Natural gas separation and purification and mercury collection system for oil and gas wells, and method of use thereof

11946,007

18/518606

November 24, 2023

A natural gas separation and purification and mercury collection system for oil and gas wells includes a cyclone separator, a condensation purification and separation mechanism, pressure buffer mechanisms, mercury collection and separation mechanisms, and natural gas storage tanks. An inlet end of the cyclone separator is communicated with an external gas source through a pressure buffer mechanism, and an outlet end of the cyclone separator is communicated with the condensation purification and separation mechanism through a pressure buffer mechanism. The condensation purification and separation mechanism is communicated with the mercury collection and separation mechanism through a pressure buffer mechanism. The mercury collection and separation mechanism is communicated with the natural gas storage tank through a guide tube. A method of use of the natural gas separation and purification and mercury collection system includes gas collection, gas purification, mercury separation, and mercury analysis.

Peking University (Beijing, CN)

Peking University (Beijing, CN)

1. A natural gas separation and purification and mercury collection system for oil and gas wells, comprising a cyclone separator, a condensation purification and separation mechanism, pressure buffer mechanisms, mercury collection and separation mechanisms, natural gas storage tanks, and a driver circuit, wherein an inlet end of the cyclone separator is communicated with an external gas source through a first pressure buffer mechanism of the pressure buffer mechanisms, and an outlet end of the cyclone separator is communicated with the condensation purification and separation mechanism through a second pressure buffer mechanism of the pressure buffer mechanisms; the condensation purification and separation mechanism is communicated with the mercury collection and separation mechanism through a third pressure buffer mechanism of the pressure buffer mechanisms; the mercury collection and separation mechanism is communicated with the natural gas storage tank through a first guide tube; each of the cyclone separator, the condensation purification and separation mechanism, the pressure buffer mechanisms, the mercury collection and separation mechanisms, and the natural gas storage tanks is provided with a control valve; the cyclone separator, the condensation purification and separation mechanism, the pressure buffer mechanisms, the mercury collection and separation mechanisms, the natural gas storage tanks, and the control valve are electrically connected to the driver circuit; at least two mercury collection and separation mechanisms are connected in parallel to each other and communicated with the pressure buffer mechanisms and the natural gas storage tanks through a shunt.

2. The natural gas separation and purification and mercury collection system for oil and gas wells according to claim 1 , wherein the mercury collection and separation mechanisms are connected to each other through a bearing frame; the bearing frame is a cylindrical frame with an I-shaped axial section; the mercury collection and separation mechanisms are embedded in a trough at a side surface of the bearing frame and distributed in parallel to an axis of the bearing frame; the pressure buffer mechanisms communicated with the mercury collection and separation mechanisms are connected to an outer side of the bearing frame; each of the mercury collection and separation mechanisms is communicated with a pressure buffer mechanism and communicated with the shunt through the pressure buffer mechanism; the shunt is connected to an upper end surface of the bearing frame; each of the mercury collection and separation mechanisms is further communicated with the natural gas storage tank through the shunt; a wall of the trough at the side surface of the bearing frame is provided with a guide way and connected to the mercury collection and separation mechanisms through the guide way; each two adjacent mercury collection and separation mechanisms are isolated by a partition; a bearing chamber is provided in the bearing frame and is coaxial with the bearing frame; the outer side of the bearing frame is provided with at least one connecting clip; a natural gas storage tank is provided in the bearing chamber; and the outer side of the bearing frame is connected to at least one natural gas storage tank through the at least one connecting clip.

