Method for improved thermal performing refrigeration cycle

Abstract

An improved refrigeration cycle is provided. The cycle provides for improved thermal performance by incorporating a refrigerant makeup tank that introduces liquid refrigerant with expanded refrigerant upstream of the heat exchanger, thereby providing a savings in either electricity costs or refrigerant.

We claim: 
     
         1 . A method for producing a liquefied gas stream from an inlet gas feed stream, the method comprising the steps of:
 cooling at least a portion of the inlet gas feed stream by heat exchange contact with an expanded refrigerant to produce the liquefied gas stream, wherein the expanded refrigerant is circulated in a refrigeration cycle; and   introducing a liquid refrigerant makeup stream into the refrigeration cycle by adding the liquid refrigerant makeup stream to the expanded refrigerant prior to heat exchange contact with the inlet gas feed stream to provide for makeup losses in the refrigeration cycle and to provide additional refrigeration to the refrigeration cycle.   
     
     
         2 . The method as claimed in  claim 1 , wherein the inlet gas feed stream is natural gas. 
     
     
         3 . The method as claimed in  claim 1 , wherein the refrigeration cycle is a nitrogen refrigeration cycle and the liquid refrigerant makeup stream originates from a liquid nitrogen tank. 
     
     
         4 . The method as claimed in  claim 1 , wherein the expanded refrigerant is nitrogen. 
     
     
         5 . The method as claimed in  claim 1 , wherein the expanded refrigerant is expanded in a device selected from the group consisting of an expansion valve, a turbo-expander, and a liquid expander. 
     
     
         6 . The method as claimed in  claim 1 , further comprising the steps of withdrawing a utility nitrogen stream from the expanded refrigerant subsequent to heat exchange contact with the inlet gas feed stream; and introducing the utility nitrogen stream to a second user for use as utility nitrogen. 
     
     
         7 . A method for producing a liquefied gas stream from an inlet gas feed stream, the method comprising the steps of:
 cooling at least a portion of the inlet gas feed stream by heat exchange contact with a nitrogen refrigeration cycle to produce the liquefied gas stream; and   adding a liquid refrigerant makeup stream into the expanded refrigerant prior to heat exchange contact with the inlet gas feed stream to provide for makeup losses in the nitrogen refrigeration cycle and to provide additional refrigeration to the nitrogen refrigeration cycle,   wherein the nitrogen refrigeration cycle comprises the steps of:   expanding a nitrogen stream to a nitrogen vapor stream;   cooling at least a portion of the inlet feed gas stream by heat exchange contact with the nitrogen vapor stream;   compressing the nitrogen vapor stream to form a compressed nitrogen vapor stream; and   cooling at least a portion of the compressed nitrogen vapor stream by heat exchange contact with the nitrogen vapor stream.   
     
     
         8 . The method as claimed in  claim 7 , wherein the expanded refrigerant is expanded in a device selected from the group consisting of an expansion valve, a turbo-expander, and a liquid expander. 
     
     
         9 . The method as claimed in  claim 7 , further comprising the steps of withdrawing a utility nitrogen stream from the nitrogen vapor stream subsequent to heat exchange contact with the inlet gas feed stream; and introducing the utility nitrogen stream to a second user for use as utility nitrogen.