1. Understanding Fuel Oils

2. Topics Introduction Refining Processes Fuel oil composition
Fuel Oil production
A Modern refinery
Refining trends with example
Conclusions
Key quality indicators
Quality trends Vs Technology
Effect of Fuel oil quality on engine performance
Storage & handling-A Recall

3. Introduction Fuel oil is Cheap but has fair CV Residual Fuel
Diesel Cycle
Low Cetane value
Hence for Low/Medium speed
Natural source
Not much can be done on quality
Engines built to suit this fuel

4. FRACTIONS FROM 3 DIFFERENT CRUDES
Viscosity,20°C
% asphaltenes
Gasoline (C5-80°)
Heavy gasoline (80-160°)
Kerosene ( °)
Middle distillate ( °)
Heavy distillate ( °)
Residue (400 +)
35.8
5.8
4.09
9.05
12.58
14.12
7.51
50.42
10.2
0.93
5.56
12.02
15.5
17.19
8.72
38.71
ARABIAN
HEAVY
LIGHT
NIGERIAN
BONNY
11.2
0.08
5.06
15.0
9.32
25.2
44.6

5. CHARACTERISTICS OF SOME CRUDE OILS
Viscosity,20 °C,cSt
Sulfur,%
Vanadium, ppm
Nickel, ppm
Asphaltenes, %
Conradson carbon,%
Arabian
light
9.2
1.8 15 5
0.7
5.1
heavy 40
2.8 30 10
2.7
Ekofisk
0.12
< 1
1.4
0.88
Nigeria
6.7
0.11 2 6
0.08
0.86
Basrah 57
3.58 54 22
8.3
Boscan
250000
5.2
1200
100
10.8
16.4
Ural
12.5 65 20

6. Refinery Process

7. Crude oil desalting
Water and inorganic salts are removed in an electrostatic field.
The main purpose of crude oil desalting is to protect the refining process units against corrosion.

8. Atmospheric distillation
Crude oil is a product with a very wide boiling range.
In an atmospheric distillation column the fractions
boiling below 360°C are distilled off under reflux, and,
according to boiling range, recovered as naphtha,
kero, and gasoil type stocks. Atmospheric distillation is
limited to a maximum temperature of 360°C, because
otherwise coking would start to occur, and this is not
desirable at this stage of crude oil refining.

9. Vacuum distillation
In order to distill off a heavier cut, without exceeding
the 360°C temperature limit, a second distillation is
done under reduced pressure: the vacuum distillation.
The distillate fraction of the vacuum distillation unit is
the feedstock for a catalytic cracking unit

10. Catalytic cracking
The main feedstock for a catalytic cracker is vacuum gasoil. The cracking operation breaks large molecules into smaller, lighter molecules. The process runs at high temperatures, and in the presence of the appropriate catalyst (crystalline aluminum silicate).
Atmospheric residue, with a low metal and MCR content, can also be used as catalytic cracker feed, necessitating an adjustment of the catalyst type.
The main purpose of a catalytic cracker is to produce light hydrocarbon fractions, which will increase the refinery gasoline yield.
Additional streams coming from the catalytic cracker are light cycle oil (increases the gasoil pool) and heavy cycle oil (base stock for carbon black manufacturing). Both streams are also used in heavy fuel oil blending.

11. Catalytic hydrocracking
Some refineries have catalytic hydrocracking as a supplementary operation to catalytic cracking.
Catalytic hydrocracking further upgrades heavy
aromatic stocks to gasoline, jet fuel and gasoil type material. The heaviest aromatic fractions of a cat cracker are the normal feedstock for a hydrocracker.
Hydrocracking requires a very high investment , but
makes the refinery yield pattern nearly independent
from the crude oil feed.

12. Visbreaking The feedstock of a visbreaker is the bottom product
of the vacuum unit, which has an extremely high
viscosity. In order to reduce that viscosity and to
produce a marketable product, a relatively mild
thermal cracking operation is performed. The
amount of cracking is limited by the overruling
requirement to safeguard the heavy fuel stability.
The light product yield of the visbreaker (around
20%) increases the blendstock pool for gasoil.

