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Page 1

CemNet Training - Course TCM01 Module 3 - Session 3

This document is for the sole use of students enrolled on course TCM01 and cannot be reprinted, reproduced or distributed without prior written consent from Tradeship Publications Ltd © 2005
http://training.CemNet.com 1

Cement Technology Training ©2005 3. Pyroprocessing

Cement Manufacturing
Technology

3. Pyroprocessing – raw mix to cement clinker.

3.3. Precalcination.

Cement Technology Training ©2005 3. Pyroprocessing

Cement Technology 3.3 Precalcination

At the end of session 3.2 we saw that the increasing thermal loads
inflicted on the burning zone, as cement kiln capacities rose,
effectively capped long and preheater capacities at ~3000 tonnes per
day.

Today, new cement kiln
projects of 10,000 tonne
per day capacity are
commonplace, as cement
companies seek the
economies of scale which
high capacity kilns can
deliver.

Cement Technology Training ©2005 3. Pyroprocessing

Cement Technology 3.3 Precalcination

At the end of session 3.2 we saw that the increasing thermal loads
inflicted on the burning zone, as cement kiln capacities rose,
effectively capped long and preheater capacities at ~3000 tonnes per
day.

These high capacities could
never be achieved with all
the thermal energy
requirements and fuel
supplied through the main
burner of the kiln.

Page 2

CemNet Training - Course TCM01 Module 3 - Session 3

This document is for the sole use of students enrolled on course TCM01 and cannot be reprinted, reproduced or distributed without prior written consent from Tradeship Publications Ltd © 2005
http://training.CemNet.com 2

Cement Technology Training ©2005 3. Pyroprocessing

Cement Technology 3.3 Precalcination

At the end of session 3.2 we saw that the increasing thermal loads
inflicted on the burning zone, as cement kiln capacities rose,
effectively capped long and preheater capacities at ~3000 tonnes per
day.

Kiln linings with sufficient
refractoriness to withstand
the burning zone thermal
loads involved are not
available.

The solution to this
problem was delivered by
precalcination technology.

Cement Technology Training ©2005 3. Pyroprocessing

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Cement Technology

In session 3.1 the chemical reactions and thermodynamics of the
conversion of raw materials to cement clinker were described.

The evaporation of any residual water, dehydration of clay
minerals, CaCO3 calcination and clinker flux formation are all
endothermic and consume large amounts of energy.

Calcination of the CaCO3 is
the most energy consuming
and endothermic of these
reactions.

3.3 Precalcination

Cement Technology Training ©2005 3. Pyroprocessing

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Cement Technology

In session 3.1 the chemical reactions and thermodynamics of the
conversion of raw materials to cement clinker were described.

The evaporation of any residual water, dehydration of clay
minerals, CaCO3 calcination and clinker flux formation are all
endothermic and consume large amounts of energy.

The solution to the burning zone
thermal load problem was to direct
the thermal energy input to the
point in the kiln where this reaction
is taking place, rather than inputing
all the thermal energy through the
main burner.

3.3 Precalcination

Page 7

CemNet Training - Course TCM01 Module 3 - Session 3

This document is for the sole use of students enrolled on course TCM01 and cannot be reprinted, reproduced or distributed without prior written consent from Tradeship Publications Ltd © 2005
http://training.CemNet.com 7

Cement Technology Training ©2005 3. Pyroprocessing

Cement Technology

Precalcination technology has resulted in a step change in the
production capacity of cement kilns.

3.3 Precalcination

Heat exchange between the kiln gases and the feed at the back of
the rotary kiln is inefficient, and therefore festoons of chains are
hung from the inside of the kiln shell to pick up the feed material
and promote this heat exchange.

0.7D

Efficient, well maintained chain
systems combined with chemical
dewatering agents are required to
reduce the thermal energy
consumption to 5000 kJ/kg clinker
and boost the kiln output to 0.8
tpd/m3

Cement Technology Training ©2005 3. Pyroprocessing

Cement Technology

Precalcination technology has resulted in a step change in the
production capacity of cement kilns.

3.3 Precalcination

Long dry cement kilns typically have a length to diameter ratio of
35:1…………..

D
L = 35xD

…..and again might be supported on 5 or more
tyre and roller stations.

Cement Technology Training ©2005 3. Pyroprocessing

Cement Technology

Precalcination technology has resulted in a step change in the
production capacity of cement kilns.

3.3 Precalcination

They can extend to 160m in
length and have production
capacities of _ million tonnes
per year.

Although 300,000 tonnes per
year is a large long dry kiln.

Long dry cement kilns typically have a length to diameter ratio of
35:1………….. …..and again might be supported on 5 or more
tyre and roller stations.

