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CEMENT GRINDING PLANT

BLAINE FINENESS FACTOR

POLYSIUS Coefficient

49,0*1000

BlaineReferenceBlaineRequired

eK

Exemple

Mill output : 100 t/h Fineness according to Blaine: 3000 cm²/g New fineness required: 3500 cm²/g K = exp ((3500-3000)/1000*0,49) K= 1,278 Expected mill output = 78,3 t/h

CEMENT GRINDING PLANT

COMPOSITE CEMENT

____________________________________________________________________________________ OPC (Ordinary Portland Cement) Composition 96 % CLINKER 4 % GYPSUM _____________________________________________________________________________________ CPC (Composite Portland Cement) Type of additives: Limestone, pouzzolane, trass, slag, fly ash, …. Properties: increase of fineness and output, decrease of initial and final strength, increase of concrete plasticity and workability, colour modification … _____________________________________________________________________________________

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CEMENT GRINDING PLANT Exemple of the additive influence on the mill output Production of cement with 15 % of limestone Composition 81 % CLINKER 4 % GYPSUM 15% LIMESTONE Cement Mill Output = 100 t/h of OPC (96 % Clinker – 4% Gypsum) Fineness = 3200 cm²/g CPC cement (81% Clinker – 4% Gypsum – 15% Limestone)) Fineness required 3200 cm²/g according to blaine Calculation of equivalent clinker fineness We consider that the limestone “gives” 2 times more fineness. X = equivalent clinker fineness 2.X = limestone fineness 3200 = (0,81+0,04) X + 0,15 2.X X = 2783 cm²/g Limestone fineness = 5565 cm²/g

CEMENT GRINDING PLANT Expected cement mill output with 15% limestone Fineness factor K = exp ((3000-2783)/1000*0,49) K=1,11 Expected mill output = 111 t/h at 3200 cm²/g with 15% limestone

BALL MILL ABSORBED POWER

Absorbed power at mill shaft / Polysius Formula

P(kW) = G x C x Di x 0,736 P = Mill power absorbed (kW) G = Ball charge weight (tons) C = POLYSIUS C Factor (-) Di = Internal mill diameter (m) Lu = Effective grinding length (m) F = Filling degree of ball charge (%) normal range : 24 –32 % d = Bulk density of grinding balls (t/m3) 4,5 – 4,6 Ball charge weight G (tons)= (π x Di² / 4) x Lu x F x d Absorbed power at mill motor shaft Pmotor(kW) = P(kW)/ ŋ ŋ = Drive efficiency ŋ= ŋ Girth gear (0,98) x ŋ Combiflex (0,97) x ŋ motor coupling (0,99) = 0,94 POLYSIUS C Factor Depends on different parameters: ball charge, kind of material, type of process, type of mill

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Cement mill / closed circuit 26 % C = 9,8 28 % C = 9,6 30% = C = 9,4 32% = C = 9,1

CEMENT GRINDING PLANT

HIGH EFFICIENCY SEPARATOR SEPOL A F R Separator efficiency

frar

fa

.11

a = % passing cumulated in fresh feed f = % passing cumulated in finish product r = % passing cumulated in separator rejects

CEMENT GRINDING PLANT TROMP Curve % 100 50 by pass 40 a = % passing between 2 sieves in the fresh feed r = % passing between 2 sieves in the grits f = % passing between 2 sieves in the finish product

SEPOL

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Sa = % passing sieve: 10 – 20 ……> 100 Sr = % passing sieve: 10 – 20 ……> 100 Sf = % passing sieve:: 10 – 20 ……> 100

100*

SrSfSrSaVf

100*

SrSfSaSfVg

100*..

.VffVrr

VrrT

Tau = By pass % This percentage represents the % of fines which has been considered by the Separator as rejects. Normal range for a high efficiency separator SEPOL with OPC cement : 5 –15% Separation cutting : diameter µm This point gives where is the limit of accuracy of the SEPOL for the cement produced. Normal value for standard OPC: 10 – 20 µm Imperfection Polysius formula kapa = d30/d70 Lafarge formula I = (d75 – d25 ) / 2 (d50)