This document discusses key parameters that affect the quality and production of Portland cement clinker: 1) The lime saturation factor (LSF) expresses the combination of lime with other oxides to form clinker compounds, and should be within 92-95% for high quality clinker. 2) The silica modulus (SM) is the ratio of silica to alumina and iron, and is typically 2-2.4% to ensure good clinkerization. 3) The alumina modulus (AM) indicates the amount of liquid phase formed, and is ideally 1.4-1.7% for high quality clinker. Tables show the effect of varying these parameters on clinker

1. 14
CHAPTER - 3
3.1 M O D U L U S
The production of the Portland cement clinker is depending on the mixture of the different
raw materials selected for this purposes after knowing the chemical composition of each
component of those materials. To have a good quality of the Portland cement clinker, it
should have , from one side, a good mixture of the raw materials and good homogenizity of
the kiln feed materials, and from other side, it is necessary to select some parameters which
affect the quality of the produced clinker according to the desired chemical and physical
properties of the clinker.
The approximate chemical compositions of the Portland clinker is indicative for the raw mix
and they are shown in the Table 3.1.
Table 3.1 Chemical Composition of Clinker [ 13 ].
Chemical Composition (%) Chemical Composition (%)
CaO 58 - 67 K2O 0 - 1
SiO2 16 - 25 Na2O 0 - 1
Al2O3 3 - 8 Mn2O3 0 - 0.3
Fe2O3 2 - 6 TiO2 0 - 0.5
MgO 0 - 6 P2O5 0 - 1.5
SO3 0.1- 3.5 LOI 0.5 - 3
3.2 Lime Saturation Modules ( Factor)
The Lime Saturation Factor (LSF) express the combination of the lime with the Iron Oxide,
the Alumina and the Silica to form the clinker compound. It is a ratio which reflect the actual
CaO content to the maximum CaO content in the clinker.
The theoretical limit for the lime saturation factor is 100 %. This is a theoretical value of the
maximum amount of the CaO that could be added to the raw mix. If more quantity of CaO
added, more than what can be theoretically ( LSF = 100 % ) combined with the Silicate, the
Alumina and the Iron , the excess quantity will remain as free lime, because it can not burn
the saturated mix.
The Calcium Oxide CaO should be carefully proportioned with the other constituents of the
raw mix. At the sintering temperature the C3S and the C2S are in solid state, whereas C3A
and C4AF are in the fusion state. the theoretical limit for the lime saturated liquid aluminate,
that can be practically binded with the compounds, is according to the following
stoichiometric functions :
)
a
1
.
3
(
7998
.
2
0848
.
60
0794
.
56
*
3
binds
S
C
in
SiO
of
part
1 3
2 
For AM  0.6385
)
b
.
1
.
3
(
1.6500
=
101.9612
56.0794
*
3
binds
A
C
in
O
Al
of
part
1 3
3
2

2. 15
For AM  0.6385
therefore under the technical condition, the lime limits with the Alumina ratio of
AM  0.6385
CaO = 2.7998 SiO2 + 1.1000 Al2O3 + 0.7024 Fe2O3 (3.2)
and with the Alumina ratio of AM > 0.6385 is,
CaO = 2.7998 SiO2 + 1.6501 Al2O3 + 0.3512 Fe2O3 (3.3)
Lea [ 35 ] have expressed the maximum calcium oxide content which can be present without
free lime appearing at the sintering temperature with the liquid presence to form the clinker
compound.
CaO = 2.7995 SiO2 + 1.18 Al2O3 + 0.65 Fe2O3 (3.4)
Then the Lime Saturation Factor for AM  0.6385 and according to the relations 3.4 is,
and the Lime Saturation Factor for AM > 0.6385 is,
Kühl [ 33 ] has refined the LSF formula for the maximum combined Lime content in the case
of AM  0.6385 , to permit for the combination of a small amount of Magnesia MgO with
C3S.
For MgO  2%
and for MgO > 2 %
)
5
.
3
(
%
O
Fe
65
.
0
O
Al
18
.
1
SiO
7998
.
2
CaO
LSF
3
2
3
2
2 


