Method for recovering and liquefying carbon dioxide in natural gas

Abstract

The invention discloses a method for recovering and liquefying carbon dioxide in natural gas, and relates to the technical field of natural gas processing. According to the device, the working table, the multi-stage absorption mechanism, the self-regeneration type alternate adsorption mechanism and the linkage part are matched to complete recovery and liquefaction of carbon dioxide in natural gas, and the linkage part is in transmission connection between the self-regeneration type alternate adsorption mechanism and the stirring and foaming integrated unit. Multiple reactions of hydrogen sulfide in natural gas are achieved, the removal effect is improved, the service life of an adsorption material is prolonged through the design of step-by-step saturation replacement of a sodium bicarbonate solution, the frequent replacement requirement is reduced, the solution can be dynamically replaced, and the continuity of the treatment process is kept. Through up-down alternate operation of the molecular sieves, water vapor adsorption and synchronous regeneration are realized, molecular sieve saturation is avoided, continuous and efficient natural gas treatment is ensured, and the overall treatment effect is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of natural gas processing, and in particular to a method for recovering and liquefying carbon dioxide in natural gas. Background Art

[0002] In the current context of growing global attention to reducing greenhouse gas emissions, the recovery and liquefaction of carbon dioxide not only helps to reduce greenhouse gas emissions, but can also be reused as a resource, such as in the food and beverage industry, chemical synthesis, and oil recovery. Among them, the recovery and liquefaction of carbon dioxide in natural gas is the most widely used. At present, the methods for recovering and liquefying carbon dioxide in natural gas mainly include pretreatment, carbon dioxide capture, cooling and compression, purification and liquefaction. Among them, the pretreatment operation is the most important step, which is used to remove hydrogen sulfide and water vapor. Hydrogen sulfide is treated by adsorption with sodium bicarbonate solution, and water vapor is treated by adsorption with molecular sieve desiccant.

[0003] However, in the existing natural gas pretreatment process, a single cartridge is used for hydrogen sulfide adsorption treatment. The volume of a single filter cartridge and the amount of adsorption material are limited. When the sodium bicarbonate solution reacts with hydrogen sulfide to saturation, its adsorption capacity will drop significantly, resulting in the inability to effectively remove hydrogen sulfide. After the adsorption capacity drops or becomes saturated, the hydrogen sulfide that is not removed will enter the subsequent treatment steps, affecting the subsequent carbon dioxide capture and liquefaction process effects. In addition, due to the limited adsorption capacity of a single filter cartridge, the sodium bicarbonate solution needs to be replaced frequently. Each time the sodium bicarbonate solution is replaced, the natural gas input needs to be stopped, resulting in long downtime during the treatment process, affecting the overall treatment efficiency and continuity.

[0004] In addition, in the existing method of using molecular sieves for adsorption pretreatment of steam in natural gas, since the dry particles in the molecular sieve are in a static state, the airflow usually flows along a fixed path, causing some molecular sieve particles close to the vents to be adsorbed and saturated first, while other particles fail to fully exert their adsorption effect. Since the adsorption capacity of some molecular sieve particles is not fully utilized, the overall adsorption efficiency is reduced, resulting in poor water vapor removal effect, and traditional molecular sieves need to be shut down for regeneration or replacement of molecular sieves after the adsorption particles are saturated. The adsorption operation needs to be stopped during the regeneration process, resulting in a discontinuous treatment process, affecting the overall efficiency and treatment capacity. Summary of the invention

[0005] The present invention provides a method for recovering and liquefying carbon dioxide in natural gas, which solves the technical problems that in the existing natural gas pretreatment process, the single-cylinder hydrogen sulfide adsorption equipment has limited volume, and the adsorption capacity of the sodium bicarbonate solution decreases significantly after saturation, resulting in the inability to effectively remove hydrogen sulfide, affecting the carbon dioxide capture and liquefaction effect, and the need to stop the machine when replacing the solution, affecting the treatment efficiency and continuity. In addition, when the molecular sieve adsorbs steam, due to uneven adsorption of dry particles in a static state, some particles need to be stopped for regeneration or replacement after saturation, resulting in reduced adsorption efficiency, discontinuous treatment, and affecting the overall efficiency.

[0006] The present invention provides a method for recovering and liquefying carbon dioxide from natural gas. Specifically, the steps of the method for recovering and liquefying carbon dioxide from natural gas are as follows:

[0007] S1. Pretreatment operation: Before extracting carbon dioxide from natural gas, the natural gas is pretreated by combining a multi-stage absorption mechanism and a self-regenerating alternating adsorption mechanism to remove hydrogen sulfide and water vapor so as not to affect the subsequent carbon dioxide capture and liquefaction process.

[0008] S2. Carbon dioxide capture: The natural gas after pretreatment is passed into a chemical container filled with amine solution, and the chemical reaction between the amine solution and carbon dioxide is used to selectively capture and absorb carbon dioxide.

[0009] S3. Cooling and compression: After the carbon dioxide capture operation in natural gas is completed, the pressure of the chemical container is reduced to release the carbon dioxide in the amine solution. The released carbon dioxide gas is cooled by the cooler and then enters the compressor to be compressed to a higher pressure.

[0010] S4. Purification operation: The cooled and compressed carbon dioxide gas is passed through a selectively permeable membrane material to purify the carbon dioxide and separate the carbon dioxide from the impurity gas.

[0011] S5. Liquefaction treatment: The purified carbon dioxide gas is further cooled to liquefaction temperature through a refrigeration cycle and then stored in a pressure vessel.

