Ideal flame
1400 deg c
Heat
1900 1450 ded c
1350 deg c
1500 deg
Short,intense and convergent flame is favourable for burning, favorable coating formation improves the refractory life. Burnerr pipe at center Burne center - this flame flame radiates radiates the heat to the the refractory r efractory surface(evenly) surface(evenly) in well distributed manner
Clinker chemistry(related to Refractory) Burning mechanism
Mechanism of clinker coating formation and Flame
Clinker chemistry Silica Silic a ratio = SiO2 / Al2O3+ Fe2O Fe2O3 3 normally normally 1.9 - 3.2 (optim (op timum: um: 2.2 - 2.6 2.6)) Silica ratio characterizes the ratio solid / liquid i.e., The amount of liquid phases in the clinker.
Alumina ratio = Al2O3 / Fe2O3 ,
normally
1.5 - 2.5
Alumina ratio characterizes the composition of the melt and its viscosity in the clinker. Low AR ( < 1.5 ) increases the Fe2O3 content, decreases the viscosity and increases the infiltration of liquid, deep into the brick
Silicic acid ratio, SAR = SiO2 / Al2O3, normally 2.5 -3.5
Optimization of rawmeal moduli for better refractory life . 8 3 O g 5 2 n l i t A a 4 / o 2 c O o f 3 i S n 5 ( o 2 . i o t i t a a r r m 2 d f o i c a i n g c a s i i c c r e 5 . l i 1 S I n
SiO2 6
S i l i c a r a t i o 4 I n c S i r e O 3 a s 2 / ( i A n g l f o r 2 O 2 m 3 + a t ( i o n F 1 e . 5 c o , M a t n ) i n g 2 O 1
3
1
Al2O3
4 3 2.5 2 1.5 1 0.75 0.5 Increasing formation of coating Alumina ratio = Al2O3 / ( Fe,Mn) 2O3
(Fe,Mn)2O3
Phase CaO-Al2O3CaO-Al2O3-SiO2 SiO2
C2S C3S
C3A
CASF -Phase diagram
Fe2O3
SiO2
CaO
Al2O3
Liquid content According to Lea and and Parker the % of liquid formed formed (S) S = 3 Al2O3 + 2.25 ( Fe2O3 + Mn2O3) + MgO Mg O + K2O K2O + Na2 Na2O O
If
( % by weight at 1450 deg) S = 30 % dense and firm coating S = 25 % good coating condit conditions ions S = 20 % loose and porous coating
Burnablity and coating index Burnability Burnabi lity index = C3S /( C3A + C4AF) Minimum burning zone temp=13000C +4.51C3S+ 3.74C2S -12.64 C4AF Coating index , AW AR > 0.64, AW = C3A + C4AF + 0.2 C2S + 2F ( = normally 27 - 32 ) AR < 0.64, AW = C3A + C4AF + 0.2 C2S + 2F When AW < 20 , No coating or very less coating When AW > 30, Excessive but unstable coating with tendency to form thick ring formation.
Liquid percentage ( by Weight) If AR > 1.38 , % L.P = 6.1 F+ M + K+ SO3 If AR < 1.38 , % L.P = 8.2 A - 5.22F+ 5.22F+M+K+N+S M+K+N+SO3 O3 at 1338 1338 deg C If AR< or = 0.64, 0.64, L.P = 3.0A+2.25F+M+K+N+SO3 at 1450 deg C
Viscosity Al2O3,K2O and Na2O increases the viscosity Fe2O3 and SO3 decreases the viscosity
Silica modulus vs liquid content AM= Al2O3/ Fe2O3 LSF= 96, AM=2 35 % i n t h i g e w y b t C n t e g n d e o c 0 5 id 4 u 1 i q t a L
30
25
20
15 1.5
2
2.5
3. SM= S/ (A=F)
3.5
4.0
Mechanism of clinker reaction
Liquid
silicate
lim e
1) At 1200 deg c the material consists of C2S, CaO, C3A and C2A all as small crystal grains 2) Viscosity and surface tension of liquid decreases with increasing temperature 3) C2S and CaO continue to undergo size enlargement with prolonged soaking in the absence of contact with the liquid.
