Method and apparatus for separating air by cryogenic distillation

Patent metadata

Field	Value
Publication number	US-9562716-B2
Application number	US-201214366701-A
Country	US
Kind code	B2
Filing date	Dec 13, 2012
Priority date	Dec 21, 2011
Publication date	Feb 7, 2017
Grant date	Feb 7, 2017

Abstract

An apparatus for separating air by cryogenic distillation comprises N air compressors (C 1 , C 2 , C 3 ) connected so as to receive air at ambient pressure and designed to produce air at a first pressure above 12 bar absolute, N being at least 3, each of the compressors being driven by a single asynchronous motor (M 1 , M 2 , M 3 ), the total power of the compressors being at least 10 MW.

First claim

The invention claimed is:

1. A method for separating air by cryogenic distillation, the method comprising the steps of:
i) sending N flows of air at approximately ambient pressure each to one of N air compressors;
ii) compressing the air using each of the N compressors to a first pressure above 12 bar absolute and below 35 bar absolute, N being equal to or greater than 3 and the total power of the N compressors being greater than 10 MW;
iii) sending the air at the first pressure from the N compressors to a single purification unit in order to remove water and carbon dioxide and cooling the air in the purification unit before sending the cooled air to a single system of columns in a single cold box where the cooled air is separated by cryogenic distillation;
iv) extracting an enriched flow from the system of columns, wherein the enriched flow is selected from the group consisting of an oxygen-enriched flow, a nitrogen-enriched flow, and combinations thereof;
v) sending the air from each of the N compressors to the system of columns through the purification unit, without sending the air at the first pressure to an air booster driven by a motor or a steam turbine; and
vi) driving each of the N compressors by a single motor, these N motors being asynchronous and having a maximum power below 25 MW.

2. The method according to claim 1 , in which all the air sent to the system of columns comes from the N compressors.

3. The method according to claim 1 , in which N is equal to 4, 5, 6, 7, 8, 9 or 10.

4. The method according to claim 1 , in which the N air compressors each send no more than 100%/N of the air that the N air compressors compress to the system of columns.

5. The method according to claim 1 , in which each of the compressors sends at least 90% of the air that each compressor compresses to the system of columns, or to the same column in the system of columns.

6. The method according to claim 1 , in which at least some of the air flow from each compressor is expanded before being sent to the system of columns.

7. The method according to claim 1 , in which each of the motors is connected to a starter of a given type, the type of starter for each motor being either direct or by reactance or auto transforming.

8. The method according to claim 1 , in which the total power of the N compressors is less than 25 MW.

9. The method according to claim 1 , in which the total power of the N compressors is greater than 25 MW.

10. The method according to claim 1 , in which the total power of the N compressors is greater than 40 MW.

11. An apparatus for air separation by cryogenic distillation, the apparatus comprising:
a single system of columns in a single cold box;
N air compressors configured to receive air at ambient pressure and designed to produce air at a first pressure above 12 bar absolute, N being at least equal to 3, wherein each of the compressors is configured to be driven by a single asynchronous motor, the total power of the compressors being at least 10 MW;
a single purification unit configured to purify air at the first pressure coming from the N compressors;
pipes configured to send purified air from the purification unit to the system of columns, a pipe for taking off a nitrogen-enriched flow from the system of columns; and
a pipe configured to remove an oxygen-enriched flow from the system of columns, the apparatus comprising an absence of a motor or steam turbine driving an air booster.

12. An apparatus according to claim 11 , in which each of the compressors comprises at least 4 stages.

Assignees

• Air Liquide
• L'Air Liquide Société Anonyme Pour L'Étude Et L'Exploitation Des Procedes Georges Claude

Inventors

• Guillard Alain

Classifications

• F25J3/04866

  Construction and layout of air fractionation equipments, e.g. valves, machines (F25J5/00 takes precedence) · CPC title

• F25J3/04

  for air · CPC title

• F25J2230/24

  Multiple compressors or compressor stages in parallel · CPC title

• F25J3/04133

  Electrical motor as the prime mechanical driver · CPC title

• F25J3/04018

  of main feed air · CPC title