A gas-liquid separation system and separation method for separating CH4 from CO2

Abstract

The application provides a gas-liquid separation system and separation method for separating CH4 and CO2, which comprises a high-pressure gas-liquid separator, a low-pressure gas-liquid separator and a heat exchanger; the working pressure of the high-pressure gas-liquid separator is higher than that of the low-pressure gas-liquid separator; the high-pressure gas-liquid separator comprises a high-pressure gas-liquid separator cylinder, the upper end of which is provided with a high-pressure inlet, the top of which is provided with a high-pressure gas outlet, and the bottom of which is provided with a high-pressure liquid outlet; the heat exchanger is used for reducing the temperature of the liquid phase inside the lower end of the high-pressure gas-liquid separator cylinder; the low-pressure gas-liquid separator comprises a low-pressure gas-liquid separator cylinder, the lower end of which is provided with a low-pressure inlet, the low-pressure inlet is connected with the high-pressure liquid outlet through a low-pressure liquid pipeline, a pressure reducing valve and a high-pressure liquid pipeline in sequence; the top of the low-pressure gas-liquid separator cylinder is provided with a carbon dioxide outlet, and the bottom of which is provided with a liquid outlet. The application can separate CH4 and CO2 respectively, and good separation effect can be achieved.

Description

Technical Field

[0001] This invention belongs to the field of gas-liquid separation technology, and specifically relates to a gas-liquid separation system and method for separating CH4 and CO2. Background Technology

[0002] With technological advancements in the natural gas industry, my country's natural gas consumption is experiencing rapid growth, leading to a growing reliance on imports and a supply shortage. Bioenergy is currently the world's largest renewable energy source, accounting for 55% of renewable energy and over 6% of global energy supply. Biomass contains carbon absorbed by plants through photosynthesis; when used for energy production, this carbon is released back into the atmosphere, achieving net-zero CO2 emissions, making it a promising clean fuel. Leveraging China's abundant biomass resources, vigorously developing the biomass-to-natural gas industry is a crucial means of effectively acquiring natural gas resources and filling market gaps. Biomass hydrothermal catalytic methane production is an emerging biomass conversion technology that utilizes the unique physicochemical properties of high-temperature, high-pressure water to convert carbon, hydrogen, and oxygen in biomass into CH4 and CO2. Therefore, to achieve CO2 enrichment while producing methane, a gas-liquid separator is needed to separate CH4 and CO2 separately.

[0003] Traditional gas-liquid separators are simple in principle and easy to manufacture, but they suffer from problems such as poor separation efficiency and high flow resistance. Currently, most gas-liquid separators used in the industrial field are single-stage separators, which cannot meet the requirements for separating CH4 gas and pure CO2 gas separately. Therefore, it is necessary to design a gas-liquid separation scheme that can not only separate CH4 and CO2 but also achieve good separation results. Summary of the Invention

[0004] The purpose of this invention is to overcome the above-mentioned problems and provide a gas-liquid separation system and method for separating CH4 and CO2, which can not only separate CH4 and CO2 separately, but also achieve good separation effect.

[0005] This invention is achieved through the following technical solution:

[0006] A gas-liquid separation system for separating CH4 and CO2 includes: a high-pressure gas-liquid separator, a low-pressure gas-liquid separator, and a heat exchanger; the operating pressure of the high-pressure gas-liquid separator is greater than the operating pressure of the low-pressure gas-liquid separator.

[0007] The high-pressure gas-liquid separator includes a high-pressure gas-liquid separator cylinder; a high-pressure inlet is provided at the upper end of the high-pressure gas-liquid separator cylinder, a high-pressure gas outlet is provided at the top, and a high-pressure liquid outlet is provided at the bottom; a heat exchanger is used to reduce the temperature of the liquid phase inside the lower end of the high-pressure gas-liquid separator cylinder.

[0008] The low-pressure gas-liquid separator includes a low-pressure gas-liquid separator cylinder. A low-pressure inlet is provided at the lower end of the low-pressure gas-liquid separator cylinder. The low-pressure inlet is connected to the high-pressure liquid outlet in sequence through a low-pressure liquid pipeline, a pressure reducing valve, and a high-pressure liquid pipeline. A carbon dioxide outlet is provided at the top of the low-pressure gas-liquid separator cylinder, and a liquid outlet is provided at the bottom.

[0009] Preferably, the high-pressure gas outlet is connected to a high-pressure gas pipeline, the other end of which is connected to a throttle valve, and the other end of the throttle valve is connected to the heat exchanger through a low-pressure gas inlet pipeline.

