Method for cooling a gaseous mixture to a low temperature

Abstract

.Iadd. .Iadd.8. A method for cooling a second gaseous mixture to low temperature and producing at least one constituent of said mixture in liquid phase, comprising: a. cooling and subjecting first gaseous mixture containing at least one component of said secong gaseous mixture, to a fractionate condensation under a first pressure, b. expanding at least two condensed fractions obtained during the fractionate condensation of said first gaseous mixture, reuniting the expanded condensed fractions with said first gaseous mixture under a second pressure lower than said first pressure, vaporizing and reheating the reunited fractions with said first gaseous mixture under said second pressure, by heat exchange with said second gaseous mixture undergoing cooling, and with said first gaseous mixture undergoing fractionate condensation, and recompressing said first gaseous mixture to said first pressure, c. reuniting under said first pressure said second gaseous mixture undergoing cooling with said first gaseous mixture undergoing fractionate condensation, when said gaseous mixture is in conditions of temperature and pressure such that a major portion of said constituent to be produced in liquid phase is condensed within said second gaseous mixture, and after the first condensed fraction of said first gaseous mixture has been withdrawn for expansion and vaporization, continuing the fractionate condensation of the mixture so obtained under said first pressure until there is obtained a last condensed fraction containing a major part of said constituent to be produced in liquid phase, d. expanding to said second pressure the last condensed fraction, and separating the last expanded fraction into a liquid portion expanded to a pressure lower than said second pressure and a residual gaseous portion for recompression with said first gaseous mixture, and withdrawing said last expanded liquid portion as a product stream, and e. prior to reuniting said first gaseous mixture and said second gaseous mixture, condensing at least partially said second gaseous mixture under a third pressure which is higher than said first pressure, and expanding said second gaseous mixture at least partially condensed to said first pressure. .Iaddend.

What we claim is:  .[.1. In a method for cooling a gaseous mixture to low temperature and producing at least one constituent of this mixture in liquid phase, comprising subjecting a first gaseous mixture to a fractionate condensation in a plurality of heat-exchange stages with at least one of the condensed fractions being expanded to a first pressure and vaporized in heat exchange with said first gaseous mixture undergoing fractionate condensation, expanding to a second pressure said at least one constituent after its condensation and withdrawing said expanded constituent as product, said first pressure being substantially higher than said second pressure, thereafter recompressing said at least one fraction to a third pressure substantially higher than said first pressure, and recombining said recompressed fraction with said first gaseous mixture; the improvement comprising progressively cooling a second gaseous mixture in a plurality of heat-exchange stages with said first mixture, said second mixture having the same main components as said first mixture, and maintaining said first gaseous mixture with said second gaseous mixture separate at least until they are under conditions of temperature and pressure such that said constituent to be produced in liquid phase is at least mostly condensed within said second gaseous mixture and said at least one condensed fraction has been withdrawn from said first gaseous mixture for expansion and vaporization..].  .[.2. A method as claimed in claim 1, said second gaseous mixture being initially at a fourth pressure substantially higher than said third pressure..]. .[.3. A method as claimed in claim 1, in which said first gaseous mixture flows within a closed cycle and all the expanded and vaporized fractions separated from said first gaseous mixture are reunited to reconstitute said first gaseous mixture..]. .[.4. A method as claimed in claim 3, in which said second gaseous mixture is subjected to a fractionate condensation, and adding at least a part of a fraction separated from said second gaseous mixture during fractionate condensation to an expanded fraction of said first gaseous mixture undergoing vaporization, thereby to compensate for losses in said closed cycle and to adjust its composition..]. .[.5. A method as claimed in claim 3, and adding at least a fraction separated during the fractionate condensation of said first gaseous mixture to a fraction separated from said second gaseous mixture at such a flow rate as to adjust the composition of said first gaseous mixture..]. .[.6. A method of utilizing a first gaseous mixture at relatively low pressure to refrigerate a second gaseous mixture at relatively high pressure, comprising establishing a refrigeration cycle in which said first gaseous mixture is subjected to fractionate condensation in a plurality of heat exchange stages with at least one of the condensed fractions being expanded and vaporized in heat exchange with said first gaseous mixture undergoing fractionate condensation, then recompressed to said relatively low pressure and reunited with said first gaseous mixture, and progressively cooling said second mixture in a plurality of said heat exchange stages..]. .[.7. A method as claimed in claim 6, and combining said first and second gaseous mixtures downstream of a plurality of said 
     
