Large ethane tanker recondensation system

Abstract

The utility model relates to the field of shipbuilding provides large -scale ethane liquid cargo ship cargo hold recondensing system. Including first gas -liquid separator, first separator connects first stage compressor, first stage compressor connects the input of second gas -liquid separator, and the second gas -liquid separator is installed with heat exchange coil, and the gas export of the top of second gas -liquid separator is connected the suction port of second stage compressor through pipeline, and the exhaust of second stage compressor connects seawater heat exchanger, and the heat exchange passage of seawater heat exchanger connects refrigeration heat exchanger, and the heat exchange passage of refrigeration heat exchanger is linked with liquid collecting tank. Through first stage gas -liquid separator to steam preliminary treatment separation, avoid the impact to compressor, through the mode of one -stage compression and one -stage condensation, can guarantee the recondensation of most liquid cargo, through the mode of two -stage compression and multistage condensation, can realize the recondensation of all liquid cargo, can effectively avoid the pollution and waste caused by the direct discharge of evaporated gas.

Description

Technical Field

[0001] This utility model relates to the field of shipbuilding, specifically to a recondensation system for cargo holds of large ethane liquid cargo ships. Background Technology

[0002] Large ethane liquefied cargo ships are used to transport various cargoes such as ethane, ethylene, and propane. They typically have multiple cargo tanks, each capable of holding different liquid feedstocks for flexible transport. The cargo tanks are generally equipped with containment systems. Since cryogenic liquefied cargoes inevitably evaporate and generate gas within the tanks, to avoid waste and excessive pressure, the generated gas is condensed and recovered through recondensation. Different feedstocks have different liquefaction temperatures, and with the increasing demand for ammonia fuel, the need for liquid ammonia transport is growing daily. Ethane liquefied cargo ships must be designed to accommodate liquid ammonia. Because loading liquid ammonia requires specific Ni content in the cargo tank steel plates, and many components of the liquefied cargo system are not designed for liquid ammonia, existing ethane carriers cannot transport liquid ammonia. Therefore, the materials used in the cargo holds and the selection of supporting systems, especially the recondensation system, must be carefully considered to ensure complete liquefaction of evaporated ammonia. Summary of the Invention

[0003] To meet the condensation capacity requirements of the recondensation system when loading different raw materials into the liquid cargo tank, especially considering the condition of loading liquid ammonia, this utility model provides a recondensation system for the cargo tanks of large ethane liquid cargo ships.

[0004] The technical solution adopted by this utility model is as follows: A large ethane liquefied cargo ship's cargo tank recondensation system includes a first gas-liquid separator. The inlet of the first gas-liquid separator is connected to the gas outlet of the liquefied cargo tank. The bottom of the first gas-liquid separator is connected to a discharge port via pipes and valves. The top gas outlet of the first separator is connected to the suction port of a first-stage compressor via pipes. The discharge port of the first-stage compressor is connected to the inlet of a second gas-liquid separator via pipes. The second gas-liquid separator is equipped with heat exchange coils. The bottom of the second gas-liquid separator is connected to a discharge port via pipes and valves. The top gas outlet of the second gas-liquid separator is connected to... The suction port and discharge port of the second-stage compressor are connected to a seawater heat exchanger. The heat exchange medium channel of the seawater heat exchanger is filled with low-temperature seawater. The heat exchange channel of the seawater heat exchanger is connected to a refrigeration heat exchanger. The heat exchange medium channel of the refrigeration heat exchanger is filled with circulating cooling medium. The heat exchange channel of the refrigeration heat exchanger is connected to a liquid collection tank. The bottom of the liquid collection tank is connected to a discharge port through a pipe. The bottom of the liquid collection tank is connected to the heat exchange coil through a branch pipe and a valve. The output end of the heat exchange coil is connected to the discharge port. The discharge port is connected to a liquid cargo tank or storage tank.

[0005] Furthermore, the exhaust port of the second-stage compressor is connected to a third-stage compressor via a branch pipe, and the exhaust port of the third-stage compressor is connected to the seawater heat exchanger.

[0006] Furthermore, pressure valves are installed on the top of the first gas-liquid separator, the second gas-liquid separator, the refrigeration heat exchanger, and the liquid collection tank, respectively, and the pressure valves are connected to the exhaust gas discharge pipe through pipelines.

