refining

1. HOW REFINING WORKS

2. CRUDE OIL
• A complex mixture containing thousands of different
hydrocarbon molecules.
- 83 to 87% Carbon
- 11 to 15% Hydrogen
- 6% Sulphur
• Paraffins - Saturated Hydrocarbon Chain
• Naphthenes - Saturated Hydrocabon Rings
• Aromatics - Unsaturated Hydrocarbon Rings

3. CDU PROCESS
• Process Objective:
- To distill & separate valuable distillates (LPG, Naphtha,
Kerosene, Diesel) & residue from Crude Feedstock.
• Primary Process Technique:
- Complex fractionational distillation
• Process Steps:
- Pre-heat the crude oil feed utilizing recovered heat from the
product streams.

4. • Process Steps (Contd…)
- Desalt & dehydrate the crude using electric field to enhance
liquid/liquid separation in Desalter.
- Heat the crude to desired temperature using fired heaters.
- Flash the crude in distillation column
- Crude distillation takes place in a tall steel tower called
fractionation column
- Column is divided at intervals by horizontal trays, having
perforations.

5. - Column kept hot at the bottom, the temperature gradually
reduces towards the top, each tray is a little cooler than the
one below
- Partly vaporized crude oil rise up the column through
perforations in the trays.
- When each fraction reaches the tray where temperature is just
below its boiling point, it condenses back into liquid hydro-
carbon.
- In this way, different fractions are gradually separated from
each other at different trays in the column.

6. - Heaviest fractions condense on the tower trays & the lighter
fractions condense on the trays higher up in the column.
- Utilise pump around cooling loops to create internal liquid
reflux & also to conserve energy.
- Products draws are on the top, bottom & sides at different
elevations.

7. FCCU PROCESS
Objective:
-To convert low value vacuum gas oils to valuable distillate
products (LPG, Gasoline & Diesel Fractions).
Process Technique:
Catalytic cracking increases H/C ratio by carbon rejection in
A fluidized bed reactor.

8. FCCU PROCESS (contd…)
Process Steps:
-Hot Vacuum Gas Oil (VGO) feed along with some steam is
dispersed into the bottom of Riser Reactor through special
distribution.
-VGO is vaporized by hot catalyst flowing from Regen.
-Cracking of the feed occurs on the surface of the catalyst
(Silica Aluminia Zeloite Catalyst). Reaction takes place in
vapour phase.
-Disengaging cyclones separate spent catalyst from product
vapors.

9. FCCU PROCESS (contd…)
- Steam strips residue entrained hydrocarbons from spent
catalyst, in stripper.
- Air burns away the carbon film known as `Coke’ from
the spent catalyst in either a “partial burn” or “full-burn”
or “full-burn” mode of operation in Regenerator.
- Air is supplied to Regenerator by an air blower & distributed
throughout the catalyst bed.
- Regenerated catalyst is separated from air in a set of cyclone
separators & returned to catalyst bed & finally enters bottom
of the Riser Reactor & Cycle continues.

10. FCCU PROCESS (contd…)
- Cracking takes place during a short time (2-4 seconds) in
a Riser reactor at high tempt. 520°C+
-Regeneration of catalyst takes place around 680°C.
- Catalyst is the carrier of heat
- Cracking is end of the4rmic reaction & heat of the reaction
is supplied by burning of coke.
……FCC unit is a real margin improver for refineries.
However, products manufactured need further treatment.

11. HYDROCRACKING
Objective:
To remove feed contaminants (nitrogen sulphur, metals) & to
convert low value vacuum gas oils to valuable products like
LPG, Naphtha, Kerosene/ATF & Diesel.
Process Technique:
Hydro-generation occurs in fixed hydro treating catalyst led
Improve H/C ratio & to remove sulphur, introgen & metals.
This is followed by one or more reactors with fixed hydro-
Cracking catalyst led to dealkylate aromatic rings, open
Naphthene rings & hydrocrack paraffin chains.

12. Process Steps:
- Preheated feed is mixed with hot hydrogen & passes through
a multi bed reactor with inter-stage hydrogen quenches for
hydro-treating the feed.
- Hydro-treated feed is mixed with additional hot hydrogen &
passes through a multi-bed reactor with quenches for first
stage hydro-cracking.
-Reactor effluents are combined & pass through high and low
pressure separators and are fed to the fractionator where
Valuable products are drawn from top, side & bottom of
fractionator.
HYDROCRACKING

13. Process Steps (contd..)
- Fractionator bottom may be recycled back for additional
conversion in hydrocracker all the way up to full conversion.
- First reaction occurs which lead to saturation of any olefinic
material present in feedstock. Followed by reaction of desul-
phurization, denitrogenation & deoxygenation. These
reactions constitute treating steps during which only limited
cracking takes place.
- When severity is increased, hydrocracking reaction is
initiated. These reactions proceed at various rates with
formation of intermediate products, e.g., saturation of
HYDROCRACKING

