Cement Grinding

CEMENT GRINDING PLANT

 BLAINE FINENESS FACTOR

POLYSIUS Coefficient

 Required   Blaine   Reference  Blaine    K   e  * 0,49 1000     Exemple

Mill output : 100 t/h Fineness according according to Blaine: 3000 cm²/g cm²/g

New fineness fineness required: 3500 cm²/g 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) 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 workabilit y, colour modification … _____________________________________________________________________________________ 1

CEMENT GRINDING PLANT  Exemple of the additive influence on the mill output 

Production of cement with 15 % of li mestone 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 ti mes more fineness. X = equivalent clinker fineness 2.X = l imestone 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 G = Ball charge weight C = POLYSIUS C Factor Di = Internal mill diameter Lu = Effective grinding length F = Filling degree of ball charge d = Bulk density of grinding balls  Ball charge weight 

(kW) (tons) (-) (m) (m) (%) (t/m3)

normal range : 24 –32 % 4,5 – 4,6

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 2

Cement mill / closed circuit  26 % C = 9,8 30% = C = 9,4

28 % 32% =

C = 9,6 C = 9,1

CEMENT GRINDING PLANT  HIGH EFFICIENCY SEPARATOR SEPOL

A

SEPOL

F R Separator efficiency

  



1  a r   a . 1   f  r    f 

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 r f



= % passing between 2 sieves in the fresh feed = % passing between 2 sieves in the grits = % passing between 2 sieves in the finish product 3

Sa Sr Sf

= % passing sieve: 10 – 20  ……> 100  = % passing sieve: 10 – 20  ……> 100  = % passing sieve:: 10 – 20  ……> 100 

Sa   Sr   Vf   *100  Sf    Sr 

Vg



Sf    Sa

 Sf    Sr 

*100

r .Vr  *100 T   r .Vr   f .Vf  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 li mit 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)

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