Indian cement industry has passed through many ups and down. It was under strict government control till 1982. Subsequently, it was partially decontrolled and in 1989, the industry was opened for free market competition along with withdrawal of price and distribution controls. Finally, the industry was completely de-licensed in July 1991 under the policy of economic liberalization and the industry witnessed spectacular growth in production as well as capacity.

1.
Indian Cement Industry: A Technology Perspective
Dripto Mukhopadhyay
Indian cement industry has passed through many ups and down. It was under strict
government control till 1982. Subsequently, it was partially decontrolled and in 1989, the
industry was opened for free market competition along with withdrawal of price and
distribution controls. Finally, the industry was completely de-licensed in July 1991 under the
policy of economic liberalization and the industry witnessed spectacular growth in production
as well as capacity. Over time, the industry has also witnessed spread of the plants in several
regions of the country as presented in Table 1- 2, which were previously concentrated in
close proximity to the raw material.
250
Capacity and production in MT
200
150
100
50
0
1950 1980 1900 2000 2009
Capacity Production
Fig 1. Capacity, Production and Capacity Utilization in Indian Cement Industry
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2.
250
200
Consumption in MT
150
100
50
0
2003‐04 2004‐05 2005‐06 2006‐07 2007‐08 2008‐09 2009‐10
Fig 2. Cement Consumption in India
100
87 83
80 74
67 75
60
40
20
0
1950 1980 1900 2000 2009
Capacity Utilization
Fig 3. Capacity Utilization in Indian Cement Industry
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3.
Table 1: Distribution of Cement Plants with Installed Capacity above 0.50 MnT
Installed Capacity above 0.5 Million Tonnes
State
No. of Plants Percentage Share
Andhra Pradesh 32 21.33
Assam 1 0.67
Bihar 1 0.67
Chhattisgarh 8 5.33
Gujarat 11 7.33
Haryana 2 1.33
Himachal Pradesh 5 3.33
Jharkhand 3 2.00
Karnataka 8 5.33
Madhya Pradesh 11 7.33
Maharashtra 9 6.00
Meghalaya 1 0.67
Orissa 4 2.67
Punjab 2 1.33
Rajasthan 18 12.00
Tamil Nadu 17 11.33
Uttar Pradesh 8 5.33
Uttarakhand 2 1.33
West Bengal 7 4.67
Table 2: Distribution of Cement Plants with Installed Capacity Less than 0.5 MNT
Installed Capacity less than 0.5 Million Tonnes
State No. of Plants Share in %
Andhra Pradesh 3 9.09
Assam 1 3.03
Chhattisgarh 2 6.06
Delhi 1 3.03
Gujarat 3 9.09
Haryana 1 3.03
Himachal Pradesh 1 3.03
Jammu & Kashmir 1 3.03
Jharkhand 2 6.06
Karnataka 3 9.09
Kerala 2 6.06
Madhya Pradesh 1 3.03
Maharashtra 1 3.03
Meghalaya 3 9.09
Punjab 1 3.03
Rajasthan 2 6.06
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4.
Technologies Adopted by Indian Cement Industry
Generally cement manufacturing process involves following stages:
1. Quarrying raw materials
2. Crushing
3. Pre-homogenization and raw meal grinding
4. Pre-heating
5. Precalcining
6. Clinker production in the rotary kiln
7. Cooling and storing
8. Blending
9. Cement grinding
10. Storing in the cement silo
India is the second largest cement producing country in the world with a distinction of
operating plants with varying capacity and varying technologies. Some of the modern plants
can be compared to the best plants in the world in terms of variety, quality and energy
efficiency. Indian cement industry remained proactive in adopting technological
advancements taking place all over the world. The share of energy inefficient wet process
plants had slowly decreased from 94.4% in 1960 to 61.6% in 1980. Currently, the share of
wet process is only about 1% according to industry sources.
During the 80's and 90's, major technological advancements took place world over in design
of cement plant equipment/systems primarily in the following major areas:
a) Pre-calcination
b) High pressure grinding
c) Automation in process control
d) High efficiency particle separation
e) Clinker cooling
These resulted in significant transformation of the production process globally. The Indian
cement industry closely followed the international trend. Energy conservation has been the
prime objective that propelled major technological changes in the industry. A few recent
technologies that helped Indian cement industry to consolidate in sustained energy savings
are broadly discussed below.