[0012] The method steps for recovering and liquefying carbon dioxide in natural gas in the above steps S1-S5 need to be completed by the cooperation of a workbench, a multi-stage absorption mechanism, a self-regenerating alternating adsorption mechanism and a linkage unit.

[0013] The upper end surface of the workbench is equipped with a multi-stage absorption mechanism for multi-stage absorption and removal of hydrogen sulfide in natural gas and continuous replacement of sodium bicarbonate solution. The multi-stage absorption mechanism includes a mounting plate fixedly connected to the upper end surface of the workbench, a plurality of adsorption cylinders whose heights increase equidistantly from left to right and are fixedly connected to the front end surface of the mounting plate, and a Z-shaped connecting pipe connected to the left part of the adsorption cylinder. Two adjacent adsorption cylinders are connected to each other through the Z-shaped connecting pipe. A control valve group for controlling the flow of sodium bicarbonate solution so as to discharge the saturated sodium bicarbonate solution is arranged on the outside of the adsorption cylinder. An agitating and bubbling integrated unit for separating the natural gas input into the adsorption cylinder into a plurality of bubbles and agitating the natural gas so as to fully contact the sodium bicarbonate solution is arranged at the end of the lower transverse section of the Z-shaped connecting pipe. A self-regenerating alternating adsorption mechanism for absorbing water vapor in natural gas and automatically regenerating to extend the adsorption working time is arranged on the outside of the adsorption cylinder located on the right. A linkage part is connected to the self-regenerating alternating adsorption mechanism and the agitating and bubbling integrated unit in a transmission manner.

[0014] In one possible implementation, the stirring and foaming integrated unit includes an arc tube connected to the end of the lower lateral section of the Z-shaped connecting tube, the right part of the arc tube is equidistantly connected to a plurality of straight tubes, the upper part of the straight tube is equidistantly provided with a plurality of bubble outlet holes along the axial direction, the inner cavity of the adsorption cylinder is slidably connected to a fixed frame through a spring telescopic rod, the lower end face of the fixed frame is equidistantly fixedly connected to a plurality of rows of arc cutting plates corresponding to the straight tubes and fitted to the outside of the straight tubes through connecting columns, the upper part of the adsorption cylinder is rotatably connected to a rotating shaft, the rotating shaft is located on the outer wall of the circumference of the inner cavity section of the adsorption cylinder and is equidistantly fixedly connected to a plurality of stirring blades along the axial direction, the lower end of the rotating shaft is fixedly connected to a cam, and the upper end face of the fixed frame is fixedly connected to a shifting column for cooperating with the cam.

[0015] In a possible implementation, the self-regenerating alternating adsorption mechanism comprises two stepped rings symmetrically and slidably connected to the outside of the adsorption cylinder up and down, a plurality of connecting holes are equidistantly provided on the circumferential wall plate of the stepped ring, a plurality of air outlet holes cooperating with the connecting holes are equidistantly provided on the circumferential direction of the adsorption cylinder, and the air outlet holes are longitudinally arranged in two rows, molecular sieves connected to the connecting holes are respectively installed on the back sides of the two stepped rings, a discharge pipe is connected to the front of the molecular sieve, a strip support plate is fixedly connected to the upper end surface of the workbench, two annular heating plates corresponding to the molecular sieve are symmetrically provided on the side of the strip support plate close to the adsorption cylinder up and down, a rotating shaft is rotatably connected to the front of the strip support plate through a connecting block, a stirring component for stirring the adsorbed particles inside the molecular sieve is arranged between the rotating shaft and the molecular sieve, and a longitudinal movement component for controlling the two stepped rings to be alternately connected to the adsorption cylinder in sequence is arranged between the two stepped rings and the rotating shaft.

[0016] In one possible implementation, the longitudinal movement assembly includes a T-shaped rod fixedly connected to opposite sides of two step rings, the outside of the rotating shaft is rotatably connected to a sleeve, the outside of the sleeve is fixedly connected to a spiral paddle, the upper and lower sides of the spiral paddle are respectively fixedly connected to limiting blocks, and the side of the T-shaped rod transverse section close to the sleeve is rotatably connected to a column fork mounted on the outside of the spiral paddle.

[0017] In one possible implementation, the stirring assembly includes a rotating ring rotatably connected to the side of the molecular sieve away from the step ring, a plurality of L-shaped plates are fixedly connected to the side of the rotating ring close to the inner cavity of the molecular sieve at equal intervals in the circumferential direction, a plurality of shift forks are fixedly connected to the side of the transverse section of the L-shaped plate away from the rotating ring at equal intervals, and a friction wheel that cooperates with the rotating ring is fixedly connected symmetrically to the outside of the rotating shaft at upper and lower sides.

[0018] In a possible implementation, a guide groove is provided on the outer wall of the adsorption cylinder along the axial direction, and a guide block slidably disposed in the guide groove is fixedly connected to the inner wall of the step ring.

[0019] In a possible implementation, the linkage part includes a reciprocating motor fixedly connected to the upper end surface of the strip support plate, the output shaft of the reciprocating motor and the rotating shaft are fixedly connected to each other, and the rotating shaft and the rotating shaft are transmission-connected to each other via a pulley assembly.

[0020] In a possible implementation, the control valve group includes a connecting valve arranged at the upper part between two adjacent adsorption cylinders, a discharge valve is arranged at the lower part of the adsorption cylinder on the left, and an inlet valve is arranged at the upper part of the outer wall of the adsorption cylinder on the right.