[0010] Furthermore, the heat exchanger is located inside the lower end of the high-pressure gas-liquid separator cylinder, and a low-pressure gas outlet pipe is connected to the lower outlet of the heat exchanger, extending out of the low-pressure gas-liquid separator cylinder.

[0011] Furthermore, the heat exchanger includes several vertical pipes, which are evenly distributed around the axis of the high-pressure gas-liquid separator cylinder; the several vertical pipes converge upward in an arc shape to form an inlet and are connected to the low-pressure gas inlet pipe, and converge downward in an arc shape to form an outlet and are connected to the low-pressure gas outlet pipe.

[0012] Preferably, the lower end of the cylinder of the low-pressure gas-liquid separator is provided with a converging nozzle and a disturbance structure; the large-diameter end of the converging nozzle is connected to the low-pressure inlet, and the distance between the outlet of the converging nozzle and the inner wall of the cylinder of the low-pressure gas-liquid separator is 20-40mm; the disturbance structure is distributed around both sides of the converging nozzle.

[0013] Furthermore, the disturbance structure includes several vertically arranged cylindrical tubes.

[0014] Furthermore, the low-pressure gas-liquid separator cylinder is provided with an arc plate inside, the disturbance structure is provided on the arc plate, the front projection curve of the arc plate is an upward convex curve, and a number of first liquid guiding holes are provided on the edge of the arc plate.

[0015] Furthermore, a first separation guide plate is coaxially arranged inside the cylinder of the low-pressure gas-liquid separator, and the first separation guide plate is located above the disturbance structure;

[0016] The first separation guide plate includes a hollow cylinder with openings at the top and bottom and a hollow frustum with openings at the top and bottom. The bottom surface of the hollow cylinder is connected to the bottom surface of the hollow frustum. The radius of the bottom surface of the hollow frustum is equal to the inner diameter of the cylinder of the low-pressure gas-liquid separator.

[0017] Furthermore, a second separation guide plate is coaxially arranged inside the cylinder of the low-pressure gas-liquid separator, and the second separation guide plate is located above the first separation guide plate;

[0018] The outer surface of the second separation guide plate is a conical surface, and the inner surface is an arc surface. The bottom radius of the conical surface is equal to the inner diameter of the low-pressure gas-liquid separator cylinder, and the horizontal projection length of the arc surface is greater than the diameter of the hollow cylinder of the first separation guide plate. The second separation guide plate is provided with several gas outlets, and the edge of the hollow truncated cone is provided with a second liquid guiding hole.

[0019] A gas-liquid separation method for separating CH4 and CO2 is disclosed. A high-pressure gas-liquid separator operates at a pressure of 20-30 MPa, while a low-pressure gas-liquid separator operates at a pressure of 0.2-0.5 MPa. A mixture of CH4, CO2, and water enters the high-pressure gas-liquid separator cylinder through a high-pressure inlet for separation. A methane-rich mixture exits through a high-pressure gas outlet. A heat exchanger exchanges heat with a high-pressure liquid phase containing dissolved carbon dioxide at the bottom of the high-pressure gas-liquid separator cylinder, lowering the temperature of the high-pressure liquid phase. The cooled high-pressure liquid phase containing dissolved carbon dioxide exits through a high-pressure liquid outlet. After being depressurized by a pressure-reducing valve, it enters the low-pressure gas-liquid separator cylinder through a low-pressure inlet for further separation. Carbon dioxide gas escapes upwards, while the liquid phase flows downwards under gravity and exits through a liquid outlet.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The gas-liquid separation system designed in this invention can separate CH4 and CO2 separately. Utilizing the principle that CO2 has higher solubility at high pressure and lower solubility at low pressure, high-pressure and low-pressure gas-liquid separators are installed. In the high-pressure gas-liquid separator, CO2 dissolves in the liquid, achieving efficient CH4 separation; the liquid containing dissolved CO2 enters the low-pressure gas-liquid separator, achieving CO2 separation from the liquid phase. This invention utilizes the temperature-dependent solubility variation of CO2, incorporating a heat exchanger in the high-pressure gas-liquid separator section to lower the liquid phase temperature. This low temperature increases CO2 solubility, ensuring that CO2 does not escape during CH4 separation. This invention is applicable to gas-liquid separation in biomass hydrothermal catalytic methane production technology.

[0022] Furthermore, this invention incorporates a throttling valve. The methane-rich mixed gas is depressurized and cooled by the throttling valve to become a low-pressure, low-temperature mixed gas, which then enters a heat exchanger. Inside the heat exchanger, it exchanges heat with the high-pressure liquid phase containing dissolved carbon dioxide at the bottom of the high-pressure gas-liquid separator cylinder. This lowers the temperature of the high-pressure liquid phase, increases the solubility of carbon dioxide, and ensures that carbon dioxide does not escape. This design eliminates the need for an additional low-temperature heat source.

