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urea to ammonia
2

urea to ammonia

urea to ammonia

(OP)
I've read about a process to convert urea into ammonia for small scale uses. I'm interested because we can purchase urea much more cheaply than ammonia. Does anyone know whether such a process could be used to manufacture large quantities of ammonia, say 10 tonnes per day?

RE: urea to ammonia

Since ammonia to urea is a conventional reversible reaction, it would be natural to assume the reverse as an option. In fact, there are patents for the Urea to ammonia process. Two of them, which are commercialized for the treatment of NOx, are U2A TM by EC&C Technologies and SafeDeNOx TM by 2002 Chemiton Enterprises, Inc., both with web sites in the internet.

However, none provides a solution for the separation of ammonia from CO2 in the gaseous phase or ammonium hydroxide from bicarbonate in the liquid aqueous phase. One is a straight water-phase reaction, the other uses steam and a catalyst. Both apparently proceed through the production of an intermediate: ammonium carbamate which is stable below 65 Celsius. Expensive metallurgies may be involved.

There is, however, another reaction using the enzime urease that selectively catalyses the hydrolysis of urea in water, not covered by patents, which I believe hasn't reached industrial applications. Again the separation of CO2 and NH3 has to be provided for.

It is still a strange market situation in which urea is cheaper than ammonia, since the normal production pattern is from ammonia to urea. Is the urea you plan to purchase diluted with water or does it have impurities ?

In short, I don't know of a better approach for your plans than consulting with the above companies besides doing some digging in the internet yourselves.

RE: urea to ammonia

There's another company who you ought to contact: Siirtec Nigi, Milano, Italy. They have developed a process called AMMOGEN for producing ammonia from urea. It is targeted at Selective Catalytic Reduction systems for NOx abatement in combustion and other exhaust gases. I'm not sure what the maximum daily output of ammonia is.

As 25362 has remarked, it is somewhat unusual for urea to be cheaper than ammonia, as urea is manufactured from ammonia in the first place, but the merits of processes such as AMMOGEN and the two that 25362 mentioned do not rely on such a price relationship. Their chief advantage is that power plant operators, who are not generally well versed in any of the chemical industry's practices or culture, are absolved from the responsibility (and the cost) of handling and storing ammonia, which is a tricky substance to say the least and, these days especially, a potential target for malefactors.

AMMOGEN and its application in NOx control are described in US Patents 5,985,224 and 6,093,380.

RE: urea to ammonia

(OP)
Thanks for your help with this topic. I agree that it is unusual for urea to be cheaper than ammonia, but I believe it is due to higher transport costs and less competition for ammonia.

I have found that the urea to ammonia process also generates water and carbon dioxide. These would need to be removed, as they would foul our catalyst (we use ammonia to produce nitric acid using a platinum catalyst).

This leads to my next question - How could these contaminants be removed from the ammonia? From what I have read in US patent 6,077,491 regarding the U2A (TM)process, the composition is 20% NH3, 10% CO2 and 70% H2O. Any ideas?

RE: urea to ammonia

I feel that any additional investment in equipment and processing costs may override and annul the economic advantages of being able to purchase urea at a lower price than ammonia.

RE: urea to ammonia

I think 25362 is dead right - this way of obtaining ammonia would appear to be quite inappropriate for your process.

Do you mind my asking why you make nitric acid on such a small scale? (You mentioned 10 t/d of ammonia). It must be a fairly high-cost operation!

RE: urea to ammonia

hello,

TVA uses the urea/ammonia process in their power plants. I hesitated to respond because I can't remember who is providing the systems to them.  They did it for safety reasons.  The process is well defined, and I believe that SEMCO in Canada supplied some of the equipment, but not the technology.  Sorry I can't help more.   

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