Raw Material Grinding: Raw material grinding is a critical mechanical operation that
determines the sizing of equipment in cement plant. This process consumes about 20% of
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5.
total energy consumed in the plant. Depending on the raw materials’ physical characteristics,
various grinding systems are used in Indian cement industry:
a) Ball mills
b) Vertical Roller Mills (VRM)
c) Ball mills with high pressure grinding rolls.
d) High pressure grinding rolls
e) Horizontal roller mills
Vertical roller mills have been widely accepted for combined grinding and drying of moist
raw materials due to their excellent drying capacity and low energy consumption. While a
number of plants are still using ball mills, many have installed pre-grinders like roller press to
improve energy efficiency. Here, the extent to which the roller press is loaded determines the
efficiency of the grinding circuit. Use of roller press alone as a finish grinding equipment to
give the final product is also a new development.
Horizontal roller mill is yet another improvement in grinding systems incorporating the
advantages of vertical roller mill and roller press. An additional advantage with the horizontal
roller mill is its low space requirement. A compact horizontal roller mill with an in-built
separator is now in the process of development. This kind of a mill would eliminate many
small conveyors carrying material to separator and from separator.
The efficiency of the grinding circuit and power consumption of the mill fan largely depend
on the performance of the classifier. Perhaps classifier is the part that has undergone
maximum changes and has been the target part for efficiency improvement. A variety of high
efficiency classifiers are employed in grinding circuits.
Pyro-processing: Pyro-processing section in a cement plant comprises pre-heater, rotary
kiln and clinker cooler. This section is considered as the main element of cement plant as
cement clinker formation takes place in kiln. This section determines the size of a cement
plant as well as sizes of all other equipment. With the introduction of pre-calciners in 80's,
the size of cement plant had considerably increased. With technology upgradation, a kiln size
of 7000 tpd is considered as an economic size which was at the level of 600 tpd in 70s.
Pre-heaters can be classified into the following 5 categories irrespective of the manufacturer.
• Pre-heater without calciner
• Inline calciner with air passing through the kiln
• Inline calciner with external tertiary air duct
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6.
• Separate line calciner
• Separate line calciner with inline calciner
Cyclones are basic units in a pre-heater system. Efficiency of cyclones depends on pressure
drop and change of temperature of gas across each stage. Introduction of Low Pressure drop
(LP) cyclones has brought the pressure drop across each stage to around 50 mm WG from
around 150 mm WG in conventional cyclones. A typical 6 stage pre-heater with LP cyclones
will have a pre-heater exhaust gas temperature of around 2500C and draught of around 500
mm WG. This in turn leads to decrease in pre-heater fan power consumption. The reduced
temperatures at pre-heater exhaust contribute to environmental improvement.
The burners also play an important role in determining the thermal efficiency of the pyro
processing system. There has been a continuous effort on operating the burners with the least
possible primary air. Multi-channel burners that consume only 5% primary air are being used
in many plants. This leads to a direct thermal energy saving of 15 kcal/kg clinker. These
modern burners also facilitate easy flame control in the process.
Clinker cooler is also critical for the production process. It has dual functions, i.e. reducing
the temperature of the clinker to an acceptable level for further transport as well as grinding
and recover energy from the heat of the hot clinker by heating the cooling air. Mainly two
types of clinker coolers are used at present in cement industry. They are:
a) Grate cooler
b) Planetary cooler
Conventional grate coolers are still used by many plants due to comparatively higher thermal
efficiency though they account for several bottlenecks. There have been a number of design
improvements in grate coolers in recent times, mainly on grate plate to improve the
efficiencies simultaneously reducing the cooling air intake. More and more cement plants
with conventional grate coolers are retrofitting the coolers with high efficiency coolers. This
has resulted in low electrical energy consumption in cooling air fans and also in cooler ID
fan.