[0023] Furthermore, the heat exchanger is located inside the lower end of the high-pressure gas-liquid separator cylinder, in contact with the liquid phase, to improve the cooling effect.

[0024] Furthermore, the heat exchanger consists of several vertical pipes to increase the heat exchange area, reduce the pipe diameter, decrease the pressure-bearing wall thickness, and enhance the heat exchange effect. Several vertical pipes converge upwards in an arc shape to form an inlet and downwards in an arc shape to form an outlet. As the liquid falls, it comes into contact with the heat exchanger and flows down along the arc, reducing turbulence and preventing carbon dioxide escape.

[0025] Furthermore, a converging nozzle is installed. After the pressure is reduced by the pressure reducing valve, the liquid containing dissolved carbon dioxide flows faster through the converging nozzle. After being ejected from the nozzle, it impacts the inner wall of the low-pressure gas-liquid separator cylinder, causing it to split. It generates vortices around the disturbance structure, increasing airflow disturbance and promoting the upward escape of carbon dioxide gas. Under the action of gravity, the liquid flows downward to the bottom, thus achieving the separation of carbon dioxide.

[0026] Furthermore, the arc plate is designed to be convex upwards to prevent liquid stagnation.

[0027] Furthermore, a first separation guide plate is set up. As the carbon dioxide gas moves upward, it collides with the inner inclined surface of the hollow frustum of the first separation guide plate, separating the droplets carried by the carbon dioxide gas. The droplets flow down along the inner inclined surface of the frustum, and the carbon dioxide gas continues to flow upward through the inner surface of the hollow cylinder of the first separation guide plate, thereby improving the purity of the carbon dioxide.

[0028] Furthermore, a second separation guide plate is installed. Carbon dioxide gas rising from the first separation guide plate collides with the inner arc surface of the second separation guide plate, separating the fine droplets carried by the carbon dioxide gas. The pure carbon dioxide rises through the gas outlet and is finally discharged from the carbon dioxide outlet. The fine droplets flow down along the inner arc surface of the second separation guide plate to the outer inclined surface of the frustum of the first separation guide plate, and then flow downwards through the second liquid guiding hole to the bottom. The two-stage separation guide plate further improves the separation purity of carbon dioxide. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the gas-liquid separation system of the present invention for separating CH4 and CO2.

[0030] Figure 2 This is a schematic diagram of the fluid flow in the gas-liquid separation system of the present invention.

[0031] Figure 3 This is the present invention. Figure 1 AA section view.

[0032] Figure 4 This is the present invention. Figure 1 BB cross-section diagram.

[0033] Figure 5 This is a schematic diagram of fluid flow in the BB cross-section.

[0034] Figure 6This is the present invention. Figure 1 CC cross-section view.

[0035] Figure 7 This is a schematic diagram of the throttling valve with multiple bypasses in the gas-liquid separation system of the present invention.

[0036] The labels in the diagram have the following meanings: 01-High-pressure gas-liquid separator; 02-Low-pressure gas-liquid separator; 1-High-pressure gas-liquid separator cylinder; 2-High-pressure inlet; 21-High-pressure inlet pipe; 3-High-pressure gas outlet; 31-High-pressure gas pipe; 4-Throttle valve; 5-Low-pressure gas inlet; 51-Low-pressure gas inlet pipe; 6-Heat exchanger; 7-Low-pressure gas outlet; 71-Low-pressure gas outlet pipe; 8-High-pressure liquid outlet; 81-High-pressure liquid pipe; 9-Pressure reducing valve; 10-Low-pressure... Gas-liquid separator cylinder; 11-Low-pressure inlet; 111-Low-pressure liquid pipeline; 12-Converging nozzle; 13-Disturbance structure; 14-Arc plate; 141-First liquid guide hole; 15-Liquid guide pipe; 16-First separation guide plate; 161-Second liquid guide hole; 17-Second separation guide plate; 171-Inner arc surface; 172-Gas outlet; 18-Carbon dioxide outlet; 181-Carbon dioxide pipeline; 19-Liquid outlet; 191-Liquid pipeline; 20-Fixed bracket. Detailed Implementation

[0037] To further understand the present invention, the present invention will be described below with reference to embodiments. These descriptions are only for further explaining the features and advantages of the present invention and are not intended to limit the claims of the present invention.

