Method for the production of air gases by the cryogenic separation of air with improved front end purification and air compression

Patent metadata

Field	Value
Publication number	US-11619443-B2
Application number	US-202017122227-A
Country	US
Kind code	B2
Filing date	Dec 15, 2020
Priority date	Mar 25, 2016
Publication date	Apr 4, 2023
Grant date	Apr 4, 2023

Abstract

A method and apparatus for the production of air gases by the cryogenic separation of air with front end purification and air compression can include using an available compressed dry gas such as nitrogen, oxygen, stored purified air, or synthetic air to repressurize the adsorber without diverting any of the purified air just exiting the currently on-line adsorber or changing the flow rate of the main air compressor or air sent to the cold box. This enables the main air compressor (MAC) to operate at a relatively constant flow rate while also sending a relatively constant air flow to the cold box during this repressurization step, thereby reducing the risks of process upsets and minimizing capital expenditures related to the MAC and other warm-end equipments.

First claim

We claim:

1. A method for reducing process disturbances during pressurization of an adsorber in an air separation unit, wherein the air separation unit comprises a front end purification unit, a main air compressor, a cold box having a main heat exchanger and a distillation column system disposed therein, and an air buffer tank, wherein the front end purification unit comprises a first adsorber and a second adsorber, the method comprising the steps of:
pressurizing the first adsorber while the second adsorber operates in an adsorption cycle, wherein the step of pressurizing the first adsorber further comprises the steps of withdrawing a pressurized air stream from the air buffer tank and introducing the pressurized air stream to the first adsorber until the first adsorber is at a target pressure,
wherein the air buffer tank is in fluid communication with an outlet of the front end purification unit, wherein the method further comprises the step of continually sending a first portion of purified air flow from the front end purification unit to the air buffer tank,
wherein the first portion of purified air flow from the front end purification unit is between 0.3% to 1% of total air flowing into a booster air compressor.

2. The method as claimed in claim 1 , wherein the first portion of purified air flow is first compressed in a booster air compressor prior to being sent to the air buffer tank.

3. A method for reducing process disturbances during pressurization of an adsorber in an air separation unit, wherein the air separation unit comprises a front end purification unit, a main air compressor, a cold box having a main heat exchanger and a distillation column system disposed therein, a booster air compressor, and an air buffer tank, wherein the front end purification unit comprises a first adsorber and a second adsorber, the method comprising the steps of:
compressing an air stream in a main air compressor to form a compressed main air stream;
purifying the compressed main air stream in the front end purification unit to remove water and carbon dioxide to form a dry main air stream;
sending a first portion of the dry main air stream to the cold box for cooling and rectification therein;
boosting a second portion of the dry main air stream to a higher pressure PH in the booster air compressor to produce a boosted air stream; and
sending the boosted air stream to the air buffer tank,
wherein each of the adsorbers of the front end purification unit undergoes a processing cycle comprising a regeneration cycle, a pressurization cycle, and an adsorption cycle,
wherein during the pressurization cycle, a pressurized air stream is withdrawn from the air buffer tank and introduced to the adsorber that is undergoing pressurization,
wherein the flow rate of the boosted air stream sent to the air buffer tank is between 0.3% to 1% of the flow rate of the dry main air stream.

4. The method as claimed in claim 3 , wherein the pressurized air stream is only withdrawn from the air buffer tank and introduced to the adsorber during the pressurization cycle.

5. The method as claimed in claim 3 , wherein the boosted air stream is sent to the air buffer tank at a constant rate during the processing cycle of the front end purification unit.

Assignees

• Air Liquide

Inventors

• Kong Paul
• Pham-Huy Minh
• Yip Wendy

Classifications

• Y02C20/40

  of CO2 · CPC title

• F25J2245/50

  the recycled stream being oxygen · CPC title

• F25J2290/62

  Details of storing a fluid in a tank · CPC title

• F25J2215/02

  Mixing or blending of fluids to yield a certain product · CPC title

• F25J3/04181 Primary

  Regenerating the adsorbents · CPC title