Cteo Chapter Ii B Chemistry And 10 Clinker Facts.ppt

Chapter II - b Raw Mix Knowledge Objectives and principles Industrial Examples Tools - Exercises November 2004

Learning Objectives

By the end of this presentation you should be able to : 

Get the knowledge about raw mix chemistry



Get the link between raw mix and the 10 facts of clinker

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Content

1.

Pre-requisites to Raw Mix Knowledge

2.

LSF, Deltabc, Sir and AR

3.

C3S, C3A, Liquid Phase and Alkalies effect

4.

Free lime, C2S and C4AF effects

5.

Conclusion

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Clinker and Cement Notations Major oxides

Symbol

Notation



Calcium Oxide Silica

CaO SiO2

C S



Aluminum Oxide

Al2O3

A



Iron Oxide

Fe2O3

F



Example : C4AF means the phase (CaO)4,Al2O3,Fe2O3

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Clinker and Cement Notations

Minor oxides

Symbol

Notation



Magnesium Oxide Sodium Oxide

MgO Na2O

M N



Potassium Oxide

K2O

K



Phosphore Oxide

P2O5

P



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Cement Production 

Production Steps : RAW MATERIALS

80% of limestone (CaCO3) 20% Clay (SiO2-Al2O3) Sweeteners : bauxite, iron oxide, slag,….

Crushing and Milling <200 µm

KILN FEED

CaO (lime) 65 to 70%

Chemical Composition (weight) SiO2 Al2O3 (Silica) (Alumina) 18 to 24%

4 to 8%

Fe2O3 (Iron)

Burning 1,450°C

1 to 6% CLINKER

Formula C3S C2S C3A C4AF

Name Alite belite

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4 Main Phases Chemical Formula 3 CaO,SiO2 2 CaO, SiO2 3 CaO, Al2O3 4 CaO, Al2O3,Fe2O3

Av. % in weight 62 22 8 8

November 2004

Milling <100 µm with gypsum

CEMENT

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LSF and GSP : Calculation 

Formula : LSF 



CaO * 100 2.8 * SiO 2  1.2 * Al 2 O 3  0.65 * Fe 2 O 3

Typical Values : between 90 and 110

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2



Δbc : Calculation

Formula : the sum (SiO2+Al2O3+Fe2O3+CaO) is different from 100 so we need transformed to a % over 100

bc 

2.8 * SiO 2  1.65 * Al 2O 3  0.35 * Fe 2O 3  CaO SiO 2  Al 2O 3  Fe 2O 3  CaO



Typical Values : between



It is to set the value of C2S and then C3S.



If Deltabc is constant then the kiln feed is constant

Process Engineering Program – Raw Mix Optimization

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* 100

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Δbc : Concept 

Δbc is the difference between the theoritical CaO required and the real CaO input to maximise the C3S production through the industrial equipment.

CaO  3 * SiO 2  CaO ,3 SiO 2 ( orC 3 S ) 

It is the difference between the thermodynamic and the kinetic CaO transformed into C3S to minimise the production of free lime. So the CaO input will be less to guarantee the combination of CaO and SiO2



Get the maximum proportion of C3S with a raw material containing SiO2, Al2O3, Fe2O3 and CaO :    



To combine SiO2 into C3S, we need 2.8*SiO2 (1) To combine Al2O3 into C3A, we need 1.65*Al2O3 (2) To combine Fe2O3 into C4AF, we need 0.35*Fe2O3 (3) To get the best cement, we require the CaO theoritical : CaOth = (1)+(2)+(3)+(4) = 2.8*SiO2+1.65*Al2O3+0.35*Fe2O3 (4)

Then Δbc = CaOth - CaO real = 2.8*SiO2+1.65*Al2O3+0.35*Fe2O3- CaO

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Loss On Ignition (LOI) 

Decarbonation of CaCO3, MgCO3 CaCO 3  CaO  CO 2



MgCO 3  MgO  CO 2

Combined water in clays and organic matters (TOC)  Measured with a lab protocol (Temperature 975°C)  Calculated (estimation) LOI  0.7857.CaO %  1.089. MgO

 

Kiln feed Values LOI= 35.5% on average Clinker by definition LOI=0% in theory (0.4% in practice)

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Silica Ratio : SiR 



Formula : proportion of SiO2 to the total of Al2O3 and Fe2O3 SiO 2 SiR  Al 2O3  Fe2O3 Quality : 





It is to set the proportions of silicates (C3S and C2S) compared to the aluminates and the aluminoferrites (C3A and C4AF). A high value will increase the cement strength but the clinker reactivity may drop.

