Gas treatment system and vessel including the same

1. A gas processing system, comprising:

a Boil Off Gas (BOG) compressor which is provided with a plurality of stages, compresses Naturally generated Boil Off Gas (NBOG) generated in a liquefied gas storage tank in multiple stages, discharges the compressed NBOG, branches and supplies the discharged NBOG to a propulsion engine and a generation engine that demands pressure of gas different from pressure of gas demanded by the propulsion engine;

a boosting pump which pressurizes liquefied gas of the liquefied gas storage tank in response to the pressure demanded by the propulsion engine and discharges the pressurized liquefied gas to an outside of the liquefied gas storage tank;

a forcing vaporizer which vaporizes the liquefied gas pressurized by the boosting pump and generates forced BOG (FBOG);

a gas-liquid separator which separates the FBOG into a gas phase and a liquid phase and supplies the gas phase to be joined with the NBOG; and

a gas combustion unit which receives surplus BOG that remains after the propulsion engine and the generation engine consume BOG at a downstream side of the BOG compressor,

wherein the BOG compressor compresses the NBOG in response to the pressure demanded by the propulsion engine, and

wherein the gas-liquid separator supplies the gas phase of the FBOG that is separated into the gas phase and the liquid phase to be joined with the NBOG at an upstream side of a point where the BOG is branched to the propulsion engine and the generation engine and at a downstream side of a point where the NBOG is branched to the gas combustion unit of the downstream side of the BOG compressor.

2. The gas processing system of claim 1 , further comprising:

a controller which, when it is assumed that a speed at which a vessel is propelled in a case where the demand source completely consumes only the naturally generated BOG generated in the liquefied gas storage tank in the full load state is a predetermined speed, compares a speed of the vessel with the predetermined speed and controls a flow of the BOG or the liquefied gas in the first supply line or the second supply line.

3. The gas processing system of claim 2 , wherein when the speed of the vessel is within the predetermined speed, the controller controls the BOG within the liquefied gas storage tank to be supplied to the demand sources only through the first supply line, and

when the speed of the vessel exceeds the predetermined speed, the controller controls the liquefied gas or the BOG within the liquefied gas storage tank to be supplied to the demand source through the first supply line and the second supply line.

4. The gas processing system of claim 1 , further comprising:

a first supply line which connects the liquefied gas storage tank and the propulsion engine and is provided with the BOG compressor thereon;

a second supply line which is connected with the liquefied gas storage tank and a downstream side of the BOG compressor on the first supply line; and

a controller which compares the amount of the NBOG with the amount of fuel demanded by the propulsion engine, and controls a flow of the BOG or the liquefied gas in the first supply line or the second supply line.

5. The gas processing system if claim 4 , wherein when the amount of fuel demanded by the propulsion engine is larger than the amount of the NBOG, the controller controls the liquefied gas or the BOG within the liquefied gas storage tank to be supplied to the propulsion engine through the first supply line and the second supply line.

6. The gas processing system of claim 5 , further comprising: the gas combustion unit which processes the BOG generated in the liquefied gas storage tank, wherein when the amount of fuel demanded by the propulsion engine and the generation engine is smaller than the amount of the NBOG, the controller controls the BOG within the liquefied gas storage tank to be supplied to the propulsion engine and the generation engine or the gas combustion unit only through the first supply line.

7. The gas processing system of claim 1 , further comprising:

a re-liquefying device which re-liquefies the BOG compressed by the BOG compressor; and

a third supply line which is branched on the first supply line to be connected to the re-liquefying device.

8. The gas processing system of claim 1 , wherein the demand source is a low-speed two-stroke low pressure injection engine, and the gas processing system further includes the boosting pump which is provided on the second supply line, and pressurizes the liquefied gas stored in the liquefied gas storage tank to pressure demanded by the demand source and supplies the pressurized liquefied gas to the demand source.

9. The A vessel including the gas processing system of claim 1 , wherein the demand source is a low-speed two-stroke low pressure injection engine, and the gas processing system further includes a pump which is provided on the second supply line, and pressurizes the liquefied gas stored in the liquefied gas storage tank to pressure demanded by the demand source and supplies the pressurized liquefied gas to the demand source.

10. The gas processing system of claim 1 , further comprising:

a heater which is provided on the second supply line, and increases a temperature of liquefied gas compulsorily vaporized by the forcing vaporizer before the liquefied gas is joined with the BOG compressed by the BOG compressor.

11. The gas processing system of claim 10 , wherein when a temperature of the BOG compressed by the BOG compressor is equal to or higher than a predetermined temperature, the heater does not increase a temperature of the liquefied gas compulsorily vaporized by the forcing vaporizer, and

when the temperature of the BOG compressed by the BOG compressor is lower than the predetermined temperature, the heater increases the temperature of the liquefied gas compulsorily vaporized by the forcing vaporizer.

12. The gas processing system of claim 10 , wherein the heater is used in a light load state.

13. The gas processing system of claim 10 , wherein the demand source is a low-speed two-stroke low pressure injection engine.

14. The gas processing system of claim 10 , further comprising: wherein the boosting pump is operated in response to discharge pressure of the BOG compressor.