WO2020192193A1

WO2020192193A1 - Apparatus for the continuous preparation of natural gas hydrate microsphere

Info

Publication number: WO2020192193A1
Application number: PCT/CN2019/126567
Authority: WO
Inventors: 周雪冰; 梁德青; 龙臻; 罗金琼
Original assignee: 中国科学院广州能源研究所
Priority date: 2019-03-28
Filing date: 2019-12-19
Publication date: 2020-10-01
Also published as: CN109971519A; CN109971519B

Abstract

An apparatus for the continuous preparation of a natural gas hydrate microsphere, comprising a crystallization chamber (1), a grinding chamber (2), a microsphere preparation chamber (3), a microsphere storage chamber (4), a temperature control system, a pressure control system, a gas and solution servo system (7), and a mechanical transmission servo system. The entire process of hydrate microsphere preparation is completed in a high-pressure environment. Meanwhile, a grinding step is added into the hydrate formation and microsphere pressing preparation processes. The four processes required in the preparation of the natural gas hydrate microsphere are clearly described, that is, crystallization, grinding, pressing and storage. Moreover, hydrate formation, grinding, and microsphere pressing are completed respectively in three high-pressure gas chambers which are connected to each other. The structure of the device is clear, and the safety level and running fluency are high. The present invention may simulate a low temperature and high-pressure environment, simulating temperatures from room temperature to -20°C and pressures of 0-10 MPa, which is beneficial for enriching a natural gas hydrate dynamic research method and promoting the application of a hydrate method gas storage and transportation technology.

Description

Continuous preparation device of natural gas hydrate pellets

Technical field

The invention relates to the technical field of storage and transportation of natural gas hydrate, in particular to a continuous preparation device of natural gas hydrate pellets.

Background technique

Natural gas hydrate, or "flammable ice", is a cage-like crystalline compound composed of natural gas and water molecules with methane as the main component. Under low temperature and high pressure conditions, natural gas hydrate can exist stably. Under normal temperature and pressure, natural gas hydrate will quickly decompose to form free natural gas and water. Naturally formed gas hydrates are widely distributed in deep-sea sediments or continental permafrost. In recent years, a large number of natural gas hydrates have been discovered globally, making it an alternative energy source with great development potential. At present, the proven reserves of natural gas hydrate on a global scale are as high as 2.1×10 ¹⁶ m ³ , which is more than twice the total amount of traditional fossil energy. At the same time, the gas storage density of gas hydrate is high. 1 Standard volume of gas hydrate can store up to 160 standard volumes of gas. Compared with liquefied natural gas, natural gas hydrate storage requires milder temperature and pressure conditions, and can be used for natural gas storage and transportation. my country has abundant natural gas hydrate resources. Therefore, the development of rapid gas hydrate preparation equipment is of great significance for studying the dynamics and mechanism of natural gas hydrates, and for developing natural gas storage and transportation technologies that use hydrates as energy storage materials.

Since the pressure required for the stable occurrence of natural gas hydrates will increase significantly with the increase in temperature, the temperature at which natural gas hydrates are formed and stored in nature and experimental studies generally does not exceed 10°C. For example, at 1°C, the minimum pressure required to keep methane gas hydrate crystals stable is about 2.9 MPa. Therefore, the preparation of natural gas hydrate requires the assistance of high-pressure vessels and refrigeration equipment to complete. In addition, the formation process of natural gas hydrate is a phase change process from liquid water to natural gas hydrate crystals. The porous structure on the surface of natural gas hydrate crystals makes it difficult to form large-sized complete crystals, which is important for realizing the rapid development of natural gas hydrate and aqueous solution. The separation caused greater difficulties. At present, the natural gas storage and transportation technologies developed in China that use hydrates as energy storage materials are usually completed with hydrate slurry as a carrier, which greatly weakens the gas storage capacity of hydrates. At the same time, a large number of experimental studies have shown that the reaction kinetics of natural gas hydrate is closely related to the morphology of the hydrate. However, because natural gas hydrate can only exist stably under high pressure, it is extremely difficult to control the macroscopic and microscopic morphology of natural gas hydrate, and it has gradually become one of the bottlenecks in the study of natural gas hydrate reaction kinetics. In addition, the harsh conditions required for the rapid preparation of natural gas hydrates limit its popularity as a new type of clean energy in the public, and bring certain difficulties to the development and promotion of natural gas hydrate-related technologies.

At present, natural gas hydrate pellets with regular shapes can only be completed by pressing the prepared hydrate powder into a star mold in a liquid nitrogen environment, and the manufacturing process is complicated and cannot be continuously prepared. To realize the continuous and rapid preparation of natural gas hydrate pellets, it is necessary to overcome the following difficulties: (1) Continuous replenishment of gas and aqueous solution and continuous transfer of hydrate crystals in high-pressure environment; (2) Interaction between hydrate and aqueous solution in high-pressure environment Quick separation; (3) The hydrate crystals with regular shapes are pressed out and are not easily broken; (4) The prepared hydrate can be quickly taken out from the high-pressure environment. (5) The equipment can quickly recover methane and other greenhouse gases that are not involved in the formation of hydrates.