3. The natural gas separation and purification and mercury collection system for oil and gas wells according to claim 1 , wherein the mercury collection and separation mechanism comprises a separation tank, carriers, gold foil meshes, an aerator, a partition, a guide fan, heat exchange tubes, a temperature-humidity sensor, and pressure-flow sensors; the separation tank is a closed chamber structure with a rectangular axial section; the separation tank comprises an upper end surface provided with a gas inlet and a gas outlet, and a bottom provided with a drain outlet; the gas inlet and the gas outlet are distributed at two sides of an axis of the separation tank; the partition is embedded in the separation tank and connected to a top and a side wall of the separation tank; a distance between the partition and the bottom of the separation tank does not exceed 10% of a height of the separation tank; the partition divides the separation tank into a mercury removal chamber and a gas discharge chamber; the gas inlet is communicated with the mercury removal chamber, and the gas outlet is communicated with the gas discharge chamber; each of the carriers is a closed and circular structure, and is provided with 1-2 gold foil meshes; the carriers are embedded in the mercury removal chamber, coaxial with the mercury removal chamber, and slidably connected to an inner side of the mercury removal chamber through sliding rails; a distance between each two adjacent carriers is not less than 10 mm; the aerator is communicated with the gas inlet, located inside the mercury removal chamber, and connected to a top of the separation tank; there are at least two heat exchange tubes, comprising a first heat exchange tube located below the partition, connected to the bottom of the separation tank, and surrounding the axis of the separation tank, and a second heat exchange tube embedded in the gas discharge chamber and connected to a side wall of the separation tank corresponding to the gas discharge chamber; an outer side of the separation tank corresponding to the second heat exchange tube is provided with a pipe joint and communicated with the external condensation purification and separation mechanism through the pipe joint; the temperature-humidity sensor is embedded in the gas outlet; each of the gas inlet and the gas outlet is provided with a pressure-flow sensor; at least one guide fan is connected to the bearing frame and communicated with the gas outlet and the shunt through a second guide tube; the at least one guide fan is communicated with the natural gas storage tank through the shunt; and the at least one guide fan, the temperature-humidity sensor, and the pressure-flow sensors are electrically connected to the driver circuit.

4. The natural gas separation and purification and mercury collection system for oil and gas wells according to claim 3 , wherein at least one electric heating wire and a temperature sensor are further provided in each of the carriers; the at least one electric heating wire is spirally distributed around an axis of the carrier, and is 0-5 mm far from the gold foil mesh; the temperature sensor is coaxial with the carrier; and the at least one electric heating wire and the temperature sensor are electrically connected to the driver circuit.

5. The natural gas separation and purification and mercury collection system for oil and gas wells according to claim 1 , wherein the condensation purification and separation mechanism comprises a support frame, gas-liquid separators, a refrigeration mechanism, a condensation chamber, and pressure regulating pumps; the support frame is a frame structure with a T-shaped axial section, and an axis of the support frame is perpendicular to a horizontal plane; the condensation chamber is embedded in the support frame, coaxial with the support frame, and connected to a bottom of the support frame; the condensation chamber comprises a side wall provided with a first gas inlet and a top provided with a gas outlet; the first gas inlet is communicated with the cyclone separator, and the gas outlet is communicated with a plurality of gas-liquid separators through a second guide tube; the plurality of gas-liquid separators are embedded in an upper half of the support frame and uniformly surround the axis of the support frame; the plurality of gas-liquid separators are connected in parallel to each other and communicated with the gas outlet of the condensation chamber through the pressure regulating pumps; the refrigeration mechanism is connected to an outer side of the support frame and communicated with the mercury collection and separation mechanism through a circulation loop; and the plurality of gas-liquid separators, the refrigeration mechanism, the condensation chamber, and the pressure regulating pumps are electrically connected to the driver circuit.

6. The natural gas separation and purification and mercury collection system for oil and gas wells according to claim 5 , wherein the condensation chamber comprises a guide chamber, heat exchangers, aeration trays, and a temperature sensor; the guide chamber is a truncated cone-shaped structure; a bottom of the guide chamber is provided with a drain outlet, wherein the drain outlet is coaxial with the guide chamber; the first gas inlet is located at a side wall of the guide chamber, and is not less than 5 cm far from the bottom of the guide chamber; at least two aeration trays are embedded in the guide chamber, connected to the bottom of the guide chamber, uniformly distributed around the drain outlet, and communicated with the first gas inlet; at least two heat exchangers are embedded in the guide chamber and coaxial with the guide chamber; the at least two heat exchangers are connected to the side wall of the guide chamber; a distance between each two adjacent heat exchangers is 10-30% of a height of the guide chamber; the at least two heat exchangers are connected in parallel to each other and communicated with the refrigeration mechanism to form a closed circulation loop; and the temperature sensor is connected to a top of the condensation chamber and electrically connected to the driver circuit.

