Composite absorption column, natural gas purification system and purification method

Abstract

The application discloses a composite absorption tower, a natural gas purification system and a method. By arranging a process intensification unit and a pressure energy recovery unit below a conventional absorption tower, the pressure energy of the fluid under pressure is fully utilized, the gas under pressure impacts a power impeller and drives the impeller to rotate, and then the coaxially arranged rotor assembly is rotated, a strong centrifugal field is provided for the process intensification reaction unit, the gas-liquid two-phase mass transfer process is greatly intensified, and the gas absorption effect is promoted. The application can recover the pressure energy of the high-pressure gas, is used for the intensification of the gas-liquid mass transfer process, improves the gas absorption and purification effect, reduces the amount of the absorption solvent, thereby reduces the regeneration load and the energy consumption of the circulating system, ensures long-period, safe and stable operation of the device, and realizes the natural gas purification treatment in a high-efficiency and low-cost manner.

Description

Technical Field

[0001] This invention belongs to the field of natural gas purification technology, specifically relating to a composite absorption tower, a natural gas purification system and purification method, and particularly an energy recovery type composite absorption tower, a natural gas purification system and method. Background Technology

[0002] In the natural gas extraction process, high-pressure gas wells need to be throttled and depressurized to meet the pressure requirements of external pipelines. Generally, throttling and depressurization equipment for high-pressure gas wells includes throttle valves and turbine expanders. High-pressure natural gas contains enormous pressure energy, and the throttling process significantly wastes this pressure energy, which should be recovered and utilized.

[0003] Meanwhile, natural gas extracted from oil and gas fields typically contains acidic gases (H2S, CO2, and organic sulfides, etc.), moisture, and light hydrocarbons. These components can cause difficulties in the transportation, processing, and use of natural gas. To meet pipeline requirements or commercial quality standards, purification treatment is necessary, such as natural gas desulfurization, decarbonization, and dehydration. Currently, the mature amine absorption process, i.e., the amine liquid "absorption-regeneration" complete technology, is commonly used for gas desulfurization or decarbonization. The absorbent is mainly an alkaline aqueous solution such as DEA, MEA, MDEA, and DEPA. A typical absorption and regeneration process flow is as follows: the feed gas enters the absorption tower from the bottom and comes into countercurrent contact with the solution remaining from the top of the tower in the packing layer. The acidic gases in the gas phase are absorbed by the absorbent. The tail gas after absorption goes from the top of the tower to the separator and is then discharged. The rich solution after absorbing the acidic gases enters the regeneration tower, while the lean solution enters the absorption tower from the top after passing through a cooler. The rich solution undergoes thermal regeneration in the regeneration tower, releasing acidic gases, which are then discharged from the top of the regeneration tower. After being cooled by a cooler, the acidic gases are discharged from the system.

[0004] Currently, the "absorption-regeneration" process generally suffers from the following problems. First, the absorption process typically employs tower-type equipment, i.e., packed / plate towers. Factors affecting the absorption effect mainly include mass transfer efficiency, absorbent concentration, absorbent volume, absorbent temperature, and the degree of foaming in the absorbent. Traditional absorption towers suffer from poor mass transfer, uneven gas-liquid flow, high resistance, easy clogging of the packing, and unstable operation. Furthermore, due to impurities such as light hydrocarbon droplets and rust entrained in the gas, the absorbent exhibits severe foaming, seriously affecting the long-term, safe, and stable operation of the desulfurization unit. Simultaneously, the low desulfurization efficiency of the absorption tower results in the acidic component content in the rich solution being far below the equilibrium value. Therefore, to ensure treatment effectiveness, a large amount of amine solution is often used, leading to a high regeneration load and high energy consumption. Therefore, developing efficient absorption equipment and treatment processes that reduce solvent consumption, lower regeneration load and circulating system energy consumption while ensuring absorption and purification effects, and improve the foaming phenomenon in the solvent absorption system, is of great significance for improving the treatment effect and saving energy for such gases.

[0005] As a highly efficient process intensification device, the centrifugal reactor enhances mass transfer through centrifugal force, achieving orders-of-magnitude improvements in efficiency compared to traditional methods. It boasts advantages such as high efficiency, small size, ease of operation, and convenient maintenance. Currently, centrifugal technology has been applied in engineering fields such as selective H2S removal, flue gas desulfurization and dust removal, nanoparticle preparation, extraction, and distillation. In amine absorption systems, this technology not only provides highly efficient purification but also eliminates amine foaming, increasing the concentration of amine used and thus reducing the amine circulation volume. This significantly reduces the amine regeneration load and the energy consumption of the circulation system. However, the centrifugal reactor bed (rotor) requires a motor for power, increasing energy consumption. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a composite absorption tower, a natural gas purification system, and a method. The composite absorption tower of this invention can recover the pressure energy of high-pressure gas for enhancing the gas-liquid mass transfer process, improving the gas absorption and purification effect while reducing the amount of absorption solvent used. This reduces the regeneration load and the energy consumption of the circulation system, ensuring long-term, safe, and stable operation of the device, and achieving efficient and low-cost natural gas purification.