To sum up, develop a set of equipment that can continuously and quickly prepare natural gas hydrates with regular shapes. For quantitative research on the reaction kinetics of natural gas hydrates, determine the relevant parameters of hydrate reaction kinetics, and at the same time, enrich and expand hydrates. French gas storage and transportation methods, promotion and popularization of natural gas hydrate mining and storage and transportation technologies are of very important value.

Summary of the invention

In order to overcome the difficulties in the continuous preparation technology of natural gas hydrate pellets and realize the rapid and continuous preparation of natural gas hydrates, the present invention combines the traditional natural gas hydrate pellet preparation method and the application technology of magnetic drive devices in high-pressure equipment to provide a Continuous preparation device of natural gas hydrate pellets.

In order to achieve the above objectives, the technical solutions adopted by the present invention are as follows.

A continuous preparation device for natural gas hydrate pellets, including a crystallization chamber 1, a grinding chamber 2, a pellet preparation chamber 3, a pellet storage chamber 4, a temperature control system, a pressure control system, a gas and solution servo system, and a mechanical transmission servo system. Among them, the main body of the device is a high-pressure resistant cavity, including a crystallization bin 1, a grinding bin 2, a pellet preparation bin 3, and a pellet storage bin 4.

The crystallization chamber 1 is a cylindrical high-pressure container, as shown in Fig. 2, which is mainly used for the transformation from aqueous solution to solid hydrate, that is, the crystallization of natural gas hydrate. The bottom of the crystallization bin 1 contains an aqueous solution, and the side walls are provided with gas injection holes and water injection holes for supplementing the crystallization bin 1 with the aqueous solution and gas required for the formation of natural gas hydrate. A liquid level detector and a thermal resistance thermometer are embedded on the side wall to measure the temperature and liquid level in the crystallization chamber 1. A hollow center column is fixed at the center of the bottom of the crystallization chamber 1. A permanent magnet rod is inserted inside the center column and connected to an external motor. A magnetic drive stirring shaft is embedded outside the center column, and the permanent magnets embedded in the magnetic drive stirring shaft can be It is coupled with the magnetic field of the permanent magnet inside the center pillar. Therefore, the external motor drives the permanent magnet rod inside the center column to rotate, thereby driving the magnetic force in the crystallization chamber 1 to drive the stirring shaft to rotate. The radius of the spiral blade attached to the magnetic drive stirring shaft is slightly smaller than the radius of the crystallization chamber 1, which can stir the solution in the crystallization chamber 1. At the same time, when the natural gas hydrate is formed in the solution, the hydrate can be continuously transported upwards and is being transported. The free water in the hydrate is initially filtered out in the process. The top end cover of the crystallization chamber 1 is in the shape of an inverted funnel, and the outlet is connected with the high-pressure pipeline connecting the grinding chamber 2. The hydrate crystals transported to the top end cover of the crystallization chamber 1 are squeezed under the thrust of the spiral blades to further release the free water entrained in the crystals and enter the grinding chamber 2 through the high-pressure pipeline. The top end cover of the crystallization chamber 1 is provided with a pressure sensor and a back pressure valve for measuring and adjusting the gas pressure in the crystallization chamber 1.

The grinding chamber 2 is a cylindrical high-pressure container, as shown in Figure 2, which is mainly used to fully grind the hydrate crystals transported in the crystallization chamber 1 and to prepare and store sufficient hydrate powder for the pellets. At the same time, since the temperature and pressure in the grinding chamber 2 are the same as those in the crystallization chamber, a small amount of free water carried in the hydrate can continue to form hydrates in the grinding chamber 2 to achieve drying of the hydrate powder. The grinding chamber 2 drives three grinding rollers to rotate along the inner wall of the grinding chamber 2 through a motor to complete the grinding of hydrate crystals. The principle is the same as that of the magnetic drive stirring shaft in the crystallization chamber 1, the motor rotates through the connected permanent magnet, and then drives the magnetic drive in the grinding chamber 2 to rotate the rotating shaft. The magnetic drive rotating shaft is connected with the grinding roller through a connecting rod. Each grinding roller has its own rotation axis, and while revolving along the center of the grinding chamber 3, it also rotates around the respective rotation axis during the grinding process. In order to prevent large hydrates from hindering the grinding roller from rolling along the wall of the grinding chamber 2, the device is provided with a spring on the connecting rod and connected with the axle of the grinding roller. Therefore, when the grinding roller cannot grind larger hydrate blocks at one time, the grinding roller can be rolled along the upper surface of the hydrate without being caught by the spring contraction, and then the large hydrate can be removed by multiple rolling. The crystals are crushed to achieve the effect of grinding. The top of the grinding chamber 2 is provided with a back pressure valve and temperature and pressure sensors for adjusting the pressure in the grinding chamber 2 and measuring the temperature and pressure of the grinding chamber 2. The bottom of the grinding chamber 2 is provided with a pipeline connecting the pellet preparation chamber 3, and the ground hydrate powder can enter the pipeline through its own weight and further enter the pellet preparation chamber 3.

