Contents
Cement Grinding Important coefficient & Factors
BLAINE FINENESS FACTOR
Example
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
COMPOSITE CEMENT
OPC (Ordinary Portland Cement)
Composition
96 % CLINKER
4 % GYPSUM
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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 …
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
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
POLYSIUS C Factor
Depends on different parameters: ball charge, kind of material, type of process, type of mill
HIGH EFFICIENCY SEPARATOR SEPOL
TROMP Curve
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)
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Mohan Bevin