Download - Advancement in Cement Technology
-
8/9/2019 Advancement in Cement Technology
1/12
T3 146
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.
Fig 1. Capacity, Production and Capacity Utilization in Indian Cement Industry
0
50
100
150
200
250
1950 1980 1900 2000 2009CapacityandproductioninM
T
Capacity Production
-
8/9/2019 Advancement in Cement Technology
2/12
-
8/9/2019 Advancement in Cement Technology
3/12
T3 148
Table 1: Distribution of Cement Plants with Installed Capacity above 0.50 MnT
StateInstalled Capacity above 0.5 Million Tonnes
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 2.67Punjab 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
State
Installed Capacity less than 0.5 Million Tonnes
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 9.09Kerala 2 6.06
Madhya Pradesh 1 3.03
Maharashtra 1 3.03
Meghalaya 3 9.09
Punjab 1 3.03
Rajasthan 2 6.06
-
8/9/2019 Advancement in Cement Technology
4/12
T3 149
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
-
8/9/2019 Advancement in Cement Technology
5/12
T3 150
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
-
8/9/2019 Advancement in Cement Technology
6/12
T3 151
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
-
8/9/2019 Advancement in Cement Technology
7/12
T3 152
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
Material HandlingConventional Computer aided Computer aided
Crushing Two stage Single stageIn-pit crushing &
conveying
Conveying of
Limestone
Dumpers/Ropeway/
TippersBelt conveyors
Pipe conveyors, Belt
conveyors
GrindingBall Mills with / without
conventional classifier
VRMs, Roller Presses
with dynamic classifierVRMs, Roller Press
Pyro-Processing
Wet
Dry
-5/6 stage pre-heater
- High efficiency coller
Multi-channel burner
Dry
6 stage pre-heater
High efficiency coller
Multi-channel burner
Semi Dry
Dry
-4 stage pre-heater
- conventional coller
- Single channel burner
Co-processing WDF
Co-generation of power
Low Nox/SO2 emission
technology
Blending &
Storage
Batch Blending silosContinuous Blending
silos
Continuous Blending
silos
Multi-chamber silos
-
8/9/2019 Advancement in Cement Technology
8/12
Packing
Dispatc
Process
Energy
consump
Plant Si
Outcom
Consequ
developobtained
for respe
&
ontrol
tion level
e (TPD)
of Techno
ent to grow
ents has bwith mode
ctive grades
Note:
0.00
0.00
0.00
0.00
0.00
Bag
Relay Logic
/ PLC
90-100 kWh
900-1000 kc
300 1800
logical Ch
ing compet
en the intron technolo
of cement.
Fig
OPC - Ordina
PS
OPC
/ Hard Wired
t cem.
l/kg cl.
nges
tion witnes
duction ofies in India
. Share in T
y Portland Ce
C - Portland S
PPC
T3153
Bag
Bulk
DDC
Fuzzy lo
75-85 k
700-800
3000 60
sed in the p
igher gradeare far hig
tal Product
ment, PPC -
ag Cement
ic expert sys
h/t cem.
cal/kg cl.
00
ost de-cont
s of cementer than the
ion (in %)
ortland Pozzo
SC
Dome
Bulk
Palleti
wrappi
DDC
temNeuro
system
70-80
675-7
6000
ol era, one
. The strengBIS' speci
lana Cement
Others
silos
ing and shri
ng
uzzy expert
Wh/t cem.
0 kcal/kg cl.
12000
of the maj
th parameteied standar
k
r
rss
-
8/9/2019 Advancement in Cement Technology
9/12
Conclud
Almost
like Elec
friendly
cement,
alternate
towards
attempts
stage pr
quantity
are avail
and gen
heat rec
generate
would e
greenho
ing Remar
ll cement p
tro Static Pr
ay has dir
utilization
fuels are
protection
to recover
-heaters, hi
of heat lost
able to reco
rate electric
very syste
from was
able the ce
se gases.
0
20
40
60
80
%
ofProduction
s and Poli
ants are cu
ecipitators.
ct bearing
f waste he
few exa
f environ
he heat los
gh efficien
from the ce
er the heat
al energy.
s mainly
e heat does
ment plant
1999
y Message
rently equi
It has been
n the profit
t in cemen
ples explai
ent but als
in exhaust
y coolers
ment plants
from exhau
ore cemen
o countera
not requir
to significa
Fig 5. Shi
OPC
T3154
ped with hi
ealized that
bility and i
t plant to g
ning the c
o ecologica
gas streams
nd better r
has come d
st gas strea
plants in I
t the pow
combustio
tly contrib
t in Product
2004
P
gh efficienc
running the
age of the
enerate ele
ncern of c
l balancing.
of cement
efractory m
own signifi
s from pre
dia are exp
r shortage.
of any fo
te to the
ion
200
C+PSC
y dust colle
plant in en
company.
trical ener
ement indu
There hav
plants. Wit
anagement
cantly. Now
heater and
cted to ado
As the ele
sil fuel, su
ovement o
9
ction syste
ironmental
se of blend
y and use
stry not on
e been ma
the use of
practices, t
technologi
clinker cool
pt such was
ctrical pow
h an attem
reduction
s
ly
d
f
ly
y
6
e
es
er
te
er
t
in
-
8/9/2019 Advancement in Cement Technology
10/12
Source: A
Table 4:
Calcinatio
Combusti
Use of po
Total
Fig 6. Tre
dopted fromR
Council
Dry Proc
1200 TPD 4
Comparison
n
on of fuel
er
d of Electri
aina, S. J. (20
or Cement &
ss Kilns
-ST SP Kilns
of Carbon
To
0
0
0
0
al Energy
2), Energy E
uilding Mate
PC Kilns
K
T3155
mission fro
OPC
ne /t
.50 6
.24 2
.09 1
.83 1
onsumption
ficiency Impr
ials, paper pr
Roll
Effi
H/T Cement
m Cement
Ton
0 0.3
9 0.1
1 0.0
0 0.6
in Indian C
vement in Ind
pared for IIP
r Press &
ienc Se arators
High Effici
Mechanical
anufacturi
PPC
e /t %
7 58
8 28
9 14
4 10
ement Indus
ian Cement In
C Programme
RMs & 30
igh
ency Fans,
Conve ors
g
try
dustry, Nation
.
0 TPD Kilns
ow Pressure,
eater & Ex
al
Pre-
pert
-
8/9/2019 Advancement in Cement Technology
11/12
T3 156
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
Dry Process Kilns
120 TPD 4-ST KilnsPC Kilns
Wet to Dry Conversion
5-Stage PC Kilns
6-Stage PC Kilns & MultiChannel Burners
High Efficiency Coolers
700
900
1100
1300
1500
1700
1960 1970 1980 1900 2000
KCAL/KGCL
-
8/9/2019 Advancement in Cement Technology
12/12
T3 157
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.