        heat exchange stages..]. .Iadd.8.  A method for cooling a second gaseous mixture to low temperature and producing at least one constituent of said mixture in liquid phase, comprising: a. cooling and subjecting a first gaseous mixture containing at least one component of said second gaseous mixture, to a fractionate condensation under a first pressure,   b. expanding at least two condensed fractions obtained during the fractionate condensation of said first gaseous mixture, reuniting the expanded condensed fractions with said first gaseous mixture under a second pressure lower than said first pressure, vaporizing and reheating the reunited fractions with said first gaseous mixture under said second pressure, by heat exchange with said second gaseous mixture undergoing cooling, and with said first gaseous mixture undergoing fractionate condensation, and recompressing said first gaseous mixture to said first pressure,   c. reuniting under said first pressure said second gaseous mixture undergoing cooling with said first gaseous mixture undergoing fractionate condensation, when said gaseous mixture is in conditions of temperature and pressure such that a major portion of said constituent to be produced in liquid phase is condensed within said second gaseous mixture, and after the first condensed fraction of said first gaseous mixture has been withdrawn for expansion and vaporization, continuing the fractionate condensation of the mixture so obtained under said first pressure until there is obtained a last condensed fraction containing a major part of said constituent to be produced in liquid phase,   d. expanding to said second pressure the last condensed fraction, and separating the last expanded fraction into a liquid portion expanded to a pressure lower than said second pressure and a residual gaseous portion for recompression with said first gaseous mixture, and withdrawing said last expanded liquid portion as a product stream, and   e. prior to reuniting said first gaseous mixture and said second gaseous mixture, condensing at least partially said second gaseous mixture under a third pressure which is higher than said first pressure, and expanding said second gaseous mixture at least partially condensed to said first   
     
     
        pressure. .Iaddend. .Iadd.9.  In a method for cooling a second gaseous mixture to low temperature and producing at least one constituent of said mixture in liquid phase, comprising: a. cooling said second gaseous mixture until at least a major portion of said consituent to be produced in liquid phase is condensed within said second gaseous mixture, then expanding at least said condensed constituent to a first pressure,   b. cooling and subjecting a first gaseous mixture comprising at least one component of said second gaseous mixture, to a fractionate condensation under a second pressure which is higher than said first pressure,   c. expanding at least two condensed fractions obtained during the fractionate condensation of said first gaseous mixture, reuniting the expanded fractions with said first gaseous mixture under a third pressure which is intermediate said first and second pressures, vaporizing and reheating the reunited fractions with said first gaseous mixture under said third pressure by heat exchange with said second gaseous mixture undergoing cooling and with said first gaseous mixture undergoing fractionate condensation and recompressing said first gaseous mixture to said second pressure, the improvement comprising adjusting the composition of said first gaseous mixture in at least one component:   d. when there is an insufficient quantity of said component, subjecting said second gaseous mixture undergoing cooling to fractionate condensation, rectifying at least a part of a condensed fraction of said second gaseous mixture under at least a pressure intermediate said second and third pressure, adding at least a part of a fraction separated during said rectification to said first gaseous mixture, and   e. when there is an excess of said constituent, rectifying at least a part of a condensed fraction of said first gaseous mixture under at least a pressure intermediate said second and third pressures, and adding at least a part of a fraction separated during said rectification to said second gaseous mixture.