1. Case 3 – Increasing hydrogen partial pressure
- Case 3a – Diesel hydrotreater
increase H2/oil ratio?
purify hydrogen?
change liquid feed?
decrease pressure drop?
Case 3b – Naphtha hydrotreater
   

2. Case 4 – Pressure Drop
Situation 1 – Poor catalyst loading or poor start-up procedures
Situation 2 – Internals, catalyst strength or corrosion impurities coming into the catalyst bed
   

3. Case 4 – Pressure Drop Possible causes for pressure drop
Reactor - coking, polymerization, particles (FeS), catalyst loading, maldistribution, metal poisons
Exchangers - salts deposition, coking, polymerization, particles deposits

4. Case 4 – Pressure Drop Reasons for this high pressure drop build-up??
3/4" inert balls
Reasons for this high pressure drop build-up??
Reasons for the higher pressure drop in the second bed??
ACT mm
ACT mm
HMC mm
1/4" inert balls
3/4" inert balls
HR mm
DENSE LOAD
1/4" inert balls
3/4" inert balls

5. Case 4 – Pressure Drop

6. Case 4 – Pressure Drop
Catalyst grading bed – trickle bed reactors

7. Case 4 – Pressure Drop Scale baskets – Gas phase bed reactors
Scale baskets are needed in order to provide longer resistance to pressure drop build up.
The role of the basket is not intended to retain the fines which should be trapped on the top layer of inert balls, but to act as a fuse in case of pressure build up
They should remain clean
Vapors + fines
Vapors free of fines
Fines accumulation
Inert balls
3/4"
Inert balls
3/4"
Catalyst bed

8. Case 4 – Pressure Drop
Pressure drop must be corrected for process conditions, as gas and liquid flowrates for example
Delta P measured
Delta P predicted

9. Desulphurized product
Case 4 – Pressure Drop
Feed + H2
After start-up a very high pressure drop
Was observed across the reactor
Desulphurized product
+ H2 + H2

10. Case 5 – Hydrogenation Activity
+ 2H2S S
+ 2H2

11. Case 5 – Hydrogenation Activity
Régime thermodynamique
(HDA)
Régime cinétique
Equilibre thermodynamique
HDA
Soufre effluent (ppm)
% HDA
HDS T1 T2
Température (°C)

12. Case 5 – Hydrogenation Activity
quench
(0 t/h)
four
lit 1
lit 2
lit 3 R1 R2
Opération normale
Diminution de la température
dans le dernier lit
température

13. Case 6 – Unit Shut-Down
In the race of increasing severity in sulphur specifications - NZSD, optimising the unit shut-down and scheduling it as a non routine event is as important for the overall unit performance as a Formula 1 pit stop can be to wining
distribution tray removal
(mechanical details)
reactor inspection
under air atmosphere
regenerated catalyst pool
catalyst activation method
catalyst drying
catalyst unloading
catalyst loading
reactor cool down
Dedicated flow-bins - FUTURE

14.   Case 6 – Unit Shut-Down Cooling loop for hydrotreatment units
Air coolers 
HP separator
Gasoil cooling loop
To LP
separator
stripper Pre-heat
exchangers
Normal operating circuit
Compressor
stripper
By pass to be opened
at 150°C
Pre-heat exchangers
dryer
Air coolers 
reactor
From HP
separator
Furnace
maxi
cold
GO to storage
LP separator