[0038] See attached document Figure 1 The present invention relates to a gas-liquid separation system for separating CH4 and CO2, comprising: a high-pressure gas-liquid separator 01 and a low-pressure gas-liquid separator 02; the high-pressure gas-liquid separator 01 includes a high-pressure gas-liquid separator cylinder 1, a high-pressure inlet 2, a high-pressure inlet pipe 21, a high-pressure gas outlet 3, a high-pressure gas pipe 31, a throttle valve 4, a low-pressure gas inlet 5, a low-pressure gas inlet pipe 51, a heat exchanger 6, a low-pressure gas outlet 7, a low-pressure gas outlet pipe 71, a high-pressure liquid outlet 8, and a high-pressure liquid pipe 81. The low-pressure gas-liquid separator 02 includes a low-pressure gas-liquid separator cylinder 10, a low-pressure inlet 11, a low-pressure liquid pipeline 111, a tapered nozzle 12, a disturbance structure 13, an arc plate 14, a first liquid guide hole 141, a liquid guide pipe 15, a first separation guide plate 16, a second liquid guide hole 161, a second separation guide plate 17, an inner arc surface 171, a gas outlet 172, a carbon dioxide outlet 18, a carbon dioxide pipeline 181, a liquid outlet 19, and a liquid pipeline 191.

[0039] See attached document Figure 1The high-pressure gas-liquid separator 01 and the low-pressure gas-liquid separator 02 are connected by a high-pressure liquid pipeline 81 and a low-pressure liquid pipeline 111, with a pressure reducing valve 9 installed between them. The high-pressure inlet 2 is located at the upper end of the high-pressure gas-liquid separator cylinder 1 and is connected to the high-pressure inlet pipeline 21; the high-pressure gas outlet 3 is located at the top of the high-pressure gas-liquid separator cylinder 1 (preferably coaxial with the cylinder) and is connected to the high-pressure gas pipeline 31; the low-pressure gas inlet 5 is located at the lower end of the high-pressure gas-liquid separator cylinder 1 and is connected to the low-pressure gas inlet pipeline 51, with the low-pressure gas inlet 5 and the high-pressure inlet 2 arranged on opposite sides; the high-pressure gas pipeline 31 and the low-pressure gas inlet pipeline 51 are connected by a throttle valve 4.

[0040] Heat exchanger 6 is located at the lower end of the high-pressure gas-liquid separator cylinder 1. The upper inlet of heat exchanger 6 is connected to the low-pressure gas inlet pipe 51, and the lower outlet is connected to the low-pressure gas outlet pipe 71. The low-pressure gas outlet 7 is located at the lower end of the high-pressure gas-liquid separator cylinder 1 and is connected to the low-pressure gas outlet pipe 71. The low-pressure gas outlet 7 is arranged on the same side as the high-pressure inlet 2. The high-pressure liquid outlet 8 is located at the bottom of the high-pressure gas-liquid separator cylinder 1 (preferably coaxial with the high-pressure gas-liquid separator cylinder) and is connected to the high-pressure liquid pipe 81.

[0041] The low-pressure inlet 11 is located at the lower end of the low-pressure gas-liquid separator cylinder 10 and is connected to the low-pressure liquid pipeline 111. The converging nozzle 12 is located inside the lower end of the low-pressure gas-liquid separator cylinder 10, and the large-diameter end of the converging nozzle 12 is connected to the low-pressure inlet 11 and is fixed to the inner wall of the low-pressure gas-liquid separator cylinder 10 by welding. The central axis of the converging nozzle 12 is located at the middle of the height of the disturbance structure 13. The disturbance structure 13 is distributed around both sides of the converging nozzle 12, vertically arranged on the arc plate 14, and fixed to the arc plate 14 by welding. The arc plate 14 is located below the disturbance structure 13 and is fixed to the inner wall of the low-pressure gas-liquid separator cylinder 10 by welding. The first separation guide plate 16 is located above the disturbance structure 13 and is fixedly connected to the inner wall of the low-pressure gas-liquid separator cylinder 10 by welding; the liquid guide pipe 15 is located between the arc plate 14 and the first separation guide plate 16, distributed along the inner wall of the low-pressure gas-liquid separator cylinder 10, and is fixedly connected to the inner wall of the low-pressure gas-liquid separator cylinder 10 by welding; the second separation guide plate 17 is located above the first separation guide plate 16 and is fixedly connected to the inner wall of the low-pressure gas-liquid separator cylinder 10 by welding; the carbon dioxide outlet 18 is located at the top of the low-pressure gas-liquid separator cylinder 10 (preferably coaxial with the low-pressure gas-liquid separator cylinder); the liquid outlet 19 is located at the bottom of the low-pressure gas-liquid separator cylinder 10 (preferably coaxial with the low-pressure gas-liquid separator cylinder).

