A type b pod leak collection and disposal system and method

Abstract

The present application relates to a type B cabin leakage collection and processing system and method, the drain hole at the bottom of the type B cabin in the system is connected with a liquid collecting tray through a type B cabin leakage discharge valve, a dry nitrogen source on the ship is connected with the gas inlet end of the liquid collecting tray through a nitrogen pipeline, and the gas outlet end of the liquid collecting tray is connected with a combustible gas venting mast on the ship cabin through an exhaust pipeline. The method directly injects normal temperature or high temperature dry nitrogen provided by the ship as a heat source into the liquid collecting tray, carries out gasification and heating treatment on the leaked low-temperature liquid collected by the type B cabin, and safely discharges the combustible gas evaporated gas generated after the treatment through the combustible gas venting mast specially arranged on the ship. The present application blows and gasifies the low-temperature leaked liquid in the liquid collecting tray through normal temperature or high temperature dry nitrogen, accurately controls the evaporation rate of the low-temperature liquid, slows down the accumulation of the liquid in the liquid collecting tray and even removes the liquid, and ensures that the leakage amount of the type B cabin within 15 days does not cause the liquid collecting tray to be full and overflow.

Description

Technical Field

[0001] This invention relates to a Type B tank as defined by the International Maritime Organization (IMO) for the transport of liquefied gases or for use as ship fuel, and more particularly to a Type B tank leak collection and treatment system and method. Background Technology

[0002] Traditional Type B tanks are widely used on large LNG carriers and other liquefied gas carriers. In recent years, large commercial ships fueled by LNG have generally adopted the Type B tank structure defined by the International Maritime Organization (IMO). In actual ship applications, Type B tanks mainly have two typical structural forms: MOSS spherical tank type and SPB prismatic type. For relevant background information, please refer to "Liquefied Natural Gas Technology" by Gu Anzhong et al.

[0003] According to IMO rules, Type B compartments should take into account the possibility of leakage and be equipped with a partial secondary shielding structure (commonly known as a condensate pan) to accommodate liquefied gas expected to leak for 15 days.

[0004] In existing technologies, the measures for collecting and handling leaks from Type B tanks mainly include two types: For MOSS spherical Type B tanks, this design has been in use for decades. A sump is installed at the bottom of the tank, and then the leaking cryogenic liquid is ejected into the sea using a jet pump. For prismatic Type B tanks, the main method is to collect leaking liquefied gas by installing a sump with a sufficiently large capacity to hold 15 days' worth of liquid. Typical related patents are as follows:

[0005] CN219192498U describes a leak collection method in a cryogenic medium leakage monitoring and collection system for a type B cabin. This system features several vent pipes at the top and a cryogenic rupture device at the bottom. When a cryogenic temperature occurs, the device ruptures, and the leaked liquid flows into a liquid accumulation pan on the bottom secondary screen wall.

[0006] CN218477604U A cryogenic liquid leakage protection device applied to a type B compartment: A specially designed liquid collection tank structure for collecting leaked liquid is introduced.

[0007] CN113335457 B describes a special liquid accumulation tray structure in the liquid tank support with a leaking liquid storage structure.

[0008] CN115123462A describes a suspended cryogenic liquid leakage protection device for a type B cabin, which introduces a special liquid collection tray that does not contact the cabin deck and does not require an insulation layer.

[0009] CN115468706A describes a non-destructive monitoring system and method for leaks in marine B-type compartments, introducing a method for detecting leaks in B-type compartments using an infrared thermal imaging device.

[0010] CN116045207A describes a purging system, pressure control method, and gas leakage test method, which introduces the method for purging and sampling the gas in the insulation layer of a Type B compartment and the compartment it is located in, but does not cover the handling measures for leaked liquid from the sump.

[0011] CN115817710A describes a liquid collection tray device for receiving LNG leaks in a Type B tank, featuring a liquid collection tray with a spherical groove design on the bottom plate, which increases the evaporation rate of LNG by expanding the area of ​​the liquid collection tray.

[0012] CN115465410A describes a secondary wall enclosure system for a type B liquid tank, which uses ethylene glycol-water as a medium to forcibly vaporize the liquid in the accumulating pan and then discharges it via an exhaust fan. This scheme differs significantly from the technical approach of this invention: ethylene glycol-water is a liquid with a freezing point as low as -40°C, and since it does not directly contact LNG, there is a risk of freezing when used with LNG. Furthermore, the rapid vaporization rate can easily form large amounts of low-temperature gas clouds that can damage the deck, requiring an exhaust fan to quickly remove these gas clouds. Nitrogen, on the other hand, has a boiling point of approximately -196°C, and its direct contact with the low-temperature leaking liquid results in higher heat exchange efficiency, eliminates the risk of freezing, and is more conducive to regulating and controlling the vaporization rate.

[0013] CN108454785B describes a structure for collecting leaked liquid cargo from a Type B independent liquid tank.

