Cement Process & Energy Saving

November, 2006
Hideyuki TANAKA
Technical Expert
International Engineering Dept.,
The Energy Conservation Center, Japan1

Bird-eye View of Japanese Cement Factory
Coal yard

Water

SP &calcinerElectrostatic
Precipitator(EP Dustcollector)

Waste tireyard
Rotary kiln

Raw millcrusher

Cement silo

Shipping pierLayout of one Japanese cement factory2Chemical Compositionof Raw Materials and Cement Product
Raw Materials

(%)
CaO

Limestone

SiO2

Al2O3

SO3

47-55

CO237-43

Clay45-78

Silica77-96

10-26

Iron-ore
Gypsum

Fe2O33-9

40-90
26-41

37-59

Cements(%)
CaO

SiO2

Al2O3

Fe2O3

SO3

Portland cement

63-65

20-23

3.8-5.8

2.5-3.6

1.5-2.3

Blended cement(BF slag)

52-58

24-27

7.0-9.5

1.6-2.5

1.2-2.6

Others3Temperature Profile in Wet Process Kiln
Temperature, ℃
2000
Gas temperature
1000
Materialtemperature
DryingCalcining

Preheating
Sintering
ZoningWater content of raw meal :38 – 40%Cooling
Clinker temp : 80 – 100 ℃
Fuel

Raw meal
Kiln

Chain Curtain Zone:
20- 25% extension

CoolerClinkerTemperature Profile in Wet Process Kiln

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Chemistry of Cement ProcessHeating (℃)

DryingCalcining

Sintering100〜110

Vaporization of physically adsorbed water

110〜700

Vaporization of chemically bonded water

700〜750

Decomposition of MgCO3750〜900

Decomposition of CaCO3, Formation of 2CaO・SiO2

950〜1200

Transition to β・ 2CaO・SiO2

1200〜1300

Formation of 3CaO・Al2O3, 4CaO・Al2O3・Fe2O3

1300〜1450

Formation of 2CaO・SiO2, Sintering of Al2O3, Fe2O3,Na2O, K2O, etc
During a course of cooling, pebble-like black coloredclinker is formed, which consists of the following
components;

Cooling

150〜200

3CaO・SiO2: Referred to as Alite or C3S

2CaO・SiO2: Referred to as Belite or C2S

3CaO・Al2O3: Referred to as aluminate phase or C3A

54CaO・Al2O3・Fe2O3: Referred to as ferrite phase or C4AF

Raw Materials and Energy
required for production of 1 ton of Cement
Energy Consumption
Raw Materials (kg)

Fuel (*1)

105
99Limestone

1,095Electric power (kWh)Clay204

Silica78(*1) : kg of coal equivalent, where
HHV of coal is 6,200 kcal/kg(= 25,958kJ/kg)

Iron-ore

30

Gypsum34

Total

1,439

Base : 1 ton of cement

Fuel by kind (%)
Coal

78

Petroleum coke

13

Combustible waste

5

Heavy oil46

Heat Requirement in Burning Section
Kiln

kcal/kg-cl

Source (1)m3N/kg-cl (2)Shaft kiln

940

Yogyo Kogaku
H/B

1.65

Dry long kiln

1,487

JCA (1961)

2.62

Wet kiln

1,357

〃

2.38

Lepol kiln

954

〃

1.68

SP kiln797

JCA (1981)

1.40

NSP kiln

773

〃

1.35

Note 1: JCA: Japan Cement Association
2: Estimated based on 1.40 m3N/kg-cl in SP kiln

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Energy Management System(Cement Factory)
AspectOrganization

Monitoring

Major Activity
Accountability

Employee education (awareness)

Organization

EE&C promotion committee
Energy manager

Monitoring

Data recording & reporting toemployee

TargetingSpecific energy consumption (SEC)
Key efficiency parameters

Technology
Operation &maintenance(O&M)

Technical review (energy audit)
Housekeeping

Product yield (avoid off-specproduct)
Preventive maintenance (avoidunscheduled shutdown)
8Energy Saving Measures in Cement Factory
Raw material section

