A graded ice shell hydrate extraction device and method with enhanced self-protection effect

Abstract

This invention relates to a graded ice shell hydrate extraction device and method with enhanced self-protection effect. The extraction device includes an extraction component, a separation and desanding chamber, a storage chamber, an ice shell production chamber, and a mixing chamber. Hydrate is extracted and crushed into hydrate particles of varying sizes by the extraction component. These particles are then fed into the separation and desanding chamber for separation, stored in various storage chambers, and the residue is discharged. The hydrate particles are then fed into the ice shell production chamber, where they are coated with spherical ice shells of different sizes. Finally, they are mixed with seawater in the mixing chamber and then lifted and transported upwards. By enhancing the self-protection effect of the hydrate, its self-decomposition is slowed down. Furthermore, by analyzing the temperature and pressure information fed back from the wellbore, the particle size, flow rate, and mixing ratio of the transported hydrate particles are dynamically adjusted to control the orderly graded decomposition during the hydrate transport process. This invention enables controllable and orderly decomposition within a closed transport pipeline, improving the safety of solid-state fluidized bed hydrate extraction.

Description

Technical Field

[0001] This invention belongs to the field of natural gas hydrate extraction technology, and relates to an ice shell graded hydrate extraction device and method with enhanced self-protection effect. Background Technology

[0002] Natural gas hydrate, also known as "combustible ice", 1m 3 Natural gas hydrates can be stored at 164m³ 3 Natural gas. Natural gas hydrate deposits are widely distributed in the deep sea or in terrestrial permafrost, and are abundant. It is estimated that the reserves of combustible ice on the seabed are enough for human use for at least 1,000 years. Therefore, it is internationally recognized as an alternative energy source to traditional energy sources such as oil.

[0003] The successful trial production of solid-state fluidized bed hydrates in the South China Sea proves that this method holds promise for the commercial exploitation of natural gas hydrates in the region. Solid-state fluidized bed extraction involves crushing the hydrate ore body, mixing it with seawater to form a fluidized bed, and then transporting it via pipeline to an offshore platform for post-processing without damaging the hydrate's structure. During pipeline transport, the increasing ocean temperature gradient causes the hydrate particles inside the vertical pipe to decompose, generating a large amount of gas. This leads to a sudden increase in local pressure, raising the risk of pipeline explosions.

[0004] Therefore, it is essential to provide an extraction apparatus and method that increases the safety of hydrate pipeline transportation processes. Summary of the Invention

[0005] To avoid explosions caused by a sudden increase in pressure inside the wellbore due to hydrate decomposition during solid fluidized bed hydrate extraction and to increase the safety of hydrate pipeline transportation, this invention provides an ice shell graded hydrate extraction device and method with enhanced self-protection effect.

[0006] In a first aspect, the present invention provides an ice shell grading hydrate extraction device with enhanced self-protection effect. The extraction device includes a mining component, a separation and desanding chamber, a storage chamber, an ice shell production chamber, and a mixing chamber connected in sequence. The mining component is used to extract hydrate particles and send them to the separation and desanding chamber. The separation and desanding chamber is used to grade the hydrate particles by particle size before sending them to the storage chamber, and to discharge the residue of the hydrate particles after particle size grading. The storage chamber is used to store the hydrate particles after particle size grading and send them to the ice shell production chamber. The ice shell production chamber is used to coat the hydrate particles after particle size grading with spherical ice shells of appropriate size before sending them to the mixing chamber. The mixing chamber is used to mix the hydrate particles coated with spherical ice shells with seawater and then lift and transport them upwards.