[0007] According to the first objective of the present invention, the present invention provides a composite absorption tower.

[0008] Specifically, the composite absorption tower includes a tower body, a first baffle, a second baffle, a tower absorption unit, a process enhancement unit, and an energy recovery unit;

[0009] The first and second partitions are horizontally arranged inside the tower body, dividing the tower body into three parts from top to bottom: the tower absorption unit, the process enhancement unit, and the energy recovery unit.

[0010] The top of the absorption unit is provided with a second gas outlet, and the upper tower wall is provided with a liquid inlet; the inside of the absorption unit includes, from top to bottom, a demister, a liquid distributor, an absorption tower section, a liquid collection tray, and a liquid collection pan;

[0011] The tower wall of the process intensification unit is provided with a second air inlet and a liquid outlet; the process intensification unit includes a liquid redistributor, a rotor assembly and a drive shaft.

[0012] The pressure energy recovery unit is provided with a first air inlet and a first air outlet; the pressure energy recovery unit includes a high-pressure air chamber, a medium-pressure air chamber, a nozzle (or a guide), a power impeller and a drive shaft.

[0013] Furthermore, in the aforementioned composite absorption tower, the drain outlet of the process enhancement unit is located below the second air inlet.

[0014] Furthermore, in the aforementioned composite absorption tower, the drive shaft of the process enhancement unit and the transmission shaft of the pressure energy recovery unit are coaxially connected through the second partition.

[0015] Furthermore, in the aforementioned composite absorption tower, the medium-pressure gas chamber of the pressure energy recovery unit is fitted inside the high-pressure gas chamber and coaxially arranged. The high-pressure gas chamber is connected to the medium-pressure gas chamber through a nozzle. The power impeller is located inside the medium-pressure gas chamber and is fixedly connected to the drive shaft.

[0016] Furthermore, in the aforementioned composite absorption tower, the inlet of the liquid distributor is connected to the liquid inlet. The absorption tower section is located below the liquid distributor, and the liquid collecting tray and liquid collecting pan are located below the absorption tower section.

[0017] Furthermore, in the aforementioned composite absorption tower, the absorption tower section adopts conventional packing or tray form.

[0018] Furthermore, in the aforementioned composite absorption tower, the liquid collecting tray is a tray with gas riser holes. The form of the gas riser holes is not limited and can be a bubble cap, a floating valve, or other forms to ensure smooth gas passage. The center of the liquid collecting tray is a hollow structure, and an overflow weir is provided at the hollow edge. The lower edge of the hollow part in the middle of the liquid collecting tray is connected to the upper edge of the liquid collecting pan.

[0019] Furthermore, in the aforementioned composite absorption tower, the second air inlet of the process enhancement unit is located in the middle of the tower body, and the inlet center of the second air inlet is radially horizontal with the rotor assembly. The drain outlet is located at the lower part of the tower body. The rotor assembly is located in the middle of the tower body. The liquid redistributor is vertically positioned at the center of the rotor assembly, and the upper end of the liquid redistributor is connected to the lower end of the collection tray.

[0020] Furthermore, in the aforementioned composite absorption tower, the liquid collection tray passes through the first partition and is connected to the upper end of the liquid redistributor, and a gas phase channel is provided between the liquid collection tray and the first partition.

[0021] Furthermore, in the aforementioned composite absorption tower, the rotor structure of the rotor assembly can be a packed type, a disc type, a spiral type, a baffle type, or a composite type. The rotor assembly is mounted on a drive shaft.

[0022] Furthermore, in the aforementioned composite absorption tower, the first air inlet of the pressure energy recovery unit is located on the side of the tower body and communicates with the high-pressure gas chamber. The first air outlet of the pressure energy recovery unit is located at the lower part or bottom of the outer shell and communicates with the medium-pressure gas chamber.

[0023] Furthermore, in the aforementioned composite absorption tower, the medium-pressure gas chamber is located inside the high-pressure gas chamber, and the high-pressure gas chamber and the medium-pressure gas chamber are connected by nozzles (guides). There are two or more sets of nozzles (guides), which are evenly arranged circumferentially between the high-pressure gas chamber and the medium-pressure gas chamber.

[0024] Furthermore, in the aforementioned composite absorption tower, the power impeller of the pressure energy recovery unit is located at the center of the medium-pressure gas chamber, and can be a single-stage or multi-stage impeller. The power impeller is evenly arranged and installed on the drive shaft along the circumference.

[0025] Furthermore, in the aforementioned composite absorption tower, high-pressure gas impacts the power impeller through nozzles (guides) and drives the impeller to rotate. The power impeller drives the transmission shaft to rotate, and the transmission shaft drives the drive shaft and the rotor assembly to rotate. The strong centrifugal force field generated by the rotor rotation is used to enhance the gas-liquid process in the natural gas composite absorption tower.