The pellet preparation chamber 3 is a cylindrical high-pressure resistant container, as shown in Fig. 2, which is the core device for the preparation of natural gas hydrate pellets. The pellet preparation chamber 3 realizes the pressing of the hydrate powder and the movement of the hydrate pellets through movable hemispherical molds arranged at both ends of the cavity. Similar to the principle of the magnetically driven stirring shaft in the crystallization chamber 1, the permanent magnets embedded in the hemispherical mold and the permanent magnets connected to the motor outside the pellet preparation chamber 3 attract each other, so that the external motor can complete the control of the hemispherical mold. The hemispherical mold can move along the axis of the pellet preparation chamber 3 and rotate slowly to reduce the adhesion of the hydrate powder on the surface of the hemispherical mold. Two spherical reversing valves are arranged along the axis of the pellet preparation chamber 3, the diameter of the through hole of the spherical reversing valve is the same as the diameter of the inner cavity of the pellet preparation chamber 3, and the hemispherical mold can pass smoothly. One of the spherical reversing valves is connected to the grinding chamber 2. When the spherical reversing valve rotates 90°, the through hole of the spherical reversing valve is connected to the grinding chamber and accepts hydrate powder; when the spherical reversing valve is rotated 90° again, the through hole of the spherical reversing valve prepares the ball into the chamber 3 The two ends are connected, and the hemispherical molds at both ends of the pellet preparation chamber 3 are driven by an external motor to move into the through hole to complete the compression of the natural gas hydrate pellets. The compressed hydrate pellets and the hemispherical mold are moved to the through hole of the spherical reversing valve on the other side, and then the hemispherical molds are moved to the two ends of the pellet preparation chamber 3. The ball reversing valve on the other side is connected to the pipeline connecting the ball storage bin 4. When the prepared natural gas hydrate pellets are moved into the through holes, the spherical reversing valve is rotated 90°, and the hydrate pellets enter the pellet storage bin 4 through the pipeline by their own gravity. A back pressure valve and a pressure sensor are provided on the side wall of the pellet preparation chamber 4 to control and measure the pressure in the pellet preparation chamber 2.

The pellet storage bin 4 is a capsule-type high-pressure container, as shown in FIG. 2, for storing the prepared natural gas hydrate pellets. When the hydrate pellets fall into the pellet storage bin 4 by gravity, in order to prevent the pellets from hitting the inner wall of the pellet storage bin 3 and cause the pellets to break, the connection between the bottom of the inner wall and the side walls of the pellet storage bin 4 is designed as a circle arc. The top of the pellet storage bin 4 is provided with an exhaust valve and a fast detachable end cover, which is convenient for taking out the prepared gas hydrate pellets. The pipe connecting the small ball storage bin 4 and the small ball preparation bin 3 is provided with a spherical reversing valve. The diameter of the through hole of the spherical reversing valve is the same as the diameter of the inner cavity of the small ball preparation bin 3. At the same time, the spherical reversing valve has Better sealing effect. When the pellet storage bin 4 is decompressed, the spherical reversing valve can prevent the gas in the pellet preparation bin 3 from leaking into the pellet storage bin 4.

The temperature control system adopts circulating coolant to cool the main body of the device. The circulating cooling liquid with a constant temperature passes through the cooling liquid jacket wrapped outside the main body of the device to provide a constant temperature environment inside the main body of the device. The circulating cooling liquid passes through the low-temperature circulating cooling liquid to form a low-temperature circulating cooling liquid with a constant temperature through a cryostat. The low temperature constant temperature device includes heat exchange tube, thermoelectric sheet, electric heating wire and circulating water pump. Electric heating wires and thermoelectric sheets are attached to the outer surface of the heat exchange tube for cooling and heating, and PID is used to adjust and control the temperature of the low-temperature circulating coolant at the outlet of the heat exchange tube; the flow of the low-temperature circulating coolant is powered by a circulating water pump. In order to ensure that the natural gas hydrate pellets do not quickly decompose when taken out of the pellet storage bin 4, the pellet storage bin 4 is equipped with an independent low-temperature circulating cooling device, which can make the temperature of the pellet storage bin 4 below 0°C.

The pressure control system is mainly used to control the pressure in the main device and recover the gas discharged from the main device. In the present invention, the crystallization chamber 1, the grinding chamber 2, the pellet preparation chamber 3 and the pellet storage chamber 4 of the main device are all provided with a back pressure valve with adjustable pressure. When the equipment is running, the back pressure valve of the main device is adjusted to a uniform set value. When the gas hydrate pellets need to be taken out, only the back pressure valve of the pellet storage bin 4 needs to be adjusted to the minimum. All the gas discharged from the back pressure valve is discharged into the gas recovery tank to avoid potential safety hazards and environmental pollution caused by excessive discharge of methane gas. The gas stored in the gas recovery tank can be pressurized by a booster pump connected to the high-pressure gas cylinder and injected into the high-pressure gas cylinder again. The gas recovery tank is equipped with a pressure sensor, when the pressure in the gas recovery tank is high, the booster pump can be automatically triggered to inject gas into the high-pressure gas cylinder. In addition, the pellet storage bin 4 is connected with a vacuum pump and a high-pressure gas cylinder, and is used to vacuum and pressurize the pellet storage bin 4 after the natural gas hydrate pellets are taken out.