[0007] By adopting the above technical solution, the mining component, based on feedback from pipeline pressure data, in-situ crushes hydrates into particles of varying sizes within the reservoir and transports them to the separation and desanding chamber. The separation and desanding chamber separates the hydrate particles and sends them to the storage chamber, while simultaneously discharging the residue after hydrate particle separation, achieving in-situ backfilling of slag and reducing environmental impact. The storage chamber acts as a temporary storage container for hydrate particles of different sizes. The ice shell generation chamber introduces hydrate particles from the storage chamber and coats them with spherical ice shells of different sizes, thereby enhancing the self-protective effect of the hydrates and delaying their decomposition. The mixing chamber introduces the hydrate particles with ice shells from the ice shell generation chamber, mixes them with seawater, and then lifts and transports them upwards. This invention has the advantages of compact structure and minimal environmental disturbance. By enhancing the self-protective effect of hydrates and delaying their decomposition, it achieves controllable and orderly decomposition of hydrates within a closed transport pipeline during solid-state fluidized bed mining, improving the safety of the mining system.

[0008] Preferably, the ice shell production chamber includes a hemispherical ice tray conveyor belt, a feeding pipe, a spray pipe, spray heads, refrigeration equipment, and a discharge pipe; wherein, the hemispherical ice tray conveyor belt consists of an upper hemispherical ice tray conveyor belt and a lower hemispherical ice tray conveyor belt stacked on top of each other, the refrigeration equipment is located below the lower hemispherical ice tray conveyor belt, and the upper and lower hemispherical ice tray conveyor belts are used to generate hemispherical ice trays respectively and assemble them into a spherical ice shell; the inlet end of the feeding pipe is connected to the storage chamber, and the outlet end is located at the feeding end of the lower hemispherical ice tray conveyor belt, the lower... The feed end of the hemispherical ice grid conveyor belt extends along its length from the upper hemispherical ice grid conveyor belt, so that the hydrate particles fed from the feed pipe fall onto the lower hemispherical ice grid conveyor belt; the upper and lower hemispherical ice grid conveyor belts work together to coat the hydrate particles with the spherical ice shell; the inlet of the spray pipe is connected to the mixing chamber for feeding seawater; the outlet of the spray pipe is connected to the spray head, which is positioned above the hemispherical ice grid conveyor belt; the discharge pipe is located at the discharge end of the hemispherical ice grid conveyor belt. By adopting the above technical solution, the feeding pipe delivers hydrate particles from the corresponding storage bin into a hemispherical ice grid at a designated location. The hemispherical ice grid installed on the conveyor belt acts as a mold for ice shell formation. Two sets of conveyor belts gradually thicken the ice shell along the conveying direction and combine the hemispherical ice grids into a complete spherical ice grid after feeding, further completing the formation of the ice shell. Multiple spray heads located above the conveyor belt can evenly spray seawater from the spray pipe into all the ice grids. The refrigeration equipment located below the conveyor belt absorbs the heat of the seawater in the ice grids, causing it to cool down and freeze to form an ice shell. The discharge pipe located at the end of the conveyor belt collects the hydrate particles that have formed ice shells and sends them into the mixing bin. Each level of ice shell production bin wraps hydrate mineral particles of different sizes with an ice shell of a certain thickness, enhancing the self-protection effect of hydrates, delaying their decomposition, and realizing the controllable graded decomposition of hydrates in the solid fluidized mining process, thereby improving the safety of the mining system.

[0009] Preferably, the mixing chamber includes a seawater injection pipe and a mixing lift pipe. The seawater injection pipe is connected to the spray pipe within the mixing chamber and then communicates with the mixing lift pipe; the mixing lift pipe is connected to the discharge pipe. By adopting the above technical solution, the seawater injection pipe introduces seawater for ice shell formation and subsequent mixing and lifting, while the mixing lift pipe mixes ice shell hydrate particles of various grades with seawater and then lifts and transports them upwards. The mixing chamber enables the graded use of seawater, making the extraction system more compact, saving costs, and improving the controllability of the hydrate mixing and lifting process.

