thermal decomposition of cyclohexylamine? 1

[davefitz]

WE have a series of power plants which use organic amines to control corrosion in their condensers. Recent testing of the vacuum pump exhaust reveals these organic amines are breaking down to simpler hydrocarbons, leading to a concern regarding accumulations of flammable gases in these low pressure vessels. A review of the literature does not result in prior reports of cyclohexylamine breaking down to simple hydrocarbons.

Can anyone advise a reference or paper tha explains the thermal decomposition of cyclohexylamine- I think the max inside metal temperature of the superheater tubes may be on the order of 1050 F- 1100 F- this is sufficent to breakdown morpholne ( as reported at canadian nuclear plants) but their is no mention of simialr breakdown of cyclohexylamine.

 

[chicopee]

What were the responses of the suppliers and manufacturers?

 

[davefitz]

chicopee.

The chemical suppliers indicated that their chemicals are not to blame, and the quantities used are not high enough for concern. However, it was clearly demonstrated in the plant that the cyclohexylamine is the root source of the hydrocarbons in the vacuum pump exhaust. If we stop chem feed for 45 minuttes, the concentration of hydrocarbons drops to zero in the vac pmp exhaust, and re-starting the chem feed quickly leads to higher levels of methane and other hydrocarbons.

An interesting test to confirm flammability was to attach a plastic bag to the vac pmp exhuast and collect the vapors, the bag was then lit with a match and it exploded.

 

[mxmaciek]

Google is your friend: use the search term: "Thermal Decomposition of 3-Methoxypropylamine
as an Alternative Amine in PWR Secondary Systems" -first link should give you the answer needed (I hope conversion from Celsius to Fahrenheit would not be a problem?)

 

[25362]

It appears that cyclohexylamine itself is flammable. Flash point ~ 29 celsius.

 

[davefitz]

25362:
Yes, its LEL is 1/3 of CH4 . And the smell is quite putrid.

We had extracted a sample of the gases leaving the vacuum pump, and had it analyzed by a gas chromatograph, and the results indicated a mixture of the lower hydrocarbons, ( methane, ethane, propane , butane, etc) but it is not clear if those results were valid . The gas chromatorgrpah was not specifically programmed to recognize a complex gas such as cyclohexylamine. I am no expert on such analyzers, but if an "interfering gas" is input to a chromatograph, I suppose it will translate the results into values of those gases for which it is programmed to recognize.

Mxmaciek:
Thanks for finding this reference - although not exactly cyclohexylamine.

 

[mxmaciek]

I know, sorry but I couldn't find anything specific ad hoc. Anyway, please update the thread when data would be available, I never faced decomposition to low molecular weight hydrocarbon gases yet, as commonly confirmed decomposition products are carbon dioxide, formic and acetic acids groups.