[0026] Furthermore, in the aforementioned composite absorption tower, sealing components are installed between the rotor assembly and the reactor shell, and between the rotating shaft and the internal partition plate, to ensure that there is no leakage in the respective areas.

[0027] According to a second objective of the present invention, the present invention also provides a natural gas purification system, including the aforementioned composite absorption tower.

[0028] Specifically, the natural gas purification system includes a composite absorption tower, a low-temperature separation tank, a flash tank, a lean and rich liquid heat exchanger, a regeneration tower, a lean liquid pump, a cold energy recovery unit, a lean liquid cooler, and a filtration system.

[0029] The first inlet of the composite absorption tower is connected to the natural gas pipeline to be treated, the first outlet of the composite absorption tower is connected to the gas inlet of the low-temperature separator, the liquid inlet of the composite absorption tower is connected to the outlet of the filtration system, and the liquid outlet of the composite absorption tower is connected to the liquid inlet of the flash tank.

[0030] The gas outlet of the cryogenic separator is connected to the second inlet of the composite absorption tower via a cold energy recovery unit.

[0031] The liquid outlet of the flash tank is connected to the liquid inlet of the regeneration tower via a lean-rich liquid heat exchanger.

[0032] The gas phase outlet of the regeneration tower is connected to the regeneration gas pipeline, and the liquid phase outlet of the regeneration tower is connected to the inlet of the filtration system after passing through a lean liquid pump, a lean and rich liquid heat exchanger, a cold energy recovery unit, and a lean liquid cooler.

[0033] Furthermore, an antifreeze injection system is installed before the first air inlet of the composite absorption tower.

[0034] Furthermore, the aforementioned liquid-liquid heat exchanger is a liquid-liquid heat exchanger, and the form of the heat exchanger is not limited.

[0035] Furthermore, the cold energy recovery device is a gas-liquid heat exchanger, and the form of the heat exchanger is not limited, wherein the gas path is a cold flow path and the liquid path is a hot flow path.

[0036] Furthermore, the regeneration tower is equipped with a condenser at the top and a reboiler at the bottom.

[0037] According to a third objective of the present invention, the present invention also provides a natural gas purification method, wherein the aforementioned natural gas purification system is applied.

[0038] Specifically, the natural gas purification method includes the following steps:

[0039] (1) The high-pressure natural gas to be processed first enters the pressure energy recovery unit of the composite absorption tower. The high-pressure gas in the pressure energy recovery unit is injected into the medium-pressure gas chamber through the nozzle (guide). At the same time, the high-pressure gas becomes medium-pressure gas, which impacts the power impeller and drives the impeller to rotate, thereby driving the coaxially mounted rotor assembly to rotate. The depressurized gas enters the low-temperature separator from the first outlet of the pressure energy recovery unit.

[0040] (2) After the depressurized gas obtained in step (1) enters the low-temperature separator to separate light hydrocarbons and water, the medium-pressure low-temperature gas enters the cold energy recovery unit to exchange heat with the regenerated lean absorbent liquid, and after recovering the gas cold energy, it enters the process enhancement unit of the composite absorption tower.

[0041] (3) The medium-pressure gas recovering cold energy in step (2) enters the process enhancement unit of the composite absorption tower. The gas contacts the lean absorbent from the liquid redistributor in the rotor assembly area to carry out the gas-liquid two-phase mass transfer enhancement process and gas absorption. The gas to be treated rises to the liquid collection plate through the gas phase channel between the liquid collection plate and the first partition plate, and then is discharged from the tower absorption unit of the composite tower through the gas rise hole of the liquid collection plate from bottom to top. The lean absorbent enters through the liquid inlet and passes through the liquid distributor, absorption tower section, liquid collection plate, liquid redistributor and rotor assembly from top to bottom. After absorbing the components to be treated, it becomes rich absorbent and is discharged from the liquid outlet of the process enhancement unit and enters the flash tank.

[0042] (4) After the dissolved hydrocarbons in the rich absorbent entering the flash tank in step (3) are flashed, the rich absorbent is heated by the rich-lean heat exchanger and enters the regeneration tower. In the regeneration tower, the rich absorbent is heated and decomposed to release the absorbed components and become the lean absorbent, thus completing the regeneration of the absorbent. The high-concentration component gas released by the regeneration is then processed. The regenerated lean absorbent is pressurized by the lean absorbent pump, cooled by the rich-lean heat exchanger, cooled by the cold energy recovery unit, cooled by the lean absorbent cooler, and filtered by the filtration system before being returned to the composite absorption tower for recycling.

[0043] Furthermore, the high-pressure natural gas to be treated in step (1) may be for the purpose of removing acidic components such as H2S and CO2 or dehydration, and the components to be treated are H2S, CO2 and H2O respectively.

[0044] Furthermore, before the high-pressure natural gas to be processed in step (1) enters the composite absorption tower, antifreeze injection treatment can be selected as needed.

[0045] Furthermore, the pressure of the high-pressure natural gas to be processed in step (1) is above 2 MPa.