[0010] Preferably, the separation and desanding bin includes multiple vibrating screens arranged in stages, the storage bin includes multiple sub-storage bins arranged in stages, and the ice shell production bin includes multiple sub-ice shell production bins arranged in stages; the number of sub-storage bins and sub-ice shell production bins is consistent with the number of vibrating screens; the discharge end of each stage of the vibrating screen is connected to the corresponding sub-storage bin; the vibrating screens at each stage are stacked in a manner where the aperture decreases progressively downwards; the hemispherical ice grid size of each stage of the sub-ice shell production bin decreases progressively. By adopting the above technical solution, the multi-stage vibrating screens separate hydrate particles of different sizes and excess residue in the mixture, which fall into the storage bins at each stage. The desanding conveyor belt transports the separated mixture residue to the sand discharge port for discharge. The separation and desanding bin realizes the separation of hydrate particles of different sizes and the in-situ backfilling of slag, reducing the impact on the environment.

[0011] Preferably, the separation and desanding bin further includes a desanding conveyor belt located at the bottom of the last stage of the vibrating screen.

[0012] Preferably, the end of the sand removal conveyor belt is also provided with a sand removal port.

[0013] Preferably, the mining assembly includes a movable drill bit and an auger connected to the movable drill bit; the movable drill bit is used to dynamically adjust the gap between the crushing rollers to control the particle size of the hydrate particles; the discharge end of the auger is softly connected to the separation and desanding bin and leads to the feed end of the first-stage vibrating screen. By adopting the above technical solution, the movable drill bit mines the mineral deposits in the hydrate sediment layer, and dynamically adjusts the gap between the crushing rollers according to the feedback data of temperature and pressure in the conveying shaft to crush the hydrate particles into particles of different sizes, while the auger transports the mixture of crushed hydrate particles and other residues to the separation and desanding bin.

[0014] Secondly, the present invention provides a method for graded ice crust hydrate extraction with enhanced self-protection effect, wherein the extraction method utilizes the aforementioned graded ice crust hydrate extraction device with enhanced self-protection effect; the extraction method includes the following steps:

[0015] Step 1: Enter the mining location, explore the hydrate deposit with the sea-level mining vessel, and deploy the mining equipment to the hydrate deposit sedimentary layer mining area;

[0016] Step 2, crushing and mining: the moving drill bit of the mining component is operated to mine hydrate deposits in the sedimentary layer and crush them into particles of a certain size. The hydrate particles are then transported to the separation and desanding bin via an auger.

[0017] Step 3, separation and sand removal: hydrate particles of different sizes are screened through multiple layers of vibrating screens with progressively smaller apertures and fall into the storage bin. At the same time, the bottom layer of residue is transported to the sand removal port by the sand removal conveyor belt and discharged.

[0018] Step 4: Ice shell formation. Seawater is introduced into the ice shell formation chamber through a spray pipe and evenly sprayed onto the hemispherical ice grids on the hemispherical ice grid conveyor belt. The refrigeration equipment absorbs the heat from the seawater in the hemispherical ice grids, so that when the hemispherical ice grids move to the end of the feeding pipe, an ice layer of a certain thickness has been formed. At the same time, the feeding pipe transports the hydrate particles from each storage chamber to the ice shell formation chamber and they fall into the hemispherical ice grids at the designated position on the lower hemispherical ice grid conveyor belt at the end of the feeding pipe. Then, the upper and lower hemispherical ice grids mesh together to form a spherical ice grid, which continues to cool and freeze until the hydrate particles wrapped in a spherical ice shell are formed at the end of the hemispherical ice grid conveyor belt and fall into the discharge pipe.

[0019] Step 5, Mixing and conveying: The discharge pipe in the mixing chamber sends the hydrate particles wrapped with spherical ice shells into the mixing lifting pipe, where they are mixed with seawater injected through the seawater injection pipe and then lifted and conveyed.

