Method for operating an air separation plant

Patent metadata

Field	Value
Publication number	US-10260801-B2
Application number	US-201615382910-A
Country	US
Kind code	B2
Filing date	Dec 19, 2016
Priority date	Jun 30, 2016
Publication date	Apr 16, 2019
Grant date	Apr 16, 2019

Abstract

A method for the production of air gases with variable liquid production by the cryogenic separation of air can include the steps of sending a purified and compressed air stream to a cold box under conditions effective for cryogenically separating the air stream into an oxygen product and nitrogen using a system of columns, wherein the purified and compressed air stream is at a feed pressure when entering the system of columns; withdrawing the oxygen product at a product pressure; delivering the oxygen product at a delivery pressure to an oxygen pipeline, wherein the oxygen pipeline has a pipeline pressure; wherein during the second mode of operation, the method can include monitoring the pipeline pressure; reducing the difference between the pipeline pressure and the delivery pressure; and adjusting liquid production from the cold box. By operating the method in a dynamic fashion, additional liquid production can be realized in instances in which the pipeline pressure deviates from its highest value.

First claim

We claim:

1. A method for the production of air gases with variable liquid production by the cryogenic separation of air, the method comprising the steps of:
a) compressing air to a pressure suitable for the cryogenic rectification of air to produce a compressed humid air stream, the compressed humid air stream having a first pressure P o ;
b) purifying the compressed humid air stream of water and carbon dioxide within a front end purification system to produce a dry air stream having reduced amounts of water and carbon dioxide as compared to the compressed humid air stream;
c) compressing a first portion of the dry air stream in a booster compressor to form a boosted air stream, the boosted air stream having a first boosted pressure P B1 ;
d) introducing a second portion of the dry air stream and the boosted air stream to a cold box under conditions effective to separate air to form an air gas product, wherein the air gas product is selected from the group consisting of oxygen, nitrogen, and combinations thereof;
e) withdrawing the air gas product from the cold box, the air gas product having a first product pressure P P1 ;
f) introducing the air gas product to a pipeline, wherein the pipeline is configured to transport the air gas product to a location located downstream of the pipeline, wherein the pipeline operates at a pipeline pressure P PL , wherein the air gas product is introduced to the pipeline at a first delivery pressure P D1 ;
g) monitoring the pipeline pressure P PL within the pipeline;
h) adjusting one or more pressure set points within the cold box based on the pipeline pressure P PL , wherein the one or more pressure set points of the apparatus is selected from the group consisting of the first boosted pressure P B1 of step c), the first pressure P 0 of step a), and combinations thereof;
i) monitoring liquid product data, wherein the liquid product data is selected from the group consisting of local liquid inventory of liquid nitrogen, local inventory of liquid oxygen, spot pricing data for liquid nitrogen, spot pricing data for liquid oxygen, and combinations thereof; and
j) adjusting liquid production from the cold box based on the liquid product data monitored in step i).

2. The method as claimed in claim 1 , further comprising the step of adjusting the first product pressure P P1 based on the monitored pipeline pressure P PL .

3. The method as claimed in claim 1 , wherein the first boosted pressure P B1 is kept substantially constant during steps h) and i).

4. The method as claimed in claim 1 , wherein the cold box comprises a main heat exchanger, a system of columns having a double column composed of a lower pressure column and a higher pressure column, a condenser disposed at a bottom portion of the lower pressure column, and a liquid air gas pump selected from the group consisting of a liquid oxygen pump, a liquid nitrogen pump, and combinations thereof.

5. The method as claimed in claim 4 , wherein the air gas product is oxygen and the pipeline is an oxygen pipeline.

6. The method as claimed in claim 5 , further comprising the liquid oxygen pump, wherein the liquid oxygen pump pressurizes liquid oxygen from the lower pressure column to the first product pressure P P1 .

7. The method as claimed in claim 4 , wherein the air gas product is nitrogen and the pipeline is a nitrogen pipeline.

8. The method as claimed in claim 7 , further comprising the liquid nitrogen pump, wherein the liquid nitrogen pump pressurizes liquid nitrogen from the higher pressure column to the first product pressure P P1 .