[0046] Furthermore, the operating pressure of the pressure energy recovery unit of the composite absorption tower in step (1) is 2 to 30 MPa.

[0047] Furthermore, the operating pressure of the process enhancement unit of the composite absorption tower in step (2) should be lower than the operating pressure of the pressure energy recovery unit, and preferably the pressure difference between the two is 2-20 MPa.

[0048] Furthermore, the rotational speed of the rotor assembly in step (3) is 50 to 5000 rpm, preferably 200 to 2000 rpm.

[0049] Furthermore, the operating conditions of the regeneration tower described in step (4) can be determined and adjusted according to the specific treatment system.

[0050] The composite absorption tower, natural gas purification system, and purification method of the present invention are applicable to high-pressure gas purification treatment, including natural gas absorption desulfurization, decarbonization treatment, and natural gas absorption dehydration processes. They can also be used for enhanced absorption treatment of gas-liquid processes under other pressurized conditions, and are particularly suitable for gas treatment fields where the gas has a certain pressure drop.

[0051] Compared with the prior art, the present invention has the following beneficial effects:

[0052] 1. A process enhancement unit and a pressure energy recovery unit are arranged below the conventional absorption tower to make full use of the pressure energy of the pressurized fluid. The pressurized gas impacts the power impeller and drives the impeller to rotate, thereby driving the coaxially mounted rotor assembly to rotate. This provides a strong centrifugal field for the process enhancement reaction unit, greatly enhancing the gas-liquid two-phase mass transfer process and promoting the gas absorption effect.

[0053] 2. Compared with existing tower equipment, the process enhancement unit of the composite absorption tower of this invention greatly enhances the gas-liquid mass transfer process, which greatly reduces the size of the absorption tower equipment and saves on infrastructure and equipment investment.

[0054] 3. This invention fully recovers the pressure energy of high-pressure natural gas. Compared with pressure reduction methods such as throttling, it fully recovers the pressure energy and uses it as energy to drive the rotor assembly, thereby enhancing the absorption process. This not only gives the composite absorption tower the advantages of hypergravity equipment, but also solves the motor energy consumption problem of hypergravity reactors by utilizing the gas source pressure energy, thus achieving gas treatment efficiently and at low cost. Attached Figure Description

[0055] Figure 1 This is a schematic diagram of the composite absorption tower in this invention.

[0056] Figure 1 In the diagram, each number corresponds to: 1-tower body, 2-first baffle, 3-second baffle, 4-tower absorption unit, 5-process enhancement unit, 6-energy recovery unit; 7-second air outlet, 8-demister, 9-liquid inlet, 10-liquid distributor, 11-absorption tower section, 12-liquid collection tray, 13-liquid collection pan, 14-second air inlet, 15-liquid outlet, 16-liquid redistributor, 17-rotor assembly, 18-drive shaft, 19-first air inlet, 20-first air outlet, 21-high pressure gas chamber, 22-medium pressure gas chamber, 23-nozzle (flow guide), 24-power impeller, 25-drive shaft, 26-air riser, 27-overflow weir.

[0057] Figure 2 This is a schematic diagram of the natural gas purification system in this invention.

[0058] Figure 2In the diagram, each number corresponds to the following: 51-raw material gas pipeline, 52-antifreeze injection pipeline, 53-composite absorption tower, 54-exhaust gas pipeline, 55-medium pressure inlet gas pipeline, 56-drainage pipeline, 57-medium pressure exhaust pipeline, 58-low temperature separator, 59-light hydrocarbon and water pipeline, 60-cold energy recovery unit, 61-lean liquid cooler, 62-filtration system, 63-lean and rich liquid heat exchanger, 64-flash tank, 65-flash vapor pipeline, 66-lean liquid pump, 67-regeneration tower, 68-lean absorbent pipeline, 69-regeneration gas pipeline. Detailed Implementation

[0059] The following detailed description of a composite absorption tower, natural gas purification system, and method of the present invention, in conjunction with the accompanying drawings and embodiments, does not limit the scope of the invention.

[0060] Example 1

[0061] This embodiment provides a detailed description of the composite absorption tower of the present invention. For example... Figure 1 As shown, the composite absorption tower structure of the present invention is as follows:

[0062] The composite absorption tower includes a tower body 1, a first partition 2, a second partition 3, a tower absorption unit 4, a process enhancement unit 5, and an energy recovery unit 6; the first partition 2 and the second partition 3 are horizontally arranged inside the tower body 1, dividing the tower body into three parts from top to bottom, namely the tower absorption unit 4, the process enhancement unit 5, and the energy recovery unit 6.

[0063] The top of the absorption unit 4 is provided with a second gas outlet 7, and the upper tower wall is provided with a liquid inlet 9; the inside of the absorption unit includes, from top to bottom, a demister 8, a liquid distributor 10, an absorption tower section 11, a liquid collection tray 12, and a liquid collection pan 13.