7. The natural gas separation and purification and mercury collection system for oil and gas wells according to claim 5 , wherein each of the pressure buffer mechanisms comprises a buffer tank, an elastic diaphragm, a bearing keel, a pressure equalizing pump, a counterweight, a plurality of guide rails, pressure sensors, and a wedge; an axis of the buffer tank is perpendicular to the horizontal plane, and the buffer tank is a cylindrical closed chamber structure with a rectangular axial section; a side wall of the buffer tank is provided with at least one second gas inlet; the at least one second gas inlet uniformly surrounds the axis of the buffer tank, and a distance between the at least one second gas inlet and a bottom of the buffer tank is 5-15% of a height of the buffer tank; a top of the buffer tank is provided with a gas guide port and communicated with an external pipe through the gas guide port; the bearing keel is embedded in the buffer tank and is a spoke-shaped frame structure coaxial with the buffer tank; the bearing keel is slidably connected to an inner side of the buffer tank through the plurality of guide rails; the elastic diaphragm is wrapped around the bearing keel; the elastic diaphragm and the bearing keel jointly divide an inner space of the buffer tank into a pressure regulating chamber and a gas discharge chamber from top to bottom, wherein the pressure regulating chamber and the gas discharge chamber are independent of each other; the pressure equalizing pump is located on the bearing keel and coaxial with the bearing keel; the pressure regulating chamber and the gas discharge chamber are communicated with each other through the pressure equalizing pump; the counterweight is a circular structure coaxial with the bearing keel and is connected to an upper end surface of the bearing keel; at least two gas pressure sensors are respectively connected to the upper end surface and a lower end surface of the bearing keel and electrically connected to the driver circuit; at least one wedge is embedded in the gas discharge chamber and connected to the top of the buffer tank; and the at least one wedge has an axis perpendicular to the elastic diaphragm, and has a height not less than 10 cm.

8. The natural gas separation and purification and mercury collection system for oil and gas wells according to claim 7 , wherein a bearing spring is provided in each guide rail of the plurality of guide rails, and the guide rail is connected to the bearing keel through the bearing spring; the bearing spring is distributed in parallel to an axis of the guide rail; the upper end surface of the bearing keel is provided with a mounting groove at a position corresponding to the counterweight; and when there are two or more counterweights, the two or more counterweights are connected to the upper end surface of the bearing keel and distributed in a concentric circular structure.

9. The natural gas separation and purification and mercury collection system for oil and gas wells according to claim 1 , wherein the driver circuit is a circuit system based on either a field-programmable gate array (FPGA) chip or a programmable controller; and the driver circuit is provided with a communication port and a control interface, wherein the control interface is based on any one or a combination of a display, a button, and a potentiometer.