P.t.o
4) Prolonged tumbling of of material with droplets of clinker liquid with high surface
tension will
promote the
coalescence of these droplets among themselves rather
than
reaching and wetting of silicate and lime grains with slow drop in the
viscosity and surface tension the
tiny droplets get enough to meet one another
and
enlarge their own size leaving most of the silicates and lime away. 5) With rapid drop in the viscosity and surface tension of clinker most of the silicates
and lime grains are
drawn into the liquid even the liquid droplets get enough opportunities to meet one another and grow.
Clinker nodule
Model of clinker reactions The clinker reactions proceed in the following ways up to 700deg C : dehydration of the clay minerals with the associated lattice formations and increase in surface reactivity 700 70 0 - 90 900 0 de deg g c: calcination of CaCO3 ,partial reaction of the release of CaO with Al2O3 and Fe2O3 to C2(A,F) and C12A17 and with the active part of the silica to belite (C2S) 900 - 12 900 1200 00 de deg g c: Transformation of the calcium ferrites into liquid state and commencement of the formation of the alite (C3S) from the belite and the uncombined CaO ( free lime) Above 1350 deg c : almost complete reaction of the free lime to alite , together with further decomposition of the belite content.
Phase transformation 1. Evaporation of free water from the feed 2.Evolution of the chemically combined water 550 deg c ( required 363 Kcal / kg cl ) 3. Evolution of CO2 from CaCO3 and MgCO3 4. Formation of interim phase C2F 5. Formation of interim phase CF 6. Formation of interim phase C2S+C2AS+CF C2S+C2 AS+CF +C2F 7. Formation of interim phase C2S+C5A3+ C2S+C5 A3+ C5A+ CF + C2F 8. Formation of interim phase C2S+C3A+ C5A3+C2F+C3S
100 deg c 500 deg c
805 deg c 800 deg c 900 deg c 1000 deg c 1100 deg c 1200 deg c
9. Formation of C3A + C3S + C2S + C2F 1300 deg c ( required 511 Kcal / Kg cl )
Clinkering process
Deg C
1450 OC 1400
1200
CaCO3
1000
CaO Alite
600
Belite Beta quartz
Gamma quartz C12A7
Pre heating zone
400
C3A C2(A, F) C4AF
Calcining zone Transition zone
800
Liquid 200 Burning zone
cooling zone
Clinker moduli and their influence on the burning properties of clinker
Chemical and minerol Chemical minerologica ogica proce processes sses during during clinker clinker burning
Quasi-quantitative Quasi-quantitativ e variation of minerals with temperature
Reactions in preheater Stage-1 Evaporation of free water 0.3% 0.3 % H2O = - 3 kcal / kg .cl Stage-2 Evaporation of chemically combined water 0.7 % H2O = - 18 kcal kcal / Kg cl Oxidation of sulfides ( pyrites) Stage-3 Oxidation of sulfides, partial Decarbonation of CaCO3 and combustion of coal in the rawmix( organic matter)
310 deg c
490 deg c 640deg c
750 deg c
900 deg c
Stage-4 Oxidation of sulfides, partial Decarbonation and recarbonation Stage-5 Decarbonation or CaCO3 ( 30 -40 %) Calciner Decarb Dec arbonat onation( ion(90 90 - 95 % ). Lime reacts with 1400 deg c reactive silica
1100 deg c
820 deg c
Clinker burning 1)Radiation of heat from flame to refractory 2)Conduction of 1400 deg c heat from refractory to charge 1900 3)Convection of 1350 deg c 1450 ded c heat from particle to particle while rotating.Higher rpm 1500 deg increases the rate of convection
Heat
Higher rpm improves the thermal distribution,better distribution,better heat exchange between refractory and raw meal bed and so reduces the radiation losses