[0007] Furthermore, the circulating cooling medium is a cryogenic liquid produced by the cryogenic liquid cargo in the cargo tank or a cryogenic coolant prepared by the refrigeration unit.

[0008] Furthermore, the heat exchange channel of the seawater heat exchanger is connected to the liquid collection tank via a branch pipe.

[0009] Furthermore, the first-stage compressor, the second-stage compressor, and the third-stage compressor are installed in a sealed enclosure, and a pressure valve is installed on the top of the sealed enclosure, which is connected to the exhaust pipe.

[0010] Furthermore, the top gas outlet of the first gas-liquid separator is provided with a branch pipe that connects to the suction port of the third-stage compressor.

[0011] After adopting the above technical solutions, the beneficial effects of this utility model are as follows: the vapor is initially treated and separated by the first-stage gas-liquid separator, avoiding impact on the compressor; the re-condensation of most liquids can be ensured by the first-stage compression and first-stage condensation; and the re-condensation of all liquids can be achieved by the second-stage compression and multi-stage condensation, effectively avoiding pollution and waste caused by the direct emission of evaporated gas. Attached Figure Description

[0012] Figure 1 This is a system schematic diagram of the present invention.

[0013] In the diagram: 1. First gas-liquid separator, 2. Second gas-liquid separator, 3. Seawater heat exchanger, 4. Refrigeration heat exchanger, 5. Liquid storage tank, 6. Collection main pipe, 7. First stage compressor, 8. Heat exchange coil, 9. Second stage compressor, 10. Third stage compressor, 11. Exhaust gas discharge pipe. Detailed Implementation

[0014] The specific embodiments of this utility model will be further described in detail below with reference to the accompanying drawings: like Figure 1 As shown, the large ethane cargo ship's cargo tank recondensation system is used to re-liquefy the gas evaporated in the cargo tank by compression and to recover the liquefied cargo. It consists of a first gas-liquid separator 1, a multi-stage compressor, a second gas-liquid separator 2, a seawater heat exchanger 3, a refrigeration heat exchanger 4, a liquid storage tank 5, and related pipes and valves.

[0015] Evaporated gas in the liquid cargo tank enters the first gas-liquid separator 1 through a pipe. In the first gas-liquid separator 1, the liquid cargo mixed in is collected at the bottom of the separator and can enter the collection manifold 6 through a pipe. Gas from the gas outlet at the top of the first gas-liquid separator 1 enters the suction port of the first-stage compressor 7 through a pipe. After compression, it enters the second gas-liquid separator 2. The second gas-liquid separator 2 is equipped with a heat exchange coil 8. A low-temperature medium passes through the heat exchange coil 8. The compressed gas exchanges heat with the low-temperature medium and is liquefied. The liquefied cargo is collected in the second gas-liquid separator 2 and connected to the collection manifold 6 through a pipe and valve at the bottom. Gas that is not liquefied in the second gas-liquid separator 2 enters the suction port of the second-stage compressor 9 through a pipe at its top. The gas compressed by the second-stage compressor 9 enters the seawater heat exchanger 3, or the gas compressed by the second-stage compressor 9 enters the third-stage compressor 10 for further compression, and the compressed gas then enters the seawater heat exchanger 3. The top gas outlet of the first gas-liquid separator 1 is equipped with a branch pipe that connects to the suction port of the third-stage compressor 10. Different compression methods are selected based on the condensation point of the evaporated gas through valve control.

[0016] Seawater heat exchanger 3 uses circulating seawater as the cooling medium. Due to the different freezing points of different raw materials, steam with a higher freezing point is completely liquefied after heat exchange in seawater heat exchanger 3 and then enters the storage tank 5 through a pipeline. For liquids with a lower freezing point, seawater heat exchange cannot completely liquefy them, so they enter the refrigeration heat exchanger 4 through a pipeline. The refrigeration heat exchanger 4 is a shell-and-tube heat exchanger, and its heat exchange tubes are filled with a low-temperature heat exchange medium prepared by a refrigeration unit to liquefy the liquids cooled by seawater heat exchanger 3. The liquefied liquids then enter the storage tank 5 through a pipeline or are directly discharged into the collection main pipe 6.

