07. clinker burning ordonez 2005.ppt

1. Clinker burning process and its
influence on the refractory material
Hugo Ordóñez

2. What is the goal of
clinker burning ?

3. The production of
GOOD QUALITY
cement...
OF COURSE !

4. What is quality?

5. Quality of cement
Characteristics & Properties:
•Chemical Composition
•Strength
•Workability Setting Behavior,
•Chemical Resistance ..Etc.

6. Where does quality come from ?
Quality of Cement: (Characteristics &
Properties: Strength, workability, setting
behavior, chemical resistance etc.)
Chemical & mineralogical composition
of the clinker
Mechanical
handling of
clinker
(grinding)
Chemical &
mineralogical
composition
of raw mix
Chemical
composition
of fuels
Circulation
phenomena

7. Polished section showing clinker minerals

8. Some Q.P. Correlate with mineralogical
parameters Strength=F(stereological
data)
90 days compressive strength N/mm2

9. Grind ability of clinker in dependence of
mineralogical parameters (Ak= belit corrected
specific alit content)

10. Starting Points
Available Raw materials & fuels
Available process equipment
Available knowledge

11. Constraints
Raw Materials Process equipment Cement
Chemical Comp. Mining/Quarrying eq. Quality requirements
Mineralogical Comp. Crushing equip. ASTM
Physical state Pre-blending equip. DIN
Quarry: RM grinding system ISO
Degree of mixing RM homogeneizing
Deleterous compounds
Kiln system BS
Selective mining
Use of correctives
Cement grinding system LOCAL STANDARDS
RM purchasing
Packing/Distpatch Special cements

12. Chemical Composition of cement raw materials and mix
Limestone Marl Clay Sand Raw mix
Weight %
Ig. Loss 40-44 2-42 1-20 Up to 5 32-36
SiO2 0,5-3 3-50 37-78 80-99 12-16
Al2O3+TiO2 0,1-1 1-20 7-30 0,5-3 2-5
Fe2O3+Mn2O3 0,1-0,5 0,5-10 2-15 0,5-2 Up to 2
CaO 52-55 5-52 0,5-25 0,1-3 40-45
MgO 0,5-5 0,5-5 Up to 5 Up to 0,5 0,3-3
SO3 Up to 0,1 0,1-4 Up to 3 Up to 0,5 Up to 1,2
K2O Up to 0,3 Up to 3,5 0,5-5 Up to 1 0,2-1,4
Na2O Up to 0,1 Up to 0,2 0,1-0,3 Up to 0,5 Up to 0,3
Cl- 0,01-0,1
F- 0,02-0,07

13. Minor compounds and traces found in natural raw
materials and cement raw mix
Element Clay minerals Limestone and Marl Raw mix (mix ratio 25/75
without dust)
ppm (10-4 weight %)
V 98-170 10-80 32-102
Zn 59-115 22-24 31-47
Cr 90-109 1,2-16 23-39
Ni 67-71 1,5-7,5 18-23
Pb 13-22 0,4-13 4-15
As 13-23 0,2-12 3-15
Cd 0,016-0,3 0,035-,1 0,04-0,15
Tl 0,7-1,6 0,05-0,5 0,21-0,78
Cl 15-450 50-240 40-290
F 300-990 100-940 300-950
Br 1-58 5,9 4,7-18,9
I 0,2-2,2 0,25-0,75 0,24-1,1

14. Coal ash composition
Hard coal Lignite
Compound USA England Germany Germany
weight %
SiO2 20-60 25-50 25-45 8-18
Al2O3 10-35 20-40 15-21 4-9
TiO2 0,5-2,5 0-3 - -
Fe2O3 5-35 0-30 10-45 2-6
CaO 1-20 1-10 2-4 25-40
MgO 0,3-4 0,5-5 0,5-1 0,5-6
K2O+Na2O 1-4 1-6 1-5 0,6-3
SO2 0,1-12 1-12 4-10 0-50