[0042] See attached document Figure 1 , Figure 3In this invention, the heat exchanger 6 is coaxially installed with the high-pressure gas-liquid separator cylinder 1 and located at the lower end of the high-pressure gas-liquid separator cylinder 1. The low-pressure, low-temperature gas exchanges heat with the high-pressure liquid phase containing dissolved carbon dioxide at the bottom of the high-pressure gas-liquid separator cylinder 1 inside the heat exchanger 6, thereby lowering the temperature of the high-pressure liquid phase and increasing the solubility of carbon dioxide, ensuring that carbon dioxide does not escape. The heat exchanger 6 consists of several vertical pipes, with 6-12 pipes. The vertical pipes are long and thin to increase the heat exchange area, reduce the pipe diameter, reduce the pressure-bearing wall thickness, and enhance the heat exchange effect. The vertical pipes are evenly distributed around the axis of the high-pressure gas-liquid separator cylinder 1. Several vertical pipes converge upward in an arc shape to form an inlet and downward in an arc shape to form an outlet. When the liquid falls, it comes into contact with the heat exchanger 6 and flows down along the arc, reducing disturbance and preventing carbon dioxide escape. The heat exchanger 6 is connected to the inner wall of the high-pressure gas-liquid separator cylinder 1 by welding through a fixed bracket 20. Each vertical pipe is equipped with a fixed bracket 20 to prevent deformation of the vertical pipe.

[0043] See attached document Figure 1 In this invention, the converging nozzle 12 is coaxially installed with the low-pressure inlet 11 and connected to the low-pressure liquid pipeline 111. The end face radius of the converging nozzle 12 decreases along the axis, and the maximum diameter end face coincides with the low-pressure inlet 11. The fluid entering from the low-pressure inlet 11 passes through the converging nozzle along the axis on the same horizontal plane and the flow velocity increases. The maximum end face radius of the converging nozzle 12 is equal to the radius of the low-pressure inlet 11, and the minimum end face radius is 1 / 2 to 1 / 3 of the maximum end face radius. The axial length of the converging nozzle 12 is less than the inner diameter of the low-pressure gas-liquid separator cylinder 10, and the distance between the nozzle outlet and the inner wall of the low-pressure gas-liquid separator cylinder 10 is 20-40 mm, with a reserved gas injection channel.

[0044] See attached document Figure 1 , Figure 4 , Figure 5 In this invention, the disturbance structure 13 consists of several slender cylindrical tubes, numbered 50-70. The tops of the cylindrical tubes are sealed, and fluid at a certain velocity generates vortices around the cylindrical tubes, increasing airflow disturbance. The cylindrical tubes are arranged in a trapezoidal shape around both sides of the converging nozzle 12, symmetrical about the axis of the converging nozzle 12. The disturbance structure 13 is set in the form of cylindrical tubes to ensure the disturbance effect while maximizing the number of tubes arranged within a certain space, thus improving separation.

[0045] See attached document Figure 1 , Figure 5In this invention, the arc plate 14 is coaxially mounted with the low-pressure gas-liquid separator cylinder 10; the horizontal projection radius of the arc plate 14 is equal to the inner radius of the low-pressure gas-liquid separator cylinder 10; the front projection curve of the arc plate 14 is an upward convex curve, and the central angle is set to 45°-90° to ensure that the liquid will not accumulate; the arc plate 14 has a number of first liquid guiding holes 141 around its perimeter, set to 4-12, so that the liquid flows down from the holes along the arc plate 14 and then is discharged; the number of first liquid guiding holes 141 is evenly distributed around the axis of the arc plate 14.

[0046] See attached document Figure 1 In this invention, the first separation guide plate 16 is coaxially installed with the low-pressure gas-liquid separator cylinder 10. The first separation guide plate 16 includes a hollow cylinder with openings at the top and bottom and a hollow frustum with openings at the top and bottom. The bottom surface of the hollow cylinder overlaps and connects with the bottom surface of the hollow frustum. The gas and liquid fluids collide with the inclined surface inside the hollow frustum from bottom to top and separate. The inner surface of the hollow cylinder guides the separated gas upward. The radius of the hollow cylinder is equal to the radius of the bottom surface of the hollow frustum. The radius of the bottom surface of the hollow frustum is equal to the inner diameter of the low-pressure gas-liquid separator cylinder 10. The radius of the bottom surface of the hollow frustum is 1 / 2 to 1 / 3 of the inner diameter of the low-pressure gas-liquid separator cylinder 10. The inclination angle of the inclined surface inside the hollow frustum is 20-45°. A second liquid guiding hole 161 is provided on the hollow frustum. The second liquid guiding hole 161 corresponds one-to-one with the first liquid guiding hole 141.

