Fuel gas supply system and method of an lng carrier

Abstract

A fuel gas supply system of an LNG carrier is provided for supplying fuel gas to a high-pressure gas injection engine of an LNG carrier, wherein LNG is extracted from an LNG storage tank of the LNG carrier, compressed at a high pressure, gasified, and then supplied to the high-pressure gas injection engine.

1 . A fuel gas supply system of a liquefied natural gas (LNG) carrier for supplying fuel gas to a high-pressure gas injection engine of the LNG carrier, the fuel gas supply system comprising:
 an LNG storage tank;   a fuel gas supply line connected from the LNG storage tank to the high-pressure gas injection engine of the LNG carrier;   means for compressing the LNG installed in the fuel gas supply line between the LNG storage tank and the high-pressure gas injection engine; and   means for gasifying the LNG installed downstream of the compressing means in the fuel gas supply line, to gasify the compressed LNG.   
   
   
       2 . The fuel gas supply system of an LNG carrier according to  claim 1  wherein the compressing means is configured to extract LNG from the LNG storage tank, compress the extracted LNG at a high pressure, and supply the compressed LNG toward the high-pressure gas injection engine. 
   
   
       3 . The fuel gas supply system of an LNG carrier according to  claim 1  wherein the compressing means comprises one pump. 
   
   
       4 . The fuel gas supply system of an LNG carrier according to  claim 3  wherein the compressing means further comprises another pump. 
   
   
       5 . The fuel gas supply system of an LNG carrier according to  claim 3 , further comprising:
 a heat exchanger installed downstream of the one pump in the fuel gas supply line; and   a boil-off gas liquefaction line connected from an upper portion of the LNG storage tank, passing through the heat exchanger, to one side of the LNG storage tank, the boil-off gas liquefaction line configured to liquefy boil-off gas generated in the LNG storage tank.   
   
   
       6 . The fuel gas supply system of an LNG carrier according to  claim 4 , further comprising:
 a heat exchanger installed between the one pump and the other pump in the fuel gas supply line; and   a boil-off gas liquefaction line passing through the heat exchanger from an upper portion of the LNG storage tank and connected between the heat exchanger and the gasifying means.   
   
   
       7 . The fuel gas supply system of an LNG carrier according to  claim 3 , further comprising:
 a recondenser installed downstream of the one pump in the fuel gas supply line; and   a boil-off gas liquefaction line connected from an upper portion of the LNG storage tank, passing through the recondenser, and to the LNG storage tank.   
   
   
       8 . The fuel gas supply system of an LNG carrier according to  claim 1  wherein the gasifying means is a heater. 
   
   
       9 . The fuel gas supply system of an LNG carrier according to  claim 1  wherein LNG is extracted from the LNG storage tank and then compressed to approximately 20 to 300 bar gauge pressure. 
   
   
       10 . The fuel gas supply system of an LNG carrier according to  claim 5  wherein the boil-off gas generated in the LNG storage tank is not compressed in a gaseous state at a high pressure, and thus is not used as fuel gas of the high-pressure gas injection engine. 
   
   
       11 . The fuel gas supply system of an LNG carrier according to  claim 1  wherein the LNG storage tank is designed to withstand a pressure increase due to the boil-off gas so as to allow a pressure increase due to the boil-off gas generated in the LNG storage tank during the voyage of the LNG carrier. 
   
   
       12 . A fuel gas supply method of a liquefied natural gas (LNG) carrier for supplying fuel gas to a high-pressure gas injection engine of the LNG carrier, comprising:
 extracting LNG from an LNG storage tank of the LNG carrier;   compressing the extracted LNG to meet the pressure requirements for the high-pressure gas injection engine;   gasifying the compressed LNG; and   supplying the gasified LNG to the high-pressure gas injection engine.   
   
   
       13 . The fuel gas supply method of an LNG carrier according to  claim 12 , further comprising:
 extracting a boil-off gas from the LNG storage tank; and   exchanging heat between the LNG and the boil-off gas before supplying the LNG to the high-pressure gas injection engine.   
   
   
       14 . The fuel gas supply method of an LNG carrier according to  claim 13 , further comprising:
 liquefying the boil-off gas; and   returning the liquefied boil-off gas to the LNG storage tank.   
   
   
       15 . The fuel gas supply method of an LNG carrier according to  claim 13 , further comprising:
 increasing a temperature of the LNG via the exchanging of heat between the LNG and the boil-off gas before supplying the LNG to the high-pressure gas injection engine;   liquefying the boil-off gas; and   supplying the liquefied boil-off gas to the high-pressure gas injection engine.   
   
   
       16 . The fuel gas supply method of an LNG carrier according to  claim 12 , further comprising:
 mixing the LNG with the boil-off gas extracted from the LNG storage tank; and   supplying the mixture of the LNG and the boil-off gas to the high-pressure gas injection engine.   
   
   
       17 . The fuel gas supply method of an LNG carrier according to  claim 12  wherein the LNG is gasified by being heated. 
   
   
       18 . The fuel gas supply method of an LNG carrier according to  claim 12 , further comprising:
 allowing a pressure increase due to the boil-off gas generated in the LNG storage tank during the voyage of the LNG carrier.   
   
   
       19 . The fuel gas supply method of an LNG carrier according to  claim 12  wherein the LNG pressure for the high-pressure gas injection engine ranges from about 20 bar to about 300 bar gauge pressure. 
   
   
       20 . The fuel gas supply method according to  claim 13  wherein the boil-off gas generated in the LNG storage tank is not compressed in a gaseous state at a high pressure, and thus is not used as fuel gas of the high-pressure gas injection engine.