[0020] Preferably, the extraction method further includes: Step 6, adjustment of operations, by analyzing the temperature and pressure data fed back from the wellbore, operating the control system on the sea-level extraction vessel, adjusting the gap between the moving drill bit crushing rollers to control the particle size of the hydrate particles, and adjusting the various stages of ice shell feeding pipes, spray pipes, and mixing feeding pipes to control the flow rate and mixing ratio of the ice shell hydrate particles, thereby achieving controllable and orderly decomposition of the hydrate within the conveying wellbore. By adopting the above technical solution, this invention is based on the solid-state fluidized bed extraction method of hydrates, and employs a method in which hydrate particles are first crushed into different particle sizes and separated before being mixed with seawater and returned along the wellbore, and then a self-protective ice shell is generated before being mixed with seawater and lifted upwards. By strengthening the self-protective effect of the hydrate, the decomposition rate of the hydrate is slowed down. By analyzing the temperature and pressure data fed back from the wellbore, the particle size of hydrate particles and the mixing amount of ice shell hydrate particles of different sizes can be flexibly adjusted. This enables the controlled and orderly decomposition of hydrate particles during the lifting process, avoiding explosions caused by a sudden increase in pressure inside the wellbore due to hydrate decomposition. This improves the safety of hydrate mining using the solid fluidization method and also enables in-situ backfilling of slag, reducing the impact on the hydrate reservoir structure and the environment.

[0021] In summary, the present invention has at least one of the following beneficial technical effects:

[0022] The present invention provides an ice-shell graded hydrate mining device and method with enhanced self-protection effect. The separation and desanding chamber can separate hydrate particles of different sizes, realize the graded decomposition of hydrates, and simultaneously achieve in-situ backfilling of slag, reducing the impact on the hydrate reservoir structure and environment. The ice-shell generation chamber slows down the decomposition rate of hydrates by wrapping the surface of hydrate particles with ice shells of uneven size. The mixing chamber adjusts the mixing ratio of hydrate particle sizes to achieve controllable and orderly decomposition of hydrate particles during vertical pipeline transportation, thereby improving the safety of solid-state fluidized bed hydrate mining. Attached Figure Description

[0023] One or more embodiments are illustrated by way of example with reference to the accompanying drawings. These illustrations do not constitute a limitation on the embodiments, and unless otherwise stated, the figures in the drawings are not to be limited by scale.

[0024] Figure 1 This is a schematic diagram of the structure of a graded ice shell hydrate extraction device for enhancing self-protection effect according to the present invention.

[0025] Figure 2 This is a schematic diagram of the ice shell generation chamber of the present invention.

[0026] Explanation of reference numerals in the attached diagram: 1. Mining component; 11. Movable drill bit; 12. Screw auger; 2. Separation and desanding bin; 21. Vibrating screen; 22. Desanding conveyor belt; 3. Storage bin; 4. Ice shell production bin; 41. Hemispherical ice grid conveyor belt; 42. Feeding pipe; 43. Spray pipe; 44. Spray head; 45. Refrigeration equipment; 46. Discharge pipe; 5. Mixing bin; 51. Seawater injection pipe; 52. Mixing lifting pipe. Detailed Implementation

[0027] The following combination Figures 1 to 2 The present invention will be further described below.

[0028] As the background technology indicates, natural gas hydrates, also known as "combustible ice," are flammable and produce far less pollution than coal and oil. Furthermore, natural gas hydrates are distributed in the deep sea or onshore permafrost, with enormous reserves, and are internationally recognized as a potential alternative energy source to oil. The solid-state fluidized bed extraction method for hydrates operates entirely within the seabed hydrate-rich area, preserving the original temperature and pressure conditions of the natural gas hydrates. This prevents significant decomposition of the hydrates, enabling in-situ development and avoiding potential engineering geological hazards and the greenhouse effect caused by hydrate decomposition. However, the solid-state fluidized bed extraction method also has limitations. During pilot solid-state fluidized bed extraction of marine hydrates, as hydrate particles continuously rise along the wellbore, the annular temperature between the coiled tubing and drill pipe continuously increases while the pressure decreases. When a phase equilibrium is reached, the hydrate particles decompose, generating a large amount of gas that transforms the annular liquid-solid flow into a complex gas-liquid-solid multiphase flow. When the pressure accumulates to a certain level, accidents such as pipeline explosions may occur. The inventors discovered that the decomposition rate of hydrates at normal pressure and below freezing point is significantly lower than in other temperature ranges; this phenomenon is termed the unique self-protection effect of hydrates. The existence of this unique self-protection phenomenon indicates that hydrates possess good stability within specific low-temperature ranges. The basic consensus among scholars regarding the fundamental cause of this self-protection effect is that the ice layer formed during hydrate decomposition effectively prevents further decomposition. This provides strong theoretical and experimental evidence for developing hydrate-based methods for storing and transporting natural gas.

