System for collecting submarine combustible ice in-situ combustion gas and controlling flow and pressure

Abstract

The invention discloses a seabed combustible ice in-situ combustion gas collection and flow and pressure control system, and relates to the technical field of deep sea combustible ice development and utilization. A combustible ice storage cabin communicates with a methane gas drying treatment cabin through a first pipeline, and a first gas control valve is arranged on the first pipeline; the methane gas drying treatment cabin is communicated with the gas combustion chamber through a second pipeline, the second gas control valve is arranged on the second pipeline, the oxygen storage cabin is communicated with the gas combustion chamber through a third pipeline, and the third gas control valve is arranged on the third pipeline. And the first gas control valve, the second gas control valve and the third gas control valve are all in electric signal connection with the multi-mode gas pipeline control system. According to the invention, gas circuit integrated management of the whole process from seabed collection, in-situ decomposition to floating fire making of combustible ice can be realized, and the automation and intelligence level of the system is improved.

Description

Technical Field

[0001] This invention relates to the field of deep-sea combustible ice development and utilization technology, and in particular to a control system for in-situ combustion gas collection, flow and pressure control of seabed combustible ice. Background Technology

[0002] Seafloor cold seeps and natural gas hydrate deposits contain abundant methane resources, existing in a stable phase under high pressure and low temperature in a natural environment. How to release and utilize this chemical energy in an orderly manner under in-situ conditions is a cutting-edge direction for marine resource development and clean energy utilization. Deep-sea scenarios place multiple demands on gas supply stability, accurate proportioning, and safety: high environmental pressure, low temperature, and water-containing and impurity-laden media; methane is prone to recrystallization and frosting during decomposition and throttling; any downstream back pressure fluctuations will cause upstream gas distribution drift, directly affecting combustion stability and the controllability of energy output. Currently, there is a lack of a comprehensive control system to realize the collection, in-situ decomposition, and in-situ conversion of combustible ice, resulting in low levels of system automation. Furthermore, how to implement a complete pipeline and control system for multi-channel gas staged pressure stabilization, drying and purification, precise proportioning, and interlocking protection in the seafloor environment, incorporating the resource-energy conversion process into a measurable, adjustable, and verifiable engineering framework, is a problem that needs to be solved. Therefore, there is an urgent need for a control system for the in-situ combustion gas collection and flow and pressure control of seafloor combustible ice to address the aforementioned technical problems. Summary of the Invention

[0003] The purpose of this invention is to provide a control system for the collection, flow and pressure of combustion gases in seabed combustible ice, in order to solve the problems existing in the prior art. This system can realize integrated gas path management of the entire process of combustible ice from seabed collection and in-situ decomposition to buoyancy, thereby improving the automation and intelligence level of the system.

[0004] To achieve the above objectives, the present invention provides the following solution: This invention provides a control system for in-situ combustion gas collection and flow and pressure control of seabed combustible ice, including a combustible ice storage chamber, a methane drying chamber, a gas combustion chamber, an oxygen storage chamber, a multi-mode gas pipeline control system, a first gas control valve, a second gas control valve, and a third gas control valve. The combustible ice storage chamber and the methane drying chamber are connected via a first pipeline, and the first gas control valve is disposed on the first pipeline. The methane drying chamber and the gas combustion chamber are connected via a second pipeline, and the second gas control valve is disposed on the second pipeline. The oxygen storage chamber and the gas combustion chamber are connected via a third pipeline, and the third gas control valve is disposed on the third pipeline. The first gas control valve, the second gas control valve, and the third gas control valve are all electrically connected to the multi-mode gas pipeline control system.

[0005] In some embodiments, a fourth gas control valve, a pressure relief valve, and an exhaust gas treatment chamber are also included. The exhaust gas treatment chamber is connected to the gas combustion chamber via a fourth pipeline. The fourth gas control valve is installed on the fourth pipeline. The pressure relief valve is installed at the outlet of the exhaust gas treatment chamber. Both the pressure relief valve and the fourth gas control valve are electrically connected to the multi-mode gas pipeline control system.

[0006] In some embodiments, a methane gas storage chamber is also included, the inlet of which is connected to the outlet of the methane gas drying chamber, the outlet of which is connected to the gas combustion chamber, and the second gas control valve is disposed on the pipeline between the methane gas storage chamber and the gas combustion chamber.

[0007] In some embodiments, the second gas control valve includes a first switching valve, a first stage pressure reducing valve, and a first electrically controlled proportional valve connected in series, with the first switching valve disposed near the methane gas storage chamber and the first electrically controlled proportional valve disposed near the gas combustion chamber.

[0008] In some embodiments, the third gas control valve includes a second switching valve, a second stage pressure reducing valve, and a second electrically controlled proportional valve connected in series. The second switching valve is located near the oxygen storage chamber, and the second electrically controlled proportional valve is located near the gas combustion chamber.

[0009] In some embodiments, a pressure relief water storage tank is also included. The first gas control valve includes a first inlet, a second inlet, a first outlet, and a second outlet. The first inlet is connected to the lower outlet of the combustible ice storage tank, the second inlet is connected to the upper outlet of the combustible ice storage tank, the inlet of the pressure relief water storage tank is connected to the first outlet, and the inlet of the methane gas drying treatment tank is connected to the second outlet.

