De-NOx reactor fouling

[ponderer]

There is a De-NOx reactor in our CDU(Crude Distillation Unit) heater system.

The effluent gas from the heater enter this reactor.

It is a selective catalytic reactor with ammonia injection.

From time to time. we encounter high pressure drop in the reactor. Especially when this plant start up after a long
time shut down.

We use #6fuel oil with sulfur content of 1% in this heater.

 

[lpgii]

I don't have my references here at home with me, but this sounds like NH3 salt deposition (ammonium sulfate and bisulfate) and plugging the catalyst bed. The SO3 formed in the combustion process reacts with injected ammonia to form the salts. At lower temperatures (below maybe 230-250degC) these can get sticky and foul the catalyst bed. Need to watch temperature control into the catalyst bed.