[0029] In view of this, the present invention proposes a graded ice shell hydrate extraction device and method to enhance self-protection effect.

[0030] In a first aspect, embodiments of the present invention disclose a graded ice shell hydrate extraction device with enhanced self-protection effect, referring to... Figure 1 and Figure 2 This enhanced self-protection ice shell tiered hydrate extraction device includes an extraction component 1, a separation and desanding chamber 2, a storage chamber 3, an ice shell production chamber 4, and a mixing chamber 5. These components are sequentially connected. The extraction component 1, based on pipeline pressure data feedback, crushes the hydrate into particles of varying sizes in situ within the reservoir and transports them to the separation and desanding chamber 2. The separation and desanding chamber 2 separates the hydrate particles and sends them to the storage chamber, while also discharging the separated residue for in-situ backfilling of slag, reducing environmental impact. The storage chamber 3 serves as a temporary storage container for hydrate particles of different sizes. The ice shell production chamber 4 introduces hydrate particles from the storage chamber and coats them with spherical ice shells of varying sizes, thereby enhancing the hydrate's self-protection effect and delaying its decomposition. The mixing chamber 5 introduces the hydrate particles forming the ice shell from the ice shell production chamber, mixes them with seawater, and then lifts and transports them upwards.

[0031] Reference Figure 1 The mining assembly 1 includes a movable drill bit 11 and an auger 12. The movable drill bit 11 can be a roller cone drill bit with a built-in crushing roller and adjustable roller gap to control the particle size of the crushed particles. The movable drill bit 11 is installed at the feed end of the auger 12 and can mine and crush mineral deposits within the hydrate sediment layer. The discharge end of the auger 12 is softly connected to the separation and desanding chamber 2, and the auger 12 can transport the crushed hydrate particles and other residue mixture to the separation and desanding chamber.

[0032] Reference Figure 1 The separation and desanding bin 2 includes a multi-stage vibrating screen 21 and a desanding conveyor belt 22. The vibrating screen 21 is installed at a certain slope on the inner wall of the separation and desanding bin 2, and its ends are connected to the storage bins at each stage. The aperture of the multi-stage vibrating screen 21 decreases progressively downwards, enabling the separation of hydrate particles of different sizes and excess residue in the mixture, which then fall into the respective storage bins. The desanding conveyor belt 22 is located at the bottom of the separation and desanding bin 2. The input end of the desanding conveyor belt 22 is located at the feed inlet of the separation and desanding bin 2, and the output end is located at the discharge outlet of the separation and desanding bin 2. The desanding conveyor belt transports the separated mixture residue to the discharge outlet for discharge, achieving in-situ backfilling of the slag.

[0033] Reference Figure 1The multi-stage storage chamber 3 can consist of multiple hollow chambers, each connected to the end of a vibrating screen 21 at each stage within the separation and desanding chamber 2. The storage chamber 3 is connected to the ice shell production chamber 4 via a feeding pipe 41. The multi-stage storage chamber 3 can serve as temporary storage containers for hydrate particles of different sizes.

