Cement Mannual

Quality Control Raw Mix Chemistry * Lime Saturation Factor (LSF) Formula

Limiting Range For Raw Mix = 95 - 110 For Clinker = 0.66 - 1.02

Caox100 2.8 Sio2+ 1.2 Al2O3 + 0.65 Fe2O3 Preferable Range For Raw Mix = 1.06 For Clinker = 0.93 - 0.95

Effect - HIGH LSF * Imparts harder burning & entails higher fuel consumption. * Excessive free lime contents in clinker. * Deteriarate refractory lining. * Increase rediation from shell. * Increase Kiln Exit Gas temperature. * Increase C3S contents, Reduce C2S content. * Improve the grindability characterististic of clinker. * Tends to produce unsound cement. * Causes slow setting with high strengths of cement. Effect - LOW LSF * Low lime contents lower will be be strength. * Easy Buring * Slightly more liquid phase.

* Less Dust. * Silica Modulas (SM) Formula

Limiting Range For Raw Mix = 2 - 2.5 For Clinker = 1.9 - 3.2

Sio2 Al2O3 + Fe2O3 Preferable Range For Raw Mix = 2 - 2.2 For Clinker = 2 -2.2

Effect - HIGH SM * Results in Hard burning & high fuel consumption. * Difficults in coating formation. * Deteriorates the kiln lining. * Increase C2S and Reduce C3S will be decrease. * Radiation from shell is high. * Causes unsoundness of cement. * Results in slow setting and hardening of cement. Effect - LOW SM * Increase liquid phase. * This improve burnability of clinker and the formation of coating in kiln. * Better granulometry-less Dust. * Improve cooler efficiency. * Big clinker balls when too low.

* Slightly lower C3S in clinker. * Alumina Modulas (AM) Formula

Limiting Range For Raw Mix = 1.2 - 1.8 For Clinker = 1.5 - 2.5

Al2O3 Fe2O3 Preferable Range For Raw Mix = 1.25 - 1.3 For Clinker = 1.3 - 1.4

Effect - HIGH AM * Impacts hard burning & high fuel consumption. * Reduce liquid phase and kiln output. * Increase C3A and Decrease C4AF. * Increase viscosity of liquid in raw mix. * Tends to render quic setting and strong at early eages. Effect - LOW AM * If AM is too low and raw mix is without free lime, clinker sticking and balling is high. * Liquid start at lower temperature. * Better granulometry. * Slightly lower C3S in clinker. * Free Silica (Sio2) -

Range -

As low as possible

Effect - HIGH Free Sio2 * Increase power and fuel consumption. * Difficults in coating formatiom. * Deteriorates refractory lining. Normally in Kiln free Silica not more than 3% is desirable. * Magnesia (Mgo) Range -

0.0 - 6.0 %

Effect - HIGH Mgo * Leads to unsoundness by forming periclase. * Crystals when Mgo more than 2% . * Reduce viscosity and surface tension of clinker liquid. * Tend to ball easilly in the burning zone. * High contents of Mgo may causes expansion during hydration. * Alkali (Na2o + K2o) Range Effect - High Alkali

0.2 - 0.30 %

* Improve burnability. * Increase liquid. * Easy coating Formation. * External and Internal alkali cycle formation. * Sulphur (S) Range -

0.50 - 1.00 %

Effect - High Sulphur * More than 2.5 - 4 % cause sulphate expansion. * Chocking of the preheater and formation of kiln coating. * Chlorides (Cl) Range -

0.50 - 1.00 %

Effect - High Chloride * Forms more volatile (K+N) Cl and cause operational problem, due to its complete vaporization in the burning zone. * Increase ring formation. * Los of Ignition (LOI) Formula

0.44Caco3 + 0.524 Mgco3 + …………..+ Combined H2O + Organic matter.

