1. Refinery Structure- Evolution
Mainly fractionation by distillation
For production of industrial fuels
Topping Refinery
Hydro treating units added for fuels
quality improvement
Hydroskimming Refinery
Addition of several conversion processes
to improve: fuels recovery efficiency,
further quality improvement, process
heavier fractions / crudes & energy
efficiency
Conversion Refinery

2. Processing of light crude
Processing of light crude, even in a complex/modern refinery with FCC,
hydrocracking etc. does not yield a satisfactory product distribution.
The amounts of fuel oil are too high.

3. Processing of heavy oil
For heavy oil the situation is even worse with ~ 50% fuel oil being produced even in a complex /modern refinery.
Fuel oil is worth < original crude. The value of the products decreases in the order: gasoline> kerosene/gas oil > crude oil > fuel oil.
Bottom of the barrel treatment is vital
Challenge – Meeting Strict Quality standards & Increasing Demand

6. Gasoline Specs-India

7. Diesel Specs- India

8. Structure of refinery

9. Flow Scheme of modern oil refinery

10. Catalytic processes in refinery

11. Petroleum refining processes

12. Petroleum Refining- Types of Operations
Fractionation (distillation)-
Separation of crude oil in atmospheric and vacuum distillation towers into groups of hydrocarbon compounds of differing boiling-point ranges called "fractions" or "cuts."
Conversion Processes
Changing the size and/or structure of hydrocarbon molecules via different processes:
Decomposition (dividing) by thermal and catalytic cracking;
Unification (combining) through alkylation and polymerization; and
Alteration (rearranging) with isomerization and catalytic reforming.
Treatment Processes
For additional processing and to prepare finished products.
Removal or separation of aromatics / naphthenes/ impurities / undesirable contaminants.
Chemical or physical separation e.g. dissolving, absorption, or precipitation
Desalting, drying, hydro de-sulfurization, sweetening, solvent refining, solvent extraction, and solvent de-waxing.

13. Processes in Oil Refining
Physical
Thermal
Catalytic
Distillation
Visbreaking
Fluid Catalytic Cracking
Solvent extraction
Delayed coking
Hydrotreating
Solvent dewaxing
Fluid cocking
Catalytic Reforming
Propane deasphalting
Flexi coking
Catalytic dewaxing
Blending
Hydrocracking
Isomerization
Alkylation
Etherification
Polymerization

14. Petroleum - Properties
Density
Specific gravity - Ratio of mass of specific volume to mass of the same volume of water, both at the same temperature
API Gravity
Degrees API = (141.5/Specific gravity at 60/60 °F) – 131.5
Viscosity- cP- Flow characteristics
Kinematic viscosity/fluidity = Viscosity/ Specific gravity
Carbon residue (wt%)
Carbonaceous residue left out after destructive distillation- non-volatile part of petroleum/petroleum products
Ramsbottom method- ASTM D 189 IP3
Conradson method - ASTM D 189 IP4
Viscosity and Asphaltenes, Nitrogen & Sulfur contents increase with
increasing carbon residue
Indicates the potential for coke formation
Signify Light/Heavy character of Crude oil

15. Petroleum - Properties
Aniline point
Temperature at which exactly equal parts of two components are
Miscible- Aniline & Any petroleum fraction/oil
Increases slightly with molecular weight
Increases rapidly with paraffinic character/
Higher the aniline point- lower is the aromatics content in the fraction
Reid vapor pressure (RVP)
A measure of the volatility of gasoline. It is defined as the absolute
vapor pressure exerted by a liquid at 100 °F (37.8 °C) as determined
by the test method ASTM-D-323.
RVP differs slightly from the True Vapor pressure (TVP) of a liquid
due to some small sample vaporization and the presence of water
vapor and air in the confined space of the test equipment, i.e. the RVP
is the absolute vapor pressure and the TVP is the partial vapor pressure

16. Petroleum - Properties
Cloud point
The temperature of the test specimen at which wax crystals have formed sufficiently to be observed as a cloud from a petroleum fraction
Applicable for petroleum products and biodiesel fuels
An index of the lowest temperature of their utility for certain applications.
Petroleum blending operations require a precise measurement of the cloud point.
Smoke point
Provides an indication of the relative smoke producing properties of kerosines and aviation turbine fuels in a diffusion flame.
Related to the hydrocarbon type composition of such fuels, esp. aromatics
More aromatic the fuel the smokier the flame.
A high smoke point indicates a fuel of low smoke producing tendency.
The smoke point is quantitatively related to the potential radiant heat transfer from the combustion products of the fuel.