[0034] Reference Figure 1 and Figure 2 The ice shell production chamber 4 includes a hemispherical ice tray conveyor belt 41, a feeding pipe 42, a spray pipe 43 and spray heads 44, a refrigeration device 45, and a discharge pipe 46. Two sets of hemispherical ice tray conveyor belts 41 are fixedly installed inside the ice shell production chamber 4. The hemispherical ice trays on the two sets of conveyor belts 41 are combined into a complete spherical ice tray after exiting through the feeding pipe 42. The hemispherical ice trays on the conveyor belts 41 can act as molds for ice shell formation. The two sets of conveyor belts 41 allow the ice shell to gradually thicken along the conveying direction and, after feeding, combine the hemispherical ice trays into a complete spherical ice tray, further completing the ice shell formation. The inlet end of the feeding pipe 42 extends into the storage chamber 3, and the outlet end of the feeding pipe 42 is positioned on the starting side of the upper hemispherical ice tray conveyor belt 41 and above the ice tray at a designated position on the lower hemispherical ice tray conveyor belt 41. The feeding pipe 42 is equipped with an intelligent control valve, which can deliver hydrate particles from the corresponding storage chamber 3 into the hemispherical ice tray at the designated position and control the feeding speed. A spray pipe 43 is located above the conveyor belt and is equipped with an intelligent control valve. Multiple spray heads 44 are installed on the spray pipe 43 and evenly distributed on both sides of the outlet end of the feeding pipe 42, which can control the even spraying of circulating water required for ice shell formation into the hemispherical ice tray. A refrigeration device 45 is located below the lower hemispherical ice tray conveyor belt 41 and close to the upper ice tray of the hemispherical ice tray conveyor belt 41. A discharge pipe 46 is located at the end of the conveyor belt and is equipped with an intelligent control valve, which can collect hydrate particles that have formed ice shells falling from the ice tray and send them into the mixing chamber. Each level of ice shell production chamber 4 is connected to each level of storage chamber 3. The size of the ice grid in each level of ice shell production chamber 4 decreases progressively, which can encapsulate hydrate mineral particles of different sizes with ice shells of a certain thickness. By enhancing the self-protection effect of hydrates, the solid fluidized mining process can achieve controllable and graded decomposition of hydrates.

[0035] Reference Figure 1The mixing chamber 5 includes a seawater injection pipe 51 and a mixing lift pipe 52. The seawater injection pipe 51 branches into various levels of spray pipes 43 within the mixing chamber 5 and then connects to the mixing lift pipe 52. The seawater injection pipe 51 introduces seawater for ice shell formation and subsequent mixing and lifting. The mixing lift pipe 52 connects to the discharge pipes 46 within each level of the ice shell production chamber 4. The mixing lift pipe 52 mixes the ice shell hydrate particles output from the discharge pipes 46 within each level of the ice shell production chamber 4 with seawater and then lifts and transports them upwards. Both the seawater injection pipe 51 and the mixing lift pipe 52 are equipped with intelligent control valves, which can control the amount of mixed seawater and the upward conveying rate, improving the controllability of the hydrate mixing and lifting process.

[0036] Secondly, embodiments of the present invention disclose a method for graded extraction of ice shell hydrates based on the self-protection effect of hydrates, comprising the following steps:

[0037] Step 1: Enter the mining location, explore the hydrate deposit with the sea-level mining vessel, and deploy the mining equipment to the hydrate deposit sedimentary layer mining area;

[0038] Step 2, crushing and mining: the active drill bit 11 of the mining component 1 is operated to mine hydrate deposits in the sedimentary layer and crush them into particles of a certain size. The hydrate particles are then transported to the separation and desanding chamber 2 via the screw conveyor 12.

[0039] Step 3, separation and sand removal: hydrate particles of different sizes are screened through multiple layers of vibrating screens 21 with progressively smaller apertures and fall into storage bins 3 at each level. At the same time, the bottom layer of residue is transported to the sand removal port by the sand removal conveyor belt 22 and discharged.

[0040] Step 4: Ice shell formation. Seawater is introduced into the spray pipes 43 of each ice shell formation chamber 4 and evenly sprayed by the spray heads 44 onto the hemispherical ice grids set on the hemispherical ice grid conveyor belt 41. The refrigeration equipment 45 absorbs the heat of the seawater in the hemispherical ice grids, so that when the hemispherical ice grids move to the end of the feeding pipe 42, an ice layer of a certain thickness has been formed. At the same time, the feeding pipe 42 transports the hydrate particles in each storage chamber 3 to the ice shell formation chamber 4 and falls into the hemispherical ice grids at the designated position on the lower hemispherical ice grid conveyor belt 41 at the end of the feeding pipe 42. Then, the upper and lower hemispherical ice grids mesh to form a spherical ice grid and continue to cool and freeze until a complete spherical ice shell is formed at the end of the hemispherical ice grid conveyor belt 41 and falls into the discharge pipe 46.