[0014] CN219406816U describes a type B compartment bulkhead enclosure system, which uses a bracket to isolate the collection box from the hull structure for collecting leaked liquid in type B compartments.

[0015] In addition, many technical solutions are being considered to address the issue that if the sump for collecting cryogenic leaked liquid in the Type B compartment overflows, it will cause enormous damage to the hull structure. One solution is to insulate the hull structure below the sump by covering it with thermal insulation to prevent damage.

[0016] As can be seen from the above patent information, apart from the traditional LNG ejector method of directly removing the effluent pan, recent patent applications, although differing in the structure of the effluent pan, share almost identical core methods for handling cryogenic leaks: all employ a sufficiently large effluent pan for direct collection; or, to further consider the risk of effluent pan overflow, add additional thermal insulation to the hull structure below the Type B compartment for protection. Some solutions employ thermal insulation to cover the effluent pan, some increase the effluent pan area to allow natural vaporization of the cryogenic liquid, and others use ethylene glycol-water as a heating medium to directly vaporize the cryogenic liquid.

[0017] Traditional ejector solutions are very expensive, and directly discharging cryogenic flammable and explosive liquids into the sea is also extremely dangerous, as it can easily form flammable and explosive gas clouds on the water surface. On the other hand, using a sump to completely contain 15 days of leakage would result in an excessively large sump volume. If the leakage is significantly greater than the theoretical calculation, there is a risk of the sump overflowing. If the cryogenic liquid comes into direct contact with the ship's structural steel, which is not resistant to low temperatures, it could even lead to a serious accident that causes the ship's structure to break. Summary of the Invention

[0018] To address the shortcomings of two existing typical Type B tank leak collection and treatment technologies, this invention proposes a novel Type B tank leak collection and treatment system and method. By purging and vaporizing the cryogenic leaking liquid in the sump with dry nitrogen gas at room temperature or high temperature, and precisely controlling the evaporation rate of the cryogenic liquid, the accumulation of liquid in the sump is slowed down or even eliminated, ensuring that the leakage volume in the Type B tank within 15 days will not cause the sump to overflow. Given that the nitrogen purging process will vaporize the cryogenic liquid and generate a large amount of flammable gas, which could easily lead to increased pressure inside the tank; and that excessively low vapor temperature could cause damage to the hull structure due to low tank temperature, the entire nitrogen purging process employs a combination of precise flow control and precise pressure control. By slowly and quantitatively purging and vaporizing the cryogenic liquid over a long period (e.g., more than 15 days), the overflow of the sump is avoided, and in better cases, the liquid in the sump can be emptied, while also preventing overpressure or a cryogenic environment in the tank.

[0019] To achieve the above objectives, the technical solution of the present invention is: a B-type compartment leak collection and treatment system, including a sump, a nitrogen gas source pipeline, and an exhaust pipeline. The vent hole at the bottom of the B-type compartment is connected to the sump through a B-type compartment leak discharge valve. The dry nitrogen gas source on board is connected to the inlet end of the sump through a nitrogen pipeline. The outlet end of the sump is connected to the combustible gas venting mast on the ship through an exhaust pipeline.

[0020] Furthermore, the nitrogen gas source pipeline is equipped with a primary pressure reducing valve, a manual valve, a pipeline safety valve, a pressure sensor, a flow sensor, a secondary pressure reducing valve, a manual flow regulating valve, and a differential pressure sensor; the exhaust pipeline is equipped with an exhaust pressure regulating valve and a cabin safety valve; and the liquid collection pan is equipped with a temperature sensor, a liquid level sensor, a liquid level switch, and a combustible gas detector.

[0021] Furthermore, the bottom surface of the sump tray is suspended from the mounting base, with a gap of 40mm to 250mm, thus forming a cold bridge for heat transfer between the low-temperature liquid received by the bottom surface and the hull base. This prevents the mounting base of the sump tray from becoming too cold. If necessary, foaming insulation material can be injected or stacked insulation material can be inserted into the space between the bottom surface of the sump tray and the mounting base to further improve the insulation effect. Insulation pads are installed between the hull structure base and the mounting base of the sump tray to ensure that the hull structure is at room temperature. Fastener gaskets made of fiberglass, polytetrafluoroethylene, or wood insulation material are installed between the mounting base of the sump tray and the fasteners.

[0022] Furthermore, at least one layer of nitrogen purging coils is installed inside the liquid accumulation pan. Purging holes are drilled in various directions on the multiple layers of nitrogen purging coils as needed. The bottom layer of nitrogen purging coils blows out nitrogen to vaporize the cryogenic liquid, while the upper layer of nitrogen purging coils blows out nitrogen to mix with the cryogenic evaporating gas and raise the temperature. The bottom layer of nitrogen purging coils has holes in the downward and horizontal directions to blow out nitrogen for cryogenic liquid vaporization. The holes in the upward direction blow out nitrogen to raise the temperature of the cryogenic evaporating gas. By setting up the nitrogen purging coils and the purging vaporization and heating method, the cryogenic liquid can be vaporized, the liquid accumulation can be reduced, and the formation of excessively low-temperature gas clouds that could damage the hull structure can be avoided.

