Ammonia in waste stream

[jaypar]

I have a 25000 scfm waste stream at 200 deg.F oxidizer. It has around 30 lb/h of ammonia. It also contains 300 lb/h of alcohol in addition to around 1.5 lb/h of NMOC's (Silazanes). I have 0.18 lb/h of particulates.

I cannot use a catalytic system given my particulate and silzane loading. Neitehr can I use a RTO for the same reasons.

If I use a thermal oxidizer, I am worried about NOX.

Question:
Given the above issues what are my options?
How much NOX will I generate from Ammonia destruction if my thermal oxidizer is at say 1500 deg.F?

THanks

 

[bimr]

It would be helpful if you would include the industry or process that you are involved with.

Have you thought about using a water based scrubber?

 

[jaypar]

THanks bimr,

THis is a exhaust from process and drying area. Hope this helps

 

[25362]

What I've learned from Air Pollution Control Engineering by Noel de Nevers (McGraw-Hill) is that on post-flame treatments of combustion of fuels, ammonia is actually used as an NOx reducing agent in the reactions:

6NO + 4NH3 => 5N2 + 6H2O​

in the presence of oxygen:

4NO + 4NH3 + O2 => 4N2 + 6H2O, and​

2NO2 + 4NH3 + O2 => 3N2 + 6H2O​

These reactions, if uncatalysed, can be carried out at temperatures in the 1600-1800 deg F range. Below 1600 deg F reactions are too slow, above 1800 deg F the dominant reaction is

NH3 + O2 => NO + 3H2O,​

which increases rather than decreases the NO content. Thus, it is to be understood that temperature plays an important role in the reduction of NOx.

I suggest you do a Google search for equipment suppliers, for example, under the rubric "ammonia waste incineration". I found the following site that may be of interest:

http://www.johnzink.com/products/therm_ox/pdfs/tp_nitrogen.pdf

 

[JEB66]

25362 is exactly right. Injecting NH3 into a furnace in the 1600 to 1800 deg f range is the basis for SNCR's

 

[jaypar]

Thankyou 25362 and JEB66 for your response.
The reaction you indicated are typical of NOX destruction when we add anhydrous ammonia in SCR or SCNR after burner. In my waste stream, I have ammonia around 30 lb/h which will be destructed/combusted in thermal oxidizer. Do you anticipate the same reactions to occur in this case too?
Thanks,

SANJAY

 

[JEB66]

My background and expierence is in power boilers. So I do not know much about thermal oxidizers. My belief is that if the temp range is 1600 to 2000 Deg F, the NH3 will reduce NOx.

Every time I have injected NH3 too high in the furnace, the NOx took a step up. Whenever I get it in the correct temp range, NOx steps down. Then I just have to worry about overinjecting and forming Ammoninum bisulfate when the NH3 slip reacts with the SO3.

 

[mbeychok]

.
Jaypar:

Some of the previous responders have told you that you might get some non-catalytic NOx removal from the combustion of the ammonia in your thermal oxidizer. In the petroleum refining industry, that is known as Thermal DeNox.

That won't take place by itself ... it takes some very knowledgeable and careful design to get Thermal DeNox to work. Also, you should be aware that Thermal DeNox only achieves 40 to 70 percent NOx removal.

I suggest you read this paper by ExxonMobil Research and Engineering (the developer of the Thermal DeNox process)and scroll down to page 4 of this 8-page pdf document:

http://www.prod.exxonmobil.com/refi...ntal_Leading_Edge_TechnologyPetrotech2003.pdf

Milton Beychok
(Contact me at www.air-dispersion.com)
.