Range : 



Typical Clinker : Average value 2.65  SiR between 2.2 and 3.3 White Clinker : SiR between 7 and 10

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Silica Ratio : SiR 

Production :

Too high Liquid phase reduced Reduce burnability Risk of over-burnt free lime No coating (high wall losses Brick wear 

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Silica Ratio : SiR Kiln Feed SiR 2003 Values 3.40

3.20

3.00

S iR

2.80

2.60

2.40

2.20

2.00

Works

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Alumina Ratio : AR 



Formula : proportion of Al2O3 to Fe2O3 Al 2O3 A/ F  Fe2O3 Quality : 

 



It is to set the proportions of aluminates (C3A) compared to the the aluminoferrites (C4AF). A high value will increase the C3A and the setting time. For 0.63, C3A=0%

Range : 



Typical Clinker : Average value 1.90  AR between 0.75 and 2.60 White Clinker : 10

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Alumina Ratio : AR



Production :   

It is linked to the liquid phase composition. A high AR will increase the liquid phase viscosity. A low AR will increase the liquid phase proportion.

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Alumina Ratio : AR Kiln Feed AR 2003 Values 3,20

2,70

AR

2,20

1,70

1,20

0,70

0,20

Works

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Equivalent Alkalies (eqNa2O) 

K2O and Na2O are alkalies EqNa 2 O  Na 2 O %  O .658 * K 2 O %



SO3 and EqNa2O molar ratio SO 3 EqNa 2 O





SO 3% EqNa 2 O

x 0.775

SO3 Excess SO 3 excess  SO 3 clin ker  1.29 * EqNa 2 O

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Main Objective Produce clinker which is a mix of 4 main phases 

C3S (Alite)

3CaO.SiO2

Tricalcium Silicate



C2S (Belite) 2CaO.SiO2

Dicalcium Silicate



C3A

3CaO.Al2O3

Tricalcium Aluminate



C4AF

4CaO.Al2O3.Fe2O3

Tetracalcium Alumino-Ferrite

So we need to input in the kiln CaO, SiO 2, Al2O3 and Fe2O3 in the right proportions to combine (or react together)

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Rankin Diagrams

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Study Case : Assumptions Product team requires from us a clinker with : C3S Clinker

60-62%

C3A Clinker

8.5%

Liquid Phase

25%

Free Lime Clinker 100 % Pet Coke SO3 Clinker

EqNa2O Clinker

Process Engineering Program – Raw Mix Optimization

1.2%

1.7%

0.6%

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Clinker C3S (alite) Alite is the main phase of the clinker which gives strength. The values are between 58% to 72%. 5th Rule of the « 10 basic Facts on Clinker » Increasing clinker C3S (to the detriment of C2S) improves strength at 1, 2, 3 and 7 days. Key figures : +10% C3S  +2 to +5 MPa for early strengths After 28 days, the gain may be less because of the C2S contribution.

Process Engineering Program – Raw Mix Optimization

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Clinker C3S (Bogue calculation) Alite % can be estimated as a pure C3S with the following formulas 

From a kiln feed analysis, the chemistry has to be transformed to a clinker analysis (LOI=0%)



with no free lime  Potential



With the clinker free lime and SO3t (Kiln feed + combustible effect)

SiO 2 Clin ker  SiO 2 ki ln feed .

100 100  LOI ki ln feed

C 3S  4.07.C  7.6.S  6.72. A  1.43.F 

Bogue

C (1)  C  FCaO  0.7.SO3  1.26CO 2 C 3S  4.07.C (1)  7.6.S  6.72. A  1.43.F

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Clinker C3S (Example)

SiO2 Al2O3 Fe2O3 CaO

Kiln Feed 13.49 3.30 2.21 41.28

"Potential Clinker" 20.94 5.13 3.43 64.08

"Bogue clinker" 20.94 5.13 3.43 64.08

Real Clinker 20.69 5.24 4.09 64.28

LOI CaO(1)

35.58 -

0.00 64.08

0.00 61.89

0.17 62.08

C3S Alite

-

62.28 -

53.35 -

54.43 63.40

FCaO SO3 T.

