Stijn - 6-12-2004 at 01:35
Hello,
I'm doing a project on the production of adblue at the Technical University of Delft. Our aim to purify fertilizer-grade urea into process-grade
urea. This means we have to seperate formaldhyde and biuret from the urea. Any ideas how to do this?
Marvin - 6-12-2004 at 05:53
I was under the impression any free formaldehyde would react with urea to form an adduct so maybe uits the adduct you need to remove?
Standard lab purification for urea last I looked was fractional crystalisation from water not exceeding 50C.
Stijn - 6-12-2004 at 06:05
Yes we need to remove the adduct. The adduct is UF, urea-formaldehyde. This is the problem. I'm a mechanical engineer so I do not have a chemical
background. It might be quite easy, but I don't have any idea how to do this... I was thinking of adding an absorbent to remove the UF?!
vulture - 6-12-2004 at 14:01
Does formaldehyde form a bisulfite adduct?
Marvin - 8-12-2004 at 10:07
Fractional crystalisation should work well, UF should not be very soluable in water. You may even get away with making a concentrated solution in
water (so there is some residue) and filtering.
So long as the solution is kept under 50C there should be no noticable decomposition to furthur biuret.
Since adblue is a solution in water anyway, furthur dilution should result in adblue (or an adblue equivalent solution) directly.
Stijn - 8-12-2004 at 10:44
Problem is that the urea is supplied in prills. We need to heat the prills to above the melting point for urea (+/- 135C) to solute the urea in water
properly, don't we?! And then there is decomposition to further biuret. Is fractional crystalisation then still an option? Thank for your comment
anyway Marvin!
Marvin - 8-12-2004 at 17:07
You should have said you were using a prilled form. No it should not be needed to melt them to dissolve in water, have you tried grinding them first?
Urea tends to be rather soluable, I suspect the prills you have are coated with something.
Stijn Harms
Stijn - 9-12-2004 at 00:40
Yes the urea is coated with Urea Formaldehyde. Our aim is to make adblue out of fertilizer grade urea. So we need to purified it. So indeed after
grinding it's quite easy soluble in water.
Two boudary conditions for the proces are that we have to produce 5000L/day and that everything has to fit in a standard skid. So maybe fractional
crystallisation would not be fast ebough??!
Stijn - 9-12-2004 at 03:04
Marvin, the percentage of the formaldehyde that we need to seperate is not very high. The fertilizer-grade urea has 0.18wgt% urea-formaldehyde and we
need 0.01wgt%. Isn't it so that when you solute this in water you just have formaldehyde in water? So, what about reverse-osmosis? that should
work to my opinion?!