Limits for tall columns H/L Ratios and Overall

[jamesbanda]

I'm looking for some overall reference for guideance for when it is economic to split a column into two or when you just make the design MUCH taller..

For example when you have a 1.8 meter 60 meter tall and want many more stages:
> is it still economic to go for 80 meters by 1.8 tall ?
> at that stage do you go for two 40 meter tall columns ?

> Or say for 100 meter tall columns etc..?

I guess it is always more cost effective to go with a single trayed column..but what really sets the boundaries..? civil foundations bending moments.. safe wind loads..as by the time you have purchased two columns, spare pumps etc.. the cost for two columns is much more.

I guess like a pen so to speak that you have limits which are unsafe to design..? it seems to make pratical sence for this.. I've yet to see a reference or guidelines I've only completed designs after the decisions were made about no of columns etc..

Comments appreciated..

 

[MJCronin]

I believe that you should perform a detailed study in order to make this determination.

Get the installation priced both ways, consider maintenance, job site specifics, delivery time etc and then make a judgement.

A column that is 80 meters tall put this in a special class.

http://www.eng-tips.com/viewthread.cfm?qid=253448

 

[Berenger]

Usually the major determinants are the properties of the inlet stream and, MORE IMPORTANTLY, the desired specifications of the product. Can you achieve the desired product spec with one tower? Also, you have to consider the pressure drop across the tower. A bigger tower means a higher pressure drop, a thicker and more expensive column (manufacturing and operating).