[0047] See attached document Figure 1 , Figure 6 In this invention, the second separation guide plate 17 is coaxially installed with the low-pressure gas-liquid separator cylinder 10; the outer surface of the second separation guide plate 17 is a conical surface, and the inner surface is an arc surface 171. The conical surface can guide the gas to the carbon dioxide outlet, and the gas and liquid fluids can undergo gas-liquid separation by colliding with the arc surface 171, separating out fine droplets; the bottom radius of the conical surface is equal to the inner diameter of the low-pressure gas-liquid separator cylinder 10, and the inclination angle of the conical surface is 20-45°; the horizontal projection length of the arc surface 171 is greater than that of the first separation guide plate (16). The diameter of the cylindrical surface and the horizontal projection length of the arc surface 171 are preferably 1.1-1.3 times the inner diameter of the hollow cylinder in the first separation guide plate 16, to ensure that the liquid does not mix with the gas rising from the inner surface of the hollow cylinder when it flows down along the arc surface 171, thus avoiding adverse effects; the second separation guide plate 17 is provided with a number of gas outlets 172 to allow the gas to pass upward and then be discharged; the number of gas outlets 172 is evenly distributed around the axis of the second separation guide plate 17; the number of gas outlets 172 is set to 12-24.

[0048] See attached document Figure 1In this invention, the liquid guide tube 15 is located between the first liquid guide hole 141 and the second liquid guide hole 161, corresponding one-to-one with the first liquid guide hole 141; the uppermost end of the liquid guide tube 15 is located 5-8mm below the second liquid guide hole 161, and the lowermost end is located 5-8mm above the first liquid guide hole 141, ensuring that the liquid flowing down along the inner frustum surface of the first separation guide plate 16 and the liquid flowing down along the arc plate 14 can flow smoothly to the bottom of the low-pressure gas-liquid separator.

[0049] See attached document Figure 7 In this invention, multiple bypasses can be set to reduce pressure, so as to prevent the gas from cooling and freezing, which would damage the throttle valve and render it unusable.

[0050] This invention relates to a gas-liquid separation system for separating CH4 and CO2. The design conditions are: a high-pressure gas-liquid separator with an operating pressure of 20-30 MPa and a low-pressure gas-liquid separator with an operating pressure of 0.2-0.5 MPa. The separation target is a mixture of high-pressure CH4, CO2, and water. The purpose is to separate CH4 gas and pure CO2 gas using the gas-liquid separation system of this invention.

[0051] The working process of the gas-liquid separation system for separating CH4 and CO2 according to the present invention is as follows: Refer to the appendix. Figure 2The high-pressure gas-liquid two-phase fluid enters the high-pressure gas-liquid separator cylinder 1 through the high-pressure inlet 2 for separation. Under the action of gravity, the high-pressure liquid phase containing dissolved carbon dioxide accumulates at the bottom of the high-pressure gas-liquid separator cylinder 1, while the methane-rich mixed gas is discharged through the high-pressure gas outlet 3. After being depressurized and cooled by the throttle valve 4, it becomes a low-pressure, low-temperature mixed gas, which then enters the heat exchanger 6 through the low-pressure gas inlet pipe 51. In the heat exchanger 6, it exchanges heat with the high-pressure liquid phase containing dissolved carbon dioxide at the bottom of the high-pressure gas-liquid separator cylinder 1, which lowers the temperature of the high-pressure liquid phase and increases the solubility of carbon dioxide, ensuring that carbon dioxide does not escape. After cooling, the high-pressure liquid phase containing dissolved carbon dioxide is discharged from the high-pressure liquid outlet 8. After being depressurized by the pressure reducing valve 9, it enters the low-pressure gas-liquid separator cylinder 10 through the low-pressure inlet 11 for separation. The liquid containing dissolved carbon dioxide has an increased flow velocity after passing through the converging nozzle 12. After being ejected from the nozzle, it impacts the inner wall of the low-pressure gas-liquid separator cylinder 10, causing diversion. It generates vortices around the slender disturbance structure 13, increasing the airflow disturbance. The carbon dioxide gas escapes upward, while the liquid flows downward under the action of gravity to the arc plate 14 and then flows downward along the arc plate 14 through the first liquid guide hole 141 to the bottom of the low-pressure gas-liquid separator cylinder 10. During the upward movement of the carbon dioxide gas, it collides with the inclined surface of the hollow frustum of the first separation guide plate 16, separating the carbon dioxide. The gas carries liquid droplets, which flow down the inner inclined surface of the frustum and through the liquid guide pipe 15 to the bottom of the low-pressure gas-liquid separator cylinder 10. The carbon dioxide gas continues to flow upward through the inner surface of the hollow cylinder of the first separation guide plate 16, colliding with the inner arc surface of the second separation guide plate 17, separating the fine liquid droplets carried by the carbon dioxide gas. The pure carbon dioxide flows upward through the gas outlet 172 and is finally discharged from the carbon dioxide outlet 18. The fine liquid droplets flow down the inner arc surface of the second separation guide plate 17 to the outer inclined surface of the frustum of the first separation guide plate 16, and enter the liquid guide pipe 15 through the second liquid guide hole 161 to the bottom of the low-pressure gas-liquid separator cylinder 10. The pure liquid at the bottom of the low-pressure gas-liquid separator cylinder 10 is discharged through the liquid outlet 19.

