1. Crude oil Treatment process
Hydrotreatment
Amine recovery

2. Hydrotreater
BP-UK

3. Hydrotreatment What is hydrotreatment?
It is a process to catalytically stabilize and/or remove undesirable elements from products or feedstocks by reacting them with hydrogen.
 Stabilization usually involves converting unsaturated hydrocarbons such as olefins to paraffins.
Undesirable elements removed by hydrotreating include sulfur, nitrogen, oxygen, halides, and metals.

6. Difference between Hydrotreating and Hydrocracking
Hydrotreating and hydrocracking both can be called Hydroprocessing

8. PROCESS VARIABLES
The principal operating variables are temperature, hydrogen partial pressure, and space velocity.
Liquid Hourly Space Velocity (LHSV)= Volumetric flow rate/volume
Weight Hourly Space Velocity (WHSV)= Mass flow rate/catalyst mass
Increasing temperature and hydrogen partial pressure increases sulfur and nitrogen removal and hydrogen consumption.
Increasing hydrogen partial pressure also increases hydrogen saturation and reduces coke formation.
Increasing space velocity reduces conversion, hydrogen consumption, and coke formation.
Although increasing temperature improves sulfur and nitrogen removal, excessive temperatures must be avoided because of the increased coke formation.

9. PROCESS VARIABLES
Typical ranges of process variables in hydrotreating operations are

14. Hydrotreatent Reactions
Convert Organic S to Hydrogen Sulfide
Convert Organic N to Ammonia
Convert Organic O to Water
Convert Organic halides to Hydrogen Halides
Saturate Olefins
Saturate Aromatics
Remove Metals

15. Desulfurization
Increasing Difficulty

17. Denitrogenation
Denitrogenation is usually more complex than desulfurization.

18. Oxygen Removal

19. Olefin Saturation
Olefins are unstable components and they polymerize in presence of oxygen
Olefin saturation is very rapid and exothermic reaction

20. Aromatic Saturation
Aromatics present as 1, 2, 3 or more rings structure
Aromatic saturation is a stepwise reaction
Aromatic saturation is an exothermic reaction

21. Aromatic Saturation

22. Halide Removal

23. Metals Removal
Lead, mercury, arsenic, silicon, nickel, vanadium, sodium
Compounds that contain metals decompose in reactor and deactivate catalyst
The metal deposited on catalyst cannot be removed by regeneration

24. Lead poisoning effect on catalyst activity

25. Arsenic poisoning effect on catalyst activity

26. Sodium poisoning effect on catalyst activity

27. Ease of hydrotreatment reactions

32. Guard Reactor

33. Hydrotreatment Catalyst
Solid consisting of a base alumina impregnated with metal oxides
Pellets shaped as cylindrical or pills
For Desulfurization, Co-Mb catalyst is used
For Desulfurization, Denitrogenation and Aromatic saturation, Ni-Mb catalyst is used

34. Sulfur recovery
Hydrogen sulfide created from hydrotreating is a toxic gas that needs further treatment
Solvent extraction: using diethanolamine (DEA) dissolved in water separates the H2S gas from the process stream (DEA should be recovered) 34

35. H2S separation_ Amine Unit35

36. DEA Chemistry
DEA: weak organic base to absorb acid gases of H2S and CO2 from gas streams.
Chemical Structure: DEA = [HO(CH2)2]2 - NH
C2H4OH \
N - H /
The reaction of DEA with H2S and CO2 are equilibrium reactions:
H2S: R2NH + H2S ⇋ R2NH2SH
CO2: 2R2NH + H2O + CO2 ⇋ (R2NH2)2CO3
where R = HO(CH2)2
Absorption
Absorption is favoured by high pressures and low temperatures 36

37. Amine Regeneration Regeneration is favoured: low P and high T
Acid gas components are boiled out of the amine solution
The required heat input to the reboiler:
Sensible heat required to bring the rich amine from the inlet temperature (~95°C) to the column base temperature (~127°C) 
Heat of reaction to desorb the acid gas components.  
Heat of vapourisation to generate sufficient water vapour within the column to strip the acid gas components in the amine
Need to ensure that temperatures are maintained below 130°C to prevent amine degradation and subsequent amine corrosion 37

38. DEA Properties Amine Strength: Amine Loading: Ideally 25-27wt% DEA
Higher amine concentrations = higher regenerator boiling temperatures and increased corrosion rates
Lower amine concentrations = higher circulation rates and thus increase energy requirements for pumping and regeneration
Amine Loading:
Amine Loading = mol (H2S) + mol (CO2) mol (DEA)
Target is an amine loading of 0.3 – 0.5 mol/mol 38

39. End of Chapter Nine