Corrosion due to acid gas (NH3 & H2S) burning firebox vertical tube furnace

[novriandi14]

Dear all,
We have furnace for crude oil service prior to fractionation column, the type are vertical multi coil where the inlet tube materials are A335 P9 & outlet tube A312 TP316. The furnace designed with combination fuel oil fuel & gas fuel.

at this time we have a problem in our acid gas treating unit that normally treat a acid gas that contain NH & H2S before release to atmosphere,
Flow : 2000 kg/hr
%wt: : 55.1%NH3, 9.2%H2S dan sisanya H20
Temp : 100 oC
Press : 1.0 kg/cm2

then due to problem at treating unit problem, the acid gas temporarily we flow & burn in furnace chamber at radian sect. temp. 843oC (limited as design to prevent tube skin temperature escalation dan prevent creep to the tube material, regarding these problem what is the effect of NH3 & H2S reaction at 843oC temp. to tube material in short time period & longtime period specially in tube corrosion and metallurgy.
and then what the effect reaction of N2, NOx, NH3 excess and SOx, H2S excess to tube material.?

Thanks for your response.

Best regard.


Novriandi

 

[cloa]

Too complicated to analyse- something for corrosion consultant to gather the relevant papers if there are any and probably conduct testing to see if there is potential problem.

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[blacksmith37]

Hot metal (> 350F ) should have no corrosion problems (caused by SO3 condensation). But sounds like possible "hot corrosion" and ,during shut-down , Cl and polythionic SCC.

 

[novriandi14]

Thanks Cloa & blacksmith37
Yes we consider regarding the high temperature corrosion but where i can find some reference regarding this matter?
NH3 burn with the air to form NOx also decompose to N2 in very high temperature (in this problem furnace radian section limited to 843 oC and tube skin temp limited to 473 oC) and the second what is effect of H2S that form in SOx as product of combustion will to make deterioration in tube at high temperature?

regarding the condensation and during shutdown we can prevent it by neutralizing with soda ash right?

Thanks

 

[blacksmith37]

The problems I mentioned would only apply to 316. If it is sensitized ,soda ash mat not prevent polythionic SCC. And sodium sulfate promotes Hot Corrosion (many years ago Dr Rapp (Penn State) published much on hot corrosion). In a hot oxidizing atmosphere ,NH3 and H2S should not be present.
The primary corrosion concern is SO3 ( H2SO4) condensing at locations below 350F.