)
6
.
3
(
%
3512
.
0
6500
.
1
7998
.
2 3
2
3
2
2 O
Fe
O
Al
SiO
CaO
LSF



)
7
.
3
(
O
Fe
65
.
0
O
Al
18
.
1
SiO
7998
.
2
MgO
75
.
0
CaO
LSF
3
2
3
2
2 



)
8
.
3
(
O
Fe
65
.
0
O
Al
18
.
1
SiO
7998
.
2
MgO
5
.
1
CaO
LSF
3
2
3
2
2 



)
c
.
1
.
3
(
0.3512
=
159.6782
56.0794
binds
CaO
in
O
Fe
of
part
1 3
2
)
d
.
1
.
3
(
1.1000
=
101.9612
56.0794
*
2
binds
AF
C
in
O
Al
of
part
1 4
3
2
 
3.1.e
0.7024
=
159.6782
56.0794
*
2
binds
AF
C
in
O
Fe
of
part
I 4
3
2

3. 16
The lime saturation factor approach the unity as a theoretical limit value. It means, it is
perfect combination of four Oxides with zero free lime.
The value of the Lime Saturation Factor regarding the clinker composition is within the range
of 88 % to 98 %. But for the standard Portland cement clinker, and to have a high quality
of the clinker the lime saturation factor is in the range of 92 % to 95 %.
3.2.1 Effect of the Lime Saturation Factor.
The Lime saturation factor has a great effect on the clinker formation. It is one of the most
important factor that characterize the physical properties of the clinker.
Table 3.1 The effect of the variation of the Lime Saturation Factor.
LSF 93 94 95 96 97 Increase
AM 1.5 Constant
SM 2 Constant
Component Percentage (%)
HLS 15.4 16.7 18.05 19.34 20.61
LLS 82.3 81.6 80.35 79.10 77.87
SS 1.34 1.30 1.273 1.24 1.21
Iron 0.345 0.334 0.323 0.31 0.301
C3S 52.9 55.3 57.67 59.99 62.28
C2S 20.4 18.12 15.90 13.71 11.56
C3A 9.60 9.53 9.46 9.36 9.32
C4AF 12.80 12.70 12.61 12.52 12.43
Liq. 29.89 29.68 29.47 29.26 29.06
BI 2.36 2.49 2.61 2.74 2.86
BF 107.7 108.7 109.73 110.74 111.75
Table 3.1 shows, for a given raw materials, the effect of the variation of the Lime saturation
factor on the raw mix composition and on the physical properties of the clinker. The sign
means increase and the sign means decrease. It is noticed that the variation of the lime
saturation factor affects intensively the raw mix composition and the physical properties of
the clinker.
3.2.1.1 High Lime Saturation Factor.
- The raw mix with high LSF is difficult to burn, which reflect for high fuel consumption.
- Shows low setting.
- High strength at early ages.
- Tend to produce unsoundness cement which is not acceptable.