The gas and solution servo system is mainly used to continuously replenish the high-pressure gas and aqueous solution consumed by the formation of hydrate to the crystallization chamber 1. The gas servo device is mainly composed of a high-pressure gas cylinder and a gas pressure reducing valve. When the gas pressure in the crystallization chamber 1 is lower than the set pressure, the high-pressure gas in the gas cylinder will directly replenish gas into the crystallization chamber 1 through the pressure reducing valve. The solution servo device is mainly composed of a constant pressure pump and a liquid level detector. The liquid level detector arranged in the crystallization chamber 1 measures the liquid level of the aqueous solution in the crystallization chamber 1 to adjust the water supply amount and rate of the constant pressure pump to the crystallization chamber 1.

The mechanical transmission servo system mainly controls the movement of the rotating shaft and the connecting rod in the main device, including the motor of the crystallization chamber 1 connected to the spiral blades to drive the stirring shaft, the grinding chamber 2 is connected to the motor of the magnetic drive to drive the stirring shaft, and the ball preparation chamber 3 The motor connected to the spherical reversing valve, the motor connected to the movable hemispherical mold in the pellet preparation bin 3, and the motor of the spherical reversing valve on the pipeline connecting the pellet storage bin 4 and the pellet preparation bin 3 are composed. Among them, the mechanical transmission servo system is mainly composed of the motor connected to the magnetic force of the spiral blade in the crystallization chamber 1 to drive the stirring shaft, the motor connected to the magnetic drive of the rotating shaft in the grinding chamber 2 and the motor of the movable hemispherical mold in the ball preparation chamber 3 All are stepping motors; the motor connected to the ball reversing valve in the ball preparation chamber 3 and the ball storage bin 4 and the ball preparation chamber 3 are connected to the ball reversing valve on the pipeline. The motor is only used to control the ball reversing valve Switch.

The present invention combines the traditional natural gas hydrate pellet preparation method and the application technology of the magnetic drive device in the high-pressure equipment. The preparation process of the hydrate pellets is completed in a high-pressure environment. At the same time, the hydrate formation and pellet suppression are both completed. The grinding process is added to the preparation process, which clarifies the four processes of hydrate crystallization, grinding, pressing and storage required for the preparation of natural gas hydrate pellets. In addition, the hydrate formation, grinding, and pellet pressing are respectively completed in three interconnected high-pressure gas chambers, so that the structure of the equipment is clear and has high safety and smooth operation. In addition, the addition of the high-pressure gas recovery device improves the reusability of the high-pressure gas, improves the safety of the equipment, and also reduces the production cost and environmental pollution. The invention can simulate the low-temperature and high-pressure environment from room temperature to minus 20°C and 0-10 MPa, and is beneficial to enriching gas hydrate dynamic research methods and promoting the application of hydrate gas storage and transportation technology.

Description of the drawings

Figure 1 is a working principle diagram of the continuous preparation device of natural gas hydrate pellets of the present invention;

Figure 2 is a schematic structural diagram of a continuous preparation device for natural gas hydrate pellets of the present invention;

In the figure: 1 crystallization warehouse; 2 grinding warehouse; 3 pellet preparation warehouse; 4 pellet storage warehouse; 5 low temperature constant temperature device a; 6 low temperature constant temperature device b; 7 solution servo device; 8 high pressure gas cylinder; 9 gas recovery tank; 10 booster pump; 11 vacuum pump.

detailed description

The present invention will be further described below in conjunction with the drawings and specific embodiments.

Figure 1 shows the working principle diagram of the continuous preparation device of natural gas hydrate pellets. Its core components are four high-pressure resistant chambers, including the crystallization chamber 1, the grinding chamber 2, the pellet preparation chamber 3, and the pellet storage chamber 4 . When the device is running, water and high-pressure gas pass through the crystallization chamber 1, the grinding chamber 2, the pellet preparation chamber 3, and the pellet storage chamber 4 to form natural gas hydrate pellets. The pressure in the high-pressure resistant cavity is adjusted and controlled by the pressure control system, and the temperature is controlled and adjusted by the cryostat a and the cryostat b respectively. Among them, the cryostat a is used to adjust the temperature of the crystallization chamber 1, the grinding chamber 2 and the pellet preparation chamber 3; the cryostat b is used to adjust the temperature of the pellet storage chamber 4. The gas and solution servo system is used to provide the crystallization chamber 1 with high-pressure gas and water required for the formation of natural gas hydrate. The mechanical transmission servo system is used to control the rotation of the magnetic drive stirring shaft and the magnetic drive rotation shaft in the crystallization chamber 1 and the grinding chamber 2, the translation of the hemispherical mold in the pellet preparation chamber and the rotation of the spherical reversing valve.