15. Minor elements in coal ash
Hard coal Lignite
Compound ppm (10-4 weight %)
Cl 100-2800 1000-1300
F 50-370 n.a.
Br 7-11 n.a.
I 0,8-11,2 n.a.
Zn 16-220 1-70
Cr 5-80 0,9-8
Ni 20-80 0,6-1,9
Pb 11-270 0,8-6
As 9-50 0,3-9
Cd 0,1-10 0,1-2,4
Tl 0,2-4 0,07-0,3
V 30-50 2-7

16. Chemical composition of AFR
Waste oil Bleaching earth Acid sludge Pet coke Used tires
Heat content 8300-10100 3000-5700 3200-5400 7200-8300 6450-8000
Kcal/Kg
Component weight %
Ash 0,1-0,3 40-70 2-6 2,5-4 12,5-18,6
S 0,2-0,7 0,5-1,8 10-16 5-6 1,3-2,2
Alkalis 0,003-0,04 0,1-1,3 0-0,3 0,06-0,16 <0,01
Cl 0,01-0,22 <0,001-0,005 0,3 0,0013 0,2
Component ppm
Zn 240-3000 <10-480 56-3900 n.a 9300-20500
Cr <5-50 2-11 20-330 5-104 97
Ni 3-30 <0,01-30 8-87 300-35 77
Pb 10-21700 2-2500 150-6400 6-102 60-760
Cd 4 <,01-2 9-50 0,01-0,3 5-10
Tl <0,02 0,2 0,03-0,07 0,04-3,1 0,2-0,3

17. Chemical composition ranges for various materials
related to cement manufacturing
OPC

18. Cement Modulus
cement modulus calculation typical values statement
Lime Standard 100 ⋅(CaO + 0,75 ⋅MgO ) 85 - 9 5 content of CaO, which
KStIII =
2,8 ⋅SiO 2 + 1,18 ⋅Al 2 O3 + 0,65 ⋅Fe 2O 3 (Portland cement) can technically be bond
(KSt III) to SiO 2 , Al2 O 3 and Fe 2O 3
95 - 1 00
(high -grade cem .)
Hydraulic modulus CaO 1.7 - 2.3 ratio of CaO to the
HM =
SiO 2 + Al 2O3 + Fe 2O3 hydraulic factors SiO 2,
(HM) Al2O 3 and Fe 2O 3
Silica ratio SiO 2 1.9 - 3.2 characterizes the ratio
SR =
Al 2O 3 + Fe 2O3 solid/liquid , i.e. the
(SR) (Opt.: 2. 2 - 2.6! ) amount of liquid phases
in the clinker
Alumina ratio Al 2 O 3 1.5 - 2.5 characterizes the
AR =
Fe 2 O 3 composition of the melt
(AR ) (possibly : and its viscosity
< 1 .5 ; > 2 .5 )
Na 2 O K 2 O Cl
Alkali-Sulphate -ratio + − 0.8 - 1.2 characterizes the ratio
62 94 71
ASR =
SO alkali versus sulphate
3
(ASR ) 80

19. Normal ranges for cement module

20. Clinker module and their influence on the burning
properties of clinker

21. Liquid phase at 1450°C as function of SR

22. Alumina Modulus

23. Two types of raw meal with different burnabilities
Raw meal a Raw meal b

24. Burnability Index

25. Melt behavior from clinker sample (post mortem burnability test)
Melt starts to appear
at this point
1600 °C
1620

26. Summary of Reactions During Clinker Burning
Temperature Process Chemical change
°C
< 200 Drying None
None
100-400 Dehydration
Decomposition of clay minerals, e.g.,
400-750 Al4(OH)8Si4O102(Al2O3.2SiO2)+4H2O
with formation of metakaolinite
Decomposition of metakaolinite and
Al2O3.2SiO2Al2O3 + 2SiO2
other compounds, with formation of
reactive oxide mixtures
600-900
Decomposition of limestone. Formation CaCO3CaO+CO2
of CS and CA 3CaO+2SiO2+ Al2O32(CaO.SiO2) +CaO.Al2O3
600-1000
Uptake of lime by CS CA, formation of
800-1300 CS + C  C2S 2C+S  C2S
C4AF
CA + 2C  C3A CA + 3C + F  C4AF
Further uptake of lime by C2S
1250-1450 C2S + C  C3S