4. 17
- For LSF higher than 97 %, the free lime could remain at high level even with more fuel is
supplied to the kiln burner.
3.2.1.2 Low Lime Saturation Factor.
- Lower value of LSF produce a low strength cement.
- Low lime saturation factor generate coating formation inside the kiln.
- Raw mix with low LSF correspond to a high C2S and low C3S.
- Quick stetting.
- Produce a poor quality cement.
- Containing excessive silica and alumina.
- Reducing CaO and increasing SiO2 reduce the strength of the cement.
- Change of 1% of the LSF give a change in burnability equal to a change of 0.1 SM of the
same raw mix.
3.3 SILICA MODULUS
The Silica Modulus - SM - or Silica ratio is the second very important modulus for the clinker
production which, other than the effect in the preheater and in the kiln, characterizes the
quality of the clinker. The Silica modulus gives an indication of how well the raw mix
clinkerisation will be in the kiln. A large variation of the Silica ratio in the clinker is an
indication of poor uniformity and homogenesity in the kiln material feed.
The Silica modulus is presented as the ratio of the Silica to the total combined of the alumina
and the Iron.
The Silica Modulus is limited between 1.8 % and 3.5 %. Practically, for the production of the
Portland cement clinker, the Silica modulus is preferred to be selected in the range of 2 % and
2.4 %. For high Siliceous cement or for white cement production, the Silica modules may
have higher value than the above indicated value.
The selection of the lower or higher Silica modules than the indicated range depends on the
mineralogical composition of the raw mix and on the other chemical constituents.
3.3.1 Effect of the Silica Modules.
The existence of the Silica constituent in the Portland cement raw mix has a great influence
on the quality of the cement and on the pyro-process it self. The physical and the chemical
properties of the cement is depend on the proportion of the Silica content which is expressed
by the Silica Modulus formula. There is a range for the Silica Modulus to be used to produce
a good Portland cement. The selection of the higher or lower Silica Modulus, than the
practical range, has an advantage and disadvantage on the pyro-process and on the kiln
operation.
)
9
.
3
(
O
Fe
O
Al
SiO
SM
3
2
3
2
2



5. 18
Table 3.2 The effect of the variation of the Silica Modulus.
SM 2 2.1 2.2 2.3 Increase
AM 1.5 Constant
LSF 0.95 Constant
Component Percentage (%)
HLS 18.05 24.82 31.08 36.89
LLS 80.35 72.79 65.81 59.31
SS 1.27 2.16 2.98 3.74
Iron 0.323 0.22 0.126 0.04
C3S 57.67 58.59 59.44 60.23
C2S 15.90 15.74 15.6 15.46
C3A 9.46 9.09 8.75 8.43
C4AF 12.61 12.12 11.66 11.24
Liq. 29.47 28.36 27.34 26.39
BI 2.61 2.76 2.91 3.06
BF 109.73 110.82 111.89 112.97
Table 3.2 shows, for a given raw materials, the effect of the variation of the Silica Modulus
on the raw mix composition and on the physical properties of the clinker. The sign
means increase and the sign means decrease. It is noticed that the variation of the Silica
Modulus affects intensively the raw mix composition where as this effect is small on the
physical properties of the clinker.
3.3.1.1 High Silica Modulus.
- The high Silica Modulus selection for the portland cement production has the following
effect :
- The raw mix will have tendency to be more difficult to be burned, which lead to high fuel
consumption and which reflect to the increase of the production cost.
- The liquid phase of the clinker will be reduced.
- The free lime will have the tendency to be increased.
- The coating in the kiln will have poor properties.
- The Silica is an abrasive composition, therefore the high silica modulus will deteriorate
the kiln bricks lining, which increase the heat radiation from the kiln shell.
- The cement will have a slow setting and slow hardening.
- The resistance against the chemical and atmospheric attack will be intensified.
- The cement with high Silica modulus shows a low early strength (up to 10 days), but later,
this strength progress faster with the age and become higher than that of the low Silica
modulus.
- In case if the silica modulus exceed 3 %, the kiln operation will be unstable, and it will
have a high thermal load.