LOI should not be more than 4% Effect - High LOI * LOI calculated by heating up a 10 gram cement sample platinum crucible to 900 - 1000 C for 15 minutes until a constant weight is obtained. The weight loss of the sample due to heating is then determined. A high loss on ignitin can indicate prehydration and carbonation. * Which may be caused by improper and prolonged storage or adulteration transport or transfer. The hihger the LOI the less strength the cement will develop. * Potential Clinker Composition - R.H Bouge developed a method for calculating the C3S, C2S, C3A & C4AF from the chemical ananlysis. Tri-calcium Silicate (C3S) = Limiting Range -

45 - 65 %

4.071 ( Cao - FreeCao ) - 7.6 Sio2 + 6.72 Al2O3 + 1.43 Fe2O3 + 2.85 So3 Preferable Range -

50%

Function Alite harhens faster than C2S and contributes to early strength formation. C3S has a high heat of hydration (500 kJ/kg). It is resistant to sulpher attack. High content of C3S will increase strength at all ages. Di-Calcium Silicate (C2S) = Limiting Range -

15 - 25 %

2.867 Sio2 - 0.7544 C3S Preferable Range -

20%

Function Belite hardens slowly and contibutes more to late strength development.It is resistant to sulpher attack.

It has a low heat of hydration (250 kJ/kg). The content of C2S in low heat cement used for the castings of large foundation is high. Tri-Calcium Aluminate (C3A) = Limiting Range -

2.65 Al2O3 - 1.69 Fe2O3

6 - 11 %

Preferable Range -

7.5 - 8 %

Funtion Calcium Aluminate sets quickly and contributes to the early strength but minimally to the final strength. C3A also has a high heat of hydration liberating a large amount of heat during the first few days of hardening (900 kJ/kg) Cements with low percentages of C3A are resistant to soil and water containing sulphates. Higher concentrations of C3A can react with sulphate causing expansion and crack formation exposing more C3A leading to further penetration of sulphates. Tetra-Calcium Alumino Ferrite (C4AF) = 3.043 Fe2O3 Limiting Range -

10 - 16 %

Preferable Range -

12 - 13 %

Funtion Calcium Alumino Ferrite has a minimal effect on the strength of cement. Contributing only to the final strengths. C4AF gives a dark color to the cement and is avoided in the manufacture of white cement. * Free Lime (FCao) - Uncombined lime in the clinker is know as free lime. Formula

0.33 ( LSF - 95 ) + 1.8 ( SM-2) + 0.93 x S45 + 0.56 x C125 LSF = Lime Saturation Factor

SM = Silica Modulas S45 = Sio2 Residue on 45 microns sieve, % C125 = CaCo3 Residue on 125 microns sieve, % In the Clinker, If LSF More than 100 -

Always contain in excess free lime.

Less than 100 -

Presence of free lime - very little amount

* Burning Index (BI) - For Clinker This is indicator of the ease of burning for a given clinker. The higher the index number, The harder the

clinker is to burn. Formula

Limiting Range -

C3S C3A + C4AF 2.5 - 4.0 %

Preferable Range -

2.6 - 2.8 %

* Burning Factor (BF) - For Clinker The burnability factor is used as a guidline for kiln operator to show if a given clinker is easier or harder to burn. Higher burnabilty factor yield a clinker that is harder to burn. Conversely, lower factors make the clinker easier to burn. Formula

LSF + 10 SM - 3 ( Mgo + Alkalies )

Limiting Range -

100 - 200 %

Preferable Range -

106 - 110 %

* Burning Temperature (BT) Formula

1300 + 4.51 x C3S - 3.74 x C3A - 12.64 x C4AF

* Clinker Liquid Phase (LP) - Empirical formula at 1450 C

Formula Limiting Range -

1.13 C3A + 1.35 C4AF + Mgo + Alkali 22 - 30 %

Effect - A High Liquid Content * Formation of dence clinker. * Easy buring. * Hard grinding. Effect - A LOW Liquid content * Porous clinker. * Hard burning. * % Ash absorption in clinker (% AA) -

Preferable Range -

25 - 29 %

Formula

Coal Consumption (TPH) x Ash content in fuel (as fired basis), % Clinker Production (TPH) Range -

1.5 - 2.0 %

* Raw Mix Clinker Ratio (RMCK) - Dust to kiln Formula

100 - % Ash Absorption in Clinker 100 - Loss of Iginition (LOI)