-

0.00 -

0.71 2.12

0.71 2.12

LSF SiR AR

95.62 2.45 1.50

95.62 2.45 1.50

95.62 2.45 1.50

96.13 2.22 1.28

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Clinker Alite and C3S C3S and Alite % in Clinker

C3S Bogue Alite

90.0

80.0

70.0

60.0

%

50.0 40.0

30.0

20.0

10.0

0.0

Works

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Clinker C3S Optimisation CaO  3 * SiO 2  CaO ,3 SiO 2( orC 3 S ) 

Get the maximum proportion of C3S with a raw material blend containing CaO associated with SiO2, Al2O3, Fe2O3 :

CaO (1) +

CaO(2) +

Fe2O3

C4AF : 0.35xFe2O3

Al2O3 SiO2

CaO(3)

C3A : 1.65xAl2O3 C3S : 2.8xSiO2 CaOth= 2.8xSiO2+1.65*Al2O3+0.35*Fe2O3

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Clinker C3S Optimisation 

Assumptions : Input alkalies, Sulfur, Magnesia and iron % 





 

Step 1. Set desired A/F ratio  Calculate Al2O3 Step 2. Set desired SR ratio  Calculate SiO2 Step 3. Set desired LSF  Calculate CaO Step 4. Check Sum total all oxides Step 5. Check Potential Clinker    

C3S C3A C2S C4AF

Process Engineering Program – Raw Mix Optimization

Oxides EqNa2O SO3 MgO

% 0.6 0.4 2.3

Fe2O3

3.15

A/F

1.77590562 Al2O3

5.59410269

SR

2.48560919 SiO2

21.734422

LSF

95.1234344 CaO

66.22

Sum

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100 Sum

100.00

Compounds C3S C3A C2S C4AF Free Lime

Potential 62.24 9.50 15.38 9.58 -

Adjusted 55.00 9.50 20.84 9.58 1.50

Target 55 9.5

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Clinker Alkalies Alkalies are important constituents of the clinker.The regularity is getting more and more important. The values are between 0.3% to 1%. Effect on Liquid Phase. N° 7 and 10 Rules of the « 10 basic Facts on Clinker » • Alkalies, whatever their form, are never favorable to 28-day compressive strength. Key figures : + 0.1 % Eq Na2O total  -1 N/mm2 @ 28 days • If clinker SO3 is increased beyond the molar saturation of alkalies, an increase in both clinker fineness and grinding energy is noted. Key figures : +1% Excess SO3 --> + 5 kWh/t @ 350 m2/kg excess SO3 = SO3 clinker - 1,29 (% Eq. Na2O total) Process Engineering Program – Raw Mix Optimization

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EqNa2O and SO3 (Example)

SiO2 Al2O3 Fe2O3 CaO

Kiln Feed 13.49 3.30 2.21 41.28

"Potential Clinker" 20.94 5.13 3.43 64.08

"Bogue clinker" 20.94 5.13 3.43 64.08

Real Clinker 20.69 5.24 4.09 64.28

LOI SO3 total

35.58 1.79

0.00 2.78

0.00 2.12

0.17 2.12

Na2O total K2O total

0.03 0.33

0.05 0.51

0.05 0.51

0.07 0.49

Eq Na2O SO3/EqNa2O

0.25 5.61

0.38 5.61

0.38 4.28

0.39 4.19

Na2O Soluble K2O Soluble Pyritic SO3

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0.03 0.40 0.47

0.74

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Clinker EqNa2O (typical values) Alkalies eqNa2O in Clinker 1.20

E q N a 2 O in C lin k e r

1.00

0.80

0.60

0.40

0.20

0.00

Works

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Clinker SO3% (typical values) SO3t % , Clinker 3.00

2.50

SO3

2.00

1.50

1.00

0.50

0.00

Works

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Clinker C3A and Alkalies C3A is an important phase of the clinker for the obtention of the liquid phase. It interacts with sulfate addition and early performances. The values are between 2% to 12%. 8th and 9th Rules of the « 10 basic Facts on Clinker » • At optimum sulfate addition for early ages, soluble alkalies, especially alkali sulfates, improve early strength. It is function of the C3A %. Key figures : + 0.1 % Eq. Na2O soluble --> + 0.5 à 1.5 N/mm2 @1 day • The molar saturation of alkalies by SO3 in the clinker facilitates workability control. If there is more alkalies than sulftates the C3A form is transformed from cubic to orthrhombic. Then there is a risk of poor workability and ageing. Process Engineering Program – Raw Mix Optimization

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Clinker C3A (Bogue calculation) C3A % can be estimated as a pure C3A with the following formulas 



From a kiln feed analysis, the chemistry has to be transformed to a clinker analysis (LOI=0%) with no free lime  Potential 

Bogue

SiO 2 Clin ker  SiO 2 ki ln feed .