Clinker burning section

Finishing section

First step

1) Selection of raw materials
2) Management of particlefineness3) Management of grindingmedia

1) Prevention of unscheduledshutdown2) Selection of fuel3) Prevention of leakage

1) Management ofparticle fineness2) Management ofgrinding media

Secondstep

1) Replacement of fan rotor2) Improvement oftemperature and pressure
control system
3) Improvement of mixing &homogenization system
4) Installation of closed
circuit mill (separator)

1) Use of industrial waste(waste tire, etc)
2) Heat recovery of pre-heater
exhaust gas and cooler
exhaust gas (drying of raw
material and generation ofelectricity)
3) Replacement of cooler dust
collection from multicloneto EP

1) Installation ofclosed circuit mill(separator)
2) Installation of feed
control system

Third step1) Conversion from wetprocess to dry process
2) Replacement of ball or tube
mill by vertical roller mill
3) Pneumatic transfer of raw
material to mechanicaltransfer1) Conversion of fuel frompetroleum to coal
2) Conversion of SP to NSP
3) Conversion of planetary
cooler to grate cooler

1) Use of industrialwaste(slag, pozzolan)

9Boundary of Heat Balance
Exhaust gas
Raw material
TTF

gas flowmaterial flowTO
2

Air leakPreheater
Section

TKiln
SectionT1ry airOO

Fuel oil22FTTT

Air leakT

Trial & Error Method
TT

Measured orassumed
calculated

CoolerexhaustventCooler
SectionT2ry air
Clinker10Collecting Data (Wet Process)-1
Dry raw material (dry RM)

t/hWater content in wet raw material

wt% on wet RM(40)

Clinker yield-(0.65)

Clinker temp at cooler exit

deg C

Heat of clinkering (calcination & sintering) kcal/kg-cl
Specific heat of clinker (Cp)kcal/kg-cl・deg C 0.192

Fuel rate (kiln)

m3N/hSpecific gravity of fuelkg/m3N

Specific heat of fuel (Cp)kcal/kg・deg C

Low heat value of fuelkcal/m3N

Fuel temperature

deg C

Fuel rate (precalciner)

kg/m3N

Exhaust gas temp at kiln or preheater exit deg C
O2 in exhaust gas

Vol %CO2 generation in calcination

m3N/kg-cl

Specific heat of exhaust gas

kcal/m3N・deg C 0.338

0.27
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Collected Data (Wet Process)-2
Kiln surface temperature (average)

Deg C

Surface aream2

Convection coefficient (hc)kcal/m2・hr・deg C(10.9)

Radiation coefficient (hr)kcal/m2・hr・deg C(21.0)

Emissivity-0.95

Preheater surface temperature (average)

deg C

NA

Surface aream2

NA

Convection coefficient (hc)kcal/m2・hr・deg C(10.0)

Radiation coefficient (hr)kcal/m2・hr・deg C(19.1)

Emissivity-0.95

Cooler surface temperature (average)

deg C

Surface aream2

Convection coefficient (hc)kcal/m2・hr・deg C(13.0)

Radiation coefficient (hr)kcal/m2・hr・deg C(25.0)

Emissivity-0.95

Ambient temperature (outdoor)

deg C
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Items Listed on Heat Balance Table
Heat Input

Heat Output

Heat of combustion of fuelI1

Heat for clinkering

O1

Sensible heat of fuelI2

Sensible heat of clinker at cooler exit

O2

Sensible heat of wet raw material

I3

Sensible heat of cooler exhaust ventO3

Sensible heat of combustion air

I4Heat for evaporating water in raw material O4
Sensible heat of kiln or preheater
exhaust gas

O5

Radiation heat on kiln surface

O6

Radiation heat on preheater surface

O7

Radiation heat on cooler surface

O8

Unaccountable heat losses

O9

Base of temperature : Ambient air temperature
Base of heat amount : kcal per kg of clinker (kcal/kg-cl)
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Thank you!

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