8 replies to this topic

[breizh]

Mattprole ,

Difficult to support your query ! Need more input from you about what you want to achieve , the quantity involved, the type of process, the concentration of NH4OH,....

I'm sure if you define better your request you will get answer(s).


Breizh

[Hulman]

Dear Mattprole,
I m surprise that reading your post of exess ammonia neutralization means 29.4wt% of ammonia. In my plant that sort of concentration is not considered as exess chemical. we reutilize it. Generally speaking (dont know exactly hourly flow of your excess ammonia as well as your main operation) but considering just the concentration of your ammonia to be nutralized (if neutralization is your final option), you will deal pretyt much with high heat formation. Also you need to put into consideration of safety factor by conducting your neutralization at lower level of concentration - this means you are dealing with dilution, water addition before neutralization. As for the acid for neutralization, it was depend on acid availability on your plant-in-situ.

However, just an alternative option, dealing with 29% ammonia (which i assume constantly produced) you could also check the possibility to just diversified your product by proposing some other aspect of production such as saltation process which produced much more valuable product. I just dont see the benefit of just trhowing off that sort of concentrated ammonia. I cant tell you more, because i dont have a clue exactly what kind of process do you operate down there. But generally speaking, it is just based on common sense alone, it will be beneficial not to dispose your ammonia on that level concentration. Maybe you could consult your supervisor to check the availability of other material in-situ, and finding a creative and proposal to reutilize your ammonia economically.

Regards,


Hulman Siagian

Hello, this is my first post on these forums. I'm hoping someone can help me out.

I am a co-op student at a coal plant, and a supervisor of mine has requested my opinion on the best method to neutralize some excess aqueous ammonia. I have no experience with ammonia, so I am unsure how to proceed. Sulfuric acid in the form of 66 Baume (93% Acid by weight) would appear to be an economic choice for neutralizing ammonia, as we have some left over from a previous project. Acetic Acid has also been proposed as a potential neutralizing agent (and we are currently leaning towards Acetic Acid as the more environmentally safe option).

Ideally, upon application of the neutralizing agent we'd like the resultant solution to have a pH near 7 so as to be safe to discharge into river water.


If there are standard methods for neutralizing aqueous ammonia I'd certainly appreciate the info. Ideally I'd like to know what proportions / conditions are appropriate to facilitate complete reaction between the proposed acid and the excess ammonia.

Any information at all would be greatly appreciated.

Edit:
I've recently learned that the wt % of the ammonia we wish to neutralize is 29.4%. We are currently leaning towards Acetic Acid as the neutralizing agent, as it turns out we have some left on site, and my research indicates the product, Ammonium Acetate, is biodegradable. Maintaining environmentally sound levels of chemical is very important in this process.

I'd also like to mention that this is the first time that this plant has had to neutralize our excess ammonia, typically we'd just sell it.

~ Mattprole

[kkala]

Some remarks on the matter, subject to comments.
1. 29.4% aqueous NH3 (41.6 kg NH3 / 100 kg H2O) has an overhead NH3 partial pressure of ~470 mm Hg (0.6 Atm)at 20 oC. See Perry, 7th ed, Table 2-123, Ammonia. Probably reported 29.4% content does not represent free NH3, but total NH3 (including salts of NH4); or else this aqueous solution has to be handled in closed conduits & drums. In the second case a way out might be atmospheric neutralization tank / conduits with strong negative air pressure over the liquid, leading resulting air to a washing column for neutralization (but what will happen if relevant air fun fails should be defined in the HAZOP study).
2. For strong acids & bases we considered instantaneous neutralization in the past, on the condition that the neutralization tank is well agitated to ensure homogeneity. Probably this is also the case for weak acids & bases (well agitated in a common tank), since partial dissociation can be thought as instantaneous; resulting neutralization is a result of ionic equilibrium. Nevertheless "kinetics" data would be welcomed.
3. Seeing that (NH4)2SO4 is a form of fertilizer, it may not create environmental damage (but look into possible eutrophism in the receiver). Be aware of thermal effects of 93% H2SO4. In drawings of waste water treatment I have seen it introduced for neutralization under pH control and strong agitation. In practice a plastic neutralization column was "burnt" around the point of H2SO4 introduction.
4. Proportions should be stoichiometric (under effective tank agitation) to result in a pH close to 7 in the neutralized solution.
CH3COOH is a weak acid. Its advantage over H2SO4 is that the titration curve of CH3COOH is less steep compared to H2SO4 at the vicinity of neutralization point. So a slight acid excess by error will lower pH much less in case of CH3COOH than in H2SO4. This is my understanding, yet H2SO4 used for neutralization (as mentioned) indicates this is not a serious problem (or a way out has been applied, not known to me).
5. More information would be useful, including flow-rates, as breizh has already pointed out.

Edited by kkala, 21 May 2011 - 04:44 PM.

[kkala]

Previous post of kkala assumed continuous neutralization of mentioned aqueous NH3. But due to Hullman's post it is now known this is collected spill-over from truck unloading. I assume personnel had masks on, to collect it into a drum. And now it has to be neutralized before disposal.
First thought can be to send the aqueous NH3 content to a specialized company for neutralization and disposal.
Second thought to try neutralization in situ, if feasible. But drum may not have possibility for agitation. If so, you may transfer the liquid into another drum, agitated, having also enough corrosion resistance to the acid. A forced venting system would be probably needed, if vessel is atmospheric.
Heat effect should be estimated, though this may become insignificant by lower the acid flow rate (thus prolonging neutralization time).
Vessel material should be proper for acid corrosion. Advise on the procedure would be welcomed, due to no practical experience on the subject.

[breizh]

Hi ,
Attached a link where you will get a lot of info related to a Nh4OH :

http://www.rmtech.ne...information.htm

Hope this helps

Breizh

[Madhan Kumar]

Hi,

We have a similar situation where we have to neutralize mother liquor containing about 20 % ammonia, 10 % water and remaining methanol.

We used to adjust the pH to 6 using sulphuric acid, precipitating out ammonium sulphate followed by filtration, thus separating ammonia as

ammonium sulphate leaving methanol with traces of ammonia. The filtrate will be processed further for next step and ammonium sulphate is being sold as

byproduct.

Hope this may help you

Cheer's
MK_Chem

[kkala]

Aqueous ammonia storage and handling (referenced bt breizh in his recent post) excludes storage in Atmospheric tanks. This has to be considered, when reading previous posts by kkala; storage of aqueous NH3 in atmospheric storage tanks is not recommended, even by "forced" venting. Drums should be used for this purpose, with design pressure of 30 psig (assumed as minimum), PRV and vacuum breaker.