[0041] Step 5, mixing and conveying: the spherical ice shell hydrate particles in the mixing chamber 5 are sent into the mixing lifting pipe 52 and mixed with the seawater injected by the seawater injection pipe 51, and then lifted and conveyed.

[0042] Step 6: Adjustment work. By analyzing the temperature and pressure data fed back from the wellbore, the control system on the sea-level mining vessel is operated to adjust the gap between the moving drill bit crushing rollers to control the particle size of the hydrate particles. The flow rate and mixing ratio of the ice shell hydrate particles are controlled by adjusting the ice shell feeding pipes, spray pipes and mixing feeding pipes at each stage, thereby achieving controllable and orderly decomposition within the conveying pipeline.

[0043] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., 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 graded ice shell hydrate extraction device with enhanced self-protection effect, characterized in that, The mining unit includes a mining assembly (1), a separation and desanding chamber (2), a storage chamber (3), an ice shell production chamber (4), and a mixing chamber (5) connected in sequence. The mining assembly (1) is used to extract hydrate particles and feed them into the separation and desanding chamber (2); The separation and desanding bin (2) is used to classify the hydrate particles by particle size and then send them into the storage bin (3), and to discharge the residue of the hydrate particles after particle size classification. The storage chamber (3) is used to store the hydrate particles after particle size classification and send them to the ice shell production chamber (4). The ice shell production chamber (4) is used to coat the hydrate particles after particle size classification with spherical ice shells of appropriate size, and then send them into the mixing chamber (5). The mixing chamber (5) is used to mix the hydrate particles encased in spherical ice shells with seawater and then lift and transport them upwards. The ice shell production chamber (4) includes a hemispherical ice grid conveyor belt (41), a feeding pipe (42), a spray pipe (43), a spray head (44), a refrigeration device (45), and a discharge pipe (46). The hemispherical ice grid conveyor belt (41) is composed of an upper hemispherical ice grid conveyor belt and a lower hemispherical ice grid conveyor belt stacked on top of each other. The refrigeration device (45) is installed below the lower hemispherical ice grid conveyor belt. The upper hemispherical ice grid conveyor belt and the lower hemispherical ice grid conveyor belt are used to generate hemispherical ice grids respectively and combine them into a spherical ice shell. The inlet end of the feeding pipe (42) is connected to the storage bin (3), and the outlet end is located at the feed end of the lower hemispherical ice grid conveyor belt. The feed end of the lower hemispherical ice grid conveyor belt extends from the upper hemispherical ice grid conveyor belt along the length direction so that the hydrate particles fed from the feeding pipe (42) fall onto the lower hemispherical ice grid conveyor belt. The upper hemispherical ice grid conveyor belt and the lower hemispherical ice grid conveyor belt work together to make the hydrate particles be wrapped in the spherical ice shell. The inlet of the spray pipe (43) is connected to the mixing chamber (5) for feeding seawater; the outlet of the spray pipe (43) is connected to the spray head (44), which is located above the hemispherical ice grid conveyor belt. The discharge pipe (46) is located at the discharge end of the hemispherical ice grid conveyor belt (41).

2. The ice shell grading hydrate extraction device with enhanced self-protection effect according to claim 1, characterized in that, The mixing chamber (5) includes a seawater injection pipe (51) and a mixing lifting pipe (52). The seawater injection pipe (51) is connected to the spray pipe (43) inside the mixing chamber (5) and then connected to the mixing lifting pipe (52). The mixing lifting pipe (52) is connected to the discharge pipe (46).

