Q & A > Question Details
I am working in hydrotreater and i want to know, can we inject wash water to REAC during the catalyst sulfiding stage ? What are the advantages and disadvantages of injecting during the catalyst sulfiding stage ?
13/09/2019 A: Ganesh Maturu, Self, maturu.ganesh@gmail.com
Generally there is no advantage of injecting wash water during sulfiding when DMDS is used as sulfiding agent and feed is in circulation.

1. H2S rich gas present in reactor effluent and recycle gas during sulfiding stage which is produced from DMDS injection. If we add water, H2S loses to water as H2S solubility in water is very high. This will increase DMDS requirement unnecessarily.
2.There is no NH4HS formation as NH3 presence in recycle gas is almost negligible.
3. Since liquid is recycled back to feed surge drum during sulfiding stage, no other possiblility of NH3 accumulation in the system because of feed nitrogen.
4. If you add NH3 to Reactor which is done during sulfiding stages for cracking catalysts, it may be possible to establish wash water circuit for some time. Just check if any NH3 injection during sulfiding stage for Ur catalyst system.
5. During sulfiding we generally calculate H2O formed in Separator boot to estimate Sulfur pick up on catalyst. Adding water without any major advantage will not give correct estimation of sulfur pickup due to water formation. However this is only approximation and other means available to check sulfur pickup on catalyst.

If you go for feed only sulfiding, we cant control H2S content in recycle gas as we continuously give fresh feed to the system which contains some sulfur content in feed, we have following options.
1. Continuously purge recycle gas from purity vent line to maintain not more than required H2S in recycle gas circuit.
2. Sometimes it is possible with purge, it may not be possible to maintain required purity. Add wash water intermmitently to remove H2S in system.
3. In last option, if we still see higher H2S in recylce gas than required, start recycle gas scrubber for 1-2 minutes which will significantly reduce H2S in recycle gas and hence should be considered as last option.
11/09/2019 A: Eric Vetters, ProCorr Consulting Services, ewvetters@yahoo.com
I'm not sure why you want to. During catalyst sulfiding there won't be any ammonia present so little risk of having ABS or ammonium chloride to formation to worry about. Operation is likely to be a significantly reduced flows during sulfiding of the catalyst, so getting water evenly distributed to the REAC tubes won't be very easy.

Without any ammonia present the H2S can form an acidic aqueous phase so water wash would help dilute that and reduce corrosion somewhat; however, the duration of this step is so short that overall corrosion damage should be minimal. I would not bother with it, unless you want it done and out of the way before you get busy with presulfiding and the rest of the start up so it doesn't get forgotten.