[0021] It can be seen from the above technical solutions that the present invention has the following advantages:

[0022] In the present invention, the three adsorption cylinders in the multi-stage absorption mechanism cooperate with each other to perform multi-stage adsorption treatment, so that the hydrogen sulfide in the natural gas can undergo multiple reactions, thereby improving the removal effect of hydrogen sulfide and ensuring that the subsequent carbon dioxide capture and liquefaction processes are not affected. Moreover, due to the design of multi-stage adsorption, even if the sodium bicarbonate solution in a certain stage of the adsorption cylinder is saturated, the subsequent adsorption cylinders can still continue to play an adsorption role, thereby improving the reliability of adsorption and ensuring that the hydrogen sulfide is fully removed.

[0023] In the present invention, the sodium bicarbonate solution is saturated step by step starting from the leftmost adsorption cylinder, and then a new sodium bicarbonate solution is introduced from the rightmost adsorption cylinder, and the old solution is pressed out step by step. The first saturated sodium bicarbonate solution will be replaced by the new solution, thereby extending the use time of the adsorption material in each adsorption cylinder, reducing the need for frequent replacement, and realizing dynamic replacement of the adsorption material without stopping the input of natural gas, maintaining the continuity of the treatment process, and improving the overall treatment efficiency.

[0024] In the present invention, the natural gas introduced into the adsorption cylinder is separated into fine bubbles by stirring the integrated bubble-making unit, which greatly increases the gas-liquid contact area and enhances the reaction rate of hydrogen sulfide and sodium bicarbonate solution. The separated natural gas bubbles are then stirred by rotating the stirring blades, so that the bubbles move circumferentially during the floating and rising process. The movement path of the bubbles in the solution is more complicated, which further prolongs the residence time of the bubbles in the sodium bicarbonate solution, ensures that the hydrogen sulfide and the sodium bicarbonate solution are fully mixed, and improves the adsorption efficiency of hydrogen sulfide. At the same time, stirring can also ensure that the bubbles are evenly distributed in the solution, avoids the situation where the local solution is saturated while other parts of the solution are not fully utilized, and ensures that the hydrogen sulfide in the natural gas is removed to the maximum extent.

[0025] In the present invention, by controlling the upper and lower molecular sieves to move up and down synchronously and alternately, a molecular sieve adsorbs water vapor in natural gas while the other molecular sieve is heated and regenerated at the same time. Regeneration can be performed before the molecular sieve is saturated with adsorption, thus avoiding the molecular sieve being in a saturated state for a long time, ensuring that each molecular sieve works in an optimal state, improving the adsorption effect, and thus continuously processing natural gas. At the same time, it can also avoid stopping for the regeneration process, ensuring that the entire processing process is carried out continuously, and improving the overall efficiency.

[0026] In the present invention, the dry particles in the molecular sieve are stirred by a stirring component so that the airflow path is no longer fixed, ensuring that all dry particles can evenly participate in the adsorption, while preventing excessive use of some particles, ensuring that each particle can give full play to its adsorption capacity, improving the removal effect of water vapor in natural gas, ensuring the quality of pretreatment, and improving the overall adsorption efficiency of the molecular sieve. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0028] Figure 1 A diagram of the method for recovering and liquefying carbon dioxide from natural gas provided by the present invention.

[0029] Figure 2 The present invention provides an overall structural diagram.

[0030] Figure 3 This is a schematic cross-sectional structure diagram of the multi-stage absorption mechanism provided by the present invention.

[0031] Figure 4 This is a partial structural schematic diagram of the stirring and foaming integrated unit provided by the present invention.

[0032] Figure 5 A flow path diagram of natural gas in a multi-stage absorption mechanism provided by the present invention.

[0033] Figure 6 This is a schematic diagram of the installation structure of the self-regenerating alternating adsorption mechanism provided by the present invention.

[0034] Figure 7 This is a first cross-sectional schematic diagram of a partial structure of the self-regenerating alternating adsorption mechanism provided by the present invention.

[0035] Figure 8 This is a second cross-sectional schematic diagram of a partial structure of the self-regenerating alternating adsorption mechanism provided by the present invention.

[0036] Fig. 9 This is a schematic cross-sectional view from a front perspective of a partial structure of the self-regenerating alternating adsorption mechanism provided by the present invention.

[0037] The above drawings include the following reference numerals:

[0038] 1. Workbench; 2. Multi-stage absorption mechanism; 21. Mounting plate; 22. Adsorption cylinder; 23. Z-shaped connecting pipe; 24. Control valve group; 241. Connecting valve; 242. Discharge valve; 243. Inlet valve; 25. Stirring and foaming integrated unit; 251. Arc tube; 252. Straight tube; 253. Foaming hole; 254. Spring telescopic rod; 255. Fixed frame; 256. Arc cutting plate; 257. Rotating shaft; 258. Stirring blade; 259. Cam; 2510. Shifting column; 3. Self-regeneration alternating adsorption mechanism; 31. Step ring; 32, connecting hole; 33, air outlet; 34, molecular sieve; 35, discharge pipe; 36, strip support plate; 37, annular heating plate; 38, stirring assembly; 381, rotating ring; 382, ​​L-shaped plate; 383, fork; 384, friction wheel; 39, longitudinal movement assembly; 391, T-shaped rod; 392, sleeve; 393, spiral paddle; 394, limit block; 395, column fork; 310, rotating shaft; 4, linkage part; 41, reciprocating motor; 42, pulley assembly; 5, guide groove; 6, guide block. DETAILED DESCRIPTION

[0039] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific embodiments disclosed below.