Cement Grinding: Cement grinding is another energy intensive operation. Cement
grinding consumes around 25-30% of the total energy consumed in a cement plant. Typical
cement grinding systems in use are:
• Open circuit mills
• Closed circuit mills
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7.
• Roller press with open circuit ball mill
• Roller press with closed circuit ball mill.
• Roller press in finished mode
• Vertical roller mill
• Horizontal roller mill
For many years Ball Mills were in use in open circuit and closed circuit mode. In recent past,
roll press as has been introduced and this has led to substantial reduction in energy
consumption. Use of vertical roller mill for cement grinding is also very recent and the
performance results are reported to be encouraging. Horizontal roller mills combine the
advantages of roll press and vertical roller mill. These mills are reported to be highly energy
efficient. Horizontal roller mills are best suited for slag grinding.
Separator is crucial equipment in cement mill section as it has direct bearing on production
and quality of cement and energy consumption. High efficiency separators are used in
modern cement plants and old plants are also going for a retrofit. Apart from these, auxiliary
items like mill liners and diaphragms have also been improved continuously over time and
these items in different designs are available contributing to energy reduction in cement
grinding.
Table 3: Technology of Indian Cement Industry at a Glance
Low Technology Plants Modern Plants Global Technology
Mining and
Conventional Computer aided Computer aided
Material Handling
In-pit crushing &
Crushing Two stage Single stage
conveying
Conveying of Dumpers/Ropeway/ Pipe conveyors, Belt
Belt conveyors
Limestone Tippers conveyors
Ball Mills with / without VRM’s, Roller Presses
Grinding VRM’s, Roller Press
conventional classifier with dynamic classifier
Wet Dry
Semi Dry Dry 6 stage pre-heater
Dry -5/6 stage pre-heater ‐ High efficiency coller
-4 stage pre-heater - High efficiency coller ‐ Multi-channel burner
Pyro-Processing
- conventional coller ‐ Multi-channel burner Co-processing WDF
- Single channel burner Co-generation of power
Low Nox/SO2 emission
technology
Continuous Blending Continuous Blending
Blending & Batch Blending silos
silos silos
Storage
Multi-chamber silos
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8.
Dome silos
Bag Bag Bulk
Packing &
Palletiz
zing and shrin
nk
h
Dispatch Bulk
wrappi ing
Relay Logic / Hard Wired
d
DDC DDC
/ PLC
Process c
control
Neuroffuzzy expert
Fuzzy log expert sys
gic stem
system
m
Energy 90-100 kWh/ cem.
/t 75-85 kW cem.
Wh/t 70-80 k
kWh/t cem.
consump ption level 900-1000 kca
al/kg cl. 700-800 k
kcal/kg cl. 675-74 kcal/kg cl.
40
Plant Siz (TPD)
ze 300 –1800 3000 –60
000 6000 – 12000
Outcome of Techno
e ological Cha
anges
Consequent to grow
wing competi
ition witness in the post de-contr era, one of the majo
sed p rol or
developm
ments has be the introduction of h
een higher grades of cement. The streng parameters
gth
obtained with moder technolog in India are far high than the BIS' specif
rn gies a her e fied standard
ds
for respective grades of cement.
s
80.00
8
60.00
6
40.00
4
20.00
2
0.00
OPC PPC PSC
P Others
Fig 4 Share in To Product
4. otal tion (in %)
Note: OPC - Ordinar Portland Cement, PPC - Portland Pozzolana Cement
ry P
PSC - Portland Sl Cement
C lag
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9.