10. A method of use of the natural gas separation and purification and mercury collection system in oil and gas wells according to claim 1 , comprising the following steps: S 1 : gas collection: vacuuming the cyclone separator, the condensation purification and separation mechanism, the pressure buffer mechanisms, the mercury collection and separation mechanisms, and the natural gas storage tanks; driving, after the vacuuming, the electric heating wire of the mercury collection and separation mechanism to heat the gold foil meshes to 500-700° C., and holding the temperature for 3-5 min; cooling, after the holding, the gold foil meshes naturally to room temperature; conducting, by the pressure buffer mechanism, a pressure regulation on high-pressure natural gas collected from an oil or gas well, and delivering the regulated natural gas to the cyclone separator; and separating, by the cyclone separator, a solid particle and a liquid droplet in the natural gas to generate gaseous natural gas as initial experimental gas; S 2 : gas purification: conducting, by the pressure buffer mechanism, a secondary pressure regulation on the experimental gas generated in step S 1 ; delivering, after the secondary pressure regulation, the experimental gas to the condensation purification and separation mechanism; condensing, by the condensation purification and separation mechanism, an impurity in a vaporous form in the experimental gas through a low-temperature environment; retaining the impurity separated in droplet and crystal forms in the condensation purification and separation mechanism; conducting, by the condensation purification and separation mechanism, gas-liquid separation on the experimental gas after the condensation purification; and conducting a secondary purification on the experimental gas to generate stable-pressure and clean experimental gas; S 3 : mercury separation: conducting, by the pressure buffer mechanism, a pressure regulation on the stable-pressure and clean experimental gas generated through the secondary purification in step S 2 ; delivering the stable-pressure and clean experimental gas to the mercury collection and separation mechanisms, and detecting a total input amount of the experimental gas entering the mercury collection and separation mechanisms; allowing, when the stable-pressure and clean experimental gas passes through the mercury collection and separation mechanism, the gold foil meshes in the mercury collection and separation mechanism to react with mercury in the stable-pressure and clean experimental gas so as to generate amalgam, thereby separating the mercury from the natural gas; delivering, after the mercury separation, the natural gas to the natural gas storage tank; and comparing a storage capacity of the natural gas in the natural gas storage tank with the total input amount of the experimental gas delivered to the mercury collection and separation mechanism to acquire a separated mercury content; and S 4 : mercury analysis: collecting, after the experimental gas is collected by the natural gas storage tank, the amalgam generated by the reaction in the mercury collection and separation mechanism; transferring the collected amalgam to a mercury analysis device for analysis, and then determining an isotopic content of the amalgam; and comparing a determined value with the mercury content acquired in step S 3 , and making a correction to acquire an accurate natural gas content and an accurate mercury content in a mixed gas collected from the oil or gas well.

11. The natural gas separation and purification and mercury collection system for oil and gas wells according to claim 2 , wherein the mercury collection and separation mechanism comprises a separation tank, carriers, gold foil meshes, an aerator, a partition, a guide fan, heat exchange tubes, a temperature-humidity sensor, and pressure-flow sensors; the separation tank is a closed chamber structure with a rectangular axial section; the separation tank comprises an upper end surface provided with a gas inlet and a gas outlet, and a bottom provided with a drain outlet; the gas inlet and the gas outlet are distributed at two sides of an axis of the separation tank; the partition is embedded in the separation tank and connected to a top and a side wall of the separation tank; a distance between the partition and the bottom of the separation tank does not exceed 10% of a height of the separation tank; the partition divides the separation tank into a mercury removal chamber and a gas discharge chamber; the gas inlet is communicated with the mercury removal chamber, and the gas outlet is communicated with the gas discharge chamber; each of the carriers is a closed and circular structure, and is provided with 1-2 gold foil meshes; the carriers are embedded in the mercury removal chamber, coaxial with the mercury removal chamber, and slidably connected to an inner side of the mercury removal chamber through sliding rails; a distance between each two adjacent carriers is not less than 10 mm; the aerator is communicated with the gas inlet, located inside the mercury removal chamber, and connected to a top of the separation tank; there are at least two heat exchange tubes, comprising a first heat exchange tube located below the partition, connected to the bottom of the separation tank, and surrounding the axis of the separation tank, and a second heat exchange tube embedded in the gas discharge chamber and connected to a side wall of the separation tank corresponding to the gas discharge chamber; an outer side of the separation tank corresponding to the second heat exchange tube is provided with a pipe joint and communicated with the external condensation purification and separation mechanism through the pipe joint; the temperature-humidity sensor is embedded in the gas outlet; each of the gas inlet and the gas outlet is provided with a pressure-flow sensor; at least one guide fan is connected to the bearing frame and communicated with the gas outlet and the shunt through a second guide tube; the at least one guide fan is communicated with the natural gas storage tank through the shunt; and the at least one guide fan, the temperature-humidity sensor, and the pressure-flow sensors are electrically connected to the driver circuit.

12. The natural gas separation and purification and mercury collection system for oil and gas wells according to claim 11 , wherein at least one electric heating wire and a temperature sensor are further provided in each of the carriers; the at least one electric heating wire is spirally distributed around an axis of the carrier, and is 0-5 mm far from the gold foil mesh; the temperature sensor is coaxial with the carrier; and the at least one electric heating wire and the temperature sensor are electrically connected to the driver circuit.

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