6. 19
3.3.1.2 Low Silica Modulus.
The results of the low silica modulus are as the following :
- The reduction of the Silica Modulus by increasing the iron or the alumina by keeping
constant the silica composition content, it will produce an excessive liquid at the normal
temperature which will wash the coating. It means the attack of the bricks lining will be
increased.
- The clinker burnability will be improved with the reduction of the silica modulus.
- The clinker production is relatively dense.
- The low silica modulus will increase the probability of the thick coating formation and the
possibility of balls and ring formation inside the kiln which can block the kiln. It means,
it leads to the reduction of the kiln feed.
- The dusty clinker condition inside the kiln will be reduced, which reflect to improve the
clinker nodulization.
- In case of lowering the silica modulus more than practical range, it will lead to the kiln
difficulties due to much clinker melting in the kiln and reflect to a snow man formation in
the cooler.
- The cement with low Silica modulus shows an high early strength (up to 10 days) then
the strength progress slowly with the age.
3.4 SILICA ACID MODULUS.
Silica acid modulus is represented by the following equation.
)
10
.
3
(
3
2
2
O
Al
SiO
SAM 
This modulus express the coating conditions on the kiln lining during the clinker burning.
The range of this modulus is limited between 2.4 % to 3 %. The best results can be obtained
when the SAM is between 2.5 % and 2.7 .
3.5 ALUMINA MODULUS.
The Alumina modulus express the composition of the liquid phase in the clinker. It gives an
indication of the amount of the melt which will be formed in the selected raw mix. The
presence of the liquid in the kiln is very important factor, because it promotes the other
reaction which occur mainly in solid state.
The following formula represent the Alumina - Iron ratio which characterises the composition
of the melt, because the Alumina and the iron oxide are almost completely melted at the
clinkering temperature.
)
11
.
3
(
3
2
3
2
O
Fe
O
Al
AM 
The alumina modulus value is in the range of 1.3 % to 2.5 %. To obtain a good clinker
quality, it is preferable to use the Alumina modulus in the range between 1.4 % and 1.7 %.
Table 3.3 The effect of the variation of the Alumina Modulus.

7. 20
AM 1.4 1.45 1.5 1.55 1.6 Increase
SM 2 Constant
LSF 0.95 Constant
Percentage Composition (%)
HLS 22.87 20.33 18.05 15.80 13.76
LLS 74.65 77.7 80.3 82.75 85.3
SS 1.77 1.51 1.27 1.05 0.83
Iron 0.55 0.44 0.32 0.20 0.09
C3S 58.22 57.94 57.67 57.41 57.15
C2S 15.46 15.70 15.90 16.07 16.26
C3A 8.71 9.10 9.46 9.81 10.15
C4AF 13.13 12.87 12.61 12.36 12.12
Liq. 29.32 29.40 29.47 29.54 29.61
BI 2.66 2.64 2.61 2.59 2.57
BF 109.83 109.77 109.73 109.70 109.68
Table 3.3 shows, for a given raw materials, the effect of the variation of the Alumina
Modulus on the raw mix composition and on the physical properties of the clinker. The sign
means increase and the sign means decrease. It is noticed that the variation of the
Alumina Modulus affects intensively the raw mix composition whereas this effect is very
small on the physical properties of the clinker.
The Iron has a favorable influence on the formation of the cement compound. The higher
iron content contribute to an easier burning which reflect to low fuel consumption. But it
produce a hard, dense clinker which require more energy to grind, it means it increase the
production cost.
3.5.1 Effect of Alumina Modulus.
- Clinker with high Alumina modulus produce a cement with high early strength. But in
burning zone, the reaction between the calcium oxide and the silica is very difficult.
- A high Alumina modulus, with a low value of the silica modulus, guides to a fast setting
cement.
- High Alumina modulus results in hard burning which reflect to a high fuel consumption.
- Clinker with high Alumina modulus tends to render cement quick and strong at the early
ages.
- The low Alumina modulus reduce the clinkering temperature and increase the specific
fuel consumption. It facilitates the formation of the cement compound at a lower
temperature, it increase the liquid phase and kiln production. It helps to produce a high
C3S content, and it increase the probability for the clinker balling in the kiln.