[0010] In some embodiments, the methane gas drying chamber is provided with a mechanical demisting unit, a coarse drying layer and a fine drying layer arranged sequentially along the gas flow direction. The mechanical demisting unit is used to remove liquid droplets and mist droplets, the coarse drying layer is used to absorb moisture, and the fine drying layer is used to lower the gas dew point.

[0011] In some embodiments, the coarse drying layer is filled with activated alumina or silica gel, and the fine drying layer is filled with 3A molecular sieve.

[0012] In some embodiments, the gas combustion chamber is provided with an ignition electrode and a flame monitoring device. The ignition electrode is used to ignite the methane gas, and the flame monitoring device is used to monitor the state of the combustion flame. The controllers of the flame monitoring device and the ignition electrode are both electrically connected to the multi-mode gas pipeline control system.

[0013] In some embodiments, both the first stage pressure reducing valve and the second stage pressure reducing valve include a primary pressure reducing valve and a secondary precision pressure reducing valve. An electronic back pressure regulating device is provided between the first electronically controlled proportional valve and the gas combustion chamber, and between the second electronically controlled proportional valve and the gas combustion chamber. The electronic back pressure regulating device is used to maintain a constant pressure difference across the electronically controlled proportional valve.

[0014] The present invention achieves the following technical effects compared to the prior art: The present invention provides a control system for in-situ combustion gas collection and flow and pressure control of combustible ice on the seabed. This system integrates combustible ice seabed collection, in-situ decomposition gas production, methane drying and purification, combustion oxygen supply, and pipeline regulation into a continuous closed-loop operation unit. It realizes the entire gas path connection from in-situ seabed treatment to surface combustion application, simplifies the structural layout and operation process of seabed operation equipment, and reduces intermediate transfer and external processing links. The first gas control valve, the second gas control valve, and the third gas control valve are uniformly controlled by a multi-mode gas pipeline control system with centralized electrical signals. Based on the combustible ice decomposition rate, methane gas concentration, combustion chamber combustion requirements, and chamber pressure parameters, it can realize the synchronous opening and closing, flow ratio, and on / off timing intelligent adjustment of multiple gas paths, replacing manual step-by-step operation, reducing the difficulty of remote operation on the seabed, improving the system response speed and operating condition adaptability, and realizing adaptive and programmed gas path management. An independent methane gas drying chamber is installed to pre-treat and purify the methane produced from the decomposition of methane hydrate, preventing water-containing or impurity-containing gases from entering the combustion chamber and causing problems such as unstable combustion, flameout, pipeline corrosion, and equipment scaling and blockage. Combined with an independent oxygen storage chamber for targeted oxygen supply, the methane equivalence ratio is precisely matched to achieve stable, efficient, and complete combustion, while reducing incomplete combustion byproducts and extending the service life of underwater equipment. Furthermore, a multi-mode gas pipeline control system, linked to multiple dedicated control valves, can simultaneously achieve precise flow ratios of methane and oxygen and dynamic adjustment of pipeline and chamber pressures. This avoids pressure fluctuations from methane hydrate decomposition affecting the pipelines and prevents safety hazards caused by excessively high or low combustion chamber inlet pressure, maintaining internal system pressure balance, adapting to the extreme high-pressure and variable-pressure environments of the seabed, and improving system operational stability. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of the layout of the in-situ combustion gas collection and flow and pressure control system for seabed combustible ice in some embodiments of the present invention.

[0017] In the diagram: 1-Multi-mode gas pipeline control system; 2-Combustible ice storage chamber; 3-Methane gas drying treatment chamber; 4-Gas combustion chamber; 5-Oxygen storage chamber; 6-First gas control valve; 7-Second gas control valve; 8-Third gas control valve; 9-Methane gas storage chamber; 10-Pressure relief water tank; 11-Fourth gas control valve; 12-Waste gas treatment chamber; 13-Pressure relief valve. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] The purpose of this invention is to provide a control system for the collection, flow, and pressure of combustion gases in seabed combustible ice, in order to solve the problems existing in the prior art. This system can realize integrated gas path management throughout the entire process of combustible ice collection, in-situ decomposition, and ignition upon buoyancy, thereby improving the automation and intelligence level of the system.

[0020] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0021] like Figure 1 As shown, the present invention provides a control system for in-situ combustion gas collection and flow and pressure control of seabed combustible ice, including a combustible ice storage chamber 2, a methane gas drying chamber 3, a gas combustion chamber 4, an oxygen storage chamber 5, a multi-mode gas pipeline control system 1, a first gas control valve 6, a second gas control valve 7, and a third gas control valve 8. The combustible ice storage chamber 2 and the methane gas drying chamber 3 are connected through a first pipeline, and the first gas control valve 6 is installed on the first pipeline. The methane gas drying chamber 3 and the gas combustion chamber 4 are connected through a second pipeline, and the second gas control valve 7 is installed on the second pipeline. The oxygen storage chamber 5 and the gas combustion chamber 4 are connected through a third pipeline, and the third gas control valve 8 is installed on the third pipeline. The first gas control valve 6, the second gas control valve 7, and the third gas control valve 8 are all electrically connected to the multi-mode gas pipeline control system 1.

