3 replies to this topic

[adw07]

Hi all,

I am designing an air separation unit (ASU) and carbon dioxide purification unit (CPU) for a 550 MW coal power plant.

The CPU unit is fairly straightforward, but I am having trouble getting to grips with the ASU.

There seem to be a lot of different variations, each with advantages and disadvantages, and I am struggling to find information about all of them.

Can anyone please point me in the direction of some good information about ASU design, where I can read about the best layouts, etc. Thanks

If anyone has done anything similar would appreciate any advice, diagrams, schematics, etc. Cheers

[Art Montemayor]

Adwo7:

What KIND of ASU are you designing? This is a very important point you fail to identify. There is no such thing as only one type of air separation unit. For example, are you principally interested in producing pure oxygen (99.5%+ vol.)? - or are you more interested in Nitrogen? - or Argon? Even if you want ALL of these components in their pure state, HOW do you want them and at what conditions? For example, do you want them as gases or as saturated liquids?

You are very wrong in stating that “The CPU unit is fairly straightforward”. It may be to you, but it certainly isn’t to your readers because we simply don’t know what it is that you want to produce.

Please take the time and make the effort to communicate concisely and in detail about what it is that you need to know. We want to help; but you must make the effort to help us help you.

[adw07]

Thanks for your reply - I will try to be more specific:

I am designing a cryogenic distillation process for the Air Separation Unit.

1) The aim is to produce high purity oxygen (~ 95-99%), as a gaseous feed for the power plant combustion unit.

2) There will be no constraint on nitrogen purity, as it will be turbo-expanded back to the atmosphere and used to cool the incoming air feed.

I have read that the standard configuration here is two columns - one at HP (4-8 bar) and one at LP (~ 1 bar).

I am trying to find the best feed position(s), arrangement of columns, column pressures etc. in order to satisfy my requirements stated in (1) & (2) above. Thanks for any help

[Art Montemayor]

Adw07:

Obtain a copy of the book:

Cryogenic Systems

Author: Randall Barron

McGraw-Hill publisher

1966

Library of Congress Card # 66-1583107-003820-1

This book will explain how the process design of an air separation column is done and gives you examples.

What you are undertaking (process design of an air separation column) has been done countless times – since the 1890’s, starting with Carl von Linde in 1898. So you are merely repeating what a lot of other people have already done – and “optimized”. If you use the SEARCH feature in our Forums, you will find a lot of write-ups and threads where I have discussed, sketched, and explained exactly what you propose – including Linde’s and Claude’s early and pioneering work on this subject.

99% vol. of Oxygen purity is NOT considered “high” purity gas. I have consistently produced 99.9% vol. Oxygen in a Linde Double Column 50 years ago. So you should be easily able to carry out this design. There is probably a lot of more design and details on air separation in the literature and publishing today – especially in the internet.

Good Luck.