2. For optimum clinker quality
• The kiln feed chemistry must be of low
variability ( must be good uniformity)
• The raw meal must be adequately ground
• The coal ash must be uniformly
incorporated into the clinker
• The clinker must be rapidly cooled from
the burning zone temperature.
3. CHEMICAL COMPOSITION OF
CLINKER
*
COMPOSITION NORMAL RANGE CONTENT
SiO2 - (S)
Al2O3 - (A)
Fe2O3 - (F)
CaO - ( C)
20-22 %
5-6 %
3-4 %
63-66 %
‘main element’. This 4 oxide
containing 95% chemical
composition in clinker
MgO
SO3
K2O
Na2O
Loss on ignition
0.5-3.0 %
0.3-1.0 %
0.3-1.0 %
0.05-0.3 %
0.4-0.7 %
‘minor element’ Containing 5
% from overall clinker
composition
TiO2
Mn2O3
Chloride
Florine
Cr2O3
0.1-0.5 %
0.01-0.10 %
0.01-0.10 %
0.01-0.05 %
0.01-0.05 %
‘traces element’
4. During burning process the four
main constituent of clinker are
successively formed
1. C3A
2. C4AF
3. C2S
4. C3S
Temperature bet 1260 0C – 1338 0C
Temperature bet 1260 0C – 1338 0C
Temperature bet 1338 0C – 1420 0C
Temperature bet 1338 0C – 14200C
5. BOGUE FORMULA
C3S = 4.07C-7.6S-6.72A-1.47F
C2S = 2.867S-0.754C3S
C3A = 2.65A-1.69F
C4AF = 3.04 F
Where C = total CaO-free CaO-0.7SO3
S = total SiO2-Insoluble residue
6. CLINKER MINERALOGY
• Alite for C3S-tricalcium silicate
3CaO+SiO2 Ca3SiO5
• Belite for C2S-Dicalcium silicate
2CaO +Al2O3 Ca2SiO4
• Aluminate for C3A-Tricalcium aluminate
3CaO+Al2O3 C3A
• Ferrite for C4AF- Tetracalcium alumino ferrite
4CaO+Al2O3+Fe2O3 Ca4Al2O10
Major compounds
8. NAME SHORT
NAME
‘MINERAL
NAME
PROPORTION NORMAL
RANGE*
PROPERTIES
(CLINKER+ GYPSUM)
Tricalcium silicate C3S Alite 16 parts 50-62 Strength 28 days
Dicalsium silicate C2S Belite 2 parts 10-24 Long term strength
Tricalcium aluminate C3A Aluminate 1 parts 5-12 Setting time, early
strength
Tetracalcium
aluminaferrite
C4AF Ferrite 1 parts 7-12 No effect on strength
but gives a dark color
4 MAJOR COMPOUNDS IN CLINKER
* Depend on type of cement produce
By Bogue calculation only give potential clinker phase but by microscopic can
Determine the real clinker phase.
9. C3S (Alite Properties)
• Main strength constituent in cement
• Higher initial strength and good final
strength
• Rapid hydration
• Contains impurities: Mg, Al, Fe
• Typically 50-62 % of clinker
• Difficult to burn kiln feed if C3S >65%
10. C2S (Belite) properties
• Low early strength but good final strength
• Slow hydration
• Contains impurerities:alkalis,Al,Fe,flouride
• Typically 16-24 % of clinker
• Clinker grindability adversely impacted by
higher C2S.
11. C3A Properties
• Rapid hydration- gypsum added to control rate
• Early strength
• Typically 5-12 % of clinker
• Importance impact on clinker quality:
-Plasticity/workability
-Resistance to sulfate in soil/water exposure.
12. C4AF Properties
• Governs the color of cement i.e
higher C4AF = darker cement
• Hardly any strength development
• Slow to moderate hydration
• Typically 7- 12 %
13. Alkali Equivalent (NaEq)
Na2O+0.658K2O
• Combines both alkalis expressed to equivalent
Na
• Importance for product specification
• Influence cement performance
• Setting time decrease with increase the alkali
sulfate.
-can lead to flowability problem
-can react with same aggregates and lead to
concrete durability problems
• Influence kiln stability as volatile compounds
16. HARD BURNING CLINKER- VERY BIG ALITE CRYSTAL-LOWER
28 DAYS STRENGTH
OVER BURN-HIGH TEMPERATURE OR LONG FLAME
17. 16/5/03-X50 Alite sixe 138 um
5/5/03-X50 Alite sixe 53 um-dusty clinker
23/10/0-X50 PC 100 %- Alite sixe 138 um
1 2
3
Photo1: Large fused alite crystal due to slow passage at
highTemp. Through burning zone & Reducing condition
Photo2: dusty clinker product -due to raw mix difficult to burn the
temperature in burning zone very high and too long, in sufficient
nodulation taken place
Photo3: Large alite cystal size, hard burning.
18. Large free lime cluster due to coarse limestone particle in raw feed
RAW MIX FINENESS
25. REDUCING/OXIDISING
• Reducing condition if:
- Lack of Oxygen
- Poor mix of fuel and fuel
- Coarse of fuel particles
• Symptoms:
- CO2
- SO2
- Volatilization
• Oxidizing condition if:
- Enough oxygen
- Good Mix (burner)
- Fine Fuel
• Signs:
- Stable O2
-Reduced amount of
build-up
- improve kiln stability
26. Factors effecting clinker reactivity
• CHEMICAL COMPOSITION
-C3S, C2S, C3A, C4AF, SO3, ALKALIS, FREE LIME.
• PARTICLE SIZE DISTRIBUTION OF RAW MEAL
200UM, 90UM, 63UM
• MINEROLOGY FORMATION
C3S- CRYSTAL SIZE, BIGGER/SMALLER
SHAPE-ROUND OR SHARP EDGE
C3A- ORTHOROMBIC
- CUBIC (if more soluble alkali-sulfate)
- Periclase
27. FACTORS INFLUENCING
CLINKER TEXTURE
Influence parameters Specific factor
Raw mix properties -chemical composition, major &
minor elements
-fineness and Mineralogy
-homogeneity
Fuel type - Coal ash
Burning condition -burning time/temperature
- Kiln atmosphere O2(reducing
condition), NOX
Cooling condition -rate of cooling
28. HOW TO INCREASE CLINKER
REACTIVITY?
• Increase the C3S ( but not more than 65%)
• Fast cooling rate
• Fast heating rate, need short flame & hot
• Ovoid over burning to control alite size max
40um
• Control the SO3/Alkali >1
• Optimize the PSD of raw meal
• Homogenity of raw meal
• Avoid reducing condition environment inside kiln.