[0040] See also Figure 1 and Figure 2 The present invention provides a technical solution: a method for recovering and liquefying carbon dioxide from natural gas. The specific steps of the method for recovering and liquefying carbon dioxide from natural gas are as follows:

[0041] S1. Pretreatment operation: Before extracting carbon dioxide from natural gas, the natural gas is pretreated by combining a multi-stage absorption mechanism 2 and a self-regenerating alternating adsorption mechanism 3 to remove hydrogen sulfide and water vapor so as not to affect the subsequent carbon dioxide capture and liquefaction process.

[0042] S2. Carbon dioxide capture: The natural gas after pretreatment is passed into a chemical container filled with amine solution, and the chemical reaction between the amine solution and carbon dioxide is used to selectively capture and absorb carbon dioxide.

[0043] S3. Cooling and compression: After the carbon dioxide capture operation in natural gas is completed, the pressure of the chemical container is reduced to release the carbon dioxide in the amine solution. The released carbon dioxide gas is cooled by the cooler and then enters the compressor to be compressed to a higher pressure.

[0044] S4. Purification operation: The cooled and compressed carbon dioxide gas is passed through a selectively permeable membrane material to purify the carbon dioxide (the selectively permeable membrane material used is specifically a polyimide membrane) to separate the carbon dioxide from impurity gases (such as nitrogen, methane, etc.).

[0045] S5. Liquefaction treatment: The purified carbon dioxide gas is further cooled to liquefaction temperature through a refrigeration cycle and then stored in a pressure vessel.

[0046] The method steps for recovering and liquefying carbon dioxide in natural gas in the above steps S1-S5 need to be completed by the workbench 1, the multi-stage absorption mechanism 2, the self-regeneration alternating adsorption mechanism 3 and the linkage part 4.

[0047] A multi-stage absorption mechanism 2 for removing hydrogen sulfide from natural gas by multi-stage absorption and simultaneously being able to continuously replace the sodium bicarbonate solution is installed on the upper end surface of the workbench 1.

[0048] See also Figure 2 , Figure 3 and Figure 5In this embodiment, the multi-stage absorption mechanism 2 includes a mounting plate 21 fixedly connected to the upper end surface of the workbench 1, a plurality of adsorption cylinders 22 whose heights increase from left to right and are fixedly connected to the front end surface of the mounting plate 21 at equal distances, and a Z-shaped connecting pipe 23 connected to the left part of the adsorption cylinder 22. Two adjacent adsorption cylinders 22 are connected to each other through the Z-shaped connecting pipe 23. A control valve group 24 for controlling the flow of sodium bicarbonate solution so as to discharge the saturated sodium bicarbonate solution is arranged on the outside of the adsorption cylinder 22. An agitating and bubbling integrated unit 25 for separating the natural gas input into the adsorption cylinder 22 into a plurality of bubbles and agitating the natural gas so as to fully contact the sodium bicarbonate solution is arranged at the end of the lower transverse section of the Z-shaped connecting pipe 23. The control valve group 24 includes a connecting valve 241 arranged at the upper part between the two adjacent adsorption cylinders 22, a discharge valve 242 is arranged at the lower part of the adsorption cylinder 22 located on the left, and an inlet valve 243 is arranged at the upper part of the outer wall of the adsorption cylinder 22 located on the right.

[0049] Before absorbing hydrogen sulfide in natural gas, the external sodium bicarbonate solution is introduced into the inlet valve 243, and then the sodium bicarbonate solution is introduced into the adsorption cylinder 22 located on the right. As the liquid level of the sodium bicarbonate solution flowing into the right gradually rises, the sodium bicarbonate solution then flows into the remaining adsorption cylinders 22 from right to left in sequence through the connecting valve 241 until all the adsorption cylinders 22 are filled with sodium bicarbonate solution, and then the connecting valve 241, the inlet valve 243 and the discharge valve 242 are all controlled to be closed, and then the natural gas is introduced into the adsorption cylinder 22 located on the leftmost part. In the Z-shaped connecting pipe 23, the natural gas flows along the Z-shaped connecting pipe 23 and enters the stirring and bubbling integrated unit 25, and is then divided into a plurality of bubbles by the stirring and bubbling integrated unit 25 and enters the lower position of the inner cavity of the adsorption cylinder 22, and then the natural gas bubbles move upward under their own buoyancy, and the natural gas bubbles move from bottom to top in the sodium bicarbonate solution so that the hydrogen sulfide is fully absorbed, and after moving to the upper part of the adsorption cylinder 22, the bubbles enter the next Z-shaped connecting pipe 23, and then repeat the above movement steps, (the specific flow path of the natural gas in the multi-stage absorption mechanism 2 is as shown in FIG. Figure 5 As shown in FIG. 2 , the natural gas in the next adsorption cylinder 22 again performs the movement steps in the previous adsorption cylinder 22 , thereby performing multi-stage adsorption of hydrogen sulfide in the natural gas.

[0050] After a long period of adsorption treatment of natural gas, the sodium bicarbonate solution in the adsorption cylinder 22 located on the far left will first be adsorbed to saturation, and then the inlet valve 243, the connecting valve 241 and the discharge valve 242 will be controlled to open at the same time, and the saturated sodium bicarbonate solution in the adsorption cylinder 22 on the far right will slowly flow out from the discharge valve 242, and the new sodium bicarbonate solution from the outside will gradually be introduced into the adsorption cylinder 22 located on the right through the inlet valve 243. Since the heights of the three adsorption cylinders 22 gradually increase from left to right, the newly introduced sodium bicarbonate solution will press the sodium bicarbonate solution to flow from right to left, thereby pressing the sodium bicarbonate solution in the right adsorption cylinder 22 into the left adsorption cylinder 22 until the sodium bicarbonate solution in the adsorption cylinder 22 on the left is completely pressed out, and then the inlet valve 243, the connecting valve 241 and the discharge valve 2442 will be controlled to be closed at the same time, and the natural gas will continue to be adsorbed and pre-treated until the sodium bicarbonate solution in the adsorption cylinder 22 on the left is saturated again, and then the above steps will be repeated again.

