Ammonia/Air Flammability Limits

[pgmtech]

The flammability limits of ammonia/air mixtures are well documented at atmospheric pressure, but I am looking for the limits at pressure up to 140 psig. I know that at 130 psig the lower flammability limit is around 11.2-11.5% by volume. Does someone know where I can find a graph or table with the flammability limits at various pressures?

 

[25362]

I see that you already found that the 16% LFL at atmospheric conditions dropped to 11.2-11.4% at 130 psig. Although I don't have the values for anhydrous ammonia's HFL at higher pressures, I can quote a previous thread (124-31528) where the dependence on pressure was given as follows:

UFL[sub]p[/sub] = UFL + 20.6 (logP +1)

P is given in megapascals. UFL is the vol% in gas + air at atmospheric conditions, in this case 25%.

In the case in question, at 140 psig (=157 psia = 1.082 MPa) the estimated new UFL = 25 + 20.6 (log 1.082 + 1) = 46.3%. Showing the sensitivity of the UFL to pressure, and the broadening of the explosivity range.

The same comment I made then, I repeat here:
When the pressure is atmospheric P = 0.1 MPa, the log becomes -1, and the addition cancels out.