Figure 2 is a system diagram of the continuous preparation device of natural gas hydrate pellets. The following describes the functions of each system:

1. The main preparation process of the natural gas hydrate pellets is: the high-pressure gas and aqueous solution in the crystallization chamber 1 form a natural gas hydrate slurry under a specific temperature condition, and the initial filtration of the magnetically driven stirrer in the crystallization chamber 1 contains a small amount of freedom. The natural gas hydrate crystals of water are pushed to the grinding chamber 2. In the high-pressure environment of the grinding chamber 2, the small amount of free water attached to the natural gas hydrate crystals will continue to form natural gas hydrates with the high-pressure gas until the free water disappears and dry natural gas is obtained. Hydrate crystals. At the same time, the grinding roller continuously grinds the natural gas hydrate crystals, so that the natural gas hydrate powder in the grinding chamber 2 has a relatively uniform particle size. Then, the natural gas hydrate powder enters the through hole of the spherical reversing valve connected to the grinding chamber 2 in the pellet preparation chamber 3 under the action of gravity. When the through hole of the spherical reversing valve is in communication with the inner cavity of the pellet preparation chamber 3, the hemispherical molds on both sides of the pellet preparation chamber 3 move to the through hole of the spherical reversing valve to complete the alignment of the hydrate powder therein.的pressed into shape. Subsequently, the prepared natural gas hydrate pellets are clamped by the hemispherical molds on both sides to move into the through hole of the spherical reversing valve connected to the pellet storage bin 4. When the hemispherical molds on both sides are separated and moved out of the through hole of the spherical reversing valve, the spherical reversing valve connects the through hole with the ball storage bin 4 by rotating, and the prepared natural gas hydrate pellets are affected by gravity. Go down into the ball storage bin 4. After closing the ball reversing valve connecting the pellet preparation bin 3 and the pellet storage bin 4, quickly release the high pressure gas in the pellet storage bin 4, and open the top end cover of the pellet storage bin 4 to obtain the prepared Gas hydrate pellets.

2. The working process of the temperature control system is: turn on the circulating water pumps in the two sets of low temperature and constant temperature devices and set the constant temperature. In the process of preparing hydrate pellets, the two sets of low temperature and constant temperature devices maintain the same set temperature, so that the temperature in the high pressure resistant cavity is uniform and constant. When the natural gas hydrate pellets in the pellet storage bin 4 need to be taken out, the set temperature of the cryostat for cooling the pellet storage bin 4 is adjusted to below 0°C. When the process of preparing and removing the pellets is over, the set temperature of the two sets of cryostats are slowly adjusted to room temperature, and finally closed.

3. The working process of the pressure control system is: adjust the back pressure value of all the back pressure valves of the high pressure chamber to the set pressure, and then use the vacuum pump 11 to vacuum all the high pressure chambers. When the vacuum is completed, the high-pressure gas in the high-pressure gas cylinder 8 is slowly injected into the crystallization chamber 1 through the gas injection hole of the crystallization chamber 1 and finally the pressure in all the high-pressure resistant chambers is kept consistent. When it is necessary to take out the natural gas hydrate pellets in the pellet storage bin 4, quickly adjust the back pressure valve of the pellet storage bin 4 to quickly reduce the pressure in the pellet storage bin 4 to atmospheric pressure. During operation, the high-pressure gas escaping from each back pressure valve due to the local overpressure of the high-pressure-resistant cavity and the exhaust of the pellet storage bin 4 will be collected in the gas recovery tank 9 and passed through the booster pump 10 in time. Pump into the high-pressure gas cylinder 8 again for recycling.

4. The working process of the gas and solution servo system is: First, let the gas in the high-pressure gas cylinder pass through the gas servo device, that is, the pressure reducing valve, and inject high-pressure gas into the crystallization chamber 1, and wait until the pressure in the high-pressure resistant chamber reaches the set value. After constant, turn on the solution servo device, that is, the constant pressure pump, and inject the solution into the crystallization chamber 1. During the operation of the equipment, the constant pressure pump adjusts the water replenishment amount and rate according to the liquid level of the aqueous solution measured by the liquid level detector in the crystallization chamber 1. When the preparation process of the hydrate pellets is finished, the solution and gas servo systems are turned off successively.

5. The working process of the mechanical transmission servo system is as follows: First, ensure that the two ball reversing valves in the pellet preparation chamber 3 are in communication with the cavity, and ensure that they are located at the connecting pipes of the pellet preparation chamber 3 and the pellet storage bin 4 Keep the ball reversing valve open to ensure that the ball reversing valve between the pellet preparation bin 3 and the pellet storage bin 4 is in a closed state. When the solution servo system injects the solution into the crystallization chamber 1, turn on the magnetic drive stirring shaft of the crystallization chamber 1 and the magnetic drive rotation shaft of the grinding chamber 2. When the hydrate crystals in the grinding chamber 2 are fully ground and a certain amount of hydrate is stored When powder is prepared, the spherical reversing valve in the pellet preparation chamber 3 and the grinding chamber 2 is opened, so that the ground hydrate powder is filled into the through hole of the spherical reversing valve. Subsequently, the spherical reversing valve is rotated again to make its through hole communicate with the pellet preparation chamber 3. The motor controlling the movement of the hemispherical mold in the pellet preparation chamber 3 is turned on to drive the hemispherical molds on both sides of the cavity of the pellet preparation chamber 3 to move to the through hole of the spherical reversing valve connected to the pellet preparation chamber 3 to complete the ball pressing. Subsequently, the natural gas hydrate pellet is clamped by the hemispherical mold and moved to the through hole of the spherical reversing valve connected to the pellet storage bin 4. Finally, the hemispherical molds on both sides are separated and removed from the through hole of the spherical reversing valve. The mechanical transmission servo system drives the ball reversing valve connected to the ball storage bin 4 to rotate, so that the natural gas hydrate pellets roll down to the ball storage bin 4 under its own gravity. When the hydrate pellets need to be taken out from the pellet storage bin 4, the ball reversing valve at the connecting pipe of the pellet preparation bin 3 and the pellet storage bin 4 must be closed first, so that the pellet preparation bin 3 and the pellets are stored The high-pressure gas in the chamber 4 is no longer connected. After the hydrate pellets are taken out from the pellet storage bin 4 and closed again, the ball reversing valve at the connecting pipe between the pellet preparation bin 3 and the pellet storage bin 4 is opened again. After the preparation process of the hydrate pellets is completed, the magnetic drive stirring shaft of the crystallization chamber 1 and the magnetic drive rotation shaft of the grinding chamber 2 and other mechanical transmission servo equipment are successively closed.

