Process and device for production of nitrogen

Claim 1

In a process for production of nitrogen by low-temperature rectification of air wherein an air feed stream is compressed and divided into a first partial stream and a second partial stream, said first partial stream is cooled and fed to an elongated vertical rectification zone having an upper part and a lower part, and a nitrogen product stream is discharged from the upper part of said rectification zone, the improvement wherein said second partial stream is separately further compressed, cooled, expanded and also fed to said rectification zone; said first partial stream, before being fed into said rectification zone, is brought into indirect heat exchange with a bottom liquid of said rectification zone; and said bottom liquid is brought into heat exchange with nitrogen gas at the head of said rectification zone whereby bottom liquid evaporates to form a residual gas and said nitrogen gas partially condenses, and at least a portion of said residual gas is used for regeneration of a purification stage for purifying said air feed stream, said purification stage being upstream of the division of said air feed stream.

Claim 17

An apparatus for production of nitrogen by low-temperature rectification, comprising: a first compressing means for compressing an air feed stream; a single-stage rectification column; a feed conduit in fluid communication with said first compressor and said rectification column; a branch conduit connected to said feed conduit upstream of said rectification column for dividing the air feed stream into a first partial stream, which flows through said feed conduit, and a second partial stream, which flows through said branch conduit; said branch conduit communicating with a second compressing means, a heat exchange means for cooling said second partial stream, expansion means for expanding resultant cooled second partial stream, and said rectification column; said feed conduit communicating with a heat exchange means wherein said first partial stream undergoes heat exchange with separation products from said rectification, and communicating with a second heat exchange means, prior to delivery of said first partial stream to said rectification column, wherein said first partial stream undergoes heat exchange with a bottom liquid from said rectification column; wherein an upper section of said rectification column is provided with an evaporator-condenser for evaporating a bottom liquid from said rectification column to form a residual gas stream and for partially condensing nitrogen gas; and further comprising conduit means communicating with the bottom of said rectification column and heat exchange means wherein bottom liquid from said rectification column undergoes heat exchange with said residual gas stream prior to evaporation of said bottom liquid in said evaporator-condenser.

Claim 18

An apparatus for production of nitrogen by low-temperature rectification, comprising: a first compressing means for compressing an air feed stream; a single-stage rectification column; a feed conduit in fluid communication with said first compressor and said rectification column; a branch conduit connected to said feed conduit upstream of said rectification column for dividing the air feed stream into a first partial stream, which flows through said feed conduit, and a second partial stream, which flows through said branch conduit; said branch conduit communicating with a second compressing means, a heat exchange means for cooling said second partial stream, expansion means for expanding resultant cooled second partial stream, and said rectification column; said feed conduit communicating with a heat exchange means wherein said first partial stream undergoes heat exchange with separation products from said rectification, and communicating with a second heat exchange means, prior to delivery of said first partial stream to said rectification column, wherein said first partial stream undergoes heat exchange with a bottom liquid from said rectification column; wherein an upper section of said rectification column is provided with an evaporator-condenser for evaporating a bottom liquid from said rectification column to form a residual gas stream and for partially condensing nitrogen gas; and further comprising conduit means communicating with the bottom of said rectification column and heat exchange means wherein bottom liquid from said rectification column undergoes heat exchange with said residual gas stream prior to evaporation of said bottom liquid in said evaporator-condenser.