Method for cooling a single-component or multi-component stream

Abstract

The invention relates to a method for cooling a single-component or multi-component stream, in particular a hydrocarbon-rich fraction, by indirect heat exchange with the refrigerant mixture of a refrigerant mixture circuit. The refrigerant mixture is compressed in at least two stages and is separated into a lower-boiling refrigerant mixture fraction compressed to the ultimate pressure of the refrigerant mixture circuit and at least one higher-boiling refrigerant mixture fraction compressed to an intermediate pressure. The latter is pumped (P 11 ) to the pressure of the former and the two fractions are combined before or immediately on commencement of indirect heat exchange.

1 . A method for cooling a single-component or multi-component stream, said method comprising:
 cooling a single-component or multi-component stream by indirect heat exchange with a refrigerant mixture of a refrigerant mixture circuit,   compressing said refrigerant mixture in at least in two stages and separating said refrigerant mixture into a lower-boiling refrigerant mixture fraction, compressed to the ultimate pressure of the refrigerant mixture circuit, and at least one higher-boiling refrigerant mixture fraction, compressed to an intermediate pressure,   pumping (P 11 ) said higher-boiling refrigerant mixture fraction ( 5 ) to the pressure of said lower-boiling refrigerant mixture fraction ( 8 ), and   combining said higher-boiling refrigerant mixture fraction with said lower-boiling refrigerant mixture fraction ( 8 ) before or immediately on commencement of indirect heat exchange with said single-component or multi-component stream (E 1 ).   
     
     
         2 . The method according to  claim 1 , wherein the pumping (P 11 ) of said higher-boiling refrigerant mixture fraction ( 5 ) takes place in a single-stage manner. 
     
     
         3 . The method according to  claim 1 , wherein the pumping (P 11 ) of said higher-boiling refrigerant mixture fraction ( 5 ) takes place in a multi-stage manner. 
     
     
         4 . The method according to  claim 1 , wherein the combining of the higher-boiling ( 5 ′) and lower-boiling ( 5 ′) refrigerant mixture fractions takes place in a region of the heat exchanger (E 1 ) which is designed especially for this purpose. 
     
     
         5 . The method according to  claim 2 , wherein the combining of the higher-boiling ( 5 ′) and lower-boiling ( 5 ′) refrigerant mixture fractions takes place in a region of the heat exchanger (E 1 ) which is designed especially for this purpose. 
     
     
         6 . The method according to  claim 3 , wherein the combining of the higher-boiling ( 5 ′) and lower-boiling ( 5 ′) refrigerant mixture fractions takes place in a region of the heat exchanger (E 1 ) which is designed especially for this purpose. 
     
     
         7 . The method according to  claim 1 , wherein the higher-boiling ( 5 ′) and lower-boiling ( 5 ′) refrigerant mixture fractions are combined to form a combined mixture stream which is a two-phase stream, said combined mixture stream is then cooled and condensed in the heat exchanger (E 1 ), and then said combined mixture stream is expanded and subsequently evaporated in the heat exchanger (E 1 ) while cooling said single-component or multi-component stream by indirect heat exchange. 
     
     
         8 . The method according to  claim 7 , wherein the combined mixture stream is compressed in a first compressor stage to said intermediate pressure, delivered to a first separator (D 11 ), and said higher-boiling refrigerant mixture fraction is drawn off from the sump of said first separator (D 11 ) and subjected to said pumping (P 11 ) whereby its pressure is increased to the pressure of said lower-boiling refrigerant mixture fraction ( 8 ). 
     
     
         9 . The method according to  claim 8 , wherein a gas phase drawn off from said first separator (D 11 ), delivered to a second compressor stage and compressed to the desired ultimate pressure of the refrigerant mixture circuit, the resultant compressed gas is fed to a second separator (D 12 ), and said lower-boiling gaseous refrigerant mixture fraction is removed from the head of said second separator (D 12 ) and subsequently combined with said higher-boiling refrigerant mixture fraction. 
     
     
         10 . The method according to  claim 9 , wherein a liquid fraction removed from the sump of said second separator (D 12 ) is expanded and then recycled back to said first separator (D 11 ). 
     
     
         11 . The method according to  claim 1 , wherein said single-component or multi-component stream is a hydrocarbon-rich fraction. 
     
     
         12 . The method according to  claim 11 , wherein said hydrocarbon-rich fraction contains which contains nitrogen, said hydrocarbon-rich fraction is condensed by said indirect heat exchange with said refrigerant mixture, and a concentrated nitrogen fraction recovered from the condensed hydrocarbon-rich fraction.