[0023] Furthermore, the total theoretical volume of the sump tray is the total cumulative leakage of the B-type tank over 15 days minus the amount of cryogenic liquid removed by nitrogen purging and vaporization within 15 days; the number of sump trays is as follows: one sump tray is installed at the lowest point of the spherical tank-type B-type tank, and multiple sump trays are installed at the front, back, left, right and the lowest point of the bottom of the prism-type B-type tank.

[0024] Furthermore, the Type B compartment is a spherical tank or a prismatic tank, or other structural forms besides spherical tank or prismatic tank. The medium inside the Type B compartment is any one of LNG, LPG, liquid ammonia, liquid hydrogen, or liquid carbon dioxide, or other media besides LNG, LPG, liquid ammonia, liquid hydrogen, or liquid carbon dioxide. The heat source used for vaporizing and heating the cryogenic liquid is nitrogen, carbon dioxide, argon, or other inert gases, and an electric heater is used as an auxiliary when necessary.

[0025] A method for collecting and treating leaks in a Type B compartment involves using a Type B compartment leak collection and treatment system. Dry nitrogen, either at room temperature or high temperature and supplied on board, is injected directly into the liquid collection pan as a heat source to heat and vaporize the leaked cryogenic liquid collected in the Type B compartment. The resulting combustible gas vapor is then safely discharged through a specially installed combustible gas venting mast on board.

[0026] Furthermore, the dry nitrogen provided on board, whether at room temperature or high temperature, has a dew point below -40°C and a pressure above 0.2 MPa. Normal temperature nitrogen is usually used, or, to save nitrogen consumption and for better vaporization of cryogenic liquids, the nitrogen is preheated to +80°C to +100°C.

[0027] Furthermore, the nitrogen pressure is set between 10 and 70 kPa by using a primary pressure reducing valve. The opening of the primary pressure reducing valve is controlled by a pressure sensor to achieve precise PID regulation of the nitrogen pressure. Alternatively, a mechanical primary pressure reducing valve can be used to mechanically adjust the pressure to the set value. The primary pressure reducing valve is configured with one in use and one in standby, or a bypass valve can be provided without a standby valve.

[0028] Furthermore, by combining a secondary pressure reducing valve with a flow sensor, precise PID regulation of nitrogen flow is achieved. By controlling the flow of nitrogen injected into the accumulator pan, the vaporization rate of cryogenic liquid in the accumulator pan is precisely limited, thus preventing the risks of overpressure in the ship's cabin and cryogenic gas masses caused by the vaporization of large amounts of cryogenic liquid.

[0029] Furthermore, the pressure in the ship's compartment is normally controlled between -20kPa and 70kPa by the exhaust pressure regulating valve. The opening of the exhaust pressure regulating valve is controlled by the differential pressure sensor to achieve precise PID regulation of the ship's compartment pressure. When the ship's compartment pressure is high and an alarm is triggered, the over-control protection method of directly cutting off the secondary pressure reducing valve is adopted to prevent nitrogen from continuing to enter the ship's compartment.

[0030] Furthermore, by employing a multi-dimensional approach—using a level switch to detect the liquid level, a temperature sensor to detect the low temperature, and a combustible gas detector to detect the combustible gas—the actual occurrence of cryogenic liquid leakage in the Type B compartment is confirmed. This triggers the automatic opening of the primary and secondary pressure-reducing valves and initiates precise PID control for nitrogen purging. The level sensor further detects the difference between the expected and actual changes in the liquid level in the accumulator. By automatically or manually adjusting the flow rate setpoint of the secondary pressure-reducing valve, the nitrogen flow rate is increased or decreased to adjust the cryogenic liquid vaporization rate, thereby precisely controlling the liquid level in the accumulator and limiting its rapid rise.

[0031] The beneficial effects of this invention are:

[0032] The novel B-type cabin leakage collection and treatment system and method provided by this invention achieves beneficial gas supply effects through the following means:

[0033] (1) By using dry nitrogen at room temperature or high temperature as a heat source, the leaked cryogenic liquid collected in the Type B compartment is heated and vaporized. The vaporized flammable gas is then safely discharged to a specially designed flammable gas venting mast on the ship. This method provides a safer, more reliable, and controllable way to handle leaked cryogenic liquids. Compared to the traditional method of directly using a jet pump to discharge the collected leaked cryogenic liquid into the sea, creating an explosive cloud of flammable gas on the sea surface and around the ship, this method is safer and less costly. Compared to the various patented technologies in recent years that use a sufficiently large sump to hold more than 15 days' worth of leaked cryogenic liquid, this method is safer. By promptly vaporizing the cryogenic liquid and lowering the sump level, the significant risks associated with leaked cryogenic liquid overflow are avoided.