[0022] The system integrates seabed collection of combustible ice, in-situ decomposition for gas production, methane drying and purification, combustion oxygen supply, and pipeline regulation into a continuous closed-loop operation unit. This breaks down the barriers between segmented devices, enabling seamless gas path connection from in-situ seabed treatment to surface combustion application. This significantly simplifies the structural layout and operational procedures of seabed equipment, reducing intermediate transfer and external processing steps. The first gas control valve 6, the second gas control valve 7, and the third gas control valve 8 are centrally controlled by a multi-mode gas pipeline control system 1. Based on the combustible ice decomposition rate, methane production concentration, combustion chamber requirements, and internal pressure parameters, the system can intelligently adjust the synchronous opening and closing, flow ratio, and on / off timing of multiple gas paths, replacing manual step-by-step operation. This reduces the difficulty of remote seabed operation, improves system response speed and adaptability, and achieves adaptive, programmed gas path management. An independent methane gas drying and treatment chamber 3 is set up to pre-treat the methane produced by the decomposition of combustible ice by removing water and purifying it. This prevents water-containing or impurity-containing gases from entering the combustion chamber, which could cause unstable combustion, flameout, pipeline corrosion, and equipment scaling and blockage. Combined with an independent oxygen storage chamber 5 for targeted oxygen supply, the methane combustion equivalence ratio is precisely matched to achieve stable, efficient, and complete combustion, while reducing incomplete combustion byproducts and extending the service life of underwater equipment. A modular structure with physical separation between the combustible ice storage chamber 2, methane gas drying and treatment chamber 3, gas combustion chamber 4, and oxygen storage chamber 5 is adopted. Each functional chamber performs its own function. In the event of a failure in a single chamber or pipeline, the gas path can be independently cut off via the corresponding control valve without affecting the basic functions of other modules, reducing the risk of cascading failures. The modular structure also facilitates subsea deployment, module replacement, and subsequent maintenance and component upgrades. Furthermore, through the multi-mode gas pipeline control system 1, multiple dedicated control valves can be linked to simultaneously achieve precise flow ratio of methane and oxygen and dynamic adjustment of pipeline and chamber pressure. This can not only avoid the impact of gas pressure fluctuations from the decomposition of combustible ice on the pipeline, but also prevent safety hazards caused by excessively high / low combustion chamber inlet pressure, maintain internal pressure balance of the system, adapt to the extreme environment of high pressure and variable pressure on the seabed, and improve the stability of system operation.

[0023] In some embodiments, the control system for in-situ combustion gas collection and flow and pressure control of seabed combustible ice further includes a fourth gas control valve 11, a pressure relief valve 13, and an exhaust gas treatment chamber 12. The exhaust gas treatment chamber 12 is connected to the gas combustion chamber 4 via a fourth pipeline. The fourth gas control valve 11 is installed on the fourth pipeline, and a pressure relief valve 13 is installed at the outlet of the exhaust gas treatment chamber 12. Both the pressure relief valve 13 and the fourth gas control valve 11 are electrically connected to the multi-mode gas pipeline control system 1. The system realizes integrated closed-loop management of the entire gas path for combustible ice seabed collection, in-situ decomposition, gas drying, controlled combustion, exhaust gas treatment, and safe pressure relief. It forms a complete operation link from raw material gas production to combustion product discharge, without intermediate breakpoints, greatly improving the continuity and integration of seabed in-situ operations, adapting to the narrow and complex seabed operating environment, and simplifying the overall layout of underwater equipment. A dedicated exhaust gas treatment chamber 12 is added, forming an independent exhaust gas passage with the combustion chamber via a fourth pipeline and a fourth gas control valve 11. This chamber purifies, neutralizes, and collects the exhaust gas, residual combustible gases, and impurities generated during combustion, preventing direct emissions of combustion exhaust gases that pollute the seabed environment, meeting marine ecological protection requirements, reducing the risk of damage to the underwater operating environment, and improving the system's environmental performance. The exhaust gas treatment chamber 12 is a pressure-resistant, sealed container. Its interior can be equipped with condensation units or adsorption packing as needed for partial condensation or adsorption of moisture and impurities. After the combustion products enter the exhaust gas treatment chamber 12, they receive a certain volume buffer, reducing the disturbance of pressure fluctuations to the upstream proportional valve's operating area; furthermore, the quality of the discharged gas can be improved through the internal treatment unit.

[0024] A pressure relief valve 13 is installed on the exhaust gas treatment chamber 12. The pressure relief valve 13 is an adjustable throttling valve controlled by the multi-mode gas pipeline control system 1. In the deep-sea stable combustion mode, the pressure relief valve 13 maintains a small opening, allowing the overall system pressure to change slowly over time. In the surfacing pressure relief mode, the multi-mode gas pipeline control system 1 gradually increases the opening of the pressure relief valve 13 according to the preset pressure relief curve, and reduces the supply of methane and oxygen to ensure that the internal pressure of the system decreases at a limited rate, avoiding structural impact or instantaneous flame extinguishing due to excessively rapid changes in internal and external pressure differences.