[0052] In this embodiment of the invention, the mixed fluid entering through high-pressure inlet 2 has a temperature of 50°C and a pressure of 20 MPa. Under these conditions, the solubility of CO2 is 29.24 mL / mL water. The high-pressure gas separated by high-pressure gas-liquid separator 01 is depressurized and cooled by throttle valve 4 to become low-pressure, low-temperature gas. The low-pressure, low-temperature gas exchanges heat with the high-pressure liquid phase at the bottom of the high-pressure gas-liquid separator cylinder 1. The high-pressure liquid phase is cooled to a low-temperature, high-pressure liquid phase of 20°C. At this point, the solubility of CO2 is 36.38 mL / mL water. The increased solubility of CO2 prevents CO2 from escaping and ensures the separation of CH4. The low-temperature, high-pressure liquid phase is depressurized to 0.2 MPa by pressure reducing valve 9 and enters low-pressure gas-liquid separator 02 through low-pressure liquid pipeline 111 for CO2 separation. At this point, the solubility of CO2 is 1.71 mL / mL water. The solubility of CO2 is significantly reduced, and pure CO2 gas can be separated.

[0053] This invention separates CH4 and CO2 separately by setting up high-pressure and low-pressure gas-liquid separators. A throttling valve 4 and a heat exchanger 6 are cleverly incorporated into the high-pressure gas-liquid separator 01. Utilizing the change in CO2 solubility with pressure and temperature, CO2 is ensured to remain dissolved in water, resulting in efficient CH4 separation. In the low-pressure gas-liquid separator 02, a three-stage gas-liquid separation process is implemented using both turbulence and collision. The liquid containing dissolved carbon dioxide first undergoes a vortex-like flow around the turbulence structure 13 for the first separation, then a second separation occurs due to collision with the first separation guide plate 16, and finally a third separation occurs due to collision with the second separation guide plate 17. This efficient separation of fine droplets carried by CO2 gas achieves excellent CO2 separation results.

[0054] The low-pressure gas-liquid separator 02 in this invention is suitable for general chemical gas-liquid separation processes. By increasing disturbance and collision to perform multiple gas-liquid separations, the gas-liquid separation effect is improved. Compared with the gravity sedimentation method, it can effectively reduce the size of the gas-liquid separator and reduce the cost of gas-liquid separation.