13. Coking (delayed coking, fluid coking, flexicoking)
Coking is a very severe thermal cracking process, and
completely destroys the residual fuel fraction. The
yield of a coker unit is lighter-range boiling material,
which ultimately goes to the blending pool for the
lighter products, and coke, which is essentially solid
carbon with varying amounts of impurities. The
heavier distillate fraction of a coker can be used as
feedstock for a hydrocracker

14. Catalytic reforming and Isomerization
Both processes are in fact catalytic reforming, and are intended to upgrade low octane naphta fractions of the crude distillation unit into high octane components for gasoline production. The type of catalyst and the operating conditions determine if the reforming is mainly to iso-paraffins, or to aromatics. The terminology “reforming” is generally used for the change to aromatics, while the change to iso-paraffins is referred to as “isomerization”. Isomerization is normally done on a lighter fraction(C5/C6), while reforming is done on the heavy naphtha fraction (C7 and heavier, up to 150°C).

15. Alkylation
Process intended to increase the yield of valuable gasoline blend components. Alkylation is a catalyst steered combination reaction of low molecular weight olefins with an iso-paraffin to form higher molecular weight iso-paraffins. The feed to the alkylation unit is C3 and C4s from the catalytic cracker unit, and iso-butane.

16. Hydrotreating
A hydrotreating process is, as the name indicates, a process, which uses hydrogen to remove impurities from product streams, and replaces them with hydrogen. Hydrotreating is generally used to remove sulphur (very low sulphur limits in the specifications of gasoline and gasoil) and is then called hydro-desulphurization. It is a catalytic process. The process is generally used on kerosene and gasoil fractions. Residual hydro-desulphurization is an existing process, and is in theory feasible, but the economics are not favorable.

17. Merox
A merox unit is used on naphtha and kerosene streams. It is a catalytic process which is not intended to remove the sulphur from the stream, but to convert mercaptan sulphur type molecules (corrosive, and with a very obnoxious smell) into disulphide type molecules.

18. Modern Refinery Atmospheric Distillation Vaccum Distillation
Reforming
Vaccum Distillation
Catalytic cracking
Hydrocracking
Visbreaking
Deasphalting

19. Atmospheric distillation

20. Vaccum distillation

21. Vaccum distillation + FCCU

22. Vaccum distillation + FCCU + VB

23. REFINERY SCHEMES Gas Reforming Visbreak. Hydrocr. Coking FCC NaphtaAD VD
Reforming
Visbreak.
Hydrocr.
Coking
FCC DA
Naphta
Gasolines
Kerosene
Diesel oils
Heavy fuels SR 1 2 3
Kero,Diesel
Heavy fuels
H2, no Heavy
Fuels 4
Asphalts

24. About Fuel oil

25. Straight run marine gasoil and distillate
Marine diesel
type MDO are manufactured from kero, light, and heavy gasoil fractions.
For DMC type gasoil, up to 10–15% residual fuel can be added.
Straight run IFO 380 mm2/s (at 50°C)
This grade is made starting from the atmospheric residue fraction (typical viscosity of about 800 mm2/s at 50°C) by blending with a gasoil fraction.
Straight run lower viscosity grade IFOs
Blending to lower grade IFOs is done from the IFO 380 mm2/s (at 50°C) using a gasoil type cutterstock or with marine diesel.

26. Complex Refineries
The main marine fuel blending components from a Fluidized Bed Catalytic Cracking (FCC) type refinery with visbreaker are the same distillates as those from a straight run refinery (light and heavy diesel) as well as light cycle (gas) oil (LC(G)O) and heavy cycle oil (HCO) from the catcracker and visbroken residue from the visbreaker.
Atmospheric residue is used as feedstock for the vacuum unit and will only seldom be available for fuel blending.

27. Complex Refineries Marine gasoil (MGO/DMA)
A new blend component has appeared — LC(G)O (light cycle (gas) oil) — which contains about 60% aromatics. Due to the high aromatic nature of LC(G)O, the density of a marine gasoil blended with LC(G)O will be higher than when using gasoil of an atmospheric distillation type refinery. No performance or handling differences with atmospheric type gasoil
Distillate marine diesel (MDO/DMB)
Distillate marine diesel typically has a lower cetane number than marine gasoil, and a higher density. With the production slate of a catalytic cracking refinery, distillate marine diesel therefore contain a higher percentage of LC(G)O than marine gasoil.