27. Chemical and Mineralogical processes during clinker burning
Clay minerals
Temperature°C

28. and Dissociation Speed of limestone Heating Rate
CaCO3CaO+CO2
• Low HR (100 °K/min): DS depends on transport phenomena (gas-
heat): heat flow to and gas transport from the inner of the
limestone particles. • High particle size and HR (250 °K/min): DS
hindered by low heat conductivity and high CO2 partial pressure.
• High HR (450 °K/min): Increased reactivity of CaO with SiO2
(from 800 to 1000°C). No recrystalization and defects in crystal
lattice. • Kiln speed: lower rpm produce higher HR.
• Alkali's (up to 2%) increase DS by lowering activation energy for limestone.

29. CaCO3CaO+CO2
Decomposition rate of limestone is increased by
• Increase in temperature of raw meal
• Lowering CO2 partial pressure in
combustion gas • Lowering dust load
of the combustion gases • Lowering
particle size of raw meal • Decreasing
crystal content of CaCO3

30. Sintering
(Reactions with liquid phase) • Starts at 900-1000 °C
(calcium silicates and aluminates. No C3S formation)
• Free CaO starts decreasing at above 1250 °C (as melts
appear and C3S formation accelerates).
• Viscosity of melt affected by circulation phenomena
(low melting point compounds) and AR.
• Reversion from C3S to C2S can occur at isothermal
conditions. C3S  C2S + C

31. Sintering Temperature
• At 1250 °C: mostly C2S forms • Below 1450 °C:
C3S formation too slow. • Reversion from C3S to
C2S possible • Above 1450 °C: quantity of melt
increases, viscosity decreases. Sintering reaction
rate increases.
• Above 1500 °C: cost/benefit too high.

32. Heating rate •High HR at 1450°C: high
reactivity, no
between 900-1300 °C
recrystalization •High HR at
1700 °C good strength due
to high C3S with small
crystal size. Too expensive.
•Belite cement: possible
Free lime
through very fast cooling,
1000 °K/min (crystal lattice
defects/disturbances) but
technically unfeasible...yet!

33. Alite formation is reversible
Belite + CaO Alite
Reaction equilibrioum is shifted by:
• Temperature changes (+R;-L)
• Change in quantity of melt ((+R; -L)
• Change in melt viscosity (+L; -R)
• Change in heating velocity (1200-1450 °C) (+R; -L)
• Clinker cooling rate (1450-1200) (+eq. “Freezes” -L)
• Length of time kept at isothermal conditions (above 1350°C) (+L; -
R)

34. Influence of cooler type

35. Particle size
Tolerance for particles with average diameter
+ 100 micrometer (raw meal):
Calcite, < 1%
Quartz < 6%
(by Weight)
Optimum calcite average size for C3S formation
15 microns

36. Scanning electron microscope photograph of a quartz
grain 200 micrometer average diameter

37. Big quartz grains surrounded by belite ring do not let
sintering to C3S to proceed due to lower reaction rate (low
surface area).
1620

38. Homogeneity criteria
Allowed variability of LSF, SR, AR in terms of
variation coefficient:
< 1% VC= Std. Dev./Average
(clinker; hourly data)

39. Why hourly?

40. LSF, hourly samples
Average 94,8
Standard Deviation 3,5
103
101
99
97
95
93
91
89
87
85
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
HORA