9. The method as claimed in claim 1 , wherein the first product pressure P P1 is adjusted based upon the monitored pipeline pressure P PL .

10. The method as claimed in claim 1 , wherein the liquid production from the cold box is a liquid selected from the group consisting of liquid nitrogen, liquid oxygen, and combinations thereof.

11. The method as claimed in claim 1 , wherein a process controller, in communication with a plurality of flow indicators, pressure indicators, and control valves, is configured to perform steps g) through i).

12. A method for the production of air gases by the cryogenic separation of air, the method comprising a first mode of operation and a second mode of operation, wherein during the first mode of operation and the second mode of operation, the method comprises the steps of:
compressing air, in a main air compressor, to a pressure suitable for the cryogenic rectification of air to produce a compressed humid air stream, the compressed humid air stream having a first pressure Po;
purifying the compressed humid air stream of water and carbon dioxide within a front end purification system to produce a dry air stream having reduced amounts of water and carbon dioxide as compared to the compressed humid air stream;
compressing a first portion of the dry air stream in a booster compressor to form a boosted air stream, the boosted air stream having a first boosted pressure P B1 ;
sending boosted air stream and the remaining portion of the dry air stream to a cold box under conditions effective for cryogenically separating the air stream to form a gaseous air gas product using a system of columns, wherein the purified and compressed air stream is at a feed pressure P F when entering the cold box, wherein the air gas product is selected from the group consisting of oxygen, nitrogen, and combinations thereof;
withdrawing the gaseous air gas product from the cold box at a product pressure P PO ;
delivering the gaseous air gas product at a delivery pressure P DO to an air gas pipeline, wherein the air gas pipeline has a pipeline pressure P PL ;
monitoring the pipeline pressure P PL ;

wherein during the second mode of operation, the method further comprises the steps of:
reducing the difference between the pipeline pressure P PL and the delivery pressure P DO ; and

monitoring liquid product data, wherein the liquid product data is selected from the group consisting of local liquid inventory of liquid nitrogen, local inventory of liquid oxygen, spot pricing data for liquid nitrogen, spot pricing data for liquid oxygen, and combinations thereof; and
adjusting liquid production from the cold box based on the monitored liquid product data,
wherein the step of reducing difference between the pipeline pressure P PL and the delivery pressure P DO further comprises adjusting one or more pressure set points within the cold box based on the pipeline pressure P PL , wherein the one or more pressure set points is selected from the group consisting of the first boosted pressure P B1 , the first pressure P 0 , and combinations thereof.

13. The method as claimed in claim 12 , wherein the step of reducing difference between the pipeline pressure P PL and the delivery pressure P DO further comprises adjusting the product pressure P PO .

14. The method as claimed in claim 12 , wherein the product pressure P PO and the delivery pressure P DO are substantially the same.

15. The method as claimed in claim 12 , wherein the air gas product is oxygen, wherein the cold box comprises a main heat exchanger, a system of columns having a double column composed of a lower pressure column and a higher pressure column, a condenser disposed at a bottom portion of the lower pressure column, and a liquid oxygen pump.

16. The method as claimed in claim 12 , wherein a process controller, in communication with a plurality of flow indicators, pressure indicators, and control valves, is configured to perform the steps in the second mode of operation.

Assignees

• Air Liquide
• Lair Liquide Sa Pour Letude Et Lexploitation Des Procedes George Claude

Inventors

• Kong Paul
• Pham-Huy Minh
• Yip Wendy

Classifications

• F25J3/04412 Primary

  in a classical double column flowsheet, i.e. with thermal coupling by a main reboiler-condenser in the bottom of low pressure respectively top of high pressure column · CPC title

• F25J2290/60

  Details about pipelines, i.e. network, for feed or product distribution · CPC title

• F25J3/04527

  Integration with an oxygen consuming unit, e.g. glass facility, waste incineration or oxygen based processes in general · CPC title

• F25J3/04836

  Variable air feed, i.e. "load" or product demand during specified periods, e.g. during periods with high respectively low power costs (F25J3/0483 takes precedence) · CPC title

• F25J3/04296

  Claude expansion, i.e. expanded into the main or high pressure column · CPC title