COMPRESSED NATURAL GAS CARGO SHIP AND GAS UNLOADING SYSTEM AND GAS UNLOADING CONTROL METHOD THEREFOR

摘要

Disclosed is a compressed natural gas cargo ship (100), comprising a ship hull, multiple sets of gas unloading systems and a main gas discharge pipe. Each set of gas unloading system comprises a gas storage unit, a gas unloading unit (40) and a control unit. The unloading unit (40) comprises a tank (43) storing a liquid medium, a pump (44) supplying the liquid medium to the storage unit and a liquid medium connecting pipeline comprising a control valve bridge (461). A main liquid-return control valve (48) and a buffer tank (47) are provided on a liquid return pipe of the liquid medium connecting pipeline, a liquid level meter is provided in the buffer tank (47), the liquid level meter monitors whether or not the liquid level in the buffer tank (47) during the liquid return process has reached a monitoring point and returns a monitoring signal to the control unit, the control unit controls the activation and deactivation of the main liquid return control valve according to the monitoring signal such that liquid remains in a pipeline between the monitoring points of the tank and the buffer tank. Further disclosed is a gas unloading control method. Long-distance marine transportation of CNG can be achieved with the use of the compressed natural gas cargo ship and the gas unloading control method, and compressed natural gas onboard the ship can be quickly, highly efficiently and safely unloaded into a CNG receiving terminal on land.