Process and apparatus for the liquefaction of a natural gas stream utilizing a single mixed refrigerant

An apparatus suitable for the liquefaction of a natural gas stream, the apparatus including compressor means, aftercooler means, phase separation means and a cold box, the improvement comprising:

• the cold box having no phase separator therein;
• a warm end heat exchanger and a cold end heat exchanger disposed within the cold box;
• a first expansion valve disposed in the cold box but outside of the cold end heat exchanger;
• a second expansion valve disposed in the cold box between the warm end and cold end heat exchangers;
• refrigerant line means connected to the phase separation means, the refrigerant line means including a vapor line and a liquid line both extending from the phase separation means and through the cold box for transporting refrigerant fluid through the cold box without passing through a phase separator in the cold box;
• the vapor refrigerant line extending through the warm end heat exchanger and cold end heat exchanger, through the first expansion valve, back through the cold end and warm heat exchangers and to the compressor means;
• the liquid line extending through the warm end heat exchanger and being connected to the vapor line through the second expansion valve;
• an adjustable flow valve in the cold box, the adjustable flow valve being disposed between the warm end and cold end heat exchangers and connected between the liquid line and vapor line upstream of the second expansion valve for flowing excess liquid from the liquid line to the vapor line;
• and
• means connected to the adjustable flow valve for adjusting the adjustable flow valve to control the rate of fluid flow therethrough.

In a cooling apparatus wherein the cooling apparatus includes:

• a cold box having warm end and cold end heat exchangers therein;
• at least one compressor means and phase separation means external of the cold box;
• and refrigerant line means extending from the phase separation means through the warm end and cold end heat exchangers in the cold box, the refrigerant line means including a vapor line and a liquid line, the improvement comprising:
• the cold box not having a phase separator therein;
• first and second expansion valves in the cold box, the first expansion valve being disposed outside of the cold end heat exchanger and the second expansion valve being disposed between the warm end and cold end heat exchangers;
• the vapor line extending through the warm end heat exchanger and cold end heat exchanger, through the first expansion valve, back through the cold and warm end heat exchangers and to the compressor means;
• the liquid line extending from the phase separation means and through the warm end heat exchanger;
• an adjustable flow valve in the cold box disposed between the warm end and cold end heat exchangers and connected directly between the liquid line and vapor line upstream of the second expansion valve;
• means connected to the adjustable flow valve for adjusting the adjustable flow valve to control the rate of fluid flow therethrough, whereby excess liquid in the liquid line is conveyed to the vapor line and compensated for in the apparatus without using a phase separator in the cold box.