[ahto555]

Hi all!

Might be stupid question.
29% (w/w) ammonium hydroxide as catalyst is used. After chemical reactions and substrate washing less than 10% (w/w) ammonia water is left.
Any low energy input technology applicable at small industrial level available to re-concentrate it back to 29%?

[roy]

Hi ahto...

I think you should define your system more detailed. For example, is it batch or continuous, what reaction is occurred there, and in what way does the NH4OH concentration is decreased (whether it is reacted, diluted, or vaporized during the process).

I don't think it is reacted. The concentration decreased possibly due to dilution or vaporization.

If it were the dilution, you can strip the NH4OH by heating the low-concentrated solution using equipment like simple batch distillation, and cooled down the vapor. Since the vapor contains more NH3 than H2O, you have to add certain amount of water before condensation so the water dissolved NH3 vapor and form NH4OH. The condensate will be more concentrated with NH4OH. But, you have to use very cool water since NH4OH will easily vaporizes at room temperature.

If it it were the vaporization loss, you may use reflux reactor. So that, the NH3 vapor will condenses as it leaves the reactor.

Sorry if my answer doesn't help you lot...hehehehhe

[ahto555]

Dear roy!

It is batch process, small amount of ammonia reacts with lignin in biomass. There is no vaporization loss. The major ammonia loss is because of biomass washing with water so due to dilution.

[roy]

Hi Ahto!

I think you can enrich the NH4OH by simple distillation principle by heating the diluted solution and cool down the vapors. Since 10% w/w NH4OH solution boils at about 50 deg C (120 F), heating the solution at 50 deg C will vaporizes most of NH4oh as NH3 and H2O. This vapor is then cooled using water-cooled condenser that NH3 and H2O condenses and form H2O.But, saturated concentration of NH4OH in water is about 35%. So, condensing the vapor will give you concentrated NH4Oh solution (35% w/w) but most of NH3 you recovered will be loss as vapor. So, I think you need to contact the vapor with water to minimize NH3 loss.

However, this process required much energy for heating. But I think, you can heat the solution using another hot liquid (if any) in your process. To optimize cooling process, you may done the cooling at night, so you have cooler water..hehe

Another idea will be using activated carbon. But I don't know whether the HN4OH will be adsorbed or not. If it's adsorbed, this process will be prospective since no need of heating abundant amount of diluted solution and the activated carbon can be reused.

If you have any idea regarding this, I'll be glad to discuss it, Ahto. It will help me to learn too..hehe