[0025] In some embodiments, the in-situ combustion gas collection and flow and pressure control system for seabed combustible ice further includes a methane storage chamber 9. The inlet of the methane storage chamber 9 is connected to the outlet of the methane drying chamber 3, and the outlet of the methane storage chamber 9 is connected to the gas combustion chamber 4. A second gas control valve 7 is installed on the pipeline between the methane storage chamber 9 and the gas combustion chamber 4. The addition of an independent methane storage chamber 9 forms a dedicated buffer storage unit for the dried gas, which can temporarily buffer the purified methane output from the methane drying chamber 3, smooth out the gas flow fluctuations caused by the unstable in-situ decomposition rate of combustible ice and gas production fluctuations, avoid the imbalance of gas intake in the combustion chamber caused by the sudden increase or decrease in gas production, ensure the continuous and stable methane gas source entering the combustion chamber, and maintain stable combustion conditions. The methane storage chamber 9 serves as a gas path buffer and pressure stabilizer, mitigating pressure pulsations during upstream decomposition and drying processes. This reduces the impact of pressure fluctuations on downstream pipelines, control valves, and the combustion chamber structure, minimizing pipeline vibration and component fatigue wear. It also extends the service life of core underwater pneumatic components and the combustion chamber, enhancing the system's structural stability and operational reliability under high-pressure conditions on the seabed. The methane storage chamber 9 is a high-pressure storage chamber used to store processed, dried methane gas. Its design pressure is determined based on the operating water depth and combustion duration, and can be, for example, at the 10 MPa level. The multi-mode gas pipeline control system 1 estimates the total amount of collected methane based on pressure changes within the methane storage chamber 9, providing boundary conditions for subsequent combustion operations.

[0026] In some embodiments, the second gas control valve 7 includes a first switching valve, a first stage pressure reducing valve, and a first electrically controlled proportional valve connected in series. The first switching valve is located near the methane storage chamber 9, and the first electrically controlled proportional valve is located near the gas combustion chamber 4. The third gas control valve 8 includes a second switching valve, a second stage pressure reducing valve, and a second electrically controlled proportional valve connected in series. The second switching valve is located near the oxygen storage chamber 5, and the second electrically controlled proportional valve is located near the gas combustion chamber 4. This series connection of the switching valve, stage pressure reducing valve, and electrically controlled proportional valve ensures staged pressure stabilization while using the electrically controlled proportional valve to compensate for changes in the pressure difference across the valve, maintaining a relatively constant flow rate of methane and oxygen entering the gas combustion chamber 4. This structure can maintain a stable equivalence ratio and flame size under long-term combustion conditions in the deep sea, avoiding the problem of fluctuating flame size or even extinguishing due to changes in environmental pressure and pressure accumulation within the chamber, as seen in existing technologies. This provides a reliable guarantee for the continuous acquisition of deep-sea fire sources. The on / off valve enables rapid switching of the gas path, allowing for quick cutoff during emergencies and maintenance, serving as the first line of defense for safety isolation. The staged pressure reducing valve is responsible for staged pressure reduction and buffering pressure surges, preventing high-pressure gas from directly entering the combustion chamber and causing safety hazards. The electronically controlled proportional valve provides precise flow regulation and differential pressure compensation, enabling fine-grained control.

[0027] It should be noted that pressure sensors and temperature sensors are installed in the combustible ice storage chamber 2, methane storage chamber 9 and oxygen storage chamber 5. Mass flow meters are installed on the downstream pipelines of the second gas control valve 7 and the third gas control valve 8. All the collected signals are sent to the multi-mode gas pipeline control system 1 to realize closed-loop control and safety interlock.

[0028] In some embodiments, the in-situ combustion gas collection and flow and pressure control system for seabed combustible ice further includes a pressure relief water tank 10. A first gas control valve 6 includes a first inlet, a second inlet, a first outlet, and a second outlet. The first inlet is connected to the lower outlet of the combustible ice storage tank 2, and the second inlet is connected to the upper outlet of the combustible ice storage tank 2. The inlet of the pressure relief water tank 10 is connected to the first outlet, and the inlet of the methane gas drying treatment tank 3 is connected to the second outlet. A liquid outlet is provided at the lower part of the combustible ice storage tank 2, which is connected to the pressure relief water tank 10 via the first gas control valve 6; a gas outlet is provided at the upper part, which is also connected to the methane gas drying treatment tank 3 via the first gas control valve 6, thereby realizing two pipelines for liquid phase discharge and gas phase transfer on the same tank.

[0029] During operation, the multi-mode gas pipeline control system 1 first switches the first gas control valve 6 to the position connected to the pressure relief water tank 10, and slowly opens the valve to allow some seawater from the combustible ice storage tank 2 to flow into the pressure relief water tank 10. As the liquid is discharged, the total pressure inside the combustible ice storage tank 2 decreases, and the combustible ice, which was originally in the stable zone, begins to decompose, generating methane gas which rises to the upper space of the tank. The depressurization rate is determined by both the opening degree of the first gas control valve 6 and the volume of the pressure relief water tank 10 to avoid the impact of sudden pressure drops on the tank structure and the combustible ice decomposition process.