[0034] (2) The nitrogen source pressure is precisely PID regulated by a combination of primary pressure reducing valve and pressure sensor. When the nitrogen injection pressure is too high, the nitrogen is directly discharged through pipeline safety valve 4 to avoid the risk of rapid overpressure caused by excessive nitrogen injection pressure in the cabin.

[0035] (3) By combining the secondary pressure reducing valve with the flow sensor, the nitrogen flow rate is precisely PID regulated, thereby precisely limiting the vaporization rate of the cryogenic liquid in the accumulator pan and preventing the risk of overpressure and low temperature caused by the vaporization of a large amount of cryogenic liquid.

[0036] (4) The pressure in the cabin is precisely PID regulated by a combination of exhaust pressure regulating valve and differential pressure sensor, and the excess gas accumulated in the cabin due to the vaporization of cryogenic liquid and nitrogen injection is discharged in time. When the pressure alarm is high, the secondary pressure reducing valve and the nitrogen gas source in the cabin are directly cut off. When the pressure is very high, the cabin safety valve 11 is used to directly release pressure in an emergency to avoid the risk of cabin overpressure.

[0037] (5) The liquid level switch, temperature sensor and combustible gas detector installed in the liquid sump are used to confirm the actual situation of cryogenic liquid leakage in the B-type compartment from multiple dimensions, thereby triggering automatic or manual nitrogen purging and vaporization operation. The liquid level sensor is used to further confirm the change in liquid level in the liquid sump, thereby verifying the actual effect of nitrogen purging and vaporization. If necessary, the remote automatic control method or the on-site manual operation of the valve can be adopted to adjust the setting value of the pressure and flow rate of the above-mentioned purging nitrogen to increase or decrease the cryogenic liquid vaporization rate in order to accurately control the liquid level in the liquid sump and limit the liquid level from rising too quickly.

[0038] (6) When necessary, nitrogen gas can be heated by nitrogen gas source to save nitrogen consumption and achieve a more favorable vaporization and heating effect for cryogenic liquids.

[0039] (7) By setting up two or more layers of nitrogen purging coils, the bottom layer of the coil blows out nitrogen to vaporize the cryogenic liquid, and the upper layer of the nitrogen coil blows out nitrogen to mix with the cryogenic evaporating gas; especially when the liquid accumulation pan is shallow, only one layer of coil can be set up, with downward and horizontal openings to blow out nitrogen for cryogenic liquid vaporization; and upward openings to blow out nitrogen to raise the temperature of the cryogenic evaporating gas. The above coil setup can both vaporize the cryogenic liquid and reduce liquid accumulation, and avoid the formation of excessively low-temperature gas masses that could damage the hull structure.

[0040] (8) By comprehensively applying the above measures, the theoretical volume of the liquid accumulator is reduced to the total leakage of the B-type compartment over 15 days minus the amount of cryogenic liquid removed by nitrogen purging and vaporization within 15 days. Compared with the traditional liquid accumulator scheme, the size and volume of the liquid accumulator can be significantly reduced, thereby reducing costs and saving layout space.

[0041] (9) Through the comprehensive application of the above measures, the bottom of the B-type cabin does not need to be covered with heat insulation material for protection, thus saving ship construction costs.

[0042] In summary, this invention first collects potentially leaking liquid from Type B compartments using a sump tray. Then, dry nitrogen at room temperature or high temperature is supplied from the ship, pressurized to a slightly positive pressure, and the nitrogen flow rate is precisely controlled to limit the evaporation rate of the cryogenic liquid. Finally, the dry nitrogen at room temperature / high temperature, slightly positive pressure, and controllable flow rate is introduced into one or more coils at the bottom of the sump tray. The cryogenic liquid in the sump tray is blown in through numerous tiny purge holes distributed on the coils, heating and vaporizing the cryogenic liquid. This results in the cryogenic liquid slowly vaporizing under controllable conditions. The nitrogen at room temperature or high temperature blown out from the upper coils further mixes and heats the cryogenic vaporized gas, ensuring that the sump tray will not overflow within 15 days, nor will it damage the ship's structural steel, which is not resistant to low temperatures, due to excessively rapid liquid evaporation forming a large amount of cold gas. Finally, by introducing the mixture of flammable gas vaporized from vaporization and nitrogen into a specially designed flammable gas venting mast on the ship, the leakage liquid in the Type B compartment can be effectively collected and treated. This avoids the risk of directly discharging low-temperature flammable and explosive liquids into the sea, as well as the risk of damaging the ship's structure if the liquid overflows from the sump. Attached Figure Description

[0043] Figure 1 This is a diagram of the Type B cabin leakage collection and treatment system of the present invention;

