Raw material gas liquefying device and method of controlling this raw material gas liquefying device

A raw material gas liquefying device comprising:

• a feed line in which a raw material gas flows through a raw material flow path in order from a heat exchanger, to a liquefied refrigerant storage tank which stores a liquefied refrigerant therein, and to a feed system Joule-Thomson valve;
• a refrigerant circulation line including a refrigerant liquefaction route and a cryogenic energy generation route, wherein in the refrigerant liquefaction route, a refrigerant flows through a compressor, then in order from the compressor to a high-temperature-side refrigerant flow path of the heat exchanger, to a circulation system Joule-Thomson valve, the liquefied refrigerant storage tank, and to a first low-temperature-side refrigerant flow path of the heat exchanger, and then returns to the compressor, and while in the cryogenic energy generation route, the refrigerant flows through the compressor, then in order from the compressor to an expansion unit, and to a second low-temperature-side refrigerant flow path of the heat exchanger, and then returns to the compressor;
• a temperature sensor which detects a temperature, which is either:
• (i) a first temperature of the refrigerant at an exit side of the high-temperature-side refrigerant flow path of the heat exchanger;
• or (ii) a second temperature of the raw material gas at an exit side of the raw material flow path of the heat exchanger;
• a liquid level sensor which detects a refrigerant storage tank liquid level which is a liquid level in the liquefied refrigerant storage tank;
• and
• a controller which determines whether or not the refrigerant storage tank liquid level is within a predetermined allowable range or outside the predetermined allowable range, and wherein
• in a case where the liquid level is outside a predetermined allowable range, the controller manipulates an opening rate of the feed system Joule-Thomson valve based on the liquid level so that the liquid level falls into the predetermined allowable range;
• and
• in a case where the liquid level is within the predetermined allowable range, the controller manipulates the opening rate of the feed system Joule-Thomson valve based on the temperature detected by the temperature sensor so that the temperature reaches a predetermined temperature set value.