[0064] The tower wall of the process intensification unit 5 is provided with a second air inlet 14 and a liquid outlet 15; the process intensification unit 5 includes a liquid redistributor 16, a rotor assembly 17 and a drive shaft 18.

[0065] The pressure energy recovery unit 6 is provided with a first air inlet 19 and a first air outlet 20; the pressure energy recovery unit 6 includes a high-pressure air chamber 21, a medium-pressure air chamber 22, a nozzle (or guide vane) 23, a power impeller 24 and a drive shaft 25; the drive shaft 18 of the process enhancement unit 5 and the drive shaft 25 of the pressure energy recovery unit 6 are coaxially connected through the second partition 3.

[0066] The medium-pressure air chamber 22 of the pressure energy recovery unit 6 is fitted inside the high-pressure air chamber 21 and is coaxially arranged. The high-pressure air chamber 21 is connected to the medium-pressure air chamber 22 through the nozzle 23. The power impeller 24 is located inside the medium-pressure air chamber 22 and is fixedly connected to the drive shaft 25.

[0067] The absorption tower section 11 is located below the liquid distributor 10, and the liquid collecting tray 12 and liquid collecting pan 13 are located below the absorption tower section 11. The liquid collecting tray 12 is a tray with gas rise holes to ensure smooth gas passage. The center of the liquid collecting tray 12 is hollow, and an overflow weir 27 is provided at the hollow edge. The lower edge of the hollow part in the middle of the liquid collecting tray 12 is connected to the upper edge of the liquid collecting pan 13.

[0068] The second air inlet 14 of the process enhancement unit 5 is located in the middle of the unit tower. The drain outlet 15 is located at the lower part of the unit tower, and the rotor assembly 17 is located in the middle of the unit tower. The liquid redistributor 16 is vertically arranged at the center of the rotor assembly 17, and the upper end of the liquid redistributor 16 is connected to the lower end of the liquid collection tray 13. The liquid collection tray 13 passes through the first partition 2 and is connected to the upper end of the liquid redistributor 16, and a gas phase channel is left between the liquid collection tray 13 and the first partition 2.

[0069] The first air inlet 19 of the pressure energy recovery unit 6 is located on the side of the unit tower and communicates with the high-pressure air chamber 21. The first air outlet 20 of the pressure energy recovery unit 6 is located at the lower part or bottom of the outer shell and communicates with the medium-pressure air chamber 22. The medium-pressure air chamber 22 is located inside the high-pressure air chamber 21, and the high-pressure air chamber 21 and the medium-pressure air chamber 22 are connected by nozzles (guides) 23. There are two or more sets of nozzles (guides) 23, which are evenly distributed circumferentially between the high-pressure air chamber 21 and the medium-pressure air chamber 22. The power impeller 24 of the pressure energy recovery unit 6 is located at the center of the medium-pressure air chamber 22, and the power impeller is evenly arranged along the circumference of 24 and mounted on the drive shaft 25.

[0070] When the composite absorption tower of the present invention is working, the high-pressure gas impacts the power impeller 24 through the nozzle (guide) 23 and drives the impeller to rotate. The power impeller 24 drives the transmission shaft 25 to rotate, and the transmission shaft 25 drives the drive shaft 18 to rotate and drives the rotor assembly 17 to rotate. The gas-liquid process is enhanced by the strong centrifugal force field generated by the rotor rotation.

[0071] Example 2

[0072] This embodiment describes the natural gas purification system of the present invention in detail.

[0073] like Figure 2 As shown, the natural gas purification system of the present invention includes the aforementioned composite absorption tower. Specifically, the purification system includes a composite absorption tower 53, a low-temperature separation tank 58, a flash tank 64, a lean and rich liquid heat exchanger 63, a regeneration tower 67, a lean liquid pump 66, a cold energy recovery unit 60, a lean liquid cooler 61, and a filtration system 62.

[0074] The first inlet 19 of the composite absorption tower 53 is connected to the raw material gas pipeline 51, the first outlet 20 of the composite absorption tower 53 is connected to the gas inlet of the low temperature separator 58, the liquid inlet 9 of the composite absorption tower 53 is connected to the outlet of the filtration system 62, and the liquid outlet 15 of the composite absorption tower 53 is connected to the liquid inlet of the flash tank 64.

[0075] The gas outlet of the cryogenic separator 58 is connected to the second inlet 14 of the composite absorption tower 53 via the cold energy recovery unit 60. The liquid outlet of the flash tank 64 is connected to the liquid inlet of the regeneration tower 67 via the lean-rich liquid heat exchanger 63. The gas phase outlet of the regeneration tower 67 is connected to the regeneration gas pipeline 69, and the liquid phase outlet of the regeneration tower 67 is connected to the inlet of the filtration system 62 via the lean liquid pump 66, the lean-rich liquid heat exchanger 63, the cold energy recovery unit 60, and the lean liquid cooler 61.