[0055] Through the above specific embodiments, the original intention, technical solution, implementation process, and scientific value of the present invention have been further clarified. It should be particularly emphasized that these embodiments are merely illustrative examples of the present invention and are not intended to limit the invention. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A gas-liquid separation system for separating CH4 and CO2, characterized in that, include: A high-pressure gas-liquid separator (01), a low-pressure gas-liquid separator (02), and a heat exchanger (6); the working pressure of the high-pressure gas-liquid separator (01) is greater than the working pressure of the low-pressure gas-liquid separator (02); The high-pressure gas-liquid separator (01) includes a high-pressure gas-liquid separator cylinder (1); the high-pressure gas-liquid separator cylinder (1) is provided with a high-pressure inlet (2) at the upper end, a high-pressure gas outlet (3) at the top, and a high-pressure liquid outlet (8) at the bottom; a heat exchanger (6) is used to reduce the temperature of the liquid phase inside the lower end of the high-pressure gas-liquid separator cylinder (1). The low-pressure gas-liquid separator (02) includes a low-pressure gas-liquid separator cylinder (10), a low-pressure inlet (11) is provided at the lower end of the low-pressure gas-liquid separator cylinder (10), and the low-pressure inlet (11) is connected to the high-pressure liquid outlet (8) in sequence through a low-pressure liquid pipeline (111), a pressure reducing valve (9), and a high-pressure liquid pipeline (81); a carbon dioxide outlet (18) is provided at the top of the low-pressure gas-liquid separator cylinder (10), and a liquid outlet (19) is provided at the bottom; The lower end of the cylinder (10) of the low-pressure gas-liquid separator is provided with a tapered nozzle (12) and a disturbance structure (13); the large-diameter end of the tapered nozzle (12) is connected to the low-pressure inlet (11), and the distance between the outlet of the tapered nozzle (12) and the inner wall of the cylinder (10) of the low-pressure gas-liquid separator is 20-40mm; the disturbance structure (13) is distributed around both sides of the tapered nozzle (12); the disturbance structure (13) includes several vertically arranged cylindrical tubes; The high-pressure gas outlet (3) is connected to a high-pressure gas pipeline (31), and the other end of the high-pressure gas pipeline (31) is connected to a throttle valve (4). The other end of the throttle valve (4) is connected to the heat exchanger (6) through a low-pressure gas inlet pipeline (51). The heat exchanger (6) is located inside the lower end of the high-pressure gas-liquid separator cylinder (1). The lower outlet of the heat exchanger (6) is connected to a low-pressure gas outlet pipeline (71), and the low-pressure gas outlet pipeline (71) extends out of the low-pressure gas-liquid separator cylinder (10).

2. The gas-liquid separation system for separating CH4 and CO2 according to claim 1, characterized in that, The heat exchanger (6) includes several vertical pipes, which are evenly distributed around the axis of the high-pressure gas-liquid separator cylinder (1); the several vertical pipes converge upward in an arc shape to form an inlet and are connected to the low-pressure gas inlet pipe (51), and converge downward in an arc shape to form an outlet and are connected to the low-pressure gas outlet pipe (71).

3. The gas-liquid separation system for separating CH4 and CO2 according to claim 1, characterized in that, The low-pressure gas-liquid separator cylinder (10) is provided with an arc plate (14) inside. The disturbance structure (13) is provided on the arc plate (14). The front projection curve of the arc plate (14) is an upward convex curve. Several first liquid guiding holes (141) are provided on the edge of the arc plate (14).

4. The gas-liquid separation system for separating CH4 and CO2 according to claim 1, characterized in that, The low-pressure gas-liquid separator cylinder (10) is coaxially provided with a first separation guide plate (16), which is located above the disturbance structure (13). The first separation guide plate (16) includes a hollow cylinder with openings at the top and bottom and a hollow frustum with openings at the top and bottom. The bottom surface of the hollow cylinder is connected to the bottom surface of the hollow frustum. The radius of the bottom surface of the hollow frustum is equal to the inner diameter of the low-pressure gas-liquid separator cylinder (10).

5. The gas-liquid separation system for separating CH4 and CO2 according to claim 4, characterized in that, The low-pressure gas-liquid separator cylinder (10) is coaxially provided with a second separation guide plate (17), which is located above the first separation guide plate (16). The outer surface of the second separation guide plate (17) is a conical surface, and the inner surface is an arc surface (171). The bottom radius of the conical surface is equal to the inner diameter of the low-pressure gas-liquid separator cylinder (10). The horizontal projection length of the arc surface (171) is greater than the diameter of the hollow cylinder of the first separation guide plate (16). The second separation guide plate (17) is provided with several gas outlets (172), and the edge of the hollow truncated cone is provided with a second liquid guide hole (161).

6. A gas-liquid separation method for separating CH4 and CO2, characterized in that, Based on the gas-liquid separation system of claim 1, the working pressure of the high-pressure gas-liquid separator is 20-30 MPa, and the working pressure of the low-pressure gas-liquid separator is 0.2-0.5 MPa. The mixed fluid of CH4, CO2 and water enters the high-pressure gas-liquid separator cylinder (1) through the high-pressure inlet (2) for separation. The mixed gas rich in methane is discharged through the high-pressure gas outlet (3). The heat exchanger (6) exchanges heat with the high-pressure liquid phase containing carbon dioxide at the bottom of the high-pressure gas-liquid separator cylinder (1), which lowers the temperature of the high-pressure liquid phase. After cooling, the high-pressure liquid phase containing carbon dioxide is discharged through the high-pressure liquid outlet (8). After being depressurized by the pressure reducing valve (9), it enters the low-pressure gas-liquid separator cylinder (10) through the low-pressure inlet (11) for separation. The carbon dioxide gas escapes upward, and the liquid phase flows downward under the action of gravity and is discharged through the liquid outlet (19).

Images