Air separation method and apparatus to produce nitrogen

A method of separating air to produce a nitrogen product comprising:

• separating the air by a low temperature rectification process employing a distillation column to produce an oxygen rich liquid column bottoms and a nitrogen rich vapor tower overhead and a head condenser to condense at least part of the nitrogen rich vapor tower overhead to reflux said distillation column;
• said low temperature rectification process including:
• dividing an oxygen enriched liquid stream composed of said oxygen rich liquid column bottoms into first and second partial streams;
• expanding said first partial stream to create a temperature difference between said first partial stream and said nitrogen rich vapor tower overhead and introducing said first partial stream as a coolant stream into said head condenser so that heat is transferred from said at least part of the nitrogen rich vapor to said coolant stream thereby causing said condensation of said at least part of said nitrogen rich vapor tower overhead;
• vaporizing said second partial stream;
• expanding said second partial stream with the performance of work to produce a refrigerant stream utilized to at least partially refrigerate said low temperature rectification process;
• and
• extracting a product stream from a remaining part of said nitrogen rich vapor tower overhead not utilized in said distillation column as said reflux to form said nitrogen product.

An apparatus for separating air to produce a nitrogen product, said apparatus comprising:

• a filter for filtering the air;
• a compressor connected to the filter for compressing the air;
• an after-cooler for removing heat of compression from the air;
• a pre-purification unit for purifying the air;
• main heat exchange means for cooling the air to a temperature suitable for its rectification;
• a distillation column configured to rectify the air into an oxygen rich liquid column bottoms and a nitrogen rich vapor tower overhead;
• a head condenser connected to said distillation column to condense at least part of the nitrogen rich vapor tower overhead to reflux said distillation column;
• vaporization means for partially vaporizing an oxygen enriched liquid stream composed of said oxygen enriched liquid column bottoms;
• a phase separator connected to said vaporization means for separating said oxygen enriched liquid stream into liquid and vapor phases;
• said phase separator connected to said head condenser so that heat is transferred from said at least part of the nitrogen rich vapor to a coolant stream made up of a liquid phase stream composed of said liquid phase, thereby causing said condensation of said at least part of said nitrogen rich vapor tower overhead and vaporization of said coolant stream to form a vaporized coolant stream;
• a pressure reduction valve interposed between said phase separator and said head condenser to expand said liquid phase stream and thereby create said coolant stream and a temperature difference between said coolant stream and said nitrogen rich vapor tower overhead;
• said phase separator also connected to said main heat exchange means so that a vapor phase stream composed of said vapor phase partially warms;
• expansion means connected to said main heat exchange means for expanding said vapor phase stream with the performance of work to produce a refrigerant stream;
• said main heat exchange means in communication with said expansion means so that said refrigerant stream fully warms within said main heat exchange means;
• means for extracting a product stream composed of a remaining part of said nitrogen rich vapor tower overhead not utilized in said distillation column as said reflux to form said nitrogen product;
• and
• said main heat exchange means connected to said product stream extracting means so that said product stream fully warms within said main heat exchange means.

An apparatus for separating air to produce a nitrogen product, said apparatus comprising:

• a filter for filtering the air;
• a compressor connected to the filter for compressing the air;
• an after-cooler for removing heat of compression from the air;
• a pre-purification unit for purifying the air;
• main heat exchange means for cooling the air to a temperature suitable for its rectification;
• a distillation column configured to rectify the air into an oxygen rich liquid column bottoms and a nitrogen rich vapor tower overhead;
• a head condenser connected to said distillation column for condensing at least part of the nitrogen rich vapor tower overhead to reflux said distillation column against vaporizating a coolant stream made up of a first partial stream composed of said oxygen rich liquid column bottoms, thereby to form a vaporized coolant stream;
• a pressure reduction valve connected to said head condenser to expand said first partial stream and thereby to create said coolant stream and a temperature difference between said coolant stream and said nitrogen rich vapor tower overhead;
• vaporization means for vaporizing a second partial stream composed of said oxygen rich liquid column bottoms;
• said vaporization means connected to said main heat exchange means so that said second partial stream partially warms;
• expansion means connected to said main heat exchange means for expanding said second partial stream with the performance of work to produce a refrigerant stream;
• said main heat exchange means in communication with said expansion means so that said refrigerant stream fully warms within said main heat exchange means;
• means for extracting a product stream composed of a remaining part of said nitrogen rich vapor tower overhead not utilized in said distillation column as said reflux to form said nitrogen product;
• and
• said main heat exchange means connected to said product stream extracting means so that said product stream fully warms within said main heat exchange means.