[0076] Example 3

[0077] This embodiment provides a detailed description of the natural gas purification method of the present invention. (In conjunction with...) Figure 1-2 The working process of the natural gas purification system and method provided by the present invention is as follows:

[0078] The high-pressure natural gas to be processed first enters the pressure energy recovery unit 6 of the composite absorption tower 53. The high-pressure gas in the pressure energy recovery unit 6 is injected into the medium-pressure gas chamber 22 through the nozzle (guide) 23. At the same time, the high-pressure gas becomes medium-pressure gas, which impacts the power impeller and drives the impeller to rotate, thereby driving the coaxially mounted rotor assembly 17 to rotate.

[0079] After depressurization, the gas enters the cryogenic separator 58 through the first outlet 20 of the pressure energy recovery unit 6. After depressurization, the gas enters the cryogenic separator 58 and separates light hydrocarbons and water. The medium-pressure cryogenic gas then enters the cold energy recovery unit 60 to exchange heat with the regenerated lean absorbent. After recovering the cold energy of the gas, it enters the process enhancement unit 5 of the composite absorption tower 53.

[0080] In the process enhancement unit 5, the medium-pressure gas comes into contact with the lean absorbent from the liquid redistributor 10 in the rotor assembly 17 area to enhance the gas-liquid two-phase mass transfer process and absorb gas. The gas being treated rises to the liquid collection tray 12 through the gas phase channel between the liquid collection tray 13 and the first partition plate 2, and then passes through the gas riser hole of the liquid collection tray 12 from bottom to top through the tower absorption unit 4 of the composite tower 53 and is discharged. The lean absorbent enters through the inlet 9 and passes from top to bottom through the liquid distributor 10, the absorption tower section 11, the liquid collection tray 13, the liquid redistributor 10 and the rotor assembly 17. After absorbing the components to be treated, it becomes a rich absorbent and is discharged from the drain port 15 of the process enhancement unit 5 and enters the flash tank 64.

[0081] After the dissolved hydrocarbons are flashed out of the rich absorbent in flash tank 64, it is heated by the lean-rich liquid heat exchanger 63 and enters the regeneration tower 67. In the regeneration tower 67, the rich absorbent is heated and decomposed to release the absorbed components, becoming a lean absorbent, thus completing the regeneration of the absorbent. The high-concentration component gas released during regeneration is then processed. The regenerated lean absorbent is pressurized by lean liquid pump 66, cooled by lean-rich liquid heat exchanger 63, cooled by cold energy recovery unit 60, cooled by lean liquid cooler 61, and filtered by filtration system 62 before being returned to composite absorption tower 53 for recycling.

[0082] Example 4

[0083] This embodiment provides a specific application case of a natural gas purification system.

[0084] use Figure 1 The composite absorption tower shown is selected. Figure 2 The purification system shown decarbonizes natural gas from a gas field. The CO2 concentration in the natural gas is approximately 10% (V). It is treated using a mixed amine absorbent consisting of 40% MDEA, 10% DEA, and 50% H2O (mass concentration). The natural gas feedstock pressure is ≥6 MPa, the absorption pressure is 1 MPa, and the regeneration pressure is 0.3 MPa.

[0085] High-pressure natural gas first enters the pressure energy recovery unit 6 of the composite absorption tower 53. The high-pressure gas in the pressure energy recovery unit 6 is injected into the medium-pressure gas chamber 22 through the nozzle (guide) 23. The 6MPa high-pressure gas is transformed into 2MPa medium-pressure gas, which impacts the power impeller and drives the impeller to rotate, thereby driving the coaxially mounted rotor assembly 17 to rotate. After the pressure is reduced, the medium-pressure gas is separated into light hydrocarbons and water in the low-temperature separator 58 and then enters the cold energy recovery unit 60 to exchange heat with the regenerated lean absorbent. After recovering the cold energy of the gas, it enters the process enhancement unit 5 of the composite absorption tower 53.

[0086] In the process enhancement unit 5, the medium-pressure gas comes into contact with the lean absorbent from the liquid redistributor 10 in the rotor assembly 17 area, and undergoes a gas-liquid two-phase mass transfer enhancement process and gas absorption. The treated gas rises to the liquid collection tray 12 through the gas phase channel between the liquid collection tray 13 and the first partition plate 2, and then is discharged from the bottom to the top through the gas riser hole of the liquid collection tray 12 and the tower absorption unit 4 of the composite tower 53. This can achieve a CO2 concentration of less than 0.5% (V) in the treated natural gas.

[0087] The lean absorbent flows from top to bottom through the liquid distributor 10, the absorption tower section 11, the collection tray 13, the liquid redistributor 10, and the rotor assembly 17. After absorbing the components to be treated, it becomes a rich absorbent and is discharged from the drain port 15 of the process enhancement unit 5. It then enters the flash tank 64 to flash out dissolved hydrocarbons and is heated by the lean-rich liquid heat exchanger 63 before entering the regeneration tower 67. In the regeneration tower 67, the rich absorbent is heated and decomposed to release the absorbed components, becoming a lean absorbent, thus completing the absorbent regeneration. The high-concentration CO2 gas released during regeneration is then processed. The regenerated lean absorbent is pressurized by the lean liquid pump 66, cooled by the lean-rich liquid heat exchanger 63, cooled by the cold energy recovery unit 60, cooled by the lean liquid cooler 61, and filtered by the filtration system 62 before being returned to the composite absorption tower 53 for recycling.