[0051] Multi-stage adsorption treatment is carried out through three adsorption cylinders 22, so that the hydrogen sulfide in the natural gas can undergo multiple reactions, thereby improving the removal effect of hydrogen sulfide and ensuring that the subsequent carbon dioxide capture and liquefaction process is not affected. Moreover, due to the design of multi-stage adsorption, even if the sodium bicarbonate solution in a certain stage of the adsorption cylinder 22 is saturated, the subsequent adsorption cylinder 22 can still continue to play an adsorption role, thereby improving the reliability of adsorption and ensuring that the hydrogen sulfide is fully removed. The sodium bicarbonate solution is saturated step by step starting from the leftmost adsorption cylinder 22, and then a new sodium bicarbonate solution is introduced from the rightmost adsorption cylinder 22, and the old solution is pressed out step by step. The first saturated sodium bicarbonate solution will be replaced by the new solution, thereby extending the service life of the adsorption material in each adsorption cylinder 22, reducing the need for frequent replacement, and realizing dynamic replacement of the adsorption material without stopping the input of natural gas, maintaining the continuity of the treatment process, and improving the overall treatment efficiency.

[0052] See also Figure 3 In this embodiment, a self-regenerating alternating adsorption mechanism 3 is provided outside the adsorption cylinder 22 located on the right, which is used to absorb water vapor in natural gas and can automatically regenerate to extend the adsorption working time. The self-regenerating alternating adsorption mechanism 3 and the stirring and bubbling integrated unit 25 are jointly connected by a linkage part 4.

[0053] See also Figure 3 and Figure 4The stirring and foaming integrated unit 25 includes an arc tube 251 connected to the end of the lower lateral section of the Z-shaped connecting tube 23, and a plurality of straight tubes 252 are equidistantly connected to the right side of the arc tube 251. A plurality of bubble outlet holes 253 are equidistantly provided on the upper part of the straight tube 252 along the axial direction. The inner cavity of the adsorption cylinder 22 is slidably connected to a fixed frame 255 through a spring telescopic rod 254, and a plurality of rows of arc cutting plates 256 corresponding to the straight tubes 252 and fitted on the outside of the straight tubes 252 are equidistantly fixedly connected to the lower end surface of the fixed frame 255 through a connecting column. The upper part of the adsorption cylinder 22 is rotatably connected to a rotating shaft 257, and the rotating shaft 257 is located on the outer wall of the circumference of the inner cavity section of the adsorption cylinder 22 and is equidistantly fixedly connected to a plurality of stirring blades 258 along the axial direction. A cam 259 is fixedly connected to the lower end of the rotating shaft 257, and a shifting column 2510 for cooperating with the cam 259 is fixedly connected to the upper end surface of the fixed frame 255.

[0054] While the natural gas is introduced into the adsorption cylinder 22, the linkage part 4 is controlled to operate, and the linkage part 4 then drives the rotating shaft 257 to rotate, and the rotating shaft 257 then drives the cam 259 to rotate synchronously. During the rotation of the cam 259, when its raised portion rotates to conflict with the lever 2510, it will squeeze the lever 2510 to move leftward, and the lever 2510 will then drive the arc cutting plate 256 to move leftward along the surface of the straight pipe 252 through the fixing frame 255 and the connecting column. At the same time, when the fixing frame 255 moves to the left, it will pull the spring telescopic rod 254 to be stretched. When the raised portion of the cam 259 When it is rotated to separate from the lever 2510, the spring telescopic rod 254 in the stretched state will reset and contract, pulling the fixed frame 255 to move to the right, and the fixed frame 255 then drives the arc cutting plate 256 to move to the right, and the arc cutting plate 256 is driven to move back and forth laterally on the upper part of the straight tube 252 through the cooperation of the cam 259 and the lever 2510. During the horizontal reciprocating motion, the arc cutting plate 256 intermittently passes through the bubble outlet 253, thereby separating the natural gas into small bubbles, greatly increasing the gas-liquid contact area, and enhancing the reaction rate of hydrogen sulfide and sodium bicarbonate solution.

[0055] As the shaft 257 rotates, it also drives the stirring blades 258 to rotate. Then the stirring blades 258 rotate and stir the natural gas bubbles, causing the bubbles to move in a circumferential direction during the floating and rising process. The movement path of the bubbles in the solution is more complicated, further extending the residence time of the bubbles in the sodium bicarbonate solution, ensuring that the hydrogen sulfide and the sodium bicarbonate solution are fully mixed, thereby improving the adsorption efficiency of hydrogen sulfide. At the same time, stirring can also ensure that the bubbles are evenly distributed in the solution, avoiding the situation where the local solution is saturated while other parts of the solution are not fully utilized, thereby ensuring that the hydrogen sulfide in the natural gas is removed to the maximum extent.

