Effects of Various Factors on Burnability and Impact on Clinker Quality | Clinker chemistry

Lecture-10: Effects of Various Factors on Burnability and Impact on Clinker Quality by Dr. K. Mohan.
Dr K Mohan is an internationally renowned and an acclaimed cement scientist. He is a former Director General of National Council for Cement and Building Materials (NCCBM).
He holds a Ph.D. degree in Cement Chemistry from University of Aberdeen, Scotland, U.K
Effects of Modulii:
Lime Saturation Factor (LSF) (Limiting Range 0.66 -1.02, Preferable Range 0.92 - 0.96)
Higher LSF will results;
.Harder to burn raw mix
. Increases C3S in clinker
. Reduces C2S in clinker
. High free lime in clinker
. High fuel consumption
. Deteriorates refractory lining
. Increases radiation from kiln shell
. Increases kiln exit gas temperature
. Tends to produce unsound cement
. Causes slow setting with high strength of cement
. Improves the grindability characteristics of clinker
Silica Modulus (SM) (Limiting Range 1.9 -3.2, Preferable Range 2.1 - 2 7)
Heigher SM results;
. Harder burning of raw mix
. High fuel consumption
. Difficulty in coating formation
. Radiation from kiln shell is high
. Deteriorates refractory lining
. Results in slow setting and hardening of cement
. High free lime
Alumina Modulus (AM) (Limiting Range 1.2-2.5, Preferable Range -1.3 - 1.6)
Higher AM results;
. Harder burning of raw mix
. High fuel consumption
. Increases C3A and decreases C4AF
. Increases both C3S and C2S (C3S C2S)
. Reduces liquid phase and kiln output
. Increases viscosity of liquid phase at constant temperature
. If AM is too low and raw mix is without free silica, clinker sticking and balling is too high
. AM determines the role of fluxes in raw mix
AM 1.23 - Al2O3 acts as flux
AM 1.23 - Fe2O3 acts as flux
Minor Non - Volatile Components
Free Silica
(Limiting Range 0- 3%, Preferable Range - As low as possible)
Higher Free Silica:
. Increases fuel and power consumption
. Causes difficulty in coating formation
. Deteriorates refractory lining
. Increases radiation of heat from kiln shell
MgO
(Limiting Range 0- 5%, Preferable Range - 0 - 3%)
Higher MgO:
. Favours C3S formation
. Tendency for balling in burning zone
. Affects kiln operation
. Causes unsoundness in cement
SrO
(Limiting Range 0- 4%, Preferable Range - 0.5 - 1.0%)
Higher SrO:
. Accelerates combination of CaO in solid phase
. Lowers sintering temperature
. Tends to release free lime by alite decomposition
Cr2O3
(Limiting Range 0- 2%, Preferable Range - 0.3- 0.5%)
Higher Cr2O3 :
. Decomposes C3S into C2S and free lime
Alkalies (Limiting Range 0- 1%, Preferable Range - 0.2 - 0.3%)
Higher Alkali:
. Improves burnability at lower temperatures and deteriorates at higher temperatures, when (K+N) 1
. Increases liquid content and coating formation
. Lowers the solubility of CaO in melt
. Breaks down alite phase
. Creates operational problems due to external and internal cycle
Sulphur Compounds (Limiting Range 0- 4%, Preferable Range - 0.5 -2%)
Higher Sulphur Compounds:
. Acts as an effective mineraliser and modifier of alkali cycle by forming less volatiles
. Lowers the appearance temperature of liquid phase by about 100oC and increases ionic mobility of oxides
. Improves burning of raw mix at lower temperature and deteriorates at high temperature
P2O5 (Limiting Range 0- 1%, Preferable Range - 0.3 -0.5%)
Higher P2O5:
. Accelerates theclinkerisation reaction
. Reduces the intensity of internal cycle
. Reduces C3S content
Fluoride (Limiting Range 0-0.6 %, Preferable Range - 0.03 -0.08%)
Higher Fluoride:
. Leads to modification of the kinetics of all burning reactions
. Lowers the temperature of C3S formation by 150 - 200oC
Chloride (Limiting Range 0-0.6 %, Preferable Range - Upto 0.015%)
Higher Chloride:
. Forms more volatiles and causes operational problems due to its complete volatilisation in burning zone
Effect of MgO and SO3on formation of clinker phases and alite polymorphism:
• SO3 hindered the formation of C3S by increasing the formation temperature by 100 °C.
• SO3 could promote the formation of C2S rims, indicating the dissolution of C2S.
• MgO enhanced the formation of C3S in both the blank and SO3-bearing clinkers.
• MgO favoured the formation of Monoclinic M3 type alite, whereas SO3 could stabilize Monoclinic M1 alite.
Influence of MgO and SO3on kinetics of Alite formation:
• If the MgO content is high and SO3 content is low, alite is formed immediately after reaching the burning temperature but with raising degree of conversion, the rate of alite formation is decreasing.
• Low content of MgO and high content of SO3 delays the beginning of alite formation and increases its growth rate.

[@omprakashkushwaha7926]

Thanks sir for continuing your valuable information. 😍

[@gosula.amaralingeswararao8698]

Ur explanation is good sir

[@justinaudrieesbra9448]

Thank you !

[@MaheryRandria-ej7ro]

Can you give an protocole to find the free silica in the clinker?

[@rohandambal7382]

Thanks 🙏 sir

[@AllInOne-ry8dq]

sir can you tell about effect of using bauxite instead clay in kiln feed?

[@shalinikaushal1630]

In our area mgo content is around 5% in limestone. using sweetener to improve the cement grade which is little expensive .Plz suggest if mgo can be reduced upto 2-3%.

[@RaghuRaghu-mk1en]

What difference alkali ring and sulphur ring