28. Complex Refineries Blended marine diesel (MDO/DMC) IFO-380
With atmospheric type refining, blended marine diesel (MDO/DMC) can contain up to 10% IFO with either marine gasoil (MGO/DMA) or distillate marine diesel (MD)/DMB). With complex refining, blended marine diesel (MDO/DMC) no longer corresponds to a specific composition and extreme care needs be used when blending this grade to prevent stability and/or combustion problems.
IFO-380
This grade is usually manufactured at the refinery and contains visbroken residue, HCO and LC(G)O These three components influence the characteristics of the visbroken IF-380 Vacuum distillation reduces the residue yield to about 20% of the crude feed, unavoidably leading to a concentration of the heaviest molecules in this fraction. Visbreaking converts about 25% of its vacuum residue feed into distillate fractions. This means that about 15% of the original crude remains as visbroken residue. The asphaltene1, sulphur and metal content in visbroken residue are 3 to 3.5 times higher than in atmospheric residue. Visbreaking affects the molecular structure: molecules are broken thermally and this can deteriorate the stability of the asphaltenes.

29. Complex Refineries
HCO (typical viscosity at 50°C: 130 mm2/s) contains approximately 60% aromatics, and is a high-density fraction: the density at 15°C is above 1 kg/l (typically 1.02). It is the bottom fraction of the FCC unit. The catalytic process of this unit is based on an aluminum silicate. Some mechanical deterioration of the catalyst occurs in the FCC process, and the resulting cat fines are removed from the HCO in the refinery. This removal however, is not 100% efficient, and a certain amount (ppm level) of cat fines remains in the HCO, and from there end up in heavy fuel blended with HCO. The aromaticity of HCO assists in ensuring optimum stability for the visbroken fuel blend.
LC(G)O (typical viscosity at 50°C: 2.5 mm2/s) has the same aromaticity as HCO, but is a distillate fraction of the FCC unit, with a distillation range comparable to that of gasoil. With a typical density of 0.94 kg/l at 15°C, it is used to fine-tune the marine heavy fuel oil blending where generally a density maximum limit of kg/l has to be observed.

30. RESIDUE OR HEAVY FUEL OIL
CHEMICAL COMPOSITION
RESIDUE OR HEAVY FUEL OIL
MALTENES
ASPHALTENES
"OIL"
"RESINS"
SATURATED
AROMATIC

31. Components OIL RESIN ASPHALTENES Molecular weight < 800
Mixture of paraffins,naphthenes & aromatic
RESIN
Molecular weight ~ 1000
condensed aromatics with aliphatic ring chains
ASPHALTENES
Molecular weight between 1000 ~ 2000
Highly condensed aromatics

32. Conclusions-Macro level
Fuel oil yield drop
More of fluxing
Less of lighter components
More complications due to types of crudes

33. Conclusions-Micro level
Increased density
Increased Viscosity
Increased carbon residue
Increased asphaltenes
Increased sulphur
Reducing heating value ????
Increasing trace metals ????
Instability
Incompatibility

34. Key Quality Indicators
Specific gravity
Weight per unit volume
Flash point
Safe operating temperature
Viscosity(Kinematic)
Resistance to flow
Pour Point
Lowest Flowable temperature
Sulphur content
% wt of Sulphur in Fuel oil
Calorific value
Heat per unit weight

35. Key Quality Indicators
Ash Content
Inorganic & non combustible matter
CCAI
Ignition quality
Conradson carbon residue(CCR)
Residual matter

36. HFO CHARACTERISTICS

37. Effects of quality parameters on engine performance

38. Viscosity Injection Characteristics Injector pump wear
Droplet size of microns
10-15 Cst at nozzle tip
Injector pump wear
Fuel flow properties
Preheating to correct viscosity at nozzle tip
Certain cases upto 150 deg C

39. FUEL INJ VISC INJ VISC
13 CST CST

40. Ignition Characteristics(CCAI)
Shell proposed
Calculated Carbon Aromaticity Index
D-140.7LOG LOG (V+.85)-80.6
D:Specific 15deg C
50 deg C
Nomographic method most suitable
Max acceptable around 900
BP's CCI also used
Diesel Index
(API gravity*aniline point deg F)/100

41. Sulphur SOx + water ----> Sulphuric acid Temp drops below dew point
Corrosion
Cold corrosion
Control of temperatures
Lubricant