[0056] See also Figure 6 , Figure 7 , Figure 8 and Fig. 9In this embodiment, the self-regeneration alternating adsorption mechanism 3 includes two stepped rings 31 symmetrically slidably connected to the outside of the adsorption cylinder 22, and a plurality of connecting holes 32 are equidistantly provided on the circumferential wall plate of the stepped ring 31. A plurality of air outlet holes 33 cooperating with the connecting holes 32 are equidistantly provided on the circumferential direction of the adsorption cylinder 22, and the air outlet holes 33 are arranged in two rows in the longitudinal direction. Molecular sieves 34 connected to the connecting holes 32 are respectively installed on the back sides of the two stepped rings, and the front part of the molecular sieve 34 is connected to a discharge pipe 35. A strip support plate 36 is fixedly connected to the upper end surface of the workbench 1. Two annular heating plates 37 corresponding to the molecular sieve 34 are symmetrically arranged on the side of the strip support plate 36 close to the adsorption cylinder 22, and the strip The front part of the support plate 36 is rotatably connected to a rotating shaft 310 through a connecting block, and a stirring component 38 for stirring the adsorbed particles inside the molecular sieve 34 is arranged between the rotating shaft 310 and the molecular sieve 34. A longitudinal movement component 39 for controlling the two step rings 31 to be alternately connected to the adsorption cylinder 22 in sequence is arranged between the two step rings 31 and the rotating shaft 310. A guide groove 5 is axially provided on the outer wall of the adsorption cylinder 22, and a guide block 6 slidably arranged in the guide groove 5 is fixedly connected to the inner wall of the step ring 31. The moving path of the step ring 31 is limited by combining the guide block 6 and the guide groove 5, so that the step ring 31 can only move along the axial direction of the adsorption cylinder 22.

[0057] See also Figure 6 and Figure 7 The linkage part 4 includes a reciprocating motor 41 fixedly connected to the upper end surface of the strip support plate 36, the output shaft of the reciprocating motor 41 and the rotating shaft 310 are fixedly connected to each other, and the rotating shaft 257 and the rotating shaft 310 are connected to each other through a pulley assembly 42.

[0058] See also Figure 6 , Figure 7 , Figure 8 and Fig. 9 The longitudinal movement assembly 39 includes a T-shaped rod 391 fixedly connected to the opposite sides of the two step rings 31, a sleeve 392 is rotatably connected to the outside of the rotating shaft 310, and the sleeve 392 and the rotating shaft are in interference fit. A spiral paddle 393 is fixedly connected to the outside of the sleeve 392 310, and the upper and lower sides of the spiral paddle 393 are respectively fixedly connected to the limiting block 394, and the side of the lateral section of the T-shaped rod 391 close to the sleeve 392 is rotatably connected to a column fork 395 mounted on the outside of the spiral paddle 393.

[0059] After the hydrogen sulfide is adsorbed by the multi-stage absorption mechanism 2, the natural gas finally enters the adsorption cylinder 22 located on the right, and then flows into the connecting hole 32 from the air outlet 33, and then flows into the molecular sieve 34. When passing through the molecular sieve 34, the steam in the natural gas is adsorbed. The reciprocating motor 41 is controlled to drive the rotating shaft 310 to rotate reciprocatingly. The rotating shaft 310 then drives the rotating shaft 257 to rotate through the pulley assembly 42. The reciprocating rotation of the rotating shaft 257 can make the stirring and bubble-making integrated unit 25 operate. The reciprocating rotation of the rotating shaft 310 will also drive the sleeve 392 to rotate; when the rotating shaft 310 rotates counterclockwise: the rotating shaft 310 will drive the spiral paddle 393 to rotate synchronously through the sleeve 392, and the spiral paddle 393 will squeeze after rotating. The column fork 395 moves downward, and then drives the step ring 31 downward through the T-bar 391. At this time, the connecting hole 32 on the upper step ring 31 is connected with the upper row of air outlet holes 33, and the connecting hole 32 on the lower step ring 31 is staggered with the lower row of air outlet holes 33. The rotating shaft 310 and the sleeve 392 change from a relatively static state to a relatively rotating state. The sleeve 392 stops rotating, and the rotating shaft 310 continues to rotate. The natural gas passes through the upper molecular sieve 34 and then flows out from the upper exhaust pipe, while the molecular sieve 34 at the lower portion does not pass natural gas. At this time, the molecular sieve 34 at the lower portion is in contact with the lower annular heating plate 37, and the lower annular heating plate 37 is controlled to heat the lower molecular sieve 34 to promote its regeneration.

[0060] When the rotating shaft 310 switches to clockwise rotation: the rotating shaft 310 drives the spiral paddle 393 to rotate synchronously clockwise through the sleeve 392, and the spiral paddle 393 then squeezes the column fork 395 to make it gradually move upward, and the column fork 395 then drives the step ring 31 to move upward through the T-shaped rod 391 until the connecting hole 32 on the upper step ring 31 is misaligned with the upper exhaust hole 33, and the lower step ring 31 moves up and drives the lower connecting hole 32 to be connected with the lower exhaust hole 33. At this time, the natural gas enters the lower molecular sieve 34 for steam adsorption, and the upper molecular sieve 34 suspends the input of natural gas, the sleeve 392 stops rotating, and the rotating shaft 310 continues to rotate. The upper molecular sieve 34 is driven to move upward and contacts with the upper annular heating plate 37, and then the upper annular heating plate 37 is controlled to operate to heat and regenerate the upper molecular sieve 34.

[0061] By controlling the upper and lower molecular sieves 34 to move up and down synchronously and alternately, one molecular sieve 34 can adsorb water vapor in natural gas while the other molecular sieve 34 is heated and regenerated at the same time. The molecular sieve 34 can be regenerated before it is saturated with adsorption, thus avoiding the molecular sieve 34 being in a saturated state for a long time, ensuring that each molecular sieve 34 works in the best state, improving the adsorption effect, and allowing the equipment to continuously process natural gas. At the same time, it can also avoid stopping the regeneration process, ensuring that the entire processing process is continuous, and improving the overall efficiency.