In the following, the method of using the continuous preparation device of natural gas hydrate pellets is applied to the measurement experiment of the crystal growth process of methane hydrate crystals at 2°C and 4MPa as an example to describe its use. The methane gas used in the experiment comes from Guangzhou Puyuan Gas Co., Ltd., with a purity of not less than 99.9%. The water used to form methane hydrate is distilled water, which is prepared in the laboratory.

The general working process is divided into three steps in chronological order: sample injection, preparation of hydrate pellets and instrument finishing.

In the sampling process, first check the pressure in the high-pressure gas cylinder to make it 4 MPa higher than the working pressure, ensure that the solution servo system contains sufficient aqueous solution, and ensure that the two spherical reversing valves in the pellet preparation chamber 3 are in the same cavity Keep the ball reversing valve in the connected state of the ball preparation chamber 3 and the ball storage bin 4, and ensure that the ball reversing valve between the ball preparation chamber 3 and the ball storage bin 4 is in an open state. Disabled. Turn on the circulating water pumps in the two sets of cryostats and set the constant temperature to 2°C and keep the two sets of cryostats at the same set temperature to make the temperature in the high-pressure resistant chamber uniform and constant. Adjust the back pressure value of all the back pressure valves of the high pressure chamber to 4 MPa, and then use the vacuum pump 11 to vacuum all the high pressure chambers. Subsequently, the gas in the high-pressure gas cylinder is passed through a gas servo device, that is, a pressure reducing valve, and high-pressure gas is injected into the crystallization chamber 1. After the pressure in the high-pressure resistant chamber reaches the set value and is constant, the solution servo device, namely the constant pressure pump, is turned on to inject the solution into the crystallization chamber 1. When the solution servo system injects the solution into the crystallization chamber 1, the magnetic force driving the stirring shaft of the crystallization chamber 1 and the magnetic force driving the rotating shaft of the grinding chamber 2 are turned on.

During the preparation of hydrate pellets, the aqueous solution in the crystallization chamber 1 interacts with the high-pressure gas in a high-pressure and low-temperature environment to form a large number of fine natural gas hydrate crystals in the aqueous solution. Under the action of filtration and lifting by the magnetically driven stirrer, part of the larger hydrate crystals are moved to the top of the crystallization chamber and enter the grinding chamber 2 through the connecting pipeline. After the hydrate crystals enter the grinding chamber 2, the larger hydrate crystals are crushed by the grinding action of the grinding roller, and the entrained free water and high-pressure gas continue to form hydrates until the hydrate in the grinding chamber 2 reaches a dry powder state. Accumulate at the bottom of the grinding chamber 2. The spherical reversing valve in the pellet preparation chamber 3 and the grinding chamber 2 is opened, so that the ground hydrate powder is filled into the through hole of the spherical reversing valve. Subsequently, the spherical reversing valve is rotated again to make its through hole communicate with the pellet preparation chamber 3. The motor controlling the movement of the hemispherical mold in the pellet preparation chamber 3 is turned on to drive the hemispherical molds on both sides of the cavity of the pellet preparation chamber 3 to move to the through hole of the spherical reversing valve connected to the pellet preparation chamber 3 to complete the ball pressing. Subsequently, the natural gas hydrate pellet is clamped by the hemispherical mold and moved to the through hole of the spherical reversing valve connected to the pellet storage bin 4. Finally, the hemispherical molds on both sides are separated and removed from the through hole of the spherical reversing valve. The mechanical transmission servo system drives the ball reversing valve connected to the ball storage bin 4 to rotate, so that the natural gas hydrate pellets roll down to the ball storage bin 4 under its own gravity. When the number of natural gas hydrate pellets in the pellet storage bin 4 reaches a certain amount, use a low-temperature thermostat to reduce the temperature of the pellet storage bin 4 to -10°C and close the connecting pipes between the pellet preparation bin 3 and the pellet storage bin 4 Ball reversing valve at the Quickly reduce the pressure in the pellet storage bin 4, open the top end cover of the pellet storage bin 4, and take out the prepared natural gas hydrate pellets. The high-pressure gas discharged from the pellet storage bin 4 enters the gas recovery tank and is pressurized to the pressure in the high-pressure gas cylinder by the booster pump, so that the discharged high-pressure gas is recovered into the high-pressure gas cylinder. Finally, the opened small ball storage bin 4 is sealed again and evacuated, and the temperature of the small ball storage bin 4 is kept consistent with the temperature in other high pressure chambers by using a cryostat. Then slowly open the spherical reversing valve at the connecting pipe between the pellet preparation bin 3 and the pellet storage bin 4 to keep the pressure of the pellet storage bin 4 consistent with the pressure in other high pressure chambers.

