Cement

1. Chapter 2
Chapter 2
Version 07/2007
From Raw Material Grinding to Kiln Feed Bin

2. KHD Humboldt Wedag GmbH
Limestone / Clay
+ Corrective Components
Gas Conditioning
Waste Gas Cleaning
CaCO3
SiO2
Al2O3
Fe2O3
Raw Meal-Silo
• Homogenisation
• Stock Piling
Wednesday, January 28, 2009 2
Fuel Preparation
Raw Material Grinding
Stack
Cooler Waste Air
Cement
Thermal Process
•Pre-Heating
•Calcination
•Clinker Burning
•Clinker Cooling
Finish Mill
Pre-Blend Pile

3. KHD Humboldt Wedag GmbH
2 From Raw Material Grinding to Kiln Feed Bin
2. 1 Overview about raw meal grinding technology
2. 2 Homogenisation Silo
2. 3 Kiln Feed – Dosing and Transport
Wednesday, January 28, 2009 3

4. KHD Humboldt Wedag GmbH
Limestone / Clay
+ Corrective Components
Gas Conditioning
Waste Gas Cleaning
CaCO3
SiO2
Al2O3
Fe2O3
Raw Meal-Silo
• Homogenisation
• Stock Piling
Wednesday, January 28, 2009 4
Fuel Preparation
Raw Material Grinding
Stack
Cooler Waste Air
Cement
Thermal Process
•Pre-Heating
•Calcination
•Clinker Burning
•Clinker Cooling
Finish Mill
Pre-Blend Pile

5. KHD Humboldt Wedag GmbH
2. 1 Overview about raw meal grinding technology
Objectives of raw material grinding
Fineness
Increasing the surface of the raw material (fineness) for a good reactivity in the kiln system. This is
necessary because of saving fuel costs and to maintain a clinker with good quality properties, e.g. free
lime content.
Typical demand on raw meal fineness
12 -15 % retaining on 90 µm sieve
2 % retaining on 200 µm sieve
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2 % retaining on 200 µm sieve
Drying
Drying of the raw material to utilise the Pre-Heater waste gas energy and to prevent clogging of raw meal
into the silo and transport devices to the kiln system.
Typical demand on raw meal humidity
Water in raw meal: <1%
Homogenisation
To maintain a homogenous product of the raw material mixture (limestone, shale, iron, sand….) after mill
before entering the homo silo.
Typical demand on raw meal homogeneity
Standard deviation of CaO mean value: < 1,0

6. KHD Humboldt Wedag GmbH
Raw Material Mix to Raw Mill
From Blending Bed From Silo
Limestone Clay or Iron Sand
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Limestone Clay or
Shale
Iron Sand
SiO2,
Al2O3,
Fe2O3
X-Ray
Analyser
Raw Mill
Homogenisation
Silo
Belt Scale

7. KHD Humboldt Wedag GmbH
2. 1. 1 Ball Mill
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8. KHD Humboldt Wedag GmbH
Ball Mill - Flowsheet for Raw Meal Grinding
Feed
Bag Filter
Cyclone
Separator
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Ball Mill
Feed
Hot Gas
(from Pre-Heater
or Hot Gas Generator)
Product to Homo Silo
Bucket Elevator
Classifier

9. KHD Humboldt Wedag GmbH
2. 1. 2 Roller Press
Wednesday, January 28, 2009 9

10. KHD Humboldt Wedag GmbH
Roller Press - Flowsheet for Raw Meal Grinding
Bag Filter
Bucket Elevator
Cyclone
Separator
Wednesday, January 28, 2009 10
Raw Material
Feed
Hot Gas
(from Pre-Heater
or Hot Gas Generator)
Product to Homo Silo
Classifier
Roller Press

11. KHD Humboldt Wedag GmbH
2. 1. 3 Vertical Mill
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Hot Gas

12. KHD Humboldt Wedag GmbH
Vertical Mill - Flowsheet for Raw Meal Grinding
Wednesday, January 28, 2009 12

13. KHD Humboldt Wedag GmbH
2. 1. 4 Classifier – KHD V Separator
1
1
1
1-
- material feed
material feed
2
2
2
2-
- air inlet
air inlet
3
3
3
3-
- fines+air outlet
fines+air outlet
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4
4
4
4-
- rejects
rejects
3
3-
- fines+air outlet
fines+air outlet