8. 21
3.6 HYDRAULIC MODULUS.
The hydraulic modulus characterises the produced Portland cement clinker by the raw mix
ratio of the chemical composition of the material, such as the calcium Oxide and other
hydraulic factors, i.e, SiO2, Al2O3 and Fe2O3, which is represented by the following ratio so
called hydraulic modulus.
This formula demonstrates that the hydraulic modulus characterises the cement clinker by the
ratio of the CaO and the total hydraulic factors.
The hydraulic modulus of the portland cement clinker is limited in the margin of 1.7 % to 2.3
%. For a good quality of the Portland cement clinker the hydraulic modulus can be selected
as HM = 2
3.6.1 Effect of the Hydraulic Modulus.
The increase of the hydraulic modulus it will result :
- More heat required to burn the clinker. It means, the fuel consumption will increase
which reflect to the increase of the production cost.
- The initial strength set-up and the heat of hydration will increase.
- The resistance to the chemical attack decrease.
- The volume stability of the cement will be poor.
The reducing of the hydraulic modulus less than 1.7 %, the cement will show insufficient
strength.
3.7 MOLAR RATIO.
The most of the circulating elements in the kiln cold zone and in the kiln feed end are the
alkalis such as Na2O, K2O, Cl, SO3 etc. These compositions evaporate from the raw mix and
from the fuel oil used to burn the materials when the limit value of the molar ratio attain its
maximum value. The molar ratio is presented by the following formula.
)
12
.
3
(
O
Fe
O
Al
SiO
CaO
HM
3
2
3
2
2 


)
13
.
3
(
%
906
.
70
Cl
2034
.
94
O
K
9774
.
61
O
Na
0582
.
80
SO
R
.
MO
2
2
2
3




9. 22
In this formula the SO3 in the molar ratio is the total SO3 content in the Raw materials and in
the fuel.
The molar ration which varies in the range of 0.6 % - 1.2 % is a stoichiometric relation
between the Sulfate, the potassium, the chloride and the Sodium in the clinker. At this
maximum value of the molar ratio the alkalis will react with the other compounds on which
the dust carried along the gas stream and then the coating formation will start. To avoid this
phenomena, it is necessary to reduce or to neutralize the molar ratio of the used raw mix and
the used fuel. Neutralization of the molar ratio at its limit value means that no excess sulfur
will be available to combine with the other compounds.
There is different options to neutralize the molar ratio :
- To reduce the sulfur content in the raw materials by selection of the Quarry area which
have minimum sulfur composition.
- To reduce the sulfur content in the fuel oil by selection of the fuel oil brand which have
low content of sulfur.
- To increase the content of the K2O, Na2O and Cl2. It is difficult to increase the K2O
composition, because the availability of this composition in the raw materials for the
cement industry is poor. It is possible to increase the Na2O content composition by
adding to the raw mix the Soda ash (Na2CO3) or Chlorine Salt (NaCl). But in the case of
high content of the Cl, then no change will appear in the molar ratio, addition to this
negative result, there will be the possibility for the generation of the corrosive gas in the
system. Using the Soda ash (Na2CO3) to neutralize the molar ratio will be preferable, but
we have to consider with it, the addition of the cost by import / transport this material
from other area then the plant area.
3.7.1 Calculation of Molar Ratio.
Raw Mix component has the following compositions :
RMSO3 = 0.21 % K2O = 0.38 % (3.14)
Na2O = 0.15 % Cl2 = 0.01 %
SO3 content in fuel oil used in the kiln and in the F.C.
FSO3 = 3.3 % (3.15)
Rcl = Raw Meal / Clinker conversion factor= 1.6967
Kf = Raw Mix kiln feed ( Kg/h) = 261000
Fu = Total fuel consumption (Kg/h) = 12836
3.7.1.1 Sulfur in the Fuel.

