Purification of nitrogen trifluoride by continuous cryogenic distillation

A process for recovering NF3 from a multicomponent fluid containing NF3 having a first volatility, one or more components less volatile than NF3, and one or more components more volatile than NF3, said process using a first distillation column and a second distillation column, each distillation column having a top and a bottom, comprising the steps of:

• feeding said multicomponent fluid to said first distillation column at a first feed location;
• removing said components less volatile than NF3 from the bottom of said first distillation column;
• withdrawing a mixture containing NF3 and said components more volatile than NF3 from said first distillation column at a location above said first feed location;
• feeding said mixture to said second distillation column at a second feed location;
• feeding a cryogenic liquid to said second distillation column at a location above said second feed location;
• removing said components more volatile than NF3 from the top of said second distillation column;
• and
• removing a stream of NF3 from the bottom of said second distillation column.

A process for recovering NF3 from a multicomponent fluid containing NF3 having a first volatility, one or more components less volatile than NF3, and one or more components more volatile than NF3, said process using a first distillation column and a second distillation column, each distillation column having a top and a bottom, comprising the steps of:

• feeding said multicomponent fluid to said first distillation column at a first feed location;
• feeding a cryogenic liquid to said first distillation column at a second feed location above said first feed location;
• removing said components more volatile than NF3 from the top of said first distillation column;
• withdrawing a mixture containing NF3 from said first distillation column at an intermediate location between said first feed location and said second feed location;
• feeding said mixture to said second distillation column at or near the top of said second distillation column;
• removing a vapor stream from the top of said second distillation column;
• feeding said vapor stream to said first distillation column at a location above the first feed location;
• removing a stream of NF3 from the bottom of said second distillation column;
• and
• removing said components less volatile than NF3 from the bottom of said first distillation column.

A process for recovering NF3 from a multicomponent fluid containing NF3 having a first volatility, one or more components less volatile than NF3, and one or more components more volatile than NF3, said process using a first distillation column and a second distillation column, each distillation column having a top and a bottom, comprising the steps of:

• feeding said multicomponent fluid to said first distillation column at a first feed location below the top of said first distillation column;
• feeding a cryogenic liquid to the top of a distillation column selected from the group consisting of said first or second distillation column;
• withdrawing a mixture containing NF3 from said first distillation column;
• feeding said mixture to said second distillation column at a second feed location;
• separating NF3 from said mixture in said second distillation column;
• and
• removing a stream of NF3 from said second distillation column.