14. Process Steps (contd..)
,,,,,,,,,
of aromatics, which are subsequently cracked into lighter
products.
- Hydrocracking catalyst comprises of a hydrogenation
function in combination with a strong cracking function.
Hydrogenation function is provided by sulphided metals such
as cobalt, molybdenum & nickel. An acidic support, usually
alumina, attends to the cracking function.
Nitrogen compounds & ammonia produced by hydrogenation
interfere with acidic activity of the catalyst. Generally these
undesirable compounds from feed are removed before it is
charged cracking reactor.
HYDROCRACKING

15. Process Steps (contd..)
- Dsulphurization, denitrogenation reactions as well as hdro-
cracking are exothermic. Catalyst inventory is divided
among a number of fixed beds. Reaction tempt is
controlled by introducing part of the recycle gas as a
quench medium between beds.
HYDROCRACKING

16. • Objective:
- To convert low value resid to valuable distillate products
naphtha, diesel and coker gas oil.
• Process Technique:
- Thermal cracking increases Hydrogen/Carbon ratio by
carbon rejection
• Process Steps:
- Preheat resid & provide primary condensing of coke drum
vapors by introducing feed to the bottom of the main fra-
ctionator.
DELAYED COKING

17. - Heat the coke drum feed by fired heaters.
- Flash superheated feed in a large. Residue remains in coke
drum to crack further until only coke is left. Often the
heaviest part of the fractionator products is recycled to feed &
vapors leave the top of the coke drum and goes back to
fractionator, where products are separated to desired
fractionations.
- Petroleum coke is removed via hydro jetting from coke drum
offline.
- The term “delayed” intended to indicate that coke formation
does not take place in the furnace but in a large coke drum
after the furnace.
DELAYED COKING

18. - Coke drums are filled / empties batch-wise, though all the
rest of the plant operates continuously.
- Plant usually has two coke drums, each having adequate
capacity for one day coke production.
- Thermally cracked products – distillates are not suitable
for commercial use and require further treatment / refinement
in order to improve the quality, particularly sulphur and
olefins content.
DELAYED COKING

19. •Objective:
- To convert low-octane naphtha into a high octane reformate
for gasoline blending and / or to provide aromatics (BTX)
for petrochemical plants. Reforming also produces high
purity hydrogen for hydro-treating process.
•Process Technique:
- Reforming reactions occur in chloride promoted fixed catalyst
beds; or continuous catalyst regeneration (CCR) beds where
the catalyst is transferred from one stage to another, through
a catalyst regenerator and back again.
CATALYTIC REFORMING

20. Desired reactions include:
- Dehydrogenation of naphthenes to form aromatics.
- Isomerisation of Naphthenes.
- Dehydro-cyclization of paraffins to form aromatics &
- Isomerisation of paraffins.
Hydrocracking of paraffins is undesirable due to increased
light ends make.
•Process Steps:
- Naphtha feed and recycle hydrogen are mixed, heated and
sent through a series of reactors having furnaces in between.
CATALYTIC REFORMING

21. - Each bed requires heat input to drive the reactions, these
having enothermic reactions.
- Finally the effluent is separated and hydrogen being recycled
or routed for hydro-treating.
- Reformat product can be further processed to separate
aromatic components or be used for gasoline blending.
The main reactions of Reforming are:
• Dehydrogenation of naphthenes, yielding aromatics &
hydrogen.
• Dehydro – is omerisation of alky & cyelopentanes to
aromatics and hydrogen.
CATALYTIC REFORMING

22. • Isomerisation of paraffins and aromatics
• Dehydrocyclisation of paraffins to aromatics and hydrogen
• Hydrocracking of paraffins and napthenes to lighter,
saturated praffins at the expense of hydrogen.
The process reshapes the molecules of the feed in a reaction
in the presence of platinum catalyst. Hydrocarbons in the
C6 – C10 paraffin's get converted to aromatics.
• The reactions takes place concurrently & also sequentially.
Majority of reactions, involve conversion of paraffin's &
napthleness and result in increase in octane number and net
production of hydrogen. Reactions are highly end
CATALYTIC REFORMING

23. othermice, which requires continuous supply of process heat
to maintain reaction tempt in catalyst beds. Hence, it is
typically done in four reactors in series with furnaces in
between for maintaining high reactor bed tempt.
• Reaction takes place at the surface of catalyst and are very
much dependent on right combination of interactions between
platinum, its modifiers or activators, the halogen and catalyst
carrier.
• Generally Bimetallic Catalyst Plantinum-Rhenium is used
in Reforming Process. Main advantage of Rhenium is higher
stability under reforming conditions & disadvantage is that
CATALYTIC REFORMING

24. catalyst becomes more sensitive towards poisonous &
process upsets. To stimulate the `acidity’ of catalyst
chloride promoter is used.
• Feedstock naphtha drawn from CDU, is hydrotreated to
remove sulphur or nitrogen compounds in order to prevent
poisoning of expensive catalyst.
• Hydrotreated naphtha is routed through stabilizer to remove
C5 and C6 fractions. C5 stream get cracked to produce FG. &
C6 gets converted to benzene and is unwanted for toxicity.
CATALYTIC REFORMING