3. The ice shell grading hydrate extraction device with enhanced self-protection effect according to claim 1, characterized in that, The separation and sand removal chamber (2) includes multiple vibrating screens (21) arranged in a grade; the storage chamber (3) includes multiple sub-storage chambers arranged in a grade; and the ice shell production chamber (4) includes multiple sub-ice shell production chambers arranged in a grade. The number of sub-storage bins and sub-ice shell production bins is the same as the number of vibrating screens (21); the discharge end of each level of vibrating screen (21) is connected to the corresponding sub-storage bin; The vibrating screens (21) at each level are stacked in such a way that the aperture decreases step by step; the size of the hemispherical ice grids in the sub-ice shell production chambers at each level decreases step by step.

4. The ice shell grading hydrate extraction device with enhanced self-protection effect according to claim 3, characterized in that, The separation and desanding bin (2) also includes a desanding conveyor belt (22) located at the bottom of the last stage of the vibrating screen (21).

5. The ice shell grading hydrate extraction device with enhanced self-protection effect according to claim 4, characterized in that, The sand removal conveyor belt (22) is also provided with a sand removal port at its end.

6. The ice shell grading hydrate extraction device with enhanced self-protection effect according to claim 4, characterized in that, The mining assembly (1) includes a movable drill bit (11) and an auger (12) connected to the movable drill bit (11). The movable drill bit (11) is used to dynamically adjust the gap between the crushing rollers and thus control the crushing particle size of the hydrate particles; the discharge end of the auger (12) is softly connected to the separation and sand removal bin (2) and leads to the feed end of the first-stage vibrating screen (21).

7. A method for graded extraction of ice crust hydrates with enhanced self-protection effect, characterized in that, The mining method employs an ice-shell graded hydrate mining device with enhanced self-protection effect as described in any one of claims 1 to 6; the mining method includes the following steps: Step 1: Enter the mining location, explore the hydrate deposit with the sea-level mining vessel, and deploy the mining equipment to the hydrate deposit sedimentary layer mining area; Step 2, crushing and mining: the active drill bit (11) of the mining component (1) is operated to mine hydrate deposits in the sedimentary layer and crush them into particles of a certain size. The hydrate particles are then transported to the separation and desanding chamber (2) through the screw conveyor (12). Step 3, separation and sand removal: hydrate particles of different sizes are screened through multiple layers of vibrating screens (21) with progressively smaller pore sizes and fall into storage bin (3). At the same time, the bottom layer of residue is transported to the sand removal port by the sand removal conveyor belt (22) and discharged. Step 4: generating an ice shell. Seawater is fed into the ice shell production chamber (4) through the spray pipe (43) and evenly sprayed by the spray head (44) onto the hemispherical ice grids set on the hemispherical ice grid conveyor belt (41). The refrigeration equipment (45) absorbs the heat of the seawater in the hemispherical ice grids, so that when the hemispherical ice grids move to the end of the feeding pipe (42), an ice layer of a certain thickness has been formed. At the same time, the feeding pipe (42) transports the hydrate particles in each level of storage chamber (3) to the ice shell production chamber (4) and falls into the hemispherical ice grids at the designated position on the lower hemispherical ice grid conveyor belt at the end of the feeding pipe (42). Then, the upper and lower hemispherical ice grids mesh to form a spherical ice grid and continue to cool and freeze until the hydrate particles wrapped in the spherical ice shell are formed at the end of the hemispherical ice grid conveyor belt (41) and fall into the discharge pipe (46). Step 5, mixing and conveying: The discharge pipe (46) in the mixing chamber (5) sends the hydrate particles wrapped with spherical ice shells into the mixing lifting pipe (52) and mixes them with the seawater injected by the seawater injection pipe (51) before lifting and conveying them.

8. The method for graded ice shell hydrate extraction with enhanced self-protection effect according to claim 7, characterized in that, This mining method also includes: Step 6: Adjustment work. By analyzing the temperature and pressure data fed back from the wellbore, the control system on the sea-level mining vessel is operated to adjust the gap between the moving drill bit crushing rollers to control the particle size of the hydrate particles. The flow rate and mixing ratio of the ice shell hydrate particles are controlled by adjusting the ice shell feeding pipes, spray pipes and mixing lifting pipes at each stage, thereby achieving the controllable and orderly decomposition of hydrates in the conveying wellbore.

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