In the instrument sorting process, first turn off the solution servo system to convert all the solution in the crystallization chamber 1 into hydrates, and then turn off the magnetic drive stirrer in the crystallization chamber 1. The hydrate powder stored in the grinding chamber continues to pass through the pellet preparation chamber to form hydrate pellets, until the hydrate powder in the grinding chamber is completely removed, and then the magnetic drive rotating shaft in the grinding chamber 2 is closed. After all the hydrate pellets in the storage bin 4 with pellets are taken out, turn off the gas servo system and adjust the back pressure valve on the high pressure resistant chamber to gradually reduce the gas pressure in the high pressure resistant chamber, and the discharged high pressure gas enters the gas After the recovery tank is pressurized by the booster pump, the discharged high-pressure gas is recovered into the high-pressure gas cylinder. Finally, the vacuum pump 11 evacuates all the high-pressure-resistant chambers and turns off all power equipment to complete the maintenance and arrangement of the experimental instruments.

The above-mentioned embodiments only express the implementation of the present invention, and the description is relatively specific and detailed, but it should not be understood as a limitation on the scope of the invention patent. It should be pointed out that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can be made, and these all fall within the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention should be subject to the appended claims.

Claims

A continuous preparation device of natural gas hydrate pellets, characterized in that:

Including crystallization bin (1), grinding bin (2), pellet preparation bin (3), pellet storage bin (4), temperature control system, pressure control system, gas and solution servo system, and mechanical drive servo system. , The crystallization bin (1), grinding bin (2), pellet preparation bin (3) and pellet storage bin (4) constitute the main body of the device;

The crystallization chamber (1) is a cylindrical high-pressure container, the central axis is at an inclination angle of 15-30° to the vertical, the bottom is filled with aqueous solution, and the side wall is equipped with gas injection holes and water injection holes to supplement the natural gas hydrate crystallization needs A hollow center column is fixed in the center of the bottom, and the center column is connected to the outside atmosphere. A permanent magnet rod is inserted inside the center column and connected to an external motor. A magnetic drive stirring shaft is embedded outside the center column. , The magnetic field of the permanent magnet inlaid in the stirring shaft and the permanent magnet rod inside the center column are coupled with each other. The external motor drives the permanent magnet rod inside the center column to rotate and then drives the magnetic force to drive the stirring shaft. The magnetic force drives the stirring shaft with spiral blades. , The radius is slightly smaller than the radius of the crystallization bin (1), which can stir the solution in the crystallization bin (1). The top end cover of the crystallization bin (1) is in the shape of an inverted funnel and is transported to the top end of the crystallization bin (1) The natural gas hydrate crystals at the cover are squeezed under the thrust of the spiral blades to release the free water entrained in the natural gas hydrate crystals and enter the grinding chamber through the high-pressure pipeline (2);

The grinding chamber (2) is a cylindrical high-pressure container, the central axis is parallel to the horizontal direction, the upper side of the side wall is provided with a feed inlet connected to the crystallization chamber (1), and the bottom of the side wall is provided with a pellet preparation chamber (3) The connected discharge port has a hollow center column at the central axis, which communicates with the outside atmosphere. A permanent magnet rod is inserted into the center column and connected to an external motor. The center column is embedded with magnetic force to drive the rotating shaft. The permanent magnets embedded in the magnetic drive rotating shaft are coupled with the magnetic field of the permanent magnet rods inside the center column. The external motor drives the permanent magnet rods inside the center column to rotate and then drives the magnetic force to drive the rotating shaft. Three grinding rollers are driven by the connecting rods and magnetic force. The rotating shaft is vertically connected, and the magnetic drive rotating shaft drives the grinding roller to rotate and revolve on the side wall of the grinding chamber under the drive of an external motor to grind natural gas hydrate crystals into powder. The powder of natural gas hydrate crystals falls into small balls under the action of gravity. Warehouse(3);

The pellet preparation chamber (3) is a cylindrical high-pressure container, the central axis is parallel to the horizontal direction, and there is a movable hemispherical mold at each end of the cavity, and two spherical reversing valves are arranged along the central axis. The through hole diameter of the two spherical reversing valves is the same as the diameter of the small ball preparation chamber, the hemispherical mold can pass smoothly, one of the spherical reversing valves can be connected to the grinding chamber (2), and the other spherical reversing valve It can be connected with the small ball storage bin (4), and the spherical reversing valve connected with the grinding bin (2) can receive the natural gas hydrate crystal powder from the grinding bin (2), and can turn to close the grinding bin ( 2) The passage with the pellet preparation warehouse (3); the spherical reversing valve connected with the pellet storage warehouse (4) can transfer the prepared gas hydrate pellets to the pellet storage warehouse (4), and can The 90° turn to close the passage between the pellet storage bin (4) and pellet preparation bin (3); the hemispherical mold is driven by an external motor to complete the compression of the gas hydrate pellets, and the gas hydrate is replaced by the spherical reversing valve Push the ball to the ball storage bin (4);

