Single Mixed Refrigerant LNG Production Process

Abstract

A simple and efficient single mixed refrigerant process for cooling and liquefying a hydrocarbon feed stream, such as natural gas. The process employs a closed-loop single mixed refrigerant process for refrigeration duty. The refrigerant compressed to a high pressure using at least three stages of compression and two intercoolers (both producing liquid). A hydraulic turbine is used to expand the high pressure refrigerant before it flows into the main heat exchanger.

1 .- 25 . (canceled) 
     
     
         26 . A method for liquefying a hydrocarbon stream using a mixed refrigerant, the method comprising:
 (a) cooling and condensing the hydrocarbon stream and a cooled two-phase high pressure refrigerant stream in a main heat exchanger against an expanded refrigerant stream to form a liquefied hydrocarbon stream, a condensed refrigerant stream, and a vaporized refrigerant stream;   (b) expanding the condensed refrigerant stream to form the expanded refrigerant stream, wherein at least a portion of the expansion is performed using a hydraulic turbine;   (c) compressing the vaporized refrigerant stream in a first compression stage to a first pressure to form a low pressure compressed refrigerant stream;   (d) cooling the low pressure compressed refrigerant stream in a first ambient cooler to form a cooled two-phase refrigerant stream;   (e) separating a combined cooled two-phase refrigerant stream into a first cooled vapor stream and a first cooled liquid stream;   (f) compressing the first cooled vapor stream in a second compression stage to a second pressure to form a medium-pressure compressed stream;   (g) pumping the first cooled liquid stream to a third pressure to form a pumped first cooled liquid stream;   (h) cooling the medium-pressure compressed stream in a second ambient cooler to form a cooled medium-pressure compressed stream;   (i) separating the cooled medium pressure compressed stream into a second cooled vapor stream and a second cooled liquid stream;   (j) compressing the second cooled vapor stream in a third compression stage to the third pressure to form a two-phase high-pressure compressed stream;   (k) combining the pumped first cooled liquid stream with the two-phase high-pressure compressed stream to form a combined two-phase high-pressure compressed stream;   (l) cooling the combined two-phase high-pressure compressed stream in a third ambient cooler to form the cooled two-phase high-pressure compressed stream;   (m) expanding the second cooled liquid stream through an expansion valve to form an expanded cooled stream; and,   (n) combining the expanded cooled stream with the cooled two-phase refrigerant stream to form the combined cooled two-phase refrigerant stream.   
     
     
         27 . The method of  claim 26 , wherein the expansion of step (b) is provided by a hydraulic turbine followed by an expansion valve. 
     
     
         28 . The method of  claim 26 , wherein the second compression stage operates at a temperature of approximately 96.8° F. 
     
     
         29 . The method of  claim 26 , wherein the expanded refrigerant stream provides the sole refrigeration duty for step (a). 
     
     
         30 . The method of  claim 26 , wherein the flow of the refrigerant in steps (a) through (n) defines a closed loop refrigeration cycle and all of the refrigerant flows through the hydraulic turbine in step (l). 
     
     
         31 . The method of  claim 26 , wherein the main heat exchanger comprises a warm bundle and a cold bundle contained within separate shells. 
     
     
         32 . The method of  claim 26 , wherein the main heat exchanger additionally comprises a middle bundle located between the warm bundle and the cold bundle. 
     
     
         33 . The method of  claim 26 , wherein the hydrocarbon stream comprises natural gas. 
     
     
         34 . The method of  claim 26 , wherein the main heat exchanger comprises a warm end and a cold end and the expanded refrigerant stream is introduced into the main heat exchanger at the cold end. 
     
     
         35 .- 36 . (canceled)