[0088] Comparative Example 1

[0089] The composition and pressure of the natural gas feedstock are the same as in Example 1. The difference lies in the fact that the natural gas decarbonization equipment adopts a traditional tower-type device. The entire gas-liquid contact process of the traditional tower is carried out under constant gravity. Due to the limitation of gravity, the gas-liquid contact flow is slow, the mass transfer coefficient is not high, resulting in a low mass transfer rate. The content of acidic components in the rich liquid is far below the equilibrium value, so it is necessary to increase the amount of absorbent. In order to avoid severe foaming of the absorbent, the amine concentration is generally controlled at about 30%. Compared with Example 1, to achieve the same treatment effect, the tower height of this comparative example is increased by 30%, and the amount of amine used and the regeneration energy consumption are increased by about 20%.

[0090] Comparative Example 2

[0091] The composition and pressure of the natural gas feedstock are the same as in Example 1. The difference lies in the fact that the natural gas decarbonization equipment uses a conventional hypergravity device. The drive of the conventional hypergravity reactor bed (rotor) requires a motor to provide power. Under the same operating conditions as in Example 1, the system's power consumption increases by more than 25%. In Example 1, a process enhancement unit and a pressure energy recovery unit were arranged below the conventional absorption tower. The pressure energy of the gas source solved the motor energy consumption problem caused by the centrifugal field provided by the hypergravity device, achieving natural gas purification efficiently and at low cost.

Claims

1. A composite absorption tower, characterized in that, It includes the tower body, the first baffle, the second baffle, the tower absorption unit, the process enhancement unit, and the energy recovery unit; The first and second partitions are horizontally arranged inside the tower body, dividing the tower body into three parts from top to bottom: the tower absorption unit, the process enhancement unit, and the energy recovery unit. The top of the absorption unit is provided with a second gas outlet, and the upper tower wall is provided with a liquid inlet; the inside of the absorption unit includes, from top to bottom, a demister, a liquid distributor, an absorption tower section, a liquid collection tray, and a liquid collection pan; The tower wall of the process intensification unit is provided with a second air inlet and a liquid outlet; the process intensification unit includes a liquid redistributor, a rotor assembly and a drive shaft; The pressure energy recovery unit is provided with a first air inlet and a first air outlet; the pressure energy recovery unit includes a high-pressure air chamber, a medium-pressure air chamber, a nozzle, a power impeller, and a drive shaft; The drive shaft of the process enhancement unit and the transmission shaft of the pressure energy recovery unit are coaxially connected through the second partition.

2. The composite absorption tower according to claim 1, characterized in that, The medium-pressure air chamber of the pressure energy recovery unit is fitted inside the high-pressure air chamber; the high-pressure air chamber is connected to the medium-pressure air chamber through a nozzle.

3. The composite absorption tower according to claim 1, characterized in that, The power impeller is located inside the medium-pressure air chamber and is fixedly connected to the drive shaft.

4. The composite absorption tower according to claim 1, characterized in that, The liquid distributor inlet is connected to the liquid inlet; and / or, The absorption tower section is located below the liquid distributor; and / or, The liquid collecting tray and liquid collecting pan are located below the absorption tower section.

5. The composite absorption tower according to claim 1, characterized in that, The liquid collecting tray is a tray with gas rise holes; and / or, The liquid collection tray has a hollow center and an overflow weir at the hollow edge; and / or, The lower edge of the hollow section in the middle of the liquid collecting tray is connected to the upper edge of the liquid collecting plate.

6. The composite absorption tower according to claim 1, characterized in that, The second air inlet of the process enhancement unit is located in the middle of the unit tower, and the inlet center of the second air inlet is radially horizontal with the rotor assembly. The drain outlet is located at the lower part of this unit tower body; The rotor assembly is located in the middle of this unit tower body; The liquid redistributor is vertically positioned at the center of the rotor assembly, and its upper end is connected to the lower end of the liquid collection tray.

7. The composite absorption tower according to claim 1, characterized in that, The liquid collection tray passes through the first partition and is connected to the upper end of the liquid redistributor, and a gas phase channel is left between the liquid collection tray and the first partition.

8. The composite absorption tower according to claim 1, characterized in that, The first air inlet of the pressure energy recovery unit is located on the side of the unit tower and communicates with the high-pressure air chamber. The first air outlet of the pressure energy recovery unit is located at the lower part or bottom of the outer shell and communicates with the medium-pressure air chamber.

9. The composite absorption tower according to claim 1, characterized in that, The power impeller of the pressure energy recovery unit is located at the center of the medium-pressure air chamber. It adopts a single-stage or multi-stage impeller, and the multi-stage impellers are evenly arranged around the circumference and installed on the drive shaft.

