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- Posts: 4
- Joined: Wed Jan 24, 2018 5:05 am
So I have a fascinating yet difficult GC extraction problem to solve.
I have some thermodegradative organic acids which have a low vapor pressure, along with other compounds that need extraction.
The amount of raw materials to be processed may be on the order of tons per year, and the C.B.A. for using liquid chromatography or one of the other methods is just not good enough to justify it, the low costs associated with GC are a major selling point of the technology.
However, given the low VPs of our target compounds and the thermodegradation, a high operating temperature is an impossibility unless the process is fast enough (my research suggests it isn't).
Thus, I'm having to adapt a technique which is (as far as I can tell) only used for analytics and not production.
So my constraints are vast.
The inlet pressure needs to be close to or just slightly above or below standard atmospheric pressure (1.5 bar-0.5 bar absolute pressure). The outlet pressure should be near a vacuum (0.1-0.3 bar). The average column pressure is maintained below atmospheric so that the low temperature required can still boil the compounds I'm trying to isolate.
The only engineered silica which has the pressure drop characteristics I need are particles of 0.2mm<x<1mm. Obviously the theoretical plate number and plate height are bad compared to smaller particles.
I can increase the total plate number by lengthening the column, as the pressure drop is small enough that I can easily manage several meters of column length and still achieve the low system pressures required.
However, I'm concerned that in my quest to reach a high enough plate number, that I'm going to cause significant band-broadening due to the low efficiency of the system. How bad can this problem get with a plate height and column length as high as mine will need to be?
Obviously great care is going into the stationary phase, as we need high affinities that are quite different for each compound in order to increase our plate number/reduce plate height.
First question really, is how much lost efficiency and band-broadening becomes inevitable with particles of this size?
Thank you for the help and suggestions.