100 100  LOI ki ln feed

C 3 A  2.65.C  1.69.F

C 3 A  2.65.C  1.69.F

Process Engineering Program – Raw Mix Optimization

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Clinker C3A (Example)

SiO2 Al2O3 Fe2O3 CaO

Kiln Feed 13.49 3.30 2.21 41.28

"Potential Clinker" 20.94 5.13 3.43 64.08

"Bogue clinker" 20.94 5.13 3.43 64.08

Real Clinker 20.69 5.24 4.09 64.28

LOI CaO(1)

35.58 -

0.00 64.08

0.00 61.89

0.17 62.08

C3A Rietveld

-

7.80 -

7.80 -

6.96 2.40

FCaO SO3 T.

-

0.00 -

0.71 2.12

0.71 2.12

LSF SiR AR

95.62 2.45 1.50

95.62 2.45 1.50

95.62 2.45 1.50

96.13 2.22 1.28

Process Engineering Program – Raw Mix Optimization

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Clinker C3A Bogue C3A and Rietveld C3A % in Clinker

C3A Bogue C3A tot

14.0

12.0

10.0

%

8.0

6.0

4.0

2.0

0.0

Works

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Liquid Phase : LP Formula : Al2O3 and Fe2O3 are the main constituents.



@ T  1450 C ; LP  3.0 Al 2 O 3  2.25 Fe 2 O 3  MgO  Na 2 O  K 20

Optimum : 25%. Viscosity is crucial.



Too low (<20%) Hard burning No coating Risk of brick damage 



Too low (>30%) Easy burning Too much Coating Risk of brick damage 

Other temperatures (T=1338°C and T=1400°C)

Process Engineering Program – Raw Mix Optimization

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Liquid Phase (Example)

Al2O3 Fe2O3 MgO Na2O K2O

Kiln Feed 3.30 2.21 1.69 0.03 0.33

"Potential Clinker" 5.12 3.43 2.62 0.05 0.51

Real Clinker 5.24 4.09 3.12 0.07 0.49

LOI

35.58

0.00

0.17

LP @ 1450°C LP @ 1338°C

-

26.27 27.01

28.60 28.63

AR

1.49

1.49

1.28

Process Engineering Program – Raw Mix Optimization

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Clinker LP (typical values) Liquid Phase (@1450°C), Clinker 31.00

29.00

27.00

LP

25.00

23.00

21.00

19.00

17.00

15.00

Works

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Clinker Free lime Kiln feed LSF target below stoechiometric ratio to minimise clinker free lime. It is the main production parameter to operate the kiln. 4th Rule of the « 10 basic Facts on Clinker » Increasing the clinker free lime content reduces both initial and final setting times in the same proportion. Key figures : When free CaO increases from 0.5 to 1.5%, initial set decreases by about 40 to 50 minutes. This impact may vary greatly from clinker to clinker (-10 to -100 minutes).

Process Engineering Program – Raw Mix Optimization

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Clinker C2S (belite) Belite is the second phase which gives long term strength. The values are between 58% to 72%. 6th Rule of the « 10 basic Facts on Clinker » For a given Blaine specific surface (SSB), grinding energy increases with C2S content. Conversely, it decreases with increasing C3S. Key figures : +10% C2S, (or -10% C3S) => +5 kWh/t (@ 3500 cm2/g). 0% C2S, (or -10% C3S) => +5 kWh/t (@ 3500 cm2/g).

Process Engineering Program – Raw Mix Optimization

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Clinker Belite and C2S C2S % in Clinker

Bélite C2S Bogue

35.0

30.0

25.0

%

20.0

15.0

10.0

5.0

0.0

Works

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Clinker C4AF and Color C4AF is an important phase of the clinker for the obtention of the liquid phase. It is linked to the color through the iron addition. The values are between % to %. No Rules of the « 10 basic Facts on Clinker »

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Clinker C4AF C4AF % in Clinker

C4AF Bogue C4AF

16,0

14,0

12,0

%

10,0

8,0

6,0

4,0

2,0

0,0

Works

Process Engineering Program – Raw Mix Optimization

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Conclusion 

Raw mix control is key on clinker properties



Minor elements are getting more and more important to customer (alkalies, MgO, chlorine, LOI…). Standards have to be met and regularity is crucial for good relationship with the customer.

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