[0030] When the multi-mode gas pipeline control system 1 detects that the pressure inside the combustible ice storage chamber 2 has recovered and is approaching the preset upper limit, it controls the first gas control valve 6 to close the pressure relief branch and switch to the position connected to the methane gas drying chamber 3, opening the upper gas phase passage and introducing the methane gas accumulated in the upper space of the chamber into the methane gas drying chamber 3. Through repeated alternating pressure relief and evacuation, the combustible ice gradually decomposes under controlled conditions, and the generated methane gas is continuously transferred and dried until the solid phase inside the combustible ice storage chamber 2 is basically gone.

[0031] In some embodiments, the methane gas drying chamber 3 is internally arranged with a mechanical demister unit, a coarse drying layer, and a fine drying layer sequentially along the gas flow direction. The mechanical demister unit removes droplets and mist, the coarse drying layer absorbs moisture, and the fine drying layer lowers the gas dew point. This three-stage structure, arranged sequentially along the airflow direction, forms a gradient dehumidification system. It processes large droplets, large amounts of free water, and dries at low dew point depths in a progressive manner, gradually reducing the gas moisture content. Compared to a single drying unit, this improves overall drying efficiency and final gas drying depth, stably lowering the methane gas dew point to the level required for deep-sea combustion, meeting the requirements for long-term stable combustion. The mechanical demister unit prioritizes intercepting and separating macroscopic droplets, mist, and seawater droplets carried in the airflow, reducing the amount of liquid water entering the coarse and fine drying layers from the source. This prevents liquid water from directly washing over and soaking the adsorbent materials, preventing the drying layers from saturating too quickly and accelerating failure, extending the service life and replacement cycle of the coarse and fine drying layers, and reducing the frequency and cost of underwater equipment maintenance.

[0032] In some embodiments, the coarse drying layer is filled with activated alumina or silica gel, and the fine drying layer is filled with 3A molecular sieve. The coarse drying layer, using activated alumina or silica gel, has a large capacity and rapid pre-dehydration capability for methane gas streams with high water content, preferentially removing a large amount of free water and most of the water vapor from the gas stream, and undertaking the main dehumidification load; the fine drying layer, using 3A molecular sieve, has a pore size that only allows water molecules to enter, enabling deep fine drying of methane and reducing the gas dew point to an extremely low level. The two form a gradient adsorption system that coarsely removes a large amount of water and finely removes residual water, balancing high-load processing capacity with ultimate drying precision.

[0033] It should be noted that, if necessary, a sintered metal filter element can be installed at the outlet of the methane gas drying chamber 3 to trap any desiccant powder that may fall off and prevent it from entering the subsequent high-pressure chamber.

[0034] In some embodiments, an ignition electrode and a flame monitoring device are installed in the gas combustion chamber 4. The ignition electrode is used to ignite the methane gas, and the flame monitoring device is used to monitor the state of the combustion flame. The controllers of both the flame monitoring device and the ignition electrode are electrically connected to the multi-mode gas pipeline control system 1. Automatic ignition is achieved through the ignition electrode, and the flame monitoring device collects flame state signals in real time. The entire process requires no underwater manual intervention or external ignition assistance. It can independently complete the entire process of ignition, stable combustion, and status feedback, perfectly adapting to remote, unmanned, and long-term underwater operation scenarios, improving system automation and operational independence. The flame monitoring device continuously monitors the combustion state online and can identify various operating conditions such as normal flame, weak flame, uneven burning, and flameout in real time. It uploads the signals to the main control system in real time, solving the technical problem of not being able to observe the combustion state with the naked eye or judge the combustion state on-site in the confined space of the deep sea, providing a reliable basis for the system to make rapid decisions.

[0035] In some embodiments, both the first and second stage pressure reducing valves include a primary pressure reducing valve and a secondary precision pressure reducing valve. Electronic back pressure regulating devices are installed between the first electronically controlled proportional valve and the gas combustion chamber 4, and between the second electronically controlled proportional valve and the gas combustion chamber 4. These devices maintain a constant pressure difference across the electronically controlled proportional valves. The outlet of the methane gas storage chamber 9 is connected to the gas combustion chamber 4 via a second gas control valve 7. The second gas control valve 7 is preferably composed of a first on / off valve, a primary pressure reducing valve, a secondary precision pressure reducing valve, an electronic back pressure regulating device, and the first electronically controlled proportional valve connected in series. The primary pressure reducing valve reduces the pressure of the methane gas from the high-pressure chamber to the medium-high pressure zone, and the secondary precision pressure reducing valve further stabilizes the pressure to a range close to the working pressure of the gas combustion chamber 4. The electronic back pressure regulating device controls a substantially constant pressure difference across the first electronically controlled proportional valve, reducing the impact of downstream back pressure fluctuations on the flow rate. The first electronically controlled proportional valve changes its opening degree under the command of the multi-mode gas pipeline control system 1, forming a closed-loop control with a mass flow meter installed downstream, thereby achieving continuous and adjustable methane supply flow.