14. KHD Humboldt Wedag GmbH
2. 1. 4 Classifier – KHD LS Separator
3
3
1
1-
- material feed
material feed
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4
4 1
1 2
2
4
4-
- rejects
rejects
1
1-
- material feed
material feed
2
2-
- air inlet
air inlet
3
3-
- fines+air outlet
fines+air outlet

15. KHD Humboldt Wedag GmbH
2. 1. 4 Classifier – KHD VSK Separator
Finematerial,
Finematerial,
Product
Product
Material
Material-
-
inlet
inlet Transportgas,
Transportgas,
Hotgas
Hotgas
Wednesday, January 28, 2009 15
Coarse
Coarse
Material, to mill
Material, to mill
Coarse Material
Coarse Material
from dynamic Classif.
from dynamic Classif.

16. KHD Humboldt Wedag GmbH
2. 2 Homogenisation Silo
Objectives of Homogenisation Silo
Homogenisation
Blending of fine product (raw meal) after raw mill to maintain a homogenous composition of
raw meal as kiln feed.
Wednesday, January 28, 2009 16
Typical demand on kiln feed homogeneity:
Standard deviation of CaO from mean value: < 0,3
Stockpiling
Stockpiling of kiln feed to maintain 24h/d of kiln operation if raw mill is not in operation.
Typical kiln feed capacity:
Kiln feed amount to maintain 24 – 48 h kiln operation

17. KHD Humboldt Wedag GmbH
Homogenisation Silo
Wednesday, January 28, 2009 17

18. KHD Humboldt Wedag GmbH
Blending Effect
The Blending effect of a modern Silo
is given to 10 – 20:1 (depending on homogeneity
of raw meal after raw mill).
The blending effect is generally determined as
the ratio between the standard deviation S of one
Wednesday, January 28, 2009 18
the ratio between the standard deviation Sin of one
significant chemical parameter of the input (e.g. CaO)
and the standard deviation of the same parameter Sout
of the output from the homo silo, as follows:
Blending effect = Sin/ Sout

19. KHD Humboldt Wedag GmbH
2. 3 Kiln Feed – Dosing and Transport
After discharging from the Homogenisation Silo the raw meal is entering the Kiln Feed Tank.
The Kiln Feed Tank works as a buffer before the raw meal is passing the Weight Feeder.
Wednesday, January 28, 2009 19
After Weight Feeder the raw meal is entering the Transport Device (e.g. Bucket Elevator,
Airlift) to the top of the Pre-Heater Tower, into the kiln system.

20. KHD Humboldt Wedag GmbH
2. 3 Kiln Feed – Dosing and Transport
Wednesday, January 28, 2009 20

21. KHD Humboldt Wedag GmbH
Rotary Weight Feeder (Pfister System)
Raw Meal
Inlet
The objective of the weight feeder is to maintain a defined flow of material into the system.
Wednesday, January 28, 2009 21
Raw Meal
Outlet
Load Cell
Kiln Feed Amount = f(Motor Speed)
Motor

22. KHD Humboldt Wedag GmbH
Air Slide
Air slides often used as transport device for fine, solid materials (kiln feed) in horizontal
direction. The airslide is inclined to maintain the material flow.
Wednesday, January 28, 2009 22

23. KHD Humboldt Wedag GmbH
Bucket Elevator
Bucket elevators
are used for the
vertical transport
of bulk materials.
Wednesday, January 28, 2009 23

24. KHD Humboldt Wedag GmbH
Air Lift System
Air Lift Systems are used for the vertical transport of
fine, bulk materials.
Compared to a bucket elevator the investment costs
are lower but the operational costs are higher
(compressed air and therefore electrical energy
demand).
Wednesday, January 28, 2009 24

25. KHD Humboldt Wedag GmbH
Rotary Air Lock
Rotary Air Locks are used as a transfer or shut off device to feed fine materials
into a gas tight system, e.g. feeding of raw meal into the Pre-Heater.
Another function is to protect equipment (e.g. screw conveyor) which is
connected to a silo from the full load of the material column.
Scraper
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Scraper

26. KHD Humboldt Wedag GmbH
Kiln Feed Tank Air Slide
From Homo Silo
From Homogenisation Silo to the Pre-Heater, Kiln System
Wednesday, January 28, 2009 26
Kiln Feed Tank
Air Slide
to
Weight Feeder
Bucket Elevator
(or Air Lift)
Rotary Air Lock
To Pre-Heater