17. Petroleum- Properties
Pour point
The lowest temperature at which it will pour or flow under prescribed conditions. It is a rough indication of the lowest temperature at which oil is readily pumpable.
Can be defined as the minimum temperature of a liquid, particularly a lubricant, after which, on decreasing the temperature, the liquid ceases to flow.
UOP K factor ( Watson Characterization factor)
K = 3√ TB/ S TB- Average molal BP in Deg.Rankine ; S- Sp.gravity at
60°F

18. Crude Assay- Properties that determine
the processibility, product pattern &
hence the cost of the crude

19. These fractions need go through regular
refining processes to yield fuels of acceptable grade

20. Thermal Processes:
Cracking & Coking

21. Desalting Objectives Process Effective desalting
Removal of water, inorganic salts, water soluble metals & suspended
solids from crude oil –Prevention of corrosion, fouling & plugging of equipments
Process
Two stage desalting is carried out, with removal of most of the water at first
stage, followed by addition of dilution water in the second stage to extract
soluble salts & metals. Process conditions are °C and psi.
Surfactants are added to demulsify & achieve proper separation and remove
water by settling. Application of electrostatic coalescing is also adopted
Effective desalting
1 kg salt/1000 bbl
Chlorides ppm

22. MS Rana et.al. Fuel,86,1216,2007

23. MS Rana et.al. Fuel,86,1216,2007

24. Thermal cracking Dubbs process- Universal Oil Products (UOP)
Thermal cracking of reduced crude at °C & psi
Major products- Gasoline & middle distillates
Soaking of light & heavier fractions & further cracking
Thermal cracking of Reduced crude oil
Feedstock; API gravity 25 °C ; IBP- 227°C
Cracking parameters- 500 °C ; Soaker pressure; 225 psi
Product yields (Vol%)
With recycle of H. Oil W/o recycle of Heating oil
Gas
Naphtha
Heating oil
Residuum

25. Visbreaking Process Benefits
Viscosity-breaking- Cracking to reduce the viscosity
A mild form of thermal cracking of the residue (10% conversion), at psig
pressure at °C to reduce viscosity/ pour point.
Liquid phase cracking. Process optimized to minimize coke formation
Water injected with the feed to provide turbulance & control temperature
Residue from Atmos. / Vac. distillation units can be used
Coil/Furnace type- high temp. & short residence time
Soaker type- Lower temp. & longer residence time
Benefits
5-10% conversion leads to 5 fold decrease in viscosity
Reduction in pour point
Less coke formation vis-a vis other processes
Blending of LHO to FO minimized
Product stability is the issue- Olefinics

26. Visbreaking- Yield pattern
Luisiana Vacuum Residue
Arabian Light Atm. residue
Feed stock
Gravity API
Carbon residue
Sulfur wt %
11.9
10.6
0.6
16.9
3.0
Product yields
Naphtha
6.2
7.8
Light gas oil
6.3
Heavy gas oil
70.8
Residuum
Sulfur wt %
88.4
11.4
15.0
20.9
1.3
5.0
Feedstock
From
Process
Typical products To
Residual
Atmospheric tower & Vacuum tower
Decompose
Gasoline or distillate
Hydrotreating
Vapor
Hydrotreater
Residue
Stripper or recycle
Gases
Gas plant

27. Visbreaking- Process variations
Aquaconversion
Catalytic process in slurry mode
Oil soluble catalyst and water
Alkali metal catalysts activate the
transfer of hydrogen from water as H+
Coke formation is reduced
Hydrovisbreaking
Treatment with hydrogen at mild
conditions
3 reactors:
1. Visbreaking- Mild cracking with H2
2. Demetallation
3. Hydrocracking
Reactors 2 & 3 use Co-Mo-Alumina
catalyst for removal of metals and
cracking of heavier molecules.
Less Coke formation
Better quality product- demetallized

28. Delayed coking
The feed is subjected to thermal cracking, in a coke drum, under high pressure & temperature psig & °C
Held (delayed) ~24 hours for the process to get completed
Two coke drums used, one for processing and the other for coke
removal & cleaning
Virtually eliminates residue fraction-forms solid carbon/fuel
Highly aromatic coke, retains S,N & metals
Naphtha, LGO & HGO – used for gasoline/diesel/FCCU after hydrotreating
Luisiana Resid
Kuwait Resid
Feed stock
Gravity API
Carbon residue
Sulfur wt %
12.3
13.0
0.7
6.7
19.8
5.2
Product yields
Naphtha
22.8
26.7
Light gas oil
18.4
28.0
Heavy gas oil
37.6
Coke
Sulfur wt %
23.7
1.3
30.2
7.5