[0044] Figure 2 This is a typical side view of the effusion tray;

[0045] Figure 3 This is a typical top view of the effusion tray;

[0046] In the diagram: 1 is the ship's dry nitrogen gas source; 2 is the primary pressure reducing valve; 3 is the manual valve; 4 is the pipeline safety valve; 5 is the pressure sensor; 6 is the flow sensor; 7 is the secondary pressure reducing valve; 8 is the manual flow regulating valve; 9 is the differential pressure sensor; 10 is the exhaust pressure regulating valve; 11 is the cabin safety valve; 12 is the combustible gas venting mast; 13 is the B-type cabin leak discharge valve; 14 is the liquid collection tray; 15 is the temperature sensor; 16 is the liquid level sensor; 17 is the liquid level switch; 18 is the combustible gas detector; 19 is the vent hole. ; 20 is a vent; 21 is the bulkhead of the Type B compartment; 22 is a leakage channel inside the compartment insulation layer; 23 is the insulation layer of the Type B compartment; 24 is the ship compartment; 101 is the cryogenic liquid leakage pipe of the Type B compartment; 102 is the nitrogen purging pipe; 103 is the bottom surface of the sump for receiving cryogenic liquid; 104 is the mounting base of the sump; 105 is the thermal insulation pad; 106 is the hull structure base; 107 is the fastener such as fixing bolts or screws; 108 is the fastener gasket made of thermal insulation material; 109 is the nitrogen coil inside the sump. Detailed Implementation

[0047] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0048] like Figure 1 As shown in the figure, the present invention provides a novel B-type compartment leak collection and treatment system, including a shipboard dry nitrogen source 1, a primary pressure reducing valve 2, a manual valve 3, a pipeline safety valve 4, a pressure sensor 5, a flow sensor 6, a secondary pressure reducing valve 7, a manual flow regulating valve 8, a differential pressure sensor 9, an exhaust pressure regulating valve 10, a compartment safety valve 11, a combustible gas venting mast 12, a B-type compartment leak discharge valve 13, a liquid collection tray 14, a temperature sensor 15, a liquid level sensor 16, a liquid level switch 17, and a combustible gas detector 18.

[0049] The vent hole at the bottom of the B-type compartment is connected to the sump 14 via the B-type compartment leak discharge valve 13. The dry nitrogen source 1 on board is connected to the inlet of the sump 14 via the nitrogen source pipeline. The outlet of the sump 14 is connected to the combustible gas venting mast 12 on the ship via the exhaust pipeline.

[0050] The nitrogen gas source pipeline is equipped with a primary pressure reducing valve 2, a manual valve 3, a pipeline safety valve 4, a pressure sensor 5, a flow sensor 6, a secondary pressure reducing valve 7, a manual flow regulating valve 8, and a differential pressure sensor 9.

[0051] The exhaust pipe is equipped with an exhaust pressure regulating valve 10 and a cabin safety valve 11.

[0052] The liquid collection tray 14 is equipped with a temperature sensor 15, a liquid level sensor 16, a liquid level switch 17, and a combustible gas detector 18.

[0053] The system is equipped with several manual valves 3, which are used to switch between primary and standby valves, as well as for necessary pipeline isolation maintenance and repair. Pipeline safety valves 4 are used to prevent overpressure after the primary pressure reducing valve, typically at approximately 1.1 times the pressure setpoint. Flow sensor 6 is used to accurately measure nitrogen flow. Secondary pressure reducing valve 7 is used to regulate nitrogen injection flow. Differential pressure sensor 9 is used to monitor the pressure difference between the cabin and atmospheric pressure. Type B cabin leakage discharge valve 13 is used to release cryogenic leaked liquid accumulated at the bottom of the Type B cabin into a sump tray 14. Level switch 17 is used to detect when a small amount of liquid has just formed in the sump tray 14.

[0054] Type B compartments can be spherical, prismatic, or other special structural forms. The medium inside a Type B compartment can be LNG, LPG, liquid ammonia, liquid hydrogen, liquid carbon dioxide, or other media. The heat source for vaporizing and heating the cryogenic liquid can be nitrogen, carbon dioxide, argon, or other inert gases, and can also be supplemented with electric heaters and other measures.

[0055] Figure 2 and Figure 3 for Figure 1 A schematic diagram illustrating the typical structural principle of the liquid accumulation plate 14. Wherein:

[0056] 101 is the cryogenic liquid leak pipe of the Type B compartment; 102 is the nitrogen purging pipe; 103 is the bottom surface of the sump for receiving cryogenic liquid, made of cryogenic-resistant material; 104 is the sump mounting base, made of cryogenic-resistant material; 105 is the heat insulation pad; 106 is the hull structure base, which can be made of ordinary steel or cryogenic-resistant material; 107 is the fastener such as fixing bolts or screws; 108 is the fastener gasket made of heat insulation material; 109 is the nitrogen coil inside the sump 4, generally one or more coils are set slightly above the bottom surface 103 of the sump, and another one or more coils are set in the middle of the sump, depending on the size and depth of the sump. When the sump is small or shallow, only the bottom coil can be set, and when the sump is deep, multiple coils can be set; 110 is the nitrogen coil purging hole, generally with a diameter of 2-4 mm, and a maximum of 10 mm.

