System and apparatus for providing low pressure and low purity oxygen
A hybrid system which utilizes high purity oxygen from a local pipeline, which is blended with low purity oxygen from an on-site or local cryogenic distillation system, thus resulting in a blend of intermediate quality which satisfies the needs of the customer. In order to offset the operating and energy costs associated with this fairly low profit margin intermediate purity oxygen, high purity nitrogen at high pressure is simultaneously exported to the local pipeline, thereby acting as a credit to the overall system.
1. A method for providing low pressure and low purity oxygen, comprising:
a) providing a cryogenic distillation system, wherein said cryogenic distillation system produces a first liquid oxygen stream and a liquid nitrogen stream, wherein said first liquid oxygen stream is at a first pressure;
b) providing a second oxygen vapor stream, wherein said second oxygen vapor stream has a higher purity and a higher pressure than said first liquid oxygen stream, said second oxygen vapor stream coming from a pipeline;
c) cooling and reducing the pressure of said second oxygen vapor stream to approximately said first pressure, thereby at least partially condensing said second oxygen stream;
d) combining said at least partially condensed second oxygen stream and said first liquid oxygen stream to produce an intermediate purity liquid oxygen;
e) vaporizing said intermediate purity liquid oxygen in a first indirect heat exchanging device, thereby producing an intermediate purity oxygen vapor stream;
f) increasing the pressure of said liquid nitrogen stream by a pressure increasing device, thereby producing a high pressure liquid nitrogen stream; and
g) exchanging heat between cooling gaseous feed air to said cryogenic distillation system, said cooling second oxygen vapor stream, said high pressure liquid nitrogen stream, and said warming intermediate purity oxygen vapor stream, in a second heat exchanging device, thereby producing a warm intermediate purity oxygen vapor stream, and a vaporized high pressure nitrogen stream.
2. The method of claim 1 , wherein the pressure of said first liquid oxygen stream is increased prior to combining with the at least partially condensed second oxygen stream.
3. The method of claim 1 , wherein said intermediate purity liquid oxygen is vaporized by condensing a portion of feed air.
4. The method of claim 1 , wherein said cryogenic distillation system further comprises a high pressure column and a low pressure column.