[0062] See also Figure 6 , Figure 7 , Figure 8 and Fig. 9 In this embodiment, the stirring assembly 38 includes a rotating ring 381 rotatably connected to the side of the molecular sieve 34 away from the step ring 31, a plurality of L-shaped plates 382 are fixedly connected to the side of the rotating ring 381 close to the inner cavity of the molecular sieve 34 at equal intervals in the circumferential direction, a plurality of shift forks 383 are fixedly connected to the side of the lateral section of the L-shaped plate 382 away from the rotating ring 381 at equal intervals, and a friction wheel 384 that cooperates with the rotating ring 381 is fixedly connected to the outside of the rotating shaft 310 symmetrically up and down.

[0063] When the longitudinal shift assembly 39 drives the step ring 31 to move downward, the upper rotating ring 381 conflicts with the upper friction wheel 384, and the lower rotating ring 381 and the lower friction wheel 384 are displaced from each other. The rotating shaft 310 rotates while driving the friction wheel 384 to rotate. The friction wheel 384 then drives the rotating ring 381 to rotate through the rotating ring 381, and the rotating ring 381 then drives the shift fork 383 to rotate synchronously. During the rotation of the shift fork 383, the dry particles in the molecular sieve 34 are stirred to move. When the longitudinal shift assembly 39 drives the step ring 31 to move upward, the upper rotating ring 381 and the friction wheel 384 are displaced from each other and separated, and the lower rotating ring 381 moves up until it conflicts with the lower friction wheel 384, and then the rotating shaft 310 drives the lower rotating ring 381 to rotate through the lower friction wheel 384, and the lower rotating ring 381 then drives the lower fork 383 to rotate, stirring the dry particles in the lower molecular sieve 34. By stirring the dry particles in the molecular sieve 34, the airflow path is no longer fixed, ensuring that all dry particles can participate in adsorption evenly, while preventing some particles from being overused, ensuring that each particle can give full play to its adsorption capacity, thereby improving the removal effect of water vapor in natural gas, ensuring the quality of pretreatment, and improving the overall adsorption efficiency of the molecular sieve 34.

[0064] In the description of the present invention, it is to be understood that the terms “center”, “longitudinal”, “lateral”, “length”, “width”, “thickness”, “up”, “down”, “front”, “back”, “left”, “vertical”, “horizontal”, “top”, “bottom”, “inside”, “outside”, “clockwise”, “counterclockwise”, “axial”, “radial”, “circumferential”, etc., indicating orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0065] In addition, the terms "first", "second", "number one", "number two" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first", "second", "number one", "number two" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "multiple" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0066] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0067] The embodiments of this specific implementation method are all preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Therefore, all equivalent changes made based on the structure, shape, and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for recovering and liquefying carbon dioxide from natural gas, characterized in that: The specific steps of the method for recovering and liquefying carbon dioxide in natural gas are as follows: S1. Pretreatment operation: Before extracting carbon dioxide from natural gas, the natural gas is pretreated by combining a multi-stage absorption mechanism (2) and a self-regenerating alternating adsorption mechanism (3) to remove hydrogen sulfide and water vapor so as not to affect the subsequent carbon dioxide capture and liquefaction process; S2. Carbon dioxide capture: The natural gas after pretreatment is passed into a chemical container filled with amine solution, and the chemical reaction between the amine solution and carbon dioxide is used to selectively capture and absorb carbon dioxide; S3, cooling and compression: After the carbon dioxide capture operation in natural gas is completed, the pressure of the chemical container is reduced to release the carbon dioxide in the amine solution. The released carbon dioxide gas is cooled by the cooler and then enters the compressor to be compressed to a higher pressure; S4, purification operation: purifying the carbon dioxide through the cooled and compressed carbon dioxide gas through a selectively permeable membrane material to separate the carbon dioxide from the impurity gas; S5, liquefaction treatment: the purified carbon dioxide gas is further cooled to liquefaction temperature through a refrigeration cycle and then stored in a pressure vessel; The method steps for recovering and liquefying carbon dioxide in natural gas in the above steps S1-S5 need to be completed by the workbench (1), the multi-stage absorption mechanism (2), the self-regeneration alternating adsorption mechanism (3) and the linkage part (4); wherein: The upper end surface of the workbench (1) is provided with a multi-stage absorption mechanism (2) for removing hydrogen sulfide from natural gas by multi-stage absorption and simultaneously being able to replace the sodium bicarbonate solution without stopping the gas; The multi-stage absorption mechanism (2) comprises: A mounting plate (21) fixedly connected to the upper end surface of the workbench (1), a plurality of adsorption cylinders (22) whose heights increase equidistantly from left to right and are fixedly connected to the front end surface of the mounting plate (21), and a Z-shaped connecting pipe (23) connected to the left side of the adsorption cylinder (22), two adjacent adsorption cylinders (22) are connected to each other via the Z-shaped connecting pipe (23), and a control valve group (24) for controlling the flow of the sodium bicarbonate solution so as to discharge the saturated sodium bicarbonate solution is arranged outside the adsorption cylinder (22); The end of the lower transverse section of the Z-shaped connecting pipe (23) is provided with an integrated stirring and bubbling unit (25) for dividing the natural gas input into the adsorption cylinder (22) into a plurality of bubbles and stirring the natural gas so as to fully contact the natural gas with the sodium bicarbonate solution; The adsorption cylinder (22) located at the right part is provided with a self-regenerating alternating adsorption mechanism (3) for absorbing water vapor in natural gas and being able to automatically regenerate to extend the adsorption working time. The self-regenerating alternating adsorption mechanism (3) is connected to the stirring and bubbling integrated unit (25) by a linkage part (4) in a transmission manner.