[0057] The specific structure of the accumulator plate 14 is as follows:

[0058] The bottom surface 103 of the accumulator tray for receiving cryogenic liquid is suspended from the mounting base 104 of the accumulator tray, with a gap of not less than 40 mm and generally not more than 250 mm. This creates a cold bridge for heat transfer between the cryogenic liquid received on the bottom surface and the hull base, preventing the temperature of the mounting base 104 of the accumulator tray from becoming too low. If necessary, foaming agent insulation material can be injected into the space between the bottom surface 103 of the accumulator tray and the mounting base 104 of the accumulator tray, or stacked insulation material can be inserted to further improve the insulation effect.

[0059] A heat-insulating pad 105 is further installed between the hull structure base 106 and the sump mounting base 104 to ensure that the hull structure is at room temperature. If necessary, the fastener 107 can be a low-temperature resistant bolt. When using fasteners made of ordinary materials that are not resistant to low temperatures, a fastener gasket 108 made of heat-insulating materials such as fiberglass, polytetrafluoroethylene, or wood is installed between the sump mounting base 104 and the fastener 107.

[0060] The nitrogen coil 109 inside the accumulator 4 is generally a double-layer coil (the principle of a single or multi-layer coil is similar). The level switch 17 is installed at a position close to the height of the bottom coil. Once the level switch 17 detects an accumulator alarm and the temperature sensor TT15 detects a low-temperature alarm, the nitrogen purging system automatically or manually initiates the purging process. The ambient or high-temperature nitrogen purged through the purging hole 110 of the bottom coil vaporizes the cryogenic liquid. The cryogenic vapor produced after the cryogenic liquid vaporizes further mixes with the ambient or high-temperature nitrogen purged through the purging hole 110 of the upper coil to raise the temperature of the vapor, preventing the formation of a cryogenic gas cloud that could damage the hull structure. Finally, the mixture of vapor and nitrogen is vented out through the opening at the top of the accumulator 14 and further discharged into the combustible gas venting mast 12 through the exhaust pressure regulating valve 10 or its bypass valve on the hull.

[0061] This invention provides a novel method for collecting and treating leaks in a Type B cabin. The novel method employs a different approach from traditional methods that involve directly spraying cryogenic leaked liquids into the sea or using a large-capacity collection pan. Instead, it uses ambient or high-temperature dry nitrogen as a heat source, directly injecting it into the collection pan 14 to heat and vaporize the collected cryogenic leaked liquid. The resulting combustible gas vapor is then safely discharged through a specially designed combustible gas venting mast 12 on board.

[0062] The specific implementation method of the present invention is as follows:

[0063] The ship provides one dry nitrogen gas source, with the following specific requirements: the dew point must be below -40°C and the pressure is generally above 0.2 MPa. Normal temperature nitrogen is usually used, but to save nitrogen consumption and for the more favorable vaporization effect of cryogenic liquids, the nitrogen can also be preheated to about +80°C, but it must not exceed +100°C.

[0064] The primary pressure reducing valve 2 sets the downstream nitrogen pressure between 10 and 30 kPa, with a maximum of 70 kPa. Precise pressure regulation using a PID control method can be achieved by controlling the opening of the primary pressure reducing valve 2 via pressure sensor 5. Alternatively, a mechanical primary pressure reducing valve 2 can be used for automatic pressure regulation. Generally, one primary pressure reducing valve 2 is configured for operation and one for standby; alternatively, a standby valve may not be provided, with only one bypass valve.

[0065] By combining the secondary pressure reducing valve 7 with the flow sensor 6, the nitrogen flow rate is precisely PID regulated. By controlling the flow rate of nitrogen injected into the liquid collection pan, the vaporization rate of the cryogenic liquid in the liquid collection pan is precisely limited, thus preventing the risks of overpressure and low temperature caused by the vaporization of a large amount of cryogenic liquid.

[0066] The secondary pressure reducing valve 7 is used to regulate the nitrogen injection flow rate. Based on the theoretical calculations of the cryogenic liquid leakage rate of the Type B chamber, the volume of the accumulator tray 14, and the total cryogenic liquid leakage over 15 days, the theoretical nitrogen flow rate range for vaporizing the cryogenic liquid in the accumulator tray 14 is calculated. The intermediate value is selected as the nitrogen flow rate setpoint (the setpoint can be modified according to actual application results). By comparing the actual nitrogen flow rate of the flow sensor 6 with the setpoint, the opening of the secondary pressure reducing valve 7 is controlled, forming a precise PID control method for flow regulation. This achieves precise limitation of the vaporization rate of the cryogenic liquid in the accumulator tray by precisely controlling the flow rate of nitrogen entering the accumulator tray 14.