29. Fluid Coking & Flexi Coking
Both FLUID COKING (1954) and FLEXICOKING (1976) use fluid bed technology
Thermally convert heavy oils such as vacuum residue, atmospheric residue,
tar sands bitumen, heavy crudes, deasphalter bottoms & other heaviers
Heat for the process is supplied by partial combustion of coke. Remaining coke is
withdrawn as product
Feed is injected into a fluidised bed with hot coke particles. Steam is injected at the
bottom for fluidization
New coke formed is deposited as a thin layer on the surface of circulating coke
particles; Coking vessel temp °C;residence time sec.
FLEXICOKING goes one step beyond FLUID COKING: in addition to
generating clean liquids, FLEXICOKING also produces a low-BTU (90 BTU/Cu.ft
or 800 Kcal/m3) gas in one integrated processing step that can virtually eliminate
petroleum coke production. ~ 95 % coke conversion is achieved

31. Fluid coking- Flexibility
Feed Quality- Conradson carbon- 15.5; Gravity I°API- 6.4, LV below 1000°F-8.0%; S- 2.6 %; N- 1.0 %; Ni- 283 ppm; V-126 ppm
Low ReactorTemp High ReactorTemp
Yields
Hydrogen sulfide H
C1-C C
C5-215°F °F
400°F to End point
Gross coke
Net coke
Coke
Sulfur %
Ni ppm
V ppm

33. Flexicoking- Product pattern
Vac.Residue properties
Arabian Light
Iranian Heavy
Gravity °API
6.5
5.1
Conradson carbon wt %
19.2
21.4
Sulfur Wt %
4.29
3.43
Nitrogen wt %
0.34
0.77
V+Ni ppm 90
525
Yield across Flexicoking
( Wt %)
C3 gas
9.8
9.9
C4 saturates
0.6
C4unsaturates
1.3
C5- 360°F naphtha
11.2
11.0
°F Gas oil
53.7
50.8
Gross coke
23.4
26.4
Purge coke
1.1
1.2
Coke gas (vol%)
13.1
15.5
Property
Flexicoke
Fluid coke
Bulk density lb/ft3 50 60
Particle density
lb/ft3 85 95
Surface area
m 2/g 70 12
Av.Particle size μ
120
Sulfur wt %
2.0
6.0
After particulate removal
After sulfur removal
H2S vppm
7100
<10
COS vppm
150
<5
NH3 vppm
<3
HCN vppm
Nil
Solids lb/Mscf
0.0042
Sulfur wt%
9.7
,0.04

34. Thermal Processes-Comparison
Visbreaking
Delayed coking
Fluid coking
Mild heating at psi; °C
Reduction in viscosity
Low conversion `10%
Heated coil or drum
Moderate heating at °C & 90 psig
Soak drums at °C .Processes continues till complete coking occurs
Coke removed hydraulically
Coke % Yield 30%
Severe heating at 10 psi °C
Fluid bed with steam
Cracking on fluidized coke
Higher yield of < C5
Less/no coke yield
Fuel grade gas

35. Liquid products from thermal processing require further treatments for use as fuels
MS Rana et.al. Fuel,86,1216,2007

36. Propane deasphalting
Generic name- Solvent Deasphalting (SDA) to yield DeAsphalted Oil (DAO)-Feeds- Vac residue/bitumen
Coke-forming tendencies of heavier distillation products are reduced by removal of asphaltenic materials by solvent extraction.
Liquid propane is a good solvent. Butane, pentane, Heptane or mixture of solvents are also commonly used.
Vacuum residue is fed to a counter current deasphalting tower.
Deasphalting is based on solubility of hydrocarbons in propane, i.e. the type of molecule; Alkanes dissolve in propane whereas asphaltenic materials (aromatic compounds), ‘coke-precursors’ do not.
Asphalt is sent for thermal processing.
Deasphalted oil can be used as Lube oil base feedstock (LBFS) or as feed to FCCU

37. Propane deasphalting
DAO from propane de-asphalting has the highest quality but lowest yield, possibly due to low critical temp.97°C & Max extraction temp-82 °C
Mixtures of propane & n-butane more suitable for better extraction.
Using pentane may double or triple the yield from a heavy feed, but at the expense of contamination by metals and carbon residues that shorten the life of downstream cracking catalysts due to their increased solubility.
Choice of solvent & extraction conditions are critical

38. Propane deasphalting
Propane/Oil ratio- 6:1 to 10:1 by vol.

39. Deasphalting process - Data
Parameters
Feedstock
Deasphalted Oil
Asphalt
Crude Vol % 23
49.8 Vol% feed
50.2 Vol% feed
Gravity, °API
6.8
18.1
-1.3
Conradson carbon wt % 15
5.9
SUS at 210°F
75000
615
Ni wppm
73.6
3.5
V wppm
365
12.4
Cu+Fe wppm
15.5
0.2
SUS-Sabolt Universal Seconds –ASTM D 2161-Related to kinematic viscosity