2. The method for recovering and liquefying carbon dioxide in natural gas according to claim 1, characterized in that: The stirring and foaming integrated unit (25) comprises an arc-shaped tube (251) connected to the end of the lower transverse section of the Z-shaped connecting tube (23); the right part of the arc-shaped tube (251) is connected to a plurality of straight tubes (252) at equal intervals; the upper part of the straight tube (252) is provided with a plurality of bubble outlet holes (253) at equal intervals along the axial direction; the inner cavity of the adsorption cylinder (22) is slidably connected to a fixing frame (255) via a spring telescopic rod (254); the lower end surface of the fixing frame (255) is fixedly connected to a plurality of equidistantly connected bubbling holes (253) via a connecting column. An arc-shaped cutting plate (256) is arranged corresponding to the straight tube (252) and is fitted on the outside of the straight tube (252); the upper part of the adsorption cylinder (22) is rotatably connected to a rotating shaft (257); the rotating shaft (257) is located on the outer circumferential wall of the inner cavity section of the adsorption cylinder (22) and is fixedly connected to a plurality of stirring blades (258) equidistantly along the axial direction; the lower end of the rotating shaft (257) is fixedly connected to a cam (259); and the upper end surface of the fixed frame (255) is fixedly connected to a shifting post (2510) for cooperating with the cam (259).

3. The method for recovering and liquefying carbon dioxide in natural gas according to claim 2, characterized in that: The self-regeneration alternating adsorption mechanism (3) comprises two stepped rings (31) symmetrically slidably connected to the outside of the adsorption cylinder (22) in an upper and lower direction, a plurality of communication holes (32) are evenly spaced on the circumferential wall plate of the stepped ring (31), a plurality of air outlet holes (33) cooperating with the communication holes (32) are evenly spaced on the circumferential surface of the adsorption cylinder (22), and the air outlet holes (33) are arranged in two rows in the longitudinal direction, and molecular sieves (34) connected to the communication holes (32) are respectively installed on the back sides of the two stepped rings, and the front part of the molecular sieve (34) is connected to a discharge pipe (35), and the upper end surface of the workbench (1) is fixedly connected to a strip support The strip support plate (36) is provided with two annular heating plates (37) corresponding to the molecular sieve (34) symmetrically arranged on one side of the strip support plate (36) close to the adsorption cylinder (22), the front part of the strip support plate (36) is rotatably connected to a rotating shaft (310) through a connecting block, a stirring component (38) for stirring the adsorption particles inside the molecular sieve (34) is arranged between the rotating shaft (310) and the molecular sieve (34), and a longitudinal movement component (39) for controlling the two step rings (31) to be connected to the adsorption cylinder (22) alternately in sequence is arranged between the two step rings (31) and the rotating shaft (310).

4. The method for recovering and liquefying carbon dioxide in natural gas according to claim 3, characterized in that: The longitudinal movement assembly (39) comprises a T-shaped rod (391) fixedly connected to opposite sides of two step rings (31); the rotating shaft (310) is externally rotatably connected to a sleeve (392); the sleeve (392) is externally fixedly connected to a spiral paddle (393); the spiral paddle (393) is respectively fixedly connected to limit blocks (394) at the upper and lower sides; and a column fork (395) sleeved on the outside of the spiral paddle (393) is rotatably connected to a side of the transverse section of the T-shaped rod (391) close to the sleeve (392).

5. The method for recovering and liquefying carbon dioxide in natural gas according to claim 3, characterized in that: The stirring assembly (38) comprises a rotating ring (381) rotatably connected to a side of the molecular sieve (34) away from the step ring (31); a plurality of L-shaped plates (382) are equidistantly fixedly connected to a side of the rotating ring (381) close to the inner cavity of the molecular sieve (34); a plurality of shift forks (383) are equidistantly fixedly connected to a side of a transverse section of the L-shaped plate (382) away from the rotating ring (381); and a friction wheel (384) cooperating with the rotating ring (381) is symmetrically fixedly connected to the outside of the rotating shaft (310) in an upper and lower manner.

6. The method for recovering and liquefying carbon dioxide in natural gas according to claim 3, characterized in that: The outer wall of the adsorption cylinder (22) is provided with a guide groove (5) along the axial direction, and the inner wall of the step ring (31) is fixedly connected with a guide block (6) slidably arranged in the guide groove (5).

7. The method for recovering and liquefying carbon dioxide in natural gas according to claim 3, characterized in that: The linkage part (4) comprises a reciprocating motor (41) fixedly connected to the upper end surface of the strip support plate (36); the output shaft of the reciprocating motor (41) and the rotating shaft (310) are fixedly connected to each other; and the rotating shaft (257) and the rotating shaft (310) are connected to each other in a transmission manner via a pulley assembly (42).

8. The method for recovering and liquefying carbon dioxide in natural gas according to claim 1, characterized in that: The control valve group (24) comprises a connecting valve (241) arranged at the upper part between two adjacent adsorption cylinders (22), a discharge valve (242) arranged at the lower part of the adsorption cylinder (22) located at the left part, and an inlet valve (243) arranged at the upper part of the outer wall of the adsorption cylinder (22) located at the right part.

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