[0067] In the event that the actual leakage rate in the Type B compartment does not match the theoretically calculated leakage rate, especially if the actual leakage is significantly higher, the accumulator tray 14 may overflow, potentially causing serious consequences such as cryogenic liquid damage to the ship's deck. In this case, the liquid level sensor 16 can detect a continuous rise in the liquid level. The nitrogen flow rate setpoint can be increased, or the manual flow control valve 8 can be manually opened to increase the nitrogen flow rate and accelerate the cryogenic liquid vaporization rate. The manual flow control valve 8 can also be used in situations where the secondary pressure reducing valve 7 malfunctions or other situations require manual flow adjustment.

[0068] Differential pressure sensor 9 is used to monitor the pressure difference between the cabin and atmospheric pressure to prevent overpressure or significant negative pressure in the cabin. Normal cabin pressure is controlled between -10 kPa and 20 kPa, with a minimum of -20 kPa and a maximum of 70 kPa. A preset cabin pressure setpoint (e.g., +10 kPa) is compared with the measurement value from differential pressure sensor 9 to control the opening of the exhaust pressure regulating valve 10, forming a precise PID control method for cabin pressure regulation. Furthermore, when the cabin pressure significantly exceeds the set pressure value (e.g., +20 kPa), the control system automatically closes the secondary pressure reducing valve 7, cutting off the inlet nitrogen flow and preventing further overpressure in the cabin.

[0069] When the cabin pressure rises uncontrollably and exceeds the safety setting range, the cabin safety valve 11 is triggered (e.g., +25 kPa) to release the cabin pressure in an emergency and prevent further overpressure in the cabin.

[0070] The injected nitrogen and the evaporation generated by the vaporization of the cryogenic liquid are ultimately discharged safely and centrally through the combustible gas vent mast 12, preventing the cryogenic liquid from being discharged into the sea and forming an explosive cloud of combustible gas.

[0071] Type B compartment leakage discharge valve 13 is used to discharge cryogenic leakage liquid accumulated at the bottom of Type B compartment into the sump 14.

[0072] The number of sump trays 14 depends on the shape of the Type B tank; there may be one or more. Typically, for spherical tanks like MOSS, only one sump tray is needed at the lowest point of the sphere, while for prismatic tanks, multiple sump trays are needed on the front, back, left, and right sides of the Type B tank floor. Each sump tray 14 is equipped with a complete leak collection, detection, and nitrogen purging system, typically including: a Type B tank leak discharge valve 13, a temperature sensor 15, a level sensor 16, a level switch 17, and a combustible gas detector 18.

[0073] The level switch 17 is used to detect when a small amount of liquid has just formed in the sump tray 14, thereby triggering an early alarm to remind personnel to perform the aforementioned nitrogen purging and vaporization of the cryogenic liquid. The temperature sensor 15 is used to further detect whether the liquid in the sump tray 14 is a cryogenic liquid, preventing false alarms caused by water accumulation. In addition, the combustible gas detector 18 can further confirm whether there is cryogenic liquid leaking from the Type B compartment in the sump tray.

Claims

1. A leak collection and treatment system for a type B cabin, characterized in that: The system includes a sump tray, nitrogen gas supply pipeline, and exhaust pipeline. The vent hole at the bottom of the Type B compartment is connected to the sump tray via a Type B compartment leak discharge valve. The ship's dry nitrogen gas supply is connected to the inlet of the sump tray via a nitrogen pipeline, and the outlet of the sump tray is connected to the combustible gas vent mast on the ship's deck via an exhaust pipeline. The bottom of the sump tray is suspended from its mounting base, with a gap of 40mm to 250mm, creating a cold bridge between the cryogenic liquid on the bottom and the hull base to prevent the mounting base from becoming too cold. If necessary, foamed insulation material or stacked insulation material can be injected into the space between the bottom of the sump tray and the mounting base to further improve the insulation effect. Insulation pads are installed between the hull structure base and the sump tray mounting base to ensure the hull structure remains at room temperature. Fiberglass, PTFE, or wood insulation materials are installed between the sump tray mounting base and the fasteners. Fastener gaskets are used; at least one layer of nitrogen purging coils is installed inside the sump; purging holes are drilled in various directions on the multiple layers of nitrogen purging coils as needed; the bottom layer of nitrogen purging coils blows nitrogen to vaporize the cryogenic liquid, the upper layer of nitrogen purging coils blows nitrogen to mix with the cryogenic evaporating gas and raise the temperature; the bottom layer of nitrogen purging coils has holes facing downwards and horizontally to blow nitrogen for cryogenic liquid vaporization; the upward-facing holes blow nitrogen to raise the temperature of the cryogenic evaporating gas; the nitrogen purging coils and the purging vaporization and heating method can vaporize the cryogenic liquid, reduce sump accumulation, and avoid the formation of excessively low-temperature gas clouds that could damage the hull structure; the total theoretical volume of the sump is the total cumulative leakage of the B-type tank over 15 days minus the amount of cryogenic liquid treated by nitrogen purging and vaporization within 15 days; the number of sumps is as follows: one sump is installed at the lowest point of a spherical tank-type B-type tank, and multiple sumps are installed at the front, rear, left, right and the lowest point of the bottom of the prism-type B-type tank.