[0036] Similar to the methane storage chamber 9, the oxygen storage chamber 5 is an independent high-pressure gas storage chamber. Its outlet is connected to the gas combustion chamber 4 via the third gas control valve 8. The structure and operation of the third gas control valve 8 are basically the same as those of the second gas control valve 7. It also adopts a combination of two-stage pressure reduction, electronic back pressure, and electronic proportional valve regulation to achieve precise control of oxygen flow. To suppress the risk of backfire, check valves and flame arresters are preferably installed downstream of both the methane and oxygen lines, and a flow-limiting structure and electrical isolation design are adopted at the inlet of the gas combustion chamber 4.

[0037] The gas combustion chamber 4 is a pressure-resistant, sealed cavity, equipped with an ignition electrode and a flame monitoring device inside, and pressure and temperature measuring points arranged externally. During normal operation, the multi-mode gas pipeline control system 1 sets target mass flow rates for both methane and oxygen based on the target flame power and excess air coefficient, achieving precise proportioning by adjusting the valve positions of the second gas control valve 7 and the third gas control valve 8. After successful ignition, the flame monitoring device continuously provides feedback on the combustion status. If abnormalities such as flameout or backfire occur, the system immediately reduces power or shuts down the interlock.

[0038] In summary, the multi-mode gas pipeline control system 1 divides the system operation into at least three modes according to the task flow: acquisition and decomposition mode, deep-sea stable combustion mode, and buoyancy depressurization mode.

[0039] 1. Acquisition and Decomposition Mode: In this mode, the system focuses on the controlled decomposition of methane hydrate and the drying and transfer of methane gas. The multi-mode gas pipeline control system 1 periodically controls the first gas control valve 6 to switch between the pressure relief branch and the gas transfer branch, so that the pressure in the methane hydrate storage chamber 2 fluctuates within a set range, ensuring the decomposition rate while avoiding drastic pressure changes; at the same time, it monitors the dew point at the outlet of the methane gas drying chamber 3, and when the dew point approaches the threshold, it can automatically reduce the decomposition rate of methane hydrate or trigger the desiccant regeneration / replacement process.

[0040] 2. Deep-sea stable combustion mode: In this mode, the methane storage chamber 9 and the oxygen storage chamber 5 continuously supply gas to the gas combustion chamber 4 through the second gas control valve 7 and the third gas control valve 8. The multi-mode gas pipeline control system 1 performs closed-loop control of the two mass flow rates according to the preset power curve, and maintains the overall system pressure within the target range through the exhaust gas treatment chamber 12 and the pressure relief valve 13, thereby achieving long-term stability of flame size and thermal power.

[0041] 3. Floating depressurization mode: Upon completion of the mission and the start of ascent, the multi-mode gas pipeline control system 1 reduces the supply of methane and oxygen to the minimum required to maintain a small flame, gradually decreasing the opening of the second gas control valve 7 and the third gas control valve 8. Simultaneously, it adjusts the opening of the exhaust passage and pressure relief valve 13 of the exhaust gas treatment chamber 12, releasing the system's internal gases at a predetermined pressure drop rate. When it is determined that the flame cannot be maintained under safe conditions, the system automatically executes the flameout and shutdown interlock, and continues to complete the staged release of residual pressure.

[0042] A specific application example is that when carrying out an in-situ combustion and ignition acquisition task in a cold seep area on the seabed at a water depth of about 1500m, the in-situ combustion gas collection, flow and pressure control system for seabed combustible ice is configured and operated with the following parameters.

[0043] System pre-tuning and diving phase Before operation, the combustible ice storage chamber 2, the pressure relief water storage chamber 10, the methane gas drying treatment chamber 3, the methane gas storage chamber 9, and the exhaust gas treatment chamber 12 are evacuated and subjected to strength and sealing tests. High-purity oxygen at a rated pressure of 20 MPa is introduced into the oxygen storage chamber 5, and a small amount of methane gas is pre-charged into the methane gas storage chamber 9 for ignition preheating, with a pre-charge pressure of approximately 1.0 MPa. The multi-mode gas pipeline control system 1 is set to "collection and decomposition mode," with all valves leading to the combustion chamber (second gas control valve 7, third gas control valve 8) kept closed, and the pressure relief valve 13 at its minimum opening. The system is then deployed to the target sea area via the operating platform or remotely operated vehicle.

[0044] Combustible ice collection and decomposition stage It should be noted that the actual liquid discharge volume, methane hydrate decomposition and transfer time, and other parameters of the device are related to the sampler's methane hydrate sampling volume. Taking a small-volume sampler as an example, after reaching the target water depth, the front-end sampling device operates at the seabed cold seep, introducing methane hydrate and associated seawater into the methane hydrate storage chamber 2 under pressure. The pressure inside the chamber is adjusted and stabilized at approximately 10 MPa after a short buffer period. When the volume fraction of solid methane hydrate in the chamber reaches the preset value, the multi-mode gas pipeline control system 1 controls the first gas control valve 6 to open the liquid phase branch connected to the pressure relief water tank 10, slowly discharging some seawater from the chamber at a liquid flow rate of 20–25 mL / min. This causes the pressure inside the methane hydrate storage chamber 2 to drop from approximately 10 MPa to approximately 2 MPa within approximately 3 minutes. As the pressure decreases, the methane hydrate inside the chamber begins to decompose, producing methane gas. The pressure inside the chamber slowly rises from approximately 2 MPa to approximately 5 MPa during the decomposition process.

