7 replies to this topic

[raya0709]

Hello

 

Do anyone have idea of the typical number of stages in a cryogenic distillation column? I have carried out the Mccabe Thiele Method and I got 11 stages. If anyone can help me out will be of great help. Thanks. 

 

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Regards

raya0709

[thorium90]

There isnt a typical number. It is a calculated or estimated number. You gotta provide more details.

Edited by thorium90, 15 March 2013 - 12:08 AM.

[raya0709]

Hello

 

Thanks for replying. I'm in the midst of designing the column and I have read that, usually cryogenic columns are 10-stories high and big in diameter. I was just wondering if 11 stages sounds ridiculous. Also, now I'm confused if to design a binary continuous column or a double tower column. 

 

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Thanks & Regards

[thorium90]

you read from a book that cryogenic columns are usually 10-stories high and big in diameter? That book is not a good book to read. Definitely. Or you misunderstood it..

 

So why do you think 11 stages is ridiculous? Have you read it somewhere?

 

You are confused about what type of column to design? And why is that so?

[Art Montemayor]

Raya:

 

Thorium90 is absolutely correct.

 

First of all, you as a student must learn to be specific when you communicate with other engineers.  We only deal in specifics.  For example, are you referring to an air separation distillation column – or to natural gas liquids (NGL) separation?  Both are cryogenic operations.  Do you see what I mean?

 

Additionally, what capacity are you relating to?  It makes a big difference in determining the size of the required distillation column.  The type of internals and the size of separation between transfer stages also makes a big difference.

 

I have operated both air separation columns and NGL units.  One column I had in Piura, Peru was fabricated by Air Liquide and the cold box was made of mahogany wood.  It produced gaseous oxygen at 99.9% purity by volume and was approximately 9 feet tall.

 

I also operated Air Products air separation columns producing gas and liquid products in such countries as Jamaica, Trinidad, Lima-Peru, and even La Paz, Bolivia.  These columns varied in height, but the tallest was around 25 feet.  I have been involved in projects with much bigger columns – such as Messer and Linde.  These were much larger – around 35 – 40 feet hight.  I don’t know where you have your information about a column being 10 stories (100 feet) high.  Please be specific.

 

To proceed with your design simply apply the basic design criteria of determining  the correct number of stages, applying adequate and logical separation between stages, applying the Brown-Souders relationship for the column diameters and you should be OK.

 

If you want or need specific help, you must be specifc.

 

 

[raya0709]

Hello

 

First of all thanks for the replies and I apologize for not being specific. I'm attempting to design a cryogenic distillation column but I'm rather confused now if to design it as the double tower Linde distillation columns or as a binary continuous distillation column. I'm producing of oxygen purity 95 mole% and my inlet includes 79 mole% of nitrogen and 21 mole% of oxygen (assuming no argon). Concerning the 11 stages, I did a mass balance around the binary column and carried out the mccabe-thiele method and attained 11 theoretical stages. I do not have any idea of the typical number of stages in a cryogenic distillation column, but I've read in research papers that, cryogenic distillation column are usually expensive and tall in height with many stages. So, 11 stages sounded kind of ridiculous to me..

 

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Regards

[raya0709]

Sorry, I would like to add on that, the production of 95 mole% purity of liquefied oxygen is to feed it into a GE Gasifier, and that requires 2278 tonne of oxygen per day. 

[thorium90]

Perhaps what you mean is cryogenic distillation is expensive relative to the more common, "hotter" distillation due to the need to create the "cold". As for tall, all columns are taller than your average human....

Anyway, the point of your post is to find out if 11 theoretical stages can perform the job? Maybe you can post your spreadsheet here, Im sure Art would find it a joy to look at how you calculate for the double tower Linde distillation column.