Microsoft Word master thesis report fina doc

Reaction section
Separator section
oily
water
sewer
oily
water
sewer
flare
flare
water
sour
water
water
sour
H
2
1, 2, 3, 4, 5, 6 : different sources of naphtha
full range 
naphtha
heavy 
naphtha
light 
naphtha
air condenser
separator purge 
to saturated gas 
recovery
off-gas to 
saturated gas 
recovery
Figure B-1-1: Naphtha hydrotreating process flow diagram

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1.4.1. Reaction section 
Hydrotreating is performed in two steps: the first one is the partial hydrogenation of diolefins 
into olefins, and the second one is hydrogenation of olefins, desulfurization and 
denitrification.
Catalyst in the first reactor selectively hydrotreats the naphtha feed. Diolefins and a part of 
olefins present in the feed are hydrogenated in liquid phase. 
In the second reactor, two catalysts are present: The first one (first bed of the reactor) for 
hydrogenation and silica removal and the second one (second and third bed of the reactor) for 
aromatic hydrogenation, desulfurization and denitrification.
Reactions occurring within the process are principally desulfurization, denitrification, 
hydrogenation and elimination of metals. 
Desulfurization 
Principal sulfur compounds in naphthas are mercaptans, aliphatic and cyclic sulfides and 
disulfides. These compounds react readily with hydrogen to produce the corresponding 
saturated compound, releasing H
2
S. 
Denitrification 
Typical nitrogen compounds in naphthas are methylpyrrol and pyridine. Nitrogen is removed 
by the breaking of the C-N bond producing an aliphatic compound and ammonia. 
Hydrogenation 
Hydrogenation is the addition of hydrogen to an unsaturated hydrocarbon to produce a 
saturated product. 
Elimination of arsenic and other metals 
In naphthas, arsenic and other metals are usually in organo-metallic form. After 
hydrogenation in the hydrotreater reactor, the hydrogenated form reacts with the hydrotreater 
catalyst forming a bimetallic compound. Arsenic and other metals are physically adsorbed on 
the catalyst. 
Prior to the air condenser, water is injected in order to dissolve chloride, sulphide and 
ammonium salts, which precipitate at low temperature. Water is recovered in the boot of the 
separator drum.