[0017] The storage tank 5 is used to recover liquefied liquid cargo. The bottom of the storage tank 5 is connected to the main collection pipe 6. A branch line is also provided at the bottom of the storage tank 5, which, controlled by a valve, supplies cryogenic liquid cargo to the heat exchange coil 8 within the second gas-liquid separator. This cryogenic liquid cargo exchanges heat with the vapor in the second gas-liquid separator 2, reducing its temperature or condensing it. The cooled liquid cargo then enters the main collection pipe 6 through the pipeline. The recondensed liquid cargo entering the main collection pipe 6 ultimately returns to the cargo tank or storage tank.

[0018] To ensure system safety, pressure valves are installed on the top of the first gas-liquid separator 1, the second gas-liquid separator 2, the refrigeration heat exchanger 4, and the liquid storage tank 5, respectively. The pressure valves are connected to the exhaust gas pipe 11 via pipes. The first-stage compressor 7, the second-stage compressor 9, and the third-stage compressor 10 are installed in a sealed enclosure. A pressure valve is installed on the top of the sealed enclosure and is connected to the exhaust gas pipe 11.

Claims

1. A recondensation system for cargo holds of a large ethane liquid cargo ship, characterized in that, The system includes a first gas-liquid separator. The inlet of the first gas-liquid separator is connected to the gas outlet of the liquid cargo tank. The bottom of the first gas-liquid separator is connected to a discharge port via pipes and valves. The top gas outlet of the first separator is connected to the suction port of a first-stage compressor via pipes. The discharge port of the first-stage compressor is connected to the inlet of a second gas-liquid separator via pipes. A heat exchange coil is installed inside the second gas-liquid separator. The bottom of the second gas-liquid separator is connected to a discharge port via pipes and valves. The top gas outlet of the second gas-liquid separator is connected to the suction port of the second-stage compressor via pipes. The discharge port of the second-stage compressor is connected to a seawater heat exchanger. Low-temperature seawater flows through the heat exchange medium channel of the seawater heat exchanger. The heat exchange channel of the seawater heat exchanger is connected to a refrigeration heat exchanger. A circulating cooling medium flows through the heat exchange medium channel of the refrigeration heat exchanger. The heat exchange channel of the refrigeration heat exchanger is connected to a liquid collection tank. The bottom of the liquid collection tank is connected to a discharge port via pipes. The bottom of the liquid collection tank is connected to the heat exchange coil via branch pipes and valves. The output end of the heat exchange coil is connected to the discharge port. The discharge port is connected to the liquid cargo tank or storage tank.

2. The large ethane liquid cargo ship cargo tank recondensation system according to claim 1, characterized in that, The exhaust port of the second-stage compressor is connected to the third-stage compressor via a branch pipe, and the exhaust port of the third-stage compressor is connected to the seawater heat exchanger.

3. The large ethane liquid cargo ship cargo tank recondensation system according to claim 1, characterized in that, Pressure valves are installed on the top of the first gas-liquid separator, the second gas-liquid separator, the refrigeration heat exchanger, and the liquid collection tank, respectively, and the pressure valves are connected to the exhaust gas pipe through pipelines.

4. The large ethane liquid cargo ship cargo tank recondensation system according to claim 1, characterized in that, The circulating cooling medium is a cryogenic coolant prepared by the cryogenic liquid cargo or refrigeration unit in the liquid cargo tank.

5. The large ethane liquid cargo ship cargo tank recondensation system according to claim 1, characterized in that, The heat exchange channel of the seawater heat exchanger is connected to the liquid collection tank through a branch pipeline.

6. The large ethane liquid cargo ship cargo tank recondensation system according to claim 1, characterized in that, The first-stage compressor, the second-stage compressor, and the third-stage compressor are installed in a sealed enclosure. A pressure valve is installed on the top of the sealed enclosure and is connected to the exhaust pipe.

7. The large ethane liquid cargo ship cargo tank recondensation system according to claim 1, characterized in that, The top gas outlet of the first gas-liquid separator is provided with a branch pipe that connects to the suction port of the third-stage compressor.

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