher degree than in the first layer, and the gas that has reached a predetermined standard is discharged via a third heat exchanger.
A method for recovering VOCs using the VOCs recovery system according to claim 11. In the third step, the absorbing liquid in the second layer of the absorption tower is used for spraying in the second layer, and when the liquid level of the absorbing liquid in the second layer exceeds the overflow mouth of the overflow small tube, the absorbing liquid in the second layer overflows and enters the absorbing liquid in the first layer of the absorption tower.
A method for recovering VOCs using the VOCs recovery system according to claim 11. In the fourth step, the top outlet of the desorption tower has a recovery circuit connected to the horizontal recovery tank via a second heat exchanger and a vacuum pump in this order, the heated VOCs gas is recovered from the top outlet of the desorption tower via the recovery circuit, cooled with circulating water by the second heat exchanger, and then introduced into the horizontal recovery tank by the vacuum pump, the VOCs gas is condensed and liquefied, the liquefied VOCs gas is recovered, and the unliquefied VOCs gas is introduced again into the absorption tower for treatment.
A method for recovering VOCs using the VOCs recovery system according to claim 11.