42. Conradson Carbon residue
Formation carbon deposits
"Trumpets"
Injection characreristics are altered
lower the speed more the tolerance for CCR
Indicative of apshaltene content
CCR% = 2* asphaltenes

43. Ash Na,V,Si,Fe compounds Cooler valve seats etc Hot Corrosion
At melting points they form deposits
Hard At hot spots
Cooler valve seats etc

44. Calorific Value heat energy contained Emperical formulae FUEL OILS HSD
GCV(btu)=1.8( d*d)
d-Spec 60 deg F
FUEL OILS
GCV=80.84*C H+22.24S
C,H,S % OF carbon,hydrogen & Sulphur

45. Calorific Value Specific Energy (Gross) MJ/kg
Qg = ( p2 10-6) [ (x+y+s)] (0.01s)
Specific Energy (Net) MJ/kg
Qn = ( p p10-3) [1-0.01(x+y+s)]
(9.420s x)
p = the density at 15 °C, kg/m³ x = the water content, % (m/m) y = the ash content, % (m/m) s = the sulphur content, % m/m

46. Typical % of C,H,S

47. Storage & Handling

48. MODEL OF ASPHALTENE MOLECULE
CH2
CH3 CH CH
CH2
CH3 N
CH2
CH3
CH3 O
CH2
CH2
CH3
CH3
CH2 S
CH2
CH3
CH2 CH
CH2 S
CH2
CH3
CH3
CH3

49. ASPHALTENES CHARACTERISTICS
Polycondensed aromatic structures with few alkyl chains
Contains hetero-atoms: S, N, O
Contains metals: V, Ni, Na
Not soluble in oil
Size of the micellar unit: A
Cannot boil even under reduced pressure
Molecular structure depends on crude oil origin

50. RESINS CHARACTERISTICS
Chemical structure close to asphaltenes structure but:
LONGER ALKYL CHAINS
LESS CONDENSED RINGS
MORE SOLUBLE IN OIL
Molecular structure depends on crude oil origin
Presence necessary to provide a good stability to the fuel

51. HEAVY FUEL OILS DISPERSED AND STABLE FLOCULATED
Resins ensure seperation of heavy asphaltene molecules. Flocculated Asphaltene molecules tend to form sludge and settle at the bottom of the tank.

52. Instability Asphaltenes "peptized" by resins
Instability occurs when this peptization breaks
Apshaltenes "flocculate"
Precipitation occurs
Filter clogging,Overloading of Centrifuge,deposits in tanks
"No more a major problem"

53. Incompatibilty When 2 different source FO's mix
Effects will be similar to Instability
ASTM D 4740 "spot test"
"Avoid mixing FO's from different refineries"

54. Pre-Preparation Settling Purification Clarification Homogenisation
Additives
Costly
Uncertain efficiency
Filteration

55. UNBURNT PARTICLES PROBLEM ORIGIN SOLUTION
EMISSIONS OF UNBURNT PARTICLES
HEATING SURFACES FOULING
FREQUENT BOILER CLEANING
COST OF EMISSION LIMITATIONS
ORIGIN
NEED OF COMBUSTION IMPROVER
VERY LOW METAL CONTENT
SOLUTION
ADDITIVE B

56. ISO 8217 FUEL STANDARD FOR MARINE DISTILLATE FUELS

57. ISO 8217 FUEL STANDARD FOR MARINE DISTILLATE FUELS

58. ISO FUEL STANDARD 8217, 1ST REVISION 1996, FOR MARINE RESIDUAL FUELS

60. Revision of ISO 8217 Release end 2005, early 2006 ? Main changes :
Fuel grades basis viscosity at 50 °C instead of 100 °C
RMC 10 no longer exists
RMA 30 , RMB 30 and RMD 80 : lower max. density
Water content : max. 0.5 v/v % for all grades
Ash content :
Fuel grades with a max ash of m/m % : no changes
Fuel grades with a max ash of 0.20 m/m % : new max limit : 0.15 m/m %
Sulphur content : as of RME 180 : 4.5 m/m % max.
Limits for used lubricating oils (ULO): A fuel shall be considered to be free of ULO if one or more of the elements Zn, P and Ca are below or at the specified limits (resp. 30/15/15 mg/kg)

62. FUEL VISC
Temp cSt

63. THANK YOU