10. A natural gas purification system, characterized in that, Includes the composite absorption tower according to any one of claims 1-9.

11. The natural gas purification system according to claim 10, characterized in that, include: Composite absorption tower, low temperature separation tank, flash tank, lean and rich liquid heat exchanger, regeneration tower, lean liquid pump, cold energy recovery unit, lean liquid cooler and filtration system; The first inlet of the composite absorption tower is connected to the natural gas pipeline to be treated, the first outlet of the composite absorption tower is connected to the gas inlet of the low-temperature separator, the liquid inlet of the composite absorption tower is connected to the outlet of the filtration system, and the liquid outlet of the composite absorption tower is connected to the liquid inlet of the flash tank. The gas outlet of the cryogenic separator is connected to the second inlet of the composite absorption tower via a cold energy recovery unit. The liquid outlet of the flash tank is connected to the liquid inlet of the regeneration tower via a lean-rich liquid heat exchanger. The gas phase outlet of the regeneration tower is connected to the regeneration gas pipeline, and the liquid phase outlet of the regeneration tower is connected to the inlet of the filtration system after passing through a lean liquid pump, a lean and rich liquid heat exchanger, a cold energy recovery unit, and a lean liquid cooler.

12. The natural gas purification system according to claim 11, characterized in that, An antifreeze injection system is installed before the first air inlet of the composite absorption tower.

13. The natural gas purification system according to claim 11, characterized in that, The liquid-liquid heat exchanger is a liquid-liquid heat exchanger; and / or, the cold energy recovery unit is a gas-liquid heat exchanger, wherein the gas path is a cold flow path and the liquid path is a hot flow path.

14. The natural gas purification system according to claim 11, characterized in that, The regeneration tower is equipped with a condenser at the top and a reboiler at the bottom.

15. A method for purifying natural gas, characterized in that, The natural gas purification system according to any one of claims 10-14, wherein the purification method comprises the following steps: (1) The high-pressure natural gas to be processed first enters the pressure energy recovery unit of the composite absorption tower. The high-pressure gas in the pressure energy recovery unit is injected into the medium-pressure gas chamber through the nozzle. At the same time, the high-pressure gas becomes medium-pressure gas, which impacts the power impeller and drives the impeller to rotate, thereby driving the coaxially mounted rotor assembly to rotate. The depressurized gas enters the low-temperature separator from the first outlet of the pressure energy recovery unit. (2) After the depressurized gas obtained in step (1) enters the low-temperature separator to separate light hydrocarbons and water, the medium-pressure low-temperature gas enters the cold energy recovery unit to exchange heat with the regenerated lean absorbent liquid, and after recovering the gas cold energy, it enters the process enhancement unit of the composite absorption tower. (3) The medium-pressure gas recovering cold energy in step (2) enters the process enhancement unit of the composite absorption tower. The gas contacts the lean absorbent from the liquid redistributor in the rotor assembly area, and the gas-liquid two-phase mass transfer enhancement process is carried out and the gas is absorbed. The gas being treated rises to the liquid collection tower plate through the gas phase channel between the liquid collection plate and the first partition plate, and then is discharged from the tower absorption unit of the composite tower through the gas rise hole of the liquid collection tower plate from bottom to top. The lean absorbent enters through the liquid inlet and passes through the liquid distributor, absorption tower section, liquid collection plate, liquid redistributor and rotor assembly from top to bottom. After absorbing the components to be treated, it becomes rich absorbent and is discharged from the liquid outlet of the process enhancement unit and enters the flash tank. (4) After the dissolved hydrocarbons in the rich absorbent entering the flash tank in step (3) are flashed, the rich absorbent is heated by the rich-lean heat exchanger and enters the regeneration tower. In the regeneration tower, the rich absorbent is heated and decomposed to release the absorbed components and become the lean absorbent, thus completing the regeneration of the absorbent. The high-concentration component gas released by the regeneration is then processed. The regenerated lean absorbent is pressurized by the lean absorbent pump, cooled by the rich-lean heat exchanger, cooled by the cold energy recovery unit, cooled by the lean absorbent cooler, and filtered by the filtration system before being returned to the composite absorption tower for recycling.

16. The natural gas purification method according to claim 15, characterized in that, The components to be processed in step (1) of the high-pressure natural gas are H2S, CO2 and H2O.

17. The natural gas purification method according to claim 15, characterized in that, Before the high-pressure natural gas to be processed in step (1) enters the composite absorption tower, antifreeze is injected as needed.

18. The natural gas purification method according to claim 15, characterized in that, The pressure of the high-pressure natural gas to be processed in step (1) is above 2 MPa; and / or The operating pressure of the pressure energy recovery unit of the composite absorption tower in step (1) is 2~30 MPa.

19. The natural gas purification method according to claim 15 or 18, characterized in that, In step (2), the operating pressure of the process enhancement unit of the composite absorption tower is lower than that of the pressure energy recovery unit. Preferably, the pressure difference between the two is 2~20 MPa.

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