SLAG MILL-1 GRINDING MEDIA WEAR RATE CALCULATION FROM FREE HEIGHT MEASUREMENT

Mill Size :- 16.685 Mtr. Length * 4.8 Mtr. Diameter MONO CHAMBER

* Ball Mill Circulation Factor -

Formula - 1

Example -

Fresh Feed (TPH) + Coarse Return (TPH) Fresh Feed (TPH) CF

=

CF

=

Range -

Formula - 2

Example -

90 + 180 90

=

270 90

3 2.1 - 3.1

Residue of Coarse Return % - Residue of Fines % Residue of Coarse Return % - Residue of Seperator feed % CF

=

CF

=

Range -

21.1 - 9.2 21.1 - 16.4 2.532 2.1 - 3.1

=

11.9 4.7

* Ball Mill Circulation Load - Normal Range of circulating load in conventional close circuit ball mill is around 100 -200 %

Formula - 1 Example -

( Circulating Factor - 1 ) x 100 % CL

=

CL

=

( 2.532 - 1 ) x 100 % 153.20%

* Ball Mill Filling % - The degree of ball charge varies with in the limit of 25 and 45 % . A ball charge below 25 % causes sliding of the balls. A ball charge above 45 % causes disturbances along with the trajectories of the grinding media. The degree of ball charge between 28 % and 34 % . The first mill compartment, where the grinding media is performed by impact alone should contain ball of 100 - 60 mm diameter. The second mill compartment, where comminution is performed by impact & friction ( Mostly by friction ) should be should be charged with balls of 60 - 17 mm diameter. Measuring the filling degree - There is two method to measure the filling of grinding media inside the mill. * Free Height Method - by measuring the free height b/w the charge and the ceilling of the plates in the midle point. Mill Charge volume loading % -

Formula -

112.5 - 125 ( H/D )

Example -

= 112.5 - 125 ( 3.1195/4.66 )

H - Empty height above grinding media (mts) D - Effective Dia of mill (mts) H - 3.1195 D - 4.66

= 112.5 - 83.677 =

28.82%

Note - 112.5 & 125 are come for calculation from grinding chart and grinding volume in ball mill. * Visible Angle Method - It is the number of plates visible inside the mill knowing the total number of plates per ring or rotation of the mill.

Formula -

N - Total number of plates per ring n - Number of visible plates

( n x 360/N )

* Ball Mill Critical Speed - The critcal speed Nc is the speed where the centrifugal force at mill lining is equal to the gravitational force.

Formula -

Nc -

42.3 D 0.5

Nc - Critical Speed N - Revolution per minute in RPM Di - Inside mill diameter in meter

Example -

Nc

=

42.3 3.62 x 0.5

Nc

=

22.232

Practical Speed Formula -

Example -

32 D 0.5 Np

=

32 3.62 x 0.5

Np

=

16.81

Normal Ball Mill are 74 - 76 % of critical speed. Formula -

N%

Example -

N%

Operating Speed x 100 % Nc =

16.7 x 100 %

22.232 N%

=

75%

* Ball Mill Operational speed of Mill -

Formula -

Example -

Critical Speed of Mill x 0.71

=

22.232 x 0.71

=

15.784 RPM

* Ball Mill Wear Rate - Ball Mill grinding media wear rate mostly b/w for cement mill 35 gms/ton of clinker.

Formula -

Wear Rate ( Gm / MT of Material )

Initial WT of wear part during installation - Final wt of wear part during removal in gms Total Material ground / Crushed during perod in MT Note - For VRM, the Roller as well as table wears are calculated individually as well as totally.

* Ball Mill Seperator Efficiency - Fines Efficiency

Formula -

Example -

( 100 - Rf ) x 100 ( 100 - Rr ) x C

=

=

( 100 - 9.2 ) x 100 ( 100 - 16.4 ) x 2.532

Rf - Residue of fines Rr - Residue of seperator feed C - Circulation Factor

Traget - 70 - 90 %

42.90%

* Ball Mill Percentage of Recirculation from CA fan -

Formula -

Bag Filter Inlet Volume x 100 Circulation air fan volume

Bag Filter volume - 62790 m3/hr Circulationg air fan volume - 323400 m3/hr

Example -

= 62790 x 100 % 323400 =

19.41%

* Ball Mill Velocity of Mill -

Formula -

Example -

Mill vent volume / Net effective area 3600 = 48690 / 10.74 3600 = 1.25 m / s

Mill vent volume - 48690 m3/hr Net effective area - 10.74 m2

media (mts)

s per ring

e - 323400 m3/hr