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OVERVIEW
What is Cetane Number?
How do we improve Cetane Number?
How does Cetane Number impact engine operation?
WHAT IS CETANE NUMBER
Cetane number is a numerical representation of the ignition delay of a given fuel
• The number is defined as the equivalent % n-Cetane (n-Hexadecane) in a blend with α-methylnaphthalene
n-Cetane has a CN of 100
α-methylnaphthalene has a CN of 0
Due to difficulties working with α-methylnaphthalene, it was replaced with heptamethylnonane
Heptamethylnonane has a CN of 15
n-Cetane (n-Hexadecane)
α-methylnaphthalene
Heptamethylnonane
CN = % N-cetane + 0.15 (% Heptamethylnonane)
HOW DO WE IMPROVE CETANE NUMBER –PHYSICAL DELAY
Physical delay is influenced by:
Density and temperature of air in cylinder
Velocity and turbulence of air
Atomization, penetration and shape of fuel spray
Properties of fuel:
Density
Viscosity
Surface tension
Specific heat
Heat of vaporization
Vapor pressure
Vapor diffusivity
HOW DO WE IMPROVE CETANE NUMBER –CHEMICAL DELAY
Chemical delay is influenced by rate of free radical formation
Fuel is heated to high temperature where weaker bonds break, forming free radicals
Once a sufficient concentration of free radicals is reached, combustion occurs
Cetane Number Improvers increase rate of free radical production
HOW DO WE IMPROVE CETANE NUMBER –CETANE NUMBER IMPROVER
2-ethylhexyl nitrate (CI-0801)
Most widely used CNI
Di-tert-butyl peroxide (CI-0808)
Nitrogen content of fuel is limited eg. CARB
Relative effectiveness of 75% vs 2-EHN
More expensive than 2-EHNRange of Cetane improvement in middle distillate fuels using CI-0801
EFFECT OF CRUDE OIL SOURCE ONDIESEL FUEL COMPONENT QUALITY
Light Gasoil
ex Arab Light
Crude
Light Gasoil
ex Forties
Crude
Light Gasoil
ex Nigerian
Crude
Light Gasoil
ex Venezuela
Crude
Cut Point, °C 235 - 280 235 - 280 235 – 280 235 - 280
Density,
g/cm3
0.8259 0.8368 0.8757 0.8439
Sulphur, wt% 0.72 0.09 0.11 0.32
Cetane Index 53.5 49.5 37.7 50.1
Cetane
Number
54.3 52.2 41.3 50.4
EFFECT OF PROCESS UNIT TYPE ON DIESEL FUEL COMPONENT QUALITY
Non
Hydrotreated
LCGO
Hydrotreated
LCGO
Hydrocracker
Gasoil
Coker Gasoil
Cut Point, °C 205 - 343 205 - 343 205 - 343 205 - 343
Density, g/cm3 0.9613 0.9294 0.8498 0.9196
Sulphur, wt% 1.35 0.24 0 Crude dependent
Cetane Index 23.4 28.4 56.0 36.1
Cetane Number 21.0 24.1 57.8 32.6
EFFECT OF DISTILLATION CUT ONDIESEL FUEL COMPONENT QUALITY
Heavy Naphtha
ex Forties
Crude
Light Kerosene
ex Forties
Crude
Heavy
Kerosene ex
Forties Crude
Gasoil ex
Forties Crude
Cut Point, °C 150 - 190 190 - 235 235 - 280 280 - 343
Density, g/cm3 0.7870 0.8136 0.8368 0.8614
Sulphur, wt% 0.01 0.03 0.09 0.21
Cetane Index 35.5 44.1 49.5 50.6
Cetane
Number
37.8 46.0 51.7 54.9
CETANE NUMBER AND ENGINE OPERATION
Shorter ignition delay improves several factors of engine operation
Improved cold-weather starting
Less white smoke at start-up
Shorter warm-up time
Lower emissions
Decreased noise
Increased engine durability
Possible fuel economy improvement
0.00
0.20
0.40
0.60
0.80
1.00
1.20
36 40 44 48 52 56
Hyd
roca
rbon
g /b
hp-h
r
Cetane number
Without CNI
With CNI
EFFECT OF CN ON HC EMISSIONS
1.00
1.20
1.40
1.60
1.80
2.00
2.20
2.40
2.60
2.80
3.00
38 40 42 44 46 48 50 52 54 56
CO
em
issi
ons,
g/b
hp-h
r
Cetane Number
Without CNI
With CNI
EFFECT OF CN ON CO EMISSIONS
5.40
5.60
5.80
6.00
6.20
6.40
6.60
6.80
38 40 42 44 46 48 50 52 54 56 58
NO
x E
mis
sion
, (g/
kWh)
Cetane Number
Without CNI
EFFECT OF CN ON NOX EMISSIONS
1.00
1.20
1.40
1.60
1.80
2.00
2.20
2.40
2.60
2.80
3.00
38 40 42 44 46 48 50 52 54 56
CO
em
issi
ons,
g/b
hp-h
r
Cetane Number
Without CNI With CNI
EFFECT OF CN ON PARTICULATE EMISSIONS
0
20
40
60
80
42 46 50 54 58
Whi
te S
mok
e (%
)
Cetane Number
Without CNI
With CNI
EFFECT OF WHITE SMOKEIN A DI DIESEL ENGINE
5.40
5.60
5.80
6.00
6.20
6.40
6.60
6.80
38 40 42 44 46 48 50 52 54 56 58
NO
x E
mis
sio
n, (
g/k
Wh
)
Cetane Number
Without CNI
With CNI
Expon. (With CNI)
THE EFFECT OF CNI AND TEMPERATUREON ENGINE NOISE AT IDLE (900 RPM)
ECOCLEAN® TECHNOLOGY
To improve the performance of diesel fuel in modern-day diesel engine systems
Corrosion Inhibition
CetaneNumber
Thermal Stabili-zation
Detergency/Dispersancy
Dehazing/
Demulsifi-
cation
Antifoam