The small ball storage bin (4) is a capsule-shaped high-pressure container with an exhaust valve and a quick-detachable end cover on the top. The pipe connected to the small ball preparation bin (3) is equipped with a spherical reversing valve. The diameter of the through hole of the reversing valve is the same as the diameter of the cavity of the ball preparation chamber (3). At the same time, the spherical reversing valve has a better sealing effect. When the ball storage bin (3) is decompressed, the spherical reversing valve It can prevent the gas in the pellet preparation bin (3) from leaking into the pellet storage bin (4);

The temperature control system is used to adjust the temperature of the main body of the device to maintain a low temperature and constant temperature;

Pressure control system, used to control the pressure of the main body of the device and recover the gas discharged from the main body of the device;

The gas and solution servo system is used to continuously replenish the gas and aqueous solution consumed by the formation of natural gas hydrate crystals to the crystallization chamber (1);

The mechanical drive servo system is used to control the rotation of the magnetically driven stirring shaft and the magnetically driven rotating shaft in the crystallization chamber (1) and the grinding chamber (2), the translation of the hemispherical mold in the small ball preparation chamber (3) and the spherical reversing valve And the rotation of the ball reversing valve in the ball storage bin (4).
The continuous preparation device of natural gas hydrate pellets according to claim 1, characterized in that:

The temperature control system includes a low temperature constant temperature device a and a low temperature constant temperature device b. The low temperature constant temperature device a is used to control the temperature of the crystallization chamber (1), the grinding chamber (2) and the pellet preparation chamber (3), and the low temperature constant temperature device b is used to control For the temperature of the ball storage bin (4), the two low-temperature thermostats each include a set of heat exchange tubes, thermoelectric chips, electric heating wires, temperature sensors and circulating water pumps. The electric heating wires and thermoelectric chips are all attached to the outside of the heat exchange tubes. The surface is cooled and heated, and PID is used to adjust the temperature of the low-temperature circulating coolant at the outlet of the heat exchange tube;

The low-temperature thermostat device forms a low-temperature circulating coolant with a constant temperature. The low-temperature circulating coolant circulates in the coolant jacket coated on the outer layer of the high-pressure container with the power provided by the circulating water pump to realize the control of the temperature in the high-pressure container .
The continuous preparation device of natural gas hydrate pellets according to claim 2, characterized in that:

The pressure control system includes a high-pressure gas cylinder, a booster pump, a pressure sensor set in the crystallization chamber (1), a grinding chamber (2) and a pellet preparation chamber (3), a back pressure valve and a gas recovery tank, as well as a pressure sensor set in the pellet The exhaust valve and the gas recovery tank of the storage bin (4); the gas stored in the gas recovery tank can be pressurized by a booster pump connected to the high-pressure gas cylinder and injected into the high-pressure gas cylinder again.
The continuous preparation device of natural gas hydrate pellets according to claim 3, characterized in that:

The gas and solution servo system includes a gas pressure reducing valve, a constant pressure pump and a liquid level detector; the constant pressure pump is connected to the water injection hole of the crystallization chamber (1), and the crystallization chamber (1) can be continuously supplied with natural gas hydrate during operation The aqueous solution consumed by crystallization; the liquid level detector is embedded in the side wall of the crystallization chamber (1) to detect the height of the solution level in the crystallization chamber (1) in real time; the pressure reducing valve and the gas injection hole and high pressure gas of the crystallization chamber (1) The bottles are connected to continuously replenish the gas consumed by the crystallization of natural gas hydrate into the crystallization chamber (1).
The continuous preparation device of natural gas hydrate pellets according to claim 4, characterized in that:

The mechanical transmission servo system includes the motor connected to the permanent magnet rod in the crystallization chamber (1), the motor connected to the permanent magnet rod in the grinding chamber (2), the motor connected to the spherical reversing valve in the ball preparation chamber (3), and the ball preparation The motor connected to the hemispherical mold in the bin (3), and the motor connected to the spherical reversing valve on the pipe connecting the small ball storage bin (4) and the small ball preparation bin (3);

The motor connected to the permanent magnet rod in the crystallization chamber (1), the motor connected to the permanent magnet rod in the grinding chamber (2), and the motor connected to the hemispherical mold in the grinding chamber (3) are stepping motors; the small ball preparation chamber (3) The motor connected to the ball reversing valve and the ball reversing valve on the pipeline connecting the small ball storage bin (4) and the small ball preparation bin (3) are only used to control the switch of the ball reversing valve.
The continuous preparation device of natural gas hydrate pellets according to claim 5, characterized in that:

The three grinding rollers in the grinding chamber (2) are connected with the magnetic drive rotating shaft through a hard rod, and centered on the magnetic drive rotating shaft, they are evenly distributed on the side wall of the grinding chamber (2). The radius of the grinding rollers and the hard rod The length ratio is 5:1. The grinding roller has a bearing between the axle and the roller, which can revolve around the magnetic drive shaft while rotating around its own axle as the center.
The continuous preparation device of natural gas hydrate pellets according to claim 6, characterized in that:

The axle of the grinding roller is connected with the spring embedded in the hard rod. When the axle receives a force along the length of the hard rod, the spring can change the distance between the grinding roller and the center of the magnetic drive rotating shaft by extending and contracting.
The continuous preparation device of natural gas hydrate pellets according to claim 7, characterized in that:

The connection between the bottom of the inner wall of the small ball storage bin (4) and the side wall is designed in an arc shape.