Conclud
ding Remark and Polic Message
ks cy
Almost a cement pl
all lants are cur
rrently equip
pped with hi efficienc dust collection system
igh cy ms
like Electro Static Pr
recipitators. It has been r
realized that running the plant in env
t e vironmentall
ly
friendly w has dire bearing o the profita
way ect on ability and im
mage of the company. U of blende
Use ed
cement, utilization o waste hea in cemen plant to g
of at nt generate elec
ctrical energ and use o
gy of
alternate fuels are a few exam
mples explaining the co
oncern of ce
ement indus
stry not onl
ly
towards protection o environm
of ment but also ecological balancing. There hav been man
. ve ny
attempts to recover the heat lost in exhaust gas streams of cement plants. With the use of 6
t t s h
stage pre
e-heaters, hi efficienc coolers a better re
igh cy and management practices, th
efractory m he
quantity of heat lost from the ce
ement plants has come down signific
d cantly. Now technologie
w es
able to recov the heat from exhau gas stream from pre-
are availa ver ust ms -heater and c
clinker coole
er
and gene
erate electric energy. M
cal More cement plants in In
t ected to ado such waste
ndia are expe opt
heat reco
overy system mainly to counterac the powe shortage. As the electrical powe
ms t ct er er
generated from wast heat does not require combustion of any fos fuel, suc an attemp
d te s e n ssil ch pt
would en
nable the ce
ement plant to significan contribu to the m
ntly ute movement of reduction i
f in
greenhou gases.
use
80
% of Production
60
40
20
0
1999 2004 2009
OPC PP
PC+PSC
Fig 5. Shif in Producti
ft ion
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10.
Table 4: Comparison of Carbon E
n Emission from Cement M
m Manufacturin
ng
OPC PPC
%
Ton /t
nne % Tonn /t
ne
Calcinatio
on
0.50 60
6 0.3
37 58
Combustio of fuel
on
0.24 29
2 0.1
18 28
Use of pow
wer
0.09 11 0.0
09 14
Total
0.83 10
00 0.6
64 100
0
VRMs & 300 TPD Kilns
00
1200 TPD 4-ST SP Kilns
4
Low Pressure, Pre-
L
PC Kilns
s Rolle Press & H
er High heater
h & Ex
xpert
Effic
ciency Separators
s
Dry Proce Kilns
ess
High Effici
iency Fans,
Mechanical Conveyors
KW
WH/T Cement
Fig 6. Tren of Electric Energy C
nd cal Consumption in Indian Cement Indus
n stry
Source: A
Adopted from R
Raina, S. J. (200 Energy Ef
02), fficiency Impro ovement in Ind Cement In
dian ndustry, Nation
nal
Council f Cement & Building Mater
for B rials, paper pre
epared for IIPE Programme
EC e.
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11.
1700
120 TPD 4-ST Kilns
PC Kilns
1500
Dry Process Kilns Wet to Dry Conversion
1300
5-Stage PC Kilns
1100
6-Stage PC Kilns & Multi
Channel Burners
900
High Efficiency Coolers
700
1960 1970 1980 1900 2000
KCAL/KG CL
Fig 7. Trend of Thermal Energy Consumption in Indian Cement Industry
Source: Adopted from Raina, S. J. (2002), Energy Efficiency Improvement in Indian Cement Industry, National
Council for Cement & Building Materials, paper prepared for IIPEC Programme.
Production of blended cement is also another outcome of the new researches in theindustry.
Blended cements are hydraulic binders in which a part of portland cement is replaced by
other hydraulic or non-hydraulic materials. They display some superior properties directly
related to durability apart from normal properties of Portland cement. It has been found that
fly ash generated in thermal power plants and slag generated in steel plants is suitable for
manufacture of blended cements. Fly ash or slag is inter-ground with cement clinker to
produce blended cement. Many developed countries started using such blended cements in
large quantities in construction of critical structures such as rocket launch pads, sea water
jetties, large dams etc. Production of blended cements directly increases the plant capacity
without any need for creating additional clinker making capacity. This reduces the limestone
usage and fuel usage in cement plants and in turn lessens the greenhouse gases emissions.
Increasing scarcity of good quality coal and power at an attractive price and an ever
increasing energy cost to total production cost are forcing the Indian cement industry to look
for alternate fuels. Use of cheap alternate fuels like lignite, pet coke, rice husk, groundnut
shells etc. is in practice now. In some European cement plants the cost of fuel is reported to
be zero due to the use of 100% waste fuels. In fact, in many cases the cement plants are paid
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12.
for burning the municipal and industrial wastes in such places. Indian cement industry should
also look for such alternatives. However, this requires development of infrastructure at
cement plant site as well as waste generation and collection infrastructure.
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