10. 23
3.7.1.2 Sulfur in the Raw Meal
Total Sulfur in the fuel and in the Raw Meal.
3.7.1.3 Alkali.
Then the Molar ratio will be:
3.8 SULFATE MODULUS - DEGREE OF SULFATIZATION.
3.8.1 In the Clinker.
)
16
.
3
(
.
cl
.
Kg
/
KgSO
10
*
87
.
6
K
R
*
F
*
065
.
32
0582
.
80
*
100
F
S 3
3
f
U
SO
Fu
CL
3 


)
17
.
3
(
.
cl
.
Kg
/
KgSO
10
*
3934
.
3
R
100
RM
S 3
3
CL
RM
3
SO 


)
18
.
3
(
.
cl
.
Kg
/
KgSO
10
*
0263
.
1
S
S
S 3
2
RM
Fu
tot




)
a
19
.
3
(
.
cl
.
Kg
/
KgNa
10
*
545
.
2
R
*
100
O
Na
N 2
3
CL
2 


)
b
19
.
3
(
cl
.
Kg
/
O
KgK
10
*
4475
.
6
R
*
100
O
K
K 2
3
CL
2 


)
c
19
.
3
(
cl
.
Kg
/
KgCl
10
*
1697
.
0
R
*
100
Cl
C 2
3
CL
2 


)
20
.
3
(
197
.
1
906
.
70
C
2034
.
94
K
9774
.
61
N
0582
.
80
S
R
.
MO 0
0
tot




(3.21)
94.2034
O
K
+
61.9774
O
Na
*
0.5185
80.0582
SO
=
SR
2
2
3
cl

11. 24
0.8  S Rcl < 1.2
3.8.2 For the Cement.
SRcc 40 < SRcc < 100
3.9 TOTAL CARBONATE.
The most important substance of the raw meal for the Portland cement production is the
calcium carbonate which constitute about 70 % - 80 % of the raw mix. When the carbonates
are heated sufficiently they decompose, evolving CO2 , and leaving behind the related Oxides.
The temperature of the dissociation depend upon the carbonate, which determines the
dissociation pressure, and upon the potential pressure of the CO2 in the surrounding
atmosphere. The dissociation pressure of the CaCO3 become 10332.3 mm w.g at a
temperature about 900 o
C, i.e the dissociation occures at this temperature in an atmosphere of
CO2. When the raw meal is burned and calcined to around 900 o
C - 930 o
C, the calcium
carbonate dissociates with splitting of the carbon di-oxide, and the calcination degree attain
86 % - 92 %.
The total carbonate can be calculated from the raw mix using the following formula:
Tc = CaCO3 + MgCO3 (3.23)
The decomposition of the raw meal, as it was mentioned above, is a endothermic reaction,
and is expressed by the following stoichiometric relation.
CaCO3 = CaO + CO2 + h (3.24)
100.089 56.079 44.010
The reaction heat h = Cp * T - is standard reaction enthalpy and have different value
given by various authors. For instance according to Kainer [ 28 ] the reaction heat h =
401.26 kcal/kg, as per Rosemann [ 47 ] it is equal to 425 kcal /kg and as per IHI [ 24 ] it
is equal to 491.8 kcal/kg.
The dissociation of the Magnesium carbonate gives ;
Mg CO3 = MgO + CO2 + h (3.25)
84.321 40.311 44.010
Then the total Carbonate will be,
or
)
22
.
3
(
O
K
8499
.
0
O
Na
2918
.
1
100
*
SO
R
S
2
2
3
cc


MgO
*
311
.
40
321
.
84
CaO
*
079
.
56
089
.
100
Tc 


12. 25
Tc = 1.7848 CaO + 2.0918 MgO (3.26)
and the generated amount of the CO2 is calculated by the following equation:
MCO2 = 0.7848*CaO + 1.0918*MgO Kg/Kg.cl. or (3.27)
Where CaO and MgO are the percentage of calcium Oxide and Magnesium Oxide in the
clinker.
or
MgO
*
311
.
40
010
.
44
CaO
*
079
.
56
010
.
44
M 2
CO 

 
3.28
/kg.cli.
Nm
311
.
40
56.079
Cao
*
22.264
=
M 3
CO2 






MgO