2. The B-type cabin leakage collection and treatment system according to claim 1, characterized in that: The nitrogen gas source pipeline is equipped with a primary pressure reducing valve, a manual valve, a pipeline safety valve, a pressure sensor, a flow sensor, a secondary pressure reducing valve, a manual flow regulating valve, and a differential pressure sensor; the exhaust pipeline is equipped with an exhaust pressure regulating valve and a cabin safety valve; the liquid collection pan is equipped with a temperature sensor, a liquid level sensor, a liquid level switch, and a combustible gas detector.

3. The B-type cabin leakage collection and treatment system according to claim 1, characterized in that: Type B compartments are spherical, prismatic, or other structural forms besides spherical or prismatic. The medium inside Type B compartments is any one of LNG, LPG, liquid ammonia, liquid hydrogen, or liquid carbon dioxide, or other media besides LNG, LPG, liquid ammonia, liquid hydrogen, or liquid carbon dioxide. The heat source for vaporizing and heating cryogenic liquids is nitrogen, carbon dioxide, argon, or other inert gases, with an additional electric heater if necessary.

4. A method for collecting and treating leaks in a Type B cabin, employing the Type B cabin leak collection and treatment system as described in any one of claims 1-3, characterized in that: Dry nitrogen, either at room temperature or high temperature, provided on board, is used as a heat source and injected directly into the liquid collection pan to heat and vaporize the leaked cryogenic liquid collected in the Type B compartment. The resulting flammable gas vapor is then safely discharged through a specially designed flammable gas venting mast on board.

5. The method for collecting and treating leaks in a Type B cabin according to claim 4, characterized in that: The dry nitrogen supplied on board has a dew point below -40°C and a pressure above 0.2MPa. Normal temperature nitrogen is usually used, or the nitrogen is preheated to +80°C to +100°C to save nitrogen consumption and achieve a more favorable vaporization effect for cryogenic liquids.

6. The method for collecting and treating leaks in a Type B cabin according to claim 4, characterized in that: The nitrogen pressure is set between 10 and 70 kPa by using a primary pressure reducing valve. The opening of the primary pressure reducing valve is controlled by a pressure sensor to achieve precise PID regulation of the nitrogen pressure. Alternatively, a mechanical primary pressure reducing valve can be used to mechanically adjust the pressure to the set value. The primary pressure reducing valve is configured with one in use and one in standby, or a bypass valve can be provided without a standby valve.

7. The method for collecting and treating leaks in a Type B cabin according to claim 4, characterized in that: By combining a secondary pressure reducing valve and a flow sensor, the nitrogen flow rate is precisely PID regulated. By controlling the flow rate of nitrogen injected into the accumulator pan, the vaporization rate of the cryogenic liquid in the accumulator pan is precisely limited, thus preventing the risks of overpressure in the ship's cabin and cryogenic gas masses caused by the vaporization of a large amount of cryogenic liquid.

8. The method for collecting and treating leaks in a Type B cabin according to claim 4, characterized in that: The pressure in the ship's compartment is normally controlled between -20kPa and 70kPa by the exhaust pressure regulating valve. The opening of the exhaust pressure regulating valve is controlled by the differential pressure sensor to achieve precise PID regulation of the ship's compartment pressure. When the ship's compartment pressure is high and an alarm is triggered, the over-control protection method of directly cutting off the secondary pressure reducing valve is adopted to prevent nitrogen from continuing to enter the ship's compartment.

9. The method for collecting and treating leaks in a Type B cabin according to claim 4, characterized in that: By employing a multi-dimensional approach—using a level switch to detect the liquid level, a temperature sensor to detect the low temperature, and a combustible gas detector to detect the combustible gas—the system confirms the actual occurrence of a cryogenic liquid leak in the Type B compartment. This triggers the automatic opening of the primary and secondary pressure-reducing valves and initiates precise PID-controlled nitrogen purging. Furthermore, the level sensor detects the difference between the expected and actual liquid level changes in the sump. By automatically or manually adjusting the flow rate setpoint of the secondary pressure-reducing valve, the nitrogen flow rate is increased or decreased to adjust the cryogenic liquid vaporization rate, thereby precisely controlling the liquid level in the sump and limiting its rapid rise.

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