41. LSF Accumulated deviation from
set point (211 hours, random
period )
8,00 T2
7,00 T4
T3
6,0
0
5,0
0
T1
4,00
3,00
2,00
1,00
0,00
-
1,00
-

42. True meaning of the average
If I drink four beers
and you drink none In
AVERAGE, each one
DRANK 2 BEERS !

43. Free CaO =F Particle Size, Temperature)

44. Alite crystal size distribution of two clinkers from a long dry process kiln
before and after a change over a raw material with improvement in
burnability

45. Fluxes
Lower melting temperature Effects on quality
and melt viscosity • (-) Sett. time
• (+)Strenght (Cr)
•Heavy metals (Ba, Sr, Ce,
• (+)Grindability
Cr, P,Ti, Zn) act as fluxes at up
to 3% Wt. (V2O5,Cr2O3, BaO)
at 0,5% wt.
•They must bind with
clinker to be active.

46. Mineralizers
•Accelerate C3S formation Effects on quality
without melt appearance.
(+)Grindability (V2O5,Cr2O3,
•Ba, Cr, P, SO3 act as Min.
BaO) at 0,5% wt.
At optimun conc. of 0,2-
Cr at up to 0,5% enhances
1% Wt.
C3S formation.
•Ce, Cr, Mn, Ti, Zn, Co, Pb
At +0,5%, decomposes C3S
at up to 4% act as Min.
Increase late strength (F)
•F enables complete
sintering at 1200-1300 °C (-) grindability (F)
(at 0,3-0,6% Wt.)

47. AFRS May Contain Fluxing and
Mineralizing Compounds in
Dangerous Concentrations !!!!

48. Chemical and Mineralogical processes during clinker burning
Clay minerals
Temperature°C

49. Thermo-Chemical profile of a long wet kiln
chains
COOLING
Preheating zone CALCINING ZONE TRANS. SINTER
ZONE 5 MIN
33 min ZONE 25 ZONE
75 MIN
MIN
TIME

50. Thermo-Chemical profile of a 4 stage preheater kiln
Length/diameter...
.aprox. 14/1
DiameterXLength (2500 tpd) 4.8 X67 and 5x74 (mxm)
Speed of rotation...
.aprox. 2 rpm
Secundary firing...
..none
Calcination extent in pre-calciner...
.aprox 40 %

51. Thermo-Chemical profile of a pre-calciner kiln
Length/diameter...
.aprox. 14/1
DiameterXLength (2500 tpd) 4.0 X56 and 4.4x64 (mxm)
Speed of rotation...
.aprox. 3 rpm
Secundary firing...
..up to 65% with tertiary air
Calcination extent in pre-heater...
.up to 95%

52. Frecuency distribution of alite chord lenghts for two types of kiln

53. Potential and modal constituend phases

54. Physical properties

55. In summary
We can not go further into the many details of clinker burning in this
brief overview. But we already know that clinker burning is a very
complex process, which must be thoroughly understood for each
particular system, as every production arrangement is
characterized by its own “constellation of variables”. Although some
generalizations can be made, it is fundamental to assess the
relative importance or “weight” of the individual factors
generating an effect or combination of outcomes upon the
refractory materials.
Only this basic understanding may enable us to look at the questions
concerning refractory materials from a rational perspective. This
includes proper selection, which means matching specific products
with specific requirements at different parts of the system. But it
also means the development of engineering concepts and
installation methods for the refractory materials to be suited to
the desired optimisation of the system.

56. Refractory Selection Criteria
• Refractory must be suited to particular requirement of
the system •Phenomena within the system must be
understood clearly
•Zones must be clearly defined and monitored along time as
conditions in a cement plant always change
•Customer usually has more knowledge of the relevant
operating conditions of their systems
•Refractory supplier usually has more experience with the
application of refractory products to particular cases...many
cases...thousand of systems.
Best achieved by close cooperation between
cement producer- Refractory
supplier

57. Thank you very much
for your attention!