3 replies to this topic

[bob789]

hi,


i am doing a group design project, where we can design a process to remove oxygen from air. We have decided to base our project our cryogenic removal of oxygen from air but at same time will have to discuss our reasons behind not going with processes like pressure swing absorbtion, membrane separation, low power electrolytic processes. I have been left with the task gathering as much information about the cryogenic process and the other ones.

i was wondering if anyone could could guide me and help me out with information on these processes, i have been in the university library and there is some brief stuff about wat is a cryogenic process and nothing more, and thats why now i have resulted to the net!

thanks

[riven]

Very fast reply on membranes.

First pressure swing adsorption or absorption?

Second membrane separation.
Current state of the art in membrane processing arguably focuses on the use of facilitated transport membranes such as palladium membranes. These membranes use a chemical reaction to enhance the transport of one of the components (oxygen, hydrogen or even CO2 depending on specifics of membrane). While the ultimate aim of these membranes is to operate a ambient or close to ambient temperatures, permeability’s at these temperatures are extremely low. Thus high areas are needed and Pd is not cheap. Currently thus these membranes are being tested (not aware of any commercial process) at temperatures in the region of 650 to 1000C. Not a cheap equipment design.
Furthermore there are other issues. Pd membranes are fragile so how do you install them into a module (similar to that of a shell and tube exchanger). I am aware of no commercially available process for sealing Pd membranes though there are quite a number under licence or in development.
Also the stability of these membranes has not been demonstrated. Pd is quite easy to poison. Also impurities like CO or CO2 could simply block the membrane pores.
Another issue is their manufacture. Stabilisation time of the membrane after manufacture (per tube I guess average manufacture time is approx 1 week+) is not uniform and currently not repeatable. Some samples need to be stabilised for weeks, some only require a day.

Membrane process for cryogenic separation of air or recovery of oxygen is a long term goal of research. Despite the likes of articles from universities which appear very positive, the technical, economic and hell safety aspects of the process have yet to be proven. There is some ability but humans are always optimistic about pessimistic situations. Give it 10 years for first pilot.

[Art Montemayor]

Bob:

It is exceedingly difficult for me to accept a statement that an engineering student cannot find any information on Oxygen production within a U.K. University. Great Britain contains tons of technical information within its university libraries.

Tell us specifically what University you attend in Great Britain and what technical resources you have researched with no results. I am sure that our members can help you find the information you seek within the U.K. I started my engineering career in Industrial Gases and operating Air Separation Columns for the bulk production of liquid Oxygen and liquid Nitrogen was one of my initial assignments. I know the industry well - here and in the U.K. I dare say that there is literally tons of information on the subject.

[astro]

Bob, I'd agree with Art, you don't appear to have tried very hard. I threw out this search:
Keywords: air separation cryogenic

One find in that search (towards the top of the first page) was this paper:
ASU Process Description, PFD & HMB

How's that for dishing it up for you? Hopefully this gets you more than just started. If you ask me your job is almost done and dusted.

When you've digested the plethora of data that is in fact literally at your fingertips, let us know if you need any gaps filled. All the best.