[0045] When the pressure rises to the upper threshold of approximately 5 MPa, the multi-mode gas pipeline control system 1 controls the first gas control valve 6 to close the liquid phase branch and immediately switch to the gas phase branch connected to the methane drying chamber 3, opening the upper gas outlet to introduce the methane gas accumulated in the upper space of the combustible ice storage chamber 2 into the methane drying chamber 3. Each switch lasts 2–3 minutes, causing the pressure inside the chamber to drop from approximately 5 MPa back to approximately 2 MPa. The system then reopens the liquid phase branch to drain water, reduce pressure, and decompose, repeating this cycle until the pressure fluctuation significantly decreases, indicating that the combustible ice inside the chamber has essentially decomposed. The entire decomposition and transfer process lasts approximately 10–15 minutes.

[0046] Methane gas drying and high-pressure storage stage The wet methane gas entering the methane drying chamber 3 first passes through a mechanical demisting unit to remove entrained droplets, then sequentially passes through a coarse drying layer filled with activated alumina and a fine drying layer filled with 3A molecular sieves. The linear velocity of the methane gas within the desiccant bed is controlled at 0.05–0.1 m / s to ensure sufficient contact time. When the dew point sensor at the drying module outlet detects that the gas dew point is consistently below -20°C, the drying is considered successful. The dried methane gas then enters the methane storage chamber 9, where the final pressure can reach 10–12 MPa, corresponding to the collection of tens of standard cubic meters of methane gas. If the dew point rises to a preset threshold (e.g., -10°C), the multi-mode gas pipeline control system 1 automatically reduces the decomposition rate of the combustible ice storage chamber 2, and if necessary, issues a prompt to replace or regenerate the activated desiccant.

[0047] Deep-sea stable combustion and flame maintenance stage After methane acquisition is complete, the multi-mode gas pipeline control system 1 switches to "deep-sea stable combustion mode." First, the on / off valves of the second gas control valve 7 and the third gas control valve 8 are opened, allowing methane and oxygen to pass through their respective two-stage pressure reduction units, reducing their pressure from 10–12 MPa and 20 MPa to a medium pressure range of approximately 0.8 MPa, respectively. The pressure difference across the electronically controlled proportional valve is then stabilized at 0.2 MPa via an electronic back pressure device. Subsequently, using the mass flow meter as feedback, the methane supply flow rate is controlled to 0.6 Nm³. 3 / h, oxygen supply flow rate is 0.9 Nm 3 / h corresponds to an excess air coefficient of approximately 1.3.

[0048] Under the aforementioned gas supply conditions, the ignition electrode in the gas combustion chamber 4 is activated to complete ignition. After the flame presence detection signal stabilizes, the multi-mode gas pipeline control system 1 automatically enters the stable combustion control state, finely adjusting the opening of the two proportional valves according to the preset thermal power curve to maintain the pressure in the combustion chamber within the range of 0.6 to 0.7 MPa and the temperature within the set range. The combustion products enter the exhaust gas treatment chamber 12 through the outlet, where a buffer volume of approximately several liters is provided. The condensation unit inside the exhaust gas treatment chamber 12 causes some water to separate and collect at the bottom of the chamber, thereby reducing the impact of water vapor on the downstream exhaust channel.

[0049] During the stable combustion phase, to ensure flame continuity, the multi-mode gas pipeline control system 1 monitors the instantaneous flow rates of both methane and oxygen in real time. When the flow rate of either path deviates from the target value by more than ±3%, the corresponding proportional valve opening is automatically adjusted for compensation. If the compensation is ineffective, a fault alarm and power reduction strategy are triggered.

[0050] Ascent depressurization and hatch opening for fire-starting phase After in-situ combustion is completed, the system begins to ascend with the work platform or remotely operated vehicle, and the multi-mode gas pipeline control system 1 switches to "ascent and depressurization mode". In this mode, the mass flow rates of methane and oxygen are first slowly reduced to 20% to 30% of their initial values ​​to maintain only a small, stable flame in the gas combustion chamber 4; at the same time, the opening of the depressurization valve 13 is gradually increased, so that the internal pressure of the exhaust gas treatment chamber 12 and the system connected to it is slowly reduced at a rate of 0.05 MPa / min.

[0051] Throughout the ascent process, the multi-mode gas pipeline control system 1 continuously monitors the pressure and flame presence signal of the gas combustion chamber 4. When the pressure in the gas combustion chamber 4 drops below 0.15 MPa or the flame signal becomes unstable, it automatically executes the flameout and shutdown interlock, closes the second gas control valve 7 and the third gas control valve 8, and keeps the pressure relief valve 13 at a moderate opening to continue releasing residual pressure until the internal pressure of the system is basically consistent with the external atmospheric pressure.

[0052] In scenarios where maintaining a flame is crucial for the mission, the flame in the gas combustion chamber 4 can be sustained until the device exits the water by appropriately increasing the minimum gas supply flow rate during the ascent process. Then, the flame transfer operation can be completed in a safe environment. At this time, the multi-mode gas pipeline control system 1 makes subtle compensations to the two gas supply lines based on actual pressure changes, ensuring that the flame size and stability meet the ignition requirements.