Page 8

CemNet Training - Course TCM01 Module 3 - Session 3

This document is for the sole use of students enrolled on course TCM01 and cannot be reprinted, reproduced or distributed without prior written consent from Tradeship Publications Ltd © 2005
http://training.CemNet.com 8

Cement Technology Training ©2005 3. Pyroprocessing

Cement Technology

Precalcination technology has resulted in a step change in the
production capacity of cement kilns.

3.3 Precalcination

These kilns are particularly
suited to desert climates where
there was no water available to
slurry the raw materials.

Thermal energy efficiency is
better than long wet kilns as the
water in the slurry does not
have to be evaporated.

Long dry cement kilns typically have a length to diameter ratio of
35:1………….. …..and again might be supported on 5 or more
tyre and roller stations.

Cement Technology Training ©2005 3. Pyroprocessing

Cement Technology

Precalcination technology has resulted in a step change in the
production capacity of cement kilns.

3.3 Precalcination

Festoons of chains are again
used to promote heat exchange
between the feed and kiln gases
at the back of the kiln.

However, as the feed is a dry
powder these kilns are prone to
high dust losses.

Long dry cement kilns typically have a length to diameter ratio of
35:1………….. …..and again might be supported on 5 or more
tyre and roller stations.

Cement Technology Training ©2005 3. Pyroprocessing

Cement Technology

Precalcination technology has resulted in a step change in the
production capacity of cement kilns.

3.3 Precalcination

Festoons of chains are again
used to promote heat exchange
between the feed and kiln gases
at the back of the kiln.

Long dry cement kilns typically have a length to diameter ratio of
35:1………….. …..and again might be supported on 5 or more
tyre and roller stations.

These dust losses adversely
impact on the thermal
efficiency and productivity of
the kilns.

Page 14

CemNet Training - Course TCM01 Module 3 - Session 3

This document is for the sole use of students enrolled on course TCM01 and cannot be reprinted, reproduced or distributed without prior written consent from Tradeship Publications Ltd © 2005
http://training.CemNet.com 14

Cement Technology Training ©2005 3. Pyroprocessing

Cement Technology

Precalcination technology has resulted in a step change in the
production capacity of cement kilns.

3.3 Precalcination

FL Smidth Suspension Preheater (SP)

We will discuss the design and operation of
suspension preheaters further in a later session
of the course.

Cement Technology Training ©2005 3. Pyroprocessing

Cement Technology

Precalcination technology has resulted in a step change in the
production capacity of cement kilns.

3.3 Precalcination

FL Smidth Suspension Preheater (SP)

Thermal energy consumption of 3500 kJ/kg
clinker is typical, although this can be reduced
to 3000 kJ/kg clinker in exceptional cases.

Specific output of 2.10 tpd/m3 is typical,
although in excess of 2.70 tpd/m3 can be
achieved in exceptional cases.

Cement Technology Training ©2005 3. Pyroprocessing

Cement Technology

Precalcination technology has resulted in a step change in the
production capacity of cement kilns.

3.3 Precalcination

With the addition of precalcining furnaces at the base of the
preheater and before the rotary kiln all the thermal work of
precalcination has been taken out of the rotary section of the kiln.

Typical kiln productivity
has risen to over 4.10
tpd/m3.

The length of these kilns
has reduced to 70m, or less.

Page 15

CemNet Training - Course TCM01 Module 3 - Session 3

This document is for the sole use of students enrolled on course TCM01 and cannot be reprinted, reproduced or distributed without prior written consent from Tradeship Publications Ltd © 2005
http://training.CemNet.com 15

Cement Technology Training ©2005 3. Pyroprocessing

Cement Technology

Precalcination technology has resulted in a step change in the
production capacity of cement kilns.

3.3 Precalcination

With the addition of precalcining furnaces at the base of the
preheater and before the rotary kiln all the thermal work of
precalcination has been taken out of the rotary section of the kiln.

The space required and
footprint of modern
precalciner kilns is only _
that of long wet kilns…..
……while, output has been
more than tripled to over
10,000 tonnes per day with
the largest precalciner kilns.

Cement Technology Training ©2005 3. Pyroprocessing

Cement Technology

Precalcination technology has resulted in a step change in the
production capacity of cement kilns.

3.3 Precalcination

With the addition of precalcining furnaces at the base of the
preheater and before the rotary kiln all the thermal work of
precalcination has been taken out of the rotary section of the kiln.

Some Indian cement
companies have been able
to boost the output of their
kilns to over 7.00 tpd/m3.

We will explore the ways
they have done that in
succeeding sessions of the
course.

Cement Technology Training ©2005 3. Pyroprocessing

Cement Manufacturing
Technology

3. Pyroprocessing – raw mix to cement clinker.

3.3. Precalcination.

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