[0053] As can be seen from the above specific examples, the system described in this invention can achieve controlled decomposition of combustible ice, deep drying and high-pressure storage of methane gas, precise supply of methane and oxygen in a precise ratio, and controlled depressurization and flame maintenance throughout the entire ascent process under given water depth and operating conditions, thus verifying the engineering feasibility and operational reliability of the technical solution of this invention in actual deep-sea environments.

[0054] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A control system for in-situ combustion gas collection and flow and pressure control of seabed combustible ice, characterized in that: The system includes a combustible ice storage chamber, a methane gas drying chamber, a gas combustion chamber, an oxygen storage chamber, a multi-mode gas pipeline control system, a first gas control valve, a second gas control valve, and a third gas control valve. The combustible ice storage chamber and the methane gas drying chamber are connected via a first pipeline, and the first gas control valve is located on the first pipeline. The methane gas drying chamber and the gas combustion chamber are connected via a second pipeline, and the second gas control valve is located on the second pipeline. The oxygen storage chamber and the gas combustion chamber are connected via a third pipeline, and the third gas control valve is located on the third pipeline. The first gas control valve, the second gas control valve, and the third gas control valve are all electrically connected to the multi-mode gas pipeline control system.

2. The control system for in-situ combustion gas collection and flow and pressure control of seabed combustible ice according to claim 1, characterized in that: It also includes a fourth gas control valve, a pressure relief valve, and an exhaust gas treatment chamber. The exhaust gas treatment chamber is connected to the gas combustion chamber via a fourth pipeline. The fourth gas control valve is installed on the fourth pipeline. The pressure relief valve is installed at the outlet of the exhaust gas treatment chamber. Both the pressure relief valve and the fourth gas control valve are electrically connected to the multi-mode gas pipeline control system.

3. The control system for in-situ combustion gas collection and flow and pressure control of seabed combustible ice according to claim 1, characterized in that: It also includes a methane gas storage chamber, the inlet of which is connected to the outlet of the methane gas drying chamber, and the outlet of which is connected to the gas combustion chamber. The second gas control valve is installed on the pipeline between the methane gas storage chamber and the gas combustion chamber.

4. The control system for in-situ combustion gas collection and flow and pressure control of seabed combustible ice according to claim 3, characterized in that: The second gas control valve includes a first switching valve, a first stage pressure reducing valve, and a first electrically controlled proportional valve connected in series. The first switching valve is located near the methane gas storage chamber, and the first electrically controlled proportional valve is located near the gas combustion chamber.

5. The control system for in-situ combustion gas collection and flow and pressure control of seabed combustible ice according to claim 4, characterized in that: The third gas control valve includes a second switching valve, a second stage pressure reducing valve, and a second electronically controlled proportional valve connected in series. The second switching valve is located near the oxygen storage chamber, and the second electronically controlled proportional valve is located near the gas combustion chamber.

6. The control system for in-situ combustion gas collection and flow and pressure control of seabed combustible ice according to claim 1, characterized in that: It also includes a pressure relief water storage tank. The first gas control valve includes a first inlet, a second inlet, a first outlet, and a second outlet. The first inlet is connected to the lower outlet of the combustible ice storage tank, the second inlet is connected to the upper outlet of the combustible ice storage tank, the inlet of the pressure relief water storage tank is connected to the first outlet, and the inlet of the methane gas drying treatment tank is connected to the second outlet.

7. The control system for in-situ combustion gas collection and flow and pressure control of seabed combustible ice according to claim 1, characterized in that: The methane gas drying chamber is equipped with a mechanical demisting unit, a coarse drying layer, and a fine drying layer arranged sequentially along the gas flow direction. The mechanical demisting unit is used to remove liquid droplets and mist droplets, the coarse drying layer is used to absorb moisture, and the fine drying layer is used to lower the gas dew point.

8. The control system for in-situ combustion gas collection and flow and pressure control of seabed combustible ice according to claim 7, characterized in that: The coarse drying layer is filled with activated alumina or silica gel, and the fine drying layer is filled with 3A molecular sieve.

9. The control system for in-situ combustion gas collection and flow and pressure control of seabed combustible ice according to claim 1, characterized in that: The gas combustion chamber is equipped with an ignition electrode and a flame monitoring device. The ignition electrode is used to ignite the methane gas, and the flame monitoring device is used to monitor the state of the combustion flame. The controllers of the flame monitoring device and the ignition electrode are both electrically connected to the multi-mode gas pipeline control system.

10. The control system for in-situ combustion gas collection and flow and pressure control of seabed combustible ice according to claim 5, characterized in that: Both the first stage pressure reducing valve and the second stage pressure reducing valve include a primary pressure reducing valve and a secondary precision pressure reducing valve. An electronic back pressure regulating device is provided between the first electronically controlled proportional valve and the gas combustion chamber, and between the second electronically controlled proportional valve and the gas combustion chamber. The electronic back pressure regulating device is used to maintain a constant pressure difference across the electronically controlled proportional valve.

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